US3723924A - Shunt trip and undervoltage device - Google Patents

Abstract

Undervoltage and shunt trip units for a multi-phase molded case circuit breaker are each constructed with a primary latch operated by the armature of an electromagnet. The primary latch acts through a secondary latch to hold an intermediate member in latched position, wherein the latter holds an actuator in its inactive position. When the latches are released to release the intermediate member, a coiled tension spring acting directly upon the actuator moves the latter to a tripping position to trip the contact latching mechanism of the circuit breaker. Another spring, separate from the actuator operating spring, biases the magnet armature away from the magnet yoke so that adjustment of the armature spring will not alter the force with which the actuator is moved to its tripping position.

Description

United States Patent 1 Shaffer et al.

[54] SHUNT TRIP AND UNDERVOLTAGE DEVICE [75] Inventors: Howard R. Shaffer, Glenside, Pa.;

Albert Strobel, Cherry Hill, NJ.

[58] Field of Search ..335/20, 7, 169, 170, 174, 21

[56] References Cited I UNITED, STATES PATENTS 6/1967 Shaffer .....335/20 3,175,064 3/1965 Myers..... 1,292,651 l/19l9 Rippl ..335/7 [4 1 Mar. 27, 1973 FOREIGN PATENTS OR APPLICATIONS Primary Examinerl-lar0ld Broome Attorney-Ostrolenk, Faber, Gerb & Soffen [57] ABSTRACT Undervoltage and shunt trip units for a multi-phase molded case circuit breaker are each constructed with a primary latch operated by the armature of an electromagnet. The primary latch acts through a secondary latch to hold an intermediate member in latched position, wherein the latter holds an actuator in its inactive position. When the latches are released to release the intermediate member, a coiled tension spring acting directly upon the actuator moves the latter to a tripping position to trip the contact latching mechanism of the circuit breaker. Another spring, separate from the actuator operating spring, biases the magnetarmature away from the magnet yoke so that adjustment of the armature spring will not alter the force with which the actuator is moved to its tripping 7 position.

9 Claims, 11 Drawing Figures Great Britain .335/169 v Patented March 27, 1973 3,723,924

4 Sheets-Sheet 1 Patented March 27, 1973 4 Sheets-Sheet 2 ATTORNEYS Patented Match 27, 1973 4 Sheets-Sheet 5 ATTORNEYS Patented March 27,'1973 4 Shoets-Sheet 4 M EUR m b E SHUNT TRIP AND UNDERVOLTAGE DEVICE This invention relates to molded case circuit breakers in general, and more particularly relates to constructions for auxiliary undervoltage and shunt trip units.

Shunt trip and undervoltage auxiliary units for tripping the contact holding latch of multi-phase molded case circuit breakers are disclosed in U. S. Pat. No. 3,175,064 issued Mar. 23, 1965 to F. E. Myers for f-Shunt Trip and Undervoltage Device" and U.S. Pat. No. 3,324,428 issued June 6, 1967 to H. R. Shaffer for Shockproof Shunt Trip Unit for Tripping Open the Contacts of a Circuit Breaker. Auxiliary tripping units of these types are used for the opening of a circuit breaker independently of the magnitude of load current. The undervoltage device automatically operates to trip the circuit breaker when line voltage falls below a predetermined safe level and the shunt trip device is used to open the circuit breaker from a location remote thereto.

A primary object of this invention is to provide shunt trip and undervoltage devices that incorporate most of the desirable features of similar prior art devices in a novel and improved structure. In particular, as will hereinafter be seen, auxiliary tripping units, constructed in accordance with teachings of the instant invention include the following desirable features.

1 Adjustment of the auxiliary unit is not required after mounting in a circuit breaker.

2. The auxiliary unit is readily mounted in a circuit breaker by two screws that are readily accessible for tightening at the front of the circuit breaker.

3. Undervoltage and shunt trip units are interchangeable without the necessity of adjusting any parts of the circuit breaker. I

4. The units are relatively compact.

5. The actuator for the auxiliary unit is constructed and mounted for large overtravel.

6. Adjustment of the magnet armature opening spring force is independent of the spring force which moves the actuator to its tripping position.

7. The spring which operates the actuator to its tripping position acts directly on the latter rather than through intermediate members, thereby substantially reducing sliding and other friction forces present in prior art devices having one or more members interposed between the actuator and its operating spring.

8. The pivots for all levers are on a common frame element to facilitate the holding of close tolerances between pivot centers.

9. The units are shock-proof without the addition of counterweights in that their respective armatures are balanced and pivoted at their centers.

The foregoing object and features as well as additional objects and features of the instant invention will become readily apparent after reading the following description of the accompanying drawings in which:

FIG. I is a plan view of a circuit breaker with a portion of its cover cut away to reveal an auxiliary trip unit constructed in accordance with teachings of the instant invention.

FIGS. 2 and 3 are side elevations of a shunt trip unit constructed in accordance with teachings of the instant invention. In FIG. 2 the unit is in its latched position, and in FIG. 3 the unit is tripped.

FIG. 4 is a side elevation of the primary latch member for the shunt trip unit of FIGS. 2 and 3.

FIGS. 4A and 4B are a plan view and a front elevation, respectively, of the primary latch member of FIG. 4, looking in the directions of the respective arrows 4A4A and 4B-4B.

FIG. 5 is a side elevation of an undervoltage unit constructed in accordance with teachings of the instant invention, with the unit being in its latched position.

FIG. 6 is a front elevation of the unit of FIG. 5, looking in the direction of arrows 6-6 of FIG. 5.

FIG. 7 is a side elevation of the primary latch member of FIG. 5.

FIGS. 7A and 7B are a plan view and a front elevation, respectively, of the primary latch member of FIG. 7, looking in the direction of the respective arrows 7A7A and 7B7B of FIG. 7.

Now referring to the figures. Multi-phase molded case circuit breaker 10 of FIG. 1 is provided with auxiliary shunt trip unit (FIGS. 2 and 3), secured by two machine screws 16 to the forward surface 17 of metal bracket 18 mounted to wall 19 of plastic housing 21 for replaceable trip unit 20. Shunt trip unit 15 includes an electromagnet consisting of generally U-shaped yoke 23 having one leg thereof extending through energizing coil 25 and movable armature 24 pivotally mounted at its mid-point to pin 26. Cable 27, having connector 28 at one end thereof, is connected at its other end to magnet coil 25. Cable 27 passes through washer-like strain relief member 98 mounted to the rear end of insulating arm 29 whose forward end is secured by rivets 31 to leg 32 of frame member 33.

Screw 34 extends through clearance aperture 36 in primary latch member 35 and secures the latter to the forward surface of armature 24. Clearance hole 37 in rearwardly extending leg 38 of member 35 provides clearance for pivot pin 26. One end of coiled tension spring 39 is hooked into aperture 41 in forwardly extending arm 42 of primary latch member 35. The other end of spring 39 is connected to one end of adjusting screw 43 which extends through a clearance aperture in ear 44 of frame member 33 and is threadably engaged by adjusting nut 45. Thus, it is seen that spring 39 biases armature 24 in a clockwise direction about pivot pin 26, thereby tending to form an air gap between armature 24 and pole face 46 of yoke 23, as shown in FIG. 2.

With armature 24 spaced from pole face 46, latching tip 47 of primary latch 35 engages the left lower portion 51a of secondary latch 48. The latter is pivotally mounted at pin 49 to frame member 33. In turn, the right lower extension 51 of secondary latch 48 engages hooked portion 52 of intermediate member 50, thereby maintaining the latter in its latched position shown in FIG. 2.

Intermediate member 50 is pivoted at pin 53 mounted to frame member 33. Cam surface 54 at the end of intermediate member 50 remote from hook 52 is in engagement with surface 55 of actuator 56. The latter is pivotally mounted to pin 57, also secured to frame member 33 in parallel relation to pivot pins 26, 49 and 53. Coiled tension spring 58 is secured at one end thereof directly to the rear of actuator 56 and the other end of actuator spring 58 is secured to pivot pin 53.

Bar 59 at the forward end of actuator 56 engages adjustable length extension 61, threadably mounted near the freeend of tripper bar extension 62. Lock-nut 63 maintains extension 61 in its adjusted position. When actuator 56 is released and is moved counterclockwise by spring 58, actuator ear 59 moves to the left with respect to FIG. 2 to engage extension 61, thereby pivoting common tripper bar 64 in a counterclockwise direction to release the contact holding latch means (not shown) for the overcenter spring mechanism (not shown) which operates movable contact arm 65 to bring movable contact 66 into and out of engagement with stationary contact 67.

With shunt trip unit in its latched position of FIG. 2 and contacts 66, 67 in engagement, the free end of spring element 68 extending from intermediate member 50 is spaced from contact arm 65. Energization of operating coil 25 causes armature 24 and primary latch member 35 mounted thereto to pivot in a counterclockwise direction with latch tip 47 moving forward of lower left extension 51a of secondary latch 48. The

sion 68 to pivot intermediate member 50 in a counter-- clockwise direction so that cam surface 54 acts on actuator surface 55 to pivot actuator 56 in a clockwise direction to its inactive position of FIG. 2. In addition,

after intermediate member hook 52 moves forward of secondary latch extension 51, intermediate member surface 69 engages secondary latch 48 and pivots the latter in a counterclockwise direction, so that extension 51a thereof moves clear of primary latch tip 47 and permits armature 44 to move to its fully open position of FIG. 2. Thereafter, as contact arm 65 moves to maintain intermediate member 50a in the latched position of FIG. 5 wherein cam surface 54 thereof maintains actuator 56 in its inactive position, shown in FIG. 5. With the circuit breaker contacts closed, when the voltage energizing coil a falls below a predetermined value, the flux generated by current flowing in coil 25a is insufficient to exert a holding force in excess of the opening force generated by spring 39.

Thus, the latter rotates armature 24 and primary latch member 35a carried thereby in a clockwise direction, so that primary latching tip 47a moves below secondary latch extension 51b and secondary latch 48 counterclockwise direction to operate common trip bar latch 48 counterclockwise until lower leftextension 51b thereof is clear of primary latching tip 47a. Thereafter, resetting hump 50b moves armature 24 into engagement with pole face 46. In this position of armasothat the magnet coil 25a energized sufficiently to hold armature 24 against pole face 46, as contact arm closed circuit position, the elements of shunt trip unit 15 assume the operative latching positions shown in FIG. 2.

Now referring more particularly to FIGS. 5-7B. Except for the four areas noted below, undervoltage trip unit 75 is of the same construction asshunt trip unit 15.

That is, shunt trip unit 15'does not have shading coil 74 ofundervoltage trip unit 75; latch tip 47a of undervoltage unit primary latch member 350 is different than shunt trip unit primary latch member 35; undervoltage trip unit holding coil 25a is rated for continuous duty, whereas shunt trip unit operating coil 25 is rated for intermittent duty; and shunt trip unit intermediate member 50 is not provided with hump 50b found in undervoltage unit intermediate member 50a. Hump 50b engages the rear surface of armature 24' as intermediate moves to closed circuit position the elements of undervoltage trip unit move to their respective positions'shown in FIG. 5.

It is noted that even though extension 61 of tripper bar extension 62 is illustrated as being adjustable, in practice, because of the relatively large travel of actuator ear 59, extension 61 need not be adjustably mounted to tripper bar 64.

Although there have been described preferred embodiments of this novel invention, many variations and modifications will now be apparent to those skilled in the art. Therefore, this invention is to be limited not by the specific disclosure herein but only by the, appending claims.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows.

i 1. An auxiliary unit for tripping the contacts of a circuit breaker to open position and acting independently of circuit breaker load current; said auxiliary unit including an electromagnet having a core and an armature biased toward a first position away from said core and movable to a secondposition closer to said core than said first position, a latch means operable by said armature, an intermediate member held in a latched position by engagement with said latch means, an actuator held in an inactive position by said intermediate member, and biasing means for operating said actuator to a tripping position to trip a circuit breaker contact latching mechanism when-the actuator is no longer restrained by said intermediate member; said actuator being positioned at one end of said intermediate member and said latch means being positioned at the there is a spring, independent of said biasing means other end thereof; said intermediate member being mounted intermediate its ends to a first pivot; said first pivot being closer to said one end than to said other end; a second pivot to which said armature is mounted; said latch means including a primary latch connected to said armature for movement thereby and a secondary latch held in latching position by engagement with said primary latch; said intermediate member held in said latched position by engagement with said secondary latch; a third pivot to which said secondary latch is mounted; a fourth pivot to which said actuator is mounted; and a common member to which all of said pivots are mounted.

2. An auxiliary unit as set forth in claim 1 in which the second pivot extends generally through the center of the armature.

3. An auxiliary unit as set forth in claim 1 in which biasing said armature to its said first position; and means for adjusting the loading of said spring.

4. An auxiliary unit as set forth in claim 3 in which said biasing means comprises a tension spring connected at one end to said actuator and at the other end to said first pivot.

5. An auxiliary unit as set forth in claim 1 in which the primary and secondary latches are reset by forces applied thereto through said intermediate member.

6. An auxiliary device as set forth in claim 1 in which the intermediate member is maintained in latched position when said armature is in said first position.

7. An auxiliary device as set forth in claim 1 in which the intermediate member is maintained in latched position when said armature is in said second position.

8. An auxiliary unit as set forth in claim 1 in which there is a spring extension for said intermediate member through which a relatching force is applied to said unit; said spring extension being connected to said intermediate member at a point located between said first pivot and said other end of said intermediate member.

9. An auxiliary unit as set forth in claim 8, said one end of said intermediate member engages said actuator; and a cam means at the area of engagement between said one end and said intermediate member.

Claims (9)

1. An auxiliary unit for tripping the contacts of a circuit breaker to open position and acting independently of circuit breaker load current; said auxiliary unit including an electromagnet having a core and an armature biased toward a first position away from said core and movable to a second position closer to said core than said first position, a latch means operable by said armature, an intermediate member held in a latched position by engagement with said latch means, an actuator held in an inactive position by said intermediate member, and biasing means for operating said actuator to a tripping position to trip a circuit breaker contact latching mechanism when the actuator is no longer restrained by said intermediate member; said actuator being positioned at one end of said intermediate member and said latch means being positioned at the other end thereof; said intermediate member being mounted intermediate its ends to a first pivot; said first pivot being closer to said one end than to said other end; a second pivot to which said armature is mounted; said latch means including a primary latch connected to said armature for movement thereby and a secondary latch held in latching position by engagement with said primary latch; said intermediate member held in said latched position by engagement with said secondary latch; a third pivot to which said secondary latch is mounted; a fourth pivot to which said actuator is mounted; and a common member to which all of said pivots are mounted.

2. An auxiliary unit as set forth in claim 1 in which the second pivot extends generally through the center of the armature.

3. An auxiliary unit as set forth in claim 1 in which there is a spring, independent of said biasing means, biasing said armature to its said first position; and means for adjusting the loading of said spring.

4. An auxiliary unit as set forth in claim 3 in which said biasing means comprises a tension spring connected at one end to said actuator and at the other end to said first pivot.

5. An auxiliary unit as set foRth in claim 1 in which the primary and secondary latches are reset by forces applied thereto through said intermediate member.

6. An auxiliary device as set forth in claim 1 in which the intermediate member is maintained in latched position when said armature is in said first position.

7. An auxiliary device as set forth in claim 1 in which the intermediate member is maintained in latched position when said armature is in said second position.

8. An auxiliary unit as set forth in claim 1 in which there is a spring extension for said intermediate member through which a relatching force is applied to said unit; said spring extension being connected to said intermediate member at a point located between said first pivot and said other end of said intermediate member.

9. An auxiliary unit as set forth in claim 8, said one end of said intermediate member engages said actuator; and a cam means at the area of engagement between said one end and said intermediate member.

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