US1835596A - Vacuum circuit breaker - Google Patents

Description

Dec. 8, 1931.

R.PELLNHHD ET'AL VACUUM CIRCUIT BREAKER Filed June 2s, 1928 ATT'ORNEY Patented Dec. 8, 1931 marre 'RUDOLF HELLMUNI), 0F SWISSVAII'JE, AND

PENNSYLVANIA, ASSIGNORS TO WSTINGHOUSE'ELECTRIC D MANUFACTURING smreal' PATENT oFrIcE ROBERT C. DICKINSON, E WILKINSBURG,

COMPANY, A CORPORATION 0F PENNSYLVANIA vacuum cmcurrnnmxnn Application lled June 23,

Our invention relates to circuit breakers and particularly to enclosed circuit breakers in which the contactsthereof are separated in a vacuum.

An object of our invention is to provide a circuit breaker of the vacuum type wherein 'access to the interior of the circuit-breaker housing for the purpose of inspection or repair may be conveniently obtained and wherein the construction of the circuiti usually employed in vacuum circuit breakers `A further object of our invention is to provide a circuit breaker of the vacuum type wherein the circuit-breaker operating member is pivotally mounted on the circdit-I breaker housing and wherein the opening through which the operating member extends, is sealed by means of a vsylphon connected to the housing and to the operating member and laterally displaceable Yby the operating member in order to minimize dei flection of the walls of the sylphon and to obtain a maximum openingmovement of the circuit breaker contacts.

These and other objects that will be made apparent throughout the' further description of -our invention are attainedv by means of the aparatus hereinafter described and illustrated in the accompanying drawings,l wherein Figure 1 is a side view of a circuit breaker embodying features of our invention, and

Fig. 2 is a longitudinal section through the circuit breaker shown in Fig. 1 taken on the line II-II thereof.

Referring to the drawings lthe circuit breaker apparatus'comprises a metal housing 3 provided with a metal cover 4 that 192s. serial No. 287,805.

is welded at 5to the side walls of the housing. The cover 4 is provided with an opening 6 through which the stationary contact member 7 of the circuit breaker extends into the housing. The contact member 7 is supported upon` a conducting rod 8 that is secured to a cover plate 9 which serves to close the opening 6. The rod 8 is provided with a terminal 11 to which one of the conductors, (not shown), may be connected in the usual manner. f

The cover 9'is insulated Jfrom the `cover 4 by means of a porcelain or glass insulating bushing 12, and a non-rigid seal is provided 'between the plates 9 and 4 for preventing injury to the bushing by inserting lead packing washers 13 and 14 between the said plates and the ends of the insulating bushing. Flexible annular flanges 15 and 16 are soldered to the ends of the insulating bushing and to the plates 9 and 4, respectively, in

which annular grooves 20 are provided for receiving the solder thus forming a gas-V tight closure for the opening 6 in the housing, and linsulating the stationary contact member 7 from the housing.

A movable contact member 17 is mounted upon an operating member 18 that is pivotally carried byfa bracket 19 having an annular ilange 21 welded to the side wall of the housing 3. ,The operating member 18 eX- tends through the opening 22 that is partiallyclosed by the bracket 19 and is provided with a threaded socket 23 for receiving the threaded end of an insulating operating arm 24. A flange sleeve 25 is welded to the operating member 18, and the opening 22 is sealed by means of a metal sylphon or bellows 26 that is welded tothe bracket collar 21, at one end, and to the flanged sleeve 25 at the other end, thus making a gas-tight joint at the place of emergence of the operating member from the casing 3.

A'lexible conductor. 27 is clamped, at one end, to the contact member 17 by means of a clamp 28 and, at the other end, to a terminal 29 by means of a clamp 31. It will be noted that the terminal 29 'is conductively connected to the housing which may be grounded, if desired.1

The condition of the contacts may be determined by viewing them. through a glass 'window 32 that serves to close an opening 33 in the housing 3. A flanged bushing 34 is Welded to the casing 3, andthe window 32 is supported .by the packing gasket 35 that are retained in place by a metal ring 36 and screw clamps 37 having adaptable screws 38 engaging the outer face of the flange of the bushing 34.

Vents 30 and'30a are provided in the covers 9 and 4, respectively, which establish communication between the interior of the housing 3l and* the space between the packing washers 13 and f14, respectively, and the iexible ianges 15 and 16, respectively, for balancing the pressure on both sides of the washers and relieving them from stresses incident to the low pressure withinthe housing.

The cover 9 is retained in position by stud bolts 10 threaded into lugs l0a and the bolts 10 are surrounded by insulating bushings 1017 that extend through openings in the cover 9 and insulating spacing bushing 10. The cover 9-is, therefore, insulated from the cover 4.

It will be understoodthat it is desirable to maintain a vacuum in the the order of .001 millimeters or less of mercury within the casing at all times. Ordinarily, the metal housing will be made sutliciently tight vagainst leakage to maintain the vacuum, but, when desirable, any suitable exhaustf means, such a vacuum pump or a vaporizable chemical getter, may be provided to assist s uch mantenance.

It has been found that-the bombardment of electrons emanating from the electrodes or contacts or conductors thereof detrimentally affect the lead gaskets 13 and 14 because the distance between the contact conductors 8 and the inner edges of the gaskets 13 and 14 is greater than the mean free path of the electrons. When electrons are discharged in a container wherein a rare atmosphere is maintained, and are permitted to move unobstructed, their velocities become exceedingly high, and when they have been permitted to move substantially through their mean free path, their` collision with molecules of the atmosphere is practically certain to cause further electrons to be released. The released electrons move at terrific velocities. When such electrons strikea metal surface, the molecules at`the immediate surface are also exploded and the metal vaporized. The electrons discharged from the conductor, if

Hthey do not collide with molecules of the atmosphere, collide withthe walls of the con-v tainer athigh destructive velocity and cause volatilization of the metal. Vaporized f metal released from the gaskets and elsewhere in the casin ordinarily, is deposited upon the inner sur aces of the insulator bushform of a spool within the insulating bushing 12, the lower 'flange 41 thereof, being clamped between the cover 4 and the lead gasket 14 andV insulated from the conducting rod 8, thereby shielding the gaskets and insulating bushing from the moving electrons. The distances between the cylindrical portion of theshield and the conducting rod 8 and between the end portion of the shield and cover 9 are considerably less than the mean free path of the electrons. It has been found that the interference afforded by the shield prevents numerous coll1sions with the molecules of the atmosphere within the container and the attaining of destructive velocities and protects the lead gaskets from the bombardment of electrons, thereby preventing deposit of metal upon the interior lof the insulator bushing 12.

Itwill be noted that, by reason of the `the contact 17 for opening the circuit, with a minimum deflection of lthe bellows walls and, consequently, the life of the bellows is materially increased. While vWe have illustrated but one embodiment of our invention, it will be apparent to those skilled in the art that various changes, modifications, substitutions, additions'and omissions may be made in the apparatufs illustrated without departing from the spirit and scope of our invention, asset forth in the appended claims.

We claim as our invention: 1. A vacuum circuit breaker comprising a housing for containing a rareied atmosphere, a contact member within the housing, a movable switch member within the housing for engaging. the contact member and extend- A ment of the switch member.`

2. A vacuum circuit breaker comprisinga metal housing having an opening therein, a contact member the housing, a conducting member for the contact member extending through the said. opening, a closure for the opening for supporting the conducting member, an insulating* bushing surroundc operating with the rst contact mem er, and

ing the conducting member for supporting the closure and for insulating the closure from the housing, a second contact member conductively connected to the housin for coa metal shield surrounding the conducting member and insulated therefrom, and disposed between the conducting member and the interior of the said bushing for intercepting electrons discharged from the said conducting member.

3. A vacuum circuit breaker comprising a metal housing having an opening therein, a

contact member within the housing, a conducting member for the contact member extending through the said opening, a closure for the opening for supporting the conducting member, an insulatino' bushing surrounding the conducting mem er for supporting the closure and for insulating the closure :from the housing, non-rigid metal washers disposed between the ends of the bushing and the housing and closure member respectively, A means insulated from the closure member for clamping the closure in operative relation to the housing, a second contact member consubscribed our names this 15th day of June,

ductivel'y connected to the housing for cooperating with the first contact member, and a metal shield surrounding the conducting member for intercepting the electrons discharged, from the conducting member and preventlng the collision of the electrons with the said washers.

4. 'A vacuum circuit breaker compris/ing a` metal housing having a contact member conductively connected thereto and provided with an opening a cover for the opening, an insulating cylindrical bushing aligned with the opening and disposed between the cover and the housing,` malleable metal sealing washers disposed at the ends of said bushing and constituting a gas-tight seal between the bushing and the housing and cover, re-

spectively, a second contact member conductively carried by the cover and extending Athrough the said bushing, and a cylindrical the interior 'of said bushing and the said shield insulated from and surrounding the second contact and having a flange at its innermost end clamped between the innermost washer and the housing for intercepting the electrons discharged from the second contact member and preventing their collision with washer.

In testimony whereof, we have hereunto 192s. 'RUDOLF HELLMUND.

ROBERT o. picKiNsoN.

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