Apparatus and its use 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 first orifice (22) for receiving core glass from a first source (12), and a second orifice (28) vertically spaced beneath and aligned with the first orifice. A chamber (30) surrounds the second orifice and communicates with the second orifice through a metering gap (42) between the first and second orifices. Casing glass is delivered from a second source (40) to one side (44) of the chamber such that glass flows by gravity from both the first and second sources through the orifices to form the cased glass stream. In accordance with one aspect of the present invention, the metering gap (42) is of non-uniform dimension around the chamber, providing greater resistance to glass flow through the metering gap on a side thereof adjacent to the side of the chamber that receives casing glass from the second source and less resistance to glass flow through the metering gap on the side thereof remote from the side of the chamber that receives the casing glass.

Description: The present invention is directed to delivery of a glass stream for-forming glass charges or gobs for glassware manufacture, and more particularly to an 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-0 722 907 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. A second orifice is vertically spaced beneath and aligned with the first orifice. An annular chamber has an annular gap between the first and second orifices. A heated tube delivers casing glass from a second glass source to the annular chamber that surrounds the gap. 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 documents address and overcome problems theretofore extant in the art, further improvements remain desirable. For example, a problem remains concerning uniformity of distribution of casing glass thickness around the circumference of the core glass stream. EP-A-0 722 908, on which the preamble of claim 1 is based, teaches that the dimensions of the annular gap between the first and second orifices, both in the direction parallel to local glass flow therethrough and the direction perpendicular to local glass flow therethrough, are chosen to provide flow resistance sufficient to create a uniform inward flow of casing glass at all points circumferentially around each gap. This means a high resistance in the gap, compared to a relative low resistance along the remaining flow lines in the supply passage. In implementation of this technique, it has been found that the casing glass can vary in thickness by a ratio of up to 2/1 around the circumference of the core glass stream. Summary of the Invention It is therefore a general object of the present invention to provide an apparatus for delivering a cased glass stream that obtains improved uniformity of casing glass thickness around the circumference of the cased glass stream. The invention is defined in claims 1 and 9. In the apparatus of the invention, the metering gap between the aligned orifices is dimensioned with respect to the surrounding chamber, and the feed from the source of casing glass is made so as to provide a more uniform resistance to casing glass flow throughout the entire casing glass flow path - i.e., from the casing glass feed around the chamber and through the metering gap. In a preferred embodiment of the present invention, a plurality of cased glass streams are formed by feeding core and casing glass through a plurality of orifice pairs surrounded by the casing glass chamber, and in which the metering gaps between all pairs of orifices are dimensioned with respect to each other and with respect to the surrounding chamber and the casing glass feed so as to provide substantially uniform and identical casing glass thickness at all of the cased glass streams. The apparatus for forming the cased glass stream includes a first orifice for receiving core glass from a first source, and a second orifice vertically spaced beneath and aligned with the first orifice. A chamber surrounds portions of the orifices and communicates therewith through a metering gap arranged between the first and second orifices. Casing glass is delivered from a second source to one side of the chamber such that glass flows by gravity from both the first and second sources through the orifices to form the cased glass stream. In accordance with one aspect of the present invention, the metering gap between the orifices is of non-uniform dimension around the chamber, providing greater resistance to glass flow through the metering gap on a side thereof adjacent to the inlet side of the chamber that receives casing glass from the second source, and less resistance to glass flow through the metering gap an the side thereof remote from the inlet side of the chamber. In the preferred embodiments of the present invention, the metering gap between the orifices is dimensioned such that resistance to glass flow varies as a predetermined function of angle, preferably a uniform function of angle, around the annular chamber and the metering gap. The dimension of the metering gap parallel to glass flow most preferably remains constant around the metering gap, while the dimension perpendicular to glass flow varies as a function of angle around the gap. Most preferably, the dimension of the metering gap perpendicular to glass flow varies by forming the opposed gap surfaces an angulated planes, so that this dimension varies trigonometrically around the gap. In an implementation of the present invention having a plurality of first and second orifices disposed in aligned pairs and each separated by an associated metering gap, with all of the orifice pairs being surrounded by the casing glass chamber, at least one of the metering gaps is dimensioned differently from the other metering gaps to equalize resistance to glass flow as between or among the metering gaps from the source of casing glass through the chamber. In the preferred implementation of this aspect of the invention, three orifice pairs are disposed in a line parallel to the side of the chamber coupled to the source of casing glass. The metering gap at the center of the orifice pairs is dimensioned an a side thereof remote from the casing glass feed to provide less resistance to glass flow than at the corresponding sides of the other two orifice pairs. In this way, there is improved uniformity of resistance to glass flow from the casing glass feed through and around the chamber to both the front and back sides of the various metering gaps. 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 the orifice rings and metering gap in the system of FIG. 1, being taken substantially along the line 2-2 in FIG. 3; and FIG. 3 is a schematic diagram that illustrates glass flow in a three-stream embodiment of the present invention. 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 spout 14 that has an opening 16 at the lower end thereof. Spout 14 is surrounded by a protective case 18, preferably constructed of non-magnetic metal such as stainless steel. A tube 20 controls delivery of core glass from spout 14 through opening 16 to and through at least one first orifice 22 carried by an upper orifice ring 24 beneath spout 14. A lower orifice ring 26 carries at least one second orifice 28 positioned beneath orifice(s) 22 and axially aligned therewith. Orifice 28 is surrounded by an annular chamber 30 formed between orifice rings 22, 26. Chamber 30 communicates with orifice 28 by means of a lateral metering space or gap between orifices 22, 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 European applications. 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. As shown in FIG. 2, the gap 42, which meters flow of casing glass from chamber 30 to orifice 28, has both a first dimension (horizontal in FIG. 2) parallel to the direction of glass flow through gap 42, and a second dimension (vertical in FIG. 2) perpendicular to the direction of glass flow from chamber 30 through gap 42. In accordance with the preferred embodiment of the present invention illustrated in FIG. 2, the second dimension of metering gap 42 perpendicular to glass flow is greater on the side of gap 42 remote from casing glass inlet 44 to chamber 30 than on the side of gap 42 adjacent to the casing glass inlet. Inasmuch as casing glass inlet 44 opens to one side of chamber 30, as opposed to opening entirely around chamber 30, casing glass must flow a greater distance from inlet 44 around chamber 30 to the back side of gap 42 than from inlet 44 directly across chamber 30 to the adjacent front side of metering gap 42. This greater distance of flow results not only in a pressure drop due to frictional resistance, but also heat loss and a temperature drop which increases viscosity. By dimensioning the gap non-uniformly as described immediately above, resistance to glass flow through the metering gap itself at least partially, and preferably substantially completely, compensates for the greater distance of glass travel so as to provide substantially uniform resistance to glass flow throughout the entire glass flow path from inlet 44 through chamber 30 to orifice 28. In the specific embodiment illustrated in FIG. 2, the upper surface of orifice ring 26 surrounding orifice 28 is formed on a horizontal plane, while the opposing lower surface of orifice ring 24 surrounding orifice 22 is formed on a plane angulated with respect to horizontal so that the cross-sectional dimension to glass flow varies trigonometrically from the side of gap 42 adjacent to inlet 44 to the side of gap 42 remote from inlet 44. FIG. 3 schematically illustrates an embodiment of the present invention for providing three cased glass streams. Three pairs of aligned orifices 22a,28a, 22b,28b and 22c,28c are disposed in a line parallel to the side of chamber 30 into which casing glass inlet 44 opens. It will be appreciated in FIG. 3 that the path of glass travel from inlet 44 around chamber 30 to the back side of orifice pair 22b, 28b is substantially longer than the path of travel to the back sides of pairs 22a, 28a and 22c, 28c. Thus, in this embodiment of the invention, the metering gap of orifice pair 22b, 28b may be dimensioned differently from that of orifice pairs 22a, 28a and 22c, 28c, particularly at the back side of orifice pair 22b, 28b, so as to improve uniformity of resistance to glass flow to all points around all metering gaps, and thereby improve uniformity of deposition of casing glass around the circumferences of the core glass streams.

Claims: Apparatus (10) for forming a cased glass stream having an inner core glass surrounded by an outer casing glass, said apparatus including first wall means (24) surrounding a first orifice (22), means (14 to 20) for delivering core glass from a first source (12) through said first orifice (22), second wall means (26) surrounding a second orifice (28) vertically spaced beneath and aligned with said first orifice (22), said first and second wall means (24, 26) forming a chamber (30) having an outlet in the shape of an annular gap (42) which is formed by said wall means (24, 26) of said first and second orifices and has a first dimension parallel to local glass flow and a second dimension perpendicular to local glass flow, and means (32 to 38) for delivering casing glass from a second source (40) to the inlet side (44) of said chamber (30) such that glass flows by gravity from said first (12) and second (40) sources through said orifices to form said cased glass stream, characterized in that said annular gap (42) has non-uniform first and/or second dimensions around the circumference thereof for providing greater resistance to glass flow through said annular gap (42) on the side thereof adjacent to said inlet side (44) of said chamber (30) and less resistance to glass flow through said annular gap on the side thereof remote from said inlet side (44) of said chamber (30). The apparatus (10) set forth in claim 1 wherein said annular gap (42) is dimensioned such that said resistance to glass flow varies as a predetermined function of angle around said chamber (30). The apparatus (10) set forth in claim 2 wherein said predetermined function is a uniform function of angle. The apparatus (10) set forth in any preceding claim wherein one of said first and second dimensions is uniform around said gap while the other of said first and second dimensions varies around said gap. The apparatus (10) set forth in claim 4 wherein said second dimension is a width which is determined by the distance between said first and second wall means (24, 26) forming said first' and second orifices, said width varying around said gap (42). The apparatus (10) set forth in claim 5 wherein said annular gap (42) is formed by opposed planar surfaces of said first and second wall means (24, 26) at said first and second orifices (22, 28), at least one of said surfaces being angled with respect to alignment of said orifices (22, 28). The apparatus (10) set forth in any preceding claim comprising a plurality of said first and second orifices (22, 28) disposed in aligned pairs each separated by said wall means (24, 26) forming said orifices, with all of said orifice pairs being surrounded by said chamber (30), and wherein at least one of said annular gaps (42) is dimensioned differently than other of said annular gaps to equalize resistance to glass flow as among said annular gaps (42) from said second source through said chamber. The apparatus (10) set forth in claim 7 comprising three (22a, 28a; 22b, 28b; 22c, 28c) of said orifice pairs (22, 28) disposed in a line parallel to said inlet side (44) of said chamber (30), and wherein the annular gap (42) at the center of said pairs (22b, 28b) is dimensioned on the side thereof remote from said inlet side (44) of said chamber (30) to provide less resistance to glass flow than at sides of the other two orifice pairs (22a, 28a; 22c, 28c) remote from said inlet side (44) of said chamber (30). Use of the apparatus (10) according to one of the claims 1 through 8 for forming a cased glass stream having an inner core glass surrounded by an outer casing glass.

Inventors: DEMBICKI MICHAEL T, SCOTT GARRETT L, DEMBICKI, MICHAEL T., SCOTT, GARRETT L.
Applicants: OWENS BROCKWAY GLASS CONTAINER, OWENS-BROCKWAY GLASS CONTAINER INC.
Application year: 1998
Main classification: C03B7
IPC codes: C03B7, C03B17