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TRIM AND TILT
MODES OF OPERATION (THREE PISTON SYSTEM)
13
MODES OF OPERATION
(Three Piston System)
The three piston trim/tilt hydraulic assembly
achieves trim and tilt movement through the fol-
lowing modes of operation.
Trim-OUT / Tilt-UP Mode
When the UP switch is pressed, the trim/tilt motor
rotates clockwise (as viewed from pump end) and
turns the pump gears.
Fluid pressure passes through the UP shuttle
valve to the DOWN shuttle valve, mechanically
opening the DOWN check valve.
Fluid pressure pushes the UP check valve off its
seat, and fluid passes through the valve to the
bottom of all cylinders, pushing the pistons UP.
Fluid is pushed from the top of the tilt cylinder by
the piston and returns to the pump through the
open DOWN check valve.
In the trim range, fluid is pushed from the top of
the trim cylinders by the pistons and returns to
the reservoir.
Only fluid from the top of the tilt cylinder is
returned to the pump. Because the cylinder rod
displaces some fluid, that volume is less than the
volume of the bottom of the tilt cylinder. So, addi-
tional fluid is drawn into the pump from the reser-
voir.
When all the cylinders are completely extended,
the pressure increases until the UP relief valve
opens at the tilt-up stall pressure (approximately
1500 psi (10342 kPa)).
1. Up shuttle valve
2. Down shuttle valve
3. Down check valve
4. Up check valve
5. Tilt cylinder
6. Trim cylinders
7. Up relief valve
DRC3462
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