1.  Field of the Invention
The present invention relates generally to a pumping device, and in particular to a pumping device that can be manually or pneumatically operated to selectively suck liquid into a container and to drain the liquid out of the container. 
2.  The Related Art
Replacement and/or replenishment of oil is one of the most important jobs for maintenance and repairing of automobiles.  Often, the oil is drained from the oil pan by simply removing the oil drain plug that blocks a drain hole formed in the bottom of the oil pan whereby oil is allowed to freely flow out of the drain hole.  This is not an efficient way for draining oil from the automobile engine and may cause undesired contamination to the surroundings.  Oil pumping devices or oil draining devices are available.  However, such oil pumping devices have a complicated structure and can only be manually or pneumatically operated.  In Taiwan Patent Application No.  90215858, filed by the present inventor, an oil pumping device that can be operated both manually and pneumatically is disclosed.  However, such as conventional device still suffers certain drawbacks that can be further improved. 
Thus, the present invention is aimed to provide a pumping device that overcomes the drawbacks of the conventional devices.