US2069641A - Electric circuit interrupter - Google Patents

Description

' Feb. 2, 1937. R. E. BOLD ET AL 2,069,641

ELECTRIC CIRCUIT INTERRUP'IIER Filed July 26, 19:54

Inventor's Raf'ph E. Bold, Char-le R BTOWH, Lela-ho! S. Hobson,

Patented Feb. 2, 1937 UNITED STATES PATENT OFFICE ELECTRIC cmcorr mrEaaUP-mn Application July 26, 1934, Serial No. 737,064

ZClaims. (circa-146) Our invention relates to electric circuit interrupters, more particularly to those of the heavyduty type, as oil circuit breakers. In heavy duty operation, as for example reversing control for.

steel mill apparatus, circuit interrupters are called upon not only emciently to make and break a power circuit but to withstand many heavy-current interruptions without inspection or replacement of the contact structure. Each interruption of a high intensity are results in a certain degree of burning of the contact material which is generally coppenthereby necessitating a rugged and arc-resisting contact structure. Furthermore, the momentary current-carrying capacity of the breaker, as during a short circuit must be maintained at a high rated value.

A principal object of our invention is the provision of an improved circuit interrupter of the aforesaid type which shall have high interrupting and current-carrying capacities and be simple, rugged and durable in construction.

Our invention will be more fully set forth in the following description referring to the accompanying drawing, and the features of novelty which characterize our invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Referring to the drawing, Fig. 1 is an elevational view, partly in section, of circuit interrupter contact structure in the closed circuit position embodying our invention; Fig. 2 is an elevational fragmentary view of one pole of the circuit interrupter of Fig. 1 in the open circuit position, and'Fig. 3 is an end view, partly in section, of the apparatus shown in Fig. 2.

Fig. 1 illustrates the fixed and movable contact structure of an oil circuit breaker in the closed circuit position thereof. Thev contact structure comprises a pair of stationary or relatively fixed contact structures l and 2 electrically connected to the lead-in conductor studs 3 and 4, respectively, of the breaker and arranged to be interconnected in the closed circuit position by a movable conducting bridging member 5. The aforesaid contact structure isimmersed in a body of suitable arc-extinguishing or insulating liquid 6 and the circuit is opened and closed by means of an operating or lift rod 1 which is suitably connected to the bridging member 5 for lowering and raising the same within the oil body 6 with respect to the stationary contact structure.

The circuit breaker in its entirety is not ,disclosed in the interest of clearness, and a detailed description of the same is believed unnecessary for complete understanding of the present invention other than to point out that the circuit breaker housing or tank may, if desired, be provided with structure for effecting the well known oil blast operation wherein the break atone end of the bridging member is adjacent an exhaust passage of a pressure-confining chamber in which the contact structure isdisposed, so that arcing pressure generated at the other break is effective to direct a blast of oil through the are at the firstnamed break.

- The stationary contact structure of each pole of the circuit breaker comprises an adapter 8 of conducting material supported by and electrically connected to the associated conductor stud, and contact members which are connected to and carried by the adapter. For the purpose of conducting heavy currents through the breaker, finger contact members 9 are secured to one portion of the adapter so as to be engaged and 'spread apart by a coacting wedge-shaped contact portion H! of the movable bridging member 5 as best illustrated by Fig. 3. This clearly involves a wiping action tending to maintain clean the-contact surfaces. The finger contact members 9 may be of any suitable and. well known construction including a pairof opposed contact portions ll electrically connected, as by flexible leads IE, to the adapter 8 and biased towards each other as by leaf springs is likewise connected to the adapter 8. In the closed circuit position illustrated by Fig. 1, the contact portions H are biased into good contact engagement with the opposite sides of the wedge-shaped contact portion III, with the result that high currents may traverse the contact structure without overheating or damage to the breaker.

In case of interruption of heavy currents we have found that comparatively massive butt contact structure used in conjunction with the aforesaid flnger-type contacts above described results in greatly improved operation of the breaker. To this end each adapter is connected to and sup ports a comparatively massive butt contact member H comprising in the present instance a blo;k of suitable contact material, as copper, which is electrically connected to the adapter as by flexible braided conductors l5 and is resiliently mounted with respect thereto as by compression springs Ii which are seated within sockets l1 and ID of the adapter and butt contact, respectively. As best illustrated by Fig. 2, the butt contact I is guided for limited reciprocal movement by means of a P ir of bars or plates", each bar being mounted in alined slots 20 and 2| and having slots 22 and 23 coacting with pins 24 and 25 aflixed to the adapter and butt contact, respectively.

Referring particularly to Fig. 3, the butt contact member l 4 is provided with a plane contact surface arranged to be engaged by a. corresponding butt contact member ZE forming an extremity of the bridging member 5. The contact portion 26 is likewise of comparatively massive structure and may be in the form of a solid block of conducting material as copper.

Upon initiation of the circuit opening movement and subsequent to separation of the current-carrying contacts 9 and III, the butt con-- tacts I 4 and 26, which serve as the arcing contacts, are maintained in good contact engagement by the follow-up action of compression springs l5 and also by the attractive influence of the magnetic fields set up by parallel currents flowing in a generally horizontal direction through the large contact surfaces of the butt contacts E4 and 26. There is, therefore, no arcing at the'finger contacts, as more clearly indicated by Fig. 3, so that the contact surfaces thereof are unimpaired for heavy current duty. The arcing between the buttcontacts M and 26 may be interrupted in any suitable manner, as by the oil blast method previously described.

The comparatively massive structure of the arcing contacts not only provides a large heat dissipating surface but also provides an adequate amount of contact material for the arcing contacts even after a great many circuit interrupting operations. It will be apparent from the drawing that the heat dissipating surface of each,

contact portion I4 and 26 is comparable to or greater than that of a wedge-shaped contact In. By way of example, we have found that a circuit-interrupter embodying our invention has a contact life of the order of approximately fifteen times longer than previous contact constructions.

Upon closing of the circuit interrupter by upward movement of the bridging member 5, butt contacts I and 26 first engage, comprising the springs l6, and thereby maintaining high pressure contact for carrying heavy currents from the instant of contact closing to the final engagement of contacts 9 and I ll. i

It should be understood that our invention is not limited to specific details of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in the art without departing from the spirit of our invention,

aoeaeu What we claim as new and desire to secure by Letters Patent of the United States is:

1. An electric circuit interrupter comprising a pair of fixed contacts, each of said contacts including an adapter, opposed finger contacts for carrying heavy currents connected to said adapter, and a comparatively massive arcing contact block mounted for lost motion with respect to said adapter and means including springs seated in recesses in said adapter and block contact resiliently biasing said butt contacts away from said adapter, and a movable bridging member for interconnecting said fixed contacts having a centrally positioned lift rod, wedge-shaped contact portions disposed at opposite sides of said lift rod for engaging said finger contacts; and block-like arcing butt contact portions likewise massive as compared with the current carrying contacts at the extremities of said bridging member for engaging the first-named block contacts, said first-named butt contacts and said blocklike contact portions each having a heat dissipating surface comparable to or greater than that of one of said wedge-shaped contact portions, said resilient means maintaining said block contacts in engagement subsequent to separation of said finger and wedge contact portions.

2. An electric circuit interrupter comprising a pair of fixed contacts, each of said contacts including an adapter, finger contacts for normally carrying heavy currents connected to said adapter, an arcing contact comprising a block massive as compared with said finger contacts,.

a pair of guide plates at opposite sides of said block connected respectively to said block and adapter, said plates having a pin and slot connection with respect to said adapter, a flexible conductor electrically connecting said adapter to said block contact and means positioned between said guide plates resiliently biasing said block contact away from said adapter, and-a movable bridging member for interconnecting said fixed contacts having a centrally positioned lift rod, wedge-shape contact portions disposed at opposite sides of said lift rod for engaging said finger contacts, arid block-like arcing butt contact portions likewise massive as compared with the current carrying contacts at the extremities of said"- bridging member for engaging the first named block contacts.

RALPH E. BOLD. CHARLES R. BROWN. LELAND S. HOBSON.

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