A NEW AND IMPROVED ARCHIMEDIAN SCREW WHICH I CALL DEVAINES SCREW
Year: 1845

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CHARLES.
HENRY JOSEPH FORRET, of Lille, in France, but now of Great Saint Helen's,
Bishopsgate Street, in the City of London, Gentleman, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by
Her Royal Letters Patent under the Great Seal of Great Britain, bearing
date at Westminster, the Fourth day of August, in the ninth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said Charles Henry Joseph Forest, Her especial license, full power, sole
privilege and authority, that I, the said Charles Henry Joseph Forest, my
executors, administrators, or assigns, or such others as I, the said Charles
Henry Joseph Forest, my executors, administrators, or assigns, should at any
time agree with, and no others, from time to time and at all times during
the term of years therein expressed, should and lawfully might make, use,
exercise, and vend, within England, Wales, and the Town of Berwick-upon-
Tweed, and in the Islands of Guernsey, Jersey, Alderney, Sark, and Man,
and in all Her Majesty's Colonies and Plantations abroad, the Invention of
"A NEW AND IMPROVED ARCHIMEDIAN SCREW WHICH I CALL DEVAINES SCREW,"
communicated from abroad; in which said Letters Patent is contained a
proviso that I, the said Charles Henry Joseph Forest, shall cause a par-
ticular description of the nature of the said Invention, and in what manner the
same is to be performed, to be inrolled in Her said Majesty's High Court of
Chancery within six calendar months next and immediately after the date
of the said in part recited Letters Patent, as in and by the same, reference
being thereunto had, will more fully and at large appear.

page_text: NOW KNOW YE, that in compliance with the said proviso, I, the said
Charles Henry Joseph Forest, do hereby declare that the nature of the
said Invention, and the manner in which the same is to be performed, are
fully described and ascertained in and by the following statement thereof,
reference being had to the Tables hereunto annexed, that is to say :-
sin. i'
cos. i
sin. i
==
The Invention consists in producing an Archimedian screw, the new form of
which allows it to be constructed with all kind of metals and substances, and
also in a manner such as it can be put in motion under all given inclinations,
and be employed as an hydraulic motive power, or as a machine working by
itself. With the ordinary screw the thread has the form of a left surface, the
generator of which is a right line perpendicular to the axis of the screw, the
director being an helix having the same axis. To construct the improved
screw, I take also for the director of the surface of the thread an helix which
I trace upon the cylindrical surface of a certain radius r. Supposing, for
example, rod 048, i being the angle which the axis of the screw is to make
with the horizon, and being the ratio of the circumference to the diameter,
viz., 8.1415. I determine the rotation P of the screw in such a manner as
to produce P=20Thus, in the above example, if I take i=35°,
wherein cos.=0.819, sin. i=0.573, and 1428, I obtain for rotation of
the thread of the screw P=0d 482. This being established, I take for the
generator of the surface of the thread of the screw the tangent of the helix
above described. I call the virtual nucleus or axis of the screw the
cylinder of the radius r, which in the example herein-before mentioned is
Od 48. For facilitating the ulterior description of the process, I will call R the
radius of the effective nucleus, and R the radius of the internal surface of the
envelope or coating. I calculate the volume of water that it will give on each
revolution of the screw, of which the radius shall be R and r, by multiplying
cos, i by the co-efficient. That gives the Table No. 1 according to the
number of the threads of the screw, and the value of B. I subtract from that
volume that of a screw of which the radii shall be R and r, calculated in the
same manner; and the difference is the volume of water that gives on each
revolution the screw of which the radii are R and R. By taking here
R=0 0675, and R=0d 23, the volume in case of three threads is
O cubit d .029, r being the radius of a cylindrical surface concentric to the
screw. The angle X, under which the surface of the thread meets it, is given
by the expression cos. a ✓ ✓ ✓ cos. i. I place the centre of the circum-
ference, to which ends the coating of the screw, the lower part at a certain
distance from the level of the water in the basin where it is immersed,
sin, i

page_text: expressed by R³- cos. i, the distance being measured according to the ver-
tical. I take for the length of the screw L that which is given by the formula
L+R+ R), H being the vertical distance of the lowest
point from the superior aperture of the coating to the level of the water
into the inferior basin. I take preferably for R some large values, but which
nevertheless do not exceed that which satisfies the following relation:-
P
+ tangent are 2-1-✓(21, being the separation of the threads
parallelly measured to the axis of the screw. I take preferably for 1, if
the number N of the threads be 1, 2, 3, 4, 5, 6, 8, or 10, the value departing
very little from the following:-7+5; 4, 5; 4; 3, 8; 3, 6; 3, 4; 3, 2. When
the screw is to be acted upon by a powerful force, I take a great number of
threads and a great value for r. If the screw is very heavy, I preferably use
for the angle i a quantity such as I approximatively, co.i=2.
i
sin, i
If the screw
is to be moved with velocity, I take in preference a value for i such as
CIRI being here the radius of the helix which is run over by the
points of the liquid contained in the screw, the relative velocity of which is
the mean relatively to that of the apparatus. I prefer small to great velocities.
When I use great velocities, as the apparatus is constructed to operate under a
certain inclination, I place it a little more obliquely to the horizon; or, again,
without changing the inclination of the screw, I separate the thread from the
coating. In such
case I terminate the coating, firstly, laterally by two
generators, the first of which is in the vertical tangent plan to the vertual
axis or nuclus of the side where the thread is raising in the assending motion
of the screw, and is not under the axis of the screw, and of which the second
generator is at a distance from the vertical plan, passing through the axis, as
shewn by the Table 11., the distances above being reckoned from the side
where the thread rises, and those in less quantity from the side where it
declines. Secondly, I terminate the coating at the inferior part, on the helix
of the same directions, and of the same rotation, that the screw which inter-
sects the extreme generators of the coating, such are herein-before set, in
their point of union with the level of the water in the lower basin. Thirdly,
I end the coating at upper part in such a manner that it raises in the least
possible way above the level of the water in the upper basin, or, still better,
according to an helix of the same direction and of the same rotation as the
screw which intersects the extreme generators herein-before described, above
the level of the water of the higher basin, at a distance equal to that of the
space between two consecutive threads, such a distance being reckoned

page_text: sin.
according to the generators. In this last case place a sucker or a flood-
gate in the canal of discharge. When the screw is to be a motive power I
lower that helix parallelly to itself, in such a manner that the feeding water
can pass in toto by the cuts it forms. When the screw is constructed of
metal I preserve to the thread the form herein-before mentioned, being that
of a developing surface. When I curve or turn down that surface upon a plan,
the helix which is set upon the cylinder of the radius r, and which I take as a
director, is turned down upon a circumference of a circle the radius of which is
2i.
In the example herein-before mentioned that radius is 0rd 1467. I
form the joints with the sheets composing the thread according to the gene-
rators of the surface. These generators are placed in the turned-down or
seam according to the tangents to the circumference of the radius 2 i.
An entire revolution of the thread after the setting is into the seam to a full
revolution, as sin. i as to I, according to the preceding example. That revo-
lution, therefore, forms the five hundred and seventy-three thousandth parts
of a revolution. An helix of radius r, after being placed, is turned down upon
the circumference of concentric circle to the former, and which has for radius
the number of the spirals of the thread after the setting
being n. The superficy of that part of this thread included between the
cylindrical surfaces of the radius R and R is deducted from the formula
Thus, in the preceding example, the helix, according which the
threads intersect the centre of radius R=0 0675, is turned down according to
a circumference of 0 168 of radius; and the helix, according which the thread
meets the coating of the radius R=0d 23, is turned down upon a circumference
of Ord 420 of radius, and the surface of the thread is by running yard of
0sq.yd 613.
1
sin.
R2, R2
sin. i
cos. 2 i
+ siu. 2 i
I show in Figure 3 the shape I gave to the metallic sheets with which I com-
pose the thread. I always terminate the thread at the lower part to a generator,
when I end it at the top part to a plan perpendicular to the axis of the screw,
where it has the form of the developing of the circle of radius r.
In the
turning down of the helicoid surface, that curve is the developing of the circle
of radius. In the herein-mentioned example this curve ought to be
that shewn by Figure 4. When the thread is metallic it forms the nucleus
or axis, and the coating is of wood or of metals. If they are of wood the
thread joins to it, either in a groove or by supporters, or again by a jutting-out
formed with jointed pipes. If they are made of metal, the coating is constructed
by twisting round bands between the threads, and more generally the axis is
provided with channellings shaped in the form of an helix. I joint the sheet

page_text: T
sin. 2 i
of iron by means of rivets, those of zinc-copper by soldering, and those of cast
iron by using iron pins. When I construct the thread of wood I take for
joints some plans which are tangent to the vertical axis. They are perpen-
dicular to the surface of the thread. When the elements intersecting two joints
are not very large, I obtain very approximately their inferior and superior fronts
by means of Figure 3, by conducting to them, at convenient distances one
from the other, some tangents to the internal circumference such tangents are
like, of which the radius is
These elements are inserted between two
consequtive tangents and the two external circles. I apply these elements to the
axis without penetrating it. If, however, I wish, on account of the joining,
that they should penetrate that axis, I substitute, in case of need, for the deve-
loping surface of the thread, a left surface, by using for generator, in the plan
passing through the axis of the screw, a right surface approaching as near as
possible the curve of intersection of the same plan with the developing surface.
When I construct the thread of curved elements I use shingle-nailed helix like
upon the axis, taking care to lessen the one from the other according to the heli-
cord profile of the thread. I sometimes also place these shingles as developing
from the circle in plans perpendicular to the axis. The Figure 4 shews the
shape to be given to them in a plan. When the screw is to raise the water,
and if I take a fall of water for moving power, I construct the screw double
the external one, serving as a coating for the other; and I give to them such
dimensions that the product of the volume of water poured by each revolution
of the descending screw, multiplied by the elevation from whence the water
descends, is larger than the volume of the water poured by the ascending
screw multiplied by the elevation to which it raises the water. I take for the
difference of these quantities of action a quantity capable of overpowering
the frictions, and of giving to the apparatus the required velocity. I end each
screw in the inferior basin as if they were separated. When the internal
screw is prolonged under the basin where ends by the lower part the external
screw, I cause the edge of the basin to turn round the coating of the internal
screw, between that coating and the axis of the external screw, in such a
manner as I am not compelled to slope the edge of that basin, and to cause the
water to be lowered in it for the passage of the internal screw. Relatively
to the descending or moving screw, when it is to work with velocity, I shorten
the thread at the superior part in such a manner, that when the water is
penetrating through helicoid channel, it has acquired the required velocity
paralelly to the axis of the screw. When a screw employed as a motive
power is to be worked alone, and with a great velocity, and raise the axis a
ittle higher for immersion. Where a screw employed as a motive power is

page_text: adapted at its lower part, I choose the fixed rather than the moveable
coating. I prolong for the motive screw the coating on the side where the
thread is descending in the rotatory motion of the screw, a little further than
the limits exhibited by Table 11. Relatively to motive or other screws of
large size, in case of small falls of water, and if they are not provided with a
moveable coating, I replace it at a certain zone on the higher part of the
screw by a fixed coating, as I have before. If I resume the application of
the rules herein-before described to the screw which I have chosen as an
example, it will be easy to perceive that to construct my new Archimedian
screw I have to operate as follows; that is to say, I must set a cylindrical
axis of the radius Rord 0675, at Figure 1, Drawing 1. I envelope its
surface upon a plan like Figure 2 of the same Drawing, trace upon it some
parallel lines between them at an equal distance, and in a manner so that the
part of the generater intersected by three consecutive intervals be equal
to P=0d 432=0, the angle i being of 35°, and the radius r of the
virtuat axis being 0.048. Such a surface, being twisted round the axis of
the screw, will delineate the tract of the helices according to which the threads
are to be in contact with the said axis cut in a metallic sheet, which is level,
some pieces having the shape as shewn by Figure 3. These pieces are
placed between four lines; namely, first, two concentric circumferences, the
first having for radius ini ✓R2+ in, or ord 42, R being the radius of
the internal surface of the coating (R=0 23), and the other sin. ✓R2+
=0d 168; and, secondly, two right lines being tangent to a third cir-
cumference, this one being concentric to the two first, having for radius
sin.
1
COB.
cos.
0rd 147. These pieces must be soldered end to end, according to the
tangent, as if they were joints relatively to the piece which is to terminate
at the top of the screw, Figure 4. I must substitute for the terminating|
tangent the developing of the circle having for radius 0rd 147. I form thus
an annular surface, making in contour a number of revolutions which may be
to the number which it has to perform when it has been set at 0.573, or
sin. is to 1. Leave for the joining of that annular surface, as well as along
the internal circle as along the external, a small jutting-out part, as shewn
in Figures 3 and 4. By dotted lines split that one of the jutting parts which
is along the internal circle in small bands, which are to be turned down upon
the axis to fix them to it; turn down upon the anvil the thread, according
to the helicoidal shape it is to have after being set and adapted; then to the
axis of the screw, according to the curves which I have traced upon it
according to the process herein-before mentioned, compose the coating of

page_text: Rs
narrow staves, so as to form a cylinder with a circular basis, the internal front
of which having a radius R of 0rd 23. Develop that front upon a plan, Figure 5.
Trace in that plan equidistant and parallel lines intersecting the generators of
the cylindrical surface in parts of 3, or of Ord 144 in length. These lines will
shew, on the internal front of the staves, the point of union of the threads of
the screw. Delineate upon it, according to these lines, some saw cuts under an
angle of 36°, as Figure 6, as it is to that angle that corresponds a consinus
equal to * cos. i, or to ✓ (0.23) (0.048)³ x cos. i. The angle i, under
which the screw is to work, is that which the dotted line A, B, Figure 1, is to
make with the axis of the screw. That dotted line points the level of the
water in the basin into which the screw is to be immersed by its lower part.
Figure 7 shews the shape of the screw at its upper part. Figure 8 shews
that shape at the lower part. These two Figures exhibit the iron or wood
works by which the edges of the threads are made steady to the top and
bottom. These works are also exhibited by the Figures 3 and 4.
R
Figure 9 is an elevation of the lower iron or wood work, drawn separately.
The coating is surmounted with hoops, and the axis is provided with pivots
and other essential mechanism too well known to be described, being in that
respect similar to the other Archimedean screw.
And having now fully described my Invention, and the manner in which the
same is to be performed, I wish it to be understood that I do not confine
myself rigidly to the detail of the several parts of the machinery herein
described as composing the component parts of an Archimedean screw, nor do
I claim as my Invention the several parts with which the screw can be con-
structed, except so far as they may be employed in the manner I have
employed them in carrying out my Invention; but what I consider and claim
as my Invention is,-
First, to give to an Archimedian screw an unlimited number of threads.
Secondly, to establish a useful connexion between the number of threads
and the rotation of the threads, as well as between the said rotation and the
inclination of the screw.
Thirdly, the facility of changing according to circumstances the diameters of
the axis of the said screw.
Fourthly, the means of causing the diameter of the coating to be deter-
mined by the capicity I give to the screw.
Fifthly, the facility of giving to the screw a length not exclusively deter-
mined by its diameter, but, above all, determined according to the relative
elevation of the basins to be put into communication.

page_text: Sixthly, the constructions of a double screw.
Seventhly, the applications of the Archimedean screw, as I have described,
o be worked as a motive power, and also working by itself.
In witness whereof, I, the said Charles Henry Joseph Forret, have
hereunto set my hand and seal, this Fourth day of February, in the
year of our Lord One thousand eight hundred and forty-six.

page_text: OWING for the several values of the co-efficients serving to multiply the
radii of the virtual centre, to obtain-Firstly, the values of the arc, which
measured upon the internal surface of the casing from its most elevated
generator, and, according where the directions are placed, the horizontal
generators of the thread ends to the last one of the generators of the
casing which reaches the hydrophore volume-Secondly, the distance
R sin., to which is placed that generator of the vertical plan passing
through the axis of the screw. is the ratio of the radius of the casing