Method for production of safety/rupture discs having pre-calculated breaking threshold

Abstract

A method for production of safety/rupture devices having pre-calculated breaking threshold comprises the steps of providing a plate ( 2 ) having at least one metallic surface ( 2 a ); making at least one cut ( 5 ) in said surface ( 2 a ) of said plate ( 2 ) to define a frangible line of pre-established rupture. The step of making at least one cut ( 5 ) is obtained by application of a laser beam ( 8 ) directly onto said metallic surface ( 2 a ).

1 - 38 . (canceled) 
   
   
       39 . A method for production of safety/rupture devices with pre-calculated breaking threshold, comprising the steps of:
 providing a plate ( 2 ) having at least one metallic surface ( 2   a );   making at least one non-trough cut or notch ( 5 ) in said surface ( 2   a ) of said plate ( 2 ) to define a frangible line of pre-established rupture, said step of making at least one non-through cut or notch ( 5 ) being obtained by application of a laser beam ( 8 ) directly onto said metallic surface ( 2   a ).   
   
   
       40 . A method as claimed in  claim 39 , wherein said laser beam ( 8 ) has an average power included between 10 and 80 W. 
   
   
       41 . A method as claimed in  claim 39 , wherein said laser beam ( 8 ) has an average power included between 20 and 60 W. 
   
   
       42 . A method as claimed in  claim 39 , wherein said laser beam ( 8 ) has an average power included between 35 and 45 W. 
   
   
       43 . A method as claimed in  claim 39 , wherein said step of applying said laser beam ( 8 ) comprises the step of carrying out at least one passage of said laser beam ( 8 ) on said surface ( 2   a ) along a working line. 
   
   
       44 . A method as claimed in  claim 39 , wherein said step of applying said laser beam ( 8 ) comprises the step of carrying out a plurality of passages of said laser beam ( 8 ) on said surface ( 2   a ) along said working line. 
   
   
       45 . A method as claimed in  claim 39 , wherein the step of carrying out said passage of said laser beam ( 8 ) is obtained by moving said laser beam ( 8 ) at a speed included between 50 and 300 mm/s. 
   
   
       46 . A method as claimed in  claim 45 , wherein the step of carrying out said passage of said laser beam ( 8 ) is obtained by moving said laser beam ( 8 ) at a speed included between 100 and 250 mm/s. 
   
   
       47 . A method as claimed in  claim 39 , further comprising the step of making a plurality of non-through cuts or notches ( 5 ) in said metallic surface ( 2   a ). 
   
   
       48 . A method as claimed in  claim 39 , wherein said laser beam ( 8 ) has a wavelength included between 1000 and 1100 nm. 
   
   
       49 . A method as claimed in  claim 48 , wherein said laser beam ( 8 ) has a wavelength included between 1047 and 1064 nm. 
   
   
       50 . A method as claimed in  claim 39 , wherein the laser beam ( 8 ) is of the pulsed type, a time of each pulse being included between 10 and 80 ns. 
   
   
       51 . A method as claimed in  claim 39 , wherein the power and/or number of passages and/or pulse duration and/or displacement speed and/or stroke of the laser beam ( 8 ) vary during the step of carrying out said at least one non-through cut or notch ( 5 ) in order to vary the cut depth. 
   
   
       52 . A method as claimed in  claim 39 , wherein the step of providing said plate ( 2 ) comprises the step of curving said plate ( 2 ) so as to obtain a concave or convex conformation; said step of curving said plate ( 2 ) being carried out before the step of making said non-through cut or notch ( 5 ). 
   
   
       53 . A method as claimed in  claim 39 , further comprising the step of creating a region of deformation initiation ( 7 ), close to the centre of the plate ( 2 ). 
   
   
       54 . A method as claimed in  claim 53 , wherein said step of creating the region ( 7 ) of deformation initiation is obtained by locally reversing the concavity of the plate ( 2 ). 
   
   
       55 . A method as claimed in  claim 54 , wherein the step of locally reversing the concavity of the plate ( 2 ) is obtained by applying a laser radiation close to the centre of the plate ( 2 ) so as to deform said region. 
   
   
       56 . A method as claimed in  claim 53 , wherein said step of creating the region of deformation initiation ( 7 ) is obtained by locally modifying the crystalline structure and/or thickness of said plate ( 2 ). 
   
   
       57 . A method as claimed in  claim 39 , further comprising a step of creating at least one breaking initiation region ( 6 ) placed at said at least one non-through cut or notch ( 5 ); said breaking initiation region ( 6 ) comprising a portion of the plate having a smaller thickness than the average thickness of the plate ( 2 ). 
   
   
       58 . A method as claimed in  claim 57 , wherein said step of creating at least one breaking initiation region ( 6 ) is obtained by removing a portion of the plate ( 2 ) by laser radiation. 
   
   
       59 . A method as claimed in  claim 39 , wherein said peripheral non-through cut or notch ( 5 ) is shaped like an arc of a circle and is made at the periphery of a central portion ( 4 ) of said plate ( 2 ); said non-through cut or notch ( 5 ) having a first ( 5   a ) and a second ( 5   b ) ends facing each other. 
   
   
       60 . A method as claimed in  claim 59 , wherein said non-through cut or notch ( 5 ) has an increasing depth on moving away from said first ( 5   a ) and second ( 5   b ) ends.