US2814023A - Rotary contact follower for variable inductances - Google Patents

Description

Nov. 19, 1957 M, ALEXY 2,814,023

ROTARY CONTACT FOLLOWER FOR VARIABLE INDUCTANCES Filed July 31, 1953 7, v 1 2 F1 1 w I N IE N TOR.

M22716!!! IRA/ 2x7 d TTORNE 1 United States Patent ROTARY CONTACT FOLLOWER FOR VARIABLE INDUCTANCES Matthew R. Alexy Philadelphia, Pa., assignor, by mesnc assignments, to the United States of America as rep resented by the Secretary of the Air Force Application July 31, 1953, Serial No. 371,684 2 Claims. (Cl. 339-9) This invention relates to continuously variable inductors and more particularly to rotatable inductors and electrically contact follower means therefor.

The present invention is especially applicable in the field of variable inductances of the type having a continuously rotatable inductance element comprising a helical coil having an axis of rotation about which it turns, an electrically conducting rod mounted substanually parallel to said axis on winch a contact follower tIlCul'lS may move in connection with the coil. Such contact follower means comprises a rotatable metal wheel fixed against rotation with the coil and slidably held by said rod in contact with said coil. Means are provided for rotating said coil to vary the contact position of said wheel wnereby the effective inductance value of said coil is altered through said contact means and another point on the coil. The coil mentioned usually consists of a metal wire conductor on a suitable supporting form and arranged as uniformly spaced turns of a helical winding, the rotatable contact wheel being urged toward and into contact with a single turn of the wlnding.

While adapted for relatively slow speed adjustment and lower frequency ranges of operation such as the present radio broadcast band, prior art devices of this type as represented by the trolley wheel contact means shown and described in the Patent 2,295,384 of September 8, 1942, to Charles F. Cole, Jr., would be relatively ineffectual at higher speeds and frequency now required. For example, a low contact resistance between the wire of the inductor and the shaft on which the contact means revolves is very important especially in high frequency circuits. Some devices introduce contact resistance at the point of contact with the inductor and others internaliy or at the area of contact with the shaft.

Accordingly, it is an object of this invention to provide an improved rotary contact structure for high speed rel- -atively high frequency tuning inductors and the like which rotary operates with a minimum of contact resistance between an inductor and the shaft means on which the contact structure is mounted.

in many types of communication equipment, such as remotely controlled airplane transmitters and the like, it is often necessary to change the tuning of a resonant circuit very rapidly over a wide frequency range.

Accordingly, it is a further object of this invention to provide an improved rotary contact device for a rotary tuning inductor which is capable of operation at extremely high speeds of rotation in contact with said inductor and with a minimum of contact resistance in a conductive connection with said inductor there through.

Very often in inductive windings of the type referred to there may be variations in certain dimensions of the parts involved, such as variations in the mean diameter of the successive coil turns, which may result in jamming of the contact at high speeds.

Accordingly, it is a further object of this invention to provide an improved rotary follower contact means for a high speed rotary inductor which is capable of following any axial or longitudinal eccentricities within the inductor and to maintain a low effective contact-resistance connection therewith at all times.

It is also a further object of this invention to provide a rotary contact system for a variable inductor of the rotary type wherein no perceptible increase in torque is introduced due to dimensional variations of the contacting eiectrical elements involved.

In accordance with the present invention, there may be provided a rotary follower type contact which is employed as an electrical conductor or variable tap for a rortary inductor comprising a space wound coil. The follower includes four essential elements. The first element is a flat disk contact having a tapered surface around its periphery provided with a shaft receiving sleeve which extends axially from one side of the disk and an externally threaded radially-split hollow hub extending axially from the other side. A second flat disk contact element having a tapered surface around its periphery is provided with a series of slots to receive the hub of the first flat disk and interlock therewith. A cap element is internally threaded to engage the threaded hub of the first disk to contact element. A compression spring is fitted on a sleeve of the second disk and inside the hub of the first disk. This spring urges the second flat disk into contact with the first flat disk so that the tapered surfaces form a groove at the peripheries of the disks for gripping one turn of the space wound coil and rotating therewith, as well as traversing the length of the space wound coil when it is rotated at high speed on a supporting guide shaft extending along the periphery of the coil.

The advantages of the invention may be seen from the following detailed description, when read in conjunction with the accompanying drawing, and the novel features thereof are defined in the appended claims.

in the drawing:

Figure l is a side elevational view of a continuously variable inductance device provided with rotary contact means embodying the invention;

Figure 2 is an exploded view in perspective of the rotary contact means of Pignre l, on a greatly enlarged scale, showing constructional details thereof; and

Figure 3 is a detail crossectional view of a portion of the device of Figure l on the same enlarged scale as Figure 2, showing the operation relation of the parts of the contact means with an inductor portion of the device.

Referring to the drawing, wherein like parts in the various figures are designated by like reference numerals, and with reference to Figure 1 in particular a coil form or drum 23 provides an insulating support for an inductor comprising a uniformly spaced coil winding 30 attached thereto and is mounted to rotate on a shaft 34 journaled in a pair of spaced end plates 24 and 26. The shaft 34 and the inductor on the coil form are rotated through a gear 33 on the shaft 34 and a meshing drive gear 36 carried on the end of a drive shaft 40 also journaled in one of the end plates.

A rotary follower or contact device 24} is slidably mounted on a fixed shaft 22 which extends in a direction normal helix angle of coil 3%) and substantially parallel to the axis of the coil. Two circular disks 54 and 56 are of such a diameter as to make contact with a single turn of the coil 30, substantially as shown in Figure 3.

Upon rotation of the coil form 28, the rotary contact device 29 is moved longitudinally in a direction substan tially parallel to the axis of the coil 3t}. Different rotary follower positions are illustrated by the dotted lines in Figure 1. Movement of the rotary follower effects a change in the inductance of the coil 30 with respect to the point of contact. For tuning resonant signal circuits the inductor is connected at one end such at a terminal to ground through the shaft 34 while the shaft 22 follower 24), as will be-desc rihed, permits extre'mely'good electrical 'contactbetween the coil 36 and the rotary fol lower 2!} when the speed of rotation of the coil is extremely high. Such high speedresponse is oftenn'ecessary in communication equipment associated with aircraft andthe like. 7

Referring more particularly to Figure 2 of the drawing, the rotary follower contact 20 is shownin an exploded view. A first flat disk 56 has an integral sleeve 56a on one side which is adapted-to receive the fixed shaft 22 with a smooth rotational fit. On theother side of this disk is an externally threaded radially-split hollow huh 56b. A second flat disk 54*has an'integral sleeve 54:: on one side which is also'adapted to'receive th'e fixed shaft 22 with a smooth rotational fit. Openings or slots 54]) in the second disk are adapted to receive the hollow hub 56b of the first disk when the two disks are moved into face-toface contact with each other as indicated in Figure 3. Both disks 54'and 56 have an angularly tapered surface 58 around their peripheral ed es. A cap element t) is internally threaded (the threads not shown) and adapted to engage the externally threaded hub 56b of the first flat disk. A compression spring 52 is adapted to be positioned on the sleeve 54a of the second flat disk 54. Thisspring is'disposed between the sleeve 54a and the hub 56b so that it biases the second disk 54 into contact with the first disk 56 when the cap 50 is threaded on to the hub 56b. The angular tapered surfaces 58 provide a groove to permit better electrical contact between the two disks and the coil by providing a greater surface area on the disks to contact the coil.

Referring more particularly to Figure 3, the rotary follower contact 29 is mounted on the fixed shaft 22 with the fiat disks 54 and 56 inoperating engagement with the coil 3%). The spacing between the shaft 22 and the spaced coil 36 is such that there is a pressure between the rotary follower 2d and the engaged turn of the coil. This pressure is to insure good electrical contact between the coil and the follower. The spacing between the shaft 22 and the spaced coil 34} is such that the positioning of these elements will result in a small gap between the disks 56 and 54 with the turn of the inductor forced between them as shown. In the event that there are any variations in the dimensions of the coil 30 the pressure exerted by the coil winding will cause the gap between the two disks 54 and 56 to vary against the biasing action of the spring 52; Despite any variations in dimensions of the coil, it is seen that the rotary follow still maintains firm electrical contact with the coil.

The present invention provides a means whereby the lowest possible contact resistance between the wire of the inductor and the shaft it rotates about, by reducing to the minimum the number of elements involved. It may be seen that the fiat disk 56 electrically connects the tap on the coil 30 to the fixed shaft 22. In parallel therewith the disk 54 electrically connects the tap on the coil directly with the shaft 22. This feature is of particular importance for high speed operation at high frequencies.

This invention further provides simplified mechanical structures includingmeans to compensate for variations 7 from the nominal dimensions of the parts involved. This feature is very important for high speed operation. In the construction of the present embodiment of the invention, the coil conductor is resiliently gripped between two relatively movable dish edges each of which may move independently of the other to conform to irregulations in the conductor pulse. This feature has contributed to the successful operation of the device in high speed remote control tuners for mobile communication systems and the like which operate at relatively high frequencies.

Another feature provided in accordance with this inusual rollers for contact members.

I V p 4 i vention is that involving the means for providing minimumtorqu'e with no perceptible increase even with dimensional variations of the elements involved. Mounting of the follower at an angle normal to the helical angle of the coil permits the minimum torque even when the coil is rotated at high speeds.

The compact and sturdy construction of the rotary follower described in-this'z application is such that op-' eration at very high speed's 'up-to-l800 or more revolutions per minute is possible.

The rotary follower jsuch as described is subject to less friction and resulting};wear-than wiper arms or the Consequently there is the further advantage" of longer wear" to be "derived from the use of the rotary follower, such as described, as a contact member in a high frequency variable in ductor unit.

What is claimed isz 1. A rotary. follower contact device for spacewound rotary variable coils and' the like comprising a first flat disk contact elementhavingan axially extending sleeve adapted. to receivea guideshaftonone side and having an externally threaded radially; split hollow hub axial-.

ly extendin'gtherefromand a tapered surface about the periphery. thereof-on the other side, a second fiat disk contact elementhavin'geonone 'side' an axially extending sleeve; adapted toreceive said guide shaft and having slots extending through said'element toreceive and in-- terlock' with said'hub andhaving a tapered surface around the periphery of-tne other side of said second element, said tapered surfaceson said contact elements being on facing sides of said elements'to-form a groove around the periphery of said device, a cap element internally threaded and attached to the threaded hub of said first fiat diskcoutactelement; and a'compression spring surrounding the sleeve of said second disk and locatedin the-hub of said first disk, whereby the. spring is efiective to bias the second disk into contact with the first disk.

2. Arotary follower contact device for a space wound inductance coil'and the like comprising in combination a first circular flat disk, .a tapered surface portion about the periphery of said first disk on one side, an integral axially extending sleeve member on the other side of said first disk adapted to receive and rotate on a guide shaft, a plurality ofthreaded radially split hub elements extendingraxially, from the one side of said first disk, a second circular flat disk having central openings adapted to receive said threaded hub elements of said first disk, a second sleeve member extending axially from one side ofsaid second circular'flat-disk adapted to receive and rotate on said guide-shaft, a tapered surface portion about the periphery of said second disk on the other side, said disk being mounted with said tapered surface portions adjacent to form a peripheral groove extending aroundthe periphery ofsaid device, a spring member disposed around said second sleeve member of said second disk, and an internallythreaded cap member detachably secured to the threaded portions of said threaded hub elements of said first disk to compress the spring member and eifectre'silient biasing of said second disk towards said-first disk.

References'Cited'in the file of this patent

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