Normal Brake Servovalve
Figure 013
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Normal Brake Servovalve - Static Characteristics
Figure 014
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Normal Brake Servovalve - Flow Characteristics
Figure 015
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INTENTIONALLY BLANK
1 1
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Normal Brake Servovalve - Schematic
Figure 016 (SHEET 1)
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Normal Brake Servovalve - Schematic
Figure 016 (SHEET 2)
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-
the pressure of the slide valve on the flapper becomes the same as the magnetic force on the flapper
-
the flapper moves away from the nozzle 1 and goes back to its initial position
-
the slide valve stays at the set position.
When the control current to the coil is decreased to the minimum (anti-skid control):
-
the flapper moves nearer the nozzle 1
-a larger pressure decrease occurs across jet 2 than jet 1
-
the pressure at the one end of the slide valve is more than the pressure at the opposite end
-
the slide valve moves to connect port B to port C.
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(Ref. Fig. 017, 018)
The safety valve is a hydraulic valve that automatically closes when the
flow of fluid through it is more than a specified limit.
The valve has a body that has a bore through the center. Two other bores,
the inlet and outlet ports, connect to the center bore. The center bore
has different diameters:
-
the large end holds a valve and a spring
-
the small end supplies a seat for the valve.
A threaded plug keeps the valve and spring in position and seals the open end of the center bore. The spring keeps the valve away from the seat. The valve has an external flange and an internal bore. Holes go through the flange and another hole goes through to the bore.
With the unit pressurized and no flow from the outlet port, the pressures in chambers X and Y are equal. The spring holds the valve in the open position. When fluid flows through the holes in the valve flange to the outlet port, the pressure in chamber Y decreases. The pressure in chamber X moves the valve nearer to the valve seat. The flow of fluid around the valve to chamber Y controls the rate of travel of the valve. When the flow from the outlet port stops, the pressures in chambers X and Y become equal and the valve stays opens.
If the fluid flow from the outlet port is more than the specified limit, the pressure in chamber X becomes more than the pressure in chamber Y. This causes the valve to move against the valve seat and prevents fluid flow from the outlet port. The pressure in chamber X keeps the valve closed.
If the threaded plug is manually operated, the pressure in chamber X is released and the spring moves the valve back to the open position.
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Safety Valve
Figure 017
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Safety Valve - Schematic
Figure 018
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K. Tachometer
(Ref. Fig. 019)
A tachometer, held in a carrier, is installed in each axle of the MLG. A drive shaft connects the tachometer to the related wheel.
The tachometer has a casing with a front end plate. A drive shaft comes out of the end plate. The casing has an electrical connector and contains a stator assembly and a rotor assembly. The stator assembly includes a toothed ring, a coil assembly and four permanent magnets. The coil assembly connects to the pins of the electrical connector. The rotor assembly includes a rotor and its drive shaft. A drive coupling is attached to the end of the shaft.
When the related wheel turns, the rotor causes an alternating current to flow in the coil assembly. The frequency and the amplitude of the current is in proportion to the wheel speed.
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Tachometer
Figure 019
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