EP0104458B1 - Centrifuge sieve and process for its production - Google Patents

Abstract

In a centrifuge sieve drum, wherein the inner surface of the drum is lined with a support arrangement carrying wear-resistant sieve or screen rods, there is obtained a compensation of the different thermal expansions of the sieve rods and the support arrangement in that, the sieve rods comprise an axially extending web and the support arrangement comprises identically shaped grooves or slots engaged by the webs. Each web and its associated groove or slot may be designed, for example, as a dovetail guide. Thus, while the sieve rods may expand or contract in longitudinal direction or in the direction of the lengthwise axis of the drum, the sieve rods are, however, immovable in radial direction and in circumferential direction. Such a support arrangement can be efficiently manufactured by simultaneously cutting, such as by milling the grooves or slots and sieve openings or slots in a convex outer surface using a triple cutter, such as a milling cutter, and by subsequently bending the supporting arrangement to form a concave surface and inserting the same into the drum.

Description

The invention relates to a centrifuge sieve with a support provided on the inside of a centrifugal drum, which carries sieve bars made of wear-resistant material and running in the axial direction of the centrifugal drum.

Centrifuge sieves are known from DE-A 2830388 or US-A 4259136, in which the sieve rods protecting the centrifugal drum from wear are attached to the drum supporting structure by means of adhesive bonds. To compensate for the different thermal expansion of the sieve bars and the support structure consisting of a material with a different coefficient of thermal expansion, elastic intermediate layers are provided in these connections, e.g. Rubber intermediate elements. However, these are not sufficiently durable in operation. In addition, they allow mobility in several directions, which allows undesired and impermissible deformations of the sieve bars and support structure against each other. Another disadvantage is the poor manufacturability, in particular the difficult and unsuitable for mass production assembly of the sieve bars on the inside of the centrifugal drum or the support structure.

The centrifuge described in US Pat. No. 3,100,746, in which the sieve rods rest loosely in a groove at least at one end, has similar disadvantages, since here too an uncontrolled movement and deformation of the sieve rods is possible and, in addition, to prevent the sieve rods from falling out to prevent, only operation with a vertical axis is possible, and only if the centrifugal drum is conical.

In the older, but not prepublished EP-A 71 012, which belongs to the state of the art according to Art. 54 (3) EPC, but is not important for the inventive step, is a centrifugal sieve with a centrifugal drum on the inside provided support structure, which carries in the axial direction of the centrifugal drum, made of wear-resistant material sieve bars. To compensate for different thermal expansions, the sieve bars are each firmly and non-displaceably connected to the support structure at one point, while grooves or screws are provided at all other connection points and are movable in axially extending slot-shaped holes. However, replacing defective or worn sieve bars is troublesome, and the manufacture of such a centrifuge sieve is complicated and labor intensive.

The invention has for its object to avoid the above-mentioned disadvantages of the prior art and in particular to create a centrifuge sieve in which the sieve rods are durable, temperature and corrosion resistant, movable in a defined manner against the supporting structure and connected to it and easy to assemble , with the sieve rods being easily exchangeable without the operation and shape of the centrifuge being restricted.

According to the invention, this object is achieved in that either the sieve bars or the support structure have webs which engage in grooves or slots of the same shape in the other part, so that the sieve bars can only be moved in the axial direction with respect to the support structure.

A particularly advantageous solution is obtained if the sieve bars on the support surface with the support structure have dovetails running in the axial direction of the centrifugal drum and the support structure has slots in the form of a geometrically corresponding dovetail guide.

• Fig. 1 ein Zentrifugensieb in Perspektive,
• Fig. 2 einen Axialschnitt dieses Zentrifugensiebes,
• Fig. 3 einen Ausschnitt der Trommelaussenwand dieses Zentrifugensiebes,
• Fig. 4 einen Ausschnitt der Trommelaussenwand eines anderen Zentrifugensiebes und
• Fig. 5-9 verschiedene Beispiele der Verbindung von Siebstäben und Stützwerk.

The invention is explained on the basis of the exemplary embodiments shown in the figures. Show it:

• 1 is a centrifuge sieve in perspective,
• 2 shows an axial section of this centrifuge sieve,
• 3 shows a section of the outer drum wall of this centrifuge sieve,
• Fig. 4 shows a section of the drum outer wall of another centrifuge screen and
• Fig. 5-9 different examples of the connection of sieve bars and support structure.

The centrifuge sieve shown in FIGS. 1, 2 and 3 has a centrifugal drum T with a drum diameter from the decimeter to the meter range, on the inside of which a sieve-like support structure 1 rests, on the inside of which a plurality of, for example made of a hard material, in turn serves as wear protection or another suitable material existing sieve bars 2 with a thickness of a few millimeters and a length of up to about 30 cm in the axial direction of the centrifugal drum are attached at a small lateral distance from one another.

The support structure 1 is made of a suitable metal, for example steel, and has sieve slots 3 or holes for the filtrate to pass through during centrifugation. Instead, however, the support structure can also consist of a framework of rings which are connected to one another by axially parallel rods, so that the required sieve slots are created between the rods. On the inside of the drum T, annular webs 4 are provided, on which the supporting structure 1, which can also have annular webs 7 on the outside, possibly rests on spacers 8, a path for the filtrate to pass through the spaces 5 between the sieve bars 2, the underlying slots 3 of the support structure 1, the space 9 between the support structure and the drum and the slots 6 offset from the sieve bar spaces are formed in the drum T. If the slots are not or only slightly offset from one another, the spacers can also be dispensed with.

The sieve bars 2 can be made of a wear-resistant hard material, e.g. Melt basalt or sintered material such as sintered ceramic or cemented carbide, e.g. Aluminum oxide or tungsten carbide. If the requirements are somewhat lower, a suitable wear-resistant steel can be used as the material or a particularly wear-resistant steel, e.g. Plastic reinforced with glass or carbon fibers or another suitable material. Since temperature fluctuations of up to 100 ° C can occur during operation of the centrifuge, the materials of the sieve rod, e.g. Tungsten carbide, and the supporting structure, e.g. Steel, when fastening the sieve bars 2 to the supporting structure 1, precautions are taken for a length compensation in order to avoid deformations and breakage of the sieve bars. For this purpose, 2 dovetail-shaped webs 10 are provided on the support surface of the sieve bars, which engage in corresponding, identical grooves or slots 11 in the support structure.

The described arrangement and guidance of the sieve bars causes the sieve bars 2 to be immovable in the radial direction, but a length compensation is possible in the longitudinal direction, that is to say in the axial direction of the centrifugal drum. Movement in the circumferential direction is made impossible by the axial alignment of the grooves 11.

Due to the arrangement described, a defined mobility of the sieve bars against the supporting structure is only possible in the main direction of expansion, i.e. the longitudinal direction of the sieve bars, and this is done using only very durable and temperature and corrosion resistant materials. Compared to known centrifuge sieves with elastic rubber or plastic connecting elements, the arrangement described could multiply the service life in practical operation and significantly improve the corrosion resistance. Another advantage is the much easier interchangeability of the sieve bars, since the webs of the sieve bars only have to be inserted into the corresponding dovetail guide, and that opened bars are held in their entire length by the special guide.

FIG. 4 shows another example in which a plurality of layers of sieve bars 2 ¹ , 2 ² are arranged a short distance behind one another in the axial direction, the connection of sieve bars 2 ¹ , 2 ² and supporting structure 1 again by means of webs and slots 11 ¹ and 11 ² eg in the form of a dovetail guide. Between the sieve bars 2 ¹ , 2 ² several rows of sieve slots 3 ¹ , 3 ^{2 are} provided in the support structure 1, through which the filtrate can flow off. In comparison to the first example, the use of several layers of sieve bars allows a longer length of the sieve drum, up to several meters. This is particularly advantageous for sintered materials that only allow a limited rod length. In this embodiment, the support structure can also consist of several parts arranged one behind the other in the axial direction, each support structure part, for example, carrying only one sieve bar layer, but it is also readily possible to provide several, for example two, layers, the introduction of the sieve bars into the slots can be done from both sides.

It should be noted that, instead of providing a support structure 1 separate from the drum T, it can be firmly connected to the drum or the inner part of the drum T can serve as a support structure on which the sieve bars 2 rest directly and that with the required grooves or slots 11 is provided.

Various expedient, geometric shapes of the webs 10 and slots 11 are shown in FIGS. 5-9.

In the example according to FIG. 5, the sieve bars 2 have webs 10 with a rectangular cross-section on their support surface 12 on the supporting structure 1 which extend in the axial direction. Corresponding slots 11 are provided in the supporting structure 1, into which the webs 10 fit exactly and are possibly clamped.

Conversely, as shown in FIG. 6, the webs 10 can also be provided on the supporting structure 1, while the sieve bars are provided with corresponding slots 11.

In order to prevent the rods 2 from falling out with a rectangular cross section of the webs 10 if the narrow dimensional tolerances required here are not complied with, the cross section of the webs 10 and slots 11 according to FIG. 7 is expediently chosen to be trapezoidal, i.e. in the form of a dovetail guide.

Securing the rods against falling out is also possible with a different geometric shape of the webs, e.g. As shown in FIG. 8, with a rounded shape with a constriction 13 near the support surface 12 and a corresponding design of the slot with an inward expansion.

As shown in FIG. 9, a plurality of parallel webs 10 ¹ , 10 ² can also be provided on the same part, for example on the sieve bars ² .

Furthermore, the slots can be designed as deeply limited grooves, as shown in the examples described above, or as deep slots, e.g. the support structure consists of separate bars, which are connected at the ends at most.

In the examples described and possible further modifications within the scope of the inventive concept, it is ensured that the sieve bars can expand and contract practically unhindered in the direction of the drum axis, but are immobile in the circumferential and radial directions. The assembly and replacement of the sieve bars is extremely easy.

Claims (8)

1. Centrifuge sieve with a supporting frame (1), provided on the inner side of a centrifugal drum (T), carrying sieve bars (2) which run in axial direction of the centrifugal drum and consists of wear-resistant material, whereby selectively the sieve bars (2) of the supporting frame (1) have projections (10), which engage in grooves or slits (11) of the same shape in the other part, so that movement of the sieve bars with respect to the supporting frame is only permitted in the axial direction.

2. Centrifuge sieve according to Claim 1, characterised in that the projections (10) are provided on the sieve bars (2) and the grooves or slits (11) are provided on the supporting frame.

3. Centrifuge sieve according to Claim 1 or 2, characterised in that the projections (10) have a rectangular cross-section.

4. Centrifuge sieve according to Claim 1 or 2, characterised in that the projections (10) have a constriction (13).

5. Centrifuge sieve according to Claim 4, characterised in that the projections (10) have a trapezoidal cross-section and form a dovetail guideway with the grooves or slits (11).

6. Centrifuge sieve according to one of Claims 1 to 5, characterised in that the sieve bars (2) or respectively the supporting frame (1) have (has) several projections (10) or respectively grooves or slits (11) running parallel to each other.

7. Centrifuge sieve according to one of Claims 1 to 6, characterised in that the sieve bars (2) consist of sintered material, in particular sintered ceramics such as aluminium oxide, cast basalt or sintered carbide such as tungsten carbide.

8. Centrifuge sieve according to one of Claims 1 to 7, characterised in that the supporting frame (1) carrying the sieve bars (2) is formed by the inner part of the centrifugal drum (T).

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