TM 5-3805-260-24Bowl DownWhen the bowl valve spool in control valve (3) is heldin DOWN position (A), the oil from pump (20) in line (16)goes out of the control valve through line (5) into thehead ends of bowl cylinders (2). The DOWN position ofthe bowl valve spool also opens a passage for the oil invent line (8) to go through the control valve to the tank.The pump oil in the head ends of cylinders (2) moves thepistons and rods, connected to the bowl, down andlowers the bowl. The pistons push the oil from the rodends of the bowl cylinders and opens carry check valves(4). The check valves open because the oil in vent line(8) can go to the tank. The rod end oil, pushed throughvalves (4), goes through line (9), through control valve(3), through return oil line (13) into the filter and tank(19).Relief valve (10) in control valve (3) prevents high oilpressure damage to the parts in the oil circuit of pump(20). If pump oil pressure increases to approximately2525 psi ( 177 kg/cm2) (17 425 kPa) the pressure opensthe relief valve and the pressure can not increase anyfarther.Release the control lever and a spring on the bowlvalve spool moves it to HOLD position (B). Now, thepump oil goes to the filter and tank and the passage forthe oil in vent line (8) is closed. The stopped oil in ventline (8) keeps the carry check valves closed. The bowlcan not go down because the pistons, in the bowlcylinders, can not push oil through the closed carrycheck valves.Bowl Up (No Illustration)Hold the control lever in the UP position and it keepsthe bowl valve spool in UP position (C), in control valve(3). The UP position of the bowl valve spool opens apassage to the tank for the oil in vent line (8) and alsolets the pump oil, in the control valve, go through line (9)to carry check valves (4). With vent line (8) open to thetank, the pump oil in line (9) goes through carry checkvalves (4) into the rod ends of bowl cylinders (2). Thepump oil moves the pistons and rods, connected to thebowl, up to lift the bowl. The pistons push the oil out ofthe head ends, of the bowl cylinders, through line (5) tocontrol valve (3). The oil goes through the control valveand through return oil line (13) into the filter and tank(19).Release the control lever and the spring on the bowlvalve spool moves it to HOLD position (B). The HOLDposition of the bowl valve spool closes the passage tothe tank for the oil in vent line (8) and carry check valves(4) close. The movement of the bowl stops when thecheck valves close and the bowl control lever must bemoved to either lower or lift the bowl.4-17
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