Patent Application
20050103947
This application is not referenced in any pending applications.
This application is not referenced in any microfiche appendix.
1. Field of the Invention
The present invention relates to balancing assemblies for rotating members. More particularly, the invention relates to self-aligning balancing assemblies for large cylindrical members, and even more particularly, to a self-aligning flange for mounting on opposing ends of a large cylindrical drum assembly.
2. Background
Industry is replete with many examples of large cylindrical drums that must be rotated for various reasons. For example, factories in the paper industry must employ large heavy drum assemblies for receiving and storing rolls of kraft paper. The road construction industry uses road machines having large drums with cutting blades embedded on the drum surface for abrading rock during road construction.
These cylindrical drum assemblies are generally massive and require a high torque motor or engine to initiate rotation of the drum and to maintain rotation during operation. Although the drum assemblies are rotated at a low number of revolutions per minute (rpm), the high mass of the drum results in several problems. First, the centrifugal force produced by the rotation of a high mass structure is extreme even at low rpm and necessitates a robust, heavy duty gear box to transmit the rotational force of the motor to the drum. Often, a separate gear box and motor assembly is used on each of the opposing ends of the axis about which the drum rotates. In such a configuration, one gear box and motor assembly is structured for clockwise rotation and the opposing gear box and motor assembly is structured for counter-clockwise rotation so that their rotational force combines to rotate the drum in a single direction. These gear box and motor assemblies distribute the force required to rotate the drum so that less robust gear boxes and motors may be used.
Second, if the drum is unbalanced around the axis of rotation so as to produce an oscillating radial force, this radial force will excessively wear the gear box and motor so as to cause premature failure. When using a pair of opposing gear box and motor assemblies, the centerline of both assemblies must be perfectly aligned to reduce radial forces and resultant wear on the bearings of these assemblies; otherwise the misalignment will cause premature failure of the bearings. This alignment may be achieved by precise machining and balancing of the drum. However, such machining and balancing for drums with diameters in excess of 12 inches and lengths in excess of five feet requires large, heavy duty, and expensive machines to turn the massive drums and cut away excess metal. High precision is difficult to attain when dealing with such heavy, bulky structures. Additionally, the removal, shipping, and replacement of the drum in its installed location is expensive in terms of required man power. The removal, shipping, and replacement can also be further complicated by the fact that machines employing such heavy drums, e.g. road equipment, are often used in remote locations where transportation is difficult and knowledgeable maintenance personnel are unavailable.
Third, during use, the drum is loaded by the work against which it rotates, e.g. the road surface for a cutting drum or the uneven winding of paper on a takeup drum in a paper plant. This loading coupled with the massiveness of the drum causes a small amount of deflection which also results in unbalancing of the drum assembly.
Fourth, even if the drum is perfectly balanced about its axis of rotation, the gear box must be positioned precisely so that the shaft is exactly colinear with the axis of rotation. This requires that the mounting surfaces for the gear box must be machined to very precise tolerances. On a large machine, this is very difficult and expensive, and, while it improves the initial misalignment, it does not help with the deflection problem.
As can be seen, there is a need for a method and apparatus to maintain the balance of a massive rotating drum assembly, reduce the requirement for close precision in the physical balancing process for the drum, and dynamically adjust for in-use deflection of the drum so that balance about the axis of rotation is maintained.
The present invention satisfies the needs discussed above. In one aspect of the invention, an apparatus comprises a self-aligning flange for aligning a centerline of a motive force means with a centerline of a rotating member supported by a frame, where the self-aligning flange comprises an annular ring providing a mounting surface for the motive force means, the annular ring having a rim and four radially aligned projections on the rim with the projections circumferentially spaced 90° apart; and a circular well in the frame with the circular well having an interior surface with four slots therein, each slot longitudinally aligned with the centerline of the rotating member and spaced about the interior surface to receive the projection of the annular ring in axial sliding contact therein. In this arrangement, the centerline of the motive force means is aligned with the centerline of the rotating member and the projections move axially within their respective slots as the rotating member rotates so that the centerline of the motive force means maintains alignment with the centerline of the rotating member as the centerline of the rotating member oscillates from unbalancing forces.
In another aspect of the invention, a motive force means is provided for both ends of a rotating cylindrical drum, where the motive force means is mounted on a self-aligning flange having the configuration described above.
In still another aspect of the invention, a cutting apparatus having a self-aligning drum assembly is provided, where each end of the drum is maintained in rotation by a gear box and a motor assembly, the gear box and motor assembly being held in alignment with each other by a pair of annular rings supporting the gear box and motor assembly, the rim of each annular ring being allowed to move axially within a limited distance, the movement being urged by the oscillations generated by any imbalance from (a) the inherent rotational symmetry of the drum, (b) deflections from the load applied to the drum, or (c) departures in the mounting surfaces from normal (90°) orientation with the centerline of the drum.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims. For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be made to the accompanying drawings and descriptive matter in which there are illustrated preferred embodiments of the invention. The foregoing has outlined some of the more pertinent objects of the invention. These objects should be construed to be merely illustrative of some of the more prominent feature and applications of the present invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or by modifying the invention within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the invention and the detailed description of the preferred embodiments in addition to the scope of the invention illustrated by the accompanying drawings.
The following detailed description shows the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made for the purpose of illustrating the general principles of the invention and the best mode for practicing the invention, since the scope of the invention is best defined by the appended claims. The invention is capable of other embodiments and of being practiced or carried out in a variety of ways. It is to be understood that the phraseology and terminology employed herein are for the purpose of description and not of limitation.
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Fixedly mounting the gear box 110 to the self-aligning flange 200 with a spherical outer diameter allows the gear box 110 to align itself with the opposite gear box unit. Projections 260 in the rim of the self-aligning flange 200 engage slots 270 cut in the support housing 60 to prevent rotation while still allowing movement for alignment and for thermal expansion. Misalignment of the mount surfaces of the cutter drum are also compensated for.
Other modifications of the invention could be made without departing from its scope. For example, the inner diameter or surface of the support housing 60 could also be made spherical to provide increased bearing area and reduced wear. However, this variation loses the axial movement that compensates for length variations due to manufacturing tolerances or thermal expansion. As another example, the self-aligning flange could be manufactured with grooves cut in the rim, or outer diameter, to match “keys” or splines in the inner surface of the support housing. In other words, the projections would in this example extend from the inner surface of the support housing rather from from the outer surface, or rim, of the self-aligning flange.
As has been demonstrated, the present invention provides an advantageous apparatus and method for maintaining alignment and balance of a massive rotating cylindrical drum within close tolerances. While the preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims shall be construed to include both the preferred embodiment and all such variations and modifications as fall within the spirit and scope of the invention.
