CYLINDER HEAD GP 2876829 - Caterpillar

Illustration 4 g03035299
(5) Main control valve
(21) Boom priority valve
(53) Boom regeneration PRV
Illustration 5 g06137632
Hydraulic schematic for BOOM RAISE and STICK IN
(7) Boom I control valve
(18) Pilot control valve
(19) Boom II control valve
(21) Boom priority valve
(40) Stick I control valve
(41) Stick regeneration valve
(42) Stick II control valve
(43) Pilot control valveDuring combined operations of BOOM RAISE and STICK IN, the pilot oil pressure from the pilot control valve for the boom (18) activates the pressure reducing valve for boom priority (21). The pressure reducing valve for boom priority (21) causes oil flow priority to the head end of the boom cylinders (1) 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 pilot control valve (43) for the stick flows through boom priority valve (21) to stick II control valve (42). As the joystick for the boom is moved farther from the NEUTRAL position during a BOOM RAISE operation, pilot oil pressure from pilot control valve (18) for the boom increases. This gradual increase in pilot oil pressure causes the spool in boom priority valve (21) to shift.A portion of the pilot oil that flows to stick II control valve (42) from pilot control valve (43) is routed to the hydraulic tank. The pilot oil pressure that acts on the stick II control valve decreases. The stick II control valve 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 (18) 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 g06137638
Hydraulic schematic for BOOM LOWER with regeneration
(1) Boom cylinders
(2) Line
(3) Line
(7) Boom I control valve
(9) Port
(11) Boom drift reduction valve
(12) Port
(13) Load check valve
(14) Parallel feeder passage
(18) Pilot control valve
(19) Boom II control valve
(23) Idler pump
(24) Pilot pump
(25) Drive pump
(31) Passage
(35) Passage
(45) Passage
(46) Spool
(47) Port
(48) Port
(49) Port
(50) Port
(51) Boom head end pressure sensor
(52) Line
(53) Proportional reducing valve
Illustration 7 g06014369
Boom I control valve (BOOM LOWER with regeneration)
(7) Boom I control valve
(9) Port
(11) Boom drift reduction valve
(12) Port
(13) Load check valve
(14) Parallel feeder passage
(19) Boom II control valve
(26) Spring
(27) Spring
(28) Spool
(31) Passage
(32) Passage
(37) Spool
(38) Spring
(39) Spring
(46) Spool
(47) Port
(48) Port
(50) Drain port
(54) Passage
(55) Return Passage
(56) Passage
(57) Center bypass passage
(58) Passage
(59) Passage
(60) Passage
(61) Check valve
(62) Passage
(63) PassageDuring a BOOM LOWER operation, the oil delivery from only drive pump (25) is supplied to boom cylinders (1) through boom I control valve (7). Boom I control valve (7) operates alone. Boom II control valve (19) has a regeneration circuit that functions during the BOOM LOWER operation. This