Abstract: Three embodiments of a hydraulic safety mechanism are adapted to adjust the speed setting for an engine upon a reduction of pressure in a chamber, due for example, to loss of lubricating pressure, overspeeding of the engine or overheating, for example. In each embodiment, a speed control element for the engine is maintained in a normal operating position by a piston and cylinder combination which hydraulically blocks the chamber from the fluid drain in a normal operating position, the piston responding to reduced pressure in the chamber by communicating the chamber with the drain the piston thereby being hydraulically unlatched and permitting the speed control element to be repositioned to a reduced speed setting. A restrictive orifice, preferably of variable size and self-cleaning construction, regulates communication between the hydraulic circuit and the chamber. In another embodiment the safety mechanism includes a solenoid and accumulator chamber to adapt it for remote operation.

Abstract: A pneumatic control system is described including a plurality of annunciators in which movable shuttle elements indicate normal and abnormal conditions. In the event an abnormal condition is sensed causing the shuttle element in any of the annunciators to move to the abnormal position, a bias pressure is applied to brake means in the annunciators to lock the position of the shuttle elements which have not moved. Thus, those of the annunciators which are not associated with an abnormal condition continue to indicate the normal condition.