Improvements in Steam Engines.
Year: 1888

page_text: Improvements in Steam Engines.
We, HENRY HERMAN WESTINGHOUSE and FRANCIS MARION RITES, both of
Pittsburgh, in the County of Allegheny, State of Pennsylvania, and United States of
America, mechanical engineers, do hereby declare the nature of our invention to be
as follows:
The object of our invention is to effect the utilization of the expansive force of
steam or other elastic fluids, when applied in engines of the compound type, more.
completely and perfectly than has heretofore been practicable, by the avoidance of
an intermediate reduction of pressure, and a loss of motive fluid in filling clearance
spaces, unaccompanied in either case by the performance of useful work, both of
which objections obtain to a greater or less degree in prior constructions.
To this end, our invention, generally stated, consists in a novel method of and
means for effecting the distribution functions of a compound engine, by supplying
motive fluid, throughout a portion of the stroke of the piston, to a preliminary or
high pressure cylinder and a continuously communicating clearance space, expanding.
such motive fluid in said cylinder and clearance space throughout the remaining portion
of the stroke, exhausting the motive fluid directly into a secondary or low pressure
cylinder, expanding the motive fluid between the primary and secondary cylinders
throughout a portion of the stroke of the piston of the latter, terminating the stroke
of said piston under simple expansion and coincidently compressing motive fluid in.
the preliminary cylinder and clearance space to initial pressure, and finally exhausting
the motive fluid from the secondary cylinder.
The distinguishing feature of our invention is the coincident effection of low
pressure expansion, and high pressure compression within a space of determined
volume, and the maintenance of high pressure terminal compression uniformly at
initial pressure, independently of variations of load or pressure, by corresponding
variations in the grade of expansion, the variations of pressure at the point of high
pressure compression compensating the variations of the point of high pressure
compression, and terminal high pressure compression being thereby caused to be
equal to initial pressure, at all grades of expansion in operation. The high pressure
compression curves produced in indicator diagrams will necessarily vary with varia-
tions of initial pressure, but their terminal, in the several variations, will coincide,
in each case, with the initial pressure.
In the practice of our invention we provide a compound engine, which may be of
any suitable and preferred type-having a preliminary.or high pressure cylinder and a

page_text: secondary or low pressure cylinder, one or more, each being fitted with a proper
piston and connections through which the motive force exerted upon the pistons
is applied in the performance of work. Motive fluid, as steam or other expansive
fluid, is admitted to the high pressure cylinder, exhausted therefrom to the low
pressure cylinder, and thence exhausted to the atmosphere or to a condenser, or
to a third cylinder if desired, by a suitable distribution valve mechanism, of such
construction that the grade of expansion or point of cut off in the cylinders can be
varied from time to time, in accordance with variations of load or pressure or both,
such variation of the point of cut off being preferably effected automatically, as by a
governor. We further provide a clearance space or chamber of determined capacity
substantially greater than that required for a fluid passage, which chamber may be
located in a valve chest, port, two valve chests and a connecting passage, or two or
more of these members, and which is constantly open to the high pressure cylinder.
In operation, motive fluid is supplied to the preliminary or high pressure cylinder
and clearance space, and after having been expanded in the former is exhausted into
the secondary or low pressure cylinder, effecting the preliminary portion of the stroke
of the piston of the latter under compound expansion exerted between the.
preliminary and secondary cylinders. The supply of motive fluid to the scondary
cylinder is cut off at the proper point in the stroke and the clearance chamber
coincidently closed, high pressure compression being commenced by such closure.
The remainder of the stroke of the piston of the secondary cylinder is effected under
simple expansion, and the motive fluid enclosed in the preliminary cylinder and
clearance chamber is meanwhile compressed to initial pressure at the terminal of the
stroke. The next succeeding supply of motive fluid to the preliminary cylinder
is subject to no reduction of pressure in filling the clearance chamber, as it meets
therein a previous supply of equal pressure which is utilized in the exertion of
such pressure upon the piston of the preliminary cylinder in the stroke about to be
made.
The tendency of variations of the grade of expansion, in the operation of the
engine, to involve different degrees, respectively, of terminal high pressure compres-
sion, is counteracted and compensated for, under our invention, by effecting each and
every grade of low pressure expansion coincidently with the initiation of high
pressure compression within a clearance space of such volume as has been determined
by experimental research to be requisite to admit of the degree of terminal
compression being raised to, without exceeding that of initial pressure at the com-
mencement of the stroke.
The practice of our invention involves a substantial departure from that which has
heretofore generally prevailed, to wit, that of reducing clearance to the least measure
practicable. We have discovered and demonstrated by experiment as the basis of our
present invention that such reduction of clearance is unnecessary to the successful
and economical utilization of the expansive force of motive fluids, and further that a
material advantage is attained by an increase of clearance much beyond the degree
heretofore deemed desirable or even admissable, when employed as an agent in
effecting compression to initial working pressure, such advantage being by our
invention rendered continuously available, under the conditions existing in ordinary
service, by a distribution of motive fluid which maintains the correspondence of
terminal compression and initial pressure without disturbance from the variations of
pressure and load which are normally encountered and provided for in the operation
of the standard constructions known and approved in present steam engineering
practice.
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page_text: COMPLETE SPECIFICATION.
Improvements in Steam Engines.
We, HENRY HERMAN WESTINGHOUSE and FRANCIS MARION RITES, both of
Pittsburgh, in the County of Allegheny, State of Pennsylvania, and United States of
America, mechanical engineers, do hereby declare the nature of our invention for
IMPROVEMENTS IN STEAM ENGINES and in what manner the same is to be performed,.
to be particularly described and ascertained in and by the following statement :-
The object of our invention is to effect the utilization of the expansive force of
steam or other elastic fluids, when applied in engines of the compound type, more
completely and perfectly than has heretofore been practicable, by the avoidance of an
intermediate reduction of pressure, and a loss of motive fluid in filling clearance
spaces, unaccompanied in either case by the performance of useful work, both of
which objections obtain to a greater or less degree in prior constructions.
To this end, our invention, generally stated, consists in a novel method of and
means for effecting the distribution of a compound engine, by supplying motive
fluid, throughout a portion of the stroke of the piston to a preliminary or high
pressure cylinder and a continuously communicating clearance space, expanding such
motive fluid in said cylinder and clearance space throughout the remaining portion
of the stroke, exhausting the motive fluid directly into a secondary or low pressure
cylinder, expanding the motive fluid between the primary and secondary cylinders
throughout a portion of the stroke of the piston of the latter, terminating the stroke
of said piston under simple expansion and coincidently compressing motive fluid
in the preliminary cylinder and clearance space to initial pressure, and finally
exhausting the motive fluid from the secondary cylinder. The improvements claimed
are hereinafter fully set forth.
To completely attain the recognized economic advantage of cylinder compression it
is necessary that the same shall be finally raised to the degree of initial pressure,
or that exerted upon the piston at the commencement of the stroke, and there being,
in the operation of a compound engine in practical service, frequent variations in
pressure or load, or both, the attainment of the advantage above referred to is further
necessarily dependent upon the correspondence of terininal compression with initial
pressure, at each of the different grades of expansion or initial motive fluid pressure
under which the engine may, from time to time be operated. Such maintenance of
correspondence of terminal compression with initial pressure, independent of variations
of load or motive fluid supply pressure, which we do not know or believe to have
been effected prior to our invention, we attain by preventing variations of the point
of initial compression from inducing variations in the degree of terminal compression,
through the induction of corresponding variations in pressure at the point of initial
compression.
The distinguishing feature of our invention is the coincident effection of low
pressure expansion, and high pressure compression within a space of determined
volume, and the maintenance of high pressure terminal compression uniformly at

page_text: initial pressure, independently of variations of load or pressure, by corresponding
variations in the grade of expansion, the variations of pressure at the point of high
pressure compression compensating the variations of the point of high pressure
compression, and terminal high pressure compression being thereby caused to be
equal to initial pressure, at all grades of expansion in operation. The high pressure
compression curves produced in indicator diagrams will necessarily vary with
variations of initial pressure, but their terminal, in the several variations, will
coincide, in each case, with the initial pressure.
The practical application of our invention in effecting the distribution of motive
fluid, that is to say, in. the performance. of the several functions involved in the
exertion of the expansive action of such fluid upon the pistons of a compound engine,
is exemplified in and will be explained by reference to the construction and operation
of the mechanisms shown in the accompanying drawings, in which Figure 1 is a vertical,.
longitudinal, central section through a single acting compound engine illustrating our
invention; Figs. 2 and 3, vertical transverse sections through the same, at the
lines a, x, and y, y, respectively, of Fig. 1; Fig. 4, a side view, in elevation, of a
double acting tandem compound engine, illustrating another application of our in-
vention; Fig. 5, a horizontal longitudinal central section through the cylinders and
valve chests of the same, and; Fig. 6, a diagram illustrating the form of indicator
curves developed in the operation of an engine constructed in accordance with our
invention.
In the instance shown in Figures 1 to 3 inclusive, our invention is applied in a
single acting compound engine having a preliminary or high pressure cylinder 1 and
a secondary or low pressure cylinder 2, which are secured, side by side, to the top of
a closed crank case 5, constituting the bed or support of the engine and serving also
as a tank or receptacle for the lubricating material of the journals and crank pins of
the crank shaft 4, the journals 50 of which rotate in bearings 41, fixed in the ends of
the crank case 5. The cylinders 1 and 2 are fitted, respectively, with pistons 7 and 8,
which are coupled by connecting rods 9, to the crank.pins of double cranks 10, set
oppositely or with their pins 180 degrees apart, on the crank shaft 4.
Motive fluid is admitted to the high pressure cylinder 1, exhausted therefrom to the
low pressure cylinder 2, and thence exhausted into the atmosphere or into a con-
denser, by a single distribution valve, which reciprocates in a valve chest 3, provided
with nozzles or passages 15 and 11, to which a supply and an exhaust pipe are
respectively connected, and communicating with the high and the low pressure
cylinders by ports 12 and 14. The valve chest is preferably lined with a bushing 40,
communicating by proper series of ports, with the supply and exhaust passages 15
and 11, and the cylinder ports 12 and 14. The distribution valve, which in this
instance is of the piston type, is composed of a high pressure section 38, and a low
pressure section 39, which are secured upon and reciprocate coincidently with a valve
stem 16, actuated by an eccentric 20, which is mounted freely upon the crank shaft 4,
and is varied and adjusted in position relatively to the crank line, so as to effect
variation of the degree of expansion in accordance with variations of pressure or load,
or both, by an automatic cut off governor of any suitable and preferred construction,
which is mounted upon a supporting wheel 25, fixed upon the crank shaft 4. The
valve stem 16, is connected, by a link 44, to one arin of a bell crank lever 45,
pivoted in bearings on the lower pressure cylinder 2, the other arm of said lever
being coupled by a ball and socket joint or equivalent flexible connection, to an
eccentric rod 19, secured to the strap 21 of the eccentric 20.
The distance between the sections 38 and 39 of the distribution valve and their
relation in position and degree of traverse to the port 12, of the high pressure
cylinder, are so fixed that the space within the valve chest bushing 40, between the
sections 38 and 39, together with that within the port 12, shall constitute a clearance
space or chamber 42, the capacity of which bears substantially the same ratio to the
volume of the high pressure cylinder, as that of the latter to the volume of the low
pressure cylinder, and which is continuously in communication with the high pressure
cylinder.

page_text: The ratio indicated is that which we have found in practice to develop the most
perfect results, but it will be obvious that the capacity of the clearance chamber may
be increased or diminished, relatively to that recommended by us, although with a
corresponding variation from maximum useful effect. Thus, for example, experiment
has shown that a clearance chamber having only twenty-four per cent. of the capacity
of the high pressure cylinder may be employed, with a valve which is so set as to cut
off at different points in the two cylinders respectively, compression being in such
case commenced later and yet carried to boiler pressure, but such construction
involves the disadvantage that the valve must be set out of square, and the lead on one
side increased and on the other side correspondingly diminished.
The valve section 38 opens and closes the port or series of ports in the valve
bushing 40, communicating with the supply passage 15, thereby performing the
functions of admission and cut off for the high pressure cylinder, the cut off being
effected at different points in the stroke of the piston respectively, in accordance
with the variations of position of the eccentric 20 by the governor. The travel of
the valve is such that the high pressure port 12, is continuously open, and hence the
exhaust and compression of the high pressure cylinder are effected independently of
the valve section 38, the duty, of which, other than as a boundary of the clearance
space 42, is limited to the functions first above stated. The valve-section 39 effects
the opening and. closure of the lower pressure port 14, and thereby performs the
functions of admission, cut off, exhaust, and compression for the low pressure cylinder,
and also those of exhaust for the high pressure cylinder during the period of the
stroke in which the low pressure port 14 is open and the valve bushing ports of the
supply passage 15 are closed, and of compression for the high pressure cylinder during
the period in which both the low pressure port 14, and the valve bushing ports of the
supply passage 15 are closed. In each case, moreover, the valve section 39 acts as
an end boundary of the clearance space 42.
In operation, motive fluid supplied from the passage 15 to the clearance chamber
and the space above the piston 7 of the preliminary or high pressure cylinder 1,
effects the downward movement of said piston, at substantially initial pressure
throughout the preliminary portion of its stroke, at a point in which, regulated by
the governor, under existing conditions of load and pressure. the valve section 38
closes the ports communicating with the passage 15 and cuts off the supply of motive
fluid, the remainder of the stroke of the high pressure piston being effected by the
expansion of the motive fluid previously admitted and remaining in the clearance
chamber and high pressure cylinder. In the further traverse of the valve, the valve
section 39 opens the low pressure port 14, and admits the motive fluid contained in
the clearance chamber and high pressure cylinder to the low pressure cylinder, which
motive fluid effects the preliminary portion of the stroke of the low-pressure piston 3,
under compound expansion exerted between the smaller and larger cylinders. The
distribution valve has meanwhile commenced its traverse in the opposite direction, in
the course of which, at a point regulated by the governor, its section 39 closes the low
pressure port 12, cutting off the supply of motive fluid from the low pressure cylinder
and coincidently closing the clearance chamber 42, and thereby commencing high
pressure compression. The remaining portion of the stroke of the low pressure
piston is effected under simple expansion, that is to say, by the expansion of the
motive fluid enclosed in the low pressure cylinder, the motive fluid enclosed in the
high pressure cylinder and clearance chamber being meanwhile, in and by the upward
stroke of the high pressure piston, compressed at its terminal to initial pressure.
Further movement of the valve in the same direction effects the exhaust of the motive
fluid which has impelled the low pressure piston, and admits motive fluid to the
clearance chamber and high pressure cylinder for the next succeeding stroke of the
piston of the latter, such new supply being subject to no reduction of pressure in
filling the clearance chamber, as it meets therein a previous supply of equal pressure,
which is utilized in the exertion of such pressure upon the high pressure piston in the
stroke about to be made.
Figs. and illustrate our invention as applied in a double acting tandem

page_text: compound engine, the high and low pressure cylinders 1 and 2, of which are
secured in line axially upon a bed plate 26, their pistons 7 and 8, being fixed upon a
common piston rod 6, the cross head of which is coupled by a connecting rod to the
pin of a crank on the shaft 4, in the usual manner. The ports 12 and 12", of the high
pressure cylinder 1, are governed by a distribution valve 38, reciprocating in a valve
chest 3, to which the steam pipe 15 is connected, and the ports 14 and 14, of the low
pressure cylinder 2, are governed by a distribution valve 39, working in a valve
chest 3ª. The valves 38 and 39 are simultaneously operated in and throughout their
traverse in each direction, the stems 16 and 16, to which they are respectively
secured, being coupled to a rocker arm 19", which is in turn connected to the
eccentric rod 19. The eccentric which operates the valves is mounted adjustably
upon the crank shaft and is, as in the former instance, varied and controlled in
position by an automatic cut off governor, carried by a supporting wheel or case 25,
fixed upon the crank shaft.
The valve 38 of the high pressure cylinder, is composed of three pistons, a, b, b,
connected at suitable distances one from the other, to the valve stem 16, the central
piston a, controlling a port or series of ports 12, through which steam is admitted
from the steam supply pipe 15 to the valve chest, and the end pistons b, b, which are
of the same diameter as the central piston a, having no valve function proper and
serving merely to prevent variation of pressure upon opposite sides of the central
piston from acting on the governor. The valve 39, of the low pressure cylinder, is
composed of four pistons, d, d, e, e, secured upon the valve stem 16", the intermediate
pistons e, e, governing ports or series of ports communicating with the induction
and eduction ports 14", leading from the valve chest to the ends of the low pressure
cylinder 2, and a port or series of ports 14, leading to the exhaust pipe 11. The ond
pistons d, d, act similarly to those b, b, of the high pressure valve, having no valve
function proper, that is as to port opening and closure, and being provided to prevent
variations of pressure on the outer sides of the centre pistons e, e, from reacting on
the governor. The valve chests 3 and 3ª are connected by low pressure steam supply
pipes 15 and 15°, each of which communicates at one end with constantly open ports
in the valve chest 3 of the high pressure cylinder and at the other with ports in the
low pressure valve chest 3", which, when uncovered by one of the valve pistons e, e,
lead into the ports 14, of the opposite ends of the low pressure cylinder. The end
spaces beyond the valve pistons 6, b, and d, d, in the valve chests 3 and 3ª, may be
open to the atmosphere or exhaust pipe, or be connected in each chest by.:
communicating pipe.
a
The high and low pressure valves 38 and 39 are coincidently operated by the
eccentric rod, 19 and rocker arm 19", and the point of cut off is, as heretofore, varied
by the adjustments of the eccentric effected by the governor. The clearance chamber
is in this instance made up of the spaces within the ports of the cylinder and valve
chest and low pressure supply pipes, and between the end and central pistons of the
high pressure valve and end and intermediate pistons of the low pressure valve. It
will be seen that as in the former case, said chamber is continuously in communication
with the high pressure cylinder, and that the high pressure valve performs the functions
of admission and cut off only, those of high pressure exhaust and compression and of
low pressure admission, cut off, exhaust and compression, being performed by the low
pressure valve.
Variations of the grade of expansion in the operation of the engine, would, under
previous practice, involve different degrees, respectively, of terminal high pressure
compression, from the fact that greater or less volumes of motive fluid, are, pro-
portionately to the lateness or earliness of the cut off, admitted to the high pressure
cylinder, while the compressive action of the piston, being exerted through the
same space in each case, is uniform at all points of cut off. In the practice of our
invention, we counteract and compensate for such tendency to variation of the degree
of terminal compression above or below initial pressure, by effecting each and every
grade of low pressure expansion coincidently with the initiation of high pressure
compression within a clearance space of such volume as has been determined by

page_text: experimental research to be requisite to admit of the degree of terminal compression
being raised to, without exceeding that of initial pressure at the commencement of
the stroke. Each change of the point of cut off is consequently accompanied by a
corresponding change of pressure at the point of initial compression, (which point
corresponds with the point of cut off) due to the greater or less amount of motive
fluid which has been expanded from the high pressure cylinder into the low pressure
cylinder, so that the later the cut off and the less the volume of motive fluid on
which compression is to be exerted, the greater will be the pressure of said volume,
and conversely, the earlier the cut off and the greater the volume of motive fluid to
be compressed, the less will be its pressure.
It will be seen that the practice of our invention involves a substantial departure
from that which has heretofore generally prevailed, to wit, that of reducing clearance
to the least measure practicable. We have discovered and demonstrated by experiment
as the basis of our present invention that such reduction of clearance is unnecessary
to the successful and economical utilization of the expansive force of motive fluids,
and further that a material advantage is attained by an increase of clearance much
beyond the degree heretofore deemed desirable or even admissible, when employed as
an agent in effecting compression to initial working pressure, such advantage being by
our invention rendered continuously available, under the conditions existing in ordinary
service, by a distribution of motive fluid which maintains the correspondence of terminal
compression and initial pressure without disturbance from the variations of pressure
and load which are normally encountered and provided for in the operation of the
standard constructions known and approved in present steam engineering practice.
The diagram, Fig. 6, illustrates a series of three superposed indicator cards, x, y, z,
according substantially with cards taken, under different degrees of expansion
respectively, from an engine constructed in accordance with our invention. It will
be seen that the points of cut off correspond in the two cylinders and that as the
pressure at the beginning of high pressure compression changes, the point at which
compression begins also changes, in such manner that compression reaches and
terminates at the same point, i.e. initial pressure, for the several points of cut off.
From the instances herein exemplified, it will be apparent that the structural
features and conditions of the application of our improvement may be modified in
various particulars, in the discretion of those skilled in steam engineering practice,
without departing from the spirit and governing principle of our invention and we
do not therefore limit ourselves to the specific construction herein described and shown,
mechanical equivalents therefor, when similarly combined and co-operating corre-
spondingly to effect the result attained by our invention, being considered by us to
be within its proper and legitimate scope.
It will be further obvious that our
invention is, without departure from its governing principle or substantial change of
structural elements, equally applicable in engines of more than one expansion as in
the single expansion engines selected for illustration.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the saune is to be performed, we declare that what we
claim is :
1. In a compound engine, the combination, substantially as set forth, of a high and
a low pressure cylinder of different volumes respectively, a valve or coincidently
operated set of valve sections effecting the distribution functions of said cylinders, .
and a clearance chamber of determined volume substantially greater than that required
to serve as an avenue for the passage of motive fluid, said clearance chamber being
interposed between the cylinders and communicating continuously with the high
pressure cylinder.
2. In a compound engine, the combination, substantially as set forth, of a high
and a low pressure cylinder of different volumes respectively, a valve or coincidently
operated set of valve sections effecting the distribution functions of said cylinders, a
variable cut off mechanism coupled to and actuating said valve, and a clearance
chamber of capacity sufficiently great to permit, (at all points of cut off and variations

page_text: of boiler pressure) of compression to initial pressure, said clearance chamber being
interposed between the cylinders and communicating continuously with the high
pressure cylinder.
3. In a compound engine, the combination, substantially as set forth, of a high and
low pressure cylinder of different volumes respectively, a valve or coincidently
operated set of valve sections effecting the distribution functions of said cylinders, a
variable cut off mechanism coupled to and actuating said valve, and a clearance
chamber or passage, of substantially the same ratio in capacity relatively to the high
pressure cylinder as that of the high pressure cylinder to the low pressure cylinder,
said chamber being interposed between said cylinders and being continuously. open
to the high pressure cylinder.
4. The improvement in the method of distributing motive fluid in compound
engines which consists in supplying the same to a preliminary or high pressure.
cylinder and a continuously communicating clearance chamber of determined volume
substantially greater than that required to serve as an avenue for the passage of motive
fluid, exhausting the same under compound expansion into a secondary or low pressure
cylinder, and thereafter closing the exit from said clearance chamber and raising
high pressure compression to initial pressure therein, substantially as set forth.
5. The improvement in the method of distributing motive fluid in compound
engines which consists in raising high pressure compression to initial pressure in
a chamber of suitable determined volume,, without limitation by or disturbance from
variations of load or initial pressure, by commencing high pressure compression
coincidently with low pressure expansion, substantially as set forth.
6. The improvement in the method of distributing motive fluid in compound
engines which consists in supplying the same to a preliminary or high pressure
cylinder and a continuously communicating clearance chamber of suitable determined
volume, exhausting the same under compound expansion into a secondary or low
pressure cylinder, varying the grade of simple expansion in the same direction in
both the high and the low pressure cylinders, and effecting high pressure compression
to initial pressure in the clearance chamber by initiating said compression coincidently
with each and every variation of the grade of low pressure expansion, substantially
as set forth.
7. The improvement in the method of distributing motive fluid in compound
engines which consists in counteracting and compensating for the tendency of
variations of the point of cut off to induce variations in terminal high pressure
compression, by corresponding variations of pressure at the point of initial compression;
resultant upon variations of the point of cut off, substantially as set forth.
Dated this 17th day of November A.D. 1888.
Witnesses,
J. SNOWDEN BELL.
R. H. WHITTLESEY.
HENRY HERMAN WESTINGHOUSE.
FRANCIS MARION RITES.
Abel & Imray,
28, Southampton Buildings, London, W.C.,
Agents for the Applicants.