Fishburn, Gold & Litman
Adjustable drop nipple for sprinkler heads
 An adjustable drop nipple for sprinkler heads is disclosed which comprises a stationarily mounted collar with internal threads that receives an externally threaded nipple, and whereupon rotating the nipple a portion of its length is caused to retract into the collar or extend from it, depending on the direction of rotation, in order to precisely regulate vertical elevation of a sprinkler head attached to the lower end of the nipple. An effective seal against leakage of water is achieved by use of one or more O-rings on the nipple which abut a smooth bore section inside the collar. 
Central Sprinkler Corporation
A
A62C
inventional
James R.
Anderson