JPS599429Y2 - Tape guide device with automatic centering action for tape feeding - Google Patents

Description

[Detailed description of the invention] The present invention has a guide surface for a tape-shaped record carrier, in particular a magnetic tape, which is fed at high speed, which is limited at the top and bottom by guide flanges, on which the magnetic tape is generally moved. The magnetic tape is conveyed through a film of air which is generated in the space between the tape and the guide surface or flange surface, and which space is arranged such that the magnetic tape is fed in a flat position on the guide surface. This invention relates to a tape guiding device of the type described above.

A large number of types of tape guiding devices for tape-shaped information carriers, in particular magnetic tapes, which are transported at high speeds, are already known, including air film guiding devices.

Nevertheless, quite a number of problems have been identified, particularly with regard to friction and tape centering.

These problems are particularly important when recording and playing back video signals due to the high tape feed rates required.

In this case, in order to provide the necessary storage capacity for a sufficient length of video program on a magnetic tape of reasonable length, a large number of tracks with very small track widths are required.

For example, such a video system operates at a tape speed of 3 m/sec, with 12,000 m/hour of magnetic tape being sent along the magnetic head.

Due to physical and economic limitations of reel size, signals are recorded on a large number of parallel tracks, and different tracks are sequentially scanned by repeatedly feeding the tape back and forth along a magnetic head.

This leaves a 600 m tape reel with 30 parallel tracks available for recording and playing back a 90 minute program.

In such a system, the tape is 30 mm per programm.
Due to the repeated feeding, special anti-wear measures have to be taken, which can be done by means of a pneumatic tape guide.

In addition to the necessity of accommodating approximately 30 parallel tracks on the tape, the tape must have an economical width for the consumer, for example 6.3 mm.

The track density on such tapes is unimaginably high.

In this case, the manufacturing tolerance for the width of such a tape is track width 1
We cannot overlook the fact that it is only a matter of minutes (6.
If there are 30 parallel tracks on a 3 mm wide magnetic tape, the track width is typically 0.15 mm and the gap between adjacent tracks is 0.05 mm).

Conventional known tape guiding devices attempt to create track head centering by means of vertical guiding flanges on either side of the tape path.

However, it has been determined that there must be a small spacing between the tape and the guide flange to reduce friction, especially at high tape feed rates.

This spacing prevents accurate tape guidance, since any lateral deviation of the tape relative to the flange leads to longitudinal centering errors, which manifest themselves in a degraded quality of signal reproduction.

It has further been determined that the friction of the tape with the conventional flanges causes undesirable longitudinal vibrations of the tape, which are known as tape flutter (scrape flak) and can severely degrade image quality in video systems.

The guide surface itself may be curved into a concave shape, and if necessary, pressurized air may be sent between the concave guide surface and the tape on the guide surface to create air between the guide surface and the tape. The present applicant has also proposed creating a cushion so that the tape is straight in the width direction during tape feeding [Utility Application No. 50-150277].
U.S. Pat.
979037].

However, this tape guide device is made in one piece, so it is troublesome to manufacture, the cost is high to achieve the required dimensional accuracy, and the flange portion that regulates the tape guide surface has a vertical wall shape. Because of this, there was a possibility that the side edges of the tape could be touched and damaged during high-speed tape feeding.

The object of the invention is to provide a tape guiding device which is simple to manufacture and which is generally advantageous.

Next, the present invention will be briefly explained.

The present invention overcomes the above-mentioned friction and centering problems in conventional tape feeding devices by providing an improved pneumatic tape guiding device.

The tape guide device according to the present invention has an inclined surface on the flange, and the distance between the center lines of these inclined surfaces is equal to the tape width.
Thus, during tape feeding, the tape side edges are guided by the inclined surfaces and the tape is thereby centered in the central position.

During operation, a film of pressurized air may be provided between the tape and the flange ramp sufficient to maintain the tape in said central position symmetrically with respect to the centerline of the tape guide.

Manufacturing errors that appear as tape width fluctuations do not affect the centering of the tape position in the tape guide device according to the invention, since the tape is automatically aligned vertically relative to the tape guide device according to the respective tape width. This is because it is centered on

This prevents tape from shifting within the guide and achieves extremely accurate track head centering and thus improved image quality.

Additionally, tape flutter is greatly reduced, presumably because the tape side edges are pushed away from the slope by the air film.

Next, a description will be given in connection with the drawings.

FIG. 1 shows an embodiment of a self-centering pneumatic tape guide (hereinafter simply referred to as an air guide).

Due to their shape and arrangement, a pair of mutually cooperating guide halves 20 are guided along a centrally arranged scanning head 40 between the guide halves 2o of a record carrier 30, in particular a magnetic tape. Define the part.

The arrangement of the guide halves 20 is suitably symmetrical with respect to the head 40, which allows tape feeding in two directions.

Suitably each half of the guide device has the form of a hollow cylinder, for example with a radius of 2.5 cm, and the two halves 20 have a small spacing, for example equal to half the radius (1.25 cm). Therefore, the head 40 is located within this gap.

As can be seen from FIGS. 2 and 3, the guide surface 24 is provided with an air outlet slit 22 in the center, which makes it possible to form an air film between the tape and the guide surface.

In this case, the air outlet 22 is formed consistently in the form of a slit on the circumferential line of the above-mentioned hollow cylinder.

However, it is also possible to use other suitably configured air outlets in a suitable arrangement to generate a defined air film, for example multiple slits, circular holes or pores in a porous material. be.

The illustrated slit 22 is provided between the contact points 23' and 23'' between the tape 30 and the guide surface 24, respectively, forming a seal in the direction of tape movement for an air film.
Depending on whether the tape is on its way to a take-up reel (not shown), on its way to an ejection reel (not shown), or on its way through head 40, Or it no longer makes contact with the guide device at the rear.

A pair of flange inclined surfaces 26. 26' are provided on opposite sides of the tape movement path of the guide surface 24.

These seven-lung ramps 26, 26' have a mutual spacing at their respective root lines that is less than the minimum tape width of the tape used.

As shown in FIG. 3, a tape having an average tape width rests at the side edges approximately at the center line of the sloped surfaces 26, 26'.

Furthermore, the inclined surface 26. 26' with respect to the guide surface 24
An angle .alpha. in the range of 5 DEG has been found to be suitable, and likewise generally good results have been obtained when obtuse angles are used.

FIG. 3 shows one embodiment of a tape guiding device, here an inclined surface 26. The root line of 26' is below the level of the guide surface 24.

This embodiment allows the guide surface 24 and the flange slope 26 to be cut without using precision cutting tools. 26' making it possible to form sharp longitudinal edges 28.

However, good results have also been obtained when the root line is at the same height as the guide surface 24 but rounded in the middle with a radius of, for example, 0.075 mm.

During operation of the tape feed, a pressurized air supply (not shown) is connected to the outlet 22 in both guide halves 20 and applies appropriate pressure to the tape 30, the guide surface 24 and the ramps 26, 26'. , which causes the tape to be moved away from the guide surface 24 and to a central position corresponding to the tape width.

In practice, a standard width of 6.3 mm tape is 3 m/sec.
350-500 mm water column at a tape speed of c.
0.05 by a pressure of 35 to 50 mbar)
It has been found that a tape tension of 6 kg (approximately 0.56 newtons) is sufficient to lift it into the center position.

The air film is indicated at 50 in FIG.

The tape 30 is applied to the above-mentioned inclined surfaces 26, 26 on this air film.
', the center axis of the tape 30 is almost always aligned between the guide halves, even though tape width variations occur, which are discernible as lateral sliding of the line of contact between the tape side edges and the ramp. It coincides with the longitudinal central axis of the guide surface 24 of the section 20.

This prevents tape deviations in the vertical plane despite production-induced tape width variations, thus ensuring and thereby reducing the exact centering of the scanning head on the track to be scanned. A playback quality that has not yet been achieved is achieved.

In addition, sufficient air pressure is adjusted to create a pressure drop between the tape side edge and the adjacent flange slope to ensure that the tape is vertically centered between the flanges. If this is the case, tape flutter is significantly reduced, since the tape side edges are pushed away from the flange ramps, thereby reducing physical contact and therefore friction.

Although only one embodiment of the tape guide device according to the present invention has been described above, it goes without saying that numerous embodiments and modifications are possible within the scope of the gist of the present invention.

[Brief explanation of the drawing]

The drawings show one embodiment of the tape guide device according to the present invention, and FIG. 1 is a plan view of the tape guide device according to the present invention;
FIG. 2 is an enlarged plan view of the l portion in FIG. 1, and FIG. 3 is a side view of the same. The correspondence between the main parts of the illustrated apparatus and the symbols is as follows: 10... tape guide device, 20...
...Both halves of the guide device, 22...Air outflow slits, 23' and 23''...Contact points, 24...
... Guide surface, 26 and 26' ... Flange slope, 28 ... Edge, 30 ... Tape, 40 ... Magnetic head, 50 ... ...Air film.

Claims (1)

[Scope of utility model registration request] A guiding device for a recording tape, in particular a magnetic tape, which is fed at high speed through a fixed recording/playback head, consisting essentially of a fixed guiding bearing surface, said guiding bearing surface extending between a base and a base. bounded by a pair of angled flanges spaced apart with a spacing less than the width of the tape;
The inclined flanges form an obtuse angle with respect to the guide water surface, and are provided with a curved bearing surface through which the tape is fed, and a pair of corresponding guide members spaced apart from each other are arranged, both of which The recording/reproducing head is disposed in the gap between the guide members, the guide members define a path for the tape, each guide member has a curved bearing surface, and the guide members define a path for the tape, and each guide member has a curved bearing surface. The member has a contact portion through which the tape enters the guide device in close proximity to the curved bearing surface and a contact portion through which the tape exits the guide device,
A pressurized air supply device is connected to the curved bearing surface of both the guide members between the contact portions, and thereby connects the tape, the guide bearing surface, the inclined flange, and the contact portions. generating a substantially constant pressure air film along the air chamber formed by the tape to lift the tape off the guide water surface to a position where the horizontal distance between the inclined flanges is substantially equal to the tape width; A tape guiding device characterized in that it maintains the tape centered with respect to the centerline of a guiding bearing surface.