GB1576484A - Tape decks - Google Patents

Description

(54) IMPROVEMENTS IN AND RELATING TO TAPE DECKS (71) We, ITT CONSUMER PRODUCTS (UK) LIMITED, a British Company, of Maidstone Road, Foots Cray, Sidcup, Kent, DA14 5HT, England, 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 cassette tape decks.

Known forms of cassette tape decks comprise a chassis made from a sheet metal stamping. This chassis has fixed on it all the components necessary to operate the tape cassette with the exception normally of the audio playback and record amplifiers and associated circuitry It is common to have a motor which directly drives a capstan via a band for drawing the tape past the tape head and to take indirect drives from the band and the capstan to rotate the tape spools both to maintain a correct winding tension and to provide fast forward and backward winding of the tape. To engage and disengage these indirect drives there is provided a row of manual controls mounted on one end of the chassis to control the various functions of the deck. Mechanical linkages connect these controls with various idler wheels to move them into and out of engagement with the motor drive band and capstan.

A very large number of linkages is required and in many cases with close telerances on the dimensions. Furthermore the assembly of these linkages onto the chassis is a different task. This requires a heavy investment in plant machinery to automate the production sufficiently to be able to produce the deck at a competitive price.

In another known deck three motors are employed, two capstan motors and one motor for fast winding and rewinding by means of pulleys and/or belts. Solenoids are used in this deck to operate a complex mechanism similar to a conventional mechanical deck.

It is an object of the present invention to simplify the construction of a cassette tape deck.

According to the present invention there is provided a tape cassette deck comprising a main chassis, first and second motors secured to the chassis for driving the respective tape spools, a third motor for driving a capstan, a sliding chassis carrying a tape head, a resilient pinch wheel, and a solenoid actuator mounted on the main chassis and coupled to move the sliding chassis between a retracted position in which the head and pinch wheel do not operatively engage the tape of a cassette and a forward position in which the head and pinch wheel do operatively engage the tape of a cassette and a forward position in which the head and pinch wheel do operatively engage the tape.

In order that the invention can be clearly understood reference will now be made to the accompanying drawings in which: Fig. 1 is a perspective view of a cassette tape deck and control module according to an embodiment of the invention Fig. 2 is an underside view of the deck and plan view of the module of Fig. 1, Fig. 3 is a circuit diagram of the control module of Figs. 1 and 2, and Fig. 4 is a wiring diagram of the control module and deck.

Referring to Figs. 1 and 2 the deck comprises a main chassis 1 and a sliding chassis or carrier 2 mounted on the main chassis so that it can slide backwards and forwards on the chassis 1 in the directions 2a. The carrier carries a playback and record head 3, a rubber pinch wheel 4 rigidly mounted on the carrier, and an erase head 5. The carrier is located laterally by means of slots 6 and 7 which are guided on pins 8 and 9 rigidly secured to the chassis underneath: The carrier leaf springs 10 and 11 each have a recess holding a ball captive against the upper surface of the carrier. Other bearing points (not shown) are formed by pimples on the underside of the carrier which bear on the surface of the chassis. Other ways of sup porting the carrier are possible. As seen more clearly ,in Fig. 2 a solenoid 12 has an armature 13-connected via a resilient link 14 to a pin 15 projecting downward from the chassis 2 through a slot 16 in the chassis 1.

-The pin is secured to the chassis 2 by a screw 17 (Fig. 13 just ahead of a further lateral restraining slot 18 and associated guide pin 19.:at the back of slot 18 is a resilient' buffer pad 20. The solenoid when energized, draws the carrier inwards so that the pinch wheel 4 engages a capstan drive spindle 21 of the capstan wheel 22 for driv ing the tape past the heads. A preferred form of solenoid is described in our co pending Application No. 8549/77 (Serial No. ). The heads 3 and 5 will engage the tape of a tape cassette (not shown) when in position located generally by the pins 8 and 9 and the height is deter mined by collars 8a and 9a and studs 86 and 96. When the solenoid is de-energised a spring 25 (Fig. 2) connected betwen the chassis and the pin 15 ensures the chassis 2 returns to its' rest position as is shown in the drawings.

The capstan wheel 22 is driven from a capstan drive motor M1 having a drive pulley wheel 27 and a drive belt 28 is located on the wheel 27 and in a groove 29 in the surface of the capstan wheel 22.

Each hub 23 and 24 is driven by its own indepedent d.c. motor M2 and M3 (Fig. 2) secured to the underside of the chassis. Pre ferably these motors have a negligible "cog ging" action created by the attraction of the metal armature to the permanent magnet field. A coreless armature motor would be suitable. In the main the motor M3 is more critical in this respect. A conventional tane position indicator 32 is mounted on the chassis and is driven by a drive belt 33 from the wind-on motor M3 by a pulley 34 mounted on the spindle of that motor.

A multi-pin connector socket 35 is mouned underneath the chassis and all the leads from the motors and the solenoid are wired into this socket. The leads from the heads are not shown but are taken to a separate plug. They can be in the same plug.

A wiring harness 36 connects the cassette deck with a control module 37 via plugs 38 and 39 and a socket 40 on the module.

It is possible to do away with the plug and socket at one end of the cable.

Module 37 comprises six switches 41 to 46 for controlling the rewind, record, stop, start, fast forward, and pause modes respectively of operation of the deck. Other modes, such as cue and review, are also possible. The push buttons are interlocked so that press intone button automatically releases the previous selection except for the pause con -trol, -whidh is independently, operable. The switches each have an upper set of contacts connected to an upper printed circuit board 47 and a lower set of contacts connected to a lower board 48 and the circuit and wiring diagrams of Figs. 3 and 4 are incorporated in the module 37.

Referring now to Fig. 3 the circuit basically comprises a solenoid drive circuit part 50 which controls the position of the sliding chassis 2, a wind motor control circuit part 51 which applies the correct voltage to the wind motors M2 and M3 and an: automatic stop circuit part 52 which receives a ripple voltage from the motors M2 and M3 caused by commutation in these motors and senses when this ripple ceases (i.e. at the ends of the tape) and automatically switches off the supply to all three motors Ml, M2 and M3.

Referring in greater detail to Fig. 3 the solenoid drive circuit part 50 comprises a pair of transistors T1 and T2 effective to provide a holding current through the solenoid 12 from the 12v supply via the start switch SW1, steering diode D1 and pause switch SW2 which is initially closed.

Initially the start switch SOW 1 is open and pause switch SW2 is closed and closure of SW1 by depressing the start push button 44 (Fig. 2) causes capacitor C, to be charged.

This has the effect of turning transistor T1 hard on to provide a relatively heavy initial current for about 1 second through the solenoid so that the carrier 2 moves firmly into its operative position. Diode D9 protects the base/emitter junction of transistor Tl. When the capacitor C1 is charged the charging current, suitably limited by R1, falls to zero and the transistor T2 provides the lower holding current via resistor R2 and transistor T1, turns off. It is not essential to use two transistors; it would be possible to arrange one transistor to provide both the heavy initial current and the subsequent holding current.

Broken lines 51 encompass the wind motor control circuit part. This comprises tran sistors T3 and T4 which apply, at the output terminal t the drive voltage to the motors M2 and M3 during fast rewind and fast forward, respectively. When the switch 41 (Fig. 4) is depressed this connects terminal t1 to motor M3 and terminal t2 to motor M2. When the switch 45 is depressed this connects terminal t, to motor M2 and terminal t2 to motor M3.

Referring now to the automatic stop cir cuit part shown within the broken line 52, the terminal t2 and t4 are connected respec tively to the motors M3 and M2. During normal playback, fast forward wind and rewind, each wind-on motor generates a ripple voltage due to the commutation in motor. Capacitors (:1 and C4 provide a.c.

coupling t9 the positive terminal of diode D8 where the a.c. ripple is amplified by transistor T5 and the amplified signal at the collector of T5 is of the order of 1 volt, Steering diode D3 prevents the HT supply from the rewind button feeding back to the capstan motor M1 and the solenoid drive circuit (see Fig. 4). The output from T5 is a.c. coupled by capacitor C5 to a voltage doubler rectifier formed by diodes D4 and D5 providing a d.c. voltage. -This is applied to the base of transistor Te, which is thus turned on. Te acts as a switch controlling a complementary bistable circuit formed by transistors T7 and T3 via steering diode D6.

In one stable state when transistor Te is on transistors T7 and T5 are both off and lamp L1 remains unlit. In other words as long as the ripple voltage from either motor is present and holding transistor T6 on then the auto stop circuit part recognises that the tape is still running and has not yet come to an end.

However when the tape comes to an end both motors M2 and M3 will stop and therefore the ripple voltage will cease. Consequently Te will switch off, the collector voltage of Te rises and Te switches on causing T7 to switch on, owing to the negative action of the bistable, which thus holds T5 on and causes the lamp L1 to light. The collector of T7 therefore rises from near chassis or earth potential to about 9 volts which causes transistor T9 to turn on and this "steals" the base voltage from transistor T4 bringing it to earth potential. Transistor T4 switches off and T5 switches off with the result that the drive voltage to the motor M2 or M3 connected to terminal t1 is switched off.

Also as the voltage at the collector of T7 rises the base voltage of T2 falls to its emitter potential, thus switching off and releasing the solenoid 12 so that the pinch roller 4 and tape heads 3 and 5 are moved away from the cassette tape.

Referring now to Fig. 4 each of the six control switches 41 to 46 comprises a double pole double throw slide switch with dual sets of connection terminals, one connected with the board 47 and another with the board 48 (Fig. 2). The wiring depicted in Fig. 4 will now be explained by reference to the control switches one by one.

Starting first with the fast forward switch 45, when this is depressed the wiper bridges the lower terminals. The wipers of the other switches will be in the upper rest position.

Operation of switch 45 causes terminal t2 to be connected to motor M3 and terminal t is connected to motor M2. Operation of switch 45 also provides power to the wind motor control circuit 51 established through the b and c terminals and the PLAY or START switch 44.

Also the terminals t5 and t4 for operation of the auto stop circuit 52 are connected respectively to motors M3 and M2 per manentlv.

While M3 is stationary there is no signal from the motor through terminal t2 to the emitter of transistor T10 and therefore T14 is initially: cut off, but as the motor M2 begins to rotate, M3 is also caused to rotate and an output voltage from M3 begins to develop at the terminal t2. The negativegoing portions of this signal are passed by the diode D2 so that, depending on the speed of rotation of M3 and hence the-state of wind (i.e. at the beginning of forward wind M3 will rotate slowly but towards the end it will be rotating more quickly than M2) the emitter of T10 receives a greater or lesser negative bias with respect to earth and so a greater or lesser current accordingly is drawn through T10 which thus controls the base of T4. This causes the output voltage at t1 to M2 to decrease the faster M3 goes so that the effect is to slow motor M2 towards the end of forward wind.

At the end of the tape run the ripple voltage detected by the auto stop circuit 52 at terminal t3 ceases and so the output from the wind motor control circuit ceases and motor M2 is de-energised.

The wind operation is carried out by the re-wind switch 41. This basically reverses the connections between the motor M2 and M3 and terminals t1 and t2 so that motor M3 is connected to terminal t1 via 45e, 45d, 44e, 44d, and motor M2 is connected to terminals t2 via 41b, 41c.

The PAUSE control switch 46 acts, when operated, to de-energise the solenoid 12 and prevents the autostop circuit working. The solenoid 12 is de-energised by opening the contact of SW2, which is represented in Fig.

4 by 46d and 46e.

The autostop circuit is prevented from operation, when the tape transfer stops, by means of switch P2 which is represented by 46e and 46f in Fig. 4. When closed this switch maintains transistor Te on thus preventing the bistable circuit T7 and Te latching. Also switch P3 is operated represented by 46b and 46c (Fig. 4) which removes the base voltage from transistor T4 and thus temporarily de-energises motor M2 via terminal t1. All three switches SW2, P2 and P3 are contained in switch 46.

The PLAY switch 44 when operated connects the power supply to the capstan motor M1 via contacts 44b and 44c. It also connects terminal t, to motor M2 to tension the tape, about 3 volts being necessary for this, via terminals 44e and 44f. The back tension caused by the counter drive 32, 33 and 34 for motor M3 is sufficient to keep a satisfactory back tension on the tape. Switch 44 also causes the solenoid 12 to be energised via terminals 44b, 44c and 46d, 46e.

The STOP switch basically disconnects the power supply by releasing all the other switches by a latching bar (not shown).

The RECORD. switch controls the record/ playback amplifier and is not shown in detail. A safety. device would be incorporated in .the form of a switch which senses whether a - pre-recorded cassette has been placed on the deck, in which case this switch remains unoperated to prevent accidental erasure of the recording. Further of Ferric/chrome tape switch would be incorporated in a manner known in the art.

Although electromechanical switching has been .described, touch controls would :also be used, with or without a remote control arrangement using for example ultrasonic signals.

WHAT WE CLAIM IS:- 1. A tape cassette deck comprising a main chassis, first and second motors secured to the chassis for driving the respective tape spools, a third motor for driving a capstan, a sliding chassis carrying a tape head, a resilient pinch wheel, and a solenoid actuator mounted on the main chassis and coupled to move the sliding chassis between a retracted position in which the head and pinch wheel do not operatively engage the tape of a cassette and a forward position in which the head and pinch wheel do operatively engage the tape.

2. A deck according to claim 1, in which the pinch wheel is mounted on the sliding chassis.

3. A deck according to claim 2, in which the pinch wheel determines the forward limit of. movement of the sliding chassis into the second position.

4. A deck according to claim 2 or 3, wherein the sliding chassis is biassed towards the retracted position by a first relatively weak spring and is coupled to the solenoid by a resilient link which is relatively strong and which determines the pinch roller pressure with the capstan of the deck.

5. A deck according to claim 1, '2, - 3 or 4, wherein the main chassis comprises a-first flat portion carrying underneath it the capstan flywhel and the spool motors, the sliding chassis being mounted on top of the first portion, and a second stepped-down portion connected to the first portion and having the solenoid and capstan motor mounted side-by-side on top of it, the shaft of the capstan motor and the armature of the solenoid projecting through apertures in the stepped-down portion.

6. A cassette' -deck substantially as hereinbefore described with reference to Figs. 1 and 2 - of the accompanying drawings.

7. A deck according to any preceding claim operatively coupled only by electric leads with a set of manual controls and an electric circuit whereby to control PLAY, PAUSE, FAST FORWARD, REWIND, RECORD and STOP functions of the deck.

8. A deck according to claim 7 wherein the circuit is connected to sense the ripple voltage of at least one of the spool motors and is arranged to cause the dlck to revert to the STOP mode when the ripple voltage ceases at the end of the tape.

9. A deck according to claim 7 or 8 wherein the circuit is arranged to sense the ripple voltage of one of the spool motors and to so control the voltage supplied to the other motor in response thereto as to reduce the applied voltage towards the end of the tape in the fast forward or rewind mode and thus slow the tape transfer towards the end of the tape.

10. A deck according to any one of claims 1 to 6 operatively coupled with a set of manual controls and an electric circuit, the circuit being substantially as hereinbefore described with reference to Figure 3 and Figure 4 of the accompanying drawings.

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

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. the power supply by releasing all the other switches by a latching bar (not shown). The RECORD. switch controls the record/ playback amplifier and is not shown in detail. A safety. device would be incorporated in .the form of a switch which senses whether a - pre-recorded cassette has been placed on the deck, in which case this switch remains unoperated to prevent accidental erasure of the recording. Further of Ferric/chrome tape switch would be incorporated in a manner known in the art. Although electromechanical switching has been .described, touch controls would :also be used, with or without a remote control arrangement using for example ultrasonic signals. WHAT WE CLAIM IS:-

1. A tape cassette deck comprising a main chassis, first and second motors secured to the chassis for driving the respective tape spools, a third motor for driving a capstan, a sliding chassis carrying a tape head, a resilient pinch wheel, and a solenoid actuator mounted on the main chassis and coupled to move the sliding chassis between a retracted position in which the head and pinch wheel do not operatively engage the tape of a cassette and a forward position in which the head and pinch wheel do operatively engage the tape.

2. A deck according to claim 1, in which the pinch wheel is mounted on the sliding chassis.

3. A deck according to claim 2, in which the pinch wheel determines the forward limit of. movement of the sliding chassis into the second position.

4. A deck according to claim 2 or 3, wherein the sliding chassis is biassed towards the retracted position by a first relatively weak spring and is coupled to the solenoid by a resilient link which is relatively strong and which determines the pinch roller pressure with the capstan of the deck.

5. A deck according to claim 1, '2, - 3 or 4, wherein the main chassis comprises a-first flat portion carrying underneath it the capstan flywhel and the spool motors, the sliding chassis being mounted on top of the first portion, and a second stepped-down portion connected to the first portion and having the solenoid and capstan motor mounted side-by-side on top of it, the shaft of the capstan motor and the armature of the solenoid projecting through apertures in the stepped-down portion.

6. A cassette' -deck substantially as hereinbefore described with reference to Figs. 1 and 2 - of the accompanying drawings.

7. A deck according to any preceding claim operatively coupled only by electric leads with a set of manual controls and an electric circuit whereby to control PLAY, PAUSE, FAST FORWARD, REWIND, RECORD and STOP functions of the deck.

8. A deck according to claim 7 wherein the circuit is connected to sense the ripple voltage of at least one of the spool motors and is arranged to cause the dlck to revert to the STOP mode when the ripple voltage ceases at the end of the tape.

9. A deck according to claim 7 or 8 wherein the circuit is arranged to sense the ripple voltage of one of the spool motors and to so control the voltage supplied to the other motor in response thereto as to reduce the applied voltage towards the end of the tape in the fast forward or rewind mode and thus slow the tape transfer towards the end of the tape.

10. A deck according to any one of claims 1 to 6 operatively coupled with a set of manual controls and an electric circuit, the circuit being substantially as hereinbefore described with reference to Figure 3 and Figure 4 of the accompanying drawings.