Method and unit for forming tubular lengths of web material particularly in a labelling machine

Abstract

An example includes a method for forming tubular lengths of linear web material. The example can include winding a portion of linear web material in a tubular configuration such that opposite vertical ends of said linear portion overlap. The example can include welding said overlapping ends to fix said linear portion of linear web material in sleeve configuration. This welding can include heating up at a first temperature a first region of said portion over the whole of which said ends overlap and heating up at a second temperature lower than said first temperature a second region of said portion adjacent to said first region, said ends of said portion of linear web material overlapping over only a part of said second region.

1 . A method for forming tubular lengths of web material, comprising:
 winding a linear portion of the web material in a tubular configuration such that opposite vertical ends of said linear portion overlap; and   welding said overlapping ends to fix said linear portion of web material in sleeve configuration, comprising:
 heating up at a first temperature a first region of said portion over the whole of which said ends overlap; and 
 simultaneously heating up at a second temperature lower than said first temperature a second region of said portion adjacent to said first region, said ends of said portion of said web material overlapping over only a part of said second region. 
   
     
     
         2 . The method according to  claim 1 , wherein said first temperature is sufficiently high for producing the welding of said overlapping ends of said portion, whereas said second temperature is sufficiently high for producing the welding of a trailing edge of said portion to a cylindrical surface of sleeve label without causing the latter to melt. 
     
     
         3 . The method according to  claim 1 , wherein said first region is linearly separated from a trailing edge of said portion of said web material by an arc having a predetermined length. 
     
     
         4 . The method according to  claim 3 , wherein said first and second regions are angularly separated by an angle subtended by said arc of said predetermined length. 
     
     
         5 . A unit for forming tubular lengths of web material, comprising:
 a winding body to receive and wrap a portion of said web material into a tubular configuration with opposite ends overlapping; and   a sealing device comprising:
 a working surface adapted to cooperate with said portion of said web material wrapped around said winding body to weld said overlapping ends so as to obtain a sleeve label; and 
 a controller to control a temperature of said working surface to assume selectively at least a first temperature and a second temperature, said first temperature being higher than said second temperature, 
 wherein said working surface is configured to assume said first temperature when cooperating with a first region of said portion at which said ends fully overlap, and to assume second temperature when cooperating with a second region of said portion substantially adjacent to said first region, said ends overlapping over a part of said second region. 
   
     
     
         6 . The unit according to  claim 5 , wherein said winding body is configured to controllably rotate about a relative axis by an angle subtended by an arc of a predetermined length separating said first and second regions. 
     
     
         7 . The unit according to  claim 6 , wherein the web material comprises a label. 
     
     
         8 . The unit according to  claim 5 , wherein the winding body is to receive and produce the complete wrapping of the portion of said web material. 
     
     
         9 . The unit according to  claim 5 , wherein said second region is adapted to cooperate with said portion of said web material wrapped around said winding body at a second corresponding sleeve label region, over only a part of which said ends overlap. 
     
     
         10 . A method for forming tubular lengths of web material, comprising:
 winding a linear portion of web material in a tubular configuration such that opposite vertical ends of said linear portion overlap; and   welding said overlapping ends to fix said linear portion of web material in sleeve configuration, comprising:
 heating up at a first temperature a first region of said portion over which said ends overlap; and 
 heating up at a second temperature lower than said first temperature a second region of said portion adjacent to said first region, said ends of said portion of said web material overlapping said second region. 
   
     
     
         11 . The method according to  claim 10 , wherein said first temperature is sufficiently high for producing the welding of said overlapping ends of said portion, whereas said second temperature is sufficiently high for producing the welding of a trailing edge of said portion to a cylindrical surface of sleeve label.