Abrasive tool making process – material – or composition – With carbohydrate or reaction product thereof
Patent
1987-05-08
1989-05-30
Schmidt, Frederick R.
Abrasive tool making process, material, or composition
With carbohydrate or reaction product thereof
51283R, 51240GB, 51110, B24B 724
Patent
active
048338320
DESCRIPTION:
BRIEF SUMMARY
This invention relates to glass polishing, more particularly to polishing of sheet glass.
Until the development of the so-called float glass process it was, generally speaking, difficult and time consuming to produce plate glass with an acceptably flat surface. As the human eye is capable of seeing even small depressions or hills with a depth or height of at most a few microns as imperfections in a glass surface, it is in practice necessary to produce sheet glass with extremely flat surfaces for glazing or for other architectural purposes.
The float glass process revolutionised the production of plate glass. However, as the process requires to be operated continuously and as the capital cost of the plant is high, it has had the effect in practice of reducing the available types of glass so that only a small number of different colours and thicknesses of plate glass sheet are currently commercially available. Hence an architect is effectively restricted in his choice of glazing materials to that range of colours which operators of the float glass process have found to be the most generally acceptable in the market.
One of the major advantages of the float glass process is that the "as produced" glass sheets have surfaces which are sufficiently flat for use in the building industry without further treatment. Thus there is no need to subject float glass sheets to polishing steps before they can be used.
When it is desired to impact increased strength and/or fire resistance to sheet glass, metal wire mesh can be embedded in the glass while it is in a semi-fluid state using a rolling technique. However this procedure destroys the surface characteristics of the resulting cast wire glass sheet and it is necessary to flat grind and to polish both faces of the wire glass sheet in order to improve the flatness of its faces and its transparency before it can be accepted for use in the building industry.
Production of wired glass is not directly possible in the float glass process. Thus in practice polished wired glass is produced on the last existing "polished plate glass" lines. Daily production of such polished plate glass units is generally from about 80 tons to about 100 tons per day. Such a polished plate glass line integrates all stages of manufacture from mixing the raw materials, melting, cooling, mechanical flat grinding and polishing of both faces, cutting and packaging.
For manufacture of wired glass sheets additional equipment is incorporated in the corresponding polished plate glass line, including the necessary wire feed arrangement and one or more sets of rolls for embedding the wire mesh in the still hot, semi-fluid glass. The capital cost of such units is high.
Typical methods of polishing of faces of glass sheet adopted heretofore include the use of fibre wheels in conjunction with cerium oxide grinding paste after the faces have been flat ground with sand on iron wheels.
It is also known to polish the edges of glass sheets with diamond edged grinding wheels and to use such wheels also for imparting a bevelled edge to glass sheets. Diamond edged grinding wheels are also used for shaping optical glass, e.g. for production of lenses.
GB-A-No. 1114474 describes a system for the surfacing of flat sheets of glass and other hard materials. As shown in FIG. 1A of GB-A-No. 1114474, such a surfacing system may include use of a plurality of grinding wheels arranged one after another along the path of movement of a glass sheet. As indicated in FIG. 1 each grinding wheel is wider than the sheet of glass 11 to be ground. According to the description at page 3, lines 45 to 51 it is envisaged that the grinding wheels have arcuate segments having a radial dimension of 1.5 inches (38.1 mm), lying between 31 and 29.5 inches (787.4 and 749.3 mm) from the axis of the grinding wheel 10. In other words each wheel is at least 5 feet (1524 mm) in diameter.
In such a system periodic replacement of the grinding wheels is necessary. In view of their size, the cost of replacement wheels is correspondingly high.
Although the su
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Jacquemin Jean-Marie
Lindsey Alan F.
Depuydt Patrick
Rose Robert A.
Schmidt Frederick R.
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