Receptacles – End wall structure – Joint or seam between sidewall and end wall
Patent
1997-10-24
2000-04-04
Pollard, Steven
Receptacles
End wall structure
Joint or seam between sidewall and end wall
220624, 215371, B65D 600
Patent
active
060450010
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to the design of a bottom or base area--in this technical context referred to as "bottom or base geometry"--of plastic bottles, which are made of a preform (an injection-moulded parison) in two blow-moulding steps (application of high internal pressure). These plastic bottles are hot-washable, i.e. their geometry may not change noticeably at a temperature of above 60.degree. C. or 75.degree. C. The mentioned temperature concerns the temperature of the washing fluid at which the bottles must remain thermostable; slight geometric deformations which do not affect mechanical strength or stability are permissible.
BACKGROUND OF THE INVENTION
In most cases plastic bottles are made of PET, which forms a single or multi-layer bottle wall. In the bottom area, the bottles must have a safe stand and have ability to withstand internal pressure. In this context, "stability" denotes stability during normal use. Another type of stability mentioned above is thermostability when hot-washing the bottle and thus the pre-condition for a reusability of the bottle. The bottom area must have an additional feature, i.e. it must be "inspectable", a term which experts in this technical field use to characterize an unobstructed view through the bottom area in direction of the bottle axis. Inspection of the bottom must not be affected by shadows and other optical refraction, because this would make visual inspection of the empty bottle by a camera or the eye impossible.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a bottom geometry for plastic bottles which is thermostable (thermally stable) and avoids shadow effects, i.e. allows full inspection, so that residual washing liquid (from cleaning) or foreign matter (impurities) located in the container can be reliably (fully) spotted before the bottle is filled. It is an object of the present invention to allow full inspection of the bottle without making concessions regarding the bottom diameter, as is the case in the art, where the bottle is given for example a substantially hemispherical outwardly oriented bottom geometry which is circumferentially reduced in diameter as the bottle is pressed in a plastic support ring to provide a secure support surface.
This solution impairs the ability of inspection because the plastic support, which is the reason for the reduction in diameter of the bottle base, is opaque. Functionally, its geometry is such that--even if it were transparent--a full, shadow-free inspection of the empty bottle through the bottom would be impossible.
The present invention offers a triform solution to the above problem, namely the use of a truncated cone of frustoconical bottom insert (Claim 1) or a manufacturing process in which in a first blow-moulding step, a preform is given a frustoconical bottle bottom, which bottom develops a wavy cross-section after removal from the mould (Claim 9), or an apparatus for carrying out said process, in which a first blow mould is provided with a frustoconical bottom and a second blow mould has a substantially dome-shaped bottom (Claim 11).
The shape of the substantially dome-shaped mould bottom according to Claim 11 is adapted to the geometry of the bottom of the bottle, as removed from the first blow mould (Claim 16), so that the bottom geometry is insubstantially changed in the second blow-moulding step, the only modification being that the basic shape of the bottom becomes more distinct. Identical geometry, however, does not mean identical dimensions (measurements), but only identical shape (relative position of the part shapes and the part shapes themselves).
The bottom develops its basic architecture after being removed from the frustoconical bottom insert, which has a substantially plane or even (flat) lateral surface, or after shrinking, which causes detachment from said insert. Surprisingly, it turned out that the wave structure developing in the bottom architecture after removal or shrinkage already is a thermostable botto
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Continental Pet Deutschland GmbH
Pollard Steven
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