GB878839A - Hydraulic tensioning control for power strapping machines - Google Patents

Abstract

878,839. Bundling machines. SIGNODE STEEL STRAPPING CO. April 7, 1959 [April 9, 1958], No. 11696/59. Class 94(1). [Also in Group XXIV] In a bundling machine of the kind in which a steel strip is passed round the bundle and is overlapped tensioned and sealed, means for accurately regulating the applied tension comprises a lost motion arrangement in the feed rolls drive whereby a worm gear slidable on a power driven shaft, which gear drives one of the feed rolls, is capable of moving axially against adjustable resistance when the tension reaches a certain value and thus reducing the driving effect on the rolls. The invention is described 'as incorproated in the machine forming the subject of Specification 862,471 and is the same in all respects except that of tension control. The seals used may be as described in Specification 749,926. The drive to the feed rolls is supported by a motor Fig. 1, (not shown), through a shaft 18. Fixed on the shaft 18 is a worm 194 for operating the sealing mechanism, as in the above mentioned machine, and a worm 78 which drives the feed roll shaft 44 and is axially slideable on splines 106 on a collar 108 fixed to the shaft 18. The worm 78 has a cylindrical bore 100 in which an extension 98 of the shaft 18 operates as a piston. A sealing ring 102 forms with the piston and bore an annular chamber 122, inlet to and exit from which of hydraulic fluid contained in a sump 80, is via radial apertures 124, bore 126, valve means 132, 148 and a passage 128 in the shaft extension. The valve 132 seats in the bore at 134 and permits exit from the chamber against the pressure of a spring 140. The valve 148 seats in the valve 132 and permits inlet against a light spring 158. The compression of the spring 140 is adjustable by a wheel 172 to vary the strap tension. Operation. After the strap has been fed round the bundle and overlapped, the motor is reversed so that shaft 44 is driven, clockwise as shown, to take up slack in the strap and tension it. The chamber 122 is at full capacity with the valve 132 closing-its exit. When the tension approaches the desired value, pressure rises in the chamber due to increased thrust between the worm 78 and worm'wheel 74 so that the valve 132 lifts. The worm 78 may thus move, to the left as shown, as liquid is forced from the chamber, with the result that the driving effect is reduced. Movement of the worm slides a yoke 242 on a shaft 222 permitting a shipper Figs. 2, 3, (not shown), on bearings 224 to release a spring clutch as in the earlier machine to drive the sealing mechanism. After sealing, operation of the motor reversing switch permits the worm 78 to return, the valve 148 opening to admit fluid to the chamber. When the worm is back to its original position, it again drives the shaft 44 to feed strapping round the next bundle. Specification 775,926 also is referred to.