Method and apparatus for delivering a cased glass stream

Abstract: Apparatus (10) for forming a cased glass stream having an inner core glass surrounded by an outer casing glass includes a spout (13) for receiving core glass from a first source (12) and delivering such glass through a first orifice (22). A second orifice (28) is vertically spaced beneath and aligned with the first orifice, and is surrounded by an annular chamber (30) that communicates with the second orifice through the gap between the first and second orifices. A tube (32) delivers casing glass from a second source (40) to the annular chamber in such a way that glass flows by gravity from the first and second sources through the orifices to form the cased glass stream. The core glass delivery spout includes a reservoir (12) for receiving and holding the core glass, and having at least one lower opening (16) of a first diameter. An orifice ring (24) is positioned beneath the reservoir, and has at least one opening of second diameter less than the first diameter aligned with the first opening and forming the first orifice (22). A collar of uniform inside diameter equal to the first diameter extends from the first opening to the orifice ring, and thereby spaces the reservoir from the orifice ring so as to increase hydrostatic head pressure on glass flowing from the reservoir through the first orifice. The core glass reservoir is surrounded by a metal casing (18), and the casing glass delivery tube extends through a notch in the sidewall of the core glass casing. An air-cooled liner controls heat transfer from the casing glass delivery tube to the core glass reservoir.

Description: The present invention is directed to delivery of a glass stream for forming glass charges for glassware manufacture, and more particularly to a method and apparatus for delivering a so-called cased glass stream in which an inner or core glass is surrounded by an outer or casing glass layer. Background of the Invention It has heretofore been proposed to provide a cased glass stream for forming glassware having layered wall segments. EP-A-0 722 707 and EP-A-0 722 908 disclose techniques for delivering such a cased glass stream in which core glass from a first source is delivered through a first orifice of a first orifice ring. A second orifice of a second orifice ring is vertically spaced beneath and aligned with the first orifice. A gap is arranged between the first orifice ring and the second orifice ring and is surrounded by an annular chamber that communicates with the second orifice through the gap between the first and second orifice rings. A heated tube delivers casing glass from a second glass source to the annular chamber. Glass flows by force of gravity from the first and second sources through the first orifice and the gap in such a way that a cased glass stream emerges from the second orifice. This cased glass stream may be sheared by conventional techniques to form individual cased glass gobs for delivery to conventional individual section glassware forming machines. Although the techniques disclosed in the noted patent applications address and overcome problems theretofore extant in the art, e.g. the gravitational force that forces the core glass through the orifices is increased here so as to increase flow rate and uniformity of the cased glass stream, further improvements remain desirable. For example, the heated tube that delivers the casing glass to the annular chamber passes closely adjacent to the core glass reservoir, and it has been found desirable to control heat exchange between the casing glass delivery tube and the core glass reservoir and glass delivery elements. Summary of the Invention The invention is based on the problem of controlling the heat exchange between the casing glass delivery tube and the glass delivery elements, and, preferably, the core glass reservoir. The invention is defined in claims 1 and 14. In an embodiment of the invention, the apparatus for forming a cased glass stream having an inner core glass surrounded by an outer casing glass includes a spout for receiving core glass from a first source and delivering such glass through a first orifice of a first orifice ring. A second orifice ring is vertically spaced by a gap beneath and aligned with the first orifice ring, and the gap is surrounded by an annular chamber. A tube delivers the casing glass from a second source to the annular chamber in such a way that glass flows by gravity from the first and second sources through the second orifices to form the cased glass stream. In accordance with the present invention, the core glass delivery spout includes a reservoir for receiving and holding the core glass, and having at least one lower outlet opening of first diameter. The first orifice of the first orifice ring is of a second diameter which is less than the first diameter. A collar of uniform inside diameter equal to the first diameter extends from the outlet opening to the first orifice ring, and thereby spaces the reservoir from the first orifice ring so as to increase hydrostatic head pressure on glass flowing from the reservoir through the first orifice. The collar is externally surrounded by an electrical resistance-heating element for heating the collar and thereby promoting flow of glass from the reservoir through the collar, particularly during initiation of glass flow. The collar in the preferred embodiment of the invention is of ceramic composition, and has an inner liner of metal such as platinum for preventing leakage of glass through the collar in the event of fracture. The collar and the reservoir form an abutment joint surrounding the opening at the bottom of the reservoir, and this joint is cooled to control leakage of glass through the joint. The joint cooling mechanism preferably comprises a segmented hollow band through which cooling air flows. In accordance with another preferred embodiment of the present invention, the core glass reservoir is surrounded by a protective casing. A vertically oriented notch or pocket is formed in this casing for receiving the heated casing glass delivery tube, An air-cooled metal band heat exchanger is positioned in the casing notch between the casing and the tube to control heat transfer between the tube and the casing, and thus between the casing glass delivery tube and the core glass reservoir. Brief Description of the Drawings The invention, together with additional objects, features and advantages thereof, will be best understood from the following description, the appended claims and the accompanying drawings in which: FIG. 1 is a fragmentary elevational schematic diagram of a glass delivery system in accordance with a presently preferred embodiment of the invention; FIG. 2 is a fragmentary sectional view on an enlarged scale of a portion of the delivery system illustrated in FIG. 1; FIG. 3 is a sectional view taken substantially along the line 3-3 in FIG. 2; FIG. 4 is a sectional view taken substantially along the line 4-4 in FIG. 2; FIG. 5 is an exploded plan view of the reservoir/collar cooling assembly illustrated in FIG. 4; and FIG. 6 is a sectional view of one of the cooling band elements illustrated in FIG. 5. Detailed Description of Preferred Embodiments FIG. 1 illustrates a system 10 for delivering a stream of cased glass. A first forehearth 12 delivers core glass to a reservoir or bowl 14 that has at least one opening 16 (usually several openings) at the lower end thereof. Reservoir 14 is surrounded by a protective casing 18, preferably constructed of non-magnetic metal such as stainless steel. A tube 20 controls delivery of core glass from reservoir 14 through opening 16 to and through a first orifice 22 carried by an upper orifice ring 24 beneath reservoir 14. A lower orifice ring 26 carries a second orifice 28 positioned beneath orifice 22 by a gap and axially aligned with the first orifice. The gap is surrounded by an annular chamber 30 formed between portions of the orifice rings 22, 26. The lateral space or gap allows the casing glass to flow through the lower orifice 28. Annular chamber 30 is coupled by a delivery tube 32 to the opening 34 at the lower end of a casing glass spout 36. Spout 36 includes a delivery control tube 38, and is coupled to a casing glass forehearth 40. Delivery tube 32 is resistance heated by control electronics 42 for maintaining flow of casing glass to chamber 30. To the extent thus far described, system 10 in FIG. 1 is essentially the same as disclosed in above-noted EP-A-0 722 907 and EP-A-0 722 908. The former of such applications is directed in particular to construction of casing glass delivery tube 32, while the latter of such applications is directed in particular to construction of orifice rings 24, 26. FIG. 2 illustrates core glass spout 13 in greater detail. An extension collar 44 extends from the lower end of reservoir 14 to the upper end of orifice ring 24. Collar 44 has a uniform inside diameter equal to the diameter of opening 16 in reservoir 14 and greater than the inside diameter of orifice 22 in orifice ring 24. Collar 44 is preferably of ceramic composition, as are reservoir bowl 14 and orifice ring 24. Collar 44 thus serves to elevate reservoir 14 with respect to orifice ring 24 so as to increase hydrostatic pressure on the core glass that flows from reservoir 14 through orifice 22, and thereby increase both core glass and casing glass flow rates. Collar 44 is surrounded by an electrical resistance heating element 46 (FIGS. 2 and 3) to boost heating of collar 44 from that caused by conduction from gas burner assemblies at reservoir 14 and lower orifice ring 26. Such heating of collar 44 helps promote core glass flow, particularly during startup. A cylindrical sheath 48 of platinum or other corrosion-resistant metal lines the inner surface of collar 44, having an outwardly projecting circumferential flange 50 captured between the lower end of reservoir bowl 14 and the upper end of collar 44. Platinum sheath 48 prevents leakage of glass through extension collar 44 in the event of cracking or fracture of the latter. A lip may also be formed at the lower end of sheath 48 to help reenfcrce the sheath and hold it in position over collar 44. Inasmuch as reservoir 14 and collar 44 comprise different ceramic castings, glass can leak at the joint between the lower end of the reservoir bowl and the upper end of the collar. Externally applied heat to collar 44 can aggravate this leakage, and prevent slowing and hardening of leaking glass by devitrification. In order to cool this joint enough to cause glass devitrification and thereby arrest leakage, an air-cooled metal band 52 (FIGS. 2 and 4-6) radially outwardly surrounds this joint. Band 52 comprises four identical hollow arcuate segments 54. Each segment has an inlet 56 which interiorily extends from one end into the hollow segment to adjacent the opposing end, and from which air can flow along the inner wall surfaces of each segment to an air outlet 58. The four segments 54 are clamped in end-adjacent position surrounding the reservoir/collar joint by means of a clamp ring 60. Clamp ring 60 is circumferentially compressed by means of a coil spring 62, which accommodates expansion of clamp ring 60 and cooling band 52 caused by thermal expansion of collar 44 and reservoir 14. Joint temperature is monitored and cooling air is routed through band 52 so as to maintain the temperature of the joint sufficiently low so as to cause devitrification of glass leakage, while sufficiently high to insure that devitrified glass crystals do not form within the main glass stream. Delivery tube 32 extends downwardly from casing glass spout 36 closely adjacent to and intersecting core glass reservoir casing 18. In order to accommodate passage of delivery tube 32, , a pocket or notch 64 is formed in the sidewall of casing 18. This notch or pocket allows delivery tube 32 to nest closer to orifice ring 24 and orifice 22. An air-jacketed metal liner plate 66 is disposed within notch 64 between delivery tube 32 and the material of casing 18. Air flow is directed through plate 66 to maintain plate 66 and casing 18 at a temperature low enough to reduce glass leakage while hot enough to minimize thermal disturbances to glass flow either through orifice 22 or delivery tube 32. Cooling air is delivered to plate 66 by means of inlet tubes 68.

Claims: An apparatus for forming a cased glass stream having an inner core glass surrounded by an outer casing glass, said apparatus including: a spout (13) for receiving core glass from a first source (12) and delivering such glass through a first orifice (22) formed by first orifice forming means (24), second orifice forming means (26) forming a second orifice (28) vertically spaced beneath and aligned with said first orifice, a gap being provided between said first orifice forming means (24) and said second orifice forming means (26) and an annular chamber (30) surrounding said gap and communicating with said second orifice (28) means (32, 34, 36) for delivering casing glass from a second source (40) to said annular chamber such that glass flows by gravity from said first and second sources through said orifices to form said cased glass stream, the spout comprising a reservoir (14) for receiving and holding said core glass and having at its lower end at least one outlet opening (16) of a first diameter, said first orifice forming means (24) including an orifice ring (24) positioned beneath said reservoir (14) and having said first orifice (22) which is of a second diameter less than said first diameter and aligned with said outlet opening (16) a collar (44) extending from said outlet opening (16) to said orifice ring (24) and thereby providing a spacing between said reservoir (14) and said orifice ring (24) so as to increase hydrostatic pressure on glass flowing from said reservoir (14) through said first orifice (22), said collar (44) and said reservoir (14) forming an abutment joint surrounding said outlet opening (16), characterized in that means (52) for cooling said joint is provided so as to control leakage of glass through said joint, and in that said collar (44) has an uniform inside diameter equal to said first diameter. The apparatus set forth in claim 1 further comprising means (46) disposed externally around said collar (44) for heating said collar and thereby promoting flow of glass from said reservoir (14) through said collar. The apparatus set forth in claim 1 or 2 wherein said heating means (46) comprises electrical heating means. The apparatus set forth in claim 1, 2 or 3 wherein said collar (44) is of ceramic composition. The apparatus set forth in any of claims 1 to 4 wherein said collar has a metal liner (48) extending from said first opening (16) to said orifice ring (24) for preventing leakage of glass through said collar in the event of fracture of said collar. The apparatus set forth in any of claims 1 to 5 wherein said cooling means (52) comprises a hollow band (54) surrounding said joint and means for delivering cooling air to said band. The apparatus set forth in claim 6 wherein said band (54) is circumferentially segmented around said collar for accommodating thermal expansion of said collar. The apparatus set forth in claim 7 further comprising clamp means (60, 62) for holding said segmented cooling band in place around said joint. The apparatus set forth in claim 8 wherein said clamp means (60, 62) include spring means (62) for maintaining clamping pressure on said band segments while accommodating expansion as a result of heating of said reservoir and collar. The apparatus set forth in any of claims 1-9 wherein said spout (13) further comprises a casing (18) surrounding said reservoir (14), said casing having a side notch (64) through which extends said means (32) for delivering casing glass from said second source (40) to said annular chamber (30). The apparatus set forth in claim (10) wherein said means for delivering casing glass comprises a heated tube (32), and wherein said apparatus further comprises means (66) in said notch (64) for controlling heat transfer between said tube and said casing (18). The apparatus set forth in claim 11 wherein said heat transfer controlling means (66) comprises an air cooled metal band heat exchange. A method of forming a glass stream comprising a first inner layer and a second outer layer wherein the method comprises the following steps: providing a spout (13) comprising a reservoir (14), a collar (44) and means (22) forming a first orifice, the reservoir (14) being connected through an abutment joint to said collar (44), which extends vertically downward to said means (24) forming said first orifice (22), delivering molten glass from a first source (12) through said spout and through said first orifice (22), providing a resistance heated tube assembly (32) having an inlet end and an outlet end providing means (26) forming a second orifice (28) in vertically spaced aligned relation below said first orifice (22), providing a gap between said first orifice forming means (24) and said second orifice forming means (26) providing an annular chamber (30) around said gap, providing a resistance heated tube assembly (32) having an inlet end and an outlet end, positioning said tube assembly such that its outlet end is connected to said annular chamber (30) and its inlet end is connected to a second glass source (40), delivering glass from said first source through said first orifice to and through said second orifice, and delivering glass from said second source through said resistance heated tube assembly (32) and from the outlet end of said resistance heated tube assembly to said annular chamber and into the gap such that said glass from said second source provides an outer layer to said glass from said first source and the glass stream flowing through said second orifice comprises said first inner layer and said second outer layer. characterized by the step of providing means (52) for cooling said abutment joint between the reservoir (14) and the collar (44) so as to control leakage of glass through the joint. The method set forth in claim 13 including providing an electrical heating element (46) about said collar (44) to boost heating of said collar (44) above that caused by conduction from gas burner assemblies at the reservoir (14) and the lower orifice ring (26). The method set forth in claims 13 or 14 including providing a casing (18) about said electrically heated collar (44) and providing a generally vertical notch (64) in the lower end of said casing adjacent said annular chamber (30) into which said tube assembly (32) is positioned. The method set forth in claim 15 including providing cooling means (66) adjacent to said notch (64). The method set forth in claim 16 wherein said step of providing cooling means (66) comprises providing a hollow chamber and delivering cooling air through said chamber. The method set forth in claim 17 wherein said step of providing said casing (18) comprises making said casing of non-magnetic metal. The method set forth in claim 18 wherein said step of providing said casing (18) comprises making said casing of stainless steel.

Inventors: SCOTT GARRETT L, SCOTT, GARRETT L.
Applicants: OWENS BROCKWAY GLASS CONTAINER, OWENS-BROCKWAY GLASS CONTAINER INC.
Application year: 1997
Main classification: C03B7
IPC codes: C03B17, C03B7, C03B9