User Manual

Actuation pressure increases under the spool valve (6) that creates the balance of hydraulic force on the top and
bottom of the spool.
The weak spool spring (5) now acts on the spool. This closes the spool very slowly. As the spool remains open,
actuation pressure continues to flow past the spool to intensifier piston (8) and to plunger (10) . The injection
pressure in the nozzle and in the plunger cavity increases very quickly when the nozzle check is held in the
closed position.
Main Injection
Cross section of main injection cycle
(1) Solenoid
(3) Armature
(4) Seated pin
(6) Spool valve
(7) Check ball for intensifier piston
(16) Check piston
(19) Nozzle check
(22) Drain
Main injection begins when the solenoid (1) is re-
energized. The magnetic field is instantly created and
the force of the magnetic field lifts the armature (3)
and the seated pin (4) . The upper seat closes off the
flow of actuation pressure and the upper seat opens the
check piston (16) and the bottom of the spool (6) to
the drain (22) . The hydraulic force that holds the
nozzle check (19) closed quickly dissipates and the
injection pressure opens the nozzle check. This is the
start of main injection. A difference in hydraulic
forces on the spool is also created. This difference
forces the spool downward. The check ball (7) for the
intensifier piston is held in the closed position when
the spool is in this position. Main injection continues
if the solenoid remains energized.