IMPROVEMENTS IN DRESSING MILLSTONES AND IN APPARATUS THEREFOR
Year: 1868

page_text: LETTERS PATENT to Henry Robinson, of Bridge Mills, Lewisham,
in the County of Kent, for the Invention of "IMPROVEMENTS IN
DRESSING MILLSTONES AND IN APPARATUS THEREFOR."
Sealed the 1st June 1869, and dated the 4th December 1868.
PROVISIONAL SPECIFICATION left by the said Henry Robinson at
the Office of the Commissioners of Patents, with his Petition, on
the 4th December 1868.
I, HENRY ROBINSON, of Bridge Mills, Lewisham, in the County of
Kent, do hereby declare the nature of the said Invention for "IMPROVE-
MENTS IN DRESSING MILLSTONES AND IN APPARATUS THEREFOR," to be as.
follows:-
These improvements relate to machines for forming curved or convolute
lines or cracks on the surface of millstones, and consists in causing
the said lines or cracks, near the periphery or skirt of the stone to
be wider apart or coarser than those near the centre, so that the
wear on all parts of the stone will be equal; thus obviating the

page_text: existing disadvantage of the surface near the periphery of the stone
- wearing away before the surface near the centre thereof by reason
of the difference in the speed of the various portions of the said
surface.
In order to carry out my Invention I place in or near the ove
or centre of the stone a shaft rotated by steam power or otherwise,
the said shaft having fastened thereto by set screws or their equi
valents a horizontal frame to which rotary motion is imparted by
the shaft, and on which slides a tool holder having a diamond or
other hard substance fixed therein, the said tool holder being provided
with a nut having a single thread or part of a thread cut therein,
the said nut being free to turn partially around in the socket in
which it is held. Through the said nut, and fixed in suitable bearings
in either end of the frame, is a screw having a variable pitch, the
said pitch being comparitively fine at the inner and and gradually
increasing towards the outer end of the screw, so that as the tool
holder is moved along the said screw from the centre to the periphery
the cracks become wider apart or coarser in proportion as the pitch
of the screw increases. The feed motion may be imparted to the
said screw in any convenient or known manner, and any other means
may be employed for supporting the screw and causing the cutting
tool to rotate; 'the main object to be attained being the formation of
the cracks or lines wider apart or coarser towards the periphery than
near the centre of the stone, so that the wear and tear on the surface
thereof shall be more equal.
SPECIFICATION in pursuance of the conditions of the Letters Patcut,
filed by the said Henry Robinson in the Great Seal Patent Office
on the 4th June 1869.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, HENRY
ROBINSON, of Bridge Mills, Lewisham, in the County of Kent, send 3
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Fourth day of December, in the year of our
Lord One thousand eight hundred and sixty-eight, in the thirty-second

page_text: year of Her reign, did, for Herself, Her heirs and successors, give and
grant unto me, the said Henry Robinson, Her special licence that I, the
said Henry Robinson, my executors, administrators, and assigns, or such
others as I, the said Henry Robinson, my executors, administrators,
and assigns, should at any time agree with, and no others, from time
to time and at all times thereafter during the term therein expressed,
should and lawfully might make, use, exercise, and vend within the
United Kingdom of Great Britain and Ireland, the Channel Islands,
and Isle of Man, an Invention for "IMPROVEMENTS IN DRESSING MILL-
STONES AND IN APPARATUS THEREFOR, upon the condition (amongst others)
that I, the said Henry Robinson, my executors or administrators, by
an instrument in writing under my, or their, or one of their hands and
scals, should particularly describe and ascertain the nature of the said
Invention, and in what manner the same was to be performed, and
cause the same to be filed in the Great Seal Patent Office within six
calendar months next and immediately after the date of the said Letters
Patent.
"
NOW KNOW YE, that I, the said Henry Robinson, do hereby declare
the nature of my said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the
following statement and accompanying Sheet of Drawings (that is to
say) :-
This Invention relates to machines for forming curved or convolute
lines or cracks on the surface of millstones, and consists in causing the
said lines or cracks near the periphery or skirt of the millstone to be
wider apart or coarser than those near the centre, so that the wear on all
parts of the stone will be equal, thus obviating the existing disadvantage.
of the surface near the periphery of the stone wearing away before the
surface near the centre thereof by reason of the difference in the speed
of the various portions of the said surface.
In order that the Invention may be clearly understood I will proceed
to describe the same with reference to the accompanying Sheet of
Drawings, in which Fig. 1 represents an elevation of the machine for
dressing millstones; Fig. 2, a plan of the same; Fig. 3, a detached
view in elevation of the sorew and nut; and Fig. 4a section of the
same.
In order to carry out my Invention I place in or near the eve or

page_text: the said shaft 6 having secured thereto by set screws or other suitable
means a horizontal frame c to which rotary motion is imparted by the
shaft b, and on which slides a tool holder d, having a diamond or other
hard substances fixed thereto, the said tool holder being provided with a
nut e, having a single thread or part of a thread cut therein, the said
nut being free to turn partially around in the socket in which it is held
in a direction at right angles to its axial line, so as to allow for the
variation in the pitch of the screw, which is fixed in suitable bearings
in either end of the said frame, and passes through the said nut.
The
pitch of the screw f is comparitively fine at the inner end and gradually
increases towards the outer end, so that as the tool holder is moved along
the said frame by the rotation of the screw from the centre to the
periphery of the stone the cracks become wider apart or coarser in pro-
portion as the pitch of the screw increases.
The feed motion may be imparted to the screw in the manner shewn in
Figs. 1 and 2, or in any other convenient manner, and any other means
may be employed for supporting the screw and causing the cutting tool
to rotate, the main object to be attained being the formation of the
cracks or lines wider apart or coarser towards the periphery than near
the centre of the stone.
Having now described the nature and particulars of my said Invention
I wish it to be distinctly understood that I do not claim the rotation of
the shaft 6 and frame c for forming curved or convolute lines or cranks
on millstones in the manner described; but what I do claim is the
screw, having a variable pitch and turning in the nut e, by which
means the diamond or other cutting tool is caused to travel faster as it
approaches the periphery of the millstone, where the cracks are made
coarser than near the centre thereof, thus preventing the stone from
wearing away faster at the skirt or periphery than near the centre as at
present.
In witness whereof, I, the said Henry Robinson, have hereunto