Abrading – Abrading process – Utilizing fluent abradant
Reexamination Certificate
2003-04-14
2004-06-01
Wilson, Lee D. (Department: 3723)
Abrading
Abrading process
Utilizing fluent abradant
Reexamination Certificate
active
06743077
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a wide-wheel grinding machine having at least one grinding head attached to a machine frame by a cross arm and having a drive motor for the grinding head which is mounted at one end of the cross arm.
2. Description of Related Art
Wide-wheel grinding machines have been established for several decades as a generic type of grinding machine. These grinding machines are very large, being between 1.5 and 3 meters in height and from one meter to several meters in length, depending on the number of grinding heads. The width of the machine, which may be from one meter to more than three meters, is typical. As a rule, a wide-wheel grinding machine is adapted to the specific needs of the situation, especially the width of the work pieces to be ground. One work piece after the other is guided continuously through the machine. Therefore, in the technical jargon, larger installations are referred to as a grinding line, which includes conveyance toward and away from the grinding machine. A typical application is grinding rough plywood boards. In most cases, the top and bottom surfaces are ground over the entire width simultaneously. Rough plywood boards have an excess thickness of 0.5 mm or more immediately after pressing and should be brought within a thickness' tolerance of at most ±{fraction (3/100)} mm after the grinding operation. The thickness tolerance must be maintained uniformly over the entire surface. A very high surface quality is demanded for the finished ground work piece. Roll pass grinding as the first stage of grinding requires powerful motors for removal of the large quantities of material involved. Accordingly, the enormous grinding work necessitates extremely high precision and stability of the machine, especially the machine frame, when working with boards several square meters in size. In the case of wide-wheel grinding machines, a wide variety of abrasive media are used. This depends first on the type of grinding procedure, whether roll pass grinding, fine grinding or sanding pad grinding. Primarily, grinding belts, grinding drums or brush rollers are used for this purpose. In addition to the above-mentioned grinding of boards, the generic wide-wheel grinding machine is also used in many other areas, e.g., for wood-core plywood boards, doors and also fiber-reinforced plaster, board, cement fiberboard and floor coverings in addition to both hard and soft fiberboard and plywood as well as other laminates and sheet rock, rubber coverings and parquet, cork and straw boards, and also for metal polishing in particular. As a consequence of the variety of different applications, a manufacturer of wide-wheel grinding machines will manufacture two identical machines only in exceptional cases, in contrast with other machine tools. Each machine is tailored to the specific client needs. An attempt is made to standardize the height adjustment of individual structural groups within the machine as much as possible, especially the grinding heads as well as the guide rolls and drive rolls. Nevertheless, actual practice so far has shown that work done in assembling the machines represents a major cost factor. Before a wide-wheel grinding machine can be shipped to a client, it is completely assembled at the manufacturing plant, including the drive and the controller, and all the important functions are tested in a test run. In the state of the art, the great variety of client needs have prevented more extensive standardization. In any case, this invariably included a good or even better quality with respect to the working result. Practice has shown repeatedly that machine vibration is an important factor affecting the quality of the working result. The two dominant vibration sources include the drive on the one hand and the site of the grinding action on the other hand. Resonance phenomena anywhere in the area of the wide-wheel grinding machine constitute a third vibration source which should not be underestimated. Any change in the design of a wide-wheel grinding machine always brings surprises in the matter of machine stability because of the virtual impossibility of calculating everything in advance. Therefore, any change entails risks accordingly. Furthermore, vibration effects of building parts, in particular the floor on which the machine stands, have also been known to occur. Harmful vibrations can be counteracted by a solid concrete floor or foundation. German Utility Model 94 14 952 describes a wide-wheel grinding machine having at least one grinding head mountable by cross arm on a machine frame and a drive motor for the grinding head and having a detachable connection at the other end with respect to the machine frame.
U.S. Pat. No. 5,070,224 and the corresponding German Patent 38 41 413 describe a wire eroding machine where the portal frame may be made of a mineral casting. It is proposed that the portal bridge be designed as an independent module having a cuboid solid body and hollow body. The portal bridge is designed to be replaceable and rigidly connectable to the side walls by means of the connecting devices to permit different machine designs. The object of German Patent 38 41 314 is to create independent, compatible and interchangeable modular units of having different designs with modifiable dimensions by using a modular system so that the units can be assembled to form machine constructions that can be adapted individually to the given processing jobs without impairing the rigidity and vibration resistance of the machine frame.
German Patent 37 34 895 proposes a concrete frame or an internal circular grinding machine to achieve the goal of a uniform mass and rigidity as well as an appropriate cast frame. The concrete frame is designed as a double-T shape in its longitudinal direction, and a peripheral steel frame is integrally cast in the standing surface of the concrete. Steel wire pieces with a diameter of 0.4 to 0.7 mm and a length of approximately 30 mm are preferably added to the cement concrete. The following are mentioned as advantages of the solution according to German Patent 37 894:
The mass of the concrete frame is approximately the same as that of a comparable cast frame and has the same rigidity due to the double-T design.
The thermal capacity of a concrete frame is approximately twice as great as that of a cast frame and its damping effect is three to four times greater.
There is no complicated reinforcement due to the uniform distribution of steel wire pieces in the concrete.
The design of the concrete frame in the form of a double-T shape creates cavities to accommodate machine-specific modules.
Concrete is a disadvantage if changes in the machine concept are necessary later and if permanent connections must be established between the machines frame and the modular components. The difference in thermal expansion of concrete and steel may cause additional problems in specific applications where there are great temperature differences.
SUMMARY OF THE INVENTION
The object and goal of the invention was to find means and methods of developing a low-vibration concept for wide-wheel grinding machines that would allow inexpensive production without sacrificing the quality standards of the machine, in particular the machine stability. An important partial goal was also the possibility of individual adaptability of the wide-wheel grinding machine to clients' specifications.
The wide-wheel grinding machine according to the present invention is characterized in that the machine frame is composed of a mineral casting module and a cross arm with the cross arm being designed as a metal profile and fixedly connected to the mineral casting module at the motor side.
The present inventors have recognized that in the case of the wide-wheel grinding machine, the cross arm supporting the grinding head is advantageously integrated into the concept of the machine frame as a central portion of this generic grinding machine design in general. In state-of-the-art wide-wheel grinding
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Grant Alvin J.
Steinemann Technology AG
Wilson Lee D.
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