An Improved Method of Grinding Mother-of-pearl and other Shells, and Apparatus therefor.
Year: 1892

page_text: Date of Application, 12th Sept., 1892-Accepted, 5th Nov., 1892
An Improved Method of Grinding Mother-of-pearl and other Shells,
and Apparatus therefor.
I JOHANN FRIEDRICH CROSINSKY of 8, Mariannenplatz, Berlin, in the Empire
of Germany, Manufacturer do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement :--
Mother-of-pearl and other shells have heretofore been reduced to a pre-
determined thickness by grinding them flat or even first on one side and then on
the other. For this operation very skilled workmen have been necessary to obtain
equal thickness throughout. By reason of the brittle nature and vaulted shape of
the shells it has not been possible to grind plates of comparatively large size
without making excessive demands on the skill of the workmen, or producing a
large number of broken pieces or spending a long time in the grinding.
According to my improved method these shells are ground simultaneously on
both sides between two sand stones turning in the same direction, one stone being
supported in a fixed bearing, whilst the other possesses a yielding bearing for
enabling the distance between the two stones, after adjustment to a certain
minimum distance, to be increased as the pressure between the two stones
augments.
In the accompanying drawing I have shown apparatus which I use for carrying
my aforesaid method into practice, but it will be understood that the arrangement
of the same is susceptible of various modifications. The essential feature of the
improved apparatus lies in the two grindstones a, b adapted to turn in the same
direction and consisting mostly of moderately fine sand stone. The bearings cd for
the shafts of the two stones are arranged each upon a slide f, g so that the slides,
and therefore also the stones, can be caused to approach and recede from each
other. The slide g at the rear taken from the stand of the workman, is provided
with a female thread, whilst the slide fin front possesses a smooth bore.
A shaft e
carrying a hand wheel / passes without a screw thread through the bore in the
slide and with a screw thread through the nut of the slide g.
Two adjusting
collars i, are arranged upon the shaft, and a somewhat powerful plate spring k is
provided between the inner side of the frame of the apparatus and the slide f. It
will be readily understood that by turning the said hand wheel the distance between
the two stones a, b can be changed and that when the pressure between the two
stones becomes greater than the pressure of the spring the stone a will move back.
The rear stone b is actuated by a belt passing round the step pulley m; the
turning movement is transmitted by means of a belt n from the rear stone b to the
front stone a. In order to adapt it to the varying distance between a and b
the belt n can be adjusted by means of a roller p and a hand wheel q.
The workman taking his place in front of the stone a holds with both his hands
the shell to be ground and tries to conduct the same gradually with its entire
surface between the stones a and b. Any projecting unevenesses and the excessive
thickness of the shell are thereby ground off until the thickness of the shell is not
greater than the adjusted distance between the stones a and b. In case the front
stone a, when the rotation takes place in the direction which is indicated by arrows
and which may also be reversed, should suddenly carry away the shell owing to a
specially thick part thus causing the shell to pass below the line of operation, the
stone can yield to obviate injury to or breakage of the very brittle shell.
The characteristic feature of the improved method lies in the fact that the two
stones rotate in the same direction, therefore their operative grinding surfaces move
in opposite directions at the point of operation as indicated by arrows in Figure 1.
FD071

page_text: In this manner it is possible to grind brittle shells of a very large size without
breaking the same.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
:-
First. The improved method of grinding mother-of-pearl and other shells to any
desired thickness by conducting the same between two stones turning in the 'same
direction, one stone being supported so as to be capable of yielding for the purpose
of obviating the breakage of the shells, substantially as herein described with
reference to the accompanying drawing.
Second. For carrying out the method set forth in the first claim the employment
of apparatus comprising two grindstones a, b turning in the same direction and
enabling their distance from each other to be changed by an adjusting screw e
whilst one of thein is supported so as to yield, a belt n adapted to be kept stretched
by a roller being used for transmitting the rotary motion from one stone b to the
other stone a, substantially as herein described with reference to the accompanying
drawing.
Dated this 12th day of September 1000
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.