US3617957A

US3617957A - Locking devices for washing machines or electromechanical appliances with bimetallic element

Info

Publication number: US3617957A
Application number: US783372A
Authority: US
Inventors: Norberto Brighenti
Original assignee: Texas Instruments Inc
Current assignee: Texas Instruments Inc
Priority date: 1968-12-12
Filing date: 1968-12-12
Publication date: 1971-11-02
Anticipated expiration: 1988-11-02

Abstract

A safety interlock for the door of electrical appliances such as washing machines comprises a thermostatic element heated by electrical power supplied to the appliance causing it to deflect. The deflection causes a locking member to slide into a mating aperture in a slide plate when the slide plate is biased into position by a hook on the appliance door. Once the locking member is in locking position, the door cannot be opened until the thermostatic element cools after deenergization. Means are provided for preventing excessive deformation of the thermostatic element and a shunt current path is provided to limit the amount of current passing through the thermostatic element and/or heater. Two forms of thermostatic elements and heaters therefor are disclosed.

Description

United States Patent [72] Inventor Norberto Brighenti Naples, Italy [21] App1.No. 783,372

[22] Filed Dec. 12, 1968 [45] Patented Nov. 2, 1971 [73] Assignee Texas Instruments Incorporated Dallas, Tex.

[54] LOCKING DEVICES FOR WASHING MACHINES 0R ELECTROMECHANICAL APPLIANCES WITH BIMETALLIC ELEMENT 8 Claims, 1 1 Drawing Figs.

[52] U.S. Cl 337/77,

[51] Int. Cl H01h27/06,

I-lOlh 61/06 [50] Field of Search ZOO/61.62, 61.63, 6164; 210/149; 3 l0/4.1; 337/77, 97, 98, 103

[56] References Cited UNITED STATES PATENTS 3,096,413 7/1963 Gryctko et a1 337/83 IJX 3,458,675 7/1969 Del Gaudio 337/92 X 3,062,937 11/1962 Flanagan..... 337/97 X 2,738,072 3/1956 Knight..... 210/149 2,539,185 l/l95l Dayton 310/4.1

Primary Examiner-Bernard A. Gilheany Assistant Examiner-Dewill M. Morgan AuorneysI-laro1d Levine, Edward J Connors, J r. and John A. I-Iaug ABSTRACT: A safety interlock for the door of electrical appliances such as washing machines comprises a thermostatic element heated by electrical power supplied to the appliance causing it to deflect. The deflection causes a locking member to slide into a mating aperture in a slide plate when the slide plate is biased into position by a hook on the appliance door. Once the locking member is in locking position, the door cannot be opened until the thermostatic element cools after deenergization. Means are provided for preventing excessive deformation of the thermostatic element and a shunt current path is provided to limit the amount of current passing through the thermostatic element and/or heater. Two forms of thermostatic elements and heaters therefor are disclosed.

m a 7 13 10 a l a u i 24 26' I7 24 2a 5 a 5 i PATENTEU m2 m1 SHEET 2 [IF 4 in (i LOCKING DEVICES FOR WASHING MACHINES OR ELECTROMECIIANICAL APPLIANCES WITI-I BIMETALLIC ELEMENT The present invention relates to an improvement for safety devices that are mounted for example on washing machines for the purpose of preventing the opening of the cover during the periods in which the motor is running and when the washing machine is in the water-heating phase and of permitting the opening of the cover, in the absence of power, only after a predetermined delay.

As is known, one type of device for locking the cover and releasing it again after a predetermined time interval is essentially composed of a bimetallic element which, through the effect of heat, is deformed, causing movement of a ratchet. This ratchet projects from the device and engages with a fastening device for the cover of the washing machine preventing it from moving and therefore opening of the cover.

In the absence of power, through the effect of the accumulated heat or thermal inertia, the bimetallic element takes a certain time to cool and thus return the ratchet to the original position in order to allow the opening of the cover.

In these devices the bimetallic element, since it is usually connected electrically in series with the machine, is considerably stressed since it must intervene both when the machine consumes the minimum power (when it is in the washing phase) and when it consumes the maximum power (when it is in the water-heating phase or when it is at the start of the centrifuging phase. It is therefore necessary to dimension the bimetallic element sufiiciently large and permit it a substantial expansion or bending so as to avoid permanent deformations. This invariably results in cumbersome devices.

To avoid excessive overall dimensions and to limit the stress on the bimetallic member it has already been suggested to periodically interrupt the electric power for heating the bimetallic element when the latter has reached a predetermined deformation. In this case, the bimetallic element will, at the maximum power, be strongly stressed only when in cooling down it reestablishes its power supply input and to avoid a permanent deformation it is necessary to permit it a larger displacement; consequently, the device will be more cumbersome than is strictly required under the actual operating conditions.

In general in washing machines where a device according to the invention finds special application the space between the basket and the outer plate is reduced to a minimum and therefore the devices which are therein inserted must be simple and efficiently conserve space.

Other safety means, also in addition to the described devices, are used for the purpose of interrupting the power supply of the machine when its lid is open.

In general, switches are used whose control, with appropriate adjustments, is effected by the cover of the washing machine itself.

It is an object of the present invention to provide an inexpensive safety device, of small dimensions, which is equipped with means for protecting the bimetallic member against excessive stresses and one which can incorporate means for preventing the supply of electric power to the washer when the cover of the latter is open.

Other objects and features will be in part pointed out hereinafter.

According to the invention, the locking device includes in combination a thermostatic or bimetallic element electrically connected in series in the electrical supply circuit of the apparatus to be protected; the electrical connection being arranged so as to obtain joulean heating of the bimetallic element; means for limiting the deformation of the bimetallic element, means actuated by the bimetallic element for the mechanical safety locking of the apparatus to be protected; means for connecting in parallel with the bimetallic element an electrical resistance element to reduce the current flowing through it. the resistance element being in a heat exchange relation with the bimetallic element in order to maintain a constant deformation in the presence of the electrical load part apparent and in that determines the subsequent deformation. The apparatus includes further means for interrupting the electrical supply to the washing machine controlled by a sliding plate in such a manner that there is no need for any regulation to be made in the machine to obtain the deenergization in the position desired for the opening of the cover.

The present invention will now be described with reference to a preferred fonn of the invention which is given only by way of example as shown in the attached drawings, wherein:

FIG. 1 shows the device according to the invention seen along the transversal section A-A of FIG. 2.

FIG. 2 shows the section B-B of FIG. 1

FIG. 3 shows the device according to the invention in the operating position according to the transversal section C-C of FIG. 4.

FIG. 4 shows the section D-D of FIG. 3.

FIG. 5 shows a plan view of the sliding plate.

FIG. 6 shows a device according to a second embodiment of the invention in the resting position according to the transversal section A-A' of FIG. 7.

FIG. 7 shows the section B'B' of FIG. 6.

FIG. 8 shows the invention along section c'-c' of FIG. 7.

FIG. 9 shows the device according to the invention in the operating position according to the transversal section D'-D' of FIG. 10.

FIG. 10 shows the section 5-5 of FIG. 9.

FIG. 11 shows the plan view of the sliding plate.

Referring to the drawings, as seen in FIG. 2, 4, 7 and I0 terminals l and 2 of the locking device are provided for electrical connection in series with the power supply of the machine to be protected.

In FIGS 1 and 2, the bimetal 3 which is generally U-shaped in configuration is shown in the resting position. A first end is fastened to the terminal I and, the other end is fastened to an elongated stationary contact arm 4 which also carries contacts 5 and 8. An arm 7 extends from terminal 1 in cantilever fashion and is located in underlying parallel relation to one leg of bimetal 3. One end of a U-shaped elastic lamina 6 of predetermined electrical resistance is fastened to the free end of arm 7 and is located in underlying parallel relation to the other leg of bimetal 3.

Stationary contact arm 4 and the free end of lamina 6 are provided with contact elements 8 and 9 respectively which in this condition are electrically separated.

One end of a flexible lamina member 10 is attached to the central bright portion of the bimetal 3 with the other end of member 10 engaging in slot 11 of ratchet 12. Also mounted on the bight portion of bimetal 3 and interposed between member 10 and lamina 6 is an insulating button 13. The ratchet I2 is slidable in

slots

14 and 15 of the cover 16 and box 17 respectively. p I

Terminal 2 ends in a contact extension 18 on which, by means of a spring 19, the movable contact 20 is supported. The spring 19 is linked to a slide 21 which engages in the slot 23 of sliding plate 24.

The cover 16 and box 17 are locked by means of any con ventional joining members 25 on the fixed plate 26.

Between the box 17 and the plate 26 moves the sliding plate 24 which is controlled as it is shown in FIG. 3 by the hooking member 27 of the washing machine.

Spring 28 located in opening 29 returns the sliding plate 24 to the position of FIGS. 1 and 2 when the lid of the washing machine is open.

When the lid of the washing machine is closed hooking member 27 causes sliding plate 24 to move into the position shown in FIGS. 3 and 4.

During this movement the plate 24 entrains the slide 21 and thus the spring 19 which in passing beyond the position of the extension 18 forces the movable contact 20 to move from the position shown in FIG. 2 to that shown in FIG. 4 and thus make theelectrical contact so that the machine is able to function.

As can be seen from FIG. 2, it is possible to insert in the device other contacts 30 which can serve to obtain the opening of all the powerlines which supply the machine.

When the motor of the washing machine starts to run the bimetal, through the joulean effect, deforms itself and moves the ratchet 12 from the position shown in FIG. 1 to that of FIG. 3. In this position the ratchet 12 is inserted in the slot 22 of the sliding plate 24.

In this position the plate 24 cannot make further movements thus preventing a clearing of the hooking member 27.

During its movement the bimetal pushes, with the insulating button 13, the resistance 6 until the contact 9 bearing on the contact 8 connects, in parallel with the bimetal, the resistance 6. At this moment the current subdivides between the resistance 6 and the bimetal to such an extent that through the latter passes only a small part of the current. That is, when button 13 transmits the motion of bimetal 3 to effect closing of contacts 8 and 9, the current will flow from terminal 1 either through bimetal 3 to stationary contact arm 4, or through arm 7, lamina 6, contacts 9 and 8 to stationary contact arm 4 and thence to stationary contact 5, movable contact 20, extension 18 to terminal 2.

When the washing machine draws a heavy current the bimetal is maintained constantly in the position of FIG. 3 by the joulean effect of the small current running through it and by the heat which is imparted to it through radiation of the resistance 6.

If a strong current were suddenly to pass through the device it would cause the bimetal in response to 2R heating and after the operating position has been reached to move even beyond that point. However, in accordance with the invention, its thrust would be cushioned by the

elastic members

6 and 10 which would hinder it from deforming itself permanently.

In some machines wherein the vibrations are very substantial and in order to prevent vibrations from opening the electrical contact 8-9 resulting in the bimetal carrying the whole amount of current, the ratchet 12 may be provided with a small magnet 31. When the ratchet 12 is in the position of FIG. 3 it is attracted toward the

plates

24 and 26 which are made of magnetic material thus conferring an added force upon the contact 8-9 such that it affords a sufficient stability to resist the effects caused by the vibrations. When the bimetal cools down the elastic force stored up during its movement separates the magnet thus returning the ratchet 12 to the position ofFIG. 1.

When the machine has finished the washing cycle or when there is a sudden lack of power the bimetal cools down within a predetermined safety period so as to permit the opening of the lid only when the rotating basket has stopped. L

Turning noL to FIGS. 6-11, a modification of Lthe invention is shown. As in the FIGS. 1-5 embodiments, the locking device is connected electrically in series with a power supply of the machine by means of

connectors

101 and 102.

In FIGS. 6 and 7, bimetal 103, shown in the resting position, is fastened to the terminal 101 at one end.

On the second end 118 of bimetal 103 is fastened resistance 104 which is wound around the bimetal and around the plate 105 that has the purpose of electrically and thermally insulating bimetal 103.

Also on end 118 of bimetal 103 is fastened an elastic lamina 106 which engages in slot 107 of ratchet 108.

Ratchet 108 is slidably mounted in slot 109 of the insulating case 110 and is pressed by the lamina 106 against the inner wall of the cover 111.

The second end of the resistance 104 is fastened to the platelet 112 to which are fastened the line contact 113 and short-circuitlng contact 114.

This contact is located on the attachment 115 of the small plate 112 on which is made a threaded hold 116 which engages the screw 117 that is located between the walls of screw 111 and case 110.

Screw 117, when turned, deforms the attachment 115 and therefore determines the movement of the contact 114.

As a result, there is obtained the adjustment of contact 114 and a shunt circuit contact 120 described below.

On terminal 101 is fastened the elastic lamina 119 having a predetermined electrical resistance as a function of the particular heating desired and of the current running through it.

At the center of the lamina 119 is fastened the short circuit contact 120. Terminal 102 ends with the contact attachment 121 on which, by means of spring 122, the movable contact 123 is supported. The spring 122 is connected to the slide 124 which engages in the slot 125 of the sliding plate 126.

The cover 111 and the case 110 are locked by conventional joining members 127 on the fixed plate 128.

Between case 110 and plate 128 moves sliding plate 126 which is operated, in FIG. 9, by hooking member 129 of the washing machine. L

Spring 130 located in slot 131 returns sliding plate 126 to the position shown in FIGS. 6 and 7 when the lid of the washing machine is open.

When the lid of the washing machine is being closed member 129 operates plate 126 which moves from the position of FIGS. 6 and 7 and to the position of FIGS. 9 and 10.

During this movement plate 126 pulls along slide 124 and thus spring 122 which, in passing beyond the position of extension 121, forces movable contact 123 to move from the position shown in FIG. 7 to that of FIG. 10 thus making electrical contact for the machine to be able to function. When the washing machine or other appliance is in any washing or operating phase, the bimetal L103, through the joulean efiect, deforms itself moving ratchet 108 from the position of FIG. 6 to that of the FIG. 9.

In this position since ratchet 108 is in slot 132 of plate 126, the plate is not able to make further movements and therefore prevents the release of the hooking member 129 of the lid of the washing machine.

During the phase of its movement bimetal 103 pushed the end part of the elastic resistive plate 119 until contact 120 bears on contact 114 and connects resistance 104 in parallel with the resistive section of the elastic lamina 119.

At this moment, the current subdivides between the resistance 104 and lamina 119 in such a way that only a small part of the current will pass through the resistance 104.

The movement of the contact 114 through the screw 117 determines a variation of the displacement of the bimetal 103 which permits a regulation of the periods of intervention of the device.

If the device were suddenly traversed by a strong current and the bimetal, to get rid of the accumulated heat, would have to move beyond its operating position; once the said operating position has been reached. Its thrust would be cushioned by the elastic members 106 and 119 which would hinder it from deforming itself permanently.

In view of the above it will be seen that the several objects of the invention are achieved and other advantageous results attained.

It is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

As many changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description as shown in the accompanying drawings, shall be interpreted as illustrative and not in a limiting sense, and it is also intended that the appended claims shall cover all such equivalent variations as come within the true spirit and scope of the invention.

I claim:

1. In an electrical apparatus having an access door, a safety interlock comprising:

a housing;

a locking member movably mounted in the housing and movable into and out of locking position;

means for moving the locking member into and out of locking position, the means including a thermostatic element which upon deflection causes Lmovement of the locking member;

a current path for energizing the interlock, the path including the thermostatic element;

means for partially shunting a portion of the current path around the thermostatic element upon energization of the interlock and a predetermined deflection of the thermostatic element;

a slide plate mounted in the housing, the plate provided with a cam surface adapted to be engaged by a member on the door of the appliance, the slide plate slidable when cammed;

a stationary contact mounted in the housing;

a movable contact arm mounted in the housing and adapted to move into and out of engagement with the stationary contact, the contact and contact arm included aselements in the current path; and

means to move the movable contact arm into and out of engagement upon sliding movement of the slide plate.

' 2. A safety interlock according to claim 1 in which the thermostatic element is a generally U-shaped bimetallic member and a spring element connects the bight portion of the bimetallic member to the locking member.

3. A safety interlock according to claim 3 in which a magnetic element is located within the locking member.

4. A safety interlock according to claim 1 in which the movable arm is pivotally mounted and means are provided from biasing the movable contact arm against the pivotal mount, the means movable from one side of the pivot to another side upon movement of the slide plate to cause movement of the contact arm.

5. A safety interlock according to claim 1 in which a plurality of switches are provided in the housing; and the slide plate is adapted to actuate and deactuate the switches upon movement thereof.L L

6. In an electrical apparatus having an access door, a safety interlock comprising:

a housing;

means for moving the locking member into and out of locking position, the means including a thermostatic element which upon deflection causes movement of the locking member, the thermostatic element being a generally U-shaped bimetallic member and a spring element connects the bight portion of the bimetallic member to the locking member;

a current path for energizing the interlock, the path including the thennostatic element;

means for partially shunting a portion of the current path around the thermostatic element upon energization of the interlock and a predetermined deflection of the thermostatic element including a generally U-shaped flexible resistor placed in parallel face-to-face relation with the bimetallic member;

a shunting contact mounted on a free end of the resistor and movable into and out of engagement with a stationary shunting contact; and

a motion transfer button mounted on the bight portion of the bimetallic member adapted on deflection of the bimetallic member to bias the resistor to cause the shunting contact to engage the stationary shunting contact. X

7. In an electrical apparatus having an access door, a safety interlock comprising:

a housing;

means for moving the locking member into and out of locking position, the means including a thermostatic element which upon deflection causes movement of the locking member;

a curren path for energizing the interlock, the path Including the thermostatic element;

a terminal; the thermostatic element being an elongated member fixed to the terminal on an end thereof;

a heater serially connected to the member and in heat transfer relation thereto;

a flexible member connected to another end of the elongated Xmember and Lalso to the locking member;

means for partially shunting a portion of the current path around the thermostatic element upon energization of the interlock and a predetermined deflection of the thermostatic element including an elongated shunt resistor attached on an end thereof to the terminal, another end of the shunt resistor attached to the flexible member;

a stationary shunt contact mounted in the housing; and

a movable shunt contact mounted on the shunt resistor and adapted to move into and out of engagement with the stationary shunt contact upon movement of the elongated member.

8. A safety interlock according to claim 7 including means to adjust the position of the stationary shunt contact.

i t l 3

Claims

1. In an electrical apparatus having an access door, a safety interlock comprising: a housing; a locking member movably mounted in the housing and movable into and out of locking position; means for moving the locking member into and out of locking position, the means including a thermostatic element which upon deflection causes movement of the locking member; a current path for energizing the interlock, the path including the thermostatic element; means for partially shunting a portion of the current path around the thermostatic element upon energization of the interlock and a predetermined deflection of the thermostatic element; a slide plate mounted in the housing, the plate provided with a cam surface adapted to be engaged by a member on the door of the appliance, the slide plate slidable when cammed; a stationary contact mounted in the housing; a movable contact arm mounted in the housing and adapted to move into and out of engagement with the stationary contact, the contact and contact arm included as elements in the current path; and means to move the movable contact arm into and out of engagement upon sliding movement of the slide plate.

2. A safety interlock according to claim 1 in which the thermostatic element is a generally U-shaped bimetallic member and a spring element connects the bight portion of the bimetallic member to the locking member.

5. A safety interlock according to claim 1 in which a plurality of switches are provided in the housing; and the slide plate is adapted to actuate and deactuate the switches upon movement thereof.

6. In an electrical apparatus having an access door, a safety interlock comprising: a housing; a locking member movably mounted in the housing and movable into and out of locking position; means for moving the locking member into and out of locking position, the means including a thermostatic element which upon deflection causes movement of the locking member, the thermostatic element being a generally U-shaped bimetallic member and a spring element connects the bight portion of the bimetallic member to the locking member; a current path foR energizing the interlock, the path including the thermostatic element; means for partially shunting a portion of the current path around the thermostatic element upon energization of the interlock and a predetermined deflection of the thermostatic element including a generally U-shaped flexible resistor placed in parallel face-to-face relation with the bimetallic member; a shunting contact mounted on a free end of the resistor and movable into and out of engagement with a stationary shunting contact; and a motion transfer button mounted on the bight portion of the bimetallic member adapted on deflection of the bimetallic member to bias the resistor to cause the shunting contact to engage the stationary shunting contact.

7. In an electrical apparatus having an access door, a safety interlock comprising: a housing; a locking member movably mounted in the housing and movable into and out of locking position; means for moving the locking member into and out of locking position, the means including a thermostatic element which upon deflection causes movement of the locking member; a current path for energizing the interlock, the path including the thermostatic element; a terminal; the thermostatic element being an elongated member fixed to the terminal on an end thereof; a heater serially connected to the member and in heat transfer relation thereto; a flexible member connected to another end of the elongated member and also to the locking member; means for partially shunting a portion of the current path around the thermostatic element upon energization of the interlock and a predetermined deflection of the thermostatic element including an elongated shunt resistor attached on an end thereof to the terminal, another end of the shunt resistor attached to the flexible member; a stationary shunt contact mounted in the housing; and a movable shunt contact mounted on the shunt resistor and adapted to move into and out of engagement with the stationary shunt contact upon movement of the elongated member.