Method of forming a twin sheet plastic pallet using preforming

Claim 1

A method of forming a twin sheet plastic article comprising the steps of: providing a male mold having protrusions; providing a female mold having a molding surface configuration differing from said male mold and having cavities generally complemental to said protrusions; thermoforming a first plastic sheet substantially to said male mold protrusions; then thermoforming said first plastic sheet to said female mold including said cavities; thermoforming a second plastic sheet to said male mold while said first plastic sheet is maintained in said female mold; and then knitting said first and second sheets together at selected interfaces by applying pressure between said male and female molds.

Claim 2

A method of forming a twin sheet plastic article comprising the steps of: providing a male mold having protrusions; providing a female mold having a molding surface configuration differing from said male mold and having cavities generally complemental to said protrusions; thermoforming a first plastic sheet substantially to said male mold protrusions; then thermoforming said first plastic sheet to said female mold including said cavities; thermoforming a second plastic sheet to said male mold while said first plastic sheet is maintained in said female mold; and then knitting said first and second sheets together at selected interfaces by applying pressure between said male and female molds.

Claim 5

A method of forming a twin sheet plastic pallet of the type including a generally planar platform structure and a plurality of hollow legs extending downwardly from said platform structure and openings in the upper face of said platform structure, said method comprising the steps of: providing a male mold having a downwardly facing platform molding surface and a plurality of downwardly extending leg molding protrusion surfaces; providing a female mold having an upwardly facing platform molding surface and a plurality of upwardly opening leg molding cavity surfaces said surfaces in said female mold having configurations differing from said male mold surfaces and said leg molding cavity surfaces being generally complemental to said downwardly extending leg molding protrusion surfaces on said male mold; thermoforming a first plastic sheet substantially to said male molding surfaces; then thermoforming said first sheet to said female molding surfaces to form a platform portion and upwardly opening hollow leg portions; thermoforming a second plastic sheet to said male molding surfaces to form a platform portion and downwardly extending hollow leg portions while said first sheet is maintained on said female molding surfaces; and then knitting said first and second sheets together at selected interfaces to form said pallet by applying pressure between selected said male and female molding surfaces.

Claim 6

A method of forming a twin sheet plastic pallet of the type including a generally planar platform structure and a plurality of hollow legs extending downwardly from said platform structure and openings in the upper face of said platform structure, said method comprising the steps of: providing a male mold having a downwardly facing platform molding surface and a plurality of downwardly extending leg molding protrusion surfaces; providing a female mold having an upwardly facing platform molding surface and a plurality of upwardly opening leg molding cavity surfaces said surfaces in said female mold having configurations differing from said male mold surfaces and said leg molding cavity surfaces being generally complemental to said downwardly extending leg molding protrusion surfaces on said male mold; thermoforming a first plastic sheet substantially to said male molding surfaces; then thermoforming said first sheet to said female molding surfaces to form a platform portion and upwardly opening hollow leg portions; thermoforming a second plastic sheet to said male molding surfaces to form a platform portion and downwardly extending hollow leg portions while said first sheet is maintained on said female molding surfaces; and then knitting said first and second sheets together at selected interfaces to form said pallet by applying pressure between selected said male and female molding surfaces.

Claim 9

A method of forming a twin sheet plastic pallet formed of an upper and a lower plastic sheet and utilizing an upper male mold having downwardly extending leg protrusions and a lower female mold having a molding surface configuration differing from said male mold and having upwardly opening leg cavities, said method comprising the steps of: positioning a heated lower sheet between the spaced upper and lower molds; moving the upper male mold downwardly to bring the leg protrusions into contact with the upper face of the lower sheet and form a seal as between the periphery of the upper male mold and the peripheral upper surface of the lower sheet; thermoforming the lower sheet upwardly toward the molding surfaces of the upper male mold; then raising the lower female mold into position immediately beneath the upper male mold with the lower sheet positioned therebetween; then thermoforming the lower sheet downwardly against the molding surfaces of the lower female mold; separating the molds with the formed lower sheet remaining with the lower female mold; positioning a heated upper sheet between the spaced molds while the formed lower sheet remains with the lower female mold; thermoforming the upper sheet to the molding surfaces of the upper mold; and then bringing the molds together to selectively fuse the upper and lower sheets and form the twin sheet pallet.

Claim 10

A method of forming a twin sheet plastic pallet formed of an upper and a lower plastic sheet and utilizing an upper male mold having downwardly extending leg protrusions and a lower female mold having a molding surface configuration differing from said male mold and having upwardly opening leg cavities, said method comprising the steps of: positioning a heated lower sheet between the spaced upper and lower molds; moving the upper male mold downwardly to bring the leg protrusions into contact with the upper face of the lower sheet and form a seal as between the periphery of the upper male mold and the peripheral upper surface of the lower sheet; thermoforming the lower sheet upwardly toward the molding surfaces of the upper male mold; then raising the lower female mold into position immediately beneath the upper male mold with the lower sheet positioned therebetween; then thermoforming the lower sheet downwardly against the molding surfaces of the lower female mold; separating the molds with the formed lower sheet remaining with the lower female mold; positioning a heated upper sheet between the spaced molds while the formed lower sheet remains with the lower female mold; thermoforming the upper sheet to the molding surfaces of the upper mold; and then bringing the molds together to selectively fuse the upper and lower sheets and form the twin sheet pallet.