US2778906A

US2778906A - Variable resistor or potentiometer construction

Info

Publication number: US2778906A
Application number: US367028A
Authority: US
Inventors: Lauren M Burgess
Original assignee: ACTON LAB Inc
Current assignee: ACTON LAB Inc; ACTON LABORATORIES Inc
Priority date: 1953-07-09
Filing date: 1953-07-09
Publication date: 1957-01-22
Anticipated expiration: 1974-01-22

Description

Jan. 22, 1957 L. M. BURGESS 2,778,906

VARIABLE RESISTOR OR POTENTIOMETER CONSTRUCTION Filed July 9, 1953 2 Sheets-Sheet 1 Jan. 22, 1957 L. M. BURGESS 2,778,906

VARIABLE RESISTOR OR POTENTIOMETER CONSTRUCTION Filed July 9, 1953 2 Sheets-Sheet 2 fi-5. a; 22 :1

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(Z ffaz/wgeg United States Patent VARIABLE RESISTOR OR POTENTIOMETER CGNSTRUCTION Lauren M. Burgess, Lexington, M'ass., assignor, by mesne assignments, to ActonLaboratories, Iuc., Acton, Mass.

Application July 9, 1953, Serial No. 367,028

2 Claims. (Cl. 201-48) The present invention relates to a variable resistor or potentiometer construction, and. more particularly to such construction suited for relatively small and economically manufactured devices.

The increased use of servo-mechanisms, computer apparatus, and the like has emphasized the need for relatively small compact variable resistors or otentiometers. In spite of the fact that such potentiometers have a case, which is only /8 of an inch in diameter or less, the accuracy obtained is surprisingly high, and hence the tolerances permitted in meeting the specifications of these devices are relatively small. In general, however, such tolerance specifications have a tendency to increase manufacturing costs. Accordingly it would be desirable to provide improved types of construction which will enable the manufacture of relatively small, compact, inexpensive, and yet reasonably accurate variable resistor devices or potentiometers.

it, therefore, is an object of the present invention to provide an improved compact precision potentiometer construction which is simple and economical to manufacture.

Still another object of the invention is to provide an improved precision potentiometer construction having wiper and contact arm structures which are easy to assemble.

Other and further objects of the present invention subsequently will become apparent by reference to the following description taken in conjunction with the accompanying drawings wherein:

Figure 1 is a longitudinal cross-sectional view of a variable resistor or potentiometer constructed in accordance with the present invention;

Figure 2 is a rear view of the device shown in Figure 1 with the rear cover removed;

Figure 3 is a front view of the device shown in Figure 1;

Figure 4 is a longitudinal cross-sectional view of another embodiment of a variable resistor or potentiometer;

Figure 5 is a rear view of the resistor shown in Figure 3 with the cover removed; and

Figure 6 is a rear view of the device shown in Figure 4.

Referring to Figures 1, 2 and 3 there is shown a variable resistor or potentiometer constructed in accordance with the teaching of the present invention, and having a cylindrical casing or housing 11 provided at the rear with a cover 12. Within the housing 11 there is provided a coaxial boss 13 which carries a metal bearing member 14 having a threaded portion 15. The threaded portion 15 is adapted to be engaged by a suitable fastening nut so that a one hole mounting is provided for the variable resistor or potentiometer. To preclude rotation of the member 14 in the hole, the front side of the casing 11 is provided with a protuberance or button 16 arranged to fit into a recess or hole in the supporting bracket or mounting panel for the potentiometer.

The bearing member 14 carries a shaft 17 having a groove 18 into which is fitted a snap'ring 19 adjacent the forward end of the bearing member 14. The inner end of the shaft 17 is provided witha knurled portion 21 separated from the rest of thev shaft by an annular recess 22. The annular recess 22: and. the knurled portion 21 are embedded in a molded wiper arm support 23. A suitable spacing. washer 24 is interposed between the arm 23 and the inner end of. the boss 13. The arm 2'3v at its outer end is provided with a stud 25 of suitable configuration for receiving a contact arm and slip ring contacts.

The inner end of the boss: 13 is provided with a slip ring 26 connected by a conductor 27 to a soldering post or connector 28 extending through the lower portion of the cylindrical wall of the casing 11. A. plurality v of similar posts 29 are provided in the cylindrical wall. 11 forconnection to the resistance. wire 31 of a resistance element wound on a supporting card 32, which is fitted within: the cylindrical wall 11 and insulated therefrom by a suitable sheet of insulating material 33. It will: be noted that depending from the boss 13 is a radially extending fin or projection 34 which is to serve as a stop for the motion of the contact arm support 23 and the electrical contacts carried thereby.

Referring particularly to Figures 1 and 2 it will be observed that the stud 25 of the supporting arm 23 is engaged by a unitary metal structure having a flat portion 35 provided with an aperture having on opposite sides of the stud friction engaging spring members 36. From Figure 1 it will be noted that the front end of the flat member 35 extends inwardly a distance sutficiently so that it will engage the fin 34 when the shaft 17 is rotated 180 from the position shown. The inner end of the member 35 carries two depending arms 37, each provided with precious metal contacts 38 which engage the slip ring 26. As may be seen from Figure 2 a portion of the fiat member 37 is bent at an angle to form a member 39 having a curved contact portion 41 which engages the resistance wire of the resistance element.

Figures 4, 5 and 6 show another construction wherein most of the parts are similar to the parts shown in Figures 1, 2 and 3, hence they have been given similar reference characters. The principal difference between Figures 1 and 4 is the cover construction and the construction of the unitary contact member which serves as a contact arm against the resistance element and the cooperating contacts, which otherwise would engage a slip ring. Mounted on the free end of the arm 23 is a unitary structure of metal having a flat portion provided with a suitable aperture for fitting about the stud 25 and having spring friction engaging and retaining lock members 136. The flat portion of the member 135 extends toward the front of the casing 11 a distance sufiicient to engage the fin 34 so as to stop the motion of the arm 23. One end portion of the member 135 is reversely bent as at 139, and terminates in a curved contact portion 141. The flat member 135 toward the rear of the casing 11 is provided with two depending arms 137, each terminating in precious metal contacts 138. The members 138 engage a contact plate 126 which is connected to a soldering post 128. Suitably mounted on the rear cover 12 are additional contact plates 129 which are connected to the ends of the resistance wire 31 of the resistance element.

From the foregoing embodiments shown in the drawings it will be noted that the present construction is extremely simple having a minimum number of parts requiring a minimum of machining and assembly work. It is comparatively simple to assemble the shaft 17 into position and to hold it thereby the retaining lock spring 19. The very simple snap in operation will either put into position the wiper arm and slip ring contacts shown in Figure 1 or the corresponding apparatus shown in Figure 4.

While for the purpose of illustrating and describing the present invention certain preferred embodiments have been shown in the drawings, it is to be understood that the invention is not to be limited thereby since such modifications are contemplated as may be commensurate with the spirit and scope of the invention set forth in the accompanying claims.

I claim as my invention:

1. The combination in a precision variable resistor or potentiometer having a cylindrical casing provided with a resistance element, said casing having an end wall carrying a shaft, a cover for said casing, said cover carrying a flat metal plate and a plurality of electrical terminals for said plate and said resistance element, an insulated arm fixed to the inner end of said shaft, said arm at its outer end having a stud, and a unitary contact structure having an opening and cooperating lugs to frictionally engage said stud to hold said structure in position, said structure having a member carrying a contact for engaging the resistance element and a plurality of members carrying contacts for engaging the plate on said cover.

2. The combination in a precision variable resistor or potentiometer having a cylindrical casing provided with a resistance element adjacent the inner cylindrical wall, said casing having an end wall provided with a boss, a shaft carried by said boss, an arm of insulating material molded on to the inner end of said shaft, said arm at its outer end having a radially projecting stud, a continuous metal surface carried by said casing and connected to a terminal mounted on said casing, a plurality of terminals mounted on said casing connected to said resistance element, and a unitary contact structure for engaging said resistance element and said continuous metal surface, said contact structure having an opening and adjacent locking lugs to receive the stud of said arm to frictionally lock said structure in position on said arm, said structure having a resilient arm carrying a contact for engaging said resistance element, and a plurality of resilient members each carrying a contact for engaging said continuous metal surface.

Schellenger Oct. 24, 1939 Searles et al. Dec. 23, 1952 man...