Abstract: This invention relates to apparatus for separately storing and subsequently mixing two components of a substance to be dispensed.

Abstract: An atomizing pump (FIG. 1) has a piston (3) slidable in a cylinder (5) to expel liquid from a pump chamber (4). A valve member (8) is slidable in a stem (6) of the piston defining a liquid delivery duct (7). A separately formed cylindrical extension (11) of the valve member is movable in and out of sealing contact with the valve member to open and close a liquid inlet port (105) to the chamber (4). The valve member has a core (102) projecting within the cylindrical extension and having a projecting stop formation (103) which co-operates with a stop formation (104) on the cylindrical extension to limit lost motion between the valve member and cylindrical extension. The valve member is biased into an extended position by a spring acting on the stop member projecting from the core so that the spring extends between the core and the cylindrical extension. This arrangement helps maintain alignment between the pump components and resists buckling of the spring.