IMPROVEMENTS IN STEAM ENGINES
Year: 1868

page_text: PROVISIONAL SPECIFICATION left by Robert Meldrum at the Office
of the Commissioners of Patents, with his Petition, on the 20th
March 1868.
I, ROBERT MELDRUM, of Pittormie, Cupar, in the County of Fife,
North Britain, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN STEAM ENGINES," to be as follows, that is to say :-
This Invention has for its object, by an improved construction and
arrangement of parts, to obtain a great economy of fuel in steam
engines.
The improvements are applicable with two or more cylinders, but will
be more conveniently and clearly described in connection with one only.
The cylinder has in connection with it any suitable existing arrangement
of valves and valve gear for admitting steam into the opposite ends
of it alternately, and such an arrangement is preferred as can be
regulated by a governor to cut off the steam at various parts of the
stroke. Communications are formed between the two ends of the

page_text: cylinder and a cistern containing water, and these communications
are controlled by valves actuated either along with or independently of
the steam valves. The cylinder is provided with a piston having a
rod which passes out through a stuffing box in the ordinary way, and
is connected to a revolving crank shaft or to a pump rod. The steam
after forcing the piston to one end of the cylinder is condensed by the
ingress of the water, and the piston being simultaneously acted upon
by steam on the opposite side returns in the opposite direction; after
which the steam which produced the return stroke is in its turn
condensed in the same way. The water is of such a heat as to barely
condense the steam, so as to cool the cylinder as slightly as possible
between each stroke, and so as to avoid as much as possible loss that
would be caused by premature condensation of the steam on its first
entering the cylinder.
An important feature of the Invention is the arrangement for 1
returning part of the water to the boiler and part to the cistern.
In one modification suitable for a vertical steam cylinder, a tubular
rod is fixed to the under side of the piston, and works like a pump
plunger in a barrel fixed to the bottom end of the cylinder. The water
above the piston enters the tubular rod by a float valve (which closes 2
when surrounded with steam), and on the piston rising the water passes
out of the rod into the pump barrel by a valve at the bottom, which
prevents its return. The descent of the plunger or rod then forces the
water through valves in two pipes, one leading to the boiler and the
other to the cistern. A pipe fitted with valves communicates between
the bottom of the pump barrel and the bottom of the cylinder, and the
water finds its way thereby from the latter into the pump barrel.
In the case of horizontal cylinders a separate pump may be used to
draw off the water from the cylinder and force it back into the boiler
and cistern, the inlet to the pump having branch pipes communicating a
with the opposite ends of the cylinder. With these arrangements. the
water in the cistern if commencing cold will gradually become heated,
and the economical working of the engine will depend on the nice
adaptation of the temperature of the water to the pressure and quantity
of steam employed. Where there is an abundant supply of cold water 3
the heat may be prevented from becoming too great by admitting a
stream of cold water into the cistern by an adjustable tap or valve, the

page_text: excess of hot water being allowed to overflow; or the cistern or tank
may be of an extensive shallow form, so that the water in it may cool
with sufficient rapidity; or the hot water may be passed through tubing
or vessels constructed in any convenient way to expose a sufficiently
large surface to atmospheric radiation.