Improvements in Motor Compressors.
Year: 1899

page_text: PROVISIONAL SPECIFICATION.
Improvements in Motor Compressors.
I, JAMES ATKINSON, of The Woodlands, Marple, Cheshire, Engineer, do hereby
declare the nature of this invention to be as follows..
The object of this invention is the construction and operation of motor com-
pressors for various purposes of a simple and effective kind. They may be
arranged in several ways.
I will first describe a simple arrangement which is
the one I prefer to use for many purposes and then I will describe more compli-
cated arrangements adapted for special purposes.
In the simple arrangement the motor compressor consists mainly of one piston
and one cylinder, in which the piston has a recipro-cating virtical motion. One
end of the cylinder is the motor end to which steam (or other gases under com-
pression) is suitably admitted and exhausted; the other end of the cylinder is the
compressing end by which air, (or other gases), to be compressed is drawn in,
compressed and delivered.
The regulation of the motor fluid and of the fluid to be compressed is performed
entirely by means of ports and passages constructed in the piston and in the
cylinder which are opened and closed at suitable times by the movements of the
piston. The piston reciprocates at a very high rate of speed, which may, in a
small machine, be as much as some thousand double strokes per minute; it is of
considerable length, is very light, may be without any packing rings, (at any rate
in the smaller sizes) and is a good easy sliding fit in the cylinder.
The cylinder has four sets of ports in it, each consisting of a number of equally
spaced holes drilled through the walls in the same horizontal plane. Commencing
from the bottom, the first is the steam admission holes, the second the steam
exhaust holes, the third the air suction holes and the upper row the compressed air
delivery holes. Each set of holes communicates with an external chamber of
ample capacity and the ample capacity of these chambers is of considerable im-
portance owing to the extremely short intervals of time during which the ports for
the passage of the steam and air are open. The lowest chamber is kept supplied
with the steam which is the motive fluid and the lower end of the cylinder may be
inserted in it so as to keep it hot: it may also form a substantial base.
The piston in vertical section may be of a form similar to the letter H. The
piston is so long that in its extreme reciprocations it does not uncover any of the
cylinder ports with its ends, but a port for each side of the piston is formed in the
piston preferably consisting of a concentric groove turned on its external surface
communicating with a number of holes, equally spaced, to the inside.
The action is as follows:-
Assume that the piston is near the lower part of its stroke, moving upwards and
the lower steam port in the piston is about to coincide with the steam admission
port, steam is admitted which drives the piston upwards; at about the same time
the air port in the upper side of the piston opens to the air suction and air is
drawn in, compressed by the upward movement of the piston which continues till

page_text: the air port opens to the air delivery port and some of the compressed air is
delivered. If the energy imparted to the piston is not all taken up by the work
done on the air, the piston continues its course upwards shutting in a quantity
of compressed air which makes a perfectly elastic cushion and converts the upward
excess energy into downward energy. As the air port in the piston again passes
the air delivery port in the cylinder a little more compressed air may be delivered
but sufficient air is left in the cylinder end to assist the piston in continuing and
completing its downward motion. At about the same time that the compressed
air is being delivered exhaust is taking place through the steam port in the
piston opening to the exhaust port in the cylinder, thus reducing pressure on the
under side the piston and allowing its downward motion to proceed with such
energy that an elastic cushion of steam may be necesary to bring it up and reverse
its motion again upwards, through the steam port in the piston may have passed
and opened the steam port in the cylinder admitting fresh steam on the downward
motion. This freshly admitted steam adds its force to still more steam admitted
as the piston moves upwards giving upward energy to compress the air above the
piston which has been increased in quantity by air drawn in at about the same
time that fresh steam was admitted. The piston is thus driven up and down at
an extremely rapid rate.
Care should be taken to proportion the clearance spaces to suit the steam pres-
sure and the air compression pressure having due regard to the exhaust and air
suction pressures, so as to ensure ample steam expansion and no excessive air
compression and I prefer to make these compression spaces easily adjustable so
as to get the best proportions. They may be readily calculated on the assumption
that the compression and expansion lines for the portions of the strokes when the
ports are closed are similar to such lines when no heat is given out or absorbed
excepting that due to work done, the rapidity of the strokes being so great as to
make this assumption practically correct.
Air can be compressed very economically in this manner by comparatively small
cheap machines having no external moving parts and being little liable to injury
from wear or other causes. The rapid reciprocation prevent any material loss
from cooling and heating due to surface contact. The ports though narrow can
have ample area as they may include the whole circumference in the form of
circumferential grooves. Care being taken that no unbalanced side strain is
put on the piston which is an easy sliding, practically frictionless fit very little
power is absorbed in driving it. There being no other moving part frictional loss
is almost eliminated. As the piston practically will cease to wear when it gets
into proper order there will be very little leakage loss. Any excess of energy
stored up in the piston at any end stroke is reversed and put back into the piston
for the next return stroke with practically little or no loss by the steam and air
cushions.
The machines are more or less self governing owing to the pistons flashing
more rapidly past the ports in the cylinder if the stroke increases owing to excess
of power over work done and this action may be increased by the addition of
short pipes or passages to the cylinder or piston ports, more particularly the steam
admission port, the action of the short pipes being to initially restrain movement
of the fluid, but only initially. If the strokes shorten so as only to open the ports
once at each end stroke full volumes pass and power is increased. For the purpose
of assisting this self governing arrange the steam ports so that they are opened
a little earlier than the air ports.
For starting I arrange a sliding collar round the air delivery ports holes which,
(either by hand), or automatically almost closes them when there is no pressure
in the delivery chamber but opens them wide as this pressure approaches the
desired delivery pressure.
This simple arrangement is suitable for compressing air by steam power to a
pressure about the same as the steam pressure though considerably varying
pressures may be used. For high pressures two or more may be used so as to

page_text: give multiple expansion and stage compression, working independently of each
other, the steam passing in stages from any higher pressure machine to the next
lower pressure machine and the air from any lower pressure one to the next higher
pressure one, being cooled between each compression if the most economical result
is to be obtained.
When it is desired to compress air to a much higher or much lower pressure than
that of the steam, I make the piston of two diameters there is thus a chamber
between the two diameters which I make of suitable capacity and connect to the
atmosphere by suitable cocks or valves. If the chamber is in free communication
with the atmosphere it has no appreciable effect on the working result, if closed
excepting to an inward opening selfacting valve the mean pressure is above
atmospheric pressure thus assisting the piston in the direction of the larger dia-
meters, if the self acting valve opens outwards the mean pressure is below
atmospheric pressure and the piston is arrested in the direction of the smaller
diameter and if there is no communication to the atmosphere the chamber has
the effect of increasing the rate of the reciprocations of the piston.
changes can be made whilst the machine is running the use of this chamber will
enable it to work under the best conditions for considerably varying circumstances.
For larger machines especially if intended to compress to a higher pressure gases
already under pressure I use a double acting motor and a double acting (or single
acting) compressor placed together on the same axial line and couple the two
I use the same
pistons with a piston rod working through a gland or glands.
provision for cushioning, the same arrangement of chambers, the same arrange-
ments for self governing and similar ports excepting that one exhaust port in the
motor cylinder and one suction port in the double acting compression cylinder
will be sufficient.
As these
For double acting motor and compressor cylinders the ports may be con-
veniently arranged in a different manner there being two ports in each cylinder and
three ports in each piston. If the steam end is at the bottom the lower port in
the cylinder is the admission port for both sides of the piston and the upper port
the exhaust port; the lower port in the piston is the admission port for its upper
side being connected by suitable passages, the middle port is the steam admission
and exhaust port for the lower side and the upper port is the exhaust port from
the upper side. Similar ports are used for the compressing cylinder.
The cylinder and its attachments should have considerable weight so as to
absorbe vibrations also may be attached to springs or suspended from springs to
prevent the transmission of vibrations.
I wish it to be understood that modifications in the arrangements of ports may
be made whilst still retaining the essential features of this invention.
Dated this 2nd day of September 1899.
Improve
I, JAMES ATKINSON, of Station Road, late of The Woodlands, Marple, Cheshire,
5 Engineer, do hereby declare the nature of this invention and in what manner the
same is to be performed, to be particularly described and ascertained in and by
the following statement:
-
The object of this invention is the construction and operation of motor com-
They may be
pressors for various purposes of a simple and effective kind.
arranged in several ways. I will first describe a simple arrangement suitable for

page_text: many purposes and then other arrangements which may be more suitable for
other conditions or circumstances.
For the purpose of more clearly explaining my invention I append three sheets
of drawings in which Fig. 1 Sheet 1 is a vertical sectional elevation of the simple
single acting arrangement, Fig. 2 Sheet 2 is a vertical sectional elevation of a
double acting arrangement, and Figs. 3, 4, 5 and 6 Sheet 3 are diagrams showing
the fluid action.
The arrangement shown in Fig. 1 Sheet 1 shows a deep light piston a, free to
reciprocate vertically in a cylinder b. The lower end of the cylinder is the motor
end to which steam (or other gases under compression) is admitted, expanded
doing work, and exhausted; an annular chamber c of ample capacity being kept
supplied with steam and the annular chamber d is an ample receiver for the
exhaust steam from which it may pass to the atmosphere or condenser. The upper
end of the cylinder 6 is the compressor end into which air (or other gases) is
drawn, compressed and from which it is delivered in a compressed state, e being
a large annular suction chamber to which the air is admitted and f a large com-
pressed air chamber from which the compressed air is led to a larger receiver or
to wherever it may be required.
The regulation of the motor fluid and the fluid to be compressed is performed
by means of ports or passages constructed in the piston a and the cylinder b
which are opened and closed at suitable times by the movements of the piston a.
The piston a is of considerable length, is very light and is a good, easy sliding
fit in the cylinder b. It reciprocates at a very high rate of speed making in
small and moderate sized machines many thousand double strokes per minute.
The cylinder b as shown has four sets of ports in it, each consisting of a number
of equally spaced holes drilled radially into the walls of the cylinder 6 from the
outside and communicating with a narrow groove turned out of the bore of the
cylinder so as to give ample area. Commencing from the bottom, the first port g
is the steam admission port communicating with the steam chamber c, the second
is the steam exhaust porth communicating with the steam exhaust chamber d,
the third is the air admission port i communicating with the air suction chamber e,
and the fourth and highest port is the compressed air delivery port com-
municating with the compressed air chamber f.
It is of great importance that the chambers c, d, e and ƒ should be of ample
capacity owing to the extremely short intervals of time during which the ports
are open. To enable the machines to give their full duty and to assist in their
self regulation they should be large enough to prevent any material rise or fall
of pressure as the fluid is drawn from them or delivered to them, so that their
connecting pipes are not depended on for the sudden and rapidly intermittent
movements of the fluid which otherwise would set up wave action in these pipes,
as well as interfere with free and unrestricted movement.
The steam chamber c encloses the steam end of the cylinder b and keeps it hot.
The piston a is of such a length that it does not uncover any of the ports in
the cylinder with its ends, but is provided with a steam port 7 for the steam side
and an air port m for the air side, there ports are formed by turning narrow
grooves in the cylindrical surface of the piston a communicating by means of a
number of equally spaced holes with the inside.
The action is as follows:-
Assume that the piston a is near the lower end of its movement and the port
coincides with the steam port g, steam is admitted which drives the piston a
upwards at about the same time the port m coincides with the air admission
port and air is drawn in compressed by the upward movement of the piston «
which continues till the port m opeus to the air delivery port k and some of the
compressed air is delivered into the chamber f. If the energy imparted to the
piston a is not all taken up by the work done on the air, the piston a continues
its course upwards shutting in a quantity of compressed air which makes a
perfectly elastic cushion and converts, practically without loss the upwards

page_text: excess energy into downwards energy. As the air port m again passes the
delivery port f a little more compressed air may be delivered but
sufficient air is left compressed in the cylinder end above the piston a
to drive it downwards and to complete its downward stroke. At
about the same time that the port m in the piston coincides with the
delivery port the port in the piston coincides with the exhaust port h in
the cylinder 6 and steam is exhausted from the lower end of the cylinder b
below the piston a, thus reducing pressure on its underside and allowing its
downward motion to proceed with such energy that an elastic cushion of steam
may be necessary to arrest it and reverse its motion again upwards, though the
port in the piston may have opened and passed the steam admission port y
admitting fresh steam, the elastic cushion of steam shut in the steam end of the
cylinder 6 will, practically without loss, convert the downwards excess energy
into upwards energy.
As the port again passes the port g fresh steam is
admitted and the piston is forced rapidly upwards. At about the same time that
the port coincides with the port g the port m coincides with the air suction port i
and air is drawn in above the piston a to replace the air delivered in the previous
upward stroke. The piston a is thus driven up and down at an extremely rapid
rate.
Care should be taken to proportion the clearance spaces to suit the steam
pressure and air compression pressure having due regard to the exhaust and air
suction pressures so as to ensure ample steam expansion and no undue com-
pression of the air. These clearance spaces may be made readily adjustable so
as to suit any special conditions. They may be easily calculated on the assump-
tion that the compression and expansion lines for the portions of the strokes
when the ports are closed are similar to such lines when no beat is given out or
absorbed excepting that due to work done on the fluids which are being com-
pressed or expanded, the rapidity of the strokes being so great as to make this
assumption practically correct.
The machine is more or less self governing owing to the ports 7 and m in the
piston flashing more rapidly past the ports g, h, i, k in the cylinder if the stroke
increases in length due to excess of power over work done and this action may be
increased by the addition of short pipes or passages to the ports, more particularly
the steam admission port g. In Fig. 1 Sheet 1 a narrow annular passagen is
shown leading from the steam chamber c to the steam admission port 9. The
action of this passage n is to initally restrain the movement of the steam entering
the cylinder, but only initially. If the strokes shorten so as to open the ports
only once at each end stroke and keep them open during the pause before the
return stroke commences, full volumes pass and more power is imparted to the
piston. For the purpose of assisting this self governing I may arrange the steam
ports g and a little closer together than the air ports and k so that they open
a little in advance.
To explain the actions of the fluids in the machine more completely I have
illustrated their actions in diagrams Figs. 3, 4, 5 and 6 Sheet 3, in which the
machine is assumed to be using steam of about four atmospheres above atmo-
spheric pressure, exhausting into the atmosphere and compressing air from atmo-
spheric pressure to about four atmospheres.
Fig. 3 shows the steam pressure lines and
Fig. 4 the air pressure lines when doing an average duty. Figs. 5 and 6 show
similar lines when the pressure in the air receiver rises above the four atmo-
spheres pressure, the amount of air delivered is automatically reduced as the
pressure rises. As the amount of air delivered is reduced it will be seen that
the work done in the air compressing end of the machine is also reduced, requir-
ing less power developed on the steam side, under these circumstances the stroke
of the piston increases, the steam port 7 flashes very rapidly past the steam
admission port g and very little steam enters; it also flashes past the exhaust
port and the exhaust is also reduced. This self governing action will clearly

page_text: be understood by the diagrams which also show the action of the fluids. It will
be seen from them that at each stroke of the piston some steam is always left in
the steam end of the cylinder and fresh steam admitted to it to give the required
upward energy, also that some air is always contained in the air end of the
cylinder which is compressed by the piston in its upwards motion and a sufficiency
of this compressed air is left in for the purpose of driving the piston downwards.
To prevent too much air being forced out of the upper end of the cylinder,
should there be no air pressure in the chamber f, (at starting say,) I may provide
some means of partially closing the air delivery port k. In Fig. 1 Sheet 1 a
ring o is shown partially closing this port k, this ring o is so adjusted as to let
a little pass at starting and as the pressure in the chamber f rises, the piston r
is forced upwards in its short cylinder against an adjustable spring s, the ring
is connected to the piston r by the yoke pand vertical rods (which latter are not seen
in the drawing) so that as the piston rises the ring o also rises until finally it is
clear of the port and there is an uninterrupted outlet for the compressed air from
the cylinder whenever there is a sufficient pressure in the chamber f. This
arrangement will not be necessary in all instances and it may also be arranged to
be operated by hand instead of automatically.
0
The simple arrangement as above described is suitable for compressing air by
steam power to a pressure somewhat similar to the steam pressure used and
though there may be considerable difference in these pressures it would not be
suitable in all instances. It may be constructed having the piston and cylinder
of one diameter at the steam end and a larger diameter at the air compressing end
if required to deliver a large volume of air at a lower pressure or a smaller
diameter for a smaller volume at a higher pressure.
For larger machines, especially if intended to compress to a higher pressure
gases already under pressure, or to deal with gases other than air, say for instance
ammonia for refrigerating purposes, I prefer to use the double acting arrange-
ment shown in Fig. 2 Sheet 2. I employ a double acting motor cylinder 1 and
a double acting compressing cylinder 2. The cylinders are fixed one above the
other and their diameters may be in any desired proportion, the two pistons are
connected by piston rods which may be conveniently joined by a suitable coupling
as shown or a through piston rod may be used, thus the rapid reciprocations of
the motor piston are communicated to the compressing piston.
The various ports may be arranged somewhat differently to the method shown
in Fig. 1 Sheet 1 there being two ports in the cylinders and three in the pistons.
7 is a steam port in the cylinder 1 communicating between the steam chamber 3
and both sides of the steam piston, the lowest port in the piston being connected
by means of a series of holes in the body of the piston to the upper side of the
piston and the middle port in the piston similarly connects to the underside of
the piston. 4 is the exhaust chamber, 8 is the exhaust port in the cylinder and
connects by means of the middle port in the piston to the lower side of the piston
and by means of the upper port in the piston for the upper side, the fluid action
being exactly similar to that described for the single acting steam side of the
arrangement shown in Fig. 1 Sheet 1 excepting that it takes place for both sides
of the piston so as to make it double acting. Similar ports are provided for the
compressing end, 5 being the suction chamber and 6 the compressed air chamber.
the fluid action being also the same as that shown and described in connection
with Fig. 1 Sheet 1 excepting that it is double acting.
I wish it to be clearly understood that modifications in the arrangements of
ports may be made without departing from the essential features of this in-
vention, as for instance, the upper port of the piston of the steam end of the
arrangement shown in Fig. 2 Sheet 2 may be cut off at the upper steam exhaust
port and the exhaust allowed iree exit so long as the piston opens the exhaust
port, also the lower portion of the piston of the compressing end may be cut off
at the lower suction port as for many purposes there would be sufficient govern-

page_text: ing and cushioning actions, without these extensions of the pistons and without
them a cheaper machine can be constructed.
In connection with these machines I may use any suitable steam or air throttle-
ing arrangement for slowing down or more fully controlling their operation.
Air or other gases can be compressed very economically in this manner bv
comparatively small, cheap machines, having no external moving part (excepting
the piston rod of the double acting arrangement,) and little liable to injury from
wear or other causes. The steam is very economically distributed and the admis-
sion and delivery of the air to be compressed is also economically controlled as
will be seen from an inspection of the diagrams 3, 4, 5 and 6 Sheet 3, also owing
to the extremely rapid reciprocations of the pistons the losses from heating and
cooling, condensing and reevaporation, which are so serious in ordinary steam
engines, are extremly small. The ports though narrow car have ample area as
they may include the whole of the circumference. The piston when once it has
worn down to a free, sliding fit will absorbe very little energy in friction as there
is no unbalanced side pressure on it, though free, very little leakage will take
place and further wear will practically cease: as there is no other moving part,
except the piston rods in double acting arrangements, the total losses from
friction will be extremely small. Any excess energy stored up in the piston at
the end of any stroke is reversed and put back into the piston to assist in the
next stroke with little or no loss, by the steam and air cushions.
The machines may be arranged to use the steam expansion in stages, by
preference using two or more machines for this purpose; also the air may be
compressed in stages being cooled between each stage if desired. More than two
pistons may be connected so as to reciprocate in a similar number of cylinders.
The cylinders and their attachments should have considerable weight so as to
absorbe vibrations, they may also be fixed on springs or suspended from springs
so as to prevent the transmission of vibrations."
When used for compressing ammonia, say, a double acting motor piston may
drive a single acting compressing piston so as to relieve excessive pressure on the
piston rod gland of the compressor.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is:-
1. The arrangement and construction of a single acting motor compressor
having a very rapidly reciprocating free piston working in a suitable cylinder one
end of which is the motor end the other end being the compressing end the steam
or other motive fluid and the air or other gas to be compressed being controlled
by ports in the piston and in the cylinder opened and closed at proper times by
the movement of the piston the whole machine operating substantially as
described and illustrated in Fig. 1 Sheet 1 and Figs. 3 4 5 and 6 Sheet 3.
2. The arrangement and construction of a single acting motor compressor such
as described in Claim 1 having self governing and cushioning arrangements
operating substantially as described and illustrated in Fig. 1 Sheet 1 and
Figs 3 4 5 and 6 Sheet 3.
3. The arrangement and construction of a double acting motor compressor
having two very rapidly reciprocating pistons free excepting for their attachment
to each other the one piston working in a suitable double acting motor cylinder
and the other piston working in a connected suitable double acting compression
cylinder the steam or other motive fluid and the air or other gas to be compressed
being controlled. by ports in the cylinders and in the pistons opened and closed at
proper times by the movements of the pistons the whole machine operating
substantantially as described and illustrated in Fig. 2 Sheet 2 and Figs. 3 4 5
and 6 Sheet 3.
4. The arrangement and construction of a double acting compressor such as
described in Claim 3 having self governing and cushioning arrangements sub-

page_text: stantially as described and illustrated in Fig. 2 Sheet 2 and Figs. 3 4 5 and 6
Sheet 3.
5. In motor compressors such as described in Claims 1 and 3 the use of the
ring o see Fig. 1 Sheet 1 or any mechanical equivalent operated by means of the
pressure in the compressed air chamber for by hand so as to prevent the too free
delivery of compressed air from the cylinder when the air pressure is low in the
chamber substantially as described and illustrated in Fig. 1 Sheet 1.
6. In motor compressors such as described in Claims 1 and 3 the combination
and use of the large chambers cle and f Fig. 1 Sheet 1 and 3 4 5 and 6 Fig. 2
Sheet 2 for the steam supply and exhaust and the air supply and delivery with
or without passages such as n Fig. 1 Sheet 1 as described and illustrated."
7. In direct acting motor compressors such as described in Claims 1 and 3 80
arranging the steam ports that they open a little in advance of the air ports for
the purpose of assisting the self governing of the machine as described and
illustrated.
8. The general arrangement and construction of direct acting motor com-
pressors substantially as described and illustrated.
Dated this 2nd dow of July, 1000
JAMES ATKINSON.