US2830161A - Variable resistors - Google Patents

Description

A rifi 1958 J. J. WILENTCHIK 2,330,161

VARIABLE RESISTORS Filed April 9, 1953 INVENTOR. JERZY J WILENKHJK A TT'ORNE $1 United States Patent VARIABLE RESISTGRS Jerzy J. Wilentchik, Yonkers, N. Y.

- Application April 9, 1953, Serial No. 347,638

9 Claims. (Cl. 201-56) My invention is directed generally to variable resistances for electric circuits, such as rheostats, potentiometers, voltage dividers and the like, with a particular emphasis placed on functionally adjustable, ganged and multi-turn potentiorneters.

An object of my invention is to provide a potentiometer that can be adjusted manually to maintain a desired pretermined relationship between the voltage output and the shaft rotation, such adjustments being performed by simple screw-driver adjustment at respective points of the resistance track.

A further object of my invention is to provide an exceptionally compact, functional potentiometer of higher accuracy of performance than commercially available products of same size.

It is a further object of my invention to provide novel means for mounting helical, multi-turn resistance elements into a housing.

Further object of my invention provides a novel guide arrangement for the wiping contact in a multi-turn potentiometer, wherein, a helical edge projecting internally from the resistance housing guides the wiping contact along the length of the resistance element.

Still further object of my invention provides novel means for obtaining electrical connection between a contact having a combined rotary and translatory motion and a stationary terminal.

Yet further object of my invention provides means for turning a multi-turn potentiometer shaft continuously in one direction without injury to the instrument, while in presently available, commercial instruments of this type, the shaft rotation is limited by mechanical stops to a given number of turns. This eliminates instruments destruction, in the event of faulty control of potentiometer drive means.

Another object of my invention provides a multi-turn resistance winding for use as a multi-ganged potentiometer by separating respective sections of the winding, or by arranging several resistance elements on a common core and providing them with respective wiping contacts operated by a common shaft. j

Another object of my invention provides novel means for gauging several potentiometer units on a common shaft by joining their housings together with a fusible substance, solidifying upon application.

Still another object of my invention describes a novel design of an adjustable, spring-loaded contact, attachable to a resistance winding at desired points thereof, as improvements to my copending applications on the subject of functionally adjustable potentiometers.

F or a better understanding of my invention and its features of novelty, reference should be had to the accompanying drawings and to the following specification describing preferred embodiments of my invention.

In the drawings:

Fig. 1 is a partly sectional, partly broken view taken along the axis of a multi-turn, functionally adjustable potentiometer, according to the invention.

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Fig. 2 is a side view (partly in section) of the contact assembly taken along the lines 22 of Fig. 1.

Fig. 3 is a sectional, partly broken view of the contact assembly taken along the axis of a modified multiturn potentiometer according to the invention.

Fig. 4 is a sectional, partly broken view of the contact assembly taken along the axis of a modified multiturn potentiometer according to the invention.

Fig. 5 is a sectional view of a mandrel for mounting a multi-turn winding into internally grooved housing of a design seen in Figs. 1, 3 and 4 according to the invention.

Fig. 6 is a sectional side view of friction clutch arrangement between the potentiometer shaft and the wiping contact assembly.

Fig. 7 is a cross-sectional view of an adjustable resistor seen in sectional view in Fig. l. i

Fig. 8 is a view of a wiping spring employed in variable resistor of Figs. 1 and 7, according to the invention.

Fig. 9 is a schematic diagram of electrical connections of Fig. 1.

Fig. 10 is a partly sectional, partly broken view of a potentiometer comprising a pair of sections ganged on same shaft according to the invention.

Referring first to Figs. 1 through 9, there is seen a cylindrical housing 22 made of insulating material, provided with a helical groove 23 extending along the length of its internal circumference, forming a helical edge separating adjacent grooves. Within the groove 23, there is disposed a resistive conductor wire 25. The wire 25 is wound on a helical core 26 to form a large number of minor turns around it. The wire 25 is preferably a bare or uncoated wire, and if the core 26 is of non-conductive material, the wire 25 may be wound directly thereon. In the preferred construction, however, the core 26 is of conductive material, providing a thin coating of insulating material which separates the minor turns of wire 25 from the core 26. Further, the wire 25 may be bare when space wound or coated when close-1y wound.

The potentiometer shaft 27 extends through a flanged bushing 31, the latter in turn being supported by a pair of bearing surfaces in respective front and rear plates 28 and 29, both mentioned plates being attached securely to the housing 22 by means of screws (not shown). The axial play of the bushing 31 is largely eliminated by a flange 48 at one side of the plate 29 and by an insulating bushing 33 at the other side thereof. A tubular channel 32 made out of electrically conductive material may be pinned or otherwise securely attached to the bushing 31, but insulated from it by means of the bushing 33. The channel 32 traverses the turns of the winding 21 and is provided with U-shaped groove 34 extending therealong. The bushing 33 extends somewhat beyond the extremities of the channel 32 and serves as a support and insulator for a stationary, helical spring 35' in pressure engagement with the channel 32. One end of the spring 35 extends through a groove 49 to the external surface of the housing 22 and is soldered or otherwise securely connected to instruments output terminal 36. A contact tip 37 made usually out of a precious alloy material and mounted .for resiliency at one end of a flat U bent spring 38 is provided with a hole in the central section thereof 'for mounting on a contact guide 39; the other end 46 of the spring 38 is shown extending beyond the groove 34, in pressure engagement with the channel 32. The guide 39 comprises a disc 41 slidable snugly along the groove 34 and a pin 42 provided with a head 43 to fit snugly the groove 23 in the housing 22. The spring 38 is held securely between the head 43 and the disc 41, while the body of the pin42 is pressed into a hole in the disc 41. Thus, the potential of the wiping contact 37 is transferred to the output terminal 36 via the spring 38, the guide pin 42, the disc 41, the channel 32 and the spring 35. The bushing 31 may be made out of metallic material acquiring spring qualities when heat treated, such as Phosphor bronze, stainless steel and others. It hasa split section 47 seen more clearly in Fig. 6, consisting of three longitudinal band saw cuts 120 degrees apart providing 3 leaves 56. The leaves 50 are bent somewhat inwardly and heat treated to provide proper spring temper. In assembly, the shaft 27 is passed through the split section 47 in the bushing 31 and retained in one permanent longitudinal position by the leaves 56 which provide enough tension to entrain the bushing 31 in rotation of the shaft 27 without any slip. However, if the contact guide 39 encounters mechanical stops built into the unit to limit its movement, the shaft 27 will be still free to rotate, while the bushing 31 is stationary, without damage to the instrument. The shaft 27 may be provided with a knurled section (not shown) at the point of engagement with the leaves 55) so as to enhance the friction grip between those two members. Axial movement of the shaft 27 under impact should be not objectionable, since it does not affect the wiping contact 37, and even more, since the shaft 27 may be restored easily by light tapping to the original position or to any position desired by the user. For numerous applications it may be desirable to supply potentiometer unit without shaft 27, and let the user slip it directly into the shaft of the drive unit without resort to conventional shaft couplings. The principle of the slipping coupling between the shaft and the contact assembly may facilitate considerably the procedures of gauging and phasing of several potentiometer units on a common shaft. Finally, if a permanent connection between the shaft 27 and the bushing 31 may be desired, this can be accomplished simply and conveniently by driving a pin (not shown) from the flange 43 into the shaft 27.

Whichever way of connection between the shaft 27 and the bushing 31, it is obvious that as the shaft 27 is rotated, the guide 39 will be displaced along the channel 32 and the contact 37 along respective turns of the winding 21. Design modifications of the arrangement described with reference to Figs. 1 and 2 will be obvious to all skilled in the art and include:

(1) Elimination of the bushing 31 and providing a direct connection between the shaft 27 and the channel 32.

(2) Making the channel 32 and the components of the guide 39 out of a non-conductive material and providing an alternative way of connecting the output terminal 36 to the wiper 37, via a separate conducting member carried by'the shaft 27, connected through a flexible wire conductor to the spring 38 and through a stationary spring element to the output terminal 36. Such construction eliminates of course the use of an insulating bushing 33.

(3) Variation in the form of the guide 39 identified in Fig. 3 as 39a, to provide it with a pair of edges 46 extending into each first and third convolution of the groove 23.

(4) Provision of a second groove 44 in the housing 22a, in the middle of the edge 24a and providing the guide 39 with a pair of edges 45 extending into adjacent sections of the groove 44 to guide the contact 37 'along the length of the channel 32. It may be pointed out that numerals provided with a subscript a. refer to similar components seen in Fig. l, where they are identified by the same numeral without the subscript a.

For mounting of the winding 21 inside the housing 22, a special method described with reference to Fig. is evolved employing a mandrel 51 provided with a helical groove 52. The crest 55 of the groove 52 is V-shaped. The winding 21 is arranged along the length of the crest 55 prior to mounting inside the housing 22. A pair of holes 53 is drilled through the core 26, and the winding 21 is held securely in position by means of a pair of spring loaded pins 54 placed through the holes 53. The outside diameter of the crest 55 is such, that when provided with the winding 21, the housing 22 may be screwed thereon, the edge 24 of the housing 22 cooperating threadingly with the groove 52 and the resistance 21 being disposed within the groove 23. When the mandrel 51 is placed within the housing 22, the pins 54 may be pulled inwardly through handles 56, releasing the winding 53 into the groove 23, subsequently, the mandrel 51 may be withdrawn by a rotary and translatory motion. It is assumed that due to inherent spring qualities of the winding 21, it will tend to spread outwardly about its axis assuming maximum outside diameter inside the groove 23. To assist in the process of reexpansion, one end of the winding 21 may be pinned to the housing 22 by a pin, a screw or other suitable means, and a rubber roller may be passed subsequently along the length of the winding 21 to stretch it against the external circumference of the groove 23. Subsequently, tl e other end of the winding 21 is fastened securely to the housing 22 in assembly. No holes are of course drilled in the section of the core 26 traversed by the wiping contact 37 so as not to injure the wire 25. The actual assembly procedures may of course vary somewhat from the above description, but are comprehended in this invention as long as they serve the purpose of disposing a multi-turn winding in a helically grooved housing, wherein the depth of said groove is more than the diameter of the winding core.

it may be pointed out that mechanical stops to limit the travel of the contact assembly 3? may be obtained by providing stop pins (not shown) in the track 34 of the channel 32 or in the housing 22 to interfere with axial motion of the guide 39.

Referring back to Fig. l, the housing 22 is provided with a plurality of uniformly or non-uniformly spaced openings 61 facing radially respective convolutions of the winding 21 at predetermined points thereof. Each one of the openings 61, being generally of circular crosssection but of varying diameter in the various sections thereof contains an adjustable resistor 62 provided with a spring loaded contact 63 in conductive engagement with the winding 21. A resistor 62 consists of a longitudinal slotted core 64 made of insulating material, provided with a single or multi-layer resistance winding 65. A helical spring 66 provided with a wiping extension 67 and seen more clearly in Fig. 8 is disposed in a groove 79 on a helically grooved rotor 63 made out of electrically conductive material, the wiping extension 67 being movable in conductive engagement with the bottom layer of the winding 65 through the slot 69 in the core 64. One end of the winding 65 is connected to a terminal 71 through a suitable groove in a flange 72 of the core 64. The terminal 71 is held securely in position by a retaining ring 73. The other terminal 74 sits loosely on external circumference of rotors extension 68a and is prevented from slipping otf by a retaining ring 75. The retaining rings 73 and 75 are of conventional split design and may be snapped in assembly into respective grooves in the core 64 and the rotor 68. The rotor 68 houses internally the contact 63 and the helical spring 78. The annular end of the rotor 68 is crimped slightly to prevent separation of the contact 63 and the spring 78. The rotor 68 is provided with a screw driver slot at the extension 68a enabling adjustment of the spring extension 67 through the slot 69 along the length of the bottom layer of the winding 65. To prevent axial motion of the rotor 68 with respect to the core 64, the retaining ring 75 may be bent to form an open helix and provide tension between the two above mentioned members. The terminal 71 of a respective resistor 62 is connected by means of a flexible conductor 81 to a terminal 74 of the next consecutive resistor 62, which is seen more clearly in Fig. 9. The terminals 74 of the first and last resistor 62 on the winding 21 may be generally considered as input voltage terminals of the winding 21. It is seen that in this style of wiring, parallel connections are obtained of consecutivesections of the winding 21 with respective, adjustable resistors 62. The resistance of each thus shunted section may be varied by adjustment of the wiping extension 67, providing the effect of a nonlinear potentiometer winding. It is seen further that if the winding 65 is of a multi-layer style, much higher sectional resistance values can be obtained with the same wire diameter, but the adjustment is limited to a certain resistance range. The resistors 62 may be held securely in place by means of a pressure of screw fit between the flange 72 and the opening 61 and by means of shellack, varnish or other solidifying substance upon application. An enamelled wire is used for the winding 65, the insulation being removed from the bottom layer along the slot 69.

It isnnderstood that my invention is not limited to uniform wire wound resistors but takes into consideration the possibility of making the windings 21 and 65 out of carbon, deposited metal or varying diameter wire. Further, the resistors 62 may be designed so that the rotor 68 is permanently connected to the winding 21 by welding or other means and the core 64 is rotatable about said rotor. It may he often desired to gang several Potentiometers on a common shaft extending throughout the length of the ganged sections, such arrangement being seen in Fig. and consisting of two ganged sections, in practice the number of such sections may be of course much larger. A single turn resistance winding 111 is shown retained in position by means of an insulating ring 113 coupled by means of screws 114 to a housing 112, the latter being formed of an non-conductive material. The housing 112 is enclosed in an external metallic housing 115 providing a front plate 133 and a bearing 116 for a split bushing 131. The bushing 131 is retained in position by a flange 132 on one side of the face 11 and by a retaining ring 134 at the other side thereof. An insulator disc 118 mounted on the bushing 131 carries a pair of interconnected, resiliently mounted wiping contacts 119 and 121 engaging the resistance 111 and a slipping ring 124 respectively. The shaft 117 is provided with a knurled section 135 in pressure engagement with a split section 136 of the bushing 131. The

split section 136 provides a resilient coupling between the shaft 117 and the disc 118 as was explained more fully in a similar mechanical arrangement described with reference to Figs. 1 and 6. The shaft 117 may extend into subsequent potentiometer housings and be connected therein to respective wiper carrying discs in the same manner as described above. The housing 112 is provided with a plurality of circumferentially located openings 125 which may contain respective resistors 62, their design and way of connecting being described more fully with respect to Figs. 1, 7, 8 and 9 but not shown in Fig. 10. It is further understood that the housings 112 and 115 are provided with respective openings to enable bringing out the input and output voltage connections, and that special protection is provided to prevent a short circuiting of those connections by the housing 115 by means of insulator bushings (not shown in Fig. 10). The resistance elements 111 of respective ganged sections may be phased one in relation to another by turning of the potentiometer housing and of the bushing 131 of each section in relation to the shaft 117 which is maintained stationary during the phasing operation. Upon final adjustment, the adjoining housings may be soldered, welded or otherwise joined together by means of a substance applied in liquid or semi-liquid form at the bordering line between respective housing 115, solidifying upon application. This manner of connecting of adjoining housings elem-inates the use of clamps employed in present art. It is understood that the bearings 116 in respective front plates 133 with exception of the front plate in the first ganged section, may be made slightly oversize to allow for excentricity in the shaft 117, bearings 116 and mounting surfaces 123. Thus, the shaft117 is supported by a bearing 116 in the first potentiometer section and by a bearing in the end plate 128 of the last potentiometer section which may be soldered or otherwise connected to its respective housing a, the housings 115 and 115a being substantially similar.

Another way of ganging several single or multi-turn potentiometers on a common shaft and in a common housing consists of use of a multi-turn winding arranged similarly to the winding 21 in the housing 22 seen in Fig. 1. The effect of several windings is obtained by breaking the resistance wire at each convolution of the winding 21, thus obtaining several windings, all of them arranged on the same core 26, or by winding the core 26 with several spaced windings. A U channel formed of insulating material and carrying several guides 39 may be employed or alternatively one guide may carry sev eral wiping contacts 37 adapted for simultaneous displacement along respective windings on the core 26. The guides 39 are formed of insulating material and the connection to' outside terminals is accomplished by means of Wire conductors connected to respective springs 38 and brought to the outside of the housing 22 through respective holes in the helical edge 24. The direct manner of connecting is possible in this arrangement because the rotation of the shaft is limited to less than 360. This method of ganging of potentiometer sections is not limited to multi-turn cores 26, but could be employed effectively in units provided with circular, single turn cores on which several separate, spaced windings could be placed, the shaft rotation will be however limited to a fraction of 360.

While the invention has been described with reference to certain embodiments, it is to be understood that the same have been given merely by way of illustration and not as limitation upon the scope of the invention.

I claim: 1

1. In a variable resistor, in combination a resistance element providing one or more turns about an axis, a rotor of annular cross-section journalled to turn about said axis, a wiping contact controlled by said rotor to move in conductive engagement and along the length of said element, shaft extending through the annular section of said rotor, resilient friction means active between said rotor and said shaft to provide friction coupling for entrainment of said rotor in rotary motion of said shaft and externally accessible means for angular adjustment of said rotor in relation to saidshaft.

2. In the variable resistor of the type described, in combination, resistance element providing at least one turn about an axis, a rotor of annular cross-section journalled to turn about said axis, a wiping contact attached fixedly to said rotor but electrically insulated therefrom, adapted for displacement along the length and in conductive engagement with said element, and resilient coupling means common to said rotor for entrainment thereof by friction in rotary motion of a drive shaft extending through the annular space of said rotor.

3. The combination according to claim 2, wherein said rotor is a metallic bushing having slots, the sections of said bushing between respective ones of said slots being bent inwardly to provide resilient friction coupling with a drive shaft extending through the annular space of said rotor.

4. In combination, a housing providing a wall, an electrically conductive element within said housing adjacent said wall, an aperture in said wall facing said electrically conductive element, an electrically conductive member having annular cross-section providing opening at one end thereof, means to attach said member rigidly within said aperture with said opening facing said element, a rod formed of electrically conductive material having one end disposed in the annular section of said member, free to slide therealong, the other end thereof extending beyond said opening, means for preventing the separation of said rod from said member and spring element disposed in said annular section acting against said internally disposed end of said rod to maintain the protruding end in conductive engagement With said electrically conductive element.

5. A method of mounting a multi-turn, electrically conductive element in a helical groove in a housing, providing a helically grooved mandrel, said resistance element being disposed along the ungrooved section of said mandrel parallelly to the grooved section thereof, means to attach said element securely onto said mandrel, means to advance said mandrel into said housing and to withdraw it therefrom, and means to release said element from said mandrel into said helical groove in said housing, when said mandrel reaches a predetermined position in said housing.

6. In a variable resistor, the combination of: a housing providing a wall, an elongated resistance element within said housing adjacent said wall, said wall providing a plurality of openings opposite said resistance element, contact means disposed adjustably on said resistance element, a plurality of pins formed of electrically conductive material disposed in respective ones of said openings and making electrical connectionwith said resistance element at respective points thereof, and a plurality of adjustable electrically resistive elements attached mechanically to said housing, connected electrically to respective ones of said pins, each of said resistive elements comprising a resistance member, a nonconductive, slotted core to support said member, wiping means adjustable in conductive engagement with said resistance member along the length of slot in said core, and a pair of electrical connections, one from said 'wiping means to a respective one of said pins and another one from one end of said resistance member to another one of said pins.

7. A method of ganging a plurality of variable resistance elements about a common axis, providing a housing for each of said elements, said elements being attached securely to respective ones of said housings, said housings being arranged coaxially one relative another, a rotor extending through said housings journalled to turn about said axis and to control respective ones of said resistance elements, means to turn each of said housings about said axis for angular adjustment of said resistance elements relative said rotor and means to join respective of said housings one to another by means of a compound applicable in fluid or in semi-fluid form at the bordering line between respective ones of said housings, said compound hardening upon application and forming a permanent bond between said housings.

8. A method of ganging a plurality of variable resistance elements about a common axis, comprising a plurality of metal housings, a plurality of resistance elements rigidly secured unto respective ones of said housings, but insulated therefrom, a plurality of annular bushings journalled in respective ones of said housings to turn about said axis, a plurality of Wiping contact adjustable along respective ones of said resistance elements and controlled by respective ones of said bushings, a shaft extending throughout respective ones of said bushing, resilient coupling means between said shaft and respective ones of said bushings to entrain said bushings in the rotation of said shaft, means to turn respective ones of said bushings and said housings one relative another and relative said shaft for angular adjustment of said wiping contacts relative respective ones of said resistance elements, and a substance applicable in fluid or semifluid form at bordering line between respective ones of said housings to harden upon application and form a permanent bond between said housings.

9. In a potentiometer of the type described, in combination, a resistance element disposed helically about an axis to provide a plurality of turns, a rotor journalled to turn about the axis of said helically disposed element, a contact assembly including a guide, a contact carrier and a contacting member, all elements of said contact assembly being of electrically conductive material, said guide extending in a direction substantially parallel to said axis and being entrainable in the rotation of said rotor but electrically insulated therefrom, means for attaching said contacting member to said carrier,-means for entraining said carrier in the rotation of said guide and for advancing it along the length of the latter while said contacting member is moved along and in conductive engagement with said resistance element, and stationary wiping means in conductive engagement with said guide, said rotor comprises an annular insert provided with resilient coupling means for entrainment ment thereof by friction in rotary motion of a drive shaft extending through the annular space of said'insert.

References Cited in the file of this patent UNITED STATES PATENTS 1,773,609 Yoshiyasu Aug. 19, 1930 2,122,370 Harrison et a1. June 28, 1938 2,138,938 Plensler Dec. 6, 1938 2,353,199 Stolfel et al. July 11, 1944 2,371,159 Erb Mar. 13, 1945 2,543,228 Burgess Feb. 27, 1951 2,558,326 Van Dyke June 26, 1951 2,662,149 Wilentchik Dec. 8, 1953 FOREIGN PATENTS 417,621 ermany Aug. 17, 1925

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