Method for blow-molding containers, and machine for said method

Patent metadata

Field	Value
Publication number	US-10434698-B2
Application number	US-201314424645-A
Country	US
Kind code	B2
Filing date	Oct 23, 2013
Priority date	Oct 29, 2012
Publication date	Oct 8, 2019
Grant date	Oct 8, 2019

Abstract

A method and machine for blow-moulding containers, the method involves selecting at least one characteristic point of the pressure in the container; for each selected point, defining a triggering criterion, and a pre-defined value thereof; during a production and data acquisition cycle, measuring the pressure in the container; for each selected point, defining a setpoint time for triggering, in the subsequent production cycle, the switch to the sub-phase after the characteristic point, such that: if the actual value of the criterion is ≤ to the pre-defined value, the setpoint time is the time at which the criterion has assumed a value equal to the predefined value, and if the actual value of the criterion is strictly higher than the pre-defined value, the setpoint time is after the actual time and is defined such that, at that time, the criterion assumes a value close to or coinciding with the pre-defined value.

First claim

The invention claimed is:

1. A method for producing thermoplastic containers by stretch-blow molding including a series of production cycles during each of which a new container is produced, each production cycle comprising a pre-blow-molding phase where a preform is connected through a nozzle to a pre-blow-molding air system so that the preform becomes a container ready to be blow molded during an overall blow-molding phase, the method comprising successively at least the following sub-phases:
conducting blow molding or a series of blow moldings by connecting the container successively to increasingly higher-pressure air systems;
then performing a recovery or a series of recoveries by connecting the container successively to increasingly lower-pressure recovery air systems, until a final recovery where the container is connected to a final air system;
then performing a degassing by connecting the container to atmospheric pressure; and
finally opening the mold by disconnecting the nozzle,
wherein at least one characteristic point of the pressure in the container is selected that is taken from selectable points that are:
when there are several blow moldings, the transition between two successive blow moldings, and
when there are several recoveries, the transition between two successive recoveries, and
the transition between the final recovery and the degassing,

wherein, for each selected characteristic point,
a scanning time zone is determined where the selected characteristic point is found,
a triggering criterion is determined, the triggering criterion representing a progress status of an air pressure stabilization between two receptacles during at least the scanning time zone, the two receptacles being defined by the container and one of the air systems to which the container is connected before the selected characteristic point, and
a predetermined value of the criterion is determined,

wherein, during a data acquisition phase that extends over at least one production cycle, the pressure is measured in the container to register a pressure curve along at least the scanning time zone of each selected characteristic point,
wherein, for each selected characteristic point, the following are determined from the pressure curve measured:
an actual instant corresponding to said selected characteristic point,
an actual value of the criterion at the selected characteristic point, and
a target instant to trigger, in a subsequent production cycle, the passage to the sub-phase that is subsequent to the selected characteristic point, such that:
when the actual value of the criterion is less than or equal to the predetermined value, the target instant is the instant for which the criterion has assumed a value equal to the predetermined value, and
when the actual value of the criterion is strictly greater than the predetermined value, the target instant is subsequent to the actual instant and is determined to ensure that at the target instant, the criterion assumes a value approaching or coinciding with the predetermined value.

2. The method according to claim 1 , wherein, for at least one selected characteristic point, the triggering criterion is the absolute value of the pressure difference between the container and the air system to which the container is connected during the sub-phase immediately before the characteristic point,
the method further comprises measuring, during the production and data acquisition cycle, the pressure in the air system to which the container is connected before the selected characteristic point.

3. The method according to claim 1 , wherein for at least one selected characteristic point, the triggering criterion is the absolute value of the slope of the first derivative of the pressure measurement in the container.

4. The method according to claim 1 , wherein a time increment is determined that is adapted to one of the at least one selected characteristic point and to the triggering criterion and wherein, when the actual value of the triggering criterion at said selected characteristic point is greater than the predetermined value, the target instant for the subsequent production cycle is equal to the actual instant for the cycle that has just been measured, increased by the increment.

5. The method according to claim 1 , wherein when the actual value of the triggering criterion at one of the at least one selected characteristic point is greater than the predetermined value, the triggering criterion is simulated subsequent to the actual instant, and
wherein the target instant for the subsequent cycle is equal to the instant for which the simulated criterion assumes a value equal to the predetermined value.

6. The method according to claim 1 , wherein a predetermined final degassing pressure threshold is determined, and, from the curves of pressures measured,
an actual instant of the end of blow molding and the pressure in the container just before the opening of the mold are determined, and
a target instant of the end of blow molding for the subsequent production cycle is determined, the target instant of the end of blow molding being prior to, equal to, or subsequent to the actual instant of the end of blow molding depending on whether the pressure in the container just before the opening of the mold is respectively greater than, equal to, or less than the final degassing pressure threshold.

7. The method according to claim 6 , wherein when the mean pressure in the container over a predetermined period of time before the opening of the mold is less than the final degassing pressure threshold, a target instant of the end of degassing is determined for which the pressure measured in the container is equal to a predetermined threshold, and
wherein the target instant of the end of blow molding for the subsequent production cycle is subsequent to the actual instant of the end of blow molding for a period of time equal to the period of time that passes from the target instant of degassing to an instant of the actual opening of the mold.

8. The method according to claim 6 , wherein when the mean pressure in the container over a predetermined period of time before the opening of the mold is greater than the final degassing pressure threshold, the target instant of the end of blow molding for the subsequent cycle is determined,
by going back a predetermined period of time to the actual instant of the end of blow molding, or
by simulating the pressure in the container as if there had not been any opening of the mold, by determining a target instant of degassing for which the simulated pressure is equal to the final degassing pressure threshold, the target instant of the end of blow molding then being prior to the actual instant of the end of blow molding for a period of time equal to the period of time that passes from an instant of an actual opening of the mold to the target instant of degassing.

9. The method according to claim 6 , further comprising:
during primary production cycles:
monitoring the mean pressure in the recovery system and determining a transition primary production cycle defined by the mean pressure in the recovery system reaching a predetermined threshold,
using a single blow molding from the highest-pressure air system from a first primary production cycle to the transition primary production cycle, and
determining an initial position of the beginning of the first recovery at least during the first primary production cycle;

during secondary production cycles subsequent to the primary production cycles:
using a plurality of blowing sub-phases and a plurality of recoveries for each secondary production cycle, and
selecting the characteristic point of the beginning of a

Assignees

• Sidel Participations

Inventors

• Lemble Thierry

Classifications

• B29L2031/7158

  Bottles · CPC title

• B29C49/786

  Temperature · CPC title

• B29C49/783

  blowing pressure · CPC title

• B29D22/003

  Containers for packaging, storing or transporting, e.g. bottles, jars, cans, barrels, tanks · CPC title

• B29C49/18 Primary

  using several blowing steps (B29C49/16 takes precedence) · CPC title