IMPROVEMENTS IN STEAM ENGINES AND BOILERS
Year: 1869

page_text: PROVISIONAL SPECIFICATION left by John Duncan Gauldie and
Thomas Alexander Marshall at the Office of the Commissioners
of Patents, with their Petition, on the 20th February 1869.
We, JOHN DUNCAN GAULDIE and THOMAS ALEXANDER MARSHALL,
both of Glasgow, in the County of Lanark, North Britain, Engineers, do
hereby declare the nature of the said Invention for "IMPROVEMENTS IN
STEAM ENGINES AND BOILERS," to be as follows, that is to say :-
This Invention has for its object to obtain simple and convenient
arrangements of steam engines and boilers; and in carrying out the
improvements in steam engines it is proposed to use high-pressure steam
in cylinders of comparatively small size and working at a comparatively
quick rate with valve gear which can be varied or adjusted by means of
a governor so as to keep the engine at a nearly uniform rate notwith-
standing considerable variations in the load.
The improvements in steam boilers are designed to obtain a large
increase of efficient heating surface in a simple way, and can be
conveniently applied to old boilers as well as to new ones.

page_text: In the improved arrangement of steam engine a steam admission valve
or valves separate from the exhaust valve or valves is or are actuated by
a rod connected to a vibrating quadrant or arc, such arc being worked
from an eccentric on the shaft by a short rod which can be shifted
along the arc. The shifting of the eccentric rod on the arc alters the
travel of the valve so as to cut off the steam sooner or later, whilst the
arrangement gives a suitable lead under all circumstances. The arc rod
is shifted through the intervention of links and levers by the longi-
tudinal movement of a tube fitted with a key and groove on a revolving
shaft, and this tube has two enlarged bosses with screw threads formed
on them, those on one being right-handed and those on the other left-
handed. Pieces formed like sectors of screwed nuts are fixed on a
rocking piece, which is connected to a governor of any convenient kind,
and when the engine's rate exceeds or falls short of the proper rate one
of the screwed sectors is by the governor put into gear with one of the
screwed bosses of the tube, and the rotation of that tube causes it to
screw itself along, and so shift the arc rod, whereby the steam will be
cut off sooner or later in each stroke, as required, and the engine will be
restored to its proper rate. No throttle valve is required with this
improved arrangement. Instead of the reversely screwed bosses being
arranged to act in connection with an eccentric rod and quadrant they
may be fixed directly on the spindle of a revolving cylindrical valve, the
ports in such valve and those leading to the cylinder being shaped
obliquely on their closing sides, so that the longitudinal adjustment
caused by the action of the governor will cause them to close sooner or
later in each revolution.
The improvements in boilers consist in fixing inclined tubes below the
water surface in the outer shell of any convenient form of boiler, such
tubes being screwed from the inside and having their outer ends closed;;
they project out into the furnace or flue space, and their inclination
induces a rapid change or circulation of the water in them, which
promotes the production of steam.