Hydraulic System Main Oil Circuit - Yale A7S1 Service Manual

8000 YRM 2199
1. CONNECTING TILT CYLINDER INTERFACE B
The interfaces "2" and "1" of valve body connect
separately with front and rear housing of the tilt
cylinder piston. When spool valve is pulled out,
(control lever pulled back) the high-pressure fluid
enters into interface "2" (item 2, Figure 42), while the
oil in the rear cavity returns to the tank. In this case,
the mast is tilted backward.
When the spool valve is pushed in (control lever is
pushed forward), high pressure oil enters connector
"1", (item 1, Figure 42) by high pressure oil, and the
lock valve in spool works to make "2" connect with low
pressure. When engine is off or stopped, there is no
high-pressure oil for auto-lock inside the spool valve to
act. In this case the interface "2" cannot be connected
with low pressure, and the mast will not tip forward and
there is no back pressure in tilt cylinder.

HYDRAULIC SYSTEM MAIN OIL CIRCUIT

The high-pressure oil from the steering control unit is
routed to the multi-way pump, and is split into two
2. CONNECTING TILT CYLINDER INTERFACE A
Figure 42. Tilt Auto-lock Valve
parts by the priority spool within the multi-way valve.
High pressure oil is divided to either go to the hydraulic
control valve or the SCU (Steering Control Unit). When
the lift or tilt spool valves are at the neutral position,
the high-pressure oil returns to tank. When lift spool
valve is pulled, the high-pressure oil passes through
the velocity fuse, and then pushes the piston of the
lifting cylinder up. When lift spool valve is pushed, the
lower part of lift cylinder piston is connected with low
pressure, allowing the piston to drop, depending on
mast weight and cargo weight. The oil flowing out from
lift cylinder then passes through the velocity fuse for
the lowering speed to be controlled. When the tilt spool
valve is operated, the high-pressure oil may flow into
the front cavity of tilt cylinder, while the other side is
connected with low pressure. This causes the mast to
tilt backward or forward.
Hydraulic System
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