Magnetic recording/playback apparatus

Abstract: The invention is concerned with a magnetic recording/playback apparatus in which a magnetic tape is paid out from a tape cassette and wound around a cylindrical rotary head cylinder, having a rotary head built therein, over a predetermined angle to record/playback signals through the rotary head, and more particularly, with a tape guide post driving mechanism, a pinch roller pressing mechanism and a tension servo mechanism. Specifically, the invention provides a tape guide post driving device which can reduce the size, weight and thickness of the apparatus by ensuring a large angle of rotation of a rotating member, which includes a tension arm, in a direct manner. Also, the invention realizes a pinch roller pressing mechanism in which a sufficient stroke can be obtained even when a cam gear is reduced in its diameter and can provide a sufficient stroke even with a small amount of rotation. Further, the invention prolongs the service life and achieves a remarkable reduction in both the number of parts used and the number of assembling steps by using a pad brake (brake member), instead of a band brake, for braking a rotating member and bringing the brake member into full contact over the former's entire surface with the member being braked.

Description: The present invention relates to a tape guide post driving mechanism. DESCRIPTION OF THE PRIOR ART In a conventional magnetic recording/playback apparatus such as VTR, a cam groove for a cam gear adapted to turn a tension arm is generally formed by utilizing a swing cam. Because this arrangement entails a difficulty in enlarging an angle of turn of the tension arm, it has been required to increase the turn angle through another arm. A tension post driving mechanism in the prior art will be described below with reference to the drawings. Figs. 24 and 25, respectively, show states, in which a tension post is stored in a cassette, and is in a tape running position. When a tape is withdrawn out of a tape cassette in Figs. 24 and 25, driving force of a loading motor 30 is transmitted to a cam gear 34 through a dual gear comprising gears 31a, 31b, a dual gear comprising gears 32a, 32b, and a dual gear comprising gears 33a, 33b. The cam gear 34 comprises a swing cam in such a manner that as a cam engagement portion 91a of a cam lever 91 moves along a cam groove 34a defined in the cam gear 34 from a position near the center of the cam gear 34 toward the outer periphery, a speed-up gear portion 91b of the cam lever 91 is rotated to turn a tension arm 90 to a large extent so that a tension post 9 is turned to a tape running position shown in Fig. 25. When the tension post 9 turns to the tape running position, the cam engagement portion 91a of the cam lever 91 becomes free from the cam groove 34a and, thereafter, the cam lever 91 is balanced by the braking force of a tension band 98 wound around the circumference of a reel stand 99, spring force of a tension spring 92, and tensile force of a magnetic tape wound around the tension post 9, thereby controlling a tape tension. However, when the tension post is moved to at least two predetermined positions, the above conventional arrangement has suffered from such a first problem to be solved by the present invention that the cam lever 91 is needed as a separate member in order to obtain a large angle of turn of the tension arm 90 and, since the cam groove 34a of the cam gear 34 is formed to extend from a position near the center of the cam gear 34 to a position near the outer periphery, it is difficult to form another cam groove for a different purpose, which is problematic in reducing the size, weight and thickness of a magnetic recording/playback apparatus. EP-A- 0 087 952 discloses a tape guide post driving device having no separate can lever. SUMMARY OF THE INVENTION To solve the above-mentioned first problem, the present invention has its object to provide a tape guide post driving device which can ensure a large angle of rotation of a rotating member, including a tension arm, in a direct manner, and can reduce the size, weight and thickness of the VTR. To solve the above first problem, a tape guide post driving device as defined in claim 1 is provided. With that arrangement, an angle of rotation, through which the rotating member including the tension arm is moved to at least two predetermined positions, can be directly made large, and the need of increasing the angle of rotation of the rotating member through a separate member is eliminated. Further, since the cam can be formed by only a region near the outer periphery of the cam gear, a region in the vicinity of the center can be used for another cam. Thus, the above arrangement remarkably contributes to reduction of the size, weight and thickness of the magnetic recording/playback apparatus. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a top plan view of a tape guide post driving device in a magnetic recording/playback apparatus according to one embodiment of the present invention before a tape loading operation. Fig. 2 is a top plan view of the tape guide post driving device in the magnetic recording/playback apparatus according to one embodiment of the present invention after the tape loading operation. Fig. 3 is a schematic top plan view for explaining a running path of a magnetic tape established by the tape guide post driving device. Fig. 4 is a perspective view for explaining the running path of the magnetic tape established by the tape guide post driving device. Fig. 5 is a perspective view showing principal parts of a loading post driving device in Fig. 1. Fig. 6 is a perspective view showing principal parts of the loading post driving device. Fig. 7A is a top plan view of a cam gear in the loading post driving device. Fig. 7B is a cross-sectional view of the cam gear in the loading post driving device. Fig. 7C is a bottom view of the cam gear in the loading post driving device. Fig. 8 is a top plan view showing a state where boats are guided along loading guides immediately after starting the tape loading operation in the loading post driving device. Fig. 9 is an explanatory view showing one state of a drive gear train in a process of the tape loading operation in the loading post driving device. Fig. 10 is an explanatory view showing another state of a drive gear train in a process of the tape loading operation in the loading post driving device. Fig. 11 is a cross-sectional view showing an arrangement of a swing plate in the loading post driving device. Fig. 12 is a top plan view showing an operation in which a pinch arm is driven by a cam gear in the tape guide post driving device. Fig. 12A is a top plan view of first and second pinch charge arms. Fig. 13 is a top plan view showing the operation in which the pinch arm is driven by the cam gear in the tape guide post driving device. Fig. 14 is a top plan view showing the operation in which the pinch arm is driven by the cam gear in the tape guide post driving device. Fig. 15A is a top plan view showing an operation of an auxiliary guide post in the tape guide post driving device. Fig. 15B is a top plan view showing an operation of an auxiliary guide post in the tape guide post driving device. Fig. 16 is a view showing a principal arrangement of the tape guide post driving device before the tape loading operation. Fig. 17 is a view showing a principal arrangement of the tape guide post driving device after the tape loading operation. Fig. 18 is an enlarged view showing principal parts of the tape guide post driving device. Fig. 19 is an enlarged view showing principal parts of the tape guide post driving device. Fig. 20 is an enlarged view showing principal parts of the tape guide post driving device. Fig. 21 is an enlarged view showing principal parts of the tape guide post driving device. Fig. 22 is an enlarged view showing principal parts of the tape guide post driving device. Fig. 23 is an enlarged view showing principal parts of the tape guide post driving device. Fig. 24 is a view showing a principal arrangement of a tape guide post driving device in a prior art magnetic recording/playback apparatus before the tape loading operation. Fig. 25 is a view showing a principal arrangement of the tape guide post driving device in the prior art magnetic recording/playback apparatus after the tape loading operation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A first embodiment of the present invention will be described hereinafter with reference to the drawings. Figs. 1 and 2 are top plan views of a tape guide post driving device in a magnetic recording/playback apparatus according to a first embodiment of the present invention before and after an operation of loading a magnetic tape, respectively, Fig. 3 is a schematic top plan view for explaining a running path of the magnetic tape in the tape guide post driving device, Fig. 4 is a perspective view showing a principal section of the running path, and Figs. 5 and 6 are perspective views showing principal parts of the tape guide post driving device. First, an operation of a loading post will be briefly explained by referring to Figs. 1 to 4. In Figs. 3 and 4, denoted by the reference numeral 1 is a chassis and 2 is a tape cassette charged on the chassis 1. A supply reel 3 and a take-up reel 4 are provided in the tape cassette 2. When the tape cassette 2 is charged on the chassis 1, a loading roller post 8 at the supply side, a tension post 9 and an inclined post 16; first and second loading roller posts 10, 11 at the take-up side; and a pinch roller 12 and an auxiliary guide post 23 are positioned inside of a magnetic tape 13 and in recessed portions 5, 6, 7 formed in the front surface of the tape cassette 2, respectively. Denoted by the reference numerals 14, 15 are a boat at the supply side and a boat at the take-up side on which the supply side loading roller post 8 and the take-up side first and second loading roller posts 10, 11 are mounted upwardly, respectively. The supply side boat 14 is also provided with the inclined post 16, in addition to the supply side loading roller post 8, the inclined post 16 being inserted into the recessed portion 5 along with the supply side loading roller post 8. Denoted by the reference numeral 17, 18 are an arc shape loading guide at the supply side and an arc shape loading guide at the take-up side both disposed along the circumference of a rotary head cylinder 19 as shown in Figs. 1 and 2, the guides 17, 18 operating to guide the supply side boat 14 and the take-up side boat 15 during an operation of loading the magnetic tape 13, respectively. As shown in Fig. 5, the supply side loading guide 17 is arranged in such a manner that it becomes higher as it comes nearer to a position where the tape loading operation is completed, and the take-up side loading guide 18 is arranged in such a manner that it becomes lower as it comes nearer to a position where the tape loading operation is completed. The rotary head cylinder 19 is attached substantially vertically with respect to the chassis 1. When the supply side boat 14 is moved along the supply side loading guide 17, the supply side loading roller post 8 winds the magnetic tape 13 withdrawn out of the supply reel 3 around the rotary head cylinder 19 in a direction extending obliquely upwardly toward the left side as viewed in Fig. 4. When the take-up side boat 15 is moved along the take-up side loading guide 18, the take-up side loading roller post 10 winds the magnetic tape 13 withdrawn out of the take-up reel 4 around the rotary head cylinder 19 in a direction extending obliquely downwardly toward the right side as viewed in Fig. 4. At this time, the supply side loading roller post 8 is in a posture of being inclined slightly backward at the position where the tape loading operation is completed, because of the slope of the loading guide 17 which becomes gradually higher toward that loading terminal position; and the take-up side first and second loading roller posts 10, 11 are in postures of being inclined slightly forwardly at the other position where the tape loading operation is completed, because of the slope of the loading guide 17 which becomes gradually lower toward that other loading terminal position. Thus, as shown in Fig. 4, the magnetic tape 13 which is supplied to the rotary head cylinder 19 by means of the supply side loading roller post 8 is introduced from the upper portion of the rotary head cylinder 19 obliquely downwardly toward the lower portion thereof. At a position where the magnetic tape 13 leaves from the rotary head cylinder 19, the magnetic tape 13 is turned so as to be introduced along a gently sloped path of the tape extending obliquely upwardly from the lower portion of the cylinder 19 through the take-up side first loading roller post 10. While being maintained to be slightly inclined forwardly by the take-up side second loading roller post 11, the magnetic tape 13 is introduced obliquely upwardly along the gently sloped path. Denoted by the reference numeral 20 is a capstan provided on the chassis 1 outside a location where the tape cassette 2 is to be charged, the capstan 20 being supported at its upper and lower ends by bearings 21 and attached to the chassis 1 such that it is inclined relative to the chassis at an angle substantially equal to those of the take-up side loading roller posts 10, 11 at the loading terminal position. The inclined capstan 20 is brought into full contact with the magnetic tape 13 over is entire width which is introduced obliquely upwardly from the take-up side loading roller post 11 along the sloped path and is inclined forwardly. At the completion of the tape loading operation, the capstan 20 is in press-contact with the pinch roller 12 which is moved from the position of the recessed portion 7 of the tape cassette 2 so that the magnetic tape 13 is held between the capstan 20 and the pinch roller 12 to be driven. Incidentally, the pinch roller 12 is arranged to have an inclination at the same angle as that of the capstan 20 in order to be in full contact with the capstan 20 over entire width of the tape. Denoted by the reference numeral 22 is an audio-control head provided at a location in the vicinity of the capstan 20 between the take-up side second loading roller post 11 at the loading terminal position and the capstan 20. The audio-control head 22 is attached to the chassis 1 in such a manner that it is inclined at the same angle as that of the capstan 20 in order to facilitate contact between the audio-control head 22 and the magnetic tape 13 which is inclined forwardly and introduced obliquely upwardly along the sloped path from the take-up side second loading roller post 11 to the capstan 20. Denoted by the reference numeral 23 is an auxiliary guide post which moves in an interlocking relationship with the pinch roller 12 such that it is positioned in the recessed portion 7 of the tape cassette 2 before starting the tape loading operation, and it moves together with the pinch roller 12 at the completion of the tape loading operation, thereby guiding the magnetic tape 13 traveling between the capstan 20 and the pinch roller 12 to take the same toward a fixed inclined post 24. As regards the magnetic tape 13 fed from the take-up side second loading roller post 11 through the capstan 20 and the auxiliary guide post 23 while maintaining the forwardly-inclined posture, torsion of the magnetic tape 13 generated when the tape travels from the sloped path into a horizontally running path is corrected by the fixed inclined post 24 which is slantingly attached to the chassis 1 before the magnetic tape 13 reaches the tape cassette 2, then permitting the magnetic tape 13 to be wound around the take-up reel 4 of the tape cassette 2. Denoted by the reference numeral 25 is a capstan motor for driving the capstan 20, the motor 25 being inclinedly fixed to the chassis 1. With such an arrangement, it becomes unnecessary to provide the capstan 20 below the position where the tape cassette 2 is to be charged. Therefore, a thickness of the chassis 1 is restricted, so that it is readily possible to realize a thin magnetic recording/playback apparatus. Next, the description concerning a driving mechanism for the loading posts in the magnetic recording/playback apparatus according to one embodiment of the present invention will be given below. Referring again to Fig. 1, the driving force of a loading motor 30 is transmitted to a cam gear 34 through a dual gear comprising gears 31a, 31b, a dual gear comprising gears 32a, 32b and a dual gear comprising gears 33a, 33b. As shown in Figs. 7A, 7B and 7C, the cam gear 34 is formed in its upper half with a first intermittent gear portion 35 which has a non-toothed portion 35a in its part and is meshed with the gear 33b to transmit the driving force of the loading motor 30, and in its lower half with a second intermittent gear portion 36 which has a non-toothed portion 36a in its part and is used for transmitting the driving force to the loading roller posts 10, 11 through a take-up side ring gear 39. As described above, the first intermittent gear section 35 has the non-toothed portion 35a which is provided to have a part of a tension regulator arm 90, which is adapted to move the tension post 9 during the tape loading operation, abut against a cam wall 37c provided on the first intermittent gear portion 35. Insofar as the tension regulator arm 90 can be controlled by any other means, the first intermittent gear portion 35 may be in the form of a full-toothed gear of which teeth are formed on the entire outer periphery. Furthermore, a cam portion 37 is formed on the top surface of the cam gear 34 and used for controlling the pinch roller 12 to press-contact with or separate from the capstan 20. Since the first and second intermittent gear portions 35, 36 and the cam portion 37 are integrally formed into the cam gear 34 as one piece, the thickness of the cam gear 34 can be reduced. The mechanism for driving the loading roller posts 8, 10, 11 by the second intermittent gear portion 36 of the cam gear 34 will now be described with reference to Fig. 9 which is a top plan view of a gear train. Denoted by the reference numeral 38 is a ring gear at the supply side for driving the supply side loading roller post 8 and 39 is a ring gear at the take-up side for driving the take-up side loading roller posts 10, 11, these ring gears 38, 39 being provided below the rotary head cylinder 19 in such a manner that the center points of rotation of the ring gears are offset from each other. A toothed section 40 extending over a predetermined range on the outer periphery of the take-up side ring gear 39 is arranged so as to mesh with the second intermittent gear portion 36 of the cam gear 34. There are respectively provided first and second non-toothed portions 40a and 40b at intermediate and rear end portions of the toothed section 40 when viewed in a direction of an arrow a which corresponds to a direction of rotation of the ring gear 39 during loading the magnetic tape, the first and second non-toothed portions being capable of engaging with or disengaging from terminal ends 36a and 36b of the second intermittent gear portion 36 for the purpose of ensuring the start-up of the loading operation. A toothed section 41 extending over a predetermined range on the outer periphery of the supply side ring gear 38 is cooperatingly connected with the toothed section 40 of the supply side ring gear 39 through an intermediate gear 42, one gear 43a of a dual pendulum gear 43 held in mesh with the intermediate gear 42, and the other gear 43b of the pendulum gear 43. The intermediate gear 42 and the pendulum gear 43 are pivotally mounted on a swing plate 45 which is swingably attached at its one end to a shaft 44 provided on the chassis 1. A shaft 47 which is mounted upright on the chassis 1 is fitted into an elongated opening 46 formed at the other end of the swing plate 45 in order to control swinging movement of the plate 45. Also as seen from a cross-sectional view of Fig. 11, the pendulum gear 43 is provided integrally with a plate 43c. Denoted by the reference numeral 49 is a charge arm turnably supported by a shaft 48 which is mounted upright on the swing plate 45, with a torsion coil spring 50 fitted around the outer circumference of the shaft 48. The torsion coil spring 50 has one end secured to the charge arm 49 and the other end secured to a bent portion 45a of the swing plate 45. As a result, the charge arm 49 is always urged to turn in a direction of an arrow A in Fig. 9. Denoted by the reference numeral 51 is a link which has one end rotatably connected with the plate 43c by a pin 51a and the other end rotatably connected with the charge arm 49 by a pin 51b. With such an arrangement, the pendulum gear 43 is always urged through the link 51 to rotate in a direction of an arrow B in Fig. 9. It is needless to say that while the pendulum gear 43 is making one rotation, the charge arm 49 performs reciprocal swinging movement about the shaft 48. The supply side ring gear 38 is provided with a fixed arm 52 at the front end of the toothed section 41 thereof when viewed in a direction of an arrow b which corresponds to a direction of rotation of the ring gear 38 during loading the magnetic tape. The fixed arm 52 has a drive shaft 53 at the supply side which is mounted upright at the distal end portion of the fixed arm 52. The take-up side ring gear 39 is provided with a fixed arm 54 at the front end of the toothed section 40 thereof when viewed in the direction of the arrow a which corresponds to the direction of rotation of the ring gear 39 during loading the magnetic tape. The fixed arm 54 has a drive shaft 55 at the take-up side which is mounted upright at the distal end portion of the fixed arm 54. As will be seen from Fig. 5, the supply side boat 14 is vertically movable attached to the supply side drive shaft 53. The supply side boat 14 includes at its rear end a holder portion 57 adapted to engage with a stepped portion 17a provided along the outer periphery of the supply side loading guide 17. The holder portion 57 has a pair of claws 57a adapted to engage with the lateral face of the stepped portion 17a. Thus, the supply side boat 14 is guided along the supply side loading guide 17. Likewise, as will be seen from Figs. 5 and 6, the take-up side boat 15 is vertically movably attached to the take-up side drive shaft 55. The take-up side boat 15 includes at its rear end a holder portion 59 adapted to engage with a stepped portion 18a provided along the outer periphery of the take-up side loading guide 18. The holder portion 59 has a pair of claws 59a adapted to engage with the lateral face of the stepped portion 18a. Thus, the take-up side boat 15 is guided along the take-up side loading guide 18. The supply side drive shaft 53 and the take-up side drive shaft 55 are designed so as to move along the outer peripheries of the supply side loading guide 17 and the take-up side loading guide 18, each having an arc shape, when the supply side ring gear 38 and the take-up side ring gear 39 rotate in the direction of the arrow b and in the direction of the arrow a during loading the magnetic tape, respectively. In this way, the supply side boat 14 and the take-up side boat 15 are guided stably without disengaging from the outer peripheries of the supply side loading guide 17 and the take-up side loading guide 18, respectively, in course of the loading operation of the tape. Moreover, the supply side boat 14 is forced to gradually rise higher as it comes nearer to the loading terminal position, while the take-up side boat 15 is forced to be gradually lowered as it comes nearer to the loading terminal position. The mechanism of making the pinch roller 12 press-contact with the capstan 20 through the cam portion 37 of the cam gear 34 will now be described. In Figs. 12 and 13, the cam portion 37 of the cam gear 34 comprises a cam groove 37a extending in the circumferential direction and a bent cam groove 37b so bent toward the center as to press the pinch roller 12 against the capstan 20 after the tape loading operation. Denoted by the reference numeral 60 is a pinch rod which moves in an interlocking relationship with the cam portion 37 of the cam gear 34, and has at one end an elongated hole 61 extending in a direction of length of the pinch rod 60 and a cam follower 62 adapted to engage with the cam grooves 37a, 37b formed in the cam portion 37. The elongated hole 61 is fitted over a shaft 63 of the cam gear 34. The other end of the pinch rod 60 is connected through a pin 66 with one end of a first pinch charge arm 65 pivotally supported by a shaft 64 mounted upright on the chassis 1. As shown in Fig. 12A, the first pinch charge arm 65 has the other end to which a second pinch charge arm 68 is pivotally supported at its middle portion through a pin 67. A spring 69 is interposed between the one end of the first pinch charge arm 65 and one end of the second pinch charge arm 68. A pin 70 provided at the other end of the second pinch charge arm 68 is fitted into an elongated hole 73 at one end of a pinch arm 72 turnably attached to the chassis 1 through a pin 71, and the pinch roller 12 is attached to the other end of the pinch arm 72 at the same inclination as the capstan 20. As shown in Fig. 15, an arm 74 has one end which is pivotally supported by a shaft 75 mounted upright on the chassis 1, and the other end provided with the auxiliary guide post 23 extending upwardly therefrom at the same inclination as the capstan 20. Further, the arm 74 is connected with the pinch arm 72 via a link 76. The operation of loading the magnetic tape by means of the above-mentioned mechanism will be next described in more detail. Figs. 9 and 10 are explanatory views each showing a state of the gear train in a process of the tape loading operation. Figs. 1 and 9 illustrate a state of the gear train before starting the tape loading operation. In this state, the supply side boat 14 and the take-up boat 15 are located at unload positions at the beginning ends of the supply side loading guide 17 and the take-up side loading guide 18, respectively. As shown in Fig. 3, the tension post 9, the supply side loading roller post 8 and the inclined post 16 are inserted in the recessed portion 5 of the tape cassette 2; and the take-up side first and second loading roller posts 10, 11 are inserted in the recessed portion 6. Additionally, the pinch rod 60 is forcedly moved in a direction of an arrow c by means of the cam follower 62, so that the pinch roller 12 is retreated at the position most remote from the capstan 20 through the first and second pinch charge arms 65, 68 and the pinch arm 72. And, in a similar manner to the pinch roller 12, the inclined guide post 23 is also retreated at the position most remote from the capstan 20 by means of. the arm 74 which moves in an interlocking relationship with the pinch roller 12. As a result, as shown in Fig. 3, the pinch roller 12 and the inclined guide post 23 are both inserted in the recessed portion 7 of the tape cassette 2. As soon as the loading operation is started, as shown in Fig. 9, the cam gear 34 rotates in a clockwise direction, whereupon the second intermittent gear portion 36 is positively meshed with the toothed section 40 of the take-up side ring gear 39 because the terminal end 36a of the second intermittent gear portion 36 is received in the first non-toothed portion 40a of the ring gear 39. Thereafter, the take-up side ring gear 39 rotates in the direction of the arrow a by further rotation of the second intermittent gear portion 36, while the supply side ring gear 38 rotates in the direction of the arrow b through the pendulum gear 43 and the intermediate gear 42 both rotating in an interlocking relationship with the take-up side ring gear 39. Accordingly, the supply side boat 14 is driven in the loading direction by means of the drive shaft 53 provided on the fixed arm 52 of the supply side ring gear 38. At this time, the drive shaft 53 arcuately moves by means of the supply side ring gear 38, while the holder portion 57 of the supply side boat 14 moves linearly along a straight portion at the beginning end of the supply side loading guide 17. Therefore, the supply side boat 14 gradually comes nearer to the guide side as the boat 14 moves. After the holder portion 57 of the supply side boat 14 shifts into the circular portion of the supply side loading guide 17, as shown in Fig. 8, the front end portion of the supply side boat 14 moves along the outer periphery of the supply side loading guide 17. Thereafter, the supply side boat 14 is moved stably because it is supported by the drive shaft 53 and the holder portion 57, whereby the magnetic tape 13 is withdrawn out of the tape cassette 2 and wound around the rotary head cylinder 19 uniformly and surely by the supply side loading roller post 8. The take-up side boat 15 is also moved in a manner similar to the supply side boat 14 and thus the description thereof will not be repeated. In succession with this, just before completing the loading operation when the supply side and take-up side boats 14, 15 abut against respective stoppers 86, 87 shown in Fig. 5, the second intermittent gear portion 36 of the cam gear 34 is not meshed from the toothed section 40 of the take-up side ring gear 39 because the terminal end 36b of the second intermittent gear portion 36 is disengaged from the second non-toothed portion 40b of the ring gear 39, as illustrated in Fig. 10. In this state, the charge arm 49 being urged to turn in the direction of the arrow A tends to rotate the pendulum gear 43 in a direction of an arrow C through the link 51. This urging torque forces the take-up side ring gear 41 to rotate in the direction of the arrow a, so that the take-up side boat 15 is pressed against the stopper 87 through the take-up side drive shaft 55 for precise positioning. Simultaneously, the urging torque imposed on the pendulum gear 43 in the direction of the arrow C tends to rotate the intermediate gear 42 in a direction of an arrow D, whereby the supply side ring gear 38 is forced to rotate in the direction of the arrow b, so that the supply side boat 14 is pressed against the stopper 86 through the supply side drive shaft 53 for precise positioning. The loading operation is completed in this way. Even when the timing of pressing the supply side boat 14 against the stopper 86 is somewhat offset from the timing of pressing the take-up side boat 15 against the stopper 87, an adjustment is made by the swing plate 45 slightly swinging in any direction around the shaft 44, so that the supply side boat 14 and the take-up side boat 15 are positively pressed against the stoppers 86 and 87, respectively. When the cam gear 34 further rotates in the clockwise direction after completing the loading operation, as shown in Figs. 2, 12 and 13, the cam follower 62 provided on the pinch rod 60 is forced to enter the bent cam groove 37b of the cam portion 37 so as to pull the pinch rod 60 in a direction of an arrow d. As a result, the first pinch charge arm 65 is rotated in the clockwise direction about the shaft 64 to push the second pinch charge arm 68 in a direction of an arrow g. Then, the pinch arm 72 is turned through the pin 70 in an anti-clockwise direction about the pin 71 by virtue of the resilient force of the spring 69 to press-contact the pinch roller 12 with the capstan 20. Therefore, an angle of rotation required for press-contacting the pinch roller 12 with the capstan 20 becomes about 90° in this embodiment, which angle is nearly 1/2 of that required in the prior art. Further, since the radial length of the cam portion 37 required for press-contacting the pinch roller 12 with the capstan 20 is essentially only about 2/3 of the radius of the cam gear 34 in this embodiment, the size of the cam gear 34 can be reduced to a remarkable extent. Simultaneously, as shown in Fig. 15, the link 76 is pushed for turning the arm 74 in the clockwise direction about the shaft 75 for locating the auxiliary guide post 23, provided at the one end of the arm 74, to be interposed between the capstan 20 and the inclined post 24 as shown in Fig. 2. Thereby, the gently sloped path of the magnetic tape 13 extending from the take-up side loading roller post 11 to the capstan 20 is favorably maintained. Next, during an operation of unloading the magnetic tape, the cam gear 34 rotates in the anti-clockwise direction in Fig. 10 to release the press-contacting movement of the pinch roller 12. Then, the second intermittent gear portion 36 of the cam gear 34 is positively meshed with the toothed section 40 of the take-up side ring gear 39 because the terminal end 36b of the second intermittent gear portion 36 is received in the second non-toothed portion 40b of the ring gear 39. Accordingly, the take-up side ring gear 39 is rotated in a direction of an arrow g which corresponds to the rotating direction in the unloading operation, while the supply side ring gear 38 is rotated through the pendulum gear 43 and the intermediate gear 42 in a direction of an arrow f which corresponds to the rotating direction in the unloading operation. At the time illustrated in Fig. 9 when the supply side loading roller post 8 and the take-up side loading roller post 10, 11 are received in the recessed portions 5 and 6 of the tape cassette 2, respectively, the second intermittent gear portion 36 of the cam gear 34 can disengage from the toothed section 40 of the take-up side ring gear 39 because the terminal end 36a of the second intermittent gear portion 36 is positioned in the first non-toothed portion 40a of the ring gear 39. At this time, the charge arm 49 is being urged to turn in the direction of the arrow A by the torsion coil spring 50, thus tending to rotate the pendulum gear 43 in the direction of the arrow B through the link 51. Accordingly, the take-up side ring gear 39 is forcedly rotated in the direction of the arrow g to be pressed against a stopper 100a, fixedly mounted on the chassis 1, for precise positioning. Simultaneously, the rotating force of the pendulum gear 43 in the direction of the arrow B urges the intermediate gear 42 to rotate in a direction of an arrow E, whereby the supply side ring gear 38 is forcedly rotated in the direction of the arrow f to be pressed against a stopper 100b, fixedly mounted on the chassis 1, for precise positioning. Thereafter, when the cam gear 34 further rotates in the anti-clockwise direction through about 30° from the state of Fig. 9, the tape cassette 2 is ejected (by means of a not-shown arrangement). It is needless to say that during the above process, the supply side ring gear 38 and the take-up side ring gear 39 are both not rotated from the state of Fig. 9 to maintain their press-positioned states against the stoppers 100a and 100b, respectively. Next, the description concerning a driving mechanism for the tension post according to one embodiment of the present invention will be given below. Figs. 16 and 17, respectively, show states, in which a tension post is stored in a cassette, and is in a tape running position. In Figs. 16 and 17, the cam gear 34 and the tension arm 90 are contacted with each other at their cam portions 35d, 90a. As the cam gear 34 rotates when a tape stored within a cassette is to be drawn out, the tension arm 90 is greatly turned together with the tension post 9 near a tape running position shown in Fig. 17 while the cam portion 90a shifts contactingly from the cam portion 35d provided on the outer periphery of the cam gear 34 to the cam portion 35f. Force tending to turn the tension arm 90 is given by the spring force of a tension spring 92 and transmitted to the tension arm 90 through a spring hook 95. When the cam gear 34 further turns in the tape running position, the cam portion 90a of the tension arm 90 is made free from the cam portion 35f of the cam gear 34 and, thereafter, the tension arm 90 is balanced by the braking force of a pad 96a of a pad arm 96 contacting with a reel stand 94, the spring force of the tension spring 92, the tensile force of the magnetic tape 13 wound around the tension post 9, thereby controlling a tape tension. The contact state between the cam portions 90a to 90c of the tension arm 90 and the cam portions 35d to 35f of the cam gear 34 will be explained in detail with reference to Figs. 18 to 23 for clarifying how the tension arm 90 is turned. Fig. 18 is an enlarged view of the tension arm 90 and the cam gear 34 in Fig. 16. While the biasing force of the tension spring 92 acting in a direction shown by an arrow A applies on the tension arm 90 to turn the same about a center 90o of rotation in a direction shown by an arrow C, a cam 90aa of the cam portion 90a of the tension arm 90 contacts with the cam portion 35d of the cam gear 34, so that the tension arm 90 is stopped and thus the tension post 9 provided on the tension arm 90 is kept to be positioned in the cassette. Fig. 19 shows a state, in which the cam gear 34 rotates about a center 340 of rotation in a direction shown by an arrow B, and thus the tension arm 90 begins to turn with a cam 90ab of the cam portion 90a contacting with the cam portion 35e. Fig. 20 shows a state, in which the cam gear 34 further rotates in the direction B, so that the cam 90aa of the cam portion 90a contacts with the cam portion 35e and the tension arm 90 further turns in the direction C to permit the tension post to be pulled out near substantially the tape running position. Figs. 19 and 20 show a state, in which the cam portion 90a provided with the cam 90aa and the cam 90ab is set to be positioned between the center of the tension arm 90 and the center of the cam gear 34 and toward the center of the tension arm 90, so that a small angle of rotation required for an angle of turning of the tension arm 90 suffices the cam gear 34. Figs. 21 and 22 show a state, in which a cam 90ac of the cam portion 90a contacts with the cam portion 35f near the outer periphery of the cam gear 34, and the biasing force of the tension spring 92 acting in the direction A applies on the tension arm 90 to turn the same about the center 90o of rotation in the direction C whereby the tension post is kept in a position where it is restricted by the cam portion 35f. The cam gear 34 further rotates whereby the cam portion 90a of the tension arm 90 and the cam portion of the cam gear 34 are brought in non-contact with each other as shown in Fig. 23 and the tension arm 90 is no longer restricted by the cam of the cam gear 34 and terminates movement to a position where tape tension can be controlled, or the tape running position. Accordingly, Fig. 23 corresponds to the enlarged view of the tension arm 90 and the cam gear 34 shown in Fig. 17. It is needless to say that by rotating the cam gear 34 from the state of Fig. 23 in a direction opposite to the direction B, the tension arm 90 can be rotated in a direction opposite to the direction C and the tension post 9 can be returned to the original position inside the cassette. It is also needless to say that the above arrangement my be applied to another unit than the tension arm so long as the unit includes a cam gear and a rotating member rotatable by the cam gear. As described above, with the arrangement of the tape guide post driving device of the present invention, only the cam gear can directly ensure a large angle of turn for the tension arm, and so it is not necessary to increase the angle of turn by means of a separate member. Also, since the cam can be defined around the outer periphery of the cam gear, a region in the vicinity of the center is available for other uses. Thus, the invention contributes to reduction of the size, weight and thickness of the magnetic recording/playback apparatus to a remarkable extent. In addition, the present invention makes it possible to greatly reduce the angle of rotation of the cam gear required for the press-contacting operation of the pinch roller, and also greatly shorten the radial length of the cam portion of the cam gear. As a result, the cam gear can be greatly reduced in size, which also contributes to reduction in size of the entire VTR to a remarkable extent.

Claims: A tape guide post driving device comprising a gear (34) having a cam (35d-35f), a rotating member (90) adapted to be drivingly turned upon rotation of the gear (34), a tape guide post (9) provided on said rotating member (90), and a cam-shaped portion (90a-90c) provided on said rotating member (90) and driven by said cam (35d-35f) of said gear (34) to turn said rotating member (90) and said tape guide post (9) to at least two tape running positions and hold them there, characterized in that in the position of the rotating member (90) in which the tape (13) is not withdrawn from the cassette said cam-shaped portion (90a-90c) of said rotating member (90) is positioned between a center (90o) about which said rotating member (90) turns, and a center (34o) of said gear (34) and near the turning center (90o) of said rotating member (90), said cam-shaped portion (90a-90c) being driven by the cam (35d-35f) of said gear (34) near an outer periphery of said gear (34).

Inventors: ASAOKA TETSUKI, KONISHI AKIO, KURUMATANI HIROSHI, MORIYASU YOSHITADA, NAGASAKI EIJI, SYUUKE TAKESHI, UEDA SIGEO, YOSHIO HIDEAKI, ASAOKA, TETSUKI, KONISHI, AKIO, KURUMATANI, HIROSHI, MORIYASU, YOSHITADA, NAGASAKI, EIJI, SYUUKE, TAKESHI, UEDA, SIGEO, YOSHIO, HIDEAKI
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1992
Main classification: G11B15
IPC codes: G11B15