Year: 1886

page_text: I, GEORGE EDWIN Dow, of number 114 Beale Street, in the city and county of
San Francisco, and State of California, one of the United States of America,
Machinist 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 Invention relates to certain improvements in compressors for air or gas, and
is particularly applicable to that class in which the medium is compressed in two or
more stages by means of receiving and delivery-cylinders, in each of which the
compression is partially performed. It consists of compressing-cylinders, having
their axes in the same line, and the pistons connected with the piston-rod in such
a manner as to be actuated simultaneously, and so that no stuffing-boxes are
exposed to the heat arising from final compression.
It also consists in an improved means for surface cooling, and in certain details
of construction, all of which will be more fully explained by reference to the
accompanying drawings, in which―
Figure is a longitudinal section of my improved compressor.
Figure 2 is an enlarged longitudinal section of one cylinder with valves,
passages, and water-jacket.
Figure 3 is a view of the receiving end of the cylinder, showing a half-section
through line N O, Figure 2, the piston being removed.
Figure 4 is a view of the delivery end of the cylinder, showing a half-section
through PQ, Figure 2, the piston being removed.
Figure 5 is a modification of the cylinder A, showing the eduction valves of the
receiving-chamber A¹, placed in the piston.
Figure 6 shows the apparatus, with the cylinders set side by side.
A A are cylinders, having ends A¹ and A³ of different diameters, their axes being
in the same line, so that their pistons B B, may be connected together, and operate
simultaneously. a is the piston-rod extending through the receiving ends of the
cylinders A, and connecting with their pistons.
In the present case I have shown a steam-engine K, placed in line between the
two cylinders, so that the piston-rod extends into the engine-cylinder, and is con-
nected with its piston, thus enabling the single engine to operate both compressing.
pistons at once.

page_text: CC are the induction-pipes, through which air or other medium is admitted to
the receiving ends of the cylinders A, passing through the inwardly-opening
valve L, when the piston moves towards the opposite end of the cylinder.
When the piston returns, the valve L closes, and the valve M opens, allowing
the air or medium which is being compressed to pass through the pipe D, and into
the pipe J, and thence through E into the intermediate chamber.
Both cylinders A, are surrounded by chambers S, and R, through which water is
caused to circulate by means of pipes V, so as to convey away the heat developed
by the compression of the air or other medium.
Within the chamber R, which surrounds the cylinder A³, are concentric pipes G,
and H, arranged in rows, as shown in Figure 4, so that the water circulates around
them.
The air or gas in passing from the receiving chambers, through the intermediate
chambers into the smaller or discharge ends of the cylinders, is conducted through
the cooling-tubes G, and H, so that the heat resulting from the first compression
will be taken up and conveyed away by the passing water.
The pistons in each of the cylinders A A, are formed with a large and a small
end, the large end fitting the larger portion of the cylinder, and the smaller end
fitting the smaller portion. These two are united by a web or hollow and open
connecting portion, so that they operate together, and the valve T opens through
the smaller end of the piston into the discharge end of the chamber A². The
pipe J connects the two pipes D, which lead from the valves M into the receiving
ends of the cylinders, and also extending beyond these pipes, connects with the
pipes E, which open into an annular space F, surrounding each cylinder, between
the larger and smaller portion thereof.
The exterior pipes H, of the cooling system are screwed into holes in the side of
the annular chamber F, nearest the surrounding space R, of the smaller portion of
the cylinder, and they extend nearly to the end of this space, and themselves
have their outer ends closed, as shown.
The smaller and inner pipes G, pass through the chamber F, screwing into the
opposite wall, and opening into the intermediate chamber or space between the
larger and smaller ends of the piston.
These smaller pipes extend concentrically within the larger ones H, and nearly
to their closed ends, so that when the piston in the larger portion of the cylinder is
moving toward the rear end, it forces the air behind it through the inner tubes G,
thence back between the tubes G, and H, and into the annular space F, from
which it escapes through the pipe E.
As water is freely admitted into the chamber R, within which these numerous
tubes are situated, it will be seen that the heat developed in the compression of
the air, will be nearly or quite all conveyed away by the water.
The operation of the apparatus will then be as follows:-Supposing the pistons
to be moving toward the right, in the direction shown by the arrows, Figure 1,
the larger portion of the right hand cylinder will be receiving air upon one side of
the piston through the valve L, and the pipe C.
The air which is upon the opposite side of this larger portion of the piston, will
be forced through the tubes G, and H, and thence into the pipe E, and the pipe J, as
before described, passing along the pipe J, until it meets the air which is being
forced through the pipe D of the left hand cylinder by its piston, which is also
moving toward the right, and discharging air through the valve M, as shown.
These two bodies of air uniting, continue on through the pipe E, and through
the pipes H, and G, in the chamber R, of the left hand cylinder, entering the space
behind the larger portion of the piston of the cylinder.
As this amount of air is more than is necessary to fill the larger portion of the
cylinder, the surplus escapes through the valve T in the smaller end of the piston
into the discharging end A' of the left hand cylinder.

page_text: At the same time, the air contained in the discharge end of the right hand
cylinder is being compressed and forced outward through the valve U, and the
pipe I, to the receiver or point of consumption.
When the movements of the pistons are reversed, the same action takes place in
the reverse manner, that is, the air is admitted into the receiving end of the left
hand cylinder and is forced from the intermediate chamber through the cooling
pipes, and the pipes E, and J, into the intermediate chamber and the discharge
chamber of the right hand cylinder; this operation being continued at each.
reciprocation of the pistons.
As a quantity of air equal to the contents of the chamber A¹ must be compressed
into the chamber A² of the opposite cylinder from the intermediate chamber with
each displacement, it will be seen that the compression created in the receiving
chamber is a fixed quantity, and is governed by the relative volumes of the two
chambers.
The intermediate chambers of the cylinders being maintained in communication
with each other by means of the pipe or conduit J, the air or gas in passing into
the latter on its way from one chamber to the other, is conducted through the
cooling tubes G, and H, as before described, so that the heat resulting from the
first compression, is taken up by the surrounding water.
The apparatus here described is simple in construction, not liable to derangement
or excessive wear, and high speeds may safely be employed without injury to the
machine, as no liquids are used in the cylinders to take up the heat of compression
as in other machines, the perfect cooling of the air or gas by the means shown and
described, and subdividing the work into two or more stages, gives ample time to
take up the heat in the jackets, and greatly reduces the amount of resistance
offered to the compression, and consequently takes less power to run the machine.
The compressor requires but two piston-rod stuffing-boxes, each one of which is
easily maintained as the piston-rod passes into the receiving-chamber only, where
the pressure and heat is low, no matter how high the final pressure may be, and
the packing is not exposed to the numerous difficulties arising from exposure to
high pressure and temperature, as in dry compressors of the ordinary construction.
Although I prefer the general arrangement of parts and method of operation
herein shown, I do not wish to limit myself to this precise construction, as other
arrangements of cylinders, valves, or passages may be easily substituted, without
departing from the essential features of the invention; thus, the cylinders might
be set side by side, and the pistons operated by a rotating shaft having cranks set
opposite to each other, so that the pistons may move coincidently and in opposite
directions, as shown in Fig. 6.
A modification of the cylinder is shown in Figure 5, in which the eduction-
valves M, of the receiving end of the cylinder are placed in the large end of the
piston, thus dispensing with the passage D.
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 combination in an air-compressor of two or more sets of cylinders, each
comprising two cylinders of unequal size, placed in line, and communicating freely
with each other at their adjacent ends, pistons fitting the two cylinders, and
connecting with each other so as to move simultaneously, the piston-rods con-
necting with the larger pistons, and extending through the outer heads of the
same, so as to be actuated by a suitable motor, induction and eduction-valves
within the outer head, through which air is admitted to, and discharged from, the
outer side of the larger piston, pipes connecting the discharge-valve with the space
between the larger and the smaller pistons of two corresponding sets of cylinders,
and valves by which the air may pass from this space through the smaller pistons,
to the outer ends of their cylinders, in combination with discharge or eduction

page_text: valves, connecting the outer ends of the smaller cylinders with the storage reservoir,
substantially as described.
2. The combination in an air-compressor of the cylinders connected together in
series, each set comprising two cylinders of unequal diameter standing in line, with
their adjacent ends opening into each other, having pistons connected together so
as to operate simultaneously, with induction and eduction valves, and connecting
pipes, as shown, in combination with a chamber concentric with and exterior to
the smaller cylinder, a series of concentric pipes extending into this chamber, and
connected with the air-conducting pipes and passages, so that the air must pass
through these cooling pipes, substantially as described.