Patent Abstract:
A tape guide post mechanism for guiding running of a tape includes: a post arm, the post arm including a tape guide post, around which the tape is looped at a predetermined angular distance, and which guides running of the tape, and a hole; an arm shaft which engages with the hole and rotatably supports the post arm, wherein an external side surface of the arm shaft is in contact with the hole at at least two points in the vicinity of an upper opening of the hole and at at least two points in the vicinity of a lower opening of the hole.

Full Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a tape guide post mechanism for use in a magnetic recording/reproducing apparatus, such as a videotape recorder (VTR).  
           [0003]    2. Description of the Related Art  
           [0004]    In recent years, there has been a growing demand for decreases in size and cost of magnetic recording/reproduction apparatus, such as VTRs, camcorders, etc.  
           [0005]    Hereinafter, a tape guide post mechanism for use in a conventional magnetic recording/reproducing apparatus is described.  
           [0006]    [0006]FIG. 6 is a plan view of a magnetic recording/reproducing apparatus which uses a conventional tape guide post mechanism. FIG. 6 shows that a tape  2  has been pulled out from a cassette  1  by tape guide posts  8 ,  9 ,  10 , and  13 , and looped around a rotatable head cylinder  6 . In this state, recording/reproduction of data or information to/from the tape  2  can be performed. In FIG. 6, some parts are omitted (i.e., not shown) for clarity of illustration.  
           [0007]    As shown in FIG. 6, the tape  2  is wound around an S-reel  4   a  and a T-reel  5   a  stored in the cassette  1 . For clarity of illustration, the external shape of the cassette  1  is represented by a dashed line. Reference numeral  3  denotes a base of a magnetic recording/reproducing apparatus, on which the cassette  1  is mounted. Reference numeral  4  denotes an S-reel bed, which is rotatably and axially supported on the base  3 . The S-reel bed  4  is engaged, and rotates integrally, with the S-reel  4   a.    
           [0008]    Reference numeral  5  denotes a T-reel bed, which is rotatably and axially supported on the base  3 . The T-reel bed  5  is engaged, and rotates integrally, with the T-reel  5   a . Reference numeral  15  denotes a tension arm (post arm). The tension arm  15  has: a tension post  8 , which is one of the tape guide posts, and which is one of the constituent elements of a tape running system; and a hole  15   a . The base  3  has a tension arm shaft  14 , which is provided so as to penetrate through the hole  15   a , so that the tension arm shaft  14  rotatably supports the tension arm  15 . Reference numeral  18  denotes a tension band, one end of which is supported by a shaft  15   b  formed in the tension arm  15 , and the other end which is fixed to the base  3  with a band fixture screw  19 . The intermediate portion of the tension band  18  is wound around a cylindrical portion  20  of the S-reel bed  4 . The tension arm  15  is urged by an urging spring  15   a  around the tension arm shaft  14  in a counterclockwise direction.  
           [0009]    Reference numeral  6  denotes a rotatable head cylinder provided on the base  3 . The rotatable head cylinder  6  has a rotatable magnetic head, through which a signal is recorded in/reproduced from the tape  2  that is looped around the rotatable head cylinder  6 . Reference numeral  7  denotes a S1-post, which is one of the tape guide posts. Reference numeral  11  denotes a T1-post, which is one of the tape guide posts. The S1-post  7  and the T1-post  11  are fixed to the base  3 , and are constituent elements of the tape running system. Reference numeral  9  denotes a S2-post, which is one of the tape guide posts. Reference numeral  10  denotes a T2-post, which is one of the tape guide posts. The S2-post  9  and the T2-post  10  are constituent elements of the tape running system. Reference numeral  12  denotes a capstan shaft, and reference numeral  100  denotes a pinch roller. The tape  2  which is sandwiched by the capstan shaft  12  and the pinch roller  100  is driven in a forward/reverse direction by forward/reverse rotation of the capstan shaft  12 . Reference numeral  13  denotes a T3-post, which is one of the tape guide posts, and is a constituent element of the tape running system. The T3-post  13  is formed in a T3-arm  17  which is a post arm. The T3-arm  17  has a hole  17   a . A T3-arm shaft  23   a  which is formed on the base  3  is provided so as to penetrate through the hole  17   a , so that the T3-arm shaft  23  a rotatably supports the T3-arm  17 . FIG. 6 shows that the tape  2  has been pulled out of the cassette  1  by the tension post  8 , the S1-post  9 , the T1-post  10 , and the T3-post  13 , which are driven by driving means not shown in FIG. 6.  
           [0010]    The tape running system shown in FIG. 6 is now described. The tape  2  pulled out from the S-reel  4   a  is first looped around the S2-post  7  on the base  3 , and then, looped around the tension post  8  and the S1-post  9 . Further, the tape  2  is looped around the rotatable head cylinder  6 , and around the T1-posts  10  and the T2-posts  11 . Thereafter, the tape  2  is looped around the capstan shaft  12  and the T3-post  13 . Thereafter, the tape  2  is wound around the T-reel  5   a.    
           [0011]    Hereinafter, an operation of the tape guide post mechanism of the conventional magnetic recording/reproducing apparatus having the above described structure is described with reference to FIGS. 7 through 9.  
           [0012]    [0012]FIG. 7 is a cross-sectional view showing the T3-arm  17  of the conventional tape guide post mechanism. FIG. 8 is a cross-sectional view showing the state of the T3-arm  17  when a tape tension is applied to the T3-arm  17 . FIG. 9 is a perspective view showing the details about engagement between the hole  17   a  of the T3-arm  17  and the T3-arm shaft  23   a.    
           [0013]    In FIG. 7, the tape  2  is not looped around the T3-post  13 . The hole  17   a  of the T3-arm  17  is rotatably engaged with the T3-arm shaft  23  a formed on the base  3 . The T3-arm  17  is prevented by a stoppage ring  21  from being upwardly disengaged from the T3-arm shaft  23   a . Further, some space  22  is necessarily provided between the internal wall surface of the hole  17   a  and the external side surface of the T3-arm shaft  23   a  such that the T3-arm  17  is rotatable around the T3-arm shaft  23   a.    
           [0014]    When the tape  2  is looped around the T3-post  13  so as to have a predetermined contact area therebetween which corresponds to a predetermined angular distance around the T3-post  13  so that the tape  2  can run, tape tension Ta is applied to the T3-post  13  as shown in FIG. 8. Due to tape tension Ta, a rotation moment is caused in the T3-arm  17  and the T3-post  13  in the direction of arrow M. Accordingly, the T3-arm  17  slightly rotates in the direction of arrow M as shown in FIG. 8. As a result, the internal wall surface of the hole  17   a  of the T3-arm  17  is in contact with the external side surface of the T3-arm shaft  23   a  at an upper contact point  30  and a lower contact point  31  as shown in FIG. 9.  
           [0015]    [0015]FIG. 9 shows the slanted T3-arm  17  only in the vicinity of the T3-arm shaft  23   a . As seen from FIG. 9, a hole centerline  33  between the center of the upper opening of the hole  17   a  of the T3-arm  17  (“upper hole center  32   a ”) and the center of the lower opening of the hole  17   a  of the T3-arm  17  (“lower hole center  32   b ”) is slanted with respect to the longitudinal axis of the T3-arm shaft  23   a . Herein, the T3-post  13  is a constituent element of the tape running system. The amount and direction of slant of the T3-post  13  must be accurately determined.  
           [0016]    However, in the above conventional structure, there are problems as described below with reference to FIGS. 8 and 9. Due to small, external disturbing factors, such as a variation of tape tension Ta, a variation of friction force generated between the T3-post  13  and the tape  2 , etc., the position of the upper contact point  30  unstably shifts in a direction indicated by arrow B of FIG. 9, and the position of the lower contact point  31  unstably shifts along a direction indicated by arrow C of FIG. 9. That is, the slant of the hole center line  33  with respect to the axis of the T3-arm shaft  23  a is varied, and the amount and direction of slant of the T3-post  13  are unstable. Also, shift of the positions of the upper contact point  30  and the lower contact point  31  is caused by the attitude change or vibration of the magnetic recording/reproducing apparatus, and as a result, the amount and direction of slant of the T3-post  13  are unstable.  
           [0017]    Furthermore, the magnitude and direction of the force applied to the T3-post  13  due to the tape tension are different between a case where the tape  2  runs in a forward direction and a case where the tape  2  runs in a reverse direction. Thus, when the running direction of the tape  2  changes between the forward and reverse directions, the positions of the upper contact point  30  and the lower contact point  31  shift, so that the amount and direction of slant of the T3-post  13  are unstable. As described above, in the conventional structure, the amount and direction of slant of the T3-post  13  are essentially and necessarily unstable because of the attitude change or vibration of the magnetic recording/reproducing apparatus, a change in the running state of the tape  2 , such as the running direction of the tape  2 , the tape tension, or the like.  
         SUMMARY OF THE INVENTION  
         [0018]    According to one aspect of the present invention, a tape guide post mechanism for guiding running of a tape, includes: a post arm, the post arm including a tape guide post, around which the tape is looped at a predetermined angular distance, and which guides running of the tape, and a hole; an arm shaft which engages with the hole and rotatably supports the post arm, wherein an external side surface of the arm shaft is in contact with the hole at at least two points in the vicinity of an upper opening of the hole and at at least two points in the vicinity of a lower opening of the hole.  
           [0019]    In one embodiment of the present invention, the external side surface of the arm shaft has a cylindrical shape; and an internal wall surface of the hole of the post arm does not have a cylindrical shape.  
           [0020]    In another embodiment of the present invention, the external side surface of the arm shaft does not have a cylindrical shape; and an internal wall surface of the hole of the post arm has a cylindrical shape.  
           [0021]    In still another embodiment of the present invention, the internal wall surface of the hole of the post arm has a polygonal shape.  
           [0022]    In still another embodiment of the present invention, the internal wall surface of the hole of the post arm has a hexagonal shape.  
           [0023]    In still another embodiment of the present invention, the external side surface of the arm shaft has a polygonal shape.  
           [0024]    In still another embodiment of the present invention, the external side surface of the arm shaft has a hexagonal shape.  
           [0025]    In still another embodiment of the present invention, the internal wall surface of the hole of the post arm has a different shape at the upper opening and the lower opening of the hole.  
           [0026]    According to another aspect of the present invention, a tape guide post mechanism for guiding running of a tape includes: a post arm, the post arm including a tape guide post, around which the tape is looped at a predetermined angular distance, and which guides running of the tape, and a hole; an arm shaft which engages with the hole and rotatably supports the post arm, wherein an external side surface of the arm shaft has a first shape and an internal wall surface of the hole of the post arm has a second shape which is different from the first shape.  
           [0027]    In one embodiment of the present invention, one of the first shape and the second shape is cylindrical, and the other of the first shape and the second shape is non-cylindrical.  
           [0028]    According to the present invention, a simply structured, inexpensive tape guide post mechanism can be obtained, where a slant of a tape guide post does not vary even in the presence of the attitude change or vibration of the magnetic recording/reproducing apparatus, a change in the running state of a tape, such as the running direction of the tape, the tape tension, or the like.  
           [0029]    According to the present invention, a jolt between an arm shaft and a hole formed in a post arm may be avoided, while the arm shaft may be rotatably engaged with the post arm. As a result, a simply structured, in expensive tape guide post mechanism can be realized, where a slant of the longitudinal center line of the arm shaft with respect to the longitudinal axis of the hole of the arm post rarely varies.  
           [0030]    According to the present invention, an external side surface of the arm shaft has a cylindrical shape, while an internal wall surface of the hole of the post arm does not have a cylindrical shape. With such a simple and less expensive contrivance, the external side surface of the arm shaft is in contact with the hole at two points in the vicinity of an upper opening of the hole and at two points in the vicinity of a lower opening of the hole. Due to such an arrangement, a jolt between the arm shaft and the hole formed in the post arm is avoided, while the arm shaft can be rotatably engaged with the post arm. As a result, a simply structured, inexpensive tape guide post mechanism can be realized, where slant of the longitudinal center line of the arm shaft with respect to the longitudinal axis of the hole of the arm post rarely varies.  
           [0031]    According to the present invention, an external side surface of the arm shaft does not have a cylindrical shape, while an internal wall surface of the hole of the post arm has a cylindrical shape. Therefore, the external side surface of the arm shaft is in contact with the hole at two points in the vicinity of an upper opening of the hole and at two points in the vicinity of a lower opening of the hole. Due to such an arrangement, a jolt between the arm shaft and the hole formed in the post arm is avoided, while the arm shaft can be rotatably engaged with the post arm. As a result, again a simply structured, inexpensive tape guide post mechanism can be realized, where a slant of the longitudinal center line of the arm shaft with respect to the longitudinal axis of the hole of the arm post rarely varies.  
           [0032]    Thus, the invention described herein makes possible the advantages of providing a simply structured, inexpensive tape guide post mechanism where the slant of a tape guide post does not vary even in the presence of the attitude change or vibration of the magnetic recording/reproducing apparatus, a change in the running state of a tape, such as the running direction of the tape, the tape tension, or the like.  
           [0033]    These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0034]    [0034]FIG. 1 is a cross-sectional view of a tape guide post mechanism according to embodiment 1 of the present invention.  
         [0035]    [0035]FIG. 2 is a perspective view showing in detail engagement between a hole and a shaft in the tape guide post mechanism according to embodiment 1.  
         [0036]    [0036]FIG. 3 is a cross-sectional view of a tape guide post mechanism according to embodiment 2 of the present invention.  
         [0037]    [0037]FIG. 4 is a perspective view showing in detail engagement between a hole and a shaft in the tape guide post mechanism according to embodiment 2.  
         [0038]    [0038]FIG. 5 is a perspective view showing in detail engagement between a hole and a shaft in the tape guide post mechanism according to still another embodiment of the present invention.  
         [0039]    [0039]FIG. 6 is a plan view of a magnetic recording/reproducing apparatus which uses a conventional tape guide post mechanism.  
         [0040]    [0040]FIG. 7 is a cross-sectional view showing a T3-arm of the conventional tape guide post mechanism.  
         [0041]    [0041]FIG. 8 is across-sectional view showing the state of the T3-arm of the conventional tape guide post mechanism when a tape tension is applied to the T3-arm.  
         [0042]    [0042]FIG. 9 is a perspective view showing the details about engagement between a hole of the T3-arm and a T3-arm shaft in the conventional tape guide post mechanism. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0043]    Hereinafter, embodiments of the present invention will be described with reference to the drawings.  
         [0044]    (Embodiment 1)  
         [0045]    [0045]FIG. 1 is a cross-sectional view of a tape guide post mechanism according to embodiment 1 of the present invention. FIG. 2 is a perspective view showing in detail the engagement between a hole and a shaft in the tape guide post mechanism according to embodiment 1. The structure and operation of a magnetic recording/reproducing apparatus which uses the tape guide post apparatus of embodiment 1 are the same as those of the above-described conventional magnetic recording/reproducing apparatus, except for the T3-arm  17  and relevant elements thereof. Thus, only the T3-arm  17  and the relevant elements thereof are described below with reference to FIGS. 1 and 2.  
         [0046]    In FIGS. 1 and 2, reference numeral  17  denotes the T3-arm, which is a post arm. Reference numeral  13  denotes a T3-post for guiding the tape  2 . The T3-post  13  is combined with the T3-arm  17 , so that they work as a single integral element. Reference numeral  26  denotes a hole formed in the T3-arm  17 . In this embodiment, the internal wall surface of the hole  26  is not a cylindrical shape but the shape of a square pole. Reference numeral  23   a  denotes a T3-arm shaft formed on the base  3 , the external side surface of which has a cylindrical shape. The T3-arm shaft  23   a  extends through the hole  26  of the T3-arm  17  and rotatably supports the T3-arm  17 . Reference numeral  21  denotes as top page ring for preventing the T3-arm  17  from being upwardly disengaged from the T3-arm shaft  23   a . In FIG. 2, the stop page ring  21  and the base  3  are omitted.  
         [0047]    An operation of the tape guide post mechanism of embodiment  1  having the above structure is described with reference to FIGS. 1 and 2.  
         [0048]    When the tape  2  is looped around the T3-post  13  so as to have a predetermined contact area therebetween which corresponds to a predetermined angular distance around the T3-post  13 , tape tension Ta is applied to the T3-post  13  as shown in FIG. 1. Due to tape tension Ta, a rotation moment is caused in the T3-post  13  in the direction of arrow M. Accordingly, the T3-arm  17  slightly rotates in the direction of arrow M as shown in FIG. 1. As a result, the external side surface of the T3-arm shaft  23   a  is in contact with the square, non-cylindrical internal wall surface of the hole  26  of the T3-arm  17  at four points, i.e., at upper contact points  24   a  and  24   b  and lower contact points  25   a  and  25   b  as shown in FIG. 2. Due to this four-point contact, the axial center line  28  of the hole  26  between the center of the upper opening of the hole  26  (“upper hole center  27   a ”) and the center of the lower opening of the hole  26  (“lower hole center  27   b ”) is kept at a constant slant with respect to the longitudinal axis of the T3-arm shaft  23   a.    
         [0049]    As described above, according to embodiment  1 , the external side surface of the T3-arm shaft  23   a  is a cylindrical shape, and the internal wall surface of the hole  26  of the T3-arm  17  is not a cylindrical shape but the shape of a square pole. Thus, when the axis of the T3-arm shaft  23   a  is slanted with respect to the longitudinal axis of the hole  26 , the T3-arm shaft  23   a  is in contact with the hole  26  of the T3-arm  17  at the two upper contact points and the two lower contact points. Due to such an arrangement, the occurrence of a jolt between the T3-arm shaft  23   a  and the hole  26  of the T3-arm  17  is avoided. Thus, a simply structured, inexpensive tape guide post mechanism can be realized, where a slant of the longitudinal center line of the T3-arm shaft  23   a  with respect to the longitudinal axis of the hole  26  of the T3-arm  17  rarely varies even in the presence of the attitude change or vibration of the magnetic recording/reproducing apparatus, a change in the running state of a tape, such as the running direction of the tape, the tape tension, or the like.  
         [0050]    (Embodiment 2)  
         [0051]    The structure and operation of a magnetic recording/reproducing apparatus which uses the tape guide post apparatus of embodiment 2 are the same as those of embodiment 1 and the above-described conventional magnetic recording/reproducing apparatus, except for the T3-arm  17  and relevant elements thereof. Thus, only the T3-arm  17  and the relevant elements thereof are described below with reference to FIGS. 3 and 4.  
         [0052]    [0052]FIG. 3 is a cross-sectional view of a tape guide post mechanism according to embodiment 2 of the present invention. FIG. 4 is a perspective view showing the details about engagement between a hole and a shaft in the tape guide post mechanism according to embodiment 2.  
         [0053]    In FIGS. 3 and 4, reference numeral  17  denotes the T3-arm, which is a post arm. Reference numeral  13  denotes a T3-post for guiding the tape  2 . The T3-post  13  is combined with the T3-arm  17 , so that they work as a single integral element. Reference numeral  26  denotes a hole formed in the T3-arm  17 , the internal wall surface of which is a cylindrical shape. Reference numeral  23   a  denotes a T3-arm shaft formed on the base  3 , the external side surface of which is not a cylindrical shape but rather the shape of a square pole. The T3-arm shaft  23   a  extends through the hole  26  of the T3-arm  17  and rotatably supports the T3-arm  17 . Reference numeral  21  denotes a stoppage ring for preventing the T3-arm  17  from being upwardly disengaged from the T3-arm shaft  23   a . In FIG. 4, the stop page ring  21  and the base  3  are omitted.  
         [0054]    An operation of the tape guide post mechanism of embodiment 2 having the above structure is described with reference to FIGS. 3 and 4.  
         [0055]    When the tape  2  is looped around the T3-post  13  so as to have a predetermined contact area therebetween which corresponds to a predetermined angular distance around the T3-post  13 , tape tension Ta is applied to the T3-post  13  as shown in FIG. 3. Due to tape tension Ta, a rotation moment is caused in the T3-post  13  in the direction of arrow M. Accordingly, the T3-arm  17  slightly rotates in the direction of arrow M as shown in FIG. 3. As a result, the external side surface of the T3-arm shaft  23   a  is in contact with the internal wall surface of the hole  26  of the T3-arm  17  at four points, i.e., at upper contact points  24   a  and  24   b  and lower contact points  25   a  and  25   b  as shown in FIG. 4. Due to this four-point contact, the axial center line  28  of the hole  26  between the center of the upper opening of the hole  26  (“upper hole center  27   a ”) and the center of the lower opening of the hole  26  (“lower hole center  27   b ”) is kept at a constant slant with respect to the longitudinal axis of the T3-arm shaft  23   a.    
         [0056]    As described above, according to embodiment 2, the external side surface of the T3-arm shaft  23   a  is not a cylindrical shape but the shape of a square pole, and the internal wall surface of the hole  26  of the T3-arm  17  has a cylindrical shape. Thus, when the axis of the T3-arm shaft  23   a  is slanted with respect to the longitudinal axis of the hole  26 , the T3-arm shaft  23   a  is in contact with the hole  26  of the T3-arm  17  at the two upper contact points and the two lower contact points. Due to such an arrangement, occurrence of jolt between the T3-arm shaft  23   a  and the hole  26  of the T3-arm  17  is avoided. Thus, a simply structured, inexpensive tape guide post mechanism, where slant of the longitudinal center line of the T3-arm shaft  23   a  with respect to the hole  26  of the T3-arm  17  is rarely varied even in the presence of the attitude change or vibration of the magnetic recording/reproducing apparatus, a change in the running state of a tape, such as the running direction of the tape, the tape tension, or the like, can be realized.  
         [0057]    In embodiment 1, the hole  26  of the T3-arm  17  has the shape of a square pole for the clarity of explanation, but the shape of the hole  26  is not limited thereto. The hole  26  may have any shape so long as the T3-arm shaft  23   a  is in contact with the hole  26  at at least two upper contact points and at least two lower contact points. For example, the hole  26  may have the shape of a hexagonal or other polygonal shaped pole.  
         [0058]    In embodiment 1, the upper and lower openings of the hole  26  have the same square shape. However, according to the present invention, it is not necessary to form the hole  26  such that the upper and lower openings have the same shape. FIG. 5 shows still another embodiment of the present invention. In FIG. 5, the upper opening of the hole  26  has a square shape, and the lower opening of the hole  26  has a hexagonal shape.  
         [0059]    In embodiment 2, the T3-arm shaft  23   a  has the shape of a square pole for the clarity of explanation, but the shape of the T3-arm shaft  23   a  is not limited thereto. The T3-arm shaft  23   a  may have any shape so long as the T3-arm shaft  23   a  is in contact with the hole  26  at at least two upper contact points and at least two lower contact points. For example, the T3-arm shaft  23   a  may have the shape of a hexagonal or other polygonal shaped pole.  
         [0060]    As described above, a simply structured, inexpensive tape guide post mechanism can be obtained, where slant of a tape guide post is not varied even in the presence of the attitude change or vibration of the magnetic recording/reproducing apparatus, a change in the running state of a tape, such as the running direction of the tape, the tape tension, or the like.  
         [0061]    Various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the scope and spirit of this invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the description as set forth herein, but rather that the claims be broadly construed.

Technology Classification (CPC): 6