Planetary gear transmission systems or components – Steering by driving
Reexamination Certificate
2001-12-06
2003-04-29
Wright, Dirk (Department: 3681)
Planetary gear transmission systems or components
Steering by driving
C475S028000, C440S075000, C244S060000
Reexamination Certificate
active
06554729
ABSTRACT:
TECHNICAL FIELD
This invention relates to a simplified steering system for vehicles that operate primarily in fluids (e.g., boats and airplanes) and, more particularly, to a simplified steering system that permits the vehicle (i.e., boat or plane) to be steered at all times by a conventional steering actuator without necessitating the use of steered wheels or rudders.
BACKGROUND
Our earlier inventions (e.g., U.S. Pat. No. 4,776,235 to V. E. Gleasman et al.) make it possible to steer track-laying vehicles with a single steering wheel in the same manner as other highway vehicles are steered. In these earlier steer-drives, a pair of standard differentials or a pair of standard reduction gear drives (e.g., also see U.S. Pat. No. 4,895,052 to V. E. Gleasman et al.) are interconnected as part of a hydro- (or electro-) mechanical system that is inserted in the vehicle's drivetrain between the vehicle's transmission and track propulsion shafts. These steer-drives add and subtract steering torque to and from driving torque that is supplied to each of the respective tracks of the vehicle, thereby permitting the vehicle to be steered with a conventional steering wheel without requiring any simultaneous locking or braking of either one of the tracks.
While the prior art systems just identified above operate satisfactorily, they are relatively large and mechanically complex. Since these steer-drive systems do not replace the conventional engines and transmissions necessary for automotive vehicles, they require additional space and add weight. Therefore, it is commercially desirable to achieve reductions in the size and weight of steer-drives. Such size and weight reductions are primarily limited by the size and strength of the materials required to transfer the vehicle's driving torque from its engine and transmission through to the vehicle's propulsion elements.
The maximum torque being transmitted by the various elements positioned throughout the vehicle's drivetrain is determined by the output of the engine and by any increases in the mechanical advantage of that engine output by virtue of the various gear ratio speed reductions realized throughout the drivetrain. For instance, if the drivetrain includes a mechanical speed-reduction unit that reduces the speed of a given rotational input shaft by a ratio of 2:1, this results in a mechanical advantage that effectively doubles the torque being transmitted, thus requiring a doubling of the strength of the speed-reduction unit's elements compared to other similar drivetrain elements that normally rotate at higher speeds.
In this regard, standard planetary gear drives (e.g., those shown in several different arrangements in the prior art patents referred to above) provide a limited range of speed-reduced outputs. [NOTE: “Standard planetary drives” consist of a sun gear, an exterior ring gear, and planet gears in mesh with both the sun gear and the ring gear, the planet gears being supported by the arms of a carrier. Such planetary drives can be used in many different ways to provide a variety of positive and negative speed reductions, namely, the input can rotate any one of the components (the sun gear, the ring gear, or the carrier), while output can be taken from either of the other components. However, for practical use in combining steering and driving torque, input is received through the sun gear.] According to automotive textbooks, with input to the sun gear, standard planetary gear drives are all limited in actual practice to producing speed-reduced outputs that range between 2.5:1-5:1. That is, the elements of such planetary gear drives must be made large enough to support the 2.5- to 5-times increase in torque that results from their built-in gear reduction. Therefore, these prior art planetary drives must include elements that are stronger (larger and heavier) than would be needed for components providing lesser speed reductions.
The subject invention was conceived during the testing of a new prototype steer-drive vehicle when trying to develop a further variation of our earlier steer-drive systems that would be lighter and more compact. While the invention uses the same basic steer-drive concepts for combining steering and driving torque, it replaces key elements of prior art steer-drives with a known and relatively simple gear arrangement that, in this new combination, results in a new steer-drive that is not only more compact and lighter in weight but, surprisingly, is also simpler mechanically and reduced in cost. Further, this simpler, lighter, and more compact steer-drive is applicable as well to non-automotive vehicles that operate primarily in fluids, namely, boats and airplanes.
SUMMARY OF THE INVENTION
In its primary application, this steer-drive is designed for use on tracked vehicles which not only operate off-road but are specifically intended to be driven on paved roads at typical highway speeds. As is well known in the automotive world, most standard vehicles driven at highway speeds normally rotate the axles which directly drive the vehicle's tires at an overall speed reduction ratio of about 4-5:1 relative to the vehicle's engine. One of the key objects of the invention is to realize most of this normal overall speed reduction as close as is practical to the drive axles that directly drive the vehicle's tracks or propellers. That is, the steer-drive of the invention is intentionally and preferably designed to provide a speed ratio (between the input to the steer-drive, i.e., the output of the vehicle's transmission, and the output of the steer-drive itself) that is as close to 1:1 as is practical without actually matching 1:1.
Prior art steer-drives use pairs of standard differentials or pairs of standard reduction gear drives, the latter being located in proximity to the vehicle's drive axles. The steer-drive disclosed herein uses neither a combination of standard differentials nor standard reduction gear drives. Instead, the desired combination of driving and steering torque is achieved by respective left and right orbital gear drive units. [NOTE: Orbital gear arrangements (sometimes identified as “reverted epicylic gear trains”) are well known, e.g., see U.S. Pat. No. 5,186,692 entitled “Hydromechanical Orbital Transmission” issued to V. E. Gleasman et al.]
The orbital gear portions of the steer-drive units disclosed herein are quite simple in format, comprising only an input gear and an output gear interconnected by at least one orbiting cluster gear. As used in this invention, these orbital drive units are preferably designed to transfer driving torque at speed ratios selected to be as close to 1:1 as is practical and, in any event, at ratios less than can be practically achieved with the standard reduction gear drives shown in prior art steer-drives. [NOTE: When used for steer-drive purposes, orbital gear drives must operate at some ratio greater than or less than 1:1. Practical considerations determining the selection of such gear ratios will be discussed in greater detail below, and the disclosed preferred orbital drive units are designed so that, when the additions and subtractions of steering torque are ignored, driving torque is transferred through each unit at a ratio of 1:1.36.]
Each orbital unit has an input gear and an output gear aligned along the same first axis and interconnected by at least one orbiting cluster gear mounted for rotation on an orbit shaft positioned parallel with the first axis. The orbit shaft is supported in a housing that also rotates about the first axis. When rotation of the housing is prevented, the rotation of the input gear drives the cluster gear which, in turn, causes rotation of the output gear (e.g., at a speed ratio of 1.36:1). However, rotation of the housing supporting the orbit shaft causes the cluster gear to orbit about the input and output gears; and even though the speed of rotation of the input gear remains constant, such orbital movement of the cluster gear results in a vari
Alexander Warren R.
Gleasman Keith E.
Gleasman Vernon E.
Horton Robert C.
Eugene Stephens & Associates
Polster Morton A.
Torvec Inc.
Wright Dirk
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