Flush sprinkler

A flush fire protection sprinkler comprising:

• a body defining a passage having an inlet for connection to a source of fire protection fluid under pressure and an outlet for delivery of fire protection fluid toward a region to be protected, said body defining a seat about said outlet and a rim coaxial with said outlet and having an inner circumferential lip, said flush fire protection sprinkler having a first, standby condition with said outlet closed to flow and a second, active condition with said outlet open to flow,
• a sealing member engaged upon said seat,
• a deflector mounted to said body, said deflector, in said standby condition of said flush fire protection sprinkler, being positioned to urge said sealing member into sealing engagement upon said seat, and said deflector, in said active condition of said flush fire protection sprinkler, being positioned to deflect flow of fire protection fluid from said outlet over an area of the region to be protected, and
• a thermally responsive element assembly, comprising:
• a plate member having a conical upstanding rim extending radially outward in a direction of fire protection fluid flow from said outlet and defining a plurality of slots extending radially inward from an outer edge of said conical, upstanding rim,
• a retaining member having a hub and a plurality of elongated retainer fingers terminating in enlarged fingertip portions defining engagement structure, said elongated retainer fingers having a radially inward bias, toward a hub axis, and engaged in said plurality slots, with said enlarged fingertip portions disposed radially outside an outer surface of said conical, upstanding rim,
• a thermally responsive element disposed between said plate member and said hub, said thermal responsive element actuating in response to a heat condition above a predetermined temperature, and
• a pressure loading element mounted to said hub for applying pressure to said thermally responsive element, initial adjustment of said pressure loading element drawing said hub relatively away from said plate member, with said outer surface of said conical upstanding rim urging said enlarged fingertip portions of said elongated retainer fingers radially outward to bring said engagement structure of said enlarged fingertip portions into engagement with said inner circumferential lip, further adjustment of said pressure loading element pressuring said sealing member in sealing engagement upon said seat,
• said thermally responsive element, in a heat condition above said predetermined temperature, actuating to allow pressure of fire protection fluid flow from said outlet to urge said plate member away from said outlet, permitting said elongated retainer fingers to contract toward said hub axis under said radially inward bias, disengaging said engagement structure of said enlarged fingertip portions from said inner circumferential lip, said thermally responsive element assembly thus disengaging from said body to move away from said outlet.