IMPROVEMENTS IN SLIDE-VALVES OF STEAM AND OTHER ENGINES
Year: 1884

page_text: I, WILHELM SCHMIDT of Brunswick do hereby declare the nature of said
Invention for "IMPROVEMENTS IN SLIDE-VALVES OF STEAM AND OTHER ENGINES,"
to be as follows:-
This invention relates to slide-valves for steam, gas, and other fluid pressure
engines.
The improved valve gear has the peculiar feature, that the expansion valve is
moved direct by 'an excentric, while the main valve has no positive motion, but
is periodically coupled with and uncoupled from the expansion valve by means of
a special device.
In further describing the invention reference will be made to the accompanying
drawings, Figs I to VII, which show two different arrangements of slide-valves
embodying this invention.
The main valve g, Figs I and II, is similar to an ordinary slide valve having
three steam ports a, b, adapted to periodically communicate with the steam
ports a, b, c of the cylinder.
The expansion valve has in its base recesses o o¹, which form with the recesses 7º, 2º¹
a sort of hollow frame. The main valve g, which may have similar recesses,
contains two perforations s s¹ extending from its base to its upper side.
For securing or arresting the freely movable main valve ġ when the machine
runs empty, two week springs f, fi may be employed.
The mode of operation is as follows:
In the position corresponding to Fig I the engine-piston is at the right hand end
of its stroke, and the space K of the cylinder communicates with the exhaust
port 61 leading into the atmosphere or to the condenser.
But the condenser has also a sucking effect on the recess o of the expansion
valve, so that the latter is firmly coupled with the main valve by the pressure of
steam in the steam chest.
The main valve will be dragged with the expansion valve as
long as the recess o
(and consequently also o¹) remains closed against the interior of the valve chest,
but as soon as the port a communicates at its lower end with the steain space of
the valve-chest (Fig VI) the pressure on the top of the valve is balanced by the
pressure from below, the connection between the two valves ceases and the lower
valve g remains stationary while the upper valve continues its motion to the end
of its stroke, see Fig. VII.

page_text: In this position the recess o¹ communicates already with the port c¹ (through the
port c) and therefore with the expanded steam in the steam cylinder.
When the valve commences its motion to the right, the difference of pressure in
the recesses is already sufficient to cause a suction or coupling action between the
two valves, in consequence of which the lower valve will be dragged along until
the port c communicates below with the steam space of the valve chest, which
terminates the connection between the two valves.
It is evident that the valves would also work without the ports 8, 81, but these
ports are advantageous in as much as they temporarily suck up any vapours which
may pass between the two valves through leakage, thereby ensuring a permanent
good working of the valve.
These recesses may be employed in various expansion valves, for instance,
Meyer's or Rider's valve gear. If the expansion valve m is made of two halves,
the recesses o,
o must be applied separately in the two halves of the same and
connected with each other by a U shaped canal't passing through the main valve
as shown in dotted lines on Fig. I.
Fig. IV shows a modification of the improved valve gear, in which the ports 8, 8¹
serving to temporarily take up any steam escaped through leakage, are not
intended to communicate with the steam ports a¹, c¹, but with the exhaust port b¹,
which communication is maintained during the motion of the valve. For this
purpose notches n, n¹ are provided in the valve-face of the cylinder and projec-
tions &,, adapted to effect the coupling and uncoupling of the valves in a manner
analogous to the modification Fig. I.
In the position represented by the drawing the coupling takes place through the
exhaust port b', recess n, duct's and recess o. The coupled valve moves towards
the left until the edge 3 is situated over 2, whereupon the connection between the
The expansion valve continues to move until the end of its stroke,
in which position the lower valve is again coupled to the upper one, because tlie
notch o communicates with the duct s.
valves ceases.
At this moment the latter terminates in the port a¹, and as the latter is not
covered along its whole width by the part e, the port a will also communicate
with the exhaust port b.
In order to ensure a constant sucking action or adhesion between the two valves
during the whole motion of the main valves, the recesses n, n¹ have been provided
in the valve-face of the cylinder.
Dated thin 7th 1 of th
1004

page_text: I, WILHELM SCHMIDT, of Brunswick, in the German Empire, Engineer, do
hereby declare the nature of my invention for IMPROVEMENTS IN SLIDE-VALVES
OF STEAM AND OTHER 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 to slide-valves for steam, gas, and other fluid pressure
engines.
The improved valve gear has the peculiar feature, that the expansion valve is
moved directly by an excentric, while the main valve has no positive motion, but
is periodically coupled with and uncoupled from the expansion valve by means of
a special device.
In further describing the invention reference will be made to the accompanying
drawings, Figs I to VII, which show two different arrangements of slide-valves
embodying this invention.
Fig I is a longitudinal vertical section, and Fig II a horizontal section of a valve
chest. Fig III shows a longitudinal section and Fig IV a plan of a modification;
Figs V to VII are diagrams showing the relative position of the engine-piston and
valves and serving to explain their function. The corresponding position of the
crank and eccentric is indicated at the side of these figures.
The main valve g, Figs I and II, is similar to an ordinary slide valve having
three steam ports a, b, c, adapted to periodically communicate with the steam
ports a, b, c, of the cylinder.
'
The expansion valve m has in its base recesses o, '0', which form with the recesses
,, a sort of hollow frame. The main valve g, which may have similar recesses,
contains two perforations s, s¹, extending from its base to its upper side across the
ports a and c.
For securing or arresting the freely movable main valve g, when the machine
runs empty, two weak springs f, f¹, may be employed.
The mode of operation as follows:
In the position corresponding to Fig I the engine piston is at the right end of
its stroke (see Fig V), and the space K of the cylinder communicates with the
exhaust port b', leading into the atmosphere or to the condenser.`
But the condenser also produces a diminution of pressure in the recess o of the
expansion valve, so that the latter is firmly coupled with the main valve by the
pressure of steam on the back of the valve m. The main valve g will be dragged
with the expansion valve m, as long as the recesso (and consequently also o¹)
remains closed against the interior of the valve chest, but as soon as the port a
communicates at its lower end with the steam space of the valve-chest, (Fig VI),
the pressure on the top of the valve is balanced by the pressure from below, the
connection between the two valves ceases, and the lower valve g remains stationary,
while the upper valve continues its motion to the end of its stroke, see Fig VII.
In this position the recess o¹ communicates already with the port c¹. (through the
port c,) and therefore with the expanded steam in the steam cylinder.
When the valve commences its motion to the right, the pressure in the recesses
is already sufficiently low to cause a suction or coupling action between the two
valves, in consequence of which the lower valve will be dragged along until the
port c communicates below with the steam space of the valve chest, which
terminates the connection between the two valves.
It is evident that the valves would also work without the perforations or
auxiliary ports 8, 81, but these ports are advantageous inasmuch as they temporarily

page_text: suck up any vapours which may pass between the two valves through leakage,
thereby ensuring a permanent good working of the valve.
These recesses may be employed in various expansion valves, for instance,
Meyer's or Rider's valve gear. If the expansion valve m is made of two halves,
the recesses o, o¹, must be applied separately in the two halves of the same and
connected with each other by a U shaped-canal tlprovided in the main valve, as
shown in dotted lines on Fig I.
t
Figs. III and IV show a modification of the improved valve gear, in, which the
ports 8, s', serving 'to temporarily take up any steam escaped through leakage, are
not in communication with the steam ports a', c, but with the exhaust port 61,
which communication is maintained during the motion of the valve. For this
purpose notches n, n¹, are provided in the valve-face of the cylinder, and pro-
jections,, adapted to effect the "coupling and uncoupling of the valves in
a manner analogous to that described for Fig I.
: In a position approaching that represented by the drawing, the suction takes
place through the exhaust port b', recess n', duct s' and recess. o: The coupled
valves move towards the left until the edge 3 has passed over the left hand
edge 2 of the valve face of the cylinder, whereupon the connection between the
valves ceases.
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The expansion valve continues to move until the end of its stroke, in which
position the lower valve is again coupled to the upper one, because the recess o
communicates with the duct 8.
At this moment the latter terminates in the port a', and as the latter is not
covered along its whole width, the port a¹ will also communicate with the exhaust
port b¹.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same to be performed; I declare that what
I claim is
1. A pair of slide valves adapted to slide upon each other and provided at
their contact surface with recesses adapted to periodically communicate with the
exhaust space or exhaust port of the engine for the purpose of reducing the
pressure between the said valves and causing them to move together, substantially
as described.
2. The combination of a main valve having auxiliary ducts s, s¹, crossing the
main ports a, c, with an expansion valve adapted to slide on the back of the main
valve, the contact surface of one or both of the valves being provided 'with
recesses o, o¹, communicating with the ducts 8, 81, substantially as and for the
purpose described.
This oth
CATA
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