APPARATUS FOR VACUUM FORMING HOLLOW PLASTIC ARTICLES

• US 3,597,799 A
• Filed: 02/24/1969
• Issued: 08/10/1971
• Est. Priority Date: 02/24/1969
• Status: Expired due to Term

• Current Assignee: Herbert J. Earle
• Original Assignee: Herbert J. Earle
• Inventors: Earle, Herbert J.
• Application Number:
  US04/801,446
• Time in Patent Office: 897 Days
• US Class Current: 425/174
• CPC Class Codes: B29C 51/18 Thermoforming apparatus
• CPC Class Codes: B29C 51/267 Two sheets being thermoformed in separate mould parts and joined together while still in the mould B29C49/0691 takes precedence

Abstract

An apparatus for forming at least one planar sheet of heatfusible plastic into a hollow article by heating the plastic sheet to its fusion temperature; folding the heated sheet so as to bring preselected portions of the sheet together and holding other portions thereof spaced apart; and fusing the contacting portions together. An open frame supports and holds opposite edges of the heat-fusible plastic sheet during the heating of both planar surfaces of the sheet and the moving of the sheet parallel to a two section hinged planar mold. The edges of the sheet also may be preheated before its planar surfaces are heated. A vacuum is applied to draw the heated sheet into the mold cavities and concurrently the heated sheet is released form its supporting frame. The mold is then folded to fold the plastic sheet between the folded sections of the mold, which sections are then clamped in their folded positions. If desired, a sheet of insulation, such as of plastic foam, may be inserted between the folded portions of the sheet before the mold sections are folded together. Next these clamped sections are pressed to fuse together preselected portions of the folded sheet. These preselected portions may have been further heated before fusion and a cooling medium may be circulated through the mold sections to set the formed article. Compressed air then may be applied to one of the mold sections to release the article from that one section as the mold is opened. Lastly, air and/or a pusher is employed to eject the article from the other mold section.

Claims

2. An apparatus according to claim 1 wherein said heating means includes means for preheating the peripheral edges of said sheet before heating its planar surfaces.

3. An apparatus according to claim 1 wherein said heating means includes upper and lower heating elements.

4. An apparatus according to claim 1 wherein said transfer mechanism includes a frame means rotatable relative to said heating elements and said mold sections to successively position said frame means in alignment with said heating means and said mold sections.

5. An apparatus according to claim 1 including mechanical means for urging the heated sheet toward said coplanar mold sections.

6. A folding molding machine for forming hollow articles from at least one sheet of thermoforming plastic material, comprising:

a. a frame for holding opposite edges of a heated sheet of thermoforming plastic material, b. a pair of molds located in the same plane and hinged together along their adjacent sides, and having air ducts and holes in each of said molds, c. means for sucking air through said holes for holding said heated sheet against both said molds, and releasing said sheet from said frame, d. means for folding said molds together with said heated folded sheet sandwiched between them, e. means for locking said molds in their folded position, f. movable means for relatively pressing said molds toward each other until said articles formed from said folded sheet are fused and set, g. means for unlocking said molds and blowing air through the holes in one of saiD molds for release of said set articles therefrom, and h. means for unfolding said molds and ejecting said articles from the other of said molds.

7. A machine according to claim 6 wherein said ejecting means includes means for pushing said articles away from said molds.

8. A machine according to claim 6 wherein said ejecting means includes means for blowing air through said holes in said other mold.

9. An apparatus according to claim 1 wherein said transfer mechanism includes means for moving said heating means away from said sheet in said frame, whereby said transfer mechanism may move said frame relative to said heating means to adjacent said mold sections.

10. An apparatus according to claim 1 including mechanical means for moving said first and second coplanar mold sections toward said heated sheet before moving said mold sections toward each other.