| 摘要 |
A heat sealing assembly, for sealing and simultaneously cutting through at least two layers of thermoplastic film is disclosed. It is particularly adapted for use with a vertical form, fill and seal machine for packaging flowable materials, e.g. chocolate fudge sundae topping. The heat sealing assembly comprises two jaws (11, 12) and an electrical impulse heat sealing element, at least one of the jaws being capable of transverse motion and adapted to collapse a tubular film made from the thermoplastic film and passing between the jaws, the first of the jaws having said element mounted thereon and the second of the jaws having a resilient pad (31) mounted thereon, wherein: i) the element comprises two flat elongated fins of metal (21, 22) adjoined by an arcuate elongated segment of metal (23), each lateral edge of the elongated segment being adjoined to a lateral edge of one of the elongated fins, the planes of said fins meeting at an angle of from 140 to 180 degrees, said segment being on the excluded angle side of the planes, the width of each fin being from 1000 to 4000 mum and the thickness of each fin being 125 to 500 mum; ii) the first jaw (11) is constructed of metal and has an element base, said element base (15) consisting of two flat surfaces (16, 17) which meet at an elongated apex (35) at an angle which is substantially the same as the angle between the planes of the elongated fins (21, 22) of said element, the element and element base being constructed such that there is an air gap between the apex (35) and the arcuate elongated segment (23) of the element, and one or two longitudinal clamping surfaces (13, 14), each of said clamping surfaces being adjacent to the element base and having a plurality of transverse slots (26, 27) therein such that the unslotted area of each of the clamping surfaces is from about 20 to about 60 % of the total area of said clamping surface; and iii) the second jaw (12) has the resilient pad (31) mounted on the face which is adapted to cooperate with the first jaw, the resilient pad, the element base and the clamping surfaces of the first jaw being adapted such that when the first and second jaws are moved into contact with one another the resilient pad and the clamping surfaces firmly hold the thermoplastic films therebetween, and the resilient pad and the elongated segment of the heat sealing element exert sufficient force upon one another that when the heat sealing element is electrically heated the thermoplastic films are sealed and severed by the heat sealing element. |
