Improvements in Expansion Valves and Gear for Steam Engines.
Year: 1890

page_text: Date of Application, 18th Mar., 1890-Accepted, 19th Apr., 18:0
COMPLETE SPECIFICATION.
Improvements in Expansion Valves and Gear for Steam Engines.
We, EDWARD NAPIER GALLOWAY and JOHN HENRY BECKWITH, both of Knott
Mill Iron Works, Manchester, 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:-
Our invention relates to the construction of a combined slide and expansion valve
for a steam engine and the gear for working the latter as we shall describe referring
to the accompanying drawings.
Fig. 1 is a side view of a horizontal engine to which our invention is applied,
the slide cover and expansion slide being removed to shew the parts of the main
slide valve.
Fig. 2 is a part plan with slides and case shewn in section.
Fig. 3 is a side view of a modified arrangement of the gear.
Referring to Figs. 1 and 2, A is the main slide valve having in its body a steam
passage a with two ports from it on the one side opening to the cylinder facing, and
with a number of ports opening through a facing on the back of the slide; against
this facing works the expansion slide B which has corresponding ports through it.
By thus subdividing the ports, a very small movement of the expansion slide B
relatively to the main slide suffices for the admission of steam to the passage a and
for its cut off. The main slide valve A is worked in the usual way from an eccentric C
which with its rod is omitted in Fig. 1 and 3 to avoid confusion. For working the
expansion slide as shewn in Figs. 1 and 2 we provide on the crank shaft a second
eccentric D working a circularly slotted link E in the slot of which is free to move
the end block of an arm e. This arme can be moved up or down, either by hand
when the cut off is to be adjusted manually, or it may be moved by a governor. The
arme through a bell crank lever F moves up and down a vertical rod G having a
horizontal slot g, in which is engaged one arm of another bell crank H. This bell
crank is pivotted on a bracket projecting down from the main slide rod K, and its
vertical arm is jointed to the rod L of the expansion slide B. As the main slide rod K
moves to and fro carrying with it the bell crank H, the expansion slide rod I, which
is jointed to H is moved to and fro along with the main slide rod K, and if there were
no relative movement of the rod L the expansion slide B would remain closing the
ports of the main slide A as shewn in Fig. 2. But, owing to the movement of the
link E and the consequent up and down movement of the slot g, the bell crank H is
caused to rock on its pivot thereby imparting to the rod La motion relatively to that
of K, such that the expansion slide B is caused to move along the face of A opening
and closing its ports. According as the arme is moved more or less up the slot of E
the motion of Land B relatively to K and A is varied in such a manner as to effect
cut off sooner or later in the stroke of the main slide valve. The gear may be some-
what simplified by adopting the arrangement shewn in Fig. 3 in which figure parts
corresponding to those in Figs. 1 and 2 are marked with corresponding letters. In
this construction by arranging the bell crank F below and the bell crank H above,
and allowing the link G to oscillate freely without controlling it as in Fig. 1 by a
radius M so as always to move parallel to itself, the slot shewn in Fig. I is
dispensed with.
Although we have shewn the main slide valve A as having its two ports towards
the cylinder communicating with each other and with those for the expansion slide by
a passage a, obviously the cylinder ports might be quite separate each communicating
with one or with several ports governed by the expansion slide. Also instead of a
single main slide valve with its expansion valve situated at the middle of the cylinder,
there might be two separate main slide valves each with its expansion valve near the

page_text: ends of the cylinder, the two main valves being worked by the one rod K, and the
two expansion valves being worked by the other rod L. Also instead of the link E
worked by an eccentric as shewn, any known type of link and gear for working it
may be employed provided the movement and position of the link are such as to give
to a lever such as the required motion.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, we declare that what wo
claim is
In combination with a main slide valve and an expansion slide working on its
back, a bell crank pivotted on the main slide rod, having its one arm jointed to the
expansion slide rod, and its other arm worked from a slotted link moved by an
eccentric, substantially as and for the purpose set forth.
Dated this 18th day of March 1890.
ABEL & IMRAY,
Agents for the Applicants.