IMPROVEMENTS IN MILLSTONES, ALSO APPLICABLE TO GRINDING DISCS AND CYLINDERS OR ROLLERS
Year: 1880

page_text: PROVISIONAL SPECIFICATION left by Friedrich Carl Glaser at the Office
of the Commissioners of Patents on the 22nd June 1880. A communication
by Hermann Schomburg, of Berlin, in the German Empiro.
FRIEDRICH CARL GLASER, Engineer and Patent Agent, of No. 80, Linden Strasse,
Berlin, in the German Empire. "IMPROVEMENTS IN MILLSTONES, ALSO APPLICABLE
TO GRINDING DISCS AND CYLINDERS OR ROLLERS." [A communication by Hermann
Schomburg, of Berlin, in the German Empire.]
This Invention relates to composite millstones, in which the grinding surface
consists of bars of hard material, suitable for grinding, bedded in other material
forming the body of the millstone. It has been found that the grinding surfaces
of such stones wear very unequally, the outer circumference becoming worn much
more rapidly than the inner portions which first act on the grain. According to
one part of the present Invention this defect is obviated by making the bars
forming the grinding surface tapering in width, so that the extent of grinding
surface presented by them shall increase towards the circumference in proportion
as the surface of the stone increases; and, according to another part of the
Invention, the part of the stone forming the recesses or grooves between the
grinding bars is formed together with the central portion of the stone of one and
the same mass of artificial stone.
Figs. 1 and 2 of the accompanying Drawings shew respectively a cross section
and an underside plan of the abovo described improved construction of millstone.
A are the before described grinding bars, which may be of burnt or baked porous
or non porous porcelain or ceramic material, or they may be of suitable natural
stone. In employing porous porcelain the porosity may be either regular or
irregular. B are the grooves, and O is the central portion of the stone, theso being
formed in one piece.
The stones are prepared as follows:-The "set" or inclination of the grinding
bars having been marked out on a horizontal plate the bars A are placed in
corresponding positions upon the same, and the spaces B between them, as also
the central space at C, are filled in with a plastic compound of magnesite and
quartz, which on hardening forms a cohering mass suitable for millstones.
The jointing together of the plates to form the millstone is effected in such
manner that the surface of the bars remains in the above described increasing
proportion corresponding to the increase of area of the stone.
The grinding bars, when of porcelain, ceramic, or other artificial material, can be

page_text: rendered porous by admixture with the material, before burning or baking, of
various combustible substances or mixtures, such as particles of wood, charcoal,
vegetable, or other fibre or seeds, the porosity being made regular or irregular as
may be desired, or porosities, holes, or grooves may be produced in the mass by
treating with machinery or by stamping in any known manner, and such porosity 5
or grooving may be effected as indicated at Fig. 3, so that the grinding surfaces
have at the inner part, at d, larger holes or grooves than at the outer end at c.
The same construction, as above described, may also be applied to grinding discs
or rollers.