SEGMENT GP-SPROCKET 2589791 - Caterpillar

Boom Priority
Illustration 5 g06067958
Hydraulic schematic for BOOM RAISE and STICK IN
(4) Pilot control valve (bucket and boom)
(6) Pressure reducing valve for boom priority
(43) Stick II control valve
(44) Pilot control valve (stick and swing)During combined operations of BOOM RAISE and STICK IN, the pilot oil pressure from the pilot control valve for the boom (4) activates the pressure reducing valve for boom priority (6). Pressure reducing valve for boom priority (6) causes oil flow priority to the head end of the boom cylinders during this combined hydraulic operation.When the joystick for the stick is moved to the STICK IN position, a portion of the pilot oil from the pilot control valve for the stick (46) flows through the pressure reducing valve for the boom priority (6) to the stick II control valve (43). As the joystick for the boom is moved farther from the NEUTRAL position during a BOOM RAISE operation, pilot oil pressure from the pilot control valve for the boom (4) increases. This gradual increase in pilot oil pressure causes the spool in the pressure reducing valve for the boom priority (6) to shift gradually.A portion of the pilot oil that flows to stick II control valve (43) from the pilot control valve for the stick (44) is routed to the hydraulic tank. The pilot oil pressure that acts on stick II control valve (43) decreases. Stick II control valve (43) shifts toward the NEUTRAL position. The amount of oil flow from the main pumps to the stick hydraulic circuit decreases. This action causes a greater portion of the oil flow from the main pumps to flow to the head end of the boom cylinders.Since the pilot oil pressure from the pilot control valve for the boom (4) directly corresponds to the amount of movement or position of the joystick a gradual change to boom priority occurs. Thus, boom priority is controlled by the position of the joystick for the boom and boom priority automatically activates when the joystick reaches a certain position during a BOOM RAISE operation.Boom Lower
Illustration 6 g06067796
Hydraulic schematic for BOOM LOWER
(2) Line (oil flow from boom cylinder rod end)
(3) Line (oil flow to boom cylinder head end)
(4) Pilot control valve (bucket and boom)
(5) Drain line
(6) Spool (boom regeneration valve)
(7) Valve
(8) Boom drift reduction valve
(9) Drain line
(10) Passage
(11) Center bypass passage
(12) Parallel feeder passage
(13) Load check valve
(14) Return passage
(15) Control valve (boom I)
(16) Orifice
(17) Boom regeneration valve
(18) Control valve (stick II)
(19) Line
(20) Port
(21) Pilot line
(23) Drive pump
(24) Idler pump
(25) Pilot pumpIntroduction
When the boom is lowered, oil from drive pump (23) is supplied to boom cylinders through control valve (15).The BOOM LOWER operation contains a regeneration circuit. When the joystick for the boom is moved to the BOOM LOWER position, orifice (16) in boom I control valve (15) and boom regeneration valve (17) are operational in the boom hydraulic circuit. The return oil flow from the head end of boom cylinders flows through boom regeneration valve (8) to the rod end of the boom cylinders. The boom