US3792401A

US3792401A - Thermally responsive electrical device

Info

Publication number: US3792401A
Application number: US00267272A
Authority: US
Inventors: P Anderson
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1972-06-29
Filing date: 1972-06-29
Publication date: 1974-02-12
Anticipated expiration: 1991-02-12
Also published as: DE2329642A1; CA977805A; AU5663473A; DE7321781U; ZA734363B; ES416155A1; BE801424A; AU476175B2; GB1431576A; FR2191243A1; BR7304657D0; FR2191243B1; CH570035A5

Abstract

An electrical control device or relay characterized by a pair of relatively separable contacts, means for moving the contacts between open and closed positions and comprising a latch member movable between unlatched and latched positions corresponding respectively to the open and closed positions of the contacts, three pole units of which each pole unit comprises a bimetal element responsive to current flow to effect heating thereof, a slide assembly associated with the bimetal elements of the pole unit and comprising first and second slides and a lever, the slide assembly being movable as a unit to move the latched member to the unlatched position when all of the bimetal elements are oerated, the lever being pivotally mounted on the second slide and engageable with the latch member, the first slide being movable in response to movement of at least one bimetal element to move the latch member through the lever to the unlatched position, the second slide being limited against movement when at least one of the bimetal elements is unoperable, and the first slide contacting the lever at a location between the location of mounting of the lever on the second slide and of engagement between the lever and the latch member.

Description

United States Patent Anderson Feb. 12, 1974 THERMALLY RESPONSIVE ELECTRICAL [57] ABSTRACT DEVICE An electrical control device or relay characterized by Inventor? Paul Anderson Beaver a pair of relatively separable contacts, means for mov- [73] Assigneez Westinghouse Electric Corporation, ing the contacts between open and closed positions Pittsburgh, Pa. and comprising a latch member movable between unlatched and latched positions corresponding respec- [22] Filed: June 1972 tively to the open and closed positions of the contacts,

[21] Appl. No.: 267,272

[52] U.S. Cl 337/49, 337/95, 337/l0l [51] Int. Cl. H0lh 37/30 [58] Field of Search 337/37, 38, 39, 49, 52, 62,

Primary ExaminerBernard A. Gilheany Assistant Examiner-A. T. Grimley Attorney, Agent, or Firm-L. P. Johns three pole units of which each pole unit comprises a bimetal element responsive to current flow to effect heating thereof, a slide assembly associated with the bimetal elements of the pole unit and comprising first and second slides and a lever, the slide assembly being movable as a unit to move the latched member to the unlatched position when all of the bimetal elements are oerated, the lever being pivotally mounted on the second slide and engageable with the latch member, the first slide being movable in response to movement of at least one bimetal element to move the latch member through the lever to the unlatched position, the second slide being limited against movement when at least one of the bimetal elements is unoperable, and the first slide contacting the lever at a location between the location of mounting of the lever on the second slide and of engagement between the lever and the latch member.

1 Claim, 8 Drawing Figures PATENTEDFEBI 2 7 3392401 FIG.5

PATENTEI] FEB 1 2 I974 FIG? TI-IERMALLY RESPONSIVE ELECTRICAL DEVICE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to electrical control devices and more particularly to thermally actuated relays.

2. Description of the Prior Art Most relays of the thermally controlled overload type have included disadvantages of varying features which contribute to the overall inefficiency of the relay and therefore dissatisfaction on the part of the user. Generally, most relays of prior construction have been unduly large for a given rating and therefore covered larger areas on a mounting panel than was necessary. In addition, most prior relays covered only percent increments of a range of current and were not readily adjustable from the front or in place on the mounting panel.

Moreover, thermally actuated relays of prior construction have not included a means for sensing the status of current in a single phase. Rather, most prior relays have included polyphase sensing means which function only when all of the phases incurred current overloads.

SUMMARY OF THE INVENTION It has been found in accordance with this invention that the foregoing disadvantages may be overcome by providing a thermally actuated relay comprising avpair of relatively separable contacts with means for actuating the contacts between open and closed positions, which means comprise a latch member movable between unlatched and latched positions corresponding respectively to the open and closed positions of the contact, a plurality of pole units which comprise bimetallic means including a bimetallic element responsive to current flow to effect heating thereof, a slide assembly associated with the bimetallic elements of the pole unit and comprising first and second slides and a lever, the slide assembly being movable to move the latch member to the unlatched position when all of the bimetal elements are operated, the lever being pivotally mounted on the second slide and engageable with the latch member, the first slide being movable in response to movement of at least one bimetal element to move the latch member through the lever to the unlatched position, the second slide being limited against movement when at least one of the bimetal elements is unoperable and the first slide contacting the lever at a location between the location of mounting of the lever on the second slide and of engagement between the lever and the latch member, whereby when less than all of the bimetal elements respond to a predetermined amount of current in the pole units the first slide moves the lever against the latch member at a greater speed than where both slides move simultaneously.

The advantage of the device of this invention is the provision of means for covering a wider range of current and sensing single phase overloads as well as providing means extending through the housing for manually tripping, resetting, and adjusting the overload relay rating of the device.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a side elevation view showing the manner in which a thermally actuated relay is positioned with respect to a contactor;

FIG. 2 is a front elevation view of the relay;

FIG. 3 is a top plan view of the relay;

FIG. 4 is a rear elevation view of the relay;

FIG. 5 is a view similar to FIG. 4 showing the actuating parts in the tripped position;

FIG. 6 is a horizontal sectional view taken on the line VIVI of FIG. 4;

FIG. 7 is a view similar to FIG. 6 showing the slide mechanism in an alternative position; and

FIG. 8 is an exploded view of one of the bimetal elements.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1 an electrical control device or thermally actuated relay is generally indicated at 10 and is shown in conjunction with a contactor 12 with which the relay is designed to function for the purpose of controlling a load such as a three phase motor. The contactor is of a conventional construction such as shown in US. Pat. No. 3,368,l71, issued Feb. 6, 1968, to .l. P. Conner et al. A conductor 14 is disposed between a terminal 16 of the contactor 12 and a terminal 18 of the relay 10.

In accordance with this invention, the relay 10 comprises a molded insulating housing 20 which includes a front wall 22 (FIG. 4), a top wall 24, a bottom wall 26, and

opposite side walls

28 and 30. The walls 24-30 extend from the front wall to form an open chamber or cavity 32 for receiving the operating parts of the relay. The cavity 32 of the housing 20 comprises three chambers which are separated by

insulating barriers

34, 36, and 38 which are integral parts of the molded housing. As shown in FIGS. 2 and 3 the

barriers

34, 36, and 38 extend across the top wall and downwardly over a portion of the front walls to provide spaces in each of which a line terminal assembly for each pole unit is located. Each line terminal assembly comprises among other things, a terminal conductor 40 which is an L- shaped member extending through an opening in the top wall 24 and into the cavity 32 where it is retained in place by screw 42. The housing is provided with a cover 44 (FIGS. 1 and 3) where it is retained in place by spaced screws 46 which are seated in threaded apertures 48 (FIG. 4). The combination of the housing 20 and the cover 44 provide the completely enclosed cavity 32 in which the relay mechanism is enclosed.

The relay mechanism comprises an operating mechanism 50 and an actuating mechanism 52 which are suitably supported within the internal chamber or cavity of the housing operating The perating mechanism 50 comprises a conducting frame 54, which is an L shaped member extending through an opening in the top wall 24 to the front side (FIG. 2) where it is provided with a terminal including a terminal screw 56, and which is secured in place on the front wall 22 by a screw 58. The conducting frame 54 is provided with a pair of upstanding parallel prongs 60 and 62 (FIG. 4) which serve as mounting means for other associated parts of the operating mechanism 50. Among other things those parts include an adjustment bracket 64, a latch arm or compensating bimetal 66, a contact arm 68, a reset rod 70, and a compression spring 72. The purpose of the operating mechanism 50 is to provide for latching and unlatching of the contact arm 68 for the purpose of opening and closing a circuit through a stationary contact 74 and a movable contact 76.

The stationary contact 74 is mounted on the upper end of a U-shaped terminal member 78 the lower end of which is electrically secured to a terminal strip 80 which extends through an opening in the front wall 22 (FIG. 2) where a terminal screw 82 is attached. The adjustment bracket 64 is pivotally mounted on the prong 60 and includes a lower end portion 84 which is out-turned at substantially right angles to the body of the bracket 64 and which is provided with a notch in which the lever member or compensating bimetal 66 is seated and pivotally mounted. The upper end of the adjustment bracket 64 is associated with an adjustment knob 86 which is rotatably mounted in the top wall 24 of the housing 20 and which includes a cam surface 88 for adjusting the position of the bracket 64 in accor-' dance with different current ratings. A more detailed description of the adjustment knob 86 is disclosed in Pat. No. 3,265,831. Suffice it to say, the upper end of the bracket 64 is movable to a broken line position 64a (FIG. 4) whereby the lower end of the bracket moves clockwise around the pivot 60 to a position nearer the barrier 38.

The latch arm 66 includes an out-turned upper end portion 90 which in the latched position extends across the upper end of the cam arm 68 as shown in FIG. 4; and which in the unlatched position (FIG. 5) is retracted to the left, whereby the cam arm 68 is in its uppermost position due to the action of the compression spring 72. The lower end of the latch arm 66 is associated with a slide assembly generally indicated at 92 which is described hereinbelow. When the lever arm is in the latched position, as shown in FIG. 4, it is retained there by a compression spring 94 which is disposed between the latch member and the barrier 38 above the end portion 84 of the adjustment bracket 64.

The upper end of the contact arm 68 is divided into three positions, the intermediate portion 96 of which is disposed on the right side of the prong 62 as viewed in FIG. 4 and the outside portions of which one portion 98 is shown are disposed on the left side of the prong. Accordingly, the prongs guide the vertical movement of the contact arm as it rises in response to the pressure of the compression spring 72, or as it is lowered in response to pressure of the reset arm 70. As was set forth above, when the arm 68 is in the lower position, as shown in FIG. 4, the movable contact 76 mounted on the lower end of the arm is in a closed circuit relationship with the stationary contact 74, thereby closing the circuits through a coil in the contactor 12 (FIG. 1) in a conventional manner.

On the other hand, when the contact arm 68 is in the elevated position as shown in FIG. 5 so that an open circuit exists between the

contacts

74 and 76, the movable contact 76 may be in contact with a second stationary contact. Thus, a second stationary contact 100 is provided at the lower end of a terminal strip 102 extending through an opening in the front wall 22 of the housing which is provided with a terminal screw 104 for the purpose of providing a normally open contact that is used for an alarm circuit when stationary contact 76 is in the unlatched or open position with respect to the stationarycontact 74.

Although the latch arm 66 may be merely a lever pivoted at the end portion of the adjustment bracket 64 as described above, the member may also be an ambient temperature compensating bimetal member for purposes well known in the art.

When the latch arm 66 is in the unlatched position,

as shown in FIG. 5, so that the contact arm 68 is uppermost with contact 74.and 76 in the open position, the reset rod 70 is also in its uppermost position because the lower end of the rod rests upon the outturned portion 68a of the bracket. In that position the upper end portion of the reset rod 70 is uppermost to indicate to the user that the relay is in the tripped position. In order to reset the relay and close the circuit through the

contact

74 and 76, the upper ends of the rods 70 is merely depressed against the pressure of the compression spring 72 until the upper end of the intermediate portion 96 of the bracket moves below the end portion of the latch member 66, whereupon the spring 94 rotates the latch member 66 counterclockwise across the upper endof the intermediate portion 96 thereby holding the contact arm 68 in the lower position as shown in FIG. 4. During the resetting operation a projection 70a extending below the lower end of the rod 70 depresses the spring-like terminal member 78 on which the stationary contact 74 is mounted, and retains the contact in the trip-free or open position during resetting of the movable contact-Upon release of the rod 70 after resetting the contact a compression spring 104 raises the rod sufficiently to enable the spring-like terminal member 78 to raise the stationary contact 74 into a closed circuit relationship with the contact 76. a

The actuating mechanism 52 comprises a plurality of bimetal members, the number of which correspond to the number of pole units on the relay. Inasmuch as there are three pole units 40 disclosed (FIGS. 2 and 3) there are three bimetal units provided in the relay 10. Each bimetal member includes a bimetal element responsive to current flow through the particular pole unit to which it is attached. Each bimetal member is disposed in a portion of the cavity 32 between the side wall 28, and the

barriers

34, 36, and 38. Moreover, each bimetal member includes a heater 106, a bimetal element 108, and a sheet of insulating material therebetween, as shown more particularly in the exploded view of FIG. 8.

The actuating mechanism 52 is connected to a terminal assembly which includes a terminal 112, a terminal screw 114, a wire cable 116 and a connector 118. The bimetal member also includes a mounting bracket 120, an insulating washer 122, a conducting washer 124, an insulating member 126, a support 128, a pair of insulating sleeves 130, an insulating washer 132 and mounting

screws

134 and 136. The screw 134 is engaged in an opening 138 of the connector 118 and the screw 136 is engaged in an opening 140 of the mounting bracket 120, the latter of which is connected to the terminal conductor 40 by the screw 42. The circuit through the actuating mechanism 52 passes from the terminal 112, the cable 116 and the connector 118 through the screw 134 to the support 128 from where it moves down the right side of the bimetal element 108 and up the left side, through the conducting washer 124 to the left side of the heater 106 and up the right side thereof where the current is transmitted to the mounting bracket 120 and then to the terminal conductor 40. When an overload occurs in the current passing through the heater 106, the bimetal 108 is deflected to the right as viewed in FIG. 4. As shown in FIG. 8 the lower end of the bimetal element 108 in cludes a projection 142 which cooperates with the slide assembly 92 to move the lower end of the latch member 66 from the latched position to the unlatched position as indicated by the broken line position (FIG.

As shown in FIGS. 4 and 6, the slide assembly 92 comprises a pair of

slide members

144 and 146 as well as a lever 148. The slide member 144 is an elongated member extending along one side of the spaced projections 142 and includes

transverse portions

150, 152, and 154 each of which engages one of the projections 142. Likewise, the slide 146 extends along the opposite side of the projections 142 and includes

transverse portions

156, 158 and 160 which engage opposite sides of the projections 142 corresponding to the

projections

150, 152, and 154, respectively. The lever 148 is pivotally mounted on the slide member 146 and extends across the transverse portion 154 and includes a projection 162 that is in contact with the latch member 66. In addition, the lever 148 includes a projection 164. As shown in FIG. 4, the lever 148 has a top surface recess 166 in which the transverse portion 154 is seated with the projection 164 in contact with the wall of the recess 166.

Accordingly, when all of the phases incur an overload current of sufficient magnitude to deflect all of the bimetal elements 108, the projections 142 of the bimetal elements moves to the right as viewed in FIG. 4 against the

transverse portions

150, 152, and 154 of the slide member 144 which motion is transmitted through the lever to the slide member 146 and ultimately to the latch member 66. When the latch member is deflected to the broken line position, 66a, the relay is tripped or unlatched and the movable contact 76 moves to the open position (FIG. 5).

As the bimetal elements 108 cool to normal temperature the slide assembly returns to the position of FIG. 6 and the relay is ready for resetting in the manner described above.

When less than all of the bimetal elements 108 are deflected, the bimetal element which is not deflected, such as the bimetal element having the projection 142a (FIG. 7), remains in fixed position and prevents the slide member 146 from moving to the right by virtue of pressure against the transverse portion 156. As a result the other deflecting bimetal elements move the slide member 144 to the right and apply a pressure through the transverse portion 154 to the projection 164 on the lever 148 which in turn rotates clockwise about its pivot point 168 (FIG. 7), and thereby increasing the travel of the projection 164 against the latch member 66. The increase of travel is a ratio of a/b, where a is the distance between the

points

168 and 162 and b is the distance between the

points

168 and 164. Thus, so long as a is greater than b the relay is tripped sooner than when less than all of the bimetal elements are heated.

Finally, the outer end of the slide member 144 extends externally of the housing where it is available for manual tripping when necessary.

Accordingly, the device of the present invention provides an overload relay that occupies a minimum of panel space, provides the adjustment knob in the front top portion of the relay for the convenience of the user, as well as provides tripping means for the relay where all or less than all of the bimetal elements are actuated.

What is claimed is:

1. An electrical control device comprising a first stationary contact, a movable contact, means for activating the contacts between open and closed positions and comprising a latch member movable between unlatched and latched positions corresponding respectively to the open and closed positions of the contacts, a plurality of pole units, each pole unit comprising bimetal means including a bimetal element responsive'to current flow to effect heating thereof, a slide assembly associated with the bimetal elements of the pole unit and comprising first and second slides and a lever, the slide assembly being movable as a unit to move the latch member to the unlatched position when all of the bimetal elements are operated, the lever being pivotally mounted on the second slide and engageable with the latch member, the first slide being movable in re sponse to movement of at least one bimetal element to move the latch member through the lever to the unlatched position, the second slide being limited against movement when at least one of the bimetal elements is unoperable, the first slide contacting the lever at a location between the location of mounting of the lever on the second slide and of engagement between the lever and the latch member, whereby when less than all of the bimetal elements respond to a predetermined tion.

Claims

1. An electrical control device comprising a first stationary contact, a movable contact, means for activating the contacts between open and closed positions and comprising a latch member movable between unlatched and latched positions corresponding respectively to the open and closed positions of the contacts, a plurality of pole units, each pole unit comprising bimetal means including a bimetal element responsive to current flow to effect heating thereof, a slide assembly associated with the bimetal elements of the pole unit and comprising first and second slides and a lever, the slide assembly being movable as a unit to move the latch member to the unlatched position when all of the bimetal elements are operated, the lever being pivotally mounted on the second slide and engageable with the latch member, the first slide being movable in response to movement of at least one bimetal element to move the latch member through the lever to the unlatched position, the second slide being limited against movement when at least one of the bimetal elements is unoperable, the first slide contacting the lever at a location between the location of mounting of the lever on the second slide and of engagement between the lever and the latch member, whereby when less than all of the bimetal elements respond to a predetermined amount of current in the pole units the first slide moves the lever against the latch member at a greater speed than where both slides move simultaneously, the device being enclosed within a housing and the first slide having an end portion external of the housing whereby the contacts may be manually tripped to the open position.