US1950341A - Rheostat - Google Patents

Description

March 6, 1934.

H. A. FOOTHORAP RHEOSTAT Filed May 29, 1930 am. t

Patented Mar. 6, 1934 UNITED STATES RHEOSTAT Harry A. Foothorap, Harrisburg, Pa., assignor to Elliott-Fisher Company, New York;N; Y., a corporation of Delaware Application May 29, 1930, Serial No. 457,036

1 Claim.

My invenion relates to electrical resistance devices and more particularly to improvements in rheostats for interposing variable resistance in a circuit to control for instance the speed of a 5 motor.

The principal object of my invention is to provide a rheostat which may be accurately regulated and set to predetermine the speed of a motor and which when so regulated or set is proof 1 against accidental or unauthorized change.

Another and salient object of my invention is to provide a small light rheostat for use in any capacity in which economy in weight and space is essential, for instance in a motor driven typewriter carriage to regulate the speed thereof.

To the accomplishment of the above, and other objects, presently apparent, there has been illustrated in the accompanying drawing a preferred embodiment of my invention which will be set forth in detail in the following description and particularly defined in the claims appended thereto.

In said drawing,

Figure 1 is a view in transverse section of a rheostat constructed according to my invention,

Figure 2 is a view in front elevation with the cover plate removed and drawn to a reduced scale,

igure 3 is a sectional view taken on the line 30 3-3 of Figure 1 and also drawn on a reduced scale,

Figure 4 is a fragmentary sectional view taken on the line 44 of Figure 3 and drawn on an enlarged scale,

Figure 5 is a similar the line 4-4 of Figure 3.

Referring now to my novel rheostat, 8 is the casing thereof constructed of light metal, in the form of a cylinder open at its front and provided 40 with an integral back plate 9 having an inwardly extending concentric shoulder 10.

Within the casing 8 is a cylindrical support 12 of insulating material for mounting the resistance element presently described. The support 5 12 is open at its rear side and provided with an axial hub member 13, and a radial flange 14 at its rear edge for a purpose presently apparent. Mounted upon the front of the support 12 is a radial L shaped conductor bar 15 (Figs. 3 and 4) 50 having a hub portion 16 located axially of the hub member 13 and secured to the face of the support 12 by a plug 17, projecting through a suitable opening 17' in the casing 8. Screws, one of which is shown at 18, passing through the back 55 plate 9, and through suitable bosses, one of which 3 sectional view taken on is shown at 19 (Fig. 1) on the support 12, secure said support to the plate 8, the inner edge of said support 12 seating on the shoulder 10 whereby it is centered in the casing. The support 12 is narrower than the casing 8 to providea space 0 20 between its front edge and the front end of the casing for a purpose presently apparent.

The resistance element comprises a coil of wire 21 closely wound around a flat core 22, in this instance a flat strip of insulating material, and :5 partially surrounding the support 12 with its ends terminating adjacent each side of the conductor bar 15, its front edge overhanging the front end of the support and its rear edge insulated from the casing by the flange 14. The opposite ends 7 of the core 22 are secured to the support 12 by binding posts 23 and 24, (Figs. 1 and 3) respectively, post 23 having the form of a plug socket (see Fig. 5) to which access may be had through a suitably disposed opening 25 in the 7 periphery of the casing 8. The ends of the coil 21 are connected to said binding posts, as will be understood.

A sleeve 26 is rotatably mounted in the hub members 13 and 16. The front end of the sleeve 5 26 projects across the space 20 and has secured thereon, by means of a pin 27, a collar 28, the outer end of which is formed with step shoulders 29 and 30, respectively. A resilient contact member in the form of a radial arm 31 is mounted a on the shoulder to rotate with the sleeve 26 and collar 28 and wipe over the outer edge of the coil 21. The current is thus conducted from the coil 21 to the collar 28 from whence it passes to the conductor bar 15 by means of a bowed spring washer 32 disposed on the sleeve 26 intermediate said collar 28 and the hub 16 of said bar.

A circular dial plate 33 is suitably fixed upon the shoulder 29, as by the collar 34, to rotate with the sleeve 26 and spaced from the arm 31 by a spacing washer 35. The dial plate is suitably graduated to indicate in ohms, through an aperture in a cover plate 38, the resistance set up in a circuit by different sections of the coil 21 engaged by the contact arm 31.

In front of the dial plate 33 a spider bracket 36 is suitably secured in the casing 8, as by screws 37. The cover plate 38, which closes the open front end of the casing, is attached to the bracket as by screws 39, (Fig. 2). The bracket 36 and cover plate 38 are provided with aligned sight openings 40 and 41, respectively.

Secured within the sleeve 26, as by the pin 27,

is a spindle 42 having a rear end portion of small- 1 1o er diameter than the inside of the sleeve and adapted to receive a suitably insulated tubular key 43 which may be inserted through a keyhole 44 located in the back plate 9 of the casing. The spindle 42 has a wedge-shaped intermediate portion 45, whereby the end of the key may be caused to frictionally engage said spindle so that the sleeve 26 and parts carried thereby may be turned to the desired setting and the key then withdrawn.

Suitably located stop lugs 46' are provided on the support 12 to limit movement of the contact arm 31. A collar 47 is removably mounted upon the rear end or the sleeve 26 as by the set screw 48 so that said sleeve may be adjusted longitudinally to regulate the tension exerted by the con tact arm 31 and washer 32 to secure ease of operation together with perfect contact and to take up wear on the parts.

The manner or connecting the rheostat in a circuit is immaterial to the present invention. but it will oi course be understood that the connection is made to the plug 17 and the socket 23.

What I claim is:

In a rheostat, a closed casing, a resistance element therein, a sleeve rotatable from within the casing only and having a relatively smaller pilot spindle therein for rotating the same. a contact rotated by said sleeve and cooperating with the resistance element, and a tubular tool insertible at will from outside the easing into the sleeve and over the pilot spindle.

HARRY A. FOOTHORAP.

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