Patent ID: 6851473

Claim:
Apparatus for injecting a fluid into the ground material around a borehole in the ground, wherein: the borehole is defined by a borehole-wall, which has, at a depth below the ground surface, an aperture through which fluid can pass from inside the borehole into the surrounding ground material; the apparatus includes a chamber-wall, which defines a hollow chamber; the hollow chamber is located in the borehole, adjacent to the aperture, and the chamber-wall defining the hollow chamber includes a portion of the borehole-wall, being a portion that is contiguous with the aperture; the chamber-wall includes a movable-wall; the apparatus includes an operable movable-wall actuator, which is effective, when operated, to move the movable-wall and thereby to change the volume of the hollow chamber; the chamber-wall is provided with an operable inlet valve; the apparatus includes an inlet conduit for conducting a supply of the fluid from a reservoir outside the chamber-wall to the inlet valve; the hollow chamber is so sealed and configured in the borehole that, when the movable-wall is moving in the sense in which the volume of the chamber becomes smaller, the chamber-wall constrains fluid to pass out from the chamber, into the ground, through the aperture; the inlet valve is so arranged that, when fluid in the hollow chamber is at a lower pressure than fluid in the inlet conduit, the inlet valve can open, thereby permitting fluid to pass through from the inlet conduit into the hollow chamber; the structure and configuration of the apparatus in the borehole is such that operation of the movable-wall can change the fluid capacity of the hollow chamber from a maximum volume V-max to a minimum volume V-min liters; and the difference between V-max and V-min is at least one liter.