Adjustable mold for forming containers

An adjustable mold for transforming a heated plastic sheet into a rectangular container, said mold comprising:

• a bottom wall having a substantially horizontal upper surface and first and second substantially vertical side edges perpendicularly intersecting each other to define a right-angle corner;
• a first substantially vertical sidewall having an end at said corner and a side extending therefrom alongside said first side edge, said first sidewall being vertically moveable relative to said bottom wall so that said side thereof is moveable upward and downward relative to said upper surface;
• a second substantially vertical sidewall having an end and a side extending therefrom alongside said second side edge at least to said first sidewall end, said second sidewall being vertically moveable relative to said bottom wall so that said side thereof is moveable upward and downward relative to said upper surface, said second sidewall being horizontally moveable relative to said bottom wall so that said end thereof is moveable toward and away from said first sidewall end;
• a third substantially vertical sidewall having an end and a side extending therefrom parallel with said first sidewall side at least to said second sidewall end, said third sidewall side extending vertically upward from said upper surface, said third sidewall being horizontally moveable relative to said bottom wall so that said end thereof is moveable toward and away from said second sidewall end and so that said third sidewall side is moveable toward and away from said first sidewall side;
• and
• a fourth substantially vertical sidewall having an end at said first side edge and a side extending therefrom parallel with said second sidewall side at least to said third sidewall end, said fourth sidewall side extending vertically upward from said upper surface, said fourth sidewall being horizontally moveable relative to said bottom wall so that said side thereof is moveable toward and away from said second sidewall side;
• wherein said first sidewall is horizontally stationary relative to said bottom wall, said first sidewall end slideably abuts said second sidewall side, and said first sidewall side slideably abuts said first side edge and said fourth sidewall end;
• wherein said second sidewall end slideably abuts said third sidewall side, and said second sidewall side slideably abuts said second side edge and said first sidewall end;
• wherein said third sidewall is vertically stationary relative to said bottom wall, said third sidewall end slideably abuts said fourth sidewall side, and said third sidewall side slideably abuts said second sidewall end;
• wherein said fourth sidewall is vertically stationary relative to said bottom wall, said fourth sidewall end slideably abuts said first sidewall side, and said fourth sidewall side relatively abuts said third sidewall end;
• and
• wherein said second sidewall is rigidly mounted on an actuatable member for both horizontal and vertical movements therewith relative to said bottom wall, and said third sidewall is slidably mounted to said actuatable member for only horizontal movements relative to said bottom wall in a first direction along with said member toward and away from said first sidewall, and in a second direction relative to said member parallel with said first sidewall;
• whereby said bottom wall and said sidewalls define a variable rectangular cavity for receiving the plastic sheet and forming it into the container.