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N. 33, May - June 2007
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 | IP in practice
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| Patent of the month
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Float glass
It may be surprising but the glass we use in modern windows,
furniture or cars is quite a new invention. Until the 19th century, window glass was produced by blowing
large cylinders or disks and cutting them into flat pieces. During the
19th century, glass for windows was
made from roundels or using the cylinder method. The first flat glass
production method was invented and patented in 1848 by an English engineer
named Henry Bessemer. He was the first to achieve a continuous ribbon of flat
glass.
UK's Pilkington Brothers reached a milestone in the modernisation of
glass production technology. They developed a continuous ribbon glass using a
molten tin bath on which the molten glass flows laterally unhindered to its
limit under the influence of gravity and surface tension. This invention
dramatically lowered glass prices by reducing the production cost on the
polishing process.
Nowadays, float glass is made by melting raw materials. The raw
materials are mixed together and fed into a large furnace that is natural gas
or fuel oil fired. Then it goes to a float bath (tin bath). The glass flows out
onto the tin surface forming a floating ribbon with a perfectly smooth glossy
surface on both sides and an even thickness of approximately 4 mm. Next, the
sheet is transported on rollers on which it cools. At the end of the rollers
(around 100 meters) the glass is cut into pieces.
Pilkington Brothers obtained a patent for their invention in 1959.
The global market for flat glass in 2005 was approximately 41 million tonnes.
At the level of primary glass manufacture this represents a value of around $19
billion. Pilkington is the leading world glass company. It has manufacturing
operations in 24 countries and sales in 130.
Pilkington flat glass industry – summary
Float glass on
Wikipedia
Flat glass patent
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