MXPA97007139A - Method and apparatus for supplying a contrachap devidry current - Google Patents

Abstract

The present invention relates to an improved apparatus for forming a plywood or shell glass stream, having an inner central glass surrounded by a plywood or outer shell, the apparatus includes means for supplying the core glass from a source source through a first hole, means forming a second hole, spaced vertically below and aligned with the first hole with an annular chamber surrounding the second hole and communicating with the second hole through a space between the first and second holes and means for supplying the plywood from a second source to the annular chamber, in such a way that the glass flows by gravity from the sources through the holes to form the glass stream wrapping

Description

METHOD AND APPARATUS FOR SUPPLYING A PLYWOOD GLASS CURRENT FIELD OF THE INVENTION The present invention is directed to the supply of a glass stream to form glass fillers or masses of molten glass for the manufacture of glassware and more particularly with a method and apparatus for supplying a current call for plywood or casing in which an internal or central glass is surrounded by an outer or envelope glass layer.

BACKGROUND AND BRIEF DESCRIPTION OF THE INVENTION The provision of a plywood or shell glass stream to form glass articles having wall segments in layers has been proposed so far. US Patent Applications Nos. 08 / 374,371 and 08 / 374,372 disclose techniques for supplying such a stream of plywood, in which the core glass from a first source is supplied through a first hole. A second hole is spaced vertically below and aligned with the first hole and is surrounded by an annular chamber communicating with the second hole through the space between the first and second holes. A heated tube supplies the plywood from a second glass source to the annular chamber surrounding the second orifice. The glass flows by the force of gravity from the first and second sources through the first and second orifices, of such REF: 25646 so that a current of plywood or casing arises from the second hole. This plywood glass stream can be cut by conventional techniques to form wrapping molten glass masses for delivery to conventional individual section glass article forming machines. Although the techniques described in the indicated patent applications address and overcome the problems hitherto existing in the art, further improvements are still desired. For example, since the layer of plywood is relatively thin, it is necessary that the plywood glass supply mechanism be capable of supplying glass at very low traction speeds, such as in the order of five to ten tons per day. In addition, the plywood supply conduit must be able to stop the flow for an extended period of time, such as up to forty-five minutes during installation and start-up, without the flow control tube freezing at duct bottom. It has been proposed in the aforementioned applications to provide an arrangement of gas burners inside the plywood conduit above the glass tank for convection and radiant heating of the glass tank in an effort to maintain a high temperature of the glass . These prior art constructions operate satisfactorily during normal operation, but are not as efficient as desired during startup or periods of non-use. It is therefore a general object of the present invention to provide a method and apparatus of the described character for supplying a stream of plywood, in which the plywood supply conduit is adapted to supply glass at a very low traction speed, which it includes a zero flow traction speed, for an extended period of time without freezing or malfunctioning. In general, the foregoing and other objects of the present invention are carried out by configuring the plywood glass supply conduit for improved heat transfer to, and improved heat retention within, the plywood glass reservoir or bath within the conduit . To accomplish this a variety of structural and functional improvements are implemented as compared to conventional glass conduit designs. Specifically, in a plywood glass conduit having one or more conduit tubes for controlling the flow of glass through one or more conduit openings, the ratio of the surface area of the glass container occupied by the pipe (s) of the duct to the surface area of the total plywood glass deposit is not more than 15%, more preferably not more than 10% and more preferably approximately 8%. This surface area of the glass deposit, enlarged compared to the order of 25% to 27% in conventional pipe designs, promotes heat transfer to the glass tank, directly from gas burners and radiant walls of the duct and covers above the glass tank. The depth of the glass reservoir is also reduced compared to conventional conduits to promote heat transfer from the reservoir surface through the reservoir to the gas surrounding the conduit opening. The ratio of the surface area of the deposit to the deposit depth in preferred embodiments of the invention is at least 50/1 and more preferably at least 75/1 compared to conventional ratios of the order of 28/1 to 32 /1. Furthermore, according to another aspect of the present invention, the free space above the glass tank is enlarged to provide more volume for the combustion of gas without contact of the gas flames with the surface of the tank and a larger area for the heat transfer by radiation from the side wall of the duct and cover to the surface of the glass tank. The number of holes in the gas burner increases for an additional heat transfer to the glass tank. The housing holding the plywood glass duct is designed such that an annular support surface of the duct is brought into contact with the duct radially outwardly of the duct opening (s) to reduce the heat transfer of the duct. plywood glass flowing through the opening. An increased insulation is provided between the outer wall surface of the plywood glass duct and the inner wall surface of the housing for further reduction of heat transfer.

BRIEF DESCRIPTION OF THE DRAWINGS The invention, together with objects, features and additional advantages thereof, will be better understood from the following description, the appended claims and the accompanying drawings in which: Figure 1 is a schematic diagram in fragmentary elevation of a glass supply system, according to a presently preferred embodiment of the invention; Figure 2 is a fragmentary sectional view on an enlarged scale of the plywood supply conduit of the system of Figure 1; Figure 3 is a schematic plan view of the plywood glass supply conduit of Figure 1 comparing the surface area of the actual glass tank with the portion of the surface area occupied by the pipe of the duct; Figures 4A and 4B are fragmentary schematic diagrams illustrating the depth of the plywood glass container according to the present invention; Figure 5 is a sectional view taken substantially along line 5-5 of Figure 2; and Figure 6 is an exploded view of a portion of the gas burner mechanism illustrated in Figure 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Figure 1 illustrates a system 10 for supplying a stream of plywood or shell. A first antecryol or refining furnace 12 supplies the central glass to a duct 14 having at least one opening 16 (usually several openings) at the lower end thereof. The conduit 14 is surrounded by a protective enclosure 18, preferably constructed of a non-magnetic metal such as stainless steel. A tube 20 controls the supply of the central glass from the conduit 14 through the opening 16 and through a first hole 22 carried by an upper perforated ring 24, below the conduit 14. A lower perforated ring 26 carries a second orifice 28 positioned under the hole 22 and aligned axially therewith. The hole 28 is surrounded by an annular chamber 30 formed between the perforated rings 24, 26. The chamber 30 communicates with the hole 28 by means of a lateral space between the holes 22, 28. The annular chamber 30 is coupled by a tube 32 to the opening 34 at the lower end of a conduit 36 of plywood or casing. The conduit 36 includes a supply control tube 38 and is coupled to a refining furnace or forehearth 40 of the plywood. The supply tube 32 is heated by resistance by electronic control components 42, to maintain the flow of the plywood to the chamber 30. To the extent described so far, the system 10 of FIG. 1 is essentially the same as the one shown in FIG. describes in the North American patent applications indicated above Nos. 08 / 374,371 and 08 / 374,372. The first such application is directed in particular to the construction of the plywood supply tube 32, while the last such request is directed in particular to the construction of the perforated rings 24, 26. The descriptions of such requests, both of which are assigned to the assignee hereof, are incorporated by reference herein for purposes of the background of the invention. In conventional glass supply duct designs, flow is stopped by temporarily lowering the duct tube, so that it contacts the bottom of the duct. While the flow is stopped, the perforated ring is externally capped or replaced with a hole that has no openings. Then the hole rises from the bottom of the duct. This can be done within a few minutes to prevent the duct tube from freezing at the bottom of the duct. To prevent such freezing, it is conventional practice to raise the tube periodically during the change of the orifice to spray the fresh hot glass through the conduit and to reheat the outlet hole. Once the duct is covered and the tube rises, the convection of the glass will keep the bottom glass inside the duct sufficiently fluid to restore the flow at a later time when the external plugs are removed. However, in the plywood system 10 illustrated in Figure 10, the outlet end of the plywood glass duct 36 is attached to the supply tube 32 and thus is not exposed for plugging or replacement. From here, the flow control tube 38 and the control 39 (Figure 2) provide the only means to stop the flow of plywood. It has been found through the implementation of the present invention to be described that the tube 38 of the duct can be spliced on the bottom of the duct 36 for more than forty-five minutes without freezing and after that rising to successfully reopen the conduit for the flow of the glass. The piping 36 of plywood is illustrated in greater detail in Figure 2. The conduit 36 is surrounded by an outer housing 44 of metal, such as steel. The housing 44 has an upper flange 46 and a lower support ring 48. The support ring 48 engages and holds the lower end of the conduit 36 in a position spaced radially outwardly from the conduit opening (s) 34. of plywood, to minimize heat transfer between the plywood that flows through the opening 36 and the housing 44. Specifically, the support ring 48 has an annular rim 47 that extends upwardly with a flange that engages and holds the radially outer flange of a plateau 51 surrounding the opening 34 of the conduit. There is thus a minimum contact area between the ring 48 and the conduit 36, to reduce the heat transfer between them. The support ring 48 is of a specific construction to reduce heat transfer therethrough. The volume of the air space between the conduit 36 and the housing 44 is filled with high efficiency insulating material, such as multiple layers 50 of insulating material marketed under the trademark MICROTHERM and the remainder is filled with aggregate insulation 49. The upper flange 46 of the shell 44 holds a gas manifold 52 (Figures 2, 5 and 6) which is connected to a gas source not shown. A plurality of burner elbows 54 (FIG. 2) extend from the corresponding openings 55 (FIG. 6) in the manifold 52 and are respectively coupled to the corresponding gas nozzles 56. Each gas nozzle 56 extends radially inwardly to engage with the gas nozzles 56. a corresponding nozzle opening 58, which are arranged collectively in an array around four burner blocks 60. The burner blocks 60 are supported on the upper rim of the plywood glass duct 36, such that the flares of the gas extend radially inwardly over the glass reservoir in the duct 36. A series of cover blocks 62 are held by the burner blocks 60 and near the upper end of the conduit 36. The conduit 36 and the cover blocks 62 are of ceramic construction to absorb heat from the gas flares and re-irradiate the heat to the surface 63 of the reservoir glass inside the duct 36. Thus, the heat necessary to maintain the temperatures of the molten glass inside the duct 36 comes from two sources, the gas burners on the duct area and the latent heat of the supplied glass of the forehearth or refining furnace. , usually at a temperature of 1093 ° C (2000 ° F) to 1260 ° C (2300 ° F). If this glass were flowing at a sufficiently high speed through the conduit 36, no additional heating would be necessary. However, due to the very low traction rates involved in the flow of the plywood, additional heat is provided by means of the gas burners (in addition to the heat, applied to the supply pipe 36 by the electronic components 42). The heat supplied by the gas burners displaces the heat losses and minimizes temperature variations due to changes in the glass flow. The flames of the burner generate heat on the bath of the molten glass in the free space between the surface 63 of molten glass and the blocks 62 of covers. Flames of the burner should not hit directly on the surface of the molten glass, which could cause the undesirable generation of bubbles. Figure 3 illustrates the exposed surface area of the glass reservoir within the conduit 36 as compared to the surface area occupied by the conduit tube 38. According to one aspect of the present invention, the ratio of the surface area occupied by the tube 38 to the actual surface area of the glass reservoir within the conduit 36 (that is, the area of the tube is excluded) does not exceed 15%, more preferably it does not exceed 10% and more preferably is about 8%. In the specific example illustrated in Figure 3, the area occupied by the tube 38 is 213 square centimeters (33 square inches), while the surface area of the molten bath within the conduit 36 surrounding the bath but not including the Tube 38 is 2587 square centimeters (401 square inches), a ratio of approximately 8.2%. These preferred ratios are compared with the ratios of approximately 24% to 27% common in conventional conduits. By increasing the surface area of the molten glass bath in relation to the volume of the bath the efficiency of the radiant heat of the glass bath increases. According to another feature of the present invention, illustrated in Figures 4A and 4B, the depth of the glass bath is reduced compared to the prior art. This improves heat transfer from the surface of the glass 63 to the bottom of the conduit 36. The ratio of the surface area of the glass (tube 38 is excluded) to the depth of the glass is preferably at least 50/1 and more preferably at least 75/1. (All ratios are based on measurements in similar units, such as square inches to square inches, square inches to inches, etc.) In the example illustrated in Figure 4A, the bath or glass tank has a surface area of 2587 square centimeters (401 square inches) and a depth of 19 centimeters (7.5 inches), to result in a ratio of approximately 53.5 / 1. In the example of Figure 4B, the surface area ratio of 2587 square centimeters (401 square inches) to a depth of 10.8 centimeters (4.25 inches) is approximately 94.4 / 1. The decrease in the depth of the glass deposit as discussed above has the additional advantage, according to another aspect of the present invention, of increasing the clearance above the glass container for gas combustion and heating. By increasing the free space, the side walls of the duct become exposed and cooperate with the cover blocks to contribute to the radiant surface heating of the glass bath. That is, there is an additional surface area for the absorption of heat from the flames of the burner and a corresponding additional surface area for the re-irradiation of the heat to the surface of the glass tank. In the configurations illustrated in Figures 4A and 4B, the clearance between the surface of the glass container and the upper edge of the duct is approximately 13.65 cm (5 3/8") versus 8.57 cm (3 3/8"). of the prior art. The combined radiation area (covering blocks plus side walls) is 4497 square centimeters (697 square inches), versus approximately 1613 square centimeters (250 square inches) to approximately 3064 square centimeters (475 square inches) in the prior art. The ratio of the total radiant surface area to the surface area of the glass deposit is approximately 1.7 / 1. As shown in Figure 5 and 6, the design of the plywood glass duct of the present invention preferably has eighteen holes of the gas burner, as compared to ten to fourteen holes of the burner in the corresponding conventional designs. This represents a 28% increase in burner capacity over the design of ten burners. The ratio of the free radiant surface area (side walls plus cover blocks) to the burner orifices is thus approximately 38.7, compared to the ratios in the range of approximately 25 to 34 with conventional designs. The holes of the burner are preferably disposed at least 12.7 cm (five inches) above the surface 63. Compared to conventional constructions having a conduit 36 of similar radius, the radius of the housing 44 increases almost 10% , to provide approximately an increase of 30% in volume for the insulation 50, 49. It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, property is claimed as contained in the following

Claims (15)

1. Claims 1. An improved apparatus for forming a plywood or shell glass stream, having an inner core glass surrounded by a plywood or outer shell, the apparatus includes means for supplying the core glass from a first source through a first hole , means forming a second hole, spaced vertically below and aligned with the first hole with an annular chamber surrounding the second orifice and communicating with the second orifice through a space between the first and second holes and means for supplying the glass plywood from a second source to the annular chamber, such that the glass flows by gravity from the sources through the orifices to form the enveloped glass stream, the means for supplying the plywood comprises a conduit for receiving and maintaining the plywood in a reservoir that has a first surface area top exposed and having at least one lower opening, a conduit tube disposed within the conduit for movement within the reservoir towards and from the at least one opening for opening and closing the aperture, the tube occupies a second area in the surface of the reservoir and a plurality of heating means arranged around the conduit above the first surface for heating the glass reservoir, the improvement is characterized in that the temperature of the glass reservoir is maintained at a low traction rate, wherein the second surface area has a relation to the first surface area that does not exceed fifteen%.
2. 2. The apparatus according to claim 1, characterized in that the ratio is not more than 10%.
3. 3. The apparatus according to claim 2, characterized in that the ratio is about 8%.
4. 4. The apparatus according to claim 1, characterized in that the means for supplying the plywood is constructed in such a way that the deposit in the duct has a depth below the heating means in such a way that the ratio of the first surface area to the depth is at least 50/1.
5. 5. The apparatus according to claim 4, characterized in that the depth ratio is at least 75/1.
6. 6. The apparatus according to claim 4, characterized in that the duct has a side wall and a cover that is superimposed on the tank and wherein the duct has a free surface area of the side wall and the cover on the tank with a relation to the first surface area of at least 1.7 / 1.
7. 7. The apparatus according to claim 6, characterized in that the heating means comprises a plurality of gas burners having orifices above the surface of the tank, the free surface area having a relation to the number of burner orifices of minus 35/1.
8. 8. The apparatus according to claim 7, characterized in that the holes are arranged above the first surface by a distance of at least 12.7 centimeters (five inches).
9. 9. The apparatus according to claim 1, characterized in that the means for supplying the shell glass further comprise means for supporting the conduit, including a shell surrounding the conduit and forming a supporting surface of the annular conduit which is coupled with the conduit radially outwardly from the at least one opening to reduce heat transfer to the shell of the shell glass flowing through the opening.
10. 10. An improved method for forming a stream of plywood, in which the glass of first and second sources is supplied to a pair of aligned holes such that the glass of the second source forms a shell around an inner glass core of the first source, the improvement is characterized in that the glass is supplied from the second source by: (a) forming a conduit having a side wall and a bottom with an opening through which the glass flows from the second source, (b) positioning a duct tube within the duct for movement to and from the opening, (c) regulating the flow of the glass through the opening to form a plywood deposit within the duct around the tube, (d) supplying heat to the reservoir of glass from above the reservoir within the conduit and (e) sizing the conduit with respect to the tube, such that the glass reservoir has a first surface area that excludes the tube and the tube occupies a second surface area at a ratio of no more than 15% to the first surface area.
11. 11. The method according to claim 10, characterized in that the ratio is not more than 10%.
12. 12. The method according to claim 11, characterized in that the ratio is about 8%.
13. 13. The method according to claim 10, characterized in that step (c) comprises the step of regulating the flow of glass, in such a way that the deposit has a depth below the first surface of not more than 1/50 of the first Superficial area.
14. 14. The method according to claim 13, characterized in that the depth ratio is not more than 1/75.
15. 15. The method according to claim 13, characterized in that the duct has a cover that is superimposed on the side wall and the duct, the side wall and the duct cover define a free surface area of the duct on the tank in a relationship to the first surface area of at least 1.7 / 1. SUMMARY OF THE INVENTION An apparatus for forming a stream of plywood is described, having an inner central glass surrounded by an external plywood, which includes a first hole (22) for receiving the central glass of a first source (12). A second hole (28) is spaced vertically below and aligned with the first hole and is surrounded by an annular chamber (30) communicating with the second hole through the space between the first and second holes. A conduit (36) supplies the plywood from a second source through a tube (32) to the annular chamber, such that the glass flows by gravity from the first and second sources through the holes to form the stream. of glass wrapped. A plurality of gas burners (58) are arranged in the conduit above the glass container. The plywood supply conduit is configured for improved heat transfer to, and improved heat retention within, the plywood glass reservoir within the conduit. Specifically, the surface area (63) of the glass reservoir is enlarged and the depth of the glass reservoir is reduced. The free space above the glass tank is extended to accommodate the gas flares of more burners and increase the surface heat radiation to the glass tank. The housing (44) holding the conduit is designed such that a conduit support surface (47) engages with the conduit radially outwardly from the opening (s) (34) of the conduit, to reduce heat transfer to the plywood housing that flows through the opening.