Abstract: A boom overload protection apparatus generally used in the protection of derrick-type hydraulic equipment having a boom or power arm for lifting or maneuvering heavy objects. A sensing rod is longitudinally connected to said boom in such manner as to sense boom overload relative to a predetermined allowable degree of flex. As boom overload is sensed, the sensing rod mechanically actuates a sensing valve through tensional or compressive forces applied thereto. The sensing valve, in turn, releases the fluid pressure in pressure release lines connected to overstress valve means. This release of fluid pressure actuates the overstress valve means which is connected in controlling relation to each hydraulic cylinder and winch drive to thereby disable boom stress-inducing operation of the same until such over-stress condition may be relieved.

Abstract: This invention relates to an overload protection apparatus for hydraulic multi-function equipment. It is applicable to equipment sharing a common pressure and return line and in which functional operation of the equipment is interrelated such as to expose certain elements to overpressure conditions. The system includes an overload or overstress valve having a manifold to which the power lines of all of the actuators, except the principal actuator which responds to an overstress condition, are connected. These connections are directed through check valves so that fluid within the lines will be directed only to the overstress valve. A pilot valve connected to the power side of the principal cylinder controls a pressure actuated control valve in the manifold to control and open a passage to the reservoir.