JPH04124618U - injection mold - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent long core pins from bending during injection molding. [Structure] An injection mold having an inner mold as a relatively long rod-shaped core pin 26 with a relatively small diameter, and outer molds 22, 28a, 28b, and 28c that cover the core pin 26, A holding member 42 that holds the tip 26a of the core pin 26 when injecting the injection molding material.
is provided on the outer mold 22 to prevent the core pin 26 from bending.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This invention is suitable for injection molding of reel hubs for compact video tapes, for example. Regarding improvements.

0002

[Conventional technology]

Generally, when processing resin etc. into various shapes, injection molding is generally used. This is commonly done, but this processed product is made of resin with elongated holes etc. When a product is required, an elongated rod-shaped injection mold is used. It is being In this case, if the diameter of this rod-shaped mold is relatively large, the problem is Although this does not occur, if the rod-shaped mold has a relatively small diameter, repeated injections may Due to the pressure at the time of release, the rod-shaped mold may not be able to withstand the repeated pressure and may gradually bend. there were. This situation can be considered as a resin product, such as a compact bidet for VHSC (registered trademark). This will be explained by taking a reel hub used for an cassette as an example. Figure 5 is a compact An external perspective view showing a reel hub used in a video cassette, and FIG. 6 is a sectional view thereof. It is. As shown in the figure, this reel hub 2 is erected on a circular flange portion 4. It has a tape winding part 6, and this tape winding part 6 has a tape winding part 6 along the longitudinal direction. A groove-shaped tape locking part 8 is formed, and a groove-shaped tape locking part 8 is formed on the end of the tape (not shown). It is designed to secure the girder clamp. Then, the upper end of this tape winding section 6 The part is configured as an upper flange attachment part 10 to which an upper flange (not shown) is attached. , its center is formed into a convex shape that comes into contact with a leaf spring (not shown) during this rotation. A flat spring receiving portion 12 is provided.

0003 Further, at the center of the tape winding section 6, there is an insertion hole 14 into which a rotation support shaft is inserted. It is formed in the insertion hole rib 16, and around the insertion hole rib 16, as shown in FIG. A fillet relief is provided to prevent the insertion hole 14 from becoming eccentric due to shrinkage when the resin cools. A portion 18 is formed. Then, the outer surface of the insertion hole rib 16 and the tape winding The inner surface of the handle 6 is connected to the inner surface of the handle 6 by three reinforcing ribs 20 . A compact cassette tape having a reel hub configured in this way is manufactured by VH Compatible with the S (registered trademark) standard type tape, and compared to the conventional standard type. It is 1/3.5 the size of the original, and records internally for 30 minutes in standard mode. The reel hub 2 is small because it incorporates a tape with a length of The diameter of the loop winding portion 6 becomes extremely small. Furthermore, the surface of the tape winding part 6 has a recessed part. Since the tape locking portion 8 is formed in a shape, the rotation support shaft insertion hole 14 has a height. While the length H is approximately 13 mm, the diameter D is approximately 3 mm. It is an extremely long hole.

0004 The injection mold for molding the reel hub configured as described above is shown in Figure 8. A fixed side mold 22 is formed into a concave shape to form the outer frame of the tape winding section. and a movable mold 24 that is movable in opposition to this mold 22. , the resin product is taken out by opening the mold at parting line 23. ing. The movable mold 24 is moved to the center of the recess 25 for forming the tape winding part. It has a rod-shaped core pin 26 for forming a rotation support shaft insertion hole to be inserted. The outer periphery of the pin 26 has a predetermined gap from its surface, that is, the insertion hole rib 16 The outer pin for forming the relief part is divided into three parts in the circumferential direction with a gap corresponding to the thickness of 28 is provided. Then, the fixed side mold 22 formed in this way and the movable side mold 22 are connected to each other. A resin product is manufactured by injecting resin from the gate 30 into the gap between the side mold 24 and the side mold 24. It is designed to be molded.

[0005]

[Problem that the idea aims to solve]

By the way, a convex plate spring receiving portion located at the center of the upper end of the tape winding portion 6 12 is located on the center line of the rotation support shaft insertion hole 14, so that the gate 30 cannot be provided in the center of the upper flange mounting part 10, and the rotation support shaft insertion hole At a position eccentric from the upper center of the forming core pin 26 in either direction in the radial direction. I had no choice but to set it up. For example, as shown in the figure, the upper center of the core pin 26 If the gate 30 is installed at a position shifted to the left from the The resin that has entered the plastic space 32 flows into the gate 30 around the core pin 26. Gap 34a for forming insertion hole ribs nearer and insertion hole ribs farther from gate 30 When comparing the forming gap 34b, the resin enters the closer gap 34a. It is also easy to receive pressure such as holding pressure applied just before the end of the resin injection operation. . This is because the resin in the gap 34a closer to the gate tends to have a higher density. This means that the injection molding operation is repeated over a long period of time. Then, the core pin 26 is, for example, a cantilever beam that always receives a load from one side. The situation is the same as in the example shown, so that the core pin 26 gradually moves to the right in the illustrated example. It tends to fall to the side. For this reason, when this reel hub was commercialized, In the worst case, if the flange part 4 causes surface fluctuation, the side of the case that houses the reel The product may not be able to fit onto the rotation support shaft provided, or it may not rotate even if it does fit. In some cases, defective products were produced.

[0006] This phenomenon can be solved by reversing the fixed mold and the movable mold and attaching the gate 30 to the flange part. The same applies to the case where the mold is located on the bottom side of No. 4. The bending of the rotation support shaft insertion hole 14 can also be measured using a This is done quite carefully by inserting the shaft and actually rotating the reel using a jig. Then, measure this warpage by applying a gauge to the surface of the flange part 4 and take it into account. However, it was difficult to obtain accurate values. This invention focuses on the above-mentioned problems and was devised to effectively solve them. It is something that was given. The purpose of this invention is to prevent the core pin from bending during injection molding. The object of the present invention is to provide an injection mold that can be used for injection molding.

[0007]

[Means to solve the problem]

In order to solve the above problems, this invention has a relatively small diameter and a long length. an inner mold having a core pin formed into a relatively long rod shape; and an outer mold substantially covering the surface of the core pin with a predetermined gap therebetween. In the injection mold, the outer mold includes a front part between the inner mold and the outer mold. A retainer for holding the tip of the core pin when injecting injection molding material into the gap. It is configured to form a holding member.

[0008]

[Effect]

Since the present invention is constructed as described above, the relatively long length formed in the inner mold The core pin is held at its tip by a holding member extending from the outer mold. This prevents the core pin from misaligning.

[0009]

【Example】

Below, one embodiment of the injection mold according to the present invention will be described in detail based on the attached drawings. Ru. Figure 1 is an enlarged sectional view showing the main parts of an injection mold according to the present invention, and Figure 2 is an enlarged sectional view showing the main parts of an injection mold according to the present invention. It is a top view of the movable side metal mold|die used for this. In this invention, as shown in Figures 1 and 2, The configuration other than that is the same as the conventional configuration shown in Figure 8, so we will not explain that part. Omitted. As shown in the figure, the fixed side mold 22 has a tape winding section formed with an open downward direction. A concave portion 25 is formed at the center of the upper end of the concave portion 25 for use with a convex plate spring. A recessed portion 40 for forming a receiving portion is formed with a downwardly open side. From this recess 40 Gate 3 for injecting resin into the cavity space 32 with slight eccentricity in the lateral direction 0 is formed. On the other hand, below the fixed side mold 22, there is a movable side mold 24 (Fig. 8) is provided. This movable side mold 24 is for forming the tape winding part. Core pin 26 for forming a rotation support shaft insertion hole inserted from below into the center of the recess 25 The outer periphery of the core pin 26 has a predetermined gap from its surface. The meat relief is divided into three parts in the circumferential direction separated by a gap corresponding to the thickness of the insertion hole rib 16. Outer pins 28a, 28b, and 28c for forming portions are provided so as to be freely inserted and removed from below. There is. These core pins 26 and outer pins 28a, 28b, 28c are for insertion hole ribs. The portions other than the gap, that is, the lower end portions are in close contact with each other.

0010 Then, the adjacent outer pins 28a, 28b, 28c for forming the relief portions are aligned. A gap 19 for forming auxiliary ribs is formed at a slight distance between them. follow The outer mold that covers the core pin 26, which is the inner mold, covers the upper surface of the core pin 26. The fixed side mold 22 that covers the core pin 26 and the movable side mold 24 that covers the side surface of the core pin 26 have their respective thickness reliefs. It is constituted by outer pins 28a, 28b, and 28c for forming ridges. Then, on the fixed side mold 22 that constitutes a part of the outer mold formed in this way, A holding member 42 for holding the tip 26a of the core pin 26 is provided. Ru. Specifically, this holding member 42 is attached to the circular tip portion 26a of the core pin 26. For example, the corresponding circular circles are placed at equal intervals of 120 degrees on the fixed side mold 22 facing the Three pilot pins 44 provided on the circumference (in the illustrated example, for simplicity of drawing) Each of these spigot pins 44 protrudes and retracts from the side of the cavity space 32. Currently configured.

[0011] The tip end 44a of each pilot pin 44 is formed into a tapered shape, and the upper end 44a is tapered. The core pin 26 is configured to come into contact with the peripheral edge of the tip 26a of the core pin 26. It is configured so as not to come into contact with the outer pins 28a, 28b, and 28c for forming relief portions. ing. On the other hand, the peripheral edge of the tip 26a of the core pin 26 has, for example, 120 degree equal intervals. Therefore, it comes into contact with and receives the tapered tip 44 of the pilot pin 44. Three pilot pin receiving portions 46 are formed. This pilot pin receiving part 46 is shaped like the inside of a mortar, for example, and the tip 4 of the pilot pin is It is configured to make sure contact with 4.

0012 Next, the operation of this embodiment configured as above will be explained. First, prior to the resin injection molding operation, the fixed side mold 22, the movable side mold 24, and the Outer pins 28a, 28b, 28c for forming relief portions and rotation support shaft insertion holes. Assemble the core pin 26, and then remove each pilot pin 44 of the holding member 42 from the cavity. The tip of the core pin 26 is extended into the space 32 with its tapered tip 44a. Holding the end portion 26a from three directions, centering the core pin 26 and clamping the mold. Let's do it. At this time, the tapered tip 44a of the spigot pin 44 and the core pin 26 The receiving portions 46 are joined at the surface and therefore fit into each other as the mold is tightened, Accurate positioning of the core pin 26 is achieved. The resin is then injected into the cavity as an injection molding material through the gate 30 in a normal manner. Injection molding is performed by injecting into the space 32.

[0013] By this injection molding, the resin flowing from the gate 30 is used to form the core. A bending pressure is applied to the pin 26 in the opposite direction of the gate 30, but as described above, The tip 26a of the core pin 26 is securely held by the three spigot pins 44. Because it is aligned, it will not bend and there will be no misalignment. In addition, since the tip 44a of the spigot pin 44 is tapered, This does not come into contact with the outer pins 28a, 28b, and 28c for forming meat relief parts. , no undesirable bending pressure is applied to this outer pin. In this way, according to this embodiment, the tip portion 26a of the core pin 26 is held and the core is removed. This prevents the rotary support shaft from collapsing, so you can always obtain a properly straight rotation support shaft insertion hole. Wear.

[0014] In the above embodiment, the shape of the pilot pin receiving portion 46 is adjusted to the inside of the mortar. Although the shape is not limited to this, for example, as shown in FIG. 3, the tip of the core pin 26 The receiving portion 46 is formed by cutting the end portion diagonally at 120 degree intervals, and Accordingly, the tip 44a of the spigot pin 44 is also tilted so as to make surface contact with this cut surface. It is also possible to cut it into three pieces and install three pilot pins 44 at 120 degree intervals. stomach. Further, the number of pilot pins 44 may be three or more or three or less, for example, as shown in FIG. As shown in FIG. In other words, one core pin 26 is provided at a position facing the bending stress. Good too. In addition, this invention is not limited to molding reel hubs, but also molds thin and long core pins. Of course, it can be applied to all cases where it is used as

[0015]

[Effect of the idea]

As explained above, according to the present invention, the following excellent effects can be achieved. I can do that. This prevents the core pin from bending, so it always remains unbent. It is possible to obtain a straight insertion hole for the rotation support shaft, making it possible to manufacture products with good quality. I can do that. In addition, when determining the eccentricity of the product, it is also necessary to determine the eccentricity of the mold (core pin). This makes it possible to calculate easily.

[Brief explanation of drawings]

FIG. 1 is an enlarged sectional view showing the main parts of an injection mold according to the present invention.

FIG. 2 is a plan view of a movable mold used in the present invention.

FIG. 3 is an enlarged sectional view of main parts showing another embodiment of the present invention.

FIG. 4 is a plan view of a movable mold showing still another embodiment of the present invention.

FIG. 5 is an external perspective view showing the reel hub.

6 is a longitudinal sectional view showing the reel hub shown in FIG. 5. FIG.

7 is a cross-sectional view showing the reel hub shown in FIG. 5. FIG.

FIG. 8 is a sectional view showing a conventional injection mold for a reel hub.

[Explanation of symbols]

2... Reel hub, 4... Tape locking part, 6... Tape winding part, 22... Fixed side mold (outer mold), 24... Movable side mold, 26... Core pin (inner mold), 26a... Tip part ,2
8a, 28b, 28c...outer pin (outer mold), 30...
Gate, 42... Holding member, 44... Pilot pin, 46a
... Pilot pin receiving part.

Claims (1)

[Scope of utility model registration request] 1. An inner mold having a core pin formed in the shape of a rod having a relatively small diameter and a relatively long length;
In an injection mold, the injection mold has an outer mold that substantially covers the surface of the core pin of the inner mold with a predetermined gap therebetween. An injection mold characterized in that a holding member is formed to hold the tip of the core pin when injection molding material is injected into the gap between the core pin and the core pin.