JPH0371009B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mold for blow molding hollow plastic containers, such as bottles, and to demolding such containers. In one aspect, the present invention relates to a mold component that facilitates demolding of a blow molded hollow plastic container from the mold described below. Another aspect of the invention relates to blow molding using such mold parts.

Blow molding of plastic hollow containers, especially bottles, has become very important in the packaging industry. Only about 68 cm ³ to several liters (2.3 ounces to several pounds)
Plastic hollow containers having a volume of up to 1,000 yen have been molded from a variety of thermoplastics including polyvinyl chloride, polyethylene terephthalate, polyacrylonitrile, polyethylene, and polypropylene. Processes for blow molding containers have recently been developed, many of which have production rates of several thousand containers per hour. One of the primary methods of blow molding hollow plastic containers uses a preform that is blown into the desired container shape.
The preform, often in the shape of a test tube, is generally injection molded or shaped at one end into the shape of a neck;
It is made by molding, that is, closing the other end of an extruded tube. However, blow molding methods commonly use a blow mold having the required container shape and volume. High production rates (e.g. 1
As container sizes increase (thousands of containers per hour) and as container sizes increase, it becomes even more important to easily and completely release the molded containers from the blow mold. Such ease of demolding not only increases production rates but also reduces scrap generation, waiting time and container distortion. Current methods and molds provide satisfactory mold release for blow molding relatively small containers (i.e., containers with volumes up to about 2 liters and relatively small bases) at high speeds. but a somewhat larger container (for example, 5
(20 liters), which was not entirely satisfactory, especially when blowing at high speeds into containers with relatively large bottoms. In the case of large containers with thin walls, the bottom area is large, the walls are thin, and the height is generally large compared to the diameter or cross-sectional area, so the bottom of the container adheres to the mold in the blow molding method. This is especially troublesome. These factors, combined with the fact that the container is warm when it is released from the mold, cause the container to warp if it sticks to the surface of the mold, particularly the mold surface that forms the bottom of the container.

Producing hollow plastic containers by blow molding at high speeds precludes, if not prohibits, the use of mold release agents. This is especially because the release agent accumulates on the mold surface, making it difficult to decorate containers or attach adhesive labels, and removing the accumulated layer of release agent is expensive. This is because it will cause you to wait. Therefore, it is desirable to easily release the container from the mold without using a mold release agent. In particular, conventional methods for producing large containers at high speeds have not been able to easily release them from the mold.

Accordingly, one object of the present invention is to overcome the demolding problems of prior art methods and apparatus for blow molding plastic hollow containers. Another object of the present invention is to provide mold parts that facilitate release of blow molded plastic hollow containers from the mold. Another object of the invention is to
To provide a method for blow molding a hollow plastic container, which allows the container to be easily released from the mold.

To facilitate demolding of blow-molded plastic hollow containers, it is now known which mold parts contact the outside surface of the bottom of the plastic hollow container during molding, and the mold parts that contact the outside surface of the bottom of the plastic hollow container during molding A portion has at least one groove communicating around the periphery of the outer surface, the groove being sized and shaped to prevent plastic material of the container from penetrating the entire depth of the groove during molding. Furthermore, a method has been found for blow molding a hollow plastic container which facilitates the release of the container from the mold. at least a portion contacting the outer surface of the bottom of the container has at least one groove communicating around the periphery of this surface, the groove being dimensioned to prevent plastic material of the container from penetrating the entire depth of the groove. It has a shape.

Referring in detail to the drawings, a mold assembly 10 is shown in FIG. 1 in a closed position containing a blow-molded thermoplastic polymer bottle 11, the mold assembly having a laterally movable mold section 12. It can be seen that it has a movable mold part 13 according to the invention in its position at the end of the bottle blow molding stage. The mold part 13 has a passage 14 through which a cooling liquid circulates and a convex curved surface 15 on which a groove 16 is provided. Preform 17 and the first
The mold part 13 in the position , in which the surface 15 is in contact with the closed outer end of the preform 17 prior to blow molding, is shown in dashed lines. During the molding operation, the preheated preform 17, shown in phantom, is suspended within the closed mold assembly 10 by clamps, not shown, which grip the open end of the preform and hold it against the mold. When closed, it is integral with the top of the mold assembly (not shown). The mold part 13 is raised into a first position into contact with the heated preform 17 by means not shown (for example hydraulic or pneumatic). Compressed air is introduced into the heated preform by means of a blow tube (not shown) to inflate it laterally and to stretch it axially. As the preform stretches, it pushes the mold part 13 from the first position to the second position against a preset biasing force acting in the opposite direction. By means not shown, a cooling liquid is circulated through the mold section 12 and through the passages 14 of the mold part 13 to cool the neck (not shown), walls and bottom of the bottle 11. Once the bottle 11 has been blow molded, the mold is opened by moving the mold section 12 laterally away from the bottle 11. Mold part 12 is mold part 1
3, the mold part 13 is moved downward away from the bottom of the bottle 11, and the release of the bottle 11 from the mold is completed. Another heated preform is brought into position within the mold, and mold part 13 is pulled up into a second position to engage mold part 12, and the mold part 13 and preform gripping clamp (not shown) are brought together. The molding process is repeated by closing the mold section 12 around the bottle 11 and blow molding the bottle 11. As is known,
Mold part 12 with neck shaping protrusions not shown
and the mold part 13 and the preform clamp (not shown) when in the solid line position form a mold cavity 18 which determines the blow expansion limits and shape of the bottle 11. If the shape of the mold cavity (container) allows,
For example, if the bottom of the container is flat or convex, mold section 12 can form a portion of the bottom wall of the mold cavity.

Referring to FIG. 2, mold part 13 according to the invention
One side of this is shown. The surface 21 of the mold part 13 in FIG. 2 has a radial groove 22 intersecting the circular grooves 23, 24 and extending from the preform receiving recess 25 to the periphery of the surface 21. During blow molding of plastic hollow containers (e.g. bottles) using the mold parts shown in FIG. After being positioned in contact with the preform receiving groove 25, the grooves 22, 23, 24 are expanded to cover their entire depth without penetration of preform material. The width and depth dimensions of the grooves 22, 23, 24 are selected to prevent the plastic of the container from penetrating the entire depth of the grooves during blow molding. The pattern of grooves 22, 23, 24 and preform receiving grooves 25 in surface 21 of FIG. 2 is particularly suitable for surface 21 of mold part 13 of the invention for use in the apparatus and method described below.

FIG. 3 is a vertical sectional view taken along the line A-A in FIG. be. Also shown in FIG. 3 are the two-piece cap 30 and stem 32 of the mold part. The mold part of FIG. 3 extends through the stem 32 and cap 30 to circulate cooling fluid through the mold part and the surface 2.
It is desirable to have an internal passageway 32 for cooling 1 and thus thermally setting the shape of the molded plastic against surface 21.

4-8 illustrate different groove patterns that can be used on the surface of mold parts of the present invention. FIG. 9 shows another shape of the surface of the mold part of the invention and another pattern of grooves provided on the surface.
The groove patterns of FIGS. 4-8 and 9 each form at least one groove communicating with the periphery of the surface. FIG. 4 shows a pattern of eight radial grooves extending from the center of the surface of the mold part of the present invention to a circular periphery 42. FIG. 5 shows a pattern of four radial grooves extending partially toward the center from a circular periphery 52 on the surface of the mold part of the present invention. FIG. 6 shows one circular groove 61 in the surface of the mold part of the invention having one radial groove 62 centrally extending therefrom. FIG. 7 shows the intersection of four radial grooves 73 extending partially towards the center from the circular periphery 74 of the mold part of the invention and two spaced concentric circular grooves 71, 72. The pattern is shown. FIG. 8 shows a helical groove pattern extending from the center of the surface of the mold part of the present invention to a circular periphery 82. FIG. 9 shows a rectangular surface in which a pattern of two grooves 91 are positioned, each groove extending from a separate side of the periphery 92 of the surface, parallel to the bisector of the surface, to each adjacent neighbor of the periphery. The mold part of the invention is shown extending to the sides. A preferred embodiment of the mold part of the present invention is shown in FIGS. 2 and 3.

According to the invention, a mold for blow-molding hollow plastic containers is provided with a mold part which facilitates the release of the container from the mold, the surface of said mold part being in contact with the outer surface of the bottom of the container being molded. At least a portion of the container has at least one groove communicating with the periphery of the surface and is sized and shaped to prevent the groove from penetrating the entire depth of the plastic groove of the container. Furthermore, the present invention provides a method of blow molding a hollow plastic container that facilitates release of the container from the mold, the method providing a method for blow molding a hollow plastic container, the method comprising molding at least a portion of the surface of the mold part around the periphery of the surface. comprising blow molding the bottom of the container in pressure contact with a mold part having at least one groove communicating with the groove, the groove being dimensioned to prevent the plastic of the container from penetrating the entire depth of the groove. and shape.

Still further, the present invention provides a mold having a side wall molding section and a bottom wall molding section for blow molding the thermoplastic polymer container, the bottom wall molding section being at least partially adapted to facilitate release of the container from the mold. the mold part having at least one groove in communication with the periphery of the surface contacting at least a portion of the outer surface of the bottom of the container; sized and shaped to prevent penetration to the full depth of the area.

The invention will be described in more detail in connection with a typical blow molding process. As will be readily understood by those skilled in the art, the following description is intended to be illustrative and not limiting, and the present invention may be embodied in a variety of different embodiments. In one blow molding method according to the invention, a heated test tube-shaped injection molded preform, held in a clamp by a threaded neck, is suspended within a mold cavity. A mold having a mold part of the invention is constructed by a blowing fluid (e.g., air) under pressure placed inside the preform which is closed around the preform and presses the preform against the walls of the mold cavity. and inflate it. The mold is then opened and the blown container is removed. Another embodiment of the method of the invention uses a movable mold part of the invention that contacts the closed outer end of the preform and moves within the cavity of the mold in response during blow molding of the container. can. The movable mold part is moved into contact with the bottom outer surface of the heated preform held in a clamp suspended within the mold cavity. As the preform expands by blowing a fluid under pressure (e.g. air) into the interior of the preform, the mold parts move further away from the expanding preform until they reach the walls of the mold cavity and become integral with it. Pushed. These methods employ a piece mold having two side pieces or sections that form the sides and shoulders of the container and a bottom piece of the invention that forms the bottom (i.e., the closed end) of the container. Can be implemented. When using this mold, the blow-molded container is attached to the preform support clamp and the bottom of the mold when the side pieces of the mold are displaced away from the container to release the blow-molded container from the mold. Supported by products. Such support prevents undesirable movement of the container or distortion of its sides when the side pieces of the mold are moved away from the container. The bottom part of the mold is then removed from the blow molded container. However, when demolding with prior art methods, the bottom part of the mold (i.e., the part of the prior art mold that presses against it to form the bottom of the container) is removed from the mold, especially when removed from a large blow-molded container. Movement of the bottom part of the container often distorts the container, and in extreme cases can even pull the container from the preform support clamp. In carrying out the method described above, the present invention facilitates release of the blow-molded container from the bottom mold part in a manner that prevents the container from undesirably distorting and/or being pulled out of the preform support clamp. This has the advantage of increasing the strength of the bottom of the container.

Various embodiments of the mold parts of the present invention can be used to implement this method. One embodiment of the mold part of the invention may have internal passages for conducting cooling or heating fluids or cooling and heating fluids through the part, and another embodiment of the mold part of the invention may have It is movable within the cavity of the mold. A further embodiment of the mold part of the invention is a fixture. The mold parts of the present invention can have one or more grooves, the grooves being sized and shaped to prevent the plastic of the container from penetrating throughout their depth.

The mold part of the invention has at least one groove in its surface contacting the outer surface of the bottom of the container that communicates with its surroundings. However, in practicing the invention, a plurality of grooves in various patterns can be formed on the surface of the mold part that contacts the outer surface of the bottom of the container. Thus, for example, a plurality of grooves may be (1) a pattern of radial grooves extending from the center of the surface to the periphery, or (2) a pattern of radial grooves, some or all of which extend partially from the periphery to the center of the surface. (3) a pattern consisting of a radial groove extending partially from the periphery to the center of the surface combined with one or more circular grooves intersecting it; or (4) a spiral pattern extending from the center of the surface to the periphery. (5) A pattern of one or more grooves having passages parallel to the bisectors of the surface and communicating around the periphery of the surface. In addition to using a variety of patterns, grooves having a wide range of sizes and shapes can also be used, provided the groove size and shape is such that the plastic of the container does not penetrate the entire depth of the groove. Therefore, the dimensions and, to some extent, the shape of the grooves will depend upon the plastic being molded into the container and the blow molding conditions used to mold the container. Therefore, the temperature and blowing pressure (ie, fluid pressure) used to form the container from the preform are factors that govern the dimensions of the groove. The thickness of the bottom wall of the container is also considered, along with the deformation characteristics of the plastic at the temperatures and pressures at which the container is blown. The mold parts of the present invention include, for example, 0.127 mm (0.005 inch) to 6.35 mm
(0.250 inch) range width and 0.025 (0.001 inch)
Grooves having depths ranging from 1.90 mm (0.075 inch) to 1.90 mm (0.075 inch) can be used, and the width and depth must be such as to prevent the plastic of the container from penetrating the entire depth of the groove. The term "groove and width" as used in the present invention refers to the dimension across the opening of the groove.The width at a certain depth from the opening of a certain groove used in the mold part of the present invention is wider than the width at the opening of the groove, for example, T - It is like a slot groove. However, the width dimension at the opening of the groove is such that it meets the aforementioned dimensions and requirements. The shape of the grooves used in the mold parts of the invention can vary widely. Thus, the groove may be V-shaped, flat-bottomed U-shaped, curved-bottomed U-shaped, T-shaped and key-shaped.

In preferred mold parts and methods of the invention, the grooves are
Widths from 0.127mm (0.005") to 6.35mm (0.250") and 0.025mm (0.001") to 1.90
mm (0.075 inch) and a V-shape or flat-bottomed U-shape, the mold part has an internal passageway for conducting fluid and a preform receiving recess, and a mold cavity. forming at least a portion of the cavity bottom forming wall of the mold cavity by the force of the expanding preform from a first position contacting the outer surface of the bottom of the preform within the mold cavity prior to blow molding; movable to a second position.

The present invention also provides a method of blow molding a plastic container, the method comprising forming a thermoplastic polymer in pressure contact with a bottom mold part that forms at least a portion of the outer surface of the bottom of the container. and at least a portion of the surface of the mold part that contacts the outer surface of the bottom of the container communicates with the outer periphery of the surface.
The groove has a size and shape to prevent the thermoplastic polymer from penetrating the entire depth of the groove during blow molding. Various embodiments of this method can be practiced by those skilled in the art, including but not necessarily limited to (1) further circulating a cooling fluid through the mold part during blow molding;
(2) substantially continuously contacting the closed end of the preform with the surface of the mold part during blow molding, and (3) pressing the mold part of the present invention in contact with the closed end of the preform. to inflate the preform and move the mold parts in the direction of axial expansion of the preform and bias the mold parts in a direction opposite to the direction of axial expansion of the preform, but during blow molding of the container. (4) heating the preform; and (4) heating the preform.

[Brief explanation of drawings]

FIG. 1 shows the lower part of a plastic hollow container blown into the mold by vertically cutting the lower part of the mold having the mold parts of the invention and also the mold of the invention in contact with the preform before blow molding. FIG. 2 is a top view of the surface of the mold part of the present invention showing the pattern of grooves on the surface of the mold part and the central preform receiving recess; FIG. A-A in Figure 2
4 to 8 are diagrams showing different groove patterns on the surface of the mold part of the present invention, and FIG. 9 is a diagram showing different shapes and surfaces of the mold part of the present invention. It is a figure showing the different groove patterns on the top. 10... Mold assembly, 11... Container, 12...
... Side wall molding part, 13 ... Mold parts, 18 ... Mold cavity, 21 ... Mold surface, 22, 41, 51, 6
2, 73... Radial groove, 23, 24, 61,
71, 72... circular groove, 25... recess, 32...
Internal passage, 42, 52, 63, 74, 82, 92
……neighborhood.

Claims (1)

[Scope of Claims] 1. A mold having a side wall forming portion and a bottom wall forming portion for blow molding a thermoplastic polymer container, the bottom wall forming portion being at least partially adapted to facilitate release of the container from the mold. Consists of mold parts to
The mold part has a surface contacting at least a portion of the outer surface of the bottom of the container, the surface having a periphery and at least one groove communicating with the periphery, the groove being heated during blow molding of the container. A mold characterized in that it has dimensions and shape that prevent the plastic polymer from penetrating the entire depth of the groove. 2. The mold of claim 1, wherein the mold part is movable within the mold cavity. 3. A mold according to claim 2, wherein the mold part has a recess that contacts at least a portion of the outer surface of the closed end of the preform. 4. A mold according to claim 3, wherein said mold part has an internal passageway for transporting fluid. 5. A mold according to claim 4, wherein said mold part has a pattern of radially extending grooves. 6. The mold of claim 4, wherein said mold part has a pattern of radially extending grooves intersecting at least one circular groove. 7. Said groove has a width ranging from 0.127 mm to 6.35 mm.
7. The mold of claim 6 having a depth in the range 0.025 mm to 1.90 mm. 8. A method for blow molding thermoplastic polymer containers, comprising the step of blow molding the bottom of the container in a mold having a side wall molding section and a bottom wall molding section for blow molding the thermoplastic polymer container. the bottom wall molding portion comprises at least a portion of a mold part that facilitates demolding of the container from the mold, the mold part having a surface that contacts at least a portion of the outer surface of the bottom of the container; a periphery of the container and at least one groove communicating with the periphery, the groove having a size and shape to prevent the thermoplastic polymer from penetrating the entire depth of the groove during blow molding of the container. How to characterize it. 9. The method of claim 8, wherein the step of blow molding the bottom of the container is carried out by pressing the preform article against a mold part having a recess contacting at least a portion of the closed end. 10. The method of claim 9, wherein the step of blow molding the bottom of the container is carried out by pressing against a mold part having an internal passageway for transporting fluid. 11. The method of claim 10, wherein blow molding the container bottom is carried out by pressing against a mold part having a pattern of radially extending grooves. 12. The method of claim 11, wherein blow molding the container bottom is carried out against a mold part having a pattern of radially extending grooves intersecting at least one circular groove. 13. Blow molding the bottom of the container comprises:
Widths ranging from 0.127mm to 6.35mm and 0.025mm to 1.90
13. The method according to claim 12, which is carried out by pressing against a mold part having a groove with a depth in the range of mm. 14. The method of claim 13, further comprising the step of forming the preform in contact with the mold part.