INJECTOR APPARATUS

An injector apparatus () for injecting fluid under pressure into an associated chamber () is provided. The injector apparatus () includes a first piston () defining a first working area facing an associated chamber (), a high pressure piston () defining a high pressure working area facing a high pressure chamber (), and a control piston () defining a control piston working area facing a control chamber (). The first piston () is moveable with a body of the injector apparatus () to compress fluid in the high pressure chamber () using the high pressure piston (), while movement of the first piston () is selectively controllable by controlling the fluid in the control chamber (). The first working area is larger than the control piston working area and the control piston () working area is larger than the high pressure working area.