WO2000012399A1

WO2000012399A1 - Valve sack of paper, method for manufacturing the same and method for filling the same

Info

Publication number: WO2000012399A1
Application number: PCT/FI1998/000808
Authority: WO
Inventors: Valter Sievers; Pentti Rikassaari
Original assignee: Upm-Kymmene Corporation
Priority date: 1998-08-28
Filing date: 1998-10-19
Publication date: 2000-03-09
Also published as: FI981843A0; FI981843A

Abstract

The application presents a valve sack of paper with a bottom closed by glueing and a valve on the other end through which the sack is filled. The valve has a bottom-side wall (10) bent towards the bottom, or a sack-side wall (4') bent towards the sack. Thus the valve is naturally slightly ajar which enables the placing of the sack onto a fill pipe as reliably as possible.

Description

VALVE SACK OF PAPER, METHOD FOR MANUFACTURING THE SAME AND METHOD FOR FILLING THE SAME

Background to the technology

5 The invention relates to paper sacks and concerns a valve sack, its manufacture and use

When manufacturing valve sacks of paper, a tube is formed of a one- or several-layer paper web, the tube is cut into pieces of desired length, and the ends are closed to form a bottom by first folding inwards the thinner end flaps and on top of these the wider bottom flaps In all

10 comers except the valve comer the bottom flaps are glued to the end flaps The valve comer is left unglued which enables the filling of the sack through a valve In a filled sack the material presses against the bottom of the sack thus closing the valve Inside the valve, on the bottom-side wall, a separate valve piece is usually further attached to improve strength and closability

15

A valve sack is usually machine-filled so that the valve of a sack positioned valve bottom upwards is placed on a fill pipe through which material is portioned into the sack A problem with this is that the valve does not always open thoroughly so that the sack could be pushed directly to the pipe Unless the fill pipe is properly placed in the valve, material can be spilled

20 on the outside of the sack or the sack hanging on a wrong position can easily break Since every effort should be made to prevent material ending up anywhere else but inside the sack, it is essential to ensure that prior to portioning there is a correctly positioned sack on the pipe Conventionally this has required a person continuosly attending to the sacking machine Using person-operated machines, however, means that a high speed cannot be reached More

25 modem automatic sacking machines therefore employ, for example, a system based on optical sensors preventing such portioning This way, higher speed can be achieved and the need of labour is reduced But still case error situations reduce the capacity of the machine and increase the amount of rejected sacks

30 General description of the invention

A valve sack according to claim 1 has now been invented Prefered embodiments of the invention are presented in other claims

In a sack according to the invention the bottom-side wall of the valve is bent towards the bottom or the sack-side wall is bent towards the sack This ensures that the sack can be placed on the fill pipe as well as possible the valve mouth being already slightly ajar The opening can be further accelerated by pressing the valve from the sides before the valve is pushed onto the fill pipe

Drawings

The attached drawings form a part of the detailed description of the invention and they show a sack according to the invention. In the drawings

Fig 1 shows a valve end of a sack blank prior to the formation of a bottom, Fig 2 shows a bottom when folded flaps are formed on it,

Fig 3 shows a bottom when the forming sheet of a valve is glued on it and lines of adhesive needed for the closing of the bottom are applied on it,

Figs 4 1 and 4 2 show the manufacturing steps of the foπning sheet of a valve,

Fig 4 3 shows a forming sheet of a valve glued to its place, and Fig 5 shows an opened valve of a ready-made sack

Detailed description

In a sack according to the invention the bottom-side wall of the valve is bent towards the bottom or the sack-side wall is bent towards the sack The term bent as used in this application inludes all kinds of bent shapes, such as angular shapes

The bottom-side wall of the valve can be made bent particularly by attaching to the bottom on the place of the valve, preferably on the inside, a special forming sheet The sheet can have a stiffer middle part It can be made of a thicker material Particularly it can contain more material layers than the edge parts The foπning sheet can be made of, for example, several paper flaps glued either overlapping or on top of one another The front edge of the forming sheet can be double-fold, particularly the edge can be folded towards the valve. Bending can also be achieved by suitable creasings or glueings longitudinal to the bottom.

The sack-side wall of the valve can be made bent particularly by forming on the end flap from above one or several creasings longitudinal to the bottom. Alternatively a stiffener, such as extra material, can be added to a suitable place.

According to the figures, the ends of a flattened blank cut from a paper tube are closed on a so-called bottom machine. There (see Fig. 1) end flaps 4/4' on both sides are folded inwards along a diagonal fold line 3 reaching from the edges 1 of the blank to the end 2, wherein at the same time the topmost side folds open along a transversal fold line 5 forming side flaps 6 and 6'. On all comers except the valve comer, a longitudinal cut 7 reaching from the end of the blank to the diagonal fold line has been formed limiting from the end flap 4 a sealing flap 8 (see FI-A-954823). On the folded end and side flaps are formed (Fig. 2) by pressing from above to both sides of the transversal fold line a transversal forming crease 9. On the valve end flap 4' and the side flaps a forming sheet 10 of a valve is glued (see Fig. 3).

The forming sheet (Fig. 4.1 - 4.3) is formed of two overlapping paper flaps 11 and 12 glued together. The flaps are glued together with a line of adhesive (13) longitudinal to the flap ending approximately one third of the length of the forming sheet before the inner end of the flap. The outer end of the forming sheet is folded under along a crease 14 to form an end hem 15. The overlapped part forms a thicker and stiffer middle part 22.

The forming sheet 10 is glued to the end flap 4' and the side flaps 6, 6' the end hem downwards with longitudinal lines of adhesive 16. These lines of adhesive are formed outside the fold lines 17 along which bottom flaps 18' and 18 are folded from the side flaps. On top of the end flaps, bottom flaps and forming sheet, bottom lines of adhesives 19, 20 and 21 are applied and the bottom flaps are folded and attached by pressing. On top a bottom cover sheet 23 (Fig. 5) of the width of the bottom is glued with lines of adhesive longitudinal to the bottom. On the valve end, the end of the bottom cover sheet is folded underneath the sheet and the sheet end is slightly (approx. 5 mm) more inside than the outer end of the forming sheet. The bottom of a ready-made sack is folded against the side body and the sacks are piled up as bundles

The forming sheet 10 forms a bent roof for the valve (Fig 5) The glue seal 13 of the sheet tightens and stiffens the structure of the sheet as a result of which the sheet bends Transversal bending 15.1 downwards of the sheet (Fig 4.3) increases the stiffness and bending of the front edge of the sheet Longitudinal overlapping and application of glue area as well as longitudinal foldings 15 2 upwards form to the area a point of discontinuity of stiffness Along the point of discontinuity the sheet locked inside the bottom with glue settles to the desired shape Accordingly the edges of the end flap 4' tend to bend outwards along the forming creases 9 Even the valve of a flattened sack taken from a bundle opens naturally sligtly ajar like a spring When the valve is in addition pressed from the sides the valve opens to a multiangular opening which allows the sack to be placed on a fill pipe very reliably and fast Reliability is further increased by that there is no transversal edge on the end flap 4' inside the valve with which the front edge of the fill pipe head could collide

In a filled sack the loose inner ends of the flaps 11 and 12 of the forming sheet 10 increase tightness

The sack is suitably made of multilayer, preferably two-layer paper tube To add strength, the sack layers can be glued together at certain points as presented in the publication FI-A- 945727 Critical points include particularly the end edge and comers of the bottom of a filled sack

The sacks can be made with conventional tube or bottom machines A bottom machine only needs to be added equipment for attaching the forrning sheet 10 which is a relatively simple additional stage The forming creases 9 can be made with equipment already existing in the bottom machine

Forming also stiffens the valve wherefore forces and speeds (with for example air jets or suctions) greater than before can be used in guiding the sack to the fill pipe without the valve bending to a wrong position Thus the sacks can be made of modem papers thinner and stronger than before For example, a two-layer sack can be made of sack papers of approx 60 g m

Using a sack according to the invention reduces particularly the amount of poorly-placed sacks on the fill pipe on automatic sacking machines wherein the capacity of the machine can be utilized as efficiently as possible. Correspondingly the speed of the machines can be increased. Savings in the costs also occur with the decrease in the amount of sacks that must be rejected. The sack is well suitable also for modem high-efficiency sacking machines into which the sacks are fed from special sack rolls. The speeds of this type of machines are very high. For example, the filling time of a sack of 25 kg could be around 0.9 s.

Claims

1. A valve sack of paper comprising a bottom closed by glueing comprising end flaps (4, 4') folded inside along a diagonal fold line (3) and end flaps (18, 18') folded on top of these along a transversal bottom fold line (17) so that the area between the end flap and the bottom flaps on one end of the bottom is open forming a valve in which there is a bottom-side wall and a sack-side wall, characterized in that the bottom-side wall of the valve (10, 18', 18) is bent towards the bottom or the sack-side wall (4') of the valve is bent towards the sack.

2. A sack according to claim 1 in which sack there is on the bottom-side wall a forming sheet (10) bent towards the bottom attached to the bottom flaps (18', 18) .

3. A sack according to claim 2 in which the forming sheet (10) has on the middle a stiff middle part (22) to the direction of the bottom fold line (17).

4. A sack according to claim 3 in which the stiff middle part (22) of the forming sheet (10) is formed of paper layers (11, 12) on top of one another.

5. A sack according to claim 4 in which the forming sheet (10) is formed of two paper flaps (11, 12) glued together from their edges overlappingly.

6. A sack according to one of the claims 2 - 5 in which the front edge (14) of the forming sheet (10) is folded double-fold.

7. A sack according to claim 6 in which the front edge (14) of the forming sheet is folded inside the valve.

8. A sack according to one of the claims 1 - 7 in which there is on the sack-side wall of the valve (4') one or several forming crease (9) to the direction of the side fold line (16), such as a crease along which the end flap folds to be bent towards the sack.

9. A method for manufacturing a valve sack of paper in which method a blank is cut from a paper tube, end flaps are folded inwards along a diagonal fold line on its end and on top of these along a transversal bottom fold line bottom flaps are folded and attached by glueing so that on one end of the bottom the area between the end flap and the bottom flaps is open forming a valve in which there is a bottom-side wall and a sack-side wall, characterized in that the bottom-side wall of the valve is formed bent towards the bottom or the sack-side wall of the valve is formed bent towards the sack.

10. A method for filling a sack made according to one of the claims 1 - 8 or according to claim 9, characterized in that inside a valve a fill pipe is placed and material is lead into the sack through the pipe wherein preferably the valve is pressed from the sides before a fill pipe is placed inside it.