JP2787638B2 - Method of manufacturing fixed drum for rotating magnetic head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a fixed drum of a rotary magnetic head which records or reproduces signals on a magnetic tape by using a rotary magnetic head such as a video tape recorder (hereinafter referred to as VTR). It relates to improvement of the method.

[0002]

2. Description of the Related Art In a VTR, the number of rotary heads varies depending on the model, even in the case of the same format. When compatible playback is performed between VTRs having different numbers of rotary heads, the rotary magnetic head enters the magnetic tape. Also, due to the influence of the tape vibration generated at the time of detachment, local bending and color unevenness of the reproduced screen occurred, and the reproduced image quality was significantly deteriorated. FIG. 3 is a perspective view of a fixed drum of a conventional rotary magnetic head in which measures are 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 either the vicinity of the entry portion or the detachment portion of the magnetic tape, or in the vicinity thereof, so that the magnetic head enters and leaves the magnetic tape. There has been proposed a method of weakening the impact and sufficiently relaxing the generated tape vibration.

[0003]

When the fixed drum as shown in FIG. 3 is manufactured, the following problems occur depending on the processing accuracy of the convex portion.

FIGS. 4 and 5 are enlarged views of the vicinity of a portion of the fixed drum 1 where the magnetic tape enters. FIG. 4 shows an example in which an arc-shaped lead 7 formed on the fixed drum 1 for regulating the lower end of the tape 2 in the vicinity of the tape entry part and the convex part 3 are very close to each other. FIG. 5 shows an example in which the protrusion 3 is located below the lead 7. As described above, 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 did not have reproducibility. In any case, if the relative positions of the protrusions 3 and the leads 7 deviate, they interfere with each other, causing a problem.

[0005] Further, as shown in FIG. 5, when the hit point at the time of plastic working of the convex portion 3 is at the portion of the fixed drum outer peripheral portion 8 below the lead 7, the plastic working of the convex portion 3 in the case of FIG. When the plastic working of the convex portion 3 is performed in the stage of finishing the fixed drum 1, a chuck (not shown) fixing the fixed drum 1 is deformed. Also, there is a problem that the life of the chuck is shortened.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to accurately read out the plastic working of a convex portion of a fixed drum for preventing the magnetic tape from vibrating when the rotating magnetic head enters or separates from the magnetic tape. To avoid interference.

[0007]

SUMMARY OF THE INVENTION A method for manufacturing a fixed drum of a rotary magnetic head according to the present invention comprises the following steps. First, as a first step, the upper end of the fixed drum is cut in the circumferential direction by a certain height to a diameter substantially equal to the diameter of the tape running surface to be processed later. Next, as a second step, the tape running surface is cut below the portion cut as described above so as to form a lead. Next, as a third step, a convex portion is formed on the upper end portion of the fixed drum cut in the first step by a plastic working toward the outside at an entry portion or a detachment portion of the tape.

[0008]

According to the manufacturing method described above, the convex portion for the interference action of the magnetic tape at the tape entry or exit portion can be plastically processed with high precision so as not to interfere with the leads.

[0009]

FIG. 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, there are formed arc-shaped leads 7 whose tops for regulating the lower end of the magnetic tape are cut off. The outer shape of the outer periphery 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 entry portion and the separation portion of the fixed drum 1, the convex portion 3 formed by plastic working is formed to reduce the impact of the magnetic head entering and leaving the magnetic tape and to reduce the tape vibration generated. 4 are provided. Further, in order to facilitate plastic deformation of the convex portions 3 and 4, thin portions 5 and 6 are provided which are formed by shaving the inner peripheral side of the fixed drum near the convex portions 3 and 4. The tape is guided along 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 the present embodiment.

A magnetic tape 2 is wound around a fixed drum 1,
The vehicle travels 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 the arc at the vertex of the slanted surface of the lead 7.

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

Reference numeral 3-1 denotes a tip position of the plastic working tool when the convex portion 3 is provided by plastic working. Tool tip position 3-
1 is located near the upper end surface 1-1 of the fixed drum 1, the protrusion 3
Becomes extremely sharp at the portion of the fixed drum upper end surface 1-1, and the tape 2 wound around the fixed drum 1 and running is damaged. Therefore, the tool tip position 3-1
Needs to 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 cut 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.

A method of processing a fixed drum having a shape obtained by cutting off the apex of the slope of the lead 7 will be described. At the time of finishing the fixed drum before the processing that is larger than the diameter of the tape running surface 9, before processing the lead 7, the outer peripheral upper end of the fixed drum 1 is circumferentially extended by a predetermined height, for example, the convex portion 3. Cut by the same diameter as the diameter of the tape running surface to be processed later. This portion may be slightly larger than the diameter of the tape running surface 9 because the tape does not slide. next,
The tape running surface 9 is cut, and the lead 7 is processed. Thereafter, the upper end of the fixed drum 1 at the tape entry portion or the release portion, which is a portion obtained by cutting off the apex portion of the lead slope, is shaved to form thin portions 5 and 6, and plastic working is performed outward from the inside of the thin portion. To form the projections 3 and 4.

[0018]

According to the present invention, the vicinity of the top of the slope of the lead is scraped off, and a bumping projection can be formed in this portion in a desired shape and position with high precision by plastic working. Due to the buffering action, it is possible to eliminate screen bending and color misregistration occurring on the reproduction screen.

[Brief description of the 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 a tape entry portion in 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 a relationship between a protrusion and a lead is not good;

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

[Explanation of symbols]

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

Claims (1)

(57) [Claims] 1. A first step of cutting the upper end of a fixed drum to a diameter substantially equal to a diameter of a tape running surface to be processed later by a constant height in a circumferential direction, and forming the tape running surface so as to form a lead. A second step of cutting, and a third step of forming an outwardly projecting convex portion by plastic working at an upper end portion of the drum cut in the first step and at an entrance portion or a detachment portion of the tape, Are sequentially performed.