Improvements in Grabs and Excavators.
Year: 1889

page_text: Date of Application, 1st Mar., 1889
Complete Specification Left, 2nd Dec., 1889-Accepted, 11th Jan., 1890
PROVISIONAL SPECIFICATION.
Improvements in Grabs and Excavators.
SIDNEY MANTHORP COCKBURN 66 Victoria Street Westminster S.W. do hereby
declare the nature of this invention to be as follows:-
This invention relates to improvements in clip gear for opening & closing grabs
& excavators with a single chain, and is to be used; by preference in combination
with the ordinary differential barrel as used in grabs at present.
Two double-headed hooks are hinged onto the crosshead of the grab, and kept in
the position they assume when in gear with the suspender with one pair of heads by
springs or weights. When the other pair of heads are in gear with the frame of the
grab the bucket is held open.
The suspender consists of a cast iron pipe of suitable length with a notch all
round, about 6" from the bottom end; into which the hooks on the crosshead gear
for opening the bucket. With the above arrangement the grab is released from the
suspender by one continuous downward movement of the chain and that part of the
suspender below the notch makes the gearing of the hooks for keeping the bucket
open, a matter of certainty.
Dated this 28th day of February 1889
COMPLETE SPECIFICATION.
Improvements in Grabs and Excavators.
SIDNEY MANTHORP COCKBURN 66, Victoria Street Westminster 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:
The object of this invention is the production of an automatic clip gear. as applied
to Grab buckets of all descriptions; of simpler construction and more certain in its
action, in automatically releasing the bucket open from the suspender than those at
present in use.
To carry out my invention I construct an apparatus consisting of two double headed
hooks, each pivotted to the crosshead of the grab, by means of a pin working in a
slot, by preference I make the slot in the hook and fix the pin. One pair of heads
engage with a circular casting, having a notch or shoulder all round, at a suitable
distance from the bottom edge; suspended from the head of a crane jib, to cause the
grab to open, the other pair of heads engage with the frame of the grab to retain it
open. I prefer to make the outer pair of heads engage with the suspender and the
inner pair with the frame.
Springs are attached to the hooks and to the crosshead of the grab, which serve to
keep the hooks in their normal position, but this is not the particular purpose for
which I use the springs or place them in the position they occupy. The springs are
so placed that their line of action is at right angles to the bearing faces of the outer
pair of heads of the hooks; or at a slight angle to this position, to give the hooks a
tendency to slip further onto the shoulder. The line of action of the load on the
hooks transmitted to the suspender, when the pins are resting in the bottom of the
slots, makes an angle with the line of action of the springs, of such magnitude as is
required to insure the hooks slipping off the suspender, which slipping off prevented,
until such time as it may be permitted, by the action of the slots in the hooks, which
allow openings in the frame of the grab, into which the hooks press when engaging

page_text: with the shoulder on the suspender; to change their positions by the time the pins
rest in the bottom of the slots, so that the hooks are prevented from slipping off the
suspender by the frame of the grab, until such time as they are permitted to do so by
a change in the position of the frame. When the slipping is permitted, the springs
cause the hooks to engage instantly with their inner pair of heads with the frame of
the grab.
;
The engagement with the frame being made doubly sure by that portion of the
suspender below the shoulder preventing the hooks from being pulled out of gear with
the frame, until they are properly locked.
The form of construction I prefer to use at present is shewn in Figs. 1, 2 & 3.
Fig. 1. shews the position of the parts when the grab is shut and the hooks just
lifted into the suspender.
Fig. 2. shews the positions of the parts when the hooks have been lowered onto
the suspender, the pins resting in the bottom of the slots, and the change of position
of the openings in the frame of the grab, whereby the hooks are prevented by the
frame of the grab from slipping off the suspender.
Fig. 3. shews the grab just released and falling from the suspender, as soon as
the fall is arrested by the crane chain, the pins will travel to the bottom of the
'slots.
In Fig. 1, 2 & 3. the double headed hooks are lettered A. The slots in the hooks B.
The tension springs C. The pins fixed in the crosshead D. The frame of the grab E.
The openings in the frame into which the hooks press when passing into the sus-
pender F. The openings in the frame into which the hooks slip, allowing the grab to
fall from the suspender G. The line of action of the tension springs H H. The
line of action of the load on the hooks when the pins rest in the bottom of the
slots II. The crosshead of the grab J. The links of the grab K. The suspender L.
The shoulder on the suspender M. The portion of the suspender below the
shoulder N.
The action of the apparatus is as follows:-Commensing with the grab being raised
from the ground shut, the top part of the hooks A strike against the bottom corner
of the suspender L, the books are pressed thereby into the openings F F in the
frame E. When they come to the shoulder M they fly out, by the action of the
springs C. C. and the position of the parts in Fig. 1 are obtained.
The grab is now lowered, the hooks resting in the shoulder, and on account of the
action of the springs, having no tendency to slip off the shoulder. Lowering
continues, and the whole and every part of the grab, with the exception of the hooks,
move downwards until the pins rest in the bottom of the slots. The parts at this
instant assuming the positions shewn in Fig. 2. In which it will be seen that the
openings F have moved downwards and past the head of the hooks, which cannot
now slip off the shoulder.
The downward movement of the crosshead J is now arrested and much of the
weight of the grab is resting on the hooks A. A. the line of action H H of this load,
gives the hooks a tendency to slip off the shoulder M, as the load is much greater
than the force acting in the line of action of the springs, but the slipping is at present
prevented by the frame of the grab.
Lowering still continues; the frame E moving downwards and the grab opening.
When the opening G in the frame passes the hooks they immediately slip from the
shoulder M, and are instantly pulled downwards by the springs and are locked in
gear with the frame, the part N of the suspender preventing their flying out of the
openings while the hooks are falling.
Fig. 3 shews this position: the instant of falling from the suspender.
As soon as the crane chain arrests the face of the grab, the pins will travel down
the slot and rest on the bottom, and the grab will be suspended in the air open.
The grab now being dropped on the ground the crosshead will move up, an amount
sufficient to raise the hooks clear of their engagement with the frame, and the springs
will cause the hooks to assume their normal position; which ends the cycle of
operations.

page_text: Having now particularly described and ascertained the nature of ny said invention,
and in what manner the same is to be performed, I declair that what I claim
is:-
1st. An apparatus constructed substantially as described and for. the purpose set
forth, whereby a hook, so loaded, that when rested on a shoulder, it has no tendency
to slip off, may be given a tendency to slip off by a change in the line of action of
the load on the hook.
2nd. The combination of a hook with a limited amount of movement, with a spring
or its equivalent; whereby the hook is made to engage instantly with the frame of
the grab, when released from a shoulder on the suspender, substantially as described.
3rd. The combination of a slot in a hook with the particular position of an
opening in the frame, whereby the opening may move its position, in such a manner
that the hook cannot slip into it by the time it is given a tendency to slip from the
shoulder on which it was resting, substantially as described.
4th. The portion N of the suspender whereby the hooks are prevented from
disengaging from the frame E until they have had time to become locked in position,
substantially as described.
Dated this 30th day of November 1889.