Patent ID: 8884884

Claim:
An apparatus comprising: a touch sensitive surface; a first eccentric rotating mass (ERM) actuator coupled to the touch sensitive surface, the first ERM actuator comprising a motor, an ERM housing, a shaft and a mass coupled to the shaft that is adapted to rotate on an axis; a constraining device coupled to the mass; and a drive circuit adapted to generate an alternating current (AC) signal coupled to the ERM actuator; wherein the constraining device prevents the mass from a complete rotation on the axis when the signal is coupled and generates vibrations on the touch sensitive surface via an inertial force through the ERM housing; wherein the constraining device substantially limits a rotation of the mass to a direction along a perpendicular axis that is generally perpendicular to the touch sensitive surface, wherein the inertial force is applied generally along the perpendicular axis, and the constraining device limits movement of the mass in both directions of the perpendicular axis by constraining the mass on both sides of the perpendicular axis relative to the mass; wherein the AC signal is bidirectional and drives the mass in both directions of the perpendicular axis.