Patent ID: 7416139

Claim:
A sprinkler comprising: an inlet connectable to a source of operating fluid, wherein the operating fluid is water for normal operation, or compressed air to blow water out of the sprinkler to prevent freezing during cold weather; a turbine having a rotor which is driven by the incoming operating fluid and a flow directing stator; and a speed control mechanism located in the fluid flow path which is responsive to behavior exhibited by the operating fluid when that fluid includes compressed air, but is not exhibited by the operating fluid when that fluid does not include compressed air to limit the rotational speed of the turbine when the operating fluid includes compressed air, but which has substantially no limiting effect on rotational speed of the turbine when the operating does not include compressed air, irrespective of the pressure of the operating fluid, within an expected operating pressure range for both water and air, the speed control mechanism including a flow restrictor located in a turbine discharge flow path for the turbine; wherein the turbine rotor is located in a chamber; the flow restrictor includes a discharge port for the rotor chamber; and the area of the discharge port is selected such that the flow of the driving fluid through the rotor chamber is limited when the fluid is compressed air, but is substantially unaffected when the fluid is water; and wherein driving fluid for the rotor enters the rotor chamber through a plurality of inlet ports; and the area of the rotor chamber discharge port exceeds the total area of the inlet ports.