Patent GB-1491143-A (GB)
Title: Hydraulic servo valve controlled cupping press
IPC: B21D24/00
Filed: 1975-01-20
Abstract: 1491143 Cutting-out and shaping MTS SYSTEMS CORP 20 Jan 1975 [21 Jan 1974] 2375/75 Heading B3Q [Also in Division G3] In a drawing die press assembly, Fig. 1 (for the seamless drawing of metal cups as a first stage in production of seamless drawn cans) the drawing motion of the punch 98 is sensed by transducer 91 to provide a feedback signal in a servo system controlling punch movement, an hydraulic assembly, Fig. 3, or Figs. 4, 10 (not shown) containing a piston to move the punch, and an actuator for a blank cutter whose movement precedes that of the punch. Pressing operation: Figs. 1, 3.-The hydraulic arrangement shown in Fig. 3 is provided at each of a plurality (eight) of positions on the assembly, being controlled conjointly such that cutting edge 72 and hold-down pad 105A engage the material, further motion of the cutting edge 72 severing a blank 98A whence the punch 98 is advanced to press the cup, the material being held by the pad 105A until most of the pressing is complete, thus controlling the material drawing, the last part of the pressing taking place with the pad 105A; retracted by ledge 113 when the cutting edge is retracted; disengaged from the material. The timings and motion rates of the cutting/holding, and pressing operations are displayed in Figs. 8, 9 respectively (not shown). Facility may be provided, Figs. 4, 10 (not shown), for fluid cooling of the punch, and an air blast is provided to remove the formed cup from the punch. A motion transducer (not shown) is additionally provided for the cutting edge motion. Arrangement 101, 106 enables the hold down pad to tilt, in the event of uneven material, without causing bending. The plurality of dies are coupled by fluid manifolds, a telescoping arrangement, Fig. 6 (not shown), enabling centre-to-centre spacing of the dies to be adjusted for changing dies or to optimize material use. The upper and lower supports 12, 14, Fig. 1 are designed to deflect symmetrically under the pressing stress, to keep the punch and die substantially aligned. The upper support 14 may be lifted by hydraulic means 16 for die changing, a round headed member (30A, 35), Fig. 2 (not shown), engaging a sleeve (31) to ensure accurate support positioning. Should two or more thicknesses of material be trapped under the pad 105A the pressing will not take place. Control system: Fig. 7.-The cutting edge and hold-down pad of each die is controlled by a servo valve controller 203 controlled from computer 200, waveform generator 204 having means 206, 206A to set the up and down rates, set point and span being set at 207, 205. A feedback signal is combined with the resultant signal at summing point 205A to provide a control signal to amplifier 213 gain being adjusted at 212. The punch for each die is controlled by a similar controller 230 a single waveform generator 233 being used for all punches and having adjustment facility for up, and down rates. Coupling between the controllers, having upper and lower limit switches for the cutting edge, and draw punch ensures that drawing does not take place until a cut has been made, that the cutting edge/hold down pad are retracted for the latter part of the punching cycle and that a cycle of operations can only be initiated with the punch at its upper position. A servo fault detector 210 and indicator lamp 211 are provided.