Abstract:
A magnetic tape recording/reproducing apparatus adapted for loading a magnetic tape cassette has a magnetic head, a magnetic tape loading mechanism that loads and unloads a magnetic tape cassette and loads and unloads a magnetic tape within the magnetic tape cassette to the magnetic head, the magnetic tape loading mechanism assuming a plurality of operating states and an optical detector for optically detecting a shifting of the magnetic tape loading mechanism from one operating state to another operating state. By using non-contact type optical detectors instead of contact-type detectors to detect a shift of operating states from one state to another, the reliability of detection readings can be improved and at the same time the problem of wear on the conventional electrode pattern can be eliminated.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a magnetic tape recording/reproducing apparatus, and more particularly, to a digital audio tape recorder (hereinafter “DAT”) streamer in which a motor rotates a cam gear to put the DAT streamer into one of a plurality of different operating modes. 
     2. Description of the Related Art 
     DAT streamers are used as large-capacity external memory back-up devices for computers. The typical DAT streamer is composed of a cam gear rotated by a motor, with a variety of mechanisms activated in response to the rotation of the cam gear so as to put the DAT streamer into a magnetic tape cassette load mode, a tape insert mode, a recording/reproducing mode and the like. Such a configuration requires that the shifting of the operating modes be detected with a high degree of reliability. 
     An example of a conventional DAT streamer operating mode shift detection device is shown in FIGS. 1A and 1B. As can be appreciated from the drawings, such a device consists of a rotating plate  11  rotating in synchrony with a cam gear. Three leaf spring contacts  12 - 1 ,  12 - 2  and  12 - 3  are disposed on the rotating plate  11  in such a way as to slide over an electrode pattern  14  of predetermined shape of a circuit board  13 , so that a shifting of operating modes is detected by a combination of the output of the contacts  12 - 1 ,  12 - 2  and  12 - 3 . 
     The operating mode shift detection device described above is a metal contact type. As a result, the reliability of the detection readings is easily affected by the intensity of the pressure of the contact, the quality of the grease, the presence of dirt and dust, and so on. The reliability of the detection readings can be improved by increasing the intensity of the pressure of the contact. However, doing so increases the wear on the electrode pattern  14  and shortens its life. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is a general object of the present invention to provide an improved and useful magnetic tape recording/reproducing apparatus in which the problems described above are eliminated. Another more specific object of the present invention is to provide a magnetic tape recording/reproducing apparatus capable of detecting an operating mode shift with a high degree of reliability. 
     The above-described objects of the present invention are achieved by a magnetic tape recording/reproducing apparatus adapted for loading a magnetic tape cassette, comprising: 
     a magnetic head; 
     a magnetic tape loading mechanism loading and unloading a magnetic tape cassette and loading and unloading a magnetic tape within the magnetic tape cassette to the magnetic head, the magnetic tape loading mechanism assuming a plurality of operating states; and 
     an optical detector for optically detecting a shifting of the magnetic tape loading mechanism from one operating state to another operating state. 
     According to the invention described above, the operating mode shift detection device is a non-contact type. Accordingly, the effect of the presence of dirt and dust on the reliability of the detection readings is much reduced as compared to the contact-type operating mode shift detection device. As a result, the reliability of detection readings can be improved and at the same time the problem of wear on the electrode pattern  14  can be eliminated. 
     Additionally, the above-described objects of the present invention are also achieved by a magnetic tape recording/reproducing apparatus adapted to load a magnetic tape cassette, comprising: 
     a magnetic head; 
     a cam gear rotatably driven by a motor; 
     a magnetic tape loading mechanism operated by the rotation of the cam gear, the magnetic tape loading mechanism loading and unloading the magnetic tape cassette and loading and unloading a magnetic tape inside the magnetic tape cassette to the magnetic head, the magnetic tape loading mechanism assuming a plurality of operating states; 
     a rotating member rotating in synchrony with the cam gear and having a plurality of optical detectors; 
     a switch detecting a loading of the magnetic tape cassette; and 
     a control circuit detecting a shifting of the magnetic tape loading mechanism from one operating state to another operating state based on an output from the plurality of optical detectors and an output from the switch. 
     According to the invention described above, by using the output of the switch detecting the loading of the magnetic tape cassette it becomes possible to reduce the number of photosensors to a small number. Accordingly, even a rotating member having a relatively small diameter is adequate to accommodate the optical detectors. 
     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 
     FIGS. 1A and 1B are top and side views of an example of the prior art, respectively; 
     FIG. 2 is a diagram showing a plan view of an embodiment of a DAT streamer according to the present invention; 
     FIGS. 3A,  3 B,  3 C,  3 D,  3 E and  3 F are schematic views of states of operating modes of the DAT streamer shown in FIG. 2; 
     FIG. 4 is a diagram showing a portion of the operating mode shift detection device shown in FIG. 2; 
     FIG. 5 is a diagram showing a portion of the operating mode shift detection device shown in FIG. 2; 
     FIGS. 6A,  6 B,  6 C,  6 D and  6 E are diagrams for explaining the operation of the operating mode shift detection device; 
     FIG. 7 shows a first variation of the operating mode shift detection device; 
     FIG. 8 shows a second variation of the operating mode shift detection device; and 
     FIG. 9 shows a third variation of the operating mode shift detection device. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A description will now be given of an embodiment of the present invention with reference to the accompanying drawings. 
     FIG. 2 is a diagram showing a plan view of an embodiment of a DAT streamer according to the present invention. The DAT streamer  20  has a motor  21 , a mode gear  22 , a cam gear  23 , a cassette housing mechanism  24 , loading poles  25 ,  26 , a rotating drum  27  having rotating magnetic heads  27   a,  a capstan  28 , a pinch roller  29  and a head cleaning member  30 . 
     When a DAT cassette  31  is inserted into a cassette housing  32 , the DAT streamer  20  motor  21  starts and begins to rotate in the forward direction and, as shown in FIG.  4  and FIG. 5, the cam gear  23  rotates via a reduction gear mechanism  33  and the mode gear  22  in a counter-clockwise direction within an angle of approximately 330 degrees. A first cam and a second cam are formed on an upper surface and a lower surface of the cam gear  23 . When the cam gear  23  rotates the cassette housing mechanism  24 , the loading poles  25 ,  26  and the pinch roller  29  are activated and the DAT streamer  20  is put into a variety of operating modes. Thereafter, when the motor  21  reverses the cam gear  23  reverses, that is, rotates in a clockwise direction, and the DAT streamer operates in the reverse of the order described above. 
     In actuality, the cam gear  23  rotates clockwise or counter-clockwise to a predetermined angle in response to buttons operated by an operator and stops at that predetermined angular position. Here, for simplicity of explanation, it is assumed that the cam gear  23 , being at a reference position, is rotated counter-clockwise to a final position and thereafter rotated clockwise to a final position and returned to the reference position. 
     When the cam gear  23  rotates clockwise the DAT streamer  20  is in an unload mode. Here it is defined that the mode of the DAT streamer  20  when the cam gear  23  rotates counter-clockwise is a “load mode”. 
     Initially, the DAT streamer  20  is in an eject mode shown in FIG.  3 A. When the cam gear  23  begins to rotate counter-clockwise, a link not shown in the drawing is moved by a first cam  23   a,  which is depicted in FIG. 5, the cassette housing mechanism  24  is operated so as to load a cassette, the DAT cassette  31  is partly moved and the DAT streamer  20  is put into a semi-eject mode shown in FIG.  3 B. Thereafter, the DAT cassette  31  is loaded and the DAT streamer  20  is put into an unthread mode shown in FIG.  3 C. 
     Next, a link and a slide plate, neither of which is depicted in the drawing, are moved by the second cam  23   b,  which is depicted in FIG. 5, the loading poles  25 ,  26  are moved toward the rotating drum  27 , magnetic tape  34  is extracted from the loaded DAT cassette  31  and wound around the rotating drum  27  as shown in FIG.  3 D. At this time the pinch roller  29  is not yet pressed against the capstan  28  and the DAT streamer  20  is in a stop mode. 
     Next, as shown in FIG. 3E, the pinch roller  29  is pressed against the capstan  28 , the magnetic tape  34  is run and the DAT streamer  20  is put into a recording/reproducing mode. 
     Finally, as shown in FIG. 3F, the head cleaning member  30  is contacted with the rotating drum  27  to clean the magnetic heads  27   a  and the DAT streamer  20  is put into a rotating head cleaning mode. 
     As the cam gear  23  is rotated clockwise, the DAT streamer  20  changes from the recording/reproducing mode shown in FIG. 3E to the stop mode shown in FIG. 3D to the unthread mode shown in FIG. 3C to the semi-eject mode shown in FIG. 3B, and finally to the eject mode shown in FIG.  3 A. 
     In actuality, the operating mode data from the operating mode shift detection device  40  that detects the shifting of the various operating modes is supplied to a control circuit  41 . An operator operates the control panel  42 , operating mode commands are input to the control circuit  41  from the operating panel  42 , the control circuit  41  outputs a motor drive signal based on the operating mode information and operating mode commands and the motor drive circuit  43  drives the motor  21 . The motor  21  is driven in response to the controls operated by the operator, the cam gear is rotated through a predetermined angle in either a clockwise or counter-clockwise direction and stopped thereat and the DAT streamer  20  is put into the desired operating mode. 
     Next, a description will be given of the operating mode shift detection device  40 . 
     As shown in FIG.  4  and FIG. 5, the operating mode shift detection device  40  comprises a mode gear  22  synchronized to the cam gear  23  and rotating in the reverse direction of the cam gear  23 , first and second annular ribs  22   a,    22   b  formed on an upper surface of the mode gear  22 , a first photocoupler  51 , a second photocoupler  52 , a cassette loading recognition switch  53  and a portion of the control circuit  41 . FIG. 4 shows the DAT streamer  40  in an eject mode state. 
     The first and second annular ribs  22   a,    22   b  are formed integrally with and concentrically on the upper surface of the mode gear  22 . The first annular rib  22   a  is composed of rib portions  22   a   1  and  22   a   2  as well as notched portions  22   a   10  and  22   a   11 . The second annular rib  22   b  is composed of rib portion  22   b   1  and notched portion  22   b   10 . The first photocoupler  51  and the second photocoupler  52  have a U-shaped main body on which light-emitting elements and light-receiving elements are disposed so as to be opposed to each other. The first and second photocouplers  51  and  52  are fixedly mounted on a printed circuit board  54  that is itself mounted on the chassis, so as to cover an upper surface of the mode gear  22 . 
     The first photocoupler  51  straddles the first annular rib  22   a.  Light from a light-emitting element is cut off by the rib portions  22   a   1  and  22   a   2  and does not reach a light-receiving element. Instead, light from the light-emitting element is received at the light-receiving element via the notched portions  22   a   10  and  22   a   11 . The first photocoupler  51  is at a level LOW “0” when the light-receiving element is not receiving any light and outputs a signal that becomes a level HIGH “1” when the light-receiving element is receiving light. The first annular rib  22   a  has a predetermined shape so that the photocoupler  51  outputs the signal shown in FIG. 6D in response to the rotation of the mode gear  22 . 
     The second photocoupler  52  straddles the second annular rib  22   b.  Light from a light-emitting element is cut off by the rib portion  22   b   1  and does not reach a light-receiving element. Instead, light from the light-emitting element is received at the light-receiving element via the notched portion  22   b   10 . The second photocoupler  52  is at a level LOW “0” when the light-receiving element is not receiving any light and outputs a signal that becomes a level HIGH “1” when the light-receiving element is receiving light. The second annular rib  22   b  has a predetermined shape so that the photocoupler  51  outputs the signal shown in FIG. 6E in response to the rotation of the mode gear  22 . 
     The cassette loading recognition switch  53  is provided at a location pressed by a bottom surface of the DAT cassette  31 . The cassette loading recognition switch  53  is at a level HIGH “1” when the light-receiving element is not receiving any light and outputs a signal that becomes a level LOW “0” when the light-receiving element is receiving light. The cassette loading recognition switch  53  outputs the signal shown in FIG.  6 C. 
     The control circuit  41  mentioned above performs the detection of the shifting of the twelve operating modes depending on the combination of signals from the first photocoupler  51 , the second photocoupler  52  and the cassette loading recognition switch  53 . The twelve shifts of operating modes consist of the six shifts when loaded and the six shifts when unloaded. 
     In a case in which a single sensor outputs a “0” or “1” signal, two sensors are inadequate for detecting the twelve shifts of operating modes and, accordingly, three are required. However, it is difficult to fit three such sensors on the mode gear  22  due to restricted space. Here, the cassette loading recognition switch  53  is employed as a third sensor. 
     FIG. 6A shows a change in combination signal in order starting from the first photocoupler  51  signal, the second photocoupler  52  signal and the cassette loading recognition switch  53  signal, when the DAT streamer  20  is in the load mode. FIG. 6B shows a change in combination signal when the DAT streamer  20  is in the unload mode. 
     When commencing the loading mentioned above, a signal “100” is supplied to the control circuit  41  in the order of first a signal from the first photocoupler  51 , then a signal from the second photocoupler  52  and finally a signal from the cassette loading recognition switch  53 . 
     The mode gear  22  is synchronized with the cam gear  23  and rotates clockwise. When the mode gear  22  begins to rotate, the combination signal changes to “110” and the control circuit  41  detects that the DAT streamer  20  is in the eject mode. When the mode gear rotates to approximately 55 degrees the combination signal changes to “111” and the control circuit  41  detects that the DAT streamer  20  has shifted from eject mode to the semi-eject mode. When the mode gear  22  further rotates to approximately 110 degrees the combination signal changes to “001” and the control circuit  41  detects that the DAT streamer has shifted from the semi-eject mode to the unthread mode. When the mode gear  22  further rotates to approximately 230 degrees the combination signal changes to “011” and the control circuit  41  detects that the DAT streamer  20  has shifted from the unthread mode to the stop mode. When the mode gear  22  further rotates to approximately 310 degrees the combination signal changes to  010  and the control circuit  41  detects that the DAT streamer has shifted from the stop mode to the recording/reproducing mode. When the mode gear  22  further rotates to approximately 335 degrees the combination signal changes to “000” and the control circuit  41  detects that the DAT streamer  20  has shifted from the recording/reproducing mode to the rotating head cleaning mode. 
     If in this state an unload is carried out, then the combination signal changes from “000” to “010” and the control circuit  41  detects that the DAT streamer  20  has shifted to a rotary head cleaning mode during the unload mode. When the mode gear rotates counter-clockwise to approximately  310  the combination signal changes to  011  and the control circuit  41  detects that the DAT streamer  20  has shifted from a rotating head cleaning mode to a recording/reproducing mode. When the mode gear  22  further rotates to approximately 230 degrees the combination signal changes to “001” and the control circuit  41  detects that the DAT streamer  20  has shifted from a recording/reproducing mode to a stop mode. When the mode gear  22  further rotates to approximately 110 degrees the combination signal changes to “011” the control circuit  41  detects that the DAT streamer has shifted from the stop mode to the unthread mode. When the mode gear  22  further rotates to approximately 55 degrees the combination signal changes to “110” and the control circuit  41  detects that the DAT streamer  20  has shifted from the unthread mode to the semi-eject mode. When the mode gear  22  further rotates to approximately 0 degrees the combination signal changes to “100” and the control circuit  41  detects that the DAT streamer  20  has shifted from the semi-eject mode to the eject mode. 
     The first photocoupler  51  and the second photocoupler  52  do not contact either the first or second annular ribs  22   a,    22   b,  so the presence of dirt, dust and so on does not affect the output of the “0” and “1” signals. Accordingly, the shifting of the DAT streamer between operating modes can be detected with a high degree of reliability and without fear of wearing out moving parts. 
     Additionally, two photocouplers disposed opposite the mode gear  22  are sufficient because the cassette loading recognition switch  53  output is used. Accordingly, the mode gear  22  with its limited diameter can easily accommodate the first and second photocouplers  51  and  52 . 
     Next, a description will be given of variations of the operating mode shift detection device  40 . 
     FIG. 7 shows a first variation of the operating mode shift detection device  40 A. In this operating mode shift detection device  40 A, a black-and-white pattern  60  is formed on a mode gear  22 A, with photosensors  61  and  62  mounted on a printed circuit board not shown in the drawing detecting the black-and-white pattern  60 . 
     FIG. 8 shows a second variation of the operating mode shift detection device  40 B. In this operating mode shift detection device  40 B, annular ribs  70  are formed on top of a cam gear  23 B, with first and second photocouplers  51 B and  52 B mounted on a printed circuit board not shown in the drawing detecting the annular ribs  70 . 
     FIG. 9 shows a third variation of the operating mode shift detection device  40 C. In this operating mode shift detection device  40 C, a black-and-white pattern  60 C is formed on a cam gear  23 C, with photosensors  61 C and  62 C mounted on a printed circuit board not shown in the drawing detecting the black-and-white pattern  60 . 
     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 inventor 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. 10-281556 filed on Oct. 2, 1998, the entire contents of which are hereby incorporated by reference.