GB2324995A

GB2324995A - Paper sack closure using hot melt adhesive

Info

Publication number: GB2324995A
Application number: GB9709371A
Authority: GB
Inventors: Ian Samuel
Original assignee: KORSNAES PAPER SACKS Ltd
Current assignee: KORSNAES PAPER SACKS Ltd
Priority date: 1997-05-08
Filing date: 1997-05-08
Publication date: 1998-11-11
Also published as: GB9709371D0

Abstract

A paper sack 26 has an opening which may be within a paper sleeve 25. Hot melt adhesive 28 is applied to an inner surface of the opening so that the sack can be closed, after filling, by applying heat and pressure to the opening. The hot melt adhesive may be applied as a strip, using a wheel or a jetting, extrusion or fibrising gun. The sack may be gusseted or ungusseted and may be single-ply or multi-ply, in which case the plies may be adhered together around the sacks opening by a water based glue.

Description

Paper Sacks This invention relates to the closure of an open end, or mouth, of a paper sack, after the sack has been filled. The sack may be gusseted or ungusseted and may be single-ply or plural-ply (usually known as "multi-ply"). The sack may have a closed end opposite the open end.

The invention is particularly applicable to a paper sack which is filled by a chute or nozzle of which the throat is just smaller than the fully-opened mouth of the sack.

Examples of the possible types of sack to which the invention can be applied are:open-ended sewn sacks; pinch sacks; open-ended pasted sacks; satchel sacks; and selfopening sacks; whether in gusseted or ungusseted format.

According to a first aspect of the invention, there is provided an open-ended paper sack having a closure means in the form of a hot melt substance applied to an inside surface of the sack at its open end.

According to a second aspect of the invention, there is provided a paper sack which has been filled through an opening at one end of the sack, the said opening thereafter having been closed by application of heat to the open end so as to melt a hot melt substance applied to an inside surface of the sack at the said end.

In either case, the hot melt substance may be in the form of a strip extending transversely of the sack and the sack may be a plural-ply sack of which the plies are adhered together around the open end by means of a water-based glue.

According to a third aspect of the invention, there is provided a method of closing the open end of a paper sack according to the first aspect of the invention, comprising the step of applying heat thereto.

The invention will be described by way of example with reference to the accompanying drawings, wherein: - FIGS. 1A and 1B are a front diagranmatic elevation and a side diagrammatic elevation respectively of a two-ply gusseted pinch sack which has been filled and then closed in accordance with the invention; FIG. 2 is an illustration of two webs of paper drawn from two large reels; FIG. 3 represents a section of the webs after being drawn from the reels of FIG. 2; FIGS. 4A, 4B and 4C illustrate patterns of hot melt obtained respectively from a fiberising gun, a single nozzle jet gun and an extrusion gun (not shown); FIGS. 5A, 5B and 5C respectively illustrate three different sack types, namely, a gusseted pinch sack, and open ended sewn sack and an open ended pasted sack; FIG. 6 illustrates a gusseted sack; FIG. 6A illustrates the gusseted sack of FIG. 6 with the open end convexulated; FIG. 7 shows a sack with a valve formed by a paper sleeve; and FIG. 8 shows the paper sleeve enlarged.

Referring to FIGS. 1A and 1B, there is shown a sack 10 which has been made longer than is necessary for the sack 10 to contain the product being filled, so that a closure can be made on the open end after filling. The excess height 'V' is known as the "ullage", as shown in FIGS. 1A and 1B. All sacks that it is required to close after filling are made longer than is necessary to contain the product being filled so that a closure can be made. The sack 10 illustrated in FIGS. 1A and 1B is a two-ply gusseted pinch sack.

Referring to FIG. 2, the sack 10 of FIGS. 1A, 1B is formed from two webs of paper 12, 13, drawn respectively from two large reels 14, 15. (A sack may alternatively be singleply or have three or more plies.) FIG. 3 represents a section of the webs 12, 13, just after being drawn from the reels 14, 15 ofFIG. 2.

A repeating pattern of hot melt lines 16, 16, ... across the whole web width is deposited on the upper surface 17 of the top ply 12. This surface 17 will become the inside of the sack 10 ofFIGS. 1A, 1B.

FIG. 3 shows the perforator knife pattern 18, the inside ply 12 and the outside ply 13.

The start position and the length of each series of adhesive lines 16 coincide with the ullage length U of the sack 10.

An individual hot melt adhesive line 16 can be formed using for example a jetting gun (not shown) with one or more orifices, an extrusion gun (not shown) or a fibrising gun (not shown). Three typical "laydown" adhesive patterns 19a, 19b and 19c from, respectively, a jetting gun (not shown) with one or more orifices, an extrusion gun (not shown) and a fibrising gun (not shown) are illustrated in FIGS. 4A, 4B and 4C.

Another possible form of application of hot melt adhesive is via a wheel, not shown.

For a single- or multi-orifice jetting gun and an extrusion gun, it is ideal if the deposited lines are countervailed upon closure viz. the opposing faces of the sack inside have adhesive lines which are not coincidental.

Thus full or partial coverages across the web can be chosen, dependent on the level of product containment required after filling.

A manufacturing machine (not shown) will thence take the webs 12, 13 through an interply section where, usually, a water based glue is deposited on either the outside face ofthe inner ply 12, or, more preferably, on the inner face 20 (FIG. 3) ofthe outside ply 13 around the perimeter of the open end of the sack. For sacks having more than two plies, the interply methodology is repeated on the further plies (not shown) so that all plies are bound in the area of the internal hot melt adhesive.

From then on, manufacturing machines may differ in installed equipment, but all should include devices either to pre-perforate the web with a stepped knife as illustrated in FIG.

3, or to part-off the sacks from a formed tube - in which case all plies should be straightcut simultaneously. In either case, the start of the hot melt adhesive application is dependent upon where the knife cut will be.

Whatever the format of the sack, the application of the hot melt adhesive should obey the same rules. FIGS. 5A, 5B and 5C illustrate three sack types 21a, 21b and 21c, namely, a gusseted pinch-type sack 21a, an open-ended sewn sack 21b and an openended pasted sack 21 c.

Each sack type 21a, 2 lib and 21c has the adhesive applied in the same place relative to the sack mouth.

After filling, non-gusseted sacks can be sealed immediately using a range of commercially available equipment.

As regards gusseted sacks, it is proposed to use existing commercially available equipment to convexulate, that is, open out, the gusset regions of the sack so to form a uniform thickness for the application of the heating tool as illustrated at 22 in respect of sack type 21 a in FIG. 6A. In this case the hot melt adhesive applied to the gusset regions 23 will be angled due to the deformation of the sack top.

The filled sack is then closed by reactivation of the hot melt adhesive by proprietary available heating appliances, not shown.

Referring to FIGS. 7 and 8, the invention can readily be applied to the formation of a paper sleeve 25 formed to be used as a valve within a paper sack 26, as the paper sleeve 25 is a miniature tube formed by a similar tubing process, but using a single ply of paper, as the process used for forming a sack of the kind described above. FIG. 7 shows the sack 26 complete with sleeve valve 25. An enlargement of the sleeve 25 is shown in FIG. 8, wherein the paper overlap 28 is gummed together by a water-based adhesive.

The shaded area 29 of the sleeve 25 has hot-melt adhesive applied to the inside surface of the sleeve, that is, the surface hidden from view, around the perimeter of the sleeve 25.

Claims

CLAIMS:

1. An open-ended paper sack having a hot-melt adhesive applied to an inside surface of the sack at its open end, for subsequent closure of the sack by application of heat with pressure to the sack, so as to heat and melt the adhesive.

2. A paper sack which has been filled through an opening at one end of the sack, the said opening thereafter having been closed by application of heat to the open end so as to melt a hot-melt adhesive applied to an inside surface of the sack at the said end.

3. A sack as claimed in claim 1 or 2, wherein the hot melt adhesive is in the form of a strip extending transversely of the sack.

4. A sack as claimed in claim 1,2 or 3, wherein the sack is a plural-ply sack of which the plies are adhered together around the open end by means of a water-based glue.

5. A method of closing the open end of a paper sack as claimed in claim 1, comprising the step of applying heat thereto.

6. A paper sack having a valve formed by a paper sleeve, the paper sleeve having hotmelt adhesive applied to its inside surface around the perimeter of the sleeve, for subsequent closure of the sleeve by application of heat with pressure to the sleeve so as to heat and melt the adhesive.

7. A method of closing the paper sleeve of a paper sack as claimed in claim 6, comprising the step of applying heat to the paper sleeve so as to melt the hot-melt adhesive.