US3743992A

US3743992A - Thermally responsive electrical control device for polyphase currents

Info

Publication number: US3743992A
Application number: US00277940A
Authority: US
Inventors: J Ramsey; P Anderson
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1972-08-04
Filing date: 1972-08-04
Publication date: 1973-07-03
Anticipated expiration: 1990-07-03
Also published as: AU5852273A

Abstract

An electrical control device or overload relay characterized by relatively movable contacts with means for operating the contacts between open and closed positions and comprising an actuating bar, a plurality of pole units, each pole unit comprising an actuating bimetal element including an intermediate element and an outside element on each side thereof, the bimetal elements being spaced apart and disposed on one side of the actuating bar, a pair of levers between the bimetal elements and the actuating bar, one lever having one end portion in pivotal contact with the actuating bar and having another end portion in pivotal contact with the intermediate bimetal element on the side of the bimetal element opposite the actuating bar, and each lever having an intermediate portion in pivotal contact with the corresponding outside bimetal element and on the side thereof facing the actuating bar.

Description

United States Patent Ramsey et al.

July 3, 1973 Inventors: James B. Ramsey, Paul T. Anderson,

both of Beaver. Pa.

Primary Examiner-Velodymyr Y. Mayewsky Atmrney- A. T. Stratton. L. P. Johns et al.

[ 5 7 ABSTRACT An electrical control device or overload relay characterized by relatively movable contacts with means for operating the contacts between open and closed positions and comprising an actuating bar, a plurality of pole units, each pole unit comprising an actuating bimetal element including an intermediate element and an outside element on each side thereof, the bimetal elements being spaced apart and disposed on one side of the actuating bar, a pair of levers between the bimetal elements and the actuating bar, one lever having one end portion in pivotal contact with the actuating bar and having another end portion in pivotal contact with the intermediate bimetal element on the side of the bimetal element opposite the actuating bar, and each lever having an intermediate portion in pivotal contact with the corresponding outside bimetal element and on the side thereof facing the actuating bar.

5 Claims, 8 Drawing Figures PATENTEB JUL 3 ms aware Fig 4.

. PMENTEBJUL 3 am am 2 W 2 FIG.6.

1' Q ml 1 THERMALLY RESPONSIVE ELECTRICAL CONTROL DEVICE FOR POLYPHASE CURRENTS BACKGROUND OF THE INVENTION l. Field of the Invention This invention relates generally to electric control devices and more particularly to thermally actuated relays.

2. Description of the Prior Art Most thermal overload relays that are commercially available for the protection of three-phase motors have two phases normally provided with heaters or heatersolder pot units to operate a common control switch with provision for the later addition of a third heater or heater-solder pot unit to provide protection for all three phases. An example of such a relay is disclosed in U.S. Pat. No. 3,265,831 issued Aug. 9, 1966 to James B. Ramsey and Paul T. Anderson. In such a relay the addition of a third heater element increases the total heat generated so that the trip current rating is less than that for the condition where only two heater elements are used. In the relay of the foregoing patent, this characteristic is compensated for by providing a different heater application table for three-phase protection than for two-phase protection. Thus, different heaters are used for three-phase protection thanv for two-phase protection. Such an arrangement is not entirely satisfactory because use of the tables might be confusing and when a third heater is added, the heaters for the other phases must also be changed. Moreover, where three heaters are used, the possibility of nuisance trip-outs is significantly increased.

U.S. Pat. No. 2,713,623 discloses a thermally actuated control device comprising three bimetal strips with levers disposed between the strips and a control bar. The disadvantage of the construction and operation of the device of that patent is that it requires all of the bimetal strips to function continuously. Moreover, it is not useful where the bimetals strips are heated by separately installed heating elements and the user has the option of installing either two or three heating elements.

SUMMARY OF THE INVENTION It has been found in accordance with this invention that the foregoing problems may be overcome by providing an electrical control device having three pole units, each unit comprising an actuating bimetal element, cooperating contact means, means for operating the contact means between open and closed positions and including an actuating bar common to all of the bimetal elements, the bimetal elements being spaced apart and on one side of the actuating bar, a first lever between the bar and one of the end or outer bimetal elements, a second lever between the bar and the other of the end or outer bimetal elements, each lever having one end portion in pivotal contact with the actuating bar and having another end portion in pivotal contact with the intermediate bimetal element on the side thereof opposite the actuating bar, each lever having a central portion in pivotal contact with the corresponding end bimetal element and on the side thereof facing the actuating bar, one of the levers extending between the intermediate bimetal element and one end bimetal element and the other lever extending between the intermediate bimetal element and the other end bimetal element, the movable contact being supported for movement about a first axis and the actuating bar being movable about a second axis, whereby movement of at least one of the end bimetal elements toward the actuating bar in response to a thermal overload relative to the center or intermediate bimetal element causes the contacts to move to the open position.

The advantage of the device of this invention is that it permits the addition of a heater in the third phase without appreciably changing the trip current rating and therefore enables the use of the same heater for two or three phases.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of an overload relay embodying the principles of this invention;

FIG. 2 is a side elevational view of the relay seen in FIG. 1;

FIG. 3 is a sectional view taken generally along the line III-III of FIG. 2;

FIG. 4 is a sectional view taken generally along the line IV-IV of FIG. 2;

FIG. 5 is an exploded perspective view of parts of the relay mechanism;

FIG. 6 is a sectional view taken generally along the line VI--Vl of FIG. 2;

FIG. 7 is a side elevational view of the plug-in heater member seen in FIGS. 1 and 3; and

FIG. 8 is a plan view of the plug-in heater member seen in FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENT This invention is an improvement in the art of thermal overload relays of the general type disclosed in our US. Pat. No. 3,265,831 issued Aug. 9, 1966.

Referring to the drawings, there is shown in FIGS. 1-4 and 6, an overload relay 3 comprising a molded insulating housing part 5 and a molded insulating housing part 7 which

housing parts

5 and 7 are secured together by means of two bolts 8 (FIG. 2). As shown in FIGS. 3, 4, and 6, each of the

housing parts

5 and 7 comprises a backwall with four sidewalls extending therefrom to form an open cavity for receiving parts of a relay mechanism 9. The cavity of the housing part 5 comprises three spaces with the adjacent spaces being separated by insulating barriers 10 that are molded integrally with the housing part 5. The barriers 10 are shown in dotand-dash lines in FIG. 6 and one of the barriers is shown in full lines in FIG. 4. The cavities of the

housing parts

5 and 7 form an internal compartment when the

parts

5 and 7 are secured together. The relay mechanism 9 (FIGS. 3-6) comprises an operating mechanism 13 and an actuating mechanism 15, which structures are suitably supported within the internal compartment of the

insulating housing

5, 7.

The operating mechanism 13 comprises a conducting supporting frame 19 having a terminal 21 formed integrally therewith, which frame 19 is supported on the housing part 7 by means of a screw 23 (FIG. 6). A screw 25 (FIG. 2) is provided to connect the terminal 21 and, therefore, the conducting frame 19 is connected in an electric circuit. A generally U-shaped movable contact arm 27 having two contacts 29 (only one being shown in FIG. 6) at the outer end thereof, is pivotally supported in pivots 31 (FIG. 5) in two leg portions 32 of the frame 19. An overcenter spring 33 is supported under tension at one end in a V-shaped notch 35 (FIG. in the frame 19, and at the other end in a suitable opening 37 in the bight portion of the U- shaped contact arm 27. An adjusting member 39 having two legs 41 is pivotally supported on the frame 19 by means of a supporting pin 43 that passes through openings in the legs 32 of the frame 19 and through openings in the legs 41 of the adjusting member 39. An operating structure 47 comprising a member 49 having an extension 50 and a compensating bimetal member 51 suitably supported on the member 49, is pivotally supported on two legs 53 of the adjusting member 39 by means of a pin 55 that passes through suitable openings in legs 57 of the member 49 and also through suitable openings in the legs 53 of the adjusting member 39. Though the member 51 is preferably a compensating bimetal member, it may be merely a lever of noncompensating metal.

A conducting stationary contact structure 61 comprising two stationary contact arms 63, each having a stationary contact 65 disposed at the free end thereof, is secured to the housing part 7 by means of a screw 69 (FIG. 6). A conducting terminal 70 is provided on the stationary contact structure 61. A screw 71 (FIG. 2) is provided to enable connection of the stationary contact structure 61 in an electric circuit. As can be seen in FIG. 6, the contacts 29 on the movable contact arm 27 cooperate with the stationary contact 65.

Another conducting stationary contact structure 77 (FIG. 5) comprising a generally rigid conductor having a conducting terminal part 79 at one end thereof and a resilient conducting member 81 supported thereon is secured to the housing part 7 by means of a screw 83 (FIGS. 2 and 6). Two contacts 85 (only one being seen in FIG. 6) are securedto the resilient conductor 81. A screw 87 (FIG. 2) is provided to enable connection of the stationary contact structure 77 in an electric circuit. The operating mechanism 13 also comprises a resetting bar 89 that is provided for resetting the actuated movable contact structure in a manner to be hereinafter more specifically set forth.

The actuating structure comprises three pole units, each of which pole units comprises an actuating bimetal means including

elements

99, 100, and 101. As can be seen in FIG. 6, the actuating bimetal elements 99-101 are aligned side-by-side and structurally parallel and separated by the insulating barriers 10. Each of the bimetal elements 99-101 is mounted on a supporting member 103 (FIGS. 3 and 4) each of which members 103 is connected to the housing part 5 by a screw 105. A calibrating screw 107 is provided in each pole unit to permit positioning of the initial position of the associated bimetal elements in order to permit calibration of the overload relay 3. A separate V-shaped pivot 113 (FIGS. 3 and 4) is molded integrally with the housing part 5 at each of two opposite sides of the housing part 5. A generally U-shaped electrically insulating cross bar 117, having a generally V-shaped notch 119 (FIG. 5) at the free end of each of the two opposite legs thereof, is pivotally supported on the pivots 113 on the housing part5. As shown in FIG. 4, the bight part of the cross bar 1 17 can move freely below the insulating barriers 10. A projection or button 121 (FIG. 6), molded integrally with the actuating or cross bar 117, is provided adjacent the bimetal element 100. A projection 123 (FIGS. 4-6) is provided on the other side of the bar 117 and is positioned to engage the compensating bimetal 51 (FIGS. 4 and 6).

Moreover, lever means such as

levers

124 and 125 are disposed between the bar 117 and the

bimetal elements

99 and 101, respectively. The

levers

124 and 125 are molded members of electrically insulating material and have similar tapered pivot points 126 seated in V- shaped notches 128 at opposite ends of the bar 117. As shown in FIG. 6 the

levers

124 and 125 extend through the spaces between the

bimetal elements

99, 100, and 101 and the end portions 130 of the levers are disposed behind or on the side of the element 100 remote from the bar 117. Each

lever

124 and 125 includes a projection 131 that contacts the element 100. Each

lever

124 and 125 also includes a projection 132 that contacts the

bimetal elements

99 and 101.

Two springs 127, each of which is disposed at one end in a depression 219 (FIG. 5) in the cross bar 117, and at the other end against stop means molded integrally with the housing part 7, are provided to bias the cross bar 117 against the pivots 113 and also against the actuating bimetal element 100. The insulating barrier 133 fits between the insulating barriers 10 (FIG. 4) of the housing part 5 and suitable ledges formed on the housing part 7. An opening 135 (FIGS. 4 and 6) is provided in the barrier 133 to permit passage therethrough of the projection 123 of the cross bar 117. A compression spring 139 (FIGS. 3 and 6) is supported between the barrier 133 and the adjusting member 39 to bias the adjusting member 39 and operating structure 47 in a counterclockwise (FIG. 6) direction about the pivot 43.

Each of the pole units of the relay 3 comprises a controlling circuit comprising a conducting terminal strip 141 (FIGS. 1-3) that is secured to the housing part 7 by means of screws 143, and a conducting terminal strip 145 that is secured to the housing part 5 by means of screws 147. Connecting means 151 is supported at the free end of each of the terminal strips 141, and connecting means 153 is supported at the free end of each of the strips 145, both of which connecting means 151 and 153 are provided in order to enable connection of the relay 3 in an electric circuit.

In each pole unit, the terminal strips 141 and 145 are bridged by a removable heater member indicated generally at 161 in FIGS. 1 and 3, and shown in detail in FIGS. 7 and 8. For the purpose of this invention, each pole unit, or only the two outside units may be provided with a heater member 161. By providing a metal jumper 161a between the

terminal strips

141 and 145, one heater member 161 may be omitted for the middle bimetal element 100 without altering the effective operation of the device as will be set forth below. As shown in FIG. 3, when the

housing parts

5 and 7 are secured together, a separate opening 162 for each pole unit is formed in proximity to the

terminal conductors

141 and 145, with the adjacent openings being separated by cooperating insulating barriers of the

housing parts

5 and 7. The openings 162 provide access to enable the heater members 161 to extend into the internal compartment.

As shown in FIGS. 7 and 8, each of the heater members 161 comprises a generally L-shaped and rigid conducting support wire 163 and an insulating spacing member 165 which

members

163 and 165 are held together by a conducting rivet type eyelet 167. A generally cylindrical electrically insulating tube 169 is disposed over the lower end of the wire 163 and held in position by means of engagement of the lower end thereof with another wire 171 that is brazed to the lower end of the support wire 163. The wire 171 is a helical type heater wire that is disposed over the insulating tube 169 and is brazed at the other end thereof to a conductor 173 that is supported on the insulating spacer 165. The conductor 173 is secured to the spacer 165 by means of a rivet-type conducting eyelet member 175. The insulating tube 169 is preferably a ceramic member to better withstand heat. The heater member comprises the rigid supporting wire 163 that also serves as part of the electric circuit through the heater member 161.

As is best seen in FIGS. 1 and 3, each of the replaceable heater members 161 is secured to a pair of the

terminals

141 and 145 by means of screws 181 and 183, respectively. When the heater members 161 are in place, the controlling circuit through the outside pole unit of the relay 3 extends from a conductor that would be connected to the terminal conducting strip 141 by the connecting structure 151, through the terminal 141, the supporting conductor 163 (FIG. 7), the heating conductor 171, the conductor 173, the terminal strip 145, to a conductor that would be connected to the terminal strip 145 by the connecting means 153.

In operation, the middle or intermediate bimetal element 100 is in direct contact with the projection 121 of the cross bar 117. The outside bimetal elements 99 are in indirect contact with the cross bar 117 by means of the

levers

124 and 125. When only the two outside

bimetal elements

99 and 101 are heated by heater elements, the lever 124 rotates substantially counterclockwise about its projection 131. Likewise, the lever 125 rotates substantially clockwise about its projection 131. Under overload conditions, the cross bar 117 moves far enough that the projection 123 operates to control the switch. Though the middle bimetal element 100 may not be provided with a heater element, actually the element moves a small amount due to stray heat and mechanical pressure at the projections 131.

However, when a heater element is added to heat the middle bimetal element 100, the element 100 moves much further to thereby shift the locations of the projections 131. As a result, the outside

bimetal elements

99 and 101 must then travel further in order to cause the cross bar 117 to move far enough to operate the control switch. This action compensates for the increased heat produced by the third heater, so that by the proper choice of dimensions of the

levers

124 and 125 and by proper calibrating limits, the trip current rating can be made essentially the same whether two or three heater elements are employed. Accordingly, this invention accomplished the objective of a thermal overload relay employing two heater elements to which a third heater element can be added without significantly changing the trip current rating.

During movement of the cross bar 117, the projection 123 (FIG. 4) moves to move the compensating bimetal member 51 clockwise (FIG. 6) about the pivot 55. This clockwise (FIG. 6) movement of the bimetal 51 effects a clockwise movement of the operating structure 47 (FIG. 6) about the pivot 55, during which movement, the projection 50 (FIGS. 5 and 6) on the operating structure 47 engages the contact arm 27 to move the contact arm 27 clockwise about the pivots 31, during which movement the spring 33 passes to an over-center position to snap the movable contact arm 27 clockwise to a position wherein the contacts 29 engage the stationary contacts (FIG. 6).

As shown in FIG. 6, the contacts 29 are disposed on each of two opposite sides of the contact arm 27. Thereafter, if the relay is set for a hand-resetting operation, the resetting bar 89 can be manually depressed against the bias of a compression spring 193 (FIG. 4), which spring is disposed between a lower ledge 195 on the insulating housing part 7 and an upper ledge 197 on the reset bar 89, during which movement the lower end 201 (FIG. 5) of the reset bar 89 operates to flex the resilient conducting arm 81 upward (FIG. 6), which movement, because of the engagement of the contacts 85 on the resilient contact arm 81 with the contacts 29 on the movable contact arm 27, rotates the movable contact arm 27 in a counterclockwise direction about the pivots 31 whereupon the overcenter spring 33 moves overcenter to snap the contact arm 27 in a clockwise direction back to the position in which it is seen in FIG. 6.

If the predetermined current persists in the pole unit I which plate 202 engages a ledge on the reset bar 89 to 7 move the bar 89 downward to a lower position. The plate 202 and bar 89 are retained in the lower automatic position by means of a screw 205 (FIG. 2). Thereafter, after the operating structure has been operated to move the contacts 29 into engagement with the contacts 85, the position of the flexed contact arm 81 (FIGS. 5 and 6) is a position that holds the movable contact arm and the spring 33 from going overcenter so that the spring 33 will automatically move the contact arm 27 back into engagement with the stationary contact 75 when the

bimetal elements

99, or 101 has cooled and flexed back to the position wherein the projection 50 (FIGS. 5 and 6) on the operating structure 47 no longer biases the contact arm 27 into the actuated position.

When the parts of the relay are in the position seen in FIG. 6, and conductors are connected to the terminals 21 and 70 (FIGS. 2 and 6) by means of the

screws

25 and 71, the relay is in a normally closed position. When the relay is in this normally closed position, a circuit extends from the terminal 21 (FIG. 6), through the conducting bracket 19, the movable contact arm 27, the movable contacts 29, the stationary contacts 65, the stationary contact arm 63, the stationary contact structure 61, to the terminal strip 67. When the relay is actuated to the other operating position previously described, in which position the movable contacts 29 are disengaged the stationary contacts 85, the relay is moved actuated to an open position, and, thereafter, the relay is reset either manually or automatically back to the closed position in the manner previously described.

The relay could also be wired to be a normally open relay by merely connecting the conducting lines to the terminals 21 and 79 (FIG. 6) by means of the screws 25 and 87 (FIG. 2). When the relay is so wired, and the parts are in the position seen in FIG. 6, the controlled circuit is normally open, and, when the structure is actuated to move the contacts 29 into engagement with the contacts 85, a circuit is closed from the terminal 21, through the conducting bracket 19, the movable contact arm 27, the movable contacts 29, the stationary contacts 85, the resilient stationary contact arm 81, to the terminal strip 79. Thus, when the parts of the relay are in the position seen in FIG. 6, the controlled circuit is normally open and is actuated to the closed position from which it is reset back to the open position seen in FIG. 6.

The relay 3 is adjustable to be actuated by different values of current, within a certain range, by rotation of an adjusting cam knob 209 (FIG. 6) having a cam surface 211 at the inner end thereof. As can be seen in FIG. 3, the knob 209 has a shaft 213 at the center thereof which shaft is rotatably supported on the housing part 7. A compression spring 215 is provided to bias the knob 209 to the right as seen in FIG. 3, to hold the knob in position on the housing part 7. When the parts are assembled, the cam surface 211 of the adjusting knob 209 engages an extension 215 (FIG. 5) on the support member 39. Upon rotation of the knob 209, the cam surface 21 1 operates against the extension 215 (FIG. 6) to move the member 39 about the pivot 43, against the bias of the spring 139, to thereby move the pivot 55 and, therefore, the operating structure 47 and compensating bimetal 51 about the pivot 43, during which movement, the bimetal arm 51 of the operating structure 47 is moved to vary the initial position of the bimetal arm 51 relative to the extension 123 on the cross bar 1 17 Thus, the adjustment provides that varying degrees of movement of the actuating bimetal 101 will move the spring 33 and movable contact arm 27 to the actuated position.

The adjustment provided by the adjusting knob 209 is an adjustment within a limited range. The relay can be adjusted within a larger range by providing different rated replaceable heater members 161 in the relay. As was previously described, each of the heater members 161 is readily removable from the assembled relay so that these members can be replaced by other heater members that are constructed with either higher or lower heat generating characteristics. Thus, the amount of heat generated in the controlling circuit can be varied by replacing the heater members 161. The differently rated heater members can be provided to provide differently rated relays and the adjusting knob 209 can be operated to provide an additional plus or minus adjustment of any particular rated relay.

The relay is also provided with means to compensate for changes in ambient temperature. As can be seen in FIG. 6, the operating structure 13 is actuated by deflection of any of the

bimetal elements

99, 100 or 101, which deflection pivots the cross bar 117 to operate against the compensating bimetal 51. The highexpansion sides of the bimetal element and also of the compensating bimetal 51 are the upper sides, as viewed in FIG. 6. Thus, upon a rise in ambient temperature, if one of the actuating

bimetal elements

99, or 101 is flexed downward (FIG. 6) the compensating bimetal member 51 will also be flexed downward to provide that there will be no effective variance of the operating characteristics of the relay. Thereafter, if the ambient temperature drops, both of the bimetal elements 99-101 and 51 will be flexed upward to provide that this variance of the ambient temperature will not substantially affect the operating characteristics of the relay.

Accordingly, the thermally electric control device of this invention provides for a thermal overload relay employing two heater elements to which a third heater element can be added without significantly changing the trip current rating. This objective is accomplished in a relatively uncomplicated manner, at no increase in space required, and at relatively small cost.

What is claimed is:

1. An electric control device comprising a stationary contact, a movable contact, means for operating the contacts between open and closed positions, three pole units, each pole unit comprising an actuating bimetal element, an actuating bar common to all of the bimetal elements, the bimetal elements being spaced apart and on one side of the actuating bar, a first lever between the bar and one of the outer bimetal elements, a second lever between the bar and the other of the outer bimetal elements, each lever having one end portion in pivotal contact with the actuating bar and having another end portion in pivotal contact with the intermediate bimetal element on the side thereof opposite the actuating bar, and each lever having an intermediate portion in pivotal contact with the corresponding outer bimetal element and on the side thereof facing the actuating bar, whereby movement of at least one of the outer bimetal elements toward the actuating bar in response to a thermal overload relative to the intermediate bimetal element causes the contacts to move to the open position.

2. The electrical control device of claim 1 in which one lever extends between the intermediate bimetal element and one outer bimetal element which contacts said lever and the other lever extends between the intermediate bimetal element and the other outer bimetal element.

3. The electrical control device of claim 1 in which the movable contact is supported for movement about a first axis and the actuating bar being movable about a second axis.

4. The electrical control device of claim 1 in which the actuating bar is in contact with the intermediate bimetal element.

5. The electrical control device of claim 4 in which the actuating bar has end portions extending beyond the outer bimetal elements, and in which the levers are pivotally mounted on opposite end portions of the actu-

Claims

5. The electrical control device of claim 4 in which the actuating bar has end portions extending beyond the outer bimetal elements, and in which the levers are pivotally mounted on opposite end portions of the actuating bar.