Tape guide mechanism for recording and reproducing device

Abstract: A tape guide mechanism for a VTR includes a pair of first guides (5,6) disposed respectively at a tape entrance side and a tape exit side of a cylinder and positioned immediately adjacent to the cylinder, a pair of second guides (7,8) disposed adjacent to the pair of first guides, respectively, and a third guide (14) provided in a path of travel of a tape extending between the first guides and the second guides, so as to prevent opposed surfaces of the tape, disposed respectively at the tape entrance side and the tape exit side, from being contacted with each other. The third guide may be of a rotary type and be disposed remoter from the cylinder than the first guides.

Description: BACKGROUND OF THE INVENTION This invention relates generally to a recording and reproducing device in which a tape is wound or extended around a cylinder over a wide angle, and more particularly to a tape guide mechanism for such a recording and reproducing device which prevents opposed tape surfaces, disposed in the vicinity of tape guides adjacent to a tape entrance side and a tape exit side of the cylinder, from being contacted with each other, and also ensures a stable travel of the tape. Conventionally, with respect to a magnetic recording and reproducing device of the rotary head-type (hereinafter referred to as "VTR") and particularly to a VTR with an integral camera, there has been proposed a system in which, in order to obtain a compact and lightweight construction of the device and also to achieve the compatibility (which enables the use of the same format) of this device with other conventional devices, the reduction of the diameter of the cylinder is achieved by increasing the angle of winding of a tape around the cylinder. US-A-4 338 641 discloses a tape recording device employing means for twisting a tape along a tape traveling path by pulleys. Some of first, second, third and fourth pulleys have arranged their axes at an angle of 90° relative to the axes of the other pulleys, thereby avoiding any angle of incline of a pulley at production. For example, US-A-4 510 538 (corresponding to Japanese Unexamined Publication No. 58-101579) discloses a small-diameter cylinder system for a VTR of the β type. In this technique, one-head system is adopted for the purpose of reducing the diameter of the cylinder, and in order to obtain the same format as that of a conventional two-head system in which the angle of winding of a tape around a cylinder is 180°, the angle of winding of a tape round the cylinder of this one-head system is increased or widened to 300°. In this case, since the rotational frequency of the cylinder is 60 r.p.s., a vertical scanning speed of the camera is not changed; however, since the angle of winding of the tape around the cylinder is as small as 300°/360°, an effective horizontal scanning must be completed during a period corresponding to 300°, and signals are recorded with the compression of the time performed about 20% in the horizontal direction. Recently, there has been an increasing demand for VTRs with an integral camera, and therefore the device tends to become more and more compact and lightweight, and in order to meet a demand for a low cost construction now attainable by a rapid development of memories, there have been proposed small-diameter cylinder systems capable of recording and reproduction which incorporate memories specially designed for compressing and expanding the horizontal scanning speed. In the above system, in order to achieve a more compact and lightweight construction of the device, it is necessary to reduce the number of the memories as much as possible so as to achieve the low cost design, and it is also necessary to reduce the diameter of the cylinder as much as possible, in which case the tape winding angle is required to be as close to 360° as possible. Fig. 7 shows one example of a condition in which a wide-angle loading operation has been completed. Figs. 8 and 9 are enlarged perspective views showing the vicinity of the tape entrance side and the tape exit side of the cylinder. In these Figures, a cassette 2 contains a magnetic tape 1 wound on a supply reel 2a and a take-up reel 2b. The magnetic tape 1 is wound around the cylinder 3 over an angle of not less than 300°, and therefore in the loading-completed condition, that portion of the tape 1 disposed in a tape path 1a extending between first and second guides 5 and 7 at the entrance side of the cylinder 3 is very close to that portion of the tape 1 disposed in a tape path 1b extending between first and second guides 6 and 8 at the exit side of the cylinder 3. Therefore, the above system suffers from the following problems (1) and (2): (1) In the tape loading-completed condition, the guides 5 and 6 as well as the guides 7 and 8 are disposed very close to each other at the entrance side and exit side of the cylinder 3. In this condition, when the tape 1 is in a stop mode, the tension of the tape 1 is reduced, so that the tape is loosened. As a result, the opposed portions of the tape 1 disposed respectively in the tape paths 1a and 1b are contacted with each other. (2) Even when the tape 1 is subjected to a predetermined tension during a travel thereof, the distribution of the tension in the direction of the width of the tape 1 may become uneven because of irregularities of mounting of the guides, in which case the tape 1 travels with its upper edge portion loosened. As a result, the opposed portions of the tape 1 disposed respectively in the tape paths 1a and 1b are brought into contact with each other, as in the stop mode. SUMMARY OF THE INVENTION With the above problems (1) and (2) in view, it is an object of this invention to provide a tape guide mechanism for a recording and reproducing device, having a tape loading mechanism for winding a tape around a cylinder over a wide angle, in which in the guides disposed respectively at a tape entrance side and a tape exit side of the cylinder, opposed surfaces of the tape are prevented from being contacted with each other, and the loosening of the tape can be restrained, thereby enabling a stable travel of the tape. This object is achieved by tape guide mechanisms comprising the features according to claim 1 and 11, respectively. Further embodiments are defined in the dependent claims. According to the present invention, there is provided a tape guide mechanism comprising a pair of first guides disposed respectively at a tape entrance side and a tape exit side of a cylinder and positioned immediately adjacent to the cylinder, a pair of second guides disposed adjacent to the pair of first guides, respectively, and a third guide provided in a path of travel of a tape extending between the first guides and the second guides, so as to prevent opposed surfaces of the tape from being contacted with each other. With this construction, when because of the distribution of the tension of the tape, the tape travels with its upper edge portion loosened, or when the tension of the tape is reduced at the time of stopping the tape, so that the whole of the tape is loosened, the displacement of the tape in the direction of the thickness thereof is restrained. Opposed surfaces of the tape, disposed in the vicinity of the guides at the tape entrance side and the tape exit side of the cylinder, are easily and certainly prevented from being contacted with each other. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a plan view of a recording and reproducing device incorporating a tape guide mechanism according to an embodiment of the present invention; Fig. 2 is a side-elevational view of the recording and reproducing device of Fig. 1; Fig. 3 is a perspective view of the recording and reproducing device of Fig. 1; Fig. 4 is a perspective view showing the tape guide mechanism according to the embodiment; Figs. 5 and 6 are side-elevational views explodedly showing the tape guide mechanism; Figs. 7, 8 and 9 are illustrations of problems generated in the device according to the prior art; and Figs. 10, 11, 12, 13 and 14 are illustrations showing modified forms of a third guide used in the tape guide mechanism of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will now be described with reference to the drawings. Fig. 1 is a plan view of a magnetic recording and reproducing device provided with a third guide for preventing opposed portions of a tape from being contact with each other. Fig. 2 is a side-elevational view of the device of Fig. 1, and Fig. 3 is a perspective view of the device, and Fig. 4 is an enlarged perspective view of the third guide. In these Figures, those parts identical to those of Figs. 7, 8 and 9 are designated by identical reference numerals, respectively. The third guide 4 of a cylindrical shape is so provided as to prevent that portion of the tape 1, disposed in a tape path 1a extending between a first guide 5 close to the cylinder 3 and a second guide 7, from being contacted with that portion of the tape 1 disposed in a tape path 1b extending between a first guide 6 close to the cylinder 3 and a second guide 8. More specifically, the third guide 4 is provided between the first guides 5 and 6 and the second guides 7 and 8. Guides 1a, 11b, 11c and 11d are provided to form a tape path at a tape entrance side of the cylinder 3, and guides 12a, 12b and 12c are provided to form a tape path at a tape exit side of the cylinder 3. Reference numeral 9 denotes a capstan, reference numeral 10 denotes a pinch roller, and reference numeral 13 denotes a chassis. The operation of the above tape guide mechanism will now be described with reference to the drawings. Fig. 1 shows a tape loading-completed condition in which in a recording mode or a reproducing (playback) mode, the tape 1 in a cassette 2 has been pulled out along a loading path A and been wound around the cylinder 3 over a wide angle slightly less than 360°. As shown in Figs. 5 and 6, the opposed portions of the tape 1 disposed respectively in the tape paths 1a and 1b are contacted respectively with the opposite sides of the third guide 4 partially embedded in a guide plate 15, and are extended or wound around the third guide 4 over a predetermined angle. When the tape 1 is thus kept in the condition shown in Fig. 1, the loosening of the tape which develops in the tape paths 1a and 1b (Figs. 7, 8 and 9) in the tension-reduced condition in the stop mode in the tape loading-completed condition, as well as the loosening of the tape developing when limiting the travel of the travelling tape, is absorbed, and as a result the opposed portions of the tape 1 disposed respectively in the tape paths 1a and 1b are prevented from being contacted with each other. Also, when the tape 1 travels for recording signals on the tape or reproducing the signals therefrom, the opposed portions of the tape 1 are contacted with the opposite sides of the third guide 4, respectively, and therefore the displacement of the tape 1 in the direction of the width thereof is restrained, thereby ensuring a stable travel of the tape 1. Figs. 10, 11 and 12 show a modified third guide of a flattened shape, and Figs. 13 and 14 show another modified third guide of a rotary roller-shape. These two guides will now be described below. Referring to the third guide 4 of a flattened shape, when the tape 1 is in the stop mode in the loading-completed condition as shown in Fig. 10, opposed surfaces of the tape 1 are prevented by the third guide 4 of a flattened shape from being contacted with each other. When the tape 1 travels under a predetermined tension as shown in Fig. 11, the opposed portions of the tape 1 are hardly brought into contact with each other, and therefore it is necessary to reduce the travelling load of the tape 1, and the tape 1 travels without contacting the third guide 4. The third guide 4 of a rotary roller-shape is contacted with opposed surfaces of the tape 1 at tape paths 1a and 1b, as shown in Figs. 13 and 14, and is rotated in response to the travel of the tape 1. With this construction, the travelling load of the tape 1 is reduced, and also the loosening of the tape which would develop in the tension-reduced condition as in the stop mode, as well as the loosening of the tape which would develop when limiting the travel of the travelling tape, can be absorbed, thereby preventing the opposed portions of the tape, disposed respectively in the tape paths 1a and 1b, from being contacted with each other. Also, when the tape 1 travels for recording signals on the tape or reproducing the signals therefrom, the opposed portions of the tape 1 travel while contacting the opposite sides of the third guide 4, respectively, and since the third guide 4 has a rotary roller-shape, the fluctuation (i.e., uneven travel) of the tape in its longitudinal direction can be restrained, thus achieving the effect of reducing the jitter. For reducing the jitter, the third guide can be designed to serve also as an impedance roller. In this case, for example, the upper end of the third guide is increased into a greater diameter as shown in Figs. 13 and 14, so as to increase the inertia moment. According to the present invention, even in the system in which the diameter of the cylinder is reduced in order to achieve a compact and lightweight construction of the device, the contact between the opposed surfaces of the tape at the guides disposed near the entrance side and exit side of the cylinder can be prevented positively and easily by the third guide. And besides, the loosening of the tape can be easily eliminated. Therefore, the tape travel performance as well as the reliability can be enhanced. Further, since the distance between the first guides 5 and 6 as well as the distance between the second guides 7 and 8 can be reduced, the angle of winding of the tape around the cylinder can be easily increased. As a result, a compact and lightweight construction of the device can be easily achieved. The present invention can be embodied in other forms than the above-mentioned embodiments. The above-embodiments are merely examples of the present invention. The scope of the present invention is specified in the appended claims. Various modifications and changes can be made within the scope of the appended claims.

Claims: A tape guide mechanism for use in a recording and reproducing device in which signals are recorded on and reproduced from a tape (1), wound around an outer peripheral surface of a cylinder (3), respectively by signal recording means and signal reproducing means mounted on said cylinder (3), said tape guide mechanism comprising: (a) a pair of first guides (5, 6) disposed respectively at a tape entrance side and a tape exit side of said cylinder (3) and positioned adjacent to said cylinder in a condition in which the winding of said tape (1) around said cylinder is completed, so as to define a posture of entrance of said tape to said cylinder and a posture of exit of said tape from said cylinder, respectively; and (b) a pair of second guides (7, 8) disposed adjacent to said pair of first guides (5, 6), respectively, so as to change a direction of travel of said tape (1), characterized by : (c) a third guide (4) provided between said pair of first guides (5, 6) and said pair of second guides (7, 8) and disposed along a path of travel of said tape, said third guide (4) keeping opposed surfaces of said tape, disposed along said tape travel path, away from each other by a distance greater than a predetermined value, thereby preventing said opposed surfaces of said tape (1) from being contacted with each other. A tape guide mechanism according to claim 1, in which said third guide (4) is disposed between a signal recording surface of that portion of said tape, disposed in the tape travel path extending between said first guide (5, 6) and said second guide (7, 8) disposed at the tape entrance side of said cylinder (3), and a signal recording surface of that portion of said tape (1) disposed in the tape travel path extending between said first guide (5, 6) and said second guide (7, 8) disposed at the tape exit side of said cylinder. A tape guide mechanism according to claim 2, in which said third guide (4) is contacted by the signal recording surface of said tape (1) between said first guides (5, 6) and said second guides (7, 8) in the tape travelling condition. A tape guide mechanism according to claim 2, in which said third guide (4) is rotatable about a fixed axis. A tape guide mechanism according to claim 3, in which said third guide (4) is rotatable about a fixed axis. A tape guide mechanism according to claim 1, in which said third guide (4) has a cylindrical shape. A tape guide mechanism according to claim 2, in which said third guide (4) has a cylindrical shape. A tape guide mechanism according to claim 3, in which said third guide (4) has a cylindrical shape. A tape guide mechanism according to claim 4, in which said third guide (4) has a cylindrical shape. A tape guide mechanism according to claim 5, in which said third guide (4) has a cylindrical shape. A tape guide mechanism for use in a recording and reproducing device in which signals are recorded on and reproduced from a tape (1) wound around an outer peripheral surface of a cylinder (3), respectively by signal recording means and signal reproducing means, said tape guide mechanism comprising: (a) a pair of first guides (5, 6) disposed respectively at a tape entrance side and a tape exit side of said cylinder (3) and positioned adjacent to said cylinder in a condition in which the winding of said tape around said cylinder is completed, so as to define a posture of entrance of said tape to said cylinder and a posture of exit of said tape from said cylinder, respectively; and (b) a pair of second guides (7, 8) disposed adjacent to said pair of first guides (5, 6), respectively, so as to change the direction of travel of said tape (1); charactezised by : (c) a third guide (4) rotatable about a fixed axis, said third guide (4) being remoter from said cylinder (3) than said first guides. A tape guide mechanism according to claim 11, in which said third guide (4) is disposed between a path of travel of said tape (1) at a tape entrance side of said cylinder (3) and a path of travel of said tape at a tape exit side of said cylinder, said third guide (4) being contacted by a signal recording surface of said tape. A tape guide mechanism according to claim 12, in which said third guide (4) has a circular transverse cross-section.

Inventors: NAGAI KYUICHIROU, OGIRO KENJI, SHIMIZU HIROKAZU, NAGAI, KYUICHIROU, OGIRO, KENJI, SHIMIZU, HIROKAZU
Applicants: HITACHI LTD, HITACHI, LTD.
Application year: 1991
Main classification: G11B15
IPC codes: G11B15