JPS59112472A - Tape reel for video cassette - Google Patents

Abstract

PURPOSE:To make a work for removing a gate mark unnecessary and to improve productivity by providing an injection molding gate on the head of a fixing projection for passing through the other flange, in a hub end part which is injection molded in one body with one flange. CONSTITUTION:One flange 1b and a hub 2 are injection molded and formed in one body, a center projection 3 and a fixing projection 4 of the hub 2 are made to pass through the other flange 1a, and the other flange 1a is fixed by melting the head of the fixing projection 4 by means of ultrasonic welding. In this case, a molding resin injecting gate G is provided on the head of the fixing projection 4, by which when the other flange 1a and the hub 2 are fixed, the gate mark G is melted simultaneously, therefore, the productivity and yield are improved and the manufacturing cost can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a tape reel for video cassettes, and in particular to a video cassette tape reel that takes into account gate marks that remain on the hub after injection molding of this type of tape reel made of plastic. Regarding tape reels for cassettes.

2. Description of the Related Art Recently, video cassettes in which a magnetic tape for recording and reproducing video and audio is housed in a casing have been produced in large quantities as recording and reproducing equipment has become widespread. However, the tape reel that wraps and holds the tape inside the casing is made of plastic, although its size varies depending on the recording/playback method used by each company and the length of the recording/playback time. In terms of form, they have something in common in that they have almost the same basic configuration.

Examples of this are shown in FIGS. 1 to 3.

Generally, this kind of tape reel has a pair of flanges Ia,
lb are connected at a distance in the axial direction by a hub 2, one flange Ib is integrally molded with the hub 2 in advance, but the other flange Ia is molded separately and then placed on the corresponding end of the hub 2. and is fixed to the hub 2 by crushing the head of the fixing protrusion 4 provided at the end by ultrasonic welding. Of course, a magnetic tape (not shown) is wound around the outer peripheral surface 2a of the hub 2.

FIG. 2 shows a longitudinal section of such a hub 2 (FIGS. 1 and 3 II-
TI line), Fig. 3 shows the cross section (Fig. 2 line m-m),
To explain each in detail, on the end surface of the hub on which the separate flange la rests, there is a protrusion 3 on the central shaft 2 that is pressed by an elastic piece (not shown) in the cassette casing, and After penetrating the flange Ia, a fixing protrusion 4 is provided whose head is crushed by ultrasonic welding and deformed as shown by the imaginary line 4', thereby pressing down on the separate flange.

On the other hand, from the bottom of the flange 1b fixed to the hub 2, a hollow cylindrical space is bored through the flange and hung inside the hub, into which the drive shaft or reel support shaft of the recording/playback device is fitted. do. That is, this cylindrical space that is open only at one end serves as a receiving space 5 for a support shaft on the recording/reproducing device side.

As is well known, the support shaft of such a recording/playback device has ribs protruding outward in the radial direction at appropriate intervals in the circumferential direction in the portion that protrudes into the support shaft receiving space 5. , ribs 6 extending radially inward from the inner wall surface of the support shaft receiving space 5 at appropriate intervals in the circumferential direction and extending in the axial direction.
is provided. That is, the rib on the supporting shaft side fits into and engages with one of the relative grooves 7 formed between adjacent ribs, thereby transmitting the rotation of the supporting shaft to the reel and vice versa. The rotation of the reel is then transmitted to the support shaft.

Generally, in addition to this configuration, a double cylindrical structure is used, with the part that defines the outer peripheral surface of the hub being an outer cylinder part 8 and the part that defines the internal support shaft receiving space an inner cylinder part 9, and the two are connected by a connecting bar 10. ,
Many are connected with ,,. This is not only to save material, but also to prevent the wall thickness of the hub from becoming unnecessarily thick in the radial direction, and to prevent distortion due to uneven curing during curing after molding.

In a tape reel with such a known configuration, precision is required in the position and finish of the center protrusion 3, the diameter of the outer peripheral surface of the hub, finish, strength, and the inner diameter and spacing of the engagement rib with the support shaft on the recording/playback device side. The most important issues are the uniformity of finish, strength, etc., but at the same time, what is often considered a problem is the treatment of gate marks, so-called gate marks G, when these parts are injection molded using resin.

However, conventionally, this gate mark G has been placed in a position that is as inconspicuous as possible, and therefore, this gate has been placed at the center P of the ceiling surface of the support shaft receiving space 5 of the hub as the most commonly selected position. (Figure 2). However, even if provided at this location, these gate marks G vary considerably from product to product, and often remain as quite large protrusions.
Depending on the degree, it may even become an obstacle to inserting the support shaft into the recording/playback device. In this case, no matter how much you increase the precision of other parts, it becomes meaningless. Therefore, after molding, it is necessary to carefully manage the material and remove any remaining material, which is extremely undesirable.

The present invention has been made in view of the drawbacks of this conventional example. That is, in this type of tape reel for video cassettes, which requires extremely high precision, even if the precision problem has been overcome, the problem of injection molding gate marks still remains, which is an attempt to be rationally solved.

In accordance with such an object, the present invention has the following features as shown in FIG.
It is proposed that the injection molded gate of the hub 2 and the flange 1b integrally molded therewith be brought to the head of one of the fixing projections 4 of a separate flange la.

In this way, even if the gate mark G remains as a large protrusion on the top of the fixing protrusion 4 as a result of injection molding, as shown in the fourth figure, the above-mentioned separate flange 1a can be removed. Since this fixing protrusion 4 is crushed in order to fix it, the gate mark G becomes a part of the crushed protrusion 4' shown by the imaginary line and is absorbed and disappears without a trace. Therefore, a separate operation for removing the gate mark G is no longer necessary, and productivity is greatly improved. Generally, a plurality of fixing protrusions of this kind are provided at appropriate intervals in the circumferential direction, and the present invention may be applied to one of them.

In this way, according to the present invention, there is no need to take into account the gate marks G that are expected to remain as a result of integral molding of the hub and one flange, and the accuracy of other parts is reduced. The unreasonableness that the entire product becomes defective due to this gate mark G even though the gate mark G has been successfully produced can be fundamentally solved. In addition, when applying the present invention, a desirable configuration to also adopt is to make the wall thickness of the inner cylinder portion 9 as uniform as possible at various locations in the circumferential direction, as shown in the cross section of FIG. be. That is,
In the conventional example shown in FIG. 3, the wall thickness of the inner cylinder portion 9 is determined by the thickness of the inner cylinder portion 9 where the ribs 6, .
It is quite thick at point a, while it is quite thin at point 9b where groove 7 is located. This is because problems such as stress not being well dispersed or uneven curing occurring during curing after molding may occur, affecting product precision.

Therefore, as shown in FIG. 5, even where the rib 6 is provided, the slit 11 is formed by continuously cutting out the thickness behind the rib 6 in the axial direction.
As shown by a', it is preferable that the thickness of the groove portion 8b be approximately the same as C. Incidentally, in FIGS. 3 and 5, reference numeral 13 is a well-known notch for tape end processing.

In any case, as detailed above, according to the present invention, it is possible to omit all related work such as removing the gate mark G on the hub, which could have caused the entire product to be defective. However, since the gate mark G completely disappears when the product is assembled, it is possible to obtain extremely rational results that improve production efficiency and yield, and ultimately reduce costs.

[Brief explanation of the drawing]

Fig. 1 is a side view of an example of a tape reel for a normal video cassette, Fig. 2 is a vertical cross-sectional view taken along line II-II in Fig. 1, and Fig. 3 is a cross-sectional view taken along line m-■ in Fig. 2. , FIG. 4 is a vertical cross-sectional view similar to FIG. 2 to which an embodiment of the present invention is applied, and FIG.
The figure is a cross-sectional view of the modified example taken along the line v--v in FIG. 4. In the figure, Ia and lb are flanges, 2 is a hub, 3 is a central projection, 4 is a separately molded flange fixing projection,
5 is a receiving space for the support shaft on the side of the recording/reproducing device. Applicant: Co., Ltd.
Figure 4 Figure 5 3 9/a 171 L6 9 & 7 ga゛IL Figure 3

Claims (1)

[Scope of Claims] Consisting of a pair of flanges, and a hub that connects the pair of flanges at a distance in the axial direction, and has a support shaft receiving space therein for receiving a support shaft of a recording/reproducing device. The hub and one of the pair of flanges are integrally injection molded, while the other flange facing the one flange is fixed while passing through a central protrusion provided at the end of the hub corresponding to the flange. plastic that is molded as a separate body through which the fixing protrusion passes through, and the flange that is molded on the separate body is fixed to the corresponding hub end by crushing the head of the fixing protrusion that has passed through it by ultrasonic welding. A tape reel for a video cassette produced by a manufacturer, wherein the resin injection gate for molding the hub and one flange integrally molded thereto is disposed at the head of the fixing protrusion in the mold. tape reel.