SCREENING DEVICE

Description

[0001] The invention relates to a screening device which is preferably designed in the form of a screening basket, wherein the screening device has screening slots or gaps formed between profiled screening bars, and the screening bars are received at their base region in receiving recesses of support elements adapted to the base region geometry and are permanently fastened to these.

[0002] Such screening devices are also called "bar screens." These screening devices can be designed in a flat form as screen plates or in a rounded form as screen baskets.

[0003] From DE 10 2014 011 679 A1, profiled screen bars and screening devices are known, which are preferably designed in the form of a screen basket. These devices have specially profiled screen bars, specifically in such a way that the respective radii upstream and downstream of the slot-generating flanks in the head region of the screen bar have a common center point. The screening device made from such screen bars is cylindrical and can be divided into segments or regions in the axial direction, whereby the regions with different profile depths always have a substantially constant slot width. The production of these specially designed screen bars and their head region is complex, and therefore there is a need for a more cost-effective production of screening devices of this type.

[0004] DE 169 09 316 C2 discloses a method for manufacturing a screening device with controlled, irregular sorting slots, as well as screening devices and their use. This discloses the adjustability of the profile depth of a cylindrical bar screen basket. The screen basket has variable slot widths and / or different profile depths, whereby both core sizes can always be varied. A screening device, preferably in the form of a cylindrical screen basket, is constructed from these profile bars known from this document.

[0005] Finally, from DE 44 32 842 A1 a sorting device with a conical design is known, wherein the slot widths change in the direction of the flow path from the material inlet side to the reject outlet side, in such a way that the slot width becomes smaller in the direction of the flow path from the material inlet side to the reject outlet side.

[0006] US Pat. No. 5,255,790 A discloses a screen basket for sorting / classifying, in particular, fiber suspensions, consisting of parallel bars with slot-shaped screen gaps between them. To create an irregular screen surface, the end faces of the bars facing the inlet side of the fiber suspension are inclined and provided with ribs or bulges.

[0007] A screening device of the generic type having the features of the preamble of patent claim 1 is described in WO 2018 / 039719 A1.

[0008] The invention therefore aims to provide a screening device made of conventional screening bars, which for example have a triangular profile, in which the sorting efficiency is improved, there is a low tendency to clogging, and higher throughput quantities can be achieved as well as an overall gentle sorting process can be realized.

[0009] According to the invention, a screening device in the form of a screen basket is provided, with screening slots or gaps formed between profiled screen bars. The screen bars are triangular in profile and are accommodated at their base region in receiving recesses of support elements adapted to the base region geometry and are permanently attached to these. The screening device is divided in the flow direction, starting from a material inlet side to the reject outlet side, into at least a first treatment zone A and a second treatment zone B, with the diameter on the material inlet side being larger than on the reject outlet side.The screening device is characterized in that the profile bars are arranged in such a way that, with a constant slot width between adjacent profile bars, the profile bars have a profile depth t1 in the first treatment area A and a profile depth t2 in the second treatment area B, wherein the profile depth t1 in the first treatment area A is smaller than the profile depth t2 in the second treatment area B, wherein the profile depth increases in steps starting from the material inlet side to the direct outlet side.

[0010] The screening device according to the invention is designed in such a way that different profile depths and / or different angles are present at a tangent to the screening device's surface, but a substantially constant slot width is maintained, so that screening or sorting processes can be carried out with different operating conditions in the direction of flow through the screening device from the stock inlet side to the reject outlet side. This allows for higher throughput rates and, in particular, improved sorting efficiency.

[0011] If the screen bar in the upper section of the screen basket is flatter or has a smaller profile depth, smaller flow vortices and less turbulence are achieved, and the likelihood of dirt particles being forced through the screen slots or gaps is reduced. Thus, the screening device according to the invention results in an overall more efficient and gentle sorting process.

[0012] The thickening of the fiber suspension steadily increases toward the reject outlet side. To prevent the screening process from coming to a standstill due to the risk of clogging, a greater profile depth is implemented in the area toward the reject outlet side. This increases turbulence in this area, improves fluidization of paper fibers in the suspension, and reduces the tendency to clogging. Furthermore, the contaminant load thickens and concentrates in the area toward the reject outlet side. This contaminant load increases wear, so the greater profile depth in this area increases the stock volume in the flow, thereby improving creep strength and extending the service life of the profile or screen basket.

[0013] According to preferred embodiments of screening devices, the screen bars can be aligned axially to the screen basket axis, or alternatively, they can be aligned linearly inclined to the screen axis. Or, according to a further preferred embodiment, the screen bars can be aligned discontinuously curved relative to the screen basket axis. The orientation of the screen bars is selected according to and tailored to the screening tasks and screening treatments.

[0014] In particular, the profile bars have a substantially triangular profile. The slot width can range from 0.05 mm to 0.8 mm, preferably from 0.1 mm to 0.4 mm.

[0015] The profile bar width is preferably in a range of 2.0 mm to 8 mm, and preferably between 2.0 mm and 4.0 mm.

[0016] The invention is explained in more detail below using preferred embodiments with reference to the accompanying drawings. The drawing shows: Fig. 1 is a schematic view of a screen basket according to the invention with at least two different screening areas between the material inlet side (inlet) and a reject outlet side (reject); Fig. 2 is a schematic sectional view of a screen basket according to Fig. 1 in cooperation with a rotor equipped with blades; Fig. 3 shows a schematic sectional view of another embodiment of a screening device in cooperation with a likewise conically designed rotor; Fig. 4 shows a schematic view of a section of a screening device in which the screen bars are aligned axially to the screen basket axis; Fig. 5 shows a further preferred embodiment of a variant of a screening device in which the screen bars are aligned with a linear inclination to the screen basket axis; and Fig. 6 shows a schematic sectional view of a variant of a screening device in which the screen bars are aligned with a discontinuous curve to the screen basket axis.

[0017] In the figures of the drawing, identical or similar parts are provided with the same reference numerals.

[0018] In Fig. 1 An embodiment of a screening device, designated overall by 1, is shown, which is divided into at least two different treatment areas A, B in the flow direction, starting from the material inlet side (inlet) to the reject outlet side (reject). Arrows indicate the inlet on the material inlet side 2 and the reject on the reject outlet side 3. The direction of the accepted material flow is also indicated by arrows in conjunction with the designation "acceptable material."

[0019] On the right side of Fig. 1 In an enlarged detail view, the corresponding arrangement of profile bars 4 is shown next to the treatment areas A, B.

[0020] As from Fig. 1 As can be seen overall, the profile bars 4 are arranged such that, with a constant slot width w between adjacent profile bars 4 in the screen basket axis direction, the profile depth t increases from the stock inlet side to the reject outlet side, and the diameter of the screening device 1 is larger at the stock inlet side 2 than at the reject outlet side 3. The screening device 1 according to the invention is thus designed conically in a predetermined manner, namely such that the diameter of the stock inlet side 2 is larger than at the reject outlet side 3.

[0021] In the treatment area A, three adjacent sieve bars 4 are shown, which have a profile width Br, a distance from profile bar 4 to profile bar 4 of P1, a profile bar head width b1 and a profile depth t1, whereby between adjacent profiled sieve bars 4, 4 sieve slots or gaps are formed, which have a slot width w.

[0022] The sieve bars 4' in the treatment area B have a profile head width B, a distance from profile bar 4' to profile bar 4' of P2, a profile bar head width b2, whereby the profile depth is specified as t2.

[0023] As can be seen from this illustration, in the preferred example, the screening bars 4 are arranged with a profile depth t1 in treatment area A, and the profile bars 4' are arranged with a profile depth t2 in treatment area B. In both treatment areas A and B, the slot width w is constant. The profile depth t1 in treatment area A is smaller than the profile depth t2 in treatment area B, or in other words, the profile depth t increases from treatment area A, designated there by t1, to treatment area B at t2. Furthermore, the diameter of the screening device 1 is larger at the stock inlet side (inlet) 2 than at the reject outlet side 3 (reject).

[0024] Fig. 2 schematically illustrates a screening device 1 according to Figur 1 in conjunction with an internally rotating rotor 6, which is equipped with vanes 7. Since the screening device 1 according to the invention is conical, Fig. 2 The gap between the wings 7 and the inner wall of the screening device 1 becomes smaller, starting from the material inlet side 2 toward the reject outlet side 3. This significantly increases the screening efficiency.

[0025] In Fig. 3 an alternative embodiment is shown in which the screening device 1 cooperates with an internally running rotor 6', which is also equipped with vanes 7'. In this case, the design is such that the rotor 6' is also conical like the screening device 1, such that starting from the stock inlet side 2 in the direction of the reject outlet side 3, the diameter of the rotor 6' becomes smaller. Thus, the vanes 7' also follow the conical design of the screening device 1. The gap between the vanes 7' of the rotor 6' and the inner wall of the conically designed screening device 1 therefore remains essentially constant from the stock inlet side 2 to the reject outlet side 3.

[0026] After Fig. 4 the profile bars 4, 4' are aligned axially to the screen basket axis 4 as a preferred embodiment of the screening device 1.

[0027] In Fig. 5 the profile bars 4, 4' serving as sieve bars are aligned linearly inclined at an angle α to the sieve basket axis as a preferred embodiment of the sieve device 1.

[0028] As from Fig. 6 Finally, as can be seen, the profile bars 4, 4' are discontinuously curved relative to the screen basket axis as a preferred embodiment of the screening device 1.

[0029] In particular, it is essential in the invention that the profile bars 4, 4' are arranged in such a way as to correspond to the corresponding treatment area that, with constant slot widths w between adjacent profile bars 4, 4' in the screen basket axis direction, the profile depth t1, t2 increases from the stock inlet side 2 to the reject outlet side 3, and the diameter of the screening device 1 is larger on the stock inlet side 2 than on the reject outlet side 7, so that a conical design of the screening device 1 according to the invention is obtained. This allows the screening device 1 to be adapted in the flow direction to the respective requirements, circumstances, and treatment conditions and to be specifically matched to them. List of reference symbols

[0030] 1Screening device in total 2Material inlet side (feed) 3Reject outlet side (reject) 4Profile bars 4, 4' 6Rotor 6' 7Vanes Treatment area in Fig. 1 above BTreatment area in Fig. 1 below wSlot width tProfile depth BrProfile head width P 1 - P 2 Distance from profile bar 4, 4' to profile bar 4, 4' b 1 , b 2 Profile bar head width

Claims

1. Screening device (1) in the form of a screen basket, with screen slots or screen gaps formed between screen bars (4, 4'), which screen bars (4, 4') are triangular in profile and their base area is accommodated in receiving recesses of support elements adapted to the geometry of the base area and is permanently attached to these, wherein, in the direction of flow from a fabric inlet side (2) to the reject outlet side (3), the screening device (1) is divided into at least a first treatment area (A) and a second treatment area (B), and the diameter of the screening device (1) is larger on the fabric inlet side (2) than on the reject outlet side (3), characterized in that the profiled bars (4, 4') are arranged in such a way that, with a constant slot width (w) between adjacent screen bars (4, 4'), the bars (4, 4') have a profile depth (t1) in the first treatment area (A) and a profile depth (t2) in the second treatment area (B), wherein the profile depth (t1) in the first treatment area (A) is smaller than the profile depth (t2) in the second treatment area (B), with the profile depth (t1, t2) increasing in steps starting from the fabric inlet side (2) to the reject outlet side (3).

2. Screening device (1) according to claim 1, characterized in that the screen bars (4, 4') are aligned axially in relation to the screen basket axis.

3. Screening device (1) according to claim 1, characterized in that the screen bars (4, 4') are designed to be linearly inclined with respect to the screen basket axis.

4. Screening device (1) according to claim 1, characterized in that the screen bars (4, 4') are aligned in a discontinuously curved manner with respect to the screen basket axis.

5. Screening device (1) according to any one of the preceding claims, characterized in that the slot width (w) is in a range of between 0.05 mm and 0.8 mm, preferably of between 0.1 and 0.4 mm.

6. Screening device (1) according to any one of the preceding claims, characterized in that the profiled bar width (b1, b2) is in a range of between 2.0 mm and 8.0 mm, preferably of between 2.0 mm and 4.0 mm.