IMPROVEMENTS IN ROTARY PUMPS AND ENGINES
Year: 1883

page_text: LETTERS PATENT to Edwin Bryan Donkin of Southwark Park Road
Bermondsey for an Invention of "IMPROVEMENTS IN ROTARY PUMPS AND
ENGINES"
PROVISIONAL SPECIFICATION left by the said Edwin Bryan Donkin at
the Office of the Commissioners of Patents on the 13th January 1883.
EDWIN BRYAN DONKIN of Southwark Park Road Bermondsey
MENTS IN ROTARY PUMPS AND ENGINES "
" IMPROVE-
This Invention has for its object improvements in rotary pumps and onginges
applicable especially for drawing or forcing air but also applicable for drawing or
forcing other fluids and as motive power engines.
For this purpose I form a rotary pump or engine of an outer casing with its two
ends flat and parallel with one another-Through one end is passed a shaft or axis.
On the inner face of the end of the casing this is surrounded by a disc which lies
in a recess in the end so that the inner face of the disc and end are level with one
another.
Projecting from the disc is a crank pin which extends to the opposite end of the
casing and there passes through a disc which is concentric with the crank axis
and capable of revolving in an aperture in the end of the casing. On the outer
side of this disc the crank pin has fixed upon it a crank arm carrying a stud
or axis concentric with the crank shaft and this is supported in a suitable fixed
bearing.
Within the casing the crank pin passes through the centre of a partition the
ends of which fit against the two ends of the casing.
When the crank shaft or axis is revolved it carries the partition with it. Tho
partition is not fixed to the crank pin but is loose upon it and its movements are
so controlled that it makes a half revolution cach time that the crank shaft makes
complete revolution.
If the crank shaft is horizontal the partition starting say from a horizontal
position below the shaft does not again assume a horizontal position until it again
eturns to the same horizontal position below the shaft. Two ports are led from
he casing (inlet and outlet) it inay be from below the partition when in this
Price B21

page_text: horizontal position and the casing and partition are so shaped that a portion of the
casing between the ports then fits against the centre of the under side of the
partition. The casing is also so shaped that as the crank shaft is revolved and
the partition is carried round with it some portion of the sides or extremities of
the partition is always in contact with some portion of the casing between the
ports and so that the opposite extremities of the partition are also always both
in contact with the inner circumference of the casing.
In this way when the crank shaft is rotated air or other fluid is continuously
being drawn into the casing through the inlet and expelled through the outlet.
One way in which the movement of the partition may be controlled so as to
cause it to make half a revolution for each revolution of the crank axis is as
follows:-
The partition is formed with a short tubular neck surrounding the crank pin
where it passes through the circular disc before mentioned-Outside the disc it has
fixed upon and concentric with it a hollow wheel or disc.
In the outer face of this wheel or disc are two grooves at right angles to
one another and one of them is in a line with the length of the partition.
Fitting in each groove is a bar-each bar at its centre is carried by a pin-
around which it can revolve-These pins are carried by an outer fixed casing.
One pin is vertically below the central line of the crank shaft and the other
above it and they are at the same distance as the crank pin from this central
line the bar carried by the lower pin is also maile to slide in the groove which
is in a line with the length of the partition. As the partition and hollow disc or
wheel at its end are carried round by the crank pin the disc or wheel slides to
and fro along the bars and in its movement also causes each bar to make one half
revolution for each revolution of the crank shaft and so the partition also can only
make one half revolution during the same time.
The pin which the lower bar turns around may be a fixed pin and an arm may
be carried up from its end inside the interior of the hollow wheel or disc to carry
a bearing for the short axis of the crank arm which as before mentioned is at this
end of the crank pin.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Edwin Bryan Donkin in the Great Seal Patent Office on the
13th July 1883.
EDWIN BRYAN DONKIN of Southwark Park Road Bermondsey
MENTS IN ROTARY PUMPS AND ENGINES
23
"IMPROVE.
This invention has for its object improvements in rotary pumps and engines
applicable especially for drawing or forcing air but also applicable for drawing or
forcing other fluids and as motive power engines.
In the Drawings hereunto annexed I have shewn examples of pumps or engines
constructed according to my invention. Figure 1 is a transverse section and
Figure 2 a longitudinal section of one form of the pump or engine. Figures 3
and 4 are similar views of a modified form of this pump or engine Figures 5
and 6 are similar views of another form and Figure 7 a transverse section of
another modification. In Figures 1 and 2 A is the casing or cylinder its inner
surface is in transverse section approximately a cardioid curve that is a curve along
which any point upon a circle is carried when that circle is caused to roll around
a second stationary circle of equal diameter. B is an oblong piston through the
centre of which passes a crank pin C carried by an axis D the centre of which
would coincide with the centre of the stationary circle above mentioned. The
radial distance between the central line of the axis D and the central line of the
crank pin is made somewhat less than the radius of the above mentioned circle-
and the extreme point of the inward bend of the cardioid curve is also cut off as
shown so that the piston B may at the centre be of sufficient thickness to give it
the requisite strength. As the piston is carried round by the crank it is caused
to make a half revolution for each complete revolution of the crank axis. The
ends of the piston are made to fit closely up to the ends of the casing and the
curve of the casing is such that the edge of the piston which is at any time furthest
from the inward bend of the casing always fits up to the side of the casing in
whatever position the crank may be.
When the piston is in the position shewn at Figure 1 it is at right angles to
a line radial to the axis which passes through the centre of the crank pin and the
extremity of the inward bend A* of the casing is made to fit up to the centre of
the top side of the piston.
The piston is made to taper from its centre to its two side edges and the inward
bend of the casing is so shaped that when the crank axis is revolved and the piston
carried round by the crank arm one side of this portion A* of the casing always
fits against one side of the piston until the piston comes into a position at right
angles to that in which it is shown the inward bend of the casing then fits to the
edge of the piston. A still further movement of the piston brings its opposite.
side into contact with the other side of this portion A* of the casing and so the
piston is carried round continuously making as before stated half a revolution for
ench complete revolution of the crank shaft.
E is an inlet port for admitting air or other fluid to the casing and F the outlet
port by which it is expelled from the casing. The inward bend of the casing
eparates these two ports and always fitting to the piston as above described
revents the passage of fluid directly from one to the other.
It will be seen that by making the casing to bend inwards in the manner
hewn and always to fit to the piston at this point that ports of very large size
nay be made use of whereas if the casing did not at this point fit to the piston the
ize of ports which could be used would be very restricted,

page_text: In order to control the movement of the piston as it is carried round by the
crank pin so as to keep its ends always close to the sides of the casing without
rubbing against them I control the movements of the piston in the following
manner.
The crank pin C is made to project from a disc G on the axis D this disc is
received in a recess at one end of the casing A.
The other end of the crank pin passes through a disc H which is concentric with
the crank axis and which is free to revolve in a corresponding hole in the opposite
end of the casing.
A tubular neck projecting from the end of the piston also passes through this
disc. Outside the disc it has upon it a boss from which project rods I these at
their onds have projections J extending from them parallel with the crank pin and
these carry pairs of parallel guide bars K in the form of a right angled cross-
one pair of guide, bars is parallel with the piston and the other at right angles
to it.
Between each pair of guide bars is an oblong block L turning on a pin M carried
by a casing A¹ fixed to the end of the casing A. The pins M are on opposite sides
of and equidistant from the crank axis.
A radial line drawn through the extremity of the inward bend of the cardioid
curve passes through the centre of one pin-the other is on the opposite side of
the crank axis both of them are at the same distance from the axis as the crank pin
that carries the piston. The two pins M are connected by a bar N. The crank
pin has at its end an arın Cx carrying a pin which is concentric with the crank
axis and this pin is received in a bearing formed to receive it in the centre of the
bar N.
As the piston is carried round by the crank pin the blocks L are turned on the
pins M each making a half turn for every complete revolution of the crank-and
in order that the ends of the blocks may not strike one against the other as they
revolve the blocks are at their ends cut away on one side so as to reduce them to
half the thickness of their central part and so that the extreme ends of one block
are in a different plane to the extreme ends of the other block. In this way blocks
of longer length can be used than would otherwise be practicable. The end of the
casing which receives the disc H is made in two parts to enable the disc H to be
put into place between them.
In the modification shewn at Figures 3 and 4 no casing A' is used but the guide
blocks L and the pins which carry them are on the inside of one end of the
casing A. The same letters of reference are marked on the parts of these figures
as in Figures 1 and 2.
In the modification shown at Figures 5 and 6 the construction is the same ns
shewn at Figures 1 and 2 except that the tubular neck at the end of the piston
which passes through the disc H has upon it an internal toothed wheel O which
gears with a fixed toothed wheel P carried by the interior of the end of the
casing A this toothed wheel being concentric with the crank axis. It is not
essential that the wheels O and P should be toothed they might be plain untoothed
wheels.
In the modification shewn at Figure 7 the pump or engine is made double that
is two pumps or engines such as shewn at Figures 1, 3 or 5 are placed together
whilst the pistons B instead of being made to fit at all times against a point A* of
the casing are made to fit at all times one against the other. The two pistons are
also set as shewn so that when one piston is parallel with the crank arms which
carry it the other piston is at right angles thereto so as to equalize the flow of fluid
through the pump or engine. The movement of each of the pistons may be
controlled in either of the ways hereinbefore described.
Having thus described the nature of my invention and the manner of performing
the same I would remark that I am aware that it has before been proposed to
construct engines or pumps with a piston carried by the pin of a crank revolved
in a casing of a form approaching somewhat to a cardioidal form but in this caso

page_text: the extremities of the side edges only of the piston were made to fit up to the
curved interior of the casing. With such a construction the size of inlet and
outlet ports which could be used was of necessity extremely limited-but by making
the extremity of the inward bend of the casing to fit to the sides of the piston
ports of large dimensions may be employed as in this way a division is always
formed between the two ports.
Also by making the casing with the curve bending inwards at one point to make
a heart shaped figure I am able to make the piston of much less width than would
otherwise be practicable.
The improved means herein before described for controlling the movement of the
piston also enables the movement of the piston to be more efficiently controlled
than heretofore.
What I claim as my improvements in rotary pumps.and engines is:-
First The construction of rotary pumps or engines substantially as herein before
described with reference to Figures 1. 2. 3. 4. 5 and 6.
Second-The construction of rotary pumps or engines substantially as herein
before described with reference to Figure 7.
Third The improved means for controlling the movement of the piston
substantially as herein before described with reference to Figures 1. 2. 3 and 4 of
the drawings.
Fourth In order to control the movement of the piston of pumps or engines of
the class herein before described making the crank pin which carries the piston
and also a tubular neck on the piston to pass through a disc concentric with the
crank axis and capable of revolving in a circular aperture in the end of the casing
and controlling the movements of the piston by mechanism outside the casing
substantially as described.
Fifth In pumps or engines in which a piston is carried by the crank pin of a
crank revolving in a casing of a somewhat cardioidal form forming the pump or
engine in such manner that the inlet and outlet ports are separated the one from
the other by the inward bend of the casing being made to fit to the piston
substantially as herein before described.
In witness whereof 1 the said Edwin Bryan Donkin have hereunto set my
hand and seal this eleventh day of July in the year of our Lord One
thousand eight hundred and eighty three.
n BANIZTA