GB2078431A - Video signal recording and/or reproducing apparatus - Google Patents

Abstract

A video signal recording and/or reproducing apparatus comprises a guide drum 34 having at least one rotating head for recording and/or reproducing video signals. Tape 22 is drawn from within a cassette 10 and loaded into a specific tape travel path including a part wherein the tape is in wrapping contact with a part of the guide drum. A single impedance roller 50 contacts the tape loaded in the predetermined tape travel path. The impedance roller is disposed in the tape travel path between the tape supply reel 23 and the guide drum. The roller acts as a flywheel to suppress tape jitter. It is mounted on a pivoted arm 52 with an erase head 51, see also Fig. 6 (not shown). Provision of a second such roller on the take-up side, as in a prior apparatus (GB 1 526 175), is unnecessary as the improvement in jitter suppression is negligible. <IMAGE>

Description

SPECIFICATION Video signal recording and/or reproducing apparatus The present invention relates generally to video signal recording and/or reproducing apparatus, and more particularly to a video signal recording and/or reproducing apparatus in which a recording tape is drawn from a cassette and loaded into a specific tape travel path, through which it may travel stably, and in which it can be of further miniaturized and lightened construction.

In general, video signal recording and/or reproducing apparatus, particularly those for use in homes, are being miniaturized. For this reason, the tape travel paths are becoming shorter, but is no charge in their complexity of such apparatus. One result is an increase of the wrapping angles of the tape around the tape guide members. This increased angle gives rise to fluctuations in tape travel. When there is a fluctuation in the tape travel speed, jitter appears in the reproduced picture, which causes the picture to become poor. Accordingly, there is a particular requirement for stabilization of the tape travel in a video signal recording and/or reproducing apparatus.

In view of this requirement, an apparatus has been proposed by the specification of British Patent No. 1,526,175 entitled "AU TOMATIC LOADING VIDEO RECORDER WITH SPACED STABILIZING" of which applicant is the same as that of the present application. This apparatus comprises two impedance rollers each of which respectively contacts the tape loaded onto tape supply side path and onto tape take-up side path with respect to a guide drum.

The present inventor has investigated how to supply side impedance roller and the takeup side impedance roller operate or serve for suppressing jitter in the above described apparatus. This investigation reveals various technical matters, which are recited below.

(1) In a relationship between the tape travel path and the guide drum, causes for fluctuating tape travel speed around the tape guide drum will exist in the tape travel path preceding to a clamp and driving part comprising a pinch roller and a capstan, in the tape travelling direction. When examining the tape supply side and tape take-up side separately, factors of tape travel speed fluctuation generally exist at the tape supply side, a principal one being a fluctuation in load for drawing the tape from the supply reel. In the tape travel path at the tape take-up side, the sliding contact of the tape onto the audiocontrol head may be given as the factor for causing the tape travelling speed to fluctuate around the guide drum, but this sliding contact little affect the tape travel around the drum.

Accordingly, it may be supposed that stabil ization of tape travel around the guide drum is effected mainly by the operation of the sup ply-side impedance roller and the take-up side impedance roller works only supplementarily.

An experiment has also revealed that the above estimation is true. This is, as will be described far below, effect of the supply-side impedance roller for suppressing jitter is re markable, but the jitter suppressing effect of the take-up side impedance roller is hardly recognized in particular. The jitter can be suppressed to an extent such that it involves no difficulty in practical application, even though the take-up side impedance roller is omitted, i.e., only the supply-side impedance roller is used.

(2) The impedance roller is generally effective for stabilizing the tape travel, but is not prefer able for miniaturizing and lightening the appa ratus.

(3) The impedance rollers is generally adapted to move from a retracted non-tape-contacting position thereof to an operational position where it contacts with the tape. With this construction, the position of the impedance roller tends to change either when the orienta tion of the apparatus is changed or when the apparatus is subjected to external impact. Any change in the position of the impedance roller may lead to change in the tape travel path.

When portability is to effected, omission of the impedance roller is preferable. In particu lar, any fluctuation in position of the take-up side impedance roller results in change of the distance along the tape travel path from the guide drum to the control head, this distance being required to be kept with high accuracy.

(4) The impedance roller is a rotational struc ture having sufficient energy of inertia and rotating responsive to the travel of the tape contacting therewith. The impedance roller therefore inevitably involues eccentric rotation, which even though limited to a very small value, causes the tape path to change which in turn develops jitter and wow and flutter.

Accordingly, it is a general object of the present invention to provide a novel and use ful video signal recording and/or reproducing apparatus which attains miniaturization and lightening in weight of the apparatus without accompanying any deterioration of stabiliza tion of the tape travel whatsoever. The pre sent invention is made by taking the above stated technical matters into consideration.

The present invention provides a video sig nal recording and/or reproducing apparatus comprising: a guide drum having at least one rotating head for recording and/or reproduc ing video signals, loading means for drawing out a tape accommodated within a cassette and loading said tape in a specific tape travel path including a part wherein the tape is in wrapping contact with a predetermined arcu ate portion of said guide drum, and a single impedance roller making contact with the tape thus loaded in said predetermined ace travel path, said impedance roller being disposed at a position between the tape supply reel and the guide drum in the tape travel path and rotating with a peripheral speed equal to a travel speed of the tape in said predetermined tape travel path, thereby stabilizing the travel speed of the tape on the arcuate portion of said guide drum.

Another and specific object of the invention is to provide a video signal recording and/or reproducing apparatus having a single impedance roller for raking contact with the tape in its travel path on the supply side with respect to the guide drum, and having no impedarce roller in the tape travel path on the take-up side. By this revision, the tape travels around the guide drum in a stable manner and furthermore, the apparatus is miniaturized and lightened in weight.The apparatus of the present invention is the most suitable for portable type apparatus.

Other objects and further features of the present invention will be apparant from the following detailed description sa@forth in conjunction with the accompanying drawings.

Figure 1 is a plan view showing one embodiment of a video signal recording and/or reproducing apparatus according to the present invention, in a stop mode state; Figure 2 is a plan view showing the appa- ratus of Fig. 1 in a recording and/or reproducing mode state.

Figure 3 is a vertical section showing a vertical guide roller and a mounting support; Figure 4A and Fig. 4B are a plan view and and elevation respectively showing an upper drive ring structure; Figure 5A and Fig. 5B are a plan view and an elevation respectively showing a lower drive ring structure; Figure 6 is a vertical section showing an impedance structure, taken along the line VI- VI in Fig. 1 as viewed in the arrow direction; Figure 7 is a frequency analysis graph indicating jitter component in an apparatus in which no impedance roller is provided; Figure 8 is a frequency analysis graph indicating jitter component in an apparatus according to the present invention, that is, in an apparatus in which a single impedance roller is disposed on the tape supply side; and Figure 9 is a frequency analysis graph indicating jitter component in an apparatus in which the impedance rollers are disposed both on tape supply side and tape take-up side.

For recording or reproducing. a cassette (cartridge) 10 is placed in a loading position in the recording/reproducing apparatus, as indicated by two-dot chain line in Fig.

Sloping guide poles 11 and 13 and vertical guide rollers 12 and 1 14, a tention pole 16 on a tension arm 15. and a capstan 17 respectively enter an opening in the bottom of the cassette 10 and fit into the interior thereof.

These members are disposed on the inner side of the tape.@. magnetic tape guide poles 20.

and 21 guide tape in its span between a tape supply roll 18 and a take-up roll19. When the cassette 10 is placed in its operational position, a supply teel and a taks-up teel (neither being shown) respectively rit onto a supply side teel disc 28 and a taks-up side teel disc 24 contained within cassette 10.

The sioping guide pole 11 and the vertical guide roller 13 are mounted on a slide mount ing support 25, and the sioping guide pole 12 and the vertical guide roller 14 are on the other slide mounting support 26. The vertical guide roller 13 ( or14) comprises a guide roller member 27 which fits rotatbly on a support shart 28 vertically embeaded to the mounting support 25 (or 26 as indicated in Fig. 3 Between a lange 28a of the shaft 28 and the mounting suppor. 25 (or 26) is interposed a rubber spacer 29 in a state of being compressed. This rubber spacer 29 affords superior vibration preventing or insulation property to the vertical guide roller 13 (or 14).The mounting supports 26 and 26 are respectively positioned on a sub-chassis 30 in a state where projections provided on the bottom thereof are inserted to and fitted into guid grooves 31 and 32 formed on the subchassis 30. The sub-chassis 30 is provided above a main chassis 33.

A guide drum 34 comprises an upper rotary drum provided with video heads and a lower fixed drum, and is provided onto the subchassis 30. The upper rotary drum is fixed on a rotary shaft of a head motor 35, and is rotated directly by means of the same motor 35.

On the main chassis 33. are supported an upper drive ring structure 38 indicated in Figs. 4A and 4B and a lower drive ring structure 37 indicated In Figs. 5A and 5B, in rotatable manner and stacked arrangement.

The upper drive ring structure 36 comprises a ring 39 having gear teeth 39a formed therearound throughout a predetermined angle range, a slide memeber 40 fitted to the ring 39, and a coil spring 41 for urging the slide member 40 to move in tho circumferential direction of the ring 39. Similary, the lower drive ring structure 37 comprises a ring 42 having gear teeth 42a, a ti slide member 43, and a coil spring 44. Connecting pins 4b and 46 projecting downwards from the mounting supports 25 and 26 respectively inserted into a slot 40a the slids member 40 and a slot 43a on the slide mema,er 49.

An impedance roller 50, which constitutes an essential part ol the present invention, is disposed on tape -- - - side with respect to the guide drum 34. Referring further to Fig.

6, the impedance roller 50 is supported togehter with a full width erasing head 51 on a support arm 52 pivoted at its end confronting the loaded cassette 10 on a pin 53 embedded to the sub-chassis 30. The support arm 52 is urged to rotate clockwise by a spring 54 having large spring force, but it is limited in this rotation in a state where a shaft 55 for supporting the impedance roller 50 abuts at lower end thereof against a longitudinal end of a slot 56 formed on the sub-chassis 30.

The impedance roller 50 have entered into the tape travel path to be formed, as shown in Fig. 1. The support arm 52 is further pushed downwards onto the sub-chassis 30 by a compression coil spring 57 fitted around the shaft 53. The shaft 53 has a guide roller 53 rotatably fitted thereto.

The impedance roller 50 is made of iron, thus having large inertia of moment sufficient for suppressing very minute fluctuations in the tape speed. The impedance roller 50 is rotatably supported, with respect to the radial direction thereof, by a pair of plain bearings 59 and 60 made of a specific synthetic resin, and, with respect to the thrust direction, i.e., gravity direction, by a pivot bearing wherein a seat 61 made of a specific synthetic resin rests on a conical pivot at the top of the shaft 55. With this construction, the rotational resistance at the bearings is minimized to assure smooth rotation of the impedance roller 50.

It is to be observed that no impedance roller is provided on the tape take-up side with respect to the guide drum 34.

When a recording (or reproduction) mode starting operation is performed in a state shown in Fig. 1, a tape loading motor (not shown) start, to rotate, and drive gears (not shown) are rotated at reduced speed by way of a worm-gear mechanism (not shown). Due to the rotation of the drive gears, the ring structures 39 and 42 respectively start to rotate, from their positions indicated in Fig.

4A and Fig. 5A, clockwise and counterclockwise directions. As the ring structures 39 and 42 rotates, the guide pole mounting supports 25 and 26 respectively move, along the guide grooves 31 and 32, in the directions of arrows Al and Bi. The guide poles 11 and 12, and the guide rollers 13, 14 intercept the magnetic tape 22 and draw it out of the cassette 10. The mounting supports 25 and 26 move up to their final positions shown in Fig. 2, where the vertical guide rollers 12 and 14 respectively make pressed contact at lower parts thereof with corresponding V-shaped grooves 70a and 71a of stoppers 70 and 71 fixed on the sub-chassis 16. The mounting supports 25 and 26 are thereby held at their final positions with good stability.

As the guide pole mounting support 25 moves, the tension arm 15 is rotated counterclockwise about a staft 72 responsive to a force of a coil spring 73, to a position indicate by two-dot chain line in Fig. 1, where it is caught by an L-shaped arm 74. In a final stage of loading operation, the L-shaped arm 74 is engaged with a projection 42a on the ring 42 rotating counterclockwise and is thereby turned clockwise about the shaft 75, which causes the tension arm 15 to turn further counterclockwise to a position indicated in Fig. 2, thus tensing a brake band 76.

When the guide pole mounting support 25 reaches a position where it confronts the support arm 52, the vertical guide roller 13 is pressed into contact against a side cam 52a of the support arm 52 and pushes the support arm 52 aside. That is, the support arm 52 is turned counterclockwise counter to the force the spring 54, and the erasing head 51 and the impedance roller 50 are thereby receded temporarily, as indicated by two-dot chain line in Fig. 1, from the moving path of the mounting support 25. As the mounting support 25 passes by the side cam 52a, the support arm 52 is again returned to its original position by the force of the spring 54, and the erasing head 51 and the impedance roller 50 respectively make contact with the tape 22 which has just loaded onto the tape travel path.

It is to be observed that both the erasing head 51 and the impedance roller 50 are provided on the same support arm 52. By this arrangement, simple construction is afforded, in compared with arrangement wherein the impedance roller and the erasing head are mounted on separate support arms. Further, the pivotal point of the support arm 52 is locaded at its end confronting the loaded cassette 10. By this arrangement, the angular range of the support arm 52 which swings upon the above stated tape loading operation can be limited to narrower range, in campared with the arrangement wherein the support arm is pivoted at its end opposite to the cassette 10 loaded, which leads to miniaturization of the apparatus.

In addition, as the drive ring structure 37 turns counterclockwise, a slide lever 77 is forced by a spring 78 to slide rightward as viewed in Fig. 1, which causes a support arm 70 to rotate counterclockwise about a pin 80, thus bringing a pinch roller 81 to a position near the capstan 17, as indicated by two-dot chain line in Fig. 1. When the tape loading operation is completed, a latch-type plunger 82 is energized, and a toggle mechanism comprising links 83, 84, and 85 is operated to turn a pinch roller pressing arm 86 counterclockwise about a shaft 87. The arm 86 pushes at its free end a pinch roller shaft 88, and the pinch roller 81 is thereby pressed against the capstan 17.

Upon completion of the automatic tape loading, the apparatus assumes a state indicated in Fig. 2. The tape 22 is drawn from the tape roll 18 on the tape-supply side past the tension pole 16, the guide roller 58, and the full-width erasing head 51. Thereafter, it comes into contact the impedance roller 50. The tape 22 is further guided and changed in direction by the vertical guide roller 13 and the sloping guide pole 11. The tape is held in a wrapping helical around the guide drum 34.

While the tape 22 is thus in wrapping contact, a video signal is recorded thereon and reproduced therefrom by the rotating video heads within the drum 34.

After leaving the guide drum 34, the tape 22 is guided and changed in direction by the sloping guide pole 12 and the vertical guide roller 14. Then, the tape 22 contacts the recording and reproducing head 89 for audio and control signals and a guide roller 90. The tape 22 thereafter is clamped between and driven by the pinch roller 81 and the capstan 17. Then it enters the cassette 10 and is wound on the tape roll 19.

The capstan 17 is fixed to a flywheel 91 and is rotated by a motor 92. The take-up side reel disc 24 is driven to rotate in the tape winding direction by means of a reel driving motor 93 by may of an idler 94.

During the recording/reproducing mode of operation, the impedance roller 50 rotates with a peripheral speed equal to a tape travel speed of the tape 22, and operates to prevent very minute fluctuations in the tape speed on the tape supply side from being transmitted to the tape speed on the guide drum side, whereby the take travel around the guide drum 35 is held remarkably stable, and jitter is remarkably supperssed. Here, since the impedance roller 50 rotates smoothly with the aid of the pivot bearing, jitter can be further suppressed effectively.

Next, description is given of the result of experiment that how effective impedance roller 50 is for suppressing jitter.

In a case where no impedance roller is disposed along the tape travel path, the jitter component is developed as indicated by a curve I in Fig. 7. When the impedance roller 50 is disposed on the tape supply side with respect to the guide drum 34, as in the case of the apparatus of the present invention, the jitter component becomes as indicated by a curve II in Fig. 8. From this, it will be observed that the impedance roller 50 on the tape supply side serves effectively for suppressing jitter component. The jitter is suppressed to an extent such that it gives rise to no difficulty in practical use.

Further, in an apparatus wherein an impedance roller is provided on the tape take-up side with respect to the guide drum, in addition to the above stated impedance roller 50, the jitter component has been measured. The result is as indicated by a curve Ill in Fig. 9.

When comparing the curve III with the curve II, it will be noted that noticeable difference cannot be observed therebetween. From this, it will be understood that the impedance roller disposed on the tape take-up side serves little for jitter suppression, and that provision of the impedance roller on the tape take-up side, in addition to the impedance roller on the tape supply side, does not affords the effect by that much.

Based on the results of the experiment as stated above, the present invention is made on the recording / reproducing apparatus.

Furthermore, since no impedance roller is disposed on the tape take-up side, the apparatus can be of small size and light weight by the extent corresponding to omission of the impedance roller on the take take-up side. In addition, no provision of impedance roller on the tape take-up side can eliminate a cause for changing tape path length between the guide drum 34 and the head 89, the tape path length being required to be kept accurately in, view of tracking control operation, due to undesired rotation of an arm for supporting the impedance roller when subjected to external impact. Accordingly, the apparatus shows an excellent anti-vibration property, and is thereby most suitable as portable type apparatus.

When a stop operation is performed during the recording/reproducing mode of operation, the ring structures 36 and 37 rotate in the direction opposite to the direction at the time of tape loading, and the guide pole mounting suports 25 and 26 in the direction indicated by arrows A2 and B2, without colliding with the impedance roller 50, to their original positions. The apparatus thereby assumes the original state indicated in Fig. 1.

Further, this invention is not limited to this embodiment but various variations and modifications may be made without departing from the scope of the invention.

Claims (5)

1. A video signal recording and/or reproducing apparatus comprising: a guide drum having at least one rotating head for recording and/or reproducing video signals; loading means for drawing out a tape accommodated within a cassette and loading said tape in a specific tape travel path including a part wherein the tape is in wrapping contact with a predetermined arcuate portion of said guide drum; and a single impedance roller making contact with the tape thus loaded in said predetermined tape travel path, said impedance roller being disposed at a position between the tape supply reel and the guide drum in the tape travel, path and rotating with a peripheral speed equal to a travel speed of the tape in said predetermined tape travel path, thereby stabilizing the travel speed of the tape on the arcuate portion of said guide drum.

2. A video signal recording and/or reproducing apparatus as claimed in claim 1 in which said impedance roller is of pivot bearing supporting structure.

3. A video signal recording and/or reproducing apparatus as claimed in claim 1 in which said impedance roller is disposed between a full-width erasing head and said loading means positioned when the tape loading operation has completed.

4. A video signal recording and/or reproducing apparatus as claimed in claim 1 which further comprises: a rotatable support arm for supporting said impedance roller, in a freely rotatable manner a spring member for urging said rotatable support arm in the direction toward the tape travel path, and means for limiting the rotation of said rotatable support arm at its rotational position where said impedance roller makes contact with said tape, responsive to tape loading operation, said loading means pushing said rotatable support arm aside, said rotatable support arm thereby rotating counter to said spring means for temporarily retracting said impedance roller so that it does not interfere with the loading operation of said loading means.

5. A video signal recording and/or reproducing apparatus as claimed in claim 4 in which said rotatable support arm has a pivot part confronting the initial position of said tape loading means.