US2536012A - Carbon pile rheostat - Google Patents

Description

Dec. 26, 1950 E. P. TURNER 2,536,012

CARBON PILE RHEOSTAT Filed April 1, 1949 3 sheets-sheet 2 Z9 .ZNVENTR WRNW Dec. 26, 195@ E. P. TURNER 25361)@ CARBON PILE RHEOSTAT Filed April l, 1949 3 Sheets-Shave?l 5 INVENTR ATTORNEY Patented Dec. 26, 1950 PATENT OFF-ICE Y Claims.

Thisainventioniirelatesitoi:oarbonipilefrheostats f orcontrollers and more. particularly; ton carbon pile -,rheostats f used to control lthe' starting, .stop pingsl and: speedYI of! a..y sewingtt'machinexelectric moton:

Onefof "the obj erts of thislirlventionr` is torpro.- videfaf singlef carbon pilerrheostat :which conrpact,L easily assembledi and .which;allows .the` ope erating.` button to .be actuated.over.. aawidev range at -a'zcons'tant pressure and therebyfvary the ree sistance of the. carbonipile*A at auniformiL ratio.

Another object 1 ofi: this invention is' thefprovisionzotV a: thinzmeta'l "supportiforg themarbonzpile,

which supportisA insulatedzirom. the"l carbon pile and: is formed with*i laterally projecting heat dissipating ns for the purpose or.: conducting heataway from theipila Another; objectofi thisainvention. is'.A the` pro.- visiorn of ai toggleaspring :actuator lwhich has the quintuple; function of'fopposi-ng'. movement of the pressureebutton; conducts; the electrical current; acts'. as azswitch for turning-the electrical currentfonzand off: appliesxpressure tottheecarbon pile and short-circuits. the: carbompileg tofobtain fullispeed offthe motor;l

With the above and otherfobjects-.inlviewas will hereinafter.' appear; the invention comprises thevv devices, combinations: and arrangements of parts hereinafter set*- forth: and illustratedy inthe accompanying drawings ofa preferredembodiment of" the" invention, from whichy the several features .of the inventionz'andY the. advantages; attained .thereby will be readily understoodby those skilled in' the art.

Inthe drawings:.

Fig. lista; top planrvievv-of azsinglepileoarbon` .controllers embodying theeV invention', the;y coverandtpush button.. being g removed. to; expose; the parts-beneath.

Fig: 2 is. alongitudinal section :taken .substantially alongl thee line 2 2v of L thecontroller shown inFig. LWthzthe cover-plate appliedthereto;

, Figs; Brand: i are? transversefvertical. sections taken :along lthe .line 3--3 and 4 4, respectively, ,OFgwZi- Figi'. 5 bottom planview. of thewrem'ovable cover for the controller.

6,-isfa top'planview similarftofFig. 1, the spring actuator forl compressingv the carbon pile being-.removed= tofexposefthe parts beneath.

Fig. 'lis atoplplanview ofthefmetalsupport for the ,carbon-pile..

Fig. 8 is an endl elevation on the.v controller as shownin Fig. 1.

Fig..9.is a `top planv4 viewof4 asinglepile carbon contrpllerA similar. to.. thatishownf. in. Fig... l with 21- azmodiiied form of` mechanism for compressing the carbon pile.

Fig.y lO'isal longitudinal sectional view'taken substantially along the line Ill-of Fig. 9'.

Figgll isatransverse sectional view taken substantiallyA along the line I IJ-I Iof Fig. 9.

In thev embodiment of this invention shown inLFigs. 1 to 8, inclusive, the improvedcontroller comprises' a hollowcasingformed by arectangularly-fshaped and'substantially liat base I9, and a..rectangularly shaped top or cover II, each beving-.preferably moulded in-one-piece'vfrom phenolic condensation material or'artiiieial resin. The parts: Ill/and` II are detachably secured-together by means of corner screws I3 which are screwed in. corner, lugs. I4 formed on the topy I I. The screws I3 also function to hold the rubber feet lzin'position onthe corners ofthe base i0.

Carried by the baseA IIJ.L is asubstantially rectangularly shapedrsheet-metal member, indicated generall'yas I S (Figs. l andv 7), formed in one pieceandihaving a tubularv longitudinal central .portion I 'I f which `.en'lbraces and supports al single carbon disk pile I8; The sheet metalv member alsoghas'oppositely directed legror. heat dissipating iinzportions I9 and, 2l! Whichare securedto .the base I0 bythe screws 2-I. This member IG is. coated-withal' dielectric porcelain enamel so asl to.electricallyinsulate thezcarbon' pile from Vits support. The advantage ofthe above described support. for the carbon-pile is that theA sheet metalmember Ilirapidly conducts heatgenerated inthe. carbon pileaway from the pile/and spreads itA over; a large areathus preventing concentration ofitheheat in the pile..

Formed ori-the insulatingbase la is'anupstandf ling lug 231 having agroove-24 (Figs. 1 and 2) `formed inits upper face. A: T-shaped compres-.- sion plunger' 23 is slidably fitted in the groove 24-` and extends through a cap 25.- at one endA of the pile. Theenlargedv endy 2'!Y of -tbe'plunger 2S islocated within. the cylindricall portion I'I of the sheet metal member I6 and in contact with the .carbon pile I8.

Atthe other end of the pile,. the base. It) is formed witntwospaced upstanding lugs 28 each of which is providedwith a vertical slot 29 (Figs. 1 and 4) thereby providing conlining shoulders for anut 3b. Threaded. inthe nut is a screWf3I havingfoneof` its endsextendingthrough the cap 32 and:- into engagement with they carbon pile. Thevother end of the screw Sl: is formed with a screw driver slotso that' it may be adjusted longitudinally of thepile for the purpose `of-V varying the initial pressure on the pile.

Y Located ,at one vside of: and parallel. tothe .car-

bon pile I8 is a resilient copper conductor strip 33 which is secured to the base Il] by means of a screw 34 (Figs. 3 and 6). A flexible electrical conductor 35 is electrically connected to the strip 33. Formed on the strip 33 is a laterally extending portion 33 (Figs. l and 6) which is electrically connected to the adjustable screw 3 I. On the opposite side of the carbon pile, a resilient copper conducting strip 3l is secured to the base I by a screw 38 vand is electrically connected to a flexible electrical conductor 39.

The tops of the lugs 28 are slotted to receive a pivot-pin 40 formed with a reduced portion near each end. In order to provide means for varying the pressure on the carbon pile there is provided a U-shaped spring or resilient metal member having limbs 42, 42', the free ends of which are bent back upon themselves to encircle and embrace the reduced portions of the pivot pin 40 anchored in the slots formed in the tops of the lugs 28. The connecting portion 43 of the U- shaped member lies in a notch 44 formed in the endwise movable plunger 26.

For the purpose of bending or flexing the U- shaped spring centrally of its length to cause it to act as a toggle joint and apply pressure on the carbon pile |18 there is slidably mounted in the cover or top I I a manually operable push button or pedal 45. The pedal 45 has two depending guides 46 which are slidably received in guiderways 4'I formed in the top I l and two depending lugs 48 which straddle the carbon pile and rest upon the limbs 42, 42 of the U-shaped actuating spring.

In the operation of the above described motor controller or rheostat, when the pedal 45 is depressed by the operator the downward movement of the pedal causes the lugs 48 to flex the limbs 42, 42' of the U-shaped spring downwardly and the initial downward movement of the limb 42' 4 Figs. 9 to 11, inclusive, the rheostat is not actuated by a foot pedal but is adapted to be mounted on the sewing machine or similar cabinet in a substantially Vertical position and operated by a pull rod having one end connected to a treadle and its other end connected to the controller. In this modification, the casing comprises a base A and removable cover B forming a housing for a carbon pile compression unit which is identical with that shown in the preceding figures. The diierence in the two constructions resides in the substitution for the push-pedal 45 of a pullblock 50 slidably mounted in suitable guideways formed in the casing. The pull block 50 is molded from phenolic thermosetting material with a metal insert pull plate 5I which is adapted to be connected to a pull rod. Connected to the pull block 50 by the nut andbolt 52, 53, (Fig. 10) are two L-shaped arms 54 which have their free ends pivoted at 55 t0 the depending limbs of bell-crank levers 62 located on opposite sides of the carbon pile I8 and pivoted at 56 to the upstanding arms 51 of a U-shaped bracket 58 which is secured to the base A by the screws 59. Springs 5U each having one of their ends connected to the L- shaped arms 54 and their other end connected to an upstanding lug 6I formed on the bracket 58 serve to yieldingly maintain the above described parts in the position shown. Pivoted to causes the limb 42 to engage the resilient conducting strip 3'I and the circuit is thereby closed through the carbon pile resistor I8.

The circuit at this time is as follows: From the lead 39 through the conductor strip 3'I and U- shaped metal spring to the metal plunger 26, through the plunger 26 and carbon pile I8 to the screw 3I, thence through the laterally extending portion 33 of the strip 33 to the lead 35.

It will be observed that further downward movement of the pedal causes further flexing of the limbs 42, 42 of the U-shaped spring and as one end of the spring is anchored by the pivot pin 40 the plunger 26 is forced against the carbon pile thereby compressing it. It will be understood that the limbs 42, 42 are, in eiect, toggle joints which allow the operating button or pedal 45 to be actuated over a Wide range at a constant pressure to thereby vary the resistance of the carbon pile at a uniform ratio.

Continued downward movement of the pedal 45 causes the limbs 42, 42' to be further ilexed thereby gradually increasing the pressure exerted on the carbon pile until the pressure is at a maximum and the electrical resistance oered by the pile is at its minimum. At this point the limb 42 engages the spring conductor strip 33 which lies relatively close to the base I0, as shown in dotted lines in Fig. 2. When the limb 42 engages the other arm of the bell-crank lever 62 at'63 is a member 64 which connects the arms of the bellcrank levers and extends over the carbon pile I8. The member 64 is formed with shoes 65 which centrally engage the limbs 42 and 42 of the U- shaped spring. Y

From the above it will be understood that when the pull-block 5B is moved to the left as viewed in Figs. 9 and l0 the arms 54 will swing the bellcrank lever 62 about its pivot 56 thereby causing the shoes 65 to ilex the limbs 42, 42 of the U- shaped spring in the same manner and for the same purpose as the lugs 48 of the pedal member 45 when the latter is depressed.

Having thus set forth the nature of the invention, what I claim herein is:

l. A controller for electric motors comprising a base, a carbon pile resistor carried by said base, a U-shaped spring having its limbs arranged parallel to said carbon pile, means for anchoring the free ends of said limbs, and manually controlled mechanism for engaging and simultaneously flexing each of said limbs intermediate their ends for the purpose of varying the pressure applied to the carbon pile resistor.

2. A carbon disk resistor for electric motors comprising a base, a sheet metal support carried by said base and having a coating of insulating material on its outer surface, a carbon pile carried by said support, a U-shaped spring for applying pressure to said carbon pile, manually controlled mechanism for engaging and simultaneously iiexing the limbs of the U-shaped spring, and a flexible electrical conductor located beneath one of the limbs and adapted for engagement said heath each limb and arranged so that when the limbs are initially flexed one of said strips is engaged by'one of the limbs to connect the carbon pile in series in the circuit and when the limbs are completely flexed the other strip is engaged to short circuit the carbon pile.

4. A controller for electric motors comprising a base, a sheet metal carbon pile support coated with electrical insulating material secured to said base, said support being formed with a longitudinal tubular portion and oppositely directed heat dissipating fins extending laterally from said tubular portion, a carbon pile carried by the tubular portion of said support, a plunger extending into said tubular portion and in contact With one end of said carbon pile, a U-sliaped spring having its limbs located on opposite sides of said carbon pile and its connecting portion in engagement with said plunger, and mechanism for applying pressure to the limbs of said U- shaped spring to shift said plunger relative to said carbon pile for the purpose of applying pressure to said carbon pile.

5. A controller for electric motors comprising a base, a sheet metal carbon pile support coated with electrical insulating material secured to said base, said support being formed with a longitudinal tubular portion and oppositely directed heat dissipating fins extending laterally from said tubular portion, a carbon pile carried by the tubular portion of said support, a plunger extending into said tubular portion and in contact with one end of said carbon pile, a ilat spring anchored to said base and having resilient limb portions, and mechanism for applying pressure to each of said limb portions transverse to their length and intermediate their ends to cause said plunger to apply a gradually varying pressure to said carbon pile over a, Wide working range of said mechanism.

6. A controller for electric motors comprising, a support, a carbon pile resistor carried by said support, a compression plunger located in one end of said carbon pile, a U-shaped spring having its limbs located on opposite sides of said carbon pile and its connecting portion operatively connected to said compression plunger, means for -anchoring the free ends of the limbs of said U-shaped spring to said support at points adjacent the other end of said carbon pile, and manually operable means for simultaneously flexing both limbs of said U-shaped spring to shift said plunger relative to said carbon pile for the purpose of applying pressure on said carbon pile.

7. In a controller for electric motors having a support and a resistor secured to said support, the improvement which consists in varying the pressure upon said resistor over a wide range by means of a spring having limbs located on opposite sides of said resistor and arranged substantially parallel thereto, one end of each of said limbs being anchored adjacent one end of said resistor and the other end of the limbs being connected to apply pressure to the other end of the resistor, and manually operable mechanism for flexing said limbs simultaneously at points intermediate their ends to produce a toggle action and thereby vary the resistance of the carbon pile at a substantially uniform ratio.

EDGAR P. TURNER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,460,815 Hynes July 3, 1923 1,581,957 Keller Apr. 20, 1926 2,371,772 Naul Mar. 20, 1945

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