Improvements in Mechanism for Working Dredging or Excavating Buckets, Grabs, and similar Apparatus,
Year: 1889

page_text: Date of Application, 10th July, 1889-Accepted, 24th Aug., 1889
COMPLETE SPECIFICATION.
Improvements in Mechanism for Working Dredging or Excavating
Buckets, Grabs, and similar Apparatus,
I, HENRY DAVIES, of "Heathfield," Blairgowrie Street Old Canterbury Road,
Petersham, in the Colony of New South Wales, Engineer, 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, reference
being had to the accompanying drawings:-
My invention has for its object the improvement of mechanical contrivances used
for working self-acting Grabs, Buckets, Grabs with tines or claws, and other apparatus
used for performing the operations of dredging, excavating, digging, raising and
discharging or depositing.
My improvements consist in the removal of the usual counterbalance weight or
counterbalance barrel, suspended in chains or running in racks at the back of the
crane, or other contrivances operating by means of a complicated system of messenger
chains, pitch chains and wheels, and the substitution therefor of two chain or rope
barrels mounted on one shaft each having its own independent brake, and both
connected with a winding engine, winch, or hoist from which variable and differential
motions are imparted to them by means of wheels and pinions which may be either
bevel, mitre, spur, or friction wheels and pinions.
My invention is illustrated by the accompanying drawings, in which the same
letters are used throughout the various views to indicate similar parts.
In sheet 1, Figure 1 is a side elevation of a grab dredger and crane fitted with
my improved mechanism. In sheet 2 Figure 2 is a front elevation of the same,
omitting the jib. Figure 3, in sheet 1, is a sectional elevation in detail, showing
a form of my differential gear in which bevel or mitre-wheels and pinions are
used. In sheet 2, Figure 4 is a sectional elevation in detail showing another form
of my differential gear in which spur-wheels and pinions are used; and Figure 5
is a sectional elevation of a form of my differential gear in which the mechanism
consists of pinions gearing into a spur-wheel and an internally toothed wheel.
In Figures 1 and 2, A, A', A, A, are essential parts of a steam crane such
as is ordinarily used in conjunction with grabs for the purpose of excavating or
dredging. B is a bucket grab; B, B", B, B are the various parts and con-
nections necessary to effect the operation of opening, closing raising and lowering
the same when in use. C is a bearing formed in the side frames or cheeks of
the winch to receive the main shaft. D is the main shaft E is a loose barrel
for receiving the closing chain, which is connected to the yoke B₁ of the grab.
GG are the brake treads formed upon the barrels E and F. G and G are
brakes. H is a friction pulley transmitting motion to the friction-wheel I. J is
an eccentric placed in the eye of the friction-wheel and operated by means of
lever J to produce contact between the friction pulley H and wheel I. K is a
driver keyed to the main shaft and engaging the friction-wheel I by means of the
crank arm L working in the slot M formed in the said friction-wheel. N is a disc
keyed upon the main shaft carrying the pinions 0 0 upon the studs 0' 01.
PP are wheels secured to the barrels E and F, and gearing with the pinions O O.
I make the barrels E and F of the same or different diameters, as may be most
suitable for the particular work to be performed; but for working a bucket grab,
such as is shown in Figures 1 and 2, I prefer to make the barrels of different
diameters, as shown in Figures 2 and 3, and to arrange the gearing as shown in
Figures 1, 2, and 3, from which it will be seen that the two barrels E and F are loose
on the main shaft D of the winch from which they receive a differential motion by
means of one or more bevel pinions 00 mounted on a disc N made fast on the main
shaft D and turned by it. The pinions carried by the disc run loose on their bearings

page_text: and engage with the wheels P P fixed on the ends of the barrels, so as either to give
motion to, or receive motion from either barrel according to requirements.
In the arrangement shown by Figure 4 the disc N carries one or more pairs of
spur-wheels or pinions, each pair of two sizes running loosely on bearings placed
parallel with the axis of the main shaft, the spur-wheels or pinions gearing with two
spur toothed wheels fixed one upon the end of each barrel.
In another form of my mechanism shown by Figure 5 I transmit motion to the
barrels by means of one or more spur pinions which are made to gear with an
internally toothed wheel attached to one barrel, and an externally toothed wheel
attached to the other barrel. The barrels are made of any suitable diameter according
to the system of wheel gearing used, and the work to be performed in each particular
case, certain modifications being necessary to obtain a variable differential motion of
the two barrels when used for the purposes set forth. To each barrel I attach the
necessary brake-treads, which are operated by independent brakes and levers. The
disc N is made to revolve in either direction, and is under the control of the brake Ju
may make the disc N run loose on the shaft and give it motion by means of a ring
fixed on it exterior to the pinions, the said ring being either smooth or toothed and
being turned by friction belting or spur gear.
I
My invention serves to operate many kinds of grabs, and the arrangement
shown by Figures 1, 2, and 3 is that which I use preferably for working a bucket
grab such as is shown in Figures 1 and 2. In this method the closing-chain or
rope B is coiled around and secured to the barrel B' of the grab, and is led
thence over one of the jib head pulleys to the barrel E, to which its other extremity
is secured. The opening-chain or rope B, secured to the cross-bar or yoke Bil
of the grab, is led over the other jib head pulley and thence to the barrel F, to
which its other extremity is secured. The friction-wheel I is mounted loose on an
eccentric J placed on the main shaft, the eccentric being operated by a lever J', which
brings the friction-wheel into contact with the driving-pulley H, or in contact with
the brake-pad J¹ Figures 1 and 2. In the friction-wheel I construct a radial slot M
to receive the crank pin L attached to the driver K, which is keyed upon the
main shaft. When the eccentric J is turned in one direction the friction-wheel is
made to engage with the driving-pulley, thus giving the required motion to the
main shaft upon which the barrels are placed. By a reverse movement of the
eccentric the main shaft is arrested, contact being produced between the wheel's
face and the brake-pad. The various motions required to operate the grab are
effected as follows:-If the grab is suspended as shown in the drawing, the wheel I
being on the brake-pad J, and it is desired to open it, the brake G¹ of the
opening-barrel F is applied; the lever J is then operated so as to gently release
the wheel I, when the grab will open and the spoil will be discharged; the grab
is then swung into the required position for descent. The grab may now be said to
be ready for lowering for the purpose of excavating, to accomplish which, the wheel I
being still kept free, the brake G¹ is to be judiciously eased, when the descent will be
made, both chains being finally allowed to over-run a little in order that the grab may
strike with its full weight on the material to be lifted and press with the greatest
possible effect upon it. During the subsequent operation of closing, which is effected
by again applying the opening-brake G¹, care should be taken that the opening chain
is well paid out and quite slack. By operating the lever J' contact is now made
between the friction-wheel I and the driving pulley H, the grab will then be made to
close upon the material to be excavated. The opening-brake G is then released and the
grab will at once be raised with its contents to any desired elevation and may be
swung into the original position, ready to again discharge the spoil.
An important feature in connection with the cut made by the grab actuated by my
gear is that it rests with a maximum force upon the material to be excavated and is
not deprived of the least part of its effectiveness by the operation of the opening-
chain, which in most other appliances used for this purpose lifts the grab partly off its
work at this period when it is desirable for it to press most forcibly upon the ground.
In other mechanism for operating grabs it has also been observed that there is

page_text: considerable difficulty in releasing and raising the grab when it has closed upon an
immovable object such as a snag: but with this invention it is merely requisite to
pay out the closing-chain Bui quite slack and apply the closing-brake G" and
placing the wheel I and pulley H in contact haul on the opening-chain B¹¹, when
the grab will open and release the snag.
It has hitherto been found that grabs bave a difficulty in operating on refractory
ground such as hard clays and certain impacted and cemented sands: much of this
difficulty is removed by the property which my gear possesses of enabling the grab
to gnaw or repeatedly bite at the ground before finally cutting it. This is effected as
follows: The grab being open and resting on the ground, some slack chain is paid
out and the brake G¹ being applied the winch is made to haul on the closing-chain B¹¹,
but only to make a partial closing; brake G¹ is released and slack chain is again paid
out; brake G is then applied, and the winch is made to haul on the opening
chain B, when the grab will open, and so on, repeating the operation of gnawing
the surface until a good hold is obtained, when the final cut is made as before
described.
An additional advantage associated with the use of my differential gear is that the
depth at which it will work a grab effectively is not limited, and it does not require
any adjustment of weights and pulleys to suit variations of depth.
My gear does away with the severe shocks such as are incident to the use of other
mechanism when the weight of the grab and excavated material contained therein is
being transferred from one chain to the other. It is also to be noted that in lieu of
the chains which are imperatively used with other arrangements I can substitute iron
or steel wire ropes, and that whether chains or ropes be employed they may be
much lighter that those required by other systems because with my gear each chain
does half the work.
My invention may be operated by means of either hand, steam, or any other motive
power.
Having thus described the nature of my invention and the manner in which the
same is carried into effect, I desire to state that I do not confine myself to the precise
form of the mechanism hereinbefore described and shown for working self-acting
grabs, buckets and claws and the like apparatus, as the requisite differential motion of
the barrels may be obtained by mechanical variations of my method.
I make no claim for the device of the grabs, buckets, or claws, nor vel for the
principle of working such apparatus by means of winches or cranes, but what I believe
to be new is the particular arrangement and combination of mechanism for the
purpose of operating grabs, buckets, claws and the like apparatus herein before
described and illustrated in the accompanying drawings and what I claim is :-
1. The combination of two loose barrels and brakes and the wheels and pinions
differentially geared operating the same, substantially as described and shown in
Figures 1, 2, 3, 4, and 5 by the lettered E, F, G, G¹, G", N, O, O', and P, for the
purposes set forth.
2. The combination of two barrels and brakes with differential gearing constructed
in such a manner that although the relative number of revolutions made by each
barrel may vary yet the sum of the revolutions made in one direction by the barrels
shall bear a constant proportion to the number of revolutions made by the shaft from
which they are driven for the purposes set forth.
Dated this Twenty third day of May 1889
HENRY DAVIES.
Witness,
Haseltine, Lake & Co.,
45, Southampton Buildings, London, Agents for the Applicant.
JOHN J. STONE,
Civil Engineer.