CA1218445A - Shock hazard protection system - Google Patents
Shock hazard protection systemInfo
- Publication number
- CA1218445A CA1218445A CA000459274A CA459274A CA1218445A CA 1218445 A CA1218445 A CA 1218445A CA 000459274 A CA000459274 A CA 000459274A CA 459274 A CA459274 A CA 459274A CA 1218445 A CA1218445 A CA 1218445A
- Authority
- CA
- Canada
- Prior art keywords
- load
- shock hazard
- electrical
- coil
- appliance
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 230000035939 shock Effects 0.000 title claims abstract description 43
- 230000004044 response Effects 0.000 claims description 9
- 238000007654 immersion Methods 0.000 abstract description 11
- 238000013459 approach Methods 0.000 abstract description 4
- 230000007246 mechanism Effects 0.000 abstract description 3
- 239000004020 conductor Substances 0.000 description 52
- 238000001514 detection method Methods 0.000 description 20
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 15
- 230000001012 protector Effects 0.000 description 14
- 239000003990 capacitor Substances 0.000 description 7
- 230000007935 neutral effect Effects 0.000 description 7
- 230000006378 damage Effects 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 239000002674 ointment Substances 0.000 description 4
- 241000282472 Canis lupus familiaris Species 0.000 description 3
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 3
- 230000008901 benefit Effects 0.000 description 3
- 229910052709 silver Inorganic materials 0.000 description 3
- 239000004332 silver Substances 0.000 description 3
- KJBWWVTTZNVMKW-LPYMAVHISA-N 1-(dipyridin-2-ylmethylideneamino)-3-[(E)-(2-hydroxyphenyl)methylideneamino]thiourea Chemical compound Oc1ccccc1\C=N\N\C([S-])=[NH+]/N=C(c1ccccn1)c1ccccn1 KJBWWVTTZNVMKW-LPYMAVHISA-N 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 230000006835 compression Effects 0.000 description 2
- 238000007906 compression Methods 0.000 description 2
- 230000000881 depressing effect Effects 0.000 description 2
- 230000000994 depressogenic effect Effects 0.000 description 2
- 230000036541 health Effects 0.000 description 2
- 230000036039 immunity Effects 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 238000004804 winding Methods 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 208000027418 Wounds and injury Diseases 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- PBAYDYUZOSNJGU-UHFFFAOYSA-N chelidonic acid Natural products OC(=O)C1=CC(=O)C=C(C(O)=O)O1 PBAYDYUZOSNJGU-UHFFFAOYSA-N 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 210000004124 hock Anatomy 0.000 description 1
- 208000014674 injury Diseases 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 238000009877 rendering Methods 0.000 description 1
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H3/00—Mechanisms for operating contacts
- H01H3/32—Driving mechanisms, i.e. for transmitting driving force to the contacts
- H01H3/50—Driving mechanisms, i.e. for transmitting driving force to the contacts with indexing or locating means, e.g. indexing by ball and spring
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H83/00—Protective switches, e.g. circuit-breaking switches, or protective relays operated by abnormal electrical conditions otherwise than solely by excess current
- H01H83/02—Protective switches, e.g. circuit-breaking switches, or protective relays operated by abnormal electrical conditions otherwise than solely by excess current operated by earth fault currents
Abstract
SHOCK HAZARD PROTECTION SYSTEM
Abstract of the Disclosure:
The present invention teaches a new and novel system for protecting people and property against electrical shock. The invention includes a number of preferred and other embodiments which have this as their goal, but which represent a number of distinctive and novel approaches to solving prior art problems.
By way of example only, and without limiting the scope of this invention, these approaches include novel immersion detecting circuits, broken wire test circuits, electromechanical circuit breaking means including coil/plunger arrangements, and relay circuit breaking mechanisms cooperative with associated circuitry, all of which are able to be incorporated as a system wholly within the load (appliance) and its associated cord set (including a "plug").
Abstract of the Disclosure:
The present invention teaches a new and novel system for protecting people and property against electrical shock. The invention includes a number of preferred and other embodiments which have this as their goal, but which represent a number of distinctive and novel approaches to solving prior art problems.
By way of example only, and without limiting the scope of this invention, these approaches include novel immersion detecting circuits, broken wire test circuits, electromechanical circuit breaking means including coil/plunger arrangements, and relay circuit breaking mechanisms cooperative with associated circuitry, all of which are able to be incorporated as a system wholly within the load (appliance) and its associated cord set (including a "plug").
Description
lZ18f~45 SHOCK HAZARD PROTECTION SYSTEM
This invention relat~s generally to electrlcal hazard prevention, and ~ore specifically to a shock hazard preventlon system for disconnectlng an electrical load from an electrical source when a shock hazard condltion exists within the load.
Devices for protectlng human life and property against electrical shock and damage re~ultlng from a shock hazard condition within an electrlcal load are known. For example, the model No. 6199 ground fault circuit interruptor (GFCI) marketed by the assignee of the present invention is capable of sensing and re~ponding to the inadvertent grounding of the neutral conductor of an A-C electrical distributio~ system. It is noted, however, that in certain applications the utilization of such a GFCI is not practical.
In partlcular, the ~FCI is a relatively expensive and complex device which requires the utilization of several transformers. In addition, the GFCI is often hardwired in a wall outlet or receptacle and is neither portable nor readily dlsconnected. Thus, unless each outlet in which an electrical device such as, for example, an appliance is to be utilized is protected by a GFCI, the user of the appliance is sub~ect to possible injury if a shock hazard condition should exist in conjunction with a non-protected outlet.
In addition, in certain environments the utllization of a conventional GFCI would not afford any shock hazard protection to the user of an appliance. More specifically, a ~r~
~Z18~4~i conventional GFCI devlce of the type known to appllcants wlll not be effective or work if the user of an electrical appllance drops the appliance in ~ plastic insulated bathtub.
Another potentlal drawback, exists regarding the use of a GFCI for certaln types of portable electrical appliances such as, for example, a hair dryer. Although the owner of a hair dryer may have his or her residence outlets adequately protected by GFCI devices, it is possible that other places, such as hotels, the residence of relatives, friends, etc., where it l~
desired to use the hair dryer may not be protected by such devices.
Accordingly, it is clear that what is needed is a shock hazard protector which is as~ociated with the appliance to be protected itself rather than with the electrical outlet in which the appliance is plugged and energlzed. It is believed that prior to the present invention, this need has gone unfulfilled.
A need exists for a shock hazard protector which possesses attributes including having a minimum nu~ber of components, reliability, cost and portability.
It is accordingly a general object of this invention to overcome the aforementloned limitations and drawbacks assoclated with the known devices and to fulfill the needs mentioned by providing a hazard protection system having all of the desirable attributes noted above.
~2~8~S
It ls a particular object of the present invention to provide a shock hazard protector capable of dl~connecting an electrical source from an electrlcal load in respon~e to th~
detection of a shock hazard condition within the electrical load.
Another object of the present invention i~ to provide a shock hazard protector capable of detecting and respondlng to a -water-related shock hazard condition within an electrical appliance.
A further object of the present invention is to provide a shock hazard protection system, as above, incorporatlng immersion detection circuitry.
A still further object of this invention is to provide a shock hazard protection system, as above, wherein a feature is provided for detecting a possible break or discontinuity ln a sensing or guard wire.
Yet another object of this invention is to provide a ~ystem, as above, wherein a solenoid-type electromechanical mechanism acts as a circuit breaking or interrupting means.
A further object is to provide such a sy~tem wherein a relay and associated circuitry and mechanical means enable the desired result.
Yet a further object of this invention i~ to provide a detection system which detects or senses the presence of a conductive medium, and which causes an event in response thereto D
~2~ 4~i Another ob~ect of this inventlon is to provide a detection sy~tem whlch detect3 or sense~ the absence of the presence of a conductive medium, and which causes an event in response thereto.
Other ob~ects wlll be apparent from the following detailed description and practlce of the lnventionO
The foregolng and other objects and advantages which will be apparent in the following detailed de~cription of the preferred embodiment, or in the practice of the inventlon, are achieved by the invention disclosed herein, which generally may be characterized as a hazard protector. The hazard protector includes detecting means associated with a load for detecting a hazard condition within the load, an interrupting means assoc~ated with a source to which the load 1~ operatively connected, and conducting means connected between the detecting means and the interrupting means. In response to the detection of a hazard condition within the load ~y the detecting means, the interrupting means operatively disconnects the source from the load.
Serving to illustrate exemplary em~odiments of the lnvention are the drawings, of which:
Fig. 1 is a perspective-type view of a hair dryer and 1ts associated cord set incorporating the system according to the present invention;
~2~4~5 Fig. 2 is a block dlagram of the shock hazard protector, ln accordance wlth the present lnvention;
Fig. 3 ls a schematic dlagram of one embodlment of the shock hazard protector, in accordance with the present lnvention;
Fig. 4 is a schematic dlagram of a second embodiment of the shock hazard protector, in accordance with the present invention;
Fig. 5 is an enlarged partlal sectional elevatlonal view taken through a cord set plug of a relay embodiment of the present invention;
Fig. 6 is a partial fragmentary sectional plan view taken along the line 6-6 of Fig. S:
Fig. 7 is a schematic circuit diagram of the embodiment of the present invention associated with Flgs. 5 and 6;
Fig. 8 is an elevational vlew of the cord set plug illustrated ln Fig. 1 and taken along line 8-8 of that sa~e Fig. 1 depictlng the assembled plug with its cover removed;
Fig. 9 is a partial sectional elevational vlew taken along line 9-9 of Fig. 8;
Fig. 10 is a sectional view taken along line 10-10 of Fig. 8;
Fig. 11 is a fragmentary sectional vlew taken along line 11-11 of Fig. 8; and Fig. 12 is an exploded-type perspective view of components of the present inventlon illustrated in Fig. 8.
121~4~5 Referring now ln more detail to the drawings, Flg. 1 i~
presented in its form to lllustrate a hair dryer 12 and lts associated cord ~et 14 a~ wholly containing and con~tltut~ng or comprlsing the shock hazard protection system 10 of the present invention. It is applicants' intention and desire to emphaslze -here the fact that this invention contemplates an electrical appliance, such as of the personal health care type (halr dryers, etc.) wh~ch possesses all of the features and advantage~ of the lnvention. It is also an intention of appllcants to provlde the system of the present invention in the form of an OEM product available for sale to manufacturers of such appliances.
A plug assembly 16 is illustrated in Fig. 1 as including polarized blades 18 extending from housing 20. Whereas commercially available hair dryers, as an example of a personal health care appliance, normally include a cord set having two conductors or wires, a third wire 22 is illustrated in the case of cord set 14 electrically communicating with a bare copper wire 24 whose path (in the example given in Fig. 1) includes proximity to and looped circult near a dryer housing opening through which
This invention relat~s generally to electrlcal hazard prevention, and ~ore specifically to a shock hazard preventlon system for disconnectlng an electrical load from an electrical source when a shock hazard condltion exists within the load.
Devices for protectlng human life and property against electrical shock and damage re~ultlng from a shock hazard condition within an electrlcal load are known. For example, the model No. 6199 ground fault circuit interruptor (GFCI) marketed by the assignee of the present invention is capable of sensing and re~ponding to the inadvertent grounding of the neutral conductor of an A-C electrical distributio~ system. It is noted, however, that in certain applications the utilization of such a GFCI is not practical.
In partlcular, the ~FCI is a relatively expensive and complex device which requires the utilization of several transformers. In addition, the GFCI is often hardwired in a wall outlet or receptacle and is neither portable nor readily dlsconnected. Thus, unless each outlet in which an electrical device such as, for example, an appliance is to be utilized is protected by a GFCI, the user of the appliance is sub~ect to possible injury if a shock hazard condition should exist in conjunction with a non-protected outlet.
In addition, in certain environments the utllization of a conventional GFCI would not afford any shock hazard protection to the user of an appliance. More specifically, a ~r~
~Z18~4~i conventional GFCI devlce of the type known to appllcants wlll not be effective or work if the user of an electrical appllance drops the appliance in ~ plastic insulated bathtub.
Another potentlal drawback, exists regarding the use of a GFCI for certaln types of portable electrical appliances such as, for example, a hair dryer. Although the owner of a hair dryer may have his or her residence outlets adequately protected by GFCI devices, it is possible that other places, such as hotels, the residence of relatives, friends, etc., where it l~
desired to use the hair dryer may not be protected by such devices.
Accordingly, it is clear that what is needed is a shock hazard protector which is as~ociated with the appliance to be protected itself rather than with the electrical outlet in which the appliance is plugged and energlzed. It is believed that prior to the present invention, this need has gone unfulfilled.
A need exists for a shock hazard protector which possesses attributes including having a minimum nu~ber of components, reliability, cost and portability.
It is accordingly a general object of this invention to overcome the aforementloned limitations and drawbacks assoclated with the known devices and to fulfill the needs mentioned by providing a hazard protection system having all of the desirable attributes noted above.
~2~8~S
It ls a particular object of the present invention to provide a shock hazard protector capable of dl~connecting an electrical source from an electrlcal load in respon~e to th~
detection of a shock hazard condition within the electrical load.
Another object of the present invention i~ to provide a shock hazard protector capable of detecting and respondlng to a -water-related shock hazard condition within an electrical appliance.
A further object of the present invention is to provide a shock hazard protection system, as above, incorporatlng immersion detection circuitry.
A still further object of this invention is to provide a shock hazard protection system, as above, wherein a feature is provided for detecting a possible break or discontinuity ln a sensing or guard wire.
Yet another object of this invention is to provide a ~ystem, as above, wherein a solenoid-type electromechanical mechanism acts as a circuit breaking or interrupting means.
A further object is to provide such a sy~tem wherein a relay and associated circuitry and mechanical means enable the desired result.
Yet a further object of this invention i~ to provide a detection system which detects or senses the presence of a conductive medium, and which causes an event in response thereto D
~2~ 4~i Another ob~ect of this inventlon is to provide a detection sy~tem whlch detect3 or sense~ the absence of the presence of a conductive medium, and which causes an event in response thereto.
Other ob~ects wlll be apparent from the following detailed description and practlce of the lnventionO
The foregolng and other objects and advantages which will be apparent in the following detailed de~cription of the preferred embodiment, or in the practice of the inventlon, are achieved by the invention disclosed herein, which generally may be characterized as a hazard protector. The hazard protector includes detecting means associated with a load for detecting a hazard condition within the load, an interrupting means assoc~ated with a source to which the load 1~ operatively connected, and conducting means connected between the detecting means and the interrupting means. In response to the detection of a hazard condition within the load ~y the detecting means, the interrupting means operatively disconnects the source from the load.
Serving to illustrate exemplary em~odiments of the lnvention are the drawings, of which:
Fig. 1 is a perspective-type view of a hair dryer and 1ts associated cord set incorporating the system according to the present invention;
~2~4~5 Fig. 2 is a block dlagram of the shock hazard protector, ln accordance wlth the present lnvention;
Fig. 3 ls a schematic dlagram of one embodlment of the shock hazard protector, in accordance with the present lnvention;
Fig. 4 is a schematic dlagram of a second embodiment of the shock hazard protector, in accordance with the present invention;
Fig. 5 is an enlarged partlal sectional elevatlonal view taken through a cord set plug of a relay embodiment of the present invention;
Fig. 6 is a partial fragmentary sectional plan view taken along the line 6-6 of Fig. S:
Fig. 7 is a schematic circuit diagram of the embodiment of the present invention associated with Flgs. 5 and 6;
Fig. 8 is an elevational vlew of the cord set plug illustrated ln Fig. 1 and taken along line 8-8 of that sa~e Fig. 1 depictlng the assembled plug with its cover removed;
Fig. 9 is a partial sectional elevational vlew taken along line 9-9 of Fig. 8;
Fig. 10 is a sectional view taken along line 10-10 of Fig. 8;
Fig. 11 is a fragmentary sectional vlew taken along line 11-11 of Fig. 8; and Fig. 12 is an exploded-type perspective view of components of the present inventlon illustrated in Fig. 8.
121~4~5 Referring now ln more detail to the drawings, Flg. 1 i~
presented in its form to lllustrate a hair dryer 12 and lts associated cord ~et 14 a~ wholly containing and con~tltut~ng or comprlsing the shock hazard protection system 10 of the present invention. It is applicants' intention and desire to emphaslze -here the fact that this invention contemplates an electrical appliance, such as of the personal health care type (halr dryers, etc.) wh~ch possesses all of the features and advantage~ of the lnvention. It is also an intention of appllcants to provlde the system of the present invention in the form of an OEM product available for sale to manufacturers of such appliances.
A plug assembly 16 is illustrated in Fig. 1 as including polarized blades 18 extending from housing 20. Whereas commercially available hair dryers, as an example of a personal health care appliance, normally include a cord set having two conductors or wires, a third wire 22 is illustrated in the case of cord set 14 electrically communicating with a bare copper wire 24 whose path (in the example given in Fig. 1) includes proximity to and looped circult near a dryer housing opening through which
2~ an on-off switch a3sembly 26 extends, and thence upward to another loop proximate a dryer houslng air inlet opening through which fan 28 driven by motor 30 pulls air to be heated by heating coil 32 before ex~ting the dryer housing air outlet openlng ln 34~S
which grill 34 iq positioned. After leavlng the second loop descrlbed as being ad~acent the air lnlet opening, wire 22 extends to a thlrd loop ad~acent grill 34a Since heater coll 32 carries and operates on current ln the "hot" or pha~e llne, and wlth the provlslon of conductor or wire 24 wired a~ part of the neutral side of the llne, the presence of a conductive medlum such as, but not llmlted to, moisture or water between them will create a conductlve path ,contemplated by the lnvention as enabllng lnterruptlon of current to the load 12O This embodiment ls disttnguishable from another embodiment of the present lnventlon wherein a pair of conductors, as opposed to a single guard or sensing conductor 24, are located at or near moisture/water housing penetratlon polnts.
Configurations of one or more senslng or guard conductors other than those illustrated hereln are contemplated as comlng withln the scope of this invention.
Re~erring to Flg. 2, a block diagram of a shock hazard protector according to the present invention is illustrated. As shown therein, it comprises a source operatively connected to a load by first and second conductors 110 and 120, respectively, a detector 200 associated with the load, a control circuit 300 connected to the detector by a sensing or third conductor 130, and an interruptor clrcuit 400 assoclated with the source and connected to the control circuit 300. In the ca~e of an electrical A-C source, conductors 110 and 120 are tied to a phase and the neutral termlnal, respectively, of the A-C source.
~2~84~1S
.
In the normal mode of operation, thfit ls, ln the absence of a hazard cond~tlon wlthln the load, the control clrcult 300, which changes from a flrst state to a second ~tate ln response to the detection of a hazard condltion wlthln the load, remains in the first ~tate. Upon the detection by detector 200 of a predefined fault or hazard condition withln the load, the control circuit 300 change~ from the first to the second state, whlch cause3 the interruptor circuit 400 to operatively di~connect the source from the load.
It ls noted that the present invention contemplstes certain applications where the system sensitivity need not be ~ccurately controlled, and the control clrcuit 300 can be eliminated. In this situat~on the interruptor clrcuit 400 is connected to the detector 200 by the third conductor 130, and responds directly to the detection by detector 200 of a hazard condition within the load.
In either situation, the sensing or third conductor 130 communicates the presen~e of the hazard condition wlthin the load to the control circuit 300 or the interruptor clrcuit 400.
Referring now to Fig. 3, a 3chematic diagram of one embodiment of the invention particularly suited for use in con~unction with water-related shock hazard condltions wlthln an electrical appliance operatively connected to an A-C source (not shown) by electrical conductor~ 110, 120, respectively, 19 lllu~trated. As shown therein, detector 200 comprlse~ a pair of ~Z~8k~5 hazard or ~mmer~ion detectlon conductor~ 210 and 220, which are positioned in a non-contacting relatlonship and contalned wlthln the electrical load. A pair of immersion detectlon cond~ctors 210 and 220 are preferably located in proximity to each port of the appliance to be protected where water can enter.
For ease of description, it will be assumed that the appliance o be protected only contalns one port or opening through which water may enter. For this sltuation, one end of ,one of the pair of immersion detection conductors 210 is operatively connected to the phase terminal of an A-C source (not shown) via electrical conductor 110, and one end of the second of the pair of immersion detection conductors 220 ls connected ~o the load end of the third electrical conductor 130. The other ends of lmmersion detection conductor~ 210, 220 are unconnected and are maintained in a spaced-apart relationship, typically for example, not more than one inch.
Shock hazard or lmmersion detection conductor3 210, 220 may comprise, for example, a pair of bare electrlcal conductors or a pair of conducting plated lines on a printed circuit board or other physical configurations that will enable a conductive path between the unconnected ends thereof.
Control circuit 300 comprises a solid state switching control circult and includes a first resistor Rl connected in-line between the gate of a silicon controlled rectifler SCR
and the source end of the third electrical conductor 130.
~Z184~S
Res~stor Rl llmlt~ the current applled to the gate of the SCR.
In addltlon, control clrcuit 300 includes a parallel network comprlsing resistor R2, capacltor C and diode D connected between the gate and cathode of the SCR. These component~ provide a measure of noise immunity and protection agalnst damage acros~
the gate to cathode ~unction of the SCR.
Interruptor circuit 400 comprise~ an electromechanical lnterrupting circuit and includes an energlzing coll L and a flrst and second contact or swltch Sl, S2 connected in-llne with the first and second electr~cal conductors 110, 120, respectively. Switches Sl and S2 are responsive to the flow of current through energlzing coil L and are closed when such current is not flowing. In response to the f low of such current they switch from the normally closed po~ition to the shock hazard condltion open position. One end of energizing coil L is connected to the fir3t electrical conductor llO and the other end thereof is connected to the anode of the SCR. The cathode of the SCR is operatively connected to the second electrical conductor 120.
12~ 5 The existence of a water-related shock hazard condition within the electrical appliance is detected when both unconnected ends of the pair of immerslon detection conductors 210, 220 are immersed in the w~ter. More specifically, the lmmerslon of both unconnected ends of the palr of immersion detectlon conductors 210, 220 causes the electrical A-~ source to be operatiYely connected to the gate of the SCR v~a the path provlded by the first electrical conductor 110, the first immersion detection conductor 210, the electrically conducting path provided by the water in which the unconnected ends of the first and second lmmersion detection conductors 210, 220 are immersed, the second lmmersion detection conductor 220, the third electrical conductor 130, and resistor Rl. In response thereto, the SCR switches from the normally non-conducting state to the shock hazard condition conducting state, thereby providing a path for current to flow through the energizing coil L causing switches Sl and S2 to switch from the normally closed position to the shock hazard condition open position and thus operatively disconnecting the A-C source from the electrical appliance.
To insure that the shock hazard protector is operable prior to utllization of the appliance it protects, a test circuit (not shown) comprising, for example, a resistor in series with a normally open switch connected between the pair of immersion detection conductors 210, 220 may be utilized. Closing the normally open switch causes the resistor to be connected across ~Z~8445 the immersion detectlon conductors and, if the shoc~ hazard protector is operatlng, as described above, causes the A-C source to be operatlvely dlsconnected from the appliance. Preferably, the test clrcuit i~ contained within the electrical appllance.
In con~unction with sald test circuit, diode D could be replaced with a light-emitting-diode (LED~. If the LED is illuminated with the test swltch in the closed position lt indicate~ that the shock hazard protector is not operating properly.
Preferably, electrical conductors 110, 120 and 130 comprise a three wire conductor having an A-C source compatible plug at the source end, the control circuit 300 and interruptor circuit 400 are contained in the plug, and the detector 200 is contained wlthin the appliance.
Thus in the case where the electrical appliance 15, is, for example, a hair dryer, the detector 200 would be located internally within the dryer and, as noted above, in proximity to each port thereof where water can enter the dryer. It should be emphasized here that while water is given as the electrically conductive medium, thi~ invention contemplates a response to any electricaliy conducting medium, such that the appliance i~
electrically disconnected from the A-C source ln response to the presence of such a conductive medium.
Exemplary values for the circuit lllustrated in Figure
which grill 34 iq positioned. After leavlng the second loop descrlbed as being ad~acent the air lnlet opening, wire 22 extends to a thlrd loop ad~acent grill 34a Since heater coll 32 carries and operates on current ln the "hot" or pha~e llne, and wlth the provlslon of conductor or wire 24 wired a~ part of the neutral side of the llne, the presence of a conductive medlum such as, but not llmlted to, moisture or water between them will create a conductlve path ,contemplated by the lnvention as enabllng lnterruptlon of current to the load 12O This embodiment ls disttnguishable from another embodiment of the present lnventlon wherein a pair of conductors, as opposed to a single guard or sensing conductor 24, are located at or near moisture/water housing penetratlon polnts.
Configurations of one or more senslng or guard conductors other than those illustrated hereln are contemplated as comlng withln the scope of this invention.
Re~erring to Flg. 2, a block diagram of a shock hazard protector according to the present invention is illustrated. As shown therein, it comprises a source operatively connected to a load by first and second conductors 110 and 120, respectively, a detector 200 associated with the load, a control circuit 300 connected to the detector by a sensing or third conductor 130, and an interruptor clrcuit 400 assoclated with the source and connected to the control circuit 300. In the ca~e of an electrical A-C source, conductors 110 and 120 are tied to a phase and the neutral termlnal, respectively, of the A-C source.
~2~84~1S
.
In the normal mode of operation, thfit ls, ln the absence of a hazard cond~tlon wlthln the load, the control clrcult 300, which changes from a flrst state to a second ~tate ln response to the detection of a hazard condltion wlthln the load, remains in the first ~tate. Upon the detection by detector 200 of a predefined fault or hazard condition withln the load, the control circuit 300 change~ from the first to the second state, whlch cause3 the interruptor circuit 400 to operatively di~connect the source from the load.
It ls noted that the present invention contemplstes certain applications where the system sensitivity need not be ~ccurately controlled, and the control clrcuit 300 can be eliminated. In this situat~on the interruptor clrcuit 400 is connected to the detector 200 by the third conductor 130, and responds directly to the detection by detector 200 of a hazard condition within the load.
In either situation, the sensing or third conductor 130 communicates the presen~e of the hazard condition wlthin the load to the control circuit 300 or the interruptor clrcuit 400.
Referring now to Fig. 3, a 3chematic diagram of one embodiment of the invention particularly suited for use in con~unction with water-related shock hazard condltions wlthln an electrical appliance operatively connected to an A-C source (not shown) by electrical conductor~ 110, 120, respectively, 19 lllu~trated. As shown therein, detector 200 comprlse~ a pair of ~Z~8k~5 hazard or ~mmer~ion detectlon conductor~ 210 and 220, which are positioned in a non-contacting relatlonship and contalned wlthln the electrical load. A pair of immersion detectlon cond~ctors 210 and 220 are preferably located in proximity to each port of the appliance to be protected where water can enter.
For ease of description, it will be assumed that the appliance o be protected only contalns one port or opening through which water may enter. For this sltuation, one end of ,one of the pair of immersion detection conductors 210 is operatively connected to the phase terminal of an A-C source (not shown) via electrical conductor 110, and one end of the second of the pair of immersion detection conductors 220 ls connected ~o the load end of the third electrical conductor 130. The other ends of lmmersion detection conductor~ 210, 220 are unconnected and are maintained in a spaced-apart relationship, typically for example, not more than one inch.
Shock hazard or lmmersion detection conductor3 210, 220 may comprise, for example, a pair of bare electrlcal conductors or a pair of conducting plated lines on a printed circuit board or other physical configurations that will enable a conductive path between the unconnected ends thereof.
Control circuit 300 comprises a solid state switching control circult and includes a first resistor Rl connected in-line between the gate of a silicon controlled rectifler SCR
and the source end of the third electrical conductor 130.
~Z184~S
Res~stor Rl llmlt~ the current applled to the gate of the SCR.
In addltlon, control clrcuit 300 includes a parallel network comprlsing resistor R2, capacltor C and diode D connected between the gate and cathode of the SCR. These component~ provide a measure of noise immunity and protection agalnst damage acros~
the gate to cathode ~unction of the SCR.
Interruptor circuit 400 comprise~ an electromechanical lnterrupting circuit and includes an energlzing coll L and a flrst and second contact or swltch Sl, S2 connected in-llne with the first and second electr~cal conductors 110, 120, respectively. Switches Sl and S2 are responsive to the flow of current through energlzing coil L and are closed when such current is not flowing. In response to the f low of such current they switch from the normally closed po~ition to the shock hazard condltion open position. One end of energizing coil L is connected to the fir3t electrical conductor llO and the other end thereof is connected to the anode of the SCR. The cathode of the SCR is operatively connected to the second electrical conductor 120.
12~ 5 The existence of a water-related shock hazard condition within the electrical appliance is detected when both unconnected ends of the pair of immerslon detection conductors 210, 220 are immersed in the w~ter. More specifically, the lmmerslon of both unconnected ends of the palr of immersion detectlon conductors 210, 220 causes the electrical A-~ source to be operatiYely connected to the gate of the SCR v~a the path provlded by the first electrical conductor 110, the first immersion detection conductor 210, the electrically conducting path provided by the water in which the unconnected ends of the first and second lmmersion detection conductors 210, 220 are immersed, the second lmmersion detection conductor 220, the third electrical conductor 130, and resistor Rl. In response thereto, the SCR switches from the normally non-conducting state to the shock hazard condition conducting state, thereby providing a path for current to flow through the energizing coil L causing switches Sl and S2 to switch from the normally closed position to the shock hazard condition open position and thus operatively disconnecting the A-C source from the electrical appliance.
To insure that the shock hazard protector is operable prior to utllization of the appliance it protects, a test circuit (not shown) comprising, for example, a resistor in series with a normally open switch connected between the pair of immersion detection conductors 210, 220 may be utilized. Closing the normally open switch causes the resistor to be connected across ~Z~8445 the immersion detectlon conductors and, if the shoc~ hazard protector is operatlng, as described above, causes the A-C source to be operatlvely dlsconnected from the appliance. Preferably, the test clrcuit i~ contained within the electrical appllance.
In con~unction with sald test circuit, diode D could be replaced with a light-emitting-diode (LED~. If the LED is illuminated with the test swltch in the closed position lt indicate~ that the shock hazard protector is not operating properly.
Preferably, electrical conductors 110, 120 and 130 comprise a three wire conductor having an A-C source compatible plug at the source end, the control circuit 300 and interruptor circuit 400 are contained in the plug, and the detector 200 is contained wlthin the appliance.
Thus in the case where the electrical appliance 15, is, for example, a hair dryer, the detector 200 would be located internally within the dryer and, as noted above, in proximity to each port thereof where water can enter the dryer. It should be emphasized here that while water is given as the electrically conductive medium, thi~ invention contemplates a response to any electricaliy conducting medium, such that the appliance i~
electrically disconnected from the A-C source ln response to the presence of such a conductive medium.
Exemplary values for the circuit lllustrated in Figure
3 are as follows: Rl-2000 ohms, R2-1000 ohms, C-0.1 mlcrofarads, D-lN4004, SCR-2N5064.
Referring now to Figure 4, a schematic diagram of a second embodlment of the present lnvention particularly suited lZ18~5 for use in conjunctlon with water-related shock haz~rd condltion~
withln an electrlcal appl~ance is lllustrated. Thls embodlment provldes an addltlonal feature not present in the first embodiment illustrated in Flgure 3. In partlcular, the embodiment lllustrated ln Figure 3, provides ~hock hazard protection if any of electrical conductors 110, 120, ~ndivldually or in combination, are ~roken, but does not provide shock hazard protection if electrical conductor 130 ls broken. The embodlment lllustrated in Flgure 4 provides an additional measure of shock hazard protectlon by rendering the electrlcal appllance lnoperative if any of electrlcal conductors 110, i20 and 130, individually or ln combination, are broken.
This additlonal measure of protectlon is provided by the addition of a flrst diode Dl connected in serle~ between the second immersion detectlon conductor 220 and the thlrd electrical conductor 130, the replacement of the capacitor conn~cted between the gate and cathode of the SCR wlth an appropriate charglng capacitor, the addltion of a flrst charging clrcult comprlslng reslstor RN and diode DN connected between the flrst and third electrical conductors 110, 130, the addition of a zener diode in series w~th the dlode connected between the gate and cathode of the SCR, the addltion of a second charglng cir~ult comprlslng resistor Rp and dlode Dp connected between the flrst electrlcal conductor 110 and the gate of the ScR, and the ellmlnatlon of resistor R2 connected between the gate and cathode of the SCR.
~Z~ 5 The operation of the clrcult illustrated ln Flgure 4 is as follows. Assumlng that the sensing or third conductor 1~0, is in tact, the appliance ls not lmmersed in water and that lt ls energized, durlng the negative half cycle of the A-C signal on electrlcal conductor llD a negative charging path vla diode DN, resistor RN, third conductor 130, resistor Rl provides charge to-capacitor C, thereby charging it negatively. During the positive half cycle diode DN blocks, however a positive charglng path via resistor Rp and diode Dp provides charge to capacltor C, thereby charging it positively. Since the time constant of resistor RN
and capacitor C, ls roughly 33 times greater than the time constant of resistor Rp and capacitor C, the capacitor C charges much faster ln the negative sense, so that under steady state conditions a negative voltage exists on the gate of the SCR
thereby keeping it in a non-conducting state. In order to limit that negative voltage to a value that would not damage the gate to cathode ~unction of the SCR a three volt zener diode is added in series with diode D2, also in parallel with capac~tor c.
The next condition to look at is a broken third conductor 130. Under thls condition a negative charging path no longer exists for the negative voltage to be lmpressed on capac~tor C, and, therefore during positive half cycles capictor C wlll discharge positlvely and eventually the voltage on the gate of the SCR will get high enough to trip the SCR, causing it to switch to the conducting state thereby operatlvely dis-~218~9~5 connectlng the A-C ~ource from the appliance, puttlng you in a safe conditon. Exemplary value~ for the circuit lllustrated ln Figure 4 are a~ follows: Dl, D2, DN, Dp-lN 4004, RN-30,000 ohms, Rp-l,000,000 ohms, Rl-2000 ohms, C-l microfarad,SCR-2N5064, Z-3 volt zener dlode.
Preferably, the components comprlsing the first charging circuit RN, DN and diode Dl are contained within the electrlcal appllance and are water proof, the components comprising the second charging circult Rp, Dp and the zener diode D are contalned in the plug.
It is noted that with minor modifications the above de~cribed invention has many other applications. For example, in the situation where the electrical appliance comprises a power tool, such as, a drill, having an electrically conducting hou~ing the teachings of the present invention may be utilized by eliminating immer~ion detection conductor 220 and connecting the third electrical conductor 130 to the electrically conducting housing. The immersion ln water of the unconnected end of shock hazard detection conductor 210 provides an electrically conductive path between the shock hazard detection conductor and the electr~cally conducting housing of the drill causing, as described above, the drill to be operatively dlsconnected from the A-C source.
12~8~5 Referrlng now to an embodiment of the pre~ent invention which utllizes the approach of a relay mechanlsm to accompllsh the circuit interrupting goal of the invention, Fig. 5 lllustrates a shock hazard protector embodiment of a plug assembly 510 formed wlth a housing wlth a ba~e and cover body halves 512 and 514, respectively, ~oined at a housing reference -line 516. A strain relief 518 comprlses par~ of cord 520 and, in cooperative combination with the shape and contour of annular surfaces 522, 524, 526 and 528, serve~ as a means for protectiny the integrlty of electrical connections durlng use.
Blades 530 extend outwardly from surface 532 of hou~ing half 512 and serve the function of matingly and electrically engaging electrical contacts wlthln a receptacle (not shown) or electrical outlet in the home, for example. h fixed contact 534 ls associated and integral wlth each of the blades 53D, contacts 534 being fixed or stationary as opposed to movable when assembled.
A pair of movable contacts 536 are provided and are integral with leaf springs 538 which, in turn, are anchored by means of eyelets 540 extending through openings in an end portion of the leaf sprlngs 538 spaced from the movable contacts 536.
These eyelets further extend through openings through a printed clrcuit board 542 supported by ledges 544 and 546 ad~acent upstanding walls 548 and 550, as shown in Fig. 5.
12~8g~S
A tab 552 assoclated with each leaf sprlng 538 further anchors the leaf spring~ to the prlnted circult board ln sFaced relationship with respect to the aforesaid eyelets, thereby serving an additional function of preventing undesirable rotatlon of the leaf springs 538, assuring alignment and reliably repeated engagement between the fixed and movable contacts 534 and 536, respectlvely. Leaf springs 538 are configured to normally bias the movable contacts 536 away ~rom the flxed contacts 534 when ln an unstressed condition, thereby normally interrupting an electrical path between these contacts. The ends of leaf springs 538 are formed with upstanding flanges 554 to which conductors 556 are connected.
A plunger or core 558 is disposed vertically within a bobbin coil 560, as illustrated in Fig. 5. A reset button 564 contacts the uppermost portions of plunger 558, while a butterfly cross bar 562 extends laterally across the plug housing and in contact with upper surfaces of leaf springs 538. The upward biasing forces of leaf springs 538 maintain the cross bar 562, plunger_558 and reset button 564 in the positions shown in Flg.
20 S, while a metal strap 566 extends about portlons of coll 560 as shown. The cross sectional shape of reset button 564 is polygonal, such as square, to prevent rotation thereof, while the cross sectional shape of core or plunger 558 is round to provide maximum electromagnetic efficiency in its interaction with bobbin coil 560. Fig. 6 lllustrates in a cross sectional view what appllcants refer to as the "butterfly" with arms 568 belng 3played outwardly from a center rivet member 570 allgned wlth plunger 558.
In operation, power for the printed clrcult board electronic components is supplied by a copper path on the board via pins 572 extending downwardly from t~e bobbin coii 560.
Prior to a shock hazard predetermined condition, the ~ystem of Flg. 5 ls "set" by means of depressing set or reset button 564 lnwardly, which results in movement of the plunger and the cro~s bar against the opposing biasing forces of leaf sprlngs 538.
Thls depression of the set or reset button will re~ult ln movement of the leaf springs untll the movable contacts engage the fixed contacts, thereby completing an electrical circuit.
The completion of the electrical circuit ~ust described re~ults in current flow to the bobbin coil which, ln turn, electromagnetically "keeps" and holds the plunger in lts depressed position unt~l an interruption of such current flow.
The interengagement of the movable and fixed contacts further serves to enable the supply of power to the load or appliance with which the inventive assembly of Fig. 5 is associated, again, until an interruptlon in current flow to the bobbin coll.
In the event of the presence of a shock hazard condition, as a result of the operation of circuitry of Fig. 7 described in detail below, current to the bobbin coll is interrupted, with the result that the upward biaslng forces of 12184~S
leaf springs 538 rapldly cau~e a separation of th2 movable contacts away from the fixed contacts, thereby in turn causing an interruption o~ power from the source through the blade~ to the load or applianc~.
Referring now to Fig. 7 of the drawings, the aforesaid circuitry associated with the devlce of Fig. 5 is lllustrated with like components ln Figs. S and 7 carrying llke reference characters. With the relay of Fig. 5 being fed with half wave rectifled alternatlng current, or pulsating direct current, there is some current flow during the negative half cycle or the half cycle other than that when line current is flowing. A free wheellng dlode FWD continues current flow.
The main contacts Mc are normally open. When lt 1B
des~red to turn ~n the appliance after plugging it lnto a receptacle power source, pushing a momentary double pul~ Dp with respect to the normally open switch (set or reset button 564).
This applies half wave rectifled direct current to the bobbln coil. This results in applying a voltage from the phase line through the double pole slngle throw switch DPST, through a diode Dl, thence through the bobbin coll, with the other end of the coil going through anoth~r contact of the double pole swltch to neutral. Thus, by pushing the swltch or reset button, the coil is energi~ed, and the main contact Mc is closed.
12184~C;
Once the maln contact Mc is closed, a parallel path for the current ls provided through another dlode D2,~such that there is current flow from phase through diode D2 through the coll wlth lts free wheeling dlode ln parallel wlth lt, thence through the collector of a transistor Ql~ the emitter of the transistor Ql belng connected to neutral. The transistor is kept on by a reslstor going from phase to the base. Rl ls the resistor between phase and the base.
Once the coil energlzes itself as descrlbed, the tran3istor is turned on and then the momencary contact in the DPST is released and the coil is self-holdlng. Snould the load or appllance be dropped into water, creatlng a shock hazard conditlon, the current in a sense line ls rectlfled by diode D3 and a re~istor R2 puts a negative voltage onto the base of the transistor. A capacitor Cl is provided between the transi~tor base and the emitter which will essentially store whatever voltage was present to smooth it out. By setting the value of R2 relatively small wlth respect to the value of Rl, the time constant of the negatlve current is shorter than that of the po~itive current and in this way there is a negative charge turning off the transistor with the result that the movable contacts separate from the fixed contacts (Fig. 5).
~2~
The reader i~ cautioned no~ to con~true the examples presented in thls specificatlon, ~uch as ln de~crlbing halr dryers or other appliances, a~ limlting the inventlon to these examples. Any electrical appllance or apparatus wlth which a shock hazard may be as~ociated is contemplated a~ being favorably affected by the advantages and features of the present lnvention.-Referrlng now to another embodiment of the pre3entinvention lllustrated in Figs. 8-12, whereln a novel electro-mechanlcal and electromagnetic combination serv~es a circuit interrupting or breaklng function, as well as other functions. In Fig. 8 a plug assembly 600 of the type designated reference character 16 in Fig. 1 is shown with cover housing half 602 removed to illustrate base housing half 604 with its assembled ~ubassemblles in place. A pair of movable contact arms 606 and 608 are each anchored at their respe_tive angled depending legs 610 and 612 within slots or recesses 614 and 616 of base housing half 604. Near end~ 618 and 620 of movable arms 606 and 608, re~pectively, remote from their ends 610 and 612, silver contacts 622 snd 624 are rivoted to it~ arm.
Flexible conductors 626 are welded at 628 to depending legs 610 and 612 at one of thelr ends, and at their other ends 630 the flexible conductors are welded to plug insertion blades 632. Blades 632 are configured with mounting shoulders 634 so as to be held relatively integral with base 604 when a~sembled.
~Z11~ 5 Movable contact arm~ 606 and 608 ~re normally biased ln the dlrection shown ln phanto~, lines wlthin Flg. 11 such that they blas the silver contacts 622 and 624 away from flxed sllver contact~ 636 and 638 which are riveted to fixed contact terminal~
5 640 and 642, respectively. The flxed contact terminals 640 and 642 themselves are phys~cally and electrically connected to a printed circuit board 644 which carrles one of the electrlcal circuit embodiments described above and contemplated by the ,lnvention.
A latch member 646 formed with a tang 648 is assoclated with each movable contact arm and each is mounted and pivoted at its upper end on pivot points 650 formed on legs 652 of a set/reset button 654. At their lower end~ 656, latche~ 646 are formed with downward bend or leg, as viewed in Fig. 11, these latter legs glving the latches structural stablllty f~r added reliability. The full lines of Fig. 11 illustrate latches 646 in -their latched or set position, wlth tangs 648 holding the ends of movable contact arms 606 and 608 such that movable sllver contacts 622 and 624 are in physical and electrical engagement with fixed silver contacts 636 and 638, thereby enabling current flow through blades 632 from a source such as an electrical receptacle to a load, such as hair dryer 12.
- ~Z~84~5 Reset button 654 is normally biased ln a direction away from blades 632 by mesns of hellcal compression 3prings 658 ~hown in Figs. 9 and 12, for example. Springs 658 are held captive between and exert forces agalnst opposing ~urfaces 660 and 662 of the underside of the reset button 654 and a metalllc frame 664 (see Fig. 9). Set/reset button 654 is vislble to the user through a window 668 formed within cover housing half 602 and preferably carries indicia of the type illu~trated in Flg. B to draw attention to its functlon.
When the movable contact arms 606 and 608 are ln the positions shown ln Fig. 11 in phantom outllne, resting against a wall 666 formed in base housing half 604, ~uch that the electrlcal circult is in an interrupted state with the movable and fixed contacts spaced in opposition with respect to one another, the user of the present invention is able to close the circuit, assuming no hazard condition is present, by depressing with his or her finger the set/reset button 654. This depression of the button 654 cause~ latches 646 to move ln the same direction as the movable button 654 and in sliding engagement wlth the ends of ~he movable contact arms 606 and 608 until and such that tangs 648 ride over these arm ends. Release of the formerly depressed button 654 result~ in its only partlally returning under the influence of springs 658 towards lts original position, with a resulting pulllng of the movable contacts 622 ~Z~8~5 and 624 lnto engagement wlth their respective opposing contacts 636 and 638 by latch tangs 64B agalnst the undersldes of the movable arm ends, thereby settlng the system and closlng the clrcuit. Latches 646 and thelr tang~ 648 hold the movable contacts ln the last posltlon ~ust descrlbed until a hazard condition is sensed or detected. In such an event, a plunger 67 shown in Figs. 8 and 9 as being normally biased away from lt~
assoclated winding or coil 672 by means of a helical compresslon spring 674 is caused to rapldly approach the core of coll 672 as a result of lts belng energized. Plunger 670 i9 formed wlth a neck 676 adjacent its end remote from coil 672, with whlch a clevis 678 of what wlll here by referred to as a banger 680 matlngly engages. Banger 680 ig further formed with pairs of trip and reset dogs 682 and 684 movable paths that coinclde with latch 6~6. Upon energization of coil 672, trip dogs 682 rapldly come into contact with and "bang" against the surfaces of latches 646 facing wall 666, forclbly disengaging the latches 646 and thelr tangs 648 from the movable contact arms, with the result that these arms return to their rest positions against wall 666 and interrupt current flow through the movable and fixed contacts. Once the current is interrupted, the compression forces within spring 674 cause the plunger 670 and ~ts lnterconnected banger 680 to return to the position illu~trated in Fig. 9, with the reset dogs 684 coming into contact wlth and b1asing the latches 646 against the ends of the movable contact arms 606 and 608.
~2~ 5 Frame 664 compri3es part of the magnetic circult associated with an operatlng winding or coll 672, and for that purpose encloses ~ portion of the coil. A ~traln relief 686 formed ln the insulation of a cord set 688 18 ~hown in Flgs. 8 and 9 held between opposing annular walls 690 and 692, respectively, of housing halves 602 and 604 which, in turn, are .
releasably secured together by means of fasteners 694. Cord set 688 corresponds to the cord set 14 illustrated ln Flg. 1.
Fig. 8 illustrates the printed circult ~oard 644 ln broken-line outline in the position it occupies atop the banger assembly and the fixed contacts. Fig. 8 further illustrates the three wires, phase/neutral 6g6 and the guard or ~enslng wire 698 whlch extend through and as part of cord set 688, through the strain relief 686, and into the confines of plug assembly 600.
Sensing wire 698 corresponds to the third wlre 22 of Flg. 1 which electrically communicates with a sensing wire in the load, such as senslng wlre 24 of Fig. 1, ~nd wire 698 is coupled to the PC
board 644 whlle the phase and neutral lines are electrlcally secured to the fixed contact termlnals 640 and 642. Termlnals 640 and 642 are ~oft soldered to the PC board 644 by means of mountlng tabs 700.
The present invention thus provides the user with a shock hazard protection system which: has a reponse time that conforms ~o Underwriters Labor~tories requlrements; is trlp free;
possesses a double pole interruptlng mechanism wlth an air gap switch; operates wlth reverse polarity; requires only ~ 2 pole receptacle; operates in an ungrounded environment, such as a plastic tub; ls of a reasonable size and cost; provldes the user with a visible trip indication; meets Underwriters Laboratories ,overload, short circuit, and endurance requirements; possesses electrical noise immunity so a~ to minlmize false tripplng;
provides protection in the event the cord is broken, with proper polarity assumed; provides adequate strain relief; is usable with a combination switch/receptacle; and provides protection whether the load or appliance switches are on or off, or are at medium or high settings~
The em~odiments of the present invention herein descrlbed and disclosed are presented merely as examples of the invention. Other embodiments, forms and structures coming within the scope of this invention will readily suggest themselves to those skilled in the art, and shall be deemed to come within the ~cope of the appended claims.
Referring now to Figure 4, a schematic diagram of a second embodlment of the present lnvention particularly suited lZ18~5 for use in conjunctlon with water-related shock haz~rd condltion~
withln an electrlcal appl~ance is lllustrated. Thls embodlment provldes an addltlonal feature not present in the first embodiment illustrated in Flgure 3. In partlcular, the embodiment lllustrated ln Figure 3, provides ~hock hazard protection if any of electrical conductors 110, 120, ~ndivldually or in combination, are ~roken, but does not provide shock hazard protection if electrical conductor 130 ls broken. The embodlment lllustrated in Flgure 4 provides an additional measure of shock hazard protectlon by rendering the electrlcal appllance lnoperative if any of electrlcal conductors 110, i20 and 130, individually or ln combination, are broken.
This additlonal measure of protectlon is provided by the addition of a flrst diode Dl connected in serle~ between the second immersion detectlon conductor 220 and the thlrd electrical conductor 130, the replacement of the capacitor conn~cted between the gate and cathode of the SCR wlth an appropriate charglng capacitor, the addltion of a flrst charging clrcult comprlslng reslstor RN and diode DN connected between the flrst and third electrical conductors 110, 130, the addition of a zener diode in series w~th the dlode connected between the gate and cathode of the SCR, the addltion of a second charglng cir~ult comprlslng resistor Rp and dlode Dp connected between the flrst electrlcal conductor 110 and the gate of the ScR, and the ellmlnatlon of resistor R2 connected between the gate and cathode of the SCR.
~Z~ 5 The operation of the clrcult illustrated ln Flgure 4 is as follows. Assumlng that the sensing or third conductor 1~0, is in tact, the appliance ls not lmmersed in water and that lt ls energized, durlng the negative half cycle of the A-C signal on electrlcal conductor llD a negative charging path vla diode DN, resistor RN, third conductor 130, resistor Rl provides charge to-capacitor C, thereby charging it negatively. During the positive half cycle diode DN blocks, however a positive charglng path via resistor Rp and diode Dp provides charge to capacltor C, thereby charging it positively. Since the time constant of resistor RN
and capacitor C, ls roughly 33 times greater than the time constant of resistor Rp and capacitor C, the capacitor C charges much faster ln the negative sense, so that under steady state conditions a negative voltage exists on the gate of the SCR
thereby keeping it in a non-conducting state. In order to limit that negative voltage to a value that would not damage the gate to cathode ~unction of the SCR a three volt zener diode is added in series with diode D2, also in parallel with capac~tor c.
The next condition to look at is a broken third conductor 130. Under thls condition a negative charging path no longer exists for the negative voltage to be lmpressed on capac~tor C, and, therefore during positive half cycles capictor C wlll discharge positlvely and eventually the voltage on the gate of the SCR will get high enough to trip the SCR, causing it to switch to the conducting state thereby operatlvely dis-~218~9~5 connectlng the A-C ~ource from the appliance, puttlng you in a safe conditon. Exemplary value~ for the circuit lllustrated ln Figure 4 are a~ follows: Dl, D2, DN, Dp-lN 4004, RN-30,000 ohms, Rp-l,000,000 ohms, Rl-2000 ohms, C-l microfarad,SCR-2N5064, Z-3 volt zener dlode.
Preferably, the components comprlsing the first charging circuit RN, DN and diode Dl are contained within the electrlcal appllance and are water proof, the components comprising the second charging circult Rp, Dp and the zener diode D are contalned in the plug.
It is noted that with minor modifications the above de~cribed invention has many other applications. For example, in the situation where the electrical appliance comprises a power tool, such as, a drill, having an electrically conducting hou~ing the teachings of the present invention may be utilized by eliminating immer~ion detection conductor 220 and connecting the third electrical conductor 130 to the electrically conducting housing. The immersion ln water of the unconnected end of shock hazard detection conductor 210 provides an electrically conductive path between the shock hazard detection conductor and the electr~cally conducting housing of the drill causing, as described above, the drill to be operatively dlsconnected from the A-C source.
12~8~5 Referrlng now to an embodiment of the pre~ent invention which utllizes the approach of a relay mechanlsm to accompllsh the circuit interrupting goal of the invention, Fig. 5 lllustrates a shock hazard protector embodiment of a plug assembly 510 formed wlth a housing wlth a ba~e and cover body halves 512 and 514, respectively, ~oined at a housing reference -line 516. A strain relief 518 comprlses par~ of cord 520 and, in cooperative combination with the shape and contour of annular surfaces 522, 524, 526 and 528, serve~ as a means for protectiny the integrlty of electrical connections durlng use.
Blades 530 extend outwardly from surface 532 of hou~ing half 512 and serve the function of matingly and electrically engaging electrical contacts wlthln a receptacle (not shown) or electrical outlet in the home, for example. h fixed contact 534 ls associated and integral wlth each of the blades 53D, contacts 534 being fixed or stationary as opposed to movable when assembled.
A pair of movable contacts 536 are provided and are integral with leaf springs 538 which, in turn, are anchored by means of eyelets 540 extending through openings in an end portion of the leaf sprlngs 538 spaced from the movable contacts 536.
These eyelets further extend through openings through a printed clrcuit board 542 supported by ledges 544 and 546 ad~acent upstanding walls 548 and 550, as shown in Fig. 5.
12~8g~S
A tab 552 assoclated with each leaf sprlng 538 further anchors the leaf spring~ to the prlnted circult board ln sFaced relationship with respect to the aforesaid eyelets, thereby serving an additional function of preventing undesirable rotatlon of the leaf springs 538, assuring alignment and reliably repeated engagement between the fixed and movable contacts 534 and 536, respectlvely. Leaf springs 538 are configured to normally bias the movable contacts 536 away ~rom the flxed contacts 534 when ln an unstressed condition, thereby normally interrupting an electrical path between these contacts. The ends of leaf springs 538 are formed with upstanding flanges 554 to which conductors 556 are connected.
A plunger or core 558 is disposed vertically within a bobbin coil 560, as illustrated in Fig. 5. A reset button 564 contacts the uppermost portions of plunger 558, while a butterfly cross bar 562 extends laterally across the plug housing and in contact with upper surfaces of leaf springs 538. The upward biasing forces of leaf springs 538 maintain the cross bar 562, plunger_558 and reset button 564 in the positions shown in Flg.
20 S, while a metal strap 566 extends about portlons of coll 560 as shown. The cross sectional shape of reset button 564 is polygonal, such as square, to prevent rotation thereof, while the cross sectional shape of core or plunger 558 is round to provide maximum electromagnetic efficiency in its interaction with bobbin coil 560. Fig. 6 lllustrates in a cross sectional view what appllcants refer to as the "butterfly" with arms 568 belng 3played outwardly from a center rivet member 570 allgned wlth plunger 558.
In operation, power for the printed clrcult board electronic components is supplied by a copper path on the board via pins 572 extending downwardly from t~e bobbin coii 560.
Prior to a shock hazard predetermined condition, the ~ystem of Flg. 5 ls "set" by means of depressing set or reset button 564 lnwardly, which results in movement of the plunger and the cro~s bar against the opposing biasing forces of leaf sprlngs 538.
Thls depression of the set or reset button will re~ult ln movement of the leaf springs untll the movable contacts engage the fixed contacts, thereby completing an electrical circuit.
The completion of the electrical circuit ~ust described re~ults in current flow to the bobbin coil which, ln turn, electromagnetically "keeps" and holds the plunger in lts depressed position unt~l an interruption of such current flow.
The interengagement of the movable and fixed contacts further serves to enable the supply of power to the load or appliance with which the inventive assembly of Fig. 5 is associated, again, until an interruptlon in current flow to the bobbin coll.
In the event of the presence of a shock hazard condition, as a result of the operation of circuitry of Fig. 7 described in detail below, current to the bobbin coll is interrupted, with the result that the upward biaslng forces of 12184~S
leaf springs 538 rapldly cau~e a separation of th2 movable contacts away from the fixed contacts, thereby in turn causing an interruption o~ power from the source through the blade~ to the load or applianc~.
Referring now to Fig. 7 of the drawings, the aforesaid circuitry associated with the devlce of Fig. 5 is lllustrated with like components ln Figs. S and 7 carrying llke reference characters. With the relay of Fig. 5 being fed with half wave rectifled alternatlng current, or pulsating direct current, there is some current flow during the negative half cycle or the half cycle other than that when line current is flowing. A free wheellng dlode FWD continues current flow.
The main contacts Mc are normally open. When lt 1B
des~red to turn ~n the appliance after plugging it lnto a receptacle power source, pushing a momentary double pul~ Dp with respect to the normally open switch (set or reset button 564).
This applies half wave rectifled direct current to the bobbln coil. This results in applying a voltage from the phase line through the double pole slngle throw switch DPST, through a diode Dl, thence through the bobbin coll, with the other end of the coil going through anoth~r contact of the double pole swltch to neutral. Thus, by pushing the swltch or reset button, the coil is energi~ed, and the main contact Mc is closed.
12184~C;
Once the maln contact Mc is closed, a parallel path for the current ls provided through another dlode D2,~such that there is current flow from phase through diode D2 through the coll wlth lts free wheeling dlode ln parallel wlth lt, thence through the collector of a transistor Ql~ the emitter of the transistor Ql belng connected to neutral. The transistor is kept on by a reslstor going from phase to the base. Rl ls the resistor between phase and the base.
Once the coil energlzes itself as descrlbed, the tran3istor is turned on and then the momencary contact in the DPST is released and the coil is self-holdlng. Snould the load or appllance be dropped into water, creatlng a shock hazard conditlon, the current in a sense line ls rectlfled by diode D3 and a re~istor R2 puts a negative voltage onto the base of the transistor. A capacitor Cl is provided between the transi~tor base and the emitter which will essentially store whatever voltage was present to smooth it out. By setting the value of R2 relatively small wlth respect to the value of Rl, the time constant of the negatlve current is shorter than that of the po~itive current and in this way there is a negative charge turning off the transistor with the result that the movable contacts separate from the fixed contacts (Fig. 5).
~2~
The reader i~ cautioned no~ to con~true the examples presented in thls specificatlon, ~uch as ln de~crlbing halr dryers or other appliances, a~ limlting the inventlon to these examples. Any electrical appllance or apparatus wlth which a shock hazard may be as~ociated is contemplated a~ being favorably affected by the advantages and features of the present lnvention.-Referrlng now to another embodiment of the pre3entinvention lllustrated in Figs. 8-12, whereln a novel electro-mechanlcal and electromagnetic combination serv~es a circuit interrupting or breaklng function, as well as other functions. In Fig. 8 a plug assembly 600 of the type designated reference character 16 in Fig. 1 is shown with cover housing half 602 removed to illustrate base housing half 604 with its assembled ~ubassemblles in place. A pair of movable contact arms 606 and 608 are each anchored at their respe_tive angled depending legs 610 and 612 within slots or recesses 614 and 616 of base housing half 604. Near end~ 618 and 620 of movable arms 606 and 608, re~pectively, remote from their ends 610 and 612, silver contacts 622 snd 624 are rivoted to it~ arm.
Flexible conductors 626 are welded at 628 to depending legs 610 and 612 at one of thelr ends, and at their other ends 630 the flexible conductors are welded to plug insertion blades 632. Blades 632 are configured with mounting shoulders 634 so as to be held relatively integral with base 604 when a~sembled.
~Z11~ 5 Movable contact arm~ 606 and 608 ~re normally biased ln the dlrection shown ln phanto~, lines wlthin Flg. 11 such that they blas the silver contacts 622 and 624 away from flxed sllver contact~ 636 and 638 which are riveted to fixed contact terminal~
5 640 and 642, respectively. The flxed contact terminals 640 and 642 themselves are phys~cally and electrically connected to a printed circuit board 644 which carrles one of the electrlcal circuit embodiments described above and contemplated by the ,lnvention.
A latch member 646 formed with a tang 648 is assoclated with each movable contact arm and each is mounted and pivoted at its upper end on pivot points 650 formed on legs 652 of a set/reset button 654. At their lower end~ 656, latche~ 646 are formed with downward bend or leg, as viewed in Fig. 11, these latter legs glving the latches structural stablllty f~r added reliability. The full lines of Fig. 11 illustrate latches 646 in -their latched or set position, wlth tangs 648 holding the ends of movable contact arms 606 and 608 such that movable sllver contacts 622 and 624 are in physical and electrical engagement with fixed silver contacts 636 and 638, thereby enabling current flow through blades 632 from a source such as an electrical receptacle to a load, such as hair dryer 12.
- ~Z~84~5 Reset button 654 is normally biased ln a direction away from blades 632 by mesns of hellcal compression 3prings 658 ~hown in Figs. 9 and 12, for example. Springs 658 are held captive between and exert forces agalnst opposing ~urfaces 660 and 662 of the underside of the reset button 654 and a metalllc frame 664 (see Fig. 9). Set/reset button 654 is vislble to the user through a window 668 formed within cover housing half 602 and preferably carries indicia of the type illu~trated in Flg. B to draw attention to its functlon.
When the movable contact arms 606 and 608 are ln the positions shown ln Fig. 11 in phantom outllne, resting against a wall 666 formed in base housing half 604, ~uch that the electrlcal circult is in an interrupted state with the movable and fixed contacts spaced in opposition with respect to one another, the user of the present invention is able to close the circuit, assuming no hazard condition is present, by depressing with his or her finger the set/reset button 654. This depression of the button 654 cause~ latches 646 to move ln the same direction as the movable button 654 and in sliding engagement wlth the ends of ~he movable contact arms 606 and 608 until and such that tangs 648 ride over these arm ends. Release of the formerly depressed button 654 result~ in its only partlally returning under the influence of springs 658 towards lts original position, with a resulting pulllng of the movable contacts 622 ~Z~8~5 and 624 lnto engagement wlth their respective opposing contacts 636 and 638 by latch tangs 64B agalnst the undersldes of the movable arm ends, thereby settlng the system and closlng the clrcuit. Latches 646 and thelr tang~ 648 hold the movable contacts ln the last posltlon ~ust descrlbed until a hazard condition is sensed or detected. In such an event, a plunger 67 shown in Figs. 8 and 9 as being normally biased away from lt~
assoclated winding or coil 672 by means of a helical compresslon spring 674 is caused to rapldly approach the core of coll 672 as a result of lts belng energized. Plunger 670 i9 formed wlth a neck 676 adjacent its end remote from coil 672, with whlch a clevis 678 of what wlll here by referred to as a banger 680 matlngly engages. Banger 680 ig further formed with pairs of trip and reset dogs 682 and 684 movable paths that coinclde with latch 6~6. Upon energization of coil 672, trip dogs 682 rapldly come into contact with and "bang" against the surfaces of latches 646 facing wall 666, forclbly disengaging the latches 646 and thelr tangs 648 from the movable contact arms, with the result that these arms return to their rest positions against wall 666 and interrupt current flow through the movable and fixed contacts. Once the current is interrupted, the compression forces within spring 674 cause the plunger 670 and ~ts lnterconnected banger 680 to return to the position illu~trated in Fig. 9, with the reset dogs 684 coming into contact wlth and b1asing the latches 646 against the ends of the movable contact arms 606 and 608.
~2~ 5 Frame 664 compri3es part of the magnetic circult associated with an operatlng winding or coll 672, and for that purpose encloses ~ portion of the coil. A ~traln relief 686 formed ln the insulation of a cord set 688 18 ~hown in Flgs. 8 and 9 held between opposing annular walls 690 and 692, respectively, of housing halves 602 and 604 which, in turn, are .
releasably secured together by means of fasteners 694. Cord set 688 corresponds to the cord set 14 illustrated ln Flg. 1.
Fig. 8 illustrates the printed circult ~oard 644 ln broken-line outline in the position it occupies atop the banger assembly and the fixed contacts. Fig. 8 further illustrates the three wires, phase/neutral 6g6 and the guard or ~enslng wire 698 whlch extend through and as part of cord set 688, through the strain relief 686, and into the confines of plug assembly 600.
Sensing wire 698 corresponds to the third wlre 22 of Flg. 1 which electrically communicates with a sensing wire in the load, such as senslng wlre 24 of Fig. 1, ~nd wire 698 is coupled to the PC
board 644 whlle the phase and neutral lines are electrlcally secured to the fixed contact termlnals 640 and 642. Termlnals 640 and 642 are ~oft soldered to the PC board 644 by means of mountlng tabs 700.
The present invention thus provides the user with a shock hazard protection system which: has a reponse time that conforms ~o Underwriters Labor~tories requlrements; is trlp free;
possesses a double pole interruptlng mechanism wlth an air gap switch; operates wlth reverse polarity; requires only ~ 2 pole receptacle; operates in an ungrounded environment, such as a plastic tub; ls of a reasonable size and cost; provldes the user with a visible trip indication; meets Underwriters Laboratories ,overload, short circuit, and endurance requirements; possesses electrical noise immunity so a~ to minlmize false tripplng;
provides protection in the event the cord is broken, with proper polarity assumed; provides adequate strain relief; is usable with a combination switch/receptacle; and provides protection whether the load or appliance switches are on or off, or are at medium or high settings~
The em~odiments of the present invention herein descrlbed and disclosed are presented merely as examples of the invention. Other embodiments, forms and structures coming within the scope of this invention will readily suggest themselves to those skilled in the art, and shall be deemed to come within the ~cope of the appended claims.
Claims
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In combination with a load operatively connected to a source, detecting means associated with said load for detecting a shock hazard condition associated with said load, and conducting means connected to said detecting means, circuit interrupting means comprising:
a pair of first and second contacts supported for engagement and disengagement with respect to one another, a coil electrically connected to said detecting means via said conducting means, a magnetizable plunger member having portions thereof disposed within said coil and movable in response to energization of said coil, frame means for defining a path of a magnetic field generated by said coil, and latch means with portions thereof in the path of said plunger member for influencing the disengagement of said first and second contacts.
a pair of first and second contacts supported for engagement and disengagement with respect to one another, a coil electrically connected to said detecting means via said conducting means, a magnetizable plunger member having portions thereof disposed within said coil and movable in response to energization of said coil, frame means for defining a path of a magnetic field generated by said coil, and latch means with portions thereof in the path of said plunger member for influencing the disengagement of said first and second contacts.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US55826283A | 1983-12-05 | 1983-12-05 | |
| US558,.262 | 1983-12-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1218445A true CA1218445A (en) | 1987-02-24 |
Family
ID=24228841
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000459274A Expired CA1218445A (en) | 1983-12-05 | 1984-07-19 | Shock hazard protection system |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US4595894A (en) |
| CA (1) | CA1218445A (en) |
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| US11610751B2 (en) | 2019-12-09 | 2023-03-21 | Leviton Manufacturing Co., Inc. | Circuit breakers incorporating reset lockout mechanisms |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4010432A (en) * | 1975-10-22 | 1977-03-01 | General Electric Company | Electrical receptacle equipped with ground fault protection |
| US4163882A (en) * | 1977-12-05 | 1979-08-07 | Baslow Floyd M | Adapter for standard electrical wall fixtures |
| US4518945A (en) * | 1980-11-17 | 1985-05-21 | Leviton Manufacturing Company, Inc. | Remote control system |
-
1984
- 1984-07-19 CA CA000459274A patent/CA1218445A/en not_active Expired
-
1985
- 1985-04-01 US US06/716,991 patent/US4595894A/en not_active Expired - Lifetime
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4823225A (en) * | 1987-08-18 | 1989-04-18 | Associated Mills Inc. | Bipolar immersion detection circuit interrupter |
Also Published As
| Publication number | Publication date |
|---|---|
| US4595894A (en) | 1986-06-17 |
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Legal Events
| Date | Code | Title | Description |
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| MKEX | Expiry |