Toro Groundmaster Series Service Manual page 105

Cutting Unit (or Implement) Idle
Raising the Cutting Unit (or Implement)
Lowering the Cutting Unit (or Implement)
Floating the Cutting Deck (or Implement)
Groundsmaster ® 3200, 3300 and 3310
19240SL Rev A
pump output flows to the steering control valve before supplying the lift and
charge circuit needs so that the steering circuit has priority.
When the lift system is not actively raising, lowering, or floating (idle), fluid flow
enters the hydraulic manifold at the P port. Hydraulic pressure will try and raise
the lift arms until the pressure opens logic cartridge LC and provides a fluid path
to exit the manifold. When the logic cartridge opens is controlled by adjusting
the logic cartridge to the desired weight transfer (counterbalance). Refer to
the traction unit Operator's Manual for additional counterbalance adjustment
information.
When the lift switch is set to the Raise position, solenoid valve SV1 is energized,
holding logic cartridge LC closed. Hydraulic flow is directed through de-energized
solenoid valve SV2 to the front (cap end) of the lift cylinders. The hydraulic
pressure against the cylinder pistons extends the lift cylinders. At the same time,
the pistons push the hydraulic fluid in the lift cylinders out and to the hydraulic
manifold. The extending lift cylinders cause the cutting unit (or implement) to
raise. When the cylinders reach the end of their stroke, or if the lift arms are
prevented from raising, the relief valve (R4) in the steering control valve opens
and directs the hydraulic flow through the manifold and back to the gear pump
(P2) until the lift switch is released. The lift circuit pressure is limited to 7,000 to
7,500 kPa (1,015 to 1,088 psi). A check valve in solenoid valve SV2 prevents
the cylinders from lowering.
When the lift switch is set to the L
to open a path for fluid trapped at the front (cap end) of the lift cylinder pistons to
escape. The weight of the cutting unit (or implement) causes the cylinders to
retract and lower the lift arms. The speed which the cylinders lower is controlled
by a check orifice (OR at manifold port C1). The escaping fluid combines with
the remainder of the flow from the gear pump (P2) to pass through the open
logic cartridge (LC) and exit the manifold. As the cylinders retract, the cylinder
pistons draw hydraulic fluid from the hydraulic manifold into the rear (rod end) of
the lift cylinders.
As the cutting unit moves over terrain with changing elevation, the lift arms are
allowed to move up and down (float). The lift cylinders are allowed to extend and
retract if necessary when floating. After the cutting unit is fully lowered, solenoid
valve SV2 remains energized to hold a path open for fluid at the front (cap end)
of the lift cylinder piston to flow in either direction if necessary. Hydraulic fluid
is allowed to flow from the manifold to and from the rear (rod end) of the lift
cylinders as well.
position, solenoid valve SV2 is energized
OWER
Page 5–19 Hydraulic System: Hydraulic Flow Diagrams