CERTAIN IMPROVEMENTS IN STEAM ENGINE VALVES, AND IN THE MODE OF WORKING THE CAND
Year: 1855

page_text: LETTERS PATENT to William Kenworthy, of Blackburn, in the County of
Lancaster, Manufacturer, for the Invention of "CERTAIN IMPROVEMENTS IN
STEAM ENGINE VALVES, AND IN THE MODE OF WORKING THE CAND
Sealed the 25th April 1856, and dated the 7th November 1855.
PROVISIONAL SPECIFICATION left by the said William Kenworthy at
the Office of the Commissioners of Patents, with his Petition, on the
7th November 1855.
I, WILLIAM KENWORTHY, of Blackburn, in the County of Lancaster,
5 Manufacturer, do hereby declare the nature of the said Invention for "CERTAIN
IMPROVEMENTS IN STEAM ENGINE VALVES, AND IN THE MODE OF WORKING THE
SAME," to be as follows:-
I propose to work the flat slide (D valve). or other form of steam engine
valve by the crank or éccentric motion, and to shut off the steam, open the
valve, and exhaust the same at any desired difference of the angle of the crank
or part of the, stroke, by which the steam can be worked expansively to any
required degree of of expansion.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Kenworthy in the Great Seal Patent Office on the
3rd May 1856.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
KENWORTHY, of Blackburn, in the County of Lancaster, Manufacturer, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Royal
Letters Patent, bearing date the Seventh day of November, in the year of our
Lord One thousand eight hundred and fifty-five, in the nineteenth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said William Kenworthy, Her special licence that I, the said William Ken-
worthy, my executors, administrators, and assigns, or such others as I, the said
William Kenworthy, my executors, administrators, 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 "CERTAIN IMPROVEMENTS
IN STEAM ENGINE VALVES, AND IN THE MODE OF WORKING THE SAME," upon the
condition (amongst others) that I, the said William Kenworthy, by an instru-
ment in writing under my hand and seal, 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 Royal Letters Patent..
NOW KNOW YE, that I, the said William Kenworthy, do hereby declare
the nature of the said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement (that is to say):-
My Invention consists of working steam expansively with flat slides or
D valves, or with any other form of steam engine valve, by a crank or common
eccentric motion in combination with a differential eccentric, and a modification
in the construction of the valves; or I work the ordinary valves by a differential
eccentric alone, whose curvature is generated by a crank in motion, by which
all concave or intermitting obstructions are avoided to the greatest practica
degree. By working steam expansively economization of fuel is effected to a
very great extent, as by the principles of expansion we obtain from one-fourth
to six-tenths of a cylinder full of steam, being the mechanical effect of a whole
cylinder full; hence the advantage is sufficiently manifest. It is unnecessary

page_text: for me to describe the various parts of steam engines, or the different forms
and positions in which steam engine valves are worked, such being well under-
stood, and having little if any reference to the principle to be carried out by
these improvements; therefore I will proceed in the simplest way. I possibly
.I'
Scan to explain the construction and effect of differential eccentrics, scrolls, or
cams to be used for opening and closing the thoroughfares for the steam and
exhaust corresponding to time or the angles required. I would here observe,
that the circular eccentric and slide valves are peculiarly adapted to the
use of the steam engine where expansion is not an object in a pecuniary point
of view. The crank in giving rectilinear reciprocating motion exactly agrees.
and harmonizes with the circular eccentric in giving the same motion, and the
admirable properties of the crank having been so often demonstrated by
practical experience, and the highest mathematical investigation, I intend to
retain, as far as possible, the principle of the crank in working valves, avoiding
as much as practicable all angular or irregular motions, and giving thereby the
same gentle return motion which is possessed by the circular eccentric now in
use. To work steam expansively to any ordinary degree by a crank or the
circular eccentric motion is impracticable under the present arrangements and
usual construction of the eccentric for working the valves; for instance, let it
be required to cut off the steam at one-fourth of the stroke, or when the crank
pin is at an angle of sixty degrees from the return of the stroke, and to expand
ninety degrees to open for steam eight-tenths of an inch; this would require
the valves to travel twelve inches, and the radius or the valve crank to be six
inches, that is, the angle to open or close the steam being thirty degrees, the
versed sine of which is 1339, we have 1339 x 6 = 8034, or eight-tenths
very nearly; and this length of traverse will require the lap of the valve to be
nearly eight and-a quarter inches (1.3661 x 6 = 8.1966 inches) to expand the
steam; that is, the valve facing would be eight and a quarter inches greater
than the thoroughfare, which would become impracticable, as the return of the
valve crank or eccentric would close the exhaust so early as to prevent the
engine working at all; and if less lap be adopted to suit the closing of
he exhaust, then the opening of the exhaust will be too early, and consequently
vaste the steam without the desired effect being obtained. Hence the
ion could not be carried out as required. It will be easily conceived by the
expan-
ractical engineer, or any person conversant with this subject, that the lap
eing eight and a quarter inches, which, added to the height of the thoroughfare,
ay, two and three quarter inches, the height of the facing of the valve to suit
ne port or thoroughfare would require to be eleven inches to expand the steam
he required time to correspond to one-fourth the cut off, without the possibility

page_text: of agreeing with the time' or angle required to close the exhaust opening;
therefore the valvé crank or common eccentric is not adapted for the object
sought. To meet this difficulty, and preserve the peculiar adaptation of the
slide valve to the use of steam engines, it is necessary to deviate from the
common eccentric and circular hoop, and substitute a differential one to work
with in parallel facings or in a square hoop, and to modify the curvature as to
suit the requirements of expansion; still we may approximate very near to the
circular eccentric in giving easy motion in the practical working of the valves.
Therefore for quick velocities I first adopt a loose lap or double slide, say, the
present valve or slide to regulate the steam opening, and the slide lap to
regulate the exhaust opening, each being worked by its respective eccentric,
the steam valve having the common circular eccentric or crank, and the exhaust
slide a differential one, generated by the motion of a crank, which, with the
other parts of my improvements, are shewn in the accompanying four Sheets
of Drawings, with the figures and the letters of reference thereon. Now, if
we consider the eleven-inch slide or facing, as before alluded to, to be cut in
two parts of its height, or say, one part five inches, and the other part four and
a half inches, and one part placed in front and parallel with the other, it will
be obvious that the total height of the two facings can be so varied as to suit
any cut off that may be required, and thereby regulate the time of the exhaust
to suit the required cut off; that is, the slides are made to elongate to expand
the steam and close together in closing the exhaust opening. The steam slide
is first adjusted to the required opening for the steam to agree with the angle
at which the steam is to close in the ordinary way, which in this case is equal
to sixty degrees, and the exhaust slide is worked by the differential eccentric
or double scroll a, b, c, c, d, a, as seen in Fig. 3, Sheet 2, the eccentricity of
which must always be equal to twice the exhaust opening, and the curvature
so constructed as to open the exhaust in sixty degrees, and close the same in
one hundred and twenty degrees; the sum of which is equal to one hundred
and eighty degrees; or half a revolution of the crank, or one stroke of the
piston. To carry out this principle I adopt the following practical method:-
Figs. 1 and 2; Sheet 1, are a front elevation and section and ground plan
of a drawing table. a, b, c, and d represent the top of the table; 0, 0, vertical
shafts, upon each of which is fixed the wheel W of seventy-two teeth. These
wheels are driven by the endless screws or worms E, E, so that one turn of the
handle A or B will give an angular motion of five degrees to each of the shafts.
Upon the top of one shaft I fix the slotted crank q, o', and on the other the
circular disc D, upon the face of which may be fixed drawing paper, or other
suitable medium for delineating the diagram of the eccentric curve. The crank

page_text: pin C can be adjusted by the screw q¹ to any radius, so as to give any required
traverse to the parallel frame F, F, F, F. The diameter of the disc D is divided
into twelve equal parts by parallel lines, which denote the twelfth parts of the
stroke or versed sines, the angles of which are denoted on the rim of the dise,
which is divided into three hundred and sixty degrees. Now, one turn of the
handle A, as already stated, will cause the disc to move five degrees, and by
the index in front of the table one turn of the handle is divided into ten parts,
which will denote half a degree on the disc, which is sufficiently near for all
mechanical purposes. On the shafts m, A, and m, B, is coiled a length of tape
or fillet forming two scrolls or coils S, f, S, by which differential speeds can be
given to the crank. The said fillet scrolls may be either fast or loose on their
axes at pleasure. The mitre wheels m, m, are for giving equal speeds to the
handles A and B, which also may be fast or loose on their respective axes as
required. The parallel frame slides on the bearings 5, 6, 7, and 8, and on one
of the ends of the frame are fixed the two small spring paper holders h, h,
to hold the slip of paper T, on which can be marked off the proportional
parts of the traverse of the valves to correspond with the angles required.
If a pencil be fixed at the point P and made to press upon the disc, the
handles A and B being turned with equal speeds, the motion of the crank pin
C will cause the pencil to delineate an eccentric curve on the disc, but the cur-
vature of such eccentric will not be truly circular, but somewhat elliptical or
flat at the opposite points a, c, as shewn by the outer curve a, b, c, d, a, in
Fig. 2, Sheet 2, which would be the true form if required to work against a
fixed point. If required to work against rollers or bowls the curvature would
again be changed, but if to work against two straight plates or parallel facings,
the tangential intersections, as hereafter described, will delineate a true
circular eccentric. Again, if the motion of the disc be constant, and the crank
accelerated in speed by the coiling and uncoiling of the tape or fillet S, f, S, it
will be perceived that the delineation on the disc will be a differential
eccentric or double scroll, whose curvature will correspond to the encreasing
speeds given to the crank in compound proportion to the change of the two
diameters produced by the coiling and uncoiling of the tape or fillet. Differential
eccentrics thus drawn are free from any unpleasant knocking or intermittent
motion; having no pause or dwell in working the valves, and the form of curve
being convex, obtained by drawing right lines on the edges of the parallel
sides 1, 2, 3, 4, seen Fig. 1, Sheet 1, tangential intersections are produced
forming a curve, which will admit of being worked between two parallel
facings, or within a hoop having four parallel sides, as shewn in Fig. 1,
Sheet 2; or if a traverse motion be given to the pencil holder from the

page_text: crank pin C, and made to slide at right angles to the moving frame FF, F, F, .
the compound motions will cause the point of the pencil to trace the correct
curve without the aid of intersections. I would here remark that the sum of
the areas of the two fillet scrolls or coils is always the same, that is, the sum
of the squares of the two diameters in every stage is constant; therefore from
this property their respective diameters can be easily calculated to answer the
conditions of construction; thus, one turn of the handle A or B is equal to five
degrees, and the crank and disc must always go half round in one and the same
time, that is, in thirty-six turns of the handle, or one hundred and eighty degrees;
and if the crank pin C is to go ninety degrees, or eighteen turns, whilst the disc
goes one hundred and twenty degrees, or twenty-four turns, that is to say, if A
is to make one-third whilst B-makes one-fourth of a revolution, and both to
make half a revolution in the same time, the respective diameters to commence
the construction of the differential eccentric are determined as follows:-Let
a denote the lesser diameter in number of coils, then +36 is the greater
diameter, to commence the setting out; also x + 24 and x + 36 -18 denote
the intermediate diameter; therefore as the sum of the squares is constant,
we have x²+(x + 36)² = (x + 24)² + (x + 18), which equation solved gives
=
9633 coils, and a +36 69 coils; then taking one coil as the initial
unit and encreasing the diameter one-sixteenth of an inch each turn, we
get 2 inches lesser diameter on A, and 4 inches greater
diameter on B. A general formula might here be given, but these calculations
are unnecessary, as by these arrangements any person of ordinary capacity can
by a few trials proportion the diameters of the fillet scrolls to make the
traverse required correspond to the respective angles, and complete the half
revolution of the crank simultaneously with a half revolution of the disc upon
which the differential eccentric is to be delineated. And in the whole of these
arrangements it must be borne in mind that half a revolution of the crank pin
C must always be coincident in time with half a revolution of the revolving
dise D. to carry out the true proportion in giving the correct construction to the
eccentric required.
Differential eccentrics or cams constructed upon this my improved principle
are applicable to work the ordinary steam valves now in use with considerable
advantage, and although I am fully aware that a kind of tappets or cams have
been used for this purpose to a limited extent, whose forms of construction
admit of being worked against bowls or rollers, giving intermittent motion by
alternate dwells or pauses, the working of such valves would be greatly
improved by using differential eccentrics or cams constructed on the principle
berein set forth. Again, let it be required to construct a differential eccentric

page_text: to cut off steam at five-twelfths of the stroke for a common flat slide or D valve
engine. First fix upon the size of the boss to suit the diameter of the crank
shaft, then set the crank pin C'on the drawing table so that its radius will
give the eccentricity required to traverse the valves. Now, five-twelfths of the
stroke corresponds nearly to an angle of eighty degrees, that is to say, the steam
must be shut off when the crank pin is at an angle of eighty degrees. And
suppose we begin to open and close the exhaust when the piston is one-
sixteenth of the stroke from its terminus, or at an angle of thirty degrees nearly
from the return of the engine crank, or, in engineering phraseology, begin to
open the exhaust at 5 o'clock and close the same at 11 o'clock: we have then
to close the steam opening in forty degrees to expand by lap in seventy, to open
exhaust equal to lap in thirty, and to open for steam at the opposite end in
forty, making a total of one hundred and eighty degrees, or one half a revolu-
tion. And supposing the thoroughfare to be three inches and the lap two-
thirds of the thoroughfare, equal to two inches, the steam opening one inch
and a half, we shall require a traverse of seven inches; then say, close steam
opening one inch and a half, equal to forty degrees, expand by lap two inches,
equal to seventy degrees, exhaust opens two inches, equal to thirty degrees,
open for steam one inch and a half, equal to forty degrees, total seven inches
and one hundred and eighty degrees. The construction or setting out will be
as follows: First make the radius or small crank on the drawing table equal
to three inches and a half, so that half a revolution will give a traverse of seven
inches; then set off on the dise upon which the eccentric is to be delineated or
drawn the respective angles, as before named, which is readily done by turning
the handle A, or from the ring of the disc, which shews the number of degrees;
adjust the fillet scrolls so that the motion of each angle will correspond to the
respective lineal distances. marked on the strip of paper T required to be
traversed in the same tinie, which will be easily done by a few trials, then
turning the handle A slowly, and drawing right lines or tangents between the
two parallel sides 1, 2, and 3, 4, on the disc to form numerous intersections,
we get the required eccentric, as represented on Sheet 3, which will exactly
agree with a crank motion at different speeds, the two half revolutions being
completed in one and the same time. The constructions will be mathematically
correct, and work the valves in the order as required; and so for any other
cut off that may be required, as shewn in Fig. 4, Sheet 2, which represents
an eccentric for cutting off at one-third of the stroke for common slide or
D valves. These eccentrics will work in a square hoop similarly to the one
shewn in Fig. 2, Sheet 4. By these arrangements for drawing or constructing
differential eccentrics, scrolls, cams, hearts, or tappets, we attain the greatest

page_text: practical accuracy, and virtually make the diagrams of the eccentric corre-
spond to the required diagrams of the engine. I am aware that differential
angles and tangential intersections can be produced geometrically, but the
process is both tedious and difficult, whereas by my improved mode or
method the correct curve can be delineated in a few minutes.
Having thus fully described the nature and particulars of my said Invention,
and the manner of carrying the same into practical effect, I desire it to be
distinctly understood that I do not confine myself to the exact details herein
set forth, as such may be varied or modified without departing from the
principle thereof. But I claim as my Invention, and which to the best of my
knowledge and belief has not been hitherto used within this realm, the use of
differential eccentrics without concave or dwelling parts, giving smooth and
easy motion to the working of steam engine valves, whether the same be single
or double slide, or any other form of valves, for the purpose of using steam
expansively or otherwise, and working against parallel sides, or within a square
hoop, and the apparatus for the construction of such eccentrics, as herein
described, and illustrated in the accompanying four Sheets of Drawings.
In witness whereof, I, the said William Kenworthy, have hereunto set
my hand and seal, this Twenty-third day of April, One thousand eight
bundred and fifty-six.
WILLIAM KENWORTHY. (L.S.)
Signed, sealed, and delivered by the within-named
William Kenworthy, in the presence of
E. J. HUGHES, Patent Agent,
Manchester.