IMPROVED DREDGING OR EXCAVATING APPARATUS OR MECHANISM
Year: 1875

page_text: PROVISIONAL SPECIFICATION left by Thomas Williamson at the Office
of the Commissioners of Patents, with his Petition, on the 4th May
1875.
I, THOMAS WILLIAMSON, of the City of Glasgow, in the County of
Lanark, North Britain, Engineer, do hereby declare the nature of the
said Invention for "IMPROVED DREDGING OR EXCAVATING APPARATUS OR
MECHANISM," to be as follows:―
This said Invention has reference to improvements in the construction
and action of or mode of working a dredging or excavating vessel or
apparatus,, which are essentially improvements upon the apparatus
described in reference to and shown in Figures 4, 5, and 6, of Sheet 3
of the Drawings appended to the final Specification of the Patented
Invention of Fenner Ballou Taylor, dated 1st December 1871, and
Numbered 3258; and the nature and novelty of this Invention or
improved excavating or dredging machine, consist in hinging each of
the two, three, or four excavating diggers or sections forming the shell
of the bowl-shaped vessel at their inner upper edge by double joints to
an improved long joint on the outer perimeter of an improved inner
large, heavy, and preferably round or other shaped open weight, and

page_text: have each a strong central rib or arm secured up the centre extending
above the hinge and weight as levers, with all their upper ends abutting
on the upper part of the weight or on a short central spindle when all
the diggers are opened, and each connected by a toggle link projecting
in and down from the upper end of the bow lever to snugs on the lower
end of this rod, to the top of which the main closing and lifting chain is
attached. The lower inner digging end of each section or spade is
connected by a segmental bar or other arm to the upper inner end of
the bow arm, near to the joint of the toggle link used in the said
Patent of Fenner Ballou Taylor, or it might be jointed by a screw rod
and loose link to the said snugs at the lower end of the central rod,
instead of the equivalent loose closing chains as in Taylor's said Patent.
The other main or opening, hanging, and lowering chain is attached by
an open ring (for the other chain to pass through) and long double
links, or it might be short separate chains to the outer part of each bow
lever, and near the upper outer edge of each digger, as in Taylor's said
Patent, and that of Sylvester Franklin Schoonmaker, No. 704, dated
8th March 1866, and John Taggart, No. 319, dated 9th February 1854,
the one chain (as usual) being let go or slackened, while the other is
acting and sustaining the whole apparatus.
By another arrangement the lower end of the central rod might be
attached by short toggle links horizontally to each digger when open, to
near the middle of the inner segmental arm, or it might be to the centre
of two angled arms rigidly connected to the bow arm and digger at top
and near the point, so as to close the diggers. In this case the toggle
links would have most power when beginning to close the diggers, and
would be vertical when closed, and not have most power at the last and
be horizontal as in the first case, or as in Taylor's. The frame weight to
which the diggers are hinged might be round or polygonal, and either
quite open in the centre or have arms with an eye as a partial guide to
the short central rod for closing the diggers as stated, and although long
joints are described and preferred for hinging the diggers, yet double
joints at some distance apart would do nearly as well, as in the arrange-
ment of Taylor's said Patent.
Another important improvement of this said Invention consists in
actuating this improved excavator, so constructed, by a single main
lifting and lowering winding chain attached to the top of a sliding sleeve
or socket locking rod, working on the top end of the short rod for

page_text: closing and raising the excavator, closed and locking into or below
notches in it by a catch bar and links or palls pressed in by springs when
free to do so, by lowering the main chain and upper sliding rod,
which at the same time slackens the outer double links or short chains
attached to the outer part of each digger or its bow lever below, and to
eyes near the top of the locking sliding rod, and not to an open ring as
in the former case where a central chain had to work up through it.
The locking bars or links would be pressed out or unlocked (when the
excavator had to be opened to discharge or empty the contents and
lower it open by the said double outer links or short chains) by a light
rope for the purpose, attached to the one arm of a light oscillating frame
or duplex lever arrangement with reverse links jointed to the catch links
or bars, when turned in one direction against the power of the pressing or
locking springs, and a second rope might be similarly attached to the
opposite arm or the swivelling disengaging lever frame, so as to pull the
catches into gear by the same positive mechanism which disengages
them, instead of or in addition to the power and action of the springs for
that purpose, which spring would always insure the catches remaining
locked until disengaged by the light rope as before stated. Otherwise
these duplex arms could be made to automatically engage and disengage
the locking bars or links, by coming into contact with a stop attached to
the fixed frame or weight of the excavator when lowered, and when
raised to the top where the excavator had to be opened to discharge the
material, then the lever might come in contact with a stop attached to
the fixed hoisting framing above.
Another improved mode and means of working such dredgers or
excavators by one main chain, consists in attaching this chain to the
sliding central bush or antifriction rolling centre of a duplex or open
link (such as used for reversing the slide valves of engines), and
attaching the chain of the central spindle of the excavator to one end of
the link, and the shackle of all the short outer opening chains of the
diggers to the other end of the reversing link, which might be tilted by a
light rope from above, so as to throw the carrying point of the main
chain to either end of the link, so as to hang the excavator either close
or open, according to the end of the link in action.
A further improvement consists in jointing a long beam or lever by a
short link to the upper end of a stationary or central rod attached to the
weight or frame of the excavator with a griping shoo on its outer end,

page_text: .
near which it is jointed to the upper of two vertical acting toggle links,
the lower arm of which is fulcrumed to the joint pin of each digger, the
central joint of the toggle links being coupled by a short link to the
upper joint of the bow arm of each digger, all so that as the excavator is
lowered open, the outer ends of the levers and shoes are clear of the sides
of the cylinder being sunk, but so soon as the central rod is pulled upon
to close the diggers, they straighten the toggle links and raise the outer
ends of the beams, and cause the shoes to gripe on the lower part of the
sides of the cylinder being sunk, so as to force the diggers while they
are closing down into the material to be excavated, while the last part
of the action of closing the spades would relieve the upper end of the
toggle links and griping shoes, so that the excavator might be lifted full
of the material excavated.