US1924105A - Electrical resistor - Google Patents

Description

Aug. 29, 1933. H. L. BRADLEY ELECTRICAL RESISTOR Filed June 24. 1929 2 Sheets-Sheet 1 1933. H. L. BRADLEY 1,924,105

ELECTRICAL RESISTOR Filed June 24. 1929 2 Sheets-Sheet 2 I v M/deesfw I L5; 14 J% /7 /Z. 5/7177; i dmm Patented Aug. 29, 1933 UNITED STATES PATENT OFFICE ELECTRICAL RESISTOR consin Application June 24, 1929. Serial No. 373,399

11 Claims. (01. 201-50) This invention relates to certain new and useful improvements in variable resistors and refers more particularly to voltage dividers or potentiometers. As is well known in the art, potentiometers consist of a pair of resistor units, the

resistance of which is simultaneously and inversely varied and in the present invention the resistor units are composed of quantities of com-' pressible powdered material having the desired conductive characteristics as in a co-pending application Serial No. 321,336 filed, November 23, 1928.

It is an object of this invention to provide a potentiometer of simplified and compact design to be particularly adaptable for use in radio receivers.

Another object of this invention resides in the provision of an improved potentiometer in which the resistor units are arranged on a common 1ongitudinal axis and have a common means for varying their resistance.

Another object of this invention resides in the provision of a potentiometer having a pair of resistor units mounted on a common longitudiapplying member which simultaneously regulates the pressure on both units.

A further object of this invention resides in the provision of an improved potentiometer having a shaft extending through both resistor units for actuating a common pressure member and which likewise provides means for securing the elements assembled.

And a still further object of this invention resides in the provision of a potentiometer having a casing with a plunger disposed transversely and medially thereof to divide the same into separated compartments which are filled with powdered resistance material whereby movement of the plunger increases the pressure on the resistance material at one side thereof and decreases the pressure on the material at the other side and. vice versa.

With the above and other objects in view which will appear as the description proceeds, my

invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

In the accompanying drawings, I have illustrated two complete examples of the physical embodiment of my invention constructed accordnal axis and separated by a movable pressure' ing to the best mode I have so far devised for the practical application of the principles thereof, and in which:

Figure 1 is a transverse, sectional view taken through a potentiometer embodying my invention with parts in elevation;

Figure 2 is a cross sectional view taken thrgaugh Figure l on the plane of the line 22, an

Figure 3 is a fragmentary, sectional view taken through Figure 2 on the plane of the line 3-3.

Figure 4 is a view similar to Figure 1 illustrating a slightly modified form of my invention;

Figure 5 is a viewpartly in section and partly in elevation, taken through Figure 4 on the 7 plane of the line 5-5, and

Figure 6 is a fragmentary detail view taken through Figure 5 on the plane of the line 6-6.

Referring now more particularly to the accompanying drawings, in which like numerals designate like parts throughout the several views, nu-

.., merals 5 and 6, respectively, designate an upper The shaft 10 has an enlarged exteriorly s5 threaded portion 11 formed thereon, which is substantially equi-distant from the ends of the sections 5 and 6, and disposed between the ends of central projections or bosses 12 and 13 carried by the casing sections 5 and 6, respectively, and through which the shaft projects. The lowermost end of the shaft is reduced at a point in line with the bottom of a counter-bore 14 formed in the outer end of the section 6 to receive a washer 15 which is secured thereon by riveting or the like to maintain the shaft freely rotatable but non-longitudinally movably assembled with the section 6.

The bottom of the cup-shaped section 6 is substantially covered by a metal washer or apertured plate 16 which is secured in position by rivets 17, one of which also passes through one end of a terminal lug 18 to electrically connect the same with the plate. A recess 19 formed in the outer bottom of the section receives the terminal lug 18 and thus prevents turning thereof about its attaching rivet 17.

The terminal 18 forms one of the end terminals of the potentiometer and through the plate 16 is electrically connected with the one of the reno sistor units which consists of a quantity of powdered resistance material substantially filling the section 6. The other resistor unit 21 is likewise formed of powdered resistance material and is disposed in the upper section 5 being electrically connected with the other end terminal 22 in a similar manner through a plate 23 likewise secured in the bottom of the section 5, as clearly ilustrated in Figure l. The terminal 22 like the terminal 18 is prevented from turning about its point of securement by being disposed within a recess 24 formed in the upper outer face of the section 5.

;The units 20 and 21 are separated by a plunger 25 threaded on the portion 11 of the shaft and comprising a metal disc 26 on each side of which a washer or disc 27 of larger diameter and formed of felt or other similar material, is disposed. Metallic discs 28 tied together by rivets 29 or the like maintain the felt washers assembled with the disc 26. As the diameter of the felt washers is sufliciently large to have a snug engagement with the walls of the casing sections it will be seen that as the shaft 10 is rotated by means of a knob or the like 30 fixed to its outer end, the frictional engagement of the felt discs with the casing walls holds the plunger against rotation to effect longitudinal movement thereof, which simultaneously and inversely varies the pressure on the resistor units 20 and 21 and thus increases or decreases their resistance.

The aperture 8 in the casing section 5 through which the upper end of the shaft 10 extends is larger than the opening 9 in the section 6 and has its inner end provided with a hexagonally shaped counter-bore 31 and with a second comparatively shallow counter-bore 32. A metal sleeve or bushing 33 having a hexagonal head or flange and whose aperture is such as to snugly receive the shaft 10 extends through the aperture 8 and has its head or flange disposed in the hexagonal counter-bore 31 to prevent turning of the bushing.

The enlarged apertured end of a terminal lug 34 through which the bushing 33 extends is also received in the counter-bore 31, being impinged between the bottom of the counter-bore and the 'head of the bushing. The other end of the terminal 34 extends through an opening 35 in communication with the counter-bore 31, and is confined in a recess 36 with its end projecting beyond the periphery of the casing to provide the neutral or central terminal of the potentiometer, which ,is electrically connected with the plunger 25, through the bushing 33 and the shaft 10 and thus with the adjacent faces of the resistor units.

The bushing 33 and consequently the terminal lug 34 are maintained in position by a second bushing 37 formed of insulating material and constituting the projection 12 which engages the upper end of the threaded portion 11. The upper end of the bushing 37 has a stepped flange 38, the outermost portion of which is received in the shallow counter-bore 32 confining the hexagonal head of the bushing 33 in its hexagonal counter-bore. Displacement of the bushing 37 is prevented by the washer 23 whose inner periphery engages the smaller stepped portion of the flange 38 and thus extends over the outer larger portion. In this manner the attachment of the plate or washer 23 in the bottom of the casing section 6 secures the bushings 33 and 37 and the terminal lug 34 against displacement.

In assembling the potentiometer the lower half of the casing or section 6 in which the shaft 10 has been secured, is filled with the desired quantity of powdered resistance material and the plunger 25 is then threaded on the shaft which closes the section open end and permits the same to be turned to insert the shaft through the casing section 5 which has also been filled with the proper amount of powdered material. After the sections are engaged with each other a split ring 39 is secured in an annular recess 40 formed in the shaft at a point adjacent the end of the bushing 33 which thus holds the sections against separation.

The projected end of the bushing 33 is preferably threaded to receive a clamp nut 41 by which the device may be clamped to any suitable panel support in the conventional manner.

In use, the felt washers 27 of the plunger never pass the line of joint between the casing sections 5 and 6 thereby preventing the possible loss of powdered material between the casing sections without necessitating the provision of means for providing a tight joint therebetween.

In the structure described, it is possible that an extreme degree of compression will cause a resistor element to retain its compressed state and create a space between it and the plunger when the plunger is moved in the opposite direction. This is objectionable as it would interrupt the circuit, and therefore, the modification depicted in Figures 4, 5 and 6, is so designed that an electrical connection is always maintained between the outer terminals and the central or neutral terminal.

In this form of the invention, the construction and assembly of the several elements is materially simplified. The spindle 10 which is rotatably but non-longitudinally movably assembled with the casing section 6 is journaled in a bushing 42 mounted in the aperture 9 with its lower flange 43 positioned in the counterbore 14. The upper end of the bushing is extended through an apertured flange 44 which is preferably of hexagonal shape and recessed in the bottom of the casing, to be swedged over, as at 45, to secure the bushing and the flange in position.

A ring 46 is secured in an annular groove 4'1 formed in the bottom of the casing adjacent its outer periphery, by rivets 43 or the like, one of which passes through the terminal 18 so that the resistor unit or element 20 electrically connects the annular ring 46, and the hexagonal flange 44.

The aperture 8 in the casing section 5, through which the upper end of the spindle 10 extends, mounts a bushing 49, on the lower end of which a hexagonal flange 50 is formed to be received in a similarly formed recess in the bottom of the casing, a swedged over portion 51 maintaining the bushing 49 assembled with the casing section 5. The bushing 49 takes the place of bushng 33 of that form of my invention illustrated in Figures 1 to 3, and likewise has its outer end threaded to receive the nut 41 by which the device is clamped to a suitable panel or the like. The casing section 5, like the section 6, also has a ring 46 secured in a groove 47 with the terminal 22 electrically connected therewith through one of its securing rivets 48.

The construction of the plunger 25 is also simplified and consists of a disc or plate 52 having a central hub 53 pressed therefrom which is passed through an aperture in a second disc 54 and is riveted over its outer face to maintain the axial shaft extending through the casing sections discs against separation, a felt washer 55 being impinged between the two discs. The neutral terminal 34 which is electrically connectedwith the shaft or spindle 10 and thus with the hexagonal flanges 44 and '50, has its;

innerapertured end 56 impinged between the flange 43 of the bushing 42 and the bottom of the counterbore14, see Figure 6.

Thus-it -wi1l-be seen that as the circuit from the neutral terminal to either of the outer terminals is completed by the resistorv elements bridging the space between the rings 46 and the flanges 44 and 50, the circuit remains unbroken at all times.

From the foregoing description, taken in connection with the accompanying drawings, it will be readily apparent to those skilled in'the art to which an invention of the character described appertains, that I provide an improved potentiometer which isextremely compact and in which strainis never placed on the'panel, nor is there ever a tendency to spread the two casing sections, as all strains are absorbed by the shaft. For instance, in Figure 1, the parts are illustrated in the positions at which the upper resistance unit 21 is under maximum compression between the end wall of the casing section 5 and the plunger and as the plunger is threaded on the shaft and the shaft is retained against longitudinal movement with respect to the section, through the split ring 39 and the bushing 33, all strains are retained within the confines of the upper casing and in no way impart any stress to the lower casing.

Furthermore, it will be obvious that the adjustment of the resistance values of its units may be readily and quickly accomplished without longitudinal movement of the adjusting screw.

What I claim as my invention is:

1. In a potentiometer of the character described, a casing comprising axially aligned sections, a compressible resistor element in each section, a pressure member separating the resistor elements, a member extending through both sections to secure the same against separation, and means whereby said second member serves to actuate the pressure member to simultaneously and inversely vary the resistance of the resistor elements. V

2. In a potentiometer of the character described, a casing comprising axially aligned sections, a compressible resistor element in each section, a pressure member operable to simultaneously and inversely vary the resistance of the resistor elements, and a single means for actuating the pressure member and securing the casing sections together.

3. In a potentiometer of the character described, a casing comprising axially aligned sections, a compressible resistor element disposed within each section, a pressure member operable to compress either resistor element between it and its respective casing section end wall, a member axially aligned with the resistor elements and the casing sections for actuating thepressure member, and means whereby the strains incidental to the compression of either resistor element are carried by the actuating member.

4. In a potentiometer of the character described, a casing comprising axially aligned sections, a compressible resistor element disposed within each section, a pressure member operable to compress either resistor element between it and its respective casing section end wall, an

and threaded in the pressure member whereby rotation of the shaft actuates the pressure member. andmeans connecting the shaft with each casing section wherebythe strains incidental to the compression of each resistor element are carried by the shaft and the respective section without imparting stress to the other section.

5. An-electrical resistance device comprising, an adjusting element, a movable member mounted on the medial portion of the adjusting element, means for moving saidmember axially with respect to the adjusting element upon rotation of the adjusting element, compressible resistor elements on opposite sides of said "movable member, and abutments on .the end portions of the adjusting elements outwardly of the resistor elements, and between which and said movable member the resistor elements are compressible upon movement of the movable member,

6. An electrical resistance device comprising, compressible resistor elements, an adjusting element extending axially through the resistance elements, and provided with a screw thread, a movable member mounted on said screw thread and separating the resistance elements, abutments connected with the end portions of the adjusting element and engaged with the resistance elements whereby each element is confined between one abutment and said movable member, rotation of the adjusting element in one direction moving said movable member toward one abutment to compress one resistance element and relieve the pressure of the other and vice versa.

7. An electrical resistance device comprising compressible resistance elements, an adjusting element extending through said resistance elements, a movable member mounted on the medial portion of said adjusting element and separating the resistance elements from each other, means whereby rotation of the adjusting element imparts movement to said member axially with respect to the adjusting element, casing sections enclosing the resistance elements, and means for holding the casing sections against axial movement with respect to the adjusting element whereby movement of said movable memberupon rotation of the adjusting element-in one direction compresses one of the resistance elements between it and one casing section and movement of said member in the other directionupon opposite rotation of the adjusting element-- compresses the other resistance element between it and the other casing section.

8. An electrical resistance device comprising, a pair of compressible resistor elements having a common axis, a pressure member between the resistor elements and engaged with their adjacent faces, fixed walls between which and the pressure member the resistor elements are compressible, an adjusting shaft extending through the resistor elements and the pressure member, and having a threaded connection with the pressure member, and supporting means for the shaft fixed with respect to said fixed walls and with which the shaft has a freely rotatable but non-longitudinally movable connection whereby rotation of the shaft moves the pressure member toward one fixed wall or the other.

9. An electrical resistance device comprising, a pair of compressible resistor elements having a common axis, a pressure member between the resistor elements and engaged with their adjacent faces, fixed walls between which and the pressure member the resistor elements are compressible, an adjusting shaft extending through one resistor unit and having a threaded connection with the pressure member, and supporting means for the shaft fixed with respect to said fixed walls and with which the shaft has a freely rotatable but non-longitudinally movable connection, whereby rotation of the shaft moves the pressure member toward one fixed wall or the other.

10. An electrical resistance device comprising, a pair of axially aligned compressible resistor elements, a pressure member between the resistor elements and engaged with the adjacent faces thereof, an adjusting member co-axial with the common axis of the resistor elements and having a threaded connection with the pressure member, an enclosing casing having spaced walls substantially parallel with each other and the pressure member and engaging the resistor elements to cooperate with the pressure member to compress the resistor element, and means freely rotatably,

but non-longitudinally movablyconnecting the adjusting member with the casing spaced walls, whereby the pressure membermay be readily adjusted by rotation of the adjusting member to vary the degree of compression of the resistor elements.

11. An electrical resistance device comprising, a pair of compressible axially aligned resistor elements, a pressure member between the resistor elements and engaged with their adjacent faces, fixed walls engaging the opposite faces of the resistor elements and between which and the pressure member the resistor elements are compressible, an adjusting shaft in substantially axial alignment with the common axis of the resistor elements and connected with the pressure member so that movement of the adjusting shaft in one direction or the other moves the pressure member toward one fixed wall or the other, a support for the adjusting shaft fixed with respect to the fixed walls, and means for moving the adjusting shaft.

HARRY L. BRADLEY.

Images