Automatic scoop positioning device for mechanical shovel

Claim 1

In a mechanical shovel of the type having a scoop, main support arms on which said scoop is pivotally mounted, scoop control means on said main support arms, at least one scoop control actuator cylinder operating said scoop control means and controlling the angular position of said scoop with respect to said main support arms, said scoop control cylinder having a piston dividing said cylinder into first and second chambers, a maiN hydraulic fluid distributor, said main distributor including a scoop control valve the operation of which determines the angular position of said scoop by controlling the flow of hydraulic fluid to said scoop control cylinder, said scoop control valve, having a valve member moving between a first position controlling said valve to direct fluid to said first chamber of said scoop control cylinder to move said scoop toward an emptying position, and a return position controlling said valve to direct fluid to said second chamber of said scoop control cylinder to return said scoop to operating position, biasing means biasing said valve member to an intermediate neutral position where said scoop control cylinder is hydraulically isolated, the improvement comprising an automatic scoop positioning device having latching means, biasing means urging said latching means to latch said valve member in said return position when said valve member is moved to said return position, at least one auxiliary distributor mounted on said scoop control cylinder, said auxiliary distributor being hydraulically connected between said main distributor and said second chamber of said scoop control cylinder, and having a movable distributor member, biasing means biasing said distributor member towards a first position where said distributor directs said fluid to said second chamber of said scoop control cylinder, and an arm rigidly attached to the piston rod of said scoop control cylinder, said arm in operation of said shovel moving said distributor member against the action of said biasing means as said scoop control cylinder moves said scoop in said return direction, said auxiliary distributor diverting said fluid to lock open said latching means when said scoop reaches a predetermined operating position thereby releasing said valve member, stopping said returning movement of said scoop and locking said scoop in said predetermined operating position, said auxiliary distributor member returning to said first position and releasing said latching means when said scoop is next moved to said emptying position, thereby setting said latching means for a subsequent operating cycle, said distributor member of said auxiliary distributor having a hollow portion adjacent one end, said hollow portion being closed by a threaded stopper, a return spring biasing said distributor member to said first position acting on said stopper, said spring reacting against and enclosed by a cap on the end of said auxiliary distributor, said distributor member having two adjacent regions of reduced diameter, said distributor having two cooperating chambers, a first chamber communicating with said main distributor and a second chamber communicating with said second chamber of said scoop control cylinder, said two adjacent regions of reduced diameter forming communicating passageways between said first and second chambers when said auxiliary distributor member is in said first position and interrupting said communication when said auxiliary distributor member is in said predetermined position corresponding to said predetermined operating position of said scoop, a third chamber in said auxiliary distributor, said third chamber communicating with said latching means, radial apertures in said hollow portion of said auxiliary distributor member, said radial apertures forming, together with said hollow portion of said auxiliary distributor member, a passageway communicating with said first chamber and said third chamber, a ball valve in said hollow portion allowing fluid flow only from said first chamber to said second chamber.