JPS5938092B2 - Method and apparatus for forming multilayer plastic hollow products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a method and apparatus for forming hollow plastic articles from thermoplastic sheets, and more particularly to a novel method and apparatus for forming multilayer hollow plastic articles.

A number of methods have been developed for producing multilayer hollow plastic articles with an inner wall of plastic material of desired properties and an outer wall of plastic material exhibiting other desired properties.

For example, U.S. Pat. No. 3,122,598 (Berger
) discloses a method of molding decorative plastic products using injection moldability. US Pat. No. 2,710,987 (Sherman) discloses a method and apparatus for forming multilayer plastic products using extrusion blow molding. Furthermore, U.S. Patent No. 3,71? , 735 (Alyl) discloses a method for blow molding a barrier container from a layer obtained by injecting thermoplastic onto a preformed inner wall. Although these known processes provide suitable hollow products with the required properties, the equipment required to carry out these processes is expensive, the operating costs are high, and the time required makes them prohibitive for commercial use. has not yet achieved remarkable success.
Thermoforming has traditionally been used to form hollow products using single-layer or multi-layer sheets of plastic material, but for example, it is difficult to achieve oxygen permeation resistance, carbon dioxide diffusion resistance, and long-term use under normal pressure. It has never been employed commercially to form hollow articles with container properties, such as properties that allow storage.

Conventionally, thermoforming has been used to form hollow products from multilayer sheets, but it has drawbacks in that individual thermoplastic materials can be arbitrarily recovered and reused after thermoforming. In particular, the present invention is a method of heating a thermoplastic sheet to soften it by first heating it, and then molding the thermoplastic sheet in a plastic state by applying suction or pressurization to a mold under the action of fluid compression. Related to molding method.

In the suction method, a low pressure is generated in the male die using pressure in a pressure box generated by compressed air, for example, to press the softened sheet against the male die. In the pressurized method, for example, while creating a vacuum inside the male mold, a softened thermoplastic sheet is pressed against the male mold by atmospheric pressure (or pressurized fluid). Combining these two methods can be applied to a variety of applications and is easier to control, so it is preferable to employ this combination method in many cases. SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and apparatus for thermoforming multilayer hollow plastic products which is improved so as to overcome the drawbacks of the known technology.

Other objects and advantages of the invention will become apparent from the following description of embodiments of the invention. The present invention seeks to provide a method and apparatus for thermoforming multi-layer hollow articles containing a plurality of treatment zones, in which a thermoplastic heated to a plastic state is locally applied to a thermoplastic sheet.

A layered hollow product is formed by bringing the layered portion of thermoplastic material into close proximity to a female mold and a cooperating male mold and applying a suitable pressure differential known in the thermoforming process thereto. Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Note that the same reference numerals in the figures indicate the same parts. The type of thermoplastic or heat deformable material employed in the process of the invention will be determined by economics and the intended use of the hollow product being produced. Thermoplastic resins suitable for various applications and suitable for thermoforming include high impact resistant polystyrene, polyptadiene, styrene, butadiene mixtures or copolymers, polyvinyl chloride and related vinyl polymers, polyaromatic monomers, nylon, formaldehyde. Polymers, polyethylene, polypropylene, nitrocellulose, cellulose, acetate, cellulose proprionate, acetate ptylate, polymethymethacrylate, ethyl cellulose, benzyl cellulose, cellulose ester, etc. 1 and 2, there is shown a novel thermoforming assembly 10 embodying the principles of the present invention, which includes a preform section 12 and a forming section 14.

As is well known to those skilled in the art, the thermoforming assembly 10 includes a conventional motor as well as a timer, such as gauges, timer circuits, safety devices, etc., for automatically and continuously operating the thermoformer assembly. Although assemblies are provided, these assemblies are not shown for the sake of clarity. Preforming section 12 includes a supply roller assembly 16, a heating section 18, and processing sections A (or 20), B (or 22), and C (or 24). The molding section 14 includes a molding section D (or 26) and a cooling section E (or 28), which will be described in detail later.
The feed roller assembly 16 includes a shaft 30 rotatably supported on a support member 32 mounted on a foundation F.

Wound around this shaft 30 is a sheet or strip of thermoplastic selected depending on the particular properties desired to be imparted to the wall of the product. The heating section 18 is provided with a source of active electromagnetic radiation, such as an infrared lamp 36, as a means for softening the thermoplastic sheet prior to indexing into sections beyond the preform section 12. Although this heating section 18 is necessary in some cases, in most thermoforming operations, the underlying thermoplastic sheet can be thermoformed using only the latent heat of the molten thermoplastic applied to the thermoplastic sheet. It is possible to locally heat up to the desired temperature, thus eliminating the need for a separate heating section. A drum 38 attached to a shaft 40 rotatably supported by a support member 42
A seat support assembly including a seat support assembly is installed on the foundation G. A chain belt 44 is endlessly hung over the drum 38 to support the thermoplastic sheet through the preforming process, and the links forming the chain belt 44 are provided with retaining members 46 to complete the thermoforming assembly 10. To ensure that the sheet 34 can pass through the preformed part 12 of.

In FIG. 3, processing section A (rotated 90 times from the position of FIG. 1) includes extrusion assembly 50, positioning assembly 5,
2 and a support assembly 54.

The extrusion assembly 50 consists of a cylindrical body 56 having a cylindrical chamber 58 in the center of which is located an extrusion screw 60 for extruding the plastic material, as is well known to those skilled in the art. Extrusion assembly 50 includes an L-shaped extrusion nozzle 62 suitably threaded within cylinder 56 and flaring downwardly toward thermoplastic sheet 34 .

The end of this nozzle 62 is ground to mate with a gate plate 64 having an orifice 66 that controls the amount of heated thermoplastic applied locally to the sheet 34. The gate plate 64 is attached to a fluid cylinder 70 via a rod member 72 so as to be reciprocally movable. Positioning assembly 5
2 is a cylinder rod 7 linked with a fluid cylinder 78;
6. Includes an enclosure 74 attached to 6.

The surrounding frame 74 is provided to limit any local portion of the thermoplastic sheet 34 to which the second thermoplastic material 68 is applied in a plastic state. Enclosure 74 is provided with a passageway 80 for circulating an intermediate heat transfer fluid that controls the temperature of enclosure 74 so that thermoplastic sheet 34 is transferred to the next processing station. The second
The outer surface of the thermoplastic material 68 provides a somewhat fixed outer boundary of this second thermoplastic ladle 68. Support assembly 5
4 consists of a support piece 82 containing fluid passages 84 for circulating an intermediate heat transfer medium so as to minimize distortion of the sheet 34 during the local application process. The support piece 82 is reciprocatably attached to a fluid cylinder 86 via a cylinder rod 88. FIG. 4 (processing section B) includes a guide assembly 90, a shaping assembly 92, and a support assembly 9.
4 is shown.

Guide assembly 90 is similar to positioning assembly 52 of process section A and consists of an enclosure 96 that includes passageways 98 for circulating an intermediate heat transfer fluid. The enclosure 90 is reciprocatably attached to a fluid cylinder 100 via a cylinder rod 102. The shaping assembly 92 includes a stamper base 104 having an intermediate heat transfer passageway 106 and is reciprocably mounted to a fluid cylinder 108 via a rod 110. The peripheral shape of the stamper base 104 is made to match the inner shape of the enclosing frame 96 as much as possible to prevent the second thermoplastic material 68 from spilling out between the two as much as possible. Further, depending on the relationship between the final thermoplastic material distribution and the product shape, the contact surface of the stamper base 104 is specially shaped so that the second thermoplastic material 68 is distributed in an arbitrary (non-uniform) manner. It may be configured into a shape. Support assembly 94 includes a support piece 112 having a passageway 114 for circulating an intermediate heat transfer fluid.

The support piece 112 is reciprocally movable with the cylinder rod 118.
It is attached to fluid cylinder 116 via. In FIG. 5, processing section C is provided with an initial molding assembly 120 consisting of a mold assembly 122 and a molding plate assembly 124.

The mold/assembly 122 is reciprocally movable as a cylinder/
It includes a mold 126 attached to a fluid cylinder 128 via a rod 130. The molded plate γ assembly 24 is reciprocably connected to the fluid cylinder 1 via the cylinder rod 136.
It consists of a molded plate 132 attached to 34. The mold 126 and the mold plate 132 are provided with passages 138 and 140, respectively, for circulating an intermediate heat transfer medium. The forming section 14 of the assembly 10 of the present invention illustrated in FIG.
Consists of.

As shown in FIG. 6, molding section 26 includes a blow mold half 154 mounted for horizontal movement to a vertically movable platen 156 in a manner well known to those skilled in the art. Below the mold half 154 is a threaded plate 158 attached to a fluid cylinder 160 via a cylinder rod 162. The individual processing units arranged on the rotary table 152 are placed in the chamber 16 of the rotary table 152.
6 and is held by a plate 168 for vertical movement.

Rotary table 152 has passageways 170 and 172 that communicate with chamber 166 on either side of piston 164 . At the center of the piston 164 is a cylindrical passage 174.
is formed, and an extensible core pin 176 is disposed therein for reciprocating movement. The core pin 176 is provided with a passageway 178 and an orifice 180 for introducing an expansion medium into the preform, as described in more detail below. Core pin 1
A conical support member 182 is provided at the end of 76 . A cylindrical sleeve 190 is fixed to the upper surface of the piston 164, and a top plate 192 is attached to this.

Plate 1 including a cutting blade 195 and having a cylindrical elastic material fixed thereto
94 is attached so that it can be screwed into the threaded portion of the plate 168.
In the unactuated state, the resilient material 196 is generally cylindrical, but in the compressed state it is forced outwardly against the thermoplastic material, thereby forcing the thermoplastic material against the threaded plate 158, as described in more detail below. The threaded portion 198 of the molded container 200 is molded. In FIG. 7, the cooling section or processing section 28 is similar to the forming section or processing section 26 described in connection with FIG.
remains in

Each cooling or treatment section 28 has a conical end support 2.
06 and interlocks with a fluid cylinder 208. As is clear from FIG. 2, the rotary table assembly 150 is provided with four processing sections 28. A processing section F is provided for taking out the molded container or product 200 to a conveyor assembly (shown in the figure) for sending the molded container or product 200 to a process such as inspection, filling and packaging.

In operation of the apparatus of the invention, the rolls move in concert with the movement of the chain belt 44 in accordance with the operating cycle of the apparatus, which is determined in particular by the size and wall thickness of the product to be formed, the type of thermoplastic material, etc. A sheet-like thermoplastic material 34 is fed out from the sheet. The thermoplastic sheet 34 is heated to a plastic state while passing under an infrared lamp 36, which is a source of active electromagnetic radiation. While the sheet 34 is indexed into the processing station A, the enclosure 74 is lowered by the action of the fluid cylinder 78 and the sheet 34 is indexed into the processing station A.
Contact with 4. At the same time (or back and forth), the support piece 82 is raised to a position where it comes into contact with the lower side of the seat 34 under the action of the fluid cylinder 86 . Orifice 66 of gate plate 64
is coaxially aligned with the extrusion nozzle 62 and the second thermoplastic material 68 is
Upon initiation of extrusion, screw 60 of extrusion assembly 50 advances in a manner well known to those skilled in the art. Moderate amount of 2nd
Once the thermoplastic material 68 has been applied, the gate plate 64 moves in response to the action of the fluid cylinder 70 to block the flow of plastic material. The enclosure frame 74 and the support piece 82 return to their initial positions;
The thermoplastic sheet 34 containing the second thermoplastic material 68 is in the processing section B.
will be allocated to. In the processing section B shown in FIG.
12 is a thermoplastic sheet 34 under the action of a fluid cylinder 116.
It has risen to the point where it makes contact with the lower side of.

The enclosure 96 is lowered into contact with the sheet 34 in response to the action of the fluid cylinder 100 while the stamper base 104 is moved into contact with the second thermoplastic material 6 by the action of the fluid cylinder 108.
8 is lowered to a position where it is distributed over a portion of the sheet 34. After a period of time, in response to sequential activation of fluid cylinders 108, 116, and 100, stamper base 104 is raised, support piece 112 is lowered, and enclosure 96 is vertically raised to its initial position. Next, thermoplastic sheet 3
4 is indexed to processing section C. In the processing section C shown in FIG. 5, the mold 126 is vertically lowered by the action of the fluid cylinder 128, and at the same time, the mold plate 132 is raised by the action of the fluid cylinder 134 to form the preform 210. do.

After a certain period of time, mold 126 and mold plate 132 return to their initial positions under the action of fluid cylinders 128 and 134, respectively, and thermoplastic sheet 34 is indexed to processing station D. In FIG. 6, which shows the processing section E of the molding section of the apparatus 10 of the present invention, after the preform 210 has been indexed, the mold half 154 and the threaded plate 158 are driven to the position of operational cooperation. .

Pressurized fluid is introduced from passageway 170 into the portion of chamber 166 above piston 164 to lower piston 164 along with sleeve 190 and plate 192 so that elastic material 196
The preformed body 210 is pressed outwardly and pressed against the plastic material.
A part of the screw mold 158 is pressed against the screw mold 158. The blow pin 176 is then raised as disclosed in my commonly assigned application (U.S. Patent Application No. 2,556) and the blow pin 176 is Pressurized fluid medium is introduced through passageway 178 and orifice 180. After maintaining the pressurization operation for a certain period of time, the mold half 15
4 and the screw mold 158, and the pressurization is weakened to such an extent that the blow molded product 200 does not collapse or expand even if the mold 158 is separated and removed. After blowing, compressed fluid is introduced into passageway 172 while passageway 170 is communicated with the atmosphere to return piston 164 to its original position and return elastic material 196 to its uncompressed state to restore its generally cylindrical shape. The screw mold 158 is moved back by the action of the cylinder 160, and the molding plate 13
2 is separated and returned to the initial position, the rotary table 152 is indexed by 60 positions. Incidentally, the sheet 34 is in the processing section D.
During processing, portions of sheet 34 are rotated on table 152 until final trimming and removal of the product is performed as it is cut at an angle represented by line 218 in FIG. 2 by an assembly (not shown). After trimming and removal, residual material is removed and sent to a thermoplastic reclamation process (not shown). In the processing section E, the conical holding member 204 is lowered by the action of the cylinder 208 to hold the product 2.
It is in contact with the bottom of 00, and this contact relationship is maintained over the next three cycles.

In the final treatment section F, the pressure in the passage 172 is increased to cause the piston 164 to move its upper part against each other under the action of the fluid cylinder 214 in which the trimming mold 212 is interlocked with the cylinder rod 216, as shown in FIG. Alternately, residual material may be trimmed from the hollow product 200 by raising it above the matching rotary table height.
By using methods and means other than those described above, the cylinder 208 of the product removal section or part of the above process may be used.
It will be readily understood by those skilled in the art that the product may be trimmed.

It is also obvious to those skilled in the art that if it is desired to form a multilayer of two or more types of thermoplastic materials before forming a preform in the processing section C, a plurality of processing sections A and B should be installed in sequence. Bye. Depending on the type of hollow product, the processing section C may be omitted. Moreover, although the case has been described in which the hollow product is molded using a female mold, it goes without saying that it may also be molded using a male mold as a core. A rotary molding assembly may be used to mold single layer hollow articles from heated thermoplastic sheets.

As already mentioned, the latent heat of the molten thermoplastic alone can bring the underlying thermoplastic sheet up to the thermoforming temperature (by the time this part reaches the forming part), making it possible to There is no need to specially heat the sheet. Since it is possible to make various changes to the present invention in light of the above disclosure, the present invention can be implemented in forms other than the above embodiments.

[Brief explanation of the drawing]

FIG. 1 is a side view partially showing the main parts of the device of the present invention in cross section, FIG. 2 is a simplified plan view of the device in FIG. 1, and FIG. 3 is a heated thermoplastic sheet FIG. 4 is a partial vertical cross-sectional view of the first processing section of the apparatus of the present invention for locally applying the second thermoplastic material heated to FIG. 5 is a partial vertical sectional view of the third processing section of the apparatus of the present invention for preforming the applied portion of the thermoplastic material, and FIG. 6 is a partial longitudinal sectional view of the second processing section. Fourth aspect of the present invention apparatus for forming a hollow product from a coated part
FIG. 7 is a partial vertical sectional view of the fifth processing section of the apparatus of the present invention, which cools the molded product before being removed from the apparatus of the present invention. 10...Thermoforming assembly l8 12...
Preforming section, 14... Molding section, 16...
- Supply roller assembly, 18... heating section,
20...processing section, 22...processing section, 2
4... Processing section, 26... Molding section, 28
・・・・・・Cooling part.

Claims (1)

[Claims] 1. A method for thermoforming a hollow product from a thermoplastic sheet, comprising locally applying a moldable thermoplastic to the thermoplastic sheet to form a multilayer. , forming the article from the thermoplastic layer. 2. Claim 1 also includes the step of controlling the amount of the thermoplastic material in the moldable state before molding the hollow product.
The method described in section. 3. The method of claim 2, further comprising the step of preforming the overlay before molding the hollow product. 4. The method of claim 1, further comprising the step of locally applying a second moldable state plasticizer onto the overlay before molding the hollow article. 5. The method according to claim 1, wherein the thermoplastic sheet is heated before local application. 6 a member for supplying a thermoplastic sheet; a member for locally applying a fluidized thermoplastic to the thermoplastic sheet;
A member for distributing the thermoplastic material to be applied onto the thermoplastic sheet, a blow mold member for molding the hollow product using a fluid medium, and a member for taking out the molded hollow product. An apparatus for producing hollow products having multiple layers. 7. The apparatus of claim 6, wherein said localized application member includes a pusher member for applying said fluid state thermoplastic. 8. The apparatus of claim 6, wherein said localized application member includes an enclosure to restrict the flow of said fluidized thermoplastic. 9. Apparatus according to claim 6, further comprising a mold member for molding a preform from the material before molding the hollow product with the molding member. 10. Apparatus according to claim 6, which also includes a member for supporting the thermoplastic sheet during the localized application and distribution process. 11. The apparatus of claim 6, further comprising a second member for locally applying another thermoplastic and a second member for distributing said second flow state thermoplastic. 12. The apparatus according to claim 6, wherein the mold member is arranged on a rotating table. 13. The apparatus according to claim 6, further comprising a heating member for increasing the temperature of the sheet prior to local application. 14. The apparatus of claim 6, wherein said mold member includes an extensible blow pin. 15. Apparatus according to claim 14, including a support member for tightening the bottom of the hollow product with the extensible blow pin while the mold member cools the molded hollow product. 16 An improved molding assembly for molding a hollow article from a thermoplastic sheet to which a heated thermoplastic has been locally applied, the molding assembly having a plurality of chambers therein, each comprising a working portion of the assembly. A molded table member,
a piston having an orifice formed therein and reciprocatingly disposed in each of the chambers; a core pin disposed within the orifice so as to extend therethrough for passage of a fluid medium; a mold member disposed and interlocked therewith and having a cavity therein matching the shape of the hollow article; and a member for introducing a fluid medium through the core pin to align the thermoplastic sheet with the cavity. ,
A molded assembly consisting of: 17. According to claim 16, at least one of the processing sections following the processing section in which the mold member is arranged is provided with a support member for holding the molded product together with the extensible core pin. Assembly as described. 18. The assembly according to claim 16, wherein a holding member is attached to the piston to hold a cylindrical elastic member therebetween. 19. An assembly according to claim 18, wherein the mold member is provided with a separately operated thread forming member. 20. The apparatus according to claim 16, further comprising a member for introducing a cooling fluid medium into the hollow product after the hollow product is formed. 21. Apparatus according to claim 16, further comprising a member for retracting the piston from the chamber so that a trimming mold member can separate the hollow article from residual thermoplastic material.