JP2004009616A - Injection molding mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide injection molding for a small molded part having an undercut part inside. <P>SOLUTION: A pair of slant blocks A7, B8 and a pair of shut-off pins A9, B10 are fixed to a fixing side template 4 so as to be projected to a movable side mold 3 side. A pair of sliding core A16, B17 being operated along a parting line 1 are arranged on a sliding base 15 built in a movable template 14. A cavity 18 is formed between both sliding cores 16, 17 which are closed. A pair of slant pins A23, B24 supported by a shaft of a holder 21 are guided by an outer wall surface 25a of a nest 25 and an inner wall surface 15a of the sliding base 15 and both become a mold component forming an inner wall surface of a resin molded article. Projected parts 23a, 24a fitted in the undercut part of the molded article are formed at its tip part. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an injection mold, and more particularly, to an inner punching structure of an injection mold for molding a molded article having an undercut portion inside.
[0002]
[Prior art]
2. Description of the Related Art In recent years, plastic molded products have been widely used in various industrial products for the purpose of improving material properties, facilitating production of parts, facilitating assembly, reducing weight, reducing costs, and the like, and are mass-produced using injection molding machines. Some of such plastic molded articles have an undercut portion inside, such as a bottle cap.
[0003]
An example of an injection mold for molding such a plastic molded product will be described with reference to the drawings. FIG. 6 is a cross-sectional view of a main part of a conventional injection molding die, omitting a fixed die. In FIG. 6, reference numeral 63 denotes a movable die, and shows a state of the movable die immediately after the mold is opened. I have. Reference numeral 91 denotes a molded product. The molded product 91 has a pair of opposed undercut portions 91a inside. Reference numeral 71 denotes a movable-side mounting plate, 72 denotes a spacer block, 73 denotes a movable-side receiving plate, and 74 denotes a movable-side mold plate, which are sequentially laminated. Other details of the configuration are publicly known and will be omitted.
[0004]
Reference numeral 79 denotes an ejector plate, and reference numeral 80 denotes an ejector plate. The ejector plate 80 is driven by a cylinder (not shown) to move between the movable mounting plate 71 and the movable receiving plate 73. 81 is a commercially available slide unit fixed to the lower part 79 of the ejector plate. Reference numeral 82 denotes a slide plate that slides in the base of the slide unit, and reference numeral 83 denotes an inclined pin holder that is pivotally supported by the slide plate 82 and swings. Reference numeral 84 denotes an inclined pin whose one end is fixed to the inclined pin holder 83. Reference numeral 85 denotes a slide core having a projection 85a that fits into the undercut portion 91a, and is fixed to the other end of the inclined pin 84. The inclined pin 84 passes through the escape hole 73 a of the movable-side receiving plate 73 and is slidably fitted in the inclined hole 74 a of the movable-side mold plate 74. Two sets of such a combination of the slide core 85, the inclined pin 84, and the slide unit 81 are provided so as to correspond to the pair of undercut portions 91a.
[0005]
Next, the operation of this mold will be described. First, when the resin is cooled and cured while maintaining the pressure for a certain period of time by injecting the molten resin, the mold is opened as shown in FIG. FIG. 7 is a cross-sectional view of a main part of the movable mold 63 showing a state where the ejector plate is driven to remove a molded product. As shown in FIG. 7, when the lower part 79 of the ejector plate is raised, the two slide cores 85 are lifted up via the two inclined pins 84 and push up the molded product 91. At this time, the two inclined pins 84 are guided by the inclined holes 74a and rise obliquely, so that the two slide cores 85 and the two slide plates 82 move in directions approaching each other. Therefore, the protrusion 85a of the slide core 85 comes off from the undercut portion 91a of the molded product 91, and the molded product 91 comes off the mold. When the mold is a horizontal type, the molded product 91 falls by its own weight. Return the ejector plate and close the mold to prepare for the next molding operation.
[0006]
[Problems to be solved by the invention]
However, as described above, it is necessary to use a slide unit in order to injection-mold a molded product having an undercut portion inside. Since the slide unit is complex and has many parts, and requires a large ejector space in the mold, if the molded product is small and a large number of products are to be taken, such a mold configuration should be used. Could not be adopted.
[0007]
The above invention has been made to solve such a conventional problem, and an object thereof is to provide an injection mold having a mold structure capable of taking a large number of small molded products having an undercut inside a product. It is to provide.
[0008]
[Means for Solving the Problems]
Means of the present invention for solving the above problems is an injection molding die for molding a resin molded product with an undercut, which comprises a fixed mold and a movable mold, wherein an undercut portion of the molded product is provided. A mold member having a protrusion to be fitted is disposed on the ejector plate so as to project into the cavity, and the mold member is simultaneously moved in the mold opening and closing direction and the vertical direction with opening and closing of the mold. In the injection mold described above, the mold member includes a frame-shaped slider, an inclined pin, and a support shaft that supports the inclined pin on the slider, and the two ejectors provided with the slider on the movable mold. It is characterized by sliding between the plates.
[0009]
Further, the projection is formed integrally with the inclined pin, and a pair of the inclined pins are disposed so as to face each other with the projection as a back.
[0010]
Further, the inclined pin is guided and slid by a wall surface of a nest provided in the cavity and a wall surface of a fixed plate parallel to the wall surface.
[0011]
Further, the cavity is formed between a pair of slide cores provided in the movable mold, and the slide core is driven by a pair of opening / closing pins provided in the fixed mold. And
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view of a main part of an injection molding die according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing an example of a molded product molded by the injection molding die. 3 is an enlarged cross-sectional view of the tip of the inclined pin, FIG. 4 is a cross-sectional view of a main part of the injection molding die when the die of FIG. 1 is opened, and FIG. 5 is an injection molding die showing a step of removing a molded product. It is principal part sectional drawing of.
[0013]
First, the configuration of an injection mold according to an embodiment of the present invention will be described with reference to FIG. In FIG. 1, reference numeral 1 denotes a parting line that divides the cavity of the injection molding die, 2 denotes a fixed die attached to a fixed side of the injection molding machine, and 3 denotes a movable side of the injection molding machine. It is a movable mold. First, the configuration of the fixed mold side will be described. Reference numeral 4 denotes a fixed mold plate that constitutes the fixed mold 2, and reference numeral 5 denotes a runner plate incorporated in the center of the fixed mold plate 4. A vertical runner portion 4a, which is a resin flow path with a taper, is formed at the center thereof.
[0014]
Reference numeral 6 denotes a gate bush fixed so as to be connected directly below the vertical runner portion 4a. The tip of the gate bush 6 slightly protrudes from the parting line 1 of the fixed side mold plate 4 to form a gate 6a which is an outlet of the resin. Reference numerals 7 and 8 denote a pair of slope blocks A and B having slopes fixed to the fixed mold plate 4, and protrude into the movable mold plate 14. Reference numerals 9 and 10 denote a pair of opening / closing pins A and B screwed to the fixed template 4, respectively. It reaches the inside of the plate 13.
[0015]
Next, the configuration of the movable mold 3 will be described. Reference numeral 11 denotes a movable-side mounting plate, 12 denotes a spacer block, 13 denotes a movable-side receiving plate, and 14 denotes a movable-side mold plate, which are stacked and fixed in this order. Reference numeral 15 denotes a slide base which is a fixed plate incorporated in the movable mold plate 14, and reference numerals 16 and 17 are provided on the slide base 15 so as to be openable and closable by opening and closing pins A9 and B10. Are a pair of slide cores A and B operating along. Reference numeral 18 denotes a cavity formed between the slide cores 16 and 17. The gate 6a is fitted into the top of the cavity 18. Both slide cores A16 and B17 have inclined holes through which opening / closing pins A9 and B10 are inserted, and have slopes at both ends in the sliding direction that are in close contact with the slope blocks A7 and B8.
[0016]
Reference numerals 19 and 20 are above and below the ejector plate, and are disposed in an ejector space surrounded by the spacer block 12. Reference numeral 21 denotes a pair of holders which are mold members that slide in a space formed by a counterbore formed on the ejector plate upper 19 and an upper surface of the ejector plate lower 20, and 22 is a support fixed to the holder 21. Axis. Reference numerals 23 and 24 denote a pair of inclined pins A and B which are supported by the holder 21 by the support shaft 22. The end surfaces of the inclined pins A23 and B24 are made to coincide with the lower surface 20 of the ejector plate so as to withstand the resin pressure at the time of injection. Reference numeral 25 denotes a nest fixed to the slide base 15 and disposed in the cavity 18. The inclined pins A23 and B24 have parallel portions guided by both outer wall surfaces 25a of the nest 25 and both inner wall surfaces 15a of the slide base 15 parallel to the nest 25. Form the inner wall. The other configuration of the above injection molding die is common to a general injection molding die, and therefore the description is omitted.
[0017]
Here, with reference to FIG. 2, a molded product formed by the injection mold will be described. FIG. 2A is a side view of a battery cap of a thermometer as a resin molded product, FIG. 2B is a front view, and FIG. 2C is a central sectional view thereof. In FIG. 2, reference numeral 31 denotes a bag-shaped battery cap, which has a gate position 31a at a position corresponding to an apex, and has undercut portions 31b and 31c on both sides of the center of the inner wall surface. Reference numeral 32 denotes a battery held in the thermometer main body, and the protrusions on both sides of the thermometer main body engage with the undercut portions 31b and 31c, respectively. FIG. 3 shows the details of the tip portions of the inclined pins A23 and B24. Protrusions 23a and 24a corresponding to the undercut portions 31b and 31c of the battery cap 31 are formed on the rear sides of the opposed inclined pins A23 and B24. Have been.
[0018]
Next, a molding process using the injection mold will be described with reference to FIGS. After the fixed mold 2 and the movable mold 3 are closed and the molten resin is injected into the cavity 18 from the gate 6a and the pressure is maintained for a certain time, the resin is cooled and hardened to form the battery cap 31. You. Next, at the same time when the movable mold 3 is opened, the resin on the gate 6a side is separated from the gate position ear a. At this time, the slope blocks 7 and 8 of the fixed mold plate 4 are disengaged from the slopes of the slide cores A16 and B17, and the slide cores A16 and B17 are opened on the slide base 15 on both sides by the action of the opening and closing pins 9, 10. However, the battery cap 31 remains locked and held by the projections 23a and 24a of the inclined pins A23 and B24.
[0019]
Next, as shown in FIG. 5, the upper 19 and lower 20 of the ejector plate are raised, and the inclined pins A23 and B24 are pushed up. Then, since the inclined pins A23 and 24B are guided by the wall surfaces 15a and 25a of the slide base 15 and the insert 25, the holder 21 slides between the upper and lower ejector plates 19 and 20 as shown by arrows, and Move closer. By this operation, the projections 23a, 24a of the inclined pins A23, B24 come out of the undercut portions 31b, 31c of the battery cap 31, so that the battery cap 31 becomes free. For example, when the die is a horizontal type, It falls under its own weight. Here, the ejector stroke is, for example, 30 mm, and this value is determined according to the amount of undercut. Finally, the mold is closed in the reverse order of opening and ready for the next molding.
[0020]
Next, effects of the injection molding die according to the embodiment of the present invention will be described. Since the tips of the inclined pins A23 and B24 are made thinner and the undercuts 23a and 24a are formed therein, the undercuts 23a and 24a can be inserted into the cavity 18 through a narrow gap outside the nest 25. In addition, since the rear ends of the inclined pins A23 and B24 are pivotally supported by the frame-shaped holder 22, the number of parts is reduced from three in the past to three, and a unit having a small and simple structure can be obtained. As a result, the cost of the mold can be reduced. Therefore, a small bag-shaped molded product having undercut portions 31b and 31c inside, such as a battery cap 31 of a thermometer, could be molded without using a slide unit. In addition, since the ejector space can be reduced, a multi-cavity injection molding die can be realized.
[0021]
【The invention's effect】
As described above, according to the present invention, a mold member is provided on an ejector plate, and simultaneously moves in the opening and closing direction and the vertical direction with opening and closing of a mold so as to protrude into a cavity. In an injection mold having a projection fitted into an undercut portion, the mold member includes a frame-shaped slider, an inclined pin, and a support shaft that supports the inclined pin on the slider, and the slider is movable. Sliding between the two ejector plates arranged on the side mold allows injection molding of small resin molded products with an undercut inside, greatly reducing the number of parts and shortening the number of steps. It has become possible to achieve cost reduction of a molded article.
[0022]
In addition, since the slide core and the inclined pin are integrated and the driving mechanism is simple, space saving and cost reduction of the die set are achieved, and high quality products can be supplied to users at low cost.
[Brief description of the drawings]
FIG. 1 is a sectional view of a main part of an injection mold according to an embodiment of the present invention.
2 (a) is a side view, FIG. 2 (b) is a front view, and FIG. 2 (c) is a cross-sectional view illustrating a molded product of an injection mold according to the present invention.
FIG. 3 is an enlarged cross-sectional view of a tip end portion of an inclined pin of the injection mold of FIG. 1;
FIG. 4 is a cross-sectional view of a principal part explaining the operation of the injection mold of FIG. 1;
FIG. 5 is a cross-sectional view of a principal part explaining the operation of the injection mold of FIG. 1;
FIG. 6 is a sectional view of a main part of a conventional injection molding die.
FIG. 7 is a cross-sectional view of a principal part explaining the operation of the injection mold of FIG. 6;
[Explanation of symbols]
2 Fixed mold 3 Movable mold 9 Opening pin A
10 Opening pin B
15 Slide base (fixed plate)
15a Wall 16 Slide core A
17 Slide core B
18 Cavity 19 Ejector plate upper 20 Ejector plate lower 21 Slider 22 Support shaft 23 Inclined pin A
23a projection 24 inclined pin B
24a protrusion 25 nest 25a wall 31 battery cap (molded product)
31b, 31c Undercut 32 Battery

Claims (4)

An injection molding mold for molding a resin molded product with an undercut, comprising a fixed mold and a movable mold, wherein a mold member having a projection fitted into an undercut portion of the molded product is provided in a cavity. In an injection molding die arranged on an ejector plate so as to protrude, and wherein the die member is simultaneously moved in a die opening and closing direction and a vertical direction with opening and closing of the die, the die member is a frame. Injection molding, comprising: a slider, an inclined pin, and a support shaft for supporting the inclined pin on the slider, wherein the slider slides between two ejector plates disposed on the movable mold. Mold. 2. The injection-molded metal according to claim 1, wherein the projection is integrally formed with the inclined pin, and a pair of the inclined pins are disposed so as to face each other with the projection as a back. Type. The injection molding according to claim 1 or 2, wherein the inclined pin slides while being guided by a wall surface of a nest provided in the cavity and a wall surface of a fixed plate parallel to the wall surface. Mold. The cavity is formed between a pair of slide cores provided in the movable mold, and the slide core is driven by a pair of opening / closing pins provided in the fixed mold. An injection mold according to any one of claims 1 to 3.

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