US Patent 6997446 Spring member for rotational action

The rotational spring includes a base member which is in the form of a ring and includes elements for fixedly attaching it to a body of an appliance, such as a power toothbrush, which includes a drive element such as a drive shaft portion of a motor. Also included is an upper member in the form of a disc having a central opening through which the drive shaft is fitted, such that the disc member rotates with rotation of the drive shaft. Three leg members extend between the upper disc member and the base ring member. The spring is made from a material and is so configured and arranged that it has a symmetric spring rate for clockwise and counter-clockwise rotation.