Patent ID: 7281374

Claim:
A hydraulic device for elevating/lowering a chair comprising: a foot pump which absorbs oil by an ascent of an operation lever, which discharges oil stored by a stepping-on of the operation lever, and which discharges stored oil by a stepping-on of the operation lever to a lowest position; a check valve which is opened by the oil pressure of the oil discharged from the foot pump, which is opened when the foot pump is lowered to the lowest position, and which allows the oil from the non-return side to pass to allow it to return to an oil tank through the foot pump; an elevating/lowering cylinder which is for elevating/lowering a seat part and which is coupled with the non-return side of the check valve through flow rate regulating means such as an orifice; and an accumulator storing part of oil when oil from the foot pump is supplied through the first check valve; wherein the device stores part of oil supplied from the foot pump in the accumulator and supplies it also to the elevating/lowering cylinder so as to elevate it, the device keeps the elevating/lowering cylinder ascending by oil stored in the accumulator when oil supply from the foot pump is stopped, and the device allows oil inside the accumulator and elevating/lowering cylinder to return to the oil tank through the inside of the foot pump when the check valve is opened by the foot pump.