Patent ID: 8025491

Claim:
An air pump having selectable low pressure and high pressure modes, including: a big cylinder and a small cylinder being fitted to each other to define a telescopic cylinder; a head connected with one end of said telescopic cylinder; two pistons being placed in said big and small cylinders and dividing said cylinders into a big and a small chamber; a pressure relief valve being placed in said big cylinder and connected with said big chamber: a valve seat being placed at an outer end of said big cylinder and connected with a first pipe, there being a pit with a curved bottom provided on said valve seat; there being a bore provided at the bottom of said pit and communicating with the inside of said big cylinder; a sealed member placed in said pit for sealing said bore; a cover being mounted at said big cylinder and covering said valve seat; a switch with a switching end that bulges out of said cover being placed between said valve seat and said cover and able to switch between an open position and a closed position, said switch having an extrusive portion and an intrusive portion corresponding to the face of said valve seat; when said switch being in the closed position, said extrusive portion facing to the pit of said valve seat and pushing said sealed member forward to said pit and sealing said bore, when said switch being in the open position, said intrusive portion facing to the pit of said valve seat and providing a space for said sealed member to move, so, the bore of said pit being not sealed.