Improvements in Machinery for Compressing Air and other Gases
Year: 1888

page_text: Date of Application, 17th Aug., 1888
Complete Specification Left, 11th May, 1889-Accepted, 22nd June, 1889
PROVISIONAL SPECIFICATION.
Improvements in Machinery for Compressing Air and other Gases
I, WILLIAM HENRY NORTHCOTT 7 St. Mary's Road, Peckham, London, S.E.
Engineer do hereby declare the nature of this invention to be as follows:-
My improved compressing pump is formed of a main cylinder having within it a
piston with two trunks or projections upon one side of it. One of these trunks is
within the other, and the inside trunk is appreciably smaller than the other. The first
stage of compression-the entire compression is performed in three stages-is effected
in the space between that side of the piston where there is no trunk and the main
cylinder cover. The second stage of compression is effected in the annular chamber
formed between the main trunk and main air cylinder. The third stage of compression
is effected in a small cylinder formed within the smaller trunk-the piston for this
latter cylinder being formed as a projection from the main cylinder cover. There are
of course suitable valves of the ordinary kind for admitting the air into the first
compressing chamber-from the first to the second, from the second to the third, and
from the third off to the cooling coil.
The main air cylinder is surrounded with a casing into which water is forced by an
ordinary pump or other means, or preferably by the action of the apparatus itself as
hereafter described. The circulating or cooling water is caused to flow through the
apparatus in contact with the external wall of the main cylinder, the internal wall of
the main trunk, the external wall of the central cylinder, and in some cases in contact
with the cylinder cover and round the projecting piston of the small cylinder, also in
most cases around a cooling coil through which the air is passed after compression,
and in some cases into a chamber containing another coil for a purpose hereafter
described. The precise direction of flow of the cooling water may vary according to
circumstances.
When the cooling water is circulated by the apparatus itself, I utilize the annular
space between the two trunks, as a pump barrel, and as this barrel reciprocates with
the compressing piston I fit it into an annular plunger, or two cylindrical plungers-
such annular or cylindrical plungers being held stationary and supported by two
tubular supports attached below to any convenient stationary part. These tubular
supports are furnished with suction and delivery valves and put into connection
with the water supply on the one hand and with the water casing on the other.
In order to lubricate and cool the internal parts and packings of the compressing
chambers, it is found necessary to admit with the Gas to be compressed, a small stream
of cold water, and pure distilled water is found best for the purpose. To conveniently
provide this distilled water I employ a small condensing coil placed in the chamber
before referred to, and which may or may not be directly attached to the compressing
cylinder. I take a jet of steam, from the exhaust pipe of the engine driving the
compressor, or elsewhere, and lead the same into this coil where the steam is condensed
into water and cooled by the waste circulating water as already described. The
distilled water may be led to the compressor inlet valve direct or to a storage tank.
Before the air or gas can be employed it is generally necessary that the water mixed
with the compressed gas shall be separated from it, and this is usually done by passing
the wet compressed air into a small pipe leading downwards into a much larger one
with an air outlet on the top and a water outlet at the bottom. As this does not
separate the whole of the water, I employ a compound separating vessel, formed of
two or more of the ordinary separators, and I pass the air from one to the other so
that moisture leaving the first vessel at the air outlet may be deposited in a
second vessel, or in a third or fourth where the air or gas is required very dry.
The central piston of the air compressor is exposed to the highest pressure and

page_text: needs a packing that will remain tight under such high pressure and withstand the
friction and temperature that obtain in the working of the apparatus. I therefore in
some cases employ a metallic cup in place of the ordinary leather cup and I stamp or
otherwise form such cups out of brass, copper or other metal least affected by the
particular gas under compression and the water or other lubricant used therewith.
Dated this 14th day of August 1888
COMPLETE SPECIFICATION.
Improvements in Machinery for Compressing Air and other Gases.
1, WILLIAM HENRY NORTHCOTT, of 7, St. Mary's Road, Peckham, in the county
of Surrey, 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 :-
My improved compression pump is formed of a main cylinder having within it a
piston with two trunks or projections upon one side of it. One of these trunks is
within the other and the inside trunk is appreciably smaller than the other. The first
stage of compression-the entire compression is performed in three stages-is effected
in the space between that side of the piston where there is no trunk and the main
cylinder cover. The second stage of compression is effected in the annular chamber
formed between the main trunk and main air cylinder. The third stage of compression
is effected in a small cylinder formed within the smaller trunk. The piston in this
latter cylinder being formed as a projection from the main cylinder cover.
are of course suitable valves of the ordinary kind for admitting the air into the
first compressing chamber, from the first to the second, from the second to the third,
and from the third off to the cooling coil.
There
The main air cylinder is surrounded with a casing into which water is forced by an
ordinary pump or other means, or preferably by the action of the apparatus itself as
herinafter described. The circulating or cooling water is caused to flow through the
apparatus in contact with the external wall of the main cylinder, the internal wall
of the main trunk, the external wall of the central cylinder and in some cases in
contact with the cylinder cover and round the projecting piston of the small cylinder,
also in most cases around a cooling coil through which the air is passed after
compression and in some cases into a chamber containing another coil for a purpose
herinafter described. The precise direction of flow of the cooling water may vary
according to circumstances.
When the cooling water is circulated by the apparatus itself I utilize the annular
space between the two trunks as a pump barrel and as this barrel reciprocates with the
compressing piston I fit into it an annular plunger or two cylinderical plungers-such
annular or cylinderical plungers being held stationary by two tubular supports attached
below to any convenient stationary part. These tubular supports are furnished with
suction and delivery valves and put in connection with the water supply on the one
hand and with the water casing on the other. In order to lubricate and cool the
internal parts and packings of the compressing chambers it is found necessary to
admit with the gas to be compressed a small stream of cold water, and pure distilled
water is found to answer best for this purpose. To conveniently provide this distilled
water I employ a small condensing coil placed in the chamber before refered to and
which may or may not be directly attached to the compressing cylinder. I take a jet
of steam from the exhaust pipe of the engine driving the compressor or elsewhere and
lead the same into this coil where the steam is condensed into water and cooled by the
waste circulating water as already described. The distilled water may be led to the
compressor inlet valve direct or to a small storage tank. Before the air or gas can be
employed it is generally necessary that the water mixed with the compressed gas shall
be separated from it and this is usually done by, passing the wet compressed air into a
small pipe leading downwards into a much larger one with an air outlet on t
the top

page_text: nd a water outlet at the bottom. As this does not separate the whole of the water I
mploy a compound separating vessel formed of two or more of the ordinary
eparators and I pass the air from one to the other so that moisture leaving the
rst vessel may be deposited in a second vessel or in a third or fourth where the air
r gas is required very dry.
The central piston of the air compressor is exposed to the highest pressure and
eeds a packing that will remain tight under such high pressure and withstand the
riction and temperature that obtain in the working of the apparatus. I therefore
mploy in some cases a metalic cup in place of the ordinary leather cup and I
tamp or otherwise form such cups out of brass, copper or other metal least
ffected by the particular gas under compression & the water or other lubricant used
herewith.
nerewith.
DESCRIPTION OF DRAWINGS.
Figs. 1 and 2. are sectional elevations and Fig. 3 is a plan of one form of my air
compressor. Figs. 4 and 5 show modified forms of the same & Figs. 6, 7 & 8 special
parts of the air compressing apparatus.
In Figs. 1, 2 & 3. A is the main cylinder having within it a piston B. with two
trunks or projections C. D. The process of compression is effected in three stages-
air drawn in at the valves E. E is compressed by the piston B. past the valves G. G.
into the annular space F.
It is there forced through the passages H. H. and past the valve I. into the
small cylinder J. where it receives the third stage of compression. The piston K.
of this small cylinder projects from the main cylinder cover. From this cylinder
the air or gas is forced past the valve L. into a cooling coil M. and thence off
at N.-The escape valve is shewn at O. Figs. 3 and 5. The main air cylinder is
surrounded by à casing through which water is circulated by a pump or other
means. As shown the water is circulated by the apparatus itself, the space P. P.
between the two parts or trunks C. D. being formed into a water pump with
plungers Q. Q. The plungers QQ are made tubular to serve also as suction and
delivery pipes. They are continued downwards where their lower ends are fixed to a
steam cylinder or to some other suitable support. The plungers are therefore
stationary and act by the reciprocation upon thein of their barrels P. P.
The plunger pipes QQ are connected at the bottom to the valve box R by two
horizontal pipes T. T. The valve box has a suction valve S¹ and a delivery valve S.
With this arrangement of pump the water received from below the valve S¹ passes
this valve into the two branch pipes T. T. thence up the tubular plungers Q Q. and
into the pump barrels P. P. This would be on the suction stroke.
On the return stroke the water is forced by the passages U. U. into the remaining
part of the annular water chamber and this being filled, down the tubular plungers,
along the pipes T. T. and into the valve box R. Thence it passes up the pipe V. into
the external water casing and following the direction of the arrows it passes away to
the coil vessel as shown. A small part W. of the main water casing is chambered off
to cause the water to flow as indicated.
The cooling water may be discharged from the coil chamber or it may be further
utilised as herein described. The water may be circulated by any other convenient
means and its direction of flow altered to suit circumstances provided it is so circulated
as to keep the working parts cool. In Fig. 4. the air is conveyed from the chamber F.
by an external pipe H¹ thus leaving the annulus P. clear, and in this case I prefer to
make the pump plunger annular with tubular supports as before and with valves as in
Fig. 1. or placed as in Fig. 4.
The air cooling coil is here shown in the main water casing but it may be placed in
a separate vessel as herinbefore described.
In Fig. 5. the air is taken from F. to J. by a series of small holes or passages h. h.
made in the metal surrounding the third compressing cylinder. This also leaves the
water space P. clear for an annular plunger. To obtain distilled water for injection, I

page_text: in some cases provide a small condensing coil and chamber X. of similar construction
to the air cooling coil M. and chamber shewn in Fig. 1.
I lead a small quantity of steam from any convenient source but preferably from
the exhaust pipe or drain cocks of the steam cylinder driving the compressor, into
the coil of X. at Y. and take it off as cold water at Z. When this condensing
coil is employed, water leaving the air cooling coil M. passes to the chamber X.
as may be seen in Fig. 3. where it condenses the steam and passes off finally as
shown by the arrows. The distilled water drawn off at Z. may be conveyed direct
to the valves E. E. or one of them, or to a small storage tank. The vessel is not
necessarily attached to the compressor. When the steam for condensation is taken
from the drain cocks I place two small non-return valves on the drain pipe to
prevent the water passing back into the cylinder, and I prefer to collect the drain
water from the cylinder in a small collecting vessel placed between these non-
return valves and the coil.. In Figs. 1 and 2. the compressing piston is shown
worked direct from a continuation of a steam piston rod, but any convenient
method actuating the piston may be adopted. Fig. 6. shews my compound separating
apparatus formed of two or more of the ordinary separating tubes.
The damp air from the cooling coil is passed from one to the other of these
separators as shown by the arrows, so that moisture not deposited in the first may
be caught in the second or the succeeding tubes. The water deposited may be
blown off by separate cocks to each tube or the tubes may communicate at the
bottom and be blown off by one valve. Figs. 7 & 8. shew my metallic packing
cups a. is the cup, b. b. are holes for admitting pressure to distend the cup; c, Fig. 8.
is a leather, or asbestos or Woodite ring I use in some cases to prevent leakage at the
joint behind it.
Having now particularly described and ascertained the nature of my said Inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :
1. The combination of parts forming a three stage air or gas compressor substan-
tially as described and illustrated in the accompanying drawings.
2. The compound piston forming with the main cylinder three compressing
chambers and a water vessel substantially as described.
3. The condensing coil and appurtenances used in conjunction with any form of
compressor substantially as and for the purpose described.
4. The compound separator apparatus substantially as described for use with my
own or other compressing pumps.
5. The metallic packing rings or cups as hereinbefore described and illustrated
in the accompanying drawings for packing the high pressure pistons of compressing
pumps.
Dated this 11th day of May 1889.