Oil suction pump

1. An oil suction pump comprising: an oil storage cylinder, a pumping mechanism, and a cap;

wherein the pumping mechanism includes a body mounted beside the oil storage cylinder, a drive rod accommodated in the body, a plug fixed on a bottom of the drive rod, and a pressure relief valve secured on a bottom of the body;

wherein the cap is disposed on the body and the oil storage cylinder, and the cap includes a connector configured to connect with an oil tube and communicating with the oil storage cylinder, an end of the drive rod is extended out of the cap, and the drive rod has a press lever connected on a top thereof, the cap further includes a first air conduit communicating with the body and the oil storage cylinder, a first one-way valve assembly connected with the first air conduit and received in the oil storage cylinder, and a second air conduit defined in the cap, wherein the second air conduit has an inlet segment located outside the cap, an outlet segment opposite to the inlet segment, and an pump segment defined between the inlet segment and the outlet segment and communicating with the oil storage cylinder, the cap further includes a second one-way valve assembly accommodated in the oil storage cylinder and connected with the pump segment, and the second air conduit accommodates a pressure reducing valve.

2. The oil suction pump as claimed in claim 1 , wherein the first one-way valve assembly has a first spring and a first valve, and the first spring is mounted in the first air conduit, the first valve is pushed by the first spring to close the first air conduit, wherein the second one-way valve assembly has a second spring and a second valve, and the second spring is fixed in the pump segment, wherein the second valve is pushed by the second spring to close the pump segment.

3. The oil suction pump as claimed in claim 2 , wherein the cap further includes a first air delivery tube connected with an opening of the first air conduit and accommodated in the oil storage cylinder, the first air conduit has multiple first orifices defined on an outer wall thereof, and the first air conduit has a first close element moving upward by ways of a buoyant force so as to close the multiple first orifices; the cap further includes a second air delivery tube connected with the pump segment, wherein the second air delivery tube has multiple second orifices defined on an outer wall thereof, and the first air conduit has a second close element moving upward by ways of the buoyant force so as to close the multiple second orifices.

4. The oil suction pump as claimed in claim 1 , wherein the plug has a first disc, a second disc, and a rubber ring, wherein a gap is defined between the first disc and the body so that air flows in the gap, the second disc has at least one recess configured to flow the air, and the rubber ring is defined between the first disc and the second disc and is pushed by the first disc or the second disc, wherein when the rubber ring is pushed by the first disc, the rubber ring shields the gap between the first disc and the body.

5. The oil suction pump as claimed in claim 1 , wherein the cap further includes a handle arranged on a top thereof.

6. The oil suction pump as claimed in claim 1 , wherein the cap further includes a silencer fixed inside the outlet segment.