EP0696662B1 - Cylindrical screen using a rotor - Google Patents

Abstract

The cylindrical sieve, has an inner rotor (1) formed of one or more cylindrical surface sections (2). They are formed by right angle triangles, where the two perpendicular sides (3) match the base (3) of the cylinder and a height. The oblique side (5) is the hypotenuse.

Description

The present invention relates to sieves cylindrical with internal rotor and more particularly with the sieves used in the industry of the pulp.

It is known in the pulp and especially in the recycling industry for old papers, to use cylindrical sieves that operates either centrifugally, the product to filter flowing from the inside to the outside of the sieve, or centripetally the product flowing in the opposite direction, i.e. from the outside towards the interior (see document EP 0 436 888 A). These sieves tend to become clogged with the fact that fibers, especially long fibers have tendency to stick across the sieve holes. To remedy this, it is known to cause pressure variations or turbulences, downstream or in upstream of the sieve so as to detach the fibers which are pressed across the holes.

To cause these pressure variations or turbulence, it is known to have inside the sieves a cylindrical rotor provided with means which cause pressure variations and / or turbulence.

These means can be fins (often called "foils"), protrusions arranged on the surface of a cylinder or even extra thicknesses provided at the surface of a cylinder.

The present invention relates to this type of rotor, but it is completely different from the rotors known in that the rotor is no longer a cylinder but is consisting of one or more surface portions cylindrical which, when developed to a plan are right triangles, both sides of which perpendiculars correspond respectively to a generator and at the base of the cylinder and whose the hypotenuse is oblique.

These cylindrico-triangular surfaces can be provided along their oblique side with protuberances that can be profiled.

Figure 1, quatre exemples, numérotés 1a à 1d de dispositifs connus;

Figure 2, une vue latérale d'un mode de réalisation d'un rotor selon l'invention;

Figure 3 une vue selon la flèche F de la figure 2;

Figure 4, une vue en développé du rotor de la figure 2;

Figure 5, une vue en développé d'une variante de réalisation;

Figure 6, une vue en coupe d'un exemple de réalisation d'une protubérance.

By way of nonlimiting example and to facilitate understanding of the invention, the accompanying drawings show:

Figure 1, four examples, numbered 1a to 1d of known devices;

Figure 2, a side view of an embodiment of a rotor according to the invention;

Figure 3 a view along arrow F of Figure 2;

Figure 4, a developed view of the rotor of Figure 2;

Figure 5, a developed view of an alternative embodiment;

Figure 6, a sectional view of an exemplary embodiment of a protrusion.

Figure 1 shows four examples (1a, 1b, 1c, 1d) of known rotors. 1a shows a rotor cylindrical which carries four fins: when these fins scroll along the inner surface of the sieve (not shown), they cause a front slight overpressure and at the back a slight depression. This results in a pressure beat which has the effect of detaching the fibers which have plated across holes (holes or slots) in the sieve and this as well when the sieve is in centrifugal than centripetal. In 1b and 1c, there is shown a cylindrical rotor whose surface has protuberances: these protuberances produce turbulence and small variations in pressure. In 1d, a rotor is shown consisting of two offset half-cylinders, which causes a sudden increase in pressure followed by gradual decrease.

The rotor shown in Figures 2 to 4 is of a entirely different design.

Referring to these three figures, we see that the rotor 1 does not consist of a cylindrical surface regular, whose developed would be a rectangle but consists of a portion of cylindrical surface 2. In the example shown, there are three portions of cylindrical surfaces 2a, 2b, 2c but there could be have only one and there may be more than three. The Figure 5 is a developed view of a rotor does comprising only one portion of cylindrical surface.

Referring to Figures 4 and 5, we see that each cylindrical surface portion (2 in Figure 5; 2a, 2b, 2c in Figure 4) is, when developing a triangle rectangle whose base 3 corresponds to the base of the cylinder and side 4 is the height, or again to a generator of the cylinder. Sides 3 and 4 are perpendicular and side 5, oblique, constitutes the hypotenuse of the right triangle.

When wrapping the developed surface shown at Figure 4, we obtain the rotor shown in Figures 2 and 3, of which we can say that the surface is cylindrico-triangular.

By way of simplification, we will denote below each portion of cylindrico-triangular surface by the term "lobe". The rotor of Figures 2 to 4 is therefore three lobes; while that of Figure 5 is a lobe.

The invention is not limited to the examples shown : there must be at least one lobe, but there can be have two, three, four or more.

This very special configuration of the rotor means that when it turns inside the screen, the wall internal of the latter is sometimes opposite a wall, sometimes opposite an absence of a wall. It results in a permanent recycling of refusals and therefore a significantly more efficient sieving. On the other hand, fibers which could agglomerate on edge 5 slide along it.

We can, as shown in Figures 2 to 5 have protuberances on the lobe wall similar to those illustrated in Figure 1b.

According to the present invention, these protrusions 6 are arranged along the oblique side 5 of each lobe 2.

When there are several lobes, as is shown in Figure 4, the protrusions are offset from each other.

Preferably, these protrusions have the form shown in Figure 6, i.e. their section decreases regularly from their front side (relative to the direction of rotation of the rotor) up to their back side.

Also preferably, the lobes are cut in a thin sheet and to strengthen them, we have the interior of each lobe a reinforcement 7, constituted by a curved sheet metal which is connected at its base to a disc 8 integral with a sleeve 9 threaded on a motor shaft (not shown).

Claims (6)

1. Cylindrical sieve inside which a rotor turns provided with means causing pressure variations and/or turbulences, characterized in that the said rotor (1) consists of one or more portions of cylindrical surfaces (2) which, when they are developed, are right-angled triangles of which the two perpendicular sides (3, 4) correspond respectively to the base of the cylinder (3) and to a height (4) and of which the oblique side (5) constitutes the hypotenuse.
2. Sieve according to claim 1, characterized in that each portion of the cylindrico-triangular surface or lobe (2) bears a plurality of projections (6).
3. Sieve according to claim 2, characterized in that the projections (6) are arranged along the oblique side (5).
4. Sieve according to claim 3, characterized in that the projections (6) are offset from one lobe (2) to another when there are several lobes.
5. Sieve according to any one of claims 2 to 4, characterized in that the cross section of each projection (6) decreases from its front part to its rear part.
6. Sieve according to any one of the preceding claims, characterized in that each lobe (2) is cut out from a metal sheet which is reinforced by a web (7) carried by a disc (8) secured to a sleeve (9).

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