IMPROVEMENTS IN DREDGING APPARATUS
Year: 1874

page_text: LETTERS PATENT to John Henry Johnson, of 47, Lincoln's Inn
Fields, in the County of Middlesex, Gentleman, for the Invention
of "IMPROVEMENTS IN DREDGING APPARATUS."-A communication from
abroad by Alphonse Couvreux, of Paris, in the Republic of France.
PROVISIONAL SPECIFICATION left by the said John Henry Johnson
at the Office of the Commissioners of Patents, with his Petition, on-
the 15th July 1874.
I, JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County
of Middlesex, Gentleman, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN DREDGING APPARATUS,” a communication
to me from abroad by Alphonse Couvreux, of Paris, in the Republic of
France, to be as follows:-
This Invention has for its object the facilitating of the discharge from
the buckets and the transport along the receiving trough or tray of a
dredging machine of materials, such, for example, as earth and sand of

page_text: a clayey nature, which have a tendency to adhere to the surfaces with
which they are brought into contact.
In order to effect these objects it is proposed to arrange in the interior
of each bucket of the chain of buckets a movable bottom and back, the
range of motion of which is limited by a stop capable of sliding in a
groove or slot formed in the fixed back of the bucket, so that when. the
bucket arrives at the top and is tilted by turning on its own centre, the
movable bottom with the back will first slide a certain distance with the
materials it contains, and then being suddenly arrested in its motion by
the arrival of the stop at the end of the groove or slot, a shock or jerk
will be produced, which will have the effect of detaching the materials
and causing them to fall into the trough or tray provided for their
reception, the movable bottom with its back being subsequently replaced
in the normal position by the refilling of the bucket after its descent.
The movable back may be connected to the fixed back by pins or rivets
passing through the slot, and forming the sliding stop herein-before
referred to, such pins or rivets being secured to a plate working against
the back of strengthening bars or strips, with which the fixed back is at
that part provided. Apertures are provided in the ordinary back and
bottom of the bucket for the purpose of admitting air between the parts
at the time when the bucket is inverted, the apertures in the bottom
also serving for the discharge of any earth or sand which may have been
introduced between the movable bottom and the fixed bottom during the
filling of the bucket.
In some cases, in lieu of employing a movable back and bottom, the
requisite shock or jerk may be obtained by causing the bucket itself to
fall or move forward a short distance, so as to loosen or detach the
adherent materials, but the former arrangement is preferred.
It is also proposed to apply to the upper end of the troughs or trays
into which the materials from the buckets are discharged a series of
screws or helices, which are rotated at a high velocity, so as to divide
the mass of material at the moment of its descent, and prevent its
accumulating at that part. These screws or helices have the effect not
only of working up the materials, but also of projecting them at a certain
velocity in the direction of the trough or tray, their blades being so
curved at their extremities as to ensure the materials being projected in
the required direction.

page_text: Each screw or helice may be composed of two or any other suitable
number of blades arranged opposite to each other, and shaped in the
manner described; and two or any other convenient number of the
screws or helices may be employed with the pairs of blades, by pre-
ference breaking joint with each other, such screws or helices being
carried on a shaft disposed in the centre or axial line of the trough or
tray, and driven by gearing or otherwise from the motive-power engine
of the apparatus.
The trough or tray is also provided with a channel or gutter on its
under side, and extending throughout its length, for the passage of
water which is introduced therein, and caused to traverse the same by
means of a powerful pump, driven by the engine or otherwise. This
channel or gutter may be formed of sheet metal bent round to the
required shape, and attached to the bottom of the trough or tray. It is
closed at its lower extremity, and apertures are formed on its upper side
or in the bottom of the trough or tray, by which means the liquid is
caused to enter the trough or tray underneath the materials, which have
a constant tendency to adhere thereto, and to continually loosen or detach
such materials, and conduct them along towards the shore or other place
where they are required to be discharged. This arrangement admits of
an undue inclination of the trough or tray, necessitating the increased
height of the machine being obviated, whilst at the same time the
materials may be conducted automatically to any required distance with
greater facility than heretofore.
25 SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said John Henry Johnson in the Great Seal Patent
Office on the 13th January 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex,
30 Gentleman, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Fifteenth day of July, in the year of
our Lord. One thousand eight hundred and seventy-four, in the 38th
year of Her reign, did, for Herself, Her heirs and successors, give

page_text: Figure 3 is a sectional clevation of a portion of a dredging machino
shewing an improved mode of constructing and arranging the trough or
tray, and the application of certain accessories thereto.
shewing an improved mode of constructing and arranging the trough or
tray, and the application of certain accessories thereto.
Figure 4 is a transverse section of the trough or tray.
And Figure 5 is a detail of a portion of the apparatus detached, which
will be herein-after referred to.
According to the said Invention, in order to ensure the discharge of
earth and sand of a clayey nature, there is disposed in the interior of an
ordinary or other bucket a of a dredging machine a moveable bottom b
and back c, which are maintained in the bucket a simply by means of
two pins d, d', capable of traversing a groove or slot e, formed in the
fixed back of the bucket, which is at that part strengthened by means of
two iron strips f. The two pins d, d', are secured to a plate g, which
combines the parts together and slides over the iron strips f, thus
ensuring the parallelism of the motion which the movable bottom withi
its back has in the bucket a, as herein-after described. The red lines in
Figure 2 indicate the position which the movable back and bottom
assume when the bucket is inverted. By means of this arrangement, as
soon as the bucket having arrived at the top of the apparatus becomes
tilted or turns to an inclined position, the moveable bottom 6 slides a
certain distance with the materials which it contains, and then being
suddenly arrested by the stop d' coming into contact with the end of the
groove or slot e in the bucket a shock or jerk is produced, which has
the effect of detaching the materials, thereby causing them to fall into
the trough or tray. The movable bottom is forced back into its place at
the lower part of the bucket when the latter arrives at the bottom of its
course by the introduction of the earth or sand, so that the bucket may
be completely refilled, to be again discharged in the manner herein-
before indicated. The movability of the bottom and the internal back
in nowise impairs the strength of the bucket, as those portions of the
bucket do not come into operation at the time of the filling. The
motion of the back and the bottom is all that is required to ensure the dis-
charge of the adherent materials, their weight detaching them from the
fore part of the bucket when the bucket is inverted. It is indispensable
however to the efficient working of the apparatus to form in the external
bottom and back of the bucket a orifices for the admission of air
between those parts and the movable bottom and back at the time

page_text: when the bucket is inverted. These openings, which are made of a
large size, are also intended to admit of the escape of any carth or sand
which may have entered the space between the movable bottom band
the fixed bottom at the time of filling the bucket.
In some cases, in lieu of employing a movable back and bottom, the
requisite shock or jerk may be obtained by causing the bucket itself to
fall or move forward a short distance, so as to loosen or detach the
adherent materials, but the former arrangement is preferred.
In order to ensure the automatic passage along the trough or tray of
the argillaceous sands or earth discharged from the bucket without
resorting to an undue inclination of such trough or tray, which would
necessitate an excessive height of the dredging machine, two means
operating simultaneously are employed. These means consist,―
First. In the employment of dividing or disintegrating screws or
helices.
Second. In the application of a current of water to the lower part of
the trough or tray.
At the part where the materials discharged from the buckets enter the
trough or tray 1, (Figure 3,) there is disposed a series of screws or helices i,
(Figures 3 and 5,) which are rotated at a high velocity, so as to instan-
taneously divide the mass at the moment of its descent and prevent its
accumulating at that part, as would be the case were this apparatus not
employed. The screws or helices i have the effect not only of working
or breaking up the materials, but also of projecting them at a certain
velocity in the direction of the trough or tray 1, and thus forcing the
mass to move in the required line, the blades of the screws or helices
being so shaped or curved at their extremitics as to prevent the materials
from being projected laterally, whilst directing them horizontally along
the trough or tray 7, which is to conduct them to the shore.
The screws or helices i are composed of blades arranged opposite to
cach other, and made of the form herein-before described, and they are
mounted on a shaft j, placed in the centre or axial line of the trough or
tray 1, and actuated by means of pinions and spur wheels %, to which
motion is imparted by the motive-power engine, the relative proportions
of the wheels of the gearing being so arranged as to cause the shaft to
be driven at a velocity of, say, about one hundred revolutions per
minute.

page_text: In order to further ensure the continuous passage of the materials
along the trough or tray 1, the latter is provided on its under side with a
channel or gutter m, formed by preference of sheet metal bent round to
the required shape, and attached to the bottom of the trough or tray.
Into this channel or gutter water is introduced under pressure through a
pipe n, which is supplied by any convenient means, say, for example, by
a powerful pump driven by the engine or otherwise. The channel or
gutter m is closed at its lower end, and apertures m² are formed at
intervals in the bottom of the trough or tray over the channel or gutter
in order to admit of the passage of the liquid, which thus enters beneath
the materials which it is required to conduct along, thus constantly
loosening or detaching them from the surfaces of the trough or tray, to
which they have a tendency to adhere.
It will be seen from the foregoing description that the argillaceous
sand or earth discharged from the buckets being immediately worked up
or disintegrated by the screws or helices i, and projected in the direction
of the trough or tray 1, will continue to descend along the latter, which
may thus be extended at a slight inclination to any required distance
from the place at which the materials are extracted by the dredging
apparatus.
It has been ascertained that as the density of the earth or sand which
has to be discharged exceeds that of water, liquid introduced from the
upper side of the trough or tray or discharged from the buckets remains
on the surface of the materials, and consequently is not capable of con-
ducting such materials readily along with it in its motion. By this
improved system however the materials are constantly raised to a slight
extent, and separated or detached by the water which enters between
them and the curved surface of the trough or tray, so that they are sub-
jected to a series of propulsive actions, which cause them to circulate
without any stoppage to the extremity of the trough or tray, the angle
of the latter being nevertheless sufficiently flat to admit of the required
extension of the length of the trough or tray being obtained without the
necessity for making the arriving point of the materials at an undue
elevation.
By the employment or combination of the two means herein-before
described the uniform and continuous passage of earth and sand of a
clayey adherent nature discharged by the buckets is ensured, and the

page_text: extraction and transport by mechanical means of materials of this
nature, which result has never hitherto been attained, may thus be
readily effected.
When the materials elevated by the dredging apparatus are required
to be conducted only a very short horizontal distance it is not absolutely
necessary to use the hydraulic trough or tray, or the dividing or disin-
tegrating screws or helices, as the trough or tray may in that case be
arranged at an inclination sufficient to ensure the descent of the
materials projected down it without the employment of any further
means.
Having now described and particularly ascertained the nature of the
said Invention, and the manner in which the same is or may be used or
carried into effect, I would observe in conclusion that what I consider
to be novel and original, and therefore claim as the Invention secured
to me by the herein-before in part recited Letters Patent is,―
First. The application and use to and with a dredging machine of
buckets so arranged as that a shock or jerk is imparted to the materials
contained in such buckets for the purpose of detaching or separating
them therefrom, such shock or jerk being obtained by the fall or descent
to a limited distance of the bucket or of a movable bottom and back
applied thereto, substantially as herein-before described and illustrated
by the accompanying Drawings.
Second. Dividing or disintegrating during their fall or descent the
materials elevated by the dredging machine for the purpose of pre-
venting their accumulation at the summit of the receiving and delivering
trough or tray, and of facilitating their passage along the same, sub-
stantially as herein-before described and illustrated by the accompanying
Drawings.
Third. The application and use to and with the receiving and delivering
trough or tray of a dredging machine of a series of screws or helices so
constructed and arranged as and revolving at a velocity sufficient not
only to divide or disintegrate the materials falling from the buckets, but
also to project such materials in the direction of the trough or tray, sub-
stantially as herein-before described and illustrated by the accompanying
Drawings.

page_text: Fourth. The admission at the under side of the trough or tray of a
dredging machine, and beneath the materials to be transported, of
streamlets of water under pressure for the purpose of separating or
detaching such materials from the surfaces of the trough or tray, and
causing them to descend uniformly along the same, substantially as
herein-before described and illustrated by the accompanying Drawings.
In witness whereof, I, the said John Henry Johnson, have to this
my Specification set my hand and seal, the Eleventh day of
January, One thousand eight hundred and seventy-five.