US3413590A - Potentiometer - Google Patents

Description

Nov. 26, 1968 J, G. wooos ET AL 3,413,590

POTENTIOMETER Filed July 13, 1967 2 Sheets-Sheet 1 INVENTORS JOHN G. WOODS GEORGE W. WOOD ave 1% ATTORNEY Nov. 26, 1968 Filed July 13, 1967 J, cs. wooos ET AL 3,413,590

POTENTIOMETER 2 Sheets-Sheet 2 INVENTORS.

ATTORNEY United States Patent Filed July 13, 1967, Ser. No. 653,067 6 Claims. (Cl. 338-180) ABSTRACT OF THE DISCLOSURE A potentiometer comprising a rectangular housing having an enclosed rectangular cavity therein. A resistance element extends longitudinally along one side wall of the cavity at the bottom of the cavity. The ends of the resistance element are mounted in the clip portions of terminals which extend along the side wall of the cavity and are secured between the top and bottom wall of the cavity. The terminals have leads extending through the bottom wall of the cavity and project beyond the housing. A collector member extends longitudinally along the opposite side wall of the cavity and is secured between the top and bottom walls. The collector member has a lead extending through the bottom wall and projecting beyond the housing. A threaded shaft is rotatably supported in the housing and extends longitudinally through the cavity between the resistance element and collector member. The shaft extends beyond one end of the housing to permit rotation of the shaft. A contact carrier is mounted on the shaft within the cavity for longitudinal movement along the shaft upon rotation of the shaft. A contact member is mounted on the contact carrier for movement therewith. The contact member has one arm slidably engaging the resistance element and a second arm slidably engaging the collector member.

Background With the trend toward miniaturization of electronic devices, there has been developed several types of miniature variable resistors or potentiometers. One such type of miniature potentiometer is the rectilinear potentiometer. This type of potentiometer includes an elongated resistance element and an elongated collector member arranged in parallel, spaced relation in a rectangular housing. A threaded shaft is rotatably supported on the housing and extends parallel to the resistance element and collector member. A contact is mounted on the shaft so that rotation of the shaft moves the contact longitudinally along the shaft. The contact slidably engages the resistance element and the collector member. In designing this type of potentiometer, it is desirable that the parts of the potentiometer be of simple design and capable of being easily assembled together. This is of particular importance in a miniaturized potentiometer wherein the parts are extremely small in size and therefor difficult to handle. In addition, the design of the parts must provide a rugged construction which will operate properly both mechanically and electrically.

Summary It is an object of the present invention to provide a novel rectilinear potentiometer.

It is another object of the present invention to provide a rectilinear potentiometer which can be easily assembled so that it is inexpensive to manufacture.

It is a further object of the present invention to provide a rectilinear potentiometer having a novel resistance element and terminal mounting means therefor.

It is a still further object of the present invention to provide a rectilinear potentiometer having a novel contact and means for assembling the contact on a contact carrier.

Other objects will appear hereinafter.

Brief description of the drawings For the purpose of illustrating the invention, there is shown in the drawings a form which is presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.

FIGURE 1 is a perspective view of the potentiometer of the present invention.

FIGURE 2 is a top plane view of the potentiometer of the present invention with the cover removed.

FIGURE 3 is a longitudinal, sectional view taken along line 33 of FIGURE 2.

FIGURE 4 is a longitudinal sectional view taken along line 4-4 of FIGURE 2.

FIGURE 5 is a transverse, sectional view taken along line 55 of FIGURE 3.

FIGURE 6 is a perspective view of the contact carrier of the potentiometer of the present invention.

Description of the invention Referring to the drawings, the potentiometer of the present invention is generally designated as 10. In general, the potentiometer 10 comprises a rectangular housing 12, a resistance element 14 mounted in and extending longitudinally along a side Wall of the housing 12, a collector member 16 mounted in and extending longitudinally along the other side wall of the housing, a threaded shaft 18 is rotatably mounted on the housing and extends longitudinally therethrough between the resistance element 14 and the collector member 16, and a contact 20 carried on the shaft and slidably engaging the resistance element 14 and the collector member 16. Rotation of the shaft 18 moves the contact 20 longitudinally in the housing 12 to vary the resistance value of the potentiometer 10.

The housing 12 comprises a rectangular bottom section 22 and a rectangular cover plate 24, both of an electrical insulating material, such as a plastic or ceramic. The bottom section 22 has a rectangular cavity 26 in its top surface to provide the bottom section 22 with a pair of parallel side walls 28 and 30, a front end wall 32, a rear end wall 34 and a bottom wall 36. The front end wall 32 and rear end wall 34 have aligned, longitudinally extending bearing grooves 38 and 40 respectively in their top surfaces. The bearing groove 38 extends completely across the front end wall 32 whereas the bearing groove 40 extends only partly across the rear end Wall 34 from its inner surface. A retainer groove 42 is provided in the top surface of the front end wall 32 and extends transversely across the bearing groove 38. A longitudinally extending guide groove 44 is provided in the inner surface of the bottom Wall 36 in alignment with the bearing grooves 38 and 40.

The cover plate 24 extends over and is secured to the top surface of the bottom section 22 so as to enclose the cavity 26. The cover 24 may be secured to the bottom section 22 by a suitable cement. The cover 24 has a shallow, rectangular cavity 46 in its inner surface which mates with the cavity 26 in the bottom section 22. A longi tudinally extending guide groove 48 is provided in the top surface of the cavity 46 directly over the guide groove 44 in the bottom wall 36. A retainer groove 49 is provided in the bottom surface of the cover plate at the front end of the cover plate. The retainer groove 49 mates with the retainer groove 42 in the front end wall 36 of the bottom section 22.

Resistance element 14 comprises a rod of an electrically insulating material, such as a plastic or ceramic, which is shown to be substantially D-shaped, in transverse cross section, and a resistance material on the surface of the rod. The resistance material may be a film of any well-known resistance material coated on the surface of. the rod or a resistance wire helically wound around the rod. No matter what type of resistance material is used, it should provide a longitudinally extending path along the curved surface of the rod. The resistance element 14 is mounted in a pair of terminals 50. Although the rod is shown as having a flat surface to help properly position the rod, the rod can be circular in transverse cross-section.

Each of the terminals 50 comprises a flat strip of electrically conductive metal having a tapered lead portion 52 at one end, a retainer arm 54 extending upwardly from the top end of the mounting portion, and a curved clip portion 56 at the top end of the lead portion along side of the bottom end of the retainer arm 54. The terminals 50 extend along the inner surface of the side wall 28 of the housing 12 at the end walls 32 and 34. The terminals 50 extend through narrow openings 58 in the bottom wall 36 so that the clip portions 56 are seated on the bottom wall and the lead portions 52 project beyond the bottom wall. The retainer arms 54 are of a length to extend to the inner surface of the cover plate 24 so that the terminals 50 are held in place between the bottom wall 36 and the cover plate 24. The terminals 50 at the opposite ends of the resistance element 14 are identical except that the clip portions 56 are on opposite sides of the retainer arms so that the clip portions are adjacent their respective end Walls of the housing. The ends of the resistance element 14 are seated in the clip portions 56 so that the resistance element is clamped between the clip portion 56 and the retainer arm 54 of each of the terminals 50.

The collector member 16 comprises a flat rectangular strip 60 of an electrically conductive metal seated on the bottom wall 36 of the housing '12 and extending along the side wall 30 between the end walls 32 and 34. As shown in FIGURE 4, the height of the collector strip 60 is substantially equal to the height of the resistance element 14. At the ends of the collector strip 60, retainer arms 62 extend perpendicularly from the collector strip to the cover plate 24. The end edges of the retainer arms 62 fit into grooves 64 and 66 in the inner surfaces of the end walls 32 and 34 respectively (see FIGURE 2). A tapered lead 68 extends from the bottom edge of the collector strip 60 through an opening 70 in the bottom wall 36 of the housing 12 and projects beyond the bottom wall. The collector member 16 is held against the bottom wall of the housing 12 by the cover plate 24 engaging the retainer arms 62 and is held against lateral movement by the retainer arms fitting in the grooves 64 and 66.

Shaft 18 has a bearing portion 72 at one end which is rotatably supported in the bearing groove 40 in the rear end wall 34 of the housing 12, and a bearing portion 74 adjacent its other end which extends through and is rotata'bly supported in the bearing groove 38 in the front end wall 32 of the housing. Thus, the shaft 18 extends longitudinally across the cavity 26 in the housing 12 parallel to and in between the resistance element 14 and contact member 20. Between the bearing portions 72 and 74, the shaft 18 has a threaded portion 76. At the front bearing portion 74, the shaft 18 has an annular flange 78 which fits into the mating retainer grooves 42 and 49 in the front end wall 32 and cover plate 24. This prevents longitudinal movement of the shaft 18 with respect to the housing 12 but permits the shaft to rotate with respect to the housing. The front end of the shaft 18 projects beyond the front end wall 32 of the housing 12 and has an enlarged head 80 thereon by which the shaft can be rotated.

A substantially Y-shaped contact carrier 82 of an electrical insulating material, such as a plastic, is mounted within the cavity 26 in the housing 12 between the resistance element 14 and the collector member 16. As shown in FIGURE 6, the contact carrier 82 has a substantially rectangular leg 84 and a U-shaped head 86 on the top of the leg 84. Aligned notches 88 are provided in the top edges of the arms of the head 86 and a notch 90 is provided in the bottom edge of the leg 84 in vertical alignment with the notches 88. The contact carrier 82 is seated in the cavity 26 of the housing 16 with the bottom edge of the leg 84 fitting in the guide groove 44 in the bottom wall 36, the arms of the head 86 encompassing the threaded portion 76 of the shaft 18, and the top ends of the arms of the head fitting in the guide groove 48 in the cover plate 24. The inner surface of the head 86 of the contact carrier 82 is threaded to mate with the threaded portion 76 of the shaft 18. The threads may be preformed in the head 86 or the head may grip the threads of the shaft sufficiently tight so that the shaft threads form the threads in the surface of the head. Since the contact carrier 82 is prevented from rotating by the guide grooves 44 and 48, rotation of the shaft 18 causes the contact carrier to move longitudinally along the shaft. Contact 20 comprises a substantially U-shaped strip of an electrically conductive metal having a rounded base 92 and a pair of arms 94 and 96 extending from the base 92. The arms 94 and 96 have outwardly extending contact projections 98 and 100 respectively adjacent their free ends, and inwardly extending fingers 102 and 104 respectively at their free ends. As shown in FIGURE 5, the contact 20 is mounted on the contact carrier 82 with the base 92 extending across the open top of the head 86 and fitting in the notches 88, and the arms 94 and 96 extending downwardly along the leg 84. The arms 94 and 96 normally diverge from each other. When mounted on the contact carrier 82, the arms 94 and 96 are pressed together until they are substantially parallel so that they will fit between the resistance element 14 and the collection member 20. The contact projection 98 on the arm 94 slidably engages the resistance material on the resistance element 14, and the contact projection 100 slidably engages the collector strip 60 of the contact member 16. The resiliency of the arms 94 and 96 holds the projections 98 and 100 against the resistance element and collector strip respectively. The fingers 102 and 104 fit into the notch 90 in the leg 84 of the contact carrier '82 so as to prevent tilting of the contact 20 with respect to the contact carrier. As the contact carrier 82 is moved longitudinally along the shaft 18 by rotating the shaft, the contact 20 is moved along the resistance element 14 and collector member 16 so as to electrically connect the resistance element to the collection member.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification as indicating the scope of the invention.

We claim:

1. A potentiometer comprising:

a rectangular housing of an electrical insulating material, said housing having an enclosed rectangular cavity therein formed by a pair of parallel side walls, a pair of end walls extending between the side walls, a bottom wall and a top wall;

a resistance element within said cavity and extending along one of said side walls;

a pair of metal resistance element terminals extending along said one side wall at the ends of the resistance element and being clamped between the top and bottom walls of the housing each of the resistance element terminals comprising a fiat strip of an electrically conductive metal having a retainer arm extending along the one side Wall of the housing between the top wall and the bottom wall, a lead portion extending from the bottom end of the retainer arm through and projecting beyond the bottom wall of the housing and a curved clip portion at the top end of the lead portion and along side of the bottom end of the retainer arm, said clip portion being seated on the bottom wall of the housing and extending around and engaging the resistance element;

a collector member within the cavity and extending along the other side wall of the housing;

a threaded shaft extending longitudinally through the cavity substantially parallel to the resistance element and the collector member and being rotatably supported in the end walls of the housing, said shaft projecting beyond one end of the housing so as to be accessible for rotation of the shaft;

a contact carrier within said cavity and engaging the shaft so that rotation of the shaft moves the contact carrier longitudinally along the shaft; and

a metal contact mounted on said contact carrier and slidably engaging the resistance element and the collector member.

2. A potentiometer in accordance with claim 1 in which the collector member comprises a flat, rectangular strip of an electrically conductive metal seated on the bottom wall and extending along said other side wall between the end walls, a separate retainer arm extending perpendicularly from each end of the strip to the top wall, and a lead extending from the bottom edge of the strip through and projecting beyond the bottom wall.

3. A potentiometer in accordance with claim 2 in which the end walls of the housing have narrow grooves therein extending between the top wall and bottom wall adjacent the said other side wall and the ends of the retainer arms of the collector member extend into said grooves.

4. A potentiometer in accordance with claim 1 in which the contact carrier comprises a body of an electrical in-- sulating material mounted in the cavity between the resistance element and collector member and extending around and engaging the threaded shaft, and the contact comprises a substantially U-shaped strip of an electrically conductive metal having a rounded base extending across the top of the contact carrier and over the shaft and a pair of arms extending downwardly along the sides of the contact carrier, one of said arms slidably engaging the resistance element and the other of said arms slidably engaging the collector member.

5. A potentiometer in accordance with claim 4 in which the contact carrier has a notch in and extending across its bottom surface and each of the arms of the contact has a finger on its end which extends into the notch.

6. A potentiometer in accordance with claim 4 in which the arms of the contact normally diverge from each other but are parallel when mounted on the contact carrier so that the resiliency of the metal holds the arms into en gagement with the resistance element and the collector member.

References Cited UNITED STATES PATENTS 3,124,779 3/1964 'Caddock et at. 338

FOREIGN PATENTS 680,809 2/1964 Canada.

ROBERT K. SCHAEFER, Primary Examiner. H. J. HOHAUSER, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,413,590 November 26, 1968 John G. Woods et a1.

It is certified that error ap patent and that said Letters Paten shmm below:

pears in the above identified t are hereby corrected as In the heading to the printed specification, lines 4 and 5,

"IRC, Inc., Philadelphia, Pa." should read TRW Inc., a corporation of Ohio Signed and sealed this 10th day of March 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr.

testing Officer Commissioner of Patents

Images