Process and device for the stretching of plastics sheets

Claim 1

An apparatus for producing stretched solid thermoplastic sheet material comprising an axially rotating blow head for blowing a tubular sheet of solid thermoplastic sheet material, a pair of heated squeeze rollers disposed adjacent the blow head for flattening and welding together the blown tubular sheet of solid thermoplastic material, a pair of rotatably mounted disks disposed adjacent and after the heated squeeze rollers in contact with the edges of the flattened and welded together sheet material, heating means arranged to apply heat to the edges of the sheet material contacting the disks, the disks being disposed at a divergent angle with respect to the edges of the sheet material, pressure applying means disposed on the opposite sides of said sheet material from the disks and adjacent the disks for applying pressure to the edges of the sheet material to urge them in forceful contact with the circumferential surfaces of the disks whereby the formation of air pockets between the edges and the disks is prevented and the edges are maintAined in firm engagement with the circumferential surface of the disks by atmospheric pressure to laterally stretch the sheet of thermoplastic material in accordance with the divergent angle of the disks without using any mechanical means gripping over the edges of the sheet, and the distance between the axially rotating blow head and the pair of heated squeeze rollers is approximately from one-half to ten times the diameter of the outlet from the axially rotating blow head.

Claim 2

An apparatus for producing stretched solid thermoplastic sheet material comprising an axially rotating blow head for blowing a tubular sheet of solid thermoplastic sheet material, a pair of heated squeeze rollers disposed adjacent the blow head for flattening and welding together the blown tubular sheet of solid thermoplastic material, a pair of rotatably mounted disks disposed adjacent and after the heated squeeze rollers in contact with the edges of the flattened and welded together sheet material, heating means arranged to apply heat to the edges of the sheet material contacting the disks, the disks being disposed at a divergent angle with respect to the edges of the sheet material, pressure applying means disposed on the opposite sides of said sheet material from the disks and adjacent the disks for applying pressure to the edges of the sheet material to urge them in forceful contact with the circumferential surfaces of the disks whereby the formation of air pockets between the edges and the disks is prevented and the edges are maintAined in firm engagement with the circumferential surface of the disks by atmospheric pressure to laterally stretch the sheet of thermoplastic material in accordance with the divergent angle of the disks without using any mechanical means gripping over the edges of the sheet, and the distance between the axially rotating blow head and the pair of heated squeeze rollers is approximately from one-half to ten times the diameter of the outlet from the axially rotating blow head.

Claim 4

An apparatus for producing stretched solid thermoplastic sheet material comprising an axially rotating blow head for blowing a tubular sheet of solid thermoplastic sheet material, a pair of heated squeeze rollers disposed adjacent the blow head for flattening and welding together the blown tubular sheet of solid thermoplastic material, a pair of rotatably mounted disks disposed adjacent and after the heated squeeze rollers in contact with the edges of the flattened and welded together sheet material, heating means arranged to apply heat to the edges of the sheet material contacting the disks, the disks being disposed at a divergent angle with respect to the edges of the sheet material, pressure applying means disposed on the opposite sides of said sheet material from the disks and adjacent the disks for applying pressure to the edges of the sheet material to urge them in forceful contact with the circumferential surfaces of the disks whereby the formation of air pockets between the edges and the disks is prevented and the edges are maintained in firm engagement with the circumferential surface of the disks by atmospheric pressure to laterally stretch the sheet of thermoplastic material in accordance with the divergent angle of the disks without using any mechanical means gripping over the edges of the sheet, and the distance between the axially rotating blow head and the pair of heated squeeze rollers is approximately from one to three times the diameter of the outlet from the axially rotating blow head.

Claim 5

An apparatus for producing stretched solid thermoplastic sheet material comprising an axially rotating blow head for blowing a tubular sheet of solid thermoplastic sheet material, a pair of heated squeeze rollers disposed adjacent the blow head for flattening and welding together the blown tubular sheet of solid thermoplastic material, a pair of rotatably mounted disks disposed adjacent and after the heated squeeze rollers in contact with the edges of the flattened and welded together sheet material, heating means arranged to apply heat to the edges of the sheet material contacting the disks, the disks being disposed at a divergent angle with respect to the edges of the sheet material, pressure applying means disposed on the opposite sides of said sheet material from the disks and adjacent the disks for applying pressure to the edges of the sheet material to urge them in forceful contact with the circumferential surfaces of the disks whereby the formation of air pockets between the edges and the disks is prevented and the edges are maintained in firm engagement with the circumferential surface of the disks by atmospheric pressure to laterally stretch the sheet of thermoplastic material in accordance with the divergent angle of the disks without using any mechanical means gripping over the edges of the sheet, and the distance between the axially rotating blow head and the pair of heated squeeze rollers is approximately from one to three times the diameter of the outlet from the axially rotating blow head.

Claim 6

An apparatus for producing stretched solid thermoplastic sheet material comprising an axially rotating blow head for blowing a tubular sheet of solid thermoplastic sheet material, a pair of heated squeeze rollers disposed adjacent the blow head for flattening and welding together the blown tubular sheet of solid thermoplastic material, a pair of rotatably mounted disks disposed adjacent and after the heated squeeze rollers in contact with the edges of the flattened and welded together sheet material, heating means arranged to apply heat to the edges of the sheet material contacting the disks, the disks being disposed at a divergent angle with respect to the edges of the sheet material, pressure applying means disposed on the opposite sides of said sheet material from the disks and adjacent the disk for applying pressure to the edges of the sheet material to urge them in forceful contact with the circumferential surfaces of the disks whereby the formation of air pockets between the edges and the disks is prevented and the edges are maintained in firm engagement with the circumferential surface of the disks by atmospheric pressure to laterially stretch the sheet of thermoplastic material in accordance with the divergent angle of the disks without using any mechanical means gripping over the edges of the sheet, and the overall length is approximately five meters.

Claim 7

An apparatus for producing stretched solid thermoplastic sheet material comprising an axially rotating blow head for blowing a tubular sheet of solid thermoplastic sheet material, a pair of heated squeeze rollers disposed adjacent the blow head for flattening and welding together the blown tubular sheet of solid thermoplastic material, a pair of rotatably mounted disks disposed adjacent and after the heated squeeze rollers in contact with the edges of the flattened and welded together sheet material, heating means arranged to apply heat to the edges of the sheet material contacting the disks, the disks being disposed at a divergent angle with respect to the edges of the sheet material, pressure applying means disposed on the opposite sides of said sheet material from the disks and adjacent the disk for applying pressure to the edges of the sheet material to urge them in forceful contact with the circumferential surfaces of the disks whereby the formation of air pockets between the edges and the disks is prevented and the edges are maintained in firm engagement with the circumferential surface of the disks by atmospheric pressure to laterially stretch the sheet of thermoplastic material in accordance with the divergent angle of the disks without using any mechanical means gripping over the edges of the sheet, and the overall length is approximately five meters.