JPH05185465A - Method for injection molding of molded item having external thread and injection molding apparatus therefor - Google Patents

Abstract

PURPOSE:To simplify the working process, reduce the cost of a molded item and manufacture an injection molding apparatus for the molded item with a simple structure inexpensively in production of the molded item having integrally an external thread. CONSTITUTION:In an injection molding apparatus wherein a fixed mold 12 and a movable mold 14 forming a cavity 17 under a mold clamping condition are provided and an ejector device 24 for the molded item 3 is provided, a freely openable core 41 for molding an external thread is provided on either one of the fixed mold 12 or the movable mold 14 and the molding core 41 has an external thread molding part communicating with the cavity 17 under this closed condition and an ejector device 24 is provided in such a way that it is interlocked with mold release of the molded item 3 and releasing of the external thread is allowably opened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method for a molded product having a male screw and an injection molding apparatus for the molded product.

[0002]

2. Description of the Related Art A safety sign pole, which is a molded product 3 having a male screw 2 for mounting an electric lamp 1 therein, as shown in FIG. 10, is provided on a hollow pole body 4 and a bottom portion of the pole body 4. The electric lamp mounting portion 5 is composed of a base 6 and a screw portion 2 projecting downward from the base 6. The pole body 4 has a base portion 9 that supports the marker portion 7 via a conical marker portion 7 having a downward opening and a step portion 8 protruding radially outward from the outer periphery of the lower end of the marker portion 7.
It consists of and.

Conventionally, as the injection molding method of such a molded product 3, a method of embedding an insert component having a male screw in the pedestal 6 or a male screw molded core having a thread engraved and then rotating the molded product is used. There was a method of releasing the mold.

[0004]

However, in the former method among those described above, the insert parts are usually loaded manually by the operator, so that the working process cannot be simplified and the material is different. Since it has insert parts, it is necessary to remove the insert parts at the time of material cost / inventory management increase and recycling (collecting defective moldings and used moldings and reusing them as resin material). was there.

Further, in the latter case, since it has a complicated structure and has a rotary type male thread molding core which is easily broken and an expensive mold has to be manufactured, the cost becomes high and when the diameter of the screw is large. Had a problem that shrinkage caused by shrinkage occurred on this surface portion and impaired the appearance. Therefore, the present invention has been made in view of the above problems, and a first object thereof is to automatically perform from mold clamping to release of a molded product when producing a molded product integrally having a male screw. An object of the present invention is to provide an injection molding method capable of simplifying the working process and reducing the cost of a molded product.

A second object of the present invention is to provide an apparatus which is useful for using the above-mentioned injection molding method and which has a simple structure and is inexpensive, for injection molding the above-mentioned molded article. is there. Furthermore, a third object of the present invention is to prevent the occurrence of sink marks due to resin shrinkage on the surface portion of the molded product even when the diameter of the screw is large, and to improve the strength of the screw portion. To provide.

[0007]

In order to achieve the above object, the present invention takes the following technical means. That is, the present invention provides a method of injecting a resin into a cavity defined by a fixed die and a movable die to injection-mold a molded article integrally having a male screw, wherein either one of the fixed die and the movable die is used. Injecting an externally openable male screw molding core provided in the cavity in a closed state at the time of mold clamping and performing injection molding, and releasing the molded product after the injection molding and in the mold open state while opening the closed molding core. Is characterized by.

Further, according to the present invention, in an injection molding apparatus having a fixed die and a movable die that define a cavity in a mold clamped state, and an ejector means for a molded article, one of the fixed die and the movable die is provided. An openable male screw molding core is provided on one side, and the molding core has a male screw molding portion that communicates with the cavity in this closed state, opens in conjunction with the mold release of the molded product and allows the male screw to separate. As described above, the ejector means is provided.

Further, according to the present invention, the male screw forming portion is provided from a midway portion of the protruding body forming portion which communicates with the cavity in the male screw forming core and in the closed state, and the protruding body forming portion with respect to the male screw. It is characterized in that it is provided radially outward and radially.

[0010]

Since the openable and closable male screw molding core provided in either the fixed mold or the movable mold is communicated in a closed state with the cavity defined by the fixed mold and the movable mold during mold clamping, When the molten resin is injected into, the male screw is molded integrally with the molded product.

Next, the mold is opened, and the molded product is released from the ejector means. At this time, since the molding core is interlocked with the mold release of the molded product and is projected while opening so as to allow the mold release of the male screw, the mold product integrally having the male screw is easily released.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, which shows the overall configuration, 11 is a fixed die plate, which has a fixed die 12 which is a female die. A moving die plate 13 has a moving die 14 which is a male die. Reference numeral 15 is a mold clamping cylinder, and 16 is an injection nozzle, which injects molten resin into a cavity 17 (shown in FIG. 2) defined by the fixed mold 12 and the movable mold 14 in the mold clamped state.

In FIG. 2, a fixed die 12 is a runnerless type die, in which an injection nozzle 16 is directly connected to one end side, and a safety mark pole which is an example of a molded article 3 shown in FIG. A female die portion 18 for molding the outer surface is formed, and further, a plurality of guide pin holes 19 are provided outside the female die portion 18. 2-9, details of the mobile mold 14 are shown.

In these figures, the movable die 14 is a receiving plate having a male die portion 20 for molding the inner surface of the safety sign pole 3.
21 and a movable mounting plate 23 mounted on a surface of the receiving plate 21 opposite to the male part 20 via a spacer block 22,
And ejector means 25 for releasing the molded product. As shown in FIGS. 2 to 4, the male part 20 of the backing plate 21 is
A conical portion 25 that molds the inner surface of the marker portion 7 of the molded product 3, and a ring-shaped stepped portion that is provided on the outer circumference of the conical portion 25 in a large-diameter manner.
26 and the outer periphery of the ring-shaped stepped portion 26 and the base of the molded product 3.
9 It is composed of a square step 27 that molds the inner surface.

The ring-shaped stepped portion 26 has a tapered core fitting insertion hole 28 whose inner portion has a small diameter at a symmetrical position with respect to the center of the cone.
And a plurality of ejector pin holes 29 are provided. In addition, the square step portion 27 is provided with a ring-shaped rib groove 30 and a plurality of ejector pin holes 29. And
A guide pin 31 and a return pin hole 32 are provided in four directions on the outside of the male part 20.

The ejector pin means 24 is the receiving plate.
A protruding plate 33 slidably provided in the mold opening and closing direction between the movable mold mounting plate 23 and the movable mold mounting plate 23; and a coil-shaped spring 34 for urging the protruding plate 33 toward the movable mold mounting plate 23 side. Mainly composed of a projecting cylinder 35 that projects the projecting plate 33 toward the fixed mold against the spring 34. On the receiving plate 21 side of the projecting plate 33, the molding core fitting hole 28 of the receiving plate 21,
A molding core projecting pin 36, an ejector pin 37, and a return pin 38 are projectingly provided at positions corresponding to the ejector pin hole 29 and the return pin hole 32, respectively.

As shown in FIGS. 5 to 9, the tip of the molding core projecting pin 36 is provided with a pair of male thread molding cores 41 whose end 40 on the cavity side can be opened and closed via a pivot pin 39. .. The pair of molding cores 41 are substantially semi-cylindrical with a taper such that the diameter on the side of the pivot pin 39 is small so as to be fitted into the molding core fitting hole 28 of the receiving plate 21, and is shown in FIGS. In this closed state, it has a protruding body forming portion 42 that communicates with the cavity 17, and a male screw forming portion 43 that is provided from the middle of the protruding body forming portion 42. The protrusion forming part 42
Is a part for molding the pedestal 6 of the molded product 3, and the male screw 2
Radially outwardly and radially with respect to, ie, FIG.
In FIG. 7, a pair of flat plate-shaped projection molding portions 42a parallel to the open / close surface 44 of the molding core 41 in a closed state, and a pair of projection molding portions 42b perpendicular to the projection molding portion 42a. Is becoming Further, a coil spring 45 for biasing the cavity side ends 40 of the pair of molding cores 41 in the opening direction, which does not communicate with the cavity when the molding cores are closed, is provided in the middle of the male screw molding portion 43 and the pivot pin 39. A spring storage hole 46 for storing the inside is provided.

Therefore, when the male screw molding core 41 is projected from the molding core fitting insertion hole 28, since the diameter on the side of the pivot pin 39 is small, a gap is formed between the male thread molding core 41 and the molding core fitting insertion hole 28. At this time, the cavity side end 40 is opened by the spring 45 in the spring storage hole 46. The opening / closing amount of the cavity side end portion 40 is such that a pair of molding cores 41
It is set by the taper angle and the amount of protrusion. Therefore,
If there is a space around the protruding portion of the molding core 41 that allows the male screw 2 and the like to be released and the molding core 41 opens, the molded product 3 can be molded, and the degree of freedom in designing the mold increases.

Next, a molding method using the apparatus of the embodiment will be described. First, as shown in FIGS. 2 and 7, the mold clamping cylinder
By operating 15 and clamping the fixed mold 12 and the movable mold 14, the cavity 17 for molding the molded product 3 is defined. At this time, since the return pin 38 of the movable die 14 contacts the fixed die 12, the protruding plate 33 is moved to the movable die mounting plate 23 side.
Molded core 41 and ejector pin 37 connected to 33
Are interlocked and inserted into the receiving plate 21. Therefore, the molding core
41 is a protruding body forming portion that communicates with the cavity 17 in a closed state 42
And a male screw forming part 43.

Next, when the molten resin is injected into the cavity 17 by the injection nozzle 16 in this mold clamping state, the projection molding portion
Since the 42 and the male screw molding portion 43 communicate with the cavity 17, the pedestal 6 and the male screw 2 are molded integrally with the molded product 3. Then, the mold is opened after the resin is cooled and solidified. next,
When the ejecting cylinder 35 is operated, the molding core ejecting pin 36, the ejector pin 37, and the return pin 38 are simultaneously ejected via the ejecting plate 33. At this time, as shown in FIGS. 8 and 9, the molding core 41 provided at the tip of the molding core projecting pin 36 is at the same time as the ejector pin 37 and the spring.
Since it is projected while being opened to allow the male screw 2 to be detached by 45, the pedestal 6 having the integrally molded male screw 2 is released together with the molded product 3.

The present invention is not limited to the above embodiment.

[0022]

According to the injection molding method of a molded product of the present invention, an openable and closable male screw molding core provided in one of a fixed mold and a movable mold is communicated with the cavity in a closed state at the time of mold clamping. It is possible to perform injection molding, and after the injection molding and in the mold open state, the molded product integrally having the male screw can be released while opening the closed molding core. The work process can be simplified, and since insert parts made of different materials are not required, low-cost molded products can be mass-produced.

Further, according to the injection molding apparatus of the present invention, one of the fixed mold and the movable mold is provided with an openable and closable male screw molding core, and the molding core communicates with the cavity in this closed state. Since the ejector means is provided with a portion, which is interlocked with the mold release of the molded product and allows the male screw to be released and opened, it is not necessary to separately provide a drive mechanism for rotating the molded core, It can be molded with a mold that has a simple structure and is inexpensive. Also, if there is a space around the protruding portion of the molding core that allows the male screw to be released and the molding core can be opened, it is possible to mold a molded product having a male screw. ..

Further, a male screw forming portion is provided in the male screw forming core and from a middle portion of the protruding body forming portion communicating with the cavity in the closed state, and the protruding body forming portion is radially outward with respect to the male screw. Because of the radial arrangement, it is possible to form a high-strength screw portion with less shrinkage due to resin shrinkage on the surface of the screw portion.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view showing a clamped state of a fixed die and a movable die.

FIG. 3 is a vertical cross-sectional view showing a released state of a molded product.

FIG. 4 is a side view of a movable die.

5 is an enlarged view of part A in FIG.

FIG. 6 is an enlarged view of part B in FIG.

7 is a plan sectional view of FIG.

FIG. 8 is an explanatory view showing a state of a main part of a molded product during the protrusion thereof.

FIG. 9 is an explanatory diagram showing the state of the main parts when the protrusion of the molded product is completed.

FIG. 10 is a partial cross-sectional side view of a molded product.

[Explanation of symbols]

 12 Fixed type 14 Movable type 17 Cavity 24 Ejector means 41 Male thread molding core 42 Projection body molding section 43 Male thread molding section

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location B29L 1:00 4F 31:34 4F

Claims (3)

[Claims] 1. A method of injecting a resin into a cavity defined by a fixed die and a movable die to injection-mold a molded article integrally having a male screw, wherein either the fixed die or the movable die is provided. When the mold is closed, the male screw molding core that can be opened and closed is communicated with the cavity in a closed state for injection molding, and the molded product is released after the injection molding and in the mold open state while opening the closed molding core. An injection molding method of a molded product having a characteristic male screw. 2. An injection molding apparatus comprising a fixed die and a movable die that define a cavity in a mold clamped state, and an ejector means for molded articles, wherein the fixed die and the movable die can be opened and closed. A male thread molding core, the molding core having a male thread molding portion communicating with the cavity in the closed state, and the ejector so as to interlock with the mold release of the molded product and allow the male thread to be released. An injection molding device provided in the means. 3. An external thread forming part is provided in a male thread forming core and from a middle part of the protruding part forming part which communicates with the cavity in the closed state, and the protruding part forming part is radially outward with respect to the external thread. The injection molding apparatus according to claim 2, wherein the injection molding apparatus is provided radially and radially.