METHOD OF FEEDING WRAPPING MATERIAL IN A PRODUCT PACKAGING MACHINE, AND A RELATIVE FEED UNIT

Abstract

Wrapping material is supplied to the folding stations of a packaging machine, such as a cigarette packer, by a method that includes a step of dividing a continuous strip of multilayer material into single leaves, and a step of feeding the leaves to a wrapping unit; the step of dividing the continuous strip into leaves combines a first stage in which a partial cut is made in the strip by means of a laser device, leaving at least one layer of the multilayer strip intact, and a second stage in which a single leaf is detached by means of a tear device, separating along a score line created by the partial cutting step.

Description

This application claims priority to Italian Patent Application BO2009A000453 filed Jul. 15, 2009, the entirety of which is incorporated by reference herein.

BACKGROUND OF THE INVENTION

The present invention relates to a method of feeding wrapping material in a product packaging machine, and to a feed unit for implementing such a method.

Conventional units of the type in question comprise means by which a continuous strip of paper material is decoiled from a roll, a cutter device by which the strip is divided into discrete leaves, and feed means by which the single leaves are supplied to a unit or line for wrapping products, such as groups of cigarettes, by way of example.

In conventional feed units, the cutter device generally comprises a pair of counter-rotating rollers equipped with blades, stationed along the path followed by the continuous strip and placed as close as possible to the wrapping line.

This type of placement is preferable, in order to avoid transferring the leaves along relatively long feed paths, though not always easily accomplished due to the dimensions and general layout of the machine.

Self-evidently, in effect, long transfer distances dictate the use of highly complex and costly guidance and inspection systems, needed in order to ensure that the leaves are handled gently and positioned correctly at the moment of initial contact with a relative product directed onto the wrapping line.

In addition to this drawback, there is the fact that the blades used in cutting devices of the aforementioned type require frequent sharpening and replacement.

It is also a common practice to use multilayer wrapping materials in packaging machines of the type referred to above.

Materials of this type afford distinctive properties in terms of strength, appearance and tightness by virtue of their multilayer construction, consisting for example in a layer of paper material and at least one layer of thermoplastic material.

The object of the present invention is to provide a method of feeding wrapping material in a product packaging machine such as will be unaffected by the drawbacks mentioned above in connection with the prior art, which derive from the enforced positioning of a relatively bulky cutting device in close proximity to the wrapping line of the machine.

A further object of the present invention is to provide a unit capable of implementing the method disclosed.

SUMMARY OF THE INVENTION

The stated objects are duly realized in a method according to the invention for feeding wrapping material in a product packaging machine, which includes a step of dividing a continuous strip of multilayer material into single leaves, and a step of feeding the leaves to a wrapping unit; the step of dividing the continuous strip into leaves combines a first stage in which a partial cut is made in the strip by means of a laser device, leaving at least one layer of the multilayer material intact, and a second stage in which a single leaf is detached by means of a tear device, separating along a score line created by the partial cutting step.

The stated objects are realized similarly in a feed unit according to the invention, comprising a laser device by which weakening lines are scored in the continuous strip at intervals corresponding to the length of the single leaves, and a tear device, located in close proximity to the wrapping unit of the packaging machine, comprising first and second pairs of rollers rotating substantially tangential one to another, with the rollers of the second pair driven at a tangential velocity greater than that of the rollers of the first pair in such a way as to separate the single leaves forcibly along the score lines.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in detail, by way of example, with the aid of the accompanying drawings, in which:

FIG. 1 is a schematic front view of a unit for feeding wrapping material according to the present invention;

FIG. 2 shows a detail of FIG. 1, enlarged and illustrated in cross section;

FIG. 3 shows the detail of FIG. 2, viewed in perspective.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIG. 1, numeral 1 denotes a product packaging machine, for example, a cigarette packer designed to wrap products 2 consisting in groups of cigarettes illustrated schematically as parallelepiped blocks.

The machine 1 comprises a frame 3 of which the front presents a vertical bulkhead 4 and, mounted to the bulkhead, a unit or device 5 by which wrapping material is fed to a wrapping unit, or wrapping line 6, in receipt of products 2 advancing along a horizontal conveyor 7.

The feed unit 5 comprises a shaft 8 disposed transversely to the bulkhead 4, carrying a roll 9 from which a continuous strip 10 of wrapping material is decoiled along a path P established by a plurality of guide rollers 11a, 11b and 11c, ordered along a feed direction indicated by the arrow denoted F in FIG. 1 and rotatable about axes parallel to the axis of the shaft 8.

The advancing strip 10 is cut partially at a position denoted 12, lying between two of the aforementioned rollers 11a and 11b, by a laser device illustrated schematically as a block denoted 13.

Located at a further position 14 downstream of the guide roller denoted 11c, along a vertical leg of the feed path P, is a tear device 15 by which single leaves 16 are separated from the continuous strip 10 and released to the wrapping unit 6, where each one will be wrapped around a respective product 2.

The tear device 15 comprises a first pair of rollers and a second pair of rollers, denoted 17 and 18 respectively. The rollers of each pair 17 and 18 rotate substantially tangential one to another, with the rollers of the second pair 18 driven at a tangential velocity greater than that of the rollers of the first pair 17.

With reference in particular to FIGS. 2 and 3, the strip 10 of wrapping material decoiled from the roll 9 is of multilayer construction, comprising a layer 19 of paper material and a layer 20 of polypropylene and, sandwiched between the two, a layer 21 of polyethylene terephthalate.

Polyethylene terephthalate (PET) is a thermoplastic resin especially suitable for use in contact with food products, which also has the property of being substantially insensitive at least to certain frequencies utilized by laser cutting devices.

In operation, as the strip 10 passes through the partial cut position 12, it is exposed to the action of the laser device 13 at regular intervals, according to the length of the single leaves 16; more exactly, the laser beam will score a line 22 across the strip, cutting through the layer 19 of paper material and penetrating only as far as the PET layer.

These score lines 22 made by the laser device serve to weaken the strip 10, so that when drawn along a further leg P1 of the feed path P and into the position denoted 14, it will be separated at the weakened areas by the tear device 15 into a succession of single leaves 16.

Adopting a method and a unit 5 for feeding strip material according to the invention, in contrast to methods typical of the prior art, the device 13 employed to make a partial cut in the strip 10 of wrapping material can be positioned at any convenient distance from the wrapping unit, and the single leaves 16 of material also fed correctly to the wrapping line 6 without the need to install complex guidance and inspection systems.

Claims

1) A method of feeding wrapping material in a product packaging machine, including a step of dividing a continuous strip of multilayer material into discrete leaves, and a step of feeding the leaves to a wrapping unit, wherein the step of dividing the continuous strip into leaves combines a first step in which a partial cut is made in the strip by means of a laser device, leaving at least one layer of the multilayer material intact, and a second step in which a single leaf is detached by means of a tear device, separating along a score line created by the partial cutting step.

2) A method as in claim 1, including a step of feeding the continuous strip along a predetermined path subsequent to the partial cutting step and prior to the step of detaching the discrete leaf.

3) A unit for feeding wrapping material in a product packaging machine, operating by the method as in claim 2, wherein the multilayer strip comprises a layer of material substantially insensitive to the cutting frequencies used by the laser device.

4) A feed unit as in claim 3, wherein the tear device comprises a first pair of rollers and a second pair of rollers, the rollers of each pair rotating substantially tangential one to another, and the rollers of the second pair rotating at a tangential velocity greater than that of the rollers of the first pair.

5) A feed unit as in claim 3, wherein the layer of material insensitive to laser frequencies is polyethylene terephthalate (PET).

6) A feed unit as in claim 5, wherein the strip comprises an outer layer of paper material.