Machine element or mechanism – Elements – Gear casings
Reexamination Certificate
1999-09-30
2001-03-20
Wright, Dirk (Department: 3681)
Machine element or mechanism
Elements
Gear casings
Reexamination Certificate
active
06202507
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the field of speed reducers, such as single and multiple-stage gear reduction machines. More particularly, the invention relates to a technique for forming a support housing for a shaft-mounted speed reducer which facilitates manufacturing and reduces the overall number of parts and machining steps required for the manufacture of the final speed reducer product.
2. Description of the Related Art
A variety of applications exist for speed reducers, particularly for gear-type speed reduction sets. In industrial applications, for example, speed reducers are commonly employed to reduce the rotational speed of an input shaft to a desired output range. While such speed reducers may be used, inversely, to increase speed of an output shaft as a function of the input shaft rotational speed, they are more commonly employed as reducers, coupling a prime mover such as an electric motor or internal combustion engine to a driven application. Depending upon the speed and torque requirements, and the overall speed reduction ratio, speed reducers in industrial applications may include single or multiple stages. Moreover, in most applications the gear ratio of the speed reducer is fixed, with changes in input-to-output ratios being varied by varying the input speed, by gear transmissions, variable-speed sheave drives, and so forth.
In single-stage gear reducers, an input pinion or gear secured to an input shaft or hub meshes with an output gear secured to an output shaft or hub. The gear reduction ratio is defined by the parameters of the input pinion and the output gear in accordance with well established formulae. In multiple-stage gear reduction sets, multiple sets of intermeshing pinions and gears successively reduce speeds of input, intermediate, and output shafts or hubs to obtain a gear reduction ratio which is a product of the reduction ratios of the successive stages.
Speed reducers designed for industrial, mining, material handling, and similar applications, are typically configured in one of several designs to accommodate the application requirements, space constraints, and so forth. For example, certain applications may permit a gear reducer to be mounted securely on support feet on a machine frame, while other applications may call for securing the speed reducer directly to an input or output shaft or hub as an overhung load. In one particular product configuration of the latter type, a support housing is generally designed to present an output hub or shaft from which the gear reducer itself may be hung. When installed, the gear reducer housing is restrained from rotation so as to permit torque to be transferred to the supporting shaft or hub as the input shaft is driven in rotation and the input speed is reduced through the internal gearing.
Gear reducer housings are often one of the more complex and costly components of a gear reducer. For industrial gear reducers, housings are commonly cast and subsequently machined to form the necessary sealing surfaces, bearing support surfaces, access ports, and so forth. For speed reducers designed to be support on shafts or hubs as overhung loads, front and rear housing or shell portions are typically designed and manufactured separately, and mated with one another in sets to enclose an internal cavity in which the gears, pinions, shafts, bearings and other components are positioned.
Conventional designs of gear reducer support housings suffer from numerous drawbacks. For example, as noted above, the components are generally separately designed and manufactured as differently configured parts, adding significant cost and inventory to the overall product configuration. Machining process must typically be specifically adapted to the housing geometries, often requiring multiple fixtures for supporting and presenting the castings for machining. Moreover, where a family of gear reducers includes multiple sizes, ratings, gear reduction ratios, and number of stages, separate and distinct housing configurations are often designed, again multiplying the number of separate components in the family of products, and resulting in considerable additional cost, engineering and machining time, and inventory requirements.
There is a need, therefore, for an improved configuration of gear reducer support housings. There is a particular need for an improved approach which could reduce the overall number of parts in a single gear reducer design, as well as throughout a gear reducer product family. There is also a need for an improved design which can be easily formed and manufactured, with a reduction in the number of separate fixtures and operations involved in machining of a raw housing casting.
SUMMARY OF THE INVENTION
The invention provides a novel technique for configuring a speed reducer housing designed to respond to these needs. The technique may be employed in any suitable gear reducer design, but is particularly well suited to shaft or hub-mounted speed reducers. The overall housing design, and inventive features of the design may be adapted to accommodate both single-stage gear reducers and multiple-stage reducers. Where desired, the housing may accept both single and multiple-stage reduction sets, depending upon the particular features machined in the original casting. Additional features of the inventive technique may facilitate machining and fixturing operations, ultimately allowing all or virtually all machining operations to be accomplished on a housing component in a single fixture.
In accordance with a presently preferred configuration, the housing in accordance with the present technique is designed as a pair of mirror-image housing shells, the original castings for which are identical. Thus, from a single casting, the housing shell components may be formed by appropriately machining bearing support surfaces, apertures, access ports, and so forth. The casting may be advantageously configured with fixture regions or pads along a peripheral surface, such that sealing surfaces required to mate the housing components may be machined without removing the original casting from a machine fixture. Subsequent machining operations may also be performed in the same fixture. Still additional features of the housing may include securement apertures for attaching the housing shells to one another. These may be cast directly into the housing components, and may include angularly-offset fastener slots disposed at mirror-image locations with respect to a centerline of the housing shell. Thus, when the identical housing shell castings are subsequently machined and later joined in the final product, casting tolerances are sufficient to permit the housing shells to be secured to one another by virtue of the alignment of the slots with one another.
The technique thus permits a cost effective design of speed reducers in which the number of separate castings and machining operations is significantly reduced. The reduction in the number of separate parts may be further optimized through coordination of the design of the individual speed reducers in a family of products. Overall costs and inventory are thereby reduced.
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Gerasimow A. M.
Horn John J.
Reliance Electric Technologies LLC
Wright Dirk
Yoder Patrick S.
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