Improvements in Furnace Air Blowing Engines for Water-tube Boilers.
Year: 1897

page_text: PROVISIONAL SPECIFICATION.
Improvements in Furnace Air Blowing Engines for Water-tube
Boilers.
WILLIAM HENRY ALLEN and RICHARD WILLIAM ALLEN, Engineers, of Queen's
Engineering Works, Bedford, do hereby declare the nature of this invention
to be as follows:-
The object of our invention is to improve the working of furnace air blowing
engines which are used for forcing air through furnaces of water-tube boilers of
the type known as Belleville or other similar make, or any other purpose.
39
In these engines where the air compressing pump cylinder is driven direct from
a steam engine and is placed at tandem either above or below the steam cylinder,
the piston of which is driven by means of a crank & connecting rod, it is difficult
to run the plant at a few number of revolutions per minute, the reason being
that as the piston of the air compressing cylinder reaches the end of its stroke and
the crank-pin its dead centre, the air is compressed to a high pressure and the
tendency of this is to bring the engine and pump to rest. Flywheels are fitted
to the crank-shaft to overcome this tendency and if the speed of the engine
is maintained at about 80 revolutions per minute it will work in a satisfactory
manner. If, however, the speed is reduced below this figure the plant is generally
brought to a standstill.
The object of our invention is:—
(1) To enable us to run this combined plant at a much lower speed than the
above without requiring to fit heavier flywheels, and
(2) To be able to reduce the pressure of air compressed in the cylinder and
(the discharge pipes or receiver) to a minimum.
To do this we fit a suitable by-pass valve to the air compressing cylinder in such
a way that the air which is being compressed on, the one side of the air compressing
piston can be transferred to the other side during the whole period of this
stroke.
This valve can be made as a screw-down valve or a plug cock and is so arranged
that by turning the handle on the spindle of a screw-down valve more or less
or twisting the handle of a plug cock through a larger or smaller angle, the
quantity of air by-passed from one side of the air compressing piston to the other
side can be regulated according to the amount of air and pressure required.
By this means we are able to run the plant at any speed and against any
pressure which may be found necessary.
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page_text: Improvements in Furnace Air Blowing Engines for Water-tube
Boilers.
WILLIAM HENRY ALLEN and RICHARD WILLIAM ALLEN, Engineers, of Queen's
Engineering Works, Bedford, do hereby declare 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 our invention is to improve the working of furnace air blowing
engines which are used for forcing air through the furnaces of water-tube boilers of
the type known as "Belleville or other similar make.
In these engines where the air compressing pump piston is driven direct from
a steam engine and is placed at tandem either above or below the steam cylinder,
the piston of which is driven by means of a crank and connecting rod, it is difficult
to run the plant at a low number of revolutions per minute, the reason being
that as the piston of the air compressing cylinder reaches the end of its stroke and
the crank-pin its dead centre, the air is compressed to a high pressure and the
tendency of this is to bring the engine and pump to rest. Flywheels are fitted
to the crank-shaft to overcome this tendency and if the speed of the engine
is maintained at about 80 revolutions per minute the plant will work in a satis-
factory manner. If, however, the speed is reduced below this figure the plant
is generally brought to a standstill.
The object of our invention is:-
(1) To enable us to run this combined plant at a much lower speed than the
above without requiring to fit heavier flywheels, and
(2) To be able to reduce the pressure of air compressed in the cylinder and
the discharge pipes or receiver to a minimum.
To do this we fit a suitable by-pass valve to the air compressing cylinder in such
a way that the air which is being compressed on the one side of the air compressing
piston can, when it is required to reduce the pressure, he transferred partially or
wholly to the other side during the whole period of the stroke.
This valve can be made as a screw-down valve or a plug cock and is so arranged
that by turning the handle on the spindle of the screw-down valve more or less
or twisting the handle of the plug cock through a larger or smaller angle, the
quantity of air by-passed from one side of the air compressing piston to the other
side can be regulated according to the amount of air and pressure required.
By this means we are able to run the plant at any speed and against any
pressure which may be found necessary.
To make our meaning quite clear we give a section of the air compressing
cylinder fitted with our by-pass valve. The illustration shews a screw-down by
pass valve, but a plug-valve can be used instead if found more convenient, the
effect on the working of the plant being the same.
The drawing shews a section through the air-compressing cylinder and the by-
pass valve.
P is the air-compressing piston driven by a rod or rods R from the
cross-head of the steam engine or in any other convenient way. Fis the air inlet
branch which admits air into the chamber E. From this chamber the air is
admitted to the top end of the air cylinder through the port B or to the bottom end
through the port B, by the valve which is worked up and down by means of an
eccentric. The air is delivered under pressure into the chamber AA and from
this chamber into the discharge branch Q from which it is distributed to the
furnaces. The ports B, B, have openings b, b, which can be put into connection
with one another by means of the by-pass valve D. By this means the pressure

page_text: of the compressed air and the speed of the engine can easily be regulated to any
desired extent. When the valve C is closed as shewn in the drawing there is
no connection between the top and bottom ends of the air cylinder and the full
compression of the air is obtained. When it is necessary to reduce the pressure
of the air or the speed of the engine, the valve C is opened, the top and bottom ends
of the air cylinder are put into communication with one another and the air is
partly by-passed and only partially compressed.
With a suitably designed valve the compression can be regulated from maximum
to zero. When the maximum compression is required the valve is closed and no
air by-passed; with zero compression the whole of the air is by-passed. Between
these two extremes any degree of compression can be obtained by regulating the
opening of the valve C by means of the handle H.
Having now particularly described and ascertained the nature of our said in-
vention and in what manner the same is to be performed, we declare that what we
claim is:-
1st. The arrangement of a screw-down by-pass valve arranged in such a way
that communication can be established between the top and bottom ends of the
air compressing cylinders of furnace air blowing engines. The amount of
lift of this valve regulating the quantity of air by-passed and consequently the
pressure of compression and also the speed of the engine, to any desired extent,
all substantially as described and illustrated.
2nd. The arrangement of a plug valve instead of a screw-down valve for the
purposes above mentioned, all substantially as described.
Dated this 20th day of August 1898.
WILLIAM HENRY ALLEN.
RICHARD WILLIAM ALLEN.