Improvements in Air Compressors.
Year: 1891

page_text: R
COMPLETE SPECIFICATION.
[Communicated from abroad by EBENEZER HILL, of No. 112, West Avenue,
South Norwalk, Connecticut, United States of America, Mechanical
Engineer.]
Improvements in Air Compressors.
I, HENRY HARRIS LAKE, of the firm of Haseltine, Lake & Co., Patent Agents,
45 Southampton Buildings in the County of Middlesex, 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 :-
Reference being made to the accompanying drawings forming part of this
application, and which represents in
Figure 1, a side view looking from the right of Fig. 4.
Figure 2, a top or plau view, the air-receivers or inter-coolers and reservoir
removed to show the mechanism beneath.
Figure 3, a side view, the reverse of Fig. 1.
Figure 4, end view from the left of Fig. 1.
Figure 5, transverse section of the principal cylinder cutting through the
relief valve.
Figure 6, longitudinal section through the principal cylinder and the single
acting final compressor adjacent to it.
This invention relates to an improvement in that class of air-compressors which
are designed to compress the air to a very great extent.
Formerly, air-compressors of this class were composed of two single acting
cylinders, a large cylinder as the primary compressor, and a smaller cylinder as the
auxiliary compressor, the air from the first cylinder being led to the second cylinder
directly or indirectly.
During the first part of the operation, that is, when the machine first started, and
before the air in the reservoir had been compressed, the first cylinder would be
doing its full share of the work, but the second or smaller cylinder would be doing
practically nothing, hence the machine would "go heavy" on one side, and light on
the other, if however, double acting cylinders were used for both primary and
auxiliary, the stroke would be the same in both directions, perfectly balanced, but
for the smaller or auxiliary cylinder, it is impracticable to make it double acting
for the reason that it is extremely difficult, and practically impossible, to construct
the piston for the auxiliary cylinder so that it will work perfectly tight in both
directions hence in the attempt to employ a small double acting or final compressor,
the air will escape from one side of the piston to the other side, and thus
materially retard or interfere with the proper action of the pump, and such
leak cannot be readily ascertained.
In the use of a single acting cylinder however, the packing for the piston may be
made outside, where any escape or leak will be observed, and so applied as to be
practically tight, hence it is that in all practical air-compressors, the auxiliary or
final compressing cylinder is made single acting.
In the operation of the single acting cylinder, the power is employed only in one
direction, the piston running free in the opposite direction, consequently there is a
very considerable loss of power, as well as an irregular use of that which is
employed, which produces undue strain upon the machinery.
The object of my invention is primarily to overcome this difficulty, and the
invention consists in combining in an air-compressor, double acting cylinders as the
primary compressors, with a pair of single acting cylinders oppositely arranged as
the supplemental or final compressors, and whereby an even resistance is produced
in all parts of the machine, and in details of construction fully hereinafter described,
and particularly recited in the claim.

page_text: A, represents the bed of the apparatus, and B, the steam-cylinder, arranged upon
the bed, C, the driving-shaft supported in pillow-blocks DD, and to which the
power from the steam-cylinder is applied, in the usual manner, and substantially as
in steam-engines, the details of construction whereby the steam-power is imparted to
the driving-shaft, it is unnecessary to describe, as they do not differ materially from
steam-engines in general use, and may be any suitable mechanism between the
steam-cylinder and the driving-shaft, whereby the reciprocating movement of the
piston will be converted into the rotary movement of the shaft.
EE, represent a pair of fly-wheels, made fast to the driving-shaft, one upon
each side of the bed. F represents the first or principal compressing cylinder, and
G the second compressing cylinder; these are arranged upon the bed, made fast
thereto, and in line with cach other, as clearly seen in Figs. 1 and 2. Between the
two cylinders F and G a cross-head H is arranged in suitable parallel longitudinal
guides I, and in connection with which is a piston-rod J, extending from one side
of the cross-head to the piston of the principal cylinder F, and upon the other side
a like piston-rod K, which extends to the piston of the cylinder G, the respective
rods working through stuffing-boxes L M on the cylinder, in the usual manner for
packing the rods of such cylinders. These cylinders are both double-acting, and
are of common construction, so that the pistons both working together, take air upon
one side as they move in one direction, and on the return force that air out of the
cylinder, and take air upon the other side of the piston, and so continuing, each
movement of the piston taking and receiving air.
The cross-head H is connected by rods on each side to cranks P on the driving-
shaft, and so that each revolution of the driving-shaft will impart full reciprocating
movement to the cross-head H, and the respective pistons connected thereto.
Above the cylinders FG, a receiver R is arranged, and suitably supported, here
represented as of cylindrical shape, and to which the principal cylinder F,
discharges through a connection passage S, see Figs. 2 and 3. The second
cylinder G, draws from the receiver R, through a pipe T, which leads directly
from the receiver R, to the respective ends of the cylinder G, as seen in
Figs. 2 and 3, and so that the air which has been forced into the receiver R
from the cylinder F, will be drawn therefrom by the cylinder G through the said
pipe T. The cylinder G discharges from its respective ends through a pipe E U,
which leads into a second receiver W, arranged parallel with the receiver R,
see Figs. 1 and 2.
The receivers R W are provided with a supply of water through pipes X, in the
usual manner, to reduce the temperature of the air forced into the respective
receivers, and this water may circulate around the cylinder as through a pipe Y,
represented as leading into the principal cylinder, as seen in Fig. 1, this
circulation of water however constitutes no part of my present invention and
is therefore only referred to to indicate the purpose of the pipes represented
in the drawing.
In the illustration I have represented the mechanism for the valves of the
principal cylinder as oscillating valves, the valve-gear being common and well
known, operated directly from the driving-shaft, so that induction and eduction
valves are opened and closed at the proper time, this mechanism being well
known, and for which any other known mechanism may be substituted, and
as such mechanism constitutes no part of my present invention, do not
particularly describe it.
In combination with two double-acting cylinders I employ two single-acting
cylinders a and b; these are arranged at the side of the cylinders F G, and parallel
therewith, as seen in Fig. 2. The piston-rod d of the cylinder a is connected
to the cross-head on one side, and the piston-rod e of the cylinder is connected
to the cross-head on the opposite side, so that under the reciprocating movement
of the cross-head, one piston enters its cylinder as the other is withdrawn from its
cylinder, consequently each of the cylinders a operate to force air in one
direction only, the action of the one cylinder is opposite to the action of the other

page_text: cylinder, and each takes air on the return stroke; these cylinders a bare of like
area, so that one substantially counterbalances the other. The cylinder a draws
air from the receiver W through a pipe connecting directly to the cylinder a and
on the return stroke after having so drawn the air from the receiver W, the air is
discharged through a pipe g. The cylinder draws air from the same receiver W
through a pipe H, connecting directly to the cylinder, and discharges the air so
drawn through a pipe i, the pipes g and being connected to a common discharge 1,
see Fig. 1, thus the four cylinders connected and operating, present an equal
resistance at all times when the machine is in operation, the one single acting
cylinder counterbalancing the other, so that there may be a perfect uniformity in
the action of the machine, and this irrespective of the pressure, that is to say, on
the first starting of the machine, the resistance will be as regular as when the
highest pressure is attained, thereby avoiding the wear and tear of the machine dne
to one single acting cylinder.
It will be understood that the inlet or discharge check-valves are employed for
the respective cylinders as usual in air-compressing apparatus.
It sometimes occurs that the principal cylinder will deliver more air than is
desirable, that is to say, the full capacity of the cylinder will be greater than
desirable; to adapt the principal cylinder to deliver less air than it takes, I
provide a relief valve m, see Fig. 5, this valve consists of the movable valve n,
attached to or made as a part of a screw-spindle o, working through a stuffing-box,
the spindle provided with a hand-wheel at its outer end, by which the spindle may
be rotated to draw the valve from or force it to its seat, the opening through the
valve-seat is into the principal cylinder, and from the chamber outside the valve
an escape-pipe r, conducts air which may escape to any desirable point. This
valve is arranged about midway of the length of the cylinder, but so that the
piston may pass the valve opening, consequently if the valve be open, air will
escape during the first part of the advance of the piston, and until the piston has
passed the valve opening, the quantity of air to be compressed by the piston will
therefore be reduced according to the amount which is permitted to escape during
the first part of the movement of the cylinder and may be greater or less accordingly
as the valve is adjusted.
If the valve be opened sufficiently to permit all the air in advance of the piston
to escape, then the capacity of the cylinder will be but one half its stroke in each
direction, and as the escape opening is reduced, the quantity of air delivered by
the piston will be correspondingly increased, the initial pressure thus being
regulated, it necessarily follows that the regulation will be continued through all
the cylinders to the reservoir, as the pressure of each cylinder succeeding the
principal cylinder will vary according to the pressure produced by the first
cylinder.
To produce a packing around the piston of the final compressing cylinders a b,
and so that air cannot escape from the eylinders, the piston ends of the cylinders ab
are arranged in a support 2, as seen in Fig. 6, this support being a part of the
surrounding case, which forms the cooler for the cylinders, this figure representing
only the cylinder as the end of the cylinder projects beyond the face of the
support 2, which surrounds that end of the cylinder.
The stuffing-box 3, which surrounds the piston 4, is secured directly to the face
of the support 2, and outside the end of the cylinder, so that the stuffing-box
practically covers or incloses the end of the cylinder. The stuffing-box is recessed
to form a chamber 5 around the piston 4, and outside the end of the cylinder. The
ends of the chamber 5, one of which is formed by the stuffing-box and the other
by the end of the cylinder, are made concave in longitudinal section, as clearly
seen in Fig. 6; into these ends of the chambers which form seats, the packings 6, 7,
are respectively arranged; these packings are made from leather or other flexible
material, and are of ring shape corresponding to the diameter of the piston and
the chamber 5, and the packing rings are concavo-convex shape in longitudinal
section, corresponding to the concave shape of the respective ends of the chamber,

page_text: and so as to seat therein, as shown; the inner sides of these packing rings therefore
rest directly upon the piston, and they form the ends of the chamber, consequently
any pressure produced in this stuffing-box chamber 5, will tend to force the packing
close upon the piston and against the outer wall of the chamber to completely pack
the joint.
To produce pressure within the chamber, and so as to hold the packing rings 67
in their proper position, and at the same time lubricate the pistons, I provide a
reservoir 8, which is in the form of a hollow cylinder, similar to, but of smaller
capacity than the air receiver, and arranged parallel therewith and above the
cylinders a b, as seen in Figs. 3 and 4. From this reservoir a tube 9 leads to the
stuffing-box chamber 5 of the cylinder a, and a like tube 10 leads to the stuffing-box
chamber of the cylinder . The reservoir 8 is supplied with lubricating material,
which readily flows into the respective stuffing-box chambers, and so that those
chambers are constantly filled with lubricating material through which the
respective pistons work.
As the pistons of these final compressors operate, at first air will escape in small
quantities around the piston into the stuffing-box chambers, thence in accordance
with nature's laws, the air will pass directly to the reservoir, and so continue until
the pressure is attained in the reservoir to substantially counterbalance the pressure
of the air, escaping around the piston, and this pressure will force the packing-
rings upon the piston, and prevent further escape of air. The outer ring 6, prevents
the escape of the lubricating material outside the stuffing-box, and also prevents the
passage of air in that direction, all the air which escapes passing directly to the
reservoir, consequently there is no possible escape of air from the cylinder
around the piston, and at all times the piston is properly lubricated.
As heretofore constructed, the head 11 for the closed end of these final com-
pressing cylinders, has been fitted to the face of the support or chamber surrounding
the cylinder, but a serious difficulty is experienced in properly packing the joint
between the face and head, so as to prevent the escape of air, the strain upon
this head being so great that the joint is easily affected.
To overcome this difficulty, I make the end of the cylinder to be closed to an
extent beyond the face of the surrounding surface, as at 12, Fig. 6, and construct
the head to fit closely upon the end of the cylinder without contact with the
surrounding surface, and then bolt the head directly to the surrounding surface
and outside the cylinder, as indicated in Figs. 4 and 6. The cylinder is constructed
with a shoulder 13 near the closed end, so as to take a bearing in the surrounding
casing as a resistance against the head, and so that the head may be drawn hard
upon the end of the cylinder, and force the shoulder 13 to a solid bearing in the
surrounding casing.
Under this arrangement I am enabled to make a metal packing close and tight,
and one which is not affected by the strain brought upon the head under the action
of the piston.
Thus constructed and arranged the cylinder is supported against longitudinal
movement entirely at one end, the other end resting in its bearing free to slide
therein, so that the expansion and contraction of the cylinder is provided for
entirely at the stuffing-box end, where the packing adjusts itself to such
longitudinal expansion and contraction of the cylinder. This arrangement adds
materially to the efficacy of the complete fitting and stability of the joint at the
closed end of the cylinder.
The lubricating passages may be regulated say as by screw-valves 14, see Fig. 3,
or cut off completely should occasion require.
In some cases the intermediate or second compressing cylinder may be dispensed
with, the two oppositely single acting final compressors working in combination
with that one cylinder the same as with the two. The arrangement of the single
acting cylinder whereby it is supported rigidly at one end without longitudinal
movement, but free at the other end for such longitudinal movement under
expansion and contraction independent of its stuffing-box, may be applied to

page_text: other single-acting air-pumps. It will be evident that in such case other known
packing may be substituted for the peculiar packing which I have described.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed as communicated to
me by my foreign correspondent I declare that what I claim is:-
First. In an air-compressor the combination of a principal double acting air-
compressing cylinder, mechanism substantially such as described to impart
reciprocating movement to the piston of said principal cylinder, a receiver into
which the said double acting cylinder discharges, a pair of single acting cylinders
of equal capacity but arranged to operate in opposite directions, and in connection
with the mechanism by which the piston of the principal cylinder is operated,
connection from the said receiver to each of the said single acting cylinders,
whereby one of said single acting cylinders draws from the said receiver in one
direction, and the other single acting cylinder draws from the receiver in the
opposite direction, and the said two single acting cylinders operating to
deliver air on the return strokes but in the opposite direction, substantially as
described.
Second. In an air-compressor, the combination of a principal double-acting
cylinder, and a second double-acting cylinder arranged in line with each other, a
cross-head arranged between said two cylinders in longitudinal parallel guides,
mechanism substantially such as described to impart reciprocating movement to said
cross-head, the piston-rod of each of said cylinders in connection with said cross-
head, and whereby the reciprocating movement of the cross-head imparts like recipro-
cating movement to the pistons of the respective cylinders, a receiver into which
the said principal cylinder discharges, a connection from said receiver of the
principal cylinder to the second cylinder, a second receiver into which the said
second cylinder discharges, a pair of single acting pumps arranged upon opposite
sides of said cross-head, and parallel with the double acting cylinders, the pistons
of said single acting cylinders connected at opposite points to the said cross-
head, with connection from each of said single acting cylinders with the
second receiver, whereby each of said cylinders in its turn draws from the said
second receiver, and both discharge in opposite directions, substantially as
described.
Third. In a compressing-pump, the pump cylinder rigidly supported at one end
without longitudinal movement, its other end supported, but free for longitudinal
movement, the free end of the pump extending beyond the face of its support,
combined with a stuffing-box around the piston at the said free end of the cylinder,
the said stuffing-box recessed corresponding to the said free end of the cylinder,
and so that the said free end of the cylinder may enter the said stuffing-box, the
box secured to the face of the support around the cylinder, the end of the said
cylinder forming one end of the chamber in the stuffing-box, the said chamber of
the stuffing-box, provided with a packing, substantially as described.
Fourth. In a compressing pump the combination of the pump cylinder supported
rigidly at one end against longitudinal movement, that end of the cylinder extending
beyond the face of its support, the head for that closed end of the cylinder
arranged to bear directly upon the projecting end of the cylinder, but secured to
the surrounding surface without contact therewith, the other end of said cylinder
arranged in a support free for longitudinal movement, a stuffing-box at the said
free end of the cylinder, and a packing within said box around the piston, sub-
stantially as described.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.