Plastic and nonmetallic article shaping or treating: processes – Direct application of fluid pressure differential to... – Including application of internal fluid pressure to hollow...
Patent
1996-12-04
1998-08-18
Timm, Catherine
Plastic and nonmetallic article shaping or treating: processes
Direct application of fluid pressure differential to...
Including application of internal fluid pressure to hollow...
264542, 425526, 425531, 425535, 425536, B29C 4918, B29C 4932, B29C 4950
Patent
active
057955336
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for the manufacture of hollow articles from thermoplastic materials by blow moulding, the operation being carried out under heat. In said method a thermally plasticated parison is extruded continuously or discontinuously from a downstream parison die, is grasped by a previously opened blow mould as the mould parts are closed, and is severed from the following material, and then inflated by introduction of a blowing medium into the parison portion, known as the "preform", disposed in the mould and forced against the mould cavity wall. When preforms are formed in this manner from an extruded parison formed in a parison die from material emerging from an extruder, the term "extrusion blow moulding" --in contrast to "injection blow moulding" -- is used.
The invention also relates to a device for carrying out the method.
A much-used method of this generic type consists of the following steps,
From the die of the blowing head shaping the thermally plasticated parison, a parison is extruded between the open parts of a blow mould and, when said parison has reached the required length, said mould closes around this parison portion, which then forms the preform and is subsequently severed from the following material. The closed mould with the preform is then moved laterally out of this parison or preform station into a blowing station, in which a blowing and calibrating mandrel is inserted from above into the open end of the preform,
While the preform in the closed mould in the blowing station is being shaped to form the hollow article and subsequently cooled by means of cooling channels incorporated into the mould, a new parison portion emerges from the blowing head in the parison station. This process can be temporally coordinated with the shaping and cooling and removal of the finished blow-moulded hollow article in the blowing station in such a way that a preform of precisely the correct length is present in the preform station when the open mould has travelled back from the blowing station into the preform station to receive a new preform. This method is also known as the "shuttle method" or "method with top calibration".
According to a different method, often known as "bottom calibration", which, however, is usually used for the production of relatively large hollow articles from about 30 liters and above, e.g. tanks, a blowing and calibrating mandrel is used which is disposed below the blow mould in the perpendicular part of the blowing head. Either the lower, tubular preform, which is in any case open, travels over the upright blowing mandrel and the mould closes after this has taken place, or the mould first closes around the preform and then the blowing mandrel travels vertically upwards into the open end and then inflates the preform to form the hollow article, after which, the mould is opened again after cooling and the finished hollow article is removed from the mould, which is now open. In this method only discontinuously produced preforms can be used with a stationary blowing head, and the extrusion of a parison portion from the blowing head can only commence when the previously inflated hollow article has been removed from the open mould.
In methods of the aforementioned kinds for producing hollow articles from plastic by inflating a preform in a blow mould, the time taken from the reception of a parison in the blow mould until the subsequent reception of a new preform in the same mould is known as the cycle time.
From German Patent DE-A-2052460, it is known to combine the aforementioned "shuttle method" and the "method with bottom calibration" in order to reduce the aforesaid cycle time, and, to this end, to move the blow mould together with the preform received thereby, with the downwardly disposed blowing mandrel, which is moveable together with the blow mould, between a parison receiving station and a laterally displaced station, which in this case is only a removal station, i.e. to inflate the preform to form the hollow article already on the path between the pa
REFERENCES:
patent: 3204018 (1965-08-01), Hagen
patent: 3504396 (1970-04-01), Button et al.
patent: 3579622 (1971-05-01), Shaw et al.
patent: 3833700 (1974-09-01), Adomaitis
LandOfFree
Method and device for the manufacturing of hollow articles made does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and device for the manufacturing of hollow articles made , we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and device for the manufacturing of hollow articles made will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1112223