Land vehicles – Wheeled – Running gear
Reexamination Certificate
1998-06-05
2001-03-27
Johnson, Brian L. (Department: 3618)
Land vehicles
Wheeled
Running gear
Reexamination Certificate
active
06206422
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an agricultural vehicle having a cab resiliently supported on the chassis of the vehicle.
Conventionally, agricultural vehicles, such as tractors, include a chassis rigidly connected to the vehicle wheels. Because it is unsprung, the vehicle chassis follows the contour of the ground. It is common for the cab, or operator station, to be mounted directly on the chassis and to rely only on springing in the operator's seat to improve operator comfort. This however is not entirely satisfactory and it has therefore been proposed to support the cab on rubber mounts that provide an improved degree of cushioning.
A further suspension system, disclosed in U.S. Pat. No. 4,043,584, enables the cab to be resiliently mounted on the vehicle chassis. In the latter proposal, stabilizer linkages are provided on the tractor fore and aft of the cab to limit the movement of the pivotal connection of the stabilizer linkages to the cab to essentially a vertical movement which lies in a vertical plane including the longitudinal centers of the vehicle chassis and the cab. A sway or yaw limiting mechanism as well as a pitch limiting mechanism are provided to limit the pitch and roll of the cab as it moves through the vertical plane relative to the vehicle chassis.
The present invention seeks to provide an agricultural vehicle with cab suspension that has a less complex and less costly suspension geometry.
SUMMARY OF THE INVENTION
According to the present invention, there is provided an agricultural vehicle having a chassis and a cab mounted on the chassis, wherein the fore end of the cab is mounted on the chassis for pivotal movement about a transverse axis but is prevented from moving relative to the chassis in a vertical plane, and the aft end of the cab is resiliently supported on the chassis and is connected to the chassis by means of a linkage that permits movement of the aft end of the cab in a vertical direction towards and away from the chassis while preventing transverse movement of the aft end of the cab.
The terms “fore”, “aft” and “transverse” as used herein are all referenced to the longitudinal centerline of the chassis with the vehicle moving in a forward direction. The term “vertical” refers herein to the direction perpendicular to the rear wheel axle, i.e. the normal to the plane of contact of the wheels with the ground. The term “plumb vertical” is used to mean true vertical as would be indicated by a plumb line. The terms “pitch”, “yaw” and “roll” are likewise referenced to the longitudinal axis of the chassis, roll being rotation of the cab about a longitudinal axis, pitch about a transverse axis and yaw about a vertical axis.
As opposed to the cab suspension described in U.S. Pat. No. 4,043,584, which allows both the fore and aft ends of the cab to move vertically relative to the chassis, the suspension of the present invention fixes the fore end and only allows movement of the aft end of the cab. In other words, the cab in the present invention can pivot at its fore end about a transverse axis but cannot, as a whole, move vertically on the chassis without pitching.
The invention recognizes that the operator seat is located well back in the cab and it is at the back of the cab that movement is required to provide operator comfort. The fore end of the cab on the other hand contains the steering and other control mechanisms and allowing vertical movement of the cab at its fore end merely introduces complexity without offering any particular advantage from the point of view of shock isolation.
The movement of the aft end of the cab in relation to the chassis may be constrained to the vertical direction by the use of any suitable form of linkage. For example, a roller may be fixed on the cab to follow a linear track fixed to the chassis. In the preferred embodiment of the invention, however, a Watts linkage is used to connect the aft end of the cab to the chassis.
The Watts linkage preferably comprises a relatively short double arm lever rotatably mounted on the chassis and two relatively long levers extending in opposite directions from the ends of the double arm lever to pivot points fixed to opposite sides of the cab.
It is advantageous for the shorter lever to be vertical and the two longer levers to be substantially horizontal when the vehicle is at rest on a level surface.
It is preferred for the mounting at the fore end of the cab to be a gimbal mounting that allows the cab to roll and pitch relative to the chassis and to provide a generally transversely extending rod (herein termed a Panhard rod) connected at its one end to the chassis and at its other end to a point on the cab. If the Panhard rod is of variable length, then by shortening and lengthening the effective length of the rod, the cab can intentionally be made to roll relative to the chassis. If a level sensing means is provided in the cab, then its output signal can be used to set the length of the Panhard rod so that the cab may remain plumb vertical when one wheel of the vehicle is in a furrow or when driving along a banked surface.
The effective length of the Panhard rod may in this case be varied by rotating a lever or an eccentric connecting one end of the rod to the chassis or to the cab.
The aft end of the cab may be resiliently supported on the chassis by means of two springs located under the aft end of the cab. Damping of oscillations can be effected by means of hydraulic shock absorbers within the springs or by means of rubber bushes built into the various pivots of the Watts linkage.
It is also possible to incorporate a spring and damper into the Panhard rod to allow some degree of damped roll as the vehicle is being driven.
The present invention also provides, in accordance with a second aspect, an agricultural vehicle having a chassis, lifting equipment, and a cab mounted on the chassis, wherein one end of the cab is mounted on the chassis for pivotal movement about a transverse axis but is prevented from moving relative to the chassis in a vertical plane and the other end of the cab is releasably supported on the chassis, wherein coupling means are provided on the said other end of the cab for connection to the lifting equipment of the vehicle, Lo permit the cab to be pivoted about its said one end relative to the chassis by the action of the lifting equipment.
The provision of a fixed pivot at one end of the cab, preferably its fore end, allows the cab to be tilted away from the chassis to provide access for servicing and maintenance. The second aspect of the invention allows advantage to be taken of such a cab suspension geometry and the existence of lifting equipment on the vehicle, to simplify the task of gaining access to components of the chassis lying beneath the cab. In particular, it is possible to attach the adjustable top link of a three point hitch of a tractor to its cab to support the weight of the cab as it is disconnected at its other end from the chassis.
REFERENCES:
patent: 4043584 (1977-08-01), Wagner et al.
patent: 4440437 (1984-04-01), Hahm et al.
patent: 4558881 (1985-12-01), Manteufel
patent: 4776606 (1988-10-01), Stephenson et al.
patent: 4805322 (1989-02-01), Lemire et al.
patent: 4817730 (1989-04-01), Winter
patent: 5346018 (1994-09-01), Koster
patent: 5404958 (1995-04-01), Weiss
patent: 5458359 (1995-10-01), Brandt
patent: 0121968 (1984-10-01), None
patent: 1244296 (1971-08-01), None
patent: 1403751 (1975-08-01), None
patent: 1485350 (1977-09-01), None
patent: 2129379 (1984-05-01), None
patent: 8703259 (1987-06-01), None
patent: 9308065 (1993-04-01), None
Johnson Brian L.
Miller Larry W.
New Holland North America Inc.
Stader J. William
Winner Tony
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