Self-righting toothbrush

A self-righting toothbrush, comprising:

• a head section, a tail section and a medial section, said medial section being disposed at a junction of said head section and said tail section in a longitudinal direction of said toothbrush;
• said head section mounting a set of bristles that extend in a frontward direction;
• said tail section having a rearward lateral asymmetry that extends in a rearward direction that is generally opposite to said frontward direction;
• said medial section having a pivot surface configured to contact a horizontal support surface at a pivot point, said pivot surface allowing said toothbrush to roll on said support surface;
• said pivot point lying on said pivot surface and representing its instantaneous point of contact with said support surface at any given rotational position of said toothbrush, said pivot point lying in a vertical plane that is substantially perpendicular to a rolling direction of said toothbrush;
• said head section and said tail section having a respective head section center of mass and a tail section center of mass;
• said toothbrush being in a stable orientation when said toothbrush is in a bristles up position in which said bristles extend vertically away from said support surface, and wherein said head section center of mass and said tail section center of mass are substantially aligned in said vertical plane;
• said tail section center of mass being laterally spaced from said vertical plane due to said rearward lateral asymmetry so as to assume non-neutral unstable positions when said toothbrush is in a non-bristles up position with said bristles extending in a non-vertical direction;
• said non-neutral position of said tail section center of mass producing a net rotational moment that tends to induce said toothbrush to roll to said bristles up position;
• said pivot surface remaining in contact with said support surface at all rolling positions of said toothbrush;
• and
• said pivot surface comprising a rearward protrusion, a lateral protrusion on each side of said rearward protrusion, and a frontward protrusion, said rearward protrusion, said lateral protrusions and said frontward protrusion forming a substantially continuous curve of selected shape.

A self-righting toothbrush, comprising:

• a head section, a tail section and a medial section, said medial section being disposed at a junction of said head section and said tail section in a longitudinal direction of said toothbrush;
• said head section mounting a set of bristles that extend in a frontward direction;
• said tail section having a rearward lateral asymmetry that extends in a rearward direction that is generally opposite to said frontward direction;
• said medial section having a pivot surface configured to contact a horizontal support surface at a pivot point, said pivot surface allowing said toothbrush to roll on said support surface;
• said pivot point lying on said pivot surface and representing its instantaneous point of contact with said support surface at any given rotational position of said toothbrush, said pivot point lying in a vertical plane that is substantially perpendicular to a rolling direction of said toothbrush;
• said head section and said tail section having a respective head section center of mass and a tail section center of mass;
• said toothbrush being in a stable orientation when said toothbrush is in a bristles up position in which said bristles extend vertically away from said support surface, and wherein said head section center of mass and said tail section center of mass are substantially aligned in said vertical plane;
• said tail section center of mass being laterally spaced from said vertical plane due to said rearward lateral asymmetry so as to assume non-neutral unstable positions when said toothbrush is in a non-bristles up position with said bristles extending in a non-vertical direction;
• said non-neutral position of said tail section center of mass producing a net rotational moment that tends to induce said toothbrush to roll to said bristles up position;
• said pivot surface remaining in contact with said support surface at all rolling positions of said toothbrush;
• said pivot surface comprising a rearward protrusion, a lateral protrusion on each side of said rearward protrusion, and a frontward protrusion, said rearward protrusion, said lateral protrusions and said frontward protrusion forming a continuous curve of selected shape;
• and
• said frontward protrusion comprising a protuberance at a central peak thereof to provide rotational instability when said toothbrush in a bristles down position in which said bristles extend vertically toward said support surface.