GB557951A - Improvements relating to machines for perforating metal strips - Google Patents

Abstract

557,951. Punching. SHAW, J. Oct. 26, 1942, No. 15017. [Classes 83 (ii) and 83 (iv)] A machine for punching metal strips, such as stringers for the edges of aircraft sections, has means for passing one or more strips together with a perforated pattern bar over resiliently supported locating plungers mounted in fixed relation to the punches. The stringers 10 are passed through the machine over a series of guide rollers arranged before and after the actual punching station that incorporates similar rollers 19, 20, supporting the stops at 25 and guiding their lateral flanges at 26. Two stringers 10, Fig. 6, are secured in recesses in a crossbar 11 by wing nuts 16 on bolts with heads 15 fitting the stringers. A central slot in the crossbar receives the pattern bar 2 secured by a setscrew 12 and by dowels. The holes in the flanges 9a usually differ from those in the flanges 9b and the bar 2 has corresponding sets of holes 8a, 8b. A hand lever 35 pivoted at 36 slides a cam bar 37, Fig. 4, that engages the heads 38a, 38b of locating plungers, rendered resilient by springs 28, to cam the plunger not required out of action according to the flanges being punched. A corresponding grid of cam bars 41a, 41b, 42a, 42b, acting as gags for the punches 32a, 32b, 33a, 33b and cam bars 40a, 40b acting as gags for locating punches 30a, 30b is slid by direct hand pressure to immobilize the punches corresponding to the inactive locating plunger. The punches are guided by holes in a crossbar 29 secured to the bolster and sleeves 5 on the punch head slide on pillars 6 carried by the bolster. In operation the shank and pattern bar are turned by hand until the engagement of a hole in the pattern bar by the resilient plunger is felt to have effected rough location. On descent of the punch head the locating punch effects precise location immediately prior to the punching. Rubber buffers 49 engage the work prior to punching and act as hold-downs. The cam bars in the grid are separated by spacers 43 and connected by end bars carrying stops that limit the movement. Pins 46, 48 in the bolster carry additional guide rollers 45 adjacent the punches to secure precision on the location of the lines of holes.