Patent ID: 7648345

Claim:
Pump apparatus ( 1 ) including: a first container including a chamber ( 304 ), an inlet ( 302 ) and an outlet ( 305 ), the chamber being pressurisable to effect discharge through the outlet; a control apparatus for causing periodic pressurisation and depressurisation of the chamber as part of a pressurization/depressurization cycle in response to a level of liquid in the first container, wherein the control apparatus includes a pilot valve ( 318 ) located in a second container ( 310 ) connected to receive liquid from the first container from a source other than said outlet when the level of liquid in the first container rises to a first predetermined level, the pilot valve being configured to open when the liquid level in the second container is sufficiently high, and to trigger a pressurisation of the chamber of the first container, and to close in response to the liquid level in the second container falling below a second predetermined level, which triggers the depressurisation, the state of the pilot valve determining pressure within a portion ( 326 ) of the apparatus, and a shuttle valve ( 340 ) configured to change state directly in response to the pressure within the portion of the apparatus, the state of the shuttle valve determining whether motive gas enters into, or is vented from, the first container, thereby implementing the pressurisation/depressurisation cycle.