Improvements in Air Compressors.
Year: 1891

page_text: Date of Application, 12th May, 1891-Accepted, 13th June, 1891
COMPLETE STMUTLICATION.
[Communicated from abroad by EBENEZER HILL, of 112, West Avenue, South
Norwalk, Connecticut, United States of America, Mechanical Engineer.]
Improvements in Air Compressors.
*1, 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 Speci-
fication, and in which
Figure 1, represents a side view of the compressing cylinder and the outlet
mechanisms, portions broken away at one end of the cylinder to show the parts
in section the outlet valve at the broken end of the cylinder being on the opening
movement.
Figure 2, transverse section through the rod K. on line - showing the commec-
tion between the rod and the valve, crank enlarged.
Figure 3, sectional view of the outlet valve G and its connecting mechanism at
the left hand end of the cylinder as having just completed its closing movement,
enlarged.
Figure 4, longitudinal section through one of the crank-arm bearings, and
Figure 5, end view of the same showing a modification in obtaining the over-
motion between the valve connection and the valve.
Figure 6, side view of a cylinder and the valve operating mechanism illustrating
a modification in the connection with the outlet valves.
Figure 7, modification in the formation of the frictional working surfaces for the
valve.
Figure 8, another modification in the valve connections.
This invention relates to an improvement in that class of air-compressors in
which the valves are mechanically operated for the escape of the compressed air
from the cylinder.
Under the more general construction of this class of air-compressors, the valves
are set so as to open at a predetermined point in the movement of the piston, and
this point intended to be when the pressure in the cylinder shall have reached the
pressure in the receiver. For illustration, suppose the pressure outside the valve
in the receiver, or whatever it may be, is fifteen pounds that pressure under ordinary
circumstances will be attained in the cylinder when the piston has reached its half
stroke in the cylinder.
Now if under this positive arrangement of the valve with relation to the piston,
it be desired to reduce the pressure in the receiver or outside the valve, say to ten
pounds, the continued action of the machine will still compress the air to the same
extent in the cylinder, and discharge it under a pressure of fifteen pounds, because
the valve would not ordinarily open until the time when that pressure of fifteen
pounds in the cylinder had been attained. On the contrary if it be desired to
increase the pressure in the receiver, the valve will open before the receiver pressure
has been reached in the cylinder. In the first case the valve is opened too late, and
in the latter case opened too early, the results of thus opening the valve are too well
known to require particular description, hence when such change in pressure is
desired, a corresponding resetting of the valve is necessary to a perfect working of
the machine.
The object of this invention is the construction of a valve gear which will open
or permit the valve to automatically open whenever the pressure upon the cylinder
side of the valve shall equal or substantially equal the pressure upon the back of

page_text: the valve, and so that the difficulties before mentioned will be overcome, and the
invention consists in providing for an over-motion of the parts with which the
valves are mechanically engaged, and through which the power is applied to
the valves, and during which over-motion the valves are independent of the power,
combined with means independent of such power, which during such over-motion
may operate upon the valves to automatically open the valves when the valves are
brought to an equilibrium by the pressure in the cylinder, on the cylinder side of
the valve, equalling the pressure on the out or receiver side of the valve, the valve
itself being held to its seat by the pressure of the air in the receiver or on the back
of the valve.
In illustrating the invention I show only so much of an air-compressor as necessary
to the understanding of the invention, and in this illustration I represent the valves
as oscillating valves. A represents the compressing cylinder, B the piston-rod,
C the inlet opening for one end of the cylinder, and D the inlet opening for the
other end of the cylinder. I do not show the valve-gear for the two inlet valves
as it is well known, and unnecessary to the illustration of the invention.
E represents one outlet-valve-chamber, to which a passage F leads from the
cylinder the valve-chamber is cylindrical, and in the chamber the valve G is
arranged, which oscillates within the chamber, and so as to close and open the
passage F.
The peculiar characteristic of this valve is that it is held by abnormal
friction, for illustration, as will be seen on reference to the valve in Figures 1 and 3,
in which the valve is provided with a much greater working surface than is
necessary for the opening and closing movement of the valve, and so that as the
valve is moved from the open position Fig. 1, to the closed position in Fig. 3, the
valve is moved over a very much greater space than is necessary to simply close
the valve. This increase of surface of the valve produces the abnormal friction
under the pressure of the air from the receiver on the back of the valve, over what
it would be were no provision made for such abnormal friction.
The valve at the opposite end is of the same construction and arrangement for
the outlet at that end of the cylinder, H, representing the cap upon the chamber
at that end. The valve G is operated by an arm I outside the chamber, partly
broken away in Fig. 1, and the valve at the other end by a similar arm J, there
being a rocking movement imparted to these two arms to alternately open and
close the valves, so that each valve will open for the proper discharge from its side
of the piston.
The two arms are connected by a rod K, and to this rod K a reciprocating
movement is imparted from the eccentric, through the eccentric-rod L, and so that
the reciprocating movement of this rod K is constant in both directions. If
therefore the connection between the rod K and the two valves be unyielding,
the valves will open at a positive predetermined time with relation to the
piston, and that time will be according as the eccentric is set with relation to the
crank.
Instead of making the connections between the rod K and the respective arms
of the valves positive, I make the connections through longitudinal slots in the rod,
a slot L for the arm I, and into which slot the crank-pin M of the arm 1 extends.
A like slot N is made at the opposite end of the rod K, into which the crank-
pin of the arm J enters. Fig. 2 represents a transverse section through the rod
cutting through one of these slots, and showing the engagement with the arm 1.
From these slots it follows that the rod moving in one direction, say as indicated
by the arrow in Fig. 1, which is the opening movement for the valve, the crank-
pin M is bearing against the then active end of the slot L in the rod K, and so
that the continued movement of that rod will produce the continued opening of the
valve; the arm J of the other valve is at the same time being operated upon by
the same end of its slot. N, and will so continue to act until the valve G be wide
open at its end of the cylinder, and the valve at the opposite end of the cylinder
will be fully closed. Now on the return of the rod K, it will have a movement to
the extent of the length of the slots before it will engage the respective valves, but

page_text: when the now advancing end of the slot comes into engagement with the arms of
the respective valves, the valves will be returned until the valve G is closed, and
the valve at the opposite end opened, thus I produce an over-motion between the
actuating-rod and the respective valves.
The valve G is exposed upon its back to the pressure of the air in the receiver,
or whatever it may be, and when in the closed position, say as seen in Fig. 3, the
valve is held to its seat by such pressure, the pressure producing a friction between
the valve and its scat corresponding to such pressure, and this friction resists the
opening movement of the valve.
The arm of the valve G is provided with a spring P, the tendency of which is
to turn the arm and the valve G in the opening direction, and the other valve
arm J is provided with a like spring R, having the same opening tendency upon its
valve. These springs are adjusted so as to substantially overcome the natural
friction between the valves and their respective seats, and also to overcome, the
practical difference of pressure upon the two sides of the valve due to the difference
of exposed area, so that the spring or auxiliary power itself will act upon the valve
when the pressure is alike upon both sides of the valve.
In rapid running machines this auxiliary power should be a little greater than
required to produce the movement of the valve when the equilibrium is actually
produced, in order that the valve may arrive at the point of opening the escape
passage just as the pressure in the cylinder has reached the pressure in the receiver,
or outside the valve, and so that if the valve were otherwise free, the springs will
operate to throw the valves to the open position.
When the valve G reaches its extreme closed position as seen in Fig. 3, the rear
end of the slot L is bearing against the crank-pin of the arm J. At this time the
piston is on its return stroke toward the valve G, and the air pressure upon the
back of the valve is at its maximum. As the rod K commences its return, the slot
permits a considerable extent of movement of that rod K without action upon the
valve, in due time however, the other or forward end of the slot will come against
the crank-pin of the arm 1 of the valve G, and then the movement of the valve
will commence, and continue during the movement of the rod K.
Now the over-
motion of the slot L is on the opening side of its crank-piu, so that on that side the
valve is free, that is to say, the valve is now free to be turned by some other power
than that of the eccentric, towards its open position, therefore whenever the
pressure on the cylinder side of the valve, produced under the advancing movement
of the piston, shall have risen to an extent equal to the pressure upon the back of
the valve, then the valve is free from the friction produced by the air pressure,
now the valve spring comes into action, and will turn the valve in advance of the
rod, the crank-pin of the valve passing forward in the slot of the rod, and this
movement will occur whenever that equilibrium upon the valve is produced,
irrespective of the position of the piston in the cylinder. For illustration, suppose
in the regular running of the machine, fifteen pounds pressure is the pressure
desired, and that the slots will come into action when that fifteen pounds pressure is
attained in the cylinder, or midway of the stroke of the piston. Now if the
pressure on the back of the valve should, from any cause, be reduced say to ten
pounds, the advancing piston will have produced that pressure of ten pounds
before it reaches the said midway position, and when that ten pounds pressure is
reached, the valve will have been brought into equilibrium, and the spring or
auxiliary power will come into action upon the valve, and throw it toward its
open position, as I have described, and allow this air under ten pounds pressure to
escape.
This illustration will be sufficient to the understanding of the operation of the
over-motion between the rod and the valves.
The operation is the same upon the valves at both ends of the cylinder, one
valve opening as the rod moves in one direction, while the other one closes, and
nice-versa.
As the direct engagement of the rod with the respective valve-arms would.

page_text: produce a thump." I introduce a cushion between the rod and the crank-arms to
relieve the 'blow which would otherwise occur: In the best construction of such a
cushion, I make the respective ends of the rod K tubular and introduce therein a
piston S this piston has a limited amount of longitudinal movement in the rod,
and independent of the rod to the extent of the required over-motion; these pistons
are connected with the respective arms, preferably by the crank-pin extending into
the respective pistons.
The tubular portion of the rods form a cylinder within which the piston S works,
the cylinder terminates in a head T at the rear end, and a similar head U at the
forward end, the heads being distant from each other greater than the length of
the piston as much or little more than the extent of over-motion required between
the connecting-rod K and the respective valves. The piston S fits closely, and as
it works toward either head U or T, cushions therein, and this cushioning is
produced whether the valve be operated by power, or whether through the rod
itself, in the one case the piston cushions against the head in the rod, and in the
other case the head of the rod cushions upon the piston.
Under this construction the slots in the rod may be of greater length than the
required over-motion, the pistons S and their respective heads of the cylinders,
limiting the extent of over motion, and this extent may be adjusted say by the
introduction of a set-screw a which will form a stop to strike that head of the
piston.
I represent dash-pots V W such as usually employed in this class of valve-gear
as a cushion for the opening movement of the valves, but these are not essential to
the invention.
Instead of making the over-motion in the form of a slot in the rod through which
the crank-pin of the valve-arm works, the over-motion may be attained between the
crank-arm and the spindle or valve, as seen in Figs. 4 and 5. In this illustration
1 represents the crank-arm, the valve spindle projecting through a bearing d.
The crank-arm fits the spindle, but is permitted a certain amount of rotation equal
to the over-motion required. This is produced by a spline or key e in the spindle,
and an elongated recess in the hub of the crank, so that the crank may engage
the spindle at either end of the said recess, so that there will be the same interval
of time between the engagement of the valve and the connecting mechanism as in
the first illustration.
h
Under the illustration thus far, the outlet valves are represented as operated
through an eccentric-rod independent of the rod which operates the inlet valves, but
the same result may be attained by a single rod, as seen in Fig. 6. In this
illustration represent the same outlet valve-arms I J.
represent the crank-
arms of the inlet-valves as on the same side of the cylinder as the crank-arms of the
outlet valves; these inlet valve-arms ghare connected by a rod i, which rod extends
directly or indirectly to the single eccentric which is to operate the valves. The
inlet-valve-arm g at one end is connected with the outlet-valve arm I at the same
end of the cylinder, this connection is in the form of a cylinder 7, hung upon a
projection from the arm, and a piston m in the cylinder from which a rod n extends
to, and is hung to the crank-pin of the arm 1. The piston M has a movement in
its cylinder corresponding to the over-motion required for the outlet valve, as before
described.
As represented in Fig. 6, the valve arm g is in the position of the inlet-valve
closed, and the valve-arm I in the position of the outlet valve at the same end of
the cylinder open; in this position the piston m rests upon the inlet arm end of the
cylinder, then as the arm g is turned to open the inlet valve, its movement is
imparted to the arm I of the outlet valve, and produces the corresponding closing
movement of the outlet valve. On the return or closing movement of the inlet
valve
the cylinder will be free to move upon the piston without effect upon the
arm I of the outlet valve, and until the other end of the cylinder comes into contact
upon the opening valve side of the piston, when the opening of the outlet valve
will commence, but if in the meantime the pressure in the cylinder has produced
ولا

page_text: the before mentioned equilibrium of the outlet valve, then the auxiliary power will
come into action upon the valve, and will remove it, forcing the piston m into the
cylinder, thus operating in the same manner as does the piston in the connecting
rod K of the first illustration. This piston and cylinder in this modification, also
operates as a cushion, as described for that in the first illustration. The cylinder
and piston connection is alike at both ends of the cylinder. The illustration which
1 have thus made with relation to a rotating or oscillating valve, will be sufficient
to enable others to apply this over-motion and auxiliary power to outlet valves of
other constructions with the same result.
is
I have represented the valve as an unbalanced valve, and so that the pressure of
the air upon the back of the valve serves to produce friction upon the seat of the
valve to hold it in its place until the equilibrium is produced, that equilibrium being
produced directly through the escape port over which the valve works, but the
power of the air upon the valve may be otherwise produced, and so as to employ
what is commonly called a balance valve. This modification is illustrated in Fig. 7,
in which E represents the cylindrical valve chamber in which the valve
arranged to oscillate, F represents the passage from the cylinder, which divides into
two passages F, that lead through ports into the valve chamber E at
diametrically opposite points. The valve is constructed with two working surfaces
for the said two cylinder-ports, and so that when in the closed position, as seen in
Fig. 7, the pressure from the cylinder comes upon the valve at diametrically
opposite points, and thus counterbalance each other. The valve chamber E leaves
the opposite sides of the valve exposed in the chamber. E' represents the outlet
passage to the receiver, the pressure from the receiver is therefore upon opposite
sides of the valve alike, this will produce what is called a balance valve, because
the pressure is alike upon the valve under all conditions, and the friction of the
valve is not affected by such pressure.
To produce the necessary friction to hold the valve, a plate G may be introduced,
corresponding to the surface of the valve-chamber, and so as to lie in the chamber
at one side of the valve, its inner surface exposed to the pressure of the chamber,
and so that the pressure in the chamber will hold the plate against the surface of
the chamber with frictional contact according to such pressure. The said plate is
adapted to engage the valve, and so as to oscillate with the valve, as indicated in
broken lines Fig. 7, hence there will be a friction opposed to the movement of the
valve according to the friction between the said plate G and the surface upon
which it works.
To produce a counter balance upon this plate, the surface of the chamber upon
which the plate G works is recessed, as seen at E2, and into this recess a passage F2
leads from the cylinder escape passage, and so that air from the cylinder under
pressure, will pass into the recess E, and produce a pressure upon the plate G
opposed to the pressure on the reverse side of the plate from the receiver, the result
of this will be substantially the same as when the pressure is directly upon the back
of the valve.
This illustration will be sufficient to indicate that the frictional surface to control
the non-positive force to operate the valve, may be the valve itself, or a surface
substantially in connection with, or so as to move with the valve.
I have illustrated the auxiliary power as springs, but it will be understood that
such auxiliary power may be any of the known equivalents therefor, as a weight,
for illustration, the piston of the dash-pot V W may be a weight sufficient to thus
operate upon the valve without the employment of springs, or the weight of the
valve itself may be so great that its own gravity will serve as the auxiliary
power to throw the valve toward the open position when the valve is in a state of
equilibrium.
The auxiliary power may be omitted and the valve moved positively when the
connection shall have reached the extreme of the over-motion in the opening
direction. Under this arrangement the opening movement of the valve will occur
while the connection under the action of the eccentric is moving with its greatest

page_text: velocity, so that the valve will be opened quickly, and the engagement between the
connection and the valve for such opening will not occur until the pressure on the
cylinder side of the valve, substantially counter-balances that upon the back of
the valve, hence the application of very slight power will be necessary to open the
valve.
Or, the opening movement of the valve may be produced entirely by the auxiliary
power, while the closing movement will be positively produced by the eccentric
connection, the slot or over motion in the connection being of so great length that
the connection will not come into engagement with the valve until after the before
mentioned equilibrium on the valve has been produced, say as seen in Fig. 8, where
the slot I in which the crank-pin works is made open at its outer end, so that
contact between the rod K and the valve in the opening direction is impossible, the
opening movement of the valve being produced only by the auxiliary power, and
this power will be applied, as before described, whenever the pressure upon the
inside of the valve shall have produced the equilibrium of the valve.
I have represented the cushions as produced by air, but it will be understood that
any of the known substitutes for air to form the cushion may be employed.
The term receiver as used herein to indicate from whence the pressure comes on
the back of the valve, is to be understood as not limited to an actual receiver
where the air is to be stored, but includes all devices into which the air may be
discharged from the air-compressor, and whereby the pressure of the air so
discharged is brought to bear upon the back of the valve.
I am aware that air-compressors have been constructed in which a positive
movement is imparted to the outlet-valve in the closing direction, with an auxiliary
power to give to the valve its opening movement, and in which the opening
movement of the valve will not occur until the pressure in the cylinder
substantially equals the pressure in the receiver, but in such construction there has
been combined a mechanism adapted to catch and positively lock the valve so soon
as it reaches its closed position, and hold the valve so locked until such mechanism
is disengaged through the operation of the pressure in the cylinder, therefore do
not wish to be understood as claiming broadly holding the outlet valve of an air-
compressor until the pressure in the cylinder substantially equals the pressure in
the receiver, the essential feature of my invention being holding the valve upon its
seat by friction produced by the differential pressures in the cylinder and receiver,
and until those pressures have been brought into equilibrium, and whereby the
before mentioned locking or controlling mechanism is avoided, and the valve left
free and uncontrolled except by said friction, and the auxiliary force which
produces the opening movement of the valve.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed as communicated to me by
my foreign correspondent L.declare that what I claim is :-
First. In an air-compressor, a valve arranged to open and close the outlet
passage from the compressing cylinder, the back of the valve exposed to the
pressure of the air in the receiver, and the face of the valve to pressure from the
cylinder, and whereby the said valve will be frictionally held substantially stationary
upon its seat until the pressure upon its face equals the pressure upon its back, a
connection from the eccentric to said valve, arranged to impart positive movement
thereto in the closing direction, but the said connection substantially disengaged
from the said valve in the opening direction, combined with an auxiliary power
substantially such as described in connection with said valve, the said valve being
otherwise uncontrolled, the said auxiliary power adapted to impart the opening
movement to said valve when the pressure upon the face of the valve substantially
equals the pressure upon its back.
Second. In an air-compressor, a valve arranged to open and close the outlet
passage from the compressing cylinder, the back of the valve exposed to the
pressure of the air in the receiver, and the face of the valve to pressure from the

page_text: cylinder, and whereby the said valve will be frictionally held by such pressure
from the receiver substantially stationary upon its seat until the pressure upon the
face of the valve from the cylinder substantially equals the pressure upon the
back of the valve from the receiver, a connection from the eccentric to said valve,
arranged to impart positive movement thereto in both opening and closing, but
said connection constructed with a space between its points of engagement with
the valve in both opening and closing, and so as to produce an over-motion of said
connection independent of said valve, the said valve being uncontrolled during
such over-motion except by the pressure upon its back and face, substantially as
described, and whereby an independent movement of the valve is permitted during
such interval of over-motion.
Third. In an air-compressor a valve arranged to open and close the outlet
passage from the compressing cylinder, the back of the valve exposed to the
pressure of the air in the receiver, and the face of the valve to pressure from the
cylinder, and whereby the said valve will be frictionally held by such pressure
from the receiver substantially stationary upon its scat until the pressure upon the
face of the valve from the cylinder substantially equals the pressure upon the
back of the valve from the receiver, a connection from the eccentric to said valve,
arranged to impart positive movement thereto in both opening and closing, but the
said connection constructed with a space between its points of engagement with the
valve in both opening and closing, and so as to produce an over-motion of said
connections independent of said valve, combined with an auxiliary power sub-
stantially such as described in connection with said valve, and arranged to impart
opening movement to said valve when the said equal pressure upon the back and
face of the valve occurs, the said valve being uncontrolled as to its opening
movement except as to its frictional contact and said auxiliary power, substantially
as described.
Fourth. In an air-compressor, a valve arranged to open and close the outlet
passage from the compressing cylinder, the back of the valve exposed to the
pressure of the air in the receiver, and the face of the valve to pressure from the
cylinder, combined with a connection from the eccentric, with a cylinder and piston
between the said valve and the said connection, and said piston and cylinder
forming an over-motion between the said connection and the valve, and also
forming a dash-pot between said connection and valve, substantially as described.
Fifth. In an air-compressor a valve arranged to open and close the outlet
passage from the compressing cylinder, the back of the valve exposed to the
pressure of the air in the receiver, and the face of the valve to pressure
from the cylinder, combined with a connection from the eccentric, with a
cylinder and piston between the said valve and the said connection, the
said piston and cylinder forming an over-motion between the said connection
and the valve, and also forming a dash-pot between said connection and
valve, with an auxiliary power in connection with said valve independent of said
eccentric connection, substantially as described, and whereby said auxiliary power
will operate upon the said valve independent of the said eccentric connection when
the pressure upon the valve shall be substantially equal upon both its back and
face.
Sixth. In an air-compressor, a valve arranged to open and close the outlet
passage from the compressing cylinder, the back of the valve exposed to the
pressure of the air in the receiver, and the face of the valve to pressure from the
cylinder, combined with a connection from the eccentric, with a cylinder and piston
between the said valve and the said connection, the said piston and cylinder
forming an over-motion between the said connection and the valve, the end of the
cylinder which produces the positive opening movement of the valve provided with
an adjusting screw whereby the extent of over-motion between the connection and
the valve may be adjusted, substantially as described.
Seventh. In an air-compressor, a valve arranged to open and close the outlet
passage from each end of the compressing cylinder, the back of the outlet valve

page_text: exposed to the pressure of the air in the receiver, and the face of the valve to
pressure from the cylinder, a rod K connecting said valves, and adapted to receive
reciprocating movement from the eccentric, the said rod constructed with a
cylinder at each end, a piston in each of said cylinders, the said pistons being in
connection with said valves, and through which pistons the reciprocating movement
of the rod is imparted to the respective valves to open and close the same, the
said pistons permitting a.. predetermined amount of over-motion between said rod
and the piston, substantially as described.
Eighth. In an air-compressor, a valve arranged to open and close the outlet
passage from each end of the compressing cylinder, the back of the outlet valve
exposed to the pressure of the air in the receiver and the face of the valves to
pressure from the cylinder, a rod K connecting said valves, and adapted to receive
reciprocating movement from the eccentric, the said rod constructed with a
cylinder at each end, a piston in each of said cylinders, the said pistons being in
connection with said valves, and through which pistons the reciprocating movement
of the rod is imparted to the respective valves to open and close the same, the
said pistons permitting a predetermined amount of over-motion between said rod
and the pistons, combined with an auxiliary power applied to each valve inde-
pendent of said rod, and whereby said auxiliary power is applied to open the
valves independent of the rods when the said valves shall have been brought into
equilibrium by the pressure from the cylinder on the face of the valve counter-
balancing the pressure on the back of the valves.
Dated this 12th day of May 1891.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.