Telescopic sinking hydrant

Claim 1

A retractable sprinkler for an irrigation system having main and ancillary conduit means alternately supplied with water under pressure; comprising: a stationary cylinder communicating at its bottom with said main conduit means and at its top with said ancillary conduit means; a first-stage riser tube having an open lower end with a first piston head guided in said cylinder for vertical reciprocation under water pressure from said main and ancillary conduit means between a retracted position near the cylinder bottom and an elevated position near the cylinder top, said first-stage tube having an inner and an outer peripheral wall defining an annular channel therebetween; a second-stage riser tube having a closed lower end with a second piston head guided in said inner wall for vertical reciprocation under said water pressure between a retracted and an elevated position relative to said first-stage tube, said second-stage tube penetrating an otherwise closed upper end of said first-stage tube and having an axial bore terminating in an outlet at the top thereof; first stop means in said cylinder defining a first clearance between the cylinder top and said first piston head in the elevated position of the latter, said first clearance being open to said ancillary conduit means and communicating with said annular channel through a set of first radial holes near the lower end of said outer wall; second stop means in said first-stage tube defining a second clearance between said upper end thereof and said second piston head in the elevated relative position thereof, said inner wall being provided near said upper end with a set of second radial holes connecting said second clearance with said annular channel, said axial bore being connected at the bottom thereof via a set of third radial holes with an annular peripheral groove of said second piston head, said inner wall being further provided below said second radial holes with a set of vertical slots extending in the elevated relative position of said second-stage tube from the level of said peripheral groove to a level below the undersurface of said second piston head whereby a flow path for incoming water is formed in the elevated positions of said tubes from said main conduit means via said cylinder, the open lower end of said first-stage tube, said slots, said peripheral groove, said third radial holes and said bore to said outlet; and a sleeve in said channel closing said slots from without, said sleeve having vertical passages forming with said first and second radial holes a flow path extending to said ancillary conduit means for the retraction of said second-stage tube under water pressure from the latter conduit means and for the escape of water trapped in said second clearance upon an ascent of said second-stage tube under water pressure from said main conduit means.