Patent GB-782625-A (GB)
Title: Double action sheet metal drawing press
IPC: B21D24/12
Filed: 1955-12-29
Abstract: 782,625. Cupping. BLISS CO., E. W. Dec. 29, 1955 [Jan. 4, 1955], No. 37224/55. Class 83 (4). In a double-action sheet-metal drawing press having a blankholder and a draw slide the press driving mechanism comprises a pair of horizontal shafts parallel and symmetrically spaced apart with respect to the press front to rear centre line, means to oppositely rotate said shafts including a pair of gears secured to each of said pairs of shafts and spaced apart, an eccentric secured to the inside face of each of said gears, said eccentrics being symmetrically arranged about the press left to right centre line, and toggle means journalled in the crown of said press including a pair of rockshafts parallel to said pair of shafts and spaced thereabove in a common horizontal plane, a rocking beam on the far side of each rockshaft, link means pivotally connecting adjacent rocking beams and rockshafts, strap means drivingly connecting said rocking beams to said eccentrics, and operating link means connecting said rockshafts to said blank holder. The double-action press comprises a base 12 and a crown 22 supported by side members 18 and 20. The draw slide 26 is slidably mounted within the blank holder slide 28 above the bolster 30 of the press and both are driven from a common main drive shaft 34 having a flywheel 36, and clutch and brake unit 38 belt driven from a motor 42. The main drive shaft is geared to a pair of drive shafts 44 and 46. Pairs of eccentric drive gears 104 and 106 and 108 and 110 are secured to the drive shafts 44 and 46 respectively and a pair of idler pinions 112 and 114 are mounted on a shaft 116 and engage with pinions 100 and 102 on an intermediate shaft 98. The eccentric drive gears 108 and 110 engage with pinions 100 and 102 and the drive gears 104 and 106 with idler pinions 112 and! 114. The draw slide 26 is directly driven from a pair of eccentric discs 48 and 50 secured to the drive shafts 44 and 46 by means of eccentric straps 52 and 54 which form links 56 secured to the draw slide. The draw slide adjusting means comprises screws 62 driven from motors 68. The draw slide and blank holder are counterbalanced by pneumatic surge tank cylinders 74 and 76. In order to provide a dwell in the stroke of the blankholder, toggle link means are connected to pairs of eccentric discs 78, 80 and 82, 84 which are secured to drive shafts 44 and 46 respectively (Fig. 7). The eccentric discs 78, 80 and 82, 84 are encircled with straps 117 which form links 118 for pivotal engagement with pairs of rocking beams 120 and 122 (Fig. 2) attached to another set of rocking beams 138 and 140 by links 136. Links 86 connect the rocking beams 138 and 140 to the crossheads 88 which are adjustably attached to the blankholder 28. In operation, the draw slide is reciprocated with simple harmonic motion by eccentric discs 48 and 50 whereas the blankholder by means of its eccentric and toggle link drive means, will reciprocate downwardly, after which a dwell period ensues for approximately one quarter of the cycle to hold the blank while the draw slide is passing through the working portion of its stroke. Thereinafter the blankholder will withdraw together with the draw slide to stroke top dead centre while the work is being removed from the press.