Trailer Braking Effort Controlled
Page 49
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BRAKING effort on a trailer can be varied in ratio to the load carried, by means of a new control valve introduced by.Feeny and Johnson, Ltd., 134, Ealing Road, Wembley, Middlesex. .
The valve is inserted in the pipe line running to the vacuum power unit of
the trailer. It is just over 1 in. in diameter and about 5 ins. long. The valve head, which is in one piece with the control spindle, is given an extremely fine taper, with a parallel portion at the top, which is made a perfect fit in the bore forming the valve chamber. The bottom of this valve is faced-off truly and seats on the base of the chamber.
With the control handle in the "full power" position, the valve remains seated, and the maximum effort is exerted on the trailer brakes. Moving the lever to the "mediarn"-notch has the effect of raising the valve a distance which has to be accurately determined, as the " leak " to atmosphere is controlled by the gap formed between the periphery of the tapered valve head and the edges of its housing.
The minimum predetermined effort on the trailer brakes is obtained by moving the, control lever to a third notch. As the lever is designed to work over a face cam, the control is infinitely variable from zero to maximum, but for practical purposes three definite stages have been provided.
It is simple, reasonable in price, and particularly easy to install.