Plastic article or earthenware shaping or treating: apparatus – Female mold and means to shape parison directly by internal...
Reexamination Certificate
2000-03-28
2001-03-06
Davis, Robert (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Female mold and means to shape parison directly by internal...
C425S117000
Reexamination Certificate
active
06196828
ABSTRACT:
FIELD OF THE INVENTION
This invention-relates generally to blow-molded articles, and relates more specifically to blow-molded articles of double-walled construction.
BACKGROUND OF THE INVENTION
Blow molding is a well-known fabrication method for thermoplastic components. The process generally involves the molding of a hollow tube, or “parison,” of molten thermoplastic, that is lowered from an overhanging extrusion head to a position between halves of a reciprocating mold. As the mold halves close, air or some other gas is injected into the parison; the increase in air pressure within the parison caused by such injection forces its walls into the contours of the cavities of the mold halves and thus forms the parison into a desired molded shape. The resulting component has molded walls that surround a hollow chamber. Blow molding has proven to be particularly popular for the production of large parts that would require unduly large molding injection molding machines.
One type of blow molding that has been used successfully for large components that require structural rigidity is the so-called “double-walled” blow molding process. In this process, mold halves are most often designed as distinct core and cavity halves (rather than as two cavities, as would be the case for blow-molded bottles or other containers). The core portion of the core mold half extends within the cavity as the mold halves close. In addition, the mold halves for double-walled components are configured so that the molded components have “full-perimeter flash”; i.e., after molding the component has excess material, or “flash”, around the perimeter defined by mating surfaces of the mold halves. This contrasts with single-walled components, in which the parison is inflated entirely within closed mold cavities, and the molded component has flash only on its top and bottom portions. Blow-molded components have distinct inner and outer walls that surround a hollow space, with the inner wall having been formed by the core and the outer wall having been formed by the cavity, with the inner and outer walls being separated by the weld line remaining after the flash is removed. In a typical double-walled component the inner and outer walls are positioned proximate to one another and can have “pinched-off” areas, in which the inner and outer walls are contiguous.
One distinct advantage provided by double-walled blow-molded components is the capability for adjacent regions of the inner and outer walls to differ significantly in their localized contour. For example, a region of the outer wall may have a relatively flat profile, while the adjacent region of the inner wall can contain numerous projections, recesses, and the like, with the profile of either localized region failing to impact significantly the appearance or structural integrity of the other. Such differences in localized inner and outer wall contour are less likely to be successfully achieved in injection-molded components because the inclusion of substantial detail in the inner wall can have a deleterious effect on the dimensional stability, appearance, and even strength of the outer wall. Another performance advantage conveyed by double-walled components stems from the formation of the hollow chamber within the inner and outer walls, as it can provide an air cushion that protects items contacting the inner wall.
For these reasons, double-walled components have proven to be particularly popular for protective containers and carrying cases. Detailed contour that mates with, matches, supports, or captures portions of an item to be carried within the carrying case can be included in the inner wall of the double-walled component even as the outer wall has a generally flat, appearance-sensitive surface. Further, the air cushion between the inner and outer walls helps to protect the item. Thus, the container has the detail and structure necessary to support, transport and protect the item and also provides the desired aesthetic appeal, and does so without the manufacturer having to produce two separate inner wall and outer wall parts.
One problem confronting manufacturers of double-walled containers is the attachment of a manufacturer's label to the container. Typically, a paper or plastic label is adhesively bonded or otherwise attached to the outer surface of the one side of the container. However, these labels can easily peel off or tear, either of which can adversely impact the appearance of the container. The lack of durability of these labels is particularly problematic for carrying cases for power tools and the like, which are typically subjected to significant abuse during conventional use. Another alternative is to mold the manufacturer's logo directly into the case, but this limits the manufacturer to using a logo which is the same color as the case itself.
In view of the foregoing, it is an object of the present invention to provide a double-walled container with a durable identifying label.
It is also an object of the present invention to provide a method for producing a double-walled container having a durable identifying label.
It is a further object of the present invention to provide a mold suitable for producing a double-walled container with a durable identifying label.
SUMMARY OF THE INVENTION
These and other objectives are satisfied by the present invention, which includes a thermoplastic article having a molded-in insert suitable for use as an identifying label. The thermoplastic article comprises a double-walled body formed of a thermoplastic material and having outer and inner walls and a molded-in insert. The body includes an insert portion in which the inner and outer walls are at least partially contiguous. The insert, which is preferably thermoplastic, has outer surfaces defining one or more visible portions of the insert. The insert also includes runner sections connecting the visible portions which are recessed from the insert outer surface. The insert is attached to the body insert portion such that the insert outer surface is exposed (and thus visible) and the runner sections are embedded in the body insert portion. The resulting article has a durable visible insert that can withstand abuse similar to that withstood by the article itself. Preferably, the article includes ribs protruding outwardly from the body inner wall, which can assist the insert portion and insert in remaining generally flat.
Such an article can be formed by a method which includes as a first step providing a mold comprising a pair of mating mold halves. A first of the mold halves includes a cavity portion having a first insert section, and a second of the mold halves includes a core portion having a second insert section. Next, an insert such as that described above is positioned within the insert section of the cavity portion of the first mold half so that the insert outer surface contacts the insert section and so that the runner sections of the insert are spaced away from the insert section. A molten thermoplastic parison is then lowered between the mold halves, and the mold halves are closed to capture a portion of the parison therebetween so that the core portion of the second mold half extends within the cavity portion of the first mold half. The parison is inflated to force the parison to contact the core and cavity portions of the mold halves such that an insert portion is formed in the article which includes the insert and in which the inner and outer walls of the article are at least partially contiguous. As described above, the insert is positioned within the insert portion such that the insert visible portions are exposed in the outer wall and the runner sections are embedded within the article insert portion. Preferably, the method further comprises venting air from the cavity portion at positions adjacent the visible portions of the insert, as doing so can improve material flow over the runner sections of the insert.
A mold that can be employed to form an article of the present invention comprises a pair of mating mold halves, a first of
Davis Robert
Delta Consolidated Industries
Myers Bigel & Sibley & Sajovec
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