GB1585084A

GB1585084A - Tape recorders

Info

Publication number: GB1585084A
Application number: GB1857176A
Authority: GB
Original assignee: NORTH EAST AUDIO Ltd
Current assignee: NORTH EAST AUDIO Ltd
Priority date: 1977-04-25
Filing date: 1977-04-25
Publication date: 1981-02-25

Description

(54) IMPROVEMENTS RELATING TO TAPE RECORDERS (71) We, NORTH EAST AUDIO LIMITED, a British Company, of 5, Charlotte Square, Newcastle-upon-Tyne, NE1 4XF, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to tape recorders in which a recording medium is transferred from one reel to another.

As is well known, in a tape recorder of the cassette type, the tape is permanently secured at its ends to the motor-driven reels of the cassette. It has been found that when the tape is being fast wound, difficulties can occur when the end of the tape is reached as will be more fully explained hereinafter and which may result in damaging or even braking the tape. Various forms of end-of-tape sensing devices are known but it would be necessary to provide two such devices to cater for fast winding of the tape in either direction and this would be uneconomic.

According to the invention, there is provided a tape recorder in which a recording medium is transferred from one reel to another, said reels being driven via clutch mechanisms that can slip at different torque values dependent upon the direction of rotation, the clutch mechanism associated with one of said reels being capable of slipping at a lower torque value than the clutch mechanism associated with the other reel when rotating in one direction, and the clutch mechanism associated with the other of said reels being capable of slipping at a lower torque value than the clutch mechanism associated with the one of said reels when rotating in the opposite direction.

According to one embodiment each clutch mechanism comprises a pair of clutch plates having engaging teeth thereon, the inclination of the faces on one side of the teeth to the plane at right angles to the axis of the clutch being greater than the inclination to said plane of the faces on the other side of the teeth.

To allow for the fast winding of the tape in either direction, a pair of such clutch mechanisms would be provided with the inclination of the tooth faces being disposed in opposite senses on the respective clutch mechanisms.

According to a preferred embodiment, the faces of the teeth are inclined at 15" and 45" respectively to the plane at right angles to the axis of the clutch.

The invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a diagram illustrating the problem to be overcome, Figure 2 is a vertical section through a cassette deck incorporating clutches in accordance with the invention, Figures 3 to 5 are views of the upper clutch plate of one of the clutches, Figure 6 shows the lower clutch plate of said one clutch, Figures 7 and 7a illustrate the formation of the clutch teeth, Figures 8 to 10 are views of the upper clutch plate of the other clutch, Figure 11 shows the lower clutch plate of the other clutch, Figures 12 and 12a illustrate the formation of the clutch teeth, and Figure 13 is a diagrammatic fragmentary view illustrating the differential action of the clutch mechanisms.

Referring first to Figure 1, the reel A of a cassette recorder is being fast driven in the direction of arrow a and the reel B is freely rotating in the direction of the arrow b. As the end of tape position approaches, as indicated in E1, the tape C is still moving in the direction of the solid arrow. At a point E2 however, further rotation of the reel B in the same direction will tend to rewind the tape on to the reel B in which case the direction of movement of the tape is reversed as indicated by the dotted arrow. This does in fact occur for a short time until equilibrium is reached, notwithstanding that the reel A is being positively driven. The use of clutch mechanism according to the present invention overcomes this disadvantage.

Referring to Figures 2-13, 10 is a cassette deck having the driving spindle 11 of a motor 12 extending through a hub 13 on the deck.

A clutch mechanism comprises a lower plate 14 fixed to the shaft 11 and an upper plate 15 slidably engaging the shaft 11, as more fully described below. The clutch plate 15 has a tubular portion 16 having an hexagonal outer face upon~which is mounted a reel hub 17 having an hexagonal opening therein to engage the tubular portion 16. The reel hub 17 is provided with splines 18 for known purposes not relevant to the present invention.

A cap 19 is secured to the upper end of the shaft 11 and a spring 20 is located between the lower face of the reel hub 17 and the upper face of the clutch plate 15. The clutch plate 15 is formed with an annular V-groove 21 for known purposes not relevant to the present invention.

Referring now to Figures 3-7a, Figures 3-5 are corresponding front, back and side elevations of the upper clutch plate of one of the clutches. The circular clutch plate 22 has a central aperture 23 for slidably engaging the motor shaft 11 and is formed with teeth 24.

The plate 22 also has a tubular portion 25 of hexagonal external cross-section for engagement by the reel hub 17.

Figure 6 shows the lower clutch plate of the clutch. The circular clutch plate 26 is formed with a central aperture 27 for attachment to the motor shaft 11 and with teeth 28 for engagement with the teeth 24 of the clutch plate 22. The formation of the teeth 28 is illustrated in Figures 7 and 7a which are developed views at different radii on the clutch plate. It will be seen that the clutch teeth are irregular in cross-section, having faces 28a inclined at a small angle to a plane at right angles to the axis of the clutch and faces 28b inclined at a substantially greater angle thereto.

The teeth on the clutch plate 22 are correspondingly formed.

Figures 8-10 show the upper catch plate of the other clutch, Figure 11 the lower clutch plate thereof, and Figures 12 and 12a the formation of the clutch teeth. These figures are similar to those illustrating the one clutch and will not be described in detail except to point out that the positioning of the inclined faces of the clutch teeth is of course reversed.

Figure 13 is a diagrammatic fragmentary view illustrating the differential action of the clutch mechanisms.

Clutch plate A, which corresponds to clutch plate 22, is shown approaching engagement with the clutch plate B which corresponds to clutch plate 26, with the faces 30 of the teeth on plate A coming into engagement with the faces 31 of the teeth on plate B and the faces 32 of the teeth on plate A coming into engagement with the faces 33 of the teeth on plate B.

The faces 30 and 31 are inclined at an angle to to a plane at right angles to the axis of the clutch and the faces 32 and 33 at an angle a thereto which is substantially smaller than the angle ,B.

The force exerted by the spring 20 is represented by P. It will be readily appreciated that when the clutch plate B is being driven in the direction of the arrow X with the faces 32 and 33 in driving engagement, a smaller torque is required to disengage the clutch than when the clutch plate B is being driven in the direction of the arrow Y when the faces 30 and 31 are in driving engagement. As stated hereinbefore, the angle a is made as small as practicable in order to effect disengagement of the clutch in one direction at the smallest torque.

It will also be seen that the provision of a pair of oppositely acting differential clutches in the mechanism of a cassette recorder as described above, will enable the clutches to disengage immediately at the end-of-reel posi tion when fast winding in either direction.

The clutch plates may be made of any suit able material but are advantageously made of nylon.

WHAT WE CLAIM IS: 1. A tape recorder in which a recording medium is transferred from one reel to another, said reels being driven via clutch mechanisms that can slip at different torque values dependent upon the direction of rota tion, the clutch mechanism associated with one of said reels being capable of slipping at a lower torque value than the clutch mech anism associated with the other reel when rotating in one direction, and the clutch mech anism associated with the other of said reels being capable of slipping at a lower torque value than the clutch mechanism associated with the one of said reels when rotating in the opposite direction.

2. A tape recorder according to claim 1, wherein each clutch mechanism comprises a pair of clutch plates having engaging teeth thereon, the inclination of the faces on one side of the teeth to the plane at right angles to the axis of the clutch being greater than the inclination to said plane of the faces on the other side of the teeth.

3. A tape recorder according to claim 2, wherein each clutch mechanism comprises a lower clutch plate fixed to a shaft, an upper clutch plate slidably engaging said shaft, the upper clutch plate having a tubular portion on which is mounted a reel hub, a cap at the upper end of said shaft for retaining the reel hub, and a spring located between the lower face of the reel hub and the upper face of the upper clutch plate.

4. A tape recorder according to claim 3, wherein the reel hub is provided with splines.

5. A tape recorder according to claim 3 or 4, wherein the upper- clutch plate is formed with an annular V-groove.

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

Claims

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

Referring to Figures 2-13, 10 is a cassette deck having the driving spindle 11 of a motor 12 extending through a hub 13 on the deck.

A clutch mechanism comprises a lower plate 14 fixed to the shaft 11 and an upper plate

15 slidably engaging the shaft 11, as more fully described below. The clutch plate 15 has a tubular portion 16 having an hexagonal outer face upon~which is mounted a reel hub

17 having an hexagonal opening therein to engage the tubular portion 16. The reel hub

17 is provided with splines 18 for known purposes not relevant to the present invention.

A cap 19 is secured to the upper end of the shaft 11 and a spring 20 is located between the lower face of the reel hub 17 and the upper face of the clutch plate 15. The clutch plate 15 is formed with an annular V-groove 21 for known purposes not relevant to the present invention.

Referring now to Figures 3-7a, Figures 3-5 are corresponding front, back and side elevations of the upper clutch plate of one of the clutches. The circular clutch plate 22 has a central aperture 23 for slidably engaging the motor shaft 11 and is formed with teeth 24.

The plate 22 also has a tubular portion 25 of hexagonal external cross-section for engagement by the reel hub 17.

Figure 6 shows the lower clutch plate of the clutch. The circular clutch plate 26 is formed with a central aperture 27 for attachment to the motor shaft 11 and with teeth 28 for engagement with the teeth 24 of the clutch plate 22. The formation of the teeth 28 is illustrated in Figures 7 and 7a which are developed views at different radii on the clutch plate. It will be seen that the clutch teeth are irregular in cross-section, having faces 28a inclined at a small angle to a plane at right angles to the axis of the clutch and faces 28b inclined at a substantially greater angle thereto.

The teeth on the clutch plate 22 are correspondingly formed.

Figures 8-10 show the upper catch plate of the other clutch, Figure 11 the lower clutch plate thereof, and Figures 12 and 12a the formation of the clutch teeth. These figures are similar to those illustrating the one clutch and will not be described in detail except to point out that the positioning of the inclined faces of the clutch teeth is of course reversed.

Figure 13 is a diagrammatic fragmentary view illustrating the differential action of the clutch mechanisms.

Clutch plate A, which corresponds to clutch plate 22, is shown approaching engagement with the clutch plate B which corresponds to clutch plate 26, with the faces 30 of the teeth on plate A coming into engagement with the faces 31 of the teeth on plate B and the faces 32 of the teeth on plate A coming into engagement with the faces 33 of the teeth on plate B.

The faces 30 and 31 are inclined at an angle to to a plane at right angles to the axis of the clutch and the faces 32 and 33 at an angle a thereto which is substantially smaller than the angle ,B.

The force exerted by the spring 20 is represented by P. It will be readily appreciated that when the clutch plate B is being driven in the direction of the arrow X with the faces 32 and 33 in driving engagement, a smaller torque is required to disengage the clutch than when the clutch plate B is being driven in the direction of the arrow Y when the faces 30 and 31 are in driving engagement. As stated hereinbefore, the angle a is made as small as practicable in order to effect disengagement of the clutch in one direction at the smallest torque.

It will also be seen that the provision of a pair of oppositely acting differential clutches in the mechanism of a cassette recorder as described above, will enable the clutches to disengage immediately at the end-of-reel posi tion when fast winding in either direction.

The clutch plates may be made of any suit able material but are advantageously made of nylon.

WHAT WE CLAIM IS: 1. A tape recorder in which a recording medium is transferred from one reel to another, said reels being driven via clutch mechanisms that can slip at different torque values dependent upon the direction of rota tion, the clutch mechanism associated with one of said reels being capable of slipping at a lower torque value than the clutch mech anism associated with the other reel when rotating in one direction, and the clutch mech anism associated with the other of said reels being capable of slipping at a lower torque value than the clutch mechanism associated with the one of said reels when rotating in the opposite direction.
2. A tape recorder according to claim 1, wherein each clutch mechanism comprises a pair of clutch plates having engaging teeth thereon, the inclination of the faces on one side of the teeth to the plane at right angles to the axis of the clutch being greater than the inclination to said plane of the faces on the other side of the teeth.
3. A tape recorder according to claim 2, wherein each clutch mechanism comprises a lower clutch plate fixed to a shaft, an upper clutch plate slidably engaging said shaft, the upper clutch plate having a tubular portion on which is mounted a reel hub, a cap at the upper end of said shaft for retaining the reel hub, and a spring located between the lower face of the reel hub and the upper face of the upper clutch plate.
4. A tape recorder according to claim 3, wherein the reel hub is provided with splines.
5. A tape recorder according to claim 3 or 4, wherein the upper- clutch plate is formed with an annular V-groove.
6. A tape recorder according to any of

claims 2 to 5, wherein the faces of the teeth of the clutch plates are inclined at 150 and 45" respectively to the plane at right angles to the axis of the clutch.
7. A tape recorder according to any of claims 2 to 6, wherein the clutch plates are made of nylon.
8. A tape recorder substantially as herein before described with reference to the accom panying drawings.