Improvements in Motors, especially applicable to Tramways.
Year: 1895

page_text: Date of Application, 26th June, 1895-Accepted, 17th Aug., 1895
COMPLETE SPECIFICATION.
Improvements in Motors, especially applicable to Tramways.
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I, RANALD MACINTOSH MACDONALD, of 71, Cathedral Square, Christchurch,
in the Provincial District of Canterbury, in the Colony of New Zealand, 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:
This invention relates to that class of motors which are used more especially for
the propulsion of tram-cars and the like, and has for its object the more efficient
and economical working of the same.
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Hitherto when motors have been used which depend upon the combustion of gas
whether compressed or otherwise; for the source of their power, it has been usual
to use a considerable quantity of water for cooling the cylinder which would other-
wise become overheated; and again when compressed air has been used as a motive
power it has been usual to employ a quantity of hot water for the purpose of heating
the cylinders the parts of which would otherwise be liable to become choked with
or snow and in order to secure the compressed air being worked to more
economical advantage.
ice or
Now my invention is designed to overcome the necessity which has existed for
carrying the comparatively large quantity of water which has hitherto been used
and consists in the combined use of two different motive fluids such as gas and
compressed air, in one motor either in the same or separate cylinders so that the
exhaust gases which leave the cylinder in which gas is employed in a heated
condition may be utilised to heat the cylinder in which compressed air is
employed and the exhaust from the compressed air cylinder may be used to cool
the cylinder in which gas is employed as the motive fluid.
I also use the gases which are exhausted in a heated condition to heat the
compressed air prior to its.admission to the motor cylinder.
The accompanying drawings illustrate my invention.
Fig. 1 is a diagrammatic view illustrating my invention as adapted, to two
cylinders of one motor using gas and compressed air respectively.
Fig. 2 is a similar view illustrating the method of employing gas and compressed
air alternately in the same cylinder.
Similar letters of reference indicate the same parts in all the figures.
Referring first to Fig. 1.
The engine cylinder (a) is similar to those commonly used when compressed air
is the motive power. and the cylinder (b) is constructed after the manner of the
ordinary gas engine cylinder.
Each of the cylinders is provided with an outer casing (a¹) (6¹) forming annular
spaces or jackets (c) and (d) which may if desired contain water.
The hot exhaust gases from the gas cylinder (b) are conveyed by the exhaust
pipe (e) to the lower part of the jacket (c) from whence they pass upwards and
after imparting some of their heat to the cylinder (a) either directly, or indirectly,
through the medium of water contained in the jacket are either exhausted into the
atmosphere or conducted by another pipe (e¹) to the vessel (f) for the purpose of
heating compressed air contained within it, which is used as the motive power in
the cylinder (a).
The vessel (f) may be constructed with a jacket similar to the engine cylinders
into which the exhaust gas may be conducted, or a coiled copper pipe or pipes may be

page_text: employed arranged within the vessel as shown in the drawing, through which the
exhaust gases are conducted and as much as possible of their remaining heat
extracted before they are finally exhausted to the atmosphere through pipe (h).
The exhaust cold air from the cylinder (a) is conducted by a pipe (g) into the
lower part of the jacket (d) in which it is employed for cooling the cylinder (b)
either directly or through the medium of water and is then exhausted through the
pipe (i) into the atmosphere.
In Fig. 2 the cylinder is provided with a piston (k) one side of which (a) is
operated upon by compressed air controlled by a valve and valve gear common to
engines in which compressed air is used, the opposite side of the piston (b) is
operated upon by gas; controlled by a valve common to gas engines, and exploded
within the cylinder in the ordinary way.
The cylinder may be surrounded by a jacket containing water as in the previous
instance, and if desirable either the exhaust gases or exhaust air or both of them
may be led into it as shown, but it will probably be convenient to dispense with the
jacket the cylinder itself being alternately heated and cooled by the combustion of
the gas and expansion of the compressed air within it.
It is evident that there are in practice many modes of carrying my invention
into effect the employment of any mode being dependent upon the circumstances of
the particular case; for instance I might employ gas and compressed air alternately
on one or both sides of the piston in one cylinder, or gas on one side and compressed
air on the other as described in reference to Fig. 2 or I might use separate
cylinders for the different motive powers, as described in reference to Fig. 1.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:
1. The improvements in motors substantially as and for the purposes herein
described and illustrated in the accompanying drawings.
2. The improvement in motors consisting in the employment in one cylinder of
two different motive powers, such as gas and compressed air, the heating of the
cylinder due to the use of one power being counteracted by the cooling effect
produced by the employment of the other substantially as and for the purposes
herein described and illustrated in the accompanying drawings.
3. The improvement in motors consisting of the combination of an engine in
which gas is used as a motive power with an engine in which compressed air is
employed; the exhaust gases from the gas cylinder being used to heat the
compressed air engine cylinder and the exhaust air being used to cool the gas
engine cylinder substantially as and for the purposes herein described and illustrated
in Fig. 1 of the accompanying drawings.
4. A motor cylinder provided at one end with the valve commonly employed
when compressed air or similar motive fluid is used upon one side of a piston only
and provided at the other with the valve commonly employed when gas power is
used, the respective valves controlling the admission and exhaust of the respective
motive powers upon opposite sides of a piston within the cylinder as and for the
purposes herein described and illustrated in Fig. 2 of the accompanying drawings.
Dated this 26th day of June 1895.