IMPROVEMENTS IN MOTIVE POWER ENGINES AND IN FITTINGS FOR BOILERS EMPLOYED THEREWITH, PARTS OF WHICH IMPROVEMENTS ARE APPLICABLE TO OTHER SIMILAR PURPOSES
Year: 1876

page_text: PROVISIONAL SPECIFICATION left by John Gillott and William Arnold at
the Office of the Commissioners of Patents on the 12th May 1876.
JOHN GILLOTT and WILLIAM ARNOLD, both of Barnsley, in the County of York,
Engineers. "IMPROVEMENTS IN MOTIVE POWER ENGINES AND IN FITTINGS FOR
BOILERS EMPLOYED THEREWITH, PARTS OF WHICH IMPROVEMENTS ARE APPLICABLE TO
OTHER SIMILAR PURPOSES."
Our Invention relates more particularly to the construction and arrangement of
the pistons, slide valves, and air pumps of steam or other motive power engines, and
to the safety valves of steam boilers, but is also partly applicable to other purposes
for which like apparatus are employed.
The first part of our Invention has reference to pistons, and consists in the appli-
cation to a piston of devices or contrivances by means of which one or more spiral
springs enclosed in the piston are compressed in the direction of its circumference in
such a manner as to adjust the pressure of the packing rings against the cylinder so
as to maintain a steam-tight fit, whilst at the same time reducing the friction to a
minimum. These devices or contrivances may consist of levers, a cam or wedge, or
a combination of them; but we employ by preference a worm wheel made hollow,
and formed on its interior with a right and left-handed screw thread, with which
engages a corresponding inale screw, such worm wheel being actuated by a worm, so
that when the latter is turned by means of a key passing through the piston cover
the screws are forced out against lugs cast on the inside of an internal V ring, thereby
pressing the latter against the springs, and forcing the packing rings into contact
with the cylinder. The piston cover is also threaded for the reception of a nut for
setting the worm fast when the piston is properly adjusted. The (adjustment, which
is best accomplished with the pressure of steam or other motive fluid against the
piston), may be readily obtained if desired without removing the cylinder cover by
providing an opening for the introduction of a key opposite the aperture in the
piston cover. This part of our Invention is also applicable to the pistons or plungers
of pumps, and to other like purposes.
Our Invention relates, 2ndly, to slide valves, and consists according to one modi-
fication in providing in the interior of the valve a table formed or attached across
the opening of the exhaust port, the upper surface of which table is planed parallel
with the face of the cylinder for the reception of an upper valve face which is also
truly planed so as to work over it. The valve is made open at the back, whereby
it is relieved of the pressure of the steam or other motive fluid which is received and
sustained by the table.

page_text: According to another modification a plate is fitted to bear against the upper valve
face, which is formed on a ring resting upon an elastic packing contained in the
body of the valve. This plate is maintained in contact with the upper valve face
by incans of springs placed between it and the steam sliect cover, but which admits
of its rising in case of the engine priming; set screws or wedges are provided for the
purpose of adjusting the plate to the ring as required.
Our Invention relates, 3rdly, to safety valves for steam boilers, and consists,
according to one modification, in constructing the valve with a double annular face
fitting corresponding annular seats with which the valve may be maintained in
contact by means of the ordinary lever arrangement, or, as is preferred, by means of
a weight or weights attached to or suspended from the under side of the valve in any
suitable manner.
The weight or weights is or are enclosed in a dome or cover in
order to prevent them from being tampered with when the boiler is empty.
According to another modification the safety valve is made in two parts, forming
a duplex valve, the two valves of which are of different areas. The small valve has
its seat in the large one, and is maintained in contact therewith by means of a
weight connected to or suspended from its under side, whilst the large valve is kept
to its seat by means of a weighted lever in the ordinary manner. The top of the
large valve is made to cover the small valve, and is provided with openings for the
exit of the steam which passes the small valve when it is opened by the excess of
pressure in the boiler, thereby relieving the large valve of a portion of its load.
Our Invention relates, 4thly, to air pumps, fand consists, as applied, to vertical
engines, in placing the pump barrel below the level of the foot and delivery valves,
so that the water and air and uncondensed steam can flow freely out of the con-
denser. This arrangement admits of the employment of a piston in substitution for
the costly bucket ordinary used, and also of the pump and valves being made of
much smaller dimensions than are usually required. The principle is also applicable
to horizontal engines, the pump in that case being made double-acting.