Abstract:
A mechanism for restricting a lateral position of a tape traveling in a longitudinal direction is disclosed, that comprises a base having a convex portion, a guide directly disposed on the convex portion, a lower flange having an opening through which the convex portion passes, the lateral position of said lower flange against said base being movable between the front edge of said base and the bottom edge of said guide, and a member for pressing said lower flange to the bottom edge of said guide.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a mechanism for restricting the lateral position of a tape traveling in the longitudinal direction and in particular, to that for use with a magnetic tape device.  
           [0003]    2. Description of the Prior Art  
           [0004]    [0004]FIG. 1 is a disassembled view showing an example of the structure of a conventional tape traveling restricting device. FIG. 2 is an assembled view showing the structure of the tape traveling restricting device shown in FIG. 1. Referring to FIG. 1, the conventional tape traveling restricting device comprises a guide base  11 , a lower flange  12 , a guide  13 , an upper flange  14 , and a securing screw  15 . The securing screw  15  has a thread portion. The thread portion is formed at a forward edge of the securing screw  15 . The lower flange  12 , the guide  13 , and the upper flange  14  have respective openings through which the securing screw  15  smoothly passes. Likewise, the guide base  11  has a thread portion so that the guide base  11  is mated with the securing screw  15 .  
           [0005]    As shown in FIG. 2, the lower flange  12 , the guide  13 , and the upper flange  14  are successively mounted on the guide base  11 . Last, the securing screw  15  is threaded to the guide base  11  through the openings of the lower flange  12 , the guide  13 , and the upper flange  14 . Thus, the lower flange  12 , the guide  13 , and the upper flange  14  are secured on the guide base  11 .  
           [0006]    Now, a bottom edge  11   a  of the guide base  11  is referred to as guide reference edge A. In addition, the distance from the guide reference edge to an upper edge  11   b  of the guide base  11  is denoted by B. Thus, the thickness of the guide base  11  (namely, the distance B) includes a dimensional tolerance ±a. The thickness of the lower flange  12  is denoted by C. Likewise, the thickness C includes a dimensional tolerance ±β.  
           [0007]    On the other hand, in the state that the lower flange  12 , the guide  13 , and the upper flange  14  are secured on the guide base  11  (see FIG. 2), the position of a bottom edge  13   a  of the guide  13  is referred to as tape traveling reference edge. When the tape is traveled, it is preferred to minimize the difference between the tape traveling reference edge and the reference edge of the magnetic tape (the tape reference edge).  
           [0008]    Although the upper flange  14  may be a tape traveling reference edge, in this case, the upper flange  14  does not directly contact the guide base  11 .  
           [0009]    Other related art references of such a tape traveling restricting device are disclosed in for example Japanese Utility Model Registration Laid-Open Publication No. 61-72750 (referred to as Document 1), Japanese Patent Laid-Open Publication No. 1-302563 (referred to as Document 2), Japanese Patent Laid-Open Publication No. 3-203854 (referred to as Document 3), and Japanese Patent No. 2806885 (referred to as Document 4). According to the technology of Document 1, the inner diameter of a roller post is downwardly increased. According to the technology of Document 2, a convex portion is formed on a tape contacting edge of a lower ceramic guide. According to the technology of Document 3, the upper edge of a lower flange is inclined at a predetermined angle. According to the technology of Document  4 , a magnetic tape is laterally pressed by an upper flange.  
           [0010]    However, the related art references have the following disadvantages. As a first disadvantage, since the lower flange  12  and the guide  13  are successively mounted on the upper edge  11   b  of the guide base  11 , the tape traveling reference edge has the dimensional tolerances of the two parts of the guide base  11  and the lower flange  12  (namely, (±α)+(±α)). This situation also takes place in the case that the upper flange is a reference edge. As a result, since the tape is unstably traveled, information cannot be correctly read and written from/to the tape.  
           [0011]    As a second disadvantege, in addition to a highly accurate dimensional tolerance of the guide base  11 , since a highly accurate dimensional tolerance of the lower flange  12  is required. Thus, the final product becomes expensive. The above-described documents do not disclose means for solving such disadvantages.  
         SUMMARY OF THE INVENTION  
         [0012]    The present invention is made from the above-described point of view. An object of the present invention is to provide a tape traveling restricting device that allows a tape to be stably traveled and that is fabricated at low cost.  
           [0013]    According to an aspect of the present invention, there is provided a mechanism for restricting a lateral position of a tape traveling in a longitudinal direction, comprising: a base having a convex portion; a guide directly disposed on the convex portion; a lower flange having an opening through which the convex portion passes, the lateral position of the lower flange against the base being movable between at most the front edge of the base and the bottom edge of the guide; and a member for pressing the lower flange to the bottom edge of the guide.  
           [0014]    The mechanism may further comprise: an upper flange disposed on the guide; and a screw for securing the upper flange to the guide.  
           [0015]    In the mechanism, the member may be a washer.  
           [0016]    In the mechanism, the washer may be a wave washer.  
           [0017]    In the mechanism, the washer may be a spring washer.  
           [0018]    In the mechanism, the washer may be a countersink washer.  
           [0019]    In the mechanism, the member may be a spring.  
           [0020]    In the mechanism, the spring may be a leaf spring.  
           [0021]    In the mechanism, the spring may be a coil spring.  
           [0022]    In the mechanism, the member may be a rubber.  
           [0023]    These and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of the best mode embodiment thereof, as illustrated in the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0024]    [0024]FIG. 1 is a disassembled view showing an example of the structure of a conventional tape traveling restricting device;  
         [0025]    [0025]FIG. 2 is an assembled view showing the structure of the tape traveling restricting device shown in FIG. 1;  
         [0026]    [0026]FIG. 3 is a disassembled view showing the structure of a tape traveling restricting device according to a preferred embodiment of the present invention;  
         [0027]    [0027]FIG. 4 is an assembled view showing the structure of the tape traveling restricting device shown in FIG. 3;  
         [0028]    [0028]FIG. 5 is a schematic diagram showing a deformation of a wave washer;  
         [0029]    [0029]FIG. 6 is a plan view showing the overall structure of a guide base portion; and  
         [0030]    [0030]FIG. 7 is a front view showing the overall structure of the guide base portion. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENT  
       [0031]    Next, with reference to the accompanying drawings, a preferred embodiment of the present invention will be described. FIG. 3 is a disassembled view showing the structure of a tape traveling restricting device according to the preferred embodiment of the present invention. FIG. 4 is an assembled view showing the structure of the tape traveling restricting device shown in FIG. 3. FIG. 5 is a schematic diagram showing a deformation of a wave washer (that will be described later). FIG. 6 is a plan view showing the overall structure of a guide base portion. FIG. 7 is a front view showing the overall structure of the guide base portion shown in FIG. 6.  
         [0032]    First of all, the overall structure of the guide base portion will be described. Referring to FIGS. 6 and 7, two sets of lower flanges  2 , guides  3 , upper flanges  4 , and securing screws  5  are symmetrically disposed as left and right assemblies at left and right positions on the upper edge of a guide base  1 . A magnetic head  7  is disposed between the left and right assemblies. In each of the assemblies, the guide  3  is secured to the guide base  1  by the securing screw  5  in a state of being pinched by the upper flange  4  and the lower flange  2 . In addition, a wave washer  6  (omitted in FIGS. 6 and 7) is disposed between the lower flange  2  and the guide base  1 .  
         [0033]    A magnetic tape  8  is wound around the left and right guides  3  with a winding angle of for example  10  to  20  degrees. The magnetic tape  8  is traveled to the left or right in the state that the magnetic tape  8  contacts a magnetic head  7 . The magnetic head  7  reads and writes information from/to the magnetic tape  8  that is being traveled. To accurately read and write information from/to the magnetic tape  8 , it is necessary to minimize the difference between the tape traveling reference edge and the reference edge of the magnetic tape  8  (tape reference edge).  
         [0034]    Next, with reference to FIG. 3, the structure of the tape traveling restricting device will be described. The tape traveling restricting device comprises the guide base  1 , the lower flange  2 , the guide  3 , the upper flange  4 , the securing screw  5 , and the wave washer  6 . The securing screw  5  has a thread portion. The thread portion is formed at a forward edge of the securing screw  5 . The upper flange  4  and the guide  3  have respective openings through which the securing screw  5  smoothly passes. The guide base  1  has a thread portion in which the securing screw  5  is screwed.  
         [0035]    On the other hand, the lower flange  2  has a larger opening than each of the openings of the upper flange  14  and the guide  3 . A convex portion  1   b  is formed on an upper edge  1   a  of the guide base  1 . The diameter of the convex portion  1   b  is sufficient so that the convex portion  1   b  is almost mated with the lower flange  2 .  
         [0036]    As shown in FIG. 4, the wave washer  6  and the lower flange  2  are almost mated to the convex portion  1   b  of the guide base  1 . The guide  3  and the upper flange  4  are mounted on the lower flange  2 . The securing screw  5  is threaded to the guide base  1  through the openings of the wave washer  6 , the lower flange  2 , the guide  3 , and the upper flange  4 . Thus, the lower flange  2 , the guide  3 , and the upper flange  4  are secured on the guide base  1 .  
         [0037]    In other words, a bottom edge  3   a  of the guide  3  directly contacts the convex portion  1   b  of the guide base  1 . The lower flange  2  is disposed between the bottom edge  3   a  of the guide  3  and the guide base  1  in such a manner that the lower flange  2  can be vertically moved. To travel the magnetic tape  8 , the lower flange  2  must contact the bottom edge  3   a  of the guide  3 . Thus, the wave washer  6  that is a resilient member is disposed between the lower flange  2  and the guide base  1 . In addition, the upper flange  4  is placed on an upper edge  3   b  of the guide  3 . Thereafter, the securing screw  5  is tightened. As a result, the tightening force of the securing screw  5  (downward pressure) and the resilience of the wave washer  6  (upward pressure: see FIG. 5) cause the lower flange  2  to contact the guide  3 . In this case, the dimensional tolerance from the reference edge of the magnetic tape  8  to the tape traveling reference edge is only the dimensional tolerance ±α of the guide base  1 .  
         [0038]    While the magnetic tape  8  is being traveled, the magnetic tape  8  may jump in lateral direction which is perpendicular to the tape traveling direction. However, the magnetic tape  8  is restricted by the lower flange  2  and the upper flange  4  in lateral direction. Since the lower flange  2  is pressed with very strong resilient force of the wave washer  6 , the lower flange  2  is fixed in lateral direction. In addition, the tape reference edge of the magnetic tape  8  almost matches the tape traveling reference edge.  
         [0039]    According to the preferred embodiment of the present invention, the wave washer  6  is used to cause the lower flange  2  to contact the guide  3 . Alternatively, a spring washer, a countersink washer, a leaf washer, a coil spring, a rubber member, or the like can be used. With such a substitute member, the same effect as the preferred embodiment can be accomplished.  
         [0040]    Since the dimensional tolerance from the guide reference edge to the tape traveling reference edge is only the dimensional tolerance of the guide base, a magnetic tape can be stably traveled. In addition, information can be more accurately read and written from/to the magnetic tape than before.  
         [0041]    In addition, according to the present invention, since the dimensional tolerance of the lower flange can be alleviated, the cost of the final product can be reduced.  
         [0042]    Although the present invention has been shown and described with respect to the best mode embodiment thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions, and additions in the form and detail thereof may be made therein without departing from the spirit and scope of the present invention.