GB2126984A - Sack - Google Patents

Abstract

A coal sack or the like of plastics film material, has hand-holes or means adapted to form hand-holes in the region of the mouth of the sack such that the upper end of the sack can be folded to align the hand-holes forming a single grip or handle for lifting the sack. The hand-holes are preferably inclined across the corners on each face of the sack, at an angle of from 70 DEG to 85 DEG to the machine direction of the film. <IMAGE>

Description

SPECIFICATION A sack This invention relates to a sack, particularly but not exclusively of the kind used for relatively small quantities, typically from 3 to 25 Kg and usually about 10 Kg, of solid fuels or horticultural, chemical and building materials.

Sacks of this kind may be made from a wide variety of materials including paper, textile and plastics materials and multi-layered structures such as laminates and co-extrusions thereof.

Among the problems associated with such sacks is the disproportion between the capacity of the sack and the strength of the material from which the sack is made or can economically be made, this being the cause of tearing particularly in the region of the point at which the sack is lifted.

One object of the present invention is to mitigate this problem without significantly increasing manufacturing costs by resorting to the use of stronger and more expensive materials.

According to this invention we propose a sack having or adapted to form hand-holes disposed around the upper end of the sack adjacent its mouth such that the upper end can, in use, be folded to align the hand-holes so forming a single grip or handle for lifting the sack.

The ability to fold the mouth of the sack to provide a single grip or handle not only facilitates handling in that the sack can be carried in one hand, but also produces a better distribution of the load yielding an improved carrying capacity as compared with conventional sacks.

As stated above, the sack may be made from any of the materials from which conventional sacks are made. We have found the invention especially advantageous when applied to sacks formed from plastics material, particularly blown or cast films, and prefer to use flexible polyalkylene materials particularly low density, linear or high density polyethylene, which may include the usual additives e.g. stabilizers, slip agents, anti-static agents, pigments etc., and may be printed or plain.

In the preferred embodiment, the sack comprises a tube of material one end of which is sealed, by single or multiple heat seals, to form the bottom of the sack and may have gussetted or pleated sides produced by folding-in the side edges of the tubular body to form one or more W-folds prior to closing and sealing the bottom end.

Alternatively, the sack may be made by folding a sheet of material and sealing or otherwise securing the folded sheet to form side and bottom edges of the sack.

Conventional plastics sacks provided with a carrying handle are reinforced either by locally increasing the material gauge or applying a patch through which the handle is cut thus allowing a wide variation in the mechanical properties of the plastics film, particularly yield point, break load and elongation. Although reinforcing patches may be applied to sacks according to the present invention we have found this not to be necessary since an acceptable load distribution can be achieved by appropriate positioning of the hand holes relative to the sack per se and in the case of sacks made from plastics material, the material structure, in particular the machine direction of the plastics film. In the case of sacks formed from tubular film, the machine direction coincides with the direction from the top to the bottom of the sack.

Furthermore, one advantage of the present invention is that by avoiding the need for reinforcing patches in the region of the handholes, the sack is better suited for automatic production and handling during filling thereof.

In general, any number of hand holes may be provided consistent with the requirement that the upper or mouth end of the sack can be folded to align the hand-holes so as to form a single grip or handle.

We prefer the minimum distance between each hand-hole or cut-out and the upper end edge of the sack to be in the range 40-60 mm and the minimum distance between each hand-hole or cut-out and the side fold or seam to be from 1020% of the width of the sack.

A preferred embodiment of sack has four handholes or cut-outs, these being arranged symmetrically with respect to a longitudinal axis of the bag, one in each upper corner of the sack on each face of the sack and such that the cut-outs on one face register with the cut-outs on the other face of the sack.

If desired, for example, to provide greater load carrying capacity, an additional pair of cut-outs may be formed, one in the middle of each of the two faces of the sack adjacent the mouth thereof.

in this latter case, the upper end of the sack is, in use, folded twice to align all of the cut-outs in order to provide a single grip or handle.

The symmetrically arranged cut-outs or handholes in the corners of each face of the sack are inclined across the corners in order to provide the desired load distribution, the angle of inclination preferably being between 5 and 15 to the mouth of the sack, which, in the preferred embodiment corresponds to an angle of from 850 to 700 to the machine direction of the blown film.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings of which: Figure 1 shows a sack according to the present invention; Figure 2 and 3 and Figure 4 illustrate different ways in which the sack of Figure 1 can be folded to provide a single grip or carrying handle; Figure 5 shows another sack according to the present invention; Figure 6 illustrates how the sack of Figure 5 is folded to provide a single grip or carrying handle; Figure 7 is a diagram showing a preferred position and orientation of cut outs or hand-holes; and Figure 8 shows details and dimensions of the cut outs or hand-holes.

The preferred embodiment of sack according to the present invention is shown in Figure 1, the sack being formed from an extruded tubular film of plastics material 10 which is folded flat and sealed at one end with a single bar heat seal to form the bottom 12 of the sack. Four cut outs 14 (two shown) or perforations adapted to provide handholes as will be described below with reference to Figure 7, are formed by cutting through the folded film in two positions at the upper end of the sack adjacent its mouth 15, and at the same distance from the respective edge folds 16 and 18.

In use the sack is filled to a level specified at the design stage and heat sealed (as indicated at 20) below the cut outs 14.

For carrying the sack, the upper end of the sack is folded as illustrated in Figures 2 and 3 so as to align the cut outs 14 and form a single grip or carrying handle.

Alternatively, the cut outs 14 may be aligned as shown in Figure 4, such that the middle web 30 of the fold lies below the level of the aligned cut outs 14 providing the grip or handle.

If desired, the sack may have six cut outs 14 arranged in three pairs (Figures 5 and 6) formed by also cutting through the flat tube midway between the edge folds. In this case, when the upper end is folded back upon itself to form a triple fold, all six of the cut outs 14 are aligned to produce a stronger grip or handle suitable for carrying heavy loads.

The sacks described above are especially suited for sales, to domestic consumers, of relatively small quantities, typically of the order of 10 Kg, for example, for smokeless fuel or fertilizer.

Flexible containers for solid fuel having a 10 Kg capacity are preferably formed of low density or linear polyethylene or combinations thereof to produce optimum properties. In the case of a 10 Kg container, the film thickness should be of the order of 100 to 125 microns blown under conditions to produce typically a low density polyethylene having a minimum yield strength of 1 5 N/mm2 in the machine direction and a minimum break load of 21 N/mm2 in the same direction. Alternatively, using a linear type polyethylene these figures would be typically for yield 11 N/mm2 and break load 40 N/mm2 suitable allowance being made for the film thickness adjustment for specific duties, locations or commodities required by the user. For sacks constructed with side welds similar film properties are desirable in the film circumferential direction.

Figure 7 specifies the preferred position and orientation of the cut outs or hand-holes, in relation to the width W of the sack which is typically 430-560 mm. The cut outs or handholes may be circular, oval, parallel sided or any other, preferably smoothly contoured (to minimise the risk of tearing), shape suitable for receiving the hand. The preferred shape is shown in Figures 7a and 7b and typical dimensions suitable for a 10 Kg sack are set out in Figure 7b.

As stated above, the hand-holes need not be cut out during manufacture. They may be defined by a line, of weakness, preferably formed by cutting a line of perforations, as shown in Figure 7b so that the hand-holes are in fact formed by pushing out the waste plastics materials within the line of weakness when it is first necessary to lift the bag. Also, as illustrated in Figure 7, the line of weakness need not define a closed loop so that waste plastics material remains attached along the upper edge of the hand-hole both for reinforcement and to provide a more comfortable grip for the user.

Claims (10)

1. A sack having or adapted to form hand-holes disposed around the upper end of the sack adjacent its mouth such that the upper end can, in use, be folded to align the hand-holes so forming a single grip or handle for lifting the sack.

2. A sack according to claim 1 and comprising a tube of material one end of which is sealed or otherwise secured to form the bottom of the sack.

3. A sack according to claim 2 and having gussetted or pleated sides produced by folding-in the side edges of the tubular material prior to sealing the bottom end.

4. A sack according to claim 1 and comprising a sheet of material which is folded and sealed or otherwise secured to form a side and the bottom and edge of the sack.

5. A sack according to any one of the preceding claims wherein the sack has four hand-holes or cut-outs, arranged symmetrically with respect to a longitudinal axis of the sack, one in each upper corner of the sack on each face of the sack and such that the cut-outs on one face register with cut outs on the other face of the sack.

6. A sack according to claim 5 and having an additional pair of cut-outs formed one in the middle of each of the two faces of the sack adjacent the mouth thereof.

7. A sack according to claim 5 or claim 6 wherein the symmetrically arranged cut-outs or hand-holes are each inclined across the corner of the face in which it is formed.

8. A sack according to any one of the preceding claims and formed of plastics film material the hand-holes or cut-outs being inclined at an angle of from 700 to 850 to the machine direction of the film.

9. A sack according to any one of the preceding claims and formed from plastics film.

10. A sack according to claim 9 wherein the plastics film comprises flexible polyalkylene material preferably low density, linear or high density polyethylene.

1 A sack constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.