Multi-filament Bristles for Toothbrushes

Abstract

The invention relates to a bristle, e.g., for toothbrushes, and a corresponding manufacturing method whereby the bristle has at least two coextruded filaments of different materials in the longitudinal direction, and the cross-sectional area of at least one of the filaments decreases toward the free end of the bristle.

1 . A bristle for use in toothbrushes, the bristle comprising:
 at least two coextruded filaments comprising different materials, the filaments extending in a longitudinal direction and comprising:
 a first filament having a cross-sectional area that decreases towards the free end of the bristle wherein the first filament is erodable by an etchant, and 
 a second filament that is essentially resistant against the etchant. 
   
   
   
       2 . The bristle according to  claim 1 ,
 wherein the cross-sectional area of the first filament decreases steadily.   
   
   
       3 . The bristle according to  claim 1 ,
 wherein the cross-sectional area of the second filament is essentially constant in the longitudinal direction of the bristle.   
   
   
       4 . The bristle according to  claim 1 ,
 wherein the bristle forms a taper towards a free end,   
   
   
       5 . The bristle according to  claim 1 ,
 wherein the second filament is at least partially surrounded radially by the first filament.   
   
   
       6 . The bristle according to  claim 1 ,
 wherein the second filament extends further in the axial direction than the first filament.   
   
   
       7 . The bristle according to  claim 1 ,
 wherein the second filament is rounded or chamfered at a free end.   
   
   
       8 . The bristle according to  claim 1 ,
 wherein the first and second filaments have different.   
   
   
       9 . The bristle according to any one or more of the preceding  claim 1 ,
 wherein at least one of the filaments comprises a polyamide material.   
   
   
       10 . A method for processing bristles for use, in a toothbrush, the method comprising:
 providing at least two coextruded filaments comprising different materials, the filaments extending in the longitudinal direction and comprising:
 a first filament, and 
 a second filament that is essentially resistant against an etchant, 
   eroding at least a partial region of the first filament in an area of a free end of the bristles by a chemical etching process, the etching process at least partially exposing the second filament.   
   
   
       11 . The method according to  claim 10 , wherein the etching process erodes at least some areas of a sheath of first filaments that are arranged to surround an inner core of the bristle. 
   
   
       12 . The method according to  claim 10 , comprising a plurality of first filaments, wherein the etching process exposes the free ends of a plurality of the first filaments. 
   
   
       13 . The method according to  claim 10 , further comprising, after completing the etching process, grinding the bristle ends such that the ends are chamfered or rounded. 
   
   
       14 . The method according to  claim 10 , further comprising securing the bristles on a bristle carrier before beginning the etching process. 
   
   
       15 . A toothbrush comprising:
 a bristle carrier,   a plurality of bristles secured on the bristle carrier, each bristle comprising:
 at least two coextruded filaments comprising different materials, the filaments extending in a longitudinal direction and comprising:
 a first filament having a cross-sectional area decreasing towards the free end of the bristle such that the filament is erodable by an etchant and 
 a second filament that is essentially resistant against the etchant. 
 
   
   
   
       16 - 17 . (canceled) 
   
   
       18 . The bristle according to  claim 4  wherein the taper forms a conical shape. 
   
   
       19 . The bristle according to  claim 4  wherein the taper forms a pointed edge. 
   
   
       20 . The bristle according to  claim 1 , wherein the first and second filaments have a different flexural rigidity. 
   
   
       21 . The bristle according to  claim 9 , wherein the polyamide comprises at least one of nylon, PA6.6, PA6.10, or PA6.12. 
   
   
       22 . The bristle according to  claim 1 , wherein at least one of the filaments comprises a polyester material. 
   
   
       23 . The bristle according to  claim 22 , wherein the polyester comprises at least one of polyethylene terephthalate (PET) or poly-butylene terephthalate (PBT).