Method and apparatus for preventing boom overload

Abstract From the Canadian patent

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 longitudi- Dally 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 mechancially 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 …