Decelerating fluid actuator for snowplows and other heavy machinery

This disclosure concerns an invention relating generally to actuators for heavy machinery, and more specifically to fluid actuators (i.e., hydraulic and/or pneumatic actuators) used in snowplows to reposition plow moldboards with respect to the plowing vehicle. A plow including a plowing vehicle and a moldboard has a decelerating fluid actuator which allows adjustable positioning of the moldboard with respect to the plowing vehicle. The cylinder has first and second ports which are successively blocked as the piston is retracted within the cylinder, with the second port being blocked after the first port during retraction. An enclosure is provided outside the cylinder, with the enclosure interior defining a passage between the ports and connecting the ports to a fluid supply. The flow area of the passage between the ports is adjustable to create a restriction. As a result, when the piston begins retraction, the retraction speed is dictated by flow through both ports, and when the piston retracts to a sufficient degree that the first port is blocked, retraction speed is dictated by the flow through the second port and the passage. The size of the passage may be varied by insertion and removal of differently-sized restrictors therein, or by the degree of insertion or removal of a restrictor within the passage. The foregoing arrangement allows the fluid actuator to move the moldboard at a first speed with respect to the plowing vehicle over a portion of its range of motion, and at a lower second speed over the remainder of its motion. Thus, the retraction speed of a moldboard may be reduced as it approaches the plowing vehicle, decreasing the possibility of collision and damage.