Telescopic sinking hydrant

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.

FIELD OF THE INVENTION 
This invention relates to a retractable two-stage sprinkler to be used in 
stationary rural irrigation systems for high-stem farm products. 
BACKGROUND OF THE INVENTION 
A known sprinkler of this type comprises a stationary guide cylinder which 
is connected to a primary and a secondary water-supply conduit and 
surrounds two telescopically interfitted riser tubes, i.e. a double-walled 
outer first-stage tube and an inner second-stage tube in which there is 
mounted a movable piston for remote control of the operation of the 
sprinkler. 
The drawbacks of the known retractable two-stage sprinkler lie in the 
presence of axial bores in the pistons of both telescopic stages through 
which water flows out ineffectively when the tubes are raised above the 
ground surface, thus reducing considerably the lifting force of the 
pistons, as well as in the need for a movable piston with remote control 
in the second stage, which requires frequent resetting and reduces the 
operational reliability of the sprinkler. 
In our copending application Ser. No. 029,476, filed Apr. 12, 1979, there 
has been disclosed a single-stage retractable spray head or sprinkler with 
a hollow piston whose axial bore is connected by means of radial holes to 
an annular groove in the external surface of the piston head, the upper 
part of the guide cylinder surrounding that piston having two sets of 
radial holes on different levels which are embraced from the outside by a 
ring chamber. 
OBJECT OF THE INVENTION 
The object of our present invention is to provide an improved two-stage 
sprinkler of the general type referred to which fully utilizes the 
available water pressure of an associated conduit system and, in its 
extended position, prevents water leakage without the need for an external 
ring chamber of the kind disclosed in our above-identified copending 
application. 
SUMMARY OF THE INVENTION 
We realize this object, in accordance with our present invention, by the 
provision of a set of vertical slots near the closed upper end of the 
inner peripheral wall of the double-walled first-stage riser tube which, 
in a fully elevated relative position of the second-stage riser tube with 
a piston head thereof contacting that upper end, extend between the space 
underneath this piston head and an annular peripheral groove thereof. The 
groove, in turn, communicates through a set of radial holes with the 
interior of the second-stage tube and thus with an outlet at the top of 
the latter tube, the slots being externally closed by a sleeve which is 
located in the annular channel formed by the walls of the first-stage tube 
and is provided with vertical passages such as external flutes. Together 
with another set of radial holes present in the inner tube wall above the 
slots and a further set of radial holes near the bottom of the outer tube 
wall, these passages provide a flow path for the escape of water trapped 
above the piston head of the second-stage tube in the last phase of its 
rising stroke, when both tubes are elevated by water pressure from a main 
conduit opening into the bottom of the guide cylinder, and for the 
retraction of the second-stage tube by water pressure from an ancillary 
conduit opening into the top of that cylinder.

SPECIFIC DESCRIPTION 
In the drawing we have shown a two-stage sprinkler comprising a stationary 
cylinder 1 for the guidance of a piston head 3 at the lower end of a 
first-stage (outer) riser tube 21 having inner and outer peripheral walls 
16 and 17 which define an annular channel 6 between them. Tube 21 has a 
closed upper end 20 penetrated by a second-stage (inner) tube 22 whose 
axial bore 11 terminates at the top in an outlet 10 and is closed at the 
bottom by a piston head 12, except for a set of radial holes 13 by which 
bore 11 communicates with an annular peripheral groove 14 of this piston 
head. The piston head 3 of tube 21 is downwardly open but internally 
restricted by an annular shoulder 2. Stops 23 and 24 of piston heads 3 and 
12 abut the top 25 of cylinder 1 and the upper end 20 of tube 21, 
respectively, when the sprinkler is fully extended above ground with both 
tubes in their fully elevated positions as shown in FIG. 1. 
The bottom of guide cylinder 1 has a port communicating with a main or 
primary supply conduit 18 through a branch pipe 19; an ancillary or 
secondary supply conduit 4 communicates via another port with a clearance 
maintained by the stops 23 between the top 25 of the cylinder and the 
elevated piston head 3. A set of radial holes 5 in the outer tube wall 17, 
just above its junction with piston head 3, connects that clearance with 
channel 6 whose upper end communicates with a similar clearance, formed by 
the stops 24 between tube end 20 and piston head 12 in the elevated 
position thereof, via another set of radial holes 9 in the inner tube wall 
16. The latter wall is further provided, below the level of holes 9, with 
a set of vertical slots 7 whose upper boundaries are flush with that of 
groove 14 in the illustrated top position of piston head 12 and whose 
lower boundaries then lie below the undersurface of this piston head 
whereby a flow path is established between the interior of tube 21 and 
bore 11 of tube 22. The slots 7 are externally closed by a surrounding 
sleeve 8 located in channel 6, this sleeve having vertical outer flutes 15 
whereby water trapped above piston head 12 in the final phase of its 
ascent can escape through holes 9, flutes 15 and channel 6 into the 
clearance above piston head 3. 
The operation of the telescopic sprinkler in accordance with the invention 
is as follows: 
When the water pressure in the main supply conduit 18 is turned on, the 
water enters through branch pipe 19 into the space below the piston head 3 
in the stationary cylinder 1 and begins to lift the first-stage tube 21 
and the second-stage tube 22 of the telescopic sprinkler. When tube 11 
reaches its upper limiting, water passes through the slots 7 in the inner 
wall 16 of tube 21 and through the ring groove 14 as well as radial holes 
13 of piston head 12 into the axial bore 11 of tube 22 and thence to a 
nonillustrated irrigation attachment supported thereby. The water from the 
spaces above the piston heads 12 and 3 of stages 22 and 21 is forced, 
respectively, through the radial holes 9, the vertical grooves 15 of 
sleeve 8 and annular channel 6 as well as through the radial holes 5 into 
the ancillary conduit 4. To retract the telescopic tubes into the 
stationary cylinder 1, the water pressure in conduit 4 is turned on 
whereupon the water enters the space above the piston head 3 and then 
passes through the holes 5, the vertical flutes 15 and the holes 9 into 
the space above piston head 12. Piston head 3 comes to rest on the bottom 
of the stationary cylinder 1 whereas piston head 12 seats on shoulder 2 of 
stage 21 while the water from the spaces under the two piston heads is 
forced through branch pipe 19 into the main supply conduit 18.