Telescopic sinking hydrant

摘要

A two-stage retractable sprinkler comprises a first-stage riser tube, with inner and outer walls forming an annular peripheral channel and with a first piston head at its open lower end guided in a stationary cylinder, and a second-stage riser tube with a second piston head at its closed lower end guided in the first-stage tube. The second piston head has a peripheral groove communicating with an axial bore of its tube through radial holes through which water entering the bottom of the guide cylinder can pass to an outlet at the top of the second-stage tube by way of a set of vertical slots, formed near the top of the inner wall of that tube, after both tubes have been elevated by the water pressure. The slots are sealed from without by a sleeve in the annular channel which has external flutes forming passages for the retraction of the second-stage tube under water pressure and for the escape of water from the closed top of the first-stage tube, via other radial holes in the inner and outer walls thereof, when the second-stage tube is extended.