Film clamp for film sealing apparatus and method

Abstract

Film clamp for the lower or stationary jaw of a sealing machine, particularly the lower or stationary jaw of an L-bar sealing machine. Preferably the film clamp is constructed of a thermally conductive material and is configured to effectively dissipate heat. A closed loop feedback system can be used to regulate the applied power to the sealing element in order to maintain its temperature within a predetermined range to help prevent overheating of the film clamp and other jaw components.

What is claimed is:  
     
         1 . Apparatus for sealing a plastic film, comprising: 
 a top jaw assembly and a bottom jaw assembly housing a sealing element, said top jaw assembly and bottom jaw assembly being movable with respect to each other;    a source of power to heat said sealing element to a temperature effective for sealing said plastic film; and    a film clamp in said bottom jaw assembly having at least one surface for positioning said film with respect to said sealing element.    
     
     
         2 . The apparatus of  claim 1 , wherein said bottom jaw assembly is stationary and said to jaw assembly is movable.  
     
     
         3 . The apparatus of  claim 1 , wherein said film clamp comprises a plurality of projections for dissipating heat.  
     
     
         4 . The apparatus of  claim 1 , further comprising a spring in said bottom jaw for biasing said film clamp towards said top jaw assembly.  
     
     
         5 . The apparatus of  claim 4 , wherein said biasing of said film clamp maintains said film out of contact with said sealing element after the sealing operation has been completed.  
     
     
         6 . The apparatus of  claim 1 , wherein said film clamp is movable between a first pre-sealing position wherein said at least one surface positions said film above and out of contact with said sealing element and a second sealing position wherein said at least one surface positions said film in contact with said sealing element.  
     
     
         7 . The apparatus of  claim 6 , wherein said film clamp is movable between said first and second positions upon the application of pressure from said top jaw assembly.  
     
     
         8 . The apparatus of  claim 6 , further comprising at least one spring in said bottom jaw assembly supporting said film clamp, and wherein said at least one spring is in a compressed state when said film clamp is in said second position.  
     
     
         9 . The apparatus of  claim 1 , wherein said film clamp is substantially U-shaped and comprises a base and a pair of opposite sides terminating in a respective pair of free ends.  
     
     
         10 . The apparatus of  claim 9 , wherein said opposite sides of said film clamp taper inwardly towards said sealing element.  
     
     
         11 . A method for sealing film about an article, comprising: 
 providing upper and lower sealing jaws movable with respect to each other, said lower sealing jaw comprising a sealing element and a film clamp;    compressing said film between said upper sealing jaw and said and lower sealing jaws so as to cause said film to contact said film clamp; and    further compressing said film between said upper sealing jaw and said lower sealing jaw so as to cause said film to contact said sealing element to seal said film.    
     
     
         12 . The method of  claim 11 , wherein during said first compressing step said film clamp is in a first pre-sealing position wherein said film clamp positions said film out of contact with said sealing element and during said further compressing step said film clamp is in a second sealing position wherein said film clamp positions said film in contact with said sealing element.  
     
     
         13 . The method of  claim 12 , further comprising terminating compression of said film to cause said film clamp to return to said first position.  
     
     
         14 . A method for sealing film about an article, comprising: 
 providing a movable upper jaw and a stationary lower jaw, said lower jaw comprising a sealing element and a film clamp;    positioning said sealing film between said upper and low jaw;    moving said upper jaw towards said lower jaw and forcing said sealing film on said film clamp above said sealing element; and    contacting said upper jaw and said lower jaw so as to force said film to contact said sealing element to seal said film.    
     
     
         15 . The method of  claim 14 , wherein said film clamp is movable between a first non-sealing position wherein said film clamp positions said film out of contact with said sealing element and a second sealing position wherein said film clamp positions said film in contact with said sealing element.  
     
     
         16 . The method of  claim 15 , further comprising terminating contact between said upper and lower jaws to cause said film clamp to return to said first position.