CERTAIN IMPROVEMENTS IN STEAM ENGINES, AND IN THE VALVES CONNECTED THEREWITH, WHICH SAID IMPROVEMENTS IN VALVES ARE ALSO APPLICABLE TO SAFETY VALVES
Year: 1858

page_text: PROVISIONAL SPECIFICATION left by Ellis Rowland and John Dewhurst
at the Office of the Commissioners of Patents, with their Petition, on
the 5th November 1858.
We, ELLIS ROWLAND, of Manchester, in the County of Lancaster, Engineer,
and JOHN DEWHURST, of the same Place, Engineer, do hereby declare the
nature of the said Invention for "CERTAIN IMPROVEMENTS IN STEAM ENGINES,
AND IN THE VALVES CONNECTED THEREWITH, WHICH SAID IMPROVEMENTS IN VALVES
ARE ALSO APPLICABLE TO SAFETY VALVES," to be as follows:-
The first part of these improvements relates to steam engines, and consists
in a novel and peculiar arrangement and construction thereof. The piston
consists of a hollow ram oscillating upon a hollow bearing at a point situated
about the middle of its length, and each end of this double piston works in a
cylinder, both cylinders being furnished with a steam-tight gland or packing,
through which the piston slides or works, the extreme ends of each cylinder
(or of only one if preferred), are connected to a crank upon the shaft to be
driven. The hollow shaft or bearing upon which the piston oscillates may
either be made to form a valve itself, or be furnished with a disc valve in
such a manner that the oscillating motion of the hollow piston shall open
and close the slide valve so as to admit or shut off the steam which passes
through the pistons into the cylinders alternately, and forcing or driving the
cylinders to and from the centre of oscillation impart the required rotatory
motion to the crank and shaft, the steam being exhausted after each stroke
from the side opposite to the supply pipe.

page_text: A second part of the Invention relates to those portions of the engine
known as the "throttle" and "diminishing valves."
In our improved "throttle" valve, the valve is mounted loosely upon a
central vertical spindle, the top of which is connected to the "governor " of
the engine, and is also secured to a receiver which rises and falls in a tank
of mercury, a second and similar arrangement being placed beneath the valve
so that the whole weight of the valve, and its spindle and receivers, may float
upon the mercury and form an equilibrium valve. The lower end of the
central spindle projects beyond the case of the apparatus, so that when the
engine exceeds a given speed the action of the "governor" will force the
spindle down, and cause it to press against a lever and open a valve to allow
the steam to escape, and reduce the speed. The diminishing valve is similar
in principle, but in this valve only one receiver and tank is required, and the
valve remains open whilst the steam continues at a given pressure, but is
partially or quite closed when such pressure is exceeded.
Thirdly, our Invention relates to the "safety valve," which is also con-
structed so as to balance the weight of the valve, &c., by supporting or floating
it upon mercury. The valve acts in the ordinary manner, excepting that
should the valve be fixed in its seating, the pressure of the steam will force
the mercury out of the tank and effect its escape. This description of valve
may also serve as an indicator of the pressure of steam by means of a float
upon the mercury, and provided with a suitable index.