Patent GB-1514535-A (GB)
Title: Method and apparatus for automatically strapping package
IPC: B65B13/32
Filed: 1975-07-16
Abstract: 1514535 Seaming non-metallic sheet material M TAKAMI 16 July 1975 [18 July 1974 28 Dec 1974 13 March 1975] 29896/75 Heading B5K Overlapping portions of a thermoplastic strap B looped around a package are welded by electrically heating a metal plate heater 25 to substantially 500 to 700 C.; discontinuing the passage of electric current through the heater 25; inserting the heater, when it has cooled to substantially 400 to 500 C., between the overlapping strap portions to melt these portions; pressing the strap portions against the heater 25; and withdrawing the heater 25 whilst continuing to press the strap portions together. The cooling of the heater 25, before insertion, results in an even temperature over the surface thereof. The package strapping machine comprises a case 11, Fig. 1, on which the package to be strapped is located, a strap guide channel 12 formed with an internal dovetail groove 41 containing strap guiding rollers 42, strap forwarding rollers 15 rotatable by a motor 45, strap tension-adjusting rollers 16, a strap supply reel 13 drivable by a motor 14 to tension the strap B about a package, and a motor 43 for rotating a cam shaft 36, Fig. 3, having cams 37, 40, Figs. 2 and 3, thereon. A table 17 is positionable at a level slightly higher than the openings of the channel 12 but lower than the upper wall of the case 11 so as to make no contact with a package thereon. Below the table 17 are mounted a vertically movable clamp 18; a table 20 rockable in the longitudinal direction of the strap B about a pivot 19; a strap cutting heater 21 fitted by a screw 32 to the table 20 and movable up and down therealong; a vertically movable pressing device 22 and a vertically movable clamp 23. A spring 27 urges the table 20 to its upright position. The strap fusing heater 25 is mounted on a table 39, Fig. 3, and, through a link 38, is reciprocable by the cam 37. The cams 40 reciprocate the clamps 18, 23, the heater 21 and the device 22. The heaters 21, 25 comprise electrically heated metal plates and together with a bimetallic strip (46), Figs. 5 and 6 (both not shown), are mounted in the secondary circuit of a transformer (44). In operation, a package is placed on the case 11 and an actuating switch (not shown) is depressed. The rollers 15 are driven to feed the leading end of the strap B through an aperture 26 in the clamp 18 and a groove 30 in the plate 20 and into the groove 41. After leaving the channel 12, the strap end is fed to overlap the strap beneath the table 17. The motor 43 starts to rotate the shaft 36 so that the clamp 18 is raised to clamp the leading end of the strap against the table 17. Simultaneously, the heaters 21, 25 are energized by a cam (48), Fig. 4 (not shown), on the shaft (36) closing a switch. The motor 43 is then interrupted and the motor 14 is actuated to rotate the reel 13 to tension the strap B about the package until it reaches a pre-determined tension at which the motor 14 is stopped and the motor 43 re-started. When the heaters 21, 25 have reached a pre-determined temperature, the bimetallic strip (46) closes a switch to turn off power for the heaters 21, 25. The clamp 23 is raised, the clamp 18 is lowered and the heater 21 is raised to cut the strap at the underside of the overlapping portions. Then the heater 25, at the required temperature, moves in between the overlapping strap portions and is followed by the raising of the device 22 to applying pressure to the overlapping portions with the heater 25 sandwiched therebetween. After less than one second, the heater 25 is withdrawn and pressing by the device 22 continues until the overlapping portions have welded together. The device 22 and the clamp 23 descend and the table 17 moves laterally from between the case 11 and the package. In modifications, instead of the bimetallic strip being provided to switch off the heaters 21, 25 when the required temperature is reached, either a timer switch, Fig. 7 (not shown), or a camcontrolled switch, Fig. 8 (not shown), is provided in the primary circuit of the transformer (44). In a further modification, Fig. 10 (not shown), two bimetallic strips (46), (63) are provided, the strip (63) being deformable equivalently to the strip (46) to compensate for changes in atmospheric temperature.