Conclusiones: algunas reflexiones finales

1. Brake spring 2. Drive shaft 3. Spacer 4. Case 5. Disc 6. Plate 7. Brake ring 8. Brake piston 9. Housing 10. Piston

11. Cylinder 12. Valve plate

13. Reverse prevention valve 14. Center shaft

15. Center spring 16. Safety valve 17. Check valve 18. Check valve spring 19. Shuttle valve 20. Shuttle valve spring

STRUCTURE AND FUNCTION

Swing lock valve Operation

1. When swing lock solenoid valve is deactivated a. When the swing lock solenoid valve is

de-activated, the pressurized oil from the main pump is shut off and port B is connected to the tank circuit. Because of this, brake pis-ton (7) is pushed down in the direction of the arrow by brake spring (1), so disc (5) and plate (6) are pushed together and the brake is applied.

2. When swing lock solenoid is excited

a. When the swing lock solenoid valve is ex-cited, the valve is switched, and the pres-surized oil from the main pump enters port B and flows to brake chamber a. The pres-surized oil entering chamber a overcomes the force of brake spring (1), and brake pis-ton (7) is pushed up in the direction of the arrow. Because of this, disc (5) and plate (6) separate, and the brake is released.

SWING MOTOR

STRUCTURE AND FUNCTION SWING MOTOR

Relief valve portion Outline

The relief valve portion consists of check valves (2) and (3), shuttle valves (4) and (5), and relief valve (1).

Function

When the swing is stopped, the outer port cir-cuit of the motor from the control valve is closed, but the motor continues to rotate under inertia, 50 the pressure at the output side of the motor becomes abnormally high and this may damage the motor. To prevent this, the abnormally high pressure oil is relieved to port S from the outlet port of the motor (high-pres-sure side) to prevent any damage to the motor.

Operation

1. When starting swing

a. When the swing control lever is operated to swing right, the pressure oil from the pump passes through the control valve and is supplied to port MA. As a result, the pres-sure at port MA rises, the starting torque is generated in the motor and the motor starts to rotate. The oil from the outlet port of the motor passes from port MB through the control valve and retums to tank.

2. When stopping swing

a. VVhen the swing control lever is retumed to neutral, the supply of pres-sure oil from the pump to port MA is stopped. With the oil from the outlet port of the motor, the return circuit to the tank is closed by the control valve, 50 the pressure at port MB rises. As a re-sult, rotation resistance is generated in the motor, 50 the braking effect starts.

b. If the pressure at port MB becomes higher than the pressure at port MA, it pushes shuttle valve A (4) and chamber c becomes the same pressure as port MB. The oil pressure rises further until it

reaches the set pressure of relief valve (1). As a result, a high braking torque acts on the motor and stops the motor.

c. When the relief valve (1) is being actu-ated, the relief oil and oil from port S passes through check valve B (3) and is supplied to port MA. This prevents cavi-tation at port MA.

STRUCTURE AND FUNCTION SWING MOTOR

Reverse prevention valve (swing dampening) Operation diagram

1. Valve body 2. Spool (MA side) 3. Spring (MA side) 4. Plug

5. Spool (MB side) 6. Spring (MB side) 7. Plug

Explanation of effect

STRUCTURE AND FUNCTION SWING MOTOR

Outline

This valve reduces the swing back generation in the swing body by the inertia of the swing body, the backlash and ngidity of the machinery system, and the compression of the hydraulic oil when the swing is stopped. This is effective in preventing spillage of the bad and reducing the cycle time when stopping the swing (the po-sitioning ability is good and it is possible to move swiftly to the next job).

Operation

1 . When brake pressure is being generated at port MB

a. Pressure MB passes through the notch and goes to chamber d, spool (5) pushes spring (6) according to the difterence in area D1 > D2, moves to the left, and MB is connected to e.

b. When this happens, pressure MA is below the set pressure of spring (3>, 50 spool (2>

d9es not move. For this reason, the pres-sure oil is closed by spool (2) and the brak-ing force is ensured.

2. Aftermotorstops

a. The motor is reversed by the closing pres-sure generated at port MB. (1 st reversal>

When this happens, reversal pressure is generated at port MA. Pressure MA goes to chamber a, so spool (2) pushes spring (3) and moves to the right, and MA is nected to B. At the same time, b is con-nected to f through the drili hole in spool (5), 50 the reversal pressure at port MA is bypassed to port T to prevent the 2nd re-versal.

STRUCTURE AND FUNCTION

a. Port PB (from control valve) b. Port PA (from control valve) c. Port T (to tank)

e. Port P (from travel speed solenoid valve)

Specifications Model

Item PC290LC-6k PC290NLC-6k

Type HMV60ADT-2

Theoretical

Delivery Min 100 cc/rev 100 cc/rev Max. 160.8 cc/rev

Set pressure 34.79 MPa

(355 kg/cm²)

Rated Lo 1310 rpm 1310 rpm

speed Hl 2107 rpm 2107 rpm

Brake

releasing 1.18 MPa

pressure (12 kg/cm²)

Travel speed

switch pressure 0,78 MPa

(8 kg/cm²)