Year: 1888

page_text: Date of Application, 8th Feb., 1888
Complete Specification Left, 8th Nov., 1888
Complete Specification Accepted. 21st Dec.,
1888
I HENRY GRAFTON of 113 Cannon Street in the City of London Engineer do hereby
declare the nature of this invention to be as follows:-
This Invention relates to a grab bucket for dredging, excavating, unloading grain,
and other similar purposes. This improved grab bucket is worked by a single chain,
it may be opened whether it be loaded or not, when hung up by its frame at the
jib head, or when resting on the ground or other support, or when suspended at any
intermediate point by the hoisting chain alone. Consequently, it may be opened in
mid-air to discharge its load without being hung up by its frame at the jib head, or
when under water in order to release its hold in case it should make a "false grab"
i.e. catch hold of an object too heavy to raise.
In its general construction, the grab is preferably of the ordinary type in which
the hoisting chain is wound on the larger part of a barrel to obtain the necessary
purchase, branch chains wound on the smaller part of the barrel, being connected to a
cross head sliding up and down in the frame and connected by rods to the outer parts
of the jaws. The barrel shaft is mounted to slide in vertical guides in the frame, but
to obtain the point of resistance necessary to enable the cross head to be drawn down
to close the bucket jaws, the barrel shaft is engaged by catches which retain it at the
lower part of the frame so long as the weight of the grab is borne by the hoisting
chain and barrel. The catches are operated by springs or weights which, when the
hoisting chain is relieved of the weight of the grab and load (in any of the ways
hereafter mentioned) cause the catches to become disengaged from the barrel shaft
to allow the barrel to be raised in the frame along with the sliding cross-head. The
action of the catches and their springs is such that when the catches are engaged with
the barrel shaft, the springs tend to draw the shaft down in its guides and cause the
shaft to be released from the catches, but this tendency is counteracted until the
hoisting chain is relieved of tension. When the grab bucket is open the springs and
catches are acted on by one or both of the jaws and thereby held in position to permit
the re-engagement of the barrel shaft with the catches when the barrel shaft is lowered
in its guides.

page_text: For the purpose of opening by hanging up the grab to the jib head, the frame is
provided with catches at top which, when the grab is raised in the closed position by
winding in the hoisting chain, engage with a flanged tube dependent from the jib
head and through which the hoisting chain passes. When thus suspended, the weight
being taken off the hoisting chain, the springs release the catches that hold down the
chain barrel, and the latter may then be drawn up in the frame along with the sliding
cross heal, by again winding in the hoisting chain, thereby opening the grab, the grab
being thus opened within a less vertical distance below the jib head than at present
done by similar buckets, which is of advantage in certain cases. The catches by
which the frame is hung up, tend to fall into position for engagement with the
suspension tube, but are so acted on directly or indirectly by the sliding cross head
when the latter nears its highest position in the frame whilst opening the grab, that
they tend to fall off from the suspension tube, and to fall off, immediately they are
relieved of the weight of the grab, thus allowing the grab bucket to be lowered in the
open position. Instead of the hoisting chain being relieved of the weight by catches
making a positive engagement with the suspension tube (which involves a hoisting
motion of the chain in order to release them) the engagement may be of a frictional
or yielding character offering sufficient resistance to support a part of the weight of
the grab and allow the springs of the barrel holding catches to operate and release the
barrel. By the continued lowering off of the chain after the bucket reaches the
ground, the barrel descends alone in the guides and is re-engaged by its catches. By
then pulling on the hoisting chain, the barrel is revolved, the cross head drawn down,
and the jaws closed together.
The release of the barrel from its catches is similarly effected, if the grab, instead of
being hung up to the jib head is lowered with its load on to the ground or other
support. The operation of opening the grab in mid-air when not hung up to the jib
head, depends upon the springs effecting the release of the barrel-holding catches at
the moment when, by a sudden slackening of the hoisting chain, the latter is partly
relieved of the weight of the grab in consequence of the inertia of the grab and lond.
Under these circumstances, the barrel is released and the grab is opened by the same
relative motion of the parts, the frame and jaws in this case, however, having a
descending movement, while the barrel and cross head remain at about the same
actual height.
Dated this 8th day of February 1888.
H. GRAFTON.
By A. M. & Win. Clark,
53, Chancery Lane, London,
Patent Agents.

page_text: Purposes.
I, HENRY GRAFTON, of 26 Willes Road, Kentish Town, in the County of Middlesex,
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:-
This Invention relates to a grab bucket or digger for dredging, excavating,
unloading grain, depositing a load under water or elsewhere, and for other purposes
for which grab buckets are commonly employed.
This improved grab bucket is worked by a single chain and upon any ordinary
crane provided with the suspension tube at the jib head hereafter referred to; and it
may be opened (whether it be loaded or not) when "hung up" at the jib-head in the
usual way and also without adventitious aid when resting on the ground or other
underneath support. It may therefore, be caused to open, whether under water or
not, either for the purpose of releasing its hold in case it should make a
false grab
(that is to say in case it should catch hold of an object which it is unable to raise or
in caso it should close without grabbing anything) or for the purpose of depositing a
load of concrete or other material.
"
The opening of the grab bucket, when "hung up" at the jib head, is effected
within its own length, that is to say without elongation of the apparatus by the
dropping of the frame, as is usual, in other grab buckets whether worked by one or
two chains and consequently, as the grab bucket occupies a less vertical distance,
measured downwards from the jib head, when it is opened than when it is closed, it
can deposit its load at a greater height for the same amount of lift than can be done
by other buckets in which the frame is lowered in the act of opening. Further, this
improved grab bucket is distinguished from other single chain grab buckets by the
fact that it may be adapted to be opened (when suspended by the hoisting chain
alone) at any intermediate point in mid-air without the use of any special suspension
gear, which could heretofore only be done by a grab bucket worked by two separate
chains.
This improved grab-bucket may therefore, have all the advantages appertaining to
a double chain grab bucket without the attendant disadvantage of requiring a special
crane with double gear to work the two chains.
The Invention consists essentially in the means whereby the grab-bucket is enabled
to be worked by a single chain in the manner above described and with the above
mentioned advantages; and this is accomplished mainly by making that part of the
opening and closing gear which is intended to rosist the pull of the hoisting chain,
vertically movable independently of the frame and by providing self-engaging and
self-releasing retaining gear whereby such vertically movable part is at required times
automatically retained at the lower part of the frame for the purpose of acting as an
abutment ""fulcrum" or point of resistance necessary for reversing the direction

page_text: of pull of the chain, the effect of the pull being direct when said part is free or
movable and reversed when it is retained. This vertically movable abutment for tho
chain is employed in combination with a vertically sliding cross-head for working the
bucket jaws, the said abutment and cross-head being movable together in the upward,
and independently in the downward, direction. The "abutment"
may therefore,
descend alone and become retained at the lower part of the frame whilst the cross-head
remains in the raised position until by the reversal of the effect of the pull on the
chain, the upward pull on the chain is converted into a downward pull ou the sliding
cross-head.
It should be here observed that the term "abutment" or "fulcrum" is herein used
in a wide sense, and in the example illustrated it includes the chain barrel its axle and
its appurtenances.
The retaining gear by which the "abutment" is held down in the frame, as above
mentioned, is both self-engaging and self-releasing, that is to say when not engaged
with the abutment it tends to assume the position of engagement and when engaged
it tends to fall out of engagement with the abutment but is prevented from so doing
by the strain upon it due to the weight of the bucket. The disengagement of the
retaining gear and the consequent release of the abutment is permitted by the cessation
of the strain upon the retaining gear which occurs whenever the hoisting chain is
temporarily relieved of the weight of the bucket. By the release of the "abutment,”;
the upward pull of the chain is permitted, to raise the sliding cross head and thereby
to open the bucket jaws.
This temporary relief of the hoisting chain may be obtained either by supporting
the grab by its frame at the jib-head or by landing it on the ground or elsewhere or
by slacking the chain when the grab is already engaged in the ground. The
temporary relief may also be obtained (when it is required to open the bucket in
mid-air without hanging it up at the jib-head) by suddenly permitting the bucket to
descend quickly for a short distance. During the short interval when by the more or
less free falling of the bucket and load through space, the strain on the retaining gear
is relieved the self-releasing tendency of the retaining gear is permitted to assert itself
which it does instantaneously, the retaining gear being, for the particular purpose of
this mid-air opening of the bucket, actuated by a power which acts independently of
gravity, whereas in other cases the said gear may be actuated entirely by weights.
Reference is to be had to the accompanying drawings forming part of this
specification, wherein figure 1 is a front elevation of the grab-bucket closed, parts
being broken away to shew the details more clearly. Figure 2 is a side elevation.
Figure 3 is a sectional elevation of the same, looking towards the right, the bucket
being open and the barrel being in section on two different planes. Figure 4 is a
detail view of the hanging up catches. Figures 5, 6 and 7 are detail views of the
retaining gear. Figure 8 shows the substitution of weights for springs to actuate the
retaining gear when what I have termed the mid-air opening of the bucket is not
required. Figures 9 to 15 are perspective views illustrative of the general operation
of the apparatus in different positions and circumstances. Figure 9 shows it in the
operation of grabbing; figure 10 shows the grab going up loaded and just about to be
hung up at the jib head; figure 11 shows the grab "hung up" and discharged at the
jib head. Figure 12 shows the action of disengaging the grab from the suspension
tube at the jib head. Figure 13 shows the grab as in the act either of depositing a
load on the ground or of releasing itself after making a "false grab." Figures 14
and 15 illustrate the operation of discharging at an intermediate point in mid-air.
The bucket proper is constructed of two halves or jaws A A hinged at a to the main
frame B and connected to a cross head C fitted to slide up and down in the frame B,
by links D jointed to the jaws at d and to the cross head C, the opening and closing
motions of the jaws being respectively produced by the upwardly and downwardly
sliding motion of this cross head as usual.
22
The hoisting chain E may work the jaws of the bucket without multiplication of
power, but it is usually preferred to obtain "purchase or multiplication of power for
the purpose of more forcibly closing the jaws of the bucket when embedded in the

page_text: ground and for this purpose power multiplying gear of any ordinary kind may be
employed, that shown in the drawings being of the ordinary kind based on the
principle of the well known Chinese windlass.
It is this gear, whether of the kind shown or any other and whether purchase gear
or not, that acts as an abutment or fulcrum for reversing the direction of pull of the
hoisting chain E. In the example illustrated the hoisting chain E is attached to and
wound on the part F of a barrel and branch chains E' are attached to and wound on
the parts F of the same barrel of less diameter than the part F, the chains E being
connected to the sliding cross head C. The barrel turns loose on a hollow
axle H which is fast to slide blocks H' fitted to slide up and down the frame B.
In order, however, to afford the point of resistance necessary to enable the upward
pull on the hoisting chain E to be converted into a downward pull on the chains E' by
the unwinding of the former and the winding up of the latter on their respective
positions FF of the barrel, and thereby to enable the cross head to be drawn down
and the bucket jaws A to be closed, the barrel axle is at proper times retained at the
lower part of the frame B by the self acting gear noxt described.
This retaining gear consists of catches which connect the barrel-axle with the frame,
said catches being acted on either by springs or by weights, according as the mid-air
discharge of the bucket is or is not required. In the example now being described
springs are employed to actuate the catches in the direction of release in opposition to
weights which actuate them in the direction of engagement. I are stationary catches
or stops fixed to the frame B having lugs i in position for engagement by stirrup
shaped catches projecting downward from the same cross-shaft K in order that the
action of the catches shall be simultaneous at both sides of the bucket, the shaft K
passing through the hollow axle H of the chain barrel. The catches k tend to fall into
position of engagement by the weight of an arm or arms I fixed to shaft K at about
right angles to the stirrup catches and when the barrel descends in the frame the
stirrups first strike against the rounded tops of the lugs i, and slipping past them, then
fall into engagement with the said lugs, as shewn in figures 2 and 5. This descent of the
barrel or abutment occurs when the grab has been lowered in the open position for the
purpose of digging, the barrel then descending to the position shewn in dotted lines
in figure 3 whilst the cross-head is held up in the frame by the open jaws A resting
on the ground. The catches are actuated for the purpose of effecting the release of
the "abutment" or "fulcrum" through arms K' which project from the shaft K in
the opposite direction to, and may be in one with, the weighted arms L, the outer
ends of said arms K¹ being brought into line with springs J (or, in certain cases,
weights, as shewn in figure 8) contained in, and guided by, tubular boxes carried by,
and moving up and down with, the sliding cross-head C. The springs or weights J
are applied to act in opposition to the weights L on the ends of the arins K¹ when the
sliding cross-head C is drawn down in the frame, the relative arrangement being such
that they come into operative position only when the cross-head has been so far drawn
down that the bucket jaws have been about two-thirds closed and have therefore
obtained a good grip of the ground so that the upward pull on the chain E will put
considerable pressure on the contacting faces of k and i which have previously become
engaged by the action of the weighted armis L when the abutment was lowered in the
frame, as shewn in dotted lines in figure 3 above referred to.
The cross head C descends beyond the point at which the springs or weights meet
the arms the springs or weights yielding to permit of such further downward
motion necessary for the complete closure of the jaws A. During the descent of the
barrel alone, the chain E winds up on the part F and the chains E' unwind from the
parts of the barrel and the drawing down of the cross-head C to close the jaws, is
effected by the reverse winding of the chains when, the barrel being retained by the
gear 1, K, so as to act as an abutment, the upward pull on the hoisting chain E is
converted into a downward pull on the chains E.
The opening of the bucket jaws is effected by the pressure of the springs or weights J
on the arms K' overcoming the weights L whenever the pressure between i and kis
relieved in any of the ways above mentioned.

page_text: For the purpose of opening the jaws by hanging up the grab to the jib head, the
frame B is provided with catches M at top which, when the grab is raised in the
closed position (as shown in figures 1, 2 and 10) strike against a flanged tube N fixed
just below the jib head and through which tube the hoisting chain freely passes. The
catches M having struck, and risen just above, the flange of the tube N are caused to
fall inwards, so that they will hang thereon when the grab is slightly lowered for that
purpose. When the grab is thus supported by the catches M, as shewn in figures 1,
2, 4, and 11, and the hoisting chain E is sufficiently slacked off to be relievod of
tension due to the weight of the grah, the springs or weights J are at liberty to act
and effect the rolease of the barrel from the retaining gear 1, K, in the manner above
described. When the barrel has been thus released, the grab jaws are opened to
discharge the load by again winding up the hoisting chain at the crane, as in hoisting,
thereby drawing the barrel up in the frame and carrying up along with it, the cross-
head C, as shewn in figures 3 and 11.
It will be seen that as the opening of the grab jaws is effected by a rising motion of
the cross-head C whilst the frame B remains stationary, the grab is opened, within a
less vertical distance measured downwards from the jib head than can at present be
done with similar grab buckets in which it is the cross-head C which is hung up to the
jib head whilst the frame B is allowed to descond. This is a great advantage
as it increases the altitude at which the grab can discharge its load from a crane jib
at a given height.
The catches M. normally tend to fall into position for engagement with the tubo N,
as above described, but are so acted on directly or indirectly by the sliding cross-
head C when the latter nears its highest position in the frame in the operation of
opening the grab as last described, that they tend to fall off from the flanged tubo N
and do fall off immediately they are relieved of the weight of the grab. This occurs
when the cross-head quite reaches the uppermost limit of its motion whereupon the
chain E supports the weight of the grab and the catches M fall out of engagement, as
shewn in dotted lines in figure 4, leaving the grab bucket free to be lowered
in the open position ready for repeating the operation of digging, as shewn in
figure 9.
This self-ongagement and disengagement of the catches M is effected by pivoting
the catches on axes m in the top cross-member of the main frame Band providing them
with horizontal outwardly projecting tail-pieces me which act as weights tending to
throw the catches outwards. The catches are fast on their axes m and upon the latter
are loosely mounted tumbler weights O having shoulders o on their bosses which
engage with cross-pins m² in the axes m so as to form a sort of clutch which permits
limited independent motion of the tumbler weights and of the catches. The tumbler
weights O respectively act in opposition to the tail weights m³ of the catches to which
they are applied and the tail weights m¹ are thereby overcome so long as the tumbler
weights are free to act. The catches M are thus normally held in position for
engagement but when the cross-head nears its highest point in the frame, the tumbler
weights are lifted by it, as shewn in figure 4, and rendered inoperative whereupon
the tail weights m¹ are free to act and disengage the catches from the tube N, as shewn
in dotted lines in figure 4 and in figure 12, as soon as the catches are relieved of the
weight of the grab which occurs when the guide blocks of the cross-head meet the
top cross-member of the frame B or other stop limiting their upward motion in the
frame.
The opening of the grab jaws is effected in the manner before described if the loaded
grab instead of being hung up at the jib-head is landed by being lowered on to the
ground or other underneath support. The chain E being thus relieved of the weight,
the barrel is released and, by a hoisting motion of the chain E, is drawn up in the
frame, carrying up with it the cross head C, whereupon the grab is opened and the
load is gently deposited, as shewn in figure 13.
Similarly, should the apparatus make a "false grab," i.e. seize a rock or other
object which it cannot raise, all that is necessary is to slacken out the hoisting chain a
little whereupon the jaws are caused to release their hold, providing that they had so

page_text: far closed that the springs or weights J have come into operation which they are
timed to do early enough for those cases which are likely to occur in practical
"working.
This
The operation of opening the grab at any intermediate point in mid-air without the
aid of the suspension tube N, depends on the springs Jeffecting the release of the
abutment or barrel from its retaining gear at the moment when, by a sudden lowering
off of the hoisting chain, the retaining gear is momentarily relieved of strain.
action is based on the theory that if the loaded grab were to fall freely (as it would do
were the chain to break) the gravity of the bucket and load would exert no pressure
on the retaining gear, and the springs (which are equally operative whether the grab
be falling or at rest) would consequently assert their power and disengage the barrel.
For this particular purpose weights are not available as they would be without action
on the retaining catches when both are falling freely. The action agrées in practice
with the above described theory except in so far as the free falling of the grab is checked
by the friction and inertia of the chain E and its winding gear on the crane. This moro
or less free falling of the grab through a very small space is performed under the
control of the brake on the crane, which is suddenly released and reapplied after a
momentary interval. The opening of the grab under these circumstances is accom-
panied by the same relative motion of the parts, the frame and jaws having however
in this particular case, a descending motion whilst the barrel and cross-head remain at
about the same actual position in space as will be seen by comparing the relative
positions of figures 14 and 15 which shew the grab before and after being thus
opened. In this case therefore, no advantage in the way of discharging at an
increased height is obtained, over grab buckets worked by two chaius, the advantage
as compared with such grabs being that no special winding gear on the crane is
required.
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 :-
1. A single chain grab bucket wherein the bucket jaws are both opened and closed
by an upward motion of the hoisting chain and wherein that part of the bucket
closing gear which acts as an
25
" abutment or "fulcrum" to reverse the effect of the
pull of the chain, is movable up and down the frame but is automatically retained at
the lower part of the frame so long as it is required to reverse the effect of the pull of
the chain and is automatically disengaged whenever (after the bucket has been
partially closed) the hoisting chain is relieved of strain (by the grab bucket being
hung up or otherwise supported) the said abutment being theu free to be drawn up in
the frame and carry up with it a sliding cross-head or its equivalent, for the purpose of
opening the bucket jaws, as specified.
:
2. A single chain grab bucket wherein the bucket jaws are both opened and closed
by an upward motion of the hoisting chain and wherein that part of the bucket-
closing gear which acts as an abutment" or "fulcrum" to roverse the effect of the
pull of the chain, is movable up and down the frame but is automatically retained at
the lower part of the frame so long as it is required to reverse the effect of the pull
of the chain and is automatically disengaged by the agency of spring power applied as
described, which is permitted to act whenever (after the bucket has been partially
closed) the hoisting chain is momentarily relieved of strain by the falling of the grab
bucket through a small space, as specified.
3. In a single chain grab bucket, the combination with a sliding crosshead for working
the bucket jaws and with an "abutment" or "fulcrum" whereby the upward pull of
the chain is converted into a downward pull of the sliding crosshead, and which abut-
ment is also vertically movable in the frame, of spring or weight actuated retaining
gear which, when the bucket is open and the abutment descends in the frame, becomes
automatically engaged with, and retains, the said abutment at the lower part of the
frame for the purpose of reversing the effect of the pull of the chain, and which, when

page_text: the bucket is closed, tends to become disengaged and does become so disengaged when
relieved of the weight of the grab, as specified.
4. In a single chain grab bucket, the combination with a
sliding crosshoad for
working the bucket jaws and with an " abutment or "fulcrum" whereby the
upward pull of the chain is converted into a downward pull of the sliding crosshead
and which abutment is also vertically movable in the frame, of spring or weight-
actuated retaining gear which when the bucket is open and the abutinent descends in
the frame becomes automatically engaged with, and retains, the said abutment at the
lower part of the frame for the purpose of reversing the effect of the pull of the chain,
and which, when the bucket is closed, tends to become disengaged, and of hanging
up gear applied to the frame of the grab and adapted to engage with an overhead
support for the purpose of relieving the hoisting chain of the weight of the grab and
so permitting the disengagement of the abutment from the retaining gear, as and for
the purpose specifiod.
5. In a single chain grab bucket, the combination with the frame and with the
sliding crosshead, of hanging up catches adapted to automatically connect the frame
with an overhead support and to be so acted on by the sliding crosshead when the
latter rises in the frame that the disengagement of the grab frame from the overhead
support is automatically effected when said catches are relieved of the weight
of the grab, as specified.
H. GRAFTON.
By A. M. & Wm. Clark,
53, Chancery Lane, London,
Patent Agents.