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
5 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
10 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
15 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,
20 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.
25
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.
30 The '370 invention discloses collapsible tubular laminates useful as bag
3
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
5 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.
10 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
15 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
20 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
25 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 block30 bottom bags and valve-making related to them. However, there are no automated
4
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
5 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
10 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
15 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
20 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
25 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
30 the width of the bag.
5
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.
5 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
10 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.
15
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.
20 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
25 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
30 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.
6
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
5 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
10 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
15 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
20 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.
25 List of parts:
1. Cut piece of Fabric
1A. Bottom end Open end of cut piece of fabric
1B, 1C. Corner of cut piece of fabric
1D. Top end or Stitched end of cut piece of fabric
30 2. Conveyor table
3. Lower fabric/sheet
7
4. Upper fabric/sheet
5. Perforations
6. First device
7. First pneumatic cylinder P1
5 8. Upper clipper
9. Lower clipper
10. Gripping mechanism
11. Upper suction means
12. Lower suction means
10 13. Press assembly
14. Swivelling mechanism / hinge
15. Spreader bar
16. Rotary cylinder (16A, 16B, 16C)
17. Frame
15 18. Third pneumatic cylinder P3
19. Collapsible platform
20. Second pneumatic cylinder P2
21. Punch pad
22. Suction source/ vacuum blower
20 23. Pneumatic pressure (P1’, P2’, P3’, P4’, P5’, P6’)
24. Support sheet
25. Inward fold
26. Cut at the top edge of cut piece
25 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:
30 - Stage A shows the tubular fabric roll
- Stage B shows the tubular fabric cut to a required length
8
- Stage C shows the cut piece of fabric with a fold formed at the bottom
edge
- Stage D shows the bottom edge(1D) folded and sewn
- Stage E shows diamond shape formed at the top edge(1A)
5 - Stage F shows unsewn top edge with valve shape fully formed
- Stage G shows cut top edge with valve shape fully formed
- Stage H shows folded top edge with valve in place
- Stage I shows both edges sewn and high depth valve bag form
10 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
15
Figures 5, 5A, 5B, 5C shows perspective views of apparatus with different stages
of method of valve formation
Detailed Description Of Invention with reference to drawings:
20 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
25 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
30 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,
9
- 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
5 - 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.
10
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
15 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
20 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
25 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
30 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
10
piece has now two open ends – a bottom end (1A) and a top end (1D). The top
edge or end (1D) 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
5 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
10 piece with a valve (Figures 2G, 2H, 2I) 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).
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
20 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
25 (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
30 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
11
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
5 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
10 (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
15 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.
20
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).
25 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
30 of the cut piece can move into the open bottom end (1D). The position of press
12
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
5 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
10 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
15 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
20 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
25 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.
30 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
13
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 2I.)
5 The bag with its bottom end (1A) completely sewn and the top end (1D) 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)
10 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).
15 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 (P1’,
P2’) (23). Upper suction means (11) also comprises of perforations (5) which is
20 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
25 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
30 the first pneumatic cylinder (7) can be facilitated with the help of any
commercially available electronic devices to move in required coordinate manner.
14
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
5 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
10 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.
15 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
20 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
25 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
30 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.
15
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
5 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 (1B) at the bottom end (1A) at a
cutting station,
10 b. folding and stitching top end (1D) of said cut piece at said bottom folding
and stitching station,
c. forming an inward fold (25) at the bottom end (1A) 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),
15 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.
20 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
25 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
30 mechanism (10),
16
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
5 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
10 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
15 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
20 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
25 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).
30 In yet another embodiment of the method, said movement of said press assembly
is enabled by a third pneumatic cylinder (18).
17
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
5 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
10 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.

We Claim:

1. An apparatus for making valve in a pillow-shaped sacks made from cut
pieces of tubular fabric moving on a conveyor table (2), said apparatus
consisting of a number of stations positioned sequentially:
5 - a cutting station where in tubular fabric is cut into cut piece (1) having
a near corner (1C), and a far corner (1B) at the bottom end (1A),
- a bottom folding and stitching station where top end (1D) of the cut
piece of fabric (1) is folded and stitched,
- an inward fold forming station wherein an inward fold (25) is made at
10 the bottom end (1A) of the cut piece (1),
- an edge cutting station where in cut is made at the inward fold (25)
end of said cut piece, and
- an edge folding and stitching station wherein the inward folded end of
the cut piece of fabric (1) is folded and stitched,
15 characterised in that said inward fold forming station incorporates corner
folding station that has a spreader bar (15), a first device (6), a collapsible
platform (19), a press assembly (13), and a rigid support sheet (24), wherein:
- said first device (6) comprises a gripping mechanism (10) for gripping
individual layers (4, 3) of said cut piece (1), and upper and lower
20 suction means (11, 12) to separate said layers (4, 3),
- the plane of said collapsible platform (19) is flush with the conveyor
table (2) in its normal position and which is capable of swinging
around a swivelling mechanism (14) whose axis is parallel to direction
of travel of said cut pieces (1),
25 - said spreader bar is pivoted at its one end on a rotary cylinder (16A)
and capable of rotating in a plane parallel to that of said cut piece (1),
- said press assembly (13) is capable of moving perpendicularly to the
plane of said cut piece (1) and limits the rotational movement of said
spreader bar (15),
30 - said support sheet (24) is affixed to and capable of moving in tandem
with said upper suction means (11).
19
2. The apparatus as claimed in claim 1, wherein said lower suction means (12) is
capable of moving in tandem with said collapsible platform (19).
3. The apparatus as claimed in claims 1 and 2, wherein said upper suction means
5 (11) is capable of moving axially perpendicularly to the plane of said cut
piece (1).
4. The apparatus as claimed in claims 1 to 3, wherein said gripping means (10)
consists of an upper clipper (8) and a lower clipper (9), each of said clippers
10 being capable of swinging around a respective rotary cylinder (16B, 16C).
5. The apparatus as claimed in claims 1 to 4, wherein said swinging movement
of said collapsible platform (19) is enabled by a pair of second pneumatic
cylinders (20).
15
6. The apparatus as claimed in claims 1 to 5, wherein said swinging movement
of said lower suction means (12) is enabled by a rotary cylinder (16C).
7. The apparatus as claimed in claims 1 to 6, wherein the axial movement of
20 said upper suction means (11) is enabled by a first pneumatic cylinder (7).
8. The apparatus as claimed in claims 1 to 7, wherein said press assembly (13) is
a rectangular member of length at least equal to the length of said spreader
bar (15).
25
9. The apparatus as claimed in claims 1 to 8, wherein said movement of said
press assembly (13) is enabled by a third pneumatic cylinder (18).
10. The apparatus as claimed in claims 1 to 9, wherein length of said spreader bar
30 (15) is between 40% to 70% of the width of said cut piece (1).
20
11. The apparatus as claimed in claims 1 to 10, wherein said swivelling
mechanism (14) is a pair of hinges.
12. A method of making valves in a pillow-shaped sacks made from cut pieces of
5 tubular fabric (1) moving on a conveyor table (2) using apparatus as claimed
in claims 1 to 10, said method comprising 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 (1B) at the bottom end (1A) at a
cutting station,
10 b. folding and stitching top end (1D) of said cut piece at said bottom folding
and stitching station,
c. forming an inward fold (25) at the bottom end (1A) of said cut piece at
said inward fold forming station,
d. making a transverse cut at the edge of said inward folded bottom end
15 (1A),
e. folding said cut edge at said inward folded bottom end (1A) at said edge
folding and stitching station, and
f. stitching said cut edge at said folding and stitching station,
characterised in that said step (c) comprises the following sub-steps:
20 i. putting down said pressure assembly (13) onto said cut piece (1) 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 (1) and separating said
layers (3, 4) from each other by moving respective suction means (12,
25 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 around its swivelling mechanism
(10),
30 v. swinging said spreader bar (15) to bring the near corner (1C) towards
said pressure assembly (13), and forming an inward fold (25),
21
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,
5 viii. pressing the inward fold (25) with said support sheet (24).
13. The method as claimed in claim 12, wherein in 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
10 said cut piece (1).
14. The method as claimed in claims 12 and 13, wherein in step iii, said upper
clipper (8) and said lower clipper (9) are rotated around a respective rotary
cylinder (16B, 16C) and placed them in a position to grip respective layers (4,
15 3).
15. The method as claimed in claims 12 to 14, wherein in steps iv and vii, said
swinging movement of said collapsible platform (19) is enabled by a pair of
second pneumatic cylinders (20).
20
16. The method as claimed in claims 12 to 15, wherein in steps v and vi, said
swinging movement of said spreader bar (15) is carried out using said rotary
cylinder (16A).
25 17. The method as claimed in claims 12 to 16, wherein the axial movement of
said upper suction means (11) in steps ii and vii is enabled by a first
pneumatic cylinder (7).
18. The method as claimed in claims 12 to 17, wherein said press assembly (13)
30 is a rectangular member of length at least equal to the length of said spreader
bar (15).
22
19. The method as claimed in claims 12 to 18, wherein said movement of said
press assembly is enabled by a third pneumatic cylinder (18).
20. The method as claimed in claims 12 to 19, wherein length of said spreader bar
5 (15) is between 50% to 70% of the width of said cut piece (1).
21. The method as claimed in claims 12 to 20, wherein said swivelling
mechanism (14) is a pair of hinges.
10 22. A method of making of pillow-shaped sacks with a higher (deep) width valve
by using the apparatus as claimed in claims 1 to 11 and method as claimed in
claims 12 to 21.
23. A pillow-shaped sack having a valve made using a method as claimed in
15 claims 12 to 23, characterised in that said valve has been has a depth greater
than 40% of the width of the said sack.
24. The pillow-shaped sack as claimed in claim 23, wherein said valve has a
depth of between 40% to 70% of the width of said sack.