US2459917A - Speed regulating motor drive - Google Patents

Description

Jan. 25, 1949.

B. w. CARRINGTbN SPEED REGULATING MOTOR DRIVE 2 Sheets-Sheet 1 Filed May 30, 1945 Jan. 25, 1949. B. w. CARRINGTON 2,459,917

SPEED REGULATING MOTOR nnzvm Filed May so, 1945 2 Sheets-Sheet 2 v INV YNTOR. I

Patented Jan. 25,1949

2,459,917 SPEED REGULATING MOTOR DRIVE Blake W. Carrington, ,Elyria, Ohio, assignor to The General Industries Company, Elyria, Ohio, a corporation of Ohio Application May 30, 1945, Serial No. 596,749

'7 Claims.

My invention relates to motor drives for phonographs and relates more particularly to a speed regulating motor drive for phonograph turntables.

In the present state of the art, phonograph mechanisms commonly comprise an ancillaryrecord recording mechanism, which adds considerably to the load imposedupon the motor and power transmission means for driving the turntable from said motor, and moreover, such turntable load varies greatly under the varying conditions of use of the mechanism.

My invention relates to that type of turntable drives, now commonly in use whereof a relatively small annular driving roller ordinarily aflixed to a motor shaft engages frietionally, effects driving of the turntable by pressure engagement of a peeripheral rubber tread of an interposed idler wheel transmits power from said motor driven roller to an annular surface of the turntable.

It is well known that occasional loads such as those resulting from the engagement of a recording stylus with a record disc blank, to cut a record, applies a greater load to the disc'supported turntable than is imposed thereon by the frictional effects of' a phonograph reproducer needle, and that either of said needles impose a much greater load upon the turntable driving mechanism when the needle is positioned nearer to the periphery of the record disc than to a more central portion of the disc.

In the past, the motors employed to drive such phonograph mechanisms have usually been of the asynchronous alternating current type and commonly are equipped with a motor speed governor.

However, in frictional drive transmissions of the above referred-to type, the frictional driving engagement, particularly as between the roller and idler wheel, results in slippage therebetween,

this slippage efiect being much greater under conditions of greatest turntable loads, and in such a situation the use of a motor speed governor has not been found to adequately maintain the turntable speed within a desirable range since the slippage effects are not reflected in proportionately increased motor loads. imposition of such greater loads seriously reduces the turntablerotational speed to as much as in some cases, while the motor speed is only reduced to some such value as 1 to 1 /2%.

It has beenpreviously proposed to compensate for increased turntable loads by'the provision of a speed compensating means wherein a tapered motor driving roller flexibly amxed to a motor shaft is longitudinally reciprocable thereon to vary the driving ratio between the motor roller and the idler wheel of a turntable drive of the above said type.

The compensating longitudinal movement of the roller in the said prior mechanism was, however, only responsive to variations in torque eifect vas between the load imposed by the idler wheel upon said roller, and such torque effect due to the aforesaid slippage between the roller and idler, was not always truly proportional to the variations in load upon the turntable.

Consequently, the

I find it to be the fact that the slippage effects, as between the turntable and the idler wheel, are relatively negligible as compared to the slippage effect as between the idler wheel and the motor roller, and my present invention therefore is directed towards the regulation of turntable speed by varying the driving ratio between the motor roller and the idler wheel more truly according to the reactive torque exerted between the idler wheel and the turntable.

In the mechanism of my present invention herein disclosed, wherein the motive effort serving to vary said driving ratio is proportional to the driving torque exerted between the idler wheel and turntable, I am'able to introduce, as a feature of additional improvement, a suitable configuration of the tapered motor roller driving surface to compensate for variations in motor speeds which are susceptible to a re-determination for all possible motor loads, in an eminently satisfactory manner.

In the herein disclosed embodiment of my present invention, the driving ratio between the motor and the turntable is properly varied, according to the varying loads imposed upon the turntable, by suitably tilting a properly longitudinally configured motor roller in such manner as to vary the annular line of engagement of the idler wheel on different longitudinally disposed portion; of the roller, and in the disclosed preferred embodiment, I preferably tilt the entire motor with the roller rigidly affixed to the motor shaft in such manner as to substantially maintainthe desired turntable speed even though the motor speed is considerably reduced, and the turntable subjected to widely varying loads.

An object of my invention is to provide an improved speed regulating mechanism adaptable for use in connection with a phonograph turntable or the like, which is subjected to considerable variationsin load during a desired period of operation.

Another object of my invention is to achieve graph turntable or the like as a result of a reactively bodily movable idler wheel interposed between a motor driven roller and an annular,

driving roller and the motor shaft carrying said roller.

' proaches a more vertical position such as indi- Other objects of my invention and the invention itself will become more apparent by reference to the drawings and to the inspection of the present specification, in which drawings:

Fig. 1 is a top plan view of a portion of a phonocated by the line 22 when the turntable is subjected to a relatively heavy load, such as is effected by the retarding effect of a recording needle when recording upon the most radially outwardly disposed portion of a largest size disc record blank. i

The variation or inclination of the motor roller axis is permitted by a pivotal mounting, for the motor and, in view of the driving roller being spaced from the turntable flange a distance less than the diameter of the idler wheel engaging said flange and roller, is caused by lateral movements of the roller when traversing the turntable jflange in a direction opposite to the direction of rotation of said flange responsive to increased graph turntable herein shown as broken away to show therebelow a portion of the turntable rim like parts are designated by like reference characters, at 1, I show, in cross section, a horizontal base plate which is apertured at Inc, and at 2 I show asup-plemental plate apertured at 211?, which is connected to and suspended from the base plate by mounting screws 3 with interposed rubber grommets t. At 5 I show a shiftable slide plate mount for carrying an idler wheel 5 having a rubber tread wheel and peripheral portion i, said wheel ii journalled for rotation on a bearing extension of a wheel post 9 which is rigidly carried at its base on the supplemental slide plate ii and, asbest shown in Fig. 1, the periphery of the wheel 5 is resiliently constrained by the spring 23 to engage the inner surface ll of the turntable flange ill. a i

The spring 23 is secured to apin 24 carried by the base plate i, and to an endportion 23a of the slide plate, which has an elongated opening 5', through which a fulcrum and slide guide pin 48, secured to said base plate, is projected.

The spring 23 normally maintains the periph cry of the idler wheel in simultaneous engagement with the periphery of a driving roller [4 which is preferably rigidly afiixed to the shaft I5 of a motor 85 and with the surface ll of said turntable flange. 'Theportions of the idler with the wheel axis at 36, being lightly pressed to normally maintain such contacts by the spring 23. In any event, such portions should preferably be separated at least 90 apart and a distance substantially less than the length of the diameter of the wheel.

The driving roller Hi may be originally separate from the shaft l5 and rigidly secured theretoby a drive fit, or both may be unitarily formed as a single piece. For either construction, in the present specification, I employ the term roller for the part I4, and shaft for the part 45. My invention may obviously be employed with the tiltable roller separately mounted and driven by the motor in any suitable way.

In the embodiment illustrated, when the mechanism is operating under light loads, the axis of the motor shaft and driving roller is preferably inclined about 12 from a vertical position, as indicated by the line 22--22, Fig. 2, and apturntable loads. Such travel of the wheel tends to wedge the idler wheel between the turntable flange and the roller, and since the roller is yield ably mounted, the roller is thereforeforced outwardly an amount proportional to the reactive effort of the idler wheel to travel; the roller is therefore tilted to an extent which is proportional to the amount of load imposed upon the turntable.

Tilting of the roller is permitted, in the cum 7 bodiment illustrated, by the illustrated mech anism wherein the motor i6 is provided with two laterally disposed lugs I! which fit into like slots l8 of an inverted U-shaped bracket '59, the yoke portion 28 of the bracket together with end portion of the plate 2 being secured by the grommets 4 and screw 3' to the main supporting plate i and the two arms 2! and 2| extending downwardly from the yoke to provide trunnion hangers for said motor trunnion lugs ll.

The motor is thus suspended, by its oppositely extending lateral lugs, H, from thesupporting plate l at one side of the motor shaft axis 2'2 and to the same side of the axis of symmetry 23 of the motor and motor casing, and similarly of the center of mass or weight of the motor. Therefore, the motor will tend to tilt and will tilt until restrained against further tilting by engagement at the point l3 on the periphery of the idler wheel 6. o

The longitudinally tapered profile of the outer surface of the. drivin roller through the major portion of its length,indicated byL, is, in the embodiment illustrated, relied upon for driving engagement with the idler wheel periphery under the varying conditions of turntable load.

The roller surface portion indicated at L is alike longitudinally tapered, preferably curvilinearly, throughout its circumference, and when the parts are assembled as shown the tapering curvature is radial to an axis such as indicated at a which preferably is located closely to the horizontal plane of the idler wheel 6, said axis a also being preferably disposed substantially above the trunnions l1 andpreferablyin the vertical plane thereof. 7

The'position of the axis a may be varied within the concept of the present invention with changes in the profile of the roller and changes in position of the trunnion axis,-the described and illustrated relationship being preferred for the embodiment illustrated, which is designed for a home recording and record reproducing phonograph, operable by a relatively small, inexpensive motor. 7 I

The counterbalancing tensile spring 28 is provided for adjusting, by way of limitation, the motor tilting effect of the weight of the motor ill, the adjustment being effected by rotation of the adjustment screw 29 which passes loosely through an aperture of the supplemental mounting plate. 2 and is screw threaded through an opening 3!} through a lever 3% which bears against said supplemental plate 2 by shoulders 32.

The extreme end 33 of the lever 3| projects through an elongated slot 3d of supplemental plate 2 to prevent lateral movement of the lever end, the shoulders 32 affording a fulcrum portion for the lever.

It will be clear that, by turning the screw 29 in either direction, the tension of the spring 28 may be varied whereby a desired portion of the weight of the motor may be counterbalanced, such adjustment being a simple means of compensation for slight variation in weight of the motor and for such inequalities asmay be present inthe quantity production of the motor drive mechanism described.

It will also be obvious that, instead of a counterbalancing spring, an adjustable weight may be employed; any such alternative counterbalance means being comprehended by this disclosure although I prefer the use of an adjustable spring.

The idler wheel resists the force exerted upon it by the weight of the motor through the roller It by reason of pressure exerted by the tension spring 23, and, because of the engagement of the tread l or the wheel 6 with the periphery of the turntable; also, during operational driving of the turntable, when the-idler wheel 6 is rotated in the direction of the arrow 25, Fig. l, to rotate the turntable in the direction 26, Fig. 1, the tractive effort by the wheel e upon the turntable rim creates an effort of the wheel 6 to roll on the turntable flange whereby to move bodily in the direction 21, which is opposite to the direction of rotation of said flange, thus tending to further tilt said roller towards a more erect position in opposition to the weight efiect of the motor tending to limit such action.

In operation, the motor being energized from a source of suitable electric current and with the motor driving roller i l engaging the idler wheel 5, the idler wheel being in frictional engagement with the rim H of the turntable, the turntable will be rotated by power of the motor through said roller and idler, in the usual direction of rotation, which, viewed'from the top as in Fig. 1-, is clockwise. If it were not for the resistance of the turntable to movement, the idler wheel would drive the turntable without any shifting of its axis of rotation in the direction of the arrow 21'.

However, rotation of the turntable ofi'ers a resistance or a load to the driving mechanism which is variably increased when a reproducing or recording needle rests upon the upper turntable surface, and consequently, the reactive efict of the load imposed by the turntable upon the idler wheel tends to cause the idler wheel to roll along the turntable flange ii)" in a counterclockwise direction, as indicated by the arrow 21; and, if

such load happens to be a light load, the line 22,

Fig. 2, would represent the resultant angle of inclination of the axis of the tilted driving roller is and motor shaft 5.

If, however, the turntable is caused, by any greater load effect, to increasingly resist driving by the idler, the idler wheel will bodily shift further in the said direction along the flange l0, thereby-causing the driving roller to be further tilted toward a more vertical attitude to a-degree which is commensurable with the amount of turntable resistance or load efiect, such tilting being about the axis of the aligned trunnions [1.

In the embodiment illustrated, the normal light load inclination of the motor axis may be such as is illustrated in Fig. 2, wherein the axis is tilted to about 12 from the vertical, whereas, responsive to a heavier turntable load, the bodily displacement of the idler 6, in the direction 2'! to reduce the inclination of the roller axis from the vertical is about 7, as indicated by the line 22'.

The solid line showing of the roller l4 may be, in the embodiment described, the light load position thereof, and the dotted line showingof the same roller, indicated at 35, may be taken as indicating the position of the roller responsive to anincreased reactive movement of the idler axis under a condition of very heavy load imposed upon the turntable.

By comparing the relative positions of the roller at M and 35, it is important that the longitudinal curvilinear profile of the roller is such as to cause the periphery of the idler to respectively engage different longitudinally disposed portions of the roller outer surface, which are respectively of relatively increased diameters and to a degree which will effect the necessary turntable speed compensation for'both heavy and light loads.

In the above examples if the turntable load is a maximum heavy load wherein the driving roller will be forced to the dotted line position, indicated in Figs. 1 and'Z at 35, the reactive lateral movement of the axis at of the idler wheel will cause such axis to take a position 46', and the idler wheel tread will en age a more counterclockwise located point i2 of the turntable flange, which for light loads would be engaged at the point l2.

The important result is, that when engaged by a roller surface of greater diameter, the idler wheel will be driven at a greater rotational rate thus compensating for the substantial reduction in the turntable speed, which otherwise would be the result of the load imposed upon said turntable.

In this manner, the speed ratio between the roller andthe idler is so increased as to compensate for the slightly lowered motor speed and, more importantly, to compensate for the effect of increased slippage between the contacting surfaces of said idler and driver roller, as well as a certain amount of slippage between the turntable flange and idler wheel, the latter effect however is slight.

The longitudinal contour of the'roller I4 is so made as to achieve a greater difference in driving ratio between the roller and idler than would be necessary were slippage prevented or at least considerably reduced, and, if a more powerful motor which would better maintain'the roller speed under load were used. However, an important advantage of my invention is, that, by merely properly providing the proper contour for the roller, the increase in slippage and the decrease in motor speed can be compensated for and an inexpensive driving unit may thus be employed and still achieve a substantially constant turntable speed.

It is clear that, instead of the idler wheel directly engaging the surface H of the turntable flange Ill, such a surface may be provided by an annular element afixed to and carried by said flange, or may be secured in any way to the turntable ill, or any part rotating therewith, and I therefore herein use the term turntable flange in the broad sense ofcomprehending within such term any such annular element sup:

idler roller having peripheral portions of the same or diiferent diameters, since, for instance,

it is obvious that the idler may comprise two separater/heel treads interconnected in any suitable way, the periphery of one being engaged by the driving roller i l and the other being engaged by the turntable flange.

I therefore contemplate that the term wheel, be employed herein as comprising any such tan dem or similar wheel arrangement, the precise form of the wheel and the precise form of the driven annulus not being'of the essence of the present invention, which more specifically resides in the tiltable driving roller in combination with any suitable idler wheel interposed between such driving roller and drivenannular and variably tilting said roller by the effect of reactive translatory movement of any such idler wheel in response to varying loads imposed upon said turntable; r r

Thev above relationships, as set forth, relate to -an embodiment of my invention actually constructed and successfully operated, but within the bounds of my present invention the same may be widely varied within the broad concepts of my invention.

Under the two conditions or" roller inclinae tion, indicated by the lines 22 and 22, the tilting of the roller is accompanied by an upward movement thereof since such roller is being tilted about the axis of the trunnions H, which axis is disposed substantially laterally of the roller.

The particular positioning of the different parts, and the axis of longitudinal curvature of the outer roller surface may be varied within the scope of the present invention, and in the em bodiment illustrated the axis a of the roller surface curvaturehas been positioned approximately equidistantly from theaxis of the trunnions H,

and the most remote curved longitudinal surface of the roller. 7

Having described my invention in connection with a preferred embodiment thereof, I am aware that numerous and extensive departures may be made therefrom without however departing from the spirit of my invention and'the scope of the appended claims.

I claim:

i. A speed compensating frictional drive for a phonograph turntable comprising an upwardly tapered motor driven roller, an idler, and a pendant turntable flange disposed in sequential frictional driving engagement for driving said turn-- table from said roller through said idler, said roller and idler being normally aligned on a minor chord of the turntable, and with said'reller and flange being engageable with difierent regions of the periphery of the idler which are relatively separated a distance less than the idler diameter,

motor loads to tend to reactively roll along said flange in such direction as to exert a thrust eifect upon said roller to tilt it about its tilting axis and resultantly elevate said roller, said roller having an annular upwardly tapered outer surface, said outer surface engageable with the periphery of said idler throughout all roller tilting positions, and a motor for driving said roller.

2. The speed compensating turntable drive as set forth in claim 1 characterized by the roller thereof in all longitudinally extending portions of its outer annular surface being so longitudinally curvilinearly convexly tapered that the subtended chord of the engaged roller surface will extend substantially parallel to the axis oi" rotation of the idler.

3. A speed compensating frictional drive for a phonograph turntable subjected to varying loads comprising a motor driven roller, an idler and. a pendant turntable flange disposed in sequential frictional driving engagement for driving said turntable from saidroller through said idler, said rollerand idler being normally aligned on a minor chord of the turntable, and with said roller and flange being engageable with different regions of the periphery of the idler which are relatively separated a distance less than the idler diameter,

the engaged portion of said turntable flange adapted for frictional driving by the roller driven idler in a rotative direction generally orresponding to the direction of the idler axis from said roller, a fixed support for said roller, hinging means interconnecting said fixed support and said roller, adaptedtopermit said roller to be laterally tilted about an axis relatively disposed below the plane of the idler, resilient means causing said roller when normally engaged by said idler to yieldably exert pressure thereon, said idler being responsive to the reactive efiect of increased motor loads to tend to reactively roll bodily along said flange in such direction as to exert a thrust effect upon said roller to angularly displace it with respect to its'tilting axis, and said roller having a longitudinally tapered annular outer surface en'gageable with the periphery of said idler throughout all roller tilting positions, the axis of tilting of said roller being so disposed below said roller surface and laterally thereof, and the direction of tapering of said roller being such that the recited thrust eifort of said idler is effective to so bodil displace said roller so as to substitute alroller portion of greater diameter for engagement with said idler perip ery, responsive to relatively increased turntable loads.

4. In a speed regulating motor driven turntable transmission the combination with a pcripheral pendant turntable flange, an idler wheel disposed below the turntable, a motor driven upwardly tapered annular roller for frictionally drivingsaid idler wheel, the portions of the periphery of said idler wheel engaged by said flange and said roller ,being relatively spaced substantially less than 180 apart, said roller being so mounted as to be tiltableabout an axis disposed laterally thereof and below the level of the roller to dispose differently longitudinally spaced portions of its tapered outer surface for engagement with the idler wheel responsive to varying degrees of tilting, means resiliently maintaining said idler wheelin simultaneous engagement with said roller and said turntable flange, said idler wheel upon said increased load conditions of said turntable adapted to reactively travel bodily along said flange in a direction opposite to the direction of rotation of the flange whereby said wheel by a resulting thrust exerted upon the roller is adapted to tilt said roller to present a relatively difierent longitudinally disposed region of its outer surface which is of relatively larger diameter to engagement with the idler wheel to increase the relative rotational speed of the idler with respect to the roller speed, the form of said taper and the axis of tilting being such as to increase said speed ratio proportionatel to the increased load of the turntable tending to lower its speed of rotation to approximately maintain the normal turntable speed.

5. In a speed regulating motor driven turn-- table transmission, the combination with a turntable, an idler wheel disposed below the turntable, a motor driven longitudinally tapered annular roller for frictionally driving said idler wheel, means supporting said turntable, wheel, and roller, the portions of the periphery of said idler wheel respectively engaged by said turntable and said roller being relatively spaced less than 180 apart, hinge means to join said roller and said supporting means to adapt the roller to be hingedly movable about an axis disposed longitudinally of the idler and laterally of theidler axis, means resiliently maintaining said idler wheel in simultaneous engagement with said roller and said turntable, and resilient means yieldably resisting said hinging movement of the roller, said idler wheel upon said increased load conditions of said turntable adapted to reactively travel bodily along said turntable in a direction opposite to the direction of rotation of the turntable whereby said wheel upon a resulting thrust exerted upon the roller is adapted to tilt said roller on its hinging axis to present a longitudinally different region of its outer surface and which is of relatively larger diameter to engagement with the idler wheel to increase the relative rotational speed of the idler with respect to the roller speed, the form of said taper and the axis of tilting being such that the engagement of said idler wheel with the substituted portion of the roller is effective to increase the driving ratio between said roller and turntable proportionately to the increased load of the turntable to maintain the rotational speed of the said turntable substantially constant.

6. In an automatic speed compensating motor drive of the type employing serially related motor roller, idler wheel and turntable flange frictional driving elements, said idler wheel being so disposed between said roller and said turntable flange, and the direction of rotation of said roller being such as to drive said turntable in a clockwise direction viewed from above the turntable, a floating mount for said idler wheel adapted to reactively float in such a direction responsive to increased loads upon the turntable, meanwhile maintaining contact with said flange as to exert proportionately increased pressures upon said roller, said roller being tapered throughout its idler wheel engaging longitudinal extent and said roller being tiltable about an axis disposed substantially longitudinally beyond said roller and substantially to one side of a downward projection of the roller axis, said roller adapted to be tilted by engagement by said reactively floating idler responsive to increased loads imposed upon the turntable to substitute a diflerently longitudinally disposed portion of the roller periphery which is of greater diameter for engagement With the idler to maintain a substantially constant turntable speed.

7. The speed compensating turntable drive as set forth in claim 6 characterized by the roller thereof in all longitudinally extending portions of its outer annular surface being longitudinally curvilinearly convexly tapered to present relatively increased roller diameters for engagement with the idler wheel periphery as the roller is increasingly tilted, the relative diameters in all idler engaging portions of the roller being proportional to the sum of rotational speed losses occasioned by frictional slippage between the idler, said roller, said turntable flange and additionally the reduction in motor speed caused by increased load upon the motor.

BLAKE W. CARRINGTON.

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

UNITED STATES PATENTS Number Name Date 383,680 Westinghouse,

Jr., et a1 May 29, 1888 2,148,759 Le Grand Feb. 28, 1939 2,241,483 Schneider May 13, 1941 2,313,798 Carrington Mar, 2, 1943

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