Patent ID: 6716006
Filing Date: 2004-04-06
Classification: F04B

Abstract:
A pump comprising a nozzle assembly, a central tube in communication with the nozzle assembly, a first tube enclosing the central tube and being slidable relative to the central tube and a second tube enclosing the first tube and being slidable relative to the first tube, wherein the central tube has a first end received in the nozzle assembly and provided with a first air pad so that the central tube is able to have an air tight engagement with the nozzle assembly and a second end received in the first tube and having a first piston assembly, the first piston assembly being provided with a block slidably received in the first tube and having a recess in the block to receive therein a first seal and a second seal so as to have an air tight engagement with an inner periphery of the first tube, a first passage defined in a bottom defining the recess to communicate with the central tube, the first tube having a first casing securely formed on a first end of the first tube to enclose the second end of the central tube, an air channel defined between the first casing and an outer periphery of the central tube, a second air pad received in the air channel to selectively control air flowing into the air channel and a room defined between the inner periphery of the first tube and the outer periphery of the central tube, the improvements comprise:the first tube has a second end provided with a second piston assembly which includes a second block slidably received in the second tube and the second tube has a second casing enclosing the second block, a first air channel is defined between the second casing and the first tube to receive therein a third air pad to selectively control air flowing to a room between the first tube and the second tube when the second piston assembly moves, and the second block has a cutout to receive therein a first unidirectional valve and a second unidirectional valve whereby the second piston assembly forms an air tight engagement with an inner periphery of the second tube, a second passage being defined in a bottom defining the cutout to communicate with a linking tube which is located in the first tube to communicate the second tube to the central tube.