US2506482A

US2506482A - Push-pull rheostat

Info

Publication number: US2506482A
Application number: US66055A
Authority: US
Inventors: Hugh W Batcheller
Original assignee: Ark Les Electronic Products Corp
Current assignee: Ark Les Electronic Products Corp
Priority date: 1948-12-18
Filing date: 1948-12-18
Publication date: 1950-05-02
Anticipated expiration: 1967-05-02

Description

May 2, 1950 PUSH-PULL RHEOSTAT Filed Dec. 18, 1948 z- 2 mm H M ""fimmmmuunz 54 FIG. 3 50 48 H. w. BATCHELLER iNVENTOR HUGH W. BATCHELLER ATTYS Patented May 2, 1950 UNITED STATES PATENT OFFICE PUSH-PULL RHEOSTAT Hugh W. Batcheller, Newton Highlands, Mass,

assignor to Ark-Les Switch Corporation, Watel-town, Mass, a corporation of Massachusetts Application December 18, 1948, Serial No. 66,055

3 Claims.

This invention relates to rheostats of the pushpull type wherein a contact element is pushed or pulled along a coil of resistance wire to any desired position, the contact element and an end of the resistance coil being connected to leads from an electric circuit, whereby any desired number of turns of the resistance coil can be cut into or out of the circuit.

An object of the invention is to provide a rheostat which is simple and rugged in structure and which is made of parts which are easily and cheaply made and assembled. As hereinafter described in more detail, a rheostat is provided in which a helical resistance coil is embedded and secured in a slot which extends through an insulating housing member which is a rectangular block about as thick as the diameter of the coil. To this block is attached a boxlike member of sheet metal or any other suitable material, thus forming an enclosure in which a contact member is movable in contact with successive turns of the coil, a portion of each turn being exposed through the slot in the insulating block.

For a more complete understanding of the invention reference may be had to the following description thereof and to the drawing of which:

Figure 1 is an exploded View of a rheostat embodying the invention;

Figure 2 is a plan view of the same;

Figure 3 is a section on the line 33 of Figure 2; and

Figure 4 is a section on the line 44 of Figure 2.

The rheostat illustrated in the drawing includes a housing comprising a top member or block It which is preferably of suitable refractory material. This top member is of substantial thickness and is provided with a central longitudinal slot 12 extending through the member from top to bottom. This slot is of sufficient width to receive a helical coil I A of resistance wire, the diameter of this coil being substantially equal to the width of the slot, the length of the coil being substantially equal to the length of the slot. The walls of the slot converge slightly toward each other near the bottom thereof, as indicated at [6 in Figure 4. Thus, when the coil i 4 is inserted in the slot l2, it does not fall through but is caught by the converging lower portions of the side walls. In order to maintain the coil permanently in place, a layer of refractory cement 20 is applied to each of the side walls of the slot. The portions of the turns of the coil I4 which bear against the side walls of the slot are embedded in the cement 20, the latter gripping the coil firmly when it hardens. Since the cement is restricted to the side walls of the slot, portions of the coil remain ex-,T posed at the top of the member 15 and also at the bottom of the slot I2. Before the coil 14 is inserted in the slot 12 in the course of assem bling the rheostat, an end thereof is secured to a terminal member 22. As indicated in Figures 1 and 3, this member may conveniently be made of a strip of metal such as copper or brass bent to a U shape. One leg of the U is punched and tapped to form a threaded hole 24 to receive a binding screw 26 by which the end of a wire can be attached to the terminal 22. The mid portion of the terminal 22 is provided with a struck-up strip 28 under which an end of the coil I4 is thrust. The struck-up element 28 is then pressed down to pinch the wire and thus to make a good electric connection between the coil [4 and the terminal 22. The terminal and coil can then be inserted as a unit in the member H], the slot l2 being provided with an extension 30 of reduced width to accommodate the screw 26 when the terminal is assembled with the block In as indicated in Figure 3.

The other member of the housing is a boxlike receptacle 40 of sheet metal such as soft steel which is pressed into suitable shape as shown in Figure 1. The receptacle 40 is preferably provided with a number of up-standing cars 42 adapted to be bent into recesses 44- in the sides of the block In so as to overlap shoulders 46 in the recesses 44. These ears, when r thus bent, hold the housing members It! and 40 in assembled relationship in which they enclose a chamber 48 which is ventilated through the slot l2.

Slidable in this chamber is a contact member 50 which has an element 52 arranged to engage the portion of the coil I4 exposed through the bottom of the slot [2. The element 52 is resiliently pressed against the coil I4 by any suitable means. For this purpose, the contact member 50 may be made of spring metal such as brass and be bent into U shape, one leg of which presses against the floor of the receptacle 40, which is opposite to the bottom of the block, the other leg of the member 50 terminating in the element 52 which is pressed against the coil I4. The contact member 50 is attached to the end of a stem 54 which slides through a bearing member 56 at One end of the receptacle 4!]. The end of the stem 54 may conveniently be secured to the contact member 50 by peening a reduced end moves from turn to turn of the coil. Since the The element 52 thus element 52 and the terminal 22, are connected 7 in an electric circuit, such movement results in cutting in or cutting out successive turns of the coil 14, thus increasing or decreasing the electrical resistance in the circuit in the usual manner. In the rheostat illustrated on thedrawing, the bearing member 55 is grounded, the terminal 22 being adapted to be connected to the'charged wire of the circuit.

I claim:

1 rheostat having a housing which includes a block of insulating material having: a longitudinally extending slot therethrou h, said slot being slightly narrowed at the bottom thereof, a helical coil of resistance wire secured in said MB? d amete 9 said i ens u a lly equal to the width of the slot, said housing also including a conducting member spacedbelow the bottom or ,said slot, acontact element sl-ida'bie in said housing with a portion resiliently pressing against the portion of the coil exposed through the bottom ofsaid slot and a portion pressing against said conducting member, and a terminal mounted on said block and electrically connectedto an end of said coil.

rheostat havin a housing which includes an elongated block 011 insulating material having a longitudinal slot therethrough, said slot being slightly narrowed at the bottom thereof;,

said housing also including a box-like sheet metal member secured to the block and forming a chamber therewith, a helical coil of resistance wire secured in said slot, said coil having a length and diameter substantially equal to the length and width respectively of said slot, a contact member slidable in said chamber in simultaneous contactv with the portion of the 'coil exposed through the bottom of said slot and with said sheet metal housing member, an operating -stern attached to said contact member and projecting out through an end of said sheet metal member, and a terminal on said block electrica-lly connected to an end of said coil.

3. In a rheo stat, an elongated block of refractory material having a longitudinally extending; slot therethrough from top to bottom, said slot being slightly narrowed at its bottom, a helical coil of resistance wire in said slot, said coil having a diameter substantially equal to the width of said slot whereby said coil seats against the side walls of the slot where it narrows at its bottom, a layer ofreiractory cement on each side wall of said slot in which adjacent portions of the turns of saidcoil are embedded to anchor the coil in the slot, and a terminal membermountedon said block and electrically connect ed to an end of said: resistanc wire.

nersaencns CITED The ollowin r ferences r o re ord the file of this uatent: UNIT D $TATE llzEN'I Number Name Date 1,539,266 Mountford May '26, 1-925 1;, e2 ,23s Campbell Mar. 15," 192:2 2', 30e, 152 Batcheller Dec; a2, 1942 2,420,807 Aufiero May 2 0', 1-94?