CA2064519A1 - Support ring with wear strip - Google Patents
Support ring with wear stripInfo
- Publication number
- CA2064519A1 CA2064519A1 CA002064519A CA2064519A CA2064519A1 CA 2064519 A1 CA2064519 A1 CA 2064519A1 CA 002064519 A CA002064519 A CA 002064519A CA 2064519 A CA2064519 A CA 2064519A CA 2064519 A1 CA2064519 A1 CA 2064519A1
- Authority
- CA
- Canada
- Prior art keywords
- glass sheet
- foil
- support rail
- glass
- covering
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 239000011521 glass Substances 0.000 claims abstract description 94
- 239000011888 foil Substances 0.000 claims abstract description 32
- 229910052751 metal Inorganic materials 0.000 claims abstract description 31
- 239000002184 metal Substances 0.000 claims abstract description 31
- 239000007769 metal material Substances 0.000 claims abstract description 8
- 230000000284 resting effect Effects 0.000 claims description 3
- 238000007669 thermal treatment Methods 0.000 claims description 2
- 238000005299 abrasion Methods 0.000 claims 1
- 239000002131 composite material Substances 0.000 abstract 1
- 239000004760 aramid Substances 0.000 description 16
- 229920003235 aromatic polyamide Polymers 0.000 description 16
- 238000005496 tempering Methods 0.000 description 15
- 239000000463 material Substances 0.000 description 13
- 229910001385 heavy metal Inorganic materials 0.000 description 12
- 238000007493 shaping process Methods 0.000 description 8
- 238000001816 cooling Methods 0.000 description 6
- 239000000835 fiber Substances 0.000 description 6
- 239000005011 phenolic resin Substances 0.000 description 6
- KXGFMDJXCMQABM-UHFFFAOYSA-N 2-methoxy-6-methylphenol Chemical compound [CH]OC1=CC=CC([CH])=C1O KXGFMDJXCMQABM-UHFFFAOYSA-N 0.000 description 5
- 238000005452 bending Methods 0.000 description 5
- 229920001568 phenolic resin Polymers 0.000 description 5
- 206010073306 Exposure to radiation Diseases 0.000 description 4
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 description 3
- 239000011810 insulating material Substances 0.000 description 3
- 230000002093 peripheral effect Effects 0.000 description 3
- 229920006389 polyphenyl polymer Polymers 0.000 description 3
- 230000002787 reinforcement Effects 0.000 description 3
- 239000005341 toughened glass Substances 0.000 description 3
- 229910000831 Steel Inorganic materials 0.000 description 2
- 229920006231 aramid fiber Polymers 0.000 description 2
- 125000003118 aryl group Chemical group 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- WSFSSNUMVMOOMR-NJFSPNSNSA-N methanone Chemical compound O=[14CH2] WSFSSNUMVMOOMR-NJFSPNSNSA-N 0.000 description 2
- 229910001120 nichrome Inorganic materials 0.000 description 2
- 238000010791 quenching Methods 0.000 description 2
- 230000000171 quenching effect Effects 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 238000013022 venting Methods 0.000 description 2
- 150000001408 amides Chemical class 0.000 description 1
- 239000010425 asbestos Substances 0.000 description 1
- 125000006297 carbonyl amino group Chemical group [H]N([*:2])C([*:1])=O 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 239000011152 fibreglass Substances 0.000 description 1
- 239000005357 flat glass Substances 0.000 description 1
- 239000012634 fragment Substances 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229920006158 high molecular weight polymer Polymers 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 239000012774 insulation material Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000005281 nonmetallic glass Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000002028 premature Effects 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- 229910052895 riebeckite Inorganic materials 0.000 description 1
- 229920002050 silicone resin Polymers 0.000 description 1
- 230000008719 thickening Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B35/00—Transporting of glass products during their manufacture, e.g. hot glass lenses, prisms
- C03B35/14—Transporting hot glass sheets or ribbons, e.g. by heat-resistant conveyor belts or bands
- C03B35/20—Transporting hot glass sheets or ribbons, e.g. by heat-resistant conveyor belts or bands by gripping tongs or supporting frames
- C03B35/202—Transporting hot glass sheets or ribbons, e.g. by heat-resistant conveyor belts or bands by gripping tongs or supporting frames by supporting frames
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Re-Forming, After-Treatment, Cutting And Transporting Of Glass Products (AREA)
- Furnace Housings, Linings, Walls, And Ceilings (AREA)
Abstract
ABSTRACT
Apparatus for supporting a glass sheet comprising support rail means of rigid metal similar in shape and outline plan to the outline shape of a bent glass sheet, one or more insulating members of non-metallic material having a coefficient of thermal conductivity less than that of the support rail means superimposed over the support rail means and a thin elongated metal foil having a smooth upper glass contacting surface superimposed over each insulating member of non-metallic material. The thickness of the foil is sufficiently thick to enable the foil to be durable when a bottom edge corner of a glass sheet slides thereover and sufficiently thin to enable the composite of foil and glass supporting member to have a thermal conductivity approximating that of said glass supporting member in the absence of said foil.
Apparatus for supporting a glass sheet comprising support rail means of rigid metal similar in shape and outline plan to the outline shape of a bent glass sheet, one or more insulating members of non-metallic material having a coefficient of thermal conductivity less than that of the support rail means superimposed over the support rail means and a thin elongated metal foil having a smooth upper glass contacting surface superimposed over each insulating member of non-metallic material. The thickness of the foil is sufficiently thick to enable the foil to be durable when a bottom edge corner of a glass sheet slides thereover and sufficiently thin to enable the composite of foil and glass supporting member to have a thermal conductivity approximating that of said glass supporting member in the absence of said foil.
Description
2 ~
SUPPORT RING WITH WEAR STRIP
BackRround of the Invention 1. Field of the Inventlon This invention relates to a device for transferring hot glass sheets, and in particular relates to th~ type of transfer device that re~urns empty to a shaping station for shaping and/or transferring successive hot glass sheets to a cooling station for heat strengthening or tempering.
2. TechnoloRY Problems and Patents of Interest The prior art has provided devices for transferring hot glass sheets which comprise an outline or ring-type mold of relatively rigid metal that includes an outline upper surface which conforms to the shape of a glass sheet to be transferred slightly inboard of its periphery. The glass sheet is heated and either pressed to shape between an upper mold and the ring-type mold or between complementary molds and subseguently transferred to the ring-type mold or sagged by heat and gravity to the shape provlded by the upper shaping surface of the mold. After the glass sheet is shaped, it is transferred while supported on the ring-type mold to a quenching station where it is quenched suddenly and rapidly by applying cold air blasts against the supported lower surface and the upper exposed surface of the glass sheet.
Heating the glass sheet to its softening temperature followed by sudden chilling develops a stress pattern characteristic of tempered glass that includes a surface zone highly stressed in compression surrounding an interior zone stressed in tension. This stress pattern reduces the tendency of the tempered glass sheet to bre&k, particularly lf the surface zone is highly stressed. Furthermore, if tempered glass is fractured, it forms a 2 ~
number of small particles that are less dangerous than relatively large, ~agged fragments that result from the breakage of untempered glass.
When a shaped glass sheet contacts a hot, heavy metal rail during this rapid cooling, glass breakage can result from surface venting due to high tension stresses established locally at the glass-metal contact areas. The prior art has recognized ~hat the difference in heat conductivity between the glass sheet supported on the mold and the relatively heavy metal mold ring during rapid cooling causes these high tension stresses in the hot shaped glass sheet in the areas contacting the glasq supporting rail. Hence, in recent years, the art has developed a ring-like member having a glass sheet supporting surface composed of non-metallic material having a low coefficient of thermal conductivity to insulate the glass from the heavy metal ring mold.
One effective non-metallic material used as a glass engaging member of a ring-type support consists essentially of a phenolic resin, preferably polyphenyl formaldehyde, reinforced with fibers composed of an aromatic polyamide composition. This reinforced material is popularly termed aramid and will be so identified hereafter in this specification.
The material used to engage the glass is reinforced structurally either by thickening its lower portion, which makes a ring-like member used as a non-metallic tempering ring awkward to handle because of the thickness needed for rigidity, or the glass engaging material is hugged and surrounded by a relatively heavy metal rail slightly larger than the outline of the supported glass sheet or otherwise reinforced to impart rigidity to the non-metallic glass engaging material. Tempering ring structures comprising a ring-like member of aramid reinforced with a hugging heavy metal support ring have produced results superior to the prior art by maintaining the glass sheet in contact with the fiber reinforced phenolic resin material in spaced 20~4~1~
relation over the heavy metal rail of the tempering ring. However, still better results are desired to be consistent with an objective of manufacturing larger glass sheets of more complicated shapes than in the prior art with even less marking or venting than previously experienced.
U.S. Patent No. 3,586,492 to McMaster discloses a glass sheet support for a press shaping apparatus. The support includes an endless ring frame having teeth with extended edge portions that contact the surface of the glass sheet along it periphery. A wire mesh is disposed over the edges for contacting the sheet.
U.S. Patent No. 3,741,743 to Seymour discloses a glass sheet shaping frame for engaging the peripheral portion of a glass sheet during shaping and tempering. A pair of spaced apart rigid rail are positioned about the periphery of the glass sheet and a screen member spans between the rails to provide a glass sheet engaging surface. The screen member is preferably a heavy gauge mesh overlaid by a fine wire mesh.
U.S. Patent No. 3,973,943 to Seymour discloses an outline ring~like transfer device for supporting shaped glass sheets after they are shaped and during the time they are rapidly guenched. The device includes a rigid, outline metal rail having an outline slightly smaller than that of the shaped glass sheet and a bar or plurality of closely spaced bar members of non-metallic materi~l having a lower heat transfer coefficient than that of the rigid metal rail. The bar members are mo~mted in hugging relation against the rigid metal rail in position to conform to the outline rail. An upper edge portion of the bar or bar members is disposed above the upper edge of the rigid metal rail in a position to provide a glass sheet supporting surface in spaced relation above the upper edge of the rigid metal rail. The bar or bar members of the Seymour patent are composed of a laminated structure, such as 2~6~ 9 fiber glass cloth or asbestos woven paper layers or the like, bonded together with a silicone resin binder or a phenolic resin binder. The glass engaging materials of this patent have been replaced by superior aramid materials disclosed in the following patent.
U.S. Patent Nos. 4,282,026 and 4,361,432 to McMaster et al. disclose the use of a helical spring wound over a solid heavy metal tempering ring closely adjacent to the glass to space the glass from direct contact with the heavy metal tempering ring and thus reduce the cooling rate differences between the glass and the metal. The helical spring in these patents do not shield the glass from direct exposure to radiation from a closely ad~acent tempering ring.
U.S. Patent No. 4,356,018 to McMaster discloses a method and apparatus for deep bending glass sheets. The lower bending mold is of a ring-type construction and includes a wire mesh covering to prevent chilling of the heated glass sheet when it is received by the ring mold for bending.
U.S. Patent Nos. 4,363,163 and 4,421,482 to McMaster disclose non-metallic materials such as aromatic polyamid fibers wound around metal rotating conveyor rolls. However, these patents are limited to the use of such materials as a covering for rotating conveyor rolls for conveying hot glass sheets during thermal treatment and do not suggest using these materials to shield glass sheets from direct exposure to radiation from closely ad~acent heavy metal tempering rings.
U.S. Patent No. 4,525,196 to Fecik et al. discloses a structure in which an exterior metal rail slightly larger than the outline of the supported sheet is used to reinforce a bar or bar portions of phenolic resin reinforced with aramid fibers to provide a support plane inboard of the metal reinforcement rail and above the upper edge of the metal reinforcement rail.
2~6~ 9 The superior physical characteristics of the phenol resin ~preferably polyphenyl formaldehyde reinforced by aramid aromatic polyamide fibers) is discussed in this patent and its disclosure, including a detailed discussion of these characteristics, and is incorporated within this specification by reference. It is noted in passing that the glass engaging member spaces the glass, particularly its edge portion, from the heavy metal reinforcement rail but does not shield the glass from direct exposure to radiation from a closely adjacent heavy metal reinforcing rail.
U.S. Patent Nos. 4,556,407 and 4,556,408 to Fecik et al. disclose spaced metal rails supporting a plurality of blocks spaced above the level of the metal rails to provide spaced support members of a non~metallic material that support hot glass sheets for tempering. The glass engaging members are adjustable in position relative to the spaced rails in both patents and may be pivotal, as in U.S. Patent No. 4,556,407. The glass engaging members of these patents do not shield the glass from direct exposure to radiation from closely adjacent metal rails.
U. S. Patent Application Serial No. 07/590,713 of George R. Claassen et al., filed October 1, 1990, provides a tempering ring construction that further minimizes the thermal effect on the supported glass sheet due to a support member. More particularly, a rigid steel ring is used to reinforce the structural rigidity of an aramid ring-like member whose upper surface engages the glass sheet. The aramid member is constructed and arranged above the rigid steel ring in a position to shield the supported glass sheet's marginal edge portion from substantial direct exposure to heat radiated from a closely adjacent metal support ring when the metal support ring reinforces the aramid ring-like member. The aramid ring-like member also insulates the glass sheet from direct conduction of heat from the slower cooling support ring of 2 ~
heavy metal so as to permit the glass to avoid the establishment of steep thermal gradients during quenching that cause high tension stresses in the glass which may in turn cause glass breakage.
A preferred heat insulating material available commercially that is useful for the glass-engaging ring-like member of this invention is a phenolic resin, preferably polyphenyl formaldehyde, reinforced with aramid fiber available from Spalding Fiber Company, Inc., of Buffalo, New York under the tradename ARR-2~. The term "aramid" is a generic name for a class of aromatic polyamide fibers, preferably synthetic aromatic polyamids that are high molecular weight polymers in which amide linkages (CONH) occur along the molecular chain. Aramid is available from E.I. duPont deNemours and Company, Delaware, under the tradename KEVLAB~. While this material has preferred low thermal conductivity properties, its durability after repeated exposure at elevated temperature to sliding of the bottom edge corner connecting the bottom ma~or surface of the glass sheet to its edge surface leaves something to be desired. It is de~qirable to improve the durability of the insulation material without significantly reducing the heat insulation properties of a structure that improves the durability problem.
The~e and other benefits of this invention will be better understood in the light of a study of a description of preferred embodiment which follows.
Brief DescriDtion of this Invention This invention provides a support rig for shaping and~or tempering heat softened glass sheets that uses a thin metal foil between the previously exposed upper glass sheet engaging 3urface of the insulating member of non-metallic low thermal conductivity material and the sliding 2~64~
edge portion of the glass sheet. It has been found that a metal foil having a thickness of on the order of 0.010 inch (0.25mm) or le~s provides a smooth glass contacting surface that has better durability than the non-metallic low thermal conductivity material and does not cause the resulting structure to have heat-insulating properties significantly inferior to that of the non-metallic low thermal conductivity material that is not covered by said metal foil.
This and other benefits of this invention will be better understood in the light of a description of a preferred embodiment and structural equivalents that follows.
Brief Descri~tion of the Drawin~s Figure 1 is a perspective view of a glass sheet ring incorporating novel features of this invention.
Figure 2 is an enlarged cross-sectional view of a sheet supporting portion of the ring depicted in Figure 1.
Figure 3 is a fragmentary side view of the supporting portion depicted in Figure 2, with the supported glass sheet omitted for clarity.
Figure 4 is a view similar to Figure 2 of an alternate embodiment of this invention.
Description of Preferred Embodiments Although the present invention is illustrated in combination with a ring type structure that may be used to both shape a hot glass sheet and/or support a hot glass sheet during a cooling operation, preferably tempering, it should be appreciated that the invention may be used in other operations where excessive wear of non-metallic, thermally insulating materials is a concern.
2 ~ i 9 Figure 1 shows a perspective view o a ring 10 supported by frame 11 that includes an insulating structure comprising a plurality of peripherally spaced, thermally insulating fingers 12, e.g. aramid fingers, extending laterally inward over a metal support ring or rigid outline rail 14 having the general outline configuration corresponding to that of a glass sheet 6 to be supported. Referring to Figures 2 and 3, each finger 12 thermally insulates a supported glass sheet G from ring 10 and has an upper surface 16 and a lower surface 18. Rail 14 is preferably a solid member provided with a peripherally extending continuous outer frame portion 20 and a plurality of spaced apart, inwardly extending pro~ections 22 whose upper surfaces support the inner portions of a corresponding finger 12 along its lower surface 18. A series of elongated clamps 24 are arranged in end-to-end relation over different portions of the outer frame 20 of outline rail 14. Each clamp 24, which is probably a rigid metal bar, is provided with an attachment means 26. Although not limiting in the present invention, in the particular embodiment shown in Figures 1-3, the attachment means 26 includes one or more screws extending through clamp 24 which engage a threaded aperture located along the outer frame 20 of outline rail 14.
Each finger 12 has an outer portion that rests on the peripherally extending frame portion of rigid outline rail 14 and is clamped in sets by clamps 24 to rail 14. The exact number of fingers 12 secured to ring 14 by a longitudinal curvature of rigid outline rail 14 depends on the size and peripheral curvature of the glass sheet 6 to be supported. Clamps 24 and attachments 26 secure the fingers 12 to rigid outline ra~l 14 so that each finger 12 extends laterally inwardly over a corresponding inwardly extending pro~ection 22 to provide circumferentially spaced supports for the perimeter portion of a supported glass sheet in thermally insulated relation rom ring 2 ~
structure 10. In ~he particular embodiment of the invention shown ln Figures 1-3, the inwardly directed end 28 of each finger 12 is flush with the generally vertlcal face 30 of pro~ection 22, but such an arrangement i9 not required.
Rigid outline rail 14 is machined to be contoured to conform to the elevational and marginal edge shape desired for the glass sheet G, with the upper surface 32 of rigid outline rail 14 and pro~ections 22 inclined downwardly and inwardly. When the rlng 10 is used to initially bend a flat heat softened glass sheet, the spaced fingers 12 restlng on pro~ections 22 initially support a flat glass sheet G along its sharp edge corner formed between its peripheral edge surface and its lower ma~or surface as depicted in solid lines in Figures 2 and 4. After bending, glass sheet G is supported along its marginal edge portion in an inwardly and downwardly oblique plane parallel to upper surface 32 of rigid outline rail 14 and upper surf~ce 16 of fingers 12. A finger 12 is preferably applied with its inner end portion resting substantially flush on the upper surface 32 of a corresponding pro~ection 22 before a clamp 24 secures a set of ad~acent fingers 12 to the outer frame of outline rail 14 to improve the flush contact between fingers 12 and pro~ections 22 of outline rail 14. Clamping forces the fingers 12 to conform into the localized orientation of the rigid metal pro~ections 22 of outline rail 14.
With continued reference to Figures 2 and 3, a covering 34, preferably a metal foil such as but not limited to nichrome ribbon or the like, is applied over upper surface 16 of each finger 12 before a set of the latter is clamped to upper surface 32 of rigid outline rail 14 to provide a wear strip that prctects each finger 12 against premature wear. Although not required, the inwardly directed end 36 may be folded downward over the 2~6~
end 28 of finger 12. The thickness of foil 34 is such that the combination of foil 34 and finger 12 has a heat conductivity that does not differ materially from that of finger 12 without its cover of thin foil 34. Thus, breakage of glass sheets in production has not increased appreciably and the durability of the fingers 12 has increased appreciably.
Although not limiting in the present invention in one particular embodiment, the fingers 12 were aramid members which were 2 inches long by 0.25 inch wide by 0.25 inch high (5.08 cm by 0.64 cm by 0.64 cm). The fingers 12 were sized to overlay a 0.75 inch (1.91 cm) high rigid outline rail 14 having 0.25 inch (0.64 cm) wide pro~ections 22 spaced 0.25 inch (0.64 cm) apart and extending 0.50 inch (1.27 cm) from an outer portion 1.50 inch (3.81 cm) wide. The thin foil 34 was a nichrome ribbon having a width of 0.25 inch (0.64 cm) and a thickness on the order of 0.010 inch (0.25 mm).
Figure 4 shows an alternate embodiment of this invention wherein a metal foil 134 covers only the outer portion of surface 16 of finger 12 where the sharp glass edge corner slides over fingers 12. The surface of the glass about its marginal edge comes into direct contact with an uncovered inner surface portion of fingers 12 only after glass sheet sliding over metal foil 134 due to bending is complete. The effect of any heat capacity of the thin metal foil 134 on the glass edge is further reduced without unduly raising the danger of damage to fingers 12.
It is also withln the scope of this invention to construct the fingers 12 in such a manner that the laterally outer end of each of a set of fingers is interconnected by an outer frame portion (not shown) which overlays the upper surface 32 of outline ring 14 along outer frame 20.
Clamps 24 force the multifingered members, including both the fingers 12 and outer connecting portions, to conform more closely to the upper surface 32 2~6 '9 ~
of a local circumferential portion of rigid outline rail 14 when they clamp the members thereagainst. If desired, the individual foll members 34 may be interconnected in a similar manner.
It is also contemplated that the foil members 34 may be individually glued to each finger 12. As an alternative, the foil 34 may be laminated to a non-metallic insulating material prior to cutting and/or shaping the fingers 34.
While the embodiments of this invention previously described have been limited to those having laterally inwardly extending fingers, it is understood that the thin foil may be applied to cover the upper glass edge supporting surface of any insulating member having any convenient shape to space a glass sheet from direct exposure to a metal outline ring and that any convenient manner of securlng the thin foil to the tempering ring structure other than clamping may be used to keep the foil interposed between a bare glass engaging member of low heat capacity non-metallic material and the glass without departing from the gist of this invention.
Conforming to the requirements of the patent statutes, the inventors have described and illustrated what they presently consider to be preferred embodiments of their invention. However, it is understood that variations may be made within the limits defined by the claimed sub~ect matter that follows without departing from the gist of this invention.
SUPPORT RING WITH WEAR STRIP
BackRround of the Invention 1. Field of the Inventlon This invention relates to a device for transferring hot glass sheets, and in particular relates to th~ type of transfer device that re~urns empty to a shaping station for shaping and/or transferring successive hot glass sheets to a cooling station for heat strengthening or tempering.
2. TechnoloRY Problems and Patents of Interest The prior art has provided devices for transferring hot glass sheets which comprise an outline or ring-type mold of relatively rigid metal that includes an outline upper surface which conforms to the shape of a glass sheet to be transferred slightly inboard of its periphery. The glass sheet is heated and either pressed to shape between an upper mold and the ring-type mold or between complementary molds and subseguently transferred to the ring-type mold or sagged by heat and gravity to the shape provlded by the upper shaping surface of the mold. After the glass sheet is shaped, it is transferred while supported on the ring-type mold to a quenching station where it is quenched suddenly and rapidly by applying cold air blasts against the supported lower surface and the upper exposed surface of the glass sheet.
Heating the glass sheet to its softening temperature followed by sudden chilling develops a stress pattern characteristic of tempered glass that includes a surface zone highly stressed in compression surrounding an interior zone stressed in tension. This stress pattern reduces the tendency of the tempered glass sheet to bre&k, particularly lf the surface zone is highly stressed. Furthermore, if tempered glass is fractured, it forms a 2 ~
number of small particles that are less dangerous than relatively large, ~agged fragments that result from the breakage of untempered glass.
When a shaped glass sheet contacts a hot, heavy metal rail during this rapid cooling, glass breakage can result from surface venting due to high tension stresses established locally at the glass-metal contact areas. The prior art has recognized ~hat the difference in heat conductivity between the glass sheet supported on the mold and the relatively heavy metal mold ring during rapid cooling causes these high tension stresses in the hot shaped glass sheet in the areas contacting the glasq supporting rail. Hence, in recent years, the art has developed a ring-like member having a glass sheet supporting surface composed of non-metallic material having a low coefficient of thermal conductivity to insulate the glass from the heavy metal ring mold.
One effective non-metallic material used as a glass engaging member of a ring-type support consists essentially of a phenolic resin, preferably polyphenyl formaldehyde, reinforced with fibers composed of an aromatic polyamide composition. This reinforced material is popularly termed aramid and will be so identified hereafter in this specification.
The material used to engage the glass is reinforced structurally either by thickening its lower portion, which makes a ring-like member used as a non-metallic tempering ring awkward to handle because of the thickness needed for rigidity, or the glass engaging material is hugged and surrounded by a relatively heavy metal rail slightly larger than the outline of the supported glass sheet or otherwise reinforced to impart rigidity to the non-metallic glass engaging material. Tempering ring structures comprising a ring-like member of aramid reinforced with a hugging heavy metal support ring have produced results superior to the prior art by maintaining the glass sheet in contact with the fiber reinforced phenolic resin material in spaced 20~4~1~
relation over the heavy metal rail of the tempering ring. However, still better results are desired to be consistent with an objective of manufacturing larger glass sheets of more complicated shapes than in the prior art with even less marking or venting than previously experienced.
U.S. Patent No. 3,586,492 to McMaster discloses a glass sheet support for a press shaping apparatus. The support includes an endless ring frame having teeth with extended edge portions that contact the surface of the glass sheet along it periphery. A wire mesh is disposed over the edges for contacting the sheet.
U.S. Patent No. 3,741,743 to Seymour discloses a glass sheet shaping frame for engaging the peripheral portion of a glass sheet during shaping and tempering. A pair of spaced apart rigid rail are positioned about the periphery of the glass sheet and a screen member spans between the rails to provide a glass sheet engaging surface. The screen member is preferably a heavy gauge mesh overlaid by a fine wire mesh.
U.S. Patent No. 3,973,943 to Seymour discloses an outline ring~like transfer device for supporting shaped glass sheets after they are shaped and during the time they are rapidly guenched. The device includes a rigid, outline metal rail having an outline slightly smaller than that of the shaped glass sheet and a bar or plurality of closely spaced bar members of non-metallic materi~l having a lower heat transfer coefficient than that of the rigid metal rail. The bar members are mo~mted in hugging relation against the rigid metal rail in position to conform to the outline rail. An upper edge portion of the bar or bar members is disposed above the upper edge of the rigid metal rail in a position to provide a glass sheet supporting surface in spaced relation above the upper edge of the rigid metal rail. The bar or bar members of the Seymour patent are composed of a laminated structure, such as 2~6~ 9 fiber glass cloth or asbestos woven paper layers or the like, bonded together with a silicone resin binder or a phenolic resin binder. The glass engaging materials of this patent have been replaced by superior aramid materials disclosed in the following patent.
U.S. Patent Nos. 4,282,026 and 4,361,432 to McMaster et al. disclose the use of a helical spring wound over a solid heavy metal tempering ring closely adjacent to the glass to space the glass from direct contact with the heavy metal tempering ring and thus reduce the cooling rate differences between the glass and the metal. The helical spring in these patents do not shield the glass from direct exposure to radiation from a closely ad~acent tempering ring.
U.S. Patent No. 4,356,018 to McMaster discloses a method and apparatus for deep bending glass sheets. The lower bending mold is of a ring-type construction and includes a wire mesh covering to prevent chilling of the heated glass sheet when it is received by the ring mold for bending.
U.S. Patent Nos. 4,363,163 and 4,421,482 to McMaster disclose non-metallic materials such as aromatic polyamid fibers wound around metal rotating conveyor rolls. However, these patents are limited to the use of such materials as a covering for rotating conveyor rolls for conveying hot glass sheets during thermal treatment and do not suggest using these materials to shield glass sheets from direct exposure to radiation from closely ad~acent heavy metal tempering rings.
U.S. Patent No. 4,525,196 to Fecik et al. discloses a structure in which an exterior metal rail slightly larger than the outline of the supported sheet is used to reinforce a bar or bar portions of phenolic resin reinforced with aramid fibers to provide a support plane inboard of the metal reinforcement rail and above the upper edge of the metal reinforcement rail.
2~6~ 9 The superior physical characteristics of the phenol resin ~preferably polyphenyl formaldehyde reinforced by aramid aromatic polyamide fibers) is discussed in this patent and its disclosure, including a detailed discussion of these characteristics, and is incorporated within this specification by reference. It is noted in passing that the glass engaging member spaces the glass, particularly its edge portion, from the heavy metal reinforcement rail but does not shield the glass from direct exposure to radiation from a closely adjacent heavy metal reinforcing rail.
U.S. Patent Nos. 4,556,407 and 4,556,408 to Fecik et al. disclose spaced metal rails supporting a plurality of blocks spaced above the level of the metal rails to provide spaced support members of a non~metallic material that support hot glass sheets for tempering. The glass engaging members are adjustable in position relative to the spaced rails in both patents and may be pivotal, as in U.S. Patent No. 4,556,407. The glass engaging members of these patents do not shield the glass from direct exposure to radiation from closely adjacent metal rails.
U. S. Patent Application Serial No. 07/590,713 of George R. Claassen et al., filed October 1, 1990, provides a tempering ring construction that further minimizes the thermal effect on the supported glass sheet due to a support member. More particularly, a rigid steel ring is used to reinforce the structural rigidity of an aramid ring-like member whose upper surface engages the glass sheet. The aramid member is constructed and arranged above the rigid steel ring in a position to shield the supported glass sheet's marginal edge portion from substantial direct exposure to heat radiated from a closely adjacent metal support ring when the metal support ring reinforces the aramid ring-like member. The aramid ring-like member also insulates the glass sheet from direct conduction of heat from the slower cooling support ring of 2 ~
heavy metal so as to permit the glass to avoid the establishment of steep thermal gradients during quenching that cause high tension stresses in the glass which may in turn cause glass breakage.
A preferred heat insulating material available commercially that is useful for the glass-engaging ring-like member of this invention is a phenolic resin, preferably polyphenyl formaldehyde, reinforced with aramid fiber available from Spalding Fiber Company, Inc., of Buffalo, New York under the tradename ARR-2~. The term "aramid" is a generic name for a class of aromatic polyamide fibers, preferably synthetic aromatic polyamids that are high molecular weight polymers in which amide linkages (CONH) occur along the molecular chain. Aramid is available from E.I. duPont deNemours and Company, Delaware, under the tradename KEVLAB~. While this material has preferred low thermal conductivity properties, its durability after repeated exposure at elevated temperature to sliding of the bottom edge corner connecting the bottom ma~or surface of the glass sheet to its edge surface leaves something to be desired. It is de~qirable to improve the durability of the insulation material without significantly reducing the heat insulation properties of a structure that improves the durability problem.
The~e and other benefits of this invention will be better understood in the light of a study of a description of preferred embodiment which follows.
Brief DescriDtion of this Invention This invention provides a support rig for shaping and~or tempering heat softened glass sheets that uses a thin metal foil between the previously exposed upper glass sheet engaging 3urface of the insulating member of non-metallic low thermal conductivity material and the sliding 2~64~
edge portion of the glass sheet. It has been found that a metal foil having a thickness of on the order of 0.010 inch (0.25mm) or le~s provides a smooth glass contacting surface that has better durability than the non-metallic low thermal conductivity material and does not cause the resulting structure to have heat-insulating properties significantly inferior to that of the non-metallic low thermal conductivity material that is not covered by said metal foil.
This and other benefits of this invention will be better understood in the light of a description of a preferred embodiment and structural equivalents that follows.
Brief Descri~tion of the Drawin~s Figure 1 is a perspective view of a glass sheet ring incorporating novel features of this invention.
Figure 2 is an enlarged cross-sectional view of a sheet supporting portion of the ring depicted in Figure 1.
Figure 3 is a fragmentary side view of the supporting portion depicted in Figure 2, with the supported glass sheet omitted for clarity.
Figure 4 is a view similar to Figure 2 of an alternate embodiment of this invention.
Description of Preferred Embodiments Although the present invention is illustrated in combination with a ring type structure that may be used to both shape a hot glass sheet and/or support a hot glass sheet during a cooling operation, preferably tempering, it should be appreciated that the invention may be used in other operations where excessive wear of non-metallic, thermally insulating materials is a concern.
2 ~ i 9 Figure 1 shows a perspective view o a ring 10 supported by frame 11 that includes an insulating structure comprising a plurality of peripherally spaced, thermally insulating fingers 12, e.g. aramid fingers, extending laterally inward over a metal support ring or rigid outline rail 14 having the general outline configuration corresponding to that of a glass sheet 6 to be supported. Referring to Figures 2 and 3, each finger 12 thermally insulates a supported glass sheet G from ring 10 and has an upper surface 16 and a lower surface 18. Rail 14 is preferably a solid member provided with a peripherally extending continuous outer frame portion 20 and a plurality of spaced apart, inwardly extending pro~ections 22 whose upper surfaces support the inner portions of a corresponding finger 12 along its lower surface 18. A series of elongated clamps 24 are arranged in end-to-end relation over different portions of the outer frame 20 of outline rail 14. Each clamp 24, which is probably a rigid metal bar, is provided with an attachment means 26. Although not limiting in the present invention, in the particular embodiment shown in Figures 1-3, the attachment means 26 includes one or more screws extending through clamp 24 which engage a threaded aperture located along the outer frame 20 of outline rail 14.
Each finger 12 has an outer portion that rests on the peripherally extending frame portion of rigid outline rail 14 and is clamped in sets by clamps 24 to rail 14. The exact number of fingers 12 secured to ring 14 by a longitudinal curvature of rigid outline rail 14 depends on the size and peripheral curvature of the glass sheet 6 to be supported. Clamps 24 and attachments 26 secure the fingers 12 to rigid outline ra~l 14 so that each finger 12 extends laterally inwardly over a corresponding inwardly extending pro~ection 22 to provide circumferentially spaced supports for the perimeter portion of a supported glass sheet in thermally insulated relation rom ring 2 ~
structure 10. In ~he particular embodiment of the invention shown ln Figures 1-3, the inwardly directed end 28 of each finger 12 is flush with the generally vertlcal face 30 of pro~ection 22, but such an arrangement i9 not required.
Rigid outline rail 14 is machined to be contoured to conform to the elevational and marginal edge shape desired for the glass sheet G, with the upper surface 32 of rigid outline rail 14 and pro~ections 22 inclined downwardly and inwardly. When the rlng 10 is used to initially bend a flat heat softened glass sheet, the spaced fingers 12 restlng on pro~ections 22 initially support a flat glass sheet G along its sharp edge corner formed between its peripheral edge surface and its lower ma~or surface as depicted in solid lines in Figures 2 and 4. After bending, glass sheet G is supported along its marginal edge portion in an inwardly and downwardly oblique plane parallel to upper surface 32 of rigid outline rail 14 and upper surf~ce 16 of fingers 12. A finger 12 is preferably applied with its inner end portion resting substantially flush on the upper surface 32 of a corresponding pro~ection 22 before a clamp 24 secures a set of ad~acent fingers 12 to the outer frame of outline rail 14 to improve the flush contact between fingers 12 and pro~ections 22 of outline rail 14. Clamping forces the fingers 12 to conform into the localized orientation of the rigid metal pro~ections 22 of outline rail 14.
With continued reference to Figures 2 and 3, a covering 34, preferably a metal foil such as but not limited to nichrome ribbon or the like, is applied over upper surface 16 of each finger 12 before a set of the latter is clamped to upper surface 32 of rigid outline rail 14 to provide a wear strip that prctects each finger 12 against premature wear. Although not required, the inwardly directed end 36 may be folded downward over the 2~6~
end 28 of finger 12. The thickness of foil 34 is such that the combination of foil 34 and finger 12 has a heat conductivity that does not differ materially from that of finger 12 without its cover of thin foil 34. Thus, breakage of glass sheets in production has not increased appreciably and the durability of the fingers 12 has increased appreciably.
Although not limiting in the present invention in one particular embodiment, the fingers 12 were aramid members which were 2 inches long by 0.25 inch wide by 0.25 inch high (5.08 cm by 0.64 cm by 0.64 cm). The fingers 12 were sized to overlay a 0.75 inch (1.91 cm) high rigid outline rail 14 having 0.25 inch (0.64 cm) wide pro~ections 22 spaced 0.25 inch (0.64 cm) apart and extending 0.50 inch (1.27 cm) from an outer portion 1.50 inch (3.81 cm) wide. The thin foil 34 was a nichrome ribbon having a width of 0.25 inch (0.64 cm) and a thickness on the order of 0.010 inch (0.25 mm).
Figure 4 shows an alternate embodiment of this invention wherein a metal foil 134 covers only the outer portion of surface 16 of finger 12 where the sharp glass edge corner slides over fingers 12. The surface of the glass about its marginal edge comes into direct contact with an uncovered inner surface portion of fingers 12 only after glass sheet sliding over metal foil 134 due to bending is complete. The effect of any heat capacity of the thin metal foil 134 on the glass edge is further reduced without unduly raising the danger of damage to fingers 12.
It is also withln the scope of this invention to construct the fingers 12 in such a manner that the laterally outer end of each of a set of fingers is interconnected by an outer frame portion (not shown) which overlays the upper surface 32 of outline ring 14 along outer frame 20.
Clamps 24 force the multifingered members, including both the fingers 12 and outer connecting portions, to conform more closely to the upper surface 32 2~6 '9 ~
of a local circumferential portion of rigid outline rail 14 when they clamp the members thereagainst. If desired, the individual foll members 34 may be interconnected in a similar manner.
It is also contemplated that the foil members 34 may be individually glued to each finger 12. As an alternative, the foil 34 may be laminated to a non-metallic insulating material prior to cutting and/or shaping the fingers 34.
While the embodiments of this invention previously described have been limited to those having laterally inwardly extending fingers, it is understood that the thin foil may be applied to cover the upper glass edge supporting surface of any insulating member having any convenient shape to space a glass sheet from direct exposure to a metal outline ring and that any convenient manner of securlng the thin foil to the tempering ring structure other than clamping may be used to keep the foil interposed between a bare glass engaging member of low heat capacity non-metallic material and the glass without departing from the gist of this invention.
Conforming to the requirements of the patent statutes, the inventors have described and illustrated what they presently consider to be preferred embodiments of their invention. However, it is understood that variations may be made within the limits defined by the claimed sub~ect matter that follows without departing from the gist of this invention.
Claims (10)
1. An apparatus for supporting a hot shaped glass sheet of given size and outline during thermal treatment comprising:
rigid support rail means with an upper surface similar in shape and plan outline to said outline shape of said shaped glass sheet;
at least one discrete insulating member of a non-metallic material having a coefficient of thermal conductivity less than that of said support rail means constructed and arranged to space said supported glass sheet over said support rail means;
means to secure said insulating member in a position overlaying at least a portion of said support rail means;
a thin, elongated abrasion resistant covering having a smooth upper glass sheet contacting surface; and means to secure said covering in overlaying relation to said upper surface of said insulating member to enable an edge portion of said supported glass sheet to slide thereover without harming said insulating member.
rigid support rail means with an upper surface similar in shape and plan outline to said outline shape of said shaped glass sheet;
at least one discrete insulating member of a non-metallic material having a coefficient of thermal conductivity less than that of said support rail means constructed and arranged to space said supported glass sheet over said support rail means;
means to secure said insulating member in a position overlaying at least a portion of said support rail means;
a thin, elongated abrasion resistant covering having a smooth upper glass sheet contacting surface; and means to secure said covering in overlaying relation to said upper surface of said insulating member to enable an edge portion of said supported glass sheet to slide thereover without harming said insulating member.
2. The apparatus as in claim 1 wherein said covering is a metallic foil.
3. The apparatus as in claim 2 wherein said foil has a thickness sufficiently thick to be durable when exposed to said glass sheet sliding thereover and sufficiently thin such that said insulating member combined with said foil covering has a thermal conductivity approximately that of said insulating member in the absence of said foil covering.
4. The apparatus as claim 2 wherein said rigid support rail means has a generally continuous outer frame portion and a plurality of inwardly extending projections, said upper surface of said support rail means being formed by said outer frame portion and said projections slope downwardly and inwardly, generally corresponding to the contour of said glass sheet about its outline and further wherein said at least one discrete insulating member includes a plurality of insulating members each of which comprises an elongated finger having an inner portion supported on a corresponding projection of said support rail means and an outer portion supported on said outer frame portion.
5. The apparatus as in claim 4 wherein said insulating member securing means and said covering securing means includes a clamp member having means to secure adjacent sets of said fingers and corresponding foil coverings to said upper surface of said support rail means.
6. The apparatus as in claim 4, wherein said metal foil covering includes a strip superimposed over only an outer portion of each said fingers, said foil being constructed and arranged relative to said finger such that a glass sheet positioned on said apparatus is supported with its corner edges resting on said foil covering when said glass sheet is in a flat configuration but is supported with said edges resting laterally inward of said foil covering on an exposed portion of said upper surface of said finger when said supported glass sheet is in a bent configuration.
7. The apparatus as in claim 4 further including means to interconnect selected adjacent fingers.
8. The apparatus as in claim 4 further including means to interconnect selected foil coverings.
9. The apparatus as in claim 4 wherein said foil covering and said finger are laminated together to form an integral structure.
10. The invention or inventions substantially as herein described and with reference to any of the preceding claims.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US71615591A | 1991-06-17 | 1991-06-17 | |
| US716,155 | 1991-06-17 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2064519A1 true CA2064519A1 (en) | 1992-12-18 |
Family
ID=24876983
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002064519A Abandoned CA2064519A1 (en) | 1991-06-17 | 1992-03-31 | Support ring with wear strip |
Country Status (3)
| Country | Link |
|---|---|
| CA (1) | CA2064519A1 (en) |
| FR (1) | FR2677638A1 (en) |
| IT (1) | IT1258968B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5679124A (en) * | 1995-08-02 | 1997-10-21 | Glasstech, Inc. | Cooling ring assembly for controlling stresses in a formed glass sheet |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5385786A (en) * | 1993-02-09 | 1995-01-31 | Glasstech, Inc. | Apparatus and method for controlling stresses in laminated automotive glass |
-
1992
- 1992-03-31 CA CA002064519A patent/CA2064519A1/en not_active Abandoned
- 1992-06-10 IT ITMI921430A patent/IT1258968B/en active IP Right Grant
- 1992-06-12 FR FR9207078A patent/FR2677638A1/en not_active Withdrawn
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5679124A (en) * | 1995-08-02 | 1997-10-21 | Glasstech, Inc. | Cooling ring assembly for controlling stresses in a formed glass sheet |
| US5865866A (en) * | 1995-08-02 | 1999-02-02 | Glasstech, Inc. | Method for controlling stresses in a formed glass sheet |
Also Published As
| Publication number | Publication date |
|---|---|
| ITMI921430A1 (en) | 1993-12-10 |
| IT1258968B (en) | 1996-03-11 |
| FR2677638A1 (en) | 1992-12-18 |
| ITMI921430A0 (en) | 1992-06-10 |
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| EEER | Examination request | ||
| FZDE | Discontinued |