Patent Description:
There are many processing lines and conversion lines wherein the web cutting systems are already in usage. The conventional knife arrangements of prior art patent have proved to be highly successful in the handling of sheet materials of the types listed therein, namely 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 for example as 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 directly against an anvil, 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 opposes 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 elongation under stress 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 of, for example, <CIT>, the required elongation will occur between the knife and the winding 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.

Also as an example, <CIT> ('<NUM>) discloses web cutter for cutting a web of material into web portions of a predetermined size. The '<NUM> invention further discloses a cutter system which is placed perpendicular to the direction of the web. Such '<NUM> invention does not disclose about the cross cutting method or technique of web cutting. Since the cross cutting method is advantageous during high speed cutting, so the '<NUM> invention lacks the precise cutting of web with high speed moving wet.

A device for cutting polywoven bags is known from <CIT>, which includes a cutting bed and rubber rollers. <CIT> discloses an inkjet printer with diagonal media cutter with a cutting platform onto which the continuous moving media from an unwinder is conveyed and passes through a set of web guiding rollers, a pre-draw roller assembly and post-draw roller assembly, a cross cutter apparatus having moveable knife assembly, mounted for diagonal cut at an inclined angle between said roller assemblies, wherein said cross cutter apparatus is capable of cutting said media into pieces using said movable knife assembly in between of the rollers on the cutting platform.

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

The main objective of the present invention is to provide a cutting apparatus or device or system to facilitate accurate cutting of a continuously moving web made of woven plastic.

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

Another objective of the present invention is to provide a cutting device or system which provides flexibility in handling of different specification webs without much alteration in the device or system.

The web or fabric cutting apparatus of the present invention comprises a transport table for the workpiece movement and a movable knife, the knife being preferably guided along an orbit. The web cutting apparatus 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. When the knife is in an orbit, it can be guided at a uniform speed, reducing power consumption for the gear motor or the drive, increasing life and reducing maintenance.

The knife, in the form of a blade, is mounted on a conveyance means, such as a belt. The conveyance means rotates in a direction that is nearly transverse to the direction of movement of the unrolling web or fabric.

The roll carrying a fabric that needs cutting into pieces is unwound from an 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 unwound fabric travels on a transportation means or a conveyance means onto a cutting platform. The conveyance means may be operated using driven rollers, for example. 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 means of the apparatus disclosed herein which essentially is a cutting device which comprises at least one movable knife, wherein the knife is guided along an orbit, which in the circumferential direction, substantially transversely to the longitudinal transport direction aligned endless belt to which at least one blade is fixed. The endless belt runs around two rollers, at least one of the two rollers is driven by a motor with speed controller, preferable a servomotor. The knife severed the incoming workpiece across the width by travelling at controlled speed based on incoming workpiece traverse rate.

The cut made using the device disclosed herein is of high quality, i.e. a smooth and precise cut is produced.

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.

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

<FIG> shows the apparatus of the present invention which is a web or fabric cutting apparatus (<NUM>) which facilitates accurate cutting of a continuously moving web (<NUM>) made of woven fabric such as plastic. The apparatus (<NUM>) comprises of a first side plate (<NUM>) and a second side plate (<NUM>) which are connected to and supported by a base frame structure (<NUM>) and cross cutting apparatus (<NUM>) with moving knife assembly (<NUM>). The base frame structure (<NUM>) is constructed of a plurality of the rectangular cross-sectional members which are jointed or welded together to form a sturdy base.

In one of the embodiments, the side plates (<NUM>, <NUM>) are constructed in the form of a thick plates and are attached to the base frame structure (<NUM>) by any kind of joining means such as welding, bolting or screwing to form a rigid member.

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

The apparatus (<NUM>) also comprises of a pre-draw roller assembly (<NUM>) and post-draw roller assembly (<NUM>). Using a cross cutter apparatus (<NUM>), the cutting of the moving web (<NUM>) takes place in between of the rollers (<NUM>, <NUM>) on the cutting platform (<NUM>), whereby the continuous web (<NUM>) is converted into the web cut pieces (<NUM>). The pre draw roller assembly (<NUM>) and post draw roller assembly (<NUM>) are individually constructed in such a way that they both have a plurality of rollers mounted on a single shaft.

As shown in <FIG>, the apparatus (<NUM>) further comprises of first tension rollers assembly (<NUM>) and second tension roller assembly (<NUM>) which are used for the holding of the web (<NUM>) and also presses the web (<NUM>) from above onto the pre-draw roller assembly (<NUM>) and post-draw roller assembly (<NUM>) all over the traverse web length with the help of pneumatic cylinders such that web (<NUM>) lies between the roller assemblies (<NUM>, <NUM>, <NUM>, and <NUM>). The first pneumatic cylinder (<NUM>) and second pneumatic cylinder (<NUM>) works together in the downwards direction and pushes the first tension roller assembly (<NUM>) at both ends. The first and second pneumatic cylinders (<NUM>, <NUM>) are connected to the tension roller assembly (<NUM>) via a first lever (<NUM>) and second lever (<NUM>) respectively. The said connection can be obtained by any mechanical method of bolting, screwing or using bush or bearing arrangement such that the downwards movement of the cylinders (<NUM>,<NUM>) facilitates the movement of the first tension roller assembly (<NUM>) to press the web (<NUM>) against the pre draw roller (<NUM>).

Further, the first tension roller assembly (<NUM>) and second tension roller assembly (<NUM>) are responsible for maintaining adequate tension in and holding of the web (<NUM>) during cutting so that clean and accurate cutting takes place. This web tension is created by the difference in speed between the pre-draw roller assembly (<NUM>) and post -draw roller assembly (<NUM>). The post-draw roller assembly (<NUM>) speed measured in rpm is slightly higher than the speed of pre-draw roller assembly (<NUM>), the rpm of pre draw roller assembly (<NUM>) is controlled by the first motor (<NUM>) and the rpm of post draw roller assembly (<NUM>) is controlled by second motor (<NUM>). Such difference in the rpm is also required to pull the web (<NUM>) in the direction of web movement axis (<NUM>).

In the same way, a third pneumatic cylinder (<NUM>) and fourth pneumatic cylinder (<NUM>) work together in the downward direction and push the second tension roller assembly (<NUM>) at both ends. The third and fourth pneumatic cylinders (<NUM>, <NUM>) are connected to the second tension roller assembly (<NUM>) at the ends via a third lever (<NUM>) and fourth lever (<NUM>) respectively. The said connection can be obtained by any mechanical method of bolting, screwing or using bush or bearing arrangement such that the downward movement of the cylinders (<NUM>,<NUM>) facilitates the movement of the second tension roller assembly (<NUM>) to press the web (<NUM>) against the post draw roller (<NUM>).

It is evident from the <FIG> that, pre draw roller assembly (<NUM>) and post draw roller assembly (<NUM>) are identical in construction with plurality of rollers. These rollers can be chosen from the set of rolling members such that while drawing the web (<NUM>) in the direction of web movement axis (<NUM>) the rollers provide negligible friction to the surface of web (<NUM>) due to which the web (<NUM>) does not get damaged. The first tension roller assembly (<NUM>) and second tension roller assembly (<NUM>) also comprises of plurality of rollers mounted on a first and second rod (<NUM>, <NUM>) respectively thereby connecting the rod (<NUM>, <NUM>) individually with the at least two brackets (<NUM>).

<FIG> shows the internal construction of the cross cutter apparatus (<NUM>), comprising of a moving cutting assembly (<NUM>) mounted on endless belt (<NUM>), two parallel plates, a front plate (<NUM>) and a rear plate (<NUM>) which are mounted at a prescribed gap as shown in <FIG> that is maintained by a set of top flat spacer (<NUM>) and a set of bottom cylindrical spacers (<NUM>). The front and rear plates (<NUM>, <NUM>) can be constructed from a metallic or non-metallic plate which can bear the load of the other supporting members. Cross cutter apparatus (<NUM>) is located on the cutting platform (<NUM>) at an inclined angle α as shown in <FIG> perpendicular in direction with respect to the web movement direction (<NUM>) and cross cutter apparatus (<NUM>) mounted on the first side plate (<NUM>) and second side plate (<NUM>) via first holding block (<NUM>) and second holding block (<NUM>). The said mounting can be achieved by any mechanical means such as bolting, screwing or welding.

The cross cutter apparatus further comprises of a rear plate (<NUM>) wherein at the ends of the said rear plate (<NUM>), a first pulley (<NUM>) and at the other end a second pulley (<NUM>) are mounted. The said first pulley (<NUM>) is connected to third pulley (<NUM>) via first stationary housing (<NUM>) and a first rotating shaft (<NUM>) and on the other end second pulley (<NUM>) mounted on the rear plate (<NUM>) is connected with the adjustment bracket (<NUM>) as shown in <FIG> and second rotating shaft (<NUM>).

By moving the adjustment bracket (<NUM>) as shown in <FIG>, the second pulley (<NUM>) can be moved farther from the first pulley (<NUM>). Such movement is required to increase or decrease the tension in the first endless belt (<NUM>) which passes over the pulleys (<NUM>,<NUM>).

Further, the third pulley (<NUM>) is driven by fourth pulley (<NUM>) shown in <FIG> through endless second belt (<NUM>). Hence, the rotation is transmitting from third motor (<NUM>) as shown in <FIG> which is mounted on first side plate (<NUM>) to fourth pulley (<NUM>) and from fourth pulley (<NUM>) to third pulley (<NUM>) which are connected through endless second belt (<NUM>) and then from third pulley (<NUM>) which are directly coupled to first pulley (<NUM>) and finally from first pulley (<NUM>) to second pulley (<NUM>) which are connected through endless first belt (<NUM>).

In one of the embodiments, the pulleys can be selected from the set of round grooved members having toothed or non-toothed profile, such that profile can be of any shape or size which can drive the belts along with it. Also, these pulleys are efficient enough to transmit the motor power and drive the belts smoothly.

In another embodiment, the belts can be selected from set of flexible members having toothed profile same as of pulleys and can withstand the wear and tear. The belts can be of any type such as flat belts, V belts, round belts, spring belts, multi groove belts, timing belts, speciality belts or of any kind known to person skilled in art.

Movable knife assembly (<NUM>) mounted on the first endless belt (<NUM>) which makes movable knife assembly (<NUM>) rotates in the orbit that is circumferential on the path of the first endless belt (<NUM>) which runs over the first pulley (<NUM>) and second pulley (<NUM>) to cut the web fabric in to workpiece smoothly.

As can be seen from <FIG>, the said movable knife assembly (<NUM>) is further supported and guided by the guide rails in between first pulley (<NUM>) and second pulley (<NUM>) on top and bottom positions. The said guide rails are mounted on the front plate (<NUM>) and rear plate (<NUM>) in such a manner that opposite guide rails face each other. The first Guide rail (<NUM>) and the second guide rail (<NUM>) are mounted on the front plate (<NUM>) at top and bottom position where as the third guide rail (<NUM>) and fourth guide rail (<NUM>) are mounted on the rear plate (<NUM>) exactly opposite to the first guide rail (<NUM>) and second guide rail (<NUM>) as shown in <FIG>.

In one of the embodiments, these guide rails (<NUM>, <NUM>, <NUM>, and <NUM>) may be made of any shape such as u shape cross section or any other cross section such as v shape, curve shape such that the movable knife assembly moves freely through it.

<FIG> shows perspective view of the cross cutter apparatus (<NUM>) comprises of front protective cover (<NUM>) and a swivel cover (<NUM>). Front protection cover (<NUM>) covers the knife (<NUM>) moving path to avoid any accident and pulley cover (<NUM>) is also provided to cover the rotating part to avoid any accident. At the top of the cross cutter apparatus (<NUM>) one swivel cover (<NUM>) is provided for the changing of the knife (<NUM>) when the knife (<NUM>) is worn-out so that there is no need to open the whole cross cutter apparatus (<NUM>) for changing the worn out knife which has to be done periodically. Further, the cross cutter apparatus (<NUM>) is driven by the third motor (<NUM>) which is coupled with the fourth pulley (<NUM>) and is connected to the third pulley (<NUM>) via endless belt (<NUM>).

In one of the embodiments, the front protective cover (<NUM>) may be constructed of a sheet metal or plate bend to form a rigid body which can withstand the external impact if occur during the cutting process.

In another embodiment, the swivel cover (<NUM>) can also be constructed of a sheet metal or plate bend to form a rigid surface. Also, the swivel cover (<NUM>) can be opened and closed whenever the blade (<NUM>) of the movable knife assembly (<NUM>) requires to be changed when it is worn out. Such change can take place by driving the movable knife assembly (<NUM>) to position D (<NUM>) and thereby opening the swivel cover (<NUM>). The position D (<NUM>) can be determined by set of sensors (not shown) which governed the stoppage of the movable knife assembly (<NUM>).

<FIG> shows the movable knife assembly (<NUM>) which comprises of knife holding bracket (<NUM>) on which the knife (<NUM>) is located and mounted through the knife holding plate (<NUM>) such that knife (<NUM>) lies between the holding bracket (<NUM>) and holding plate (<NUM>). The knife (<NUM>) can be selected from set of any sharp object which is capable of cutting the web (<NUM>) perfectly and smoothly without any hindrance.

The movable knife assembly (<NUM>) further comprises of first guide pin (<NUM>) and a second guide pin (<NUM>) that are clamped between the first side sheet (<NUM>) and second side sheet (<NUM>) in such a way that it forms a rigid body. First side sheet (<NUM>) and second side sheet (<NUM>) are mounted on the knife holding bracket (<NUM>) that creates the prescribed gap (not shown) between both the sheets so that the swivel action of guide pins can take place smoothly. First side sheet (<NUM>) and second side sheet (<NUM>) are constructed in arc-shaped form so that they are able to run on the circular periphery of the first pulley (<NUM>) and second pulley (<NUM>).

Further, the said movable knife assembly (<NUM>) also comprises of first opening (<NUM>) and second opening (<NUM>) for positioning of first endless belt (<NUM>) through which, the movement of the movable knife assembly (<NUM>) is driven.

<FIG>, shows perspective view of movable knife assembly (<NUM>) wherein guide pin (<NUM>) moves along the profile of the fourth guide rail (<NUM>) and second guide rail (<NUM>). As mentioned earlier, the movable knife assembly (<NUM>) is connected to the first endless belt (<NUM>) such that the said movable knife assembly (<NUM>) is driven by the first endless belt (<NUM>) along the path as defined by the first endless belt (<NUM>).

<FIG> and <FIG> show the top view of cross cutter apparatus (<NUM>) and schematic view of the cutting operation. As shown in the <FIG> and <FIG> cross cutter apparatus (<NUM>) is mounted at an inclined angle α perpendicular in direction with respect to the web (<NUM>) movement direction axis (<NUM>).

Cutting speed of cross cutter is set in such a way so that time required by the knife (<NUM>) to travel from position A (<NUM>) to position B (<NUM>) is same as the time required taken by the fabric to move from position C (<NUM>) to position B (<NUM>).

Inclined mounting of cross cutter apparatus (<NUM>) provides the flexibility to the system to set the driving speed of the cutter knife (<NUM>) with respect to the continuous moving web (<NUM>).

The present invention also provides a method of cutting a moving web (<NUM>). The said method uses the apparatus (<NUM>) for cutting a moving web (<NUM>) disclosed on the foregoing pages. The method of the cross-cutting of the moving web (<NUM>) according to the present invention comprises of following steps:.

The method disclosed herein has further embodiments described as follows.

In one of the embodiments, the rotational speed of said post-draw roller assembly (<NUM>) is slightly higher than the rotational speed of the pre-draw roller assembly (<NUM>) and wherein the rotational speed of said pre draw roller (<NUM>) is controlled by a first motor (<NUM>) and the rotational speed of said post draw roller (<NUM>) is controlled by a second motor (<NUM>).

In another embodiment, the cutting speed of said cross cutter (<NUM>) is set in such a way that time required by said knife (<NUM>) to travel from a position A (<NUM>) on first longitudinal edge (<NUM>) of fabric (<NUM>) to a position B (<NUM>) on the second longitudinal edge (<NUM>) of said fabric (<NUM>) is same as the time required by the fabric (<NUM>) to travel the distance between the position on said second longitudinal edge (<NUM>) that corresponds to said position A to position B (<NUM>).

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 scope of the invention, as defined by the claims.

Claim 1:
An apparatus for cutting a web (<NUM>) of woven sheet material, characterised in that said apparatus comprises:
- a first side plate (<NUM>) and a second side plate (<NUM>) connected to and supported by a base frame structure (<NUM>);
- a cutting platform (<NUM>) onto which the continuous moving web (<NUM>) from an unwinder is conveyed and passes through a set of web guiding rollers (<NUM>, 6A, and 6B) so as to maintain proper tension and, thereby avoiding shrinkage of the web (<NUM>);
- a pre-draw roller assembly (<NUM>) and post-draw roller assembly (<NUM>), both individually constructed to have a plurality of rollers mounted on a single shaft;
- a cross cutter apparatus (<NUM>) having moveable knife assembly (<NUM>), mounted at an inclined angle between said roller assemblies (<NUM>, <NUM>),
- a first tension rollers assembly (<NUM>) and second tension roller assembly (<NUM>) respectively mounted corresponding to said pre-draw assembly (<NUM>) and post-draw assembly (<NUM>);
- a pair of pneumatic cylinders, namely a first pneumatic cylinder (<NUM>) and a second pneumatic cylinder (<NUM>) connected to said first tension roller assembly (<NUM>) using a first lever (<NUM>), and a second lever (<NUM>), respectively, and another pair of pneumatic cylinders, namely third pneumatic cylinder (<NUM>) and a fourth pneumatic cylinder (<NUM>) corresponding to said second tension roller assembly (<NUM>), connected to said second tension roller assembly (<NUM>) using a third lever (<NUM>), and a fourth lever (<NUM>), respectively,
wherein said cross cutter apparatus (<NUM>) is capable of cutting said web (<NUM>) using said movable knife assembly (<NUM>) in between of the rollers (<NUM>, <NUM>) on the cutting platform (<NUM>), whereby the continuous web (<NUM>) is cut into the web cut pieces (<NUM>).