A NEW OR IMPROVED LINK MOTION FOR WORKING THE SLIDES OR VALVES OF STEAM AND OTHER FLUID PRESSURE ENGINES
Year: 1884

page_text: I, ARCHIBALD DOUGLAS BRYCE-DOUGLAS of Seafield, Ardrossan, in the County
of Ayr, Engineer do hereby declare the nature of my Invention for "A NEW OR
IMPROVED LINK MOTION FOR WORKING THE SLIDES OR VALVES OF STEAM AND
OTHER FLUID PRESSURE ENGINES" and in what manner the same is to be
performed to be particularly described, and ascertained in and by the following
statement:-
.
.
My Invention relates to the arrangement of levers and links for working the
slides or valves of steam or other fluid pressure engines in such a manner that the
movement of the piston rod and connecting rod is utilised for giving to the slide or
valve the movements required for stopping, starting or reversing or variable
expansion, without the use of eccentrics or cams. The levers and links which I
employ for this purpose may be variously arranged to suit particular forms and
conditions of the engines to which they are applied, as illustrated by the accom-
panying Drawings, in all of which, corresponding parts are marked by similar
figures of reference. No. 1 is an arrangement suitable for a steam engine having
the cylinder situated at the top of the framing, the piston rod passing through the
cylinder bottom and connected to the crank below. I provide a beam 1, which
may be that for working the air pump, mounted on a stationary fulcrum 2, and
connected at one end to the piston rod crosshead, so that this beam oscillates in
time with the strokes of the piston. On a pin 3 on this beam, I mount a curved
link 4, on which is fitted a sliding block that is linked by a rod 5 to the slide or
valve rod 6. I connect a pin 7 on the main connecting rod by a link 8, to the
middle joint of a pair of toggle-links 9 and 10 of which 9 is pivotted on the beam 1,
and 10 is jointed to a radius rod 11. This radius rod is pivotted on a stationary
fulcrum, and a pin on it is connected by a link 12 to an arm of the curved link 4.
By means of these connections, the link 4 receives a motion corresponding nearly
with that of the link that is usually worked-by two eccentrics. The rod 5 being
linked by a rod 13 to an arm 14, by moving this arm, the block at the lower end
of 5 can be slid along the curved link 4, and thus the slide or valve rod 6 can be
made to receive movements corresponding with those obtained by the use of
the ordinary double eccentrics and link motion, suitable for either direction
of the engine's motion and for various degrees of cut-off and expansion
the diagram No. 2, for the beam 1 is substituted a lever 1 having the curved
In

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link 4 mounted on a pin 3 beyond the fulcrum 2 of the lever, and the radius rod 11
is arranged as a two, armed lever. In the diagram N° 3 the curved link 4 is
mounted in an inverted attitude on a beam 1, such as that shewn in Nº. 1; and in
the diagram No. 4 the inverted link is mounted on a lever 1, such as that shewn in
No. 2. In the diagram No. 5, a straight guide 11 is substituted for the radius rod 11
shewn in the other Figures.
No. 6 shews the arrangement applied to a locomotive. No. 7 shews it applied to
a direct acting horizontal engine. The diagram N°. S shews a similar arrangement
of levers and links for effecting the movement of the slide or valve rod when it is'
not required to reverse the engine or vary the cut off, in which case a simple bell
crank lever 4 is substituted for the curved link 4, above described.
Having now particularly described and ascertained the nature of my Invention
and in what manner the same is to be performed, I hereby declare that I make no
general claim to the working of engine slides or valves by notion derived from"
that of the piston rod and connecting rod, but what I claim is―
In combination with 'the beam or lever 1, worked by the piston rod and the
curved link or bell crank 4 pivotted on 1, the system of toggle links and their
connections, 8, 9, 10, and 12, and radius rod or guide 11, whereby a rocking motion
is imparted to 4, suitable for working the slide or valve rod, substantially as herein
described.