US1938396A - Electrical resistor - Google Patents

Description

Dec. 5, 1933. G. E. MEGOW ELECTRICAL RESISTOR Original Filed Deo.

16, 1929 2 Sheets-Sheet 1 wu/f@ 7210/755 1 /Vegan@ Dec. 5, 1933. G. E. MEGow 1,938,396

ELECTRICAL RES ISTOR Original Filed Deo. 16, 1929 2 Sheets-Sheet 2 .Sanna Patented Dee 5,1933

UNITED STATES PATENT OFFICE Y 4 usarse ELECTRICAL aEsIsroa orIgImI eppueeaen neeember 1s, 1929, semi No. 414,439.- Divided and this application Septem- 1 ber 1,2, Isso. serai No. 491,496v

Claims. (Cl. 20'1-54) This invention relates to certain new and useful improvements in electrical resistors and refers more particularlyto resistor elements for use with rheostats, potentiometers and the like of the type employed in radio apparatus.

In radio apparatus and especially radio receivers space is at a premium and the physical dimensions of the various elements entering into the construction must be kept within relatively small limits. A

Itis also desirable, and in many instances necessary that the resistor units of the rheostats, particularly the potentiometer used for volume control, have special resistance curves to meet certain requirements of design. 'This necessitates a diierence in electrical resistance at diii'erent portions of the unit, and heretofore this has beenimpossible from a commercial standpoint in the small space available. It is, therefore, an object of this invention to provide a resistor unit which is so constructed as to enable any desired distribution of local resistance values so that practically any particular resistance curve may be obtained. I

A more specic object of this invention resides in the provision of a resistor unit which is 4composed oi' a plurality of separate resistance elements arranged in stacked relation and provided with` contact elements' inte d between the resistor elements to ail'ord good electrical contact between any portion oi the unit and the selector element oi the rheostat or potentiometer with which it is used.

A further object of this invention is to provide a resistor unit of the character described wherein the separate resistance elements entering, into its construction have the same physical dimensions, but diiIerent electrical resistance values so that by the selection of the proper elements the unit may be built up to have any desired resistance characteristics.

And a stillU further object of this v invention resides in the provision oi' a resistor unit comprising alternate resistance elements and metal contacts, themetal contacts extending slightly beyond the resistance elements to provide a series of contact points to aiiord goodelectrical contact between any portion of the'unit and a selector element engageable therewith.

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 under- -member of potentiometers, which are stood 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 one complete example of the physical embodiment of my invention constructed according to the vbest mode I have so far devised for the practical application of the principles thereof, and in which Figure 1 is a view partly in vertical section and 65 partly in elevation of a potentiometer equipped with a resistor unit constructed in accordance with this invention; A Figure 2 is a view looking at the rear of they potentiometer with parts broken away to illustrate structural details;

Figure 3 is a transverse sectional view taken .throughv Figure 2 on the plane of the line 3 3;

Figure 4 is a fragmentary detail view taken transversely through one end portion of the 7l resistor unit and illustrating the manner of connecting the ends thereof with line terminals; I Figure 5 is an enlarged transverse sectional view of a portion of the resistor element to illustrate itsspecic construction; g

yFigure 6 is a diagrammatic view of the potentiometer;

Figure 7 graphically illustrates the relationship between the resistance and the movement of the actuating member of a conventional potentiometer, and

Figures 8 and 9 graphically illustrate by plotted curves, diil'erentrelationships between the resistance and percent of rotation of the actuating possible 9o with resistor units oi' this invention.

'I'his application is a division and continuation in part oi.' my application Serial Number 414,439 tiled December 16, 1929, and as hereinbefore stated, reiersparticularly to resistor units per se, and while the drawings illustrate the same .as embodied in a potentiometer construction, it is obvious that they are not restricted to this particular use. f

The resistor unit consists oi' a l plurality of 100 resistance elements in the form of discs 10 formed of 'carbonaceous material or other suitable substance andarranged in alternate stacked relation with metal discs 11. 'I'he metal discs 11 prei'- erably have their peripheral edge,l portions pro- 1n. jecting beyond the discs 10 to protect the resistance elements and to aord good electrical contact between any portion of the unit and a selector arm slidable longitudinally across the unit.

The plurality of'alternate resistance elements 110 and contact discs are maintained in proper 'stacked relation by any suitable compression means and when the unit is employed in a rheostat or potentiometer asv illustrated, it is situated in a trough-like chamber or compartment 12 extending across the upper portion of the potentiometer housing 13. One end of the unit abuts against an end plate 14 which is positioned at one end of the trough-like chamber 12 and has an arm 15 extended rearwardly therefrom through a suitable 'opening in the housing 13 to be electrically connected with a line terminal 16, the end of which projects above the top of the housing to facilitate the attachment of a conductor thereto. i

The other end of the resistance unit is engaged by the inner end of an adjusting screw 17 threaded in an opening in an end plate 18 similar to the plate 14 from which an arm 19 extends through the bottom of the trough-like chamber 1 2 to be connected with a second line terminal 20 which, like the terminal 16 also projects above the top of the housing 13.

The plates 14 and 18 are firmly held against spreading by their engagement with the end Awalls of the chamber 12, so that the application of pressure on the unit by means of the screw 17 places the same in any desired state of compression. This enables the overall resistance of the-unit to be adjusted to insure that all units of the same rating will actually have the/same overall resistance values.`

Both end walls of the chamber 12 are slotted,

` as at 21, the slot adjacent the end plate 18 affording access to the adjusting screw '17, and the slot at the opposite side providing accessto the unit. The rst mentioned slot is preferably illled with a suitable sealing substance to prevent further manipulation of the screw after the desired adjustment has been made.

The housing 13 is substantially of rectangular A shape, having its open side closed by a cover 22 secured thereto by screws 23 or thev like, and having a wall 24 extending from one side wall to the other to divide the chamber 12 from the major portion of the housing interior. The bottom wall 25 of the housing has a centrally bored boss 26 provided with a bushing or sleeve 27 which affords a bearing for an operating or drive shaft 28. The bushing 27 is non-rotatably secured in the housing bore by having its inner end provided with a hexagonal flange 29 which is received in a correspondingly shaped counterbore in .the housing bottom wall 25.

The outer end of the bushing 27 is exteriorly threaded to receive a clamping nut 30. by which the housing structure may be clamped to a panel or other support 3l, through an opening in which the sleeve 27 extends. AThe shaft 28 is freely rotatable in the sleeve 27. but is held against longitudinal movement therein by having its outer end oi' enlarged diameter to provide a shoulder which engages vthe adjacent end of the bushing or sleeve and has an operating knob 32 secured thereto, and at its inner end by a washer 33 nonrotatably secured on the shaft by swedging the 'adjacent portion of the shaft over the same, as at 34. An arm 35-projected from the washer 33 is engageable with an abutment 36 on the division wall 24 to limit the rotation of the shaft 28 to less than a complete turn.

The extreme inner end of the shaft 28 is serrated, as at 37, and is frictionally engaged with the curved surface of a'segment 38 pivotally mounted in the housing on a stud 39. The stub 39 is secured to the housing bottom wall 25 and is electrically connected, as at 40, with the lower end of a terminal member 41 which extends upwardly to project above the top of the housing similar to the line terminals 16 and 20,'the medial portion of the terminal member 41 being enlarged and apertured to encircle the bored boss 26,as best illustrated in Figure 2.

'Ihe segment 38 which is formed of insulating material carries a contactor arm 42 which extends upwardly to Wipe across the side of the resistor unit in electrical engagement with its contact eiements 11. The contactor 42 is preferably struck from spring sheet copper or the like and its inner end 43 is of segmental shape to be secured to the segment 38 by tubular rivets 44 and 45.

The tubular rivet 45 is of such diameter as to receive the stud 39 and a washer 46 riveted tothe outer end of the stud maintains the segment 38 and its contactor arm assembled with the stud. In this manner electrical continuity is established between the terminal member 41 and the contactor arm so that the member 41 provides the center terminal'of the potentiometer.

Any practical range of resistance may be covered by a unit constructed in accordance with this invention, and practically any desired resistance characteristics are obtainable, as it is possible to, without changing the physical dimensions of the individual resistance elements, supply these elements inany desired electrical resistance values and by selecting resistance elements lof the desired different resistance values, the unit may be given any particular resistance curve.

To more clearly. bring 4out this feature of the 110 invention reference is directed to Figures 6 to 9, inclusive, wherein Figure 7 graphically illustrates the relationship between the resistance in Ohms to the per cent of rotation ofan actuating member of a conventional potentiometer having an ordinary resistor unit. In many instances, however, it is necessary that different portions of the resistor unit be provided Iwith greater or .less electrical resistance values so that certain desired resistance curves may be obtained and in Figures 8 and 9 two typical resistance curves are plotted to illustrate different performances obtainable with a unit constructed in accordance with this invention.

The diagrammatic illustration of the potentiometer illustrated in Figure 6 is given to clarify Figures 7, 8 and 9 and depicts the legs A--B and B-Cof the potentiometer.

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 this character appertains that I provide an electrical resistor unit which is particularly well adapted for use with rheostats of modern radio apparatus, as it covers a wide range of resistance values and provides any desired practical resistance characteristics withinthe small space available.

What I claim as my invention is: l

1. A resistance unitfor use with rheostats and the like, comprising a plurality of self-supporting resistance discs, a plurality of contact discs, all of said discs having unobstructed opposite surfaces for direct contact with each other andY being arranged in stacked relation with the contact discs interposed 'between certain of the resistance discs, a supporting trough to receive the discs and to hold them in stacked relation, said trough having a longitudinally extending opening as wide as the diameter of the discs so as to per- 156 mit ready edgewise removal and insertion of any individual disc or number of discs without disturbing the other discs and with the contact discs `projected beyond the peripheral edges of the resistance discs at least at one point in their circumierence, and adjustable means for applyin pressure to the stack of discs.

2. A resistance unit for use with rheostats and the like comprising, a plurality of resistance discs having substantial contact resistance, a plurality of contact discs, said discs being arranged in stacked relation with the contact discs interposed between certain of the resistance discs. a supporting trough to. retain the discs in stacked relation, said trough having a longitudinally extending opening as wide as the diameter of the.

discs and all of said discs having iiat unobstructed opposite surfaces to enable ready edgewise insertion or removal of any individual disc or number of discs from the stack without disturbing the others, and adjustable means for applying pressure to the stack to regulate the degree of intimacy between the adjacent flatsurfaces of the discs, whereby the contact resistance of the resistance discs is utilized to adjust the overall resistance of the unit.

l3. A resistor for use with rheostats and the likel comprising, a stack of discs, a supporting trough having a longitudinally extending opening as wide as the diameter of the discs, said discs being maintained in stacked relation by the trough with a. side portion of the stack exposed, and retainingmeanstoholdthestackofdiscsinthe trough, said retaining means being readily re leasable and the discs being flat throughout, whereby any disc or number of discs is removable and insertable edgewise from and into the trough.

l4. A resistor for use with rheostats and the like comprising, a compressible stack of discs, a supporting trough having a longitudinally extending opening as wide as the diameter of the discs, said discs being maintained in stacked relation by the trough, and common means to hold the stack of discs in the trough and to place the stack in compression and determine the overall resistance of the resistor, said common means being readily releasableand the discs being flat throughout whereby any disc or number of discs is removable and insertable edgewise from and into the trough.

5. An electrical resistance unit comprising, a plurality of resistance discs, a plurality of contact discs, said discs being arranged in stacked relation with the contact discs interposed between certain oi the resistance discs, a supporting trough having a. longitudinally extending opening as wide as the diameter of the discs to receive and hold the discs in proper stacked relation with one side portion of the stack exposed,

and retaining means to hold the stack of discs

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