FI125633B - visibility Cylinder - Google Patents

Description

strainer Cylinder

Background of the Invention

The invention relates to a screening cylinder for purifying or sorting a fibrous mixture, the screening cylinder having a cylindrical screening surface formed by screening gaps between the screening screen faces and the screening screen.

Screening cylinders are used, inter alia, for cleaning and sorting the fiber mixture. The screening cylinder of screening yarns has substantially parallel screening yarns disposed adjacent to each other, spaced apart, having a front surface substantially oriented in the direction of feed of the fiber mixture to be cleaned or screened. The front surfaces of the screen yarns and the screen gaps between screen yarns together form the cylindrical screen surface of the screen cylinder.

U.S. Pat. No. 5,415,294 discloses a screen surface formed adjacent to one another at a distance spaced substantially parallel to one another, and the slits between them, i.e. screen slits. The front surface of the screen yarns has ridges or grooves spaced apart in the longitudinal direction of the screen yarn to retain solids in the fluid being treated with the screen.

DE 19625726 C1 discloses a screen surface consisting of screening yarns disposed substantially parallel to one another and gaps, i.e. screening gaps therebetween. The front surface of the screening wire has higher and lower sections alternating longitudinally of the screening wire.

Brief Description of the Invention

An object of the invention is to provide a new type of screen cylinder.

The screening cylinder of the invention is characterized in that the profiling contour that limits the profiling area to the rest of the screen surface of the screen comprises at least one curved portion when viewed from the normal direction of the screen front.

The screening cylinder for purifying or sorting the fiber mass mixture comprises screening yarns spaced apart so that the front surfaces of the screening yarns and the screening gaps between screening yarns together form the cylindrical screening surface of the screening cylinder. The front surface of the at least one screening wire of the screening cylinder comprises profilings which are projections and / or recesses formed on the front surface of said screening wire. The profiling contour that limits the profiling area to the rest of the screen surface of the screen yarn comprises at least one curved portion when viewed from the normal direction of the screen screen front surface.

Profiling or recesses or projections formed on the screen surface of the screen yarn may cause small flow disturbances, i.e. microturbulences, to the fibrous mixture passing on the screen screen front surface, which will break the fiber blocks and thereby increase the capacity of the screen. Increasing the turbulence of the screen surface of the screen cylinder also reduces pulp deposition, which also increases the capacity of the screen. When the profiling or recess or projection is shaped so as to have at least one curved portion, the design of said curved portion allows flow disturbances, i.e. microturbulences, to be caused to the pulp mixture to be treated so that the flow losses of the pulp mixture in the screen cylinder are not substantially increased.

According to one embodiment, the contour line of the at least one profiling is circular.

According to one embodiment, the at least one profiling has a conical or truncated cone cross-section in the direction normally defined by the screen surface.

According to one embodiment, the contour line of the at least one profiling is elliptical.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in greater detail in connection with the preferred embodiments, with reference to the accompanying drawings, in which: Fig. 4 is a schematic view of a second screen cylinder viewed from the end of the screen wires and cross-sectioned; 6 is a schematic view of a fourth screen cylinder at the end of the screening webs, see FIG. Figure 9 is a schematic view of the screen cylinder of Figure 8 viewed in the direction of the screen surface; Figure 10 is a schematic view of a fifth screen cylinder viewed from the end of the screen webs; and Figure 11 is a schematic view of the screen cylinder of Figure 10; schematically some possible profiling of the screen surface in the direction of the screen surface.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 schematically shows a top view and a cross-sectional view of one of the screen cylinders 1 which can be used to purify or sort the fiber mixture. Fig. 2 schematically shows a screen cylinder 1 of Fig. 1 as viewed from the end of the screen wires 2 and a cross-sectional line A-A of Fig. 3 and schematically shows a screen cylinder 1 of Fig. 2 viewed in the direction of a screen surface 8. The screening cylinder 1 comprises screening yarns 2 having a first side panel 3 and a second side panel 4. The screening yarns 2 are spaced apart about the entire circumference of the screening cylinder 1 so that screening slots 5 between the opposite sides of adjacent screening yarns 2 are substantially oriented. 1 to 3, the surfaces 7 of the screening yarns 2 directed to the inside of the screening cylinder 1 form the front surfaces 7 of the screening yarns 2, which together with the screening slots 5 form the screening cylinder 8 8. The direction of the flow of the fiber mass mixture relative to the screen surface 8 of the screen cylinder 1 is schematically illustrated by arrow F, whereby the first lateral side 3 of the screen wire 2 forms the front side 3 of the screen screen 2. in the upper cylinder 1 substantially in the opposite direction relative to the flow direction F of the pulp mixture and the second lateral side 4 of the screen yarn 2 forms the rear side 4 of the screening yarn 2 which is substantially parallel to the direction F of the fiber flow. Correspondingly, the first side edge 7 'of the front surface 7 of the screening yarn 1, i.e. the front edge 7' of the front surface 7, is formed by the edge of the screening screen 2 in a substantially opposite direction to the feed stream F of the fiber mixture 1. forming the leading edge 7 of the screening yarn 2, which in the screening cylinder 1 is oriented substantially in the same direction as the direction F of the feed mass flow of the fiber mixture. The direction from the front edge 7 'of the front surface 7 of the screening yarn 2 to the trailing edge 7' forms the width direction WD of the screening yarn 2, which is transverse to the longitudinal direction LD of the screening yarn 2. The liquid in the pulp mixture fed to the screen surface 8 and the size portion of the fibers in the pulp mixture 5 flow from the inlet side 6 of the screening cylinder 1 through the screening slots 5 and the other separable material remains inside the screen cylinder 1 for removal as a reject.

The screening yarns 2 are secured to the support bars 11 forming the support elements 11 of the screening cylinder 1 at appropriate intervals along the axis of the screening cylinder 1 so that the screening threads 2 remain sufficiently rigid and firm. Further, support rings 12 can be mounted around the support rods 11, which support the support bars 11 and receive in the screen cylinder 1 the forces created by the differential pressure due to different varying pressures on its screen surface 8, thereby reinforcing the structure of the screen cylinder 1. Fig. 1 further shows an end ring 13 mounted on the ends of a screening cylinder 1, by means of which the screening cylinder 1 can be supported on a screen frame structure which, for reasons of clarity, is not shown in the figures. In Fig. 1, the structure of the support rods 11 and the support rings 12 with respect to the diameter of the screen cylinder 1 is shown to be substantially larger than they typically are in reality.

Figures 2 and 3 further show recesses 14 formed in the front surface 7 of the screening wire 2, i.e. in the region of the front surface 7. The recesses 14 are equally spaced apart in the longitudinal direction LD of the screening wire 2 in the front surface 7 of the screening wire 2. The recesses 14 are profiling formed on the front surface 7 of the screening yarn 2, which is intended to influence the flow or flow properties of the fiber mass mixture fed to the screening cylinder 1 on the screen surface 8. For clarity, said profiling is not shown in Figure 1.

The region of recess 14 or, in other words, recess 14 is delimited or delimited from the rest of the front surface 7 of the screening yarn 2 by a contour line 16 or an edge 16 in FIG. 3 when depressed 14 schematically viewed by the arrow N in FIG. wherein said viewing direction is thus opposite to the direction of the arrow indicated with respect to the direction. When said contour line 16 is elliptical, the profiling area formed on the front surface of the screening yarn comprises a plurality of curved portions delimiting a contouring line 16 from the rest of the screening front surface, such profiling being viewed from the normal N direction of the front surface 7 of the screening yarn. The curved portions of the elliptical profiling contour line 16 can be considered to have a total of four, i.e., the sides 17a, 17b and the ends 17c and 17d of the ellipse.

Fig. 4 is a schematic view of another screening cylinder 1 as seen from the end of the screening yarns 2 and taken along the sectional line B-B shown in Fig. 5 and schematically showing the screening cylinder 1 according to Fig. 4 in the direction of the screening surface 8. 4 and 5, the profilings formed in the front surface 7 of the screening yarns 2 are recesses 14 having a contour line 16 when the recess 14 is schematically viewed from the normal N direction of the front surface 7 of the screening yarn 2 shown by arrow N in FIG. Thus, the contour of the circular recess 14 is defined as a profiling in which the profiling area is limited from the rest of the screen surface to a contour comprising a single curved portion, i.e. a circle ring, when viewed from the normal direction of the screen surface.

Fig. 6 is a schematic view of a third screen cylinder 1 as viewed from the end of the screen yarns 2, and sectioned along the sectional line C-C shown in Fig. 7, and Fig. 7 schematically shown in the direction of screen surface 8 of Fig. 6. In the screen cylinder 1 of Figs. 6 and 7, the profilings are implemented as projections 15 which extend upwards or outwards from the front surface 7 of the screen wire 2 and whose contour line 16 is elliptical. Thus, the shape 16 of the elliptical profiling in the form of a projection 15 also comprises a plurality of curved portions, i.e. portions 17a, 17b, 17c and 17d, when the projection 15 is schematically viewed from the normal direction of the front surface 7 of the screen.

Fig. 8 is a schematic view of a fourth screen cylinder 1 as viewed from the end of the screen yarns 2 and taken along a sectional line D-D in Fig. 9 and schematically shown in the direction of screen screen 8 according to Fig. 8. In the screen cylinder 1 of Figs. 8 and 9, the profilings are implemented as projections 15 which extend upwards or outwards from the front surface 7 of the screen wire 2 and whose contour line 16 is circular. Thus, the circular profiling line 16 in the form of a projection 15 is formed by a single curved portion, i.e. a circle ring, when the projection 15 is schematically viewed in the normal direction of the front surface 7 of the screening yarn 2 shown by arrow N.

Profiling formed on the front surface 7 of the screening wire 2 of the screening cylinder 1 causes microturbulence in the fiber mass mixture flowing through the screening surface 4. This microturbulence disrupts the fiber flocs in the fiber blend and increases the capacity of the screen with a screening cylinder of the kind shown. Said increase in turbulence can also reduce the deposition of pulp on the screen surface, which also increases the screen capacity.

Said profiling thus forms a flow field for microturbulence or, in other words, flow disturbances on the screen surface 8 which hates the pulp mixture. When the profiled contour line 16 comprises at least one curved portion, the curved portion of the profiling corresponding to the curved portion of said contour causes a flow disturbance in which said hating portion of the fibrous mixture is forced to boil a longer flow distance than that portion of the fibrous mixture. Said adjacent flow portions of the fiber blend are thus subjected to a separating effect, said effect increasing the separation of the fibers passing through said adjacent flow portions. However, the flow disruption caused by the curved portion of the profiling does not substantially increase the flow loss of the fiber blend in the screen cylinder, which occurs when the profiling comprises only straight edges. Thus, the profiling formed on the face of the screen yarn, whether formed as a recess or projection, is formed such that the contour line separating or delimiting the profiling area from the rest of the screen surface comprises at least one curved portion when viewed from the normal direction of the screen. the loss of anger in the fiber mixture to be cleaned or sorted is smaller than before.

In the screening cylinders 1 according to Figures 2-9, the front surface 7 of the screening wire 2 is inclined, whereby a step is formed between two adjacent screening yarns 2, which causes turbulence in the fiber mass mixture passing on the screen surface. The turbulence caused by such a step is clearly greater in intensity than the turbulence caused by the profiling on the front surface 7 of the screening wire 2, and thus the profiling shown can be used to fine-tune the operation of the screen surface 8. In addition to screening cylinders such as those shown in Figs. 2-9, the front surface profiling of screening wire 2 shown may also be used in screening cylinders where the screen surface 2 has a non-inclined front face 7.

The bottom surface 17e (Fig. 2) of the recesses 14 shown in Figs. 2-5 and the outer surface 17f (Fig. 6) of the projections 15 shown in Figs. 6-9 are curved so that the bottom surface 17e of the recesses 14 or the outer surface 17f of the projections 15 do not substantially increase Flow losses from recesses 14 and projections 15 comprising an elliptical contour line 16 may also be minimized such that the transverse cross-sectional shape of said recesses 14 or projections 15 is tapered toward the bottom of the recess 14 or the top of the projection 15 as shown in Figs.

Fig. 10 is a schematic view of a fifth screen cylinder 1 as viewed from the end of the screen wires 2 and a cross-sectional view along the sectional line E-E shown in Fig. 11, and Fig. 11 schematically shown in the direction of screen screen 8. As shown in Figures 4 and 5, the screening cylinder 1 of Figures 10 and 11 has recesses 14 formed on the front surface 7 of the screening yarns 2 having a contour line 16 when depressed 14 is schematically viewed from the normal direction of the front face 7 of the screening wire 2. However, the recess 14 shown in Figs. 10 and 11 differs from the recess 14 shown in Figs. 4 and 5 in that the recess 14 of Figs. 10 and 11 has a conical cross-section, the bottom surface 17e of the recess 14 having a sharp angle. The sharp tip of the bottom surface 17e of the recess 14 enhances the microturbulence caused by the recess 14 into the fibrous mixture. Of course, said recess may also be formed in the form of a truncated cone. Of course, instead of a recess, the cone-shaped profiling can also be realized as a projection, said protrusion preferably having a frustoconical shape.

Figures 12 to 15 schematically show some possible profiling of the front surface 7 of the screening yarn 2 as viewed in the direction of the front surface 7 of the screening yarn 2. The profiles shown in Figures 12-15 are formed as recesses 14 but could also be formed as projections 15.

The recesses 14 shown in Fig. 12, whose contour line 16 is elliptical, are arranged to extend over the entire width of the front surface 7 of the screen wire 2, i.e. from the front edge 7 'of the screen surface 2 to the rear edge 7'. Also, the projection in the form of a projection having an elliptical contour line could be arranged to extend over the entire width of the front surface 7 of the screen wire 2 from the front edge 7 'to the rear edge 7' of the screen surface 2. The projection in the form of a projection could also be adapted to extend beyond the front surface 7 of the screen wire 2 in the width direction beyond the front edge 7 'and / or the rear edge 7' of the screen surface 2 of the screen wire 2.

The recesses 14 shown in Fig. 13, whose contour line 16 is circular, are arranged to extend over the entire width of the front surface 7 of the screen yarn 2, i.e. from the front edge 7 'of the screen surface 2 to the rear edge 7'. Also, the projection in the form of a projection having a circular contour line 16 could be arranged to extend over the entire width of the front surface 7 of the screen yarn 2 from the front edge 7 'to the rear edge 7' of the screen surface 2. The circular profiling in the form of a projection could also be adapted to extend beyond the front surface 7 of the screen wire 2 in the width direction beyond the front edge 7 'and / or the rear edge 7' of the screen surface 2.

The recesses 14 shown in Fig. 14, whose contour line 16 is circular, are arranged to provide a pattern extending substantially over the entire width of the front surface 7 of the screening yarn 2, resembling the pattern of a golf ball surface. A plurality of small successive profilings result in several successive microturbulences in the width direction of the screen. Also, the positioning of the projections having a circular contour 16 in the form of a projection on the front surface of the screen yarn 2 could be implemented in a similar manner.

Figure 15, in turn, depicts recesses 14 whose contour line 16 comprises both curved portions and straight portions such that the profiling sides 17g and 17h are formed by straight portions and the profiling ends 17c and 17d are formed by curved portions, i.e. portions comprising one or more curvature radii. . The curved portions 17c and 17d mentioned in Fig. 15 consist of arc portions of a circle. The profiling of FIG. 15 also fluidly controls the flow of the fiber blend flow so that the pulp and impurities contained therein do not adhere to the profiling, causing flow stoppage or so-called wire forming, which would be detrimental to sorting, reducing sorting capacity and reducing sorting.

In addition to the shaping of the profiles, i.e. the shape of one or more curved portions of the profiles, the microbubble turbulence caused by the fiber mixture can be influenced by the size of the profiles, i.e. the dimensions of the profiling. For example, the total length L of the profiling, which is schematically shown in Figure 3, can be determined for profiling. The total length L of the profiling may vary with respect to the kind of micro-turbulent effect desired on the screened fiber blend 8 to be formed. For example, the total length L of profiling can be determined relative to the width W of the front surface 7 of the screening yarn 2, i.e., the distance between the front edge 7 'and the trailing edge 7' of the screening yarn 2 in the plane of the front surface 7. 6 mm. For example, the total length L of the profiling may be 30 to 300% of the width W of the front surface 7 of the screening yarn 2. Thus, 300% means that the total length L of the profiling is three times W of the front surface 7 of the screening yarn 2. is about 88% of the width W of the front surface 7 of the screening yarn 2. In the embodiment shown in FIG. 12, the total length L of the screening yarn 2 is about 115% of the width W. The total length L of the elliptical recess 14 is greater than 100% as a result of the recess 14 being disposed in an oblique direction over the entire width of the front surface 7 of the screening wire 2. When the profile shape line is circular, the total length L of the profile is the same as the diameter of the circle.

The overall width of the elongated profiling, i.e. the largest dimension in the direction perpendicular to the total length L of said profiling, may be, for example, 10-80% of the width W of the front surface 7 of the screening yarn. Said elongated profiling is the dimension in the plane 7 of the front surface 7 of the screening yarn 2 is greater than the dimension of that profiling in another direction in the plane 7 of the front surface 7 of the screening yarn 2. Said elongated profilations are thus, for example, elliptical recesses 1 or projections 15 shown in Figures 3 or 7 or rectangular recesses 14 shown in Fig. 15 for example.

By orienting the elongated profiling with respect to the longitudinal direction LD or the width direction WD of the screening yarns 2, the flow behavior of the fibrous mixture can be affected. Thus, for the elongated profiling, the direction of the profiling direction AD can be determined. The profiling direction AD can be determined, for example, as the angle between the imaginary center line of the profiling and the width direction WD of the screening yarn 2, which is schematically shown in Figure 3. The profiling direction AD may vary with respect to the desired fiber surface blend. The value of the bearing angle can vary from 0 to 90 degrees. By adapting the elongated profiling to a direction angle AD in which the profiling reverses the flow of the fiber blend from the screening mode of the screen provided with a screen cylinder to the reject of the screen, the flow of the fiber blend and particularly impurities in the fiber blend to be treated. Thus, the AD angle can be from 10 to 80 degrees, whereby profiling can effectively promote the transfer of impurities towards the reject. In the embodiment of Figure 3, the directional angle AD of the elliptical recess 14 is about 45 degrees. Profiling having an overall length L of about 300% relative to the width W of the front surface 7 of the screening wire 2 may be positioned at the forward surface of the screening wire 2, for example, at an angle of AD of about 70-75 degrees. Thus, at the aforementioned angles of profiling, AD, the fiber blend flows to some extent in the transverse direction against the elongated profiling, whereby the profiling reverses the flow direction of the fiber blend to the direction of flow towards the reject of the screen.

Also, the height H of the projection 15 or the depth D of the recess 14 can be influenced by the microturbulence produced by the profiling. The height H of the projection 15 may be determined, for example, as the maximum distance of the outer surface 17f of the projection 15 from the plane 7 of the front surface 7 of the screening yarn 2 and is schematically depicted in FIG. 2. The height H of the projection 15 may be, for example, 5-50% of the width W of the front surface 7 of the screening yarn 2. The depth D of the recess 15 may, for example, be 5-30% of the width 7 of the front surface 7 of the screening thread.

In the embodiments of Figures 2-15, the shape of the contour line 16 formed on the front surface 7 of the screen yarn 2 is in the form of a circle, an ellipse or a rectangle rounded at its ends. The shape of the profiling contour line 16 may also differ from the above shapes, provided that the profiling contour line 16 has at least one curved portion when viewed from the normal N direction of the front surface 7 of the screening wire 2. Thus, the shape of the contour of the profiling may resemble, for example, a semicircle, an oval or a crescent moon.

It will be obvious to a person skilled in the art that as technology advances, the basic idea of the invention can be implemented in many different ways. The invention and its embodiments are thus not limited to the examples described above, but may vary within the scope of the claims. Thus, it is clear that in the screening cylinder, either all or only part of the screening yarns may comprise the profiling shown. In addition, profiling both as recesses and projections can be formed on the same screening wire. Profiling can be made on the front surface of the screening wire 2 by, for example, cold or hot rolling, water cutting, machining such as milling, drilling or grinding, or sparking, stamping or forging.

Claims (10)

A screening cylinder (1) for purifying or sorting a fibrous mixture, the screening cylinder (1) having a cylindrical screening surface (8) formed by screening slits (5) between the screen surfaces (2) of screen screens (2) and screen screens (2). and wherein in the screen cylinder (1) the front surface (7) of the at least one screen wire (2) comprises profilings (14, 15) which are projections (15) and / or recesses (14) formed on the front surface (7) of said screen wire (2). characterized in that the contour line (16) of the profiling (14, 15) which limits the area of profiling (14, 15) to the rest of the screen surface (7) of the screening yarn (2) comprises at least one curved portion (17a, 17b, 17c, 17d) when considering the profiling (14, 15) from the normal (N) direction of the front surface (7) of the screening wire (2). Screening cylinder according to Claim 1, characterized in that the contour line (16) of the profiling (14, 15) delimiting the area of the profiling (14, 15) from the rest of the front surface (7) of the screening wire (2) comprises at least one curved portion (17a). 17b, 17c, 17d), at least one straight portion (17g, 17h) when the profiling (14, 15) is viewed from the normal (N) direction of the front surface (7) of the screening wire (2). Screening cylinder according to claim 1, characterized in that the contour line (16) of the at least one profiling (14, 15) is circular. Screening cylinder according to Claim 3, characterized in that the cross-section of the at least one profiling (14, 15) in the direction defined by the normal (N) front surface (7) of the screening wire (2) is substantially conical or truncated. Screening cylinder according to one of the preceding claims, characterized in that the contour line (16) of the at least one profiling (14, 15) is elliptical. Screening cylinder according to one of the preceding claims, characterized in that the profiling is a projection (15) having a height (H) of 5 to 50% of the width (W) of the front face (7) of the screening wire (2). . Screening cylinder according to one of the preceding claims, characterized in that the profiling is a recess (14) having a depth (D) of 5 to 30% of the width (W) of the front surface (7) of the screening wire (2). . Screening cylinder according to one of the preceding claims, characterized in that the total length (L) of the profiling (14, 15) is 30 to 300% of the width (W) of the front face (7) of the screening wire (2). 9. Screening cylinder according to one of Claims 5 to 8, characterized in that the profiling (14, 15) has an angle (AD) of 0 to 90 degrees, more preferably 10 to 80 degrees relative to the width direction (WD) of the screening wire (2).