Skytrak 6042 Service Manual User Manual download pdf (Page 286)

Hydraulic System

8.54

Model 6042 Legacy Origin 7/02

8.8.23 Attachment Tilt and Slave Circuit

Description

System pressure is applied in the attachment tilt and

slave cylinder circuit (Fig. 8-11 and Fig. 8-12) from the

attachment tilt section of the main control valve.

Fluid flow is directed to either side of the attachment tilt

and slave cylinder pistons by shifting of the spool valve in

the attachment tilt section of the main control valve

assembly. The spool valve is shifted by the operator

joystick and its associated control cable.

Moving the joystick BACKWARD controls attachment tilt

UP. Moving the joystick FORWARD controls attachment

tilt DOWN.

a. DOWN Position (Fig. 8-11)

With the joystick moved FORWARD, the

attachment tilts DOWN. The spool valve in the

main control valve is shifted so system pressure

is directed to the rod end of the attachment tilt

cylinder and the slave cylinders.

The extension of the slave cylinders is fixed by the

position of the boom so that only the attachment tilt

cylinder is retracted to tilt the attachment downward. The

pilot pressure opens the counterbalance valve. The open

counterbalance valve allows return oil from the base of

the attachment tilt cylinder to flow to ports of the

attachment tilt section of the main control valve, to the

unloader valve, to the oil cooler, to the return filter and

then to the reservoir.

If system pressure reaches 3,250 ±100 psi (224 ±7 bar)

the main relief will open and allow hydraulic oil to return

to the return filter and to the reservoir. In any case, if the

return filter becomes restricted, hydraulic oil will bypass

the filter when the pressure reaches 25 psi (1,7 bar).

b. UP Position (Fig. 8-12)

With the joystick moved BACKWARD, the

attachment tilts UP. The spool valve in the main

control valve is shifted so system pressure is

directed to the base end of the attachment tilt

cylinder and the slave cylinders.

If system pressure reaches 3,250 ±100 psi (224 ±7 bar)

the main relief will open, allowing hydraulic oil to flow to

the return filter and to the reservoir. If the return filter

becomes restricted, hydraulic oil will bypass the filter

when the pressure reaches 25 psi (1,7 bar).

Return oil from the rod side of the attachment tilt cylinder

is directed back to the attachment tilt section of the main

control valve through the spool valve, to the unloader valve, to

the oil cooler, to the return filter and then to the reservoir.

If the return filter becomes restricted, hydraulic oil will

bypass the filter when the pressure reaches

25 psi (1,7 bar).

8.8.24 Pump, Unloader Valve and Cooling

Circuit Description

In the pump, unloader valve and cooling circuit

(Fig. 8-13), the pump draws fluid from the hydraulic

reservoir and sends pressurized fluid to the unloader

valve.

The unloader valve regulates maximum system operating

pressure for various vehicle functions. It sends fluid to the

main control valve and to the secondary function manifold.

When fluid from the unloader valve is returned to the

reservoir, it is sent through the hydraulic oil cooler first.

8.8.25 Auxiliary Hydraulics Circuit Description

The auxiliary hydraulics circuit (Fig. 8-14 and

Fig. 8-15) functions can be achieved by

moving the auxiliary attachment control lever.

Moving the control lever to the left controls

auxiliary function in one direction, usually

forward, if the auxiliary device is so designed. Moving the

control lever to the right controls auxiliary functions in

reverse, or the opposite direction.

a. Female Coupler Pressurized (Fig. 8-15)

With the auxiliary attachment control lever

moved to the right, pressure will shift the

auxiliary spool valve, allowing oil to flow from the

auxiliary spool valve to the female connection of

the auxiliary hydraulics coupler. From the coupler, fluid

flows to the attachment, back to the male auxiliary

coupler, to the auxiliary spool valve, to the unloader valve,

to the oil cooler, to the return filter and then to the

reservoir.

b. Male Coupler Pressurized (Fig. 8-14)

With the auxiliary attachment control lever moved

to the left, pressure will shift the auxiliary spool

valve, allowing system pressure to flow from the

auxiliary spool valve to the male connection of the

auxiliary hydraulics coupler. From the coupler, fluid flows

to the attachment, back to the female auxiliary coupler, to

the auxiliary spool valve, to the unloader valve, to the oil

cooler, to the return filter and then to the reservoir.

MT3780

MT3790

MA7250

MA7270

MA7260

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Skytrak 6042 Service Manual User Manual Page 286

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Skytrak 6042 Service Manual User Manual Page 286

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