IMPROVEMENTS IN COMPRESSING AIR AND IN THE APPARATUS EMPLOYED THEREFOR.
Year: 1872

page_text: LETTERS PATENT to Addison Crittenden Rand, of New York, in
the United States of America, but at present residing at Glasgow,
in the County of Lanark, North Britain, for the Invention of
"IMPROVEMENTS IN COMPRESSING AIR AND IN THE APPARATUS EMPLOYED
THEREFOR.
"
Sealed the 25th February 1873, and dated the 16th September 1872.
PROVISIONAL SPECIFICATION left by the said Addison Crittenden
Rand, at the Office of the Commissioners of Patents, with his
Petition, on the 16th September 1872.
I, ADDISON CRITTENDEN RAND, of New York, in the United States
of America, but at present residing at Glasgow, in the County of
Lanark, North Britain, do hereby declare the nature of the said Invention
of "IMPROVEMENTS IN COMPRESSING AIR AND IN THE APPARATUS EMPLOYED
THEREFOR," to be as follows, that is to say :-
==
This Invention, which has for its object improvements in machinery
or apparatus employed in compressing air for actuating air engines, coal
cutting machines, rock boring machines, and for other purposes in which
compressed air is employed, consists in arranging the cylinder or vessel
in which the air is compressed within a jacket or water space extending

page_text: around the sides and ends of the said cylinder or vessel, and by the
water contained in which the heat generated in compressing the air is
absorbed or taken up. The apparatus may be made either single or
double acting, when double acting inlet and outlet valves are placed in
each end of the cylinder or vessel through which the air passes into
and when compressed is conducted away from the cylinder or vessel.
These valves are enclosed within a tube or casing surrounded by the
water space, and a sleeve is also formed at each end of the cylinder or
vessel which surrounds the piston rod and is filled with water. The
rod of the piston which projects through both ends of the cylinder is
formed hollow at one or both ends, so that the water contained in the
sleeves may pass down the interior thereof, and into the centre of
the piston itself which has a hollow channel formed circumferentially
therein. A pipe or pipes situated in the hollow portion or portions of
the piston rod communicates or communicate with the end of the
channel opposite to that at which the water is introduced into tho
interior of the piston, and through which pipe or pipes the water after
circulating through the water space or jacket, hollow piston rod and
piston, so as to absorb the heat generated in compressing the air in the
cylinder or vessel is conducted away from the apparatus.
The piston of the air compressing cylinder or vessel is formed serrated
at its periphery, or where it bears against the sides of the cylinder or
vessel and into the hollow portion of its serrated periphery packing
rings are placed. Communication is effected between the channel in
the interior and the hollow portions at the periphery of the piston by
means of short channels or ducts through which a small portion of the
water contained in the channel in the interior of the piston passes
outwards and forms a film of water between the piston and the interior
of the cylinder or vessel, thereby lubricating the piston.
When the air compressing cylinder herein-before described is placed
horizontally it is preferred to connect it to a crank to which is also
coupled the piston rod of an oscillating steam cylinder inclined at an
angle, and when the air compressing cylinder is inclined the steam
cylinder is placed horizontally. By means of this arrangement the
greatest power of the piston of the steam cylinder is obtained at the
instant of greatest pressure in the air compressing cylinder or vessel.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Addison Crittenden Rand, in the Great Seal
Patent Office on the 15th March 1873.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ADDISON
CRITTENDEN RAND, of New York, in the United States of America,
but at present residing at Glasgow, in the County of Lanark, North
Britain, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Sixteenth day of September, in the
year of our Lord One thousand eight hundred and seventy-two, in the
36th year of Her reign, did, for Herself, Her heirs and successors, givo
and grant unto me, the said Addison Crittenden Rand, Her special
license that I, the said Addison Crittenden Rand, my executors,
administrators, and assigns, or such others as I, the said Addison
Crittenden Rand, my executors, administrators, or 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 COMPRESSING AIR AND IN THE APPARATUS EMPLOYED
THEREFOR," upon the condition (amongst others) that I, the said Addison
Crittenden Rand, my executors or administrators, 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 Addison Crittenden Rand, 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 accom-
panying Drawings and to the letters and figures marked thereon, that is
to say :-
The said Invention consists in a certain combination of a double
acting pump or single air compressing cylinder and its piston with a
steam cylinder and its piston when the two pistons are connected to one
and the same revolving shaft by a crank pin common to both, whereby

page_text: great simplicity is attained and a compression of the air or gas kept
up subject to an approximation of the power exerted by the steam
to the resistance encountered at various points throughout both strokes
of the pump, and in the means used for absorbing the heat generated by
the compression of the air.
And in order that my said Invention may be fully understood. I
shall now proceed more particularly to describe the same, and for that
purpose shall refer to the several Figures on the annexed Sheet of
Drawings, the same letters of reference indicating corresponding parts in
all the corresponding Figures.
Figure 1 of the Drawings represents a longitudinal section of an
oscillating steam engine and double acting air pump combined and
arranged in accordance with this Invention; Figure 2 is a diagram in
illustration of the manner of determining the proper inclination of the
steam cylinder relatively to the air compressing cylinder.
L in Figure 1 represents the steam engine cylinder; e its piston rod,
and d the pin of the crank M by which the engine shaft N is revolved;
C is the air compressing cylinder or barrel of a double acting air pump;
D, its piston; E, the piston rod; and c the connecting rod by which the
piston D is driven from the crank pin d of the engine; the engine
cylinder L is set in an oblique position relatively to the air cylinder C.
This is all important in my improvement and the proper inclination of
the cylinder L is determined by the point or distance in the stroke at
which the steam is cut off.
Figures 2, 3, and 4 of the Drawing illustrate by diagrams the methods
of determining this angle of inclination for the oscillating and for the
fixed cylinder forms of steam engine; Figure 2 gives the angle suitable
to the conditions which obtain in the engine of which Figure 1 is a
large sectional Drawing; in this arrangement the air is required to be
compressed eight volumes into one, the steam to be cut off at three-
eighths of the stroke, and the steam cylinder is of the oscillating form.
To determine the proper angle of inclination for these conditions, first,
take in the compasses the length of the crank of the engine, or the
distance from the centre of the shaft to the centre of the crank pin, and
describe the circle of rotation g of the crank pin d (Figure 2), and
through the centre of this circle draw an indefinite line h, which also
passes through the centre of the air cylinder, then take in the compasses

page_text: the length of the connecting rods of the air cylinder C, and with one
leg upon either point of the intersection of the circle of rotation by the
line à lay off upon that line the position i, j, of the centre of the
cross head pin at the two extreme ends of the stroke of the air
compressing piston; the points k, k, represent the limit of that portion
of each stroke of the air compressing piston at which the required
compression or density is reached namely ths of the stroke, the
compression being eight volumes into one or eight atmospheres; the
points k, k', are therefore placed at one-eighth of the stroke from
either end.
With the compasses opened to the length of the connecting rod f, set
one leg upon the point k nearest the crank, and mark upon the upper
half of the circle of rotation g the position of the crank pin d, then with
the compasses opened as before set one leg on the point ' farthest from
the crank, and mark on the lower half of the circle of rotation g the
position of the crank pin at the corresponding point of the return
stroke; having established the position of the crank pin for the instant,
when the desired compression is attained for the oscillating form of
machine, I next require to determine the distance from the centre of the
trunnion of the steam cylinder to the centre of the crank pin at the
instant when the steam is cut off. This distance is found as follows:-
1st, take the distance, already determined, from the centre of the
trunnion to the centre of the crank shaft, namely, from a to 6 (Figure 2*)
and from it subtract the length of the crank b, c, the remainder a, c, is
the required distance for the upper dead point.
2ndly, to this distance add that part of the length of the stroke at
which the steam is cut off (namely ths) and the sum will be the
distance from the centre of the trunnion to the centre of the crank pin
at the required point; take this distance in the compasses and with one
leg placed on the point d in the upper half of the circle of rotation describe
the indefinite arc / (Figure 2). For the lower dead point add the length
of the crank b, c', (Figure 2º) to the distance b, a, between the centre of
the trunnion and the centre of the shaft, and the sum is the required
distance.
part of the
3dly, from the distance thus obtained subtract that
length of the stroke at which the steam is cut off (namely
remainder will be the distance from the centre of the trunnion to the
ths) and the

page_text: centre of the crank pin at the required point; take this distance in the
compasses, and with one leg placed on the point d' in the lower half of
the circle of rotation describe the arc to intersect the arc l, a right
line m drawn from this point of intersection through the centre of the
shaft, forms approximately with the line h the proper angle or inclination
of the steam cylinder.
Figure 3 is a diagram showing the proper inclination (obtained as
above-described) of an oscillating steam cylinder under different conditions
of pressure of air and cut off of the steam. The angle of inclination as
there shewn is adapted to fine atmospheres, maximum air pressure, and
a cut off of steam at four-tenths of the stroke in the steam cylinder.
For determining the proper inclination of a fixed steam cylinder with
connecting rods, let the points d, d, Figure 4, in the circle of rotation g
of the crank pin be established by the method described above. Then
take in the compasses the length of the steam connecting rod, and with
one leg set on the upper point d, describe an indefinite arc l, next with
the compasses unchanged place one leg on the opposite lower point d³,
describe a second arc so as to form part of a line with the first, with
the intersection of the curves towards the air cylinder. Obtain the
length of that part of the stroke of the steam piston which lies between
the two points of the cut off.
In Figure 4 the cut off is assumed for illustration at two-cights of the
stroke from either end of the steam cylinder, and the space intervening
between them is two-eights of the stroke. Then find a point on one of
the arcs 1, 1, where these arcs separate from each other by the distance
between the two points of cut off in the steam cylinder, which distance
is shewn in Figure 4 at two-eighths of the stroke. A right line m drawn
from that point through the centre of the shaft forms with the line / the
proper angle of inclination of the steam cylinder.
Figures 5 and 6 are diagrams representing under different conditions
the theoretical effort of the steam and resistance of the air multiplied
into the transmitting power of the crank pin at all points of the forward
and return strokes of the engine. They are intended to illustrate the
advantage of inclining the steam cylinder by shewing the approach to
equality between the effort and resistance which this arrangement of
machinery secures.
lincs air.
The dotted lines indicate steam and the full

page_text: Figure 5 represents the conditions which obtain in Figure 2, and to
which the machine represented in Figure 1 is adapted. The air is
supposed to be compressed to eight atmospheres or one hundred and three
pounds effective, the initial pressure of the steam to be seventy pounds
to the square inch, and the steam cut off at three-eighths of the stroke.
In Figure 6 the final air pressure is supposed to be five atmospheres, or
fifty-nine pounds effective, and the initial steam pressure forty pounds to
the square inch, the steam being cut off at four-tenths of the stroke.
The proper inclination of the steam cylinder to suit these conditions is
shewn in diagram Figure 3.
The compressor described in this Specification is so constructed as
to remove the excessive heat generated by the compression of air by
providing for its rapid absorption and conduction through all inclosing
surfaces, which surfaces are kept cool by a free circulation of water
behind them.
It becomes economically very important to absorb the excessive heat
during the process of compression and before the air leaves the com-
pressing cylinder. To illustrate this by example:-Let air at 60° be
compressed in perfectly nonconducting vessels, five volumes into one,
the increased heat generated will be about 484°, and the resistance due
to that increase of heat will be about ninety-three per cent. above that
which is due to five atmospheres' compression, or equal to about 9.64
atmospheres. But if the absorption can go on during the stroke of the
piston nearly as rapidly as the heat is generated, only a small portion
of this increased resistance will be encountered.
Ample experiment has proved that the conducting power of metals
is capable of absorbing all objectionable heat, with sufficient rapidity to
allow any desirable speed in the movement of the compressing piston,
provided the absorbed heat can be carried away from the metal by a
flowing current of water surrounding it but out of contact with the
air itself.
A piston of twelve inches diameter, compressing to four atmospheres,
has been moved for several consecutive hours at the speed of more than
four hundred and fifty feet per minute, producing only a slight, and
quite unobjectionable warming of the machinery. .

page_text: The compressing cylinder C shewn in Figure 1 of the Drawing, is
composed of three concentric shells, which form two annular spaces
around the working cylinder. The outer shell and space included
within it act as a condenser to any moisture in the air, and is a convenient
passage for the air after compression. The shells are marked in the
Drawing C, C', and C³. The spaces are marked S and S'; the outer
double cylinder C', C³, is cast in one piece; the inner one C, in which
the piston works, and which I name the working cylinder is cast and
turned separately, and fitted to bearings in the outer one, it is preferably
of bronze, or of some metal of more rapid conducting capacity than
iron, and is merely a thin lining resting upon bearings (not shewn in
the Drawings) which are placed at intervals on the sides, and against
bearings at top and bottom which are continuous throughout its length,
these latter divide the adjacent space S into two parts, for the purpose
of making the circulation of the water more complete. The heads of
the cylinder are also made hollow with duplicate chambers, for air and
water passages. These passages are marked A and W in the Drawing.
The piston D and piston rod E are also made hollow, with passages in
the former to allow the flow of water. The piston rod extends through
both heads of the cylinder, and the part which extends beyond during
the extreme outward stroke is enclosed in a water tight casing F.
A tube T somewhat smaller than the bore of the piston rod is fixed
at the extreme end of the casing and extends through the bore B of
the piston rod to the farther end of the cylinder; where the end is open
a gland or diaphragm G is fastened in the bore of the piston rod at the
piston; this gland is fitted to and slides over the tube T and stopping the
flow of the water outside the tube T compels it to pass through suitable
pipes or passages P placed on opposite sides of the diaphragm, into,
around, and out of the piston, before its course can be continued
through the bore of the piston rod beyond. J is a perforated lantern
brass fitted round the piston rod as shewn and arranged relatively to the
current of cooling water so that the water shall have access to and
circulate round the piston rod, whereby the exterior surface of such rod
is kept wetted.
The air valves V and V₁are of the class usually called bonnet or
conical valves, they are operated both ways principally by air pressure
unduced hr the action of the machine but are held to place by slight

page_text: The inlet or induction valves V open directly from the interior of the
working cylinder to the external air, through casings K which pass
through both shells of the cylinder head; they are mounted in moveable
housings for facility of repair.
The outlet or delivery valves V' are hollow cases which can readily be
drawn out from the valve chamber K' by removing the cap H. The
lubrication of the working cylinder by water is effected through an
annular space around the piston between the two sets of packing rings.
In the Drawing the space is marked I, it is filled constantly with water
by the pressure which causes the circulation, and wets the whole inner
periphery of the working cylinder as the piston passes through it.
The water for cooling may be introduced into the cylinder by a pump,
either attached or independent, or it may be supplied through a simple
pipe from a head affording suitable pressure. It enters at the outer
stroke end and passes directly through a tube to the annular space S
adjacent to the working cylinder; this space, as before-mentioned, is
divided longitudinally into two parts, by continuous bearings at top
and bottom; the water moves in this space the entire length of the
cylinder, when it passes into the hollow head opposite the end at which
it entered; thence passing around the valve chambers, piston rod, and
outside of the outlet air chambers, it passes into the opposite side of the
annular space S adjacent to the working cylinder, and returning the whole
length enters the hollow head near which it was first admitted to the
machine; from this head it moves through several small passages into the
hollow casing F, which extends beyond the end of the cylinder, and
contains the prolonged piston rod E and the small tube T; from this
casing it passes into the bore of the piston rod and flows forward to the
gland G at the piston. This gland cuts off the direct passage of the
water outside the tube T and forces it through suitable pipes or passages
P on opposite sides of the gland, into, around, and out of the piston,
whence it continues its course along the bore of the piston rod beyond
the gland to the open end of the tube T, and entering there passes
back through the tube out of the machine.
The automatic action of the air valves is perfectly simple. As the
piston moves away from either head of the cylinder the inlet valves
open and admit the outer air to fill the space swept through by the
piston. As soon as the end of the stroke is reached, the pressure on

page_text: both sides being equalized, the valves are closed by the light spiral
springs; as the piston returns it compresses the air which has been
drawn into the cylinder, until its density somewhat exceeds that of the
receiving tank or reservoir, when the outlet valves open, and the com-
pressed volume is forced through them, the valves closing automatically 5
when the end of the stroke is reached.
Having now described and particularly ascertained the nature of my
said Invention, and the manner in which the same is, or may be used or
carried into effect, I would observe in conclusion, that what I consider
to be novel and original, and therefore claim as the Invention secured 1
to me by the herein-before in part recited Letters patent is,-
First. The combination of the double acting pump, cylinder, and its
piston D, with the steam cylinder Land its piston, the revolving shaft N
and crank pin d, common to both pistons, when said cylinders are
arranged in angular relation to each other, substantially as and for the 1
'purposes herein described.
".
Second. In combination with the reciprocating piston D and suitable
valves and connections for receiving air and delivering it in a compressed
condition the thin lining cylinder C, made in a separate piece from the
-supporting cylinder C³, with provisions for circulating water in the space 2
⚫between them, substantially as and for the purposes herein specified.
Third. In connection with the above I claim the within described
arrangement of the circulating passages for the cooling water, so that
the said cooling medium shall circulate in contact with the entire
sides and both ends of the cylinder in which the air is received and 2
compressed.
Fourth. The water space I arranged between two series of packing
rings in the piston, in combination with suitable provisions for
admitting water thereto, so that the water is presented directly against
the inner surface of the cylinder while confined against escape by the 3
packing on either side, all substantially as herein set forth.
Fifth. The casing O and tube T arranged substantially as shewn
relatively to the hollow piston D and tubular piston rod E, with
provisions for leading the water to and through the same, as herein
specified.
3

page_text: Sixth. The valve chambers K, K³, extending through the water
chamber in the cylinder ends, and arranged relatively to the cylinder and
piston, and to the valves and circulating currents of water and air as
specified.
Seventh. In combination with the water chambers on the cylinder
ends I claim the removable valve cases or tubes K, extending through
such chambers and adapted to be readily removed with their contents,
and applied again without disturbing the other parts, as herein set forth.
In witness whereof, I, the said Addison Crittenden Rand, have to
this my Specification set my hand and seal, this Founteenth
day of March, One thousand eight hundred and seventy-three.
ADDISON CRITTENDEN RAND. (L.S.)