the steam and exhaust ports
Year: 1887

page_text: I, FRANK WILLIAM Dodd, of 16 Osborne Road, Forest Gate in the County of Essex,
Engineer, do hereby declare the nature of this invention to be as follows:-
The object of this invention is to simplify the construction of single acting motive
power engines, by removing the necessity for valve gear, for opening and closing the
steam and exhaust ports.
The connecting rod I secure to its trunk piston, by means of a hollow plug, which
forms a kind of T head to the rod, and rocks like the plug of a tap in its seat, which
is formed by boring a hole transversely through a solid portion of the piston.
One of the ends of the hollow plug is open to permit of its taking steam from the
steam supply port when it is in coincidence therewith.
In the periphery of the plug I make one or more ports for supplying steam to the
working cylinder, corresponding openings being made through the piston to conduct
the steam to the front or steam side of the piston.
The exhaust port will be at about the level of the supply port. To prevent both
ports being open at the same time, and yet to allow of a proper duration of the steam
supply, the piston may be extended forwards, so as to keep the supply port, which is
elongated, always covered, as respects the working cylinder.
The exhaust port may consist of any number of openings around the cylinder, which
openings may be jacketted to collect the exhaust steam and conduct it to a discharge
pipe.
The steam will be admitted to the cylinder at the end of the return stroke of
the piston, by reason of the rocking motion of the connecting rod having brought the
steam passage or passages of the rocking plug coupling into line with those of the
piston.
The steam will then flow to the face of the piston, the supply being kept up until
the port or the steam passages are closed. The expansion of the steam thus supplied
to the face of the piston will force back the piston, which will now close the supply
port, and as it completes its stroke, open the exhaust port.

page_text: On the completion of the throw of the crank, the piston will be driven inwards to
its starting position, closing the exhaust port, and opening the steam port to the steam
channels of the piston as before.
The supply port, may, instead of delivering the steam into the interior of the
rocking plug, deliver it into a recess or indentation formed on its periphery. This
recess or indentation will be put into communication with the working cylinder
during the outward stroke of the piston, in the manner previously described.
A similar recess or indentation on the periphery of the rocking plug, to that
described for regulating the steam supply, may be used to assist in carrying away the
exhaust steam during the inward stroke, such recess or indentation having a suitable
port in connection with it, and being so placed as to be opened to the working
cylinder during the inward stroke.
By my invention it will be seen that the complications of valve gear, and the
disadvantages connected therewith, are removed, and provision is thereby made for
constructing single action engines in a far more economical manner than heretofore.
Dated this 24th day of November 1887.
NEWTON & SON,
Agents for the Applicant.

page_text: COMPLETE SPECIFICATION.
Improvements in Single Action Steam and other Motive-power
Engines.
I, FRANK WILLIAM DODD of 16 Osborne Road, Forest Gate, in the County of
Essex, Engineer, do hereby declaro the nature of this Invention and in what manner
the same is to be performed, to be particularly described and ascertained in and by
the following statement :—
The object of this invention is to simplify the construction of single-acting motive-
power engines, by removing the necessity for valve gear, for opening and closing the
steam and exhaust ports.
In the arrangement of engine which I will first describe, I secure the connecting
rod to its trunk piston by means of a hollow plug, which forms a kind of T head to
the rod, and rocks like the plug of a tap in its seat, which is formed by boring a
hole transversely through a solid portion of the piston.
One of the ends of the hollow plug is open to permit of its taking steam from the
steam supply port cored out in the cylinder.
In the periphery of the plug, I make one or more ports, and corresponding
openings through the piston head, to conduct the steam to the front or steam side of
the piston.
The exhaust port in the cylinder will be at about the level of the supply port, and
may consist of any number of openings around the cylinder, which openings may be
jacketted to collect the exhaust steam, and conduct it to a discharge pipe.
In the accompanying drawing, Fig. 1 shews in sectional view, and Fig. 2 in
longitudinal sectional elevation, a pair of single action horizontal engines constructed
according to my invention.
AA are the working cylinders, cast in one with a connecting chamber A*. B B
are the trunk pistons, to which are fitted the connecting rods (C. These rods are
coupled, by a hollow T head, to the base of their respective pistons, and, by socketted
ends, to a crank pin of the crank shaft, common to both rods. These rods are held to
the crank pin by bracing rings, and are free to oscillate independently of each other.
The crank shaft D has its bearing in a hollow flanged casting E, which is secured
by bolts to one side of the chamber A*.
The cylinders A A are jacketted to form steam ways for the exhaust steam, there
being ports a in the cylinders to connect with the exhaust passages a¹, which are in
communication with an exhaust steam pipe.
a² are the steam supply ports for the two engines. They are connected together by
a passage a³, cored out in the casting, which passage is also connected, with the steam
supply pipe.
The ports a are always covered by their respective pistons, which are formed with
elongated passages b for leading the steam into the sockets prepared to receive the
hollow T heads of the connecting rods, and a similar arrangement of passages 6* is
provided in the pistons for the discharge of the exhaust steam.

page_text: These Theads or plug couplings, which are free to rock, like the plug of a tap, in
their sockets, to provide for the oscillatory movements of the piston rods, have open
ends, and are therefore in direct communication with the steam passages of their
respective pistons.
From these oscillating heads, the steam passes to the front of the pistons by ports c,
when they are brought into coincidence with ports ¹³ in the head of the piston, and
when the steam has expanded in the front of the piston, it escapes by the port 62
through a passage in the rocking plug coupling, and off by the ports a and
passages a¹ to the exhaust pipe.
Instead of fitting the pistons with packing, as is usual, I prefer that the cylinders
should carry elastic packing, as shewn in the drawing, and for securing the plug
coupling of the rod to the piston, and ensuring a steam tight joint, its open ends
are bevelled inwards to fit conical seats formed for it in the ends of the piston
socket.
From the foregoing description it will be understood that steam will be admitted to
each cylinder at the end of the return stroke of its piston, by reason of the rocking
connecting rod having brought the steam ports cc into coincidence with the steam
ports 66 of the piston head.
The steam will then flow to the face of the piston, the supply being kept up until,
by the advance of the piston, the port a' is closed. The steam admitted to the
cylinder will, by its expansion, complete the outward stroke of the piston, the oscil-
lating head rod meanwhile closing the ports e c, and opening the port ² to the
exhaust passage c', which is at that time in communication with the exhaust passage 6*
of the piston, and, through it, with the exhaust port a and passage a' of the cylinder.
As the piston completes its outward stroke, the port a in the cylinder will be entirely
uncovered, thus enabling the main portion of the exhaust steam to escape directly
through it. By the completion of the throw of the crank, the piston will be driven
inwards to its starting position, first opening the port a² to the steam passage b of
the piston, and then bringing into coincidence the ports 162 with the ports cc,
whereby a fresh supply of steam is admitted to the face of the piston.
The supply port may, instead of delivering the steam into the interior of the rocking
plug, deliver it into a recess or indentation formed on the periphery of that plug.
This modification is shewn in the sectional view Fig. 3, where B is the trunk
piston detached from its cylinder, and fitted, as before, with a connecting rod C,
having a hollow T head or plug coupling. The space in this plug coupling is
divided up into two passages 1, 2, through which the live and exhaust steam
respectively pass.
is the supply port in the head of the piston, and 62 is the exhaust port in the
piston head.
The passage 1 is provided with an inlet and outlet port c c', and the passage 2
with an inlet and outlet port c³ ³, the latter of which communicates with the exhaust
passage b*.
The steam from the supply port enters the passage of the piston, and, by the
port c, passes to the passage 1; thence, through the port c¹ and the port 61, to the face
of the piston.
When, by the rocking of the piston rod as the piston advances, the port is closed,
the exhaust port 62 will be opened, and admit the exhaust steam to the passage 2,
whence it will pass, by the port c³, to the exhaust passage b*, and escape thence by
the exhaust port and passage of the cylinder.
Figs. 4, 5, and 6, shew a third form of engine, in various views, in which a con-
siderable portion both of the rocking plug coupling and of its seat, as used in the
second arrangement, are dispensed with.
A constant pressure is maintained in the central or connecting chamber, whereby
the connecting rods are constantly subjected to tensile strain, thus rendering it
expedient to construct the ports in that portion of the seat of the rocking plug
nearest the crank.

page_text: It will be seen that the portion of the rocking plug and its seat furthest from
the crank, has been removed. This arrangement ensures a lighter construction of
piston rod than in the previously described arrangements.
Fig. 4 shews, in sectional plan view, one of a pair of single action engines, the
cylinders of which are, at their open ends, in constant communication with the steam
boiler: thus, a pressure of steam, (during the working of the engines) is always
maintained on the interior of the trunk pistons, which consequently balance each
other in their movements against the retarding pressure of the steam.
Fig. 5 is a longitudinal vertical section of the same engine, the piston being, as in
Fig. 4, at the end of its return stroke.
Fig. 6 is a similar view of the engine to Fig. 5, but shewing the piston advanced
some one third of its stroke, or to a point where it has cut off the supply of
steam.
In these Figures, b is the inlet passage in the piston for conveying the steam by
the port 6' to the head of the piston, and 63 is the exit port by which the exhaust
steam passes to the passage b*, and, thence by the port and passage a a¹ of the
cylinder, to the exhaust pipe.
The rocking of the oscillating rod C, caused, as before, by the traverse of its piston,
opens and closes, alternately, the ports 616* in the piston head, there being, in this
case, no ports c c¹³ to be brought into coincidence with the ports 61 6².
When the piston rod C is at one extreme of its oscillation, the convex face of
the T head closes, say, the admission port in the head of the piston, and, when
at its other extreme position, it will close the exit port, precisely as when the whole
cylindrical surface of the T head coupling is used.
The admission of steam to the passage bis cut off by the advance of the piston, as
before, and the constant pressure of the steam within, or at the back of the piston,
serves to hold the piston in close contact with the T head of the piston rod.
From the foregoing explanation, it will be understood, that other surfaces of revo-
lution, such as cones and spheres, may be employed to take the place of the cylindrical
surfaces of the rocking plugs above mentioned.
It will also be understood that by my invention, the complications of valve gear,
and the disadvantages connected therewith, are removed, and provision is thereby
made for constructing single action engines in a far more economical manner than
heretofore.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is :-
The arrangements above described, whereby, in single action engines, the trunk
piston and its oscillating rod are enabled to control the admission of steam to the
cylinder, and the escape of the exhaust steam therefrom, as and for the purpose
above set forth.