Metal fusion bonding – Process – With shaping
Reexamination Certificate
2000-05-25
2002-09-03
Dunn, Tom (Department: 1725)
Metal fusion bonding
Process
With shaping
C228S122100
Reexamination Certificate
active
06443353
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. § 119 of German Patent Application No. 199 23 865.0, filed on May 25, 1999, the disclosure of which is expressly incorporated by reference herein in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process for producing fittings for the mechanical processing, in particular the refining, of aqueous paper stock. The invention also relates to fittings made by the process.
2. Discussion of Background Information
Fittings (sometimes referred to as processing elements, processing tools, segments, refiner tooling, linings, disks, or fillings) of this type are primarily used for refining paper fibers, dispersing impurities in the paper stock, or fiberizing, i.e., breaking up, paper fiber agglomerates. They are used in refiners, fiberizers, or dispersers. Examples of these devices include U.S. Pat. No. 2,654,295 to Sutherland, U.S. Pat. No. 4,813,621 to Kleinhans, U.S. Pat. No. 5,200,038 to Brown, and U.S. Pat. No. 5,779,168 to Meltzer, the disclosures of each of these documents being herein incorporated by reference in their entireties.
Such machines typically have at least one rotor and at least one stator with either disk-shaped or cone-shaped surfaces to which the fittings are mounted so that a gap can form between them. Many fittings have bars and grooves on their working surfaces, so that they are also referred to as “sets of bars.” Other fittings have the shape of toothed rings. Moreover, it is known that, in addition to the shape of such bars, grooves, and teeth, the material of which fittings consist also affects the processing of the stock. Additionally, the running wheels used inpulpers can also utilize fittings in the sense referred to herein, with which the wet reduction of the introduced stock material is carried out.
With the aid of such fittings, the paper fibers can be effectively mechanically processed in a pumpable suspension, i.e., with a solids content of about 2-8%, or as a tough, high-consistency substance.
However, as a result of their use in fiber processing, the fittings are constantly exposed to wear and must therefore be replaced at certain intervals. This wear often causes their processing effect to change during the life of the fittings, e.g., reducing their ability to process the fibers efficiently. Moreover, since their shape, and in particular the shape of their edges as well as the surface of the fittings strongly influence the processing effect, any wearing of these surfaces reduces their ability to efficiently process the fibers.
Considerable efforts are being made to develop fittings with varied shapes and material selections. It has become evident from these efforts that particularly suitable materials may be used for these processing elements. However, many of these materials have properties which can cause severe problems when the material is used in the base body of the fitting. Accordingly, materials which are very hard and brittle and thus do not have the necessary toughness are not particularly useful for the base body. Furthermore, such hard and brittle materials are relatively expensive and laborious to produce. Moreover, compared to commonly used metallic materials, these can only be worked at great expense.
The base body of a conventional processing tool provides the connection of the processing elements to the other components of the processing machine, e.g., those of a refiner. Owing to the high forces which typically occur in such a refiner, the strength requirements for the base body are particularly high. Additionally, it must be possible to fix the fittings, and in particular the base body of the fitting, firmly to the refiner. For this purpose, high-stress screws, for example, are typically required. However, because of such demands, a particularly strong and tough material is required.
From German Application No. DE 196 03 548 A1, which is expressly incorporated by reference in its entirety, discloses a known process for producing fittings in which the fittings are assembled from separately produced parts. This document discloses the use of a very expensive high-temperature soldering process under vacuum and/or an adhesive process. However, these processes, while suitable per se, cannot always be used because they are too expensive for many applications. Moreover, when less expensive processes are selected, they do not always produce fittings having adequate strengths.
SUMMARY OF THE INVENTION
The invention is directed to a process for producing fittings so that production is simplified and which is particularly suitable such that hard materials can be used for the processing elements. The invention is also directed to fittings made by the process.
With the aid of the process, it is possible to produce the desired shapes of the processing elements relatively simply. It can be particularly advantageous for the hard material body, which can often be worked easily, to be pre-made or pre-formed in the desired shape. Accordingly, this shape should essentially correspond to the processing element which will be manufactured later. Thus, by utilizing a solidification process, in particular a curing after penetration with a binder, the processing element can receive the properties needed for its use. Accordingly, the labor-intensive working or processing of hard-structures can be omitted. In certain embodiments of the invention, for example, the hard material body can contain a hard metal powder or can be made from compacted hard metal powder. Moreover, it can also be provided with a polymer matrix which readily melts away or evaporates during processing so as to leave cavities which can be penetration with a binder.
A solder, such as a nickel based solder, can be advantageously selected as the binder for carrying out the process. This binder can be applied in a bonding composition as a paste or can be laid on the surface in the form of a foil or foils, and/or masks. Additionally, both the hard material body and the binder can be present as foils or plates, such that they can advantageously be worked together, e.g., they can be cut together into the desired outline shape. The penetration and bonding which occurs with the hard material body takes place at appropriately high temperatures. Accordingly, it is advisable for the hard metal body as well as the base body to be heated to the required soldering temperature. Alternatively, at least at the bonding contact surfaces and/or the upper surface of the hard material body can be so heated.
In this manner, a processing element can be formed having a homogeneous structure, in which as a rule, cavities, e.g., surface cavities, are eliminated. In order to improve bonding between the hard material body and the base body, it is advisable to apply binder also at the contact surfaces of the two bodies which are to be joined. Since, as a rule, the processing elements are provided with grooves (e.g., channels between refiner knives or bars), it may be advisable to take measures in order to prevent the permanent filling these grooves with the binder. This may be accomplished by applying an agent to the grooves which prevents them from being wetted with the binder. Alternatively, the grooves can be filled with temporary bodies or structures which prevent the binder from entering the grooves. Accordingly, these bodies would later be removed to expose the binder free grooves. Of course, any conventional agent may be utilized for this purpose. Moreover, other masking and/or anti-wetting techniques may also be used.
Under certain circumstances, it may also be advisable to construct the processing element in several layers. For example, this can occur by successively processing and/or stacking several hard material bodies of the same shape in layers. Thus, in a first working step, a hard material body could be brought into contact with the base body and be penetrated with the binder so that a firm bond is formed with the base body. Thereafter, a required number of furt
Kleinschnittger Hans Herrmann
Schneid Josef
Dunn Tom
Johnson Jonathan
Voith Sulzer Papiertechnik Patent GmbH
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