Improvements in Rotary Engines.
Year: 1897

page_text: Date of Application, 7th Dec., 1897-Accepted, 26th Feb.,
1898
Improvements in Rotary Engines.
I, LUTHER HENRY WATTLES, residing at No. 122, Roger Williams Avenue,
in the City and County of Providence, and State of Rhode Island, U.S.A.,
Mechanical 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
by the following statement and accompanying drawings:
My invention relates to rotary engines of the class in which the steam or other
force acting against the revolving piston is used expansively.
In engines of the type referred to it has been proposed in some cases to employ
swinging valves which are further adapted for use as abutments, and in other
instances the mechanically movable abutments have been independent of the valve
mechanism.
There are objections or disadvantages inherent in such former engines; that is
to say, the limited degree of steam expansion as well as the increased percentage
of "clearance" or added steam space render them less efficient; the per centage of
working friction is materially increased by reason of the multiplication of moving
parts, such as levers and connections, necessarily employed to actuate the valves
and abutments.
The object I have in view is to produce a rotary engine in which the dis-
advantages above referred to are to a great extent eliminated and resulting in a
greater degree of efficiency. Moreover, my improved engine is capable of running
more regularly and smoothly, and with less vibrations, and at the same time being
comparatively noiseless, except the slight sound produced by the action of the
liberating valve-gear when the cut-off takes place. In my improved engine the
steam enters the cylinders at substantially steam-chest pressure, because the steam
ports are very short; the latter in turn not being uncovered until they are fully
open to the piston.
In carrying out my invention I employ a revolving piston, preferably ellipsoidal
in form, the two bearing faces thereof being in engagement with the bore of the
cylinder. At one side of the cylinder and directly communicating therewith is
formed a circular projection or wing in which is mounted an oscillating ported
steam-chest, also constituting an abutment, having an independently movable
steam valve therein for controlling the flow of steam from said chest into the
cylinder. A well-known form of governor-controlled detachable valve-gear is used
for automatically cutting off the steam at any point within its range of action,
while at the same time positively acting mechanism combined with a revolving
cam oscillates the steam-chest back and forth on its axis in unison with the piston's
movement.
In the accompanying drawings, Fig. 1 is a front end elevation of my improved
rotary engine. Fig. 2 is a corresponding back end view. Fig. 3 is a plan view.
Fig. 4 is a side elevation, viewed from the left of Fig. 1. Fig. 5 is a transverse
section, taken substantially on line of Fig. 4. Fig. 6 is a similar sectional
view, showing the relation of the piston and valve-carrying steam-chests while the
steam ports are open. Fig. is a horizontal section, taken on line yy of Fig. 1,

page_text: portions of the valve-gear being omitted. Fig. 8 is a front end elevation, corres-
ponding with Fig. 1, showing a modification embodying a double cylinder engine
having a single steam-chest or swinging abutment. Fig. 9 is a corresponding
back end elevation. Fig. 10 is a transverse section, taken substantially through
the centre of the engine, the ports being in the normal position. Fig. 11 is a 5
vertical section, taken substantially on line aa of Fig. 9, and Fig. 12 is a partial
section through line of Fig. 11.
I would state here that the engine as drawn is adapted to run in one direction
only. In order to adapt it to travel in the opposite direction the arrangement of
the steam-chests, valves and piping should be reversed.
In my improved rotary engine A, again referring to the drawings, the frame
or casing a consists of a single casting, the center portion being bored out to form
the concentric cylinder c, and having oppositely arranged side wings or extensions
bb; these latter are also bored and communicate directly with the cylinder and
form circular chambers for the oscillating steam-chests d. To the front and rear 1
ends or faces of the said casting a are secured heads or covers a³, a¹, respectively.
The curvature of the centre and side cylinders cb intersect each other interiorly
at points both above and below a line drawn horizontally between or through their
centers, the vertical distance between such points being say about one-half the
diameter of the main or piston-carrying cylinder.
The piston pis secured to the main or driving shaft r, the latter extending
centrally through the cylinder and its heads a a¹ and through stuffing-boxes, in
any suitable manner.
2
The piston itself (p) I prefer to make elliptical in form and also solid, sub-
stantially as shown in Fig. 5. The two ends or contact faces of the piston are 2
provided with steam-tight packings p³, thus preventing the steam from escaping.
As thus constructed and arranged it will be seen that a crescent-shaped steam space
is produced on each side of the piston.
The combined steam-chest and abutment members d d are hollow and are turned
to fit the bore of the side chambers bb; the vertical sides of the abutments are con- 3
cave, and adapted to form a continuation of the bore of the main cylinder c. In
the arrangement represented in Figs. 5 and 6 it will be seen that the steam is
admitted to both sides of the piston and at substantially diagonally opposite points,
thus giving four impulses, as they may be termed, to the piston per revolution.
Each abutment dis provided interiorly with a steam-valve which controls the 3
admission of steam into the cylinder c, via the steam port formed in the wall of
the abutment. Between the said port and the inner edge of the member d is located
a steam packing p2 adapted to frictionally engage the adjacent side of the revolving
piston and thus prevent steam from escaping into the exhaust passage. The steam-
chests d have an intermittent oscillatory movement on their axes of about 90°; 4
the normal position being represented in Fig. 5. In order to prevent live steam
from passing into the chambers 6 the outer or ported walls of the abutments are
provided with packing members dª.
The steam-chests or abutments & are hollow, as before stated, and are mounted
on hollow valve rods communicating with the steam pipe connections. In Fig. 7 1 4
have represented one of the abutments as being cut longitudinally through its
center. As drawn, the member d is open at each end and is secured to the front
and rear heads g, g¹. The latter head g¹ has an integral hollow stem or trunnion e²
extending through a cap g screwed into the corresponding cover a¹; the outer or
free end of the stem part being mounted in a fixed stuffing-box C, soon to be 5
described. Motion is imparted to the steam-chest d through the medium of an
arm or lever h secured to the stem e².
The opposite or front end of the steam-chest or oscillating abutment is secured
to the corresponding head g, the latter having a short tubular extension mounted to
turn in the front cap g³, screwed into the cover a². The head g is bored out to freely 5
receive the hollow valve-stem e, the rear end of the latter being closed and supported
in the said head gl. In order to produce a free passage for live steam into the

page_text: steam-chest d from the hollow stem the end portion of the stem e is cut away
or grooved peripherally for the purpose, as shown at e. The front portion of the
stem e is mounted in a stuffing-box C.
It will be seen, referring to Figs. 5 and 6, that the portion of the hollow valve-
stem e within the steam-chest is provided with a continuously open steam passage e!
and an oppositely arranged short arm e³. To this latter is attached the cut off
valve v, which is kept in engagement with the seat formed within the steam-chest,
by means of the steam pressure and the auxiliary springs v¹. From the foregoing
it is obvious that live steam may be admitted into the steam-chest from both ends
simultaneously, or from either end, thus balancing the pressure within the
chest, etc.
From the description thus far made it is clear that the oscillatory movements
of the steam-chest d alone will if properly timed operate to uncover the port d³,
thus admitting live steam into the cylinder c and forcing the piston ahead, sec
arrow direction; but the action of the member d in such case is more wasteful of
steam, and in effect would be the equivalent of and operate substantially the same
as though the steam-chest itself were a valve. By the addition of a valve proper,
as v, having an oscillatory movement independently of that of the chest in which
it is mounted the steam may by suitable mechanism be cut off automatically at any
point (within its range) in the stroke or angular movement of the piston, thereby
practically converting the rotary piston type of engine into one having sub,
stantially the efficiency of reciprocating-piston engines provided with automatically
operating cut-off valve-gear. And by means of suitable mechanism the valve v
may be set at any desired point, thereby providing the engine with a fixed cut-off;
the inner surface or valve seat of the steam port in this case being opened and
closed by traveling across the face of the valve v.
The said stuffing-boxes for the valve-stems e e² are arranged in the outer heads
or brackets C secured to both the cylinder-heads a² a¹ at the center of the steam-
chest chambers b. See Figs. 3, 4, 7, &c. The upper side of each bracket has a
nozzle or hub f into which the lower end of the branch steam pipe s¹ enters;
the said hub having an opening communicating directly with the annular space f*,
which latter in turn communicates with the hollow valve-stem through holes f³
formed in the side of the inner gland member f'; thus it will be seen that the steam
is in continuous communication with the interior of the oscillating steam-chest.
The gland f is kept in position by means of the enlarged cap gland f screwed
into the outer end of the bracket, the check-nut f³ serving to prevent the cap from
unscrewing.
As drawn, the main steam pipes is provided with four branches which are
screwed into the four brackets C, thereby ensuring the presence of steam in the steam-
chests dat substantially boiler pressure; the steam-chests also forming to some
extent reservoirs for the steam.
The exhaust opening is shown as being located at or near the point of inter-
section of the cylinders c and b, and at the side of the steam-chest opposed to the
steam port d. An outlet pipe communicates with said exhaust opening t¹.
Where two chests d are employed two exhaust pipes are used. See Figs. 1 and 4.
These may be united into a single larger pipe if desired.
The mechanism for oscillating the steam-chests d on their axes may be described
as follows: To the rear end of the piston rod or shaft r is secured a suitably shaped
cam D, see Fig. 2, which in revolving vibrates the two-arm or bell-crank levers E,
pivoted to the upper and lower sides of the frame or casing a. The free end of each
lever carries a roller c², the same being in engagement with the cam's surface. The
other arm of the lever is jointed to a connection 1, which in turn is jointed to
the short arm h, secured to the hollow stem e² of the steam-chest d.
may be employed, in lieu of a track-cam, for the purpose of keeping the said rollers
A spring st
in continuous contact with the cam. Thus it will appear that the oscillatory move-
ments of the steam-chests are coincident with certain parts of the piston's move-
ment; the form of the cam being such say that it causes the port d³ of the steam-

page_text: chest to be quickly opened and closed, and while the piston is making one-fourth of
a revolution. Fig. 6 shows the relation of the parts while steam is passing from
the chest into the cylinder. In this case the relative movements of the chest to
the piston are invariable, since the cam is fixed to the shaft. Obviously a slight
change may be made by altering the position of the cam, or a cam having a different
form may be substituted.
In order to convert the engine into one adapted to automatically cut-off the steam
at different points in the piston's stroke, I have represented a well-known form of
fly-ball governor B, arranged to control the movements of the cut-off valve &
mounted within the steam-chest d. The governor being driven by a pulley i
secured to the driving-shaft from which a belt passes to and over a similar
pulley of the governor. In this device (see Fig. 1, &c.) a steam valve-arm or
lever m (see also Fig. 7) is secured to the valve-stem e; the upper end of said lever
is adapted to hook onto or frictionally engage a shoulder formed on the vertically
arranged pivoted latch-lever k, resisted by a spring . The lower or opposite end
of the lever m is adapted to bear snugly against the pin m² secured to and extending
horizontally from the collar m6, the latter in turn being mounted to turn in a recess
formed in the front cap g; and since the collar m6 is fixed to the stem or trunnion
of the front head g of the steam-chest it is evident that its movements are actuated
and controlled by the latter at all times. It will be seen too (see Fig 1) that the
latch-lever is adapted to hold the cut-off valve stationary while the steam-chest
is being swung ahead to uncover the steam port, see Fig. 6. Meanwhile, should
the load upon the engine be reduced the speed of the governor will, for the instant,
be slightly accelerated, thereby (through the medium of the arm m³, connection l,
lever m³ and cam-lever m³, shown in Fig. 1) causing the latch-lever to be forcibly
detached from the latch end of the valve-arm m, the spring at the same time
quickly swinging the valve across and closing the port d, thus cutting off live
steam from the cylinder. The arm m is jointed to a connection 2, the latter being
When the member m
jointed to a stiff spring located at the base of the frame a.
is thus tripped or released the spring instantly swings it ahead until arrested by
the pin m² of the collar m, the tension of the said spring maintaining the parts in
snug contact meanwhile.
I would further state that the steam port 3 is thus kept closed during not only
the completion of the forward stroke but also during the return stroke or movement,
the steam-chest and valve meanwhile traveling in unison, as just stated. At the
end of the return stroke the valve-arm m automatically hooks on to or engages the
latch-lever ; the action of the revolving cam D again swinging the steam-chest
ahead from the now stationary valve v, thereby uncovering the steam port into the
cylinder, the port remaining open until again closed by the action of the valve-gear,
as before described.
While the foregoing 'description of my improved rotary piston engine relates
more particularly to one in which a single steam cylinder and piston combined with
two oppositely arranged valve-carrying steam-chests or abutments d are employed,
my invention is equally applicable and practicable in cases where two cylinders
and a single steam-chest are used, the latter having two oppositely arranged steam
ports and valves adapted to communicate with both cylinders simultaneously. In
the former construction, employing a single piston, steam is admitted into the
cylinder four times during each revolution of the piston, while in the other cr
latter case, having two cylinders and a single steam-chest provided with two
valves, the steam is admitted into each cylinder twice per revolution. Now, by
assuming that the cylinders, speed and steam pressure are the same in both cases,
it will be evident that the volume of steam used and the power thus developed by
the engines are substantially the same. In some respects, however, the duplex-
cylinder engine having a single steam-chest or abutment possesses advantages over
the first named construction.
In Figs. 8 to 12, inclusive, I have represented such a modification of my improved
rotary engine. In this case the engine is provided with two transversely separated

page_text: cylinders c and an interposed oscillatory double-ported steam-chest d; the functions
of the latter being substantially the same as in the single-cylinder engine provided
with a pair of single-ported steam chests.
The engine shown in Figs. S, &c., has a single steam-chest d, as just stated; it,
however, is provided with top and bottom steam-ports d³, and two cut-off valves v
secured to and controlled by the axial movements of the central tubular valve-stem
or shaft e. The mechanism for oscillating the combined steam-chest and abut-
ment d is such that the latter admits steam twice into each cylinder per revolution
of the pistons p, thereby permitting the steam to be expanded to a greater degree.
To the back end of each of the piston-rods or shafts is secured a spur gear n,
these two intergearing with the intermediate idler gear ¹, thus ensuring simul-
taneous rotary action of the pistons. Below and parallel with the axis of the steam-
chest d is mounted a revolving shaft 7 extending through the frame a. On the
back end of this, shaft is fixed a small gear n² meshing into gear n¹; its diameter,
as drawn, being just one-half that of the said driving-gears. By means of this
construction and arrangement the shaft will revolve in the same direction as
the shafts r, and at twice the speed. If desired driving pulleys may be secured
to any or all of the shafts.
As drawn, see Fig. 8, the engine is provided with mechanism for oscillating the
steam-chest d on its axis, whereby steam may be admitted to the cylinders during
nearly one-half of the piston's stroke or movement. It is also provided with
mechanism adapted to be adjusted or set so as to cut off the steam, through the
medium of the valves v, at different points; the movements of said mechanism
being actuated by the lower or quick-running shaft r¹.
The following is a description of the mechanism referred to: To the shaft ri is
secured a suitably-shaped track-cam F which actuates the two-arm lever E¹;
the vertical arm of the lever being jointed to a connection ', in turn jointed to the
end of the short lever h, the latter being secured to the outer end of the hub of the
inner front head g of the chest. See also Fig 11. Thus it is clear that the chest d
will vibrate a fixed or invariable angular distance by and in unison with the revolv-
ing cam F.
The cut-off valve mechanism is driven by an eccentric n³ secured to shaft ; the
work of the eccentric being transmitted to a swinging quadrant-shaped slotted
link o, sliding block o¹ mounted in the link, block-supporting lever o³, connec-
tion of jointed to the lever o and to a short arm h² secured to the tubular stem or
trunnion e passing centrally through the said front head g of the chest; a stuffing-
box and gland m¹ rendering the parts steam-tight. See Figs. 8 and 11. The
stem e extends into the steam-chest and is provided with oppositely arranged exten-
sions and steam openings e¹. See also Fig. 10. The upper and lower sides of
the chest d form ported seats for the valves v, substantially as hereinbefore
described. The valves are attached to the said members e³, springs v¹ maintain-
ing them in yielding contact with the seats. The link o is suspended from the
short connection 2 jointed to the short end of the pivoted operating or hard
lever o; the outer portion of the latter being adapted to engage the notched bar o³,
in a well-known manner. Obviously the valves v may, within fixed limits, be set
or adjusted to cut off the steam at various points, corresponding with the positions
of the lever 03.
The opposite or rear head g¹ of the steam-chest & has the corresponding end of
the valve-stem e seated therein, see Fig. 11. The hub or trunnion portion e² of said
head extends through and turns in the central hub of the outer head or cover a¹ of
the engine frame; the last-named hub forming an axle for the gear n to revolve on.
The outer ends of the members e e² extend into the stuffing-boxes C for the purpose
of receiving live steam from the corresponding pipes s communicating therewith,
substantially as before described, thus balancing the internal pressure on the chest
and valves.
In order to maintain practically steam-tight joints at the two ends of the

page_text: pistons p, I have provided them with circular flanges 23 fitting the bore of the
cylinders c. See Fig. 12. The peripheries of said flanges are in frictional engage-
ment with freely turning inclosed collars a mounted on the hubs of the two
heads gg of the steam-chest d. See also Fig. 11. It will be seen that the inner
faces of the front and back heads or covers 2 have integrally formed exten-
sions at these latter are turned to fit the bore of the steam-chest chamber b, and
are counter-bored to freely receive the said collars ; the opposite sides of the
head portions as being cut away to receive the said revolving flanges 23, see Fig. 12.
In my improved rotary engine it will be seen that the relative movements of the
oscillating steam-chests to the continuously revolving piston are such that the force
of the steam acting upon the piston is resisted both by the walls of the cylinder and
that portion of the ported side or periphery of the steam-chest contiguous to the
piston, the said peripheral surface thus forming an abutment and presenting a vary-
ing area to the steam; the steam space or expansion chamber of the steam cylinder
at the same time increasing in area until the steam-chest completes its forward
movement, the piston meanwhile being forced ahead by the steam. While this is
taking place the steam-chest is in engagement with the piston's surface by means
of a suitable steam-packing device, as 22, thereby preventing steam from flowing
through into the exhaust passage; in fact the arrangement is such that the packing
is in constant contact with the piston. This applies equally as well to the single-
piston duplex steam-chest arrangement as to the engine having two pistons and a
single-steam-chest.
In case the engine is provided with a governor-controlled detachable valve-gear,
say of the
Corliss" type, substantially as represented in Fig. 1, any material
variations in the speed or load will be automatically corrected by the action of the
mechanism, combined with the valve v mounted within the steam-chest; the result
being to release or trip the valve at a corresponding point in the steam-chest's move-
ment, at which instant of release the force of the spring rotates the valve ahead
and across the steam-port of the chest, thus cutting off the flow of steam into the
cylinder. Obviously, the steam then confined in the cylinder expands until the
piston travels past the point of release, or exhaust opening t¹.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:-
1. In a rotary engine of the class described, the combination with a rotating
piston and its adjunctive devices, of a movable hollow abutment forming the live
steam chest, and having a port therethrough arranged to open into the steam
cylinder, and a mechanically actuated valve mounted in said steam chest and in
direct engagement with its port, substantially as described.
2. In a rotary engine, the combination with a rotating piston and the steam
cylinder therefor, of a cylindrical chamber, as b, arranged parallel with and in-
tersecting said steam cylinder, an oscillatory ported steam-chest or hollow abut-
ment & mounted in said chamber having a concave side coextensive with the bore of
the steam cylinder, and a mechanically actuated steam valve mounted in the steam
chest and controlling the port opening, substantially as described.
3. In a rotary engine, a mechanically actuated ported hollow abutment or steam
chest having a hollow stem or trunnion in continuous communication interiorly
with the steam supply, and an independently movable cut off valve mounted within
the abutment having a hollow stem in continuous communication with the steam
supply, said valve stem being provided with an opening through which the steam
passes into the abutment chamber d', substantially as described.
4. The combination, with the steam cylinder and a revoluble piston mounted
therein, of a ported oscillatory steam-chest or abutment having a concave side form-
ing the complement of the bore of said cylinder and arranged in the path of the
piston, and further provided with means for maintaining steam-tight the surfaces of
the piston and steam-chest when in engagement with each other, and
8

page_text: mechanically actuated cut-off or steam valve mounted in the said steam-chest for
closing the port thereof, substantially as described.
5. In a rotary engine, the combination with a suitably mounted elliptical-shaped
driving piston, as p, adapted to rotate continuously in one direction, of an oscillat-
ing steam-chest, as d, having a port through its wall for admitting steam from the
chest directly into the steam cylinder to actuate the piston, arranged whereby the
movement of the chest uncovers the said port into the cylinder after the piston has
traveled past the steam chest, and a mechanically actuated cut-off valve mounted
in the steam-chest adapted to close the port thereof, substantially as described.
6. In a rotary piston engine, the combination of an oscillatory steam-chest pro-
vided with a port through which live steam flows into the cylinder to actuate the
piston, a hollow stem e rigidly secured to one end of sail steam-chest for conduct-
ing steam into it, a valve mounted in the steam-chest and adapted to close the port
of the latter, a hollow stem e extending through the opposite end of the steam-chest
also adapted to conduct live steam thereto and having said valve secured thereon,
aud independent mechanisms connected with the said two hollow stems for actuat-
ing the steam-chest and valve, substantially as described.
7. In a rotary engine, a suitably mounted oscillatory combined steam-chest and
abutment adapted to receive live steam through both ends thereof, thus equalizing
the pressure within it, a port extending through the steam-chest wall through which
steam flows into the steam cylinder, and a governor-controlled valve mounted in
the steam-chest adapted to close said port automatically, substantially as set forth.
8. In a rotary engine, the combination with a ported steam-chest in continuous
communication with the steam supply, and mechanism for intermittingly oscillat
ing the steam-chest an invariable angular distance of a valve mounted in said
steam-chest, and mechanically actuated liberating valve-gear adapted to close said
port through the medium of said valve at various points within its range of action.
9. In a rotary-piston engine, the combination with an oscillating steam-chest
provided with an outlet port, and a central hollow stem or trunnion, as e², secured
to the chest and in direct communication both with the steam supply and the in-
terior of the chest, of a valve v mounted within the said steam-chest and arranged to
overlap the port thereof, and a central hollow stem or trunnion, as e, secured to the
valve and in direct communication both with the steam supply and the interior of
the chest, the said valve-stem extending through an end of and capable of being
actuated independently of the steam-chest.
10. In a rotary-piston engine, the combination with a pair of suitably mounted
transversely separated pistons geared together and revolving in unison in one
direction, of an oscillatory combined steam-chest and abutment d in continuous
communication with the steam supply interposed between and communicating with
both the said pistons, oppositely located steam ports formed in the chest walls
through which steam enters the steam cylinders simultaneously, a pair of oppositely
arranged valves mounted within the steam-chest adapted to close said steam-ports,
and independent mechanisms for actuating said steam-chest and its valves, sub-
stantially as described.
11. In a steam engine, the combination with the cylinder thereof and an oscil-
latory steam-chest communicating therewith, of a revoluble non-cylindrical piston
mounted in said cylinder, the piston having fixed at each end thereof a circular
flange, as 3, fitting the bore of the cylinder and an inclosed annular collar, as a³,
mounted exteriorly to the end of the steam-chest and adapted to turn freely on the
latter's journal or hub, the edges or pheripheries of the said flange and collar being
in frictional engagement, thus forming steam-tight joints at the ends of the piston,
substantially as described.
12. In a steam engine, the combination with a pair of laterally separated rotary,
elliptical pistons p having circular flanges, as p³, at the opposite ends thereof whose
diameters are substantially the same as the length of the major axes of the pistons.
of an oscillating steam-chest or hollow abutment d located centrally between and
parallel with said pistons, and having the two end portions of said abutment pro-

page_text: vided with circular flanges counterbored into the corresponding heads or covers and
in engagement with the periphery of said piston flanges, substantially as herein-
before described and for the purpose specified.
Dated this 7th day of December 1897.
LUTHER HENRY WATTLES,
F. Wise Howorth,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicant.