BALL BEARING 2974677 - Caterpillar

Boom Raise (Low Speed)
When the joystick for the boom is moved less than half of the travel distance for BOOM RAISE, low pilot oil pressure is supplied to boom I control valve (7) and boom II control valve (14) .When the boom is raised at a low speed, boom I control valve (7) opens and boom II control valve (14) remains closed. The force of spring (26) and spring (28) in boom I control valve (7) is less than the force of spring (27) and spring (29) in boom II control valve (14) . Because of the low pilot oil pressure, boom I control valve (7) will open and boom II control valve (14) will remain closed.The oil delivery from drive pump (22) now flows to the head end of boom cylinders (1) . Without the oil delivery from idler pump (23) , the cylinder rod movement slows down when the boom is raised. The low speed operation of the boom is performed.Boom Priority
Illustration 3 g01429955
Hydraulic schematic for BOOM RAISE and STICK IN (7) Boom I control valve (39) Stick I control valve (14) Boom II control valve (20) Boom priority valve (40) Stick regeneration valve (41) Stick II control valve (42) 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 (20) . The pressure reducing valve for boom priority (20) 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 the pilot control valve for the stick (42) flows through boom priority valve (20) to stick II control valve (41) . 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 (20) to shift gradually.A portion of the pilot oil that flows to stick II control valve (41) from pilot control valve (42) 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