US1586618A - Method and apparatus for drawing sheet glass - Google Patents

Description

June 1 1926.

E?.g T. FERNGREN METHOD AND APPARATUS FOR 1'3R.'\W.Ul(`x- SHEET GLASS d 3 Sheets-#Sheet l D Filed uw v. 1922 June 1 1926. 1,586,618

E. T. FERNGREN ME'IHOD ANDAPPARATUS FOR DRAWING SHEET GLASS -Filed July 7. 1922 3 Sheets-Sheet 2 .lune 1 1926. 1,586,618

E. T. FERNGREN METHOD AND APPARATUS FOR DRAWING SHEET GLASS Filed July '7. 1922 3 Sheets-Sheet 5 /N VEN roe fnac/7 Z'rrggo HY ,4 7' 7' GENE Y Patented June 1, 1926.

UNITED STATESI PATENT OFFICE.

ENOCH T. FERNGREN, OF TOLEDO, OHIO, ASSIGNOR TO THE LIBBEY-OWENS SHEET GIASS COMPANY, OF TOLEDO, OHIO, A CORPORATION OF OHIO.

METHOD AND APPARATUS FOR DRAWING- SI'IEET GLASS.

Application mea July 7,

This invention relates to the art of drawing a continuous sheet of glass, and more glass with smooth unwrinkled surfaces.

1While the invention is not limited to use with any one system of producing sheet glass, it is illustrated in connection with a sheet drawing apparatus of the general type tet forth in the patent to Colburn, 1,248,809,

granted December 4, 1917. In this system, a continuous sheet of glass is drawn upwardly from a bath of molten glass, and then, while still in a somewhat plastic condition, although substantially set in linal sheet form, is bent into a horizontal plane and carried off into a leer. As is well-known in this art, some means must be provided to maintain the width of the sheet during its period of formation, else it will gradually narrow away until no sheet is left. In the patented process referred to, a pair of knurled rollers grip the edge portion of each sheet near its source, the rollers being driven at a lower rate of speed than that at which the sheet is being drawn upwardly. These rollers act both to feed up glass into the edges of the sheet, and also to hold down on the sheet edges and maintain a longitudinal tension in these edges. Above these` rollers the sheet narrows up to some extent due to the contraction when cooling and attenuation of the sheet under longitudinal stress, but the final sheet is produced of a constant and uniform width and thickness.

According to the present invention, the knurled edge-rollers above described are retained, but their surface conformation is so modified that the sheet edges are rolled out with an edge bead or thickened portion. This thickened edge is gripped and held out during the formative period of the sheet while the thickness determining attenuation is taking place, by a series of superposed pairs of idler rollerswhich prevent the lateral con- I "rh 1922. Serial No. 573,292.

traction of the sheet, and impart a lateral stretch or tension to the sheet. At the same time, the bead or thickened edge is gradually liattened or ironed out by these gripping rollers so that the final sheet edges are of much the same proportions as those resulting from the original Colburn process. The sheet is thus maintained under practically constant lateral and longitudinal stresses during its formation period and until it becomes set in final sheet form. This works to produce a somewhat wider sheet, and also to prevent the formation of cords and wave lines as well as areas of unequal thickness.

lVllile the sheet is being subjected to the drawing stresses above described, it is also given a temperature treatment which tends to relieve the high surface tension normally present in drawn sheet glass, and to equalize the stresses within the body of the sheet. The forming sheet is subjected to successive cooling and heating treatments, whereby a chill is first driven into the body of the sheet, and then the surface portions are reheated to relieve the excessive surface cooling.

The invention also involves improved forms of cooling and heating means for carrying out the temperature treatments referred to above.

Other objects and advantages of the invention will become apparent from the following detailed description of one approved form of the apparatus.

Referring to the accompanying drawings:

Fig. 1 is an elevation showing a face view of the vertically rising sheet with the width maintaining rollers operating upon the edges thereof. For the sake of clearness the cooling and heating mechanisms are partially broken away in this view. The drawpot containing the molten glass is shown in transverse vertical section.

Fior. 2 is a horizontal section taken sub` stantlally on the line 2 2 of Fig. 1.

Fig. 3 is a horizontal section taken substantially on the line 3-3 of Fig. 1.

Fig. 4 is an end elevation of one of the width maintaining units.

Fig. 5 is a detail plan view of one pair of the knurled edge rollers which form the sheet edge.

Figs. 6 to 11, inclusive, are similar views f j 'a of the successive pairs of edge holding rollers, taken in ascending order throughout one series.

Fig. 12 is a longitudinal section throughout the sheet-drawing apparatus, showing somewhat diagrammatically the several temperature controlling units.

Fig. 13 is an enlarged section through one of the improved cooling units.

Fig. 14 is an enlarged perspective of a portion of one of the shields used to control the action of the surface heaters.

Fig. 15 is a detail section illustrating the operation of these shields.

Fig. 16 is a. diagrammatic section through the sheet during its formative period, to illustrate the effect of the heat treatment.

Referring first more particularly to Figs. 1 to 4 and 12, the sheet 1 is drawn upwardly from the molten glass 2 in pot 8, and bent laterally, while still in a somewhat plastic condition, over bending roller 4 and then carried off horizontally through suitable flattening mechanism into a leer. At 5 in Fig. 12 are shown coolers (preferably of the type containing water or other cooling fiuid), which act to form a` stiffer and more tenacious surface layer on the molten glass 2 and also to cool the surfaces of the sheet near the source. This action permits of a greater speed of draw for the sheet. The coolers 5 have been omitted in Figs. 1 to 4 for the sake of clearness, these being old in machines of this type. It should be understood that the sheet 1 might be drawn continuously upward, instead of bent laterally over the roll 4 as here illustrated. This present invention has to do with the sheet during its formative period and is not concerned with the specific mechanism used for imparting longitudinal pull to the sheet, or for handling and disposing of the finished sheet.

In the Colburn machine, (and in the present apparatus in modified form), a pair of edge forming rollers G are employed at or near the source of each edge of the sheet. These rolls are driven at a speed slower than the sheet is being drawn, thus feeding the glass into the sheet edges and simultaneously providing a drag 0r tension on the edges of the sheet between these rolls and the bending roll 4. This serves to hold the sheet substantially to width and allows the process to be carried on continuously. 7ater or other cooling fluid flows in and out of the rolls G, acting to preserve the metallic rollers in the intense heat and simultaneously cooling the sheet edges which contact therewith, forming a more tenacious, stiffer edge portion. However, the sheet does not entirely maintain its initial width after leaving the edge forming rolls, but narrows away somewhat, as illustrated by the dotted lines a: in Fig. 1, due to the attenuation of the sheet, and the contraction while cooling. It is the object of the sheetedge holding mechanism now about to be described to elastically hold the sheet out to substantially its initial width during its formative period thus imparting a lateral stretch or tension to the sheet, avoiding the formation of corrugations or waves, and improving the quality and smoothness of the sheet surface.

In the present apparatus, the edge forming rollers G have been retained, and function much the same as in the previously7 described apparatus. However, the surface conformation of the rollers has been slighty modified. The rollers are no longer truly cylindrical, but are tapered to a smaller diameter near their rear ends as at 7, forming a. wider groove between the pair of rollers at this point, which acts to roll out a bead or thickened portion 8 at. the edge of the sheet. It is this thickened edge that is gripped by the pairs of holding rollers, hereinafter described, to hold the sheet to width.

As the width maintaining mechanisms atthe two sides of the sheet are substanti-ally duplicated, a description of one will suffice for both. Mounted (as hereinafter described) above the edge holding rolls G, is a series of superposed pairs of edge-holding rolls which grip into the thickened edge 8 and hold the sheet substantially to its initial width. The apparatus here shown by way of example, employs sii; pairs of these rolls numbered 9, 10, 11, 12, 13 and 14, respectively. The first pair of rolls 9, (Fig. 6), bites into the thickened edge 8, forming groove 15, the thicker portion 8 back of the grooves acting as a wedge to prevent the sheet pulling out from between the rollers. rlhe successive pairs of rollers 10 to 14, (Figs. 7 to 11), engage in the grooves 15, and function both to hold the sheet to width and at the same time to gradually flatten out the thickcned edge S, so that the sheet leaves the last pair of rollers 14 with the edges of substantially the same thickness as the sheet. This is desirable as it facilitates the subsequent bending of the sheet about the roller 4, and the handling of the sheet in the flattening and annealing mechanism. This process of ironing out the thickened edges may be accomplished either by arranging the axes of the successive pair of rollers at successively decreasing angles to the plane of the sheet, or by varying the contour of the successive roller surfaces throughout the series. ln the preferred form of the apparatus here shown both expedients are combined, as best illustrated in Figs. G to 11. These rollers act upon the sheet while it is passing through that zone wherein the sheet remains semi-plastic, and is still susceptible to the ironing or flattening process without danger of cracking the sheet. As the sheet passes beyond the upper pair of rollers 14 its temperature condition and the internal stresses have been so modified that thereis little tendency for further contraction.

The pintles 16 for the set of rollers at one Side of the sheet edge, have bearings in a bracket-arm 17 which is a fixed extension of supporting member 18, which is pivoted at 19 for swinging movement in a vertical plane, in the main carrier member 20. The pintles 21 for the set of rollers on the opposite side of the sheet edge, have bearings in a bracket-arm 22 pivoted at 23 in the supporting member 18. In normal operating position the bracket arms 17 and 22, and the rollers carried thereby, are arranged at symmetrical angles at the two sides of the sheet edge but bracket 22 is capable of being swung away from the plane of the sheet, to facilitate the starting operation when the sheet is drawn up -by means of a bait and must be pulled into place between the normal operating positions of the holding rollers. An operating lever 24 is pivoted at 25 on carrier 20, and a rod 26, adjustable in length by turnbuckle 27, connects this lever with the bracket arm 22. Rod 26 is pivoted at 28 to bracket arm 22, and at the other end is pivoted to pin 29 journaled vertically in lever 24. By manipulating lever 24 the bracket arm 22 and the set of rollers carried thereby may be swung into or out of engagement with the sheet edge 8. The parts may be held in normal operating position by a removable bolt or peg 30, inserted through mating holes in the lever 24 and carrier 20.

There is an upwardly extending arm 31 on the pivoted supporting member 18, and a similar arm 32 projects up from the carrier 20. A rod 33 is pivoted at one end at 34 to the arm 31, and the other end of the rod passes freely through an aperture in the enlarged end 35 of a pin 36, horizontally pivoted in arm 32. Adjusting nuts 37 engage the threaded end of rod 33 at either side of member 35. By suitably manipulating these adjusting nuts, the supporting member 18 may be swung about pivot 19,

and the inclination of the edge holding rollers from the vertical can be varied as found desirable. In this way the path that the sheet edge is forced to follow by these holding rollers may be varied to get the proper degree of tension inthe sheet at various heights about the molten source 2.

The outer portion of carrier 20, which is of non-circular cross-section to prevent rotary movement thereof, is slidably mounted in the block 38, which in turn is slidably mounted in the main supporting member 39. Support 39 is fixed in any suitable manner to the beams 40 at the sides of the machine. Support 39 may also carry the supporting 'sheet by spring 44. The rollers are driven from shaft through gearing 46.

Block 38 is held fixed in adjusted position within support 39, by adjusting bolt 47 whose threaded central portion 48 engages a threaded lug 49 extending down from block 38, and whose ends are held against longitudinal movement but are freely rotated in lugs 50 o-n support 39. By rotating bolt 47, the edge holding rollers may be adjusted in or out, parallel to the plane of the glass sheet 1.

A reduced end portion 51 of carrier 20, extends out through a plug 52 screwed into the end of block 38. A compression spring 53 surrounding end portion 51 and confined between the end of carrier 2O and the plug 52, yieldingly limits the outward movement of carrier 20. A second compression spring 54 surrounds member 51 and is confined between plug 52 and an adjusting nut 55 mounted on the threaded end 56 of member 51. The spring 54 is placed under a suitable initial tension by nut 55, and the inward pull of the sheet 1, as it tends to contract or attenuate, will further compress the spring 54. This compressed spring will then constantly exert a yielding outward pull or tension on the sheet 1 as it is drawn.

When this apparatus is installed supporting base 42 for the edge forming rollers 6 will first be adjusted within the main support 39 until the edge forming rolls are properly positioned for t-he desired width otl sheet. The corresponding normal inward position of the edge-holding rollers is then adjusted by means of bolt 47, and the proper inclination of the series of rolls is obtained by adjusting nuts 37. By adjusting nut the desired tension to be applied to the sheet is obtained. These adjustments once properly made, the apparatus should require very little attention.

In operation, the drawing of the sheet is started by means of a bait, as is usual in machines of this type. The edge-forming rollers 6 are first clamped in position at the base of this sheet, and then the edge-holding rolls are clamped on the thickened sheet edge 8. The first pair of rollers 9 bite rather deeply into the plastic glass and form the grooves 15, the successive pairs of rollers als there above engaging in these grooves, and also iattening out the bead of glass behind the grooves. As these rollers are all idlers, and turn freely in their bearings, very little resistance is offered by them to the normal longitudinal attenuation of the sheet edge. The lengthwise drawing and stretching of the sheet takes place much the same as if the lateral stretching roll-ers were not used. As these two tensioning and stretching forces are exerted simultaneously at right-angles to one another, over that plastic area of the sheet in which it is taking form, no opportunity is offered for the sheet to contract or draw up into waves or other irregularities.

Referring now more particularly to Figs. 12 to 16, inclusive, the means for giving the temperature treatment to the sheet of glass during this formative period, will be described. As already noted coolers 5 are used to provide the more tenacious surface glass on pool 2, and to stiften the sheet 1 at its source. A cooler 7 5 may also be provided to cool the under side of the sheet and the bending roll 4 just before these come in contact with one another. rli`hese coolers are all parts of the present apparat-us as disclosed in the Colburn patent, referred to above.

l/Vith the system as above set forth, only the surface portions of the sheet are initially chilled, and the sheet is drawn with a hotter core which must gradually cool off during the subsequent cooling and annealing process. This hotter and less tenacious glass tends to drag behind, and will not pull up as evenly and steadily as the cooler more tenacious surface glass. This, together with the unequal stresses set up in the cooler surfaces and the hotter interior of the sheet, tend to produce corrugations and waves in the sheet surfaces, as the sheet shrinks and attempts to stabilize the various stresses produced within its structure.

In the present system a pair of additional coolers are employed to locally chill the sheet just above the so-called meniscus, or body of glass 57, from which the sheet is drawn. These coolers are preferably vof a type which will positively drive a chill into the sheet struct-ure. In the improved type of cooler here shown 13), a waterjacketed pipe 58 extends horizontally across the machine parallel to and adjacent the sheet surface. Air under pressure is forced through this pipe, and may escape through a series of apertures 59, arranged at intervals in the pipe walls. A circulation of cold water is maintained through the passages 60 in the hollow walls of pipe 58. An enclosing shield or defiector G1, having a directing slot 62 placed close to the sheet surface, surrounds the pipe 5S. The air forced out through apertures 59 escapes from the shield, (as indicated by the arrows), in an even horizontal stream against the adjacent surface of the glass sheet. The water-cooled walls of the pipe 5S, not only cool the air passing through the pipe and the apertures 59, but also the surrounding air enclosed in the shield or detiector 61. By this mechanism, an even steady stream of cold air is forced against the sheet surface which drives a chill deep into the sheet structure.

Immediately above these air-coolers G1 are located a pair of heaters, which act to reheat the surface portions of the sheet, and relieve the excessive surface tension. These heaters, as here shown are simply a pair O of gas-pipes 63, having a series of burner openings which direct a horizontal sheet of flame against the adjacent surface of the passing sheet. To modify and regulate the effect of these flames at different points across the sheet, shields or screens (Se, (Figs. 14 and 15), may be used. Each of these screens comprises a supporting bar or frame 65, and a transverse series of refractory or heat-resisting panels GG, which have support` ing stems 6T adjustably held in the frame 65. rIhese panels may be dropped to the desired degree between the flames and the glass sheet, and act to deflect a large part of the heating fiame away from the sheet and thus modify its effect thereon. If a less intense heat is desired at the center portion of the sheet, the panels toward the center will he adjusted lower so as to cut off a greater portion of the flames than those nearer the sheet edges.

The general effect of this successive heating and cooling treatment may be best described by referring to the diagram shown in Fig. 16. In this graphic illustration, the colder glass is indicated by longitudinal shade lines. rhe coolers 5 create a rather stilll tenacious surface layer 68 on the molten pool 2, and the meniscus 57, and it is from these surface layers that the sheet surfaces are drawn. In the zone between a and the coolers G1 operate, and as shown at 69, a chill is driven deep into the sheet. In the zone between L and c, the surface reheaters G3 act upon the sheet, and the chill in the surfaces is partly removed. This relieves the surface tension, and the sheet structure now embodies the internal cool and tenacious portions TO, upon which the main tensional and stressing forces are now exerted, and outer softened and less tenacious skin portions. Perhaps a somewhat hotter central core 71 will still exist within the sheet. As the sheet rises beyond c, and gets out of the influence of the heaters (53, the surface portions will again be cooled by the surrounding atmosphere, and the entire sheet structure will attain a substantially uniform temperaturc condition as indicated at- 72. Obviously, the different temperature areas within the sheetare not as distinct as indicated in the diagram, but will blend into one another, but the object sought is to so treat the sheet in the zone from a to 0 that the sheet will emerge with the internal stresses balanced and stabilized. It is in this zone from a to c that the edge holding ro-llers are active and in this zone the greatest amount of lengthwise attenuation takes place. While the coolers 61 are acting on the sheet in zone 1f-Z), the greatest stresses are set up in the sheet, and the greatest shrinkage tends to take place. At this time the sheet is securely held against lateral shrinkage by the edge rollers. In the zone b-c, the stresses are greatly relieved or modified, at least in the surfaces of the sheet, and by the time the sheet passes out of the sidewise stretching zone c c, its temperature and general plastic consistency7 throughout its structure will be quite uniform, and it will be past that stage of temperatures when elasticity is pronounced, and it will be substantially fixed as to width. Any further contraction that may take place will be uniformly distributed throughout the sheet structure and will not wrinkle or disturb the smooth flat surface portions.

Claims:

1. In the art of drawing sheet glass from a mass of molten glass, the method of maintaining lateral tension in the sheet during the formative period, consisting in forming thickened edge portions on the sheet at the sheet source. gripping the thickened portions between rolling surfaces after they have passed beyond their place of formation and immediately adjacent thereto and holding the sheet against its tendency to contract.

2. In the art of drawing sheet glass from a mass of molten glass. the method of maintaining lateral or side tension on the sheet while in the formative period, consisting in forming thickened edge portions on the sheet at the sheet source, gripping these thickened portions-at a series of adjacent points and holding the sheet against its tendency to contract.

3. In the art of drawing sheet glass from a. mass of molten glass, the method of maintaining lateral or side tension on the sheet while in the formative period, consisting in forming thickened edge portions on the sheet at the sheet source, gripping these thickened portions at a series of adjacent points and holding the sheet against its tendency to contract, and simultaneously flattening out the thickened edge to approximately the normal thickness of the sheet.

4. The method of forming sheet glass, consisting in drawing the sheet from a source of molten glass, forming thickened edge portions or beads on the sheet at its source, grasping the thickened edges and holding the sheet against contraction at a series of adjacent points until the sheet becomes set, and simultaneously iiattening out the thickened portions.

5. In the continuous drawing of sheet glass vertically, that procedure which consists in clutching the opposite edges of the sheet with horizontall movable and elastically adjusting stretc ling devices which at their respective contact points with the glass are so related therewith as to permit vertical movement of the .said edges in the line of draw, in moving said devices in opposite directions on the horizontal plane while thus related to the edges of the vertically advancing sheet and stretching the same horizontally.

6. In the continuous drawing of sheet glass vertically, that procedure which consists in clutching the opposite edges of the sheet with horizontally movable and elastically adjusting stretching devices which at their respective contact points with the glass are so related therewith as to permit vertical movement of the said edges in the line of draw, in moving said devices in opposite directions on the horizontal plane and creating a live constant compensating cross tension through the sheet by elastic adjustment of vthe opposing clutching devices toward and from the same in conformity with the variables of material resistance of the glass under vertical drawing stress in the sheet area in transit between said devices.

7. That practice in the art of drawing sheet glass which consists in forming grooves in the border glass along the opposite edges of the sheet as it is being drawn, in engaging rolling edge-gripping means with said grooves as they are forming, in communicating stretching tension across that area of the sheet which in transit has its border. portion progressively engaged with said rolling means and in simultaneously effecting this area of the glass by temperature treatment to secure a uniform plasticity therein as the transverse tension is relaxed.

8. That practice in the art of drawing sheet glass which consists in securing a hold on the plastic glass along the opposite borders of the sheet as it is being drawn with opposite sets of rotating devices which in succession are adapted first to groove in and then to Hatten out the said borders of the glass as the sheet as a whole is advancin in the line of draw, in communicating wi ening stress to the sheet area extending between said devices and in acting on the glass while it is being thus drawn and tensioned to then and thereafter secure uniform and balanced temperature conditions throughout the thickness of the sheet.

9. In an apparatus for drawing sheet glass, mechanism for maintaining lateral or side tension on the sheet comprising means adjacent the sheet source for forming thickened edges on the sheet, and',Il rotary means for grasping these thickened edges after they have passed beyond the forming means and immediately adjacentthereto and resisting the tendency of the sheet to contract.

10. In an apparatus for drawing sheet glass, mechanism tor maintaining lateral or side tension on the sheet comprising means adjacent the sheet source for forming thickened edges on the sheet, and pairs of rollers engaging these thickened edges after they have passed beyond the forming means and immediately adjacent thereto and holding the sheet against inward contracting while it is being pulled longitudinally between the rollers.

11. In an apparatus for drawing sheet glass. mechanism for maintaining lateral or side tension on the sheet comprising means for forming thickened edges on the sheet at the sheet source. and pairs of idler rollers engaging these thickened edges immediately adjacent the edge forming means and holding the sheet against inward contracting while it is being pulled longitudinally between the rollers.

12. In an apparatus for drawing sheet glass, mechanism for maintaining lateral or side tension on the sheet comprising a pair of driven rollers forming each sheet edge at the sheet source, and a pair of idler rollers engaging each sheet edge as formed by the driven rollers.

13. In an apparatus tor drawing sheet glass, a container tor a pool ot molten glass from which the glass sheet is drawn, al pair of driven rollers enga ging and forming each sheet edge. a bending member about which the formed sheet is detlected, and a pair of idler rollers gripping each sheet edge between the driven rollers and the bending member.

14. In an apparatus for drawing sheet glass, a container for a pool ot' molten glass from which the glass sheet is drawn. a pair of driven rollers engaging and forming each sheet edge, a bending member about which the formed sheet is deflected, and plurality of pairs ot idler rollers gripping each sheet edge between the driven rollers and the bending member.

15. In an apparatus for drawing sheet glass. mechanism for maintaining lateral or side tension on the sheet, comprising means for forming thickened edges on the sheet at the sheet source, and means grasping these thickened edges at a series of acljacent points and resisting the tendency ot the sheet to contract, these means also gradually ironing out the thickened edges as the sheet is drawn therethrough.

16. In an apparatus Jfor drawing sheet glass, mechanism for maintaining lateral or side tension on the sheet, comprising means for forming thickened edges on the sheet at the sheet source, and pairs of rollers engaging these thickened edges and holding the sheet against inward contracting while it is being pulled longitudinally between the rollers, the sheet engaging faces ot the successive pairs ot rollers being positioned at varying angles to the plane of the sheet, to gradually flatten out the thickened edge.

17. An apparatus tor drawing sheet glass, comprising means for drawing` the sheet from a mass ot molten glass, pairs ot driven rollers positioned adjacent the sheet source and forming thickened edges on the glass sheet, and a series ot pairs of gripping rollers engaging the thickened edges at successive points to resist the contraction of the sheet.

18. An apparatus tor drawing sheet glass, comprising means for drawing the sheet 'trom a mass ot molten glass. pairs o't driven rollers positioned adjacent the sheet source and forming thickened edges on the glass sheet.r and a series ot pairs of gripping rollers engaging the thickened edges at successive points to resist the contraction ot the sheet, the sheet engaging faces of the successive pairs ot gripping rollers being positioned at gradually diminishing angles to the plane of the sheet to gradually flatten out the thickened edge.

19. An apparatus for drawing sheet glass, comprising means for drawing the sheet from a mass of molten glass, pairs of driven rollers positioned adjacent the sheet source and forming thickened edges on the glass sheet. a series of pairs of gripping rollers engaging the thickened edges at successive points to resist the contraction of the sheet, and means for adjusting the position of the gripping rollers parallel to the plane of the sheet to vary the tension imparted to the sheet.

20. In the process of drawing sheet glass,

the method ot relieving internal stresses,

consisting in loca1lyooiingtldraiv"sheet near its source, immediately thereafter heating the "slit surfaces to relieve the surface f tension, and simultaneously holding out the edges of the sheet to impart lateral tension to t e Klreeiawliile it is setting.

Q1. A means for positively cooling a sheet of glass during the drawing process. comprising a water-jacketed supply pipe for air or other cooling fluid, the pipe being per-- torated at intervals to provide a series of air-jets. and a detlector partially enclosing the pipe to direct the lluid against the sheet surface.

22. Means for heating the surfaces of a drawn sheet of glass to relieve the surface ensi on. comprising burners directing a sheet of flame against the sheet surface as the sheet is drawn past the burners, and a series of adjustable shields arranged between the burners and the sheet surfaces tol modify the heating el'ect at different portions of the sheet area.

23. Means for heating the surfaces of a drawn sheet of glass to relieve the surface tension, comprising burners directing a sheet of flame against the sheet surface as the sheet is drawn past the burners, and a series ot refractory shields suspended across the width of the sheet between the burners and the sheet surface, the shields being independently adjustable to modify the hea-ting effect on different portions of the sheet area.

24. In an apparatus for drawing sheet glass, mechanism for maintaining lateral or side tension on the sheet, comprising means for form-ing thickened edges on the sheet, and pairs ot yieldingly mounted rollers engaging these thickened edges and holding the sheet yieldingly against inward contracting while it is being pulled longitudinally between the rollers.

25. In an apparatus for drawing sheet glass, mechanism for maintainiiig lateral or side tension on the sheet comprising a series of pairs of yieldingly mounted rollers engaging the edges of the sheet and holding the sheet yieldingly against inward contraction while it is being pulled longitudinally between the rollers.

26. The combination with means for drawing sheet glass lengthwise, of devices for stretching the sheet laterally, the same comprising members resiliently sensitive and movable toward and from the edge portions of the sheet, rolling sheet-gripping elements mounted on the members and adapted to be rotated by the edge glass of the sheet as it is drawn, and means for adjusting the members to vary the amount of stretch which is to be given to the sheet laterally.

27. The combination with means for drawing sheet glass, of devices for stretching the sheet laterally, the same in duplicate comprisingsupporting mechanisms and rolling parts adapted to hold onto and to ormatively act on the glass along theA opposite edges of the sheet as it is drawn, and means connected with said mechanism for maintaining an adjustable elastic pull on the said rolling parts away from the line of advance of the edges of the sheet while the rolling parts are engaged with the edge Glass.

b Signed at Toledo, in the county of Lucas, and State of Ohio, this 5th day of July,

ENO CH T. FERNGREN.

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