IMPROVEMENTS IN STEAM ENGINES AND APPLIANCES IN CONNECTION THEREWITH
Year: 1879

page_text: LETTERS PATENT to James Noah Paxman, of the Firm of Davey, Paxman, &
Company, of Colchester, in the County of Essex, Engineer, for the Invention
of "IMPROVEMENTS IN STEAM ENGINES AND APPLIANCES IN CONNECTION
THEREWITH."
Sealed the 16th December 1879, and dated the 20th June 1879.
PROVISIONAL SPECIFICATION left by the said James Noah Paxman at the
Oilice of the Commissioners of Patents on the 20th June 1879.
JAMES NOAH PAXMAN, of the Firm of Davey, Paxman, & Co., of Colchester, in the
County of Essex, Engineer. "IMPROVEMENTS IN STEAM ENGINES AND APPLIANCES
IN CONNECTION THEREWITH.
"
The improvements relate in the first place to what is known as automatic
expansion gear for steam engines.
The steam cylinder is provided with a main slide valve working in a valve-chest
in the usual way. In addition thereto I provide another valve-chest, through
which the steam passes into the main valve-chest by a suitable port or ports.
These ports are opened or closed by means of the expansion or cut off valve, which
is so actuated that it opens and closes the port or ports under its control during
each stroke of the piston in the steam cylinder.
The expansion or cut off valve is actuated by a kind of link motion consisting of
two eccentrics with bands and rods, and a sliding link coupling the ends of the rudy
farther from the eccentrics. The link works up and down on a pin in the end of
the expansion valve spindle by means of a rotatory or other suitable governor
driven by the engine. The aforesaid eccentrics are mounted side by side on a stud
or shaft which rotates in suitable bearings, and is driven from the engine by
elliptical or circular toothed gearing or its equivalent, in such a way that the
eccentrics make two revolutions for every one revolution made by the engine crank
shaft.
I call one of the aforesaid eccentrics the positive eccentric, and the other the
negative eccentric. The positive eccentric causes the expansion valve to open the
ports, and admit steam to the main valve chest, and the negative eccentric operates
in closing the ports and shutting off steam from the main valve chest. The position
of the link on the pin in the end of the valve spindle determines which eccentric

page_text: has most influence on the cut off valve, in causing it to close the ports sooner or
later after the piston has commenced its stroke. The aforesaid position of the link
being determined by the governor, the speed and admission of steam to the engine
is thereby automatically regulated.
My improvements relate, secondly, to the arrangement of the condenser and air
pump of horizontal condensing engines. I place the condenser below or on one
side of the cylinder, and the air pump beside or near the cylinder, and I drive the
air pump directly by an eccentric and rod from the crank shaft, or by means of a
rocking shaft and suitable connecting rods, the rocking shaft being actuated by a
rod connecting it with the main crank pin or main connecting rod. In this way I
reduce the space occupied by horizontal condensing engines, and save excavation of
the soil beneath their foundations.
My improvements relate, thirdly, to the cross head of the piston or other rod
which is made with suitable adjustable guide pieces. A hardened steel pin is
shrunk or otherwise secured into the connecting rod; this pin works into brasses
or other suitable adjustable bearings, which are fixed in the cross head, and are
screwed by a cover plate with suitable bolts and nuts.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said James Noah Paxman in the Great Seal Patent Office on the 20th
December 1879.
JAMES NOAH PAXMAN, of the Firm of Davey, Paxman, & Company, of
Colchester, in the County of Essex, Engineer. "IMPROVEMENTS IN STEAM ENGINES
AND APPLIANCES IN CONNECTION THEREWITH."
My Invention relates to improvements in what is known as automatic expansion
gear for steam and other engines.
The steam cylinder is provided with a main slide valve working in a valve chest
in the usual way. In addition thereto, I provide another valve chest through.
which the steam passes into the main valve chest by a suitable port or ports. At
the back of the main slide valve I place a spring or springs so as to prevent the
steam escaping past the back of the main slide valve into the main slide valve chest,
and thus forming a reservoir at the ends of the main valve chest. These ports
between the expansion or cut off valve chest and the main valve chest are opened
or closed by means of the expansion or cut off valve, which is so actuated that it
opens or closes the port or ports under its control during each stroke of the piston
in the steam cylinder. Instead of a second valve chest as hereinbefore described, I
can make a single valve chest to answer the same purpose by placing a plate with
suitable openings between the main slide valve and the expansion or cut off valve,
which above mentioned openings will serve as the port or ports herein before
described, as being opened or closed by the expansion or cut off valve.
The expansion or cut off valve is actuated by a kind of link motion, consisting of
two eccentrics with bands and rods, and a sliding link coupling the ends of the
rods further from the eccentrics. The link works up and down on a pin in the end
of the expansion valve spindle by means of a rotatory or other suitable governor
driven in the usual way by the engine. The aforesaid eccentrics are mounted side
by side on a stud or shaft which rotates in suitable bearings, and is driven from the
engine by elliptical or circular toothed gearing or its equivalent in such a way
that the eccentrics make two revolutions for every one revolution made by the
engine crank shaft. By this method, the lead is equal all through, and the steam
is cut off more instantaneously than by any other method.
I call one of the aforesaid eccentrics the positive eccentric, and the other the
negative eccentric. The positive eccentric causes the expansion valve to open the
ports and admit steam to the main valve chest, and the negative eccentric operates
in closing the ports and shutting off steam from the main valve chest. The
position of the link on the pin in the end of the valve spindle determines which
eccentric has most influence on the expansion or cut off valve in causing it to close
the port or ports sooner or later after the piston has commenced its stroke. The
aforesaid position of the link being determined by the governor, the speed and
admission of steam to the engine is thereby automatically regulated.
In order to clearly explain the nature of my Invention, I refer to the accom-
panying Drawings.
Figure 1. is a side elevation of an engine with my expansion gear fitted to it.
Figure II. is a plan of the same.
Figure III. is a front end elevation of the same.
The letters are the same in all the Drawings and Figures. A is the steam
cylinder; B is the piston; C is the usual slide valve; C, C, are the springs that I
place at the back of the slide valve C as herein before described; D is the expansion
or cut off valve chest hereinbefore described, through which the steam passes into
the main valve chest by the ports E, E, E. When I make a single valve chest
instead of two valve chests as hereinbefore described, D' is the plate with the
suitable openings E, E, E, between the main slide valve and the expansion or cut

page_text: off valve as herein before described. These ports or suitable openings E, E, E, are
opened or closed by the expansion or cut off valve F herein before described. G is
the expansion or cut off valve spindle. H is the sliding link which works up and
down on the pin I in the end of the expansion or cut off valve spindle G as herein-
before described. K, K', are the two eccentrics with bands and rods which
actuate the expansion or cut off valve F through the expansion or cut off valve
spindle G, mounted side by side on the stud or shaft M which is driven from the
engine by elliptical or circular toothed gearing L, L', as hereinbefore described.
N is the governor driven by the engine which determines the position of the link
H on the pin I in the end of the valve spindle G, by means of the lever and rod
0, 0¹, as herein before described.
Having thus particularly described and clearly explained my Invention, and in
what manner the same is used, I now state my claims in my said Invention to be
as follows:-
1. The expansion or cut off valve fitted in the second valve chest to the main
valvo chest as hereinbefore described and actuated by the link motion, consisting of
two eccentrics with bands and rods, and a sliding link in the manner hereinbefore
described, whereby the steam is cut off instantaneously.
2. Instead of a second valve chest as hereinbefore described, a single valve chest
may be made to answer the purpose by substituting a plate with suitable openings
between the main slide valve and the expansion or cut off valve as hereinbefore
described.
3. The determination by the governor of the action and effect of the before
mentioned expansion or cut off valve as herein before described, which governor
being driven by the engine, the speed and admission of steam to the engine is
thereby automatically regulated as hereinbefore described.
4. The application of the said improvements as hereinbeforo described in
automatic expansion gear to every kind of engine, whether high or low pressure,
condensing, or non condensing marine, locomotive, portable or fixed, and whether
the motive power employed be stenin, gas, air, or any other, in the manner and for
the purpose herein before described, and declared and shown in the accompanying
Drawings.
In witness whereof, I, the said James Noah Paxman, have hereunto set my
hand and seal, this Nineteenth day of December, in the year of our Lord
One thousand eight hundred and seventy nine
Witness,
MALCOLM CHARLES MACRAY,
26, Budge Row, E.C.
JAMES NOAH PAXMAN. (L.S.)