Patent Number: 6,167,606

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

Abstract: The screwdriving device (9) according to the invention has a control device (22) which uses a sensor system (18) to determine a characteristic variable (K) which characterizes a screwdriving moment (M.sub.v) of the screw connection (10) 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.sub.i). In this case, the drive variable (n) is initially set to a value which corresponds to a value (K.sub.0) to be expected of the characteristic variable (K) and its magnitude is in any case less than a desired value (K.sub.req) 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.

Inventors: Mueller; Gerold (Stuttgart, DE), Wolf; Peter (Leinfelden-Echterdingen, DE), Veitinger; Heinz (Murrhardt, DE)

Assignee: Robert Bosch GmbH

International Classification: B25B 23/14 (20060101); B25B 23/145 (20060101); B23P 19/06 (20060101); B23Q 017/00 ()

Expiration Date: 01/02/2018