MOMENT MONITORING SYSTEM FOR HYDRAULIC-PISTON TYPE CRANES

Cranes, forklift trucks, and other burden manipulation apparatus generally comprise an elongate boom or analagous burden member that exerts a controllably variable moment, as effected through a hydraulic-piston, etc., with respect to the normally stably supported weighty base member of the apparatus. The present invention discloses a moment monitoring system so as to caution or apprise the apparatus operator that the burden member moment has attained an arbitrarily prescribed subcritical-level which is quantitatively below the moment critical-level (i.e., the burden moment at which the base member and the entire apparatus is rendered unstable, tipped, or otherwise rendered inoperative). The moment monitoring system generally comprises hydraulic pressure differential sensing means extending between the two sides of the hydraulic-piston reciprocatable plunger, the differential sensing means being actuatably connected through a ram portion of a reciprocatable hydraulic pump including therewithin an isolated hydraulic metering fluid which exerts variable pressure upon a suitable pressure-responsive device such as a Bourdon-tube, at least one hydraulic-electrical transducer including a said pressure-responsive device and which transducer is electrically connected to a warning indicator for warning the apparatus operator that an arbitrarily prescribed subcritical-level of burden moment has been attained, and yieldable resistance means (such as as weighted pivotal lever) which means increasingly resists effects of the pressure-responsive device at steeper boom angles thereby compensating for progressive decreases in the burden moment critical-level mathematical value coincident with progressively steeper boom angles.