Wrapping apparatus
US4387552A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 12, 1980 |
| Grant date | Jun 14, 1983 |
| Priority date | — |
| Expiry date | Dec 12, 2000 |
Classification
- Technology area (CPC A)Human Necessities
- CPC primaryA01F2015/076
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
A process and apparatus for pre-stretching a plastic film material above its yield point in a roller assembly comprising at least two rollers connected for rotation at different speeds during a load wrapping operation. The downstream roller is at least partially driven by the film web connected to a turntable while the upstream roller rotates at a predetermined speed slower than that of the downstream roller to induce film elongation between the rollers. The force on the film between the roller assembly and the load is reduced by a powered constant torque device connected to the rollers to bring the force to the load down to a level permitting the film elongation between the roller assembly and the load to be equal to (balanced) or less than the elongation incurred between the rollers. The force from the torque device required to bring elongation on the load in balance with the elongation between the rollers will be equal to the difference between the force required to elongate the film between closely spaced rollers and the force required to hold the elongation after the film leaves the rollers corrected for the mechanical advantage and friction of the pre-stretch device. Since th…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.