IMPROVEMENTS IN THE EXPANSION GEAR OF STEAM ENGINES
Year: 1878

page_text: LETTERS PATENT to Constantine de Negri, of 68, Stainford Street, Blackfriars,
in the County of Surrey, Engineer, for the Invention of "IMPROVEMENTS IN
THE EXPANSION GEAR OF STEAM ENGINES."
PROVISIONAL SPECIFICATION left by the said Constantine de Negri at tho
Office of the Commissioners of Patents on the 4th September 1878.
CONSTANTINE DE NEGRI, of 68, Stamford Street, Blackfriars, in the County of
Surrey, Engineer. "IMPROVEMENTS IN THE EXPANSION GEAR OF STEAM
ENGINES."
This Invention relates to improvements in the construction of engines, whereby
they are simplified and yet work on the most economical principle.
An engine constructed in accordance with my Invention, which might be either
high pressure or condensing, would have two slide valves, the principle one working
in the ordinary manner the inlet and exhaust steam, whilst the back valve works
the cut off, either automatically from the governors or by a lever, wheel, or like
arrangement at the command of the engine driver.
To construct a horizontal, stationary, or portable high-pressure engine with this
variable expansion gear, I cast or fix two bearings on the back of the main valve,
to carry the valve rod free to oscillate, but shouldered to prevent its lateral motion
without the valve, leaving enough room for the back valve to work freely between
the valve rod and main valve, by means of a screw or thread fastened on the valve
rod, and working either into a nut or between two rollers fixed near the centre of
the back valve. Now, following the valve rod out of the steam chest through the
stuffing box, I have a part of it either squared or feathered into a bush, so that the
rod can move laterally in the bush, and the bush can revolve or oscillate in a fixed
bearing provided for it, without being itself able to be moved laterally. Proceeding
further along the valve rod, I have attached to it a socket joint, into which a ball
on the end of the eccentric rod fits, and which forms the connection between the
Drine S1

page_text: eccentric and valve rods. Now, returning to the above-mentioned bush, I have a
short lever projecting from one of its shoulders, with a small roller free to revolve
on the lever's end, and fitting freely in a cam, which, when made to revolve on a
verticle axis, would impart, through the roller, to the short lever an intermittent rise
and fall, causing the valve rod to oscillate, at regular intervals between each direction,
in the outside bearing, stuffing box, and bearings on back of the main valve. Again,
within this cam, I cut a quick thread, into which the governor sleeve either screws
or carries rollers that fit, the sleeve being mounted upon the governor spindle in the
usual manner, and the governors being driven positively from the engine shaft.
Now, if when the back valve is in one of its two extreme positions on the main
valve, the one port or set of ports is open and the other shut, and when in the other
extreme position, the other port or set of ports is open, and the first one closed, and
if also the cam on the governors is so arranged, when the governors are down, as to
cut off the steam, say at half stroke, it will be clear that, provided the thread on
the governor sloove, when drawn through the cam gives it a lead, the cut-off will
come into action the earlier or later in proportion to the rise or fall of the
governors.
To construct other sorts of engines it can readily be understood how, according
to circumstances, it might be arranged to vary the cut-off by means of a lever or
hand wheel acting upon a similar bush to the sleeve of the governors.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Constantine de Negri in the Great Seal Patent Office on the 4th
March 1879.
CONSTANTINE DE NEGRI, of 68, Stamford Street, Blackfriars, in the County of
Surrey, Engineer. "IMPROVEMENTS IN EXPANSION GEAR OF STEAM ENGINES."
This Invention relates to improvements in the construction of engines, whereby
they are simplified and yet work on the most economical principle.
An engine constructed in accordance with my Invention, which might be either
high pressure or condensing, would have two slide valves, the principle one working
in the ordinary manner the inlet and exhaust steam, whilst the back valve works
the cut-off, either automatically from the governors or by a lever, wheel, or like
arrangement at the command of the engine driver.
To construct a horizontal, stationary, or portable high-pressure engine with this
variable expansion gear, I cast or fix two bearings on the back of the main valve,
to carry the valve rod free to oscillate, but shouldered to prevent its lateral motion
without the valve, leaving enough room for the back valve to work freely between
the valve rod and main valve, by means of a screw or thread fastened on the valve
rod, and working either into a nut or between two rollers fixed near the centre of
the back valve. Now, following the valve rod out of the steam chest through the
stuffing box, I have a part of it either squared or feathered into a bush, so that the
rod can move laterally in the bush, and the bush can revolve or oscillate in a fixed
bearing provided for it, without being itself able to be moved laterally. Proceeding
further along the valve rod, I have attached to it a socket joint, into which a ball
on the end of the eccentric rod fits, and which forms the connection between the
eccentric and valve rods. Now, returning to the above-mentioned bush, I have a
short lever projecting from one of its shoulders, with a small roller free to revolve
on the lever's end and fitting freely in a cain, which, when made to revolve on a
vertical axis, would impart, through the roller, to the short lever an intermittent
rise and fall, causing the valve rod to oscillate at regular intervals between each
direction, in the outside bearing, stuffing box, and bearings on back of the main
valve. Again, within this cam I cut a quick thread, into which the governor sleeve
either screws or carries rollers that fit, the sleeve being mounted upon the governor
spindle in the usual manner, and the governors being driven positively from the
engine shaft.
Now, if when the back valve is in one of its two extreme positious on the main
valve, the one port or set of ports is open and the other shut, and when in the other
extreme position the other port or set of ports is open, and the first one closed, and
if also the cam on the governors is so arranged, when the governors are down, as
to cut off the steam, say at half stroke, it will be clear that, provided the thread
on the governor sleeve, when drawn through the cam gives it a lead, the cut-off
will come into action, the carlier or later in proportion to the rise or fall of the
governors.
To construct other sorts of engines it can readily be understood how, according
to circumstances, it might be arranged to vary the cut-off by means of a lever or
hand wheel acting upon a similar bush to the sleeve of the governors.
In order that my Invention may be thoroughly understood, I proceed to explain
the annexed Sheet of Drawings, similar letters being employed to denote the corre-
sponding parts in the four views.
Figure represents a cross section through the steam cylinder, steam chest, and
valves, Figure 2, a side elevation, Figure 3, an end elevation; and Figure 4, a
plan, part sectional of those parts of a portable engine, to which my Invention has
reference. a being the main valve, with the bearings or lugs b and c cast on it, which
carry the valve rod d, on which last is fastened by pins, the tube e, with the thread of
a screw on it, and also acting as shoulders to prevent the valve rod moving laterally

page_text: without the valve a; fis the back valve, with two rollers shown, for the thread on e
to work between. g is that part of the valve rod which is squared and can work
laterally in the bush h, which again is free to oscillate in the fixed bearing i. kis
the socket joint into which fits the ball (dotted) on the end of the eccentric rod m,
forming the connection between the eccentric and valve rods. Now, in Fig. 3 can
be seen the lever n fixed to one of the shoulders of the bush h, with a small roller
at the end of it, which works in the can o, this last being screwed over a quick
thread cut on the sleeve 2 of the governors q. The governors are driven from
the engine shaft through the medium of the bevil wheels s, t, u, and v, and side
shaft x.
Now, it is clear that the cutting off of steam from either side of the cylinder is
brought about by the rising and falling of the lever n through the medium of the
thread on the tube e, which at the same time opens the ports between the valves on
the opposite side preparatory to the main valve a getting into position for taking
steam on the other side. Also, that if the engine is set to cut off steam, say at half
stroko at its proper speed, should the speed tend to increase, the governors flying
out bring about an earlier rise and fall of the lever n through the earlier relative
position given to the cam o, thereby cutting off steam carlier and returning the
engine to its regular speed.
Having now described the nature of my Invention, and the manner in which the
same is to be carried out, I wish it to be understood that I do not confine myself to
the use of a cam for imparting the oscillating motion to the lever n, as herein-before.
described, but might in its place, by turning the lever n in a vertical position, use
a small eccentric to be mounted in the same way as the cam o, but what I claim as
novel is,―
Firstly. The simplifying of a double-valved engine, by having at the same time
only one stuffing box and gland in the steam chest, ono valve rod, and one eccentric
rod.
Secondly. The combination of a reciprocating and oscillating motion imparted to
the valve rod, as herein-before described.
Thirdly. The thread attached to the valve rod, and working into a nut or
between two rollers, imparting a differential motion to the valves, as herein-before
described.
Fourthly. The general arrangement, as herein described and shewn.
In witness whereof, I, the said Constantine de Negri, have hereunto set my
hand and seal, this Third day of March, in the year of our Lord One
thousand eight hundred and eighty-nine.
A DE NEARL
C.
C DE NEGRI
(L.S.)