GB1581577A

GB1581577A - Tape recording and/or playback apparatus

Info

Publication number: GB1581577A
Application number: GB19293/77A
Authority: GB
Original assignee: Philips Gloeilampenfabrieken NV
Current assignee: Koninklijke Philips NV
Priority date: 1976-05-12
Filing date: 1977-05-09
Publication date: 1980-12-17
Also published as: AT345576B; JPS5816538B2; DE2719098B2; FR2351469A1; IT1084593B; FR2351469B1; ES458642A1; DE2719098C3; JPS52138907A; DE2719098A1; ATA347376A

Description

(54) TAPE RECORDING AND/OR PLA YBACK APPARATUS (71) We, N.V. PHILIPS GLOEILAMP ENFABRIEKEN, a limited liability Company, organised and established under the laws of the Kingdom of the Netherlands, of Emmasingei 29, Eindhoven, the Netherlands, 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: - The invention relates to a recording and/ or playback apparatus having a tapethreading device which is rotatable between first and second positions and which comprises a tape guide pin which in the first position of the threading device is engageable with a record carrier in the form of a magnetic tape supported on the apparatus and which, by rotation of the threading device into the second position, can lay a portion of the tape in a helical path around at least a part of the cylindrical surface of the drum of a rotary magnetichead drum assembly, and comprising a drive means for rotating the threading device, which means comprises an electric motor whose direction of rotation is reversible and by which can be driven a gear wheel which cooperates with a gear ring on the threading device, starting and selection of the direction of rotation of the motor being effected with an actuating element of the apparatus, and the motor being switched off by one or the other of two switches which are actuated by means controlled in accordance with the direction of rotation of the threading device. Such an apparatus is known from, for example, United States Patent Specification 3,740,492.

In another apparatus which is known from United States Patent Specification 3,735,053, a traction device is provided as the drive means for rotating the threading device, in which, for example, a cable is connected to the threading device via a spring, the cable being passed round a pulley which can be driven by a motor. In order to define the two positions of the thread ing device this apparatus comprises stops which directly cooperate with the threading device, so that the drive means may have an excess stroke.

In all equipment of this type the record carrier should be laid on and lifted off the respective drum surface by the threading device in an accurate and reliable manner.

To execute these operations, which are referred to as "threading" and "unthreading" of the record carrier, the drive means for the threading device has to be started and subsequently the threading device has to be brought accurately into its two positions with the aid of said drive means, after which the drive means has to be stopped again. These operations, which must be performed in an accurate manner, should not be adversely affected by other apparatus functions being switched on or off.

According to the invention there is provided a recording and/or playback apparatus having a tape-threading device which is rotatable between first and second positions and which comprises a tape guide pin which in the first position of the threading device is engageable with a record carrier in the form of a magnetic tape supported on the apparatus and which, by rotation of the threading device into the second position, can lay a portion of the tape in a helical path around at least a part of the cylindrical surface of the drum of a rotary magnetic-head drum assembly, and comprising a drive means for rotating the threading device, which means comprises an electric motor whose direction of rotation is reversible and by which can be driven a gear wheel which cooperates with a gear ring on the threading device, starting and selection of the direction of rotation of the motor being effected with an actuating element of the apparatus, and the motor being switched off by one or the other of the two switches which are actuated by means controlled in accordance with the direction of rotation of the threading device, wherein for defining the two positions of the threading device there are provided stops which directly cooperate with said device, wherein between the motor and said gear wheel there is pro vided a differential gearing having two driven gear wheels of which one cooperates with the gear wheel and the other with an arm which is pivotable by the motor via the differential gearing from a first end position into an intermediate position and from this intermediate position into a second end position and in the reverse direction, a disengageable retaining device being provided for retaining the arm in the intermediate position, wherein each of the two switches for switching off the motor is arranged to be opened by the arm when the latter is in a respective one of its two end positions and closed by the arm when the latter is in the other end position, wherein when the threading device is in either of its two positions the arm is movable via said other driven wheel of the differential gearing and when the arm is in the intermediate position the threading device is rotatable via said one driven wheel, and wherein the retaining device is disengaged to release the arm when, or substantially when, one or the other of the two positions of the threading device is reached.

The retaining device may be constituted by a latch comprising a detent which retains the arm in its intermediate position with a force which, measured at the differential gearing, is greater than the force required for rotating the threading device. Alternatively, the retaining device may be constituted by a latch comprising a stop which via actuating means is released by the threading device directly before said device reaches the relevant one of its two positions. The stop may, for example, consist of a latch which engages with a recess in the arm when the threading device is moved from the one position to the other. In one embodiment of the invention the latch stop is constituted by a toggle lever which is pivotable intermediate its ends about a fixed axis on the apparatus and which is arranged to be pivoted via said actuating means out of a latching position by the threading device directly before this device reaches the relevant one of its two positions, each of the two free ends of the toggle lever is disposed in the path of movement of an end of a respective one of two latching levers, said end of each latching lever being hooked for engagement with and guidance of the respective end of the toggle lever, the two latching levers are mounted on a reciprocable slide which is articulated to the pivotable arm the latching levers being spaced from one another in the direction of movement of the slide with their hooked ends facing and forming mirror images of each other, and being pivotable in opposite directions against the action of a spring, and the pivotal axes of the two latching levers and the toggle being disposed on a straight line which extends parallel to the direction of movement of the slide, and in the intermediate position of the pivotable arm the toggle lever occupies its latching position, in which it extends parallel to the direction of movement of the slide, under the influence of the latching levers and blocks the slide in both directions of movement via the latching levers, and when the toggle lever is pivoted out of this latching position in one direction or the other a respective one of the two latching levers is pivoted by the toggle lever against the action of spring so that the slide is unlatched in the direction of movement in which the slide was blocked via this latching lever.

Any convenient form of differential gearing may be used. Preferably, however, the differential gearing is a spur-gear differential and comprises two planet gear wheels which mesh one with each of the two driven wheels of the differential gearing and which are carried by a carrier wheel driven by the motor, and said one driven wheel is rigidly mounted on a shaft on which said gear wheel is also rigidly mounted and about which said other driven wheel and said carrier wheel are freely rotatable, said other driven wheel meshing with a toothed segment on a free end of the pivotable arm.

The apparatus may comprise a spring which cooperates with the pivotable arm and is stressed by movement of the arm from its intermediate position to one of its two end positions, and which when the motor is switched off acts through a forcetransmission path comprising the arm, the differential gearing and said gear wheel to keep the threading device in engagement with the relevant stop.

It can be seen that the position of the pivotable arm can serve to indicate whether the threading device is being rotated or has assumed one of its two positions, or whether the drive means for the threading device is in the switched-on or switchedoff condition. This can be utilised by providing latching elements which are arranged to be actuated by the arm and which, depending on the position of the arm, influence the operation of adjustable control members for controlling the modes of operation of the apparatus. Thus, erroneous operation of the apparatus during either a record-carrier threading or unthreading operation and in the two positions of the threading device are precluded.

Embodiments of the invention will now be described in more detail with reference to the accompanying diagrammatic drawings, in which Fig. 1 is a plan view of the relevant parts of a video recording and/or playback apparatus according to an embodiment of the invention in which the retaining device is constituted by a latch comprising a detent, the threading device being shown in the first position, in which the record carrier is in the unthreaded condition and the drive means is switched off, Fig. 2 is a sectional view taken on the line II-II in Fig. 1, Fig. 3 is another plan view of the embodiment of Fig. 1 which shows the positions of the various parts at a specific instant during a threading operation of the record carrier, with the drive means switched on, Fig. 4 also shows the embodiment of Fig. 1 in plan view with the threading device in the second position, in which the record carrier is looped around part of the drum surface and the drive means is switched off again, Fig. 5 is a view similar to Fig. 1 showing an embodiment with a retaining device which is constituted by a latch comprising a stop, and Fig. 6 shows the positions of the various parts in the embodiment of Fig. 5 at a specific instant during a record-carrier threading operating, with the drive means switched on.

The recording and/or playback apparatus shown in Fig. 1 to 4, in the present example an apparatus for recording and playing back video signals, comprises a deck plate 1, which carries a drum 2 which consists of a stationary section 3 and a section 5 which can be rotated via a spindle 4, on which section 5, for example, two magnetic heads 6 are mounted. The cylindrical surface of the drum 2 serves for guiding a record carrier in the form of a magnetic tape with which the magnetic heads 6 then cooperate at the location of this surface. Such a record carrier 7 is accommodated in a cassette 8 which can be placed on the deck plate of the apparatus in a predetermined position.

Inside the cassette the record carrier extends from a first reel via guide rollers 9, 10 and 11 to a coaxial second reel, the part of the record carrier between the guide rollers 10 and 11 extending across an opening of the cassette, so that it can be pulled out of this cassette and looped around the drum.

To pull the record carrier out of the cassette and loop it around the cylindrical surface of the drum 2, in the present instance over a circumferential range of 1800 of the drum surface, a threading device 12 is provided which consists of a circular ring 13 which is rotatably journalled around the drum and which carries two tape guide pins 14 and 15 which are disposed behind the part of the record carrier 7 which extends between the guide rollers 10 and 11 when the cassette is placed on the apparatus, as can be seen in Fig. 1. The threading device is rotatable between first and second positions, for which purpose a drive means 16 is provided which has a motor 17 whose direction of rotation is reversible and by which a gear wheel 18 can be driven which meshes with a gear ring 19 on the circumference of the ring 13 of the threading device.

In the first position of the threading device the record carrier is disposed wholly in the cassette, but the tape guide pins 14 and 15 of the threading device are already disposed behind the record carrier, as shown in Fig. 1. If the threading device is now rotated by the drive means 16 in a clockwise direction, as indicated by the arrow 20, the guide pin 14 engages with the record carrier and pulls it out of the opening in the cassette whilst at the same time laying the record carrier on the drum surface as shown in Fig. 3. After a rotation of the threading device through substantially 1800 this device has reached its second position, in which the record carrier is looped 1800 around the drum surface, as is shown in Fig. 4. The tape guide pin 15 then guides the portion of the record carrier extending between the guide roller 11 and the guide pin 14 so that it does not contact the portion extending between the guide pin 14 and the guide roller 10, which portion is in contact with the drum. Owing to a corresponding inclination of the drum and of the guide pins 14 and 15 respectively relative to the plane of the deck plate, the record carrier is looped around the drum surface in a helical path, so that the magnetic heads 6 scan adjacent oblique tracks on the record carrier. For the sake of simplicity the inclination of the drum and the guide pins is not shown in the drawings. In order to lift the record carrier from the drum surface and return it into the cassette, the threading device is rotated in an anti-clockwise direction from the second position to the first position, which is again effected with the aid of the drive means 16, the direction of rotation of the motor 17 then being reversed in comparison with its first rotation described above.

Simultaneously, the record carrier is driven in a corresponding direction, so that the loop which has been pulled out of the cassette is returned into the cassette. These operations are generally referred to as "threading" and "unthreading" of the record carrier, the unthreaded condition corresponding to the first position and the threaded condition to the second position of the threading device.

To start the drive means 16 a manually operable actuating element 21 is provided by means of which a switch 23 for closing the circuit 22 of the motor 17 and two switches 24 for reversing the direction of rotation of the motor can be actuated.

For stopping the motor 17 its circuit includes two switches 25 and 26 which are alternately operative in accordance with the position of the switch 23. When the threading device is in the first or second position, always one of these switches is closed and the other is open, the two switches being opened or closed depending on the direction of rotation of the threading device. Thus, the actuating element 21 can start either a threading or an unthreading operation, at the end of which, after the relevant position of the threading device is reached, the drive means is switched off by the switch 25 or 26 which was closed being opened, whilst the switch 25 or 26 which was open is already closed after the beginning of the relevant operation so as to prepare the drive means for the next rotation of the threading device in the opposite direction.

For exactly defining the two positions of the threading device, stops 27 and 28 are provided which are engageable by a projection 29 on the ring 13 of the threading device, so that the range of rotation of this device is limited accordingly. A differential gearing 30 is included between the motor 17 and the gear wheel 18 which cooperates with the threading device, one driven wheel 31 of said gearing driving the gear wheel 18 and the other driven wheel 32 actuating an arm 33 which is pivotable between two end positions about a spindle 39. This arm 33 cooperates with a disengageable retaining device in the form of a latch which in the present example consists of a spring-loaded ball-type detent 34, which retains the arm in an intermediate position between the two end positions with a force which, measured at the differential gearing, is greater than the force required for rotating the threading device, so that the retaining device is disengaged to release the arm only when the first or second position of the threading device is reached.

The differential gearing is a spur-gear differential, the driven wheel 31 being rigidly mounted on a shaft 35 which is rotatably journalled in the deck plate 1 and on which the gear wheel 18 which cooperates with the threading device is also rigidly mounted.

The driven wheel 32 for actuating the arm 33, and a carrier wheel 38, are freely rotatable about the shaft 35. The carrier wheel 38 is driven by the motor 17 via a belt 37 and carries two rigidly connected coaxial planet wheels 36 of the differential gearing which mesh with the driven wheels 31 and 32. At one end 40 the arm 33 has a toothed segment 41 which meshes with the driven wheel 32 of the differential gearing.

In its two end positions the arm 33 actuates the switches 25 and 26 via connections 42 and 43 respectively, which are shown diagrammatically.

A detailed description is now given of the operations of threading and unthreading the record carrier, starting from the situation when the apparatus is put into operation. Before the apparatus is put into operation the threading device is in the first position (Fig. 1). The drive means 16 for the threading device is switched off, the circuit for the motor 17, as shown in Fig.

1, being opened by the switch 25, which is actuated by the arm 33. The switch 26, which is also actuated by the arm 33, is closed but has no effect because the switch 23, which can be actuated by means of the actuating element 21, is also open.

The arm 33 is in one of its two end positions. In this first position of the threading device a cassette can be placed on the apparatus, with the tape guide pins 14 and 15 of the threading device disposed behind the record carrier 7.

If the record carrier is now to be threaded, the actuating element 21 is actuated so that the switches 23 and 24 are set to the positions shown in Fig. 3. The switch 23 then closes the circuit for the motor 17 via the closed switch 26, the switch 24 producing a rotation of the motor in the anti-clockwise direction as viewed in the drawings. Via the belt 37 the motor 17 now drives the carrier wheel 38 of the differential gearing 30. For rotating the threading device 12 a greater force is required than for rotating the arm 33 away from its end positions, so that the gear wheel 18 which cooperates with the threading device, and the driven wheel 31 of the differential gearing which is rigidly connected to the gear wheel 18, should initially be considered locked. In this situation, when the carrier wheel 38 of the differential gearing rotates, the upper of the two planet wheels 36 of said gearing, which planet wheel meshes with the locked wheel 31, rolls around the latter and both planet wheels are thereby rotated, with the result that the wheel 32 of the differential gearing is driven. The number of teeth on the driven wheels 31 and 32 and the number of teeth on the planet wheels 36 are such that when the carrier wheel 38 rotates in an anti-clockwise direction the driven wheel 32 rotates in a clockwise direction, so that the arm 33 is pivoted out of the first end position shown in Fig. 1 in the anti-clockwise direction. As the arm 33 pivots the switch 26 remains closed, so that the circuit for the motor 17 remains closed. The switch 25 also is now closed by the arm 33 via the connection 42, but for the time being this has no consequences for the motor circuit because the switch 23 acts in combination with the switch 26.

The arm 33 now pivots until it is retained in the intermediate position by the latch 34, as is shown in Fig. 3. The latch now exerts a force on the arm 33 which, measured at the differential gearing, is greater than the force which is needed to rotate the threading device. This means that the arm 33 should now be regarded as locked, so that the driven wheel 32 of the differential gearing also is now locked and, owing to the continued rotation of the carrier wheel 38, the lower of the planet wheels 36, which meshes with the locked wheel 32, rolls around the latter with the result that the other wheel 31 is driven in the anticlockwise direction. This rotary movement of the driven wheel 31 is now transmitted to the threading device 12 via the gear wheel 18, so that this device is rotated in a clockwise direction. During this rotation of the threading device its tape guide pin 14 engages with the record carrier 7 and loops it around the surface of the drum 2. Thus, the actual threading operation of the record carrier has started.

When the threading device has reached its second position (Fig. 4) its projection 29 engages the stop 28 so that the threading device is halted and the gear wheel 18 and the driven wheel 31 of the differential gearing are thus locked. However, as the carrier wheel 38 of the differential gearing is still being driven, the upper planet wheel rolls around the locked driven wheel 31 again, so that the other wheel 32 is again driven in a clockwise direction. As a result of this, the arm 33 is disengaged from the latch 34 and further moved in an anti-clockwise direction. This continues until the arm 33 opens the switch 26 via the connection 43, so that the circuit for the motor 17 is interrupted and thus the drive means 16 is switched off and the arm 33 remains in its second end position as is shown in Fig. 4. The threading device is then in its second position and the record carrier is in the threaded condition.

If the record carrier is now to be unthreaded again, the switches 23 and 24 are reset to their original positions shown in Fig. 1 by actuation of the actuating element 31. The motor is thereby started with the switch 23 via the switch 25, which is already closed, the switches 24 producing a clockwise direction of rotation for the motor. As initially a greater force is required for rotating the threading device than for actuating the arm 33, the arm 33 is now first pivoted in a clockwise direction via the driven wheel 32 of the differential gearing until it is again retained in its intermediate position by the latch 34, the open switch 26 being closed again by the arm 33 through the connection 43. As soon as the arm 33 is retained, the force from the motor is transmitted to the threading device 12 via the driven wheel 31 of the differential gearing, so that the threading device is rotated in an anti-clockwise direction. This continues until its projection 29 engages the stop 27 so that the threading device is halted and the force is again transmitted to the arm 33 via the driven wheel 32 of the differential gearing, as a result of which this arm is disengaged from the latch 34 and is again pivoted in the clockwise direction until via the connection 42 the switch 25 opens, so that the circuit for the motor 17 is interrupted and the drive means 16 is switched off. The arm 33 is then again in its first end position, so that the unthreading operation has been completed.

As can be seen from the foregoing, the steps which have been taken ensure that the sequence of movements for the threading and unthreading operations is performed exactly, which sequence consists of three defined cycles, namely, the switchingon of the drive means whilst the threading device is still stationary, the subsequent rotation of the threading device and execution of the actual threading or unthreading operation, and finally the switching-off of the drive means again whilst the threading device is stationary, the two positions of the threading device thus also being exactly defined. A further advantage is that mounting of the complete drive unit is entirely non-critical. The individual drivable parts, such as the threading device 12, the gear wheel 18 which cooperates therewith, the differential gearing 30 and arm 33, may be assembled in arbitrary rotational positions relative to each other because the complete arrangement, including the arm 33, upon actuation of the actuating element 21, automatically assumes the end position defined by the actuating element 21, namely, either the first or the second position of the threading device.

Furthermore, the use of gear wheels in the drive means assures a reliable force transmission with satisfactory efficiency.

As the instantaneous position of the arm 33, which is always in a defined position relative to the threading device owing to the continuous positive engagement of the gear wheels of the drive means, exactly indicates the operating position of the threading device or whether this device is being rotated or whether the drive means is switched on or off, it is found to be effective if a slide 44 is connected to the arm 33 and arranged to actuate latching elements 45 and 46 with which functions of adjustable control elements 47 and 48 can be influenced for switching-on modes of operation of the apparatus depending on the position of the arm 33. The slide 44, which is slidable in its longitudinal direction, is guided by two pins 50 which engage in a longitudinal slot 49 in the slide, and comprises a projection 51 and 52 at each end, the projections 51 serving to connect the slide to the arm 33 by projecting into an aperture 53 formed in the arm.

The projection 52 of the slide co-operates with the latching elements 45 and 46, which take the form of pivotable levers loaded by springs 54 and 55 and the free ends 56 and 57 respectively of which are disposed in the path of the control elements 47 and 48 respectively. As an example the control element 47 may serve for switching on the fast rewind mode of operation and the control element 48 for switching on the fast-wind mode of operation of the apparatus. The slide 44 furthermore has a projection 58 on one side which co-operates with a stationary stop 59 when the arm 33, after the rotation of the threading device into its second position, is pivoted further in the anti-clockwise direction from its intermediate position into its second end position. A spring in the form of a resilient wire 60 is disposed on the arm 33 and is fixed to the arm at one end and engages with the projection 51 on the slide at its other end, so that it tends to keep the projection 51 positioned against one of the ends of the oblong aperture 53, as a result of which the slide can engage with the arm 33 and can be disengaged therefrom under and against the action of the spring 60.

If the threading device is in the first position and the drive means 16 is switched off, the arm 33 will be in the end position shown in Fig. 1. The spring 60 then keeps the projection 51 of the slide 44 positioned against the end of the aperture 53, thus defining a position of the slide in which its projection 52 is located between the latching elements 45 and 46, which engage with this projection 52 under the influence of the springs 54 and 55. In this position of the latching elements 45 and 46 their free ends 56 and 57 are located directly in front of the ends of the control elements 47 and 48 respectively, so that these elements cannot be actuated and the corresponding apparatus functions are blocked. Consequently, the fast wind or rewind mode of operation of the apparatus cannot be switched on in the first position of the threading device. When a record-carrier threading operation is being performed and the arm 33 reaches its intermediate position (Fig. 3), the spring 60 still keeps the projection 51 of the slide 44 positioned against the end of the aperture 53 in the arm 33. The slide 44 has then reached a position in which its projection 52 is still located between the latching elements 45 and 46, so that these elements keep the control elements 47 and 48 blocked. When the threading device has reached the second position and the arm 33 leaves its intermediate position to move towards its second end position, the slide 44 is moved further by the spring 60 so that the projection 52 of the slide no longer lies between the latching elements 45 and 46 and these elements are now moved towards each other at their ends 56 and 57 under the influence of the springs 54 and 55, as can be seen in Fig. 4. In this position of the latching elements 45 and 46 the two control elements 47 and 48 can be actuated alternately, because both latching elements are pivoted upon the actuation of either one of the control elements, so that the other control element is blocked by the associated latching element.

Before the arm 33 reaches its second end position, the lateral projection 58 of the slide 44, moving with the arm 33, engages the stop 59 so that the slide is halted. However, as the arm 33 is moved further by the drive means 16 and the projections 51 of the slide 44 can now move no further, the spring 60 is deflected until the end position of the arm 33 is reached. As soon as the arm 33 has reached this end position the drive means is switched off and the carrier wheel 38 of the differential gearing is no longer driven, as a result of which the planet wheels 36 of said differential gearing consti normally provided pressure roller with which the record carrier can be held against a capstan, can be influenced in accordance with the instantaneous position of the arm 33 and the slide 44 respectively; this also applies to the actuation of brakes or the execution of electrical switching operations.

In the embodiment of Figs. 5 and 6 the disengageable retaining device for the arm 33, which retains said arm in its intermediate position, is formed by a latch 61, which can be released by the threading device 12 via a control or actuating means 62 directly before said device reaches the relevant first or second position. The latch 61 consists of a toggle lever 64 which is pivotable about a spindle 63 which is fixed in the apparatus. The toggle lever can be pivoted in opposite directions from a central latching position (to be described), in which it retains the arm 33 in its intermediate position, into two positions by means of the control means 62, in which positions the arm 33 is no longer retained and can be pivoted again.

The two free ends 65 and 66 of the toggle lever 64, which carry rollers 67 and 68 respectively, are each disposed in the path of movement of an end 69 and 70 of a latching lever 71 and 72 respectively, which ends are hooked for engagement with and guidance of the ends 65 and 66 respectively of the toggle lever 64. The two latching levers 71 and 72 are pivotable about spindles 74 and 75 on the longitudinally reciprocable elongate slide 44, which is again articulated to the arm 33. The latching levers are spaced longitudinally of the slide with their hooked ends 69 and 70 facing and forming mirror images of each other, and are pivotable in opposite directions against the action of a tension spring 73 which is connected to the hooked ends 69 and 70 of the levers. The pivot spindles 74 and 75 of the two latching levers and the spindle 63 of the toggle lever are disposed on a straight line 76 which extends parallel to the slide and which is represented by a dash-dot line. The latching levers 71 and 72 are biased by the spring 73 in anti-clockwise and clockwise directions respectively into latching positions which are defined by stops 77 and 78 respectively on the slide 44. The toggle lever 64, which is journalled on the fixed spindle 63, is so arranged relative to the latching levers 71 and 72, which are pivotably mounted on the slide 44, that in the intermediate position of the arm 33 the toggle lever 64 extends substantially parallel to the slide 44 under the influence of the latching levers, which are then in engagement with the two free ends 65 and 66 of the toggle lever, so that the latter, which is then in its previously mentioned latching position, blocks the slide 44 and thus the arm 33 in both directions of movement via the two latching levers 71 and 72, which are then in their latching positions. This can be seen in Fig.

6, which is to be discussed in more detail hereinafter. By pivoting the toggle lever out of its latching position by means of the control means 62, one or the other of the two latching levers is pivoted out of its latching position against the action of the spring 73 so that the slide 44 is released in the direction of movement in which it was blocked via this latching lever.

As previously stated the toggle lever 64 is pivoted out of its central latching position by the threading device 12 via the control means 62 directly before the threading device reaches the relevant first or second position. For this purpose two actuating pins 79 and 80 are mounted on the threading device 12, and in the path of movement of these pins is located a first lever arm 81 of a bell-crank lever 83 which is pivotable, about a spindle 82 which is fixed in the apparatus, which lever forms part of the control or actuating means 62.

These means further include a link 84 which at one end is articulated to the second lever arm 85 of the bell-crank lever 83 and at the other side is articulated to the toggle lever 64 near the end 66 thereof.

The operation of this embodiment will now be described in more detail, assuming that the threading device is in its first position in which the record carrier is in the unthreaded condition, which situation is shown in Fig. 5. The switches 23 and 24, the switches 25 and 26, the arm 33 and the slide 44 are then in positions identical to the positions of these elements in the first embodiment shown in Fig. 1. The latch 61 is in a position in which it was set during the preceding unthreading operation by the actuating pin 80 on the threading device 12 wa the lever 83 and link 84. In this position of the latch 61 the toggle lever 64 has been pivoted out of its latching position in the clockwise direction to pivot the latching lever 72, which cooperates with the free end 66 of the toggle lever, in the anti-clockwise direction out of its latching position against the action of the spring 73. The other latching lever 71 is kept in its latching position by the spring 73, in which position it engages with the stop 77 on the slide 44.

For threading the record carrier the actuating member 21 is actuated, so that the switches 23 and 24 are set to the positions shown in Fig. 6, which corresponds to the situation of Fig. 3 for the first embodiment. As previously described for the first embodiment, the motor 17 first moves the arm 33 out of its end position via the differential gearing 30, because for this a smaller driving force is required than for the rotation of the threading device 12.

The arm 33 is consequently pivoted in the anti-clockwise direction, so that the slide 44, which is articulated to the arm, is moved in the direction of the arrow 86.

Upon this movement of the slide 44 the latching levers 71 and 72 move with the slide so that the latching lever 71, which is in its latching position, moves towards the toggle lever 64, which is journalled on the fixed spindle 63, and the latching lever 72, which is kept out of its latching position by the free end 66 of the toggle lever, moves away from the pivoted axis of the toggle lever 64. The latching lever 72 is thereby free to be pivoted in the clockwise direction by the spring 73 and, through the cooperation of its hooked end 70 with the free end 66 of the toggle lever 64, pivot the toggle lever in the anti-clockwise direction.

The toggle lever then accordingly resets the link 84 and through it the bell-crank lever 83.

As a result of the sequence of movements described above the toggle lever 64 is moved to its central latching position under the influence of the latching lever 72 which is pivoted by the spring 73, in which position the toggle lever extends parallel to the slide 44. Just before the toggle reaches its latching position the first lever arm 81 of the bell-crank lever 83 engages the actuating pin 80 which is mounted on the threading device 12, for this pin is now disposed in the path of movement of the arm 81, because during the preceding unthreading operation the pin resets the lever arm 81 in order to release the retaining device constituted by the toggle lever 64 and the latching levers 71 and 72. As the threading device 12 is stationary, the lever arm 81 is blocked and the bell-crank lever 83, the link 84, the toggle lever 64 and the latching lever 72 assume a position in which the free end 65 of the toggle lever 64, which is now substantially in its latching position, cooperates with the end 69 of the latching lever 71, which is held in its latching position by the spring 73, to prevent the latching lever 71 from moving further in the direction of the arrow 86. In this way the slide 44 and thus the arm 33 are also prevented from being moved further. The arm 33 is now in its intermediate position, in which it is held by the toggle lever, so that in a similar manner to that of the first embodiment the threading device 12 is rotated by the motor 17 via the differential gearing 30 whilst the arm 33 is retained in its intermediate position.

As soon as the threading device 12 starts moving, the actuating pin 80 moves away from the first lever arm 81 of the bellcrank lever 83 so that the latching lever 72 is free to be pivoted fully by the spring 73 into engagement with the stop 78 and thereby assume its latching position. In this position, during the succeeding unthreading operation the lever 72 functions in a similar way to the latching lever 71 during the threading operation described above. During this movement of the latching lever 72 the toggle lever 64 is also slightly pivoted to bring it fully into its central latching position, in which its two free ends engage with the two latching levers 71 and 72 so that the toggle lever 64 is retained in its latching position, in which it holds the arm 33 in its intermediate position via the latching lever 71 and the slide 44. The link 84 and the bell-crank lever 83 also assume a corresponding intermediate position. This situation is shown in Fig. 6. In this Figure the threading device is shown in full lines rotated through approximately 90" towards its second position.

Immediately before the threading device 12 reaches its second position, the actuating pin 79 engages with the first lever arm 81 of bell-crank lever 83 of the control means 62, as is indicated by the dotted lines in Fig. 6, and pivots this lever. The force which is thus exerted on the lever 83 by the actuating pin 79 is transmitted to the toggle lever 64 via the link 84 so that the toggle lever is moved in an anti-clockwise direction sufficiently far out of its latching position that it no longer blocks the slide 44. Through the toggle lever the latching lever 71 also is moved out of its latching position against the action of the spring 73, so that a further movement of the slide 44 in the direction of the arrow 86 and thus a pivoting movement of the arm 33 out of its intermediate position becomes possible. Immediately after the retaining device for the arm 33, which device is constituted by the toggle lever 64 and latching levers 71 and 72, has been released, the projection 29 on the threading device engages the stop 28, so that the threading device has reached its second position. As previously described with reference to the first embodiment, the motor 17 then drives the arm 33 via the differential gearing 30, so that this arm is pivoted in the anti-clockwise direction from its intermediate position into its second end position. This moves the slide 44 and thus the latching levers 71 and 72 in the direction of the arrow 86, so that the latching lever 71 which has already been rotated out of its latching position, moves towards the toggle lever, and the latching lever 72, which is in its latching position, moves away from the toggle lever. In this way the latching lever 71 is pivoted further in the clockwise direction and the toggle lever 64 further in the anti-clockwise direction.

This continues until the arm 33 has reached its second end position, in which it opens the switch 26 via the connection 43, so that the circuit 22 for the motor 17 is interrupted and thus the arm 33 is no longer driven. The toggle lever 64 and the two latching levers 71 and 72 then assume a position, not shown, which is the reverse of the position of these elements shown in Fig. 5. Thus the threading operation is completed, the threading device 12 being in its second position and the record carrier being in the threaded condition. The record carrier can be subsequently unthreaded by an analogous unthreading operation. This operation is not described because it is performed simply by a reverse sequence of movements to the sequence of movements described above for the threading operation.

As is evident from the foregoing, the device for retaining the pivotable arm in its intermediate position, which device in the present embodiment is constituted by the latch 61, is controlled by the threading device itself. Thus it is assured that the retaining device allows the arm to be moved only when the threading device has reached, or substantially reached, one or the other of its two positions, so the threading device is transferred from one position to the other in a particularly reliable manner.

WHAT WE CLAIM IS: 1. A recording and/or playback apparatus having a tape-threading device which is rotatable between first and second positions and which comprise a tape guide pin which in the first position of the threading device is engageable with a record carrier in the form of a magnetic tape supported on the apparatus and which, by rotation of the threading device into the second position, can lay a portion of the tape in a helical path around at least a part of the cylindrical surface of the drum of a rotary magnetic-head drum assembly, and comprising a drive means for rotating the threading device, which means comprises an electric motor whose direction of rotation is reversible and by which can be driven a gear wheel which cooperates with a gear ring on the threading device, starting and selection of the direction of rotation of the motor being effected with an actuating element of the apparatus, and the motor being switched off by one or the other of two switches which are actuated by means controlled in accordance with the direction of rotation of the threading device, wherein for defining the two positions of the threading device there are provided stops which directly cooperate with said device, wherein between the motor and said gear wheel there is provided a differential gearing having two driven gear wheels of which one cooperates with the gear wheel and the other with an arm which is pivotable by the motor via the differen- tial gearing from a first end position into an intermediate position and from this intermediate position into a second end position and in the reverse direction, a disengageable retaining device being provided for retaining the arm in the intermediate position, wherein each of the two switches for switching off the motor is arranged to be opened by the arm when the latter is in a respective one of its two end positions and closed by the arm when the latter is in the other end position, wherein when the threading device is in either of its two positions the arm is movable via said other driven wheel of the differential gearing and when the arm is in the intermediate position the threading device is rotatable via said one driven wheel, and wherein the retaining device is disengaged to release the arm when, or substantially when, one or the other of the two positions of the threading device is reached.

2. An apparatus as claimed in Claim 1, wherein the retaining device is constituted by a latch comprising a detent which retains the arm in its intermediate position with a force which, measured at the differential gearing, is greater than the force required for rotating the threading device.

3. An apparatus as claimed in Claim 1, wherein the retaining device is constituted by a latch comprising a stop which via actuating means is released by the threading device directly before said device reaches the relevant one of its two positions.

4. An apparatus as claimed in Claim 3, wherein the latch stop is constituted by a toggle lever which is pivotable intermediate its ends about a fixed axis on the apparatus and which is arranged to be pivoted via said actuating means out of a latching position by the threading device directly before this device reaches the relevant one of its two positions, wherein each of the two free ends of the toggle lever is disposed in the path of movement of an end of a respective one of two latching levers, said end of each latching lever being hooked for engagement with and guidance of the respective end of the toggle lever, wherein the two latching levers are mounted on a reciprocable slide which is articulated to the pivotable arm, the latching levers being spaced from one another in the direction of movement of the slide with their hooked ends facing and forming mirror images of each other, and being pivotable in opposite directions against the action of a spring, and the pivotal axes of the two latching levers and the toggle lever being disposed on a straight line which extends parallel to

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. reached its second end position, in which it opens the switch 26 via the connection 43, so that the circuit 22 for the motor 17 is interrupted and thus the arm 33 is no longer driven. The toggle lever 64 and the two latching levers 71 and 72 then assume a position, not shown, which is the reverse of the position of these elements shown in Fig. 5. Thus the threading operation is completed, the threading device 12 being in its second position and the record carrier being in the threaded condition. The record carrier can be subsequently unthreaded by an analogous unthreading operation. This operation is not described because it is performed simply by a reverse sequence of movements to the sequence of movements described above for the threading operation. As is evident from the foregoing, the device for retaining the pivotable arm in its intermediate position, which device in the present embodiment is constituted by the latch 61, is controlled by the threading device itself. Thus it is assured that the retaining device allows the arm to be moved only when the threading device has reached, or substantially reached, one or the other of its two positions, so the threading device is transferred from one position to the other in a particularly reliable manner. WHAT WE CLAIM IS:

1. A recording and/or playback apparatus having a tape-threading device which is rotatable between first and second positions and which comprise a tape guide pin which in the first position of the threading device is engageable with a record carrier in the form of a magnetic tape supported on the apparatus and which, by rotation of the threading device into the second position, can lay a portion of the tape in a helical path around at least a part of the cylindrical surface of the drum of a rotary magnetic-head drum assembly, and comprising a drive means for rotating the threading device, which means comprises an electric motor whose direction of rotation is reversible and by which can be driven a gear wheel which cooperates with a gear ring on the threading device, starting and selection of the direction of rotation of the motor being effected with an actuating element of the apparatus, and the motor being switched off by one or the other of two switches which are actuated by means controlled in accordance with the direction of rotation of the threading device, wherein for defining the two positions of the threading device there are provided stops which directly cooperate with said device, wherein between the motor and said gear wheel there is provided a differential gearing having two driven gear wheels of which one cooperates with the gear wheel and the other with an arm which is pivotable by the motor via the differen- tial gearing from a first end position into an intermediate position and from this intermediate position into a second end position and in the reverse direction, a disengageable retaining device being provided for retaining the arm in the intermediate position, wherein each of the two switches for switching off the motor is arranged to be opened by the arm when the latter is in a respective one of its two end positions and closed by the arm when the latter is in the other end position, wherein when the threading device is in either of its two positions the arm is movable via said other driven wheel of the differential gearing and when the arm is in the intermediate position the threading device is rotatable via said one driven wheel, and wherein the retaining device is disengaged to release the arm when, or substantially when, one or the other of the two positions of the threading device is reached.

the direction of movement of the slide, and wherein the intermediate position of the pivotable arm the toggle lever occupies its latching position, in which it extends parallel to the direction of movement of the slide, under the influence of the latching levers and blocks the slide in both directions of movement via the latching levers, and when the toggle lever is pivoted out of this latching position in one direction or the other a respective one of the two latching levers is pivoted by the toggle lever against the action of said spring so that the slide is unlatched in the direction of movement in which the slide was blocked via this latching lever.

5. An apparatus as claimed in any of the preceding Claims, wherein the differential gearing is a spur-gear differential and comprises two planet gear wheels which mesh one with each of the two driven wheels of the differential gearing and which are carried by a carrier wheel driven by the motor, and wherein said one driven wheel is rigidly mounted on a shaft on which said gear wheel is also rigidly mounted and about which said other driven wheel and said carrier wheel are freely rotatable, said other driven wheel meshing with a toothed segment on a free end of the pivotable arm.

6. An apparatus as claimed in Claim 1 or 2, comprising a spring which cooperates with the pivotable arm and is stressed by movement of the arm from its intermediate position to one of its two end positions, and which when the motor is switched off acts through a force-transmission path comprising the arm, the differential gearing and said gear wheel to keep the threading device in engagement with the relevant stop.

7. An apparatus as claimed in any of the preceding Claims, comprising latching elements which are arranged to be actuated by the arm and which, depending on the position of the arm, influence the operation of adjustable control members for controlling the modes of operation of the apparatus.

8. A recording and/or playback apparatus substantially as herein described with reference to Figs. 1 to 4 or Figs. 5 and 6 of the accompanying drawings.