Method of welding sheets,particularly shrink-on-sheets which have been wrapped around a pallet cargo and apparatus therefor

Claim 3

Apparatus for welding the marginal portions of sheet material, particularly of shrink-on-sheet material, wrapped around the cargo on loaded pallets, comprising means for moving individual loaded pallets along an advancing path of travel, means for stretching a wall of the sheet material transversely across the advancing path of travel of the loaded pallets so that the loaded pallets are enveloped in the sheet material as the pallet moves into the wall of sheet material, a welding device for welding vertically extending portions of the sheet material on the downstream side of the loaded pallet after it has been enveloped by the sheet material, and severing means for cutting the sheet material in vertical direction at the location of the vertical weld effected by said welding device for separating the sheet materiaL enveloping the loaded pallet from and forming a new wall of sheet material for enveloping the next loaded pallet, wherein the improvement comprises that said means for moving individual loaded pallets comprises a base frame extending upwardly above the advancing path of travel of the loaded pallets, a guide rail mounted on said frame above the advancing path of travel and inclined downwardly in the advancing direction of the loaded pallet so that its forward end in the advancing direction is lower than its rearward end, a claw slidably mounted on said guide rail for movement therealong in the advancing direction of the loaded pallet, a tiltable retaining arm secured to the rearward end of said guide rail for pivotal movement about a horizontal axis in the advancing direction of the loaded pallet, a welding device attached to the lower forward end of said guide rail for welding the upper margin portions of the sheet material located above the loaded pallet, and said welding device including transport wheels inclined relative to the sheet material for guiding the upper edges of the upper marginal portions of the sheet material during the welding action.

Claim 4

Apparatus for welding the marginal portions of sheet material, particularly of shrink-on-sheet material, wrapped around the cargo on loaded pallets, comprising means for moving individual loaded pallets along an advancing path of travel, means for stretching a wall of the sheet material transversely across the advancing path of travel of the loaded pallets so that the loaded pallets are enveloped in the sheet material as the pallet moves into the wall of sheet material, a welding device for welding vertically extending portions of the sheet material on the downstream side of the loaded pallet after it has been enveloped by the sheet material, and severing means for cutting the sheet material in vertical direction at the location of the vertical weld effected by said welding device for separating the sheet materiaL enveloping the loaded pallet from and forming a new wall of sheet material for enveloping the next loaded pallet, wherein the improvement comprises that said means for moving individual loaded pallets comprises a base frame extending upwardly above the advancing path of travel of the loaded pallets, a guide rail mounted on said frame above the advancing path of travel and inclined downwardly in the advancing direction of the loaded pallet so that its forward end in the advancing direction is lower than its rearward end, a claw slidably mounted on said guide rail for movement therealong in the advancing direction of the loaded pallet, a tiltable retaining arm secured to the rearward end of said guide rail for pivotal movement about a horizontal axis in the advancing direction of the loaded pallet, a welding device attached to the lower forward end of said guide rail for welding the upper margin portions of the sheet material located above the loaded pallet, and said welding device including transport wheels inclined relative to the sheet material for guiding the upper edges of the upper marginal portions of the sheet material during the welding action.

Claim 5

Apparatus, as set forth in claim 2, wherein said welding device for welding the vertically extending portions of the sheet material includes a pair of oppositely disposed welding jaw assemblies including welding jaws and clamping jaws arranged laterally of said welding jaws, and a motor for urging said welding jaws against each other with a constant force during the entire welding operation.

Claim 6

Apparatus, as set forth in claim 2, wherein said guide rail together with said claw, said retaining arm, and said welding device mounted thereon are adjustable in elevation.

Claim 7

Apparatus, as set forth in claim 3, wherein means are arranged for spring biasing and movably guiding said clamping jaws which hold the sheet material in a predetermined position during the vertical welding operation, and said clamping jaws being positioned on the upstream and downstream side of said welding jaws in said welding jaw assemblies in the advancing direction of the loaded pallets.

Claim 8

Apparatus, as set forth in claim 3, wherein a mounting plate is associated with each of said welding jaw assemblies, a continuous chain, motor driven means for driving such continuous chain and for forming a pair of chain runs, a guide arm for connecting each of said mounting plates to one of the chain runs of said continuous chain, one of said mounting plates extending laterally of said welding jaw assembly, a second mounting plate associated with said welding jaw assembly from which the one of said mounting plates extends laterally, cylinder guides positioned on said second mounting plate, said cylinder guides connected at the ends thereof opposite said second mounting plate to said welding jaws of said welding jaw assembly associated therewith, spring biased guide slides mounted on said cylinder guides and connected to said movably guided clamping jaws associated with said welding jaw assembly incorporating said cylinder guides.

Claim 9

Apparatus, as set forth in claim 6, wherein said motor drive means for said continuous chain comprises a motor having a reversible polarity and arranged to afford a reducible torque on said welding jaw assembly through the medium of said chain.