426 STEPHENSON'S PATENT 



forming the connection with the spindle in this manner, they are enabled to keep in 

 close contact, although the position of the spindle should be altered ; and the regulator 

 plate is still made to turn with the spindle. 



The two plates are ground together, so that when the regulator plate is turned round 

 and covers the openings, the passage is closed completely steam-tight ; the under 

 side of the regulator plate, and the solid space between the openings in the other 

 plate, are both hollowed a little in the middle, as shewn in the section through the 

 centre of each, in fig. 13, so that they touch only for a space of three quarters of an 

 inch round the edge. This diminishes the labour of grinding them, as there is so 

 much less surface to grind, and also ensures their fitting round the edges, where 

 alone it is required ; for the little steam that will pass through the hollow between 

 the plates when the regulator is partially open, is of no consequence, as it will only 

 slightly increase the quantity of steam passing through. 



The other end of the box a, (Plate XC.,) is fixed by a flanch to the back plate 

 of the fire-box ; and an opening is cut in the plate corresponding to the inside of 

 the box, which is closed by a plate, having the stuffing-box/', fixed on to its 

 inside with its gland g. The spindle of the regulator turns steam-tight in 

 this stuffing-box, a collar on the spindle resting against the end of it ; and the 

 handle, //, is fixed on the end of the spindle, moving between two brass arcs, z", 

 (Plate XC., and fig. 1, Plate XCII.,) which are connected together at the ends, and 

 bolted on to the fire-box : these arcs serve as guides for the handle when moved, 

 and stop it at each side. In fig. 1, Plate XC., the regulator is shewn quite open; 

 but if it were made to turn round, it would immediately begin to contract the pas- 

 sage for the steam, and when turned a quarter round, the passage would be com- 

 pletely closed. The motion of the handle is therefore through a quarter of a circle, 

 or half a quadrant on each side of the vertical position. When the handle is put 

 down on the right hand side, the regulator is shut, and when down on the left side, 

 it is full open ; and in intermediate positions the regulator is proportionally open, 

 except for the small distance at each end along which it is passing over the over- 

 lap. The area of passage through the regulator when full open, is 21 '9 square 

 inches, or a little more than the area of the steam pipe, which is 19'6 square inches. 



This is the form of regulator that is most frequently used, as it is simple in its 

 construction and not liable to get out of order, and particularly as it is very 

 uniform and regular in its action ; and excepting the small overlap, the degree of 

 opening is exactly proportionate to the amount of motion of the handle. Another 

 contrivance that is also used for the purpose, consists of a conical valve like a 

 safety valve, which closes the end of the steam pipe; and is drawn away gra- 

 dually from its seat, when turned round with the handle, by means of a fixed pin 



