Improvements relating to Machinery for Compressing Air.
Year: 1890

page_text: Date of Application, 25th Sept., 1890
Complete Specification Left, 2nd July, 1891-Accepted, 8th Aug., 1891
PROVISIONAL SPECIFICATION.
Improvements relating to Machinery for Compressing Air.
I, JAMES MCCULLOCH, of Rio Tinto, in the Kingdom of Spain, Engineer do
hereby declare the nature of this invention to be as follows :-
1
My invention relates to machinery for compressing air, and is designed to
improve the construction and increase the efficiency of such machinery.
In some of the air compressing machines heretofore constructed, the steam
cylinder and the air compressing cylinder are arranged in line with each other,
and the machine is so constructed that the piston of the steam cylinder commences
and terminates its stroke simultaneously with that of the air compressing cylinder.
Therefore the latter part of the compression stroke, that is to say, the part thereof
during which the air in the cylinder is at or near its maximum pressure, has to be
effected by the momentum imparted to the pistons by the steam during the previous
portion of the stroke, the steam-cylinder having to be opened to the exhaust before
the termination of the stroke. It is evident that, with this arrangement, the useful
effect of the steam cannot be properly utilized.
An important feature of my present invention is the construction of an air-com-
pressing machine with a crank-shaft arranged between the steam cylinder or
cylinders and the air cylinder or cylinders, the said crank-shaft being coupled
by suitable connecting rods with the piston-rods of the steam and air cylinders.
Another important feature of my said invention is the construction of the
machine in such a manner that, when the piston of the air-compressing cylinder
is performing the latter part of its compression stroke and is consequently working
against the maximum pressure of air, the piston of the steam cylinder will be at or
near the middle of its stroke and will be subjected to the full, or nearly the full
pressure of the steam. Moreover I connect the said pistons with the crank shaft
in such a manner that, when the crank connected with the air-compressing piston is
at or near its dead centre, the crank connected with the steam piston will be in a
very favourable position for utilizing the force of the steam.
By the above described improvements I provide an air-compressor which will
operate much more efficiently than the air-compressors heretofore constructed,
whether with the air and steam cylinders in line with each other or arranged side
by side.
By my said improvements, moreover, I avoid the conduction of heat from the
piston-rod of the steam cylinder to that of the air-cylinder, which takes place in
air compressors heretofore constructed with the steam cylinder in line with the air
cylinder.
In carrying my said invention into practice, I find it advantageous to provide
between the two cylinders a three-throw crank-shaft the centre crank of which is
coupled by means of a suitable connecting rod with the piston of one of the said
cylinders, while the two outer cranks, which are at a right angle or at any other
suitable angle to the centre crank, are coupled by a forked connecting rod, or by a
pair of connecting rods and a cross-head, with the piston of the other cylinder,
sufficient space being left between these connecting rods, or between the two parts
I find it convenient in
of the fork, to permit the free rotation of the centre crank.
practice to arrange the centre crank at about a right angle to the outside cranks.
thus ensure that the piston of the steam cylinder shall be just commencing its
stroke by the time the piston of the air-compressing cylinder has half completed its
compression stroke. I may,
however, arrange the cranks at any other suitable angle
to one another for the purpose of my invention.
In some instances, instead of the three-throw crank-shaft above mentioned, I

page_text: employ a short single-throw crank-shaft supported in suitable bearings and having
a crank-disc secured upon each extremity thereof, the two crank-discs being
connected by a forked connecting rod, or by a pair of connecting rods and a
cross-head, with one piston, while the centre crank is connected with the other
piston.
The steam cylinder and air cylinder are not necessarily exactly in line with each
other. I sometimes arrange between the said cylinders a double-throw crank, the
pins of which are coupled by suitable connecting rods to the pistons of the steam
and air cylinders respectively.
Dated this 25th day of September 1890.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements relating to Machinery for Compressing Air.
I, JAMES MCCULLOCH, of Rio Tinto, in the Kingdom of Spain, Engineer, 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 machinery for compressing air, and is designed to
improve the construction and increase the efficiency of such machinery.
The air-compressing machines heretofore employed in which the steam-cylinder
and the air-compressing cylinder are arranged in line with each other, are so
constructed that the piston of the steam-cylinder commences and terminates its
stroke simultaneously with the piston of the air-compressing cylinder. It is,
therefore, evident that, as the steam-cylinder must be opened to the exhaust
before the termination of the compression-stroke, the latter part of such stroke,
that is to say, the part thereof during which the air in the air-compressing cylinder
is at or near its maximum pressure, has to be effected by the momentum generated
during the previous portion of the stroke, consequently, with this arrangement, the
useful effect of the steam cannot be properly utilized.
Moreover, in such air-compressing machines, the piston-rods of the steam and
air cylinders are usually connected directly without the intervention of a crank-
shaft.
Now an important feature of my present invention is the construction of an air-
compressing machine in such a manner that, when the piston of the air-compressing
cylinder is performing the latter part of its compression-stroke, and is, consequently,
working against the maximum pressure of air, the piston of the steam-cylinder will
be at or near the middle of its stroke and will be subjected to the full, or nearly the
full pressure of the steam. Moreover I connect the said pistons with a crank-shaft
in such a manner that, when the crank connected with the air-compressing piston is
at or near its dead centre, the crank connected with the steam-piston will be in a
very favourable position for utilizing the force of the steam.
I accomplish the desired result by the construction of the machine with a crank-
shaft arranged between the steam cylinder or cylinders and the air cylinder or
cylinders, and coupled, by suitable connecting-rods, with the piston-rods of the said
steam and air cylinders.
By my improvements, I provide an air-compressor which will operate much more
efficiently than the air-compressors heretofore constructed, whether the air and
steam cylinders are arranged in line with each other or otherwise.
By my said improvements, moreover, I avoid the conduction of heat from the
piston-rod of the steam-cylinder to that of the air-cylinder, which takes place in
the air-compressors heretofore constructed in which the piston-rods of the steam-
cylinder are directly connected with those of the air-cylinder.

page_text: In the accompanying drawings, I have shown how my said invention may be
conveniently and advantageously carried into practice.
Figure 1 is a plan, and
Figure 2 a side elevation showing part of an air-compressing machine having my
improvements applied thereto, and
Figure 3 is a plan of part of another air-compressing machine, in which my
said improvements are embodied.
Like letters indicate corresponding parts throughout the drawings.
A is the base-plate or foundation-plate. B is the crank-shaft; C, D are the
connecting-rods which couple the same to the pistons of the steam and the air-
compression cylinders respectively. These cylinders are not shown in the drawings,
as the construction of the said cylinders forms no part of the present invention.
E, E are fly-wheels fixed upon the crank-shaft B.
In the arrangement shown in Figures 1 and 2, a three-throw crank-shaft B is
provided, which is supported in suitable bearings A' situated midway, or about
midway between the steam and the air-compression cylinders. The centre crank b
is coupled by means of the connecting-rod C with the piston of the steam cylinder,
while the two outer cranks 6, 6, which are at a right angle to the centre crank b,
are coupled by a forked connecting-rod D (or they may be coupled by a pair of
connecting rods and a cross-head) with the piston of the air-compressing cylinder,
sufficient space being left between the two parts of the fork to permit the free
rotation of the centre crank. I find it convenient in practice to arrange the centre
crank at a right angle, or approximately at a right angle to the outside cranks.
thus ensure that the piston of the steam-cylinder shall be just commencing its
stroke by the time the piston of the air-compressing cylinder has half completed its
compression-stroke. I may, however, arrange the cranks at any other suitable
angle to one another for the purpose of my invention.
I
In the arrangement shown in Figure 3, there are two inner cranks b, bat a right
angle to each other, connected respectively by the rods C, C with the pistons of
two steam-cylinders; and two outside cranks 1, coupled respectively by the
connecting-rods D, D, to the pistons of two air-compressing cylinders. Each of the
outside cranks is arranged approximately at a right angle to the adjacent inner
crank, for the purpose above specified.
In some instances, instead of using a three-throw crank-shaft, such as that shown
in Figures 1 and 2, I employ a short single-throw crank-shaft supported in suitable
bearings and having a crank-disc secured upon each extremity thereof, the two
crank-discs being connected, by a forked connecting-rod, or by a pair of connecting-
rods and a cross-head, with the piston of the steam-cylinder, while the centre
crank is connected with the piston of the air-compressing cylinder, or vice versa.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I wish it understood
that I claim :-
First. An air-compressor in which a crank-shaft having cranks at a right angle
or other convenient angle to each other, is situated between the steam and air
cylinders and is coupled to the pistons thereof, substantially as hereinbefore
described and for the purposes specified.
Second. An air-compressor having my improvements incorporated therewith or
embodied therein as above described and as shown in Figures 1 and 2, or in
Figure 3 of the accompanying drawings.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.