GB2272322A - Autoreverse mechanism for a tape recorder - Google Patents

Abstract

A running direction change-over plate 10 is provided to change the running direction of a tape. The running direction change-over plate 10 is moved either leftwards or rightwards by a transmission gear 22 when the latter is rotated half a turn in mesh with a partially de-toothed gear 12 to which rotational force is transmitted from a drive motor via a frictional rotation transmission mechanism. Reaction force acts on the running direction change-overplate 10 at the end position of its leftward or rightward movement, whereby the transmission gear 22 is urged in the rotation-continuing direction. As a result, the running direction change-over plate 10 is held at the end position of its leftward or rightward movement. <IMAGE>

Description

AUTOREVERSE MECHANISM FOR TAPE RECORDER BACKGROUND OF THE INVENTION 1) Field of the Invention This invention relates to an autoreverse mechanism for a tape recorder, which mechanism occupies a smaller space and provides fail-proof change of tape direction when drive motor rotation is reversed.

2) Description of the Related Art: As is disclosed in Japanese Utility Model Publication (Kokoku) No. HEI 3-41295, an autoreverse mechanism for a tape recorder, said mechanism permitting a change of tape running direction in response to a change-over in the direction of rotation of a motor, is constructed of a pinch roller change-over mechanism, a running direction change-over mechanism, and a mechanism for holding a running direction change-over plate, which is movable between two end positions and actuates the pinch roller change-over mechanism, at one of the two end positions.

The pinch roller change-over mechanism has two cams, which are formed at an interval therebetween on the running direction change-over plate, and two support arms on which pinch rollers are supported, respectively. Movement of the running direction change-over plate toward one of the end positions selectively causes the corresponding cam to rotate the associated support arm so that the pinch roller supported on the support arm is brought into abutment under pressure against the corresponding capstan.

The running direction change-over mechanism is composed of a Y-shaped rockable lever having a leg portion and a pair of arm portions extending upwardly and outwardly from an upper end of the leg portion, said rockable lever being connected to the running direction change-over plate, cam gears disposed at free ends of the arm portions of the rockable lever, respectively, and a switching gear pivotal responsive to each changeover in the direction of rotation of a motor.

The switching gear therefore revolves in response to each change-over in the direction of rotation of the gear so that the switching gear is selectively brought into meshing engagement with one of the cam gears to rotate the cam gear. As a result of the rotation of the cam gear, its cam causes the rockable lever to turn in a predetermined direction. This turning motion of the rockable lever then moves the running direction change-over plate towards the corresponding end position.

Further, the switching gear is always maintained in meshing engagement with an intermediate gear to which rotation is transmitted from the motor. When the direction of rotation of the intermediate gear is changed as a result of reversal of motor rotation, the switching gear revolves, together with a pivot plate on which the switching gear is supported, on and along an outer periphery of the intermediate gear in the same direction as the direction of rotation of the intermediate gear.

The design provides that the pivoting force for the switching gear is produced by resistance to rotation of the switching gear itself. To always maintain the switching gear and the intermediate gear in meshing engagement, the pivot plate is supported at a fulcrum of pivotal motion coaxially with an axis of rotation of the intermediate gear.

The holding mechanism is composed of the running direction change-over plate, a chassis, and an overcenter spring extending between the running direction change-over plate and the chassis. When the running direction change-over plate is moved by turning motion of the rockable lever to a position beyond a neutral point of the over-center spring, the resilient force of the over-center spring causes the running direction change-over plate to move further in the moving direc tion and then holds the running direction change-over plate at the end position of the movement.

In the autoreverse mechanism described above, it is designed to cause the switching gear to revolve responsive to each change-over in the direction of rotation of the motor and then to change over the direction of movement of the running direction changeover plate by using the revolving motion of the switching gear. A wide space is needed therefore to permit the revolving motion of the switching gear, resulting in the inconvenience that limitations are imposed on the layout of parts on the chassis.

Since the pivot plate is designed to turn by resistance to rotation of the switching gear itself, its pivoting power is extremely low. It is therefore necessary to devise a support for the pivotal motion of the pivot plate so that no resistance is applied to rotation. A reduction in the resistance to rotation of the pivot plate, however, involves the potential problem that the pivot plate may be caused to turn even when an impact is applied externally to a tape recorder, so that the reliability of the mechanism is lowered.

If a lube oil is coated to the pivot plate with a view toward reducing the resistance to turning of the pivot plate, the lube oil adsorbs dirt. Adsorption of more dirt conversely results in higher resistance. Accordingly, it is possible to coat a lube oil only in an extremely limited amount and only to extremely limited places.

Since the over-center spring is used as the holding mechanism for holding the running direction changeover plate at one of its end positions, a space is required to permit a swinging motion for the over-center spring. To retain this space, limitations are imposed on the layout of parts on the chassis.

SUMMARY OF THE INVENTION An object of the present invention is to provide an autoreverse mechanism for a tape recorder, which mechanism provides excellent reliability and allows tape direction reversal within a compact space.

In one aspect of the present invention, there is thus provided an autoreverse mechanism for a tape recorder, comprising: a pinch roller change-over mechanism for selectively pressing one of pinch rollers, which are arranged in a pair, against a corresponding one of capstans; a rotational force transmission change-over me chanism for selectively changing over, from one to another, rotation transmitting routes which extend from a reversible motor to reel shafts, respectively; a running direction change-over member having an engaging portion and arranged for linear movement, whereby the pinch roller change-over mechanism is changed over;; a partially de-toothed gear having a first and second de-toothed peripheral portions and a first and second toothed peripheral portions formed between the first and second de-toothed peripheral portions, one of said toothed peripheral portions being engageable with a drive gear, which is rotated by the motor, to turn the partially de-toothed gear in a normal or reverse direction but, when the first or second de-toothed peripheral portion is located opposite the drive gear, transmission of rotational force from the drive gear to the partially de-toothed gear being cut off; a trigger gear to which rotational force is transmitted from the motor via a frictional rotation transmitting mechanism, whereby said trigger gear causes the partially de-toothed gear to turn in a normal or reverse direction; ; a transmission gear having a contact portion engageable with the engaging portion of the running direction change-over member, said transmission gear being rotatable approximately half a turn in mesh with the other toothed peripheral portion of the partially de-toothed gear so that the running direction changeover member can be moved linearly; means for transmitting, when the running direction change-over member has moved to immediately before an end position of its linear movement, reaction force to the contact portion of the transmission gear, said reaction force acting on the running direction changeover member, whereby the transmission gear is rotated further in the same direction as it has rotated until that time; and stopper means with which the contact portion of the transmission gear is maintained in contact when the first or second de-toothed peripheral portion is located opposite the transmission gear, whereby any further rotation of the transmission gear is prohibited so that the running direction change-over member is held at a predetermined position.

Preferably, said transmitting means is an inclined face formed at a part of the engaging portion and the inclined face is inclined relative to the direction of linear movement of the running direction change-over member. The transmission gear can be pro vided with a resilient member which, when the transmission gear has rotated to bring the contact portion of the transmission gear into contact with the stopper means, urges the transmission gear in the same direction as the transmission gear has rotated until that time.

The contact portion of the transmission gear may engage the engaging portion of the running direction change-over member via a rockable member as said transmitting means. The rockable member can be arranged for pivotal motion at an end thereof on the engaging portion of the running direction change-over member and for linear movement at an opposite end thereof along an imaginary line extending at a right angle relative to the direction of movement of the running direction change-over member and passing through the central axis of rotation of the transmission gear; and between the ends of the rockable member, the rockable member has as said transmitting means a guide portion in which the contact portion of the transmission gear is fitted.

In the present invention, meshing engagement between the partially de-toothed gear and the drive gear is controlled by changing over the direction of rotation of the trigger gear which is rotated by the motor via the frictional rotation transmitting mechanism.

Resulting rotation of the partially de-toothed gear then drives the transmission gear, whereby the running direction change-over plate is moved. Since all the gears are rotatably supported, for example, on a chassis without pivotal motion, their stable operation is assured and further a reduction in the overall dimensions of the autoreverse mechanism is feasible.

Rotational force of the motor is transmitted to the running direction change-over member via the partially de-toothed gear and, after the change-over member has been moved, the route of transmission of the rotational force of the motor is cut off. Nevertheless, the change-over member can be held stably at one of the end positions of its movement owing to the use of reaction force acting on the change-over member.

The contact portion of the transmission gear, which causes the running direction change-over plate to move, is brought into contact with the stopper means at the position that the transmission gear has rotated approximately half a turn, so that the transmission of rotational force from the drive gear to the transmission gear is cut off. As a result, reaction force acting on the running direction change-over plate urges the transmission gear to rotate in the direction that the contact portion is maintained in abutment against the stopper means. This makes it possible to hold the running direction change-over plate at an end position of its linear movement.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings, in which: FIG. 1 is a plan view of an autoreverse mechanism according to a first embodiment of the present invention as incorporated in a drive mechanism of a tape recorder; FIG. 2 is a fragmentary plan view of the autoreverse mechanism of FIG. 1; FIG. 3 is an exploded perspective view of the autoreverse mechanism of FIG. 1; FIG. 4 is a rear view of the autoreverse mechanism of FIG. 1; FIG. 5 is a fragmentary plan view of an autoreverse mechanism according to a second embodiment of the present invention; FIG. 6 is a fragmentary plan view of an autoreverse mechanism according to a third embodiment of the present invention; and FIG. 7 is a plan view illustrating a relationship among forces acting in the autoreverse mechanism of FIG. 6.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS Referring first to FIGS. 1 through 4, the autoreverse mechanism according to the first embodiment of the present invention will be described. In the tape recorder illustrated in FIG. 1, a pair of capstans 3a,3b are rotatably mounted on a chassis 1. These capstans 3a,3b are driven in the same direction by a motor 2. In association with these capstans 3a,3b, pinch rollers 4a,4b are arranged on pivotal support arms 5a,5b, respectively. Between the paired capstans 3a,3b, a head mounting plate 7 with a magnetic head 6 mounted thereon is disposed movably forward and rearward on the chassis 1. When the head mounting plate 7 moves forward to a tape reproducing position, the magnetic head 6 is brought into sliding contact with a tape of an unillustrated tape cassette so that signals are reproduced.

On the chassis 1, a running direction change-over plate 10 is also arranged movably in a direction per pendicular to the direction of movement of the head mounting plate 7, namely, in a horizontal direction as viewed in FIG. 1. The running direction change-over plate 10 can be moved to a left-hand end position or to a right-hand end position, again as viewed in FIG. 1, by a running direction change-over mechanism disposed on a lower side of the chassis 1 as will be described subsequently herein, whereby the running direction of the tape can be changed over.

Further, each movement of the running direction change-over plate 10 to the left-hand end position or the right-hand end position causes an unillustrated rotation transmitting mechanism to operate in such a manner that one of reel shafts 8a,8b, which are rotatably mounted on the chassis 1, is selectively rotated. This rotation transmitting mechanism is designed in such a manner that, when the running direction change-over plate 10 has moved to the left-hand end position or the right-hand end position, rotation of the motor 2 can be transmitted to one of the reel shafts 8a,8b, said one reel shaft 8a or 8b being on the side that the pinch roller 4a or 4b has been brought into abutment under pressure against the associated capstan 3a or 3b.

A pinch roller change-over mechanism 12 for se lectively bringing one of the pinch rollers 4a,4b against the corresponding capstan 3a or 3b is constructed of a pivot plate 13 turnably attached to the head mounting plate 7, a wire spring 14 supported on the pivot plate 13 turnably together with the pivot plate 13, and a movable plate 16 having a connecting portion 15, through which the movable plate 16 is connected to the pivot plate 13, and movably supported on the head mounting plate 7.

The movable plate 16 is connected at one end thereof to the running direction change-over plate 10 so that, when the running direction change-over plate 10 is moved toward the left-hand end position or the right-hand end position, the connecting portion 15 of the movable plate 16 hence causes the pivot plate 13 to turn clockwise or counterclockwise together with the wire spring 14. When the wire spring 14 approaches one end 14a or 14b thereof the corresponding one of the capstans 3a or 3b as a result of this turning motion of the wire spring 14, the other end 14b or 14a of the wire spring 14 moves away from the other capstan 3b or 3a.

When the head mounting plate 7 is at the tape reproducing position, the free end 14a or 14b of the wire spring 14, said free end having been turned in the direction approaching the corresponding capstan 3a or 3b as a result of movement of the running direction change-over plate 10, causes the corresponding support arm 5a or 5b to pivot so that the associated pinch roller 4a or 4b is brought into abutment under pressure against the corresponding capstan 3a or 3b.

FIG. 1 illustrates the state that the right-hand pinch roller 4b has been brought into abutment under pressure against the right-hand capstan 3b.

When the running direction change-over plate 10 moves leftwards from the state depicted in FIG. 1, the movable plate 16 connected to the running direction change-over plate 10 also moves leftwards. This movement of the movable plate 16 causes the pivot plate 13, which is connected to the movable plate 16, to turn clockwise on the head mounting plate 7. Then, the wire spring 14 also turns together with the pivot plate 13 so that the left-hand free end 14a causes the support arm 5a to turn counterclockwise. As a consequence, the left-hand pinch roller 4a is brought into abutment under pressure against the corresponding capstan 3a.On the other hand, the right-hand support arm 5b is pivoted counterclockwise so that the right-hand free end 14b of the wire spring 14 causes the right-hand pinch roller 4b to move away from the corresponding capstan 3b.

In FIG. 1, the wire spring 14 maintains the right-hand pinch roller 4b in abutment under pressure against the corresponding capstan 3b. Reaction force of the abutment under pressure is transmitted to the running direction change-over plate 10 via the pivot plate 13 and the movable plate 16. As a result, the reaction force acts to move the running direction change-over plate 10, which has assumed the right-hand end position, leftwards and to urge it in the same direction.

The running direction change-over mechanism, which causes the running direction change-over plate 10 to move horizontally, is provided on the lower side of the chassis as illustrated in FIG. 2. FIG. 2 shows on an enlarged scale the right-hand capstan 3b, as viewed in FIG. 1, and its peripheral elements. The chassis 1 and the running direction change-over plate 10 are both shown in phantoms.

The running direction change-over plate 10 is provided with an engaging portion, i.e., a guide hole 18 in which a contact portion, i.e., a square pin 22a of a below-described transmission gear 22 is fitted.

When the transmission gear 22 rotates, the square pin 22a presses one of side walls 18a,18a of the guide hole 18 to move the running direction change-over plate 10 leftwards or rightwards against the reaction force described above.

The guide hole 18 is also provided with inclined faces 18b,18b which, after the running direction change-over plate 10 has been moved to the right-hand or left-hand end position by the square pin 22a, presses the square pin 22a against one of the end portions, i.e., stop portions lb,ld of an arcuate slot la formed in the chassis 1 as shown in FIG. 3.

Rotatably supported on the lower side of the chassis 1 also include a flywheel 19 attached to the capstan 3b, a small-diameter gear, i.e., a drive gear 20 integral with the fly wheel 19, a partially detoothed gear 21 with a first de-toothed peripheral portion 21a located opposite the drive gear 20, and the transmission gear 22 located opposite a second detoothed peripheral portion 21b of the partially detoothed gear 21.

Although not shown in FIG. 3, an endless belt is mounted on an outer periphery of the fly wheel 19 to transmit rotation of the motor 2. When the direction of rotation of the motor 2 is switched, the direction of rotation of the flywheel 19 is also changed over so that the flywheel 19 rotates in the same direction as the motor 2.

The capstan 3b is also provided with a trigger gear 23, which has a diameter smaller than the drive gear 20 and is located above the drive gear 20. As is shown in FIG. 3, a sleeve 23a of the trigger gear 23 is split in two parts. To mount the trigger gear 23 on the capstan 3b, it is necessary to force the capstan 3b to enter the sleeve 23a. Since the diameter of the capstan 3b is greater than that of the sleeve 23a, the sleeve 23a is outwardly expanded so that the sleeve 23a is fitted on the capstan 3b. The diameter and shape of the sleeve 23a are determined such that the capstan 3b can be fitted in the sleeve 23a by an extremely small force and the engagement between the sleeve 23a and the capstan 3b is loose enough to form a frictional rotation transmitting mechanism to be described next.

Owing to the frictional rotation transmitting mechanism, the trigger gear 23 rotates following the rotation of the capstan 3b but, when excessive load is applied to the trigger gear 23, stops so that slippage occurs between an inner peripheral wall of the sleeve 23a and an outer peripheral wall of the capstan 3b.

As shown in FIG. 3, the partially de-toothed gear 21 consists of a large-diameter gear 21c, which is always rotatable in mesh with the trigger gear 23, and a small-diameter gear formed integrally in an upper-andlower relation with the large-diameter gear 21c. The small-diameter gear is provided on an outer peripheral wall thereof with a first and second de-toothed peripheral portions 21a,21b and a first and second toothed peripheral portions 21d,21d arranged between the first and second de-toothed peripheral portions 21a,21b. In the partially de-toothed gear 21, there is also formed an arcuate groove 21e in which a stopper lc extending downwardly on the lower side of the chassis 1 is received.

It is to be noted that the large-diameter gear 21c and the small-diameter gear of the partially detoothed gear 21 are shown in a divided form in FIG. 3 to clarify their association with the other gears.

The central angle of the arcuate groove 21e is set at such a value that the stopper lc is maintained in contact with ends 21k,21m of the arcuate groove 21e when the first and second de-toothed peripheral portions 21a,21b are located opposite the drive gear 20, respectively.

A sleeve 21f of the partially de-toothed gear 21 is split in two parts so that, when the partially detoothed gear 21 is mounted on a support shaft le provided on the chassis 1, the sleeve 21f is first widened by the support shaft 13 and then fitted in a groove lf of the support shaft le. Outer walls of sleeve portions 21g,21g, which make up the sleeve 21f, and the partially de-toothed gear 21 are connected together by arms 21h which extend in substantially the same direction as the de-toothed peripheral portions 21a,21b and are resiliently deformable. Spaces 21j are formed between the sleeve portions 21g and arms 21h and the partially de-toothed gear 21.

If the free edge of a first tooth of the toothed portion 21d is brought into contact with the free edge of one of the teeth of the drive gear 20 upon initiation of meshing engagement between the toothed portion 21d and the drive gear 20, the arms 21h are resiliently deformed by rotational force of the drive gear 20 so that the partially de-toothed gear 21 is moved radially to avoid edge-to-edge locking.

The transmission gear 22 is eccentrically provided with the square pin 22a so that, when the transmission gear 22 is mounted on the chassis 1, the square pin 22a extends through the arcuate slot la formed in the chassis 1, projects above an upper side of the chassis 1 and fits in the guide hole 18 of the running direction change-over plate 10.

The central angle of the arcuate slot la of the chassis 1 is set at such a value that the square pin 22a is brought into contact with the stop portion lb or ld of the arcuate slot la when the transmission gear 22 is rotated slightly more than half a turn following rotation of the partially de-toothed gear 21 owing to meshing engagement between the transmission gear 22 and one of the toothed portions 21d,21d of the partially de-toothed gear 21.

As is illustrated in FIG. 4 which is a view of the same part as that shown in FIG. 2 but seen in an opposite direction, a resilient member 24 is disposed on the lower side of the chassis 1. When the running direction change-over plate 10 has moved leftwards or rightwards as a result of rotation of the transmission gear, the resilient member 24 urges the transmission gear 22 in the direction of its rotation at the end of its rotation. This resilient force of the resilient member 24 applies auxiliary force sufficient to further ensure the holding of the transmission gear 22 at the end of its rotation.

When the running direction change-over plate 10 has moved rightwards as shown in FIG. 2, the square pin 22a is at a position turned slightly beyond a path 25 which extends across an axis of rotation of the transmission gear 22 and indicates movement of the running direction change-over plate 10. At this position, the square pin 22a is in contact with the stop portion lb of the arcuate slot la in the chassis 1.

The square pin 22a is therefore pressed against the stop portion lb of the arcuate slot la by the spring force of the resilient member 24 and also by a force component acting on the square pin 22a via the inclined faces of the guide hole 18 on the basis of reaction force of the wire spring 14, said reaction force acting on the running direction change-over plate 10. As a consequence, the transmission gear 22 is held securely at the end position in the direction of its rotation. Since the transmission gear 22 is held at the end position in the direction of its rotation, the running direction change-over plate 10 is also held at the position moved to the right-hand side.

Operation of the autoreverse mechanism according to the first embodiment will now be described.

In the state illustrated in FIG. 1, the righthand pinch roller 4b is maintained in abutment under pressure against the capstan 3b. When the capstan 3b is rotated counterclockwise by the motor 2, the tape is fed from the left-hand side to the right-hand side.

The tape so fed is taken up by the right-hand reel shaft 8b.

At this time, one of the ends, i.e., the end 21k of the arcuate groove 21e in the partially de-toothed gear 21 is in contact with the stopper lc so that the partially de-toothed gear 21 is prevented from further rotation with the first de-toothed peripheral portion 21a located opposite the drive gear 20. The force under which the end 21k can be maintained in contact with the stopper lc is obtained as a result of frictional contact between the sleeve 23a and the capstan 3a.

The transmission gear 22, which is located opposite the second de-toothed peripheral portion 21b of the partially de-toothed gear 21, has moved the running direction change-over plate 10 rightwards. The reaction force of the wire spring 14 therefore urges the running direction change-over plate 10 leftwards. This urging force presses the square pin 22a counterclockwise via the inclined faces 18b,18b of the guide hole 18.

Accordingly, the square pin 22a is pressed by the urging force against the stop portion lb of the arcuate hole la in the chassis 1 and moreover, the transmission gear 22 is urged toward the end of its rotation by the spring force of the resilient member 24.

The transmission gear 22 is therefore held in the state that the second de-toothed peripheral portion 21b of the partially de-toothed gear 21 is located opposite the transmission gear 22, whereby the running direction change-over plate 10 is held in the right-hand position.

When the autoreverse mechanism is actuated in the above-described state to change over the running direction, the direction of rotation of the motor 2 is immediately reversed. Then, the direction of rotation of each of the flywheel 19, capstan 3b, drive gear 20 and trigger gear 23 is changed over so that the trigger gear 23 rotates clockwise as viewed in FIG. 2.

The direction of rotation of the partially detoothed gear 21 by the trigger gear 23 is also changed over, whereby the partially de-toothed gear 21 rotates counterclockwise. The toothed peripheral portion 21d is accordingly brought into meshing engagement with the drive gear 20. When the partially de-toothed gear 21 begins counterclockwise rotation under rotational force of the drive gear 20, the transmission gear 22 which has been located in opposition to the second de-toothed peripheral portion 2lb is also brought into meshing engagement with the toothed peripheral portion 21d so that the transmission gear 22 begins to rotate clockwise.

When the transmission gear 22 begins clockwise rotation, the square pin 22a presses one of the side walls 18a,18a, said one side wall 18a being on a side closer to the reader as viewed in FIG. 3 and on the left-hand side as viewed in FIG. 2, of the guide hole 18 while moving through the guide hole 18. As a result, the running direction change-over plate 10 is caused to move leftward as viewed in FIG. 1. The toothed peripheral portion 21d of the partially detoothed gear 21 causes the transmission gear 22 to rotate half a turn or slightly more so that the first de-toothed peripheral portion 21a is located opposite the transmission gear 22.

The second de-toothed peripheral portion 21b, on the other hand, is located opposite the drive gear 20 at this time and the opposite end 21m of the arcuate groove 21e of the partially de-toothed gear 21 is maintained in contact with the stopper lc. The partially de-toothed gear 21 is therefore prevented from rotation. Since the capstan 3b continues clockwise rotation, counterclockwise rotational urging force is applied to the large-diameter gear 21c via the trigger gear 23 and the partially de-toothed gear 21 is therefore held at the stopped position.

The clockwise rotation of the transmission gear 22 causes the running direction change-over plate 10 to move leftwards so that the movable plate 16 is also moved leftwards. As a result, the connecting portion 15 causes the pivot plate 13 to turn clockwise. By the turning motion of the pivot plate 13, the wire spring 14 causes the left-hand support arm 5a to turn counterclockwise so that the left-hand pinch roller 4a is brought into abutment under pressure against the lefthand capstan 3a to feed the tape leftwards.

At the same time, the wire spring 14 causes the right-hand support arm 5b to turn counterclockwise so that the right-hand pinch roller 4b is separated from the right-hand capstan 3b.

In the course of the leftward movement of the running direction change-over plate 10, the running direction change-over plate 10 actuates the rotational force transmission change-over mechanism. The rotational force transmission mechanism transmits the rotational force of the motor 2 to the left-hand reel shaft 8a, whereby the left-hand reel shaft 8a takes up the tape fed out between the left-hand pinch roller 4a and the left-hand capstan 3a. At the same time, transmission of rotational force from the motor 2 to the righthand reel shaft 8b is cut off.

As has been described above, the direction of rotation of each of the partially de-toothed gear 21 and the transmission gear 22 in the first embodiment of the present invention is changed over by switching the direction of rotation of the motor 2, whereby the running direction change-over plate 10 is moved leftwards or rightwards to change the running direction of the tape either leftwards or rightwards.

When the left-hand pinch roller 4a is brought into abutment under pressure against the left-hand capstan 3a, reaction force by the wire spring 14 urges the running direction change-over plate 10 so that the running direction change-over plate 10 moves rightwards.

By the urging force, the inclined faces 18b,18b formed in the guide hole 18 of the running direction changeover plate 10 press the square pin 22a against the stop portion ld so that the transmission gear 22 is urged clockwise. As a result, the transmission gear 22 is held at the stopped position.

Because the running direction of the tape is changed over by switching the direction of rotation of the motor 2, it is no longer necessary to move any gear or gears in the first embodiment so that the autoreverse mechanism requires less space.

Further, the mechanism for holding the running direction change-over plate 10 at one of the left-hand and right-hand end positions is constructed of the in clined faces 18b,18b of the guide hole 18, the stop portions 1bold for preventing any further rotation of the transmission gear 22 beyond half a turn or slightly more than half a turn, and the resilient member 24 for urging the transmission gear 22 in the rotationcontinuing direction. The holding mechanism can therefore save space. Further, it is not necessary to pivot any gear or gears so that each change-over operation of the tape running direction can be effected smoothly without failure.

In the first embodiment described above, the stop portions lb,ld which prevents the transmission gear 22 from rotating further beyond half a turn or slightly more than half a turn are the opposite ends of the arcuate hole la. The stop portions are however not limited to such opposite ends. As shown as the second embodiment in FIG. 5, for example, it is possible to form a recess 31b in each edge 31a of a guide hole 31 of the running direction change-over plate 30 and then to use one of walls of the recess 31b as a stop portion 31c and the other wall 31d as a wall for pressing the transmission gear in the direction of rotation.

Where the center of each recess 31b is arranged on an imaginary line which extends across the axis of rotation of the transmission gear 22 and indicates movement of the running direction change-over plate 10, the running direction change-over plate 10 can be held at one of the end positions of its movement even when the rotation of the transmission gear 22 is limited to half a turn because the square pin 22a is maintained in engagement with the recess 3lb.

Although the contact portion has been described as a square pin, it may be in the form of a circular pin.

The autoreverse mechanism according to the third embodiment will next be described with reference to FIGS. 6 and 7, in which like elements of structure to the corresponding ones of the first embodiment will be identified by like reference numerals.

A pin B provided at an end of a rockable plate 41, i.e., a rockable member as an urging means, is rotatably received in a support hole 40a of a running direction change-over member 40.

The rockable plate 41 is also provided with a guide slot 41a, as a guide portion, and a pin C. A circular pin 42a, as a contact portion, of a transmission gear to be described subsequently herein is fitted in the guide slot 41a. The pin C is provided at an opposite end of the rockable plate 41. The pin C is fitted in a slot 39a formed in a chassis 39. The slot 39a is provided along an imaginary line which extends at a right angle relative to the direction of movement of the running direction change-over plate 40 and through a central axis of rotation of the transmission gear 42.

The guide slot 41a is formed between the pin B and the pin C.

When the transmission gear 42 rotates clockwise from the state of FIG. 6, the circular pin 42a moves along and through the guide slot 41a so that the rockable plate 41 turns counterclockwise about the pin C.

The pin B, which is provided at the turning free end of the rockable plate 41, causes the running direction change-over plate 40 to move in the direction indicated by arrow G.

Rotatably supported on a lower side of the chassis 39 are the flywheel 19 mounted on the capstan 3b, the drive gear 20 arranged integrally with the flywheel 19, the partially de-toothed gear 21 with the first de-toothed peripheral portion 21a being located opposite the drive gear 20, and the transmission gear 42 positioned opposite the second de-toothed portion 21b of the partially de-toothed gear 21.

Although not shown in FIG. 6, an endless belt is mounted on the outer periphery of the flywheel 19 to transmit rotation of the motor 2. When the direction of rotation of the motor 2 is switched, the direction of rotation of the flywheel 19 is also changed over so that the flywheel 19 rotates in the same direction as the motor 2. Above the drive gear 20, the trigger gear 23 having the smaller diameter than the drive gear 20 is rotatably mounted on the capstan 3b via the frictional rotation transmitting mechanism.The partially de-toothed gear 21 has the first and second de-toothed peripheral portions 21a,21b and first and second toothed peripheral portions 21d,21d arranged between the first and second de-toothed peripheral portions 21a,2lb. In addition, the partially de-toothed gear 21 is also provided with the large-diameter gear 21c, which is always maintained in meshing engagement with the trigger gear 23, and the arcuate groove 21e in which the stopper lc extending from the lower side of the chassis 39 is fitted.

The central angle of the arcuate groove 2le is set at such a value that the stopper lc is maintained in contact with the end 21k or 21m of the arcuate groove 21e when the first or second de-toothed peripheral portion 21a or 21b is located opposite the drive gear 20.

The transmission gear 42 is provided with the circular pin 42, which extends through an arcuate hole 39b formed in the chassis 39 and projects above an upper side of the chassis 39. The central angle of the arcuate hole 39b in the chassis 39 is set at such a value that the circular pin 42a is brought into contact with a stop portion 39c or 39d when the transmission gear 42 has rotated half a turn or slightly more than half a turn in accordance with rotation of the partially de-toothed gear 21 as a result of meshing engagement between the transmission gear 42 and one of the toothed peripheral portions 21d,21d.

FIG. 7 illustrates how the reaction force F of the running direction change-over plate 40 acts on the transmission gear 42 via the rockable plate 41 when the running direction change-over plate 4 assumes an end position of its movement in the direction indicated by arrow D shown in FIG. 6.

When the reaction force F of the running direction change-over plate 40 acts on the pin B in the direction indicated by arrow G, the rockable plate 41 is pivoted and urged counterclockwise about the pin C.

This urging and pivoting force f acts in such a way that the circular pin 42a is pressed in a direction perpendicular to a longitudinal edge 41b of the guide slot 41a.

If the force f is directed to a left-hand side relative to a line which connects the center 0 of the circular pin 42a with the center P of the transmission gear 42, component force t of the urging and pivoting force f acts in a direction which faces leftwards from the center 0 of the circular pin 42a as viewed in FIG.

7 and is perpendicular to a line connecting the center O of the circular pin 42a with the center P of the transmission gear 42.

As a result, the component force t acting on the circular pin 42a begins to make the transmission gear 42 turn counterclockwise. The circular pin 42 is, however, in contact with the stop portion 39d of the arcuate hole 39b as depicted in FIG. 6 so that the transmission gear 42 is prevented from turning counterclockwise. The transmission gear 42 is therefore stably held in the stopped state.

According to the third embodiment, the reaction force of the running direction change-over plate 40 continues to urge the transmission gear 42 in a rotation-continuing direction owing to the provision of the rockable plate 41 even when the transmission gear 42 is rotated slightly smaller than half a turn. It is therefore possible to hold the running direction change-over plate 40 stably at one of the end positions of its movement.

Claims (6)

CLAIMS:

1. An autoreverse mechanism for a tape recorder, comprising: a pinch roller change-over mechanism for selectively pressing one of pinch rollers, which are arranged in a pair, against a corresponding one of capstans; a rotational force transmission change-over mechanism for selectively changing over, from one to another, rotation transmitting routes which extend from a reversible motor to reel shafts, respectively; a running direction change-over member having an engaging portion and arranged for linear movement, whereby the pinch roller change-over mechanism is changed over;; a partially de-toothed gear having a first and second de-toothed peripheral portions and a first and second toothed peripheral portions formed between the first and second de-toothed peripheral portions, one of said toothed peripheral portions being engageable with a drive gear, which is rotated by the motor, to turn the partially de-toothed gear in a normal or reverse direction but, when the first or second de-toothed peripheral portion is located opposite the drive gear, transmission of rotational force from the drive gear to the partially de-toothed gear being cut off; a trigger gear to which rotational force is transmitted from the motor via a frictional rotation transmitting mechanism, whereby said trigger gear causes the partially de-toothed gear to turn in a normal or reverse direction;; a transmission gear having a contact portion engageable with the engaging portion of the running direction change-over member, said transmission gear being rotatable approximately half a turn in mesh with the other toothed peripheral portion of the partially de-toothed gear so that the running direction changeover member can be moved linearly; means for transmitting, when the running direction change-over member has moved to immediately before an end position of its linear movement, reaction force to the contact portion of the transmission gear, said reaction force acting on the running direction changeover member, whereby the transmission gear is rotated further in the same direction as it has rotated until that time; and stopper means with which the contact portion of the transmission gear is maintained in contact when the first or second de-toothed peripheral portion is located opposite the transmission gear, whereby any fur ther rotation of the transmission gear is prohibited so that the running direction change-over member is held at a predetermined position.

2. An autoreverse mechanism according to claim 1, wherein said transmitting means is an inclined face formed at a part of the engaging portion and the inclined face is inclined relative to the direction of linear movement of the running direction change-over member.

3. An autoreverse mechanism according to claim 1, wherein the transmission gear is provided with a resilient member which, when the transmission gear has rotated to bring the contact portion of the transmission gear into contact with the stopper means, urges the transmission gear in the same direction as the transmission gear has rotated until that time.

4. An autoreverse mechanism according to claim 1, wherein the contact portion of the transmission gear engages the engaging portion of the running direction change-over member via a rockable member and the transmitting means is the rockable member.

5. An autoreverse mechanism according to claim 4, wherein the rockable member is arranged for pivotal motion at an end thereof on the engaging portion of the running direction change-over member and for linear movement at an opposite end thereof along an imaginary line extending at a right angle relative to the direction of movement of the running direction change-over member and passing through the central axis of rotation of the transmission gear; and between the ends of the rockable member, the rockable member has as said transmitting means a guide portion in which the contact portion of the transmission gear is fitted.

6. An autoreverse mechanism substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.