IMPROVEMENTS IN MEANS FOR ACTUATING THE VALVES OF DIRECT ACTING FLUID PRESSURE ENGINES
Year: 1885

page_text: COMPLETE SPECIFICATION.
I ARTHUR WILLIAM LOVELL REDDIE of the Office for Patents 6 Bream's
Buildings, Chancery Lane in the County of Middlesex, Patent Agent do hereby
declare the nature of the invention for "IMPROVEMENTS IN MEANS FOR ACTUATING
THE VALVES OF DIRECT ACTING 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:-
This invention relates generally to that, class of engines which are known as
"direct acting" that is to say, those engines in which the piston rod acts upon the
load directly and not through the medium of a crank. The invention relates morė
particularly to the means by which the induction and exhaust valve is operated to
admit and exhaust the steam to and from the cylinder.
In this class of engines no fly-wheel or other heavy moving part is employed to
distribute and equalize the power, and the moving parts of the engine are usually
made so light as to acquire but little momentum during the stroke. This being
the case it has been found impossible in practice to operate the induction and
exhaust valve directly from the piston rod of the engine in the manner common in
other classes of engines, because when the valve has been moved to its centre or
into such position as to shut off the further ingress of steam to the cylinder behind
the advancing piston, the little momentum which the moving parts have, will not
be sufficient to cause the piston to advance so as to complete the stroke of the.
valve; and thus the engine will be brought to rest before the valve can be moved
sufficiently far to open the induction port and admit steam in front of the piston to
start it upon its return stroke. This fact has made it necessary in this class of
engines to provide some means by which the valve can be operated, or at least
made to complete its stroke independently of the movement of the main piston and
piston rod. It is to an apparatus for this purpose that the present invention

page_text: •
particularly relates, it being the object of the invention to provide means by which,
after the valve has been carried through a part of its stroke by the movement of
the main piston and piston-rod, it is made to complete its stroke independently of
the movement of these parts. It is also the object of the invention to provide
means for this purpose which shall be positive in its action, not liable to be
rendered inoperative by wear or leakage, and which shall at the same time give
the best distribution of the steam to secure a smooth and quiet action of the
engine.
As a full knowledge of the invention and of its mode of operation can only be
imparted by a detailed description of the apparatus in which it is embodied a
further preliminary description will not be given, but the apparatus will now be
described in detail reference being had to the accompanying drawings in which
Fig 1 is a plan view of a direct acting engine provided with a valve operating
mechanism embodying the present invention the cover of the steam chest being
removed.
"
Fig: 2 is a cross section of the same taken upon the line x x of Fige: 1 and 3.
Fig 3 is a longitudinal section of the same taken upon the line v v of Figs: 1
and 2.
:
Fig: 4 is a longitudinal section upon an enlarged scale taken upon the line z z of
Fig: 2; and
Fig: 5 is a similar view showing the parts in a different position.
Referring to said figures it is to be understood that the engine there shown as
embodying the invention consists of a steam power cylinder 100, having the usual
piston 99 and piston-rod 98, the latter being arranged to act directly upon the pump-
plunger or other load (not shown) which the engine is to move. The cylinder 100
is provided with the usual steam chest 97 having an opening 96 through which
the steam is admitted from the boiler or other source of supply and with an
ordinary D-valve, 95, which controls the induction and exhaust ports 10-11, and
exhaust outlet, 12, of the cylinder, in the usual manner.
The valve rod 94 enters the steam chest 97 through a stuffing box in the usual
manner, and is operated from the piston rod 98 through any suitable form of
connection, as the cross-head 90, link 91, lever 92 and link 93.
The rod 94, instead of being connected directly to the valve 95, is connected to
a yoke 50 which passes around the valve and is arranged to move freely back and
forth upon shoulders or ledges 13 formed upon the sides of the steam chest. The
yoke 50 is of such length as to afford considerable lost motion between it and the
valve so that during the first part of the stroke of the piston 99 the yoke will
move idly without giving any movement to the valve and will only commence to
move the valve as the piston nears the end of its stroke.
"
Mounted upon the top of the valve is a small auxiliary cylinder 89 which may
be made integral with the valve or secured thereto, and which is provided with a
piston 14, the rod 15 of which passes through the end of the cylinder and is
secured to the end of the chest 97. The attachment of the rod 15 to the chest may
be effected in any convenient manner, but the rod will preferably be attached in
the manner shown in the present case, so that when the top 88 of the chest is
removed, the valve 95, including the auxiliary cylinder 89 and its piston and
piston rod, can be readily lifted out of the chest.
The cylinder 89 is provided at its opposite ends with induction and exhaust
ports 3-4 which pass laterally and open upward through the face of a narrow
shoulder or projection, 17, formed on the side of the valve 95, and upon which is
arranged a small B-valve 18 which is slightly greater in length than the valve 95.
The shoulder 17 which forms a seat for the valve 18, is provided just outside the
ports, 34 with vertical ducts or ports, 5-6, which open downward through the
Tower face of the valve, 95, in such position that, as the valve is moved back and
forth, they are brought into communication respectively with two small ducts or
ports 1-2 which extend from the face of the seat 16, upon which the valve 95
reciprocates, to its ends so as to open into the chest 97,

page_text: The valve 95 is also provided with a third vertical duct or port 7, located
midway between the ports 5-6 and in line therewith, which opens downward into
a channel 8 formed in the valve seat 16, and is provided with a lateral port 9
which opens into the cavity 19 of the valve.
The valve 18 is held in position upon its seat by means of a bearing piece 20,
which is secured to the side of the valve; and its stroke in each direction is limited
or controlled by means of projections 40 formed upon its upper side which engage
with this bearing piece 20.
The operation of the apparatus just described is as follows:-assuming the engine
to be in motion, and the piston 99 to have commenced its stroke from the right
toward the left hand end of the cylinder 100. As it proceeds upon its stroke
in this direction, the lever 92 will move the valve rod 94 and the yoke 50
slowly towards the right, and this will continue until the piston has arrived at
about the middle of its stroke, at which time the yoke 50 will come into contact
with the projecting end of the valve 18, and move said valve from the position
shown by dotted lines in Fig: 5, to the position shown by full lines in Figs: 4
and 5; thereby opening communication between the ports 4-6. As the piston 99
continues its stroke from this point, the yoke 50 will come into contact with the
valve 95 and commence to move said valve forward so as to gradually close the
port 11 and cut off the admission of steam to the cylinder, and this will continue
until the valve arrives in the position shown in Figs: 3 and 4 in which posi-
tion it will cut off the further admission of steam to the cylinder in front
of the piston so that the latter will be arrested. The lever 92 is so propor-
tioned however, that when the valve has been moved to this position, the
piston 99 will have arrived at the end of its stroke, as also shown in Fig: 3. As
soon, however, as the valve arrives in the position just stated the port 6 will be
brought into communication with the port 2, as shewn in Fig: 4, so that the live steam
from the chest 97 will pass through the ports, 2-6-4, into the right hand end of the
cylinder 89. The piston 14 of this cylinder, being held stationary by its rod 15,
the steam thus admitted will act upon the end of the cylinder so as to force it, and
with it the valve 95, over to the position shown in Fig: 5; and thus complete the
stroke of the valve and open the port 10 to admit steam in front of the piston 99 to
start it upon its return stroke; and at the same time open the port 11 to permit the
steam already upon the opposite side of the piston to be exhausted through said
port and the outlet 12. As the piston proceeds upon its return stroke the yoke 50
will be moved in the opposite direction until it is brought into contact with the
opposite end of the valve 18, when it will shift said valve from the position shown
in Figs 4 and 5 back to that shown by dotted lines in Fig: 5, so as to close the
port 6 and open communication between the ports 4-7, and thus permit the
steam in the cylinder 89 to be exhausted through the port 9 into the exhaust
outlet 12, and at the same time open communication between the ports 3-5. As
the piston 99 advances and completes its stroke, the valve 95 will be moved back
to its centre, which will bring the port 5 into communication with the port 1 so
as to admit steam through the ports, 1,-5,-3, into the opposite end of the
cylinder 89, which will operate in the manner already stated to complete the
stroke of the valve in this direction and again reverse the movement of the
piston 99; and so the operation will continue to be repeated, the valve 95 being
moved to its centre at each stroke by the piston 99, and then from its centre on to
complete its stroke, by the action of the steam in the cylinder 89.
If at any time the speed of the engine should be accelerated to such an extent
that the piston 99 should not be arrested as soon as the valve 95 arrives at its
centre, the further movement of the piston would carry the valve past the centre
and thus at once open the induction port leading to the front of the piston and
admit live steam to that end of the cylinder so as to cushion the piston and
prevent it from coming into contact with the cylinder head.
It will be observed that sufficient space is left between the ports 3-4 and the
heads of the cylinder 89, so that the steam confined in this space after the

page_text: piston 14 has covered the ports, will form a sufficient cushion to prevent the ends
of the cylinder from coming into contact with the piston.
The ports 1-2 will preferably be located, as shown, so that they will be out of
communication with the ports 5-6 when the valve is at the limit of its stroke in
either direction, thus cutting off the steam from the cylinder 89 and preventing
loss from leakage past the piston 14 while the piston 99 is making the stroke.
These ports may, if desired, be provided with suitable cocks or valves, as 21,
by which the amount of steam allowed to pass through these ports can be
regulated thus providing an efficient means for timing the movement of the
valve. By this means the movement of the valve can be so delayed that the
piston 99 will be made to have a pause at the end of each stroke.
If the valve 18 should become worn, or, for any reason, should fit imperfectly,
so as to permit the steam to leak past it and enter the cylinder 89 before the valve
has been moved into position to open communication between the ports 1-5,
or 2-6; such steam will find an escape through port 5 or 6, channel 8, and the
ports 7 and 9, to the exhaust outlet 12, and thus prevent a premature movement
of the valve.
It will readily be seen that the apparatus just described is simple in its
construction, not liable to get out of order; that the parts are all readily accessible
in case that repairs are needed, and that it can be produced at a comparatively
small cost. The piston 14 is much less inclined to get out of line or stick than
the double chest plungers commonly employed to throw the valves of this class of
engine, and requires less machine work. It also requires much less material, and
can therefore be made, if desired, of brass or other suitable metal that will not
rust to the cylinder. The loss from leakage is also much less than in the ordinary
construction, as the steam can be cut off from the cylinder 89, after the valve has
been reversed, as already explained.
"
I would remark that my correspondents do not limit themselves to the precise
construction of devices herein shown for operating the valve rod 94, as it will
readily be seen that almost any of the ordinary devices for this purpose might
be employed in the present case without departing from the spirit of the invention.
Thus by making the valve of "B" instead of "D form, a simple tappet
movement might be employed for operating the rod 94, and in such case the lost
motion between the valve and the yoke 50 would be proportionately reduced.
But such devices would not be as desirable as the lever movement herein shown,
because the valve could not in that case be closed gradually at the end of the
stroke of the piston 99, and the engine would consequently not have the
advantage of the corresponding gradual reduction in speed at the end of the
stroke.
Neither do they limit themselves to the precise arrangement herein shown, of
the ports for admitting and exhausting the steam to and from the auxiliary
cylinder 89, as the arrangement of these ports may be varied considerably without
departing from the invention, but
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, as communicated to
me by my Foreign Correspondents, I declare that what I claim is
1. In a direct acting engine, the combination with the main cylinder, piston
and piston rod, of the main valve provided with or carrying an auxiliary cylinder
having a stationary piston and piston rod and suitable ports for admitting and
exhausting steam, the valve, 18, arranged to control the admission and exhaust of
the steam to and from the auxiliary cylinder, and connections, substantially as
described, by which the valve 18 is moved through its whole stroke, and the main
valve through a part of its stroke by the main piston, the whole being arranged
and operating substantially as described.
2. In a direct acting engine the combination with the main valve, 95, carrying
the auxiliary cylinder 89 having the stationary piston and piston rod and suitable

page_text: ports for the admission and exhaust of the steam to and from said auxiliary
cylinder, which ports are only brought into communication so as to admit the
steam after the valve 95 has been moved through a part of. its stroke, the valve 18
for controlling the exhaust, and connections, as the yoke 50, valve rod 94, &c., by
which the valve 18 will be moved to open the exhaust of the auxiliary cylinder 89,
before the valve 95 commences its stroke, substantially as described.
3. In a direct acting engine the combination with the main cylinder, piston and
piston rod, of the main valve provided with or carrying an auxiliary cylinder
having a stationary piston and piston rod and suitable ports for admiting and
exhausting steam, the valve 18, for controlling the admission and exhaust of the
steam to and from the auxiliary cylinder, connections for operating the valve 18
from the main piston and the channel, 8, arranged to communicate with the
ports 5, 6 and 7 substantially as described.
4. In a direct acting engine, the combination with the main cylinder, piston and
piston rod, of the main valve provided with or carrying an auxiliary cylinder
having a stationary piston and piston-rod, the valve, 18, arranged to control the
admission and exhaust of the steam to and from the auxiliary cylinder, and
suitable ports for the admission and exhaust of the steam, which are so arranged
that after the valve, 18, has been moved through its whole stroke and opened the
exhaust, the main valve must then be moved through a part of its stroke before
the admission of the steam to the auxiliary cylinder can take place, all substan-
tially as described.