JPH01263023A - Manufacture of hollow body composed of thermoplastic material and blow molding die - Google Patents

Abstract

PURPOSE: To manufacture bellows of a uniform thickness by providing side split flat surfaces perpendicular to split flat surfaces including a longitudinal axis in a mold, enlarging an inserted parison in the state that the mold is separated axially, and mating until mold segments are brought into contact with one another. CONSTITUTION: A blowing mold 1 has blowing mold segments 1a to if so that the segments are separable along a longitudinal split flat surfaces including a longitudinal central axis 7, and separably movable in a direction of the axis 7. An interval of inner ends 5a to 5e of the bellows of the mold is larger than an axial interval of the ends of the finish bellows. An internal pressure is loaded to the parison 6. When a thermoplastic material is brought into contact with inner ends 5a to 5e of the bellows of the mold, the individual segments are mated. Extended material is urged into an intermediate chamber and brought into contact with the outer ends of the bellows of the mold as near as possible. An axial interval is shortened, and the material is cast in a region for forming an outer fold of the bellows while holding uniform thickness.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention has two half parts, the dividing plane of which includes the longitudinal axis of the hollow body, and the two halves can be separated from each other in the radial direction and pressed together. The parison is inserted into a blow mold, which can be expanded radially by internal pressure, and
The present invention relates to a method for producing hollow bodies, in particular bellows, made of thermoplastic material and to a blow mold for carrying out this method.

[Conventional technology]

The manufacture of hollow bodies as well as bellows is generally carried out in a blow molding tool by radially expanding the thermoplastic material under internal pressure. The thermoplastic material then contacts the inner profile of the tool cavity. This inner profile corresponds to the outer profile of the finished hollow body.

During this radial deformation process of the thermoplastic material, the expanded material first reaches the profile area which is the most inwardly projecting area and, in the case of bellows, the area which later forms the inner apex of the bellows. be. The material then extends into the outwardly projecting tip space. therefore.

Only when the thermoplastic material completely contacts the tool cavity is the bellows 9. An outer cusp is formed.

According to practice, this deformation ensures a flow of material between the contact points forming the inner tip.

This forces undesired wall thickness variations. According to known manufacturing methods, the wall thickness of the finished bellows is significantly greater in the area of the inner tip of the bellows than in the wall section extending towards the outer tip. This undesirably thinning (weakening) of the wall thickness of the outwardly extending wall section reduces the service life of the hollow body as a whole and, in particular, of the bellows. The bellows is the first to fail at this point with its undesirably thin and weak wall thickness.

[Problem of the present invention]

The object of the invention is to provide, starting from the method mentioned at the outset, a method for producing hollow bodies, in particular bellows, with as uniform a wall thickness as possible from a thermoplastic material and a blow mold for carrying out this method. It's about doing.

[Means to solve the problem]

The gist of the method of the present invention that solves the above problems is that the blow molding mold is provided with at least one horizontal dividing plane that is transverse to the dividing plane including the longitudinal axis and perpendicular to the dividing plane,
With the blow mold moved axially apart, the inserted parison is expanded and the blow mold segments are then extended until the blow mold segments abut each other in the transverse parting plane or transverse parting planes. [Operations and effects of the present invention] As in the conventional method, the present invention first expands the parison in the radial direction and presses the bellows together in opposite directions in the axial direction. Make contact with the part that has penetrated inside. In this first state of deformation, each blow mold segment is pulled apart from each other.

In short, the axial spacing between the inner tips of the bellows of the blow mold segment is larger in this state than the axial spacing between the inner tips of the finished bellows.

By this point, in short, during radial deformation.

In order to ensure a very uniform wall thickness of the hollow body to be deformed and to maintain this wall thickness even in the area located between the inner tips of the respective bellows, each blow mold segment is pressed together axially. Ru. Then, further internal pressure is applied,
The blow mold segments are pressed together while further expanding the thermoplastic material between the inner tips of the bellows. This can also be done with a constant air volume, but the pressure increases. The pressing reduces the axial spacing between adjacent inner bellows tips of the blow mold. In this way,
The material, which previously had a relatively large axial length, is exposed despite the radial internal pressure that later forces the thermoplastic material outward toward the bellows outer tip of the blow mold.
The deformation is such that an afterflow of material occurs from a relatively large axial length. In the final state where the blow molds are fully pressed together and the inner profile of the blow mold corresponds to the outer profile of the finished bellows, the material contacts the outer tip of the bellows of the blow mold and
The wall thickness is kept almost uniform.

Further developments of the method according to the invention are described in claims 2 to 5.

The construction of a blow mold for carrying out the method of the invention is described in claims 6 to 7''!.

〔Example〕

The blow mold, designated as a whole by the reference numeral 1, consists - as already mentioned - of two complementary halves. In the following, the term "blow mold segments" means that there are in each case two such blow mold segments.

The blow mold 1 includes a plurality of blow mold segments 1a,
It consists of 1b, 1c, 1d, 1e, and if. The blow mold 1 and thus its blow mold segments can be divided along a longitudinal dividing plane that includes its longitudinal solid axis 7 . Blow molding mold segments 1a to 1f each complement the ring member. Blow molding mold segments) 1a-1f further include:
Horizontal dividing planes 3a, 3 extending in the horizontal direction with respect to the vertical dividing plane
b, 3c, and 3e.

These transverse dividing planes 3a-30 correspond to the bellows outer tips 4a, 4b, 4 of the blow mold seen in the illustrated embodiment.
Contains c, 4d, and 4e.

The inner tip of the bellows of the blow mold is designated by 5a.

5b, 5c, and 5e.

The blow mold segments can be moved away from each other in the direction of the longitudinal axis 7, as can be seen in particular from FIG. As can be seen from FIG. 5, the bellows inner tips 5a, 5 of the blow molding mold
The mutual spacing of b, 5c, 5e is greater than the mutual axial spacing of the inner tips of the finished bellows, as can be seen in FIG. Apply internal pressure to parison 6.

When the thermoplastic material thereby contacts the bellows inner tips 58-5e of the blow mold, the individual blow mold segments are pressed together, as shown, for example, in the right-hand region of FIG. During this pressing, the expanded material is forced into the intermediate chamber to come as close as possible to contact with the bellows outer tip of the blow mold. In this case, due to the short axial spacing, the material flows with a substantially uniform wall thickness into this pressed region forming the outer fold of the bellows.

4 through 1 show the sequence of pressing of the blow mold segments until they assume their final positions. This pressing order can also be performed in a different order and chronological order.

Although the parison 6 is only shown in FIG. 5, it goes without saying that it always exists inside the blow-molding die in which it is pressed together. Reference numeral 6a indicates the parison area which will later become the inner tip of the bellows.

Another embodiment of the blow mold 10 is illustrated in FIGS. 6, 7, 8, and 9. In this case, parison 1
1 is inserted into a blow mold 10 consisting of blow mold segments 10a, 10b and then expanded by internal pressure.

6 to 9, only one of the two halves of the blow mold is shown. In this embodiment, the blow mold 10 includes two ring-shaped blow mold segments 10a,
It is equipped with 10b.

These can be separated and pressed together in the direction of the longitudinal axis 17 along the blow mold section 10c.

As can be seen from FIG. 7, parison 11 has already been expanded to nearly its maximum width. The blow mold segments 10a, 10b are then pushed together axially in the direction indicated by the arrow 13 (see FIG. 8) and finally reach their end position (see FIG. 9), in which the transverse parting plane 14 is formed. touch each other.

The key point of the invention is that the blow mold is not only divided in the longitudinal direction, but also in the transverse direction.

In that case, the blow mold is divided laterally, which is already known for known molds consisting of a plurality of rings or ring segments, but an important point of the invention is that the blow mold is divided laterally. The mold segments are mutually K! 1
1] being able to move in the direction.

In short, it is important that the blow mold segments or segment halves are movable radially as well as axially.

[Brief explanation of the drawing]

The drawings show only one half of the blow molding mold according to the present invention in longitudinal section, and FIG. 1 shows a state in which the blow molding mold segments according to an embodiment of the present invention are pressed together in the axial direction. Figures 2, 3, 4 and 5 are views showing the blow mold segments of Figure 1 pulled apart to various positions, Figures 61, 7 and 8. The figures show the blow-molding mold segments according to another embodiment of the present invention separated to various positions, and FIG. 9 shows the blow-molding mold segments pressed together. 1... Blow mold, 1a, 1b, 1c, 1d. 1e, 1f...Blow mold segment, 3a. 3b, 3c, 3e - transverse division plane, 4a, 4b. 4c, 4ci, 4e - bellows outer tip, 5a. 5b, 5c, 5e...bellows inner tip, 6...parison, I...vertical axis line, 10...blow mold,'
, Q a , 10 b...Blow mold segment. 10c... Blow mold part, 11... Engraving of parison drawing (no change in content) Procedural amendment (method) August 23, 1988

Claims (1)

[Claims] 1. A parison is placed in a blow molding mold having two half parts, the dividing plane of which includes the longitudinal axis of the hollow body, and the two half parts being able to separate from each other in the radial direction and press together. Insert
In a method for manufacturing hollow bodies, in particular bellows, of thermoplastic material by expanding this parison radially under internal pressure, a blow mold (1; 10) is provided with longitudinal axes (7;
17), at least one transverse dividing plane (3a; 3
b; 3c; 3d; 3e; 14) is provided, the inserted parison (6; 11) is expanded with the blow mold (1; 10) moved axially apart, and then
Blow mold segment (1a; 1b; 1c; 1d; 1
e; 1f; 10a; 10b) is the horizontal dividing plane (3a; 1
4) or multiple horizontal dividing planes (3a; 3b; 3c; 3
d; 3e) until they touch each other in the blow molds (1;
10) A method for manufacturing a hollow body made of a thermoplastic material, characterized in that the materials are pressed together in opposite directions in the axial direction. 2. The radial expansion of the parison (6; 11) while the blow mold (1; 10) is moved axially apart is determined by at least the smallest outer diameter, especially the bellows inner tip (5a; 5. The method according to claim 1, wherein the process is carried out up to the outer diameter of the wall region of the blow mold, which defines 5b; 5c; 5e). 5. The area remaining between the bellows inner tips (5a; 5b; 5c; 5e) is radially expanded to at least approximately the final outer diameter of the bellows outer tips (4a; 4b; 4c; 4d; 4e); or The method described in 2. 4. Radial expansion of the area remaining between the bellows inner tips (5a; 5b; 5c; 5e) and simultaneous axial shortening of this part of the blow mold segments (1a; 1b; 1c)
1d; 1e; 1f) are pressed together in the axial direction. 5, blow mold segment (1a; 1b; 1c; 1d
5. The method as claimed in claim 1, wherein the axial pressing of steps 1e: 1f) is carried out on different sides. 6. A blow-molding mold for carrying out the method according to any one of claims 1 to 5, which blow-molding mold is provided with an inner profile corresponding to the finished outer profile of the hollow body, in particular the bellows. , in a type in which the blow molding mold is divided into two halves along a dividing plane including the vertical axis, a horizontal dividing plane (3a; 3b; 3c: 3d; 3e), the transverse dividing plane extends to include the bellows outer tip, and the individual blow mold segments (
1a; 1b; 1c; 1d; 1e;
c; 3d; 3e) until they touch each other; furthermore, the blow molds (1; 10) have an inner profile corresponding to the outer profile of the finished bellows in axial contact. A blow molding mold for producing a hollow body made of thermoplastic material. 7, Blow mold segment (1a; 1b; 1c; 1d
; 1e; 1f) is formed into a ring shape.