JPH028564B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention enables a synthetic resin magnetic tape reel formed with a two-layer structure to be molded inseparably and at low cost using synthetic resins with similar shrinkage rates. There is a particular thing.

As is well known, a magnetic tape reel (hereinafter abbreviated as tape reel) around which magnetic tape for recording is wound is injection molded from synthetic resin.
When synthetic resin products cool and solidify, thicker parts tend to solidify slower than thinner parts, so when tape reels are injection molded at once using a set of molds,
It is known that sink marks cause dents on the outer circumferential surface of a thick-walled portion, for example, on the outer circumferential surface of a thick-walled portion that has protrusions, double reinforcing ribs, etc. on the inner circumferential side of the peripheral wall. This occurrence of sink marks is a phenomenon peculiar to synthetic resins and cannot be avoided. Therefore, when forming a precision tape reel, it is necessary to integrally mold the tape reel with a ring body using a material with a low shrinkage rate, or to combine the tape reel with the ring body. It was formed as a male mold with a two-layer structure with a cortical layer around its outer periphery, but
When integrally molded using a material with low shrinkage rate, the material is expensive and molding takes time, and when molding with a two-layer structure, it is difficult to form the orbicularis and the cortical layer in a way that cannot be separated. .

Therefore, this invention was developed by researching whether it is possible to mold a tape reel made of synthetic resin with a two-layer structure so that it cannot be detached and at a low cost.The outer ring part of the ring body has uneven thickness, and the sink marks peculiar to synthetic resins can be effectively eliminated. By using this technique to create a dent on the outer circumferential surface of the outer ring that is too large to be formed with a punching die, it is possible to easily make the ring and the skin layer formed on its outer periphery impossible to separate, and to reduce the shrinkage rate. This invention led to the invention that it can be molded with an inexpensive synthetic resin similar to that of .

Next, the method for forming a tape reel according to the present invention will be explained based on the drawings of the embodiment.
The ring body 2 is composed of a ring body 2 which is primarily formed, and a skin layer 10 which is later formed on the outer circumference of the ring body 2 as a male mold. Several hub pawls 21 are provided protrudingly spaced at equal intervals, an outer ring part 3 is provided on the outer periphery of the inner ring part 7, which is thicker than the inner ring part thickness t1, and the clamp bites into the outer ring part 3 from the outer periphery toward the inner periphery. A groove 4 is provided, and a concave groove 5 concentric with the inner ring part 7 is bored at an appropriate depth on the upper surface 2a and lower surface 2b of the outer ring part 3, excluding the part where the clamp groove 4 is formed.
Thin protrusions 6 are provided at least on the upper and lower outer edges of the outer ring portion 3 by the grooves 5, so that the outer ring portion 3 has uneven thickness such that it is thickest at the center and thinnest at the upper and lower outer edges. Injection molding is performed on the outer peripheral surface 3a of the outer ring portion 3 so that a recess a of a size that cannot be formed with a punching die is created by utilizing the shrinkage difference due to uneven thickness, and the recess a is in the center part where the wall thickness is the thickest. It has a large depression.

The skin layer 10, which is formed later on the outer periphery of the outer ring part 3 using the ring body 2 as a male mold, is injection molded with a skin layer width h2 of approximately 1/2 or less of the outer ring part width H before the outer ring part 3 is cooled and solidified. As a result, the cortical layer 10 fills up to the recess a of the outer circumferential surface 3a, and due to the formation of this cortical layer 10, the outer circumferential surface 3a of the ring body outer ring section 3 is further depressed, and conversely, the protrusions 6 at the upper and lower outer edges are formed. is plastically deformed to warp outward, the outer peripheral surface 3a becomes a drum-shaped arcuate surface 3b, and a cortical layer 10 is formed up to the arcuate surface 3b.

The reason why the outer circumferential surface 3a of the outer ring part 3a is recessed into the drum-shaped arcuate surface 3b is that when the ring body 2 is made into a male mold and the outer periphery of the outer ring part 3 is filled with skin layer forming resin, the outer ring part 3 of the ring body 2
The molecules and atoms forming the outer periphery of the outer ring 3 may be heated by the skin layer forming resin that is molded later, further delaying the cooling and solidification of the thick central portion, or due to the heating of the skin layer forming resin. It is thought that this occurs due to a change in the arrangement of the parts, or a difference in heat dissipation between the thick and thin parts. This seems to be because the outer circumferential surface 3a of the outer ring portion 3 is further pressed by the pressure of the skin layer forming resin.

This state can be confirmed by longitudinally traversing the tape reel 1 or by cutting out the skin layer 10 and comparing the outer circumferential surface 3a of the ring body outer ring 3 before and after the skin layer 10 is formed.

The two-layer peripheral wall 13 composed of the outer ring part 3 and the skin part 10 of the ring body 2 cannot be separated in the axial direction, and is attached to the skin part 10 formed continuously on the outer periphery of the clamp groove 4. Therefore, co-rotation becomes impossible.
In addition, the cortical layer 10 is thinner than the outer ring part 3, or the ring body 2
Since it is formed with a significantly smaller amount of resin than the amount of resin formed in , almost no dents a due to sink marks occur on the outer surface 11 of the peripheral wall 13, that is, on the outer surface 11 of the skin layer 10. Even if sink marks occur in the cortical layer 10,
Since it only occurs with respect to the formation thickness of the skin layer 10, it is significantly less than when the circumferential wall 13 of the tape reel 1 is integrally molded at once, and the circumferential wall 13 can be formed precisely as designed.

In the figure, reference numeral 14 indicates several through holes bored in the groove 5.

Experimental example A As shown in Figures 6 and 7, the outer diameter D of the ring body 2 is 20 mm,
Outer ring width H is 2.6mm, protrusion width h is 0.4mm, groove depth t is 0.3mm, outer ring thickness T is 4mm, inner ring thickness t.
1 is 1.8mm, inner ring width h1 is 2.1mm, groove 5 is 1.4φ
In the tape reel 1, the ring body 2 having a through hole 14 formed therein is a male type, and a skin layer 10 having a skin layer width h2 of 1 mm is later formed on the outer periphery of the outer ring part 3. A recess a of 0.1 to 0.5 mm was formed on the outer circumferential surface 3a of No. 3, the size of which could not be formed with a punching die. However, at the drilling position of the through hole 14, the recess a of the outer peripheral surface 3a is 0.
It was only ~0.1mm, which was smaller than the others. An axial force was repeatedly applied to the outer ring portion 3 and the cortical layer 10 upside down, but they did not separate.

Experimental Example B The ring body 2 of the same size as the above Experimental Example A was used, the formation of the grooves 5 on the upper and lower surfaces 2a and 2b of the outer ring part 3 was omitted, and the ring body 2 of the outer ring part 3 without the protrusions 6 was made into a male type. year,
When the skin layer part 10 was formed on the outer periphery, a dent a was formed on the outer circumferential surface 3a of the outer ring part, but it was smaller than in Example A, and there was little digging of the skin layer part 10 into the outer peripheral surface 3a. When the same force as in Experimental Example A was repeatedly applied upside down to the ring body outer circumferential portion 3 and the cortical layer 10, the cortical layer 10 came off from the outer ring portion 3 and was separated.

As described above, the method for forming a tape reel according to the present invention involves making the wall thickness of the outer ring portion 3 of the ring body uneven in thickness, and creating a dent a due to a sink mark on the outer circumferential surface 3a of the outer ring portion 3 of the ring body.
The ring body 2 is made into a male mold, and a cortical layer part 10 is formed on the outer periphery of the outer ring part 3. Therefore, the cortical layer 10 and the orbicularis 2 are made of a synthetic resin material with the same shrinkage rate, or a synthetic resin material with a similar shrinkage rate,
Resin materials can be used efficiently. Circium 2 and cortex 1
By mixing a different coloring agent into the resin material forming the tape 0 and making the ring 2 and the skin layer 10 different colors, it is possible to obtain a tape reel 1 that exhibits aesthetic beauty.

Furthermore, a tape reel 1 having the same accuracy as the present invention
As a means for obtaining
As shown in Fig. 5, it is also possible to mold the wheel body 2 so that it becomes an undercut of the concave curved surface B, but if the concave curved surface B has a small concavity, the mold cannot be removed even if the concave curved surface B has a small concavity. However, if the ring body 2 is so undercut that the mold can be removed, the skin layer 10 provided on the outer periphery will also come off, and if the ring body 2 has a concave curved surface B that cannot be formed with a punching die. must be molded with split mold C, and split mold C
When molding is performed, burrs are formed at the mold matching locations, production efficiency is poor, and mold costs are high.

Therefore, the method for forming the tape reel according to the present invention is to form the tape reel with a two-layer structure, and the thickness of the outer ring part is the thickest at the center and the thinnest at the upper and lower outer edges. The uneven thickness is made, and the sink mark caused by the uneven thickness is used to form an indentation on the outer circumferential surface of the outer ring part, which is too large to be formed with a punching die.At the same time, the primary formed ring body is cooled and solidified. A skin layer is previously formed on the outer periphery of the outer ring part, and the skin layer further curves the concave surface of the outer circumferential surface into an arcuate surface, so that the skin layer is formed up to the arcuate surface. Since it is molded, even if it is a two-layer peripheral wall consisting of an outer ring part and a skin part, it can be made non-separable. Furthermore, production efficiency can be improved by molding in a shorter time than with a single-layer tape reel, and by using a synthetic resin with a similar shrinkage rate, material costs can be reduced, and the peripheral wall can be precisely formed. Moreover, since it has a two-layer structure, it is also possible to provide a unique and colorful tape reel. Furthermore, there is no need to provide a convex part on the mold and use the convex part to form a recess on the outer circumferential surface of the outer ring part, or to form unevenness on the outer circumferential surface to prevent detachment, so there is no need to use an expensive mold. Nor.

[Brief explanation of drawings]

1A and 1B are plan views showing the tape reel forming method according to the present invention, 2A and 2B are side views thereof, 3A and 3B are YY enlarged cross-sectional views of 1B, and 4
5 is a side view of a conventional door roller, FIG. 6 is an enlarged sectional view of FIG. 1A, FIG. 7 is an enlarged sectional view of FIG. 1B, and FIG. Figure 8 A,
B is an enlarged sectional view of a main part showing an example of forming a peripheral wall part. 1... Tape reel, 2... Ring body, 2a, 2b
... Upper and lower surfaces of the ring body, 3 ... Outer ring portion, 3a ... Outer peripheral surface, 3b ... Arc-shaped surface, 4 ... Clamp groove, 5 ...
Concave groove, 6... Convex strip, 7... Inner ring part, 10... Cortical layer part, 11... Cortical layer outer surface, 13... Peripheral wall, 14...
...Through hole, 20...Hub hole, 21...Hub pawl, a...
...Concavity on the outer circumferential surface of the ring body, b...Flash, C...Split mold, D...Outer diameter of the ring body, H...Outer ring width, h...
Convex width, h1...inner ring width, h2...cortical layer width,
T...Outer ring thickness, t...Concave groove depth, t1...Inner ring thickness.

Claims (1)

[Claims] 1. A ring in which a hub pawl 21 is provided protruding from the inner periphery of the inner ring portion 7 toward the hub hole 20, and is provided so as to bite into the clamp groove 4 from the outer periphery of the outer ring portion 3 toward the inner periphery. body 2 and
In this method of forming a magnetic tape reel in which a skin layer 10 is provided on the outer periphery of the ring body, a concave groove concentric with the inner ring part 7 is formed on the upper surface 2a and the lower surface 2b of the outer ring part 3, excluding the part where the clamp groove 4 is formed. 5, and the concave grooves form thin protrusions 6 at least on the upper and lower outer edges of the outer ring part, so that the outer ring part has the thickest thickness at the center and the thinnest protrusions at the upper and lower outer edges. Then, injection molding is performed so that a recess a of a size that cannot be formed with a punching die is created on the outer peripheral surface 3a of the outer ring part, and then the ring body is used as a male mold and a skin layer part 10 is formed on the outer periphery of the outer ring part. The synthetic resin magnetic tape reel is formed such that the skin layer is formed up to the recess on the outer circumferential surface of the outer ring part, and the peripheral wall 13 having a two-layer structure consisting of the outer ring part and the skin layer part cannot be separated. Molding method. 2 Concavity a generated on the outer peripheral surface 3a of the outer ring portion 3
is formed by utilizing the sink mark caused by the difference in shrinkage due to uneven thickness, and the depression is further curved in the skin layer 10 provided later on the outer periphery of the wheel body 2 to form an arcuate surface 3b of 0.1 mm or more. 2. The method of forming a magnetic tape reel according to claim 1, wherein the skin layer is formed up to an arcuate surface.