JPH0612747A - Stationary drum of rotary magnetic head and its production - Google Patents

Abstract

PURPOSE:To form projecting parts for buffer into shapes and at positions desirable for plastic working with good accuracy by chipping off the slope of a lead near its vertex and providing the projecting parts in the part above the chipped off part. CONSTITUTION:The top end on the outer periphery of a stationary drum 1 is chipped off as much as a prescribed height, for example, by the diameter of the projecting part 3, in the circumferential direction to the same diameter as the diameter of a tape traveling surface 9 to be worked later before working of the lead 7 at the time of finishing the stationary drum prior to working having the diameter larger than the diameter of the tape traveling surface 9. The tape traveling surface 9 is then chipped off and the working of the lead 7 is executed, by that, the stationary drum is produced. The wall at the top end of the stationary drum 1 of the cut where the vertex part of the slope is cut off is thereafter planed to form thin parts 5 and 6. The projecting parts 3 and 4 are then formed by plastic working from the inner side toward the outer side. As a result, the projecting parts 3, 4 for buffer are formed to and in the desired shapes and positions with the good accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a fixed drum of a rotary magnetic head for recording or reproducing a signal on a magnetic tape by using a rotary magnetic head such as a video tape recorder (hereinafter referred to as VTR). It is a thing.

[0002]

2. Description of the Related Art In VTRs, the number of rotary heads varies depending on the model even if they are of the same format. When compatible playback is performed between VTRs having different numbers of rotary heads, the rotary magnetic head rushes into the magnetic tape. Also, due to the influence of the tape vibration that occurs when the tape is detached, local bending and color unevenness of the playback screen occur, and the playback image quality is significantly degraded. FIG. 3 is a perspective view of a fixed drum of a conventional rotary magnetic head in which the countermeasure is taken. Outer peripheral portion 8 of fixed drum 1
The lead 7 is continuously cut into an arc shape. The edge of the magnetic tape (not shown) is regulated by the slope of the lead 7 and runs along the tape running surface 9. Protrusions 3 and 4 are provided by plastic working on the thin portions 5 and 6 provided in the vicinity of the entry portion and the removal portion of the magnetic tape, or in the vicinity thereof, respectively. A method has been proposed in which the shock is weakened and the generated tape vibration is sufficiently relaxed.

[0003]

When manufacturing the fixed drum as shown in FIG. 3, the following problems occur due to the processing accuracy of the convex portions.

FIGS. 4 and 5 are enlarged views of the fixed drum 1 in the vicinity of the magnetic tape entry portion. FIG. 4 shows an example in which the arc-shaped lead 7 formed on the fixed drum 1 that regulates the lower end of the tape 2 near the tape entry portion and the convex portion 3 are very close to each other. FIG. 5 is an example in which the convex portion 3 is located below the lead 7. Thus, when the convex portion 3 is plastically processed,
Due to the thickness of the outer peripheral portion 8 of the fixed drum 1, the shape of the convex portion 3 was not uniform or reproducible. In any case, if the relative position between the convex portion 3 and the lead 7 is deviated, they interfere with each other, which causes a problem.

Further, in the case of the plastic working of the convex portion 3 as shown in FIG. 5, in the case of the outer peripheral portion 8 of the fixed drum below the lead 7, when the plastic working of the convex portion 3 in the case of FIG. A force considerably larger than the force at the time is required, and when the convex portion 3 is plastically worked at the stage of finishing the fixed drum 1, the chuck (not shown) fixing the fixed drum 1 is deformed. There is also a problem that the life of the chuck is shortened.

In view of the above problems, an object of the present invention is to accurately lead the plastic working of the convex portion of the fixed drum for preventing the vibration of the magnetic tape which occurs when the rotary magnetic head is thrust into and out of the magnetic tape. To do so without interfering with.

[0007]

In the fixed drum of the present invention, the inclined surface of the lead is scraped off near its apex, and a convex portion is provided above the scraped portion.

[0008]

With the above structure, the convex portion for cushioning the magnetic tape at the tape entry portion or the tape removal portion can be plastically worked with high precision so as not to interfere with the leads.

[0009]

1 is a perspective view of a fixed drum according to this embodiment.

On the outer periphery of the fixed drum 1 of the rotary magnetic head device, an arcuate lead 7 is formed by cutting off the apex that regulates the lower end of the magnetic tape. The outer shape of the outer circumference 10 of the fixed drum 1 at the portion where the apex is cut off is made substantially equal to the outer shape of the tape running surface 9.

In the vicinity of the tape advancing portion and the tape detaching portion of the fixed drum 1, a convex portion 3 and a convex portion 3 formed by plastic working are provided in order to reduce the impact of the magnetic head entering and leaving the magnetic tape and loosen the generated tape vibration. 4 are provided. Further, in order to facilitate the plastic deformation of the convex portions 3 and 4, thin-walled portions 5 and 6 in which the thickness of the inner peripheral side of the fixed side drum in the vicinity of the convex portions 3 and 4 is shaved are provided. The tape is guided by the slope of the lead 7 and runs along the tape running surface 9.

FIG. 2 is an enlarged view of the vicinity of the convex portion 3 near the tape entry portion of the fixed drum 1 of this embodiment.

The magnetic tape 2 is wound around the fixed drum 1,
The vehicle runs while being restricted by the slope of the lead 7. A portion 11 indicated by a broken line in the drawing is a part of an arc of the apex portion of the sloped surface of the lead 7 that has been scraped off.

The convex portion 3 is a position where the magnetic tape 2 is in sliding contact with the fixed drum 1, and a signal other than a video signal to be recorded and reproduced is recorded or an area of the tape where no signal is recorded. It is provided to correspond to.

Reference numeral 3-1 is the tip position of the plastic working tool when the convex portion 3 is provided by plastic working. Tool tip position 3-
1 is near the upper end surface 1-1 of the fixed drum 1, the convex portion 3
Has a very sharp shape at the upper end surface 1-1 of the fixed drum, and damages the tape 2 wound around the fixed drum 1 and running. Therefore, the tool tip position 3-1
Must be located at a distance from the upper end surface 1-1 of the fixed drum to some extent, and near the extension of the slope of the lead 7.

It is desirable that the distance between the scraped upper end edge 12 of the lead 7 and the fixed drum upper end surface 1-1 be equal to or larger than the diameter of the convex portion 3 within a range that does not affect the running accuracy of the tape 2.

An example of a method of processing the fixed drum having a shape obtained by cutting off the apex of the slope of the lead 7 will be described.
When finishing the fixed drum before processing which is larger than the diameter of the tape running surface 9, before the processing of the lead 7, the outer peripheral upper end of the fixed drum 1 is circumferentially moved by a predetermined height, for example, the convex portion 3. The diameter is cut to the same diameter as the tape running surface 9 to be processed later. Since the tape does not come into sliding contact with this portion, it may be slightly larger than the diameter of the tape running surface 9. Next, the tape running surface 9 is cut and the leads 7 are processed to manufacture the tape. After that, the meat at the upper end of the fixed drum 1 at the part where the apex of the slope is cut off is shaved to form thin parts 5 and 6, and the convex parts 3 and 4 are formed by plastic working from the inside to the outside.

[0018]

EFFECTS OF THE INVENTION It is possible to scrape off the vicinity of the top of the inclined surface of the lead, and form a buffering convex portion in this portion by plastic working in a desired shape and position with high precision. Due to the buffering effect, it is possible to eliminate screen bending and color misregistration that occur on the playback screen.

[Brief description of drawings]

FIG. 1 is a perspective view of a fixed drum according to the present invention.

FIG. 2 is an enlarged view of the vicinity of the tape entrance portion of FIG.

FIG. 3 is a perspective view of an example of a conventional fixed drum.

FIG. 4 is an enlarged view of an example in which the relative position between the protrusion and the lead is not good.

FIG. 5 is an enlarged view of another example in which the relative position between the protrusion and the lead is not good.

[Explanation of symbols]

 1 Fixed drum 3,4 Convex part 5,6 Thin part 7 Lead 8 Outer peripheral part 9 Tape running surface

Claims (2)

[Claims] 1. A protrusion protruding outward from a thin portion of a part of an upper end of a fixed drum having a tape running surface and an edge of a tape provided on an outer periphery of the fixed drum, the tape being outside the tape running surface. A fixed drum for a rotary magnetic head, comprising: a lead having an inclined surface projecting toward one side, and the lead is scraped off at the apex of the inclined surface below the convex portion. 2. The upper end of the drum is cut to a diameter substantially equal to the diameter of the tape running surface to be processed after a certain height in the circumferential direction, and then the tape running surface is cut to form a lead. A method for manufacturing a fixed drum of a rotating magnetic head, which is characterized.