Rotation detecting mechanisms for tape recording and/or reproducing apparatus

Abstract: A rotation detecting mechanism for a tape recorder includes a movable shut-off lever (74) for setting at least a reproducing lever (24) or a head base (80) at a stop state position, with the reproducing lever (24) or the head base (80) being previously set to a reproducing state position, a movable changeover lever (46) for interchangeably setting forward or reverse transporting directions of magnetic tape (3), and a switching device (53, 54) for selectively shifting and setting the shut-off lever (74) or the changeover lever (46). A movable trigger lever (56) is provided for selectively triggering the switching device (53, 54), and a rotation detection lever 65 is rotationally biased in a direction which is in accordance with the rotation and the rotational direction of a reel block (6, 7) of the tape recorder. A cam gear (30) rotatable perpetually in one direction includes a first cam surface (71a) guiding one end (68a) of the detecting lever (65) when the detecting lever is rotationally biased in one direction, a second cam surface (71b) guiding the one end (68a) of the detecting lever (65) when the detecting lever is rotationally biased in the other direction, a detecting pawl (72) protrudingly formed between and independently of the first and second cam surfaces (71a, 71b), and a centre ring section (71c) responsive to cessation of rotation of the reel block (6, 7) to guide the one end (68a) of the detecting lever (65) released from rotational biasing towards a rotational trajectory of the detecting pawl (72). The detecting pawl (72) thrusts the one end (68a) of the detecting lever (65) so that the other end (70) of the detecting lever (65) actuates the trigger lever (56).

Description: This invention relates to rotation detecting mechanisms for tape recording and/or reproducing apparatus, and in particular to such mechanisms suitable for use in so-called auto reverse mechanisms for automatically reversing the running direction of a magnetic recording tape when the end of the tape is reached in the recording or reproducing mode, or in so-called auto shut-off mechanisms for automatically setting the apparatus to a stop mode when the end of the tape is reached. There has been proposed apparatus (hereinafter referred to as a tape recorder) for recording and/or reproducing information signals on a recording tape, such as a magnetic recording tape, wherein the tape recorder is provided with an auto-reverse function for reversing the tape feed direction or with an auto shut-off function for establishing a stop mode when the end of the tape is reached in the recording or reproducing mode. This type of tape recorder is provided with rotation sensing or detecting means whereby cessation of rotation of rotatable members such as reel blocks, gears or pulleys which rotate with the transporting of the recording tape may be sensed. One known type of rotation sensing or detecting means is an optical sensing means for sensing rotation of a rotatable member in which the rotatable member is provided with portions of different light reflectivity or slits, light is irradiated on these portions or slits, and changes in the intensity of the light reflected from or transmitted through the rotatable member are detected, thereby sensing the rotation or cessation of rotation of the rotatable member. Also known are magnetic or electrical sensing means for sensing the rotation of a rotatable member. In order to sense the rotation of a rotatable member by optical means in a tape recorder, it is necessary to use light emitting and light receiving elements as well as the electrical circuitry for driving the sensing elements, thus complicating the construction of the tape recorder. EP-A-0 215 627 discloses a tape recording apparatus employing a mechanical rotation detecting means. According to the present invention there is provided a rotation detecting mechanism for tape recording and/or reproducing apparatus, the mechanism comprising: a movable shut-off lever for setting at least a reproducing lever or a head base at a stop state position, said reproducing lever or the head base having been previously set to a reproducing state position; a movable changeover lever for interchangeably setting a forward or a reverse transporting direction of magnetic tape; switching means for selectively shifting and setting said shut-off lever or said changeover lever; and a movable trigger lever for selectively triggering said switching means; characterised by a detecting lever rotationally biased in a first or a second direction which is in accordance with the rotation and the rotational direction of a tape reel driving block and released from rotational biasing when the tape reel driving block rotation stops; and a cam gear rotatable continuously in one direction, said cam gear including a first cam surface for guiding one end of said detecting lever when said detecting lever is rotationally biased in said first direction, a second cam surface for guiding said one end of said detecting lever when said detecting lever is rotationally biased in said second direction, a detecting pawl protrudingly formed between and independently of said first cam surface and said second cam surface, and a narrowed cam groove section provided on a cam groove formed by said first and second cam surfaces to guide said one end of said detecting lever when released from rotational biasing, towards a rotational trajectory of said detecting pawl, said detecting pawl being operable to thrust said one end of said detecting lever so that the other end of said detecting lever actuates said trigger lever. A preferred embodiment of the present invention, to be described in greater detail hereinafter, provides a rotation detecting mechanism for a tape recorder in which rotation of rotatable members or components such as reel blocks, gears or pulleys may be sensed without resorting to provision of electrical sensing means, and in which power consumption may be lowered, allowing the power source to be reduced in size. In the preferred mechanism, rotation of the rotatable members may be detected accurately despite a simplified construction. Also, reduction in size and weight of the tape recorder may be achieved. The preferred mechanism includes a rotation sensing cam member having a cam groove for guiding a movable member of a detecting lever rotationally biased in a direction depending on the rotational direction of the reel block, and a detecting pawl protrudingly formed within the cam groove. This cam groove has one edge for guiding the movable member when the detecting lever is rotationally biased in one direction and the other edge for guiding the movable member when the detecting lever is rotationally biased in the other direction. There is provided a cam surface at least at one location in which the movable member guided by the one edge and the movable member guided by the other edge assume the same position. The detecting pawl is provided on the shifting trajectory of the cam surface. In the rotation detecting mechanism according to the preferred embodiment of the present invention, when the reel block is at a standstill and the detecting lever is no longer biased rotationally, the movable member of the detecting lever remains at a position to which it has been shifted by the cam surface of the rotation sensing cam member. The halted state of the reel block may be detected by abutment of the detecting pawl on the movable member. The rotation sensing cam member is provided with two or more projections for shifting the cam member to the cam surface, so that the movable member can be brought accurately to a position on the shifting trajectory of the detecting pawl without being affected by backlash or the like of the member or members supporting the detecting lever. The invention will now be described by way of example with reference to the accompanying drawings, throughout which like parts are referred to by like references, and in which: Figure 1 is a plan view showing the lower surface of a chassis base plate of a tape recorder to which an embodiment of the present invention is applied; Figure 2 is a plan view showing the upper surface of the chassis base plate of the tape recorder shown in Figure 1; Figure 3 is a plan view showing a normal-reverse switching mechanism in the normal state of the tape recorder shown in Figure 1; Figure 4 is a plan view showing the normal-reverse switching mechanism in the reverse state of the tape recorder shown in Figure 1; Figure 5 is a plan view showing a trigger mechanism of the tape recorder shown in Figure 1; Figure 6A is a plan view showing the main parts of the trigger mechanism of Figure 5 upon starting a triggering operation; Figure 6B is a plan view showing the main parts of the trigger mechanism of Figure 5 in the course of the triggering operation; Figure 7A is a plan view showing the main parts of the trigger mechanism of Figure 5 upon termination of the triggering operation; Figure 7B is a plan view showing the main parts of the trigger mechanism of Figure 5 in the course of a returning operation; Figure 8 is a plan view showing the main parts of the trigger mechanism of Figure 5 as the end of the restoration operation is approached; Figure 9 is a plan view showing a tape end detecting mechanism of the tape recorder, with portions thereof being shown broken away; Figure 10 is a plan view showing the tape end detecting mechanism of Figure 9 and showing the state of detection of the tape end, with portions thereof being shown broken away; Figure 11 is a plan view showing a shut-off mechanism and a mode switching mechanism of the tape recorder; Figure 12 is a view similar to Figure 11, showing the state in which the mode of the mode switching mechanism has been switched; and Figure 13 is a perspective view showing a supporting mechanism for the pinch rollers and the magnetic head of the tape recorder. In the embodiment to be described, the present invention is applied to an auto-reverse type small-size tape recorder making use of a compact cassette. Referring initially to Figures 1 and 2, the general configuration of the tape recorder and the tape running driving system will be explained. As shown in Figure 2, a tape cassette 4 accommodating therein a magnetic tape 3 wound about a pair of reel hubs 1, 2 is mounted horizontally on a tape cassette attachment section 5a provided on the upper surface of a chassis base plate 5. First and second reel blocks 6, 7 and first and second capstan shafts 8, 9 are rotatably supported on the chassis base plate 5, while first and second pinch rollers 10, 11 arranged to be brought into and out of contact with the first and second capstan shafts 8, 9 and a magnetic head 12 acting as a recording/reproducing head are also provided on the chassis base plate 5. When the tape cassette 4 is attached to the tape attachment section 5a on the chassis base plate 5, the reel hubs 1, 2 of the tape cassette 4 are engaged with reel engaging shafts 6a, 7a of the reel blocks 6, 7, while the magnetic tape 3 accommodated in the tape cassette 4 is placed on the capstan shafts 8, 9, so that the magnetic head 12 may be brought into sliding contact with the magnetic tape 3. On the front side of a main body of the player, in which the chassis base plate 5 is enclosed, there are provided operating mode select buttons including a record/reproduce button 13, a stop button 14, a fast feed button 15 and a rewind button 16. On the lower side of the base plate 5, a thin flat type driving motor 17 is provided, as shown in Figure 1, while first and second capstan pulleys 18, 19 used simultaneously as capstan flywheels are secured to the lower ends of the first and second capstan shafts 8, 9. On the lower side of the chassis base plate 5, an intermediate pulley is rotatably mounted by means of a supporting shaft 20b provided on the base plate 5 substantially halfway between the first and second reel blocks 6, 7. An inversion pulley 21 is rotatably mounted by means of a support shaft 21a provided on the base plate 5 in juxtaposition with the second capstan pulley 19 disposed on the left-hand side as shown in Figure 1. The drive power of the motor 17 is transmitted from a drive pulley 22 mounted to the end of a drive shaft 17a of the motor 17 to the first and second capstan pulleys 18, 19, the intermediate pulley 20 and the inversion pulley 21 via an endless belt 23 interconnecting the pulleys 18 to 21. The belt 23 is formed of a resilient material such as rubber and is placed about the drive pulley 22. The belt 23 is extended between the second capstan pulley 19 and the intermediate pulley 20 and is placed about the first capstan pulley 18 and the inversion pulley 21. The belt 23 is extended between the second capstan pulley 19 and the intermediate pulley 20, so that it is wound about the second capstan pulley 19 and the intermediate pulley 20 from the outer peripheral side to transmit the drive power of the motor 17 to the second capstan pulley 19 and to the intermediate pulley 20. When the drive motor 17 is rotationally driven in the direction of an arrow A shown in Figure 1, the second capstan pulley 19 and the intermediate pulley 18 are rotated clockwise in Figure 1, while the inversion pulley 21 and the first capstan pulley 18 are rotated counterclockwise in Figure 1. The reproducing button 13, the stop button 14, the fast feed button 15 and the rewind button 16 are respectively provided at the ends of a reproducing lever 24, a stop lever 25, a fast feed lever 26 and a rewind lever 27. The reproducing lever 24, the stop lever 25, the fast feed lever 26 and the rewind lever 27 are provided on the lower surface of the chassis base plate 5, as shown in Figure 1, and are mounted for reciprocating in the forward direction shown by an arrow B in Figure 1, and in the reverse direction shown by an arrow B′, with respect to the chassis base plate 5. The levers 24, 25, 26 and 27 are biased to protrude in the reverse direction shown by the arrow B′ in Figure 1, that is from the upper side edge in Figure 1 of the chassis base plate towards the outside of the chassis base plate 5, by torsion coil springs 13a and 15a supported respectively by supporting pins 13b and 15b provided upright on the lower surface of the chassis base plate 5. A locking plate 28 is provided on the levers 24, 25, 26 and 27 for interconnecting the levers 24 to 27. The lock plate 28 is mounted in the directions shown by arrows D and D′ in Figure 1, which are orthogonal to the shifting directions of the levers 24 to 27, that is, in the left and right horizontal directions in Figure 1, with slide guide pins 101, 102 mounted upright on the chassis base plate 5 inserted into and carried within elongate openings 103, 104 each having its longer axis extending along the longitudinal direction. The locking plate 28 has engaging openings 28a, 28b, 28c and 28d into which are respectively engaged pawls 24a, 25a, 26a, 27a which are provided on the levers 24, 25, 26, 27, respectively. The locking plate 28 is also biased by a torsion coil spring 90 mounted by a supporting pin 90a in turn mounted on the chassis base plate 5 so as to be shifted in the direction of the arrow D in Figure 1. Within the engaging openings 28a, 28b, 28c, 28d in the locking plate 28, there are formed inclined guides 28e, 28f, 28g, 28h abutting on the associated pawls 24a, 25a, 26a, 27a, such that, by the shifting operation along the forward direction of the arrow B in Figure 1, which is the direction of inserting the levers 24 to 27 with respect to the chassis base plate 5, the locking plate 28 is shifted in the direction of the arrow mark D′ in Figure 1 against the force of the torsion coil spring 90. Within the engaging openings 28a, 28c, 28d associated with the pawls 24a, 26a, 27a, of the reproducing lever 24, the fast feed lever 26 and the rewind lever 27, there are provided retaining pawls 28i, 28j, 28k arranged to be engaged with the pawls 24a, 26a, 27a, respectively. When moved in the forward direction shown by the arrow B in Figure 1, which is the inserting direction with respect to the chassis base plate 5, the reproducing lever 24, the fast feed lever 26 and the rewind lever 27 are locked with the pawls 24a, 26a, 27a thereof retained by the retaining pawls 28i, 28j, 28k, respectively. The locked state of the reproducing lever 24, the fast feed lever 26 and the rewind lever 27 is released when the stop lever 25 is shifted in the inserting direction thereof with respect to the chassis base plate 5, that is in the forward direction shown by the arrow B in Figure 1. On the locking plate 28, there is provided a switch plate 29 which overlies the locking plate 28. The switch plate 29 is mounted for reciprocating along the directions shown by the arrows D and D′ in Figure 1, orthogonal to the shifting direction of the levers 24, 25, 26, that is, in the left and right horizontal directions as shown in Figure 1, by having slide guide pins 101, 102 supporting the locking plate 28 inserted into and supported within elongate openings 105, 106 each having its long axis extending in the longitudinal direction. The switch plate 29 is mounted with the pawls 24a, 25a, 26a engaging in engaging openings 29a, 29b, 29c bored in association with the pawls 24a, 25a, 26a, which are provided in the levers 24, 25, 26, respectively. The switch plate 29 is biased by the tension spring 107 so as to be urged in the direction shown by the arrow D in Figure 1, that is, in the same direction as that for the locking plate 28. Inclined guide surface sections 29d, 29e are provided within two of the engaging openings 29a and 29c in the switch plate 29 which are associated with the pawls 24a and 26a of the reproducing lever 24 and the fast feed lever 26. An inclined guide surface section 29f is provided at one end of the switch plate 29 facing the pawl 27a of the rewind lever 27 of the switch plate 29. The switch plate 29 is shifted along with the locking plate 28 in the direction of the arrow D′ in Figure 1, against the bias of the tension spring 107, by being shifted in the forward direction shown by the arrow B in Figure 1, that is, in the direction of inserting either the reproducing lever 24, the fast feed lever 26 or the rewind lever 27. When one of the reproducing lever 24, the fast feed lever 26 or the rewind lever 27 is actuated in the direction shown by the arrow B in Figure 1 and the switch plate 29 is shifted in the direction shown by the arrow D′, the start switch (not shown) is actuated. By actuation of the start switch, electric power is supplied to the drive motor 17, the reproducing circuit or the recording/reproducing circuit thereby rotating the drive motor 17 and actuating the reproducing or recording/reproducing circuit (not shown) connected to the magnetic head 12. As a result of driving of the driving motor 17, the first and second capstan pulleys 18, 19 and the intermediate pulley 20 are rotationally driven by means of the belt 23. It is to be noted that the first and second capstan pulleys 18, 19 are driven rotationally in mutually opposite directions. The intermediate pulley 20 is coaxially integrally formed with a small diameter gear section 20a meshing with a first gear section 30a of a cam gear 30 attached to the lower surface of the chassis base plate 5. The cam gear 30 is carried by a supporting shaft 110 mounted upright on the chassis base plate 5, and is mounted rotatably on the lower side of the chassis base plate 5. The cam gear 30 has the first gear section 30a formed on its outer periphery, and is provided on its planar surface 30b with a cam groove 71 constituting a tape end detecting mechanism, as will be subsequently described. The cam gear 30 is provided centrally with a second small-diameter gear section 30c, which is mounted coaxially to the cam gear 30 with the intermediary of a friction member, as shown in Figure 1. The second gear section 30c meshes with an intermediate gear 31. The intermediate gear 31 is rotatably supported by a supporting shaft 32a mounted upright on the end of an intermediate gear supporting lever 32 pivotally mounted about a supporting shaft 110 carrying the cam gear 30. That is, the intermediate gear 31 is actuated by rotation of the intermediate gear supporting lever 32 as the gear 31 meshes with the second gear section 30c of the cam gear 30. When the reproducing lever 24 is thrustedly actuated in the direction shown by the arrow B in Figure 1, the intermediate gear supporting lever 32 is rotated in the direction shown by arrows E or E′ in Figure 1 by a normal-reverse changeover device, as will be subsequently described. Since the friction member is interposed between the first and second gear sections 30a and 30c of the cam gear 30, when the member or section rotated in mesh with the second gear section 30c offers a lesser rotational resistance, the second gear section 30c is rotated with the rotation of the drive motor 17. However, when the member or section rotated in mesh with the second gear section 30c offers a larger rotational resistance, the second gear section 30c is not rotated with rotation of the drive motor 17. The first and second reel blocks 6, 7 are coaxially provided with first and second reel block gears 33, 34 on the lower surface of the chassis base plate 5. The second reel block gear 34 mounted to the second reel block 7 meshes with an inversion gear 35. When the reproducing gear 24 is thrustedly actuated in the forward direction shown by the arrow B in Figure 1, the intermediate gear 31 is moved between the first reel block gear 33 and the inversion gear 39, by the rotation of the intermediate gear supporting lever 32, so as to be engaged selectively with the first reel block gear 33 or the inversion gear 35. Thus, as the drive motor 17 is driven rotationally, one of the first and the second reel blocks 6, 7 is driven rotationally in a predetermined direction, and the reel hubs 1, 2 engaging with the reel blocks 6, 7 are thereby rotated to take up the magnetic tape 3 in the normal or reverse direction. At a chevron-shaped end of the fast feed lever 26, there is rotationally mounted a fast feed idle gear 36 on a supporting shaft 36a. When the fast feed lever 26 is thrustedly actuated in the direction of the arrow B in Figure 1 and shifted in the forward position, the fast feed idle gear 36 meshes with the inversion gear 35 and the first gear section 30a of the cam gear 30 simultaneously. That is, when the fast feed button 15 is thrustedly actuated in the direction of the arrow B in Figure 1, and the drive motor 17 is thereby driven rotationally, the rotation of the first gear section 30a of the cam gear 30 is transmitted via the fast feed idle gear 36 to the inversion gear 35, so that the reel block 7 is driven rotationally at a higher speed. Similarly, at a chevron-shaped end of the rewind lever 27, there is rotatably mounted a rewind idle gear 37 on a supporting shaft 37a. When the rewind lever 27 is thrust in the direction of the arrow B in Figure 1 and thereby shifted in the forward position, the rewind idle gear 37 simultaneously meshes with the first reel block gear 33 and the first gear section 30a of the cam gear 30. That is, when the rewind button 16 is thrustedly actuated in the direction of the arrow B and the drive motor 17 is driven rotationally, the rotation of the first gear section 30a of the cam gear 30 is transmitted to the first reel block gear 33 through the rewind idle gear 37, so that the first reel block 6 is driven rotationally at a higher speed. Referring now to Figures 1, 3 and 4, the normal-reverse changeover device will be explained. At an L-shaped end of the reproducing lever 24, towards the inner side of the chassis base plate 5, there is connected a transmission lever 39 by means of a limiting spring 38, as shown in Figure 3. The transmission lever 39 is rotatably carried by a supporting shaft 39a mounted upright on the lower surface of the chassis base plate 5. A spring retainer 39b for the limiting spring 38 is formed at one end of the transmission lever 39, while an engaging section 39c engaging with a recess 40b on one lateral side of a magnetic head shifting lever 40 is formed at the other end of the lever 39. The lever 39 is connected to the reproducing lever 24 by the limiting spring 38 installed under tension between the spring retainer 39b and a spring retainer 24b formed at the end of the reproducing lever 24. Since a tension spring is used as the limiting spring 38, when the reproducing lever 24 is thrustedly actuated in the direction shown by the arrow B in Figure 1 and thereby shifted in the forward direction, the transmission lever 39 is turned counterclockwise as shown by an arrow F in Figure 3, under the force of the limiting spring 38, about the supporting shaft 39a, so as to follow up with the forward movement of the reproducing lever 24. The purpose of the limiting spring 38 is to prevent an excessive force from being applied to the transmission lever 39 in that the spring 38 is extended when the thrust force is further applied to the reproducing lever 24 in the forward direction shown by the arrow B in Figure 3 after the transmission lever 39 has been rotated to and positioned at a predetermined position, as will be later described. By such rotation of the transmission lever 39, the engaging portion 39c formed at the other end of the transmission lever 39 is similarly turned counterclockwise in the direction shown by the arrow F in Figure 3 to shift the magnetic head shifting lever 40 in the direction shown by the arrow G in Figure 3. The magnetic head shifting lever 40 is mounted on the lower surface of the chassis base plate 5 so as to be reciprocated in the same directions as those for the reproducing lever 24, the stop lever 25, the fast feed lever 26 and the rewind lever 27, that is, in the directions shown by the arrows G and G′ in Figures 1 and 3, so that the shifting lever 40 is reciprocated in the directions shown by the arrows G and G′ by the rotational movement of the transmission lever 39. At the other end of the magnetic head shift lever 40, there is mounted a magnetic head engaging pawl 40a, as shown in Figures 1 and 3. As will be described subsequently, the magnetic head engaging pawl 40a is engaged with the rotatably supported magnetic head 12. That is, as the reproducing lever 24 is shifted in the forward direction, as indicated by the arrow B in Figure 3, the magnetic head 12 is moved towards the inside of the tape cassette 4 and into contact with the magnetic tape 3 to establish the reproducing mode. The magnetic head shifting lever 40 rotatably supports a pinch roller shifting lever 41 by the intermediary of a supporting shaft 41a mounted upright on the shift lever 40. The pinch roller shifting lever 41 is provided with first and second pinch engaging pawls 42, 43 and first and second abutting arms 44, 45, with the supporting shaft 41a as the centre of rotation. In the reproducing mode, the pinch roller shifting lever 41 is rotated in one of the directions shown by arrows H or H′ in Figure 3, so that the associated side of the first or second pinch roller 10, 11 supported so as to be brought into or out of contact with the first or second capstan shaft 8 or 9 (as will be later described) is moved into abutment with the first or second capstan shaft 8 or 9 through one of the first and second pinch roller engaging pawls 42 and 43. The magnetic tape 3 is extended between the first and second pinch rollers 10, 11 and the first and second capstan shafts 8, 9, and is clamped by one of the first and second pinch rollers 10 and 11 abutting on the associated one of the first and second capstan shafts 8 and 9. The magnetic tape 3 is fed depending on the direction of rotation of the first or second capstan shafts 8 and 9. The direction of rotation of the pinch roller shift lever 41 is controlled by a changeover lever 46. As shown in Figure 3, the changeover lever 46 is mounted for reciprocation in the direction shown by an arrow I or I′ in Figure 5, being guided by slide guide pins 112, 113 which are mounted upright on the lower surface of the chassis base plate 5 and inserted into and supported within slide guide openings 146a, 146b, each having its long axis extending in the longitudinal direction. The changeover lever 46 is provided with first and second abutting projections 47, 48 abutting on first and second abutting arms 44, 45 of the pinch roller shifting lever 41 Thus, in the reproducing mode, when the changeover lever 46 is shifted towards the one side indicated by the arrow 1 in Figure 3, the first abutting arm 44 and the first abutting projection 47 abut against each other so that the pinch roller shifting lever 41 is turned clockwise in the direction of the arrow H about the supporting shaft 41a. In this manner, the second pinch roller engaging pawl 43 causes the second pinch roller 11 to be shifted in a direction in which it abuts against the capstan shaft 9 on the other side. On the other hand, when the changeover lever 46 has been shifted towards the other side indicated by the arrow I′ in Figure 4, the second abutting arm 45 and the second abutting projection 48 abut against each other to cause the pinch roller shifting lever 41 to be turned counterclockwise as indicated by the arrow H′ in Figure 4, such that the first pinch roller engaging pawl 42 causes the first pinch roller 10 to shift in a direction in which it is abutted against the first capstan shaft 8. As the ends of the first and second abutting arms 44, 45 of the pinch roller shifting lever 41, there are respectively provided first and second engaging pawls 44a, 45a. When the magnetic head shift lever 40 is shifted in the direction shown by the arrow G in Figures 3 and 4 by the thrusting operation of the reproducing lever 24 in the forward direction shown by the arrow B in Figures 3 and 4, the engaging pawls 44a, 45a abut on the ends of first and second arms 50, 51 projectingly mounted to both sides of the intermediate gear shifting lever 49 which is rotatably mounted about a support shaft 20b mounted in turn on the lower surface of the chassis base plate 5. The intermediate gear shifting lever 49 is rotationally actuated by abutment of the first and second engaging pawls 44a, 45a with the first and second arms 50, 51, so as to follow the rotation of the pinch roller shifting lever 41. On one side of the intermediate gear shifting lever 49, there is provided an engaging arm 52 engaging with the lever 32. Thus, when the shifting lever 49 is turned in the direction shown by the arrow J or J′ in Figures 3 and 4 about the supporting shaft 20b, the lever 32 is also turned responsive thereto in the direction shown by the arrow E or E′ in Figures 3 and 4, about the supporting shaft 110, so as to be shifted in a direction in which the intermediate gear 31 mounted to the end of the intermediate gear supporting lever 32 meshes with the inverting gear 35 or with the reel block gear 33. When the reproducing lever 24 is actuated in the forward direction shown by the arrow B in Figures 3 and 4, the reproducing lever 24 is shifted slightly in the forward direction so as to be retained subsequently after the magnetic head shifting lever 40 is positioned following the regulation of the movement of the magnetic head shifting lever 40 in the upward direction as indicated by the arrow G in Figure 1. When the magnetic head shifting lever 40 is positioned and retained, the movement of the transmission lever 39 is also terminated. Thus, when the reproducing lever 24 is retained at the forward position in which it has been actuated in the direction shown by the arrow B in Figures 3 and 4, the limiting spring 38 is extended slightly for biasing the magnetic head shifting lever 49 to be moved further upwards as indicated by the arrow G in Figure 3. The magnetic head shifting lever 40 is positioned by controlling the shifting of the pinch roller shifting lever 41 by the switch lever 46 and by the intermediate gear shifting lever 49, rotation of which is controlled in operative association with the intermediate gear 31 meshing with a predetermined gear. The bias of the limiting spring 38 applied to the magnetic head shifting lever 40 is transmitted via the pinch roller shifting lever 41 to the intermediate gear shifting lever 49 and to the changeover lever 46. The biasing force transmitted to the intermediate gear shifting lever 49 is transmitted via the intermediate gear supporting lever 32 to the intermediate gear 31. When the intermediate gear 31 is to be physically separated from the inverting gear 35 or from the first reel block gear 33 meshing with the gear 31, the magnetic head shifting lever 40 is necessarily moved against the biasing force of the limiting spring 38. In this manner, the intermediate gear 31 is not separated physically from the inverting gear 35 or from the first reel block gear 33 meshing with the intermediate gear 31. The intermediate gear shifting lever 49 is provided with a rotation control pawl 49a engaging in a sector-shaped opening 40c in the magnetic head shifting lever 40. In the reproducing mode, the rotation control pawl 49a is engaged in a larger diameter portion of the sector-shaped opening 40c, so that the intermediate gear shifting lever 49 may be turned in the direction indicated by arrows J or J′ in Figure 3 with the supporting shaft 113 as the centre of rotation. Thus the supporting lever 32 having its other end engaged in the engaging arm 52 of the intermediate gear shifting lever 49 is also rotated to follow the rotation of the intermediate gear shifting lever 49 so that the intermediate gear 31 attached to one end of the intermediate gear shifting lever 49 will be engaged with the reel block gear 33 or with the inverting gear 35. In other than the reproducing mode, that is when the reproducing lever 24 is shifted in the reverse direction as indicated by the arrow B′ in Figures 1 and 3 so that the magnetic head shifting lever 40 is moved in the direction shown by the arrow G′ in Figures 1 and 3 (so as to be returned to its original position), the rotation control pawl 49a is engaged in the lesser diameter portion of the sector-shaped opening 40c to control the rotation of the intermediate gear shifting lever 49 and that of the intermediate gear supporting lever 32 connected to the shifting lever 49, such that the intermediate gear 31 mounted to one end of the supporting lever 32 is not engaged with the first reel block gear 33 nor with the inverting gear 35. Meanwhile, the changeover lever 46 is controlled in its position as a function of the rotational position of a changeover interrupted gear 53, which is rotatably mounted at a position of meshing with the first gear section 30a of the cam gear 30 by means of a supporting shaft 53a mounted upright on the chassis base plate 5, and is provided with first and second interrupted portions 53n, 53r, at two positions displaced by 180° from each other. This changeover interrupted gear 53 is provided with an offset cam section 54 engaging in an engaging recess 46a formed on one side end of the changeover lever 46. When the changeover interrupted gear 53 is in its normal position, that is when the first interrupted portion 53n faces the first gear section 30a of the cam gear 30, with the interrupted gear 53 not meshing with the cam gear 30, as shown in Figure 3, the offset cam section 54 abuts on an upright inner lateral side 46b of the recess 46a on the right-hand side as shown in Figure 3 for positioning the switch lever 46 at one position or a normal position shifted in the direction shown by the arrow 1 in Figure 3. When the changeover interrupted gear 53 is in the reverse position, as shown in Figure 3, that is when the second interrupted portion 53r faces the first gear section 30a of the cam gear 30, with the changeover interrupted gear 53 not meshing with the cam gear 30, the offset cam section 54 abuts on the other upright inner lateral side 46c of the recess 46a towards the left as shown in Figure 4 for positioning the changeover lever 46 at the other or a second position or the reverse position shifted in the direction indicated by the arrow I′ in Figure 4. With the changeover interrupted gear 53 positioned in the above normal or reverse position, the changeover lever 46 is also positioned in the first or normal position or in the second or reverse position, so that the pinch roller shifting lever 41 is selectively turned in the direction shown by the arrow H or H′ in Figures 3 and 4. In this manner, recording or reproduction in the normal or reverse direction is performed, in which one of the second or the first pinch rollers 11, 10 is abutted against the respective one of the second or first capstan shafts 9, 8. On one planar surface of the changeover interrupted gear 53, there are formed first and second positioning projections 55n, 55r at two positions spaced by 180° from each other. The projections 55n, 55r are selectively abutted on a trigger lever 56 and biased to be rotated by a trigger mechanism (as will be later described) in a direction in which they are thrust against the trigger lever 56 for positioning the gear 53 in the normal or reverse position. The trigger mechanism will now be explained by referring to Figures 1 and 5 to 8. The trigger lever 56 constituting the trigger mechanism is formed substantially in the form of a letter L, as shown in Figures 1 and 5, and is mounted for movement in the reverse direction as indicated by an arrow L′ in Figures 1 and 5 and in the forward direction as indicated by an arrow L, as a result of a pair of slide guide shafts 114, 115 mounted upright on the lower surface of the chassis base plate 5 being engaged in slide guide openings 116, 117 formed in a main body 56a of the trigger lever 56, each having its longer axis extending in the longitudinal direction of the main body 56a, and as a result of the slide guide shafts 114, 115 being guided within the slide guide openings 116, 117. The trigger lever 56 is biased by a first spring plate 57 attached to the chassis base plate 5 in the return direction indicated by the arrow L′ in Figure 5. The trigger lever 56 has its abutment edge 56c at the end of a bent portion 56d on one end of the main body 56a abutting on and engaging with one of the positioning projections 55n, 55r of the changeover interrupted gear 53. The trigger lever 56 is shifted in the reciprocating direction indicated by the arrow L′ or L in Figure 5 by a changeover lever 61 reciprocally mounted to the chassis base plate 5 in juxtaposition with the reproducing lever 24, the stop lever 25, the fast feed lever 26 and the rewind lever 27, and a trigger transmission lever 63 pivoted by the thrusting operation of the changeover lever 61. When the changeover lever 61 is thrust and slid in the forward direction indicated by the arrow L in Figure 5, the trigger lever 56 has its abutment edge 56d positioned along the outer periphery of a rotational trajectory of the first and second positioning projections 55n, 55r. When in the above normal or reverse position, the changeover interrupted gear 53 has its first or second positioning projections 55n, 55r biased to be rotated clockwise as indicated by the arrow C in Figure 5, that is in a direction thrusting the abutment edge 56c of the trigger lever 56. Thus, as shown in Figures 3 and 4, when the changeover interrupted gear 53 is in the above normal or reverse position, a straight line interconnecting an abutting point between the end abutment 53b of the offset cam section 54 and the one upright inner lateral side 56b or the other upright inner lateral side 46c of the engaging recess 46a of the changeover lever 46 and the centre of the supporting shaft 53a which is the centre of rotation of the changeover interrupted gear 53 does not run parallel to the reciprocating direction of the changeover lever 46. This changeover lever 46 is biased to be moved towards a neutral position by a torsion spring 59 mounted to the chassis base plate 5. Thus the changeover interrupted gear 53 is perpetually biased by the changeover lever 46 so as to be rotated in the direction shown by the arrow C in Figure 5. In the reproducing mode, the changeover lever 46 is biased towards its neutral position not only under the bias of the torsion spring 59 and the limiting spring 38 but also by biasing means operative to bias the first and second pinch rollers 10, 11 to be displaced away from the associated first and second capstan shafts 8, 9. Thus, when the reproducing lever 24 is moved forward and retained, as described hereinabove, the changeover lever 46 cooperates with the intermediate gear shifting lever 49 to control the pivoting of the pinch roller shifting lever 41 for positioning the magnetic head shifting lever 40 at a position to which it has been shifted in the direction indicated by the arrow G in Figure 1. The biasing force of the limiting spring 38, applied to the magnetic head shifting lever 40, is transmitted by way of the pinch roller shifting lever 41 to the changeover lever 46. Those portions of the first and second abutment arm sections 44, 45 of the pinch roller shifting lever 41 that are abutted by the first and second abutment projections 47, 48 are formed as inclined surfaces 44b, 45b, so that the limiting spring 38 acts to bias the changeover lever 46 to its neutral position. On the other hand, the pinch roller shifting lever 41 is biased towards a neutral point of rotation under the bias acting to shift the first and second pinch rollers 10, 11 in a direction away from the associated first and second capstan shafts 8, 9. In similar manner to the bias afforded by the limiting spring 38, this bias acts to shift the changeover lever 46 towards its neutral position. The changeover interrupted gear 53 is rotationally biased, as described above, when in the above-described normal or reverse position, so that it is pivoted slightly when the trigger lever 56 is slid in the forward direction shown by the arrow L in Figure 5. At this time, the first and second interrupted portions 53n, 53r of the interrupted gear 53 are shifted away from the position of facing the first gear section 30a of the cam gear 30, with the interrupted gear 53 meshing with the first gear section 30a. At this time, since the first gear section 30a is driven rotationally by the drive motor 17, the changeover interrupted gear 53 is rotationally driven in the direction shown by the arrow C in Figure 5 and positioned after being turned through 180° by abutment of one of the abutment projections 55n, 55r with the abutment edge 56c of the trigger lever 56. In this manner, the normal position and the reverse position for the reproducing or recording mode are interchanged by the rotation through 180° of the changeover interrupted gear 53 and the resulting shifting of the changeover lever 46 from the first position shifted as shown by the arrow I in Figure 3 to the second position shifted as shown by the arrow I′ in Figure 4, or from the second position shifted in the direction shown by the arrow I′ in Figure 4 to the first position shifted in the direction shown by the arrow 1 in Figure 3. The changeover lever 61 for reciprocating the trigger lever 56 in the direction shown by the arrow L in Figure 5 is mounted for reciprocation in the direction shown by the arrow M or M′ in Figure 5, with respect to the chassis base plate 5, with a pair of slide guide shafts 118, 119 on the chassis base plate 5 engaging in slide guide openings 120, 121 of the lever 61 each having its longer axis extending lengthwise of the lever 61. The changeover lever 61 is biased by a second spring plate 60 mounted on the chassis base plate 5 so as to be shifted in the return direction shown by the arrow M′ in Figure 5. Thus the changeover lever 61 has an engaging portion 61b on its lateral side engaging with the end of the spring plate 60, so that the lever 61 is biased to be shifted by the spring plate 60 in the return direction shown by the arrow M′ in Figure 5. A changeover button 58 is also mounted on one end of the changeover lever 61. On the changeover lever 61, a changeover transmission lever 62 is pivotally mounted by means of a supporting shaft 62a mounted upright on the lever 61. On thrusting the changeover lever 61, the changeover transmission lever 62 is abutted and engaged by a trigger transmission lever 63 pivotally mounted via a supporting shaft 122 mounted upright on the chassis base plate 5, as shown in Figure 6A. The trigger transmission lever 63 has an abutment section 63a facing the bent portion 56d projectingly mounted to the other side of the trigger lever 56 which is biased in the return direction shown by the arrow L′ in Figure 5 by the first spring plate 57 attached to the chassis base plate 5 as previously described. The trigger transmission lever 63 is positioned so as to be controlled in its rotation in the direction opposite to that indicated by an arrow N in Figure 5 by the abutment section 63a abutting on and engaging with a retaining pin 63c facing the bent portion 56d. The trigger transmission lever 63 having its abutment section 63a facing the bent portion 56d of the trigger lever 56 is rotated by means of the changeover transmission lever 62 as indicated by the arrow N in Figure 5 by the trigger lever 61 being actuated in the direction shown by an arrow M in Figure 6. The trigger transmission lever 63 causes the trigger lever 56 to be shifted in the direction shown by the arrow L′ in Figure 5. The changeover transmission lever 62 has a lever abutment section 62b at one end facing an abutment section 63b formed at one end of the trigger transmission lever 63 towards the direction shown by an arrow M in Figure 5 which is the forward direction of the reciprocation of the changeover lever 61. The changeover transmission lever 62 has a rotation control section 62c at its other end abutting on a retaining projection 61a provided on a portion of the changeover lever 61 to control the rotation in the direction opposite to that shown by an arrow O in Figure 5. When the changeover lever 61 is actuated in the forward direction shown by the arrow M in Figure 5, a lever abutment portion 62b formed at one end of the changeover transmission lever 62 abuts on and engages with the abutment section 63b formed at one end of the trigger transmission lever 63 to thrust the abutment section 63b thus rotating the trigger transmission lever 63 in the direction shown by the arrow N in Figures 6A and 6B. At this time, the changeover transmission lever 62 is controlled in its rotation opposite to the direction of the arrow O in Figures 6A and 6B by the rotation control section 62c formed at the other end of the lever 62 abutting on and engaging with the retaining projection 61a provided on the changeover lever 61. With the trigger transmission lever 63 pivoted in this manner, the bent portion 56d is engaged with the abutment section 63a formed at one end of the trigger transmission lever 63 and the abutment section 63a is thrustedly actuated to shift the trigger lever 56 in the forward direction of the reciprocation, as indicated by the arrow L in Figure 6B. The normal direction and the reverse direction for reproduction may be interchanged by such shifting of the trigger lever 56 in the forward direction of the reciprocation as indicated by the arrow L in Figure 6B. When the changeover lever 61 is further slid in the forward direction of reciprocation as indicated by the arrow M in Figures 6A and 6B, the trigger transmission lever 63 is further rotated in the direction shown by the arrow N in Figure 6B to release the engagement between the abutment section 63b at the other end of the trigger transmit lever 63 and the abutment portion 62b at one end of the changeover transmission lever 62, thereby causing the abutment portion 62b of the changeover transmission lever 62 to pass by and be spaced from the abutment section 63b of the trigger transmission lever 63. This releases the thrusting of the trigger transmission lever 63 by the changeover transmission lever 62, so that the trigger lever 56 is shifted under the bias of the first spring plate 57 in the return direction shown by the arrow L′ in Figure 7, until arriving at the initial position shown in Figure 5. The trigger transmission lever 63 is rotated in the return direction shown by the arrow N′ in Figure 7 until arriving at the position of abutting on the bent portion 56d of the trigger lever 56 in which the abutment section 63a is returned to its initial position. When the changeover lever 61 is shifted under the force of the second spring plate 60 in the return direction shown by the arrow M′ in Figure 7A, the abutment section 62b of the changeover transmission lever 62 abuts on and engages with the abutment section 63b of the trigger transmission lever 63, as shown in Figure 7B. At this time, the trigger transmission lever 63 is returned to its initial position, as shown in Figure 7B, so as to be positioned by the retaining pin 63c. The changeover transmission lever 62 is rotated by the abutment section 63b in the direction opposite to that indicated by the arrow O in Figures 7B and 8, so that the abutment section 62c is spaced apart from the retaining projection 61a. When the changeover lever 61 is returned to its initial position shown in Figure 5, the changeover transmission lever 62 is rotated in the direction shown by the arrow O in Figure 8 so as to be forcibly returned to its initial position (shown in Figure 5) by the rotation control section 62c at the other end abutting on a return projection 64 provided on the chassis base plate 5. Thus, when the changeover lever 61 is returned to its initial position, the rotation control section 62c of the changeover transmission lever 62 is clamped between the returning projection 64 and the retaining projection 61a. The tape end detection mechanism will now be explained, referring to Figures 1, 9 and 10. The tape end detection mechanism is shown in Figure 9 and comprises a detecting lever 65 having one end engaging in a cam groove 71 formed on one planar surface 30b of the perpetually rotated cam gear and having its other end engageable with the aforementioned trigger lever 56. The detecting lever 65 is formed as one piece typically from synthetic resin and, as shown in Figure 9, has a main body 69 with an opening 65a. A profiling projection 68a engaging in the cam groove 71 is formed at one end 68 of the main body 69 and a trigger lever thrust section 70 is projectingly provided at the other end of the main body 69 opposite to the profiling projection 68a. With the opening 65a of the main body 69 of the detecting lever 65, there is provided a flexural arm 67 that may be extended and contracted in the direction of elongation and which has a cylindrical end fulcrum 66 with the other end 68 as the connecting portion. This flexural arm 67 is formed by a plurality of bent sections of reduced thicknesses in the form of a spring. The detecting lever 65 is so formed that the fulcrum 66 and the trigger lever thrust section 70 are situated on a substantially straight line. The detecting lever 65 is rotatably supported with the gear shaft 33a as the rotational centre by having the fulcrum 66 at the end of the flexural arm 67 supported by the gear shaft 33a of the first reel block gear 33, by means of a friction member such as a coil spring, and by having the profiling projection 68a engaging in the cam groove 71 formed in the cam gear 30. In the detecting lever 65, the flexural arm 67 is extended or contracted as the cam gear 30 is rotated and the profiling projection has variable engaging positions in the cam groove 71. The trigger arm thrust section 70 is advanced or returned with extension and contraction of the flexural arm 67. The cam groove 71 formed on the planar surface 30b of the cam gear 30 and engaged by the profiling projection of the detecting lever has an outer peripheral cam surface 71a and an inner peripheral cam surface 71b. Within the cam groove 71, there is formed a centre ring 71c having a distance r1 between the outer peripheral cam surface 71a and the inner peripheral cam surface 71b equal to the diameter r2 of the profiling projection 68a. Within the cam groove 71 at a position on the same rotational trajectory as the centre ring 71c and spaced a predetermined angle from the centre ring 71c, there is projectingly formed a trigger pawl 72 independently from the outer peripheral cam surface 71a and the inner peripheral cam surface 71b. In the reproducing mode, when the tape cassette 4 is attached in position and the magnetic tape 3 is in the running state in the tape cassette 4, the first reel block 6 is rotated in one or the other direction. At this time, the fulcrum 66 is rotationally biased by one reel block gear 33 via the friction member for rotationally biasing the detecting lever 65. When reproduction or recording is performed in the normal direction, for example, the detecting lever 65 is rotationally biased so that the profiling projection 68a is directed towards the outer periphery of the cam gear 30 and, when reproduction or recording is performed in the reverse direction, the detecting lever 65 is rotationally biased so that the profiling projection 68a is directed towards the inner periphery of the cam gear 30. In the reproducing mode, since the cam gear 30 is driven rotationally by the drive motor 17 in the direction shown by an arrow Q in Figure 9, the profiling projection 68a is moved so as to follow the contour of the cam groove 71. When reproduction or recording is performed in the normal direction, for example, the profiling projection 68a is moved as it is guided by the outer peripheral cam surface 71a of the cam groove 71 and, when reproduction or recording is performed in the reverse direction, the profiling projection 68a is moved as it is guided by the inner peripheral cam surface 71b of the cam groove 71. In this manner, during running of the magnetic tape 3, the profiling projection 68a is moved along the outer peripheral cam surface 71a or the inner peripheral cam surface 71b, due to rotation of the first reel block 6 and the rotational driving of the drive motor 17, so that the projection 68a is moved by being guided along the outer peripheral cam surface 71a or the inner peripheral cam surface 71b, without abutting against the trigger pawl 72, even after passing the centre ring section 71c. When the magnetic tape 3 has reached its end in the reproducing mode, rotation of the first reel block 6 and that of the first reel block gear 33 are terminated. Rotational bias is thus no longer applied to the detecting lever 65. The rotation of the second reel block 7 ceases, so that rotation of the second reel block gear 34 and the inverting gear 36 also ceases. Rotation of the intermediate gear 31 meshing with one of the first reel block gear 33 and the inversion gear 35 ceases while that of the second gear section 30c of the cam gear 30 also ceases. However, since the second gear section 30c is mounted on the cam gear 30 by means of the friction member, rotation of the first gear section 30a and the cam gear 30 continues. When the profiling projection 68a of the detecting lever 65 reaches the centre ring section 71c in the cam groove 71, by rotation of the cam gear 30, until arrival at a position on the shifting trajectory of the trigger pawl 72, the detecting lever 65 is no longer biased rotationally by the reel block gear 33, so that the profiling projection 68a is left at the position on the shifting trajectory of the trigger pawl 72. That is to say, the detecting lever 65 is at a standstill at a predetermined position, as indicated in Figure 9. On further rotation of the cam gear 30 in the direction shown by the arrow Q in Figure 9, the trigger pawl 72 provided within the cam groove 71 abuts on the profiling projection 68a. On still further rotation of the cam gear 30, the flexural arm 67 is thrustedly biased so as to be compressed in the direction shown by an arrow R in Figure 10. The profiling projection 68a thrust by the trigger pawl 72, is shifted to approach towards the fulcrum 66 with compression of the flexural arm 67. As a result of such thrusting of the profiling projection 68, the flexural arm 67 is compressed in the direction shown by the arrow R in Figure 10, while the main body 69 of the lever 65 is shifted in the same direction with respect to the fulcrum 66. When the lever main body 69 is thrust in the direction of the arrow R in Figure 10, the trigger lever thrusting section 70 provided on the other end of the lever main body 69 in opposition to a mating thrust pawl 56b provided on the trigger lever 56 thrusts the mating pawl 56b to shift the trigger lever 56 in the forward direction shown by the arrow L in Figure 10 for interchanging between the normal direction and the reverse direction for reproduction or recording, in the manner described hereinabove. It is to be noted that, when guided and shifted by the inner peripheral cam surface 71b, the profiling projection 68a of the detecting lever 65 is guided by the first projection on the inner peripheral cam surface 71b so as to be moved more peripherally outwardly than the centre ring section 71c, before reaching the centre ring section 71c within the cam groove 71. Therefore, in both the normal or reverse directions in the reproducing or recording mode, the profiling projection 68a is guided, when proceeding to the centre ring section 71c, from the more peripherally outer side than the centre ring section 71c, that is, along the outer peripheral cam surface 71a of the cam groove 71. Thus, in both the normal and reverse directions of the reproducing or recording mode, the profiling projection 68a may be positioned accurately without being affected by backlash due to the reaction force to the rotational bias caused by the frictional member provided in the fulcrum 66. After passing through the centre ring section 71c, the profiling projection 68a is guided by the second projection 71e on the outer peripheral cam surface 71a towards the more peripherally inner side of the cam groove 71, and is corrected in its position so as to lie correctly on the shifting trajectory of the trigger pawl 72. In the fast feed and rewind modes, for preventing the profiling projection 68a of the detecting lever 65 from abutting on the trigger pawl 72 on the cam gear 30, a detecting lever shifting member 73 is provided that is shifted in operative association with the shifting of the magnetic head shifting member 40. The detecting lever shifting member 73, formed as a torsion coil spring, carries a central coil part 73a on a supporting shaft 125 mounted on the chassis base plate 5, and is rotatably mounted for rotation about the supporting shaft 125. The detecting lever shifting member 73 has one arm section 73b engaging with one side of the magnetic head shifting lever 40 and, in the fast feed and rewind modes, has its other arm section 73c abutting on and engaging with one side of the detecting lever 65 for rotationally biasing the detecting lever 65 in the direction shown by an arrow 5 in Figure 9 in which the profiling projection 68a proceeds towards the inner periphery of the cam groove 71. The tape recorder is set in the reproducing mode and, when the magnetic head shifting lever 40 is shifted in the direction shown by the arrow G in Figure 10, the detecting lever shifting member 73 is turned clockwise in Figure 9 by way of the one arm section 73b so that the abutting engagement of the other arm section 73c is released to allow for rotation of the detecting lever 65. The shut-off mechanism will now be explained by referring to Figures 1, 11 and 12. The shut-off mechanism includes a shut-off lever 74 and a shut-off transmit lever 75. As shown in Figure 11, the shut-off lever 74 is mounted on the lower surface of the chassis base plate 5, with a mating thrust section 74b bent at right angles with respect to the main body of the lever 74a facing the rotational trajectory of the offset cam section 54 of the changeover interrupted gear 53, and with a thrusting section 74c at the end of the bent portion facing one end of the locking plate 28. The shut-off lever 74 is mounted for rotation about a supporting shaft 126 on the lower surface of the chassis base plate 5 by having the bent proximal end of the shut-off lever 74 supported by the supporting shaft 126, with the thrusting section 74c being formed at the proximal end of the lever 74. The shut-off transmit lever 75 is mounted for rotation via a supporting shaft 127 mounted at one end of the locking plate 28, with a mating thrust member 75a at one end of the lever 75 facing the thrusting member 74c at the other end of the shut-off lever 74. The shut-off transmit lever 75 is rotationally biased counterclockwise or in the direction shown by an arrow T in Figure 11 in which the mating thrust section 75a intrudes into a space between the locking plate 28 and the mating thrust section 74c of the shut-off lever 74 and into abutment with the shut-off lever 74. In the reproducing mode, when the changeover interrupted gear 53 is rotated in the direction shown by the arrow C in Figure 11 in which the changeover interrupted gear 53 is pivoted from the reverse position to the normal position, the shut-off lever 74 has its mating thrust section 74b thrust by the offset cam section 54 so as to be rotated in a direction shown by an arrow U in Figure 11. When the shut-off lever 74 is rotated in this manner, the thrusting section 74c at the other end thrusts one end of the locking plate 28 by means of the mating thrust section 75a of the shut-off transmit lever 75 to shift the locking plate 28 in the direction shown by the arrow D′ in Figure 11. When the locking plate 28 is shifted in the direction shown by the arrow D′, the reproducing lever 24 thrust in the forward direction of reciprocation and locked by the locking plate 28 with the pawl section 24a engaging in the retaining pawl 28i is unlocked in the forward direction of reciprocation and the reproducing mode is released to terminate the reproducing or recording operation. The shut-off transmit lever 75 is controlled in its rotational bias position brought about by the torsion spring 76 by abutment of the mating thrust section 75a with the locking plate 28. The shut-off transmit lever 75 has its other end facing the side formed with the mating thrust section 75a facing and abutting with the other end of the changeover lever 61, so that, as the changeover lever 61 is thrust in the forward direction shown by the arrow M in Figure 11, the shut-off transmit lever 75 is rotated counterclockwise, that is in the direction opposite to that shown by an arrow T in Figure 11, against the force of the tension spring 76. When the shut-off transmit lever 75 is rotated by being thrust by the changeover lever 61, the mating thrust member 75a is disengaged from the space between the locking pate 28 and the thrusting section 74c of the shut-off lever 74, so that actuation of the mating thrust member 75 by the shut-off lever 74 becomes impossible, and hence the thrusting of the locking plate 28 by the shut-off lever 74 also becomes impossible. Thus, since the changeover lever 61 is shifted in the forward direction as indicated by the arrow M in Figure 11, so that the shut-off transmit lever 75 is rotated counterclockwise or in the direction opposite to that shown by the arrow T in Figure 11, the locking plate 28 is not thrust even when the changeover interrupted gear is rotationally driven and the shut-off lever 74 is turned in the direction shown by the arrow U in Figure 11. When rotated as shown in Figure 12, the shut-off transmit lever 75 has its mating thrust section 75a confronted by the inclined surface of the chevron-shaped portion of the shut-off lever 74, so that when the lever 75 is returned counterclockwise or in the direction shown by the arrow T in Figure 12 under the bias of the tension spring 76, it thrusts the thrusting section 74c of the shut-off lever 74 to turn and restore the shut-off lever 74 to its initial position. The mode changeover mechanism will now be explained, referring to Figures 1, 11 and 12. The mode changeover mechanism makes a changeover between modes of actuating and not actuating the shut-off mechanism when the reproducing or recording mode is switched from the normal direction to the reverse direction. As shown in Figures 11 and 12, the mode changeover mechanism is constituted by a mode changeover lever 77 for rotating the shut-off transmit lever 75. The mode changeover lever 77 is pivotally supported by the supporting shaft 127 mounted upright on the lower surface of the chassis base plate 5, with an actuating portion at one end of the lever 77 abutting on the mating portion 75b projectingly provided at one end of the shut-off transmit lever 75 and with an actuating portion 78 at the other end of the lever projecting outwardly of the chassis base plate 5. When the mode changeover lever 77 is rotated in the direction shown by the arrow U in Figure 11 via the actuating portion 78, an actuating portion 77a of the lever 77 thrusts the mating portion 75b of the transmit lever 75 to turn the shut-off transmit lever 75 in the direction shown by the arrow T in Figure 11 against the bias of the tension spring 76. As the shut-off transmit lever 75 is rotated in the direction opposite to that shown by the arrow T in Figure 11, rotation of the locking plate 28 by the shut-off lever 74 becomes impossible, while the shut-off mechanism cannot be actuated, as shown in Figure 12. A resiliently deformable retaining arm 77b is projectingly provided on one side of the mode changeover lever 77. The retaining arm 77b is selectively engaged and retained in plural retaining recesses 77c, 77d provided in the chassis base plate 5, as shown in Figures 11 and 12, for positioning the mode changeover lever 77 in the predetermined position. The supporting mechanism for the first and second pinch rollers 10, 11 and the magnetic head 12 will now be explained by referring to Figure 13. The magnetic head 12 and the first and second pinch rollers 10, 11 are mounted to a cassette holder 79 rotatably mounted to the chassis base plate 5 via a pivot shaft 79a, as shown in Figure 13. The magnetic head 12 is mounted to a recessed head mounting section 80b formed halfway along a magnetic head supporting arm 80 that is pivotally supported in the directions shown by the arrows W and W′ in Figure 13 by having its proximal end carried by a supporting shaft 80a mounted upright in one corner of the cassette holder 79. Tape guides 81, 84 are mounted on the magnetic head supporting arm 80 so as to be situated on either side of the magnetic head 12. Tape guides 82, 83 are similarly provided on each side of the magnetic head 12. The pinch rollers 10, 11 are rotatably supported on the ends of first and second pinch roller supporting arms 85, 86 pivotally mounted within the cassette holder 79. More specifically, the first pinch roller supporting arm 85 carrying the first pinch roller 10 is pivotally mounted by having its proximal end supported by the supporting shaft 90a of the magnetic head supporting arm 80, while the second pinch roller supporting arm 86 carrying the second pinch roller 11 is also pivotally mounted by having its proximal end supported by a supporting shaft 86a mounted upright at the other corner of the cassette holder 79 facing the supporting shaft 80a. Pinch roller thrust springs 87, 88 in the form of torsion coil springs are placed respectively about the supporting shaft 80a supporting the first pinch roller supporting arm 85 and the supporting shaft 86a supporting the second pinch roller supporting arm 86. Return springs 80b, 86b in the form of torsion coil springs are placed respectively about the supporting shafts 80a, 86a for rotationally biasing the first and second pinch roller supporting arms 85, 86 in the directions in which the associated pinch rollers are shifted away from the capstan shafts 8, 9 respectively. In the above-described tape recorder, when the reproducing mode is selected, the magnetic head shifting lever 40 is shifted in the direction shown by the arrow G in Figure 1, and as described hereinabove, the magnetic head engaging pawl 40a provided at one end of the magnetic head shifting lever 40 engages and thrusts the rear side of the magnetic head supporting arm 80 to turn the arm 80 in the direction shown by the arrow W in Figure 13 to advance the magnetic head 12 mounted in the middle of the magnetic head supporting arm 80 in a direction causing the head to be slidingly contacted with the magnetic tape 3. The pinch roller shifting lever 41 is shifted along with the shifting lever 40 which is pivoted in the direction shown by the arrows H or H′ in Figure 3. The rotational direction of the shifting lever 41 is determined in dependence upon whether the running direction of the magnetic tape 3 is normal or reverse. Thus, when the normal or reverse running direction of the magnetic tape 3 is selected, the shifting lever 41 is pivoted in the direction shown by the respective arrows H or H′ in Figure 3. When the normal running direction of the magnetic tape 3 is selected, the first pinch roller engaging pawl 42 engages with one end 88a of the pinch roller thrusting spring 88 to thrust the pinch roller supporting arm 86 from its rear side, thereby turning the arm 86 in a direction in which the second pinch roller 11 approaches the second capstan shaft 9. When the reverse running direction of the magnetic tape 3 is selected, the second pinch roller engaging pawl 43 engages with one end 87a of the pinch roller thrusting spring 87 on the side associated with the first pinch roller supporting arm 85, thereby thrusting the pinch roller supporting 85 from the rear side to turn the arm 86 in the direction in which the first pinch roller 10 approaches the first capstan shaft 8. When the pinch roller supporting arms 85, 86 are pivoted as described hereinabove, the ends 87a, 88a of the pinch roller thrust springs 87, 88 engaging with the front sides of the pinch roller supporting arms 85, 86 are thrust from their rear sides by the pinch roller engaging pawls 42, 43, so that the pinch roller supporting arms 85, 86 are rotationally biased by the other ends 87b, 88b of the pinch roller thrust springs 87, 88 in the directions shown by respective arrows X and X′ in Figure 11, thus rotationally biasing the pinch rollers 10, 11 into pressure contact with the capstan shafts 8, 9. The cassette holder 79 is locked in the tape cassette attachment position by having a mating locking member (not shown) engaged with a locking member 89a of a cassette holder locking lever 89 reciprocatingly mounted to the chassis base plate 5, in the state in which the cassette holder 79 has been pivoted to the tape cassette attachment position with the tape cassette 4 being attached to the tape cassette attachment section. Referring to Figure 1, a cassette holder locking lever 89 for locking the cassette holder 79 in the tape cassette attachment position is mounted for reciprocating movement with respect to the chassis base plate 5, with slide guide shafts 127, 128 on the chassis-base plate 5 engaging in slide guide openings 130, 131 formed in the cassette holder locking lever 89 so that their long axes extend in the longitudinal direction of the cassette holder locking lever 89. The cassette holder locking lever 89 is perpetually biased in the direction shown by an arrow Y in Figure 1 in which a lock lever biasing spring 90 mounted on the chassis plate 5 has one end 90c engaged with a spring retainer 89b on one side of the cassette holder locking lever 89 to engage the locking member 89a with a mating locking member of the cassette holder 79, thereby locking the cassette holder 79 at the tape cassette attachment position. The locking lever biasing spring 90 has its other end 90b thrusting and biasing the locking plate 28 in the direction shown by the arrow D in Figure 1. A cassette holder opening button 91 is provided at the end of the cassette holder locking lever 89 protruding outwardly of the chassis base plate 5. As the cassette holder opening button 91 is actuated, so that the cassette holder locking lever 89 is thrust in the direction opposite to that shown by the arrow Y in Figure 1 against the force of the locking lever biasing spring 90, the locking member 89a is shifted in the same direction and out of engagement with the mating locking member of the cassette holder 79 thereby setting the cassette holder 79 for free rotation, such that the cassette holder 79 may be rotated towards the outside from the tape cassette attachment position to allow for insertion and removal of the tape cassette 4. On the other hand, when the reproducing lever 24, the fast feed lever 26 or the rewind lever 27 is actuated, that is when the reproducing mode, the fast feed mode or the rewind mode is selected, the switch plate 29 is shifted in the direction shown by the arrow D′ in Figure 1, so that the slide plate 29 has one end confronted by a projection 89b formed on one side of the cassette holder locking lever 89 to inhibit thrusting of the cassette holder locking lever 89 in the direction shown by an arrow Y in Figure 1. Therefore, even when the cassette holder opening button 91 is actuated, shifting of the cassette holder locking lever 89 in the direction shown by the arrow Y in Figure 1 is inhibited to maintain the state of the cassette holder 79 in which the cassette holder 79 has been pivoted to and locked at the tape cassette attachment position. Although an illustrative embodiment of the present invention has been described hereinabove, variations and modifications of the described arrangement are possible. For example, various levers may be changed in shape or structure from those shown in the above-described embodiment. In addition, various gears used in the above embodiment may be replaced by idlers formed, for example, of rubber or like material. The present invention is also not limited to auto-reverse type tape recorders using standard size tape cassettes, but may instead be applied to other types of auto-reverse type recording and/or reproducing apparatus. In the rotation detection mechanism for the tape recorder as described above, when the reel block is halted and the detecting lever is no longer biased rotationally, a movable member of the detecting lever remains stationary at a position in which it has been shifted by a rotation detecting cam member, and a detecting pawl may abut on this movable member for detecting the halted state of the reel block.

Claims: A rotation detecting mechanism for tape recording and/or reproducing apparatus, the mechanism comprising: a movable shut-off lever (74) for setting at least a reproducing lever (24) or a head base (80) at a stop state position, said reproducing lever (24) or the head base (80) having been previously set to a reproducing state position; a movable changeover lever (46) for interchangeably setting a forward or a reverse transporting direction of magnetic tape (3); switching means (53, 54) for selectively shifting and setting said shut-off lever (74) or said changeover lever (46); and a movable trigger lever (56) for selectively triggering said switching means (53, 54); characterised by a detecting lever (65) rotationally biased in a first or a second direction which is in accordance with the rotation and the rotational direction of a tape reel driving block (6, 7) and released from rotational biasing when the tape reel driving block rotation stops; and a cam gear (30) rotatable continuously in one direction, said cam gear (30) including a first cam surface (71a) for guiding one end (68a) of said detecting lever (65) when said detecting lever (65) is rotationally biased in said first direction, a second cam surface (71b) for guiding said one end (68a) of said detecting lever (65) when said detecting lever (65) is rotationally biased in said second direction, a detecting pawl (72) protrudingly formed between and independently of said first cam surface (71a) and said second cam surface (71b), and a narrowed cam groove section (71c) provided on a cam groove formed by said first and second cam surfaces (71a, 71b) to guide said one end (68a) of said detecting lever (65) when released from rotational biasing, towards a rotational trajectory of said detecting pawl (72), said detecting pawl (72) being operable to thrust said one end (68a) of said detecting lever (65) so that the other end (70) of said detecting lever (65) actuates said trigger lever (56). A mechanism according to claim 1, wherein said first and second cam surfaces (71a, 71b), said detecting pawl (72) and said narrowed cam groove section (71c) are formed on the same surface (30b) of said cam gear (30). A mechanism according to claim 1 or claim 2, wherein a clearance allowing passage of at least said one end (68a) of said detecting lever (65) is provided between said first cam surface (71a) and said detecting pawl (72). A mechanism according to claim 1, claim 2 or claim 3, wherein said narrowed cam groove section (71c) is formed integrally with and as a continuation of said first and second cam surfaces (71a, 71b). A mechanism according to claim 4, wherein at least two narrowed cam groove sections (71c) are formed by said first and second cam surface (71a, 71b). A mechanism according to any one of the preceding claims, wherein said detecting lever (65) is rotatable about a pivot (33a) and slidable in a direction normal to the axial direction of said pivot (33a), said detecting lever (65) being rotationally biased in a direction which is in accordance with the rotation and the rotational direction of said tape reel driving block (6, 7) and being slidable by being thrust at said one end (68a) by said detecting pawl (72) thereby actuating said trigger lever (56) at said other end (70). A mechanism according to claim 6, wherein said detecting lever (65) is formed integrally with a return spring member (67) for biasing said detecting lever (65) against the direction in which it is thrust by said detecting pawl (72). A mechanism according to any one of the preceding claims, wherein said switching means includes an interrupted cam gear (53) provided with a shut-off cam section (54) driven intermittently in contrast to a drive gear (30a) continuously driven rotationally and selectively driving said shut-off lever (74), a switching cam section (54) for selectively driving said changeover lever (46), at least two mating locking sections (55n, 55r) and an interrupted gear teeth section (53n, 53r), and rotational bias means (59) for rotationally biasing said interrupted cam gear (53) in one direction. A mechanism according to claim 8, wherein said trigger lever (56) is engagable with said mating locking sections (55n, 55r) and operable to lock rotation of said interrupted cam gear (53) at a position in which said interrupted gear teeth section (53n, 53r) is confronted by said driving gear (30a), said trigger lever (56) being continuously biased (57) in a direction of engagement with said mating locking sections (55n, 55r).

Inventors: KOGA NORIYUKI, KOGA, NORIYUKI
Applicants: SONY CORP, SONY CORPORATION
Application year: 1989
Main classification: G11B15
IPC codes: G11B15