Improvements in the Construction and Operation of Steam Pumping Engines.
Year: 1887

page_text: Date of Application, 2nd Aug., 1887.
Specification Accepted, 20th Sept., 1887.
COMPLETE SPECIFICATION.
Improvements in the Construction and Operation of Steam Pumping
Engines.
We, LUIGI D'AURIA of No. 1428 Arch Street in the City of Philadelphia Penn-
sylvania United States of America, Civil Engineer and HENRY MARTYN ROBERT,
Lieutenant Colonel of Engineers U.S.A. residing at No. 4214 Walnut Street, Phila-
delphia 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 that is to say:-
It is well understood that the most economical way of operating steam engines is to
allow the steam to expand in the cylinders but this necessarily produces a varying
propelling force and piston speed.
In direct-acting non-rotative steam pumping engines that is those without fly-wheels,
however, experience has shown that a practically uniform piston speed is absolutely
necessary in order to obtain satisfactory results. In other words, a nearly constant
propelling force must be maintained upon the pump piston throughout its stroke and
for this reason when steam is to be used expansively, a device is required to equalize
the varying force of the engine.
Expanding steam in compound cylinders without cut-off and using considerable
receiver space, is a well known method to reduce the variations of the propelling force
of the engine under expansion. This has been adopted in duplex direct-acting non-
rotative pumping engines where to obtain a practically constant propelling force the
remaining inequalities of the latter are balanced by a varying back pressure caused
upon the piston of the low pressure cylinder by cushioning valves placed in the
exhaust passages of the same. But expansion under such restrictions can afford but a
very little economy and other devices have been sought for to equalize the propelling
force in non-rotative direct-acting pumping engines both single and duplex under any
grade of steam expansion in simple as well as compound cylinders. Means to this
effect are described in Letters Patent No. 292,525 granted January 29th 1884 in the
United States of America to C. C. Worthington and in the corresponding English
Specon. No. 2342 A.D. 1884 in connection with duplex direct-acting pumping engines

page_text: in which a portion of the power at the beginning of the stroke is absorbed and after-
wards partially utilized to assist the piston towards the end of the stroke.
This is sufficient to show that in non-rotative direct-acting pumping engines
whether single or duplex, simple or compound, steam expansion without a device to
equalize the power propelling the pump piston, is considered impracticable, if not
impossible. In fact whenever it has been attempted a peculiarly spasmodic action
of the piston has been observed accompanied by very dangerous concussions upon the
pump.
The object of this Invention is to dispense with the devices or mechanisms now
employed to equalize the varying power propelling the pump piston in single or
duplex non-rotative direct-acting pumping engines using steam expansively in simple
or compound cylinders and avoid the spasmodic action and concussions under any
grade of steam expansion by a simple and economical method.
In non-rotative direct-acting pumping engines using steam expansively without
device to equalize the propelling force which acts upon the pump piston the motion of
the latter is accelerated for the first part and retarded for the second part of the stroke,
while the large body of water in the discharging main preserves by virtue of its inertia
a practically uniform velocity corresponding to the main velocity of the pump piston.
Under such conditions the level of water in the air chamber must oscillate about a
mean level at each stroke of the pump. It has been ascertained that this oscillation
in the case of a uniformly accelerated and retarded stroke will cause alternately
condensation and expansion of the air volume in the air chamber to the extent of one
fourth of the volume displaced by the pump piston per stroke or in other words the
air volume will vary from its mean volume at each stroke by an amount equal to one
eighth of the pump piston displacement per stroke and in actual practice this proportion
varies but slightly.
With the ordinary air chamber used in non-rotative direct-acting pumping engines
the above condensation and expansion would cause dangerous variation of pressure
upon the pump and to this variation of pressure are due the results of spasmodic
motion and concussions experienced in such pumping engines and these inconveniences
can be avoided by maintaining a practically constant pressure in the air chamber.
This can be done by greatly enlarging said chamber over the ordinary capacity, and
in practice it is preferred to employ this plan of obtaining the desired constant
pressure.
The extent of variation of the air volume in the air chamber having been ascertained
to be what is stated the desired or necessary size of the enlarged air chamber to carry
out the invention can then be determined according to the work required of the pump.
For example if it were desired to make the pressure so uniform that the variation from
the mean pressure would not be more than about one per cent., then the enlarged air
chamber should have an air volume about thirteen times as large as the displacement
of the pump piston per stroke.
In ordinary non-rotative direct-acting pumping engines, the air chamber does not
exceed in volume twice the displacement of the pump piston per stroke. Moreover,
owing to the uniformity of speed under which those pumping engines are operated no
air chamber is in reality required, and for this reason, no provision is ordinarily made
for keeping the chamber supplied with air, so that the chamber becomes filled with
water and inoperative.
The Invention may be carried into effect with various constructions of apparatus
but in the accompanying drawing is illustrated one construction which may be used
although the invention is not confined to the details illustrated.
Figure 1 is a side view partly in section of a non-rotative direct acting simple
cylinder duplex pumping engine with the improvements and Figure 2 is an end view
of the same illustrating also the auxiliary air pump.
A. A¹ are the steam cylinders and B. the pumps the corresponding pistons of the
steam cylinders and the pumps being mounted at opposite sides of the piston rods, as
usual.
In fact the steam pump illustrated is, with the exception of the cut-off sub-
stantially the same as the well known Blake direct-acting simple cylinder duplex

page_text: pumping engine and the steam valves a of the steam cylinders are operated by the
usual mechanism from the piston rods, the steam valve of one cylinder being operated
from the piston rod of the other cylinder in the ordinary way.
Any convenient form of cut off valve may be employed, but in the drawing is shown
a simple form which may be used. The cut-off valve a¹ is a plain slide, which is
operated by its own engine by means of a lever and tappet t acting on the stems of
the slide, the tappet t or stops on the stem being adjustable to cut off at any fraction
of the stroke.
D, is the ordinary air chamber of the steam pumps, which may itself be made of
enlarged size to carry my invention into effect, but it is preferred in practice to pro-
vide for the enlargement of the chamber by connecting with the ordinary chamber D
a supplementary air chamber or tank D' and a valve d may be provided between
the two.
To feed this enlarged air chamber with the amount of air which may be absorbed
by the water passing through the pump and also to fill such chamber with air at a
certain pressure before the engine started, there is used, in connection with it, an
auxiliary air feed pump or compresser E which can be operated intermittently or other-
wise to supply air to the chamber or tank through the pipe e.
It is well known that in hydraulic elevators a reservoir has been used in connection
with the steam pump to maintain a constant pressure on the elevator but so far as is
known the steam pumps for working these elevators have always been constructed to
work with a uniform propelling force upon the pump piston.
This Invention however involves the novel principle of working a non-rotative
direct-acting steam pumping engine expansively with a varying propelling force and
piston speed and preventing consequent spasmodic action and concussion by maintaining
a constant air pressure upon the water in the pump.
Having now particularly described and ascertained the nature of our said Invention
and in what manner the same is to be performed we declare that what we claim is.
1st. The mode herein described of operating direct acting non-rotative steam
pumping engines, said mode consisting in working the said engine expansively with
a varying propelling force upon the pump piston and preventing spasmodic action and
concussions by maintaining a constant air pressure upon the water in the pump
substantially as set forth.
2nd. A direct-acting non-rotative steam pumping engine adapted to use steam
expansively with a varying propelling force upon the piston pump and provided with
means to prevent spasmodic action and concussions said means consisting of an
enlarged air chamber equal to more than twice the displacement of the pump piston
per stroke substantially as set forth.
örd. A direct acting non-rotative steam pumping engine adapted to use steam
expansively with a varying propelling force upon the pump piston and provided with
an enlarged air chamber having a volume more than twice the displacement of the
pump per stroke to prevent spasmodic action and concussions and having a pump to
supply air to said chamber substantially as described.
Dated this 2nd day of August 1887