IMPROVEMENTS IN EXPANSION VALVE GEAR FOR STEAM ENGINEB
Year: 1884

page_text: I, JAMES GILLIES, of Glasgow in the county of Lanark, Engineer, do hereby
declare the nature of my said Invention for "IMPROVEMENTS IN EXPANSION
VALVE GEAR FOR STEAM ENGINEB," to be as follows:―
This Invention consists of improvements in expansion valve gearing for steam
engines, and has for its object to effect by the employment of extremely simple
devices, the automatic cutting off of steam at any part of the stroke.
In carrying out my Invention, an ordinary slido valvo or similar valve is
employed to distribute the steam, and is operated by the usual eccentric; and on
the back of the slide valve is fitted a "gridiron" valve or multiple-ported valve
forming the cut off or expansion valve which is operated from the slide valve rod
by means of the arrangement which I will now describe. The slide valve rod is
jointed at a point near the eccentric, the longer portion of the rod being carried by
guides, and the shorter part being rigidly connected to the eccentric strap. At or
near the joint an arm is formed or fixed on the short length of the valve rod at
or nearly at right angles to it, and this arm is connected by a short link to an
oscillating bar which is carried by a bracket and to which the expansion valve rod
is connected. The end of the arm on the slide valve rod has, in addition to its
to and fro motion along with the rod, a vibratory or oscillating motion on the
joint as a centre, this motion being due to the action on the eccentric strap of the
rotation of the eccentric. This oscillating motion of the arm is greatest when
the valve rod nears each end of its stroke; and the arm being connected to the
oscillating bar to which the (expansion valve rod is connected, the compound
motion of the arm is communicated to this rod, so that the expansion valve moves
during part of the stroke with the slide valve, and at a certain point of its stroke,
the oscillating motion of the arm acts on the expansion valve and traverses it to
close the open ports on the back of the slide valve, the steam being thereby cut off.
The expansion valve rod is not connected directly to the oscillating arm which acts
on it, but to a sliding bar carried by it; and by moving this sliding bar so that
the point at which the valve rod is attached is nearer or further from the centre
of oscillation, the point at which the expansion valve is traversed over the slide
Din 077

page_text: valve to cut off the steam inay be varied within very considerable limits. In order
to effect the cutting off at the proper time to maintain a steady action of the
engine under variations of load, the end of the expansion valve rod, or of
the sliding bar to which it is attached, is connected to the governor, so that the
variations of speed of the engine may through the governor collar be made to
vary the position of the expansion valve rod relatively to the centre of oscillation
of the bar by which it is actuated, and thereby to effect the cut off earlier or later
in the stroke.

page_text: COMPLETE SPECIFICATION.
I, JAMES GILLIES, of Glasgow, in the County of Lanark, Engineer, do hereby
declare the nature of my said Invention for "IMPROVEMENTS IN EXPANSION
VALVE-GEAR FOR STEAM ENGINES," and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement:
My Invention consists of improvements in expansion valve, gearing for steam
engines, and has for its object to effect, by the employment of extremely simple
devices, the automatic cutting-off of steam at any part of the stroke. :
The Invention is illustrated in the accompanying Drawings, in which Figure 1
is an elevation, and Figure 2 is a sectional plan of a steam engine fitted with my
improved valve gear, and Figure 3 is a view of the valve gear in detail.
În carrying out my Invention, an ordinary slide valve, or similar valve A, is
employed to distribute the steam, and is operated by the usual eccentric C and
rod; and on the back of the slide valve A is fitted a "gridiron" valve or multiple
ported valve B, forming the cut-off or expansion valvo which is. operated from the
slide valve rod by means of the arrangement which I will now describe. The
slide valve rod is jointed at a point near the eccentric, the longer portion D of
the rod being carried by guides E; and the shorter part D¹ being rigidly connected
to the eccentric strap C¹; at or near the joint, an arm d is formed or fixed on the
short length of the valve rod at or nearly at right angles to it, and this arm & is
connected by a short link d¹ to an oscillating bar f, at d² which is carried by a
bracket F, and to, which the expansion valve rod G is connected. The end of the
arm on the slide valve rod has, in addition to its to-and-fro motion along with
the rod, a vibratory or oscillating motion on the joint o as a centre, this motion
being due to the action on the eccentric strap C₁ of the rotation of the eccentric C.
This oscillating motion of the arm d is greatest when the valve rod nears each end
of its stroke; and the arm being connected to the oscillating bar f to which the
expansion valve-rod is connected, the compound motion of the arm d is com-
municated to this rod so that the expansion valve B moves during part of the
stroke with the slide valve A, and at a certain point of its stroke the oscillating
motion of the arm facts on the expansion valve B, and traverses it to close the
open ports a in the back of the slide valve, the steam being thereby cut off.
The expansion valve rod G is not connected directly to the oscillating arm f which
acts on it, but to a sliding bar f¹ carried by it, and by moving or adjusting this
sliding bar so that the point at which the valve rod G is attached, is nearer or further
from the centre of oscillation F¹, the point at which the expansion valve B is
traversed over the slide valve A to cut off the steam, may be varied within very
considerable limits. In order to effect the cutting-off at the proper time to
maintain a steady action of the engine under variations of load, the end of the
expansion valve rod G, or of the sliding bar f¹ to which it is attached, is connected
to the engine governor by means of a rod or lever f³, and is raised or lowered
thereby, so that the variations of speed of the engine may, through the governor
collar, be made to vary the position of the expansion valve rod G relatively to the

page_text: centre of oscillation F¹ of the bar f by which it is actuated, and thereby to effect
the cut-off earlier or later in the stroke. A counterbalancing weight H is con-
nected to the rod G to overcome the weight of the rod and thereby to relieve the
strain on the governor.
.>
The improved valve gear is arranged to suit the rotation of the crank shaft in
the direction shown by the arrow. When the engine is intended to run in the
opposite direction, the arm d on the eccentric rod D' is formed on the upper sido
instead of the lower side of the rod, and the position of the fixed centre of
oscillation F¹ of the arm f is also reversed, that is placed below the eccentric rod.
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. The combination of parts forming the improved expansion valve gear
herein described and illustrated.
Second. The combination of the jointed valve rod and arm & operated by the
eccentric, with the oscillating barf to which the expansion valve rod is connected,
substantially as herein set forth.
Third. The combination of the valve rod D¹ and arm d with the sliding and
oscillating bar, arranged to be shifted by hand or automatically from the governor
to vary the cut-off of an expansion valve substantially as herein set forth.