EP2656919B1 - Filter for a waste separation apparatus - Google Patents

Description

The present invention relates to a sieve according to the preamble of claim 1.

Disposal of waste is increasingly subject to stricter regulations on the treatment of different types of waste. One goal is to reduce waste by as complete as possible biological decomposition of the organic fraction. A prerequisite for this is an effective separation of waste mixtures into an organic fraction (biomass) and an impurity fraction. In general, all those components which interfere with the treatment of the organic components, such as composting or other biological processes, or which devalue the resulting product, are regarded as impurities. If the impurities are deposited sufficiently effectively, the organic fraction can be subjected to an effective decomposition process (fermentation, composting). But also the impurity fraction can be processed better, e.g. by further separation in metal and non-metal. In the end, this also achieves a reduction in the amount that can be disposed of, for example, in a landfill as an inert fraction.

A suitable waste separator in the form of a hammer mill is from the patent application EP-A-1 350 569 known to the applicant. It has a shaft with movably mounted flails in a cylindrical steel housing. By means of a fast rotation of the shaft, the flails smash and shred the raw material fed to the machine and simultaneously convey it axially forward. A mounted in the wall of the housing sieve with separates the sufficiently shredded substances, so that only material that is not crushed, on the output side Arrives at the end of the housing. For example, such material is too tough to be crushed. Typically, these are plastic parts or foils.

The recent regulations for the production of compostable material place stricter requirements on contaminants, such as plastics, in shredded material suitable for composting. In particular, their share may amount to a maximum of 0.1%. An almost unavoidable measure to meet these requirements is the use of finer sieves, i. of sieves with pores of smaller diameter. So that overall but not the throughput decreases, a common measure is to increase the number of pores or holes accordingly. As a rule of thumb, the entire area of the holes may need to be kept constant or even increased, so as not to reduce throughput. The higher number of holes, however, requires more production time. In addition, the stability of the screen must not be reduced, so its material thickness can not be reduced. Conceivable is the use of high strength material, e.g. of wear-resistant steel. However, this is accompanied by a decreasing suitability to bring the screen into the required curved shape. Both effects increase the costs or make even a sieve, which could meet the requirements, economically uninteresting. In the case of thicker material due to lower wear resistance, the reduced hole diameter leads to increased volume resistance, as a result of which the throughput decreases. For this reason, the general rule is that the hole diameter must be at least as large as the sheet to be drilled is thick.

An object of the present invention is to provide a sieve, which reduces the impurity fraction, and a Reduction of throughput and service life to avoid. Preferably, such a sieve is also more economical to produce.

Such a sieve is specified in claim 1. The further claims indicate preferred embodiments.

Fig. 1

Längsschnitt durch eine schematische Darstellung einer Hammermühle mit einem erfindungsgemässen Sieb;

Fig. 2

schematisierte vergrösserte Darstellung der Wechselwirkung zwischen Schlegel und Sieb;

Fig. 3

getrennte Darstellung der Komponennten eines Siebs; und

Fig. 4

Ausschnitt eines zusammengefügten Siebes.

The invention will be explained with reference to an embodiment with reference to the figures. Show it:

Fig. 1

Longitudinal section through a schematic representation of a hammer mill with a novel sieve;

Fig. 2

schematized enlarged representation of the interaction between flail and sieve;

Fig. 3

separate representation of the components of a sieve; and

Fig. 4

Section of a assembled sieve.

A hammer mill 1 ( Fig. 1 ) has substantially a circular cylindrical housing 3, in which a central shaft 5 is mounted. Drive and storage of the shaft 5 are not shown and may be carried out according to the prior art. The hammer mill 1 can total the construction of the EP-A-1350569 which is hereby included in the description.

On the shaft 5, the flails 9 are rotatably held in bearing blocks 7. Upon rotation of the shaft 5 (arrow 11), the flails 9 are urged by the centrifugal force in an approximately radial orientation, whereby they press the raw material pieces 13 to the lateral surface 15 with screen 16 of the housing 3 and push over them (s. figure 2 ). The forces acting on the pieces 13, centrifugal forces are symbolized by the arrows 17. The particles of a size smaller than the hole diameter 18 resulting from comminution of the raw material by the flails 9 pass through the sieve 16.

The housing 3 is essentially a circular cylinder and comprises in principle a circular cylindrical wall or lateral surface 15 and two end plates 19, 21. At a suitable location, for example near the end plate 19, there is a provision such as a feed hopper (not shown) for the Feeding raw material. Accordingly, at or within the second end plate 21 is a provision such as a discharge opening for constituents of the raw material, which could not be crushed enough in the hammer mill 1, especially so the impurities. Further precautions are taken, such as an inclination of the housing 3 or an inclination of the flails 9, so that the raw material in the hammer mill 1 moves from the plate 19 to the plate 21.

The cylinder wall 15 consists to a large part or in total of the sieve 16, which is composed of an inner shell 25 and an outer shell 26. Inner casing 25 has inner casing bores 27, which are arranged in alignment with corresponding outer casing bores 29. Inner sheath 25 and outer sheath 26 also have a matching hole pitch. The inner casing bores are decisive for the separating effect and are therefore designed with the screen hole diameter 18. The mainly affected by the wear inner jacket 25 is made of a wear-resistant steel, which is characterized by a high strength. This steel is characterized, for example, by the following strength parameters: The R _m value is at least 600 and preferably at least 1000. (R _m : tensile strength in Newton per square millimeter [N / mm ² ] according to ISO standard).

For the outer shell 26, however, a steel of medium strength, for example with an R _m value of at least 340 N / mm ^2, but which is at least 400 N / mm ² smaller than the Rm of the inner jacket 25, is sufficient. Preference is given to R _m values of 340 N / mm ² to 590 N / mm ² and particularly preferably from 490 N / mm ² to 590 N / mm ² .

The thicknesses of inner jacket 25 and outer jacket 26 are approximately identical, for example, with a deviation of at most 50% of the respective thicker part. Preferably, however, they are nominally the same thickness. Outer jacket 26 and inner jacket 25 are joined together by one of the common types of connection such as welding. This results in the required strength and dimensional stability to find use as a sieve.

Sieves of conventional, single-layered construction must have a thickness of approximately twice S (S: thickness of inner sheath [Si] or outer sheath [S _a ]) in order to achieve the required strength and dimensional stability. In order to ensure the machinability and ductility of material as strong as required for the present application, in conventional, single-layered construction only steels with relatively low strength values can be used. In practical use, this results in short service lives. In addition, making the screen bores in thick-walled material is more difficult and requires more time.

The currently preferred way to make such holes is laser drilling. Preferred are cylindrical holes. In thick-walled material are the required small holes but relative to their diameter long and thus inhibit the flow of material. In addition, there is a high risk of blockage in the present application. Conical expansion from the outside to suppress these effects is not realistic given the large number of holes required.

In the sieve according to the present invention, however, the holes are made separately in the outer shell 26 and the inner shell 25. First, the holes are therefore drilled in relatively thin material (thickness Si or S _a ), which is possible with less expenditure of time. In the inner casing 25, the bores 27 can easily be made with the smaller diameter 18 than that 30 of the bores 29 in the outer casing 26 (see Fig. 3 ). Due to the fact that the inner sheath holes 27 have only a small length, in the preferred embodiment half of the total material thickness Si + S _a = 2S, the resistance to passing material is reduced and the risk of clogging is also reduced. Due to the smaller thickness of the material of the inner shell 25 this is also despite the high strength of its material in the required shape, here circular cylinder or part of a circular cylinder jacket, bendable, but still has a long service life.

In addition, despite the smaller hole diameter, the rule mentioned above, that the hole diameter must not fall below the plate thickness. Thus, diameters of the holes 27 in the inner jacket 25 are possible, for example, amount to only at most 80% of the total material thickness Si + S _a or at most 60% thereof or in particular also approximately equal to the thickness of the inner jacket 25, wherein to improve the separation effect smaller hole diameter are preferred.

The bores 27, 29 are preferably produced by laser drilling. Other types such as mechanical drilling or punching are also conceivable, but require more time and are kosteninteniver.

The material for the outer shell 26 is a steel of a quality that can be well processed and bendable. For the inner jacket 25, a steel is used with a high wear resistance, which is therefore deformable and processable only as a thin-walled material. After joining the outer jacket 26 with the inner shell 25, wherein the holes are arranged in alignment with each other, which requires that match the perforations of outer shell 26 and inner shell 25, resulting in a sieve 16 of the required wear resistance and dimensional stability. Preferably, the connection of the jackets by welding connections.

Welding is pointwise at the edge of the screen and in particular continuously at the end faces, which rest against the connection plates. If the sieve represents the entire cylinder jacket 15, it will also be welded according to the joint of the axially adjacent, axially extending edges.

The sieve has a ratio of hole area to total area of at least 30%. Another measure is that the distance between two holes is at least 60% of the diameter 18 of a hole.

• Verwendung von drei oder mehr Mänteln, die zu einem Sieb zusammengefügt sind.
• Die Bohrungen im Innenmantel 27 weisen einen Durchmesser von höchstens 10 mm auf, bevorzugt von höchstens 6 mm. Denkbar sind auch kleinere Durchmesser je nach Material, das bearbeitet wird, und je nach den Anforderungen an den maximalen Gehalt an Störstoffen.
• Innen- und Aussenmantel sind sind durch andere Verbindungsarten wie bspw. Schrauben, Nieten oder Kleben verbunden, gegebenfalls auch durch Kombinationen dieser Verbindungsarten untereinander und mit Schweissen.
• Das Sieb weist für andere Einsatzarten, z.B. als Rüttelsieb, generell eine andere Form auf, z.B. flach. Im flachen Zustand ist zwar der Vorteil, mit verringertem Aufwand ein Sieb von gebogener Form herzustellen, ohne Bedeutung, jedoch bleibt der Vorteil, mit geringerem Aufwand ein Sieb von erhöhter Trennwirkung und Verschleissfestigkeit und geringerer Verstopfungsgefahr herstellen zu können.
• Die Löcher, insbesondere die des Innenmantels, können verschiedene Durchmesser aufweisen, z.B. in axialer Richtung abnehmend, z.B. um die Trennwirkung an die in Wanderungsrichtung des Rohmaterials generell abnehmende Teilchengrösse anzupassen, oder gleichmässig verteilt zur generellen Modifikation der Trennwirkung.
• Der Anteil der gesamten Lochfläche kann anders gewählt werden, z. B. kleiner sein, wodurch die Stabilität des Siebs vergrössert wird, oder auch grösser für höheren Durchsatz, wenn die Anforderungen an die Stabilität geringer sind. Ein denkbarer Lochflächenanteil in diesem Sinne ist 25 % bis 50 %

From the foregoing description, modifications and additions will be apparent to those skilled in the art without departing from the scope of the invention as defined by the claims. Particularly conceivable are:

• Use of three or more coats assembled into a sieve.
• The holes in the inner shell 27 have a diameter of at most 10 mm, preferably of at most 6 mm. Also conceivable are smaller diameters depending on the material that is processed, and depending on the requirements for the maximum content of impurities.
• Inner and outer sheath are connected by other types of connection such as screws, rivets or gluing, if necessary, also by combinations of these types of connection with each other and with welding.
• The screen has for other types of applications, such as vibrating screen, generally a different shape, eg flat. In the flat state, although the advantage of producing a sieve of curved shape with reduced effort, without meaning, but the advantage remains, with less effort to produce a sieve of increased separation efficiency and wear resistance and less risk of clogging.
• The holes, in particular those of the inner shell, may have different diameters, for example decreasing in the axial direction, for example in order to adapt the separation effect to the particle size generally decreasing in the direction of migration of the raw material, or evenly distributed for the general modification of the separating effect.
• The proportion of the total hole area can be chosen differently, for. B. smaller, which increases the stability of the screen, or even greater for higher throughput, when the requirements for stability are lower. A conceivable hole area proportion in this sense is 25% to 50%

Claims (12)

1. Screen (16) for a waste separation device (1), more particularly a hammer mill, characterised in that it comprises at least an inner screen plate (25) of a metal of higher strength and an outer screen plate (26) of lower strength whose hole pitches coincide and which are joined to form a metal composite so that the screen can be provided with smaller holes (27).
2. Screen (16) according to claim 1, characterised in that the inner screen plate (25) has holes (27) whose diameter (18) is preferably 5 to 15 % smaller than the diameter (30) of the respective aligned holes (29) in the outer screen plate (26) in order to reduce the passage resistance of the holes.
3. Screen (16) according to one of claims 1 or 2, characterised in that the inner screen plate (25) is made of a highly wear-resistant steel.
4. Screen (16) according to one of claims 1 to 3, characterised in that the outer screen plate (29) is made of a steel of medium strength.
5. Screen (16) according to one of claims 1 to 4, characterised in that the diameter (18) of the holes (27) in the inner screen plate (25) is at most 10 mm, preferably at most 6 mm.
6. Screen (16) according to one of claims 1 to 5, characterised in that the entire cross-sectional area of the holes (27) in the inner screen plate (25) amounts to at least 30 %, preferably at least 35 % of the total surface area of the inner screen plate (25).
7. Screen (16) according to one of claims 1 to 5, characterised in that the entire cross-sectional area of the holes (27) in the inner screen plate (25) amounts to 25 % to 50 % of the total surface area of the inner screen plate (25).
8. Screen (16) according to one of claims 1 to 7, characterised in that the distance between the holes (27) of the inner screen plate (25) is at most equal to the thickness (S) of the metal composite of the screen.
9. Screen (16) according to one of claims 1 to 8, characterised in that the inner and outer screen plates (25, 26) are connected to each other by an inseparable connection, preferably by at least one of welding, screwing, riveting, and bonding.
10. Screen (16) according to claim 9, characterised in that the connection is made on the entire surface area, in the form of regularly arranged punctual connections, and/or provided at the edge, the latter connection being partly continuous and/or punctual.
11. Screen (16) according to one of claims 1 to 10, characterised in that the screen is curved, the outer screen plate (26) being arranged radially outside the inner screen plate (25) and the mean curvature radius preferably being at most equal to 35 % of the largest distance between two edges of the screen.
12. Screen (16) according to one of claims 1 to 11, characterised in that the diameter of the holes in the inner screen plate (25) is smaller than the thickness S of the metal composite, preferably at most 80 % and more preferably at most 60 % of the thickness of the metal composite and most preferably substantially equal to the thickness (Si) of the inner screen plate (25).

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