Abstract:
A magnetic tape recording/reproducing apparatus has a tape loading mechanism which performs a tape loading operation by moving a post from an original position to a loading position so as to extract a magnetic tape from a loaded cassette and a tape unloading operation to return the magnetic tape to within the cassette, the tape loading mechanism comprising a spring member, the spring member being disposed so as to deform during the tape unloading operation, the tape unloading operation terminating after the spring member deforms, the deformed spring member urging the post to return to the original position. The tape unloading operation terminates after the cam plate returns to an original position and the drive cam plate moves relative to the cam plate while the spring member deforms. Hence, the post is urged by the spring and securely returns to its original position.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a magnetic tape recording and/or reproducing apparatus (hereinafter referred to as a magnetic tape recording/reproducing apparatus), and more particularly, to a digital audio tape recorder (hereinafter “DAT”) streamer used as a large-capacity external memory back-up device for computers. 
     2. Description of the Related Art 
     The DAT streamer uses a DAT tape cassette. The DAT tape cassette is loaded in the DAT streamer, a magnetic tape is extracted from the DAT tape cassette by tape guide posts in a tape loading operation and thereafter the magnetic tape is driven between a capstan and a pinch roller. Recording information to and reproducing information from the magnetic tape is carried out by a high-speed rotary drum, that is, a rotary head. After recording and reproduction is completed, the magnetic tape is returned to the DAT tape cassette in a tape unloading operation, after which the DAT tape cassette may be ejected. 
     In order for the DAT tape cassette to be ejected smoothly, it is important that the tape guide posts having flanges at a top and a bottom thereof be securely returned to their original positions at the stage at which the tape unloading operation is completed. If the tape guide posts are not returned to their original positions, then when the DAT tape cassette is ejected a lengthwise edge of the magnetic tape may contact an upper flange of the top of the tape guide posts, thus damaging the magnetic tape. 
     In order to facilitate an understanding of the problem, a description will now be given of the related art. 
     The conventional DAT streamer tape loading mechanism has a motor, a cam gear, a cam plate, a cam plate arm, and tape guide posts. When the DAT tape cassette is loaded, the motor rotates the cam gear. The rotation of the cam gear is transmitted to the cam plate via the cam plate arm, the cam plate moves, the tape guide posts move in a direction away from the DAT tape cassette and the operation of loading the tape by pulling the magnetic tape out from the DAT tape cassette is performed. When recording and reproduction are stopped, the motor again rotates the cam gear, the rotation of the cam gear is transmitted to the cam plate via the cam plate arm, the cam plate moves so as to move the tape guide posts in a direction so as to return to the DAT tape cassette and the magnetic tape is returned to within the DAT tape cassette in a tape unloading operation. 
     Among those parts related to the tape guide posts is a spring for pressing the tape guide posts against a stopper near the rotary drum. In the tape loading operation described above, the operation terminates in a state in which the spring is stretched and the tape guide posts are pressed against the stopper due to the spring force of the stretched spring, and there is no problem. 
     In the tape unloading operation, however, there is no pressing of the tape guide posts against the stopper, so the position of the tape guide posts when the tape unloading operation terminates is dependent upon the accumulation of dimensional tolerances of the various parts that comprise the tape loading mechanism and the precision with which the DAT streamer has been assembled, and hence varies with each assembled DAT streamer. Normally such variation does not present a problem. On occasion, however, the tape guide posts end their travel at a position relatively far from their proper final position, and when the DAT tape cassette is ejected in such cases there is a possibility that the lengthwise edge of the magnetic tape hits the top flanges of the guide posts, thus damaging the magnetic tape. 
     In actuality, in those cases in which the tape guide posts do not fully return to their original positions the positions at which the parts are mounted are adjusted so as to permit the tape guide posts to return to their original positions. However, such adjustment is troublesome. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide an improved and useful magnetic tape recording/reproducing apparatus in which the disadvantages described above are eliminated. 
     Another and more specific object of the present invention is to provide a magnetic tape recording/reproducing apparatus in which a spring urges the tape guide posts back to their original positions. 
     The above-described objects of the present invention are achieved by a magnetic tape recording/reproducing apparatus comprising: 
     a tape loading mechanism which performs a tape loading operation by moving a post from an original position to a loading position so as to extract a magnetic tape from a loaded cassette and a tape unloading operation to return the magnetic tape to within the cassette, 
     the tape loading mechanism comprising a spring member, the spring member being disposed so as to deform during the tape unloading operation, the tape unloading operation terminating after the spring member deforms, the deformed spring member urging the post to return to the original position thereof. 
     According to the invention described above, regardless of the cumulative tolerance that is the accumulation of the tolerances of the individual parts that together form the tape loading mechanism and regardless of the lack of precision with which the magnetic tape recording/reproducing apparatus is assembled, the loading posts  12 ,  13  can be urged by the spring member and reliably returned to their original positions in a state in which the tape loading mechanism terminates a tape unloading operation. Accordingly, the magnetic tape does not get caught on the loading posts either when one cassette is ejected or when another cassette is loaded into the apparatus. Additionally, it is possible to do without the adjusting mechanism for slightly shifting the installation positions of the parts so that the loading posts return to their original positions, such adjusting mechanism required conventionally whenever the loading posts do not fully return to those original positions. 
     Additionally, the above-described objects of the present invention are also achieved by a magnetic tape recording/reproducing apparatus comprising: 
     a tape loading mechanism which performs a tape loading operation by moving a post from an original position to a loading position so as to extract a magnetic tape from a loaded cassette and a tape unloading operation to return the magnetic tape to within the cassette, 
     the tape loading mechanism comprising: 
     a cam plate that moves in a first direction from an original position so as to cause the post to extract the magnetic tape from the loaded cassette, the cam plate moving in a second direction opposite to the first direction to the original position thereof and moving the post to the original position thereof so as to cause the post to return the magnetic tape to within the cassette; 
     a drive cam plate mounted on the cam plate so as to be slidably movable within a predetermined range in the first direction and the second direction, a force for moving the cam plate acting on the drive cam plate; and 
     a spring member disposed between the cam plate and the drive cam plate, 
     the tape unloading operation terminating after the cam plate returns to the original position thereof and the drive cam plate moves relative to the cam plate while the spring member is deformed, the deformed spring member urging the post to return to the original position thereof. 
     According to the invention described above, a simple structure for urging the loading posts back to their original positions can be achieved, comprising a cam plate, drive cam plate and spring member. 
     Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagram showing a tape unloading state of a tape loading mechanism of an embodiment of a DAT streamer according to the present invention; 
     FIG. 2 is an exploded view of an overstroke mechanism of the tape loading mechanism of FIG. 1; 
     FIG. 3 is a schematic diagram of a tape loading operation and a tape unloading operation of an embodiment of a DAT streamer according to the present invention; 
     FIG. 4 shows a state in which the tape unloading operation of an embodiment of a DAT streamer according to the present invention has been completed; 
     FIG. 5 shows a state in which the tape loading operation of an embodiment of a DAT streamer according to the present invention has been completed; 
     FIG. 6 shows a state of an overstroke mechanism of a state in which a tape loading operation has been completed (prior to the beginning of a tape unloading operation); 
     FIG. 7 shows a state of the overstroke mechanism just after the beginning of a tape unloading operation; 
     FIG. 8 shows a state of the overstroke mechanism at a final stage of a tape unloading operation; and 
     FIG. 9 shows a state of the overstroke mechanism upon completion of a tape unloading operation. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A description will now be given of an embodiment of the present invention, with reference to the accompanying drawings. 
     For ease of explanation, a summary description will first be given of a tape loading operation and a tape unloading operation of an embodiment of a DAT streamer  10  according to the present invention, with reference to FIG.  3 . 
     Prior to the loading of the DAT tape cassette  20 , the supply reel tape guide post  11 , loading posts  12 ,  13 , take-up reel tape guide post  14  and pinch roller  15  are located at positions indicated by the two-dot chain line lines in FIG.  3 . These positions are also the same positions as when a tape unloading operation is completed, and correspond to the position of a concavity  21  of a front side of the loaded DAT tape cassette  20  as can be seen in FIG.  4 . The loading posts  12 ,  13  have flanges at a top and a bottom thereof. 
     The DAT tape cassette  20  is loaded into the apparatus by first being moved horizontally and then being dropped downward, with the supply reel tape guide post  11 , the loading posts  12 ,  13  the take-up reel tape guide post  14  and the pinch roller  15  positioned inside the concavity  21 . Once the DAT tape cassette  20  is loaded the tape loading operation commences, the tape guide post  11 , the loading posts  12 ,  13 , the tape guide post  14  and pinch roller  15 , respectively, each move along the paths indicated by the dotted lines to the positions shown in FIG. 3, magnetic tape  22  is extracted from the loaded DAT tape cassette  20  by the loading posts  12 ,  13 , the supply reel tape guide post  11 , the take-up reel tape guide post  14  and wound around the rotary drum  16  having a rotary head  16   a  such that the magnetic tape  22  forms a predetermined tape path, with the pinch roller  15  pressed against the rotating capstan  17  as shown in FIG.  5 . 
     Next, the magnetic tape  22  is sandwiched between and driven by the pinch roller  15  and the capstan  17 , guided by the tape guide post  11 , the loading posts  12 ,  13  and the tape guide post  14  and driven in a forward direction indicated by an arrow F. Information is either recorded to the magnetic tape  22  by the rotary head  16   a  or the rotary head  16   a  reproduces information recorded on the magnetic tape  22 . When the capstan motor reverses and the capstan  17  is rotated in a counter-clockwise direction, the magnetic tape  22  is run slightly in a reverse direction indicated by an arrow R. The recording of information to the magnetic tape  22  is carried out while reproducing the recorded location to verify that recording has been carried out. Accordingly, the capstan  17  repeatedly rotates alternately in the counter-clockwise direction and the clockwise direction, thereby repeatedly running the magnetic tape  22  alternately in the forward direction and the reverse direction. 
     When the stop button is pressed and the recording of information and the reproducing of information are terminated the tape unloading operation begins, the tape guide post  11 , loading posts  12 ,  13 , tape guide post  14  and pinch roller  15 , respectively, each move along the paths indicated by the dotted lines so as to move in a direction opposite to that described above and thereby return to within the DAT tape cassette  20 , with the magnetic tape  22  being unwound and returned to within the DAT tape cassette  20 . When the tape guide post  11 , loading posts  12 ,  13 , tape guide post  14  and pinch roller  15  return to their original positions as indicted by the two-dot chain line lines in FIG. 3, the tape unloading operation terminates. The DAT tape cassette  20  is then moved first upward and then outward, and automatically ejected. 
     Next, a description will be given of a tape loading mechanism  30 . 
     FIGS. 1 and 4 show a state after the termination of a tape unloading operation. FIG. 5 shows a state after the termination of a tape loading operation. 
     The tape loading mechanism  30  has an overstroke mechanism  31  that functions during a tape unloading operation, and more specifically, that functions during the final stage of a tape unloading operation. 
     The tape loading mechanism  30  is mounted on a top surface of a chassis  32  of the DAT streamer  10  and has a motor  33 , a reduction gear mechanism  34 , a cam gear  35 , a cam plate arm  36 , a cam plate  37 , a drive cam plate  38 , loading posts  12 ,  13  and an overstroke mechanism  31 . For ease of explanation a description of the overstroke mechanism  31  will be deferred until later. 
     The cam gear  35  has a cam groove  35   a  and is supported by a shaft  71  mounted on the chassis  32 . The cam plate arm  36  has a pin  36   a  at one end and a pin  36   b  at the other end, and is supported by a shaft  72  on the chassis  32  with the pin  36   a  engaging the cam groove  35   a . The pin  36   b  is indirectly connected to the cam plate  37 . For ease of explanation a description of this part will be deferred until later. 
     The cam plate  37  has slots  37   a ,  37   b  which engage pins  73 ,  74  so that the cam plate  37  is slidably movable in a lateral direction indicated by arrows X 1 -X 2  in for example FIG.  1 . The pin  73  functions as a stopper, receiving an X 2 -side edge  37   a   1  of the slot  37   a  so as to determine a slide position P 1  of the cam plate  37  in an X 1 -direction slide position. The cam plate  37  is related to the tape guide post  11 , loading posts  12 ,  13 , tape guide post  14  and pinch roller  15 . When the cam plate  37  slides in the X 2  direction from the P 1  position to a P 2  position, the cam plate  37  causes the tape guide post  11 , loading posts  12 ,  13 , tape guide post  14  and pinch roller  15  to move from positions shown by two-dot chain line lines in FIG. 3 to positions shown by solid lines in FIG.  3 . Conversely, when the cam plate  37  slides in the X 1  direction from position P 2  to position P 1 , the cam plate  37  causes the tape guide post  11 , loading posts  12 ,  13 , tape guide post  14  and pinch roller  15  to move from positions shown by solid lines in FIG. 3 to positions shown by two-dot chain line lines in FIG.  3 . For convenience of illustration, FIG.  4  and FIG. 5 show only the loading posts  12 ,  13 . 
     The loading posts  12 ,  13  and the component parts related to the loading posts  12 ,  13  are mounted on a sub-chassis  39  itself mounted on a top side of the chassis  32 . The loading posts  12 ,  13  are themselves mounted on respective bases  40 ,  41 . Arms  42 ,  43  are supported by a pin  44  on a bottom surface of the sub-chassis  39 . A spring  45  is disposed between the arms  42 ,  43  and the arms  42 ,  43  usually rotate as a single assembly. Similarly, arms  46 ,  47  are supported by a pin  48  on a bottom surface of the sub-chassis  39 , with a spring  49  disposed between the arms  46 ,  47  such that the arms  46 ,  47  usually rotate as a single assembly. The arm  42  and the base  40  are coupled by a link  50  and the arm  46  and the base  41  are coupled by a link  51 . A roller  43   a  on the arm  43  engages a concavity  37   c  of the cam plate  37  and a roller  47   a  on the arm  47  engages a concavity  37   d  of the cam plate  37 . 
     The tape loading operation commences from the state shown in FIG.  1  and FIG.  4 . When the motor  33  starts and rotates forward, the cam gear  35  is rotated counter-clockwise via the reduction gear mechanism  34  and the cam plate arm  36  is rotated clockwise, the cam plate  37  is slid in the X 2  direction, the arm  42  is rotated counter-clockwise and the arm  46  is rotated clockwise and the bases  40 ,  41  are moved along guide grooves  52 ,  53  in the sub-chassis  39 . When the cam plate  37  reaches a final stage at position P 2 , then, as shown in FIG. 5, the springs  45 ,  49  are stretched, the bases  40 ,  41  are pressed against stoppers  54 ,  55  on top of the sub-chassis  39  and the tape loading operation terminates. The loading posts  12 ,  13  are fixedly positioned on either side of the rotary drum  16 . 
     The tape unloading operation commences from the state shown in FIG.  5 . When the motor  33  starts and rotates in reverse, the cam gear  35  is rotated clockwise via the reduction gear mechanism  34  and the cam plate arm  36  is rotated counter-clockwise, the cam plate  37  is slid in the X 1  direction, the arm  42  is rotated clockwise and the arm  46  is rotated counter-clockwise and the bases  40 ,  41  are moved along guide grooves  52 ,  53  in the sub-chassis  39  to their original positions, where the tape unloading operation terminates. 
     Next, a description will be given of the overstroke mechanism  31 . 
     As shown in FIG.  1  and FIG. 2, the overstroke mechanism  31  is configured so that the drive cam plate  38  is mounted on cam plate  37 , with a tension coil spring  60  stretched between the cam plate  37  and the drive cam plate  38 . 
     As shown in FIG. 2, the drive cam plate  38  has pins  38   a ,  38   b  and a slot  38   c  at an X 2 -side end, the slot  38   c  being elongated in a Y 1 -Y 2  direction. An extension  38   d  for a spring is provided at an X 1 -side end of the drive cam plate  38 . Reference numeral  38   c   1  is an edge portion of the slot  38   c  on the X 1  side of the slot  38   c , of a length equal to half the length of the slot in the Y 1 -Y 2  direction. 
     The cam plate  37  has slots  37   e ,  37   f  extending in the X 1 -X 2  direction and expanded in a Y 1  direction on an X 2 -Y 1  side portion of the cam plate  37 , an extension  37   g  for retaining a spring and an edge  37   i . The edge  37   i  has a receiving edge portion  37   i   1  extending in the Y 1 -Y 2  direction and a retreating edge portion  37   i   2  extending from a Y 1  side of the receiving edge portion  37   i   1  in a direction midway between the Y 1  direction and the X 1  direction. 
     The pins  38   a ,  38   b  respectively engage slots  37   e ,  37   f  and, further, tension coil spring  60  is strung between extension  37   g  and extension  38   d  so as to mount the drive cam plate  38  on the cam plate  37 . The drive cam plate  38  is urged by the force of the tension coil spring  60  so as to slide in the X 2  direction relative to the cam plate  37 , with the force of the tension coil spring  60  urging the pins  38   a ,  38   b  against the edges  37   e   1 ,  37   f   1  of the slots  37   e ,  37   f . Accordingly, the drive cam plate  38  and the cam plate  37  act completely as a single assembly in the X 2  direction and act elastically as a single assembly in the X 1  direction. That is, when the load against the slide of the cam plate  37  in the X 1  direction is smaller than the force of the tension coil spring  60 , the cam plate  37  slides together with the drive cam plate  38  as a single unit. When the load exceeds the force of the tension coil spring  60 , then the tension coil spring  60  is stretched and the drive cam plate  38  slides in the X 1  direction relative to the cam plate  37 . 
     During a tape loading operation, the cam plate arm  36  is rotated in a clockwise direction, the drive cam plate  38  is pulled in the X 2  direction, the pins  38   a ,  38   b  press against the edges  37   e   1 ,  37   f   1  of the slots  37   e ,  37   f  and the cam plate  37  and the drive cam plate  38  are slid in the X 2  direction as a single unit. 
     During a tape unloading operation, the cam plate arm  36  is rotated counter-clockwise from the state shown in FIG. 5 to the state shown in FIG.  4  and FIG.  1 . When the cam plate arm  36  is rotated counter-clockwise, the pin  36   b  pushes the drive cam plate  38  in the X 1  direction and this force is transmitted to the cam plate  37  via the tension coil spring  60  and the cam plate  37  is slid in the X 1  direction. 
     Here, the cam plate arm  36  and the cam plate  37  and the pin  73  are constructed so that, at a stage at which the cam plate arm  36  is rotated to a position just slightly prior to the position shown in FIG.  4  and FIG. 1, the cam plate  37  is returned to a position P 1  and the X 2 -edge  37   a   1  of the slot  37   a  contacts the pin  73 . 
     Accordingly, when the cam plate arm  36  is rotated to a position just slightly prior to the position shown in FIG.  4  and FIG. 1, the X 2  edge  37   a   1  of the slot  37   a  contacts the pin  73  and the cam plate  37  is returned to position P 1 . 
     The cam plate arm  36  continues to rotate until reaching the position shown in FIG.  4  and FIG.  1 . This rotation is an overstroke. In the final stage of rotation, the drive cam plate  38  slides in the X 1  direction relative to the cam plate arm  36  while further stretching the tension coil spring  60  as shown in FIG. 9, absorbing the overstroke of the cam plate arm  36 . 
     Additionally, when the drive cam plate  38  slides in the X 1  direction relative to the cam plate  37 , then, as shown in FIG. 9, pins  38   a ,  38   b  separate from edges  37   e   1 ,  37   f   1  of slots  37   e ,  37   f  and the force of the tension coil spring  60  acts to slide the cam plate  37  in the X 1  direction. Accordingly, the cam plate  37  is reliably returned to and held at position P 1  by the force of the tension coil spring  60  pressing the X 2  edge  37   a   1  of the slot  37   a  against the pin  73 . 
     Accordingly, the loading posts  12 ,  13  are reliably returned to the positions shown in FIG. 4 regardless of the lack of precision with which the DAT streamer  10  is assembled, the level of cumulative tolerance of the individual parts which comprise the tape loading mechanism  30  or the variations in the precision with which the tape loading mechanism  30  is assembled. As a result, the DAT tape cassette  20  is ejected without either the top flanges of the loading posts  12 ,  13  or the other posts interfering with the lengthwise edge of the magnetic tape  22  and hence without damage to the magnetic tape  22 . Similarly, neither the loading posts  12 ,  13  nor the other posts interfere when a separate DAT tape cassette is loaded, and consequently there is no damage from the lengthwise edge of the magnetic tape hitting the loading posts  12 ,  13  when loading a DAT tape cassette. Additionally, the conventional adjustment mechanism is no longer required. 
     It should be noted that in the final stage of counter-clockwise rotation of the cam plate arm  36 , the pin  36   b  is positioned toward the Y 1  end of the slot  38  as shown in FIG. 9, so as to be disposed opposite to retreating edge portion  37   i   2  of edge  37   i . Accordingly, when pin  36   b  moves along an arc centered about the shaft  72 , the pin  36   b  moves without interference with the edge  37   i  of the cam plate  37  and the overstroke mechanism operates without hindrance. 
     Next, a description will be given of an operation of the above-described overstroke mechanism  31  in the final stage of rotation of the cam plate arm  36  from the state shown in FIG. 5 to a state just prior to the state shown in FIG.  4 . 
     The overstroke mechanism  31  is configured so as to not operate at the above-described final stage of rotation of the cam plate arm  36 . 
     That is, when the cam plate arm  36  is in the state shown in FIG. 5, then, as shown together in FIG. 6, the edge  38   c   1  of the slot  38   c  substantially aligns with the receiving edge portion  37   i   1  and the retreating edge portion  37   i   2  is withdrawn in the X 1  direction from the edge  38   c   1  of the slot  38   c . Additionally, the cam plate arm  36  is in a rotation position that is substantially in the Y 1 -Y 2  direction, with the pin  36   b  that moves along an arc centered on the shaft  72  positioned toward a Y 2  side of the slot  38   c . The relation between the pin  36   b  and the edge  37   i  is such that the pin  36   b  is positioned to oppose the receiving edge portion  37   i   1 . 
     In the state in which the tape unloading operation is commenced as shown in FIG. 5, the rollers  43   a ,  47   a  are pressed against the cam plate  37  by the force of the stretched springs  45 ,  49  in a state in which the load that slides in the X 1  direction of the cam plate  37  is large. Accordingly, when the cam plate arm  36  begins to rotate counter-clockwise and pin  36   b  begins to move in the X 1  direction, the tension coil spring  60  is stretched and the drive cam plate  38  moves slightly in the X 1  direction relative to the cam plate and, as shown in FIG. 7, pin  36   b  is put into a state of direct contact with the receiving edge portion  37   i   1  of the cam plate  37 , the cam plate  37  is directly pressed by the pin  36   b  and begins to move in the X 1  direction. Accordingly, even in a state in which the cam plate  37  load is large, the cam plate  37  begins to move reliably and smoothly in the X 1  direction. 
     As the cam plate  36  rotates counter-clockwise the pin  36   b  gradually moves toward the Y 1  side of the slot  38   c . When the cam plate arm  36  rotates to a state just prior to the state shown in FIG. 4, the pin  36   b  as shown in FIG. 8 is separated from the receiving edge portion  37   i   1  and at this stage the overstroke mechanism  31  is first enabled to operate. 
     During the rotation of the cam plate arm  36  to the state just prior to the state shown in FIG. 4, the pin  36   b  directly presses the receiving edge portion  37   i   1  of the cam plate  37 , the force of the pin  36   b  is directly transmitted to the cam plate  37  and the cam plate  37  is moved in the X 1  direction. Accordingly, even if, for example, the bases  40 ,  41  get stuck as they are being moved along the guide grooves  52 ,  53  in the sub-chassis  39  so as to return to their original positions, the cam plate  37  is directly pressed by the pin  36   b  and moved at substantially a constant speed. Accordingly, the bases do not move suddenly after temporarily stopping but instead move at substantially a constant speed. Accordingly, when the magnetic tape  22  is rewound and returned to within the DAT tape cassette  20 , the magnetic tape  22  is neither subjected to strong tension nor does the magnetic tape  22  slacken. Instead, a substantially constant tension is maintained on the magnetic tape  22  and consequently the magnetic tape  22  is not damaged. 
     It should be noted that it is not necessary to provide the receiving edge portion  37   i   1  described above and limit the operation of the overstroke mechanism  31  if a spring having a large spring constant is used for the tension coil spring  60  described above. However, in doing so, when the tape unloading operation terminates the force with which the X 2  edge  37   a   1  of the slot  37   a  presses against the pin  73  may become too large and thus affect the useful life of the DAT streamer  10 , which is undesirable. The present embodiment provides the receiving edge portion  37   i   1  so as to limit the operation of the overstroke mechanism  31  and uses a tension coil spring  60  having a small spring constant. Accordingly, when the tape unloading operation terminates the force with which the X 2  edge  37   a   1  of the slot  37   a  presses against pin  73  is small and does not affect the useful life of the DAT streamer  10 . 
     Additionally, it is also possible to include within the cam plate arm  36  a mechanism achieving the same function as the overstroke mechanism  31 . 
     Additionally, the present invention is not limited to the DAT streamer  10  but is applicable to an ordinary video tape recorder as well. 
     The above description is provided in order to enable any person skilled in the art to make and use the invention and sets forth the best mode contemplated by the inventors of carrying out the invention. 
     The present invention is not limited to the specifically disclosed embodiment, and variations and modifications may be made without departing from the scope of the present invention. 
     The present application is based on Japanese Priority Application No. 11-009770 filed on Jan. 18, 1999, the entire contents of which are hereby incorporated by reference.