Fire protection sprinkler head

A fire protection sprinkler head of the automatic type including a latch for retaining a valve closure in standby position until a thermally responsive element releases the latch at a preset temperature to thereby release the closure to allow flow of fire-retarding fluid, the latch including a catch, typically in the form of a lip extending radially inwardly from the sprinkler body, a radially inwardly biased spring detent, and relatively separable, detent restraining elements. In the preferred embodiment, the sprinkler includes a deflector adapted to be retained and released by the latch, and the restraining elements are adapted to mutually define therebetween a generally circumferential groove for forcing a ring-form spring detent radially outward into engagement with the catch to secure the latch in standby position, and are further adapted to move relative to each other when the thermally responsive element reaches the preset temperature to permit the spring detent to relax radially inwardly to disengage from the catch whereby the latch is released from standby position.