Semi-trailer Lifting and Steering Systems
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Ingenious New Device for Controlled Load Superimposition With Novel Arrangement of Casto ring Front Trailer Wheels
VARIATION of the superimposed load in an articulated outfit is one of the features outlined in a recent patent specification, in which is also described a novel steering arrangement for the front wheels of the trailing unit. Machines of this type cannot definitely be defined, because when there is no superimposition of weight they are tractors and trailers, whilst, when the lifting gear is brought into operation to its fullest extent and the forward trailer wheels are raised from the ground, they are, in effect, articulated outfits. For simplicity, therefore, we will, in outlining the features of this invention, refer to the two units as the tractor and the trailer.
Full particulars of the arrangement are contained in specification No. 463,510, by J. Donaldson-Hudson, 19, Lightbody Street, Liverpool, 5. Its main points can be seen in the accompanying drawings.
The drawbar is of immense rigidity and incorporates an hydraulic cylinder, which, when supplied with fluid from a pump mounted at the front, depresses the front end of the bar, thus transferring the weight of the load and trailer from the front trailer wheels to the tractor driving wheels. Provision is made for screw adjustment of the effective length of the vane mechanism.
Of novel design, the front wheels of the trailer, of which • there may be a considerable number .mounted, adjoining each other, on a common aide, are carried in an inverted U-shaped frame, resembling that used for the front roll of a road roller. This has a material castor action and is free to pivot in its support. The last-named is secured to semielliptic springs, on which the trailer frame is suspended.
It is clear, then, that when the outfit is rounding a bend, the front trailer wheels will automatically align themselveS, and follow a truecourse, causing no interference, with the steering. Moreover, they may be employed to carry their full share of the load, or this may be lessened to any desired degree by partial or full transference of weight to the rear tractor wheels.