US1814807A - Contact structure - Google Patents

Description

July 14, 1931. J HUBER 1,814,807

CONTACT STRUCTURE Filed Aug. 29, 1929 Inventor": Herman J. H. HubeT", b cm/ His Actor heg.

Patented July 14, 1 931 UNITED STATES PATENT OFFICE].

HERMAN J. H. HUBER, OF UPPER DARBY, PENNSYLVANIA, A SSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK CONTACT STRUCTURE Application filed August 29, 1929. Serial No. 389,303.

My invention relates to switch contact structure and more particularly to a contact structure for use in circuit breakers having comparatively large interrupting capacity.

. It is a well known fact that excessive heating may result from poor contact at the contacting surfaces of a switch structure traversed by large currents, and that any arrangement tending to decrease the contact resistance results in increased efliciency of It is an object of my invention to provide a structure for decreasing the resistance between contacting surfaces, and to utilize the.

magnetic forces of the current traversing the switch for further improving contacting engagement between the switch elements.

A further object of my invention is the provision of a brush contact member interposed between a stationary and a movable contact, wherein the mounting of said mem her is not included in the path traversed by current through the brush member and contacts.

My invention will vbe more fully set forth in the following description referring to the accompanying drawing,.and the features of novelty which characterize my invention will be pointed out with articularity in the claims annexed to and orming a part of this specification.

Referring .to the drawing, the single figure thereof illustrates a circuit breaker strucpartly in section, embodying my invention. I

\ Although for the purposes of illustration my invention is shown in connection with an oil circuit breaker of a well known type, it

shall be understood that it is not limited thereto but is broadly applicable to any type of switching structure for handling lar e currents. l

eferring to the drawing, a tank or housing 1, containing an insulating fluid 2, as oil, has mounted at its upper part a pair of insulating bushings 3 for su portingand insulating the conductor stu s 4 with respect to the housing. The insulating bushings within which the conductor studs are disposed extend within the circuit breaker housing and beneath the level of the oil body 2, as is well understood in the art.

At the lower end of the conductor studs are mounted members 5 comprising blocks of conducting material, as copper, electrically connected to the conductor, studs. Each of the blocks 5 comprises depending flanges, or sides, two sides of which form a support for a transversely extending pivot pin 6 providing a pivotal mounting for a brush contact member 7. The brush contact member'- 7 is interposed between block 5 and a movable contact blade or bridgin member 9 having an operating rod 10 for e ecting opening and closing movement of the switch. Member 7 comprises a plurality of laminae of conductingmaterial, as copper, clamped together as by riveting or by clamping means 11 inter mediate their ends in the form of a sheaf. The sheaf of laminae may be reinforced by a member composed of phosphor bronze, for

example, disposed along the top lamina. The

opposite ends of the sheaf of laminae are bevelled as illustrated, so as to make good contacting engagement with the plane surfaces of the stationary and movable contacts, comprising the inner face of flange 5a, andthe upper face of blade 9, which are disposed substantially at right angles to each other. The contacting tips of the individual laminae are preferably formed of silver, since this metal serves to provide better contact between conducting members immersed in an oil body. This'is apparently due to the fact that sludge in the oil, which normally tends to increase the resistance at the contacting surfaces, does not impair to such a great ex-' tent the electrical contact between silver and another conducting material.

In order to provide better conducting engagement between the opposite ends of the brush member and the stationary and movable contacts, the pivotal mounting 6, which may be loosely fitted if desired,'is disposed intermed'ate the ends of the laminae and offset with despect to the sheaf so that there may be a limited pivotal movement of the brush- As illustrated, this pivotal. movement is comparatively slight, and in practice may be of the order of about 1/32 of an inch, the brush member in its clockwise movement engaging the lower surface of flange 5b, of block 5, this surface serving as a limiting member. lit is to be further noted at this point that the offset arrangement of the pivotal mounting permitsv the current traversing the switch to flow directly through block 5. the individual laminae of brush 7, and the bridging contact blade 9, thereby eliminating the mounting of the brush from the path traversed by current. The advantage of this arrangement is at once apparent when it is realized'that a movable support may often form a comparatively high resistance contact for current passing through the mounting, whereas in the present arrangement, the current divides and passes in parallel through theindividual laminae. Acordingly, the laminae, if desired, may be insulated, as by enamel. from each other to reduce heating, since it is not neces sary that the current pass from one'lamina to another as in the case where the laminae are clamped as a sheaf to the lower end of a conductor stud.

In operation, it sometimes happens that the movable contact blade in travelling to its closed position tends to overtravel this position to a. certain extent, thereby setting up stresses in the apparatus depending on the force of the closing movement. In order that such overtravel of the movable blade may be permitted without damage to the contact structure, the sheaf of laminae has a certain degree of flexibility so that overtravel of the blade 9 simply results in flexing of the brush member and a resultant wiping action along the contacting surfaces of both the stationary and movable contacts. This wiping action furthermore serves to maintain the contacting surfaces clean and to prevent formation of substances thereon tending to increase the contact resistance. Moreover the wiping action between the brush member and contacting surfaces is not limited to a condition wherein the contact blade overtravels its normal. position, but occurs to a certain extent upon each closure of the circuit breaker due to the pivotal mounting of the brush contact. v

Another factor tendingto maintain the brush contact member in good contacting engagement with its cooperating contacting surfaces while the contacts are closed, is the magnetic force of the current traversing the switch. It will be apparent upon inspection of the drawing that the magnetic forces of currents passing through the contact structure tend to force the brush member into wedging engagement along its bevelled edges with the stationary and movable contacts thereby maintaining a very good contact during operation of the circuit breaker.

In other words, the magnetic forces, which tend to force the blade 9 downwardly, cause eia-so? the opposite ends of the laminae of each brush to be wedged towards the more constricted area between the stationary and movable contacting surfaces. In case of a large rush of current through the circuit breaker, the brush member tends to be wedged into even firmer engagement with its coacting contacting surfaces, and thereby tends to reduce heating at the contacts by such'large currents.

The construction and method of making the brush contact member are comparatively simple in that straight laminae may be clamped into a sheaf and machined at the ends to produce the bevel desired. Replace- 'ment of the brush member is facilitated by the removable pivot pin 6, which may be slid through the sides of member 5, thereby permitting the brush member to be removed.

Although no secondary or arcing contacts have been illustrated or described in connec tion with my invention, the same being deemed unnecessary for a. complete understanding thereof, it shall be understood that the usual types of secondary contacts ordinarily used with inverted brush contacts may be employed.

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

1. A switch contact structure comprising a pair of stationary contact members each having a plane contacting surface, a relatively movable contact bridging member, a pair of brush members each comprising a plurality of laminae of conducting material, each brush member interposed between a stationary contact and said movable bridging member whereby each lamina engages at its opposite ends the corresponding plane contacting surface and said bridging member, and means for mounting said brush members so that the magnetic forces of the current traversing said switch force the opposite ends of said laminae into good contacting engagement with said contact and bridging members.

2. A switching structure comprising a stationary conductor stud having a plane contacting surface, a relatively movable contact member having a contacting surface disposed at an angle to said first-named contacting surface, and a brush member comprising a sheaf of laminae of conducting material interposed between said stationary and movable contacts within said angle whereby the magnetic forces of the current traversing said switching structure tend to force the opposite ends of said laminae into good contacting engagement with said contacting surfaces respectively.

3. A switching structure comprismg a stationary contact, a relatively movable contact having a contacting surface disposed substantially at right angles to the contacting surface of the stationary contact, and a brush member comprising a sheaf of laminae of conducting material interposed between said rectly engage contacts, the opposite ends of said brush member being bevelled whereby the magnetic forces of the current traversing said switching structure tend to force the opposite ends of the laminae into individually good contacting engagement with said contacts recurrent traversing said switching structure divides between said laminae in passing between said contacts.

5. A switching structure comprising a stationary contact, a relatively movable contact, and a brush member pivotally mounted on said stationary contact, and interposed between the contacting surfaces of said stationary and movable contacts, said brush member comprising a plurality of laminae of conducting material whose opposite ends dithe contacting surfaces of said contacts respectively in the closed circuit position.

6. A circuit breaker structure comprising i a stationary conductor studhaving a plane contacting. surface, a relatively movable contact blade'whose contacting surface is disosed substantially at right angles to sa1d st-named contacting surface, and a brush member comprisin a sheaf of copper laminae mounted for limited pivotal movement with respect to said conductor stud, sa1d brush member engaging at its opposite ends said contacting surfaces whereby current traversing said structure passes through sa1d laminae between said blade and conductor stud independently of said pivotal mountlng.

7. A circuit breaker structure comprlsing a stationary conductor stud, a relatively movable contact blade, and a resilient brush member comprising a sheaf of laminae of conducting material interposed between said stud and blade and mounted for limited pivotal movement on said conductor stud whereby an appreciable overtravel of said contact blade may be permitted during its closing movement, closing movement of said blade serving to force the opposite ends of said brush into good contacting engagement with sa1d stud and blade.

8. In an oil circuit breaker, structure for insuring good electrical contact between the stationary and movable switch members comprising a stationary conductor stud, a movable contact blade, a brush member compris ing a sheaf of laminae of conducting material interposed between said stud and blade, said laminae provided with silver tips at the opposite ends thereof, and a pivotal mounting for said brush member on said conductor stud, saidpivotal mounting disposed intermediate the ends of said laminae and offset with respect thereto whereby current traversing said circuit breaker passes directly through said lam inae independently-of said mounting.

- 9. In circuit breaker apparatus, the combination with stationary and movable contacts, of a brush contact member interposed between the contacts comprising asheaf of laminae of conducting material, and means for mounting said member for limited pivotal movement with respect to the stationary contact, the opposite ends of said laminae each engaging the stationary and movable contacts respectively with limited wiping action upon closure of the movable contact.

10. The combination with an oil circuit breaker comprising a pair of stationary conductor studs and a movable bridging member immersed in an oil body, of contacting structure interposed between said conductor studs and bridging member comprising a contact block secured at the lower end of each conductor stud, and a brush contact comprising a sheaf of laminae of conducting material pivotally mounted intermediate its ends upon each of said contact blocks, each brush contact being engaged at one end by the bridg ing member during closing movement thereof whereby the opposite end is forced into good contacting engagement with its corresponding contact block.

In witness whereof, I have hereunto set my hand this 26th day of August, 1929.

HERMAN J. H. HUBER.

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