Patent GB-1400618-A (GB)
Title: On-off sprinkler
Inventor: MEARS J W
IPC: F16K17/38
Filed: 1972-11-08
Abstract: 1400618 Fluid-pressure servomotor systems ITT INDUSTRIES Inc 8 Nov 1972 [8 Nov 1971] 51446/72 Heading G3P [Also in Division A5] An automatic "on-off" sprinkler involving main valve means operated by a pilot valve in fluid communication therewith is characterized in that the pilot valve is actuated by a bi-metal disc which resiliently biases the pilot valve to a closed position and which moves the pilot valve member between open and closed positions by movement of its centre relative to its peripheral edges, in a so-called "snap" action. Figs.1 and 2 show the "off" and "on" positions of the sprinkler. In Fig.1 sprinkler body 10 defines threaded opening 12, flow passage 14 and outlet 16. Cylindrical chamber 20 is formed between the outer wall of 10 and internal walls 18, 22, and further chamber 28 and threaded opening 26 are defined by wall 22 and lower wall 24 of 10. Chambers 20 and 28 communicate via passage 30, and chamber 28 leads to flow passage 14 via passage 32. Fitted in opening 12 is threaded inlet member 34 providing axial flow passage 38 therethrough and annular valve seating surface 39 as its inner end. Piston assembly 40 closing the upper end of chamber 20 comprises stepped piston 42 whose upper and lower members 46, 44, slidably fit in bore 38 and chamber 20 respectively, O-rings 54 and 74 in grooves 56 and 72 ensuring fluid seal. The piston has fluid ports 53 in upper part 46 and has axial bores 48, 50, 52 of increasing size. Strainer 84 and restriction member 82 with orifice 86 are retained in bore 50 by ring 80, and coil spring 90 acting between ring 80 and wall 22 biases the piston towards seat 39. The area of piston assembly 40 subject to pressure in chamber 20 exceeds that in passage 38 and the piston 42 will therefore normally be maintained in the closing position. The pilot valve assembly 100 comprises a member 102 having threaded cylindrical part 104 which engages in opening 26, radial flange 106, and axial bore 108 which houses pilot valve 110. The valve has cylindrical portion 112 which slides in bore 108 and cavity 28, and is of a length such that inner end 120 abuts seat 31 surrounding passage 32, O-rings 116 and 122 being provided at 118, 124 respectively. Bi-metal disc 126 is centrally screwed into the outer end of valve 110 and peripherally secured to radial flange 106 by screws 132. Disc 126 is cupped and its  convex surface urges valve 110 towards the closed position. The disc is designed to move with a "snap" action towards the reverse cup shape at e.g. 185F and to return to its original shape at e.g. 100F. Conventional deflector 130 is suspended from outlet 16 by yoke 131. When the sprinkler is installed and the water supply turned on, water passing through orifice 86 fills chambers 20, 28 and maintains piston assembly 40 against valve seat 39. Bi-metal disc 126 maintains pilot valve 110 closed to the passage of water from 28 to 32. In the event of a rise in temperature around disc 126 to e.g. 185F, disc 126 reverses its curvature in a "snap" motion dislodging pilot valve 110 from seat 31 and opening passage 32 to fluidflow from chamber 28. When water pressure in chamber 20 has dropped sufficiently, mains pressure in 38 overcomes the force of spring 90 and moves piston assembly 40 to the Fig.2 position and water is discharged via ports 53 to outlet 16. When the fire is extinguished and disc 126 cools to e.g. 100C it reverts to its original conformation and closes pilot valve 110. Chambers 28, 20 again fill with water and the increased pressure therein eventually restores piston assembly 40 to the Fig.1 or "off" position.