US 1755314 A
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Description (OCR text may contain errors)
April 22 A. .1. CARTER v RHEOS'IAv \T AND POTENTIOMETER Flled June 11, 1928 g UlmmmlUlWIHNIIIHNHUIIWIWI"lllllllllmulmmu1|11111111.11
l"mmm"IUWllilH"NM1NIIIIHIIIINHIIIIllllllluulw11111111111"- /ZMfJ/Z j@ L/ Cargo?" Patented Apr. 22, 1930 UNITED STATES PATENT OFFICE ALVA J. CARTER'OF CHICAGO, ILLINOIS, ASSIGNOR TO' CARTER RADIO COMPANY, OF v CHICAGO, ILLINOIS, A CORPORATION 0F ILLINOIS nHEosTAT AND rorEnTIoi/IETB Application med June 11,
,resistance is connected in circuit and for increasing the resistance at a gradually higher rate as the resistance included in the circuit increases.`
It is also an object of this invention to -provide a rheostat or potentiometer yconstruction such that-the resistance-range and cur- 'rent carrying capacity of the rheostat are capable of. meeting a wide variety of voltage and current control requirement. Thus for example in the case`of\the heating 'current for the filament of vacuum tubes, my rheostat ,may be utilized with tubes having muchdifferent requirements of current for the same voltage.
In carrying out this invention, I employ a rheostat winding wherein the length ofeach turn varies from one end to the `other and wherein the spacing of the turns relative to each other may be varied in the different portions .of the rheostat winding.
To further'the adaptability of the devicev for use with different apparatus requirmg different current capacity for various voltp ages, my invention also contemplates the use' of wire having a relatively low resistance for a portion of the wi-nd and a wiring having a relatively high resistance for the remainder thereof.
I attain the aforementioned objects by the.
device illustrated in the accompanying drawings in'which:
Fig. 1 is an elevation ofa rheostat including my device and illust-rating the connections therefor;
Fig. 2 is a section on the line 2-2 of Fig. 1;
Fig. 3 is a detailed v ew ci one' toria of resistance` winding 1928. Serial N0. 284,387.
Fig. is a view similar to Fig. 3 'of a slightly modified form of winding; and
Fig. 5 is a detailed view-of a further modiication.
Referring now in detail to the drawings, the rheostat consists of a base 10 of. molded phenol condensation product or similar matei rial having the upstanding rim 11 and provided with the annular groove 12 immediately adjoining the interior of the rim 11 and 1n which the resistance unit 13 is adapted ,to be mounted. The unit 13 consists of a core 14 and winding 15 which will be' hereinafter described in det-ail. This unit 13 extends through most of the circumference of the rim 11 and is secured thereto by means of the terminal screws 16 and 17 at the opposite' ends thereof which screws contact with the ends of the winding 15 and may be connected to the'apparatus with which a rheostat is to be used.
The base 10 is connected to a supportin stud 18 by which itmay be mounted upon a suitable support and clamped -thereon by means of the nuts 19 and 20 in ay well known manner. Supporting stud 18 has a head 21 within the recess-of the base,10 which Qooperates with the nuts 19 to clamp the base 10 firmlyl thereon. The connecting member 22' is also held in place by the nut 19 and has a portion extending upwardly as at 23 along vthfeinner wall of the rim 11 to connect with the wiring terminal 24, the base 10 being slotted to4 permit passage of the upturned ortion 23 of the member 22 therethrough.
A shaft 25. is journaled in the member 18 and has non-rotatably mounted thereon the members 26 and 27 which engage the member 21 to make electrical contact therewith. The
member 27 as shownhas the. upturned fiange 28 engaging the projecting portion-29 of member 26 so that they rotate together and vthe member 26 is provided with the downturned portion 30 cooperating with the stop projections 31 and 32 so as to limit the rotation thereof andprevent the connecting portion 33 of member 27 from moving entirely off .the resistance element 13. AA disc -34 rests o n'top of the member 26 and may be used for indicating the total resistance of the element gradually increases in width from one end to the other so that each turn of wire thereon is of greater length as they approach the large end of the strip.
Also, in the right hand portion substantially to the point 36 of the winding 15, thespacing of the turns of the .wire is gradually decreased from the wide spacing at the eX- treme right hand end of the strip to a comparatively small spacing at the point 36, and, from this point to the left hand end of 'the strip, the spacing is substantially the same between the turns.
The advantage of winding the wire in this manner in addition to making the strip of varying size -throughout its length lies in the fact that it permits a greater rotation of the controlling handle 37 for unit change in resistance when a comparatively small amount of resistance is in the circuit, and, as the amount of resistance in the circuit increases, the amount of rotation per unit change of resistance decreases gradually. If the turns were placed the same distance apart throughout the length of the strip, the initial step of rotation would increase the resistance a much greater proportion of the whole amount of resistance in the circuit.
v That is not the case with the gradually decreasing spacing between the turns of the wires in the winding as illustrated in Fig. 3. This spacing makes it possible to more nearly approach a logarithmic increase `in the resistance as the contact member is rotated thereover to increase the total amount of rel properly spacing the windings and properly and succeeding amounts included by the presistance in the circuit, since it is possible by taperlng the strip 14 to make the amount of resistance added by each degree, of rotation have the same roportion to the total resistance included in the circuit as the previous it possible to use the rheostat interchange-- ably for use with apparatus requiring a relatively low resistance and a high current capacity, and apparatus requiring a relatively high resist-ance and lower current carrying capacity. The difference in resistance between the portions of the windings shown in Figs. 2 and 4 may be provided either by making the portions between the points 38 and 39 of larger wire having the same specific Also, whenever it is desired, a resistance unit may be made in the form shown in Fig. 5 wherein the spacing between the turns of wire gradually decreases from thelextreme right hand end of the windingto the extreme left hand end thereof. By utilizing the form shown in Fig. 5, the change in resistance per unit length of the strip may be made to bear a constant ratio to the total resistance between the unit of length selected and either end of the strip'which is exceedingly desirable in use of certain types of apparatus such as the filament current control in radio sets.
From the above description it is thought that the construction and advantages of this device will be clear to those skilled in this art.
Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:
1. A device of the character described comprising an insulating base having wound thereon a resistance wire the adjacent turns yof which gradually decrease in distance apart and increase in length from one end to the other of the strip.
2. A resistance unit comprising a strip of insulating material gradually increasing in cross-sectional perimeter from one end to the other thereof and a resistance wire wound upon said strip each turn of which is spaced a less distance from the preceding turn from the smaller end of the insulating strip to the larger end.
In witness whereof, I hereunto subscribe my name this'26th day of May A. D., 1928. ALVA J. CARTER.