JPS5827396Y2 - Video tape recorder task head touch - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a video tape recorder having a rotating head drum to which a video head is attached. This invention relates to a tach-head device that generates and detects accompanying pulses.

An example of a videotape recorder having this type of tack head device is a helical scan type videotape recorder in which two video heads are attached to a rotating head drum (this example will be explained below, and will be referred to simply as a VTR).
) are known.

The tack head device in this VTR has a U-shaped magnetic core on the fixed head drum side provided in correspondence with the rotary head drum in order to generate and detect two 60 Hz tack pulses per rotation of the rotary head drum. Generally, two tack heads are attached and one magnetically permeable magnetic path member such as an iron piece is provided on the rotating head drum side.

In this tack head device, the magnetic path member is also rotated as the rotary head drum rotates, and a magnetic path is formed when the magnetic path members cross the head coils of two tack heads attached to the fixed head drum. However, by lowering the magnetic resistance of this tuck head coil, a bus voltage is induced in each tack head coil.

The relative mounting of the magnetic path member and the tack head is necessary because the point at which this pulsed voltage is generated, that is, the point at which the magnetic path member crosses the tack head coil, must coincide with the point at which the video head starts contacting the tape. The position is designed with extreme precision, and requires highly accurate installation work.

For this reason, the design should allow for fine adjustment of the mounting position of either the tack head or the magnetic path member, or
Alternatively, a method has been used in which the pulse and pulse voltages induced in the tuck head coil are electrically delayed and the delay time is finely adjusted.

The present invention has been made in view of these points, and provides a tack head device that allows precise and easy fine adjustment of the relative positional relationship between the tack head and the magnetic path member.

The present invention will be explained below with reference to the drawings of the embodiments, and the same or equivalent parts in each drawing are given the same reference numerals.

FIG. 1 is a plan view of the rotary head drum seen from above, and FIG. 2 is a sectional view taken along line A- in FIG.

In FIG. 1, two video heads 21 and 22, which alternately trace the tape surface, are precisely mounted on a cutting line A-B passing through the center of the rotary head drum 1 using a jig.

Using this tangent line A-B as a reference line, two circular first and second adjustment holes 3 and 4 with different diameters are placed at positions equidistant from the center on a normal line A'-B' that is perpendicular to this line at the center. is drilled.

The first adjustment hole 3 is a simple hole, and the second adjustment hole 4 is inserted with a bent leg piece 51 of a magnetically conductive magnetic path member, such as an iron piece 5, attached to the rotary head drum 1.

The width of this bent leg piece 51 is as shown in FIG.
The diameter of the adjustment hole 4 is approximately equal to that of the adjustment hole 4.

The iron piece 5 extends along the inner hole edge of the second adjustment hole 4.
It is attached by screws 71 and 72 fitted into long holes 61 and 62 provided in the rotary head drum 1 so as to slide as shown by the arrow in the figure.

On the other hand, as shown in the sectional view of FIG.
A fixed head drum 8 is provided on the lower side corresponding to the tack head 9 having a magnetic core 91 on the fixed head drum 8.
is installed.

As shown by the dotted line in FIG. 1, two tuck heads 9 are arranged along the other tack head 10 at positions corresponding to the first and second adjustment holes 3 and 4 on the normal line A'-B'. Ru.

Therefore, when the rotary head drum 1 rotates, the iron piece 5 also rotates and its folded leg piece 51 is attached to the tack head 9.10.
The magnetic core 9L11 is closely crossed, and at this time, the magnetic resistance is lowered and a pulsed voltage is detected by the tack heads 9 and 10.

Here, the gap G between the bent leg piece 51 of the iron piece 5 and the magnetic core 91 of the tack head 9 needs to be maintained at 100 to 200 microns in practice, and at the point where the video heads 21 and 22 begin to contact the tape. They must be directly facing each other.

For this purpose, the iron piece 5 is adjusted and fixed by slightly sliding the bent leg piece 51 along the inner edge of the second adjustment hole 4.

In other words, the diameter of the second adjustment hole 4 is 101! In other words, the width of the bent leg piece 51 of the iron piece 5 is 101! If W, by rotating the leg piece 51 by 5 degrees, the leg piece 51 moves about 440 microns in the circumferential direction of the rotary head drum 10 with respect to the magnetic core 91 of the tuck head 9, and the leg piece 51 and the magnetic core The gap G with 91 is adjusted by a change of 25 microns.

Moreover, the relative positional change of the leg piece 51 with respect to the magnetic core 91 at this time is sufficient as a practical adjustment range and does not pose a problem.

As described above, the present invention enables adjustment in extremely minute units, simplifies the structure, and facilitates initial dimensional design.

Furthermore, it can be realized without requiring any special members compared to the prior art, and has a practical effect.

In the present invention, the width of the leg piece 51 of the iron piece 5 does not necessarily have to be approximately equal to the diameter of the second adjustment hole 4, and it is possible as long as the leg piece 51 can slide at least along the inner hole edge. It is.

Further, the drilling positions of the first and second adjustment holes 3 and 4 are limited to the positions shown in the drawings of the embodiment, since the closer to the outer periphery of the rotary head drum 1 there is less error in the detection time of pulse voltage generation. It's not a thing.

Furthermore, the holes in the first adjustment hole 3 are for balancing the mass around the shaft in order to improve the rotational balance of the rotary head drum 10, and do not necessarily have a diameter different from that of the second adjustment hole 4. In consideration of this point, the iron pieces 5 may be configured to have the same diameter to make the work of attaching the iron piece 5 easier.

Of course, it is also possible to omit this first adjustment hole 3.

[Brief explanation of the drawing]

Fig. 1 is a plan view from above of the rotary head drum showing the device according to the present invention, Fig. 2 is a sectional view taken along line A-A' shown in Fig. 1, and Fig. 3 is a plan view from above of the main part of the present invention. FIG. 4 shows a sectional view of FIG. 3. DESCRIPTION OF SYMBOLS 1... Rotating head drum, 21. 22... Video head, 3... First adjustment hole, 4... Second adjustment hole, 5...
...Magnetic path member, 51...Bending leg piece, 61, 62...
・Long hole, 71, 72... Screw, 8... Fixed head drum, 9゜10... Tack head, 91, 11...
・Magnetic core.

Claims (1)

[Scope of utility model registration request] In a video tape recorder comprising a rotary head drum to which a video head is attached, and a tack head having a magnetic core fixed to the rotary head drum, as the rotary head drum rotates, the vicinity of the magnetic core of the tack head a magnetically permeable magnetic path member that crosses the rotary head drum, and a circular adjustment hole drilled along the circumference of the rotary head drum, the magnetic path member being slidably attached along the edge of the adjustment hole; A tack head device for a Toshita video tape recorder, characterized in that the gap distance between the magnetic core and the magnetic path member is adjusted by this sliding motion.