Agricultural implement with spring cushion for vertically adjustable

Abstract

An agricultural implement has a main pull-type frame carrying a first set of ground-engaging tillage tools and a subframe carrying a second set of tillage tools. A lift mechanism including an hydraulic cylinder operated from the operator's position on the tractor pulling the implement adjusts the height of the subframe relative to the main frame to set the working depth of the tools on the subframe. A preload spring cushion mechanism is interposed between the main frame and the hydraulic cylinder to permit the subframe to lift for smaller obstacles and be reset by the spring without actuating the pressure relief valve. The force of the spring assists in resetting the subframe to its desired working depth after the obstacle is passed. In the illustrated embodiment, the spring cushion mechanism has an increasing moment arm as the spring compresses thereby to equalize the resetting force applied to the lift mechanism; and it is preloaded so that the operator can adjust the operating depth of the subframe. The hydraulic system includes a pressure relief bypass valve actuated at a predetermined pressure to permit fluid to flow between the rod and butt ends of the cylinder, permitting the cylinder to extend and the subframe to raise when a larger obstacle is encountered by the tools on the subframe.