GB2029933A - Improvements in pinch rollers for cassette tape recorders - Google Patents

Abstract

A pinch roller 10 for a magnetic tape recorder is mounted for rotary and tilting movement on a stationary pin 20 so as to be able to rotate on an axis parallel to that of the driving capstan. The roller has an axial cavity 12 of a diameter larger than that of the pin. <IMAGE>

Description

SPECIFICATION Improvements in pinch rollers for cassette tape recorders The present invention relates to pinch rollers used in magnetic tape recorders.

It is well known that the pinch roller is pushed against the tape driving capstan so that the magnetic tape gripped therebetween is driven by the capstan thus passing on the reading and recording magnetic heads of the cassette recorder.

The pinch roller usually comprises a cylinder having a surface of a yield material and being supported by a stationary shaft or pin integral with a support that is movable from a position where the roller is forced against the capstan to a position remote therefrom.

With such a construction a problem arises in having the capstan axis exactly parallel to the axis of rotation of the idle pinch roller, which capstan comprises a secion of a cylindrical rigid shaft that is rotated at the desired speed.

As a matter of fact, if the two axes were not parallel to each other, the tape would be released from the gripping action exerted by the capstan and pinch roller, thus moving either upwards or down wards according to the angle formed therebetween.

The most obvious solution to the problem is to provide the two axes as parallel to each other as possible. This solution, however, has a drawback firstly in the high costs for manufacturing elements having extemely strict tolerances and secondly in the strains to which elements such as spindles and supports are subjected to in the long run.

Many solutions according to the prior art use movable guides, such as rollers or pulleys which, however, are costly and furthermore cannot be used in cassette tape recorders.

Other solutions use stationary guides which, be sides being costly, make the structure of the device complex and are also excessively bulky to be used in cassette tape recorders where the space available is very reduced.

According to the present invention there is pro vided the combination of a pinch roller and a supporting pin for use in magnetic cassette tape recorders to push the magnetici tape against the driving capstan, wherein said roller has an axial cavity having a diameter larger than the diameter of said supporting pin, except for an area of limited axial dimension where said cavity and said pin are usually pivotally engaged with each other, and wherein said combination comprises stopping means allowing said roller to move angularly but limiting the axial movements thereof with respect to the pin, the parts being so arranged that said roller can move angularly with respect to said pin so that it can rotate about an axis of rotation parallel to the I axis of rotation of said capstan.

The present invention will now be described in greater detail, by way of example with reference to the accompanying drawing, wherein: Figure 1 is a diagrammatic axial sectional view of a preferred embodiment of the pinch roller; Figure 2 to 6 are similar sectional views of other embodiments; and Figure 7 shows, in an exaggerated way, how a pinch roller accommodates a capstan inclined in respect to the geometric axis of the pinch roller support.

Referring to Figure 1 the pinch roller 10, comprises a cylindrical body 11 having an axial cavity 12 and an outer covering 13 of a yielding material that engages the tape to grip the same against the capstan (not shown).

A dome 14 made of a yielding material and having a downwardly open spheric cavity 15 therein is integral with the inner part of cavity 12 and, accordingly, cylinrical body 11.

The stationary pin supporting pinch roller 10 comprises a cylindrical body 20 having a smaller diameter than cavity 12 and carrying a head 21 on the upper end thereof. The head 21 has a diameter substantially equal to the diameter of the cavity 15 of the dome 14 and it is connected to the body 20 through a neck 22.

The stationary pin 20 is integrally formed with a movable flat support 23.

With such an arrangement the roller 10 can assume any inclined position with respect to pin 20 and particularly a suitable inclined position in which the roller 10 can rotate about an axis parallel to the axis of rotation of the capstan. Moreover, with such a construction, the roller 10, the cylindrical surface of which is pushed in engagement with the capstan (not shown) by movable support 23, will automatically incline to the position in which the axis of rotation thereof is immediately parallel to the axis of rotation of the capstan, through suitable angular movements of dome 14 in respectto head 21.

It will be seen that the construction of the embodi mentshown in Figure 1, by which the roller 10 can be fitted over support 20 by slightly forcing elastic dome 14 to fit over spherica head 21, gives the pinch roller the further advantage of being readily assembled without manual operations, thus reducing the manufacturing costs.

As will be seen from the drawing, the structure described with reference to Figure 1 is substantially the same as the embodiments shown in Figures 2, 3 and 4, with the only difference that these embodiments do not comprise the snap-on articulated joint between roller 10 and supporting pin 20.

The pinch roller and the respective supporting pin as shown in these Figures have such a structure as to allow the roller axis to rotate with respect to the pin axis. In these Figures identical parts similar to the parts of the embodiment shown in Figure 1 are indicated by the same numerals provided with A in Figure 2, B in Figure 3 and C in Figure 4.

In the embodiment shown in Figure 2, the pinch roller 10A comprises an axial cavity 12A having an inner surface comprising two identical surfaces having the shape of two truncated cones placed on upside down on top of the other and connected to each other at the smaller bases thereof.

Accordingly, axial cavity 12B that receives pin 20 when the device is assembled, is flared and has increasing diameters from the centre to the two ends thereof. When the pinch roller is not in operation the engagement of the cylindrical surface of the cavity with the pin 20A occurs at the middle part 16 having the smallest diameter.

The axial movement of pinch roller 10A with respect to the pin 20A are limited by upper and lower circlips 24 and 25 received into suitable grooves on the pinch roller 1 OA that also has two axially directed annular grooves 18' and 19' formed on faces 18 and 19 thereof.

Also with this structure roller 10A can rotate about any axis of rotation different from the geometric axis of pin 20A parallel to the axis of rotation of the capstan.

It will be evident to those skilled in the art that the foregoing also refers to the embodiments shown in Figures 3 and 4.

With respect to Figure 3, thr axial cavity 12B of the roller 1 OB has larger diameter than the pin 20B, but an annular embossment 16B having a hole of a diameter slightly larger than the diameter of the pin 20B protrudes from the cylindrical surface of this cavity. The axial movement of roller 1 OB with respect to the pin 20B also limited by circlips 24B and 25B in this embodiment.

The embodiment shown in Figure 4 is very similar to the embodiment of Figure 3, with the only difference that the pin 20C is shorter and annular embossment 16C projecting outwardly from the surface of the axial cavity 12C of the roller is placed between a circlip 24C carried by the upper end of the pin 20C and a shoulder 25C forming the base thereof.

The embodiments shown in Figures 5 and 6 are basically identical with the embodiments described above, with the difference that the larger engaging surface of the stationary pin with the axial cavity of the roller is a portion of the pin and not of the roller.

In these Figures the parts identical with or similar to the parts shown in the preceding Figures are indi cated by the same reference numbers provided with a D and E, respectively.

In the embodiment of Figure 5 the surface of the axial cavity 12D of the roller 10D is perfectly cylindrical and receives a pin 20D having a larger diameter at its centre 16D and decreasing diameters towards the upper and lower ends thereof.

Circlips 24D and 25D carried by the top and the bottom of the pin 20D limit the axial movements of the roller 1 OD with respect to the pin 20D.

In the embodiment of Figure 6 both the inner surface of axial cavity 12E and the outer surface of the pin 20E are cylindrical and have different dia meters. However, the pin 20E comprises an outward ly protruding annular embossment 16E at its centre, which embossment 16E has a diameter slightly smaller than the cavity 12E.

Circlips 24E and 25E carried by the bottom and the top of the pin 20E limit the axial movement of roller 1 OE with respect to the pin 20D.

it should be noted now that in all the embodiments the engaging surfaces of the stationary pin with the axial cavity receiving the same may have a more or less convex profile in order to facilitate the inclining movements of the roller with respect to the axis.

Claims (11)

1. The combination of a pinch roller and a supporting pin for use in magnetic cassette tape recorders to puch the magnetic tape against the driving capstan, wherein said roller has an axial cavity having a diameter larger than the diameter of said supporting pin, except for an area of limited axial dimension where said cavity and said pin are usually pivotally engaged with each other, and wherein said combination comprises stopping means allowing said roller to move anugularly but limiting the axial movements thereof with respect to the pin, the parts being so arranged that said roller can move angularly with respect to said pin so that it can rotate about an axis of rotation parallel to the axis of rotation of said capstan.

2. The combination according to claim 1, wherein the wall of said cavity of said roller has integral therewith a dome of a yielding material having an axially arranged spheric seat, and said pin comprises a spheric seat, and said pin comprises a spheric head arranged to be pivotally received in said spheric cavity, the unit comprising said dome and said head forming both said engaging area of limited axial dimension and said stopping means limiting the axial movements of said roller with respect to said pin.

3. The combination according to claim 1, wherein said axial cavity of said roller comprises two cavities having the shape of two truncated cones jonted in the middle at the smaller bases thereof forming said engaging area of limited axial dimension.

4. The combination according to claim 1, wherein said cavity comprises an inwardly protruding annular embossment at its centre, said embossment having a hole of a diameter larger than the diameter of said pin, forming said engaging area of limited axial dimension.

5. The combination according to claim 1, wherein said pin comprises two identical parts having the shape of two truncated cones joined in the middle at the larger bases thereof forming said engaging area of limited axial dimension.

6. The combination according to claim 1, wherein said pin comprises an outwardly protruding annular embossment having a diameter slightly smaller than the diameter of said axial cavity of said roller, said embossment forming said engaging area of limited axial dimension.

7. The combination according to claims 3 and 5, wherein said truncated-cone surfaces are fitted together by an arcuated surface.

8. The combination according to claim 4, where in said stopping means limiting said axial move ments of said roller with respect to said pin comprise a circlip placed on top of said pin and an embossment protruding outwardly from the bottom of said pin and integral therewith, said annular emboss ment of said roller being received between said circlip and said annular embossment.

9. The combination according to any one of claims 3 to 7, wherein said stopping means comprise circlips placed on top of said pin and at the bottom thereof.

10. The combination according to any one of claims 3 to 8, wherein annular grooves are formed on the two axially directed annular faces of said roller.

11. The combination of a pinch roller and a supporting pin for use in magnetic cassette tape recorders, constructed substantially as herein de scribed with reference to and as illustrated in any one of Figures 1 to 6.