Abstract:
An intermittent gear member, which intermittently rotates alternately in first and second opposite rotational directions within an angular range of 360° or less, includes a disk part, a gear part formed over a predetermined angular range on the circumferential surface of the disk part, and a rotation stopper cam part formed on the toothless part of the circumferential surface of the disk part so as to protrude therefrom, the toothless part corresponding to the range other than the range over which the gear part is formed. The gear part and the rotation stopper cam part are provided in the same plane.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to an intermittent gear member, an intermittent gear mechanism, and a magnetic recording and reproduction apparatus using the same.  
           [0003]    2. Description of the Related Art  
           [0004]    [0004]FIGS. 1A and 1B are diagrams showing a conventional intermittent gear mechanism  10 . The intermittent gear mechanism  10  includes an intermittent gear member  20  as a driven gear member and a gear member  30  as a driving gear member. The intermittent gear member  20  includes a gear part  21  formed over the range of an angle of α1, a concave arcuate rotation stopper cam part  22  formed over the range of an angle of α2, and a mechanism gear part  23 . The rotation stopper cam part  22  and the gear part  21  are provided at different levels. The mechanism gear part  23  is provided at a higher level than the rotation stopper cam part  22 . The gear member  30  includes a gear part  31  opposing the gear part  21  and a convex arcuate cam part  32  opposing the rotation stopper cam part  22 .  
           [0005]    Initially, the gear part  21  and the gear part  31  are engaged with each other. When the gear member  30  is rotated in the direction of the arrow A 1 , the intermittent gear member  20  is rotated in the direction of the arrow B 1 . When the intermittent gear member  20  is rotated approximately an angle of α1, at the same time that the gear part  31  disengages the gear part  21 , the rotation stopper cam part  22  fits with the cam part  32 . As a result, the rotation of the intermittent gear member  20  is restricted, so that the intermittent gear member  20  stops and stays in this rotational position. When the gear member  30  starts rotating in the reverse direction indicated by arrow A 2 , the intermittent gear member  20  remains stationary. As the gear member  30  is rotated, the cam part  32  disengages the rotation stopper cam part  22 , so that the gear part  31  engages the gear part  21  so as to start rotating the intermittent gear member  20  in the direction of the arrow B 2 . The mechanism gear part  23  causes a mechanism to operate.  
           [0006]    [0006]FIGS. 2A and 2B are diagrams showing another conventional intermittent gear mechanism  40 . The intermittent gear mechanism  40  includes an intermittent gear member  50  as a driven gear member and a gear member  60  as a driving gear member. The intermittent gear member  50  includes a gear part  51  formed over the range of an angle of α1, a toothless part  52  formed over the range of an angle of α2 with no gear teeth, and a mechanism gear part  53 . The intermittent gear member  50  is rotationally biased in the direction of the arrow B 2  by a torsion coil spring  54 . The gear member  60  includes a gear part  61  and an arcuate cam part  62 .  
           [0007]    Initially, the gear part  51  and the gear part  61  are engaged with each other. When the gear member  60  is rotated in the direction of the arrow A 1 , the intermittent gear member  50  is rotated in the direction of the arrow B 1 . When the intermittent gear member  50  is rotated approximately an angle of α1, the gear part  61  is disengaged from the gear part  51 , so that the cam part  62  opposes the toothless part  52 . Thus, the transmission of rotation from the gear member  60  to the intermittent gear member  50  is cut off, so that the intermittent gear member  50  comes to a standstill. The intermittent gear member  50  is rotationally biased in the direction of the arrow B 2  by the torsion coil spring  54  so that an end tooth  51   a  of the gear part  51  comes into contact with the cam part  62  so as to restrict the rotation of the intermittent gear member  50 . Thus, the intermittent gear member  50  is controlled to stay in this rotational position. When the gear member  60  is rotated a predetermined angle in the reverse direction indicated by arrow A 2 , the cam part  62  is released from the toothless part  52 , and the gear part  61  engages the gear part  51  so that the intermittent gear member  50  starts rotating in the direction of the arrow B 2 .  
         SUMMARY OF THE INVENTION  
         [0008]    In the intermittent gear mechanism  10  of FIGS. 1A and 1B, the intermittent gear member  20  has the rotation stopper cam part  22  and the gear part  21  provided at different levels. Therefore, the intermittent gear member  20  becomes as thick as H 1  and is difficult to reduce in thickness.  
           [0009]    In the intermittent gear mechanism  40  of FIGS. 2A and 2B, the intermittent gear member  50  does not include a rotation stopper cam part. Therefore, the intermittent gear member  50  has a reduced thickness of H 2 . However, the end tooth  51   a  and the cam part  62  rub against each other so as to cause frictional wear, thus deleteriously affecting the useful life of the intermittent gear mechanism  40 . Moreover, the torsion coil spring  54  requires an increase in the number of components of the intermittent gear mechanism  40 .  
           [0010]    Accordingly, it is a general object of the present invention to provide an intermittent gear member and an intermittent gear mechanism in which the above-described disadvantages are eliminated, and a magnetic recording and reproduction apparatus including the same.  
           [0011]    More specific object of the present invention is to provide an intermittent gear member reduced in thickness, an intermittent gear mechanism reduced in the number of components and free of the problem of frictional wear, and a magnetic recording and reproduction apparatus using the same.  
           [0012]    The above objects of the present invention are achieved by an intermittent gear member intermittently rotatable alternately in first and second opposite rotational directions within an angular range of 360° or less, the intermittent gear member including: a disk part; a gear part formed over a predetermined angular range on a circumferential surface of the disk part; and a rotation stopper cam part formed on a toothless part of the circumferential surface of the disk part so as to protrude therefrom, the toothless part corresponding to a range other than the range over which the gear part is formed, wherein the gear part and the rotation stopper cam part are provided in a single plane.  
           [0013]    According to the above-described intermittent gear member, the gear part and the rotation stopper cam part are provided in the same plane. Therefore, the intermittent gear member of the present invention is reduced in thickness compared with the conventional intermittent gear member whose gear part and rotation stopper cam part are provided-in different planes.  
           [0014]    The above objects of the present invention are also achieved by an intermittent gear mechanism including: a driving gear member rotatable alternately in first and second opposite rotational directions; and a driven gear member that is rotatable in a third rotational direction within an angular range of 360° or less by rotation transmitted from the driving gear member in the first rotational direction, stoppable at a position to which the driven gear member is rotated after the transmission of the rotation is cut off, and rotatable in a fourth rotational direction opposite to the third rotational direction by rotation transmitted from the driving gear member when the driving gear member rotates in the second rotational direction, wherein: the driving gear member includes a driving gear part formed circumferentially over a first predetermined angular range, and an arcuate cam part formed circumferentially adjacent to the driving gear part; and the driven gear member includes a disk part, a gear part formed over a second predetermined angular range on a circumferential surface of the disk part, and a rotation stopper cam part formed on a toothless part of the circumferential surface of the disk part so as to protrude therefrom and correspond to the arcuate cam part of the driving gear member, the toothless part corresponding to a range other than the range over which the gear part is formed, the gear part and the rotation stopper cam part being provided in a single plane.  
           [0015]    The above-described intermittent gear mechanism includes an intermittent gear member of the present invention. Therefore, the intermittent gear mechanism of the present invention is reduced in thickness compared with the conventional intermittent gear mechanism.  
           [0016]    The above objects of the present invention are further achieved by a magnetic recording and reproduction apparatus including: a holder transporting mechanism for transporting to a loading position a holder in which a tape cassette may be loaded; a rotary drum around which a magnetic tape of the tape cassette may be wound a predetermined angle so as to slide thereon; a tape guide member for guiding a running position of the magnetic tape pulled out of the tape cassette in the holder in the loading position; a shifting mechanism for shifting the tape guide member to a predetermined position; and an intermittent gear mechanism, the intermittent gear mechanism including: a driving gear member rotatable alternately in first and second opposite rotational directions; and a driven gear member that is rotatable in a third rotational direction within an angular range of 360° or less by rotation transmitted from the driving gear member in the first rotational direction, stoppable at a position to which the driven gear member is rotated after the transmission of the rotation is cut off, and rotatable in a fourth rotational direction opposite to the third rotational direction by rotation transmitted from the driving gear member when the driving gear member rotates in the second rotational direction, the driving gear member including a driving gear part formed circumferentially over a first predetermined angular range and an arcuate cam part formed circumferentially adjacent to the driving gear part, and the driven gear member including a disk part, a gear part formed over a second predetermined angular range on a circumferential surface of the disk part, and a rotation stopper cam part formed on a toothless part of the circumferential surface of the disk part so as to protrude therefrom and correspond to the arcuate cam part of the driving gear member, the toothless part corresponding to a range other than the range over which the gear part is formed, the gear part and the rotation stopper cam part being provided in a single plane, wherein the driven gear member of the intermittent gear mechanism is rotated in one of the third and fourth rotational directions so as to transport the holder to the loading position, and rotated in the other one of the third and fourth rotational directions so as to return the holder to an initial position thereof.  
           [0017]    The above-described magnetic recording and reproduction apparatus includes an intermittent gear mechanism of the present invention. Therefore, the magnetic recording and reproduction apparatus of the present invention is reduced in thickness compared with the conventional magnetic recording and reproduction apparatus. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    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, in which:  
         [0019]    [0019]FIGS. 1A and 1B are diagrams showing a conventional intermittent gear mechanism;  
         [0020]    [0020]FIGS. 2A and 2B are diagrams showing another conventional intermittent gear mechanism;  
         [0021]    [0021]FIG. 3 is a perspective view of a magnetic recording and reproduction apparatus according to an embodiment of the present invention;  
         [0022]    [0022]FIG. 4 is a plan view of the magnetic recording and reproduction apparatus according to the embodiment of the present invention;  
         [0023]    [0023]FIG. 5 is a perspective view of a gear mechanism of the magnetic recording and reproduction apparatus according to the embodiment of the present invention;  
         [0024]    [0024]FIGS. 6A and 6B are a perspective view and an elevational view, respectively, of an intermittent gear member according to the embodiment of the present invention;  
         [0025]    [0025]FIGS. 7A and 7B are a perspective view and an elevational view, respectively, of a driving ring gear member according to the embodiment of the present invention;  
         [0026]    [0026]FIG. 8 is a diagram showing an intermittent gear mechanism according to the embodiment of the present invention;  
         [0027]    [0027]FIGS. 9A through 11B are diagrams showing a series of movements of the intermittent gear mechanism in the case of rotating the driving ring gear member in a first direction according to the embodiment of the present invention; and  
         [0028]    [0028]FIG. 12A through 13 are diagrams showing a series of movements of the intermittent gear mechanism in the case of rotating the driving ring gear member in a second direction opposite to the first direction according to the embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0029]    A description will now be given, with reference to the accompanying drawings, of an embodiment of the present invention.  
         [0030]    First, a schematic description will be given, for convenience of description, of a magnetic recording and reproduction apparatus  100  to which an intermittent gear mechanism is applied according to the embodiment of the present invention.  
         [0031]    As shown in FIGS. 3 through 5, the magnetic recording and reproduction apparatus  100  is a streamer employed, for instance, as external storage for a computer. The magnetic recording and reproduction apparatus  100  includes: a holder  101  in which a tape cassette (not shown in the drawings) is inserted; a holder transporting mechanism  102  that transports the holder  100  to a loading position; a tape loading mechanism  103  that pulls out a magnetic tape (not shown in the drawings) wound around the reels of the tape cassette; a rotary drum unit  104  around which the magnetic tape is wound a predetermined angle by the tape loading mechanism  103 ; reel driving mechanisms  105  and  106  that rotate the reels of the tape cassette; a pinch roller mechanism  107 ; and a main chassis  108  supporting these mechanisms.  
         [0032]    A support ring member  110  (FIG. 5) is fixed to the center of the main chassis  108 . A driving ring gear member  111 , an R ring gear member  112 , and an L ring gear member  113  are superimposed to be supported by the support ring member  110  so as to be rotatable independent of one another. The driving ring gear member  111  may be formed of a material having a high sliding characteristic. A tape guide post unit  114  is fixed to the R ring gear member  112  and a tape guide post unit  115  is fixed to the L ring gear member  113 .  
         [0033]    As shown in FIG. 5, a gear member  120 , an intermittent gear member  121 , an intermittent gear member  122 , a gear assembly  123 , a gear assembly  124 , and an intermittent gear member  125  are provided around the driving ring gear member  111  on the main chassis  108 . The intermittent gear member  122  may be formed of a material having high rigidity.  
         [0034]    When a motor  130  is started, its rotation is transmitted through the gear member  120  to the driving ring gear member  111  so that the driving ring gear member  111  is rotated counterclockwise. During the transmission, the rotation is decelerated. The rotation of the driving ring gear member  111  is transmitted to the intermittent gear members  121 ,  122 , and  125  (FIG. 5) in predetermined timing, so that the intermittent gear members  121 ,  122 , and  125  are intermittently rotated. The rotation of the intermittent gear member  121  causes the holder transporting mechanism  102  (FIGS. 3 and 4) to operate to load the tape cassette. When the intermittent gear member  122  is rotated, the L ring gear member  113  is rotated clockwise via the gear assembly  123 , and simultaneously, the R ring gear member  112  is rotated counterclockwise via the gear assemblies  123  and  124 . As a result, the tape guide post units  114  and  115  are shifted so that the magnetic tape is pulled out of the tape cassette to be wound around the rotary drum unit  104 . The rotation of the intermittent gear member  125  causes the pinch roller mechanism  107  to operate so that a pinch roller  135  presses the magnetic tape against a capstan  136 , thereby pinching the magnetic tape.  
         [0035]    The magnetic tape is driven, pinched and held by the pinch roller  135  and the capstan  136 , so as to run back and forth along the rotary drum unit  104  so that information may be recorded on the magnetic tape.  
         [0036]    Next, a description will be given of the intermittent gear member  121  and the driving ring gear member  111 .  
         [0037]    As shown in FIGS. 6A and 6B, the intermittent gear member  121  includes: a disk part  121   a , a gear part  121   b  formed over a predetermined angular range of α10 on the circumferential surface of the disk part  121   a ; a rotation stopper cam part  121   c  formed like a flange protruding from a toothless part  121   a   1  of the circumferential surface of the disk part  121   a ; and a gear part  121   d  disposed at the upper surface of the disk part  121   a . No gear tooth is formed on the toothless part  121   a   1 , which is a part of the circumferential surface of the disk part  121   a  other than the part on which the gear part  121   b  is formed. The gear part  121   b  and the rotation stopper cam part  121   c  are provided in the same plane (or at the same level) S 1 . The intermittent gear member  121  has a low-profile thickness of H 10 .  
         [0038]    The gear part  121   b  is formed of a plurality of gear teeth  121   b   −1  through  121   b   −n . Gear teeth  121   b   −(n+1)  and  121   b   −(n+2)  represented by the dotted lines in FIG. 6A are the first and second imaginary teeth in the case of extending the gear part  121   b  in the counterclockwise direction.  
         [0039]    The rotation stopper cam part  121   c  has a cam surface  121   c   1 . The cam surface  121   c   1 , which is shaped so as to correspond to a later-described arcuate cam  111   c  of the driving ring gear member  111 , has a concave arcuate shape.  
         [0040]    A recess  140  is formed between the rotation stopper cam part  121   c  and the tooth  121   b   −n . An end face  121   c   2  of the rotation stopper cam part  121   c  in the clockwise facing direction coincides with a (right) flank of the second imaginary tooth  121   b   −(n+2)  in the clockwise facing direction. This allows, as will be described later, a gear part  111   b  of the driving ring gear member  111  to smoothly engage the gear part  121   b.    
         [0041]    Reference numeral  141  denotes a line that connects the center O 121  of the intermittent gear member  121  and the center O 111  of the driving ring gear member  111  (see FIGS. 7A and 7B) when the intermittent gear member  121  is in a stationary state. The rotation stopper cam part  121   c  has a projection angle of α11 in the clockwise direction with respect to the line  141  and a projection angle of α12 in the counterclockwise direction with respect to the line  141 , where α12&gt;α11. That is, the rotation stopper cam part  121   c  projects in the counterclockwise direction with respect to the line  141  (α12) at an angle larger than it projects in the clockwise direction with respect to the line  141  (α11). Therefore, the length L 10  of the cam surface  121   c   1  is large so that the intermittent gear member  121  may be stably controlled to remain in a stationary or stopped state.  
         [0042]    As shown in FIGS. 3 and 4, the gear part  121   d  is engaged with a rack  102   a  of the holder transporting mechanism  102 .  
         [0043]    As shown in FIGS. 7A and 7B, the driving ring gear member  111  includes: the gear part  111   b  formed over a predetermined angular range of α20 on the circumferential surface of a ring part  111   a ; and the arcuate cam part  111   c  circumferentially adjacent in the clockwise direction in FIG. 7A to the gear part  111   b . The gear part  111   b  and the cam part  111   c  are positioned in the same plane (or at the same level) S 2 . The driving ring gear member  111  has a low-profile thickness of H 11 . The gear part  111   b  is formed of a plurality of gear teeth  111   b   −1  through  111   b   −n . The first tooth  111   b   −1  and the last tooth  111   b   −n  have a greater tooth depth than the other teeth  111   b   −2  through  111   b   −(n−1)  (that is, the teeth  111   b   −1  and  111   b   −n  project a greater distance from the circumferential surface of the ring part  111   a  than the teeth  111   b   −2  through  111   b   −(n−1) ) so as to ensure the later-described operation of pushing the rotation stopper cam part  121   c . In this embodiment, both the first tooth  111   b   −1  and the last tooth  111   b   −n  have a greater tooth depth than the other teeth  111   b   −2  through  111   b   31 (n−1) . Alternatively, however, only the last tooth  111   b   n  that pushes the rotation stopper cam part  121   c  may have a greater tooth depth than the other teeth  111   b   −1  through  111   b   −(n−1) .  
         [0044]    [0044]FIG. 8 is a diagram showing an intermittent gear mechanism  150 . The intermittent gear mechanism  150  includes the driving ring gear member  111  as a driving gear member and the intermittent gear member  121  as a driven gear member that are engaged with each other.  
         [0045]    Both the driving ring gear member  111  and the intermittent gear member  121  are low-profile, so that the intermittent gear mechanism  150  is reduced in thickness.  
         [0046]    Next, a description will be given of the transmission of rotation in the intermittent gear mechanism  150 .  
         [0047]    [0047]FIG. 9A is a diagram showing the initial state, wherein the tooth  121   b   −1  is engaged between the teeth  111   b   −1  and  111   b   −2 .  
         [0048]    The driving ring gear member  111  is rotated approximately 273° in the A 1  direction to come to a standstill. After being maintained in a stationary state, the driving ring gear member  111  is rotated in the A 2  direction to return to its initial (original) position.  
         [0049]    When the driving ring gear member  111  is rotated in the A 1  direction, the gear part  111   b  engages with the gear part  121   b  so as to start the rotation of the intermittent gear member  121  in the B 1  direction so that the state shown in FIG. 9B is entered. Thereafter, while continuing to rotate the driving ring gear member  111  in the A 1  direction, the state shown in FIG. 10A, the state shown in FIG. 10B, and the state shown in FIG. 11A are successively entered. In the state of FIG. 10A, the tooth  111   b   −(n−2)  engages between the teeth  121   b   −(n−1)  and  121   b   −n  so that the intermittent gear member  121  is rotated in the B 1  direction, while the teeth  111   b   −(n−1)  and  111   b   −n  are about to enter the recess  140  formed between the tooth  121   b   −n  and the rotation stopper cam part  121   c . In the state of FIG. 10B, the teeth  111   b   −(n−1)  and  111   b   −n  have entered the recess  140  so that the tooth  111   b   −(n−1)  pushes the tooth  121   b   −n , while an end part  111   c   1  of the cam part  111   c  is about to come into contact with the cam surface  121   c   1  of the rotation stopper cam part  121   c . In the state of FIG. 11A, the teeth  111   b   −(n−1)  and  111   b   −n  are pulled out of the recess  140  while the end part  111   c   1  of the cam part  111   c  comes into contact with the cam surface  121   c   1  of the cam part  121   c  so that the rotation stopper cam part  121   c  is positioned along the cam part  111   c.    
         [0050]    Thereafter, the transmission of rotation in the A 1  direction from the driving ring gear member  111  to the intermittent gear member  121  is cut off, such that only the driving ring gear member  111  may rotate in the A 1  direction while the intermittent gear member  121  remains in a stationary state without rotating as shown in FIG. 11B. The intermittent gear member  121  is maintained at the position at which the intermittent gear member  121  is stopped with the position of the cam surface  121   c   1  of the cam part  121   c  being controlled by the cam part  111   c . When the intermittent gear member  121  is stopped, the cam surface  121   c   1  of the cam part  121   c  is in contact with the circumferential surface of the cam part  111   c  of the driving ring gear member  111 . Since the length L 10  (FIG. 6A) of the cam surface  121   c   1  is increased, the intermittent gear member  121  is stably controlled to its stop position. That is, the cam surface  121   c   1  of the rotation stopper cam part  121   c , by having a larger surface from the line  141  in the counterclockwise direction than in the clockwise direction in FIG. 6A, provides stable control of the intermittent gear member  121  to its stop position. The pressure angle of the rotation stopper cam part  121   c  at the contact point of the cam surface  121   c   1  (that is, α12) is preferably larger than or equal to 30° so as to prevent the cam part  111   c  of the driving ring gear member  111  from biting the rotation stopper cam part  121   c  when the driving ring gear member  111  rotates in the A 1  direction.  
         [0051]    In the case of rotating the driving ring gear member  111  in the A 2  direction, the transmission of rotation to the intermittent gear member  121  is started after the rotation of the driving ring gear member  111  is started. In a reverse order of the above-described disengaging sequence, the gear part  111   b  and the gear part  121   b  start engaging each other successively through the state of FIG. 12A, which corresponds to FIG. 11A, the state of FIG. 12B, which corresponds to FIG. 10B, and the state of FIG. 13, which corresponds to FIG. 10A.  
         [0052]    [0052]FIG. 12A shows the state where the end part  111   c   1  of the cam part  111   c  reaches the cam surface  121   c   1  of the rotation stopper cam part  121   c  while the tooth  111   b   −n  is about to come into contact with the end face  121   c   2  of the rotation stopper cam part  121   c . The greater tooth depth of the tooth  111   b   −n  ensures that the tooth  111   b   −n  comes into contact with the end face  121   c   2  of the rotation stopper cam part  121   c .  
         [0053]    [0053]FIG. 12B shows the state where the tooth  111   b   −n  pushes the end face  121   c   2  of the rotation stopper cam part  121   c  to rotate the intermittent gear member  121  in the B 2  direction so that the teeth  111   b   −(n−1)  and  111   b   −n  enter the recess  140 .  
         [0054]    [0054]FIG. 13 shows the state where the tooth  111   b   −(n−2)  is engaged between the teeth  121   b   −(n−1)  and  121   b   −n  while the teeth  111   b   −(n−1)  and  111   b   −n  are pulled out of the recess  140 .  
         [0055]    As was mentioned above, the end face  121   c   2  of the rotation stopper cam part  121   c  coincides with the right flank of the second imaginary tooth  121   b−(n+ 2 )  (FIG. 6A) This facilitates the teeth  111   b   −(n−1)  and  111   b   −n  fitting in the recess  140  smoothly and the tooth  111   b   −(n−2)  also smoothly engaging between the teeth  121   b   −(n−1)  and  121   b   −n , so that the gear part  111   b  of the driving ring gear member  111  smoothly engages with the gear part  121   b  of the intermittent gear member  121 .  
         [0056]    Thereafter, the transmission of rotation from the driving ring gear member  111  to the intermittent gear member  121  is started, and the initial state of FIG. 9A may be entered via the state of FIG. 9B.  
         [0057]    Since no spring member for rotationally biasing the intermittent gear member  121  is necessary, the intermittent gear mechanism  150  has a reduced number of components compared with the above-described prior-art intermittent gear mechanism  40 . Further, since the intermittent gear member  121  is not rotationally biased, the problem of frictional wear is prevented from occurring.  
         [0058]    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.  
         [0059]    The present application is based on Japanese priority application No. 2002-178241, filed on Jun. 19, 2002, the entire contents of which are hereby incorporated by reference.