US2502537A - Circuit breaker - Google Patents

Description

Patented Apr. 4, 1950 CIRCUIT BREAKER Ernst Speck, Los Angeles, Calif., assignor to Zinsco Electrical Products Company, Los Angeles, Calif.

Application November 26, 1948, Serial No. 62,045

3 Claims. 1

This invention relates generally to circuit making and breaking devices, and more particularly to electric circuit breakers which are automatically operable either thermally or magnetically in response to abnormal current overload.

An object of this invention is to provide a circuit breaker particularly adapted, although not necessarily, for use in performing its protective function in conjunction with a manually operable switch, with the invention being structurally characterized by means which insures a firm and positive physical engagement between the relatively movable contacts of the breaker under heavy spring pressure, so as to reduce electrical resistance at the contacts to a minimum, yet render the circuit breaker extremely sensitive and practically effortless in tripping in response to sustained overloads within a preselected narrow range, whereby to obtain identical and precise overload performance as well as cool operation and quick resetting of the breaker.

Another object of this invention is to provide a circuit breaker which obtains its sensitivity and dependability of operation within the narrow range of current overloads by means of a substantially frictionless latching element introducing a force reducing couple which minimizes stress at the point of latching the circuit breaker in set position, to a negligible amount as compared to the heavy friction loads imposed by heavy contact-engaging springs on trip release devices of circuit breakers heretofore proposed, which cause such breakers to run hot at near rated loads and to be sluggish and undep'endable in operation.

Another object of this invention is to provide a circuit breaker of the thermal, bi-metal type in which the mechanical force exerted by the bimetal element in tripping the breaker is greatly reduced, thereby avoiding distortion or "permanent sett of the bi-metal element and resulting inaccuracies or failure of the breaker operation With these and other objects in view, this invention resides in the combinations, arrangements and functional relationships of elements as set forth in the following specification and particularly pointed out in the appended claims.

In the accompanying drawings,

Figure 1 is: a view in side elevation, of one form of circuit breaker embo y g this invention, with a cover plate removed to show the mechanism .of the circuit breaker in set position, and withcertainpartsinsecflonforthesakeof Figure 2 is a view similar to Figure 1, with the circuit breaker in tripped position;

Figure 3 is a view similar to Figure 1, with the positions of the parts of the mechanism during the act Of resetting and immediately prior to latching in set position; and

Figures 4 and 5 are transverse sectional views taken on the lines 4-4 and 5-5, respectively, of Figure 1, and looking in the directions of the respective arrows.

Referring specifically to the drawings, this invention in its illustrated embodiment comprises a hollow base suitably formed of a molded electrical insulating compound and having an open side closed by a cover ll (Figures 4 and 5) of similar material secured to the base by suitable fastening members l2.

A U-shaped metal bracket i3 is confined in a fixed position in the base III by lugs l4, l5 and I6, and is provided with aligned, V-shaped notches II in which seat pivot lugs l8 outstruck from the sides of a U-shaped switch or contact arm it freely movable between the sides of the bracket I3 and carrying a movable contact adapted to engage a stationary contact 2| secured to a flexible bus contact 22.

A pigtail 23 electrically connects the contact arm IS with the bracket l3, and a second pigtail 24 connects the bracket with a bi-metallic or thermal trip member 25 secured to a load contact bar 26 having a wire terminal 21 provided with a wire clamping screw 28. From the foregoing, it will be clear that when the contact arm is in the extreme position shown in Figure 1 wherein the movable contact 20 engages the stationary contact 2|, that a branch circuit will be closed between the bus contact 22 and the wire terminal 21.

Interposed between the contact arm l9 and the trip member 25 is a mechanism composed of a trigger 30 pivotally mounted at one end in the base I 0 by a pin 3| and having connected thereto intermediate its ends, one end of a heavy overcenter spring 32, the other end of which is connected to a pin 33 carried by the contact arm 19. Co-acting with the trigger 30 and the trip member 25 is a latch pivotally mounted in the base ill by a pin 4!. The latch 40 is of U-shaped cross section to freely receive the trigger 30 between the sides thereof for engagement of the latching nose or tip 42 of the trigger with the keeper shoulder 43 at one end of the latch adjacent to its pivot pin 4|.

At its other end remote from the pivot pin 4|. the latch 40 is Provided with a latching toe 44 which is engageable by the free end of the flexible arm 45 of the trip member 25 so as to be retained thereby in the set position shown in Figure 1. A coil spring 48 is mounted on the pivot pin ll and has one leg 41 eng i g a cross bar I on the latch, and another leg 4| awalllll ofthebase lllsoastourgethelatch ll to its tripped position shown in Figure 2.

A segmental shaped operating member ll having a finger piece it projecting through a slot 51 in the base III, is mounted in the latter for oscillating movement about the axis of the pivot lugs II by means of arcuate flanges 5| on opposite sides of the member riding in arcuate grooves I! in the base and in the cover II. when the circuit breaker occupies its set position shown in Figure 1, movement of the operating member 55 manually in one direction or the other will actuate the contact arm is by engagement of one end it or the other end ll of the operating member with the contact arm is, so as to shift the spring 32 to one side or the other of the axis of the pivot lugs is.

Thus, the contact arm 18 will be instantly moved to one extreme position wherein the movable contact 20 engages the stationary contact II as shown in Figure 1, or another extreme position wherein the movable contact is disengaged from the stationary contact as shown in Figure 2. A ball 65 mounted in a bore 88 in the flnger piece it is urged by a spring 61 into engagement with the base lug II for coaction with cam faces I and 69 on the lug, in insuring positive and free moving action of the operating member.

When the circuit breaker occupies its tripped position shown in Figure 2, the end I of the operating member 55 is engageable by a wiping action with a cam surface It on the trigger ill to actuate the latter in resetting the circuit breaker as will be fully described later in the operation of the invention. It will also be noted that the trip member 25 is interposed between a, stationary magnet II and a movable magnet I2 pivoted at II in the base It. The movable magnet is attracted to the stationary magnet by the magnetic force created at the time of a short circuit, go as to strike and actuate the trip member 25 in order to trip the circuit breaker magnetically in the event of such a short circuit or extreme overload.

The operation of the invention is as follows:

With the circuit breaker in its set positionand the switch closed as shown in Figure 1, current will be free to flow through a branch circuit between the bus contact 22 and the terminal 21. It will be noted that although the movable contact in is being maintained in firm, positive engagement with the stationary contact II by the heavily loaded spring 32, which results in excessive friction at the point of engagement of the trigger nose 42 with the keeper shoulder 43 of the latch 40, that this friction is reduced to a negligible amount at the point of engagement of the latch toe 44 with the trip member 25. This favorable and practically frictionless latching feature is due to the introduction of a force reducing couple having a relatively short lever arm between the axis of the pivot pin 4| and the point of engagement of the trigger nose 2 with the adiacent keeper shoulder 43, and a relatively long lever arm between the axis of the pivot pin ll and the point of engagement of the latch toe II with the trip member 25.

Thus, any sustained overload, will, by heating the bimetallic trip member 25, flex same with but negligible opposition from the heavy spring loading of the contact arm ll, so as to disengage the latch toe 44 and instantly release the trigger ll which is now free to move to the position shown in Figure 2 wherein it strikes the end CI of the operating member 55. This movement of the trigger under the urging action of the spring 32 shifts the spring from one side of the axis of the pivot lugs II to the other, to thereby instantly move the contact arm I! to the position shown in this figure and open the switch.

To reset the circuit breaker, the operating member 55 is moved from the position shown in Figure 2, for wiping coaction of its end Ii with the cam surface ll of the trigger II in moving the trigger towards its latching position with respect to the keeper shoulder ll of the latch ll. As the spring 40 has swung the latch 40 to the extreme position shown in Figure 2. the trigger nose 4! is free to pass behind the keeper shoulder 48. During the flnal portion of the latching movement of the trigger, it strikes the cross bar 48 as shown in Figure 3, and swings the latch to its set position. The flexible arm 45 of the now cooled trip member 25 has been restored to its normal'position shown in Figure 1, and is suflicientl flexed by the wiping action of the latch ll during its latching movement, to be re-engaged by the toe ll of the latch so as to retain the latter in its set position shown in this flgure.

As the trigger nose 42 is now behind the keeper shoulder 43, the circuit breaker is reset with the switch open. The circuit between the bus contact 22 and the terminal 21 is now reestablished by manually moving the operating member II to its extreme position shown in Figure 1, so as to cause the contact arm I! to be moved thereby until the spring 32 over the axis of the pivot lugs II and restores the contact arm to its extreme position shown in this figure. wherein the movable contact II flrmly engages the stationary contact 2! under the heavy pressure imposed thereon by the heavily loaded spring 32.

Should a short circuit occur, the magnetic force created thereby will cause the movable magnet l2 to be drawn towards the stationary magnet II and to thus strike the flexible arm 45 of the trip member 25 so as to move same to its releasing position with respect to the latch ll, thereby tripping the circuit breaker and opening the circuit as above described. The circuit breaker is reset by restoring the operating member I! to its position shown in Figure 3 and until the latch II is I again retained in its set position by the trip member. The operating member is then moved to its position shown in Figure 1 to again close the circult.

From the foregoing description, it will be manifest that irrespective of the heavy pressure imposed by the spring 32 upon the contacts 2. and II to insure a minimum of electrical resistance .therebetween, the latch ll interposed between the trigger it and trip member It removes the high friction latching load from the trip member, so that the latter will respond with practically no opposition from the spring 32 by releasing the latch 40 within a preselected narrow range of temperatures, thus insuring trippi of the circuit breaker with great accuracy when subiected to a sustained overload, and enabling high precision calibration of the circuit breaker to be effected.

I claim:

1. A circuit breaker comprising: a base formed of electrical insulating material; a contact arm pivoted to said base and capable of being turned amass-1 through a limited arc with relation to said base to and from open and closed positions; a movable contact carried on a first end on said contact arm; a trigger on, and capable of being swung through a limited arc in relation to, said base, said trigger having a first latching nose on its free end; an overcenter tension spring having one end secured to said contact arm near said first end of said contact arm and having its other end secured to said trigger intermediate the ends thereof, said spring being so placed as to tend to hold said contact arm in both its open and closed positions; a stationary contact carried on said base in such a position as to be engaged by said movable contact when said contact arm is in its closed position; a latch pivoted on, and capable of a movement through a limited arc in relation to said base and having a keeper toe so placed on one end of said latch as to engage said first latching nose on said trigger and having a second latching nose on the other end thereof; a spring so placed as to turn said latch about the pivot of said latch in such a direction as to release said first latching nose from the restraint of said keeper toe; trip means including a trip member having one and secured to said base and a free end thereof having releasable engagement with said second latching nose; an operating handle pivoted on said base and capable of being swung in a limited arc with relation to said base to and from open and closed positions; a first projection formed on said handle and so placed that when said handle is moved to its open position, said projection moves said trigger into a position where the first latching nose of said trigger is engaged by the keeper toe of said latch and said first projection also moves said contact arm from its closed position toward its open position; a second projection formed on said handle and so placed that when said handle is moved from its open to its closed position it moves said contact arm from its open position toward said closed position; a stationary magnet engage said first latching nose on said trigger and having a second latching nose on the other end thereof; a spring so placed as to turn said latch about the pivot of said latch in such a disecured to said base; a movable magnet pivoted to said base and so placed that it can be moved toward said fixed magnet and when so moved will release said second latching nose from said trip means; and an electrical conductor through which electric current flows to said contact arm, said conductor being so placed that it induces a magnetic flux in said stationary and movable magnets and causes the free end of said movable magnet to move toward said fixed magnet.

2. A circuit breaker comprising: a base formed of electrical insulating material; a contact arm pivoted to said base and capable of being turned through a limited arc with relation to said base to and from open and closed positions; a movable contact carried on a first end on said contact arm; a trigger on, and capable of being swung through a limited arc in relation to, said base, said trigger having a first latching nose on its free end; an overcenter tension spring having one end secured to said contact arm near said first end of said contact arm and having its other end secured to said trigger intermediate the ends thereof, said spring being so placed as to tend to hold said contact arm in both its open and closed positions; a stationary contact carried on said base in such a position as to be engaged by said movable contact when said contact arm is in its closed position; a latch pivoted on, and capable of a movement through a limited arc in relation to said base and having a keeper toe so placed on one end of said latch as to rection as to release said first latching nose from the restraint of said keeper toe; trip means including a trip member having one end secured to said base and a free end thereof having releasable engagement with said second latching nose, said trip member consisting of a bimetallic strip through which passes the current passing through said stationary and movable contacts, said strip being so placed that when heated above a critical temperature its free end is released from contact with said second latching nose; an operating handle pivoted on said base and capable of being swung in a limited arc with relation to said base to and from open and closed positions; a first projection formed on said handle and so placed that when said handle is moved to its open position, said projection moves said trigger into a position where the first latching nose of said trigger is engaged by the keeper toe of said latch and said first projection also moves said contact arm from its closed position toward its open position; a second projection formed on said handle and so placed that when said handle is moved from its open to its closed position it moves said contact arm from its open position toward said closed position; a stationary magnet secured to said base; a movable magnet pivoted to said base and so placed that it can be moved toward said fixed magnet and when so moved will release said second latching nose from said trip means; and an electrical conductor through which electric current flows to said contact arm, said conductor being so placed that it induces a magnetic flux in said stationary and movable magnets and causes the free end of said movable magnet to move toward said fixed magnet.

3. A circuit breaker comprising: a base formed of electrical insulating material; a contact arm pivoted to said base and capable of being turned through a limited arc with relation to said base to and from open and closed positions; a movable contact carried on a first end on said contact arm; a trigger on, and capable of being swung through a limited arc in relation to, said base, said trigger having a first latching nose on its free end; an overcenter tension spring having one end secured to said contact arm near said first end of said contact arm and having its other end secured to said trigger intermediate the ends thereof, said spring being so placed as to tend to hold said contact arm in both its open and closed positions; a stationary contact carried on said base in such a position as to be engaged by said movable contact when said contact arm is in its closed position; a latch pivoted on, and capable of a movement through a limited arc in relation to said base and having a keeper toe so placed on one end of said latch as to engage said first latching nose on said trigger and having a second latching nose on the other end thereof; a spring so placed as to turn said latch about the pivot of said latch in such a direction as to release said first latching nose from the restraint of said keeper toe; trip means including a trip member having one end secured to said base and a free end thereof having re leasable engagement with said second latching nose; an operating handle pivoted on said base and capable of being swung in a limited arc with relation to said base to and from open and closed tions; a first projection formed on said handle so placed that when said handle is moved its open position. said projection moves said triage;- into a position where the first latching of said trizler is engaged by the keeper toe of said latch and said first projection also moves said contact arm from its closed position toward its open position; and a second projection formed on said handle and so placed that when said handle is moved from its open to its closed position it moves said contact arm from its open position toward said closed position.

ERNST BPECK.

The following references are of record in the I summons crmn file of this patent:

UNITED STATES PATENTS Number

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