US2478296A - Multiple position switch with movable contact mounted on an insulated shaft - Google Patents

Description

g- 1949- D. G. M ARN ETAL 2,478,296

MULTIPLE POSITION SWITCH WITH MOVABLE CONTACT MOUNTED ON AN INSULATED SHAFT Filed Feb. 15, 1947 l l 27 v 23 3 32 22 A9 2/ Patented Aug. 9, 1949 MULTIPLE POSITION SWITCH WITH MOV- ABLE CONTACT MOUNTED ON AN INSU- LATED SHAFT Donald G. McArn and Percy E. Cook, Pittsburgh, Pa., assignors to Allis-Chalmers Manufacturing Company, Milwaukee, Wis., a corporation of Delaware Application February 13, 1947, Serial No. 728,250

Claims. (01. 200-11) This invention relates in general to improvements in electric switches, and more particularly to a selector switch of the type in which a contact shoe is movably mounted on a rotary shaft to cause selective bridging of a plurality of contact studs.

When a selector switch is built with a rotary shaft, it is generally advantageous to make the shaft of metallic material to obtain a shaft having a, relatively large resistance to mechanical efforts for its size. However, the presence of an electrically conductive shaft increases the difficulty of preventing fiashovers and surface discharges between switch elements operating at different potentials. It is therefore a general practice either to mount the movable contact on the shaft through insulating means, or to space the fixed contacts at a relatively great distance from the shaft. Both solutions render the switch relatively bulky and expensive.

By embedding the shaft in an actuating member of insulating material having a portion serving as a handle and a portion serving as a journal, the shaft may be made to support the movable contact without interposition of insulating material therebetween. The fixed contacts may then be disposed relatively close to the shaft without raising serious problems of insulation. The shaft may advantageously protrude into a cavity of the actuating member to serve as a fulcrum for the movable contact. A stop may also be provided on the actuating member to engage a fixed member when the shaft is in a predetermined position without thereby reducing the effectiveness of the shaft insulation, and to limit the movement of the movable contact when the actuating member is removed from the switch base.

It is therefore an object of the present invention to provide a multiple position switch in which the distance between a metallic shaft and adjacent fixed contacts may be reduced to a minimum.

Another object of the present invention is to provide a multiple position switch in which a movable contact is conductively mounted on a metallic shaft without thereby impairing the insulation between adjacent fixed contacts.

Objects and advantages other than those above set forth will be apparent from a consideration of the following description when read in connection with the accompanying drawing, in which:

Fig. 1 is a view in side elevation of a switch embodying the different features of the present invention.

Fig. 2 is a plan view of the embodiment illustrated in Fig. 1, and

Fig. 3 is a view of the embodiment illustrated in Fig. 1 partly in rear elevation and partly in vertical cross section taken along line III-III in Fig. 1.

Referring more particularly to the drawing by characters of reference, numeral 6 generally designates a switch base for a selector switch of a type adapted for effecting different connections between taps of a transformer winding. Base 6 is of generally slab-like shape and may be made of any suitable insulating material, such as molded synthetic resin. A bore I provided in base 6 has its axis substantially perpendicular to the body of the base. Bore I may be of uniform or non-uniform diameter, provided that its crosssection is circular at every point along its axis.

Base 6 is also provided, on both faces thereof, with a plurality of shoulders 8 molded integrally therewith and uniformly spaced on a circle centered on the aXis of bore 1. Shoulders 8 may be all of uniform height, or may include a shoulder 9 which is made of greater height than the other shoulders and protrudes above the shoulder level for limiting the movement of the switch. Shoulders 8 serve for mounting a plurality of contact studs H, which are thus likewise uniformly spaced on a circle centered on the axis of bore I.

Studs I I may be shaped in any suitable known manner to provide secure fas-tenin of the studs in base 6. For example, the studs may be corrugated so as to interlock with the material of the base during the process of molding the base. Studs II are suitably shaped, at one extremity to provide a path for the movement of a movable contact shoe, and at the other extremity to provide for fastening current conductors thereto by soldering, crimping or otherwise.

The shaft I2 of the switch is made of suitable metallic material such as brass. Shaft i2 is of smaller diameter than bore I and is partially embedded in an actuating member generally de nated I3. Member I3 may be made of any suit" able insulating material such as molded synthetic resin. Secure fastening of shaft I2 in member I3 is obtained in any suitable known manner, as by making the shaft corrugated so as to inter" lock with the material of member I 3 during molding thereof.

A portion of member i3 within which shaft I2 is embedded is of circular cross section to define a journal portion I 4 fitting into bore I of base 6. The lower portion of shaft I2 protrud- 7 common potential.

ing from journal I4 is provided with a circular groove or other indentation to receive a removable locking device such as a horseshoe shaped Washer I5. A bushing l6 surrounding the protruding extremity of shaft I2 is locked between base and washer lIi'to prevent actuating member its from being withdrawn from bore I. The

upper extremity of shaft I2 protrudes into a cavity I? provided in member i3ladjacent the level of the contact surfaces of studs II.

The upper extremity of shaft I2 is shaped to define a pin l8 serving as a fulcrum for the movable contact shoe IQ of the switch. The shoe may be made of any suitable conductive material such as hard rolled sheet copper. The stud-engaging portion 2! of shoe [9 may be made V- shaped to impart a snap action to the switch. Shoe it may be further provided with a pair of parallel guide portions 22 adapted to slide along opposiite vertical walls of cavity ll. Shoe I9 is formed with a hole of sufficient size to permit rocking movement of the shoe about pin it, which extends through the hole.

Shoe E9 is biased toward studs it by suitable resilient means such as a helical spring 23 actin between shoe I9 and an extension of the upper wall of cavity Il'. Spring it is prevented from moving out of operating position by a boss 24 provided on member 53 and by another boss formed on shoe IS by indenting the shoe as at 25.

The lower wall of cavity ii is provided with a projection 25 serving as a stop. The upper portion of member i3 is shaped to form a handle 2'3, which may be shaped as a pointer to indicate toe position of the switch. The entire switch, or the switch with th exception of handle El, may be immersed in a suitable insulating liquid (not shown).

It will be apparent that when studs ii are connected to conductors at different potentials, shoe it, the pair of studs in contact therewith and shaft it are brought'to a predetermined Direct flashovers between e other studs and the shaft are effectively preted by the portion of insulating member I3 surrounding the shaft. Shoulders 3 and memalso oppose to surface discharges between studs ii and shaft 52 a creepage distance which may be made as large as desired without increasthe between the studs and the shaft.

When handle 2? is turned to change the connections effected by the switch, shoe i9 rides on top of one or another stud 5!. As a result of the l shape of shoe portion 2i, a torque is exerted on member 53 by spring 225 through shoe I e and the stud l l contact therewith. After the apex of shoe portion 2! has passed over a stud, such torque ca ses shoe l9 to move further into an ot po: ion bridging another pair of studs ll. obsr stops when equal torques are exerted thereon by spring 53 through shoe I 5 and the two studs ll contact therewith. Movement of member l3 into the new position takes place with a snap action, so that no additional means are required to cause the member to stop in predetermined positions. Shoe I9 always stops in a position where spring 23 applies substantially equal pressures between shoe portion 23 and the two studs l l in contact therewith.

During all movements of member l3, spring 23 biases downward the portion of shoe I9 extending into cavity ll, whereby the shoe is caused to remain securely anchored on pin l3.-

When an attempt is made to rotate member I3 through a complete revolution in the one or the other direction, member I3 is stopped in one or another contact-making position by engagement of one of the lateral surfaces of stop 26 with shoulder 9. In this manner it is possible to prevent certain movements of the switch which might introduce disturbances in the operation of the circuits controlled thereby.

The actionof spring 23 tends to cause journal portion It to be withdrawn from bore I, but such action is prevented by washer I5 and bushing It. By removing washer I5 member 13 may be removed frombase 6, Shoe I9 is then no longer supported by studs II, but its movement under the action of spring 23 is limited by application of th shoe against the upper surface of stop 26.

Member I3, shoe l9 and spring 23 may thus be handled as a unit, and may therefore also be assembled together prior to mounting on base 5. It will be understood however that regardless of whether or not member I3 is assembled on base 5, shoe [9 and spring 23 may easily be removed from cavity Il by tilting the shoe so as to cause disengagement thereof from pin I8. Conversely, shoe l8 and spring 23 may be mounted in cavity I'l while member I3 is assembled on base d The steps involved in assembling and disassembling the switch may thus be effected in whatever sequence is found most convenient.

Although but one embodiment of the present invention has been illustrated and described, it will be understood by those skilled in the art that Various changes and modifications may be made therein without departing from the spirit'of the invention or from the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. A switch comprising a base of insulating material provided with a'bore, a plurality of contact studs mounted on said base, said studs being uniformly spaced on a circle-centered on the axis of said bore, a metallic shaft of diameter smaller than the diameter of said bore, an actuating member of insulating material comprising a. journal portion in which said shaft is embedded; said journal portion being inserted in said bore and extending over the entire length of said bore for supporting said member for rotational movement about said axis, a contact shoe movably mounted on said shaft to bridge a selected pair of adjacent said studs, and resilient means acting between said actuating member and said shoe for biasing said shoe toward said studs.

2. A switch comprising a base of insulating material provided with a bore, a plurality of contact studs mounted on said base, said studs being uniformly spaced on a circle centered on the axis of said bore, a metallic shaft of diameter smaller than the diameter of said bore, an actuating member'of insulating material compris ing a journal portion in which said shaft is embedded, said journal portlon being inserted in said bore for rotational movement of said member about said axis, said actuating member being provided with a cavity, one extremity of said shaft protruding into said cavity, a contact shoe rockably mounted on said extremity of said shaft to bridge a selected pair of adjacent said studs, and resilient means acting between awall of said cavity and said shoe for biasing said shoe toward said studs. l

3. A switch comprising a base of insulating material provided with a bore, a plurality of contact studs mounted on said base, said studs being uniformly spaced on a circle centered on the axis of said bore, a metallic shaft of diameter smaller than the diameter of said bore, an actuating member of insulating material comprising a journal portion in which said shaft is embedded, said journal portion being inserted in said bore for rotational movement of said member about said axis, said actuating member being provided with a cavity, one extremity of said shaft protruding into said cavity, a contact shoe rockably mounted on said extremity of said shaft to bridge a selected pair of adjacent said studs, resilient means acting between a wall of said cavity and said shoe for biasing said shoe toward said studs, said resilient means tending to withdraw said journal portion from said bore, and. means attached to the other extremity of said shaft to retain said journal portion in said bore against the action of said resilient means.

4. A switch comprising a base of insulating material provided with a bore and with a plurality of shoulders, said shoulders being uniformly spaced on a circle centered on the axis of said bore and comprising a protruding shoulder of greater height than the remaining said shoulders, a plurality of contact studs mounted on said shoulders, a metallic shaft of diameter smaller than the diameter of said bore, an actuating member of insulating material comprising a journal portion in which said shaft is embedded, said journal portion being inserted in said bore for rotational movement of said member about said axis, a contact shoe movably mounted on said shaft to bridge a selected pair of adjacent said studs, resilient means acting between said actuating member and said shoe for biasing said shoe toward said studs, and a stop member on said actuating member to stop the rotation of said actuating member upon engagement of said stop member with said protruding shoulder.

5. A switch comprising a base of insulating material provided with a bore and with a plurality of shoulders, said shoulders being uniformly spaced on a circle centered on the axis of said bore and comprising a protruding shoulder of greater height than the remaining said shoulders, a plurality of contact studs mounted on said shoulders, a metallic shaft of diameter smaller than the diameter of said bore, an actuating member of insulating material comprising a journal portion in which said shaft is embedded, said journal portion being inserted in said bore for rotational movement of said member about said axis, said actuating member being provided with a cavity, a contact shoe movably mounted on said shaft to bridge a selected pair of adjacent said studs, resilient means acting between said actuating member and said shoe for biasing said shoe toward said studs, and a stop member projecting from a wall of said cavity, said stop member having a surface against which said shoe is applied under the action of said resilient means when said actuating member is withdrawn from said bore to limit the movement of said shoe, said stop member having another surface which is applied against said protruding shoulder upon movement of said actuating member into a predetermined position to stop said actuating member.

DONALD G. McARN.

REFERENCES CITED UNITED STATES PATENTS Name Date Siegel June 27, 1939 Number Certificate of {forrection Patent N 0. 2,478,296 August 9, 1949 DONALD G. McARN ET AL.

It is hereby certified that error appears in the above numbered patent requiring correction as follows:

In the signature to the printed specification, for DONALD G. McARN. read DONALD G. McARN. PERCY E. 000K.

and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office. Signed and sealed this 14th day of March, A. D. 1950.

THOMAS F. MURPHY,

Assistant Oommissz'oner of Patents.

Certificate of Correction Patent N 0. 2,478,296 August 9, 1949 DONALD G. McARN ET AL.

It is hereby certified that error appears in the above numbered patent requiring correction as follows:

In the signature to the printed specification, for DONALD G. MoARN. read DONALD G. McARN. PERCY E. 000K.

and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Ofiice. Signed and sealed this 14th day of March, A. D. 1950.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

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