Robert Boschgmbh

Gerold Mueller

Peter Wolf

Gerhard Keuper

Heinz Veitinger

Ingo Kallfass

Reiner Kurz

Uwe Maier

Sönke Jessen

A plurality of valves are triggered so that a first valve is triggered by a first trigger signal and a second valve is triggered by a second trigger signal, the first trigger signal and the second trigger signal are each generated by generating a pulse width modulated frequency signal of the first frequency fand a dither signal of the second frequency f, where f&#x3e;f, the trigger signal is generated by modulating the clock pulse duty factor of the frequency signal with the dither signal, and the dither signals of the first trigger signal and of the second trigger signal are synchronized with one another at chronological intervals.

Method for triggering a plurality of valves, and control block having a plurality of valves

The screwdriving device (,) according to the invention has a control device (,) which uses a sensor system (,) to determine a characteristic variable (K) which characterizes a screwdriving moment (M,) of the screw connection (,) and/or an emitted moment (M) of the impact screwdriver, during or after at least one pulse emission from the impact screwdriver to the screw connection, and defines a drive variable, for example a required drive speed (n) for the next impulse emission, as a function of the determined characteristic variable (K,). In this case, the drive variable (n) is initially set to a value which corresponds to a value (K,) to be expected of the characteristic variable (K) and its magnitude is in any case less than a desired value (K,) for the final screw connection state. This prevents the desired screwdriving moment being exceeded even after the first impulse emission in the event of unfavorable screwdriving conditions. Instead of this, the desired final screw connection state is approached step by step, in a controlled manner.

Method for tightening a screw connection by means of an impact screwdriver having a variable speed electric drive motor

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Stuttgart, Germany

Gerold Mueller