Method and apparatus for welding polymer fabrics

Abstract

The apparatus is adapted to weld ultrasonically two or more layers of fabric 14. The fabrics 14 may be a woven or non-woven fabric of nylon, polyethylene or other polymeric material. It comprises two opposed ultrasonically vibratable horns ( 1, 1 a ) so spaced one from another that the layers of fabric ( 3 ) may be passed between them. At least one, optionally both, of the two horns ( 1, 1 a ) is vibratable in axial mode.

1 . An apparatus for welding ultrasonically two or more layers of fabric comprising two opposed ultrasonically vibratable horns so spaced one from another that the layers of fabric may be passed between them.  
     
     
         2 . An apparatus as claimed in  claim 1 , wherein at least one of the two horns is vibratable in axial mode.  
     
     
         3 . An apparatus as claimed in  claim 2 , wherein both horns are vibratable in axial mode.  
     
     
         4 . An apparatus as claimed in  claim 3 , wherein the relative phase between the vibrations of the horns is so variable that, for constant amplitude vibrations, the energy to be imparted varies between a minimum at phase difference Ø=0° and a maximum at phase difference Ø=180°.  
     
     
         5 . An apparatus as claimed in  claim 3 , wherein the frequencies at which the horns are adapted to vibrate are so variable that one is vibratable at a frequency plus or minus between 1 and 20% of the frequency of the other.  
     
     
         6 . An apparatus as claimed in  claim 5 , wherein one horn is adapted to vibrate at a frequency plus or minus 10% of the frequency of the other.  
     
     
         7 . An apparatus as claimed in any one of  claims 2  to  6 , wherein one axially vibratable horn has an end face angled with respect to the vibrational axis, and the second axially vibratable horn is vibratable in a direction substantially perpendicular to said end face.  
     
     
         8 . An apparatus as claimed in  claim 2 , wherein one horn is vibratable in an axial mode and an opposed co-operating horn is vibratable in a torsional mode.  
     
     
         9 . An apparatus as claimed in any one of the preceding claims, further comprising a source of air or other cooling fluid directed generally toward a zone in which welding takes place.  
     
     
         10 . An apparatus as claimed in  claim 9 , wherein the source of air or other cooling fluid comprises a passageway extending substantially longitudinally of at least one of the welding horns to exit centrally of the welding zone.  
     
     
         11 . An apparatus as claimed in  claim 9 , wherein the source of air or other cooling fluid comprises a passageway extending longitudinally of at least one of the welding horns, at least one of the or each said passageway difurcating to permit exit of air or cooling fluid through a plurality of annularly spaced outlets.  
     
     
         12 . A method of welding ultrasonically two or more layers of fabric comprising the steps of providing two opposed ultrasonically vibratable horns spaced one from another, and passing the layers of fabric between them whilst vibrating ultrasonically the horns.  
     
     
         13 . A method as claimed in  claim 12 , wherein at least one of the two horns is vibrated in axial mode.  
     
     
         14 . A method as claimed in  claim 13 , wherein both of the horns are vibrated in axial mode.  
     
     
         15 . A method as claimed in  claim 14 , wherein the horns are vibrated with a relative phase difference between them, said phase shift being variable between Ø=0° for minimum energy and Ø=180° for maximum energy.  
     
     
         16 . A method as claimed in  claim 14  wherein the horns are so vibrated that one vibrates at a frequency plus or minus between 1 and 20% of the frequency of the other.  
     
     
         17 . A method as claimed in  claim 16 , wherein the horns are so vibrated that one vibrates at a frequency plus or minus 10% of the frequency of the other.  
     
     
         18 . A method as claimed in  claim 13 , wherein one horn is vibrated in an axial mode whilst an opposed co-operating horn is vibrated in a torsional mode.  
     
     
         19 . A method as claimed in any one of  claims 12  to  18 , further comprising the step of directing air or other cooling fluid toward a zone in which welding takes place.