JPH04270616A - Hollow body made of plastic and its mold structure - Google Patents

Abstract

PURPOSE:To mold precisely a hollow body, prevent generation of flashes and make correction also of a mold easy, by a method wherein the diameter of a confronting part of half-split bodies is made larger than that of the other part, a space between them is made a slope and further a core mold is formed so that the core mold is ejected from a mold split line by dimensions corresponding to a thermal shrinkage quantity. CONSTITUTION:When half-split bodies are confronted with each other, mold clamping is performed and molten resin is cast, even if a confronting part 51 is shrinked thermally, a slope 53 in the vicinity of the confronting part 51 is shrinked as the same is stuck close to a slope 81 of a mold part, and therefore, a gap is not generated between the confronting part 51 and a mold surface. Furthermore, if it is in the case where it is formed so that an end face of the confronting part 51 ejected from a mold split line by dimensions corresponding to a thermal shrinkage quantity, even if the confronting part 51 is shrinked thermally, the confronting parts 51 are stuck firmly to each other, consequently, a gap is not generated between the confronting parts 51 and the slope 53 is stuck far reliably to the mold surface 81. Consequently, at the time of the secondary injection, it does not happen that the molten resin leaks out on an inner and outer surfaces of the other part 52 from the confronting part 51, generation of flashes which are harmful from an external appearance point of view can be prevented without fail and correction also of a mold is easy.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] This invention relates to a hollow plastic body and a mold structure thereof, and more particularly to a structure of a hollow body that can prevent the occurrence of burrs caused by heat shrinkage, and a structure of a mold for molding the hollow body. .

0002

BACKGROUND OF THE INVENTION When producing synthetic resin products, blow molding or injection molding are generally used. for example,
When manufacturing hollow products using the blow molding method, the molten resin is extruded into a cylindrical parison using an accumulator head, and both sides of the parison are sandwiched between molds.
It is common to mold hollow products by blowing air into the interior, but in this case, relatively large burrs are created on the top and bottom of the product due to the mold, and nozzle holes for air blowing remain in the product. However, there are problems in that it is impossible to obtain a completely sealed hollow product, and furthermore, it is difficult to manufacture a product with a uniform wall thickness. On the other hand, when manufacturing hollow products using the injection molding method, a method has been proposed in which the hollow molded product is divided into two halves, each of which is injection molded, and the outer peripheries of the abutting parts of both halves are joined with molten resin. (
For example, JP-A-61-226060, JP-A-62
(Refer to Japanese Patent Laid-open No. 87315 and Japanese Patent Application Laid-Open No. 63-237917), this case has the advantage that completely sealed hollow products and hollow products with complicated shapes can be easily produced.

0003

[Problems to be Solved by the Invention] However, in conventional hollow bodies made of plastic injection molding, the product halves are abutted as they are in the mold, and the outer periphery of the abutting portion is injected and hardened with molten resin. Therefore, due to the structure, heat shrinkage of the abutting part of the halves creates a gap between the abutting part and the molding surface, and molten resin flows from the abutting part to the outer surface of other parts, causing burrs. However, if burrs occur, they must be removed, which is unfavorable in terms of manufacturing. In view of these problems, it is an object of the present invention to provide a plastic hollow body that can prevent the appearance of harmful burrs caused by thermal contraction.

0004

[Means for Solving the Problems] Therefore, the plastic hollow body according to the present invention is produced by making cylindrical half bodies obtained by plastic injection molding collide with each other in a mold, and injecting molten resin around them. In the hollow body obtained by hardening,
The gist is that the outer diameter near the abutting part is larger than the other outer diameter of the cylindrical part, and a slope is formed between them. Here, the present invention can be applied to any product obtained by abutting cylindrical halves in a mold and injecting molten resin around the abutting part, such as infusion products. It can also be applied to octopus tubes, etc. In addition, in this case, if the abutting parts of the halves are made to protrude beyond the mold parting line by a dimension corresponding to the amount of heat shrinkage during the primary molding, the protruding parts will be strongly abutted during the secondary injection molding.
The inclined surface near the abutting portion is reliably brought into close contact with the mold surface, and the adverse effects of heat shrinkage can be further reduced. That is, according to the present invention, there is provided a mold for molding a cylindrical half-piece product in which the outer diameter near the abutment part is larger than the other outer diameter of the cylindrical part, and the space between them is sloped. It is possible to provide a mold structure for a hollow plastic body, characterized in that a core mold for primary injection is formed such that the abutment part of the half body projects beyond the mold parting line by a dimension equivalent to the amount of thermal contraction.

[0005]

[Function] In the present invention, the outer diameter near the abutment part of the half body is made larger than the other outer diameter of the cylindrical part, and there is a slope between them, so that the half body is When the bodies are brought together and molten resin is injected into the outer periphery of the abutting part, even if the abutting part shrinks due to heat, the inclined surface of the abutting part is in close contact with the inclined surface of the inner surface of the mold part, and as a result, the molten resin is There is no chance of burrs forming around the parts. In addition, if the core mold for primary injection is formed so that the abutting part of the halves protrudes beyond the mold parting line by a dimension equivalent to the amount of heat shrinkage, the protruding part will abut firmly during secondary injection molding, and the abutting part The neighboring sloped surfaces are reliably brought into close contact with the mold surface, and the adverse effects of heat shrinkage are further reliably reduced.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below based on specific examples shown in the drawings. 1 and 2 show a plastic hollow body according to an embodiment of the invention. FIG. 1 shows the structure of a cylindrical hollow product 5 with a closed cross section. This hollow product 5 has a cylindrical shape as a whole, and the outer diameter of the half body 50 near the abutting part 51 is set to be larger than the outer diameter of the other cylindrical part 52.
An inclined surface 53 is formed between the cylindrical portion 1 and the other cylindrical portion 52, and a resin 54 is injected into the outer periphery of the abutting portion 51. Also,
FIG. 2 shows an irregularly shaped cylindrical hollow product 6 which is open at both ends. This hollow product 6 is constructed by abutting and joining a pair of half bodies 60 and 65, and the abutting part 61 of the half body 60 is formed to have a larger diameter than the other part 62, and there is a slope between the two halves 60 and 65. A surface 63 is provided, and a resin 64 is injected into the outer periphery of the abutting portions 61 and 66 of the half bodies 60 and 65.

Further, FIGS. 3 to 7 show the structure of a mold for molding a plastic hollow body having the above structure, and this is similar to that shown in FIG.
The mold structure for molding the hollow product 5 is shown. In the figure, a mounting frame 11 is provided on a bed 10 of an injection molding machine 1, a die slide type mold 2 is supported on the mounting frame 11, and a molten resin injection mechanism 3 is mounted on the bed 10. Disposed facing the mold 2, the injection mechanism 3 includes a hopper 30 for storing molten resin and a nozzle 31 for injecting the molten resin.
, a pressurizing cylinder 32 and a drive device 33 that moves the nozzle 31 forward and backward. The mold 2 is constructed by disposing a slide mold 22 between a movable mold 20 and a fixed mold 21, and the slide mold 22 is provided with a die slide cylinder 23 for sliding it in the vertical direction. is provided with a mold opening/closing cylinder 24 for opening and closing it. In addition, the fixed mold 21 and the sliding mold 22
Sprues 210, 220, and 221 are bored in the mold parting surface of the slide mold 22 so as to communicate with the mold parting surface, and a female mold part 22 is formed in the mold parting surface of the slide mold 22.
2 and a male part 223 are formed. Also, movable type 2
0 mold parts 222, 223 on the slide mold 22 side
A female mold part 200 and a male mold part 201 are formed by mold matching to form a cavity in the shape of a divided body divided into two parts, and the runner 20 that leads to the mold parts 200 and 201
2 and a gate 203 are formed.

Here, using FIGS. 6 and 7, the male and female mold parts 2 are
To explain the structure of 00, 201, 222, and 223, the female mold parts 200 and 222 have a substantially cylindrical shape, which is the outer shape of the half body 50, and there is a part near the mold parting surface that is continuous with the inclined surface 80. A stepped portion 81 for forming the half body abutting portion 51 is formed. On the other hand, the male parts 201 and 223 have a substantially cylindrical shape, which is the inner shape of the half body 50, and a bonding resin 54 is formed on the outer periphery of the male parts 201 and 223.
A protruding part 82 for forming the injection recess 56 is formed, and the end face of the abutting part 51 is formed between the protruding part 82 and the cylindrical part 83 by a dimension t corresponding to the amount of thermal contraction than the parting line. has been done.

Next, the functions and effects will be explained. When manufacturing a hollow product, first the slide mold 22 is set to the first mold clamping position, the movable mold 20 is advanced by the mold opening/closing cylinder 24, the molds are aligned as shown in FIG. 4, and the movable mold 20 and Male and female mold parts 200 and 223 of the slide mold 21
, 201 and 222, a half-shaped cavity is formed by dividing the product into two, and in this state, the drive device 33
is activated, the nozzle 31 is advanced, and the pressurizing cylinder 32
is operated and the molten resin in the hopper 30 is injected. Then, the molten resin flows through the sprues 200, 220 and runner 2.
02 and the gate 203 into the cavity of the mold part to manufacture the left and right halves 50. Thereafter, the nozzle 31 is retracted and the mold opening/closing cylinder 24 is operated to open the movable mold 20, and the molded half body 50 is placed inside the female mold parts 200, 222 of the movable mold 20 and the slide mold 22. The runner 202 is ejected while being held. When the primary molding is completed, the slide mold 22 is slid from the first mold clamping position to the second mold clamping position by the die slide cylinder 23, and the movable mold 20 is advanced and the slide mold 22 is moved as shown in FIG. The molds are matched and the female mold parts 200, 2
When the half bodies 50 in 22 are abutted and molten resin is injected in that state, the molten resin passes through the sprues 200, 221, the runner 202 and the gate 203, and is injected into the cavity of the mold part. The hollow product 5 is manufactured by joining the outer peripheries of the abutting portions 51.

At this time, when the half bodies 50 are abutted and mold-clamped, the slope 53 near the abutting portion 51 of the half body 50 is aligned with the slope 81 near the parting line of the female molds 200 and 222. They are in close contact with each other, and even if the abutting part 51 shrinks due to heat when injecting molten resin (see arrow A in FIG. 7), the inclined surface 53 near the abutting part 51 will remain the inclined surface of the mold parts 200, 222. As a result of shrinking while remaining in close contact with 81, no gap is generated between the abutting portion 51 and the mold surface. In addition, since the tip of the abutting part 51 of the half body 50 is made to protrude beyond the mold parting line, the abutting part 51
Even if the abutting parts 51 are thermally shrunk (see arrow A in FIG. 7), as a result of the abutting parts 51 being firmly adhered to each other, no gaps are generated between the abutting parts 51, and the slope near the abutting parts 51 is The surface 53 is securely brought into close contact with the mold surface 81. As a result, during the secondary injection, the molten resin does not leak from the abutting portion 51 to the inner and outer surfaces of the other portion 52, and the generation of burrs that are harmful to the appearance can be reliably prevented. In addition, a movable mold 20 and a slide mold 2
In the male mold parts 201 and 223 of No. 2, the end face of the abutment part 51 between the protruding part 82 and the cylindrical part 83 is formed so as to protrude from the mold parting line by a dimension t corresponding to the amount of heat shrinkage.
It is also easy to modify the type.

[0011]

[Effects of the Invention] As described above, according to the plastic hollow body according to the present invention, the abutment portion of the plastic half body is made larger in diameter than the other portion, and the space between them is formed as a slope. Even if heat shrinkage occurs, it is possible to reliably prevent the occurrence of burrs that are harmful to the appearance. Further, according to the mold structure of the plastic hollow body according to the present invention, the mold for molding the hollow body has the above-mentioned structure, and the abutting portion of the half body projects beyond the mold parting line by a dimension equivalent to the amount of heat shrinkage. Since the core mold is formed, the hollow body having the above structure can be molded with high precision, and the generation of burrs can be more reliably prevented, and mold correction can be easily performed.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a plastic hollow body according to an embodiment of the present invention.

FIG. 2 is a partially sectional view showing a plastic hollow body according to another embodiment of the present invention.

FIG. 3 is a schematic configuration diagram showing an injection molding machine equipped with a mold for molding a hollow body according to an embodiment of the present invention.

FIG. 4 is a sectional view showing the state of the mold during primary injection.

FIG. 5 is a sectional view showing the state of the mold during secondary injection.

FIG. 6 is a sectional view of essential parts showing the state of the mold during primary injection.

FIG. 7 is a sectional view of a main part showing the state of the mold at the time of secondary injection.

[Explanation of symbols]

Claims (2)

[Claims] Claim 1: In a hollow body obtained by abutting cylindrical halves obtained by plastic injection molding against each other in a mold and injecting and hardening a molten resin around the cylindrical halves, the outside near the abutting part is The diameter is larger than the other outer diameter of the cylindrical part,
A plastic hollow body characterized by having an inclined surface formed between an outer diameter portion near a large-diameter abutting portion and another outer diameter portion smaller than this. 2. A mold for molding a product having the above shape, characterized in that the core mold for primary injection is formed so that the abutting portion of the half body protrudes beyond the mold parting line by a dimension equivalent to the amount of heat shrinkage. type structure.