Motor vehicles – Steering by driving – Combined with manual steering
Reexamination Certificate
2000-08-29
2001-09-04
Oberleitner, Robert J. (Department: 3613)
Motor vehicles
Steering by driving
Combined with manual steering
Reexamination Certificate
active
06283235
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to zero turn transaxles and, more specifically, relates to an integrated zero turn hydrostatic transaxle. Zero turn transaxles are known in the art and provide for independent control of each of the drive wheels of the vehicle with which such transaxles are utilized. An example of one such transaxle may be found in U.S. Pat. No. 5,078,222 to Hauser et al. entitled “Zero Turn Transaxle” which issued on Jan. 7, 1992. Specifically, the '222 patent discloses a zero turn transmission having two identical mirror image reduction drives powered by independent self-contained hydraulic power units. Additionally, Eaton has developed and marketed zero turn transaxles as their Eaton Models 771 and 781. The Eaton Model 771 is an assembly with one pump and one motor where two mirror image Eaton Model 771 assemblies, a right and a left, are required for zero turn drive. The Eaton Model 781 consists of two units similar to the Eaton Model 771 joined together to make one assembly.
While the known zero turn transaxles work for their intended purpose, they do suffer from some deficiencies which it is the object of the subject invention to overcome. For example, implementing a zero turn drive is seen to be relatively costly owing to the requirement that two separate and distinct mirror image transaxles are needed which transaxles require individualized construction. Additionally, the currently utilized housings in which the transaxle components are carried are seen to undesirably add to the cost and time of manufacture in that they are constructed from at least two main housing sections joined along a seam or split line. Specifically, the use of at least two main housing sections requires relatively tighter tolerances in the manufacture of the housings in that each housing section must properly align to ensure that the components encased therein are properly supported and capable of operating without binding. Furthermore, the use of two non-similarly oriented transaxles to effectuate zero turn drive is seen to cause the tracking efficiency of the two drive wheels to vary with respect to one another since transaxles having non-identical construction and orientation will experience different operating conditions (e.g., different biasing, tolerances, design variances, etc.). In addition, currently utilized zero turn transaxles have been seen to have a relatively large footprint which undesirably increases the wheel base when used to implement zero turn drive and which also places a limit on the size of the vehicle with which the transaxles may be used. From the foregoing, it is seen that a need exists for an improved zero turn transaxle.
SUMMARY OF THE INVENTION
Accordingly, it is a general object of the present invention to provide a zero turn transaxle which may be manufactured at a relative cost savings. It is a more specific object of the present invention to provide an unhanded zero turn transaxle wherein the same transaxle may be utilized for both left handed and right handed drive. It is a further object of the present invention to provide a zero turn transaxle in which, when used as a pair to implement zero turn drive, the left handed and right handed drive track similarly. Another object of the present invention is to provide a transaxle having a seamless main housing section. A further object of the present invention is to provide a zero turn drive having a relatively smaller wheel base and a transaxle having a relatively smaller footprint, and an improved parking brake mechanism.
Other objects and advantages of the present invention will be apparent to those of skill in the art from the teachings herein.
In accordance with objectives of the invention, a zero turn transaxle is provided where both of the transmission units are identical in construction, with the output drive shaft for the vehicle axle being adaptable to be modified for either left drive or right drive.
An improved parking brake mechanism as part of the gear train of the transmission is also incorporated in the present invention.
Advantageous axle and shaft arrangements are also taught herein.
A better understanding of the objects, advantages, features, properties and relationships of the invention will be obtained from the following detailed description and accompanying drawings which set forth illustrative embodiments and which are indicative of the various ways in which the principles of the invention may be employed.
REFERENCES:
patent: 5860884 (1999-01-01), Jolliff
patent: 6010423 (2000-01-01), Jolliff
Hauser Raymond
Sporrer Ronald
Bartz C. T.
Hyatt John E.
Hydro-Gear Limited Partnership
Jarosik Gary R.
McDonough Thomas C.
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