CA1063220A - Switch for electrical wall receptacle with ground fault protection - Google Patents

Abstract

SWITCH FOR ELECTRICAL WALL RECEPTACLE
WITH GROUND FAULT PROTECTION

ABSTRACT OF THE DISCLOSURE
An electric receptacle with ground fault pro-tection characterized by an insulating rectangular housing adapted for mounting in a wall outlet box. The housing comprises opposite end and edge walls with front and rear sides open and with a transverse partition dividing a chamber formed by the ends and side walls into a pair of side-by-side compartments. Partition aperture means between the compartments and the first compartment communicating with the open front side and the second compartment communi-cating with the open rear side. Receptacle components are disposed in the first compartment and electronic components are disposed in the second compartment, and the components in each compartment are so disposed as to minimize the space requirements for the receptacle. The receptacle components include a contact arm which carries one contact for each of two pairs of contacts and the arm is movable between open and closed positions of the contacts and is operatively connected to a latch member releasably holding the arm in the contact closed position. Ground fault sensing means for monitoring the flow of current through the receptacle is provided for releasing the latch member, whereby the con-tacts on the arm are opened and closed sequentially.

Description

BACKGROUND OF THE INVENTION
Field of the Invention:
This invention relates to an electric receptacle for a wall outlet box.

Description of the Prior Art:
The prior art of ground ~ault lnterrupter recep-tacles is limited at present, because they are in the development stage. A dl~iculty with such receptacles heretofore has been that receptacles with ground fault protection have been too large to mount in a conventional wall outlet box without the use o~ a fixture or extension block. One reason ~or the large size 18 that the receptacle with ground fault monitors contains a great number of elec-tronlc componentsJ æuch as relays and solenoids. But a needexists for a receptacle with ground fault protection and having a compact size to enable insertion into a standard wall outlet box and which provides satls~actory electrlcal perrormance. One type of electric receptacle assembly with ground fault protection is that sho~n ln U.~. Patent No.
3, 81~J 579 issued May 28, 1974 to Doyle, et al.
Most receptacles with ground fault protection have involved various problems. First, the standard wall outlet box has been used ~ith receptacles without ground fault protection. Mani~estly, a receptacle havlng ground fault protectlon means involves additional parts that must be a~sembled in the same space as the original receptacle.
mere is also a problem of nuisance tripping incurred by the magnetic flux developed by the power source conductors which necessarily pass through the sensor coil of the ground fault detector. More particularly, the segments of the conductor are proximate to the coil due to the requirements of com-pactness of the assembly. As a result the magnetic flux in each conductor causes the coil to respond to current im-balances not incurred by real ground fault causes. In

- 2 -45,771 addition, other segments of the conductors on the opposite side of the sensor coil are connected to a contact carrier switch arm which must be free to move in response to ground fault causes and uninhibited by any mechanlcal force due to the wire.
Assoclated with the foregolng has been a need ~or a trip-free construction by which the receptacle cannot be reset so long as a ground fault continues to exist. It is desirable to provide the trip-free feature even though a reset button is held manually in place.
SUMMARY OF THE INVENTION
In accordance with this invention it has been found that the foregoing problems may be overcome by the provision of a compact electric receptacle adapted for mounting in a standard wall outlet box, comprising an insulating housing smaller than a standard wall outlet box and having opposite edge walls and opposite end walls forming open ~ront and rear sides, a partition within the housing and dividing the housing into side-by-side first and second compartments, the first compartment communicating with the open ~ront side and the second compartment com-municating with the open rear side, the partition having aperture means between the compartments, the partition having at least one portion nearer the open front side than the remaining portions thereof, receptacle components in the first compartment and electronic components in the second compartment; the receptacle components comprising socket means for receiving the plug of an electric appliance, contacts movable between open and closed positions ~or interruptably connecting the socket means to a power source, 45, 771 i a contact arm carrylng one of the contacts, a latch member releasably engaging the contact arm, operatlng means for moving the contacts to their open positlon ln response to a ground fault; the electronic components comprising ground fault responsive means for monitorlng the flow o~ current in the conductcrs and delivering a fault signal to the oper-ating means in response to a current imbalance ln the con-ductors, and said responsive means comprising a toroidal coil through which the conductors extend.
The electric receptacle also comprises a first pair of cooperable contacts operable between open and closed positions, a second pair of cooperable contacts operable between open and closed positions, an operating mechanism including a contact arm carrying one contact of each pair of contacts and movable between open and closed positions of the contacts, a latch member releasably holding the arm in the closed position, bias means engaging the arm for urging the arm to the open position when the latch member is re-leased, a pivot rib for the contact arm, the bias means urging the arm to pivot about the first pair of contacts during an initial movement of the arm when released to open the second pair of contacts and to then pivot about the pivot rib during a final movement of the arm to open the first pair of contacts, ground fault sensing means for monitoring the flow of current through the socket means, and release means responsive to the ground fault sensing means for releasing the latch member from the contact arm, whereby the first and second pairs of contacts are opened sequen-tially. In addition to the foregoing the electrlc recep-tacle includes third contact means located in the path of 45,771 \

movement of the arm at the open position thereof, the thirdcontact means being operatively connected to open a clrcult through the release means when the arm ls ln the open posi-tlon, the third contact means comprlslng a contact button in detachable engagement wlth one of the conductors of the power source when the arm ls in the closed position, and resillent means for urging the button in the closed position when the arm ls not ln the open posltlon.
BRIEF DESCRIPTION OF THE DRAWINGS
Flgure 1 ls an elevational vlew of the front side of an electric receptacle in accordance with this lnventlon.
Flg. 2 ls an elevatlonal view of the rear slde thereof.
Fig. 3 is a vertical sectional vlew taken on the llne III-III of Flg. 1 with some parts in exploded vlew and showlng ln additlon the wall plate and wall outlet box in whlch the electric receptacle ls dlsposed.
Flg. 4 ls a vertlcal sectlonal view taken on the llne IV-IV of Fig. 3.
Flg. 5 ls a vertlcal sectlonal vlew taken on the llne V-V of Flg. 3.
Flg. 6 ls a vertical sectional vlew taken on the llne VI-VI of Flg. 4 and showing the contact arm ln the closed posltion.
Fig. 7 is a fragmentary sectlonal view showlng the contact arm in an lntermedlate posltion.
Fig. 8 is a view slmllar to Fig. 6 and showing the contact arm ln the open posltion.
Fig. 9 is a fragmentary sectlonal view of another embodlment showing the manner in which the shunt wlres are 45,771 :1063220 disposed.
Flg. 10 is a wirlng dlagram of the receptacle assembly.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The electric receptacle with ground fault pro-tection of this lnvention is generally indicated at 11 ln Fig. 10. It is connected by a single phase, two-wire line to an AC power source 13, the two-wire line consisting of a line conductor 15 and a grounded neutral conductor 17.
Although a single phase, two-wire system is disclosed, it is understood that conventional single phase or polyphase circuits consistlng of three or four wires may be used.
The conductors 15, 17 extend through the recep-tacle 11 to socket means which include a line terminal 19, a neutral terminal 21, and a ground terminal 23, to which a load, such as an electrical appliance, is detachably con-nected in a conventional manner. The receptacle 11 com-prises ground fault detection means included within a broken line rectangle generally lndicated at 27 and comprising a differential transformer including a toroidal core 29 and a ground fault sensor for trip circuit 31. As disclosed in f~c o~,^c~"~,O"~:~
the prior art, such as~U.S. Patent No. 3,813,579, the line and neutral conductors 15, 17 pass through the toroidal core 29 thereby essentially comprising single turn primary wind-ings of the core. A secondary winding 33 consists of a plurallty of turns around the core and comprises a part of the trip circuit 31. The conductors 15, 17 also pass through a grounded neutral transformer 35 whlch is respon-sive to a fault on the load side of the differential trans-former or core 29. The purpose and construction of the 1063220transformer 35 is set ~orth more particularly in U,S.
Patent No. 3,930,187 issued December 30, 1975 to John J~ Mlsencik. Operating means 39 comprise a solenold by which the contact arm is actuated ~rom the closed to the open position thereby opening circuits between palræ of contacts 47, 49, contacts 51, 53, and contacts 55, 57. The elec~ronic portions o~ the receptacle 11 are contained within the broken line rectangle 27 as will be æet ~orth more particularly below.
The electromechanical components oi the receptacle 11 are contained wlthin the broken llne rectangle 37 and comprise an insulatlve contact arm 41, a reset mechanlsm 43, and a test button 45.
As shown in Fig. 3 the receptacle 11 is located within an outlet box 59 which is mounted within an opening 61 of a wall 63. The several components of the receptacle 11 are contained within an insulative housing 65 which iæ
contained within the box 59 on a mounting plate 67 which is secured in place at peripheral areas in contact with the wall 63 at 69 by mounting screws 71 extending between the plate and the outlet box 59. A cover plate 73 is mounted over the mounting plate 67 and is secured in place by screws 75.
The insulative housing 65 is a rectangular member having opposite edge walls 77, 79, oppoæite end walls 81, 83, and opposite front and rear side openings 85, 87. A
partition 89 extends across the interior of the housing 65 between opposite walls 77, 79, 81, 83, to divide the in-terior of the housing lnto separate compartment~ 91, 93 corresponding respectively to the broken line rectangles 37, 45,771 .

27 as shown in Fig. 10. Spaced aperture means, such as an opening 95, are provided between opposite sldes of the compartments 91, 93 to enable passage of wires such as the llne and neutral conductors 15, 17. As shown ln Fig. 3, the partltion 89 includes spaced longitudlnal portlons 89a, 89b, 89c, 89d, 89e which are disposed at varlous lateral posi-tlons between the front and rear side openings 85, 87. The partitlon 89 provldes varlous recesses such as recesses 97 and 99, on the slde of the compartment 91, and recesses 101, 103 on the slde of the compartment 93. By provldlng the partltion 89 wlth partltion segments 89a-e of dlfferent depths, the varous recesses, such as recesses 97-103 having different locations with respect to the front rear side openings 85, 87, enable the assembly of the several parts comprlsing the electronic and mechanical components into a more compact arrangement than would be possible if the partition 89 were a single planar member extending across the interior of the housing between the opposite end walls 81, 83.
Moreover, the several recesses 97-103 enable the locatlon of the several electronic and mechanical components in place with a minimum of mounting parts. The recesses hold several parts in place and prevent their shifting from position once they are seated in their predeslgned locationsO
Accordingly, the partition performs the two-fold purpose of separating the electronic and mechanical portions from each other to prevent debris from the mechanical side, such as fumes resulting from arcing during opening and closing of the contacts, from contaminating the electronic side; and of conserving space in order to minimize the overall size of the housing 65 while providing an outlet receptacle with ground ~ault protection. In addition the housing 65 in-cludes a back cover 105 which is secured ln place by spaced screws 107. me electronic or g~ und ~ault components 29, 31, 35 are contained within the second compartment between the partltlon 89 and the back cover 105. me so-called mechanical components 39, 41, 43, 45, 47-57, are contained within the compartment 91 between the partltion 89 and the mounting plate 67.
In Figures 1 and 2 the front and rear sides of the receptacle 11 are shown in the assembled condition. me receptacle 11 is of the duplex type with one terminal above and another terminal below the reset and test buttonæ 43, 45. me reset and test buttons 43, 45 as well as the upper and lower receptacles or sockets 19, 21, 23 are disposed generally in the planar sur~ace o~ the front side o~ the receptacle. As shown in Fig. 3, a ~ront cover insert 109, shown in exploded position with respect to the receptacle 11, is disposed within an opening 111 in the cover plate 73 and is provided with aligned openings each group for the terminal~ 19, 21, 23, as well as the reset and test buttons ~3, 45.
AB shown ln Fig. 5 the electronic components com-prising the ground ~ault protection portion of the recep-tacle 11 are contained within the compartment 93 between the partition 89 and the back cover 105. Generally those com-ponents comprise the toroidal core 29, the trip circuit 31, the operating means 39, and the grounded neutral transformer 35. Inasmuch as the detail description of these parts i8 set ~orth in the aforementioned U.S. Patent Nos. 3,813,579 and

3 ,930,1B7, the description o~ those portlons i8 l~mited to the parts that are essential to the operatlon o~ the in-vention disclosed herein.
me lead conductor 15 (Fig. 2) extends through the back cover 105 into the compartment 93 (Fig. 6) where lt is connected to a contact bracket 113 whlch carrles the current throu~h an aperture ln the partition 89 to contacts 47, 49 in the compartment 91. From there the current moves through a contact plate 115 which læ secured to the contact arm 41.
The circuit contlnues through a shunt which is a continu-ation of the conductor 15 that passes through an aperture 117 in the partitlon 89, and through the core 29. As shown in Flg. 5, the line conductor 15 extends from the core 29 to a splice 119 having a splice insulator 121 and then through the grounded neutral transformer 35 to a receptacle con-ductor 123 (Fig. 4) to which the conductor 15 i8 electrically secured such as by a spot weld (not shown). me receptacle conductor 123 extends between and is an integral part of the pair of line terminals 19 (upper and lower), whereby a circuit is maintained to both terminals.
In a simllar manner a circuit through the neutral conductor 17 extends through the back cover 105 tFig. 2) into the compartment 93 (Fig. 5) where the conductor is secured, such as by a weld, to a contact bracket 125 which extends through an aperture in the partition 89 to the com-partment 91 (Fig, 6) where the circuit paæses through the closed contacts 53, 51. The movable contact 51 is mounted on a contact plate 127 on the contact arm 41. From there the circuit passes through a shunt which is part of the 45,771 neutral conductor 17 which extends through the aperture 117 and then through the core 29 into the compartment 93. The conductor 17 includes a splice 129 (Fig. 4~ having a splice insulator and continues through the grounded neutral trans-former 35 to a receptacle conductor 133 to which lt is secured electrically, ~uch as by a spot weld (not shown).
Like the receptacle conductor 123, the conductor 133 is an lntegral part of both the upper and lower neutral terminals 21 between which it extends to provide a circuit through the lower terminal 21.
In the event that it is necessary to connect other receptacles having no ground fault protection units in the same circuit with the receptacle 11, a line conductor 135 (Fig. 5) and a neutral conductor 137 may be added by con-necting said conductors at the ~unction of the line and neutral conductors 15, 17 to the receptacle conductors 123, 133, respectively, whereby feed through to the other re-ceptacles is obtained.
In accordance with this invention as shown in Fig.
5 the line and neutral conductors 15, 17 are twisted around each other ~or at least one complete cycle coaxially of each other at the portion of the conductors ad~acent the toroidal core 29 in order to eliminate nuisance tripping caused by surge currents in the conductors. The twisted conductors having magnetic fluxes have a cancelling effect upon each other and therefore do not influence the coil of the core 29.
In the closed circuit position of the contact arm 41 (Fig. 6) a latch plate 139 retains the arm in said posi-tlon. For that purpose the latch plate 139 comprises a 45,771 shoulder 141 which engages an edge 143 of the contact plate 115, thereby holding the arm 41 in sald positlon against the pressure of a coll spring 145 so that clrcuit~ through the llne conductor contacts 47, 49 as well as through the neutral conductor contacts 51, 43 are closed. Under prede-termined conditlons of overload current the operatlng means 39 whlch lncludes a solenold 147 havlng a plunger 149, ls actuated agalnst the latch plate 139 to move the plate to the posltlon shown ln Flg. 8 so that the coll sprlng 145 moves the contact arm 41 to the open position of the contact.
In accordance with this lnventlon the contact arm 41 rotates about two di~ferent pivot points durlng the move-ment of the arm between the closed and open posltlon as shown in Figs. 6 and 7. A pivot polnt 151 extends through a hole 153 having tapered sides and having a lower slde which provides a clearance 155 with the pivot polnt ln the closed posltion of the arm 41. When the latch plate 139 ls moved to the unlatched positlon (Fig. 7) the clearance 155 around the plvot point 151 prevents the arm from contacting the plvot polnt so that the sprlng 145 moves the plate counter-clockwlse lnitlally around a plvot between the contacts 51, 53.
Moreover, ln accordance with this invention, the contact plate 115 strikes a button 157 (Fig. 8) on a pin 161 and against a spring 163 so that the contact 57 is moved from the contact 55 whlch ls a flange portion o~ the contact bracket 113. Llkewise, in accordance with this invention the clearance 155 between the arm 41 and the pivot point 151 no longer exists so that continued movement of the arm now depends upon pivot about the pivot point 151, causing the 45,771 contacts 51, 53 to separate as shown in Fig. 8. Thus, the several pairs of eontacts open and close sequentlally and not simultaneously.
The sequential operation o~ the contact arm 41 provides ~or maintenance o~ a clrcuit through the trlp clrcult 31 during openlng and closlng of the contacts. So long as the receptacle 11 ls properly wired, the neutral line will close before the hot line closes, because of the typlcal relay design, and there will be no problem ln case of continulng ground fault. However, ln case of reverse polarity, due to inadvertent wlrlng of the receptacle, the neutral llne becomes the hot llne and will close before the neutral line closes which, without the thlrd contact or contact means 55, 57, would not provide the protection agalnst ground fault. Accordingly, the button 157 havlng a coll spring 163 to hold it in the upper position (Fig. 6) provides protection against ground fault in case of reverse polarity or miswiring of the receptacle, because lt closes before both of the line and neutral contacts and energizes the trip circuit 31 as soon as the contacts 51, 53 close.
In addition, in the open position the contacts 51, 53 have a smaller gap 165 (Fig. 8) than a gap 167 between contacts 47, 49. Moreover, the length of the control arm 41 between the plvot polnt 151 and the contact 51 is less than that between the pivot point 151 and the contact 49. Thus, when the arm 41 is moved to the closed position, the contacts 51, 53 close before the contacts 47. 49.
The arm 41 is moved to the closed posltlon by a manual reset button 169 located on a bracket 171 that ls slldably mounted in grooves (not shown) in the housing 65.

45,771 The lower end of the bracket is spring biased upwardly by a coil spring 173 (Fig. 3). The latch plate 139 ls pivotally mounted to move between the latched and unlatched positions (Figs. 6 and 8) and is retalned in place by an L-shaped flexible member 175, the upper end of whlch is secured to the bracket 171 and the lower end oP whlch is secured, such as by a spot weld, to the latch plate 13g. Thus, each time the solenoid plunger 149 is driven against the lower end of the latch plate 139, the plate rotates clockwise ~rom the latched to the unlatched positions (Figs. 6 and 8). When the reset button 169 is depressed against the sprlng 173, the latch plate moves down and the shoulder 141 moves below the edge 143 o~ the contact plate 115, whereby the latch plate rotates counterclockwise under in~luence of the flexible member 175. Upon release of the reset button 169 the spring 173 raises the reset button assembly and the contact arm 41 to the closed position of Fig. 6.
During resetting o~ the contact arm 41 to the closed position the arm ~irst rotates on the plvot point 151 `at 177 (Fig. 8) until the contacts 51, 53 engage each other.
Thereafter, the pivot point for the arm moves to the point of contact between the contacts 51, 53 until the contacts 47, 49 are closed. During the initial period of movement o~
the contact arm 41 to the closed position, the pin 161 ls urged upwardly by the spring 163 until the contacts 55, 57 are closed, thereby closing the circuit through the trip circult 31 which ln turn continues to operate the solenoid 149 to prevent the arm 41 from remaining in a closed contact position until an existing ground ~ault is elimlnated.
Moreover, in accordance wlth thls invention as 45,771 1~63220 shown in Figs. 5 and 6j the conductors 15, 17 extend across one side o~ the core ~7, and through the central opening therein where the conductors are retained in place by suit-able means to prevent any movement of the conductors within the core. Such suitable means may lnclude an islet 177 (Flg. 6) having a flange 179~ The lslet ls crimped tightly around the conductors 15, 17 and ls seated within the opening of the core 29 with the flange 129 disposed against the partition 89. The flange 179 is preferably seated within an enlarged portion 181 of the aperture 117 to further limit any movement of the assembly by clamping the assembly in place between the core 29 and the partition 89.
Between the islet 177 and the arm 41,the conductors 15, 17, having similar insulating sleeves 183, are connected to the contact plates 115, 127 at joints 185, 187, respectively.
The segments of the conductors 15, 17 next ad~acent the ~olnts 185, 187 are of ample lengths and are preferably arcuate to minimize as much as possible any influence of the conductors may have on movement of the arm 41. Thus, the 20 provision of more than enough length of the segments of the conductors 15, 17 ad~acent the arm 41 permits the arm to move uninhibitedly in response to the downward pressure of the spring 145 when the latch plate 139 is actuated.
Another embodiment o~ the invention is shown in Fig. 9 in which the insulated conductors 15, 17 extend through the hole in the core 29 where they are retained by suitable clamping means such as a segment 189 of heat shrink tubing which grips or clasps the conductors tightly together wl'chin the core. In addition the insulatlng sleeve 183 on the conductors 15, 17 are clamped between the core 29 and ` 45,771 the partition 89, whereby the ample arcuate uninsulated portions of the conductors 15, 17 are free to move ln response to movement of the arm 41.
Accordingly, the electric receptacle of thls invention avolds many disadvantages of prlor art receptacles and provides advantages that have not been avallable here-tofore, Those advantages lnclude a more compact receptacle unlt whlch flts lnto a standard wall outlet box, llne termlnals secured ln place and formed for maximum straln rellef on the electrical contact gap, and a partltlon wall enabllng the placement of each component in its lntended locatlon so that movement of the solenold mechanlsm and the reset mechanlsm are avolded thereby provlding greater reli-ability without the use of additional fasteners.

Claims (10)

What is claimed is:

1. An electric receptacle for mounting in a wall outlet box for connecting an electrical load to the con-ductors of a power source, comprising socket means for receiving a plug of an electrical load, a first pair of cooperable contacts operable between open and closed posi-tions, a second pair of cooperable contacts operable between open and closed positions, an operating mechanism including a contact arm carrying one contact of each pair of contacts and movable between open and closed positions of the con-tacts, a latch member releasably holding the arm in the closed position, bias means engaging the arm for urging the arm to the open position when the latch member is released, a pivot rib for the contact arm, the bias means urging the arm to pivot about the first pair of contacts during an initial movement of the arm when released to open the second pair of contacts and to then pivot about the pivot rib during a final movement of the arm to open the first pair of contacts, ground fault sensing means for monitoring the flow of current through the socket means, and release means responsive to the fault sensing means for releasing the latch member from the contact arm, whereby the first and second pairs of contacts are opened sequentially.

2. The electric receptacle of claim 1 in which the contacts on the arm are located at opposite ends there-of, and the pivot rib is located intermediate the contacts.

3. The electric receptacle of claim 1 in which the other contacts of each pair are located on opposite sides of the arm.

4. The electric receptacle of claim 3 in which the pivot rib is nearer one contact than the other.

5. The electric receptacle of claim 1 in which the first pair of contacts are connected to the neutral conductor of the power source and the second pair of con-tacts are connected to the line conductor of the power source.

6. The electric receptacle of claim 5 including reset means for returning the contacts to the closed posi-tion, and the contacts being unclosable by the reset means during continued existence of a ground fault.

7. The electric receptacle of claim 6 in which third contact means are located in the path of movement of the arm at the open position thereof, the third contact means being operatively connected to open a circuit through the release means when the arm is in the open position.

8. The electric receptacle of claim 7 in which the third contact means comprises a contact button in de-tachable engagement with one of the conductors of the power source when the arm is in the closed position, and resilient means for urging the button in the closed position when the arm is not in the open position.

9. The electric receptacle of claim 8 in which the contact button is engaged with the line conductor.

10. The electric receptacle of claim 8 in which the contact button is closed before the arm reaches the closed position of the contacts.