IMPROVEMENTS IN STEAM ENGINES AND BOILERS
Year: 1860

page_text: PROVISIONAL SPECIFICATION left by Thomas Richardson Yarrow and
Walter Montgomerie Neilson at the Office of the Commissioners of
Patents with their Petition, on the 10th February 1860.
We, THOMAS RICHARDSON YARROW, of Arbroath, in the County of Forfar,
and WALTER MONTGOMERIE NEILSON, of Glasgow, in the County of Lanark,
both Engineers, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN STEAM ENGINES AND BOILERS," to be as follows:-
This Invention relates to various improvements in the arrangement and
construction of the parts of steam engines and boilers, some of these improve-
ments being in further development of the plans described in the Speci-
fication of Letters Patent granted to Thomas Yarrow, under date the 18th
March, 1857 (No. 758) for "Improvements in Locomotive Steam Engines.".
An improvement applicable to the furnaces described in the Specification
referred to, consists in placing at the front of the fire-box and below the tubes
and transverse inclined arch or midfeather a series of air bars placed nearly
vertical for the admission of air directly to the fire. This air screen or grating
may be built up of separate bars, or may consist of one or more pieces having
numerous elongated or otherwise shaped openings for the passage of air.
A second improvement in these furnaces consists in substituting for the
ordinary fire door a plate loosely hinged to the top of the aperture so as to
open inwards, and which when closed hangs in a more or less inclined
position. This door pulsates or moves intermittently from the action of the

page_text: draught, and admits air to the furnace in such a way as to act very bene-
ficially. The fire-door aperture is formed by flanging out the fire-box and
boiler shells, and rivetting the flanges together.
An improved piston, constructed according to this Invention for locomotive
and other steam engines, is formed with an external packing ring cut into
four or other convenient number of segments. This external ring is backed
or lined by an inner ring, also cut into as many segments as the outer one,
the two being arranged to break joint. The inner ring is formed with a small
ridge or bead round its middle, which fits in a groove cut round the inside of
the outer ring, whilst this ridge or bead is extended into a tongue at each
joint of the outer ring, which tongue projects to the outer surface to prevent
the passage of steam at the joint. An improved spring for this and other
pistons consists of a steel band or hoop, which is corrugated across its breadth,
and which is placed within the rings in a slightly compressed state. With
this plan of spring and packing ring either a junk ring may be used, or the
piston body may have both flanges or discs formed upon it.
The improvements in boilers are more particularly designed for those of
locomotive steam engines, but are also applicable to other boilers. These
improvements have reference to the superheating or drying of the steam; and
according to one modification, a steam chest is formed along the top of the
boiler, and communicates with the main part of the boiler by a series of
tubular or other small vertical passages crossing a horizontal flue of
chamber through which a portion of the fire gases pass. In the case of a
locomotive engine, the said portion of the fire gases may be introduced into
the superheating flue by passages formed through the roof of the fire-box.
The front end of the flue discharges into the smoke-box, and a valve is pro-
vided to shut off the fire gases from the superheating flue when the steam
is not being used, and this valve may be so connected with the handle of the
'regulator" or steam supply valve, as that one movement simultaneously
shuts off the steam and the superheating fire gases. The steam of course passes
to the cylinders from the superheated steam chest. According to a second
modification, a transverse vertical plate is inserted near the smoke box end of
a locomotive boiler so as to divide the internal boiler space into two compart-
ments, the tubes being continued through both, and the front space forming
a superheating space. The steam passes from the main boiler space by a
pipe having its inlet in the upper part of a steam dome and its outlet at or
near the bottom of the superheating space. This second plan may be further
modified by introducing a combustion chamber or fire gas space between the
main boiler space and the superheating space. This fire gas space is pro-

page_text: vided with a separate chimney or other outlet, which is closed when the engine
is in action, but is opened when the engine is not working to allow the fire
gases to pass off without passing through the tubes of the superheating space.
The fire-gas space may be surrounded with water, such water being either
that of the main boiler or the feed water on its way to the main boiler; or
another compartment may be formed in the boiler between the superheating
space and the smoke box for heating the feed water prior to its introduction
into the main boiler space. The superheating space may be formed at other
points in the boilers' length according to the amount of superheating thought
desirable.
The present Invention further comprehends improved apparatus applicable
to the feed arrangements of locomotive and other boilers. This apparatus
consists of (one or more but) by preference two vertical pipes or elongated
chambers of any convenient form and of considerable length (say five or
six feet.) These chambers communicate with the feed pumps at their lower
ends, whilst a portion of the exhaust steam of the engine is admitted at their
upper ends, and condensing, heats the feed water contained in them.