US1798389A - Electric switch - Google Patents

Description

2 Sheets-Shet 1 March 31, 1931 M/wv, n @//7 ELECTRIC SWITCH Filed April 14. 192e 2 sheets-sheet" 2 Patented Mar. 31, 1931 UNITED STATES PATENT OFFICE JOSEPH D. WOOD, 0F WOLLASTON, MASSACHUSETTS, ASSIGNOR TO CONDIT ELECTRICAL MANUFACTURING CORPORATION, OF SOUTH BOSTON, MASSACHUSETTS, A CORPO RATION OF MASSACHUSETTS ELECTRIC SWITCH Application led April 14,

This invention relates to oil immersed electric switches of the type especially adapted for service in underground compartments, such as manholes, and which may be connected directly to metallic-sheathed conductor-cables. A switch of this general type is described in my co-pending application Serial No. 745,994, filed October 27, 1924.

A manhole may at times contain a considerable amount of water and an electric switch contained therein may often be partly under water or even completely submerged. Under such conditions, water may enter the switch casing and seriously damage the switch as well as interrupt the serviceon the circuit controlled by the switch. The provision of a Huid-tight casing, while a satisfactory solution for some types of apparatus such as transformers, is open to objections in the case of oil switches due to the difficulties experienced in venting the gases generated by the arc during circuit interruption.

It is an object of this invention to provide an electric switch of such construction that it will function reliably to control its circuit even when completely submerged in water, and more specifically to provide a switch so constructed that no water can enter the switch casing, or atfect the conducting comf pcnents of the switch, and gas generated during circuit interruption cannot collect within the casing to build up harmful pressures therein but can vent freely at a. low pressure.

Frequently switches for manhole use are suspended above the bottom of the manhole on a suitable supporting structure ot steel or wood in an attempt to protect them from water which may be presentin the bottom of the manhole. One objection to this practice lies in the increased expense of the manhole construction. Moreover it is desirable to support all apparatus in a manhole free from the side walls to allow room for proper 1926. Serial No. 102,055.

racking of incoming and outgoing cables thereon.

An object of this invention is to provide a switch for this type of service adapted to be supported directly upon the floor of a manhole and so constructed that water can not enter the oil receptacle.

An oil switch must occasionally be y inspected to insure satisfactory operation. The contact members in particular need regular attention and t-he oil in the receptacle disposed about the contact members must be renewed or filtered occasionally. Where an oil switch is located in a manhole, it is obviously desirable that the switch should be inspected in position since there is seldom suflicient space available in the manhole for disassembling the switch. Furthermore, due to the method of connecting the lead sheaths of the cables to the switch casing by soldered joints, it would be an expensive procedure to disconnect the switch from its conductor cables and remove it from the manhole every time it was desired to inspect the contacts.

A further object of this invention is to provide an electric switch for use in underground compartments so constructed that its oil receptacle can be removed and access can be gained to the cooperating switch members without disconnecting the switch from its conductor cables or moving it appreciably from its normal position in the manhole.l

A further object is generally to improve the construction and performance of electric switches.

Fig. 1 illustrates diagrammatically a manhole with a single pole electric switch embodying the invention contained therein.

Fig. 2 is a plan view of the switch embodying the invention. Y

Fig. 3 is a sectional elevation of the switch taken along lines 3 3 of Fig. 2.

As here shown, the electric switch embodying the invention includes an enclosing casing consisting of two detachably connected upper and lower sections. The upper section includes a top wall l0 comprising a cover and integral and depending peripheral walls l2, which walls are adapted to enclose and surround the oil receptacle of the switch and are terminated at about the level ot the bottom of the oil receptacle. The lower ends of said walls are provided with a peripherally outstanding flange 14 to which the upper end of the lower casing section is adapted to be secured. T he lower casing section comprises essentially a tube which is open at the top and Y bottom and lhas the straight side walls i6 to the lower end of which the peripheral outstanding flange 18 is secured in 4any suitable manner, as by welding, to provide a kbase which will rest upon the floor of the manhole and support the switch securely in an upright position. The upper end .ot the .side wall of the lower casing is formed or provided with the peripherally outstanding llange 20 which is adapted to be secured detachably against the flan-ge 14 ot the upper casing section in any suitable manner as by .the bolts 2.2. A packing 24 is interposed between said two flanges to provide a gas tight joint thereat. The side walls of the lower casing section are provided `with a series ot openings 23 near the bottom end of the section, whereby the gases liberated during circuit interruptions may escape from the switch casing; and any water in the manhole may enter the casing.

The casing thus formed is air-tight at its upper end and is open only at its bottom, so that air or other gases contained therein are entrapped when water enters the bottom of the casing and thereby prevent the water from rising unduly within the Casing'.y

The elec ric switch herein shown embodying the invention is va single pole switch although the invention may be applied equally well to multi-pole switches ifA desired.

The switch includes an oil receptacle 26 disposed in the compartment provided in the upper casing section and spaced from the side walls thereof whereby to provide a peripheral passage 28 communicating with the space above the oil in said oil receptacle and the expansion space vA of lthe lower casing .sec-

tion. The upper edge ot the oil receptacle is preferably spaced from the top or cover of the upper casing section as at 30 whereby to proviee 're'e communication between the space above the oil and said peripheral passage 28. The oil receptacle is preferably snpported yieldingly in position and to this end rests upon a platform member 32. Said platform-member extends laterally on opposite sides of the oilreceptacle and is slidable on vertically extended supporting rods 34, which rods are disposed in the peripheral passage 28 between the 'oil receptacle and the side walls l2 of the upper casing section. Nuts 36 are adjustably screw-threaded on the lower ends of said rods 84 and helical compression springs 38 are interposed between said nuts and said platform-member 32 whereby yieldingly to support the receptacle in position and permit it to move downwardly upon an excess of pressure in the gas space above the oil in the receptacle. Said supporting rods 34 are formed with reduced upper end porti-ons'40 which are extended through the top 10 of the upper casing section and nuts 42 are screwthreaded on the ends of vsaid rods whereby to secure them fniedly to the casing.

Packing washers 44 are interposed between the top or" the casing and said nuts 42, or other suitable means may be provided, whereby to ins-ure gas tight join-ts between the casing and said rods. Y V

The stationary and movable switch members are contained within the oil receptacle. Said stationary switch members include insulating bushings 46 which are provided with collars 48 at their upper ends, which collars may be secured to the bushings -by cement or other suitable means.l Said collars are provided with outstanding langes 50 .by which the bushings are depende-ntly secured rigidly to the top of the casing. The lower ends of the bushings may .be provided with enlarged recesses and metallic yerrules 52 may be fixed in vsaid recesses by cement or otherwise. Said ferrules may be formed or provided with outstanding langes 54 which are adapted to bear against the lower ends of the bushings and receive the pressure of the movable swi-tch member. Y

Cable connectors 56 arev disposed within said errules 52 and are provided with cable receiving recesses 58 therein. Sai-d cable connectors are provided with reduced and eX- ternally screw-threaded ends 60 which are screw-.threaded inl said 7ferrules and are extended downwardly therethrough. Check nuts 62l may be screw-threaded on said extended ends 60 and bear against said ferrules whereby to loch said cable-connectors re-y movably in position and also to provide an oil tight joint thereat although it is not vital that the joint be strictly oil tight. A Contact member 64 may be screw-threaded on the lower end .of each cable connector and locked in position thereon by the check nut 66.

The switch casing is provided with transformer wells 68, which wells are contained in the upper casing section above the top l() and are disposed above and in axial alignment with the passages through the insulating bushing 46 and are adapted to contain current transformers for actuating the tripping mechanism of the switch to open the circuit on an overload. The top-openings of said wells 68 are removably sealed in a fluid tight manner by the cover plates 70 which'cover plates are removably secured to the top or" the casing in any suitable manner as by bolts 7 2. Said cover plates 70 are formed or provided with upstanding necks 74 provided with lll) cable-openings therethrough which are disposed in vertical alignment with said transformer wells and the passages in the insulating bushings.

The conductor cables 76 are extended directly into the switch and through the bush-- ings and tothe contact members of the switch. To this end, the conductor cables are passed directly through the openings in the necks 74 of the cover plates and downwardly through the middle of said wells and into the longitudinal passages in said bushings. The metallic sheaths 78 of said cables are inserted into said necks and are terminated therein and said sheaths are permanently connected in a fluid-tight manner to said removable cover plates by suitable means as solder 80. The insulating core 82, of said conductor cable is extended downwardly through said transformer wells 68 and thereby forms the insulating means interposed between the conductors of said cable and said transformers. This particular arrangement is highly desirable in that the casing dimensions may be materially reduced over the dimensions of the usual type of switch wherein the current transformer is disposed about a relatively thick porcelain insulator. The insulation 82 may terminate at a suitable distance below said transformer well, although preferably the insulation is carried downwardly to the lower end of the bushing as illustrated. The insulation is removed from the lower end of the cable to expose the conductors 84 thereof and said conductors are disposed in the cable recesses 58 of said cable connectors and soldered or otherwise secured electrically thereto.

The movable switch member includes an insulating rod 86 anda bridging or brush member 88, which brush member is adapted to engage the stationary contact members 64 of the switch in the usual manner. The upper end of said switch rod 86 is preferably reduced in diameter and extends through the top of the casing into a mechanism well 90 which well is extended along the length of the switch casing and is disposed between and isolated from the transformer wells 68. A cover 92 forms a removable fluid tight closure for the open top of said mechanism well.

The upper end of said rod 86 is attached to a supporting bar 94 of the operating mechanism, which mechanism may be of any suitable character.

The switch is arranged to be supported normally directly on the bottom of the manhole by the lower casing section. According to this invention, the switch is also arranged temporarily to be supported independently of its supporting base for the purpose of withdrawing the oil receptacle and inspect ing the switch. To this end, the upper casing section is provided with a plurality of outstanding brackets 19 which are disposed at the lower end of the upper casing section and extend suficiently beyond said flange 14 laterally to permit jacks 21 to be placed upon the floor of the manhole directly beneath said brackets and engage the ends thereof. By removing said bolts 22 the upper and lower casing sections are adapted to be freed from positive engagement so that by cooperation of the jacks 2l with said brackets 19 the upper casing section containing the oil immersed switch may be slightly raised, allowing said lower casing section to be withdrawn from its normal position beneath the switch. The vertical movement of the upper casing and the switch contained therein is permitted due to the relatively flexible nature of the conductor cables 76.

The oil receptacle herein shown then may be lowered from its normal position about the switch members and withdrawn from beneath the upper casing section.

The outer switch casing herein shown provides a vertically disposed cylindrical shell or standpipe which is closed at the top and open at the bottom. Water which may collect in the manhole is free to enter the lower casing section through the openings 23 and entrap the air in the casing, and the entrapped air prevents the water from rising sufficiently high in the casing to interfere with the proper operation of the switch. The construction and arrangement 'of the casing is such that even under the most adverse conditions, when the switch may be completely submerged, the head of water without the switch will be insufficient to force water up any considerable distance within the casing.

Vhen the switch opens under a heavy overload the gases resulting from circuit interruption collect in the space above the level of oil in the oil receptacle, and in the enclosing casing above the water level therein. Upon suiiicient gas accumulation, the static pressure of the entrapped air and gas is sufficient to overbalance the static head of water in the manhole and force water out of the casing, until the gas is vented from the casing through the openings 23.

The static pressure of the gas in the casing obviously will be low and cannot be more than that vdue to the head of water in the manhole.

The water in the manhole is cool and so chills the switch-gases before they escape from the surface of the water and prevents their combustion when commingled withk the air above the surface of the water.

The construction may be otherwise modi :nl

tions, and an oil receptacle contained'in said upper casing section and in fluid communication with said lower casing section, having separable circuit` controlling switch members therein, both sections having provision for being independently supported.

2. An electric switch having an upper casing'section, an oil receptacle disposed within said casing section, cooperating stationary and movable switch members containedwithin said oil receptacle, a lowervcasing section connected with and arranged normally in supporting relation beneath said upper casing section, and'said upper casing section having provision for being supported independently oi' said lower casing section.

3. An electric switch having an oil receptacle with cooperating switch members contained therein, an lupper casing section enclosing said oil receptacle, a lower casing section detachably connected with and forming a base for said upper casing section and said oil receptacle, and said upper casing section having provision for being supported independently of said lower Vcasing section.

l. An electric switch including an oil receptacle having cooperating stationary and movable contacts therein, an upper casing enclosing said oil receptacle, a lower casing forming a supporting base for said upper casing, and means whereby said upper casing is adapted to be supported in elevated position above said lower casing, whereby to permit the removal of said lower casing and the lowering of said oil receptacle to gain access to said contacts. y v

5. An electric switch having an outer casing including Van upper and a lower section, stationary and movable switch members supported by and disposed within said upper casing, an oil receptacle removably disposed about said switch members and within said upper casing section and means carried by said Lipper casing section whereby said upper casing section is'adapted to be supported independently of said lower casing section.

6. An electric switch having a casing including a closed top anda side wall depending below said top to provide a compartment open at the bottom, and an open top oil receptacle in the upper portion of and in fluid communication with said compartment and spaced laterally from said side wall, separable switch members contained in said receptacle, said depending sidewall having` an open passage at the lower end thereof below thevv bottom of said receptacle. y

7. An electric switch having a metal casing including a closed top and side walls depending below said top to provide an enclosing and gas venting compartment, switch members contained in the upper portion of said compartment, and an open top oil receptacle disposed in the upper portionof lsaid compartmentabout said switch members with the open top thereof beneath the top wall of said casing, said casing extended downwardly for a substantial distance below the bottom ot said oil receptacle and being freely open to the atmosphere at its bottom end.

8. An electric switch having an oil receptacle with cooperating separable contacts contained therein, an enclosing casing comprising a top wall and depending side walls extending well below the bottom of said oil receptacle and providing thereat an entrapped body of air which prevents entrance yof water into said oil receptacle when the switch is immersed in water, said casing adapted to be gas tight at the top, but freely vented at the bottom.

9. The combination of a standpipe closed at the top and open at the bottom, and an oil immersed electric switch contained in the upper portion only ot and supported by said standpipe and arranged to vent thereinto.

10. rlhe combination of a standpipe closed at the top and open at'the bottom, and an oil immersed electric switch contained in the upper portion only of and arranged in free communication with the interior of said standpipe.

11. An electric switch having a casing which is closed at the top and is open at the bottom and provides a large vented gas-eX- pansion spacel at the bottom, an oil receptacle disposed in the closed upper part only of said large casing above said gas-expansion space, cooperating switchV members contained in said receptacle, and means providing fluid communication between said receptacle and space. f

12. An electric switch having a casing which is closed at the top and is 4open at the bottom and comprises upper and lower detachably-connected sections, 'an oil receptacle contained mainly in said upper section, cooperating switch members contained in said oil receptacle, and said detachable lower sec; tion constituting a vented gas expansion space for said oil receptacle.

13; An electric switch adapted to be immersed in water, said switch comprising a vertical casing of substantial height which is closed at the top and is open at the bottom,

and an oil receptacle having cooperating switch members therein contained in the upper portion of said casing and arranged to vent therein, the water having ingress into said casing through the bottom-opening to entrap a confined body of air in the closed upper position of said casing over the water therein and the switch-gases having egress from said casing through the bottom-opening therein.

14. An electric switch comprising a casing having upper and lower detachably-connect ed sections arranged in free fluid communication with each other, an oil receptacle con-'` tained within said` casing and largely in said upper compartment, switch members immersed in the oil, said upper section adapted to be raised to permit the removal of said lower section, and flexible conductor cables connected with the upper casing-section, said flexible conductor cables adapted to yield and thereby to permitsaid upper casing-section to be elevated above said lower casing-section.

In testimony whereof, I have signed my name to this specication.

JOSEPH D. WOOD.

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