GB2122760A - Measuring torque on cassette player spindles - Google Patents

Abstract

A test cassette for measuring torque on the winding spindles of a cassette player comprises two reels (3) each comprising a hub portion (11) which is engageable with one of the winding spindles and an outer portion (13) on which a test tape (5) is wound and which is rotationally coupled to the hub portion by a spring (17) which permits limited rotational displacement of the outer reel portion relative to the hub portion due to torque between the two portions. For measuring the displacement, and therefore the torque, the hub portion is formed with an annular disc (19) provided on one side with a ring of indicating marks (23) and the outer reel portion has a flat annular section (21) which overlies the annular disc and is formed with a ring of windows (25) which correspond to the indicating marks and through which an opto-electronic device (27) can detect relative displacement between the windows and the marks and transmit a reading of this displacement to a location which may be remote from the cassette. <IMAGE>

Description

SPECIFICATION Test cassette for measuring torque on a winding spindle or spindles of a cassette player The invention relates to a test cassette for measuring torque on a winding spindle or the winding spindles of a cassette player, the cassette comprising two rotatable reels on which a test tape can be wound and which are arranged to fit one on each of the winding spindles and one or each of which comprises a first portion which is engageable with one of the winding spindles for rotation therewith and a second portion on which the test tape can be wound and which is rotationally coupled to the first portion by spring means which permit limited relative rotational displacement between the two portions against spring force.

A test cassette of this type is known from DE-OS 2110 400. In this known cassette the first portion of each reel is provided with a pointer and the associated second portion with a measuring scale. In the no-load condition the pointer and the scale are in a zero position. When the cassette is in use on a cassette player and one of the winding spindles of the player is driven the two portions of the reel on that spindle are rotationally displaced relative to each other in conformity with the torque between these two portions and the torque exerted can be read on the scale. A disadvantage of this construction is that the cassette must always be visible to the person carrying out the test. In the case of a closed cassette compartment the measurement value cannot be read and cannot be transmitted to a measuring instrument.

According to the invention there is provided a test cassette for measuring torque on a winding spindle or the winding spindles of a cassette player, the cassette comprising two rotatable reels on which a test tape can be wound and which are arranged to fit one on each of the winding spindles and one or each of which comprises a first portion which is engageable with one of the winding spindles for rotation therewith and a second portion on which the test tape can be wound and which is rotationally coupled to the first portion by spring means which permit limited relative rotational displacement between the two portions against spring force, wherein the first portion of said one or each reel comprises an annular indicator disc which is provided on one side with a ring of indicating marks, and the second portion of said one or each reel comprises a flat annular section which overlies the associated indicator disc on said one side thereof and which is formed with a ring of windows corresponding to the ring of indicating marks the indicator disc, and wherein means are provided in the cassette for detecting through the windows of said one or each reel relative displacement between these windows and the associated indicating marks upon relative rotational displacement between the two portions of the reel.

The detecting means can be readily constructed to provide torque measurement values that can be read independently of the test location and the location of the test cassette, so that a dynamic torque indication can be obtained in cassette decks in which the winding spindles are not exposed. For example, the detecting means can be constructed to sense the relative displacement between the windows and the indicating marks opto-electronically and to transmit the resulting signal to an electrical measuring instrument. Thus, the measurement can be carried without the test cassette being visible, and the measurement values can be displayed in convenient form on a measuring instrument or can be recorded.

In one embodiment of the invention the second portion of said one or each reel is coupled to the first portion thereof by spring means which permit limited relative rotational displacement between the two portions against spring force in both directions from a zero position. These spring means may comprise two springs each connected at one end to the first portion of the reel eccentrically of the rotational axis of the reel and at the other end to the second portion of the reel eccentrically of said axis.

With the above embodiment it is possible to measure torque on a winding spindle in both directions of rotation. This is of particular importance for the measurement of torque on winding spindles of equipment which can play in the forward and reverse direction (reverse operation).

The detecting means may comprise for said one or each reel a reflective light-barrier which is mounted in the cassette to be stationary relative to the reel and which has measuring elements which are directed at the indicating disc of the first portion of the reel through the windows in the second portion of the reel.

A reflection light-barrier is capable of emitting light with an LED element and of receiving the reflected light via a phototransistor. Depending on the amount of light reflected the measurement values can then be processed further into electronic pulses.

Embodiments of the invention will now be described in detail by way of example, with reference to the accompanying drawings, in which: Figure 1 is a plan view of one embodiment of a test cassette according to the invention with part of the cassette housing broken away, Figure 2 is a sectional view taken on the line Il-Il in Figure 1, Figures 3a and 4a are fragmentary plan views of the indicator disc and flat annular section of the two portions of one of the reels of the cassette of Figures 1 and 2, showing large and small relative displacements between the two portions during torque measurements.

Figures 3b and 4b show the pulse lengths obtained when measuring a large torque and a small torque, and Figure 5 is a plan view of one of the reels of an embodiment of a test cassette according to the invention for carrying out torque measurements in both directions.

The test cassette shown in Figures 1 and 2 comprises a housing 1 of conventional type containing two rotatable reels 3 on which a magnetic tape can be wound to be transported along the usual path via guide rollers 7 and a felt pressure pad 9. A small length of recording tape 5 is wound on the reels. The tape has a length such that it provides a playing time, and consequently a measuring time, of approximately 1 minute.

Each reel comprises an inner, hub portion 11 which is engageable in known manner with one of the winding spindles of a cassette player for rotation therewith, and an outer portion 13 which surrounds the hub portion and isjounalled thereon, for example, by means of a ball-bearing 15. The outer reel portion 13 is coupled to the hub portion 11 for rotation therewith by a flat spiral spring 17 which is connected at its ends to the reel portions 11 and 13 respectively and which is accommodated between an annular disc 19 on the hub portion 11 and a flat annular section 21 of the outer reel portion 13 which overlies the disc 19.This coupling permits a limited rotational displacement of the outer reel portion 13 relative to the hub portion 11 against the force of the spring 17, the spring being arranged so that the displacement of the outer reel portion takes place in the reverse direction to that in which the reel rotates when acting as the take-up reel, i.e., the reel onto which the tape is being wound when the reels are in motion.

On that side of the disc 19 of the hub portion 11 of each reel which faces the annular section 21 of the outer portion 13 of the reel there is provided a ring of substantially non-reflective indicating marks 23 of sectional shape which are evenly distributed around the axis of the reel and are separated by reflective intermediate portions of the disc 19, which thus serves as an indicator disc.

In the annular section 21 of the outer portion 13 of each reel there is formed a ring of windows 25 of sectional shape which correspond in number and distribution to the marks 23 on the indicator disc 1 9 of the hub portion 11 on the reel. The side of the annular section 21 which is remote from the disc 19 may be substantially non-reflective.

Under the influence of the respective spring 1 7 the two portions 11 and 13 of each reel normally occupy a zero position relative to one another in which the windows 25 in the outer reel portion 13 are fully coincident with the indicating marks 23 on the hub portion 11, that is to say, each window 25 coincides wholly with one of the marks 23, so that, since the marks are substantially nonreflective, no light impinging on the marks will be reflected back through the windows.

On the inner side of a wall of the cassette housing 1 , opposite the annular sections 21 of the outer portions 13 of the reels 3, are two reflection light-barriers 27, only one of which is shown.

Each of these reflection light-barriers can project light through the windows 25 in the associated annular section 21 onto the respective indicator disc 19 in the direction indicated by the arrow 29 as the respective reel rotates. If the tape 5 travels freely between the reels when the reels are in motion, the two portions 11 and 13 of the take-up reel are in the zero position relative to one another and no light from the reflection light-barrier 27 associated with this reel is reflected back through the windows 25 in the outer portion 13 of the reel. If the tape 5 cannot be driven freely because it is braked in the cassette, a torque is produced between the outer portion 13 of the take-up reel and the hub portion 11 of this reel, which torque displaces the outer reel portion rotationally relative to the hub portion against the force of the coupling spring 17 between the two portions.As a result of this displacement the reflective intermediate portions of the disc 1 9 of the hub portion 11 which lie between the non-reflective marks 23 on the disc begin to appear in the windows 25 in the outer reel portion 13, and light projected from the associated reflection lightbarrier 27 is reflected back from these reflective portions through the windows 25 in the direction of the arrow 31. The reflected light is received by the reflection light-barrier and produces signals which are transmitted as measurement signals by the light-barrier to a measurement processing and display device (not shown) via leads 33.In this processing circuit the amounts of light reflected by the reflective portions of the disc 1 9 are processed into electronic pulses, the length of each pulse being determined by the amount of each reflective portion which appears in the respective window 25, which amount is in turn determined by the torque between the outer portion 13 and the hub portion 11 of the take-up reel. Since the length of the pulses is thus proportional to this torque, the circuit can generate an electrical measurement value of the torque.

Electrical circuits which are capable of converting the relative pulse lengths into a measurement value independently of the frequency (i.e., the speed of rotation of the reel) are known and any suitable circuit may be used for this purpose.

Figure 3a shows a comparatively large relative displacement between the windows 25 and indicating marks 23 of the outer portion 13 and hub portion 11 respectively of a reel, which indicates that a comparatively large torque is being exerted between the two portions of the reel. The large relative displacement between the windows 25 and marks 23 results in a correspondingly large amount of each reflective portion of the disc 19 being exposed by the respective window 25. This produces a comparatively long period of light-reflection as each window 25 and associated mark 23 pass the relevant reflection light-barrier 27, and these reflections are converted into the long pulses 35 shown in Figure 3b.

If, as shown at 37 in Figure 4a, a smaller amount of each reflective portion of the disc 19 is exposed by the respective window 25, this indicates that a smaller torque is being exerted and, as shown in Figure 4h, shorter pulses 39 are produced, which may be substantially shorter than the intervals 41 between the pulses.

Although in the cassette described above both reels are constructed for torque measurement in a manner according to the invention, it is possible to have only one reel so constructed, in which case only one reflection light-barrier would be required.

Figure 5 shows a reel of an embodiment of the invention for carrying out torque measurements in both directions of rotation of the reel. The outer portion 13' of this reel is coupled to the hub portion 11' by two coil springs 47 which are each connected at one end to a projection 45 on the periphery of the hub portion 11'. The springs extend in opposite directions from the projection 45 and at their ends remote from the projection are connected to the outer reel portion 13' at or near the periphery thereof. The springs act in tension in opposite directions on the reel portion 13' to permit limited rotational displacement of this reel portion relative to the hub portion 11' in both directions from the zero position shown in Figure 5, as indicated by the double arrow 49.

This renders the cassette suitable for the measurement of torque on the winding spindles of equipment having a playback capability in both directions.

Claims (5)

1. A test cassette for measuring torque on a winding spindle or the winding spindles of a cassette player, the cassette comprising two rotatable reels on which a test tape can be wound and which are arranged to fit one on each of the winding spindles and one or each of which comprises a first portion which is engageable with one of the winding spindles for rotation therewith and a second portion on which the test tape can be wound and which is rotationally coupled to the first portion by spring means which permit limited relative rotational displacement between the two portions against spring force, wherein the first portion of said one or each reel comprises an annular indicator disc which is provided on one side with a ring of indicating marks, and the second portion of said one or each reel comprises a flat annular section which overlies the associated indicator disc on said one side thereof and which is formed with a ring of windows corresponding to the ring of indicating marks on the indicator disc, and wherein means are provided in the cassette for detecting through the windows of said one or each reel relative displacement between these windows and the associated indicating marks upon relative rotational displacement between the two portions of the reel.

2. A test cassette as claimed in Claim 1, wherein the second portion of said one or each reel is coupled to the first portion thereof by spring means which permit limited relative rotational displacement between the two portions against spring force in both directions from a zero position.

3. A test cassette as claimed in Claim 2, wherein the spring means of the coupling between the first and second portions of said one or each reel comprise two springs each connected at one end to the first portion of the reel eccentrically of the rotational axis of the reel and at the other end to the second portion of the reel ecentrically of said axis.

4. A test cassette as claimed in Claim 1,2 or 3, wherein the detecting means comprise for said one or each reel a reflective light-barrier which is mounted in the cassette to be stationary relative to the reel and which has measuring elements which are directed at the indicating disc of the first portion of the reel through the windows in the second portion of the reel.

5. A test cassette substantially as herein described with reference to Figures 1 to 4b or Figure 5 of the accompanying drawings.