US2416972A

US2416972A - Multiple contact switch

Info

Publication number: US2416972A
Application number: US544842A
Authority: US
Inventors: Jr Albert J Williams; Raymond E Tarpley; Norma C Johnson
Original assignee: Leeds and Northrup Co
Current assignee: Leeds and Northrup Co
Priority date: 1944-07-14
Filing date: 1944-07-14
Publication date: 1947-03-04
Anticipated expiration: 1964-03-04

Description

M h 4, 1947. A. J. WILLIAMS, JR., ET'AL 2,416,972

MULTIPLE CONTACT SWITCH Filed July 14, 1944 2 Sheets-Sheet 1 IN VEN TORS 445527 .1 WILL 144, JR mum/01m TARFLEY A/dRA/A c. JO/l/VJO/V 0 1 wmadi ATTORNEY Mar h 4, 1947, A. J.'WILLIAMS, JR., E'l'AL 2,416,972

MULTIPLE CONTACT SWI TCH F led y 14, 1944 2 Sheets-Sheet 2 III 40 ATTORNEY I Patented Mar. 4, 1947 UNITED STATES PATENT orrlce MULTIPLE CONTACT SWITCH Albert J. Williams, Jr., Raymond E. Tarpley, and

Norma C. Johnson, Philadelphia, Pa., assignors to Leeds and Northrup Company, Philadelphia, Pa, a corporation of Pennsylvania 9 Claims. 1

This invention relates to electric switches of the multiple contact type and has for an object the provision of an inexpensive multiple contact, or gang, switch of sturdy construction and of improved electrical characteristics.

In radio systems, control circuits, and measuring systems it is frequently necessary to provide multiple point switches suitably to change i the circuit connections. For example, in a radie a plurality of circuits must be changed in order to change the wave band to which the radio will be responsive. In measuring circuits, it is frequently desirable to vary over a substantial range, the resistance, inductance or capacitime included in the measuring circuit.

In carrying out the present invention in one form thereof, there has been provided a multiple contact switch suitable for the foregoing systems, for resistor decades, capacitor decades, and suitable for measurements in high resistance circuits, that is, where the resistance of the circuit connected to the decade may be 01' the order of 500 megohms. Because of the relatively small size of the switch, and the resultant saving of metal, silver contacts may be used without unduly increasing the cost over multiple-point switches of the prior art. More particularly, a stator or frame, preferably molded of high grade insulating material, is provided with a plurality of inwardly extending arms, the inner end of each of which terminates in an enlarged end. The opposed surface or ends of these arms abut against a disc which may be slidably mounted on and carried by a driveshaft. Plates are securedto the disc to retain it in a predetermined position axially of the shaft. These plates overlap, or extend beyond, the enlarged ends on the pro- Jections. Each plate rests against corresponding sides of the projections and together they form bearing surfaces therewith. One or both of these plates may be a conductor, such, for example, as silver, and each is designed with a configuration suitable for carrying out desired switching operations in cooperation with stationary contacts carried by the stator. By providing the bearing surfaces near the axis of the switch and near its operating shaft, and by spacing all stationary contacts outwardly from these bearing surfaces, there is avoided the contamination of the contacts by insulation which otherwise might adhere to the contact plates and which would greatly change the electrical characteristics of the switch.

In accordance with a further aspect of the invention. a switch is provided which is particularly suited to the control of decades. For ex- Application July 14, 1944, SerialNo. 544,842 y 2 ample. in using a decade measuring device, the ten resistance values corresponding to one decade may be successively connected in the measuring circuit, followed by the first resistance of a second decade of value equal to the total resistance of the first decade. Accordingly, the resistors of the first decade are removed from the circuit and replaced by a short circuit as the first resistor of the second decade is connected in the measuring circuit. Instead of returning the switch through its ten positions, it is simply rotated from its last position directly to its zero position.

For its first ten positions, an index plate and associated spring means oifer substantial opposition during each change of switch position.

This opposition to movement is relatively uniform. However, as soon as the switch is rotated from its first or last position, toward the other of-said positions, the opposition to movement is .so greatly changed as to comprise a signalling means as to the position of the switch and as to the next position it will occupy if the knob is further rotated in the same direction.

More specifically, the positioning means, as the index plate, is provided with a zone between the first and last positions of the switch where there is a minimum oiopposition to movement. In terms of the cam faces of the index plate, there is provided a dwell between the last and the first positions of the switch.

For a more detailed explanation of the invention and for further objects and advantages thereof, reference is to be had to the following detailed description taken in conjunction with the accompanying drawings, in which:

Fig. 1 is an exploded perspective view, on an enlarged scale, of a switch embodying the inven-' tion;

Fig. 2 is a sectional elevation, on an enlarged scale, of an assembled, switch embodying the inone form has been shownas applied to a multiple-point' switch comprising a stator ill provided, Fi 3, with stationary contacts on one side thereof and, Figs. 2-4, additional contacts l6, I1, l8 andl9 mounted on the opposite side of stator i0. These stationary contacts on the line 3-3 of stationary contact through thes-tationary contact IE will be intertor 22 by any suitable means, such, for example, as by rivets, one. of which, the rivet 25, is shown in the enlarged view of Fig. 4. These contact plates 20 and 2| overlap the enlarged ends provided on each of four inwardly extending

arms

21, 28, 29 and 30, Fig. 1. The inner surfacesof each of the enlarged ends abut against the retor 22 to center it within the stator III and to 'form a radial bearing surface therefor.

Referring particularly to Figs. 4 and 5, it will be seen that each of the enlarged ends also engages opposed surfaces of plates 20 and 2| atpoints closely adjacent the edge of the rotor 22.- For example, Fig. 4, the bearing surface of each enlarged end on the inner surface of plates 20 and 2| does not extend beyond the radius32. On the other hand, the stationary contacts do not extend inwardly beyond the radius 33. This means that the bearing surfaces are separate and spaced from the cooperating contact surfaces. In consequence, insulation which may be transferred from the. projections to the contact plates 20 and 2| is not introduced between any of the contact members.

The stator l and the rotor 22 are preferably constructed of insulating material of a character which is not adversely affected by weather, particularly changing humidity. One such insulating material, known to the trade under the name of Polystyrene, may be used because of its low power factor and high resistivity even under high humidity conditions. Both the stationary contacts li--i9 and the contact plates 20- and 2! may be of coin-silver to provide a minimum contact resistance. The stationary contacts, as best shown in Fig. 4, comprise resilient arms which are spread apart by movement of a part of a disc therebetween. With the switch in the position illustrated in Fig. 3, it will be observed that an electrical circuit may be completedfrom the contact i2,-through the disc 20, to the contact IS. The contact l5, like the other contacts, is secured to the stator ill by means of a rivet "which ex-- tends not only through the contact 1-5 but also a through the contact l8, Figs. 2 and 4. Hence, this to its zero position 1 electrical circuit also includes the stationary contact iii. In the illustrated modification of the invention, this circuit also extends through the disc 2| to the stationary contact l9, Fig. 2. If the switch is rotated in a clockwise direction as viewed in Fig. 3, a circuit will be completed through the i3 but the circuit traced rupted, Inasmuch as the stationary contact I2 continues to engage the contact plate 20, this cir cult is not interrupted. By insulating the rivets the contacts and contact plates on opposite sides of the rotor 22 and stator [0 maybe electrically independent. I 1

Each of

contact plates

20 and 24 isdesigned or given a shape to, provide contact areas or surfaces of differing radii to cooperate with stationary contacts which extend inwardly in diilering degree.

In this manner, any desired circuit connections 2 70 tion and that further movement will return it to may be made or interrupted according to a particular position of the switch. Additional assemblies of stationary and movable contact plates, as indicated at Illa, may be readily mounted on the shaft 23 for simultaneous operation from an operating knoblfl.

4 The switch as a whole may be supported in an suitable manner, a bushing 42 being satisfactory for this purpose. The bushing 42 is provided with a nut 43 for panel mounting of the switch, This bushing also provides a suitable bearing for the operating shaft 24 which is provided with a split ring 44 to restrain movement thereof in one direction. Thebushing 42 has secured to it a supporting plate 45, having a down-turned end 48 which is arranged to support aball 41 biased by a spring 48 against an index plate 50. The plate 50 serves topredetermine the resting position of the operating shaft and each rotor for each of the several switch positions. The index plate 50 is secured in a fixed position by means of two downturned ends which tightly engage the lower end of the bushing 42 as viewed in Fig. 2.

The several decks or switch assemblies are supported from the plate 45 by' means of a pair of bolts 5| and 52 which extend through openings in the frame ill. The bolts SI and 52 are each provided with

bushings

53 and 54, Figs. 1 and 3, the ends of which respectively abut against the plate 45 and the frame I0. Both bolts are threaded, the nut 55, for the bolt, 52, being shown andstator l0,upon operation of the knob 40,

Ordinarily stops have been provided to limit the rotation of the switch between predetermined limits. In, accordance with the present invention, the index plate 50 is provided with a series of crests and troughs corresponding in number with the several switch positions. Though all of the contacts havenot'been shown in the drawings, it will be observed, Fig. 3, that the twelve holes in the stator Ill' provide for the mounting of twelve stationary contacts. One contact, such as contact l'4,.may' be provided to complete circuit con nections to the contact plate 20. Another switch position will ordinarily be provided for the zero or short-circuitin P sition. This leaves the ten switch positions needed for a decade- By so arranging the circuit-controlling elements, the index plate is provided with an elongated smooth surface or dwell 50a, Fig. 1, located to correspond with the movement of the switch from its tenth The effect of the regularly, or evenly, spaced crests is to present uniform opposition to movement of the switch from one circuit-controlling position to another. Initial movement therefrom is resisted by the displacement of the ball 41 against the bias of the spring 48, Fig. 2.- As soon as the peak of each crest is passed, the spring aids the turning of the switch and finally'centers the ball 41 in a trough to hold the rotor in a circuitcontrolling position.

A wholly different action takes place because of the dwell 50a. After theinitial opposition to movement, the knob 40 seems to be relatively free.

There is no pronounced opposition or assistance upon continued movement thereof. Hence, the.

operator can tell at once from the feel, from the signal due to the change in opposition to movement, that the switch has reached its last posiits zero position.

This signalling effect is highly desirable for ap-- plications where the operator prefers/to, or must,

.trolling switches to achievethe balancing of a measuring circuit such as a Wheatstone bridge.

It is again emphasized that switches embodyin: the present invention have been found satisfactory for the control of high resistance electrical circuits as well as for the control of low capacity circuits. Though such high resistance circuits were of the order of 500 megohms, yet in the open position of the switch the insulation resistance of the switch remained high as com-' pared to such 500-megohm circuits.

The low contact resistance of the switch also makes it particularly applicable to low voltage circuits,

such, for example, as those which include-thermo-- said frame for cooperation with said conductors in the same plane'as said last-named surfaces.

3. In an electrical switch of the multiple contact type in which a cylindrical rotor is supported type illustrated, it is to be understood that a less or a larger number of arms may be utilized with all or only some of them provided with the enlarged end portions which engage the inner sections of the plates carried by the cylindrical disc 22. Hence, though a preferred embodiment of the invention has been described, it will be understood that modifications may be made without departing from the scope and spirit of the invention as set forth in the appended claims.

What is claimed is:

1. In an electrical switch of the multiple contact type, the combination of a frame of insulating material having an opening through the central portion thereof, a cylindrical rotor of insulating material of substantially the same thickness as said frame, said frame having a plurality of inwardly extending arms and together forming a bearing surface for said cylindrical rotor, each of said arms being characterized by an enlarged end portion which in a direction axially of said rotor has a dimension substantially equal to the axial thickness of said rotor, means for retaining said rotor in a predetermined axial position within said frame comprising members secured to opposite sides of said rotor and extending outwardly and over said projections to form bearing surfaces for rotation of said rotor relative to said frame, at least one of said members'being a conductor, and switch contacts carried by said frame for cooperation with said conductor along a zone thereof located in the same plane with but spaced outwardly from said last-named bearing surfaces.

2. In an electrical switch of the multiple contact type, the combination of a frame of insulating material having an opening through the central portion thereof, a cylindrical rotor of-in sulating material of substantially the same thickness as said frame, said frame having a plurality of inwardly extending arms and together forming a radial bearing surface for said cylindrical rotor, each of said arms being characterized by an enlarged end portion which in a direction axially of said rotor has a dimension equal to the axial thickness of said rotor, means for retaining said rotor in a predetermined axial position within said frame comprising members secured to said rotor and extending outwardly and over said projections to form bearing surfaces for rotation of said rotor relative to said frame, both of said members being conductors, and switch contacts carried on opposite sides of within a stator by means of a plurality of arms extending inwardly from the stator and into abutting engagement with the rotor, the combination of flat contact plates secured to opposed faces of said cylindrical rotor, each of said inwardly extending arms having relatively narrow end portions which extend axially of said rotor for engagement with said contact plates to limit axial movement thereof, and stationary contacts carried by said stator for engaging said contact plates at points spaced outwardly from the area engaged by said end portions.

4. In an electrical switch of the multiple con-.

tact type in which a cylindrical rotor is supported within a'stator by means of a plurality of arms extending inwardly from the frame and into abutting engagement'with the rotor, the combination of flat contact plates secured to opposed faces of said cylindrical rotor, each of said inwardly extending arms having relatively narrow end portions which extend axially of said rotor for engagement with the inner faces of said contact plates to limit axial movement thereof, and stationary contacts carried by said frame outwardly from the area engaged by said projections, each of said contact plates being cut away in the region which lies outward of said end portions for selective engagement by the remaining radial extensions thereof with said stationary contacts. Y

5. In an electrical switch of the multiple contact type in which a cylindrical rotor is supported within a stator by means of a plurality of arms extending inwardly from the stator and into abutting engagement with the rotor, the combination of means for supporting said rotor against axial movement comprising enlarged end portions on each of said arms, contact plates secured to opposite sides of said rotor and extending in overlapping engagement with said enlarged end portions to provide a bearing surface engaged by said end portions, and contacts carried by said frame and each disposed for engagement with a contact plate at a region spaced from the area of the plate engaged by said enlarged portions but in substantially the same plane thereof.

6. In an electrical switch of the multiple contact type in which a cylindrical rotor is supported within a stator by means of a plurality of arms extending inwardly from the stator and into abutting engagement with the rotor, the combination of means for supporting said rotor against axial movement comprising enlarged end portions on each of said arms, contact plates secured to opposite sides of said rotor and extending in overlapping engagement with said enlarged end por tions to provide axial bearing surfaces engaged by opposite sides of said end portions, and contacts carried by said frame and each disposed for engagement with radial sections of one or the other of said contact plates at a region spaced from the area of the plate engaged by said enlarged end portions but in substantially the same plan thereof.

7. In an electrical switch of the multiple contact type in which a cylindrical rotor of insulating material is supported within a stator of insulating material by means of a plurality of arms extending inwardly from the stator and into abutting engagement with the rotor, the combination 01' means for supporting said rotor against axial movement comprising enlarged end portions on each of said arms, contact plates secured to D- posite sides of said rotor and extending in overlapping engagement with said enlarged end portions to provide a bearing surface engaged by said end portions, and contacts carried'by said frame I and each disposed for engagement with a contact plate at a region spaced from the'area of the plate engaged by said enlarged portions and substan-' tially in the same plane thereof.

8; In an electrical switch of the multiple contact type in which a cylindrical rotor is supported within a stator by means of a plurality of arms extending inwardly from the stator and into abutting engagement with the rotor, the combination of contact plates secured to opposed faces of said cylindrical rotor, each of said inwardly extending arms having axial extensions which engage said contact plates to limit axial movement thereof, and stationary contacts carried by said stator for engaging said contact plates in the same plane but along areas differing from the area engaged by said extensions. v

9. In an electrical switch of the multiple. contact typ in which a cylindrical rotor is supported within a stator by means of a plurality of arms extending inwardly from the stator and into abutnEFEn1-mcnscrrnn The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,186,950 Allison Jan. 16, 1940 2,125,439 Gross Aug. 2, 1938 2,319,503 Glogau May 18, 1943 FOREIGN PATENTS Number Country Date ting engagement with the rotor, the combination French Aug. 14, 1926