WO2023135516A1

WO2023135516A1 - An apparatus and a method for hemming edges of a tubular bag and a tubular bag

Info

Publication number: WO2023135516A1
Application number: PCT/IB2023/050203
Authority: WO
Inventors: Gaurav LOHIA
Original assignee: Lohia Corp Limited
Priority date: 2022-01-13
Filing date: 2023-01-10
Publication date: 2023-07-20

Abstract

Apparatus, method for hemming edges of tubular bag of woven fabric of PE/PPE or HDPE material involving opening, folding, and thermally fusing edges at a cut end of a tubular bag (1) made from woven fabric, and a tubular bag. The apparatus comprises a pre- opening unit (F), a mouth folding unit (G), and a thermal fusion unit (H) positioned sequentially. Each unit (F, G, H) has a suction mechanism (13a,13b,13c) placed above top layer (21a) of the bag (1) for opening the unsealed end (2a); a linear guide mechanism (15a,15b,15c) to actuate the suction mechanisms (13a), a support bed (22a,22b,22c) facilitated with suction mechanism and provided under a lower layer (21b) of the bag (1), and a perforated plate (16a,16b,16c). Layers (21a,21b) are separated (pre-opening unit F) at open end (2a) followed by creating inward folded edges (12) at folding unit (G), and heat fusing them at the thermal fusion unit (H).

Description

AN APPARATUS AND A METHOD FOR HEMMING EDGES OF A TUBULAR BAG AND A TUBULAR BAG

Field Of Invention

The present invention relates to an apparatus and a method for hemming edges of a tubular bag of woven fabric of PE/PPE or HDPE material so as to manufacture hemmed bags. In particular, it relates to a method for hemming a bag mainly consisting of steps of opening, folding, and thermally fusing a tubular cut piece made from woven fabric. More particularly, the present invention involves an automated method of inner folding of layers at one of the ends and sealing it to form a hemmed structure with the help of thermal fusing device used to fuse the folded layer of tubular cut pieces.

Background of Invention

In the raffia industry, a bag is particularly made up of PE/PPE or HDPE. These bags are basically of two types, woven and non-woven. Woven bags are made up of woven fabric obtained from the loom by weaving of weft and warp tapes together and are further differentiated into coated and non-coated type. Coated type bags are coated with a PE/PPE film while non-coated type of bags are just made of PE/PPE or HDPE without any layer of coating. Since the woven bags with non-coated fabric tend to fray at the edges during handling while being transported or refilled, thus they are continuously ruined. Therefore it becomes visually offensive from aesthetics perspective. They also require repair work at the packaging stations.

To prevent the fraying problem at bag edges there are many options such as widening of seams or sewing French seams, interfacing, or using pinking shears, providing zig-zag stitch or a hand stitch, using serge or tape bound edges or fabric glue, or many more other advanced techniques. Present invention also has its roots in the already known technology, known as hemming i.e., the process in which the edge is rolled flush to itself, while a seam joins the edges of two materials. Hems are commonly used to reinforce an edge, hide burrs, and rough edges, and improve appearance. Fraying is major problem in woven type non-coated bags and the present invention is related to preventing or obviating the problem of fraying edges of the bag ends and make them aesthetically more stable appealing and structurally more stable.

Further, in the industry, the general practice is to fold and seal one of the ends of the bag manually which is labour intensive work and also reduces the overall production rate. In addition, as it involves purely manual work, errors in folding can be observed and while packing over packers these folded ends might get damaged or unfolded.

Prior art documents disclose the process of hemming plastic woven bags made up of PE/PPE or HDPE material, either coated or non-coated. For instance, Patent TW M606717 U (hereinafter referred to as ‘6717) discloses a bag body looping device of a flat mouth machine, especially a bag mouth bonding device structure after the bag body is folded. It is opened and closed by two bag opening platforms. Second, each corresponding surface of the bag-opening platform is embedded with suction holes, and an electric heating plate is arranged outside the bag-opening platform. The key aspect of the invention is that the front of the bagopening platform is provided with two electric heating rods, which can be set as pivots. The bag opening platform is externally rotated to between the bag opening platforms, so that the electric heating rod and the electric heating plate can bond the bag opening after the folding to achieve the integrity of the ring opening.

However, there are some drawbacks related to the mechanism disclosed in the said patent (‘6717), such as additional pivots sealing units are required to seal the bag peripheral ends which creates the problem of additional time requirements for the sealing purpose as well as requirement of additional fitment mechanisms which increases the complexity of the mechanism. Patent (‘6717) also does not discloses anything about the infolding mechanism of the bag edges while it discloses that the folded edges are glued with the inner surface to retains the bag at the folding states before sealing which required additional gluing units and time requirement to performs the specific task.

Therefore, there is a requirement for providing a mechanism for quick preopening, folding, and thermal fusion of a bag edges in-line with the bag conversion machine so that the problem related to fraying of the edges can be obviated and at the same time to make a bag more appealing and easier to use for the further packaging station. Hence, there is a need of a suitable solution or a device to produce a bag without any fraying thread or tapes coming out from the edge of a bag.

Objects of Invention:

Accordingly, some of the objects of the present invention are as follows.

The main objective of present invention is to provide an automated apparatus used for opening, folding, and thermally fusing the edge of a bag.

Another object of the present invention is to provide an automated apparatus to prevent or obviate the problem of fraying edges of the bag ends and make them aesthetically more appealing and structurally more stable.

Another objective of present invention to provide a method to prevent the fraying of thread or tapes of the bag edges.

Further objective of the present invention is to prepare bag for easy filling of material without any obstructions from the fraying threads or tapes coming out from the edge of the bag.

Yet another objective of the present invention is to integrate the inventive apparatus with the bag conversion machine so as to increase the overall efficiency of the system in continuous line. Brief Description Of Figures:

Figure 1(a) shows the opening station for easy pre-opening of the bag and making them available for the next processing station.

Figure 1(b) shows the folding station to fold the desired edge of the bag folding inwards and make them available for the next processing station.

Figure 1(c) shows the thermal fusion station to fuse the inward folded edge of the bag.

Figure 1(d) shows the bag with one end closed and other end with hemmed edges.

Figure 2 shows the block diagram of the process of manufacturing a hemmed bag by folding one of the ends inwards and sealing it.

Figure 3 shows the isometric view of the negative gauge pressure creating mechanism used for bag mouth opening at all three processing stations

Figure 4 shows the isometric view of the pre-opening unit used to move out the fraying edges out of the bag body.

Figure 5 shows the isometric view of the mouth folding unit used for inward folding of the bag edge.

Figure 6 shows detailed view of folding mechanism used to edge folding.

Figure 7 shows the isometric view of the thermal fusion station used to fuse the inward folded edge of bag. Figure 8 shows tubular bag and its cross-section view of the folded edge and thermal fusion nugget.

Figure 9 shows isometric view of the complete invention consisting of conveyor unit, Pre-opening unit, Mouth folding unit, Thermal fusion unit.

List of Parts:

1. Tubular bag 15a. First linear guide mechanism

2. bag ends 15b. Second linear guide

2a. bottom end of bag mechanism

2b. top end of bag 35 15c. third linear guide mechanism

3. Bottom Sealed end 16 a. First Perforated plate

4. first rotor 16b. Second Perforated plate

4a. second rotor 16c. Third Perforated plate

5. first arm 17. Folding Mechanism

6. second arm 40 18a. forward liner moving

6a. initial position mechanism

6b. final position 18b. transverse linear moving

7. third arm mechanism

7a. Inward pushing arm 19. leading edge b. Side pushing arm 45 20a. Horizontal linear

8. linear rail mechanism

9. spring loaded mechanism 20b. Vertical linear mechanism

10. thermal fusion mechanism 21a. Upper layer

10a. fusion slab 21b. Lower layer

11. projection profile 50 22a. First support bed

12. inward folded edge 22b. Second support bed

13a. First suction mechanism 22c. Third support bed

13b. Second suction mechanism 23 a. First set of vacuum boxes

13c. Third suction mechanism 23b. Second set of vacuum boxes

14. Hose connection 55 23 c. Third set of vacuum boxes A. Web puller unit F. Pre-opening unit

B. Cutting unit G. Mouth folding unit

C. Folding unit H. Thermal fusion unit

D. Stitching unit I. Stacking unit

E. Conveyor unit

Summary Of Invention:

The present invention relates to an apparatus and a method/process of edge hemming for the prevention of fraying of edges of a bag made from woven fabric and making them available for further packing process. In the present invention the whole process is mainly divided into three sub-processes carried out i.e., opening of mouth using a pre- opening unit, folding of the opened mouth using a mouth folding unit, and thermally fusing the edges of the folded mouth using a thermal fusion unit one after the other to prevent the edges of bag from fraying and the apparatus of the present invention facilitates these sub-processes.

In the bag conversion machine, tubular fabric from the unwinder station unrolls to be conveyed towards the cutter where the tubular fabric is cut into flattened cut pieces of predetermined length and sent for further processing. The cut pieces have main faces made from individual layers of fabric - an upper or top layer and a lower or bottom layer. In the very next station processing station i.e., the folding unit, bottom end of the is stitched in the stitching unit, to turn the cut piece into a bag (hereafter referred to as a bag) with one end sealed and one end unsealed. Next, the bag enters through conveyer unit to the apparatus of the present invention for the process of pre-opening of the unsealed end of the tubular bag which having local welding taken place at the edges of the unsealed end due to hot cutting mechanism. The unsealed end, where the edges of the upper and lower layers of the bag are fused together, at least partially, need to be separated for further processing such as folding and thermal fusion, bottom stitching, and formation of the final bag. Hence a pre-opening station is required to open or separate the edges at the unsealed end of the bag. This is done with the help of a pair rotary mechanism used fitted with arm placed radially inwards having length nearly equal to the one forth the bag piece such that one rotor assembly is used to cover half of the bag width as shown in Figure 1(a).

Next processing station for the present invention is mouth folding station which is used to fold the edge of the unsealed end of the bag to the predetermined length in inward direction and prepare the edges at the unsealed end of the bag to fuse with the layers the bag at upcoming next station which is thermal fusion unit. Folding is done with the help of folding unit consisting of a pair of rotor arrangement with arm linkage and another arms linkage actuated with the help of liner guide mechanism which can be linear motor, pneumatic cylinder etc., which is used to push the bags in the desired shape and folding as shown in Figure 8 and then bag with folded edge is moved to the next bag station.

At the next processing station, i.e., the thermal fusion unit of the present invention, the thermal fusion of the inward folded edges with layers of the bag is done with the help of a thermal fusion device that raises the temperature to within the range of 240 ± 5°C which is sufficient for thermal fusion of PE/PPE or HDPE layers with each other. The thermal fusion devices such as ultrasonic sealing, hot roll sealing and impression sealing are used to fuse the inward folded edges of the bag such that fusion can takes placed locally with the help of required number of projections profile lying on both side of the thermal fusion device as shown in Figure 7 and the problem of the fraying associated with a bag body edge can be prevented. Next the bag with folded edges at its unsealed end is sent for bottom closing by making single or double fold at the bottom. This bottom closing can be done after the cutting operation as well. Now the prepared bag is sent to the stacker unit for further stacking and conveying to the desired location. Detailed Description Of Invention:

A general bag conversion machine used for the production of woven tubular bag consist of various unit such as web pulling unit used to unwound the fabric roll which can be of uncoated fabric/coated fabric/ gusseted fabric then a cut piece is cut from the woven fabric roll with the help of cutting mechanism which can be done either by hot cutting or cold cutting depending upon the type of the fabric being used such as coated or non-coated. Coated fabric is generally separated with the help of cold cutting mechanism and generally have very less problem of fraying due to coating layer which adheres with the fabric and resolve the problem of edge wear and tear. On the other hand, if a non-coated fabric is separated from the roll with the help of hot cutter, it will result into the localised welding on the cutting edge of the tubular cut piece which fuses the layers of the fabric together due to the intermolecular bonding of molecules takes place between the edges of the upper layer (21a) and lower layer (21b) of the cut piece due to thermal fusion. As these layers are to be separated to open the ends of the cut piece for further processing as per requirement, so during separation, the problem of fraying occurs which damages the end of the bag (1) that is eventually made from the cut piece . Hence, to prevent the problem of localised welding at the edges of bag (1) due to hot cutting of the tubular cut piece from the fabric roll, the process and apparatus of the present invention is divided into three sub processing stations namely preopening unit, mouth folding unit and thermal fusion unit.

After the cutting, the cut piece moves parallel to the cutting direction and the bottom end (2a) of the bag (1) are closed shown as bottom sealed end (3) with the help of sealing mechanism which can be stitching mechanism, gluing mechanism, thermal fusion etc. After this stage, the cut piece is turned into a bag (1) which is sealed at one end and has its other end open. As shown in the Figure 1(a), first station of the present invention is a pre-opening unit (F) used for pre-opening of the bag (1) such that the problem of localised welding due to hot cutting of the non-coated woven fabric bag can be cured so as to prevent the problem of fraying at the bag edges. A pair of rotor mechanism (4) and a first arm (5) is used to open bottom bag end of a bag (1) with the help of a negative gauge pressure creating mechanism or a first suction mechanism (13a) placed above the upper layer (21a) of the bag (1) shown in Figure 3. A first support bed (22a) with suction means is placed just below the lower layer (21b) of the bag (1) at its open or unsealed end. The first suction mechanism (13a) placed above the upper layer (21a) of the bag (1) at a stationary position, which comes down and attaches itself to the upper layer (21a) of the bag (1) and moves back up by carrying the upper layer (21a) with it with the help of a first linear guide mechanism (15a) which can be linear motor or a pneumatic mechanism as shown in Figure 3. At the same time the first support bed (22a) holds the lower layer (21b) down with the help of suction. The first linear guide mechanism (15a) can be the combination of the multiple pneumatic cylinders arranged in the series to gain the multiple linear strokes in single stroke of the mechanism. The first suction mechanism (13a) consists of a set of vacuum boxes (23a) having first hose connection (14a) on top of each vacuum box (23a) which is connected to the vacuum creating mechanism i.e., compressors or vacuum generators. As shown in Figure 3 a first perforated plate (16a) is placed just below the set of vacuum boxes (23a) or perfect contact with the bag layer and separates the layers of the bag (1) from each other. Depending upon the requirement shape, size and no of the vacuum boxes may vary from one to N, where N can be any positive integer.

As soon as the layers of the body of the bag (1) are separated out from each other, a mechanism as shown in the Figure 4, i.e., a pre-opening unit (F) consisting of a rotor mechanism (4) fitted with the first Arm (5) starts rotating in between upper layer (21a) and bottom layer (21b) of the bag opening done with the help of first suction mechanism (13a) such that all the fraying tapes/threads at the edges of the open end of the bag (1) can be spread out and prepare the bag (1) for the next processing station mouth folding unit (G) as shown in Figure 4. First arm (5) follows the semi-circular path in the direction as detailed in Figure 4, both the first arm (5) moves in the opposite direction as well as in same direction depending upon the size of the bag (1). The length of the first Arm (5) is nearly equal to the one fourth of the total bag width such that one first Arm (5) can cover almost half of the bag width. For example, if the width of the bag (1) is 600 mm, then the length of the first arm is less than or nearly equal to the 300 mm. As the width of the bag (1) varies time to time, to overcome this problem lateral sliding of the rotor mechanism (4) can be done manually or automatically. First arm (5) pulls out the fraying threads from the edges of the bag (1) and then the bag (la) is forwarded to the next processing station i.e., mouth folding unit (G). Once the rotation of the first arm (5) is done, clean opening of the mouth of the bag (1) and complete removal of the fraying of the fabrics at their edges is achieved and the first suction mechanism (13a) which is still in contact with the upper layer (21a) of the bag (1) starts moving downward and close the mouth opening of the bag (1) and moves it with the help of the conveying system in the horizontal plane.

As shown in the Figure 1(b), second station of the present invention is the mouth folding unit (G) that is used for folding the top end of bag (2b) of the bag (1) and prepare it for the up-next thermal fusion station. Similar to the pre-opening station, mouth folding unit (G) is also provided with a of suction mechanisms as shown in Figure 3, namely second suction mechanism (13b). A second support bed (22b) with suction means is placed just below the lower layer (21b) of the bag (1) in a stationary position. At the same time a second suction mechanism (13b) provided above the upper layer (21a) , comes down and makes a contact with the upper layer (21a) of the bag (1) and carries the upper layer (21a) upward with the help of a second linear guide mechanism (15b) which can be linear motor or a pneumatic mechanism. And at the same time the second support bed (22b)holds the lower layer (21b) down with the help of suction. As the opening is created between the upper layer (21a) and lower layer (21b) of the flattened bag (1), it is ready for folding of its edges at its open end (2b). A second arm (6) attached with the rotor mechanism (4a) starts rotating from the initial position (6a) to final position (6b) and touches the side edges of the bag (1). Figure 5 shows the isometric view of the mouth folding mechanism which consists of pair of folding mechanisms (17) which is in contact with the two longitudinal sides of the bag body as shown in Figure 1(b).

Folding mechanisms (17) are mirror image of each other about the mirror plane as shown in Figure 5. The pair of folding mechanisms (17) is now moved forward with the help of a forward liner moving mechanism (18a) which can be servo driven ball bearing, pneumatic driven linear guide, or electric driven linear guide etc. The folding mechanism (17) moves forward inside the bag opening nearly two times the folding width required for hemming such that leading edge (19) of the second arm (6) moves inside the bag 15-25 mm from the edge. Following this, both the folding mechanisms (17) have moved inside the mouth opening, and the second arm (6) has moved from initial position (6a) to (6b) with the help of rotor (4a) as shown in the Figure 6. The second arm (6) consists of a slot into which the side layer of the bag (1) can be inserted at later stage. After that a transverse liner moving mechanism (18b) which can be servo driven ball bearing, pneumatic driven linear guide, or electric driven linear guide etc. gives feed to the pair of folding mechanisms (17) such that both folding mechanisms (17) move away from each other in the direction of width of the bag (1) as shown in Figure 5. As soon as it touches the side edges, a third arm (7) having two tools - an inward pushing arm (7a) and a side pushing arm (7b) actuated with the help of linear feed mechanism (shown in Figure 6) such that side pushing arm (7b) pushes the side layer/edge of the fabric from outside of the bag (1) into the slot provided in-between the leading edge of the second arm (6) at the same time inward pushing arm (7a) pushes the bag edge inward (i.e., towards the main face of the bag (1)). Due to this series of arm motions folding of the edges of the tubular bag (1) in inward direction is completed as shown in Figure 8. Thereafter, the tubular bag (1) with inward folded edges (12) is moved to the up-next processing station through the conveyor bed (E). Inward folded length of the fabric is preferably in the range of 15-25 mm (however, it could be greater or smaller) depending upon the density of the fabric. Once the inward folding of the edges at the open end (2b) is done, the folding mechanisms (17) move back to the home position and the upper second suction mechanism (13b) comes down and closes the mouth opening and creates a crease at the folding edge (12) by pressing the edge with the help of second perforated plate (16b) that is provided below a set of second vacuum boxes (23b) which can be heated with the help of heating medium which can be heater, such that it will not open while reaches the up next processing station i.e., thermal fusion unit (H).

As shown in the Figure 1(c), the third station of the present invention is a thermal fusion unit (H) that is used for the thermal fusion of the inward folded edges (12) which is complete at previous station - the mouth folding unit (G). Like the two previous units (F, G), the thermal fusion unit (H) also consists of a suction mechanism - a third suction mechanism (13c). A third support bed (22c) provided with suction means is placed just below the lower layer of the bag (1). A third suction mechanism (13c) is placed above the upper layer (21a) of the bag (1) at a stationary position and which comes down and attaches itself to the upper layer (21a) of the bag (1) and moves back up by carrying the upper layer (21a) with it with the help of a third linear guide mechanism (15c) which can be linear motor or a pneumatic mechanism. At the same time third support bed (22c) holds the lower layer (21b) down with the help of suction. As the opening is created between the upper layer (21a) of the and lower layer (21b) of the bag (1), a spring loaded thermal fusion mechanism with projection profile (11) is inserted inside the open end (2b) of the bag (1). With the help of the spring-loaded nature of the mechanism, a fusion slab (10a) can be moved in a plane perpendicular to the plane of the body of the bag (1 ). The fusion slab (10a) has a number of projection profiles (11) corresponding to both upper layer (21a) and lower layer (21b) of the bag (1). These projection profiles (11) are used for causing localised fusion between the inward folded edge (12) and inside surfaces of the respective layers (21a and 21b) such that the problem of fraying is prevented.

As shown in Figure 7, localised fusion caused by the projection profiles (11) is actuated with any of the currently available thermal fusion technologies i.e., electrical heating or supply of hot air through the projection profile (11). The details of such technologies and how to actually apply them to the projection profiles (11) is known to persons skilled in the art of this invention. The fusion slab (10a) is made of any material having very low thermal deformation as the temperature of the material reaches the range of 250°C- 280°C. The fusion slab (10a) is inserted into the tubular bag (1) opening with the help of a linear rail (8) which derives its motion with the help of a linear guide mechanism which can be linear motor or pneumatic linear arrangement. First, the fusion slab (10a) moves downward with the help of the third linear mechanism (15c) such that it fuses the lower layer (21b). At the same time, the upper layer (21a) that is in contact with the third suction mechanism (13c) that comes down with the help of the third linear guide mechanism (15c) touches the upper layer (21a) with the fusion slab (10). Hence contact time between the layer of bag (1) and projection profile (11) is very short lying between 0.5-1.5 sec depending upon the thickness of the fabric layer such that melting of the layers of the bag (1) can be prevented. Once the fusion of the inward folds (12) with the respective layers of the bag (1) is complete, the third suction mechanism (13c) moves upward carrying the upper layer (21a) of the bag (1) along with it with the help of the third linear guide mechanism (15c) and in the same time fusion slab (10a) moves back to their home position with the help of horizontal and vertical linear mechanisms (20a) and (20b).

Next, the third suction mechanism (13c) is moved downward with the help of third linear guide mechanism (15c). The upper layer (21a) is released from the third suction mechanism (13c) and bag is finally pressed by third perforated plate (16c) and then bag (1) starts moving toward the stacking unit.

Due to the division of the complete process into the three sub processing stations as explained above, such that complete invention is divided into 3 groups such that at a particular time all three substations are performing their respective task and therefore the overall efficiency of the system is increased.

Following steps are involved for top hemming of a bags:

1) Pulling fabric from a fabric roll to a conveyor unit using a Web puller unit (A).

2) After the web pulling unit fabric enters the cutting unit (B) where the work piece is cutdown into a tubular cut piece of desired length with the help of the cutting mechanism which can be either hot cutting or cold cutting as per the type of the woven fabric being used.

3) After cutting down, a tubular cut piece is entered to folding unit (C) of a bag conversion line where the one of the bag ends (2) preferably bottom end of bag (2a) of tubular bag (1) is folded and moves ahead in conversion line.

4) Just after the folding unit (C), there is provided a stitching unit (D) \ which stitches the folded bottom edges of bag (2a) of the tubular bag (1) to make a bag (1) with one sealed end and one open end. 5) After the bottom end stitching, the bag (1) is moved to the next separate conveyor unit (E).

6) After entering the next conveyor unit (E), the tubular bag (1) is entering into the pre-opening unit (F) where localised welding due to hot cutting is removed with the rotor arm mechanism.

7) After the pre-opening unit (F), tubular bag (1) is entering to the mouth folding unit (G) where the upper and lower layers (21a, 21b) at the unsealed top end of bag (2b) of the tubular bag (1) are folded inward to create the inward folded edges (12).

8) After the mouth folding unit (G), the tubular bag (1) is entering thermal fusion unit (H) where the fusion of inward folded edges (12) is done with the respective layers (21a, 21b) of the bag (1).

9) After that tubular bag (1) is stacked into the staking unit (I).

It is evident from the foregoing discussion that the invention has a number of embodiments.

The preferred embodiment of the invention discloses an apparatus for hemming edges of a tubular bag (1) made from woven fabric. The characterising feature of the preferred embodiment is that the apparatus comprises a pre- opening unit (F) for pre-opening of the unsealed end of the tubular bag(l), a mouth folding unit (G) for folding the top end(2b)of the said bag, and a thermal fusion unit (H) for thermal fusion of the inward folded edges(12) wherein these unites are positioned sequentially.

In an embodiment of the preferred embodiment, the pre-opening unit (F) consists of a first suction mechanism (13a) placed above a top layer (21a) of said bag (1) for opening the unsealed end (2a) of said tubular bag (1); a pair of rotor mechanisms (4) and a corresponding pair of first arms (5); a first linear guide mechanism (15a) to actuate the linear movement of said first suction mechanisms (13a), a first support bed (22a) facilitated with a suction mechanism and provided under a lower layer (21b) of said bag (1), and a first perforated plate (16a).

In another embodiment of the preferred embodiment, the first suction mechanism (13a) consists of a set of vacuum boxes (23 a) having individual hose connection (14) on each of said set of vacuum boxes (23 a) and connected to a vacuum generator, and wherein a first perforated plate (16a) is placed just below said set of vacuum boxes (23 a).

In yet another embodiment of the preferred embodiment, the number of said vacuum boxes corresponding to each of said first suction mechanisms (13a) is more than one.

In a further embodiment of the preferred embodiment, the mouth folding unit (G) consists of a second suction mechanisms (13b) for keeping open the top end (2a) of the bag (1) , and a second linear guide mechanism (15b) to actuate the linear movement of said second suction mechanisms (13b), a second support bed (22b) facilitated with a suction mechanism and provided under a lower layer of said bag (1), a second arm (6) attached with a second rotor (4a); said second arm (6) capable of rotating from its initial position (6a) to a final position (6b) that touches the side edge of said tubular bag (1), a pair of folding mechanisms (17) that are in contact with the two longitudinal sides of the body of said tubular bag (1), said folding mechanisms (17) being able to move forward using a liner moving mechanism (18), a third arm (7) having two tools - an inward pushing arm (7a) and side pushing arm (7b) actuated with the help of linear feed mechanism such that side pushing arm (7b) pushes the side layer of the tubular bag (1) inside a slot present in between the leading edge of the second arm (6) at the same time inward pushing arm (7a) pushes the edges of upper layer (21a) and lower layer (21b)s of cut piece (1) inward towards the main faces of said tubular bag (1) to form inward folded edges (12), and a second perforated plate (16b).

In an embodiment of the previous embodiment, the second suction mechanism (13b) consists of a second set of vacuum boxes (23b) connected to said vacuum generator and below which said second perforated plate (16b) is provided along with heating means to heat to crease the inward folded edges (12).

In another embodiment of the preferred embodiment, the thermal fusion unit (H) consists of a pair of third suction mechanisms (13c) for keeping open the bottom bag end of a tubular bag (1), and a third linear guide mechanism (15c) to actuate the linear movement of said pair of second suction mechanisms (13c), a third support bed (22c) facilitated with a suction mechanism and provided under a lower layer of said bag (1), a spring loaded thermal fusion mechanism with a projection profile (11) attached to the upper layer (21a) and lower layer (21b) surfaces of a fusion slab (10a), said fusion slab (10a) being capable of moving backward and forward in a horizontal plane using a horizontal linear mechanism (20a) and up and down in a vertical plane using a vertical linear mechanism (20b), and a third perforated plate (16c). In this embodiment, the projection profile (11) is inserted inside the open end of said tubular bag (1) and provided with electrical heating or supply of hot air for heat fusing the folded edges (12).

In yet another embodiment of the preferred embodiment, the length of said first arm (5) is nearly equal to one fourth of the width of said tubular bag (1).

In an embodiment of the previous two embodiments, the first, second and third linear guide mechanisms (15a, 15b, and 15c) are in the form of a linear motor or a pneumatic mechanism. In an embodiment of the previous three embodiments, a third perforated plate (16c) is provided to press the bag (1) having heat fused folded edges (12).

In an embodiment of the previous four embodiments, the third suction mechanism (13c) consists of a second set of vacuum boxes (23c) connected to said vacuum generator and below which said third perforated plate (16c) is provided to press the bag (1) having inward folded edges (12).

In an embodiment of the invention, the liner moving mechanism (18) comprises a forward linear moving mechanism (18a) and a transverse linear moving mechanism (18b), each of which is in the form of a servo driven ball bearing, pneumatic driven linear guide, or an electric driven linear guide.

In an embodiment of the previous embodiment, the extent of said forward movement of said folding mechanism (17) is nearly two times a folding width required for hemming of said inward folded edge (12).

The invention also discloses a method for hemming edges of a tubular bag (1) made from woven fabric using the apparatus claimed in claims 1 to 13. The key steps of the method are: a. at the top end (2b) of tubular bag (1), removing localised welding using said pair of rotor mechanisms (4) and a corresponding pair of first arms (5); b. creating inward folded edge (12) at upper layer (21a) and lower layer (21b)s of tubular bag (1) at said top end (2b) using said mouth folding unit (G); c. heat fusing the inward folded edges (12) at said thermal fusion unit (H) using After the mouth folding unit (G), tubular bag (1) is entering thermal fusion unit (H) where the fusion of inward folded edge (12) is done with the bag layer, thereby forming a hem.

The invention also discloses a tubular bag made on the apparatus as disclosed in the previous embodiments using the method also disclosed herein. The key physical feature of the bag is that it has inward folded edges (12) that are hemmed by heat fusing.

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.

Claims

Claims:

1. An apparatus for hemming edges of a tubular bag (1) made from woven fabric, characterised in that said apparatus comprises: a pre- opening unit (F) for pre-opening of the unsealed end of the tubular bag(l), a mouth folding unit (G) for folding the top end(2b)of the said bag, and a thermal fusion unit (H) for thermal fusion of the inward folded edges(12) wherein these unites are positioned sequentially.

2. The apparatus as claimed in claim 1, wherein said pre-opening unit (F) consists of: a first suction mechanism (13a) placed above a top layer (21a) of said bag (1) for opening the unsealed end (2a) of said tubular bag (1); a pair of rotor mechanisms (4) and a corresponding pair of first arms (5); a first linear guide mechanism (15a) to actuate the linear movement of said first suction mechanisms (13a), a first support bed (22a) facilitated with a suction mechanism and provided under a lower layer (21b) of said bag (1) a first perforated plate (16a).

3. The apparatus as claimed in claim 2, wherein said first suction mechanism (13a) consists of a set of vacuum boxes (23a) having individual hose connection (14) on each of said set of vacuum boxes (23a) and connected to a vacuum generator, and wherein a first perforated plate (16a) is placed just below said set of vacuum boxes (23a).

4. The apparatus as claimed in claim 3, wherein the number of said vacuum boxes corresponding to each of said first suction mechanisms (13a) is more than one.

The apparatus as claimed in claim 1, wherein said mouth folding unit (G) consists of: a second suction mechanisms (13b) for keeping open the top end (2a) of the bag (1) , and a second linear guide mechanism (15b) to actuate the linear movement of said second suction mechanisms (13b), a second support bed (22b) facilitated with a suction mechanism and provided under a lower layer of said bag (1), a second arm (6) attached with a second rotor (4a); said second arm (6) capable of rotating from its initial position (6a) to a final position (6b) that touches the side edge of said tubular bag (1), a pair of folding mechanisms (17) that are in contact with the two longitudinal sides of the body of said tubular bag (1), said folding mechanisms (17) being able to move forward using a liner moving mechanism (18), a third arm (7) having two tools - an inward pushing arm (7a) and side pushing arm (7b) actuated with the help of linear feed mechanism such that side pushing arm (7b) pushes the side layer of the tubular bag (1) inside a slot present in between the leading edge of the second arm

(6) at the same time inward pushing arm (7a) pushes the edges of upper layer (21a) and lower layer (21b)s of cut piece (1) inward towards the main faces of said tubular bag (1) to form inward folded edges (12) a second perforated plate (16b). The apparatus as claimed in claim 5, wherein said second suction mechanism (13b) consists of a second set of vacuum boxes (23b) connected to said vacuum generator and below which said second perforated plate (16b) is provided along with heating means to heat to crease the inward folded edges (12).

7. The apparatus as claimed in claim 1, wherein said thermal fusion unit (H) consists of: a pair of third suction mechanisms (13c) for keeping open the bottom bag end of a tubular bag (1), and a third linear guide mechanism (15c) to actuate the linear movement of said pair of second suction mechanisms (13c), a third support bed (22c) facilitated with a suction mechanism and provided under a lower layer of said bag (1), a spring loaded thermal fusion mechanism with a projection profile (11) attached to the upper layer (21a) and lower layer (21b) surfaces of a fusion slab (10a), said fusion slab (10a) being capable of moving backward and forward in a horizontal plane using a horizontal linear mechanism (20a) and up and down in a vertical plane using a vertical linear mechanism (20b), a third perforated plate (16c), wherein said projection profile (11) is inserted inside the open end of said tubular bag (1) and provided with electrical heating or supply of hot air for heat fusing the folded edges (12).

8. The apparatus as claimed in claim 1, wherein the length of said first arm (5) is nearly equal to one fourth of the width of said tubular bag (1).

9. The apparatus as claimed in claims 7 and 8, wherein said first, second and third linear guide mechanisms (15a, 15b, and 15c) are in the form of a linear motor or a pneumatic mechanism.

10. The apparatus as claimed in claims 7-9, wherein a third perforated plate (16c) is provided to press the bag (1) having heat fused folded edges (12). The apparatus as claimed in claims 7-10, wherein said third suction mechanism (13c) consists of a second set of vacuum boxes (23c) connected to said vacuum generator and below which said third perforated plate (16c) is provided to press the bag (1) having inward folded edges (12). The apparatus as claimed in claim 5, wherein said liner moving mechanism (18) comprises a forward linear moving mechanism (18a) and a transverse linear moving mechanism (18b), each of which is in the form of a servo driven ball bearing, pneumatic driven linear guide, or an electric driven linear guide. The apparatus as claimed in claim 12, wherein the extent of said forward movement of said folding mechanism (17) is nearly two times a folding width required for hemming of said inward folded edge (12). A method for hemming edges of a tubular bag (1) made from woven fabric using the apparatus claimed in claims 1 to 13, characterised in that the method comprises the steps of: a. at the top end (2b) of tubular bag (1), removing localised welding using said pair of rotor mechanisms (4) and a corresponding pair of first arms (5); b. creating inward folded edge (12) at upper layer (21a) and lower layer

(21b)s of tubular bag (1) at said top end (2b) using said mouth folding unit (G); c. heat fusing the inward folded edges (12) at said thermal fusion unit (H) using After the mouth folding unit (G), tubular bag (1) is entering thermal fusion unit (H) where the fusion of inward folded edge (12) is done with the bag layer, thereby forming a hem. A tubular bag made on the apparatus as claimed in claims 1 to 13 using the method as claimed in claim 14, characterised in that said bag has inward folded edges (12) that are hemmed by heat fusing.