GB489050A - Improvements relating to metallic band or wire tying machines - Google Patents

Abstract

489,050. Welding; strapping-machines. SUTTON, J. R. March 20, 1937, No. 8226. [Class 83 (iv)] [Also in Group I] In a machine for tensioning metallic bands or wire ties round packages and securing the ends by welding, and having two or more fixed electrodes co-operating with complementary sequentially-operated movable electrodes for connecting the ends by a number of successive spot welds, such as is described in Specification 458,197, the fixed electrodes are isolated from the electric circuit when they are inoperative so as to avoid short circuits and thus waste of current when a weld is being effected by another pair of electrodes. The band 3 may be held at one end by a pivoted spring-released grip 4 and tensioned by a ratchet-operated knurled wheel 5 mounted on an adjustable eccentric 8. A hand-operated shaft 23 carries a cam 25 for operating a shear blade 14 for cutting the upper end of the band to length, cams 26, 28 engaging in apertures in fibre slides 20 for operating movable electrodes 16 sequentially, and a cam 27 for operating a metal cage 22 provided with a fibre base pad 31 for resiliently holding the parts during welding. The cams 26, 28 engage spring-leaf bridges 29 in the slides to give resilient pressure and the cam 27 operates through a resiliently mounted base 30. The electrodes 16 are connected to the terminal 33 of the welding circuit through metal facing sheets 35 on the slides 20 and a flexible bridge connector 36. The fixed electrodes 17 are mounted on spring arms 18 in a base provided with an insulating layer 19. The arms are bent at 40 to form the fixed contacts of switches, the movable contacts 37 of which are connected to the terminal 34 and operated so as to close the switches by cams 39 on the rear edges of the slides, so that the switches are only closed when the slides are depressed. In a modification, the resilient arms carrying the fixed electrodes may be depressed so that the electrodes are retracted through holes in a fibre pad out of contact with the work when their co-operating movable electrodes are raised. In another form, the movable electrodes 16 are carried by the plungers 41 of solenoids 46, the armatures 43 of which are pressed by springs 45 against collars 44 on the plungers and when energized engage the collars 48 on the plungers through springs 47 to force down the electrodes. The plungers are provided with insulation pieces 49 so that current from one terminal of the circuit through contacts 50, 51 to the fixed electrodes is cut off when the electrodes are raised. The current supply to the several solenoids is controlled by a rotary switch. Such switch may also incorporate contacts for controlling the current supply to the electrodes 17.