GB190227112A - Improvements in Safety Valves. - Google Patents

Abstract

27,112. Tippett, H. P., and Hayden, N. L. Dec. 9. Safety-valves.-The annular valve 9, Fig 2, closes upwards against a seat 3, and it is provided with a hollow spindle 8 carrying at the upper end a piston 11, which works in a cylinder 4 formed in the valvebox. Steam can pass to the upper end of this cylinder from the hollow spindle 8 through ports 15 in a hollow stem 13 depending from the cover 12. The ports are controlled by a valve 22 fitted steam tight in the upper end of the stem 13 and forced down on to a seat 23 by a spring 24 inside. The " mufflers " 20, 21 at the top of the valve-box are secured to a nipple 18, screwed into a head 17 on the cover 12 of the cylinder 4, by the hood 19, which covers the set-screw 29 for adjusting the compression on the spring 24. Normally, the valve 9 is kept against its seat by the pressure in the boiler. When the pressure gets too high, the valve 22 lifts and allows steam to enter the upper end of the cylinder 4 and act on the piston 11. This piston being of larger area than the valve 9, the latter is forced open, thereby allowing the steam to escape from the boiler through the passages or ports 7 outside the cylinder 4. When the pressure is reduced sufficiently to allow the valve 22 to return to its seat, the steam above the piston escapes through a port 16 in the cover 12, and the valve 9 is again seated by the pressure in the boiler. In a modification, Fig. 5, the cover 33 has no depending rim, but a central flange 34 is formed on the top of the cover through which a stem 35 on the piston 36 works. The stem 35 is provided with ports 38, and is screwed internally to receive the nipple 40, which is free to move vertically with the piston. A spring 41 may be used to keep the valve against its seat when there is no pressure in the boiler. The " mufflers " 31, 32 are screwed to the valve-box. Fig. 6 shows the spindle 42 formed in one with the piston 43.