Trip mechanism for ground-working implement

Claim 1

A tillage implement comprising: a frame; a ground-working tool; means mounting said tool on said frame for free unobstructed movement away from an operating ground-penetrating position toward a fully elevated position above the ground, said means guiding said tool during movement between said positions; said mounting and guiding means including first and second guide means on said frame and first and second follower means on said tool cooperating, respectively, with said first and second guide means so that the instantaneous center of rotation of any two points on said tool at any position intermediate said ground-penetrating position and said fully elevated position falls along a fixed path, said first guide means including a generally rearwardly extending slot on said frame that provides an elongate surface on said frame, said first follower means being movable within said slot along said surface during movement of said tool between said operating ground-penetrating position and said fully elevated position; and biasing means having one end connected to the tool and an opposite end connected to the frame for continuously biasing said tool toward said operating ground-penetrating position in all positions of said tool for yielding resisting movement of said tool away from said position and for returning said tool to said position after movement away therefrom, the effective moment arm of said biasing means, defined by the spacing between the instantaneous center and a line through the connection of said biasing means at any given position, being related to the path of movement of said instantaneous centers of rotation such that said moment arm is of minimum length when said ground-working tool is in the fully elevated position.