Improvements in Corliss or other Tripping Valve Gears for Steam Engines.
Year: 1898

page_text: Date of Application, 24th Feb., 1898-Accepted, 26th Mar., 1898
COMPLETE SPECIFICATION.
Improvements in Corliss or other Tripping Valve Gears for
Steam Engines.
We, JOHN HENRY HARGREAVES and JOHN GEORGE HUDSON, both of the Soho
Iron Works, Bolton, in the County of Lancaster, Engineers, 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:
Our said invention relates to those parts of Corliss or other tripping valve gears
which have to do with the closing of the steam distributing valves. The difference
of pressures on the back of a distribution valve and in the port over which the
valve works varies so considerably that the means provided for closing the valve is
with difficulty arranged to act with desired quickness when the preponderance
of pressure on the back of the valve is a maximum owing to the frictional
resistance due to such maximum pressure. On the other hand when the prepon-
derance of pressure is comparatively small, the closing force is greater than is
necessary, and the action abrupt and objectionable, irregularity in the working
of the valve and its gear arising therefrom. The object of our present invention
is to make the power for moving the valve approximately proportional to the
varying resistance to be overcome, for which purpose we employ means which
compensate for the differences in the pressures. Our improvements are applicable
to various arrangements of Corliss and other tripping valve gears; we however
prefer to adapt them to arrangements of the kind described in our Patent
Specification No. 2170 of 1894.
Examples of the application of our invention are shown on three accompanying
sheets of explanatory drawings which are hereinafter referred to in particularly
describing our improvements.
Figures, 1, and 2, on Sheet 1, of the drawings are sections as at right angles to
each other, showing one end of a Corliss valve and its box together with added
parts. The modification shown in these figures is to be used in connection with
dashpot apparatus such as is described in our earlier specification hereinbefore
referred to, or in connection with any other suitable arrangement of dashpot
apparatus.
Figures, 3, and 4, on Sheet 2, are a sectional plan and a vertical section of a
modification in which compensating parts are combined with steam-controlled
dashpot apparatus.
Figure, 5, on Sheet 3, is a sectional elevation and Figure, 6, is an end elevation of
some parts shown in Figure, 5, these figures showing a third mode of applying our
improvements.
In these drawings the same reference letters and numerals are used to mark
the same or like parts wherever they are repeated.
In the modification shown in Figures, 1, and 2, there is fixed on the end of the
valve chest, A, of the Corliss valve, B, a box, C, formed with a bearing for the
valve spindle, D. A lever, E, is fixed on the valve spindle and is connected by a
rod, F, to a piston, G, working in a cylinder, H, the lower end of which
communicates by a pipe, J, with the cylinder end or a passage communicating
therewith. The inner or upper side of the piston G, is subjected to the full
pressure in the valve chest, A, whilst its outer or lower side is acted on by whatever

page_text: pressure is at any time in the cylinder end. The lever, E, is so fixed on the valve
spindle, D, that the valve-chest pressure acting on the piston G, tends to close
the valve; and it follows that when the pressure in the valve ports is a minimum
and the preponderance of the pressure on the back of the valve consequently a
maximum, there will be a similar preponderance on the upper or inner side of the
piston yielding increased force for closing the valve and vice versa. The ordinary
valve-closing spring with which this modification of our improvements is combined,
is arranged and adjusted so as to overcome the inertia and normal friction of the
valve and its gear, the piston, G, dealing with the variable part of the resistance.
In the modification shown in Figures, 3, and 4, the piston, G, works in a
cylinder, H, which communicates by a pipe, K, with the valve chest, and by
a pipe, J, with the cylinder end. The rod, L, of the piston, G, works through
a stuffing box, M, and is fixed to. or formed on a piston, N, working in a cylinder
or dash-pot, P. The piston, N, is connected by a pair of links, Q, to a lever, R,
fixed on the spindle, D, of the Corliss valve, and across the links is fixed the steel
clip or catch plate, Q1, which engages with the clip, S, of the actuating gear, being
fixed to a plate, T, jointed to a lever, U, on a rocking spindle another arm, V,
being connected to the wrist plate or equivalent part of the Corliss gear. The
plate, T, is made with a horn, W, which rests on a pin in a lever, X, moved by the
governor gear so as to lift the plate, T, and clip, S, sooner or later in the stroke
in a well understood way.
Whenever the clips, S, Q 1, become disengaged the preponderating pressure on
the piston, G, moves it (to the left in Figure, 4) so as to close the valve, the
pressure acting in this way being the greater, the greater the preponderance of
the pressure in the valve chest is over that in the port and cylinder passage, and
vice versa.
The rod, L, of the piston, G, is made of such a size as by diminishing the
annular area of the piston, G, and causing the steam pressure to act against
atmospheric pressure only to the extent of the area occupied by the piston rod, will
produce a thrust suited to overcome the friction of the gear and valve apart from
the unbalanced load on the valve.
In the modification shown in Figures, 3, and 4, the closing of the valve is effected
by the pulling action of a pair of links or rods, Q; but in the modification shown
in Figures, 5, and 6, the closing action is transmitted by the pushing action of a
corresponding pair of rods, Y, the cylinder, H, and dashpot, P, being transposed
in position to suit this opposite action. A lever, R, fixed on the valve spindle, D,
has fixed to a spur-like projection on it the clip, Q1, with which engages the
clip, S, fixed to a lever, Z, jointed to a pair of levers, centered loosely on the valve
spindle, D, and connected by a forked rod to the wrist plate. The lever, Z, is
connected by a rod, Z 1, to the governor mechanism, which by its action on the
lever, Z, causes the disengagement of the clip, Q1, S, in a well known way.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed we declare that what
we claim is :-
In Corliss or other tripping valve gear, the combination with other parts of a
compensating piston controlling the movements of the valve and acted on on
opposite sides by the pressure acting on the back of the valve and the varying
pressures in the cylinder end or passage communicating therewith, the parts being
arranged and operating substantially as and for the purposes herein before described
and as shown in the accompanying drawings.
Dated this Twenty-third day of February 1898.
EDMUND HUNT.
Applicants' Agent.