CERAMIC ORIFICE RING

Abstract: An orifice ring insert (13) formed of a heat resistant metal such as 50-50 nickel-chrome alloy is dropped into position within the orifice opening (11) in the ceramic orifice ring (10). The ring (10) is counterbored (12) to receive the flange (14) of the ring (13) with sufficient clearance to permit expansion. A lock nut (15) is threaded to the lower end (17) of the insert (13). The lock nut (15) has a slope (16) to its upper surface that contacts the bottom (18) of the ceramic orifice ring (10). This slope (16) takes into consideration the relative thermal expansion rates of the metal insert (13) and ceramic orifice member (10). The nut (15) stays tight during operation, but does not crack the ceramic.

Description: The present invention relates to a metal-lined ceramic orifice ring, especially for the outlet of a molten glass containing forehearth, and to a forehearth outlet device. In the past, forehearth outlets have been closed with ceramic rings that were lined with a metal sleeve such as disclosed in US-A-3,508,,904. In this patent a liner was formed of an inverted frusto-conical configuration mounted to cover the total inner surface of the orifice ring. Resistance to the erosive and corrosive effect of moving molten glass at elevated temperature is recited as one benefit of the metal liner. The metal orifice liner has its upper edge formed with a horizontal ledge that is, in effect, clamped between the upper surface of the orifice ring and the bottom surface of the feeder bowl. However, the metal and ceramic members show different thermal expansions that lead to undesired forces around the outlet. US-A-2,433,116 discloses a platinum rhodium alloy liner for a continuous flow orifice through which molten glass for forming tubing is flowed. A metal clad, ceramic mandrel extends through the orifice member to serve as the former about which the molten glass flows in the production of glass tubing. The metal orifice liner or die appears to have its upper rim curled outwardly and downwardly with its outer rim extending into an annular space in the top of the ceramic orifice that is filled with a cement. The curled rim underlies extended wear and tends to warp due to thermal expansion. It is an object of the present invention to provide a metal-lined ceramic orifice ring and a forehearth outlet device where the differences in thermal expansion do not show detrimental effects. This problem is solved according to the teaching of claims 1 and 4. The present invention provides a metal insert for a ceramic ring which is designed to fit loosely in the opening from a horizontal dimension point of view, but is held in the opening by an annular threaded nut on the lower end of the insert. The insert is held by the threaded nut which has a specific upper sloping surface that engages the bottom of the ceramic ring to firmly hold the insert, but not crack the ring on thermal expansion. Further details of the invention will be apparent from the following description taken in conjunction with the annexed sheet of drawings, in which Fig. 1 is a vertical, sectional view through a feeder orifice member with a metal insert mounted therein, and Fig. 2 is an enlarged cross-sectional view of the orifice area and metal insert of Fig. 1. In the past, efforts to make metal inserts for orifice members that are conventionally made of refractory ceramic materials has not been successful for various reasons. Three major problems which were encountered were: the thermal expansion characteristics of the metal versus the ceramic were not properly considered; roll pins that were used to hold inserts in place would not accomodate warp and would corrode long before the life of the insert had been realized. The third problem was that prior attempts failed to take into consideration orifice ring handling and insert ring expansion during the start-up period, as well as during steady state operation. While others have tried lining the entire orifice ring member with a metal material, this creates a gross thermal inbalance due to the increased cooling caused by the large metal area. When insert rings were held from below, metal members with large bottom flanges were needed and the heat radiating surface of these metal holders would detrimentally cool the inserts and result in an impeded glass flow. Further, it was common to try to hold inserts with adhesive or mud packs that would be subject to failure, particularly in an orifice structure that was used in a gob feeder with a reciprocating plunger. In view of the problems encountered in the past, it was found that a greatly simplified system for supporting a metal ring insert in the orifice ring was desirable. With reference to Fig. 1, an orifice member 10 formed with a single opening 11 therein is counterbored at 12. A metal insert ring 13 having a horizontal flange 14 and an outside diameter somewhat smaller than the inside diameter of the orifice ring opening to avoid interference with thermal expansion of the ceramic orifice ring opening 11. The member 13 may be dropped in the opening 11 of the ring 10 and a lock nut 15 is threaded onto the lower end 17 of the metal ring 13. The upper surface 16 of the lock nut 15 is provided with a specific slope which takes into consideration the difference in thermal expansion characteristics of the metal insert ring and the ceramic orifice ring. During cold assembly the lock nut may be threaded onto the insert with the torque of a person's fingers. The slope of the upper surface 16 of the threaded lock nut 15 is calculated by the formula: where H c is the thickness of the bottom wall 18 of member 13 at the opening 11, R I is the outside radius of metal insert 13, α I is the thermal expansion rate for the insert ring material, α c is the thermal expansion rate for the ceramic orifice material, and ΔT is the temperature above room temperature. The dimensions are indicated in Fig. 2 of the drawing. As a specific example, an orifice ring 10 formed of Emhart 311 was counterbored to a 9.017 mm (0.375 inches) thickness with an orifice opening of 51.3 mm (2.02 inches). The metal ring 13 formed of stainless steel had an inside diameter of 44.45 mm (1.75 inches) and an outside diameter at the cylinder of 50.42 mm (1.985 inches). The threaded nut 15 had an outside diameter of 59.97 mm (2.361 inches). The flange 14 had an OD of 56.77 m (2.235 inches). With this configuration a successful operation of feeding molten glass was carried out at a glass exit temperature of 1150°C (2100°F) for an extended period of time without failure of the metal ring 13. The expansion rate for the ceramic orifice ring at 1150°C (2100°F) was calculated to be 0.00808 mm/mm or inches per inch, and the stainless steel had an expansion rate of 0.02375 mm/mm or inch per inch. While stainless steel has been used successfully, a preferred metal for the insert is an alloy of nickel and chromium with about 50 % of each. The use of a stainless steel insert resulted in an extended useful life of the feeder system to about 1000 hours. With the Ni-Cr alloy insert dimensioned as illustrated on the drawing, the feeder was operated for greater than 5000 hours, without appreciable change in the orifice integrity. The metal insert provides a glass feeder orifice that will retain its shape and size without change for an extended period of time. In the past, it was necessary to change ceramic orifices as frequently as every two or three weeks or 300 to 500 hours of use. The particular metal used as the insert material can be of any metal that can withstand temperatures in the 1150-1270°C (2100-230°F) range for an extended period without outgassing or changing shape. A more expansive metal that has been used at molten glass temperatures is platinum-rhodium alloys as suggestes in US-A-2,433,116. The important feature of the present invention is the use of a metal insert 13 that only embraces the small orifice opening 11 in a feeder orifice rather than lining the entire ceramic orifice member 10 with the ring held in place against the up and down movement that a feeder plunger may induce by having a lock nut 15 threaded onto the lower end 17 of the ring 13. The lock nut is provided with a slope to its upper surface 16 that engages the bottom 18 of the ceramic orifice. This slope is calculated so that during start-up of the feeder the expansion of the metal ring 13 and the expansion of the ceramic orifice 11 will be such that the nut 15 retains contact with the edge 19 of the bottom 18 of the orifice while the gap 20 between the insert 13 and orifice 11 disappears when operating temperatures are reached. Thus when the operating temperature is reached, the outside diameter R I of the metal insert 13 will have essentially the same diameter as the inside diameter of the ceramic orifice ring opening 11 and during warm-up the relative expansions are such that the nut 15 will retain the insert (13) in the orifice ring 10. While some heat loss may be experienced by the use of a metal insert ring 13, the opening 21 may be made slightly larger than the size of the glass gob to be formed so that the proper size is maintained. After start-up, the insert ring 13 will be retained in its position as well and will experience very little wear. While the present disclosure is directed to the provision of a metal insert ring in a single orifice feeder, the use of the metal rings of the invention have been used in plural gob feeders with equal success. The ease of mounting and the foolproof operation during start-up and continuous use has made the inserts of the invention valuable, since changing orifice rings every two to three weeks is no longer necessary. It is believed that with the present invention the orifice rings used in feeders for long running jobs may not need changing for close to a year. Obvious modifications may be resorted to without departing from the scope of the claims.

Claims: A metal-lined ceramic orifice ring, especially for the outlet of a molten glass containing forehearth comprising a ceramic ring (10) and a heat-resistant metal liner, characterized in that said liner is an insert (13) comprising a cylindrical metal body with external threads on the lower end (17) and a radially outwardly extending flange (14) at the upper end, said ceramic ring (10) is bowl-shaped and has a bottom wall with an opening (11) extending therethrough for receiving, and being covered by, said insert (13) with the flange (14) overlying the opening (11) and the threaded end (17) extending below the bottom wall (18) of said ceramic ring (10), said insert (13) is sized so as to fit in the covered opening (11) of said ceramic ring (10) with a predetermined annular gap (20) therebetween, an internally threaded metal nut (15) is threaded onto the threaded end (17) of the insert (13), and is formed with an outwardly and downwardly sloped upper surface (16) contacting the bottom edge (19) of the covered opening (11), and in that said sloped surface (16) has a slope matching the thermal expansion characteristics of the metal insert (13) and the ceramic ring (10). The orifice ring of claim 1 wherein the slope of said sloped surface (16) is calculated by the formula: where Hc is the height of the bottom wall (18) of the ceramic ring (10), R I is the outside radius of the cylindrical metal insert (13), α I is the thermal expansion rate for the metal insert (13), α c is the thermal expansion rate for the ceramic ring (10), and ΔT is the temperature above room temperature. The orifice ring of claim 1 or 2, wherein said gap (20) formed by the internal diameter of said covered opening (11) and the external diameter (R I ) of said insert (13) are chosen to allow for the differential thermal expansion of said ceramic ring (10) and said metal insert (13) with nut (15) such that said insert (13) will have the same outside diameter as the inside diameter of said covered opening (11) at operating temperature and said nut (15) will retain the insert (13) in said covered opening (11) during and after heat up to operating temperature. A forehearth outlet device comprising a glass feeder having a bottom wall of ceramic material with one or a plurality of openings therein, characterized in that each opening corresponds to said opening (11) as defined in any of claims 1 through 3 and in that an insert (13) of heat-resistant metal for each opening (11) is provided in accordance with any of claims 1 through 3, each said metal insert (13) defining an orifice (21) for the forehearth outlet device.

Inventors: DIFRANK, FRANK J.
Applicants: OWENS-BROCKWAY GLASS CONTAINER INC.
Application year: 1990
Main classification: C03B7
IPC codes: C03B7, C03B5