Machine element or mechanism – Gearing – Directly cooperating gears
Reexamination Certificate
1999-09-30
2001-08-14
Fenstermacher, David (Department: 3682)
Machine element or mechanism
Gearing
Directly cooperating gears
C074S4120TA, C074S60600R
Reexamination Certificate
active
06272941
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field Of The Invention
The present invention relates generally to the field of gear reducers, such as machines designed with one or multiple reduction stages for support on an input or output hub or shaft. More particularly, the invention relates to a gear reducer employing a mirror-image symmetrical layout of shaft and hub axes accommodating multiple different combinations of pinions and gears, as well as both single and multiple stages of reduction in a product family utilizing a reduced number of different original manufacturing parts.
2. Description Of The Related Art
Gear reducers of various types are ubiquitous in the field of industrial mechanical power transmission. Such gear reducers are typically employed to reduce the speed of a rotational input shaft to a desired level, and to, consequently, increase the torque applied to a load. Many different designs for such products have been proposed and are presently in use. In one particular type of gear reducer, sometimes referred to as a torque arm, one or more gear reduction stages are formed in a housing which may be supported on a machine surface, or which may be supported directly on an input or output shaft as an overhung load. To provide the range of gear reduction combinations and torque and speed ratings needed by systems design engineers, manufacturers typically offer a range of similar products through a product family, varying in each both the rating of the various components, the overall gear reduction ratio, the torque characteristics, mounting configurations, and so forth.
Gear reducers of the type described above may be configured as single or multiple-stage machines. In general, the overall gear reduction ratio of the machine is defined by the parameters of input pinions or gears, intermediate pinions and gears, and output gearing. In a single-stage reducer, the gear reduction ratio is defined by the configuration of the input pinion and output gear which intermesh with one another. In multiple-stage machines, the overall gear reduction is the product of the individual reduction ratios of the successive stages.
A significant challenge in the design of gear reducers is the layout of gearing and support shafts in a manner that will provide the desired reduction ratio, while respecting mechanical tolerances, space constraints, strength constraints, and so forth. In general, each input and output shaft or hub must be rotationally supported by support bearings and surfaces of the support housing that can withstand the anticipated loading. Intermediate shafts, supporting intermediate stage pinions and gearing, must be similarly supported by bearings for anticipated loads. Moreover, input and output shafts or hubs, and intermediate shafts must be appropriately spaced from one another to accommodate the desired gearing, the gearing itself dictating specific center distances of the various rotational axes from one another.
Attempts have been made in the past to judiciously configure gear reducer layouts, particularly the positions of various rotational axes, to accommodate more than one specific gear reducer size or rating. In particular, proposals have been made to provide several rotational axes in a symmetrical triangular configuration. The triangular configuration, in theory, allows for gear reducer housings to be employed in both single-stage and multiple-stage machines. However, in practice, these designs have proven less than optimal, particularly in view of the mechanical support and machine required by the different loading anticipated for input and intermediate shafts. Moreover, it has been found that in designs incorporating rotational shaft axes laid out in an isosceles triangle configuration, spacing constraints between the various rotational axes do not permit the degree of design flexibility in the gearing ratios that would be desired.
There remains a significant need, therefore, for an improved design for gear reducers which facilitates the selection of individual pinion and gear sets, both for single and multiple-stage machines. There is a particular need for an improved technique for the layout of a gear reducer which allows housing components to be employed across a range of reducer ratings, sizes, and numbers of stages.
SUMMARY OF THE INVENTION
The present invention provides a gear reducer system designed to respond to these needs. The novel gear reducer design of the present technique may be employed in both single-stage machines, and multiple-stage machines, but is particularly well suited to use in a family of gear reducers that may include both single and multiple-stage units. While the technique may be employed in various housing configurations, it is particularly well suited to gear reducers designed to be support on an input or output hub or shaft. The technique employs a series of rotational shaft axes laid out in a mirror-image configuration. In a preferred embodiment, four rotational axis locations are provided. The locations include two which are positioned along a longitudinal centerline of the gear reducer, and two additional axes positioned at mirror-image locations offset from the centerline. In the gear reducer itself, reduction stage shafts or hubs may be positioned about fewer than all of the rotational axis locations. In particular, in a single-stage gear reducer, a first rotational shaft or hub may be positioned along the centerline of the machine, with an output hub or shaft similarly along the centerline. Alternatively, the input or output hub or shaft may be positioned at one of the offset locations, with the other hub or shaft positioned along the centerline. In a two-stage gear reducer, input and output shafts may be positioned at the locations along the centerline with an intermediate shaft being positioned at an offset location. Alternatively, the input or output shaft location and that of the intermediate shaft may be reversed.
In general, the technique provides a gear reducer in which rotational axis supports are provided in a bilaterally symmetrical arrangement. The arrangement includes symmetry about an axis extending through at least one vertex of a quadrilateral. Center distances between the vertices along the longitudinal axis, and center distances between the two central vertices and the bilaterally symmetrical offset vertices are selected to accommodate both single and multiple stage gear sets. Housing components, bearing components, machining operations, inventories, and other costly facets of the gear reducer design and manufacturing operations may thereby be significantly reduced for a single gear reducer, as well as across a family of gear reducers sharing common components.
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Fenstermacher David
Gerasimow Alexander M.
Reliance Electric Technologies LLC
Walbrun William R.
Yoder Patrick S.
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