Thermoforming of plastic sheet material
US4475881A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 14, 1982 |
| Grant date | Oct 9, 1984 |
| Priority date | — |
| Expiry date | Sep 14, 2002 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB31F7/006
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
A method and apparatus are disclosed for holding and feeding a continuous sheet (12) of plastic in an operation such as thermoforming. Articulations (13), such as alternating waveforms, are formed on the edges of the plastic sheet (12) by heating and pressing the edges, producing inwardly facing abutment surface at the edges of the sheet. The sheet is then passed into slots (34) in guide rails (32) with the inside surfaces (35) of the guide rails (32) engaging the abutment surfaces on the plastic sheet (12) to prevent the sheet from slipping out of the guide rails. The plastic sheet is thereby held firmly so that it can be passed through such thermoforming operations as heating in an oven (14), forming with a mold at a forming station (40), and cutting the formed articles away from the remainder of the sheet by a trim press (53). The sheet is advanced in increments through the thermoforming apparatus by a sheet advance mechanism (48) which alternately grasps the sheet to advance it and then releases the sheet while the forming and trimming operations are carried out. Sheet stretching guide rails (90) hold the sheet at the mold and are mounted to move outwardly to stretch the heated…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.