Field of invention:

The invention relates to a method and an apparatus for making of pillow-shaped sacks with a valve. In particular, the invention relates to an apparatus to automate the method of making valves in pillow-shaped sacks. The valves made using the apparatus and method of the invention may also be used to make deep valves.

Background of invention:

Sacks as a packaging system are unbeatably flexible both in their ability to meet basic logistic requirements and in attracting sales. Nowadays valve sacks are used exclusively for cement and bulk material packaging, because only the valve sacks allow for the required high bagging speeds, while at the same time keeping dust in the packaging plant to a minimum. Whilst sack shapes may differ greatly, depending upon filling weight, product bulk density and pallet dimensions, two essential constructions are currently predominantly used in automate filling: the sewn sack and the pasted block bottom valve sack, a type especially suited to some automatic filling and designed to take a perfectly square shape when filled.

In particular, the demand for sacks with deep valves (valves with depth between 40% to 70% or greater of the sack width) which are manually made is increasing, as these sacks are designed for high speed filling on spout packers and are usually used to hold granular products of less dense material such as fine powders. In case of normal valve sacks, the volume of filling is higher, more time requires for the same bag as compared to denser materials thus requirement of high depth valve sacks serve the purpose.

Many ways of forming filling valves in the block-bottom type bags are available. US patent 5158370 (’370) discloses collapsible tubular laminates useful as bag valves. Such laminates comprise an inner layer of a thermoplastic polymer and many ways of forming filling valves in the block-bottom type bags are available. The '370 invention discloses collapsible tubular laminates useful as bag valves. Such laminates comprise an inner layer of a thermoplastic polymer and a metal foil layer.

The '370 invention also provides bags having such collapsible tubular laminates as filling valves. In a preferred embodiment, such laminates are located substantially entirely within the bag wherein the valve opens through a hole in a wall of the bag. It is evident from Figure 1A that the '370 invention relates to block-bottom bag and not a pillow shaped bag.

US patent 6595688 (’688) discloses a valve sleeve for a flexible bag constructed in accordance with the '688 invention includes a cylindrical tube including a heat sealable liner and protective member secured to the cylindrical tube. It further discloses that a flexible bag having a valve sleeve constructed to include a valve sleeve in accordance with the '688 invention will be resistant to the damage caused during sealing of the valve sleeve and prevent contents of the flexible bag from escaping due to the damage. It also notes that a flexible bag having a valve sleeve constructed to include a protective member in accordance with the invention will be easier to manufacture and result in less scrap and nonconforming valve bags. As with the '370 application, this invention also relates to a block-bottom bag.

US patent 73 1 1442 (’442), which is also directed to block-bottom bags, discloses an air valve for a polybag is provided that permits the escape of air from the bag as it is filled by a filling tube. The air valve consists of a plurality of slitted openings in one top corner of the bag, and a valve flap mounted in the polybag near the slitted openings that closes and seals the openings as filling material engages and moves the flap. It is evident that a lot of attention has been provided in the industry to block- bottom bags and valve-making related to them. However, there are no automated methods for making valves for cushion type bags, which are used in great numbers and which are much easier to manufacture than the block-bottom bags.

There is not so much as a hint in the available prior art to the problems faced by the pillow-shaped bag industry in automatizing the fold-making and valve making method.

Cushion type sacks, which are easier to construct are also made from woven fabric (coated or uncoated) made into of a tubular structure. The filling valve is formed by inward folding of any one comer of tubular fabric length and transverse seaming/sealing of straight open edge. The valve forming method in cushion type sacks is usually manual, labour-intensive and expensive.

The pasted block bottom sack requires higher capital investment and an additional method step - full surface extrusion coating of the woven fabric prior to its conversion into sacks. Further, in pasted block bottom sack, it is difficult to make higher width valve, where the depth of the valve is 40% or greater of the bag width. On other hand the sewn valve sack with higher depth valve is simple to manufacture, however the valve making methods are manual and therefore laborious and time consuming. This also reduces the productivity of manufacturing method of sewn valve sacks.

Techniques to make valves in pillow shaped bags are known. One example is that of Indian Patent Application no. 1171/DEL/2012, which disclosed a complex mechanism to form folded valves in pillow shaped bags. However, the device that is used to make the fold that forms the basis of the valve is made using a spreader bar that moves axially in the direction of the length of the bag. The device disclosed therein and its method of operation is such that it places inherent restrictions on the depth of the valve where the depth of the valve depends upon the width of the bag.

There is possibility of automatic normal valve bags manufacturing. However, there is no automated method for making valve bags having valve depth almost up to half the bag width or higher. Hence there is a need to provide a device to automate the method of manufacturing pillow-shaped sewn sacks with valves. There is further need for a device to automate the method of manufacturing pillow-shaped sewn sacks with deep valves

Objects of invention:

One of the major objects of this invention is to provide an automated device/apparatus for the manufacturing of sewn valve sacks with valves.

Another object of this invention is to provide a device to automate the manufacturing of sewn valve sacks wherein the valve depth is between 40% to 70% of bag width.

Another object of this invention is to provide a device to automate the manufacturing of sewn valve sacks made using woven fabric made from monoaxially drawn slit -film tape of synthetic polymer as input material.

A further object of the invention is to provide an automated method to manufacture finished top and bottom sewn sacks having valve with depth greater than 40% of the bag width.

A still further object of the invention is to provide a device by which the method of manufacturing sewn sacks with higher valve depth in a continuous production mode is achieved.

Summary of invention: The present invention discloses an apparatus and method for making sewn sacks with valves. The invention may also be used to make sewn sacks with deep valves - that is of the valve depth of between 40% and 70% of the bag width.

The invention discloses an automated method and an apparatus for making of pillow-shaped sacks with a valve. The apparatus consists of a number of stations positioned sequentially for the purposes of cutting; bottom folding and stitching; inward fold forming; edge cutting; folding and stitching. The valve forming forming station incorporates a spreader bar (15), a first device (6), a collapsible platform (19), a press assembly (13), and a rigid support sheet (24), wherein the plane of said collapsible platform (19) is capable of swinging around a swivelling mechanism (14) whose axis is parallel to direction of travel of said cut pieces (1). The inward fold (25) in a cut piece of fabric is formed by swivelling action of the spreader bar (15). The depth of the valve is determined by the position of the press assembly. The method of the invention uses the apparatus of the invention to produce a bag with a valve.

Deep valves or high depth valves are essential in filling fine particulate material or material of low density at high filling rate. One end of a section of the tubular fabric cut to a specific length is preferably folded and sewn to form one sewn end. The step of folding is important for ensuring that the filled material does not leak from the sewn end. This is followed by processing of the other end into a shape that incorporates a valve having depth greater than 40% of the width of the sack which can go up to 70% or as per the customer requirement wherein the valve formation does not depend on the width of the fabric, further followed by cutting off extra portion at the top, folding and sewing of the free end of the sack such that only the valve portion remains open for filling the sack.

List of parts:

1. Cut piece of Fabric

IA. Bottom end Open end of cut piece of fabric

IB, 1C. Corner of cut piece of fabric ID. Top end or Stitched end of cut piece of fabric

2. Conveyor table

3. Lower fabric/sheet

4. Upper fabric/sheet

5. Perforations

6. First device

7. First pneumatic cylinder PI

8. Upper clipper

9. Lower clipper

10. Gripping mechanism

11. Upper suction means

12. Lower suction means

13. Press assembly

14. Swivelling mechanism / hinge

15. Spreader bar

16. Rotary cylinder (16A, 16B, 16C)

17. Frame

18. Third pneumatic cylinder P3

19. Collapsible platform

20. Second pneumatic cylinder P2

21. Punch pad

22. Suction source/ vacuum blower

23. Pneumatic pressure (PF, P2’, P3\ P4’, P5\ P6’)

24. Support sheet

25. Inward fold

26. Cut at the top edge of cut piece

Brief description of figures:

Figure 1 shows a flow diagram of the method of invention Figure 2 and its various stages schematically show various stages of bag manufacture as it undergoes the method of valve formation:

Stage A shows the tubular fabric roll

Stage B shows the tubular fabric cut to a required length

Stage C shows the cut piece of fabric with a fold formed at the bottom edge

Stage D shows the bottom edge(lD) folded and sewn Stage E shows diamond shape formed at the top edge(lA)

Stage F shows unsewn top edge with valve shape fully formed Stage G shows cut top edge with valve shape fully formed Stage FI shows folded top edge with valve in place Stage I shows both edges sewn and high depth valve bag form

Figure 3 shows schematically an inward folded cut piece

Figure 3A shows the final folded and sewn bag with high depth valve

Figure 4 shows the perspective view of the apparatus of invention

Figures 5, 5 A, 5B, 5C shows perspective views of apparatus with different stages of method of valve formation

Detailed Description Of Invention with reference to drawings:

The term fabric used in the present application is meant to encompass woven and nonwoven fabric, sheets or flexible films made of any material suitable for sack making.

Figure 1 shows the flow diagram of the automated method of making sealed valves of depth greater than 40% in pillow-shaped sacks in which various stages of sack making method of the invention is provided. It shows in sequence: a cutting station where tubular fabric is cut to get cut piece of fabric (1) into required bag size, a bottom folding and stitching station where bottom end of the cut piece of fabric (1) is folded and stitched, of which bottom folding which may be defined in the range of 25-30 mm or as per customer requirement, a valve forming station where in valve of high depth is made, a top cutting station where in cut (26) is made which can be done by hot or cold cutting process or any other process/method which provide clear parallel cut , and a top folding and stitching station where top end of the cut piece of fabric (1) is folded and stitched of which top folding which may be defined in the range of 25-30 mm or as per customer requirement followed by sewing operation to form sack ends, or any other sequence that manufactures the sacks with the valve as shown in Figure 3A.

As an example, say if the required fabric width to manufacture sewn valve sack using conventional system is 500 mm, the maximum depth of valve which can be achieved is 225 mm or lesser whereas in case of inventive device or apparatus for same fabric width, the higher depth of valve is achieved which is 350 mm or more.

Yet another example, say if the required fabric width to manufacture sewn valve sack using conventional system is 480 mm, the maximum depth of valve which can achieved is 215 mm or lesser where as in case of inventive system for same fabric width the higher depth of valve is achieved which is 335 mm or more.

With reference to the Figure 2, which discloses the various stages of method of making valve making, the apparatus/device provided to help to convert woven or non- woven cut piece of fabric (1) material into top- and bottom-folded, and sewn and valved, bag/sack involves various manufacturing steps. As a part of the device, a feeding station equipped to receive and mount the tubular fabric roll is provided. The feeding station unrolls the fabric from the fabric roll to a desired length and feeds it to a cutting means. The fabric is next cut into individual pieces of required length (Figure 2B) that are transferred to a folding and stitching station provided with an edge folding device for folding their bottom edge (Figure 2C). The edge folding device is typically mounted on a conveyor table (2). The cut piece has now two open ends - a bottom end (1A) and a top end (ID). The top edge or end (ID) of cut fabric is folded in a single fold, or preferably a double fold, and sewn (Figure 2D) with the help of a sewing machine, which is also a provided at the folding and stitching station. The sewing machine is typically positioned after the edge folding device.

The bottom folded stitched cut piece of fabric (1) with its bottom end (1A) open for valve formation is moved over the conveying table (2) onto a collapsible platform (19) (see Figure 4) where a first device (6) to form the cut piece into a piece with a valve (Figures 2G, 2F1, 21) is positioned. The corner fold that forms the basis of the said valve is formed by spreader bar (15) which moves in a plane parallel to the cut piece around a pivot which is operated with the help of rotary cylinder (16A) or any commercially available electronic programmable controllers to facilitate the inward and outward direction of the spreader bar (15).

As shown in Figures 5, 5A, 5B, and 5C, the valve forming device of the invention has upper and lower suction means (11, 12), a spreader bar (15) and collapsible platform (19) wherein the collapsible platform (19) is capable of swivelling about at a swivelling mechanism. The swivelling mechanism (14) may be in the form of at least a pair of hinges such that the axis of rotation of the collapsible platform is parallel to the direction of movement of the cut piece. The actual movement of the collapsible platform (19) is facilitated by the pair of pneumatic cylinders, namely second pneumatic cylinders (20). The movement of the second pneumatic cylinders (20) is governed by pneumatic pressure supplied through pressure lines (P1’, P2’) (23). The upper and lower suction means (11, 12) may be in the form preferably of flat surfaces provided with perforations through which suction can be applied to the surfaces that they are contacted with. In the case of the cut piece that is positioned on the collapsible platform (19), the upper and lower suction means (11, 12) are deployed so that the individual layers or fabric sheets (4, 3) of the cut piece may be separated from each other. A recess may be formed in the collapsible platform to allow the lower suction means (12) to access the lower fabric sheet (3) during the layer separation phase. Accordingly, the lower suction means (12) may be suitably affixed to the collapsible platform (19), such that during the downward movement of the collapsible platform (19), the lower suction means (12) also moves in tandem. As the lower and upper sheets (3, 4) get separated under the action of the suction provided by lower and upper suction means (12, 11) respectively, a gripping action is necessary to securely hold the fabric sheets (3, 4) in separated state. The gripping action is provided by the upper and lower clippers (8, 9), which are preferably in the form of claws or hooks or any similar shape that allows them to take hold of the edges of the upper and lower sheets (4, 3) respectively. This allows the bottom open end (1A) to remain opened up so that the spreader bar (15) can move in the edge portion of the cut piece inwards into the mouth formed by the separated sheets (3, 4). In other words, the simultaneous downward movement of the collapsible platform (19) with lower suction means (12) and the upward movement of upper suction means (11) creates a gap between the fabric faces (3, 4), which is followed by insertion of the spreader bar (15) from one side of cut piece of fabric (1) thereby pushing one fabric corner (1C) into the space between the two faces.

The engagement of the upper (8) and lower (9) clippers is facilitated by rotary mechanisms such as rotary cylinders (16B, 16C) that allow the clippers rotate and place their gripping ends over or under the respective fabric sheets (4, 3).

The depth of the valve that will eventually form is determined by the location of a press assembly (13). The press assembly (13) may be in the form of a rectangular member capable of pressing down on the cut piece (1) once it is positioned on the collapsible platform (19). The press assembly (13) acts as a barrier for the movement of the spreader bar (15) and consequently the extent to which the edge of the cut piece can move into the open bottom end (ID). The position of press assembly (13) depends on the desired depth of the valve. The length of the press assembly (13) should be such that it restricts entire length of the spreader bar (15).

Next, the spreader bar (15) moves out of fabric, thereby folded corner shape as seen in Figure 2F is formed. Following this, the collapsible platform (19) moves upwards and assumes its normal position and the upper and lower clippers (8, 9) are disengaged from the respective fabric sheets (4, 3) by the movement of rotary cylinder (16B, 16C) so that cut piece of fabric (1) is conveyed in forward direction. As the fabric cut piece (1) is conveyed forward, a punch pad (21) forms a crease pattern on the side of the formed shape where the valve would be formed.

The motion of the spreader bar (15) inside the gap between the lower and upper cut piece of the fabric (3, 4) from corner of the cut piece of the fabric (1C) is restricted by the press assembly (13) the movement of which is controlled by a third pneumatic cylinder (18) which in turn is supplied with pneumatic pressure through a set of pressure lines (P5\ P6’) (23). The movement of the press assembly (13) may be controlled by other means such that press assembly (13) moves direction perpendicular to the movement of cut piece of fabric (1). The bottom open end (1A) of the cut piece of fabric (1), which is in the original cut state, is gripped by a gripping mechanism (10).

The fabric cut piece (1) having an inward fold (25) formed at one corner (see Figure 3) and that has been creased is next moved to a cutting zone where a required portion of the folded bottom end (1A) may be cut. As is evident from Figure 2G, the required length of top edge of fabric is cut to maintain required height of valve which is net formed. At this stage, the upper and lower fabric/sheet (4, 3) of the tubular fabric have repositioned themselves in the fold zone.

After the cutting the required portion near the edge of the folded bottom end (1A), the remaining edge at the bottom folded end (1A) of fabric cut piece (1) is suitably folded to provide a shape that ultimately forms into a valve; the folded edge is sewn appropriately to form a seam which is leak-proof for its intended purpose. (See Figures 2H and 21.)

The bag with its bottom end (1A) completely sewn and the top end (ID) sewn sufficiently, so that a valve is formed at the bottom end (1A), is next moved to a stacking station where it is stacked. Figure 4 shows perspective view of the apparatus of the present invention. The first device (6) comprises of upper and lower suction means (11 ,12) so as to hold the upper and lower fabric/sheet (4, 3) of the cut piece of fabric (1) by suction means and gripping mechanism (10) which comprises of upper and lower clipper (9,10) to hold the upper and lower fabric/sheet (4,5) is provided where in the gripping mechanism (10) is mounted on the upper and lower suction means (11,12).

The lower suction means (12) is in the form of perforations (5) which is mounted on the collapsible platform (19) and is capable of swivelling about at least a pair of hinge (14) provided and movement of which is facilitated by the pair of second pneumatic cylinders (20) they are moved by changing pneumatic pressure (PI’, P2’) (23). Upper suction means (11) also comprises of perforations (5) which is mounted on the frame (17). A planar rigid support sheet (24) having an area large enough to cover the entire area between the base of the inward fold (25) and the edge of the bottom end (1A) is provided such that pre -pressing of the upper fabric (4) after inward fold (25) formation by spreader bar (15) is done. The support sheet should be sufficiently rigid so that it is capable of holding down the cut piece without itself getting bent. The upper suction means (11) is connected to at least one pneumatic cylinder namely the first pneumatic cylinder (7). The movement of the first pneumatic cylinder (7) is governed by pneumatic pressure supplied through pressure lines (P3\ P4’) (23) which allows it to move perpendicularly to the direction of the cut piece of fabric (1). The movement of the first pneumatic cylinder (7) can be facilitated with the help of any commercially available electronic devices to move in required coordinate manner.

The upper and lower clippers (8, 9) which are mounted on the upper and lower suction means (11, 12) can be rotated by rotary cylinder (16B, 16C) or by any commercially available electronic devices such that movement of which grips the upper and lower fabric/sheet (4, 3).

During the high depth valve forming or fold forming method, the spreader bar (15) is inserted speedily in the space created and maintained a gap between the upper and lower fabric /sheet (4, 3). During its swivelling action, the actual extent along the length of the cut piece (1) to which the spreader bar (15) is pushed depends on position of the press assembly (13) and the bottom open end (1A) of the cut piece of the fabric. The side way movement of the spreader bar (15) inside the cut piece of fabric (1) facilitates the formation of valve.

Depending on the positioning of the press assembly (13) and the length of the spreader bar, a valve of a depth between 40% to 70% of the width of the cut piece (1) is formed. For example, if the press assembly (13) is positioned from the bottom edge at a distance of over 40% of the cut piece width, and if the spreader bar (15) length is also greater than 40% of the cut piece width, the depth of inward fold (25) formed would be greater than 40% of the cut piece width. A deep valve would thus be formed.

In one of the embodiments, from Figure 2G, the required length of top edge of cut piece of fabric (1) is cut to maintain required height of valve which can be formed. By changing the length of top edge of cut price of fabric (1) different height of valve is achieved for same fabric width. To enable formation of deep valves, the length of the spreader bar (15) is provided so that a suitably deep inward fold (25) is formed. Accordingly, the length of the spreader bar may be greater than 40% of the width of the cut piece (1). For shallower valves, the length of the spreader bar (15) may be suitably small.

The invention also discloses a method of making a valve. Figure 5, 5A, 5B and 5C show the apparatus of the invention with different stages of the method of valve formation. A method of making valves in pillow-shaped sacks made from cut pieces of tubular fabric (1) moving on a conveyor table (2) uses the apparatus disclosed in the foregoing paragraphs. It comprises the steps of: a. cutting at said cutting station said tubular fabric into cut pieces (1) having a near corner (1C), and a far corner (IB) at the bottom end (1A) at a cutting station, b. folding and stitching top end (ID) of said cut piece at said bottom folding and stitching station, c. forming an inward fold (25) at the bottom end (1 A) of said cut piece at said inward fold forming station, d. making a transverse cut at the edge of said inward folded bottom end (1A), and e. folding said cut edge at said inward folded bottom end (1A) at said edge folding and stitching station, f. stitching said cut edge at said folding and stitching station.

The key aspects of the method of making valve of the invention are related to the aforementioned step c. It comprises the following sub-steps: i. putting down said pressure assembly (13) onto said cut piece which is placed on said collapsible platform (19), ii. using said lower and upper suction means (12, 11) applying suction to lower and upper layers (3, 4) of said cut piece and separating said layers (3, 4) from each other by moving respective suction means (12, 11) iii. gripping securely said lower and upper layers (3, 4) respectively with said lower and upper clippers (9, 8), iv. swivelling said collapsible platform (19) around its swivelling mechanism (10), v. swinging said spreader bar (15) to bring the near corner (1C) towards said pressure assembly (13), and forming an inward fold (25), vi. retracting said spreader bar (15) to its original position, vii. swivelling said collapsible platform (19), and the upper and lower suction means (11, 12) to their original positions and stopping application of suction, viii. pressing the inward fold (25) with said support sheet (24).

In another embodiment of the method, in the aforementioned step ii said lower suction means (12) is moved in tandem with said collapsible platform (19), and said upper suction means (11) is moved axially perpendicularly to the plane of said cut piece (1).

In another embodiment of the method, in step iii, the upper clipper (8) and the lower clipper (9) are rotated around a respective rotary cylinder (16B, 16C) and placed them in a position to grip respective layers (4, 3).

In yet another embodiment of the method, in steps iv and vii, said swinging movement of said collapsible platform (19) is enabled by a pair of second pneumatic cylinders (20).

In a further embodiment of the method, in steps v and vi, said swinging movement of said spreader bar (15) is carried out using said rotary cylinder (16A).

In a still further embodiment of the method, the axial movement of said upper suction means (11) in steps ii and vii is enabled by a first pneumatic cylinder (7). In another embodiment of the method, said press assembly (13) is a rectangular member of length at least equal to the length of said spreader bar (15).

In yet another embodiment of the method, said movement of said press assembly is enabled by a third pneumatic cylinder (18).

In a further embodiment of the method, length of said spreader bar (15) is between 40% to 70% of the width of said cut piece (1).

In one more embodiment of the method, said swivelling mechanism (14) is a pair of hinges (14).

While the above description contains much specificity, these should not be construed as limitation in the scope of the invention, but rather as an exemplification of the preferred embodiments thereof. It must be realized that modifications and variations are possible based on the disclosure given above without departing from the spirit and scope of the invention. Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their legal equivalents.