Patent ID: 7789638

Claim:
A pump comprising: a base defining a pumping channel; a cylinder installed on the base, the cylinder defining a first chamber and a second chamber with a diameter different from that of the first chamber, wherein the first and second chambers are in communication with the pumping channel; a first piston movable in the first chamber; a second piston movable in the second chamber; a first tube connected to the first piston; a second tube connected to the second piston; a handle connected to the first and second tubes; and a control device installed on the handle for allowing air to travel from the first and second chambers through the pumping channel in a first mode, venting air from the second chamber through the second piston and the second tube in a second mode, and venting air from the first chamber through the first piston and the first tube in a third mode, wherein the control device comprises a first valve set installed on the first piston and a second valve set installed on the second piston, wherein each of the valve sets comprises a rod inserted through a related one of the tubes, wherein the control device comprises a switch rotatably mounted to the handle about a switch axis, with the switch controlling the valve sets through the rods; wherein the switch of the control device includes two grooves defined therein, with each of the two grooves including a deep portion and a shallow portion, and with the two grooves receiving upper ends of the rods, with each of the two grooves being concentric to the switch axis and spaced from each other; with the control device positioned in the first mode, the upper ends of the rods are positioned in the deep portions of the two grooves so that both of the first and second valve sets are closed and air is pumped from both of the first and second chambers; with the control device positioned in the second mode, the upper end of the rod exposed from the first chamber is positioned in the deep portion of the related groove so that the first valve set is closed and the upper end of the rod exposed from the second chamber is positioned in the shallow portion of the related groove so that the second valve set is open and air is pumped into the channel from the first chamber only and is vented from the second chamber through the second valve set; with the control device positioned in the third mode, the upper end of the rod exposed from the first chamber is positioned in the shallow portion of the related groove so that the first valve set is open and the upper end of the rod exposed from the second chamber is positioned in the deep portion of the related groove so that the second valve set is closed and air is pumped into the channel from the second chamber only and is vented from the first chamber through the first valve set.