Method of operating a packaging machine

Abstract

The invention relates to a method of operating a packaging machine for wrapping packaging trays for foods using a packaging film, in particular a plastic film, in which the film is supplied to a holding mechanism having two holding means spaced apart from one another to hold the supplied film at two mutually oppositely disposed sides; in which the spacing of the two holding means from one another is then adjusted: and in which a supplied tray is subsequently pressed toward the supplied film by lifting from below, wherein the holding mechanism is adjusted such that the spacing of the two holding means from one another is reduced.

Claims

1. A method of operating a packaging machine for wrapping packaging trays for foods using a packaging film, the method comprising the steps of: supplying the packaging film to a holding mechanism, wherein the holding mechanism comprises two holding means spaced apart from one another to hold the supplied packaging film at two mutually oppositely disposed sides, and wherein the packaging film is held between the two holding means at a first distance; adjusting a spacing of the two holding means from the first distance to a second distance shorter than the first distance so that the packaging film held between the two holding means is caused to sag downwardly towards a packaging tray below the packaging film; and after the packaging film is caused to sag downwardly, lifting the packaging tray from below toward the sagging packaging film in order for the packaging tray to contact and press against the sagging packaging film.

2. The method in accordance with claim 1, wherein a degree of reduction of the spacing of the two holding means from one another is based on a packaging tray type and/or on at least one dimension of the supplied packaging tray.

3. The method in accordance with claim 1, wherein a degree of reduction of the spacing is based on a height and/or a base surface area of the supplied packaging tray.

4. The method in accordance with claim 1, further comprising a step of automatically recognizing a packaging tray type of the supplied packaging tray.

5. The method in accordance with claim 4, wherein the step of automatically recognizing the packaging tray type of the supplied packaging tray is carried out by means of one of a camera and a light barrier.

6. The method in accordance with claim 1, further comprising a step of automatically determining at least one dimension of the supplied packaging tray.

7. The method in accordance with claim 6, wherein the step of automatically determining at least one dimension of the supplied packaging tray is carried out by means of one of a camera and a light barrier.

Description

(1) In this respect, the only FIGURE, FIG. 1, shows a schematic representation of a film packaging machine 1 in accordance with the invention. A schematic plan view is shown in the upper part of the FIGURE and a side view of the packaging machine 1 is shown in the lower part of the FIGURE.

(2) The packaging machine 1 comprises a film dispensing device 217, a film supply device 216, a film transport device 214, and a film cutting device 215 arranged between the film supply device 216 and the film transport device 214. A roll of a packaging film K, in particular of a plastic film, can be placed into the film dispensing device 217 and can be held there by a film holder or roll holder. An unwound end of the film K can then be transferred to the film transport device 214 by means of the film supply device 216.

(3) The film transport device 214 has two belt conveying devices 201 and 22 that are arranged spaced apart in parallel with one another to convey the supplied film K to two mutually oppositely disposed sides in a direction of transport X until the front edge of the film K has arrived at the end of the film transport device 214 at the front viewed in the direction of transport X, whereupon the film transport is stopped and the film K is cut off from the remaining film roll via the film cutting device 215.

(4) The belt conveying devices 201 and 202 are furthermore configured to hold the film K, in particular the cut-off film, clampingly at the two mutually opposite sides. For this purpose, for example, lifting actuators, not shown, can be provided such as are generally known from the prior art.

(5) The film transport device 214 is configured such that the spacing of the two belt conveying devices 201 and 202 from one another is adjustable. To adjust the mutual spacing, the first belt conveying device 201 or the second belt conveying device 202 or both belt conveyor devices 201 and 201 can be moved simultaneously transversely to the film transport direction X, in particular by means of a motor drive that is controlled by a monitoring unit of the packaging machine 1.

(6) The packaging machine 1 furthermore has a supply belt 102 via which packaging trays P to be wrapped with the film K and having food products located therein can be supplied to a lifting table 105 of the packaging machine 1. The lifting table 105 is configured to transport a respective tray P upwardly to the film K held in the film transport device 214 such that the tray P is pressed toward the tray K from below such that the film K is automatically laid around the tray P during the lifting procedure.

(7) To be able to use the packaging machine 1 for packaging trays P having high unstable side walls without crushing the weak packaging trays P during the pressing toward the film K, provision is made in accordance with the invention to reduce the mutual spacing of the two belt conveying devices 201 and 202 such that the film K that is spanned between the two belt conveying devices 201 and 202 sags at least slightly. Unlike as known from the prior art, the film K is therefore not pretensioned by increasing the spacing between the two belt conveying devices 201 and 202, but a sagging of the film K is rather intended. When the tray P is pressed toward the film K from below, a resistance exerted by the film K can therefore be minimized, with it not necessarily having to be precluded in this respect that the film K may be very slightly tensioned after the lifting of the tray P.

(8) A camera 103 with which different tray types can be recognized is provided in the run-in region of the supply belt 102. On the basis of the recognized tray type, a determination can then be made as to how much the spacing of the two belt conveying devices 201 and 202 has to be reduced to achieve a sufficiently great sagging of the film K for the respective tray type. Such an association between the tray type and the spacing reduction can be stored in a memory of the packaging machine 1. Alternatively or additionally, a light barrier 104 can be provided to determine the height of the supplied trays P, with a conclusion likewise being able to be drawn on the amount of the required reduction of the spacing from the determined height. The spacing can in particular be reduced the more, the greater the height and/or the base surface of the supplied tray P is. The light barrier 104 can in another respect also additionally be used to trigger a start signal for the packaging process.

(9) For the further wrapping of the packing trays P, the film K is led downwardly around the tray P at the sides and at the rear by means of lateral folding tongs 108a and 108b as well as by a rear folding tong 110 after the lifting of the packaging tray P and is folded beneath the tray P or beneath the base of the tray P. The tray P is subsequently pushed out of the film packaging zone by means of a pusher 109 onto a sealing plate 107, whereby the front end of the film K is also folded beneath the tray P. The sealing plate 107 is heated to a temperature at which the ends of the film K folded beneath the tray P are welded to one another and/or sealed.

(10) The packaged tray P can subsequently be transported via a transverse conveyor belt 106 to a labeling apparatus, not shown in the FIGURE, and can be provided with a label. A scale 101 is arranged beneath the supply belt 102 for this purpose and the weight of the supplied packaging trays P having the food products can be determined by it. A printer connected to the scale 101 can then print a label on which the weight of the filled tray P is indicated. The labeling apparatus takes over the label from the printer and applies it to the packaged tray P.

(11) A plastic film that is stretchable, i.e. a so-called stretch film, can be used as the packaging film. This film is thermoplastic and can be sealed or welded at a high temperature. The thickness of the film is typically in a range between 10 m and 60 m.

REFERENCE NUMERAL LIST

(12) 1 packaging machine

(13) 101 scale

(14) 102 supply belt

(15) 103 camera

(16) 104 light barrier

(17) 105 lifting table

(18) 106 transverse conveyor belt

(19) 107 sealing plate

(20) 108a lateral folding tong

(21) 108b lateral folding tong

(22) 109 pusher

(23) 110 rear folding tong

(24) 201 belt conveying device

(25) 202 belt conveying device

(26) 214 film transport device

(27) 215 film cutting device

(28) 216 film supply device

(29) 217 film dispensing device

(30) K packaging film

(31) P packaging tray (having the food product)

(32) X direction of transport