GB2096737A - Tape transport apparatus - Google Patents

Abstract

The apparatus is particularly applicable to cassette tape recorder/players for accurately and securely mounting the hubs on which the tape is wound on to the tape transport spindles to enable accurate tape transport to be achieved. The apparatus has a rotatable spindle 2 which is axially movable against the bias of a spring 4. The spindle carries cassette hub engaging means in the form of a resilient member 7 or an expansible collet. The spindle carries an abutment 9 or conical surface which engages the member 7 or collet respectively when the spindle is moved in the axial direction to urge these radially outwardly to a hub- engaging position. <IMAGE>

Description

SPECIFICATION Tape transport apparatus This invention relates to tape transport apparatus and, particularly but not exclusively, to tape transport apparatus for use with tape cassettes for tape recorders.

In a typical cassette tape recorder, the tape is wound round two hubs in the cassette housing and is transported between the two hubs for recording and playback purposes. The hubs are internally splined and are adapted to fit loosely over splined resiliently mounted drive spindles on the recorder apparatus. The clearance between the splines on the hub and the spindle is usually considerable to ensure ease of spline engagement and this arrangement has proved quite satisfactory for normal applications such as in cassette players for domestic purposes. However, the known arrangements have disadvantages when extremely high quality reproduction is required or when the environmental conditions of use are not ideal, especially when the apparatus is subjected to a great deal of vibration.

In circumstances where vibration is present, the hubs are liable to rattle, or oscillate, relative to the spindle on which they are mounted. This is not usually important on the take-up or wind-on side of the tape transport, as the cyclical tugging on the tape which results from the uneven drive is isolated from the record and replay head by the capstan and pinch roller which control the tape transport. On the supply side however, the resulting variations in tape tension can upset the smooth passage of the tape past the recording head. This arises because the tape is very slightly elastic and is therefore subject to cyclical stretching. This effect can be reduced by, for example, increasing the tape back tension in an attempt to prevent the rattle, or relative oscillation, being generated.This arrangement is only partially successful, however, in mitigating rattle and also has the disadvantage of applying extra loads to the tape and the apparatus, thereby reducing the effective life.

The present invention seeks to provide apparatus which overcomes the problems arising when a large clearance is provided between the hub and spindle.

According to the present invention there is provided tape transport apparatus including a rotatable spindle adapted to receive a tape carrying hub, and expansible hub engagement means adapted to drivingly connect the hub and spindle, the spindle or a part thereof being axially displaceable to move the hub engagement means between an expanded position and a contracted position in one of which positions the hub engagement means is adapted to drivingly connect said tape carrying hub with said spindle.

The hub engagement means may comprise a resilient member, axial movement of the spindle in a first direction causing the member to be clamped between an abutment with respect to which the spindle is relatively movable and an abutment fixed relative to the spindle for movement therewith, thereby to expand the resilient member radially to grip the hub to provide said driving connection between the hub and spindle.

In an alternative embodiment, the expansible hub engagement means comprises an expansible collet consisting of a plurality of collet segments disposed about the spindle and means on the spindle to urge the collet segments radially outwardly to a hub engaging position against a resilient bias.

Preferably the resilient bias is provided by a resilient ring or circlip around the collet segments.

Preferably the spindle includes a frusto-conical surface which when the spindle is axially displaced, is displaced to engage the collet segments to urge them radially outwardly. The arrangement may also include a fixed abutment having a fixed frusto-conical surface on to which the collet segments are urged when the spindle is axially displaced to provide a limited degree of axial movement of the collet segments, the fixed frusto-conical surface also serving to maintain the collet segments aligned.

Preferably, resilient means is provided for biassing the spindle in said first direction and the resilient means may comprise a coil spring mounted concentrically with the spindle. The hub is preferable rotatably mounted in a cassette housing but may, alternatively, comprise the hub of a spool on which said tape is wound.

The spindle may include a lead-in guide portion to guide the hub on the resilient member.

The present invention will now be described by way of example with reference to the accompanying drawings in which:~ Figure 1 shows a first embodiment in which the tape transport apparatus has hub engagement means in the form of a resilient member, and Figure 2 shows a second embodiment in which the hub engagement means comprises an expansible collet.

Figure 1 shows part of a chassis 1 of a cassette player in which a spindle 2 is rotatably supported in upper and lower ball bearings 3. The spindle is also free to move in the axial direction over a predetermined range of movement relative to the housing 1 and bearings 3. The spindle 2 is biassed downwardly in a first direction of movement by a coil spring 4 mounted concentrically about the spindle and acting between a spring stop 5 on the spindle and the inner race of the upper bearing 3.

The spindle 2 projects upwardly beyond the upper face of the housing 1. In this extended part, the spindle 2 has a portion 6 of reduced diameter around which a resilient hub engaging means 7 in the form of a rubber block is located. The upper end of the spindle 2 is conical and forms a lead-in portion or guide 8 which also provides a fixed abutment 9 for the resilient hub engaging means 7.

A further abutment is formed on a member 12 axially movable relative to the spindle 2 and includes a peripheral web 1 2a which abuts against the inner race of the upper bearing 3 and which thereby serves to locate the lower side of the hub engaging means 7 in an appropriate position.

The drawing also shows, in schematic form, part of a cassette having a cassette housing 10 in which a tape carrying hub 11 is rotatably mounted. In the usual way, the hub 11 is provided with a predetermined degree of free play in the axial direction. When the cassette is placed on the spindle 2, the conical lead-in portion 8 on each spindle locates the hub initially and centralises the hub with respect to the remainder of the cassette.

When the cassette player is in the unloaded position, an operating member which may be in the form of a lever or cam 13 is provided which urges the spindle 2 and hence the fixed abutment 9 against the bias of the spring 4 upwardly to a position in which the resilient means is unstressed. When a tape carrying cassette is pushed down onto the spindle past the lead-in portion 8, the hub 11 meets the somewhat elastic outside diameter of the resilient means 7 on which it is a slight interference fit. This interference not only ensures that the hub is accurately located on the spindle but is also sufficient to ensure that as the cassette is pushed down on the spindle the hub 11 is pushed up relative to the cassette housing until its upper surface 1 a abuts the under surface 1 Oa of the cassette housing 10.This ensures that the hub, and the reel of tape wound thereon, is located in the correct radial plane relative to the spindle.

A second action, such as closing the cassette player lid which action can also clamp the cassette and/or cause the record/play back head to engage the tape causes the lever 13 to be moved away from the spindle 2. The spindle 2 is then moved by the bias of the coil spring 4 in the said first direction of axial movement to thereby squash the resilient means 7 between the fixed abutment 9 on the spindle and the relatively movable abutment 12, which, at this stage, is being firmly urged against inner race of bearing 3. The act of compressing the resilient means 7 in the axial direction causes it to expand radially to firmly grip the hub 1 1 to thereby form a driving connection between the hub and the spindle.The hub may be the supply side of the tape transport in which case the transport of the tape will cause the hub to turn the spindle or, alternately, the spindle 2 may be deriven by known means (not shown) in which case the hub will be driven thereby and will comprise the take up side of the tape transport.

Referring now to Figure 2 there is shown an alternative embodiment utilising an expansible collet in place of the resilient member 7 of Figure 1. In other respects the embodiments are generally similar.

The spindle 20 consists of an inner spindle part 21 and an outer spindle sleeve 22 and is rotatably supported in two contiguous ball bearings 23, the outer races of which are fast in the cassette player housing 24. The spindle part 21 is axially displaceable over a predetermined range of movement and is biassed in a first direction by a concentrically mounted coil spring 25 acting between a stop 26 on the spindle and a fixed stop 27 which forms part of the spindle sleeve 22. The fixed stop 27 comprises a nut threadedly engaged with the sleeve 22 to clamp the sleeve to the inner races of the bearings so that it is rotatable but is not axially movable.

The inner spindle part 21 has on its upper end a conical lead-in guide 28 and adjacent this a frusto-conical surface 29 for engaging a collet (to be described). The spindle sleeve 22 has an annular flange 30 surmounted by a frusto-conical surface 31 opposed to the surface 29 and having the same cone angle.

A collet 32 is located about the spindle part 21 between the frusto-conical surfaces 29 and 30 and consists of three collet segments biassed inwardly and held together by a resilient ring 33 which may be an annular rubber '0' ring or a metal circlip.

The operation of this embodiment is as follows: As in the previous embodiment, when the cassette player is in the unloaded condition, a lever or cam 34 urges the spindle part 21 against the bias of the spring 25 upwardly to a position in which the collet 32 is retracted, the ring 33 biassing the collet segments inwardly. When a cassette carrying a tape wound on the hub 11 is placed on the spindle, the guide 28 guides the hub 11 on to and over the collet 32.

A second action, such as closing the cassette player lid causes the lever 34 to be moved away from the spindle part 21 which is then moved downwardly by the bias of the spring 25. The frusto-conical surface 29 thereby engages the collet segments and urges them downwardly and radially outwardly. The downward movement causes the collet segments to engage the frustoconical surface 30 on the spindle sleeve 22 and also draws the hub 11 down until it contacts the flange 30 of the spindle sleeve 22. This ensures that the hub and hence the tape wound thereon is located in the correct plane. Continued downward movement of the spindle part 21 urges the collet segments further outwardly to firmly engage the hub 11. Since the opposed frusto-conical surfaces 29, 30 have the same cone angle the collet segments are maintained accurately aligned.

The embodiments described are particularly applicable for use with miniature compact tape recorder sets but it will be appreciated that they could equally well be used with video cassettes or film, or film on tape held on large spools such as in reel-to-reel recorders.

Claims (12)

1. Tape transport apparatus including a rotatable spindle adapted to receive a tape carrying hub, and expansible hub engagement means adapted to drivingly connect the hub and spindle, the spindle or a part thereof being axially displaceable to move the hub engagement means between an expanded position and a contracted position, in one of which positions the hub engagement means is adapted to drivingly connect said tape carrying hub with said spindle.

2. Apparatus as claimed in claim 1 wherein the hub engagement means comprises a resilient member, axial movement of the spindle in a first direction causing the member to be clamped between an abutment with respect to which the spindle is relatively movable, and an abutment fixed relative to the spindle for movement therewith, thereby to expand the resilient member radially to grip the hub to provide said driving connection between the hub and spindle.

3. Apparatus as claimed in claim 1 wherein the expansible hub engagement means comprises an expansible collet consisting of a plurality of collet segments disposed about the spindle, and means on the spindle to urge the collet segments radially outwardly to a hub engaging position against a resilient bias.

4. Apparatus as claimed in claim 3 wherein the resilient bias is provided by a resilient ring or circlip extending round the segments.

5. Apparatus as claimed in claim 3 or 4 wherein the means on the spindle to urge the collet segments outwardly comprises a frusto-conical surface movable into engagement with the collet by axial movement of at least part of the spindle.

6. Apparatus as claimed in claim 5 wherein the spindle has an outer sleeve part and a central part axially movable relative to the outer sleeve part, the outer sleeve part being constrained against axial movement, said frusto-conical surface being formed on said central part.

7. Apparatus as claimed in claim 6 wherein a further frusto-conical surface opposed to said frusto-conical surface is formed on the outer sleeve part, axial movement of the control spindle part urging the collet axially into engagement with said further frusto-conical surface.

8. Apparatus as claimed in any one of the preceding claims wherein the spindle is biassed in the axial direction by a coil spring concentrically mounted about the spindle.

9. Apparatus as claimed in any one of claims 1 to 8 wherein the spindle is biassed in the direction to urge the hub engaging means to the expanded position.

10. Apparatus as claimed in any one of claims 1 to 9 wherein the spindle has a lead-in guide portion to guide the hub on to the hub engagement means.

11. Tape transport apparatus substantially as described herein with reference to and as illustrated in Figure 1 of the accompanying drawings.

12. Tape transport apparatus substantially as described herein with reference to, and as illustrated in Figure 2 of the accompanying drawings.