Waterjet cutting device

Abstract

Water jet cutting device for separating a strip from a running paper, cardboard, tissue or other fibrous web (1) in a machine for the production and / or finishing of the same with at least one nozzle (2) which has several nozzle openings (3, 4), characterized in that a water jet (5) is directed onto the fibrous web (1) via at least two nozzle openings and an air jet (6) exits from at least one further nozzle opening (4).

Description

[0001] The invention relates to a water jet cutting device for separating a strip from a running web of paper, cardboard, tissue or other fibrous material in a machine for the production and / or finishing of the same, with at least one nozzle which has several nozzle openings.

[0002] Cutting devices in paper machines of this type are known. The produced paper is trimmed in width on one or both edges. The trimmed edge strips are separated from the rest of the material web and fed into a pulper for reprocessing and return to the production process. The width of the trimmed edge strips depends on the desired format of the produced material web and is also dependent on the type of paper being manufactured.

[0003] A cutting device includes a high-pressure water jet nozzle for generating a water jet that is directed at the moving web of material and cuts it at the point of impact of the water jet.

[0004] For safety reasons, but also to protect against contamination, the water jet, after it has cut through the fiber web, is usually collected by a water collection device.

[0005] At the beginning of the separation process, the edge strip cut in the direction of travel is often still connected to the material web and must be separated from it. Shortly after the respective edge strip is cut, it therefore runs parallel to the material web.

[0006] Knock-down nozzles are used to separate and form the beginning of the edge strip. These are air nozzles whose air jet is directed at the edge strip, knocking it away from the rest of the material web and deflecting it into a discharge channel. The knock-down nozzles are connected to the paper mill's compressed air network. While the resulting edge strips are being deflected, the remaining material web is conveyed to the winding unit and wound onto a reel. A cutting device of this type is described in document WO2013127008 A1.

[0007] The cutting process must be restarted after every change of paper type or after a break in the material web. Such cutting devices have been in use for some time.

[0008] The edge trimming in the former of the paper machine, which serves to form sheets, is continuous, which is why these nozzles in particular become relatively heavily soiled.

[0009] A cutting device as described in the preamble of claim 1 is known from JP S64-11 799 A; further cutting devices are also known from DE10 2015 015 037 A1 and EP 0 870 583 A2. These known cutting devices have only one water jet nozzle opening and one air opening for each nozzle. The design, manufacturing, and adjustment effort is quite considerable.

[0010] The object of the invention is to counteract nozzle contamination while simultaneously reducing manufacturing and adjustment costs. According to the invention, this object is achieved by directing a water jet onto the fiber web through at least two nozzle openings and by allowing an air jet to exit from at least one further nozzle opening.

[0011] It was discovered that water jet cutting nozzles tend to become clogged because the high-speed water jet exiting the nozzle opening draws in air, thus causing the intake of air along with dirt and fiber particles from the area around the nozzle.

[0012] As a result, dirt accumulates around the nozzle opening, which can lead to the fiber web tearing when it is removed.

[0013] Air can be drawn into the area of ​​the emerging water jet through the air jet nozzle openings, thus hindering or even preventing the intake of contaminated air. By using a single shielding device to surround at least two water jet nozzle openings, manufacturing and adjustment costs can be minimized.

[0014] If several, preferably all, water jet nozzle openings are aligned so that their water jets hit the fiber web one after the other in the web direction, the separation becomes more intensive and, in particular, more reliable even with thick fiber webs.

[0015] In contrast, several, preferably all, water jet nozzle openings, which are aligned so that their water jets meet the fiber web side by side across the web direction, ensure a wider cut.

[0016] However, it can also be helpful to arrange several water jet nozzle openings one behind the other in the direction of travel, but very slightly offset from each other perpendicular to the direction of travel.

[0017] To prevent the ingress of contaminated ambient air as much as possible, a preferably annular air jet nozzle opening should run around the water jet nozzle openings of the nozzle and / or several air jet nozzle openings should be arranged around the water jet nozzle openings of the nozzle.

[0018] It has proven advantageous if several, preferably all, air jet nozzle openings direct their air jet onto the fiber web. The effect can be even more comprehensive if at least one air jet nozzle opening aligns its air jet parallel to a water jet from the nozzle.

[0019] The amount of air released should be measured in such a way that, on the one hand, the suction of fiber and dirt particles towards the water jets is prevented, and on the other hand, these particles are not blown towards the fiber web.

[0020] To shield the nozzle openings, the nozzle should have a wall that encloses all nozzle openings and is open towards the fiber web. The air jets prevent contaminated air from being drawn into the interior, which is open towards the fiber web, and thus also prevent dirt deposits on the inside of the wall.

[0021] The invention will now be explained in more detail using two exemplary embodiments. The accompanying drawing shows: Fig. 1: a partial cross-section through a nozzle 2; Fig. 2 and Fig. 3: a side view of nozzle 2 with differently arranged nozzle openings 3,4.

[0022] At the in Fig. In the water jet cutting device shown in Figure 1, the nozzle 2 has two nozzle openings 3 arranged one behind the other in the web direction 7, each for a water jet 5. These two water jets 5 strike a fiber web 1 one after the other in the web direction 7 and thus cut off an edge strip from the fiber web 1 with high pressure.

[0023] The fiber web 1, in the form of a paper web, runs inside a paper machine at a speed between 200 and 2,500 m / min along the cutting device.

[0024] The edge strip can be removed to produce clean web edges, but may also be necessary for transferring the fiber web 1.

[0025] When the machine starts up, the fiber web 1 is guided through the machine section by section. It is usually necessary to change the width of the edge strip during this process.

[0026] To vary the width of the cut strip, the nozzle 2 can be moved along a crossbeam running transversely to the web direction 7 of the fiber web 1. The crossbeam thus limits the cutting path of the nozzle 2 as well as the possible impact area of ​​the water jets 5 on the fiber web 1.

[0027] In contrast, the separation of the web edges in the former of the paper machine is continuous, so that the nozzles 2 become relatively heavily soiled.

[0028] To prevent contamination with rebounding water and fibers and other particles carried along from the fiber web 1, the water jets 5 are collected by a water jet collection device 9 on the side of the fiber web 1 opposite the nozzle 2.

[0029] For this purpose, the water jet collection device 9 has a corresponding collection opening 10 along the cutting path and thus in the possible impact area of ​​the water jet 5.

[0030] Due to the high pressure of the water jets 5 and to ensure a clean cut while preventing tears or even rips, the fiber web 1 must be securely supported. This support is provided by a water-permeable, continuously circulating belt 11. This belt 11 is located on the side of the fiber web 1 opposite the nozzle 2 and can, for example, be designed as a forming screen in a former for sheet formation or as a drying screen in the drying section of a paper machine. Additionally, the belt 11 can be supported by other machine parts, such as forming bars.

[0031] After being separated from the material web, the edge strip is conveyed from belt 11 into a processing system, such as a pulper.

[0032] For the separation of the edge strip, the water jet nozzles 3 are supplied with water at a pressure of up to 40 bar in the former or up to 2,000 bar in the drying section of the paper machine.

[0033] To protect the nozzle openings 3,4 from contamination and damage, the nozzle 2 has a wall 8 that surrounds all nozzle openings 3,4 and is open towards the fiber web 1.

[0034] Since the water jets 5 emerging at high speed from the nozzle openings 3 entrain air from the interior space bounded by this wall 8, air is often drawn into this interior space together with dirt and fibers from the surroundings.

[0035] As a result, dirt accumulates around the water jet nozzle openings 3. If these dirt deposits detach from the nozzle 2, they can cause tears or rips when they come into contact with the fiber web 1.

[0036] To counteract the ingress of contaminated air into the interior space bounded by the wall 8, the nozzle 2 has at least one nozzle opening 4 through which an air jet 6 is directed towards the fiber web 1.

[0037] A compressed air supply to the air nozzle opening 4 at approximately 6 bar is usually sufficient for this purpose.

[0038] The water jets 5 thus predominantly carry along only the clean, oil-free, and dry compressed air. To facilitate this, the air jets 6 from these nozzle openings 4 are aligned parallel to the two water jets 5 of the nozzle 2 and thus towards the fiber web 1.

[0039] To shield the water jet nozzle openings 3, it can be done according to Fig. 2 It may be advantageous if several air jet nozzle openings 4 are arranged evenly distributed around the water jet nozzle openings 3 of the nozzle 2.

[0040] Alternatively or additionally, shielding can be applied according to Fig.3 but can also be achieved if an annular air jet nozzle opening 4 runs around the water jet nozzle openings 3 of the nozzle 2.

Claims

[1] Water jet cutting device for separating a strip from a running web of paper, cardboard, tissue or other fibrous material (1) in a machine for the production and / or finishing of the same, with at least one nozzle (2) which has several nozzle openings (3, 4), characterized by , that a water jet (5) is directed onto the fiber web (1) via at least two nozzle openings and an air jet (6) emerges from at least one further nozzle opening (4). [2] Waterjet cutting device according to claim 1, characterized by that several, preferably all, water jet nozzle openings (3) are aligned such that their water jets (5) hit the fiber web (1) one after the other in the web direction (7). [3] Waterjet cutting device according to claim 1, characterized bythat several, preferably all, water jet nozzle openings (3) are aligned such that their water jets (5) meet the fiber web (1) side by side transversely to the web direction (7). [4] Waterjet cutting device according to one of the preceding claims, characterized by , that a preferably annular air jet nozzle opening (4) runs around the water jet nozzle openings (3) of the nozzle (2). [5] Waterjet cutting device according to one of claims 1 to 3, characterized by , that several air jet nozzle openings (4) are arranged around the water jet nozzle openings (3) of the nozzle (2). [6] Waterjet cutting device according to any one of the preceding claims, characterized by , that several, preferably all, air jet nozzle openings (4) direct their air jet (6) onto the fibrous web (1). [7] Waterjet cutting device according to one of the preceding claims, characterized by, that at least one air jet nozzle opening (4) aligns its air jet (6) parallel to a water jet (5) of the nozzle (2). [8] Waterjet cutting device according to one of the preceding claims, characterized by , that the nozzle (2) has a wall (8) that encloses all nozzle openings (3,4) together and is open towards the fiber web (1).

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