Transverse heat-sealing apparatus for continuous shrink film packaging
AssigneeE.I. du Pont de Nemours and Company
InventorsFrederick H. Fiesser, Robert V. Jeral
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Abstract
An apparatus which produces consistent transverse seals in a continuous shrink film packaging operation to package trays is disclosed. The seals are consistent as a result of constant sealing dwell-time, and are also consistently positioned with respect to the trays. Neat, leak-free packages are produced after shrinking. The apparatus is particularly useful for packaging trays of moisture-containing food products such as chicken parts.
Claims4
A transverse sealing apparatus which forms part of a continuous packaging machine which utilizes shrink film, the apparatus adapted to producing constant transverse seal dwell-times, the apparatus comprising:
- (i) a conveyor belt system consisting of a conveyor belt movable in a cyclic path over a plurality of rollers, one roller being a drive roller and the other rollers being idler rollers, the cyclic path having a horizontal portion which conveys filled trays continuously enclosed within a continuous shrink film tube along it, sections of the tube between trays undergoing a transverse seal during movement along the horizontal portion, the horizontal portion having two sections with a gap inbetween, the gap providing access for the transverse seal operation;
- (ii) a seal-head which spans the horizontal portion of the cyclic path, the seal-head being capable of moving horizontally, reciprocally along the horizontal portion, firstly in the machine direction at the same speed as the trays and conveyor-belt moves, during which time sealing occurs, and secondly back to its starting position, a plurality of idler rollers being attached to the seal-head and movable with it, those idler rollers positioned to provide the gap in the path of the conveyor-belt;
- (iii) an upper sealing-bar and a lower sealing-bar housed within the seal-head, the bars moving vertically down from above and vertically up from below respectively, the conveyor belt, the movements of the sealing-bars forcing together the tube surface between each tray consecutively, so as to form a bead-seal either side of the sealing bars when the sealing-bars contact, the sealing-bars also heat-severing the tube between the bead-seals resulting in a bead-seal at the back of tray ahead of the sealing-bars and a bead-seal in front of tray before the sealing-bars, the sealing producing sealed bags around each tray;
- (iv) a first sensor for monitoring the time contact of sealing bars occurs, at which time sealing begins;
- second sensor means to detect the position of the trailing end of a first tray and the leading end of the following tray which determines the conveyor belt speed and point of contact for the sealing bars;
- (v) computer means, based on sealing-bar contact time and conveyor-belt speed input, to provide a length of travel of the seal-head in the machine direction during which the bars are in contact and sealing is occuring, that length being proportional to the tube speed, thereby providing a constant sealing dwell-time.
Dependencies are inferred from the claim text.