LINK MOTION FOR WORKING THE SLIDES OR VALVES OF STEAM AND OTHER FLUID PRESSURE ENGINES
Year: 1885

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 "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, to stop, start, reverse, or
to vary expansion.
The motion for this purpose is derived from that of the piston rod combined
with a movement obtained from the connecting rod.
The levers and links which I employ may be variously arranged to suit the
particular forms and conditions of the engines to which they are applied, as
illustrated by the accompanying drawings, in which corresponding parts are
marked by similar figures of reference.
Fig. 1 shews an arrangement suitable for a steam engine having the cylinder
situated at the top of the framing, with 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 by a link to the piston rod
crosshead, so as to oscillate in time with the piston. On a pin 3 on the beam 1
I mount a curved link 4 to which is fitted a sliding block linked by a rod 5 to the
slide or valve rod 6. To a pin 7 on the connecting rod I joint one end of a lever 8,
the other end being jointed to a pin on a sliding block 9 which moves in a curved
or straight guide. I connect a pin on the lever 8 by a link 10 to a pin, joining
the end of a radius rod 11 (which is pivotted on a stationary fulcrum) and of a
link 12 jointed to the upper arm of the curved link 4, which thus receives a
motion corresponding nearly with that of the link usually worked by two eccentrics.
The rod 5 is linked by a rod 13 to an arm 14, by moving which the block at the
lower end of the rod 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 ordinary double eccentrics and link motion to suit either direction
of the engine's motion, and various degrees of cut off and expansion.

page_text: Fig. 2 shews diagrammatically a modified arrangement in which the beam or
lever 1 oscillates on a moveable fulcrum 2 on the end of the rod 5, and the curved
link 4 oscillates on a stationary fulcrum 3.
Fig. 3 is an arrangement similar to that of Fig. 2, a guide 11 being substituted
for the radius rod 11 of Fig. 2.
Fig. 4 shews a similar arrangement with the arm of the curved link 4 inverted.
In the arrangement shewn by Fig. 5, to the pin 7 on the connecting rod is
jointed one end of a lever 15, to a pin on which is jointed one end of a radius
rod 16 oscillating on a stationary fulcrum. A link 17 connects the other end of
the lever 15 with the arm of the curved link 4, giving it a motion similar to that
obtained with the links 8, 10, 11 and 12 in Fig. 4.
Fig. 6 shews an application to a locomotive of an arrangement such as I have
described, the guide 9 shewn in Figs. 1, 2, 3 and 4 being replaced by a radius rod 9
oscillating on the fixed fulcrum 2.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim, in respect of link motion for working the slides or valves of steam and
other fluid pressure engines, is
1. In combination with the lever 1 oscillating on a fixed fulcrum in time with
the piston and the curved link 4 mounted on the lever and fitted with a sliding
block connected to the valve rod, the lever 8 and the links 10, 11 and 12 communi-
cating rocking movement from the connecting rod to the link 4, substantially as
described with reference to Fig. 1.
2. In combination with the lever 1 oscillating on a moveable fulcrum in time
with the piston and linked to the valve rod, and the curved link 4 fitted with a
sliding block linked to or carrying the fulcrum of lever 1, the levers and links
whereby oscillating movement is communicated from the connecting rod to the
link 4, substantially as described with reference to Figs. 2, 3, 4, and 5.
3. In combination with the lever 1 oscillating on a fixed fulcrum in time with
the piston and the curved link 4 mounted on the lever and fitted with a sliding
block connected to the valve rod, the lever 8 and the links 9, 10, 11 and 12.
communicating rocking movement from the connecting rod to the link 4, substantially
as described with reference to Fig. 6.
Dental L
100