CERTAIN IMPROVEMENTS IN STEAM ENGINES AND LOCOMOTIVE CARRIAGES, PARTS OF WHICH ARE ALSO APPLICABLE FOR OTHER MOTIVE PURPOSES
Year: 1848

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ISAIAH
DAVIES, of Birmingham, in the County of Warwick, Engineer, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Royal Letters Patent under the Great Seal of the United Kingdom of Great
Britain and Ireland, bearing date at Westminster, the Second day of May,
One thousand eight hundred and forty-eight, in the eleventh year of the reign
of Her present most Excellent Majesty, Queen Victoria, did, for Herself, Her
heirs and successors, give and grant unto me, the said Isaiah Davies, my
exors, adiñors, and assigns, Her especial licence, full power, sole privilege and
authority, that I, the said Isaiah Davies, my exors, admors, and assigns, or
such others as I, the said Isaiah Davies, my exors, admors, or assigns, should at
any time agree with, and no others, from time to time and at all times during
the term of years therein expressed, should and lawfully might make, use,
exercise, and vend, within England, Wales, and the Town of Berwick-
upon-Tweed, and in the Islands of Jersey, Guernsey, Alderney, Sark, and
Man, and in all Her said Majesty's Colonies and Plantations abroad, my
Invention of "CERTAIN IMPROVEMENTS IN STEAM ENGINES AND LOCOMOTIVE
CARRIAGES, PARTS OF WHICH ARE ALSO APPLICABLE FOR OTHER MOTIVE PURPOSES; '
in which said Letters Patent is contained a proviso, that I, the said Isaiah
Davies, shall cause a particular description of the nature of my said In-
vention, and in what manner the same is to be performed, by an instrument
in writing under my hand and seal, to be inrolled in Her said Majesty's High
Court of Chancery within six calendar months next and immediately after

page_text: the date of the said in part recited Letters Patent, as in and by the same,
reference being thereunto had, will more fully and at large appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
Isaiah Davies, do hereby declare that the nature of the said Invention, and in
what manner the same is to be performed, are fully described and ascertained
in and by the present Specification thereof, reference being had to the Draw-
ings hereunto annexed, that is to say:-
My said invented improvements, in so far as they regard steam engines,
have relation to the class of steam engines known by the name of rotary
engines, and more particularly to a rotary engine invented by me, which
formed the subject of Letters Patent, for England granted to me on or about
the Twenty-seventh of April, One thousand eight hundred and forty-four,
a Specification of which. was.duly inrolled on the Twenty-sixth October
following.
In the Drawings hereunto annexed, Figure 1 to Figure 20, (both in-
clusive,) I have exhibited the general construction, and most of the details, of
a pair of rotary engines constructed on the plan of my said Patent, as modified
by my present improvements; but I propose, in the description which follows,
to confine myself to the improvements alone, referring to the Specification of
my former Patent for all those particulars in which there is no difference
between the engine in its original and in its improved form. And for the
sake of better distinguishing. in the Drawings hereunto annexed those parts
which are new from those which are old, I have colored in grey, blue, or
yellow all those parts which I claim as being improvements or to which my
improvements have immediate reference, and shewn the others in outline only.
line a,
Figure 1 is a front elevation of the pair of rotary engines aforesaid,
mounted on one shaft, some of the front parts of the left-hand engine being
left out in order to expose to view the parts beneath. Figure 2 is a top plan
of the right-hand engine, and a sectional plan of the left-hand engine on the
b. Figure 3 is a section of one of the engines on the line e, d, f, g, c, h,
of Figure 2. Figure 4 is a section on the line i, k, of Figures 1 and 2 (with
the covers of the cylinder B and the cam box Y removed, in order to show
some parts which are not exhibited with sufficient clearness in the other
Figures; and Figure 5 is an end elevation of one of the engines. A is the
main shaft, which passes continuously through the centres of the cylindrical
pistons D, D, which revolve within the fixed cylinders B, B, as also through
the partition plate G, by which the two engines are separated. The end
covers P, P, of the two fixed cylinders are 'fitted with metallic stuffing boxes,
through which the main shaft A passes in the same way as in the rotary

page_text: engine originally invented by me, and described in the Specification of my
former Letters Patent; but the stuffing boxes which I now propose to employ
are on an improved plan of construction, and such as to insure much more
effectually perfect steam tightness at the points where the shaft passes through
the cylinder covers. The details of my improvements in stuffing boxes are
separately represented in Figures 6, 7, 8, 9, 10, and 11; and these I will now
first proceed to describe.
Figure 6 is an elevation, and Figure 7 a top plan, of one of these improved
boxes; Figure 8 is a transverse section of it on the line r, 1, (Figures 7
and 9); Figure 9, a plan on the line m, n, and Figure 10 a transverse section
on the line p, q. P represents the end cover of one of the fixed cylinders B, B;
K is the packing box, the body of which is inserted into an aperture or socket
bored out for it in the cylinder cover; and K³ a flange by which, and bolts H, H,
passed through it, the box is secured to the outside of the cover. The under
side of the flange K³, and the part of the cylinder cover with which it is
brought in contact, are turned true, in order that they may fit one another
exactly. The only part of the body of the box which is in actual contact with
the sides of the socket in the cylinder cover is a rim piece k', (next to the
flange,) which is about half in inch in depth, and accurately turned to fit the
socket. Beneath this rim piece there are four hubs M, M, M, M, which
project from the body part, but not quite so far as the rim piece k¹; so that
there is free access for the steam to the back of all the body part beneath the
rim piece k. In each of these hubs there is a hole bored through and through
for the reception of a spiral spring N, the office of which will be afterwards
explained. On the inside the packing box is of two diameters, or, in other
words, it has two steps or ledges in it, No. 1 and No. 2. To the top of the
bottom step or ledge (2) there is rivetted a flat brass ring E. The space
between that ring and the step 1 is divided circumferentially into two equal
parts by two vertical stops F, F, which are passed through the body of the
box from the back, and extend over the ring E. Two sets of concentric
segments L, L, are dropped down loosely upon the ring E, one over the
other; that is to say, the first set L' consists of quarter segments of the
sectional form, separately represented in Figure 11, which rest immediately
upon the ring E, and abut at one end against one or other of the stops F, F,
(which fit into recesses s, s, made for them in the segments,) and the other
set L consists of smaller quarter segments, which rest in seats cut out for
them on the inside of the segments L'. All these segments are accurately
turned, so as to fit with nicety to and upon one another, yet with such vertical
distances between them as to allow of their being moved to the extent of about

page_text: an eighth of an inch both inwards and sidewise, and which concentric seg-
ments are moreover so placed in relation to one another that they shall every-
where break joint (as it is technically termed). T is a circular cap or cover,.
with a brass ring V of smaller diameter rivetted to the under side of it, similar
to the bottom ring E. The ring V fits into that part of the packing box
which is of the lesser of its two diameters, and immediately above the
concentric segments, while the outer rim of the cap rests upon the stop or
ledge No. 1, and is made fast to it by the bolts h, h. In the sectional view
Figure 10 the packing box and the parts L', L, T, V, which fit into it
successively, are shewn detached from one another, in order to exhibit more
clearly their mutual relations. The spiral springs N, N, before mentioned,
press at their inner ends against the concentric segments L', and at their outer
ends against the sides of the socket in the cylinder cover, while the stops F, F,
serve to prevent the concentric segments from sliding round sidewise beyond
the stops F, F. The pressure inwards of the springs N, N, serves to keep
the concentric segments in constant yet (because of the slight side-play
allowed them) nearly frictionless contact with the shaft A, however much the
inner faces of these segments may happen to vary from wear in a long course
of work; and should any steam find its way nevertheless between the sides
of the shaft and the inner faces of the concentric segments, as every joint
between any two of theso segments comes opposite a solid part in the segment
immediately behind, and the whole of the segments are covered in at top by
the double-seated cap T, it is next to impossible that any portion of the steam
should escape at the back of the packing. And again, the steam which is
left free to circulate round the back of the body part of the packing box and
to find its way through the orifices in the hubs is equally prevented by the
manner in which the concentric segments are packed together from penetrating
beyond them, but serves by its pressure against them still more effectually to
secure the steam tightness of the packing, and the more so the greater the
pressure of the steam in the cylinder may be. All the parts of this packing
box are made of iron, with the exception of the concentric segments L', L³,
and the bottom and top rings E and V, which are made, as before stated, of
brass, because these are the only working parts to which the steam can have
access, and the brass is not so liable to corrosion as iron, and sufficient pro-
vision is made for the difference in point of expansion between the two metals
by the vertical spaces between the concentric segments and by the space left
between the top of the segments and the ring V of the cover T. However,
there may be cases where the water from which the steam is generated is of
so pure a quality that there is nothing to be feared from corrosion, and also

page_text: cases in which air and not steam supplies the motive force (as in air engines
and blowing machines); and in such cases not only may all the parts of the
packing box be of iron, but the bottom ring E may be wholly dispensed with
(the depth of the under part of the box or of the segments being increased in
proportion to the depth of the ring removed).
A modification of the packing box before described is represented in
Figures 12, 13, and 14. It consists simply in placing the cap or cover Tat
the back instead of the front of the concentric segments. In all other respects
this box is the same as that already described.
In Figures 6, 7, 8, 9, 10, and 11 the packing box is supposed to be adapted
to an engine with a shaft A of four inches in diameter; and for shafts of that
size the concentric segments should be of the quarter circle there represented,
but when the shafts are of larger diameter the number of segments may be
advantageously increased in proportion to the increase in the diameter of tho
shaft. So also, when the engine shaft is of less than four inches in diameter,
the number of segments may be diminished to three, but not less, as is exem-
plified in the modification represented in Figures 12, 13, and 14. The
standard bearings X, X, of the main shaft are so constructed as to admit
readily of readjustment from time to time; so that, in the event of any do-
viation of the shaft from the perfect concentricity which it should preserve,
this can be at onco detected, and the necessary remedy applied. And an end
elevation of one of these standard bearings X, X, is given separately in
Figure 14; and a plan in Figure 14b, on the line a, b; and a section in
Figure 14°, on the line c, d. M³, NE, are brass bearings in which the shaft
immediately rests; Os is an iron lining plate, which is inserted beneath the
under brass bearing Ns; Rs is a wedge-shaped cotter, which is passed trans-
versely through and through the neck of the standard, and secured at the two
ends by the collars and nuts S5, S. Should, therefore, the brass bearing N
on the lining plate Os at any time drop out of the horizontal line, it is only
necessary to push the cotter inwards in order to restore the bearing parts to
the exact level. Ts is an index or pointer, by which it is easy to ascertain at
any time whether the shaft is working truly. On the turning this pointer
round, it should, if the shaft is in its proper position, pass just free of the shaft,
without touching; but if it comes in contact with the shaft, that is a sure
indication that the shaft has dropped out of its proper level, and requires to be
readjusted by means of the cotter and nuts, as has been just explained.
In my rotary engine as criginally constructed, and as described in the
Specification of my former Letters Patent, the cylindrical piston D had but
one lateral projection or abutment for the steam to act against; but I now

page_text: make it with two such projections or abutments s*, s*, as represented in the
section Figure 3, or, in other words, the piston, from being single-acting, is
changed into double-acting. The steam is thus made to act on opposite sides
of the shaft at one and at the same time, so that any tendency which the pres-
sure of the steam on a single abutment at one side of the shaft might have
to press the shaft from out of the centre of the fixed cylinder B is balanced
by the equal pressure on the second abutment at the opposite side, and so
neutralized. A further advantage resulting from this double action of the piston
is, that as the steam has a double area of piston surface to act upon, the power
of the engine is considerably increased without any corresponding increase in
its bulk and weight. The proper curve to be given to these abutments is
dependent on the lines described by the sliding steam stops; and directions for
producing which last will be afterwards given when treating of these stops. In
the apex of each abutment there is a recess in which a packing piece e¹ is
inserted, and behind this packing piece a blade spring, which presses out the
packing against the sides of the fixed cylinder B as the piston revolves, and so
prevents any escape of the steam between them. To lessen, however, the friction
between the packing pieces and the cylinder, the former are fixed in an oblique
position as regards the shaft, as described in the Specification of my former
Letters Patent. The mode of attaching each piston to the main shaft is as
follows:-There are three (or any other suitable number) of feathers m, m, m,
which are let into the shaft at right angles to it (see Figures 2 and 3),
and these feathers fit into grooves in the bosses of the piston, yet not so
tightly but that the shaft is left free to slide endwise to a certain extent
through the piston; that is to say, the shaft may slide a little, though
the piston itself must always rotate in one and the same plane. The main
advantage attending this arrangement is, that should there be any end pressure
on the main shaft, as not unfrequently happens, the shaft can yield sufficiently
to that end pressure to prevent any portion of the disturbing force from
being communicated to the piston, whereby one of the sources of friction
in rotary engines is entirely removed. As the piston has two abutments
or points of action, so also are there two passages A', A¹, for the admis-
sion of steam into the cylinder B, and also two sliding stops F, F, for
letting on and cutting off the steam. On the steam coming from the boiler it
flows along the pipe W (see Figure 1) into the chamber M' (containing the
expansion apparatus herein-after described), from which it passes into the
chamber Z, whence it is transmitted through one or other of three orifices,
9,7¹, s¹, and according to which of these orifices is left open by the starting, stop-
ping, and reversing valve, which is worked by the wheel L*. Supposing the

page_text: orifice to be that left open as represented in the Drawing, Figuro 3 (which
is the orifice for starting the engine), the steam passing through q' enters the
pipes o, o', and passes thence through orifices into the chambers G, Ga (one
on each side of the cylinder), from which it passes through slots or ports
in the partition plates 6, 6, and along channels A', A', in the slide F into the
cylinder B, where, coming in contact with the two abutments s*, s, of the
cylindrical piston D, it carries the piston round in the direction indicated by
the arrows. Or supposing it is required to reverse the engine, then the orifice
s' is that which is left open, and the steam takes a similar course, (but through
different passages not shewn in the Drawings,) as in the case of starting the
engine. During the time the piston abutinents s", s, are passing the passages
A', A', the sliding stops F, F, must of course bo wholly withdrawn within the
chamber G; and so also when the sliding stops are protruded across the
annular spaces H, H, between the piston and the cylinder B, the mortices in
the sliding stops must coincide with the ports in the partition plates 6*, b*, but
a movement equivalent to one of the ports at once seals the ports, and prevents
a further flow of steam to or from the cylinder until after the piston has passed
and the stop again crosses the annular
space.
To give the necessary interpositions and pauses to the single sliding stop
which was employed in the single-acting engine which formed the subject of
my former Patent, I made use of two cams of a peculiar curve, which as they
revolved came into contact with fixed curved pieces or tappets within the cam
box, and so produced the requisite to and fro movement of the stops; but it
was found in practice that there was an objectionable degree of concussion
attending the action of the cams on the fixed tappets. I propose, therefore, to
substitute for the fixed tappets friction rollers, and to give such. a curve to the
cams that they shall act on and pass over the friction rollers with as little con-
cussion as may be. In a double-acting engine, such as I have before described,
the cams and friction rollers must necessarily come twice in contact in the
course of each revolution, but one of the cams must be larger than the other.
In the annexed Drawings C represents the larger cam, and C the
smaller; Y, Y, are the boxes containing the cams. The curve to be given to
these cams is separately represented on an enlarged scale in Figures 15 and 15°,
and the mode of striking it out is shewn in the Diagram, Figure 16. Through
the centre Ob draw the line Pb, O', Qb; set off on the line Pb, O', Q, the two
distances Ob, 6b, and Ob, cb; let the distance Ob, cb, be to the radius of the
revolving piston D (see Figure 4) as the length of the lever B¹ is to be the
length of the lever G¹ (same Figure); and similarly let Ob; -, be to Ob, cb, as
the diameter of the revolving piston D is to the interior diameter of the fixed

page_text: cylinder B; then from the centre Ob, with the radius Oh, 6b, describe the circlo
Hb, Ib, K, L, and with the radius Ob, c, describe from the same centre the
circle Fb, Eb, ch. The circles thus drawn will form the foundations of the cams.
To determine the throw of the cams I next proceed as follows, begin-
ning with the throw of the smaller cam:-Through O' I draw the horizontal
line Bb, 0b, C; and from the point Eb, where this line intersects the larger
circle, I set off E, D, of a length proper for the radius of the friction roller g³,
which length must be such that the cam shall in revolving turn clear of the
boss of the friction roller; and from Db as a centre, and with a radius D', E³,
I strike the periphery of the roller g'. From Db towards Eb set off Db, eb, equal
to bb, ch. I then describe a semicircle D 12 and eb on the line eb, Db, divide
this semicircle into any number of equal parts 1, 2, 3, &c. &c. And
from these points I let fall perpendiculars cutting eb, Db, in fb, gb, hb, &c.;
from the centre 0b, with radii O, e³, O³, ƒ³, 0³, gb, &c., I describe the
arcs e³, zb, ƒ³, y³, gb, xb, &c.; then upon the large circle F³, H°, c³, I set off' an
arc F, G, subtending one half of the angle Gb, Ob, Nb, through which the
axle will have turned during the time the stop remains entirely within the
chamber G. On the same circle I also set off the arc G, H, subtending an
angle Gb, Ob, Hb, which represents the time the axle takes in turning through
an angle, which will be equal to the time which the stop takes to cross the
annular space after it has entered into the cylinder. I divide G, H, into the
same number of equal parts which the semicircle Db, 12, &c. eb, has previously
been divided into, and from the centre Ob draw the radial lines Ob, pb, 0b, q³,
Ob, b, &c.; then from the points p³, qb, rb, &c., where the radial lines inter-
sect the curves Db, pb, O, qb, &c., and with a radius equal to the radius Db, E',
describe the arcs 1, 2, 3, &c. The contour line traced by these arcs will give
the curve required. I proceed similarly to get the return curve E', Nb, Mr.
The projection of the cam on the opposite extremity of the diameter is obtained
the same way.
.
The throw from the larger cam is obtained as follows:-From Ec on the
line of Bb, O', Cb, I set off E, De, equal to Db, Eb, and with a radius Ee, Dº,
draw the circle Bb, E°; from De towards Bb I set off Do, e, equal to Db, eb;
upon Do, e, I describe the arc D°, 1', 2', &c. e; divide it into any number of
equal parts, and let fall perpendiculars to the line De, e, intersecting Do, eº, in
fo, go, ho, &c. From (b, with a radius Ob, ec, Ob, ec, Ob, fo, &c., I describe the
arcs eº, 2º, fo, yo, &c. From Ee I set off an angle E, Go, equal to the angle
subtended by the arc E, G, and Go, Ho, equal to the angle Gb, Hb. I next
divide Go, Ho, into the same number of equal parts which the semicircle is divided
into, and draw the radial lines O", pc, 0, 7º, 0b, 1º, &c.; then, from the points

page_text: of intersection p, q, and r, &c., with a radius D, E, I describe arcs 1', 21, 3¹,
&c., which will give the curve required. The return curve and the curve for
the opposite throw are obtained in precisely the same way.
While revolving, the cams press alternately on the friction rollers g³, g¹¹; that
is, the small cam Cb presses upon the roller g', and the larger cam C* upon the
roller g, twice in each revolution. This gives a to-and-fro movement to the
cam boxes Y, Y, which is communicated by the arm A* to the lever B¹ keyed
to the weigh-shaft I. The weigh-shaft I gives motion to the lever G", which
motion is communicated by the link D' to the cross head of the rod P, which
is directly connected with the sliding stop F*.
The sliding stop in the box G opposite to that just described is worked by
a similar arrangement of levérs, motion being communicated to them by the
lever E through the connecting rod F; (the course of motion is best seen in
Figure 4.) In Figures 17 and 17" I have shewn the modifications necessary
to be made in the preceding arrangements when the engine is a single-acting
one, such as I originally patented; and in Figure 17° I have given a diagram ex-
hibiting the lines for striking out the proper curve for the cam of such an engine.
..To obtain the means of giving a quick motion to the expansion valves before
mentioned as being enclosed in the chamber M, I connect with the double-
acting cam motion I*, K., expansive gear of the following description (see
Figures 5, 19, and 20):-I, K, are the two cams which are keyed to the
main shaft A outside the end bearing X of the engine. These cams are
alike in form, and the curves of both are obtained in precisely the same
way as the curves of the cams C, Cb, but to prevent mistakes I have shewn
separately by the diagram Figure 18 the mode of striking out the curves of
these expansion gear cams I*, K*.
Figures 19 and 20 shew part of the working of the expansion gear motion
on an enlarged scale. Figure 19 is a side section on the line a, b, Figures 5
and 20; and Figure 20 is an end view (with the front plates B and C re-
moved). B, B*, are connecting plates surrounding the shaft A, and enclosing
a pair of friction rollers D and E, which revolve on the peripheries of the
cams I and K; J is an axle attached to the standard X, on which is fitted
a bell-cranked lever N. The length of the straight arm of this lever is equal
to the length of a line drawn. between the centres of the friction rollers, and it
is bisected by the axle J. From each end of each friction roller there is
dependent a pair of parallel levers C, C, which are connected together by
pins O; P. The points in which O and P are fixed are exactly in the
centres of the levers C, C. The extremities of the straight arm of the bell-
crank lever previously mentioned are connected by the pins O and P to the

page_text: levers C and C. Similarly also the link Q is connected by the pins R, S,
to the lower extremities of the levers, C., C. The link Q is of the same
length as the straight arm of the bell-crank lever, and consequently of the
same length as a line joining the centres of the friction rollers. It follows
that the levers C and C and the bell-crank, lever N and the link Q will
form a parallel frame free to move round the joints O, P, R, S, and de-
pendent for support on the fixed axle J. It follows also that whatever may
be the relative positions of each opposite pair of levers, the parallelism cannot
in any degree be affected. As the engine is a double-acting one each cam
has two projections as has been already explained. Therefore, during each
revolution the friction rollers are twice thrown through a space equal to the
eccentricity of the cam. It will, therefore be evident that the levers C, C+,
work round the central fulcra O and P, and that any motion of the friction
rollers would equally turn the other extremities of the levers C, C+, so that
when by the rotation of the cams the friction rollers assume the positions
indicated by the dotted lines, the opposite extremities of the levers C*, C*,
must also assume the positions similarly indicated. The throw of the cams
and the working of this parallel system of levers correspond with the admis-
sion of steam into the cylinder B, and the motion of the stops F*, F*.
To communicate the motion to the valve, within the chamber M* there is
a connecting rod (RF), one end of which is fixed by a pin round which it is
free to move as far as the centre of the lik Q, and the other end is attached
to the weigh shaft U* T is a lever worked from the weigh shaft through the
medium of the vertical and longitudinal levers Y. X" is a fulcrum about
which the lever Tturns. Ab, Ab, are links attached at equal distances one
on each side of the fulcrum X, and communicating directly with the expansion
valve by means of the rod Nb.
The mode of working the slide is thus easily traced, but for the purpose of work-
ing expansively and regulating the degree of expansion according to the will of
the attendant engineer, there is a handle (H) which works the depending
arm of the bell-crank lever N, through the medium of the connecting rod Is.
According to the obliquity or horizontal position of the straight arm of this
lever will depend the position of the friction rollers with respect to both cams.
Another and fixed position of the friction rollers will regulate the lead of the
expansion valve in reference to the slide valve or stop F; for it is evident, that
if the friction rollers be placed by the bell-crank lever in the positions indi-
cated by the red lines Figure 20, the throw of the cams will come into action,
and the expansion valve in the chamber M* will be acted on earlier than the
This in the chamber C

page_text: The portion of my Invention relating to locomotive carriages consists in the
application thereto of the improved double-acting rotary engine herein-before
described, and in certain improvements in the manner of transmitting the
power of the engine or engines to the wheels of locomotives, of whatever
description such engine or engines may be.
Figure 21 is an elevation of a locomotive carriage with rotary engines
attached; Ad is the boiler; Dd, the fire box; Ed, framing; Fd, engine, which is
supported by checks Gd, depending from the framing; K4, main shaft of
engine; L, crank of engine; Mª and Mo, coupled driving wheel axles;
Na and Ne, cranks of the coupled driving wheels; and Od and 0%, connecting
rods working from the crank pin Rd of the engine, to the cranks fixed to
the driving axle; Sd, So, are the gabs within which the axles M4, Mo, of the
driving wheels rest, but these gabs are not made parallel and perpendicular
as usual, but of the curved form shewn in Figure 22. In order to prevent
under all circumstances any undue strain upon the rods Od and 0° the curve
given to them is composed of small segments of circles struck from the centre
Kª, as represented in the diagram Figure 22. Kd is the main axle of the
engine; M, Mo, the axles of the wheels. From the centre Kd, with the
radius K, m, & Ke, me, I' describe the arcs ab, b, c, dª, m", ƒª, mº, hª, which
represent the interior surfaces of the gabs Sd, S. The crank Md, Md, is equal
to the crank M, No, and also to the crank K, Rd; the connecting rods are
equal to each other, and to the radius K, M; then, drawing the line K, M,
a parellelogram M, Na, K, Rd, is formed, and the like will be the case in
whatever position of the gabs the centre of the axle Md may be placed; for,
suppose the wheel encounters an impediment on the rail, which causes the
axle Md to rise in the gab till it assumes the position indicated by the dotted
circle, then, as the axle slides in the periphery of a circle whose centre is Kd,
the parallelism of the action is maintained, and no unduo strain or irregular
action can possibly affect the connecting rods.
Figure 23 and Figure 24 represent a longitudinal and transverse section of
another plan for working my rotary engine, and applying it to the locomotive
purposes. K³ is a strap depending from the main axle of the carriage, and
supporting the rotary engine (G³) between the wheels. The construction or
disposition of the parts of this engine are the same as in the last application,
with the exception, that instead of having, a crank, and connecting the motion
of the crank to the driving wheels by means of connecting rods, the rotary
motion of the engine is communicated by means of two spur wheels W*, X*,
one of which is keyed to the main axle A* of the engine, and the other to the
axle of the driving wheel. The relative numbers to be given to W, X³, will

page_text: of course depend upon the nature of the work which the engine has to
perform. The pitch lines of these spur wheels are so adjusted that, supposing
them to be represented by two revolving circles, the one would roll upon
and in contact with the other end; as they are keyed to the main axle and
driving wheel axle respectively, they partake necessarily of whatever vertical
movement is given to these axles, so that no rise of these axles from inequalities
in the rails can have the effect of throwing the spur wheels out of gear.
It remains to describe those parts of my improvements which are applicable
to other motive machinery:-
First among these is, my metallic packing, which is applicable not only to
the shafts of rotary engines on my own plans of construction, but to all other
rotary engines in which shafts are used, and may be also usefully applied to
horizontal shafting of every description, especially such as is ordinarily used
in marine screw propelling in air engines and in blowing machines. It may
be used, too, with vertical shafts, though perhaps with less advantage.
Secondly, the mode I have adopted in my rotary engines of connecting the
working shaft with the piston, whereby the shaft is left free to slide through
the piston, while the piston is kept constantly in the same plane of rotation,
is equally applicable to all other rotary engines, where the shaft and piston
are directly connected together, and the injurious effects of end pressure on
the shaft are desired to be avoided.
Thirdly, the peculiar combination of parallel levers with a double-acting
cam motion, which I make use of to impart a quick motion to the expansion
valves of my improved rotary engine as before described, is also applicable to
working expansively reciprocating steam engines of all kinds, and with this
two-fold advantage, that it admits of the valves being so placed as to be always
in advance of the piston in whichever direction it moves while the engine is
at work, and enables the amount of expansion to be graduated by a single
movement of a lever or screw.
And fourthly, the peculiar curved form which I give to the gabs of loco-
motive carriages when fitted with my rotary engines, whereby any undue strain
on the connecting rods is avoided, may be also advantageously applied to other
rotary engines, as also to reciprocating engines.
And having now described the nature of my said Invention, and in what
manner the same is to be performed, I declare that the several improvements
which I claim as constituting my said Invention are as follows:-
First, I claim the improved double-acting rotary engine herein-before
described, in so far as respects the mode of packing the working shaft and the
adjustable bearings by which its parallelism is preserved; the use of two abut-

page_text: ments or projections in the cylindrical piston; the mode of connecting the
piston to the shaft; the peculiar curve given to the cams which regulate the
motion of the sliding stops; the substitution of friction rollers for the fixed
curved pieces or tappets heretofore used in combination with such cams; and
the mode of working the expansion valves by a combination of parallel levers
with a double-acting cam motion, each as before respectively described.
Second, I claim the adaptation to single-acting rotary engines of the kind
described in the Specification of my former Letters Patent of the Twenty-
seventh of April, One thousand eight hundred and forty-four, of such of the
improvements enumerated in the preceding claim as are applicable thereto, and
as have been herein-before pointed out and explained.
Third, I claim generally the improved packing box herein-before described,
in the peculiar arrangement and combination of parts of which the same consists,
and to whatever shafts or shafting the same may be employed; that is to say,
I lay no claim to the use merely of concentric segments, or to the arranging of
those segments so as to break joint, or to the employment of metallic springs
or steam to act upon those segments in any other than an inward direction;
but what I claim as the improvements peculiar to the said improved packing
box are,
, the rim picce by which the body of the box fits closely into the aperture
in the cylinder cover; the passages left for the steam at the back of the box;
the two concentric steps or ledges on the inside, one of which serves as a seat
for the concentric segments (and bottom ring, if any), and the other as a seat
for the outer rim of the top cover; the concentric segments in so far as the
outer or larger series have seats cut out in them for the inner or smaller seg-
ments, and in so far also as all of these segments have such vertical spaces
left between them as to allow of their moving as well inwards as sidewise; and
finally, the combined use of metallic springs and steam pressure to press the
said concentric segments inwards (not outwards, as usual).
Fourth, I claim the connecting of the shaft to the piston of rotary engines,
in the manner herein-before described, to whatever sort of rotary engine the
same may be applied.
Fifth, I claim the peculiar combination of parallel levers and double-acting
cani motion before described, whether the same is applied to work the expan-
sion valves of my own or of any other description of steam engines, rotary or
reciprocating, and its application also for the like or any other purpose in other
engines and machines.
Sixth, I claim the first of the modes herein-before described of connecting
the engine in locomotive carriages with the driving wheels, in so far as regards

page_text: the peculiar curve given to the gabs, and whether the said engine is of the
rotary or reciprocating kind.
And seventh, I claim the second of the modes herein-before described of
connecting the engine in locomotive carriages with the wheels, in so far as
regards the mode of mounting and fixing the engine and the gearing employed
to transmit the power of the same to the wheel.
In witness whereof, I, the said Isaiah Davies, have hereunto set my
hand and seal, this Second day of November, in the year of our Lord
One thousand eight hundred and forty-eight.
AND BE IT REMEMBERED, that on the Second day of November, in the
year of our Lord 1848, the aforesaid Isaiah Davies came before our said
Lady the Queen in Her Chancery, and acknowledged the Specification afore-
said, and all and every thing therein contained and specified, in form above
written. And also the Specification aforesaid was stamped according to the
tenor of the Statute made for that purpose.
Enrolled the Second day of November, in the year of our Lord One
thousand eight hundred and forty-eight.