Abstract:
An auto reverse mechanism in a tape recorder system having a single magnetic head for forward playback (recording) and a single magnetic head for reverse playback (recording), both mounted on a head base, comprises a select lever for selecting between forward and reverse modes, a main body plate for gear attachment, provided with a retaining groove for allowing the select lever to be manipulated in the direction of the selected mode, and a forked guide hole so formed as to permit the head base to move forward from the position of the select lever in the selected forward or reverse mode.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an autoreverse mechanism mainly in a cassette tape recorder, which is designed to ensure both the forward mode and reverse mode by a simple manipulation and a simple structure of adding minimum parts to a conventional unidirectional playback mechanism in a forward-reverse switching mechanism. 
     2. Description of the Related Art 
     A typical autoreverse mechanism of the conventional type has a slidable head base on which a second head base carrying forward and reverse heads is provided, and stitches between the forward head and reverse head. 
     The conventional autoreverse mechanism inevitably has a large size, making its compact design difficult, and has such a complex structure as to be prone to cause malfunction and make tape running adjustment difficult. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an objective of the present invention to provide and autoreverse mechanism which is designed to overcome the conventional shortcoming. 
     To achieve this object, according to one aspect of this invention, there is provided an autoreverse mechanism in a tape recorder system having a single magnetic head for forward playback (recording) and a single magnetic head for reverse playback (recording), both mounted on a head base, which mechanism comprises a select-lever retaining groove formed on a flat surface of a main body plate; a select lever, retained in the select-lever retaining groove, for selecting between forward and reverse modes; and a forked guide hole so formed as to permit the head base to move forward in inclination from a position of the select lever in the selected forward or reverse mode. 
     The above-described structure can accomplish forward and reverse modes by simply adding one part to the conventional autoreverse mechanism, thus ensuring a compact and lighter design, stable tape running operation and cost reduction, so that this mechanism is particularly suitable for use in a microcassette tape recorder. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an enlarged plan view of a cassette tape recorder equipped with a an autoreverse mechanism according to this invention; 
     FIG. 2 is a bottom view of the cassette tape recorder in FIG. 1; 
     FIG. 3 is a plan view showing a select lever, gears and a play lever in a stop mode; 
     FIG. 4 is a plan view of a head base in the stop mode; 
     FIG. 5 is a plan view illustrating the relationship among the head base, the play lever and a lock mechanism in the stop mode; 
     FIG. 6 is a plan view showing the select lever, the play lever and the gears in a forward mode; 
     FIG. 7 is a plan view depicting the head base, the gears and the select lever in the forward mode; 
     FIG. 8 is a plan view illustrating the head base, the play lever and the lock mechanism in the forward mode; 
     FIG. 9 is a plan view showing the select lever, the play lever and the gears in a reverse mode; 
     FIG. 10 is a plan view depicting the head base, the gears and the select lever in the reverse mode; 
     FIG. 11 is a plan view illustrating the head base, the play lever and the lock mechanism in the reverse mode; 
     FIG. 12 is a plan view showing the select lever, the play lever and the gears in a fast forward mode; and 
     FIG. 13 is a plan view showing the select lever, the play lever and the gears in a rewind mode. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An autoreverse mechanism according to one embodiment of the present invention as adapted for use in a microcassette tape recorder will now be described with reference to the accompanying drawings. 
     In the figures, a motor  2 , provided on the top side of a main body plate  1 , is capable of rotating forward and reversely at a variable speed. Reference numeral “ 3 ” is a play reel and reference numeral “ 4 ” is a rewind reel. A small-diameter pulley  5  is attached to an output shaft  2   1  of the motor  2  on the bottom side of the main body plate  1 . A belt  6  serves to transmit the power of the motor  2  to a flywheel pulley  8  which is provided coaxial to a capstan  7 . 
     A fixed gear  9  is provided coaxial and integral with the flywheel pulley  8 . A gear plate  10  is provided coaxial to the capstan  7  and the flywheel pulley  8  and is rotatable together with them. A notch  10   1  is formed at the top portion of the gear plate  10 . 
     An idle gear  11  engages with the fixed gear  9  on the flywheel pulley  8  via the gear plate  10 . A projection  12 , provided on the gear plate  10 , is formed as an extension of the shaft of the idle gear  11  in the illustrated example. 
     An internal gear  13  has an circular engagement surface which engages with the idle gear  11  that is rotated by the gear plate  10 , and which is approximately semicircular, concentric to the gear plate  10  in the illustrated example. 
     A play reel gear  14  coaxial to the play reel  3 . A rewind gear  15  is concentric to the rewind reel  4 . Reference numeral “ 16 ” is a head base which is placed on the top of the main body plate  1  and on which a forward-side magnetic head  16   1 , a reverse-side magnetic head  16   2 , a pinch roller  16   3 , etc. are mounted. The head base  16  is moved forward by gears while tilting the magnetic head  16   1  ( 16   2 ) upper rightward or upper leftward at a predetermined angle θ (about 4 degrees in the illustrated example) to the center of the capstan  7  as the perpendicular line. A hole  16   4  is formed in the head base  16  to receive the capstan  7 . A forked groove  16   5  of an approximately trapezoidal shape is formed in the head base  16  in such a way that as a select arm  23  moves horizontally in either the forward mode or reverse mode selected, it is set in a rightward inclined groove  16   5 ′ when the head base  16  which has moved forward in inclination is in the forward mode and it is set in a leftward inclined groove  16   5 ″ when the head vase  16  which has moved forward in inclination is in the reverse mode. In this case, the head base  16  which has moved forward toward the capstan  7  is inclined upper rightward or upper leftward at the predetermined angle θ due to restriction by the projection,  23   1 , of the select lever  23  regardless of whether it is the forward mode or the reverse mode. 
     A pair of play levers  17  and  17 ′, provided on the top surface of the main body plate  1 , have their proximal end portions coupled to attachment rods  18 , and positioning projections  17   1  and  17   1 ′ at the time their distal ends  17   2  and  17   2 ′ are turned, so that the pinch roller  16   3  on the head base  16  is moved toward or away from the capstan  7 . 
     An arm-like lock mechanism  19  serves to move the head vase  16  to the position of the play lever  17  (or  17 ′) with respect to the tape face, T 1 , of a cassette tape t and hold the stop state. The lock mechanism  19  has a first engagement portion  19   1  and a second engagement portion  19   2  on each side, which face the projection  17   1  (or  17   1 ′) of the associated play lever  17  (or  17 ′) and are to engage with each other. The first engagement portions  19   1  and second engagement portions  19   2  are formed integral with the head base  16 . As the play lever  17  ( 17 ′) turns, therefore, the lock mechanism  19  performs a locking operation or an unlocking operation. With the head base  16  at the original position, the projection  17   1  ( 17 ) of the play lever  17  ( 17 ′) engages with the associated second engagement portion  19   2  of the lock mechanism  19 . 
     A return spring  20  exerts reactive force to move the head base  16  away from the capstan  7 . 
     a horizontal select-lever retaining groove  22  is provided on the main body plate  1 . The select lever  23  is received in this retaining groove  22  in such a manner as to be horizontally movable therein. Provided at the upper center of the select lever  23  is the projection  23   1  which engages with the forked grove  16   5 . 
     SPECIFIC EXAMPLES OF ACTIONS 
     (1) Stop State 
     With the head base  16  in the stop state shown in FIGS. 3 to  5 , the head base  16  is set downward, the left and right play levers  17  and  17 ′ are free, and the gear plate  10  and the idle gear  11  are at the middle of the right and left moving positions with a line C at the center. 
     With the motor  2  stopped, the idle gear  11  is positioned almost directly on the center line C, the play lever  17  is positioned between the play reel gear  14  and the idle gear  11 , and the head base  16  is at the original position where the magnetic heads  16   1  and  16   2  are moved away from the tape face T 1 . 
     At this time, the select lever  23  is positioned downward at the center with its projection  23   1  engaging with the notch  10   1  at the top of the gear plate  10 . 
     The pinch roller  16   3  is set away from the capstan  7 , and the projection  17   1  of the play lever  17  is in engagement with the associated second engagement portion  19   2  of the lock mechanism  19  (FIG. 5) integral with the head base  16 . 
     (2) Forward Action from Stop State 
     When the head base  16  in FIGS.  3 - 5  is turned clockwise around the capstan  7  from the stop state, the gear plate  10  turns clockwise too, with the projection  12  of the idle gear  11  pushing the play lever  17  upward (in the direction of the solid arrow in FIG.  3 ). As the turning continues, the projection  12  comes free of the distal end  17   2  of the play lever  17 , so that the idle gear  11  engages with the play reel gear  14 . When the select lever  23  whose projection  23   1  has been in engagement with the notch  10   1  at the top of the gear plate  10  from the beginning of the turning action to a part of the way, is moved rightward horizontally by a predetermined distance g, the engagement is broken at which time the projection  23   1  is set in the rightward inclined groove  16   5 ′of the forked groove  16   5  in the head bases  16 . As a result, the head base  16  moves forward while being inclined upper rightward by a predetermined angle θ (about 4 degrees in the illustrated example), so that the pinch roller  16   3  comes closer to the capstan  7  and the forward-side magnetic head  16   1  contacts the tape face T 1  of the cassette tape. When the projection  12  pushes the play lever  17  and comes free of the distal end  17   2 , the projection  17   1  of the play lever  17  engages with the associated first engagement portion  19   1  (FIG.  8 ). 
     Through the above-described action, as illustrated in FIGS. 6 to  8 , the capstan  7  is pressed against the punch roller  16   3 , the head base  16  is moved forward while being inclined upper rightward by a predetermined angle and is locked by the lock mechanism  19 , the rewind reel  4  rotates clockwise as the torque is transmitted from the capstan  7  to the idle gear  11  and then to the rewind reel  4 . Then, of the right and left magnetic heads  16   1  and  16   2 , only the right magnetic head  16   1  is pressed against the tape face T 1 . 
     (3) Stop Action for Forward-to-Reverse Transition 
     As the gear plate  10  is turned counterclockwise, the projection  12  of the idle gear  11  pushes the play lever  17  downward to release the lock mechanism  19  of the head base  16 . As a result, the head base  16  comes to the state where the right magnetic head  16   1  is retracted from the upper rightward position so that both magnetic heads  16   1  and  16   2  come to the same height. The pinch roller  16   3  is moved away from the capstan  7  at which time the tape face T 1  is set free of the magnetic head  16   1  and becomes the stop state (FIGS.  3 - 5 ). 
     (4) Reverse Action from Stop State 
     The transition to the reverse action from the stop state is symmetrical or mirror-imaging to the transition to the forward action (FIGS.  6 - 8 ). 
     When the gear plate  10  is turned rightward or counterclockwise around the center line C from the stop state (FIGS.  3 - 5 ), the projection  12  of the idle gear  11  pushes the right play lever  17 ′ upward and comes free of the distal end  17   2 ′ of the play lever  17 ′, so that the idle gear  11  engages with the right gear (rewind reel gear)  1 ` 5 . When the select lever  23  whose projection  23   1  has been in engagement with the notch  10   1  at the top of the gear plate  10  from the beginning of the turning action to a part of the way, is moved leftward horizontally by a predetermined distance g′, the engagement is broken at which time the projection  23   1  is set in the leftward inclined groove  16   5 ″ of the forked groove  16   5 . As a result, the head base  16  moves forward while being inclined upper leftward by a predetermined angle θ (about 3.75 degrees in the illustrated example), so that the pinch roller  16   3  comes closer to the capstan  7  and the reverse-side magnetic head  16   2  contacts the tape face T  1  of the cassette tape. When the projection  12  pushes the play lever  17 ′ and comes free of the distal end  17   2 ′, the right first engagement portion  19   1  of the lock mechanism  19  engages with the projection  17   1 ′ of the play lever  17 ′. 
     At this time, the capstan  7  rotates symmetrically. When the head base  16  moves forward in upper leftward inclination, the magnetic head  16   2  is set to the upper leftward position to contact the tape face T 1 , thereby establishing the reverse mode (FIGS.  9 - 11 ). 
     (5) Action for Fast Forward Mode 
     In the reverse mode in FIG. 10, the gear plate  10  is turned clockwise around the capstan  7  to push the play lever  17  downward with the projection  12  of the idle gear  11 . As the projection  12  comes free of the distal end  17   2  of the play lever  17 , the idle gear  11  returns to the center position. After the select lever  23  whose projection  23   1  has been in engagement with the notch  10   1  at the top of the gear plate  10  from the beginning of the turning action to a part of the way, is moved leftward in the retaining groove  22 , the engagement is broken. 
     The head base  16  set free of the play lever  17  is retracted to return to the original position by the return spring  20 . At this time, the depressed play lever  17  stops as its projection  17   1  engages with the associated second engage portion  19   2  of the lock mechanism  19 . 
     When a motor voltage is increased in this situation by the fast forward manipulation, the rotation of the motor  2  becomes faster. When the gear plate  10  is turned clockwise again, the idle gear  11  engages with the play reel gear  14 . Since the head base  16  does not move forward at this time, the pinch roller  16   3  is set apart from the capstan  7  (FIG.  12 ). 
     (6) Action for Rewind Mode 
     In the state in FIG. 10, the gear plate  10  is turned clockwise around the capstan  7  to push the play lever  17 ′ downward with the projection  12  of the idle gear  11 . As the projection  12  comes free of the distal end  17   2 ′ of the play lever  17 ′, the idle gear  11  returns to the center position. After the select lever  23  whose projection  23   1  has been in engagement with the notch  10   1  at the top of the gear plate  10  from the beginning of the turning action to a part of the way, is moved leftward in the retaining groove  22 , the engagement is broken. 
     The head base  16  set free of the play lever  17 ′ is set back to the original position by the return spring  20 . At this time, the depressed play lever  17 ′ stops as its projection  17   1 ′ engages with the associated second engage portion  19   2 ′ of the lock mechanism  19 . 
     when the motor voltage is increased under this situation by the rewinding manipulation, the rotation of the motor  2  becomes faster. When the gear plate  10  is turned counterclockwise again, the idle gear  11  engages with the rewind reel gear  15 . Since the head base  16  does not move forward at this time, the pinch roller  16   3  is set apart from the capstan  7  (FIG.  13 ). 
     Because of the above-described structure, forward and reverse modes can be accomplished by simply adding one part to the conventional autoreverse mechanism, thus ensuring a compact and lighter design, stable tape running operation and cost reduction, so that this mechanism is particularly suitable for use in a microcassette tape recorder.