JPH0516714Y2 - - Google Patents

Description

[Detailed description of the invention] 〓Field of industrial application〓 This invention is incorporated into a cassette casing,
The present invention relates to a reel hub having a tape-shaped recording medium such as a magnetic tape wound around its outer circumferential surface, the reel hub having a rotation indicator provided by two-color molding.

〓Summary of the invention〓 This invention is a method for molding hubs used in tape cassettes such as compact cassettes by two-color molding using a rotary two-color molding machine. When moving, the primary molded body is securely held in the movable male mold while being moved, and is formed on the primary molded body and undercuts in the opening direction of the mold. The primary molded body is held and moved by the engaging part that is curved.

〓Prior art〓 A tape cassette called a compact cassette, which is widely used for purposes such as music recording, has a magnetic tape wound around a pair of reel hubs arranged inside a casing consisting of an upper and lower half. The magnetic tape is sent out from one reel and is wound on the other reel while facing the head for recording and/or playback. And Japanese Patent Application Publication No. 59-84384,
As disclosed in Japanese Utility Model Application Publication No. 59-145768, it is known that the reel hub is formed by two-color molding, which improves the design of the tape cassette or allows rotation display. It becomes possible to do it.

[Problem that the invention attempts to solve]

Such two-color molding reel hubs are usually molded using a rotary two-color molding machine. A rotary two-color molding machine forms a primary molded body by combining a male mold with a first female mold at a first position, and then opens the mold and inserts the male mold into a mold at the opposite position. In combination with the female mold No. 2, a secondary molded body is formed on the primary molded body.

In such a molding machine, when the mold is opened after molding the primary molded product, the molded product may remain in the fixed female mold. This occurs when the male mold on the movable side has good mold releasability and the female mold on the stationary side has poor mold releasability. In this situation, the primary molded body is not moved to the correct position for molding the secondary molded body, causing an accident. Therefore, if the mold releasability is deteriorated, there is a drawback that burrs occur.

The present invention was developed in view of these problems, and it is possible to solve the problem without impairing the mold releasability.
Moreover, it is an object of the present invention to provide a reel hub that can reliably hold a primary molded product and move it to the side of a mold for molding a secondary molded product.

〓Means for solving the problems〓 The present invention is a reel hub that is built into a cassette casing and has a tape-shaped recording medium wrapped around its outer circumferential surface, and has a rotating display section formed by two-color molding. In the reel hub configured to be provided, an engaging portion that is undercut with respect to the opening direction of the mold is formed on the primary molded body, and the primary molded body is moved to the mold side where the secondary molded body is to be molded. In this case, the primary molded body is held by the engaging portion.

〓Function〓According to this invention, the primary molded body can be securely held and moved to the mold for the secondary molded body by utilizing the engagement portion provided on the primary molded body side and undercutting the mold opening direction. The undercut engagement portion may be, for example, an undercut engagement hole formed on the end face of the primary molded body. In this case, if the pin is forcibly inserted through the engagement hole, the periphery of the hole may rise and cause burrs. Therefore, it is preferable to form a rib higher than this on the end face. The undercut engagement portion may also be formed on the inner peripheral surface of the reel shaft insertion hole. With this configuration, it is possible to more securely hold the molded body by utilizing the shrinkage of the molded body after molding.

〓Example〓 Fig. 4 shows a tape cassette using a reel hub according to the first example of the present invention.
The cassette casing 10 is composed of upper and lower halves 11 and 12 made of synthetic resin moldings. A magnetic tape 13 is housed in the casing 10 in a state where it is wound around a pair of reel hubs 15. The magnetic tape 13 is guided by a pair of tape guides 16, and one reel 15
It is adapted to be unwound from the reel 15 and wound onto the other reel 15. and magnetic tape 1
3 runs inside a front side wall 18 having a window 17, and is pressed against a head inserted through the window 17 with a pad 19. In order to make the magnetic tape 13 run smoothly, slippery sheets 20 are arranged above and below the reel hub 15, respectively.

Next, the structure of the hub 15 around which the magnetic tape 13 is wound will be explained. As shown in FIG. 3, the hub 15 includes a primary molded body 21 and a secondary molded body 22. These molded bodies 21, 22
are molded and combined using a two-color molding method. A pair of wing-shaped rotation display portions 23 are formed on the outer peripheral side of the primary molded body 21 on the center side. Further, a reel shaft insertion hole 24 is formed in the center thereof, and a drive pin 25 is formed so as to protrude from the inner peripheral surface thereof. Further, an undercut engagement hole 26 is formed in the end face of the rotation display portion 23 of the primary molded body 21 to securely hold the primary molded body 21. On the other hand, ribs 27 and 28 are formed on the end surface of the secondary molded body 22 on the inner and outer circumferential sides thereof, respectively. Further, a clamping recess 29 is formed on the outer peripheral surface of the secondary formed body 22, and the end of the magnetic tape 13 is clamped in this recess 29 by a claw.

Next, a molding apparatus for molding such a hub 15 will be described. As shown in FIG. 5, the two-color molding apparatus is equipped with a movable platen 31 and a fixed platen 32. A pair of male dies 33 having the same structure are attached to the movable platen 31 side symmetrically with respect to the rotation axis 47. On the other hand, the fixed platen 32 has a pair of female dies 34 and 35 having different cavity shapes and is provided at symmetrical positions with respect to the rotation axis 47. This molding device also includes two injection cylinders 37 and 38. The primary cylinder 37 injects resin into a cavity 41 formed by a male die 33 and a female die 34 through a gate 43. On the other hand, the secondary cylinder 38 injects resin into a cavity 42 formed by the male die 33 and the second female die 35 through a gate 44.

When forming the reel hub 15 using such a molding device, the male mold 33 and the first female mold 34 are combined, and the primary cylinder 37 is used to mold the first mold into the cavity 41 through the gate 43. The resin is injected to form a primary molded body 21 as shown in FIG. Thereafter, the movable platen 31 is moved in the opening/closing direction as shown by the arrow 45 to open the molds 33 and 34. Thereafter, the movable platen 31 is rotated 180 degrees as shown by an arrow 46 about the rotation axis 47. Then, the primary molded body 21 is moved to the secondary side while being held by the male die 33.

At this time, as shown in FIG. 1, since the pin 36 formed in the male die 33 is engaged with the engagement hole 26 of the undercut of the primary molded body
The next molded body 21 is not left behind in the female mold 34 on the primary side, and is securely held in the male mold 33 when the mold is opened and moved to the secondary side. This is because the shape of the pin 36 is thick at the tip side and narrow at the base side, and it is engaged with the engagement hole 26 of the undercut corresponding to this shape and is held securely.

When the primary molded body 21 is moved to the secondary side while being held by the male mold 33 and combined with the female mold 35,
Next, the second resin is injected by the secondary cylinder 38, and the second resin is injected into the cavity 42 through the gate 44. As a result, the outer secondary molded body 22 is formed. At this time, on the primary side, another male die 33 is combined with the first female die 34 to form the primary molded body 21.

Therefore, according to the reel hub 15 according to this embodiment, the operation of moving toward the secondary molded product is reliably performed, especially by the undercut engagement hole 26 formed in the primary molded product 21. The primary molded body 21 is placed in the female mold 34 on the primary side of the molding machine.
By preventing the particles from being left behind, it is possible to prevent molding troubles. Note that since the pin 36 of the male die 33 is forced through, a raised burr is formed on the surface of the primary molded body 21 due to the forced penetration. However, ribs 27 and 28 are formed on the inner and outer peripheries of the secondary formed body 22, respectively, and these ribs 2
Since the heights of 7 and 28 are increased, there is no problem caused by the raised portions.

Next, a second embodiment of the present invention will be explained with reference to FIGS. 6 to 8. In this embodiment, the reel shaft insertion hole 2 of the primary molded body 21 of the reel hub 15 is
An undercut ring-shaped recess 51 is formed on the inner peripheral surface along the base of the drive pin 25 of the male mold 3.
3, the primary molded body 21 is reliably moved to the female mold 35 side on the secondary side. That is, when moving the primary molded body 21 to the secondary side using a rotary molding machine, the undercut portion formed on the inner peripheral surface of the reel shaft insertion hole 24 of the reel hub 15 is used. be.

To explain in more detail, as shown in FIGS. 6 and 7, the reel shaft insertion hole 24 of the primary molded body 21
A ring-shaped recess 51 is formed in the inner peripheral surface of the drive pin 25 along the root portion of the drive pin 25 in the circumferential direction. On the other hand, the mold 33 of the molding machine
A ring-shaped protrusion 52 is formed on the boss 53 along the circumferential direction. Note that the boss 53 is further formed with a groove 54 extending in the axial direction for allowing the drive pin 25 to escape. The ring-shaped recess 51 is formed so as to be closer to the eject pin than the parting line of the mold, thereby shortening the forced penetration stroke and preventing mold damage due to resin scraping. We try to minimize the decrease in lifespan as much as possible.

According to such a structure, it becomes possible to utilize the shrinkage of the injection-molded primary molded body 21 after molding. Since the primary molded body 21 acts to tighten the boss 53 due to molding shrinkage, the ring-shaped recess 51 is reliably engaged with the ring-shaped protrusion 52. Therefore, even if the amount of undercut in the recess 51 is reduced, a sufficient effect can be obtained, thereby making it possible to hold the molded body 21 more reliably. Further, since the change in dimensions during shrinkage is smaller on the inner circumferential side, even if the molding conditions vary, the influence is small, and the effect of holding the molded body 21 is less likely to change.

= Effect of the invention = As described above, the present invention forms an engaging portion that is undercut with respect to the opening direction of the mold in the primary molded body, and a primary molded body in the mold for forming the secondary molded body. The primary molded body is held by the engaging portion when the molded body is moved. Therefore, the primary molded body is always moved to the secondary side, making it possible to prevent molding troubles.

[Brief explanation of drawings]

Fig. 1 is a vertical cross-sectional view of the main part showing the holding structure of the primary molded body according to the first embodiment of the present invention, Fig. 2 is a plan view of the primary molded body, and Fig. 3 is a diagram showing the primary molded body. 4 is an exploded perspective view showing the overall structure of a tape cassette using this reel hub; FIG. 5 is a sectional view of essential parts of a two-color molding device for molding the reel hub; FIG. 6 is a plan view of the primary molded body of the second embodiment, FIG. 7 is a longitudinal sectional view thereof, and FIG. 8 is a perspective view of a main part of a holding boss. In addition, in the symbols used in the drawings, 10...cassette casing, 13...magnetic tape, 15...
Reel hub, 21...primary molded body, 22...secondary molded body, 23...rotation display section, 26...engaging hole,
33...Male type, 34, 35...Female type, 36...Pin, 51...Ring-shaped recess, 52...Ring-shaped protrusion, 53...Boss.

Claims (1)

[Scope of utility model registration request] A reel hub that is incorporated into a cassette casing and has a tape-shaped recording medium wound around its outer circumferential surface, and is provided with a rotation indicator by two-color molding, with respect to the opening direction of the mold. An undercut engaging portion is formed on the primary formed body, and the above-mentioned 1 is placed on the mold side for molding the secondary formed body.
A reel hub for a tape cassette, characterized in that the first molded product is held by the engaging portion when the next molded product is moved.