Year: 1888

page_text: Communication
JOHN
Cincinnati, Ohio, U.S.A.
I, WILLIAM PRIDEAUX NAISH of 21, 22 and 23 Coleshill Street, Birmingham in
the County of Warwick, do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained in
and by the following statement:-
"
This invention relates to cut-off valves for slide valve steam engines; its object
being to provide a simple and efficient mechanism for the control of the engine by the
automatic action of the governor to secure due regulation and economy of action.
To this end, the invention consists in constructing the ordinary slide valve of the
grid iron" type with a cylindrical casing into which the admission ports of the valve
open, and providing an open piston valve to operate in said casing said piston valve
being adapted to reciprocate in said casing to control said valve ports; and in further
providing two movable cams arranged as abutment blocks limiting the reciprocal
path of said piston valve according to their relative position, and connections with tho
governor to determine said position. In the general operation of the parts, the cut-
off valve is carried as a rider upon the main valve and partakes of its motion, until,
by contact with the abutment blocks it is stopped at a shorter limit of travel, and
thus caused to move relatively across and govern the ports of the main valve.
Mechanism embodying this invention is illustrated in the accompanying drawings,
in which
Fig. 1 is a vertical section of a portion of an engine constructed according to this
invention, and
Fig. 2 is a transverse section of a detached portion of the same.
Referring now to the drawings, A. designates the ordinary three-ported valve seat of
a slide valve engine, and a¹, a², as the admission and exhaust ports and passages of
the main working cylinder. B designates the slide valve moved upon said seat by
the valve rod and the usual driving connections (not shown); 1, 2, designate
admission ports opening through the face of the valve B and into a longitudinal
cylindrical casing z cast as and upon the back of said valve; and the usual exhaust
cavity of the valve B.

page_text: C designates a piston-shell-valve fitted to reciprocate in the casing :. The said
shell valve is entirely open from end to end, is provided with peripheral openings cc
of corresponding width with the ports a' a³, as shown, and with a central parts hold
to the shell by radial arms as shown in figure 2. The radial openings may extend
over half or a greater portion of the circumference of the cylindrical casing in order
to give a free admission of steam to the main ports of the slide valve.
I prefer to cast the central parts hollow, for the reception of a rod fitted with
projecting steel heads s¹ 82, one of which is detachable to permit removal or
replacement of the rod.
The shell valve C fits the casing closely and as nearly steam-tight as possible and
may be provided with a central packing ring r
The friction between the casing
shell valve C causes the said valve to partake of the motion of the main slide
valve upon which it is carried as a rider.
This relative movement of the shell valve is however confined to a
shorter path than that of the main valve, by two inclinedly-faced abutment
blocks D D interposed as limiting terminals of said path the inclinations of the said
faces being respectively opposed to each other as shown. The blocks are mounted in
suitable guides d which may be secured to the end walls of the steam chest. As
shown these abutment blocks are adapted to move and be guided vertically, but they
may (in connection with the other mechanism hereinafter described) be arranged to
operate horizontally if preferred.
The blocks D D are suspended by links e e from the opposite ends of a lever E
secured at its centre to the shaft e¹. This shaft is journalled in the walls of the valve
chest and projects at one end through a stuffing box. To the projecting end of the
shaft e' is secured a crank or arm by which the action of the governor G is, through
suitable connecting parts (such for example as bell crank lever g and link g¹)
communicated to the shaft e', and by its oscillation the balancing lever E is deflected
and the blocks D1 and D2 moved up and down. It will be readily understood that
as one block is elevated the other is depressed, and by reason of the inclination of
the inner faces of the blocks D' and D2 being opposed to each other, a depression of
one and the relative elevation of the other enlarges or shortens the path of the shell
valve C.
Having now particularly described and ascertained the nature of the said inven-
tion, as communicated to me by my foreign correspondent, and in what manner the
same is to be performed, I declare that what I claim is :-
1. In a steam engine the combination of a "grid iron" slide valve, having admission
passages through the same registering with the seat ports, a cut-off balanced slide
valve carried as a "rider" upon the main slide valve, and normally moving therewith;
with admission openings corresponding with and governing those of the main valve;
adjustable abutment blocks arranged in the path of said cut-off valve as terminal
limits of its relative travel; and connecting mechanism between said blocks and the
governor to determine their adjustment in relation to said path, substantially as and
for the purpose set forth.
2. In automatic cut-off valve mechanism the combination of a gridiron slide valve
provided with an open longitudinal cylinder into which its admission ports open, a
shell valve open end to end in said cylinder governing said admission ports and
normally carried with said main valve as a rider, and operated by resisting its
motion relatively to the movement of said main valve substantially as set forth.
Dated this 1st day of November 1888.