Hydraulic self-leveling device for a loader bucket

Claim 1

A valve assembly which automatically cuts out manual control and governs actuation of the double acting fluid cylinder means of a work bucket to achieve leveling thereof upon boom raising comprising: a fluid pump means pumping high pressure hydraulic fluid; a manual fluid direction control means; a movable mechanical feed back linkage connected to the bucket, and to said valve assembly means; a valve means including: a housing means having a longitudinally extending bore means intersected at axially spaced intervals therealong by first, second, third, fourth and fifth port means, said first port means being connected to said manual fluid direction control means and said second port means being connected directly to said fluid pump means, said third and fifth port means being connected to said double acting fluid cylinder means on the rod side thereof and said fourth port means being connected to said double acting fluid cylinder means on the head side thereof; a valve spool means axially movable in said bore means from a neutral position blocking fluid from all port means except said first and said third port means; a link means connected to said valve spool means for transferring force from said mechanical linkage means to shift said spool means, blocking said first port means, to an operating position communicating said pump means with said rod side via said second and said fifth port means, and to open said head side via said fourth port means to dump, whereby said manual fluid direction means is cut out and said bucket is automatically maintained level to said boom; and a priority system means blocking the operation of said manual fluid control when said valve spool is in a working position.