Raising the Bowl
 | |
| Illustration 1 | g00430760 |
The Bowl is in the RAISE Position. (1) Control lever (2) Pilot valve (3) Oil from cushion-hitch pump to pilot valve (4) Line to the filters and to the hydraulic tank (6) Pilot oil to the control valves (7) Line to rod end of the bowl cylinders (8) Check valve group (two) (9) Line to head end of bowl cylinders (11) Control valve (12) Line to filters and hydraulic tank (13) Valve spool for ejector cylinders (14) Carry-check valve (two) (15) Blank (16) Return line to pilot valve (17) Bowl cylinder (two) (18) Check valve (two) for venting the oil (19) Balance line (20) Cushion-hitch pump (21) Vent line from carry-check valves (22) Hydraulic oil tank (23) Filter in hydraulic tank (24) Line from small section of the hydraulic pump to the steering system (25) Vane pump (26) Valve spool for bowl cylinders (27) Passage (six) (28) Relief valve (41) Pressure reducing valve (42) Dead engine pressure to the pilot valves (43) Shuttle valve (A) LOWER position (B) HOLD position (C) RAISE position (AA) Pressure oil from the cushion-hitch pump (BB) Pilot oil (CC) Blocked oil (DD) Oil at tank pressure | |
When control lever (1) is moved to RAISE position (C) pilot valve (2) sends a pressure signal to spool (26) through line (6) . This shifts valve spool (26) to the RAISE position for the bowl. Oil from the pump flows around valve spool (26) and through line (7) to check valve group (8) .
Oil passes through check valve group (8) . When pressure in line (7) is greater than the pressure in the rod end of bowl cylinders (17) , check valve (14) will open. This allows the pump oil to flow to the rod ends of bowl cylinders (17) . The oil pressure in the rod end of the cylinders moves the pistons upward in order to lift the bowl. The pistons push the oil out of the head ends of the cylinders through line (9) to control valve (11) . Then, the oil flows around valve spool (26) through the control valve through line (12) . Next, the oil flows to filter (23) and into hydraulic tank (22) .
When the control lever for the bowl is released, springs in pilot valve (2) shift control lever (1) to HOLD position (B) . Then, pilot valve (2) vents the pressure in line (6) to the oil tank. This will allow the springs on the end of spool (26) to shift spool (26) to the NEUTRAL position or to the HOLD position.
There is blocked oil in lines (7) and (9) . Line (19) is common to the rod end of each bowl cylinder. Line (19) equalizes the pressure between the two bowl cylinders.
When the bowl is all the way up and control lever (1) is not released, the pressure of the pump oil increases. When the pressure of the pump oil reaches 15000 ± 350 kPa (2175 ± 50 psi), relief valve (28) opens. When relief valve (28) opens, pump oil is diverted to the oil tank. The oil pressure remains constant.
When valve spool (26) is in HOLD position (B) , oil is blocked in line (21) between the valve spool and check valves (18) . Carry-check valves (14) cannot open and the bowl stays in RAISE position.
There is a small amount of oil that continually passes through passages (27) in control valve (11) .
Note: When the bowl is all the way up and the engine is shut off, the bowl will drift faster than if the engine is running.
Lowering the Bowl
When control lever (1) is moved to LOWER position (A) , pilot valve (2) sends a pressure signal to spool (26) . This signal is sent through line (16) . This signal shifts spool (26) in order to lower the bowl. Pump oil flows around valve spool (26) and through line (9) . Then, the oil flows into the head ends of bowl cylinders (17) . The oil pressure from the pump moves down the pistons. This moves down the bowl. At the same time, pressure in the spring cavity of check valve (14) is vented to the oil tank through line (21) and across spool (26) . Pressure from the rod end of bowl cylinders (17) act on the shoulder of check valve (14) . This opens check valve (14) . This allows oil to flow from the rod end of bowl cylinders (17) into line (7) . Then, the oil flows across spool (26) back to oil tank (22) through filter (23) .
When the oil in line (21) has been vented around valve spool (26) into the oil tank (22) , vent check valves (18) open.
The oil from the rod ends of bowl cylinders (17) is moved through line (7) , around valve spool (26) , through the control valve and line (12) into filter (23) , and then to hydraulic tank (22) .
When control lever (1) is released, springs in pilot valve (2) move control lever (1) to HOLD position (B) . This vents the oil pressure in line (6) to the oil tank. This allows the springs on the end of spool (26) to move spool (26) to the NEUTRAL position or the HOLD position.