IMPROVEMENTS IN THE VALVE GEAR OF LOCOMOTIVE AND OTHER ENGINES
Year: 1857

page_text: LETTERS PATENT to Charles Patrick Stewart, of the firm of Sharp,
Stewart, and Company, of the City of Manchester, Engineers, and David
Graham Hope, of the same Place, Civil Engineer, for the Invention of
T
PROVISIONAL SPECIFICATION. left by the said Charles Patrick Stewart
and David Graham Hope at the Office of the Commissioners of Patents,
with their Petition, on the 9th July 1857.
We, CHARLES PATRICK STEWART, of the firm of Sharp, Stewart, and
Company, of the City of Manchester, Engineers, and DAVID GRAHAM Hope,
of the same Place, Civil Engineer, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN THE VALVE GEAR OF LOCOMOTIVE AND OTHER
ENGINES," to be as follows:-
This invention relates to certain improvements in valve gearing applicable
to all descriptions of steam engines, but more especially to those requiring
frequent reversal of motion.
The first part of our Invention consists of an excentric and clip, the fore-
part of which is made to support a straight or curved bar or slide, having upon
it a bush or block, which is connected by a link to the reversing shaft arm.
To this link we connect the valve rod, the point of connection being taken so
that the curve described by the reversing shaft arm is such as to allow the
valve rod end to move in the required radius, the bush or block travelling in a
straight line upon the above-mentioned straight bar or slide. In cases where
a curved slide is used, we connect any convenient point upon the valve rod
with the reversing shaft arm, making the radius of the curved slide equal to

page_text: the length of the valve rod. To prevent the above-mentioned clip from turning
round with the excentric, we connect it by another link to a saddle or clip
which rests upon the crank shaft, and is free to move with the said shaft in a
vertical direction, its attachment to the boiler or framing preventing it from
turning round with the shaft.
The second part of our Invention consists of a combination whereby we
transmit the motion of the above-mentioned single excentric and clip through
two excentric rods to the opposite ends of a straight or curved link, such link
being connected in the usual manner to the reversing shaft arm, the valve rod
and slide block being fixed.
The third part of our Invention consists in transmitting motion to the
aforesaid straight or curved bar or slide with the usual suspending links,
reversing shaft, and valve rod, from the piston rod, cross head, or connecting
rod, thus leaving the crank shaft free, and dispensing with the excentrics.
For marine and stationary engines requiring frequent reversal of motion, we
propose to use either the first or second combination above referred to, but as
the position of the crank shaft is not liable to vary, we attach the excentrio
clip suspending link to any convenient fixing. For stationary engines, we
propose to use the aforesaid single excentric, and one half of the usual slide or
link, or that portion which is known as giving forward notches from centre to
full steam, leaving out the backward gear, thus enabling an ordinary stationary
steam engine fitted with slide valve to work at various degrees of expansion.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Charles Patrick Stewart and David Graham Hope in the
Great Seal Patent Office on the 9th January 1858.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, CHARLES
PATRICK STEWART, of the firm of Sharp, Stewart, and Company, of the City of
Manchester, Engineers, and DAVID GRAHAM HOPE, of the same Place, Civil
Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Ninth day of July, in the year of our Lord One
thousand eight hundred and fifty-seven, in the twenty-first year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto us, the
said Charles Patrick Stewart and David Graham Hope, Her special licence
that we, the said Charles Patrick Stewart and David Graham Hope, 3
our executors, administrators, and assigns, or such others as we, the said

page_text: Charles Patrick Stewart and David Graham Ilope, our executors, adminis-
trators, and assigns, should at any time agree with, and no others, from
time to time and at all times thereafter during the term therein expressed,
should and lawfully might make, use, exercise, and vend, within the United
Kingdom of Great Britain and Ireland, the Channel Islands, and Isle of
Man, an Invention for "IMPROVEMENTS IN THE VALVE GEAR OF LOCOMOTIVE
AND OTHER ENGINES," upon the condition (amongst others) that we, the said
Charles Patrick Stewart and David Graham Hope, our excentors or adminis-
trators, by an instrument in writing under our, or their, or one of our or their
hands and seals, should particularly describe and ascertain the nature of the
said Invention, and in what manner the same was to be performed, and cause
the same to be filed in the Great Seal Patent Office within six calendar
months next and immediately after the date of the said Letters Patent.
NOW KNOW YE, that we, the said Charles Patrick Stewart and David
Graham Hope, do hereby declare the nature of our said Invention, and in
what manner the saine is to be performed, to be particularly described and
ascertained in and by the following statement (that is to say):-
:-
Our Invention relates to certain arrangements by which a straight reversing
link may be substituted in place of the curved link commonly employed for
imparting motion to the valves of engines requiring frequent reversal, such as
locomotives, and consists,-
Firstly, in mounting the straight link, in the same manner as the ordinary
stationary reversing link, and in connecting the sliding block, by a rod or link,
with the end of the lever or arm from the reversing shaft, usually employed to
move the valve connecting rod, the position of the reversing arm being so
arranged, that when in the centre of the are of its motion the sliding block
will be in the middle position of its link; also, in jointing the valve connecting
rod to the coniecting rod attached to the sliding block of the link, at a
distance from the point of connection or joint of the rod and sliding block.
With this arrangement the valve connecting rod partakes of the motion
imparted to the rod connecting the arm of the reversing shaft and the sliding
block, not only that motion traversing the block along the link, but that due
to the curve of the are described by the end of the arm of the reversing shaft,
but of the latter motion it only receives a diminished proportion, causing the -
joint of the valve connecting rod to nove in a curve practically equivalent to
that which would be required in the ordinary curved stationary link.
The curve required is obtained by adjusting the length of the arm from the
reversing shaft, and the distance of the joint of the valve connecting rod from
the point on the sliding block. When the valve connecting rod is jointed to

page_text: the link connecting the sliding block and arm from the reversing shaft at a
point between the joint of the sliding block and arm of the reversing shaft, tho
curve described by the end of the valve connecting rod will have its concavo
side towards the reversing shaft; but if the point of attachment of the valve
connecting rod is on the opposite side of the joint of the sliding block, the
curve made by the end of the valve connecting rod will have its convex side
towards the reversing shaft.
It will be obvious from what has been stated, that the rod connecting the
sliding block and arm of the reversing shaft becomes a lever, through which
the movements of the link are transmitted, which movements will be con-
sequently increased or diminished, according as the valve connecting rod is
attached to it on one or the other side of the joint on the block; that is,
according as the lever is made one of the second or third kind. This will
necessarily have to be taken into account in the proportion of the parts and
throw of the excentric or excentrics. The excentric or excentrics are set and
the link is suspended or sustained so that when the sliding block is in the
middle position upon its link, the valve connecting rod will be perpendicular
to the link. This method of obtaining a straight link is not only applicable to
the ordinary link motions of the class herein-before described, but to such as
form the subject of another part of our Invention, to be herein-after described,
the arrangement of which is shewn in several Figures of the accompanying two
Sheets of Drawings, and which Figures will sufficiently elucidate the preceding
description. It may be here premised, that in the accompanying Drawings
the same letters and figures of reference are used on the same and cor-
responding parts in each Figure, so that though some parts shewn in each
Figure may not be directly referred to in this description, they may be readily
understood.
Secondly, our Invention relates to the construction of straight links, which
may be employed according to the method described under the first division of
this Specification or in other methods of obtaining straight links.
In combination with our improved mechanism herein-after described, the
straight link consists in a simple bar, fixed to parts from the excentric clip,
but when employed to ordinary link notions, it consists in a straight bar
jointed with one of the excentric rods at each end.
Two modifications of our improved construction of link will be described
hereafter.
Third y, our Invention relates to an arrangement and combination of
mechanism for obtaining, regulating, reversing, and transmitting motion to
valves to work steam engines. Our Invention may be described generally to

page_text: consist in a lever having two or three arms combined with a crank, or radius
pin, or an excentric, one arm of the lever being connected with the crank,
radius pin, or excentric, the fulcrum of the lever being so arranged that it can
give way to the rectilinear motion imparted to it, the excentric, crank, or
radius pin being also arranged in a certain position relative to the crank or
piston of the engine. The combination and arrangement of mechanism above
referred to will produce a motion to work the valve of a steam engine so as to
rotate its crank in either direction, and will also give motion to a valve having
lap, that is, one which extends over the steam ports when in the central
position, so as to work the steam at various grades of expansion.
As a crank or radius pin and an excentric are mechanical equivalents, and
as excentrics only are exhibited in the examples given in the accompanying
Drawings for working the lever, the word excentric will hereafter only be
used. The lever is constituted by the clip of the excentric and a reversing
link or part of one combined together, the excentric clip forming one arm of
the lever, and the link or part of the link the other one or two arms thereof.
The excentric is placed on the crank shaft of the engine, or on a shaft
connected with the engine, driven by it uniformly with the crank shaft. The
position of the excentric in relation to the crank or piston of the engine is
obtained as follows: Set the engine with the piston at one end of its stroke,
place the valve connecting rod or slide block in the central position of its
link, in a line with the fulcrum of the link and centre of the shaft upon which
the excentric is placed. In this position, if the excentric is rotated, the valve
will receive a certain amount of traverse, the correct position of the eccentric
is that in which the valve will have arrived at one extremity of the traverse,
when the piston has arrived at one end of its stroke, and that in which the
valve travels in the opposite direction to the piston. In other words, arrange
the eccentric so that when the valve connecting rod is in the position before
described, the valve and piston will simultaneously arrive at the ends of their
strokes, and so that the valve will uncover the proper steam port, for the next
stroke, to the extent of the lead allowed to it.
The radius of the excentric must be à length equal to the sum of the length
of the lap and the lead of the valve (that is, equal to the extent of the valve
over and beyond the edge of the steam port, when in its central position, and
the space of the steam port to be uncovered at the commencement of the
stroke), when the motion is taken directly from the slide block of the link to
the valve, so that it will receive the same amount of motion as the sliding
block. But if the motion of the sliding block is not given directly to the
valve, but is transmitted through levers which increase or diminish it, then

page_text: the preceding rule as to the radius of the excentric will not apply; the
eccentric in such cases must be of such throw, as will when acting through
the levers employed, place the valve in the proper position at the end of the
stroke of the piston, this being tested by the motion taken from the middle
position of the link, in the manner described for setting the eccentric.
The proportions of the lengths of the arms of the lever, or clip and link
combined, are about one to one, but when the throw of the eccentric is fixed
upon or the lap and lead of the valve is fixed upon, and an increase of motion
in the valve is required, it is obtained by making the arms of the lever,
represented by the link, longer than that arm of the lever represented by the
excentric clip. It will be obvious that the lever or link has a compound
motion, derived from the direct and angular motion given by the eccentric,
that part of the link at the fulcrum partaking solely of the direct motion,
the angular motion increasing as the distance increases from the fulcrum,
and it will be found on examination that the angular motion in one direction
is a little less than that in the other direction, and would consequently give a
rather greater admission of steam on one than on the other side of the piston,
but this is compensated by means similar to those employed to attain this
object in ordinary link motions, that is, by causing the block to slide on or in
the link as it moves backwards and forwards, so that the block will go further
from the fulcrum of the link as it travels from that side, which, but for this
compensation, would have most admission to that side which would have the
Icast admission, which is accomplished by arranging the position of the
reversing shaft, so that the fulcrum of the rod to which the valve connecting
rod is attached is on one side of the centre line of the reciprocating motion
imparted to the valve connecting rod, namely, on the opposite side to that
which is to receive the extra or compensating movement.
In engines which do not require reversing, but ouly a variable travel of the
valve, and where the position of the block in the link is regulated by a screw,
the admission of steam to the cylinder on both sides may be equalized by
placing the fulcrum of the radius bar sustaining the fulcrum of the link on
one side of the centre line of its oscillations, namely, on that side opposite to
that on which the extra movement is required.
Having now stated the principles and rules by which our improved
combination for working the valves of steam engines are constructed and
arranged, we will next describe the Figures of the accompanying Drawings,
exhibiting its practical application.
Figure 1 is a front, Figure 2 a side, and Figure 3 a plan, view of our
improved valve gear, with a straight link as applied to stationary engines

page_text: requiring to work the steam at different degrees of expansion, and also to
reverse. a represents the crank shaft; a', the crank; b, the excentric; c is
the link; e the fulerum upon which it is supported by the rods c¹; and f is the
sliding block of the link; h is the reversing shaft, and an arm from it;
k, the rods jointed to the ends of the arms ', and to the sliding block f at g;
7 is the valve connecting rod jointed to the rods k. Figures 4, 5, and 6, are
ccrresponding views of the curved link motion, also applicable to stationary
engines. Many of the parts in this arrangement being similar to those shown
in Figures 1, 2, and 3, are marked with corresponding letters of reference.
In these views the valvo connecting rod is jointed to the sliding block f, and
the slide c forms part of the eccentric clip. The combinations shewn in the
above Figures as applied to stationary engines are also applicable to locomotive
engines. Figures 7, 8, and 9 illustrate the application of our improved valve
gear to stationary engines which do not require reversing, one side of a link
only being required; in this case a screw k is arranged as shewn, having a
handle, by which the slide block f can be moved in the link c, to vary the
travel of the valve as required; the fulcrum of the radius bar e' in this and
in the other modifications above described is supposed to be held on a
bracket secured to the bed plate framing, or some part of the foundation
of the engine.
In applying our improved valve gear to locomotive engines certain arrange-
ments are necessary to keep the fulcrum e of the link in the same relative
position with the crank axle, as any change of this position would affect the
movements of the valve or link.
In the ordinary link motion, the link is sustained from the framing of the
engine; but as the action of the excentric rods is only in a horizontal direc-
tion, the vertical movements of the carriage or frame of the engine up and
down, or to and from the axle, do not sensibly affect the motion of the link or
valve, the length of the eccentric rods being great in comparison with the
extent of the vertical movement of the carriage to and from the axle.
One method of overcoming the irregularities caused by the varying position
of the axle in relation to the framing is to fix the eccentrics on a separate
shaft placed on a level with the crank axle, and supported in bearings
attached to the framing; this shaft being rotated at the same speed as the
crank shaft by toothed wheels or by other arrangements.
Another method is to make the crank shaft an intermediate shaft, or one
not having any wheels attached, the power of the engine being conveyed to
the driving wheels by coupling rods or other means.
Another method is by supporting the fulerum of the sustaining link on a

page_text: bracket resting upon or embracing the crank axle, the bracket being pre-
vented from turning or moving out of the position fixed upon, by guides
attached to the framing, which allow it to give way only to vertical movements
in the framing or axle; or this bracket is jointed to one end of the rod placed
in a borizontal position, the other end of the rod being jointed to a part
secured to the framing; or a part of the bracket embracing the axle is
extended horizontally or obliquely to as great a length as possible, and the
end is jointed to the framing of the engine. This arrangement reduces the
objectionable motion in that ratio which the length from the fulcrum of
the sustaining rod to the centre of the axle bears to the entire length of the
bracket.
Another method is more especially applicable to inside cylinder locomotives
but may be easily adapted to those having the whole of the valve gear out-
side), where the eccentrics are near together, and consists in arrangements
whereby the clip of one eccentric is made to impart motion to a lever, so as
to agree in time, direction, and extent, as near as required, with the move-
ments of a part from the clip of the other excentric, these two parts being
connected together by a rod jointed to each, so that the forces acting upon the
clip of one excentric are counteracted by the forces acting upon the other,
the centre of the lever being comparatively motionless under the action of the
two excentrics, and only requiring to be connected to the framing of the engine
by a rod placed in a horizontal position, so as to prevent the links rotating
with the eccentrics and to allow of the movements of the carriage of the
engine.
In this arrangement the excentrics and links are arranged as before
described; a centre is adopted, upon which both radius rods for sustaining
the fulcrum of the links oscillate. These radius rods are in length equal to
the distance of the fulcrum of the link from the centre of the eccentric; ono
of them has an arm extending from it at a right angle, this arm being double
the length of the radius rods; and to its end one end of another rod is
jointed, of the same length as those sustaining the fulcrum of the links; the
other end of this connecting rod is jointed to the back clip of the other
eccentric, the joint on the eccentric clip being in a line drawn from the
fulcrum of its link through the centre of the eccentric, and at a distance
from the centre of the eccentric equal to the length of the radius rods.
That centre upon which the radius rods oscillate, which sustains the fulcrum
of the links, is the one which is comparatively motionless, and is the one
attached by a connecting rod to the framing.
Figure 10 is a front view, partly in section, Figure 11 is a side view, partly

page_text: in section, and Figure 12 a plan view, of the arrangements above described,
applied to a locomotive steam engine. a represents the crank axle; a', the
crank; b, the eccentric or eccentrics; c, the links; c, the fulcrum of the
links; e the radius rods sustaining the fulcrum of the link; &, the centre on
which the sustaining rods e¹ oscillate; p¹, the rod connecting this point with
the framing of the engine; e³, an arm extending at a right angle from the
sustaining rod e¹ of the eccentric, thus forming a lever or rod connecting the
end of the arm with the back of the clip of the other eccentric; the slide
block of the link; g, the joint pin upon it; h, the reversing shaft; h', the
arm or arms from it; k, the rod or rods, connecting the arm of the
reversing shaft, and the sliding block f, and the valve connecting rod 1;
an, the ends of the valve spindles; n, the framing of the engine, or parts of
the boiler or fire box.
:
Figures 13, 14, and 15 show the improved valve gear applied to engines
having their cylinders on the outside of the framing. a' is a portion of the
driving wheel. In this case an arm p is centred on the reversing shaft h;
the end of this arm p is jointed to the segmental piece p², that fits and enters
a circular groove formed in the side of the eccentric b, as shewn. Tho
sustaining rod e¹ is connected to this arm p.
Figures 16, 17, and 18 have reference to inside cylinder engines. ³ is
the bracket embracing the crank shaft a, to which is connected the sustaining
rod e; and another rod p is jointed to a bracket on the under side of the
boiler. It is evident that the arrangement shewn in Figures 16, 17, and 18
is applicable to outside cylinder engines; a bracket p³ and a rod p³ being
employed on each side of the engine, that is, for each eccentric and link.
Figure 19 is a side view, Figure 20 a plan view, and Figure 21 an edge
view, of our improved mode of constructing straight links. In these views
the link is a round bar c, having a slide block f, bored to fit easily upon it,
the slide block being made to joint with the valve connecting rod 7, or the rod.
connecting the end of the arm of the reversing shaft with the slide block.
c' represents the ends of the eccentric rods.
In the modification shewn by Figures 22, 23, and 24, the bar c is a
parallelogram in section, and the sliding block f has a hole of corresponding
form, a slot being made in the link equal to the length of the traverse of the
sliding block f, for the pin g, which forms the centre upon which the valve
connecting rod, or the rod connected to the reversing shaft arm is jointed, the
pin passing through both link and sliding block. These links, when used in
connection with two excentrics, are suspended in the same manner as ordinary
stationary link motions, that is, either from one end or from the centre, in

page_text: which case a piece is added to one or both sides (as shown in dotted lines in
Figures 20 and 23), to which the sustaining rod is jointed.
Having now stated the nature of our improvements, and described the
modes in which they may be carried into effect, we wish it to be understood,
that although we have described our Invention as applied to steam engines
only, it is equally applicable to engines worked by air or other elastic fluid;
and we declare that we claim as of our Invention,―
Firstly, the arrangements described under the first division of this Specifi-
cation, by which a straight, reversing, or expansion link may be substituted
for the ordinary curved one, as shewn and described in reference to Figures
1, 2, and 3.
Secondly, the modes of constructing straight, reversing, or expansion links,
as described under the second division of this Specification, and shewn in
Figures 19, 20, 21, 22, 23, and 24.
Thirdly, the combinations and arrangements of mechanism described under
the third division of this Specification, for working the valves of steam engines,
and shewn in Figures 1 to 9, both inclusive.
And, fourthly, the arrangements for applying the combinations and arrange-
ments of mechanism referred to by the preceding claim to locomotive engines,
as described under the third division of this Specification, and shewn in
Figures 10 to 18, both inclusive.
In witness whereof, we, the said Charles Patrick Stewart and David
Graham Hope, have hereunto set our hands and seals, this Eighth
day of January, in the year of our Lord One thousand eight hundred
and fifty-eight
Witness,
II. B. BARLOW,
Manchester.
C. P. STEWART. (L.S.)
D. GRAHAM HOPE. (L.S.)