Patent GB-1435562-A (GB)
Title: Packaging apparatus
IPC: B65B41/14
Filed: 1973-05-03
Abstract: 1435562 Sheet forming; seaming non- metallic sheet material MAHAFFY & HARDER ENG CO 3 May 1973 [31 May 1972] 21149/73 Headings B5A and B5K [Also in Division B8] In packaging apparatus wherein first and second plastics webs 34 and 64, one of which at least has product-receiving pockets formed therein, are intermittently and convergently advanced to an assembly and sealing station 60 by respective conveyers 36 and 62, each conveyer including respective sets of clamps 40 and 96 for gripping the respective edges to ensure synchronous and controlled advance of the webs. First web feed and pocket formation.-The first web 34 is relatively flexible and is gripped by edge clamps 40 carried on a pair of opposed endless chains constituting the first conveyer 36, each clamp comprising respective cylindrical and pivotal jaws 42 and 43 which are spring- loaded to grip the web edges until released by camming ramp 49, Fig. 6 (not shown). The first web is stepwise advanced past a vertically reciprocable heater 52 and vacuum die 56 to form pockets therein, below a conveyer 59, which deposits sliced bacon into the pockets, and there to an initial seal station 60 at which respective pockets are sealed around a major portion of their peripheries to pockets formed in the second web. Second web feed and pocket formation.-The second web is of relatively stiffer transparent plastics and is advanced stepwise by a rotary turret 62 constituting the second conveyer. The turret comprises spokes 78 in driven engagement with the first conveyer to synchronize indexing of the turret with movement of the first conveyer, a series of dies 84 for thermoforming pockets in the second web, and a set of toggle-actuated clamps 96 having spring fingers 100 at each side of a respective die for clamping the side edges of the second web there against. The dies, preferably of cast or rough machined aluminium, are provided with a silicone rubber lining 120, Figs. 21 and 22 (not shown), cast in situ between the die and a machined core thus avoiding costly machining of the dies. The lining also provides a resilient counter flange 122 for a heat sealer securing the webs together as described later. The lining is preferably adhered to the die and perforated to facilitate vacuumforming of the pockets in the second web. Sealing and evacuating.-At the initial assembly seal station 60, two aligned pockets of the two webs are heat-sealed during a conveyer dwell period by a vertically-reciprocable heat sealer 68 operable to press the webs against the counter flange 122 of a respective turret die and having an impulse-type element 70 which does not seal completely around the mating pockets. During sealing, the clamps 94 are cam-released. The partially sealed package is then advanced to an evacuation and final seal station 136, Figs. 19-20 (not shown), in which the package is evacuated between vertically reciprocable shells 138 and 140 with the subsequent possible introduction of a gas, and sealing completed by a reciprocable heated platen 160. To aid evacuation, slits 144 are formed in the first web by a knife 148, Figs. 3 and 7 (not shown). During evacuation, the flexible first web pocket is forced into the second web pocket and presses the bacon slicer upwardly there against. The formed package is advanced to a station 166 at which a cardboard stiffening sheet 170 is heat sealed to the lower side of the package. Severing packages from webs.-The formed packages are severed from the webs at a severance station 180 at which a web cutter drum 182, Fig. 16 (not shown), is rolled against a platen 186 which has been lowered to a back-up position by a ram-operated toggle linkage 188. The drum has a bifurcated edge 184 to form round-corners on the package, the cardboard sheets having been provided with preformed rounded corners. The pooketted flexible first web 34 may be supported upstream of the turret by a ladderlike conveyer structure 200 movable in synchronism with the conveyer 36, Fig. 23 and 23a (not shown), while at the initial seal station 60, the web may be supported by a pivotal plate 210, Fig. 24 (not shown), which is located within the heat seal member 168 and which is moved by an advancing first web pocket from an inclined position to a horizontal position against the bias of a spring 216. The contents of the formed package, Figs. 2 and 5 (not shown), are visible through the transparent upper pocket 66, and the seal between the two webs is weaker than that between the lower flexible first web portion and cardboard sheet so that the sheet and first web portion may be separated from second web portion-along three sides to open the container. A tongue 244 formed in the card board sheet may then be pushed through a slot 252, which has previously been cut through the webs by co-operating knives 260 (one only being shown) at the evacuation station, to effect package reclosure.