Toothbrush incorporating a flexible undulating region

1. A toothbrush comprising a head and a grip handle integrally made of a plastics material and arranged along a head-handle longitudinal direction, with a neck region between the grip handle and the head, with bristles projecting from the head in a transverse direction relative to this longitudinal direction, the toothbrush having a width direction perpendicular to the longitudinal direction and to the transverse direction, longitudinally between the neck region and the grip handle is an undulating region, comprising limbs extending in the transverse direction and integrally linked by folds with troughs between the limbs, the troughs between the limbs having a transverse depth direction and containing a thermoplastic elastomer material bonded to the plastic material of said limbs, wherein the transverse directions of longitudinally adjacent pairs of limbs are aligned at an angle of 0-15° to each other, each of the four limbs having a longitudinal thickness “T” of 1.2-2.2 mm, and a transversely extending length “L” of 9-13 mm between transversely opposite folds, and a width “W” of 9-14 mm in the width direction, the four limbs defining longitudinally between longitudinally adjacent pairs of the limbs three troughs each with a transverse depth “D” of 6-11 mm, a longitudinal breadth “B” of 1-2 mm for at least 60% of the lower depth of the trough, each trough containing the thermoplastic elastomer; and wherein the thermoplastic elastomer material has a ShoreA hardness of 60-70.

2. A toothbrush according to claim 1 wherein there are four limbs.

3. A toothbrush according to claim 1 wherein the thermoplastic elastomer material occupies at least 60% of the transverse depth “D” and at least 60% of the width of at least one trough.

4. A toothbrush according to claim 1 wherein at each longitudinal end of the undulating region there is an end trough in the plastics material, bounded on one longitudinal side by an adjacent limb and on the other longitudinal side by an adjacent surface of the grip handle or head, the end troughs also containing the thermoplastic elastomer material.

5. A toothbrush according to claim 1 wherein the neck region is flattened in the transverse direction.

6. A toothbrush according to claim 1 which also includes a flexible link situated longitudinally between the undulating region and the toothbrush head.

7. A toothbrush according to claim 6 wherein the flexible link is situated in the neck region thereby dividing the neck region into two longitudinally separate parts, one on each longitudinal side of the flexible link, being a first part closer to the grip handle and a second part closer to the head.

8. A toothbrush according to claim 7 wherein the relative longitudinal proportions of the first part:second part are in the range 8.5-8.0:1.

9. A toothbrush according to claim 6 wherein the flexible link comprises a part, integral with the neck region, which is transversely and/or widthways thinned relative to longitudinally immediately adjacent parts of the neck region.

10. A toothbrush according to claim 9 wherein the part which is transversely and/or widthways thinned is surrounded around all of its transversely- and widthways-facing surfaces by a thermoplastic elastomer material.

11. A toothbrush according to claim 10 wherein the thermoplastic elastomer which surrounds the thinned part has a spherical symmetry.

12. A toothbrush according to claim 6 wherein the part of the neck region between the flexible link and the undulating region is constructed such that under the forces encountered during tooth brushing this part remains rigid relative to the flexibility of the flexible link and the undulating region.

13. A toothbrush according to claim 1 wherein the plastic material has a modulus of elasticity of at least about 500 Mpa, and is a polyamide or polypropylene.

14. A toothbrush according to claim 1 wherein the thermoplastic elastomer material is a styrene-based thermoplastic elastomer.