Method for the stretch-blowing of a container, comprising a retraction of the stretch rod during a boxing operation

Patent metadata

Field	Value
Publication number	US-9688013-B2
Application number	US-201214115717-A
Country	US
Kind code	B2
Filing date	Apr 30, 2012
Priority date	May 19, 2011
Publication date	Jun 27, 2017
Grant date	Jun 27, 2017

Abstract

A method of manufacturing a container from a blank in a stretch blowing assembly equipped with a mold provided with a wall and a mold bottom axially movable between an extended position and a retracted position and a stretch unit having a rod axially movable with respect to the wall and a device for controlling the movement of the rod. The method involves a stretch blowing phase; a boxing phase during which the mold bottom, initially in the extended position, is moved towards its retracted position, the boxing phase having a retraction operation including controlling a movement of the rod in synchronization with the movement of the mold bottom, or releasing the rod to allow the free axial movement thereof.

First claim

The invention claimed is:

1. A method of manufacturing a container from a plastic blank in a stretch blowing assembly equipped:
with a mold provided with a wall defining a cavity with an impression of the container, extending along a principal axis of the mold and a mold bottom that is axially movable with respect to the wall between an extended position and a retracted position,
with a stretch unit comprising a carriage provided with a protruding arm onto which a stretch rod is attached, the stretch rod is axially movable with respect to the wall and a control device for controlling the movement of the stretch rod,

said method comprising:
a phase of inserting the blank into the mold;
a phase of stretch blowing, during which a fluid under pressure is injected into the blank and the stretch rod is moved towards the mold bottom until locally pressing the blank against the mold bottom, the lower position of the stretch rod being adjusted so that a gap is left between a free end of the stretch rod and an upper surface of the mold bottom;
a boxing phase wherein:
the mold bottom, initially in the extended position, is moved towards the retracted position; and
a retraction operation is performed comprising:
moving the stretch rod slaved to the mold bottom, while maintaining constant the gap between the free end of the rod and the upper surface of the mold bottom, the stretch rod integrally accompanies the movement of the mold bottom, an electric command issued by the control device is slaved to move the carriage to the speed of movement of the mold bottom during the boxing phase, or
releasing the stretch rod to allow raising of the mold bottom without resistance by the stretch rod; the stretch rod being simply pushed by the mold bottom over a distance equal to the stroke distance of the mold bottom; and

stopping the stretch rod to prevent rebound of the stretch rod at an end of the boxing phase, when the mold bottom reaches the retracted position.

2. An assembly for stretch blowing containers from plastic blanks, which comprises:
a mold provided with a wall defining a cavity with an impression of the container, extending along a principal axis,
a mold bottom that is axially movable with respect to the wall between an extended position and a retracted position,
a stretch unit, a carriage provided with a protruding arm onto which a stretch rod is attached, the stretch rod that is axially movable with respect to the wall and an electromagnetic control device for controlling the movement of the stretch rod, the lower position of the stretch rod being adjusted so that a gap is left between a free end of the stretch rod and an upper surface of the mold bottom;
wherein the electromagnetic control device comprises a control unit that is programmed:
during a boxing operation comprising moving the mold bottom from the extended position to the retracted position, to:
control a movement of the stretch rod in synchronization with the movement of the mold bottom by moving the stretch rod slaved to the mold bottom, while maintaining constant the gap between the free end of the rod and the upper surface of the mold bottom, the stretch rod integrally accompanies the movement of the mold bottom, an electric command issued by the control device is slaved to move the carriage to the speed of movement of the mold bottom during the boxing phase; or
release the stretch rod of the control device to allow free axial movement and raising of the mold bottom without resistance by the stretch rod, the stretch rod being simply pushed by the mold bottom over a distance equal to its stroke distance; and

at an end of the boxing operation to provide an end stop of the stretch rod.

3. The stretch blowing assembly according to claim 2 , wherein the device for controlling the movement of the stretch rod is slaved to the position of the mold bottom.

4. The stretch blowing assembly according to claim 2 , wherein the stretch rod is disengageably mounted on a movable carriage.

5. The stretch blowing assembly according to claim 4 , wherein the stretch rod is mounted on the carriage by means of a movable connecting part.

6. The stretch blowing assembly according to claim 5 , wherein the connecting part comprises a piston mounted in a sleeve, the piston separates the sleeve into two chambers, of which at least one is connected to a fluid distributor.

7. The stretch blowing assembly according to claim 6 , wherein the piston is movable over a predetermined stroke distance equal to a stroke distance of the mold bottom.

8. The stretch blowing assembly according to claim 2 , comprising means for detecting or monitoring the position of the mold bottom.

9. The stretch blowing assembly according to claim 2 , wherein the control unit is programmed to modify, during the boxing phase, a reference value of electromotive force applied to the stretch rod.

10. A machine for manufacturing containers by stretch blowing from plastic blanks, the machine equipped with one or more stretch blowing assemblies according to claim 2 .

11. The stretch blowing assembly according to claim 8 , wherein the means for detecting or monitoring the position of the mold comprises at least one sensor connected to the control unit.

12. An assembly for stretch blowing containers from plastic blanks, comprising:
a mold defining a cavity with an impression of a container, the cavity extending along a principal axis;
a mold bottom axially movable with respect to the cavity between an extended position and a retracted position;
a stretch unit, comprising a stretch rod axially movable within the cavity;
a control unit programmed to control movement of the stretch rod so that the stretch rod is slaved to the movement or position of the mold bottom or is released to allow free axial movement of the stretch rod, the control of the movement of the stretch rod occurring during a boxing operation comprising moving the mold bottom from the extended position to the retracted position;
the control unit further programmed, at an end of the boxing operation when the mold bottom reaches the retracted position, to activate an electromagnetic stop of the stretch rod to prevent rebound of the stretch rod.

13. The assembly according to claim 11 , wherein the control unit is programmed to control, during the boxing operation, movement of the stretch rod so that the stretch rod is slaved to the movement or position of the mold bottom.

14. The assembly according to claim 11 , wherein the control unit programmed to control, during the boxing operation, movement of the stretch rod in which the stretch rod is released to allow free axial movement of the stretch rod.

15. The assembly according to claim 11 , wherein movement of the stretch rod is electromagnetically driven.

16. The method of claim 1 , wherein the control unit is programmed, during the boxing operation to control a movement of the stretch rod in synchronization with the movement of the mold bottom by moving the stretch rod slaved to the mold bottom, while maintaining constant the gap between the free end of the rod and the upper surface of the mold bottom.

17. The method of claim 1 , wherein the control unit is programmed, during the boxing operation to release the stretch rod of the control device to allow free axial movement and raising of the mold bottom without resistance by of the stretch rod.

18. The method of claim 1 , wherein the retraction operation comprises during the boxing phase moving the stretch rod slaved to the mold bottom, while maintaining constant the gap be

Assignees

• Derrien Mikael
• Deau Thierry
• Protais Pierrick
• Santais Franck
• Sidel Participations

Inventors

• Derrien Mikael
• Deau Thierry
• Protais Pierrick
• Santais Franck

Classifications

• B29C2049/7879

  Stretching, e.g. stretch rod · CPC title

• B29C49/12 Primary

  Stretching rods · CPC title

• B29C2049/4892

  Mould halves consisting of an independent main and bottom part · CPC title

• B29C49/541

  having a recessed undersurface · CPC title

• B29C49/06

  Injection blow-moulding · CPC title