Nd apparatus for heat-sealing paperboard package closure flaps

Claim 1

Heat sealing apparatus for closure of paperboard package flaps having heat-sealable coatings, including in combination: a hot air manifold having two surfaces meeting and terminating at a sharp acute angle, each surface having at least one row of openings therealong for sending hot air against two flap surfaces facings and on opposite sides of said manifold, at least one air heater connected to said manifold for supplying hot air thereto, each heater cOmprising an outer metal tubular housing having first and second closed ends and a tangential air inlet near said first closed end, an intermediate tubular metal shell inside and spaced from said outer housing except at said closed ends and supported at said closed ends to keep the spacing constant and having near said second closed end tangential aperture means and closed at both its ends, and a ceramic heater body having an inner shell on its outer surface lying inside and spaced from said intermediate shell, said ceramic heater body having a plurality of lengthwise passages each with a heating element inside said passages leading through an outlet larger than the total cross-sectional area of said lengthwise passages into said manifold at one end and said body stopping short of the closed end of said intermediate shell at the other end, whereby air enters said tangential inlet, swirls around in a passage between said housing and said intermediate shell, flows through said aperture means, swirls toward the other end in a psssage between said intermediate and inner shells and then flows back through said lengthwise passages and into said manifold at relatively low velocity and issues from said manifold openings at relatively low velocity, said manifold openings having a total area greater than the cross-sectional area of said lengthwise passages, means for supplying air under pressure to said inlet of said air heater, means for moving said package relative to said manifold, means for guiding said flaps as said package is moved, to space said flaps properly from said manifold, means for forcing said flaps against each other, and means for holding them against each other until the heated coating congeals and seals them together.

Claim 19

A method for heat-sealing two pieces of paperboard, at least one of which has been coated with heat-sealable coating, comprising moving the two pieces at the same velocity, bringing the two moving pieces into proximity generally opposite each other, heating a controlled narrow area of each piece by air only, by impinging on each moving piece a high-volume stream of low-velocity hot air along said controlled narrow area, while limiting the air impingement and heating to a small fraction of the total width of each said piece, thereby intensively heating a critical strip of the surface of each piece above the sealing temperature for said coating, immediately thereafter forcing the two moving pieces together with their heated strip surfaces against each other, to close them into sealing position, and holding them together under pressure as they move until they cool below the sealing temperature of the coating, said pieces being brough into proximity along two planes that diverge from a vertex at a sharp acute angle, said strips being spaced the same distance from said vertex, the pressure to hold the pieces together being applied as a gentle rolling pressure at many separated points while sending ambient air against said pieces in between said separated points, to cool said pieces.

Claim 20

A method for heat-sealing two pieces of paperboard, at least one of which has been coated with heat-sealable coating, comprising moving the two pieces at the same velocity, bringing the two moving pieces into proximity generally opposite each other, heating a controlled narrow area of each piece by air only, by impinging on each moving piece a high-volume stream of low-velocity hot air along said controlled narrow area, while limiting the air impingement and heating to a small fraction of the total width of each said piece, thereby intensively heating a critical strip of the surface of each piece above the sealing temperature for said coating, immediately thereafter forcing the two moving pieces together with their heated strip surfaces against each other, to close them into sealing position, and holding them together under pressure as they move until they cool below the sealing temperature of the coating, said pieces being brough into proximity along two planes that diverge from a vertex at a sharp acute angle, said strips being spaced the same distance from said vertex, the pressure to hold the pieces together being applied as a gentle rolling pressure at many separated points while sending ambient air against said pieces in between said separated points, to cool said pieces.

Claim 21

A method for heat-sealing two flaps of a paperboard carton, at least one of which has been coated with heat-sealable coating, comprising bringing the flaps into proximity along two planes diverging from a vertex at a sharp acute angle, heating a controlled narrow area of each flap as the sole heating of said flaps by impinging on each flat a high-volume, low-velocity, strip-shaped stream of very hot air along said controlled narrow area spaced the same distance from said vertex, while limiting at all times the air impingement and heating to a small fraction of the length and total distance from said vertex to the outer edge of the flap, thereby heating a critical strip of each flap above the temperature making said coating tacky, immediately thereafter forcing the two flaps together, to close them into sealing position, and holding them together under pressure until they cool below the congealing temperature of the coating, the holding step being accomplished by constantly applying rolling pressure at a series of separated points while applying ambient cooling air to cool the flaps, in between said points.

Claim 22

A method for heat-sealing two flaps of a paperboard carton, at least one of which has been coated with heat-sealable coating, comprising bringing the flaps into proximity along two planes diverging from a vertex at a sharp acute angle, heating a controlled narrow area of each flap as the sole heating of said flaps by impinging on each flat a high-volume, low-velocity, strip-shaped stream of very hot air along said controlled narrow area spaced the same distance from said vertex, while limiting at all times the air impingement and heating to a small fraction of the length and total distance from said vertex to the outer edge of the flap, thereby heating a critical strip of each flap above the temperature making said coating tacky, immediately thereafter forcing the two flaps together, to close them into sealing position, and holding them together under pressure until they cool below the congealing temperature of the coating, the holding step being accomplished by constantly applying rolling pressure at a series of separated points while applying ambient cooling air to cool the flaps, in between said points.

Claim 23

A method for heat sealing two pieces of paperboard, at least one of which has been coated with heat sealable coating, comprising bringing the two pieces into proximity generally op-posite each other, simultaneously moving the pieces relative to a duct means positioned therebetween, maintaining at least one of the pieces spaced from and out of contact with said duct means, heating a portion of each of said surfaces solely by heated gas successively impinging hot gas from said duct means at low velocity but of a volume and temperature to raise the coating above the sealable temperature onto small fractional and equal areas of said surfaces during their movement relative to the duct means, said areas lying along a narrow strip constituting a small fraction of the width of each piece, forcing the pieces together with their heated strip surfaces against each other to close them into sealing position immediately after the areas along said strip have been heated, and while they are moving past a station, applying pressure at said station against successive mutually exclusive small fractional areas of the pieces, and while moving holding them under pressure on a line substantially normal to their direction of movement while directing cooling air against said pieces until they cool below the sealing temperature of the coating.

Claim 24

A method for heat sealing two pieces of paperboard, at least one of which has been coated with heat sealable coating, comprising bringing the two pieces into proximity generally op-posite each other, simultaneously moving the pieces relative to a duct means positioned therebetween, maintaining at least one of the pieces spaced from and out of contact with said duct means, heating a portion of each of said surfaces solely by heated gas successively impinging hot gas from said duct means at low velocity but of a volume and temperature to raise the coating above the sealable temperature onto small fractional and equal areas of said surfaces during their movement relative to the duct means, said areas lying along a narrow strip constituting a small fraction of the width of each piece, forcing the pieces together with their heated strip surfaces against each other to close them into sealing position immediately after the areas along said strip have been heated, and while they are moving past a station, applying pressure at said station against successive mutually exclusive small fractional areas of the pieces, and while moving holding them under pressure on a line substantially normal to their direction of movement while directing cooling air against said pieces until they cool below the sealing temperature of the coating.