Field Of Invention

This invention relates to a cutting device and a method for efficient cutting of a web of sheet material, and particularly a moving web in a processing line.

Background Of Invention

There are many processing lines and conversion lines wherein the web cutting systems are already in usage. The conventional knife arrangements have proved to be highly successful in the handling of sheet materials such as cardboard, plastics and like materials which are relatively thick or otherwise resistant to conventional cutting knives. However, these systems have not been satisfactory for use with webs of materials which have a high tendency to elongate under stress and/or a low coefficient of friction such as, for example, woven and nonwoven plastic fibre or filament webs.

The problem which arises in the cutting of such webs derives from the basic fact that with any knife which relies for the cutting action on its passage through an inadequately supported web, as distinguished from a guillotine type knife which cuts a web directly against an anvil which supports it adequately, the tension in the web is an essential factor in the cutting action. In other words, the tension in that portion of the web which is under the action of the knife must be adequate to keep the web sufficiently taut for passage of the knife therethrough, rather than merely stretching the web without the knife penetrating it. This problem is especially acute in connection with webs which have such a high tendency to elongate under stress to the extent that they must be handled in a processing line and rewound under very low tension to prevent permanent elongation in the wound roll. A typical example of such a web is a woven plastic of such high tendency to stretching. If it is attempted to cut such a web with the knife arrangement, undesirable amount of elongation will occur between the knife and the unwinding roll causing excessive knife travel. In addition, some web materials, depending upon their coefficient of friction, will skid against the driving drum before enough tension can be developed to cut the web.

As an example, US patent 3611856 (‘856) discloses web cutter for cutting a web of material into web portions of a predetermined size. The ‘856 invention further discloses a cutter system which is placed perpendicularly to the direction of the web. The ‘856 invention a does not discloses the efficient cutting of fabric by inclining the cutter vertically to use the full surface of the blade. Thus the invention disclosed in ‘856 require frequent blade change which ultimately increases the downtime and reduces production.

Indian patent application 202011020787 (‘0787) discloses a cutting device which is for the high speed application of cutting fabric. The Patent (‘0787) further discloses a cutting device in which the cutter is rotated in the circular fashion and also the cutter is mounted inclined to the cutting platform. But the main drawback of the patent (‘0787) is that the wear of the cutting blade is frequent as the speed of cutting is high and the cutting happens by the same cutting edge every time. The results into the frequent blade change and increases the downtime, thereby reduce the production rate.

Another patent, CN209699974U (‘9974), discloses a cutting device for plastic woven bag with longitudinal scissors to cut the fabric into pieces. The Patent (‘9974) further discloses a cutting table having a first rubber roller and a second rubber roller are rotatably installed on the cutting table , and the first both ends of the rubber roller and the second rubber roller are keyed with longitudinal scissors , the two sets of longitudinal scissors are engaged with each other, and the first rubber roller. And at one end of the second rubber roller are respectively keyed with a first gear and a second gear, the first gear and the second gear in a meshing connection. The end of the second rubber roller is fixedly connected to the output shaft of the motor. The patent (‘9974) does not addresses the problem of frequent blade change and the production loss.

Thus the major problem of using conventional knife arrangement which cuts the fabric by moving in the linear fashion perpendicular to the moving fabric is that predetermined fabric length is repeatedly cut using the same cutting edge.

Therefore, the life of the cutting edge for the fabric decreases and the cutters become blunt needing frequent replacement. In conventional fabric cutting devices, the frequency of replacement of the cutter blade is high, and thus there is concern that the working efficiency of the device decreases and the workload of the operator increases, which ultimately increases the operational costs due to the increase in the number of instances of disposal of the cutter blade.

Figure 1 shows a movement of the conventional cutting device (10) with a system of cutting operation, wherein a cutting device (10) is present which parallel to the top edge (10) of cutting device and comprises of blade (30), the movement of which is shown in a broken arrow such that it is parallel to the cutting line (33). The blade (30) travels from second longitudinal edge (32) of the fabric to the first longitudinal edge (31) of the fabric. Further, the blade (30) at different positions is shown such that at each position of cutting, the cutting point (28) is the same. Cutting point (28) is the point at which object is cut wherein fabric is cut into desired length in each cycle of cutting. XI distance is calculated by measuring distance from cutting line (33) to the lower end of the blade (29) and it is found out that it is same at each and every position of cutting. Such single point cutting at cutting point (28) degrades the blade (30) which needs to be replaced frequently as physically the same cutting point (28) on the blade (30) makes the cut in each repetitive cycle of cutting. Further, due to cutting at single point in every cycle of cutting, the blade (30) tends to degrade and will eventually tear the fabric rather than cutting.

Thus, there is need for a cutting system which is not restricted only to the moving web but also for the stop and go cutting wherein the web is made stationary for a moment and is cut by the blade at a desired length, then again it is made to move for further processing.

Also, there is a need for a more efficient cutting system for continuously moving web, particularly woven plastic fabric moving at higher speed and which also overcomes the aforementioned drawbacks of the conventional systems.

Objects of Invention:

The main objective of the present invention is to provide a web cutting device to facilitate an efficient and accurate cutting of a moving web made of woven plastic.

A further objective of the present invention is to provide a web cutting device which allows rapid cutting of a moving web made of woven plastic with low maintenance cost.

Another objective of the present invention is to provide a robust system which does not require frequent change of blade.

Further objective of the present invention is to provide a system and method of vertical lifting the cutting device which improves the life of the cutting blade. Yet another objective of the present invention is to provide a web cutting device which provides flexibility in handling of different specification webs without much alteration in the device.

Summary Of Invention:

The cutting device (7) of the present invention for cutting a web or fabric comprises a transport table for the workpiece movement and a movable blade, the blade being preferably guided along an orbit in circular fashion. The blade movement can also follow a linear path from one end of web to another during one cut and reverse its direction during another cut. For high speed applications operating at speeds such as 120 - 140 cuts / min or higher, the return of the blade should be as quick as possible such that time taken by preceding web to come to the cutting region will exactly matches with the moment of the blade’s return to the region. Thus, the web cutting apparatus (1) incorporating the cutting device (7) disclosed herein enables highest throughput rates of workpieces and whereby the web cutting apparatus is advantageously used for the separation of workpieces from a woven plastic web.

Further, cutting device (7) is mounted vertically inclined, i.e., at an angle of inclination with the horizontal plane, to the cutting platform as shown in figure 2. Due to the inclined mounting of the cutting device (7) in the apparatus (1) of present invention, the movement of the blade with respect to the cutting plane is such that the cutting point on the blade (30) changes as the blade (30) advances. So, after a long run of cutting operation, the blade will not wear out as cutting happens at different locations or points.

The blade (30) is mounted on a conveyance means, such as a belt. The conveyance means rotates in a plane that is perpendicular to the direction of movement of the unrolling web or fabric. The movement of the blade (30) can be further observed as it moves from one extreme edge of the fabric to another extreme edge in manner that is inclined to the horizontal plane (or the plane of the moving web) such that the actual cutting point on the cutting edge of the blade (30) continuously changes as it moves in the transverse direction to the direction of the moving web.

The roll carrying a fabric that needs cutting into pieces is unwound from a unwinding unit. The fabric may be made of stretched plastic tape, which is optionally coated, or of plastic film, or of composite materials of fabric and plastic films. The fabric can be ventilated fabric or leno type having ventilation. The roll is not restricted to carry fabric but can also carry sheet metal or paper or carboard as well.

The unwound fabric travels on a transportation means or a conveyance means onto a cutting platform. The conveyance means may be operated using driven rollers. Adjacent to the worktable is provided a transverse transport device which is in the form of a conveyor belt (not shown), and clamping means for workpieces, such as grippers or magnets.

The separation of a leading workpiece from the continuously arriving unrolled fabric takes place by the means of the cutting device which comprises at least one movable blade or can contain a cutter which follow a linear path, wherein the blade is guided along an orbit, which moves in a circular fashion, substantially transversely to the longitudinal transport direction. The endless belt runs around two rollers, at least one of the two rollers is driven by a motor with speed controller, preferable a servo-motor. The blade severs the incoming workpiece across the width by travelling at controlled speed based on incoming workpiece traverse rate.

The cut made using the cutting device is of high quality, i.e. a smooth cut is produced. Such cut is free from fabric fraying at the ends, also the cut made is even throughout the cutting. The cuts such as of zig zag or uneven profiles are eliminated by use of the device disclosed.

The transverse transport device conveys individual workpieces, away from the work area in a transverse transport direction which is oriented orthogonally to the longitudinal transport direction. It is not necessary for the fabric to travel in the traverse direction but can be transported inline as well which will depend on the process requirement.

In a subsequent process step, once the blade has already completely cut off the single web piece from the contiguous web, it moves along its orbit to the top of the endless belt and thus out of contact with the web. The individual workpiece is conveyed away from the working area by means of the transverse transport device in the transverse transport direction.

Brief Description Of Figures in the drawings:

Figure 1 shows the movement and method of cutting fabric by conventional cutting device

Figure 2 shows the movement and method of cutting fabric by cutting device of present invention

Figure 3 shows the perspective view of the web cutting apparatus showing front side of the cutting device of present invention

Figure 3 A shows the enlarged view of the front side of the inventive cutting device

Figure 4 shows back side of the cutting device of present invention Figure 5 shows another view of the back side of the cutting device of present invention Figure 5A shows the enlarged view of the back side of cutting device of present invention with the adjustment assembly

List of Parts:

1. Web cutting apparatus 18. Adjustment knob 2. Web 19. Pointer

3. Base frame 20. Scale

4. First Side plate 30 21. Rod

5. Second Side plate 22. Adjustment lever

6. Web guide roller 23. Second connecting bracket 7. Cutting device of present 24. First slot invention 25. Adjustment hardware

8. Cutting platform 35 26. Second slot

9. Pre-draw roller assembly 27. Cutting edge

10. Top edge of cutting device 28. Cutting point 11. Post-draw roller assembly 29. Lower end of blade

12. Front cover 30. Blade

13. Back plate 40 31. First longitudinal edge of

14. First connecting bracket fabric

15. Web cut piece 32. Second longitudinal edge of 16. Adjustment assembly fabric

17. Motor 33. Cutting line

Detail Description Of Invention:

Figure 2 shows a the movement and method of cutting fabric by cutting device (7) of present invention which comprises a blade (30) the movement of which is shown by broken lines. The top edge (10) of the cutting device (7) of present invention is vertically inclined (or inclined in a vertical plane) at an angle 0 with respect to the cutting line (33). The vertical angle of orientation, also termed as angle of inclination (0), is the angle with the horizontal plane, formed between the top edge of the cutting device (10) and the cutting line (33).

The vertical angle of inclination (0) can be in the range of 0-10° or more particularly in the range of 0-5° wrt to the cutting line (33), preferably 1.5-2°. The angle of inclination (0) is kept minimum to facilitates the high-speed cutting without damaging or breaking the blade (30). The larger the angle of inclination (0), the more length of blade (30) is required to reach the fabric thus at highspeed cutting larger length of blade (30) tends to break. The cutting device (7) can also be horizontally inclined with respect to the cutting platform.

As an example, in a bag conversion machine which is used for cutting web pieces from a web roll and is operating at a speed of 120-140 cuts/minutes having the cutting device (7) with vertical angle of inclination (0) set at 12° with respect to the cutting platform, the blade length requires 8cm. It was found that at high speed the blade breaks frequently. When in the same bag conversion machine, the vertical angle of orientation is reduced to 1.5°, the blade length now require is only 2cm and in such case the blade last very long. Thus, reducing the downtime of machine for blade change.

The blade (30) travels from second longitudinal edge of the fabric (32) to the first longitudinal edge of the fabric (31) such that at each position of cutting, the cutting point (28) is different. The positions indicated by numbers 28, 28’, and 28” are cutting points obtained during cutting of the fabric by the blade (30). Further, the distances X2, X3, X4 are calculated by measuring distance from cutting line (33) to the lower end of the blade (29) and it is found out that it is different at each and every position of cutting. Such multiple position cutting at (28, 28’, 28”) increases the life of blade (30) by utilising the entire cutting edge (27) of the blade (30) such that it is not require blade (30) to be replaced frequently.

Figure 3 shows a web or fabric cutting apparatus (1) of the present invention which facilitates accurate cutting of a continuously moving web (2) made of woven fabric such as plastic. The web cutting apparatus (1) is not restricted to use fabric for cutting but can also cut the materials such as metallic or non-metallic sheets, paper, or cardboard as well.

The web cutting apparatus (1) comprises of a first side plate (4) and a second side plate (5) which are connected to and supported by a base frame structure (3) and the cutting device of present invention (7). The base frame structure (3) is constructed of a plurality of the rectangular cross-sectional members which are jointed or welded together to form a sturdy base.

The side plates (4, 5) are constructed in the form of a thick plates and are attached to the base frame structure (3) by any kind of joining means such as welding, bolting, or screwing to form a rigid member.

The apparatus (1) further comprises a cutting platform (8) onto which the continuous moving web (2) from the unwinder (not shown) is conveyed in the direction shown by dotted arrow by a pull-off driven roller (not shown) and passes through a set of web guiding rollers (6) to maintain proper tension and avoiding shrinkage of the web (2).

The apparatus (1) also comprises of a pre-draw roller assembly (9) and post-draw roller assembly (11). Using a cutting device of present invention (7), the cutting of the moving web (2) takes place in between of the rollers (9, 11) on the cutting platform (8), whereby the continuous web (2) is converted into the web cut pieces (15). The pre-draw roller assembly (9) and post draw roller assembly (11) are individually constructed in such a way that they both have a plurality of rollers mounted on a single shaft.

Figure 3 A shows the enlarged view of the cutting device of present invention (7). The front side of the cutting device (7) shows the front cover (12) which encloses the blade (30) which is driven in circular fashion by the motor (17).

Figure 4 shows the back side of the cutting device of present invention (7) with the back plate (13). The cutting device (7) is mounted on the cutting platform (8) and is connected from the back plate (13) by the side plates (4, 5). The back plate (13) of the cutting device (7) is connected with the first side plate (4) at one end via second connecting bracket (23) (which is part of an adjustment assembly (16)) and on the another end it is connected with the second side plate (5) via first connecting bracket (14), which is also a part of the adjustment assembly (16). The connections of first and second connecting brackets (14, 23) are done by bolting, welding, or riveting which provide a sturdy joint between the cutting device (7) and the side plates (4, 5). The first connecting plate (14) can be constructed by a plate or a sheet which can be metallic or non-metallic or fibre reinforced material such that it holds the cutting device (7) in upright position without any vibrations. Further, the adjustment assembly (16) comprises of second connecting bracket (23) as shown in figure 4. The second connecting bracket (23) also can be constructed by a plate or a sheet which can be metallic or non-metallic or fibre reinforced material such that it holds the cutting device (7) in upright position without any vibrations.

The web (2) is drawn by the pre-draw roller assembly (9) into the cutting region where a clear cut is made and simultaneously the post draw roller assembly pulls the cut piece (15) such that it is separated from the web (2). Figure 5 and 5A, also shows another view of the back side of the cutting device of present invention (7) with the adjustment assembly (16). The adjustment assembly (16) is provided towards the back side of the cutting device of present invention (7) and affixed to the apparatus (1) using a first side plate (4). The adjustment assembly (16) comprises of a second connecting bracket (23) having plurality of slots namely first slot (24) and second slot (26) which housed the adjustment hardware (25) and adjustment lever (22). The adjustment hardware (25) act as mechanical fasteners and provide a rigid connection between the second connecting bracket (23) and the back plate (13). The adjustment hardware (25) can be selected from the group of fasteners such hex head screw, hex soc head screws with high grade such that it bears the load of the cutting device (7).

The slots (24, 26) can be of identical dimensions but not necessary. The adjustment lever (22) is constructed by a solid shaft with circular or rectangular cross section which can bear the load of the cutting device (7) during operation of adjustment. Adjustment assembly (16) further comprises of an adjustment knob (18) which is connected to the adjustment lever (22) via rod (21). The connection between the adjustment lever (22) and rod (21) can be done by welding, riveting, bolting, or locating and restricting its movement by circlip.

A pointer (19) is mounted on the second connecting bracket (23) by bolts or rivets which points towards the scale (20) and indicated the operator how much the cutting device (7) is vertically tilt from the cutting platform (8). The scale (20) which is bolted or pasted at the back side of the cutting device (7) indicates the vertical angle of inclination (0) with respect to the cutting platform (8). The figure 4, shows a scale (20) with the range of 0-2° which is just an indication. The scale (20) and its range can be changed according to the operational requirement.

Further, for any given angle of orientation, the cutting points on the blade will vary within a range. Changing the angle of inclination (0) will ultimately change the cutting point (28) range on the blade (30), so the operator in order to increase the life of the blade (30) changes the angle of inclination (0) time to time.

Further, the vertical tilting of the cutting device of present invention (7) is done by changing the angle of inclination (0) which can be done by rotating the adjustment knob (18) as shown by the arrow in the figure 4, which moves the adjustment lever (22) into the second slot (26) in the upward direction. In such case the degree in the scale (19) changes from the initial zero and knob (18) can be rotated till the pointer (19) indicates the desire degree.

Before rotation of the knob (18) the adjustment hardware (25) to be loosened which are present at the one of the sides of the cutting device (7) and also the hardware which connects the first connecting bracket with the back plate (13) of the cutting device (7) to be loosen. After adequate adjustments, the hardware(25) to be tightened with same strength. These adjustments include changing the angle of orientation and checking whether the cutting edge (27) of blade (30) is touching the fabric on which cut is made.

As an example, when the conventional cutting device (10) is mounted on the cutting platform (8) of bag conversion machine for cutting web pieces from a web roll which is operating at a speed of 120-140 cuts/minutes, it was found that at 48 hrs of operation, operator has to change the blade (30) as the cutting edge of the blade is damaged which requires 5 - 7 mins of downtime. This downtime reduces the bag production by 600-800 bags. Whereas, when the cutting device of present invention (7) is mounted on the same bag conversion machine the blade (30) requires to be changed after 240 hrs as the cutting happens at different cutting point utilising entire cutting edge (27) of the blade (30).

The present invention also provides an efficient method of cutting a moving web (2) at the different cutting point (28) utilising the entire cutting edge (27) of the blade (30). The said method uses the web cutting apparatus (1) for cutting a moving web (2) and a cutting device of present invention (7) with the inventive adjustment assembly (16) for tilting the cutting device (7) vertically.

The method of the cutting of the moving web (2) using the cutting device (7) comprises of following steps:

• Loosening the adjustment hardware of the first connecting bracket (14) as well as hardware of the second connecting bracket (23)

• Rotating the adjustment knob (18) there by sliding the adjustment hardware (25) into the first slot (24) and adjustment lever (22) into the second slot (26)

• Recording the degree of orientation 0 by the pointer (19) pointing towards the scale (20)

• Rotating the knob (18) till the desired degree of orientation is achieved such that the cutting device (7) is vertically tilted with respect to the cutting platform (8)

• Tightening the hardware of the first and second connecting bracket (14, 23) to the original strength and upto required torque.

• Web (2) is now ready to be unwounded from unwinder and pulled by the pull-off roller from the unwinder roll.

• Web (2) passes through the web guide rollers (6) to maintain proper tension and removing shrinkage of the web (2).

• Web (2) is further pulled through the post-draw roller assembly (11) and pre-draw roller assembly (9) where proper tension is mentioned.

• Cutting device (7) cuts an efficient cut by the blade (30) at the different cutting point (28) utilising the entire cutting edge (27)

• The cut piece (15) is now separated and can be transferred to desired location.

It is therefore evident that there are a number of embodiments of the invention. In a preferred embodiment, the invention discloses a cutting device (7) provided in a web cutting apparatus (1) for cutting moving web (2) of sheet material in a processing line. The characterising features of the cutting device (7) are that it comprises a blade (30) enclosed in a front cover (12) and having its cutting edge oriented vertically. Further, a top edge (10) of said cutting device (7) is mounted at an angle of inclination (0) with the horizontal, and an adjustment assembly (16) wherein the said adjustment assembly makes said angle of inclination adjustable.

In another embodiment of the cutting device (7), the in-plane movement of said cutting device (7) is perpendicular to the direction of movement of said moving web (2).

In yet another embodiment of the cutting device (7), the direction of linear movement of the top edge (10) of said cutting device (7) is at said angle of inclination with the horizontal.

In still another embodiment of the cutting device (7), the adjustment assembly (16) itself has two connecting brackets (14, 23) that are spaced apart from each other, namely a first connecting bracket (14) for connecting a back plate (13) of said cutting device (7) at its one end to a first side plate (4) of the apparatus (1) and a second connecting bracket (23) for connecting a back plate (13) at the other end of the cutting device (7) to a second side plate (5). The adjustment assembly (16) also has an adjustment knob (18) connected to adjustment lever (22) being housed in a second slot (26) provided in the second connecting bracket (23), an adjustment lever (22) via rod (21), wherein the second connecting bracket (23) has at least two slots namely first slot (24) and second slot (26) which houses the adjustment hardware (25) and adjustment lever (22), wherein the adjustment hardwares (25) rigidly connect the second connecting bracket (23) with the back plate (13) of said apparatus (1). Finally, the adjustment assembly (16) also has a a pointer (19) mounted on the second connecting bracket (23) and which points towards an angle-measurement scale (20) fixedly attached to the back side of the cutting device (7).

In a further embodiment of the cutting device (7), the blade (30) is driven in circular fashion by a motor (17).

In a still further embodiment of the cutting device (7), the connections of said first and second connecting brackets (14, 23) to the respective second and first side plates (5, 4) are done by bolting, welding, or riveting.

In a yet further embodiment of the cutting device (7), the first and second connecting plates (14, 23) are constructed using a plate or a sheet made of metallic or non-metallic or fibre reinforced material.

In another embodiment of the cutting device (7), rotating the adjustment knob (18) moves the adjustment lever (22) into the second slot (26) in the upward or downward direction.

In yet another embodiment of the cutting device (7), the adjustment hardware (25) is selected from the group of fasteners such hex hd screw, hex soc hd screws with high grade.

In still another embodiment of the cutting device (7), the angle of inclination (0) is variable.

In another preferred embodiment of the invention, a method of the for efficient cutting of a moving web (2) of sheet material using the cutting device (7) is disclosed. It has the following characterising steps: a. loosening the adjustment hardwares of the first connecting bracket (14) as well as hardwares of the second connecting bracket (23); b. rotating the adjustment knob (18) there by sliding the adjustment hardware

(25) into the first slot (24) and adjustment lever (22) into the second slot

(26); c. recording the angle of inclination (0) by the pointer (19) pointing towards the scale (20); d. rotating the knob (18) till the desired angle of inclination is achieved such that the cutting device (7) is vertically tilted with respect to the cutting platform (8); e. tightening the respective hardwares (25) of the first and second connecting brackets (14, 23) to the original strength and upto the required torque; f. web (2) is now ready to be unwounded from unwinder and pulled by the pull-off roller from the unwinder roll. g. passing a web (2) that is ready to be unwounded from an unwinder into a cutting position; h. cutting the web (2) with said cutting device (7) using its blade (30) at the different cutting point (28) utilising the entire cutting edge (27).

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.