US2309798A - Variable resistance - Google Patents

Description

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VARIABLE RESISTANCE Original Filed Dec. 5, 1955 ATTOR EY.

Patented Feb. 2, 1943 VARIABLE RESISTANCE Erwin R. Stoekle, deceased, late of Milwaukee, Wis, by Lillian Stoekle, executrix, Milwaukee, Wis, assignor to Globe-Union Inc., Milwaukee, Wis, a corporation of Delaware Original application December 5, 1.935, Serial No.

1941, Serial No. 391,478

(Cl. 20l55) Claims.

This invention relates to an improvement in variable resistors adapted to be advantageously employed in combination with a power switch for use in a radio receiver or similar electrical sound reproduction apparatus although also capable of use as a variable resistor alone in radio receivers or in other diverse applications.

The present application is a division of the application of Erwin R. Stoekle, filed December 5, 1935, Serial No. 53,139, for Combined variable resistance and switch.

The object of the invention is to simplify and compact the structure of the resistor, render it more reliable and eiiicient in operation, afford the maximum range of adjustment, and make it practical to manufacture it with economy from materials and by means of facilities ordinarily available.

Among the more specific objects of the invention are to provide an improved and simplified means for holding the resistor and terminals of the variable resistance in place; and to improve the adjustable contact thereof and th manner of mounting, biasing, and adjusting the same, as

well as the means employed for conveying current thereto.

Other objects and advantages reside in certain novel features of the construction, arrangement, and combination of parts, which will be hereinafter more fully described and particularly pointed out in the appended claims, reference being had to the accompanying drawing forming a part of this specification, and in which:

Figure 1 is a view in longitudinal cross section taken on line ll of Figure 2 and illustrating 1 one construction in which the variable resistance of the present invention may be embodied;

Figure 2 is a view in transverse cross section taken on line 22 of Figure 1 and looking in the direction of the arrows;

Figure 3 is a group view in perspective illustrating the resistor, its split-clamping ring, the tapered terminal for maintaining the parts assembled, and the conducting ring carried by the terminal;

Figure 4 is a fragmentary detailed sectional view taken on line 44 of Figure 5; and

Figure 5 is a view in elevation looking toward the left of Figure 1 but showing the device as it appears with the metal housing cup and parts of the variable resistance removed or omitted.

Referring to the drawing it will be seen that in the embodiment of the invention therein illustrated, the variable resistance is contained in the housing, designated generally at H.

While the 55 Divided and this application May 2,

housing H may be made in various ways, it is illustrated, for the sake of example, as made up in part of a shallow metal cup 45, to the inner face of the body of which a flat disc 46 of insulating material is secured. The insulating disc 46 may be secured in place by the upset inner end 41 of a mounting bushing 48 which is in this way also connected to the apertured central portion of the body of the cup 45. The housing for the resistance also includes an annular body member 49 of insulating material, a portion of which telescopes into the metal cup 45. A resistor 50 is provided and may comprise a flexible strip having a resistive coating applied to its inner surface. The strip 56 is positioned against the inner wall of the annular housing member 49 and is secured in position by means of a split expansible clamping ring 5|, which may be made of laminated, Bakelite sheet or other insulating material or composition of appropriate elasticity or resiliency, and which has one of its side faces positioned against the inner side of an inturned annular flange 49 integral with one end of the body member 49. A locating rib, which may be integral with the housing member 49, or which may be in the form of a fiber key so tightly driven into a key-way provided therefor in the housing member 49, engages between the ends of the resistor 50 to locate the resistor in proper position in the housing 49.

Terminals 52 and 52' are electrically connected with the ends of the resistor 50 and project exteriorly of the resistance housing H. The terminals 52 and 52, save that one is of the right and the other of the left hand, are of identical construction, and, as shown in Figure 4, each has an angular portion 52 accommodated in an opening 49 provided in flange 48 and also in a groove 49 formed in the inner side face of said flange 49*, the annular portion 52 of each of the terminals having an appropriately shaped extremity 52 snugly engaging the adjacent portion of the resistor 58.

The outer periphery of the ring 5| adjacent the split is notched as at 5H to accommodate the inner extremities 52 of the terminals 52 and 52' so that the ring 5 when expanded, not only holds the resistor 59 but also the terminals 52 and 52 in place. Suitable means is provided for expanding the ring 5| so that its periphery clamps the resistor against the inner wall of the annular housing member 49 and the terminals 52 and 52 against the resistor. In the present instance it is proposed to utilize a third terminal 54 for this purpose, and to adapt the terminal to perform this function it is tapered, as clearly shown in Figure 3. In the assembly, the tapered portion of the terminal 54 engages in notches 55 and 55' formed in the confronting ends of the ring 5| at the split thereof. Thus, the tapered terminal 54, by forcing the ends of the split ring away from each other at the split, brings about the desired expansion and clamping of the resistor and the other two terminals. The terminal 54 may be formed integral with a conducting ring 51 which is disposed against the inner side face of the split ring 5|.

The movable contact of the variable resistance includes a ring-like strip 58 of spring metal and of good electrical conductivity. The strip is disposed adjacent or against one side face of a rotatable carrier disc 63 of electrical insulating material, and while the strip 58 may be supported on and fixed to the disc 63 in various ways, this is preferably and advantageously accomplished by forming an attaching tongue 65 integral with the disc, inserting the tongue 65 through a slot 66 in the disc 83, and clenching, bending, or otherwise suitably securing the tongue to the disc 63.

The strip 58 has a portion 59 bent and intensioned laterally from the mean plane of the strip to provide a collecting shoe which wipes against the conducting ring 51 and provides for passage of electric current from the conducting ring 57 to the strip 58.

The strip 58 is provided with an enlarged portion Bil which is formed with an arcuate or semicircular notch 6i to snugly receive and have good electrical contact with a contact member proper, designated as at 62. In the particular construction shown in the drawing, and which is selected merely for illustration or example, the contact member 62 is in the form of a roller or short cylinder having rounded ends, the periphery of the roller bearing directly against the resistive coating of the resistor 50. The enlarged portion 60 of the strip 58 is intensioned outwardly so as to insure good electrical contact between itself and the movable contact member 62 and between the movable contact member 62 and the resistor 50. The particular form of movable contact member 62 may, however, be varied, as this form is not an essential feature of the invention. For example, the portion 60 of the strip might in lieu of being notched be itself fashioned or shaped to constitute the movable contact member proper and to have direct wiping engagement with the resistor 50. In such event the roller 62 would be omitted entirely. Moreover, the particular formation of collector shoe 59 may be varied. The

important and essential characteristics of this feature of the invention reside in the contact strip 58 and in the way it is combined with the conducting ring 51 and the resistor 50. The strip 58 is so constituted that it intensions the movable contact member proper radially outwardly into proper electrical contact with the resistor, and it intensions the collecting shoe portion thereof laterally in a direction at right angles to the direction of bias of the movable contact member and into engagement with its conducting ring. A movable contact having a spring strip of this character is of particular advantage in connection with devices which are produced in quantity or on a commercial scale since the parts may be properly fabricated and intensioned at the factory, and uniformity of action is insured inall of the devices put out. Uniformity of action is of particular advantage or especial importance in variable resistance of this character. The strip 58 may be stamped or cut out from a single piece of metal into a pro-formed, properly shaped sub-assembly, with parts thereof precisioned intensioned and ready for final assembly.

Where the construction is such that the movable contact proper takes the form of roller 62, then the insulating carrier 63 has a portion of its periphery slightly enlarged and provided with a notch 61, which receives a portion of the roller 62, the assembly being such that the walls of the notch 61 of the disc 63 perform the function of transmitting angular movement or adjustment to the movable contacting member 62, that is, the disc 63 drives the contact member 62 and leaves to the spring strip 58 only the duty of applying the requisite outward radial pressure to the movable contact and of conveying the electrical current thereto from the terminal 54 and conducting ring 51.

The disc 63 has a non-circular opening in its center which is snugly fitted on 2. correspondingly formed inner end portion 64 of an operating shaft 64 supported for rotative movement in the bushing 48 and constrained against any axial movement by the provision of a shoulder 64 on the shaft engaging one end of the bushing 48 and by the assembly held on the inner end of the shaft by its upset end 64*. This assembly includes the carrier disc 63, just described, an appropriate spring washer 48 and a conical cup-shaped shield 90, which will be hereinafter more fully described.

With the construction as thus far described, current flows through terminal 54 and conducting ring 51 to the shoe 59 at one end of the strip 51 and thence through the strip 58 to the roller contact 62. rom the roller contact 62 the current flows through the resistor to the terminals 52 and 52'. The amount of resistance incorporated in the circuit depends upon the angular position of the contact 62 with respect to the resistor 50, and this, of course, may be conveniently adjusted by turning the shaft 64.

In the construction shown in the present application the adjustable resistance has a power supply switch, designated at 10, combined therewith. While this is advantageous in many instances, it is not essential, as the variable resistance of the present invention may be used therewith or without a power supply switch, and as the parts of the power supply switch per se form no part of the invention of the present application, they will not be described in detail. For a complete description and disclosure of such a power supply switch reference is made to the application of Erwin R. Stoekle, for Combined variable resistance and switch, filed December 6, 1935, Serial No. 53,139.

While one construction in which the invention may be advantageously embodied has been shown and described, it is to be understood that the construction shown has been selected merely for the purpose of illustration or example, and that various changes in the size, shape, and arrangement of the parts may be made without departing from the spirit of the invention or the scope of the subjoined claims.

It is claimed:

1. A variable resistance comprising a housing having a curved inner wall, a resistor disposed against said wall and comprising a thin, flexible strip having a resistive coating applied to its inner surface, a separate split clamping ring disposed within the housing and adapted to be expanded outwardly to engage the inner periphery of the resistor and clamp the resistor against the wall of the housing, and means for expanding the split ring outwardly including a tapered terminal cooperable with the ends thereof.

2. A variable resistance comprising a housing having a curved inner wall, a resistor disposed against said wall and comprising a thin, flexible strip having a resistive coating applied to its inner surface, a separate split clamping ring disposed Within the housing and adapted to be expanded outwardly to engage the inner periphery of the resistor and to clamp the resistor against the wall of the housing, and means for expanding the split ring outwardly including a tapered terminal cooperable with the ends thereof, in combination with terminals cooperable with the resistor and having portions disposed between the split ring and the resistor whereby said terminals are clamped against the resistor by said ring.

3. A variable resistance comprising a housing having a circular wall, a resistor disposed against said wall, an operating shaft rotatable with respect to said housing, a carrier disc of insulating material disposed within the housing and fixed to said shaft, a curved strip of spring metal of good electrical conductivity disposed adjacent a sideface of the disc and secured thereto so as to be supported thereon and rotatable therewith, said strip having a portion thereof intensioned radially outwardly and having a contact member pressed into wiping engagement with the resistor under the influence of said radially intensioned portion of said strip, a conducting ring mounted on the housing to one side of the strip, said strip also having another portion intensioned laterally from the mean plane of rotation of the strip and toward the conducting ring and having a collecting shoe in wiping engagement with the conducting ring under the influence of said laterally intensioned portion of the strip, and terminals connected to the resistor and to said conducting ring.

4,. A Variable resistance comprising a housing having a circular wall, a resistor disposed against said wall, an operating shaft rotatable with respect to said housing, a carrier disc of insulating material disposed within the housing and fixed to said shaft, a curved strip of spring metal of good electrical conductivity disposed adjacent a side face of the disc, said strip having an integral attaching tongue, said disc having a slot in which said tongue is inserted and secured to support the strip on and fix it to the disc for rotation therewith, said strip having a portion thereof intensioned radially outwardly and having a contact member pressed into wiping engagement with the resistor under the influence of said radially intensioned portion of said strip, conducting ring mounted on the housing to one side of the strip, said strip also having another portion intensioned laterally from the mean plane of rotation of the strip and toward the conducting ring and having a collecting shoe in wiping engagement with the conducting ring under the influence of said laterally intensioned portion of the strip, and terminals connected to the resistor and to said conducting ring.

5. A variable resistance comprising a housing having a curved inner wall, a resistor disposed against said wall and comprising a thin, flexible strip having a resistive coating applied to its inner surface, terminals engaged with the resistor, a separate split ring having notched ends adapted to engage the terminals and having its periphery adapted to engage the inner peripheral surface of the resistor, said split ring being adapted to be expanded outwardly to clamp the terminals against the resistor and to clamp the resistor against the inner wall of the housing, and means for expanding the split ring outwardly including a tapered terminal cooperable with the ends thereof.

LILLIAN STOEKLE, Executrix of the Estate of Erwin R. Stoekle, Deceased.

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