Improvements in Valves for Steam Engines, Pumps, and the like.
Year: 1893

page_text: The decision of the Comptroller-General, of the 11th day of April 1894, allowed,
under Section 18 of the Patents, &c. Act, 1883, an Amendment of this
Specification.
COMPLETE SPECIFICATION (AMENDED).
Improvements in Valves for Steam Engines, Pumps, and the like.
I, FRANZ JOSEPH WEISS, of No. 54 Weiherweg, Basle, in the Republic of
Switzerland, Civil 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 :— .
My invention relates to valves for air pumps and steam engines; the term
"air pumps" being here understood in the broadest sense, that is to say, as including
also vacuum pumps, compressors, blowers and all similar machines of this class.
The object of my invention is to provide means whereby, in air pumps, the
sectional area of the suction port for the air and, in steam engines, the sectional
area of the discharge port for the steam, upon the respective port being opened,
will be increased, preferably to double the usual size, so that the air being sucked
into, and the air steam escaping from, the cylinder, respectively, will be less
impeded or throttled in its passage, and consequently, in the case of a steam engine,
the pressure of the steam will, at once upon the discharge port being opened, be
correspondingly reduced, that is to say, in common steam engines it will be reduced
to the pressure of the outer atmosphere and, in condensing engines, to the pressure
prevailing in the condenser.
My invention consists in the particular arrangement and combination of parts as
hereinafter more fully described with reference to the accompanying drawing.
Figure is a vertical longitudinal section of a slide valve and its valve face
embodying my improvement.
Figure 2 is a siinilar section of a cylinder and connected valve chest, showing my
improved valve gear as supplied thereto.
The valve consists of the two connected portions C and B, the latter being
encased in the former and so connected therewith as to provide an intermediate
space or channel. The laps on the outer portion C extend inwardly to such a
distance only as to leave open spaces r at the ends of both cylinder ports a when
the sliding valve is in the central position shown in Figure 1, so that in this position
both spaces of the cylinder will be in communication with each other.
The valve face is of the usual construction, with this exception only that,
according to my present invention, the portions between the ports are formed wider
and provided with cup-shaped or hollow recesses A opening only towards the
valve.
Supposing the sliding valve B C to be, by means of the usual eccentric or
otherwise, moved to the right or left of its usual position shown in Figure 1, it will
then be seen that the space D which, in the case of au air pump, is connected with
the suction inlet for the air and, in the case of a steam engine, with the discharge
outlet for the steam, will thereby be caused to communicate with the one or the
other of the two cylinder ports a, while the outer space E will, at the same time, bo

page_text: caused to communicate with the respective opposite cylinder port. It will, of
course, be understood that, in the case of an air pump, the said space E outside of
the sliding valve B C forms the pressure space, that is to say, the space into which
the air is pressed, whilst, in the case of a steam engine, it is the space into which the
steam from the boiler is introduced.
Now, it will be seen that, while in the movement of the valve as above referred
to but one communication between the space E and the respective cylinder port
will be formed, the effect of the hollow portions or recesses A on the valve face
will be that two communications will be formed simultaneously for connecting the
space D with the other cylinder port, and that each of the latter communicating
passages will be of the same width as the one communicating passage at the
opposite cylinder port. Thus the sectional area of the communicating passages
connecting the space D with the one or the other side of the cylinder will actually
be doubled.
Supposing the valve rod in the position shown in Figure 2 to be moving in the
direction of the arrow, and the eccentric for actuating the valve to be so mounted
as to lag behind by 90 degrees in respect of the crank, as required in air pumps
with distributing valve motion, then the valve will be in about the position shown
and will, likewise, move in the direction indicated by the arrow; Figure 2 will then
illustrate the cylinder of an air pump, or of a pump generally, wherein the air, or
the liquid to be pumped, will be sucked through the space D and discharged under
pressure through the space E. It will be seen that the suction opening at the
port a as well as at the inner valve portion B will still correspond in width to the
full sectional area of the port, although the piston will have nearly reached the end
of its stroke and the outlet passage for the air at the valve will already have been
reduced to about half of the full width of the port a. Thus, when the cylinder
forms part of a compressor or forcing pump, it will, towards the end of the stroke,
when the speed of the piston has already become reduced, still be capable of being
filled with air having the full atmospheric pressure, even if at the middle part of
the stroke where the piston moves with its greatest speed, the cylinder space
should have become filled with rarefied air only.
In order to adapt the arrangement shown in Figure 2 to the conditions of a steam
engine, nothing more.is required than that the space D be made to connect either
with the open air or with a condenser and the space E with a steam conduit from
any suitable boiler, all the parts in every other respect remaining as shown in the
drawing and their relative positions not being materially altered. However, the
direction of the arrows in Figure 2 would, in that case, have to be reversed.
Under these conditions the steam engine here supposed to be provided with the
devices shown would run in the opposite direction to that of the air pump
previously referred to. It will thus be seen that, in the case of a steam engine as
well, the total of the sectional areas of the outlets at their narrowest portion will be
doubled, and that the same will, almost at the beginning of the stroke, have
become equal to the width of the port a, so that the cylinder will actually at the
very beginning of the stroke be capable of discharging the steam which during the
previous stroke has served for driving the piston, and that the counter-pressure of
the steam will thus as quickly as possible be reduced to the same pressure as that
prevailing in the space into which the steam is being discharged.
It will also be seen that, in order to really secure the advantage of the double
opening of the air inlet or steam outlet ports in the valve gear shown, two com-
municating passages (or "negative laps") must be made to open when the valve
is in its central position; for, if the laps of the outer valve portion C were
extended inwardly so as to fully cover the ports a, or even to extend beyond the
inner edges of the latter, when the valve is in its central position, then the
passages at the inner valve portion B, it is true, would still become doubled, but
this would then not be of any practical use, because in that case the openings at
the ports a would become smaller than the doubled passages at the inner valve
portion B.

page_text: Thus by reason of the necessity of providing the passages which connect the
wo cylinder spaces at the central position of the valve, I obtain as a concomitant
feature of this valve gear an equalization of pressure in the two cylinder spaces at
the time when the valve is in its central position or, in other words, at the time
when the piston is at or near its dead point. This secures the following advantages,
that is to say:
1st. In the case of a steam an air pump the volume effect is increased, because
the air becoming compressed within the noxious space in front of the piston, escapes
into what was previously the suction space, to be thence, during the next stroke of
the piston, carried away, and-utilized with the next quantity of air previously sucked
into that space of the cylinder.
2nd. In the case of a steam engine a saving of steam is obtained, because at the
end of the stroke the steam, before being discharged, is caused to communicate
with the noxious space in the opposite end of the cylinder, thus increasing the
pressure or weight "of the steam therein, so that, upon the valve being opened
again, less steam from the boiler will be required for refilling the said noxious
space.
$6
I am aware that such equalization of pressure,-although perhaps not practically
employed in steam engines heretofore, is per se known, and I, therefore, do not
claim this feature as my invention; the same has been here mentioned merely for
this reason, because it presents itself as a necessary concomitant feature of my
improved valve gear.
In constructing for this valve gear, the valve diagram of Zeuner's it will be
observed that, in the case of an air pump, the side indicating the discharge and, in
the case of a steam engine, the side corresponding to the admission will not differ
in any way from the usual kinds of valve gears, but that, in the case of an air
pump, the admission side and, in the case of a steam engine, the discharge side, will
be entirely different from the usual kind, as the ports upon being opened (and also
when being closed) are opened to double the width as compared with the opposite
ports; and the conditions may, according to the circumstances of any particular
case, be so chosen, that the doubling of the sectional areas will continue until the
full sectional area of the ports a will have been attained. Thus the three following
phases of movement for these ports will, in this valve gear, be obtained on the side
of admission for the air and on the side of discharge for the steam, respectively,
that is to say:
1st. The ports will rapidly and almost instantaneously open and thus continue
until the full width will be reached.
2nd. The ports will then remain open at full width during the greater part of the
piston stroke.
3rd. The ports will finally be rapidly and almost instantaneously closed again.
Thus the action of this valve gear, although the same may be driven by the
usual kind of eccentric, the same as other well known kinds of valve gears, differs
entirely from the action of the latter.
Although in describing my invention I have, by way of example, shown the
same as employed in combination with a common sliding valve, I wish it to be
understood that I do not confine myself to the particular kind of valve shown, it
being obvious, and not requiring to be particularly illustrated and described that,
in lieu of a valve as shown in Figure 1, I may, without thereby departing from the
spirit of my invention, apply the same improvement to any other well known kinds
of valve gears. Thus, in lieu of a flat sliding valve, I may employ a rotary valve
or a piston valve, and I may also, in the case of very large engines, divide the
common valve into two separate parts in the well known manner, each of these
parts working at different ends of the cylinder. It is also obvious that the common
valve shown in Figure 1 may, in the case of a steam engine, be made to act in
combination with an expansion valve and, in the case of an air pump, in combination
with back pressure valves in the usual and well known manner.

page_text: 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 I
claim is :-
1. In a valve gear the combination, with a valve substantially as described and
adapted in its central position to open communicating passages for connecting both
spaces of the cylinder, of a valve face having recessed portions, substantially as and
for the purpose set forth.
2. The valve face having the recessed portions A intermediate the cylinder
ports a.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.