Linkage mechanism for a trailer steering device

Land vehicles – Wheeled – Articulated vehicle

Reexamination Certificate

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Details

C280S446100

Reexamination Certificate

active

06257611

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a linkage mechanism which is suitable for operative association between a fifth wheel of a drive vehicle and a steerable rear axle of, for example, a trailer unit.
The term “steerable rear axle” is intended to embrace a pivotable rear axle/rear wheel assembly, as well as, pivotable rear wheels connected to a rear axle steerable under the influence of a king pin steering system.
U.S. Pat. No. 5,201,836 discloses a steering mechanism comprising a pivotal lever and a pin extending from a fifth wheel. The pin extends through an arcuate slot and then through an elongated slot in the lever. In use, the pin moves along the arcuate slot whilst moving longitudinally in the elongated slot. U.S. Pat. No. 5,201,836 does not disclose or even suggest a cam collar comprising a substantially round section opening into a substantially elliptic section.
SUMMARY OF THE INVENTION
According to a first aspect of the invention there is provided a linkage mechanism for operative association between a fifth wheel of a drive vehicle and at least one pair of steerable rear wheels, the linkage mechanism comprising a pivotable crank; a cam roller in operative association with the fifth wheel; and a cam collar in operative association with the crank, the linkage mechanism being arranged so as, in a first phase, to convey rotary movement of the fifth wheel to steering movement of the at least one pair of rear wheels and, in a second phase, to permit further rotary movement of the fifth wheel substantially without further steering movement of the at least one pair of rear wheels, characterised in that the cam collar comprises a substantially obround section opening into a substantially elliptic section and the cam roller engages against the obround section in the phase and against the elliptic section in the second phase.
Preferably, a stop means is arranged to substantially prevent further pivotable movement of the crank in the second phase.
Advantageously, the crank and the cam collar form a unitary bell crank.
Even more advantageously, the bell crank is substantially “T”-shaped.
According to a second aspect of the invention there is provided a vehicle having at least one pair of steerable rear wheels and incorporating a linkage mechanism according to a first aspect of the invention.
Preferably, the vehicle comprises a drive vehicle and trailer unit assembly, the trailer unit having the at least one pair of the steerable rear wheels.
The term “trailer unit” is intended to embrace semi-trailers.
Preferably, pivotable movement of the crank is conveyed to the at least one pair of steerable rear wheels by a hydraulic means.
More preferably, the bell crank is substantially “L”-shaped and the hydraulic means comprises a master hydraulic cylinder in fluid communication with a slave hydraulic cylinder.
Advantageously, the bell crank is substantially “T”-shaped and the hydraulic means comprises two master cylinders, each in fluid communication with a respective slave cylinder.
Alternatively, pivotable movement of the crank is conveyed to the at least one pair of steerable rear wheels by a mechanical means.
Preferably, the mechanical means comprises linkage rods or wire ropes.


REFERENCES:
patent: 4244596 (1981-01-01), Chung
patent: 4702488 (1987-10-01), Baillie
patent: 5201836 (1993-04-01), DeWitt
patent: 5536030 (1996-07-01), Bettini
patent: 6152475 (2000-11-01), Poole
patent: 0390288 (1990-10-01), None

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