Methods of and devices for continuously packaging articles in thermoshrinkable plastics film

Claim 5

A method according to claim 1, including the steps of: forming an upwardly arched loop of said lower film material rearwardly of each collection of articles, at said feed staion, prior to deposit of the next succeeding collection on said film; and wherein said heat sealing step is performed by heat sealing said upper film to the crest of said loop.

Claim 6

A method according to claim 1 wherein said lower and upper films are continuously fed to said feed station, without cutting, and are of a width exceeding the dimensions of the collections measured transversely of said path so that they project beyond these collections laterally of said path.

Claim 7

A method according to claim 2 wherein said arched loop of lower film is formed rearwardly of one collection of articles and the succeeding collection is placed and maintained on said lower film in position to hold said loop.

Claim 8

A method according to claim 2 wherein the arched loop of said lower film between two collections is formed so that its height is less than the height of each collection of articles so that, during the heat-sealing step the joint between said films is situated in a region at the front and rear sides of each collection between the top and bottom thereof.

Claim 11

A device according to claim 6 wherein said conveyor is an endless chain conveyor having equidistantly spaced pivotally mounted trays thereon on transverse axes, and means for holding said trays horizontally oriented throughout the length of said path.

Claim 12

A device according to claim 7, wherein said last-named means comprise crank arms fixed to said trays and having guide rollers fixed to their free ends, and track means adjacent said path and so configured to engage said rollers and maintain the trays in a horizontal position at all times in the upwardly directed and downwardly directed portions of said path, each tray having further rollers so positioned as to run along horizontal portions of said track means and to maintain each tray in the horizontal position along horizontal portions of said path.

Claim 13

A device according to claim 6, wherein said upwardly and downwardly directed portions of said path and said recited horizontal portion are generally in the form of an inverted open U, one of the arms of this U being sleeved by a hot air tunnel, constituting an ascending thermoshrinkage zone, while the other arm is open to the surrounding air but having above it a cooling assembly which subjects it to cold air ventilation and constitutes a descending cooling zone, at the exit from which the articles are sufficiently rigid to be capable of being handled.

Claim 14

A device according to claim 9 wherein: said upwardly directed portion of each path is of very steep slope, and saiD downwardly directed portion is of a lesser slope.

Claim 15

A device according to claim 9 wherein said hot air tunnel, comprises means defining three consecutive heating zones, the first or preheating zone being at the entry portion thereof, the second or progressive thermoshrinkage zone proper extending along said upwardly directed portion of said path and commencement of the upper horizontal portion of said path, and the third or thermoshrinkage finishing zone extending along said upper portion.

Claim 16

A device according to claim 9 wherein said tunnel includes, at its lower part, an air ventilation assembly opening into the commencement of the ascending portion close to the preheating zone; said thermoshrinkage zones including lateral groups of resistance heaters distributed therein and, in its upper portion, an air ventilation assembly opening into the finishing zone and, within this finishing zone, lateral groups of resistance heaters.

Claim 17

A device according to claim 12 wherein said first-named ventilation assembly comprises at least one blower, of the suction and delivery type, arranged to feed air upwards onto the groups of resistance heaters to provide progressively hotter air to the collections as they ascend and to re-extract this hot air at the ceiling of the ascending portion, by means of a recycling duct extending beneath the ceiling and descending to the blower along the internal walls of the ascending portion, the portion of this duct beneath the ceiling being provided with numerous intake holes.

Claim 18

A device according to claim 12 wherein the last-named ventilation assembly comprises at least one blower, of the suction and delivery type, arranged to feed air upwards onto the groups of resistance heaters to provide hot air to the collections advancing through the finishing zone towards the exit from the tunnel, and to re-extract this hot air at the ceiling of this zone, by means of a recycling duct extending beneath the ceiling of the upper part of the tunnel and descending to the blower along the internal walls of the upper portion, the portion of this duct beneath the ceiling being provided with numerous intake holes.

Claim 19

A device according to claim 14 wherein the resistance heaters are in the form of finned resistance heaters and are arranged in tiers all along the internal lateral walls of the tunnel, both in its ascending portion and in its upper portion and are placed in front of the descending hot air recycling ducts, towards the median plane of the tunnel, in order to ensure good heat distribution.

Claim 20

A device according to claim 15 wherein each ventilation assembly is arranged to deliver air into ducts having resistance heaters therein; said ducts, in the ascending portion of the tunnel, being situated in front of the recycling ducts towards the median plane of the tunnel and being perforated, in the side towards this plane, to constitute a hot air blowing chamber having perforated lateral and lower walls, the ceiling of which is traversed by the perforated portion of the recycling duct and, in the upper part of the tunnel, being situated in the same manner but to constitute a hot air blowing chamber completely surrounding the finishing zone and having perforated lateral, upper and lower walls, the perforated portion of the recycling duct being situated beneath the ceiling of this upper part of the tunnel, in front of the chamber and close to the exit from the tunnel, this tunnel being, in addition, provided with a lock at its entry and at its exit, in the form of hanging, slotted curtains, to permit the passage of the trays and their collections of articles, in order to limit the hot air losses.

Claim 21

A device according to claim 16 wherein the descending portion of said path, in which cooling is carried out, is situated so as to be exposed to the surrounding air and having thereabove a cooling assembly constituted of a ventilation assembly arranged to direct jets of cold air onto each of the collections having shrunk wrappings to accelerate their cooling.

Claim 22

A device according to claim 17 wherein each tray of the conveyor is constituted of ribs for supporting the article resting upon it, said ribs extending parallel to the direction of travel of the conveyor and parallel to one another, separated from one another by a gap exceeding the width of each arm of each of fixed forks and slightly higher than the height of said arms, whereby the upper plane of said ribs are slightly above that of a fork when they are brought by their respective tray to the horizontal at the feed and discharging stations, so that at the feed fork they raise and entrain the lower film with an article resting upon it and that at the discharge fork they lower and deposit the article with its shrunk wrapping upon the fork, without ever completely passing through the arms of these forks.

Claim 23

A device according to claim 18 wherein said oscillating device comprises a balance arm supporting an upper jaw and a lower jaw reciprocating with their respective heat sealing and cutting blades opposite each other, means for actuating said jaws so that, when their balance arm is inclined in the direction opposite to the direction of motion of the conveyor, they grip between them the upper and lower films between two successive articles, heat seal them and cut their joint during the oscillation of the balance arm in the direction of motion of the conveyor, when it is substantially in a position close to its median vertical position, they open and move apart from each other when the balance arm continues its oscillation in the same direction until the lower jaw is at a lower position close to the axis of oscillation of the balance arm and the upper jaw is at a position above the collections, this upper jaw then lowering the upper film onto the collection of articles to be wrapped while the balance arm makes its reverse oscillation to return to its initial position, at which instant the lower jaw bears up against the underside of the loop of lower film and the upper jaw bears down on the upper film so as to place it onto the top of this loop, gripping the films, and repeating the described cycle of operations.