IMPROVEMENTS IN AIR-COMPRESSING ENGINES
Year: 1879

page_text: LETTERS PATENT to Alfred Davis, of No. 5, Westminster Chambers, Victoria
Street, in the County of Middlesex, for the Invention of "IMPROVEMENTS IN
AIR-COMPRESSING ENGINES." A communication from abroad by John F.
Allen, of Brooklyn, United States of America.
Sealed the 23rd March 1880, and dated the 29th September 1879.
PROVISIONAL SPECIFICATION left by the said Alfred Davis at the Office of
the Commissioners of Patents on the 20th September 1879.
ALFRED DAVIS, of No. 5, Westminster Chambers, Victoria Street, in the County
of Middlesex. "ÍMPROVEMENTS IN AIR-COMPRESSING ENGINES." [A communication
from abroad by John F. Allen, of Brooklyn, United States of America.]
This Invention relates to a construction and arrangement of a combined steam
engine and air-compressing pump of the following description:-The steam cylinder
and the pump cylinder are placed horizontally in line with one another, the pump
cylinder being placed behind the steam cylinder at a distance sufficient to give
convenient access to the stuffing boxes. One rod for the two pistons extends
forwards to a crosshead which works in guides, and is linked by a connecting rod
to a crank on a flywheel shaft. The crosshead is made of considerable weight, so
as to absorb by its inertia a large portion of the steam force that acts on the piston
during the first part of each stroke, and to give out this force by its momentum
during the latter part of each stroke when the steam has become weakened by
expansion, and the resistance of the pump is increased by the compression of the
air within it. Instead of applying a load for this purpose to the crosshead it might
obviously be applied at any reciprocating part, such as the pistons or their rod.
The flywheel shaft carries eccentrics which work not only the steam slide but also
a slide valve for the pump commanding induction and eduction ports for the air.
By employing a slide for this purpose instead of the selfacting valves usually
employed the speed of the engine and pump can be varied as desired, there being
no loss of time and effect such as is caused at each stroke by the inertia and
momentum of self acting valves. The pump slide may also have on its back an
expansion slide, which can be adjusted so as to determine by cut off the amount of
air compression as may be desired. For the purpose of lubricating and cooling the
pump an oil vessel is provided at a level below the pump cylinder. This vessel,

page_text: which is closed, communicates at its upper part by a pipe with the slide jacket of
the pump, and at its lower part it communicates by a pipe (furnished with a stop
cock) with the pump cylinder. Within the vessel is a coil or set of pipes through
which cold water is made to circulate so as to cool the contents of the vessel but
not to mix with them. The vessel is charged with oil or with a solution of alkali
admitted at first at the suction inlet of the pump, and when it has been so charged
its contents are made to circulate through the pump by the pressure in the side
jacket communicated through the one pipe, forcing portions of the liquid to pass by
the other pipe into the body of the pump during suction, these portions being
returned to the vessel during discharge. The quantity thus caused to circulate can
be regulated by the stopcock in the pipe leading to the pump. It is of advantage
to admit sufficient liquid to fill up cavities and clearance, so that there may be no
loss of efficiency by the alternate compression and expansion of the air which would
otherwise occupy these spaces.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Alfred Davis in the Great Seal Patent Office on the 25th March
1880.
ALFRED DAVIS, of No. 5, Westminster Chambers, Victoria Street, in the County
of Middlesex. "IMPROVEMENTS IN AIR-COMPRESSING ENGINES." A communication
from abroad by John F. Allen, of Brooklyn, United States of America.
This Invention relates to a construction and arrangement of a combined steam
engine and air compressing pump of the following description:-The steam cylinder
and the pump cylinder are placed horizontally in line with one another, the pump
cylinder being placed behind the steam cylinder at a distance sufficient to give
convenient access to the stuffing boxes. One rod for the two pistons extends forwards
to a crosshead which works in guides, and is linked by a connecting rod to a crank
on a fly wheel shaft. The crosshead is made of considerable weight, so as to absorb
by its inertia a largo portion of the steam force that acts on the piston during the
first part of each stroke, and to give out this force by its momentum during the
latter part of each stroke when the steam has become weakened by expansion and
the resistance of the pump is increased by the compression of the air within it.
Instead of applying a load for this purpose to the crosshead it might obviously bo
applied at any part of the pistons or their rod. The fly wheel shaft carries
eccentrics which work not only the steam slide but also a slide valve for the pump
commanding induction and eduction ports for the air. By employing a slide for
this purpose instead of the self acting valves usually employed the speed of the
engine and pump can be varied as desired, there being no loss of time and effect
such as is caused at each stroke by the inertia and momentum of self acting valves.
The pump slide may also have on its back an expansion slide, which can be adjusted
so as to determine by cut off the amount of air compression as may be desired.
For the purpose of lubricating and cooling the pump an oil vessel is provided at a
level below the pump cylinder. This vessel, which is closed, communicates at its
upper part by a pipe with the slide jacket of the pump, and at its lower part it
communicates by a pipe (furnished with a stop cock) with the pump cylinder.
Within the vessel is a coil or set of pipes through which cold water is made to
circulate so as to cool the contents of the vessel but not to mix with them. The
vessel is charged with oil or with a solution of alkali admitted at first at the suction
inlet of the pump, and when it has been so charged its contents are made to
circulate through the pump by the pressure in the slide jacket communicated
through the one pipe, forcing portions of the liquid to pass by the other pipe into
the body of the pump during suction, these portions being returned to the vessel
during discharge. The quantity thus caused to circulate can be regulated by the
stop cock in the pipe leading to the pump. It is of advantage to admit sufficient
liquid to fill up cavities and clearance, so that there may be no loss of efficiency by
the alternate compression and expansion of the air which would otherwise occupy
these spaces.
DESCRIPTION OF THE DRAWINGS.
Fig. 1 is a longitudinal section; Fig. 2, a plan; and Fig. 3 a transverse section
through the pump of an air compressing engine according to this Invention. A is
the pump, and B is the steam cylinder, both of which are double acting and have
their pistons on one rod C attached to a heavy crosshead D, which works in guides

page_text: slides I and J are worked by rods L, L', from eccentrics on the shaft. When it is
not desired to vary the amount of compression effected by the pump the second
slide J may be' dispensed with. Below the level of the pump A is placed a closed
vessel T, containing a mixture of oil and water or an alkaline solution, which is
cooled by a coil W through which cold water circulates. The vessel T commu-
nicates at its upper part by a pipe X with the slide jacket of the pump, and at its
lower part it communicates by a pipe Y with the interior of the pump cylinder by
the alternations of pressure in which the lubricating fluid is caused to circulato
through the vessel T in the manner described above.
Having thus described 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 claim,―
First. The use for compressing air of a double acting pump, having its ports
governed by a slide in combination with a steam cylinder, having its piston rigidly
connected to the piston of the pump and to a heavy reciprocating weight, sub-
stantially as and for the purposes herein set forth.
Second. The use for lubricating an air compressing pump of a cooled vessel
containing lubricating liquid, and communicating with the pump and its slide
jacket by pipes through which circulation of the lubricant is caused by alternations
of pressure in the pump, substantially as herein described.
In witness whereof, I, the said Alfred Davis, have hereunto set my hand
and seal, this Twenty third day of March, in the year of our Lord One
thousand eight hundred and eighty.