Food serving paperboard container pressing apparatus employing cast-in electrical heaters

Abstract

A pressing apparatus for producing a food service paperboard container from a paperboard blank so that the paperboard container possesses an overturned rim provided with folds includes a first die and a second die that are movable relative to one another. The first die includes a first base and a first platform that is movable with respect to the first base, with the first base having a curved surface for engaging the outer periphery of the paperboard blank. The second die is positioned in opposing relation to the first die and includes a second base and a second platform that is movable with respect to the second base. The second die is movable with respect to the first die and the second base has a curved surface for engaging the outer periphery of the paperboard blank so that the outer periphery of the paperboard blank is pressed between the curved surface of the first base and the curved surface of the second base. A first cast-in heater is mounted within a recess in the first die and includes a resistor wire embedded within a thermally conductive cast-in material. A second cast-in heater is mounted within a recess in the second die and includes a resistor wire embedded within a thermally conductive cast-in material.

1 - 16 . (canceled)  
     
     
         17 . In a method of manufacturing pressed paperboard containers in a heated die set including an upper die and a lower die which reciprocate with respect to each other and cooperate with each other to form a pressed paperboard container from a paperboard blank, the improvement comprising providing at least one of the dies with a cast-in heater.  
     
     
         18 . The improvement according to  claim 17 , wherein both the upper and lower dies are provided with cast-in heaters.  
     
     
         19 . improvement according to  claim 17 , wherein the cast-in heater has an annular shape.  
     
     
         20 . The improvement according to  claim 17 , wherein the cast-in heater has a shell formed of a material selected from the group consisting of: iron-based alloys; aluminum-based alloys; copper-based alloys, magnesium-based alloys; nickel-based alloys; and titanium-based alloys.  
     
     
         21 . The improvement according to  claim 17 , wherein the upper die is a segmented die having a die base and a knock-out.  
     
     
         22 . The improvement according to  claim 17 , wherein the upper die is a segmented die having a die base and a knock-out and wherein further the upper die includes an outer press-ring.  
     
     
         23 . The improvement according to  claim 17 , wherein the lower die is a segmented die having a die base and a knock-out.  
     
     
         24 . The improvement according to  claim 17 , wherein the paperboard blank is substantially planar.  
     
     
         25 . The improvement according to  claim 17 , wherein the pressed paperboard container is selected from the group consisting of bowls, plates and platters.  
     
     
         26 . The improvement according to  claim 17 , wherein the container is a plate.  
     
     
         27 . A method of making a pressware container from a paperboard blank comprising: 
 (a) positioning the paperboard blank in a pressware die-set having upper and lower dies which reciprocate with respect to each other,    at least one of the dies being provided with a cast-in heater;    (b) maintaining the forming surface of a die provided with a cast-in heater within about 30° F. of a target forming temperature; and    (c) forming a pressware container from the blank between the upper and lower dies.    
     
     
         28 . The method according to  claim 27 , wherein the target forming temperature is above about 300° F.  
     
     
         29 . Method according to  claim 27 , wherein said target temperature of the forming surface is about 320° F.  
     
     
         30 . The method according to  claim 27 , wherein both the upper and lower dies are provided with cast-in heaters.  
     
     
         31 . The method according to  claim 28 , wherein the cast-in heater is maintained at a temperature of below about 550° F. during pressware manufacture.  
     
     
         32 . A method of making a pressware container from a paperboard blank comprising: 
 (a) positioning the paperboard blank in a pressware die-set having upper and lower dies which reciprocate with respect to each other,    at least one of the dies being provided with an electrical resistance heater, the heater including a helically-coiled resistor wire disposed in a compacted refractory material embedded in a thermally-conductive material selected from the group consisting of iron-based alloys, aluminum-based alloys, copper-based alloys, magnesium-based alloys, nickel-based alloys and titanium-based alloys;    (b) maintaining the forming surface of a die provided with an electrical resistance heater within about 30° F. of a target forming temperature, the target forming temperature being above about 300° F. while maintaining the heater at a temperature below about 550° F.; and    (c) forming a pressware container from the blank between the upper and lower dies.    
     
     
         33 . The method according to  claim 32 , wherein said target temperature of the forming surface is about 320° F.  
     
     
         34 . The method according to  claim 32 , wherein both the upper and lower dies are provided with electrical resistance heaters, the heaters including a helically-coiled resistor wire disposed in a compacted refractory material embedded in a thermally-conductive material.  
     
     
         35 . (canceled)  
     
     
         36 . The method according to  claim 34 , wherein all of the heaters are maintained at a temperature below about 550° F. during pressware manufacture.  
     
     
         37 . A method of making a pressware container from a paperboard blank comprising: 
 (a) positioning the paperboard blank in a pressware die-set having upper and lower dies which reciprocate with respect to each other,    at least one of the dies being provided with an electrical resistance heater;    (b) maintaining the forming surface of a die provided with an electrical resistance heater above about 300° F. while maintaining the heater at a temperature of below about 550° F.; and    (c) forming a pressware container from the blank between the upper and lower dies.    
     
     
         38 . The method according to  claim 37 , wherein said target temperature of the forming surface is about 320° F.  
     
     
         39 . The method according to  claim 37 , wherein both the upper and lower dies are provided with electrical resistance heaters.  
     
     
         40 . A method of making a pressware container from a paperboard blank comprising: 
 (a) positioning the paperboard blank in a pressware die-set having upper and lower dies which reciprocate with respect to each other,    at least one of the dies being provided with an electrical resistance heater, the heater including a helically-coiled resistor wire disposed in a compacted refractory material embedded in a copper-based alloy;    (b) maintaining the forming surface of a die provided with an electrical resistance heater within about 30° F. of a target forming temperature above about 300° F. while maintaining the heater at a temperature below about 550° F.; and    (c) forming a pressware container from the blank between the upper and lower dies.    
     
     
         41 . (canceled)  
     
     
         42 . The method according to  claim 40  wherein said target temperature of the forming surface is about 320° F.  
     
     
         43 . The method according to  claim 40 , wherein both the upper and lower dies are provided with electrical resistance heaters, including a helically-coiled resistor wire disposed in a compacted refractory material embedded in a thermally-conductive material.  
     
     
         44 . (canceled)  
     
     
         45 . The method according to  claim 43 , wherein all of the heaters are maintained at a temperature below about 550° F. during pressware manufacture.  
     
     
         46 . A method of making a pressware container from a paperboard blank comprising: 
 (a) positioning the paperboard blank in a pressware die-set having upper and lower dies which reciprocate with respect to each other,    at least one of the dies being provided with an electrical resistance heater;    (b) heating the forming surface of a die provided with an electrical resistance heater by operating the heater with a power input of at least about 2800 watts while maintaining the heater at a temperature of below about 550° F.; and    (c) forming a pressware container from the blank between the upper and lower dies.