IMPROVEMENTS IN MACHINERY OR APPARATUS FOR DRESSING MILLSTONES."
Year: 1877

page_text: PROVISIONAL SPECIFICATION left by John Henry Johnson at the Office of
the Commissioners of Patents on the 28th August 1877. A communication
from abroad by Charles Golay, of Paris, in the Republic of France, Engineer.
JOHN. HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex,
Gentleman. IMPROVEMENTS IN MACHINERY OR APPARATUS FOR DRESSING
MILLSTONES." A communication from abroad by Charles Golay, of Paris, in the
Republic of France, Engineer.
*
This Invention, relating to improvements in machinery or apparatus for dressing
millstones, has for its object the construction of a simple and convenient machine
capable of being worked by an ordinary or unskilled workman.
In carrying out this Invention, in order to effect this object, the table or support
for the stone is arranged in a horizontal position. With a view to enable the.
millstone to be placed in position with greater facility the table or support is
arranged at a height of, say, about 20 inches from the ground, so that the mill-
stones may be brought to it on a truck or trolly of the same height provided with
rollers. The horizontal adjustment of the millstone is effected by means of adjusting
screws.
The mechanism carrying the cutters slides upon an arm or carrier connected to
the base of the machine by means of two bolts passed through elongated holes,
which admit of the carrier being caused to assume a horizontal position for the
purpose of dressing the grooved surface of the stone, or an inclined position for the
purpose of dressing the hollow part near the central aperture or eye.
The rotatory motion of the table or support for the stone varies according as the
rotating cutter or cutters are working near the centre or the circumference of the
stone. In all cases it is very slow, and is intermittent, taking place each time the
cutting mechanisın reaches the end of its travel.
The rapidity of the motion imparted to the cutting mechanism may be varied as
required, according to the hardness of the millstones, and the amount of stone to be
taken off by means of conical pulleys of different diameters.

page_text: In this machine the spindle carrying the cutter rotates with great rapidity, and
is provided with an automatic lubricating apparatus attached to the travelling
support.
This dressing machine, which is both simple in construction and regular in its
action, may be employed both for cutting the channels in millstones and for renovating
the same when worn.
The details of the parts may be somewhat modified, but it is preferred to arrange
them in the following manner, vizt.-
The machine consists of a cast-iron base, mounted on a suitable foundation stone,
and which carries the whole of the dressing mechanism and the table or support for
the stone.
The base is provided with an annular face planed perfectly true, which carries the
cast-iron table or support, the axis of which fits exactly into and is passed through
a central boss or bearing cast in one with the base.
The millstone to be operated upon is placed on the table, and is set level by means
of adjusting screws, which act upon cast-iron discs or washers, upon which the
millstone is supported.
The tool carryer is attached to the base by bolts, which pass through elongated
holes, and admit of the most accurate adjustment of the said carryer either in a
horizontal position, or at different angles, according to the requirements of the
work.
The carrier may be turned up in order to obviate the danger of injury to it during
the operation of placing the millstone on the table.
With a view to preventing an undue strain on the bolts supporting the carrier,
when the latter is in an inclined position, an iron wedge is placed between the
lower part of the carrier and the true face of the base where it is attached.
A traveller is fitted so as to be capable of sliding along the carrier, and carries a
cutter holder, sliding in a dovetailed groove formed in the traveller. A hand wheel
serves to cause the diamonds in the discs to move towards or recede from the mill-
stone, according to the quantity of stone to be taken off, set screws being provided
for preventing their subsequent displacement.
The traveller is arranged in relation to the driving mechanism, and operated in
the following manner :-It is connected by a rod to a crank carried on a shaft,
which is driven through the intervention of gearing from the driving shaft of the
machine.
+
The stud of the crank is capable of adjustment, so as to admit of the length of
the stroke of the traveller being varied, and the connecting rod is provided for this
purpose with a flattened part having teeth or notches, the cutter or cutters being
thereby caused to work either upon the channelled surface of the stone, or upon the
hollow near the eye, as required.
The shaft driven as before mentioned carries a cam for lifting a frame which is
connected to a rod jointed to one arm of a bell-crank lever; this arm of the lever
carries a counterweight, which has a constant tendency to draw it downwards,
whilst the other arm of the said lever is connected by a rod to a lever centred on
the axis of an endless screw or worm in gear with a worm wheel on the axis of the
table supporting the millstone.
The axis of the endless screw is provided with a ratchet wheel, and the lever last
mentioned carries a pawl, so that each time the frame is raised by the cam the
pawl is moved, and imparts motion to the ratchet wheel. The endless screw by its
rotation actuates the worm wheel and table, and brings a fresh portion of the mill-
stone within the range of the cutters.
The diamonds which constitute the cutting edge of the dressing tool are let into
the peripheries of two discs mounted on each extremity of a spindle. As this
spindle rotates with great rapidity it is supported throughout its whole length by
bearings of hard brass of the best quality, which are held in an inverted plummer
block bolted underneath the cutter holder. This plummer block is provided at its
extremities with two oil reservoirs, and two small channels are formed underneath

page_text: the lower bearings, which allow the oil poured into the reservoirs in the plummer
blocks to flow to the centre of the latter, where it is taken up by a disc mounted
on the spindle, and poured over the same. After lubricating the spindle it escapes
at its extremities, and falls back into the reservoirs, to be carried up again, and so on
continuously. The oil has thus a continuous and automatic motion imparted to it,
and the lubrication of the spindle is perfect.
The cutters are driven by a gut cord passing over pulleys, and the length of
which remains unaltered by any changes in the position of the traveller.
The carrier may be made of a bridge shape, so as to obtain two points of support
if found desirable.