IMPROVEMENTS IN STEAM ENGINES
Year: 1858

page_text: PROVISIONAL SPECIFICATION left by David Rowan and Stewart Robert-
son at the Office of the Commissioners of Patents, with their Petition,
on the 20th November 1858.
We, DAVID ROWAN and STEWART ROBERTSON, of Greenock, in the County
of Renfrew, North Britain, Engineers, do hereby declare the nature of the
said Invention of "IMPROVEMENTS IN STEAM ENGINES," to be as follows, that
is to say:
This Invention relates to certain improvements in steam engines, and has
for object the obtainment of increased economy of fuel, and compactness, and
convenience of arrangement. An engine or set of engines constructed
according to a portion of this Invention comprises one or more duplex
cylinders. Each duplex cylinder consists of an outer annular cylinder, com-
bined with a central cylinder or cylindrical space. Pistons working in the
central and annular cylinders are connected by their piston rods to a cross
head or to the crank shaft, in such a way as to work together.
According to one modification the supply of steam to the cylinders is
governed by a valve or valves in such a way that the steam from the boiler
first enters the central cylinder; next passes thence to the opposite end of the
annular cylinder; and finally passes from the annular cylinder into the
condenser.
According to another modification the valve or valves may be arranged to
admit the steam first to the annular cylinder, afterwards transferring it to the
central cylinder.

page_text: Another portion of this Invention relates to an arrangement of valvular
mechanism, specially designed for application to the duplex cylinders herein-
before described, but also applicable to other double-cylinder expansive engines.
In one modification of this improved valvular mechanism a single slide valve
is used for both the central and the annular cylinders, and it works in the
steam chest on a port facing in the ordinary way. There are two sets of
ports in the port facing, and the slide valve is made duplex, one side governing
each set of ports. The end port of one set of ports leads to one end of the
central cylinder, and the other end port of the same set leads to the opposite
end of the annular cylinder, and there is a passage in the slide valve which
at the proper periods brings these two ports into communication to transfer
the steam from the central to the annular cylinder; the other set of ports are
similarly arranged, but in inverted positions. The central port in each set
leads to the condenser. The valve is worked in the ordinary way, and alter-
nately uncovers the ports leading to opposite ends of the central cylinder
for the admission of fresh steam. The ports communicating with opposite
ends of the annular cylinder are each alternately in communication with the
respective passage in the slide valve, by which they receive steam from the
central cylinder and with the hollow or cup of the slide valve by which a
communication is formed with the exhaust port, but they are never uncovered
so as to receive fresh steam. This valvular mechanism may be modified in
various ways; thus, two slide valves working simultaneously may be used, and
these may be arranged in one or in two steam chests; or the arrangement may
be applied in duplicate.