GB750046A - Improvements in metal working presses - Google Patents

Abstract

750,046. Metal-working presses. U.S. INDUSTRIES, Inc. March 8, 1954, No: 6658/54. Class 83 (4). A mechanical metal working press having a crown and bed connected by tie-rods and a reciprocating slide, has an over-load device comprising a movable member 26, Fig. 4, loaded on one side by hydraulic pressure and on the other side by air pressure and means 30, 31 acting on the hydraulic fluid in response to an overload on the press for moving the member 26 against the air pressure and thus relieving the overload. Each tie rod 10 of the press has screwed to its bottom end a member 31 carrying a cylinder 30 slidable over a piston 34 abutting against the press bed 1. The annular space 35 in the cylinder is connected through ducts 36, 37 and a flexible pipe 38 with a hydraulic cylinder 25 containing a plunger 28 carrying an air piston 26 operating in an air cylinder 24. Hydraulic fluid in a reservoir 12, Fig 5, pressurized by air admitted through pipes 16, 17, is supplied through pipe 41 and check valve 40 to the hydraulic cylinder 25 and hence fills the cylinder space 35. The air pressure also acts through a pipe 18, having a regulating valve 20, on the top of air piston 26, causing plunger 28 to pressurize the hydraulic fluid. When an overload occurs on the tie-rods, the cylinder space 35 is reduced and this causes the plunger 28 and piston 26 to be raised against the air pressure. An extension 42 of the plunger extends out of the air cylinder and in the case of an excessive overload trips a limit switch 43, Fig. 6 (not shown) which causes disengagement of the clutch driving the crankshaft or eccentric shaft of the press. Loss of hydraulic fluid in the hydraulic system causes the plunger 28 to be lowered and this permits the extension 42 to actuate further limit switches controlling a valve 15, Fig. 5, which admits pressure air below the piston 26, causing it to be raised and thus permits further liquid to enter the hydraulic system through pipe 41. The cylinder 30 and piston 34 may alternatively be provided at the upper end of each tie-rod. The press may carry dies for drawing sheet-metal.