FR2661196A1 - SCREEN FOR PURIFIER AND PULP CLASSIFIER. - Google Patents

Abstract

Screen for pulp scrubber or classifier of the type constituted by the juxtaposition of longitudinal elements in folded thin sheet with generally symmetrical U-shaped section characterized in that the perforated bottom has a corrugated profile with rounded or angular crest (20) so that the sieving surface in contact with the dough is increased very significantly.

Description

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  substantially flat wall; this wall is then machined so as to present, as for sieves with a thick wall, slots or holes accompanied by known obstacles (ribs, grooves) made in the thickness of the sheet. The object of the invention is to improve the latter type of sieve. Its subject is a sieve for a purifier or classifier of paper pulp of the type constituted by the juxtaposition of elements with a U-shaped cross section in front of which a stirring blade circulates , characterized in that the bottom of the perforated U has a wavy profile with rounded or angular crest so that the sieving surface in contact with the dough

is increased very significantly.

  The sieve according to the invention is also remarkable for the following characteristics. The bottom of the U has: at least two successive inclined perforated walls opposite, forming an angle between 45 and 90 between them; a W-shaped corrugated profile the W-profile is regular, with equal angles on the order of 60, the width of the inclined walls being approximately equal to half the width of the U; the height of the crests of the corrugated profile is small compared to the distance separating the top of the U from the stirring blade of the sieve, so that the variation of the depression produced by the blade, along the wall is insensitive. An exemplary embodiment is illustrated in the accompanying drawing in which: FIG. 1 represents a schematic view of a sieve according to the invention; Figure 2 shows a schematic perspective view of a portion of slotted screens according to the invention; FIG. 3 represents a schematic view according to a variant of FIG. 2 of a slotted sieve, with a V profile. FIG. 4 represents a variant of FIG. 3 of a sieve with holes, with an asymmetrical profile; FIG. 5 represents a variant with wavy profile with rounded ridges; FIG. 6 represents a profile view of the

figure 2.

  Referring to the drawing, it can be seen that the sieve is made of a sheet of thin thickness, preferably between 1 and 3 millimeters. It is formed of elements 1, folded in a general U shape, and juxtaposed so as to form a

sieving wall 2.

  In a known manner, the cylinder of FIG. 1 can be obtained from elements 1 of the same length, juxtaposed, welded together and curved, or else from

  of an element i wound on itself.

  According to the invention, the bottom 3 of the U is not flat but deformed longitudinally so as to present, from one wing 4 to the other 5, at least one rounded or angular crest 20 In the case of a profile with angular ridges, it then has between the two wings 4,5 a succession of at least two adjacent faces 6,7 adjacent perforated inclined with respect to the general plane 8 of the screen at an angle 12,13 between 0 and 90 In cross section the bottom of the U thus has a shape at least in V (Figure 3), or in W (Figure 2), etc. symmetrical or not, the inclination of two opposite faces 6, 7 can be of the same value or different as

illustrated in figure 3.

  The perforations, holes 10 or slots 9, are made on all the inclined faces of the bottom of the U; they are generally produced before deformation of the bottom of the U, in particular when the slots are associated with a rib in order to obtain a profile of the obstacle type. But they can also be produced after formation of the corrugated profile, in particular when simple

slots.

  The purpose of this arrangement (of folding the bottom of the U) is to increase the sieving surface for the same width of the U-shaped element, that is to say for the same

size of the screen.

  This increase in sieving surface means that the same quantity of dough can be more

quickly processed.

  The arrangement of FIG. 2 shows a wavy profile in the form of a W with angular crests. This arrangement is not limiting and the invention also relates to the profiles in Y, or with rounded crest, symmetrical or not.

(Figures 3 to 6).

  In the example of FIG. 2, the bottom of the U is folded into a symmetrical W shape. The angles 14, 14 ′, 14 "formed between the inclined walls are equal, and of the order of e. This arrangement makes it possible to double the surface 5 of

  bottom of the U and therefore double the surface of the sieve.

  As is well known, such cylindrical sieves are equipped with an unclogging blade 16 which circulates at high speed in front of the perforations; unclogging is achieved by the depression created by the

wing shape of the blade.

  According to the invention the wing moves in a direction approximately parallel to the longitudinal axis of the U-shaped elements, perpendicular to the slots 9 for example; the bottom of the U is therefore not at a constant distance from the wing; the top 15 of the pleat (s) of the V in the example of FIG. 2 is closer to the blade than the lateral end 17 of the ply In order to avoid too great a variation in the depression produced by the blade between the apex 15 and said lateral ends 17, provision is made for making folds in which the height h between the apex of the folds and the base of the U (cf. FIG. 2) is small compared to the direction D separating the apex 15 and the

blade 16.

Claims (4)

  1 Sieve for purifier or classifier of paper pulp of the type constituted by the juxtaposition of longitudinal elements in folded thin sheet metal with a generally symmetrical U-shaped section characterized in that the perforated bottom (3) has a corrugated crest profile (20 ) rounded or angular so that the sieving surface in contact   with the dough be increased very noticeably.   2 sieve for purifier or classifier of paper pulp according to claim 1 characterized in that the bottom (3) of the U has at least two walls (6,7) perforated inclined successive opposite forming an angle therebetween (14) between 45 and 90.   3 Sieve for purifier or classifier of paper pulp according to claim 2 characterized in that the corrugated profile of the bottom of the U has a shape of W. 4 sieve for purifier or classifier of paper pulp according to claim 2 characterized in that the corrugated profile has two walls (6,7) inclined in a V shape. Sieve for purifier or classifier of paper pulp according to claim 3 characterized in that the W profile is regular, with angles (14,14,14 ") equal, of the order of 60 ', the width of the inclined walls being approximately equal to the half-width of the U. 6 Sieve for purifier or pulp classifier according to claim 1 characterized in that the height h at the top of the bottom of the U is small compared to the distance D separating the top of the U from the paddle paddle (16) of the sieve, so that the variation of the depression produced by the blade, along the wall is insensitive.