a relatively low cost , manually actuated pressure build - up pump sprayer to be interfaced with a liquid container for atomizing and spraying any one of a variety of different liquids which may be stored within the container . the pump sprayer is characterized by a fewer number of components and a higher speed of assembly than that by which most conventional sprayers are characterized . the pump sprayer is also characterized by a single , axially and continuously extending pressure chamber and a continuously extending pair of bores having different diameters relative to one another . moreover , the sprayer includes a number of seals which may be selectively opened and closed at particular times during the stroke cycle so as to provide the reliable venting and efficient priming in response to a lower actuating force .