Improvements in and relating to Direct-acting Fluid Pressure Engines.
Year: 1895

page_text: Date of Application, 11th Oct., 1895-Accepted, 16th Nov., 1895
COMPLETE SPECIFICATION.
Improvements in and relating to Direct-acting Fluid Pressure
Engines.
I, THOMAS WELSH LAMONT, Engineer, Hawkhead Works, Hawkhead Road,
Paisley, Renfrewshire, do hereby declare the nature of my invention and in
what manner the same is to be performed to be particularly described in and
by the following statement in writing, that is to say :-
This invention relates to improvements in the valve gear and method of
controlling and regulating direct acting engines the motive power of which may
be steam, compressed air, or like fluid, and specially applicable as a pumping
engine.
Under my improvements there would be used a main and auxiliary cylinder
and gear, with an arrangement of ports inside, and between the main and
auxiliary cylinders, suitably operated on by an arrangement of valves, links, and
levers having notion imparted to them by the main piston rod thereby giving a
reciprocating motion to the engine, combined with a means of bringing the piston
and its connections gradually to rest at the end of the stroke and reversing
the direction of motion without shock or noise, and making it impossible for
the piston to strike the ends of cylinder and also avoiding all dead points
in the stroke.
And in order that my said invention and the manner of performing or carrying
same into practice may be properly understood, I have hereunto appended an
explanatory sheet of drawings in which the same reference letters are used to
indicate corresponding parts in all the figures where shown,
Figure 1 is a longitudinal vertical section taken through the line 9 and 10 in
Figure 3 showing the main slide valve and ports to main cylinder.
Figure 2 is a longitudinal vertical section taken through the line 9 and 10 in
Figure 3 showing the auxiliary valve and ports for operating auxiliary piston.
Figure 3 is a cross section taken through the line 7 and 8 in Figure 1.
Figure 4 is a plan view with the auxiliary cylinder, piston and valves removed
showing ports on cylinder face.
Figure 5 is a cross section taken through the line 11 and 12 in Figure 1 showing
the mechanism for imparting motion to the valves.
Figure 6 is an enlarged view of stop nuts on valve spindle showing the method
of securing same to spindle.
Referring to these drawings:-A is the main cylinder, B is the main piston, C is
the piston rod which passes through stuffing box and gland D, E is a cross head to
which the valve gear is connected, and also the rod for working a reciprocating
pump or any apparatus for which the engine is required, is the connecting link
to valve levers, H H are levers for giving motion to valve spindle M and they
swing on a pin through end of. fulcruin link 1, K is a guide-block and cross-head,
sliding on fixed guide bar L, and also on valve spindle M, and imparts motion to
valves and spindle at the proper time through stop nuts N N which are adjustable
on spindle. The link I serves as a fulcrum for levers H and oscillates on pins at
both ends. The auxiliary piston P is fixed to spindle M and is reduced in diameter
at the centre to form shoulders for bearing against and moving the valves S and T.
The valve S controls the supply and exhaust to both ends of main cylinder A
through ports W, W, and the valve T does the same to both ends of auxiliary
cylinder R through the ports Z, Z. The auxiliary slide valve T fits between the

page_text: shoulders of piston 1', but main slide valve S for operating supply and exhuist of
steam to main cylinder A is horter so that both slide valves ciuno cover their
respective ports at the same time. This is clearly shown in Figures 1 and 2. The
valve spindle M is screw-threaded for stop nuts S, N, and passing through stuffing
box and gland O is securely fixed by a nut and screwed end to auxiliary piston P.
R is the auxiliary cylinder in which auxiliary piston l' moves alternately from one
end to the other, anil the central portion serves as a steam easing. It is bolted to
main cylinder and has supplementary ports V, V, passing through to extreme ends
of main cylinder as shown on Figures 1 and 4. These ports VV are situated in
auxiliary cylinder so that piston P just covers them both, and the least movement
from central position would open either one or the other.
The action of this arrangement is as follows:-
:-
Auxiliary piston P with both slide valves S and T is moved by the main piston B,
before coming to rest, by means of the links and levers described to a little over
the central position and this puts one end of auxiliary cylinder R in communication
with pressure and the other end with exhaust whereby auxiliary piston and valves S
and T are moved by the steam pressure on piston P to the extent necessary to give
full port openings to main cylinder, and at the same time the auxiliary piston P
covers the supplementary port V to the end of main cylinder which is open to
exhaust and uncovers the one at the end open to steam pressure. The opening and
closing of supplementary ports V, V, by piston P takes place simultaneously with
the opening of steam or exhaust to the ends of auxiliary cylinder R, so that as
P steam is
soon as either supplementary port V or N is uncovered by pist
admitted to that end of auxiliary cylinder by slide valve T, and conversely as soon
as slide valve T opens either end of auxiliary cylinder to exhaust the supplementary
port in that end Vor V is covered by piston P. The drawing at Figures 1
and 2 shows piston l' and auxiliary valve T in central position, but main valve S
is still open and will cause main piston B to move in the direction of the arrow
until it passes port W, which is open to exhaust, when it will gradually be brought
to rest, by the imprisoned steam forming a cushion between the piston and the ed
of cylinder as this space is now completely closed.
The stop nuts N'N are fixed on valve spindle M in such a position as just to
move piston Pa little over the central position before main piston B comes to rest.
The auxiliary valve T will then admit steam by the auxiliary port Z to the end of
auxiliary cylinder R and at the same time the other end of auxiliary cylinder will
be opened to exhaust through the port Z. The pressure of the steam will thus
cause auxiliary piston with both slide valves S and T to move to the other end and so
reverse the steam and exhaust passages to main cylinder, but as the main piston B
still cavers port W in the cylinder the steam will only be admitted through sup
plementary port B until piston B has moved so as to uncover port W and allow
the full flow of steam. The compression and slow reversal of motion is the same
for both ends of the stroke. The main piston 13 cannot strike against the ends of
a cylinder under any conditions, although any part of the gear or connections
should break down as supplementary ports are either open to steam pressure
or closed altogether by suxiliary piston P and are never open to allow steam to
pass from the main cylinder. The amount of compression can be increased or
reduced to any extent desired by altering the position of stop nuts N N on spindle M,
and live steam may be admitted before the main piston B comes to rest if necessary.
The auxiliary ports Z Z enter the auxiliary cylinder R a sufficient distance froin
the ends, so that when piston l' moves across under the action of the steam, the
imprisoned steam at the end forms a cushion to bring the piston l' gradually to rest
without striking against the end covers.
The means employ of securing stop nuts N N to spindle M and at the same
time being easily adjusted to compensate for wear and tear of working parts will be
readily understood from Figure 6. A split pin N₁ passes through nut N at one
side of the screwed spindle M. The screw on spindle is flattened Tongitudinally on
one or both sides thus allowing the step nuts N N to be separated or brought closer

page_text: together (thereby altering the amount of steam compression at end of stroke in
cylinder) by simply taking out and replacing split pin, and it remains a perfectly
secure fastening. The depth of nut is increased to make up for the reduction of
thread surface, by flats.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed 1 declare that what
I claim is :-
First. In a direct acting fluid pressure engine, an auxiliary piston for moving
distributing valves of main and auxiliary cylinders in combination with supplementary
ports to the ends of main cylinder which are alternately opened and closed by the
said auxiliary piston substantially as herein described in reference to and shown in
the accompanying drawings.
Second. In a direct-acting fluid pressure engine placing the main ports for supply
and exhaust away from the ends of main cylinder, in combination with sup-
plementary ports placed at extreme ends and opened and closed by movement of
auxiliary piston for the purpose of forming a steam cushion at the ends of cylinder
and still allowing a small opening for steam to begin the return stroke substantially
as herein described in reference to and shown in the accompanying drawings.
Third. In a direct-acting fluid pressure engine, the combination of main and
supplementary ports to main cylinder opened and closed by auxiliary piston and
main slide valve, with adjustable nuts on spindle attached to said auxiliary piston,
moved by guide block, levers and links from main piston, for the purpose of
properly adjusting the steam cushion and reversal of motion for return stroke,
substantially as herein described in reference to and shown in the accompanying
drawings.
Dated the 10th day of October 1895.
W. R. M. THOMSON & Co.,
96 Buchanan Street, Glasgow, Agents.