Improved Valve Gear for Steam Engines.
Year: 1896

page_text: Date of Application, 29th June, 1896
Complete Specification Left, 29th Mar., 1897-Accepted, 22nd May, 1897
PROVISIONAL SPECIFICATION.
Improved Valve Gear for Steam Engines.
I, JOHN WESCOTT, of Reading Road, Wokingham, in the County of Berks,
Engineer, do hereby declare the nature of this invention to be as follows:-
My invention relates to valve gear for steam engines and has for its object a
novel arrangement of mechanism whereby a variation of the cut-off, the reversal of
the engine, or the stopping of the engine by placing the valve in an inactive
position can be effected without the use of the ordinary link motion.
According to my invention instead of making use of the usual eccentrics for
operating the valve I make use of a crank having an adjustable pin, the said crank
being carried by a shaft parallel with the main crank shaft and driven therefrom
through the medium of suitable gearing so as to rotate at the same speed as the
crank shaft. When the said crank pin has its axis in alignment with the axis of
the shaft carrying it, it is obvious that no motion will be imparted to the valve;
when, however, the crank pin is moved to one side or the other of the axis of the
shaft the steam will be admitted to the cylinder. to drive the engine in one or the
other direction, the point of the cut-off varying according to the distance of
the crank pin from the axis of rotation of the shaft carrying it.
To provide for the adjustment of the crank pin I advantageously provide the
following arrangement, that is to say, I. make the shaft carrying the said pin
hollow or cylindrical and I mount the crank pin on a nut through which a screw,
arranged diametrically across the inside of the cylinder passes. On this screw is a
gear wheel connected by a train of gearing with a shaft designed to be rotated in
one or the other direction by the longitudinal movement within the cylinder of a
rack, whereby the position of the crank pin will be correspondingly varied. The
rack is moved through the medium of a screw and nut carried on a fixed bracket
on the engine, a joint being arranged between the said screw and the rack of a kind
which will permit of the rotation of the rack with the cylinder without imparting
any rotary movement to the adjusting screw.
My arrangement of valve gearing is very advantageously used in conjunction
with an expansion valve, the said expansion valve being operated from the rod
which works the main valve through the medium of an oscillating lever connected
at one end by a rod to the stem of the main valve and at the other by a rod to the
stem of the expansion valve.
I will be obvious that my invention is applicable to either single or multi-
cylinder engines; when applied to multicylinder engines the valve of each cylinder
is operated by a separate adjustable crank, the several cranks being independently
driven from the main crank shaft but all of them being connected with a single
screw and nut or hand-wheel for effecting the adjustment of the crank pins.
Dated the 29th day of June 1896.
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.

page_text: 17
1, JOHN WESCOTT, of Reading Road, Wokingham, in the County of Berks,
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 valve gear for steam engines and has for its object a
novel arrangement of mechanism whereby a variation of the cut-off, the reversal
of the engine, or the stopping of the engine by placing the valve in an inactive
position can be effected without the use of the ordinary link motion.
According to my invention instead of making use of the usual eccentrics for
operating the valve I make use of a crank having an adjustable pin, the said crank
being carried by a shaft parallel with the main crank shaft and driven therefrom
through the medium of suitable gearing so as to rotate at the same. speed as the
crank shaft. When the said crank pin has its axis in alignment with the axis of
the shaft carrying it, it is obvious that no motion will be imparted to the valve;
when, however, the crank pin is moved to one side or the other of the axis of the
shaft the steam will be admitted to the cylinder to drive the engine in one or the
other direction, the point of the cut-off varying according to the distance of
the crank pin from the axis of rotation of the shaft carrying it.
To enable my invention to be fully understood I will describe the same by
reference to the accompanying drawings, in which :-
Figure 1 is a sectional front elevation of a steam engine having my improved
valve gear applied thereto :
Figure 2 is an end elevation of the same:"
Figure 3 is a vertical longitudinal section, drawn to a larger scale than Figures 1
and 2, of the shaft carrying the adjustable crank pin and the mechanism iu
connection with it; and,
Figure 4 is a horizontal section of the same.
In the drawings which illustrate the application of my invention to a vertical
steam engine, a is the bed or base plate of the engine b, b the standards and c the
cylinder carried by the said standards.
d is the crank shaft and e is the slide valve which in the drawing is represented
as having combined with it a cut-off valve f. g is the pin of the crank connected
by the rod g with the slide valve e and is the shaft carrying the said crank
pin g, the said shaft being mounted in the bearing brackets i, i on the bed plate a
and being driven from the crank shaft d through the medium of the gear
wheels of such relative proportions that the shaft h rotates at the same speed as
the crank shaft d.
1
The crank shaft h is made hollow, as clearly shewn in Figures 3 and 4, and the
crank pin is carried by a nut k through which passes a screw 7 supported in
bearings within the hollow shaft h in such a manner that the rotation of the said
screw will cause the nut k and consequently the crank pin g to travel in a
diametric direction across the shaft / so as to permit of placing the crank pin with
its axis in alignment with the axis of the shaft h or at a point at a greater or less
distance from the axis of the shaft h upon one side or the other.
0
On the screw is a gear wheel m connected by wheels n, n' with a shaft
designed to be rotated in one or the other direction by the longitudinal movement
within the shaft of a rack p engaging with a gear wheel q on the said shaft o
The longitudiual movement of the rack is effected by means of a screw r and nut s
the said screw being at one end connected with the rack by means of a joint, so

page_text: arranged (for instance as shewn in Figure 3) that the rack can rotate with the
cylinder without imparting rotary movement to the adjusting screw r whilst the
other end of the said screw which carries the nuts projects out of the hollow
shaft h at its axis and is supported at its free end in the bracket t. The nuts may
have formed in conjunction with it a hand-wheel by means of which the nut may
be rotated to adjust the rack; in practice, however, I find it advantageous to form
the said nut as part of a bevel wheel u with which another bevel wheel u' fixed on
a shaft carrying a hand-wheel w. engages, in such a manner that when the hand-
wheel w is rotated in one or the other direction the rack will be moved to effect
the adjustment of the crank pin.
It will be obvious that as the screw r does not partake of any rotary motion
the adjustment of the rack can be effected at any time to vary the travel of the
slide valve e.
My arrangement of valve gearing is very advantageously used in conjunction
with an expansion valve say, for instance, the valve f, shewn in Figure 1, the said
expansion valve being operated from the rod g' which works the main valve e
through the medium of an oscillating lever a connected at one end by a rod to
the spindle of the main valve and at the other end by a rod to the spindle of the
expansion valve.
y
With this arrangement it will be understood that any variations in the travel of
the main valve will be transmitted in proper proportion to the cut-off valve f.
It will be obvious that my invention is applicable to either single or multi-
cylinder engines; when applied to multicylinder engines the valve of each
cylinder is operated by. a separate adjustable crank, the several cranks being
independently driven from the main crank shaft but all of them being connected
with a single screw and nut or hand-wheel for effecting the adjustment of the
crank pins.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
clain is:-
1. A valve gear for steam engines wherein the valve is operated by a crank the
pin of which is made adjustable relatively with the shaft carrying it, substantially
as, and for the purposes, described.
2. A valve gear for steam engines wherein the valve is operated by a crank
the pin of which is adjustable for varying the travel of the valve the said pin
being carried by hollow shaft rotated from the crank shaft, substantially as
described.
3. A valve gear wherein the valve is operated by means of an aljustable crank
pin, mounting the said crank pin upon a screw arranged diametrically across a
hollow shaft the said screw being rotated in order to effect the adjustment of the
crank pin through the medium of a rack and gearing, the said rack being moved
longitudinally by means of a screw extending axially into the said hollow shaft but
not rotating therewith, substantially as described.
4. In a valve gear for steam engines wherein the main valve is driven by an
adjustable crank pin substantially as hereiubefore described and wherein a cut-off
valve is arranged in combination with the said main valve, meaus substantially as
hereinbefore described for operating the cut-off valve from the main valve.
5. The improved valve gear for steam engines hereinbefore described and
illustrated in the accompanying drawings.
Dated this 29th day of March 1897.
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.