GB1143442A - A device for tensioning a thermoplastic strap about an article and fusing together the ends of the strap - Google Patents

Abstract

1,143,442. Seaming non-metallic sheet material. M. TAKAMI. 22 Sept., 1966 [22 Sept., 1965 (2)], No. 42401/66. Heading B5K. [Also in Division F2] A device for tensioning a thermoplastic strap B, e.g. of polypropylene about an article and heat sealing the ends b, c thereof comprises a blade shaped cutting heater 19 to support the lower surface of the end c, a body 7 urged downwardly by a spring 12 to press the end c into contact with the heater 19, a handle 6 to raise and lower the body 7, and a fusing heater 18 which, simultaneously with the descent of the body 7, passes between the ends b, c and retreats after melting the facing surfaces of the ends b, c. The device comprises an eccentrically mounted feed roll 2 which can be lifted by rotation of a handle 3 anticlockwise of Fig. 1 and which has a ratchet wheel 4, Fig. 2, thereon so that the roll 2 can be stepwise rotated anticlockwise by reciprocation of a handle 5. The body 7 is movable along a guide 8 by the handle 6 which is pivotable about a pin 9. A pin 10 of the boss of the handle 6 engages a recess 11 in the body 7 urged downwardly by a spring 12. The handle 6 is constantly urged clockwise of Fig. 1, by a spring (16), Fig. 4 (not shown), but is normally held vertical by a pin 14 urged by a spring 15 into a notch 13 in the periphery of the boss of the handle 6. In use, with the roll 2 in an elevated position, the strap B is passed around the article (not shown) and the end b thereof is passed under a sliding plate 17 and under the body 7 and is secured to the base 1 of the device by a hook (not shown). The end c of the strap B is passed between the base 1 and the roll 2 and passes over the heater 19 out of the device to the right of Fig. 1. The handle 3 is rotated clockwise, i.e. returned to the position of Fig. 1, to lower the roll 2. Reciprocation of the handle 5 tensions the strap about the article. After tensioning, the handle 6 is tilted slightly clockwise so that the pin 14 is released and the pin 10 is lowered and thus the body 7 is lowered. A blade a on the body 7 contacts the end c which contacts the heater 18. Also, as the handle 6 is tilted, a reciprocator 27 pivoted at 26 to the boss of the handle 6 moves a pin 25, provided in a hollow 30 in a support 24 secured to the plate 17, to the left of Fig. 1, to slide the support 24 and the plate 17 slightly to the left so that the support 24 ceases to contact a switch 20 to cause current to be supplied to the heaters 18, 19. The end C is melted and cut across from below by the heater 19 since the end c is pressed into contact therewith by the body 7. Simultaneously with cutting, the spring 12 forces the body 7 further down and the pin 10 rotates clockwise and the handle 6 falls violently clockwise to the position of Fig. 2. The reciprocator 27 rotates clockwise to move the pin 25 and thus the support 24 and the plate 17 to the left of Fig. 1, so that the heater 18 fixed to the plate 17 slides in between the ends b, c. The body 7 presses the ends b, c with the heater 18 therebetween against the base 1. This is completed before the handle 6 has reached the position of Fig. 2. When the handle reaches this position, the reciprocator 27 has passed the pin 25 so that the plate 17 is quickly returned to the right of Fig. 2 by a spring 29 and hence the heater 18 is pulled out from between the ends b, c. Simultaneously, the support 24 contacts the switch 20 to switch off current to heaters 18, 19. The body 7, urged by the spring 12, presses the ends b, c against the base 1 to fuse them together. The handle 6 is returned to its original vertical position, Fig. 1, so that the body 7 rises. The handle 3 is moved anticlockwise to lift the roll 2 so that the device can be removed from the package. In a second embodiment, Figs. 5, 6 and 9, the end b of the strap B is positioned on the base 1 from the right hand side of Fig. 5. The roll 2 is lifted by turning the handle 3 anticlockwise of Fig. 5 and the end c is passed under the roll 2 over the end b and below the body 7. The end b is fixed by a hook (not shown) and the end c is pressed against the base 1 by returning the handle 3 to lower the roll 2. Reciprocation of the handle 5 intermittently rotates the roll, through the ratchet wheel 4, to tension the strap B about the article. Normally, a pin (50), Fig. 7 (not shown), engages a detent (49) when the handle 6 is turned towards the handle 3. A toothed rack 40 is located at the right hand side of Fig. 6, and compresses a spring 42. A gear 34, meshing with a gear 33 on the shaft 9 of the handle 6, is held at rest by a pawl 35 on a lever 36 and an operating arm 47 of a switch is located in a recess 46 of the boss of the handle 6. The handle 6 is tilted anticlockwise of Fig. 5 and an operator 51 is manually depressed to release the pin (50) from the detent (49) but rotation of the handle 6 by the spring 16 and lowering of the body 7 by the spring 12 are prevented by the end c positioned between the body 7 and the heater 19. Due to the slight tilting of the handle 6 the arm 47 comes out of the hollow 46 and is depressed by a part 45 of the periphery of the boss to turn the switch 48 on to supply current to heaters 19, 56. The heater 19 melts the end c and parts it off and the spring 12 moves the body 7 down rapidly so that the handle 6 turns rapidly anticlockwise of Fig. 6. A projection 61 engages a roller 60, Fig. 9, to move a rod 53 to the left of Fig. 5, so that the heater 56 carried thereby passes below the body 7. The descent of the body 7 is temporarily arrested by a lug 74, Fig. 5. When the handle 6 turns further anticlockwise a presser 77, Fig. 9, contacts a sliding plate 75, Fig. 5, and inserts the lug 74 into a notch (73), Fig. 8 (not shown), in the body 7 so that the body 7 presses the end c against the heater 56 which is thus sandwiched between the ends b, c to melt them. When the handle 6 rotates still further, the projection 61 comes off the roller 60 and a pin 39, Fig. 6, turns the lever 36 by pressing down the upper end thereof to release the gear 34 from the pawl 35. Immediately, the spring 42 rapidly moves the rack 40 to the left of Fig. 6, to simultaneously restore the rod 53 to its original position by pressing a pin 62, Figs. 6 and 9, and removing the heater 56 from between the ends b, c. The melted facing surfaces of the ends b, c are then pressed and sealed together by the body 7. A projection (79), Fig. 7 (not shown), on the gear 33 turns off a microswitch (78) to cut off current to the heaters 19, 56. The heater 56, Fig. 9, comprises a folded strip of a nickel-chrome alloy with an insulating plate 55 sandwiched between the two layers. Notches d are formed along the fold so that the parts e therebetween reach a high temperature. The body (7), Fig. 8 (not shown), is provided on its lower surface with a plurality of holes (70) through which shafts (71) urged downwardly by springs (72) project to contact the end c.