IMPROVEMENTS IN AND RELATING TO VALVES FOR STEAM ENGINES AND MEANS FOR ACTUATING THE SAME
Year: 1886

page_text: Date of Application, 25th May, 1886.
Complete Left, 25th Mar., 1887.
Complete Accepted, 17th May, 1887.
RESERV
Means for Actuating the same.
I, THOMAS SNOWDON, of 14 Brunswick Square, London, W.C. Consulting Engineer
do hereby declare the nature of my invention for IMPROVEMENTS IN AND RELATING
TO VALVES FOR STEAM ENGINES AND MEANS FOR ACTUATING THE SAME, to bo as
follows:-
:-
This invention relates to improvements in that class of engine in which tho
movements of the slide valve are effected by the actuating fluid direct without the
intervention of the usual eccentrics or other outside gearing. A typical form of such
an engine is shown in the Patent granted to G. T. Parnell, No. 656 of 1885.
In this type of engine as hithertofore constructed the movement of the slide valve
is effected by the piston uncovering at each end of its stroke one of two small
controlling ports leading respectively one to each end of the valve case and by this
means motion is imparted to the valve.
It is obvious that the motion of the valve as thus caused is extremely rapid and
further that it makes no return movement until the piston has reached the end of its
return stroke, and uncovered the other controlling port, hence there is no cut-off and
consequently no expansion of the steam used.
Furthermore as now constructed these engines have an an abnormally long and
heavy piston necessitated by the covering due to the valve controlling ports, thus
entailing extravagantly long stean passages as compared with the length of the stroke.
Again in this type of engine the provision made for reversing is not of a sufficiently
practical form to admit of its placing under absolute control engines of such
dimensions as would be used on board ships.
Now this invention relates to means for overcoming these defects.
To get a more even and correct motion of the valve it is caused, by means of
suitable appliances, to act upon two adjustable springs in such a manner that each
movement of the valve shall serve to put one spring in tension and the other in
compression.

page_text: By suitably regulating the strength of the springs. the return movement of the
valve would not be dependent upon the position of the piston and a variable cut-off
would be attainable.
To maintain the valve in equilibrium when placed in a vertical position an extra
strength may be given to the springs connected to the top end of the valve or it
may be suitably connected to a small piston working in a balance cylinder.
To render the act of reversing one of absolute certainty the valve is provided with
suitable means for being moved from the outside.
To overcome the objections due to the abnormally long and heavy piston and
consequent long steam passages, the valve is made of sufficient length to admit steam
direct to each end of the cylinder, and the piston is made of the usual thickness
having an annular flange on each end of it of sufficient length to cover the valvo
controlling ports, the cylinder covers having suitable inward projections, forming
with the sides of the cylinder, recesses into which the annular flanges pass at each
end of the stroke.
Means for Actuating the same.
I, THOMAS SNOWDON, late of 14, Brunswick Square, but now of 91, Guilford
Street, both in the County of Middlesex, Consulting Engineer, 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 improvements in that class of engine in which tho
movements of the slide valve are effected by the actuating fluid direct without the
intervention of the usual eccentrics or other outside gearing. A typical form of
such an engine is shown in the specification of Letters Patent granted to G. F. Parnell,
dated 16th day of January A.D. 1885 and numbered 656. The objects of this
invention are to enable a steam engine of the kind mentioned to be worked
expansively to reduce the capacity of the steam passages between the steam chest
and the respective ends of the steam cylinder; to counterbalance the weight of the
slide valve when worked in a vertical or inclined position and to enable such an
engine to be readily reversed.
1

page_text: In the accompanying sheet of drawings
Fig. 1 is a plan or top view, and
Fig. 2 a vertical central section of the cylinder, valve chest and adjacent parts of a
steam engine embodying my invention.
Fig. 3 is an end view.
Fig. 4 is a transverse section on the line A, B, Fig. 2. 1 is the engine cylinder;
2a hollow piston with semi-circular recess 2"; and 3 a piston rod. 4 is the steam
chest with inlet 5 for motive fluid. 6 is a rod formed hollow at its end portions for
a purpose hereinafter mentioned; it aids in holding the end covers firmly to the valve
chest and serves as a support or carrier for a valve for distributing motive fluid.
This valve which is of the piston type is formed with end portions 8, 8, fitted to slide.
in the valve chest and with curved segments 9, 9, for controlling the admission of
steam to and exhaust from the respective ends of the cylinder. 10 is the exhaust
cavity in the valve. The cylinder valve face is formed with ports 11 and 12 in
communication by passages 13 and 14 respectively with the interior of the cylinder.
These passages are made short and of small capacity. The valve is prevented from
turning on the rod 6 by feathers 15 fitted to the rod and sliding in a key-way groove
in the central portion of the valve. 16 and 17 are pipes in communication with
passages 18 and 19 respectively that lead to the spaces or chambers 20 and 21 situate
between the ends of the valve 7 and the end covers of the valve chest. 22 is the
main exhaust passage.
23 and 24 are exhaust openings or ports in the cylinder and
are in communication with the main exhaust passage 22. The positions of the ends.
of the pipes 16 and 17 and openings or ports 23 and 24 are such that when the
piston 2 is near the right hand end of its stroke, 16 and 23 are uncovered, whilst
when the piston is near the left hand end of its stroke, 17 and 24 are uncovered.
25 and 26 are springs of conoidal form like buffer springs; they are situated in the
spaces or chambers 20 and 21 respectively. The springs are carried by plates 27. that
may be caused to move longitudinally in the valve chest by right and left handed
screw threaded rods 28 and 29 that work in the hollow end portions of the rod 6.
Each plate is connected to its operating rod by a cross bar 30 that works in slots
formed in the rod 6 as shown in Fig. 2. 31 and 32 are nuts in the form of toothed
wheels; they are fitted on the screw threaded portions of the rods 28 and 29
respectively and are prevented from moving endwise by nuts on the ends of the rod 6
and by the frames 33. By rotating these nuts 31 and 32 in one direction by means
of a crank handle 34, shaft 35, and gear wheels 36, the springs 25 and 26 may be
caused to approach and press and hold between them the valve 7 with a greater or
less pressure depending upon the extent of longitudinal movement given to them,
whilst by turning the nuts in the opposite direction the springs may be caused to
recede from the valve so as to leave it entirely free to work as in existing engines of
this type. When the springs are equally compressed against the ends of the valve
they will tend to keep the valve in the normal position shown in the drawings so as
to prevent steam passing to either end of the cylinder 1. When, however, the piston
has nearly reached say the right hand end of its stroke, steam will pass from the
cylinder to the space or chamber 20 through the pipe 16 and passage 18 and acting
against the right hand end of the slide valve will move this valve to the left, so as to
admit steam to the right hand end of the cylinder through the port 12 and passage 14.
Assuming the springs to be pressing against the ends of the slide valve, this move-
ment of the valve will compress the spring 26 and allow spring 25 to extend or relax
itself, and this state of things will continue until the piston has moved sufficiently far
to the left to place the space or chamber 20 in communication with the exhaust
through the passage 18, pipe 16, recess 2 a in the piston, and opening or port 23.
The spring 26 will then re-act more or less quickly, depending upon the degree to
which it has been compressed, to return the valve to the position shown in the
drawings, cutting off the supply of steam, and allowing the engine to then work
expansively. When the piston reaches the left hand end of its stroke the like action
in the reverse direction will take place. The curved segments 9, 9, may have a

page_text: little outside lap as shown to prevent opening of either steam port by vibration or
excessive recoil of the springs when one of them returns the valve to its normal
position.
When the cylinder is arranged vertically one of the springs, for instance the lower
one, may be made stronger or stiffer so as to counterbalance the weight of the slide
valve:
37 and 38 are pipes respectively communicating at one end with the space or
_chamber 20 and with space or chamber 21 and at their other ends with the steam
supply pipe 39. 40 is a three-way cock, by means of which live steam may be
admitted to either of the spaces or chambers 20 or 21 or be cut off from both. By
this means live steam may be caused to operate the valve 7 in either direction to
admit steam to that end of the cylinder necessary to start the engine and ensure its
working in the desired direction; or to reverse its direction of motion after starting.
Having now particularly described and ascertained the nature of the said invention,
and in what manner it is to be performed, 1 declare that what I claim is :-
1. Adapting a steam engine of the kind referred to above in which the movements
of the slide valve are effected by steam direct without the intervention of the usual
eccentrics or other gearing to work expansively substantially in the manner herein-
above described.
2. In a steam engine of the kind referred to in the preceding claim when
constructed with the cylinder vertical or inclined, arranging a spring or springs to
serve not only for returning the slide valve sufficiently far to cut off the supply of steam
before the piston has completed its stroke, but also to counterbalance the weight of the
said valve substantially as described.
3. In a steam engine wherein the movements of the slide valve are effected by the
actuating fluid direct without the intervention of eccentrics or other gearing, pro-
viding a three-way cock so arranged that steam can be admitted by hand at will to
act on either end of the valve in order to determine or reverse the direction of motion
of the engine substantially as described and for the purpose specified.
4. In a steam engine of the kind referred to above, the combination and arrangement
of parts substantially as described and illustrated.