b. When the swing control lever (1) is set the neutral position, the time delay valve (3) shifts the neutral position and the pilot oil blocked chamber G. Then, the piston (28) is moved lower by spring (30) force and the return oil from the chamber G is drain. 3 30 28 G SH 1 1 Swing control lever 2 Swing control valve (MCV) 3 Time delay valve 4 Shuttle valve 28 Brake piston 30 Brake spring P4 2 2 4 2-20