Inclusion of small aesthetic bubbles in glass articles

Abstract

A method of forming a glass article includes introducing a particulate mixture (20) of SiC particles and carrier particles into molten glass (44, 22) contained within at least one of a forehearth (12) or a fining chamber (28) of a glass making furnace (10). The particulate mixture (20) produces seeds (S) in the molten glass such that the effluent of conditioned molten glass (18) exiting the forehearth (12), and glass articles produced therefrom, contains a higher concentration of seeds (S) than would be present without the addition of the particulate mixture (20). The concentration of seeds (S) in the glass article can be controlled by starting or stopping the addition of the particulate mixture (20).

Description

[Technical field]

[0001] The present disclosure relates to glass manufacturing, and more specifically, to methods for making glass articles that contain varying concentrations of small gas bubbles, commonly called seeds, within the glass. [Background technology]

[0002] Oxide glasses are hard amorphous solids that lack long-range order and have strong bonds between the two coordinated oxygens and the metal or metalloid atoms present in the glass. This bond provides a network that is strong and allows for a variety of structural arrangements. The term "vitreous" is often used to describe the amorphous, non-crystalline state of glass. Traditionally, glasses are produced in a continuous melting furnace that includes a melting chamber, a fining chamber, and at least one forehearth. In the melting chamber, vitrification feed material (also commonly called glass batch material) is fed through a batch feeder to the top of the molten glass bath. This material is typically heated by combustion of a mixture of fuel and oxidizer in the space above the glass bath. The combustion flame radiates heat to the molten glass bath, so that the vitrification feed material can melt, flow, and mix in the bath assisted by convection. The molten glass bath becomes more homogenized as the glass flows toward the throat that separates the melting chamber and the fining chamber. The throat allows glass to flow from a glass bath in the melting chamber to a molten glass fining bath in the fining chamber.

[0003] Certain components of the vitrification feed material - most notably raw materials such as carbonates, sulfides, oxides, sulfates, and sulfides - may introduce gas bubbles into the molten glass bath as they melt, react, or decompose in the molten glass bath in the melting chamber. Additionally, air trapped between vitrification feed material particles may also introduce gas bubbles of various sizes into the glass bath. In some industries, entrained gas bubbles are removed from the molten glass in the melting and fining chambers (a process known as "fining") to the extent necessary to meet commercial production specifications. The glass is finished so that articles formed from the glass are aesthetically appealing and exhibit a consistent appearance, especially when those articles are glass containers.

[0004] Bubble removal begins in the high temperature melting chamber as larger bubbles rise rapidly through the molten glass bath and burst when they reach the surface of the glass bath. This process may be aided by fining agents, which are secondary materials (e.g., sodium sulfate) contained in the vitrification feed material that become less soluble in the glass as the temperature of the glass increases. Gases released by these fining agents combine with and enlarge existing bubbles, thereby increasing the rate at which the enlarged bubbles rise to the top of the molten glass. The concentration of entrained bubbles in the molten glass fining bath is further reduced in the fining chamber opposite the throat. In the fining chamber, the entrained bubbles continue to rise out of the molten glass fining bath, which is aided by achieving non-turbulent flow of the bath to promote the timely rise and escape of the entrained bubbles. The molten glass fining bath is also slowly cooled in the fining chamber as the glass flows toward the forehearth. This cooling increases the solubility of certain gases in the glass, allowing smaller entrained bubbles that do not leave the molten glass fining bath to dissolve back into the glass.

[0005] The molten glass bath flows from the fining chamber of the furnace into the forehearth. The forehearth may further include an alcove that defines an elongated channel with a series of gradually decreasing temperature zones and fluidly connects the elongated channel to the fining chamber of the furnace. As the molten glass flows through the elongated channel, it is cooled at a controllable rate to increase the viscosity of the glass to a level more conducive to glass forming operations. When forming a glass container, for example, the thermally conditioned molten glass may be collected in a feeder jet of the forehearth located at the output end of the elongated channel. The feeder jet typically includes at least one reciprocatable plunger that controls the discharge of the molten glass stream or runner through at least one corresponding orifice defined in an orifice plate of the jet. Gobs of the conditioned molten glass are sheared from the glass stream and individually distributed into the blank mold via a gob distribution system. The glass gobs are then formed into parisons in the blank mold. After the parisons are formed, they are transferred to a blow mold where they are blown into glass containers. The glass container is then typically annealed and coated with one or more surface coatings.

[0006] As explained above, bubbles remaining in glass are generally considered defects because they introduce noticeable visual defects in the formed glass article. Entrained bubbles are typically classified into one of two categories: blisters or seeds. Blisters refer to bubbles with a diameter greater than 0.8 mm, and seeds refer to bubbles with a diameter of 0.8 mm or less. If it is desired to retain a certain amount of seeds in the final glass for surface decoration, glass style details, or any other reason, conventional glass processing practice dictates conditioning the vitrification feed material to help stabilize the presence of seeds in the molten glass, such as by removing chemical fining agents from the feed material. However, this conventional practice results in operational inefficiencies since commercially viable glass may not be produced while the glass composition is transitioning between different vitrification feed material formulations, and also extends the exposure of furnace refractory materials to molten glass containing relatively large amounts of entrained bubbles, which are known to accelerate the corrosion and degradation of refractory materials at melting and fining chamber temperatures. The present disclosure provides a more efficient, economical, and strategic approach to producing "seeded" molten glass that does not necessarily require adjustment of the vitrification feed material recipe. Summary of the Invention

[0007] The present disclosure relates to a method for producing conditioned molten glass and controlling seed concentration within the conditioned molten glass. Specifically, to introduce seeds and thus increase seed concentration within the conditioned molten glass effluent discharged from a forehearth of a glass-making furnace, typically through an orifice of a glass feeder, a particulate mixture including (i) silicon carbide (SiC) particles and (ii) carrier particles comprised of glass particles and / or vitrified particles is introduced into at least one of a molten glass fining bath contained within a fining chamber of the furnace or a molten glass stream contained within the forehearth. The SiC particles generate seeds that persist within the conditioned molten glass discharged from the forehearth, and thus an article containing a higher concentration of seeds than would otherwise be present can be formed from the conditioned molten glass. The carrier particles help disperse the SiC particles within the molten glass to ensure that the SiC particles do not agglomerate to generate an irregular distribution of seeds with inconsistent bubble sizes. Also, the same glass making furnace may be used to form glass articles having a lower concentration of seeds by stopping the introduction of the particulate mixture to the fining chamber and / or forehearth.

[0008] The present disclosure embodies several aspects that can be implemented separately or in combination with each other to provide a method of manufacturing glass. According to one embodiment of the present disclosure, a method of forming a glass article may include several steps. One step of the method includes providing a glass manufacturing furnace including a melting chamber, a fining chamber, and a forehearth. The melting chamber and the fining chamber are separated by a throat, and the forehearth is fluidly connected to the fining chamber. The melting chamber contains a molten glass bath into which a vitrification feed material is introduced, while the fining chamber contains a molten glass fining bath that receives glass from the molten glass bath in the melting chamber through the throat. Additionally, the forehearth includes an elongated channel along which a molten glass stream drawn from the molten glass fining bath travels. Another step of the method includes introducing a particulate mixture including SiC particles and carrier particles into at least one of the molten glass fining bath or the molten glass stream in the forehearth to generate seeds in the molten glass stream in the forehearth, thereby increasing a seed concentration in the molten glass stream in the forehearth. A further step of the method includes discharging the conditioned effluent of molten glass from the forehearth.A further step of the method includes forming a glass article from the conditioned effluent of molten glass.

[0009] According to another aspect of the disclosure, a method of forming a glass article may include several steps. One step of the method includes (a) feeding a stream of molten glass into an elongated channel of a forehearth, where the stream of molten glass is cooled along the elongated channel. Another step of the method includes (b) discharging the conditioned effluent of molten glass from the forehearth as a first set of gobs of molten glass. The conditioned effluent of molten glass has a first seed concentration. Yet another step of the method includes (c) forming a glass article from one of the first set of gobs of molten glass. Yet another step of the method includes (d) introducing a particulate mixture including SiC particles and carrier particles into at least one of the molten glass stream flowing through the forehearth or a molten glass fining bath from which the molten glass stream in the forehearth is drawn. The particulate mixture increases a seed concentration in the conditioned effluent of molten glass from a first seed concentration to a second seed concentration. The carrier particles included in the particulate mixture include at least one of cullet particles, glass frit particles, or vitrified particles. Another step of the method includes (e) discharging the conditioned effluent of molten glass from the forehearth after introducing the particulate mixture in step (d) as a second set of individual gobs of molten glass. Yet another step of the method includes (f) forming a glass article from a gob of the second set of individual gobs of molten glass. [Brief description of the drawings]

[0010] The present disclosure, together with additional objects, features, advantages, and aspects thereof, will be best understood from the following description, the appended claims, and the accompanying drawings. [Figure 1] FIG. 1 is a cross-sectional view of a glass making furnace according to one embodiment of the present disclosure; [Diagram 2] 2 is an enlarged view of a forehearth of the glass making furnace shown in FIG. 1 according to one embodiment of the present disclosure; [Diagram 3]2 is a flow chart illustrating a general method for forming a glass container from an effluent of conditioned molten glass discharged from a forehearth of the glass making furnace shown in FIG. 1 in accordance with one embodiment of the present disclosure; and [Figure 4] FIG. 2 is a side view of an exemplary glass container that may be formed from the conditioned molten glass effluent discharged from the forehearth of the glass making furnace shown in FIG. 1 according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Methods are disclosed for forming glass articles, particularly glass containers, having various concentrations of seeds without necessarily requiring adjustments to the composition of the vitrification feed material provided to the furnace. The seed concentration contained within the glass of the glass container may, in some cases, be classified as "seeded" or "non-seeded" for convenience. While the distinction between "seeded" and "non-seeded" glasses may vary depending on the consumer's needs, in certain embodiments, glasses and articles formed therefrom are considered to be "seeded" if the glass has a seed concentration of 1-100 seeds per gram of glass, or more narrowly, 4 seeds per gram of glass to 10 seeds per gram of glass. In one embodiment, glasses may be considered to be "seeded" if they exhibit a seed concentration ranging from 5.5 seeds per gram of glass to 7.5 seeds per gram of glass. Conversely, in certain embodiments, glasses and articles formed therefrom are considered to be "non-seeded" if the glass has a seed concentration of less than 1 seed per gram of glass, or more narrowly, a seed concentration ranging from 0 seeds per gram of glass to 0.5 seeds per gram of glass. Seeded glass may be desirable for a variety of glass articles, including glass containers manufactured for the spill industry, where the aesthetic appearance of the glass container resulting from the seeded glass may be utilized to build or support a brand identity or provide a different aesthetic to the general consumer.

[0012] The glass article forming method of the present disclosure is carried out using a glass manufacturing system including a continuous glass making furnace 10. The furnace 10 includes at least one forehearth 12, as shown, for example, in FIGS. 1-2. The furnace 10 receives an input of vitrification feed material 14 from a batch feeder 16 and discharges an effluent of temperature conditioned molten glass 18 from the forehearth 12. The conditioned molten glass 18 effluent may be formed into a glass article, such as a glass container. A particulate mixture 20 including (i) SiC particles and (ii) carrier particles comprised of glass particles and / or vitrified particles may be introduced to the molten glass in the furnace 10 either at the forehearth 12 or upstream of the forehearth 12 in a molten glass fining bath 22 contained within the furnace 10. The particulate mixture 20 generates seeds that persist in the conditioned molten glass 18 effluent, thus increasing the seed content of the conditioned molten glass 18 effluent. In this manner, both seeded and non-seeded glass articles, including, for example, glass containers, can be formed from the conditioned outflow of molten glass 18 by starting or stopping the addition of particulate mixture 20. No recipe changes to the vitrification feed material 14 are necessarily required.

[0013] The furnace 10 includes a housing 24 constructed from a refractory material that defines a melting chamber 26, a fining chamber 28, and a throat 30 that separates the melting chamber 26 and the fining chamber 28. Molten glass partially fills the melting chamber 26 and the fining chamber 28 and completely fills the throat 30. A molten glass bath 32 is contained within the melting chamber 26, and it is into this bath 32 that the vitrification feed material 14 is introduced. A molten glass fining bath 22 is contained within the fining chamber 28 and receives molten glass from the melting chamber 26 through the throat 30, which is submerged below the level of the molten glass bath 32 and the fining glass bath 22 to allow glass to flow from the upstream melting chamber 26 to the downstream fining chamber 28. Because the molten glass bath 32 and the molten glass fining bath 22 only partially fill their respective chambers 26, 28, a melting chamber combustion zone 34 exists within the melting chamber 26 above the molten glass bath 32 contained within the melting chamber 26, and a fining chamber combustion zone 36 exists within the fining chamber 28 above the molten glass fining bath 22. A relatively large amount of molten glass, typically between 30 tons and 1000 tons, is contained within the furnace 10 to maintain glass residence times in the melting chamber 26 and fining chamber 28 ranging from 8 hours to 72 hours. The molten glass comprising the molten glass bath 32 and the molten glass fining bath may be soda-lime-silica glass.

[0014] A batch inlet 38 is defined within the housing 24 and provides an inlet to the melting chamber 26 for delivering the vitrification feed material 14 onto the molten glass bath 32. The vitrification feed material 14 is distributed over a portion of the molten glass bath 32 as a batch blanket 40 that melts and reacts to form glass that mixes with the molten glass bath 32 over time. A glass outlet 42 is also defined within the housing 24 and provides an outlet from the fining chamber 28 through which a flow of molten glass 44 is withdrawn from the molten glass fining bath 22 and delivered to the forehearth 12. As best shown in FIG. 1, the molten glass fining bath 22 includes an upwardly flowing portion 22a and a horizontally flowing portion 22b. The upwardly flowing portion 22a extends upwardly from the throat 30 to the horizontally flowing portion 22b, where it flows perpendicular to gravity, while the horizontally flowing portion 22b flows toward and out of the fining chamber 28 through the glass outlet 42. The term "perpendicular to gravity" includes inclinations of up to 5° from true vertical.

[0015] A plurality of overhead burners 46 are mounted to the housing 24 within the melting chamber 26. Each of these overhead burners 46 combusts a combustible mixture including an oxidizer and a fuel and projects a resulting combustion flame into the melting chamber combustion zone 34 above the molten glass bath 32. These combustion flames heat the molten glass bath 32 to promote melting and reaction of the vitrification feed material 14. During operation of the furnace 10, the molten glass bath 32 may be maintained within a temperature range of 1200° C. to 1550° C. when the molten glass bath 32 is comprised of soda-lime-silica glass. Similarly, a plurality of overhead burners 48 may be mounted to the housing 24 within the fining chamber 28. Each of these overhead burners 48 also combusts a combustible mixture and projects a resulting combustion flame into the fining chamber combustion zone 36 above the molten glass fining bath 22. These combustion flames allow the molten glass fining bath 22 to be cooled at a controlled rate and serve to facilitate the rise and removal of entrained gas bubbles from the molten glass fining bath 22. During operation of the furnace 10, the molten glass fining bath 22 contained within the fining chamber 28 may be maintained within a temperature range of 1450° C. to 1150° C. when the molten glass fining bath 22 is comprised of soda-lime-silica glass.

[0016] The forehearth 12 is fluidly connected to the fining chamber 28. The forehearth 12 receives a flow of molten glass 44 from the fining chamber 28 and outputs a regulated outflow of molten glass 18 at an output flow rate D RThe forehearth 12 has a housing 50 defining an elongated channel 52 along which the molten glass 44 stream is cooled, and further includes a glass feeder 54 that provides an output of the conditioned molten glass 18. The forehearth 12 may, but need not, include an alcove (not shown) fluidly connecting the elongated channel 52 to the fining chamber 28 of the furnace 10 for delivering the molten glass 44 stream to the elongated channel 52. The housing 50 further defines an inlet 56 to the elongated channel 52 and an outlet 58 from the elongated channel 52 spaced along the length L of the elongated channel 52. The molten glass 44 stream flows from the inlet 56 to the outlet 58 of the elongated channel 52, eventually entering the glass feeder 54. The output of the conditioned molten glass 18 is discharged from the forehearth 12 as individual gobs of molten glass through the glass feeder 54, as described further below.

[0017] A plurality of overhead burners 60 are mounted within the elongated channel 52 of the forehearth 12. Each of these burners 60 combusts a combustible gas mixture and projects a combustion flame into the elongated channel 52 above the stream of molten glass 44. The overhead burners 60 are operated to condition the stream of molten glass 44, i.e., to gradually reduce the temperature T of the stream of molten glass 44 along the length L of the elongated channel 52 from a first temperature T1 at an inlet 56 of the channel 52 to a second temperature T2 at an outlet 58 of the channel 52 to homogenize the temperature of the glass and achieve a glass viscosity suitable for downstream glass forming operations, as best shown in FIG. 2. For example, in a case applicable to a glass container forming operation in which the molten glass is soda-lime-silica glass, the first temperature T1 of the stream of molten glass 44 may be in the range of 1100° C. to 1450° C., and the second temperature T2 of the stream of molten glass 44 may be in the range of 1050° C. to 1250° C. The molten glass 44 stream is more thermally homogenized at the second temperature T2 and, as a result of being at the second temperature T2, the molten glass 44 stream is heated to a temperature of about 10 1.5 Pa s~10 3 It has a glass viscosity of Pa·s.

[0018] An auxiliary inlet 62 may be further defined within the housing 50 of the forehearth 12 between the inlet 56 and the outlet 58 to allow for selective introduction of the particulate mixture 20 into the molten glass 44 stream at a controlled feed rate when the particulate mixture 20 is introduced at that location of the forehearth 12. The auxiliary inlet 62 may be a single opening providing access to the elongated channel 52 or may collectively be several such openings. The auxiliary inlet 62 receives the particulate mixture 20 from an auxiliary feeder 64 capable of metering solid particulate material. For example, the auxiliary feeder 64 may be an extruder comprising a feed tube 66 and a rotating screw 68 disposed within and surrounded by the feed tube 66. The rotating screw 68 rotates within the feed tube 66 to move a quantity of the particulate mixture 20 axially through the feed tube 66 at a controlled feed rate. The quantity of the particulate mixture 20 exiting the feed tube 66 may be fed to a guide 70 disposed in feed communication with the auxiliary inlet 62 to introduce the particulate mixture 20 into the molten glass 44 stream.

[0019] The SiC particles and carrier particles, when added to a molten glass, such as the molten glass fining bath 22 or the molten glass 44 stream, function synergistically to generate seeds S (FIG. 2) in the glass. The SiC particles may contain at least 90% by weight SiC, or in some cases at least 98% by weight SiC, with the remainder being one or more of SiO2, C, Si, Fe, and Al, as well as acceptable impurities. Such SiC particles may be commercially obtained from Rosber SA de CV, headquartered in Naucalpan de Juarez, Mexico. The carrier particles include glass particles and / or vitrified particles. The glass particles may be cullet particles, frits, or any other vitreous glass, and contain at least 50% by weight SiO2. In one embodiment, the glass particles may be soda-lime-silica glass particles, preferably when the molten glass 44 stream is also soda-lime-silica glass. Vitrified particles are particles that are not considered glass, but can be melted to a glassy state. For example, the vitrifying particles may be granules of oxide, carbonate, or other glass precursor material that, when introduced into the molten glass 44 stream, melt to form a glass containing at least 50% by weight SiO2, optionally including a glass having a soda-lime-silica glass composition.

[0020] SiC particles are typically added to the molten glass to react with oxygen and then melt into the molten glass, releasing CO2 gas, CO gas, or both CO2 gas and CO gas. The released gas(es) are entrained within the glass matrix to form encapsulated seeds S. To help ensure that the SiC particles are well dispersed, as opposed to forming clusters, so that the resulting seeds S are well distributed within the glass, the SiC particles are mixed with carrier particles in the particulate mixture 20. The properties of the particulate mixture 20 can affect the nature of the generated seeds S that advance and are maintained within the conditioned molten glass 18 effluent and the glass article formed therefrom, as well as the tendency of the molten glass 44 stream to foam.

[0021] The inclusion of SiC particles in the particulate mixture 20 generally has the effect of increasing the size and amount of seeds S produced. To that end, including too many SiC particles in the particulate mixture 20 can result in the formation of a large amount of larger seeds, resulting in foaming of the molten glass. Also, the presence of bubbles in the molten glass 44 stream is generally sought to be avoided, as the bubbles can be converted into visible streaks in the glass article formed from the glass. Furthermore, the temperature of the molten glass is inversely proportional to the size of the seeds S produced, i.e., larger seeds are produced at lower glass temperatures and smaller seeds are produced at higher glass temperatures. As a result, any or all of the following factors may be considered for their individual or collective contribution to seed formation: (1) the size of the SiC particles and carrier particles, (2) the weight ratio of SiC particles to carrier particles (SiC:carrier weight ratio) in the particulate mixture 20, (3) the amount of particulate mixture 20 added to the molten glass fining bath 22 and / or molten glass 44 stream, and (4) the location at which the particulate mixture 20 is introduced into the molten glass 44 stream.

[0022] Any one or more of the above four factors may be varied to adjust the size and / or concentration of the seeds S produced, while the applicable range of each has been determined for the production of seedable glass. For example, the particle size of the SiC may range from 10 μm to 120 μm, or more narrowly from 30 μm to 80 μm, and the particle size of the support particles may range from 50 μm to 300 μm, or more narrowly from 100 μm to 200 μm. As used herein, "particle size" refers to the measured length of the largest dimension of the particle. The SiC particles and support particles may also be included in the particulate mixture 20 in a SiC:support weight ratio ranging from 1:1000 to 1:2.5, more narrowly from 1:1000 to 1:100, 1:500 to 1:100, or even 1:500 to 1:250. The particulate mixture 20 is introduced into the molten glass fining bath 22, the flow of molten glass 44 in the elongated channel 52 of the forehearth 12, or both, to control the regulated exit flow rate D of the molten glass 18 effluent. R3, may provide a flow rate of SiC particles and support particles (by weight ratio) ranging from 0.1% to 5.0%, more narrowly from 0.4% to 0.85%, and even more narrowly from 0.5% to 0.75% of the total weight of the SiC particles and support particles. Additionally, when some or all of a particular mixture 20 is introduced into the stream of molten glass 44, the particulate mixture 20 may be added to the stream of molten glass 44 in zone 72 of forehearth 12 where the temperature T of the stream of molten glass 44 is in the range of 1100° C. to 1400° C., or more narrowly from 1275° C. to 1375° C.

[0023] The concentration of seed S in the conditioned molten glass 18 output from the forehearth 12 can be selectively changed by simply initiating the introduction of the particulate mixture 20 into the molten glass fining bath 22 and / or the molten glass 44 stream contained in the forehearth. By initiating the introduction of the particulate mixture 20, the concentration of seed S in the conditioned molten glass 18 output can be increased relatively quickly without necessarily relying on adjusting the vitrification feed material 14 recipe. This transition can be made quickly because it does not require a change in the vitrification feed material 14 recipe, which would generally be slow to produce the intended effect in the conditioned molten glass 18 and therefore may result in a large amount of transition glass that is not commercially valuable. Thus, the same glass making furnace 10 can produce glasses with significantly different seed contents and transition between the two based on the demand for each type of glass and production scheduling logistics. Also, because the concentration of glass seeds S is adjusted in the forehearth 12 or fining chamber 28, the melting chamber 26, which tends to operate at higher temperatures than the fining chamber 28 and forehearth 12, is spared the more aggressive corrosion mechanisms associated with excessively foamed glass.

[0024] During operation of the glass making furnace 10, the vitrification feed material 14 is introduced into the melting chamber 26 and distributed over a portion of the molten glass bath 32 as a batch blanket 40. The vitrification feed material 14 melts, flows and mixes into the molten glass bath 32, assisted by convection currents 74 present in the molten glass bath 32 and radiant heat provided by overhead burners 46 in the melting chamber 26. As various components of the vitrification feed material 14 react or decompose within the molten glass bath 32, they produce bubbles B. The vitrification feed material 14 may be formulated to produce any type of glass, including various oxide glasses, having a particular glass chemistry. For example, the vitrification feed material 14 may be formulated to produce a soda-lime-silica glass having a glass chemistry including 60% to 80% by weight SiO2, 8% to 18% by weight Na2O, and 5% to 15% by weight CaO, based on the total weight of the glass. In addition to SiO2, Na2O, and CaO, the glass chemistry of soda-lime-silica glass may include other oxide and non-oxide materials, including aluminum oxide (Al2O3), magnesium oxide (MgO), potassium oxide (KO), carbon, sulfates, nitrates, fluorine, chlorine, and / or elemental or oxide forms of one or more of iron, arsenic, antimony, selenium, chromium, barium, manganese, cobalt, nickel, sulfur, vanadium, titanium, lead, copper, niobium, molybdenum, lithium, silver, strontium, cadmium, indium, tin, gold, cerium, praseodymium, neodymium, europium, gadolinium, erbium, and uranium. Regardless of what other oxide and / or non-oxide materials are present in the soda-lime glass in addition to SiO2, Na2O, and CaO, the sum of these additional materials is preferably 10% by weight or less, more narrowly 5% by weight or less, based on the total weight of the soda-lime-silica glass.

[0025] The molten glass bath 32 flows from the melting chamber 26 to the fining chamber 28 through the submerged throat 30. Most of the initially formed gas bubbles B are removed along the way. The fining process begins when, in the melting chamber 26, the larger entrained gas bubbles B rise rapidly through the molten glass bath 32, while in the fining chamber 28, the smaller entrained gas bubbles B either rise through the molten glass fining bath 22 or are reabsorbed by the glass. The molten glass 44 stream is drawn from the fining chamber 28 into the forehearth 12 and received within the elongated channel 52 through the inlet 56. The molten glass 44 stream flows through the elongated channel 52 to the outlet 58, decreasing in temperature along its path from a first temperature T1 at the inlet 56 to a second temperature T2 at the outlet 58. The molten glass 54 stream is thus more thermally conditioned, decreasing in temperature and increasing in viscosity, as it travels through the elongated channel 52 of the forehearth 12.

[0026] At the outlet of the forehearth 12, the regulated outflow of molten glass 18 is discharged at a specified discharge flow rate D R The conditioned molten glass 18 is discharged from the forehearth 12 at a flow rate of 1000 rpm. The conditioned molten glass 18 outflow may be fed to a glass article forming apparatus. For commercial glass container manufacturing, for example, the elongated channel 52 is in fluid communication with a glass feeder 54 that discharges the conditioned molten glass 18 outflow as individual gobs of molten glass. As shown in FIGS. 1-2, the glass feeder 54 includes an eruption bowl 76 and a bottom orifice plate 78 that together define an eruption chamber 80. The glass feeder 54 also typically includes at least one plunger 82 that reciprocates relative to the orifice plate 78 and controls the conditioned molten glass flow held within the eruption chamber 80 through aligned orifices 84 in the orifice plate 78 to form molten glass streams. Each of the conditioned molten glass streams may be cut by a shear blade (not shown) into gobs of molten glass 86 that may be individually formed into glass containers upon delivery to a glass container forming machine.

[0027] The particulate mixture 20 can be used to adjust the concentration of seeds S in the conditioned molten glass 18 output, if necessary. By ceasing the addition of the particulate mixture 20, no seeds S are produced and the concentration of seeds S in the molten glass 44 stream in the forehearth 12 does not increase. Thus, the conditioned molten glass 18 output discharged from the forehearth 12 has a first concentration of seeds S resulting from the melting and fining operations performed in the melting and fining chambers 26 and 28 of the furnace 10. The first concentration of seeds S may be less than 1 seed per gram of glass, or more narrowly, between 0 and 0.5 seeds per gram of glass. A glass article, also including the first concentration of seeds S, may then be formed from the conditioned molten glass 18 output discharged from the glass feeder 54 as a first set of gobs of molten glass. Specifically, a single glass container is formed from one gob of the first set of gobs of molten glass in a glass container forming machine, and several different forming machines may be simultaneously operable to repeatedly form gobs from the first set of gobs of molten glass into many glass containers. A brief description of how molten glass gobs are formed into glass containers can be found below.

[0028] However, if a conditioned molten glass with a higher seed concentration is desired, the particulate mixture 20 is introduced into the molten glass fining bath 22, preferably into the horizontally flowing portion 22b, or into the molten glass 44 stream contained within the forehearth 12, preferably into the elongated channel 52. Of course, the particulate mixture 20 may also be introduced into the conditioned molten glass in the blowout chamber 80 of the glass feeder 54, or into an alcove of the forehearth 12, if desired. The particulate mixture 20 may be added according to one or more of the factors discussed above (i.e., SiC and support particle size, SiC:support weight ratio, amount of SiC particles and support particles introduced, and location where the particulate mixture 20 is added).

[0029] The particulate mixture 20 increases the concentration of seeds S in the effluent of conditioned molten glass 18 discharged from the forehearth 12 from a first concentration of seeds S to a second concentration of seeds S that is greater than the first concentration of seeds S. The second concentration of seeds S may range from 1 to 100 seeds per gram of glass, and may further be controlled using one or more of the four factors listed above to have an average diameter of the seeds S between 0.05 mm and 0.25 mm, more preferably between 0.1 mm and 0.2 mm, to provide the intended visual effect in the glass. A glass article also including the second concentration of seeds S may then be formed from the effluent of conditioned molten glass 18 discharged from the glass feeder 54 as a second set of gobs of molten glass. Specifically, a single glass container may be formed from one gob of the second set of gobs of molten glass in a glass container forming machine, as described above, and several different forming machines may be operable simultaneously to repeatedly form gobs from the second set of gobs of molten glass into many glass containers.

[0030] Glass containers may be formed from the conditioned molten glass 18 (whether or not containing the first or second concentration of seeds S) obtained from the forehearth 12 in a forming step 100, as shown in the flow diagram of FIG. 3. In a standard container forming process, the conditioned molten glass 18 outflow is discharged from the glass feeder 54 as individual gobs of molten glass 86. Each gob 86 is fed into a blank mold of a glass container forming machine. Once in the blank mold, the molten glass gob 86 is pressed or blown into a parison or preform including a tubular wall in substep 100a. The parison is then transferred from the blank mold to a blow mold of the glass container forming machine. Once the parison is received in the blow mold, the blow mold is closed and the parison is rapidly blown outwardly using a compressed gas, such as compressed air, in substep 100b into a glass container having a shape that matches the contours of the mold cavity. Of course, other approaches besides press-and-blow and blow-and-blow molding techniques may be implemented to form glass containers, including, for example, compression or other molding techniques.

[0031] The glass container formed in the blow mold is generally shown in FIG. 4 and designated by reference numeral 106. The glass container 106 has a hollow glass substrate 108 including a closed bottom 110 and a peripheral wall 112. The peripheral wall 112 extends from the closed bottom 110 and terminates in a mouth 114 that defines an opening 116 to a receiving space 118 defined by the closed bottom 110 and the peripheral wall 112. Once formed, the glass container 106 is removed from the blow mold and placed on a conveyor or other transport device. The glass container 106 is then annealed in an annealing layer in step 102 to relieve thermally induced distortions and eliminate internal stress points. Annealing the glass container 106 involves heating the glass container 106 in sub-step 102a to a temperature above the annealing point of the glass, which for soda-lime-silica glass is typically in the range of 510° C.-550° C., followed by slow cooling in sub-step 102b at a rate of 1° C. / min to 10° C. / min to a temperature below the strain point of the glass, which for soda-lime-silica glass is typically in the range of 470° C.-500° C. Additionally, any of a variety of coatings may be applied to the surface of the glass container 106 either before (hot end coating(s)) or after (cold end coating(s)) the annealing process.

[0032] The hollow glass substrate 108 defining the shape of the glass container 106 includes seeds distributed throughout the substrate 108 at a second concentration when the particulate mixture 20 is added to the furnace 10 as described above and the glass container 106 is formed from one of the individual gobs of the second set of molten glass. Distributing the internal seeds at a second concentration can provide a visually appealing and aesthetic appearance to the glass container 106. However, it is not desirable for all glass containers to have such a high concentration of seeds S, and in fact, the demand for glass containers containing much less seeds S will almost certainly be higher, if not significantly higher, than the demand for glass containers in which seeds S have been purposefully added to the glass. In that regard, to transition the output of the conditioned molten glass 18 to a lower acceptable seed concentration, the particulate mixture 20 is not introduced to the furnace 10 as described above and the glass container 106 is formed from one of the individual gobs of the first set of molten glass.

[0033] Thus, a glass making furnace and method for producing conditioned molten glass that satisfies one or more of the above-mentioned objects and goals are disclosed. The disclosure has been presented in conjunction with several exemplary embodiments, and additional modifications and variations have been discussed. Other modifications and variations will be readily suggested to those skilled in the art in view of the foregoing discussion. For example, the subject matter of each of the embodiments is hereby incorporated by reference into each of the other embodiments for convenience. The disclosure is intended to encompass all such modifications and variations that fall within the spirit and broad scope of the appended claims.

Claims

1. 1. A method of forming a glass article, the method comprising: providing a glass-making furnace (10) comprising a melting chamber (26), a fining chamber (28), and a forehearth (12), the melting chamber and the fining chamber being separated by a throat (30), the forehearth being fluidly connected to the fining chamber, the melting chamber containing a molten glass bath (32) into which vitrification feed material (14) is introduced, the fining chamber containing a molten glass fining bath (22) that receives glass from the molten glass bath in the melting chamber through the throat, the forehearth including an elongated channel (52) through which a stream of molten glass (44) drawn from the molten glass fining bath travels; introducing a particulate mixture (20) comprising SiC particles and support particles into at least one of the molten glass fining bath or the molten glass stream in the forehearth to generate seeds (S) in the molten glass stream in the forehearth, thereby increasing a seed concentration in the molten glass stream in the forehearth; Discharging an outflow of conditioned molten glass (18) from the forehearth; and forming a glass article from the effluent of the conditioned molten glass. method.

2. The method of claim 1 , wherein the carrier particles included in the particulate mixture comprise cullet particles.

3. The method of claim 1 , wherein the carrier particles included in the particulate mixture comprise glass frit.

4. 10. The method of claim 1, wherein the carrier particles included in the particulate mixture comprise vitrifying particles that melt into a glassy state when introduced into the molten glass stream.

5. 2. The method of claim 1, wherein the SiC particles in the particulate mixture have a particle size in the range of 10 μm to 120 μm, and the support particles in the particulate mixture have a particle size in the range of 50 μm to 300 μm.

6. 6. The method of claim 5, wherein the SiC particles in the particulate mixture have a particle size in the range of 30 μm to 80 μm, and the support particles in the particulate mixture have a particle size in the range of 100 μm to 200 μm.

7. 2. The method of claim 1, wherein the weight ratio of the SiC particles to the support particles in the particulate mixture is in the range of 1:1000 to 1:2.

5.

8. 8. The method of claim 7, wherein the weight ratio of the SiC particles to the support particles in the particulate mixture ranges from 1:500 to 1:

100.

9. 8. The method of claim 7, wherein the weight ratio of the SiC particles to the support particles in the particulate mixture ranges from 1:500 to 1:

250.

10. a flow rate of the combined weight of the SiC particles and the support particles in the particulate mixture into at least one of the molten glass fining bath or the molten glass stream in the forehearth is greater than or equal to a discharge flow rate (D R 2. The method of claim 1, wherein the content of the hydroxybenzoate is in the range of 0.1% to 5.0% of the total hydroxybenzoate.

11. 11. The method of claim 10, wherein the combined weight flow rate of the SiC particles and the carrier particles is in the range of 0.5% to 0.75% of the discharge flow rate of the conditioned molten glass effluent from the forehearth.

12. The method of claim 1, wherein the particulate mixture is introduced into the molten glass stream in a zone (72) of the forehearth where the temperature of the molten glass stream is in the range of 1100°C to 1400°C.

13. The SiC particles and the support particles in the particulate mixture have particle sizes in the ranges of 10 μm to 120 μm and 50 μm to 300 μm, respectively, a weight ratio of the SiC particles to the support particles in the particulate mixture is in the range of 1:1000 to 1:2.5, the particulate mixture is introduced into the molten glass stream in a zone (72) of the forehearth where the temperature of the molten glass stream is in the range of 1100°C to 1400°C, and a flow rate of the total weight of the SiC particles and the support particles in the particulate mixture into the molten glass stream in the forehearth is equal to or greater than a controlled discharge flow rate (D R 2. The method of claim 1, wherein the content of the hydroxybenzoate is in the range of 0.1% to 5.0% of the total hydroxybenzoate.

14. The method of claim 1 , wherein the conditioned molten glass effluent has a soda-lime-silica glass chemical composition.

15. 10. The method of claim 1, wherein forming the glass article from the conditioned molten glass effluent comprises forming a glass container (106) comprising a hollow glass substrate (108).

16. 1. A method of forming a glass article, the method comprising: (a) providing a stream of molten glass (44) into an elongated channel (52) of a forehearth (12), the stream of molten glass cooling along the channel; (b) discharging an effluent of conditioned molten glass (18) from the forehearth as a first set of gobs of molten glass, the conditioned effluent having a first seed concentration; (c) forming a glass article from a gob of the first set of gobs of molten glass; (d) introducing a particulate mixture (20) comprising SiC particles and support particles into at least one of the molten glass stream flowing through the forehearth or a molten glass fining bath (22) from which the molten glass stream in the forehearth is drawn, the particulate mixture increasing a concentration of seeds (S) in the conditioned molten glass effluent from the first seed concentration to a second seed concentration, the support particles comprising at least one of cullet particles, glass frit particles, or vitrified particles; (e) discharging the conditioned effluent of molten glass from the forehearth after introducing the particulate mixture in step (d) as second individual gobs of molten glass in a second set; (f) forming a glass article from one gob of the second set of individual gobs of molten glass.

17. 17. The method of claim 16, wherein the conditioned molten glass effluent has a soda-lime-silica glass chemical composition.

18. 17. The method of claim 16, wherein the glass article formed in step (c) and the glass article shaped in step (f) are each glass containers (106) comprising a hollow glass substrate (108) having a closed bottom (110) and a peripheral wall (112) extending from the closed bottom to a mouth (114).

19. 17. The method of claim 16, wherein the glass article formed in step (f) has a seed concentration ranging from 4 seeds per gram of glass to 10 seeds per gram of glass.

Images