IMPROVEMENTS IN THE CONSTRUCTION OF GRABS EXCAVATORS SUITABLE FOR DREDGING AND OTHER PURPOSES
Year: 1882

page_text: PROVISIONAL SPECIFICATION left by Joseph Thomas Jones and Joseph
Henry Wild at the Office of the Commissioners of Patents on the 29th July
1882.
JOSEPH THOMAS JONES and JOSEPH HENRY WILD both of Leeds in the County
of York Engineers, "IMPROVEMENTS IN THE CONSTRUCTION OF GRABS
EXCAVATORS SUITABLE FOR DREDGING AND OTHER PURPOSES
"
OR
This Invention relates to improvements in the construction of grabs or excavators
suitable for dredging and other purposes.
In grabs or excavators as at present constructed for the removal by dredging of
rocky débris and loose material such as results from subaqueous boring and blasting
operations, sets of curved tines or teeth are employed, such teeth being caused by
powerful toggle joints to bite into the debris and meet together enclosing, as in a
cage, a mass of shingle, sand and rock, which is then raised to the surface of the
water. It is found, however, that so soon as the grab is hoisted above the surface,
the rapid drainage of water washes out large quantities of the sand, shingle and
smaller pieces of rock from between the teeth or tines thereof, thus diminishing the
dredging capacity of the grab or excavator, to a serious extent.
If the teeth or tines are set more closely together in order to partially remedy
this defect they do not enter the ground so well, and are moreover liable to be
wedged open by large pieces of rock, or even to close upon and bring to the surface
a single piece of rock only.
To obviate these inconveniences our improvements consist in the application of a
shrouding or hood which will cover in, and enclose the cage formed by the teeth or
tines of the grab, as it leaves the ground, and will entirely prevent the loss of any
small particles which may pass through the tines. We are thereby enabled to bring
up more at each lift of the grab and are enabled to space the tines most
advantageously for the work in hand.
The shrouding is perforated with small holes to allow the water to drain out of
the material enclosed within the grab or excavator.
The shrouding preferably consists of two portions or buckets having their
peripheries curved concentrically, or nearly so, with the tines they serve to
enclose.

page_text: The shrouding is attached to the grab by means of bolts or pins passing through
holes in the end plates of the shrouding, the same bolts carrying the arms of the
grab so that when the grab is closed and raised, the joggles or catches with which
the end plates are provided will rest on the arms and be lifted by the said arms
when the grab is opened to discharge its contents.
The above arrangement may in some instances be modified by dispensing with
the circular part of the shrouding, and using only the end plates with the joggles or
catches attached for lifting them. The forks or tines in the ends of the grab may
also be dispensed with by adopting the loose shrouding thus giving greater digging
power to the grab.
We preferably use tines of unequal length in each half of the grab, as it is found
that greater penetration and less slip, or lateral dragging action, takes place with
such an arrangement.
The invention is also applicable to the raising of coal from the holds of vessels
and for removing other materials consisting of both large lumps and small pieces
or dust.