JPH0421576B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a manufacturing device for a hollow molded product made from thermoplastic resin and having open holes at both ends in the longitudinal direction. The present invention relates to an industrially advantageous manufacturing device for a hollow molded product, which uses a plastic resin as a raw material and has openings at both ends in the longitudinal direction with defined inner diameter shapes and dimensions.

The hollow molded product obtained by the apparatus of the present invention can be used as rack and pinion covers and universal joint covers in the automobile industry, industrial machinery industry, etc.

[Conventional technology]

In recent years, products manufactured using the blow molding method,
It has come to be used in the automobile industry, industrial machinery, etc. for rack and pinion covers, universal joint covers, etc. In such new applications, it is desired that the hollow molded product has openings at both ends in the length direction, and that these openings have a structure in which a shaft or the like inserted therein can be accurately fitted.

When using a conventional blow molding apparatus, the outer diameter of the resulting hollow molded product could be controlled at any part, but the inner diameter of the molded product could only be controlled at one of the openings. Even when regulating the inner diameter, it was common practice to make the surface on which the inner diameter was regulated smooth in order to release the molded product.
(See Publication No. 45-31397).

For this reason, in order to manufacture a hollow molded product having open holes with regulated inner diameter shapes and dimensions at both ends in the length direction, it is necessary to use an injection blow molding device. However, injection-blow molding equipment is expensive and unsuitable for manufacturing large molded products.

According to Japanese Unexamined Patent Publication No. 56-69127, a plastic blow molding apparatus is proposed.

The above device includes a mold for forming a hollow molded product that can be divided into a plurality of parts, and each divided part can be brought close to the central axis of the parison to close the mold, and separated from the part to open the mold, A core pin is provided below the cavity of the molding die and is capable of rising and falling within the cavity along the central axis of the parison, and is provided with a pressurized air outlet.

The above-mentioned apparatus is excellent in that it can solve the problems of the injection-blow molding method described above.

[Problem to be solved by the invention]

However, the molding apparatus proposed in JP-A-56-69127 has the following drawbacks in actual use.

(1) The parison extruded into the mold cavity may become deformed before the mold is closed.

(2) It is not possible to separate the product part from the parison part and the unnecessary parison part at the bottom when the mold is clamped, and post-processing such as cutting the disposable bag is required.

The present invention has been made in view of the above-mentioned circumstances, and eliminates the above-mentioned drawbacks of the molding apparatus proposed in JP-A No. 56-69127, and provides an industrially advantageous manufacturing apparatus for the above-mentioned hollow molded products. The aim is to make suggestions.

[Structure of the invention]

That is, the gist of the present invention is that a parison die is provided at the tip of the plasticizing device for forming the plasticized thermoplastic resin into a parison shape and extruding it downward, and below the parison die there is a parison die that can be divided into a plurality of pieces. and a hollow molded product molding die in which each divided portion can be clamped close to the center axis of the parison extruded from the parison die and opened when separated from the parison die, and the cavity of the molding die is Manufacture of a hollow molded product comprising a core pin on the lower side that is capable of rising and falling within the cavity along the central axis of the parison, has a pressurized air blowing hole, and is longer than the length of the cavity of the molding die. In the device, the core pin is composed of a core pin outer cylinder and a core pin center shaft that is longer than the length of the core pin outer cylinder and is slidable inside the outer cylinder, and further,
A heat insulating ring is provided on the outer peripheral surface near the tip of the core pin outer cylinder constituting the core pin, and has an outer diameter that can be fitted in contact with the parison. The present invention relates to a manufacturing apparatus for a hollow molded product, characterized in that it is equipped with a parison cutting plate for cutting out a parison.

Hereinafter, the present invention will be explained in detail based on the drawings, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

FIG. 1 is a longitudinal sectional side view of an example of the apparatus for manufacturing a hollow molded product according to the present invention, and FIGS. Yes, Figure 2 shows the parison being extruded into the cavity of the molding die in the open state.
Figure 3 is a longitudinal side view of the parison with the core pin inserted inside it, and the molding die is closed.
4 and 5, a longitudinal side view showing a state in which compressed air is injected into the parison and the parison is to be molded along the cavity surface of the mold, the mold is opened (not shown). ), the core pin is lowered and pulled out from the hollow molded product, FIG. 4 shows the core pin pulled out from the upper opening hole, and FIG. 5 shows the core pin pulled out from the lower opening hole.

Fig. 6 is a partially cutaway side view of a blow molded product obtained using the apparatus of the present invention, Fig. 7 is an enlarged view of the part shown in Fig. 6, and Fig. 8 is a side view of a blow molded product obtained using the conventional injection-blow molding apparatus. A partially cutaway side view of an example of a molded hollow body is shown.

In the figure, 1 is a plasticizing device cylinder, 2 is a screw, 3 is a plasticized resin, 4 is a die adapter, 5 is a breaker plate, 6 is a center core, 7 is a fixed die, 8 is a core, 9 is a parison die, 10 is a polyson die fixing ring, 11
is the core vertical drive transmission shaft, 12 is the bolt hole, 13
14 is an adjustment plate, 15 is a parison, 16 is a pre-blow air hole, 17 and 17' are hollow molded product molds, 17a and 17'a, respectively.
17b, 17'b are the upper side of the cavity, 17c, 17'c are the lower side of the cavity, 18, 18a are the mold mounting plates, 19, 19a are the upper cutout plates, 20, 20a is a lower cutout plate, 21 is a core pin center shaft, 21a is an annular groove, 22 is a core pin outer cylinder, 22a is an annular groove, 23 is a heat insulation ring, 24 is a molded product ejector plate, and 25 is a hole for compressed air injection. , 26 is an air cylinder, 26a is a cylinder rod, 27 is a cylinder mounting bracket, 28 is a bracket rod, 29 is a core pin installation stand, 29a, 29b
30 is a fixed bracket, 30 is a movable cylinder, 31 is a slide bush, 32 is a guide rod, 33 is a rod nut, 34 is a movable bracket, 35 is a movable cylinder rod, 36 is a hollow molded product, 37 and 38 are both ends, 39,40
are respectively open holes, 41 is an inner wall of the end, 42, 43
80 is a parison, 81 is a hollow molded product, 82 and 83 are both end portions, 8
Reference numerals 4 and 86 indicate inner walls of the respective ends, and reference numeral 85 indicates a disposable bag.

In the apparatus of the present invention, the plasticizing device includes:
A cylinder equipped with a built-in screw and a heater, which is used in extruders, injection molding machines, etc., is preferably used. The plasticizing device plasticizes the raw thermoplastic resin and molds it into a target object. In Figure 1,
A plasticizing device with a built-in screw inside the cylinder 1 is shown. In the passage of the plasticized resin in the cylinder 1, dirt mixed in the resin is removed at a breaker plate 5.

A parison die is attached to the tip of the plasticizing device. This parison die functions to mold plasticized resin into a parison shape.

When attaching the parison die to the tip of the plasticizing device, it is preferable to allow the parison to hang downward.

The parison die 9 is preferably placed at the tip of the fixed die 7 and the center core 6 via the die adapter 4. A passage for plasticized resin is formed between the fixed die 7 and the center core 6, and a gap for extruding the parison is formed between the parison die 9 and the core 8. The core 8 is connected below the core vertical drive transmission shaft 11 which is provided through the center core 6, and this shaft 11 has a structure that can be driven vertically by an adjustment plate 14 and a locking nut 13. It is preferable to arrange a heater outside the fixed die 7 to prevent the resin temperature from decreasing.

Centering of the parison die 9 is performed by bolts on a parison die fixing ring 10, and adjustment of the wall thickness of the parison 15 is performed by moving the core 8 up and down.

The parison 15 immediately after being extruded from the parison die 9 is soft and easily deformed, so in order to prevent this deformation, a pre-blow air hole 16 is drilled through the center core 6 and the core 8. It is best to connect it to compressed air.

Parison 15 extruded from parison die 9
is guided into the mold for forming the hollow molded product while ensuring that the cylindrical shape is not deformed. The mold for hollow molded products is
It functions to mold the parison into a hollow molded product of a desired shape.

A mold for forming a hollow molded product can be divided into a plurality of parts under the parison die, and each divided part is clamped close to the central axis of the parison extruded from the parison die and separated. The structure is such that the mold can be opened.

FIG. 1 shows hollow molded product molds 17, 17'.
is shown as a structure that can be divided into two parts. The molding molds 17, 17' are provided with cavities 17a, 17'a, respectively, for obtaining the desired molded product.
The molding molds 17, 17' are respectively attached to molding mold mounting plates 18, 18a, and these mounting plates are moved close to the central axis of the parison extruded from the parison die by a drive mechanism (not shown).
Make it possible to separate.

The feature of the apparatus of the present invention is that upper parting plates 19, 19a are provided on the upper side of the molding molds 17, 17' to cut off the parison when the molds are clamped, and lower parting plates 20, 20a are provided on the lower side. The point is that it is provided. With this cut-off plate, it is possible to separate the product part from the parison part and the unnecessary parison part at the bottom when the mold is closed, eliminating the need for post-processing such as cutting disposable bags as in the conventional method. is not necessary, and the yield of the product is also improved.

It goes without saying that the cavities 17a, 17'a carved in the molding molds 17, 17' are not limited to the structure shown in the drawings, and can be selected from various structures.

The lower side of the cavity of the mold for forming a hollow molded product is made to be able to rise and fall within the cavity along the central axis of the parison extruded from the parison die, and has a pressurized air blow-off hole, which allows the length of the cavity of the mold to be adjusted. Prepare a longer core pin. This core pin functions to regulate the shape and dimensions of the openings provided at both lengthwise ends of the molded product to a predetermined value when inserted into the parison and clamped, and to supply compressed air.

The core pin is composed of a core pin outer cylinder 22 and a core pin center shaft 21, the pin center shaft 21 is longer than the pin outer cylinder 22, and is fitted into the pin outer cylinder 22,
Make the pin slidable inside the outer cylinder. The length of the core pin is such that the tip of the pin center shaft 21 reaches the top of the upper cutout plates 19, 19a when the core pin is inserted into a mold and clamped.

By forming the annular groove 21a on the outer peripheral surface near the tip of the pin center shaft 21, it is possible to form an annular protrusion corresponding to the annular groove 21a on the inner wall of one end of the molded product. If the annular groove 22a is formed on the outer circumferential surface of the pin outer cylinder 22 at the part that contacts the mold through the parison, the annular groove 22a will be formed on the inner wall of the other end of the molded product. A corresponding annular projection can be formed.

A hole 25 for pressurized air injection is carved into the core pin,
To be able to inject compressed air into Polyson after mold clamping,
Connect to a compressed air source (not shown). This compressed air injection hole 25 is provided to penetrate through the pin center shaft 21 in the length direction, forming a groove through which the compressed air passes between the pin outer cylinder 22 and the pin center shaft 21, and also has a small hole through which the compressed air leaks into the outer cylinder. It is preferable to drill a large number of holes.

Another feature of the device of the present invention is that a heat insulating ring 23 having an outer diameter that can be fitted in contact with the parison is provided on the outer peripheral surface near the tip of the pin outer cylinder 22 constituting the core pin. Such a heat insulating ring can prevent the core pin from overheating during continuous molded product production. Furthermore, the parison can be preferably guided within the mold, and the parison can be prevented from being flattened when the mold is clamped.

The core pin is attached to the core pin installation stand 29. In the core pin installation base, upper and lower fixing brackets 29a and 29b have a plurality of guide rods arranged parallel to each other and are fixed by rod nuts 33, and a hole in the center of the upper fixing bracket 29a allows the core pin to move up and down. We are prepared. A movable bracket 3 is located below the upper fixed bracket 29a.
4, and align the outer cylinder 22 of the core pin with the hole provided in the upper fixing bracket and fix it. The movable bracket 34 moves downwardly toward the movable cylinder 30.
A movable cylinder rod 35 having one end fixed to the upper fixed bracket 29a is inserted into the movable cylinder 30. A slide bush 31 is further provided below the movable bracket 34, and a guide rod 32 of the core pin installation base is attached to this.
to be loosely fitted. FIG. 1 shows the movement of the movable bracket 3 by introducing fluid under the piston of the movable cylinder 30.
4 and shows the state in which the core pin is raised to the highest position. While the fluid supplied to the movable cylinder 30 is supplied to the upper side of the piston, the slide bush 31 is guided along the guide rod, and the movable bracket 34 can be lowered.

In order to slide the pin center shaft 21 constituting the core pin within the pin outer cylinder 22, it is sufficient to operate the cylinder 26 and the cylinder rod 26a. The cylinder 26 is mounted by a bracket rod 28 to a cylinder mounting bracket 27 secured to the underside of the moving bracket 34. The cylinder rod 26a is provided directly below the pin center shaft 21 with their longitudinal axes aligned or parallel, and is connected to the cylinder 26.

The interval at which the pin center shaft 21 slides within the pin outer cylinder 22 is such that the tip of the pin center shaft reaches inside the tip of the outer cylinder, so the cylinder 26 does not need to be very long.

A molded product ejector plate is provided on the lower side of the hollow molded product mold. This molded product ejector plate functions to release the hollow molded product (product) obtained after the molding process is completed from the core pin.

The molded product ejector plate should have a hole large enough to allow the core pin to move up and down without any problem, but not allow the molded product attached to the core pin to pass through. This molded product ejector plate is preferably placed on an upper fixing bracket 29a of a core pin installation base 29 disposed below the molding die, as shown at 24 in FIG.

An example of manufacturing a target object using the above-described hollow molded product manufacturing apparatus will be described below.

Thermoplastic resins that can be applied to the device of the present invention include polyvinyl chloride, vinyl chloride as a main component,
Vinyl chloride resins such as copolymers with copolymerizable monomers; polystyrene, rubber-reinforced polystyrene (HI-PS), styrene-acrylonitrile copolymer (AS resin), acrylonitrile-butadiene-styrene ternary Copolymer (ABS resin), (meth)acrylic acid alkyl ester-acrylonitrile-styrene terpolymer (AAS resin), (meth)acrylic acid alkyl ester-butadiene-
Styrenic resins such as styrene terpolymer (MBS resin); copolymers containing polyethylene, polypropylene, and ethylene as main components and copolymerizable monomers with them; Olefin resins such as copolymers with polymerizable monomers; acrylic resins such as polyacrylic esters and polymethyl methacrylate; Vinyl acetate resins such as copolymers with copolymerizable monomers; polyethers such as polyvinyl ether and chlorinated polyether; polyesters such as polyethylene terephthalate and polybutylene terephthalate; nylon 6, nylon 6, 6. Polyamides such as nylon 6, 10, nylon 9, nylon 11, nylon 12; polybutadiene, polyisoprene, polychloroprene, butadiene-styrene copolymer (SBR), ethylene-propylene rubber (EPR), ethylene-propylene- Diene-based synthetic rubbers such as diene monomer terpolymers (EPDM) and partially vulcanized products; synthetic rubbers other than diene rubbers such as polyurethane rubber and epichlorohydrin rubber; polysulfides; polysiloxanes, Examples include thermoplastic resins such as polycarbonate.

The above thermoplastic resin may be one type or a mixture of two or more types. Further, the thermoplastic resin may contain plasticizers, colorants, fillers, stabilizers, lubricants, etc., within a range that does not adversely affect the properties of the molded product.

As the thermoplastic resin, thermoplastic elastomers such as those that are highly elastic by themselves, or those that are imparted with elasticity by adding a plasticizer or the like can be preferably used.

First, a thermoplastic resin as a raw material is plasticized using a plasticizer, and is shaped into a parison using a parison die 9 and extruded. The parison 15 has a length that reaches the lower cutout plates 20, 20a of the mold in the open state to stop extrusion of the parison. To stop the extrusion of the parison, either stop the rotation of the screw in the cylinder, or remove the fixed die 7 and center core 6.
A special die called an accumulation head die may be used, which has a resin reservoir between the two.

A core pin raised from the bottom of the mold is inserted into the parison 14 extruded from the parison die (see FIG. 2). To insert a core pin inside the parison (a) A method of inserting a core pin after extruding the parison to a specified length;
(b) A method of extruding the parison and raising the core pin in parallel; (c) A method of extruding the parison while covering the raised core pin. When performing the above process, it is preferable to blow out compressed air from the pre-blow air hole 16 to prevent the parison from deforming.

Next, the molding die is clamped. When the mold is clamped, the parison is sandwiched between the core pin and the mold. The upper part is preferably sealed by sandwiching a parison between the annular groove 21a of the pin center shaft 21 constituting the core pin and the mold cavity upper parts 17b, 17'b. The lower portion is preferably sealed by sandwiching a parison between the annular groove 22a of the pin outer cylinder 22 constituting the core pin and the lower mold cavity portions 17c, 17'c.

When the mold is closed, the upper cutout plates 19, 19
a. The lower cutting plates 20, 20a are cut into the parison, the upper side separates the parison from the molded product, and the lower side separates the molded product from the remaining parison.

After the mold clamping is completed, compressed air is sent to the compressed air injection hole 25 to inflate the parison and mold it along the cavity surface of the molding die (see FIG. 3).

The molded product is cooled in the mold to a temperature at which it no longer deforms. After cooling, open the mold and
Remove the core pin from the molded product. To remove this core pin, first, the cylinder 26 is operated to lower only the pin center shaft 21, and the pin center shaft 21 is released from the upper end of the molded product (see FIG. 4). At this time, the parison can be preferably guided within the mold by the heat insulating ring 23 fixed near the tip of the pin outer cylinder 22, and the parison will not be flattened when the mold is clamped. can be prevented.

Subsequently, the movable cylinder 30 is operated so that the movable bracket 34 is lowered, thereby lowering the core pin. At this time, the lower end of the molded product, together with the portion of the parison that did not become a molded product, hits the ejector plate 24 and is prevented from descending, and is released from the mold (see FIG. 4).

A partially cutaway side view of a hollow molded product obtained by the apparatus of the present invention is shown in FIG. 6, and an enlarged view of the portion shown in FIG. 6 is shown in FIG.

When using the apparatus of the present invention, not only the length and shape of both lengthwise ends 37 and 38 of the hollow molded product, but also the thickness and the shape of the inner wall 41 can be regulated.
The annular protrusion 43 provided on the inner wall 41 is connected to the opening hole 40.
It is possible to accurately fit a shaft or the like to be inserted into the shaft, and the fitted portion can be completely sealed.

In the molded product manufactured by the apparatus of the present invention, one of the two opening holes provided at both lengthwise ends of the hollow cylindrical body (lower opening hole 40 in FIG. 6)
is preferably larger than the diameter of the other hole (the upper open hole 39 in FIG. 6).

FIG. 8 shows a partially cutaway side view of an example of a hollow body molded using a conventional hollow molded product apparatus. When using a conventional blow molding device, a disposable bag 85 is placed on one side.
are simultaneously formed and cut at the positions of the X line and the Y line to obtain the desired hollow molded product. When using this device, inner walls 84, 86 of both ends 82, 83, respectively.
However, it is not possible to provide an annular protrusion, and it is also difficult to adjust the thickness of both ends 82 and 83.

〔Effect of the invention〕

The present invention has particularly remarkable effects as described below, and its industrial utility value is extremely large.

(1) A core pin is inserted into the parison extruded into the mold cavity, and the outer peripheral surface near the tip of the core pin outer cylinder constituting the core pin is provided with a heat insulating ring having an outer diameter that can be fitted in contact with the parison. Therefore, the parison can be preferably guided within the mold by the heat insulating ring, and the parison can be prevented from being flattened when the mold is clamped. Therefore, since the parison is not deformed before the mold is closed, it is possible to produce a hollow molded product with less uneven thickness.

(2) Since cutout plates are provided on the top and bottom of the mold, it is possible to separate the product part from the parison part and the unnecessary part of the lower part when clamping the mold, unlike the conventional method. There is no need for post-processing such as cutting the tightened bag, and the yield of the product is also improved.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional side view of an example of a blow molded product manufacturing apparatus according to the present invention, and FIGS. 2 to 5 are longitudinal sectional side views of main parts showing steps for manufacturing a blow molded product according to the method of the present invention. Fig. 2 is a vertical sectional side view of a state in which a parison is extruded into the cavity of a molding die in an open state, and a core pin is inserted into the parison, and Fig. 3 is a vertical side view of the state in which a core pin is inserted into the parison. After the mold is closed and compressed air is injected into the parison to mold the parison along the cavity surface of the mold, FIG.
FIG. 5 shows a state in which the core pin is pulled out from the upper opening hole, and FIG. 5 shows a state in which the core pin is pulled out from the lower opening hole. Fig. 6 is a partially cutaway side view of a hollow molded product obtained by the method of the present invention, Fig. 7 is an enlarged view of the part shown in Fig. 6, and Fig. 8 is a partially cutaway side view of a hollow molded product obtained by the method of the present invention. A partially cutaway side view of an example of a hollow body is shown. In the figure, 1 is a plasticizing device cylinder, 2 is a screw, 6 is a center core, 7 is a fixed die, 8 is a core, 9 is a parison die, 15 is a parison, 17 and 17' are respective blow molding molds, and 17a , 17′a are cavities, 1
7b and 17'b are the upper part of the cavity, 1
7c and 17'c are the lower side of the cavity, 1
8, 18a are mold mounting plates, 19, 1, respectively.
9a are upper cutout plates, 20, 20, respectively.
21 is the core pin center axis, 22 is the core pin outer cylinder, 23 is the heat insulation ring, 24 is the molded product ejector plate, 25
is a compressed air injection hole, 26 is an air cylinder, 29 is a core pin installation stand, 30 is a movable cylinder, 31 is a slide bush, 32 is a guide rod, 34 is a movable bracket, 36 is a hollow molded product, 37, 38
are both ends, respectively, 39 and 40 are open holes, 41 are inner walls of the ends, 42 and 43 are annular protrusions, respectively, 80 is a parison, 81 is a hollow molded product, and 8
2 and 83 are both ends, 84 and 86 are inner walls of each end, and 85 is a disposable bag.

Claims (1)

[Claims] 1. A parison die is provided at the tip of the plasticizing device to extrude the plasticized thermoplastic resin downward in the form of a parison, and below the parison die is a device that can be divided into a plurality of pieces, and each divided portion is A mold for forming a hollow molded product is provided, which is capable of closing the parison close to the central axis of the parison extruded from the parison die, and opening the mold by separating the mold from the parison die. In an apparatus for manufacturing a hollow molded product, the core pin is capable of rising and falling within the cavity along the central axis, has a pressurized air outlet, and is longer than the length of the cavity of the mold. ,
It is composed of a core pin outer cylinder and a core pin center shaft that is longer than the length of the core pin outer cylinder and is slidable inside the outer cylinder, and the above-mentioned parison is attached to the outer circumferential surface near the tip of the core pin outer cylinder constituting the above-mentioned core pin. Equipped with an insulating ring with an outer diameter that can be contacted and fitted,
The apparatus for producing a hollow molded product is characterized in that the upper and lower sides of the hollow molded product mold are each provided with a parison cutting plate for cutting off the parison.