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

page_text: Date of Application, 8th May, 1894
Complete Specification Left, 22nd Feb., 1895-Accepted, 6th Apr., 1895
PROVISIONAL SPECIFICATION.
Improvements in Expansion Gear for 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 Application relates to a method whereby the working fluid is automatically
cut off from the working cylinders of central valve engines.
Instead of hanging the working or main eccentric or eccentrics directly on the
crank pin, we hang it or them on another eccentric or eccentrics forming a certain
angle or angles with the crank pin, the working or main eccentric or eccentrics
being placed under the control of a governor in such a manner so that its or their
travel and angle of advance is or are varied according to the position of the
governor balls, in order to vary the point of cut off.
The movement of the governor balls is transmitted to the working eccentric or
eccentrics either by fluid pressure or linkage and gearing.
Instead of hanging the working or main eccentric or eccentrics on other eccentrics
or cranks we can secure the same end by hanging an eccentric or eccentrics on a
fixed pin or pins located at a point or points in line with the crank pin and at a
point or points diametrically opposite or thereby to the fixed pin or pins we connect
the eccentric or eccentrics to the governor in such a manner that it or they receive
a movement from the governor balls in order to alter its or their travel and angular
advance, so as to vary the point of cut off. Instead of altering the cut off
automatically by the governor we can in either case vary the travel and angular
advance of the main or working eccentric or eccentrics by hand so as to give any
desired cut off.
Dated this 7th day of May 1894.
WM. CAMERON.
JOHN COCHRANE.
Improvements in Expansion Gear for Central Valve Engines
Operated by Steam or other Fluid Pressure.
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 a method whereby the working fluid is automatically
cut off from the working cylinder of central valve engines.
Instead of hanging the working eccentric or eccentrics directly on the crank
pin we hang it or them on another eccentric or eccentrics forming a certain angle
or angles with the crank pin the working or main eccentric or eccentrics being
Price 871

page_text: placed under the control of a governor in such a manner so that its or their travel
and angular advance is or are varied according to the position of the governor
balls in order to vary the point of cut-off. The movement of the governor balls
is transmitted to the working eccentric by linkage.
Instead of hanging the working or main eccentric or eccentrics on other
eccentrics or cranks we can secure the same end by hanging an eccentric or
eccentrics on a fixed pin or pins located at a point or points in line with the crank
pin and at a point or points diametrically opposite or thereby we connect the
eccentric or eccentrics to the governor in such a manner that it or they receive a
movement from the governor balls in order to alter its or their travel and angular
advance so as to vary the point of cut-off. Instead of altering the point of cut-off
automatically by the governor we can in either case vary the travel and angular
advance of the main or working eccentric or eccentrics by hand so as to give any
desired cut-off.
In order to shew clearly the nature of our invention we will proceed to describe
the annexed drawings.
Fig. 1, Sheet 1, shews an arrangement in which the working or main eccentrics
are hung on secondary eccentrics or cranks.
Fig. 2, Sheet 1, is sectional elevation shewing the governor weights and method
of connecting the weights to the eccentrics.
Fig. 1, Sheet 2, shews another arrangement whereby the same results are
attained. In this arrangement, the eccentric is hung on a pin located at a point in
line with the crank pin.
Fig. 2, Sheet 2, is a sectional elevation shewing the method of coupling the
governor weights to the eccentric. In both arrangements the governor weights
and springs are carried by a disc which is securely fixed to the crank shaft of the
engine.
Referring to Figs. 1 & 2, Sheet 1. The secondary eccentrics a a are securely
fixed to the crank pin c at a predetermined angle. The working eccentrics bb are
hung on to the secondary eccentrics and are capable of turning thereon. The
relation of the working and secondary eccentrics centres to each other and to the
centre of the crank pin are such that when the governor weights ee are in
the position shewn in Fig. 1, Sheet 1 the valve has its maximum travel the engine
being at its minimum speed within the range of variation allowed by the governor.
On the speed of the engine increasing say to the normal speed the governor weights
move outwards under the action of centrifugal force overcoming the resistance of
the springs ff. This movement is transmitted to the working eccentric by
spindles gg and link and to the working eccentric b by link and the spindle 7
and lever bringing their centres towards the centre line passing through the
crank shaft and crank pin, the result of which is to alter their angular advance and
decrease their eccentricity or throw thus causing the valve which is operated by
these eccentrics to close the steam ports earlier in the pistons stroke. On the
speed of the engine further increasing the governor weights will move further
outwards until they are running in their maximum plane of revolution when the
engine will be running at its maximum speed within the variation allowed by the
governor. This further movement will have brought the centres of the working
cccentrics b¹ nearer to the before-mentioned centre line further decreasing their
angular advance and eccentricity and will now cause the valve to close the steam
port at zero of the pistons travel.
Both the working eccentrics bare coupled to one valve of a simple engine or
valves of a compound or multi-compound engine of the central valve type.
Although two are shewn, one may be readily coupled to the valve or valves without
in any way interfering with the efficiency of the system.
Fig. 3, Sheet 1, shews the lever and block k by which the movement of the
governor weights is transmitted to the working eccentric b¹.
Instead of automatically varying the eccentricity or throw of the working
eccentrics, we can by suitably coupling the spindles gg by a rod fitted with a nut

page_text: screwed right and left hand, the ends of the spindles being fitted with suitable
levers, for that purpose, vary the eccentricity or throw and angular advance of the
working eccentrics by hand.
Referring to Figs. 1 & 2, Sheet 2. The same letters refer to similar parts in
both combinations. In this combination the eccentric is hung on a pin located on
the continuation of the line which passes through the centres of the crank shaft
and crank pin. The relation which the centre of the eccentric bears to the centre
of the crank pin is the same as in the combination referred to in Sheet 1 of the
annexed drawings and the movement of the governor weights e e causes the centre
of the eccentric 6' to move through very approximately the same path as that of
the working eccentric described in connection with Sheet 1 of the annexed
drawings and consequently the results produced are similar. These ends are
attained by hanging the eccentric b¹ on a pin m the eccentric being cut away in
order to clear the crank pin c. The movement of the governor weights ee is
transmitted to the eccentric by and through spindles gg levers nn and the
link h. The eccentric may operate the valve of a simple engine or valves of a
compound or multi-compound engine of the central valve type.
Instead of automatically varying the eccentricity or throw and angular advance
of the eccentric we can by suitably coupling together the ends of the spindles g g
vary the eccentricity and angular advance of the eccentric by hand and so obtain
any desired cut-off.
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. On a crank pin a working or main eccentric hung on a secondary eccentric
substantially as and for the purpose set forth.
2nd. The combination of a secondary eccentric secured to a crank pin, a working
or main eccentric and a governor substantially as shewn and described in connection
with Sheet 1 of the annexed drawings.
3rd. An eccentric having a suitably shaped hole to admit of a movement about
a crank pin, and hung on a pin located on a line passing through the centres of a
crank shaft and crank pin substantially as and for the purpose set forth.
4th. The combination of an eccentric hung as in the 3rd claiming clause and a
governor substantially as shewn and described in connection with Sheet 2 of the
annexed drawings.
Dated this 6th day of February 1895.
JOHN COCHRANE.
WM. CAMERON.