Plastic and nonmetallic article shaping or treating: processes – Pore forming in situ – Composite article making
Patent
1974-09-23
1977-08-02
Hoag, Willard E.
Plastic and nonmetallic article shaping or treating: processes
Pore forming in situ
Composite article making
264248, 264334, B29C 1704, B29F 500
Patent
active
040396436
ABSTRACT:
Improvements in the method for transporting and positioning thermoplastic sheets in a vacuum-forming machine are disclosed. The vacuum-forming machine has a stationary, lower platen which supports the lower mold half and an upper reciprocating platen which carries the upper mold half. This construction provides for minimal overall height of the press used in the vacuum forming and also achieves a high precision of mating of the lands of the opposed die faces so that a minimal land area is provided, permitting the formation of molded hollow enclosures from the thermoplastic sheets which have tear trims about their outer periphery to facilitate the removal of excess sheet material therefrom. The method of transferring the thermoplastic sheets between the opposed die faces of the vacuum molding apparatus includes the steps of supporting the thermoplastic sheets in upper and lower vertically spaced apart, open frameworks which are moved between heating stations and the molding station. At the molding station, the lowermost open frameworks is lowered to place the lower thermoplastic sheet in contact with the die face of the lower mold half and vacuum is applied thereto to draw the thermoplastic sheet into conforming contour with the die face. The upper platen of the press is lowered into proximity with the uppermost of the open frameworks, vacuum is applied to the upper mold half to draw the uppermost thermoplastic sheet into contour-conforming contact with the die face of the upper mold half and the upper mold half is then lowered into land contact with the lower mold half. Pressure is applied to extrude sheet material from between the opposed lands of the die faces, thereby providing a weakened tear line about the peripheral edges of the formed product.
The apparatus used in the invention includes thermoplastic sheet transfer means that comprises the open frameworks which support the thermoplastic sheets at their peripheral edges and that are mounted on transport means for moving the open frameworks and their supported thermoplastic sheets between heating and molding stations. The open frameworks are carried by carriages that are mounted on vertical track means of the transport means whereby the vertical position of the thermoplastic sheets can be readily controlled with actuator means therefor which are linked to the open frameworks and the transport means to effect vertical movement of the open frameworks. The actuator means include reciprocal piston and cylinder assemblies with ports at opposite ends of each of the cylinders and conduit means connected between the ports and selector valve means which are effective to connect the conduits between a source of pressured fluid or a fluid exhaust line. The selector valve means in the invention have null positions and are biased into the null positions to supply the source of pressured fluid to the cylinders on both sides of their pistons when the open frameworks are to be held stationary. This constructional feature eliminates creeping of the open frameworks that could be caused by leaks in the actuator assemblies.
REFERENCES:
patent: 3242245 (1966-03-01), Grieg et al.
patent: 3250660 (1966-05-01), Grieg et al.
patent: 3251668 (1966-05-01), Brymer
patent: 3311683 (1967-03-01), Alesi et al.
patent: 3462330 (1961-08-01), Greig et al.
patent: 3539416 (1970-11-01), Sanders et al.
patent: 3548043 (1970-12-01), Held et al.
patent: 3767740 (1973-10-01), Jones-Hinton et al.
patent: 3783078 (1974-01-01), Brodhead
patent: 3787158 (1974-01-01), Brown et al.
patent: 3854860 (1974-12-01), Haag
Alesi, Jr. John
Dean Donald E.
Formex Manufacturing, Inc.
Hoag Willard E.
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