Improvements in Dredgers.
Year: 1888

page_text: Date of Application, 7th Dec., 1888
Complete Specification Left, 5th Sept., 1889-Accepted, 5th Oct., 1889
PROVISIONAL SPECIFICATION.
Improvements in Dredgers.
We, WILLIAM DUFF BRUCE of 9 Victoria Chambers. Engineer. and WILLIAM
SHAPTON of 8 Great George Street, Engineer, both in the City of Westminster, do
hereby declare the nature of this invention to be as follows:-
1
This invention has for its object improvements in dredgers.
We construct a dredger with two lighters or vessels connected together by an
over-head bridge in such manner that a barge to receive the spoil can enter between
the two lighters and beneath the bridge.
The dredging is effected by means of grab buckets, which are raised and lowered
through wolls in one of the lighters. The grab is let down to the bottom, takes
its load and is lifted by tackle through the well. The tackle by which the grab is
suspended is then traversed along the bridge until the grab is over the spoil barge it
is then lowered down into the harge and opened to deliver its contents. The grabs, as
already mentioned, work through wells in one of the lighters; the hydraulic gear
which operates them is contained in the other lighter. There is a main lifting cylinder
and. ram mounted vertically, and working the main lifting chain. The chain after
passing around the sheaves of this apparatus is led away over the bridge to a carriage
similar to that of a travelling crane; it descends from a pulley on the carriage to
the grab, which it suspends it passes around a pulley upon the grab and ascending
again is led over another pulley upon the carriage, beyond which it is made fast at
the extremity of the bridge. When this chain is hauled upon the grab is raised, and
when it is slacked off the grab is lowered, and this whatever the position of the carriage
upon the bridge may be.
;
The carriage can be traversed along the bridge by chains passing from it in either
direction and led away over pulleys to a pair of hydraulic cylinders by which either
chain can be hauled upon whilst the other is slacked out. The grab requires two
chains to work it; in addition to the main chain there is a second chain from which
it is suspended when it is required that the jaws should open, the main chain at this
time being allowed to become slack. This second chain passes in the same way as the
main chain, over pulleys upon the carriage and upon the grab and its end comes to a
drum upon which it is caused to be wound by the operation of a hydraulic cylinder
which is in constant communication with the pressure main and which hauls upon a
chain wound upon another drum upon the same axis.
The weight of the grab is sufficient to draw its chain off from the drum and when
the grab is lifted the pressure in the cylinder always keeps the chain taut. When it
is desired that the jaws of the grab should open a brake is applied which holds the
drum fast, and then, when the main chain is slacked, the grab becomes suspended
by the second chain, its jaws open and the contents are delivered into the barge.
•
In place of this arrangement we sometimes cause both the chains of the grab to
pass over the pulleys of the lifting cylinder, and when it is required that the grab
should open, the chain which operates the jaws is separately hauled upon, and this is
done by means of a hydraulic cylinder, and ram. The ram as it rises from the
cylinder brings a pulley upon its head against the chain connected with the jaws.
The chain being supported on either side of the ram by two stationary pulleys; is
caused to form a loop between them and so the chain is hauled upon to the extent
requisite to open the jaws.
.
In some soils it requires much more force to cause the grab to leave the ground,
than is required afterwards to lift it out of the water. To meet this circumstance we
provide upon the lower end of the main cylinder another short cylinder containing a
ram of a larger diameter than the lifting ram. This ram carries the lower pulleys

page_text: around which the main lifting chain passes. In working the apparatus this ram
operates first and hauls upon the chain to the extent requisite to raise the grab
from the ground; then the main ram brings up the grab as high as may be
required.
Sometimes we construct a dredger more suitable to work in a sea way with one
lighter only, having in it both the wells for the grabs to work through and also the
mechanism to actuate the grabs, which in this case are simply raised and lowered ;
they are not traversed to bring them vertically over the spoil barge but in lieu of this
an inclined shoot leads away the spoil when it is dropped by the grab. The upper
end of the shoot is jointed and it hangs down so that the grab in ascending may pass
above it but when the grab is clear of this jointed flap a connection between the grab
and the flap operates to raise it, so that when the jaws are opened the flap receives
the spoil and leads it down the shoot into the spoil barge. The shoot contains a slider,
which operates to prevent the too sudden descent of the spoil, which might cause
injury to the barge or other parts. This slider is controlled by suitable gear and is
lowered gradually down the shoot so that the mass of spoil reaches the barge before
it is set free and allowed to fall.
Dated this 7th day of December 1888.
WM. DUFF BRUCE.
WM. SHAPTON.
·
COMPLETE SPECIFICATION.
Improvements in Dredgers..
We, WILLIAM DUFF BRUCE, of 9 Victoria Chambers, Engineer, and WILLIAM
SHAPTON; of 8 Great George Street, Engineer, both in the City of Westminster, 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 :-
This invention has for its object improvements in dredgers.
We construct a dredger with two lighters or vessels connected together by an over-
head bridge in such manner that a barge to receive the spoil can enter between the
two lighters and beneath the bridge.
The dredging is effected by means of grab buckets, which are raised and lowered
through wells in one of the lighters. The grab is let down to the bottom, takes its
load and is lifted by tackle through the well. The tackle by which the grab is
suspended is then traversed along the bridge until the grab is over the spoil barge it
is then lowered down into the barge and opened to deliver its contents. The grabs,
as already mentioned, work through wells in one of the lighters; the bydraulic gear
which operates them is contained in the other lighter. There is a main lifting
cylinder and ram mounted vertically, and working the main lifting chain. The chain.
after passing around the sheaves of this apparatus is led away over the bridge to a
carriage similar to that of a foundry crane; it descends from a pulley on the carriage
to the grab, which it suspends; it passes around a pulley upon the grab and ascending
again is led over another pulley upon the carriage, beyond which it is made fast at the
extremity of the bridge. When this chain is hauled upon the grab is raised, and when
it is slacked off the grab is lowered, and this whatever the position of the carriage
upon the bridge may be.
The carriage can be traversed along the bridge by chains passing from it in either
direction and led away over pulleys to a pair of hydraulic cylinders by which either
chain can be hauled upon whilst the other is slacked out. The grab requires two chains,
to work it; in addition to the main chain there is a second chain from which it is
suspended when it is required that the jaws should open, the main chain at this time
being allowed to become slack. This second chain passes in the same way as the main
chain, over pulleys upon the carriage and upon the grab and its end comes to a drum
upon which it is caused to be wound by the operation of a hydraulic cylinder which

page_text: in constant communication with the pressure main and which hauls upon a chain
wound upon another drum upon the same axis.
When it
The weight of the grab is sufficient to draw its chain off from the drum and when
the grab
lifted the pressure in the cylinder always keeps the chain taut.
is desired that the jaws of the grab should open a brake is applied which holds the
drum fast, and then, when the main chain is slicked, the grab becomes suspended by
the second chain, its jaws open and the contents are delivered into the barge.
In order that our said invention may be fully understood and readily carried into
effect we will proceed to describe the drawings hereunto annexed.
DESCRIPTION OF THE DRAWINGS.
Figure 1 is a front elevation and Figure 2 is a plan of a dredger constructed in
accordance with our invention.
a and bare two lighters firmly connected by a bridge c and with room for a spoil
barge d between them. e is a pulley carriage capable of travelling along rails laid
on the bridge. There is a pulley carriage to each grab bucket and in the dredger
represented in the drawings provision is made for working three buckets. f is a grab
bucket of well known construction, it is suspended by two chains which pass around
pulleys upon it. The chain is the main lifting chain, it is fast at both ends; it
descends to the bucket between the pulleys of the pulley carriage and it passes around
the pulleys of the bydraulic cylinder and ram g. The cylinder and ram is erected
in one of the lighters whilst the wells for the buckets are in the other.
The chain is fast at one end and at the other it is secured to the periphery of
the winding drum : this chain also descends to the grab bucket between the pulleys
of the pulley carriage e. is a small hydraulic cylinder and ram operating a chain
which is wound upon another drum on the same axis with the drum h. The chains
are wound on these drums so that when one winds the other unwinds. There is also
a third drum on the same axis and this is a break drum. k k are a pair of hydraulic
cylinders and rains; one of thein operates to haul upon a chain which is led over
guide pulleys direct to the pulley carriage e and the other to haul upon a chain k²
which is led over guide pulleys to the further side of the bridge and then returns to
the pulley carriage.
The method of working has already been described, the grab bucket is lowered with
sufficient velocity through one of the wells in the lighter the unwinding of the
chain being resisted by the constant pressure in the small hydraulic cylinder so
that the jaws of the grab are open. When the grab has taken the ground the break
is applied to hold the chain and the chain is hauled upon until the jaws of
the grab are closed. The break is then released and the grab lifted by the chain f',
the chain being at the same time taken in by the constant pressure cylinder
acting through the drums h. Then by the chain the pulley carriage is traversed
along the bridge until the grab bucket is over the spoil barge and finally by applying
the break to hold the chain 2 and lowering by the main chain the jaws are
opened and the material delivered. The return motion of the pulley carriage takes
place when the chain is hauled upon and the chain k¹ paid out
In place of the arrangement above described for opening the jaws of the grab
bucket we sometimes cause both the chains of the grab to pass over the pulleys of
the lifting cylinder, and when it is required that the grab should open, the chain
which operates the jaws is separately hauled upon, and this is done by means of a
hydraulic cylinder, and ram. The ram as it rises from the cylinder brings a pulley
upon its head against the chain connected with the jaws. The chain being supported
on either side of the ram by two stationary pulleys; is caused to form a loop
between them and so the chain is hauled upon to the extent requisite to open
the jaws.
In some soils it requires much more force to cause the grab to leave the ground,
than is required afterwards to lift it out of the water. To meet this circumstance we
provide upon the lower end of the main cylinder another short cylinder containing a

page_text: ram of a larger diameter than the lifting ram. This ram which is shown in Figure 1
at g' carries the lower pulleys around which the main lifting chain passes. In working
the apparatus this ram operates first and hauls upon the chain to the extent.requisit:
to raise he grab from the ground; then the main ram brings up the grab as high
as may be required.
Sometimes we construct a dredger more suitable to work in a sea way with one
lighter only, having in it both the wells for the grabs to work through and also the
mechanism to actuate the grabs, which in this case are simply raised and lowered;
they are not traversed to bring them vertically over the spoil barge but in lieu of this
an inclined shoot leads away the spoil when it is dropped by the grab. The upper
end of the shoot is jointed and it hangs down so that the grab in ascending may pass
above it but when the grab is clear of this jointed flap a connection between the grab
and the flap operates to raise it, so that when the jaws are opened the flap receives
the spoil and leads it down the shoot into the spoil barge. The shoot contains a slide
which operates to prevent the too sudden descent of the spoil, which might cause
injury to the barge or other parts. This slide is controlled by suitable gear and is
lowered gradually down the shoot so that the mass of spoil reaches the barge before it
is set free and allowed to fall.
The arrangement of the slide and the gear for working it is described in the
specification of the patent granted to me William Shapton No. 5157 in the year 1888.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
:-
1. A dredger substantially as described in which are two lighters connected by an
overhead bridge and a grab bucket raised and lowered from the bridge through a well
in one of the lighters.
2. A dredger substantially as described in which are two lighters connected by an
overhead bridge and a grab bucket suspended from a carriage which can be traversed
along the bridge and raised and lowered through a well in onc lighter by mechanism
contained in the other lighter.
3. A dredger substantially as described in which is a lighter or lighters and a grab
bucket suspended by two chains operated by hydraulic mechanism as herein set
forth.
4. A dredger substantially as shown by the annexed drawings.
WM. DUFF BRUCE.
WM. SHAPTON.