Patent ID: 6134887
Filing Date: 2000-10-24
Classification: E02F,F15B

Abstract:
A hydraulic control circuit for working members of a machine comprising a first assembly including first hydraulic linear actuators (1, 2) for operating respective first working members, and a second assembly including second hydraulic linear actuators (3-8) for operating respective second working members, the hydraulic circuit comprising first and second control sections (9, 10) for the first (1, 2) and second (3-8) hydraulic linear actuators, respectively, and including respective first (21, 22) and second (23-28) hydraulic spool valves, the spool of each of which can be set in a first end position corresponding to the displacement of the associated actuator in a first direction, in a central, null position, and in a second end position corresponding to the displacement of the associated actuator in a second direction opposite to said first direction, hydraulic pressure fluid supply means (11) connected in parallel to said first and second control sections (9, 10) via at least one feed line (13, 30), and a load sensing control circuit (16) associated with the first and second hydraulic spool valve (21-28) of the first and second control sections (9, 10) and operable to control the supply of hydraulic fluid to the first and second actuators in response to hydraulic signals indicative of the respective operating pressures thereof, wherein the second control section (10) includes a main hydraulic spool valve (23) and an associated priority hydrostat (20) disposed in the parallel feed line (13) and operable to control a main hydraulic actuator (3) of the second actuators, characterized in that the load sensing control circuit comprises a return line (35) from said main hydraulic spool valve (23) to the feed line (13) downstream of the priority hydrostat (20), and a series/parallel load sensing control valve (36) operable to control the communication between the return line (35) and the feed line (13) as a function of the pressure within the feed line (13), the spool of the hydraulic valve (23) incorporating a check valve (44) acting in the position corresponding to the height pressure movement of the associated main hydraulic actuator (3) controlling a working member, and a regeneration circuit (43) of the load sensing signal being associated with the priority hydrostat (20).