Manifold Assembly - Selector Valve (2524GM) Figure 016
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Selector Valve - Schematic Figure 017
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Restrictor Valve (2538GM)
Figure 018
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Check Valve (2537GM)
Figure 019
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When electrical or hydraulic power is not available the solenoids are de-energized and the spool is centralized by spring tension.
(1) Manifold Block
The manifold has drillings which connect to external ports and hydraulic connectors. Other drillings connect specified ports together. The manifold has two faces on which the selector valves are installed. The faces have fluid ports which connect to the selector valve ports (annuli).
To centralize the spool, hydraulic pressure is supplied to the pressure port and passes through annuli 3 and the pilot valve to both end caps. Clearances between the spool lands and the main valve annuli 2 and 4 connects the service ports to the return port.
(a) Solenoid
When the door solenoid 'A' is energized, the ball valve moves away from its seat to close the pilot valve orifice. Hydraulic fluid is then sent through annuli 5 to return. Because the pressures in the end caps are different, the spool moves to the right to open annuli 4. Ports 'D' and 'L' are connected to the pressure supply directly across the open spool. The return from the service ports 'C' and 'K' goes through annuli 2 and annuli 1 to the return gallery. The return gallery connects to annuli 5 and the pressure return line.
When the door solenoid 'A' is de-energized and hydraulic pressure is available the ball valve is moved on to its seat to close the valve. This stops the flow of return fluid and hydraulic fluid is sent through the pilot valve to the end cap. The spring tension and fluid pressure return the spool to the central position. Both of the solenoids operate in the same way.
(2) Restrictor Valve (2538GM)
The restrictor valve decreases the fluid pressure to reduce the MLG extension speed. When the MLG is retracted the restrictor valve lets the return fluid flow fully.
The restrictor valve has a cylindrical body with threaded connections. The body holds the valve plunger and a spring. The spring pushes the valve plunger on to an internal seat in the valve body. The valve plunger has holes to let fluid flow through it.
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Hydraulic fluid pressure (in the direction 'X') moves the valve plunger away from the seat and lets the fluid flow through the body. When fluid flows in the opposite direction, the valve closes and lets fluid flow only through the valve plunger. This decreases the flow through the body.
(3) Check Valve (2537GM)
The check valve maintains the supply pressure to the door actuator when the L/G is in operation.
The check valve has a cylindrical body which has hydraulic connections (of different dimensions) at each end. The body contains a spring that holds a poppet against a face in the body. When the check valve is in the closed position, the metal-to-metal contact between the poppet and the valve seat makes the internal seal.
The hydraulic fluid pressure on the inlet side of the valve pushes against the face of the poppet. When the pressure of the hydraulic fluid is greater than the pressure of the spring, the poppet moves away from the body face. The hydraulic fluid passes trough the valve and goes out through the outlet. If the pressure on the outlet side of the valve is more than that at the inlet side, the spring force closes the poppet. This action makes sure that hydraulic fluid can only flow in one direction.
An arrow on the body shows the direction in which the fluid flows.
(4) Selector valve 41GA, 40GA
The selector valve is a three-position electrically-operated valve and has:
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two solenoids A and B
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