Brushroll for vacuum cleaner

1. A brushroll for a vacuum cleaner, comprising:

an injection-molded brush dowel having a central rotational axis defining an origin for a first axis extending through the dowel and a second axis extending through the dowel perpendicularly to the first axis to conceptually divide the dowel into quadrants;

two bristle stiffeners integrally molded with the dowel and lying in opposing quadrants, each having a parting line which is radially spaced from and non-parallel to the rotational axis; and

a plurality of stiffened bristles protruding from the brush dowel adjacent to the bristle stiffeners;

wherein the first axis defines a line of draw for a two-piece mold forming the brush dowel and bristle stiffeners.

2. The brushroll of claim 1 , wherein the dowel and bristle stiffeners are integrally molded without any undercuts on the dowel or bristle stiffeners.

3. The brushroll of claim 1 and further comprising a plurality of unstiffened bristles protruding from the brush dowel which are non-adjacent to the bristle stiffeners.

4. The brushroll of claim 3 , wherein the stiffened and unstiffened bristles are each in tufts, and the diameter of the tufts of stiffened bristles is larger than the diameter of tufts of unstiffened bristles.

5. The brushroll of claim 3 , wherein the stiffened bristles substantially lie along a centerline which passes through the rotational axis and the unstiffened bristles substantially lie along centerlines which are offset from the rotational axis.

6. The brushroll of claim 3 , wherein the stiffened and unstiffened bristles substantially lie along centerlines which pass through the rotational axis.

7. The brushroll of claim 3 , wherein the stiffened and unstiffened bristles substantially lie along centerlines which are offset from the rotational axis.

8. The brushroll of claim 3 , wherein the stiffened bristles lie in the opposing quadrants and the unstiffened bristles lie in the other quadrants.

9. The brushroll of claim 3 and further comprising a plurality of bristle ridges projecting from the exterior surface of the dowel, wherein the stiffened and unstiffened bristles and bristle stiffeners extend from the bristle ridges.

10. The brushroll of claim 1 , wherein the bristle stiffeners wrap helically around the dowel such that each parting line is helical with respect to the rotational axis.

11. The brushroll of claim 1 , wherein the bristle stiffeners wrap angularly around the dowel such that each parting line is angular with respect to the rotational axis.

12. The brushroll of claim 1 and further comprising a plurality of bristle ridges projecting from the exterior surface of the dowel, wherein the stiffened bristles and bristle stiffeners extend from the bristle ridges.

13. The brushroll of claim 12 , wherein at least one bristle ridge of the plurality of bristle ridges comprises a leading surface and a trailing surface, as defined in relation of the direction of rotation of the brush dowel about the central rotational axis, which project from the brush dowel and are joined by an outward surface.

14. The brushroll of claim 13 , wherein at least one bristle stiffener comprises an inner stiffener surface which extends radially from the outward surface of the at least one bristle ridge to a stiffener edge which joins an upper end of the trailing surface of the at least one bristle ridge.

15. The brushroll of claim 14 , wherein the stiffener edge is positioned radially inwardly of an end of the stiffened bristles protruding adjacent to the at least one bristle stiffener.

16. The brushroll of claim 14 , wherein the trailing surface extends above the leading surface to form the at least one bristle stiffener.

17. The brushroll of claim 13 and further comprising a plurality of bristle holes in the outward surface of the at least one bristle ridge which extend at least partially into the at least one bristle ridge, wherein the stiffened bristles are received by the holes.

18. The brushroll of claim 1 and further comprising a shim between each bristle stiffener and the plurality of bristles.

19. The brushroll of claim 1 , wherein the bristle stiffeners are positioned rearwardly of the stiffened bristles, as defined in relation of the direction of rotation of the brush dowel about the central rotational axis.

20. The brushroll of claim 1 , wherein the first axis extends horizontally through the dowel and the second axis extends vertically through the dowel.