737 AMM 飞机维护手册 起落架 LANDING GEAR(57)

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C.  The outer cylinder has a trunnion on each side near the top. Trunnion pins are inserted from inside outward extending into nose gear support brackets, which are mounted on each side of the wheel well. Upon retraction and extension the trunnion pins rotate in spherical bearings in the nose gear mounting brackets. Double lugs, to which the lower drag brace is attached, are near the top on the forward side of the outer cylinder. A steering collar encircles the outer cylinder and is bolted to hold it in an annular recess. The upper torsion link is bolted to a lug on the steering collar. The lower centering cam is in the outer cylinder to mate with the one at the top of the inner cylinder on inner cylinder extension. This centering cam has an annular groove in which the rebound valve piston ring is located. An upper orifice support tube is connected to the outer cylinder. The rebound valve piston ring, in the groove around the upper centering cam, is moved against the top of its annular groove as the inner cylinder extends. The fluid, which is compressed by the diminishing cavity between the upper and lower centering cams, is restricted to escape only through the two small holes in a lip on the piston ring. A small portion of fluid will also escape through the piston rings working gap. The escaped fluid enters a cavity between the upper bearing spacer and the outer cylinder wall. The fluid is then forced through twelve holes, lengthwise in the upper bearing, into the cavity above the inner cylinder. This restricted flow of fluid acts as a snubber to slow the inner cylinder during extension.
500 
32-21-0 Page 2  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  May 15/68 

500  Nose Gear Component Location 
Feb 15/72  Figure 1  32-21-0 
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

Nose Gear Shock Strut Schematic  509 
32-21-0 Page 4  Figure 2 (Sheet 1) BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  Feb 15/72 

509  Nose Gear Shock Strut Schematic 
Aug 15/68  Figure 2 (Sheet 2) BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  32-21-0 Page 5 

Nose Gear Shock Strut Schematic  509 
32-21-0 Page 6  Figure 2 (Sheet 3) BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  Aug 15/68 

D.  Shocks to the nose gear shock strut are absorbed by the restricted flow of hydraulic fluid through the annular space between the orifice and the tapered metering pin and by the restricted flow of fluid through the rebound valve piston ring. (See paragraph C) When the inner cylinder is being compressed, the tapered metering pin, which is attached to the lower support tube in the inner cylinder, moves through the orifice in the upper support tube. This movement of the metering pin progressively reduces the area of the annular space between the orifice and metering pin. The reduction in area results in a diminishing rate of hydraulic fluid flow from the inner cylinder chamber to the upper side of the piston which produces increasing resistance to compression of the shock strut. Landing shocks and shocks incurred while taxiing are absorbed by the increasing volume of hydraulic fluid above the piston which further compresses the volume of compressed air or nitrogen in the upper end of the outer cylinder.
3.  Nose Gear Steering Collar
A.  The nose gear steering collar is at the top of the outer cylinder (Fig. 1). It is held clamped around the outer cylinder, by a bolt, in an annular recess immediately below the trunnions. Both of the two steering cylinders are connected to the steering collar and the upper end of the upper torsion link is also connected to the steering collar. When force is applied to the steering collar, by either steering cylinder, the collar transfers the force through the torsion links to turn the inner cylinder to the right or left respectively, to which cylinder force is applied to give steering action to the nose wheels.
509 
Aug 15/68  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  32-21-0 Page 7 

4.  
Nose Gear Torsion Links

A  The nose gear torsion links allow rotation between the inner and outer shock strut cylinders only when moved by the steering collar or when disconnected at their aft ends. The upper link is connected to the steering collar, and the lower link is connected to a lug on the inner cylinder (Fig. 1). The upper and lower torsion links are joined together by an apex pin at their aft ends; this locks the nose wheels in the position assumed by the steering collar without affecting strut action. Steering forces applied to the steering collar by the nose gear steering system are transmitted to the inner cylinder by the torsion links.
　
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