Harvesters – Motorized harvester – Including motorized vehicle causing transit of harvester
Reexamination Certificate
1999-07-15
2001-02-13
Pezzuto, Robert E. (Department: 3671)
Harvesters
Motorized harvester
Including motorized vehicle causing transit of harvester
Reexamination Certificate
active
06185920
ABSTRACT:
FIELD OF THE INVENTION
This invention pertains to small, low horsepower utility tractors, with articulated steering, on which an operator stands or sits near the radius of turn to reduce the tendency of having to lean into sharp turns for better control of the tractor.
BACKGROUND OF THE INVENTION
Typically, commercial lawnmowers are capable of traveling over the ground at relatively high speeds of between five and six miles per hour, are relatively stable on slopes and unpaved surfaces, and are able to move up close to objects such as trees and shrubs with sufficient control to avoid damaging the plants, and are able to extend the mower deck under fences and shrubs where ground clearances are restricted. Usually the operator will be seated or standing near the turning center of the mower so as to minimize the centrifugal force he experiences in a tight turn, which not only reduces his ability to control the mower, but also adds to his fatigue during long periods of operation.
A mower of this type is disclosed in U.S. Pat. No. 5,507,138, issued Apr. 16, 1996, entitled “Power Mower with Riding Platform for Supporting Standing Operator.”
High maneuverability is an essential characteristic of commercial landscaping mowers of this type. It is achieved by combining the propulsion and turning functions in driving the wheels. That is, on each side of the machine, independent drive wheels are powered by the engine in either forward or reverse directions. The wheels cannot steer in a conventional manner. Caster wheels are mounted in front of the mower deck allowing the machine to swivel around, turning on an axis between the rear drive wheels. The operator stands or sits at the turning axis to minimize the turning forces on him in tight turns.
A major problem with such mowers is the degree of training and skill required of the operator to efficiently operate the machine. Typically, a pair of hand levers, one on each side of the operator's station, control independent hydrostatic drives powered by the engine. The technique of driving by levers that are pushed or pulled to independently vary the speed and direction of the drive wheels. Is an acquired skill not well within the training and skill of the ordinary person familiar with driving an automobile, where the propulsion and steering are separate functions, and unlikely to be familiar with a system combining the propulsion and steering into one function using separate hand levers.
In addition, such mowers are expensive to maintain. The independent hydrostatic drive systems essentially have duplicate components and controls of non-automotive specifications. When something goes wrong with one of the dual systems, the machine cannot be operated successfully or fixed by automotive type mechanics.
Also, the caster wheels are set out ahead of the mower deck and on spindles that extend above the mower deck limiting the accessibility of the mower under low objects, such as fences, or traveling up close to buildings and trees.
SUMMARY OF THE PRESENT INVENTION
The present invention provides an engine powered, stand-on, compact tractor, which employs a steering wheel in a conventional manner to operate an articulated steering linkage the geometry of which produces the maneuverability for turning in tight quarters of the dual hydrostatic drives without the skill or training required to operate those machines proficiently.
In accordance with the invention, a light-weight compact tractor vehicle has a frame supporting a pair of drive wheels at one end and a pair of steerable wheels at the other end, spaced about as far apart as the vehicle track width, that is the wheel base is about the same as the overall width. A steering wheel operates a steering linkage, the geometry of which is such with the axles, frame and drive wheels, that at full lock of the steering wheel, the steerable wheels are turned the maximum angle defined by having their axes both intersect on or near the end of the drive wheel spindle on the inside of the turn.
The engine and transmission are mounted on the frame forward of the operator near the center of gravity of the vehicle for better stability. The transmission is above the engine. A jack shaft and drive belt pulley system connects the output of the engine drive shaft to the input shaft of the transmission. A clutch and brake pedal combined controls a cable and pulley system for operating the clutch at the same time as releasing the parking brake. In the preferred embodiment, the transmission is a hydrostatic trans-axle with a swash plate controlled by a hand lever for forward or reverse and variable speed delivered through a differential gearing housed in the transmission. Opposed axles, or output shafts, carry sprockets for driving a chain traveling down to sprockets on each drive wheel. An axle bar supports fixed wheel spindles on opposite sides of the frame rotatably mounting the drive wheels. Independent braking of the drive wheels enhances the steering that is in either a right or left full turn, the inside wheel may be braked simultaneously to achieve a tighter turning radius.
The steering linkage has a double acting actuator that is moved by the steering wheel transversely relative to the frame, right or left, imparting a rectilinear motion at either end which is translated into angular motion of the steerable wheels. Axle bars, which are allowed to rock up and down on a pivot to the frame for oscillations over uneven terrain, support spindles shafts on which the wheels are mounted. A pair of links connect the opposite ends of the actuator to spindle arms fixed to the spindle shafts for turning them either the right or left from a straight-ahead position. The length of the spindle arms in relation to the length of the links connecting them to the actuator, and the spacing of the link pivotal connection to the actuator and the pivotal mounting of the spindle shafts, which are closely adjacent and in front of the axle bars, is part of the geometry whereby the spindle shaft of each steered wheel, when in a full lock, right or left position, points toward the drive wheel on the inside of the turn so their axes intersect near the drive-wheel hub, but a least within a turning zone encompassing a horizontal rectangle of about 25% of the wheel base length in the longitudinal direction and 20% of it in the lateral direction, the mid-point of the turning zone thus being essentially the rear axle centerline.
The importance of this steering linkage geometry during full turns is to minimize tire scuffing, reducing tire life, but also the steered wheels lose some of their traction in turning if they are required to track outside the optimum turning radius.
Conventional steering geometry cannot achieve these objects because the tighter the turn radius, the worse the tire scuffing becomes due to the poor steering geometry.
Further, in the application of the invention as a lawnmower, a mower deck is provided, mounted beneath the frame of the vehicle and extending laterally between the front and rear wheels. Belt-driven blades rotating in the deck are driven in a conventional manner and discharge the grass clippings through a rear-housing projection between the rear wheels. Conventional means are provided for adjusting the height of the deck which floats with respect to the frame for the proper height of cut relative to the ground by means of a manual control accessible from the operator's position.
In accordance with this aspect of the invention. the rear discharge of the mower deck exhausts the grass clippings into a baffle housing, which is part of the tractor chassis, in that it is mounted on the tractor frame and has diverging baffle elements designed to distribute the grass clippings uniformly across the rear of the machine behind the drive tires so as to avoid the wind rowing problem of conventional mulching mowers.
Additionally, a three blade mower deck is provided in which one blade is rotated in a direction opposite to the other blades. Blade chambers have curved baffles discharging the clippings to the baffle ho
Intellprop L.C.
Lonmore L.C.
Pezzuto Robert E.
Toliver, Esq Jack E.
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