Slidewire Wiper Contact

The present invention is directed to potentiometers. More specifically, the present invention is directed to an improved movable electrical wiper contact for contacting a resistance element in a potentiometer.

An object of the present invention is to provide an improved electrical movable wiper contact.

In accomplishing this and other objects, there has been provided, in accordance with the present invention a slidewire wiper contact having a plurality of substantially constant outer diameter coils of a spirally wound electrically conductive wire. The electrically conductive wire is mounted along a line on an outer surface of the coils by an electrical conductor which, in turn, is attached to a movable arm mounted for rotational movement to drive the coils across a resistance element.

A better understanding of the present invention may be had when the following detailed description is read in connection with the accompanying drawings, in which:

FIG. 1 is a pictorial illustration of a portion of a potentiometer using an example of a slidewire wiper contact embodying the present invention,

FIG. 2 is a side view of the wiper contact shown in FIG. 1,

FIG. 3 is an end view of the wiper contact shown in FIG. 1,

FIG. 4 is an alternate embodiment of a wiper contact embodying the present invention,

FIG. 5 is an end view of the wiper contact shown in FIG. 4 and

FIG. 6 is a modified form of the wiper contact shown in either FIGS. 1 and 4.

Referring to FIGS. 1, 2 and 3 in more detail, there is shown a potentiometer or slidewire apparatus having an electrically non-conductive support plate 2 for supporting a resistance element 4 thereon. The resistance element 4 may advantageously have a semi-circular configuration to accommodate an arcuate movement of a wiper contact, as described hereinafter. The resistive element 4 may be any suitable resistance element conventionally used in potentiometers and may include, a wire wound resistance element, a deposit of an electrically resistive medium, a ribbon of resistive material, etc. A potentiometer arm 6 is rotatably pivoted at one end thereof on a support shaft 8. A flexible electrical connector 10 is attached to a rigid electrically conductive support rod 12 mounted, e.g., adhesively bonded, on the support arm 6. Alternatively, the arm 6 can be made of an electrically conductive material, e.g., copper, and the support rod 12 would also be made of copper and soldered to the arm 6. In such an arrangement, the arm 6 would be electrically insulated from the drive shaft 8 by any suitable means. A wiper contact 14 is attached to an outer end of the electrical support rod 12. The wiper contact 14 includes a plurality of substantially constant outer diameter spirally wound coils of an uninsulated electrical conductor such as a copper wire which is wound on a uniform diameter mandrel. The inner diameter surface of the coils of the electrical wire forming the electrical contact 14 are coaxially attached to the support rod 12 by any suitable means, e.g., soldering. The side and end views in FIGS. 2 and 3, respectively, show additional structural details of the wiper structure shown in FIG. 1.

In FIGS. 4 and 5, there is shown a modified form of the wiper contact structure shown in FIGS. 1, 2 and 3. In this modified form of the wiper contact of the present invention, the coils 14 are partially embedded in a molded support arm 6A, e.g., the arm 6A could be made of a thermosetting plastic material, along with the support rod 12. In FIG. 6, there is shown a further modification of the wiper contact wherein a low resistance electrically conductive material, e.g., silver, is plated along a transverse line on an outer surface of the coils of the wiper contact 14 to improve the electrical contact, i.e., reduce the resistance of the electrical connection produced by the wiper contact 14 on the resistance element 4. The wiper contact of the present invention provides the advantage of a multi-contact design which results in lower contact resistance and improves the stability of the contact by providing a degree of adaptation to mechanical eccentricities of the surface of the resistance element 4 while spreading the wear of the wiper contact over the surface of the plurality of coils forming the wiper contact. Conventional wiper contacts using either a stamped metal contact or a group of individual wires secured together in a molded structure show a tendency to spread apart when pushed across the resistive element. The present invention overcomes this problem and offers the additional advantages of elimination of sharp edges, lower manufacturing cost, increased contact density and adaptability to miniaturization which lends itself to plural wiper contact use in a single potentiometer structure.

Accordingly, it may be seen, that there has been provided, in accordance with the present invention an improved wiper contact for a slidewire potentiometer.