Method and apparatus for selective preheating of solid phase pressure formed web or sheet material

Abstract

Mold insert apparatus and a method is provided for high pressure solid phase forming of relatively thin web or sheet material. The apparatus includes a die set assembly provided with a forming die set unit having a die forming cavity which receives a forming die and an opposed high pressure chamber die set unit wherein the die set units receive material to be formed therebetween when in spaced relationship and functional to clamp the material therebetween when the die set units are in closed forming positions for solid phase forming of the material against the forming die upon introduction of high pressure fluid into the high pressure chamber die set unit. A material preheating station is provided outside but generally proximal to the die forming cavity of the forming die set unit. The preheating station includes a pair of duck-bill shaped preheating devices, with one of the devices being connected to the high pressure chamber die set unit for movement therewith while the other preheating device is connected to a stripper frame which is a part of the forming die set unit. The preheating devices open and close with the high pressure chamber die set unit and forming die set unit of the die set assembly so that preheating of web or sheet material is synchronized with forming of previously preheated material in the die set assembly. The preheating devices are provided with opposed heat insulating zones of predetermined shape which prevents the portion of material in general alignment with the insulating zones from being heated as high a temperature as material out of alignment with insulating zones. The heat insulating zones of the preheating devices are configured to conform to high force producing areas of the forming die. Selective preheating of the web or sheet before forming thus minimizes thinning of the material over the high force inducing areas of the forming die.

1 . In apparatus for high pressure, solid phase forming of relatively thin material having opposed surfaces, said apparatus including a die set assembly presenting a material forming station and provided with a forming die set unit having a forming cavity which receives a forming die and an opposed high pressure chamber die set unit, at least one of said die set units being movable with respect to the other die set unit, said die set units receiving material therebetween when the die set units are in first spaced positions and functional to clamp the material therebetween when the die set units are in second closed forming positions for solid phase forming of the material against the forming die upon introduction of high pressure fluid into the chamber die set unit, said apparatus comprising: 
 mechanism operable to receive material to be formed and to direct the material to the forming station of the die set assembly when the die set units are in said first positions thereof;    a material preheating station outside of but generally proximal to the forming cavity of the forming die set unit, said preheating station being provided with a pair of opposed material engaging preheating devices, at least one of said devices being movable relative to the other device with the devices receiving material clamped therebetween when the devices are in first spaced disposition and engaging opposed surfaces of the material when the devices are in second closed material preheating disposition,    at least one of the devices being provided with a material heating element for preheating material at the preheating station when the devices are in said second preheating disposition thereof,    each device provided with a material heating element having a heat insulating zone of predetermined shape which prevents the portion of material engaged by the devices at the preheating station that is in general alignment with the insulating zone from being heated to as high a temperature as the material out of alignment with the insulating zone; and    structure opening and closing the preheating devices at the preheating station in timed relationship to opening and closing of the die set units to effect preheating of material as other material is pressure formed in the die set assembly.    
     
     
         2 . Apparatus as set forth in  claim 1 , wherein each device provided with a material heating element has a heat insulating zone shaped to conform with certain portions of the forming die.  
     
     
         3 . Apparatus as set forth in  claim 1 , wherein each device provided with a heating element has an open insulating zone defining groove in the surface of the element that engages the material when the material is at said material preheating station.  
     
     
         4 . Apparatus as set forth in  claim 1 , wherein each device provided with a heating element has an insulating zone defining groove in the surface of the element that engages the material when the material is at said material preheating station, and insulating material at least partially filling said groove.  
     
     
         5 . Apparatus as set forth in  claim 3 , wherein each of the devices is provided with an open insulating zone defining groove in the surface of each of the elements that engages the material when the material is at said material preheating station.  
     
     
         6 . Apparatus as set forth in  claim 5 , wherein the open insulating zone defining groove in each preheating devices is aligned with the open insulating zone defining groove in the opposed preheating device.  
     
     
         7 . Apparatus as set forth in  claim 5 , wherein said insulating zone defining grooves are configured to generally conform to the perimeter of the forming die.  
     
     
         8 . Apparatus as set forth in  claim 5 , wherein said insulating zone defining grooves are each of a depth approximately 5× the thickness of the material.  
     
     
         9 . Apparatus as set forth in  claim 5 , wherein said insulating zone defining groove is configured to generally conform to the perimeter of the forming die.  
     
     
         10 . Apparatus as set forth in  claim 1 , wherein said structure includes components for connecting said at least one movable device to the high pressure die set unit so that said at least one movable device moves with the high pressure die set unit in timed relationship therewith.  
     
     
         11 . Apparatus as set forth in  claim 1 , wherein each of said pair of preheating devices is provided with a material heating element.  
     
     
         12 . Apparatus as set forth in  claim 5 , wherein each of said preheating devices includes a generally planar plate engageable with a respective opposed surface of material at the heating station.  
     
     
         13 . Apparatus as set forth in  claim 12 , wherein the insulating zone defining grooves in the plates are of a depth from about 0.01″ to about 0.50″.  
     
     
         14 . Apparatus as set forth in  claim 12 , wherein the insulating zone defining grooves in the plates are of a depth of about ½ the thickness of a respective plate.  
     
     
         15 . Apparatus as set forth in  claim 12 , wherein each of said material heating elements is a resistance heating member extending across a substantial portion of the area of each of the plates.  
     
     
         16 . Apparatus as set forth in  claim 1 , wherein said forming die set unit includes a frame member having a wall of predetermined cross-sectional thickness and disposed in generally surrounding relationship to the forming die, the devices of said material preheating station being located in disposition ranging from a position abutting the die set assembly to a position no more than about 10× the thickness of said wall of the die set assembly frame member.  
     
     
         17 . Apparatus as set forth in  claim 1 , wherein said forming die set unit includes a frame member having a wall of predetermined cross-sectional thickness and disposed in generally surrounding relationship to the forming die, the devices of said material preheating station being located in disposition ranging from a position abutting the die set assembly to a position no more than about 5× the thickness of said wall of the die set assembly frame member.  
     
     
         18 . Apparatus as set forth in  claim 1 , wherein said forming die set unit includes a frame member having a wall of predetermined cross-sectional thickness and disposed in generally surrounding relationship to the forming die, the devices of said material preheating station being located in disposition generally abutting the die set assembly.  
     
     
         19 . Apparatus as set forth in  claim 1 , wherein the forming die set unit has a frame in generally surrounding relationship to the forming die and wherein the frame of the forming die set unit and the high pressure die set unit both move unitarily after the material is clamped between the frame of the forming die set unit and the high pressure chamber die set unit, said structure including components for joining one of the preheating devices with the high pressure chamber die set for movement therewith, and said structure further including components for joining the other of the preheating devices with the frame of the forming die set unit for movement of said other preheating device with said frame of the forming die set unit.  
     
     
         20 . Apparatus as set forth in  claim 1  for forming material having die registration fiducials and wherein is included a movable bolster supporting the die set assembly for movement with the bolster, and die set assembly registration components for shifting the bolster to move the die set assembly into register with fiducials on the material prior to forming of material within the die set assembly.  
     
     
         21 . Apparatus as set forth in  claim 1  for forming material in web form and wherein is included in-feed and out-feed rollers on opposite sides of the die set assembly engageable with the web for sequentially moving selected areas of the web material into said preheating station when the die set units are in said first spaced positions thereof.  
     
     
         22 . Apparatus as set forth in  claim 1  for forming sheet material and wherein is included a sheet feeder for sequentially moving each sheet into the material preheating station and then into the die set unit assembly when the die set units are in said first spaced positions.  
     
     
         23 . In apparatus for high pressure, solid phase forming of relatively thin material having opposed surfaces, said apparatus including a die set assembly presenting a material forming station and provided with a forming die set unit having a forming cavity which receives a forming die and an opposed high pressure chamber die set unit, at least one of said die set units being movable with respect to the other die set unit, said die set units receiving material therebetween when the die set units are in first spaced positions and functional to clamp the material therebetween when the die set units are in second closed forming positions for solid phase forming of the material against the forming die upon introduction of high pressure fluid into the chamber die set unit, said apparatus comprising: 
 mechanism operable to receive material to be formed and to direct the material to the forming station of the die set assembly when the die set units are in said first positions thereof; and    a material preheating station outside of but generally proximal to the forming cavity of the forming die set unit, said preheating station being provided with a pair of clamshell defining material engaging preheating devices, at least one of said devices being movable relative to the other device with the devices receiving material clamped therebetween when the devices are in first spaced disposition and engaging opposed surfaces of the material when the devices are in second closed material preheating disposition,    at least one of the devices being provided with a material heating element for preheating material at the preheating station when the devices are in said second preheating disposition thereof,    each device provided with a material heating element having an air insulating zone of predetermined shape which prevents the portion of material engaged by the devices at the preheating station that is in general alignment with the insulating zone from being heated to as high a temperature as the material out of alignment with the insulating zone.    
     
     
         24 . In apparatus for high pressure, solid phase forming of relatively thin material having opposed surfaces, said apparatus including a die set assembly presenting a material forming station and provided with a forming die set unit having a forming cavity which receives a forming die and an opposed high pressure chamber die set unit, at least one of said die set units being movable with respect to the other die set unit, said die set units receiving material therebetween when the die set units are in first spaced positions and functional to clamp the material therebetween when the die set units are in second closed forming positions for solid phase forming of the material against the forming die upon introduction of high pressure fluid into the chamber die set unit, said apparatus comprising: 
 mechanism operable to receive material to be formed and to direct the material to the forming station of the die set assembly when the die set units are in said first positions thereof; and    a material preheating station outside of but generally proximal to the forming cavity of the forming die set unit, said preheating station being provided with a pair of clamshell defining material engaging preheating devices, at least one of said devices being movable relative to the other device with the devices receiving material clamped therebetween when the devices are in first spaced disposition and engaging opposed surfaces of the material when the devices are in second closed material preheating disposition,    at least one of the devices being provided with a material heating element for preheating material at the preheating station when the devices are in said second preheating disposition thereof.    
     
     
         25 . Apparatus as set forth in  claim 22 , wherein each of the devices is provided with a material heating element.  
     
     
         26 . Apparatus as set forth in  claim 22 , wherein is provided structure opening and closing the preheating devices at the preheating station in timed relationship to opening and closing of the die set units to effect preheating of material as other material is pressure formed in the die set assembly.  
     
     
         27 . A method for high pressure, solid phase forming of relatively thin material having opposed surfaces in apparatus which includes a die set assembly presenting a material forming station and provided with a forming die set unit having a forming cavity which receives a forming die and an opposed high pressure chamber die set unit, at least one of said die set units being movable with respect to the other die set unit, said die set units receiving material therebetween when the die set units are in first spaced positions and functional to clamp the material therebetween when the die set units are in second closed forming positions for solid phase forming of the material against the forming die upon introduction of high pressure fluid into the chamber die set unit, said method comprising the steps of: 
 preheating material at a preheating station outside of but generally proximal to the forming die cavity of the forming die set unit;    providing at least one air insulation zone at the preheating station to prevent areas of the material at the preheating station generally aligned with the insulation zone from being heated to as high a temperature as the material out of alignment with the insulating zone; and    successively shifting material to the preheating station and then to the forming station of the die set assembly after preheating of the material.    
     
     
         28 . A method as set forth in  claim 25 , wherein is included the step of applying heat to opposite sides of material at said preheating station.  
     
     
         29 . A method as set forth in  claim 25 , wherein is included the step of preheating material at the preheating station at generally the same time previously preheated material is formed in the forming station of the die set assembly.  
     
     
         30 . A method as set forth in  claim 25 , wherein is included the step of providing an air insulation zone on opposite sides of material at the preheating station.  
     
     
         31 . A method as set forth in  claim 28 , wherein is included the step of providing air insulation zones on opposite sides of material at the preheating station each of a shape correlated with the shape of the forming die.