Plastic article or earthenware shaping or treating: apparatus – With apparatus assembly or dismantling means or with idle part – For press shaping surface
Patent
1998-06-02
2000-09-05
Davis, Robert
Plastic article or earthenware shaping or treating: apparatus
With apparatus assembly or dismantling means or with idle part
For press shaping surface
29467, 249102, 425522, 425541, B29C 3330, B29C 4948
Patent
active
061133779
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to moulding of articles, in particular it relates to blow moulding apparatus, a novel moulding member and an improved method for mould replacement. It will be convenient to describe the invention with particular reference to blow moulding of containers such as thermoformable polymeric bottles, made for example from polyethylene terephthalate ("PET") although it will be appreciated that the invention may have wider application.
In conventional blow moulding of thermoformable polymeric containers air is used to expand a heated preform against a female mould cavity. The mould cavity is formed by a number of mould parts, the number of mould parts generally depending upon the complexity of the moulded container. The base configuration of the container may be formed from a single mould element and the side walls may be formed from a pair of mould halves. In conventional container blow moulding apparatus the mould halves are each mounted directly to holding arms which reciprocally bring the mould halves together during the blowing phase and separate the mould halves during the bottle ejection and preform loading phase. It may be desired to manufacture a variety of container shapes on one blow moulding apparatus and for each particular container shape a different pair of mould halves and in some cases a different base mould element will be required to define the female mould cavity.
Every time a production run of one particular container shape finishes and a new container shape is to be made with a different side wall configuration or if mould halves become unacceptably worn, it is necessary to remove the mould halves which are bolted to the holding arms and to attach the new mould halves. The mould halves must then be realigned so that they index precisely to properly form the mould cavity and so that they do not damage each other during operation. Numerous retaining bolts are conventionally required to securely hold the mould halves to the holding arms and many of the bolts are difficult to access, particularly with multi-cavity moulding apparatus. Significant time is taken up in accessing and removing these retaining bolts. Mould halves are generally heavy and awkward to hold when being repositioned and as a consequence, re-bolting of the mould halves may also take considerable time.
Disconnection and reconnection of pipes and hoses to mould halves for heat transfer media, which may either cool or heat the mould half, will take further time.
Furthermore, in conventional blow moulding apparatus there is limited scope for adjustment of the holding arms so each mould half must be adjusted in its mounting to the holding arm by way of shims or the like which may often involve trial and error. This again can be time consuming. When combined, all the time consuming factors related to changing mould halves can result in significant production down-time, especially when a blow moulding apparatus has a number of cavities to be replaced. Due to the high speeds at which such blow moulding machines operate, correct alignment of mould elements is critical. With some bottle blow moulding machines having a capacity to produce about 20,000 bottles per hour, this can easily translate to significant lost production--more so when more than one machine needs to have the mould elements changed. Furthermore, once a pair of mould halves becomes worn unacceptably through use the entire mould halves must be replaced. Mould halves may be made from large amounts of metal and to replace the entire mould half can be an expensive exercise.
Accordingly, there is a need for a method of changing mould parts in a blow moulding apparatus to reduce production down-time assuring accurate alignment of substituted mould parts without the need to readjust the apparatus before recommencing production of containers.
It is an object of the invention to provide a solution to one or more of the problems of existing blow moulding apparatus.
According to the present invention there is provided a moulding member defining a portio
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Continental PET Technologies Inc.
Davis Robert
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