US 3188590 A
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Description (OCR text may contain errors)
June 8, 1965 J. J. EARLEY ROLLER CONTACT CONCEPT Filed Feb. 18, 1963 1 N VEN TOR. Joseph J. Ear/e y Attorney United States Patent 3,188,590 ROLLER CONTAQT CQNKIEPT Joseph J. Earley, Cedar Rapids, Iowa, assigner to Collins Radio Company, a corporation of Iowa I Filed Feb. 18, 1963, Ser. No. 259,297 6 Claims. (Cl. 336-149) This invention relates in general to variable impedances, and in particular to an improved slide contact.
In electrical arts it is oftentimes necessary to provide a variable impedance which requires slide contacts. Slide contacts have a tendency to give intermittent contact if the wiper arm loses its resiliency. Also, arcing and the resulting pitting can occur.
It is an object of this invention, therefore, to provide a slide contact which comprises a pair of balls flexibly mounted on a shaft and in engagement with a coil of conducting material along which they slide, and a rod along which they roll.
Another object of this invention is to provide an improved slide contact for a variable impedance.
A feature of this invention is found in the provision for a pair of balls flexibly mounted on a shaft and in engagement with a coil of conducting material and a rod to make electrical contact between the conductor material and the rod.
Further features, objects, and advantages of the invention will become apparent from the following description and claims when read in view of the drawing in which FIGURE 1 is a prospective view of a variable impedance using the slide contactor of this invention, and FIGURE 2 is a partial sectional view through the slide contactor of the invention.
FIGURE 1 illustrates a pair of supporting plates 10 and 11 between which are mounted standotfs 12 and 13 and a conductor rod 14. The plates 10 and 11 may be made of insulating material to provide insulation for the conductor rod 14. Alternately, conductor rod 14 may be insulated from the plates 10 and 11 at either end thereof. A coil form 16 is rotatably supported between plates 10 and 11 by bearing means and a suitable shaft which carries a knob 17 at one end to rotate the coil form.
A coil 18 of conducting material is formed about the coil form 16 and is electrically connected at one end to a slip ring 19. A wiper blade 21 is supported on a bracket 22 and has an output lug 23 attached thereto. A second-output lug 24 is connected to the conducting rod 14.
The slide contact of this invention comprises a pair of balls 26 and 27 which are connected by shaft 28 that extends through openings suitably formed in the balls 26 and 27, and as shown in FIGURE 2, a spring 29 biases the balls 26 and 27 together. The shaft 28 is formed with heads 31 and 32 to bear against the spring 29 and the ball 27 respectively.
As shown in FIGURE 2 the spring 29 in combination with the shaft 28 assures intimate contact between the balls 26 and 27 and the rod 14. The structure also assures intimate contact of the balls 26 and 27 with the turns of the coil 18. It is to be noted that the diameter of balls 26 and 27 is of the same order of magnitude as the diameter of rod 14, and that the diameter of coil 18 is smaller than that of the balls 26 and 27. The distance between the turns of the coils are such that intimate contact is made by the balls between two adjacent turns. In other words, the balls are centered on the rod and between adjacent turns of the coil.
In operation, an electrical connection can be made between contact 23 and an external circuit which will connect the external circuit to the end of the coil that is connected to the slip ring 19. The contact 24 is electrically connected to the rod 14 which in turn is connected to the balls 26 and 27 by the rolling and slide contact which in turn engages two turns of the coil 18. Thus, between electrical contacts 23 and 24 will exist an impedance proportional to the number of turns of the coil between the slip ring 19 and the turns engaged by the balls 26 and 27. Since the ball engages portions of two turns, the turns closest to the slip ring 19 will be electrically connected to the rod 14 and determine the impedance selected. It has been found that the balls will roll along the rod 14 as they slide along the coil 18, and this assures that different contact points come into engagement with the rod 14 and the coil 18,
and substantially reduces pitting at the slide contact.
The knob 17 may be rotated to move the slide contact along the coil 18 by lead screw action, and a desired impedance may be selected between electrical contacts 23 and 24 in response to rotation of knob 17.
It is seen that this invention provides an improved rolling and slide contactor for a variable impedance. Although it has been described with respect to a pre ferred embodiment thereof, it is not to be so limited, as changes and modifications may be made therein which are within the full intended scope of the invention as defined by the appended claims.
1. A rolling and slide contact comprising a pair of balls formed with an opening therethrough, a shaft structure extending through the opening, a spring on said shaft biasing said balls together, a rod mounted between the balls and urging them apart, and a coil in engagement with the balls such that the balls make electrical contact between the balls and the coil.
2. In apparatus according to claim 1 wherein the shaft is formed with a head, and said spring is mounted between the head of the shaft and one of the balls to bias the balls together.
3. A variable impedance comprising a pair of supporting members, an impedance coil rotatably supported between said supporting members, a conductive rod supported between the supporting members, and a pair of balls resiliently biased together by a shaft and spring structure, and with said pair of balls mounted between the coil and the conducting rod to make electrical contact therebetween.
4. In apparatus according to claim 3, a slip ring connected to one end of the coil and a wiper blade mounted on one of the supporting members and in engagement with the slip ring, and a fixed contact lug connected to said conducting rod.
5. In apparatus according to claim 3 wherein said balls are mounted on opposite sides of the conductive rod and held apart by the coil and rod.
6. In apparatus according to claim 3 wherein shaft means limits movement of one of the balls in at least one direction, and a spring is mounted about the shaft between the other ball and a shaft head to bias the balls together.
References Cited by the Examiner UNITED STATES PATENTS 2,368,710 2/45 Hessey 338157 X LARAMIE E. ASKIN, Primary Examiner. JOHN F. BURNS, Examiner.