US 4,051,569 AGranted

Folding and sealing apparatus and method

AssigneeLouis G. Freeman Company

InventorsDavid Bruce Freeman, Michael C. Patton, Carl F. Dragan

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Abstract

An apparatus for folding and sealing the edges of a non-rigid work piece and a method of performing folding and sealing operations therewith. The apparatus comprises a press with a main cylinder, at least one auxiliary cylinder and upper and lower die assemblies for the press. The upper die assembly comprises a folding cavity plate operatively connected to the main cylinder and having a folding cavity with an electrode surrounding a part at least of the cavity. A stripper in association with the upper die assembly is independently shiftable by the at least one auxiliary cylinder between a retracted position above the folding cavity and an extended position therebelow. The bottom die assembly comprises a plate having a female cavity therein of a size and shape equivalent to that of the folded work piece and a male plug receivable within the female cavity with close tolerance. The female cavity plate and the male plug are shiftable relative to each other by the folding cavity plate and the stripper, respectively, of the upper die assembly. Means are provided to connect the electrode and the stripper to a source of high frequency electricity. In performing the folding and sealing steps, the work piece is first forced into the female cavity by the stripper to initiate the bending of the work piece edges. The work piece is thereafter forced into the folding cavity by the male plug to complete the folding step. The electrode and the stripper are thereafter connected to the source of high frequency electricity to seal the folded edges of the work piece with the stripper in one of three positions: (a) against the work piece under pressure, (b) against the work piece without pressure, and (c) retracted and out of contact with the work piece. The apparatus may also be used to seal at least a second layer to the work piece.

Claims30

Dependent claims

An apparatus for folding and sealing edges of a non-rigid work piece, said apparatus comprising cooperating lower and upper die assemblies, said lower die assembly comprising a horizontally oriented plate having a female cavity extending therethrough of a shape corresponding to that of the folded work piece, said female cavity plate being shiftable between upper and lower positions and means to resiliently bias said female cavity plate to its upper position, a male plug receivable within said female cavity with close tolerance, said male plug being shiftable between an upper position within said female cavity with its upper surface slightly below the upper surface of said female cavity plate when said female cavity plate is in its upper position and a lower position wherein said male plug is withdrawn from said female cavity when said female cavity plate is in its upper position and wherein the top surface of said plug is substantially coplanar with said top surface of said female cavity plate when said female cavity plate is in its lower position, means to bias said male plug to its upper position, said upper die assembly comprising a horizontally oriented folding cavity plate, said folding cavity plate having a shallow folding cavity therein corresponding in shape to said female cavity, said folding cavity having curved edge portions corresponding to the edges of the work piece to be folded, said folding cavity plate having at least one electrode mounted therein so as to overlie the edges of the work piece when folded, said folding cavity plate having a central depression, a stripper comprising a horizontal plate independently shiftable between an extended position below said folding cavity and a retracted position within said central depression of said folding cavity and means to connect said electrode to a source of high frequency electricity whereby when a work piece is properly aligned on said female cavity plate and said stripper is in its extended position, the folding cavity plate and the stripper may be lowered until said stripper forces said work piece into said female cavity and said male plug to its lower position initiating folding of said work piece edges, continued downward movement of said folding cavity plate shifts said female cavity plate to its lower position resulting in relative upward movement of said male plug and said stripper to cause said partially folded work piece edges to be completely folded by said inwardly curved edge portions of said folding cavity and to lie in abutment with said at least one electrode, to be sealed thereby when connection is made to said source of high frequency electricity.

A process of folding and sealing edges of a non-rigid, heat sealable work piece comprising the steps of providing a lower die assembly comprising a horizontally oriented plate with a female cavity extending therethrough of a shape corresponding to that of the folded work piece, said female cavity plate being shiftable between upper and lower positions and resiliently biased to said upper position and a male plug receivable within said female cavity with close tolerance, said male plug being shiftable between an upper position with the female cavity with its upper surface slightly below the upper surface of said female cavity plate when said female cavity plate is in its upper position and a lower position wherein said male plug is withdrawn from said female cavity when said female cavity plate is in its upper position and wherein the top surface of said plug is substantially coplanar with said top surface of said female cavity plate when said female cavity plate is in its lower position, means to bias said male plug to its upper position, providing an upper die assembly comprising a horizontally oriented folding cavity plate, said folding cavity plate having a shallow folding cavity therein corresponding in shape to said female cavity, said folding cavity having curved edge portions corresponding to the edges of the work piece to be folded, said folding cavity plate having at least one electrode mounted therein so as to overlie the edges of the work piece when folded, said folding cavity plate having a central depression, a stripper comprising a horizontal plate independently shiftable between an extended position below said folding cavity, and a retracted position within said central depression of said folding cavity, locating said work piece on said female cavity plate over said female cavity, maintaining said stripper in its extended position, lowering said upper die assembly until said stripper forces said work piece into said female cavity depressing said male plug to its lower position and initiating a fold in said edges of said work piece, maintaining the positions of said stripper, said work piece and said male plug, continuing lower of said folding cavity plate resulting in abutment of and lowering of said female cavity plate to its lower position wherein said male plug has reentered said female cavity shoving said work piece into said folding cavity to complete folding of said work piece edges and to cause them to abut said electrode, connecting said electrode to a source of high frequency electrical current to seal said folded edges, permitting said sealed edges to cool until a seal is assured and raising said upper die assembly to shift said folding cavity plate and said stripper out of contact with said lower die assembly and said work piece.

Dependencies are inferred from the claim text.