Improvements in Air Compressors.
Year: 1899

page_text: Date of Application, 2nd Oct., 1899-Accepted, 18th Nov., 1899
COMPLETE SPECIFICATION.
Improvements in Air Compressors.
We, GEORGE WASHINGTON TOLLE, of 1936, East Warne Avenue, St. Louis,
Mo., U.S.A., Engineer, and THOMAS MICHAEL GRIFFITHS, of 3818, Laclede Avenue,
St. Louis, Mo., U.S.A., Manufacturing Chemist, 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:-
Our invention has relation to improvements in air compressors, and consists
in the novel arrangement and combination of parts more fully set forth in the
specification and pointed out in the claims.
In the drawings, Fig. 1 is a vertical sectional elevation of our apparatus, show-
ing the valves set either for one of the extreme positions of both pistons of the
cylinder, or for the lowest positions of both of said pistons, this view showing
by dotted lines an intermediate position of the several parts; and Fig. 2 is a
similar elevational view (parts being broken away) showing the parts in the
reverse, or second of their extreme positions.
The object of our present invention is to interpose between the air storage tank
(or receiver) and the air pump of an air compressing apparatus, a series of two
(or more) intermediate compressor tanks or cylinders, by the reciprocations of the
pistons or movable diaphragms of which, the forcing of the air into the storage
tank is accomplished, the pistons themselves being actuated intermittently by the
action of the air pump. In the present invention we utilize the compressed air
delivered by the pump in the raising of the piston of one cylinder, to subse-
quently partially raise the piston or diaphragm of the second cylinder, and also
in a measure, to equalize the initial pressure on each side of the air pump piston
as the latter begins the work of raising the piston of said second cylinder to its
full stroke, it being understood that the raising of the piston of either compressor
cylinder results in the forcing, into the storage tank, of the air above such piston.
By this equalizing in a measure, the pressure on each side of the pump-piston
during the pumping operation, the piston of the air pump operates in an atmos-
phere the pressure of which is distributed against each face of such piston, per-
mitting the latter to operate under a minimum amount of resistance, no matter
what may be the accumulated pressure in the storage tank, this reduction of
resistance resulting in a corresponding economy of driving power and hence
economy of fuel consumed. This will be better apparent from a detailed descrip-
tion of the invention, which is as folows:
Referring to the drawings, 1 represents an ordinary double acting air pump
actuated from any suitable source of power (not shown). To the cylinder of the
pump leads an air-induction or supply pipe 2 provided with an air inlet or check
valve 3; and from the cylinder likewise leads a delivery pipe 4, the further end
of which connects by means of two connecting pipes 5, 51 to a pipe 6, whose
opposite ends are respectively connected to the bottoms of the compressors or
cylinders 7, 71, the latter resting on suitable foundations S, 8, which partially
protect the pipe 6. The latter pipe is also connected to the adjacent end of the
air induction pipe 2. Each compressor is provided with a water jacket 9 as usual,
through which cold water will circulate by way of the pipes 10, 11, the flanged
ower heads of the compressors, being bolted to the foundation. The pipe 4 is

page_text: provided with a pop safety valve 12 of any approved construction. Leading from
the upper head of each compressor is a pipe 13, 13, the base of which is provided
with an ordinary air inlet valve 14 and with a check valve 15 past which the air
forced from the compressor must flow to reach the main supply pipe 16 which
supplies air to the storage tank or receiver 17, the latter being provided with a
pipe 18 communicating with the throttle or any valve by which steam is admitted
to the engine which drives the air pump, whereby when the pressure of air
within the storage tank exceeds a certain number of pounds, the pump may be
automatically stopped. Inasmuch as this manner of cutting off the steam (or in
fact any motive power) is old, we neither claim nor show the construction by
which the same is accomplished as any form of automatic cut off may be
employed.
Each compressor is provided with a reciprocating piston or diaphragm 19 (19¹)
adapted to initially rest at the bottom of the compressor and be forced to the upper
end thereof under the action of the pump as presently to be seen. Projecting
through the upper head of the compressor 7, and extending a suitable distance
into the same, is a plunger 20, the outer projecting end of which is pivotally
connected to the short arm of a lever 21 mounted on a bracket 22 on top of the
compressor, the end of the long arm of said lever being pivotally secured to the
upper end of rod 23 which is pivotally connected to a rotatable valve-reversing
disk 24 mounted between the compressors. Secured to the disk 24 about the
same pivot as rod 23 is a rod or link 50 whose lower end is provided with a
slot 25, through which connection is established by a pin 26 with a valve actuat-
ing disk 27 mounted adjacent to the compressor, the pin 26 serving likewise to
pivotally connect the disk with the upper end of a connecting rod 28 whose lower
end is connected pivotally to the stem of a valve 29 establishing communication
between the upper end of pipe 5 and the compressor 7. Pivotally secured to the
disk 27 at a point diametrically opposite the pin 26 is the upper end of a rod 30
whose lower end is pivotally secured to the stem of a valve 31, controlling com-
munication between the pipes and 6. The features enumerated have their
counterparts on the opposite side of the machine and are designated in the draw-
ings by 20, 211, 22, 231, 50¹, 25, 26, 27, 28, 29, 30¹ and 31', respectively.
Mounted between the compressors 7, 7' below the disk 24, is an air-cylinder or
dash pot 51, the steam of the piston of which is pivotally connected to the lower
end of a connecting rod 32, whose upper end is pivotally secured to the face of
the disk 24 at a point midway between the rods 23, 231, The upper end of
the rod 32 is at its dead center, (that is, at the upper end of the vertical diameter
of the disk 24) when the rods 23, 231 have been reciprocated under the tilting of
their levers 21, 21, an amount to respectively pay out the full lengths of their
lower terminal slots 25, 25¹, against the pins 26, 261. Such intermediate position
is shown in dotted lines in Fig. 1.
The operation of the compressor is as follows: Let us assume that both com-
pressor-pistons 19, 19¹ are at the bottom of their respective chambers or cylinders,
and that the valve reversing disk has been set SO as to open the
valves 29 and 31¹ and close valve 291 and 31. For this position of
the valves the air which enters the pump cylinder by way of the
valve is pumped through the pipe 4, branch 5, passing through the
right in pipe 6, into the compressor 7 and gradually raising piston 19. When
the valves are in the position here indicated the plunger 20 is in its lowest posi-
tion, and the plunger 20¹ is in its highest position. As the piston 19 is raised
it strikes the plunger 20, forcing the same upward thereby forcing the
end of the long arm of lever 21 downward, and thus turning the
disk 24 to the right (or in the direction of the hands of a watch)
and gradually bringing the upper pivoted end of the rod 32 in line with
the vertical diameter of the disk 24, or on its "dead centre," compressing the
cushion of air above the piston of the dash pot, but in no wise disturbing the
position of the valves, it being understood as above stated, that the disk 24 has a

page_text: movement independent of that of either of the valve actuating disks 27, 271 by
reason of the slots 25, 25¹ formed at the lower ends of the rods 50, 511; and, (by
reference to Fig. 1) by the time the disk 24 has been rotated to its dead centre
as just described, the pin 26, which, before the movement of the plunger 20 as
just pointed out, was at the base of the slot 25, will now be at the top thereof,
and the pin 26 which was at the top of slot 25 will be at the bottom thereof.
A further upward movement of the piston 19 will force the plunger 20 upward its
full extent, thereby causing the disk 24 to revolve far enough to the right to
pass beyond its dead centre, the elasticity of the air cushion of the dash pot
positively drawing upon the connecting rod 32 effecting a further rotation of the
disk 24, and, from the connections as described, effecting a sudden reversal of
the valves, that is, valves 29 and 311 are closed, and valves 291 and 31 are open
(see Fig. 2) and the plunger 20' has been depressed. Under these circumstances
the piston 19 will gradually drop the air forced under it from the previous opera-
tion being now drawn into the pump by way of the open valve 31, through the
air pipe 2 and pump 1, and forced through pipe 4, branch 5', by way of valve 291
into the compressor 71, and gradually raising the piston 191 until the air pre-
viously compressed under piston 19 has been exhausted, after which the pump wil!
draw the atmospheric air through the valve 3 and force the same under piston 191
until it reaches the top of the compressor 7, it being understood that all the time
the piston 191 is rising it is forcing the air above it into the storage tank; and
while the piston 19 is dropping atmospheric air flows into the cylinder 7 above the
piston thereof, to be subsequently forced into the storage tank upon a subsequent
upward stroke of the said piston. When the piston 191 reaches the end of its
full upward stroke, the plunger 20 will have been forced upwardly and outwardly
and the valves set in the first or original position, the piston 19 now being free
to descend to the bottom of cylinder 7', the air from under it passing by way of
the now open valve 311 through pipe 2 into the air pump, and through the latter
back again into cylinder 7 by way of valve 29, the piston 19 being again raised
as before.
It will be observed that every time either of the pistons 19, 191 is raised, the
air above the same is forced or compressed into the storage tank or receiver 17.
The resistance to the upward movement or stroke of the pistons 19, 19 depends
upon the resistance which the tension of the air compressed within the receiver,
offers against the movement of said pistons; and while the compressor pistons
necessarily receive the full and direct pressure of this tension during the pump-
ing operation, the pump-piston is relieved of a large percentage of such pressure
for the reason, that, during the descent of either one of the compressor pistons,
the compressed air which is withdrawn from under it to allow for its descent, must
pass through the pump cylinder before it is delivered under the piston of the
other compressor. By being caused to pass through the pump cylinder, it equalizeз
the pressure on each side of the pump-piston, and the only resistance which the
latter encounters in its reciprocations, is the work it has to perform in forcing
into the compressor in which the piston is ascending, a sufficient amount of
atmospheric air under such ascending piston to effect the discharge of the volume
of air above it into the receiver. This work is approximately measured by the
difference in the tensions between the compressed atmosphere within which
the pump-piston operates, and the tension of the air within the receiver which the
ascending compressor piston must overcome to effect its upward stroke. Thus
it will he seen, that whatever be the tension of the compressed air which flows
from one compressor to the other, inasmuch as this compressed air must pass
through the pump cylinder, it exerts the same pressure on each side of the pump-
piston, thus balancing the latter, and reducing the work the latter has to perform
to a minimum. In the ordinary air compressor one face of the pump-piston is
always exposed to only the ordinary atmospheric pressure, the other face receiving
the full benefit of the tension of the air stored in the receiver, the pump thereby
necessitating a maximum amount of steam or other motive power, and thus con-

page_text: suming a maximum amount of fuel. By the use of my intermediate compressor
cylinders 7, 71, the conditions under which the pump operates are most favorable,
and a superior, fuel saving air compressing apparatus results.
It is of course apparent that many changes can be made without departing from
the spirit of our invention. For example, the valve reversing mechanism here
shown and described could be entirely changed, the purpose thereof being simply
to reverse the valves controlling the flow of air from one cylinder to the other,
at the proper moment.
Of course where the pump first begins to operate, that is to say, when both of
the cylinder or compressor pistons are in their lowest position, the advantage
inherent in the present system is not available, since at the first stage of the
operation, the pump merely forces atmospheric air under the piston of one of the
cylinders, such piston in turn driving the air is above it, into the receiver.
Having now particularly described and ascertained the nature of our said
invention, and in what manner the same is to be performed, we declare that when
we claim is :-
:―
1. In an air compressing apparatus, a suitable air-pump, a storage tank or
receiver, two cylinders interposed between the pump and receiver, pipe connections
establishing communication between the cylinders and the pump, a piston for
each cylinder, pipe connections between the cylinders and receiver, suitable valves
controlling the several pipes, the pump being adapted to force atmospheric air
under the piston of either cylinder, and subsequently circulating such compressed
air alternately from one cylinder to the other, and a check-valve located in the
path of the supply-pipe of the pump for permitting the flow through the pump
of additional atmospheric air into the cylinders to effect the reciprocation of the
pistons and forcing the air in front of such pistons into the receiver, the parts
operating substantially as and for the purpose set forth.
2. In an air compressing apparatus, a receiver, a series of two cylinders commu-
nicating therewith, pistons for said cylinders, an air pump, a pipe connecting the
bottoms of the cylinders with the air pump, an air induction pipe leading from
the pump to said connecting pipe, an air delivery pipe leading from the pump
and terminating in two branches which in turn communicate with said
connecting pipe, a series of controlling and air valves located in proper positions
in said pipes, whereby the pump is adapted to first pump air into one cylinder
under the piston thereof, and subsequently pump the air so forced into the other
cylinder, and then back into the first, and a check valve located in the path of
the supply pipe of the pump, for automatically providing an increase of the entire
quantity of air by fresh additions from the atmosphere with the consecutive reci-
procations of the cylinder pistons, the latter in their operations forcing the air
which is in front of, or above them, into the receiver, substantially as set forth.
3. An air compressing apparatus comprising an air pump, a receiver, two inter-
mediate communicating cylinders, pipe connections between the cylinders and
air pump valves controlling the communication between said pipe connections and
the cylinders, valve-actuating disks for said valves, a valve-reversing disk, slotted
links connecting said valve-reverse disk to said valve-actuating disks, a plunger
for each cylinder, link or lever connections between the plungers and valve-
reversing disk, a piston for each cylinder, suitable inlet and check valves for the
several pipes, an air cylinder or dash pot, and a link connection between the
piston of the dash pot and valve reversing disk, the parts operating substantially
as and for the purpose set forth.
י
1
1000
F. WISE HOWORTH.
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicants.