Harvesters – Motorized harvester – Including motorized vehicle causing transit of harvester
Reexamination Certificate
1998-07-21
2001-01-09
Will, Thomas B. (Department: 3671)
Harvesters
Motorized harvester
Including motorized vehicle causing transit of harvester
C280S124141
Reexamination Certificate
active
06170242
ABSTRACT:
TECHNICAL FIELD
The present invention relates to lawn and garden machines, in particular, to lawn mowers.
BACKGROUND
In a popular typical lawn mower design, the rider sits atop a four wheeled machine powered by an internal combustion engine. One or more blades swing about a vertical axis within a cutter deck attached to the machine, to cut grasses as the mower moves across a lawn or other turf.
The present invention is described here in terms of its application to a transmission-steerable commercial riding mower, for which it is especially useful. Such mowers are typically driven by independent hydraulic motors connected to the rear drive wheels. The front wheels are freely pivotable casters. Directional control, or steering, is obtained by differently varying the speed of the two rear wheels. It is consequently important that good traction be sustained between the rear wheels and the earth surface, especially when the mower traverses a slope, since gravity tends to pivot the front of the mower downhill. It is also important that any lawn mower maintain an evenness of grass cut. Cutter decks are typically either rigidly fixed to the underside of the mower, or they are suspended so they “float” —that is, they hang at a fixed elevation, but move upwardly upon contact with a rise in the soil surface.
Lawn mowers are generally intended for use on lawns and other surfaces which are level or gently undulating. Therefore, in most typical three and four wheel riding mowers heretofore, the wheels are directly fastened to the frame of the mower machine. However, then any vertical force or displacement on a wheel of the mower is transmitted directly to the frame (or chassis) of the machine. The frame of the mower will tilt and rise and fall according to the effects of one of the wheels. So, under certain conditions the chassis vertical motion will undesirably change the elevation of the cutter deck with respect to the lawn being cut. Another undesirable effect of lifting or tilting of the mower chassis is loss of wheel traction which is critically important in transmission steerable machines. And, undue bumpy up and down motion is discomforting to the operator.
For mowers intended for use on rougher terrains, designs have been employed which seek to mitigate the adverse effects of undulations. Among such are front and rear wheel axles which tilt about a center pivot. But, in machines with a center pivot axle, when a wheel rises, the center pivot point and the whole end of the frame necessarily also rise, albeit to a lesser degree than when the wheel is fastened directly to a frame. Therefore, there is a continuing need for further improvements in suspension systems in self-propelled lawn mowers.
SUMMARY
An object of the invention is to provide lawn mowers with drive wheel and suspension system combinations which minimize unwanted motion of the mower chassis due to turning and to traversing bumps and uneveness. Another object of the invention is to improve the constancy of contact of mower drive wheels with the surface of the earth, when a mower traverses undulating surfaces, particularly in transmission-steered mowers.
In accordance with the present invention a lawn mower has a cutter deck, a prime mover, one or more wheels at one end of the mower chassis, and a pair of drive wheels at the other chassis end powered by the prime mover. Each drive wheel is part of a drive wheel assembly, attached to either side of the chassis by suspension means which comprise a spring. The suspension means enables each drive wheel to move vertically up and down, respectively with and against force exerted by the spring, independently of the movement of the opposing drive wheel. In the generality of the invention, either the front wheels or rear wheels of a mower may be the driven wheels. In one embodiment, the mower has two front wheels and two rear wheels and the cutter deck hangs between them; each rear drive wheel is part of an assembly comprising a motor independently driven by the prime mover, and the mower is steered by varying the relative speed of the opposing drive wheels. In another embodiment, the four wheel mower has front drive wheels and conventional steerable rear wheels; and, the cutter deck is cantilevered from the front end of the machine.
In further accord with the invention, the suspension means for a mower is comprised of upper and lower link assemblies which are pivotably mounted at inner ends to the chassis and at the outer ends to the wheel assembly. In one embodiment, the lengths of the upper links and the lower links are equal, and run parallel. In another embodiment, the links are not parallel, and the lower links are longer than the upper links, preferably to an extent which makes the roll center of the machine lie at the same elevation from the earth surface as the center of gravity of the machine. In another embodiment, the spring of the suspension system is compressed when the machine is static, to thereby lessen the change in elevation of the chassis due to the operator mounting and dismounting the machine. In another aspect of the invention, each spring-suspended wheel assembly is connected to a nearby portion of the deck, so when a wheel moves upwardly against the spring, the deck portion is correspondingly lifted from its basic position.
The invention reduces the amount of vertical motion of the chassis, for example when the mower traverses uneven ground and one or both drive wheels rise or fall. As a result there is less vertical motion induced into the cutter deck. There is better contact of the drive wheels with the surface when traversing undulations, for transmission steerable machines directional control of under adverse conditions is improved.
The foregoing and other objects, features and advantages of the invention will become more apparent from the following description of the best mode of the invention and accompanying drawings.
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Kov{acute over (a)}cs Arp{acute over (a)}d F{acute over (a)}b
Michael & Best & Friedrich LLP
Will Thomas B.
LandOfFree
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