US1798390A - Electric switch - Google Patents

Description

March 31, 1931. J! WOOD 1,798,390

ELECTRIC SWITCH Filed Oct. 27, 1924 3 Sheets-Sheet 1 3 Sheets-Sheet 2 J. D. WOOD ELECTRIC SWITCH Filed Got. 27, 1924 March 31, 1931.

Mare 31, I931. w D 1,798,390

ELECTRIC SWITCH Filed Oct. 27, 1924 3 Sheets-Sheet 3 17706712021 //6 Q Tr-5 '7 /////////i7//// f r4) -WQ 07K Patented Mar. 31, 1931 UNITED STATES PATENT OFFICE.

JOSEPH J). WOOD, or QUINCY, MASSACHUSETTS, nssxeuen, B 155mm: nssmmsmrs. 'ro eonm'r ELECTRICAL MANUFACTURING conronsrron, or nog'ren, unmanagesn'r'rs, A conrom'rron or MAssAcHUsE'rrs nrnc'rnrc swrrcrr pp i a n fi d O tob 2 182 Seri l 1.- weas- This invention relates to electric switches ot the type especially'adapted for service in underground "compartments, as manholes, and the like; and also for connection with underground and metallic sheathed conductorable A manhole may sometimes contain a substantial amount or even be more or less compljetely filled with water and an electric switch therein contained may be at times partially immersed in or even more or less completely submerged in the water. It is an object of this invention to provide an electric switch of such construction that it can function reliably and repeatedly to control its circuit under these conditions and specifically to provide a switch so arranged that water can not gain access to the conducting components of the switch or to the oil receptacle in which the contact members are immersed, even though the switch may be completely submerged in water.

When a circuit interrupting arc is drawn in a body of arc-quenching fluid combustible with air, as oil, combustible gases and vapors are generated. Ordinarily, the construction oi the electric switch is such that these gases and vapors must be liberated from the switch casing as rapidly as possible in order to prevent damage to the switch. It is highly'objectionable, however, to liberate switch gases and vapors into a manhole as these gases may collect in the manhole and mix with the air therein in explosive proportions and the explosive mixture may be lgnited either by the hot vent gases from the switch or in some other manner and cause a disastrous explosion. Consequently, it is a further objectof this invention to provide an electric switch so constructed and arranged that the gases formed by the circuit interruption under load are retained within the switch casing and are not immediately vented into the manhole.

Some of the gaseous products formed upon circuit interruption are condensible while others are fixed or uncondensible under ordinary conditions; and it is a further object of this invention to provide a gas tight electric switch adapted to cool and condense the condensible portion of the gaseous products immediately after the formation thereof whereby to kee down the internal pressure within the switcli.

Upon successive circuit interruption under load, the uncondensible orfixedgases ma collect within the gas tight switchand build up a gradually increasing pressure. It is a. further object of this invention to provide means to relieve such pressure when it becomes unduly elevated, while maintaining a positive pressure within the switch easing.

A further object of the invention is the provision of a switch having means whereby the gaseous contents of the switch may have such'a high proportion of combustible gases that the resultant mixture is too rich to ignite and, consequently, there can never be an explosion of the gaseous contents in the switch.

Space is limited within the manhole and consequently, the switch should he of as small dimensions as is practicable for reliability in operation. In the usual type of electric switch, the switch terminals occupy a relatively large amount of space and,'furthermore, additional space is required to insulate the terminals from adjacent conducting members maintained at ground potential. It is an object of this invention to extend the metallic-sheathed conductor cables of the circuit adapted to be controlled by the switch directly 'into the switch and to the contact members. thereof whereby to economize in space and materials and also provide a. minimum of electrical joints in the circuit.

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

Fig. 1 illustrates diagrammatically a manhole with an electric switch embodying my invention contained therein.

yes

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

Fig. 3 is a side elevation of the switch.

Fig. 4 is a transverse sectional elevation taken along lines 44 of Fig. 3.

Fig. 5 is an enlarged perspective detail of the method of connecting the end of the con ductor cable with the contact member of the electric switch.

As here shown, the electric switch embody ing this invention includes a fluid-tight enclosing casing consisting of two detachably connected upper and lower sections. The upper section includes a top wall 10 comprising a cover and integral and depending annular walls 12, which walls are adapted to enclose and surround the oil receptacle of the switch and are terminated at about the level of 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 ofthe lower casing section is adapted to be secured. The lower casing section comprises the side wall 16 to the'lower end of which the internally ribbed and more or less spheri cally shaped bottom wall 18 is secured in any suitable manner as by welding. The upper end of the, side wall of the lower. section is formed or provided with the peripherally outstanding flange 20 which is adapted to be secured detachably against the flange 14 of the upper casing section in any suitable manner as by means of the bolts 22. A packing 24 may be interposedbetween said two flanges whereby to seal the joint thereat.

The electric switch herein shown is arranged for the control of a three-phase electric circuit and to this end is provided, in effect, with three'sets of switch components comprising stationary and movable switch members, and oil receptacles. Said sets of switch components are or may be identical and consequently but one 'set will be described. Each set 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 aperipheral passage 28 'communicatingiwith the space above the oil in said oil receptacle and the gas expansion space A of the lower casing section. The upper edge of the oil receptacle is preferably spaced. from the ton or cover of the upper casing section as at 30 whereby to provide free communication between the space above the oil and said peripheral passage 28. The oil receptacle is preferably supported yieldingly in position and to this end rests upon a platform member 32. Said platform member extends laterally on opposite sides of theoil receptacle and is slidable on vertically extended supporting rods 34 which rods are dis osed in the eripheral 7 l a passage 28'between the oil receptacle and the side walls 12 of the upper casing'section. Nuts 36 are adjustably screw-threaded on the lower end of said rods 34 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 portions 40 which are extended through the top 10 of the upper casing section and nuts 42 are screw-threaded on the ends of said rods whereby to secure them fixedly to the casing.

Packing washers 44 may be interposed between the top of the casing and said nuts 42, or other suitable means may be provided,

' whereby to provide fluid tight joints between the casing and said rods.

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. Said collars are prosaid ferrules 54 and are provided with cable receiving recesses 58 therein. connectors are provided with reduced and ex- Said cable ternally screw-threaded ends 60 which are screw-threaded in said ferrules and are extended downwardly therethrough. Check nuts 62may be screw-threaded on said extended ends 60 and bear against said ferrules whereby to lock said cable-connectors removably in position and also to provide an oil tight-joint thereat although it is not vital that the joint be strictly oiltight. A contact member 64 may bescrew-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 10 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 7 O which cover plates are removably secured to the top of the casing in any suitable manner as by of a pivoted operating lever 96.

bolts 72. said cover plates are formed or provided with upstanding necks 74 provided with cable'openings therethrough which are disposed in vertical alignment with said transformer wells and the passages in the insulating bushings.

In accordance with this invention, the con dnctor cables 76 are extended directly into the switch and through the bushings and to the 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 an d 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 fluidtight 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 trancformer wells 68 and thereby forum the insulating means interposed between the conductors of said cable and said transformers This particular arrangement is highly dc able 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 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 electricall thereto.

The movable switch member includes an insulating rod 86 and a bridgin 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 86is preferably reduced in diameter andexten ds 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 ends of said rods 86 may be secured to a common supporting bar 94. Said bar may be pivotally secured to the free end Suitable operating mechanism including the exposed operating handle 98 may be connected with said operating lever whereby the switch may be operated manually. The switch is also adapted to be opened upon overloa d by means including the trip coil 100.. which coil is adapted to be energized in any suitable manner not necessarily indicated from current transformers contained in said wells 68.

The switch may be supported in suitable manner as by laterally extended brackets 102 carried by the opposite side walls of the casing at the upper end thereof. Said brackets may rest upon and be secured to suitable frame members 104. The oil receptacles herein shown are adapted to be lowered from position about the switch members and, for this purpose, the switch is supported at a sufficient distance above the floor of the manhole to permit the oil receptacles to be lowered below the switch members and withdrawn from beneath the upper casing section of the switch when the lower casing section is removed.

The lowcr casing section is adapted to be of such vertical dimensions as to occupy a large proportion of the space required for the removal of the oil receptacle. Consequently, the volume enclosed by said lower casing section, and forming the gas expansion space of the switch, is relatively enormous as compared with the usual gas expansion space. lVhen the circuit through the switch is interrupted under load. the gases generated during circuit interruption pass over the gas space in the oil receptacle and downwardly through the lateral passages 28 into the gas expansion compartment of the lower section. The volume of this compartment is adapted to be so large, compared with the volume of gaseous products generated during circuit interruption, that the gaseous pressure rise within the switch casing is inconsiderable or at least is safely below any pressure which would damage the casing. A substantial proportion of the gaseous products are in the form of condensible vapors. By reason of the relatively large dimensions of the casing, it has a relatively large extent of surface exposed to the cool atmosph re of the manhole and, consequently, the condensible vapors are condensed and the condensate collects in the bottom of the lower casing section, thereby effecting a reduction of pressure immediately after circuit interrupt-ion. Furthermore, the peripheral. passage 28 while having a relatively large total area, has a relatively small transverse dimension and consequently, the gases passing downwardly therein in the oil receptacles are maintained in intimate contact with the cold side walls of the receptacles and the switch casing so that the condensible gases which will condense before passing into the lower expansion space of the casing, whereby the increase of pressure may be confined largely in the oil receptacles themselves.

while a substantial proportion of the gaseous products formed during circuit interruption are condensible some of the gaseous products are fixed or non-condensible under ordinary conditions. Consequently, after the switch has been interrupted repeatedly under "ilO load, the fixed gases may collect within the casing and build up a substantial pressure therein. lVhile ordinarily the accumulation of fixed gases within the casing may be inconsiderable between the periods of routine inspection and opening of the switch, it may sometimes happen that the switch may be caused to open its circuit under heavy load repeatedly within a short interval and there by the accumulation of fixed gases may be su'llicient to create a substantial amount of pressure. For this reason means may be provided to relieve the switch of such accumulation of pressure. Said means may include a venting conduit as the relief pipe 110 and a relief valve 112 disposed at the upper end of said pipe. Said relief pipe preferably communicates with the casing at the lower end thereof and is extended upwardly externally of and alongside of the switch to discharge the switch gases into the proper section of the manhole from which location they may be dissipated rapidly without forming a combustible mixture with the main body of air contained in the manhole.

The relief valve is arranged normally to close the discharge end of the relief pipe 110 and is preferably of the well known gravityoperated type although a spring 114 may be utilized to assist the action of gravity in maintaining the relief valve closed and the casing sealed. The adjustment of said valve is adapted to be such that when the gaseous pressure within the casing is increased to a predetermined value, the valve will open and relieve the pressure and close while there is still some substantial pressure within the casing so that the casing may always be more or less completely filled with a mixture so rich in combustible gases that the mixture can notexplode. The elevated position of the relief valve is advantageous also in that it normally will be above the level of any accumulation of water within the manhole.

Oil may be thrown from the oil receptacles into the bottom of the switch casing upon cir- V cuit interruption, and the oil will collect in the bottom. The amount of oil expelled from the oil receptacles, and therefore the operat ing condition of the switch may be estimated by means of an oil sump which may comprise a relatively short section of pipe 116 inserted in the bottom wall 18 of the casing and normally sealed by means of a cap 118. If, upon rem-oval of said cap, a substantial amount of oil escapes, it is an indication that the switch casing should be opened and fresh oil placed in the oil receptacles.

The construction may be otherwise modified without departing from the spirit of the invention.

I claim:

1. An electric switch having an upper oil receptacle which is closed at the top, a large gas expansion compartment disposed beneath said oil receptacle, and means providing fluid communication between said compartment and said oil receptacle, said compartment constituting means to keep down the internal pressure within the receptacle by receiving the gases formed in the receptacle during circuit interruption.

2. An electric switch having a casing providing a large gas-expansion compartment in the bottom thereof, an oil receptacle disposed a the upper part of said casing above said gas-expansion compartment, and means providing fluid communication between said upper receptacle and lower compartment, said compartment characterized by receiving the gases formed in the receptacle during circuit interruption and keeping down internal pressure within the receptacle.

3. An electric switch havinga casing providing a gas-expansion compartment in the bottom thereof, an oil receptacle disposed in the upper part of said casing above said gas expansion compartment, and means providing fluid communication between said upper receptacle and lower compartment, said gasexpansion compartment having approxi mately the volume of said oil receptacle, and characterized by receiving the gases formed in the receptacle during circuit interruption.

4. An electric switch having a fluid-tight casing comprising upper and lower detachably-connected sections, an oil receptacle and switch-members contained in the upper section and said lower section providing a gas expansion compartment for said oil receptacle.

5. An electric switch having a fluid-tight casing comprising upper and lower sections having means detachably to unite them at about the middle of the casing, an oil receptacle and switch members contained in the upper section, said lower section providing a gas-expansion compartment for said oil receptacle.

6. An electric switch having a fluid-tight casing including a closed top and side walls depending below said top to provide a compartment open at the bottom, anoil receptacle and switch-members contained in said compartment, at least mainly above the open bottom thereof, and a fluid-tight closure for the open bottom of said compartment comprising an open top receptacle having approximately the volume of said compartment.

7. An electric switch having a fluid-tight casing including a closed top and side walls depending below said top to provide a compartment open at the bottom, an oil receptacle and switch-members contained in said compartment at least mainly above the open bottom thereof, a fluid-tight closure for the open bottom of said compartment comprising an open top receptacle having approximately the Volume of said compartment, and

means to secure said closure detachably in the aforesaid relation.

8. An electric switch having a fluid-tight casing including a closed top and side walls depending below said top to provide a compartment open at the bottom, an oil receptacle disposed in said compartment and spaced from said side walls, and a closure for said casing comprising an open-top receptacle disposedabout the open bottom of said compartment, and means to secure said casing and receptacle in the aforesaid relation, said open-top receptacle constituting a gas expansion compartment adapted to receive the gases generated in the oil receptacle during circuit interruption, and the space between the oil receptacle and the side walls of said casing constituting a passage in which the gases are cooled before entering said open-top receptacle.

9. An electric switch having an enclosing casing, an oil receptacle disposed in the upper portion of said casing and the bottom portion of said casing providin an expansion compartment for said oil receptacle, the side walls of said casing being divided horizontally at about the bottom line of said oil receptacle.

10. An electric switch having an enclosing casing formed with an opening through its top wall, an insulator bushing disposed within said casing with its internal passage disposed in line with said opening, a contact member carried by the lower end of said bushing, a closure for said casing-opening comprising a cover-plate having an outstanding neck and a conductor-passage through said cover-plate and neck, means removably securing said cover-plate to said casing over the casing-opening, and a metallic-sheathed insulated line conductor extended through and having its sheath connected to said neck and extended into said bushing and connected with said contact member.

11. An electric switch having an enclosing casing provided with a conductor-passage therein, an enclosed transformer well surrounding said conductor passage, and an insulated contact member disposed in said casing beneath said transformer well. I

12. An electric switch having an enclosing casing provided with a transformer well having an opening at the top and also at the bottom thereof, an insulated contact member disposed within said casing below the open bottom of said well, and a cover-plate removably closing the open top of said well.

13. An electric switch having an enclosing casing provided with a transformer well having an opening at the top and also at the bottom thereof, an insulated contact member disposed within said casing below the open bottom of said well, and a cover-plate removably closing the open top of said well said cover-plate having an opening therethrough arranged in line with the bottomopening .of said well.

14L. An electric switch including an enclosing casing provided, with .a transformer well having an opening at the top :and also at the bottom thereof, an insulating bushing disposed within said casing about the bottom-opening of said well, and a contactmember carried by the lower end :of said bushing.

An electric switch includingan enclosing casing provided with a transformer well harin an opening at the top and also at the bottom thereof, an insulating bushing disposed within said casing about the bottomk opening of said well, ;a:contact meinber carried by the lower end of said bushing, a movable contact member cooperating with the aforesaid contact member, a flexible line conductor passed through the top and bottom openings of said transformer well, and into said bushing, and means detachably connecting said conductor and contact member.

16. An electric switch including an enclosing casing provided with an enclosed transformer well having conductor-openings in its top and bottom, an insulated contact member disposed beneath said well, and a metallicsheathed and insulated conductor-cable extended into said casing and through said conductor-openings, means connecting the conductor of said cable electrically with said contact member, and means securing the sheath of said cable to said casing, and said cable having its insulation carried through said transformer Well and outwardly therebeyond in the direction of said contact member.

17. An electric switch having an oil receptacle, a cover therefor, a separate gasexpansion compartment, and means providing a gas-passage between the upper portion of said receptacle and said compartment, said receptacle, compartment and gas passage betaining compartment whereby the condensed vapors can fall into and be retained in said gas expansion compartment.

19. An electric switch comprising an oil receptacle and a cover therefor which has a substantially flat bottom face which bears upon and overlies the top edge of the receptacle, whereby the switch is without a gas expansion chamber above the top of the receptacle, in combination with a closed chamber external of the switch and having practically the volume of the oil receptacle, and means providing gas communication between said chamber and the switch above the oil in the receptacle by which are gases can expand immediately into said closed chamber at the instant of circuit interruption, said chamber constituting the gas expansion chamber for the switch and being normally closed to the atmosphere.

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

JOSEPH D. WOOD.

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