737-300 400 500 AMM 飞机维护手册 空气 AIR(78)

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 B.  The function of the bleed valve stop mechanism is to limit the number of revolutions of the bleed valve fuel gear motor to the number of revolutions required for a complete cycle (opening-closing) of the VBV doors. This limiting function supplies the reference position for installing and adjusting the VBV actuators.
 C.  The stop mechanism consists of a housing for a hollow screw which is driven by the bleed valve fuel gear motor. This hollow screw shaft holds the main VBV flexible shaft which connects the bleed valve fuel gear motor to the master ballscrew actuator. A follower nut translates along the screw and stops the rotation of the bleed valve fuel gear motor when it reaches the ends of the screw threads.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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CFM56 ENGINES
737-300/400/500/ /MAINTENANCE MANUAL ////////////////////////
SEE A 
SEE  B 
ATTACHING POINTS STOP MECHANISM TO BLEED VALVE 
A  MOTOR FUEL GEAR BLEED VALVE  A 
TUBE VBV DRAIN 
TUBE VBV OPEN PORT  TUBE VBV CLOSED PORT  A  SEAL SECONDARY 
B 
SEAL O-RING 
OUTPUT SHAFT 
MECHANISM BLEED VALVE STOP  GEAR DRIVE 
Bleed Valve Fuel Gear Motor Location A-A Figure 3  S-M56-MM-1028-(1)-00-B PRIMARY SEAL 

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 ALL  ú ú C01 Page 5 ú Jul 15/96
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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CFM56 ENGINES
737-300/400/500/ /MAINTENANCE MANUAL ////////////////////////
SEE A 
SEE  B 
BLEED VALVE STOP MECHANISM 
A  A 
A  SHAFT OUTPUT BOOT PROTECTING  STOP DOG 
FWD  B  SHAFT FLEX MAIN  SCREW ACME  NUT FOLLOWER 
Bleed Valve Stop Mechanism Location Figure 4  S-M56-MM-0927-(1)-00-B A-A 

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
////////////////////////A / /
CFM56 ENGINES
737-300/400/500/ /MAINTENANCE MANUAL ////////////////////////
D.  The VBV feedback reverser arm is mounted on the bleed valve stop mechanism housing. The feedback reverser arm links the feedback rod from the master ballscrew actuator to the feedback cable, which is routed to the MEC. Through this linkage, the MEC constantly monitors the angular position of the VBV doors.
 4.  Bleed Valve and Master Ballscrew Actuator (Fig. 5)
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 A.  The bleed valve and master ballscrew actuator transfers the driving input from the bleed valve fuel gear motor to the ballscrew actuator system. It consists of a speed reduction gearbox and a ballscrew actuator linked to a hinged door. Speed reduction is consecutively carried out through one pair of spurgears and then by two pairs of bevel gears. The last set of bevel gears drives the ballscrew.
 B.  The ball bearing type screw and nut assembly consists of a screw, nut, ball return tube, a clamp attached to two screws and washers, and 68 balls.
 C.  The ballscrew translating nut is held during rotation by two pins which slide within two slots in the actuator body. The travel of the nut is transmitted to the door by two links. The feedback rod is attached to the feedback lever on the bleed valve door. This permits the MEC to constantly monitor the position of the bleed valve door. The output motion of the first pair of bevel gears is transferred to the other bleed valve and ballscrew actuators by the flexible shafts. The flexible shafts are driven by the two ends of the output gear of this pair of bevel gears.
 5.  Bleed Valve and Ballscrew Actuator (Fig. 6)
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