Patent ID: 8100607

Claim:
A rock anchor which includes: an elongate, hydraulically inflatable anchor tube made of a ductile material and defining a closed leading end, a trailing end, and a tube cavity extending between the ends; an end cap on a trailing end of the tube, defining a feed aperture in communication with the tube cavity for pressure feeding a liquid substance into the tube cavity for inflating the tube; pressure indicator means, carried by the end cap, configured for indicating when, as a result of pressure feeding of a liquid substance into the tube cavity, a predetermined installation pressure is reached in the tube cavity; and a non-return closure for the feed aperture, and in which: the pressure indicator means includes: a body defining a contact surface exposed to an end cap cavity defined in the end cap, the end cap cavity being in communication with the tube cavity, the body before installation of the rock anchor being in a first position thereof relative to the end cap, and the body being displaceable, under liquid pressure against the contact surface, into a second position thereof; an indicator formation, before installation of the rock anchor being in a first position thereof relative to the end cap and being displaceable into a second position thereof through displacement of the body into its second position, the second and first positions of the indicator formation being visually distinguishable from the outside of the end cap; and holding means holding the body in its first position against pressure on the contact surface, the holding means being configured for yielding when the predetermined installation pressure is reached in the end cap cavity; the end cap includes: a ferrule having opposite first and second ends, secured to the trailing end of the anchor tube so that the anchor tube extends from the first end; and an end wall at the second end; the feed aperture is defined through the ferrule; the end wall defines therethrough an indicator formation aperture for the indicator formation a portion of the ferrule, extending from the second end of the ferrule and past the feed aperture, defines a round cylindrical outer surface permitting snug sliding entry of said portion into a round entry of a collar-like coupling of a high pressure water hose.