Organización y Objeto Social Se informará sobre:

Remark:

The position numbers in the pictures of this section are referring to the hydraulic circuit diagram and the components listed in chapter 8.3 - ‘Description of the hydraulic system’. The swing circuit is a closed circuit. When braking, the rotation energy, i.e. swing momentum, of the moving superstructure is transferred back to the swing pumps and is then assisting the engines. Such a transmission is not possible in open circuit swing systems. In open circuit systems, the rota- tion energy of the moving superstructure, when being braked, can only be absorbed by throttling the flow of oil which leads to an energy loss in form of heat.

The swing pumps (6, fig 2) are variable- displacement pumps with torque control system (see description in separate chapter). The change- able internal mass of the superstructure can be efficiently rotated or braked with a variable torque. Special features of torque control:

When the superstructure is being accelerated (i.e. brought into movement) or retarded (i.e. braked from swing), the output of the swing pumps (6) is always the same as the energy consumption of the swing motors (51, fig. 3).

Altering the pressure of the control signal makes it possible to achieve any required, alterable torque of acceleration or retardation, even when the iner- tial mass of the superstructure is changing.

The torque control valve (54, fig. 2) limits the maximum torque and thereby the maximum pres- sures available on the swing motors (51). This, in turn, avoids any opening of the pressure relief valves in the swing pumps.

In the neutral position, ports (Y1) and (Y2) on the torque control valve (54) are free of pressure, i.e. the balance is in the middle position, whereby ports (X1 and X2) are connected to (P). The control chambers in the swing pump regulators are subject to balanced pressure (40 bar servo circuit pres- sure) so that the swing pumps (4) have „zero“ flow. The pressure in the swing circuit is 50 bar, pres- sure being applied from the charge pumps.

Swinging to the right

When the left hand joystick is actuated to the right servo oil flows to the pressure regulating valve (54, port Y1).

The pressure from the joystick is defining the pres- sure level in the swing system.

The main piston (11.1, fig. 1) is displaced against the spring (11.3).

Connections (X1 & P) and (X2 & T) are thereby established. Line (X2) between pressure regulating valve (54) and the regulators of the swing pumps (6) is pressurised. The pressure in the circuit is no longer balanced.

The swing pumps (6) tilt out (altered pump flow) and feed into line (B). The pressure which builds up in the line is led to the pressure regulating valve (54) through line (X 5) and acts on the pilot piston (11.2). The pilot piston has a ratio of 1:16 to the main piston (11.1).

When a state of balance is reached between the pilot force (X5) plus spring force (11.3), and pres- sure (Y1), a state of balance is also reached in the chambers of the pump regulator (6).

The pumps stop tilting out.

The pumps only continue tilting out when the reac- tion pressure (X5) drops. In this way, the pumps only supply so much oil as is being consumed by the swing motors (51).

When the swing movement is to be interrupted, the joystick is returned to its neutral 0-position. The swing motors (51) are then driven by the swinging superstructure so that they pump oil back to the swing pumps. The previous pressure line (B) is freed of pressure is led through (X6) to pilot piston (11.5). The position of the pressure regulating valve is thereby retained and the superstructure can continue to swing until its rotation energy (momentum) has dropped to zero.

Pressure relief valves in the swing pumps (6) limit the max. pressure in the swing circuit to 400 bar. At the same time, they serve as anti-cavitation valves in the system (to compensate for leakage oil losses). Oil feed to the system is carried out by the charge pumps through connection (Fa) on the swing pumps.

The swing pumps (6) are fitted with thermal switches, which pass a warning signal to the cab when the oil temperature exceeds 92° C. The warning in the cab is switched off again when the temperature drops back below 87° C.

Leakage oil from the swing motors (51) is con- ducted back to the tank through the leak line (fig. 6).

Fig. 1 Pressure regulating valve

Swinging to the left

Swinging to the left follows in the same manner as already described, but through the relevant con- nections for „left“.

Countering

The excavator operator can shorten the time taken to brake the swinging superstructure by countering - i.e. by summoning the opposite direction of swing.

The pressure regulating valve (54) receives a re- verse signal so that the regulator of the swing pumps are commanded to „tilt back“.

The swing motors (51) start to work as pumps and drive the swing pumps themselves, which in turn feed their energy back into the drive system. Sen- sitive braking is possible. Brake torque in crease / decrease is possible using the control lever. When the superstructure has come to a standstill, the pumps have returned to their zero-tilt angle. The servo valve must then be shifted back to its neutral 0-position so as to prevent the superstructure swinging off again in the direction which was nec- essary to „counter“.

Charge system (fig. 4)

Each swing pump has an internal charge pump, which is replacing loss of oil in the closed swing circuit because of internal leakage of swing pumps and swing motors. The charge pressure of 25 bar is set by an internal pressure relief valve at each swing pump.

The charge system is equipped with chip indicators ( C ) and filters (10) to avoid contamination of the closed swing circuit in case of a charge pump fail- ure

Flushing valve (fig. 5)

The flushing valve (57) ejects a defined amount of oil from the closed swing circuit at the low-pressure side during each swing operation. The corre- sponding amount of filtered and cooled oil from the hydraulic tank is fed back into the swing system by the charging pumps.

Leak oil of swing motors (fig. 6)

Separate leak oil lines transport the leak oil of the swing motors (51) back to the hydraulic tank.

Swing parking brakes (fig. 7)

The swing parking brake (52) between swing motor and gearbox is operated by a solenoid valve (104). The parking brakes are opened by servo pressure (35 bar) when the solenoid valve is active.

When the solenoid valve is inactive the hydraulic pressure is released to the tank and the parking brakes are closed by internal springs.

This means that the brakes are automatically closed when the machine is shut off or the sole- noid valve fails.

Gear oil reservoirs (fig. 8)

The gear oil level is monitored via reservoirs in which the oil level is visible without using a dip stick. The reservoirs are connected with an filling line and a breather line

8.5

HYDRAULIC CIRCUITS - SWING SYSTEM

RH 200 Diesel - 3663426e - (00) – 09.03 Page 8.5.6 - 3

Remark:

The following colour code refers only to hydraulic lines and not to components!

Colour Code Designation P Pressure oil circuit R Return oil circuit S Servo oil circuit F Flushing system C Charge system

Ref.-no. Quantity Designation further remarks 5 2 Servo- and charge pump

6 4 Swing pump

10 4 Filter for charge oil 12 4 Blocking valve

15 1 Servo pressure valve block

50 4 Swing gearbox

51 4 Swing motor

52 4 Swing parking brake

54 1 Pressure governing valve Swing balance valve 57 1 Flushing valve

60 2 High pressure filter 103 1 Proportional valve plate

104 2 Valve bank, complete Solenoid valves R 4 Gear oil reservoir for swing gearbox

Fig. 2 Swing pumps - 630833a

8.5

HYDRAULIC CIRCUITS - SWING SYSTEM

RH 200 Diesel - 3663426e - (00) – 09.03 Page 8.5.6 - 5

Fig. 4 Swing pumps and swing motors - 3663060a-01

Fig. 6 Pilot lines for swing system - 3663060f-01

8.5

HYDRAULIC CIRCUITS - SWING SYSTEM

RH 200 Diesel - 3663426e - (00) – 09.03 Page 8.5.6 - 7

Fig. 8 Charge system for swing circuit – 3663060d-01

Fig. 10 Flushing valve for swing system – 3663060f-02

8.5

HYDRAULIC CIRCUITS - SWING SYSTEM

RH 200 Diesel - 3663426e - (00) – 09.03 Page 8.5.6 - 9

Fig. 12 Leak oil lines for swing motors – 3663060c-01