GB2109143A - Turntables - Google Patents

Abstract

A turntable for example for a record player, has means (13) for mounting the turntable (12) for rotation by a drive means (16, 17) about a central axis (12a), the turntable (12) including a rim (21) having a plurality of apertures (22) therein of equal width and equally spaced around the rim (21). A light source (30) adapted to flash at a predetermined frequency may be positioned so as to shine through the apertures (22) in a direction away from the central axis (12a), said predetermined frequency and the spacing of the apertures (22) being such that the apertures (22) appear to remain stationary as the turntable (21) rotates at said predetermined speed. <IMAGE>

Description

SPECIFICATION Turntables This invention relates to a turntable having means for mounting the turntable for rotation by drive means about a central axis. It is desired accurately to rotate the turntable at a predetermined speed.

One example of such a turntable is a record player turntable on which, in use, a disc record is placed, and a transducer such as a stylus and cartridge reproduces sound encoded in the grooves of the disc record.

It is essential for disc records to be played at a constant accurately set speed of rotation, corresponding to the coding of the sound in the grooves.

Commonly, such records are adapted to be played at 45 r.p.m. or 339 r.p.m., and the turntable drive means are designed to rotate the turntable at one or other of those speeds selectively. Means are commonly provided to enable the user of the record player to make small adjustments in the speed of rotation to compensate for any variations which may occur.

However, the user needs to be able to ascertain whether or not the turntable is rotating at the required speed.

Stroboscopic arrangements are known wherein the turntable, or a mat carried on the turntable, is provided with a pattern of markings such as stripes which, when a flashing light is directed onto the rotating pattern, indicate whether or not the turntable is rotating at the desired speed. The pattern is such that the effect of the flashing light makes the markings appear stationary as the turntable rotates at the predetermined speed due to the spacing of the markings. In such prior arrangements the light is reflected from the pattern.

It is an object of the present invention to provide a new or improved turntable having means for mounting the turntable for rotation by drive means about a central axis, wherein the ascertainment of a predetermined speed of rotation is facilitated.

According to one aspect of the invention we provide a turntable having means for mounting the turntable for rotation by a drive means about a central axis, the turntable including a rim having a plurality of apertures therein of equal width and equally spaced around the rim. A light source adapted to flash at a predetermined frequency may be positioned so as to shine through the apertures in a direction away from the central axis, said predetermined frequency and the spacing of the apertures being such that the apertures appear to remain stationary as the turntable rotates at said predetermined speed.

If the apertures appear to be moving, either clockwise or anti-clockwise, the speed of rotation needs adjustment to the required speed.

The invention provides at least the following two advantages over known arrangements. First, the flashing light source is located inwardly of the turntable so that light is emitted from the apertures making the light clearly visible, even if the ambient light is bright. In prior arrangements which relied on reflected light from a pattern, it has generally been necessary to carry out a turntable speed test in dim light particularly where the light source is a light emitting diode; which is the preferred light source, for example, because such a light source requires only a low voltage supply.

Secondly, it has been necesary with prior arrange ments for a light source to be mounted on the turntable deck plate or on a plinth provided thereon radially outwardly of the turntable so that the light can be directed onto the pattern. This is avoided with the present invention.

Conveniently, the turntable is made in synthetic plastics material by a moulding operation and the apertures are moulded in during said moulding operation. However, the apertures may be provided by other methods if desired, for example, they may be drilled or stamped out subsequent to the turnt able being made.

In the case of a turntable especially intended for use on a record player, the turntable may comprise a platen on which, in use, records are placed and a generally downwardly depending edge flange in which the apertures are provided. Preferably, the flange is inclined downwardly so that a plane containing the central axis and inclined thereto cuts the platen and flange along the line which subtends an obtuse angle, thereby to facilitate a user seeing the light emitted from the apertures of the turntable.

According to a second aspect of the invention, we provide a record player comprising a turntable according to the first aspect of the invention, means to adjust the speed of rotation of the turntable, a light source adapted to flash at a predetermined frequency related to the number of apertures in said rim so that the passage of an aperture past the light source is in-phase with a flash when the turntable is rotated at said predetermined speed, the light source being mounted on the record player radially inwardly of the rim of the turntable and a transducer for playing a record on the turntable.

The record player may be rotated by any desired drive means, for example a belt drive wherein an endless resilient belt is received around the flange provided on the underside of the turntable, and around a spindle of a motor. Alternatively, a jockey pulling wheel type drive may be provided, or the turntable may be directly driven from a motor or any other drive means may be provided.

Two speed controls may be provided, one to cause the turntable to be rotated at approximately 45 or 33- r.p.m. selectively, and a second control to permit small changes to be made in the speed of rotation of the turntable so that the speed of rotation may be accurately set.

The light source may be adapted to flash at a frequency the same as the alternating current mains supply to the record player, for example 60 Hz as is most commonly provided in the U.S.A., or 50Hz as most commonly provided in the U.K.

One embodiment of the invention will now be described with reference to the accompanying drawings, wherein: Figure 1 is a diagrammatic perspective view of a record player according to the invention; Figure 2 is an e enlarged perspective view of the edge flange of the turntable of the record player of Figure 1.

Referring to the drawings, there is above a record player 10 comprising a deck plate 11 on which a turntable 12 is mounted for rotation about a central axis 12a. Aconventional centre spindle 13 is provided.

The turntable is driven by a drive means comprising a drive flange 15 provided on the underside of the turntable 12 (shown in dotted lines) and a resilient belt 16 which passes around flange 15 and a spindle 17 of a motor 18 so that as the spindle 17 rotates, the turntable 12 is rotated.

Two speed controls 19,20 are provided, the control 19 being movable to first and second positions so that when the control is moved to a first position the motor 18 is caused, in use, to rotate at a first high speed which, when transmitted to the turntable 12, through the belt 16 and flange 15, causes the turntable to rotate at approximately 45 r.p.m. When the control 19 is moved to the second position, the motor 18 is caused, in use, to rotate at a lower speed which, when transmitted to the turntable 12 through belt 16 and flange 15, rotates the turntable at approximately 3331 r.p.m.

The other control 20, is a fine speed control and is for adjusting the speed of rotation of motor 18 and hence turntable 12, by a small amount to compensate for any production variations which occur in the drive means components, and to compensate for any wear in any of the drive means components.

The turntable comprises a plate P on which a disc record may be placed, the centre hole of the disc record being placed over the centre spindle 13 of the record player. At the periphery of the platen P, there is an inclined donwardly depending edge flange 21 in which a plurality of apertures 22, in the present case 108, are provided, each aperture comprisng a central slot part 23 which extends through the flange 21 bounded by top and bottom inclined parts 24.

The turntable has a diameter of 137.5mm, each aperture 22 has a horizontal width dimension dof 3mm and between each aperture 22 is a spacing part 25, each spacing part having a horizontal width s of 5mm.

Above each aperture 22 and in each spacing part 25 between the apertures, is an embossed formation 26a, 26b, the formations 26b. The formations 26a, 26b and the inclined parts 24 provide an aesthetically pleasing appearance. In addition, the inclined parts 24 and an essentially similar configuration on the inner side of the flange 21 permit of moulding of the apertures during the turntable moulding operation without the need to provide for side coring.

Located radially inwardly of the rim 21, beneath the turntable 12, a lamp 30 is mounted, which lamp is adapted to flash at a constant frequency.

In the present case, the turntable motor 18 is a direct current motor powered through a transformer and rectifier circuit, from a 110V 60Hz mains electricity supply such as is commonly provided in the U.S.A.

The lamp 30 is a light emitting diode and is arranged to flash at mains frequency i.e. 60Hz.

Another light souce may be used if desired.

The above described frequency, turntable diameter and number of apertures 22 are adapted to place the passage of an aperture 22 past the light source in phase with a flash of light emitted from the source when the turntable rotates at 3331 r.p.m. No means are provided for checking the speed of rotation at45 r.p.m.

If desired, means may be provided whereby the frequency at which the lamp 30 flashes may be adjusted to give a different frequency, suitable to indicate a precise speed of 333 r.p.m. and 45 r.p.m.

For example, a crystal divider network may be provided to give the required number of flashes per second; in this case the flashes will not be tied to the mains frequency. Alternatively, an indication of both 339 r.p.m. and 45 r.p.m. may be provided by using a single frequency source and providing two series of holes, one series being at the desired spacing for 33 r.p.m. and the other series for 45 r.p.m.

Where the frequency of the flashing lamp 30 is not 60Hz, or where a turntable of a different radius is provided, the dimensions d and swill need to be arranged appropriately if they are to indicate when the turntable is rotating at 333 r.p.m. accurately.

It is well known how to adjust these parameters and therefore it is considered that further discussion is not necessary.

Referring again to the drawings, the record player further comprises a pick-up arm 31 mounted for movement about a horizontal axis H to lift and lower the arm 31 and about a vertical axis V to allow the pick-up arm 31 to be oved to the beginning of the record and translated across the record.

A transducer comprisng a cartridge and stylus assembly 33 is provided at the end of the pick up arm 31.

Although the invention has been described with reference to the record player 10 shown in Figure 1, if desired any other type of record player may be provided. Further, the invention has applications other than in record player turntables, for example, in machine tools where it is desired that the turntable is rotated at an exact selected speed, by adjusting the dimensions dand sand the frequency of the flashing lamp 30 as required to indicate when the turntable is rotated at the desired speed.

CLAIMS (Filed on 14/9182) 1. A turntable having means for mounting the turntable for rotation by a drive means about a central axis, the turntable including a rim having a plurality of apertures therein of equal width and equally spaced around the rim.

2. A turntable according to claim 1 wherein a light source adapted to flash at a predetermined frequency is positioned so as to shine through the apertures in a direction away from the central axis, said predetermined frequency and the spacing of the apertures being such that the apertures appear to remain stationary as the turntable rotates at a predetermined speed.

3. A turntable according to claim 1 or claim 2 wherein the turntable is made in synthetic plastics material by a moulding operation and the apertures

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (14)

**WARNING** start of CLMS field may overlap end of DESC **. edge flange of the turntable of the record player of Figure 1. Referring to the drawings, there is above a record player 10 comprising a deck plate 11 on which a turntable 12 is mounted for rotation about a central axis 12a. Aconventional centre spindle 13 is provided. The turntable is driven by a drive means comprising a drive flange 15 provided on the underside of the turntable 12 (shown in dotted lines) and a resilient belt 16 which passes around flange 15 and a spindle 17 of a motor 18 so that as the spindle 17 rotates, the turntable 12 is rotated. Two speed controls 19,20 are provided, the control 19 being movable to first and second positions so that when the control is moved to a first position the motor 18 is caused, in use, to rotate at a first high speed which, when transmitted to the turntable 12, through the belt 16 and flange 15, causes the turntable to rotate at approximately 45 r.p.m. When the control 19 is moved to the second position, the motor 18 is caused, in use, to rotate at a lower speed which, when transmitted to the turntable 12 through belt 16 and flange 15, rotates the turntable at approximately 3331 r.p.m. The other control 20, is a fine speed control and is for adjusting the speed of rotation of motor 18 and hence turntable 12, by a small amount to compensate for any production variations which occur in the drive means components, and to compensate for any wear in any of the drive means components. The turntable comprises a plate P on which a disc record may be placed, the centre hole of the disc record being placed over the centre spindle 13 of the record player. At the periphery of the platen P, there is an inclined donwardly depending edge flange 21 in which a plurality of apertures 22, in the present case 108, are provided, each aperture comprisng a central slot part 23 which extends through the flange 21 bounded by top and bottom inclined parts 24. The turntable has a diameter of 137.5mm, each aperture 22 has a horizontal width dimension dof 3mm and between each aperture 22 is a spacing part 25, each spacing part having a horizontal width s of 5mm. Above each aperture 22 and in each spacing part 25 between the apertures, is an embossed formation 26a, 26b, the formations 26b. The formations 26a, 26b and the inclined parts 24 provide an aesthetically pleasing appearance. In addition, the inclined parts 24 and an essentially similar configuration on the inner side of the flange 21 permit of moulding of the apertures during the turntable moulding operation without the need to provide for side coring. Located radially inwardly of the rim 21, beneath the turntable 12, a lamp 30 is mounted, which lamp is adapted to flash at a constant frequency. In the present case, the turntable motor 18 is a direct current motor powered through a transformer and rectifier circuit, from a 110V 60Hz mains electricity supply such as is commonly provided in the U.S.A. The lamp 30 is a light emitting diode and is arranged to flash at mains frequency i.e. 60Hz. Another light souce may be used if desired. The above described frequency, turntable diameter and number of apertures 22 are adapted to place the passage of an aperture 22 past the light source in phase with a flash of light emitted from the source when the turntable rotates at 3331 r.p.m. No means are provided for checking the speed of rotation at45 r.p.m. If desired, means may be provided whereby the frequency at which the lamp 30 flashes may be adjusted to give a different frequency, suitable to indicate a precise speed of 333 r.p.m. and 45 r.p.m. For example, a crystal divider network may be provided to give the required number of flashes per second; in this case the flashes will not be tied to the mains frequency. Alternatively, an indication of both 339 r.p.m. and 45 r.p.m. may be provided by using a single frequency source and providing two series of holes, one series being at the desired spacing for 33 r.p.m. and the other series for 45 r.p.m. Where the frequency of the flashing lamp 30 is not 60Hz, or where a turntable of a different radius is provided, the dimensions d and swill need to be arranged appropriately if they are to indicate when the turntable is rotating at 333 r.p.m. accurately. It is well known how to adjust these parameters and therefore it is considered that further discussion is not necessary. Referring again to the drawings, the record player further comprises a pick-up arm 31 mounted for movement about a horizontal axis H to lift and lower the arm 31 and about a vertical axis V to allow the pick-up arm 31 to be oved to the beginning of the record and translated across the record. A transducer comprisng a cartridge and stylus assembly 33 is provided at the end of the pick up arm 31. Although the invention has been described with reference to the record player 10 shown in Figure 1, if desired any other type of record player may be provided. Further, the invention has applications other than in record player turntables, for example, in machine tools where it is desired that the turntable is rotated at an exact selected speed, by adjusting the dimensions dand sand the frequency of the flashing lamp 30 as required to indicate when the turntable is rotated at the desired speed. CLAIMS (Filed on 14/9182)

1. A turntable having means for mounting the turntable for rotation by a drive means about a central axis, the turntable including a rim having a plurality of apertures therein of equal width and equally spaced around the rim.

2. A turntable according to claim 1 wherein a light source adapted to flash at a predetermined frequency is positioned so as to shine through the apertures in a direction away from the central axis, said predetermined frequency and the spacing of the apertures being such that the apertures appear to remain stationary as the turntable rotates at a predetermined speed.

3. A turntable according to claim 1 or claim 2 wherein the turntable is made in synthetic plastics material by a moulding operation and the apertures

are moulded in during said moulding operation.

4. Aturntable according to any one of claims 1 to 3 which is especially intended for use on a record player, and comprises a platen on which, in use, records are placed and a generally downwardly depending edge flange in which the apertures are provided.

5. A turntable according to claim 4 wherein the flange is inclined downwardly at an obtuse angle to the platen, thereby to facilitate a user seeing the light emitted from the apertures of the turntable.

6. A record player comprising a turntable according to any one of claims 1 to 5, means to adjust the speed of rotation of the turntable, a light source adapted to flash at a predetermined frequency related to the number of apertures in said rim so that the passage of an aperture past the light source is in-phase with a flash when the turntable is rotated at a predetermined speed, the light source being mounted on the record player radially inwardly of the rim of the turntable and a transducer for playing a record on the turntable.

7. A record player according to claim 6 wherein the turntable is rotated by a belt drive wherein an endless resilient belt is received around a flange provided on the underside of the turntable, and around a spindle of a motor.

8. A record player according to claim 6 wherein the turntable is rotated by a jockey pulley wheel type drive.

9. A record player according to claim 6 wherein the turntable is directly dirven from a motor.

10. A record player according to any one of claims 6 to 9 wherein two speed controls are provided, one to cause the turntable to be rotated at approximately 45 or 333 r.p.m. selectively, and a second control to permit small changes to be made in the speed of rotation of the turntable so that the speed of rotation may be accurately set.

11. A record player according to any one of claims 6 to 10 wherein the light source is adapted to flash at a frequency the same as the alternating current mains supply to the record player.

12. A turntable substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

13. A record player substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

14. Any novel feature or novel combination of features hereinbefore described and/or shown in the accompanying drawings.