Improvements in Valves and Valve Gear for Steam Engines.
Year: 1889

page_text: Date of Application, 5th Apr., 1889
Complete Specification Left, 20th May, 1889-Accepted, 22nd June, 1889
PROVISIONAL SPECIFICATION.
Improvements in Valves and Valve Gear for Steam Engines.
We, DAVID CARMICHAEL, of Ward Foundry, Dundee, in the County of Forfar,
North Britain, Engineer, and ALEXANDER MACKIE, of the same place, Draughtsman,
do hereby declare the nature of this Invention to be as follows that is to say :---
This Invention has for its object to improve the construction of valves and valve
gear for steam engines, and is applicable more particularly to valves and gear of what
is known as the "Corliss " type.
In carrying out the Invention each valve instead of being made with its acting or
port-covering part in the form of a single cylindrical segment like an ordinary
Corliss valve, is made with two narrow cylindrical segments with an opening or
port between them equal to the port opening. The concave cylindrical port face on
which the valve works is made with two ports, which communicate with one cylinder
passage. In the gable or partly annular casting in which are ordinarily formed the
admission and exhaust valve boxes for one end of the cylinder, the short additional
or branch passage to the second port can conveniently be formed in a hitherto
unutilised part of the casting without increasing the size of the casting or of the
clearance space, there being ample space for the passage except just at the middle of
the length of the valve where the convexity of the cylinder is close to the valve
box. With a given length of valve the improved construction allows of a compara-
tively small angular movement of the valve; or the advantage may be taken partly
in diminished movement of the valve and partly in increased area of the passage
and ports. We prefer to apply the same improved construction to the exhaust valves
also.
In the gear for working the improved valves and which is also applicable like
ordinary Corliss valve gear to various kinds of valves, we have fixed on each valve
spindle a lever one end of which is connected by a rod to the usual spring and
accompanying dashpot for closing the valve. The other end of the lever has fixed on
it a stud on which there is keyed a steel catch piece made with a catching edge
parallel to the axis of the stud. A recess is cut out of the middle of the catch piece
and its edge to receive the boss of a trigger fitted to turn loosely on the stud and
made with an arm extending to a position near the axis of the valve spindle and
having jointed to it a rod connecting it to the governor mechanism. Motion is as
usual given to the valve by a reciprocating rod worked by an oscillating wrist plate
or other equivalent mechanism. The rod is made with a flat end the breadth of
which
equal to the length of the catch piece, there being a slot in the middle of
the broad part for the passage of the trigger arm. The underside of the flat end
of the rod is made with steel catch edges to engage with the edges of the catch piece
which they do when moving in the direction to open the valve. The disengagement
of the rod from the catch piece, and the consequent cut of or closing movement of
the valve, is effected by a cam projection on the boss of the trigger, the motions
of the parts making this cam projection lift the rod clear of the catch piece sooner
or later in the stroke according to the position of the trigger arm as determined by .
the governor action and the adjustment of the parts.
Dated this Fourth day of April 1889
EDMUND HUNT,
Applicants' Agent.

page_text: COMPLETE SPECIFICATION
Improvements in Valves and Valve Gear for Steam Engines.
We, DAVID CARMICHAEL, of Ward Foundry, Dundee, in the County of Forfar,
North Britain, Engineer, and ALEXANDER MACKIE, of the same place, Draughtsman,
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, that is to say :-
This Invention has for its object to improve the construction of valves and valve
gear for steam engines, and is applicable inore particularly to valves and gear of what
is known as the Corliss type.
In carrying out the Invention each valve instead of being made with its acting
or port-covering part in the form of a single cylindrical segment like an ordinary.
Corliss valve, is made with two narrow cylindrical segments with an opening or
port between them. The concave cylindrical port face on which the valve works is
made with two ports, which are each equal to the port opening in the valve, and
which communicate with one cylinder passage. With a given length of valve the
improved construction allows of a comparatively small angular movement of the
valve; or the advantage may be taken partly in diminished movement of the valve
and partly in increased area of passage and ports. We prefer to apply the saune
improved construction to the exhaust valves as well as to the admission valves.
In the gear for working the improved valves and which is also applicable, like
ordinary Corliss valve gear, to various kinds of valves, we have fixed on each admission-
valve spindle a lever one end of which is connected by a rod to the usual spring and
accompanying dashpot for closing the valve. The other end of the valve lever has
fixed on it a stud on which there is keyed a steel catch piece, with which a catching
edge on the usual reciprocating rod engages when opening the valve; and a trigger
centered on the valve-lever stud and connected to the governor serves to lift the
reciprocating rod out of gear from the catch piece at the proper time.
And in order that the said Invention and the manner of performing the same may
be properly understood we hereunto append two sheets of explanatory drawings to be
hereinafter referred to, and representing examples of our improved valves and valve
gear.
Figure, 1, on sheet, 1, of the drawings is a sectional side elevation of a horizontal
steam-engine cylinder as fitted with our improved valves and valve gear, the admission
and exhaust valves and passages at one end of the cylinder being sectioned as at a
position near their middles. Figure, 2, is a section of the admission valve box and
passages as taken nearer the sides of the cylinder; and figure, 3, is a section as taken
between the positions of the sections in figures, 1, and 2,. Figure, 4, on sheet, 2, is a
transverse vertical section as taken through an admission valve box and part of the
cylinder. Figure, 5, is a plan of an admission valve, figure, 6, is a corresponding
vertical section, and figure, 7, is a sectional end elevation. Figures, 8, to 14, are
enlarged detail views of the improved parts of the valve gear. In these drawings the
same reference letters and numerals are used to mark the same or like parts wherever
they are repeated.
P.
Each admission valve, A, is made with two segmental cylindrical port-covering
segments, 21, 22, with an opening or port, 23, between them; and the two segments
are connected by cross bars, and by ends, 24, which ends are made with slots for
the crosses, 25, on the valve spindle, 26, by means of which the valve is worked.
The concave cylindrical port face in the valve box, 27, and on which the valve, A,
works is made with two ports, 28, 29, which communicate with one cylinder passage,
In the gable or partly annular casting, G, in which are ordinarily formed the admission
and exhaust valve boxes, 27, 30, for one end of the cylinder, the short additional or
branch passage, to the second admission port, 29, can conveniently be formed in a
hitherto unutilised part of the casting without increasing the size of the casting or of
the clearance space, there being ample space for the passage, except just at the

page_text: middle of the length of the valve where the convexity of the cylinder is close to the
inner side of the valve box, 27. The section in figure, 4, is taken as through
the passage, P, and shows the openings into that passage of the additional port, 29,
strengthening ribs dividing the passage from that port into several openings. The
exhaust valve, E, shown in figure, 1, is of the same construction as the admission
valve, A, but the port passages, 31, 32, in connection with which it works being on
the side of the valve box, 30, further from the cylinder can be of full width throughout
their length. If preferred, the valve box, 27, may be placed at a slightly greater
distance from the cylinder, which will allow of the passages of the added port, 29, being
made of full width up to the middle rib.
The improved valve-gear details as applied to an admission-valve spindle, 26, are
shown in sectional side elevation in figure, 8, in sectional end elevation in figure, 9,
and in sectional plan in figure, 10. The valvo spindle, 26, has fixed on it a lever, L,
in the lower end of which there is fixed a stud, S, having keyed on it a steel catch
piece, C, also shown separately in cross section in figure, 11, and in elevation in
figure, 12. This piece, C, is made with a catching edge, 33, parallel to the stud, S,
and a recess is cut out of the middle of it to receive the boss of a releasing trigger, T,
also shown separately in figures, 13, and 14, in side and edge view. This trigger, T,
is made with an arm, 34, extending to a position near the axis of the valve spindle, 26,
and having jointed to it a rod, 35, connecting it to the governor mechanism which
may be of any suitable known kind. Motion is, as usual, given to the valve by a
reciprocating rod, R, worked by an oscillating lever or wrist plate, W, or other
equivalent mechanism. The rod, R, is made with a flat end, 36, the breadth of which
is equal to the length of the catch piece, C, there being a slot, 37, in the middle of
the broad part, 36, for the passage of the trigger arm, 34. The underside of the flat
end, 36, of the rod, R, is made with steel catch edges, to engage with the edges, 33,
of the catch piece, C, which they do when the rod, R, moves in the direction for
opening the valve, and the subsequent release or cut-off movement of the valve is
effected by a cam projection, 38, on the boss of the trigger, T, the motions of the
parts making this cam projection, 38, lift the rod, R, clear of the catch piece, C, sooner
or later in the stroke of the engine, according to the position of the trigger arm, 31,
as determined by the governor action and the adjustment of the parts.
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:-
1. The improved construction of Corliss valves for steam engines, each valve being
made with two port-covering segments and being arranged to work over two ports,
substantially as hereinbefore described and as shown in the accompanying drawings.
2. The improved construction combination and arrangement of catching parts and
releasing trigger details of Corliss valve gear, substantially as hereinbefore described
and as shown in the accompanying drawings.
Dated this Eighteenth day of May 1889.
EDMUND HUNT,
Applicants' Agent.