Patent ID: 6334494
Filing Date: 2002-01-01
Classification: B25B

Abstract:
A hydraulic impact wrench comprising:an air motor; a pulsed torque generating mechanism driven by said air motor; said pulsed torque generating mechanism including a cylinder casing and a main shaft; one of said cylinder casing and said main shaft being rotatively driven by said air motor; the other of said cylinder casing and said main shaft including means for engaging a member to be torqued; an oil cylinder disposed in said cylinder casing filled with a hydraulic operating fluid; a blade mounted on said main shaft; said blade being relatively rotatable inside said oil cylinder; a high pressure chamber (H) for containing said hydraulic operating fluid; said high pressure chamber (H) being located at a specific position in the rotating direction of the oil cylinder; said high pressure chamber (H) being present on both sides of said blade; a low pressure chamber (L) having a lower pressure than that of the high pressure chamber (H) is located on the opposite side of the blade, whereby a pulsed torque is applied to the member to be torqued; a bypass passage for communicating fluid pressure between said high pressure chamber (H) and said low pressure chamber (L); a pressure leading path including first and second branch passages along said bypass passage; said first branch passage being a fixed aperture from said pressure leading path to said high pressure chamber (H); said second branch passage being a fixed aperture from said pressure leading path to said low pressure chamber (L); a relief valve; a connection between said pressure leading path and a primary side said relief valve; an automatic shutoff mechanism; and said automatic shutoff mechanism including means responsive to a pressure at said primary side of said relief valve exceeding a predetermined value for cutting off an air supply to said air motor.