US3493359A

US3493359A - Molten bath with roller for drawing a glass sheet thereover

Info

Publication number: US3493359A
Application number: US816164A
Authority: US
Inventors: Jack Lawrenson
Original assignee: Pilkington Brothers Ltd
Current assignee: Pilkington Group Ltd
Priority date: 1965-03-11
Filing date: 1969-04-08
Publication date: 1970-02-03
Anticipated expiration: 1987-02-03
Also published as: NL136460C; DE1596589B1; BE677717A; LU50611A1; GB1118711A; NL6603169A; ES323617A1

Description

Feb. 3, 1970 J. LAWRENSON 3,493,359

MOI-ITEN BATH WITH ROLLER FOR DRAWING A GLASS SHEET THEREOVER Original Filed Feb. 15, 1966 2 Sheets-Sheet 1 Attorney 5 Feb. 3, 1970 J, LAWRENS'ON 3,493,359

MOLTEN BATH WITH ROLLER FOR DRAWING A GLASS SHEET-THEREOVER Original Filed Feb. 15, 1966 2 Sheets-Sheet 2 United States Patent 3,493,359 MOLTEN BATH WITH ROLLER FOR DRAWING A GLASS SHEET THEREOVER Jack Lawrenson, St. Helens, England, assignor to Pilkington Brothers Limited, Liverpool, Lancashire, England, a corporation of Great Britain Continuation of application Ser. No. 527,472, Feb. 15, 1966. This application Apr. 8, 1969, Ser. No. 816,164 Claims prior-i; application Great Britain, Mar. 11, 1965, 10,446/ 65 Int. Cl. C03b 37/02 US. Cl. 65-182 1 Claim ABSTRACT OF THE DISCLOSURE An edge roll for engaging viscous glass as it is advanced along a molten metal surface has one or more sets of projecting peripheral teeth each set being arranged perpendicular to the roll axis and the teeth being arranged for biting into the glass surface.

This application is a continuation of application Ser. No. 527,472, filed Feb. 15, 1966, now abandoned.

This invention relates to apparatus for use in the manufacture of fiat glass, and more especially to an edge roller construction for engaging a margin or both margins of ribbon glass as it is advanced along a molten metal surface, to control the rate of advance of the ribbon along the surface.

Desirably the molten bath is a bath of molten tin or a molten tin alloy in which tin predominates and having a specific gravity greater than glass. The bath may be so constituted as to have all the charactreistics fully described in United States Patent No. 2,911,759.

It is a main object of the present invention to provide an improved edge roll for engaging a margin of a ribbon of viscous glass in order to control its rate of advance along a molten metal surface.

According to the invention there is provided an edge roll for engaging a margin of a ribbon of viscous glass as it is advanced along a molten metal surface to control the rate of advance of the ribbon, which edge roll has at least one set of peripheral teeth for biting into the surface of the viscous glass.

The peripheral teeth on the edge roll are in nature similar to the teeth of a sprocket wheel, and they bite into the margins of the ribbon of glass.

In some circumstances a single set of peripheral teeth may provide a sufiicient grip of the viscous glass. Preferably, however, the edge roll is provided with a plurality of sets of peripheral teeth, which sets of teeth are spaced apart axially of the edge roll.

Desirably the edge roll comprises a number of adjacent toothed wheels held together as an integral unit which is fixed to one end of a supporting axle. An edge roll according to the invention may, however, be machined from a single block of material with the set or sets of teeth machined around the periphery of the edge roll.

The teeth may be pointed or have curved outer edges. Preferably each tooth has a straight outer edge and the sets of teeth are so arranged that the straight edges of the teeth are out of alignment with each other, This enables the viscous glass to well upwardly effectively between the teeth and gives an even grip of the edge roll on the upper surface of the glass, without extracting too much heat from the glass.

In a preferred embodiment of the invention the edge roll comprises three toothed wheels having equal numbers of teeth.

Desirably the teeth are of symmetrical profile and the straight outer edges of the teeth are parallel to the wheel 3,493,359 Patented Feb. 3, 1970 axis. Alternatively the teeth may have an asymmetrical profile, for example the teeth may be of saw-tooth form.

Cooling of the edge roll is sometimes desirable and the supporting axle may be formed with a cylindrical bore in which is mounted a central pipe for supplying cooling fluid to the axle.

In one embodiment of the invention a solid annular collar is fixed to the end of the axle, and the toothed wheels are fixed to the outer surface of the collar.

In another embodiment of the invention the cylindrical bore of the axle opens into a cylindrical drum which is fixed to the end of the axle, the central pipe terminates within the drum, and the wheels are fixed to the outside of the drum.

A material which is not wetted by molten glass and is resistant to attack by molten glass is generally employed for fabricating the wheels. For example each toothed wheel may be made of carbon, e.g. in the form of graphite, or boron nitride, or spheroidal graphite cast iron, or stainless steel. Preferably the edge roll is so constructed that it can be cooled.

The teeth of the edge roll may, in some applications, where the viscosity of the glass is low and the pressure applied by the roll to the surface of the glass is high, cause track marks in the upper surface of the glass which extend some way inwardly towards the centre of the glass ribbon, In order to prevent the propagation of such track marks along the glass surface a sharp-edged disc may be mounted on the end of the supporting axle inwardly of the toothed wheels and axially spaced from the teeth of the innermost wheel, the diameter of the disc being of the same order as that of the toothed wheels. The disc runs a longitudinally extending groove into the upper surface of the glass and prevents the propagation of tooth marks in the glass inwardly of that groove.

The disc is made of a similar material to the toothed wheels, for example carbon in the form of graphite, or boron nitrides, or spheroidal graphite cast iron, or stainless steel.

The invention also comprehends apparatus for use in the manufacture of fiat glass in ribbon form, comprising a tank structure holding a bath of molten metal, through opposite sides of which tank structure project axles each carrying an edge roll of the kind set out above, whereby said edge rolls engage the margins of a ribbon of glass advancing along the bath of molten metal to control the rate of advance of the ribbon along the bath.

In order to exert an outwardly directed force component on each margin of the glass, the axles of the edge rolls may be inclined towards the direction of advance of the glass ribbon.

In order that the invention may be more clearly understood some embodiments thereof will now be described, by way of example, with reference to the accompanying drawings in which:

FIGURE 1 is an elevation, partly in section, of an edge roll according to the invention which is illustrated engaging a margin of a ribbon of viscous glass which is being advanced along the surface of a bath of molten metal.

FIGURE 2 is a section on line IIII of FIGURE 1,

FIGURE 3 is an elevation similar to FIGURE 1 of another embodiment of an edge roll according to the invention, and

FIGURE 4 is a section on line IVIV of FIGURE 3.

In the drawings the same references indicate the same or similar parts.

A first embodiment of the invention is illustrated in FIGURES 1 and 2 of the drawings. A ribbon 1 of viscous glass is being advanced along the surface 2 of a bath 3 of molten metal which is contained in a tank structure,

3 one side wall of which is shown at 4. The bath of molten metal is held in an elongated tank structure and is preferably a bath of molten tin or of a molten tin alloy having a specific gravity greater than glass and in which tin predominates.

As the ribbon 1 of glass is advanced along the bath 3 its temperature is regulated and both margins of the advancing ribbon of viscous glass are engaged, for example while the viscosity of the glass is within the range to l() poises, at oppositely disposed locations in the tank structure holding the bath of molten metal. An edge roll construction according to the invention for engaging the margins of an advancing ribbon of viscous glass is illustrated in FIGURES 1 and 2. In FIGURE 1 the edge roll is shown engaging one margin of the ribbon of glass 1.

The edge roll according to the invention comprises three toothed wheels 5, 6 and 7, which are in the nature of sprocket wheels and which may be made of a material which is non-wettable with respect to molten glass and is not attacked by molten glass, for example carbon in the form of graphite or boron nitride. Alternatively the wheels may be of spheroidal graphite cast iron, or stainless steel.

The three toothed wheels have equal numbers of teeth and, as shown in FIGURE 2, the teeth are of symmetrical profile. Each tooth has a straight outer edge 9, and these straight outer edges 9 of all the teeth are parallel to the axis of the wheels. The Width of the teeth 8 is less than the width of the wheels so that when the wheels are mounted, as will be described, in abutment with each other the sets of teeth are spaced apart axially of the edge roll by the annular shoulders 10 formed by the cylindrical part of the peripheries of the wheels 5 and 6.

The three wheels 5, 6 and 7 are fixed to one end of a supporting axle 11 which has a cylindrical bore 12. The axle 11 is supported in bearings 13 fitted in the side wall of the tank structure, which bearings also include sealing glands to prevent influx of external atmosphere into the headspace over the bath through the bearings fitted in the side wall 4. Beyond the outside of the tank wall 4 the supporting axle narrows to form a portion 14 of lesser diameter which is connected to a motor for driving the axle.

The inner end of the axle 11 is closed by an integral end closure 15 and a solid annular collar 16 is fixed to the inner end of the axle. There is a central cylindrical recess 17 in the collar 16 into which recess the end of the axle 11 fits, the collar 16 then being fixed to the end of the axle 11 by spot welding as indicated at 18.

Co-axial with the recess 17 the collar 16 is formed on its inner face 19 with a central boss 20 which projects inwardly of the tank structure. The outer surface 21 of the collar 16 is formed with a radial flange 22. The three toothed wheels 5, 6 and 7 are a clearance fit over the outer surface of the outer periphery 23 of the collar 16 and may each be formed with a flat, not shown, on its inner surface which keys with a flat on the periphery 23 of the collar 16. The inner wheel 7 is thicker than the wheels 5 and 6, and the annular shoulder 24 on the periphery of the wheel 7 is therefore wider than the shoulders 9 on the wheels 5 and 6.

The edge roll construction is completed by an optional feature, namely a sharp edged disc 25 formed of the same material as the wheels and which is mounted on the collar 16 inwardly of the toothed wheels. The diameter of the disc 25 is of the same order as that of the toothed wheels. The disc is pressed into abutment against the wheel 7 and the disc 25 and Wheels 5, 6 and 7 are pressed together and against the outer flange 22 of the collar by a cap 26 formed with a central aperture which fits over and is secured to the boss 20. The disc 25 is axially spaced from the teeth of the innermost wheel 7. The radius of the cap 26 is slightly greater than that of the collar 16 and this mai ta ns he d c a d W eels 5. 6 and 7 fixed to the collar 16 without the cap coming near to contact with the ribbon 1 of plastic glass.

A central pipe 27 is mounted axially in the cylindrical bore 12 and extends through the bore almost to the end of the bore. Cooling fluid is supplied to the axle 11 through the pipe 27, for example water, and circulates through the axle. Because no provisions are made to ensure good thermal connection between the wheels 5. 6 and 7 and the axle 11, the cooling of the axle 11 and the wheels 5, 6 and 7 does not entail appreciable heat extraction from the margin of the glass contacted by the edge roll.

The axle 11 is mounted through the side wall 4 of the tank structure just above the level 2 of the surface of the molten metal bath so that the teeth 8 on the wheels 5, 6 and 7 as well as the sharp edge 28 of the disc 25 bite into the top surface of the margin of the ribbon of viscous glass. As shown in FIGURE 2 the wheels are staggered as they are fixed to the collar so that the straight edges 9 of the teeth are out of alignment with each other. This maintains an even grip on the whole width of the margin of the ribbon.

Because of the axial spacing of the sets of teeth due to the annular shoulders 9 on the wheels 5 and 6 the viscous glass is able to well up between the sets of teeth as indicated at 29, and this ensures a good bite of the teeth into the upper surface of the margin of the glass without the extraction of heat from the glass by the edge roll being too great.

Because the glass is able to well up between the sets of teeth, the edge roll is able to hold the margin of the glass against transverse movement.

The part 14 of the axle 11 is connected to a motor outside the tank structure for rotating the axle at a desired speed so that the peripheral speed of the teeth 8 can be accurately adjusted. The teeth, as just mentioned, bite into the top surface of the viscous glass against the reaction due to the upthrust of the molten metal 3 on the glass, and the rate of advance of the margins of the ribbon 1 at oppositely disposed locations as accurately determined by the peripheral speed of the pair of opposed edge rolls.

The biting of the teeth 8 into the upper surface of the plastic glass necessarily deforms that upper surface in the marginal regions of the ribbon, and in cases where the viscosity of the glass is relatively low, for example about 10 to 10 poises, and when the edge roll is being pressed down into the glass in order to give good engagement of the edge roll with the glass, teeth marks may be propagated laterally along the surface of the ribbon of glass. The sharp edged disc 25 prevents the propagation of such teeth marks into the surface of the main part of the ribbon by acting as a barrier and in effect running a longitudinally extending groove into the upper surface of the glass, which groove defines the inner limit of the marginal area of the ribbon whose upper surface is marred by the biting of the edge roll teeth into the glass.

It will be understood that in cases where the inward propagation of teeth marks does not present a problem the disc 25 may be dispensed with so that the edge roll would only comprise the three toothed wheels 5, 6 and 7 fixed to the collar 16. Although three wheels are described in the preferred embodiment, in some instances only one wheel can give an advantageous result in assisting the control of the marginal speed of the ribbon of glass. Two wheels would give greater control, and while the three wheeled edge roll is preferred if even greater control is necessary four toothed Wheels may be employed. The number of wheels used will depend on how much marginal wastage of the ribbon of glass can be tolerated. Alternatively the edge roll with its peripheral teeth may be machined from a single block of material, for example a block of graphite material.

In the embodiment of FIGURES 1 and 2, although the axle 11 is cooled there are no special provisions for good thermal contact between the cooled axle 11 and the wheels 5, 6 and 7 and the disc 25.

Another embodiment of the invention with difierent cooling arrangements is illustrated in FIGURES 3 and 4, and this embodiment is simplified because it is not shown as including a barrier disc 25, although a disc 25 may be fitted if desired.

The cylindrical bore 12 of the axle 11 opens into a cylindrical drum 30 fixed to the end of the axle 11 and the central pipe 27 for conveying cooling fluid terminates inside the drum 30. The outer face of the drum 30 is formed with a peripheral flange 31 similar to the flange 22 in the embodiment of FIGURES l and 2, and three

toothed wheels

32, 33 and 34 are fixed to the outer cylindrical periphery 35 of the drum 30. For example the wheels may be keyed on to this periphery 35 in such a way that the teeth 8 on the wheels are staggered as shown in FIGURE 4. The teeth 8 each have a sharp outer edge 9 which is parallel to the axis of the edge roll. The outer wheel 32 is formed with an annular shoulder 36 which defines a space between the teeth 8 on the wheel 32 and the teeth 8 on the wheel 33.

The width of the teeth on the wheel 32 is the same as the width of the wheel, and the spacing between the teeth on the wheel 33 and those on the wheel 34 is maintained by an outwardly directed annular shoulder 37 on the inner wheel 34. There is a boss 20 on the inner face of the drum 30, and a holding cap 26 is secured to the boss 20 to maintain the three wheels in abutment with each other and against the outer flange 31.

As illustrated in FIGURE 3, circulation of the cooling fluid indicated by the arrows 38 takes place inside the drum 30 close to the

wheels

32, 33 and 34 so that there is greater cooling of these wheels than in the case of the construction with the solid collar 16 illustrated in FIG- URE l and this edge roll construction can be used where greater heat extraction from the margins of the ribbon of glass can be tolerated.

Normally the motors connected to the axles 11 of the edge rolls are regulated so that the peripheral speed of the teeth 8 of the edge rolls is regulated according to the rate at which the stabilised ribbon of glass is discharged from the bath 3 of molten metal.

More than one pair of edge rolls according to the invention may be provided spaced down the tank structure for engaging the margins of the ribbon of glass in order to provide additional control of the rate of advance of the ribbon along the bath. The edge rolls may be used anywhere along the tank structure where the viscosity of the glass is such as to permit the teeth of the edge rolls to bite into the upper surface of the margins of the glass. For example, when manufacturing fiat glass of soda-lime composition the edge rolls may engage the glass ribbon anywhere where the viscosity of the glass is within the range of 10 to 10 poises.

In the embodiments illustrated the axles 11 of the edge rolls are disposed at right-angles to the direction of advance of the glass, but if desired the axles may be inclined towards the direction of advance of the ribbon, that is inclined slightly downstream of the bath, so that an outwardly directed force component is applied to the margins of the ribbon of glass.

The invention thus provides an edge roll construction which enables improved control of the rate of advance of a ribbon of glass to be achieved as that ribbon glides along a molten metal surface.

I claim:

1. An edge roll for engaging a margin of ribbon of viscous glass as it is advanced along a molten metal surface to control the rate of advance of the ribbon, which edge roll has at least one set of peripheral teeth, arranged perpendicular to the roll axis, which teeth project from the roll for biting into the surface of the viscous glass.

References Cited UNITED STATES PATENTS 1,425,225 8/ 1922 Whittemore 20l 1,598,073 8/1926 Ferngren 6591 3,083,551 4/1963 Pilkington 65182 X ARTHUR D. KELLOGG, Primary Examiner US. Cl. X.R. 65-200, 356

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No- 3, 493, 359 Dated Februar; 3, 1970 Inventor-(s) Jack Lawrenson It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

glass to prevent the propagation of tooth marks in the glass inwardly of the groove when the teeth of the edge roll bite into the margins of the glass to advance the ribbon along the molten metal bath.

Signed and sealed this 16th day of May 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents