Improvements in and relating to Direct Acting Steam Pumping Engines.
Year: 1891

page_text: Date of Application, 17th Feb., 1891-Accepted. 11th Apr.,
1891
עגגענ- UI
Improvements in and relating to Direct Acting Steam Pumping
Engines.
We, LUIGI D'AURIA, a subject of the King of Italy, residing at 248, West
Logan Square, in the City of Philadelphia and State of Pennsylvania, one of the
United States of America, Engineer, and Lieutenant Colonel HENRY MARTYN
ROBERT, a citizen of the United States of America, residing at No. 1812 N Street,
North West, in the City of Washington, District of Columbia and United States
of America, Engineer Commissioner in and for said District of Columbia, 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:-
The invention relates to the general class of direct-acting non-rotative steam
pumping engines, single or duplex, simple or compound.
In direct-acting non-rotative steam pumping engines, especially where steam is
used expansively, the propelling force of the engine effectively employed in driving
the pump is necessarily, from the beginning up to a certain point of the stroke,
somewhat greater, and for the remaining part of the stroke, somewhat less, than
the total pressure exerted by the liquid column upon the pump plunger while in
motion. Hence, during the former part of the stroke, the excess of the effective
propelling force over the resistance of the pump performs an amount of work, which,.
being solely expended in producing an acceleration, may properly be called accele-
rative work. During the latter part of its stroke the excess of resistance over the
effective propelling force gives place to a retarding work, which in a direct-acting
non-rotative steam pumping engine running smoothly must be equal to the
accelerative work, otherwise, either the stroke will be shorter than normal, or the
piston will strike the cylinder head.
Designers of this class of pumping engines have always considered it to be
absolutely necessary to maintain upon the pump plunger, under any circumstances,
an effective propelling force practically equal to, or very slightly greater than, the
resistance of the pump. Consequently, when steam is used expansively in such
pumping engines, compensating devices are now employed which practically nullify
the accelerative work incident thereto.
The object of this invention is to provide means whereby a direct-acting non-
rotative steam pumping engine may use steam expansively without compensating
devices nullifying or reducing the accelerative work incident thereto.
In our investigation of the problem in question, we have satisfied ourselves that
the immediate effect of an increased accelerative work in a direct-acting non-
rotative steam pumping engine is the increase of its piston speed; and that when
this speed exceeds a certain limit, the action of the piston becomes concussive and
spasmodic. Whatever this limit of piston speed may be in practice, the problem is
to find means whereby the piston speed may be regulated and controlled under any
grade of steam expansion without compensating devices.
We have found that by adding to the requisite reciprocating parts of such an
engine a supplemental reciprocating weight we can so regulate and control the
piston speed under any accelerative work as to avoid concussion and spasmodic
action. Such means is suggested by a new principle, which, so far as can be
expressed in ordinary language, is as follows:
In a direct-acting non-rotative steam pumping engine using steam expansively,
the mean piston speed in feet per second varies from four and a half to five
times the square root of the accelerative work in foot-pounds, as herein defined,
divided by the square root of the sum of the products obtained by multiplying

page_text: each of the reciprocating weights in pounds set in motion at every stroke, by the
square of the velocity of its centre of gravity or centre of gyration expressed in
terms of the velocity of the piston as unit.
This sun of products may, for brevity, be called hereafter, accelerated mean
weight.
Theoretically the accelerated mean weight should include the weight of the
column of water confined between the level of the suction chamber and the
level of the air chamber, multiplied by the square of its velocity expressed in
terms of the velocity of the piston as unit; but in practice this portion of the
accelerated mean weight so far as the invention is concerned, is supposed to be only
.a sinal fraction of the total, and its being neglected in the computation can only
produce a slight difference in the value of the mean piston speed. According to
the above principle, in order to obtain a given piston speed the accelerated mean
weight in pounds must be between twenty and twenty-five times the accelerative
work in foot-pounds divided by the square of the given piston speed in feet per
second.
The number twenty corresponds to the case when the accelerative work is
performed by a constant accelerative force, and the retarding work is performed
by a uniformly increasing retarding force, which would be practically the case if
steam were used expansively in a simple cylinder cutting off at about one-half of
the stroke. The number twenty-five corresponds to the case when the accelerative
work is performed by a uniformly decreasing accelerating force, and the retarding
work by a uniformly increasing retarding force as before. Practically this is the
case when steam is expanded in compound cylinders, or when steam is cut off
very early in the stroke.
For practical purposes it may be stated that in a direct-acting non-rotative
steam pumping engine the accelerated mean weight in pounds is approximately
equal to twenty-three times the accelerative work in foot-pounds, divided by the
square of the mean piston speed in feet per second.
Now, suppose, for example, it is desired to ascertain the accelerated mean weight
in pounds which it is necessary to put upon a direct-acting non-rotative steam
pumping engine in order to obtain a mean piston speed of two feet per second,
when steam is cut off at one-third of the stroke in a simple cylinder, the stroke
being three feet, the diameter of the plunger twenty inches, and the total head
two hundred feet. Assuming an even back pressure upon the steam piston and a
constant pressure upon the plunger while in motion, the accelerative work would
be about twelve thousand foot-pounds, and consequently the accelerated mean
weight would be twenty three times twelve thousand divided by the square of two,
or about seventy-five thousand pounds. If the weights of the requisite working
parts of this pumping engine computed in the manner herein defined will make up
only say five thousand pounds of the required accelerated mean weight, then the
remaining seventy thousand pounds must be supplemented by an additional weight,
which however may be greatly reduced, provided its centre of gravity or gyration
moves with a velocity considerably greater than that of the piston. In fact, if the
velocity of the centre of gravity or gyration of the additional weight is three
times greater than that of the piston, then, in accordance with the definition
already given of the accelerated mean weight, the additional weight would have to
be about seventy-eight hundred pounds, or seventy thousand pounds divided by the
square of three."
This pumping engine, without such additional weight, would acquire a mean
piston speed of nearly seven and one-half feet per second, or nearly four hundred
and fifty feet per minute, which is nearly double the speed attained by the best
regulated crank and fly-wheel pumping engines of the larger size. With such
piston speed the engine of our example would never be able to reach the end of a
single stroke without disastrous consequences; and this may serve to explain the
reason why designers of direct-acting non-rotative steam pumping engines have
settled upon the condition, that, under all circumstances, the accelerative work must

page_text: be reduced to a minimum, or practically, nullified. Suppose, for instance, that by
means of proper devices the accelerative work instead of twelve thousand foot-
pounds be reduced to say twelve hundred foot-pounds. Then, without additional
weight, the mean piston speed in feet per second would, according to our principle,
be about four times the square root of twelve hundred divided by the square root
of five thousand (the latter being the assumed accelerated mean weight in pounds);
or about two feet per second. This is about the maximum piston speed at which
direct-acting non-rotative steam pumping engines of large size have ever been run.
Now, the total work absorbed by the pump in a single stroke is about eighty-one
thousand foot-pounds, of which the accelerative work of twelve hundred foot-
pounds only represents about one and one-half per cent. Hence it may safely be
stated that direct-acting non-rotative steam pumping engines as now constructed
could never be made to work satisfactorily with an accelerative work exceeding
two per cent. of the total work absorbed by the pump in a single stroke, for under
such conditions, and even under the conditions assumed, these pumping engines
would acquire a piston speed far exceeding their safe limit and their action would
become concussive and spasmodic.
With the above percentage of accelerative work, the accelerated mean weight in
pounds in direct-acting non-rotative steam pumping engines as heretofore constructed,
would be limited therefore to twenty-three times two percentum of the total work
absorbed by the pump in a single stroke, divided by the square of the mean piston
speed in feet per second or approximately, such accelerated mean weight would
be equal to one-half of the work in foot-pounds absorbed by the pump in
single stroke divided by the square of the mean piston speed in feet per second.
In this invention we claim only such direct-acting non-rotative steam pumping
engines whose accelerated mean weight in pounds as herein defined, exceeds the
quotient obtained by dividing the total work in foot-pounds absorbed by the
pump in a single stroke by the square of the mean piston speed in feet per second.
In the accompanying drawings is illustrated one of the various methods which
may be used to increase the accelerated mean weight, although we do not confine
ourselves to the details thereof.
Figure 1 is a side elevation, and Figure 2 is an end view of an ordinary duplex
direct-acting non-rotative steam pumping engine adapted to use steam expansively,
in which, A, and B, are the steam cylinder and the pump barrel of one side. B', is
the pump barrel of the other side and corresponding to another steam cylinder, not
shown. The pistons of, A, and B, are, as usual, carried by the same piston rod, C,
and it is to be understood that the pistons of the other set of cylinders, are also
mounted upon the same piston rod, not shown. R, and H, R', and H¹, are the
cranks and shafts, and 1, and 1, the vibrating arms ordinarily employed in duplex
direct-acting non-rotative steam pumping engines, to operate the main valves in the
steam chests, S, and S', and they are arranged as usual so that the crank and
shaft set in motion by one engine is made to operate the main steam valve belonging
to the other engine. L, and L', are extensions of the arms, 1, and 1, and are
loaded with the weights, W, and W', for the purpose of increasing the accelerated
mean weight. The position of the weights, W, and W, can, as shown, be shifted
on the arms, L, and L', and, as this shifting affects the accelerated mean weight,
it will affect also the piston speed, other things remaining the same.
cut-off valves adjusted in the steam passages of each steam cylinder, and derive
their motion from the engine to which they belong. M, and N, are connecting rods,
and a, the arms attached to the cut-off valves of one side to operate said
valves. The arms, a, are slotted in order to allow the point of cut-off to be
varied. A similar mechanism is employed to operate the cut-off valves of the
other side.
t, are
When this particular construction (or any other similar to it) is adopted,
then in computing the accelerative work, it must be remembered to subtract the
amount of work absorbed by the additional reciprocating weight, W, or W', in
the action of being lifted from its lower to its higher vertical position during

page_text: the first half of the stroke, which is retarding work. This amount of work in
foot-pounds is equal to the additional weight in pounds, multiplied by the vertical
lift of its centre of gravity in feet including the oscillating arm; but the additional
reciprocating weights in this invention are not intended to act, and are not employed
as compensating devices, in the sense now understood, but simply as means to
control and regulate the mean piston speed in the manner and according to the
principle set forth. The reason, however, for preferring such construction, is the
economy of additional weight it affords over different constructions which might
otherwise be used, as for example, the increase of the weight of the pistons, and
piston rods.
The arms, and may be extended downward instead of upward, and any
other convenient form of cut-off valves and mechanism may be adopted.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, we declare that what we.
claim is --
1. The within described art or method of regulating the mean piston speed in a
direct-acting non-rotative steam expanding pumping engine, which consists in adding
to the requisite reciprocating parts a supplemental reciprocating weight which with
the weight of the requisite reciprocating parts is so proportioned in relation to the
accelerative work, as herein defined, as so to control the accelerated and retarded
motion of the engine that concussion and spasmodic action shall be avoided.
2. A direct-acting non-rotative steam expanding pumping engine adapted to work
under steam expansion sufficient to produce an accelerative work, as herein defined,
exceeding four
per cent. of the total work absorbed by the pump in a single stroke,
and provided with an additional reciprocating weight, which when in motion, with
the requisite working parts, will produce an accelerated mean weight in pounds,
as herein defined, greater than the quotient obtained by dividing the total work in
foot-pounds absorbed by the pump in a single stroke, by the square of the mean
piston speed in feet per second.
3. In combination with a direct-acting non-rotative steam expanding pumping
engine, an additional reciprocating weight or weights connected to and oscillating
with the reciprocating parts of the pumping engine and adapted to control the
accelerated and retarded motion of the engine, thereby preventing concussion and
spasmodic action, substantially as and for the purpose set forth.
4. In combination with a direct-acting non-rotative steam expanding pumping
engine, an additional reciprocating weight or weights, as W, W', fixed or adjustable
upon the arms, L, and L', oscillating with and connected to the valve operating
arms, 1, and, as shown and for the purpose specified.
Dated this 17th day of February 1891.
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.