JPH0825204B2 - Method and apparatus for forming hollow structure from powdered thermoplastic raw material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a hollow structure by attaching a powdery thermoplastic raw material to the outer surface of a molding die, and an apparatus for carrying out this method. Regarding

[Conventional technology]

Hollow structures, such as liners for non-corrosive fluid containers,
It has been molded for a long time with various thermoplastic raw materials such as polyethylene, polypropyne, nylon, celcon, sericon and hytrel. One manufacturing method is called “roto-casting method”, in which a predetermined amount of powdery thermoplastic raw material is put into a split mold, and the powdery thermoplastic raw material is added. The mold is placed in a furnace to bring it to about the melting temperature of the powdered thermoplastic raw material and to rotate the combination about one or more axes. After free flowing, as the surface temperature approaches the melting point of the thermoplastic raw material,
Stick to the inner surface of the mold. Once the thermoplastic feedstock has been deposited over the entire interior surface of the mold, the mold is removed from the oven, cooled and the resulting structure removed from the interior of the mold.

However, this method has many drawbacks. The main one is that the wall thickness of the resulting thermoplastic raw material structure cannot be adjusted. Further, the distribution of the thermoplastic raw material in the mold during the heating / rotating step is deteriorated, which often causes pinholes in each part of the obtained structure. Also, if the wall thickness is made as small as possible over the entire surface of the structure, an extremely thick and heavy structure can be obtained. Moreover, the inside of the resulting structure generally has a rough, non-uniform surface. This rough surface can cause problems in draining the fluid when the thermoplastic structure is used as a fluid container. Also, since thermoplastic resin is non-corrosive, it is most suitable for use as a liner for fluid containers,
It is also generally difficult to adhesively bond most of the thermoplastic raw materials. Further, it is often necessary to apply a release agent to the inside of the roto-cast mold before adding the powdery thermoplastic raw material, and this release agent further deteriorates the binding property. Due to this bonding problem, in the case of manufacturing a fluid container of the type in which an inner liner molded from a thermoplastic material by a roto-casting method is bonded to an outer cell,
Often difficult.

[Problems to be solved by the invention]

Various attempts have been made to avoid problems in carrying out the roto-casting method. One method, described in U.S. Pat. No. 3,0092,099, is to spray a spinning mandrel with a solid liquid polyurethane plastic material reaction mixture. Although this method allows careful monitoring of the wall thickness, the only material for which this method can be used is a liquid reaction mixture which is sprayed from an aerosol nozzle and remains liquid on the mandrel. Similarly, the method described in U.S. Pat. No. 3,379,591 is to spray a mixture of resin and glass fiber with a cut of single fiber roving and attach it to a rotating mandrel to form a tubular body. This method is also limited to the resin-glass mixture which can be sprayed from the aerosol nozzle as a liquid and adhere thereto.

Therefore, there is a need for a method of forming a hollow structure from a powdered thermoplastic material that allows sufficient monitoring of wall thickness during manufacturing. Further, there is a demand for a method for molding a hollow structure from a powdery thermoplastic material which has a relatively smooth inner wall to which outer container cells and the like are easily joined. There is also a need for a device that can perform this method.

Therefore, it is an object of the present invention to provide a method for forming a hollow structure by attaching a powdery thermoplastic raw material to the outer surface of a heat molding die. Also, by monitoring the adhesion state of the powdery thermoplastic raw material, the wall thickness of the resulting structure is sufficiently adjusted,
It is another object to provide a method by which the occurrence of pinhole concentrating areas of the resulting structure can be avoided without introducing a heavy structure with unnecessarily thick walls. Furthermore, it is another object of the present invention to provide a method of making a hollow structure having a relatively smooth inner wall from a powdered thermoplastic material. Yet another object of the present invention is to provide a method for forming a hollow structure which can be easily joined to another material by using a powdery thermoplastic raw material having corrosion resistance.

[Means and Actions for Solving Problems]

To achieve the above and other objects and advantages, the present invention provides a method of coating a hollow mold with a commercially available mold release agent and heating. In this case, the mold is heated up to about the melting point of the thermoplastic raw material to be attached. Then, the mold is continuously rotated while a predetermined amount of the powdery thermoplastic raw material is sprayed on the outer surface of the mold. A semi-molten layer of a thermoplastic raw material having a predetermined thickness is deposited by comprehensively adjusting the adhesion amount, temperature and rotation speed. This deposition process continues until a semi-molten layer of approximately the same thickness as the desired resulting structure is deposited on the mold.

In a preferred embodiment of the method according to the invention, the adhesively bondable raw material is then sprinkled onto the semi-molten outer surface layer. next,
The mold is cooled to a low temperature, and burrs on the edges of the obtained thermoplastic raw material structure are cut to form flat edges. Further, the mold is cooled, pressurized air is introduced between the obtained structure and the mold, and the obtained structure is removed from the mold.

The preferred embodiment of the present invention further discloses an apparatus for carrying out the inventive method described above. The apparatus comprises a hollow mold having one end open and rotatably coupled to a support structure, means for heating the mold, and removably disposed above the mold. And a device for spraying the powdered thermoplastic raw material.

The spraying device includes a hopper for containing powdered thermoplastic raw material, a gate attached to the bottom of the hopper,
It consists of a rotary spreading cylinder driven by a suitable variable speed drive. Both members (hopper and spreading cylinder) are mounted on a support separate from the support structure of the mold. Since the support of the spraying device vibrates, the powdery thermoplastic raw material is uniformly distributed on the mold.

The mold support structure comprises a hollow cylinder, a portion of which is disposed inside the mold, and a suitable structure for physically supporting the hollow cylinder. This cylinder is
It is open at the exposed end outside the mold and is sealed at the other end located inside the mold. A liquid-tight bush is arranged around the hollow cylindrical body and sealed therein, and similarly, a partition wall is arranged around this bush and sealed. Since the partition wall is attached to the mold at the end of the opening of the mold, it closes the space inside the mold.

The mold is heated by heating a fluid such as oil to a temperature (at Fahrenheit) about twice the melting temperature of the thermoplastic raw material used. This fluid is introduced into the enclosed volume inside the mold through a tube arranged in the hollow support cylinder. An internal heating member disposed adjacent to and in communication with the hollow support cylinder maintains the temperature of the heated fluid. The heating is supplemented by an external radiant energy heater located around the mold.

Further, an electric thermocouple is arranged inside the molding die and attached to the hollow supporting cylindrical body to facilitate temperature control. After sufficiently adhering the thermoplastic material to the outer surface of the mold, stop the internal and external heating members, remove the heating fluid from the mold, and introduce a small amount of fluid into the mold that is at or about room temperature. And start cooling the mold.

After cooling, the thermoplastic structure obtained is removed from the mould, which is obtained from the mould, via a tube arranged inside the mould, which extends through the partition wall and the tip of the mould. This is done by introducing air between the structure and the structure.

The novel features of the present invention, and other objects and advantages are as follows.
A further understanding of this preferred embodiment will be better understood by the following description with reference to the accompanying drawings. However, the drawings are for illustration and description only, and not for limiting the present invention.

〔Example〕

Now, the drawings show a preferred embodiment of an apparatus for molding a hollow structure from a powdery thermosetting raw material according to the present invention. First, as shown in FIG. 1, a main component of this apparatus is a hollow molding die 10 rotatably attached to a support structure 13. Above one side of the mold 10, a dispensing device, generally designated by 16, is removably disposed. As shown in FIG. 2, an external auxiliary heating device 19, which is a normal radiant heater, is arranged on the opposite side of the distribution device 16 with the molding die 10 interposed therebetween.

As shown in FIGS. 2 and 4, the molding die 10 has an internal space 11, and an opening 21 is formed at one end of the internal space 11. A front support member 22 is arranged near the closed end of the molding die 10. A mounting ring 23 is connected near the opening 21 on the inner surface of the molding die 10.

The shape of the mold 10 is determined by the required shape of the structure to be manufactured. The shape of the structure made using the mold 10 shown in FIGS. 2 and 4 is that of an external fuel tank used in an aircraft or helicopter. Therefore, the mold 10 shown in FIGS. 2 and 4 generally has an aerodynamic shape that approximately corresponds to the required shape of the external aviation fuel tank. Structures having other shapes can also be formed by the method of the present invention. Therefore, the particular shape of the mold used in this example is merely exemplary and should not be construed as limiting the invention.

As shown in FIG. 3, the support structure 13 of the present invention.
Has a non-rotating hollow support beam 24 fixed to a support frame 27 (FIG. 2). As shown in FIG. 2, the mold 10 is rotatably mounted to the support structure 13 and a portion of the hollow support beam 24 is disposed in the mold 10. A cap 28 for sealing an internal space 25 of the hollow support beam 24 is attached to an end portion 24a of the hollow support beam 24 arranged in the molding die 10. On the other hand, the inner space 25 is open at the end 24b of the hollow support beam 24 on the side opposite to the molding die 10. Thus, the hollow support beam 24 constitutes a fixed conduit in the internal space 11 of the molding die 10.

The mold 10 is rotatably attached to the support structure 13 by being connected to the partition wall 30. This bulkhead 30
Are arranged around the liquid-tight bush 33, and the bush 33 is arranged around the hollow support beam 24.
10 internal spaces are hermetically closed. Mold 10 and bulkhead
A high temperature gasket 34 is provided between the
As a result, the liquid tightness is improved. Mold 10
Is connected to the partition 30 by engaging a mounting ring 23 with a bolt passing through the partition 30 or by other convenient fixing means.

Immediately and easily after completing the thermoplastic structure, the mold 10
An air tube 35 is arranged along the inner surface of the mold 10 for removal from the outer surface of the mold. One end of the air tube 35 has a mold 10
Of the air tube 35, and the other end of the air tube 35 is attached to the partition wall 30 so that the partition wall 30 is penetrated while maintaining the sealed state.

The mold 10 is rotated by connecting a speed change motor 36 fixed to the support frame 27 and a sprocket 39 attached to the partition wall 30 with a chain 41.

The distributor 16 (FIGS. 2 and 3) described above includes a support frame 45.
And a hopper 44 connected to the thermoplastic raw material storage tank. An opening is formed at the bottom of the hopper 44, and a gate 48 is attached to this opening. The gate 48 can control the amount of the thermoplastic raw material falling from the bottom of the hopper 44, and the amount of the thermoplastic raw material attached to the surface of the molding die 10 can be controlled.

Just below the hopper 44 of the support frame 45, the distribution cylinder 51
Is rotatably mounted. The distribution cylinder 51
It extends along substantially the entire length of the mold 10. In this embodiment, the distribution cylinder 51 has a smooth surface, but if the surface is roughened or roughened, the thermoplastic raw material can be more evenly adhered to the molding die 10. Become. Instead of this, the surface of the distribution cylinder 51 may be molded of rubber so that the powdery thermoplastic raw material can be attached more uniformly.

The rotation of the distribution cylinder 51 is performed by connecting a second speed change motor 56 fixed to the support frame 45 and a gear connected to the distribution cylinder 51 with a normal “V” belt type drive belt. Be seen. Further, a vibration device 60 for vibrating the hopper 44 and the distribution cylinder 51 is attached to the support frame 45. As shown in FIG. 3, the support frame
45 has a shape protruding to one side, whereby the hopper 44 and the distribution cylinder 51 are arranged directly above the molding die 10.

When distributing raw materials, the vibration device 60 and the speed change motor 56
And are activated, and the amount of thermoplastic material adjusted at the gate 48 falls on the distribution cylinder 51. Distribution cylinder 51
As a result of being rotated, a uniform flow of the thermoplastic raw material adheres to the top of the mold 10. The flow rate of the thermoplastic raw material, and thus the deposition rate of the thermosetting material onto the mold 10, is controlled by adjusting the size of the opening at the bottom of the hopper 44 by the gate 48. Here, a combination of a hopper and a distribution cylinder is used, and since a predetermined amount of thermoplastic raw material is sprayed on the rotary distribution cylinder by the hopper, the molding die 10 is used more than when the hopper is used alone.
It is possible to evenly distribute the thermoplastic raw material.

The mold 10 of the present invention is heated to a temperature (at Fahrenheit) about twice the melting temperature of the thermoplastic raw material by causing a heating fluid to flow into the internal space 11 of the mold 10. Typically, oils with flash points above 550 ° F (288 ° C) are used. Alternatively, heating can be performed using a fluid having a boiling temperature and / or an ignition temperature that is at least twice the melting temperature of the thermoplastic (at Fahrenheit). As described later, the same type of oil is used for both heating and cooling.

As shown in FIG. 2, the heating device of the present invention is
A heating fluid storage tank 63 and a cooling fluid storage tank 66 separate from this
And have. Heating fluid storage tank 63 and cooling fluid storage tank 66
Are both connected to a high temperature reversible fluid pump 71 via a suitable lead tube. The oil in the heating fluid storage tank 63 is an external heating source.
Heated by 74. This heat source 74 can be incorporated into the storage tank 63 as required. For example, an insulated electric heating member may be arranged in the storage tank 63. Also instead of this,
Devices such as commercially available oil boilers can also be used.

In the present embodiment, the heating fluid storage tank 63 and the cooling fluid storage tank 66 are connected to "on-off" type valves 67 and 68, which are provided at two separate locations. Lines 69 and 70 extend from the "on-off" valves 67 and 68, respectively, and the "on-off" valves 67 and 68 are two-way selectable "T" valves.
Each of the two selectable inlets of a "mold valve" 72 is connected. The outlet of the two-way selection type “T type valve” 72 is connected to the reversible pump 71 via a pipe line 76.

From the pump 71, heating oil or cooling oil can be made to flow into and out of the pipeline 80 through the pipeline 77.
The conduit 80 is disposed in the internal space 25 of the hollow support beam 24 and passes through the opening at the end 24b of the hollow support beam. As a result, oil is supplied to the internal space 11 of the molding die 10. The conduit 80 has a side portion 80a, and this side portion 80a
Passes through the bottom of the hollow support beam 24 and
It leads to inside. The side 80a of the pipeline 80 and the hollow support beam 2
Between 4 and 4 is liquid-tightly sealed. Side 80a of pipeline 80
Falls toward the bottom inner surface 11 of the mold 10 but does not contact the inner surface.

A second conduit 83 is also provided in the interior 25 of the hollow support beam 24, and, like the conduit 83, penetrates through the opening at the hollow support beam end 24b. This conduit 83 also has a side portion 83a, and this side portion 83a also penetrates the bottom portion of the hollow support beam 24 and descends toward the inner surface of the bottom portion of the molding die 10, but contacts the inner surface. Not. The side portions 80a and 83a of the pipeline are arranged near both ends of the closed portion of the hollow support beam 24.

In this embodiment, the heating oil is heated outside and then put into the inside 11 of the mold 10. At this time, the internal heating member 86 is used to maintain the elevated temperature of the heating oil.
In this embodiment, the conduit 83 is the end 24b of the hollow support beam 24.
It is open at one end adjacent to and is not connected to any storage tank. However, by using the pipe lines 80 and 83 as input and output means for circulating the heating oil, the heating oil heated to a higher temperature by a commercially available heat source 74 arranged outside is supplied to the inside 11 of the mold 10. It can also be circulated.

As shown in FIGS. 2 and 3, several internal heating members 86 are arranged in the space of the mold 10.
The internal heating member 86 is connected to two interface boxes 89 and 92 which are liquid-tightly attached to the hollow support beam 24. Further, the interface boxes 89 and 92 and the internal heating member 86 are liquid-tightly sealed. An electric wire passing through the hollow support beam 24 is connected to the interface boxes 89 and 92, and the electric wire operates the internal heating device 86.

As described above, in this embodiment, the internal heating member 86
Is used to maintain the temperature of the heating oil introduced into the space 11 of the mold 10. Also, several external heating devices 19 (Fig. 1) are arranged on one side of the molding die 10.
The internal heating of 10 is supplemented and the outer surface of the mold 10 is maintained at a uniform temperature. The heating device 19 is a conventional radiant heater.

Internal thermocouple 95 to monitor the internal temperature of the mold 10.
Is used. As shown in FIG. 2, these thermocouples 95
Are descending from the bottom of the hollow support beam 24 toward the inner surface of the mold 10. The thermocouple 95 penetrates the hollow support beam 24 and is liquid-tightly sealed between the two.

The oil in the heated fluid storage device 63 is heated to a temperature (at Fahrenheit) about twice the melting temperature of the thermoplastic raw material. At this time, the "on-off" type valve 67 is opened, and the two-way selection type "T type valve" 72 is turned to establish communication between the reversible pump 71 and the heating fluid storage tank 63. Then pump a small amount of heating oil
It is sent at 71 and is put into the internal space of the molding die 10 through the pipe 80. Then, the internal heating member 86 and the auxiliary heating device 19 are activated.

When cooling the molding die 10, the operation of the internal heating member 86 and the auxiliary heating device 19 is stopped, and the pump 71 is operated in the opposite direction to remove the heating oil from the inside of the molding die 10. Then valve 67
Is closed, the valve 68 is opened, and the two-way selection type “T-type valve” 72 is turned to connect the reversible pump 71 and the cooling fluid storage tank 66. Then, the cooling oil at about room temperature is sent by the pump 71 and put into the space 11 of the molding die 10. By this method, the temperature of the molding die 10 can be substantially lowered to the solidification temperature of the thermoplastic raw material used. After that, the mold 10 is cooled to room temperature without adding the cooling oil while keeping the cooling oil that was initially charged in the mold 10.

As mentioned above, instead of this method, the space of the mold 10
Circulate the oil heated by the external heat source in 11
Can be kept at high temperature. Further, cooling oil can be circulated in the same manner to promote cooling of the molding die 10. If more rapid cooling is required, cooling oil may be circulated through the external refrigeration system or waste heat exchange system.

Having described the apparatus according to the invention used to carry out the method of the invention, the method will now be described in detail.

The thermoplastic raw materials used here are 1/8 inch (3.2 mm) in diameter and 1/8 inch (3.2 m) in length, which are usually commercially available.
m) pellets. The powdery thermoplastic raw material is formed by crushing these pellets into a powder having a particle size similar to that of coarse wheat flour as a whole. Various thermoplastic raw materials in powder form can be used in the process of the present invention. “Nylon 6/6 (NYLON
6/6) ”(trademark) and“ HYTREL ”(trademark).

In the hollow structure, first, a general release agent such as "RELEASE ALL 30" (trademark) or "RELEASE ALL 50" (trademark) is applied to the outer surface of the mold 10. Later made from powdered thermoplastic raw material.
After application to the mold 10, the oil present in the heated fluid reservoir 63 is heated, in principle, to a temperature (at Fahrenheit) about twice the melting temperature of the thermoplastic used. About this method, when using a thermoplastic material that melts at about 250 ° F (121 ° C), about 500 oil is stored in the heating fluid storage tank.
Perform by heating to a temperature of ° F (260 ° C).

After heating the oil in the heating fluid storage tank 63 to about 500 ° F (260 ° C), the valve 67 is opened and the two-way selection type "T-type valve" 72 is turned to turn the heating fluid storage tank 63 into the pump 71. Let me know. Next, the pump 71 is operated in the forward direction to send heated oil into the molding die 10. Generally 50 to 75 gallons (189
To 284 liters) of heating oil is used to heat the mold 10 of this example, which is about 2.5 feet (762 mm) in diameter and about 5 feet (1524 mm) long. Then, the internal heating member 86
To maintain the temperature of the heating oil. The auxiliary external heating device 19 is also operated to keep the outer surface of the mold 10 at a uniform temperature. As a general rule, the internal temperature of the mold is 500 ° F (2
60 ℃) and keep the external temperature of the mold at 425 ° F (218 ° C)
Keep on. Next, using the motor 36, in principle, the continuous rotation of the mold is started at a speed of 1 to 3 revolutions per minute, and the powdery thermoplastic raw material distributor 16 is rotated to the top of the mold 10. Carry. Then, the distributor 16 is operated as described above, and a predetermined amount of the powdery thermoplastic raw material is fed into the molding die.
Attach to the outer surface of 10 over its entire length.

If a thermoplastic material such as "NYLON 6/6" (trademark) or "HYTREL" (trademark) is used, the mold 10 is applied at a speed of 1 to 3 revolutions per minute.
The amount of the thermoplastic material adhering to the outer surface of the mold 10 is rotated by about 0.002 to 0.005 inch (0.05 to 0.13 inch) per rotation.
mm) thickness layers gave good results. The powdery thermoplastic raw material is continuously deposited, and when the cumulative deposition layer reaches a total thickness of about 0.02 to 0.03 inch (0.51 to 0.76 mm), the deposition of the powdery thermoplastic raw material is stopped. .

In this way, by the spraying device 16, the thermoplastic raw material is uniformly attached to the entire outer surface of the mold 10, but the resulting deposited layer is examined when it is stopped, and if necessary, extremely thick. Select a part that seems to have less, and further attach the thermoplastic material there.

In order to increase the adhesive bonding of the resulting structure, the surface of this molten thermoplastic raw material structure is then coated with a material having good adhesive bonding. Typical materials that can be used in this case are glass fiber, graphite fiber,
It is a crushed fiber or a fine bulb. Particularly good results are obtained with ground glass fibers.

After coating the surface of the molten structure with such a compound having a higher adhesive bond property, the operations of the auxiliary external heating device 19 and the internal heating member 86 are stopped. Then, the pump 71 is reversed to completely remove all the heating oil from the inside of the mold 10. Then, the valve 67 is closed and the valve 68 is opened, and the two-way selection type “T-type valve” 72 is rotated to connect the cooling fluid storage tank 66 to the pump 71. Next, the pump 71 is again operated in the forward direction, and the room temperature cooling fluid, which is basically the same type of oil as that used for heating, is pumped into the inside of the mold 10. This cooling oil has an internal temperature of approximately 250 ° F (1
It is pumped into the mold 10 until the temperature drops to 30 ° C).

"Nylon 6/6 (NYLON6 /
6) ”(trademark) and“ HYTREL ”(trademark)
Thermosetting materials, such as, typically solidify at about 250 ° F (130 ° C). At this time, the burr on the edge of the solidified structure adjacent to the partition wall 30 is cut into a straight edge. Next, the mold 10 and the obtained structure are further cooled, and then this structure is molded 10
Remove from.

Mold to facilitate removal of the resulting structure
To the pipe 35 that communicates to the outside of the tip 10a of 10
Pressurized air is introduced from the side. Alternatively, pressurized air may be applied along the cut edges of the structure for removal.

Although the embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the above embodiments, and various modifications and variations are possible.

〔The invention's effect〕

As described above, the hollow structure forming method and apparatus according to the present invention uses the heated hollow forming die to adhere the powdery thermoplastic raw material while rotating, so that the thickness of the adhered layer can be easily monitored while monitoring. Can be adjusted, the distribution of the raw material is uniform, pinholes are not generated, and a smooth inner surface can be formed. Furthermore, there is an advantage that a non-corrosive fluid container can be formed by using a corrosion resistant material for the hollow structure.

[Brief description of drawings]

FIG. 1 is a perspective view of an embodiment of an apparatus for carrying out the method of the present invention for forming a hollow structure from a powdery thermoplastic raw material,
2 is a sectional view taken along the line 2-2 of FIG. 1, and FIG.
FIG. 3 is a sectional view taken along line 3-3 of FIG. 4, and FIG. 4 is a vertical sectional view of a molding die used in the apparatus of FIG. 10 …… Mold, 11 …… Internal space, 13 …… Support structure, 16
…… Distributor, 19 …… External auxiliary heating device, 21 …… Aperture, 24 …… Hollow support beam, 30 …… Differential partition, 35 …… Air tube, 36 …… Transmission motor, 44…
… Hopper, 71… Reversible pump.

Claims (27)

[Claims] Claims: 1. a. Heating a rotating mold; b. Depositing a powdery thermoplastic material on the outer surface of the heated, rotating mold; c. On the outer surface of the heated, rotating mold. A method for forming a hollow structure, which comprises spraying a powder of a material having an adhesive bond property onto the surface of the molten thermoplastic raw material structure formed in the above. 2. The method according to claim 1, wherein the spraying process is continued until the powder having a predetermined thickness is laminated on the heated and rotating mold. 3. The mold is heated to at least the melting point of the thermoplastic raw material, b. The heated mold is rotated, and c. The thermoplastic is applied to the outer surface of the heated and rotated mold. Disperse the raw material to form a semi-molten layer of the thermoplastic raw material on the forming die, d. Cool the forming die to cure the layer, and e. The hollow structure formed as a result. The method for molding a hollow structure from a thermoplastic raw material, which comprises the step of removing from the molding die. 4. Before the step (d) of cooling the mold,
The method according to claim (3), characterized in that an adhesively bondable powder is sprinkled on the outer surface of the semi-molten layer. 5. Before the step (a) of heating the mold,
The method according to claim (3), characterized in that a mold release agent is applied to the molding die. 6. A burr on one edge of the hollow structure is cut after the step (d) of cooling the mold and before the step (e) of removing the molded hollow structure. A method according to claim (3), characterized in that a flat edge is formed. 7. The step (e) of removing the hollow structure,
The method according to claim (3), wherein the method is performed by injecting air between the molding die and the molded hollow structure. 8. A space is formed inside the molding die, and a plurality of heating members are arranged in the space.
The step (a) of heating the mold is performed by causing a slight amount of heated fluid having a boiling or ignition temperature higher than the melting temperature of the thermoplastic raw material to flow into the space of the mold. The method according to claim (3). 9. The method according to claim 8, wherein the temperature of the mold is maintained by activating a heating member disposed inside the mold. 10. A step (e) of removing the hollow structure.
The heating fluid is removed, and a certain amount of fluid having a boiling or ignition temperature higher than the melting temperature of the thermoplastic raw material is caused to flow into the space of the molding die. The method according to range (8). 11. The method according to claim 8, wherein the step (a) of heating the molding die is also performed by a plurality of radiant energy heating members arranged outside the die. the method of. 12. In the step (a) of heating the mold, a heated fluid having a boiling or flashing temperature higher than the melting temperature of the thermoplastic raw material is circulated in a space formed inside the mold. The method according to claim (3), characterized in that the temperature is maintained by heating the heating fluid outside the molding die while heating the molding fluid. 13. A step (e) of removing the hollow structure.
By removing the heating fluid that was continuously heated,
The method according to claim (12), wherein the method is carried out by injecting a small amount of fluid having a boiling or ignition temperature lower than the melting temperature of the thermoplastic raw material. 14. A support structure, a mold rotatably supported by the support structure, and the mold which is heated to a temperature at least as high as the melting point of the thermoplastic raw material to form the mold. A heating device for maintaining the mold at the temperature of the above height, a rotating device for rotating the forming mold, the rotating device for rotating the forming mold, and a rotating device arranged adjacent to the forming mold. An apparatus for forming a hollow structure from a thermoplastic raw material, comprising: a spraying device for spraying a powdery thermoplastic raw material on an outer surface. 15. The mold has a first end and a second end, and the cross-sectional area of the mold has a predetermined value at the first end, Device according to claim (14), characterized in that it is continuously reduced to zero at the second end. 16. A space is formed inside the molding die, and an opening of the space is formed at the first end of the molding die. 1
The device described in 4). 17. The spraying device is provided on a support frame, a storage tank for powdered thermoplastic raw material, which is attached to the support frame and has an opening at the bottom, and the bottom of the storage tank. It has a gate capable of opening and closing the opening, a spray cylinder rotatably supported by the support frame and arranged below the gate, and means for rotating the spray cylinder. The device according to claim (14). 18. The apparatus according to claim 17, wherein the gate opens and closes the opening to control the flow rate of the powdered thermoplastic raw material. 19. A device according to claim 17, further comprising means for vibrating said support frame. 20. A support frame, a storage tank for powdered thermoplastic raw materials, which is attached to the support frame and has an opening formed in the bottom, and a opening provided in the bottom of the storage tank to open and close the opening. A powdery raw material, which comprises: a possible gate, a distribution cylinder rotatably supported by the support frame and arranged below the gate, and means for rotating the distribution cylinder. A device for spraying. 21. The apparatus according to claim 20, wherein the gate opens and closes the opening to control the flow rate of the powdered thermoplastic raw material. 22. Apparatus according to claim 20 further comprising means for vibrating said support frame. 23. A fluid storage tank in which the heating device communicates with the inside of the mold, a fluid stored in the storage tank, and a fluid having a boiling temperature higher than a melting temperature of the thermoplastic raw material; The fluid is circulated between the storage layer and the inside of the molding die, which communicates with a heat changing device which is disposed adjacent to the tank and which heats the fluid, and the inside of the storage tank and the molding die. Claims (1) characterized by having a pump device for
The device described in 6). 24. The apparatus of claim 16 further comprising a plurality of internal heating members mounted on the support structure and disposed within the mold. 25. The apparatus according to claim 16, further comprising means arranged in the mold for measuring a temperature in the mold. 26. The support structure has an inner portion disposed inside the molding die and an outer portion disposed outside the molding die, wherein an end of the inner portion. A hollow mold-supporting beam whose end is sealed and whose outer end is open; a liquid-tight bush attached to the hollow-support beam; The device according to claim 15, further comprising a partition wall that is provided and is detachably attached to the mold. 27. A removing device for removing the formed thermoplastic raw material structure is disposed in the mold.
This detaching device has a tube connected to the partition wall and the tip of the second end, and the tube communicates with the outer surface of the tip of the mold. Device according to claim (26).