Improvements in Valve-gear for Steam Engines.
Year: 1889

page_text: COMPLETE SPECIFICATION.
Improvements in Valve-gear for Steam Engines.
A communication from abroad by MARTIN E. HALL, a citizen of the city of Washington,
in the District of Columbia, United States of America, Inventor.
I, WILLIAM LLOYD WISE, of No. 46 Lincolns Inn Fields, in the County of London,
Consulting Engineer and Patent Agent, do hereby declare the nature of this inven-
tion and in what manner the same is to be performed to be particularly described
and ascertained in and by the following statement :-
This invention relates to improvements in automatic valve gearing for steam
engines, and more particularly to improvements in the invention disclosed in United
States letters patent No. 406835, granted to my correspondent July 9th 1889; the
primary object of the present invention being to keep the valve under positive control,
and in so doing to effect a complete and instantaneous cut-off of steam without any
change whatever in the lead, release, or compression; and with this end in view the
invention consists in improved mechanism for automatically regulating the passage of
steain through the valve of an engine or of cutting off the supply of steam at varying
points of the stroke of the engine when necessary to cause the engine to run with
uniform speed, and with an economical use of steam.
Referring to the accompanying drawings Figure 1, is a view in side elevation of
the invention as adapted to a single acting engine; Figure 2, is a horizontal section
on the line xx, of Figure 1; Figure 3, is a view of the cam, the inner face of the
grooved loose disc, and small eccentric upon which the loose disc turns; and Figure 4,
is a view of the inner face of the grooved fixed disc.
A, represents a grooved disc keyed to the crank shaft M. This disc has an
eccentric groove A¹, in its inner face (Figures 2, and 4). Said groove is wider
at A2, that is, on the steam side, to admit of sufficient movement of the valve to cut
off steam as hereinafter explained.
A small eccentric D, is also keyed to the crank shaft in such a position that the
loose disc C, which turns upon the eccentric D, will always have its groove C¹,
concentric to the groove A¹, of the fixed disc A.
B, is a cam loosely mounted on shaft M, between the grooved discs A, and D, and
actuated by the loose disc C, through the instrumentality of the pin b. By means of
this pin b, the loose disc C, and the cam B, are connected and made to maintain the
same relative positions to each other, but as the loose disc and cam are on different
centres, there has to be a slight slip motion between the two parts. This is
accomplished by forming a slot 6, in the loose disc for the pin b, to work in..
The loose disc C, has a wide portion C, to its groove and when in its normal
position, this wide part commences where the wide part of the groove k³, in the fixed
grooved disc ends.
The ends of the pin E, of the slide block F, (which latter works between the
disc A, C,) enter the groove A³, of the fixed disc on one side and the groove C¹, of
the loose disc on the other.
The pivoted centrifugal weights H, H, are connected with the loose disc C, by
means of the links L, L, the spring K, K, keeping these weights in until the centri-
fugal force overcomes the tensile action of the springs.
F, is the valve stem, and G, is the guide for the valve stem F¹, and slide
block F.
The action of this valve gear is as follows:
Steam being admitted to. the cylinder, the engine revolves, and the pin E, in the
slide block F, of the valve stem F¹, is confined to a narrow eccentric groove as
shown in Figure 1, for where the groove in the fixed disc is wide, that in the loose
disc is narrow, so that the combined effect of the loose and fixed discs is to give

page_text: the valve the ordinary normal movement, the cam B, not coming into play thus far
at all due to the fact that only ordinary speed has been maintained.
Now if the engine increases its speed beyond the limit of revolution for which the
governor is adjusted, the centrifugal weights H, H, fly out and by means of the
links L, L, increase the angular advance of the loose disc C, to which the links are
connected, and also the cam B. This brings a greater or less part of the wide portion
of the groove C¹, of the loose disc C, opposite or coincident with the wide portion A²,
of the groove A¹, of the fixed disc A, and it brings the cam B, into a sliding
contact with the slide block F, thus instantly cutting off steam by means of the
valve at the end of the valve stem F¹. The wide parts of the grooves of the fixed
disc A, and the loose disc C, permit the pins E, to take the movement given to the
slide block F, by the impinging of the cam B, against the block F, and the edge of
the cam B, when shifted to this position by the loose disc C, conforms to the wide
portion of the grooves in the loose disc and fixed disc so perfectly as to prevent any
play of the pin E, in the grooves, thus defining the course taken by the pins E.
As the loose disc C, and the cam B, advance together the wide part of the groove
in the disc C, overlaps the wide part of the groove in the fixed disc A, just enough to
allow the pin E, to move in them the same distance and no more that the cam B,
moves the slide block F. As soon as the normal point of release is reached, the
actuating portion of the cam having passed the slide block, the valve renews its
normal movement until the point of cut off is again reached.
Should the speed of the engine slacken so that the tension of the springs L, L, become
greater than the centrifugal force of the weights H, H, the weights will be drawn in
and the cam be actuated so as to cut off steam at a later portion of the stroke in order
to keep the engine up to its speed.
Thus it will be seen that this valve gear with a single valve gives any required
cut-off without changing the lead, release or compression, and it is to be understood
that while the drawings show the valve gear adapted to a single-acting engine, it is
also applicable to double acting engines.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
1. The combination with a shaft, a grooved rigid disc keyed thereon, a small
eccentric also keyed to the shaft, and a grooved disc loosely mounted on the small
eccentric, of a valve rod having pins which extend loosely into the grooves in the
rigid and loose disc, and an automatic centrifugal governor connected with the loose
disc whereby the angular advance of the latter relative to that of the grooved rigid
disc is increased, substantially as described.
2. The combination with a shaft, a grooved rigid disc keyed thereon, a small
eccentric also keyed to the shaft, and a grooved disc loosely mounted on the small
eccentric, of a cam loosely mounted on the shaft between the rigid and loose discs,
said cam having connection with the latter, a valve rod having pins which extend
loosely into the grooves in the rigid and loose discs, and an automatic centrifugal
governor connected with the loose disc whereby the angular advance of the latter
relative to that of the grooved rigid disc is increased, substantially as described.
3. The combination with a valve rod, and actuating crank shaft, of cam, rigid,
and loose disc mechanism located on said shaft, and an automatic centrifugal
governor having such connections with the said cam rigid, and loose disc mechanism
that their relative positions are changed according to the speed of the engine to
effectually control the movement of the valve, substantially as described.
4. The combination with a valve rod, and actuating crank shaft, of cam, rigid
and loose disc mechanism located on the crank shaft, the said rigid and loose disc
mechanism being grooved, substantially as described, and an automatic centrifugal
governor loosely connected with the rigid disc, and adapted under normal speed
to maintain such relative positions of the grooves in the rigid and loose disc
mechanism, that the valve having connection therewith is kept within its normal

page_text: limits, and when under abnormal speed to so vary the relative positions of the
grooves that the valve is given a greater throw and the supply of steam is more
limited, substantially as described.
5. The combination of a valve rod, a crank shaft, a grooved disc, (whose groove
is widest on the steam side), rigidly secured thereto and directly actuating said
valve rod and valve, whereby the admission, release and compression are normally
and invariably controlled, a cut-off cam loosely mounted on said crank shaft, and
grooved disc loosely suspended upon a small eccentric fixed to the crank shaft, each
provided with a rotary movement upon said crank shaft, as described.
6. The combination of a single valve and valve rod, a crank shaft, a grooved disc,
(whose groove is widest on the steam side) rigidly secured thereto and directly
actuating said valve rod and valve, whereby the admission, release and compression
are normally and invariably controlled, a cut-off cam loosely mounted upon said crank
shaft, and a grooved disc loosely mounted upon a small eccentric fixed to the crank
shaft, each fixed to the crank shaft, each adapted with a rotary movement upon
said crank shaft and small eccentric respectively, and operated by an automatic
centrifugal governor, whereby steam is cut off at varying points of the stroke
by said valve without change in the lead, release or compression, substantially as
described.
Dated this 13th day of December 1889.
W. LLOYD WISE..