GB2160173A - Bag - Google Patents

Abstract

A bag (10) of plastics sheet material film has two suspension holes (13, 13a) in the proximity of a rim (14) ofa filling opening of the bag. A slit (15, 15a) extends towards each hole from the rim (14) and a web (16, 16a) is present between each slit and the associated hole. <IMAGE>

Description

SPECIFICATION Bag The present invention relates to a bag, especially a bag of plastics sheet material.

Tear-off bags are known with two suspension holes in the proximity of the edge of a filling opening of the bag, such holes initially having two functions. Since bags are stacked after their manufacture so that they can be packaged in stack form, it has been proposed that the bags be impaled on pins to facilitate formation of the stack. In addition, the holes can receive pins in order to hold the bags at a point of sale, whereby one bag at a time can be manually removed from the pins so that the bag can be filled with sold goods. Similar pins are also used in manufacturing enterprises for holding such bags during filling with goods as diverse as bread and nappies. The withdrawal of the bags from the pins can be effected by guiding individual bags up off the pins or, in the case of bags lying on a table, by lowering the pins.

Both measures are awkward and require a precision device insofar as withdrawl does not take place manually.

It is also possible to forcibly draw the bags from the pins in a plane which is perpendicular to the longitudinal extent of the pins and in that case to tear open the web portions between the holes and the edge of the bag. This requires a certain force, which could be provided mechanically.

In practice, however, it is extremely difficult to produce holes at a constant spacing from the bag edge, because perforation of the bags for production of the holes is usually undertaken before transverse welding and severing of individual bags from a tube of sheet material. Since this spacing between the holes and the edge is difficult to keep constant, different degrees of force, depending on the particular spacing, are necessary to tear the bags from the pins. Since most such bags have perforations in two sheet layers, the force required to tear the web portions is correspondingly twice as great. At the same time, any variations in the width of the web portions is doubled in magnitude.

For these reasons, the separation of the bags from suspension pins can be difficult.

There is therefore a need for a bag which can be pulled off pins with relatively little force and with a force which can be substantially constant.

According to the present invention there is provided a bag of plastics sheet material provided in an end portion thereof with two spaced apart holes for reception of bag retaining elements and with a respective incision so extending from the edge of the bag at said end portion and towards each hole as to leave a tearable web portion between that hole and the free end of the incision.

In a preferred embodiment, the holes are present in the proximity of a rim forming a filling opening, an incision is present between each hole and the rim of the bag, and a web portion is present between the incision and the hole. A defined weak place is thus present between the holes and the filling rim of the bag and can be destroyed on the application of a certain force so as to allow the bag to be drawn off the retaining elements, for example pins, in a plane perpendicular to the longitudinal axes of the pins.The defined weak place consists of the web portions which, independently of the spacing of the holes from the rim of the bag, can have a constant dimension, because different spacings of the holes from the rim can be compensated for by adjustment of the length of the incisions, i.e. the dimension of the web portions can remain the same independently of the spacing of the holes from the rim if the incisions have appropriately different lenghts. As a result, bags of this kind can be withdrawn from the pins with constant force.

Preferably, the holes pass through several layers of the sheet material, but the incisions are present in only one layer and the or each other layer has cuts connecting the holes with the rim of the bag.

Consequently, the force for withdrawal of the bag from the pins is independent of whether the holes are present in only one layer or in a plurality of layers, because the web portions are present in only one layer. The or each other layer only contributes a small part of the total withdrawal force.

It is thus possible to arrange the holes in side fold portions of the bag. For example, eight perforations may be present in such a bag, yet the web portions are associated with only two of the perforations.

In place of cuts which connects the rim directly with the holes in all but one of the layers, the perforations in the or each other layer can have the form of recesses of large diameter which communicate directly with the rim.

Apparatus for use in the manufacture of a bag according to the first aspect of the invention may comprise a punching tool provided with dies for cutting the holes in said end portion of the bag and knives for producing the incisions simultaneously therewith.

With such apparatus, the punching of the holes and cutting of the incisions take place in the same operating step. As a result, the web portions have a constant width, yet this width could be varied in order to ensure a constant withdrawal force independently of the sheet material.

In the case of a bag with the holes passing through a plurality of layers of the sheet material, apparatus for use in the manufacture of such a bag may comprise a punching tool provided with dies for cutting the holes in said end portion and knives for producing the incisions and the cuts simultaneously therewith, the knives having lower blades for producing the incisions and parts of the cuts and upper blades for producing the remaining parts of the cuts.

Advantageously, the dies are provided with recesses into which the knives are inserted and secured by, for example, clamping elements such as screws. Preferably, the knives are arranged to be displaceable in the recesses radially of the dies, whereby web portions of different dimensions can be produced In order to facilitate production from a sheet material tube of bags with and without the web portions in different sheet material layers thereof, the apparatus may further comprise a plate which is provided with through passages in the region of the holes to be cut, the plate being locatable in the tube and underneath, for example, side fold portions of the tube.

Embodiments of the invention will now be more particularly described by way of example with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a first bag embodying the invention; Figure 2 is a perspective view of a second bag embodying the invention; Figure 3 is a perspective view of a third bag embodying the invention; Figure 4 is a perspective view of a stack of bags embodying the invention, the bags being held by vertical pins; Figure 5 is a perspective view of a stack of bags embodying the invention, the bags being held by horizontal pins; Figure 6 is a detail of a bag embodying the invention, showing a small spacing of the pin holes from a rim of the bag; and Figure 7 is a detail of a bag embodying the invention, showing a larger spacing of the pin holes from a rim of the bag.

Referring now to the drawings, there is shown in Fig. 1 a bag 10 of thermoplastic plastics sheet material having side walls 11 and 12, wherein the wall 12 is provided in a flat thereof with holes 13 and 13a arranged at a spacing from the end edge 14 of the flap, the edge 14 also representing one half of the rim of a filling opening of the bag. The spacing of the holes 13 and 13a from the edge 14 determines the force necessary to forcibly draw the bag off pins engaged in the holes. A respective incision 15 or 15a extends from the edge 14 towards each hole 13 and 13a and webs 16 and 16a are present between the incisions 15 and 15a and the associated holes 13 and 13a.

The webs 16 and 16a have a constant width, which ensures that a constant force is needed to tear the webs.

In Fig. 2 there is shown a bag which has inwardly folded portions extending up to open and edges 17 of the bag. The holes 13 and 13a pass through all the resulting layers of the bag constituent material at the bag open end, but webs 16 and 16a between the holes and the incisions 15 and 15a are present only in the layer represented by the side wall 12. In the remaining layers, i.e. the folded portions and the side wall 11, the incisions are in the form of cuts connecting the holes 13 and 13a directly with the edge 17 and no webs 16 and 16a are present in these layers.

A similar embodiment is illustrated in Fig. 3. In this case, however, the holes 13 and 13a and webs 16 and 16a are present only in the wall 12. Webs 16 and 16a are absent from the wall 11 as well as from the afore-mentioned folded portions. In this wall and these folded portions, perforations 13 and 13a of greater diameter are provided, the edges of such perforations reaching as far as the edge 17.

Fig. 4 shows that several bags, arranged one on top of the other, are impaled on pins 22 and 23, which extend through the holes 13 and 13a. Also shown are the incisions 15 and 15a, which do not reach as far as the holes so as to leave the webs 16 and 16a. The bags can be drawn off in the direction of arrow 24, whereby the webs 16 and 16a are torn. The webs 16 can be present in one or two sheet layers of each bag. If the bag has more than two sheet layers, they are expediently present in only one or two film layers.

Fig. 5 shows a stack of bags which can be drawn downwardly, in the direction of arrow 25, to tear the webs 16 and 16a.

Figs. 6 and 7 each show a web 16 of a width X.

However, the incision 15 in Fig. 6 has a length Y, whereas that in Fig. 7 has a length Z. By variation of the length of the incision the hole 13 can have a different spacing from the edge 14 of the bag filling opening, this spacing being compensated for by the length of the incision 15 so that the width of the web 16 always remains the same.

Fig. 8 shows that the bags can be produced from a tube and the holes 13 and 13a and incisions 15 and 15a are produced transversely in one line by a tool. A transverse weld 26 and a separating cut 27 can then be applied in a subsequent operating step. The position of the weld and cut can be varied within limits, as it is only necessary for the cut to connect with or cross the incisions 15 and 15a.

The width of the webs 16 and 16a remains constant and is not influenced by the position of the cut.

A cross-section of a fiattened tube usable in the manufacture of the bags of Figs. 2 and 3 is shown in Fig. 9, the tube having side folded portions 18 and 19 at one side and 20 and 21 at an opposite side.

Fig. 10 shows, in section, apparatus for use in manufacture of the bags, the apparatus comprising a punching tool, a plate 28, and a support 34. The punching tool comprises a crossbeam 31 carrying dies 29 and 30 for punching the holes 13 and 13a, and the plate 28 has passages 32 and 33 and is insertable into the tube, particularly between the fold portions 19 and 21 and the lower side wall 12, with the passages 32 and 33 aligned with the dies. The support 34 also has associated passages 35 and 36 so that holes 13 and 13a of different diameter and incisions 15 and 15a of different length can be produced in the walls 11 and 12 and folded portions 18 to 21.

The apparatus is also shown, partly in section, in Fig. 11. When the tube is moved in the direction of the arrow 37, two rollers 38 at the front edge of the plate 28 co-operate, with the interposition of the wall 11 and the folded portions 18 to 21, with a roller 39. The rollers 38 and 39 are provided with appropriate axles. Through this construction, the plate 28 is retained in locally fixed position.

In order to produce the holes 13 and 13a and incisions 15 and 15a shown in Fig. 2, each of the dies 29 and 30 has a circular cutting edge 40. A knife 41, which has a lower cutting edge 42 and an upper cutting edge 43, is fastened to each die. The cutting edges 40 produce the holes 13 and 13a which, according to Fig. 2, have the same diameter in all film layers. The cutting edge 42 of each knife 41 is of shorter length. Since it is spaced from the associated cutting edge 40, a gap is left to yield the web 16 or 16a in the lower wall 12. The further cutting edge 43 of each knife co-operates with the cutting edge 42 in cutting the three upper layers 11, 18 and 19, or 11, 20 and 21, so that altogether a cutting edge of greater length is present and connects directly with the cutting edge 40. This cutting edge of greater length is able to produce the incisions or cuts that are continuous from the holes to the bag edge.

In order to be able to set the width X of the web 16 or 16a independently of the bag sheet material and the thickness thereof, each knife 41 has an elongate hole 44. Each die has a continuous slot so that the respective knife is displaceable therein in the directions of the double arrow 45. The knives are secured in position by screws 46.

If the perforations 13 and 13a are to have different diameters as shown in Fig. 3, each of the dies 30 is stepped and is of smaller diameter in its lower region, so that perforations of small diameter are producible in the lower wall 12 and perforations of greater diameter in the other wall 11 and folded portions 18 to 21.

Claims (6)

1. A bag of plastics sheet material provided in an end portion threof with two spaced apart holes for reception of bag retaining elements and with a respective incision so extending from the edge of the bag at said end portion and towards each hole as to leave a tearable web portion between that hole and the free end of the incision.

2. A bag as claimed in claim 1, comprising a plurality of layers of the sheet material at said end portion, each hole extending through all of the layers but the incisions being provided in only one of the layers, the or each remaining layer being provided with cuts connecting the holes to said edge.

3. A bag as claimed in claim 2, wherein the bag is provided with folded portions in the region of side edges extending between said end portion and à further end portion opposite thereto, the holes being arranged in the folded portions.

4. A bag as claimed in either claim 2 or claim 3, wherein said cuts extend directly from the holes to said edge.

5. A bag as claimed in claim 1, comprising a plurality of layers of the sheet material at said end portion, the holes and the incisions being provided in only one of the layers and the or each remaining layer being provided with recesses which extend from said edge and which are disposed to receive retaining elements received in the holes.

6. A bag substantially as hereinbefore described with reference to any one of Figs. 1 to 7 of the accompanying drawings.