HYDRAULIC JACK

PURPOSE:To reduce a force required for operation of a handle by providing a pressure control valve which is constituted to open when a pressure in a second oil passage exceeds a given value and return oil in a second oil passage to an oil tank. CONSTITUTION:When a high load is applied on a ram 4, oil in a second oil passage 35 flows in the lower small part of the stepped through-hole 72 of a sixth oil passage 76. The pressure exceeds a given value and is increased to a value higher than the energizing force of a compression soil spring 82. Thereby, a ball valve body 81 is separated away from a valve seat 79 and a pressure control valve 78 is opened. A second oil passage 35 is brought into a state to be communicated with an oil tank 2 through the sixth oil passage 76 and oil in the second oil passage 35 fed from the large inside diameter part 7a of a pump cylinder 7 flows back to the oil tank 2 after the flow of it through the sixth oil passage 76. Thus, the ram 4 is raised only by oil delivered from the small inside diameter part 7b of the pump cylinder 7 and as a result, a rise amount of the ram 4 per one action of an operation handle is reduced.