US 6,576,171 B1Granted

Machine and process for moulding by stretching and blowing

AssigneeTetra Laval Holdings & Finance S.A.

InventorThierry Devenoges

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Abstract

Machine for the production of receptacles of plastic. A stretching rod (32) is displaced by actuating means (69) comprising a servo-motor (72) whose operation is controlled by a controller installation (73) by means of an adjustment loop (75). The blowing air is introduced into the preform via a servo-valve (60) whose operation is also controlled by this installation (73) by means of an adjustment loop (76) which can be combined with the first adjustment loop (75). It is thus possible to control in a precise manner the process of transformation of a preform into a receptacle by means of curves of stretching and pressure increase. Calibration operations of the maximum path of the stretching rod as a function of the length of the mould cavities and calibration operations of the path of positioning of the stretching rod as a function of the preform can be carried out easily and in an automated fashion, thereby ensuring excellent safety of production and very high adaptability to all conditions of production.

Claims12

Dependent claims

Process for the production of receptacles of plastic material by means of a machine comprising a chassis (1) and arranged along a transport path (20), at least one heating device (10) and a device (12) for moulding by stretching and blowing, the receptacles being formed from preforms (2) disposed on supports (7), the device (12) for moulding by stretching and blowing comprising a blowing member (54) connected to a source of fluid under pressure (58) by means of an electro-valve (60) and a stretching rod (32) adapted to be displaced by actuating means (69, 72) comprising a motor (72) connected to a control installation (73) comprising first regulating means (75) to program and control the displacement of the stretching rod (32) and second regulating means (76) to program and control the pressure increase (P) applied to the preforms (2), characterised by the fact that there is carried out by means of the control installation (73) a first calibration operation to determine the maximum path of the stretching rod (32) as a function of the length of the mould cavity (46) by advancing the stretching rod (32) to the bottom of the mould cavity and recording in the memory of the control installation the obtained path, decreased by the thickness of the bottom wall of the receptacle, and that there is carried out a second calibration operation to determine the path of positioning before stretching of the stretching rod (32) as a function of the length of the preform by advancing the stretching rod (32) to the bottom of the preform and by recording in a memory of the control installation a value depending on the positioning path and variations in the length of the preforms.

Machine for the production of receptacles of plastic material comprising a chassis (1) and arranged along a transport path (20), at least one heating device (10) and a device (12) for moulding by stretching and blowing, the receptacles being formed from preforms (2) disposed on supports (7), the device (12) for moulding by stretching and blowing comprising a blowing member (54) connected to a source of fluid under pressure (58) by means of an electro-valve (60) and a stretching rod (32) adapted to be displaced by actuating means (69, 72) comprising a motor (72) connected to a control installation (73) comprising first regulating means (75) to program and control the displacement of the stretching rod (32) and second regulating means (76) to program and control the pressure increase (P) applied to the preforms (2), characterised by the fact that the control installation (73) and its first regulating means are arranged so as to carry out a first calibration operation to determine the maximum path of the stretching rod (32) as a function of the length of the mould cavity (46) used, by advancing the stretching rod (32) to the bottom of the mould cavity and by recording in the memory of the control installation the path obtained, decreased by the thickness of the bottom wall of the receptacle, and to carry out a second calibration operation to determine the path of positioning before stretching of the stretching rod (32) as a function of the length of the preform, by advancing the stretching rod (32) to the bottom of the preform and by recording in a memory of the control installation a value depending on the positioning path and variations in the length of the preforms.

Dependencies are inferred from the claim text.