Operator sensing circuit for disabling motor of power equipment

US7034552B2 · kind B2 · utility

Inventors

• Markus Kirchner · Neuffen, DE
• Markus Neidert · Owen, DE
• Ralph Sauter · Neuffen, DE

Key dates

• Filing date: Feb 17, 2004
• Grant date: Apr 25, 2006
• Expiry date: Mar 5, 2024

Classification

• Technology area (CPC H): Electricity
• CPC primary: H03K2217/960725
• WIPO field: Basic communication processes
• WIPO sector: Electrical engineering

Abstract

A calibrated operator-sensing circuit having a microcontroller that commands a charge-transfer sensor to send a sensor charge signal to a capacitive sensing electrode. The sensor receives a discharge signal from the electrode and outputs a corresponding raw data signal to the microcontroller that in turn sends a signal that disables the motor of a unit of power equipment upon the absence of an operator's hand on a hand-gripping surface of the equipment. The capacitive operator-hand sensing electrode operates within a predetermined output capacitor discharge range that includes preselected binary digit values that designate hands-off and hands-on conditions on the hand-gripping surface. The capacitor discharge range is effective to distinguish between the presence of an operator's hand and foreign material on the gripping surface for avoiding a false hands-on signal. The operator-hand sensing electrode includes an inner dielectric material layer contiguously disposed on a metal handle portion of the power equipment, a metal sheet foil conductor material layer contiguously disposed on the dielectric material, and an outer dielectric hand-grip material having a hand-gripping surface.