Chapter 15. -PUMPS AND FORCED DRAFT BLOWERS 



VALVE PLATE 



CYLINDER BARREL 



TILTING BOX CONTROL 

 TILTING BOX 



_B END 

 (HYDRAULIC MOTOR) 



CYLINDER BARREL 



SOCKET RING 



DRIVE 

 SHAFT 



A END 



147.109 



Figure 15-10.— Exploded view of axial-piston variable stroke pump. 



In part B of figure 15-12, the tilting box is 

 set at an angle so that it is farther away from the 

 top of the cylinder barrel and closer to the bottom 

 of the cylinder barrel. As the cylinder barrel and 

 socket ring revolve, the piston is pulled outward 

 as it is carried from the bottom position to the 

 top position, and is pushed inward as it is carried 

 from the top positionto the bottom posit ion. Thus 



CYLINDER BARREL 



KEY 



SOCKET RING 



ANGLE / (THRUST AND 

 OF / RADIAL BEARINGS 

 TILT Ik NOT SHOWN) 



UNIVERSAL 

 JOINT 



TILT BOX 



DRIVE 



SHAFT FROM 



REDUCTION GEARS 



147.110 



Figure 15-11.— Diagram showing eyJoxider bar- 

 rel, socket ring, and tilting box in axial-piston 

 variable stroke pump. 



the piston makes one suction stroke (from the 

 bottom position to the top position) and one dis- 

 charge stroke (from the top position to the bot- 

 tom position) for each complete revolution of the 

 cylinder barrel. 



In part C of figure 15-12, we see the tilting 

 box set at a somewhat larger angle. Because 

 there is more distance between the cylinder 

 barrel and the socket ring at the top, and less 

 distance between them at the bottom, the piston 

 now moves further on each stroke and thus 

 displaces more liquid on the discharge stroke. 



Although we have considered the position of 

 only one piston, it is obvious that the others are 

 being similarly positioned as the cylinder barrel 

 and socket ring revolve. At any given moment, 

 therefore, some pistons are making suction 

 strokes and others are making discharge 

 strokes. In a nine-piston pump, for example, four 

 pistons will be making suction strokes, four will 

 be making discharge strokes, and one will be at 

 the end of its stroke and will therefore be mo- 

 mentarily motionless. 



Each cylindrical opening in the cylinderbar- 

 rel has a port in the face of the cylinder barrel. 

 As we have seen, each port except one will be 

 either a suctionport or a discharge port, depend- 



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