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, and which guides running of the tape, and a hole; an arm shaft which engages with the hole and rotatable supports the post arm, wherein the arm shaft has an elastic portion which presses a portion of the post arm.

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 price 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, reference numeral  2  denotes a tape, which 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 the 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   c  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 T2-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 T1-post, which is one of the tape guide posts. The S2-post  9  and the T1-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 S2-post  9 , the T1-post  10 , and the T3-post  13 .  
           [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 S1-post  7  on the base  3 , and then, looped around the tension post  8  and the S2-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 FIGS. 8 and 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 center line  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.    
           [0016]    However, the above conventional structure involves some problems as described below with reference to FIGS. 8 and 9.  
           [0017]    Since the T3-post  13  is a constituent element of the tape running system, the slant of the T3-post  13  must be accurately determined. However, 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.  
           [0018]    Further, in the case where tape tension Ta is not sufficiently large with respect to the weights of the T3-arm  17  and the T3-post  13 , upper and lower contact points are sometimes formed at positions opposite to the upper contact point  30  and the lower contact point  31 , respectively, with respect to the hole center line  33 . That is, in some cases, the T3-arm shaft  23   a  comes in contact with the hole  17   a  at an upper contact point  30   a  and a lower contact point  31   a , as shown in FIG. 9, according to the attitude of the magnetic recording/reproducing apparatus.  
           [0019]    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.  
           [0020]    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. Thus, in the conventional tape guide mechanism, the variation of the slant of the tape guidepost (T3-post  13 ) cannot be decreased without decreasing the space  22  shown in FIG. 7.  
           [0021]    For example, in a practical product design, the hole  17   a  of the T3-arm  17  is formed at high accuracy so as to have a diameter of φ3.015 mm±0.005 mm, and the T3-arm shaft  23   a  is formed so as to have an outside diameter of φ3 mm±0.005 mm, such that the space  22  is minimized. In this case, the minimum space is 0.005 mm, and the maximum space is 0.025 mm. The variation of the slant of the T3-post  13  can be minimized by minimizing the space  22  even in the case where the upper contact point  30  and the lower contact point  31  greatly shift. However, the hole  17   a  and the T3-arm shaft  23   a  have to be formed at such a high accuracy in order to minimize the space  22 .  
           [0022]    In FIG. 8, reference mark L denotes an effective shaft length of the T3-arm shaft  23   a . In a general camcorder, effective shaft length L is about 4 mm. In the case where the maximum space of 0.025 mm is obtained, the maximum slant angle θ is represented by the following expression:  
           θ=tan −1 (0.025/4)=0.36° 
           [0023]    Thus, in this case, the slant of the T3-post  13  can vary by ±0.36° at a maximum only for the reason of the largeness of the space  22 . As a matter of course, the variation of the slant of the T3-post  13  can be reduced by increasing effective shaft length L, but in such a case, the size of the recording/reproducing apparatus increases.  
           [0024]    The variation of the slant of the T3-post  13  with respect to the hole  17   a , which is caused in a production process, is generally about ±0.16° even in a product which has met the requirement for slant in a total inspection process. The variation of a slant of the T3-arm shaft  23   a  with respect to the base  3 , which is caused in the production process, is also generally about ±0.16° even in a product which has met the requirement for slant in a total inspection process. Thus, the maximum value of the sum of these variations caused in the production process and the variation of the slant of the T3-post  13 , which is caused due to the space  22 , is:  
           (±0.36°)+(±0.16°)+(±0.16°)=±0.68°.  
           [0025]    Since a tape guide post of a VTR must generally be formed in an accurate fashion only with a small variation of about ±0.5°, each of the above tolerances cannot be increased any more. Thus, in addition to highly accurate production of each element, the total inspection must be performed solely for each element, while the total inspection must also be performed for each element in an assembled product in respect to the slant of the element.  
           [0026]    In summary, in a conventional tape guide post mechanism, a hole of a post arm (in this conventional example, the hole  17   a  of the T3-arm  17 ) must be formed so as to have an accurate inner diameter; an arm shaft (the T3-arm shaft  23   a ) must be formed so as to have an accurate diameter; the slant of a tape guide post (the T3-post  13 ) with respect to the hole of the post arm must be accurately controlled; and the slant of the arm shaft with respect to the base (the base  3 ) must be accurately controlled. Accordingly, the production cost for each of these elements increases. Further, the total inspection must be performed in respect to accuracy of the slant of each element, the diameter of a hole, the diameter of a shaft, etc. As a result, the number of production steps increases, and the production cost further increases. Furthermore, the longitudinal length of the arm shaft (effective shaft length L) cannot be decreased, so that the size of the recording/reproducing apparatus cannot be decreased.  
         SUMMARY OF THE INVENTION  
         [0027]    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, and which guides running of the tape, and a hole; an arm shaft which engages with the hole and rotatable supports the post arm, wherein the arm shaft has an elastic portion which presses a portion of the post arm.  
           [0028]    In one embodiment of the present invention, an external surface of the arm shaft comes in contact with the hole of the post arm at two points in an upper opening of the hole and at two points in a lower opening of the hole.  
           [0029]    In another embodiment of the present invention, the elastic portion and remainder of the arm shaft are made of different materials or parts.  
           [0030]    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, 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 the post arm has an elastic portion which presses an external surface of the arm shaft.  
           [0031]    In one embodiment of the present invention, the external surface of the arm shaft comes in contact with the hole of the post arm at two points in an upper opening of the hole and at two points in a lower opening of the hole.  
           [0032]    In another embodiment of the present invention, the elastic portion and remainder of the post arm are made of different materials or parts.  
           [0033]    According to the present invention, a small sized, inexpensive tape guide post mechanism, in which the slant of each element is accurately controlled, and which achieves a decrease in size of a magnetic recording/reproducing apparatus, can be obtained.  
           [0034]    According to the present invention, an elastic portion of an arm shaft presses a portion of a post arm, whereby a constant rotational moment is caused in the post arm. Due to this constant rotational moment, variations in the amount and direction of the slant of the tape guide post can be reduced. As a result, a small sized, inexpensive tape guide post mechanism, which has a simple structure, in which the slant of each element is accurately controlled, and which achieves decreases in size and cost of the magnetic recording/reproducing apparatus, can be obtained. Furthermore, if an elastic portion is formed in the arm shaft, it is not necessary to form an elastic portion in the post arm, and therefore, the post arm can be formed in a simple structure as can be in a conventional structure.  
           [0035]    According to the present invention, an elastic portion of a post arm presses an external surface of an arm shaft, whereby a constant rotational moment is caused in the post arm. Due to this constant rotational moment, variations in the amount and direction of the slant of the tape guide post can be reduced. As a result, a small sized, inexpensive tape guide post mechanism, which has a simple structure, in which the slant of each element is accurately controlled, and which achieves decreases in size and cost of the magnetic recording/reproducing apparatus, can be obtained. Furthermore, if an elastic portion is formed in the post arm, it is not necessary to form an elastic portion in the arm shaft, and therefore, an inexpensive, strong arm shaft can be formed from a simply structured shaft, such as a metal carved shaft or a header shaft.  
           [0036]    According to the present invention, an arm shaft or a post arm has an elastic portion. In addition, the arm shaft comes in contact with a hole of the post arm at two contact points in an upper opening of the hole and at two contact points in a lower opening of the hole. In such a structure, the post arm is rotatable around the arm shaft, while a jolt between the arm shaft and the hole, and a variation in the relative angle between the elements, are rarely caused. As a result, a small sized, inexpensive tape guidepost mechanism, which has a simple structure, in which the slant of each element is more accurately controlled, and which achieves decreases in size and cost of the magnetic recording/reproducing apparatus, can be obtained.  
           [0037]    Thus, the invention described herein makes possible the advantages of providing a small sized, inexpensive tape guide post mechanism for use in a magnetic recording/reproducing apparatus, which has a simple structure, in which the slant of each element is accurately controlled, and which achieves decreases in size and cost of the magnetic recording/reproducing apparatus.  
           [0038]    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  
       [0039]    [0039]FIG. 1 is a cross-sectional view of an exploded tape guide post mechanism according to embodiment 1 of the present invention.  
         [0040]    [0040]FIG. 2 is a cross-sectional view of the tape guide post mechanism according to embodiment 1.  
         [0041]    [0041]FIG. 3 is a cross-sectional view of an exploded tape guide post mechanism according to embodiment 2 of the present invention.  
         [0042]    [0042]FIG. 4 is a cross-sectional view of the tape guide post mechanism according to embodiment 2.  
         [0043]    [0043]FIG. 5 is a perspective view showing the details about engagement between a hole and a shaft in a tape guide post mechanism according to embodiment 3 of the present invention.  
         [0044]    [0044]FIG. 5A is a top view showing the details about engagement between a hole and a shaft in a tape guide post mechanism according to embodiment 3.  
         [0045]    [0045]FIG. 6 is a plan view of a magnetic recording/reproducing apparatus which uses a conventional tape guide post mechanism.  
         [0046]    [0046]FIG. 7 is a cross-sectional view showing a T3-arm of the conventional tape guide post mechanism.  
         [0047]    [0047]FIG. 8 is a cross-sectional view showing the state of a T3-arm when a tape tension is applied to the T3-arm.  
         [0048]    [0048]FIG. 9 is a perspective view showing the details about engagement between a hole of a T3-arm and a T3-arm shaft. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0049]    (Embodiment 1).  
         [0050]    Hereinafter, embodiment 1 of the present invention will be described with reference to FIGS. 1 and 2.  
         [0051]    [0051]FIG. 1 is a cross-sectional view of an exploded tape guide post mechanism according to embodiment 1 of the present invention. FIG. 2 is a cross-sectional view of 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 mechanism 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.  
         [0052]    In FIG. 1, reference numeral  17  denotes the T3 -arm, which is a post arm. The T3-arm  17  has a T3-post  13 , which is one of the constituent elements of a tape running system. A T3-arm shaft  23   a  is made of a resin and fixed to a base  3 . Reference numeral  23   d  denotes an elastic portion, which is formed integrally with the T3-arm shaft  23   a . The elastic portion  23   d  has a claw  23   b . Reference numeral  23   e  denotes a tip portion of the claw  23   b , and reference numeral  23   f  denotes a lower face portion of the claw  23   b . Reference numeral  17   a  denotes a hole formed in the T3-arm  17 . In embodiment 1, the internal surface of the hole  17   a  has a cylindrical shape, but the present invention is not limited thereto. Reference numeral  17   c  denotes a step in the hole  17   a , and reference numeral  17   d  denotes an abutment portion in the hole  17   a . FIG. 1 shows the exploded tape guidepost mechanism. The T3-arm  17  is moved in the direction indicated by arrow A of FIG. 1 until the T3-arm  17  is mounted on the T3-arm shaft  23   a in place as shown in FIG. 2.  
         [0053]    An operation of the tape guide post mechanism of embodiment  1  having the above structure is described with reference to FIG. 2.  
         [0054]    In FIG. 2, the T3-arm shaft  23   a  extends through the hole  17   a  of the T3-arm  17  so as to rotatably support the T3-arm  17 . The lower face portion  23   f  of the claw  23   b  abuts the step  17   c  so that the T3-arm  17  is prevented from disengaging upwardly from the T3-arm shaft  23   a . In the meantime, the elastic portion  23   d  is elastically deformed, and the tip portion  23   e  of the claw  23   b  abuts the abutment portion  17   d  of the T3-arm  17 , such that the tip portion  23   e  presses the abutment portion  17   d  in a direction denoted by an arrow Tb. That is, a pressure Tb is applied to the T3-arm  17  in a radial direction of the T3-arm shaft  23   a , so that a rotation moment represented by an arrow M 1  is constantly applied to the T3-arm  17 . If the rotation moment represented by the arrow M 1  is sufficiently large with respect to variations in external forces, such as the weight of the T3-arm  17 , the tape tension, etc., the amount and direction of slant of the T3-post  13  can be kept constant even in the presence of the attitude change 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.  
         [0055]    As described above, according to embodiment 1 of the present invention, the elastic portion  23   d  of the T3-arm shaft  23   a  presses the abutment portion  17   d  of the T3-arm  17  in a radial direction of the T3-arm shaft  23   a , so that a jolt between the hole  17   a  of the T3-arm  17  and the T3-arm shaft  23   a  is counteracted in a predetermined direction. As a result, a variation of the slant of the T3-post  13 , which may be ±0.36° at a maximum in the conventional example, is decreased to about 0°. Thus, for example, the finishing accuracy of the internal diameter of the hole of the post arm (in embodiment 1, the hole  17   a  of the T3-arm  17 ) can be decreased; the finishing accuracy of the diameter of the arm shaft (the T3-arm shaft  23   a ) can be decreased; the accuracy of the slant of the tape guide post (the T3-post  13 ) with respect to the hole of the post arm can be decreased; or the accuracy of the slant of the arm shaft with respect to the base  3  can be decreased. Therefore, each of the parts of the recording/reproducing apparatus can be produced at a lower cost.  
         [0056]    Furthermore, the total inspection steps performed for the slant of each element, the accuracy of the diameter of each hole, and the accuracy of the diameter of each shaft can be omitted. Thus, the number of production steps can be decreased, and accordingly, the production cost can be decreased. Furthermore, even when the shaft length of the arm shaft (in embodiment 1, effective shaft length L) is decreased, the variation of the slant of the tape guide post (the T3-post  13 ) does not significantly increase. Thus, the size of the recording/reproducing apparatus can be decreased.  
         [0057]    In embodiment 1, as described above, the elastic portion  23   d  and the claw  23   b  are formed integrally with the T3-arm shaft  23   a  from the same material. However, according to the present invention, the elastic portion  23   d  and the claw  23   b  may be formed of a material different from that of the T3-arm shaft  23   a , or may be formed as separate parts from the T3-arm shaft  23   a.    
         [0058]    In embodiment 1, as described above, the elastic portion  23   d  of the T3-arm shaft  23   a  presses the T3-arm  17  in a radial direction of the T3-arm shaft  23   a . However, according to the present invention, the elastic portion  23   d  may press the T3-arm  17  in a direction different from a radial direction of the T3-arm shaft  23   a . For example, the elastic portion  23   d  may press the T3-arm  17  in a thrust direction, so that a rotation moment is generated in the T3-arm  17 , and accordingly, a jolt between the hole  17   a  of the T3-arm  17  and the T3-arm shaft  23   a  is counteracted in a predetermined direction.  
         [0059]    (Embodiment 2)  
         [0060]    Hereinafter, embodiment 2 of the present invention will be described with reference to FIGS. 3 and 4.  
         [0061]    [0061]FIG. 3 is a cross-sectional view of an exploded tape guide post mechanism according to embodiment 2 of the present invention. FIG. 4 is a cross-sectional view of the tape guide post mechanism according to embodiment 2.  
         [0062]    In FIG. 3, the T3-arm  17  is made of a resin, and has a T3-post  13 . The T3-post  13  is one of the constituent elements of a tape running system. Reference numeral  17   b  denotes an elastic portion, which is formed integrally with the T3-arm  17  in the hole  17   a of the T3-arm  17 . The elastic portion  17   b  has an abutment portion  17   e  at the tip thereof. Reference numeral  17   c  denotes a step formed in the hole  17   a . A T3-arm shaft  23   a  is made of a resin and fixed to a base  3 . Reference numeral  23   d  denotes an elastic portion, which is formed integrally with the T3-arm shaft  23   a . The elastic portion  23   d  has a claw  23   b . Reference numeral  23   e  denotes a tip portion of the claw  23   b , and reference numeral  23   f  denotes a lower face portion of the claw  23   b . FIG. 3 shows the exploded tape guide post mechanism. The T3-arm  17  is moved in the direction indicated by arrow A of FIG. 3 until the T3-arm  17  is mounted on the T3-arm shaft  23   a  in place as shown in FIG. 4.  
         [0063]    An operation of the tape guide post mechanism of embodiment 2 having the above structure is described with reference to FIG. 4.  
         [0064]    In FIG. 4, the T3-arm shaft  23   a  extends through the hole  17   a  of the T3-arm  17  so as to rotatably support the T3-arm  17 . The lower face portion  23   f  of the claw  23   b  abuts the step  17   c  so that the T3-arm  17  is prevented from disengaging upwardly from the T3-arm shaft  23   a . In the meantime, the elastic portion  17   b  is elastically deformed, and the abutment portion  17   e  abuts the external surface of the T3-arm shaft  23   a , such that the abutment portion  17   e  presses the T3-arm shaft  23   a  with force Tc in a radial direction of the T3-arm shaft  23   a.    
         [0065]    As a result, reaction force Td is generated at the abutment portion  17   e . As a matter of course, the magnitude of force Tc is equal to that of reaction force Td (Tc=Td). Thus, due to reaction force Td, a rotation moment indicated by an arrow M 2  is constantly caused in the T3-arm  17 . If the rotation moment represented by the arrow M 2  is sufficiently large with respect to variations in external forces, such as the weight of the T3-arm  17 , the tape tension, etc., the amount and direction of slant of the T3-post  13  can be kept constant even in the presence of the attitude change 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.  
         [0066]    As shown in FIG. 4, in embodiment 2, the tip portion  23   e  of the claw  23   b  does not abut the T3-arm  17 . That is, the elastic portion  17   b  does not press the T3-arm shaft  23   a  in the radial direction.  
         [0067]    As described above, according to embodiment 2 of the present invention, the elastic portion  17   b  of the T3-arm  17  presses the T3-arm shaft  23   a  in a radial direction, so that a jolt between the hole  17   a  of the T3-arm  17  and the T3-arm shaft  23   a  is counteracted in a predetermined direction. As a result, a variation of the slant of the T3-post  13 , which may be ∓0.36° as a maximum in the conventional example, is decreased to about 0°. Thus, as achieved in embodiment 1, a small sized, inexpensive tape guide post mechanism, which has a simple structure, in which the slant of each element is accurately controlled, and which achieves decreases in size and cost of the magnetic recording/reproducing apparatus, is provided.  
         [0068]    In embodiment 2, as described above, the elastic portion  17   b  and the abutment portion  17   e  are formed integrally with the T3-arm  17  from the same material. However, according to the present invention, the elastic portion  17   b  and the abutment portion  17   e  may be formed of a material different from that of the T3-arm  17 , or may be formed as separate parts from the T3-arm  17 .  
         [0069]    In embodiment 2, as described above, the elastic portion  17   b  of the T3-arm  17  presses the T3-arm shaft  23   a  in a radial direction of the T3-arm shaft  23   a . However, according to the present invention, the elastic portion  17   b  may press the T3-arm shaft  23   a  in a direction different from a radial direction of the T3-arm shaft  23   a . For example, the elastic portion  17   b  may press the T3-arm shaft  23   a  in a thrust direction, so that a rotation moment is generated in the T3-arm  17 , and accordingly, a jolt between the hole  17   a  of the T3-arm  17  and the T3-arm shaft  23   a  is counteracted in a predetermined direction.  
         [0070]    In embodiment 2, as described above, the tip portion  23   e  of the claw  23   b  does not abut the T3-arm  17 , i.e., the elastic portion  17   b  does not press the T3-arm shaft  23   a  in the radial direction. However, according to the present invention, as described in embodiment 1, the tip portion  23   e  of the claw  23   b  may be structured so as to come in contact with the T3-arm  17 , such that the elastic portion  17   b  presses the T3-arm shaft  23   a  in the radial direction. With such an arrangement, a rotation moment again can be caused in the T3-arm  17  in the direction indicated by the arrow M 2 .  
         [0071]    In embodiment 2, as described above, the elastic portion  17   b  may be formed in the hole  17   a  of the T3-arm  17 . However, according to the present invention, the elastic portion  17   b  maybe formed at a different position integrally with the T3-arm  17 , such that the elastic portion  17   b  presses the T3-arm shaft  23   a  in a radial direction.  
         [0072]    (Embodiment 3)  
         [0073]    [0073]FIG. 5 is a perspective view showing the details of engagement between a hole and a shaft in a tape guide post mechanism according to embodiment 3 of the present invention. Details of the structure and operation of the tape guide post mechanism of embodiment 3, which are the same as those of embodiment 1, are not described in this section, but only the different features are described below with reference to FIG. 5.  
         [0074]    In FIG. 5, the elastic portion  23   d  of the T3-arm shaft  23   a , which was described in embodiment 1, is not shown for clarity of illustration, but the elastic portion  23   d  of embodiment 3 has the same structure as that of embodiment 1. In FIG. 5, reference numeral  26  denotes a hole formed in the T3-arm  17 . Although, in embodiment 1, the internal surface of the hole of the T3-arm  17  (hole  17   a ) has a cylindrical shape, the internal surf ace of the hole  26  according to embodiment 3 has the shape of a rectangular prism. The T3-arm shaft  23   a  extends through a rectangular hole  26  of the T3-arm  17  so as to rotatably support the T3-arm  17 . The step  17   a  provided for preventing the T3-arm  17  from disengaging upwardly from the T3-arm shaft  23   a  is not shown in FIG. 5. As in embodiment 1, due to the elastic portion  23   d  (not shown in FIG. 5), a rotation moment is caused in the T3-arm  17  in a direction indicated by an arrow M 3  (coming somewhat up and out of the page). Reference numerals  24   a  and  24   b  are two upper contact points between the T3-arm shaft  23   a  and the hole  26  of the T3-arm  17 . Reference numerals  25   a  and  25   b  are two lower contact points between the T3-arm shaft  23   a  and the hole  26  of the T3-arm  17 . That is, the T3-arm shaft  23   a  comes in contact with the hole  26  of the T3-arm  17  at these four contact points including the two upper contact points  24   a and  24   b and the two lower contact points  25   a  and  25   b  as shown in FIG. 5. Even in this state, the T3-arm  17  is rotatable around the T3-arm shaft  23   a . In the structure of embodiment 3, even in the presence of the attitude change 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, the T3-arm shaft  23   a  comes in contact with the hole  26  of the T3-arm  17  always at the four contact points  24   a ,  24   b ,  25   a , and  25   b , and the four contact points  24   a ,  24   b ,  25   a , and  25   b  never shift. Thus, the amount and direction of the slant of the T3-post  13  are always maintained to be constant. Accordingly, with such a feature, variations in the amount and position of a center line  28  of the hole  26 , which connects 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 ”), are further reduced as compared with those of embodiment 1.  
         [0075]    [0075]FIG. 5A is a top view showing the details about engagement between a hole and a shaft in a tape guide post mechanism according to embodiment 3.  
         [0076]    As described above, according to embodiment 3 of the present invention, the external surface of the T3-arm shaft  23   a  comes in contact with the hole  26  at the two upper contact points  24   a  and  24   b  and the two lower contact points  25   a and  25   b . In such a structure, a variation in the slant of the T3-post  13  is further reduced as compared with those of embodiment 1. Therefore, a tape guide post mechanism where the slant of the T3-post  13  is accurately controlled can be obtained.  
         [0077]    In embodiment 3, 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.  
         [0078]    Furthermore, in embodiment 3, corners  40   a ,  40   b ,  40   c , and  40   d  of the upper opening of the hole  26  are not necessary so long as at least two contact points are secured. This also applies to the lower opening of the hole  26 .  
         [0079]    Furthermore, in embodiment 3, sides  41   a ,  41   b ,  41   c , and  41   d  of the upper opening of the hole  26  are not necessary to be linear so long as at least two contact points are secured. This also applies to the lower opening of the hole  26 .  
         [0080]    In embodiment 3, 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.  
         [0081]    In the above description, the above-described feature of embodiment 3 is added to the features of embodiment 1. However, the above-described feature of embodiment 3 may be added to the features of embodiment 2.  
         [0082]    As described above, according to the present invention, the slant of the tape guidepost for guiding running of the magnetic tape can be controlled in a highly accurate manner by a simple mechanism. Thus, a small sized, inexpensive tape guide post mechanism, which achieves a decrease in size of the magnetic recording/reproducing apparatus, can be obtained.  
         [0083]    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.