The present invention is related to the field of cutting units and methods for cutting preparation features in a web of sheet like material. Moreover, the present invention is related to a web of sheet like material having preparation features cut by the cutting units.
In the field of preparation of web of sheet like materials for the purpose of raising packaging containers for foodstuffs therefrom, several methods are previously known.
In one variant, a roll of web of sheet like material, is transported from a nearby or remote location and fed into a creasing and/or cutting machine. The creasing and/or cutting machine comprises a number of roll pairs, each pair carrying a male and a female die. In some variants, the pair of rolls is only carrying a male and a female creasing pattern. The creasing pattern on both dies, when transferred to a web of sheet like material, will result in a number of crease lines on the sheet like material, which in later production stages facilitate the raising of a container from the sheet like material. A second roll pair may then apply preparation features other than crease lines to the web of sheet like material, such as holes or perforations. In each case, one preparation feature is applied in one roll pair, i.e. a creasing pattern is applied in a first stage, holes are applied in a second stage and possible perforations in a third stage in the corresponding roll pair with male and female dies.
When performing a cutting operation, the protruding cutting elements are located on the male die, while the corresponding recessed portions are located on the female die.
One problem arising from the fact that different cutting and creasing operations are performed at different stages in the cutting/creasing machine is that alignment between, for example, the crease line pattern and the holes cut in the sheet like material will suffer due to alignment and manufacturing tolerances added in each cutting or creasing stage. An even greater problem will occur if several cutting and creasing operations are performed by several male/female rolls at several stages of process. Each cutting/and creasing stage will add its tolerances to the crease line pattern or other preparation feature transferred to the sheet like material. Moreover, each new stage will add more rolls to the cutting and creasing process thereby increasing the cost. One other problem with the application of preparation features in several stages is register holding and web stretch, since the web may not travel around the rolls at uniform speed at each stage and may not be wound tightly around the rolls in each creasing and/or cutting stage.
One related way of solving the alignment problem between two or more cutting operations is presented in the U.S. Pat. No. 6,203,482 to Sandford. Sandford discloses an apparatus for cutting cardboard sheets in such way that a cutting and perforation operation is performed by a pair of cutting dies, where both operations are performed in the same processing step. The end result of the combined cutting and perforation operation is a cardboard which has a lid of which one part is cut into the cardboard and where the remaining part of the lid is perforated for ease tearing off. In order to vary the depth of the perforation, the perforation knives are height adjustable by means of screws.
One drawback of the above solution is that it is not adapted for handling web of sheet like material, but rather individual blanks of carton. This makes the production process necessarily slow. Moreover, in order to set the priority order for the cutting and perforation tools and thus ensure high quality cuts, each tool needs to be separate height adjusted by means of screws, which requires very precise height adjustment. Moreover, if the priority order for the cutting and perforation tools needs to be changed, the heights need to be readjusted by means of screws.
There is thus a need for a solution which ensures proper alignment between different creasing, cutting and perforation operations in a continuous process involving a web of sheet like material which at the same times ensures high-quality preparation features with relaxed alignment requirements between the different cutting and creasing tools. Also, there is a need for a cost-effective solution where the wear of the cutting and perforation tools will be more uniform.
One additional problem arising from several simultaneous creasing and cutting operations in an industrial process is that the cutting tools wear out differently over time. Thus, for example the whole cutting knife may become blunt much earlier than the perforating knives leading to unsatisfactory preparation features on the sheet like material.
Hence, there is a need for a solution where both alignment between the different cutting and creasing operations is achieved and where the wear of the cutting and creasing tools is more uniform.
An object of the present invention is to solve the above-mentioned problem of prior art systems.
One aspect of the solution according to the present invention is presented by the cutting unit according to independent claim 1.
Preferable embodiments are present in the dependent claims 2-9.
One further aspect of the solution according to the present invention is presented by the web of sheet like according to independent claims 10.
Yet another aspect of the solution according to the present invention is presented by the method for cutting preparation features according to claim 11.
These and other advantages of the present invention will become more apparent by studying the following detailed description below.
According to a first aspect, a cutting unit for cutting preparation features in a web of sheetlike material is provided. The cutting unit comprises a first part with a rigid base portion, at least one first cutting tool configured to cut a first preparation feature in the web of sheetlike material, and at least one second cutting tool configured to cut a second preparation feature in the web of sheetlike material. The at least one first and second cutting tools are attached to the base portion and located at a distance from each other, wherein at least one of the first or second cutting tools is supported by a flexible support and wherein the flexible support is located in the rigid base portion of the first part.
In an embodiment the cutting tool further comprises a second part with at least one first rigid base portion, the second part being configured, in operation, to cooperate with the first part and the web of sheetlike material there between, such that when the first and second parts when pressed against the sheetlike material produce at least two preparation features on the packaging material. The second part thus forms an anvil for the first part, whereby precision and accuracy for the operation of the cutting unit can be improved.
The first rigid base portion in the second part may be supported by a flexible support, different from the flexible support in the first part. This allows for a relaxation of the height adjustment requirements for the first and second cutting tools in order to obtain essentially uniform wear over time.
The first part may comprise at least one third cutting tool configured to cut a third preparation feature in the web of sheetlike material, different from the first and second preparation features.
The first and second cutting tools may be supported by a first and second flexible support, respectively and wherein the hardness of the material of the first flexible support is equal to the hardness of the material of the second flexible support.
In another embodiment the first and second cutting tools are supported by a first and second flexible support, respectively and wherein the hardness of the material of the first flexible support is different from the hardness of the material of the second flexible support. Selecting the suitable hardness of the respective flexible members allows adjustment of the wear of each cutting tool such that a uniform wear may be obtained.
In an embodiment the first, second and third cutting tools are supported by a first, second and third flexible support respectively, and wherein the materials for the flexible supports each have a different hardness.
The first cutting tool may have a cylindrical shape and protrudes from the base portion. Hence the first cutting tool may be used to provide holes in the web of sheetlike material.
The second cutting tool may comprise a plurality of protrusions circularly or elliptically arranged at a distance from each other. The second cutting tool may thus be used to provide a perforation to the web of sheetlike material.
According to a second aspect a web of sheetlike material is provided. The web of sheetlike material comprises a plurality of crease lines along which the sheetlike material can be folded into a container, the web of sheetlike material further comprising a first and a second preparation feature aligned with each other. The first and second preparation features are applied by a cutting unit according to the first aspect described above.
According to a third aspect a method for cutting preparation features in a web of sheetlike material is provided. The method comprises: receiving a web of sheetlike material at a cutting and/or creasing station; passing the web of sheetlike material between a first and second parts of a cutting unit, located at a first and second cutting and/or creasing rolls, wherein the first unit comprises at least one first and at least one second cutting tool and where the second unit comprises an anvil against which the web of sheetlike material and the first part is pressed; pressing the two cutting and/or creasing rolls against the web of sheetlike material and against each other and; producing at least one first and one second preparation feature aligned with each other. In this method at least one of the first or second cutting tools are supported by a flexible support.
In the following detailed description example embodiments of the present invention are explained with reference to the accompanying drawings. It should be pointed out that these examples are for illustration purposes only and that they should not be construed as limitations of the present invention. Ultimately, the present invention is only limited by the accompanying claims.
Now,
As can be seen in the figure, the male first part 110 comprises a first cutting tool 130 in the form of a circular knife 130 and second cutting tool 140 in the form of a series of protrusions with a sharp edge which performs a perforation function. The male first part 110 comprises a base plate 122 supporting both cutting tools 130, 140. Optionally, the male first part 110 also comprises a magnetizer 170 for magnetizing portions on the packaging material containing magnetic particles passing through the cutting unit 110 for the purpose of alignment of the features cut into the packaging material with other preparation features, such as crease lines already present on the packaging material. Also, the magnetized particles may be magnetized in such a way that specific information about the packaging material is transferred.
Returning to the cutting tools 130, 140, the first cutting tool 130 is cylindrical and located in a cylindrical bore in the male first part 110. Also, the first cutting tool 130 is supported by a lower section of the base plate 122 (indicated by reference number 132 in
As can be seen in
It should however be realized that different shapes and configurations of the cutting tools 130, 140 could be utilized, such as e.g. straight or curved slits or perforations, depending on the selected application.
As can be seen from
Moreover,
The main functionality of the flexible support 144 for the second cutting tool 140 is to define a cutting priority for the two cutting tools 130, 140 such that the unsupported tool will have the highest priority and provide the best cut if the entire cutting system is set after this cutting tool. Usually, it is the first cutting tool 130 (the cylindrical knife in this case) that is given priority. However, it usually wears out the quickest, so that with the help of the flexible support 144 for the second cutting tool 140, the wear of both cutting tools 130, 140 will be evened out over time.
Moreover, the flexible support 164 in the female second part 160 serves the purpose of relaxing the conditions of height adjustment of the first and second cutting tools 130, 140 in order to obtain essentially uniform wear over time. Thus, the thickness of the flexible support 144 needs not to be adjusted with a high degree of accuracy in order to safeguard uniform wear of both cutting tools 130, 140.
It should be mentioned that in the most general sense, the flexible support defines the cutting priority for the two cutting tools 130, 140, such that in some embodiments, the second cutting tool 140 performing the perforation on the packaging material may be given priority over the first cutting tool 130 performing the hole punching on the packaging material. Moreover, there may be more than one perforation and cutting tool on the cutting unit 100, which will be shown in example embodiments further down in the text.
Although not shown in
Now, as seen from
The female second part 160 is supported by the flexible material 164 which has the effect that height adjustment between the cutting tool supported by the flexible support and the non-supported cutting tool does not have to be exact to ensure uniform wear over time.
The remaining parts of the cutting unit 200 are identical to those of the cutting unit 100 in
Finally,
It should be mentioned that some examples of the material from which the flexible support is made are rubber, springs or other flexible materials.
Also, it may be added that the cutting tools in the male first part and/or the anvils in the female second part the support may be gas suspended, e.g. by incorporating a gas cushion in the flexible support.
Also worth mentioning is that the first and second male and female parts of the cutting unit may be modular, thus they may be replaced with male and female parts which have different supports from the ones used and may cut different types of holes and perforations and also different numbers of holes and perforations into the packaging material, depending on need.
The cutting unit described above has proven to be particularly advantageous for high speed operation, where a web speed of well above 400 meters per minute is utilized. Still for this high speed accurate cutting is accomplished.
Now turning to
In
Number | Date | Country | Kind |
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16169773.5 | May 2016 | EP | regional |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2017/061616 | 5/15/2017 | WO | 00 |