US2896185A

US2896185A - Potentiometer contactor

Info

Publication number: US2896185A
Application number: US531523A
Authority: US
Inventors: Blanco Elias
Original assignee: Daystrom Inc
Current assignee: Daystrom Inc
Priority date: 1955-08-30
Filing date: 1955-08-30
Publication date: 1959-07-21
Anticipated expiration: 1976-07-21

Description

United rates Patent POTENTIOMETER C'ONTACTOR Elias Blanco, Hollywood, Calif., assignor, by mesne assignments, to 'Daystrom, Incorporated, Murray Hill, N.J., a corporation of New Jersey Application August 30, 1955, Serial No. 531,523

4 Claims. (Cl. 338-402) This invention relates to electrical contact devices and particularly to the contact structure for potentiometers having wire wound resistor elements.

It is well known that in the use of potentiometers, an adjustable contact is frequently required. With low frequency potentiometers used in stationary equipment, little difficulty is encountered in providing the desired contacts between a tap and a resistor, particularly of the wire wound type. However, with high frequency currents, and where the potentiometer is used in equipment in portable vehicles, such as automobiles, ships, and airplanes, where the potentiometer is subjected to shock and vibration, it has been found that the usual type of contact structure is not entirely reliable.

The present invention is a construction of an adjustable contact element which has been found to be stable and reliable under all operating conditions, including vibration, temperature changes, etc., and permits wire to wire adjustments in extremely small potentiometers, such as used in air-borne equipment. It is particularly suitable for making contact with resistance wires having diameters of the order of 0.0004 inch where other types of contact elements are cumbersome and uncertain. The form of the element permits a tap to be made to a single turn at a fixed point.

To provide these results, the contact element is made with one sharp or knife edge, such as the edge of a triangle, the edge being inserted between the turns of a wire wound resistor. To provide the proper degree of fine accuracy, the triangular contact element is provided with insulation on at least one side so that only one conducting side is in contact with the resistor element.

The principal object of the invention, therefore, is to facilitate the electrical contact between a fixed element and an adjustable element.

Another object of the invention is to provide a potentiometer contact which is reliable under all conditions of vibration and temperature changes.

A further object of the invention is to provide an adjustable contact for a miniature sized potentiometer which provides a reliable and finely adjustable contact between the element and the resistor element.

The novel features which are believed to be characteristic of this invention, both as to the manner of its organization and the mode of its operation, will be better understood from the following description when read in conjunction with the accompanying drawings, in which:

Fig. 1 is a front view of a contact structure embodying the invention; and

Fig. 2 is a horizontal section taken along the line 2-2 of Fig. 1.

Referring now to the drawings, Fig. 2 shows a cross section of several turns 5 of a spiral wound resistor sulation 11 thereon. The spiral turns are separated from one another as they are positioned 1n pre-formed 2,896,185 Patented July 21, 1959 ice grooves 12. The slidable contact element 13, as illustrated, has a triangular electrical conducting central body portion 6 and an insulator 7 on two sides thereof, although it is to be understood that the insulation may be only on one side, such as the left side. This permits contact of the electrical conducting portion only at the point 9 with the turn 4 of wire 5. Although the contact element 13 has been shown as a perfect triangle, it may have any suitable shape as long as the lower portion is of wedge-like configuration as illustrated.

The contact element 13 is under spring pressure of any suitable type, one type being illustrated in Fig. 1 by a resilient bar or rod 10, by which the contact is pressed between adjacent turns with a wedging action. It will be noted that the contact element 13 has considerably larger portions than the diameter of the resistor Wire 5, and these proportions are important in preventing any change in the contact resistance at the point 9 during vibration. In one construction, the diameter of the resistance wire 5 was of the order of 0.0004 inch, the height of the contact element 13 was of the order of 0.008 inch, and the thickness of the insulation 7 was of the order of 0.00005 inch. The separation between turns was of the order of 0.0001 inch. The insulation 7 may be of any suitable dielectric, such as glass or varnish. Although these dimensions were found satisfactory, variations in the relative values of the elements may be made if the biased knife-edge with one insulated side is always embodied in the con struction.

It has been found that an adjustable contact element such as above described provides a stability and reliability of contact under extreme vibratory conditions and temperature changes.

I claim:

1. An electrical contact structure comprising a contact element having a body portion with a sharp edge, with insulation on at least one side of said edge, the uninsulated side of said edge being adapted to extend between adjacent turns of a wire wound resistor element and make electrical contact at a point on one of said adjacent turns, said contacting element being many times larger than the diameter of said wire of said resistor element.

2.. An electrical contact structure in accordance with claim 1 in which the insulated side of the edge of said contact element makes contact with the other of said adjacent turns.

3. An electrical contact structure in accordance with claim 1 in which means are provided for pressing said contact member in a 'wedging direction between said adjacent turns.

4. The combination in a potentiometer having a wire wound resistor element with spaced apart turns, an electrical contact structure comprising a body of electrical conducting material having an edge portion and insulation on one side thereof cooperating to form a relatively sharp wedge-like element adapted to extend between adjacent turns of said resistor element, said wedgelike element presenting a conducting face for engaging one of said adjacent turns and an insulating face for engaging the other of said adjacent turns, and means for biasing said wedge-like element in a wedging direction between said adjacent turns, whereby said wedge-like element is forcibly retained in a contact position against displacement under forces due to shock and vibration.

References Cited in the file of this patent UNITED STATES PATENTS Rose Aug. 30, 1949 Ward -u Mar. 22, 1955