GB2126405A - Changeover mechanism for a tape recorder - Google Patents

Abstract

Changeover mechanism for a tape recorder provides interchange between operating modes without large solenoids which consume too much battery power. Gear 1 is rotated by capstan shaft 2 driven by the main motor. Half-gears 3A and 3B when driven by engagement with gear 1 rotate cams 15 and swing spring-biassed cam- followers 22 outwards about pivots 23. Return through the other half revolution of the half-gears 3A, 3B is effected by pressure of followers 22 against cams 15. These movements are controlled by stops 18 engaging projections 12 and being disengaged by swinging arms 17 by operation of devices 19. Gear 3A pulls on slide 66 to press the pinch roller towards the capstan for the record, reproduce, and fast forward modes while gear 3B swings arm 55 carrying drive rollers 57, 58 which engage respective tape-reel supports for tape take-up in forward and reverse modes, respectively. In another embodiment (Figures 2,3,10) a single half- gear with cam controls all modes, setting of different modes being detailed (Figure 10). A detection device ((27) Figures 2,3) actuated by rotation of gear (3) controls power supply to drive device 19 to prevent unwanted supply of power. Specific drive devices 19 (e.g. a solenoid) are specified (Figures 5, 6). Changeover switch operation is described (e.g. Figures 8, 11) involving charging a capacitor for return operation. Return of the nick gear(s) by spring operation offsets power failure or plug disconnection. Battery supply may be used (Figure 12). The detector device may alternatively be coupled to head or cam plate movement. <IMAGE>

Description

SPECIFICATION Changeover mechanism for a tape recorder The present invention relates to a changeover mechanism for a tape recorder for switching the drive system between different operating modes such as the recording mode, the reproducing or play-back mode, the rewind mode and the fast forward mode and the OFF state.

A tape recorder operates by selectively applying the rotational force of a drive motor in accordance with the required operating mode. The selection of the operating mode is conventionally effected by means of a large solenoid for each mode and such a solenoid consumes a large amount of electrical power. For a portable tape recorder using batteries as a power source this is a significant disadvantage.

Moreover the solenoid is required to generate a large operating force and this requires a large core using heavy iron and copper. This is unsuitable for a portable tape recorder which should be small and of light weight.

In addition the solenoid creates noise by impact when it is actuated, which is unpleasant for the operator.

On the other hand, if power failure occurs when the tape recorder is connected to mains supply and thus the supply of current to the tape recorder is interrupted, operation may stop while the components of the machine are in the driving condition. As a result a tape may be broken or the components may be subjected to excessive forces which disturb their smooth running.

To overcome these difficulties the present invention provides a changeover mechanism for a tape recorder including a drive pinion rotated by the drive motor of the tape recorder, a nick gear having a first circumferential portion which is toothed to engage the drive pinion, and a second circumferential portion which is toothless, with two dwell zones separating the first and second portions, and two abutments having the same angular separation as the dwell zones, a lock bar having a detent engageable with each of the abutments to lock the nick gear against rotation in a position in which one of the dwell zones is adjacent the drive pinion and disengageable by a swinging motion effected by a drive device, a cam mounted for rotation with the nick gear and engaging an operating link which is biassed against a cam surface of the cam which varies continuously in distance from the axis of rotation of the nick gear and cam between a maximum and a minimum distance, the arrangement of the cam surface being such that the operating link is driven outwards by the cam when the nick gear is driven by the drive pinion and the pressure of the operating link on the cam thereafter rotates the nick gear back to its initial position, and a detecting means actuated by the rotation of the nick gear to control the supply of electrical power to the drive device which disengages the detent.

With such a mechanism each operating mode may be independently set and automatically reset to the off state by the spring bias acting on the cam through the operating link without the use of electrical power for re-setting. Thus if power is interrupted the mechanism will re-set itself to the off state. Power consumption is much reduced since only a short pulse is required to release the detent and rotation of the nick gear by the drive pinion takes little power.

The invention will now be described in more detail with the aid of examples illustrated in the accompanying drawings, in which: Figure 1 is a plan view of a tape recorder showing the arrangement of the components of the tape transport mechanism, Figure 2 is a plan view of a changeover mechanism in accordance with the invention in the OFF state, Figure 3 is a plan view of the mechanism of Figure 2 in the operating state, Figure 4 is a plan view of an alternate embodiment of the changeover mechanism, Figure 5 is a detail of a drive device for a lock bar in the mechanism of Figures 2 and 3 or Figure 4, Figure 6 is a detail of an alternative drive device, Figure 7 shows the detent at the end of the lock bar, Figure 8 is a schematic circuit diagram for the control of a changeover mechanism according to the invention, Figure 9 shows voltage waveforms to illustrate the timing of the operation of the changeover mechanism, Figure 10 is a detail of a mechanism for converting the movement of the operating link of the changeover mechanism into the setting of different operating modes, Figure 11 is a more detailed circuit diagram relating the mechanisms of Figure 10 to the circuit of Figure 8, and Figure 12 is a circuit diagram for battery operation.

The plan view of Figure 1 shows the operational and functional parts of a tape-recorder assembled on a chassis 50. A pair of shafts 51 and 52 project from the upper surface of the chassis at a spacing equal to the distance between the centres of the two reel hubs of the tape cassette which is used.

The shaft 51 rotatably carries a supply reel support 53 and an outer shaft 53a for engagement with the reel hub of a tape cassette. In the same way the shaft 52 rotatably carries a wind-up or take-up reel support 53 and an outer shaft 54a for engagement with a reel hub of a tape cassette.

A first idler 57 is engageable with the circumference of the take-up reel support 54to transmit a rotational force to the reel support for forward movement of the tape. For reverse movement a second idler 58 is engageable with the supply reel support 53 and by engagement also with the periphery of the idler 57 transmits drive from the idler 57 to rotate the support 53 in the 6pposite sense to the rotation of the support 54. The idlers 57 and 58 are rotatably mounted on one arm of an L-shaped lever 55 which is pivotally mounted to the back of the chassis 50 by a pin 56.

A capstan 61 rotatably supported on the surface of the chassis 50 by way of a bearing 62 carries a flywheel 60 which is arranged below the chassis 50 and driven by a drive motor 63. The output shaft of the motor 63 carries a pulley 64 and a powertransmitting belt 64' passes around the pulley 64, the flywheel 60 and a pulley 59 which is fixed coaxially to the idler 57, the motor thus driving the capstan 61 and the idler 57.

Aflat L-shaped mounting board 66 is mounted on the surface of the chassis 50 for sliding movement in the direction of the arrow Z. A front piece 66a of the board 66 carries a recordingireproducing head 69 and a pinch roller 67 which is rotatably mounted on a supporting bracket 68. The pinch roller 67 serves in conventional manner to press the tape against the capstan 61 for forward drive so that the tape is drawn past the head 69. A side piece 66b of the mounting board 66 has at its end a hook 72 for engagement with arm end 55a of lever 55 so that when the pinch roller 67 is disengaged the lever 55 is swung to first disengage the idler 57 and then bring the idler 58 into engagement with the reel support 53 to effect reverse drive.

A tension spring 70 exerts a biassing force on the mounting board 66 tending to disengage the pinch roller 67 from the capstan 61. Atension spring acting between the lever 55 and the chassis 50 (not shown in Figure 1) biases the idler 57 towards the take-up reel support 54.

Referring now to Figures 2 and 3, which show the change-over mechanism for the tape-recorder, a drive pinion 1 is mounted on a shaft 2 which is the capstan shaft on which the flywheel 60 is mounted.

The pinion 1 is thus continuously driven by the motor 63 in an anti-clockwise direction, as shown by the arrow. The pinion 1 cooperates with a nick gear 3 which has a first circumferential portion 4with teeth for engagement with the pinion 1, a second circumferential portion 5 which is toothless and two dwell zones 6-1 and 6-2 dividing the portions 4 and 5 and located, in this embodiment, at an angular spacing about the centre of the nick gear 3 of 180 . The face of the nick gear 3 has an annular groove 8 defined between an inner wall 9 and an outer wall 10. Two abutments 11-1 and 11-2 are formed by projections 12 on the inner wall 9. Inward projections 13 on the outer wall 10 upstream of the projections 12 ensure that a detent 18 on the end of a locking bar 17 is positioned to engage the abutments 11-1 and 11-2 at each half-revolution of the nick gear.

The shaft 14 of the nick gear 3 carries a cam plate 15 with a peripheral cam surface 16 which progressively changes in distance from the shaft 14 between a minimum radius at point A and a maximum radius at point B.

Starting from the position shown in Figure 2, the detent 18 can be released from engagement with abutment 11-1 by means of a drive device 19 acting on the lock bar 17 against the action of a spring 20.

An operating link 21 engages the cam 15 through a cam follower 22 and is biased around a pivot 23 by a spring 24. The pressure on the cam follower 22 is sufficient to rotate the cam 15 so that the cam follower 22 reaches the minimum position A. The dwell zone 6-1 is thus moved round until the pinion 2 engages the toothed portion 4 of the nick gear. The nick gear 3 is thus turned through half a revolution until the position shown in Figure 3 is reached, in which the detent 18 engages the abutment 11-2 and the dwell zone 6-2 is adjacent the pinion 1. In this position the cam 15 has rotated until the maximum position B has passed beyond the cam-follower 22.

The operating link 21 has been swung anti-clockwise about the pivot 23 against the spring 24to the displaced position shown. Thus when the detent 18 is released from the abutment 11-2 the pressure of the cam follower 22 causes the cam 15 to rotate back towards the minimum position A and thus effects a half-revolution of the nick gear 3 back to the Figure 2 position, in which it is again arrested by the detent 18. A stop tooth 7 at the junction between the toothless portion 5 and the dwell zone 6-1 serves to absorb the rotational inertia of the nick gear 3 as it returns from the operating condition of Figure 3 to the inoperative condition of Figure 2.

It will be appreciated that there is no necessary positional relationship between the dwell zones 6-1 and 6-2 and the abutments 11-1 and 11-2 except that the lock bar 17 engages one of the abutments when one of the dwell zones is adjacent the pinion 1.

The drive device 19 serves to swing the lock bar 17 to disengage the detent 18 long enough for the nick gear 3 to commence its movement. In the example shown in Figure 5 the lock bar 17 is pivotally mounted on a frame 19b which carries a solenoid 19a. When the solenoid is excited the lock bar 17 is rocked about its pivots against the action of the return spring 20. In the alternative drive device shown in Figure 6 the end of the lock bar 17 consists of a metal plate which is fixed to a base body 19c.

Metal ceramics 19d are laminated to opposite sides of the lock bar 17 and the application of a positive potential to one ceramic 19d and a negative potential to the other causes deflection of the lock bar 17. In a further alternative a recently-developed element is used which shows companding deformation due to an effect of magnetic force.

In the embodiment of Figures 2 and 3 the displacement of the operating link 21 is extracted by way of an arm 25 rigid with the link 21 and acting through a spring 26. A changeover switch 27 cooperates with the arm 25 to detect the movements of the changeover mechanism effected by rotation of the nick gear 3. Changeover is initiated by the action of the driver 19 disengaging the detent 18 from the abutment 11-1 of the nick gear. Whether the operation has been correctly performed is detected by the switch 27 responding to the movement of the operating link 21. The changeover switch 27 controls supply of electrical power to the driver 19 through its switching operation, thus preventing unwanted supply of power to the driver 19.

For each changeover operation the nick gear 3 completes one revolution being driven from the inoperative condition to the operating condition by the pinion 1 and returning to the inoperative condition under the pressure of the operating link 21. The drive device 19 is only required to displace the lock bar 17 for a short period of time and thus consumes little power.

Turning to Figures 8 and 11 the changeover switch 27 serves to connect either the drive device 19 or a capacitor C which provides operating power for the device 19 to the power supply while the other is isolated from the power supply. In the embodiment of Figure 8 the contact arm of the switch 27 is in engagement with a contact 27a in the inoperative condition shown in Figure 1, connecting the drive device 19 to the power supply terminal V. When the power is switched on a positive voltage is applied to terminal V but since the transistor Trl is not turned ON no power is supplied to drive device 19. When a positive signal is applied to the terminal PLY, base current flows to the base of transistor TR, through a resistor r,. This renders TR1 conducting and current is supplied to the drive device 19 to initiate operation of the changeover mechanism.

Upon rotation of the nick gear 3 the operating link 21 is displaced and the switch 27 changes over to engage contact 27b. The drive device 19 is thus disconnected from the power supply and the capacitor C is connected for charging with the polarity seen in Figure 8. Thus, as shown in Figure 9, when a PLY input Vp shown at (a) is applied at time t1 with the power switched on, an input V5 shown at (c) is applied to the device 19. However the resulting rotation of the nick gear and changeover of the switch 27 at time t2 as shown at (b) stops the input to the device 19.

In this operating condition with the input of control circuit IC at a high level because of the PLY input, no positive voltage is applied to the base of transistor Tr2 which therefore remains in the OFF state. When the PLY input then ceases, the input to IC becomes low level and the signal applied through resistor r2 switches transistor Tr2 ON. A closed loop is then formed through the contact 27b, capacitor C, drive device 19, and transistorTr2. The drive device 19 thus operates to free the abutment 11-2 and the nick gear 3 rotates back to the inoperative condition.

In the course of this operation the operating link 21 returns and moves the switch 27 to contact 27a in readiness for the next changeover operation.

If power failure occurs or the power supply plug is disconnected during the PLY operation the voltage of terminal V drops and so does that at the PLY terminal. Therefore the voltage across capacitor C provides a high level input to the base of transistor TR2 due to the control circuit IC and the drive device 19 is energized to return the nick gear 3 to the inoperative condition by spring force without requiring drive from the motor 63.

The mechanism shown in Figures 2 and 3 is intended to effect all the changeover operations of the tape recorder through the combination of one nick gear 3 and the drive pinion 1. Figure 10 shows how the movement of the arm 25 rigid with the operating link 21 is used to effect the selected changeover. An operating bar 28 is pivotally connected to the arm 25 and the spring 26 acts on the bar 28. The bar 28 carries at appropriate intervals projections 29 for play, 30 for rewind, and 31 for fast forward, which cooperate with levers 32, 33 and 34 respectively. The levers 32 and 33 can be swung into position for engagement with the bar 28 by respective solenoids 35 and 36. The lever 34 is displaced by the application of voltage to a ceramic bimetal 37 in order to take up the position for engagement by the projection 31.The levers 32,33 and 34 when actuated operate the mechanisms for play, rewind, and fast forward through respective springs 38,39 and 40.

Figure 11 shows a circuit for control of the mechanism of Figure 10. Switches 41,42 and 43 energize the solenoids 35 and 36 and the bimetal 37 respectively and also control the drive device 19. For example, when the power switch of the taperecorder is turned ON and the switch 41 is turned ON, since the switch 27 is on contact 27a power is supplied to drive device 19. The solenoid 35 is energized to place the lever 32 in position for engagement by projection 29 of bar 28 when the operating link 21 is displaced. The mechanism for play is accordingly actuated through the spring 38 when the nick gear 3 effects the half revolution to the operating condition. As the switch 27 is changed over the supply of power to the drive device 19 and the solenoid 35 is interrupted and the capacitor C is charged.

When the required operation is terminated by switching the switch 41 off, the charge on the capacitor C is applied to the base of Tr2 by way of resistors R2 and R3 so that a closed loop is formed through the capacitor C, transistor Tr2 and drive device 19. Thus, the nick gear 3 returns to the state of Figure 2 and simultaneously the operating bar 28 and the spring 38 return to the state of Figure 10.

Figure 12 shows an example of a battery-type circuit using a battery 44 as a power supply. The drive device 19 is connected with a position sensor 45 as a detecting means and with a controller 46 comprising a start switch 46a and a stop switch 46b.

When the start switch 46a is turned on the device 19 is energized through contact 45a and the switch 45 is changed over to contact 45b. When the stop switch 46b is turned on (and the start switch 46 is simultaneously turned off) the drive device 19 is again energized and the switch 45 returned to contact 45a.

Therefore when the specified operation has been set by the drive device 19 no electrical power is consumed during that operation.

Whereas the embodiment described has used a single nick gear 3 it is possible as shown in Figure 4 to use two nick gears 3A and 3B cooperating with a single drive pinion 1. The construction and operation of each of the nick gears 3A and 3B in conjunction with respective locking bars 17 and operating links 21 is the same as that of nick gear 3 in the embodiment of Figures 2 and 3 and hence will not be described again. However in the embodiment of Figure 4 the lower nick gear 3A controls recording, reproduction and fast forward while the upper nick gear 3B controls rewind.

Thetwo lock bars 17 are extended and theirfree ends are coupled by a coupling rod 80 which holds one lock bar 17 inoperative while the other lock bar 17 is displaced by its drive device 19 so that it is not possible to initiate changeover by both nick gears simultaneously. To make the disabling of the other lock bar 17 more reliable it is preferable for the projection 12 to extend over an angular range of 100 to 150 so that the lock bar cannot return within this range.

As shown in Figure 4 the operating link 21 of the nick gear 3A is coupled by way of the spring 26 to the head mounting board 66 (Figure 1) so that when the link 21 is swung clockwise in Figure 4 by the rotation of nick gear 3A, the mounting board 66 is displaced upwards as seen in Figure 1 by the tension in the spring 26 overrunning the biassing spring 70. Thus the pinch roller 67 is pressed against the capstan 61 for operation in recording, reproduction or fast forward modes.

On the other hand when the nick gear 3B for rewind rotates the associated operating link 21 is swung clockwise and a plate spring 81 fixed to the link 21 presses against the arm end 55a of the lever 55 against the biassing spring 82 (omitted in Figure 1). The idler 57 carried by the lever 55 is thus released from contact with the reel support 54 and the idler 58 is placed in contact with the reel support 53. As the idler 58 is freely mounted in an elongated hole in the lever 55 it is displaced along the lever to engage the idler 57 and thus transmits the rotation of the idler 57 to the reel support 53 for rewind.

In the embodiment of Figure 4 it is sufficient to detect that the nick gear has commenced rotation and the structure and position of the detecting means are therefore not restricted. It may be, as in Figures 2 and 3, a changeover switch 27 cooperating with the operating link 21 or may detect that the head 69 is in contact with the tape or that the cam plate has been rotated. It is only necessary to confirm that the nick gear has rotated after the issue of an operation instruction to the drive device 19; It will be seen from the above description that the changeover mechanism described has eliminated the use of a solenoid as the driving element and thereby reduced the power consumption. Moreover each changeover operation is effected with low noise without generating impact sounds. Electrical power is not required for reset to the waiting state from each operating mode. Consequently if electrical power supply is interrupted the tape recorder is automatically re-set to the waiting state.

Since start of the changeover operation is effected by releasing the detent 18 from the abutments 11-1 and 11-2 by a slight swinging displacement of the locking bar 17, this start can be detected more reliably and a smooth changeover operation can be obtained.

Since each changeover operation uses a rotating force obtained from the drive motor 63 no additional impact noise is generated and all the changeover operations can be initiated by electrical signals.

The mechanical components for the changeover operation can all be provided compactly in the changeover mechanism, thus simplifying the construction.

Claims (7)

1. Changeover mechanism for a tape recorder including a drive pinion rotated by the drive motor of the tape recorder, a nick gear having a first circumferential portion which is toothed to engage the drive pinion, and a second circumferential portion which is toothless, with two dwell zones separating the first and second portions, and two abutments having the same angular separation as the dwell zones, a lock bar having a detent engageable with each of the abutments to lock the nick gear against rotation in a position in which one of the dwell zones is adjacent the drive pinion and disengageable by a swinging motion effected by a drive device, a cam mounted for rotation with the nick gear and engaging an operating link which is biassed against a cam surface of the cam which varies continuously in distance from the axis of rotation of the nick gear and cam between a maximum and a minimum distance, the arrangement of the cam surface being such that the operating link is driven outwards by the cam when the nick gear is driven by the drive pinion and the pressure of the operating link on the cam thereafter rotates the nick gear back to its initial position, and a detecting means actuated by the rotation of the nick gear to control the supply of electrical power to the drive device which disengages the detent.

2. A changeover mechanism as claimed in claim 1 having a second nick gear associated with the drive pinion, the second nick gear having the same structural features and its own lock bar, drive device, cam, and operating link constructed and operating in the same manner as specified for the first nick gear.

3. A changeover mechanism as claimed in claim 2 in which the first operating link is coupled to move the pinch roller of the tape recorder while the second operating link is coupled to swing over take-up drive rollers between the supports for the two tape reels.

4. A changeover mechanism as claimed in claims 1, 2 or 3 in which the or each nick gear has a groove in which the detent runs, the abutments being formed in the inner wall of the groove and the outer wall of the groove having projections upstream of each abutment to return the detent into a position in which it will engage the abutment.

5. A changeover mechanism as claimed in any of the preceding claims in which the detecting means is a changeover switch actuated by the swinging of the operating link.

6. A changeover mechanism as claimed in any of the preceding claims in which the or each nick gear has a stop tooth between the toothless second portion and that one of the dwell zones which is adjacent the drive pinion in the initial position of the nick gear.

7. A changeover mechanism as claimed in any of the preceding claims in which a control circuit for the drive device of the locking bar comprises a charging capacitor for feeding the drive device connected in parallel with the drive device across the power supply terminals.