GB1248092A - Improvements in or relating to presses - Google Patents

Abstract

1,248,092. Punching; shearing; forging; stamping. HYDREL A.G. 1 May, 1969 [2 May, 1968], No. 22173/69. Headings B3H, B3Q and B3W. A press, e.g. for shearing or punching, comprises a fixed press member (not shown) on which a tool holder 3 is mounted, a movable press member 14 on which a tool holder 2 is resiliently mounted, a first limit switch 27 which is operated when the press member 14 is a predetermined distance from the fixed press member, a second limit switch 22 which is operated during movement of the tool holder 2 against its resilient bias and control -means (not shown) controlling the movement of the press member 14 and responsive to the sequence of operation of the first and second limit switches, the arrangement being such that, if through the presence of a foreign body 7 or a too-thick blank 6 'between the tools 4, 5, the first limit switch operates before the second the control means stops further movement of-the press member 14 towards the fixed member. The tool holder 2 is fixed to a cylindrical sleeve 17 Which forms with the piston part 14a which it surrounds a chamber 18 to which -compressed air is supplied through a line 20. Two or four sleeves 10 each movable in a sleeve 81 in the holder 2-and having a head 12 are screwed into the piston part 14a. Compressed air is fed to the chamber 18 to raise the sleeve 17 and thus the tool holder 2, tool 4 and blank 6 from its position relative to the piston 14, shown at the right-hand side of the Figure, to a position in which the heads 12 are contacted by the base of their respective recesses 11 and the tool holder 2 is raised above the piston by the distance a. In normal operation as the piston 14 is raised the tool holder 2 moves upwards, floating on the compressed air cushion until the blank 6 begins to press against the upper tool 5, when the limit switch 27, vertically adjustable on the press frame, is closed by means of a projection 30 on the piston part 14a. The holder is then forced back against the resistance of the air cushion into its lowest position relative to the piston, shown at the left of the Figure, which closes the second limit switch 22, a trip pin 24 engaging a cam surface 26 on the piston part 14a. 'If an object 7 or a too-thick blank 6 is between the tools, the tool holder 2 will be moved against its air-cushion mounting to close switch 22 before the piston movement has closed switch 27 which immediately stops the piston 14. The piston control means may be hydraulic in which case it includes an electrically-operated valve electrically connected to the limit switches. In a fine-blanking or punching press a piston presses a'toothed ring against the blank prior to blanking or punching. The air-cushion may be replaced by springs, the drive may be electromechanical and the upper press member may be the movable one. The stop mechanism can be incorporated in a swaging, forging, coining or stamping press.