IMPROVEMENTS IN THE MEANS OF AND APPARATUS FOR BALANCING MILLSTONES
Year: 1869

page_text: PROVISIONAL SPECIFICATION left by Edward Lethbridge at the Office
of the Commissioners of Patents, with his Petition, on the 29th
November 1869.
I, EDWARD LETHBRIDGE, of Benson, in the County of Oxford, do
hereby declare the nature of the said Invention for "IMPROVEMENTS IN
THE MEANS OF AND APPARATUS FOR BALANCING MILLSTONES," to be as
follows:-
This Invention relates to certain improvements in the means of
effecting a true balance to millstones while in work, and in the apparatus
used for such purpose.
Heretofore cavities or perforations have been made in the periphery of
the millstone, and weights have been inserted in order to rectify irre-
gularities of action and to balance the stone while in the process of
grinding flour or other substances, but this practice has been found, with
many others for the same object, uncertain on account of the difficulty.
of final adjustment of the weight, and also of the difficulty of altering
the same when adjusted in order to comply with the requirements
which a centrifugal balance power under varying conditions should
fulfil, since if a weight of molten lead, for example, be filled into one

page_text: or more cavities in the stone it may be requisite at any time to increase
or decrease such weight according to circumstances, which would neces-
sitate the removal of the stone and almost a complete repitition of the
original work.
Now my Invention consists in a means and apparatus whereby mill-
stones may be balanced and regulated by a leverage power capable of
being changed whenever necessary by altering the situation of the
weight or weights affected by centrifugal power, and without the necessity
of removing or cutting the stones, and consequently avoiding the
stopping of the mill except for a very short time. In order to effect
these objects I propose to apply and attach to the surface of the stone a
series of, say, four (or other number) of cast-iron or other metal boxes or
elongated chambers, which are secured to the stone by means of flanges
or hubs, or fixed by plaster or cement; these chambers reach from a
point clearly within the circumference of the stone to another point free
of the shaft, and of course form in their central lines radii of the circle.
Throughout each chamber an endless screw is set in bearings at each
extremity of the chamber, being free to turn without any traverse or
longitudinal motion; the axis of the screw projects slightly beyond the
outer edge of the box, and is provided with a square head so as to be
turned by a crank or key in either direction. The square head is also
clear within the external circumference of the stone. Then I apply
within each chamber and on each endless screw a metal weight of any
desired capacity and cut with a female screw, the weight being of such
transverse section as to coincide with the section of the chamber and so
be prevented from turning, thereby receiving from the screw a motion
nearer to or further from the centre of the stone, and consequently
affording a perfect and efficient means of balancing the stone under
every condition of work to which it may be applied. The positions of
the weights may therefore be varied at will in each of the chambers
with the greatest ease, and it is manifest that an immense advantage
will be gained by this Invention over all others by the minuteness and
unerring accuracy of balancing power acquired.