US2162534A - Circuit breaker - Google Patents

Description

June 13, 1939. IAKLE IN Em 2,162,534

0 IRCUIT BREAKER Filed April 1, 1933 WITNESSES: INVENTORS.

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ATTORNEY an am Patented June 13, 1939 UNITED STATES PATENT orr ca Charlottcnburg,

, alaignors to Westlnghouse Electric & Manufacturing Company,

East Pittsburgh, Pa., a corporation of Pennivania Application April 1, 1933. serlaiNo. 683.92! In Germany April 1, 1932 Our invention relates to circuit breakers and is particularly suitable for use with circuit breakers of the trip free type.

One object of our invention is to provide a circult breaker which shall not remain in the closed position if the engaging contacts should be burned or otherwise damaged.

Another object of our invention is to provide an improved trip free circuit breaker which shall include means for automatically opening the circuit if the cooperating contact members become incapable of carrying the normal circuit current without excessive heating.

Another object of our invention is to provide a double toggle linkage for a circuit breaker where the toggle links are in straightened position when the circuit breaker is closed and transmit a large part of the opening bias to a fixed pivot so that only a small force is transmitted to the current 10 responsive latch holding one link in closed position.

A further object of our invention is to provide an improved toggle-linkage, circuit breaker operating mechanism that shall be particularly suitable for use with circuit breakers wherein safety and reliability of operation are paramount requirements.

An additional object of our invention is to provide a latching structure for a circuit breaker .30 comprising a cylindrical latching portion normally holding a latch member, with a notch through the cylindrical latching portion to permit movement of the latch member therethrough upon rotation of the cylindrical portion. 3:, In carrying out these objects'of our invention, we prefer to provide a circuit breaker mechanism. which is biased to the open position by a constant force biasing means and which is held in the closed position partly by the reaction 10 forces resulting from the contact pressure producing means. These forces are so adjusted that any appreciable decrease in the contact pressure, which must simultaneously reduce the reaction force resulting therefrom, allows the biasin 45 means to open the breaker.

The features of our invention which we believe to be new are. particularly pointed' out in the appended claims. For a full understanding of the principles of our invention and one method 50 of applying those principles, reference may be had to the accompanying drawing and specification, wherein;

Figure 1 is an elevational view, partly in section, of a circuit breaker embodying the principal 55 features of our i ve t he a ious structural elements being shown in the open circuit position.

Fig. 2 is a sectional view on the line II-iI of Fig. I.

Fig. 3 is a sectional view on the line IIIIII 5 of Fig. 1.

Fig. 4 is diagrammatic view showing the various structural elements of the circuit breaker in the closed position, and

Fig. 5 is a diagrammatic view similar to Fig. 4 10 showing the circuit breaker in the tripped position.

In this embodiment of our invention weprovide a pivotally mounted switch member assemblage,

a toggle linkage operating mechanism, a trigger for restraining the toggle linkage in the operative position, a trip device including a latch for releasably engaging the trigger, a spring for biasing the mechanism to the open position, and. means which are partially dependent upon the pressure between the cooperating contact members for holding the mechanism closed against the action of the biasing spring.

Referring to the drawing, the circuit breaker,

- which is of the double-break, push button typ 26 includes a base I of insulating material upon which is mounted a pair 0! terminals 3, a pair of stationary contact supports 5, and the frame member 0 which supports the assemblage of switch members i, the toggle operating mechanism 8, and the trip device 0.

The assemblage of switch members 1 includes a pair of contact members Ii adapted to engage the cooperating stationary contact members it which are mounted on the contact supports 5, 5

leaf spring supports it for the contact members I l, and a switch shaft ii to which one end of each.

of the spring supports II is rigidly joined. Two

support lugs l0 and ii extend outwardly from the base member 6 and pivotally engage suitable pins 40 in the ends of the switch shaft ii. A crank member 23 is provided for connecting the assemblage of switch members I with the operating mechanism l.-

As mentioned previously, the circuit breaker is of the double break type, the current flowing in one terminal 3, through the associated support I and its contact member l3, thence through the cooperating moving contact ii, the spring support arm ii, the energizing coil 59 for the trip device 9, the other spring support arm ii, and finally through the other contacts ii and i3 and the other support 5 to the second terminal 8.

The operating mechanism 8 is of the toggle linkage type and includes a push button or handie member 25 of insulating material, a pair of toggle links 21 and 29, a trigger or cradle 31' which engages one end of the toggle linkage through a pivot pin 33, a connecting link 35 intermediate the operating handle 25 and the toggle. links 21 and 29, and a spring 31 which biases the assemblage of switch members I to is pivotally fastened to the operating handle- 25 through the agency of the pin 45. The pin 45 has the further function of acting as a stop to define the upward limit of motion of the handle 25 and its associated guide pin 39. One end of the toggle link 2'! is pivotally fastened to the crank member 23 by a pin 41. A spring 49 is positioned about the guide pin 39 and as will be explained later, is utilized to secure the automatic opening feature.

The trigger 31 is pivotally supported on a pin 5| which engages a lug 53 projecting outwardly from the frame 6, and is provided with a portion 55 ending in a latch tip for engaging the latch 51 of the trip device 9.

The trip device 9 is of the conventional solenoid type and except for the particular type of construction disclosed is not an important part of my invention. The coil 59 is supported upon the main frame 6 and is, as mentioned before, electrically connected in series between the two spring contact arms l5 so as to be responsive to the current flowing in the controlled circuit. A tube 6| having a slot 63 (Fig. 1) therein extends into the center of the coil 59, and serves as a guide means for the moving armature which is biased to the unattracted position by a suitable spring. A pin 65 which is rigidly affixed to the armature extends through the slot 63 and engages the latch actuating member 51.

The cylindrical latch shaft 51 is pivotally mounted on two lugs 59 and H projecting outwardly from the frame 6, and is biased into the latched position by the spring 13, the projection 15 serving as a stop to limit its motion. The enlarged cylindrical end of the latch shaft 51 has a latch portion 11 which engages the cooperating portion 55 of the trigger 3| and which is offset from the center of rotation of the latch proper and is thus movable to release the trigger when the latch is rotated in a clockwise direction (Figs. 1, 4 and 5). The offset latch portion 11 comprises the portion of the enlarged cylindrical end of the shaft 51 which remains after a notch is provided in the shaft extending slightly more than half-way through the shaft as shown on the drawing. The straight edge of the latch portion 55 engages the enlarged end of the shaft tangentially so that the force exerted'thereon is radially of the shaft.

The circuit breaker is closed by a downward pressure on the operating handle 25, the spring 49 being compressed and tending to move the operating handle and the knee pivot pin 43 upwardly. The toggle linkage is moved from the position shown in Figure 1 to the position shown in Figure 4. During this movement the knee pivot pin is moved below the straight line position, thus locking the contacts closed as is done by conventional toggle operated mechanism. As

the handle 25 is moveddownwardiy, the crank arm 23 is rotated counterclockwise; the trigger 3| is likewise rotated but in the clockwise direction, the end 55 engaging the latch portion i? near the end of the closing operation.

The rotation of the crank arm 23 causes a tensioning of the spring 31 and, by rotating the switch shift l1, causes the movable contact members'll to engage the stationary contact members l3 thereby bending the leaf spring contact supports l5 tosupply the necessary contact pressure. The reactive force from this stressing oi the contact supports l5 acts through the crank arm 23 and the toggle link 2? as a pressure on the knee pivot pin 43 of the toggle linkage, and,

because of the over center or locked position of the linkage, will have a component opposing the spring 49. This component in combination with the similar component resulting from the tensioning of the spring 31, is of suiiicient magnitude, when adequate contact pressure exists between the cooperating contact members H and I3, to hold the circuit breaker closed.

However, if excessive Wear, burning or other damaging agencies have so altered the contact members that proper engagement therebetween is not obtained when the operating handle 5 is moved to the closed position, the circuit breaker will open automatically as soon as the handle is released, due to the inadequacy of the force component balancing the opening spring 49. This feature is of very great value in preventing continued use of damaged switches wherein the insufiicient contact pressure may cause enough heating to constitute a dangerous fire hazard.

The opening operation under these conditions is substantially the reverse of the closing operation. The spring 49 lifts the knee pivot pin 43 above the center line of the link, the toggle then collapses upwardly drawing the trigger 3i with it, the spring 31 acting through the crank member to move the contacts to the open position. The projection 79 serves as a stop for limiting the rotation of the crank member 23.

It is important to note that movement of the assemblage of switch members 1 beyond a predetermined point is equally effective. in securing automatic opening of the circuit. This follows from the fact that the distance which the knee pivot pin 43 moves beneath the center line of the toggle is proportional to the force opposing the biasing action of the spring 59. Thus, if the assemblage of switch members I rotates sufliciently far to reduce this distance below the minimum" required to balance the kneebiasing force the breaker will not remain in the closed circuit position when the operating handle 25 is released.

In the event of an overload or other predetermined electrical condition, the coil 59 of the trip device becomes energized sufiiciently to attract its associated armature. The pin 65 (Fig. 3) engages the latch actuating member 51 and, by rotating the latch against its biasing spring 13, causes the portion 11 to disengage the trigger 3i. The entire toggle linkage is then free to move to the open position under the influence of the stressed spring supports l5 and the spring 31. If the handle is not held down the spring 49 returns the various parts of the mechanism to the position shown in Figure 1. If an attempt is made to hold the circuit breaker closed the mechanism moves, following the tripping operation, to the position shown in Figure 5, the mechanism being entirely trip free.

the operating handle 25 away from thebase l-..

The release mechanism, however, assures the rapid separation oi the engaging contact members and is the preferred method of operation.

It will thus be seen that we have disclosed an improved circuit breaker operating mechanism which automatically opens the circuit if the contact, members are burned or damaged, or if the contact pressure is inadequate to prevent dangerous overheating, and in addition, we have disclosed how this feature of our invention may be embodied into a circuit breaker oi the trip-tree Further, we have disclosed a novel circuit breaker operating mechanism of the toggle linkage type which is more reliable and more satisiactory in operation than the previously known devices.

. The prin ciples which' we have disclosed are capable of wide application to circuit breakers generally, and it is our desire that the language of the accompanying claims shall beaccorded the.

broadest reasonable construction, and that our invention shall be imited only by what is cxplicitly stated in the claims and by the prior art.

- I claim as my invention:

1. In a circuit interrupter, a stationary contact member, a movable switch means including a contact member for cooperating therewith to open and close the electrical circuit through said interrupter, spring means for supplying contact pressure between said cooperating members when said interrupter is in the closed position, and an operating mechanism for actuating said switch means, said operating mechanism including a toggle linkage, means biasing the knee of said linkage to the open circuit position, and means responsive to the contact pressure between sad m cooperating members for holding the knee of said toggle in the closed circuit position against said biasing means, said holding means being releasable and causing the movable contact member to move to open circuit position upon a predcterg mined decrease in contact pressure between said cooperating members.

2. In a circuit interrupter, a stationary contact,

cooperating with said stationary .contact for opening and closing the electrical circuit through said interrupter, and an operating mechanism for actuating said switch member, said operating mechanism including a toggle linkage, means for biasing the knee of said toggle to the open circuit position, and means operable upon change in the contact pressure between said .contacts to cause said biasing means to. move the knee of said toggle and said switch member to open circuit position. 3. In a circuit interrupter, a butt contact member, a movable switch means including a contact member for making butt engagement with said butt contact and movable to open and close the electrical circuit through said interrupter, an operating mechanism for actuating said switch means, a spring for biasing said switch means to the open position, said operating mechanism including means separate from said butt contact -members operable to locksaid switch means in the closed circuit position, and said locking means being operable only when there is a predetermined contact pressure between said butt contact members.

4. In a circuit interrupter, a stationary contact member, a pivotally supported switch member, including a contact and a. leaf spring support for said contact, for cooperating therewith to open and to close the electrical circuit through said interrupter, and an operating mechanism for actuating said switch member, said operating mechanism including a pair or toggle links pivotally joined together at one end by a knee pivot pin, the other end of one link operatively engaging said switch member and the other end or the second link engaging a releasable trigger normally held by current responsive means, spring means biasing said knee pivot pin to the open circuit position, and means responsive to the movement of said switch member beyond a predetermined point for holding the knee of said toggle in the closed circuit position against said biasing means, said knee pivot pin, when said interrupter is in the closed circuit position, being free to move under the biasing action of said spring .to the open circuit position when released by said holding means.

5. In a circuit interrupter, relatively movable contact means for opening and closing the electrical circuit through said interrupter, one oi said contact means including a switch member, spring means biasing said switch member to the open circuit position when said interrupter is in the closed circuit position, and an operating mechanism for actuating said switch member, said operating mechanism including a toggle linkage and a bell crank having one arm pivoted to one end of said toggle linkage, current responsive means normally holding the other arm of said bell crank, resilient means for biasing the knee of said toggle linkage to collapsed open circuit position when said interrupter is in' the closed circuit positiomand means whereby said spring means biasing said switch member to the open circuit position holds the knee of said toggle linkage in the closed circuit position against said knee biasing means with; said toggle links and said arm in straightened position with each making only a relatively small angle with the line between the points connected thereby, and said current responsive means being movable to release said bell crank and cause the collapse of said toggle linkage in the direction in which it is a switch member having a moving contact tor biased by said knee biasing means.

6. In a circuit interrupter, a stationary contact member, a pivotally supported switch member cooperating therewith to open and to close the electrical circuit through said interrupter, spring means biasing saidswitch member to the open circuit position when said interrupter is in the closed circuit position, an electro-responsive trip device, and an operating mechanism for actuat ing said switch member, said operating mechanism including a pair 'of toggle links'pivotally joined together at one end by a knee pivot pin, the other end of one link operatively engaging said switch member and the other end or the circuit position, and means whereby the reactive force of said spring means biasing said switch member to the open circuit position holds said knee pivot pin in the closed circuit position against said spring biasing means acting on said knee pivot pin, said knee pivot pin, when in the closed circuit position, being free to move under the biasing action of said spring means to the open circuit position when the reactive force of the said biasing means falls below a certain predetermined value.

7. In a circuit interrupter, a stationary contact member, a movable contact member for cooperating therewith to open and to close the electrical circuit through the interrupter, resilient means supplying a predetermined pressure between the cooperating contact surfaces of said contact members, the reaction force of said resilient pressure securing means biasing said movable contact member toward the open circuit position when said interrupter is in the closed circuit position, and an operating mechanism for actuating said contact means, said operating mechanism including a toggle linkage the knee of which is adapted to move to the over-center po sition when said switch means is moved to the closed circuit position, a movable member to which one end of the toggle linkage is pivoted, said movable member being biased to move to a tripped position by the force of said resilient means biasing the movable contact to open circuit position, current responsive means normally retaining said movable member against said bias and being releasable to permit said movable contact to move to open circuit position, and a spring means for biasing the knee of said linkage toward the open circuit position, said resilient means, said spring, and said linkage being so correlated that the reaction force of said resilient means holds said linkage in the over-center,-

closed circuit position, against the biasing force of 'said spring, when said circuit interrupter is in the closed circuit position and normal contact pressure exists between said cooperating contact surfaces, and being so correlated that when said contact pressure falls below a predetermined value said reaction force becomes incapable of holding said toggle linkage against movement toward the open circuit position under the biasing action of said spring.

8. In a circuit interrupter, a contact actuating member movable to an open and to a closed circuit position, means normally biasing said member to the open circuit position, a contact supported upon said contact actuating member, means biasing said contact toward the closed circuit position, at least when said interrupter is in the closed circuit position, means for holding said contact actuating member in the closed circuit position against the force of said first mentioned biasing means, and means responsive to the magnitude-of the force biasing said contact to the closed circuit position for releasing said holding means when the magnitude of the force biasing said contact to the closed circuit position becomes less than a predetermined amount.

9. In a circuit interrupter, a contact actuating member movable to an open and to a closed circuit position, means normally biasing said member to the open circuit position, a contact supported upon said contact actuating member, spring means intermediate said contact and said contact actuating member which serves to bias said contact toward the closed circuit position, at least when said interrupter is in the closed circuit position, means for holding said contact actuating member in the closed circuit position against the reaction force of said spring means, and means responsive to the magnitude of the force exerted by said spring means tending to bias said contact to the closed circuit position for releasing said holding means when the magnitude of that force becomes less than a. predetermined amount.

10. In a. circuit interrupter, a contact actuating member movable to an open and to a closed circuit position, means normally biasing said member to the open circuit position, a stationary contact, a movable contact for cooperating therewith which is supported upon said contact actuating member, resilient means for biasing said movable contact toward said stationary contact at least when said interrupter is in the closed circuit position, said cooperating contacts engaging each other with a butt type engagement when said interrupter is in the closed circuit position, means for holding said contact actuating member in the closed circuit position against the force of said first-mentioned biasing means, and means responsive to the magnitude of the force biasing said movable contact toward said stationary contact for releasing said holding means when the magnitude of the force biasing said contacts into engagement with each other becomes less than a predetermined amount.

11. In a circuit interrupter, a stationary contact member, a movable switch means including a contact member for cooperating therewith to open and close the electrical circuit through said interrupter, spring means for supplying contact pressure between said cooperating members when said interrupter is in the closed position, a second spring means biasing said movable switch means to open circuit position, an'operating mechanism for actuating said switch means, said operating mechanism including a toggle linkage connected to said switch means at all times and movable upon each movement of said switch means, a third spring means biasing the knee of said link-,

age to the open circuit position, said operating mechanism transmitting one component of the force exerted by each of the first two of said spring means to said knee of the toggle linkage for holding the knee of said. linkage against movement to open circuit position by said third spring means, and the component of force exerted n the knee of said linkage by said second spring means alone being insuflicient to prevent its movement to open circuit position whereby said third spring means moves the knee of the toggle to open circuit position upon a predetermined decrease in the force exerted by the first spring means for supplying contact pressure, and current responsive means normally in latching engagement with a part of said operating mecha nism for preventing said second spring means from automatically moving said switch means to open the circuit and movable out of engagement with said operating mechanism for initiating movement of said operating mechanism and said switch means to open circuit position.

12. ha circuit interrupter, a pair of relatively movable contacts, a movable switch member for moving one of said contacts to open and close the circuit, spring means biasing said switch member to move to open position and biasing said contacts into pressure engagement, operating means for said switch member including three links, one

of said links being pivoted to said switch member at a movable point thereon, another of said links being pivoted at a fixed point, and the third of said links being pivotally connected between the first two links, means for manually moving one of said links to move said switch member to closed position, said links when in the closed position having the pivot points connecting them only a small distance away irom the straight line between the point at which said one link is pivoted to the switch member and said fixed pivot point whereby the iorce o! the bias oi said switch member is largely transmitted to said fixed pivot point and there is only a small force tending to move the pivot points connecting the links away from said straight line, means providing a stop preventing the force of said bias from moving one of the pivot points connecting the links out of its closed position adjacent to said straight line, spring means biasing the last said pivot point of the links to move away from said stop and cause opening of the contacts, the last said spring means becoming eilective to cause opening of the contacts after there has been a predetermined decrease in the pressure between said contacts, latching means normally engaging and holding one of said links to prevent the force of the first said biasing means from moving the other pivot point connecting the links out of its closed position adjacent said straight line, and said latching means being movable upon the occurrence ot a predetermined electrical condition to disengage said link and permit the first said biasing means to move the switch member to open the circuit.

13. In a circuit interrupter, a pair of relatively movable contacts, a switch member for moving one of said contacts to open and close the circult, spring means biasing said switch member to open position, operating means for said switch member including three links, one of said links being pivoted to said switch member at a point movable with the switch member, another oi said links being pivoted at a fixed point, and the third of said links being pivotally connected at each end to one of the first two links forming two knee pivot points each movable to collapsed position, means for manually moving one of said links to move said switch member to closed position, said links when in the closed position having the knee pivot points connecting them not more than a small distance away from the straight line between the point at which said one link is pivoted to the switch member and said fixed pivot point whereby the force of the bias of said switch member is largely transmitted to said fixed pivot point and there is only a small force tending to move the knee pivot points connecting the links away from said straight line to collapsed position, means providing a stop preventing the force of said bias from moving one of the knee pivot points connecting the links from its closed position adjacent to said straight line to collapsed position, a latch member normally engaging and holding one of said links to prevent the force of said bias from moving the other of the knee pivot points from its closed position adjacent said straight line to collapsed position, and said latch member'being movable upon the occurrence of a predetermined electrical condition to disengage said link and permit the biasing means to move the switch member to open the circuit.

14. In a circuit breaker, a pair of relatively movable contacts, a switching member for moving one of said contacts to open and close the circuit, spring means biasing said switching member to move to open position, operating means for said switching member including three links forming a double toggle, one of said links being pivoted to said switching member at a point thereon which is movable with the switching member upon every movement thereof, another or said links being pivoted at a fixed point, and the third oi said links being pivotally connected at each of its ends to one 0! the first two links to form the two knees of the double toggle, actuating means by which one of said links is movable to cause normal movement of said switching member to both open and close the breaker, said double toggle when in closed position being in substantially a straight line with one knee thereof under-set, current responsive latching means normally engaging and holding one of said links to prevent said under-set knee of the toggle from moving to collapsed position, said latching means being disengageable upon the occurrence of an abnormal condition to permit said knee of the toggle to move to collapsed position and cause movement of said switching member to open position, stop means holding the other knee of the toggle in over-set position when the breaker is closed, and the last said knee being movable between said over-set and collapsed positions upon movement of .said actuating means to normally open and close the breaker without disengagement of said latching means.

15. In a circuit breaker, a pair of relatively movable contacts, a switching member for moving one of said contacts to open and close the circuit, spring means biasing said switching member to move to open position, operating means for said as switching member including a pair of pivoted toggle links and a bell crank pivotally mounted at its apex and having one arm pivoted to one end of said pair of toggle links to form a double toggle therewith, actuating means by which one of said toggle links is movable to cause normal movement of said switching member to both open and close the breaker, said double toggle when in closed position opposing opening movement of said switching member and being in a substantially straight line so as to transmit most of the force biasing said switching member through the double toggle to a fixed point and so as to leave only small forces tending to collapse the double toggle at its knee pivots, current responsive latching means normally engaging and holding the other arm of the bell crank to prevent the knee pivot between the bell crank and the first said pair 01' toggle links from moving to collapsed position, said latching means being disengageable upon the occurrence of an abnormal condition to permit the last said knee pivot to move to collapsed position and cause movement of said switching member to open position, stop means holding the knee pivot of the first said pair of toggle links in over-set position when the breaker is closed, and the last said knee pivot being movable between over-set and collapsed positions upon movement of said actuating means to normally open and close the breaker without disengagement of said latching means from said bell crank.

16. In a circuit breaker, a pair of relatively movable contacts, a switching member for moving one of said contacts to open and close the circuit, spring means biasing said switching member to move to open position, operating means for said switching member including a pair of pivoted toggle links and a bell crank pivotally mounted at its apex and having one arm pivoted to one end of said pair of toggle links to form a double toggle therewith, actuating means by which one of said toggle links is movable to cause normal movement of said switching member to both open and close the breaker, said double toggle when in closed position opposing opening movement of said switching member and being in a substantially straight line so as to transmit most of the force biasing said switching member through the double toggle to a fixed point and so as to leave only small forces tending to collapse the doubletoggle at its knee pivots, current responsive latching means normally engaging and holding the other arm of the bell crank to pre vent the knee pivot between the bell crank and the first said pair of toggle links from moving to collapsed position, said latching means being disengageable upon the occurrence of an abnormal condition to permit the last said knee pivot to move to collapsed position and cause movement of said switching member to open position, stop means holding the knee pivot of the first said pair of toggle links in over-set position when the breaker. is closed, and the last said knee pivot being movable between over-set and collapsed positions upon movement of said actuating means to normally open and close the breaker without disengagement of said latching means from said bell crank, and means for causing the knee pivot of the first said pair of toggle links to move from over-set to collapsed position upon relase of said bell crank by its latching means to cause return of said actuating means to open position and to cause re-engagementof said bell crankwith its latching means.

17. In a trip device for a circuit breaker, the combination of a rotatable trip shaft, and a pivoted latching member biased for movement from a latching to a releasing position having a latch tip normally engaging said shaft to restrain said latching member in said latching position, the pivot of said latching member and the axis of said shaft being so related that said latch tip tangentially engages said shaft to exert a substantially radial force thereon, whereby substantially no rotative movement is exerted on said shaft by said latching member, said trip shaft having a transversely extending notch therein through which said latch tip moves to said releasing position upon rotation of said trip shaft to a predetermined position.

18. In a trip device for a circuit breaker, the combination of a cylindrical trip shaft mounted for rotation about a longitudinal axis, and a pivoted latching member biased for movement from a latching to a releasing position having a latch tip normally engaging the periphery of said shaft to restrain said latching member in said latching position, the pivot of said latching member and said axis of said shaft being so related that said latch tip tangentially engages the periphery of said shaft to exert a substantially radial force thereon, whereby substantially no rotative moment is exerted on said shaft by said latching member, said trip shaft having a transversely extending notch therein through which said latch tip moves to said releasing position upon rotation of said trip shaft to a predetermined position.

19. In a trip device for a circuit breaker, the combination of a rotatable trip shaft, and a pivoted latching member biased for movement from a latching to a releasing position having a latch tip normally engaging said shaft to restrain said latching member in said latching position, the pivot of said latching member being so related to said shaft that said latch tip moves along an are passing substantially through the axis of said shaft, whereby substantially no rotative moment is exerted on said shaft by said latching member, said shaft having a transverse slot extending slightly more than half-way through said shaft so that upon rotation of said shaft to a predetermined position said latch tip is released for movement along said are to said releasing position.

20. In a trip device for a circuit breaker, the combination of a cylindrical trip shaft mounted for rotation about a longitudinal axis, and a pivoted latching member biased for movement from a latching to a releasing position having a latch tip normally engaging the periphery of said shaft to restrain said latching member in said latching position, the pivot of said latching member being so related to said axis that said latch tip moves along an arc intersecting said axis, whereby substantially no rotative moment is exerted on said shaft by said latching member, said shaft having a transverse notch therein extending more than halfway through said shaft so that said latch tip may freely move along said are when said shaft is rotated to a predetermined position to release said latching member for movement to said releasing position.

PAUL KLEIN. KURT WULS'I'EN.

DISCLAIMER 2,162,534.Paul Klein, Berlin, and Kurt Wulsten, Berlin-Charlottenburg,

Patent dated June 13, 1939. Disclaimer filed Decem- CIRCUIT BREAKER.

Germany.

ber26, 1940, by the assignee, Westinghouse Electric cf: Manufacturing Company. Hereb enters this disclaimer to claims 17, 18, 19 and 20 of the patent.

[ ial Gazette January 28, 1941.]

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