Claims:We Claim,
1. A high speed plastic bag making machine (10) comprising
a. a plastic bag conveying system (115) further comprising
i. a pair of conveyor belts (121) and (122) wrapped around a pair of pick-off rollers (111) and (112) in the front and in the rear, around a pair of driving rollers (123) and (124);
ii. a first sensor (125) to sense the trailing edge of the plastic bag (110) being conveyed;
iii. a second sensor (135) to sense the rotational speed of the said pair of driving rollers (123) and (124);
b. a pair of corrugation rollers (134) and (135) that momentarily reshape the plastic bag (110) being conveyed by partly converting the kinetic energy in the plastic bag (110) into potential energy;
c. a pair of braking rollers (153) and (154) with each roller having two identically spaced teeth mounted with resilient grippers (162) and (163) and (164) and (165), the said pair of braking rollers (153) and (154) positioned at an invariable distance from the said first sensor (125) upstream of a stacking tray (160);
d. a servo actuated motor to index the said pair of braking rollers (153) and (154); and
e. a controller that receives from the said first sensor (125) trailing edge sensing input for the plastic bag (110) being conveyed and processes such input in relation to linear speed of the said pair of conveyor belts (121) and (122) computed by the said controller using the rotational speed of the said pair of driving rollers (123) and (124) provided by the said second sensor (135) and actuates the said servo motor to index by 180 degrees the said pair of braking rollers (153) and (154) such that the corresponding resilient grippers (163) and (164) on the said braking rollers (153) and (154) momentarily grip the trailing edge of the plastic bag (110) to reduce the kinetic energy of the plastic bag (110) allowing the plastic bag (110) to fall off on the stacking tray (160) while substantially maintaining its straightness.

2. A method of making plastic bags (110) using a high speed machine (10), the method comprising
a. conveying plastic bags (110) using a plastic bag conveying system (115), the system comprising
i. a pair of conveyor belts (121) and (122) wrapped around a pair of pick-off rollers (111) and (112) in the front and in the rear, around a pair of driving rollers (123) and (124);
ii. a first sensor (125) to sense the trailing edge of the plastic bag (110) being conveyed;
iii. a second sensor (135) to sense the rotational speed of the said pair of driving rollers (123) and (124);
b. reshaping momentarily the plastic bag (110) being conveyed by using a pair of corrugation rollers (134) and (135) by partly converting the kinetic energy in the plastic bag (110) into potential energy;
c. having a pair of braking rollers (153) and (154) with each roller having two identically spaced teeth mounted with resilient grippers (162) and (163) and (164) and (165) and positioning the said pair of braking rollers (153) and (154) at an invariable distance from the said first sensor (125) upstream of a stacking tray (160);
d. indexing the said pair of braking rollers (153) and (154) by a servo actuated motor; and
e. computing using a controller linear speed of the said pair of conveyor belts (121) and (122) using the rotational speed of the said pair of driving rollers (123) and (124) provided by the said second sensor (135) and processing using the said controller the plastic bag (110) trailing edge sensing input received from the said first sensor (125) in relation to the said linear speed of the said pair of conveyor belts (121) and (122) to actuate the said servo motor to index by 180 degrees the said pair of braking rollers (153) and (154) such that the corresponding resilient grippers (163) and (a64) on the said braking rollers (153) and (154) momentarily grip the trailing edge of the plastic bag (110) to reduce the kinetic energy of the plastic bag (110) allowing the plastic bag (110) to fall off on the stacking tray (160) while substantially maintaining its straightness.

3. A high speed plastic bag making machine (10) comprising
a. a plastic bag conveying system (115) further comprising
i. a pair of conveyor belts (121) and (122) wrapped around a pair of pick-off rollers (111) and (112) in the front and in the rear, around a pair of driving rollers (123) and (124);
ii. a first sensor (125) to sense the trailing edge of the plastic bag (110) being conveyed;
iii. a second sensor (135) to sense the rotational speed of the said pair of driving rollers (123) and (124);
b. a pair of corrugation rollers (134) and (135) that momentarily reshape the plastic bag (110) being conveyed by partly converting the kinetic energy in the plastic bag (110) into potential energy;
c. a pair of braking rollers (170) and (180) with each roller having three identically spaced teeth mounted with resilient grippers (172), (174), and (176) and (182), (184), and (186), the said pair of braking rollers (170) and (180) positioned at an invariable distance from the said first sensor (125) upstream of a stacking tray (160);
d. a servo actuated motor to index the said pair of braking rollers (170) and (180); and
e. a controller that receives from the said first sensor (125) trailing edge sensing input for the plastic bag (110) being conveyed and processes such input in relation to linear speed of the said pair of conveyor belts (121) and (122) computed by the said controller using the rotational speed of the said pair of driving rollers (123) and (124) provided by the said second sensor (135) and actuates the said servo motor to index by 120 degrees the said pair of braking rollers (170) and (180) such that the corresponding resilient grippers (172) and (186) on the said braking rollers (170) and (180) momentarily grip the trailing edge of the plastic bag (110) to reduce the kinetic energy of the plastic bag (110) allowing the plastic bag to fall off on the stacking tray (160) while substantially maintaining its straightness.

4. A method of making plastic bags (110) using a high speed machine (10), the method comprising
a. conveying plastic bags (110) using a plastic bag conveying system (115), the system comprising
i. a pair of conveyor belts (121) and (122) wrapped around a pair of pick-off rollers (111) and (112) in the front and in the rear, around a pair of driving rollers (123) and (124);
ii. a first sensor (125) to sense the trailing edge of the plastic bag (110) being conveyed;
iii. a second sensor (135) to sense the rotational speed of the said pair of driving rollers (123) and (124);
b. reshaping momentarily the plastic bag (110) being conveyed by using a pair of corrugation rollers (134) and (135) by partly converting the kinetic energy in the plastic bag (110) into potential energy;
c. having a pair of braking rollers (170) and (180) with each roller having three identically spaced teeth mounted with resilient grippers (172), (174), and (176) and (182), (184), and (186) and positioning the said pair of braking rollers (170) and (180) at an invariable distance from the said first sensor (125) upstream of a stacking tray (160);
d. indexing the said pair of braking rollers (170) and (180) by a servo actuated motor; and
computing using a controller linear speed of the said pair of conveyor belts (121) and (122) using the rotational speed of the said pair of driving rollers (123) and (124) provided by the said second sensor (135) and processing using the said controller the plastic bag (110) trailing edge sensing input received from the said first sensor (125) in relation to the said linear speed of the said pair of conveyor belts (121) and (122) to actuate the said servo motor to index by 120 degrees the said pair of braking rollers (170) and (180) such that the corresponding resilient grippers (172) and (186) on the said braking rollers momentarily grip the trailing edge of the plastic bag (110) to reduce the kinetic energy of the plastic bag (110) allowing the plastic bag (110) to fall off on the stacking tray (160) while substantially maintaining its straightness. , Description:FIELD OF THE INVENTION
The present invention relates to a machine and method to make plastic bags. The present invention further relates to making of plastic bags using a high speed machine that automatically stacks plastic bags.
USE OF THE INVENTION
The use of the machine and method of making plastic bags in accordance with the present invention allows significant increase in productivity whereby a greater number of plastic bags can be made in a given time using the present invention than would be the case otherwise as in absence of an invention like the present invention, the plastic bags made at a high speed will have a tendency to leave the machine losing straightness leading to improper stacking.
An advantage of the present invention is that it permits high speed making of plastic bags.
Another advantage of the present invention is that despite high speed making of plastic bags, the otherwise attendant problem of losing straightness causing curling of plastic bags while stacking is eliminated.
Yet another advantage of the present invention is that it can be used for a number of different types of plastic materials.
Further advantage of the present invention is that it can be used for a range of thicknesses of plastic bags.
Additional advantage of the present invention is that it can be used even for making plastic sheets.
Yet another advantage of the present invention is that it can automatically adapt to different plastic materials and thicknesses.
A significant advantage of the present invention is that it is simple and does not require highly skilled operators.
PRIOR ART AND PROBLEM TO BE SOLVED
High speed machines and methods to manufacture plastic bags have been patented.
US Patent No. 6,561,962 discloses an in line plastic bag machine through which a web of double ply plastic film or sheet material, e.g. a tubular plastic sheet material, is fed. The web is trained over a shuttle mechanism which reciprocates within the machine beneath a head having at least one heat blade and one perforating blade. The movement of the shuttle is synchronized with the movement of the web so that the head is moved down over a platten while the shuttle is moving; thereby, to maintain the web momentarily stationary underneath the heat blade and perforating blade as it comes down on the platten with the web of double ply plastic sheet material extending therebetween. More specifically, the present invention relates to control mechanisms in a control system for controlling the speed of the drive rollers of the machine relative to the speed of an upstream web feeding machine. Also, the reciprocating speed of the shuttle is controlled by a control mechanism relative to the speed of the web passing through the machine. Further, the speed of rotation of a secondary drive roller or chrome roller is controlled by a control mechanism to move the web at a speed slightly greater or slightly slower than the speed of the main drive roller or chrome roller. Still further, a control mechanism controls the movement of the head downwardly into engagement with the web and momentarily holding at that position (dwell) for sealing and perforating the double ply web for sequentially forming bags in the web. However, the said invention lacks any mechanism that deals with the loss of straightness of the plastic bags exiting the machine and this causes curling of the bags and as a result, the bags cannot be stacked in a proper manner. Moreover, the said invention requires an operator to constantly keep a check on the bags being processed for manufacturing. There is no mechanism provided to check the error while processing the plastic bags as which in turn causes loss in production efficiency of the plastic bags.
US Patent No. 5,695,106 discloses a bag making machine that automatically cuts off and seals plastic web with regularly spaced eye-marks. A correction system is disclosed for use when the film gets out of register with the eye-marks. When the correction system is activated, the film is advanced to the next eye-mark. The bag making machine resumes normal in-register operation without ever shutting off the machine. A method of correcting lengths of bags is further disclosed. However, the said invention requires an operator to constantly keep a check on the bags being processed for manufacturing. Also, the said invention lacks any mechanism that deals with the loss of straightness of the plastic bags exiting the machine and this causes curling of the bags and as a result, the bags cannot be stacked in a proper manner.
US Patent No. 5,230,688 discloses servo driven components of a bag machine wherein modification of well-known heat sealing bag machines increases the production capability of the machines. The use of servo drives for selected components of the bag machine permits the reduction of film acceleration and consequential peak film velocity, thus allowing faster machine cycles at the same film acceleration and consequential film velocity. However, the said invention has an inherent problem of curling of plastic bags while being stacked. The said invention also lacks a proper stacking means for the plastic bags.
The industry always endeavours to increase productivity. In the field of technology relating to the present invention, it is a constant effort of manufacturers to produce as many plastic bags as possible in a given time. While it is not uncommon to come across machines that can produce plastic bags at a high speed, the common problem faced by the manufacturers of plastic bags is that the plastic bags produced at a high rate tend to lose straightness while exiting the machine and this causes curling of the bags as a result, the bags do not stack in a proper manner ultimately leading to stoppage of the machine or forcing the manufacturers to reduce the speed of production resulting in reduced productivity. It is the avoidance of loss of straightness on leaving the machine causing curling problem during stacking of plastic bags that the present invention solves while permitting high speed of production of plastic bags of varying thicknesses and different materials.
Use of rollers that reduce the speed of the ballistic travel of the plastic bags is not unknown, however, the manual adjustment is not only time consuming, and it is not accurate. Thus, a manufacturer is forced to reduce the speed of the ballistic travel of the plastic bags so that stacking can be done properly. Also, for a different material or thickness of the plastic bag, the kinetic energy will vary and therefore, the manual adjustments have to be redone causing loss of productivity.
Thus, there is a need of a plastic bag making machine and a method that overcomes these drawbacks which allows producing plastic bags using high speed machines without causing curling during stacking.
In other words, the loss of straightness causing curling of plastic bags while being stacked is addressed by the present invention and as a direct consequence of that, plastic bags can be produced at a high speed.
OBJECTS OF THE INVENTION
The principal object of the present invention is to provide proper stacking of plastic bags produced using a high speed machine.
An advantage of the present invention is that it permits high speed making of plastic bags.
Another advantage of the present invention is that despite high speed making of plastic bags, the otherwise attendant stacking problems are eliminated.
Yet another advantage of the present invention is that it can be used for a number of different types of plastic materials.
Further advantage of the present invention is that it can be used for a range of thicknesses of the plastic bags.
Additional advantage of the present invention is that it can be used even for making plastic sheets also.
Yet another advantage of the present invention is that it is and can automatically adapt to different plastic materials and thicknesses
A significant advantage of the present invention is that it is simple and does not require highly skilled operators.
SUMMARY OF THE INVENTION
The present invention discloses a high speed plastic bag making machine (10) and a method to produce plastic bags (110) at high speed. Production of plastic bags (110) at a high speed is generally possible, however, the loss of straightness of plastic bags (110) while exiting the machine (10) causes curling problem while stacking plastic bags (110) and that forces reduction in speed at which plastic bags are produced. The present invention essentially reduces the kinetic energy of the exiting plastic bags before the plastic (110) bags get stacked. Such reduction of kinetic energy of the exiting plastic bags (110) is possible by manually adjusting the mechanism involved, but that is inefficient and inaccurate. The present invention automates such reduction in kinetic energy that permits higher upstream speed at which the plastic bags (110) can be produced and propelled towards the stacking tray (160). In absence of the present invention or a feature that can reduce the kinetic energy, plastic bags (110) produced at a high speed will have a tendency to exit losing straightness causing curling while getting stacked. In other words, with an application of an automated brake-like feature of the present invention, making of plastic bags (110) at a high speed becomes possible.
The present invention essentially is a modified version of a conventional plastic bag making machine (10). As a person skilled in the art would readily understand, a plastic bag making machine (10) also includes an unwinding means (30), some idlers (36), (37), (38) and (80), nip rollers (50) and (90), accumulators (70), motors (140), etc. There is provided a hot/cold knife (100) that cuts and seals the plastic web (20) into plastic bags (110). Instead of plastic bags (110), pouches could also be made using the present invention. There is provided a conveyor belt assembly (115) that has in the front a pair of pick-off rollers (111) and (112) respectively and in the rear a pair of driving rollers. The conveyor belts wrap around the front pick-off rollers and the rear driving rollers (123) and (124) respectively. The top pick-off (123) roller moves up and down assisting in the ballistic travel of the plastic bags (110) on the conveyor belts (121) and (122) respectively. A first sensor (125) senses the trailing edge of the moving plastic bags (110) and sends such information as an input to a controller (not-shown). A second sensor (135) senses the rotational speed of the driving rollers (123) and (124) respectively. This information is also sent to the controller (not-shown) which then calculates the linear speed of the conveyor belts (121) and (122) and therefore, the speed at which the plastic bags (110) are being propelled towards the rear end of the machine (10). As a person skilled in the art will readily understand, a pair of corrugation rollers - (134) and (135) respectively momentarily reshapes the plastic bags (110) so that the plastic bags (110) gain additional stiffness.
The present invention provides for a pair of braking rollers with several identically spaced teeth covered by resilient grippers (162), (163), (164), and (165) respectively. The pair of braking rollers - (153) and (154) is positioned upstream of the stacking tray (160) and is at a fixed distance from the first sensor (125). This pair of braking rollers (153) and (154) can be indexed using a servo actuated motor. In home or default position, the corresponding resilient grippers do not touch each other. In other words, the resilient gripper (162) on a tooth of the top braking roller (153) will not contact corresponding resilient gripper (163) on a tooth of the bottom braking roller (154); however, when indexed, either by 180 degrees or 120 degrees depending on the number of teeth, there will be a simultaneous momentary contact of the moving plastic bag (110) by corresponding resilient grippers (162) and (163) causing reduction in the kinetic energy of the plastic bag (110) before it reaches the stacking tray (160). This reduction in the kinetic energy of the plastic bags (110) allows the plastic bag (110) to substantially maintain straightness and that avoids the curling that leads to improper stacking of the plastic bags (110). Thus, the reduction in the kinetic energy of the plastic bags (110) in their ballistic travel ensures proper stacking in the stacking tray (160).
The indexing of braking rollers (153) and (154) is caused by the controller that actuates the servo motor that drives the pair of braking rollers (153) and (154). The controller uses the inputs from the first sensor (125) and the computed linear speed of the conveyor belts (121) and (122) to index the braking rollers (153) and (154) to cause the simultaneous momentary contact of the moving plastic bag (110) by corresponding resilient grippers (162) and (163) that results in reduction in the kinetic energy of the plastic bag (110) before it reaches the stacking tray (160). The reduction of kinetic energy of the exiting high speed plastic bags (110) helps substantially maintain straightness and thus the curling problem while stacking is avoided leading to proper stacking of the plastic bags (110) in a stacking tray (160).
The action of reduction of the kinetic energy of the plastic bags (110) ensuring proper stacking is automatic. In other words, nothing needs to be changed in the machine in accordance with the present invention for all types of plastic.

Brief description of the invention
Fig.1 shows the plastic bag making machine (10) in accordance with the present invention.
Fig. 2 shows part of the plastic bag making machine (10) in accordance with the present invention.
Fig. 3A shows the pair of braking rollers (153) and (154) in home position in the preferred embodiment in accordance with the present invention.
Fig. 3B shows the pair of braking rollers (153) and (154) momentarily gripping trailing edge of plastic bag (110) in the preferred embodiment in accordance with the present invention.
Fig. 4A shows the pair of braking rollers (153) and (154) in home position in another embodiment in accordance with the present invention.
Fig. 4B shows the pair of braking rollers momentarily gripping trailing edge of plastic bag in another embodiment in accordance with the present invention.

Detailed description of the invention
Referring to Fig, 1, it shows plastic bag making machine (10) in accordance with the present invention. As can be seen web (20) can be unwound from the unwinder assembly (30). Web (20) passes around idler (35) before passing around idlers (36), (37), and (38). From there, it passes through a pair of nip rollers (50) before passing through accumulator (70). From there, it passes around idler (80). Plastic bag conveying system (115) can be seen. Also, shown is a hot/cold knife (100).
Now referring to Fig, 2, it can be seen in the partial, but somewhat closer view of the plastic bag machine (10) that web (20) passes through a pair of nip rollers (90) before reaching hot/cold knife (100). As is well-known in the field, hot/cold knife (100) cuts the web (20) and also heat seals the cut pieces into plastic bags (110). Plastic bag conveying system (115) includes in the front a pair of pick-off rollers: top pick-off roller (111) and bottom pick-off roller (112). The top roller (111) moves up and down bringing the top conveyor belt (121) in contact with the bottom conveyor belt (122) assisting in ballistic travel of plastic bags (110). At the rear end of the plastic bag conveying system (115) is provided a pair of driving rollers: top driving roller (123) and bottom driving roller (124). As a person skilled in the art will readily understand, the top driving roller (123) and the bottom driving roller (124) are driven at the same speed by conveyor motor (140). Conveyor belt (121) wraps around top pick-off roller (111) and top driving roller (123). Similarly, conveyor belt (122) wraps around bottom pick-off roller (112) and bottom driving roller (124). Plastic bags (110) move in their ballistic travel downstream due to the linear movement of the conveyor belts (121) and (122) at the linear speed of the conveyor belts (121) and (122). A first sensor (125) is positioned to sense the trailing edge of the plastic bags (110) moving downstream in their ballistic travel. A second sensor (135) senses the rotational speed of the conveyor motor (140) or the rotational speed of top driving roller (123) and the bottom driving roller (124). The purpose of sensing such rotational speed is to compute the linear speed of the conveyor belts (121) and (122). There is provided a controller (not shown) that receives input from the first sensor (125) and the second sensor (135) and processes the inputs using an algorithm.
At a fixed distance from the first sensor (125) is provided a pair of braking rollers: top braking roller (153) and bottom braking roller (154). This pair of braking rollers is at an invariable distance from the first sensor (125). In between the pair of driving rollers and the pair of braking rollers is provided a pair of corrugation rollers: top corrugation roller (134) and bottom corrugation roller (135).
The pair of corrugation rollers, as is well understood by a person skilled in the art, momentarily reshapes the plastic bags (110) into a corrugated shape by partly converting the kinetic energy in the moving plastic bags (110) into potential energy. The corrugated shape of the plastic bags (110) increases the stiffness of the plastic bags (110) which inherently is low owing to the small thickness and small mass of the plastic bags (110).
As shown in Fig. 3A, top braking roller (153) and bottom braking roller (154) rotate in opposite directions. Each braking roller has two equally spaced teeth in this preferred embodiment of the present invention. Each tooth has a resilient gripper mounted on it. Thus, resilient gripper (162) is mounted on a tooth of top braking roller (153) that is 180 degrees from the tooth on which resilient gripper (163) is mounted. Resilient grippers (164) and (165) are similarly mounted on teeth of bottom braking roller (154) that are also spaced 180 degrees apart. The centre distance between the top braking roller (153) and the bottom braking roller (154), the height of the teeth, and the thickness of the resilient grippers is so selected that when the braking rollers are rotated or indexed, corresponding resilient grippers contact each other as shown in Fig. 3B. In other words, resilient gripper (163) will contact resilient gripper (164) as shown in Fig. 3 and similarly, resilient gripper (162) will contact resilient gripper (165) when there is a rotation of the braking rollers by 180 degrees. In home position of the braking rollers, there will be no contact between the corresponding resilient grippers, but as can be easily understood, due to centre distance, height of the teeth and thickness of the resilient grippers so selected, on being rotated or indexed, there will be a contact between the corresponding resilient grippers for every rotation by 180 degrees. As can be readily understood by a person skilled in the art, on being indexed 180 degrees, the braking rollers will return to the home position as shown in Fig. 3A, however, before returning to the home position, there will be a momentary contact between the corresponding resilient grippers and if there is a plastic bag (110) that is being propelled through the braking rollers, when the braking rollers are being indexed, there will be a momentary gripping of the plastic bag (110) by the corresponding resilient grippers. The controller (not shown) receives from the first sensor (125) the input of sensing the trailing edge of the plastic bag (110). The distance between the first sensor (125) and the pair of braking rollers (170) and (180) being fixed, it can be computed when the trailing edge of the plastic bag (110) will be in between the pair of braking rollers (170) and (180) using the computed linear speed of the conveyor belts (121) and (122) based on the rotational speed sensed by sensor (135). Therefore, the controller (not shown) will actuate the servo motor that indexes by 180 degrees the pair of braking rollers just at the time when the trailing edge of the plastic bags is just in between the pair of braking rollers (170) and (180). On being indexed by 180 degrees the pair of braking rollers (170) and (180) cause a simultaneous momentary gripping of the plastic bag (110) by the corresponding resilient grippers (163) and (164) before returning to default home position. This simultaneous momentary gripping of the plastic bag (110) reduces its kinetic energy. This reduction in the kinetic energy of the plastic bags allows the plastic bag (110) to substantially maintain straightness and that avoids the curling that leads to improper stacking. Thus, the reduction in the kinetic energy of the plastic bags (110) in their ballistic travel ensures proper stacking in the stacking tray (160).
As a person skilled in the art will readily understand, if each of the braking rollers (170) and (180) has three equally spaced teeth as shown in another embodiment of the present invention in Fig. 4A, the indexing will have to be by 120 degrees to achieve the same purpose as discussed hereinabove. Thus, it can readily be understood that the resilient gripper (172) of a tooth of the top braking roller (170) will be in contact with resilient gripper (186) of the bottom braking roller (180) when the pair of braking rollers is indexed by (120) from the home position shown in Fig. 4A to the position in Fig. 4B. On being indexed again by 120 degrees, resilient gripper (174) of the tooth on top braking roller (170) will contact resilient gripper (184) of the tooth on bottom braking roller (180) and so on.

Best Method of performing the Invention
The present invention is sufficiently described hereinabove, however, the best method of performing the present invention known to the inventors is to use the pair of braking rollers (153) and (154) with two equally spaced teeth, with the resilient grippers.
The controller will be programmed with an algorithm that precisely computes the timing of indexing the pair of braking rollers. The computation will be dependent on the inputs provided by the first sensor (125) and the second sensor (135). As discussed hereinabove, the controller will use the input from second sensor (135) to compute the linear speed of the conveyor belts (121) and (122) and thus, the linear speed at which the plastic bags are being propelled towards the rear end.
The material of the resilient grippers (162), (163), (164), (165), (172), (173) and (174) will have to be such that it is capable of repeatedly withstanding a separating force that causes momentary deflection and at the same time being capable of regaining its original configuration in absence of any force.
The resilience in the resilient grippers (162), (163), (164), (165), (172), (173) and (174) permits vertical deflection of the resilient grippers (162), (163), (164), (165), (172), (173) and (174) from 0.5 mm to 2 mm.
The braking rollers (153) and (154) don’t need to be changed for different types of plastic such as PP (Polypropylene), LDPE (Low Density Polyethylene), LLDPE (Linear Low Density Polyethylene), and HDPE (High Density Polyethylene). Also, the same braking rollers can function for thickness from 20 microns to 60 microns for PP; 20 microns to 80 microns for LDPE and LLDPE; and 10 microns to 50 microns for HDPE.
As a person skilled in the art will readily understand from the detailed description of the present invention, merely because some changes may be made to the method described herein above without departing from the spirit and scope of the present invention, so modified method should not be construed to fall outside the scope of the present invention as disclosed and claimed herein. All matters disclosed hereinabove or as shown in the accompanying drawing ought to be interpreted as illustrative and not in a limiting sense. For example, instead of plastic bags, pouches can be made using the present invention without departing from the scope or spirit of the present invention.
The following claims are intended to cover all of generic and specific features of the present invention described herein above and all the statements of scope of the present invention regardless of grammatical or linguistic variations might be said to fall there between.