Patent GB-862471-A (GB)
Title: Power strapping machine
IPC: B65B13/22
Filed: 1957-02-05
Abstract: 862,471. Bundling-machines. SIGNODE STEEL STRAPPING CO. Feb. 5, 1957 [Nov. 13, 1956], No. 3943/57. Class 94(1). [Also in Group XXIV] In a machine for binding bundles with metal strip, the strip S, Fig. 1, is drawn from a supply reel by mechanism 24, driven through worm and wheel gearing by a reversible electric motor 12, and fed through a guide track 34 around the bundle so that its leading end S<SP>1</SP> overlaps the standing portion S<SP>11</SP> extending from the feed mechanism. The motor is then reversed automatically to withdraw the strip from the guide track so as to shrink the loop into engagement with the bundle and at the same time to cause preliminary operation of joint-forming mechanism whereby the end S<SP>1</SP> is clamped and the flanges of a seal blank are folded about the end S<SP>1</SP> and portion S<SP>11</SP>. This preforming of the seal is not sufficient, however, to prevent movement of the portion S<SP>11</SP> relative to the end S<SP>1</SP> during the tensioning of the loop which continues until a predetermined tension is applied. The maximum tension is determined by the spring- loading of an overload-release clutch in the drive to the mechanism 24, and the release of this clutch against the action of the spring operates mechanism which re-engages a clutch in the drive to the joint-forming mechanism whereby the seal and overlapped portions of the loop are deformed into a tension-resisting joint and the loop is severed from the supply. The mechanism 24 comprises knurled rollers 144 and 148 which draw the strip S through curved guides 116, 118, Fig. 3, and cause it to pass through curved guides 132, 134, further guides 154, 156, 158 and a retractable guide 160 to the guide track 34. The curved guides are mounted between plates which are pivoted on a shaft 100 and also support the bearings of the roller 148, the pivoted assembly being urged in a clockwise direction by a spring 150 so that the roller 148 is pressed against the roller 144. The main drive shaft 18, Fig. 4, is coupled to the shaft 146 of the roller 144 by worm and wheel gearing 236, 240 and an overload-release, dog clutch 248 with inclined teeth, the driving and driven members of which are urged into engagement by a spring 276 whose compression is adjustable by a screw 284 operable by a knob 296 on the exterior of the machine casing. The reversal of the motor to effect withdrawal and tensioning of the strip is controlled by a switch 184, Fig. 1, operated by a pivoted portion 176 of the track 34 which is depressed by the loop against the action of a spring 182 when the end S<SP>1</SP> of the strip is arrested by the guide 160. The arrangement of the guides 132, 134 is such that the tensioning of the strip applies a force to the guide 132 to cause clockwise movement of the guide assembly about the shaft 100 so that the pressure between the rollers 144 and 148 is increased. The joint-forming and cutting mechanism 28, Fig. 3, is similar to that described in Specification 775,926 and is driven from the shaft 18 by worm and wheel gearing 440, 444, a one-way clutch comprising a helical spring 448, and a crank 418 having a pin 76 engaging a cross head 396 operating a push-rod 390. The spring 448 encircles a drum 426 secured to the crank 418 and a drum 446 secured to the wheel 440 and is formed at its upper end with a finger 450, Fig. 5, which is inserted in one of a series of holes 452 in the crank. At its lower end, the spring has an outwardly projecting end 454, Fig. 8, arranged to engage the ends 512, 514 of arms 496 and 498 on a control member 456 which is journalled on a slidable shaft 480 connected to a member 280 forming an abutment for the inner end of the spring 276 of the clutch 248. The member 456 is acted on by a torsion spring 560 so that the arms 496, 498 normally ride on a flange 502 on the drum 446. The starting position of the mechanism 28 is determined by a pivoted arm 458, Fig. 5, having a lug 462 which engages a notch 464 in the crank 418 to prevent clockwise movement thereof. The arm 458 is engaged by a plunger 466 loaded by a spring 474 and arranged to operate a switch 472 which controls the motor 12 in conjunction with the switch 104. During the feeding of the strip, the wheel 440 and drum 446 are rotated in a clockwise direction and the friction between the drum and spring 448 is insufficient to rotate the crank 418. When, however, the motor is reversed by the operation of the switch 184, the spring tightens on the drum and the crank is rotated anti-clockwise to operate the mechanism 28 so that a seal blank is delivered from a magazine and preformed about the overlapped portions of the loop as described above. The arm 458 is rocked against the action of the spring 474 causing the plunger 466 to operate the switch 472 so that the motor 12 remains energised after the switch 184 has been reopened by the return of the track portion 176 as the loop is withdrawn. The crank is rotated until the grip of the spring 448 on the drum 446 is loosened by the engagement of its end 454 with the end 512 of the arm 496 and then remains stationary until the torque on the clutch 248 is such as to compress the spring 276 sufficiently to allow its teeth to disengage. The resultant movement of the shaft 480 to the left, Fig. 8, moves the end 512 clear of the spring end 454 and the crank is then rotated a further amount to cause the mechanism 28 to deform the seal and overlapped portions of the loop and sever the loop from the supply. This rotation terminates when the spring end 456 engages the end 514 of the arm 498, and in this position the notch 464 is aligned with the lug 462 so that the arm 458 returns to its initial position and the switch 472 is operated to de-energize the motor 12.