Patent Description:
A compacting screw for processing waste and/or residue is known in itself, and is used for example for collection and processing of waste, as described in <CIT>. The known compacting screw is normally produced as an integral whole, wherein one end of the compacting screw - also known as the screw head - is treated by means of surfacing (or hard facing). Surfacing is a welding process in which a metal is covered by a fairly thick layer of another metal or alloy with different properties, in order to maximise the service life of the compacting screw. <CIT> discloses a plastic plasticizing device having a multi-zone screw. The document <CIT> discloses a compacting screw in accordance with the preamble of claim <NUM>.

It is an object of the present invention to create a compacting screw with a service life which is at least equal to that of the known compacting screw. In addition, it is an object to create an improved compacting screw.

At least one of these objects is achieved with a compacting screw for processing waste and/or residue as defined in claim <NUM>. Advantageous aspects of the compacting screw are claimed in the claims dependent on claim <NUM>.

The compacting screw for waste and/or residue processing comprises a screw head which is produced by means of a hardening process. The hardening process introduces irregularities into the crystal lattice of the metal alloy from which the screw head is made, so as to increase its hardness. By means of this process, the wear resistance is relatively greatly increased, whereby a compacting screw is obtained having a service life which is at least equal to that of a known compacting screw having a screw head treated by surfacing. The screw head is thus additionally treated, because this part of the compacting head is normally most heavily loaded in operation. It is also additionally possible to create an improved compacting screw by means of the hardening process, i.e. to increase the wear resistance of the screw head relatively greatly by means of the hardening process, so that a longer service life of the compacting screw can be achieved, or an improved compacting screw is produced in which a material saving and/or weight reduction is achieved for the same performance with respect to service life. The weight reduction is for example easily achieved since a screw head produced by means of a hardening process can be made thinner.

An additional advantage of the screw head produced by means of a hardening process is that the process for manufacturing a compacting screw with a relatively long service life is less labour-intensive. The hardening process to be performed on the screw head is namely far less labour-intensive than the known surfacing process. In this way, it is possible to manufacture compacting screws in large numbers not only relatively quickly but also with relatively few personnel. The hardening process also makes it possible to produce the compacting screws relatively economically.

In accordance with the invention, a layer produced by means of the hardening process is at least <NUM> thick, preferably <NUM>-<NUM> thick. The thickness of the layer depends on the desired wear resistance of the compacting screw, i.e. the thicker the layer produced by means of the hardening process, the better the compacting screw is protected against wear. It is therefore possible to treat a blade of the screw head and/or a screw head tube of the screw head, to which the blade of the screw head is attached, over its complete thickness by means of the hardening process, whereby the thickness of the hardening layer is equal to at least one of the thicknesses of the screw head blade and/or screw head tube. However, to achieve a relatively long service life, at least <NUM> is desired. The layer to be applied by means of a hardening process may thus also be made relatively thin while achieving a relatively great resistance to wear.

In accordance with the invention, the hardening process is carried out on a cast screw head. In this way, a screw head is obtained which can tolerate relatively heavy loads and has a particularly long service life.

The compacting screw comprises the screw head and a screw body connected thereto. The screw head is provided with at least one screw blade and/or the screw body is provided with at least one screw blade. The connection between the screw head and the screw body may be produced by means of force fit (e.g. a clamp connection), form fit (e.g. a bolt connection), and/or material melting (e.g. a welded connection). When the compacting screw is assembled, it may be provided with a continuously helical screw blade composed of the screw blade of the screw head and the screw blade of the screw body. By means of such a configuration of the compacting screw, waste and/or residue may be compressed, compacted and/or transported for waste processing in a particularly effective manner. The diameter of the compacting screw is at least <NUM> and/or the length of the compacting screw is at least <NUM>.

In order to create the compacting screw, in a particular aspect the screw head comprises a screw head tube or a screw head rod, in which one end of the screw head tube or screw head rod is not hardened after the hardening process, so that said end may be connected to the screw body, in particular to a screw body tube or screw body rod thereof, by means of force fit, form fit and/or material melting (e.g. a welding process). In such a fashion, a compacting screw with a particularly long service life can be manufactured relatively easily and rapidly.

The configuration of the compacting screw, with a screw head and screw body to be connected together, advantageously allows the screw head to be treated by means of the hardening process independently of the screw body. This may achieve the particularly advantageous configuration in which the screw head of the compacting screw is treated by means of a hardening process, while the screw body of the compacting screw connected to the screw head may be untreated by the hardening process.

In a further aspect, the hardening process to be used for the screw head may be carbonitriding or isothermic hardening. Both heat treatments for surface hardening of a steel screw head have been found by experiment to be particularly suitable for producing a screw head with the desired properties. By means of the thermochemical process of carbonitriding, the screw head is enriched with a combination of carbon and nitrogen in order to improve the mechanical properties of the screw head. In isothermic hardening, after austenitizing, the screw head is cooled in a warm medium and held at this temperature for a predefined duration. Then it is cooled to room temperature in air with the aim of achieving maximum toughness, wherein annealing is then no longer required.

The invention also concerns a device for processing waste or residue, comprising at least one compacting screw as described above. Preferably, the processing device comprises two of the compacting screws described in this document which are arranged parallel to each other, and which in operation are driven in contra-rotation for compressing, compacting and/or transporting the waste or residue. The processing device may be arranged fixedly or releasably on a movable device such as for example a truck. The invention also concerns a method as claimed in claim <NUM> for manufacturing a compacting screw. The aspects and advantages of the compacting screw described above are also applicable to the processing device, the use of the compacting screw, and the method for manufacturing a compacting screw; to avoid repetition, these are not discussed again.

The above-mentioned aspects will be explained below with reference to an exemplary embodiment in combination with the figures. The invention is not however restricted to the exemplary embodiment described below. Rather, a number of variants and modifications are possible which also make use of the teaching of the invention and therefore fall within the scope of protection. In particular, the possibility is mentioned of combining the properties/aspects cited individually in the description and/or shown in the figures with the properties of the claims insofar as compatible.

Reference is made to the following figures in which:.

In the figures, the same components carry the same reference signs.

<FIG> show a compacting screw <NUM> for processing waste and/or residue, i.e. a compacting screw <NUM> by means of which waste can be compressed and/or transported, inter alia. The compacting screw <NUM> comprises a screw body <NUM>, a screw head (or compacting head) <NUM>, and a screw mounting <NUM> by means of which the compacting screw <NUM> is mounted in a processing device (illustrated diagrammatically in <FIG> by the dotted line marked with reference sign <NUM>). The two dotted lines without reference sign in <FIG> indicate diagrammatically where the screw body <NUM> transforms into the screw head <NUM> and screw mounting <NUM>. A first end of the compacting screw <NUM> is formed by the screw head <NUM>, and a second end by the screw mounting <NUM>, wherein the screw body <NUM> is arranged in between. The processing device <NUM> may comprise one or two of the compacting screws <NUM> illustrated. In the variant with two compacting screws <NUM>, these may be arranged parallel to each other and mirror-symmetrically, and be driven contra-rotating in operation by means of a drive (not shown) in order to compress, compact and/or transport the waste or residue. The displacement direction in which the waste or residue is displaced using the compacting screw <NUM> is indicated in <FIG> by arrow P1. It is also possible to rotate the compacting screw <NUM> in the opposite direction, for example if the compacting screw <NUM> has seized, whereby the waste or residue may be temporarily displaced in a direction opposite the direction indicated by the arrow P1. The outlet (not shown) of the processing device <NUM> is normally located close to the end of the compacting screw <NUM> which is formed by the screw head <NUM>, while the inlet (not shown) of the processing device <NUM> is normally located close to the opposite end of the compacting screw <NUM> which is formed by the screw mounting <NUM>.

By means of a connection <NUM>, the screw body <NUM> is connected to the screw head <NUM>. In this way, it is relatively easily possible to subject the screw head <NUM> to a hardening process without applying the process to the screw body <NUM>. The compacting screw <NUM> for processing waste and/or residue may relatively easily be provided with the screw head <NUM> which is produced by means of a hardening process. In some cases, it is also possible to treat the screw head <NUM> and the screw body <NUM> with the hardening process. In this case, the screw head <NUM> and the screw body may be configured integrally, and if desired may be made of the same material.

The screw head <NUM> is produced by means of a casting process, and the material from which the screw head <NUM> is made is an alloy. After casting, the screw head <NUM> is subjected to a hardening process as claimed in this document, in order to create the compacting screw <NUM>. Carbonitriding or isothermic hardening have been found by experiment to be particularly suitable hardening processes for obtaining a screw head <NUM> with the desired properties. The layer produced by means of the hardening process on the screw head <NUM> is at least <NUM> thick. A screw head <NUM> obtained in this way creates a compacting screw <NUM> which has a relatively long service life and which can be produced relatively quickly, i.e. in particular without much manual labour. The screw body <NUM> may be produced from the same material, e.g. steel, as the screw head <NUM> but may also be made of another metal or another metal alloy.

In the compacting screw <NUM>, the screw head <NUM> is provided with at least one screw blade <NUM>, and the screw body <NUM> is provided with at least one screw blade <NUM>. The screw blade <NUM> of the screw head <NUM> comprises at least one single turn around a screw head tube <NUM> of the screw head <NUM>, and the screw blade <NUM> of the screw body <NUM> comprises at least two windings around a screw body tube <NUM> of the screw body <NUM>, as shown in <FIG>. In assembled state, the screw blades <NUM> and <NUM> create a compacting screw <NUM> which is provided with an uninterrupted helical screw blade <NUM>, <NUM>.

Viewed in the direction of a screw head tube axis <NUM>, the screw head <NUM> comprises a first free end <NUM> which is formed as a truncated cone, and a second end <NUM>. Instead of a truncated cone, a differently shaped first end <NUM> may be selected, for example a convex first end <NUM>. The second end <NUM> of the screw head tube <NUM> may be at least largely excluded from the hardening process, so that even after the hardening process, this end <NUM> remains unhardened, whereby the original material properties are not changed or only minimally changed. This end <NUM> may then be connected, for example by means of material melting (a welding process), to an end of the screw body <NUM> in order to create the connection <NUM>.

In order to obtain an improved connection <NUM> between the screw body <NUM> and the screw head <NUM>, the end <NUM> of the screw head is advantageously provided with a rim 27a running around the screw head tube axis <NUM> and having an outer diameter which is selected such that for connection, the outside of the rim 27a can be positioned almost without play against the inner wall of the screw body <NUM>, so that the screw head <NUM> and the screw body <NUM>, in particular the transition between them, can thereafter be connected together, for example by means of material melting (a welding process), relatively easily in a strong, low-maintenance fashion. In some cases, a mechanical reversal is possible for obtaining the connection <NUM>, wherein the end of the screw body <NUM> is provided with a rim which can be positioned almost without play against an inner wall of the screw head tube <NUM>, whereupon the screw head <NUM> and screw body <NUM>, in particular the transition between them, can be connected together via e.g. welding, in order to create the connection <NUM>. Connection techniques other than or additional to welding may also be used, such as for example a clamp connection and/or a bolt connection.

The diameter D (<FIG>) of the compacting screw <NUM> is at least <NUM>, and the length L of the compacting screw <NUM> is at least <NUM>.

Claim 1:
Compacting screw (<NUM>) for processing waste and/or residue, comprising a screw head (<NUM>) which is produced by means of a hardening process, wherein a first end of the compacting screw is formed by the screw head, and a second end by a screw mounting (<NUM>), wherein a screw body (<NUM>) is arranged in between, characterized in that the hardening process is carried out on a cast screw head (<NUM>) to introduce irregularities into the crystal lattice of the metal alloy from which the screw head (<NUM>) is made, and that a layer produced by means of the hardening process is at least <NUM> thick.