GB1148613A - A method of, and apparatus for forming a linear seal between two layers of a thermoplastic material - Google Patents

Abstract

1,148,613. Seaming non-metallic sheet material. COMTEX Ltd. 18 March, 1966 [18 March, 1965], No. 11552/65. Heading B5K. [Also in Division B8] A linear seal between two layers of thermoplastic material is produced by directing heated air on to a linear section while the layers are carried past the source of the hot air between grippers. In the embodiment described apparatus for sealing filled bags of thermoplastic or thermoplastic coated material comprises two endless driven chains or belts 18 which grip the mouth of a bag below a line of sealing, an opposed pair of heated blocks 26 which direct hot air on to the part of the bag to be sealed, and a pair of nip rollers 28, 30, one of which is driven by a motor 46, which press the heated parts together to form a line of sealing. The bag is carried through between the belts 18 and also between fixed guides 22 by an endless conveyer on a table (79), Fig. 1 (not shown), mounted below the sealing unit. Cooling blocks may be provided to direct cooling air on to the sealed bag after it has passed between the nip rollers, the tension and positions of which may be adjusted at 68 and 70, Fig. 2, respectively. A knife-edge may also be provided downstream of the cooling blocks, to cut off surplus material above the seal. An additional pair of heated blocks 24, serving as pre-heaters, may be used if the material of the bags is relatively thick. Air is lead to the heated blocks 24, 26 from a fan 56 through pipes 62, transverse channels being provided in the blocks to direct the air on to the bag. The vertical height of the sealing unit above the conveyer table (79), Fig. 1 (not shown), is adjustable to allow for different sizes of bag, and the separation of a pair of guide plates (98) which support the sides of the bag above the conveyer, is also adjustable. The entire assembly is mounted on a base (16) having wheels (78).