Improvements in Expansion Gear of Central Valve Engines Operated by Steam or other Fluid Pressure.
Year: 1894

page_text: Date of Application, 19th Apr., 1894
Complete Specification Left, 18th Jan., 1895-Accepted, 9th Mar., 1895
PROVISIONAL DIUITIATION.
Improvements in Expansion Gear of Central Valve Engines Operated
by Steam or other Fluid Pressure.
We, WILLIAM CAMERON of Maryport in the County of Cumberland,
Mechanical Engineer, and JOHN COCHRANE of Grahamston Engine Works,
Barrhead, in the County of Renfrew, Engineer do hereby declare the nature of
this invention to be as follows :-
This invention relates to automatic expansion gear of central valve engines,
either single or double acting and has for its object the means whereby greater
economy in the use of the working fluid is attained.
Hitherto as far as we are aware the supply of working fluid to central valve
engines has been cut off from the working cylinder by a port in the tubular piston
rod passing through a fixed plate or diaphragm or by means of a movable sleeve,
generally the former method is adopted.
In this method the point of cut off is constant for all loads consequently the only
method of maintaining a constant speed under varying loads or boiler pressure is
by increasing or decreasing the pressure of the working fluid supplied to the engine
by means of a throttle valve controlled by a governor. In this method of regulation
the full boiler pressure is available in the steam chest at one point only; that is,
when the governor is running in its minimum plane of revolution when the throttle
valve will be full open; at all other points the steam pressure in the valve chest
is less than the boiler pressure, which will drop as much as 45% when the engine
is running under its normal load and exhausting into the atmosphere.
In order to maintain practically the boiler pressure in the steam chest, and render
the same available as the initial pressure in the cylinder or high pressure cylinder
of compounds or multi-compounds we cause the piston valve to cut off the supply
of the working fluid at any point of the stroke such as from zero to g. To attain
this end and secure automatic expansion or cut off, we control the piston valve or
valves by an eccentric mounted on the crank pin in such a manner as will admit of
its travel and angular advance being varied by a governor mounted on the crank
shaft, or by hand. The movement of the governor balls is transmitted to the
eccentric by fluid pressure or by linkage and gearing.
In tandem compounds & multi compounds single or double acting having one
complete system connected to one crank, and having two or more systems coupled
to their respective cranks. One system is supposed to consist of high & low
pressure cylinders, or high intermediate and low pressure cylinders or any number
of cylinders provided always that steam at boiler pressure or thereabouts is
admitted to one and exparded in various stages in the others, being finally sent to
the atmosphere or condenser. The valve of each such system being operated by
one eccentric each of these eccentrics may be under the control of its own governor
or all may be controlled by one.
In engines single or double acting in which the high pressure cylinder alone or
in conjunction with an intermediate cylinder is or are connected to one crank and
the other intermediate or low pressure cylinders to one or more cranks, the
governor only controls that eccentric which operates the valve or valves of that
line which contains the high pressure cylinder, the other eccentrics being variable
by hand; in this way the power can be equalized between the cranks.
Dated this 18th day of April 1894
JOHN COCHRANE.
WM. CAMERON.

page_text: Improvements in Expansion Gear of Central Valve Engines Operated.
by Steam or other Fluid Pressure.
We WILLIAM CAMERON of Maryport in the County of Cumberland,
Mechanical Engineer and JOHN COCHRANE of Grahamston Engine Works
Barrhead in the County of Renfrew Engineer do hereby declare the nature of
this invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement :-
This invention relates to automatic expansion gear of central valve engines and
has for its object the means whereby greater economy in the use of the working
fluid is attained.
Hitherto as far as we are aware the supply of working fluid to central valve
engines has been cut off from the working cylinder by a port in the tubular piston
rod passing through a fixed plate or diaphragm or by means of a movable sleeve
generally the former method is adopted.
In this method the point of cut off is fixed for all loads, and the only method of
maintaining a constant speed under varying loads or boiler pressures is by increasing
or decreasing the pressure of the working fluid supplied to the engine by means of
a throttle valve controlled by a governor.
In order to maintain practically the boiler pressure in the steam chest and render
the same available as the initial pressure in the cylinder or high pressure cylinders
of compounds or multi-compounds, we cause the piston valve to cut off the supply
of the working fluid at any point of the pistons stroke as from zero to ģ.
To attain this end and secure automatic expansion or cut off, we control the
piston valve or valves by an eccentric mounted on the crank pin in such a manner
as will admit of its travel and angular advance being varied by a governor on the
crank shaft or by hand. The movement of the governor balls is transmitted to the
eccentric either by fluid pressure or by linkage and gearing.
In tandem compounds & multi-compounds having one complete system connected
to one crank and having two or more such systems coupled to their respective
cranks, one system consists of high and low pressure cylinders, or high, intermediate
and low pressure cylinders, or any number of cylinders provided always steam at
boiler pressure or thereabouts is admitted to one, and expanded in various stages
in the others being finally sent to the atmosphere or condenser. The valves of
each system being operated by one eccentric; each of these eccentrics may be
controlled by separate governors or all may be controlled by one.
In engines in which the high pressure cylinder alone or in conjunction with an
intermediate cylinder is connected to one crank the other intermediate or low
pressure cylinder being connected to one or more cranks; the governor only
controls that eccentric which operates the valve or valves of that line which
contains the high pressure cylinder the other eccentrics being made variable by
hand.
In this way the power can be equalized between the cranks.
Referring to the annexed drawings
Figs. 1, 2 & 3 Sheet 1 shew an arrangement whereby the angle of advance and
the travel or throw of the eccentric is altered and the cut off varied by the action
of the governor balls.
Figs. 4 & 5 Sheet I shew the eccentric and the means whereby the movement of
the governor balls is transmitted to the eccentric.
Figs. 1. 2. & 3 Sheet I shew another combination for effecting the same
purpose.
In both combinations the eccentric is hung on the crank pin and is directly

page_text: or rods.
coupled to the piston valve or valves which work in the tubular piston rod
Referring to Figs. 1. 2. 3. 4 & 5. Sheet I
In this combination we employ a fluid to transmit the movement of the governor
weights or balls a. a produced by centrifugal force and the action of the springs b, b.
to the eccentric, d. The fluid is contained in the cylinder, c, which is fitted with a
piston, e. This piston is coupled in any convenient way to the governor weights..
The eccentric, d. is mounted on a rectangular piece formed on the crank pin and
on which it is free to slide. Two plungers or rams g. 9, are secured to the
rectangular piece these rams work in recesses or cylinders formed in the eccentric
clearly shewn in Figs. 4 & 5 Sheet I. ducts or passages h, h run from each end of
the cylinder c through the crank pin and each ram.
When the speed of the engine reaches the minimum speed of the governor the
weights begin to move outwards, and on the speed of the engine reaching the
normal, the weights will be running in their normal plane of revolution, the piston e
being then at the middle of its travel. During this movement the fluid which was
at the bottom of the cylinder will have been forced under the end of the ram y,
and cause the eccentric to move to the left of the position shewn in Fig. 4. Sheet I
whilst the fluid contained in the recess in which the plunger 9 works will be
returned to the top end of the cylinder c in this way the eccentric will take up
positions corresponding to the positions of the governor weights. The supply of
the working fluid being cut off sooner or later according as the governor weights
are running above or below their normal plane of revolution.
The weights, springs & fluid cylinder are all located on and carried by a disc, m
which is securely fixed to the crank shaft.
Fig. 3 Sheet I shews the governor controlling eccentrics operating the valves of
cylinders driving on to, two cranks in a similar manner it may operate or control
the eccentrics of cylinders driving on to three or more cranks, suitable ducts or
passages being led from each end of the fluid cylinder e through the crank pins and
shaft to recesses in the eccentrics in which the plungers work, care being taken in
arranging the ducts or passages so as to produce in each of the eccentrics movements
in a given direction in relation to the direction in which the engine is intended to
TUD. At the end of the crank shaft shewn in Fig. 3 Sheet 1 a device is shewn
whereby the ducts or passages may be coupled up to an accumulator thus providing
means to make good any leakage which may occur. It will be apparent that each
eccentric may be varied by an independent governor, also that the eccentric may
be varied by hand instead of automatically by governor. This would be done by
doing away with the weights & springs and connecting the piston rod of the fluid
cylinder e to a bandwheel and screw either directly or indirectly, the nut in which
the screw works being carried by the disc, m.
Figs. 1. 2. & 3 Sheet II refer to a combination in which the movement of the
governor weights or ball is transmitted to the eccentric by linkage.
Similar letters refer to similar parts in both combinations.
The movement of the governor weights a. a produced by centrifugal force and
the action of the springs 6b is transmitted to the eccentric by the spindles i, i
levers j, j and links k, k. The whole being mounted on or carried by the disc, m,
which is securely fixed to the crank shaft. The eccentric, d, is hung on a suitably
formed rectangular piece on the crank pin and on which it is free to slide clearly
shewn by Fig. 3 Sheet II. On the governor weights opening out the eccentric is
caused to slide along the rectangle on the crank pin thus altering its angle of
advance and throw or eccentricity. The supply of the working fluid being cut off
sooner or later, depending upon the position of the governor weights that is when
the governor weights are running in their minimum plane of revolution, the angle
of advance of the eccentric would be a maximum, when measured from a line
running through the centre of the shaft and crank pin and the eccentricity or
throw of the eccentric would also be a maximum the supply of the working fluid
would be continued to g of the pistons stroke. On the governor weights running in

page_text: .
their maximum plane of revolution the angle of advance and eccentricity would be a
minimum and the working fluid would be cut off at zero of the pistous stroke.
Either combination may be used to operate the piston valve or valves of simple,
compound or multi-compound high speed engines, the valves being suitable arranged
in tubular piston rods.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what we
claim is
1st. In fluid pressure engines an eccentric free. to slide on a suitable piece formed
on a crank pin substantially as and for the purpose set forth.
2nd. In fluid pressure engines the combination of an eccentric a fluid pressure
cylinder and a governor substantially as described and shewn by Figs. 1 to 5
Sheet 1 of the annexed drawings.
3rd. In fluid pressure engines the combination of an eccentric a governor and
connecting links substantially as described and shewn by Figs. 1. 2. & 3 Sheet II
of the annexed drawings.
Dated this 17th dow of Ianuar 1905
JOHN COCHRANE.
WM. CAMERON.