Patent ID: 6295812
Filing Date: 2001-10-02
Classification: B66F,F15B

Abstract:
A hydraulic jack comprising:a base seat (10) including a lift arm (11) and a handle (12) pivotally mounted on the base seat (10);a hydraulic driver (2) mounted on said base seat (10) under said handle (12) and including a base member (20), said base member (20) having a piston assembly (50) mounted on one end and a fluid chamber (22) and a release path (21) contained in the other end, said release path (21) extending to said piston assembly (50) said base member (20) having two opposite sides each having a recess (23) defined therein, each of recesses (23) having a container (44) mounted thereon;a first path (231) defined in said base member (20) to communicate with said two recesses (23) of said base member (20);a release valve (40) mounted on said base member (20) to communicate with said release path (21) and partially extending out from said base member (20);a drive piston (41) slidably mounted in said fluid chamber (22) to pump the fluid into said jack;a spring (42) compressively mounted around said drive piston (41);a reversed path (24) defined in said base member (20) to communicate with said release path (21) and said recess (23), wherein said reversed path (24) is always closed by said release valve (40) unless lowering the jack;a first, second and third vertical path (25, 26, 27) each defined in said base member (20) and having a first end, a second end and a middle portion; a first, second and third horizontal path (29,30,31), said second end of said first vertical path (25) connecting to said recess (23) via a second path (28) defined in said base member (20), said first horizontal path (29) communicating with said middle portion of said first vertical path (25) and said second end of said second vertical path (26), said first horizontal path (29) having a middle portion defined to communicate with said fluid chamber (22), said second horizontal path (30) communicating with said first end of said first vertical path (25) and said piston assembly (50), said second end of said third vertical path (27) communicating with said first path (231), said third horizontal path (31) communicating with said first end of said second vertical path (26) and said third vertical path (27) to allow fluid flowing into said piston assembly (50) via said third vertical path (27);a first ball check valve (251) mounted in said first vertical path (25) between said second path (28) and said first horizontal path (29) to prevent the hydraulic fluid from reversing and flowing into said recess (23) through said second path (28);a first pressure control valve (252) mounted in said first vertical path (25) between said first horizontal path (29) and said second vertical path (30) to prevent the hydraulic fluid from reversing and flowing into said fluid chamber (22) through said first horizontal path (29);a second pressure control valve (261) mounted in said second vertical path (26) between said first and said second horizontal paths (29, 30) to prevent the hydraulic fluid from reversing and flowing into said fluid chamber (22) via said first horizontal path (29);a second ball check valve (271) is mounted in said third vertical path (27) between said first path (231) and said third horizontal path (31) to prevent the hydraulic fluid from reversing and flowing into said recess via said first path (231);a groove (32) defined at the junction between said base member (20) and said piston assembly (50) and communicating with said second horizontal path (30) and said release path (21);a cylinder (51) mounted on said base member (20) and a first chamber (511) defined in said cylinder (51);a piston (52) slidably mounted in said first chamber (511) of said cylinder (51) and partially extending through said cylinder (511) to connect to said lift arm (11); a second chamber (521) defined in said piston;an internal rod (53) securely mounted in said first chamber (51) and received in said second chamber (521) of said piston (52);a passage (531) defined along an axis in said internal rod (53), said passage (531) communicating with said third horizontal path (31) via said third vertical path (27);an inlet (532) defined in one end of said internal rod (53) near said base member (20) to communicate with said groove (32) and said first chamber (511);a through hole (533) defined to communicate with said inlet (532) and said passage (531); anda third ball check valve (534) mounted in said through hole (533) to allow the hydraulic fluid to flow from said passage (531) to said inlet (532) and prevent the hydraulic fluid from reversing and flowing into said passage (531).