Patent ID: 7798785

Claim:
A suction pump having an automatic pressure-relieving apparatus comprising: a cylinder having an oil reservoir arranged therein and a cap positioned on the top thereof wherein the cap includes an air channel; a relieving device, which is connected to the cap and in communication with the air channel; a pipework, which is positioned in the cap and has a upper opening at the top end thereof adjacent to the exterior, a lower opening at the bottom end thereof adjacent to the oil reservoir, a cannular portion defined between the upper and lower openings, and a venthole provided at the periphery thereof, whereby, the oil reservoir can be communicated with the relieving device through the lower opening, the cannular portion, the venthole and the air channel successively; a first rod settled in the cannular portion of the pipework that can move downward from the exterior to detachably seal the upper opening of the pipework; a second rod pierced through the lower opening of the pipework, and the top end of the second rod is positioned under the first rod in the cannular portion, while the lower end of the second rod is positioned under the lower opening of the pipework; a sealing component is arranged at the periphery of the second rod positioned under the lower opening for moving upward and detachably sealing the lower opening of the pipework; and a control device provided in the oil reservoir and approximately connected to the bottom of the second rod for controlling the upward and downward movements of the first and second rods.