JPH0772988B2 - Tape reel of magnetic tape cassette and manufacturing method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tape reel of a magnetic tape cassette used in a video tape recorder (VTR) or the like and a method of manufacturing the same.

[0002]

2. Description of the Related Art As shown in FIGS. 3 and 4, a magnetic tape cassette 1 used in a conventional VTR has a magnetic tape (not shown) in a cassette body 4 composed of an upper half 2 and a lower half 3. It is possible to rotatably store two tape reels 5 and 5 for supplying and winding the same, and to wind the magnetic tape around the front surface of the cassette body 4 and to open and close the front lid 4a at the front thereof. Is attached to.

The tape reel 5 is composed of an upper guide flange 6 and a lower guide flange 7. A central cylinder 8 with which a drive shaft (not shown) of the tape deck engages with the lower guide flange 7, and a reel hub for winding the tape, which is arranged outside the cylinder 8 concentrically with the central cylinder 8. 9 and
A plurality of connecting ribs 10 for connecting the central cylinder 8 and the reel hub 9 are integrally formed. In the central cylinder 8,
A drive shaft fitting concave portion 8a having an open lower portion is formed, and a plurality of engaging ribs 8 that engage with the drive shaft of the tape deck are formed on the inner wall thereof.
b is provided.

A guide edge 11a for guiding the drive shaft of the tape deck is provided on the bottom of the lower guide flange 7 along the edge of the opening of the drive shaft fitting recess 8a, and on the outside of the guide edge 11a. , The mounting hole 4b of the cassette body 4
Two annular projecting edges 11 with an engaging edge 11b loosely fitted to
Are formed concentrically and integrally with the reel hub 9. A portion between the both edges 11a and 11b is a thin portion 7a for favorably flowing a molten metal such as a synthetic resin material when molding the lower guide flange 7. A plurality of narrow ribs 12 connecting the both edges 11a and 11b are projected on the lower surface of the thin portion 7a. One of the ribs 12 is a molten metal for forming the lower guide flange 7. It is used for the injection port.

[0005]

However, in the tape reel 5 described above, any one of the narrow ribs 12 is used as a molten metal injection port when the lower guide flange 7 is formed.
However, the flow of the molten metal was poor and the formability of the lower guide flange 7 was poor.

Further, the rib 12, which serves as an injection port, is the protruding portion of the lower guide flange 7, that is, the gate corresponding to this, which is the molten metal discharge port of the molding die, is the bottom of the narrow groove of the die. Therefore, it is troublesome to manufacture the gate part, and in order to prevent the material from swelling and adhering to the outside of the gate and solidifying to make it impossible to mold, it is knocked off by visual inspection after mold release. Since it was at the bottom of the groove, it was difficult to visually recognize the state of the gate, and the workability of dropping off was poor.

Further, the thin portion 7 of the lower guide flange 7
Even in the structure in which the molten metal injection port is provided in a, there is a problem in the flow of the molten metal during molding.

Therefore, an object of the present invention is to provide a tape reel of a magnetic tape cassette and a method of manufacturing the same, in which the flow of molten metal at the time of molding is good and the moldability is improved.

[0009]

To achieve the above object, a tape reel of a magnetic tape cassette according to the present invention has an annular projecting edge at the bottom of a lower guide flange integrally having a reel hub around which a magnetic tape is wound. In a tape reel of a magnetic tape cassette integrally formed concentrically with the reel hub, a thick portion serving as a molten metal injection port is formed in a part of the protruding edge, the thicker portion being wider than the protruding edge and the bottom portion of the lower guide flange. It is characterized by being formed continuously.

Further, in the method of manufacturing the tape reel of the magnetic tape cassette of the present invention, an annular projecting edge is integrally formed concentrically with the reel hub at the bottom of the lower guide flange integrally having the reel hub around which the magnetic tape is wound. In a method of manufacturing a tape reel of a magnetic tape cassette, an injection port for supplying a molten metal from a gate of a mold to a cavity for molding the lower guide flange, a part of an annular space portion for molding the projecting edge of the cavity, It is formed wider than the annular space, and after the completion of pouring the molten metal, the molten metal filled in the injection port causes a part of the protruding edge to be wider than the protruding edge and continuous with the bottom of the lower guide flange. It is characterized by forming a thick portion.

[0011]

Therefore, since the portion of the lower guide flange serving as the molten metal injection port is made thicker, the flow of the molten metal at the time of molding the lower guide flange is improved and the formability of the tape reel is improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

Lower guide flange 20 of the tape reel
Is the same as the conventional example, the central cylinder 21, the reel hub 2
2, the connecting rib 23 is integrally formed, and the long-time one and the short-time one are dealt with by changing the diameter of the reel hub 22 and the connecting rib 23. Further, the central cylinder 21 is formed with a drive shaft fitting recess 21a having an opening at the bottom, and a plurality of engaging ribs 21 are formed on the inner wall thereof.
b is provided.

At the bottom of the lower guide flange 20,
Two annular projecting edges 24, a guide edge 24a along the edge of the opening of the drive shaft fitting recess 21a and an engaging edge 24b outside the guide edge 24a, are concentrically integrated with the reel hub 22, respectively. Are formed on both edges 24a, 24
A thin portion 20a is formed in a portion between b to improve the flow of molten metal such as a synthetic resin material when the lower guide flange 20 is formed, and the lower surface of the thin portion 20a has both edges 24a. , 24b are provided to project a plurality of narrow ribs 25.

The guide edge 24a is formed with a notch 26, a part of which is notched, and a thick portion 27 serving as a molten metal injection port for forming the lower guide flange 20 in the notch 26.
Is wider than the guide edge 24 a and is formed continuously with the bottom portion of the lower guide flange 20.

The thick-walled portion 27 is formed in a columnar shape by embedding the lower surface of the thin-walled portion 2a of the lower guide flange 20 that is the bottom thereof, and the top surface 27a of the thick-walled portion 27 is
It is formed to be substantially flush with the lower surface 20b of the lower guide flange 20, and its diameter is formed to a size that allows a gate of a molding die to be manufactured, for example, about 5 mm.

As described above, the thin portion 20a of the lower guide flange 20 is formed in the notch 26 formed by notching a part of the guide edge 24a, which is one of the protruding edges 24 formed in an annular shape.
Since the thick part 27 was piled up to serve as a molten metal injection port,
A narrow rib 25 having an injection port or a thin portion 20a
The flow of the molten metal is improved and the formability of the lower guide flange 20 is improved as compared with the case where the injection port is provided in.

Next, a method of manufacturing the lower guide flange 20 which constitutes the tape reel with the upper guide flange will be described.

The cavity for molding the lower guide flange 20 is provided with an injection port for supplying the molten metal from the gate of the mold to a part of the annular space for molding the guide edge 24a of the cavity, which is more than the annular space. It is formed to be wide and substantially flush with the portion where the lower surface 20b of the lower guide flange 20 is formed. Then, the molten metal is sequentially filled from the gate into the cavity, and by the molten metal filled in the inlet, the guide edge 24a is partially formed on the guide edge 24a after the completion of the molten metal injection.
A thicker portion 27 wider than the lower guide flange 20 and continuous with the bottom portion of the lower guide flange 20 is formed.

Therefore, in the cavity for forming the lower guide flange 20 to which the molten metal is supplied from the gate of the mold, one of the annular space portions for forming the guide edge 24a, which is one of the protruding edges 24 formed in an annular shape. The lower surface 20b of the lower guide flange 20 wider than the annular space portion.
Since the injection port for the molten metal following the gate is formed substantially flush with the part for molding the molten metal, the molten metal is provided in comparison with the one in which the injection port is provided in the narrow rib 25 or the injection port in the thin portion 20a. Is improved, the flow rate of the molten metal per unit time is increased, and the formability of the lower guide flange 20 is improved.

The top surface 27a of the thick wall portion 27 which serves as an injection port.
Corresponds to the lower surface 20b of the lower guide flange 20.
Since the gate of the mold is substantially flush with the molding surface of the lower guide flange 20, the visibility of the gate after release is not impaired.

In the present invention, the notch 26 may be provided on the engagement edge 24b on the outer peripheral side, and a similar thick portion 27 may be provided on this portion, and the notch 26 is provided on both edges 24a, 24b. The thick portion 27 larger than that in the above-described embodiment may be formed so as to extend over both cutout portions, and the shape of the thick portion 27 is not limited to a circular shape and may be a polygonal shape.

[0023]

As described above, in the tape reel of the magnetic tape cassette of the present invention, a thick portion serving as a molten metal injection port is formed in a part of an annular projecting edge integrally formed at the bottom of the lower guide flange. Is formed continuously with the bottom portion of the lower guide flange and wider than the projecting edge, so that the flow of the molten metal at the time of molding the lower guide flange is improved and the formability of the tape reel can be improved.

Further, according to the method of manufacturing the tape reel of the magnetic tape cassette of the present invention, the cavity for forming the lower guide flange is provided with an injection port for supplying the molten metal from the gate of the mold to the bottom of the lower guide flange of the cavity. In a part of the annular space that forms the annular protruding edge that is integrally formed with
It is formed wider than the annular space, and after the completion of pouring the molten metal, the molten metal filled in the injection port causes a part of the protruding edge to be wider than the protruding edge and continuous with the bottom of the lower guide flange. Since the thick portion is formed, the flow of the molten metal at the time of molding the lower guide flange is improved, the flow rate of the molten metal per unit time can be increased, and the formability of the tape reel can be improved.

[Brief description of drawings]

FIG. 1 is a bottom view of a main part of a tape reel showing an embodiment of the present invention.

FIG. 2 is a sectional view of the same main part.

FIG. 3 is a bottom view showing an example of a conventional magnetic tape cassette.

FIG. 4 is a sectional view of an essential part showing an example of a tape reel.

[Explanation of symbols]

 20 ... Lower guide flange 21 ... Center tube 22 ... Reel hub 23 ... Connecting rib 24 ... Projection edge 24a ... Guide edge 24b ... Engagement edge 26 ... Notch section 27 ... Thick section

Claims (2)

[Claims] 1. A tape reel of a magnetic tape cassette in which an annular projecting edge is integrally formed concentrically with the reel hub at the bottom of a lower guide flange integrally having a reel hub around which a magnetic tape is wound. A tape reel of a magnetic tape cassette, wherein a thick portion serving as a molten metal inlet is formed wider than the projecting edge and continuous with the bottom portion of the lower guide flange. 2. A method for manufacturing a tape reel of a magnetic tape cassette, wherein a ring-shaped projecting edge is integrally formed concentrically with the reel hub at the bottom of a lower guide flange integrally having a reel hub around which a magnetic tape is wound. An injection port for supplying the molten metal from the gate to the cavity for forming the lower guide flange is formed in a part of the annular space portion for forming the protruding edge of the cavity wider than the annular space portion for injecting the molten metal. After completion, the molten metal with which the filling port is filled forms a thick-walled portion, which is wider than the protruding edge and is continuous with the bottom portion of the lower guide flange, in a part of the protruding edge. Method for manufacturing tape reel of cassette.