US2842647A - Adjusting means for resistance trimmers - Google Patents

Description

July 8, 1958 A. s. KHOURl ADJUSTING MEANS FOR RESISTANCE TRIMMERS Filed March 18. 1954 2 Sheets-Sheet l 34 INVENTOR.

ALFRED S. KHoum -4. a Map A-r'ronmsx July 8,1958 A18. KHOURI 2,842,647

I ADJUSTING MEANS FOR RESISTANCE TRIMMERS Filed March 18, 1954 2 Sheets-Sheet 2 INVENTOR. ALFRED S-KHOUFM Q BY '78 66 8o 44 w. W 48 F16. \z 0 ATTORNEY United States Patent Union Inc., Milwaukee, Wis., a corporation of Delaware Application March 18, 1954, Serial No. 417,171

4 Claims. (Cl. 201-55) This invention relates to improvements in adjusting means for variable resistors, particularly such resistors as are initially adjusted to balance a circuit and then left in such adjusted state.

Resistances of this type are described and explained in the application of Jack S. Kilby and Alfred S. Khouri, Serial No. 394,015 for Resistance Trimmer. In such application a pivotally mounted rotor has its free end adjustably slidable along a resistance element on an insulating base. Such rotors are relatively small and it is difficult to make the adjustment without injuring the resistance element.

It is an object of this invention, therefore, to provide a rotor for a variable resistance which may be adjusted by use of a screw driver or like tool.

Another object of this invention is to provide a rotor with a permanently attached knob which may be adjusted by a screw driver or the like or by hand without fear of electrical shock, which rotor may be restricted in rotation.

The first of these objects is obtained by providing the rotor with wings having slots spaced to receive a screw driver bit or the like. The second object is obtained by securing to the rotor an insulating knob which is large enough to be gripped in the fingers and manipulated without fear of electrical shock, and also has on its face a tool receiving slot. This knob may be large enough to cover the resistance and may have a stop engaged by fingers on a mounting bracket to limit its rotation.

This invention may be best understood from the following description of a specific embodiment when read in connection with the accompanying drawings, in which:

Fig. 1 is a view in front elevation of a variable resistor having a rotor embodying the present invention;

Fig. 2 is an enlarged fragmentary sectional view taken on the line 2-2 of Fig. 1;

Fig. 3 is a perspective view of the rotor of Figs. 1 and Fig. 4 is a view in front elevation of a resistance trimmer having a rotor embodying a modification of the in vention;

Fig. 5 is an enlarged fragmentary sectional view taken on the line 55 of Fig. 4;

Fig. 6 is an exploded perspective view of the adjusting knob and rotor shown in Figs. 4 and 5;

Fig. 7 is a view in front elevation of a resistance trimmer rotor embodying a further modification of the invention, parts being broken away for sake of clarity in illustration;

Fig. 8 is a view in rear elevation of the modification viewed in Fig. 7;

Fig. 9 is a view in end elevation of the modfication viewed in Fig. 7 with parts broken away and shown in section;

Fig. 10 is a view in front elevation of a plurality of resistance trimmers like those viewed in Fig. 7 secured to 2,842,647 Patented July 8, 1958 a mounting strip in accordance with the present invention;

Fig. 11 is a fragmentary view in rear elevation of the mounting strip viewed in Fig. 10; and

Fig. 12 is a sectional view taken on the line 12-12 of Fig. 10.

In the modifications shown in Figs. 1 to 6 inclusive the resistance trimmer has an insulated base plate 10 which provides the structural support. Conductors 12 and 14 are bonded to such plate and lead from the edge of such plate to a resistance element 18 in the form of a segment of an annulus also secured to such plate. A central conductor 16 extends from the edge of such plate and terminates in an enlarged circular portion which surrounds a small opening through the plate 10. In such modifications the rotor or slider is pivotally mounted on the plate 10 by an eyelet 22 which extends through the openings in the plate 10 and rotor and is peened over on the rear side of such plate. Wire leads 24 are connected to the outer ends of the conductors.

In the modification shown in Figs. 1 and 3 a rotor 20 has integrally formed thereon a pair of upstanding wings 26 provided with slots 28 extending inwardly from the outer edges thereof. The wings 26 are close enough so that both slots can be engaged by the bit of a small standard size screw driver. The wings are far enough apart so that sutiicient rotational force may be applied to the rotor to swingably adjust it to the desired position.

In the modification shown in Figs. 4, 5 and 6 a rotor 30 has a pair of upstanding spaced wings 32. The opposite edges of these wings are provided with tooth-like projections 34 designed to engage a plastic knob 36. The wings 32 like the wings 26 are far enough apart so that the needed rotational force may be applied to the rotor for its adjustment. The knob 36 has a pair of spaced slots 38 in its bottom face which receive the wings 32. The length of the slots is such that when the knob is pressed on the wings 32 the teeth 34 will slightly gouge the edges of such slots and frictionally retain the knob in place. The diameter of the knob is large enough so that it can be readily grasped by the fingers to rotate the rotor 30. It is made of an insulating plastic which may be molded. In appearance it is obviously an insulator and hence those concerned with the adjustment of the resistance trimmer will not have any fear of getting an electrical shock. The knob may be provided with a slot 40 in its outer face for the reception of a screw driver or similar tool.

The modifications shown in Figs. 7 to 12 inclusive have an insulating base 42 on which is mounted a resistance element 44 with its ends connected to conductors 46 and 48. The resistance element encircles a small opening in the plate 42 and a central conductor 50 leads from such opening. Terminals 51 are secured by eyelets 52 to the conductors 46, 48 and 50. A conductive rotor 54 is pivotally mounted on the base 42 by a tubular pivot 56 so that its free end will slide along the resistance element 44. The rotor 54 has a pair of upstanding spaced wings 58.

An insulating manually engageable knob 60 has slots on the lower side into which the wings 58 are frictionally fitted to secure the knob to the rotor 54. The knob 60 has a skirt 62 which extends over the entire area of the resistance 44 to protect the same from manual contact when the knob is being manipulated. The central part of the knob 60 may be provided with a slot 64 for the reception of a screw driver or other like tool. A raised bar 66 on the skirt 62 provides an abutment for limiting the angular movement of the rotor 54.

In order to mount the resistance trimmer to a panel or the like, there is provided a mounting bracket 68 which has flanges 70 embracing opposite edges of the base 42 provided with edge notches 72 in which the flanges 70 are seated to provide additional gripping action. Fingers 74 may be provided on one of the flanges 70 at spaced places. These fingers overlie the skirt 62 and are in the path of the bar 66. They engage the bar. 66 and limit rotation to prevent the rotor 54 from leaving contact with the element 44. An extension on the mounting'bracket 68 may be provided with holes 76 by which it may bereadily fastened to a chassis or the 'ke.

In the modification shown in Figs. l0, l1 and 12, the resistance trimmers are identical with'that show in'Figs. 7, 8 and 9, however, the mounting bracket is formed so that a plurality of such trimmers may be mounted on one bracket and handled as a unit. The mounting bracket 78 consists of an elongated strip of metal. At proper spacing along its length there are flanges 80 which are formed up from the body of the bracket from under the plate 42. One of the flanges 80 may be provided with spaced fingers 82. The blanking shape for this flange 80 and 7 its fingers is indicated at 84 (Fig. 11). It may be desirable to provide along the bottom edge of the bracket 78 a channel-like reinforcing member 86 which will stifien the mounting bracket 74 and also provide further engagement for the resistance trimmers. To assemble a resistance trimmer to the mounting bracket it is placed on the bracket after the flanges 72 have been pressed to a vertical position. Thereafter the upper ends of the flanges are formed over the base plate 42 as indicated. The mounting plate with its multiplicity of resistance trimmers maybe secured to a panel or chassis in the usual manner.

What I claim and desire to secure by this patent is:

1. 'In a resistance trimmer having an insulating supporting plate and a resistance element fixedly mounted thereon, a flat conductive rotor pivotally mounted to said plate and having wiping engagement with said resistance, said rotor having an opening therethrough, a pivot extending from said plate through said opening to only the outerside of said rotor, said rotor having a pair of wings integral therewith and extending outwardly of said plate, said wings being diametrically positioned with respect to the center of said opening and provided with teeth extending from the sides thereof, a molded insulating knob having a 4 spaced slots adapted to receive said wings with the edges of said slots frictionally engaged by said teeth, said knob being rigidly mounted on said rotor with said wings inserted in said slots.

2. In a resistance trimmer having an insulating supporting plate with a resistance element on a side thereof, a conductive rotor independently pivotally mounted to said plate on said side, knob holding means integral with said rotor,'and an insulating knob mounted on said means and carriedthereby independent of the pivotal mounting of said rotor, said knob having a'skirt covering said resistance element and spaced therefrom whereby said resistance element is protected during manual manipulation of said knob.

3. The combination as claimed in claim 2, in which said skirt has a raised abutment thereon and in which there is a second abutment secured to said supporting plate and overlying said skirt to engage said first abutment and limit the rotation of said knob.

4. A resistance trimmer having an insulating supporting plate, a resistance element on a side of said plate, a-conductive rotor mounted on said side of said plate for movement along said resistance element, an insulating knob secured tosaid rotor and carried thereby independently of the mounting of said rotor, said knob covering said resistance element, and a mounting bracket for said resistance trimmer having flanges engaging said supporting plate from opposite sides, one of said flanges having a finger overlying said rotor, said rotor having an abutment raised therefrom engageable with said finger to limit the rotation of said rotor.

References Cited in the file of this patent UNITED STATES PATENTS Arisman Oct. 18, 1955

Images