AN AUTOMATIC DREDGER
Year: 1883

page_text: LETTERS PATENT to Edward Croft Greenway Thomas of No: 11 Norland
Square, Notting Hill in the County of Middlesex for an Invention of
"AN AUTOMATIC DREDGER
"
PROVISIONAL SPECIFICATION left by the said Edward Croft Greenway
Thomas at the Office of the Commissioners of Patents on the 23rd April
1883.
EDWARD CROFT GREENWAY THOMAS of N° 11 Norland Square Notting Hill in
the county of Middlesex "AN AUTOMATIC DREDGER
"
I provide a cigar-shaped body having a specific gravity a little in excess of that
of water, so that it will sink, but will lie on the bottom without much pressure.
At one end of this cigar-shaped body, I fix helical blades, and I hold the body
by a chain or rope attached to it by a swivel, leaving the body free to revolve.
On the body, I fix projecting arins or spikes.
When the body is thrown into a current, it sinks lying lightly on the mud at
the bottom and as it is held stationary, the current, acting on helical blades causes
the body to revolve, so that its arms or spikes revolving stir up the mud, which
the current sweeps away.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Edward Croft Greenway Thomas in the Great Seal Patent Office on
the 20th October 1883.
EDWARD CROFT GREENWAY THOMAS of N° 11 Norland Square Notting Hill in
the County of Middlesex "AN AUTOMATIC DREDGER"
I provide a cigar-shaped body having a specific gravity a little in excess of that
of water, so that it will sink, but will lie on the bottom without much pressure.
At one end of this cigar-shaped body, I fix helical blades, and I hold the body by
a chain or rope attached to it by a swivel, leaving the body free to revolve. On
the body, I fix projecting arms or spikes.
When the body is thrown into a current, it sinks, lying lightly on the mud at
the bottom, and as it is held stationary, the current, acting on its helical blades
causes the body to revolve, so that its arms or spikes revolving, stir up the mud,
which the current sweeps away.
The accompanying drawing is an elevation of an automatic dredger according to
my invention. A is the cigar shaped body which may be of metal hollow so that
it has weight enough to sink in water without pressing too heavily on the mud or
sand bottom B. On the front part of the body A are fixed helical blades C, which
may be either continuous as shewn, or may be separate segments like the blades of
a screw propeller. And on the bulge are fixed spikes D, which may be plain spikes
as shewn, or may be made of forms and in numbers to suit the character of the
material at the bottom B. The dredger being held by a rope or chain, attached to
a swivel E, in a current flowing in the direction of the arrow F, the current acting
on the blades C 'causes the body A to revolve, and the revolving spikes D. break up
and agitate the mud or sand at the bottom, so that the disturbed layer is washed
away by the current. The dredger, instead of being stationary, may be drawn
along against the current, so that it is made to revolve with increased force.
Having thus described the nature of my invention and in what manner the
same is to be performed, I claim :-
i
The construction and use of an automatic dredger arranged and operating
substantially as herein described.
In Witness whereof I the said Edward. Croft Greenway Thomas have hereunto
set my hand and seal this Nineteenth day of October in the year of our Lord'
one thousand eight hundred and eighty-three.
:
T aa THOMAS ral