US2756603A

US2756603A - Speed changing mechanisms for phonograph turntables and the like

Info

Publication number: US2756603A
Application number: US504445A
Authority: US
Inventors: Tsien Wei Hwa
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1955-04-28
Filing date: 1955-04-28
Publication date: 1956-07-31
Anticipated expiration: 1973-07-31

Description

July 31, 1956 WEI HWA TSI SPEED CHANGING MECHANISMS NOGRAFH TURNTABLE-S AND THE LI Filed April 28, 1955 2 Sheets-Sheet l J4 3.211212 /f J2 July 31, 1956 WEI HwA rsu-:N

SPEED CHANGING MECHANISMS FOR PHONOGRAPH TURNTABLES AND THE LIKE Filed April 28, 1955 2 Sheets-Sheet 2 /l/ lll 1 V NoR. l/LMD@ fixen @rra/Wr U11-tred Se@ Prem 0 SPEEDVCHANGING MECHANISMS FORA PHON()- GRAPH TURNTABLES 'AND THE LIKE Wei Hwa Tsien, New York, N. Y., assigner to :Ra-dio Corporation of America, a `corporation of Delaware Application April 28, 1955, Serial No. 504,445

s Claims. (C1. 'I4-199) diierent diameters, vand an idler wheel interposed between the element to be driven and one of the driving surfaces of the motor driven roller.

One type of variable speed mechanism lwidely 'used for driving phonograph vrecord player turntables forexample, includes a iioating idler or friction wheel interposed between the cylindrical inner surface of a pendant turntable flange and a stepped motor driven pulley or roller. The roller generally has two or three coaxial driving surfaces of different diameters to provide two or three different driving ratios between -the roller and the turntable, the driving ratios being adjusted 'so that the turntable rotates at presently standard 78, 45, 'or 33 R. P. M., depending on the type of records to be played.

To change the speed of the turntable, manually controllable mechanism is provided for selectively adjusting the relative position of the idler wheel to engage a desired one of the driving surfaces. The mechanism is of such design as to cause the idler wheel to be moved in proper sequence outwardly from a pre-engaged roller driving surface, then axially to the level of another roller step, and nally, longitudinally to engage the alternate roller step. The reason for this manipulation is to enable the idler wheel to be moved past the discontinuouspor tions of the roller (the steps), when changing from a smaller diameter driving surface to a larger diameter driving surface. v v l lt -is accordingly an object of this invention, to lprovide improved and simpliiied yplural speed driving mechanism o f the type referred to in which an idler wheelmay be moved from a smaller diameter'driving surface to alarger diameter driving surface automatically and without the Vaid of manually controlled mechanism and thus provide a speed changing operation in a simple-and reliable manner.

Anotherobject of this invention is to provide an irnproved speed changing system forphonograph record changers or recording equipment or the like, of the type including an idler wheel interposed between the element to be driven and a stepped motor driven roller, wherein theidler wheel may automatically be positioned from one-roller step to another.

-A further object of this invention is to provide an improved driving mechanism for phonograph record changers or recording equipment or the like, of the type lreferred to, which has self-positioning idler wheel means y for quickly and eiciently eifecting speed changing operations. n

A still further object of this invention is to provide an impoved'speed changing system for phonograph record players and the like, of the type includingan idler wheel 'interposed between the element to be driven a'd 2,756,603' Patented July 3l, 1956 ICC a stepped motor driven pulley or roller, wherein the idler wheel Amay be automatically moved in sequence radially away from a pre-engaged small diameter driving surface Aand then axially, to engage a larger diameter driving surface, without the aid of manually controlled mechanism.

In accordance with the invention a cam element, which in one embodiment has a planar substantially elliptical configuration, is axed to one side `of the idler wheel. The major axis of the elliptical cam elementis equal to the diameter of -the idler wheel. As noted hereinbefore the idler wheel is mounted for frictional engagement with a motor driven roller which is provided with steps or driving surfaces of progressively larger diameter along the axis thereof. The cam element is positioned on the side of the idler wheel facing in the direction of the larger diameter end of the roller. A biasing force is provided between the idler wheel and the motor driven roller such that the idler wheel is urged from the smaller diameter steps of the roller toward the larger, and suitable `manually controllable means are provided to retain the idler `wheel in engagement with the desired step of the roller. It is understood that Tthe idler wheel may be constructed to be axially movable and the drive roller stationary or vice versa. The particular modification herein described is arranged to utilize an axiallyrriovable `idler wheel.

In order to condition lthe driving mechanism to lprovide a faster speed, that is to move 4the idler wheel to' a 'larger diameter driving surface on the motor drv'en roller, the `manually controllable-means is manipulated to release the idler wheel which is then moved by the biasing force toward the next larger -s'tep portion of the roller. Ordinarily, the abrupt discontinuity of the stepped roller would prevent further movement of the idler wheel. However the periphery of the elliptically shaped cam element engages the larger driving surface and upon rotation of "the roller with the elliptical cam element in engagement therewith the periphery of the idler wheel is forced away from the pre-engaged smaller diameter driving surface. When the major axis of the cam element is normal to the roller, the idler wheel is moved axially along the roller by the biasing force until the periphery of the idler is in engagement with the larger stepportion of the roller.

The novel features which are considered' characteristic of this invention are set forthwith particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, as well asV additional objectives and advantages thereof will best be understood from the following description when read inconnection with the accompanying drawings, in which:

Figure 1 is atop plan view of a portion of a phonograph record player, partly in section and partly broken away, showing a two-speed turntable driving mechanism embodying the invention;

lFigure 2 is a sectional side view of the portion of the phonograph record player of Figure 1, taken on the section line 2-2, and showing further details of the driving mechanism; l

I Figure 3 is a sectional end View of a .portion of the phonograph record player of Figure 1, taken on the section line 3'-3;

Figure 4 is a schematic side view of the two-speed turntable driving mechanism shown in the preceding figures, wherein the idler wheel is'illustrated in a position to more clearly show the relationship of the various parts ofthe driving mechanism vfor a lower speed drive;

Figures 5 and 6 are schematic side views similar to that of lFigure 4, showing changes in the relative positions of the parts as the driving mechanism changes from a lower i speed to la'higher speed drive; and

Fig. 7 is a top plan view of an idler wheel having vanes on one side.

Referring now to the drawings wherein like reference characters are used to designate similar components throughout the various figures thereof and particularly to Figures l, 2 and 3, a sheet metal motor board 10 provides a main supporting plate for the phonograph record player. A supplemental plate 12 is supported from the motor board by three mounting screws 14. To prevent the mounting screws 14 from making metallic contact with the motor board 10, tubular rubber sleeves 16 surround the screws i4 throughout most of their length. The sleeves preferably have two portions, not shown, which are mounted respectively between the supplemental plate 12 and the motor board 18, and between the motor board 10 and the heads of the screws 14. A portion of the sleeves 16, not shown, also extends through the apertures in the motor board 10 to insure that no metallic contact is made between the screws 14 and the motor board 10.

Such an arrangement is in accord with present day common practice to prevent tonal vibrations from passing from the supplemental plate to the motor board and hence through the turntable post 18 to the turntable 20, from which such vibrations would otherwise be transmitted through a turntable supported record disk to the reproducing stylus of the phonograph.

The turntable 20 may be carried on the post 18 in any well known manner and preferably the post 18 is journalled in a bearing tube 22 for free frictionless rotation. The turntable is preferably provided with a pendant flange 24 having a smooth cylindrical inner surface 26 with which the rubber peripheral tread 28 of the idler wheel 30 is frictionally engaged whereby rotation of the idler wheel may drive the turntable at a speed determined by the rate of rotation of said idler wheel.

The hub of the idler wheel 30 is provided with a bearing sleeve 34 drive fitted therein, said sleeve being journalled on an upright post 36 rigidly secured at its lower end to a yoke portion 38 of a U-shaped slide element, generally indicated at 40. The slide element has a pair of parallel arms 42 and 44 which make bearing fittings within the slideways 48 and 50 milled in opposite sides of a hub 46. The entire slide element 40 which, by its yoke, carries the upright idler wheel post 36 and the idler wheel 30 may be moved longitudinally of and guided by the above designated slideways, subject to the restlictions imposed upon such movement by the tensile spring 52 and any engagement had by the periphery of the idler wheel 30 with the turntable flange 24 and also with a driving roller 60 carried by a shaft 56 of the driving motor 58.

The hub 46 has a cylindrical bore and is journalled upon a relatively longer standing post 66 by a bearing it, to permit said mount hub to be rotationally and axially reciprocated on the post 66. The lower portion of the post 66 is provided with an enlarged radial flange 68 and terminates in a reduced threaded end 70 which is extended through an aperture of the supplemental plate 12 whereby the post is rigidly secured by a nut 72 to the supplemental plate. The top end of the shaft 66 is provided with an enlarged head portion 64 to prevent the hub 46 from sliding off, and may also serve to limit the vertical travel of the hub as will be explained hereinafter.

A helical spring 73 is threaded on a post 66 between the mounting hub 46 and the supplemental plate 12 to spring bias the idler wheel assembly upwardly.

A planar elliptically shaped cam element 32 is positioned on the top side of the idler wheel 30. The camV element may be formed integrally with the idler wheel or may comprise a separate section which is held in place by any suitable fastening means. The major axis of the cam element is equal in dimension to the diameter of the idler wheel. Thus a portion of periphery of elliptical cam element is at the same radial distance from the axis of the upright post 36 as is the periphery of the idler wheel 30. The relative axial positioning of the idler Wheel and cam element are such that the periphery of the idler wheel makes complete contact with the roller 62 yet allows sulicient axial clearance between the cam element and the larger diameter driving surface of the motor driven roller 60, to avoid contact therewith.

The stepped roller may be constructed as an integral part of the motor shaft 56, or may be separately formed and keyed to the motor shaft. In the embodiment shown, a large diameter driving roller 60 is keyed to the top end of the shaft S6. A diameter increasing layer of tightly wound spring wire 62 is wrapped around the shaft 56 and soldered thereto below the roller 60 to adjust the diameter of the shaft to provide the proper driving ratio between the coil 62 and the idler wheel at the lower of the two desired speeds. The driving ratios selected may, for example, be such that the turntable is driven at 45 R. P. M. and 78 R. P. M., or alternativelyrat 33 R. P. Ml and 45 R. P. M. The peripheral surfaces of the roller 60 and the coil 62, thus together form a two-speed driving roller. Naturally if three driving speeds are required, it is merely necessary to provide a driving roller with three driving surfaces having properly proportioned diameters to drive the turntable at 33, 45 and 78 R. P. M., for example.

For adjusting the idler Wheel 30 to its various driving positions, a manually operated lever 74 is provided which has a laterally extending end portion 76 which extends over the rear apron of the slide element 40. The lever 74 is pivoted for movement about a pin 75 which eX- tends through a tab 78 struck up from the supplemental plate 12. The lever '74 is mounted so that the width thereof is normal to the axis of the pin 75 throughout the major portion of the length thereof to provide suf cient stiffness in operation. The opposite end 80 of the lever 74 is engaged by a pair of lingers 84 which form an integral part of a circular detent plate 82. The V-shaped end of a spring member 86 mounted on the phonograph cabinet wall is adapted for engagement with either one of two notches a, 85h on the periphery of the detent plate.

The end 76 of the lever 74 restrains the slide element 40 and the idler pulley which is mounted thereon against vertical movement under the force of the spring 73. Hence the detent mechanism should provide sucient resistance to overcome the force exerted through the lever 74 by the spring 73.

The detent plate 82 is fastened on the same shaft as a manually controllable knob 90, the shaft being rotatable in a bearing surface supported in the wall of the phonograph cabinet 88. Suitable indicia, not shown, may be provided on the outer surface of the cabinet adjacent the knob to indicate the selected speed of rotation.

Rotation of the knob 90 in a counter-clockwise direction rotates the detent plate 82 until the detent spring 86 moves out of the first notch 85a and snaps into the second notch 8517. When the detent plate 82 is moved from the position shown in Figure 2 to the alternate position, the lingers 84 carry the end 80 of the lever 74 downwardly causing the opposite end 76 of the lever to move upwardly, allowing the slide element 40 and the idler wheel 30 which is mounted thereon to move vertically under the force of the spring 73.

The operation of the speed changing mechanism as schematically illustrated in Figures 4, 5 and 6 will be described in more detail. In the position shown in Figure 4 the periphery of the idler wheel is in engagement with the small diameter roller 62 and the inner surface of the pendant turntable ilange shown in Figures 1 and 2. Since the idler wheel has a oating mount, that is, the wheel mounting is both pivotally movable and longitudinally slidable and hence can assume any position in the limited planar area, and is spring biased by the tensile spring 52 toward the motor driving roller 60, the

idler wheel will `automatically adjust itself 'for driving relation between the turntable angeand the'notr driving roller. v

The idler wheel and the 'supporting slide 'element which are supported by the hub 46 are also vertically movable under the biasing force ofthe Spring 73. In the rst detent position of the detent plate 82 as shown in Figure 3, the vertical movement is restrained by the end 76 of the controlling lever 74 in a position where the periphery of the idler wheel 30 is in engagement with the smaller diameter driving surface 62, and at a level whereby there is sucient axial clearance between the ca'm element 32 and the larger diameter driving surface 60 to avoid contact therebetween.

The idler wheel 30 'as shown in Figure 4 has been rotated so that the full dimension of the minor axis of the cam element 32 can be seen. The dimension of the minor axis of the cam element is not critical but should be small enough to permit the driving surface ofthe large roller 6i) to easily engage the periphery of the cam element when the idler wheel is allowed to move upwardly. Furthermore it should be noted that the cam element 32 need not be of an elliptical configuration, and may comprise any type of cam element on the idler wheel adapted to move the wheel radially'out of engagement with the smaller diameter driving surface. For example, there is Shown in Figure 7 an idler wheel having vanes on one side thereof which spiral from a point near the central portion to the periphery of the idler. The edges of the vanes are adapted to engage the larger diameter driving surface and move the idler wheel outwardly from the pre-engaged driving surface as described above.

Upon manual movement of the control knob 90 to the faster driving position, that is the alternate detent position `85b, the end 76 of the operating lever 74 releases the idler wheel support 40 which is then forced upwardly by the spring 73. The idler wheel 30 by itself could not clear the large driving roller 60 vand would be held against further vertical movement by the abrupt 'discontinuity between the smaller and larger steps of the d-rive roller. However in accordance with the invention the edge of the elliptically shaped cam element 32 mounted on the idler wheel engages the driving surface of the larger roller 60 and is rotated thereby to force the idler wheel radially or outwardly away from the smaller roller 62 as shown in Figure 5.

When the cam element 32 has rotated far enough that the major axis thereof is at right angles to the larger roller 60, the edge of the idler wheel 30 is in line with the edge of the larger roller since the major axis of the cam element is equal to the diameter of the idler pulley, hence the force of the spring 73 can push the idler wheel up into engagement with the larger' roller 60. The vertical travel of the idler wheel is controlled by the position of the end 76 of the lever 74 which extends over the apron of the slide element 40. However the upper limit of travel could just as well be provided by the head portion 64 of the post 66 which engages the mounting hub 46. When the idler wheel is properly positioned in the faster speed drive, the periphery thereof is in frictional engagement with the motor driven roller 60 as shown in Figure 6.

To change from a faster speed to a slower speed, the knob 9d is rotated to cause the lever 74 to depress the slide element 40 to the position shown in Figure 4. The idler wheel 3d easily slides otr the larger diameter driving surface to the smaller, and is retained in position by the action of the detent mechanism.

The improved plural speed driving mechanism described includes a self-positioning idler wheel which is adapted to transfer torque from any one of a plurality of driving surfaces of a stepped motor driven roller to a driven element. The idler wheel includes a cam element on one side thereof for moving the idler wheel .6 radially vvhen'changing from ja smaller to alarger diameter driving surface and suitable biasing 'means' to urge thve'idler toward the larger diameter surface.

What is claimed is:

l. A plural speed driving system comprising in combination, a motordriven roller having coaxial driving surfac'esof different diameters, an element to be driven, an idler wheel, means urging said idler Iwheel Vinto 'engagemerit with said motor driven roller and said element 't be driven, a cam element positioned on a side of said idler wheel which side faces in 'the direction 0f a larger diameter driving surface, biasing means for relatively urging said idler 'wheel axially toward a larger diameter driving surface of said motor driven roller, and means for retaining said idler wheel in engagement with a predetermined one of said driving surfaces.

2. A plural speed drive mechanism comprising in corn-y bination a motor driven roller having driving surfaces of ydiferent diameters, an idler wheel having a planar substantially elliptically shaped cam elementen one sid'e thereof for effecting relative movement between the roller and the idler wheel, thevmajor axis of said cam element being substantially equal to the diameter of said idler wheel, an element to be driven, means urging said idler wheel into engagement with 'said motor driven roller and said element to be driven, said cam velement positioned o'n the axial vside of said idler wheel facing in the direction of the larger diameter end of said roller, biasing means exerting an axial force between said idler wheel andsaid roller for relatively urging said idler 'wheel toward a larger diameter driving surface of said 'motor driven roller, and means for retaining said idler wheel in engagement with a predetermined one of said driving surfaces.

3. A plural 'speed driving system comprising in combination, a rnotor driven roller having driving surfaces of V'diifere'nt diameters, `an element to be driven, an idler wheel,` means urging the periphery of said idler wheel into Erictional engagement with vsaid motor driven ,roller and saidel'ement to be driven, a cam 'element positioned r'r 'aside of said idler wheel which side yfaces in the direction of a larger diameter driving surface, said can element having a driving surface substantially parallel 4to the driving surface of said idler wheel and extending from a point near the central portion to the periphery of said idler wheel, biasing means relatively urging said idler wheel toward a larger diameter driving surface of said motor driven roller, and means for retaining said idler wheel in engagement with a predetermined one of said driving surfaces.

4. ln a plural speed driving system for phonograph record players or recording equipment of the type having an idler wheel, a motor driven roller having driving surfaces of different diameters, an element to be driven, means urging the periphery of said idler wheel into engagement with a predetermined one of said driving surfaces and said element to be driven, a planar cam element on one side of said idler wheel having a major axis equal to the diameter of said idler wheel, said cam element being positioned on the side of said idler Wheel toward the larger diameter driving surface of said motor driven roller, spring biasing means for relatively urging said idler wheel toward a larger diameter driving surface of said motor driven roller and manually controllable means for retaining said idler Wheel in engagement in a predetermined one of said driving surfaces.

5. In a plural speed driving mechanism for phonograph record players of the type having turntable with an aunular pendant flange for supporting record disks to be played, a stepped motor driven roller having driving surfaces of different diameters, an axially movable self-positioning idler wheel interposed between said pendant ange and one of said driving surfaces to transfer torque from said motor driven roller to said turntable, a cam element for effecting relative movement between the roller and the idler wheel positioned on the side of said idler wheel which side faces in the direction of the larger diameter end of said motor driven roller, said cam element having a surface extending from a point near the central portion of said idler wheel to the periphery thereof, spring biasing means urging said idler wheel axially toward a larger diameter driving surface of said motor driven roller, and manually controllable means for retaining said idler wheel in engagement with a predetermined one of said driving surfaces.

6. In a plural speed driving System of the type having an element to be driven and a stepped motor driven roller having driving surfaces of different diameters; the combination comprising a self-positioning idler wheel interposed between said element to be driven and said motor driven roller, a cam element affixed to one side of said idler wheel, said cam element having a driving surface substantially parallel to the driving surface of said idler wheel and extending from a point near the central portion to the periphery of said idler wheel, and spring biasing means urging said idler wheel axially toward a larger diameter driving surface of said motor driven roller.

7. In a two-speed driving system for phonograph record players or the like, a turntable having an annular pendant flange for supporting record disks to be played, a stepped motor driven roller having two driving surfaces of different diameters, an idler wheel, a first driving position wherein the periphery of said idler wheel is in frictional engagement with the smaller diameter driving surface of said motor driven roller and said turntable ange, a planar substantially elliptically shaped cam element for effecting relative movement between the roller and the idler wheel positioned on one side of said idler wheel and having a major axis equal to the diameter of said idler wheel, spring biasing means urging said idler wheel toward the larger diameter driving surface of said motor driven roller and manually controllable means for selectively retaining said idler wheel in said tirst driving position, a second position of said idler wheel wherein the periphery of said idler wheel is in engagement with the smaller diameter driving surface of said motor driven roller and said turntable ange and the periphery of said cam element is in engagement with the larger diameter driving surface of said motor driven roller, a third driving position wherein said idler wheel is in engagement with the larger diameter driving surface of said motor driven roller and said element to be driven, and means for retaining said idler wheel in said last named position.

8. In a plural speed driving system, an element to be driven, a stepped motor driven roller having at least two driving surfaces of different diameters, an idler wheel, axially movable supporting means for said idler wheel for providing positioning of said idler wheel to transfer torque from said motor driven roller to said element to be driven, a first driving position wherein the periphery of said idler wheel is in frictional engagement with the smaller diameter driving surface of said motor driven roller and said element to be driven, a planar substantially elliptically shaped cam element positioned on one side of said idler wheel having a major axis equal to the diameter of said idler wheel, spring biasing means urging said supporting means and said idler wheel supported thereby in the direction of the larger diameter driving surface of said motor driven roller and manually controllable means for selectively retaining and releasing said idler wheel in said first driving position, a second position wherein said supporting means and idler wheel are moved axially by said spring biasing means to a position where said idler wheel is in engagement with the smaller diameter driving surface of said motor driven roller and said element to be driven, and the periphery of said cam element is in engagement with the larger diameter driving surface of said motor driven roller, a third driving position wherein said supporting means and idler wheel are axially moved by said spring biasing means to a position where said idler wheel is in engagement with the larger diameter driving surface of said motor driven roller and said element to be driven, means for retaining said idler wheel in said last named position.

References Cited in the tile of this patent UNITED STATES PATENTS