IMPROVEMENTS IN THE CONSTRUCTION OF AIR ENGINES OR AIR MOTORS
Year: 1861

page_text: LETTERS PATENT to Theodore Schwartz, of the City and State of New
York, United States of America, for the Invention of "IMPROVEMENTS IN
THE CONSTRUCTION OF AIR ENGINES OR AIR MOTORS."
Sealed the 6th May 1862, and dated the 7th November 1861.
PROVISIONAL SPECIFICATION left by the said Theodore Schwartz at
the Office of the Commissioners of Patents, with his Petition, on the
7th November 1861. .
I, THEODORE SCHWARTZ, of the City and State of New York, United States
of America, do hereby declare the nature of the said Invention for "IMPROVE-
MENTS IN THE CONSTRUCTION OF AIR ENGINES OR AIR MOTORS," to be as
follows:-
The object of this Invention is to increase the efficiency of air engines. To
this end I introduce various improvements in the construction and arrange-
ment of the working parts of such engines, the chief novelty being that the
working space of the main cylinder and of the pump cylinders is filled through-
out with heating or cooling surfaces, so closely and uniformly diffused, as
virtually to pervade the whole interior of the cylinders, and that without
detriment to the free action of the pistons. The engine is provided with two
pump cylinders and one working cylinder, each of which is fitted with a
A

page_text: double-action piston. The pumps are of different capacities, the smaller one
being for compressing cold air, and the other for exhausting the working
cylinder of the heated compressed air at the completion of each stroke. Each
cylinder is fitted with false heads, from which project outwards tubes closed at
their outer ends. Into these tubes work metal plungers carried by the
pistons. The chambers formed at the ends of the working cylinder by the
false heads are connected with the heat regenerator, which is situate imme-
diately below that cylinder, and is supported on the top of a furnace. The
piston rods of the working or main cylinder and of the large pump are
arranged in a line, and are connected to the same cross head. The motion of
the working cylinder is communicated through connecting rods to the main
driving shaft, which through a crank, crank lever, and connecting rods, com-
municate the desired reciprocating motion to the cross head of the small
pump. The generator consists of a shallow flat-sided boiler containing liquid
for conveying heat to the tubes of the main cylinder. In the bottom of the
generator is formed a series of hollow conical projections, against which the flame
of the furnace is free to play. The roof and sides of the generator are strengthened
by partitions which convert the upper space into square cells. This generator
covers the furnace, resting in a sand joint, and is supported on springs to
prevent dilatation. On either side of the generator extending along its whole
length in a narrow casing, enclosing what may be termed a flattened tube
with projecting ridges for heating air for feeding the fire. The casing is open
at one end, where it draws cold air, and flanged at its other to a duct, which
leads the heated air to the ash-pit of the furnace. In the upper part of the
furnace is a coil of pipe, connected at one end to a pipe leading from the
regenerative condenser (whose construction and office will be presently
noticed), and at its other end to a pipe leading to the valve box of the working
cylinder. The regenerative condenser consists of a tall flat vessel containing
several sets of pipes suspended by one end. Each set has three pipes, one
within the other in the intermediate pipe, serving as a lining to isolate the
centre pipe. Outside the pipes are loose filling plates which line the inside of
the vessel, and serve to contract the space surrounding the outer pipes. The
air that drives the engine it is desirable to work over and over again, for
the sake of excluding dust, and for other reasons. To facilitate this, an
accommodation vessel with a pouch-like elastic diaphragm, which pulsates to
and fro with the action of the currents, is made use of, and by its use the
difference of time and speed in the respective piston movements is compensated
for, and the supply volume is regulated to the demand. To guard the
diaphragm against the contingency of undue pressure, and to replenish air

page_text: wasted by leakage of the piston rods, two small valves are provided in the
bottom of the vessel for aspiration and ejection. In lieu of the customary
slide valve a novel construction is adopted, embracing two sets of pivot valves.
The corresponding enclosure or valve box for as far as moveable is divided on
the length into three tubular parts, the middle portion being subdivided, so as to
allow of elongation by screws; the object of this latter operation is to press
home the other joints in consolidating the whole into a compact casing braced
between end pieces cast upon the cylinder itself. Though the regular section
of the box is rectangular, it is made round at the screw joint to form an
adjustable junction more perfectly, that place requiring to be cemented or
leaded. Of the moveable parts referred to, those alone that receive the valves
are faced to the cylinder (like sliders), and need be held down with screws.
The ends of the valve box communicate externally by a flat connecting tube.
The air is received from the exhaust pump when reduced, to the temperature
and pressure of the atmosphere, and passing first to the accommodation vessel
enters the compressing pump, where it is compressed to five and a half
atmospheres, as before hinted; the heat evolved in the latter operation is
neutralized, so as to leave the air perfectly cold to the end by circulating
around the pipes in the end chambers a stream of cold water. The cold com-
pressed air, with the exception of a minor portion or side stream directed
towards the furnace (as presently to be reverted to), enters the regenerative
condenser, and is gradually heated and dilated to a degree approximating to
the wished-for temperature (say, to 435°,) by travelling upwards within the
outer pipes, which are surrounded with the exhausted hot air to be cooled.
The side stream proceeds to the furnace, and entering the coil of heating
tubes is raised to a very high temperature, say, to 600°. The current split
as above, returning in two differently heated streams, which commingle at the
entrance of the main cylinder, yields the desired temperature (of 450°) on
being thus admitted. The temperature is steadily kept up by supplying
external heat to the end pipes from the generator (whether through vapor, or
more directly through hot liquid, or otherwise,) the pressure recedes so slowly
that it is about one atmosphere at the close of the stroke, which is con-
siderably more than with ordinary expansion. At the commencement of the
return stroke the air is brought into communication with the piston of the
exhaust pump (at the side corresponding to the working side of the main
cylinder), passing from the main cylinder to the regenerator in a somewhat
sub-divided stream through the auxiliary side heaters, and traversing the re-
generator in a thinly extenuated descending current that envelopes the pipes,
causing the same to part with the chief heat, it finally gains access to the

page_text: exhaust pump when nearly cold. On leaving the exhaust pump the air
re-enters the supply pump, as first described, to be worked over again, the
same as stated.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Theodore Schwartz in the Great Seal Patent Office on the
7th May 1862.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THEODORE
SCHWARTZ, of the City and State of New York, United States of America,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Seventh day of November, in the year of our Lord
One thousand eight hundred and sixty-one, in the twenty-fifth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said Theodore Schwartz, Her special license that I, the said Theodore
Schwartz, my executors, administrators, and assigns, or such others as I, the
said Theodore Schwartz, my executors, administrators, and assigns, should at any
time agree with, and no others, from time to time and at all times thereafter
during the term therein expressed, should and lawfully might make, use,
exercise, and vend, within the United Kingdom of Great Britain and Ireland,
the Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN
THE CONSTRUCTION OF AIR ENGINES OR AIR MOTORS," upon the condition (amongst
others) that I, the said Theodore Schwartz, by an instrument in writing
under my hand and seal, should particularly describe and ascertain the nature
of the said Invention, and in what manner the same was to be performed,
and cause the same to be filed in the Great Seal Patent Office within six
calendar months next and immediately after the date of the said Letters
Patent.
NOW KNOW YE, that I, the said Theodore Schwartz, do hereby declare
the nature of my said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement, reference being had to the Drawing hereunto annexed, and to the
letters and figures marked thereon (that is to say) :-
The object of this Invention is to supersede steam for marine purposes and
generally for large engines by overcoming the cumbrousness of the present
air engine, endowing air as a motor with greatly increased efficiency, in order
to realize the pre-eminent economy and safety which are the recognized attri-

page_text: butes of that new agency. The process of obtaining motive power from air
resolves itself into three chief functions, to wit, compression, dilatation, and
expansion, the first and last of which would at most neutralize so as to
balance each other in effect, but for the intervening one, the augmented
volume gained through dilatation by expenditure of heat and elevation of tem-
perature being the source whence is due the development of power, and in
which alone this has its existence. As a consequence, the greater the range
of dilatation (that is to say, the number of degrees to be imparted to the com-
pressed air) the more power is obtained and the greater is the efficiency of the
motor. It is well known that any alteration of volume to which air may be
subjected is followed by a corresponding change of temperature, compression
producing heat and expansion cooling; hence it follows that in the process of
obtaining power the air loses in efficiency by heat evolved in the compression,
(as that curtails the range of dilatation) likewise losing by cooling in the
expansion, the latter occasioning a deficit in the return of power due to the
expenditure of compression. The heat from the compression, besides en-
croaching on the range of dilatation, lessens the effect per degree by raising
the starting point, for the increment of volume acquired per degree is smaller
the higher the temperature, so that a degree imparted to warm air is less
effective and profitable than when imparted to cold air. It is the drawbacks
arising as above through the calorific effects of compression and expansion
that have operated to render air so nearly valueless as a motor, and which the
present Invention purposes to remedy. The considerations thus presented are
not urged as novel, for while it has been attempted to obviate heating in com-
pression by surrounding the air pump with cold water, it has also been
intended that the amplified form and attendant displacement peculiar to the
piston and end bottom of the caloric engine should keep up the temperature
in the working cylinder, the benefit in this respect being very marked in
engines of very small size, yet in both cases the result has disappointed the
anticipation. Up to a comparatively recent investigation by M. Peclet, our
data concerning transmission of heat have been so vague, contradictory, and
incomplete as to cause much confusion and uncertainty, but it is now settled
beyond doubt that sudden change of temperature can be effected only through
intimate proximity amounting almost to contact; for instance, operating merely
5 on the outside of a cylinder would be powerless as a means of inducing spon-
.taneous change of temperature in the space within. Therefore, wishing to
maintain strictly constant temperature, I propose filling or virtually to permeate
the working space of each cylinder with metal surface to be so. shaped and
conditioned that it receives and supplies heat or cold in a gradual and con-

page_text: tinuous manner as required during the motion of the piston, by following this
latter without obstructing the same, thereby so perfectly diffusing and scat-
tering the effect as to extend it to every particle of air at each portion of the
stroke. The operation of thus keeping up constant or unfluctuating ten-
perature I term recuperation, and the principal methods for carrying it into
effect are the three following:-
First method. Injection of liquid the same as in ordinary condensation,
the separation and recovery of the liquid being favored by the circumstance
that the recuperation does not occupy the whole of the stroke, but leaves one
portion free. That this expedient is applicable in cooling seems obvious, but
its adaptability to heating must depend on what kind of liquid is available for
that purpose, it being apparently indispensable that the boiling point of the
liquid should be at least as high as the working temperature of the engine.
Of the known bodies that realize this condition may be mentioned paraffinized
oil, glycerine, and chloride of zinc, which being but little known among
engineers claim a brief notice. The first-named article affords a most
desirable lubricating material, and belongs to that extensive class of hydro-
carbons known as petroleum distillates, the boiling points of which present a
range extending from one hundred and seventy-six degrees up to seven hundred
degrees Fahrenheit; the perfectly neutral character of the oil and its great
cheapness much enhance its importance. Glycerine (C6, H8, 06, that is
to say, oxigenated and hydrated glycil, C3, H2), specific gravity 1.28 at
fifty-eight degrees is a neutral limpid liquid (glycil being the basic component
of fats, &c.) at once stable and persistent in the air, and which though highly
syrupy in the ordinary state, acquires the most perfect fluidity when heated;
it can sustain at least six hundred and twelve degrees distilling freely without
decomposition, the boiling point of the pure article approximating to that
temperature, but past this takes fire in the open air, burning with blue flame ;
it dissolves freely both in water and alcohol (not in ether), draws water from
the atmosphere with avidity (rivalling water as a solvent for deliquescent
salts and oxides), and holds it so tenaciously as probably not to release the last
trace till heated to at least five hundred and sixty degrees; as a consequence,
the liquid may be had to boil at any desired temperature within the wide
range of from two hundred and twelve degrees to six hundred and twelve
degrees, the best article of commerce beginning to boil at three hundred and
seventy-five degrees, and gradually rising to six hundred and twelve degrees.
Glycerine is made to part from the acid components of fat or oil and sinks to
the bottom, so that it can be tapped off on passing an emulsion of the fatty
matter in hot water through a vertical iron worm of inch pipe of half-inch

page_text: bore, heated to about six hundred and twelve degrees, subjected to the ex-
cessive inside pressure (not exceeding two thousand pounds per square inch)
to which the presence of water gives rise; the decomposing temperature
varying somewhat according to what fatty substance be used. Chloride of
zinc, commonly called butter of zinc, on account of its consistency at ordinary
temperature (which probably is owing to some water) melts at two hundred
and twelve degrees in parts, with the last trace of water at four hundred and
eighty degrees, can bear seven hundred degrees without emitting inconvenient
fumes, is stable at full red, but requiring over eight hundred degrees to boil,
extremely deliquescent, and probably would retain enough water at the tem-
perature of from four hundred degrees to four hundred and fifty degrees (the
expected working temperature of the new engine) to have a syrupy consis-
tency (if not perfect fluidity) at the common temperature; the vapor, how-
ever, is dangerously corrosive to the skin. The application of the chloride
might be promoted by admixture of water and incidental condensation.
On the whole, the injection method besides being simple, affords convenient
lubrication for the piston yet applied to heating it has the objection
that it wastes liquid through vaporization, owing to leakage of the stuffing
boxes.
Second method.-Establishing towards the inside of the cylinder, as an
extension of the working space, a cellular surface structure or amplification
of surface to be heated or cooled by outside agency, and agitating within the..
same the air in progress of expansion or compression through an expressed
piston combination or rocking gear, which for the sake of greater efficacy may
be in two parts, one fitting the cells, and playing rapidly in and out to force
the air to and from the acting surface, the other diffusing the action by
agitation towards the working piston, that is, the one to circulate the air
through the cells, the other to promulgate the effect over the length of the
working space. As the rocking gear (or rocker) is to operate through dis-
placement or dislodgement the same as pumping, it may be said to transform
the air into an extenuated current that sweeps through the cells, rubbing
against the acting surface, and keeping up brisk circulation.
To secure the requisite amount of surface in a compact form, the end struc-
ture need be subdivided into narrow compartments of more or less depth,
presenting a multitude of vacancies, cavities, or cells of annular, tubular;
conoidal, or other equivalent form, and as the rocker is to have a corresponding
shape exactly matching the cavities with a part fitting each so as to move all
but tightly in and out the end structure, it virtually constitutes an assemblage
of united pump plungers. The portion of the rocking gear designed to spread

page_text: and equallize the calorific action, properly the mixer, may be in the form of a
light circular disc with perforations like a colander. The rocker, independent
of its construction in two parts answers two purposes, vizt., to circulate the
air, and to increase the acting surface, adding its own to that of the end
structure, the travel within the latter having the effect of interchanging heat
between the bodies.
The supplying of heat or cold through external application by end structure
as contemplated, is brought about by causing the whole or each part of the
structure to be enclosed, made double, or hollowed outwards to receive on the
reverse side of the acting surface, a liquid, or vapor or air, in the form of a
current or otherwise, for maintaining the wished for temperature. In the
heating thus to be accomplished, may be employed some hydrocarbon or
other substance that affords the necessary range of temperature at con-
venient pressure without liabilility to decomposition; and it is proposed to limit
the working temperature of the engine to an average of four hundred and fifty
degrees, never to exceed five hundred degrees. Foremost among the bodies
belonging to said category should be placed the photogenic and paraffinized
distillates of petroleum, and next in order glycerine and chloride of zinc already
spoken of, all of which are pre-eminently applicable. In this connection, how-
ever, the following series of data is deserving of note, vizt., camphor fuses at
three hundred and forty-seven degrees Fahrenheit, and boils at four hundred
degrees. The hydro-carbon C 15, H 15, boils at four hundred and ninety-
one degrees. Grease generally does not decompose at less than five hundred
degrees; common resin distils without decomposition between three hundred
and ninety degrees and six hundred degrees; linseed oil boils at upwards of
six hundred and forty degrees; mercury at six hundred and sixty degrees (the
fusing point of saltpetre); paraffine at seven hundred degrees; and chloride
of zinc, as before stated, has a still higher boiling point; finally, among volatile
liquids, which are applicable on the principle of steam heating, and to be
preferred to water for the sake of obviating inconvenience from pressure, there
are the bituminous distillates already mentioned, as well as glycerine and spirits
of turpentine, this latter when fresh boiling at three hundred and thirteen
degrees. Whether adopting water or some liquid comparatively free of pres-
sure, the most convenient and efficacious form of receptacle for holding the
same is that of narrow sealed tubes to be partially filled, exposing one end
directly to the furnace fire, and making the other transmit heat for the recu-
peration, the latter end to be established either directly towards the working
space of the piston, or within an extension of the end structure or other space
contiguous thereto, and the use of such tubes may be made to subserve the

page_text: recuperation indirectly through an intermediary, as in case the liquid heating
agent requires screening from contact with the surface exposed to the flame,
or when direct application is otherwise impracticable. To complete the list of
expedients available for the recuperation, there remains to be noticed the
mode of heating known as Perkins' hot-water system, which, whatever its
drawbacks, is eminently applicable, the extensive use made of it in baking
placing its practical value beyond dispute.
When applying a liquid heating or cooling agent directly behind the recu-
perative surface immediately in contact therewith, it may be expedient to
produce circulation through pumping, which is accomplished by aid of a
piston of diminiutive size, disposed in the most ordinary way.
The incidental use of a liquid or vapor in the recuperation of heat as pro-
posed it will be perceived is attended with no consumption of the material, no
portion having access so as to commingle with the working current, the
application being altogether external, the same as in steam heating, nor does
it create any liability to explosion, for unless using liquid of very elevated
boiling point, the form of receptacle to be employed is that of narrow tubes,
so that the utmost pressure that could arise would at worst occasion only a
harmless splitting.
Regarding the general character of the second mode of recuperation, it is
to be observed that the objectionable feature of the rocking gear is that it
entails complication, but on the other hand as the movement would consist in
short rapid jerks, it has the advantage of shortening the end structure.
Third method. Employing in connection with the external application of
heat or cold through end structure as described, in place of a rocker of short
stroke, an elongated body composed of tubes or other multiform assemblage
of surfaces, so shaped that it fits into and fills the inside of said structure at
the same time measuring the full length of the working stroke, and to be made
to follow the travel of the regular piston, so as to glide steadily back and
forward in the end cavities instead of oscillating like the rocker. The body
thus substituted having the same object as the rocker, viz., to keep up
constant temperature within the working space, by pervading it with acting
surface alternately admitting the air into the end cavities and expelling it
therefrom, may be termed the recuperator. As matter of convenience the
5 recuperator can be fastened to the piston to move with it without intermission, but
it would be preferable that it should be free to linger within the end structure
to gather heat or cold during that portion of the stroke when no recuperation
is called for, as of course that would make it so much more effective, an
arrangement, however, which entails considerable difficulty and expense

page_text: of execution. As to modifications of form and arrangement which the
recuperator and corresponding end structure admit of, the field is so wide
that it would be idle to enter into it, suffice it to say, that in practice the
tubular construction takes the lead of all others. To sum up, in regard to the
three methods of recuperation described, the injection (if at all applicable)
would be the best for cooling, but for beating, the third or last method comes
nearest to what seems expedient in practice.
In the accompanying Drawing, Fig. 1 shews my improved engine in longi-
tudinal elevation, portions of the same being in section, the better to explain
the nature of its construction. The other Figures are views in detail of the
several parts detached, and will be hereafter severally referred to. There are
three double-acting pistons of six-inch stroke, viz., one ten-inch diameter in
the pump A, for getting up compressed cold air of about five and a half atmo-
pheres, gross pressure; another ditto, twelve inches diameter in the main
cylinder B, for working the compressed air, after previously increasing the
bulk of it through dilatation to upwards of four hundred and fifty degrees
Fahrenheit; and a third piston in the present case of seventeen inches diameter,
but which could be twelve, in the exhaust pump C, for contributing
vacuum action through regenerative condensation combined with pumping.
The latter two pistons are connected by keying the rods to the same cross-
head B', (shewn at Figures 2 and 3,) the respective cylinders likewise being
firmly united by braces B², and the combined action is transmitted direct to
the main shaft or crank axle D, (exhibited at Fig. 6,) through a pair of con-
necting rods D' fastened to an auxiliary cross-head D2, (as seen at Figures 4
and 5,) which clasps the crank axle (see Fig. 7).
A crank C' (see Fig. 6) fixed at the end of the axle outside the main
bearing C, (see Figures 6 and 8,) having a connecting arm C³, impels the
air pump piston by aid of an auxiliary shaft E (see Fig. 9,) this being formed
into a crank E¹ at one end (see Fig. 9), and furnished with two other
cranks E' held at right angles to the first thus transmitting the motion with
two connecting rods A' to a crosshead A³ (shewn at Figures 10 and 11) at
the end of the piston rod. The two crossheads of the piston rods are supported
on girders F, F, F, (as in Figures 2, 3, 10, and 11), and the auxiliary
crosshead D2, that has hold of the crank axle D, is steadied through the means
of an excentric G (see Figures 6 and 12), a small extension G' in the cross-
head at one end (see Figures 4 and 5) being attached by screw bolts to the
strap G of the excentric.
The cylinders A, B, and C are so made as to have an extension or auxiliary
chamber at each end with a loose bottom to shut it off air-tight from the

page_text: space devoted to the piston, and which is filled up with one-inch tubes plugged
at one end, with the other end firmly inserted in the partition bottom, and
the piston itself is closely covered at both sides with tubes to match of a little
smaller diameter, with both ends plugged, which travel loosely in and out the
end tubes, the whole arrangement exhibited by the section of the main cylin-
der B, for the number of tubes at each side of the main piston, see Fig. 13.
Figures 14 and 15 give a full-size view of a method of attaching the tubes
to the piston so as to render them self-adjusting in position; II is the body of
the furnace, and between it and the main cylinder (that is to say, placed
directly over the fire) is the generator 1', which is a shallow flat-sided
boiler containing liquid for conveying heat to the tubes of the cylinder,
and of which the bottom is a network of conical pipes I, of three-inch
depth, connected by intervening tongues or braces, the roof and sides being
strengthened with partitions I, converting the upper space into three-inch
square cells. Respecting the said bottom structure, it is to be observed
that the open conical pipes might be advantageously replaced by sealed
ones made so as to enclose permanently a small portion of liquid, and
protruding both ways through the bottom of the pan in order to .receive
the fire at one end, and promulgate the heat at the other. Again, as
regards having liquid in the generator, that might be avoided by applying
the heat direct to air. The generator and main cylinder are so con-
nected as to form but one body, large intermediate necks B³ affording open
communication to the tubes of the end chanıbers, and the whole covers the
furnace resting in a sand joint, and is supported on four springs H¹ to prevent
dilatation occasioning lateral strain on the piston rod. The fire current is
made to spread uniformly among the conical pipes by the top edge of the
chamber J rising close under the bottom of the generator so as to impinge on
the passage to the chimney J', and on escaping thus confined and diffused it
imparts itself on the way to three rounds of tubing J, situated within the
upper part of the furnace body, and which constitute the regular heater
appropriated to dilatation of compressed cold air. On either side of the
generator, extending the whole length, is a small auxiliary of the regenerative
condenser, in the form of a narrow casing K, enclosing what may be called a
flattened tube K', with projecting ridges for heating the feed current of the
fire, a disposition, the make and size of which is shewn in side elevation and
cross section at Figures 16 and 17, the casing is open at one end, where it
draws cold air, the other end being flanged to a duct K³, which descends in
-front of the furnace, leading the heated air into the ash-pit K³. Behind the
furnace facing the supply pump A is the regenerative condenser L, of which

page_text: On
Fig. 18 is a cross section; it consists of a tall flat vessel containing eight sets
of pipes, suspended by one end, the other end hanging free; each set has
three pipes one within the other, but as the intermediary one serves as a lining
to isolate the centre pipe, there are virtually two pipes available.
account of the spacious intervals outside the pipes, a pair of loose plates lining
the inside of the vessel serve to confine the outer current more closely to the
acting surface. The air that drives the engine being worked over and over
again for the sake of excluding dust, and for other reasons, there is an
accommodation vessel M, with a pouch-like elastic diaphragm M', which
pulsates to and fro with the action of the currents, and by compensating
difference of time and speed in the respective piston movements, regulates the
supply volume to the demand. To guard the diaphragm against the con-
tingency of undue pressure, and to replenish air wasted by leakage of the
piston rods, two small valves are provided in the bottom of the vessel for
aspiration and ejection. In lieu of the customary slide valve, a novel con-
struction is adopted, embracing two sets of pivot valves, like that seen in the
section on top of the main cylinder B, and which are the same in the pumps A
and C. The corresponding inclosure or valve box for as far as moveable is
divided on the length into three or strictly four tubular parts A1, A2, A³, A',
the middle portion being subdivided so as to allow of elongation by screws;
the object of this latter operation is to press home the other joints in
consolidating the whole into a compact casing braced between end pieces A
cast upon the cylinder itself. Though the regular section of the box is
rectangular, it is made round at the screw joint A³ to form an adjustable
junction more perfectly, that place requiring to be cemented or leaded, yet it
should be remarked that no pressure is admitted in that part of the box. Of
the moveable parts referred to, those alone that receive the valves, viz.,
A1 and A2, are faced to the cylinder, like sliders, and need be held down
with screws. The ends of the valve box communicate externally by a flat
connecting tube b. The two pumps A and C, and the pillow blocks or
bearings of the shafts, are held in position by a special framing consisting of
two extensive side plates like the one N¹, connected above by a general bracing
plate N, exhibited more fully in Fig. 19, and with special cross pieces or
braces for supporting the shafts (seen in Figures 6, 8, and 9. The whole
engine rests on a bed plate.

page_text: accommodation vessel M, follows the pipe M³ into the pump A, where it
becomes duly compressed to five and a half atmospheres. As before hinted,
the heat evolved in the latter operation is neutralized so as to leave the air
perfectly cold to the end, by circulating around the pipes in the end chambers
a stream of cold water admitted by the elbows C, marked at the lower part,
and escaping through those at the top d. Issuing by the pipe A³, the cold
compressed air, with the exception of a minor portion or side stream directed
towards the furnace (as presently to be reverted to) enters the regenerative
condenser L, descending to the bottom of the centre pipes, and is gradually
heated and dilated to a degree approximating to the wished for temperature,
(say, to four hundred and thirty-five degrees,) by travelling upwards within the
outer pipes, which are surrounded with the exhausted hot air to be cooled.
The side stream proceeds to the furnace by the pipe A' under the control
of the stop cock A, and entering the regular heater (or heating tubes J³)
is raised to a very high temperature, say, to six hundred degrees. The
current, split as above, returning in two differently heated streams (by
the pipes B and B³), which commingle at the entrace of the main
cylinder, yields the desired temperature of four hundred and fifty degrees
on being thus admitted. The introduction occupies two-eleventh parts of the
working stroke, and as in the course of the expansion that ensues the tempe-
rature is steadily kept up by supplying external heat to the end pipes from the
generator (whether through vapor or more directly through hot liquid or
otherwise), the pressure recedes so slowly that it is about one atmosphere at
the close of the stroke, which is considerably more than with ordinary
expansion.
At the commencement of the return stroke the air worked and expanded as
above while still retaining undiminished heat is brought into communication
with the piston of the exhaust pump C at the side corresponding to the
working side of main cylinder passing from the main cylinder to the
regenerator in a somewhat subdivided stream through the main pipe Bº,
and branch pipes B', leading through the auxiliary side heaters K, and
traversing the regenerator in a thinly extenuated descending current that
envelopes the pipes, causing the same to part with the chief heat, it finally
gains access to the pump by the pipe L', when nearly cold and of course
condensed in volume.
As the exhaust piston is just double the area of the main piston, it happens
that at the termination of the above transfer the exhausted air is rarified to
about one-third atmosphere, the calorific effect of the pumping being neutralized
by maintaining constant heat in the main cylinder and constant cold in the

page_text: pump. The notable vacuum thus attained is measurably counteracted by the
obvious necessity of recompressing the rarified cold air for ejection in the
return stroke of the exhaust piston; nevertheless, owing to the strict main-
tenance of constant temperature as above, the main piston gains considerably.
On leaving the exhaust pump the air re-enters the supply pump A, as first
described to be worked over again the same as stated.
The means thus afforded for recuperating temperature in compression and
expansion as already suggested offer signal advantages, the most important
of which may be reiterated as follows :-First, the compressed air being had
perfectly cold, ample range of dilatation is attained (say, at four hundred and
fifty degrees) without incurring the destructive heat (of six hundred degrees
nascent red heat) heretofore deemed indispensable, and without being restricted
to the single-acting principle of construction so wasteful of space. Second,
high pressure is made available to the fullest extent (it being expected to
work at from five to six atmospheres), which removes one of the chief obstacles
to rendering the motor powerful. Third, by a new mode of operation about
to be presented, considerable vacuum action is secured in addition to the high
pressure through condensation and rarification combined by an exhaust pump
not before attempted, by which the regenerator is made to perform the double
service of heater and condenser. Fourth, the supply from the air pump being
cold, and the discharge from the main cylinder retaining the full working
temperature, a greatly extended range for regeneration of heat is acquired.
In a word, in lieu of the existing overheated single-acting feeble engine, it
is expected to substitute a double-acting condensing system of great efficiency
and economy, free from the liabilities of overheating, and which admits perfect
lubrication and the use of air divested of dust, &c.
The introduction of the exhaust pump has for its object to cool and thereby
to condense the hot exhausted air discharged from the working cylinder,
making it traverse a regenerative condenser, and from thence receiving and
expanding. the same in the pump, whereby a gradual vacuum action is
engendered, partly through contraction by cooling, partly through distension by
pumping; what particularly renders that mode of operation profitable is that
by keeping up a constant temperature both in the working cylinder and pump,
the heat lost through rarification is restored and prolongs the expansion while,
on the contrary, the heat set free in bringing back the air to atmospheric
pressure to eject it, is removed and lessens the counter pressure, so that a
twofold gain is secured. To realize the full benefit of the pump, it should be
made as large as will comport with the space allotted to the engine room and
at least equal to the working cylinder.

page_text: It has been stated that the reduced working temperature allows the engine
to be double acting, consequently doubling the efficiency of air as a motor yet
in very small engines the single-acting construction is preferable, on account of
piston leakage and friction being peculiarly onerous items in that case, which
are proportionally lessened by increased diameter.
The nature and objects of the.recuperative working system having been
fully set forth, together with the means of rendering the same operative, there
remain to be stated some further peculiarities of the new engine.
The extended range for regenerative action afforded is already explained,
being such that almost all the heat that is wanted in the dilatation of
compressed cold air to be worked is thereby had gratis, leaving only a small
deficiency in the working temperature to be made up. I propose to supply this
deficiency by diverting and appropriating from the main current a certain
.diminutive portion or branch current, just large enough to receive and convey
from the furnace the exact heat to be furnished to the aggregate, over and
above what is acquired through regeneration, allowing the branch current to be
heated to six hundred degrees or even higher if practicable, and commingling
the same with the main volume at the entrance of the working cylinder.
To illustrate this, suppose that thirteen-fourteenth parts of the main current
become heated from sixty degrees to three hundred and eighty-five degrees in
traversing the regenerator, requiring the addition of only fifteen degrees to
attain the working temperature of four hundred degrees, then a branch current,
equal to one-fourteenth of the whole if heated in the furnace to six hundred
degrees, supplies the required fifteen degrees when commingled as proposed.
The branch current has the incidental advantage of serving to exhaust the
fire (lowering the chimney temperature), as it is to be observed that the main
heat of the furnace goes to the generator and is consumed in recuperation.
For the purpose of increasing the regeneration of heat beyond the range
already extended as stated, at the same time reducing the loss incurred by
the chimney by enhancing the combustion and furnace temperature, it is pro-
posed to feed the fire with hot blast by diverting from the regenerator a
portion of the hot exhausted main current, and employing the branch current
so set apart in heating the feed current of the furnace. To this end, the
regenerator is made to receive an auxiliary small heater as an extension
of the main body.
When the chief heat of the furnace is applied through the medium of a
liquid as contemplated, the otherwise difficult problem of controlling the
working temperature of the engine becomes easy of solution. The most
effective means that presents itself for the purpose is to have within the

page_text: generator a small coil of pipe, opening outwards at both ends, for the recep-
tion of a jet of water, and to administer and regulate the supply of injection,
so to be employed by the movement of a small weighted piston, actuated
by pressure (taking the place of safety valve), or by a diaphragm valve, with
sealed up liquid of appropriate boiling point, as lately patented in United
States for steam heating by J- Mason.
Amongst the drawbacks of air as motor, there is the liability of injury and
extra wear of the frictional surfaces that arises from dust and grit retained
through lubrication, and which is apt to accumulate to the extent of clogging
the moving parts. This renders it paramount that the air should be worked
over and over again without renewal, so as to limit the supply to the small
item wasted through unavoidable leakage of stuffing boxes, and which may be
readily freed of dust in the admission if necessary; but then occurs the diffi-
culty that the delivery of the exhaust pump cannot, in the nature of the case,
coincide either in time or speed with the demand of the compression pump.
This is remedied by interposing an accommodation receptacle capable of freely
expanding and contracting in volume without variation of pressure, which, by
adapting itself to the conflicting conditions, averages the action. For instance,
the receptacle may consist in a vertical cylinder open at the top, furnished
with a tightly fitting weighted piston free to rise and fall, or in place of the
cylinder may be employed a funnel-shaped vessel, with pouch-like piston
operating like bellows. In either case the vessel requires two small ordinary
valves, one for admitting air, the other for discharging excess, which ensures
uniform pressure.
The piston friction is an item of unusual importance in working air, and
which becomes extremely onerous in very small engines. The opinion prevails
that the wear and tear of the packing is reduced so as to enhance its durability
by enlarging the width, (that is to say) by allowing more wearing surface,) the
same as with a shaft bearing. This I take to be a misapprehension, in so far
as the tightening pressure per square inch, which determines the wear, is
proportioned, not to an aggregate weight (as in the case of a shaft), but to
the working pressure per square inch of the piston, which makes it immaterial
whether the packing be wide or narrow. Hence I purpose reducing the
elastic rubbing surface considerably below the customary size of metal
packings in the expectation of having less friction without increasing the wear
and also less leakage, reduced width tending to produce more closely fitting
surfaces. Touching the above, it should be remarked that the outside
dimension given to the piston to guard against careening and abrasion, rests
on considerations bearing no reference to the size or make of the elastic

page_text: packing. With a view to reduce the friction to strict accordance with the
fluctuating working pressure of the piston, a condition more difficult of attain-
ment than is generally allowed, I propose so to alter the construction as to have
two independent metal packings instead of one as usual, viz., one towards each
end of the piston, which enables the corresponding pressure to have constant
access behind the rings or segments of the packing. Further to lessen the
friction, I contemplate lining the cylinder or the piston with an alloy of great
hardness, such as is obtained with one atom iron to twelve zinc, or with two
aluminium to three iron, or to eight copper, either of which is known to be
very hard.
In horizontal engines the wearing of the piston produces a decentralization
attended with injurious strain on the rod; this is obviated by arming the head
underneath with an elastic friction shoe, to balance the weight independently
of the packing; the subdivision of this latter, as suggested, affording a con-
venient intermediate space for the shoe.
The general construction and working of the new engine being exemplified.
and explained so as to be fully understood, it is to be remarked that although
the horizontal working position is adopted in the said exposition, as possibly
affording a needful safeguard in withholding from the recuperation tubes
greasy deposit engendered by friction and dust, it is presumed that a vertical
position would be quite admissible, the greasy obstruction being susceptible of
being washed away through the help of the piston motion (pointing the tubes).
What I claim as my Invention, and desire to secure under the above in
part recited Letters Patent, is-
First, the specified means for maintaining constant temperature in com-
pression and expansion.
Second, the generator containing liquid for transmitting heat by external
action to the working cylinder.
Third, so arranging the apparatus that a portion or branch current may be
diverted from the body of compressed cold air, to be dilated to receive and
convey so much heat as is to be acquired for the purpose from the furnace,
while the rest of the main current is heated exclusively by the regenerator.
Fourth, the use of the exhaust pump as set forth, whereby the condensation
incident to regeneration of heat is made available in securing vacuum action.
Fifth, the means for assisting the operation of the regenerator by appro-
priating a portion of the heat to the feed current of the furnace through
special heater.
Sixth, the interposition of an expanding receptacle in the return passage to

page_text: the compression pump to accommodate the conditions of supply to those of
demand in working the same air over and over again.
Seventh, the means described or any mere modification thereof for con-
trolling the working temperature of the engine, and checking the accumulation
of heat.
Eighth, those certain peculiarities in the details of construction which are
illustrated in the accompanying Drawing, and have been pointed out and
described as novel, or which are specially suggested in the foregoing.
And these claims I make jointly and separately in the manner and for the
purposes herein above specified or implied.
In witness whereof, I, the said Theodore Schwartz, have hereunto
set my hand and seal, the Ninth day of April, in the year of our Lord
One thousand eight hundred and sixty-two.
THEO. SCHWARTZ. (L.S.)