PLATE 5361812 - Caterpillar

Illustration 1 g00526017
(1) Inlet manifold
(2) Orifice
(3) Chamber
(4) Valve
(5) Passage for cylinder return oil
(6) Outlet passage to tank
(7) Passage
(8) Check valve
(9) Passage The charging valve is located in inlet manifold (1) of the implement control valve. The charging valve restricts the flow of the cylinder return oil through outlet passage (6). The valve keeps oil pressure in the return oil passage of the implement control valve. The oil pressure can be used with the makeup valves to prevent cavitation in the cylinders. The charging valve is normally closed and the valve is opened by signal pressure from one of two sources.The first source of signal pressure to the charging valve is from the control valves. When an implement control lever is moved to an operating position, signal oil from the control valve spool is sent to the charging valve in inlet manifold (1). Signal oil flows into passage (9), through orifice (2), into chamber (3), and around valve (4). When the signal oil pressure is approximately 1050 kPa (150 psi), valve (4) moves upward. The valve allows the cylinder return oil in passage (5) to flow to the tank through outlet passage (6) without restriction.The second source of signal pressure to the charging valve is from cylinder return oil through passage (7) and check valve (8). When the signal pressure in passage (9) is below the return oil pressure in passage (7), check valve (8) will open. The oil flows to chamber (3) in order to move valve (4) upward. The pressure that is required in order to move valve (4) is controlled by the pressure that is needed for the makeup valve. Also, the pressure is controlled by the oil line restrictions in the hydraulic circuit.Orifice (2) is used in the circuit in order to keep the return oil in passage (7) from going to the drain. The orifice controls the loss of pressure so that the return oil pressure to the charging valve is constant.