GB1432704A - Method and apparatus for making deep drawn metal shells - Google Patents

Abstract

1432704 Cupping D C GRIGORENKO 8 June 1973 27464/73 Heading B3Q A deep-drawn metal shell having a bottom wall and a side wall is made by drawing a flat workpiece in one direction to form a cup shaped blank, immediately redrawing it in the opposite direction to turn it inside out and form a shell longer and narrower than the blank and immediately ironing the shell to elongate it and further reduce its wall thickness. As shown, strip 76 is fed vertically downwardly between flanges 75 of a guide 70 and hydraulic fluid is supplied to a pair of rams (26), Fig. 6 (not shown) to allow springs 83 to draw a die plate 39 secured to piston rods 37 to the right, Fig. 8. A die 63 carried by the plate cooperates with a punch 65 to punch a circular workpiece from the strip. Scrap is stripped from the workpiece by the return of the guide 70 which is spring-mounted on a guide plate 68. Further advance of the piston rods 37 causes a drawing die 57, within the die 63, to force the workpiece over the end of a hollow mandrel 60 mounted over a fixed bolster plate 22 to form a cup. As the rams (26) reach the end of their stroke a ram (29), Fig. 6, is energized to advance a punch 54 into engagement with the centre of the cup base to turn the cup inside out and redraw it through the cavity 59 of the mandrel 60. Movement of the punch further to the right carries the blank through ironing dies 98-100. A hemi-spherical head 46 at the rear end of the punch engages in a complementary recess in a guide plate 43 mounted on the piston rod 30 of ram (29) to allow limited floating movement of the punch to ensure its coaxial alignment with the ironing dies. As the punch reaches its fully extended condition, the plate 43 trips a switch (not shown) which reverses the ram (29) and energizes a solenoid (118), Fig. 16, to cause notched portions 112 on stripper blocks 109 to engage the rear edge of the shell as the punch is withdrawn. The apparatus comprises fixed bolster plates (21), 23 through which pass four rods 25, one at each corner. Slidable on the rods between plates (21), 22 are a guide plate (36), the guide plate 43, the die plate 39, a plate 68 which guides the die 65 and work guide 70 and a plate 77 which is fixed to the die plate 39 by rods 79 and urged away from the plate 68 by springs 83. Movement of the plate 77 towards plates 22 and 68 respectively is limited by stops 88 and 87. Between bolster plates 22 and 23 the ironing dies are fixed to rods 25. When the ram (29) is almost fully retracted the plate 43 engages the plate (36) which retracts the piston rods of the rams (26) and thus the plates 39, 68 and 77. The final portion of the movement compresses the springs 83 in readiness for the next operating cycle. The work guide 70, punch 63 and die 65 may be replaced by a holding mechanism for pre-cut circular blanks.