IMPROVEMENTS IN APPARATUS FOR DRESSING MILLSTONES
Year: 1868

page_text: LETTERS PATENT to Henry Robinson, of Bridge Mills, Lewisham, in
the County of Kent, and John Smith, of Carshalton, in the County
of Surrey, for the Invention of "IMPROVEMENTS IN APPARATUS FOR
DRESSING MILLSTONES."
Sealed the 22nd June 1869, and dated the 24th December 1868.
PROVISIONAL SPECIFICATION left by the said Henry Robinson and
John Smith at the Office of the Commissioners of Patents, with
their Petition, on the 24th December 1868.
We, HENRY ROBINSON, of Bridge Mills, Lewisham, in the County of
Kent, and JOHN SMITH, of Carshalton, in the County of Surrey, do hereby
declare the nature of the said Invention for "IMPROVEMENTS IN APPARATUS
FOR DRESSING MILLSTONES," to be as follows:-
Our improvements consist in dressing millstones so that the cracks are
made coarser or wider apart at or near the skirt or periphery of the stone
than near the centre thereof, and in order to carry out our Invention we
place in or near the eye or centre of the stone a pivot supported by a

page_text: flange, which may be screwed or otherwise fastened to the said stone
during the operation of dressing. Upon the said pivot a hollow casting
having a curved slide affixed thereto is bolted or otherwise fastened, so that
the said casting and its curved slide can revolve on the pivot by reason of
the bolt heads running in grooves cut in the flange above mentioned, the
nuts on the said bolts being screwed tight when the casting and its slide
are in a proper position for working. Across the arc of a circle formed
by the above-mentioned curved slide is placed in bearings a screwed
shaft working in a nut fixed to a slide rest, the radius of which corre
sponds to the radius of the curved slide, so that it may work backwards
and forwards thereon by the rotation of the screw, and the nut is caused
to slide in its socket so that it may adapt itself to the varying distance
between the said screwed shaft and the periphery of the slide rest; or
instead of a screw the shaft may be supplied with a worm wheel gearing
into a rack fixed to the slide rest, by which or any other similar means
the same result will be attained. Upon the slide rest is arranged a
footstep or bearing carrying a radial arm on which works the tool
holder, and the centre from which the radius of the arc of a circle formed
by the curved slide is struck must be at a greater distance from the
circumference thereof than is the centre of the millstone, so that on
rotating the screwed shaft the slide rest will be worked along the curved
slide and the inner end of the radial arm carrying the cutting tool will
be moved a less distance than the outer end of the arm, thus causing the
cracks to be coarser or wider apart at the skirt or periphery than at the
centre of the stone. The cutting tool I prefer to use is the diamond, but
any other hard substance may be employed.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Henry Robinson and John Smith in the Great
Seal Patent Office on the 24th June 1869.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, HENRY
ROBINSON, of Bridge Mills, Lewisham, in the County of Kent, and JOHN
SMITH, of Carshalton, in the County of Surrey, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-fourth day of December, in
the year of our Lord One thousand eight hundred and sixty-eight, in

page_text: the thirty-second year of Her reign, did, for Herself, Her heirs and
successors, give and grant unto us, the said Henry Robinson and John
Smith, Her special licence that we, the said Henry Robinson and John
Smith, our executors, administrators, and assigns, or such others as we,
the said Henry Robinson and John Smith, our 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 APPARATUS POR
DRESSING MILLSTONES," upon the condition (amongst others) that we, the
said Henry Robinson and John Smith, our executors or administrators,
by an instrument in writing under our, 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 we, the said Henry Robinson and John Smith, do
hereby declare the nature of our 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):
:-
Our improvements consist in dressing millstones so that the cracks
or lines are made coarser or wider apart at or near the skirt or periphery
of the stone than near the centre thereof, and in order to carry out our
Invention we place in or near the eye or centre of the stone a pivot
supported by a flange which may be screwed or otherwise fastened to
the said stone during the operation of dressing. Upon the said pivot a
hollow casting having a curved slide affixed thereto is bolted or other-
wise fastened, so that the said casting and its curved slide can revolve
on the pivot by reason of the bolt heads running in grooves cut in the
flange above mentioned, the nuts on the said bolts being screwed tight
when the casting and its slide are in a proper position. for working, or
the said grooves may be dispensed with and a check. nut used in lieu
thereof, as shewn in the Drawing. Across the are of a circle formed
by the above-mentioned curved slide is placed in bearings a screwed
shaft working in a nut fixed to a slide rest, the radius of which corre

page_text: sponds to the radius of the curved slide, so that it may work backwards
and forwards thereon by the rotation of the screw, and the nut is caused
to slide in its socket, so that it may adapt itself to the varying distance
between the said screwed shaft and the periphery of the slide rest; or
instead of a screw the shaft may be supplied with a worm wheel gearing
into a rack fixed to the saddle of the slide rest, by which or other
equivalent means the same result will be attained. Upon the slide rest
is arranged a footstep or bearing carrying a radial arm, on which works
the tool holder, and the centre from which the radius of the arc of a
circle formed by the curved slide is struck must be at a greater distance
from the circumference thereof than is the centre of the millstone, so
that on rotating the screwed shaft the sliding saddle will be worked'
along the curved slide and the inner end of the radial arm carrying the
cutting tool will be moved a less distance than the outer end of the
arm, thus causing the cracks to be coarser or wider apart at the skirt
or periphery than at the centre of the stone. The cutting tool we
prefer to use is the diamond, but any other suitable hard substance
may be employed.
In order that our Invention may be clearly understood we will proceed
to describe the same with reference to the accompanying Sheet of
Drawings, in which Fig. 1 represents a section of our improved machine,
and Fig. 2 a plan of the same.
Through the flange a of the cone 6 screwed studs c pass into nuts d
let into the millstone d', by which said studs the machine is secured to
the stone, but any other suitable means may be used for this purpose,
and studs e are also used for regulating the set or tram of the machine.
Around the cone 6 and fitting thereon at the points f is the hollow
casting g having V or other slides h, h, projecting therefrom, the centre i
from which the arc of a circle formed by the said slides is struck, being
at a greater distance from the periphery thereof than is the centre of
the millstone, as seen in Fig. 2. The upper part of the cone 6 is screwed
and carries a nut k, which serves to tighten the casting g on the said
cone while a crack is being made. This can be done instantaneously
Above the said
by means of the bar or by any other suitable means.
cone, and resting therein, is the vertical shaft m carrying the bracket n
for supporting the riggers o, around which passes the cord p for actuating
the pulley g of the diamond cutter 1, and above this shaft is a second
shaft having its bearing in the ceiling or roof and carrying the grooved

page_text: pulley 8, to which motion is imparted from a water wheel or other
motive power, and which causes the driving pulley t to rotate and give
motion to the diamond cutter, as before explained. On the V slides h, h,
is a sliding bracket or saddle u, the arc of the slide whereof is struck
from the same point as the arc formed by the slides h, h, and this sliding
bracket carries in bearings v, w, the radial arm x with the tool holder y
fixed thereto and sliding thereon, as in the ordinary construction of
millstone dressing machines. This tool holder is moved along the arm x
by the handle z actuating the levers a and b, as seen in Fig. 1. The
radial arm x is moved along the curved slides h, k, by means of the
screw e¹ working in a nut f¹ free to turn in its bearings g' and to slide
in its bearing ', so as to adapt itself to the varying distance of the screw
from the sliding bracket u caused by the circular form of the slides h, h,
and the necessary rectilinear course of the screw. The said screw c¹ is
supported in bearings and is actuated by the lever ¹ operating upon
a pawl taking into a ratchet wheel m', the extent to which the radial
arm x is desired to travel along the slide, and therefore the distance
apart of the cracks is regulated by the pin n¹ fixed in a groove in the
bracket o¹, against which pin the lever le strikes cach time it is actuated.
The lover is here shewn actuated by hand, but it may be worked auto-
matically by the machine if desired, and any other method of revolving
the screw may be adopted, and if desired a worm gearing into a rack
fixed to the sliding bracket u may be employed instead of the screw.
Instead of the radial arm a curved arm may be fixed to the pivot
on the sliding bracket or saddle, by which means the dress known
as the circular or sickle dress will be produced in the same manner.
The operation of the machine is as follows:-The radial arm x is
placed in position either parallel with the lands of the millstone or at an
angle thereto; the lever or handle is then depressed, causing the tool
holder carrying the diamond cutter to be moved along the radial
arm x, thus forming a crack. The screw c¹ is then rotated causing the
arm to be moved a short distance along the curved slides h, h. By this
means each crack or line will radiate, not from the centre of the
millstone, but from the point i, or from some point approximate thereto,
thus causing the cracks or lines to be wider apart or coarser at the
periphery of the stone than near the centre, as seen at p', and thereby
preventing the disadvantage of the stone wearing away more rapidly

page_text: near the skirt than near the centre thereof by reason of the greater
speed at which it travels at that part.
Having thus described the nature and particulars of our said Inven-
tion, we claim the flanged cone carrying the curved slides h, h, having
the arc of a circle, of which they consist, struck from a point at a
greater distance from their periphery than is the centre of the millstone,
in conjunction with the curved sliding bracket or saddle u carrying the
radial arm x, by which means the cracks are made coarser or wider
apart near the skirt of the stone than near the centre thereof, as herein
described and shewn in the Drawings.
In witness whereof, we, the said Henry Robinson and John Smith,
have hereunto set our hands and seals, this Twenty-third day
of June, in the year of our Lord One thousand cight hundred
and sixty-nine.
HENRY ROBINSON. (L.S.)
JOHN SMITH.
(L.S.)