Method for Tightening Screwed Connections, Multi-Screwing Device

A method for tightening screwed connections, each screwed connection comprised of a threaded bolt (5) and of a nut (6) screwed onto the thread (5A) of the threaded bolt (5) and supported against a base (U), wherein the screw axes (A) of the screwed connections are arranged in mutually fixed positions, by using a multi-screwing device (1) comprising screwing tools (10, 20), the screwing tools (10, 20) each comprising

• an exchangeable bushing (21), which is arranged in the screwing tool (10, 20) so as to be rotatable about a tool axis (A10, A20), and on which a tension thread (23) is provided that can be screwed to a longitudinal portion (L) of the thread (5A),
• a rotary drive (45) configured to screw the exchangeable bushing (21) onto and off the thread (5A),
• a device for longitudinally straining the threaded bolt (5) by exerting a tensile force through the exchangeable bushing (21) along the tool axis (A10, A20),
• a form-fitting tool configured to be coupled to the nut (6) for retightening the nut (6),
• the screwing tools (10, 20) each being movable in the longitudinal direction of their tool axes (A10, A20) by a longitudinal drive (50a, 50b),
• the screwing tools (10, 20) including a first screwing tool and a second screwing tool, and, by at least one actuating drive (60a, 60b), the first and second screwing tools (10, 20) being movable relative to each other in a direction that is at right angles relative to at least one of the tool axes (A10, A20),
• at one point in time, the first and second screwing tools (10, 20) being simultaneously supported against the base (U), and the exchangeable bushing (21) of the first screwing tool (10) and the exchangeable bushing (21) of the second screwing tool (20) each being screwed onto the thread (5A) of a threaded bolt (5),
• and, with the position of the second screwing tool (20) being unchanged, the method comprising:
• a) unscrewing the exchangeable bushing (21) of the first screwing tool (10) from the threaded bolt with the rotary drive (45), and raising the first screwing tool (10) with the longitudinal drive (50a):
• b) moving the first screwing tool (10) relative to the second screwing tool (20) with the actuating drive (60a, 60b) into a new position in which the tool axis (A10) of the first screwing tool (10) is aligned with the screw axis (A) of a further threaded bolt (5);
• c) in the new position, lowering the first screwing tool (10) with the longitudinal drive (50a) and screwing the exchangeable bushing (21) onto the further threaded bolt (5) with the rotary drive (45);
• d) longitudinally straining the further threaded bolt (5) by exerting a tensile force with the exchangeable bushing (21) and retightening the nut (6) while maintaining the longitudinal straining action;
• e) repeating steps a) to d) for the second screwing tool (20) while the position of the first screwing tool (10) is unchanged.