GB2174986A - Apparatus for manipulating float glass top rollers - Google Patents

Abstract

Apparatus for effecting angular manipulation of a top roller suitable for use in the manufacture of float glass to control the position of a margin of a glass ribbon floating in a float chamber comprises a top roller mounted at the distal end of a rotatable drive shaft 10 which is connected to two pivot bearings 16, 17 for relative pivotal movement about an axis A, B at each such pivot bearing and which is longitudinally movable with respect to at least one of those pivot bearings (16), a support frame 14 defining two parallel rectilinear tracks 22, 23, and means for driving the pivot bearings 16, 17 along those tracks at speeds which differ in a predetermined ratio thereby to cause the shaft 10 to swing about an axis whose position is determined by that predetermined speed ratio and the distance AB between the pivot axes. <IMAGE>

Description

SPECIFICATION Apparatus for manipulating float glass top rollers This invention relates to apparatus for effecting angular manipulation of a top rollersuitableforuse in the manufacture of float glass to control the position of a margin of a glass ribbon floating in afloat chamber.

In the well known float process for the manufacture ofglass, molten glass is continuously fed to a heated float chamber in which it spreads outto form a ribbon which floats on a bath of molten metal where it flattens out and becomes fire polished. The atmosphere in the float chamber above the bath of molten metal is maintained as a reducing atmosphere in orderto avoid oxidation ofthatmetal so that metal oxide dross will not be picked up by the ribbon to form defects in the glass produced.

As the ribbon advances towards the withdrawal end ofthe chamber, it tends to adopt an equilibrium width and thickness which depends inter alia on its viscosity and surface tension, and on the rate of feed and withdrawal of glass from the float chamber. In order to provide a measure of control overthewidth ofthe ribbon, and thus over its final thickness, it has been proposed to introduce driven top rollers into the chamberto bear againstthe margins ofthe ribbon.

Thetop rollers are causedto rotate on theirdrive shafts at a speed corresponding to the speed of ribbon advance. When the ribbon is being advanced at its equilibrium width and thickness, the drive shafts are setat right anglesto the direction of ribbon advance (orthey are raised so that the top rollers no longer contact the glass) so that they do not exert any sideways forces on the ribbon margins. However, because it is often desired to produce glass of thicknesseswhich differfromtheequilibrium thickness, it is necessary to exert forces on the ribbon margins to control the ribbon width and thus maintain the desired thickness.This is done by swinging the roller drive shafts about generally vertical axes so that the rollers rotate about axes which are obliquewith respect to the direction of ribbon advance, and they exert a variable sideways component of force on the ribbon margins to maintain the desired width and thickness ofthe ribbon, either by exerting tensile or compressive forces across the width ofthe ribbon. Such alterations in the top roller drive shaft positions should be made as accurately as possible in order to achieve consistency in the thickness of the ribbon produced with low wastage of glass.It is also to be noted that the paths followed bythe ribbon margins will vary in position across the bath from time to time as different widths and thicknesses of glass are produced, but provision can readily be madeforthat by longitudinal axial movement of the drive shafts.

Problems arise in sealing the walls of the float chamber at side ports where the roller drive shafts pass through those walls. Such sealing is important in orderto maintain the reducing atmosphere within the float chamber.

Of course those problems can be avoided by locating the rollers and their drives wholly within the float chamber, but this means that the drive motors must be proofed against the high temperatures encountered in that chamber, and this is extremely difficult.

In orderto minimise sealing problems at the side ports in the float chamber, it has been proposed to swing a roller drive shaft about an axis which lies ata face of a sidewall ofthefloat chamberorwithinthe thickness ofthatwall. This reduces the clearance necessaryto accommodate changes in the orientation of the drive shaft, and so simplifies sealing.

By way of example, it has been proposed to mount a motor driving the drive shaft on a carriage movable along concentric part circular tracks laidinthefactory floornexttothefloatchambersothattherollerdrive shaft can be swung about a vertical axis passing through the common centre of those tracks. The tracks are laid so that that common centre is within the wall thickness. In that proposal, the tracks are formed by racks, and the carriage is driven along them by pinions. It has been found that this arrangement suffers from certain disadvantages.

It is an object of this invention to provide apparatus for effecting angular manipulation of a top roller in a manner which is precise and which does not give rise to unacceptable sealing problems.

According to the present invention, there is provided apparatus for effecting angular manipulation of a top rollersuitablefor use in the manufacture offloat glass to control the position of a margin of a glass ribbon floating in afloat chamber, characterised in that such apparatus comprises a top roller mounted at the distal end of a rotatable drive shaft which is connected to two pivot bearings for relative pivotal movement about a pivot axis at each such pivot bearing and which is longitudinally movable with respect to at least one of those pivot bearings, a supportframe defining two parallel rectilineartracks, and means for driving said pivot bearings along said tracks at speeds which differ in a predetermined ratiotherebyto cause said shaft to swing about an axis whose position is determined by said predetermined ratio and the distance between said pivot axes.

Apparatus incorporating the combination of features afforded by the present invention presents several advantages over previous proposals in this field. The apparatus forms a self-contained unit which does not rely on tracks on the factory floor and which can easily be moved for example from one float chamber to another, or for maintenance. The swing axis will be at a location which is fixed in relation to the tracks, assuming that the said predetermined ratio is fixed, and by moving the supportframe,this location can be varied to that which is most convenient for any given float chamber.Because the tracks are on the supportframe rather than the factory floor, they are less likely to become clogged with factory dirt, and because they are straight, movement of the shaft pivot bearings along the tracks can be quite precisely controlled without resorting to the use of components of the highest precision, thus contributing to reliability and accuracy of the control ofthetop roller location.

The said pivot bearings may be driven in anyway consistent with achieving the desired accuracy of movement, for example, each pivot bearing drive may comprise a rack and pinion arrangement, but it is preferred that the means for driving each said pivot bearing comprises a worm. Such an arrangement is simple and convenient, and it enables substantial elimination of backlash at relatively low cost Drive is simplified when said pivot bearings comprise threaded portions riding on said worms, and this is the most preferred arrangement.

Advantageously, there is a common drive means for driving both said pivot bearings in synchronism.

This ensures proper relative motion ofthe pivot bearings. For example, if the pivot bearings are worm driven, the worms may be linked by one or more V-belts or more preferably one or more toothed belts or chains, and most preferably by gear pinions, in such a way that the worms are constrained to drive the pivot bearings at speeds which differ in said predetermined ratio. Such worms preferably have the same pitch.

When such a common drive means is provided, it is preferred that said drive means includes a single motor. This allows powered drive ofthe shaft pivot bearings without unnecessarily high cost.

Alternatively, or in addition, it is preferred that said drive means includes a manual crank, so as to permit manual drive ofthe shaft pivot bearings whenever this is desired.

Advantageously, said pivot bearings mount a carriage carrying said shaft and a shaft drive means.

This provides a compact apparatus and simplifies the transmission of power to the roller drive shaft.

In the most preferred embodiments ofthe invention, said supportframe is wheeled and provided with yacks for raising it off its wheels for fixing its location. This has the advantage of permitting easy relocation of the apparatus whenever this is required, while allowing a stable substantially immobile supportforthe apparatuswhen itis in use.

Advantageously, means is provided for monitoring changes in the angle between said shaft and said tracks. This is a very simple way of monitoring changes in the orientation of the roller drive shaft and thus of monitoring changes in the location and orientation ofthetop roller itself.

Preferably, such angle monitoring means comprises a connecting rod mounted for pivotal movement about a first axis movable parallel to the shaft axis and about a second axis on the support frame which is equidistant between the first connecting rod pivot axis and the swing axis ofthe shaft. With such an arrangement it is found thatthe connecting rod will undergo an angular displacement twice that ofthe drive shaft on movement ofthe shaft pivot bearings along the tracks, so as to allow a highly accurate measure of any changes in orientation. Such a connecting rod can be arranged to move a pointer across a scale for a sight reading of angle changes, but it is preferred that said angle monitoring means includes a pulse generator arranged to deliver a signal indicative of changes in said angle.Such a signal could,for example, be passed to control circuitryto govern drive means forthe drive shaft pivot bearings.

A preferred embodiment of the invention will now be described byway of example only with reference to the accompanying diagrammatic drawings in which: Figure lisa plan view of a float chamber of a float glass manufacturing plant equipped with two sets of the apparatus of Figures 2 and 3, Figure 2 is a plan view of a lower part only of an embodiment of apparatus according to this invention, and Figure 3 is a side elevation partly in cross section of the apparatus of Figure 2, some parts of the apparatus being omitted for simplicity in the drawing.

In the well known float process forthe manufacture of glass, as illustrated by the apparatus shown in Figure 1, molten glass 1 is poured onto the surface of a bath 2 of molten metal contained within a float chamber 3. The glass spreads out on the surface of the bath 2, and is continuously advanced as a ribbon 4 through the heated float chamber 3 where itflattens out and becomes fire polished as it floats on the bath of molten metal. The atmosphere in the float chamber 3 above the bath 2 of molten metal is maintained as a reducing atmosphere in order to avoid oxidation of that metal so that metal oxide dross will not be picked up bythe glass to form defects in the ribbon 4 produced.

As the ribbon 4 advances towards the withdrawal end 5 ofthe chamber3, ittendsto adopt an equilibrium width and thickness which depends inter alia on its viscosity and surface tension, and on the rate of feed and withdrawal of glass from the float chamber. In orderto provide a measure of control over the width ofthe ribbon, and thus over itsfinal thickness, driven top rollers 7 are introduced into the chamberto bear against the margins 8 ofthe ribbon.

The top rollers are caused to rotate by drive motors 9 on their drive shafts 10 at a speed corresponding to the speed of ribbon advance. When the ribbon 4is being advanced at its equilibrium width and thickness, the drive shafts 10 are set at right anglesto the direction of ribbon advance as shown to the right in Figure 1 (orthey are raised so thatthe top rollers no longercontactthe glass) so that they do not exert any sideways forces on the ribbon margins 8. However, whenever it is desired to produce glass of thicknesses which differfrom the equilibrium thickness, it is necessary to exertforces on the ribbon margins 8to control the ribbon width and thus maintain the desired thickness. This is done by swinging the roller drive shafts 10 about generally vertical axes such as 11 so thatthe rollers rotate about axes which are oblique with respectto the direction of ribbon advance, as shown to the left of Figure 1, and they exert a variable sideways component offorce on the ribbon margins 8 to maintain the desired width and thickness ofthe ribbon, either by exerting tensile or compressive forces across the width ofthe ribbon.

Such alterations in the top roller drive shaft positions should be made as accurately as possible in orderto achieve consistency in the thickness ofthe ribbon produced with low wastage of glass. It is also to be noted that the paths followed by the ribbon margins will vary in position across the bath from time to time as different widths and thicknesses of glass are produced, but provision can readily be madeforthat by longitudinal axial movement ofthe drive shafts 10.

As shown in Figure 1 ,the motor9 and a bearing 12 forthetop roller drive shaft 10 are mounted on a support generally indicated at 13. That support 13 is more clearly shown in Figures 2 and 3. The support 13 comprises a support frame 14and atop rollerdrive carriage 15 movable over the supportframe under the influenceofa carriage drive means. The top roller drive carriage is omitted from Figure 2, and the carriage drive means is largely omitted from Figure 3.

The top roller drive carriage 15 carries the motor9 and the bearing 1 2 for the top roller drive shaft 10. The axis of that drive shaft is shown in pecked lines at D.

The carriage 15 is itself mounted on pivot pivot bearings 16, 17which are connected to worm followers 18,19 riding on parallel worms 20,21 carried by the support frame 14. The pivot pivot bearings 16, 17 have axes A, B respectively which are coplanarwith the drive shaft axis D and intersect the axis of the respective worm 20, 21 at right angles. One pivot pivot bearing, 16, is mounted to the drive carriage 15for sliding movement in a direction parallel to the drive shaft axis D, while the other pivot pivot bearing 17 is fixed with respect to that carriage.

Operation ofthe worms 20,21 causes the pivot pivot bearings 16, 17to ride along parallel rectilineartracks 22,23.

The drive mechanism for the worms 20,21 is shown in Figure2wherethewormfollowers 18,19 are shown in their median positions. Each worm 20, 21 is mounted in bearings 24 attached tothesupport frame 14, and carries a gear pinion respectively 25,26 at one end. The primary drive source is an electric motor 27 which drives, via chain ortoothed belt 28, a sprocket 29 connected to a gearbox 30. Drive is transmitted through gearbox 30 to a first worm drive shaft 31, and by bevel gears (not shown) to a worm drive transmission shaft 32. The worm drive transmission shaft 32 in turn transmits powervia a second gearbox33 also containing bevelgearstoa second worm drive shaft 34.Each worm drive shaft 31,34 carries a gear pinion respectively 35,36 which meshes with the respective worm-mounted pinion 25,26. Bearings 37 are provided forthe ends ofthe worm drive shafts 31,34. The gearing arrangement is such that when the motor 27 is operating, the worms 20,21 (which have the same pitch) are driven at speeds which differ in a predetermined ratio. This causes the axis D ofthe drive shaft to swing about a fixed notional axis (compare 11 in Figure 1 )whose distance L along the drive shaft axis D from pivot axis B at any given time is governed by the equation (ss21/(020 = V(L L/(L+AB), where 0)20 and o)21 are the respective speeds of rotation ofthe worms 20 and 21, and AB isthe distance at that time between the pivot axes A and B.

In orderto supplement the motor 27, should this be required during setting up or other operations, a ma nua l ly operable cra nkshaft 38 is provided, mounted on the support frame 14 in bearings 39 and arrangedto drive a sprocket40 ganged tothe sprocket 29.

Reverting now in particularto Figure 3, in orderto monitor changes in the orientation of the roller drive shaft axis D, a connecting rod 41 is fixed to a pivot axle 42 carried by a bearing 43 mounted on the support frame 14to pivot about an axis Cwhich is parallel to pivot axes A and B. The distal end of the connecting rod 41 carries a pivot ring 44 having a pivot axis E which isslidable along a guide rod 45 attachedtothe drive carriage 15 in such a mannerthat the axis ofthat guide rod 45 is parallel with the drive shaft axis D and coplanarwith that axis D and the pivot axesAand B.

The effective length of the connecting rod 41, that is the distance between the pivot axes C and E, is made equal to the distance between the axis C and the roller drive shaft swing axis 11 (Figure 1). Underthose circumstances, any swing of the roller drive shaft axis through a given angle will cause the connecting rod to movethroughtwicethatangle. Such changes are monitored by incorporating a pulse generator in the bearing 43, and the pulses thus generated may beefed to control circuitry (not shown) governing the operation of the motor 27 which causes the roller drive shaft 10to swing.

The supportframe 14 is provided with caster assemblies 46 for ease of movement in installation, and is also equipped with screw jacks 47. The jacks 47 serve to anchorthe support frame 14 in its desired position. It will be appreciated that movement of those jacks 47, when they are bearing on the factory floor, will also vary the anglewhich the roller drive shaft axis D makes with the horizontal. Thus the jacks can also be used to bring a driven top roller7 (Figure 1) into or out of contact with a ribbon margin 8, and to vary the downward pressure exerted by that roller on that margin.

The support 13 carrying the top roller drive means may be positioned so that the swing axis 11 ofthe roller drive shaft is at any desired location in relation to a floatchamber3with which it isto be used. As shown in Figure 1,the support 13 is located so that that swing axis 11 is located at the outside surface of the wall ofthefloatchamber. Of course the support 13 could be located so that the swing axis 11 waswithin the thickness ofthe float chamberwall if this was found more convenient. Closure of the hole 48 through which the roller drive shaft 10 enters the float chamber3isassisted by mounting a plate 49 onthe outside ofthe float chamber wall.Packing material (not shown may be provided between the plate 49 and the roller drive shaft 10, and/or a bellowstype seal may be made between them. With such an arrangement it is found that sealing of the hole 48 against the ingress of oxidising ambient atmosphere is greatly improved even during adjustment of the top roller orientation.

Any desired fine longitudinal adjustment of the roller drive shaft 10 and hence ofthe roller7 may be catered for by mounting the shaft drive motor 9 to the top rollerdrive carriage 15via a slide 50 shown in Figure 3.

As many pairs oftop rollers and top roller manipulation mechanisms as are desired may be accommodated along the float chamber, though to simplifythe drawing, only one such pair is shown.

The actual number of such pairs oftop rollers to be used at any time will in general depend on the desired thickness ofthe glass ribbon being produced and in particular on the difference between thatthickness and the equilibrium thickness ofthe glass.

In a variant embodiment, instead of being floor mounted, the whole apparatus for effecting angular manipulation of a top roller is inverted and slung from an overhead gantry. In such variant, itwill be appreciated that the caster assemblies 46 and screw jacks 47 may be omitted.

Claims (11)

1. Apparatus for effecting angular manipulation of a top rollersuitablefor use inthe manufacture of float glass to control the position of a margin of a glass ribbon floating in a float chamber, characterised in that such apparatus comprises a top roller mounted at the distal end of a rotatable drive shaft which is connected to two pivot bearings for relative pivotal movement about an axis at each such pivot bearing and which is longitudinally movable with respectto at least one of those pivot bearings, a supportframe defining two parallel rectilineartracks, and meansfordriving said pivot bearings along said tracks at speeds which differ in a predetermined ratio therebyto causesaid shafttoswing aboutan axis whose position is determined by said predetermined ratio and the distance between said pivot axes.

2. Apparatus according to claim 1, wherein the meansfordriving each said pivot bearing comprises aworm.

3. Apparatus according to claim 2, wherein said pivot bearings comprise threaded portions riding on said worms.

4. Apparatus according to any preceding claim, wherein there is a common drive means for driving both said pivot bearings in synchronism.

5. Apparatus according to claim 4, wherein said drive means comprises a single motor.

6. Apparatus according to any preceding claim, wherein said drive means comprises a manual crank.

7. Apparatus according to any preceding claim, wherein said pivot bearings mount a carriage carrying said shaft and a shaft drive means.

8. Apparatus according to any preceding claim, wherein said supportframe is wheeled and provided with jacks for raising it off said wheels for fixing its location.

9. Apparatus according to any preceding claim, wherein means is provided for monitoring the angle between said shaft and said tracks.

10. Apparatus according to claim 9, wherein such angle monitoring means comprises a connecting rod mounted for pivotal movement about a first axis movable parallel to the shaft axis and about a second axis on the supportframe which is equidistant between the first connecting rod pivot axis and the swing axis ofthe shaft.

11. Apparatus according to claim 9 or 10, wherein said angle monitoring means comprises a pulse generator arranged to deliver a signal indicative of changes in said angle.