Patent Description:
It is well known in the art to bend or shape a flat glass sheet between a pair of shaping members having complementary shaping surfaces. Typically a heat softened glass sheet is supported on a ring mould and is bent between the ring mould and an upper unitary full surface mould.

<CIT> relates to an apparatus for forming glass, the apparatus including a lower mold, a fixing mold and an upper mold. Similar art in the display glass field includes <CIT> and <CIT>.

<CIT> relates to molding plate glass into a hollow article of ultrathin glass having a smooth surface and stable dimensions by fixing moldably heated glass to a guide ring, pressing a plunger against the glass and forcing the glass into an open part.

<CIT> relates to a flexible ring mold for shaping heat softened glass sheets wherein an inner ring having a plurality of posts which help support the ring mold and maintain the molds generally planar configuration during the initial lifting and shaping of a supported glass sheet is provided.

A press bending station is described in <CIT> that includes an annular mould and a full-face mould. Holes, selectively connected to a negative pressure source, are placed in portions of the full face mould that are determined by the configuration of the annular mould when the annular mould comes into contact with a heated glass sheet during the press bending process. The heated glass sheet is drawn by negative pressure through the holes towards the full-face mould and thus acquires its shape. The full-face mould may be covered by at least one fine mesh cloth i.e. woven stainless steel.

For manufacturing certain complex bent glass shapes which may have particular use as a pane in a vehicle window, it is sometimes not possible to bend the glass to the desired shape using a unitary press bending member. It has been found for certain shapes using a unitary press bending member, portions of the glass edge buckle during the press bending operation leading to a wrinkle in the edge of the glass that produces at least an optical distortion.

In the prior art this type of problem can be overcome by supporting the glass sheet on a lower ring mould and using an upper press bending member that is made from more than one moving part as described in <CIT>. It is described in <CIT> how the edge of the glass sheet to be bent is supported on a shaping frame, the glass sheet being first clamped at the peripheral edges thereof, following which the central region of the glass sheet is pressed to the desired curvature.

A similar two part mould is described in <CIT>.

However it has been found that when using such a two part press bending member as described in the prior art, for certain desired bent glass shapes the press bending operation may introduce very high stresses in the glass sheet during the bending operation such that the glass sheet may break whilst being shaped.

The present invention aims to at least partially overcome the above problem.

Accordingly from a first aspect the present invention provides a method of shaping a sheet of glass according to claim <NUM>.

For the avoidance of doubt, the first mould member is movable relative to the shaping support, the second mould member is movable relative to the shaping support and the first mould member is movable relative to the second mould member.

During step (v) the glass sheet is pressed between the shaping support and the first mould member with sufficient force to allow the second mould member to press bend the glass sheet during step (vi), but in step (v) the first mould member is not in the final position relative to the shaping support to provide the glass sheet with the final desired curvature in the first region thereof.

During step (vii) the glass sheet is pressed between the shaping support and the first mould member to provide the glass sheet with the final desired curvature in the first region thereof.

It has been found that by only partially clamping the first region of the glass sheet during step (v), the addition of step (vii) to further press the glass sheet in the first region between the first mould member and the shaping support reduces the amount of glass breakage during the shaping process.

Preferably prior to step (v) the press bending apparatus is configured such that prior to step (v) or during step (v), the press bending apparatus does not contact the glass sheet in the second region thereof.

Preferably prior to step (v) or during step (v), the press bending apparatus contacts the glass sheet in the second region thereof. In particular, preferably prior to step (v) or during step (v), the second mould member contacts the glass sheet in the second region thereof.

Preferably during step (vii), the second mould member is also moved relative to the shaping support to further press bend the glass sheet in the second region thereof. When the second mould member is moved relative to the shaping support during step (vii), the second mould member may also move relative to the first mould member.

Preferably when the second mould member is moved relative to the shaping support during step (vii) the movement of the first and second mould members relative to the shaping support is synchronised.

According to the invention, the first region of the glass sheet is a peripheral region of the glass sheet. Preferably the peripheral region extends around the entire perimeter of the glass sheet.

According to the invention, the second region of the glass sheet is a central region of the glass sheet.

According to the invention, the first region of the glass sheet is a peripheral region of the glass sheet, in particular a peripheral region that extends around the entire perimeter of the glass sheet, and the second region of the glass sheet is a central region of the glass sheet, the central region of the glass sheet being inboard of the peripheral region of the glass sheet.

Preferably the shaping support comprises at least one rail for supporting the glass sheet about a peripheral region thereof. Preferably the shaping support is a ring-type female mould for supporting the glass sheet in a peripheral region.

According to the invention, during step (v), the glass sheet is pressed between the first mould member and the shaping support in a peripheral region. When the shaping support comprises at least one rail for supporting the glass sheet about a peripheral region thereof, it is preferred that during step (v), the glass sheet is pressed between the first mould member and the at least one shaping rail of the shaping support in the peripheral region of the glass sheet.

According to the invention, during step (vi), the glass sheet is pressed in a central region thereof whilst the glass sheet is pressed between the first mould member and the shaping support. When the shaping support comprises at least one rail for supporting the glass sheet about a peripheral region thereof, it is preferred that during step (vi), the glass sheet is pressed in a central region thereof whilst the glass sheet is pressed between the first mould member and the at least one shaping rail of the shaping support.

Preferably the first mould member has a shaping surface and the glass sheet faces the shaping surface of the first mould member during step (v). Preferably the first mould member has at least one opening in the shaping surface thereof, the at least one opening in the shaping surface of the first mould member being in fluid communication with at least one vacuum source, the at least one vacuum source being operable to provide at least one negative pressure region at a portion of the first region of the glass sheet after step (vii). The at least one vacuum source in fluid communication with the at least one opening in the shaping surface of the first mould member may also be used to provide at least one negative pressure region at a portion of the first region of the glass sheet during at least one of the steps (v), (vi) and (vii). The at least one opening in the shaping surface of the first mould member may also be in fluid communication with a fluid source, for example compressed air, such that following the provision of at least one negative pressure region at a portion of the first region of the glass sheet after step (vii), fluid may be caused to flow through the at least one opening in the shaping surface of the first mould member.

Preferably the second mould member has a shaping surface and the glass sheet faces the shaping surface of the second mould member during step (vi). Preferably the second mould member has at least one opening in the shaping surface thereof, the at least one opening in the shaping surface of the second mould member being in fluid communication with at least one vacuum source, the at least one vacuum source being operable to provide at least one negative pressure region at a portion of the second region of the glass sheet after step (vii). The at least one vacuum source in fluid communication with the at least one opening in the shaping surface of the second mould member may also be used to provide at least one negative pressure region at a portion of the second region of the glass sheet during at least one of the steps (v), (vi) and (vii). The at least one opening in the shaping surface of the second mould member may also be in fluid communication with a fluid source, for example compressed air, such that following the provision of at least one negative pressure region at a portion of the second region of the glass sheet after step (vii), fluid may be caused to flow through the at least one opening in the shaping surface of the second mould member.

Preferably the press bending apparatus is configured such there is at least one (a first) gap between the first and second mould members. Preferably the first gap is in fluid communication with at least one vacuum source, the at least one vacuum source being operable being operable to provide at least one negative pressure region at a portion of the glass sheet opposite the first gap, the portion of the glass sheet opposite the first gap being between the first and second regions of the glass sheet. The first gap may also be in fluid communication with a fluid source, for example compressed air, such that following the provision of at least one negative pressure region at a portion of the glass sheet opposite the first gap after step (vii), fluid may be caused to flow through the first gap.

By using negative pressure to one or more selected regions of the glass during the glass bending, the glass bending process may be improved as described for example in <CIT> and <CIT>. Typically following the provision of negative pressure to one or more selected regions of the glass during the glass bending, after the source of negative pressure is terminated, air i.e. compressed air, is blown through openings in the shaping surface in contact with the glass sheet to assist with the removal of the glass sheet from said shaping surface.

Preferably the first mould member has a shaping surface with at least one opening therein and the second mould member has a shaping surface with at least one opening therein, there being at least one vacuum source in fluid communication with the at least one opening in the shaping surface of the first mould member and the at least one opening in the shaping surface of the second mould member, and wherein following step (vii) the at least one vacuum source is used to provide at least one negative pressure region at a portion of the first region of the glass sheet and at least one negative pressure region at a portion of the second region of the glass sheet.

Preferably the first mould member has a mould member cover such that during step (v) the mould member cover of the first mould member is between the first mould member and the glass sheet. Preferably the mould member cover of the first mould member comprises a cloth, more preferably an air permeable cloth. Preferably the cloth comprises at least one of stainless steel, fibre glass, poly para-phenyleneterephthalamide fibres or blends thereof, polybenzoxazole (PBO) fibres containing graphite, and various weaves of these fibres. Usually when the first mould member has a mould member cover, the mould member cover of the first mould member is between the first mould member and the glass sheet during steps (v), (vi) and (vii).

Preferably the second mould member is provided with a mould member cover such that during step (v) the mould member cover of the second mould member is between the second mould member and the glass sheet. Preferably the mould member cover of the second mould member comprises a cloth, more preferably an air permeable cloth. Preferably the cloth comprises at least one of stainless steel, fibre glass, poly para-phenyleneterephthalamide fibres or blends thereof, polybenzoxazole (PBO) fibres containing graphite, and various weaves of these fibres. Usually when the second mould member has a mould member cover, the mould member cover of the second mould member is between the second mould member and the glass sheet during steps (v), (vi) and (vii).

Preferably the first and second mould members each have a respective mould member cover, further wherein the mould member cover of the first mould member and the mould member cover of the second mould member are part of a single mould cover. During step (v) the single mould cover faces the glass sheet. Preferably the single mould cover comprises a cloth, more preferably an air permeable cloth. Preferably the cloth comprises at least one of stainless steel, fibre glass, poly para-phenyleneterephthalamide fibres or blends thereof, polybenzoxazole (PBO) fibres containing graphite, and various weaves of these fibres. Usually when the first and second mould members each have a respective mould member cover, the respective mould member cover of the first and second mould members is between the first mould member and the glass sheet and the second mould member the glass sheet respectively during steps (v), (vi) and (vii).

Preferably during step (vi) the second mould member is moved from a first position to a second position, the first position of the second mould member being displaced relative to the second position of the second mould member by more than <NUM>, preferably between <NUM> and <NUM>, more preferably between <NUM> and <NUM>.

Preferably during step (vi) the second mould member is moved by more than <NUM> relative to the first mould member, preferably between <NUM> and <NUM> relative to the first mould member, more preferably between <NUM> and <NUM> relative to the first mould member.

Preferably the first mould member has a shaping surface facing the shaping support and the second mould member has a shaping surface facing the shaping support, and before step (v) the press bending apparatus is configured such that the shaping surfaces of the first and second mould members are displaced from one another by more than <NUM>, preferably between <NUM> and <NUM>, more preferably between <NUM> and <NUM>.

During step (iii) the glass sheet is heated to temperature where the glass sheet is suitably soft (i.e. having a suitably low viscosity) to be able to be shaped by press bending, in particular by press bending between a pair of complimentary shaping members. Preferably during step (iii) the glass sheet is heated uniformly, although selected regions of glass sheet may be heated to different temperatures.

Preferably during step (iii) the glass sheet is heated to a temperature between <NUM> and <NUM>.

Preferably the glass sheet is heated before positioning the glass sheet on the shaping support. However the glass sheet may be positioned on the shaping support and then heated. The glass sheet may be heated to a first temperature before being positioned on the shaping support, and subsequently heated whilst on the shaping support to a second temperature.

Preferably the glass sheet is one sheet in a stack of glass sheets, in particular a nested pair.

Preferably following step (vii), the bent glass sheet is thermally toughened by quenching the glass sheet with jets of cooling fluid directed towards at least one of the major surfaces of the glass sheet.

Preferably following step (vii) the bent glass sheet is laminated to another glass sheet using an interlayer structure comprising at least one sheet of interlayer material. Suitable interlayer material includes polyvinyl butyral, ethylene vinyl acetate copolymer, polyurethane, polycarbonate, poly vinyl chloride or a copolymer of ethylene and methacrylic acid.

Preferably the glass sheet is supported on a ring mould having an upper shaping surface for supporting the glass sheet about at least a portion of the periphery thereof.

Preferably the first mould member is an annular ring.

Preferably the second mould member is a unitary mould that is disposed at least partially within the first mould member.

Preferably the second mould member is a radially disposed within the first mould member.

Preferably the press bending apparatus comprises more than two mould members.

Preferably at least one of the first mould member, the second mould member and the shaping support is provided with heating means.

Preferably at least one of the first mould member and the second mould member comprises at least one of ceramic, aluminium, stainless steel or iron, in particular cast iron.

Preferably the shaping support is in vertical alignment with the press bending apparatus.

Methods according to the first aspect of the present invention may be used to bend a flat glass sheet such that the bent glass sheet is curved in one or more directions. Preferably the radius of curvature in at least one of the one or more directions is between <NUM> and <NUM>, more preferably between <NUM> and <NUM>. When the bent glass sheet is curved in two or more directions, preferably two of the two or more direction of curvature are mutually orthogonal.

A suitable glass composition for the glass sheet is a soda-lime-silica glass composition.

A typical soda-lime-silica glass composition is (by weight), SiO<NUM> <NUM> - <NUM> %; Al<NUM>O<NUM> <NUM> - <NUM> %; Na<NUM>O <NUM> - <NUM> %; K<NUM>O <NUM> - <NUM> %; MgO <NUM> - <NUM> %; CaO <NUM> - <NUM> %; SO3 <NUM> - <NUM> %; Fe<NUM>O<NUM> <NUM> - <NUM> %. The glass may also contain other additives, for example, refining aids, which would normally be present in an amount of up to <NUM> %. The soda-lime-silica glass composition may contain other colouring agents such as Co<NUM>O<NUM>, NiO and Se to impart to the glass a desired colour when viewed in transmitted light. The transmitted glass colour may be measured in terms of a recognised standard such as BS EN410.

The present invention also provides from a second aspect an apparatus for shaping a sheet of glass according to claim <NUM>.

Preferably the shaping surface of the first mould member has at least one opening therein, and the at least one opening in the shaping surface of the first mould member is in fluid communication with at least one negative pressure source, in particular at least one vacuum source. Preferably the control means also controls the at least one negative pressure source to produce at least one region of negative pressure at the at least one opening in the shaping surface of the first mould member after step (vii) in the method according to the first aspect of the present invention. Preferably the control means also controls the at least one negative pressure source to produce at least one region of negative pressure at the at least one opening in the shaping surface of the first mould member during at least one of the steps (v), (vi) and (vii) in the method according to the first aspect of the present invention.

Preferably the shaping surface of the second mould member has at least one opening therein, and the at least one opening in the shaping surface of the second mould member is in fluid communication with at least one negative pressure source, in particular at least one vacuum source. Preferably the control means also controls the at least one negative pressure source to produce at least one region of negative pressure at the at least one opening in the shaping surface of the second mould member after step (vii) in the method according to the first aspect of the present invention. Preferably the control means also controls the at least one negative pressure source to produce at least one region of negative pressure at the at least one opening in the shaping surface of the second mould member during at least one of the steps (v), (vi) and (vii) in the method according to the first aspect of the present invention.

Preferably the press bending apparatus is arranged such that there is at least one (a first) gap between the shaping surface of the first mould member and the shaping surface of the second mould member when the press bending apparatus is in the first configuration, more preferably wherein the first gap is in fluid communication with at least one negative pressure source, in particular vacuum source. Preferably the control means also controls the at least one negative pressure source to produce at least one region of negative pressure at the first gap after step (vii) in the method according to the first aspect of the present invention. Preferably the control means also controls the at least one negative pressure source to produce at least one region of negative pressure at the first gap during at least one of the steps (v), (vi) and (vii) in the method according to the first aspect of the present invention.

Preferably the second mould member is radially disposed within the first mould member.

Preferably the first mould member is an annular ring and the second mould member is radially disposed within the first mould member.

Preferably the shaping surface of the first and/or second mould member comprises a cloth, preferably an air-permeable cloth. Preferably the cloth comprises at least one of stainless steel, fibre glass, poly para-phenyleneterephthalamide fibres or blends thereof, polybenzoxazole (PBO) fibres containing graphite, and various weaves of these fibres.

Preferably at least one of the first mould member and the second mould member is provided with heating means.

From a third aspect the present invention provides an assembly comprising a press bending apparatus according to the second aspect of the present invention and a shaping support for supporting a glass sheet thereon.

Preferably the press bending apparatus is vertically disposed relative to the shaping support.

Preferably the press bending apparatus is aligned with the shaping support.

Preferably the shaping support has an upper shaping surface and the upper shaping surface of the shaping support is complementary with the shaping surface of the press bending apparatus in the first configuration.

Preferably the shaping support has a concave upper shaping surface.

Preferably the shaping support is a ring mould having an upper shaping surface for supporting a glass sheet about at least a portion of the periphery thereof.

Preferably the assembly has at least three configurations, a first configuration for the assembly where the press bending apparatus is in a first arrangement and spaced relative to the shaping support by a first distance, a second configuration for the assembly where the press bending apparatus is in a second arrangement and a third configuration for the assembly where the press bending apparatus is in a third arrangement where the shaping surfaces of the first and second mould members are aligned but the press bending member is spaced relative to the shaping support by a second distance different to the first distance. Preferably the first arrangement is the same as the second arrangement.

In use it is preferred to configure the assembly such that the press bending apparatus is vertically disposed relative to the support.

Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings (not to scale), in which:.

<FIG> shows a side view schematic representation of a press bending station <NUM> for bending a sheet of glass. The press bending press station <NUM> includes a lower portion <NUM> and an upper portion <NUM>.

The lower portion <NUM> of the press bending station <NUM> includes a shaping support for supporting a glass sheet thereon. In this example the shaping support is a frame <NUM> having a base <NUM> with first and second uprights <NUM>, <NUM> extending upwards therefrom. A lower support <NUM> in the form of an annular ring is mounted on the first and second uprights <NUM>, <NUM>. The lower support <NUM> has an upper shaping surface 15a for supporting a sheet of glass thereon, as is conventional in the art i.e. the sheet of glass (not shown) is supported about a peripheral region on the upper shaping surface 15a of the lower support <NUM>.

Typically in the art the lower portion <NUM> is referred to as bending frame, or a female bending frame. Instead of a substantially annular supporting ring <NUM>, a full contact support may be mounted on the ends of the uprights <NUM>, <NUM>.

In the example of <FIG> the upper shaping surface of the lower support <NUM> is concave. The lower support <NUM> may also be referred to as a "shaping rail", or simply a "rail".

Although only two uprights <NUM>, <NUM> are shown in <FIG>, in practice there may be a plurality of uprights on which the lower support <NUM> is mounted.

The upper portion <NUM> of the press bending station <NUM> includes a press bending apparatus comprising a two part press bending member <NUM> comprising a first mould member <NUM> and a second mould member <NUM>. Examples of this type of two part mould are described in <CIT>, <CIT>and <CIT>.

With further reference to <FIG> and <FIG>, the first mould member <NUM> is an annular ring having a lower shaping surface <NUM>. The second mould member <NUM> is a unitary mould member that fits inside the central opening of the first mould member <NUM> such that the second mould member <NUM> can move vertically relative to the first mould member <NUM>. The second mould member <NUM> is radially disposed within the first mould member <NUM>.

The first mould member <NUM> has an outer peripheral wall 18a and an opposing inner peripheral wall 18b. The second mould member <NUM> has an outer peripheral wall <NUM>. The outer peripheral wall <NUM> of the second mould member <NUM> faces the inner peripheral wall 18b of the first mould member <NUM> and is spaced therefrom by a gap <NUM>. In the cross sectional view of <FIG>, the gap <NUM> is represented by two gaps <NUM> and <NUM>.

The second mould member <NUM> has a lower shaping surface <NUM>. The shaping surfaces <NUM>, <NUM> are configured to provide the desired curvature of a glass sheet in those regions of the glass sheet to be contacted by the shaping surfaces <NUM>, <NUM>, when the glass sheet is supported on the frame <NUM> i.e. on upper shaping surface 15a of support <NUM> and when the first and second mould members are in a certain predetermined arrangement.

As shown more clearly in <FIG>, the lower support <NUM> is mounted on one side on uprights <NUM>, <NUM>' and <NUM>‴ and on the opposite side on uprights <NUM>, <NUM>' and <NUM>". The uprights <NUM>, <NUM>', <NUM>", <NUM>, <NUM>', <NUM>" extend upwards from the base <NUM>, being connected at one end to the base <NUM> and at the opposite end to the lower support <NUM>. Additional uprights may be used. Reinforcing cross members between uprights may also be used.

With further reference to <FIG>, when the outer peripheral edge 20a of the second mould member <NUM> is aligned with the inner peripheral edge 18c of the first mould member <NUM>, the two part press bending member <NUM> has a shaping surface corresponding to the desired final shaping surface, as indicated by dotted line <NUM>. In this example the shaping surface of the two part press bending member <NUM> is a convex shaping surface configured to be complementary with the upper shaping surface 15a of the lower support <NUM>. The desired final shaping surface <NUM> is shown as dotted line <NUM> in the final desired position for shaping a glass sheet supported on upper shaping surface 15a of lower support <NUM> to a final desired shape.

With reference to <FIG> and <FIG>, the first mould member <NUM> is displaced relative to the second mould member <NUM> such that the shaping surface of the two part press bending member is not the desired final shaping surface for the two part press bending member. The outer peripheral edge 20a of the second mould member <NUM> is displaced from the inner peripheral edge 18c of the first mould member <NUM> by an amount <NUM>.

The first mould member <NUM> is movable in a vertical direction (shown by arrow <NUM>) by means of the linear actuators <NUM> and <NUM>. The movement of the linear actuators <NUM>, <NUM> is synchronised such that both sides of the first mould member <NUM> move upwards and downwards at the same time.

The second mould member <NUM> is movable in a vertical direction <NUM> by means of the linear actuator <NUM>.

The first mould member <NUM> and the second mould member <NUM> are both independently moveable in a vertical direction relative to one another.

The linear actuators <NUM>, <NUM> and <NUM> are mounted to a suitable gantry <NUM>, the gantry being fixed spatially in relation to the frame <NUM>.

The movement of the linear actuators <NUM>, <NUM> and <NUM> may be controlled by suitable control means (not shown), such as a computer based system.

In the configuration shown in <FIG> (and <FIG> which is an enlarged view of a portion of the left hand side of <FIG>), the shaping surface <NUM> of the first mould member is displaced from the final desired position represented by dotted line <NUM> by a vertical distance <NUM> on one side and a vertical distance <NUM>' on the other side. It is preferred for the distances <NUM> and <NUM>' to be the same.

The shaping surface <NUM> of the second mould member <NUM> is displaced from the final desired position represented by dotted line <NUM> by a vertical distance <NUM>.

The press bending station <NUM> is shown in <FIG> in a first configuration with the shaping surface <NUM> displaced by an amount <NUM> relative to the shaping surface <NUM>, as discussed above. Due to the displacement <NUM>, the two part mould <NUM> is not arranged to bend a glass sheet supported on the frame <NUM> to a final desired shape.

In <FIG> two gaps <NUM>, <NUM> between the inner peripheral wall 18b of the first mould member <NUM> and the outer peripheral wall <NUM> of second mould member <NUM> are shown. These two gaps <NUM>, <NUM> are part of a continuous gap <NUM> that extends between the first and second mould members <NUM>, <NUM>, as illustrated in <FIG>. The gap <NUM> may be in fluid communication with a suitable vacuum source to assist with shaping a glass sheet by providing negative pressure regions at the gap. As can be seen, the gap <NUM> extends to the shaping surface of the two part press bending member <NUM>.

<FIG> shows the press bending station <NUM> in a different configuration to that shown in <FIG>. In this second configuration a glass sheet <NUM> has been positioned on the frame <NUM> and is part way through a press bending process according to the present invention. The glass sheet <NUM> has a major surface <NUM> facing the two part press bending member <NUM> and an opposing major surface <NUM> facing the base <NUM> (and consequently facing the frame <NUM> and the lower support <NUM>). The major surface <NUM> of the glass sheet <NUM> is in contact with the upper shaping surface 15a (not labelled on this figure, but see <FIG>) of the lower support <NUM>.

Starting from the configuration shown in <FIG>, the first mould member <NUM> and the second mould member <NUM> have both moved downwards towards the frame <NUM> by energising respective linear actuators <NUM>, <NUM> and <NUM>. The downward movement of both the first and second mould members <NUM>, <NUM> is synchronised so that the first and second mould members <NUM>, <NUM> move downwards with no relative movement therebetween.

The downwards movement of the first and second mould members <NUM>, <NUM> towards the frame <NUM> may be in one or more stages with or without relative movement between the first and second mould members in each stage. In one example in a first stage of downward movement the downward velocity of the first and second mould members is at a first velocity u<NUM>, and in a second stage of downward movement following the first stage of downward movement, the downward velocity of the first and second mould members is at a second velocity u2. It is preferred to have u<NUM>>u<NUM> such that the first and second mould member <NUM>, <NUM> move faster in the first stage of downward movement than in the second stage of downward movement.

With reference to <FIG> and <FIG>, in the second configuration as shown in <FIG> the shaping surface <NUM> of the first mould member <NUM> has made contact with the major surface <NUM> of the glass sheet <NUM> in a peripheral region thereof. Due to the particular arrangement of the first mould member <NUM> and second mould member <NUM>, the shaping surface <NUM> of the second mould member <NUM> has also made contact with the second major <NUM> surface of the glass sheet <NUM> in a central region thereof, the central region being inboard of the peripheral region of the glass sheet. The final desired position of the first and second mould members <NUM>, <NUM> have not yet been reached.

In <FIG> the press bending station <NUM> is shown in another configuration, different to the configuration shown in <FIG> and <FIG>. Prior to this configuration the press bending station <NUM> was in the configuration shown in <FIG>.

In this third configuration shown in <FIG>, the second mould member <NUM> has moved downwards by energising the linear actuator <NUM> such that the shaping surface <NUM> of the second mould member <NUM> further contacts the major surface <NUM> of the glass sheet <NUM> in the central region thereof to press bend the central region of the glass sheet <NUM>. In this example, the shaping surface <NUM> is shown aligned with the shaping surface <NUM> (such that, with reference to <FIG>, the displacement <NUM> is zero).

In this third configuration, although the first and second mould members <NUM>, <NUM> are arranged to provide the two part press bending member <NUM> with a final desired shaping surface, the final desired position of the first and second mould members <NUM>, <NUM> has still not been reached. With reference to <FIG>, the displacement <NUM> is zero, but the vertical distance <NUM> and the vertical distance <NUM> are both greater than zero because the shaping surface <NUM> and the shaping surface <NUM> have not reached the final position indicated by dotted line <NUM>.

The final desired position for the first and second mould members <NUM>, <NUM> may be reached by further moving the first and second mould members <NUM>, <NUM> downwards towards the frame <NUM> to further press bend the glass sheet <NUM> in the peripheral and central regions thereof. In this example, in moving to the final desired position for the first and second mould members there is no relative movement between the first and second mould members such that the shaping surface <NUM> remains aligned with the shaping surface <NUM> during this further movement step. This is further described with reference to <FIG>, although due to the scale of the figures it is difficult to represent the different configurations.

In a fourth configuration shown in <FIG>, the shaping surface <NUM> of the first mould member <NUM> is aligned with the shaping surface <NUM> of the second mould member <NUM>. With reference to <FIG>, the displacement <NUM> is zero. The two part press bending member <NUM> in this arrangement has a pressing surface for pressing the glass sheet <NUM> supported on the frame <NUM> to a final desired shape and the press bending is configured such that the desired shaping surface of the two part press bending member <NUM> is also in the desired position. With reference to <FIG>, the shaping surface <NUM> and the shaping surface <NUM> both lie on the dotted line <NUM> in this fourth configuration. Starting from the configuration shown in <FIG>, the first and second mould members were both move to the desired final position at the same time such that the shaping surfaces <NUM>, <NUM> remained aligned in moving from the configuration shown in <FIG> to the configuration shown in <FIG>.

In the configuration shown in <FIG>, the gaps <NUM>, <NUM> are in fluid communication with a vacuum source (not shown) for providing a negative pressure region at the major surface <NUM> of the glass sheet <NUM> in at least the vicinity of the glass sheet facing the gaps <NUM>, <NUM>.

The vacuum source may apply a vacuum to the gaps <NUM>, <NUM> for any desired amount of time in order to improve the bending of the glass sheet <NUM>. It is preferred to apply the vacuum source to the gaps <NUM>, <NUM> after the press bending station has reached the fourth configuration described above. The vacuum may be applied in stages, with a different level of vacuum applied in one stage compared to another. The duration of the vacuum stages may be the same or different. The duration of the vacuum in one or more vacuum stage may be between <NUM> and <NUM> seconds.

In <FIG> the press bending station <NUM> is shown in another (a fifth) configuration. In this fifth configuration the two part press bending member <NUM> is essentially arranged in the same way as shown in <FIG> because the shaping surfaces of the first and second mould members <NUM>, <NUM> are aligned (with reference to <FIG> the displacement <NUM> is zero). However in contrast to the configuration of the press bending station <NUM> shown in <FIG>, the configuration of the press bending station <NUM> shown in <FIG> differs because the two part mould <NUM> had been raised relative to the frame <NUM> by suitable actuation/energisation of the linear actuators <NUM>, <NUM>, <NUM>. The first and second mould members <NUM>, <NUM> have been moved upwards in the direction of arrow <NUM>' at the same rate towards the gantry <NUM> i.e. the movement of the first and second mould members <NUM>, <NUM> upwards towards the gantry <NUM> is synchronised with no relative movement between the first and second mould members.

The bent glass sheet <NUM> is shown supported on the underside of the two part press bending member <NUM> by means of a vacuum being applied at the gaps <NUM>, <NUM> (and hence gap <NUM>, see <FIG>) to create a region of negative pressure at the major surface <NUM> of the glass sheet opposite the gap(s).

In addition to a vacuum being applied at the gaps <NUM>, <NUM>, the shaping surface <NUM> of the first mould member <NUM> may have openings therein that are in fluid communication with a vacuum source (which may be the same vacuum source as used to provide a vacuum at the gaps <NUM>, <NUM>). The vacuum source in fluid communication with the openings in the shaping surface <NUM> may also be used to support the glass sheet <NUM> on the underside of the two part press bending member <NUM>.

Furthermore, in addition to a vacuum being applied at the gaps <NUM>, <NUM> and/or at openings in the shaping surface <NUM> of the first mould member <NUM>, the shaping surface <NUM> of the second mould member <NUM> may have openings therein that are in fluid communication with a vacuum source (which may be the same vacuum source as used to provide a vacuum at the gaps <NUM>, <NUM>). The vacuum source in fluid communication with the openings in the shaping surface <NUM> may also be used to support the glass sheet <NUM> on the underside of the two part press bending member <NUM>.

A carrier ring <NUM> is shown disposed between the frame <NUM> (i.e. above the upper shaping surface 15a of lower support <NUM>) and the two part press bending member <NUM>. At a suitable time in the bending operation, the vacuum applied at the gaps <NUM>, <NUM> (or gap <NUM>) is terminated such that the bent glass sheet <NUM> is no longer supported on the underside of the two part press bending member <NUM> and instead falls therefrom to be supported by the carrier ring <NUM>. The gaps <NUM>, <NUM> (or gap <NUM>) may also be in fluid communication with a suitable fluid source such as compressed air, such that after the vacuum at the gaps <NUM>, <NUM> is terminated, fluid i.e. compressed air is caused to flow through the gaps <NUM>, <NUM> towards the glass sheet <NUM> to assist with the removal of the bent glass sheet <NUM> from the shaping surfaces <NUM>, <NUM> of the respective first and second mould members <NUM>, <NUM>.

Suitable actuators (not shown) are provided for moving the carrier ring <NUM> in the direction of arrow <NUM> away from being between the frame <NUM> and two part press bending member <NUM>. Thereafter the bent glass sheet may be deposited onto suitable conveyor means (not shown) for subsequent annealing or toughening.

As discussed above, although not shown in the figures, the shaping surface <NUM> of the first mould member <NUM> and/or the shaping surface <NUM> of the second mould member <NUM> may have at least one opening therein, said opening being in fluid communication with at least one source of negative pressure such as a vacuum source.

In addition to a negative pressure region produced at the gap <NUM>, there may be additional negative pressure regions at the or each opening in the shaping surface <NUM> of the first mould member <NUM> and/or the or each opening in the shaping surface <NUM> of the second mould member <NUM> to enable improved shape control when bending the glass sheet.

If the shaping surface <NUM> of the first mould member <NUM> has one or more opening therein for the provision of a vacuum (for example as described above in relation to the gaps <NUM>, <NUM>), any number of said openings in the shaping surface <NUM> may also be in fluid communication with a suitable fluid source such as compressed air to assist with the removal of the bent glass sheet from the shaping surface <NUM> by causing the fluid to flow through said openings towards the glass sheet after the vacuum has been terminated.

Likewise, if the shaping surface <NUM> of the second mould member <NUM> has one or more opening therein for the provision of a vacuum (for example as described above in relation to the gaps <NUM>, <NUM>), any number of said openings in the shaping surface <NUM> may also be in fluid communication with a suitable fluid source such as compressed air to assist with the removal of the bent glass sheet from the shaping surface <NUM> by causing the fluid to flow through said openings towards the glass sheet after the vacuum has been terminated.

To further illustrate the sequence of movement of the first and second mould members <NUM>, <NUM> during the shaping process according to the present invention, left hand portions of <FIG> (except with a glass sheet <NUM> on the frame <NUM>), <NUM>, <NUM> and <NUM> have been enlarged and provided as additional figures. These enlarged portions of the aforementioned figures are shown in <FIG>, <FIG> respectively. An additional <FIG> is included to show the moment during the shaping operation when the shaping surface <NUM> of the second mould member <NUM> contacts the glass sheet <NUM> in the central region thereof before shaping surface <NUM> of the first mould member <NUM> contacts the glass sheet <NUM> in the peripheral region thereof.

With reference to <FIG> and <FIG>, a glass sheet <NUM> is shown supported on the shaping surface 15a of the lower support <NUM>. The glass sheet has been suitably positioned onto the shaping surface 15a using methods known in the art. The glass sheet <NUM> has a first major surface <NUM> and a second opposing major surface <NUM>. The second major surface <NUM> contacts the upper shaping surface 15a of the lower support <NUM>. The glass sheet has been heat softened and may sag slightly in the central region thereof.

A portion of the two part press bending member <NUM> is shown (designated <NUM>') positioned above the glass sheet <NUM>. The first mould member <NUM> has shaping surface <NUM> facing the first major surface <NUM> of the glass sheet <NUM> and the second mould member <NUM> has shaping surface <NUM> facing the first major surface <NUM> of the glass sheet <NUM>.

As described above, the shaping surfaces <NUM>, <NUM> are offset from one another by displacement <NUM> because the edges 18c and 20a are not aligned.

As shown in this figure, neither shaping surfaces <NUM>, <NUM> have contacted the glass sheet <NUM>.

In <FIG> both the first and second mould members <NUM>, <NUM> have moved downwards together such that there is no relative movement between them i.e. starting from the configuration shown in <FIG>, both first and second mould members <NUM>, <NUM> moved in the direction of arrow <NUM> at the same speed. As such the shaping surfaces <NUM>, <NUM> are still not aligned and the displacement <NUM> referred to above is still present (in this case the displacement <NUM> is the same as in <FIG>). In this configuration the shaping surface <NUM> has just contacted the first major surface <NUM> of the glass sheet <NUM>. However because of the particular arrangement of the first and second mould members <NUM>, <NUM> of the two part press bending member <NUM>', the position of the first mould member <NUM> relative to the second mould member <NUM> is such that the shaping surface <NUM> has not yet contacted the first major surface <NUM> of the glass sheet <NUM> (although the shaping surface <NUM> has already contacted the first major surface <NUM> of the glass sheet <NUM>).

A different arrangement of the first and second mould members <NUM>, <NUM> of the two part press bending member <NUM>' may be used where the second mould member <NUM> is arranged relative to the first mould member <NUM> such that the shaping surface <NUM> of the first mould member <NUM> contacts the first major surface <NUM> of the glass sheet before the shaping surface <NUM> of the second mould member <NUM> contacts the first major surface <NUM> of the glass sheet. The position of the second mould member in this alternative embodiment is shown in phantom as 19a having a shaping surface 23a. It will be readily apparent that the first and second mould members may be arranged such that the respective shaping surfaces thereof contact the first major surface <NUM> of the glass sheet <NUM> at the same time when both the first and second mould members move downwards towards the frame at the same rate.

<FIG>, which is an enlarged view of a portion of the left hand side of <FIG>, shows the glass sheet <NUM> being partially pressed in the peripheral region thereof between the first shaping member <NUM> and the lower support <NUM>. Since the first and second mould members have both continued to move downwards (in the direction of arrow <NUM>) at the same rate (when starting in the arrangement shown in <FIG>), the glass sheet <NUM> is also slightly pressed in the central region thereof by the second mould member <NUM>. However the shaping surfaces of the first and second mould members still have a non-zero displacement <NUM> as described above.

<FIG>, which is an enlarged view of a portion of the left hand side of <FIG>, shows the two part press bending member <NUM>' after the arrangement shown in <FIG>, where the first mould member <NUM> has remained static relative to the lower support <NUM> and the second mould member <NUM> has moved further downwards (in the direction of arrow <NUM>) to press bend the glass sheet <NUM> in a central region thereof. The glass sheet <NUM> is sufficiently held at the peripheral region thereof by being partially pressed between the first mould member <NUM> and the lower support <NUM>. In this configuration there is no displacement between the shaping surfaces <NUM>, <NUM> of the first and second mould members <NUM>, <NUM> (displacement <NUM> is zero). The two part press bending member <NUM>' therefore has the desired final shaping surface but the two part press bending member is not in the final position to fully press bend the glass sheet <NUM> to the desired shape. This is shown in the following <FIG>.

<FIG>, which is an enlarged view of a portion of the left hand side of <FIG>, shows the two part press bending member <NUM>' after the configuration shown in <FIG> where the first mould member <NUM> and the second mould member have both moved downwards (in the direction of arrow <NUM>) at the same time i.e. there is no relative movement between the first mould member <NUM> and the second mould member <NUM>. Again there is no displacement between the shaping surfaces of the first and second mould members (displacement <NUM> is zero). The two part press bending member <NUM>' has the desired final shaping surface (because the displace <NUM> is zero) and has moved to the final position (see dotted line <NUM> in <FIG>) to fully press bend the glass sheet <NUM> to the desired shape. After this final press bending step, a vacuum may be produced at gap <NUM> (and gap <NUM>, see <FIG>) to hold the glass sheet <NUM> to the underside of the two part mould <NUM>' and to improve shape control of the bent glass sheet as discussed above.

<FIG> shows a schematic cross-sectional representation of part of a glass bending line <NUM> incorporating a press bending station <NUM> of the type shown in <FIG>, the operation of which is described with reference to <FIG>.

The glass bending line <NUM> comprises a heating furnace <NUM>, a press bending section <NUM>, which may be or may not be heated, and an annealing furnace <NUM>.

A roller conveyor bed <NUM> extends through the heating furnace <NUM>, the press bending section <NUM> and the annealing furnace <NUM> to define a path of conveyance for a glass sheet <NUM>. The roller conveyor bed comprises a plurality of rollers <NUM> configured (i.e. in a spaced apart parallel relationship) to convey a glass sheet <NUM> in the direction of arrow <NUM>. In this example the glass sheet <NUM> is shown to be in contact with the rollers <NUM>, but the glass sheet <NUM> may be positioned on a suitable carriage (not shown), the carriage being in contact with the rollers <NUM>. As an alternative to rollers <NUM>, or in addition to rollers <NUM>, an air flotation device may be used to convey the glass sheet in the direction of arrow <NUM>.

In the heating furnace <NUM> the glass sheet <NUM> is heated to a temperature suitable for bending. The furnace may incorporate any suitable heating means such as electric heating, gas heating, convective heating and microwave heating and combinations thereof as required.

Inside the press bending section <NUM> is press bending station <NUM>. When the glass sheet <NUM> is conveyed to between the frame <NUM> and the two part press bending member <NUM>, the glass sheet is positioned onto the frame <NUM> by being deposited thereon for subsequent press bending as has been described with reference to <FIG>. Methods are known in the prior art for transferring the glass sheet from the conveyor rollers <NUM> to the frame <NUM>, for example some of the conveyor rollers may be configured as drop rollers, or a vacuum platen may be used to lift the heat softened glass sheet from the conveyor rollers for depositing onto a suitably configured frame <NUM>.

With reference to <FIG> and <FIG>, the two part press bending member <NUM> is shown in electrical communication with a control means <NUM>, such as a computer, for controlling the relative movement of the first and second mould members <NUM>, <NUM> of the two part press bending member <NUM> by means of the linear actuators <NUM>, <NUM>, <NUM>. The control means <NUM> may be in electrical communication with other parts of the glass bending line <NUM>, for example the conveyor roller bed <NUM> to control the speed of the rollers <NUM> and/or the actuators (not shown) controlling the movement of carrier ring <NUM>.

The carrier ring <NUM> is shown between the press bending section <NUM> and annealing furnace <NUM> and is movable between the position shown in <FIG> and the position shown in <FIG> by suitable actuators (not shown) i.e. by moving in the direction of arrow <NUM>. A bent glass sheet supported by the carrier ring <NUM> is moved from being between the two part press bending member <NUM> and the frame <NUM> (i.e. inside the press bending section <NUM>), to being outside the press bending section <NUM>, where the bent glass sheet may then be deposited onto portion <NUM>' of the conveyor roller bed <NUM> to be conveyed into the annealing furnace <NUM> for subsequent annealing i.e. controlled cooling to ambient temperature.

Although in the figures the two part press bending member <NUM> is shown as having exposed shaping surfaces <NUM> and <NUM> as hereinbefore described, in a preferred embodiment either or both first and second mould member <NUM>, <NUM> may be provided with a protective cover to protect the shaping surface of the mould member(s) from damage and wear. The lower support <NUM> may also be provided with such a protective cover to cover the upper shaping surface 15a. When a cover is used, preferably the cover comprises a cloth made of, for example, stainless steel, fibre glass, poly-phenyleneterephthalamide fibres (e.g. Kevlar™), materials blended Kevlar™, polybenzoxale (PBO) fibres containing graphite (e.g. ZylonTM), or various weaves of these fibres.

If a protective cover is used to cover each shaping surface <NUM>, <NUM>, it is preferred to use a single cover that covers both the shaping surface <NUM> and the shaping surface <NUM>.

If a protective cover is used that covers both the shaping surfaces <NUM> and <NUM>, the protective cover should be sufficiently flexible to allow the first and second mould members to move as described hereinbefore.

Furthermore, if a protective cover is used that covers both the shaping surfaces <NUM> and <NUM>, it is preferred that the protective cover is sufficiently porous or air permeable to allow the provision of a vacuum therethrough, for example at the gap <NUM> between the first and second mould members, or at any opening that may be in the respective shaping surface of the first and second mould members as has been previously described.

It is possible to use a separate protective cover for each shaping surface <NUM>, <NUM>. This has the advantage that the gap between the first and second mould members may not be impeded by the material of the protective cover.

The downward movement of the first and second mould members <NUM>, <NUM> in moving between the configurations shown in <FIG>, <FIG>, <FIG> and <FIG> (or <FIG>) is illustrated in <FIG> (for a first example) and in <FIG> (for a second example). <FIG> show the vertical position of the first and second mould members <NUM>, <NUM> relative to the final desired position of the shaping surface of said parts represented by line <NUM> in <FIG> and <FIG>.

In <FIG>, the axis <NUM> is time in seconds, and the axis <NUM> is distance in mm.

In <FIG>, the dotted line represents the vertical displacement of the shaping surface <NUM> of the first mould member <NUM> relative to the final desired position of said shaping surface <NUM>. The solid line represents the vertical displacement of the shaping surface <NUM> of the second mould member <NUM> relative to the final desired position of said shaping surface <NUM>. The final desired position of the shaping surfaces <NUM>, <NUM> (when they are aligned, see <FIG>, <FIG> and <FIG> and the related description thereof) is at a vertical displacement of -<NUM> relative to a reference datum point of zero. The shaping surface <NUM> is at the zero reference datum point at time = zero, and the shaping surface <NUM> is at +<NUM> relative to the zero reference datum point at time = zero. That is, at the final desired position for the shaping surface <NUM> there has been a total vertical movement downwards of <NUM>, whereas for the shaping surface <NUM> there has been a total vertical movement downwards of <NUM>.

With reference to <FIG>, the relative movement of the first and second mould members <NUM>, <NUM> in a first embodiment shall be described.

At time t=<NUM> (i.e. points A and A'), the two part press bending mould <NUM> is arranged such that the shaping surface <NUM> of the first mould member <NUM> is displaced relative to the shaping surface <NUM> of the second mould member <NUM> by <NUM>. With reference to <FIG> the distance <NUM> (and hence distance <NUM>', see <FIG>) is <NUM>, the distance <NUM> is <NUM> and the displacement <NUM> is <NUM>.

After <NUM> seconds (at points B, B'), the pressing bending operation begins and both the first mould member <NUM> and the second mould member <NUM> move vertically downwards towards the glass sheet <NUM> supported on the frame <NUM>, see for example <FIG>. Both the first and second mould members <NUM>, <NUM> move downwards at the same speed (= v<NUM>) so there is no relative movement between the shaping surfaces <NUM>, <NUM> of the first and second mould members <NUM>, <NUM> during this downward movement stage i.e. between points B-C and B'-C' the movement of the first and second mould members <NUM>, <NUM> is synchronised and the displacement <NUM> remains fixed at <NUM>.

After <NUM> seconds, (at points C, C') the downward speed of the first and second mould members <NUM>, <NUM> is reduced (to speed v2) as the surface of the glass sheet <NUM> is approached. Synchronised vertical downward movement of the first and second mould members <NUM>, <NUM> is continued at speed v2 until point D, D' is reached.

After <NUM> seconds (at point D), the second mould member <NUM> continues to move vertically downwards at the speed v<NUM>. However, at point D' (which coincides in time to point D), the vertical downwards movement of the first mould member <NUM> is stopped. The press bending station is in the configuration shown in <FIG> (or <FIG>). At this point in time, the major surface <NUM> of the glass sheet <NUM> has been contacted by the shaping surface <NUM> of the first mould member <NUM> such that the glass sheet <NUM> is partially pressed between the lower support <NUM> of the frame <NUM> and the first mould member <NUM>.

Over the next <NUM> seconds, the second mould member <NUM> continues to move downwards at speed v2 to press bend the glass sheet <NUM> in the central region thereof while the glass sheet <NUM> remains partially pressed by the static first mould member <NUM>. That is, between the point D' and E', the first mould member <NUM> remains static relative to the frame <NUM> to partially press the glass sheet in a peripheral region thereof.

After <NUM> seconds (at point E') movement of the first mould member <NUM> is restarted with a downward speed (= v<NUM>) selected such that first mould member <NUM> and the second mould member <NUM> both reach the final desired position (at point F, F') at the same time. That is, between the points E and F the second mould member <NUM> continues to move vertically downwards at speed v<NUM> whilst between the points E' and F' the first mould member moves vertically downwards at speed v<NUM>.

The downwards movement of the first mould member <NUM> between points E' and F' further presses the peripheral region of the glass sheet between the upper shaping surface 15a of the lower support <NUM> and the shaping surface <NUM> of the first mould member. That is, in the peripheral region the glass sheet is further pressed between the lower support <NUM> and the first mould member <NUM> whilst the glass sheet is further press bent in the central region by the second mould member <NUM>.

It is evident that as the second mould member <NUM> continues to move vertically downwards between the points D and E, because the first mould member <NUM> is static between point D' and E' (which correspond to point D and E respectively), the separation of the shaping surfaces <NUM>, <NUM> of the first and second mould members <NUM>, <NUM> decreases. With reference to <FIG>, the displacement <NUM> decreases in between points D and E.

After <NUM> seconds, (at the points F, F') both the first and second mould members <NUM>, <NUM> have reached the final desired position and the glass sheet <NUM> is press bent to the final desired shape. The press bending station is in the configuration shown in <FIG> or <FIG>. At points F, F', the two part bending member <NUM> has a shaping surface having the final desired curvature.

In this particular example of the method according to the first aspect of the present invention (as illustrated in <FIG>), the initial separation (displacement <NUM>) of the shaping surfaces of the first and second pressing is <NUM>. The first mould member <NUM> was moved vertically downwards to a position such that the position of the shaping surface <NUM> was <NUM> away from the final position for the shaping surface <NUM>. The shaping surfaces <NUM>, <NUM> were then caused to move as described above to reach the final position at the same time indicated by points F, F, which is two seconds after the initial vertical downwards movement of both first and second mould members <NUM>, <NUM> began i.e. two seconds after the point B, B'.

By stopping the first mould member <NUM> at point D', and then restarting the downward movement of the first mould member at point E', it was found that further downward movement of the first mould member <NUM> to move the shaping surface <NUM> to the final position at the same time that the shaping surface <NUM> of the second mould member <NUM> reaches the final position i.e. at points F,F', transient stresses created in the glass sheet <NUM> during the press bending operation were reduced compared to when the first mould member <NUM> moves to the final position without stopping beforehand. That is, without the first mould member stopping at point D', but instead continuing at speed v2 until the shaping surface <NUM> of the first mould member <NUM> is at the final desired position (i.e. at -<NUM> from the zero datum) there was more glass breakage during the press bending operation.

Another test was carried out using a modified downward movement of the first and second mould members <NUM>, <NUM>.

This second example is described with reference to <FIG>. In <FIG>, the dotted line represents the vertical displacement of the shaping surface <NUM> of the first mould member <NUM> relative to the final desired position of said shaping surface <NUM>. The solid line represents the vertical displacement of the shaping surface <NUM> of the second mould member <NUM> relative to the final desired position of said shaping surface <NUM>. The final desired position of the shaping surfaces <NUM>, <NUM> (when they are aligned, see <FIG>, <FIG> and <FIG> and the related description thereof) is at a vertical displacement of - <NUM> relative to a reference datum point of zero. The shaping surface <NUM> is at the zero reference datum point at time = zero, and the shaping surface <NUM> is at +<NUM> relative to the zero reference datum point at time = zero. That is, at the final desired position for the shaping surface <NUM> there has been a total downwards movement of <NUM>, whereas for the shaping surface <NUM> that has been a total downwards movement of <NUM>.

In <FIG>, up to the points D, D' (at <NUM> seconds), the movement of the first and second mould members <NUM>, <NUM> in this second example is the same as in the first example (as illustrated in <FIG>). That is, between point B and C (and B' and C') both the first and second mould members <NUM>, <NUM> move vertically downwards at a speed of v<NUM> (with the displacement <NUM> fixed at <NUM>), and between point C and D (and C' and D') both the first and second mould members <NUM>, <NUM> move vertically downwards at a speed of v<NUM> (again with the displacement <NUM> fixed at <NUM>).

In this second example at point D, the second mould member <NUM> continues to move vertically downwards at the same speed v2 until at point F the final position is reached. The second mould member <NUM> in this second example moves downwards in the same manner as in the first example described in relation to <FIG>.

As in the first example, in the second example when the first mould member reaches point D (after <NUM> seconds) downward movement thereof is stopped. However in contrast to the first example, the first mould member remains static until the shaping surface <NUM> of the first mould member <NUM> and the shaping surface <NUM> of the second mould member are aligned (at point G, G'). With reference to <FIG>, at the point G, G' the displacement <NUM> is zero and the shaping surfaces <NUM>, <NUM> are aligned. The two part press bending member <NUM> has the final desired shaping surface (represented by dotted line <NUM> in <FIG>) but the final desired shaping surface is not in the desired final position (represented by dotted line <NUM> in <FIG>).

At this time when the displacement <NUM> is zero (which is at about <NUM> seconds), at point G' the downward movement of the first mould member <NUM> is restarted to move the shaping surface <NUM> of the first mould member and the shaping surface <NUM> of the second mould member to the final desired position.

Between the points G' and F' the movement of the first and second mould members <NUM>, <NUM> is again synchronised such that there is no relative vertical movement between the two shaping surfaces <NUM>, <NUM>. The first and second mould members <NUM>, <NUM> move vertically downwards at the same speed (=v2) until the final position F, F' is reached at vertical distance -<NUM> from the zero reference datum point. The shaping surfaces <NUM>, <NUM> are aligned and the displacement <NUM> is zero.

The press bending station is then also in the configuration as shown in <FIG> (and in <FIG>) but the relative movement between the first and second mould members during the press bending operation is different compared to the first example of the method (as described above with reference to <FIG>). The second example described above is illustrated in the <FIG>.

Such a method according to the present invention is particularly useful for bending initially flat glass sheets to a final curvature for use as a curved sheet of glass for automotive use, for example as a ply in a windscreen, or a pane for a sidelight, backlight or rooflight i.e. a sunroof. Two such curved glass sheets may be used in a vehicle windscreen, joined together by at least one ply of adhesive interlayer material such as polyvinyl butyral (PVB).

<FIG> shows a schematic side view of another press bending station <NUM>' that is essentially the same as the press bending station <NUM> as described with reference to <FIG> except that there is a single cloth <NUM> covering the first and second mould members <NUM>, <NUM> of the two part press bending member <NUM>.

The press bending station <NUM>' is shown in essentially the same configuration as the press bending station <NUM> in <FIG>. However because the first and second mould members are covered with a single cloth <NUM>, the shaping surface of the first mould member <NUM> is covered by the cloth <NUM> such that the cloth <NUM> is in direct contact with the major surface <NUM> of the glass sheet <NUM>. As such, the shaping surface <NUM> of the first mould member <NUM> and the shaping surface <NUM> of the second mould member <NUM> are in indirect contact with the major surface <NUM> of the glass sheet <NUM>.

Preferably the cloth <NUM> is an air-permeable cloth. Preferably the cloth <NUM> comprises at least one of stainless steel, fibre glass, poly para-phenyleneterephthalamide fibres or blends thereof, polybenzoxazole (PBO) fibres containing graphite, and various weaves of these fibres.

<FIG> shows a schematic side view of another press bending station <NUM>" that is essentially the same as the press bending station <NUM> as described with reference to <FIG> except that there is a first cloth <NUM>' covering the first mould member <NUM> and a second cloth <NUM>" covering the second mould member <NUM> i.e. the cloth <NUM>' covers the shaping surface <NUM> of the first mould member <NUM> and the cloth <NUM>" covers the shaping surface <NUM> of the second mould member <NUM>. In order to accommodate the two cloth covers, a second mould member <NUM>' is provided that has a slightly smaller shaping surface to accommodate the cloth extending up the outer peripheral wall 18a and the inner peripheral wall 18b of the first mould member <NUM> and the outer peripheral wall <NUM> of the second mould member <NUM>'. As such the gaps <NUM>', <NUM>' are slightly wider than the gaps <NUM>, <NUM> of <FIG>. Also because two cloths <NUM>', <NUM>" are used, the gaps <NUM>' and <NUM>' are not impeded by cloth in the vicinity of the shaping surface of the two part press bending member <NUM> (designated as <NUM> because the second mould member <NUM>' is different to the second mould member <NUM> of the two part press bending member <NUM>). The use of two or more cloths also provides an advantage in that only selected regions of the cloth may be replaced as the cloth wears due to continued use in bending glass sheets. Whilst using a single cloth requires the whole cloth to be replaced if the cloth wears, when using at least a first and second cloth, only one of the cloths may be replaced as required.

The press bending station <NUM>" is shown in essentially the same configuration as the press bending station <NUM> in <FIG>. However because the first mould member <NUM> is covered with the cloth <NUM>' and the second mould member <NUM>' is covered with the cloth <NUM>", the cloths <NUM>' and <NUM>" are in direct contact with the first major surface <NUM> of the glass sheet <NUM>. As such, the shaping surface <NUM> of the first mould member <NUM> and the shaping surface <NUM> of the second mould member <NUM> are in indirect contact with the first major surface <NUM> of the glass sheet <NUM> via cloths <NUM>' and <NUM>" respectively.

Preferably at least one of the cloths <NUM>', <NUM>" is an air-permeable cloth. Preferably the cloth <NUM>' and/or <NUM>" comprises at least one of stainless steel, fibre glass, poly para-phenyleneterephthalamide fibres or blends thereof, polybenzoxazole (PBO) fibres containing graphite, and various weaves of these fibres.

It was found that when using a method of shaping a glass sheet according to the present invention, as well as improving the wrinkle in a peripheral region of the bent glass sheet (in comparison to using a single unitary upper press bending member) the risk of glass breakage during the shaping operation i.e. the press bending operation, was reduced.

Claim 1:
A method of shaping a glass sheet (<NUM>) comprising the steps:
(i) providing a shaping support (<NUM>) for supporting the glass sheet;
(ii) providing a press bending apparatus comprising at least two (a first and a second) mould members (<NUM>, <NUM>), each of the first and second mould members being movable relative to the shaping support;
(iii) heating the glass sheet;
(iv) positioning the glass sheet on the shaping support;
(v) moving at least one of the shaping support and the press bending apparatus toward the other to press the glass sheet in a first region thereof between the shaping support and the first mould member;
(vi) moving the second mould member relative to the first mould member to press the glass sheet in a second region thereof, and
(vii) moving the first mould member relative to the shaping support to further press the glass sheet in the first region thereof between the first mould member and the shaping support,
wherein the first region of the glass sheet is a peripheral region of the glass sheet and wherein the second region of the glass sheet is a central region of the glass sheet.