Improvements in Valve Motion and Valves for Steam and other Fluid Pressure Engines.
Year: 1894

page_text: Date of Application, 28th July, 1894
Complete Specification Left, 29th Apr., 1895-Accepted, 15th June, 1895
PROVISIONAL SPECIFICATION.
Improvements in Valve Motion and Valves for Steam and other
Fluid Pressure Engines.
We JOHN COCHRANE, of Grahamston Engine Works, Barrhead in the County
of Renfrew Engineer, and WILLIAM CAMERON of Maryport in the County of
Cumberland Mechanical Engineer do hereby declare the nature of this invention
to be as follows:-
According to this invention the piston valve or valves receive two movements,
one being the same as that of the piston the other being relative to that of the
piston in order to open and close at the proper time the steam and exhaust ports in
the tubular piston rod or rods of single acting simple, compound or multi-compound
engines.
In order to attain this end and to obtain a large opening of the steam and exhaust
ports with a late release and an early compression, we move the piston valve or
valves from a point on the connecting rod which describes during a revolution of the
crank pin an elongated ellipse.
The valve or valves are coupled to this point by suitable linkage. We can also
vary the point of cut off by varying one of the points of suspension, this may be done
either by hand or by the action of a governor.
In order to reduce the dead or waste space which require to be filled with steam
retained in the cylinder during compression we place on the piston valve stem, a
ring, between the piston valve controlling the steam port & that controlling the
exhaust port. The function of the ring being to cut off communication between that
steam retained in the cylinder during compression and the exhaust steam contained
in the space between the piston valves controlling the steam and exhaust ports. By
this means the waste space is reduced to that actually required for clearance between
the piston and cylinder end.
It is to be understoood that similar rings for effecting the same purpose are
placed between the piston valves controlling the steam and exhaust ports of each
cylinder when there are more than one cylinder as in the case of compound or
multi-compound engines.
Da of L... 1904
JOHN COCHRANE.
WM. CAMERON.
COMPLETE SPECIFICATION.
Improvements in Valve Motion and Valves for Steam and other
Fluid Pressure Engines.
We JOHN COCHRANE of Grahamston Engine Works Barrhead in the County
of Renfrew Engineer and WILLIAM CAMERON of Maryport in the County of
Cumberland Mechanical 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 :-
According to this invention the piston valve or valves receive two movements
one being the same as that of the piston the other being relative to that of the

page_text: piston in order to open and close at the proper time the steam and exhaust ports in
the tubular piston rod or rods of single acting simple, compound or multi-compound
engines.
In order to attain these ends and to obtain a large opening of the steam and
exhaust ports with a late release and compression, we move the piston valve or
valves from a point on the connecting rod which describes during a revolution of
the crank pin an elongated ellipse.
The valve or valves are coupled to this point by suitable linkage.
We
We can also vary the point of cut-off by varying one of the points of suspension;
this may be done either by hand or by the action of a governor. In order to reduce
the dead or waste spaces which require to be filled with steam, retained and
compressed in the cylinder during compression, we place on the piston valve
stem a ring, between the piston valve controlling the steam port, and that
controlling the exhaust port. The function of the ring being, to cut off
communication between that steam, retained in the cylinder, and the exhaust
steam contained in the space between the piston valves controlling the steam
and exhaust ports. By this means the waste space is reduced to that actually
required for clearance between the piston and cylinder end. It is to be under-
stood that similar rings for effecting the same purpose are placed between the
piston valves controlling the steam and exhaust ports of each cylinder when
there are more than one cylinder, as in the case of compound or multi-compound
engines.
Referring to Sheet 1, Figs. 1 & 2, of the annexed drawings which shew sections
of a compound single acting central valve engine (although a compound engine is
shewn, it is to be understood that any of the hereafter mentioned combination can
be used to operate the valve or valves of simple compound or multi-compound
engines), with one arrangement of our improved valve gear and valve.
The line of piston valves is operated from the pin a located at a suitable distance
from the centre line of the connecting rod, through the link band lever c, one end
being fixed to a bracket by a pin d on which it is free to turn, the other end e
being coupled to the valves by a link. In this case the point of connection between
the connecting rod and the lever c lies between the fulcrum d and end e and the
valve consequently moves upwards (that is, the movement of the piston valve is
slower than the engine piston and the relative movement is upward). The centre
of the pin d describes an ellipse with a flattened side; this together with the action
of the link band the fulcrum c cause the valve to open and close the ports rapidly,
giving a late release and early compression. The engine is single acting and is
about to make its effective downward stroke, the direction being as shewn by the
arrow. Steam is admitted to the valve chest f and enters the high pressure
cylinder g by the ports and j in the tubular piston rod; when the stroke is about
completed, the steam is exhausted from the upper side of the piston by the port k
to the under side of the cylinder or to the atmosphere or condenser in the case of
a simple engine. The steam port his controlled by the valve and the port ; by
the ring m the exhaust port by the valve n. During the downward stroke the
valves moving upward, the valve and ring m open the ports h and j until
about of the stroke is completed when the valve and ring now moving downward
closes them, and before the completion of that stroke, the ring m passes to the
bottom side of the port, that is, the port is opened by the upper edge of the
ring m and the port & is opened by the upper edge of the valve n, the steam being
exhausted from the upper side of the piston. This continues until about of the
upward stroke is completed, when the ring m and valve n closes the ports and k
respectively, the ring m cutting off communication between the steam in the
cylinder which is now being compressed and the steam contained in the space
between the valves land n, on the completion of the upward stroke the valves and
ring occupy the position shewn in the drawing, Sheet 1. The valves controlling
the steam and exhaust ports of the low pressure cylinder go through the same
cycle. The point at which the connecting rod is coupled to the lever a may be-at

page_text: the other side of the centre line of the connecting rod, that is, at the side furthest
away from the fulcrum d the valve being coupled to the lever c between the point
of attachment to the connecting rod and the fulcrum d.
Sheet 2 Figs. 1 and 2, shew a modification of our invention. The line of valves
being connected to the end a of the link b as in the arrangement shewn in Sheet 1,
the lever c is directly hung on a pin fixed in the connecting rods d d, the long arm
of the lever c being coupled to a fixed pin by a swinging link e. The movement
of the valves is identical to that described in connection with Sheet 1 of the annexed
drawings.
Sheet 3 Figs. 1, 2 and 3, shew another modification whereby the valve or valves
is or are caused to vary the point of cut-off, the points of release and compression
being practically unchanged. The combination is similar to that shewn on Sheet 2
with the addition of a suspension link which carries the pin 1 whose position is
now variable, the angle which the link e makes with the lever c being altered by a
governor or by hand, the pin d being so placed as to cause the angle to become
more acute the earlier the steam is desired to be cut off. The dotted position of
the link e and pin h indicate the position for a cut-off of of the piston's stroke,
C when
the suspension links are preferredly equal in length to the swinging lever
so proportioned there is little or no variation in the points of release and compression
throughout the range of cut-off. The suspension links are carried by a shaft g which
can be connected to a governor, or can be coupled to a hand-wheel in any suitable
manner so as to partially rotate it.
The same letters refer to similar parts in the combination shewn on Sheets 2
and 3.
When the combination shewn on Sheet 3 is used to operate valves in connection
with single acting engines as shewn in Sheet 1, having a high pressure cylinder or
high pressure cylinder and one or more low pressure cylinders operating one crank
and having two or more cranks, when we desire to arrange automatic to all the
cylinders, we couple the suspension links f to one shaft on spindle g and place it
under the control of a governor.
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 single acting central valve engines for the purpose of operating the valves
thereof. The combination of a lever having a fixed fulcrum, a coupling link and a
connecting rod having a projection carrying a pin which describe during a revolution
of the crank pin an ellipse substantially as described and shewn in connection with
Sheet 1 of the annexed drawings.
2nd. In single acting central valve engines, a ring secured to the piston valve
stem and located between the valves controlling the steam port in the tubular piston
rod, the valve controlling the exhaust, substantially as shewn and described in
connection with Sheet 1 of the annexed drawings.
3rd. In single acting central valve engines, the combination of lever hung on to
a connecting swinging lever and a connecting rod with a projection, substantially
as shewn and described in relation to Sheet 2 of the annexed drawings.
4th. In single acting central valve engines, the combination of a lever coupled to
the piston valve or valves hung on the connecting rod, a connecting rod with a
projection, a swinging lever and suspension links, substantially as and for the
purpose set forth.
5th. The combination as in the 4th claiming clause as shewn and described in
connection with Sheet 3 of the annexed drawings.
Dadh: 07th 1^. ^f Fab 1905
JOHN COCHRANE.
WM. CAMERON.