Improvements in Vacuum Apparatus for holding Glass Plates.
Year: 1898

page_text: COMPLETE SPECIFICATION.
Improvements in Vacuum Apparatus for holding Glass Plates.
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 plate glass by vacuum action, and it con-
sists in an improved construction of the table and its chambers and supporting ribs
for the glass; in a relief-valve to limit the vacuum and in means for heating the
edge portions of the table, as shall describe referring to the accompanying
drawings.
Fig. 1 is a plan partly broken away of a table according to my invention, with
the flat packing on it. Fig. 2 is a plan looking from below. Figs. 3 and 4 are
enlarged sections on planes at right angles to each other, of one of the sections.
Fig. 5 is an enlarged detail view, shewing the juncture of two sheets over a water
channel, and Fig. 6 is a section of the release valve.
In the table I employ separate vacuum and liquid chambers side by side. Thus
in the table shewn which is preferably composed of six sections 3, I provide in
each section vacuum chambers 4, which extend alternately from each end of each
section to a point near the other end. Each of these vacuum chambers communi-
cates with a chamber 5 on the underside of the section, all the chambers 5 are
connected by branch pipes 6 and a main pipe 7 to apparatus creating a vacuum.
Between and around the vacuum chambers 4 are the liquid heating or cooling
chambers 8 which communicate with each other at alternate ends of the section.
9 is the inlet port for liquid to each section, and 10 the outlet port situated at
the diagonally opposite corner, so that the liquid has to traverse and heat or cool
the entire section before it passes out.
In Fig. 2 I shew the pipes for liquid 11 is the main supply pipe having branches
entering the end sections of the table at the points 9. The liquid traverses each
section in a circuitous course passes at 10 into connecting pipes 12 which lead to
the supply ports 9 of the adjacent sections. The two separate currents of liquid
thus continue throughout the sections to discharge pipes 13. Each section of the
table has its upper face divided into a number of cells by parallel ribs 14, grooved
to form surface channels, into which liquid passes through small holes 15 from the
liquid chambers 8. Each cell is connected by a hole 16 with one of the vacuum
chambers 4, and a packing of paper or similar material 17 being laid over the
table, the glass is placed upon this packing.
I have found considerable difficulty in obtaining uniform action over the glass
which tends to bend down in the cells, so that the glass when ground or polished
has a wavy appearance. To provide against this difficulty, I provide in each cell
a number of uniformly distributed supports, which may consist of ribs 18. I have
shewn in the drawing one arrangement of these ribs, but obviously many other
forms may be readily devised, the essential point being that they are evenly and
uniformly distributed in the cell. In order to give good support to the glass, the

page_text: area of the bearing surface of the ribs should be preferably greater than the area
of the vacuum space between them.
In order to keep the edge portions of the table at an even temperature with the
inner portions I preferably provide a steam pipe 19 formed in sections and con-
nected by pipes 20. This pipe serves to convey heat to the outer portions of the
table which ordinarily become cooler than the inner portions on account of their
greater exposure to the atmosphere and to their being less heated by the friction
of the polishing blocks or runners.
An important part of my invention consists in a relief-valve which prevents the
pressure on the glass from exceeding a predetermined limit. One form of this
valve shewn in Figure 6, consists of a casing 22 having within it an upwardly
movable valve 23 to which is hung a weight 24. The casing is connected to the
main vacuum pipe, and when the vacuum passes a certain limit, determined by
the weight, the valve rises and allows air to enter the vacuum pipe.
In order to prevent liquid from oozing up between the edges of the glass plates,
when they meet over one of the liquid channels, I place over the paper at this
point a strip 25 of impervious material, as shewn in Figure 5, otherwise the liquid
would creep on to the upper faces of the glass plates and interfere with the grinding
or polishing.
The advantages of my invention may be thus stated. The alternate arrange-
ment of the vacuum and liquid chambers, is simple in construction, and the
conductivity of the metal composing the sections ensures a practically uniform
distribution of the heating or cooling action of the liquid. The liquid is uniformly
distributed and has to traverse all parts of each section before passing to the next.
The check-valve prevents the possibility of too great pressure upon the glass.
The pipe surrounding the table and containing a heating fluid keeps the outer
parts of the table at the same temperature as the inner parts, and the impervious
strip at the meeting edges of the plates, when they are over the water channel,
prevents access of water to the upper faces of the plates.
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 table for holding glass, having vacuum chambers and chambers for liquid
communicating respectively with cells and channels on the upper face of the table,
arranged and operating substantially as described.
2. The construction of the table in sections having their vacuum-chambers con-
nected by branch pipes and a main pipe to vacuum apparatus, and the inlets and
outlets of their liquid chambers connected by pipes so arranged that the outlet
from each section is at the corner opposite to the inlet, substantially as and for the
purposes set forth.
3. The construction of the upper face of each section in cells separated by
channelled ribs and within each cell having uniformly distributed supports,
having a bearing surface greater than the area of the vacuum surface substan-
tially as described.
4. In combination with the table, a pipe for steam or other fluid at its edge
substantially as described.
5. In combination with the vacuum pipe, a relief valve loaded to give a limited
pressure on the glass, substantially as described.
6. The application of an impervious strip over a liquid channel where the edges
of contiguous glass plates meet substantially as and for the purpose set forth.
ABEL & IMRAY,
Agents for the Applicant.