Motor vehicles – Steering by driving – Independently operable drive motors
Reexamination Certificate
2002-01-25
2003-11-11
Morris, Lesley D. (Department: 3611)
Motor vehicles
Steering by driving
Independently operable drive motors
C074S60600R, C074S607000
Reexamination Certificate
active
06644425
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an apparatus used to connect hydrostatic transaxles and, more particularly, a plate or similar structure used to connect a pair of hydrostatic zero turn transaxles for use on a lawn and garden tractor or similar vehicle. Hydrostatic transaxles are known in the art and generally comprise a hydrostatic transmission mounted in a housing with reduction gearing, one or more output axles and other elements. The term transaxle is used broadly to cover both integrated units, where the hydrostatic transmission is in a common housing and oil sump with the gearing elements, and other designs where the transmission may be formed in a separate housing and oil sump.
Zero turn transaxles are also well-known in the art. One well-known design is the AgriFab Model 2500 transmission. One embodiment of this design is shown in U.S. Pat. No. 5,078,222. This 2500 transaxle generally uses a pair of hydrostatic transmissions, each of which drives a gear reduction to separately power the two vehicle axles. This arrangement permits the vehicle operator to separately drive the two drive wheels independently of one another. Another known zero turn design in the Eaton Model 751, which uses a pump and motor mounted at right angles to one another, with the hydraulic pump, motor and axle mounted in a housing. Obviously, a vehicle requires a pair of such zero turn units mounted side by side to drive the two drive wheels, and the general shape and configuration of the transaxle housing is dictated primarily by the size and shape of the vehicle frame, and similar factors.
Zero turn transaxles are generally manufactured separately from the vehicles and sold to a vehicle manufacturer for incorporation into the vehicle, such as a lawn mower or similar product. The vehicle manufacturer will generally create custom mounting arrangements to mount the zero turn transaxles separately on the vehicle frame. Each custom mounting arrangement requires costly tooling and can increase the difficulty of assembly for the vehicle manufacturer.
In addition, when two units are mounted side by side and secured to the vehicle frame at the top of the transaxle housing, there is inherently certain torque applied to the units, causing the units to flex with respect to one another, which leads to unnecessary stress and wear on various components. In such designs it has been known to provide an additional member to connect the two units together to prevent such flexing. This additional member also increases the cost of the unit.
SUMMARY OF THE INVENTION
It is an object of the invention to eliminate such problems by providing a single plate device on which both zero turn transaxles can be mounted. Such hydrostatic transaxles may have at least one cap plate on the bottom of the transaxle housing. In one embodiment, the connection plate itself forms an integral part of the two transaxle housings to close off a portion thereof, thereby eliminating the need for an additional cap piece and reducing the overall cost and weight of the unit. In a further embodiment of the invention this plate is secured to two separate and complete transaxle housings.
In a preferred embodiment of this invention, the connection plate is formed of stamped steel, which would have sufficient strength to act as a skid plate for the transaxle assembly, thus eliminating the need for such an additional piece.
A further benefit of this invention is that the two transaxle units can be assembled together with the connection plate, thus simplifying later assembly of the unit.
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Hydro-Gear Limited Partnership
Lum L.
Morris Lesley D.
Neal, Gerber & Eisenberg
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