Year: 1887

page_text: Date of Application, 30th Sept., 1887
Specification Accepted. 1st Nov., 1887
I, HENRY DAVEY, of 3 Prince's Street, Westminster, in the County of Middlesex,
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:-
My invention relates to the working of the valves of Pumping Engines in an
improved way.
The mechanism I employ is represented in the accompanying drawing, where A
and B are valve rods connected to the valves in the usual way, or by any convenient
means. In applying the gear to Cornish Engines, A is the steam valve rod, and B
the equilibrium valve rod. The rod is connected to a moving part of the engine so
as to get the motion of the piston on a reduced scale. D, E and F are cataracts,
consisting of cylinders filled with water or other fluid and having a passage leading
from one side of the piston to the other regulated by means of a plug. The
construction of the cataract is well known. The rods of the cataract pistons D and E
are connected to the steam pistons working in the subsidiary cylinders G and H.
The steam is distributed in the said cylinders G and H by means of the valves I
and K the valve I.receiving its motion, through the lever 2, from the tappets M
and Nattached indirectly or directly to the rod C, which rod has the engine motion;
the valve receiving its motion from an arm L on the piston rod of the cataract E.
The piston of the cataract D is connected, by means of a rod 0, to a lever P keyed
on the rocking shaft Q, to which shaft is also keyed the short lever R. At k,-the
outer end of the said lever R,-is fulcrumed a bent lever SS¹, the arm S being
connected by a loop to the steam valve rod A, while the arm S₁ rests at t upon a
roller fixed in the upper arm of the bell crank lever T, which bell crank lever is
fulcrumed on the shaft U and receives the motion of the engine through the rod C.
t is the actual fulcruin of the lever S S'; and the motion imparted to the valve rod A
will thus depend upon the distance between the points k and t, and as this distance
depends upon the relative motions of the engine rod C and of the subsidiary piston G
their combined action will the cut-off of steam.

page_text: B is rod for working the equilibrium valve, and receives its motion from the
subsidiary cylinder G through the lever P. If the engine should in any way lose its
load I cause the said equilibrium valve to be suddenly closed in the following way :-
A lever V is connected at its centre to the piston rod of the cataract F, one arm
being connected to the rod C, and the other to a rod Y to which is fastened a
weight W. The rod Y is connected to the arm of a bell crank lever a, which is
fulcrumed on the shaft Z. To the arm b¹ of the said bell crank lever is attached a
tappet rod c. e is a catch fulcrumed on the rod B; the upper arm of the said catch
is so arranged that it may be actuated by the tappet d, while the lower arm has a
projection which is made to protrude into the slot of the rod B, (being retained in
position by the spring g) and is made to engage with a die h fastened on the lever P
and working in the said slot f. The piston of the cataract F is regulated to travel at
a certain speed by means of a plug adjusted by the hand wheel X, Fig. 2. If now
the engine travel at its normal speed, and if the rod C be moving in the direction of
the arrow, then both the rod C and the cataract piston F will move downwards at a
relatively uniform speed; and owing to the resistance of the weight W to being
lifted the fulcruin of the lever V will be its connection with the rod Y. Should the
engine lose its load, however, the rod C would travel down faster than could the
cataract piston F, the rod of which would then become the fulcrum of the lever V,
and thus the weight W would be raised; and the tappet d, eventually striking the
catch e, would withdraw the projection on the catch e from the slot f, and by thus
releasing the die h would break the communication between the subsidiary piston G
and the valve rod B, causing the equilibrium valve to close and ultimately stopping
the engine.
Fig. 3 shews an alternative method of operating the equilibrium valve. In this
case the engine is not stopped by a sudden increase of speed but the steam is
throttled in its passage from the cylindor in the following way:-
q
The letters Z, Q and U represent the same shafts as in Fig. 1. The lever R is
keyed on the shaft Q and thus receives the motion of the subsidiary piston G, as in
Fig. 1.
To the outer end of the lever R is fulcrumed the lever m, one arm of
which is connected to the rod B, while the other rests at p on the upper arm
of the bell crank lever n. The rod connects the lower arm of the said bell crank
lever n to one extremity of the lever r; the said lever being connected at its other
extremity to the rod Y. Should the speed of the engine suddenly increase the
weight W would be raised as above-described. The position of the bell crank
lever n would thus become altered, and with it the point p; and as this point p is
the actual fulcrum of the lever m the motion imparted to the rod B would be
varied, and by this means the passage of steam through the equilibrium valve would
be throttled.
It is obvious that when this valve gear is employed to work the valves of engines
other than Cornish engines, all the inlet valves are worked as the valve rod A is
worked, and all the outlet valves are worked as the valve rod B is worked with or
without the trip e as may be considered desirable.
Having now described my invention and the manner in which it may be carried
out, I claim,
Operating the valves of Pumping Engines by the mechanism substantially as
described and illustrated.