Power plants – Pressure fluid source and motor – Input pump and rotary output motor system having...
Reexamination Certificate
2002-07-31
2004-06-29
Look, Edward K. (Department: 3745)
Power plants
Pressure fluid source and motor
Input pump and rotary output motor system having...
C060S494000
Reexamination Certificate
active
06755019
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to hydrostatic transaxles.
Hydrostatic transaxles (“HSTs”), including integrated hydrostatic transaxles (“IHTs”), are known in the art and are more fully described in, among others, U.S. Pat. No. 5,314,387, which is incorporated herein by reference in its entirety. Generally, an HST includes a center section or the like on which is mounted a hydraulic pump and a hydraulic motor. The hydraulic pump and the hydraulic motor each carry a plurality of reciprocating pistons that are in fluid communication through porting formed in the center section. As the hydraulic pump rotates, the pump pistons move axially as they bear against an adjustable swash plate where the degree of axial movement depends upon the angular orientation of the swash plate. Axial movement of the pump pistons forces a hydraulic fluid through the porting, which forces the motor pistons against a thrust bearing to thereby rotate the hydraulic motor. As the hydraulic motor rotates, hydraulic fluid is returned to the hydraulic pump through the porting. In this manner, the rotation of the hydraulic pump is translated to the hydraulic motor and the rotation of the hydraulic motor may be used to drive one or more axles of a riding lawn mower, small tractor, or the like.
Zero-turn, hydrostatic transaxles (HZTs) are also known in the art. Generally, an HZT is utilized in connection with a vehicle to provide for the independent control of each of the drive wheels of the vehicle. By way of example, HZTs are described in U.S. Pat. Nos. 5,078,222 and 6,283,235 which are incorporated herein by reference in their entirety. Additionally, Eaton has developed and marketed HZTs as their models
771
and
781
. The Eaton model
771
is an assembly with one pump and one motor where two 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
but joined together to make one assembly.
SUMMARY OF THE INVENTION
A bypass mechanism for a hydrostatic transaxle comprising a casing in which is carried a hydraulic motor that rotates on a motor running surface of a center section. The bypass mechanism includes a bypass actuator having a first end that extends from the casing and a second end that extends through an opening in the center section adjacent to the motor running surface. Connected to the bypass actuator is a bypass arm that is adapted to rotate the bypass actuator to lift the hydraulic motor from the motor running surface of the center section. A first retaining ring attached to a first groove formed in the bypass actuator adjacent to an exterior surface of the casing and a second retaining ring located in a housing bore adjacent the first retaining ring maintains the position of the bypass mechanism relative to the transaxle components.
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 that are indicative of the various ways in which the principles of the invention may be employed.
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Hydro-Gear Limited Partnership
Kershteyn Igor
Look Edward K.
Neal Gerber & Eisenberg LLP
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