IMPROVE- MENTS IN ENGINES TO BE DRIVEN BY STEAM, WATER, OR OTHER FLUID, OR FOR PUMPING
Year: 1875

page_text: LETTERS PATENT to Thomas Melvin, of Glasgow, in the County of
Lanark, North Britain, Engineer, for the Invention of "IMPROVE-
MENTS IN ENGINES TO BE DRIVEN BY STEAM, WATER, OR OTHER FLUID, OR FOR
PUMPING."
Sealed the 4th April 1876, and dated the 12th October 1875.
PROVISIONAL SPECIFICATION left by the said Thomas Melvin at the
Office of the Commissioners of Patents, with his Petition, on the
12th October 1875.
I, THOMAS MELVIN, of Glasgow, in the County of Lanark, North
Britain, Engineer, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN ENGINES TO BE DRIVEN BY STEAM, WATER, OR OTHER
FLUID, OR FOR PUMPING," to be as follows, that is to say :-
This Invention has for its object to modify and improve a simple
class of motive-power engine or pump, so that whilst economical in cost
it may act more efficiently and be less liable to get out of order than
such engines as heretofore constructed.

page_text: In carrying out the Invention according to one modification a single
cylinder is arranged to oscillate on trunnions situated between its ends,
one trunnion being mounted in a plain bearing, whilst the other
trunnion is set in a bearing fitted with a stuffing box, and has the
passages from the two ends of the cylinder led into it. The ports of the
cylinder passages are formed in the cylindrical surface of the trunnion,
and the steam is admitted to them alternately through a valve piece
fitted to work on the trunnion, and also formed with a cylindrical neck
at right angles to the trunnion, such neck being entered through
packing into the inlet pipe. The motive fluid exhausts into the space
outside of the valve piece in the trunnion box, and there is consequently
a pressure from the inlet pipe acting upon the valve piece, and keeping
it close to the cylindrical port face on the trunnion. When water or
other liquid is used as the motive fluid the combined trunnion box and
valve chest may be stationary, but when steam or other expansible fluid
is used a slight oscillation is (by means of a small eccentric on the
engine shaft or in any other convenient way), imparted to the valve
chest to obtain an effect equivalent to that got by the "lap and lead" of
an ordinary steam engine slide valve. In this case the inlet and outlet
pipes may be connected to the oscillating valve chest by flexible tubing,
or the valve chest may be formed with a nozzle entered through a
stuffing box in the inlet pipe, both being arranged concentrically with
the axis of oscillation.
In another modification the ports of the cylinder passages are formed
in a flat face on the trunnion at right angles to its axis, and the neck of
the valve is entered into the inlet passage, both being concentric with
the same axis. When steam or other expansible fluid is to be used with
this modification, the slight additional oscillation for "lap and lead" is
imparted directly to the valve piece, which has attached to it a rod
passing out through a stuffing box on the inlet pipe.
Two or more cylinders may be combined in one engine, and when
there are two cylinders the extra oscillation of one valve chest or valve
piece may be derived from the movement of the other cylinder.
Any of the modifications herein-before described can be used as a
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page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Thomas Melvin in the Great Seal Patent Office
on the 11th April 1876.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS
MELVIN, of Glasgow, in the County of Lanark, North Britain, Engineer,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twelfth day of October, in the year
of our Lord One thousand eight hundred and seventy-five, in the
thirty-ninth year of Her reign, did, for Herself, Her heirs and suc-
cessors, give and grant unto me, the said Thomas Melvin, Her
special licence that I, the said Thomas Melvin, my executors,
administrators, and assigns, or such others as I, the said Thomas
Melvin, my executors, administrators, and assigns, should at any time
agree with, and no others, from time to time and at all times there-
after during the term therein expressed, should and lawfully might
make, use, exercise, and vend, within the United Kingdom of Great
Britain and Ireland, the Channel Islands, and Isle of Man, an Invention
for "IMPROVEMENTS IN ENGINES TO BE DRIVEN BY STEAM, WATER, OR OTHER
FLUID, OR FOR PUMPING," upon the condition (amongst others) that I, the
said Thomas Melvin, my executors or administrators, by an instrument
in writing under my, or their, or one of their hands and scals, should
particularly describe and ascertain the nature of the said Invention,
and in what manner the same was to be performed, and cause the same
to be filed in the Great Seal Patent Office within six calendar months
next and immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Thomas Melvin, do hereby declare
the nature of my said Invention, and in what manner the same is to
be performed, to be particularly described and ascertained in and by the
following statement in writing, reference being had to the accompanying
Drawings, that is to say :-
My said Invention has for its object to modify and improve a simple
class of motive-power engine or pump, so that whilst economical in cost
it may act more efficiently, and be less liable to get out of order than
such engines or pumps as heretofore constructed.

page_text: Engines of the class referred to have oscillating cylinders, and the
valve action for the distribution of the motive fluid is derived from the
oscillating motion.
In one modification of my improved engines the ports of the cylinder
passages are formed in the cylindrical surface of one of the trunnions
which works within a valve piece on the trunnion. This valve piece is
formed with a cylindrical neck at right angles to the trunnion, such
neck being entered through packing into the inlet pipe in such a way,
that the pressure of the motive fluid presses the valve piece tightly
against the trunnion.
In another modification the ports of the cylinder passages are formed
in a flat face on the trunnion at right angles to its axis, the valve piece
being pressed against it as in the other modifications.
When steam or other motive fluid of an expansible nature is used,
the trunnion box and valve piece are made to oscillate to obtain an
effect equivalent to the "lead and lap" of an ordinary steam engine
slide valve.
Two or more cylinders may be combined in one engine, and when
there are two cylinders the extra oscillation of one valve piece may be
derived from the movement of the other cylinder.
Any of the modifications may be used as a pump.
And in order that my said Invention and the manner of performing
the same may be properly understood I hereunto append two Sheets of
explanatory Drawings to be herein-after referred to, and representing
modifications of my improved machines. In these Drawings the same
reference numerals are used to mark the same or like parts wherever
they are repeated.
Figure 1 on Sheet 1 of the Drawings is a side elevation, and Figure
2 is a vertical section as at right angles to Figure 1. The framing
comprises two end standards 1 carrying the crank shaft 2 in bearings at
their upper ends, whilst they are connected by horizontal pieces 3 on
which are a plain bearing 4 for one trunnion 5 of the cylinder 6, and a
trunnion box 7 into which the other trunnion 8 is entered through a
stuffing box. The cylinder passages, which are indicated by dotted lines
in Figure 1, extend both along the trunnion 8 which enters the box 7,
and in the circumferential surface of that trunnion within the box ports

page_text: 9, 10, arc formed leading into the passages, the part of the trunnion
with the ports in it being covered with a brass shell 11. The valve
piece 12 is formed with rings 13 which encircle the trunnion, and with
an inlet port 14, which when the piston is at either end of the stroke
and the cylinder 6 exactly vertical is between the ports 9, 10, whilst
these ports are then covered by segmental cylindrical parts of the valve
piece on each side of its port 14. The valve piece 12 is formed with a
cylindrical part 15 which projects through packing 16 in the inlet
passage 17, and the interior of the box 7 being in communication with
the exhaust by the outlet 18, the motive fluid exerts a pressure on the
valve piece 12, which keeps it tightly against the trunnion S. When
water is used as the motive fluid, the packing 16 of the valve piece may
be a cupped piece of leather or rubber, and the trunnion box 7 may be
stationary.
When steam or other expansible motive fluid is used the modified
arrangement shown in vertical section in Figure 3 on Sheet 2 of the
Drawings may be adopted. In this case the trunnion box 8 is itself
formed with a trunnion 19 supported in a bearing 20, and the steam
inlet pipe 21 is entered into the trunnion 19 through a stuffing box.
The exhaust takes place from the box 7 through a flexible pipe which is
not shown. A forked piece 22 which is fixed to the top of the box 7
and shown separately in Figure 4 is acted on by a small eccentric 23 on
the crank shaft 2, so as to impart a small oscillatory movement to the
box 7 and through it to the valve piece 12, and the eccentric 23 is
placed on the shaft to suit the intended direction of motion, and to cause
the ports to open to the steam a little before the commencement of the
strokes, and thus give what is known as "lead," and its usual accom-
panyment "lap.”
Figure 5 is a horizontal section of a modification in which the ports
into the cylinder passages are formed in the flat end 24 of the trunnion 8.
Figure 6 is a face view of the trunnion end showing the ports 9, 10,
there being two to each passage, and Figure 7 is a section of the valve.
piece 12 as at the line A-A, in Figure 5. The cylindrical part 15 of
the valve piece 12 is fitted with metallic packing into the passage 17, so
that the pressure of the steam tends to keep the valve piece against the
end of the trunnion. In this modification the trunnion box 7 is
stationary, and the oscillatory movement for lead and lap is given to the
valve piece 12, 15, by means of a rod 25 formed on or fixed to it, and

page_text: passing out through a stuffing box. A lever 26 is fixed on the outer
end of the rod 25 to be connected to an eccentric on the crank shaft, or
where two cylinders are combined in one engine with the cranks at
right angles the lever 26 of one cylinder may be connected to the other
cylinder.
Having thus particularly described my said Invention, and the
manner of performing the same, I have to state that I do not restrict
myself to the precise details herein described or delineated, but that
what I believe to be novel and original and claim as the Invention
secured to me by the herein-before in part recited Letters Patent is,--
1. The fitting of the valve piece (12) so as to pass through a packing
between the inlet and exhaust compartments (17,7), and in consequence
be pressed tightly against the trunnion (S), substantially as hercin-before
described.
2. The fitting of the valve piece (12) so as to oscillate, and by the
combination of its own motion with that of the trunnion (8) to give lead
and lap, substantially as herein-before described.
In witness whereof, I, the said Thomas Melvin, have hereunto
set my hand and scal, this Eighth day of April, in the year
of our Lord One thousand eight hundred and seventy-six.
Witness,
EDMUND HUNT,
Patent Agent,
Glasgow.
THOMAS MELVIN. (L.S.)