US3309471A - Rotary switch contact structure with improved washer fastening means - Google Patents

Description

March 1967 P. H. KORRELL ROTARY SWITCH CONTACT STRUCTURE WITH IMPROVE WASHER FASTENING MEANS Filed May 23, 1966 Fig. 5.

Ru wa W m mH P m 0m Fig. 4 Q

a good seal to the rotor.

United States i atent Ofiiice 3,309,471 Patented Mar. 14, 1967 Iud., assignor to Appliance Van Buren, Ind., a corpora- The present invention relates to electric switches.

In certain types of electrical switches, mechanical precision is of the utmost importance. Thus, in certain rotary type switches, the closing of the circuit should be effected within a fraction of a degree and should continue to be effected within that same fraction of the same degree throughout the life of the switch. In the United States patent to Crimmins, 2,777,908, there is disclosed a wiper type switch which is easly constructed within narrow mechanical tolerances and which has been found to maintain proper operation within narrow angular tolerances over a long and useful life. However, because of the specific design of the Crimmins switch wherein electrodes of opposite polarity are spaced relatively closely to one another, there has been found to be room for improvement in the insulation resistance and voltage breakdown between current carrying parts and between current carrying parts and ground of the Crimmins rotary switch.

One solution to this problem is disclosed in the United States patent to Korrell et al., 3,248,489. While the solution illustrated in the Korrell patent has proved to be a substantial improvement in many respects, it has not proved to be entirely satisfactory because the epoxy of that patent cannot always be depended upon to produce Consequently, important objects of the present invention are to provide an improved rotary switch wherein the electrodes are better insulated from one another than prior art switches, to provide a rotary switch which is less subject to failure than prior art rotary switches and to provide a rotary switch which has a consistently higher breakdown voltage than prior art rotary switches.

A further object of the present invention is to provide an improved rotary switch.

' Still another object of the invention is to provide a rotary switch which is less expensive to assemble than prior art rotary switches.

A further object of the invention is to provide a rotary switch which can be easily assembled and disassembled without loss of parts.

Related objects and advantages will become apparent as the description proceeds.

One embodiment of the present invention might involve in a switch includin" an element formed of insulating material, a pair of electrical contact members mounted on the element, said members each consisting of a flattened metal piece having a pair of spaced legs, said element having recesses in the face thereof which recesses receive the leg ends of the respective members, said recesses in said element and the leg ends therein of one member being spaced from the recesses and the leg ends therein of the other member, the improvement which comprises a resilient washer of insulating material having projections at the periphery thereof which grip said element and retain said washer on said element, said element having indentations therein which extend between the leg ends of one'member' and the leg ends of the other member, and said washer including raised portions formed on said washer and extending into said indentations.

The full nature of the invention will be understood from the accompanying drawings and the following description and claims.

FIG. 1 is an exploded perspective view of certain portions of the switch of the present invention.

FIG. 2 is a perspective view of a stator plate forming a part of the switch of FIG. 1.

FIG. 3 is a plan view of the structure of FIG. 1 showing it in assembled relation.

. FIG. 4 is a section taken along the line 4-4 of FIG. 3 in the direction of the arrows.

FIG. 5 is an enlarged section taken along the line 55 of FIG. 3 in the direction of the arrows.

FIG. 6 is a perspective view of a washer forming a part of the present invention.

FIG. 7 is an enlarged section taken along line 77 of FIG. 3.

For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawing and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alternations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

The illustrated switch is of the rotary type and isparticularly adapted for assembly in a dirt or water tight housing. The particular housing shown comprises a receptacle 10 with a hermetically sealed cover plate 11 and with a flange 12 for panel mounting. A shaft 15 is journalled in one side of the housing and is sealed by the packing gland 16.

Stationary contacts 17 are arranged in a circle concentric with the axis of rotation of shaft 15. The cont acts 17 may be, for example cast in the stator plate 20 of insulating material such as the thermoplastics. In the illustrated device, the stator plate is cast integrally with the peripheral flange 21 which is externally machined to a close fit in the housing receptacle 10. A key (not shown) or the like may be employed between the telescoping surfaces of the flange 21 and the housing receptacle 10 to rotationally lock the stator in the housing receptacle. The outer ends of the contact elements 17 may be bifurcated as shown to receive soldered connecting wires. The connecting wires may lead later-ally through the extension 22 of the housing receptacle 10 and out of the receptacle through the aperture 25. After the cover plate 11 is in place, the space between the aperture 25 not filled by the connecting wires may be potted by suitable plotting compound injected into the space to seal the switch.

The inner ends of the contacts 17 are machined and polished to a true coplanar surface by chucking the stator in a lathe and turning concentrically to the central bore 26 of the stator. The leading and trailing edges of each contactor surface may be milled to precisely define the rotational position of these edges with respect to the axis of the stator. Hence, by ordinary lathe turning technique, the axis of rotation of the rotor may be precisely located relative to the surface of the contacts.

The rotor of the switch comprises a disk 30 of insulating material received on the reduced diameter portion 29 and retained against rotation relative to the shaft by the straight course knurl 28. The disk bears on one side against the housing of the gland 16 to insure against axial displacement of the shaft and its rotor with respect to the stator structure. The wiper pieces 31 carried by the rotor disk are designed to bridge two adjacent contacts 17 on the stator. The present switch is a double-pole,

double-throw switch and, consequently, two of the wiper pieces are provided. Each wiper piece 31 may be stamped from a sheet of low-resistance, corrosion-resistant metal such as silver or silver alloy. Wiping surfaces 32 and 33 are pressed out by an embossing tool and polished to make extended face-to-faoe contact with the polished end surfaces of the contacts 17. Each wiper 31 is made to float on the contacts 17 by means of an elongated hinge along one side of the wiper piece, said hinge being substantially parallel to a median line through the wiping surfaces 32 and 33 of the piece.

This hinge comprises two leg portions 34 and 35, each of which terminate in hinge pins as and 37. The hinge pins are set into notches or recesses 33 and 39 on the front face of the disk 33. The recesses or notches 33 and 39 are conveniently and accurately made by casting raised embossments integrally with the face of the disk as shown. When the hinge pins 35 and 37' are held in the notches 38 and 39, the respective wiper piece 31 may pivot about the hinge but is rigidly held against rotational displacement about the shaft. Each wiper piece 31 is formed so as to straddle the hub structure 49 of the disk and the shaft 15.

It should also be mentioned that the notches or recesses 38 and 39 are of sufiicient axial depth that the hinge pins 36 and 37 are free to move axially a limited distance in the notches or recesses. Consequently, the wiper surfaces 32 and 33 may be pressed against contacts 17 of different heights. If one corner moves down, the hinge pin at the diametrically opposite corner can move up. A pair of leaf springs 41 are provided beneath the wipers 31 and function to maintain a pressure at a Single point c'ehtrally of the wipers. The leaf springs 41 each have the same general plane configuration as the wipers 31. Each spring 41 is bowed outwardly so that a central portion thereof makes point contact with a head 45 pressed into the wiper piece 31. Each spring 41 is formed with pins 42 and 43 of the same dimensions as the hinge pins 36 and 37 so that the springs 41 drop into the recesses 38 and 39, respectively. The outer corners of the bowed portion of each spring bear against the flat surface of the disk 30 to transmit a fairly strong bias to each wiper 31 through the boss 45.

The hinge pins 36 and 37 and the pins 42 and 43 are locked into the notches 38 and 39 by a non-conducting washer 46 which may preferably be formed of nylon and which is pressed over the inner end of the shaft 15. The washer 46 is formed with two radially extending portions 50, each of which has a pair of projections 51 at the distal end thereof. The projections 51 have inwardly facing surfaces 52 which taper toward one another from their proximal ends to their distal ends. The cast raised gnbossments 55, within which the recesses 38 and 39 are formed, together with the hub 40 form an embossment or boss 58, the outer periphery of which is formed with outwardly facing surfaces 59 which flare outwardly from the proximal end 60 of the boss to the distal end 51 thereof. The inwardly facing surfaces 52 of the washer 46 engage the outwardly facing surfaces 59 of the boss to retain the washer 46 in position on the boss and to thereby lock the pins 42 and 43 into the notches 38 and 39. The embossments 55 and the hub 40 are formed with a pair of radially extending indentations 65, each of which receives a raised portion 66 formed on the washer 46.

It has been found that the voltage breakdown path between the wipers 31 is much longer in view of the fact that the charge must travel around the raised portions 66 rather than directly between the legs 36 or between the legs 37. Also, the tapered nature of the surfaces 52 and 59 makes possible a snapping on of the washer 46 which firmly locks the washer 46 in position on the boss and the wipers 31 in assembled relation with the raised portions 66 in the indentations 65 and between the legs 36 and between the legs 37. Even so, the washer 46 can be easily and quickly disassembled and reassembled by snapping off and snapping on, respectively, of the washer relative to the boss 58.

It will be evident from the above description that the electrodes of the rotary switch of the present invention are better insulated from one another than in prior art switches. It will also be evident that the rotary switch of the present invention is less expensive to assemble than certain prior art switches because the washer 46 need only be snapped on rather than cemented on. It also can be seen that there is no questionable or doubtful securement involved in the snap on washer of the rotary switch of the present invention.

Whiie the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention and the scope of the claims are also desired to be protected.

The invention claimed is:

1. In a switch including an element formed of insulating material, a pair of electrical contact members mounted on the element, said members each including a flattened metal piece having a pair of spaced legs, said element having recesses in the face thereof which recesses receive the leg ends of the respective members, said recesses in said element and the leg ends therein of one member being spaced from the recesses and the leg ends therein of the other member, the improvement which comprises a resilient washer of insulating material having projections at the periphery thereof which grip said element and retain said washer on said element, said element having indentations therein which extend between the leg ends of one member and the leg ends of the other member, and raised portions formed on said washer and extending into said indentations.

2. The switch of claim 1 wherein said element is formed with a boss in which said recesses are formed, said boss having outwardly facing surfaces which flare outwardly from the proximal end of the boss to the distal end thereof, said washer projections being resilient and having inwardiy facing surfaces which are tapered toward one another from their proximal ends to their distal ends and which are complementary in configuration to said outwardly facing boss surfaces whereby said washer snaps onto said boss.

3. The switch of claim 2 wherein said element is a disk,

a shaft secured to said disk, said recesses being located atv points substantially on a diametrical line across the disk so that said members are fixed against rotational displacement on the disk.

4. The switch of claim 3 wherein said washer is formed of nylon; a plurality of metal contact elements with planar wiping contact surfaces disposed in a circle in a plane perpendicular to an axial line; said shaft being journalled on said line; said disk being coextensive with, parallel to, and spaced from said plane of the contact surfaces and keyed to said shaft; said electrical contact members being adapted to slide across said contact surfaces; said legs of each of said pairs of legs being in straddling relation to said shaft; said recesses and the leg ends of one of said electrical contact members being spaced in the direction of said plane from the recesses and leg ends of the other contact member.

No references cited.

ROBERT K. SCHAEFER, Primary Examiner.

J. R. SCOTT, Assistant Examiner.

Claims (1)

1. IN A SWITCH INCLUDING AN ELEMENT FORMED OF INSULATING MATERIAL, A PAIR OF ELECTRICAL CONTACT MEMBERS MOUNTED ON THE ELEMENT, SAID MEMBERS EACH INCLUDING A FLATTENED METAL PIECE HAVING A PAIR OF SPACED LEGS, SAID ELEMENT HAVING RECESSES IN THE FACE THEREOF WHICH RECESSES RECEIVE THE LEG ENDS OF THE RESPECTIVE MEMBERS, SAID RECESSES IN SAID ELEMENT AND THE LEG ENDS THEREIN OF ONE MEMBER BEING SPACED FROM THE RECESSES AND THE LEG ENDS THEREIN OF THE OTHER MEMBER, THE IMPROVEMENT WHICH COMPRISES A RESILIENT WASHER OF INSULATING MATERIAL HAVING PROJECTIONS AT THE PERIPHERY THEREOF WHICH GRIP SAID ELEMENT AND RETAIN SAID WASHER ON SAID ELEMENT, SAID ELEMENT HAVING INDENTATIONS THEREIN WHICH EXTEND BETWEEN THE LEG ENDS OF ONE MEMBER AND THE LEG ENDS OF THE OTHER MEMBER, AND RAISED PORTIONS FORMED ON SAID WASHER AND EXTENDING INTO SAID INDENTATIONS.

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