This invention relates to the die-cutting of flexible webs. More specifically it relates to the intermittent cutting of a flexible web as it travels along a packaging production line.
Resealable packages have been made by covering a slit in the packaging film with a pressure sensitive tape or label. The package may be fully sealed but depending on the film structure, the package would not be hermetic because of the continuous slit through the end seal. To control and contain the die cut to a limited space between the end seals of a package to maintain the hermeticity of a package made with a barrier film an intermittent cutting system can be used.
Accurate control of the intermittent operation of the die cutting is critical to its performance on a packaging line where product is being packaged. Packaging lines ramp up and down in speed, sometimes coming to a complete stop to wait for product to be packaged. This is unlike continuous rotary systems such as printing presses and converting machines, which because of high rotational mass, require careful and very slow ramping up and down, or stopping of the machine.
Traditionally die stations using rotary dies to cut flexible webs are wider than the width of the flexible web. Because they rely on bearers located on both ends of the rotary die, they are equal or a very slightly higher than the length of the die blade. Bearers maintain the cutting gap to guarantee a precise space between the anvil and the die blade pair to prevent the rotary die from crushing against the anvil when cutting through the flexible web.
In that case, the width of the web dictates the width of the die and anvil pair. Wider webs result in wider die and anvil pairs and wider dies and anvils must be of a large diameter to prevent deflection under cutting loads. Thus, the rotational mass and weight of the die and anvil pair are increased dramatically. As production speed increases poor acceleration and deceleration control result due to the very high rotational mass of the components. The precise control of acceleration and deceleration of the die is necessary for intermittent and accurate registration when die cutting the web.
There is therefore a need in the art of packaging die cutting for making accurate cuts in a traveling web. There is a further need for an intermittent die cutting device with low rotational mass that permits high-speed and accurate control of the cut slit placement on the packaging web material.
The present invention creates a resealable package opening to access the product within which employs a resealable tape or label applied over a cut slit in the packaging film. This type of resealable package is made on the packaging line where a series of slit cuts are made to a moving web and a resealable tape is applied. Further benefits of making the taped cuts on the packaging line are reduced costs of pre-applying, lower shipping costs and less inventory storage space.
To make an accurately placed die cut in a traveling web, the present device has been devised to significantly reduce the mass of the die cutting components for accurate cut placement. The result is a series of individual cuts made to the moving web at precise locations. The present device employs an anvil of a small diameter that extends the full width of the web material that provides the benefit of low rotational mass. This device further utilizes a narrow rotary die wheel which is possible because there are no anvil bearers on the ends of the die. Instead of bearers on the ends of the die, the critical nip gap between the anvil and the die is maintained by the supporting frame structure of the die station which holds the die assembly. The reacting load on the anvil is therefore the only force of making the cut. The cutting force on the anvil, which because of its small diameter may tend to flex, is counteracted by a set of support bearings below the anvil that prevent unwanted flexing. The result is a scoring of the packaging web along a slit pattern which breaks open upon the first opening of the package. In one embodiment intermittent action of the die wheel is employed. In the present device this is provided by a programmable motor which stops and starts the rotation of the die wheel during each 360-degree rotation of the wheel which is coordinated with the position of the web.
A station for a packaging line having a frame, a die assembly, a drive motor, and an anvil roller as the main components. The frame has a base with two vertical stanchions extending upwardly from either side of the base. A top cross-member is affixed across the tops of the stanchions. The die assembly includes a yoke affixed to the cross-member, a die wheel rotatably affixed to side arms of the yoke, a drive shaft affixed to the die wheel and a cutting die affixed to the circumference of the die wheel. The drive motor is mounted to the frame and is connected to the drive shaft. The drive shaft and an anvil roller extend between the stanchions and is affixed to them at opposite ends. By these mechanical relations, the cutting die is rotatable in non-contacting close proximity to the anvil roller and spaced apart by a nip having a gap for receiving a traveling web. As the web passes through the nip the web material is cut into by blades of the rotating die which necessarily span an arc of less than 360 degrees. An adhesive resealable tape or label is then applied over the cut slit.
The die station may further include anvil support bearings on the underside of the anvil roller opposite the nip which ride on a laterally translatable carriage mounted to the frame. An upper carriage carries the die assembly and is likewise laterally translatable. Both carriages may be linked together so that they always remain in alignment as they are moved together laterally. The die assembly includes adjustment means between the cross-member and the yoke for obtaining the desired nip gap between the die wheel cutting blade and the anvil roller. The die wheel is preferably magnetic, and the cutting die is affixed to the wheel by magnetism. For easy exchange of different die assemblies, a subassembly holding the die assembly can be removed from the frame without disturbing many of the other components.
In order to accurately place the cut slit pattern on the packaging web an intermittent drive system can be employed which is controlled by a programmable drive motor. The rotation of the die wheel and hence the cutting of the web is triggered by a sensor which reads eye-marks on the web upstream of the die wheel. The speed of the die wheel is matched to the web speed by a web speed sensor. High-speed operation is achieved because the operative components are constructed to have a low rotational mass. For example, the die assembly does not use bearers which then allows the width of the die to be only a little more than the width of the slit pattern which provides a very lightweight and narrow die. To further reduce the rotational mass of the reciprocating components, the anvil roller is constructed of small diameter hollow tubing backed by support bearings to prevent flexing of the lightweight anvil roller.
The specific examples provided in this summary are illustrative only of some features of the invention. From the following drawings and a detailed description of embodiments of the invention, those of skill in the art will appreciate that the objects of the invention to devise an accurate die cutting station for a packaging line have been achieved.
The orientation of package panels on web 20 are longitudinally side-by-side. As illustrated, four sides of each panel are graphically outlined. A width of each panel defines a repeat length of the web. When completed, the individual panels will form the front panel of each package. A series of individual cuts 28 will be placed on a center of each panel. As the packaging line moves through the die station 9 it passes underneath a die assembly 15. The die assembly 15 includes a die wheel 22 having a die strip with blades which cut into the web forming the slit pattern 28 in each web panel (greater detail of the die assembly 15 is shown in
The basic elements of the die station 9 include a frame (base 14, two upward extending vertical stanchions 10, 12 affixed at opposite sides of the base 14, and a top cross-member 11), the die assembly 15 rigidly suspended from the cross-member 11, and the anvil roller 21 which supports the web 20. The anvil roller 21 is positioned vertically opposite the die wheel 22 forming a nip between the die wheel cutting blades and the anvil roller 21 through which the web 20 passes. As further described in
Subsequent to the die cutting, an adhesive resealable continuous tape 24 is applied to the package web 20 which covers over each slit 28. To this end, a tape applicator assembly 29 is affixed to the frame which pulls the tape 24 from a supply reel (not shown). The adhesion of the leading portion of the tape 24 to the web 20 pulls the tape 24 from the supply while a roller applies the tape to the web 20. In similar fashion a label can be applied over each slit 28. In use, when the package is completed and filled, the user pulls down the tape or label over the slit 28 to form an opening in the package through which its contents can be removed. The adhesion of the tape 24 breaks apart the web material as the slit 28 separates when the package is first opened. Preferably, the slit pattern 28 is not cut all the way through the web 20 but leaves the web scored and weakened so that it will remain hermetically sealed until it is torn apart during its first opening. After that, the tape 24 or label can reseal the opening.
The die assembly 15 can be moved laterally on an upper carriage 41 by turning a first threaded rod 42. The anvil support assembly 33 is likewise laterally translatable on a second threaded rod 44 of equal pitch which passes through the lower carriage 43. A belt system 45 connects sprockets at the ends of the first and second threaded rods 42, 44. The belt system 45 links the rotation of the threaded rods 42, 44 so that after loosening die station retention bolts 47 and turning a crank 48, the die assembly 15 and the anvil support assembly 33 will maintain their alignment as they are moved laterally in unison.
The die assembly 15 comprises a yoke consisting of side arms 55, 56 that are connected above the die wheel 22 by a top plate 52. An adjustment block 49 is affixed to the tops of the yoke side arms 55, 56 by a shoulder bolt and adjustment bolts and set screws. The adjustment block 49 can control the distance between the cross-member 11 and the yoke side arms 55, 56 which in-turn determines the nip gap distance between the die 51 and the anvil roller 21. This gap can be accurately adjusted using a dial indicator 50 which thereby measures the relative changes in the nip gap. The secondary suspension of the die assembly 15 from the drive shaft 25 permits a tensioning of the components between the cross-member 11 and the drive shaft 25. The nip gap can be adjusted for example plus or minus 0.0025 inches by a slight flexing of the drive shaft 25. Since the force on the die wheel 22 fluctuates, increasing during each cutting period, the rigid affixation of the die assembly 15 to the frame cross-member 11 is essential to maintain a constant nip gap.
The die wheel 22 has magnets 64 by which a die strip 51 having a cutting blade in the desired slit pattern is magnetically affixed to the die wheel 22. By this construction, the cutting die 51 is held in very close proximity to the anvil roller 21 which extends the width of the die station 9. These components are selected to provide a very low rotational mass to accommodate high-speed intermittent operation. In this respect, the anvil roller 21 may be a hollow thin-walled tube having a diameter smaller than the die wheel 22.
The die strip 51 is affixed to a circular segment of a circumference of the die wheel 22 which is greater than the remaining portion of the wheel 22 which is of reduced diameter. The die wheel 22 is illustrated as a 360-degree full-circle wheel but is not limited thereto. Rather, partly circular wheels can also be employed so long as the cutting die blades span a circular portion which provides the effective cutting nip. In all cases the cutting blades span an arc of less than 360 angular degrees. Other die wheel configurations may be employed such as one having two cutting dies spaced 180 degrees apart. When the portion of the wheel 22 having the reduced diameter is adjacent the anvil roller 21, the nip gap is wide enough so that the web 20 is released and can pass beneath the wheel 22 without interference from the wheel 22.
As further described below, during the period when the web 20 is released from contact with the die wheel 22, the speed of the wheel 22 can be changed while the web 20 can continue at a constant rate as it passes through the nip and slides over the anvil roller 21. Controlled speed variation of the wheel 22 during this non-cutting released position of the die wheel 22 permits accurate placement of the slit pattern on the web 20. As described in the operation chart of
For the proper operation of the die cutting station it is essential that the cutting operation occur accurately at the speed of the packaging line. The slit in each panel must be registered at a precise longitudinal location on each panel. In most cases this requires registration with printing on the web 20. By the mechanical relations illustrated above, the die station of the present invention makes accurately placed cut slits into a travelling web. In one embodiment further described below each 360-degree rotation of the die wheel makes one slit cut into each package panel. In all cases the rotation of the die wheel is carefully regulated by a programmed controller.
The initiation of each cycle from the home position is triggered by an eye mark sensor as seen in
The foregoing represents various embodiments of the invention which are described for illustration only and is not intended to limit the invention to any particular embodiment. There may be variations and other modifications which nonetheless fall within the scope and spirit of the invention which is to be defined only by the following claims and their legal equivalents.
Number | Name | Date | Kind |
---|---|---|---|
5001950 | Fokos | Mar 1991 | A |
5775193 | Pratt | Jul 1998 | A |
8702366 | Campbell et al. | Apr 2014 | B2 |
10221022 | Campbell et al. | Mar 2019 | B2 |
20030198544 | Campbell et al. | Oct 2003 | A1 |
20040213652 | Campbell et al. | Oct 2004 | A1 |
20060162172 | Lindsey, Jr. et al. | Jul 2006 | A1 |
20090297304 | Campbell et al. | Dec 2009 | A1 |
20090320663 | Yamamoto | Dec 2009 | A1 |
20120012016 | Moeller | Jan 2012 | A1 |
20180036782 | Ehrmann | Feb 2018 | A1 |
20180117786 | Schuster | May 2018 | A1 |
20180311852 | Yoshihara | Nov 2018 | A1 |
20210114246 | Jensen et al. | Apr 2021 | A1 |
Entry |
---|
International Searching Authority, International Search Report and Written Opinion of PCT/US21/59515, dated Feb. 4, 2022, 8 pages. |
Number | Date | Country | |
---|---|---|---|
20220152862 A1 | May 2022 | US |