Abstract:
A glassware forming mold that includes a body of heat conductive construction having a central portion with a forming surface for shaping molten glass and a peripheral portion spaced radially outwardly of the central portion. A plurality of coolant passages extend in a spaced array through the peripheral portion of the mold body, and liquid coolant is directed through such passages for extracting heat from the body by conduction from the forming surface. A plurality of openings extend axially into the body radially between at least some of the liquid coolant passages and the forming surface for retarding heat transfer from the forming surface to liquid coolant in the passages.

Description:
The present invention is directed to cooling of molds in a glassware forming machine, and more particularly to liquid cooling of the blank molds and/or blow molds in an individual section machine. 
     BACKGROUND AND OBJECTS OF THE INVENTION 
     The science of glass container manufacture is currently served by the so-called individual section or IS machine. Such machines include a plurality of separate or individual manufacturing sections, each of which has a multiplicity of operating mechanisms for converting one or more charges or gobs of molten glass into hollow glass containers and transferring the containers through successive stations of the machine section. Each machine section includes one or more blank molds in which a glass gob is initially formed in a blowing or pressing operation, one or more invert arms for transferring the blanks to blow molds in which the containers are blown to final form, tongs for removing the formed containers onto a deadplate, and a sweepout mechanism for transferring molded containers from the deadplate onto a conveyor. U.S. Pat. No. 4,362,544 includes a background discussion of both blow-and-blow and press-and-blow glassware forming processes, and discloses an electropneumatic individual section machine adapted for use in either process. 
     In the past, the blank and blow molds of a glassware forming machine have generally been cooled by directing air onto or through the mold parts. Such techniques increase the temperature and noise level in the surrounding environment. Furthermore, productivity is limited by the ability of the air to remove heat from the mold parts in a controlled process, and process stability and container quality are affected by the difficulty in controlling air temperature and flow rate. It has been proposed in U.S. Pat. No. 3,887,350 and 4,142,884, for example, to direct a fluid, such as water, through passages in the mold sections to improve heat extraction. However, heat extraction by liquid cooling can be too rapid and uncontrolled, at least in some areas of the mold, so steps must be taken to retard heat transfer from the inner or forming surface of a mold section to the outer periphery in which the liquid cooling passages are disposed. Various techniques for so controlling liquid-cooling heat extraction have been proposed in the art, but have not been entirely satisfactory. 
     Mold material for manufacture of quality glassware must have the following characteristics: good wear properties, good thermal cycle resistance to cracking, good mechanical properties, good glass release properties, ease of machinability, ease of repair and economic feasibility. Ductile iron, which is defined as an iron in which free microstructural graphite is in the form of spheres, has been proposed for use as a mold material to manufacture glassware in which reduced thermal conductivity (as compared to gray iron for example) is desired. Specific examples of glassware in which ductile iron is employed as the mold material are small containers that require a small amount of heat removal in the mold equipment, such as cosmetic and pharmaceutical bottles. However, ductile iron has not been employed in manufacture of larger glassware because of its reduced heat transfer and thermal cycle resistance capabilities. Ni-Resist ductile iron has been proposed for glassware manufacture. The increased nickel content of Ni-Resist ductile iron contributes to improved glass release properties. However, standard austenitic Ni-Resist ductile iron does not exhibit desired thermal conductivity and resistance to thermal cyclic cracking. 
     It is therefore a general object of the present invention to provide a glassware forming mold, and a method of cooling such a mold, that improve temperature control stability at the mold forming surface. Another and more specific object of the present invention is to provide a mold and method of cooling in which mold surface temperature can be adjusted and dynamically controlled during the glassware forming operation. Yet another object of the present invention is to provide a mold and method of cooling in which more uniform temperature and temperature control are obtained both circumferentially and axially of the mold forming surface to tailor the overall heat transfer characteristics of the mold coolant system to achieve efficient glass forming. Yet another object of the present invention is to provide a mold cooling technique that is characterized by reduced corrosion in the cooling passages and improved operating life of the entire mold and cooling system. A further object of the invention is to provide a material for construction of a glassware mold, including either a blank mold or a blow mold, that exhibits the desirable mold properties listed above. 
     SUMMARY OF THE INVENTION 
     A glassware forming mold in accordance with presently preferred embodiments of the invention includes at least one body of heat conductive construction having a central portion with a forming surface for shaping molten glass and a peripheral portion spaced radially outwardly of the central portion. At least one passage extends through the peripheral portion of the mold, and liquid coolant is directed through the passage for extracting heat from the body by conduction from the forming surface. At least one opening is provided in the mold body extending into the body and positioned radially between the coolant passage and the forming surface for retarding heat transfer from the surface to liquid coolant in the passage. The mold preferably comprises a split mold having a pair of mold bodies with identical arrays of passages and openings. The mold may be either a blank mold or a blow mold. 
     In the disclosed embodiments of the invention, the openings have a depth into the body, either part way or entirely through the body, coordinated with contour of the forming surface and other manufacturing parameters to control heat transfer from the forming surface to the coolant passages. The openings may be wholly or partially filled with material for further tailoring heat transfer from the forming surface to the coolant passages. In a mold body having a plurality of coolant passages and a plurality of openings, the heat transfer properties of the openings may be tailored circumferentially around the mold body, such as by partially filling every other passage. Thus. the heat transfer characteristics of the mold body can be tailored both radially, axially and circumferentially of the mold to obtain desired heat transfer and forming surface temperature characteristics. 
     Endplates may be carried by the mold body for controlling flow of coolant in multiple passes through the coolant passages in the mold body. In the preferred embodiments of the invention, one of the endplates contains a fluid inlet and a fluid outlet, and channels for directing the fluid to the mold passages. The other endplate contains channels for routing fluid from the end of one coolant passage to the end of an adjacent passage. In the disclosed embodiments of the invention, liquid coolant makes four passes through the mold body before returning to the fluid sump. The number of passes through the mold body may vary upwardly and downwardly depending upon mold size, the amount of heat to be extracted, etc. It is also anticipated that the number of coolant passes for cooling a blank mold will be less than for a blow mold. 
     In accordance with yet another feature of the present invention, the liquid coolant comprises water, preferably mixed with a heat transfer fluid such as propylene glycol. Other heat transfer fluids include silicon-based heat transfer fluids, synthetic organic fluids, and inhibited glycol-based fluids. The coolant fluid control system preferably includes facility for detecting and controlling coolant composition (e.g., propylene glycol concentration), coolant temperature and coolant flow rate, and an electronic controller for controlling composition temperature and/or flow rate to achieve optimum cooling and temperature control at the mold forming surfaces. In this way, mold surface temperature can be dynamically adjusted and controlled. 
     In accordance with a further feature of the present invention, which may be employed either separately from or more preferably in combination with other features of the invention, the mold body or bodies are constructed of austenitic Ni-Resist ductile iron. Such ductile iron is preferably a Type D Ni-Resist ductile iron in accordance with ASTM-A439-84, but modified to possess increased silicon and molybdenum content. Type D2-C iron is currently employed. Silicon content is preferably in excess of 3.0%, and most preferably is 4.20%±0.20%. Molybdenum content is preferably in excess of 0.5%, and most preferably 0.70±0.10%. (All composition percentages in this application are in weight percent.) The increased silicon content decreases the thermal conductivity of the mold material. The increased molybdenum content improves thermal cycle resistance to cracking. The increased nickel content characteristic to Ni-Resist materials improves glass release properties. The austenitic Ni-Resist ductile iron mold composition in accordance with this aspect of the invention also yields desirable wear and other mechanical properties, ease of machinability and repair, and desirable economic feasibility. Austenitic ductile Ni-Resist material also provides a more stable microstructure than gray iron, for example, up to a temperature of 1400° F. 
     A method of cooling a mold for a glassware forming machine in accordance with yet another aspect of the present invention contemplates providing a mold body of heat conductive construction having a forming surface, at least one coolant passage extending axially through the body, and at least one opening that extends at least part way through the body. The opening is disposed radially between the coolant passages and the mold forming surface. Liquid coolant is circulated through the passages. Heat transfer from the forming surface to the coolant is controlled in part by controlling diameter and depth of the opening, and by optionally at least partially filling the opening to modify the heat transfer characteristics across the opening. In the preferred embodiments of the invention, at least one, and preferably all of composition, temperature and flow rate of the liquid coolant are controlled. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention, together with additional objects, features and advantages thereof, will be best understood from the following description, the appended claims and the accompanying drawings in which: 
     FIG. 1 is a perspective schematic diagram of a pair of liquid-cooled split molds in accordance with one presently preferred embodiment of the invention; 
     FIG. 2 is an exploded perspective view of one of the split mold segments or parts in FIG. 1; 
     FIG. 3 is a sectional view of one of the split mold parts in FIG. 1; 
     FIG. 4 is a top plan view of the upper endplate in the mold part assembly of FIGS. 1-3; 
     FIG. 5 is a bottom plan view of the upper endplate illustrated in FIG. 4; 
     FIG. 6 is a top plan view of the lower endplate in the mold part assembly of FIGS. 1-3; 
     FIG. 7 is a bottom plan view of the lower endplate in FIG. 6; 
     FIGS. 8-12 are schematic diagrams similar to that of FIG. 3 but showing modified embodiments of the invention; 
     FIGS. 13-15 are schematic diagrams similar to that of FIG. 3 but showing other modified embodiments of the invention; 
     FIG. 16 is a schematic diagram similar to that of FIG. 3 but showing implementation of the invention in connection with a glassware blank mold, as distinguished from the blow molds illustrated in FIGS.  3  and  8 - 15 ; 
     FIG. 17 is a top plan view of the mold body in the embodiment of FIGS. 2 and 3; 
     FIGS. 18-20 are top plan views similar to that of FIG. 11 but showing respective modified embodiments; and 
     FIG. 21 is a functional block diagram of a fluid coolant control system in accordance with a presently preferred embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1 illustrates a mold system  20  as comprising a first pair of split mold parts  22 ,  24  and second pair of split mold parts  26 ,  28 . The specific mold parts  22 - 28  illustrated comprise blow molds in a dual IS machine. However, the invention is equally useful in conjunction with the cooling of blank molds (FIG.  16 ), and in conjunction with other types of IS or rotary machines, such as single, triple and quad machines. Each mold part  22 - 28  comprises a mold body and opposed endplates. Mold part  22  will be discussed in detail in connection with FIGS. 2-7 and  17 , it being understood that mold part  26  is identical to mold segment  22 , and mold parts  24 ,  28  are the mirror image of mold part  22 . 
     Mold part  22  includes a mold body  30  having a central portion with a forming surface  32  that, together with the corresponding surface of opposed mold part  24 , forms the surface against which molten glass is shaped in a pressing or blowing operation. The molten glass thus makes contact with surface  32 , transferring heat energy at surface  32  into body  30 , which must be dissipated. Mold body  30  also includes a peripheral portion spaced radially outwardly from the central portion in which forming surface  32  is disposed. A plurality of passages extend axially in a circumferentially spaced parallel array through the peripheral portion of mold body  30 . In the embodiment illustrated, there are eight such passages  34   a - 34   h , which are angularly spaced from each other. The angular spacing between passages  34   a - 34   h  may be approximately equal increments, but would normally be in unequal increments because of non-symmetries in the mold body. Each passage  34   a - 34   h  in FIGS. 3 and 17 is of cylindrical contour and of uniform diameter throughout its length, being entirely open from the top mold body surface  30   a  to the bottom mold body surface  30   b . Positioned radially inwardly of each passage  34   a - 34   h  is a corresponding opening  36   a - 36   h . In the embodiment of FIGS. 1-3 and  11 , openings  36   a - 36   h  extend entirely axially through body  30  from surface  30   a  to surface  30   b , and are respectively positioned radially inwardly of the corresponding passage  34   a - 34   h.    
     Mold body  30  is preferably constructed of austenitic Ni-Resist ductile iron in accordance with another aspect of the present invention. Ni-Resist ductile iron is a ductile iron that has a high nickel content, typically in excess of 18%, and more preferably in excess of 21%. A presently preferred composition is a Type D2-C ductile Ni-Resist composition generally in accordance with ASTM-A439-84, but modified to possess increased silicon and molybdenum contents. The following table illustrates chemical composition of this preferred material: 
     
       
         
               
             
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE I 
               
             
             
               
                   
               
               
                 CHEMICAL COMPOSITION 
               
             
          
           
               
                   
                 Target 
                 Range 
               
               
                   
                   
               
             
          
           
               
                   
                 Carbon 
                 (%) 
                 2.80 
                 ±0.20 
               
               
                   
                 Silicon 
                 (%) 
                 4.20 
                 ±0.20 
               
               
                   
                 Manganese 
                 (%) 
                 2.10 
                 ±0.30 
               
               
                   
                 Magnesium 
                 (%) 
                 0.050 
                 ±0.010 
               
               
                   
                 Nickel 
                 (%) 
                 22.50 
                 ±1.50 
               
               
                   
                 Sulphur 
                 (%) 
                 0.010 
                 ±0.006 
               
               
                   
                 Chrome 
                 (%) 
                 0.00 
                 ±0.50 
               
               
                   
                 Phosphorus 
                 (%) 
                 0.00 
                 ±0.08 
               
               
                   
                 Molybdenum 
                 (%) 
                 0.70 
                 ±0.10 
               
               
                   
                 Iron 
                   
                 (Balance) 
               
               
                   
                   
               
             
          
         
       
     
     This material has low thermal conductivity, good corrosion resistance, good machinability and economy, and good glass release properties at the mold surface. The increased silicon content decreases thermal conductivity, while the increased molybdenum content resists thermal cyclic cracking. 
     Surfaces  30   a ,  30   b  are parallel to each other, being formed by associated parallel ledges on mold body  30 . An upper endplate  38  and an intervening gasket  40  are carried on surface  30   a , being secured to mold body  30  by a plurality of screws  42  and spring washers  43 . A lower endplate  44  and an intervening gasket  46  are secured to surface  30   b  by a corresponding plurality of screws  48  and spring washers  49 . (The screw holes are not illustrated in FIG. 11 to highlight the relationship between passages  34   a - 34   h  and openings  36   a - 36   h .) Upper endplate  38  (FIGS. 3-5) is arcuate, and has a radially opening inlet port  50  and a radially opening outlet port  52 . Inlet port  50  opens to a triangular-shaped cavity  54  on the underside of plate  38 . There are an angularly spaced pair of arcuate or chordal channels  56 ,  58  on the underside of plate  38 , and a second pair of channels  60 ,  62  are formed on the underside of plate  38  in communication with outlet port  52 . The angularly spaced ends of channels  62  and  58 , pocket  54  and channels  56 ,  60  overlie the angularly spaced ends of coolant passages  34   a - 34   h  in assembly to the mold body, as illustrated in FIG.  4 . Lower endplate  44  (FIGS.  3  and  6 - 7 ) is likewise of arcuate contour, having an upper face in abutment through gasket  46  with surface  30   b  of the mold body. Four arcuate or chordal channels  64 ,  66 ,  68 ,  69  are formed on the upper face of lower endplate  44 . In assembly, the angularly spaced ends of these channels underlie the angularly spaced ends of mold coolant passages  34   a - 34   h , as best seen in FIG.  7 . It will be noted in FIGS. 4 and 7 that the channels in the endplates are wider than the passages in the mold body. This accommodates slight misalignment due to tolerance variation or differential thermal expansion. 
     In use, inlet port  50  of upper endplate  38  is connected to a source of liquid coolant under pressure, and outlet port  52  is connected to a coolant return line. Coolant is thus routed from inlet port  50  and inlet pocket  54  downwardly (in the orientation of FIG. 3) through passages  34   d  and  34   e  to lower endplate  44 , thence by endplate  44  upwardly through passages  34   c  and  34   f , thence by endplate  38  downwardly through passages  34   b  and  34   g , and thence by endplate  44  upwardly through passages  34   a ,  34   h  and endplate channels  60 ,  62  to outlet port  52 . The cooling liquid thus makes a total of four passes through the mold body before return to the sump. The number of passes may be tailored in accordance with the principles of the invention to achieve the desired thermal gradient across the mold/coolant interface using suitable conventional computer modeling techniques. Openings  36   a - 36   h  retard heat transfer from forming surface  32  to coolant passages  34   a - 34   h  and thus control the overall heat transfer rate from the glass to the coolant. In the embodiment of the invention illustrated in FIGS. 3 and 11, passages  36   a - 36   h  extended entirely through the mold body at uniform diameter and substantially equal angular spacing. The upper and lower ends of the several passages  36   a - 36   h  are blocked by gaskets  40 ,  46 , as best seen in FIG.  3 . Openings  36   a - 36   h  thus form closed air pockets with lower heat transfer properties than the metal of the mold, and thus serve partially to retard and control heat transfer to the coolant passages by interrupting the heat transfer path. (Openings  36   a ,  36   h  are illustrated as being of lesser diameter in FIG. 11 because of the need to accommodate endplate mounting holes, as best seen in FIGS. 4-7.) 
     The number and position of openings  36   a - 36   h  are selected in accordance with desired heat transfer characteristics. For example, FIG. 18 illustrates a modification in which openings  36   b ,  36   g  are replaced by several smaller openings disposed between coolant passages  34   b ,  34   g  and forming surface  32 . FIG. 19 illustrates the use of supplemental openings  34   i - 34   o  between coolant passages  34   a - 34   h  and forming surface  32  further to restrict heat transfer from the forming surface to the coolant passages. Thus, while in general openings  36   a - 36   h  (and  36   i - 36   o ) are disposed radially between the coolant passages and the mold forming surface, precise positioning and size of these openings, as well as a number of openings, are tailored to specific applications for obtaining desired heat transfer characteristics. 
     Openings  36   a - 36   h  (and  36   i - 36   o ) are illustrated as being of uniform diameter throughout their lengths, which facilitates manufacture. In accordance with another feature of the invention illustrated in FIGS. 8-12, these openings may have different heat transfer characteristics along their axial lengths through the mold for further heat transfer control. For example, FIG. 8 illustrates a modification to the embodiment of FIG. 3, in which opening  36   d  is partially filled with a material  70  of heat transfer characteristics that are different from those of air. For example, material  70  may comprise sand, which effectively forms a filler or plug within opening  36   d . This plug of material  70  is illustrated as being positioned about mid-way along the length of the body portion of the container forming surface  32 , and thus would conduct greater heat to coolant passage  34   d  from the mid portion of the container forming surface than would be the case from the upper and lower portions of the container forming surface. Corresponding fillers or plugs  70  may be positioned in the other openings  30   a - 30   c  and  30   e - 30   h , or may be positioned in alternate openings, for example. FIG. 9 illustrates a modification in which opening  36   d  contains a first material plug  72  adjacent to the mid portion of the container forming surface, and a second plug  74  adjacent to the lower portion of the container forming surface at the container heel. Thus, the rate of heat transfer from the lower and mid portions of the container forming surface would be different from the rate of heat transfer at the upper portion of the container forming surface, and would be different from each other, in the modification of FIG.  9 . FIGS. 10 and 20 illustrate a modification in which openings  36   a - 36   h  extend only part way through the axial length of the mold body. In this modification, heat would be extracted more rapidly from the container neck area than from the container shoulder and body areas of the mold forming surface. The modification of FIGS. 10 and 20 may be employed to provide room for endplate mounting holes without substantially affecting operation. It is generally preferred that heat transfer characteristics be circumferentially uniform. 
     As noted above, all of the embodiments thus far discussed possess openings  36   a , etc. of cylindrical contour and uniform diameter. However, other passage geometries are contemplated. For example, FIG. 11 illustrates a mold body  30  in which opening  36   p  is formed by differential drilling, having end portions of greater diameter and a central portion of lesser diameter. The portion of lesser diameter may extend for a greater length than is illustrated in FIG. 11, and indeed may extend to either the upper or lower surface  30   a ,  30   b . Thus, the embodiment of FIG. 11 achieves greater heat conductivity in the central portion of the mold, as does the embodiment of FIG. 8 for example, but without the use of additional materials. FIG. 12 illustrates another modification, in which the opening  36   q  is internally threaded and receives an externally threaded plug  75 . Once again, plug  75  may be of any desired length, and may be variably positioned within opening  36   q . The embodiment of FIG. 12 has the advantage of being adjustable on the manufacturing floor. 
     In short, the principles of the present invention provide opportunity for tailoring the heat transfer characteristics of a mold to accommodate any desirable operating conditions or situations. The heat-blocking openings may be positioned between the mold surface and each coolant passage, or between the mold surface and some coolant passages. Heat transfer characteristics of the blocking openings may be tailored both axially and circumferentially of the mold body to achieve any desired differential cooling properties. FIGS. 13-15 illustrate embodiments of the invention in which coolant is introduced and withdrawn at various locations. In FIG. 13, coolant is introduced and withdrawn from the radial direction at the upper end of the mold body, as in FIGS. 1-3. In FIG. 14, coolant is introduced and withdrawn from the radial direction at the lower end of the mold body, while in FIG. 15 the coolant is introduced and withdrawn from the axial direction at the lower end of the mold body. It will be appreciated, of course, that coolant may be introduced, for example, at the upper end of the mold body and withdrawn from the lower end of the mold body in accordance with the principles of the invention. FIG. 16 illustrates application of the present invention in conjunction with a glassware blank mold  91 . The principles remain the same as in the above discussions relative to blow molds, although less heat is normally extracted from a blank mold due to the desire to maintain elevated temperature at the glass blank, and consequently fewer coolant passages and heat-blocking openings would normally be provided in conjunction with a blank mold. 
     FIG. 15 illustrates two additional modifications in accordance with the invention. A pair of plugs  92 ,  94  close the respective ends of opening  36   d  in mold body  30 . When employing mold bodies which are sufficiently porous that coolant can flow from passage  34   d  to opening  36   d , plugs  92 ,  94  prevent contact of coolant vapor with gaskets  40 ,  46 . A pair of flow adjustment needles  96  (only one is illustrated) are threadably mounted on plate  38 . Each adjustment needle has a needle point that enters a fluid passage channel in plate  38 . Needles  96  thus provide for adjustment of resistance to fluid flow at each mold part. 
     FIG. 21 illustrates a coolant circulation system  80  in accordance with one presently preferred implementation of the invention. Coolant in the presently preferred implementation of the invention comprises a mixture of propylene glycol and water. This mixture helps prevent corrosion, reduces heat transfer from the mold bodies, lubricates the pump, and helps reduce two-phase boiling in the mold coolant passages. Other coolants and blends of coolants may be used as dictated by environmental and other factors. The relative percentages of propylene glycol and water are controlled by a coolant composition control unit  82  under control of an electronic controller  84 . Likewise, there is a coolant temperature control unit  86  for sensing coolant temperature, and for heating or cooling the coolant as required under control of controller  34 . A coolant flow rate control unit  88  includes a variable output pump and suitable means for measuring coolant flow rate (and pressure if desired). Coolant may be fed from unit  88  to all mold segments connected in parallel, or may be fed through individually controllable valves  90  to the individual mold segments. Valves  90  are controlled by electronic controller  84 . Thus, controller  84  receives indication of coolant composition form unit  82 , coolant temperature from unit  86  and coolant flow rate (and pressure) from unit  88 , and provides corresponding control signals to the composition, temperature and flow rate controllers. Controller  84  also provides suitable signals to the individual valves  90 , which gives facility for controlling coolant flow to the molds individually. In any given application, one or more of the control units  82 ,  86 ,  88  and  90  may be deleted if desired. 
     There have thus been disclosed a mold, and a method for cooling a mold, for use in a glassware forming system, that fully satisfy all of the objects and aims previously set forth. Specifically, openings are provided in the mold body at a number, position, depth and content to control heat transfer between the mold surface and the coolant. This feature allows molds to be designed for specific temperature control and heat transfer characteristics. Further, control of coolant composition, temperature and/or flow rate provides dynamic control of mold surface temperature. Mold corrosion is reduced and operating life is extended. Several modifications and variations have been disclosed. Although the invention has been disclosed as being particularly useful in conjunction with individual section machines, the invention may be readily employed in conjunction with other types of glassware forming machines, such as rotary machines. Other modifications and variations will suggest themselves to persons of ordinary skill in the art. The invention is intended to embrace all such modifications and variations as fall within the spirit and a broad scope of the appended claims.