US2184763A - Circuit breaker - Google Patents

Description

Dec. 26, 1939. B. P. BAKER ET AL 2,184,763

CIRCUIT BREAKER Filed NOV. v24, 1937 2 Sheets-Sheet 1 WITNESSES: INVENTOR5 2 Ben/4mm RBa/I'er {7 p W andL/a d WDger.

Dec. 26, 1939. B. P. BAKER ET AL 2,184,763

cxncun' BREAKER Filed Nov. 24, 1957 2 Sheets-Sheet 2 WITNESSES: INVENTORS t g ,7 Ben kmm PBaker 7%W ana L /ayd WDyer.

Patented Dec. 26, 1939 Arsr orrlcs omcurr BREAKER Benjamin P. Baker, Turtle Creek, andLloyd W. Dyer, Swissvale, Pa., assigncrs to Westinghouse Electric &' Manufacturing Company,

East

Pittsburgh, Pa., a corporation of Pennsylvania Application November 24, 1937, Serial No. 176,248

21 Claims.

The invention relates generally to circuit breakers, and more particularly to the contact means of circuit breakers used in controlling moderate. voltage power distribution circuits.

Circuit breakers of the above-mentioned type are usually provided with main and arcing contacts, the arcing contacts being arranged to close prior to closing of the main contacts and to open after the main contacts have opened in order 19 that all arcing Will take pla e at the arcing C011- tacts. With such contact structures considerable difficulty has been experienced due to bouncing oi the contacts during closing of the breaker,

particularly where the simpler and more econcmicaily desirable rigidly mounted or butt type contacts are employed. The bouncing of the contacts results in undesirable secondary circuit interruptions and arcing which rapidly deteriorates I the contacts and which in some cases causes the contacts to become welded together.

An'object of the. invention is the provision of a circuit breaker embodying an improved contact means.

Another object of the invention is to provide a circuit breaker embodying an improved con-- tact means which is not subject to bouncing during operation. of the breaker.

Another object of the invention is the provision of a circuit breaker embodying relatively movable main and arcing contacts and means connecting the movable main and arcing contacts to the actuating member which insures the proper sequence of operation of the contacts and which effectively prevents bouncing thereof.

Another object of the invention is the provision of circuit breaker embodying relatively movable main and arcing contacts and a meansfor connecting the movable main and arcing contacts to the actuating mechanism which retards closing of the main contacts after the arcing contacts are closed.

a novel features that are considered charactc stic of the invention are set forth inparticular in the appended claims. The invention itself, however, both as to structure and opera tion of thevarious parts of thecontact means at a certain point in the closing operation of the breaker;

Fig. Sis a fragmentary view similar to Fig. 2, illustrating the positions of the parts of the con-" The present invention constitutes a further.

development and improvement of the contact means disclosed and claimed in Patent No. 2,100,- 102 of L. W. Dyer and G. D. Gamel, issued November 23, 1937, and assigned to the assignee of this invention. The general structure of the circuit breaker illustrated in the accompanying drawings issubstantially the same as that of the circuit breaker disclosed in the aforementioned applicatiod'except that the circuit breaker, of the present invention embodies a novel means for preventing bouncing of the contacts and for retarding the final closing movement of the main movable contacts.

Referring to the drawings, and particularly.

Figure 1 thereof, the three-pole circuit breaker illustrated includes a liquid-tight tank "I, a cover 9 therefor three pairs of insulating terminal bushings ll supported on the cover 9 and extending into the tank l, stationary contact struc-.

' tures indicated generally at l3, supported by the lower ends of the terminal bushings I I, and three bridging contact assemblages indicated generally at I5, one for each pole of the breaker (only one appearing in Fig. 1')

Each of the poles oi the circuit breaker includes a pair of bushings l l, their associated stationary contact structures it and the movable bridging contact assemblage l5 which cooperates therewith. Each of the pole structures is.

insulated from the structures of the adjacent poles by a tubularmemher ll of insulating material which is suitably positioned within the lower portion of the tank l. A body is of insulating liquid, preferably 7 ability, such as oil, is c'ontainedwithin the tank l and the level of this liquid is normally maintained sufficiently high to assure that the contact means of the breaker shall be submerged therein.

Each stationary contact structure I3 includes an L shaped frame portion 2! which is soldered or otherwise rigidly .afiixed to the lower end of the conductor 23 which extends through the supporting insulating bushing H therefor, a main,

of high arc-extinguishing.

stationary contact 25 and a stationary arcing contact 21. Both of the stationary contacts 25 and 27 are rigidly secured to the L-shaped frame 2| by means of a pair of bolts 29.

Each of the movable bridging contact assemblages I5 is supported on a rod 3| of insulating material. The three rod members 3| are mechanically interconnected at their upper ends by a tie member 33 so that the three bridging contact assemblages l5 are mounted for simultaneous movement together between open and closed circuit positions. The tie member 33 is pivotally connected by means of a link 35 to a rocker arm 3! which forms a part of the actuating mechanism of the circuit breaker. The lower end of the link 35 is pivotally connected by means of a pin 39 to the tie member 33 and the upper end of the link is pivotally connected to the bifurcated end portion of the rocker arm 31 by means of a pivot pin 4|. The link 35 permits the three bridging contact assemblages to be moved up and down to open and to closed circuit position with a substantially straight line motion.

The rocking lever 31 is pivotally supported as indicated at 43 on the frame 45, the frame being secured to the cover by means of the bolts 41. The left-hand end of the rocker arm 3'! is pivotally connected by means of a link 49 to a bell crank lever 5|. The bell crank lever 5| is pivotally supported on the frame by means of a pivot pin 53, and this lever adapts the breaker for operation by either a horizontal operating rod or a vertical operating rod. The circuit breaker illustrated is adapted for operation by the vertical operating rod 55, the upper end of which is pivotally connected to an arm of the bell crank lever 5!. by means of a pivot pin 51.

The tie member 33 and the three movable bridging contact assemblages l5 mechanically connected thereto are biased downwardly to open circuit position by the force of gravity and by means of a coil spring 59 disposed between the tie member 33 and the cover 9. The tie member 33 and the connectedmovable bridging assemblages l5 are adapted to be held in closed circuit position, as shown in Fig. 1, by a latch means (not shown). The latch means is adapted to be controlled by a suitable trip device so as to be responsive to predetermined circuit conditions to effect release of the mechanism and permit opening of the breaker.

Each of the movable bridging contact assemblages l5 comprises a main contact bridging member which consists of a rigid channelshaped member 6| of conducting material having a pair of main movable contacts 63 rigidly secured thereto for engaging the cooperating main stationary contacts 25, and an arcing contact bridging member which consists of a suitably shaped bar member 65 having a pair of movable arcing contacts 61 rigidly secured thereto for engaging the cooperating stationary arcing contacts 21. The main movable contacts 63 aresecured to the bridging member 6| either by brazing or mechanical means and the movable arcing contacts 61 are mechanically connected to the arcing contact bridging member 55 by means of pairs of bolts 69.

Each of the channel-shaped main contact bridging members 6| is adapted to slidably engage a cylindrical guide member II which is mechanically connected to the lower end of the corresponding rod 3|, and each of the cylindrical guide members 1| is provided with an enlarged upper portion 13 for engaging the bridg-' ing member 6| to effect downward movement of the bridging member during a circuit opening operation. A square plate member i5 is bolted to the lower end of each of the cylindrical guide portions H for positioning the channel-shaped bridging member 6| and for preventing that member from turning with respect to the guide 1| during operation of the breaker. A spring 1'! is interposed between each of the plate members '15 and the associated channel-shaped bridging members 8|. These springs serve to bias the bridging members 6| in the direction of the cooperating stationary main contacts 25. The guide members H and the springs 11 provide a resilient lost motion connection between the main contact bridging members 6| and their corresponding operating rods 3| and the springs Tl serve to bias the main contact bridging members 6| toward their cooperating stationary contacts 25.

Each of the main contact bridging members 6| is provided with a pair of guide studs '19, the upper ends of which are screwed into the opposite ends of the channel-shaped bridging member. These studs 19 provide a support and guide means for the associated arcing contact bridging member 65. Each arcing contact bridging member 65, as pointed out above, comprises a rigidly formed bar of conducting material, and this bar is provided with suitable openings for engaging the aforementioned guide studs 19. Springs 8| are positioned on the guide studs 19 intermediate the arcing contact bridging member- 65 and adjusting nuts 53 threaded onto the lower ends of the guide studs. These springs 8| and the guide studs '39 provide a resilient lost motion connection between the arcing contact bridging member 65 and the main contact bridging member 5|. The springs also serve to bias the movable arcing contacts 61 toward their cooperating stationary arcing contacts 21.

Both the main and arcing contacts of the circuit breaker are of the desirable and inexpensive butt type, and the disposition of the contacts is such that during a circuit closing operation the arcing contacts are engaged before the main contacts engage, and during a circuit opening operation the main contacts separate prior to separation of the arcing contacts, so that all arcing takes place between the arcing contacts.

The novel means for preventing bouncing of the movable main and arcing contacts and for retarding closing of the main contacts of each pole of the breaker comprises a dashpot device indicated generally at 85, which comprises a cylinder 81, a cooperating piston 85, and a valve 9|. The cylinder is rigidly secured to the depending sides of the main contact bridging -member 6| either by welding or by mechanical means, as indicated at $5. The piston 89 is rigidly secured to the lower portion of the arcing contact bridging member 55 by means of a plurality of rivets 91. The valve 9| consists of a plate which is gravity operated to close a valve opening 93 provided in the bottom of the cylinder 81. The dashpot devices 85 utilize the insulating liquid within the tank 1 for their operation.

The operation of the circuit breaker is briefly as follows: Upon operation of the breaker actuating mechanism, either in response to an overload or other predetermined condition, the three interconnected rods 3| for the bridging contact assemblages l5 are moved downwardly by the force of gravity and by the biasing spring 59. During the initial portion of the downward movement of the rods 3! the main contact biasing springs ll expand a predetermined amount and decrease the contact pressure of the main movable contacts 63 on the stationary contacts 25. This'is due to the fact that the plates 15 which support the lower ends of the springs Ti move downwardly with the rods 3|. After the lost motion connection between the rods 3| and the main contact bridging members BI is taken up by the enlarged portions 13 of the guides H engaging the bridging members (it, the continued downward movement of the rods 3! efiects During this downward separating movement of the main contact bridging members 6 i, the'cylinde'rs iii of the dashpot devices move downwardly with the members 6! to which they are secured" The pistons. 89 of the dashpot devices 85 remain stationary since they are securedto the arcing contact bridging members 65 which are held in closed circuit position by the biasingv action of the springs 85. i The downward movement of the cylinders 8? relative to the pistons 89 effects opening of the valves 9! so that the cylinders fill up with the insulatingliquid'or oil within the tank 1'. After the resilient lost motion connections between the arcing contact bridging members 65 and the main contact bridging members ti are taken up by the engagement of the ends of the bridging members 6! with the upper portions of the arcing contact bridging members 65, the continued downward movement of the rods 3? eiTects downward movement of the arcing contact bridging members 65 and separation\ of the movable arcing contacts 6'! from the stationary arcing contacts 21. The full open circuit position oi one of the bridging contact asserob-lages iii is illustrated in Fig. 3.

In order to extinguish the serially connected arcs drawn between the movable arcing contacts 6! and the stationary arcing contacts 21, each of the stationary contact structures l3 isprovided with an arc-extinguishing means indicated genorally at 99. The arc-extinguishing means 99 may be of the same general construction as the arc-extinguishing means disclosed and claimed in the aforementioned patent of L. W; Dyer and G. D. Gamel; No. 2,100,102.

It will be noted that in the open circuit position of the breaker, the upper portions of the arcing contact bridging members 65 engage the underside of the upper portion of the main contact bridging members til, being maintained in this position by the biasing force exerted by the springs $1. The main contact biasing springs ii are in their fully expanded positions and serve to maintain the enlarged portions 13 of the guides ii in engagement with the upper surface of the main contact bridging members 6|. In this'fllil open position of the movable bridging contact assemblages, the dashpot devices'iid are in their fully expanded positions, as shown, in 3, with their cylinders 81 filled with oil. The valves have been moved by the force of gravity to closed position covering the valve openings 93.

The operation of the breaker actuating mechanism to close the breaker eiiects upward movement of the mechanically connected insulating rods 3| from the position shown in Fig. 3 to the position shown in Fig. 1' to effect upward movement of. the movable bridging contact assemblages 55. During this upward closing movement, the arcing contacts 51 of each of the bridging assemblagesfirst engage their cooperating stationary arcing contacts 21. As each rod ill continues its upward closing movement after the arcing contacts 61- have engaged the stationary arcing contacts 21, the guide 'H' and connectingplate it move upwardly relative to main contact bridging member 6! compressing the main contact biasing spring 11.

Atomic point in the closing operation, the upward movement of each main contact bridging member 6| is prevented by the dashpot device 85 so that the reactive force exerted by the main contact biasing spring I? which has been compressed is transmitted by the dashpot device 85 to the arcing contact bridging member 65 and the arcing contacts 5'! carried thereby. Thus at this point in the. closing operation, the arcing contacts are biased with considerable force against the stationary arcing contacts M by the biasing action of the main contact spring '57. This biasing action of the spring l? on the arcing contacts and the resistance offered by the liquid within the dashpot device to downward movement of the piston 89 positively prevents any bouncing of the arcing contacts 61. I

The leakage adjustment of the dashpot device 85 may be made such that the operating rods g 3 I are moved to theirv fully closed position by the breaker actuating mechanism before the main contact bridging members iii begin their upward movement relative to the arcing contact bridging members 65. The position of the parts at this point in the closing operation is illustrated in The leakage adjustment of the dashpot device 85 in the embodiment illustrated is determined by a slightly loose'fit of the piston 89 in the cylinder iii. If desired, however, the cylinder El may be provided with an adjustable restricted opening to determine the leakage adjustment of the dashpot.

After each operating rod 35 has been moved upwardly to its fully closed position the reactive TI on the main contact bridging member Eil causes upward movement of the bridging contact member ii! and the connectcdncylinder 8'! of the dashpot device til. This upward movement of the main'bridging contact member 6! is retarded movable contacts $3. In the final closed position of the breaker, the spring 'i'i exerts a considerable biasing force on the main movable contacts 63 to maintain. them in pressure engagement with the stationary contacts 25. The final closed circuit position of the breaker is illustrated in Fig. 1.

The action of the dashpotdevice 85 in addition to preventing bouncing of the movable arcing contact 6? retards upward movement of the main contact bridginginember El relative to the arcing contact bridging member iii and thus serves to prevent bouncing oi the main movable contacts 63 The provision of the resilient lost motion connection between the main contact bridging memforce exerted by the maincontact biasing spring resilient lost motion connection between the arcing contact bridging member 65 and the main contact bridging member 6!, insures the proper sequence of opening and closing of the main and arcing contacts, so that the circuit is always initially established, and finally broken, between the arcing contacts. By this means, pitting and burning of the main contacts is reduced to a minimum and the operative life of the device is considerably increased. In addition, this means permits the use of butt type contacts throughout the interrupter, eliminating the necessity of flexible shunts and providing high-pressure low-resistance contacts. The butt type contacts are less expensive and their operation is more reliable than the older forms of contacts which use shunts, flexible brushes and the like.

The dashpot device obviates one of the main objections to the use of butt type contacts by providing a simple, reliable and inexpensive means for preventing bouncing of the contacts. The dashpot device also provides a simple means for retarding closing of the main contacts after the arcing contacts have engaged, so that the closing of the main contacts may be delayed a sufficient length of time to keep them from carrying any current during an open-close-open operation of the breaker. This is a particularly desirable feature when the breaker is used in a motor circuit. In such case the initial high rush of current will be over before the main contacts engage.

While the invention has been disclosed in accordance with the provisions of, the patent statutes, it is to be understood that various changes in the structural details thereof may be made Without departing from the spirit of the invention. It is desired, therefore, that the appended claims be given the broadest reasonable construction possible in view of the prior art.

We claim as our invention:

1. In a circuit breaker, a stationary contact, a cooperating movable contact, actuating means for moving said movable contact to open and to closed circuit position and means providing a lost motion connection between said movable contact and said'actuating means which permits free limited movement of said contact relative to said actuating means during opening movement of said actuating means and which retards limited movement of said contact relative to the actuating means during closing movement of said actuating means.

2. In a circuit breaker, a rigidly mounted solid stationary contact, a cooperating rigidly mounted movable contact, actuating means for moving said movable contact to open and to closed circuit position, means connecting said movable contact to said actuating means for movement thereby and for limited movement relative thereto, and means operable to retard relative movement of said movable contact more during closing of said breaker than during opening of the breaker to prevent rebound of said movable contact during closing of the breaker.

3. In a circuit breaker, a stationary contact, a cooperating movable contact, actuating means for moving said movable contact to open and to closed circuit position, said movable contact being movable a limited amount relative to said actuating means, and means including a fluid dashpot device for opposing and retarding relative movement of said movable contact during closing of the breaker to prevent rebound of said ber' 61 and the operating rod 3!, and the second movable contact and for permitting substantially free relative movement of said movable contact during opening of the breaker.

4. In a circuit breaker, a stationary contact, a cooperating movable contact, actuating means for moving said movable contact to open and to closed circuit position, and means providing a yielding lost motion connection between said movable contact and said actuating means including means operable to oppose and retard movement of said movable contact relative to said actuating means more during closing of said breaker than during opening of the breaker to prevent rebound of the movable contact during closing of the breaker.

5. In a circuit breaker, a stationary contact, a cooperating movable contact, actuating means for moving said movable contact to open and to closed circuit position, and means providing a resilient lost motion cnnection between said movable contact and said actuating means which permits limited movement of said movable contact relative to said actuating means, and a fluid dashpot device operable to oppose and retard relative movement of said movable contact only during closing of said breaker to prevent rebound of said movable contact.

6. In a circuit breaker, stationary main and arcing contacts, cooperating movable main and arcing contacts, actuating means for moving said movable contacts to open and to closed circuit position, means providing a resilient lost motion connection between said movable contacts and said actuating means including a device which permits free limited movement of said movable main contact relative to said movable arcing contact during an opening operation and retarded limited movement of said movable con tact relative to said movable arcing contact during a closing operation after said arcing contacts have engaged.

7. In a circuit breaker, stationary main and arcing contacts, cooperating movable main and arcing contacts, actuating means for moving said movable contacts to open and to closed circuit position, means providing a resilient lost motion connection between said main movable contact and said actuating means, means providing a resilient lost motion connection between said movable arcing contact and said movable main contact which permits limited relative movement of said contacts, and a dashpot device connecting said movable main and arcing contacts for retarding relative movement of said movable contacts more during closing of said breaker than during opening of the breaker to prevent rebound of the contacts during closing of the breaker.

8. In a circuit breaker, stationary main and arcing contacts, cooperating movable main and arcing contacts, actuating means for moving said movable contacts to open and to closed circuit position, means providing a resilient lost motion connection between said main movable contact and said actuating means, means providing a resilient lost motion connection between said movable arcing contact and said movable main contact which permits limited relative movement of said contacts, and a dashpot device connecting said movable main and arcing contacts for opposing and retarding relative movement of said movable contacts during closing of the breaker and for permitting free relative movement of said movable contacts during opening of the breaker.

9. In a circuit breaker, rigidly mounted butt type stationary main and arcing contacts, cooperating butt type movable main and arcing contacts, actuating means for moving said movable contacts to open and to closed circuit position, means including a first spring for providing a resilient lost motion connection between said movable main contact and the actuating means, said spring biasing said movable main contact toward its cooperating stationary contact, means including a second spring for providing a resilient lost motion connection between said movable arcing contact and the movable main contact, said second spring biasing the movable arcing contact toward its cooperating stationary contact, and a device interconnecting said movable arcing contact and said movable main contact whichpermits free limited movement of said movable arcing contact relative to said movable main contact during an opening operation of the breaker, and which retards movement of said movable main contact relative to said movable arcing contact during a closing operation after the arcing contacts have engaged.

.10. In a circuit breaker, rigidly mounted stationary main and arcing contacts, cooperating movable main and arcing contacts, a common actuating means for moving said movable contacts to open and to closed circuit position, means including a spring for providing a resilient lost motion connection between said movable main contact and said actuating means, said spring biasing said movable main contact towards its cooperating stationary contact, means including a second spring for providing a lost motion connection between said movable contacts, said second spring biasing said movable arcing contact towards its cooperating stationary arcing contact, a dashpot device interconnecting said movable contacts operable during a closing operation when the arcing contacts engage to transmit the reactive force of said first spring to said movable arcing contact and prevent bouncing of said contact, and to thereafter gradually transfer the reactive force of said first spring to said movable m-ain contact and to retard closing of the same.

11. In a circuit breaker, rigidly mounted stationary main and arcing contacts, bridging means movable into and out of engagement therewith comprising a main contact bridging member, an arcing contact bridging member carried thereby, a common actuating member for moving said bridging members to open and to closed circuit position, a resilient lost motion connection between said main contact bridging member and said actuating member, a resilient lost motion connection between said bridging members, and means for preventing bouncing of said bridging members during operation of the breaker.

12. In a circuit breaker, rigidly mounted stationary main arcing contacts, bridging means movable into and out of engagement therewith comprising a first rigid member of conducting material having solid main contact portions for engaging said main contacts, a second rigid mem ber of conducting material having solid arcing contact portions for engaging said arcing contacts, a common actuating member for moving said rigid members to open and to closed circuit position, means including a first spring for providing a resilient lost motion connection between said first rigid member and said actuating member, said spring biasing said first rigid member toward said main contacts, means including a second spring for providing a lost motion connection between said rigid members, said second spring biasing said second rigid member toward said arcing contacts, a dashpot device interconnecting said rigid members for preventing bouncing of the rigid members and their contact portions.

13. In a circuit breaker, rigidly mounted stationary main and arcing contacts, bridging means movable into and out of engagement therewith comprising a rigid member of conducting material having solid main contact portions for engaging said main contacts, a second rigid member of conducting material having solid arcing contact portions for engaging said arcing contacts, a common actuating member for said rigid members for moving them to open and to closed circuit position, means providing a resilient lost motion connection between said first rigid member and said actuating member, means providing a resilient lost motion connection between said rigid members, and a device interconnecting said rigid members which permits free relative movement of said rigid members during a circuit opening operation of the breaker and which retards relative movement of said rigid members during a closing operation after said secondrigid member engages said arcing contacts.

14. In a. circuit breaker, rigidly mounted stationary main and arcing contacts, bridging means movable into and out of engagement therewith comprising a first rigid member of conducting material having solid main contact portions for engaging said main contacts, a second rigid member of conducting material having solid arcing contact portions for engaging said arcing contacts, a common actuating member for moving said rigid members to open and to closed circuit position, means including a first spring for providing a resilient lost motion connection between said first rigid member and said actuating member, said spring biasing said first rigid member toward said main contacts, means including a second spring for providing a lost motion connection between said rigid members, said second spring biasing said second rigid member vtoward said arcing contacts, a dashpot device interconnecting said rigid members, said device acting to prevent bouncing of said rigid members and their contact portions and to retard closing movement of said first rigid member after said second rigid member engages said arcing contacts.

15. In a circuit breaker, rigidly mounted stationary main and arcing contacts, bridging means movable into and out of engagement therewith comprising a first rigid member of conducting material having solid main contact portions for engaging said main contacts, a second rigid member of conducting material having solid arcing contact portions for engaging said arcing contacts, a common actuating member for moving said rigid members to open and to closed circuit position, means including a first spring for providing a resilient lost motion connection between said first rigid member and said actuating member, said spring biasing said first rigid member toward said main contacts, means including a second spring for providing a lost motion connection between said rigid members, said second spring biasing said second rigid member toward said arcing contacts, a dashpot device interconnecting said rigid members, said device acting to transmit the reactive force of said first spring to said second rigid member when it engages said arcing contacts to prevent bouncing of the same, and to thereafter gradually transfer the reactive force of said first spring to said first rigid member to permit closing movement of the same with a predetermined time delay.

16. In a circuit breaker, rigidly mounted stationary main and arcing contacts, bridging means movable into and out of engagement therewith comprising a main contact bridging member, an arcing contact bridging member carried thereby, a common actuating member for moving said bridging members to open and to closed circuit position, a resilient lost motion connection between said main contact bridging member and said actuating member, a resilient lost motion connection between said bridging members for permitting limited relative movement thereof, a dashpot device interconnecting said bridging members for opposing and retarding relative movement of said bridging members only during closing of said breaker.

17. In a circuit breaker, rigidly mounted stationary main and arcing contacts, bridging means movable into and out of engagement therewith comprising a main contact bridging member, an arcing contact bridging member carried thereby, a common actuating member for moving said bridging members to open and to closed circuit position, a resilient lost motion connection between said main contact bridging member and said actuating member, a resilient lost motion connection between said bridging members, a dashpot device interconnecting said bridging members for preventing bouncing thereof and for retarding closing movement of said main contact bridging member after said arcing contact bridging member engages the arcing contacts, a container for enclosing said elements and a body of insulating liquid therein, said dashpot device utilizing the liquid in said container.

18. In a circuit breaker, rigidly mounted stationary main and arcing contacts, bridging means movable into and out of engagement therewith comprising a main contact briding member, an arcing contact bridging member carried thereby, a common actuating member for moving said bridging members to open and to closed circuit position, a resilient 1051; motion connection between said main contact bridging member and said actuating member, a resilient lost motion connection between said bridging members, a dashpot device interconnecting said bridging members for preventing bouncing thereof and for retarding the final closing movement of said main contact bridging member after said actuating member is in fully closed position.

19. In a circuit breaker, a rigidly mounted stationary contact, a cooperating rigidly mounted movable contact, actuating means for moving said movable contact to open and to closed circuit position, means mounting said movable contact for limited movement relative to said actuating means and for biasing said movable contact relative to said actuating means toward said stationary contact, and means operable to oppose and retard movement of said movable contact relative to said actuating means more during closing of said breaker than during opening of the breaker to prevent rebound of said movable contact during closing of the breaker.

20. In a circuit breaker, a stationary contact, a cooperating movable contact, actuating means for moving said movable contact to open and toclosed circuit position, one of said contacts being mounted for limited movement relative to its carrier and biased relative to its carrier toward the other contact, and means operable to oppose and retard relative movement of said contact only during closing of said breaker to prevent rebound of said contacts.

21. In a circuit breaker, a stationary contact, a cooperating movable contact, actuating means for moving said movable contact to open and to closed circuit position, one of said contacts being mounted for limited movement relative to its carrier and biased relative to its carrier toward the other contact, and a dashpot device connected to said contact for opposing and retarding said relative movement of said contact during closing of said breaker to prevent rebound of said contacts during closing of the breaker, said device permitting free relative movement of the contact during opening of the breaker.

BENJAMIN P. BAKER. LLOYD W. DYER.

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