| 摘要 |
A sprinkler designed to irrigate a certain sector of the ground comprises an upwardly sloping barrel, limitedly rotatable about a vertical axis, which terminates in a nozzle and carries two vertically oscillatable arms that are alternately effective to drive the barrel on a forward swing and on a return swing under the impact of the emitted water spray. The reverse-driving arm has a deflecting head which, on the return swing, lies in line with the nozzle and has two lands adjoining each other at an obtuse angle, i.e. a ramp face sloping upwardly in a radially outward direction and a reaction face of larger area including an acute horizontal angle with the radial direction. When the head is lowered into the path of the spray by an end stop, the impact of the water upon the ramp face pulls the reaction face into line with the nozzle against the force of a restoring spring. Another such spring, including a lost-motion connection, goes into effect in a position in which the spray impinges squarely upon the reaction face, thus tending to hold that face aligned with the nozzle but allowing the head to yield under excessive water pressure.
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