(under subclass 452) Apparatus comprising a linkage means disposed between the earth working element and the frame (1) which acts to hold the earth working element in a raised position by a link passing over a center position such that the movement due to the weight of the earth working element acts to hold it in raised position or (2) which acts to hold the earth working element in one position by a pair of links assuming a substantially in-line position (i.e., toggle).
SEE OR SEARCH THIS CLASS, SUBCLASS:
499, for tools which include a spring device for alternately biasing a tool in opposite directions during operation.
506, for spring-assisted or spring actuators which may include a spring device for biasing the actuator to raise or lower the tool.
