US1912342A - Electric switch and arc extinguishing means - Google Patents

Description

ELECTRIC SWITCH AND ARC EXTINGUISHING MEANS- Filed Aug. 19, 1930 Patented May 30, 1933 UNITED STATES PATENT ori-"ice CHESTER y1). AINSWORTH, OF IVOLLASTON, MASSACHUSETTS, ASSIGNOR TO CONDIT ELECTRICAL MANUFACTURING CORPORATION, OF SOUTH BOSTON, MASSACHUSETTS,

A CORPORATION OF MASSACHUSETTS ELECTRIC SWITCH AND ARC EXTINGUISHING MEANS Application filed August 19, 1930. Serial No. @$6,253.

This invention relates to electric switches and arc extinguishing devices therefor.

The circuit interrupting arc that is drawn between the separating Contact members of an electric switch, when the switch opens under heavy load, is difficult to extinguish, and persists usually until the arc has been attenuated to a relatively long extent. The length of duration of the heavy arc is sufficient to cause the contact members to become burned and large amounts of the oil or other liquid in which the arc is usually drawn to become vaporized, thereby building up a considerable and oi'ttimes dangerous gas pressure within the switch casing.

One of the objects of the present invention is the provision of improved means which is in intimate yContact with the arc at the time the switch opens under normal load and which is a part of the circuit interrupting elements of the interrupter and which acts to cool and rapidly to extinguish the arc, and thereby avoid severe burning of the contact members and vaporization of the oil.

Another object'of the invention is to force the arc out into a thin band or ribbon which is held against a cool insulating surface that abstracts heat from the ribbon and thereby rapidly de-ionizes and extinguishes the arc.

Another object of the invention is the provision of a relatively massive block of insulating material having a face which confronts and is close to the separable arc-ing members, and magnetic meansto blow the arc that is formed between the arcing members against the face of the block, whereby the are is cooled and extinguished.

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

Fig. 1 is a sectional elevation of such elements of an electric switch as are necessary to illustrate the invention.

Fig. 2 is a section taken along line 2-2 of Fig. 1'. f

Fig. 3 is a detail showing the relation between the arc and the cooling and arc extinguishing block.

Fig. 4 is a perspective view of a modified form of an karc-cooling block.

brush member.

Fig. 5 is a detail illustrating the arccooling block carried by a wall of the switch casing.

Fig. G is .a perspective view of the contact member supporting bracket which supports the arc cooling-block of Fig. 1.

Fig. 7 is a front view of the arc coolingblock having a further modified form of arc-engaging face.

The electric switch here shown as embodying the invention comprises stationary switch members 10, and a movable switch member 12. The stationary switch member includes an insulating bushing 14 having a conducting stud 1G. An inverted brush member, or main current carrying member, 18 is located on the lower end of the stud and is secured thereto by upper and lower clamping nuts 20, 22, respectively, which are screw threaded on said stud on opposite sides of the brush member. A stationary auxiliary contact or arcing member 24 is located beneath the Said arcing member consists of a horizontally-disposed massive cylinder of copper or other suitable material, that is located between the depending ears 26 of a supporting frame and is secured to said frame by a bolt 28. Said frame has an upper horizontal member 30 which is disposed between the brush member 18 and the nut `2O and is secured to the stud 16 by said nut. l

The movable switch member includes the lifting rod 32. A bridging member 34 of inverted channel shape is supported loosely on a stud 36 that is carried by the lower end of said lifting rod and serves to bridge and thereby electrically to connect the brush members 18 when the switch is closed. A supporting frame 38 ot' inverted channel shape is located between the depending flanges of the bridging member 34 and is rigidly secured to the stud 36 of the lifting rod. A conducting bar 40 is located between the depending iianges of said supporting frame and has a horizontal upper section which is carried by said frame, a downwardly reflexed or vertical outer section 42, a horizontal lower bottom section 44, and an. upwardly reilexed or vertical inner end section 46, said member being similarly formed at both ends although but one end being here shown. A rigid arm 48 is located between the aforesaid sections and is pivotally counected at 50 to the upper end et the inner vertical section 46. Said arm extends loosely through a slot in the outer vertical section 42 and has a biturcated ou er end between which an auxiliary movable Contact or arcing member 5l is secured. Said arcing member is similar to the stationary arcing member 24 and engages said arcing member when the switch is closed. An insulating bushing 5G surrounds the arm 4S where it passes through the slot 52 whereby to prevent electrical conf tact between said arm and the section A spring 58 bears against said bushingl and a cup G0 is seated in an aperture oi? the horizontal section la whereby to urge said arm and the areing member carried ther-cbj.' to'- ward the stationary arcing member.

Then the switch is closed, the currentpasses from one auxiliary arcing member through the rel'leXed portions of the conductor bar 4() to the other arcing member. rl`he magnetic reactions ot the upper and lower portions of the conductor d() with the contact carrying bar are such as to urge said bar upwardly toward the stationary arcing member 24 and thereby to maintain the movable arcing member in firm engagement with the stationary arcing member. The refiex'ed portions ot the conductor -iO are located as close to the arcing members as is practicable so as to set up a strong magnetic field in the arc Zone between the arcin members and at right angles to the line oi separation ot said arcing members.

The reieXed portions thus exert a strong magnetic blow-out effect on the arc and torce it outwardly or toward the insulating lining 62 located adjacent the side wall Gllof the enclosing casing.

In accordance with this invention, I provide a massive block 6G of insulating material which is vertically disposed close to the separable arcing members and between them and the casing wall. The block is suitably supported in the aforesaid position as by being secured to an extension (3S of the horizontal section SO ot the contact supporting braclet 26. The block preferably is removably secured to said extension by the bolt and nut 71. The block is provided with a vertical face 72 which closely confronts the arcingmembers and said face is oi" substantial extent both in vertical and horizontal directions sothat preferably it is of greater extent than the highly heated and conducting gas Zone ot the are. The magnetic reactions oit the retlered portions, or loop, oi the conductor l0 is such as to blow the are into intimate contact with the face 72 of the block and to spread the arc gases as a thin band 'f Fig. 3, which lies in intimate contact with the surface ot the block. The block is normally cold and thus cools the arc and thereby quickly renders the gases thereof non-conducting. The magnetic action ot the looped conductor 40 on the arc is particularly helpful since it spreads the gases out into a thin band so that the cool block van act throughout the entire thickness of the band; and it forces the gases into intimate contact with the block. Preferably the block is ot some good heat-conducting and electrically-insulating material, such as a carborinnilum block which not only has good heat conductivity for an electric insulator but also highly resistant to the action of the are. Other suitable materials, however, may be employed.

This invention is particularly adapted to a switch wherein the separable arcing members are immersed in oil and the arc is drawn beneath the surface ot the oil. lith this type of switch, the insulating block 66 preferably also is porous so that it can become impregnated with oil. The oil will be released at the surface 72 of the block when the arc is in engagement therewith and the cool oil will come into intimate contact with and cool the arc. The corborundum block aforesaid can be obtained in porous form with the pores indistinguishable to the eye. Other insulating blocks of good porosity also can be obtained readily. The insulating block not only acts by itself to cool and thereby extinguish the are, but it holds the oil surrounding the arcing members in place during circuit interruption and thereby effects an additional deionizing and extinguishing action on the arc.

lVhile in Fig. 1 the arc receiving surface 72 is plane, in Fig. 4 it is provided with transverse corrugations 76 so as to increase the length of surface that supports the arc and thereby the cooling eifect on the arc. The corrugations 76 also retain oil which increases the eifectiveness of the arrangement. In Fig. 7 the surface of the block'is grooved to provide a series of alternate arcengaging projections 76a and indentations 77, the projections being of pyramidal configuration that act upon the arc to divide it into small streams and to cool and deionize the small streams.

It is not essential that the block 66 be supported by the stationary switch member. In Fig. 5 the block is supported by the insulating lining 62, said lining having Z-shaped brackets 78 that are located in transverse grooves 80 formed in the upper and lower faces of the block so that the block is removably retained in position.

I claim:

l. A circuit interrupter comprising sepa,- rable contacts, an arc-extinguishing block of insulating material of high heat absorbing properties located parallel to the line of separation of said contacts and having a broad face which confronts said contacts, and

means to blow the arc formed between the separated contacts forcibly against the iat face of the block, said block being so close to said contacts that, in combination with the blowout means, the arcs that are formed during the opening of the interrupter under its normal load are forced intimately against said block for the major portions of their lengths and give up their heat thereto and are thereby extinguished.

2. A circuit interrupter as defined in claim 1 wherein a casing encloses said contacts and block and wherein the block is supported directly by one of said contacts and is spaced away from the side wall of said casing.

3. A circuit interrupter comprising separable contacts, an insulating block of heat absorbing material located parallel to the line of separation of said contacts and having al broad face which confronts said contacts, means to blow the arc formed between the separated contacts against the flat face of the block, said block being so close to said contacts that, in combination with the blowout means, thearc that is formed during the opening of thek interrupter under its normal load is forced against said block and gives up its heat theretoand is thereby extinguished, the arc engaging face of said insulating block being porous, and an arc extinguishing liquid contained in the pores which is liberated into the arc when the arc impinges thereagainst.

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

CHESTER D. AINSWORTH;

Images