IMPROVEMENTS IN SINGLE ACTING STEAM ENGINES
Year: 1885

page_text: "
I HAMILTON WELDON PENDRED, of Crohill, Freshford in the County of
Kilkenny, Ireland Mechanical Engineer do hereby declare the nature of my
Invention for IMPROVEMENTS IN SINGLE ACTING STEAM ENGINES and in what.
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement :-
Each Engine consists of one or more "Units." Each "Unit" consists of two
single acting cylinders, one steam distributing valve, two pistons, two connecting
rods, a crank shaft, and suitable framing and appurtenances. Two or more
Units" may be combined only one. crank shaft being used. A "Unit" may be.
simple or compound. In the first case the cylinders are both of the same diameter;
in the second case, that cylinder which first receives steam from the boiler, is
smaller than the other cylinder. In all cases the cranks are placed about one
hundred and eighty degrees from each other, so that the pistons are at opposite
ends of the cylinders at the same moment, To distribute the steam I employ a
slide valve working on a valve face, by preference formed on the closed ends of the
cylinders, in which are formed suitable ports for the passage of the steam The
action of the slide valve is such, that it first admits steam to the small cylinder,
It then cuts it off: Then it passes the steam from the small into the large
cylinder: It then admits steam into the small cylinder from the boiler, and at the
same time suffers the steam to escape from the large cylinder into the air or a
condenser. In order to give motion to the slide valve, I form in it a long groove
at right angles to its line of motion. In this groove works a long crank pin,
formed in a valve spindle, which is caused to rotate, at the same speed as the crank
shaft of the engine, by spur gearing or a pitch chain; or the aforesaid valve spindle
crank, may have a partial motion of rotation imparted to it by an excentric or its
equivalent. Although I prefer to place the slide valve on the ends of the cylinders,
as hereinbefore described I do not confine myself to that arrangent, as in some
cases it is more convenient to place the slide valve on the sides of the cylinders
nearer to the crank shaft, The valve spindle may then be vertical instead of
horizontal, or nearly so, and it may be then driven by bevil instead of spur wheels.
The two accompanying sheets of drawings show the nature of my improvements

page_text: in single acting engines. In these drawings the same parts are indicated by similar
letters, Fig. 7 is a longitudinal section of a compond engine, Fig. 2 is a cross
section of the slide valve. Fig. 3 is an external end view of the engine, shewing
the gearing for driving the slide valve. Fig. 4 is a cross section of the slide valve
shewing the modification in the valve spindle crank, when said crank does not
make a complete revolution Fig. 5 is a horizontal plan section through the crank
shaft, Fig. 6 is an end section shewing the low pressure piston &c Fig. 7 is a
plan of the slide valve, but I do not confine myself to the particular outline of
valve shewn in Fig. 7. Figs. 8 & 9 shew a spiral slot arranget which may be
employed for reversing. Fig-10-shows a modification in the relations between the
position of the cylinders and crank shaft, a right line passing through the
longitudinal axis of the cylinder will not cut the crank shaft centre, but will fall to
one side of it, Fig. 11 shows how I use a pitch chain for driving the slide valve
instead of wheel gearing Fig. 12 is an end view showing how an excentric
mounted as shown in Figs. 8 & 9 may be used to drive the slide valve, Fig. 13
shows how a disc may be used instead of an excentric, and Figs. 14 & 15 are two
diagrams intended to illustrate the mode of action of the slide valve.
A and B are the two cylinders which stand on an Iron box or frame of any
convenient form, to which are secured the bearings of the crank shaft O I prefer
to use a box of the form indicated in Fig. 7 which will hold oil & water to lubricate
the crank pins, but inasmuch as the construction of the box forms no part of my
invention I need not describe it. C & D are the high and low pressure pistons.
I do not confine myself to the shape or proportions shewn, The pistons are prolonged
in the form of trunks, which fit the cylinder closely and act as guides. It has been
found in practice that when such trunk guides are a good fit they are liable to
stick in the cylinders as a consequence of unequal expansion To prevent this
I provide a certain amount of elasticity by cutting one or more slots in the
trunks, lengthwise, reaching from the edge to the piston body proper, E is the
valve chest in which is the slide valve F In the upper side of it is the slot or
notch, or groove best seen in Figs. 2 & 3 I prefer to cast this groove on a chill,
and to finish it up by passing an emery wheel of suitable form through it. In this
groove works the long case hardened crank pin H turned out of the solid rod G G.
When the rod is caused to rotate, the slide valve will move backwards and forwards
and distribute the steam, To get the valve spindle in and out; the stuffing boxes
are fitted with enlarged bushs at the bottom, as shown, but in some cases I make the
valve chest to part longitudinaly on the axis of the valve spindle, the stuffing box
parting in like manuer, so that the rod or valve spindle G G may be lifted clean
out. The valve chest should be made of such proportion however, that the valvo
can be removed, by "upending" it, when the valve chest lid is off without
removing the valve spindle, N N₁ are steam ports one to each cylinder and X is
the exhaust passage. The continuous revolution of the valve crank spindle may
be caused in various ways. I prefer the arrangement shown in Figs. 1 & 3. On the
crank shaft is keyed the spur wheel I. This drives an idle wheel J carried on a
stud as shown, J in turn drives a third spur wheel K mounted on the end L of the
valve crank spindle G. I & K being of the same diameter, the spindle G will
revolve at the same speed as the main crank shaft O, When the engine is not
reversible K is keyed fast on L, when it is reversible, as for use in steam launchs,
the wheel K is mounted loose on the valve spindle G L. M is a handle keyed fast
on L. P is a snug cast on the boss of K. The snug bears against the handle when
the engine is in motion and compels it to rotate and with it the valve spindle G L.
In order to reverse the engine, it must be stopped and the handle turned through
so much of a revolution as will cause it to bear against the other end of the
Bug P. If steam is then readmetted to the engine it will revolve in a direction
the reverse of that in which was running when stopped.
Fig. 11 shows another arrangement, a pitch chain shown by the dotted lines S S
being employed instead of the wheels I. J. K herein before described, the engine may

page_text: then be reversed as already described the chain wheel on the valve spindle L
takeing the place of the wheel K, and driving the valve spindle G L by means of
a snug and handle as shewn in Fig. 7 at M. & P. As the wear or stretching of the
pitch chain would affect the lead of the slide valve, I mount the lower wheel R loose
on the crank shaft O and I provide it with a set screw so that it may be adjusted
on the crank shaft to keep the lead right In some cases an excentric T Fig. 12
may be used to actuate the slide valve, the crank valve spindle then makes only a
portion of a revolution as will be readily understood In order to reverse the
engine in this case the excentric may be mounted as shewn in Figs. S. 9 & 12 on a
sleeve with spiral grooves, a device so well known to engineers that no description
is necessary. The excentric rod Y is pivoted to the rocker arm T₁ keyed on the
valve crank spindle G L. A disc may be substituted for the excentric as shown in
Fig. 13. The engine may then be reversed by removing the split pin V taking the
rod Y off the crank pin in the disc, turning the engine half a revolution by hand,
and replacing the rod Y on the crank pin Z and putting in the split pin.
Fig. 10 as already explained shows a modification in which the cylinder is not
in line with the crank shaft. The object of this is to reduce the obliquity and the
angular thrust of the connecting rod during the down or steam stroke, and thereby
to diminish the friction of the guide trunk in the cylinder. During the up stroke
the obliquity will be augmented, but this is of no consequence as no work is then
being done. This arrangement is only applicable to engines which are not
reversible, I am aware that a somewhat similar device has been used in certain
small gas engines, and in donkey steam pumps, but so far as I am aware it is
entirely new as applied by me, as herin described to single acting engines for the
purpose of reducing friction In Fig. 10 the lines 1 & 2 show the centre lines of
the low pressure and of the crank shaft respectively, but it is to be understood
that I apply this device to both cylinders.
The stroke of the slide valve may be reduced by making it double ported, or a
trick valve may be employed, as such valves are quite well known I do not think it
necessary them in detail.
The diagrams Figs. 14 & 15 explain themselves They are intended to illustrate
how I use a single slide valve to distribute the steam in two cylinders, but they
do not show the actual method of application in practice. As far as relative
dimensions are concerned, they are plans of the slide valve in its place on the seat.
HP is the high pressure cylinder port. L P is the low pressure cylinder port.
EX is the exhaust port. In Fig. 14 the high pressure piston is supposed to be
near the top of its cylinder. The port HP is open and steam is passing into the
cylinder from the boiler. The steam exhausting from the low pressure cylinder is
passing as shown by the curved arrow from L P to E X through the bridge of the
slide valve the shape of which is denoted by the dotted lines. In Fig. 15 the low
pressure piston is supposed to be at the top of the cylinder, and steam is passing
from HP to L P as shown by the straight arrow through the bridge of the valve.
EX is closed by the lap of the valve which covers it. D N is the driving notch
or groove shown in end section in Figs. 2 & 4 in which the crank valve spindle H
works.
The valve I employ when the cylinders are not compounded is of the ordinary
type and requires no description. It works on a valve face with three ports in it,
one for each cylinder and one for the exhaust and it alternately puts each cylinder
in cominunication with the boiler and with the exhaust.
When it is deemed desirable to shorten the stroke of the slide valve, a doublo
ported valve may be used, such valves are so well known that they require no
description.
Any suitable form of Governor may be used, a high speed horizontal one is
shown at R Fig. 1 but no claim for a special governor is included in the
specification.

page_text: 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 is
Firstly. The construction of single acting steam engines substantialy as herein-
before described, as far that is to say as the arrangements for the distribution of
steam are concerned; but I do not claim the arrangements as they are old-for
reversing.
Secondly. I claim putting the cylinders out-of-line with the crank shaft as
shown in Fig-10-for the purpose stated.
Thirdly. I claim the cutting of alots in the guide trunks of the pistons, as
herin before described, for the purpose stated.
Fourthly. I claim the combination of two cylinders with pistons at opposite
ends of the cylinders at the same moment with the single slide distributing valve
actuated as herein before described, the cylinders being of the same or different
diameters, all as herein before described.
Signed this Thirteenth day of October 1885.