Patent ID: 7275369
Filing Date: 2007-10-02
Classification: E02F,F15B

Abstract:
1. A hydraulic control device for controlling a boom-swing frame combined motion in an excavator, comprising first and second fluid pumps (P 1 , P 2 ), a swing control spool ( 13 ) and a boom second-speed control spool ( 11 B) respectively provided on parallel lines ( 16 , 17 ) for receiving a hydraulic flow from the first pump (P 1 ) via the parallel lines ( 16 , 17 ), a boom first-speed control spool ( 11 A) for receiving a hydraulic flow from the second pump (P 2 ), a swing motor ( 1 ) actuated by the hydraulic flow supplied from the first pump (P 1 ) through the swing control spool ( 13 ), a boom cylinder ( 3 ) actuated by the hydraulic flows supplied from the first and second pumps (P 1 , P 2 ) through the boom second-speed control spool ( 11 B) and the boom first-speed control spool ( 11 A), a pilot control valve ( 24 ) for providing a pilot pressure to displace the swing control spool ( 13 ), the boom first-speed control spool ( 11 A) and the boom second-speed control spool ( 11 B), and a confluence line ( 25 ) for merging the hydraulic flow from the boom second-speed control spool ( 11 B) with that from the boom first-speed control spool ( 11 A), characterized by further comprising: a swing priority valve ( a swing priority control line (