Importance

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Abstract

In the embodiments described in the specification, a fire protection sprinkler has a sprinkler body with an axial passage for a fire extinguishing fluid, a pair of frame arms terminating at a boss disposed on the axis of the sprinkler passage and a thermally responsive arrangement disposed between the outlet of the sprinkler passage and a screw extending through the boss. The thermally responsive arrangement includes a yoke unit having a yoke base received in a spring washer mounted at the outlet end of the passage and two spaced legs projecting parallel to the axis of the passage having pointed tips and a tubular strut unit having a base with a hemispherical projection engaging the screw and a strut having a cylindrical passage containing a plug of fusible material, a piston and a ball at the outer end which is received in a recess in the yoke base. The pointed tips of the yoke legs are received in recesses in the strut base member on a line which is laterally spaced from the axis of the sprinkler to provide a selected mechanical advantage which reduces the force applied to the plug of fusible material from the force applied between the screw and the spring washer to a level at which the load applied to the plug of fusible material is sufficient to assure prompt activation when the fusible material is fused while avoiding cold flow of the fusible material.

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First Claim