Edge-bending press

Abstract

The present invention relates to an edge-bending press ( 10 ) which comprises an upper platen ( 12 ), a lower platen ( 14 ) and operating actuators ( 16 ). The operating actuators ( 16 ) are designed to cause a relative movement of the upper platen ( 12 ) and lower platen ( 14 ) towards and/or away from each other. The press ( 10 ) also comprises an upper die-holder assembly ( 22 ) which is connected to the upper platen ( 12 ) and a lower die-holder assembly ( 24 ) which is connected to the lower platen ( 14 ). Each die-holder assembly comprises a right-hand die-holder ( 222, 242 ) and a left-hand die-holder ( 224, 241 ); thus there is an upper right-hand die-holder ( 222 ), an upper left-hand die-holder ( 224 ), a lower right-hand die-holder ( 242 ) and a lower left-hand die-holder ( 244 ). The press ( 10 ) also comprises adjustment actuators ( 18 ) designed to cause a relative movement of the right-hand die-holders ( 222, 242 ) and left-hand die-holders ( 224, 244 ) towards and/or away from each other. The press ( 10 ) also comprises centring actuators ( 20 ) designed to impart a movement involving displacement of the die-holder assemblies ( 22, 24 ) along the platens ( 12, 14 ).

1 . An edge-bending press for the production of longitudinally welded pipes, comprising:
 an upper platen, a lower platen and operating actuators designed to cause a relative movement of the upper platen and lower platen towards and/or away from each other;   an upper die-holder assembly comprising an upper right-hand die-holder and an upper left-hand die-holder, said upper die-holder assembly being connected to the upper platen; and   a lower die-holder assembly comprising a lower right-hand die-holder and a lower left-hand die-holder, said lower die-holder assembly being connected to the lower platen;   characterized in that the edge-bending press also comprises:   adjustment actuators designed to cause a relative movement of said right-hand die-holders and said left-hand die-holders towards and/or away from each other, and   centring actuators designed to impart a movement involving displacement of said die-holder assemblies along said platens.   
     
     
         2 . An edge-bending press according to  claim 1 , wherein the centring actuators are hydraulic actuators and comprise adjustable safety valves able to predefine a threshold value for the pressure inside the centring actuators whereby, upon reaching a threshold value, the safety valve opens a vent so as to limit the pressure inside the centring actuators. 
     
     
         3 . An edge-bending press according to  claim 2 , wherein the safety valve is a mechanical valve which can be variably preloaded. 
     
     
         4 . An edge-bending press according to  claim 1 , also comprising a frame. 
     
     
         5 . An edge-bending press according to  claim 4 , also comprising clamping means able to keep a sheet in the correct position also in response to disturbances in the system of forces generated during operation of the press, the clamping means being mounted on the frame. 
     
     
         6 . An edge-bending press according to  claim 5 , wherein the operating actuators are hydraulic actuators. 
     
     
         7 . An edge-bending press according to  claim 6 , wherein the operating actuators comprise a main unit including a main cylinder and piston unit, and an auxiliary unit including an auxiliary cylinder and piston unit which has a working area smaller than that of the main cylinder and piston unit, the main unit and the auxiliary unit being arranged in parallel. 
     
     
         8 . An edge-bending press according to  claim 7 , wherein the adjustment actuators comprise an upper adjustment actuator mounted on the upper platen and a lower adjustment actuator mounted on the lower platen, the adjustment actuators being mounted on the respective platens so as to be able to slide in a transverse direction relative thereto. 
     
     
         9 . An edge-bending press according to  claim 8 , wherein the centring actuators are hydraulic actuators of the type comprising a cylinder and piston unit and comprise an upper centring actuator and a lower centring actuator, whereby:
 an outer casing of the cylinder of the upper centring actuator is rigidly connected to the upper platen;   an end of the piston rod of the upper centring actuator is connected to the upper adjustment actuator;   an outer casing of the cylinder of the lower centring actuator is rigidly connected to the lower platen; and   an end of the piston rod of the lower centring actuator is connected to the lower adjustment actuator.   
     
     
         10 . An edge-bending press according to  claim 1 , also comprising means for operating simultaneously, during a crimping step, the centring actuators and the adjustment actuators so as to impart to the dies a movement away from each other in the transverse direction during the approach movement in the vertical direction.