FR2489718A1 - Rotary screening drum with spaced longitudinal rods - has charging conduit which discharges by overflowing well inside the drum - Google Patents

Abstract

Rotary screening drum is of the type which has its wall made up of longitudinal, circumferentially spaced rods of triangular or trapezoidal cross-section. A loading chute charges material to be screened into one end of the drum which delivers at the other end a fraction which will not pass the screen. The loading chute now comprises a delivery conduit coaxial with the drum and extending into the drum by a distance of between one quarter and one half of the axial length of the drum. The upper part of the conduit is cut away for not less than half the length which extends into the drum. Material to be screened is delivered from the cut away section of the conduit by overflow. Pref. at least one vertical baffle is fitted in the outlet of the conduit to restrain axial discharge through the conduit. Used for screening waste water etc., e.g. effluent from abattoirs, meat packing stations, sewage stations etc. Highly efficient utilisation of drum by using the overflow conduit to spread incoming material over the broadest possible area of the screening surface.

Description

 The present invention relates to rotating screens for separating solids from a liquid in which they are suspended.

It is applicable with a view to achieving such a separation in the treatment of waste water, slaughterhouse waste, packaging residue from meat and in many other cases posing the same problems.

 It is already well known to separate solids from liquids in rotary screens comprising a perforated body of revolution mounted for rotation about a horizontal axis. The product to be treated is introduced into one of the ends of the body, the liquid falls through the perforations or interstices thereof and the solids are evacuated therefrom by the opposite end.

 It is also known to use as a cylindrical sieve wall of the body a multiplicity of parallel and very close wedge-shaped wires which extend longitudinally, as well as connecting wires which circularly surround all of the foregoing and to which all of these are found. connected. The body can take various forms, this is how the connecting wires can be established by means of a single wire wound in a helix like a helical spring. In addition, in certain sieving devices of the kind in question, but with reverse flow (see for example American patent 3,876,548 in the name of Donald P. Welles), the medium to be treated is applied to the external wall of the body so that the solids are evacuated externally while the liquid enters it, thus passing from the outside to the inside. In this case the wedge-shaped wires can be oriented longitudinally or circularly relative to the body; one can, if desired, establish them in the form of a helix with very close turns.

However, in all these embodiments, the principle of wedge-shaped wires is used.

 This term of wedge-shaped wires is somewhat ill-chosen since the wires in question would be better defined as comprising a profile of trapezoidal section. Anyway, the principle implemented is well known and is commonly used for the manhole bars, for the drainage grids and in other applications in which a liquid must pass through a plate or sieve, while the solids it holds in suspension (and which have a minimum acceptable dimension) must on the contrary not be able to pass. Things are arranged in such a way that if a solid particle having the minimum dimension can engage in the entry of an opening of the sieve, then it is ensured to have sufficient mechanical play during the rest of its passage through through the aforementioned orifice, the cross section of which increases, thus protecting as far as possible the risks of clogging of the sieve by the particles which pass through it.

 The present invention relates only to sieves with wedge-shaped wires in which the fluid product to be separated is introduced inside the rotating sieve, the solids evacuating therefrom in the axial direction and the liquids flowing radially towards the 'outside. Therefore, the explanations which follow will be limited to the use of sieves of this particular type.

 It is understood that for any kind of screen body it is desirable that the total section of the perforations is as large as possible relative to the surface of the solid area, so as to ensure the maximum passage for the liquid. The realization of the sieve by means of wedge-shaped wires is particularly effective in this respect since the orifices or interstices are virtually continuous along the entire length of the body, this continuity being interrupted only to a slight extent by the presence of circular wires .

 Experience has shown that indoor feed screens of the above type are substantially the most effective of those with rotating bodies currently used in the art. However, studies have shown that this efficiency is generally not fully achieved due to the insufficient extent of the deposit of the product to be treated on the sieving surface.

 The present invention aims to improve this state of affairs. It therefore relates to a sieve with a body made of wedge-shaped wires and comprising two open ends, namely a first intended to receive the product to be treated and a second which forms an outlet for the separated solids, this body comprising a substantially horizontal axis, while it is further provided means for driving it in rotation about said axis and means for supplying it with product by the aforementioned receiving end. The device which forms the object essentially comprises a barrel arranged co-axially to the body and of which a first end situated outside thereof receives the product to be treated, while the part which is towards the second undertakes to through the receiving end of the body and extends in it over a length representing a quarter to half that of this body, this part being cut at the top of a product outlet opening surrounded by a horizontal overflow which extends axially over a distance at least equal to half the axial length of the part in question measured from the second end of the fat.

The attached drawing. given by way of example, will make it possible to better understand the invention, the characteristics it exhibits and the advantages it is likely to provide.
Fig. 1 is a perspective view with parts broken away showing a sieve with wedge-shaped wires according to the invention.

 Fig. 2 is an elevational view in partial section.

 Fig. 3 is a cross section along 3-3 (fig. 2).

 Fig. 4 is a partial plan view of the barrel corresponding to arrows 4-4 (fig. 2).

 The screen shown comprises a hollow body 5 made of metal wire having a receiving end 6 and a solids outlet end 7. This body may be cylindrical or else slightly frustoconical, as indicated in broken lines in FIG. 2. Its longitudinal axis can be absolutely horizontal or else it can only be approximate by being slightly inclined downwards in the direction of the outlet opening.

 In the example shown, the body in question is made of wedge-shaped wires 8 oriented longitudinally and very close to one another, as well as transverse wires 9 curved in a circle around the preceding ones to which they are connected by welding.

 The means for rotating the body 5 are constituted by grooved rings 10 which rest on rollers 11 and by a motor, not shown, connected to the body itself or to at least one of the rollers 11 in the conventional manner.

 Liquids and fine solids with a particle size less than the spacing of the sieve wires pass radially through the body 5 to fall back into a receiving bowl 12 equipped with a drain 13 and provided with screens 14 for protection against spattering. As for the separated solids, they leave the apparatus via the end ring 15, which discharges them onto a weir 16, mounted at a fixed station.

 The feed device by means of which the product to be treated is deposited on the body, consists of a barrel 17 mounted on supports 18 so as to be substantially co-axial with the body 5. This barrel has one end 19 located outside the body and equipped in the known manner so as to receive this product.

 The barrel 17 comprises towards its other end a part 20 whose length roughly corresponds to that shown in the partial view of FIG. 4.

This part extends inside the body by an amount representing a quarter to a half of its length. It is cut out of an opening 21 for the outlet of the product, which is surrounded and defined by a horizontal overflow formed by the upper edge 22 of the side walls 23 of the part in question and that 24 of the wall 25 which closes the latter at the inner end of the barrel. The opening 21 preferably extends along the axis of the part 2n over a length of the latter as large as the condition under which the product which emerges from this opening does not feel able to escape through the receiving end 6 of the body 5. The minimum length of the opening 21 is at least equal to half that of the part 20, measured from its end wall 25.

 The part 20 of the barrel 17 preferably contains on the one hand at least one upstream plate 26 suitable for forming a screen against the waves and which extends transversely from the top of the barrel in the direction of the axis, d on the other hand at least one "downstream" plate 27 capable of playing the same role, but which rises towards the axis from the bottom. It is further preferably provided in this part 20 a number of ribs 28 in the form of a helical arc, intended to form guides of the liquid product stream. These ribs are slightly inclined relative to the vertical from bottom to top and in the direction of the upper edge 24 of the end wall 25. With regard to the ribs 28 experience has shown that their presence tends to stabilize the regularity of the flow over the edges 22 and 24 forming a weir. They are fixed to the walls by welding or otherwise so that their upper ends are substantially at the level of said edges 22 and 24.

 It should moreover be understood that the foregoing description has been given only by way of compensation and that it in no way limits the field of the invention from which one would not depart by replacing the details of execution described by all other equivalents.

Claims (3)

R E V E Sl 9 I C A T I o N S  1. Sieve, of the kind comprising a metal wire body with a wedge or trapezoidal profile with receiving end and outlet end for solids, the axis of this body being disposed substantially along a horizontal, while au'it is provided means for driving it in rotation about this axis and means for feeding it via its receiving end, characterized in that the feeding means comprise a barrel (17) arranged coaxially at the body (5) and having a first end (19) external to it, through which the product to be treated is brought to the barrel, while the part (20) located towards its second end (25) engages through the receiving end (6) of the body and extends therein over a length lying between a quarter and a half of that of the latter, the top of this part being cut out from an outlet opening (21) of the product, surrounded by a horizontal weir (22, 24) and which extends over the minus half the length of said part (20) measured from the aforementioned second end (25).  2. Screen according to claim 1, characterized in that the end part (20) contains on the one hand at least one upstream plate (26) forming a screen against the waves and which extends transversely from the top of this part in the direction of the axis thereof, on the other hand at least one downstream plate (27) suitable for playing the same role, but which rises from the bottom of this part in the direction of said axis .  3. Screen according to any one of claims 1 and 2, characterized in that the end part (20) of the fdt (17) contains several ribs (28) in the form of a helical arc intended to guide the current of product, these ribs being mounted on the lateral walls of said part so that their upper ends are closer together than their lower edges of the adjacent end wall (25) of the barrel (17) and are substantially level with the edges (22, 24) of the weir defined by said side walls.