Method and apparatus for forming twin sheet hollow plastic articles
First Claim
1. A method of forming a twin sheet plastic article comprising:
- providing first and second side by side clamp frames;
positioning first and second plastic sheets in the first and second clamp frames;
heating the sheets;
providing a hot forming station including a lower first mold and an upper second mold disposed laterally of and above the first mold;
moving the first and second clamp frames with the first and second sheets positioned therein to the hot forming station to position the sheets at the hot forming station with the first sheet positioned above the first mold and the second sheet positioned beneath the second mold;
molding the first and second sheets to the first and second molds respectively;
releasing one of the sheets from its clamp frame while retaining the other sheet in its clamp frame;
shifting the molds laterally to position the molds in vertically aligned and vertically spaced relation;
subjecting the molds to relative vertical movement to bring the molds together and fuse selected areas on the first sheet to selected areas on the second sheet and form the twin sheet plastic article while retaining the other sheet in its clamp frame; and
with the other sheet retained in its clamp frame and the other clamp frame empty, moving the first and second clamp frames away from the hot forming station to convey the twin sheet plastic article to a further processing station.
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Accused Products
Abstract
A method and apparatus for forming twin sheet hollow plastic articles such as plastic pallets. A pair of plastic sheets is delivered directly from an extruder and loaded directly into a pair of clamping frames. The sheets are then moved in the clamping frames into an oven where the sheets are heated, whereafter the sheets are transferred to a hot forming station where the sheets are formed into a pallet. This pallet is then transferred to a cold forming station where further processing of the pallet takes place, and then to an unloading station where the finished pallet is removed and a new set of plastic sheets from the extruder is loaded into the clamping frames. At the hot forming station the sheets are delivered in side by side relation on the sheet plane with one sheet overlying a female mold and the other sheet underlying a male mold, the sheets are molded respectively and simultaneously to the male and female molds, the female mold is shifted laterally to a position underlying the male mold, and the molds are brought together to fuse selected portions on the sheet carried by the male mold to selected portions on the sheet carried by the female mold to form the twin sheet pallet. The cold forming station includes male and female molds, corresponding generally to the male and female molds of the hot forming station, which reengage the pallet and provide further forming and curing of the pallet as a new pallet is formed at the hot forming station utilizing a new set of plastic sheets.
38 Citations
9 Claims
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1. A method of forming a twin sheet plastic article comprising:
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providing first and second side by side clamp frames; positioning first and second plastic sheets in the first and second clamp frames; heating the sheets; providing a hot forming station including a lower first mold and an upper second mold disposed laterally of and above the first mold; moving the first and second clamp frames with the first and second sheets positioned therein to the hot forming station to position the sheets at the hot forming station with the first sheet positioned above the first mold and the second sheet positioned beneath the second mold; molding the first and second sheets to the first and second molds respectively; releasing one of the sheets from its clamp frame while retaining the other sheet in its clamp frame; shifting the molds laterally to position the molds in vertically aligned and vertically spaced relation; subjecting the molds to relative vertical movement to bring the molds together and fuse selected areas on the first sheet to selected areas on the second sheet and form the twin sheet plastic article while retaining the other sheet in its clamp frame; and with the other sheet retained in its clamp frame and the other clamp frame empty, moving the first and second clamp frames away from the hot forming station to convey the twin sheet plastic article to a further processing station. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification