JP2901690B2 - Tape reel - Google Patents

Description

The present invention relates to a tape reel having good releasability.

(Prior Art) Tape reels, which are mechanical components of recorders such as video tape recorders, are required to increase productivity while avoiding manufacturing errors that affect the accuracy of recording and reproduction, and to mass-produce in a short time. .

A typical video tape cassette accommodates a pair of tape reels 2 and 2 each having a tape wound inside a case composed of an upper case 1a and a lower case 1b as shown in FIG. A guide and a guide roller are provided, and the tape is wound from one reel to the other reel via the front surface of the case.

Generally, tape reels for video tapes are disclosed in
As described in Japanese Patent No. 0923, a reel hub is formed by integrally molding a lower flange and a tape-wound hub, and an upper flange attached to an upper portion of the hub. Center pivot (protrusion) held on the upper end surface of the reel hub by a holding spring attached to the inner surface of the cassette case
, And a plurality of pins or bosses provided at equal intervals around the periphery. After the boss is fitted into the hole in the upper flange, the boss performs an integral connection between the reel hub and the upper flange by ultrasonic fusion or the like. The reel hub is an integrally formed body of the lower flange 8 and the drum hub 7, as shown in FIG.

Generally, such a reel hub is manufactured by injection molding of a resin. The gate method used in the conventional reel hub injection molding method is the spear gate method shown in FIG. 2 (a). A heater 5 is built in the inside of the gate 3, the tip 4 at the tip of the nozzle is an open gate, and the resin is melted or solidified by adjusting the heater power to open and close the gate.
The resin 6 is injected. At this time, a fluidized bed is formed on the resin along the heater, and a solidified layer is formed on the gate wall surface. The advantage of this gate system is that the spear gate 4 can be positioned in the center of the inner surface of the upper end of the hub by inserting the spear gate 4 into the inner hole of the drum-shaped hub 7 as shown in FIG. As a result, the resin flow becomes uniform, and at the same time, the protruding gate mark does not interfere with other portions, thereby improving the dimensional accuracy. However, in the spear gate method, the resin is dripped and solidified at the tip of the gate every time injection molding is performed. Therefore, it is troublesome that the resin solidified portion must be removed at the beginning of molding, and the efficiency of molding is reduced. In addition, it took time to process the solidified resin when changing the product type.

On the other hand, in the present invention, a valve gate system with good production efficiency is adopted. In this gate system, as shown in FIG. 2 (b), a valve 14 is inserted into a gate 11 which is constantly heated externally, and is moved up and down to open and close the tip of a gate chip 12. In this method, the injection pressure can be reduced because the passage of the chip 12 can be made sufficiently large, and not only can the efficiency of the injection work be improved, but also the gate resin is good at the end of the injection, and the time for releasing the residual pressure is good. Although much faster molding work is possible compared to the spear gate method, such as being unnecessary,
Larger due to the large space to accommodate the valve,
Therefore, the gate cannot be inserted from the shaft hole side of the hub. Therefore, as shown in FIG. 3 (b), the valve gate 13 must be positioned at the upper end of the hub. However, a gate mark is formed, which causes problems in accuracy and appearance. Conventionally, the valve gate 13 is almost used for forming a reel hub. Absent.

The inventor has achieved the practicality of the valve gate by solving the problem of the gate mark by forming the pivot separately as described below, but even if such an improvement is made, the shaft hole side is formed. The problem remains. More specifically, the posture of the reel hub 7 when molded as shown in FIG. 3 using the valve gate system shown in FIG.
The posture when using the spear gate is inverted upside down. Molding is performed with a core mold that defines the inner hole of the hub and the lower surface of the lower flange, and a cavity mold that defines the outer periphery of the hub and the upper surface of the lower flange. When the mold is opened after the resin is cured, the molded product remains attached to the cavity mold (upper mold), which has a large contact area, because of the large mold release resistance. It will be very difficult. Therefore, the molded product is separated from the cavity mold first,
It is then desirable to be able to separate from the core mold.

(Object of the Invention) It is an object of the present invention to improve mold releasability by injection molding using a valve gate system.

(Summary of the Invention) The present invention provides a reel hub formed by integrally molding a lower flange and a tape-wound hub, an upper flange attached to an upper end surface of the hub, and fixed to the center of the hub and penetrating the upper flange. A tape reel made of a pivot member which is exposed to the outside, and which is located at a position not reaching the lower end of the inner surface of the cylindrical shaft hole for rotating shaft insertion provided on the hub and opened downward (preferably, the shaft hole). The purpose of the invention is achieved by forming an undercut (adjacent to the lower end).

According to the present invention, when the mold is separated after the injection molding, the cavity mold is released first, and then the molded product can be protruded from the core mold.

(Specific Description of the Invention) Hereinafter, the present invention will be described in detail with reference to examples. 4 to 6 show an embodiment of a tape reel having a reel hub according to the present invention. This tape reel has a lower flange
And a reel hub 20 including a drum-shaped hub 22 integrally formed therewith. The interior of the hub is a hollow opening downward as shown in FIGS. A recess is formed in the periphery of the hub 22, and the tape clamp 23 is
It forms part of 22. The upper surface of the hub 22 has a slightly recessed central portion for mounting the upper flange 26 and a raised annular portion therearound. An upper flange 26 is attached to the upper surface. For this attachment, a plurality of bosses may be provided on the upper surface of the hub 22 as described in the above-cited publication, and these may be fitted into holes provided in the upper flange, and may be heat-fused. May be fixed by the above method. The center of the lower surface of the upper flange 26 projects slightly downward, and can fit into the recessed portion of the hub 22. The upper hub 26 has a center hole.
27 is formed to accept the pivot. The pivot 25 includes a base portion 28 having a diameter larger than the diameter of the hole 27 of the upper flange, a small-diameter portion 29 having a diameter fitting into the hole 27, and a projection 30 formed on the upper surface thereof (a portion that contacts the spring on the case side). . The lower surface of the base 28 has a recess (FIGS. 5-6) for receiving the gate mark 24.

Next, the means for facilitating release of the present invention will be described. FIG. 7 shows a first embodiment of the present invention, in which a convex portion 33 is formed on a part of a cylindrical portion 32 corresponding to a hub shaft hole of a core mold 31 (a cavity mold is not shown). . The projection has a size sufficient to provide a release resistance for leaving the reel hub 20 on the core mold side when separating the upper and lower molds. This size is selected so as not to hinder release of the reel hub later. Therefore, when the upper and lower molds are opened after molding using the valve gate, the convex portion 33 of the core mold 31 and the cylindrical portion
Since the resistance of 32 is greater than the resistance of the cavity mold, the molded reel hub 20 is separated from the cavity mold and adheres to the core mold. Then, when the molded product is pushed in the direction of the arrow by an appropriate means, the reel hub is also pushed away from the core mold. At this time, if the protrusion 33 is too high, the inner surface of the shaft hole 35 is scratched from the corresponding undercut (recess) 36 to the lower surface of the reel hub. Therefore, as shown in FIG. 8, it is preferable to provide the convex portion 33 and the corresponding undercut 36 as close to the lower surface of the hub as possible. In addition, if necessary, in addition to the above-described configuration, a portion in which the core mold and the cavity mold are in contact with each other on the outer peripheral surface of the lower flange, that is, a tooth shape in which a parting line (partition line) of the mold is formed on the outer peripheral portion of the lower flange. When the core mold is provided at the upper end of the core mold, the core mold embraces the outer periphery of the flange as shown in FIG.

(Effects) As is clear from the above description, the poor releasability, which is a problem that has arisen when molding a reel hub with a valve gate having good productivity, is achieved by adding a release resistance to the inner hole of the hub according to the present invention. Because of the undercut, release from the cavity mold occurs first, followed by release of the core mold. Therefore, the problem of the remaining cavity of the reel hub occurring when the molding method is changed is avoided, and the production efficiency is improved.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view schematically showing a magnetic tape cassette to which the present invention is applied, FIG. 2 is a sectional view showing two types of gate systems used in a conventional injection molding technique, and FIG. FIG. 4 is an exploded perspective view of a tape reel using the reel hub of the present invention; FIG. 5 is a partial cross-sectional view of the tape reel of the present invention; The figure is an exploded sectional view of the same,
FIG. 7 is a sectional view showing a reel hub of the present invention and a core mold for molding the same, FIG. 8 is a sectional view showing a reel hub of another embodiment of the present invention, and FIG. 9 is a sectional view of an embodiment of the present invention. It is sectional drawing of a lower flange outer peripheral part and a shaping | molding die. 20 Reel hub 21 Lower flange 22 Hub 24 Gate mark 25 Pivot 26 Upper flange 27 Hole 28 Base 29 Small diameter section 30 Projection 33 Projection

Continuation of front page (56) References JP-A-62-189130 (JP, A) JP-A-2-39907 (JP, A) JP-A-54-90261 (JP, A) JP-A-63-307919 (JP) , A) Japanese Utility Model 62-11283 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G11B 23/087 G11B 23/113

Claims (3)

(57) [Claims] 1. A reel hub formed integrally with a lower flange and a tape winding hub, an upper flange attached to an upper end surface of the hub, and fixed to a center of the hub and exposed through the upper flange. A tape reel comprising a pivot member, wherein the hub is provided with a gate portion at a portion supporting the pivot, and an inner surface of a cylindrical shaft hole for the rotation shaft inserted in the hub and opened downward,
A tape reel with an undercut formed where it does not reach the lower end. 2. The tape reel according to claim 1, wherein the undercut is formed adjacent to a lower end of the shaft hole. 3. The tape reel according to claim 1, wherein a parting line (partition line) of the mold is provided at an upper end portion of a tooth formed on an outer peripheral portion of the lower flange.