Method for transforming plastic preforms

Patent metadata

Field	Value
Publication number	US-10343326-B2
Application number	US-201514974924-A
Country	US
Kind code	B2
Filing date	Dec 18, 2015
Priority date	Dec 23, 2014
Publication date	Jul 9, 2019
Grant date	Jul 9, 2019

Abstract

A method for transforming plastic preforms into plastic bottles, in which preforms are introduced into blowing stations, each blowing station having at least one blow mold and a stretching rod for stretching the preform along a longitudinal axis of the preform within the blow mold, and the preforms are expanded to form the plastic bottles by being acted upon by a gaseous medium in the blow mold, wherein a wall thickness of the plastic container is measured by at least one measuring device which outputs the measured values to a closed-loop and/or open-loop control device, wherein at least a stretching speed of the stretching rod is varied by the closed-loop and/or open-loop control device at least at times and/or at least in some locations during the blowing operation, individually for each blowing station, in order to adjust a wall thickness of the plastic bottles.

First claim

The invention claimed is:

1. A method for transforming plastic preforms into plastic bottles, wherein the plastic preforms are introduced into blowing stations, wherein each blowing station comprises at least one blow mould and a stretching rod for stretching the plastic preform along a longitudinal axis of the plastic preform within the blow mould, and the plastic preforms are expanded to form the plastic bottles by being acted upon by a gaseous medium in the blow mould,
wherein
a wall thickness of the plastic container is measured by at least one measuring device, and the measuring device outputs measured values representative of wall thickness to a closed-loop and/or open-loop control device, wherein at least a stretching speed of the stretching rod is varied by the closed-loop and/or open-loop control device at least at times and/or at least in some locations during the blowing operation, individually for each blowing station, in order to adjust a wall thickness of the plastic bottles.

2. The method according to claim 1 ,
wherein
the stretching speed is the sole control variable by which the wall thickness of the plastic bottles is adjusted via the closed-loop and/or open-loop control device during the blowing operation.

3. The method according to claim 1 ,
wherein
the blowing operation comprises the following steps:
pre-blowing by acting upon the plastic preforms with a first pressure,
intermediate blowing of the plastic preforms with a second pressure which is higher than the first pressure,
finish-blowing of the plastic preforms with a third pressure which is higher than the first two pressures,

and wherein
the stretching speed of the stretching rod is varied at least during the pre-blowing and/or during the intermediate blowing and/or the stretching speed of the stretching rod is varied at an instant.

4. The method according to claim 3 ,
wherein
the stretching speed of the stretching rod is slowed at the instant.

5. The method according to claim 3 ,
wherein
at least during the pre-blowing and/or during the intermediate blowing, the stretching speed is varied in such a way that the stretching speed is slowed or accelerated during the speed changeover time intervals.

6. The method according to claim 1 ,
wherein
during the finish-blowing, the stretching rod is at a standstill inside the blow mould or at least is slowed in terms of its speed.

7. The method according to claim 5 ,
wherein
during the speed changeover time intervals, the stretching speed changes linearly as a function of the blowing time.

8. The method according claim 1 ,
wherein
each blowing station comprises at least one drive unit, which is controlled individually by the closed-loop and/or open-loop control device in such a way that the stretching speed of the stretching rod is varied.

9. The method according to claim 1 ,
wherein
the finish-blowing of the plastic bottles is started in a time-controlled manner.

10. The method according to claim 1 ,
wherein
the blow moulds are transported along a predefined transport path during the expansion of the plastic preforms and the stretching speed is also selected as a function of a position of the blow moulds along this transport path.

11. The method according to claim 1 , wherein the wall thickness of the plastic container is measured during the blowing operation.

12. The method according to claim 8 , wherein the at least one drive unit comprises a servo motor.

Assignees

• Krones Ag

Inventors

• Knapp Peter
• Steiner Andreas
• Hirdina Jochen
• Fleischer Klaus-Peter

Classifications

• B29C49/78 Primary

  Measuring, controlling or regulating · CPC title

• B29C2949/78092

  Operations & Transport · mapped topic

• B29C2949/78882

  Operations & Transport · mapped topic

• B29C49/64

  Heating or cooling preforms, parisons or blown articles · CPC title

• B29C2949/78369

  Operations & Transport · mapped topic