Apparatus and method for producing a fluid jet needled fibrous web from at least one fibrous suspension

Abstract

Plant and method for producing a fluid jet needled fibrous web (20) from at least one fibrous suspension (11), wherein the fibrous suspension (11) is applied to a screen belt (14) of an inclined screen former (10) forming a fiber web (13), which rotates around a screen suction roller (35) in a rotational direction, the fiber web (13) is acted upon with fluid jets by means of nozzle bars (48, 49) as it rotates around the screen suction roller (35), and fluid is extracted by means of at least one vacuum zone (38, 39) provided within a roller shell (36) of the screen suction roller (35).

Description

[0001] The invention relates to a system for producing a fluid jet-needled fibrous web from at least one fibrous suspension, comprising an inclined screen former, comprising a screen belt which rotates around deflecting rollers in a circular direction and has a lay-down area formed between a deflecting roller located forward in the circular direction and a deflecting roller located rearward in the circular direction, and a headbox by means of which the fibrous suspension can be laid down on the lay-down area of ​​the screen belt to form a fiber mat, and a method for producing a fluid jet-needled fibrous web from at least one fibrous suspension, with an inclined screen former.

[0002] Such a system is known from DE 10 2016 217 401 A1.

[0003] Conventional plants for the production of fluid jet-needled, usually water jet-needled, papers / nonwovens typically incorporate separate needling units featuring a circumferential screen belt whose dewatering and reflection properties are adapted to the specific production process. The needling unit is designed to allow a defined energy input via fluid jet, tailored, for example, to the production speed and product portfolio.

[0004] Skew wire paper machines, such as those used in the specialty paper industry, typically do not have a separate needle punching unit. Instead, they comprise a skew wire former with a wire belt that rotates around deflection rollers in one direction. It features a lay-down section formed between a deflection roller at the front and one at the rear, and a headbox by means of which the fiber suspension can be deposited onto the lay-down section of the wire belt to form the fiber web.

[0005] Skew wire paper machines of this type are widely used, particularly in the specialty paper industry. However, the demand for non-fluid jet-needled specialty papers is declining, so there is an effort to also use these skew wire paper machines for the production of fluid jet-needled products, especially nonwovens.

[0006] This problem is solved by a system with the features of claim 1. The invention also encompasses a method for converting a skewed wire paper machine into a system according to the invention as claimed in claim 11 and a manufacturing method with the features of claim 12.

[0007] In the system according to the invention, the deflecting roller at the front of the screen belt in the direction of rotation is designed as a suction roller with a fluid-permeable roller shell and at least one vacuum zone provided within the roller shell. Furthermore, at least one nozzle bar is provided, by means of which fluid jets under overpressure can be discharged towards the screen belt in an area where the screen belt rotates around the suction roller. Surprisingly, it has been found that this further development makes it possible to provide energy input by means of fluid jets that is suitable for producing fibrous webs other than specialty papers, e.g., wet-laid nonwovens.

[0008] While suction rollers circulating around forming or transport wire have long been used in the paper industry as dewatering and deflection rollers, it is not known that they are also suitable for removing fluid applied to the fiber web for needling. It is surprising that needling can occur in the area of ​​a suction roller despite the wire mesh being located between the fiber web and the suction roller, due to the inclined wire.

[0009] In contrast, a fluid jet needling process on cylinders, around which a fiber web is guided, is well-known from carded nonwoven technology. However, the fiber web lies directly against these cylinders, i.e., without an intervening screen belt. Furthermore, these cylinders, by design, are not suitable for withstanding the high tensile forces that a screen belt is typically subjected to compared to a fiber web.

[0010] In a preferred embodiment of the system according to the invention, the vacuum zone comprises at least one suction chamber that can be pressurized with a negative pressure. Surprisingly, it has been found that, due to this measure, the energy input from the water jets can be effectively adapted to the values ​​required for nonwoven needling.

[0011] In order to further increase the energy input possible by means of the fluid jets, a plurality of nozzle bars spaced apart from each other in the direction of rotation of the screen belt are provided in a preferred embodiment of the system according to the invention.

[0012] Furthermore, a number of vacuum zones can be formed within the roller shell.

[0013] If the nozzle bars can be supplied with a fluid independently of each other, or – particularly preferably – if the fluid pressures of the nozzle bars can be controlled independently of each other, the energy inputs can be adapted particularly well to the respective production speed and the respective product portfolio.

[0014] For this purpose, it is advantageous if - as in a further preferred embodiment - each vacuum zone is assigned to a nozzle bar in such a way that fluid emitted by the assigned nozzle bar can be extracted by means of the vacuum zone, at least substantially.

[0015] In a structurally preferred embodiment of the system according to the invention, each vacuum zone comprises a suction chamber which can be pressurized with a negative pressure.

[0016] With a view to ensuring the best possible adaptability of the energy input, each suction chamber can preferably be pressurized with a separately variable negative pressure.

[0017] In order to increase the maximum possible energy input with the fluid jets, in a particularly preferred embodiment of the system according to the invention at least one further nozzle bar is provided between the suction screen roller and the rear deflection roller above the discharge channel.

[0018] In order to be able to adjust the energy input as best as possible once again, in a preferred embodiment of the system according to the invention, each further nozzle bar is assigned a further vacuum zone such that the fluid emitted by the assigned nozzle bar can be extracted by means of the vacuum zone.

[0019] In a structurally preferred embodiment of the system according to the invention, each further vacuum zone has a suction box which is arranged below the discharge area of ​​the sieve belt.

[0020] The invention is also embodied in a method for manufacturing a plant according to the invention, in which, in an inclined wire paper machine having a wire belt which forms a lay-up zone between a front and rear deflecting roller in a direction of rotation of the wire belt, the front deflecting roller is replaced by a suction roller with a fluid-permeable roller shell and at least one vacuum zone provided within the roller shell, and at least one nozzle bar is provided by means of which fluid jets can be discharged towards the wire belt under overpressure in an area in which the wire belt rotates around the suction roller.

[0021] The invention further extends to a method for producing a fluid jet-needled fibrous web from at least one fibrous suspension, in which the fibrous suspension is applied to a screen belt of an inclined screen former, which rotates around a screen suction roller in a rotational direction, the fibrous suspension is subjected to fluid jets during its rotation around the screen suction roller, and fluid is extracted by means of the screen suction roller.

[0022] The invention will be further illustrated below with reference to the purely schematic drawings. These show: Fig. 1 shows an embodiment of a system according to the invention, and Fig. 2 shows section II in Fig. 1 in an enlarged, partially cropped representation.

[0023] The in Fig. 1 The embodiment of the system according to the invention, designated as a whole by 100, is suitable for producing a fluid jet needled fibrous web.

[0024] The system 100 comprises an inclined screen former 10 for producing a fiber web 13 consisting of fibers 12 from a fiber suspension 11. The fibers have an average fiber length of regularly >1 mm up to a maximum of 30 mm, and the fiber web 13 has a basis weight, for example, between 7 and 100 grams per square meter. For producing the fiber web 13, the inclined screen former 10 includes a circulating screen belt 14, which rotates counterclockwise around deflection rollers 15. It forms a depositing area 16, the front end of which, in the direction of rotation, is formed by a front deflection roller 15' and the rear end of which, in the direction of rotation, is formed by a rear deflection roller 15".

[0025] The inclined screen former 10 also includes a headbox 17, by means of which the fibers 12 - e.g. as a fiber suspension - are deposited to form the fiber pile 13.

[0026] In order to consolidate the fiber pile 13 into a fiber web 20, the front deflection roller 15' is designed as a screen suction roller 35. As in Fig. 2 As can be seen, the screen suction roller 35 comprises a rotatably mounted roller shell 36, which includes a plurality of bores 37. Within the roller shell 36, two vacuum zones 38, 39 are provided, each of which has a suction chamber 40, 41. The suction chambers 40, 41 each have an opening 42, 43 extending in the longitudinal direction of the screen suction roller 35, the edges 44, 45, 46 of which are sealed at least substantially gas-tight.

[0027] In the area where the screen belt 14 rests against the roller shell 36, two nozzle bars 48, 49 are provided spaced apart from each other in the direction of rotation of the screen belt. They are arranged such that pressurized fluid jets, in particular water jets, can be discharged towards the screen belt. The openings 42, 43 of the suction chambers 40, 41 are oriented such that each suction chamber 40, 41 is assigned to one of the nozzle bars 48, 49 in such a way that at least substantially the fluid discharged by the assigned nozzle bar is drawn off by each suction chamber.

[0028] Three further nozzle bars 50, 51, 52, spaced apart from each other in the direction of rotation of the screen belt 14, are arranged in the direction of rotation of the screen belt upstream of the screen suction roller 35. Inside each of these, a further vacuum zone 53, 54, 55 in the form of a suction box 56 is assigned. The further nozzle bars 50, 51, 52 serve to pre-consolidate the fibers 12 to form the fiber pile 13. The nozzle bars 48, 49, to which the vacuum zones 38, 39 of the screen suction roller are assigned, further consolidate the fiber pile to form the fiber web 20.

[0029] If there is a need for intensified consolidation, further nozzle bars and associated vacuum zones, not shown in the drawing, can be provided in the direction of rotation of the screen belt 14 behind the screen suction roller in an area 18 which slopes downwards with respect to the direction of rotation.

[0030] In section 18 of the screen belt 14, a take-off roller 19, which can be subjected to a vacuum, for example, can be provided. This roller allows the compacted fiber web 20 to be removed from the screen belt 14 and subsequently fed to it for further use or processing. Such a take-off roller 19 is particularly useful when the fiber web 20 has a low basis weight or low tensile strength, or when the rotational speed of the screen belt 14 is high. Otherwise, the fiber web can also be removed from the screen belt 14 by free movement. In this case, a take-off roller 19 is not required. Reference symbol list:

[0031] 100 plant 10 Inclined screen former 11 Fiber suspension 12 Fibers 13 Fiber web 14 Screen belt 15 Deflection rollers 15 Front deflection roller 15 Rear deflection roller 16 Discharge area 17 Headbox 18 Area 19 Take-off roller 20 Fiber web 35 Suction roller 36 Roller shell 37 Bores 38 Vacuum zone 39 Vacuum zone 40 Suction chamber 41 Suction chamber 42 Opening 43 Opening 44 Edge 45 Edge 46 Edge 47 Inner shell surface 48 Nozzle bar 49 Nozzle bar 50 Nozzle bar 51 Nozzle bar 52 Nozzle bar 53 Vacuum zone 54 Vacuum zone 55 Vacuum zone 56 Suction box

Claims

1. System (100) for producing a fluid-jet-needled fibrous web (20) from at least one fibrous suspension (11), having an inclined-wire former (10) comprising - a wire belt (14), which circulates in a direction of circulation around deflection rollers (15) and has a lay-down strand (16) formed between a front deflection roller (15') in the direction of circulation and a rear deflection roller (15") in the direction of circulation, and - a headbox (17), by means of which the fibrous suspension can be laid down on the lay-down strand (16) of the wire belt (14), characterized in that the front deflection roller (15') in the direction of circulation is designed as a wire suction roller (35) with a fluid-permeable roller jacket (36) and at least one vacuum zone (38, 39) provided within the roller jacket (36), and at least one nozzle bar (48, 49) is provided, by means of which fluid jets can be discharged towards the wire belt (14) at an overpressure in a region in which the wire belt (14) circulates around the wire suction roller (35).

2. System according to Claim 1, characterized in that the vacuum zone (38, 39) comprises at least one suction chamber (40, 41) which can be subjected to a negative pressure.

3. System according to Claim 1 or 2, characterized in that a plurality of nozzle bars (48, 49) spaced apart from one another in the direction of circulation of the wire belt (14) are provided.

4. System according to any one of Claims 1 to 3, characterized in that a plurality of vacuum zones (38, 39) are formed within the roller jacket (36).

5. System according to Claim 4, characterized in that each vacuum zone (38, 39) is assigned to a nozzle bar (48, 49) in such a way that fluid emitted at least substantially from the assigned nozzle bar (48, 49) can be extracted by means of the vacuum zone (38, 39).

6. System according to Claim 5, characterized in that each vacuum zone (38, 39) comprises a suction chamber (40, 41) which can be subjected to a negative pressure.

7. System according to Claim 6, characterized in that each suction chamber (40, 41) can be subjected to a separately variable negative pressure.

8. System according to any one of Claims 1 to 7, characterized in that, between the wire suction roller (35) and the rear deflection roller (15"), at least one further nozzle bar (50, 51, 52) is provided above the lay-down strand (16).

9. System according to Claim 8, characterized in that each further nozzle bar (50, 51, 52) is assigned a further vacuum zone (53, 54, 55) in such a way that fluid discharged at least substantially from the assigned nozzle bar (50, 51, 52) can be extracted by means of the vacuum zone (53, 54, 55).

10. System according to Claim 9, characterized in that each further vacuum zone (53, 54, 55) has a suction box (50), which is arranged below the lay-down strand (16).

11. Method for producing a system (100) for producing a fluid-jet-needled fibrous web (20) from at least one fibrous suspension (11) according to any one of Claims 1 to 10, characterized in that, in an inclined-wire paper machine having a wire belt (14) which forms a lay-down strand (16) between a front and a rear deflection roller (15', 15") in a direction of circulation of the wire belt (14), the front deflection roller (15') is formed by a wire suction roller (35) having a fluid-permeable roller jacket (36) and at least one vacuum zone (38, 39) provided within the roller jacket (36), and at least one nozzle bar (48, 49) is provided by means of which fluid jets can be discharged towards the wire belt (14) at an overpressure in a region in which the wire belt (14) circulates around the wire suction roller (35).

12. Method for producing a fluid-jet-needled fibrous web (20) from at least one fibrous suspension (11), in which method the fibrous suspension (11) is applied to a wire belt (14) of an inclined-wire former (10), with formation of a fibrous pile (13), which wire belt circulates around a wire suction roller (35) in a direction of circulation, the fibrous suspension is exposed to fluid jets during circulation around the wire suction roller (35), and fluid is extracted by means of the wire suction roller (35).

13. Method according to Claim 12, characterized in that fluid is extracted by means of at least one suction chamber (40, 41) which can be subjected to a negative pressure.

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