Improvements in Pneumatic Dredgers.
Year: 1887

page_text: Date of Application, 13th Aug., 1887
Specification Accepted, 18th Oct., 1887
Improvements in Pneumatic Dredgers.
I, WILLIAM CLARK, of the firm of A. M. and Wm. Clark, of 53, Chancery Lane, in
the County of Middlesex, Fellow of the Institute of Patent Agents, do hereby declare
the nature of this Invention (a communication to me from abroad by Jules Vernandon
and Eugène Vernaudon both of 6, Rue St. Georges Paris, France, Engineers and
Contractors, and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement :-
This invention relates to pneumatic dredgers; and the improvements consist-
1st-In the employment of cutting blades of special form for loosening at any depth
of water, the spoil to be dredged. 2nd-In the construction of the mechanism for
operating the cutters. 3rd-In the employment of a casing having rounded corners
placed at the lower end of the suction pipe for enclosing and protecting the gearing
operating the cutters. 4th-In a suspension frame or ladder pivoting and sliding on
a centre for staying the suction pipe in the middle of the well. 5th. In the general
arrangement of apparatus for breaking up the spoil, and in the special form of theblades
mounted upon a conical head.
6th. In the means for operating the conical cutter-head which is mounted on the
end of a longitudinal shaft placed above the suction pipe and driven by gearing, as
hereinafter described.
7th. In a modified form of the cutter head and blades.
8th. In the employment of valves placed upon the suction pipe, to enable the
proportion of water and spoil to be regulated.
The Invention is illustrated, by way of example, in the accompanying drawings,
wherein figures 1, 2, and 3, represent the general arrangement of the dredger,
provided, with the improvements above enumerated.
A A¹ are two sets of blades or cutters for loosening the spoil below water,
and B B is the toothed gearing for operating them. C is the casing enclosing the
gearing below water. D is the frame or ladder for suspending and staying the
suction pipe. E is the guide in which work the end gudgeons of a slotted cross bar or
guide E through which frame D works. F is the suction pipe for raising the spoil
loosened by the cutters and F' the delivery pipe. D₁ indicates, in dotted lines, the
suction pipe raised above water. The upper end of the frame D in this movement
describes the curve H in pivoting on the journals of a guide frame I through which it
slides. The frame D consists of two side members (figures 1 and 2) united by cross
and diagonal bars and moves in the guide E placed between the uprights of frame J
and is held laterally by the sides K K of the well L. This frame D stays the suction
pipe rigidly in any position for excavating or loosening the spoil to be raised.

page_text: Figure 4 is a view on a larger scale, of the cutting tool having helical blades or
cutters mounted upon a boss M, and varying in number according to the nature of
the ground. They are so constructed as to ensure their cutting action whether the
dredger is moving ahead or astern or to port or starboard. The cutters are rotated
at a sufficient speed (varying between 40 to 60 revolutions per minute) in the
direction of the arrow, for breaking up the spoil and discharging it into the mouth O
of the suction pipe, the action of the ambient column being facilitated by the spoil
being mixed with and diluted by the water.
Figure 5 is a cross-section of the suction tube F which is provided with longitudinal
external ribs N supporting standards N' carrying the bearings P of the shaft driving
the cutters and which is in lengths connected by couplings to counteract torsional
movements.
Figure 6 is an axial section, figure 7 an elevation, and figure 9 a plan, of the
driving gear at the upper end of the suction pipe. The bevel wheels are mounted in
bearings supported on the bend Q of suction pipe and are driven through a spur
wheel from a pinion R placed at the opposite side of the well, and in line axially with
the stuffing box of the elbow Q, so as to permit of the rotation of the gear about the
pinion when the suction pipe pivots on its axis.
Figure 8 is a side elevation of the lower end or mouth O of the suction pipe and
the casing enclosing the bevel gear S S and figure 10 is a plan, the casing being
removed. The longitudinal and cutter shafts pass through stuffing-box bearings and
the casing encloses the gear watertight and excludes the spoil from the gearing,
whereby the employment of wheel gearing for driving the rotary cutter is rendered
possible.
Figure 11 is a longitudinal section of a modified form of cutter-head. Figure 12
is a plan of same, with the cap of the cutter shaft bearing removed. Figure 13 is a
cross-section of the cutter. Figure, 14 is a cross-section of the suction pipe, taken
through one of the regulating valves. Figure 15 is an elevation of two of these
regulating valves, and figure 16 shews the means for operating said valves.
The cutter head is preferably formed of shear shaped blades a curved to a
cylindrical form in the direction of their breadth, and bolted in the direction of their
length to the arms b¹ of the conical head, said blades having at their convex sides,
other transverse blades cl perpendicular to the axis of the cutter head. Each
longitudinal blade carries three of these cross blades, the cross blades of three
consecutive longitudinal blades being in different planes perpendicular to the axis of
the conical head. These cross blades cut the ground in nine places, the longitudinal
blades removing and delivering the spoil towards the centre of the conical cutter head
into the mouth of the suction pipe.
The above described form of cutter head is suitable for operating on clay which
mixes difficultly with water, but where the ground is of a less cohesive nature either
the longitudinal blades or the cross blades mounted on a conical frame, may be alone
used. The length and angle of the conical head, the curvature and number of the
longitudinal blades, as also the length which the points of the cross blades should
project beyond the cone described by the edges of the longitudinal blades, would
depend upon the nature of the ground. For working in hard material, the conical
head would be made shorter and to a less acute cone, the longitudinal blades would be
more numerous and more curved and project little beyond the cone described by the
arms of the cutter head, while the cross blades would be shorter.
Besides the longitudinal blades above described, half as many blades d' are attached
at the front end of the conical cutter-head, to assist the cutter head to penetrate and
withdraw from the work. These additional cutters may not be necessary when the
angle of the cone is sufficiently wide. The rear ends of the longitudinal blades are
so shaped, that their edges describe a reverse cone to that of their working edges, so as
to enable the cutter head to be withdrawn in the event of its becoming buried by a
fall of earth.
The cutter-head consists mainly of a boss e¹ cast with arms to which the blades are
attached, the arms being strengthened by rings ff¹ cast in one therewith at the front

page_text: and rear ends of the conical head. The boss e¹ is mounted on the projecting end of
the shaft g' which is supported, as shewn in figures 11 and 12, in bushes at the ends of
a sleeve h¹ upon the end of the suction pipe, the sleeve being made in halves and filled
with tallow.
The valves are three in number; they slide upon the same seat, each covering
an orifice, said valves being adjusted by a common screw shaft alongside the suction
pipe screwing through sockets upon the valves, which are held against their seat by
springs. The valve guide is a casting, of the form shewn in figure 14, bolted to the
suction pipe and to its iron ribs and has cast on it the bearings for the screw shaft.
These regulating sluices are especially useful in the event of the cutter head becoming
buried by a fall of earth, as they allow of clear water being drawn in to drive out the
spoil from the delivery pipe. By then closing the valve, and stopping the pump, a
pressure of water is obtained which will help to free the cutter-head. The gear for
working the valve screw shaft is represented in figure 16. A vertical shaft k¹ provided
with a hand wheel m¹ passes down through a cast iron column l' on the deck of the
dredger and is geared by a bevel wheel n¹ keyed on its lower end, with a bevel wheel p¹
keyed on a horizontal shaft o¹ parallel to the pivotal axis of the suction pipe, the
wheel p' being also in gear with another bevel wheel on a third shaft q' which is made
in two telescopically sliding parts, squared so as to rotate together. The bevel wheel
on the upper end of shaft q is free to move about the horizontal axis o' rolling, in doing
so, upon the wheel p¹ with which it is held in gear by a strap pivoted on shaft of
and attached to a collar on shaft q' The shaft is geared by a bevel wheel n¹ keyed
on its lower end, with a bevel wheel on a horizontal shaft mounted on the suction
pipe parallel to its centre of motion, the bevel pinions being free to roll, the one on the
other like those at the upper end of shaft q' and the shaft is geared with the screw-
shafts by bevel gear.
Having now particularly described and ascertained the nature of the said invention,
and in what manner the same is to be performed, I declare that what I claim is ;—
1st. In a pneumatic dredger, the combination of helical blades or cutters A A¹
mounted on the lower end of the suction pipe and operated by suitable gearing
enclosed in casing C; with the suspension frame D and guide E by which the
dredging apparatus is raised out of the water, substantially as described and
represented in the accompanying drawings.
2nd. In a pneumatic dredger, the construction of cutter having shear shaped blades a',
curved to a cylindrical form in the direction of their breadth and bolted in the
direction of their length to the arms 6 of the conical head, said blades having at their
convex sides transverse blades c perpendicular to the axis of the conical head, as
herein before described and illustrated in figures 11, 12, and 13 of the drawings.
3rd. A cutter head for dredgers constructed with the blades described, and
with the blades d' attached at the front end of the conical cutter-head to assist it in
penetrating and withdrawing from the work, as herein before describod and shewn.
4th. In a pneumatic dredger, the combination with the suction pipe of regulating
sluice valves adjustable by a common screw shaft placed parallel with said pipe
whereby to allow of clear water being drawn in, in the event of the cutter head
becoming buried by a fall of earth, to drive out the spoil from the delivery pipe and
of afterwards freeing the cutter head, all as herein before described and shewn.
DL 11
1041 1
AL 1007