Heat treatment of glass sheets
AssigneeTriplex Safety Glass Company Limited
InventorsHarry Ross Scarlet Jack, Peter Henry Richards
Life of this patent
Estimating the term…
Abstract
A glass sheet to be heated, for example to a bending or a quenching temperature, is supported on its lower edge in an upright disposition and is advanced along a horizontally disposed path through a furnace. Transient support is provided for the upper edge of the sheet which support is positioned to cause the sheet to lean at a near-vertical angle as it is advanced, and thermal conditions in the furnace as well as the time the sheet is within the furnace are set in dependence on the glass thickness so as to heat the glass to the required temperature while permitting the glass to relax as it is heated only by an amount less than a maximum acceptable deformation of the sheet which depends on the use to which the sheet is to be put.
Claims33
Apparatus for heating glass sheets, for example for bending and/or toughening, comprising:
- a heating furnace through which glass sheets are to be conveyed in upright disposition;
- a conveyor for the sheets extending through the furnace and including a movable support for the lower edge of a sheet and a plurality of spaced-apart near-vertical rollers defining an inclined support extending through the furnace against which a sheet can relax as it is heated;
- and
- driving means for advancing the movable support through the furnace and for driving said near-vertical rollers at a linear surface speed the same as that of the movable support.
Apparatus for heating glass sheets, for example for bending and/or toughening, comprising:
- a heating furnace through which glass sheets are to be conveyed in upright disposition;
- a plurality of spaced-apart near-vertical rollers defining an inclined support extending through the furnace against which rollers a glass sheet can relax as it is heated;
- a plurality of bottom rollers defining a track for a carriage supporting the glass sheet which bottom rollers project through spaces between the near-vertical rollers and are mounted at an acute angle thereto;
- a mobile carriage providing support for the lower edge of the glass sheet and having faces at an angle matching the acute angle between said bottom rollers and said near-vertical rollers, which faces engage frictionally both the bottom rollers and the near-vertical rollers;
- and
- driving means connected to the near-vertical rollers and to the bottom rollers to rotate each of said rollers so that they all have the same effective linear surface speed.
Apparatus for heating glass sheets for example for bending and/or toughening, comprising:
- an elongate heating furnace including banks of electrical heaters facing opposite sides of a horizontal path of travel of glass sheets through the furnace;
- a plurality of spaced-apart near-vertical rollers defining an inclined support extending through the furnace between the banks of heaters;
- a mobile support for the lower edge of a sheet;
- means for advancing said mobile support through the furnace with a glass sheet carried thereby leaning against said rollers as it traverses its path of travel;
- and
- driving means for advancing the mobile support through the furnace and for driving said near-vertical rollers at a linear surface speed the same as that of the mobile support.
Apparatus for heating a succession of glass sheets, for example for bending and/or toughening, comprising:
- a heating furnace through which a succession of glass sheets is to be conveyed in upright disposition;
- a conveyor for the sheets extending through the furnace and including movable supports for the lower edges of the sheets and a plurality of spaced-apart near-vertical rollers defining an inclined support extending through the furnace against which the sheets can relax as they are heated;
- and
- driving means for advancing the movable supports through the furnace and for driving groups of said near-vertical rollers at different speeds in different parts of the furnace whereby successive glass sheets can be advanced simultaneously through different parts of the furnace at different speeds.
A method of heating a glass sheet to a thermal condition for further processing, the method utilizing means operable to provide support for the lower edge of the sheet during movement through a heating zone, and upwardly projecting, movable, transient mechanical supporting means extending along the heating zone and inclined at a small angle to the vertical, the method comprising:
- seating the lower edge of the glass sheet on the lower edge support means;
- leaning the upper edge of the sheet against said transient mechanical supporting means with the sheet at a small angle to the vertical;
- driving the lower edge support means and the upwardly projecting transient mechanical supporting means to advance the supported glass sheet through the heating zone;
- applying heat to the advancing glass sheet in the heating zone;
- controlling the heat transfer to the glass sheet during its advance through the heating zone to induce sufficient heat transfer to the advancing glass sheet for achieving said thermal condition for further processing while the advancing sheet relaxes against the transient mechanical supporting means;
- and
- as the sheet is heated to said thermal condition and relaxes against said transient mechanical supporting means, timing the advance of the supported glass sheet through the heating zone to limit deformation of the sheet to an amount less than the maximum deformation which is acceptable in the processed glass sheet.
A method of heating a glass sheet to a thermal condition for further processing, the method utilizing means operable to provide support for the lower edge of the sheet during movement through a heating zone, and upwardly projecting, movable, transient mechanical supporting means extending along the heating zone and providing an effective support plane inclined at a small angle to the vertical, the method comprising:
- seating the lower edge of the glass sheet on the lower edge support means;
- leaning the upper edge of the sheet against said transient mechanical supporting means with the sheet at a small angle to the vertical;
- positioning the lower edge of the sheet on said lower edge support means to offset the lower edge of the sheet from said effective support plane so that the sheet is at a small angle to said plane;
- driving the lower edge support means and the upwardly projecting transient mechanical supporting means to advance the supported glass sheet through the heating zone;
- applying heat to the advancing glass sheet in the heating zone;
- controlling the heat transfer to the glass sheet during its advance through the heating zone to induce sufficient heat transfer to the advancing glass sheet for achieving said thermal condition for further processing while the advancing sheet relaxes into further contact with the transient mechanical supporting means;
- and
- as the sheet is heated to said thermal condition and relaxes into further contact with said transient mechanical supporting means, timing the advance of the supported glass sheet through the heating zone to limit deformation of the sheet to an amount less than the maximum deformation which is acceptable in the processed glass sheet.
A method of heating a glass sheet to a thermal condition for further processing, the method utilizing means operable to provide support for the lower edge of the sheet during movement through a heating zone, and upwardly projecting, movable, transient mechanical supporting means extending along the heating zone and providing an effective support plane inclined at a small angle to the vertical, the method comprising:
- seating the lower edge of the glass sheet on the lower edge support means;
- leaning the upper edge of the sheet against said transient mechanical supporting means with the sheet at a small angle to the vertical;
- positioning the lower edge of the sheet on said lower edge support means to offset the lower edge of the sheet from said effective support plane so that the sheet is at a small angle to said plane;
- driving the lower edge support means and the upwardly projecting mechanical supporting means to advance the supported sheet through the heating zone;
- applying heat to the advancing glass sheet in the heating zone;
- controlling the heat transfer to the glass sheet during its advance through the heating zone to induce sufficient heat transfer to the advancing glass sheet for achieving said thermal condition for further processing while the advancing sheet relaxes into further contact with the transient mechanical supporting means;
- and
- as the sheet is heated to said thermal condition and relaxes into further contact with said transient mechanical supporting means, timing the advance of the supported glass sheet through the heating zone to limit relaxation of the sheet against said transient mechanical supporting means to an amount such that the value of a deformation index of the hot glass sheet represented by ##EQU3## where:
- t is the heating time in seconds, and .nu. (t) is the viscosity of the glass in poises at time t after commencement of heating;
- is less than a critical value of said deformation index determined by deformation of the sheet by an amount less than the maximum deformation which is acceptable in the processed glass sheet.
A method of heating a glass sheet to a thermal condition for further processing, the method utilizing means operable to provide support for the lower edge of the glass sheet during movement through a heating zone, and upwardly projecting transient mechanical supporting means extending along the heating zone and comprised of spaced apart, rotatable, support rollers which are inclined at a small angle to the vertical, the method comprising:
- seating the lower edge of the glass sheet on the lower edge support means;
- leaning the upper edge of the sheet against the spaced apart support rollers with the sheet at a small angle to the vertical;
- rotating the support rollers and driving the lower edge support means to advance the supported glass sheet through the heating zone;
- applying heat to the advancing glass sheet in the heating zone;
- controlling the heat transfer to the glass sheet during its advance through the heating zone to induce sufficient heat transfer to the advancing glass sheet for achieving said thermal condition for further processing while the advancing sheet relaxes against said support rollers;
- and
- as the sheet is heated to said thermal condition and relaxes against said spaced apart support rollers, timing the advance of the supported glass sheet through the heating zone to limit deformation of the sheet to an amount less than the maximum deformation which is acceptable in the processed glass sheet.
Dependencies are inferred from the claim text.