Descripfion of Mr. Arthur IVoolfs Steayn-Valve. 165 



BB bv the flanges aa. The top or cover of the steam -box 

 •C, marked with the letter D, whieh is well secured in its 

 place, has a hole through it for the rod of the valve, so con- 

 trived as to answer the purpose of a stuffing-box to make 

 the rod work up and down steam-tight, the stuffing being- 

 kept in its place by the usual means, as shown in the section. 

 Bv means of a pin or nail, h, and the two vertical pieces ee, 

 the piston rod is made fast to m, which is a cover of and 

 joined to the hollow cylinder n,v. The cover vi fits steam- 

 nght into the collar 0,0, which is made fast on the flange a a. 

 -The cylinder 71 n is open at the bottom, having a free com- 

 munication with the nmin cylinder A, and has three vertical 

 slits, one of which, S, is shown in the plate*. The sum of 

 the surface of all these slits or openings is equal to the area of 

 the opening of the collar 0, 0, in which the cylinder 71, n works. 

 When the steam acquires a sufficient degree of elastic force 

 "to raise the valve (that is, the cylinder n 77 with its cover m, 

 and the rod R) and whatever weight it maybe loaded with, then 

 the openings S, getting above the steam-tight collar 0,0, al- 

 lows the steam to pass into the steam-box C. The quantity 

 of steam that passes is proportioned to the elastic force 

 it has acquired, and the weight with which the valve i^ 

 loaded ; and the rise of the openings S above the collar 0, o 

 will be in the same proportion. This valve may be loaded 

 in any of the usual methods 5 but Mr. Woolf prefers the one 

 -shown in the drawing, in which the upper part of the rod 

 R is joined by means of a chain to a quadrant of a circle 

 O with an arm projecting from it, as represented in the 

 plate, and which carries a weight, Z, that may be moved near 

 to or further from the centre of the quadrant, according as 

 the pressure of the valve is wished to be increased or dimi- 

 nished. As the valve rises, the weight moves upwards in 

 the ,nrch 7i //, giving an increased resistance to the further 

 rising of the valve, proportioned to the greater horizontal 

 distance from the centre of O, which the weight attains by its 

 rise in the said arch, the said distance being measured in 

 the line Q/jby a perpendicular from the said line Q/> 

 passing through the centre of the weight. Thus, if the 

 weight Z press with a force equal to twenty pounds on the 

 s(juare inch of the aperture in 0,0 in its present position, 

 it will, whm it rises to the position at /, press with a 

 force ecjual to thirty pounds, and at p with a force equal 

 tf) forty pounds, on the s(juare inch ; so that the rod 

 <)Z may be made to serve at the same time as an iu- 



' These openings mav be covered with a grating. 



L 3 dex 



