JPH0523574B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an injection mold for a molded product having an internally threaded portion.

(b) Conventional technology When injection molding a molded product that has a threaded portion on the outer or inner surface, the idea of creating a relative rotation between the molded product and the mold after opening the mold to extract the molded product is an old idea. Various devices have been proposed to achieve this. An example of handling molded products with external threads is the device described in Japanese Utility Model Application No. 60-32982, and an example of handling molded products with internal threads is the device described in Japanese Utility Model Application No. 60-32982.
The devices described in Japanese Patent No. 55-163121 can be mentioned.

(c) Problems to be Solved by the Invention The apparatus described in Japanese Utility Model Application Publication No. 55-163121 extracts a molded product by rotating a core having a female thread forming part. In this case, the molded product is connected by two runners, so it does not rotate relative to the mold even though it has come out of the cavity.
Therefore, the screw action works well between the core and the core. If the gate part is cut off when the mold opens and the molded product becomes completely independent, some other method must be considered to prevent the molded product from rotating. If the cross section of the molded product is non-circular, one method is to provide a cavity plate on the moving side of the mold so that the molded product is pushed out of the cavity as the core rotates. . In this case, if the depth of the cavity and the depth of the female thread do not match, a phenomenon may occur where the inner surface of the molded product comes off the core but the outer surface does not come off the cavity, or vice versa. The present invention attempts to solve this problem.

(d) Means for Solving the Problems In the present invention, a cavity plate is attached to a movable base, and a non-circular cross-section portion of a molded product is formed by a non-circular cross-section cavity provided in the cavity plate. Further, the internal thread forming part of the rotating core that enters the non-circular cross-section cavity forms a female thread inside the molded product. The cavity plate is attached to the movable base by a connecting pin so that it can be moved toward and away from the movable base, but the maximum separation distance is limited to "the depth of the female thread part minus the depth of the non-circular cross-section cavity."
Further, the cavity plate is biased by a spring in a direction away from the movable base.

(e) Action After the molded product cools and solidifies, the mold begins to open.
The rotating core and molded parts act just like bolts and nuts, and the cavity plate initially remains drawn to the moving base. When the rotating core is rotated, the rotating core slips out of the molded product. This means that the cavity plate moves away from the moving base.
When the distance between the cavity plate and the moving base reaches its maximum value, the remaining screw engagement depth between the molded product and the rotating core is equal to the depth of the non-circular cross-section cavity. As the rotating core continues to rotate, the cavity plate will not move any further, and the molded product will now be extruded from the non-circular cross section. When the rotating core exits from the molded product, the molded product also exits from the non-circular cross-section cavity, completing the ejection.

(f) Example In the figure, 1 is a stationary block and 2 is a movable block. The fixed block 1 includes a fixed base 10 and a gate plate 11. After forming, the gate plate 11 is separated from the fixed base 10 by a certain distance, and the runner 12 falls from between them. A cavity 13 having a circular cross section, which is a part of a molding cavity, is formed in the gate plate 11, and the cavity 13 and the runner 12 are connected by a gate 14. The moving block 2 includes a moving base 20 and a cavity plate 21. The cavity plate 21 is supported by a guide post (not shown) so as to be movable toward and away from the movable base 20. 22 is a connecting pin that determines the maximum separation distance between the moving base 20 and the cavity plate 21.

The molded product 30 in this example is a worm gear having the shape shown in FIG. The molded product 30 has a toothed portion 31 in the center and shaft portions 32, 3 with a circular cross section on both sides.
3, and a female threaded portion 34 is formed in the central cavity. The shaft portion 32 is formed by the circular cross-section cavity 13 of the gate plate 11, and the tooth portion 32 and the shaft portion 33 are formed by the non-circular cross-section cavity 35 and the circular cross-section cavity 36 of the cavity plate 21. The non-circular cross-section cavity 35 naturally has the cross-section of the tooth 31. Female thread part 3
4 is molded by a rotating core 40. Rotating core 40
is supported by the movable base 20 so as to be rotatable but immovable in the axial direction, and has a female threaded portion 41 at the tip inserted into the cavity 35 with a non-circular cross section.
The rotating core 40 has a gear 42, which is meshed with a rotation transmission gear 43 rotated by an electric motor (not shown). A spring 44 biases the cavity plate 21 in a direction away from the movable base 20. The maximum distance between the cavity plate 21 and the moving base 20 is the female threaded portion 34.
The distance is set to be the depth of the non-circular cross-section cavity 35 subtracted from the depth of the cavity 35.

50 is a vibration generating plate. The vibration generating plate 50 is attached to the cavity plate 21 by a connecting pin 51 so as to be able to come into contact with and be separated from it, and is constantly pressed against the movable base 20 by a spring 52.

FIG. 1 shows the mold in the clamped state. At this time, the end surface of the rotary core 40 is in close contact with the bottom surface of the circular-section cavity 13, and is ready to form a through hole in the center of the molded product 30. When molding is performed in this state and the mold is opened, the molded product 30 and the runner 12 are cut off at the gate 14, and the molded product 30 leaves the gate plate 11 while being taken into the cavity plate 21. When the space between the gate plate 11 and the cavity plate 21 is sufficiently opened,
When rotation is applied to the rotating core 40 by the rotation transmission gear 43, the female thread molded part 41 comes out of the molded product 30, and at the same time, the cavity plate 21
It moves away from the movable base 20 due to the pressure of the spring 44. Cavity plate 21 and moving base 20
When the distance between them reaches the maximum value allowed by the connecting pin 22 (FIG. 2), the relative movement between the cavity plate 21 and the movable base 20 ends;
The rotating core 40 begins to extrude the molded article 30. The extrusion distance is the remaining screw engagement depth between the female threaded portion 34 and the female threaded portion 41, which is equal to the depth of the non-circular cross-section cavity 35. Therefore, as shown in FIG. 3, when the female threaded molded part 41 comes out of the molded product 30, the molded product 30 also reaches the final stage of detachment from the non-circular cross-section cavity 35. The molded product 30 will generally fall at this stage, but there may be some cases where some catching remains and the molded product 30 does not fall, so the vibration-generating plate 50 is used to ensure that the molded product 30 falls. That is, as shown in FIG. 3, a hydraulically driven ejector rod 60 is advanced from the molding machine to push the vibration generating plate 50 toward the cavity plate 21. When the ejector rod 60 is quickly pulled back when sufficient energy is stored in the spring 52, the vibration generating plate 50 moves from the movable base 20.
The moving block 2 vibrates throughout. As a result, the molded product 30 separates from the cavity plate 21 and falls.

(G) Effects of the Invention According to the present invention, it is possible to extrude a molded product whose outer surface has a non-circular cross-section and whose inner surface has a female thread by screw action by utilizing the detent function derived from the cross-sectional shape. Even if there is a difference between the depth of the female thread and the depth of the cavity for molding a non-circular cross-section, this is not a problem, and the timing of the exit of the female thread and the molded product from the cavity can be adjusted at the same time. The molded product can be reliably separated from the mold by matching the

[Brief explanation of drawings]

The figures show one embodiment of the present invention, and Figs.
The figure is a sectional view showing a series of operations from molding to discharge of the molded product, and FIG. 4 is a perspective view of the molded product. DESCRIPTION OF SYMBOLS 1... Fixed side block, 2... Moving side block, 20... Moving base, 21... Cavity plate, 30... Molded product, 34... Female threaded part, 3
5...Non-circular section cavity, 40...Rotating core, 41...Female thread molding part, 22...Connecting pin,
44... Spring, 43... Rotation transmission gear (rotation transmission means).

Claims (1)

[Scope of Claims] 1. An injection mold comprising the following components: (a) a cavity plate having a cavity with a non-circular cross-section for molding a non-circular cross-section portion of a molded product; (b) supporting the cavity plate; Moving base (c) supported by the moving base so as to be rotatable and immovable in the axial direction, the tip end of which is inserted into the non-circular cross-section cavity, and the tip end has a female thread molding part that forms a female thread part inside the molded product. (d) The cavity plate and the movable base are connected so as to be able to come into contact with each other, and the maximum separation distance between them is the distance obtained by subtracting the depth of the non-circular cross-section cavity from the depth of the female thread. (e) a spring that urges the cavity plate in a direction away from the movable base; and (f) a rotation transmission means that imparts rotation to the rotating core.