GB1273268A - Strapping apparatus - Google Patents

Abstract

1,273,268. Strapping apparatus. SIGNODE CORP. 29 July, 1969 [30 July, 1968], No. 38002/69. Heading B8C. In an apparatus for strapping a package P the free end of a strap is held between a first gripper 2 and an anvil 1 whilst a carrier C, in slip-feeding engagement with the strap, is driven by a chain 3 in a closed path around the package P to form a loop having regions which overlap between a sealer 9 and the anvil 1, the sealer 9 then being moved towards the anvil to seal the strap regions together and the loop being severed from the strap. A second gripper 2 on the other side of the anvil 1 then grips the new free end of the strap and the chain drive is reversed to form a second loop about the package P. Strap sealing.-A hammer 9a is mounted on a carriage 15 pivoted about a shaft 13, the force exerted by the hammer 9a on the overlapping strap regions being determined by a coil spring 14 acting between the carriage 15 and a control arm 12 pivoted to the shaft 13. The arm 12 engages a barrel cam 6 mounted on a rotatable cam shaft 4, rotation of which thus causes the hammer 9a to be urged against the strap. The hammer 9a is mounted on a torsion bar 22 secured to the carriage at 23 and from which depends a trigger 16 which engages a tooth 5a or 5b of a cocking cam 5, depending on the direction of rotation of the cam-shaft 4. As shown (Fig. 11) tooth 5b engages the trigger 16 causing the torsion bar 22 to be hoisted, thus on release of the trigger 16 the torsion bar 22, and hence hammer 9a oscillate. Teeth on the hammer 9 engage the strap and the heat generated by the friction therebetween melts the strap (which is of plastics material) and the pressure exerted on the strap by the hammer 9 causes the strapregions to fuse together. Strap positioning for severing.-Pivoting of the carriage 15 to urge the hammer 9 against the strap causes a pawl 25 on the carriage 15 to engage a catch 26 on the anvil 1 such that when the carriage 15 is pivoted away from the anvil 1, the anvil 1 is moved, against the action of a spring 28, out of the path of the strap to allow the strap to move against the package P. The pawl 25 then releases the anvil 1, which returns to its prior position. The pivoting movement of the carriage 15 also causes further carriages 19, which bear rollers 18 nested in slots 15S in the carriage 15, to move such that fingers 20 thereon project into the strap-path. Thus on drive reversal one finger 20 ensures that the anvil, when released, returns between fused strap portions and the remainder of the strap (Fig. 1 la, not shown). Strap gripping and severing.-The grippers 2 and a strap cutter 40 are mounted on a carriage 38 urged into the strap path by a spring 39. The cam shaft 4 bears a cam arm 34 which acts on a pivoted arm 35 to move the carriage 38 away from the strap path. This movement causes the grippers 2 to pivot away from the anvil 1, which anvil 1 as it returns causes the finger 20 to release the strap which then engages the anvil 1. Return of the carriage 38 causes the grippers 2 to pivot back to the anvil 1 and the cutter 40 to sever the fused loop from the strap. Strap tensioning and chain drive.-The chain 3 is double stranded, one strand 3a being trained over sprockets S 1 -S 8 and the other strand 3b carrying the carrier C. The strap is fed to the carrier C from a supply roll (not shown) via rollers R 1 -R 3 which control the back tension on the strap. From roller R 3 the strap is fed through a carrier C<SP>1</SP> and a carrier C<SP>11</SP>, these carriers being carried by a further chain 3<SP>1</SP> and being in slip feeding engagement with the strap. The chain 3<SP>1</SP> oscillates with the carriers C<SP>1</SP>, C<SP>11</SP> always being in the chain reaches shown such that these carriers serve to take up slack induced at certain phases in the strapping operation and pay the slack out at a subsequent phase.