GB778366A - Improvements in or relating to presses - Google Patents

Abstract

778,366. Mechanical presses. BLISS CO., E. W. March 2, 1955 [April 13, 1954], No. 6186/55. Class 87(2). [Also in Group XXII] A press comprises side members 12, 18 having secured thereto a bolster 31, and a platen 22 slidable between the side members and moved towards the bolster by links 68, 74 actuated by cam means 80 which provide a positive dwell in the cycle of movement of the platen. In one embodiment an upstroke press, particularly for holding workpieces together during welding, has a star-shaped platen 22 slidably guided in side frames 10, Fig. 1 (not shown), and operated on its upward working stroke towards a bolster 31 carried by the crown 52 of the press, by a cam mechanism 78, 80 which provides a period of dwell of approximately 120 degrees of cam rotation at the end of the working stroke. The cam discs 78, 80 are spaced apart on a camshaft 76 and on each of their opposed inner surfaces are cam grooves 108, Fig. 3, into which are engaged a follower 114 carried by a reciprocating shuttle beam 82 disposed between the cam discs and having a slot 116 engaging over the camshaft 76. Each end of the shuttle beam 82 is slidable along an adjustable taper block 94, 98 respectively, and has rack teeth 90, 92 respectively in engagement with pinions 56, 58 mounted on rock shafts 44, 46. At the ends of each rock shaft are mounted rock arms 60, 62 connected by links 68, 72 to brackets 38 mounted on the corners of the platen 22. As the cam rotates the shuttle beam 82 is reciprocated thereby causing the pinions to be rotated and thus. to alternately raise and lower the platen whilst maintaining a period of dwell at the end of the upstroke. Air cylinders 32 disposed one at each corner of the platen, have piston rods 42 connected to the brackets 38. The air cylinders are supplied with pressure air from a receiver 158, Fig. 9 (not shown) mounted on the crown of the press, the supply of air being controlled by valves operated in timed sequence with the rotation of the cam mechanism. The cam mechanism is driven by an electric motor 120, Fig. 9 (not shown), which drives through Vee belts a flywheel 126, Fig. 6, mounted on a shaft 128 carrying a pinion 142 in mesh with a gear 144 rigidly, connected to gears 148, 150 in mesh with gear teeth 152, 154 respectively on the cam discs. A combined clutch and brake unit 156 is provided for alternately clutching the flywheel 126 with the shaft 128, and for braking the shaft. An additional brake shoe 157 is used for stopping the flywheel when necessary. In an alternative embodiment a pair of shuttle beams operated by separate cam discs may be used, these shuttle beams driving pinions mounted on the ends of the rock shafts 44 ; the rock arms may then be placed in the centre of the rock shafts. The press may alternatively have its platen moved downwardly towards a bolster disposed on the press base. The driving mechanism for the bolster being then mounted in the base instead of in the crown.