Improvements in Apparatus for Grinding, Smoothing, Polishing Glass.
Year: 1898

page_text: Date of Application, 6th Apr., 1898-Accepted, 7th May, 1898
COMPLETE SPECIFICATION.
Improvements in Apparatus for Grinding, Smoothing,
Polishing Glass.
and
I, OLIVER IMRAY, of Birkbeck Bank Chambers, Southampton Buildings, Chancery
Lane, in the County of London, Chartered Patent Agent, do hereby declare the
nature of this invention (as communicated to me from abroad by George Augustus
Marsh, Engineer, of Pittsburgh, in the County of Allegheny, and State of
Pennsylvania, United States of America,) and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement :-
My invention relates to tables for holding glass during the operations of grinding,
smoothing and polishing, a vacuum being employed for holding the glass sheets in
place.
I have discovered that I can employ a table for this purpose having a substantial
part of its face constituting a flat supporting surface for the glass by exhausting the
air from between the glass sheet and its flat supporting surface; also by surrounding
a considerable part of a flat supporting surface which is connected to a vacuum
apparatus, by a seal; and further by laying upon the surface connected to the
vacuum, a flat covering or packing which is preferably porous, and upon which the
glass sheets are laid.
My invention consists in the above mentioned separate combinations; and further
in the construction and arrangement of the parts as described in the accompanying
drawings.
Figure 1 Sheet 1 is a plan, partially broken away, of a portion of a glass-holding
table constructed in accordance with my invention. Figure 2 is a cross-section on
the line II-II of Figure 1. Figure 3 is a view similar to Figure 1, shewing
another form of table which I prefer in practice. Figure 4 is a cross-section on the
line IV-IV of Figure 3, and Figure 5 is a perspective view of a section of another
form of table. In the form shewn in Figures 1 and 2, 2 is a portion of a table
containing vacuum chambers 3 alternating with chambers 4 containing liquid. The
upper face of this table is a flat surface provided with sunk water-channels 5
communicating with the chambers 4 by holes 6 whilst the vacuum chambers 3
communicate with the upper face of the table through holes 7, these vacuum
chambers being connected to suitable apparatus for exhausting air. I prefer to
employ water in the chambers 4 but other liquids may obviously be employed, these
chambers being connected to any suitable source of supply.
I cover the table with a flat layer of porous material, such as paper or closely woven
cloth, and I lay the glass sheets upon this packing. The vacuum apparatus being
worked, a suction is produced which holds the glass in place during the grinding or
polishing. Preferably at about the same time that the vacuum apparatus is started,
I supply water under a light pressure to the chambers 4, and this water oozing up
through the holes into the water channels and constantly moistening the packing
seals the various spaces under the glass sheets so that a sufficient vacuum is obtained
to hold the sheets in place. The water also moistens the lower faces of the glass sheets
and prevents them from being stained, and serves to regulate the temperatures of

page_text: the table, which without the liquid might rise to too high a point on account of the
heat generated by the friction of the polishing blocks upon the glass.
When one face of the glass sheets has been acted upon, the vacuum may be
destroyed, and the glass sheets may be turned over and again held by re-establishing
the vacuum.
In Figures 3 and 4 I shew a table, the upper face of which is made with cells
having supporting ribs 8 symmetrically arranged therein. This table has vacuum
chambers 9 alternating with liquid chambers 10, each cell communicating with a
vacuum chamber by a hole or holes 11, whilst the water channels are connected with
the liquid chambers by holes 12 at intervals. To convert this table, which is of the
cell or rib top class, into a table having a flat supporting surface for the sheets, I
cover its top with a thin perforated sheet of metal 13 which may be made in one
or several parts and which is fastened thereon so as to seal the various air and water
channels from each other. This sheet may be made of copper, aluminum or other
suitable material, which does not rust under the action of the water and which affords
a flat bearing surface for the glass. The perforations in this metal sheet communicate
with the various air and water channels, and when the packing is placed upon it
and the glass sheets laid upon the packing, the operation is the same as described
with reference to Figures 1 and 2.
In the form of Figure 5 I shew a table which is the same as that of Figures 1 and 2,
except that instead of the water channels I employ holes 14 which connect the flat
bearing surface with the liquid chambers.
On Sheet 2 I shew another forin of table which is intended to increase the holding
power on the sheets of glass.
Figure 1 of Sheet 2 is a plan, Figure 2 is a longitudinal section, and Figure 3 an
enlarged detail perspective.
2 is a table made in six sections, each having a flat top and provided with alternate
water and vacuum chambers 3 and 4. The vacuum chambers extend alternately from
one end of the section to points near the opposite end, thus affording between them
passages for circulation of the water or other liquid in a zig-zag course in each
section. In the upper face of each section is formed a small groove 5 extending
entirely around it near the edge and connected by small holes with the water
chambers. I also provide a sunk channel or groove 6 which in the outer sections
extends along two sides of each section while in the intermediate sections it extends
along the outer side only. This groove 6 is connected by small branch channels 7
with some of the holes 8 leading into the vacuum chambers, and thus increases the
effective area for the vacuum, preferably near the edges of the table. With this
table I employ a flat sheet of porous packing 9 which is laid over the entire top of the
table and upon this are placed the glass sheets.
On Sheet 3 I illustrate another form of the invention wherein a non-porous seal of
material such as india-rubber is used instead of the water seal.
Figure 1 of Sheet 3 is a plan of such a table. Figure 2 is a similar view partly
broken away shewing the glass sheets in place and Figure 3 is a transverse section.
2 is a hollow bed or table having a plain flat top connected by holes 3 with the
vacuum chamber 4 which communicates with any suitable vacuum forming
apparatus by a pipe 5.
provide beneath the edges of the glass sheets non-porous packing 6, which
enclose porous packings .7 of about the same thickness, that lie under the glass
sheets. The non-porous packing may be formed of strips of india-rubber or similar
material, and the porous filling of sheets of paper; or I may cut sheets of closely
woven cloth, such as moleskin, to the same size as the glass sheets and render the
edge portions of these cloth sheets non-porous by a coating of cement or by
otherwise filling the pores of the fabric.
On the vacuum being formed, the non-porous gaskets seal the edges of the sheets
so that the atmospheric pressure holds the sheets firmly down.
When one face has been ground or polished the glass is inverted and the other

page_text: face is similarly treated. The edge portions, of the sheets which may be discoloured
where they rest upon the non-porous gaskets may be cut away.
The advantages of my invention are that a more uniform bearing surface for the
glass sheet is afforded than with a cell or rib-top table, and that the flat supporting
surface obviates a marking of the glass sheets which sometimes results when they
are supported on a ribbed surface and that the table is simpler and cheaper than
those in use.
The shape and arrangement of the chambers and holes, and the form and
arrangement of the parts may obviously be varied without departing from my
invention.
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 :-
1. A glass-holding table having most of its face constituting a flat supporting
surface and connected to vacuum chambers, a chamber for liquid in the table
connected with channels in its face, and a flat porous packing arranged to cover
the flat surface substantially as described.
2. A glass-holding table having in its face a number of cells communicating with
vacuum chambers, water channels surrounding the cell and communicating with
water chambers, a flat perforated plate covering the cells, and a flat porous packing
laid upon the plate, substantially as described."
3. A glass-holding table having its top connected with a vacuum apparatus,
sealing gaskets placed beneath the edges of the glass sheets, and a flat porous filling
arranged to support the body portions of the sheets, substantially as described.
Dated this 6th day of April 1898.
ABEL & IMRAY,
Agents for the Applicant.

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