Unvulcanized tread strip for pneumatic vehicle tires

Claim 1

In a still unvulcanized tread strip, for a pneumatic vehicle tire, having at least two layers to be bonded which are disposed one upon the other in unvulcanized state this still having a plastic behavior including an outer surface of the outer layer which is smooth; the improvement comprising adjacent ones of said layers respectively being provided with different rubbery mixtures still in an unvulcanized state, said layers thus differing from one another in chemical and physical properties thereof in the still unvulcanized state and the layer to be subjected to wear in the tread strip when subsequently vulcanized being considerably thicker than the adjacent layer in a tread strip uninterrupted from side to side; and a plurality of corresponding projections and recessed portions in the respective layers which positively intermesh in the still unvulcanized state so as to impart a positive connection thereto and with that receiving a considerable enlargement of bonding surface interengagement which improves adhesion therewith in the still unvulcanized state and accordingly overcomes adhesion weaknesses so that during subsequent vulcanization there is effected a bonding together less susceptible to subsequent separation therebetween; said projections and said recessed portions having a width in a range of from about 0.5 to 3 mm, said projections and said recessed portions having a depth in a range of from about 0.5 to 2.5 mm; and said projections being in the form of ribs, said recessed portions being in the form of grooves, said ribs and grooves extending in the longitudinal direction of said tread strip; said projections being in the form of individual projections having an essentially rectangular cross-section, and said recessed portions being in the form of corresponding recesses that intermesh complementary to each other to preclude any separations which are associated with inadequate adhesion.