US2348896A - Circuit breaker - Google Patents

Description

May 16, 1944.

R. H. GIBSON ETI'AL CIRCUIT BREAKER Filed Aug. 14, 1945 2 Sheets-Sheet 1 Ollllllrll IN VEN TORS ROBERT 19.67560 & W/LL/A/V 5. mac/(m A TTOHNE Y May 16, 1944. GIBSON ET AL 2,348,896

CIRCUIT BREAKER Filed Aug. 14, 1943 2 Sheets-Sheet 2 IN VEN TORS ATTORNEY Patented May 16, 1944 UNITED STATES PATENT OFFIQE 2,348,896 cmcm'r BREAKER Robert H. Gibson, Springfield, Mass, and William D. Crocker, Sufiield, Conn, assig'nors to American Bosch Corporation, Springfield, Mass, a corporation of New Yorlr.

Application August 14, 1943, Serial No. 498,628

12 Claims.

This invention relates to circuit breakers for electric circuits, and more particularly to those the hammer or percussion type in which one of the cooperative contacts in the electrical circuit is mounted on a defiectable lever that is intermittently deflected by the hammer when actu ated by a cam or other means to separate the contacts and open or otherwise modify the cir= cult, and then returned under spring pressure to reengage the contacts and, restore the circuit. Such breakers using lobed cams have been used for example in the primary circuits of ignition generators as magnetos and battery-energized timer-distributors for the internal combustion engine driving them.-

In high speed 4-stroke-cycle engines of many cylinders, as 18 cylinders operating at times at 3000 R. P. M. which is now proposed for aircraft, the breaker interruptions occur 450 times per second. This requires a breaker of higher operating speed than formerly practical with the hammer type, but still there exists substantially the same requirements of sharpness and accuracy in successive interruptions over long periods in service. One of the important factors resulting in the failure of these prior breaker operating at such high speed is due to the bouncing or chattering of the movable contact point upon its reengagement with the normally stationary contact. Various attempts to overcome this dimculty by lightening the deflectable lever, by varying its spring bias,

by cushioning its reversal of movement at the ex" treme open position, and otherwise, have not always sufllced.

In accordance with our invention, the operating speed of breakers of the hammer type is increased materially by damping or otherwise reducing the bouncing action or tendency between the interrupter contacts by means of a damping spring which preferably exerts little or no pressure on the deflectable lever except at those times when the deflectable contact thereof bounces or tends to bounce from the stationary contact upon 'reengagement thereof, and/or which also prefer- I ably exerts pressure on the deflectable lever of an increasing amount from the instant of reengagement of the contacts. At such times the damping spring not only acts quickly and effectively to break up the oscillations of the deflectable lever at the natural period thereof, or the tendency thereof to oscillate, to thereby bring about more quickly the firm reengagement of the contacts, but also it adds its stress timely and effectively to that of the deflectable lever spring to still more quickly and reliably efiect and hold such reengagement. Thus the circuit is more quickly closed at the contacts after interruption and the defiectable lever is readysooner for its next interruption. This results in a faster operating breaker and reduces the sparking and arcing at the contacts with the reduced pitting and wear consequent thereto, and also it holds the circuit closed for a greater part of the cycle between in terruptions to permit greater magnetization oi the magnetic circuit of the ignition coil of the associated magneto or battery ignition system and to thereby increase the effectiveness of the train of ignition sparks generated.

Accordingly the primary object of our invention is to provide a circuit breaker of the hammer type with high operating speed of successive interruptions, and also with a comparatively long cyclic period of intermediate closure. We accom plish this object by means of a damping spring, preferably carried by the hammer in cooperation with the deflectable lever carrying one of the con-= tacts, the deflectable lever being spring-biased in a direction to engage the contacts and the damping spring being constructed and arranged to be stressed in a direction to engage the contacts as soon as the defiectable lever contact starts or tends to bounce upon the other contact and/or preferably as soon as the contacts are first reengaged. Preferably the spring-bias of the hammer against its actuating member, whether the hammer is a spring lever of cantilever type or a spring-biased member of pivoted type or otherwise, is greater than the stress of the damping spring and in a direction to overpower the latter, the arrangement being such that the damping spring exerts little or no pressure on the deflectable lever while being actuated by or otherwise under the control of the hammer, but exerts a rapidly increasing pressure starting immediately upon reengagement of the contacts. Preferably also the hammer is away from contact with the deflectable lever during the period of contact closure, and in that eriod the damping spring exerts pressure on the deflectable lever and thereby holds the contacts closed with greater pressure while decreasing accordingly the pressure of the hammer on the cam or other actuating member.

Another object is to provide in breakers of this general type several alternative embodiments which are simple, inexpensive and compact in construction, and which are accurate, reliable and durable in operation throughout severe conditions of service. Preferably the damping spring is fastened to the hammer in a simple manner and,

overlies the deflectable lever to cooperate therewith or with insulating material carried thereby.

Other objects and advantages will appear fromv the following description of circuit breakers of our invention taken in connection with the accompanying drawings which illustrate two embodiments thereof in application as examples to breakers, for magnetos or timer-distributors, having an 18-lobe rotatable cam as the actuating member for the hammer, and a deflectable spring lever of cantilever type for carrying one of the contacts. In these drawings:

Fig. 1 shows in plan view a circuit breaker of our invention having a spring-pressed rigid hammer of the pivoted type; Fig. 2 is a top view thereof; Fig. 3 is a horizontal section, partly in elevation, through the contact-carrying deflectable lever; Fig. 4 is a section, on an enlarged scale, on line 44 of Fig. 3; Fig. 5 shows in plan view a modified form of circuit breaker having a spring hammer of cantilever type; and Figs. 6-11 show, in plan view on an enlarged scale and partly broken away, the relative positions of the hammer and contacts at successive positions of the actuating cam between adjacent valleys thereof.

' Referring first to the embodiment of Figs. 1-4, the actuating cam I is fast on shaft 2, the cam having eighteen lobes 3 with intermediate vaiieys 4 and the shaft being driven by an associated internal combustion engine through suitable gearing at cam shaft speed for an engine operating on a ii-stroke cycle. Pivoted on the stud 5. which is suitably supported from the interrupter disc or plate 6, is a hammer or percussion memher 7 of insulating material having an integral cam follower portion 8 of suitable shape and an actuating head portion 8. This follower is held continually in engagement with the cam I by the biasing spring I which is looped on the stud II fastened to the disc 6, and which at its other end is fastened to the hammer by the rivets I2. A.- deilectable spring lever I3 of cantilever type is fastened at one end to an insulated live terminal post II supported by the disc 6 and electrically connected to the condenser lead l of the well known kind. The angle bracket I6 is adapted to be fastened in adiusted position on the disc 6 by adjusting screws, in the well known way, of which one is shown at IT. The cooperative contacts I8 and I9 are riveted respectively to the defiectable lever I3 and the upright part 20 of the bracket IS. The damping spring 2| overlies the outer end of the deflectable lever l3 and is fastened on the opposite surface of the hammer by the same rivets I2 as secure the spring I0 to the cam side of the hammer I. On the end of the deflectable lever is molded a pad 22 of insulating material on which the free end of the damping spring 2i loosely rides. The metal member 23 reenforces this insulating pad and forms a washer for the riveted-over head of contact I8. The biasing spring l0 exerts considerably more pressure on the hammer in the direction of the cam I than the damping spring 2| exerts on the hammer in the other direction, at all operative positions of both springs, so that the biasing spring always overpowers the damping spring and holds the hammer in smooth sliding engagement with the cam surface at all times.

, In the position shown in Figs. 1 and 6, in which the cam follower I of the hammer I rests in the bottom of a valley 4 between cam lobes 3, the head 9 of the hammer is separated about 0.020 inch from the deflectable lever I3. At this position the biasing spring ll exerts between the hammer and cam a pressure of about 14 ounces which increases to about 18 ounces when the follower rides on the top of the lobe. The lever II is spring-biasediin a direction to engage the contacts I0 and I! when new with a pressure of about 25 ounces between them and, with the parts in the position shown in Figs. 1 and 6, this pressure between such contacts is increased to about 35 ounces by the dampingspring II which then engages the insulating pad with a pressure of about 4 ounces. It will also be observed that in this position, and in all other positions at which the damping spring 2| exerts pressure on the deflectable lever II, theoressure of the hammer on the cam is reduced accordingly and therefore the wear of the cam lobes 3 and the follower 8 is somewhat decreased and likewise the lubricating requirement for the cam is somewhat ameliorated. Of course, this separation between the hammer and deflectable lever, and these pressures, may be variously modified from those exemplary values which have been found to give satisfactory operation.

The operation of the embodiment of Figs. 1-4 is illustrated in Figs. 6-11 and will now be described with particular reference thereto. Fig. 6 shows the relation of the parts of the breaker with the cam follower I at the bottom of a valley between adjacent lobes of cam I. In this position the contacts I8, is are held engaged with a pressure therebetween of about 25 ounces due to the spring-bias of the defiectable lever I3 and the additional pressure of about 10 ounces therebetween due to the stress of the damping spring 2|, making a total of about 35 ounces. The pressure existing between the follower I and cam I is about 14 ounces due to the biasing spring I0, less about 4 ounces due to the stress of the damping spring M in the opposite direction, making a net pressure of about 10 ounces which results in reduced wear of the follower and cam and ameliorates the lubricating requirements therebetween.

Fig. 7 shows the relation of the same parts when lthe cam is rotated to a point where the cam follower is about half way between the bottom of the valley and the top of the lobe. At this instant the head 9 of the hammer just engages the defiectable lever I 3, the breaker contacts I8, I9 still being engaged. However, since the pressure of the damping spring 2| is now reduced to substantially zero, the pressure between the contacts is reduced to that of the spring bias thereon of the defiectable lever I3 alone, amounting to about 25 ounces. At this time. the pressure between the follower 8 and the cam I is increased somewhat as a result of greater stress in the biasing spring I0, and is further increased as a result of removing the oppositely directed pressure of the damping spring II. This increase in pressure tends to hold the follower in sliding contact with the cam. Also the effectiveness of the blow of the head 0 on the defiectable lever is increased as a result of the decreased pressure between the contacts I8, I0, thereby separating them more quickly and resulting in less sparking and arcing between them upon separation thereof.

During the period in which the cam is rotating from the position shown in Fig. 'l to that in Fig. 8 where the follower I is at the top of a cam lobe, the contacts II, I! are separated about 0.010 inch and the pressure of the damping spring 2| remains substantially zero. In the position shown in Fig. 8, the bias of the deflectable lever spring is increased somewhat, and likewise l0, so that the tendency the cam is resisted'more the bias of the spring of the hammer to leave strongly, and the reversal is accomplished more readily, or in other words with less overthrow than otherwise would be the case. Any tendency of, the defiectable lever to overthrow is further resisted by the resulting pressure then exerted by the damping spring 2|.

In the period between the positions shown in Figs. 8 and 9 in which the .contacts l8, is just reengage, the bias of the defiectable lever l3 and that of the spring l act together to hold the follower 8 in its descending i. In this period also, the damping spring ill". exerts substantially no pressure on the deiiectable lever. Immediately following the position shown in Fig. 9, the head 9 of the hammer starts to leave the deflectable lever l3 and there is a tendency for the contact l8 to bounce away from the contact 59, or possibly, in some cases, an actual separation. of the contacts as indicated in Fig. ill. However, this tendency oi the contact it to bounce is instantly resisted by the damping spring ii. In the-first place, the pressure of this damping spring at the contacts increases at a high rate, due primarily to the increasing separation of the head 9 from. the deflectable lever i3 secondly due to the tendency or the actuality oi the contact it to rise from the contact i9. this way chattering between the contacts is quickly suppressed if not wholly eliminated. By giving the spring 2! such form and dimensions as produce a high rate of increasing bias during the position shown in Figs. 9 and 10, it has been found that, as a practical matter, the bouncing between the contacts is substantially suppressed or eliminated. As a result thereof, not only is the sparking and arcing between the contacts materially reduces; or eliminated in this period also, but the cyclic period of closure between the contacts is increased to thereby permit greater magnetization of the magnetic circuit oi the ignition coil of the associated magneto or battery ignition system and thus increase the efiectivness of the train of ignition sparks generated.

It has been found by testswith an oscillograph that with the parts arranged as shown and having the characteristics as noted, the cranlr shaft speed of an l8-cylinder 4-stroke engine may be increased from about 2800 R. P. M. to about 3200 R. P. M. before the engine starts to miss due to ignition failure, this result being due to both the reduction 01' elimination of the bouncing or chattering between the contacts and an increase of the cyclic period of closure of the contacts. Furthermore, it has been found that the sparking and arcing between the contacts is so reduced that the contact life is materially increased.

Fig. shows the invention applied to a breaker of well known form (see Patent 1,866,492) having a spring hammer 24 of cantilever type with a cam follower 25 of insulating material. The same rivets as 26 holding the follower to the spring also secure the damping spring 21 in position to overlie the end of the deflectable lever 28. As in the first embodiment, the contacts 29, are respectively carried by the deflectable lever 28 and the stationary support 3|. Inasmuch as the stationary support 3| for the contact 30 is insulated from 'the interrupter disc or plate carrying the post 32,

it is unnecessary in this embodiment to provide an insulating pad, as 23 in Fig. 1, on the deflectable lever.

The operation of this embodiment of circuit breaker is substantially the same as that of the of the defiectable lever Ill movement against the V first embodiment and will be understood from the foregoing description thereof.

In the event of wear of the contact points, or of the cam l or follower 8, there will occur some changes in the spring pressures 'hereinbefore noted. However, the original condition may be substantially restored by adjusting the contact 19 of Fig. 1 or the entire unit of Fig. 5, in the well known ways.

It will be understood that many changes and modifications may be made in the two embodiments heroin disclosed and that many other embodiment: may be devised, without departing from. the spirit of our invention. For instance, cams having other numbers of lobes may be used, although the improvement in the operation of the breaker, as herein noted, increases as the number of lobes increases, and also the cam may be normally stationary instead oi rotatable as herein shown, while the other elements of the circuit breaker are rotatable. Also, instead of being actuated by a cam, the hammer may be actuated in any other suitable way as for. example by an electromagnet, in connection with an ignition system. or a current or voltage regulator or other electrical device employing intermittently separating contacts. Also the deflectable levers l3 and 28 may be of the pivoted rigid type instead of the cantilever spring type, in which case there would be provided a biasing spring of appropriate strength. Also the hammer of Fig. l of insulating material may be made or other suitable material or of separate parts, although the construction herein disclosed provides an unusual degree of reliability in operation as well as of simplicity, compactness and durability in construction. Also the spring stresses as specifically noted may be variously modified, the hammer l or 24 need not be arranged to part engagement with the deflectable lever l? or 28 after the circuit contacts are engaged, and the damping spring ii or 2? can be arranged to exert considerable pressure on the defiectable lever even when the hammer engages the lever but preferably such pressure as is overpowered by the spring bias of the hammer. Also, in Fig. I, the insulating pad 23 could just as well be carried by the damping spring 28 at the end thereof. These and other changes are intended to be covered by the broad terms of the appended claims.

Having thus described our invention, what we I claim is:

1. In a circuit breaker having cooperative electrical contacts, a defiectable lever which carries one of the contacts and which is spring biased in the direction to engage it with the other contact, an actuating member, a hammer whicluis spring biased in the direction to engage it with the actuating member and which is intermittently actuated by the actuating member to move the defiectable lever against its spring bias to thereby separate the contacts, and a damping spring which is carried by the hammer in cooperation with the defiectable lever and which is constructed and arranged to be stressed in a direction to reengage the contacts whenever they bounce apart upon engagement thereof.

2. In a circuit breaker having cooperative electrical contacts, a defiectable lever which carries one of the contacts and which is spring biased in the direction to engage it with the other contact, an actuating member, a hammer which is spring biased in the direction to engage it with the actuating member to move the deflectable lever against its spring bias to thereby separat the contacts, said hammer being constructed and arranged to be out of engagement with the deiiectable lever during substantially the entire period of engagement of the contacts, and a damping spring which is carried by the hammer in cooperation with the deflectable lever and which is be stressed in a direction to engage the contacts whenever the hammer is out of engagement with the deflectable lever.

3. In a circuit breaker having cooperative electrical contacts, a deflectable lever which carries onepf the contacts and which is spring biased in the direction to engage it with the other contact, an actuating member, a hammer which is spring biased in the direction to engageit with the actuating member to move the defiectable lever against its spring bias to thereby separate the contacts, and a damping spring which is carried by the hammer in cooperation with the defiectabie lever and which is constructed and arranged to be stressed in a direction to engage the contacts whenever they bounce apart upon engagement thereof, the stress of said damping spring increasing rapidly with the extent of the bounce.

4. In a circuit breaker having cooperative electrical contacts, a defies-table lever which carries one of the contacts and which is spring biased in the direction to engage it with the other contact, an actuating member, a hammer which is spring biased in the direction to engage it with the actuating member and which is intermittently actuated by the actuating member to move the deilectable lever against its spring bias to thereby separate the contacts, which is carried by the hammer in cooperation with the defiectable lever and which is constructed and arranged to be stressed in a direction to reengage the contacts whenever they bounce apart upon engagement thereof, the spring bias oi the hammer being sufficient to overpower the bias of the damping spring at all operative positions of the deflectable lever.

5. In a circuit breaker having cooperative electrical contacts, a deflectable lever which carries one of the contacts and which is spring biased in a direction to engage it with the other contact, an actuating member, a hammer which is spring biased in a direction to engage it with the actuating member and which is intermittently actuated by the actuating member fiectable lever against its spring bias to thereby separate the contacts, and a damping spring which is carried by the hammer in cooperation with the deflectable lever and which acts on the hammer in opposition to the spring bias of the hammer.

and a damping spring to move the de- 6. In acircuit breaker having cooperative electrical contacts, a defiectabie lever which carries one of the contacts and which is spring biased in a direction to engage it with the other contact, an actuating member, a hammer which is spring biased in a. direction to engage it with the actuating member and which is intermittently actuated by the actuating member to move the defiectable lever against its spring bias to thereby separate the contacts, and a damping spring which is carried by the hammer in cooperation with the defiectable lever and which-is constructed and arranged to be stressed in the direction of the spring bias of the defiectable lever and opposite to that of the hammer.

7. In a circuit breaker having cooperative electrical contacts, a defiectable lever which carries one of the contacts and which is spring biased in a direction to tact, is

defiectable lever in contact therewith.

8. In a circuit breaker having cooperative electrical contacts,

10.111 a circuit breaker electrical and a pad of insulating material between the r damping spring and the deflectable lever to eiectrically insulate them.

11. In a circuit breaker having cooperative electrical contacts, a deflectable lever which carries one of the contacts and which is spring biased in a direction to engage it with the other springs to the hammer on opposite surfaces thereof.

12, In a circuit breaker having cooperative electrical contacts, a deflectable lever which carries one of the biased in a direction to engage it with the other fastened to the hammer and which biases it in a direction to engage the hammer with the actudeflectable lever, and a pad of insulating material carried by the defiectabie lever in engagement with the damping spring to insulate them from each other.

ROBERT H. GIBSON. WILLIAM D. CROCKER.

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