DE1805091A1 - Process for the production of hollow bodies from thermoplastic material - Google Patents

Description

R. 9282
10/22/1968

Attachment to
Patent application

ROBERT BOSOH GMBH, Stuttgart W, Breitscheidstrasse

Process for the production of hollow bodies from thermoplastic material

The invention relates to a method for producing hollow bodies made of thermoplastic material, in which one by Injection molding produced preform is reheated and expanded in a blow mold by a pressurized gas.

For example, in U.S. Patent 3,347,966 known methods of this type are thimble-shaped, according to Preforms that have cooled down after injection molding are reheated into a Blow mold introduced and inflated to bottles with the aid of a compressed gas introduced.

0 09827/1591

BAD ORIGHNAL

Robert Bosch GmbH _{Ώ nODO ni / v} _

Stuttgart ^R * ^{9282 G1 / Kra}

It has been shown that irregularities in the wall thickness and / or non-uniform heating of the preforms lead to bulges lead, which, if they do not burst, result in very thin spots in the finished wall of the bottle. Whether and how a preform will not expand unevenly, cannot be foreseen. "=

The object of the invention is to create a method according to which hollow bodies with a uniform wall thickness are made from preforms can be produced safely.

It has been found that this object is achieved when a preform after rewarming with a pressurized gas pre-expanded (pre-inflated) and then in this state over a certain Period of time is left before complete expansion.

In the case of preforms made of polyvinyl chloride, after heating down, it has become a machining pause of 5 to 10 seconds turned out to be particularly advantageous.

It is assumed that, during the machining pause, areas in the wall of the preforms which tend to bulge cool more quickly than the areas that have not yet expanded as much as a result of their smaller accumulation of material. The more strongly cooled areas experience greater strength, which prevents the bulges from expanding and thinning excessively during the final blow-molding process. In addition, the structure of the plastic is pre-oriented during the pre-expansion and is thus compensated. The later switched loading _f-stop processing increases this effect even further. Such a treatment of the structure of the preforms brings, as has also been shown, a high level of manufacturing reliability. In addition, the final blow molding can be carried out at higher speeds than according to the known Blaaver processes.

'0088-27 / 1581

Robert Bosch GmbH _{v QOao} r * \ / vm

Stuttgart ^{R # 9282 GVKra}

Purely the machine production of hollow bodies according to the invention The method has the further advantage that by dividing the blowing process into several individual steps shorter switching times can be achieved so that a higher output can be achieved despite the same number of blow molds.

Bas according to the invention method is in the drawing on one Simplified embodiment shown and wild in the following described in more detail, Ea show:

Pig, 1 to 4 different process steps "in manufacturing a plastic bottle.

A procedure in the .ritzgieir:. manufactured cup shape ;,? er? or ~. for ing 1 3 with a flask protruding radially at the edge of the opening. £; rd ir a holder 3 inserted, re the splash

2 lateral, nd a, f its underside as well as a narrow one, on the plan. 2 outer ring area of the preform. * encompassed (Pi- '·). through contact and / or radiation. = the preform is heated to a temperature that a Jüifoi '. _t in the plastic o: sr elastic area enables _s the- "* on: 1 holder 3 encompassed areas of the pre-for. * r.ling 1 are only slightly heated, so long a deformation of the parts is not possible.

After 3rwärmen of Vorfornlings is on the Plansch 2 fitted "a cap 4 which is connected via a line 5 to an air pump in communication. With the air pump 6, a precisely metered Luftrenge is pressed into the preform 1, so that this at about the twice its initial volume enlarged (Fig. 2). The pre-expanded preform 1 is left in this state for a period of about 5 to 10 seconds. The cap 4 is then removed and the preform with the holder

3 introduced into a split blow mold 7.7 '. On the splash 2 a blown nosepiece 8 is placed, which via a line 9 and a Y-valve 10 is connected to a compressed air source 11.

009827/1591

BAD ORIGHNAL

Robert Bosch GmbH " _{QOOO ni} / _Wm

Stuttgart. . ^Ro 9282 GX / km

While simultaneously blowing air into the preform 1, a stretching ram 12 guided in the blow mouthpiece 8 pulls the preform 1 lengthways until its bottom rests on the bottom of the "blow mold 7, 7" (FIG. 3). When the pressure increases, the preform 1 is expanded further, with its wall being strongly thinned, "Ibis finally lays its wall on the inner wall of the blow mold 1 ₉ 7 ° (Pig. 4).

009827/1591 SAD ORlCHNAi

Claims (5)

-S- Robert Bosch GmbH / * p qoqo π / Ym Stuttgart 6 R 9282 G1 / Km claims 1. Process for the production of hollow bodies from thermoplastic Plastic, which is a preform made by injection molding is reheated and expanded in a blow mold by a pressurized gas, characterized in that the preform after rewarming with a pressurized gas and then in this state for a certain period of time is left before it is completely expanded. 2. The method according to claim 1, characterized in that about the pre-expanded state of the preform is maintained for a period of 5 to 10 seconds. 3. The method according to claim 1 or 2, characterized in that ■ that the preform with a certain volume of a compressed gas is advanced. 4. The method according to any one of claims 1 to 3, characterized in that that the preform is expanded to twice its original volume. 5. The method according to any one of the preceding claims, characterized in that it is pre-expanded with a pressurized gas, the pressure of which is lower than the blowing pressure. Century 0098 2 7/1591 BATH ORIGINAL