IMPROVEMENTS IN STEAM Exarvas
Year: 1880

page_text: LETTERS PATENT to John McCallum, of Greenock, in the County of Renfrew,
North Britain, Engineer, for an Invention of "IMPROVEMENTS IN STEAM
Exarvas"
PROVISIONAL SPECIFICATION left by the said John McCallum at the Office
of the Commissioners of Patents on the 9th December 1880.
JOHN MCCALLUM, of Greenock, in the County of Renfrew, North Britain,
Engineer. "IMPROVEMENTS IN STEAM ENGINES."
This Invention relates to certain improvements in the construction, arrangement,
and combination of the parts of steam engines designed to render them highly
economical and effecient in action, and to obtain therefrom greater power than has
hitherto been found practicable with a minimum consumpt of fuel and steam.
The Invention consists essentially in arranging and fitting together a series of
high and low pressure engine cylinders to act as double acting high pressure and
single-acting atmospheric engines combined and connected to one crank shaft.
Under one modification of the improvements, three pairs of cylinders are
employed, and are ranged with each pair in line fitted with a single piston rod
passing through each inner cylinder into the corresponding outer cylinder, as in
tandem engines, and connected to the crank shaft at the inner ends.
Two of the cylinders are supplied with steam from the boiler or generator
alternately to each side of the pistons through D, slide, or other suitable valves
commonly used with double-acting engines, and the exhaust steam from these
cylinders is discharged into a large receiver from which the remaining four cylinders
are supplied with low pressure steam, at the inner ends of the cylinders, or under.
the pistons only, as in the common form of atmospheric engine. The exhaust
steam from these four cylinders is led to a condenser to form a vacuum beneath the
piston, and thus obtain the pressure of the atmosphere for the return stroke of the
piston.
Instead of two as described, three of the cylinders (that is, one of each pair) may
be supplied with high pressure or boiler steam, but in this case it is preferred to
cut off the steam early in the stroke and work the engines expansively, so as to
exhaust in the receiver at a low pressure, merely sufficient to raise the pistons of
ID CIT

page_text: the low pressure cylinders, and by condensation form the requisite vacuum for the
return stroke, which only would be effective for the three low pressure engine
cylinders. The pistons of each pair of high and low pressure cylinders being fitted
to one piston rod, the piston of the low pressure cylinder may be actually raised by
the power or motion of the high pressure piston in the cylinder above or below, if
the pressure of exhaust steam in the receiver is only nominal; and this steam when
admitted to the low pressure cylinders, need do little or no effective work for the
up or outward stroke, but merely from the requisite vacuum (by condensation) for
the return stroke. Or when the low pressure cylinders are longer than the high
pressure cylinders, sufficient pressure of steam may be maintained in the receiver
to overcome and raise the weight of the pistons on the larger cylinders.
Under other modifications of the improvements a single high pressure cylinder
may be used in combination with one or two or more low pressure cylinders acting
as atmospheric engines; or two or more cylinders of each kind may be operated
together, either with their piston rods connected in pairs, or connected independently
to the crank shaft. The relative positions also of the cylinders may be varied, as
for example, they may all be placed vertically, horizontally, or in an inclined
position, or, as will be found advantageous for exhausting from the high pressure to
the low pressure cylinders direct, the one set may be placed horizontally and the
other vertically, or inclined at right angles to each other, with their cranks also at
right angles.
The valves of the engines may be operated by eccentrics in the usual way, or by
cams to time the admission of steam to the high and low pressure cylinders as
required, and to each pair of such cylinders, according as the cranks are set at right
angles, or at other angles, as a third of a revolution in advance of each other.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John McCallum in the Great Seal Patent Office on the 31st May
1881.
JOHN MCCALLUM, of Greenock, in the County of Renfrew, North Britain,
Engineer. "IMPROVEMENTS IN STEAM ENGINES."
My said Invention relates to certain improvements in the construction, arrange-
ment, and combination of the parts of steam engines designed to render them
highly economical and efficient in action, and to obtain therefrom greater power
than has hitherto been found practicable with a minimum consumpt of fuel and
steam.
My said Invention consists essentially in arranging and fitting together a series
of high and low pressure engine cylinders to act as double acting high pressure and
single-acting atmospheric engines combined and connected to one crank shaft.
Under one modification of the improvements three pairs of cylinders are

page_text: employed, and are ranged with each pair in line fitted with a single piston rod
passing through each inner cylinder, as in tandem engines, and connected to the
crank shaft at the inner ends.
Two of the cylinders are supplied with steam from the boiler or generator
5 alternately to each side of the pistons, through D, slide, or other suitable valves
commonly used with double acting engines, and the exhaust steam from these
cylinders is discharged into a large receiver, from which the remaining four
cylinders are supplied with low pressure steam at the inner ends of the cylinders or
under the pistons only, as in the common form of atmospheric engine. The
exhaust steam from these four cylinders is led to a condenser to form a vacuum
beneath the piston, and thus obtain the pressure of the atmosphere for the return
stroke of the piston. Instead of two as described, three of the cylinders (that is,
one of each pair), may be supplied with high pressure or boiler steam, but in this
case it is preferred to cut off the steam early in the stroke and work the engines
expansively, so as to exhaust in the receiver at a low pressure, merely sufficient to
raise the pistons of the low pressure cylinders, and by condensation form the
requisite vacuum for the return stroke, which only would be effective for the three
low pressure engine cylinders. The pistons of each pair of high and low pressure
cylinders being fitted to one piston rod, the piston of the low pressure cylinder may
be actually raised by the power or motion of the high pressure piston in the
cylinder above or below, if the pressure of exhaust steam in the receiver is only
nominal; and this steam when admitted to the low pressure cylinders need do
little or no effective work for the up or outward stroke, but merely form the
requisite vacuum (by condensation) for the return stroke. Or when the low
pressure cylinders are larger than the high pressure cylinders, sufficient pressure of
steam may be maintained in the receiver to overcome and raise the weight of the
pistons in the larger cylinder.
Under other modifications of the improvements, a single high pressure cylinder
may be used in combination with one or two or more low pressure cylinders acting
as atmospheric engines, or two or more cylinders of each kind may be operated
together either with the piston rods connected in pairs, or connected independently
to the crank shaft. The relative positions also of the cylinders may be varied, as
for example, they may all be placed vertically, horizontally, or in an inclined
position, or, as will be found advantageous for exhausting from the high pressure to
the low pressure cylinders direct, the one set may be placed horizontally and the
other vertically, or inclined at right angles to each other, with their cranks also at
right angles.
The valves of the engines may be operated by eccentrics in the usual way, or by
cams to time the admission of steam to the high and low pressure cylinders as
required, and to each pair of such cylinders, according as the cranks are set at right
angles, or at other angles, as for example, a third of a revolution in advance of each
other.
In order that my said Invention and the manner of performing the same may be
properly understood, I have hereunto appended for that purpose a Sheet of
explanatory Drawings representing one modification of my Invention, which I shall
now describe.
Figure 1 of these Drawings is an end elevation, and Figure 2 is a front elevation
showing a steam engine of small size adapted for marine purposes, and constructed
in accordance with my Invention.
In the example of my improved engines shown in the Drawings, a single vertical
high pressure cylinder A is employed, and is secured by a flanged bracket or
brackets a over one of the low pressure cylinders. The low pressure or atmospheric
cylinders B1, B2, B3, which are also vertical and three in number, are carried by
strong open supporting standards or brackets C bolted to the engine room floor or
other usual foundation, and for convenience are ranged in a row over the crank
shaft D. Steam to drive the engines is admitted from the boiler or generator to
the high pressure cylinder A, which is double acting, by the pipe a¹, and its

page_text: admission is regulated by means of a slide valve A¹ worked by an eccentric
and connecting rod E from the crank shaft D. The steam after each effective
stroke in the high pressure escapes at a pressure considerably over the atmo-
spheric pressure through an exhaust port and slide valve A2 at the opposite side,
and by an exhaust pipe a³ into a large receiver B (provided with a safety valve b)
fitted alongside the low pressure cylinders B1, B2, B3, and supported by brackets C¹
from the main standards C. From this receiver the high pressure exhaust steam
passes by a pipe or branches 61, 62, 63, to each of the low pressure or atmospheric
cylinders B¹, B2, B3, to which it is admitted for the up stroke by a slide valve B*
fitted to each, and operated by eccentrics E' on the crank shaft D, or by quick
cams.
After the effective upward stroke the steam passes through an exhaust port
provided with a separate valve B³ and actuating eccentric E2 for each cylinder on
the side opposite the admission valve B, and escapes by small pipes 65 into a
condenser G placed at the side of the engine, and fitted with pipes g through which
the condensed steam and condensation water is withdrawn by means of ordinary
air pumps H and working connections on each side. The upper ends of the low
pressure cylinders B1, B2, B³, are open to the atmosphere, and when the steam
escapes from the under side of the cylinder piston to the condenser, the atmospheric
pressure acting above the piston drives it down as in an ordinary atmospheric
engine.
The piston rod As of the high pressure engine cylinder A passes down to and is
connected to the piston of the low pressure cylinder B2 below it, or passing through
that piston forms one continuous piston rod for the high and low pressure cylinders
in line, and is fitted by the connecting rod D¹ to a crank pin on the crank shaft D
below. The piston rods of the other two low pressure cylinders B¹, B³, are
connected to crank pins of their own on the same crank shaft D.
Having thus described my said Invention, and the manner of performing the
same, I wish it to be understood that I do not restrict myself to the precise details
herein described or delineated, but what I believe to be novel and original, and
therefore claim as the Invention secured to me by the hereinbefore in part recited
Letters Patent is,―
The arrangement, construction, and use of steam engines, in which a high
pressure double acting engine cylinder or cylinders is or are combined with one,
two, or more low pressure single acting or atmospheric engine cylinders operated by
the exhaust steam from the high pressure cylinder, substantially as and for the
purposes herein set forth or as shown in the accompanying Drawings.
In witness whereof, I, the said John McCallum, have hereunto set my hand
and seal this Twenty-eighth day of May, in the year of our Lord One
thousand eight hundred and eighty one.
JOHN M'CALLUM. (L.S.)