The Impact Sprinkler: A Jet That Knocks Itself Round

Water rises through tube 13 to a Y connection 16 with two inclined arms, 17 and 19, carrying jet nozzles 18 and 20. A pin 22 with a conical point in front of nozzle 20 breaks up part of its jet to water the ground near the sprinkler. On a post 24 above the Y, a sleeve 25 turns freely, and "A torsional spring 28 surrounds sleeve 25" between the Y and a T connection 26. From the T, a rod 29 carries "an open ended box-like member 30" whose rear wall portion 31 forms "an inclined vane or surface that is impinged by the jet of water"; a weight 34 on a short arm 33 balances it. In use, most of the jet from nozzle 20 "strikes against vane 31 and is deflected thereby against the extended plate 32 and the reaction of water leaving the latter causes the housing 30 and arm 29 to swing". The arm swings "rather than to cause the entire sprinkler to rotate backward because the resistance of spring 28 is less than the resistance offered by the friction" of flange 14 and gasket 15. Then "the torsional spring rotates the swinging assembly in the opposite direction", and member 30 "cuts through the jet from nozzle 20 and finally strikes against the extended plate 21, thereby causing the entire sprinkler to rotate" a small part of a turn. He adds that "The partial vacuum produced on the outside of vane 31" as it cuts into the jet pulls it further in and "aids materially in producing a steady, strong oscillation."

Connect an impact sprinkler head to a garden hose and set it on a stake in open lawn. With the stopwatch, count knocks per minute and time one full circle; divide to get degrees per knock and compare with the notebook. Set out cups in a line from the sprinkler at 1 m spacing and run it for 15 minutes. Measure the water in each with the measuring jug: the pattern shows how the jet and the broken-up spray share the ground. Adjust the diffuser screw in front of the nozzle and repeat.

**Orton H. Englehart** of Glendora, California, filed US 1,997,901 on 18 December 1933; it was granted on 16 April 1935. His claims cover a rotating jet arm, an oscillating arm on the same axis that strikes it, a vane in the jet and a spring between them. **Honest limits.** The inertias, friction and jet angle in the notebook are examples; the vacuum range ignores air, which in practice cuts the reach greatly.