TM 5-3895-383-24
Servo Piston Assembly
SMCS Code: 5261
Illustration 25
Section View Of The Vibratory Pump
(1) Shaft. (2) Bearing. (3) Pump housing. (4) Swashplate. (5)
Joint pin. (6) Servo housing. (7) Servo piston. (8) Barrel. (9)
Solenoid valve.
Illustration 26
Section View Of The Servo Piston
(6) Servo housing. (7) Servo piston. (10) Springs (centering). (11)
Piston rod. (12) Stroke limiter screw. (13) Locknut.
The servo control assembly controls the swashplate angle (4)
of the vibratory pump. The servo housing (6) is an integral part
of the vibratory pump. The servo housing (6) contains the
servo piston (7).
The charge circuit supplies control oil to the control valve (9)
on the vibratory pump. The control valve (9) regulates the
servo piston (7) by directing the oil flow which enters the servo
housing (6). The control valve (9) also acts on the servo piston
(7). Linear movement of the servo piston (7) mechanically
controls the rotational movement of the swashplate (4) with the
joint pin (5). When the servo piston (7) moves, the angle of the
swashplate (4) changes in the pump.
The flow of the pump output is zero when the swashplate angle
is zero. The swashplate angle is zero when the servo piston
(7) is in the center position. The servo piston (7) will return to
the center positions when the control valve (9) is not
energized. The servo piston (7) is mechanically centered by
the springs (10). The center position of the servo piston (7)
can be adjusted by loosening the locknut (13) and turning the
piston rod (11).
The pump flow is controlled by the servo piston (7). The
maximum pump output is determined when the swashplate (4)
is at the maximum angle. The maximum swashplate angle is
controlled by limiting the travel of the servo piston (7). Adjust
the stroke limiter screw (12) in order to control the travel of the
servo piston. There are two stroke limiter screws. The screws
determine the direction of travel for the servo piston (7). The
stroke limiter screws (12) are located on each end of the servo
housing (6).
11-29
