US2814956A - Phonographs - Google Patents

Description

Dec. 3, 1957 E. WENNERBO EI'AL 2,814,956

PHONOGRAPHS Filed Aug. 27, 1952 V mvmons ZZZIK VYKIVKEEO 50,5722 E wazaa BY JAM/1m ATTORNEY Unite es Patent PHONOGRAPHS Erik Wennerbo and Giista Hedberg, Motala, Sweden,

assignors to lndustrialstiebolaget Luxor, Motala, Sweden, a corporation of Sweden Application August 27, 1952, Serial No. 306,642 Claims priority, application Sweden September 7, 1951 1 Claim. (Cl. 74-199) This invention relates to a phonograph device for imparting to the turntable different speeds ofrotation, which turntable has a record supporting plane above the base-plate of the phonograph.

The phonograph records, which are now onthemarket, are recorded at either 78 or 45 or 33% R. P. M. and in order to be enabled to play all these records the phonographs must be supplied with a device, which brings about the driving of the turntable as desired with either the first or the second or the third of these speeds in dependence of the setting of a control device.

Going out from the usual construction with an intermediate wheel arranged between the driving wheel of the motor and the turntable for driving against the inside of the flange of the turntable, they have forthe purpose named above arranged three different driving wheels in the same plane, which wheels alternately can be brought into engagement with the intermediate wheel. Another construction known has the motor shaft suppliedwith axially arranged driving wheels of diiferent diameter and has a second intermediate wheel, which is coaxial with and unrotatable in relation to the first-mentioned intermediate wheel but axially displaceable relatively to the same for engaging one in turn of the driving wheels mounted on the motor shaft.

Further constructions are known, which all use the first-mentioned intermediate wheel in the power transmission between the motor and the turntable. It has, however, been evident, that with these devices for driving of the turntable its rotational speed is notsufficient even to eliminate noticeable changesof frequency. at the playing of the records. This refers especially to the two lowest speeds, 45 and 33 /3 R. P. M., at which the flywheel mass of the turntable. is not sufficient to eliminate even small irregularities in the rotation of the turntable.

Investigations now made have proved that the decidedly greatest cause of the uneven rotation of the turntable is the intermediate wheel, which cannot Without heavy expenses be made with sufiicient precision with respect to its absolute roundness as well as to its pivoting in order to eliminate this disadvantage. The price object causes here a compromise, so that it is attained to have the best possible precision for moderate costs, which, however, means that some examples of phonographs made in such a way by chance may be acceptable while others are not. An irregularity, which e. g. recurs once during every revolution of the intermediate wheel recurs many times during every revolution of the turntable and causes often repeated and audible changes of frequency.

The present invention is a radical change of the above described conventional construction and the device according to the invention also presents a quite new type of turntable suited to the new driving system, which by tests has proved to give to the turntable a perfectfunction and thus a fully satisfactory sound quality at the playing of the records is attained in spite of the fact that the simplicity of the device can cope with the constructions known and mentioned above.

Theinvention will hereinafter be described with reference to the accompanying drawing.

In the drawing:

Figure 1 in a side view shows a device according to the invention.

Figure 2 in a top view shows a turntable included in the same device.

In the drawing 1 designates a turntable which is pivoted about a shaft 2, fixed in the phonograph. The turntable is shaped in a quite new manner and consists of a plane, circular, upper portion 3, which is in a horizontal plane parallel to the base-plate 4 of the phonograph, and a ring-shaped portion 5 extending outwards and downwards from the portion 3, which portion 5 passes a recess 6 in the base-plate 4 of the phonograph. This last-mentioned portion 5 ends in an outwards directed flange 7 parallel to the upperportion 3 and supplied with a rubber rim, forming a driving path 8 for the turntable 1. The upper portion 3 is supplied-with three rubber pads 9, placed along its periphery, against which pads the records may rest during the playing.

The turntable described above may e. g. be made in such a way, that two similar turntables with the form mentioned are placed upon each other and thereby the rubber rimis inserted with a flange between the turntables along their periphery, after which the turntables are riveted together in their centre, fixing the rubber rim between them.

With the driving path 8 of the turntable 1 alternately three. difiierent portions 19, 11 and 12 of different diam.- eters of a driving wheel are engageable. The driving wheel is fixed on a driving shaft 13 of an electric motor 14. This shaft 13 is parallel to the turntable shaft 2. On the motor are fastened an upper shaft 15 and a lower shaft 16 coaxial with each other and arranged parallel to the driving shaft 13 and the turntable shaftZ. The lower shaft 16 is rotatably mounted and axially displaceable in a bottom portion 17 belonging to a U-shaped clamp, the legs 18 and 19 of which are fastened to the base-plate 4. A cross-piece 20 parallel to the bottom portion 17 extends between the legs 18 and 19. and is fastened to them. In this cross-piece 20 the upper shaft 15 is rotatably mounted in the same way as the lower shaft 16 is rotatably mounted in the bottom portion 17.

Above, the cross-piece 2% pins 21 and 22, respectively, is arranged on both sides of the upper shaft 15 and radial. to it, which pins are fixed to the legs 18 and 19, respectively, of the clamp. These pins 21 and 22 support a cam element 23, which'is fastened to the upper shaft 15 rotatably mounted about but axially not displaceable in respect to this shaft. The cam surface of the cam element 23, which cooperates with the pins 21 and 22, has three positions 24, 25 and 26.

In order to unload entirely or nearest to it the weight of the motor, i. e., the pressure of the cam element 23 against the pins 21 and 22, two springs 27 and 28 are arranged, which with their one end are fixed to the motor 14 and with their other end are fixed to the legs 18 and 19, respectively, of the clamp. These springs are further arranged in such a way that they tend to turn the motor 14 with the shafts 15 and 16 in their hearings in the bottom portion 17 and the cross-piece 20 of the clamp, so that the driving shaft 13 of the motor 14 with the portions 10, 11 and 12 of the driving wheel is brought against the driving path of the turntable 1.

The mode of operation of the above described device is as follows:

According to Figure 1 in the drawing the position 24 of the cam element 23 is in engagement with the pins 21 adjustable in three different positions, marked with the 7 before-mentioned three speeds. In the position of the cam element 23 mentioned just above the motor 14 with the shafts 15, 16 and the driving shaft 13 drops, so that the portion 11 of the driving wheel is'brought into engagement with the driving path 8 of the turntable 1, the latter one by the motor in drive being rotated at 45 R. P. M.

If a turntable speed of 33 /3 R. P. M. is desired the cam element is further rotated until the position 26 of the cam element 23 is opposite the pins 21 and 22. This means that the motor 14 with the shafts 15, 16 and the driving shaft 13 sinks further by the gravity, so that the portion 12 of the driving wheel is brought into engagement with the driving path 8 of the turntable 1, the latter one by the motor in drive being rotated at 33 /3 R. P. M.

At the displacement of the motor just mentioned the weight of the motor is counteracted by the power represented by the two springs 27 and 28, which power of course in this embodiment of the device according to the invention must be made smaller than the firstmentioned power in order to have the cam element 23 resting against the pins 21 and 22.

Preferably the device is so arranged that when the control device is moved between its different positions for changing the speed, the motor is temporarily against the action of the springs 27 and 28 so turned that the driving wheel is somewhat moved away from the driving path 8 of the turntable, which is especially important, when the motor shall be displaced in the opposite direction against the one above described, so that the steps between the portions of the driving wheel do not render this displacement unnecessarily difficult.

The device for displacing the motor axially may of course be made in other manners than is here described. Thus it is possible to arrange the cam element rotatably mounted in the base-plate of the phonograph and to have a single pin, which passes the upper shaft 15 perpendicular to its axial direction and extends in opposite directions outside the periphery of the shaft for engagement with the cam element.

Instead of having the whole motor displaceable, which has been described above, it is also possible to have only the rotor displaceable and the stator fixed without departing from the spirit of invention.

The shape of the turntable shown in the drawing has proved to be very advantageous in connection with the driving system described and it is to suppose, that maintaining the usual shape of the turntable has contributed to not using such a driving system earlier. At the usual shape of the turntable a very wide flange must be used, which has to pass the base-plate and extend somewhat below this plate in order to make the displacement of the motor possible, without esthetically spoiling the part of the phonograph above the base-plate. Such a wide flange is difficult to make, so that it will be absolutely round at the driving place.

The turntable shown and described here ends in a flange, which is parallel to the turntable plane and on this flange a rubber rim is fastened. Instead it is of course possible to use a flange without rubber rim and arrange this flange perpendicular to the turntable plane and in this case have the driving wheels of rubber or have them covered with rubber.

The device according to the invention is described with reference to a phonograph. This device may naturally also be used in a magnetic sound recording and reproducing apparatus to drive the take-up and supply reels at different speeds and such an arrangement of the device is considered also to make use of the spirit of invention.

What we claim is:

In a phonograph having a base plate provided with an opening and a turntable, means mounting the turntable for rotation on a vertical axis, said turntable comprising a plane circular record supporting portion above the base plate of the phonograph, a ring-shaped portion sloping outwards and downwards from the outer edge of said plane and extending through the opening in said base plate, a flange below said base plate on said ring-shaped portion, directed outwardly parallel to said plane, a rubber rim on said flange, a single speed driving motor arranged with its axis upright at one side of the rubber rim wholly below the base plate, a driving wheel having axially aligned portions of different diameters on said motor adapted to frictionally engage said rubber rim, and means effecting vertical movements of the driving wheel in order to bring a selected portion of the wheel in engagement with said rubber rim without moving above the base plate.

References Cited in the file of this patent UNITED STATES PATENTS 2,047,733 Harrison July 14, 1936 2,254,066 Gruber et al Aug. 26, 1941 FOREIGN PATENTS 665,144 France Apr. 30, 1929

Images