US3258324A - Glass pressing apparatus - Google Patents

Description

June 28, 1966 J. J. TOROK GLASS PRESSING APPARATUS 2 Sheets-Sheet 1 Filed Nov. 21, 1962 INVENTOR. Juuus J. TOROK BY Ejlfivi 7%a ATTORNEYS June 28, 1966 J. J. TOROK 3,

GLASS PRESSING APPARATUS Filed Nov. 21, 1962 2 Sheets-Sheet 2 IN TOR. Juuus J. OROK BY EMA/ aw ATTORNE Y5 United States Patent 3,258,324 GLASS PRESSING APPARATUS Julius J. Torok, Toledo, Ohio, assignor to Owens-Illinois Glass Company, a corporation of Ohio Filed Nov. 21, 1962, Ser. No. 239,120 8 Claims. (Cl. 65362) This invention relates to apparatus for pressing glass and particularly to plunger and mold design.

In the pressing of glass articles, a major consideration is the control of heat distribution in order that the surfaces which form the glass article are neither too hot nor too cold. If the surfaces are too hot, sticking of the glass may occur and if the surfaces are too cold, crizzling of the glass surfaces may occur.

One of the methods heretofore used for controlling the. heat distribution is by liquid cooling the plunger and mold as by the use of water. Liquid cooling is limited in its effectiveness so that the control of heat distribution has heretofore been obtained by varying the thickness of the metal of the mold or plunger. Although such a design of molds and plungers with varying thicknesses has produced some satisfactory results, in some instances, where the shape of the article is complex, it has been found thatthe variation of the thickness to compensate for heat flow in one area interferes with the heat flow in another. Thus, in the pressing of the face plates of a television tube, which have abase and peripheral flange extending at an angle from the base, considerable difficulties are encountered at the area of juncture of the base and flange of the plunger. 4

' It is an object of this invention to provide an improved apparatus wherein the heat flow distribution of the pressing member can be more accurately controlled.

It is a further object of the invention to provide such an apparatus wherein the heat flow distribution can be varied Without a complete destruction of the pressing member.

It is a further object of the invention to provide a pressing apparatus wherein the forming surface can be made of a thin flexible material which can be readily replaced at relatively low cost.

Basically, the invention comprises making the pressing plunger or mold with a hollow space which is to be filled with a fill metal cast in situ to form a core. A thermal modifying member, either more or less highly conductive than the pressing member itself, is inserted in the space and a fill metal cast in situ in the space. The thermal modifying member modifies the heat flow distribution at the desired areas while the fill metal cast in situ fills the remaining space and not only gives strength to the pressing member but, in addition, provides the desired thermal distribution through the pressing member. The thermal conductivity can be increased or decreased by proper selection of good or bad thermal modifying members. In addition, the overall heat dis tribution can be modified by melting and removing the cast fill metal and replacing it with a different fill metal having a different thermal conductivity.

In the drawings:

FIG. 1 is a vertical sectional view through a pressing apparatus embodying the invention.

FIG. 2 is a fragmentary sectional view taken along the line 2-2 in FIG. 1.

FIG. 3 is a vertical sectional view through a modified form of apparatus.

FIG. 4 is a fragmentary vertical sectional view through a further modified form of apparatus.

FIG. 5 is a fragmentary sectional View taken along the line 55 in FIG. 4.

N'Ce

Referring to FIG. 1, a mold 10 is provided into which a gob of glass is deposited by suitable means well known in the art and thereafter a plunger 11 is brought downwardly into contact with the glass and pressed to form the glass article.

As shown in FIG. 1, mold 10 comp-rises a base section 12 and a peripheral sec-tion 1 3 defining an internal molding surface 14 which has a configuration corresponding to the external configuration of the glass article which is to be formed. Peripheral section 13 includes an inwardly extending peripheral lip .15 which defines the upper end of the flange which is to be formed on the glass article.

As shown in FIG. 1, the plunger 1 1 also comprises an inner member 2 2 and an outer member 21. The outer member is of substantially uniform thickness throughout and suflicient as to withstand the forces necessary to press the article. The inner member 22 is made of a lighter gauge material such as sheet metal. The inner member 22 is spaced from the outer member 21 and includes a flange 22a which overlies flange portion 27. A metal 243 is cast in situ inthe space between the inner and outer members.

Outer member 21 includes a base portion 16 and a flange portion 17 and is mounted on a head 18 by bolts 19 threaded into flange portion 17 of the plunger 1:1. A gasket 20 is interposed between the flange 22a and head 18. Head 18 is adapted to be moved upwardly and downwardly by a suitable mechanism (not shown), known in the art, such as a hydraulic ram.

A distributor 25 is provided between the head 18 and plunger 11 and comprises a circular plate 26 and a hub 27 at the center of the plate. Bolts extend through circumferentially spaced bosses (not shown) to support distributor 26 on the lower end of head 18. A lip 26a is formed on the periphery of plate 26 and extends upwardly into contact with a gasket 20. Liquid coolant is forced under pressure through circumferentially spaced vertical openings 30 in head 18 into the space 40 between plate 26 and the lower end of the head. A plurality of nozzles is provided in the periphery of the distributor. Each nozzle comprises a plug 31 threaded into an opening in the distributor. Each plug is formed with a nozzle opening 32 which has its axis inclined horizontally to a radial plane intersecting the axis of the plunger 11. In this fashion, a plurality of streams or jets of liquid coolant are directed at the area of juncture of .the periphery of base portion 22b and flange 220 of inner memmer 22. An O-ning type gasket 33 is provided on the upper end of hub 27 to provide a seal and prevent the liquid coolant from passing from the inlet directly to the outlet opening 34 in head 18.

A disc 35 is provided below distributor 25 and includes a sleeve 36 extending upwardly into hub 27. The upper end of sleeve 36 is spaced from the base of the opening of the hub into which it extends so that disc 35 has limited reciprocating movement relative to hub 27 and, in turn, distributor 25. Bolts (not shown) locked in position by lock nuts (not shown) are provided at circumferentially spaced points along the periphery of disc 35 and extend through the disc into contact with the inner surface of base portion 16. By this arrangement, the lowermost position of disc 35 is adjusted so that the disc is always out of contact with the inner surface of the member 22.

In operation, gobs of glass are periodically fed to mold 14 and plunger 16 is moved downwardly into contact with each gob ,to form the glass article. During the operation of the forming equipment, liquid coolant is forced under pressure through openings 30 into the space between the lower end of head 18 and distributor 25. Coolant is then directed in a plurality of streams or jets at the area of juncture of the base portion 16 and flange portion 17. Since the axes of the jets are at an angle to a radial line intersecting the axis of the plunger, a rotary motion is imparted to the coolant. The liquid coolant fills the space 40 between the undersurface of plate 26 and the upper surface of disc 35 forcing disc 35 downwardly and bringing the ends of bolts into contact with the inner surface 22b of inner member 22. The restricted flow through space 39 between disc 35 and inner member 22 causes a small pressure drop which produces a differential pressure between the space 40 and the space 41 insuring that the disc 35 is urged downwardly into proper position with respect to the surface.

The undersurface of disc 35 is so shaped relative to the surface of inner member 22 of plunger 11 that the liquid, as it flows from the periphery of the base portion to the center thereof, flows at a constant velocity. In other words, the cross-sectional area of the space 41 between the lower or undersurface of disc 35 and the inner surface of base portion 16 is such that it increases in size from the periphery to the center so that a constant velocity of liquid will be permitted to flow. The liquid coolant is withdrawn through sleeve 36 and outlet 34.

The surface of the inner member 22 against which the coolant is directed is preferably roughened in order to obtain the best possible heat transfer. The roughening may be achieved by knurls or in any other suitable manner such as ribs. The roughening should be sufiicient to insure heat transfer but not so deep as to form stagnant pockets of coolant.

According to the invention, the thermal conductivity of the body of a mold or plunger can be changed readily if the interior is such that it can be readily placed in liquid form. Then the thermal conductivity can be increased or decreased by inserting good or poor thermal conducting bodies in the liquid portion. The metal liquid Wetting the surface of the insert eliminates the need for welding because a wetted surface is the equivalent of a metallurgical bond thermally. If the liquid portion is intentionally made so that it does not wet the insert, an interfacial heat barthermal insulation.

The idea and advantages of a liquid core mold or plunger are shown in FIG. 1. Assume first that the liquid metal wets the outer. and inner members 21, 22 of plunger 11. Then the temperature drops will be in the outer and inner members 21, 22 and in the metal core 23. Since the liquid metal wets the members 21, 22 there is no interfacial heat loss there.

Assuming the following conditions:

Heat flux density, 90,000 B.t.u./ft. /hr.

In the above computation the thermal conductivities of the metals were assumed to be:

Stainless steel 180 B.t .u./ft. /hr./in./ F. Core metal 320 B.t.u./ft. /hr./in./ F.

If it is assumed that the core metal does not wet the surfaces 21, 22 and the interfacial impedance is 2000 B.t.u./ ft. F./hr. then the temperature drop at each interface will be:

Since there are two interfaces the outer wall temperature will rise by 2 45=90 or 739+90=829 F. Thus, temperature control can be effected by choosing or making the core metal wet or not wet the members 21, 22. In addition, non-wettable shims of the metal can be inserted into the core metal to effect temperature rise on the outer surface. For example, assume that a two mil thick sheet is placed loosely over the inner surface of the outer member 21 such as 24 (FIG. 1). Each shim offers two surfaces, thus two surfaces will be interposed. Then the additional temperature drop would be 2 4S=90. The glass contacting temperature would be 825+90=915 F.

Thus, wetting or non-wetting properties of surfaces become very important factors and powerful aids in design of plungers and molds.

The above discussion shows that inserts can be added without additional machining in the cavity such as would be necessary in solid metal bodies. This is the greatest advantage of a metal core which can be liquified. Not only metals can be interposed into the thermal circuit but also insulating bodies such as an asbestos barrier (FIG. 1). Inserting such barriers can prevent the loss of heat at the match line (the edge of the formed glass) where excessive heat losses and low heat inputs normally cause the outer surface of the plunger to run cold. The barrier 50 cuts the loss of heat to the water-cooled inner wall 22 to a very low value, and thus raises the temperature at the match line. Thus, interface and thermal barriers reduce the heat flow and raise the temperature of the glass contacting surface.

Also, a good thermal conductor can be inserted to carry heat from points of heat concentration to points of heat deficiency. For example, at the area of juncture of the base and flange portions of the plunger, the geometry concentrates the heat causing the outer surface at the radius to run hot. By placing a copper strap 51 (FIG. 1) which is a good heat conductor between the radius and match line, heat can be conducted rier is established which can be utilized as a form of from the high flux density area to the low flux density area and thus raise the temperature at the match line, and lower it at the radius.

The remaining excess heat flux from the radius can be carried into the cooling wall by another copper strap 52 as it extends .from the radius to the inner watercooled wall 22. The amount of heat that both straps 51 and 52 carry is a function of the temperature difference at their ends and the dimensions of the straps. Since the liquid metal wets both the copper and stainless steel walls, welding or brazing the copper straps to the walls is not necessary. It is only necessary that the copper straps be held in position by any convenient means such as wedging, bracing bolts or rivets driving the casting of the core 23 into the plunger.

Another advantage of the liquefiable core center is that its thermal conductivity as a unit can be easily changed by changing the composition of the core metal. For example, if a plunger operating satisfactorily at six pressings per minute with a core of liquid is speeded up to operate at eight pressings per minute, the heat flux would increase so :much that the plunger surface would become too hot. By changing the core metal from tin to cadmium, the average thermal conductivity of the plunger is increased so much that the surface temperature drops to the normal satisfactory level. Thus, an easy change in thermal conductivity is made. without altering the design. If the plunger were made of solid metal, the entire plunger would have to be discarded or receive extensive machining.

Liquid metals may expand and contract a great deal with small changes in temperature. Thus, a practical production or mold may require expansion space. This is provided in FIG. 1 by filling the space only to a little above the match line, leaving a gas space 28 above as an expansion chamber. This gas space can be filled with a reducing or neutral gas to prevent the liquefiable core metal from oxidizing if it is subject to oxidizing. Such a gas serves the added function of thermal insulator between the plunger, the cooling water and the plunger head. By raising or lowering the level of the core metal, the thermal conductivity control can be varied. This concept can be extended to other parts of the plunger or mold. Hollow spaces can be provided which can be filled or emptied of metal as the operating surface temperature demands and thus achieve temperature control.

As shown in FIG. 4, these hollow spaces can be a thin flat tube 55 extending circumferentially. They would have maximum conductivity when full and lesser conductivity achieved by varying the level of gas and, in turn, liquefiable metal in tube 35.

As shown in FIG. 3, the use of liquid metal as a mechanically flexible heat transfer path permits the use of thin shell forming surfaces. A thin shell 40 formed by spinning, hydroforming or other low cost forming methods can be slipped over a heavier base 41 and the two connected thermally by a thin film 42 of liquefiable metal. In making the plunger shown in FIG. 3, the liquid metal is first placed in the shell 40 and then the base 41 is inserted causing the liquid met-a1 to rise and fill the thin space between the -base 41 and shell 40. The liquefiable metal 42 carries the heat from the thin shell 40 into the base metal 41 where it is dissipated by air or water cooling. If the shell 40 is damaged or worn it can be slipped off the base 41 and replaced by another one. vThis form of construction utilizes low cost material and finishing operations in replacing wearing surfaces of molds and plungers. Heretofore this has not been feasible because metallurgical bonds between the shell and base material could not be made Without voids and were otherwise excessive in cost.

I claim:

1. A pressing member for pressing gobs of molten glass into predetermined shapes comprising a body having a forming surface corresponding to a surface of the article which is to be formed,

said body comprising a first wall having said forming surface formed thereon and a second Wall spaced from the first wall and cooperating therewith to define a closed space,

at least one thermal modifying member in said space,

and a metal cast in situ in said space about said thermal modifying member and substantially filling said space,

said cast metal having a melting point which is less than the melting point of said body and which is such that the major portion of the mass of the cast metal is solid at the operating temperatures of the pressing member and has a thermal conductivity such that upon operation of the pressing member to press gobs of molten glass, heat transfer occurs 5 through the metal.

2. The combination set forth in claim 1 including an opening in said body to said space in said body whereby said cast metal can be melted and removed for replacement with a metal having a different thermal conductivity.

3. The combination set forth in claim 1 wherein said thermal modifying member is thermally metallurgically bonded to said cast metal.

4. The combination set forth in claim 3 wherein said thermal modifying member has a greater thermal conductivity than the body and the cast metal.

5. The combination set forth in claim 1 wherein said thermal modifying member has a lesser thermal conductivity than the body and the cast metal.

6. The combination set forth in claim 1 wherein said thermal modifying member comprises a hollow tube in said closed space,

said tube having at least one opening therein whereby said metal cast in situ in said body enters and partially fills said body.

7. The combination set forth in claim 1 including a head,

means for supporting said pressing member on said head,

and means for directing a coolant onto the inner wall of said pressing member,

and means for removing said coolant,

whereby liquid coolant is caused to move across the inner wall of the pressing member to cool the pressing member and as the pressing member is operated to press successive gobs of molten glass, heat transfer occurs through the body and the metal therein to the inner wall of the pressing member which is contacted by the liquid coolant.

8. The combination set forth in claim 7 wherein said outer wall has substantially unifonm-thickness.

References Cited by the Examiner UNITED STATES PATENTS 780,863 1/1905 Coleman 356 1,965,242 7/ 1934 Kelly 249-11 1 3,003,287 10/1961 Torok 653 19 5 DONALL H. SYLVESTER, Primary Examiner,

A. D. KELLOGG, Assistant Examiner.

Claims (1)

1. A PRESSING MEMBER FOR PRESSING GOBS OF MOLTEN GLASS INTO PREDETERMINED SHAPES COMPRISING A BODY HAVING A FORMING SURFACE CORRESPONDING TO A SURFACE OF THE ARTICLE WHICH IS TO BE FORMED, SAID BODY COMPRISING A FIRST WALL HAVING SAID FORMING SURFACE FORMED THEREON AND A SECOND WALL SPACED FROM THE FIRST WALL AND COOPERATING THEREWITH TO DEFINE A CLOSED SPACE, AT LEAST ONE THERMAL MODIFYING MEMBER IN SAID SPACE, AND A METAL CAST IN SITU IN SAID SPACE ABOUT SAID THERMAL MODIFYING MEMBER AND SUBSTANTIALLY FILLING SAID SPACE, SAID CAST METAL HAVING A MELTING POINT WHICH IS LESS THAN THE MELTING POINT OF SAID BODY AND WHICH IS SUCH THAT THE MAJOR PORTION OF THE MASS OF THE CAST METAL IS SOLID AT THE OPERATING TEMPERATURES OF THE PRESSING MEMBER AND HAS A THERMAL CONDUCTIVITY SUCH THAT UPON OPERATION OF THE PRESSING MEMBER TO PRESS GOBS OF MOLTEN GLASS, HEAT TRANSFER OCCURS THROUGH THE METAL.

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