IMPROVEMENTS IN STEAM ENGINES
Year: 1882

page_text: PROVISIONAL SPECIFICATION left by Alexander Melville Clark at the
Office of the Commissioners of Patents on the 5th July 1882. Commu-
nicated to him from abroad by William Farr Goodwin, of Stelton in the
County of Middlesex, State of New Jersey, United States of America.
ALEXANDER MELVILLE CLARK of the firm of A. M. &. W. Clark 53. Chancery
Lane in the County of Middlesex, Patent Agents, "IMPROVEMENTS IN STEAM
ENGINES." [Communicated to him from abroad by William Farr Goodwin, of
Stelton in the County of Middlesex, State of New Jersey, United States of
America.]
This Invention relates to improvements in steam engines for effecting one
complete revolution of the crank shaft to one stroke of the piston, and reducing the
number of valve reverses one half (as compared with the ordinary engine in which
latter two strokes of the piston produce one revolution of the crank shaft) without
changing the relations of power and speed of the piston and crank shaft, and in
which it is possible to work a piston stroke four times the throw of the crank, or
longer if desired to maintain the piston speed, or a shorter stroke may be employed
and the same power maintained by enlarging the area of the piston in proportion
as the stroke is diminished. The length of motion of the connecting couples is not
arbitrary but may vary to suit various purposes and situations, wherever steam
power and other expansive force may be employed through the medium of an
engine.
.
1
The Invention relates 2ndly to the lubrication and counterbalancing the valves.
The Invention is applicable to locomotive stationary, and other engines generally,
the form and arrangement of the parts being varied to suit the requirements of
each case.
The objects of this Invention are to make two complete revolutions of the crank
shaft where one was made before, and to require but one reverse movement of the
valve to each revolution where two were required before to effect the same
purpose. These objects are accomplished by means of a peculiar connection
(between the piston rod and crank pin) composed essentially of a toggle joint
through which the motion of the piston is applied to a bell crank or straight lever,
as the case may be, which is connected by a rod to the crank pin. The power of

page_text: the piston is applied to the middle joint of the toggle, one member of which works
on a stationary pivot, and the other is connected by its moving end to the said
lever. The piston rod is not however jointed directly to the toggle but to the
middle of a connecting link jointed at one end to the middle joint of the toggle
and at the other to a radius rod corresponding to one of the members of the toggle,
and formning therewith a Watts parallel motion so that a crosshead and slide are
not required but may be used if preferred instead of the Watts' parallel motion.
By this means the rectilinear inotion of the piston in one direction of its stroke is
converted into both an expanding and contracting motion of the toggle, the
arrangement of the parts being such that at the half stroke of the piston, the
members of the toggle are in line and are inclined opposite ways at the opposite
ends of the stroke. It is therefore obvious that one full movement of the toggle
bars from side to side produce two movements of the lever and a complete
revolution of the crank to each single stroke of the piston, thus reducing the valve
motions one half. By increasing the size of the cylinder either in length of stroke
or diameter, equal power is obtained while one half more time is gained in which
to use steam expansively and clear the cylinder of back pressure and from cramped
exhaust steam. It thus performs in part the function of a compound engine as
the action is the same as though two cylinders were used and the steam can be cut
off at any desired point of the stroke and worked expansively for the remainder.
If the steam is cut off at half stroke, then one half revolution would be effected
with live steam at full pressure, and the other half by the expansion only of the
same steam. Those advantages are very great for high speed engines and
especially for locomotives and for engines driving electric light machines. The
one half the number of the dead centres being passed without reversing the
motion of the piston, the one half of whatever is lost by reverse, of action is gained,
and also whatever is due to the continuous movement of the piston and momentum
of parts in one direction for one half the time. There is no gain or no loss in the
system of mechanism employed to effect the purposes accomplished by this
Invention. No multiplication or reduction takes place or is sought in the
practical application of the Invention which is simply designed to double the
number of revolutions per strokes of piston and dispense with one half the number
of valve reverses per strokes of piston and benefit by the advantage thus gained.
I will now describe the means by which the second objects of the Invention are
accomplished and define the Invention in relation to the economy of the valves of
an engine, this object being accomplished by the peculiar construction and arrange-
ment of the valves, their parts and bearings and means by which they are retained
in their jointed bearings steam tight and by which the steam is admitted and
discharged to and from the cylinder.
The objects sought by the improvements in the valves is thorough lubrication
and proper adjustment of pressure to ensure durability, ease of operation, per-
fection of tightness in the joint and consequent economy of steam and machinery
and these objects are accomplished by constructing and arranging the valves and
their appurtenances in such a manner that the steam passes into and out of the
cylinder under or between the two steam tight joints (instead of at one side or
over the valve). Hence there is no passage of the steam over the back of the
valve, and the pressure of the steam as it passes into and out of use and during its
time of action, tends to force the valve from its seat. It is therefore necessary to
provide a counteracting pressure of sufficient preponderence to hold the valve
properly upon its seat to ensure a steam tight joint throughout the motion of the
valve under various pressures of steam and speeds of piston and valve motion.
Hence it is necessary. for the highest attainment of valve economy to construct and
arrange the valve apparatus in such manner that whilst a cavity is provided in
the back of the valve which is filled with oil or water or soine lubricating material
that serves to constantly lubricate the valve joints without wasting the steam in
its passage by or through the valve, shall never come in contact with the oil or
unguent which is always separated from the steam by the steam tight joints
1

page_text: designed to be lubricated. The valves are of the Corliss type being of cylindrical
form with cavities or thoroughfares for the passage of the steam and the reception
of the lubricant and oscillate in cylindrical chambers provided for them in the
cylinder covers there being a steam and an exhaust valve in each cover. They are
held tight upon their seats by sleeves embracing the axes of the valves attached to
rods connected to the ends of levers whose other ends are acted on by small pistons
as hereafter described, the rods being packed to retain oil only no steam being on
the outside or back of the valves. Instead of a single rod and sleeve at the centre
of the valve there may be two connected to journals at either end of the valve.
In this case the sleeves are carried in an elongated bearing so that the valve is free
to lift from its seat when the pressure is greater in the cylinder than in the boiler,
as when water is caught between the piston and the cylinder cover.
This valve also admits of the pressure of steam on its back as hereafter
described.
It is obvious that the steam valve and its pressure sleeve being constantly
covered and immersed in oil into which the working surfaces dip in their motion,
the valve is thoroughly lubricated and that object is accomplished. The other
object of counterbalancing the outward pressure of the steam from within the
cylinder with the same pressures without steam directly on the back of the valve,
is accomplished by means of the small pistons, the cylinders of which open into the
induction port for the induction valve and into the cylinder for the exhaust valve.
The proportions of the levers are such as to compensate for the difference in the
areas of the pistons and of the valve surfaces exposed to the steam pressure. Hence
it is obvious that very small pistons are sufficient to serve the púrpose of holding
the valves steam tight upon their seats without any motion of the pistons. Hence
the leverage may be multiplied to any extent desired permitting a corresponding
reduction in areas of the piston. The pressure upon the inside of the induction
valve is constant from the induction passage and variable from the pressure of the
expanding steam in the main cylinder, hence it is necessary to take the counter
pressure from the induction port and thus insure a constant and uniform inward
pressure upon the induction valve but only preponderating over the outward
pressure sufficiently to prevent the leaking of steam into the cylinder while the
exhaust valve is open. The steam valve acts quickly in cutting off steam, and
therefore requires to be thoroughly adjusted and lubricated. The valve closes the
steam port which opens directly into the cylinder through the cover which port is
filled and constantly compensated by a corresponding ridge on the end of the
piston and therefore there are no waste spaces as in other engines. The exhaust
valve is made and adjusted in the same manner as the steam valve but as it is
forced outward by the varying pressure of the expanding steam in the cylinder it
is necessary to counterbalance it by the same expanding steam in the cylinder in
order to ensure a pressure throughout the stroke of the piston so that the outward
pressure upon the valve is counterbalanced and slightly preponderated by the
outward pressure of the same steain upon the piston reacting back upon the valve
through the medium of the lever. When there is no pressure in the cylinder
there is none upon the back of the valve except that produced by a spring on the
counterbalance piston rod which is only sufficient to prevent the oil from leaking
through the joint into the eduction passage until the exhaust valve closes and
steam again enters the cylinder. There is a covering over the back of the vales
for the purpose of retaining the oil but if the valves could be properly lubricated
without the covering cap and the joint kept steam tight the covering could be
removed and the back of the valve exposed while in operation. But the cap serves
to retain oil and to support the fulcrums of the counterbalance levers and also to
retain the heat. But if antifriction rollers were employed upon the shaft of the
valve inside of the sleeve through which to apply pressure and if the oil was intro-
duced to the valve seats through grooves in that part of the seat constantly
covered with the valve, then the cap could be dispensed with provided other
means for supporting the fulcrums of the levers were supplied. But of course the

page_text: arrangement described is the best for large engines in which the area of ports and
valve surface is very great and the pressure of steam upon the back of the valve
greatly in preponderance over the outward pressure as in other engines using the
common valve now in use. But for smaller sized engines the valves which I will
now describe are cheaper of construction. In this case the valves are counter-
balanced and held in steam tight contact upon their seats by the pressure on their
backs of live steam in the case of the steam valve and of expanding steam from the
cylinder in the case of the exhaust valve. The steam enters into the space behind
the valve through a branch from the induction passage in the case of the steam
valve and through a passage from the interior of the cylinder in the case of the
exhaust valve. By this means the necessary pressure is kept constantly upon
the backs of the valves by steam which remains in the oil space and does not
pass through the valve but rests or presses upon the oil in the oil space.
The spaces on opposite sides of the valve exposed to steam pressure are so
proportioned as to leave a preponderance of pressure upon the back of the valve
sufficient to ensure a steam tight joint without excess of pressure, thus accomplishing
the same result as in the arrangement previously described but not under such
perfect control as the latter. The pressure on the back of. the exhaust valve is
admitted through a passage located and arranged in such manner that but little
steam is retained in the small passage leading through the thickness of the metal,
from the interior of the cylinder to the oil space behind the valve and the end of
the passage entering the oil space is so located that the bridge of the valve which
- serves to close the exhaust port also serves to close the small passage to prevent
the steam which has entered the oil space from escaping while the steam is
discharging from the cylinder and to open the said passage to admit the steam
behind the valve at the instant that the exhaust port is closed and the induction
port is opened so that when the steam enters the cylinder at full pressure it presses
upon both sides of the exhaust valve, the outward pressure acting through the
port against the bridge which closes the latter forcing the valve from its seat and
through the small passage upon the back of the valve forcing the valve steam tight
upon its seat. While the steam expands during the piston stroke the passage
remains open and the pressure is the same upon the back of the valve as in the
cylinder until the pressure is exhausted when the slight pressure afforded by a
small spring between the valve rock-shaft and the valve serves to press the valve
oil-tight upon its seat until the steam is again admitted. By this arrangement the
space behind the valve and in the passage being very small and only sufficient to
admit the steam around the valve, and by covering and closing the exhaust port
which is in the cylinder cover with the inner bridge of the valve, the valve is
more perfectly and economically balanced and less steam is wasted than by the
justly celebrated Corliss engine in which oscillating slide valves are used to good
advantage compared with the common engine although not to the best possible
advantage compared with this invention. In none of the arrangements of this
invention is there any waste space to be filled with steam at full pressure except
the extremely small space in the passage to, and at the back of, the exhaust valve
which need not be more than one sixteenth of an inch around the valve over a
surface slightly larger than the area of the exhaust port the other part of the
back of the valve fitting closer but not tight enough to jam the valve, whereas in
the Corliss engine the waste spaces are considerable.
Another plan is to introduce live steam to the back of the exhaust through a
passage from the induction port and its merits consist in simplicity of construction
combined with thorough lubrication and while the pressure upon the back of the
valve is constant and largely preponderates over the outward pressure of the
expanding steam in the cylinder, the said preponderance is largely if not wholly
compensated by the copious and constant supply of oil without wasting the latter;
the oil causing the valve to act on its seat like a well lubricated journal, and
would commend itself for use in Locomotives and other high speed engines where
simplicity in the number of pieces is an essential feature.

page_text: The best form for the exhaust valve is a thoroughfare passing through it corre-
sponding in area to the port instead of an open cavity as in the steam valve. This
form of valve is best adapted for use with the pressure of live steam upon its back
as above described. A modified form of the same valve may be used both as
exhaust and steam valve but while it is good for the exhaust valve in all cases, it
is not good for the steam valve except in those cases where the inward pressure is
applied by means of levers in the manner first described, in which case the inward
and outward pressures are easily balanced. This form of valve has great merit as
it is stiff and strong; the parts should be joined by ribs in the passage to connect
the outside shell with the back of the bridge. It can be cast in one piece or
mounted on a rock shaft. The operation of the several forms of the same valve
is the same in all cases, the peculiarity of the valves being in the covering or
closing the port leading directly into and out of the cylinder (without leaving open
the space under the valve to be filled with steam in connection with the piston
space, as is the case with the Corliss and other engines) and in the means by which
the valves are held steam tight upon their seats and the inward and outward
pressures adjusted and the means by which thorough lubrication is applied to the
valves.