GB1142221A - Continuous bag making machine - Google Patents

Abstract

1,142,221. Making plastics bags from tubing. UNION CARBIDE CORP. 11 Feb., 1966 [18 Feb., 1965], No. 6188/66. Headings B5D and B5K. [Also in Divisions B6 and B8] General arrangement.-The end portion of a supply of lay-flat tubing is held by clamps 162, 164 (Fig. 7) against an internally mounted mandrel 100, the lower portion of the tubing, previously bottomed, is cut off by knives 172, 174 which cut flaps 904, 905 (Fig. 3) on both cut ends, and the remaining end length of tubing together with the mandrel 100, is then turned about a horizontal axis to a position in which a heat sealing device can weld a bottom which has been formed on the tubing during the rotation. The mandrel and clamps, together with the bottomed tube, are then restored to their initial position and the tubing is fed through a bag length ready for a further cutting operation. Each bottomed blank cut from the tubing is gripped by clamps 182, 184 which rotate in steps of 90 degrees with a table 60 (Fig. 2) through stations F, G, H, J (Fig. 3) where a valved bottom is formed at the top of the blank. In the construction described the mandrel 1, clamps 162, 164 and the knives 172, 174, are duplicated, each with its own bag-tubing supply, so that bottomed blanks are fed to the table 60 at each of two stations I, II, the table 60 making two steps of 90 degrees for each blank-making cycle in stations I, and II. The bag may be multi-ply. Folding block-bottoms (1).-The mandrel 100 (Fig. 7) has at its lower end a pair of hinged leaves (114) (Fig. 31, not shown) which can be opened by pivoted magnets 166 (Fig. 7) to spread open side flaps at the end of the tubing, thus automatically folding in end tabs. Air nozzles on the clamp 162, 164 help to hold the flaps in position. As the tubing and mandrel are subsequently rotated through 180 degrees about a horizontal axis, the side flaps are folded over the leaves (114) by folding members (154) (Figs. 10 and 11, not shown). One of the folding members preferably operates during the first 90 degrees of rotation, and the other during the second 90 degrees of rotation to ensure that the flaps are folded in succession. The flaps are then welded by a device (600) (Fig. 11). Construction of mandrel.-The mandrel 100 is supported within the tubing by rollers 102, 104, 106 mounted outside the tubing and engaging rollers (129) (Fig. 31, not shown) on the mandrel. Further external rollers engage rollers (128) (Fig. 31, not shown) on the mandrel. Spring-biased pivoted shoes (126) centre the tubing on the mandrel. Hinged portions (115) on the mandrel permit the use of wider tubing. Formation of a vacuum inside the tubing on the mandrel is prevented by an air-injection needle intermittently penetrating the film. Folding block-bottoms (2). Inserting valve sheets and anti-sift sheets.-After the bottomed blank gripped, by clamps 182, 184 (Fig. 7) is cut off by the knives 172, 174, the upper edges of the blank are laid down one on top of the other on the clamp by an air jet (177) (Fig. 8, not shown) carried by the knife 172, and are held in this position by suction cups in the top surface of the clamp. At station III (Fig. 3) a suction cup (302) (Fig. 36, not shown) lifts the upper flap so that it can be folded over the opposite clamp jaw 182, also provided with suction cups, by a horizontally reciprocating shuttle plate (334). The shuttle plate also feeds into position a length of valve sheeting (see G, Fig. 3) drawn from a roll (350) (Fig. 36, not shown). The valve sheet is then welded to the adjacent corner tab by a welding head (320) and the shuttle plate (334) is withdrawn. Towards the end of its movement a clamp (356) on the shuttle plate draws the valve sheet taut so that it can be cut by a hot wire carried on a pivoting arm (314). A silicon-rubber covered platen 80 (Fig. 2) is then inserted, by a slightly downwardly inclined movement over one end tab and under the other, so that, at station IV (Fig. 3) folding members (186) (Fig. 30, not shown) may fold the side flaps over the platen. The folding members consist of rollers, free for rotation in one direction only, and mounted so that they are pushed upwardly through apertures in the clamp jaws 182, 184 (Fig. 7) to slide inwardly over the top surface. Air-driven wiper arms and air jets ensure that one flap is folded before the other. The resulting closure is then welded. An anti-sift sheet may be inserted instead of the valve sheet. Delivering completed bags.-An air jet on the platen 80 (Fig. 2) enclosed in the top closure helps to free the bag from the platen so that it can be delivered by suction cups (802) (Fig. 41, not shown) to a delivery conveyer. Welding heads.-Each welding head for the bag-bottoms includes raised portions (420), (404) &c. (Fig. 40, not shown) producing the required pattern (Fig. 33, not shown) on the end closure. The head is electrically heated and moves through a slot in one of two clamping members (602) (Fig. 34, not shown) which may be watercooled. An air jet subsequently cools the weld. Adjusting screws (626) (Fig. 34, not shown) determine the depth of penetration of the welding head. The welds at the top of the bag are made by similar apparatus. Feeding bag tubing.-Bag lengths are drawn down by clamp 710 (Fig. 7) formed with jaws 704, 708 which grip the closed bottom end of the tubing. The stroke of the clamp 700 is controlled by a photo-cell 32 (Fig. 1) sensing marks on the film. The clamp 700 makes a further slight downward movement after the holding clamps 182, 184 have closed in order to stretch the film slightly. The tubing is drawn from a roll 12 (Fig. 1) under a roller 44 which provides a bight to permit the rotation of the end of the tubing (see General arrangement above). During those parts of the cycle where tension on the web is not necessary, an air cylinder 48 withdraws the roll 44 to avoid stretching the film. Film is withdrawn from the roller 12 by a cylinder 26 acting on a dancing roller 22 while a clamp 24, 28 is applied to the tubing. Edgesensing nozzles 18, 40 adjust the axial position of the roll 12 and of snubbing rollers 36, 38 to centre the film.