Press brake for bending sheets

Abstract

The present invention relates to a press brake for bending metal sheets wherein: at least one stopper is disposed in each slot, each stopper comprising a first wedge having a first end secured to the first slot edge and a second end forming a first surface, and a second wedge having a first end secured to the second slot edge and a second end forming a first surface; and the first surface of at least one of the first and second wedges has a central portion that is domed or protuberant relative to the other portions of said surface so that the contact between the first and the second wedges is established essentially over said central portion.

1 . A press brake for bending at least one metal sheet, said press brake comprising:
 an upper table having a bottom edge carrying first bending tools, and a lower table having a top edge carrying second bending tools, the two tables being movable relative to each other to exert a bending force on the sheet;   said press brake presenting a vertical midplane, one of said tables having, through the entire thickness thereof, two slots disposed symmetrically about the midplane, each slot having a first edge and a second edge, and an open first end opening out in a side edge of the table, as well as a closed end;   at least one stopper being disposed in each slot, each stopper comprising a first wedge having a first end secured to the first slot edge and a second end forming a first surface, and a second wedge having a first end secured to the second slot edge and a second end forming a first surface; and   the first surface of at least one of the first and second wedges having a central portion that is protuberant relative to the other portions of said surface so that the contact between the first and the second wedges is established essentially over said central portion.   
     
     
         2 . A press brake according to  claim 1 , wherein said central portion of at least one of the first and second wedges is domed. 
     
     
         3 . A brake press according to  claim 1 , wherein the first surface of the first wedge and the first surface of the second wedge both have respective central portions that are protuberant relative to the other portions of said first surfaces. 
     
     
         4 . A press brake according to  claim 3 , wherein said respective central portions are domed. 
     
     
         5 . A press brake according to  claim 1 , wherein the first surface of the first wedge and/or the first surface of the second wedge is a convex surface. 
     
     
         6 . A press brake according to  claim 1 , wherein the first surface of one of the wedges presents a concave surface while the first surface of the other wedge presents a convex surface. 
     
     
         7 . A press brake according to  claim 1 , wherein the first surface of at least the first wedge and/or of the second wedge is a spherical surface portion. 
     
     
         8 . A press brake according to  claim 1 , wherein, at least in the zone of the stoppers, the slots present constant height so that the first edge and the second edge are parallel, in the absence of bending force for bending the metal sheet. 
     
     
         9 . A press brake according to  claim 8 , wherein the first surfaces of the wedges are inclined relative to the parallel edges of the slots. 
     
     
         10 . A press brake according to  claim 9 , wherein the first surfaces of the wedges are inclined at a slope lying in the range 1% to 40%, relative to an axis that is parallel to the edges of the slots. 
     
     
         11 . A press brake according to  claim 10 , wherein said slope lies in the range 5% to 10% relative to the axis that is parallel to the edges of the slots. 
     
     
         12 . A press brake according to  claim 1 , wherein the first surface of at least one of the first wedge and the second wedge presents a plurality of inclined plane peripheral portions connecting to the central portion. 
     
     
         13 . A press brake according to  claim 1 , wherein the central portion presents a protruding height lying in the range 0.05 mm to 0.25 mm relative to the other portions of the first surface for a wedge of length substantially equal to 80 mm. 
     
     
         14 . A press brake according to  claim 1 , wherein the wedges are mounted on supports connected to respective ones of the edges of the slots. 
     
     
         15 . A press brake according to  claim 14 , wherein at least one of the supports is movable laterally, i.e. along an axis parallel to the parallel edges of the slot on which said movable support is mounted. 
     
     
         16 . A press brake according to  claim 1 , wherein the two wedges are offset relative to each other laterally, i.e. along an axis parallel to the parallel edges of the slot. 
     
     
         17 . A press brake according to  claim 1 , wherein, in the absence of bending force for bending the metal sheet, the first and second wedges present clearance between them. 
     
     
         18 . A press brake according to  claim 1 , having a plurality of stoppers disposed in respective ones of the slots symmetrically about the midplane.