| 摘要 |
<p>An emitter 1 comprises a housing 2 and a key (or 3A) fitted into the housing. The key 3 has a spigot 12 whose periphery is defined by a screw thread form 16 into a helical channel 17. The housing 2 has one end 5 open and the other end 6 closed. Barbed nipples 9 and 11 are provided spaced apart along the housing 2 to pass water to and from the interior of the housing. The helical channel 17 controls the flow rate of water from the housing. At one end, the helical channel 17 communicates with an axial passage 14 or a radial hole 14A which will register with the nipple 9 only when the key 3 is turned to a particular orientation in the housing 2 at which time it is locked from withdrawal from the housing. At the other end, the helical channel 17 registers at all times with the nipple 11 or has a chordal passage 15 which only registers with the nipple 11 when the key 3 is turned to the aforesaid orientation.</p> |
