Patent Application
20080282860
This invention relates to improvements in rotary cutting tools, and more particularly to improvements in scrap removal from rotary cutting tools.
Rotary cutting tools are useful for manufacture of carton blanks and other workpieces from sheets or webs of material. In particular, rotary die cutting tools are used in high speed cutting of a moving sheet or web of paper, paperboard, plastics or composite materials. As one example, rotary die cutting machines are used for the high speed mass production of paperboard carton blanks that are subsequently folded into the shape of cartons or boxes such as cereal and cracker boxes, etc. The cutting operations can occur by one of several methods: rotary pressure (“RP”) cutting and the “crush cut” method. In the rotary pressure cutting method, a web of material is advanced at high speed between two rotary die cutting cylinders. The cylinders are provided with cutting elements which cooperate to cut the desired shape of the carton blank out of the web as the material advances between the cylinders. The cutting elements are offset but immediately adjacent one another when cutting the web of material (somewhat like a pair of scissors), so that a cut line is defined at edges where the cooperating cutting elements meet. The cylinders rotate at the same speed so as to maintain registration of the co-acting cutting surfaces. Each rotation of the cylinders generates a discrete series of one or more cartons depending upon the size of the cartons, diameters of the cylinders, etc.
By contrast, in the crush cut method one of the cylinders, a cutting cylinder, is provided with knife blades that perform the cutting operation and the other cylinder, known as the anvil cylinder, provides a smooth surface against which the knife blades operate. The knife blades are therefore positioned directly over the anvil, instead of being offset as is the case with RP dies.
Once the carton is cut, material is sometimes left behind, for example edges and cutouts. Given the high speed operation typical of rotary cutting, this scrap material needs to be separated from the usable product in a simple, quick and reliable manner. Known techniques for scrap removal include placing a rubber spacer on a cutout area of one of the cylinders corresponding to the cutout from the web of material, and drilling and tapping holes into a second cylinder and inserting stripping pins. During the cutting action, the rubber biases the scrap material away from the first cylinder and toward the stripping pin on the other cylinder. The stripping pin temporarily captures the scrap and carries it away from the carton blanks defined by the cutting action. The stripping pins engage stripping combs mounted at a fixed position. Typically the combs have thin slots which receive the stripping pins, but which are not large enough to allow the scrap to pass. Rotation of the cylinder allows the pins to pass through the comb, but not the scrap, and so the scrap is pulled off the pin. In this manner the scrap is separated from the carton blanks.
There are several problems with this known technique for scrap removal. The technique is relatively expensive, as stripping pins and stripping comb have to be precisely manufactured and mounted. Also, small misalignments can result in the stripping comb shearing off the stripping pins. Further, over time the rubber spacers can become compressed, losing their effectiveness. In addition, there is increased demand for small volume production runs, and as each run may have a different scrap or cutout location, the mounting holes that work for one production run may not work for another production run, effectively dedicating the cylinders to a limited production of carton blanks.
It would be highly desirable to provide a rotary tool having an improved scrap removal apparatus which is of lower cost and is easier to manufacture and assemble, and to provide a scrap removal apparatus for a rotary cutting tool which is amendable to multiple lower volume production runs.
In accordance with a first aspect, a rotary cutting tool for cutting a moving web of material into blanks and scrap material, comprises an upper cutting assembly having an upper cutting element which defines a cutout area on the upper cutting assembly, a lower cutting assembly having a lower cutting element, wherein the upper cutting element and the lower cutting element are adapted to cooperate to cut the moving web of material into blanks and scrap material, and a scrap ejection element on the upper cutting assembly at the cutout area which can urge the scrap material away from the blanks and towards the lower cutting elements, wherein the scrap ejection element is formed unitary with the upper cutting element.
From the foregoing disclosure and the following more detailed description of various preferred embodiments it will be apparent to those skilled in the art that the present invention provides a significant advance in the technology of rotary cutting tools. Particularly significant in this regard is the potential the invention affords for providing a high quality, low cost rotary cutting tool. Additional features and advantages of various preferred embodiments will be better understood in view of the detailed description provided below.
It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various preferred features illustrative of the basic principles of the invention. The specific design features of the rotary cutting tool as disclosed here, including, for example, the specific dimensions of the scrap ejection elements, will be determined in part by the particular intended application and use environment. Certain features of the illustrated embodiments have been enlarged or distorted relative to others to improve visualization and clear understanding. In particular, thin features may be thickened, for example, for clarity of illustration. All references to direction and position, unless otherwise indicated, refer to the orientation illustrated in the drawings.
It will be apparent to those skilled in the art, that is, to those who have knowledge or experience in this area of technology, that many uses and design variations are possible for the rotary cutting tool disclosed here. The following detailed discussion of various alternative and preferred features and embodiments will illustrate the general principles of the invention with reference to a rotary cutting tool suitable for use in industrial applications where flat paper-like materials are to be cut. Other embodiments suitable for other applications will be apparent to those skilled in the art given the benefit of this disclosure.
Referring now to the drawings, in
Each die plate has cutting blades or elements 26, 27, preferably formed as unitary extensions of the corresponding die plate. The cylinders 14, 16 are in registry with one another so that they rotate together. When a thin web of material (for example, paperboard used to make cereal boxes) is fed between the rotating die plates 18, 20, the cutting elements or blades 26, 27 cut the thin web of material into carton blanks. Sometimes a carton design calls for a cutout. This cutout is a scrap material which must be separated from the blank.
The cutting elements 26, 27 on each die plate (or cylinder) define a cutout area 30, 70. The cutout area on each die plate corresponds to an area of the web of material which is cut and converted to scrap material. This can take on many shapes, but generally either the cutting elements entirely surround the cutout area or an edge of the web of material cooperates with the cutting elements to define the cutout area. In either situation, when the upper cutting assembly 96 cooperates with the lower cutting assembly 98, scrap is produced at the portion of the web of material corresponding to the cutout area.
A scrap ejection element 40 in accordance with a preferred embodiment is shown as a unitary extension of die plate 18. Preferably the scrap ejection element has a radial length about the same as a radial length of the die cutting elements 26. A gap in the cutout area 30 is provided to allow room for the lower cutting elements 27 when the cutting assemblies come together to cut the web of material.
The scrap ejection element 40 cooperates with the lower cutting elements 27 to separate the scrap material from the carton blanks 82. Cutout area 70 on the lower die plate 20 is adapted to receive the scrap material.
Continued rotation of the lower cutting assembly 98 away from the position where the cutting elements 26 and 27 meet to form the scrap material brings the scrap material 84 into contact with the stripper assembly 75 which is fixed to the stand 12. The stripper blade assembly engages the scrap material 84, but not the cutting elements 27. This separates the scrap material from the lower cutting elements 27, allowing the cutting elements to rotate back around to reengage the upper cutting elements 26 and repeat the process. Advantageously, the stripper blade assembly may be much simpler to construct than known scrap removal blades, as a tightly toleranced slot to engage stripper pins is not necessary with this invention.
Summarizing the process of scrap removal from the web of material, as a first step, the material is cut into carton blanks 82 and scrap material 84. Next and essentially concurrently, the scrap ejection elements urge the scrap material away from the blanks and into engagement with the lower cutting elements. Rotation of the lower cutting assembly separates the scrap material from the blanks and brings the scrap material into engagement with the stripper blade assembly. The stripper blade assembly separates the scrap material from the lower cutting assembly.
The process for scrap material removal is essentially the same as with RP dies.
Optionally, the upper cutting assembly can comprise either both a cylinder and separate die plate with cutting elements and scrap ejection elements formed as unitary extensions of the die plate (a “flexible die” as shown in the Figs.) or just a solid cylinder with unitary projections extending from the cylinder to form cutting elements and the scrap ejection element (a “solid die”). In a similar manner, the lower cutting assembly can comprise either both a cylinder and separate die plate with cutting elements formed as unitary extensions of the die plate (a “flexible die” as shown in the Figs.) or just a solid cylinder with unitary projections extending from the cylinder to form cutting elements (“a solid die”).
From the foregoing disclosure and detailed description of certain preferred embodiments, it will be apparent that various modifications, additions and other alternative embodiments are possible without departing from the true scope and spirit of the invention. The embodiments discussed were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to use the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.
This application claims priority benefit of U.S. provisional patent application No. 60/730,902 filed on Oct. 27, 2005.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US2006/042259 | 10/27/2006 | WO | 00 | 4/28/2008 |
| Number | Date | Country | |
|---|---|---|---|
| 60730902 | Oct 2005 | US |
