US2717298A - Sealed enclosing structure for electric circuit breakers - Google Patents

Description

Sept. 6, 1955 J. WOODWARD ET AL 2,717,298

SEALED ENCLOSING STRUCTURE FOR ELECTRIC CIRCUIT BREAKERS Filed July 22, 1952 Ifiv enters: Lewis J. Woodward, Ralph Baskerville,

b WMEM Th eh Attorn e5.

United States Patent SEALED ENCLOSING STRUCTURE FOR ELECTRIC CIRCUIT BREAKERS Lewis J. Woodward, Philadelphia, and Ralph Baskerviiie,

Drexel Hill, Pa., assignors to General Electric Company, a corporation of New York Application July 22, 1952, Serial No. 300,182

4 Claims. (Cl. 200-168) This invention relates to sealed enclosing structures for electric circuit breakers, and more particularly to enclosing structure for electric circuit breakers which is adapted to be pressurized so as to prevent moisture from gainingv access to the breaker parts which are disposed within the enclosure.

Circuit breakers of the type wherein the contacts are disposed within an enclosing structure which is partially filled with liquid such as oil normally are provided with suitable venting means. Such venting means is for the purpose of relieving pressure which may be due to heat losses occasioned by the flow of current through the circuit breaker conducting structure while the contacts are closed, and may also be due to gases generated by an are drawn between the contacts of the breaker during an opening operation thereof. Such venting means which relieves pressure established within the breaker enclosing structure has been for the purpose of preventing damage to the enclosure due to excessive pressures which might be developed when large currents are, interrupted and when, as a result, large quantities of gas are given off due to the decomposition of the oil surrounding the breaker contacts. In such circuit breakers, a sudden reduction in ambient temperature or in the magnitude of current being carried by the breaker conducting structure results in a substantial reduction in the temperature of the oil and of the air above the level of the oil within the circuit breaker enclosing structure. Such a temperature reduction also results in a contraction of the air above the level of the liquid, which in turn causes atmospheric air to be forced from outside the breaker through the venting port into the space above the level of the liquid. Because atmospheric air frequently con tains a substantial amount of moisture which tends to condense on the metal parts inside the circuit breaker enclosure, there is a tendency over a period of time for such moisture to weaken the dielectric strength of the oil and other insuiating parts within the circuit breaker.

One object of our invention is to prevent moisture normally contained in atmospheric air from gaining access to the interior of an enclosed circuit breaker.

Another object of our invention is to preserve the dielectric strength of oil used in electric circuit breakers by preventing moisture from atmospheric air from gaining access to the interior of the enclosing structure for the circuit breaker.

Another object of the invention is to utilize the heat or energy losses due to current flowing through the circuit breaker while the breaker contacts are closed or during arcing conditions which produce gas pressure within the circuit breaker so as to prevent the flow of atmospheric air to the interior of the breaker' Still another object of our invention is the provision of suitable pressure responsive means for maintaining the pressure within a circuit breaker enclosure at a predetermined value in excess of atmospheric pressure.

According to the invention, pressure control or regulating means is disposed within an opening formed in a 2,717,298 Patented Sept. 6, 1955 Wall of an enclosing structure for an electric circuit breaker, and such pressure regulating means is arranged to maintain some pressure above atmospheric pressure within the breaker enclosure which may be due to the heat generated and normally lost by the flow of current through the breaker.

The invention will be better understood from the following description when taken in conjunction with the accompanying drawing, in which Fig. l is a side view, partially in section, of a portion of an electric circuit breaker embodying the pressure responsive means of the invention, and in which Fig. 2 is a cross-section along the line 22 of Fig. 1.

While the invention is particularly applicable to a circuit interrupter of the type disclosed in Patent 2,069,082, Walle, granted January 26, 1937 and assigned to the assignee of this invention, it is to be understood that the invention is not limited to a circuit interrupter of the recloser type as disclosed in the Walle patent, but can be used in conjunction with other types of circuit breakers in which the contacts are mounted in an enclosing structure.

In Fig. 1, an enclosing tank 1 having an insulating lining 2 disposed therein is filled with oil to the level indicated. Secured to the tank 1 is a cover member 3 which is disposed in sealing relationship to the tank 1 as indicated by the gasket 4, which is disposed in an annular recess 5 formed in the flange 6 of the tank 1. Suitable means for maintaining the cover 3 in position are provided such as clamping bolts or lugs which are not shown in the drawing.

The contacts of the circuit breaker comprise the fixed contacts C1 and C2 and a bridging contact C3 which is connected with link '7 by member "id at pivot 72, it being understood that the circuit breaker disposed within tank 1 could be identical to the breaker disclosed in application Serial Number 19,364, McCurry et ai., filed April 6, 1948, and assigned to the assignee of this invention. it will be understood that the link '7 forms an operative connection between the inner end of the contact operating crank arm 8 and the contacts themselves in a manner identical to the corresponding parts in the above mentioned McCurry et a1. application. As is best shown in Fig. 2, crank 8 extends through an opening 9 formed in a wall of the enclosure for the circuit breaker and the outer end of the crank 8 is secured, as by keying, to the crank-shaft 10 which is journaliy supported for rotation at the bearing 11 recessed within the support structure 12. Support structure 12 is secured to the wall of the cover 3 in sealing relation as is indicated by the gasket 13. From the description thus far, it will be understood that the outer or pivoted end of the internal crank arm 8 and a portion of the shaft 10 are disposed within a pocket formed within the support 12. Rotary motion is imparted to the shaft 10 by means of the external manually operable crank handle 141, which, as is indicated in the drawing, is provided with the apertured end 15 for receiving the hooked end of a switch stick. A suitable weatherprotecting cover for the crank parts which are disposed outside the enclosure cover 3 is provided in the form of the open-bottomed cover i6, which is provided with a clamping surface 17 disposed between the support 12 and the gasket 13.

From the description of the parts thus far, it will be understood that externally applied up and down motion of the ringed end of the manual crank handle 14 imparts rotary motion to the shaft 19, since the external crank 14, like the internal crank 8, is suitably secured to the shaft 10. Rotation of shaft 10 causes the internal crank 8 to rotate with the shaft 10 acting as a pivot, thereby imparting operating motion to the contacts through the agency of the link 7. It will be understood that crank arm 8 could be connected with link 7 by any other suitable means. As illustrated, this connection comprises a pin 7/) on a pivotally mounted arm 7c, the pin 71') extending through the slot 70 and triangular opening 8a in the link 7 and the crank 8 respectively. This connection as illustrated is identical to the corresponding parts in the above McCurry et :11. application.

For the purpose of maintaining pressure within the enclosure comprising tank 1 and cover 3, at a predetermined level in excess of atmospheric pressure, a pressure responsive means in the form of a resilient annular seal 18 is provided about the shaft 10 as is best shown in Fig. 2. This seal 18 is made of natural, or preferably synthetic, rubber and it will be observed that it is in the form of a conical funnel which may be contained within a metal housing as shown and secured in sealing relation to opening 19 in the support structure 12 by means of any suitable cement material or other holding means. Furthermore, from Fig. 2, it will be understood that the resilient inner periphery of the conical seal 18 constitutes the resilient pressure relieving lip portion 20, which bears against the cylindrical surface 21 of the shaft 10. In accordance with the invention, the resilient seal 18 is constructed so that excess pressure generated within the enclosure comprising the tank 1 and its cover 3 can be expelled therethrough while afterward maintaining a residual pressure at a substantially predetermined value which is effective to exclude external atmospheric air from entering back through the seal. Such residual pressure may result from heat given off due to the fiow of current through the circuit breaker, and alternatively or additionally due to gases produced due to decomposition of the oil within the circuit breaker when an arc is drawn between the contacts. In this way, flow of atmospheric air back into the enclosure within the casing comprising tank 1 and cover 3 is effectively prevented so that moisture normally contained in atmospheric air is prevented from entering and damaging the interior parts of the breaker as, for example, by weakening the dielectric strength of the oil within the breaker tank. Gases given off when an arc is drawn upon separation of the breaker contacts, if not relieved, could cause disruptive damage to the breaker enclosing structure. Resilient seal constitutes a very effective safety valve by relieving such excessive pressure promptly by virtue of the resilient seal yielding expansively about the shaft 10.

While we have shown and described a particular embodiment of the invention, we do not wish to be limited thereto and intend in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

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

1. An electric circuit breaker comprising an enclosing tank, separable contacts disposed within said tank, a contact-operating crank arm extending through an opening in a wall of said tank and having its inner end operably connected with a movable one of said contacts, a rotatable shaft secured to the outer end of said arm to constitute a crank shaft, a support member secured in sealing relationship to said wall about said opening therein, said support having a space formed therein for receiving said crank arm and said rotatable shaft and forming a journal mounting for said crank shaft, a seal of resilient material disposed about said crank shaft and secured in sealing relation to said support, said seal having a peripheral lip portion extending toward the exterior of said tank structure and engaging said rotatable shaft in pressure tight relation for a given range of pressures, and said seal being yieldable to release pressure established in said tank in excess of atmospheric pressure by a predetermined amount.

2. An oil circuit breaker comprising an enclosing tank structure, separable contacts disposed within said structure, a contact operating crank extending into said tank structure and operatively connected to a movable one of said contacts, a rotatable shaft for said crank extending out of said tank structure through an opening therein, a resilient annular seal having its respective peripheral portions in sealed relationship with said opening and said shaft to exclude atmospheric air from said tank, one of said peripheral portions constituting a yieldable lip which extends toward the exterior of said tank structure and is radially movable in response to predetermined pressures in excess of atmospheric within said tank structure whereby to provide a relief vent for such excess pressures.

3. An oil circuit breaker comprising an enclosing tank structure, separable contacts disposed within said structure, a contact operating crank extending interiorly of said tank structure and operatively connected to a movable one of said contacts, a rotatable shaft for said crank extending exteriorly of said tank structure through an opening therein whereby to operate said crank externally, a resilient conical seal tapering toward the exterior of said tank and having its respective peripheral portions in sealed relationship with said opening and said shaft to exclude atmospheric air from said tank, one of said peripheral portions being radially yieldable away from its sealing surface in response to predetermined interior pressures in excess of atmospheric to constitute a relief vent for such pressures.

4. An oil circuit breaker comprising an enclosing tank structure, separable contacts disposed Within said structure, a contact operating crank extending interiorly of said tank structure and operatively connected to a movable one of said contacts, a rotatable shaft for said crank extending exteriorly of said tank structure through an opening therein so as to provide for operating said crank externally, and means for sealing said shaft with respect to said opening, said means comprising a resilient seal having its inner periphery disposed about said shaft and its outer periphery disposed within said opening, said seal constituting a relief vent for excess interior pressures and for preventing entry of atmospheric air, said seal having adjacent one of its peripheries a generally conically shaped portion which tapers toward the exterior of said enclosing tank structure.

References Cited in the file of this patent UNITED STATES PATENTS 991,480 Christensen May 9, 1911 1,293,842 MacDonald Feb. 11, 1919 2,081,040 King May 18, 1937 2,405,093 La Brie July 30, 1946 2,462,753 Kyle et al Feb. 22, 1949 2,488,569 Strorn Nov. 22, 1949

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