US3903493A

US3903493A - Overload relay

Info

Publication number: US3903493A
Application number: US471740A
Authority: US
Inventors: Edward L Richards; Paul R Schweinsberg; Frank D Unterberger
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1974-05-20
Filing date: 1974-05-20
Publication date: 1975-09-02
Anticipated expiration: 1992-09-02
Also published as: GB1500526A; CA1032584A

Abstract

An overload relay with a thermal tripping mechanism for releasing the separable contacts of an associated circuit interrupter in response to overload currents. The tripping mechanism comprising a latch plate and a latch lever for moving the latch plate to the unlatched position. The latch lever being biased to the latched position and being movable by one or more bimetals in the relay to the unlatched position upon the occurrence of an overload current. The latch lever being pivotally mounted on one end of an adjustment rod, the other end of which is provided with adjusting means for longitudinally moving the rod to effect a change in the spacing between the pivot point and the latch plate on one end as well as the pivot point and the point of contact of the latch lever with the bimetal.

Description

United States Patent Richards et al.

Sept. 2, 1975 l l OVERLOAD RELAY [75] Inventors: Edward L. Richards, Aliquippa;

Paul R. Schweinsberg, New Brighton; Frank D. Unterberger, Beaver, all of Pa.

[73] Assignee: Westinghouse Electric Corporation,

Pittsburgh. Pa.

[22] Filed: May 20, 1974 [2]] Appl. No.: 471,740

[52] US. Cl. 337/57; 335/42; 337/71 [51] Int. Cl.'- ..H01H 7/16 [58] Field of Search 337/55, 57, 70, 71, 72, 337/73, 74, 75, 76, 77, 82, 94; 335/10, 42, 176

[56] References Cited UNITED STATES PATENTS 3,162 739 12/1964 Klein ct al. 337/57 3,179,768 4/1965 Koval ct ill... 335/10 3,296,398 1/1967 Dowdle ct al 337/77 3,777,293 12/1973 Tuzuki 335/42 Primary ExaminerHarold Broome Attorney, Agent, or Firm-L. P. Johns I 5 7 ABSTRACT An overload relay with a thermal tripping mechanism for releasing the separable contacts of an associated circuit interrupter in response to overload currents. The tripping mechanism comprising a latch plate and a latch lever for moving the latch plate to the unlatched position. The latch lever being biased to the latched position and being movable by one or more bimetals in the relay to the unlatched position upon the occurrence of an overload current. The latch lever being pivotally mounted on one end of an adjustment rod, the other end of which is provided with adjusting means for longitudinally moving the rod to effect a change in the spacing between the pivot point and the latch plate on one end as well as the pivot point and the point of contact of the latch lever with the bi metal.

11 Claims, 3 Drawing Figures III l] T 1TH 1 55 I J 5? i l" 1 l k I, B 35 l 5.1

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OVERLOAD RELAY CROSS REFERENCE TO RELATED APPLICATIONS This invention is'related to the invention disclosed in the applications of E. J. Walker, Ser. No. 345,396, filed Mar. 27, 1973; and Edward L. Richards Ser. No. 513,370, filed Oct. 9, 1974.

BACKGROUND OF THE INVENTION 1. Field of the Invention:

This invention relates to an overload relay having a trip and a latch mechanically responsive to thermal effects incurred by abnormal currents such as overload currents and the like.

2. Description of the Prior Art:

For many years circuit interrupters have been provided which comprise overcurrent protective devices that function satisfactorily in response to abnormal currents, such as overcurrents, ground fault currents, and short circuits, that occur in an electrical distribution system. For example, a circuit breaker of that type is disclosed in US. Pat. No. 3,530,414. Although circuit breakers of that type function satisfactorily for the purposes intended, it is desirable under some circumstances to also provide for currents in excess or below the rating of the trip device of the circuit breaker. More particularly, a circuit breaker for a given rating may function entirely satisfactorily at a location which is relatively close to the current source, but function unsatisfactorily at a location which is located at a considerable distance from the current source. The difference in the circuit breaker response in the different locations is due to the differences between the voltages and current being supplied at these specific locations. It would be economically undesirable to provide a circuit breaker having specific ratings for each location along the transmission line. Accordingly, there has been a problem in providing a single circuit breaker which is adapted to functioning satisfactorily at any location along the line.

SUMMARY OF THE INVENTION In accordance with this invention it has been found that the foregoing problem may be overcome by providing a protective device for a circuit interrupter which comprises relatively movable contact means and means releasable to effect automatic openings of said contact means, the releasable means including a releasable arm movable between latched and unlatched positions, a trip device operable to effect unlatching of the releasable arm, the trip device comprising a latch plate, a trip lever, and a bimetal for each of three poles for actuating the trip lever in response to currents in excess of the rating of the trip device, the latch plates being movable by the trip lever between latched and unlatched positions, a heater for the bimetal responsive to currents in excess of the rating of the trip device, the bimetal being movable to effect movement of the trip lever to the unlatched position, adjusting means for moving the pivot point of the lever toward and away from the latch plate, the adjusting means comprising an elongated rod and a rodreceiving tubular member, inner engaging threaded means for moving the elongated rod into and out of the rod-receiving tubular member, a pivot member between the bimetal and the trip lever, the pivot member being movable by the bi metal to effect rotation of the trip lever, the trip lever being biased in a latched position of the latch plate, the pivot point of the lever being on the rod which is movable with respect to the latch plate to increase and decrease the portion of the lever between the pivot point and the latch plate as compared with the portion of lever between the pivot point and the rotation of the contact with the pivot member, and upon rotation of the tubular member in one direction, the pivot point is moved toward the latch plate and upon rotation of the tubular member in the other direction the pivot point is moved away from the latch plate.

The advantage of the device of this invention is that a circuit breaker is provided with trip device which is adapted for use in locations of varying conditions of voltage and current whereby an overload device or relay, when subjected to currents in excess of the rating of the heater element, is caused to mechanically operate a latch release plate in a linear line to open the contacts of a circuit breaker.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view, of a three-pole overload relay connected to a circuit interrupter in accordance with this invention, taken on line I-I of FIG. 2;

FIG. 2 is a plan view taken on the line IIII of FIG. 1; and

FIG. 3 is a vertical sectional view taken on the line IIIIII of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. I a three pole-circuit interrupter 5 is shown in association with an overload relay 7, both of which are mounted on a supporting base 9. The circuit interrupter 5 is preferably a three-pole structure of conventional construction, such as shown in US. Pat. No. 3,287,534, which comprises certain parts not shown in the drawings, such as pairs of cooperable contacts operable between open and closed positions, control means for opening and closing the contacts including a so-called toggle link" which in turn includes a cradle or releasable arm 11 in a housing 13 of molded electrically insulating material. In addition, the circuit breaker comprises a manually operable handle 15 by which the circuit breaker is operated between open and closed positions. The circuit interrupter 5 combined with the particular overload relay 7 provides an electrical device that is sensitive to the flow of current in specified ampere ratings to produce a mechanical force sufficient to trip open the latched contacts of the circuit interrupter.

As shown in FIG. 1, the left end of the releasable arm II is shown in latched position by reason of its connection with a latch structure generally indicated at 17. The latch structure 17 comprises a bell-crank type or latch lever 19 and a trip release plate 21. The lever 19, being pivotally mounted at 23, includes an aperture 25 in which the left end of the releasable arm I] is secured in the latch position. The right end of the lever 19 in turn is an aperture 27 at the lower end of a trip release plate 21 which is pivoted at 29. The trip release plate 21 extends through an opening 31 in a latch plate 33 (FIG. 2). When the latch plate 33 is moved to the left to the unlatched position, as set forth below, the trip release plate 21 rotates clockwise to cause the lever 19 to rotate counterclockwise and thereby unlatch the releasable arm 11 which is spring biased upwardly.

The overload relay 7 is composed of two half portions; i.e., the bimetal and tripping portions. Generally, the overload relay 7 is a three-pole structure having line terminals 35, load terminals 37, and thermal responsive means 39 (FIG. 1). The thermal responsive means 39 is disposed within the bimetal half portion within an insulating housing 41 and comprises a replaceable heater member 43, and a bimetal element 45 for each pole within the tripping half portion is a tripping unit including a cross bar 47, a trip lever 49, and adjusting means generally indicated at 51 for raising and lowering a pivot 53 of the lever 49. The tripping unit also includes the latch plate 33.

As shown in FIG. 1, the replaceable heater member 43 is a metal conductor having a specified size or diameter for a given current rating of the overload relay. The upper end of the heater member 43 is connected at 55 to the line terminal 35 and the lower end is connected to a conductor 57 the upper end of which is connected to a low terminal 37. The upper end of the bimetal element 45 is secured in place at 59 and extends downwardly therefrom in spaced relation to the heater member 43. Each pole of the relay 7 is provided with an assembly of the heater 43 and the bimetal element 45. The lower end of each bimetal 45 is located adjacent to the lower end ofa crossbar 47 which is provided at spaced intervals with a bumper 61 for engagement by a corresponding bimetal element. The crossbar 47 is composed of an electrically insulating material, is pivotally mounted at 63, and is biased in a clockwise direction by a coil spring 65. The crossbar includes a projection 67 which extends through an aperture in a barrier 69 and engages the lower end of the lever 49.

In accordance with this invention, the pivot 53 is secured in the lower end of an adjustment rod 71. The adjustment rod 71 is a part of the adjusting means 51 which also includes a rotatable knob 73 having an integral tubular member or barrel 75. A prescribed spiral groove or female thread 77 is provided in the bore of the tube member 75 and engages the groove. The upper end portion of the adjustment rod 71 is disposed in the tube member 75 and a projection or pin 79 extends from the outer surface of the rod 71 and into the spiral groove 77. Thus, when the knob 73 is rotated (FIG. 2) clockwise, the rod 71 and the pivot 53 are elevated. When the knob 73 is rotated counterclockwise, the rod 71 and the pivot 53 are lowered.

More specifically, when the pivot point 53 is lower than the position shown in FIG. 1, the distance between the pivot point and the latch plate 33 to which the upper end of the lever is attached is increased and the distance between the pivot 53 and the projection 67 on the cross bar 47 is decreased. When the pivot 53 is relatively high, the relay .trips the releasable arm 11 sooner for a given current. On the other hand, when the pivot 53 is relatively low, there is a greater delay in the tripping operation for a given current.

For a specified linear displacement of the trip release plate 33 lowering the pivot point 53 requires less movement of the crossbar 47 activated by the bimetal elements 45. Conversely. raising the pivot point 53 requires more movement of the crossbar 47 and at a greater force as activated by the bimetal elements 45.

Moreover, adjusting means 51 may be used for adapting an overload relay 7 of a specified rating to variations in current passing through the replaceable heater member 43 and thereby avoid the necessity of installing a heater member 43 of a higher lower rating than would otherwise be required. By providing the trip lever 49 with the vertically movable pivot point 53 adjustment for greater or lesser amounts of current passing through the heater member 43 may be made to attain the desired tripping condition. Accordingly, when the current passing through the heater member 43 is greater than normal, such as when the combination of the circuit breaker 5 and the overload relay 7 are installed at a location of great distance from the source of current, the pivot 53 may be raised to adjust for the increase heating effect of the heater member 43. On the other hand, when the current passing through the heater member 43 is less than normal, it is desirable to rotate the knob 73 counterclockwise in order to lower the pivot 53 and achieve a delayed tripping action. In addition to avoiding burnouts of related electrical equipment including associated circuit breaker 5 a device of this invention provides for the avoidance of nuisance tripping.

As shown in FIG. 3, a bias spring 81 is provided on the lever 49 at the location of the pivot 53 in order to rotate the lever in a clockwise direction against the projection 67 and in order to maintain the latch plate 33 in the latch position with respect to the trip release plate 21.

In summary, operating the overload relay 7 to close its three pole contacts permits the flow of current through the current parts and through the heater elements of the overload latch release unit. Current in excess of the element ratings produces an excess of heat generated by the members 43. The heat affects the bimetal elements 43 to cause their unsupported ends to deflect in the direction of the crossbar 47. The force of deflection is impressed on the crossbar which transmits its force and movement to the lower leg of the lever 49. As the lower leg is radially moved by the crossbar, a ratioed movement in the opposite direction occurs in the upper leg. This movement of the upper leg draws the linear movable plate deeper within the housing interior. That movement of the protruding plate and the magnitude of the force so exerted is the capability of this unit to trip open the suitable latch mechanisms of associated latched electrical devices. The degree of force required and length of travel required to delatch sundry latched electrical devices will vary in most instances. To achieve this result, the degree of off-set in the legs of the lever would be altered suitably and the rate of adjustment of the pivot location would be re solved as necessary to suit each such latched device requirements.

Accordingly, the device of this invention facilitates the operation of an overload relay and associated circuit breaker by providing for current flowing through the heaters at a rate in excess of the rating of the heatcrs and thereby radiate heat to the bimetal element. The heat causes deflection of the bimetal elements to move the crossbar which extends to the lower side of the trip lever. Partial rotation of the lever produces a counter-rotation to the upper end thereof to mobilize an attached latch release plate which protrudes from a housing. A specified movement of the latch plate causes the latching of the associated latch device and circuit breaker. Partial rotation, clockwise or counterclockwise, of the adjustment knob will raise or lower the adjusting rod to thereby reposition the pivot of the trip lever. Repositioning of the pivot point results in a plus or minus adjustment of the current rating of the heater members.

What is claimed is:

l. A circuit interrupting device comprising relatively movable contact means and means releasable to effect automatic opening of said contact means, the releasable means including a releasable arm movable between latched and unlatched positions, a trip device operable to effect unlatching of the releasable arm, the trip device comprising a latch plate, a trip lever, and bimetal means for actuating the trip lever in response to currents in excess of the rating of the trip device, the latch plate being movable by the trip lever between latched and unlatched position, the bimetal means comprising a bimetal and a heater therefor, the bimetal being movable to effect movement of the lever to the unlatched position, the trip lever having a pivot point, and adjusting means operatively connected to the trip lever for moving the pivot point of the lever toward and away from the latch plate in order to adjust the trip characteristics of the relay.

2. The device of claim 1 in which the adjusting means comprises an adjusting member supporting the pivot point of the lever, and the adjusting member being movable in a direction substantially normal to the latch plate.

3. The device of claim 1 in which the adjusting means comprises an elongated rod and a rod-receiving tubular, and interengaging threaded means for moving the pivot point in a direction perpendicular to the direction of travel of latch plate.

4. The device of claim 3 in which the bimetal means comprise a pivot member between the bimetal and the trip lever, the pivot member being movable by the bimetal to effect rotation of the trip lever, and the trip lever being biased in the latched position of the trip plate.

5. The device of claim 4 in which the pivot point of the lever is movable to increase and decrease the portion of the lever between the pivot point and the latch plate as compared with the portion of the lever between the pivot point and the location of Contact with the pivot member.

6. The devices of claim 5 in which the rotation of the tubular member in one direction moves the pivot point toward the latch plate and rotation of the tubular member in the other direction moves the pivot point away from the latch plate.

7. The device of claim 6 in which the trip lever is pivotally mounted on the lower end of the elongated rod.

8. A circuit interrupting device comprising relatively movable contact means and means releasable to effect automatic opening of said contact means, the releasable means comprising a releasable arm movable between latched and unlatched positions, a trip device operable to effect unlatching of the releasable arm, the trip device comprising a latch lever, a trip plate, a latch plate, a trip lever, and bimetal means which are sequentially interconnected for actuating the latch lever in response to currents in excess of the rating of the trip device, the latch lever being operable to effect unlatching of the releasable arm, the latch lever comprising one latching end portion latchingly engaging the trip plate and a second end portion for latchingly engaging the releasable arm, the trip lever being rotatable to move the latch plate, and the latch plate being slidable for rotating the trip plate out oflatching position of the latch lever for release of the releasable arm.

9. The circuit interrupting device of claim 8 in which the latch plate is operatively connected at one end to the trip lever and is provided at the other end with opening means, and the trip plate extending through the opening means.

10. The circuit interrupting device of claim 8 in which the trip plate comprises a first aperture in which the latch lever is disposed when the releasable arm is in the latched position.

11. The circuit interrupting device of claim 10 in which the latch lever comprises a second aperture in which the releasable arm is disposed when the arm is in the latched position.

Claims

1. A circuit interrupting device comprising relatively movable contact means and means releasable to effect automatic opening of said contact means, the releasable means including a releasable arm movable between latched and unlatched positions, a trip device operable to effect unlatching of the releasable arm, the trip device comprising a latch plate, a trip lever, and bimetal means for actuating the trip lever in response to currents in excess of the rating of the trip device, the latch plate being movable by the trip lever between latched and unlatched position, the bimetal means comprising a bimetal and a heater therefor, the bimetal being movable to effect movement of the lever to the unlatched position, the trip lever having a pivot point, and aDjusting means operatively connected to the trip lever for moving the pivot point of the lever toward and away from the latch plate in order to adjust the trip characteristics of the relay.

8. A circuit interrupting device comprising relatively movable contact means and means releasable to effect automatic opening of said contact means, the releasable means comprising a releasable arm movable between latched and unlatched positions, a trip device operable to effect unlatching of the releasable arm, the trip device comprising a latch lever, a trip plate, a latch plate, a trip lever, and bimetal means which are sequentially interconnected for actuating the latch lever in response to currents in excess of the rating of the trip device, the latch lever being operable to effect unlatching of the releasable arm, the latch lever comprising one latching end portion latchingly engaging the trip plate and a second end portion for latchingly engaging the releasable arm, the trip lever being rotatable to move the latch plate, and the latch plate being slidable for rotating the trip plate out of latching position of the latch lever for release of the releasable arm.