Improvements in and connected with Slide Valves.
Year: 1891

page_text: Date of Application, 15th May, 1591
Complete Specification Left, 15th Mar., 1892-Accepted, 14th May, 1892
PROVISIONAL SPECIFICATION.
Improvements in and connected with Slide Valves.
I, SAMUEL ROBINSON of 35 Hugon Road, Fulham in the County of Middlesex
Mechanical Engineer do hereby declare the nature of this invention to be as
follows:-
With slide valves constructed and fitted in the ordinary manner there is great
loss of power due to the friction produced between the valve and its seat by the
pressure of steam in the valve box, that is to say in the box which encloses the
valve. This arises from the fact that the valve box forms the vessel or com-
munication by which the steam or other motive fluid is conveyed to the valve and
thence to the cylinder or cylinders and the pressure of the valve upon its seat is
therefore equivalent to the pressure of the steam upon the area of the back of the
valve.
Now according to my invention instead of arranging for the motive fluid to
reach the valve through the valve box 1 construct one or more passages for the
purpose in the valve seat, by means of which the motive fluid reaches the valve,
and I employ the valve box as what may be termed a balance chamber. The
manner in which I prefer to carry out my invention is to provide an additional
passage on cach side of the ordinary ports in the valve seat and to form a steam
(or motive fluid) pocket at each side of the valve, these pockets respectively
covering the two additional passages. The steam from the boiler (or other fluid)
is conducted to the additional passages from which it passes to the pockets, and
thence through a port or passage to the engine cylinder in the usual way. As
the steam thus supplied would lift the valve from its seat I obviate this by
admitting steam to the valve box, but 1 do not fill this box with steam at full
pressure as this would cause the great friction that my invention is intended to
avoid; I admit steam to the valve box only in sufficient quantity, which can be
readily calculated and controlled, to produce a pressure which will balance or
approximately balance the force that tends to lift the valve.
The pockets herein before described convey the steam to the port or ports leading
to the cylinder as already explained, and they do not communicate with the other
ordinary ports or passages in the valve seat, and they are always filled with
steam.
Instead of admitting motive fluid to the valve box in order to produce a pressure
which will balance the force that tends to lift the valve I can obtain the requisite
pressure by mechanical means such for example as springs.
Dated this 8th day of May 1891.
SAMUEL ROBINSON.
COMPLETE SPECIFICATION.
Improvements in and connected with Slide Valves.
I, SAMUEL ROBINSON of 35 Hugon Road, Fulham in the County of Middlesex,
Mechanical 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 :-
With slide valves constructed and fitted in the ordinary manner there is great
loss of power due to the friction produced between the valve and its seat by the
pressure of steam in the valve box, that is to say in the box which encloses
the valve. This arises from the fact that the valve box forms the vessel or

page_text: communication by which the steam or other motive fluid is conveyed to the valve
and thence to the cylinder or cylinders and the pressure of the valve upon its seat
is therefore equivalent to the pressure of the steam upon the area of the back of
the valve.
Now according to my invention instead of arranging for the motive fluid to reach
the valve through the valve box 1 construct one or more passages for the purpose
in the valve scat by means of which the motive fluid reaches the valve, and I
employ the valve box as what may be termed a balance chamber. The manner in
which I prefer to carry out my invention is to provide an additional passage on
each side of the ordinary ports in the valve seat and to form a steam (or motive
fluid) pocket at each side of the valve, these pockets respectively covering the two
additional passages. The steam from the boiler (or other fluid) is conducted to
the additional passages from which it passes to the pockets and thence through a
port or passage to the engine cylinder in the usual way. As the steam thus
supplied would lift the valve from its seat I obviate this by admitting steam to the
valve box, but I do not fill this box with steam at full pressure as this would
cause the great friction that my invention is intended to avoid; I admit steam to
the valve box only in sufficient quantity or only at such pressure (which can be
readily calculated and controlled) as will produce a pressure which will balance or
approximately balance the force that tends to lift the valve. It is merely a question
of the relative areas and pressure to counterbalance each other.
The pockets hereinbefore described convey the steam to the port or ports
leading to the cylinder as already explained and they do not communicate with the
other ordinary ports or passages in the valve seat, and they are always filled with
steam.
In the accompanying drawings I have shown my invention applied by way of
example to an engine which in other respects is constructed substantially as
described and shown in my former Specification No. 16462 of 1890.
Figure 1 is a longitudinal elevation partly in section showing the parts in the
positions they respectively occupy when the piston of cylinder C (into which what
1 call the retained steam passes from the two other cylinders A B as described in
my former Specification) is at the middle of its stroke.
Figure 2 is a similar view but with the piston of cylinder C nearly at the end of
its return stroke.
Figure 3 is a plan (corresponding with Figure 1) with the valve box and its lid
removed.
Figure 4 is a transverse section on the line 4-4 of Figure 2.
Figure 5 is a plan view of that part of the slide valve which contains the
passage R for conducting the steam on leaving cylinder C to the exhaust port.
Figure 6 is a plan view and Figure 7 a longitudinal section of that part of the
slide valve which contains the passage P for the admission of live steam to
the cylinders A and B alternately. The passage Q for transferring the steam from
cylinder to cylinder after it has expanded in cylinder A or cylinder B as the case may
be is formed by the underside of the part of the valve shown in Figure 5. There are
six ports in the valve seat as in the engine described in my said former Specification
and these perform respectively the same functions as therein described. They are
marked respectively with the same letters K, L, M, Z, N and O, as in the drawings
annexed to the said Specification; the port K is shown in the accompanying
drawings as placed further from the port L than in the drawings of my former
Specification to allow the high pressure steam to be conducted to either of the
cylinders A and B without its being necessary to move the exhaust valve Figure 5;
the exhaust valve might however be arranged to be moved by a lever on the weigh
shaft. The port Z is arranged to conduct the "retained or expanded steam
across the valve seat from cylinder A to cylinder B (see Figure 3) and thereby
form a permanent passage between them; consequently the permanent passage
shown at J in the drawings of my former Specification and therein described is
dispensed with.
22

page_text: Figure 8 is a plan of the lid of the valve box and
Figure 9 is a plan of the valve box which according to my invention constitutes
what have hereinbefore termed the balance chamber.
Figure 10 shows the valve gear.
The high pressure steam or other motive fluid enters the engine by an opening a
in the top of the valve box lid and divides right and left to the two sides
passages ce and thence to the two ports or passages d d in the valve seat and
through these ports or passages to the two side pockets ee in the valve; these
pockets are in communication with the passage P in the valve which passage as in
the engine described in my previous Specification comes alternately opposite the
ports M and L leading respectively to the cylinders A and B. It will thus be seen
that none of the high pressure or live steam ever enters the valve box so as to press
the valve against its seat. The valve box, however, receives expanded or
"retained" steam which notwithstanding its less pressure counterbalances the upward
pressure exerted by the high pressure steam upon the inner face of the pockets in
the valve because of the larger area of the back of the valve as compared with the
area of the said pockets. The expanded or retained steam reaches the valve box
from the passage Q which is open at the sides this passage being in permanent
communication with the port Z which in turn is always in communication with that
end of each of the cylinders A and B which only receives expanded or retained
stean as explained in my former Specification and never high pressure steam unless
specially required. In order to diminish the capacity of the valve box and thereby
the amount of steam required to fill it I form projections gy on the underside of
the valve box lid b. Assuming the engine is in operation working forward by the
piston of cylinder A. and crank pin E the crank pins G and F will move together
and in the opposite direction to crank pin E while the live steam port is open.
When the crank pin G has nearly reached the horizontal position, the port M in
the valve seat is closed, the port N communicates with the exhaust port O while
port K begins to admit the expanded or retained steam for the return stroke of
crank pin G. When G has reached the vertical line or thereabouts E will have
completed its full stroke, the first half stroke by live steam and the latter part of
its stroke by expansion. Thus the piston of cylinder C has made two half strokes
or one full stroke by the expanded steam, the piston of B has also made a full
stroke by the same expanded steam because the expanded steam at the back of the
piston of A is in communication with the expanded steam on the front of the
piston B by a passage from the valve and the port Z in the valve seat. This steam
can offer no resistance to the pistons of either A or B because of the combination
of the steam and crank arrangement. The crank pin F having completed its
stroke high pressure steam next enters the port Land when F has reached the
vertical line the live steam is cut off by the valve and the steam expands to the end
of the stroke in cylinder B as it previously did in cylinder A. Thus the piston of C
has again made two half strokes by the expanded steam and the piston of A has
also made a full stroke by the expanded steam passing over the passage in the
valve and communicating with port Z. The revolution is thus complete only two
half volumes of steam have been admitted to the engine only two exhausts have
taken place each time discharging only a full volume because there are no empty
passages to fill in connection with cylinders A and B. The expanded steam does
its work on the piston of C in both directions at an approximately constant
pressure and also on the return stroke of the pistons of both A and B because of
the balance established between the pistons, permanent passage and the cranks.
The application of my invention to other engines will be readily understood.
Side passages or ports such as d d must be provided in the valve seat to receive
the high pressure fluid and pockets such as e e to cover the said passages or ports ;
and the admission of expanded or compound steam to the valve box must be
provided for; or in some cases high pressure fluid can be admitted to the valve
box to balance the pressure but the fluid thus admitted will not pass on to the
cylinders.

page_text: .
It is not essential in all cases to make the valve in two parts as shown in
Figures 5 and 6 as a single valve will in many cases suffice as will be well under-
stood, but for the engine shown in the annexed drawings a divided valve is
important because without it the engine cannot be reversed. The slip which I
provide in the flange of the excentric bush (in substantially the same manner as
described in my previous Specification) will only control one valve properly.
I therefore arrange the valve gear as follows: The top arm of the excentric
strap has two rods Im attached to it. The inner of these rods communicates
with the levers on the weigh shaft n, see Figure 10, which works the part of the
valve that carries the pockets; this rod works free and remains in
The
gear.
other rod m works on the same joint of the excentric strap but communicates with
the levers on the other weigh shaft p which works the other part of the valve,
viz. the valve of cylinder C. Only one rod is required on the bottom arm of
the excentric strap communicating with the longer arm of the lever on the weigh
shaft n.
If the rod m worked free and remained in gear also, the two parts of
the divided valve would move together in the same direction and to the same
distance provided the driving pins on the intermediate lever were the same
distance from the weigh shaft ; but I do not arrange them at the same distance
from the weigh shaft centre chiefly because it is important that the high pressure
part of the valve (that which has the pockets) should move about twice the
distance of the other part of the valve; I therefore fit the driving pins on the
intermediate lever accordingly. When the engine is required to reverse, the slip
provided in the single excentric employed is not sufficient. The live steam should
enter cylinder A through port M in the valve seat and port K should be on the
verge of closing. I have shown it fully open in the drawings to call attention
to the fact that when the engine is working backward the crank pin E, ought
to approach the downward vertical line which it will do and crank pin G should
ascend to the horizontal line which it will do during the slip of the excentric.
Consequently the piston of cylinder C has nearly finished its stroke and both
parts of the divided valve would remain still if provision were not made to cause
the exhaust part of the valve to change its position to correspond with the crank
pin G and the piston of cylinder C. Therefore the two parts of the valve must
move in opposite directions when the engine is working backwards due to the fixed
position of the crank pins or else the crank of the piston of cylinder A would be
resisted by the expanded steam on the pistons C and B and their cranks G and F.
I therefore simply change the position of the exhaust part of the valve and in so
doing the link or gap rod s which is shown out of gear, see Figure 10, is drawn into
gear and the rod m is thrown out of gear. The gap rods which is shown out of
gear is attached to the long arm of the lever on the weigh shaft n.
Both the gap
rods s and t work on the driving pins of arms u and on the weigh shaft 1). By
means of the arm the length of the gap rod s can be so adjusted or set as to give
the exhaust part of the valve the required position for the valve to open and close
at the proper times in the same way as the slip in the bush of the excentric does
for the high pressure part of the valve. Consequently the engine has, the same
power in working backwards as in working forward.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what 1
claim is :-
:-
1. In a fluid pressure engine, a slide, valve seat having one or more passages by
means of which the high pressure or live fluid reaches the valve without entering
the valve box, one or more pockets in the valve corresponding with the said
passage or passages and communicating with the ports by which the high pressure
or live fluid passes from the valve to the engine cylinder or cylinders, and a valve
box which receives expanded fluid from the engine cylinder or cylinders, or high
pressure fluid which is not to be utilized in the cylinder or cylinders, so, as to
balance the pressure of the high pressure fluid in the valve pocket or pockets

page_text: and thereby constitute what I have termed a balance chamber, substantially as and
for the purpose herein before described.
2. The particular construction or arrangement of slide valve, valve seat, valve
box, and ports or passages for the supply of high pressure fluid to the valve and of
expanded fluid to the valve box, substantially as and for the purpose hereinbefore
described with reference to the accompanying drawings.
Dated this 15th day of March 1892.
SAMUEL ROBINSON.