A metering valve apparatus comprises an enclosed shuttle member 112 defining a dosing chamber 172 between first and second ends of the shuttle member 112. Fluid communication between the dosing chamber 172 and each end of the shuttle member 112 may be selectively established or prevented by reciprocating the shuttle member between first and second positions. The shuttle member 112 preferably has a reduced diameter middle portion, with the transfer chamber 172 defined by an internal surface of an enclosure 114 and the reduced diameter external surface of the shuttle member 112. The enclosure preferably defines sealing surfaces 138, 140 which create a seal with the larger diameter surfaces of the shuttle member. Fluid bypass means, preferably longitudinal channels (160, 162, fig. 4) may be provided for bypassing the seals to allow filling of the transport chamber from fluid provided at the first end (116, fig. 2) of the shuttle member when in the first position, and to allow dispensing of fluid from the transport chamber at the second end (118, fig. 2) of the shuttle member when in the second position. Biasing means (166, fig. 4) may be provided for biasing the shuttle member towards the first position.
