Haskel 8DFD-25 Instrucciones De Funcionamiento página 12

Figure 9. Drive section on "PUSH" stroke
6.2.1 This cycling spool is held normally in the "up" position (ref. fig. 9) whenever drive air is applied to the
3/4" NPT inlet because the upper end seal is larger than the lower end seal. (note the step in the I.D. of
the sleeve.) When the valve is in the "up" position, it directs drive air to the flow tube and simultaneously
connects the opposite side of the drive piston to the "lower" exhaust port. The drive piston is powered
right ("push").
Figure 10. Drive section on "PULL" stroke
6.2.2 When the drive piston reaches the end of its stroke and opens the pilot charge valve, the cycling
spool is shifted by pilot air to the "down" position (ref. fig. 10). With the spool held in the "down" position,
drive air reverses and the drive is powered "left". The pilot charge valve then drops shut trapping pilot air
in the spool cavity holding it "down" during the full travel of the drive piston to the left ("pull"). Note also the
small orifice passage drilled through the charge valve. This provides make up pilot air directly from the
drive chamber to the trapped pilot air in case of slight leakage during the pull stroke. At the end of the
8" Drive Liquid Pumps • OM-LP-800S
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