Package making – Apparatus for contraction of cover by stretching or shrinking
Patent
1982-08-27
1985-06-25
Sipos, John
Package making
Apparatus for contraction of cover by stretching or shrinking
53588, 53441, B65B 1304
Patent
active
045245681
ABSTRACT:
A rotatable film wrapping apparatus for wrapping a load on a conveyor with an overwrap of stretched plastic film web, having a film web pre-stretching mechanism which is provided with a constant torque by a power assistance mechanism. The power assistance mechanism comprises a stationary ring adjacent a rotary ring on which the film roll and pre-stretch mechanism are mounted, and a friction roller on the rotary ring which contacts the stationary ring to transfer rotational energy to the pre-stretch device as the rotary ring rotates. The pre-stretch mechanism comprises a downstream roller across which the film is drawn to the load at a speed which varies, and an upstream roller linked by gears to the downstream roller so that the upstream roller rotates at a fixed fraction of the speed of the downstream roller to stretch film between the rollers. The energy of the friction roller is transferred through an adjustable constant torque device to the pre-stretch mechanism without controlling the speed of the pre-stretch mechanism, and since a constant torque is added to the pre-stretch mechanism, the force on the film to the load can be substantially reduced while allowing the pre-stretch drive to speed up and slow down according to the film demand from corners or changing load size. This permits higher levels of stretch, faster payout speeds, and use of less uniform film than were thought possible previously. Relatively centered loads with minimum corner protrusion may be wrapped without the constant torque device by a proper selection of gears such that the downstream roller surface speed is driven slightly below the average relative surface speed of the load.
REFERENCES:
patent: 4050220 (1977-09-01), Lancaster
patent: 4302920 (1981-12-01), Lancaster
patent: 4317322 (1982-03-01), Lancaster
patent: 4387552 (1983-06-01), Lancaster
Lancaster Patrick R.
Lancaster William G.
Lantech Inc.
Sipos John
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