Metal working – Method of mechanical manufacture – Assembling or joining
Reexamination Certificate
1998-12-09
2002-04-02
Hughes, S. Thomas (Department: 3726)
Metal working
Method of mechanical manufacture
Assembling or joining
C241S296000, C241S298000
Reexamination Certificate
active
06363601
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. §119 of German Patent Application No. 197 54 807.5, filed on Dec. 10, 1997, the disclosure of which is expressly incorporated by reference herein in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is related to a process for production of fittings for mechanical processing of suspended fibrous material. The fittings include at least one base and at least one processing element adapted to be exposed to flow of the fiber suspension during operation of the fitting.
2. Discussion of the Background Information
Fittings produced in the manner generally discussed above are used for mechanical processing of suspended fibrous material, e.g., beating of paper pulp, dispersion of contaminants and fibers as well as deflaking, i.e., breaking down of fiber agglomerations. Fittings are, e.g., built into beaters or “refiners.” The suspension in refiners has a solid content of approximately 2-8% wt. Similar pulp densities are also established in deflakers. Impellers used in pulpers may also have fittings similar in general to those discussed above, in which wet crushing of an introduced fibrous material is performed. Machines for higher pulp densities, e.g., high-consistency mills, dispersers, or kneaders, are utilized for mechanical processing the entire fibrous material, i.e., to disperse foreign matter contained therein. Such machines have at least one rotor and at least one stator with either disk-shaped or cone-shaped surfaces onto which the fittings are applied so that gaps may be formed between them. Many fittings have webs and grooves on their work surfaces, sometimes referred to as “knife fittings.” Other fittings have the shape of toothed rings. Moreover, it is known that, in addition to the shape of the webs, grooves, and teeth, the material from which these fittings are made also affects the processing of the fibrous material.
The fittings are exposed to wear and, consequently, must be replaced at specific intervals. However, during their service life, wear may cause the processing action to change because the shape and surface of the fittings have a great influence on the processing effect.
Thus, it is understandable that a significant expense, which is reflected in the specific design of shape and choice of the materials, is incurred in developing fittings. It has been demonstrated that materials which are particularly suited for use as processing elements have properties which may be very problematic for use as a base of the fitting. This is particularly true of materials which are very hard and brittle, e.g., ceramics, and, consequently, which do not have the necessary ductility for the base. Furthermore, such materials are relatively expensive, time-consuming to produce, and can be used only at great expense compared to standard metal materials.
The base of a processing tool provides a connection of the processing element to the remaining components, e.g., the components of a beater. Due to the high forces which occur in such beaters, particularly high strength requirements are required for the base. It must also be possible to reliably attach the base to the beater, in particular, via high-stress screws. Because of these requirements, a particularly strong and ductile material is essential for the producing the base.
A process for production of fittings is known from DE 196 03 548 A1, in which the fittings are assembled from separately manufactured parts. However, this publication only very generally discusses a bonding means that is applied between the base and processing element, but specifically identifies the very expensive high-temperature vacuum welding process or gluing processes. However, these processes cannot always be used, i.e., they are too expensive for many applications, and, when used in the more inexpensive processes, yield strengths which are not always adequate.
SUMMARY OF THE INVENTION
The present invention provides a process for the production of fittings in which particularly well-suited brittle materials may be used as processing elements and may be bonded relatively simply to the base.
In this regard, the process of the present invention includes producing an elastic bond between the processing elements and the base.
Thus, the present invention, as with the known production processes discussed above, may utilize different materials for the processing elements and for the base. As discussed above, this may be of significant advantage in that the selection of material for the processing element is based on a desired processing technology, whereas selection of the material for the base is primarily based on its strength and is optimized in terms of cost.
According to the features of the present invention, the connection between bases and processing elements is elastic, sufficiently precise, and, overall, cost-effective. Thus, because the parts connected together are not intended to move relative to each other, a damping action due to the elastic layer provides favorable performance. For example, the elastic layer may attenuate stress peaks and also reduce the often troublesome noise generation of these type machines. Vulcanization is a process already widespread in production engineering which has proven itself even under demanding conditions in, e.g., the chassis of motor vehicles, where it is used for the connection of steel parts which move against each other. Surprisingly, with the coupling of ceramic and steel, vulcanization provides the necessary properties for the applications to be performed by the fittings. The same is true for bonds made with elastic layers such as, e.g., silicone or elastic plastics. Thus, a homogeneous layer that adheres on both sides and cures such that it remains largely elastic may be formed, or a finished layer of elastic material may be glued on both sides.
The formation of an intermediate layer having a thickness of, e.g., between approximately 0.5-2 mm, may also compensate for any differing expansion characteristics of the joined parts. As is known, the coefficients of thermal expansion of ceramic and steel differ significantly, which causes problems with rigid connections.
It may also be beneficial that the temperatures during vulcanization or gluing may be far below the melting points of the parts joined.
Moreover, the present invention facilitates re-machining worn fittings by removing the remains of the old processing element and replacing it with a new one.
The present invention is directed to a process for production of fittings for a mechanical processing of suspended fibrous material that include at least one base and at least one processing element adapted to be exposed to flow of a fibrous suspension during operation. The process includes separately producing the at least one base and the at least one processing element, placing an elastic bonding material between contact surfaces of the at least one base and the at least one processing element, and elastically bonding the at least one base and the at least one processing element without melting the processing elements.
In accordance with another feature of the present invention, after the elastic bonding, an elastic layer having a thickness of at least approximately 0.5 mm may be formed between the at least one base and the at least one processing element. Further, after the elastic bonding, the elastic layer formed between the at least one base and the at least one processing element has a thickness of at least approximately 1.0 mm.
In accordance with another feature of the present invention, the elastic bonding may include vulcanizing the elastic bonding material. The elastic bonding material may be composed of a polymer. Further, the vulcanizing may include setting a temperature at the contact surfaces between approximately 100° C. to 150° C. The vulcanizing may include maintaining an absolute pressure of under at least approximately 3 bar. The vulcanizing may include providing an air/steam atmosphere. The polymer may b
Greenblum & Bernstein P.L.C.
Hughes S. Thomas
Jimenez Marc
Voith Sulzer Papiertechnik Patent GmbH
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