IMPROVEMENTS IN REFRIGERATING APPARATUS
Year: 1880

page_text: LETTERS PATENT to Thomas Bell Lightfoot, of the Dartford Iron Works,
Dartford, in the County of Kent, for an Invention of "IMPROVEMENTS IN
REFRIGERATING APPARATUS."
PROVISIONAL SPECIFICATION left by the said Thomas Bell Lightfoot at
the Office of the Commissioners of Patents on the 6th October 1880.
THOMAS BELL LIGHTFOOT, of the Dartford Iron Works, Dartford, in the County
of Kent. "IMPROVEMENTS IN REFRIGERATING APPARATUS."
In apparatus for effecting refrigeration by compressing, cooling, and afterward
expanding air while it is performing work, serious difficulties arise from deposition
of moisture in the form of ice and snow, causing obstruction of pipes and passages,
and also affecting the chamber in which the cold air is employed. My Invention
relates to means of overcoming these difficulties, which I effect in the following
manner-Instead of allowing the compressed and cooled air to expand to its full
extent in one cylinder, I employ two or more cylinders of different sizes in which
it expands by stages, introducing between the successive cylinders suitable vessels
or passages in which moisture is deposited in liquid form, and from which it can be
run or blown off. Thus, by the first stage of its expansion, the temperature of the
air may be sufficiently reduced to effect condensation of the greater part of its
moisture without freezing it, the more intense cold being produced in the subsequent
stages of expansion after the condensed moisture has been removed. In most cases
two stages of expansion suffice for the object in view, and in such cases, instead of
employing two separate cylinders, one cylinder with a trunk or differential piston
may be employed, the first expansion taking place in the annular space of the
cylinder, and the second expansion in its full capacity.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Thomas Bell Lightfoot in the Great Seal Patent Office on the
5th April 1881.
THOMAS BELL LIGHTFOOT, of the Dartford Iron Works, Dartford, in the County
of Kent. "IMPROVEMENTS IN REFRIGERATING APPARATUS."
In apparatus for effecting refrigeration by compressing, cooling, and afterwards
expanding air while it is performing work, serious difficulties arise from deposition
of moisture in the form of ice and snow, causing obstruction of pipes and passages,
and also affecting the chamber in which the cold air is employed. My Iuvention
relates to means of overcoming these difficulties, which I effect in the following
manner Instead of allowing the compressed and cooled air to expand to its full
extent in one cylinder, I employ two or more cylinders of different sizes in which
it expands by stages, introducing between the successive cylinders suitable vessels
or passages in which moisture is deposited in liquid form, and from which it can
be run or blown off. Thus, by the first stage of its expansion, the temperature of
the air may be sufficiently reduced to effect condensation of the greater part of its
moisture without freezing it, the more intense cold being produced in the subsequent
stages of expansion after the condensed moisture has been removed. In most cases
two stages of expansion suffice for the object in view, and in such cases, instead of
employing two separate cylinders, one cylinder with a trunk or differential piston
may be employed, the first expansion taking place in the annular space of the
cylinder, and the second expansion in its full capacity.
The accompanying Drawings represent a combined steam engine and refrigerating
apparatus arranged according to my Invention. Fig. 1 is a side elevation, and
Fig. 2 a plan of the whole apparatus. Fig. 3 is a longitudinal section of the
expansion cylinder, and Fig. 4 is a longitudinal section of the chambers for
deposition of moisture. A is the steam cylinder, and B the expansion cylinder
arranged in line with it, their pistons being fixed on one rod which is connected to
a crank on the fly wheel shaft C. Another crank on the shaft is connected to the
piston of a double acting air compressing pump D. This pump is supplied with air
by the pipe d, compresses it and discharges it into the coolers E, which are con-
veniently arranged, as shown under the engine bed, and which may be of any
known construction, as, for example, a number of tubes round which water is caused
to circulate, so as to abstract from the air a large portion of the heat developed by
its compression. From the coolers E the cooled compressed air passes to the front
slide case F of the expansion cylinder B, which has a trunk piston, as shown in
Fig. 3. A certain portion of the air is at each stroke admitted to act in the front
annular space of the cylinder B, and expands therein, performing work and becoming
considerably reduced in temperature. The exhaust air from this annular space
passes by the pipo f to a set of chambers G, in which it is caused to travel upwards
and downwards, as indicated by the arrows in Fig. 4, depositing the moisture
suspended in it. For more effectually securing deposit of the moisture, a number
of inclined screws g of wire are placed in the descending channels, so that the air
current is broken up and subdivided, the particles of moisture being more or less
retained by the wires, and gliding down along them. The moisture that collects
at the bottom of the vessels G is from time to time run off or blown off by opening
a stop cock g¹ in a pipe communicating with the bottoms of the deposit vessels.
From these vessels the air, which is still under considerable pressure, passes to the

page_text: hinder slide case H of the expansion cylinder B, and a portion of it is at each stroke
admitted to act in the full capacity of B, expanding and performing work, and
thereby having its temperature cooled to a very low degree. The exhaust air
thus refrigerated is conveyed by the pipe h to the chamber or chambers where it is
employed for refrigerating purposes. Such being the general construction and
action of the apparatus, I will now refer to certain details which I find of advan-
tage. The suction valves of the air compressing pump D, instead of being self
acting, are worked from cams c on the fly wheel shaft. An eccentric k works a force
pump K for causing circulation of water through a jacket surrounding the com-
pressing pump D, and through the coolers E. An eccentric works simultaneously
the slides of the expansion cylinder B, and of the steam cylinder A, and another
eccentric m moves cut off slides working on the backs of the main slides, as shewn
in Fig. 3. The rod of these cut off slides is made with a swivel at L, when it is
jointed to the eccentric rod, so that it can be turned round by a wrench or handle
applied at its end M. Where the rod passes through the front cut off slide N of
the expansion cylinder it is made with a screw thread, so that by turning the rod
in one direction or the other, the cut off slide can be adjusted to give more or less
expansion in the annular space of the cylinder B. The cut off slides of the steam
cylinder may be made adjustable in like manner, and also the hinder slide o of the
expansion cylinder, or the latter may be made to retain always a definite position
by fitting it, as shewn in Fig. 3, between screw collars stationary on the slide rod.
Although I have shewn a particular form and arrangement of apparatus, a
considerable portion of which is of well known construction and operation, I do not
limit myself to this, as the parts may be arranged and proportioned in many
different ways.
For example, instead of employing a single expansion cylinder B,
having a piston of differential area, so that two successive expansions of the
compressed air are effected in it, there might be two separate cylinders, one larger
than the other, so that the air might undergo its first expansion in the smaller
cylinder, and after depositing its moisture, might farther expand in the larger
cylinder.
Having thus described the nature of my Invention, and in what manner the
same is to be performed, I claim as my Invention in respect of apparatus in which
refrigeration of air is effected by compressing it, cooling it, and then permitting it
to expand while it performs work,―
First. The herein described method of separating moisture from the air by
causing the air to expand in the first instance only so far that a large portion of
its moisture is precipitated as liquid, which can be run off, the air thus in great
measure dried being afterwards farther expanded.
Second. The use of refrigerating apparatus constructed and operating substan-
tially as herein described with reference to the accompanying Drawings.
In witness whereof, I, the said Thomas Bell Lightfoot, have hereunto set my
hand and seal, this Second day of April, in the year of our Lord One
thousand eight hundred and eighty one.