DE3300378A1 - Magnetic-tape guidance device for a video recorder and player - Google Patents

Abstract

The helical 180 DEG rotary-drum wrap in a video recorder and player is ensured by a magnetic-tape guidance device which comprises guide pins for threading and guiding, which are constructed as tilt or pendulum pins. Between these guide pins and the rotary-drum wrap, one guidance pin is in each case provided which has at its upper end a flange. The lower edges of this flange, together with a stationary tape guidance for the lower edge of the tape, form a three-point guidance. The wrap angle can be changed for searching or trick effects during replay by alternatively adjusting the height of the guidance pins. This results in track following similar to the DTF system.

Description

"Deutsche Thomson-Brandt GmbH ι / P.O. Box 2060

Sheet ■ - · -. η 7730 Villingen-Schwenningen

Ο4. January 1983. - T-PA 436 -

PATENT APPLICATION

Magnetic tape guide device for a video recording and reproducing device

State of the art

The invention relates to a magnetic tape guide device according to the preamble of the first claim.

Current video magnetic tape recorders according to the helical scan system use for tape guidance in the area of Head drum a stationary, cylindrical part that contains the tape guide in the form of a helical step. The head or heads are in an annular gap arranged between the stationary and the driven drum part arranged above and on the latter attached. A one-piece head or rotary drum is subject to a patent application filed at the same time remove.

The present invention was based on the object of developing a magnetic tape guide device which a mechanical decoupling of the magnetic tape branches

BATH ORIGINAL

Deutsche Thomson-Brandt GmbH ■ P.O. Box 2060

Sheet Z '&' TTSOVillingen-Schwenningen

January 04, 1983 - T-PA 436 -

and behind the head drum causes so that low Inaccuracies in the tape guide outside the scanning unit do not affect the directional stability. Furthermore, tracking should be implemented using simple means, which can also be used for so-called Trick plays is functional.

These objects are achieved for the specified preamble of the first claim according to the invention according to its characteristic.

Further details and refinements can be found in the remaining claims and a description below to be found in an exemplary embodiment.

The inventive design of the device sees before that two deflecting pins sand so movably that they the belt to a 180 wrap around the rotary drum lead and are designed as pendulum pins themselves. Your tilting or pendulum axis is just below the Provided in the middle of the belt and results in a mobility transverse to the direction of travel of the belt. Between these deflection pins and Start or At the end of the rotary drum loop, a guide pin each is arranged in a stationary manner, which has a flange have, on the lower edge of which the tape is supported. * As a third guide point for the lower edge of the belt a tape guide is used, which is stationary at half the angle of wrap near the lower edge of the rotating drum.

- - · - ■ - - Deutsche Thomson-Brandt GmbH

P.O. Box 2060 sheets j »i - ■ _ Iq,. 7730 Villingen-Schwenningen

January 04, 1983 - T-PA 436 -

is fixed, has a rounded surface and protrudes into a groove in the rotary drum. The guide pins are alternatively designed to be height-adjustable and thus allow the screw angle to be changed by Drum and thereby an advantageous, interference-free playback without crosstalk and also so-called Search or trick operation. The branches of the magnetic tape are advantageously mechanical in front of and behind the rotary drum decoupled. This makes it possible to reduce the accuracy requirements of the entire drive to a compact one Restrict unity. It is also advantageous that there are minor inaccuracies in the tape guide outside of the tape guide do not affect tracking or tracking.

Further advantages emerge from the following description of exemplary embodiments on the basis of the Drawing that has the following figures:

Figure 1 with a simplified side view of the rotary drum and two guide and Reversing pins .;

FIG. 2 shows a plan view of a drive with the magnetic tape guide device according to the invention in conjunction with a video tape cassette;

FIG. 3 shows a partial illustration in side view of section A-B, which is shown in FIG Figure was indicated;

BATH ORIGINAL '

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Copy

"Deutsche Thomson-Brandt GmbH Postfach 2060 • Sheet

■> I VJO UQuI I ^ \ J \ J ν

'! · 7730 Villingen-Schwenningen

O4. January 1983

- T-PA 436 -

FIG. 4 shows a partial illustration of a plan view of a drive with the cut lines entered AWAY.

In Figure 1, an inclined mounted rotary drum 2 is shown, which is partially helical by a belt 20 is embraced. The inflow and outflow of the belt 20 takes place via a cylindrical deflector each if t 8. These deflection pins 8 are toggle or pendulum pins formed by moving around an axis 22 just below the tape center 23 and transversely to the tape running direction are movable. Between the guide pins 8 and the. -., Rotary drum 2 are arranged guide pins 9 and IO which have a flange near their upper end the lower edge of which is supported by the upper edge of the band 20. At half the wrap angle of the band a stationary tape guide 11 is provided near the lower edge of the rotary drum, on its rounded surface the lower edge of the band 20 is applied. The tape guide protrudes into a groove 24 in the rotary drum 2.

A drive which is connected to a video cassette 1 is shown in FIG. A pressure roller 4, the guide pins 8 as well as a guide roller 12 and a tape tension sensor have the tape 20 from the video cassette pulled out and over the guide pins 9 and 10 the rotary drum 2 is applied as required, so that the band 2O wraps around the rotary drum 2 at 180 in a helical manner. The tape is printed on the capstan 3 and runs on an audio head 5, an audio erase head 6 and an erase head 7 when the drive is put into operation and the tape 20

-'- '- - German Thomson-Brandt GmbH

P.O. Box 2060 sheets ■ - - ■ * O '7730 Villingen-Schwenningen

O4. January 1983 - T-PA 436 -

the left, full spool is transported to the empty, right spool of the video cassette. The tape transport device and the direction of rotation of the rotary drum 2 match. Due to the high speed of the rotary drum 2, the belt inlet near the deflection pin 9 air is pressed between the belt and the surface of the rotating drum 2 and an air cushion generated as it is already known from the prior art.

Figures 3 and 4 show an exemplary, alternatively acting height adjustment device for the guide pins 9 and IO. It is thus possible to make a change of the helix angle to achieve the rotary drum 2. In addition to the 'already shown and previously' in Figures 1 and 2 with corresponding item numbers Parts of the device described here a base plate 25 is shown in which the rotating drum 2 and the guide pins 9 and IO are also attached. These Fixing of the latter is in counter-rotating threaded sockets executed, which are connected to a magnetic core via pivot levers from an electrodynamic converter 21 Push rods are driven. The coils of the transducer 21 are used to control the pitch angle fed with a current that consists of the summation of the difference signal of the first half of the track and the inverted difference signal of the second half of the track formed will. The resulting height adjustment of the guide

9 and IO
pins / causes the track position of the tape 20 to be tilted

around the fixed tape guide 11.

For the mechanical decoupling already mentioned and for introducing a moment across the direction of travel of the belt

BATH ORIGINAL

"" Deutsche Thomson-Brandt GmbH

_n Π P.O. Box 2060

sheet —y \ ή ^. yyaOVillingen-Schwenningen

January 04, 1983 - T-PA 436 -

the deflection pins 8 are used, the tilt axis of which is offset by about 10% of the bandwidth. The result is a slightly distorted belt tension profile. This results in an upward force transverse to the direction of travel of the belt, which is absorbed by the following height guide pin 10 over the edge of the belt at the edge of its flange.

Since the deflection pins 8 are designed as pendulum pins and the tape 20 from the video cassette in the playing position bring, no adjustment of the same in its end position is necessary.

In summary, it should be noted that the correction signal for the track tracking via the height adjustment of the guide pins 9 and IO as well as for the capstan control from the four pilot frequencies recorded with the video signals f, - f .. is determined by differential measurement of the crosstalk from the neighboring lanes. The capstan control carried out in this way is known as ATF = automatic track following. In the so-called DTF (= dynamic track following) system, tracking is carried out using PXC elements as carriers for the video heads. The correction signal used for this is generated in a similar manner from four pilot frequencies.

Claims (1)

"Deutsche Thomson-Brandt GmU Postfach 2060 7730 Villingen-Schwenningen O4. January 1983 - T-EPA 436 - PATENT CLAIMS Magnetic tape guide device for a video recording and playback device which, with deflecting means, the tape into a helical loop on a one or deflect several heads having rotary drum, characterized in that each a deflection pin (8) on both sides of the rotary drum (2) up to a position resulting in a 180-degree loop are movable and are designed as pendulum pins by moving around an axis (22) just below the belt center line (23) and are movable transversely to the tape running direction that between these deflection pins (8) and the beginning and the end of the rotary drum contact through the respective belt section one perpendicular each to the tape run standing guide pin (9, 1O) is arranged on the base plate supporting the rotary drum axis (25) is arranged and has a flange near its upper end, on the lower edge of which Belt (20) is supported for height guidance, and that one at half the angle of wrap near the lower edge of the rotary drum The tape guide (11) fixed in place on the base plate (25) is provided, the tape guide of which is facing the lower edge of the tape and thereby the same supporting surface is rounded and which is inserted into a groove (24) of the rotary drum (2 protrudes. "*. * '. " Deutsche Thomson-Brandt GmbH η _t P.O. Box 2060 itt "" "2 ■ · · 'Λ / - 7730 Villingen-Schwenningen January 04, 1983 - T-PA 436 - 2. Magnetic tape guide device according to claim 1, characterized in that the center offset of the pendulum axes of the deflection pins (8) makes up about 10% of the bandwidth. 3. Magnetic tape guide device according to claim 1, characterized in that the guide pins (9, 10) are axially adjustable in opposite directions for a playback tape speed other than the normal recording tape speed to realize the required screw angle of the belt (20) on the rotary drum (2). Magnetic tape guide device according to claim 3, characterized in that a transducer (21) is provided which controls the guide pins (9, 1O) by receiving control currents This is influenced by the fixed values and the four pilot frequencies recorded with the video signals derived correction signal quantities, that these correction signals in a known manner Difference measurement of the crosstalk between adjacent recording tracks can be obtained and that the fixed values proportional to the speed deviations between the recording and the desired trick play. ORIGINAL BATHROOM * - 3 - "German Thomnon-Brandt Gi P.O. Box 2060 7730 Villingen-Schwennlngen O4. January 1983 - T-PA 436 - 5. Magnetic tape guide device nach.einem or more of the preceding claims, characterized characterized in that the difference signal of the first half of the track and the inverted difference signal of the second half of the track and the inlet and outlet for alternating height adjustment guide pins (9 or 10) can be used, the guide edges of which are connected to the tape guide (11) Form the three-point support of the belt (2O) and thus by changing the helix angle of the belt (20) exercise a corresponding change in the track inclination angle by tilting the tape guide (11).