Plastic and nonmetallic article shaping or treating: processes – Direct application of fluid pressure differential to... – Producing multilayer work or article
Reexamination Certificate
1999-10-18
2002-09-03
McDowell, Suzanne E. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Direct application of fluid pressure differential to...
Producing multilayer work or article
C215S396000, C215S398000
Reexamination Certificate
active
06444158
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a handled plastic container in which the container is formed by blow molding a preform and the handle is separately formed and then connected to the container during the container forming process.
BACKGROUND OF THE INVENTION
Plastic containers for holding liquids including beverages and other domestic liquids are in wide spread use. During the 1980's plastic largely replaced glass as the material of first choice for the packaging of carbonated soft drinks. Plastics such as polyethylene terephthalate (PET) offer significant savings when compared with glass in packaging such products. Plastic is lighter than glass and plastic bottles are cheaper to make and cheaper to transport than glass bottles. In addition, there are clear safety advantages when using plastic given the inherent problems with breakages when using glass. Plastic containers are also in wide use for products such as detergents and fruit juices. Such products are generally packaged in one or two litre containers with relatively large outlet openings. For ease of pouring, containers such as those made from PVC often include a handle. In the past, the handle in plastic containers formed by extrusion blow molding has been provided by blow molding a hollow and integral handle portion into the container side wall.
Given the constraints of container design, such handles are generally quite broad and often leave little room for one to firmly grasp the inside of the handle. Special molds are required in the production of such bottles, they are more difficult to blow mold than a non handled bottle and there are difficulties with stress concentrations leading to possible container failure in the areas near the junction of the handle with the rest of the container. In addition, it has not been generally possible to economically produce such handled bottles from synthetic polyesters such as PET. To extrusion blow mold PET it would be necessary to use a resin having a high intrinsic viscosity, i.e. well over 1.0. Such containers would not have the same degree of side wall orientation as a container stretch blow molded from the preform.
If an integral handle was formed in a PET container formed from a preform, a special cutting tooling would be required to remove the flashing from between the container side wall and the integrally formed handle due to the high orientation of the material.
An alternative is the use of a separate handle joined to the container. If a separate handle is utilized, it is possible to injection mold a handle which is narrower and thinner than the integral handles of the previously described blow-molded containers, and if adequately attached to the container, such handle designs are more effective and easier to use.
Various attempts have been made to attach separate handles to blow molded containers formed from preforms but these have not been altogether successful. One difficulty has been inadequate engagement of the handle with the blow molded container. For example, it has previously been proposed that such handles be connected to the plastic container by blow molding the walls of the container around retaining portions provided at the respective ends of the handle. For example, reference is made to Australian patent 637,696. In processes where the handle is pre-engaged with the preform prior to positioning the combination into the blow mold, there are problems in automating the whole process. The need to interconnect the handle with the preform prior to introducing the combination into the blow mold complicates the manufacturing process and can slow it down. This is especially so if the interconnection process occurs in a different direction to the direction of insertion of the combination into the blow mold.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method of securing a separate handle to a plastic blow molded container which enables relatively rapid manufacture and which leads to the production of a handled bottle where the handle is firmly secured.
In one embodiment, the invention utilises a molded external flange which is not subject to stretching during the blow molding process and which provides a rigid support, against which an upper end of the handle is held by a portion of the side wall of the container once the preform has been blown.
This embodiment thus achieves the desired object by positioning a preform and a handle into a blow mold and thereafter stretch blow molding the preform in such a way as to sandwich the upper end of the handle between a portion of the side wall of the formed container and a substantially flat underside of a molded external flange located on the neck of the preform. This simplifies the construction of the handle and preform, as well as simplifying the positioning of the preform and handle during blow molding to thus reduce the overall cost of manufacture, while providing a secure attachment.
More particularly, in accordance with one embodiment of the present invention there is provided a method of manufacturing a handled plastic container which includes the steps of:
(a) positioning in an open blow mould a synthetic plastics preform which includes an external flange with a substantially flat underside face, and a handle which includes an upper end with a substantially flat abutment surface;
(b) closing the blow mould and stretch blow moulding the preform beneath the flange to form a container, wherein a sidewall portion of the preform is expanded so as to sandwich the upper end of the handle between a portion of the sidewall of the formed container and the flange with the substantially flat upper abutment surface and underside face being pressed together so as to fixedly connect the handle to the blown container.
Preferably the preform and handle are brought together into position where the upper end of the handle is adjacent to the underside of the external flange by relative movement of the preform and the handle towards each other along a first path which is substantially perpendicular to a longitudinal axis of the preform.
Most preferably, the preform and handle are brought together into this position prior to their introduction into the blow mould. In such case, it is preferred that the handle and preform once brought together be introduced into the blow mould together along a second path which is also substantially perpendicular to the longitudinal axis of the preform. The first and second paths may conveniently be in the same plane so that the handle and preform may be brought together and conveyed into the open blow mould by movement along a path which has no abrupt changes in direction.
Generally, the method of the invention is used with blow moulding equipment which requires that the preform be pre-heated before introduction into the blow mould to a temperature at which it may be stretched and blow moulded (e.g., in the glass transition range). Therefore, generally the preform is hot and the handle is cold when the two are positioned in the mould.
It is preferred that the preform and the handle be unconnected when positioned in the open blow mould. However, in one embodiment of the invention further described below where the handle is attached to the container only at its upper end, it is preferred that the upper end of the handle be broad enough to clip around the preform immediately beneath the external flange.
Preferably, the upper end of the handle also includes retaining means such that upon expansion of the sidewall of the preform, the retaining means is caused to interconnect with a portion of the formed container. Most preferably, the retaining means is adapted to be integrated with a portion of the wall of the container. The retaining means may take a number of different configurations. For example, it can comprise a downwardly facing projection, such as a lug or hook. In such an embodiment, the downwardly extending projection is adapted to firmly integrate and interconnect with the plastic material forming that part of the side wall of the blown conta
Grob Rolf
Ieuan Harry L.
Krishnakumar Suppayan M.
Nahill Thomas E.
Continental PET Technologies Inc.
Finnegan Henderson Farabow Garrett & Dunner LLP
McDowell Suzanne E.
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