US2185882A - Phonograph - Google Patents

Description

Jan. 2, 1940. A, V BEDFORD 8 2,185,882

PHONOGRAPH Filed Aug. 29, 1936 2 Sheets-Sheet l Jay. 2, 1940. A. v: BEDFQRD 2,185,882

PHONOGRAPH Filed Aug. 29, 1936 2 Sheets-Sheet 2 Patented Jan. 2, 1940 PHONOGRAPH Alda V. Bedford, Collingswood, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application August 29, 1936, Serial No. 98,445

15 Claims.

This invention relates to record moving mechanisms, and more particularly to a method of and means for controlling the speed of rotation of a phonograph turntable or equivalent sound record supporting device.

In conventional phonographs, the turntable is usually driven by a suitable motor through reduction gearing or the like. Despite the care exercised in gear manufacture, slight mechanical imperfections exist therein, and these imperfections or inaccuracies produce irregularities in the rotational speed of the turntable which are deleterious to high quality reproduction of sound. In designing turntables, especially those for operation at low speeds (for example, 33 R. P. M.), it has been proposed to use flexible couplings between the driving motor and the turntable and massive rotating fly-wheels on the turntable in order to filter out irregularities caused by nonuniform pitch in gears of the speed reducing systems. While such filters may be satisfactory for irregularities of relatively high frequency, they are entirely unsuited to filter out irregularities which are of repetition frequencies of one or two times the turntable rotation frequency on account of the extreme massiveness required of the aforementioned fly-wheels for such low frequencies.

The primary object of my present invention is to provide an improved method of and means for controlling the rotational speed of phonograph turntables, or any other apparatus including a rotating member intended to be rotated at uniform speed, whereby the foregoing difiiculty is obviated.

More specifically, it is an object of my present invention to provide, in phonographs, novel means for counteracting the effect of various elements which tend to produce irregularities in the speed of the turntable where the irregularities have a whole number frequency relation to the turntable rotation frequency.

A further object of my present invention is to provide improved speed controlling means as aforesaid which is relatively simple in construction. which may be applied to existing phonoraphs without material alteration thereof, and which is highly effective in use.

In accordance with my present invention, I provide means for deliberately introduc ng additional uniformly-variable torque in the rotating system. One component of the added torque is made to vary uniformly at turntable rotation frequency and is adjustable both in phase and amplitude. The adjustment may be made while the turn- (Cl. M -604) table is rotating and preferably with test conditions under which a continuous indicating means is employed to indicate when the optimum adjustment is reached. If desired, the adjustment I may be made while listening to the reproduc- 6 tion of a recorded steady tone instead of by the use of the indicating means. Either the same means which provides the aforesaid torque component or similar other means may be employed to supply additional torque of higher frequencies of variation, such as the second or third multiples or harmonics of-the turntable rotational frequency. The added torques of each frequency may be adjusted, one at a time, to buck out the corresponding effect caused by imperfections of the driving system.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, together with additional objects and advantages thereof, will best be understood from the following description of several embodiments thereof when read in connection with the accompanying drawings in which Figure 1 is a side elevation of one form of my present invention,

Figure 2 is a partial plan and partial sectional view taken on the line 2-2 of Fig. 1, 30

Figure 3 is a similar view taken on the line 33 of Fig. 1,

Figure 4 is a similar view taken on the line 44 of Fig. 1,

Figure 5 is a similar view of a modified form of my invention, and

Figure 6 is an elevational view of the structure shown in Fig. 5.

Referring more specifically to the drawings, wherein similar reference characters indicate corresponding parts throughout, there is shown, in Fig. 1, a turntable I supported on a bearing 3 and driven by a shaft comprising-the shaft sections 5a, 5b and 5c. The shaft section 5a rotates in the bearing 3 and is coupled to the shaft section 522 by means of a flexible coupling 1 of any suitable type. The shaft section 5b is similarly coupled to the shaft coupling by a flexible coupling 9, the section 5b rotating in bearings II and I2 and having fixed thereon a flywheel l3, while the shaft section 50 rotates in bearings 15 and I7 and has a worm wheel 19 fixed thereto which meshes with a worm 2| on the shaft 23 of a driving motor (not shown). Also fixed to the shaft section 5b are a plurality changes therein are possible.

which has a plurality of rollers 3| engaging its cam surface or periphery. The rollers 3| are carried by resilient strips 33, such as spring blades, which are mounted on blocks 35 of a stationary frame and may be adjustably pressed against the cam edges of their respectively associated cams by an adjusting screw 31 threaded into an extension 39 on each of the blocks.

The cam 25 is so shaped that each roller 3| produces on the shaft a torque which varies according to a sine wave around the periphery of the cam. A circular disk eccentrically mounted on the shaft section 5b will suflice forv this purpose. The cams 21 and 29 are so shaped, respectively, as to produce two and three sine wave cycles of torque for each revolution thereof, or for each turn of the shaft section 5b. Any number of rollers may be employed in association with each cam. I have shown four rollers in association with the cams 25 and 29 (Figs. 2 and spaced physically from each other about the peripheries of the cams and effectively operated 90 apart with respect to one cycle of the torque wave produced thereby so that, by proper adjustment of the screws 31, the total torque supplied by either cam can be adjusted in amplitude and in phase over 360. The four rollers associated with the cam 21 (Fig. 3), on the other hand, are physically spaced equally over approximately of the whole cam surface, but the same 90 spacing or effect with respect to the sine wave is produced by this arrangement since the four rollers are, in this case, also distributed over a single cycle of the torque wave. In the arrangements shown in Figs. 2 and 4, the rollers are spaced over 360' of the cam surface merely for the sake of convenience from a mechanical standpoint.

The purpose of the flexible coupling 9 is to permit the speed of the fiy-wheel I3 to be made substantially steady by the torque provided by the several cams 25, 21 and 29 without having to alter the speed of the motor in the event that the worm wheel or gear l9 has non-uniform tooth pitch, as is usually the case. The inertia of the turntable l and the flexibility of the coupling 1 will act to reduce high frequency variations in the turntable speed.

In Figs. 5 and 6, I have shown a modification of my invention wherein only two rollers 3| are employed in association with the cam 25. In this modification, the springs 33 which carry the rollers 3| are secured to opposite ends of an arm 4| which is rotatably carried on the shaft section 5b midway between the ends of the arm. A

threaded extension 43 on one end of the arm 4| extends through a slot 45 in an arcuate guide member 41 which is concentric with the shaft section 51), a wing nut 49 being received by the extension 43 for clamping the arm 4! in any desired position along the guide member 41. By merely loosening the wing nut 49 and rotating the arm 4| on the shaft 5b, the rollers 3| may be adjusted circumferentially on the cam 25 to provide phase adjustment of the added torque. The same result may be effected, if desired, by arranging the arm, 4| in a fixed position and mounting the cam 25 on the shaft 517 for circumferential adjustment upon the shaft.

Although I have shown and described several embodiments of my invention, I am fully aware that many other modifications thereof and For example, the cams 25, 21 and 29 may each be placed in differof axially spaced cams 25, 21 and 29, each of ent locations in the drive system with respect to v the filtering and driving elements or-parts of the filter. Also, the flexible coupling 9 may be omitted, if desired, in which case, the motor would be required to vary its speed in response to the variable torques produced by the several cams. Furthermore, each of the cams may be made to alter the torque by supplying a variable braking effect, as by substituting brake pads for the rollers 3|. It is also possible to obtain a different type of correction by arranging the cams 25, 21 and 29 in such a manner that they will add a definite additional variable rotation to the system, as, for example, by superimposing oscillatory motion of the worm 2| along its axis. Other modifications and changes will be apparent to those skilled in the art. I therefore desire that my invention shall not be limited except insofar as is necessitated by the prior art and by the spirit of the appended claims.

I claim as my invention:

In a phonograph, the combination of a driving shaft, a turntable arranged to be driven thereby, a cam fixed to said shaft for rotation therewith, means pressingly applied-to the cam surface of said cam for applying a variable torque to said shaft as it rotates, and means for adjusting said first named means circumferentially with respect to said cam surface.

2. In a phonograph, the combination of a driving shaft, a turntable arranged to be driven thereby, a cam fixed to said shaft for rotation therewith, means pressingly applied to the cam surface of said cam for applying a variable torque to said shaft'as it rotates, means for adjusting the pressure between said first named means and said cam, and means for adjusting said first named means circumferentially with respect to said cam surface.

3. In a phonograph, the combination of a driving shaft, a turntable arranged to be driven thereby, a cam fixed to said shaft for rotation therewith, means pressingly applied to the cam surface of said cam for applying a variable torque to said shaft as it rotates, said cam being so shaped that the torque produced on said shaft varies according to a sine wave around the cam surface thereof, and means for adjusting said first-named means circumferentially with respect to said cam surface.

4. In a phonograph, the combination of a driving shaft, a turntable arranged to be driven thereby, a cam fixed to said shaft for rotation therewith, means pressingly applied to the cam surface of said cam for applying a variable torque to said shaft as it rotates, said cam being so shaped that a small whole number of sine wave cycles of torque are applied to said shaft for each revolution of said shaft, and means for adjusting said first-named means circumferentially with respect to said cam surface.

5. In a phonograph, the combination of a driving shaft, a member arranged to be driven by said shaft and adapted to support a record, means for applying to said shaft a sine wave torque, and additional means for applying to said shaft at least one other sine wave torque difiering in phase by 90 from said first-named torque.

6. In a phonograph, the combination of a driving shaft, a member arranged to be driven by said shaft and adapted to support a record, means for applying to said shaft a. uniformly variable sine wave torque one component of which varies uniformly at the rotation frequency of said member, and additional means for also greases applying to said shaft a uniformly variable torque which is a whole multiple or harmonic of the rotation frequency of said member.

'7. In a phonograph, the combination of a driving shaft, a turntable arranged to be driven thereby and rotatable in response thereto, a plurality of cams flxed to and rotatable with said shaft, and means associated with each of said cams for applying a variable torque to said shaft, at least one of said cams being so constructed and arranged as to produce a sine wave torque which varies uniformly at the rotation frequency of said turntable, andat least one other of said cams being so constructed and arranged as to produce a sine wave torque which varies uniformly, at a frequency which is a whole multiple or harmonic of the turntable rotation frequency.

8. The invention set forth in claim 7 characterized by the addition of means for varying at least one of said torques in both phase and amplitude.

9. In a phonograph, the combination of a driving motor, a shaft driven thereby, said shaft including a plurality of sections, a flexible coupling between two of said sections; said motorbeing coupled to one of said two sections, a plurality of cams fixed to the other of said two sections and rotatable therewith, and means associated with each of said cams for applying a variable torque to said shaft.

' 10. In a phonograph, the combination of a rotatable input, member having periodic variations in speed, an output member, flexible means coupling said output member to said input member, and means for applying periodic variations of torque to said output member whereby said output member is caused to oscillate with respect to said input member at the frequency of said periodic variations .to effect uniform rotation of said output member while permitting said input member to rotate with said periodic variations.

11. In phonographic apparatus having an output member intended to be rotated at a steady speed, the combination with said output member of a rotatable input member having a substantially uniform average speed and subject to undesired periodic speed variations recurring at the frequency of rotation of said input member such that said input member periodically runs first ahead and then behind its average angular position, flexible means coupling said input member to said output member, a stationary frame, and means for applying additional variable torque between said stationary frame and said output member in accordance with the instantaneous angular position of said output member relative to said frame input member and substantially independently of the speed and inertia of said output member whereby said output member is acterized by the addition of means for adjust-' lng said additional torque applying means in angular phase and in amplitude.

14. The invention set forth in claim 11 characterized in that said output member is provided with at least one cam and characterized further in that said variable torque applying means is constituted by a spring actuated follower in engagement with said cam.

15. The invention set forth in claim 11 characterized in that said output member is provided with at least one cam, characterized further in that said variabletorque applying means is constituted by a spring follower in engagement with said cam, and characterized still further by the addition of means for adjusting said spring follower angularly about said cam whereby to vary the angular phase of said additional torque.

' ALDA V. BEDFORD.

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