Automatic screwdriver or torquing tool control system

US4562389A · kind A · utility

Assignee

• Robert Bosch GmbH · DE

Inventors

• Wolfgang Jundt · Ditzingen, DE
• Gunter Schaal · Stuttgart, DE
• Fritz Schadlich · Echterdingen, DE
• Hans-Joachim Vogt · Stuttgart, DE
• Steffen Wunsch · Waldenbuch, DE

Key dates

• Filing date: Sep 27, 1983
• Grant date: Dec 31, 1985
• Expiry date: Sep 27, 2003

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y02P70/10
• WIPO field: Machine tools
• WIPO sector: Mechanical engineering

Abstract

To permit reliable turn-OFF of the motor when the torque of the motor is sufficient to provide for reliable seating of a screw or nut being driven thereby, start conditions of the motor are sensed, either in form of low-current condition or high power factor; high-torque conditions are sensed by low power factor, or high-current, in dependence on the desired torque level which results, respectively, in a comparatively steep phase angle-torque or current level-torque curve. A switch control is energized to turn-OFF the motor current if the phase angles, or the motor current, respectively, are beyond predetermined levels. To prevent in-rush current, or high power factors from affecting the operation of the turn-OFF system, timing circuits are provided to disable the turn-OFF system when the motor is first turned-ON or if the phase angle difference, as determined by time-comparator networks, between current and voltage, is below a predetermined value. Timing duration of at least one of the timing circuits can be controlled as a function of motor temperature to provide for linear response of the system, regardless of changes of motor operating parameter versus torque characteristics un…