US2717944A - Variable resistor - Google Patents

Description

Sept. 13, 1955 M. DAILY ET AL 2,717,944

VARIABLE RESISTOR Filed Feb. 18, 1954 I5 Sheets-Sheet l I7 1 g If) 5 1 5| ATM-Lu? MDazZy Idem/m .EL Amsman 7 gmvg Se t. 13, 1955 M. DAILY E A VARIABLE RESISTOR 3 Sheets-Sheet 2 Filed Feb. 18, 1954 b .miwgpd Ari Zwr M DazZy Mam/m .Er. .Amsman 2% Sept. 13, 1955 M. DAILY E L 2,717,944

VARIABLE RESISTOR Filed Feb. 18, 1954 3 Sheets-Sheet 3 United States Patent VARIABLE nusrsron Arthur M. Daily, Edwardsburg, Mich., and Mervin B. Arisman, Elkhart, Ind., assignors to Chicago Telephone Supply Corporation, Elkhart, Ind., a corporation of Indiana Application February 18, 1954, Serial No. 411,206

3 Claims. (Cl. Mil-) This invention relates to variable resistors and similar controls. Television and radio receivers, and particularly the former, employ quite a number of infrequently adjusted controls often referred to as preset controls. Several of such controls are needed in each television receiver. Hence, control manufacturers are faced with an ever increasing demand for reduction in the cost of these controls.

Since much of the cost involved in producing controls of this type is represented by direct labor, it is apparent that any operation in the manufacture of its piece parts or in the final assembly of the product which can be eliminated in all likelihood will result in a cost saving.

Accordingly, it is the primary purpose of this invention to provide a control of the character described wherein the total number of parts is materially reduced to thereby effect a double labor saving, first in the cost of producing the parts, and secondly, in the cost of assembling the same into the complete product. It is, of course, also the purpose of this invention to effect this desirable reduction in the number of parts without in anywise sacrificing performance and without eliminating the functions of the parts heretofore found necessary and essential for satisfactory operation in a control of this character. In other words, it is the purpose of this invention to reduce the number of piece parts without, however, omitting the individual and collective functions of all of the parts heretofore found necessary to satisfactory operation.

With a view toward achieving this general objective, the invention has as a more specific object the provision of a variable resistor which is so designed and constructed that the rotatable assembly, including its operating shaft, is journalled in bearings formed in the insulated base of the control and the end wall of its metal cover to thereby obviate the long shaft bushing heretofore employed.

In this connection it is another object of this invention to provide not only axially spaced side thrust bearings at the front and rear of the control but also an end thrust bearing located at the front wall of the control and provided by a portion of the end wall of the cover and the adjacent side of the drive arm or drive head.

Another object of this invention, which is directed toward the attainment of its main objective, resides in the provision of a tubular drive shaft which is inexpensively rolled up from sheet metal, and a simple manner of drivingly connecting the shaft to the drive head or drive arm which carries the spring contact fingers.

Again in this connection it is another object of this invention to provide a simple manner of detachably connecting the drive shaft with the rotatable assembly inside the control housing. Still another object of this invention directed specifically toward the simplification of the control resides in the provision of mounting ears or tangs formed integrally with the cover and projecting forwardly from its end wall.

2,7119% Patented Sept. 13, 1955 ice Another object of this invention dealing with detailed simplification of the structure with a view toward reducing the cost thereof resides in the provision of an axial pilot pin projecting rearwardly from the drive head to be journalled in a hole in the base which provides the rear wall of the control housing, and wherein this pilot pin may be either an integral part of the drive head or an extension on a rivet used to hold the elements of the drive head together.

Still another object of this invention is to so construct and arrange the pilot pin which provides side thrust support for the rear end of the rotatable assembly that the pin may be carried either by the base or the rotatable assembly, and when carried by the base may be given the additional function of holding the collector ring in place on the base.

With the above and other objects in view, which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangements 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.

The accompanying drawings illustrate several complete examples of the physical embodiments of the invention constructed according to the best modes so far devised for the practical application of the principles thereof, and in which:

Figure 1 is a longitudinal sectional View through a variable resistor embodying one form of this invention;

Figure 2 is a perspective view of the elements of the control depicted in Figure 1, shown separated from one another to better illustrate the same;

Figure 3 is a longitudinal sectional view similar to Figure 1, illustrating a second adaptation of this invention;

Figure 4 is a perspective view of the drive head of the control shown in Figure 3, together with the inner end portion of its operating shaft, which in this case is separable from the drive head;

Figure 5 is a longitudinal sectional view similar to Fig ure 1, illustrating still another embodiment of this invention;

Figure 6 is a perspective view of the rotatable assembly of the control shown in Figure 5, together with the inner end portion of its operating shaft shown separated from the assembly for clarity of illustration; and

Figure 7 is a detail sectional view illustrating a variation of the embodiment of the invention shown in Figures 5 and 6.

The control of this invention comprises in its entirety a simple stator sub-assembly 6, an equally simple rotor or rotatable sub-assembly 7 and a unitary stamped metal cover 8. This is true in each of the three embodiments of the invention illustrated, despite the fact that in the two modifications shown respectively in Figures 3 and 4 and 5 and 6, the control or operating shaft 9 is separate from the drive head 10 whereas in the structure shown in Figures 1 and 2 the shaft is an integral part of the drive head.

The stator sub-assembly 6 is the same in each of the three forms of the invention depicted. it comprises the customary circular base 11 of insulating material, and the familiar fiat split ring-shaped resistance element 12 overlying the base and secured thereto by its end terminals 13. Preferably these terminals are of the type forming the subject matter of the copending application of Arthur M. Daily, filed September 14, 1953, Serial No. 379,912. The only other part of the stator sub-assembly is a collector ring 14 which occupies the space within the resistance element and has a terminal 15 integral therewith.

The rotor or rotatable sub-assembly 7 of that form of the invention shown in Figures 1 and 2 is one integral unit, preferably molded of suitable insulating material such as a thermosetting phenolic composition. It consists of the shaft 9, a disc 17 which provides the drive head and a pilot pin or stem 18 coaxial with the shaft and projecting from the side of the head 17 opposite the shaft.

The shaft and the aligned spaced trunnion be pilot pin thus provide axially portions by which the rotor may journaled in correspondingly spaced bearings.

The usual spring contactor fingers 19 and 29 are mounted on the drive head of the rotor in position to respectively traverse the resistance element and the collector ring as the shaft is turned.

The cover 8 has a flat bottom or end wall 21 and a cylindrical side wall 22, the edge of which is seated on the peripheral portions 23 of the base in which position it is held by tangs or ears 24 extended from the side wall and bent over the base. The cover and the base thus coact to provide a housing for the instrumentalities of the control, the side wall of which is cut out as at 25 to accommodate the terminals 13. To this extent the housing follows conventional practice, but usually the end wall of the housing formed by the base is its front wall, that is, is the one adjacent to the mounting panel or wall upon which the control is mounted, but in this case it is the other end wall of the housing, namely the one provided by the bottom 21 of the cupshaped cover which is at the front.

This bottom or end wall 21 of the cover has a hole through its center, the marginal edge of which is extruded outwardly to provide a short cylindrical bearing 26 which is suitably sized to fit the shaft. The reception of the shaft in this bearing supports the rotor subassembly against side thrust but due to the relatively short axial length of the bearing the support provided thereby is not alone sufiicient to give the rotatable sub-assembly the desired stability. The present construction thus differs in this respect from the past practice of relying upon a single bearing carried by the front wall of the housing to support the rotor against side thrust. Obviously, though, for a single bearing to provide the required support for the rotor it had to be quite long, and to meet this need a long bushing was fixed to the front wall of the housing, usually the base. The bushing also served as the mounting means for the control. This arrangement is shown for instance, in the patent to Puerner No 2,594,493.

However, since it is the purpose of this invention to reduce the number of piece parts to an absolute minimum this previously used bushing, which was a separate screw machine part, is eliminated. To make this possible the pilot stem 18 which projects from the end of the rotor is journaled in a bearing hole 27 formed in the base 11.

The bearing hole 27 and the extruded bearing 26 thus provide two axially spaced bearings, one in each end wall of the housing, and which together carry the side thrust on the rotor. The necessary coaxial relationship between these bearings is assured by the manner in which the cover is assembled with the base and more specifically by the fact that the fastening tangs or ears 24 have flanking shoulders 28 which fit in notches 29 in the periphery of the base and thus accurately center the cover with the base.

This manner of assembling the cover and base also firmly holds these parts against relative axial shifting and assures that the flat bottom or end wall 21 of the cover will occupy a plane truly normal to the axis of rotation. Consequently, the inner surface of the end wall 21 may be used as a thrust bearing to carry the end thrust imposed upon the rotatable assembly by the spring arms 19 and 20, and for this purpose the front face of the disc 17 has a smooth circular rim or bead 30 which rides on the wall 21.

Rotation of the rotatable assembly imparted thereto through its shaft is limited by coacting abutments 31 and 32 respectively carried by the disc 17 and the cover 8; and since the control is intended primarily for use in situations where adjustment is infrequent, it is sufficient to provide the outer end of the shaft which protrudes from the front bearing 27 with knurling 33 and a screw driver slot 34. It is of course understood that if it is desired to adjust the rotor from the other end of the control, the pilot pin 18 could be extended to provide an operating shaft.

The mounting of the control upon a supporting panel or a wall of a chassis is conveniently effected by a plurality of tabs 35 struck forwardly from the end wall 21 to project through holes in the panel or other wall W upon which the control is to be mounted and then either twisted as shown in dotted lines or bent over; and it will be noted that when the control is so mounted the extruded bearing 26 is received in the hole in the panel or wall through which the shaft projects.

The only difference between that embodiment of the invention shown in Figures 3 and 4 and the just-described form of the invention shown in Figures 1 and 2 is that the control or operating shaft 9 is detachably connected to the disc 17 and is tubular and preferably rolled up from sheet material. To detachably secure the shaft 9' to the rotatable assembly, its inner end has two diametrically opposite spring fingers 36 projecting therefrom and received in holes 37 in the disc 17. The outer ends of the fingers 36 are provided with detent-like shoulders or abutments 33 which engage over abutments on the disc 17 provided by the rear edges of the holes 37 when the adjacent end 39 of the shaft bears against the front face of the disc. This arrangement provides a secure though detachable connection between the shaft and the disc 17 and allows the set manufacturer to determine whether or not the control is to be equipped with an accessible operating shaft.

In the third embodiment of the invention shown in Figures 5 and 6, the rotor subassembly is built up of a disc 40 of insulating material and a metal stamping 41 held together by a rivet 42. The disc 40 has the spring contactor fingers fixed thereto and the stamping 41 provides the stop plate and the switch actuator when the control has a switch combined therewith. Relative rotation between the disc 40 and the stop plate 41 is prevented by a pair of fingers 43 on the latter engaged in appropriate notches in the periphery of the disc.

in this case the shaft, though a separate element, is permanently connected to the rotor or rotatable assembly by means of fingers 44 projecting therefrom and passing through aligned holes in the disc 40 and stop plate 41, the ends of the fingers being bent over as shown in Figure 5. This arrangement achieves the required proper positional relationship between the shaft and the rotatable assembly and allows the shaft to be tubular metal.

Attention is directed to the fact that the extruded bearing 26 in this modification lies beneath, i. e. inwardly of, the plane of the front wall. This not only obviates the need for accommodating the bearing in the mounting panel or wall but more significantly brings the stationary part of the thrust bearing farther into the housing so that only a thin anti-friction washer 45 need be provided between the stop plate 41 and the center portion 46 of the end wall.

The rivet 42 not only holds the disc 40 and arm 41 together to facilitate assembly, but also has an extension 47 of reduced diameter to provide the pilot pin or stem.

If desired, a variant of this specific construction may be employed as shown, for instance, in Figure 7. In this case the pilot pin or stem 48 is fixed to the base and has a smooth running fit in a hole 49 in the disc 49, the metal stop plate 41 being cut out to provide adequate electrical clearance. This arrangement also enables the pilot pin and rolled up of sheet or stem to be used to hold a collector ring 50 in position seated flat upon the base to be supported thereby against any possible deflection by the spring contactor fingers as they traverse the same. Attention is directed to the fact that in this construction the fingers 44, by which the hollow shaft is secured to the disc 40 and stop plate 41, are staked rather than bent over. This difference between the Figure 5 and Figure 4 structures is necessitated by the need for assuring electrical clearance between the grounded shaft and the pilot pin 48 which is in contact with the collector ring 50.

From the foregoing description taken in connection with the accompanying drawings, it will be readily apparent to those skilled in this art that this invention provides a variable resistor with fewer parts than has heretofore been deemed necessary and that the desired reduction in the number of piece parts is achieved without in anywise sacrificing good performance of the control, and flows chiefly from the fact that parts which heretofore performed but a single function in the present invention perform an additional function or functions.

What we claim as our invention is:

l. A variable resistor comprising: a fiat base of insulating material having an arcuate resistance strip and a collector ring on one side thereof; a cup-shaped metal cover inverted over the side of the base at which the resistance element and collector ring are located and secured to the base to provide a housing for the resistor, the end walls of said housing being the base and the bottom of the cup-shaped cover; a bearing extruded from the bottom wall of the cup-shaped cover; the base having a bearing hole axially aligned with said extruded bearing so that the end walls of the housing have aligned bearings directly therein; a rotor assembly journalled in said bearings, said rotor assembly comprising a molded disc of insulating material of a diameter to substantially fill the housing; spring contact fingers fixed to the disc at the side thereof which faces the base, said spring contact fingers riding on the resistance element and the collector ring; a circular rim integral with and projecting from the other side of the disc, said circular rim bearing upon the bottom wall of the cupshaped cover to provide a smooth, broad thrust bearing for the rotor assembly by which the disc is located with respect to the base and the tension upon the spring contact fingers is established; a pilot pin integral with and projecting from the side of the disc which faces the base, said pilot pin being journalled in the bearing hole in the base; a shaft projecting from the disc at the side thereof which faces the bottom wall of the cup-shaped cover, said shaft being axially aligned with the pilot pin, and being journalled in the bearing extruded from the bottom wall of the cup-shaped cover and being accessible from the exterior of the cover to provide for manipulation of the rotor assembly; and mounting tabs struck out from the bottom wall of the cup-shaped cover to mount the resistor upon a supporting panel with the operating shaft accessible for operation from the other side of the panel.

2. The variable resistor of claim 1 further characterized by the fact that the shaft of the rotor assembly is tubular and formed of metal; that one end of said tubular metal shaft bears squarely against the face of the disc from which the circular rim projects; and further characterized by the provision of spring arms projecting from said end of the tubular metal shaft and engaging with a detent action in holes in the disc to thereby detachably hold the shaft and disc assembled.

3. The variable resistor of claim 1 further characterized by the fact that the disc, pilot pin, and shaft are one integral molding of insulating material.

References Cited in the file of this patent UNITED STATES PATENTS 2,172,397 Meuer Sept. 12, 1939 2,176,090 McAllister et al. Oct. 17, 1939 2,669,634 Daily et al. Feb. 16, 1954

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