Controlling Exhaust Brakes
Page 78
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ACCORDING to patent No. 886,541, H an exhaust-operated brake be applied at a high engine speed, the backpressure applied to the engine may be high enough to blow oil past the crankshaft seals. To avoid this is the object of a modification shown in the patent. (David Brown Tractors, Ltd., Meltham Mills, Huddersfield.)
The essence of the scheme is to set a definite upper limit to the developed pressure. Referring to the drawing, an exhaust throttling system of knewn type comprises an operating pedal (1) which can close a valve (2) in the outlet (3) of the exhaust manifold.
The generated pressure is limited by the inclusion of a small pre-compressed spring (4) in the pedal system. In the closed position (as shown) the lever (5) is held by the spring against a stop (6) on the rod. But if the pressure be great enough, the valve head can be forced off its seating. This action limits the maximum pressure but has no effect at the lower end of the speed range.