US2119218A - Phonograph turntable drive - Google Patents

Description

'Patented'May 31, 193

Stuart .1. Rodger, New main. Y.,-assignor to Jacob Strauss and Isidore H. Goldman, bothof I New'York, N. Y.

Application December 24, 1937, Serial No. 181,495

4 Claims.

This inventionrelates-to phonographsand more particularly to phonograph turntable drives. Stillmore particularly it-relatesto a phonograph turntable drive-capab1e of operating recording or the reproduction. Moreover the gether with instantaneous changeability from either speed to the other.

Another object of this invention is to devise such a phonograph turntable drive which drives 5 at two different speeds. from one rim on the turntable. rather than from 5 In the art of sound recording and reproducing, two separate rims as disclosed in my copending and especially in the field of .so-called instanappl cat n Serial 7 fi ua y 5, taneous sound recording and reproducing, it is 1937, thereby saving considerable expense in macustomary to employ two different speeds or ro- 'chinln and on r c ion n vo in th n c s- 10 tation of the turntable carrying the, record disk. sitlv fo versing the direct f rotation o the 10 Thus for records 12 inches 'or less in diameter a electric o l 8 a Source f P w as t rotational speed of '78 R. P.M. is commonly emchange in speed is effected. Ployed. For records greater than 12 inches in An h r bject of this invention is to'accomdiameter a speed of 33% R. P. M. is used. It. is plish the ore oin bje :W si e. friction I 15 customary in the art'to use the same equipment idlers to transmit the driving power fromthe 15 for recording and, reproducing sound at both of shaft of the electric motor used to the driving these speeds; in order-to minimize overhead and rim ..t n Use of i t d iv and investment and forconvenience, i of idlers reduces vibration and variations in speed i It is necessary that the turntablebe capable of a marked extent d is deemed c a y i being rotated at exactly-313M 0 7a 13,; iorder to obtain goodrecording and reproduction. g

' since these speeds .have become standard in the y nve ti n D v s a turntable drive p b art. It is highly desirable that the design f th of driving the turntable at either of two desired equipmentused be such that the change in rospeeds at will, while at the same time utilizing V tational speed of the turntable from ith f of friction drive and friction idlers between the drivthese speeds to the other be convenient and rapid. ing shaft. and the driven rim of the turntable.

It is also desirable that it be efiected without Referring to the accompanyingdrawing .which disassembly of any parts or with t r mo l f portrays my invention in its preferred embodi-" v the turntable. In addition, the vdrive for the ment:

- turntable.-must be quiet and free from vibration Figure i javertical sectional view alo the which would affect adversely-the quality of the line l l of F u e 2.

Figure 2 is a horizontal plan view partly in 3 section.

change in speed of the turntable have been here'- vdesigfi of the drive must be such that'long-life of allnioving parts is obtained.

v Figure 3 is a vertical sectional view along the I Various expedients for obtaining the desired,

line 33--of Figure 2. The two speed turntable drive contemplated by this invention utilizes an electric motor the shaft of which projects vertically upward below the turntable. The turntable is provided with a one downwardly extending driving rim which is 'most-conveniently located at the outer edge of 40 turntable with consequent detrimental effect .theturntable. The portion ofthe motor shaft uponthe recording or-r'e'production. Others in-, which extends or projects above thelower edge of volve removal of the turntable in order to effect this driving rim is'so constructed asito have two the change in speed. This is objectionable beportionsof different diameter, which are so calcause of the length of time required, because of culatedin relation to the diameter of the tum- 45. the inconvenience incurred and because of the table dr v ng rim that when this dr vin r is resulting wear on the parts. Y 4 .driven from the smaller portion/of the motor The principal object of this invention is to shaft it turns at, a speed of 33% R. P. M. and.

devlseaphonographtumtable' drive which 'o'ver-. that when the driving rim is driven from the comes the foregoing disadvantages and which atlarger portion of the motor shaft, .it turns 'at a 50 tains many new advantages not heretofore at--" speed of. '18 R. P. M. In placeoi' the specific tained in this art. speeds mentioned, speeds approximating thereto 'Another' object of this invention isto devise may be used. Thus in the device contemplated =a phonograph turntable drive with which vibraby this invention, I prefer to so calculate the tiofi-free anduniform operation is attained; tosizes of the parts that speeds-slightly in excess 16 tofore suggested but so far as I am aware, none of them has been entirely successful. Many of them involve gearing and undue complication to-' gether with noisy anduncertain operation and short life. Many cause excessive vibration of the of these standard speeds would theoretically obtain so as to compensate for the slight slippage encountered in practice.

The driving force of the motor is transmitted from the extending portion of the motor shaft described to the turntable driving rim by means of two rubber friction idlers disposed in a plane parallel to the turntable. These idlers are located between the motor shaft and the driving rim. One of these idlers is so disposed that upon moving the motor shaft in the proper direction the idler is driven by the smaller portion of the motor shaft and drives the turntable at the lower speed, namely 33 /3 R. P. M., by contact with the driving rim. The other of these idlers is so disposed that upon moving the motor shaft in the opposite direction the idler is-driven by the larger portion of the motorshaft and drives the turntable at the higher speed, namely 78 R P. M., by contact with thedrivirig rim.

The motor shaft is movable in a direction substantially perpendicular to a radius of the turntable. This movement is effected by mounting the motor on a movable lever which is pivoted to the panel under the turntable. The motor is capable of being placed in a neutral position in which it touches neither idler. It is also capable of being moved in either direction from this neutral position so as to cause the larger portion of its shaft to contact the idler for the higher speed or so as to cause the smaller portion of its shaft to contact the other idler for the lower speed.

The idlers used are preferably rubber rimmed metal wheels which construction gives high frictional driving power with very little vibration or fluctuation in speed. The idlers used are relatively large in diameter compared to the motor shaft (either the larger or the smaller section). This allows the motor shaft to make good frictional engagement with the idler. The idlers are relatively small compared to the size of the turntable driving rim. This allows very good contact with the turntable rim.

The idlers drive the turntable at either speed from the inside of the turntable rim. This allows a greater area of contact between the idler and the rim than if either of them were to drive against a rim which was convex as to it. Thus greater torque and a more even speed is made possible than in the construction where one idler drives a rim which is convex as to its, asin my copending application Serial No. 122,170 above identified.

Describing now the embodiment shown in the drawing: I represents a rotatable circular turntable the top portion of which is in the usual form, with a projecting pin 2 in its center to accommodate the record. Downwardly projecting shaft 3 of the turntable is of substantial diameter, say ,4 to 1 inch, and rests in the turntable bearing 4 which is of any suitable type and may comprise a closely fitting sleeve portion 5 and a steel ball Ii located in the rounded bot tom portion I of the turntable bearing.

The turntable I is of metal such as cast aluminum and is formed or machined on its under side so that a driving rim 8 adapted to be driven by frictional engagement is formed. The diameter of this driving rim is variable within wide limits, and will depend largely upon the size of the turntable, it being usually most convenient to have it near the edge of the turntable I as shown in the drawing wherein the driving rim 8 is the inner circular edge of downwar y P 'Q jecting solid edge portion 9. The driving rim 8' may be formed in any desired manner and may be machined in the turntable or may be formed separately and rigidly attached to the turntable by any suitable means.

Describing now the turntable drive itself, I represents a motor which is of any suitable type and is flexibly mounted on metal plate Ii by means of rubber mountings I2 and I3 which are of any ordinary type which permit the motor to float and which absorb its vibration to a considerable extent. The plate II upon which the motor I0 is mounted is pivoted at one end by means of pivot I4 which allows the outer end I of plate I I to move circumferentially in either of the directions indicated by arrows I 6 and I1. Motor mounting plate II is preferably located above the panel I8 which serves to hover the mechanism and as a support mounting the various parts as shown in the drawing. Thus pivot I4 for the motor mounting plate II is preferably rigidly attached to the panel LI8, as shown. At the outer end of motor mounting plate I I is located an upwardly projecting threaded member I9 which projects through panel I8. At the end of this threaded member I9 is a knurled knob 20 provided internally with threads which fit the cooperating threads of member I9. Thus when knob 20 is screwed down it locks plate II in the position in which it then is. When knob 20 is loose it is used to push plate II backwards and forwards by means of member I9, thus causing the motor I0 to move backwards and. forwards. Member I9 moves through a slot 2| the ends of which 22 and 23 act as stops to limit the movement thereof and therefore the movement of plate II and of motor I0.

As the plate II is moved in either direction away from the middle neutral position, it carries the motor I0 and consequently the motor shaft indicated generally as 24 with it in the same direction. The motor shaft 24 is therefore moved in a direction substantially perpendicular to a radius of the turntable. In the neutral position of the parts in which position the parts are shown in the drawing, the motor shaft 24 is in a neutral position in the middle of the path of its travel.

Motor shaft 24 projects upwardly beneath the turntable I as shown. The portion of the motor shaft 24 which projects upwardly beyond the lower edge 'of the driving rim 8 of the turntable is machined or otherwise constructed so as to form a larger portion 25 and a smaller portion 26. This construction may be attained by tightly fitting sleeves which are tightly fitted onto the motor shaft 24, as indicated in the drawing, or it may be attained by machining down the projecting portion of motor shaft 24, where this shaft is of suflicient size to enable this to be done. As the motor shaft 24 is moved in the direction corresponding to movement of plate II in the direction of arrow II, it drives the tumtable at the higher speed (78 R. P. M.) by means of rubber friction idler 21 which the larger porfwhen the motor is in the driving position for either idler, the point where the drivingportion 25 or 28 of the motor shaft 24 contacts the rubber l idler 21 or 28, the point wherethe idler 21 or 28 contacts the turntable driving rim 8 and the point where the axis of the idler support intersects the .circle representingthe periphery of the idler 21 or 28 are all substantially 120 apart. This. construction is not vital to theoperation of the devicebut results in the most efllcient transmission of the drivingforce from the motor shaft 24 to the turntable rim 8 at either of the two speeds Idlers 21 and 28 are not located in the same horizontal plane. Idler' .28 which contacts the upper and smaller driving portion 28 of the motor shaft is located in a plane above theplane of idler 21- which contacts the lowerand larger drivin? portion of the motor shaft.

,The idlers 21 and 28 are metal wheels having relatively thick rubber rims 29 and 38 respectively, although they may be of any other construction provided they are adapted to frictionally transmit the torque of the motor to the turntable in a satisfactory manner and are of such materials as to have desirable long wearing qualities. The use of these friction idlers is highly desirable since they act' as filters, absorbing whatever .35, minute vibrations are set up by the motor before they reach the turntable. Idlers 21 and 28 are driven by straightline engagementwith the driv ing portions of motor shaft 24 and drive the turntable i by straight lineengagement with the driving rim 8 of the turntable l.

The idlers 21 and 28 are mounted so as to rotate about bearings 3| and 32 at their center. Bearings 3| and 32 are preferably self-oiling bearings which prevents oil getting on the idler friction surfaces and .ruiningthem; by disintegrating the rubber or by destroying the frictional! engageme'nt between the idler surface and the rim or the motor shaft. I a

Idlers 21 and 28 are supported in .such a manner that they may move outwardly so as to engage the driving rim 8. v This is accomplished by means of flat supporting members 33 and 34, respect1vely,which are pivoted so as to be movable about fixedpivots 35 and 38, respectively. Idler 28 is ,55 so mounted as to rotate about pin 38 by means of its own bearing surface 82 and pin 38 is integrally fastened to supporting member 34. Idler 21 is so -mounted as to rotate about pin -31 by means of-its own bearing surface 3| and pin 81 is integrally no fastened to supporting member 83.

Idler supporting member's 33 and 34 are movable about fixed pivots 85 and", repectivel y, which are preferably integrally attached to main panel l8, as shown. I The construction shown en- 5 ables theidlers to float freely and to absorb vibration to the fullest extent. 7

The mode of operation of the device will be obvious from the foregoing description. However, it may be'descr'ibed in detail as followsi 7 The motor I8 is in its neutral position as shown in the drawing. It is started by sending an electric current through it. After ithas. come up to speed it is moved in a direction corresponding to movement of plate I I in the direction of arrow I1.

75 This movement is accomplished by moving plate.

is moved. in the other .inch in diameter and the larger part 25 is made 0.730 inch in'diameter. These sizes cause the loss in speed due to slippage.

. 3 II by means of knob 20 whereupon knob 20 is.

tightened to lock the plate II and the motor in position. As the'motor is moved in this direction the larger portion 25 of the projecting portion of the motor shaft 24 contacts idler 21 which begins 5 to rotate. As the motor is continued in its move-' ment until pin l9 touches stop 23, idler 21 which is now rotating contacts the rim 8 of the turntable causing it to rotate at the higher speed (78 R. P. M.) in the direction indicated by the arrow 10 w 38 in Fig. 2. When it is desired tocause the turntable at the other and lower speed the motor direction until pin l8 touches stop 22 and the motor drives the tumtabl'e through the smaller portion 26 of the pro- 15 .jecting motor shaft and idler 28-. Y When the apparatus is not in use, the speed control knob 20- is moved to the center position, freeing the idlers from the turntable rim 8 and the driving portions of the, motor shaft, relieving 20 thepressure and lengtheningtheir life.

As will be obvious the projecting portion of the motor shaft 24 is machined to the proper sizes so that the desired speeds are obtained. These sizes are calculated with reference to the diameter of 5 ,the driving rim 8 and withreference to the speed- 'of rotation of the motor shaft 24. Thus when using a motor having a speed of 1750 R. P. M., and a driving rim having a diameter of -16 inches, the

smaller part 28 of the motor shaft is made 0.310 .30

turntable to rotate atspeeds of 33.6 RhP. M. and

-80' R. P. M.,-respectively.' These increases over standard speeds of 78R. P. M. and 33% R. P; M. 35

have been found sufficient to allow for the slight The advantages of this drive are numerous. 'One advantage is that changein speed is secured instantlyby moving a lever, it being un- 40 necessary to remove the turntable or anyidlers to effect the change in speed. Another advantage-is that by having a neutral position in which the idlers are not under pressure, the life of the idlers is increased considerably. Also be- 5 cause it is not necessary to, remove the idlers to change the speeds, anautomatic' self-oiling bearing can be used on them. This prevents oil getting on the idlers andruining them. By having suitable'stops to limit the motor movement, 50

the correct pressure on the idlers is assured. The turntable is readily removable from the machine by simply pulling it upward, whichv gives free access to any. of the working parts. Siricethe turntable is driven at both speeds on its outer '5 -rim a greater torque is developed .at both speeds than'is-the' case where the turntable is driven at onespeed by a driving-rim which is smallin diameter as in my copending application Serial No. 122,170, above identified. Inthe device 0011- 69 templated by this invention the turntable is driven at either speed by means of an idler which contacts a driving rim which is concave relative to it, This gives better frictional transmission tothe turntable driving rim than is the case in -my application Serial No.-122,170 wherein the drive at the higher speed is'by means of a drivingirim which is. convex relative to the surface of. the driving idler. Another advantage of this invention is that the device contemplated thereby 70 makes it unnecessary to reverse the direction of the motor as it is moved from driving engagement at one speed to driving engagement at the other speed. The elimination of this reversing switch makes for sim'plicity'of construction and 7s operation and lessens the cost of construction. Also it makes possible a more rapid change of speed as it is not necessary to let the motor come to a stop before changing to the other speed.

While generally it will be desirable to operate the machine with the turntable in the horizontal plane, as shown in the drawing, it will be appreciated that if desirable it may be operated with the turntable in a vertical plane. The principle of my invention is applicable regardless of the plane in which the turntable is located.

Having described my invention, what I claim is:

1. A two-speed phonograph turntable drive capable of operating at either a lower or a higher speed comprising, in combination, a rotatable circular turntable having a downwardly extending circular driving rim, an electric motor so located that its shaft projects upwardly above the lower edge of said driving rim, the projecting portion of said motor shaft having a smaller and a larger circular driving portion, a lower speed friction idler located between the-smaller portion of said motor shaft and said driving rim, a higher speed friction idler located between the larger portion of said motor shaft and said driving rim, said motor shaft being movable in a plane parallel to the turntable in such manner that its smaller portion may drive the turntable at the lower speed through said lower speed idler and said driving rim and that its larger portion may drive the turntable at the higher speed through said higher speed idler and said driving rim.

2. A two-speed phonograph turntable drive capable of operating at either a lower or a higher speed comprising, in combination, a rotatable circular turntable having a downwardly extending circular driving rim, an electric motor so located that its shaft projects upwardly above the lower edge of said driving rim, the projecting portion of said motor shaft having a smaller and a larger circular driving portion, a lower 7 speed friction idler located between the smaller portion of said motor shaft and said driving rim, a higher speed friction idler located between the larger portion of said motor shaft and said driving rim, said motor shaft being movable in either direction along a line substantially perpendicular to a radius of the turntable and being so located that as it is moved in one direction its smallerportion drives the turntable at the lower speed through said lower speed idler and said driving rim and as it is moved in the other direction its larger portion drives the turntableat the higher speed through said higher speed idler and said driving rim.

3. A two-speed phonograph turntable drive capable of operating at either a lower or a higher speed comprising, in combination, a rotatable circular turntable having a downwardly extending circular driving rim, an electric motor so located that its shaft projects upwardly above .the lower edge of said driving rim, the projecting portion of said motor shaft having a smaller and a larger circular driving portion, a lowerspeed friction idler located between the smaller portion of said'motor shaft and said driving rim, a higher speed friction idler located between the larger portion of said motor shaft and said driving rim, said idlers being so supported that they are free to move outwardly to contact said driving rim, said motor shaft being movable in either direction along a line substantially per-'- pendicular to a radius of the turntable and being so located that as it is moved in one direction, its smaller portion drives the turntable at the lower speed through said lower speed idler and said driving rim and that as it is moved in the other direction its larger portion drives the turntable at the higher speed through said higher speed idler and said driving rim.

4. A two-speed phonograph turntable drive capable of operating at either a lower or a higher speed, comprising in combination, a rotatable circular turntable having a downwardly extending circular driving rim, an electric motor so located that its shaft projects upwardly above the lower edge of said driving rim, the projecting portion of said motor shaft having a smaller and a larger circular driving portion, a lower speed friction idler located between the smaller portion of said motor shaft and said driving rim, a higher speed friction idler located between the larger portion of said motor shaft and said driving rim, said idlers being mounted on movable supporting members so that they are free to move outwardly to contact said driving rim, said motor shaft being movable in either direction along a line substantially perpendicular to a radius of the turntable and being so located that as it is moved in one direction its smaller portiondrives the turntable at the lower speed through said lower speed idler and said driving rim and as it is moved in the other direction its'larger portion drives the turntable through said higher speed idler and said driving rim, the arrangement of the parts being such that when the motor shaft is in the driving position for either idler the point where the driving portion of -the motor shaftcontacts the idler, the point where the idler contacts the driving rim and the point where the axis of the idler supporting member intersects the periphery of the idler are all substantially 120 apart.

STUART J. RODGER.

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