GB2027525A

GB2027525A - Controlling discharge of molten glass

Info

Publication number: GB2027525A
Application number: GB7907465A
Authority: GB
Original assignee: ARMYTAGE BROS Ltd
Current assignee: ARMYTAGE BROS Ltd
Priority date: 1978-03-10
Filing date: 1979-03-02
Publication date: 1980-02-20

Abstract

Means for controlling the flow of molten glass between a day tank (2) and a forehearth (4) in a glass melting and feeding system by means of a riser (10) located in the day tank and connecting with the forehearth. The riser (10) is openable and closable by means (22, 24) movable relative to the riser in association with a level probe (20) in the forehearth, thus maintaining a constant level of molten glass in the forehearth, said movable means being in the form of a refractory tube (22) which is movable able vertically relative to the riser and which is rotatable relative to the riser so as to ensure a positive seal between tube and riser. A servo system is used to raise and lower the refractory tube 22, the servo system being actuated when the level probe detects a fall in the level of molten glass in the forehearth. <IMAGE>

Description

SPECIFICATION Level control for a day tank (furnace) This invention relates to day tanks and particularly to means for controlling the level of material in such tanks.

A day tank is a glass melting furnace having refractory walls which is used for producing molten glass for subsequent supply to a forehearth and thence to machinery or glass blowers for making up into various articles of glass ware. The day tank means of obtaining and supplying the molten glass is used in a system of operation where the day tank is charged and discharged only once in any period of 24 hours, the level of molten glass being used being between predetermined maximum and minimum levels in the day tank. In order to ensure consistency in the volume and weight of molten glass from the forehearth, a constant level of molten glass is required to be maintained in the said forehearth, and such a constant level is achieved according to the present invention by suitably controlling the flow of molten glass from the day tank to the forehearth.

According to the present invention, there is provided means for controlling the flow of molten glass between a day tank and a forehearth in a glass melting and feeding system, said means comprising a riser located in the day tank and communicating with the forehearth, said riser being openable and closable by means which are movable relative to the riser in association with a liquid level probe of the forehearth, so that a constant level of molten glass may be maintained in said forehearth. Preferably, said means will consists of a refractory tube which is movable vertically relative to the riser and which will be rotatable relative to the riser so that a positive seal between the tube and riser may be maintained.

The refractory tube and liquid level probe of the forehearth will be coupied together through a servo system so that when the liquid level probe detects a drop in the level of molten glass in the forehearth, the servo system may be used to raise the tube as necessary to allow molten glass to flow from the day tank through the riser and into the forehearth so as to restore the level of molten glass in the forehearth to the desired constant level.

The refractory tube will preferably include a co-axial plunger which is vertically reciprocable and which may be used to plug the riser in cases of emergency, or for other purposes, the plunger being reciprocable by mechanical or other means.

In order that the invention may be more readily understood, an embodiment thereof will now be described, by way of example, reference being made to the accompanying drawing, the single figure of which is a schematic view of a day tanklforehearth arrangement embodying the invention.

Referring to the drawing, there is shown a day tank 2 and an associated forehearth 4 of a glass melting and feeder system. In the day tank 2, the walls and base of which are formed of or lined with refractory material, is a refractory wall 6 which together with wall 8 of the day tank defines a riser or outlet 10 from the day tank.

The forehearth 4 to which the molten glass is fed from the day tank 2 has an outlet orifice or spout 12 which is closable by means of a vertically reciprocable tubular member 14, said tubular member 14 having therein a vertically reciprocable plunger 16 which is used to regulate the flow of glass from the forehearth 4 so as to ensure that the weight of the glass globuies 18 is maintained constant. The plunger 16 may be actuated mechanically, electrically, or by fluid pressure operated means, not shown.

Shears 19 are provided to cut ofthe globule 18so as to separate the giobule from the flow of molten glass leaving the outlet orifice or spout 12.

In order to maintain constant the level of molten glass in the forehearth, the forehearth has an associated level probe 20 which is connected via a servo system to a tubular member 22 of the day tank riser or outlet 10. The tubular member 22 is vertically reciprocable by means of the said servo system so as to allow flow of molten glass from the day tank to the forehearth as necessary to maintain the constant level in the latter, and the tubular member 22 is also rotatable by means of a standard tube drive or other means (not shown), so that the bottom of the tubular member will always seat properly and effectively seal the riser or outlet 10 when the tubular member 22 is in its down position.

Within the tubular member 22 is a vertically movable plunger 24 for assisting flow control and for sealing the outlet 10 in emergencies, the plunger 24 being raised and lowered by suitable meachanical, electrical or fluid pressure-operated means, not shown. As an added precaution in cases of emergency, or as an alternative to the plunger 24, the forehearth may be provided with a weir 26 so that any excess glass flowing into the forehearth 4 which may be due to failure of the tubular member 22 - may be directed out of the forehearth so as not to effect the level of glass in the forehearth.

In operation, the day tank is loaded with the usual constituents to form the molten glass, and when the molten glass has reached its required temperature, the tubular member 22 is raised so as to allow the molten glass to flow from the day tank through the riser or outlet 10 into the forehearth 4, the tubular member 22 being lowered to its down position as shown in the drawing when the level of molten glass in the forehearth has reached the desired level, usually in the region of 9 inches. The tubular member is lowered to its down position upon the liquid level probe 20 detecting that the required level of molten glass in the forehearth has been reached, and passing a signal to the servo system which is used to lower the tubular member.

As molten glass continues to be fed through the outlet orifice or spout 12 of the forehearth, the probe 20 detects the change in the level of molten glass in the forehearth, and via the servo system the tubular member 22 is raised so as to once again allow molten glass to flow from the day tank through the riser and into the forehearth to the desired level.

Simultaneously with the raising and lowering of the tubular member 22, the tubular member 22 is rotated about its axis by means of the standard tube drive or other means so that a good seating of the tubular member 22 on the walls of the riser or outlet 10 will be maintained. If the tubular member 22 were not rotated, then molten glass would have a tendency to leak between the bottom of the tubular member and the top of the wall 8 since the said top of the wall is likely to be worn away as the glass flows from the day tank to the forehearth.

Thus it will be seen that with means according to the invention, the level of molten glass in the forehearth can be easily and conveniently maintained, which thus results in the weight and volume of glass leaving the outlet orifice or spout of the forehearth being constant thus ensuring that articles to be manufactured from the molten glass will be uniform.

It will be appreciated that the liquid level probe 20 need not necessarily be in the position shown in the drawing, since it may be at any position from being close to the tubular member 22 to being placed near the outlet orifice or spout 12.

Claims

1. Means for controlling the flow of molten glass between a day tank and a forehearth in a glass melting and feeding system, said means comprising a riser located in the day tank and communicating with the forehearth,said riser being openable and closable by means which are movable relative to the riser in association with a liquid level probe of the forehearth, so that a constant level of molten glass may be maintained in said forehearth.

2. Means according to Claim 1, wherein said movable means consists of a refractory tube which is movable vertically relative to the riser and which is rotatable relative to the riser so as to provide a positive seal between the tube and riser.

3. Means according to Claim 2, wherein said refractory tube and said liquid level probe are coupled together through a servo system.

4. Means according to Claim 2 or Claim 3, wherein said refractory tube includes a vertically reciprocable, co-axial plunger which is used to plug the riser in cases of emergency.

5. Means according to any of Claims 1 to 4, wherein the forehearth has an outlet orifice for the passage of molten glass globules therefrom, and wherein shears are associated with said outlet orifice so as to sever the flobules from the flow of molten glass passing from said outlet orifice.

6. Means according to any of Claims 1 to 5, wherein the forehearth is provided with a weir to enable excess molten glass in the forehearth to flow therefrom and so maintain constant the level of molten glass in said forehearth.

7. Means for controlling the flow of molten glass between a day tank and a forehearth in a glass melting and feeding system substantially as herein described with reference to and as illustrated in the accompanying drawing.