| 摘要 |
<p>An emitter (1) comprises a housing (2) and a key (3 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> |
