Method for thermoforming twin sheet workpiece

• US 6,379,606 B1
• Filed: 11/17/1999
• Issued: 04/30/2002
• Est. Priority Date: 11/17/1999
• Status: Expired due to Fees

• Current Assignee: Brown Machine, LLC (Brown Machine Group Holdings LLC)
• Original Assignee: Brown Machine, LLC (Brown Machine Group Holdings LLC)
• Inventors: Chun, Victor L., Schulte, Roderick P.
• Primary Examiner(s): Silbaugh, Jan H.
• Assistant Examiner(s): SHIPSIDES, GEOFFREY P
• Application Number:
  US09/441,767
• Time in Patent Office: 895 Days
• Field of Search: 264/545, 264/248, 156/285, 156/292, 425/503, 425/504, 425/518, 425/519, 425/520, 425/521, 653/08, 652/51
• US Class Current: 264/545
• CPC Class Codes: B29C 51/082 by shaping between complementary mould parts
• CPC Class Codes: B29C 51/18 Thermoforming apparatus
• CPC Class Codes: B29C 51/261 Handling means, e.g. transfer means, feeding means B29C51/44 takes precedence
• 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
• CPC Class Codes: B29C 51/42 Heating or cooling

Abstract

A twin sheet thermoforming method and apparatus of a type using a rotary wheel to carry each of a series of clamping frames for releasably holding sheets to be formed through successive processing stations. The clamping frames can be shuttled on the wheel to be alternatively located for alignment with one of two forming tooling sets at a forming station, and to be shiftable at an unload-load station so that unloading and loading do not occur at the same location.

Claims

1. A method of making a part by individually thermoforming two separate sheets of thermoformable material including the steps of:

successively indexing each of said two sheets in individual clamping frames mounted at different locations on a transfer structure through at least one heating station for successively heating each sheet during successive heating cycles by indexing movement of said transfer structure;

indexing a first one of said sheets held in one of said clamping frames from said heating station into a forming station after undergoing a heating cycle by indexing movement of said transfer structure, and positioning said first sheet in a first tooling set including a mold and a plug assist;

thermoforming said first sheet in said first tooling set into a formed first part piece;

thereafter indexing a second one of said sheets and another of said clamping frames in which said second sheet is held, said another clamping frame mounted to said transfer structure at a location on said transfer structure trailing said location of said first sheet and clamping frame, said indexing occurring after said second sheet has undergone a succeeding heating cycle;

positioning said second sheet in a second tooling set in said forming station including a mold and plug assist, said second tooling set offset from said first tooling set;

thermoforming said second sheet in said second tooling set into a formed second part piece;

the improvement wherein one of said positioning steps includes the step of shuttling one of said sheets and clamping frames by relative movement on said transfer structure from a first shifted position to a second shifted position in order to align said one of said sheets with an associated tooling set in said forming station.

2. The method according to claim 1 wherein each of said two sheets and clamping frames are also successively indexed by movement of said transfer structure into a preheating station prior to being indexed into said heating station to be preheated prior to being finally heated in said heating station.

3. The method according to claim 1 wherein said indexing by said transfer structure is carried out by indexing a rotary wheel comprising said transfer structure.

4. The method according to claim 1 further including the step of shifting one portion of one of said first or second tooling sets into alignment with a portion of the other of said first or second tooling sets, with each one and the other tooling set portions carrying respective formed part pieces and thereafter fusing said part pieces together by forcing said tooling portions and part pieces together to make said part.

5. The method according to claim 4 wherein

each said clamping frame and associated sheet is indexed into a different said shifted position of the transfer structure to be aligned with an associated tooling set in which each is thermoformed, and wherein one of said part pieces is released from said clamping frame in which it is held after forming to allow withdrawal of said part piece with the withdrawal of said tooling set portion carrying said part piece, and the other part piece is allowed to remain in said clamping frame in which it is held and said other tooling set portion is not withdrawn after forming, and wherein said other part piece is shifted to bring both part pieces into the same shifted position when said respective tooling set portions are brought into alignment, said part carried in said other part piece associated clamping frame into an unload-load station by indexing of said transfer structure, said part released from said associated clamping frame to be able to be unloaded therefrom.

6. The method according to claim 5 further including the step of shuttling said associated clamping frame on said transfer structure to a said first shifted position thereon after unloading said part, and thereafter loading a new first sheet into said clamping frame at said first shifted position.

7. The method according to claim 4 further including the step of shifting a remaining portion of said other of said first or second tooling sets to an idle position to allow said one tooling set portion to be positioned in alignment with the other tooling set portion.