Improvements in Steam Engines.
Year: 1898

page_text: Date of Application, 15th Nov., 1898-Accepted, 22nd July, 1899
Improvements in Steam Engines.
I, WILLIAM EDGAR PRALL, of New York, in the County and State of New
York, United States of America, Steam Engineer, do hereby declare the nature
of this invention and in what manner the same is to be performed, to be par-
ticularly described and ascertained in and by the following statement :-
The invention relates to engines adapted to be driven by steam developed in
the cylinder or cylinders, and its main object is to provide for the admission of
suitable quantities of superheated water under high pressure directly to an engine
cylinder by means of a momentary contact of the piston with a tappet valve.
In the accompanying drawings
Figure 1 is a view diagramatic in character and partly in section illustrating
my improved engine;
Figure 2 is a partial section on an enlarged scale of a cylinder and valve;
Figure 3 is a partial transverse section on line 3-3 of Figure 2.
Numeral 1 indicates a tank adapted to hold water under a high pressure.
Numerals 2, 3, 4 and 5 denote the cylinders of a compound engine. Super-
heated water under high pressure is admitted from the tank to cylinder 2 and
passed from it in the form of water and vapor or steam through cylinders 2, 3, 4
and 5 in series to drive the several pistons by quadruple expansion.
A part of the invention however is independent of multiplied expansion, being
applicable to a single cylinder.
6 indicates pistons and 7 piston rods. 9 denotes a pipe leading from the bottom
of the water tank to cylinder 2. 10 denotes slide valves of usual form. 12 denotes
the valve operating cccentrics and 13 a crank shaft. 14 are connecting rods.
16 denotes exhaust conduits whereby the valve chests of the several cylinders 2,
3, 4 and 5 communicate each with the valve chest of the succeeding cylinder
enclosing a valve 10, and 16¹ denotes a final exhaust.
Water heated to about 400° F. can be admitted to cylinder 2 through valves 10
and exhausted from it through the several cylinders with the effect to start the
engine and move it with the power developed by the vaporization of the water
and the consequent expansion, but such means is impracticable for general use
and is only employed to start the engine or to utilize a more than average of
power for special occasions.
For admission of hot water I provide tappet valves situated in the path of the
piston and adapted to he opened by it very near the end of its stroke. 18 indicates
such valves and 18 guides for their stems (see Figure 3). 19 is a pipe con-
veying, water from the tank to the valve chamber 20, through a branch or
branches 21. The valve chamber 20 being in free communication with the
water space of the tank the valves 18 are normally held closed by pressure from
the tank and opened by the piston at the close of its forward stroke.
It is important that but a small quantity of water be admitted at each stroke
and the valve stem therefore extends but a small distance through the cylinder
wall and the valve is opened but an instant, the proper effect being produced by
a momentary contact with the piston. At such time the piston rod, the pitman

page_text: and the crank should be at or nearly approaching the dead center to avoid a
reversal of the engine.
The instantaneous opening and closing of the valve is characteristic of the
invention and the direct contact of the piston with a tappet valve. is the most
convenient means of effecting it, though others are not excluded provided they
open and close the valve with substantially the same effect. By use of a tappet
valve, wear and cutting, such as is incidental to -slide valves, is avoided.
A tappet valve operated as herein- set forth would not admit sufficient steam
to run an engine for if the valve stem were made long with the intent that the
piston should sooner open the valve to admit-steam for a sufficiently long period
then the engine would be reversed. That is the admission must be near the
end of the piston's path and while the crank is near the dead center, which con-
ditions preclude the admission of sufficient steam on account of the great volume
necessary for work, and a tappet valve opened by the piston could not be used in a
steam engine without special means for holding it open to admit sufficient steam
after the piston leaves it.
11
'
Obviously the engine cannot be started by the sole use of a single tappet valve
constructed and arranged as set forth. The alide valve 10 of cylinder 2 can be
operated to admit water for this purpose, or other means may be employed.
"
Said valve and similar valves for controlling the utilization of exhaust in the
several cylinders, in case of multiple expansion, can be used temporarily for
ascending steep grades or for purposes requiring an exceptional amount of power
and a cock or valve 22 in any usual way, as by a rod 23, can be provided.
24 denotes a steam pipe continuous with pipe 19 whereby the steam space of
tank 1 may communicate with each valve box or chamber 20 of cylinders 3, 4
and 5. 26 is a cock or valve back of its connection with pipe 27 to close said
pipe 24. 27 is a pipe whereby the lower or water space of tank 1 may com-
municate with the steam pipe 24, and 28 is a valve or cock to close such pipe.
29 indicates a cock or valve in pipe 9. By suitable manipulation of these valves
either hot water or steam or both may be admitted to the valve boxes and mediately
to the cylinders. The several cylinders may be protected from loss by radiation
in any usual manner. No special provision for maintaining the heat of the hot
water cylinder 2 is required on account of its small size and the very high heat of
water supplied to the entire engine through it.
The amount of water admitted to a cylinder can be regulated by the length of
the valve stem, or the manipulation of the main exhaust valve, or by throttling
the supply pipe.
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:-
1. In an engine the combination of a holder for superheated water under
pressure, an engine cylinder, a charging conduit whereby the holder and cylinder
may communicate, a piston. for the cylinder, a valve, means for momentarily open-
ing said valve to admit water to reverse the piston, said valve being closed by
pressure from the superheated water charging conduit immediately upon the
reversal of the piston, and exhausting devices, substantially as described.
2. In a compound engine, the combination of a holder for superheated water
under pressure, a charging conduit, engine cylinders having valves and valve
casings enclosing chambers in free communication with the holder and in com-
munication with the cylinders when the valves are open, exhausting devices com-
prising conduits whereby the cylinders communicate to exhaust from one to
another and finally from the engine, and pistons for said cylinders, the valves
being situated in the path of a moving part of the engine and adapted to admit
sufficient water to drive the engine by instantaneous contact at suitable intervals
with said moving part, said valves being closed by pressure from the holler
immediately upon the reversal of the pistons, substantially as described.

page_text: 3. In a compound engine, the combination of a holder for superheated water
under pressure, engine cylinders having valves and valve casings enclosing
chambers in free communication with the holder and in communication with the
cylinders when the valves are open, conduits whereby the cylinders communicate
to exhaust from one to another and finally from the engine, pistons for said
cylinders, the valves being situated in the path of the moving part of the engine
and adapted to admit sufficient superheated water to drive the engine by instan-
taneous contact at suitable intervals with said part and closed by pressure from
the holder immediately upon the reversal of the pistons, and supplementary devices
for starting the engine, substantially as described.
4. In a compound engine, the combination of a holder for superheated water
under pressure, engine cylinders having valves and valve casings enclosing
chambers in free communication with the holder and in communication with the
cylinders when the valves are open, the valves being adapted to be closed by
pressure from the holder immediately upon the reversal of the pistons, conduits
whereby the cylinders communicate to exhaust from one to another and finally
from the engine, pistons for said cylinders, said valves being situated in the path of
the moving part of the engine and adapted to admit sufficient superheated water
to drive the engine by instantaneous contact at suitable intervals with said part,
and supplementary devices for starting the engine, said devices comprising a
distinct valve and separate superheated water supply pipe, substantially as
described.
Dated thin 14th do. of Nawamba 1900
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool,
Agents for the Applicant.
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool,
Agents for the Applicant.