US2205380A - Rheostat switch - Google Patents

Description

June 25, 1940. H. w. BATCHELLER BHEOSTA'I' SWITCH Filed March 4, 1937 07 1mm l/3"";

Patented June 25, 1940 UNITED STATES PATENT OFFICE RHEOSTAT SWITCH Application March 4,

3 Claims.

This invention relates to improvements in rheostat switches such as are commonly employed in controlling heating units for automobiles.

It is an object of the present invention to provide a switch having improved structural features by which the switch can be more readily assembled and taken apart with less liability of damaging one or more of the parts in the process. It is a further object of the invention to provide a switch structure having greatly improved wearing qualities.

For a more complete understanding of the invention, reference may be had to the disclosure of an embodiment thereof in the description which follows and on the drawing of which Figure 1 is an exploded perspective view of a switch mechanism embodying the invention.

Figure 2 is a longitudinal sectional view of the assembled switch.

Figure 3 is a front elevation of the operating knob and shield.

Figure 4 is a perspective view of the shield.

Figure 5 is a rear elevational view of the housing shell.

Figure 6 is a section on the line 66 of Figure 2.

Figure 7 is a front elevational view of the base member.

The switch structure is enclosed in a cupshaped housing shell Hi, the open end of which is normally closed by a base member l2 which fits into it. The base member is preferably of refractory material such as porcelain, molded to shape, and it may be provided with a peripheral shoulder l4 against which the lip or rim of the shell bears. In order to hold the base and shell together in assembled relation, a bail'lB is provided, this bail being preferably made of resilient wire bent into a U shape. The ends of the bail are hooked as at IE! to enter a pair of inclined slots 20 in opposite side walls of the shell in. These slots slope away from the base, the re mote end of each slot having a notch 22 therein. The rear face of the base member l2 may be provided with a transverse groove 24 of suitable size to receive the transverse portion of the bail Hi. In assembling the base member and the shell, the base I2 is inserted in the shell [0 until the edge of the shell bears against the shoulder 14. The bail IE is then applied to the rear face of the base member, the transverse portion of the bail entering the groove 24. The arms of the bail are swung around until the hooked ends l8 enter the slots 20. By pressing laterally against 1937, Serial No. 128,949

the arms of the bail, the hooks l8 ride along the inclined slot 20 until they snap into the notches 22. The camming effect of the inclined slots is to put the bail under tension so that the shell is held firmly against the base member. In order to provide suitable resilience in the bail, end portions 26 of the transverse part of the bail are reversely bent so as to stand away from the bottom or the groove 24. This provides spring portions which yield sufficiently to permit the hooks [8 to enter the notches.

The inner or forward face of the base member l2 is provided with an arcuate groove or channel 3! within which is disposed a helical coil 32 of resistance wire. The diameter of the coil is less than the width of the groove 30 but greater than its depth, so that the coil projects slightly from the groove as indicated in Figure 2. At one end the groove has a portion of extra depth. In this deeper end portion of the groove the turns of the coil 32 are entirely within the groove. The groove is provided with a series of lateral recesses 34. These recesses may be on either or both sides of the groove. Prior to inserting the coil 32 into the groove, a suitable amount of cementitious material is placed in the groove. Then the coil is pressed into the cement so that the cement surrounds the portion of the coil which is actually within the groove and also fills the lateral recesses substantially flush with the face of the base member l2. These lateral recesses ensure the presence of a sufficient amount of cement to make a good bond for the coil 32, the coil being firmly embedded in the body of cement within the groove. The portion of the coil in the deeper end portion of the groove is entirely covered by cement, and the lead wire at this end of the coil is electrically connected to a metal plate 36 which is secured to the forward face of the base member as indicated in Figures 1 and 7.

Within the arc of the groove 30 and concentric therewith is a central depression All in the base member 12. A metal strip 42 extends radially from the depression 40 on the forward face of the base It and is integral with an eye 44 which projects into the recess 40. The element 42 is secured to the base as at 15 by a threaded sleeve 48 which projects through the base and receives a screw 58 at its rear end to serve as a binding post. The plate 36 is likewise secured as at 52 by a similar binding post.

The elements of the switch which cooperate with the elements carried by the base member I 3 comprise a contact shoe which may consist of a piece of sheet copper cut to suitable shape and provided with an offset contact element 62 adapted to slide across the member 42 and the plate 36, and along the coil 32, and an offset contact element G4 at its other end adapted to slide on the forward face of the eye 44. These contact elements 62 and 64 are preferably of substantial width so that they present as much wearing surface as possible for contact with the elements on which they slide. When the shoe G is in either of its extreme positions, the contact element 62 is either resting on the member 42 or is hearing on the end portion of the coil 532 remote from the plate 35. In order to rotate the shoe, it is provided with a central non-circular aperture 66. In this orifice is fitted the end portion 68 of the stem Ill. The stem is hollow, as indicated in Figure 2, and contains a plunger 12 which is pressed forward by a spring 74. The stem 70 passes through and fits in a non-circular aperture 18 in a fiber disk IS. The disk I6 has a lug 'I'l projecting from its periphery to engage a tongue I9 struck up from the shell Ill to act as a stop, thus determining the extreme angular positions of the shoe 50 which rotates with the F disk T6. The stem Ill is permanently secured in assembled relation with the disk '56 by a pair of tongues 80 which are cut and curled out from the sides of the stem by a suitable tool after the end portion of the stem has been inserted through the aperture 78. The stem 73 is pref-- erably mounted loosely in the disk It so that the end portion 68, after being passed through the aperture 66 of the shoe 60, can center itself readily in the eye 44. As indicated in Figure 2, a spring 83 surrounds the end portion til of the stem between the disk 76 and the shoe 6B. This serves to press the contact elements of the shoe constantly against the respective switch elements on the base.

Assembled with the disk iii are a pair of nested tubular members 84 and 86 which serve respectively as a lamp socket and shaft element, The socket 84 has a flange 88 at its rear end with notches 90 to receive a pair of ears 92 at the rear end of the shaft element 86. The ears 9?! pass through the notches 9i) and through suitable apertures 94 in the disk It. The ears are then bent against the rear face of the disk I6 to hold these parts permanentlyin assembled relation. The socket 84 is provided with suitable bayonet slots 84 adapted to receive the usual pins 9t on the base 98 of a lamp bulb IBIS. The tip I02 of the lamp is pressed against the yielding plunger 12 when the lamp is inserted in the socket.

For rotation of the disk 16 and the parts associated therewith, the shaft element 86 is keyed to another tubular shaft element I04 which telescopes thereon. The shaft m4 is notched as at I06 to receive a lug or key I Ila. This key is preferably formed by striking up from the shaft element 86 a pair of lugs on lines of bend which extend parallel to the axis of the shaft as indicated in Figures 1 and 6. These struck-up lugs can be made of substantial length so as to provide a strong abutment to be engaged by the edges of the key slot I06. On the outer end of the shaft I04 is a cylindrical finger knob III), the cylindrical surface thereof being preferably knurled. This knob may be made of plastic material and is preferably molded onto the outer end of the shaft member I04 so that it becomes a permanent unit therewith. As indicated in Figure 1, the forward end of the shaft member [I14 is left open so that the rays of light from the lamp I00 can shine in an axial direction. To tone down this illumination, a suitable shield IIZ of translucent material may be provided, this shield being of U shape and being wide enough to cover at least the open end of the shaft member I04. The arms H4 of the U-shaped shield project rearwardly and are adapted to fit frictionally on a pair of forwardly projecting arms H6 of a support member I20 which is keyed by a key I22 on a threaded sleeve I30, the latter being permanently attached to the shell I0 so as to form a part of the housing for the switch. As shown in Figure 3, the side portions of the finger knob III] are exposed for access so that the knob can readily be turned.

In order to provide a yielding detent so as to indicate to the operator by the sense of touch the on and off positions of the switch and to hold the switch yieldingly in such positions, the rear end I32 of the sleeve I30, which is spun against the inner face of the shell I0 so as to secure the sleeve permanently to the shell, is dented as at I34 and I36 in Figure 5. The flange 38 of the socket member 84 is pressed against the rear end I32 of the sleeve I30 by the spring 82. On this flange 38 a suitable lug or bulge I40 is formed, this bulge being adapted to ride into and out of the notches I34 and I36 when the switch is in its off and on positions respectively.

Various modifications and changes may be made in the specific construction of the improved features of the switchherein described, without departing from the spirit or scope of the invention as defined in the following claims.

I claim:

1. In an electric switch, a stationary switch element, a movable switch element, and rotatable means for moving said elements into and out of contact, said means including a tubular shaft having two telescoping parts, the inner part having a pair of adjacent lugs struck up from the wall thereof on lines of bend which are parallel to the axis of the shaft, the outer part having a notch therein the side edges of which are engaged by said lugs.

2. In a tell-tale electric switch, a housing including a sleeve projecting therefrom, a switch within said housing, means for operating said switch, said means including a tubular shaft element having its inner end portion rotatably projecting into said sleeve and a cylindrical knob on its outer end portion, a stationary shield extending diametrically across the end of said knob and covering the end of said shaft, portions of the cylindrical surface of said knob being left accessible for manipulation, and means for sup porting said shield.

3. In a tell-tale electric switch, a housing including a sleeve projecting therefrom, a switch within said housing, means for operating said switch, said means including a tubular shaft element having its inner end portion rotatably projecting into said sleeve and a cylindrical knob on its outer end portion, a support element nonrotatably mounted on said sleeve, said support element having a pair of parallel arms projecting forward above and below said knob, and a shield carried by said arms, said shield having a portion extending diametrically across the outer end of said knob and covering the outer end of said shaft but leaving the sides of the knob exposed to access for operation of the switch.

HUGH W. BATCHELLER.

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