Abstract:
The magnetic recording/reproduction apparatus of the present invention records/reproduces information on/from a magnetic tape by drawing out the magnetic tape from a tape cassette and allowing the magnetic tape to pass around a rotary head cylinder, having a rotary head, for a predetermined arc. The tape cassette is drawn by moving tape guide members located at an opening of the tape cassette. The recording/reproduction apparatus includes: a first chassis on which the tape cassette is placed; and a second chassis having thereon the rotary head cylinder. The magnetic recording/reproduction apparatus includes: a first state in which the tape cassette is placed on the first chassis by a user; and a second state in which a tape running path enabling recording/reproduction of the magnetic tape is established. The second chassis includes: a capstan shaft mounted thereon for driving the magnetic tape; a pinch roller for pressing the magnetic tape against the capstan shaft; and a pinch arm supporting the pinch roller to be rotatable, the pinch arm being swingably mounter on the second chassis. Due in part to the above, when the magnetic recording/reproduction apparatus shifts from the first state to the second state, the first chassis moves towards the rotary head cylinder, and during the movement of the first chassis towards the rotary head cylinder, the first chassis drives the pinch arm so that the pinch roller moves from the opening of the tape cassette to a vicinity near the capstan shaft.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a magnetic recording/reproduction apparatus, and more particularly, relates to a magnetic recording/reproduction apparatus provided with a mechanism of moving a sub-chassis relative to a main chassis. 
     2. Description of the Related Art 
     An example of conventional magnetic recording/reproduction apparatus is disclosed in FIGS. 11 and 12 of Japanese Patent Gazette No. 2627465. Referring to FIGS. 36 to  38 , a conventional magnetic recording/reproduction apparatus will be described. 
     In the conventional magnetic recording/reproduction apparatus  300  shown in FIGS. 26 to  38 , a pinch arm  335  and a sub-pinch arm  339  are swingably attached coaxially to a swing shaft  337  mounted on a slide chassis  301 . A swing pin  349  (FIG. 37) extends from the sub-pinch arm  339 , so as to transmit a driving force from a main chassis  351  for swinging the pinch arm  335 . 
     A main cam  353  is swingably mounted on the main chassis  351 . The main cam  353  has a pinch roller pressing groove  367 , which engages with a cam pin  389  extending from one end of a pinch operation level  369 . 
     The other end of the pinch operation lever  369  engages with a pinch pressing lever  371  which is swingably attached to a shaft mounted on the main chassis  351 . The pinch pressing lever  371  has abut faces  347 A and  347 B. 
     The abut faces  347 A and  347 B of the pinch pressing lever  371  engage with the swing pin  349  of the sub-pinch arm  339 , so as to drive the pinch arm  335  on the slide chassis  301 . 
     The above configuration requires a number of components disposed between the main cam  353  and the pinch arm  335  to drive the pinch arm  335  (e.g., the pinch operation lever  369 , the pinch pressing lever  371 , and various shafts). This prevents a reduction in the number of components and in the size of the mechanism from being realized. 
     The object of the present invention is to provide a magnetic recording/reproduction apparatus provided with a small mechanism with a reduced number of components. 
     SUMMARY OF THE INVENTION 
     The recording/reproduction apparatus of this invention records/reproduces information on/from a magnetic tape by drawing out the magnetic tape from a tape cassette and allowing the magnetic tape to pass around a rotary head cylinder, having a rotary head, for a predetermined arc, the tape cassette being drawn by moving tape guide members located at an opening of the tape cassette. The apparatus includes: a first chassis on which the tape cassette is placed; and a second chassis having the rotary head cylinder mounted thereon and guiding movement of the first chassis toward the rotary head cylinder, the magnetic recording/reproduction apparatus including: a first state in which the tape cassette is placed on the first chassis by a user; and a second state in which a tape running path enabling recording/reproduction of the magnetic tape is established, the second chassis including: a capstan shaft mounted on the second chassis for driving the magnetic tape; a pinch roller for pressing the magnetic tape against the capstan shaft; and a pinch arm supporting the pinch roller to be rotatable, the pinch arm being swingably mounted on the second chassis, wherein when the magnetic recording/reproduction apparatus shifts from the first state to the second state, the first chassis moves toward the rotary head cylinder, and during the movement of the first chassis toward the rotary head cylinder, the first chassis drives the pinch arm so that the pinch roller moves from the opening of the tape cassette to a vicinity near the capstan shaft. 
     In one embodiment of the invention, the pinch arm includes a first chassis engaging portion engaging with the first chassis, the first chassis includes a pinch arm engaging portion engaging with the first chassis engaging portion, the first chassis presses the first chassis engaging portion via the pinch arm engaging portion so that the pinch roller moves from the opening of the tape cassette to a vicinity near the capstan shaft. 
     In another embodiment of the invention, the first chassis is made of a metal plate, and the pinch arm engaging portion is formed by bending a portion of the metal plate. 
     In still another embodiment of the invention, the magnetic recording/reproduction apparatus further includes an elastic member for urging the pinch arm in a direction opposite to the capstan shaft with respect to the pinch arm. 
     In still another embodiment of the invention, the elastic member comprises a spring, and one end of the spring is hooked to the pinch arm and the other end of the spring is hooked to a spring hook portion of the first chassis. 
     Thus, the invention described herein makes possible the advantage of providing a magnetic recording/reproduction apparatus provided with a small mechanism with a reduced number of components. 
     This and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of an embodiment of the magnetic recording/reproduction apparatus according to the present invention, illustrating a state in which a cassette can be placed/removed (UNLOADED mode); 
     FIG. 2 is a plan view of a tension arm and components in the vicinity thereof of one embodiment of the magnetic recording/reproduction apparatus; 
     FIG. 3 is a plan view of one embodiment of the magnetic recording/reproduction apparatus in the UNLOADED mode, where a sub-chassis and components provided thereon are removed; 
     FIG. 4 is a plan view of a tension plate and components in the vicinity thereof of one embodiment of the magnetic recording/reproduction apparatus in the UNLOADED mode; 
     FIG. 5 is a view of a structure for driving an S boat and a T boat provided on a main chassis of one embodiment of the magnetic recording/reproduction apparatus. 
     FIG. 6 is a view of a sub-chassis driving arm of one embodiment of the magnetic recording/reproduction apparatus; 
     FIG. 7 is a view of a structure of a pinch arm and components in the vicinity thereof of one embodiment of the magnetic recording/reproduction apparatus; 
     FIG. 8 is a view of the pinch arm of one embodiment of the magnetic recording/reproduction apparatus; 
     FIG. 9 is a view of a pinch pressing arm of one embodiment of the magnetic recording/reproduction apparatus; 
     FIG. 10 is a view of a torsion coil spring of one embodiment of the magnetic recording/reproduction apparatus; 
     FIG. 11 is a cross-sectional view of a MIC-SW of one embodiment of the magnetic recording/reproduction apparatus, taken along line A—A of FIG. 1; 
     FIG. 12 is a view of one embodiment of the magnetic recording/reproduction apparatus, viewed in the direction shown by arrow B in FIG. 1; 
     FIG. 13 is a plan view of one embodiment of the magnetic recording/reproduction apparatus, illustrating a state in which a tension post and a T 4  post have protruded (LOADING  1  mode); 
     FIG. 14 is a plan view of one embodiment of the magnetic recording/reproduction apparatus, illustrating a state in which the sub-chassis has moved by a half of the entire stroke (LOADING  2  mode); 
     FIG. 15 is a plan view of one embodiment of the magnetic recording/reproduction apparatus, illustrating a state in which the apparatus is ready for recording/reproduction and fast-forwarding of a tape (PLAY mode); 
     FIG. 16 is a plan view of one embodiment of the magnetic recording/reproduction apparatus, illustrating a state in which the tape running is not performed (STOP mode); 
     FIG. 17 is a plan view of one embodiment of the magnetic recording/reproduction apparatus, illustrating a state in which the apparatus is ready for reverse reproduction and rewinding of a tape (REV mode); 
     FIG. 18 is a plan view of one embodiment of the magnetic recording/reproduction apparatus in the LOADING  1  mode, where the sub-chassis and components provided thereon are removed; 
     FIG. 19 is a plan view of one embodiment of the magnetic recording/reproduction apparatus in the LOADING  2  mode, where the sub-chassis and components provided thereon are removed; 
     FIG. 20 is a plan view of the tension plate and components in the vicinity thereof of one embodiment of the magnetic recording/reproduction apparatus in the LOADING  1  mode; 
     FIG. 21 is a plan view of the tension plate and components in the vicinity thereof of one embodiment of the magnetic recording/reproduction apparatus in the LOADING  2  mode; 
     FIG. 22 is a plan view of the tension plate and components in the vicinity thereof of one embodiment of the magnetic recording/reproduction apparatus in the PLAY mode; 
     FIG. 23 is a plan view of the tension plate and components in the vicinity thereof of one embodiment of the magnetic recording/reproduction apparatus in the STOP mode and the REV mode; 
     FIG. 24 is a plan view illustrating a state in which a boat driving arm and a sub-chassis driving arm are driven in the UNLOADED mode in one embodiment of the magnetic recording/reproduction apparatus; 
     FIG. 25 is a plan view illustrating a state in which the boat driving arm and the sub-chassis driving arm are driven in the LOADING  1  mode in one embodiment of the magnetic recording/reproduction apparatus; 
     FIG. 26 is a plan view illustrating a state in which the boat driving arm and the sub-chassis driving arm are driven in the LOADING  2  mode in one embodiment of the magnetic recording/reproduction apparatus; 
     FIG. 27 is a plan view illustrating a state in which the boat driving arm and the sub-chassis driving arm are driven in a mode which is a mode before the PLAY mode and close to the LOADING  2  mode (PRE-PLAY mode) in one embodiment of the magnetic recording/reproduction apparatus; 
     FIG. 28 is a plan view illustrating a state in which the boat driving arm and the sub-chassis driving arm are driven in the PLAY mode in one embodiment of the magnetic recording/reproduction apparatus; 
     FIG. 29 is a plan view illustrating a state in which the boat driving arm and the sub-chassis driving arm are driven in the STOP mode in embodiment of the magnetic recording/reproduction apparatus; 
     FIG. 30 is a plan view illustrating a state in which the boat driving arm and the sub-chassis driving arm are driven in the REV mode in one embodiment of the magnetic recording/reproduction apparatus; 
     FIG. 31 is a plan view illustrating a state in which the pinch arm and the T 4  arm are driven in the UNLOADED mode in one embodiment of the magnetic recording/reproduction apparatus; 
     FIG. 32 is a plan view illustrating a state in which the pinch arm and the T 4  arm are driven in the LOADING  1  mode in one embodiment of the magnetic recording/reproduction apparatus; 
     FIG. 33 is a plan view illustrating a state in which the pinch arm and the T 4  arm are driven in the LOADING  2  mode in one embodiment of the magnetic recording/reproduction apparatus; 
     FIG. 34 is a plan view illustrating a state in which the pinch arm and the T 4  arm are driven in the PLAY mode and the REV mode in one embodiment of the magnetic recording/reproduction apparatus; 
     FIG. 35 is a plan view illustrating a state in which the pinch arm and the T 4  arm are driven in the STOP mode in one embodiment of the magnetic recording/reproduction apparatus; 
     FIG. 36 is a plan view of a conventional magnetic recording/reproduction apparatus; 
     FIG. 37 is a view illustrating a pinch roller portion of the conventional magnetic recording/reproduction apparatus; 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will be described by way of example with reference to the accompanying drawings. 
     FIG. 1 is a plan view of a magnetic recording/reproduction apparatus  100  of an embodiment according to the present invention is an UNLOADED mode in which a cassette can be placed/removed. In FIG. 1, some components are omitted for simplification. 
     A tape  2  is wound on two reels (not shown) placed inside a cassette  1 . In FIG. 1, for easy viewing, only the outline of the cassette  1  is shown (by the one-dot chain lines), and only the portion of the tape  2  which extends outside the cassette  1  is shown (by the one-dot chain lines). The cassette  1  is placed on a sub-chassis  3 . An S reel base  4  and a T reel base  5  are rotatably mounted on the sub-chassis  3  and engage the two reels (not shown) inside the cassette  1 . 
     An idler  6  is swingably attached to a center gear shaft  9  extending from a main chassis  8 . A center gear  10  is rotatably attached to the center gear shaft  9 . An idler gear  7 , which is attached to a shaft of the idler  6 , is rotated by the center gear  10 , and engages with external gears of the S reel base  4  and the T reel base  5  to rotate the S reel base  4  and the T reel base  5 . A memory read switch (MIC-SW)  11  for reading data from a memory in the cassette  1  is mounted on the sub-chassis  3 . 
     A tension arm  12  is swingably mounted on the sub-chassis  3  via a tension arm shaft  13 . FIG. 2 shows a portion of the magnetic recording/reproduction apparatus in the vicinity of the tension arm  12  in detail. Referring to FIGS. 1 and 2, a tension post  14  is disposed at an end of the tension arm  12 . A tension arm regulating pin  15  is provided at the other end  16  of the tension arm  12 , which engages with a tension plate  18  (omitted in FIG. 1; see FIGS. 3 and 4) mounted on the main chassis  8  via a hole  17  formed through the sub-chassis  3  so as to regulate the movement of the tension arm  12 . 
     A tension band  19  is swingably attached at one end  124  to a shaft  20  of the tension arm  12  and at the other end  125  to a shaft  22  of a tension band regulating arm  21 . The tension band regulating arm  21  is swingably mounted on the sub-chassis  3  via a shaft  23 , and urged counterclockwise by a torsion coil spring  24 . The torsion coil spring  24  is hooked to a spring hook portion  115  disposed on the sub-chassis  3 . A tension arm stop plate  116  is secured to the sub-chassis  3  with a screw (not shown) at a position  117  after being adjusted appropriately so that the movement of the tension band regulating arm  21  is restricted by abutting against the tension arm stop plate  116 . 
     A pin  25  provided on the tension band regulating arm  21  engages with the tension plate  18  via the hole  17  of the sub-chassis  3  for restricting movement of the tension band regulating arm  21 . The tension band  19  passes around a cylinder portion  26  of the S reel base  4 . The tension arm  12  is urged counterclockwise by a tension spring  27 . An end of the tension spring  27  is hooked to a spring hook portion of the sub-chassis  3 . In this embodiment, only outlines are shown by the broken lines for all tension springs throughout the drawings for simplification. The tension band  19  is provided with protrusions  118  and  119 , while the tension arm  12  is provided with a band regulating protrusion  120 . The movement of the tension band  19  is regulated by the protrusions  118  and  119  abutting against the band regulating protrusion  120 , so as to prevent the tension band  19  from slacking and thereby being displaced from the S reel base  4 . 
     Referring to FIG. 1, a T 4  arm  28  is swingably mounted on the sub-chassis  3  via shaft  29 . A T 4  post  30  is disposed at one end of the T 4  arm  28 , and a T 4  regulating pin  31  is provided at the other end thereof. The T 4  arm  28  is urged counterclockwise by a spring (not shown). 
     Four elongate holes  36  provided through the sub-chassis  3  are engaged with four shafts  37  extending from the main chassis  8 . The sub-chassis  3  is movable forward and backward along the elongate holes  36 . 
     A cylinder  38  provided with a rotary magnetic head is mounted on the main chassis  8 , and performs recording/reproduction of signals as the tape  2  passes around the cylinder  38 . 
     An S boat  39  and a T boat  40  are provided with pins  41 A and  41 B, and pins  41 C and  41 D, respectively, which engage with an elongate hole  43  of a rail  42 , so that the S boat  39  and the T boat  40  move along the elongate hole  43 . The S boat  39  and the T boat  40  are also provided with an S 1  post  45  and an S 2  post  44  and a T 1  post  46  and a T 2  post  47 , respectively, so that the tape  2  can be put in contact with the cylinder  38  as the S boat  39  and the T boat  40  move. A rail  48  and an S 3  post  49  are disposed on the main chassis  8 . A T 3  post  51  is disposed in a capstan housing  52  which holds a capstan shaft  50 . The capstan shaft  50  is driven by a capstan motor  50 A. 
     A pinch arm  53  is swingably mounted on the main chassis  8  via a shaft  54 . A pinch roller  55  is rotatably disposed at one end of the pinch arm  53 . A pinch pressing arm  56  is also swingably attached to the shaft  54  of the pinch arm  53 . The pinch pressing arm  56  and the pinch arm  53  are urged and held together by a torsion coil spring  57 . A tension spring  58  extends between the pinch arm  53  and the sub-chassis  3 , urging the pinch arm  53  counterclockwise. A protrusion  59  of the pinch arm  53  abuts against a wall  60  of the sub-chassis  3 , so as to drive the pinch arm  53  as the sub-chassis  3  moves. 
     FIG. 3 is a plan view of the embodiment of the magnetic recording/reproduction apparatus according to the present invention in the UNLOADED mode, where the sub-chassis  3  together with the components provided thereon are removed for illustrating the structure of the main chassis  8 . 
     Referring to FIGS. 3 and 4, two elongate holes  61  formed through the tension plate  18  engage with two guide pins  62  extending from the main chassis  8 , so that the tension plate  18  is guided forward and backward by the guide pins  62 . 
     A cam groove  63  formed on the tension plate  18  engages with the tension arm regulating pin  15  described with reference to FIG. 1. A tension plate driving arm  64  is swingably mounted on the main chassis  8  via a shaft  65 . A cam gear  66  is rotatably mounted on the main chassis  8  via a shaft  67 . The cam gear  66  is provided with a cam groove  68  which engages with a cam following pin  69  extending from the tension plate driving arm  64 . A pin  70  extending from the tension plate driving arm  64  engages with a cam groove  71  formed on the tension plate  18 . The pin  25  extending from the tension band regulating arm  21  described with reference to FIG. 1 abuts against a cam  72  of the tension plate  18 . 
     Referring to FIGS. 1,  3 , and  4 , the tension plate driving arm  64  is driven by the engagement of the cam following pin  69  with the cam groove  68  of the cam gear  66 , and then the tension plate  18  is driven by the engagement of the cam groove  71  with the pin  70  of the tension plate driving arm  64 . 
     The tension arm  12  is driven and the movement thereof is regulated by the engagement of the tension arm regulating pin  15  with the cam groove  63  of the tension plate  18 . The tension regulating arm  21  is driven and the movement thereof is regulated by the engagement of the pin  25  with the cam  72  of the tension plate  18 . 
     FIG. 5 illustrates a mechanism for driving the S boat  39  and the T boat  40  mounted on the main chassis  8 . Referring to FIGS. 3 and 5, a boat driving arm  73  is swingably mounted on the main chassis  8  via a shaft  74 . A driving pin  75  extending from the cam gear  66  abuts against an internal cam  76  provided in the boat driving arm  73  so that the boat driving arm  73  is driven as the cam gear  66  swings. 
     A gear portion  77  of the boat driving arm  73  engages with a small gear portion  80  formed integrally with an S load gear  79  which is rotatably mounted on the main chassis  8  via a shaft  78 . 
     An S load arm  81  is provided to swing coaxially with the S load gear  79 . An S load link  82  is swingably coupled with the S load arm  81  and the S boat  39  via a shaft  83  and the pin  41 A, respectively. 
     A T load gear  84  is rotatably mounted on the main chassis  8  via a shaft  85  and engages with the S load gear  79 . A T load arm  86  is provided to swing coaxially with the T load gear  84 . A T load link  87  is swingably coupled with the T load arm  86  and the T boat  40  via a shaft  88  and the pin  41 C, respectively. 
     The S load arm  81  and the S load arm  79  are normally put together by means of a torsion coil spring (not shown) and swung around the shaft  78 . When the S load gear  79  is rotated clockwise, The S load gear  79  is urged counterclockwise by the torsion coil spring (not shown). Likewise, the T load arm  86  and the T load gear  84  are normally put together by means of a torsion coil spring (not shown) and swung around the shaft  85 . When the T load gear  84  is rotated counterclockwise while the T load arm  86  stands still, the T load gear  84  is urged clockwise by the torsion coil spring (not shown). 
     The S load gear  79  and the T load gear  84  are driven as the boat driving arm  73  swings, which causes the S boat  39  and the T boat  40  to move along the rail  42  via the movement of the S load link  82  and the T load link  87 . 
     FIG. 6 illustrates a sub-chassis driving arm  89  in detail. Referring to FIGS. 1,  3 , and  6 , the sub-chassis driving arm  89  is swingably mounted on the main chassis  8  via a shaft  90 . The driving pin  75  extending from the cam gear  66  abuts against an internal cam  91  provided in the sub-chassis driving arm  89  so that the sub-chassis driving arm  89  is driven as the cam gear  66  swings, as in the case of the boat driving arm  73 . 
     A guide pin  92  extends from the sub-chassis driving arm  89  and abuts against the cam plates  32  and  33  via a hole  108  in the sub-chassis  3  (see FIG.  1 ). Thus, the sub-chassis driving arm  89  is driven by the cam gear  66 , and then the sub-chassis  3  is driven by the sub-chassis driving arm  89  via the cam plates  32  and  33 . The position of the sub-chassis  3  with respect to the main chassis  8  can be adjusted by adjusting the positions of the cam plates  32  and  33  in the right and left directions. 
     Referring to FIG. 3, a timing belt  93  transmits the rotation of the capstan shaft  50  to a 2-stage gear  94  which is swingably mounted on the main chassis  8 . The 2-stage gear  94  engages with the center gear  10 . Thus, the rotation of the capstan shaft  50  is transmitted to the S reel base  4  and the T reel base  5  via the timing belt  93 , the 2-stage gear  94 , the center gear  10 , and idler gear  7 . 
     FIG. 7 illustrates a structure of the pinch arm  53  and the components in the vicinity thereof: FIG. 8 illustrates the pinch arm  53  itself, FIG. 9 illustrates the pinch pressing arm  56 , and FIG. 10 illustrates the torsion coil spring  57 . In FIGS. 7 and 8, only the outline is shown by the broken line for the pinch roller  55 . As shown in FIG. 7, the pinch arm  53  and the pinch pressing arm  56  are normally swung integrally around the shaft  54  (see FIG. 1) by means of the torsion coil spring  57 . When the pinch roller  55  abuts against the capstan shaft  50 , the pinch arm  53  and the pinch pressing arm  56  is stop swinging. In this state, when the pinch pressing arm  56  is further swung clockwise, the pinch roller  55  is pressed against the capstan shaft  50  by the repulsive force of the torsion coil spring  57 . A roller  152  is rotatably attached to the pinch pressing arm  56 . 
     Referring to FIG. 3, a pinch cam gear  95  is rotatably mounted on the main chassis  8  via a shaft  96 . A pinch driving arm  97  is swingably mounted on the main chassis  8 . A cam pin  99  extending from the pinch driving arm  97  engages with a cam groove  100  provided on the pinch cam gear  95 , so that the pinch driving arm  97  is driven by the pinch cam gear  95 . 
     Referring to FIGS. 1 and 3, the T 4  regulating pin  31  of the T 4  arm  28  abuts against a protrusion  102  of the pinch driving arm  97  via a hole  101  (FIG. 1) formed through the sub-chassis  3 . The T 4  arm  28  is therefore driven by the swinging of the pinch driving arm  97 . 
     FIG. 11 is a cross-sectional view of the MIC-SW  11 , taken along line A—A of FIG.  1 . Referring to FIGS. 1 and  11 , the MIC-SW  11  is secured to the sub-chassis  3  with a screw (not shown). A sub-chassis reinforcing plate  103  is secured to the sub-chassis  3  with a screw (not shown). A U-shaped end portion  104  of the sub-chassis reinforcing plate  103  engages with an end  105  of the MIC-SW  11  so as to reinforce the MIC-SW  11 . The MIC-SW  11  is provided with a contact  106  which comes into contact with a memory  107  located in the cassette  1  for effecting output/input of signals. When the contact  106  is pressed by the cassette  1 , the MIC-SW  11  receives a reactive force. Since the body of the MIC-SW  11  is normally made of plastic, it is vulnerable to creep deformation. According to the present invention, however, the MIC-SW  11  can be reinforced by the sub-chassis reinforcing plate  103 , allowing the body of the MIC-SW  11  to be thinned and thereby the entire apparatus to be made small. 
     FIG. 12 is a view as is seen in the direction indicated by arrow B in FIG.  1 . Referring to FIGS. 1 and 12, the boat driving arm  73  and the sub-chassis driving arm  89  are driven by the driving pin  75  extending from the cam gear  66  mounted on the main chassis  8 . Elongate holes  109  and  110  are formed through the cam plates  32  and  33 , and enable the cam plates  32  and  33  to be held movably in the right and left directions with respect to the sub-chassis  3 . Screws  111  and  112  (not shown in FIG. 1) secure the cam plates  32  and  33  at positions  113  and  114  shown in FIG. 1, respectively, after positional adjustment of the cam plates  32  and  33  by guiding the cam plates in the right and left directions with respect to the sub-chassis  3 . 
     FIGS. 13 through 17 are plan views of the magnetic recording/reproduction apparatus of this embodiment, illustrating respective states of the apparatus in order after the state in which the cassette can be placed/removed (UNLOADED mode) shown in FIG. 1 until the tape recording/reproduction mode. All of the reference numerals of the components shown in FIGS. 13 through 17 correspond to those shown in FIG.  1 . 
     FIG. 13 illustrates LOADING  1  mode in which the tension post  14  and the T 4  post  30  having protruded from the cassette  1 . FIG. 14 illustrates LOADING  2  mode in which the sub-chassis  3  has moved a half of its entire stroke. FIG. 15 illustrates PLAY mode in which the movement of the sub-chassis  3  has been completed and the tape loading, i.e., the passing of the tape  2  around the cylinder  38 , has been completed, to allow the tape to run forward from the S reel base  4  to the T reel base  5  to effect recording/reproduction, fast-forwarding, etc. of the tape. 
     FIG. 16 illustrates STOP mode in which the running of the tape is stopped. FIG. 17 illustrates REV mode in which the tape runs reverse to the direction in the PLAY mode to effect reverse reproduction, rewinding, etc. of the tape. 
     FIGS. 18 and 19 are views similar to FIG. 3, i.e., plan views of the magnetic recording/reproduction apparatus  100  according to the present invention, where the sub-chassis  3  together with the components provided thereon are removed for illustrating the structure of the main chassis  8 . All of the reference numerals of the components shown in FIGS. 18 and 19 correspond to those shown in FIG.  3 . FIGS. 3,  18 , and  19  illustrate the UNLOADED mode, the LOADING  1  mode, and the LOADING  2  mode, respectively. 
     FIGS. 20 through 23 are views similar to FIG. 4, i.e., views illustrating the tension plate  18  and the components in the vicinity thereof in detail. All of the reference numerals of the components shown in FIGS. 20 to  23  correspond to those shown in FIG.  4 . FIG. 4 illustrates the UNLOADED mode, FIG. 20 illustrates the LOADING  1  mode, FIG. 21 illustrates the LOADING  2  mode, FIG. 22 illustrates the PLAY mode, and FIG. 23 illustrates the STOP mode and the REV mode. The position of the tension plate  18  is the same in the STOP mode and the REV mode. 
     FIGS. 24 through 30 are views illustrating the state in which the boat driving arm  73  and the sub-chassis driving arm  89  are driven by the driving pin  75  extending from the cam gear  66 . 
     FIG. 24 illustrates the UNLOADED mode, FIG. 25 illustrates the LOADING  1  mode, FIG. 26 illustrates the LOADING  2  mode, FIG. 27 illustrates PRE-PLAY mode which is a mode slightly before the mode shift from the LOADING  2  mode to the PLAY mode, FIG. 28 illustrates the PLAY mode, FIG. 29 illustrates the STOP mode, and FIG. 30 illustrates the REV mode. 
     FIGS. 31 through 35 are views illustrating the state in which the pinch arm  53  on the main chassis  8  and the T 4  arm  28  on the sub-chassis  3  are driven by the pinch driving arm  97 . The T 4  arm  28  is not shown but only the T 4  arm regulating pin  31  of the T 4  arm  28  is shown in these figures. 
     FIG. 31 illustrates the UNLOADED mode, FIG. 32 illustrates the LOADING  1  mode, FIG. 33 illustrates the LOADING  2  mode, FIG. 34 illustrates the PLAY mode and the REV mode, and FIG. 35 illustrates the STOP mode. The movement of the pinch driving arm  97 , the pinch arm  53 , and the T 4  arm  28  are the same in the PLAY mode and the REV mode. 
     Hereinbelow, the operation of the magnetic recording/reproduction apparatus will be described for the respective states in order starting from the UNLOADED mode until the REV mode. 
     The UNLOADED mode will be described with reference to FIGS. 1,  3 ,  4 ,  24 , and  31 . 
     Referring to FIG. 1, the tape  2  has not been out from the cassette  1 . Referring to FIGS. 1,  3 , and  24 , the sub-chassis  3  is located at the most extended position from the main chassis  8 . The driving pin  75  of the cam gear  66  is in contact with first arc portions  121  and  122  of the internal cams  91  and  76  of the sub-chassis driving arm  89  and the boat driving arm  73 , respectively. The sub-chassis driving arm  89  and the boat driving arm  73  are both in the state of having swung clockwise to the maximum. 
     The S load gear  79  is in the state of having been rotated counterclockwise to the maximum by the gear portion  77  of the boat driving arm  73 . This state of the S load gear  79  forces the S boat  39  to be located at the most forward position in the elongate hole  43  of the rail  42  as is understood from the construction shown in FIG.  5 . Likewise, the T load gear  84  is in the state having been rotated clockwise to the maximum. This state of the T load gear  84  forces the T boat  40  to be located at the most forward position in the elongate hole  43  of the rail  42  as is understood from the construction shown in FIG.  5 . 
     Referring to FIGS. 1,  3 , and  4 , the tension plate  18  is forced to the most forward position by the tension plate driving arm  64 . The tension arm  12  is then forced to a position of having swung clockwise to the maximum by the tension band regulating pin  15  engaging with the cam groove  63  of the tension plate  18 . 
     The pin  25  of the tension band regulating arm  21  is located in a bottom concave portion  123  of the cam  72  of the tension plate  18 , while the position of the tension band regulating arm  21  is determined by the tension arm stop plate  116  (see FIG.  2 ). More specifically, the tension band regulating arm  21  is urged counterclockwise by the torsion coil spring  24  and abuts against the tension arm stop plate  116 . 
     In the above state, the tension band  19  is slacked since the end  124  thereof comes closer to the S reel base  4 . This slacking is however reduced since the other end  125  of the tension band  19  is moved away from the S reel base  4  by the tension band regulating arm  21 . 
     The slacking of the tension band  19  is also reduced since the protrusion  118  of the tension band  19  is pressed by the band regulating protrusion  120  of the tension arm  12 . Thus, the tension band  19  is prevented from being displaced from the S reel base  4  due to slacking of the tension band  19 . 
     Referring to FIGS. 1,  3 , and  31 , the pinch arm  53  is forced to a position of having swung counterclockwise to the maximum by the tension spring  58 . In this state, the pinch arm  53  is not in contact with the pinch driving arm  97 . The arm  28  is located at a position of having swung counterclockwise to the maximum. 
     Hereinbelow, the LOADING  1  mode will be described with reference to FIGS. 13,  18 ,  20 ,  25 , and  32 . 
     Referring to FIG. 13, the tape  2  has been drawn out to some extent by the tension post  14  and the T 4  post  30 . The tape  2  is also routed to pass around the S 1  post  45  located above the S boat  39  and partly pass around the cylinder  38 . 
     Referring to FIGS. 13,  18 , and  25 , the driving pin  75  extending from the cam gear  66  is still in contact with the first arc portion  121  of the sub-chassis driving arm  89 , and thus the sub-chassis  3  has not been driven, keeping the same position as in the UNLOADED mode. On the other hand, the driving pin  75  has passed along the first arc portion  122  of the internal cam  76  of the boat driving arm  73  to a concave portion  126  thereof. By the engagement of the driving pin  75  with the concave portion  126 , the boat driving arm  73  starts rotating counterclockwise. This allows the S boat  39  and the T boat  40  to move along the rail  42  in the direction in which the tape  2  is drawn out via the movements of the S load gear  79  and the T load gear  84 . 
     Referring to FIGS. 13,  18 , and  20 , the tension plate  18  is moved backward (toward the cylinder  38 ) by the tension plate driving arm  64 . With this movement, the tension arm regulating pin  15  moves in the guide groove  63  of the tension plate  18 , to allow the tension arm  12  to rotate counterclockwise to draw out the tape  2 . 
     With the movement of the tension plate  18 , the tension band regulating arm  21  is swung clockwise by the engagement of the pin  25  with a protrusion  128  of the cam  72  of the tension plate  18 . This causes the tension band  19  to be slacked with respect to the cylinder portion  26  of the S reel base  4 , making the S reel base  4  rotatable. 
     Referring to FIGS. 13,  18 , and  32 , the pinch arm  53  remains at the same position as in the UNLOADED state since the sub-chassis  3  has not moved. 
     The T 4  arm  28  allows the tape  2  to be drawn out clockwise by the abutment of the T 4  regulating pin  31  with the protrusion  102  of the pinch driving arm  97 . 
     The LOADING  2  mode will be described with reference to FIGS. 14,  19 ,  21 ,  26 , and  33 . 
     Referring to FIG. 14, the cassette  1  is moving toward the cylinder  38 , and the tape  2  passes around the cylinder  38  via the S 2  post  44 , the S 1  post  45 , the T 1  post  47 , and the T 2  post  46 . While the S boat  39  and the T boat  40  have completed the movement to respective predetermined positions, the tension post  14  and the T 4  post  30  are still under movement. Thus, a predetermined tape running path for recording/reproduction of the tape  2  has not been completed. 
     Referring to FIGS. 14,  19 , and  26 , the driving pin  75  of the cam gear  66  has passed along the first arc portion  121  of the internal cam  91  of the sub-chassis driving arm  89  to a concave portion  127  thereof. By the engagement of the driving pin  75  with the concave portion  127 , the sub-chassis driving arm  89  starts rotating counterclockwise. Thus, the sub-chassis  3  starts moving toward the cylinder  38  via the guide pin  92 . 
     The driving pin  75  has been disengaged from the concave portion  126  of the internal cam  91  of the boat driving arm  73  to come into contact with a second arc portion  129  thereof. The boat driving arm  73  is rotated when the driving pin  75  is in the concave portion  126 . On the contrary, the boat driving arm  73  is held at a fixed position when the driving pin  75  is in contact with the first and second arc portion  122  and  129 . 
     The boat driving arm  73  is located at a position of having rotated counterclockwise to the maximum. The S boat  39  and the T boat  40  have completed their movements to predetermined positions on the main chassis  8  via the engagements among the gear portion  77  of the boat driving arm  73 , the S load gear  79 , and the T load gear  84 . V-shaped respectively, engage with boat stoppers  141  and  142  provided on the main chassis  8 , so as to position the S boat  39  and the T boat  40 . 
     The S load gear  79  and the S load arm  81  rotate integrally during the movement of the S boat  39 . Likewise, the T load gear  84  and the T load arm  86  rotate integrally during the movement of the T boat  40 . The S load link  82  and the S load arm S 1  are configured so that the S boat  39  reaches a predetermined position at a time slightly before the mode shift from the LOADING  1  mode to the LOADING  2  mode. Likewise, the T load link  87  and the T load arm  86  are configure so that the T boat  40  reaches a predetermined position at a time slightly before the mode shift from the LOADING  1  mode to the LOADING  2  mode. During the remaining time until the start of the LOADING  2  mode, the boat driving arm  73  rotates the S load gear  79  clockwise and the T load gear  84  counterclockwise. As a result, since the S load gear  79  has rotated slightly relative to the S load arm  81 , a torsion coil spring (not shown) resting between the S load gear  79  and the S load arm  82  is twisted. By the repulsive force of the twisted torsion coil spring, the S boat  39  is pressed against the boat stopper  141  and secured thereto. Likewise, since the T load arm  84  has rotated slightly relative to the T load arm  86 , a torsion coil spring (not shown) resting between the T load gear  84  and the T load arm  86  is twisted. By the repulsive force of the twisted torsion coil spring, the T boat  40  is pressed against the boat stopper  142  and secured thereto. 
     Referring to FIGS. 14,  19 , and  24 , the relative positions of the tension arm  12  and the tension band regulating arm  21  with respect to the sub-chassis  2  are kept unchanged from those in the LOADING  1  mode by the tension plate  18  during the tape loading until immediately before the mode shift to the PLAY mode. More specifically, the tension arm  1  is located at a position fixed relative to the sub-chassis  3 , and the tension band  19  is kept slacked with respect to the cylinder portion  26  of the S reel base  4  by the clockwise swinging of the tension band regulating arm  21  to allow the rotation of the S reel base  4 . 
     Referring to FIGS. 14,  19 , and  33 , the protrusion  59  of the pinch arm  53  abuts against the wall  60  of the sub-chassis  3 , to rotate the pinch arm  53  clockwise as the sub-chassis  3  moves. 
     As the sub-chassis  3  moves, the T 4  regulating pin  31  extending from the T 4  arm  28  moves from the protrusion  102  of the pinch driving arm  97  to a T 4  guide  145  provided on the main chassis  8 . 
     The T 4  guide  145  also serves to hold the same relative position of the T 4  arm  28  with respect to the sub-chassis  3  as that in the LOADING  1  mode during the movement of the sub-chassis  3 . 
     Referring to FIG. 27, the PRE-PLAY mode, a mode slightly before the PLAY mode, will be described. 
     The driving pin  75  of the cam gear  66  has been disengaged from the concave portion  127  of the internal cam  91  of the sub-chassis driving arm  89  and is in contact with a second arc portion  130  thereof. 
     The sub-chassis driving arm  89  is located at a position of having swung counterclockwise to the maximum. Thus, the sub-chassis  3  has completed its movement to a predetermined position by the engagement of the guide pin  92  of the sub-chassis driving arm  89 . The boat driving arm  73  is in the same position as that in the LOADING  2  mode since the driving pin  75  is in contact with the second arc portion  129  of the internal cam  76  of the boat driving arm  73 . 
     Hereinbelow, the PLAY mode will be described with respect to FIGS. 15,  22 ,  28 , and  34 . 
     Referring to FIG. 15, the drawing out of the tape  2  from the cassette  1  has been completed, to complete the tape running path for recording/reproduction. 
     The complete tape running path will be described with reference to FIG.  15 . 
     The tape  2  drawn out from a tape supply reel (not shown) located on the left side of the cassette  1  passes around the tension post  14 , the S 3  post  49  mounted on the main chassis  8 , the S 2  post  44 , and then the S 1  post  45  in this order before passing around the cylinder  38  at a predetermined contact angle and tilt angle based on the standard for the tape recording pattern. Thereafter, the tape  2  passes around the T 1  post  46 , the T 2  post  47 , and the T 3  post  51 , so as to resume the state without torsion or a height difference from the original state when it was drawn out from the cassette  1 . The tape  2  then passes around the capstan shaft  50  which stands perpendicular to the tape passing direction and T 4  post  39  before being wound onto a winding reel (not shown) located on the right side of the cassette  1 . 
     The tension post  14 , the S 3  post  49 , the S 2  port  44 , the T 2  post  47 , and the T 4  post  30  stand perpendicular to the tape passing direction, while the S 1  post  45 , the T 1  post  46 , the T 3  post  51  are tilted with respect to the tape passing direction. 
     Referring to FIG. 28, the driving pin  75  of the cam gear  66  is in contact with the second arc portion  130  of the sub-chassis driving arm  89 . The position of the sub-chassis driving arm  89  is the same as that in the PRE-PLAY mode shown in FIG. 27, and the movement of the sub-chassis  3  has been completed. 
     The driving pin  75  is also in contact with a third arc portion  146  of the internal cam  76  of the boat driving arm  73 . 
     Referring to FIG. 5, the third arc portion  146  (range D) has a radius slightly greater than that of the second arc portion  129  (range C). A portion  147  (range E) is a hand-over portion between the second and third arc portions  129  and  146 . 
     Referring to FIG. 28, the boat driving arm  73  is rotated clockwise slightly from the position in the PRE-PLAY mode shown in FIG. 27, allowing a protrusion  149  of the boat driving arm  73  to abut against a boat driving arm stopper  148  of the sub-chassis driving arm  89 . This slight amount of return of the boat driving arm  73  in the PLAY mode from the position thereof in the PRE-PLAY mode is sufficiently smaller than the rotation phase differences between the S load gear  79  and the S load arm  81  and that between the T load gear  84  and the T load arm  86 . Accordingly, the S boat  39  and the T boat  40  are kept pressed against the boat stoppers  141  and  142 . 
     In and after the PLAY mode, therefore, the reactive force against the pressing of the S boat  39  and the T boat  40  is sustained, not by the driving pin  75 , but by the boat driving arm stopper  148  of the sub-chassis driving arm  89 . Accordingly, in and after the PLAY mode, the position of the boat driving ram  73  is determined, not by the driving pin  75 , but by the boat driving arm stopper  148 . 
     Referring to FIGS. 15 and 22, the tension arm regulating pin  15  is located in the top non-regulating portion  150  of the cam groove  63  of the tension plate  18 . In this state, the tension plate  18  is not in contact with the tension arm regulating pin  15 . 
     The pin  25  of the tension band regulating arm  21  is located at a top concave portion  151  of the cam  72  of the tension plate  18 . As in the UNLOADED mode, the position of the tension band regulating arm  21  on the sub-chassis  3  is determined when the tension band regulating arm  21  abuts against the tension arm stop plate  116 . 
     The position of the tension arm  12  is determined when the tension band  19  stretches around the cylinder portion  26  of the S reel base  4  without slacking by the tension of the tension spring  27 . A friction force is generated between the tension band  19  and the cylinder portion  26  of the S reel base  4 , and this friction force is subjected to feedback by the passing of the tape  2  around the tension post  14  with tension, whereby the tape tension is kept stabilized. 
     Accordingly, the position of the tension post  14  in the PLAY mode can be adjusted by moving the tension arm stop plate  116  to an appropriate position and securing it at this position with a screw (not shown). 
     Referring to FIG. 34, in the PLAY mode, the pinch driving arm  97  has been swung clockwise by the pinch cam gear  95 . A pressing cam portion  251  of the pinch driving arm  96  presses the roller  152  which is rotatably mounted on the pinch pressing arm  56  via a shaft. This results in that the pinch roller  55  presses against the capstan shaft  50  via the tape  2  by the force of the torsion coil spring  57 , to allow the tape  2  to run with the rotation of the capstan shaft  50 . The position of the T 4  arm  28  is held unchanged by the T 4  guide  145 . 
     The STOP mode will be described with reference to FIGS. 16,  23 ,  29 , and  35 . 
     Referring to FIG. 29, the positions of the sub-chassis driving arm  89  and the boat driving arm  73  are the same as those in the PLAY mode shown in FIG.  25 . Only the position of the driving pin  75  of the cam gear  66  is different from that in the PLAY mode. 
     Referring to FIGS. 16 and 23, the tension plate  18  is moved slightly forward from the position thereof in the PLAY mode shown in FIG. 22 by the tension plate driving arm  64 . 
     The positions of the tension arm  12  and the tension band regulating arm  21  relative to the sub-chassis  3  are the same as those in the LOADING  1  mode and the LOADING  2  mode. 
     Referring to FIGS. 16 and 35, the pinch driving arm  97  has been swung counterclockwise, and is not in contact with the roller  152  of the pinch pressing arm  56 . The pinch arm  53  is urged counterclockwise by the tension spring  58 , to abut against the wall  60  of the sub-chassis  3 . In this state, the pinch roller  55  is away from the capstan shaft  50 . 
     The REV mode will be described with reference to FIGS. 17,  23 ,  30 , and  34 . 
     Referring to FIG. 30, the positions of the sub-chassis driving arm  89  and the boat driving arm  73  are the same as those in the PLAY mode shown in FIG.  28  and the STOP mode shown in FIG.  29 . Only the position of the driving pin  75  of the cam gear  66  is different from that in the PLAY mode and the STOP mode. 
     The tension plate  18  is not moved from the position in the STOP mode. The positions of the tension arm  12  and the tension band regulating arm  21  are the same as those in the STOP mode shown in FIG.  16 . 
     The pinch driving arm  97  is rotated clockwise again from the position in the STOP mode shown in FIG. 35 to the position in the PLAY mode shown in FIG. 34, so that the pinch arm  53  resumes the state in the PLAY mode. The state of the T 4  arm  28  is kept unchanged throughout the PLAY, STOP, and REV modes. 
     Referring to FIGS. 1,  13  to  17 , the tension spring  58  extends between a spring hook portion  160  disposed on the sub-chassis  3  and a spring hook portion  161  on the pinch arm  53 . 
     The sub-chassis driving arm  89  is made of a metal plate. The wall  60  can be formed by bending a portion of the metal plate used to form the sub-chassis driving arm  89 . 
     In the above description of the embodiment according to the present invention, the cylinder  38  corresponds to the rotary head cylinder defined in the claims appended hereto, the cassette  1  corresponds to the tape cassette in the claims, the tape  2  corresponds to the magnetic tape in the claims, the sub-chassis  3  corresponds to the first chassis in the claims, and the main chassis  8  corresponds to the second chassis in the claims. The UNLOADED mode corresponds to the first state in the claims, while the PLAY mode, the STOP mode, and the REV mode correspond to the second state in the claims. The wall  60  of the sub-chassis  3  corresponds to the pinch arm engaging portion in the claims, and the protrusion  59  of the pinch arm  55  corresponds to the first chassis engaging portion in the claims. 
     Thus, according to the present invention, the tension spring  58  extends between the spring hook portion  160  on the sub-chassis  3  and the spring hook portion  161  on the pinch arm  53 . The protrusion  59  of the pinch arm  53  is pressed by the wall  60  of the sub-chassis  3  toward the capstan shaft  50  when the tape is being loaded, so as to be located near the capstan shaft  50 . In this way, a small mechanism with a simple construction and a reduced number of components can be achieved. 
     In the present invention, the sub-chassis  3  may be made of, not only a steel plate, but also an iron plate, a stainless steel plate, an aluminium alloy plate, an aluminium die-cast plate, a magnesium die-cast plate, and the like. 
     Various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the scope and spirit of this invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the description as set forth herein, but rather that the claims be broadly construed.