IMPROVEMENTS IN VALVE GEAR FOR STEAM ENGINES
Year: 1884

page_text: PROVISIONAL SPECIFICATION.
I THOMAS HUNT of Gorton Foundry Manchester in the County of Lancaster
Engineer do hereby declare the nature of said Invention for "IMPROVEMENTS IN
VALVE GEAR FOR STEAM ENGINES" to be as follows:-
My Invention has for its object to provide a valve gear for steam engines which
is capable of being readily altered for expansive action and for reversal of. the
valve or valves.
A gear constructed according to my Invention consists of a slotted link which
may be called the connecting-rod link in which slides a pin attached to any
convenient point either in or outside the longitudinal centre line of the connecting-
rod and partaking of the movement of the connecting-rod so that the pin gives a
vertical motion only to the link.
The required degree of movement imparted by the pin is determined by its
distance from the small or cylinder end of the connecting-rod, the total length of
the rod, and the length of the stroke of the piston.
The link is attached to a lever on the fixed centre of which is another slotted
link which may be called the valve link vibrating also on the same fixed centre
and to which valve link the rod connecting it with the valve is attached by a
sliding attachment by which when the rod is on one side of the centre of the valve
link the engine moves in the forward direction and when the rod is on the other
side of the centre the engine moves in the backward direction and by moving the
rod away from or nearer to the centre on either side a variation is given to the
length of the stroke of the valve to regulate expansive working to give the requisite
lead to the valve the longitudinal centre line of the connecting rod link is fixed at
an angle with the longitudinal centre line of the connecting rod when the engine
is on the centre and this angle can be varied to suit the lap and lead of the
valve.
The angle of the connecting rod link with the longitudinal centre line of the
connecting rod when the engine is moving forwards is reversed when the engine
moves in the backward direction a suitable arrangement of levers being provided
for this purpose.
OP
J. HENRY JOHNSON,
47, Lincoln's Inn Fields, London, W.C.

page_text: I THOMAS HUNT of Gorton Foundry Manchester in the County of Lancaster
Engineer do hereby declare the nature of this invention for "IMPROVEMENTS IN
VALVE GEAR FOR STEAM ENGINES and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:-
My Invention has for its object to provide a valve gear for steam engines which
is capable of being readily altered for working expansively and for varying the
lead of the valves and also for reversal of the valve or valves to reverse the
motion of the Engine.
Valve gear constructed according to my Invention consists of a slotted link
which may be called the "connecting-rod link" in which slides a pin attached to
any convenient point either in or outside the longitudinal centre line of the
connecting rod and partaking of the movement of the connecting-rod so that the
pin gives to the said link a vertical motion only. The required degree of movement
imparted by the pin is determined by its distance from the small or cylinder end of
the connecting rod, by the total length of the rod, and by the length of the stroke
of the piston The connecting rod link is attached to a lever, on the fixed centre
of which, and connected with it, is another slotted link, which may be called the
"valve link" vibrating also on the same fixed centre, to which valve link the rod
connecting it with the valve is attached by a sliding attachment, by which, when
the rod is on one side of the fixed centre on which the valve link vibrates, the
engine moves in the forward direction, and when the said rod is on the other side
of the said centre, the engine moves in the backward direction, and by moving the
rod away from or nearer to the said centre on either side, a variation is given to
the length of the stroke of the valve to regulate expansive working. To give the
requisite lead to the valve the longitudinal centre line of the connecting rod link is
fixed at an angular position with the longitudinal centre line of the connecting rod
when the Engine is on the dead centres, and this angle can be varied either when
the Engine is or is not in motion.
The said angular position of the connecting rod link with the longitudinal centre
line of the connecting rod when the Engine is on the dead centres and moving
forward, is in the reverse of that position when the engine is moving in the
backward direction, a suitable arrangement of reversing mechanism being provided
for the purpose of giving the said reverse angles to the connecting rod link.
And in order that my said Invention may be fully understood I shall now
proceed more particularly to describe the same and for that purpose shall refer to
the several figures on the annexed sheet of drawings the same letters of reference
indicating corresponding parts in all the figures.
Figure 1 is a side elevation of valve gear constructed according to my Invention,
a is the connecting rod in the longitudinal centre line of which is fixed a pin or
stud b carrying the block c which slides in the slot of the connecting rod link d

page_text: the length of the stroke of the piston in the cylinder n. The upper arm a or the
connecting rod link d is connected by the joint pine to the lever e¹ the other end
of the said lever being attached to or formed with the valve link f vibrating on the
fixed centre g. The valve link f is connected to the valve spindle h by the rod i
and block; which block can be moved to any required position in the alot of the
valve link fat or between the points and m by means of the rod k and levers k¹
and for the purpose of varying the length of the stroke of the valve and in
combination with the movement of the connecting rod link d as hereinafter
described for supplying the steam to the piston in the cylinder n to produce a
forward or backward movement of the engine.
The lower arm of the connecting rod link d is jointed by the pin o to the
link p and levers p¹ and k³ and by this means the angle of the connecting rod link d
with the longitudinal centre line of the connecting rod a, when the engine is on the
centre or dead points, is regulated and held fixed in the position required to give
the requisite lead to the slide valve, or to reverse the motion of the engine. The
full lines of the connecting rod link d show its position when the Engine is moving
in one direction and the dotted lines show its position when the Engine moves in
the opposite direction In this arrangement the movements of the connecting rod
link and the valve link are connected and dependent on each other.
8
Figure 2 is a side elevation and figure 2A a plan of an arrangement of the valve
gear in which motion is given to the connecting rod link d. from a point b outside
the longitudinal centre line of the connecting rod a In this arrangement the lower
arm d of the connecting rod link d is jointed by the pin o to the rod p and lever p¹
which latter is fixed on a shaft carrying a worm wheel or sector p³ with which
engages a worm 7 operated by a handle a and by this means the angle which the
connecting rod link stands at, relatively to the longitudinal centre line of the
connecting rod when the Engine is on the centres or dead points, is regulated and
fixed to give the requisite lead to the slide valve. In this arrangement therefore
the movements of the connecting rod link and the valve link are separate and
independent of each other, the adjustment of the block j in the slot of the valve
link, being independently effected by the lever k².
Figure 3 is a side elevation and figure 3A is a plan of another arrangement of the
said gear, As in Figure 1 the connecting rod a has in its longitudinal centre line
the pin b carrying the block c which slides in the slot of the connecting rod
link d.
The connection of the connecting rod link and valve link in this case is formed
as shewn in transverse section in Figure 3B by an arm & fixed to the side of the
link d The block j is adjusted in the slot of the valve link as before described by
the lever . The end at d² of the arm of the connecting rod link is connected by
the pin o to the rod p and lever p₁, and by this means the angle of the connecting
rod link with the longitudinal centre line of the connecting rod when the engine is
on the centres or dead points, is regulated and held fixed in the position required
to give the requisite lead to the slide valve, and direction of the movement of the
engine. In this arrangement the movements of the connecting rod link and the
valve link are separate and independent of each other.
Figure 4 is a side view of another arrangement of the valve gear. The upper
arm d¹ of the connecting rod link d is connected by the joint pin e to the valve link
lever e¹ situated backward of the valve link f.
In this arrangement also the movements of the connecting rod link and the valve
link are separate and independent of each other. The movement of the connecting
rod link being effected by the lower lever p¹, and that of the block j in the slot of
the valve link, by the upper lever .
I wish it to be understood that I do not claim broadly the obtaining of a'
movement for the slide valves from the connecting rod nor do I claim broadly the
use for that purpose of a slotted link herein called the connecting rod link in which
a pin in the connecting rod slides.

page_text: Having now particularly described and ascertained the nature of my said;
Invention and in what manner the same is to be performed I declare that what
I claim is
First. In valve gear the combination of what I have hereinbefore termed a
connecting rod link with what I have termed a valve link arranged and being
operated substantially as and for the purposes herein before described.
Second. The several arrangements and combinations of parts constituting the
valve gears substantially as herein before described and illustrated severally in
Figure 1. Figures 2 and 2 Figures 3. 3ª and 3B and Figure 4 of the accompanying
Drawings..