GB2075419A

GB2075419A - Producing bags of plastics foil

Info

Publication number: GB2075419A
Application number: GB8015276A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-05-08
Filing date: 1980-05-08
Publication date: 1981-11-18

Abstract

For producing plastics bags with printing on both sides, a double-layer sheeting is simultaneously printed from the top and bottom and taken up, on a reel 5. One layer (3) is fed to folding means 10 and carried to a single-path bag welder 11. The second layer (4) is temporarily wound up on a reel (8) for later use in the bag welder. The double layer may be a tube or folded web the sides/side of which are trimmed off to form two separate webs. <IMAGE>

Description

SPECIFICATION A method and an apparatus for producing bags of plastics foil The present invention relates to a method of producing bags of plastics foil comprising imprints on both outer sides, whereby a double-layer sheeting is carried through a printing apparatus, in which imprints are printed on the upper layer from the top at the same time as imprints are printed on the lower layer from the bottom, whereafter the sheeting is longitudinally divided to form two sheetings, each sheeting being transversely welded in a bag welder and cut up into individual bags.

By using a double-layer sheeting and by printing the imprint simultaneously from the top and the bottom, the printing time has been halved compared to the printing time necessary by the usual single-layer bag production. By the usual method, a single-layer sheeting is provided with imprints on one side and subsequently folded into a V-shape and carried to the bag welder. In order to render is possible for the reduced printing time obtained by the simultaneous top and bottom printing, to involve a corresponding increase of the production velocity of the bags, the printed sheeting has previously been carried through a double-path bag welder, wherein both layers have been longitudinally cut up along the central line, and the two double-layer sheetings are welded and divided into two rows of bags opposing each other two by two in the transverse direction.The double-path bag welder necessary for such a method is very expensive and takes up much room. Furthermore as the method requires that the front sides of the bags in both rows are printed from the same side, e.g. from the top, in the printing apparatus, and all the rear sides are printed from the opposite side, i.e. from the bottom, all the bags are uniform, i.e. that they must be produced in a rather high stock in order to make the production profitable.

By the present invention a surprisingly simple method is provided, whereby the advantages of a simultaneous top and bottom printing by the bag production are particularly favourable since the method is made applicable in connection with a usual relatively inexpensive single-path bag weider. Furthermore, it is rendered possible to obtain a more flexible production whereby two sets of bags requiring different prints and optionally of two different dimensions, may be produced by the same reel of double-layer sheeting.

The method according to the invention is characterised in that the double-layer, printed sheeting is divided by the two layers being pulled apart in their respective directions by a pull in the longitudinal direction of said layers, whereby they form two single-layer sheetings, one of said sheetings being folded into a V-shape with the printed side turning outwards and carried directly to a single-path bag welder, whereas the second single-layer sheeting is wound up on a reel subsequently used as a feeding reel, the material being unwound from said reel and folded into a V-shape and then carried to the bag welder.

Such a method utilizes to a great extent the advantage of the reduced printing time obtained by using the front and rear side printing method without requiring an expensive, double-path bag welder. This is rendered possible by the fact that the single-layer sheeting temporarily wound up on a particular reel may be folded into a V-shape and carried through the single-path bag welder in immediate continuation of the first single-layer sheeting. The method according to the invention also permits performing of one print on the upper layer of the double-layer sheeting and a second print on the lower layer. As a result two different types of bags may be produced whereby the usual minimum requirements for a profitable production by the usual double-path technique may be considerably reduced.Moreover it is rendered possible to use two different strokes at welding of the two layers in the double-layer sheeting and thereby to obtain two different bag widths from the same sheeting.

At the production, a double-layer sheeting comprising two single sheetings on top of each other, a flattened foil hose or a sheeting folded into a V-shape, may be used in a usual manner. In the latter two cases, the sheeting is trimmed in both sides of the sheeting or in one side only before pulling the layers apart. Usually the sheeting is, however, trimmed in both sides.

The invention also relates to an apparatus for producing bags of plastics foil by the above method, said apparatus comprising a single-path bag welder, bearing means for a feeding reel with sheet material and guiding and folding means adapted to fold a sheeting unwound from the feeding reel into a V-shape and carry said sheeting to the bag welder. According to the invention this apparatus is characterised in that it comprises bearing means for an extra reel and guiding means adapted to unwind in one direction one layer of a double-layer sheeting located in the bearing means of the feeding reel and under tension to carry it to winding on the extra reel at the same time as the second layer is unwound in another direction and carried to the bag welder through the guiding and folding means.

Such an apparatus, which may be produced far inexpensively than a double-path bag welder, permits a quick and reliable production of a large number of bags from a double-layer sheeting by the method according to the invention.

The invention will be described below with reference to the accompanying drawing, in which Fig. 1 is a perspective view of part of a doublelayer sheeting partly wound up, Fig. 2 is on a smaller scale a cross-sectional view through the sheeting of Fig. 1, Figs. 3 and 4 are cross-sectional views through two other embodiments of double-layer sheetings, which may be used by the method according to the invention, and Fig. 5 is a diagrammatic view of an apparatus for carrying out the method according to the invention.

A double-layer-sheeting 1 may comprise two layers of plastic located on top of each other, cf.

Fig. 2. The sheeting is carried through a printing apparatus not shown, in which the sheeting is provided with imprints from the top and from the bottom at the same time. The upper layer 3 is provided with imprints referred to by roman numerals. The roman numerals I, 11, III refer to imprints on the front side of the bags, whereas the roman numerals 1', íí', III' refer to imprints on the rear sides of said bags. It appears that the front and rear side of the same bag opposes each other in the transverse direction of the sheeting.

Correspondingly, the second layer 4 of the sheeting is provided with imprints A, B, C, D referring to the front sides of the bag and opposite these sides in the transverse direction of the sheeting the imprints A', B', C', D' referring to the rear sides of the said bags are provided.

In Fig. 2 the imprints are indicated by dotted lines.

The double-layer sheeting is wound up on a main reel subsequently used as a feeding reel 5 for a bag welder. The outer layer 4 is unwound in an upward direction, cf. Fig. 5, and carried to a reel 8, up on which it is wound. The inner layer 3 of the sheeting is unwound in a downward direction through a bypass reel 9 and on in an upward direction through a folding bench 10. At this folding bench the sheeting formed by the layer is folded over a longitudinal central line in such a manner that the cross section thereof is V-shaped.

In this shape, the sheeting is carried into a bag welder not shown but indicated by the reference numeral 11, in which the sheeting in a usual manner is welded and cut in the transverse direction to form individual bags. It is to be understood that a usual single-path bag welder may be reconstructed according to the principle illustrated in Fig. 5.

The reel 8 and the sheeting layer 4 wound thereon may subsequently be used as a feeding reel for the bag welder.

It appears from the above and from the drawing that the double-layer sheeting 1 is divided into two single sheetings independent of each other concerning the printing in such a manner that the same printing apparatus may at the same time include imprints for various types of bags, whereby the use of the equipment is more flexible.

Instead of the double-layer sheeting illustrated in Fig. 2, a sheeting may be used which is formed by a single-layer sheeting, cf. Fig. 3, bent over a central line 2, whereby the cross section of the double-layer sheeting is V-shaped. Before the reel 5 is unwound, a trimming along the line 6 in Fig. 3 is performed, whereby the double-layer sheeting is divided into two single-layer sheetings. Often a trimming is performed in the other side as indicated at the line 7.

Fig. 4 illustrates an alternative embodiment of a double-layer sheeting, said embodiment comprising a flattened hose which besides is printed in the same manner as indicated in Figs. 1 to 3. The double-layer sheeting is divided by trimming along the lines 7 in such a manner that two independent single-layer sheetings are formed corresponding to the layers 3 and 4 in Figs. 2 and 3. After the trimming the method is performed in the same manner as explained under the reference to Fig. 5.

Claims

1. A method of producing bags of plastics foil comprising imprints on both outer sides, whereby a double-layer sheeting is carried through a printing apparatus, in which imprints are printed on the upper layer from the top at the same time as imprints are printed on the lower layer from the bottom, whereafter the sheeting is longitudinally divided to form two sheetings, each sheeting being transversely welded in a bag welder and cut up into individual bags, characterised in that the double-layer printed sheeting is divided by the two layers being pulled apart in their respective directions by a pull in the longitudinal direction of said layers, whereby they form two single-layer sheetings, one of said sheetings being folded into a V-shape with the printed side turning outwards and carried directly to a single-path bag welder, whereas the second single-layer sheeting is wound up on a reel subsequently used as a feeding reel, the material being unwound from said reel and folded into a V-shape and then carried to the bag welder.

2. An apparatus for producing bags of plastics foil by the method as claimed in claim 1 and comprising a single-path bag welder, bearing means for a feeding reel with sheet material and guiding and folding means adapted to fold a sheeting unwound from the feeding reel into-a V-shape and carry said sheeting to the bag welder, characterised in that it comprises bearing means for an extra reel and guiding means adapted to unwind in one direction one layer of a double-layer sheeting located in the bearing means of the feeding reel and under tension to carry it to winding on the extra reel at the same time as the second layer is unwound in another direction and carried to the bag welder through the guiding and folding means.

3. A method substantially as described above with reference to the accompanying drawing.

4. An apparatus substantially as described above with reference to the accompanying drawing.