BACKGROUND OF THE INVENTION

The invention relates to a method for tightening screwed connections, the screw axes of which are arranged in mutually fixed positions and which are each comprised of a threaded bolt and of a nut screwed onto its thread and supported against a base.

The invention further relates to a multi-screwing device, which is particularly suitable for a method for tightening screwed connections.

A method for tightening screwed connections by use of a screwing device is known from US 2014/0350724. The device is designed to tighten or retighten a multiplicity of screwed connections arranged in a row along a flange. Each screwed connection is comprised of a threaded bolt and a nut screwed onto the thread of the threaded bolt, wherein the nut is supported against the upper side of the flange. The tightening of the screwed connection by straining, as well as the subsequent turning of the nut relative to the flange, is realized by a screwing tool, which is arranged on a self-propelled vehicle. In order to position the screwing tool above the screwed connection to be tightened in each case, the vehicle is equipped with a position sensor. Based on the position signals of the latter, the vehicle, with the screwing tool arranged on it, is driven in a controlled manner until the signals indicate that the screwing tool is in axial alignment with the screw axis of the screwed connection. For this purpose, the position signals of the position sensor are processed in a control unit into signals for driving the vehicle. The control unit is also designed to control the process of straining and retightening the nut.

A method for tightening screwed connections arranged in a row is also known from US 2010/0175240. Tightening of the screwed connections is realized by a plurality of screwing tools connected in parallel at the same time. Each of the screwing tools has a hydraulic connection, which is hydraulically connected to a common hydraulic unit. The tensioning devices are therefore connected in a hydraulic parallel circuit for parallel operation.

A screwing device in which a plurality of screwing tools can be transported together along screwed connections arranged in a row and can be moved into a position above these screwed connections is known from US 2013/0185932. The screwing tools operate hydraulically, by first mechanically longitudinally straining the threaded bolt of the respective screwed connection.

The known methods and devices are suitable for screwed connections arranged consecutively in a row, as is typical, for example, for flange screw-fastenings that connect individual tower portions of a wind power installation to one another. In this case, a ring flange of an upper tower portion is supported on the ring flange of a tower portion of the wind power installation located beneath it. The flanges are screwed together by a multiplicity of screwed connections, which are arranged in a row evenly distributed around the circumference of the flanges.

The known methods and devices are less suitable, or even unsuitable, in cases in which the screwed connections are not arranged evenly in a row, but in different positions in relation to each other.

The object of the invention is to provide a method that can be executed by a multi-screwing device and that is suitable not only for tightening screwed connections arranged consecutively in a row, but also for tightening screwed connections whose screw axes are arranged in other positions relative to one another. Furthermore, a suitable multi-screwing device is to be created.

SUMMARY OF THE INVENTION

This object is achieved by a method for tightening screwed connections, the screw axes of which are arranged in mutually fixed positions and which are each comprised of a threaded bolt and of a nut screwed onto the thread of the threaded bolt and supported against a base, by use of a multi-screwing device comprising a first screwing tool and at least one second screwing tool, the screwing tools each comprisingan exchangeable bushing, which is arranged in the screwing tool so as to be rotatable about a tool axis and which is provided with a tension thread that can be screwed to a longitudinal portion of the thread,a rotary drive for screwing the exchangeable bushing onto and off the thread,a device for longitudinally straining the threaded bolt by exertion of tensile force through the exchangeable bushing along the tool axis,a form-fitting tool that can be coupled to the nut for the purpose of retightening the nut,
the screwing tools each being movable in the longitudinal direction of their tool axes by a longitudinal drive and, by at least one actuating drive, the screwing tools being movable relative to each other in a direction that is at right angles relative to at least one of the tool axes,
both screwing tools being simultaneously supported against the base at one point in time, and the exchangeable bushing of the first screwing tool and the exchangeable bushing of the second screwing tool each being screwed onto the thread of a threaded bolt,
and, with the position of the second screwing tool being unchanged, the following steps ensuing:a) by the rotary drive, unscrewing the exchangeable bushing of the first screwing tool from the threaded bolt and, by the longitudinal drive, raising the screwing tool;b) by the actuating drive, moving the first screwing tool relative to the second screwing tool into a new position in which the tool axis of the first screwing tool is in alignment with the screw axis of a further threaded bolt;c) in the new position, lowering the first screwing tool by the longitudinal drive and, by the rotary drive, screwing the exchangeable bushing onto the further threaded bolt;d) longitudinally straining the further threaded bolt by exertion of tensile force through the exchangeable bushing and, while maintaining the longitudinal straining, retightening the nut:e) repeating the steps a) to d), this time for the second screwing tool and with the position of the first screwing tool unchanged.

In the case of this method, a multi-screwing device comprising at least two screwing tools is used, the screwing tools each comprisingan exchangeable bushing, which is arranged in the screwing tool so as to be rotatable about a tool axis and which is provided with a tension thread that can be screwed to a longitudinal portion of the thread,a rotary drive for screwing the exchangeable bushing onto and off the thread,a device for longitudinally straining the threaded bolt by exertion of tensile force through the exchangeable bushing along the tool axis,a form-fitting tool that can be coupled to the nut for the purpose of retightening the nut.

The screwing tools are each movable in the longitudinal direction of their tool axes by a longitudinal drive, and are thus designed to be movable. And, by at least one actuating drive, the screwing tools are movable relative to each other in a direction that is at right angles relative to at least one of the tool axes.

At one point in time, both screwing tools are simultaneously supported against the base. At this point in time, the exchangeable bushing of the first screwing tool and the exchangeable bushing of the second screwing tool are each screwed onto the thread of a threaded bolt, and the device for longitudinally straining the respective threaded bolt is activated in both screwing tools, i.e., both exchangeable bushings exert tensile force on the respective threaded bolt, preferably by hydraulic pressure.

Then, with the position of the second screwing tool unchanged, which screwing tool is initially still activated. i.e., exerting tensile force upon the threaded bolt, and subsequent to deactivation of the first screwing tool, the following steps are performed:a) by the rotary drive, unscrewing the exchangeable bushing of the first screwing tool from the threaded bolt and, by the longitudinal drive, raising the first screwing tool;b) by the actuating drive, moving the first screwing tool relative to the second screwing tool into a new position in which the tool axis of the first screwing tool is in alignment with the screw axis of a further threaded bolt;c) in the new position, lowering the first screwing tool by the longitudinal drive and, by the rotary drive, screwing the exchangeable bushing onto the further threaded bolt;d) longitudinally straining the further threaded bolt by exertion of tensile force through the exchangeable bushing and, while maintaining the longitudinal straining, retightening the nut;e) repeating the steps a) to d), this time for the second screwing tool and with the position of the first screwing tool unchanged.

The deactivation of the second screwing tool is effected no earlier than during step d), i.e., after the start of exerting a tensile force on the further threaded bolt. Since, at each point in time, at least one of the screwing tools is activated by applied hydraulic pressure and this screwing tool is therefore supported under strong pressure against the base, a high degree of precision is achieved in the alternating repositioning of the screwing tools.

For achieving the object of the invention, the invention additionally proposes a multi-screwing device for screwed connections, the screw axes of which are arranged in mutually fixed positions and which are each comprised of a threaded bolt and a nut screwed onto the thread of the threaded bolt and are supported against a base, comprising a first screwing tool and at least one second screwing tool, the screwing tools each comprisingan exchangeable bushing, which is arranged in the screwing tool so as to be rotatable about a tool axis and which is provided with a tension thread that can be screwed to a longitudinal portion of the thread,a rotary drive for screwing the exchangeable bushing onto and off the thread,a device for longitudinally straining the threaded bolt by exertion of tensile force through the exchangeable bushing along the tool axis,a form-fitting tool that can be coupled to the nut for the purpose of retightening the nut,characterized in that the screwing tools are each designed to be movable in the longitudinal direction of their tool axes by a longitudinal drive, and in that the screwing tools are movable relative to each other, in a direction at right angles relative to at least one of the tool axes, by at least one actuating drive.

This multi-screwing device is characterized in that the screwing tools are each designed to be movable in the longitudinal direction of their tool axes by a longitudinal drive, and in that the screwing tools are movable relative to each other, in a direction at right angles relative to at least one of the tool axes, by at least one actuating drive.

The claimed method and the claimed device are suitable not only for tightening screwed connections arranged in a row relative to each other, but also for successively tightening such screwed connections whose screw axes are arranged in other positions relative to each other, e.g., the screw axes are arranged in a transversely or obliquely offset manner in relation to each other and/or the distances from one screwed connection to another vary.

An additional advantage is that the method is suitable not only for tightening substantially vertical screw-fastenings, but also for screw-fastenings that are angled significantly relative to the vertical, and even for screwed connections that have, for example, a horizontal screw axis, and for overhead screw-fastenings. If the screwed connections are, for example, flange connections, the orientation of the flange may not only be horizontal, but also tilted or even vertical.

Overall, therefore, compared with the prior art, a more flexible method for tightening screwed connections is created, with a wide range of applications. The specially designed multi-screwing device is also characterized by high flexibility in different application situations.

It is important that the at least two screwing tools of the device can be moved relative to each other, in a direction transverse to their tool axes, by the provided at least one actuating drive. When the actuating drive is actuated, one of the screwing tools retains its position and its rotational angle, whereas the other screwing tool executes a movement at a right angle, or transversely, relative to its own tool axis. The result is a relative movement of the screwing tools.

It is also important that, at each point in time in the screw fastening process, at least one of the screwing tools is firmly connected to the respective threaded bolt. A fixed position at a particular location is thus ensured at all times. Because of the fixed position, the other, or another, screwing tool can be moved by actuation of the actuating drive to a new position above a further, not yet tightened, threaded bolt; in the new position, the tool axis of this other screwing tool is then in alignment with the further threaded bolt. The movement into this new position is effected with a high degree of precision since during the repositioning the first screwing tool retains its rigid engagement on its threaded bolt, its support on the base, and thus, as a result, its fixed position and its rotational angle.

Overall, therefore, the method is characterized by a repeated transfer into a respectively new screw-fastening position, and is therefore a “self-advancing” method, in which a rigid connection is ensured at a fixed position at all times and this connection is then abandoned, or released, at the earliest when a rigid connection is ensured at another position by screw fastening on the respective further threaded bolt.

The longitudinal straining of the threaded bolt by exerting a tensile force through the exchangeable bushing along the tool axis may be effected sequentially, partially overlapping in time or in parallel, i.e., simultaneously. In the first case, the pretensioning of two threaded bolts is realized in succession, and in the second case the pretensioning is effected at the same time. It is also possible that, for example, two screwing tools are working while a third screwing tool is being repositioned, i.e., above another screw axis.

Sensors may be used to detect the exact position of the next screw-fastening position. Their sensor systems may be designed either to detect the bolt itself that is to be strained in each case, or to detect an adjacent bolt or two adjacent bolts. The detection of the screwed connection may also be effected beneath the respective flange, for example, in case a bolt head of the screwed connection is located there.

One design of the method and of the device therefore proposes a robot control system for moving the respective screwing tool into the new position, the robot control system being sensor-controlled by a sensor designed to locate the position of the threaded bolts.

Electrical, hydraulic or pneumatic actuation is proposed for the actuator that moves transversely relative to the screw axis. Electric, hydraulic or pneumatic actuation is also proposed for the longitudinal drives operating in the longitudinal direction of the screw.

The distance between the tool axes is altered by the single or multiple actuating drive. The distance between the tool axes may be altered in various ways. For example, the alteration of the distance may be effected in a linear, i.e., rectilinear, movement or in a rectilinear movement process. This is advantageous when the screwed connections are substantially arranged in a row.

In another variant, the alteration of the distance of the tool axes is effected in a non-linear movement, and in particular by an arcuate movement or by the combination of two or more arcuate movements. Each arcuate movement, in its simplest form, is a movement along a circular path.

Preferably, the screwing tools are arranged on a common carrier. In this case, the arcuate movements are effected by swivelling the screwing tools relative to the carrier. It is also possible for the screwing tools to be swivelled simultaneously in mutually opposite swivel directions. This may be effected simultaneously or non-simultaneously.

The screwing tools may each be attached to the free end of an arm that can be swivelled about an axle located on the carrier. The longitudinal drives are independent of each other, to move the respective arm parallel to the tool axis.

It is additionally proposed that the exchangeable bushing be screwed on and off by a rotary drive. Each screwing tool is preferably assigned its own rotary drive, which thus operates independently of the rotary drive of the other tool or tools.

Also proposed is an anti-rotation device. This is designed to prevent the threaded bolt from turning concomitantly when and while the exchangeable bushing is being screwed onto the thread of the threaded bolt. Concomitant turning could result in a thread engagement between the exchangeable bushing and the bolt being too short, which could be a great risk for the subsequent bolt tensioning process.

The anti-rotation device is characterized by a holding tool that is designed to be movable back and forth between a neutral position and a counter-holding position. For at least the duration of the retightening/screwing-down of the nut, a counter-holding surface realized on the holding tool is brought into a rotation-locking bearing contact with the threaded bolt, it being understood that the location of this bearing contact is different from the longitudinal portion of the thread that is screwed to the exchangeable bushing.

Also proposed is a process control system for moving the respective screwing tool into its new, or further, position in a controlled manner. Preferably, the process control system also coordinates and controls the other functions of the screwing tools, and preferably also a controlled forward and backward movement of the additional holding tools.

Preferably, the multi-screwing device is comprised of two modules, namely a tool module, in which the screwing tools, including the device for longitudinally straining the threaded bolt and for retightening the nut, the rotary drives, the longitudinal drives, and the actuating drives are grouped together, and further comprised of a spatially separate supply module. At least the power supply for operating the device for longitudinally straining the threaded bolts is grouped in the supply module. A constituent part of the power supply is a supply line, preferably of a flexible design, which leads from the supply module to the tool module.

Preferably also a constituent part of the supply module is the electrical power supply for, inter alia, the rotary drives, the longitudinal drives and the actuating drives. As a constituent part of this power supply, a second, preferably flexible supply line leads from the supply module to the tool module.

For a largely coordinated movement of tool module and supply module, it is proposed, in one design of the method and the device, that the supply module be designed to be movable parallel to the base, preferably via rollers or wheel elements that are rotatably mounted on the supply module, and that the supply module be mechanically connected to the tool module via a flexible or articulated push or pull linkage.

In another design of the method and device, the supply module is arranged in a fixed manner at a central position, with the tool module moving around this central position from one screw-fastening to another. Also, in this alternative design, a supply line, preferably of a flexible design, leads from the supply module to the tool module.

In order to secure the threaded bolt against unwanted concomitant turning while the exchangeable bushing is being screwed on, the multi-screwing device is equipped with an anti-rotation device. The latter is comprised of a holding tool provided with a counter-holding surface that can be placed against the threaded bolt at a location other than the longitudinal portion of the thread that is screwed to the exchangeable bushing. The counter-holding tool is movable back and forth between a neutral position and a counter-holding position in which the counter-holding surface comes into rotation-locking bearing contact with the threaded bolt. The forward movement until engagement with the threaded bolt may be effected either by a motor drive or by the pressure of a spring mechanism.

Each screwing tool is provided with its own holding tool and its own drive for this holding tool. Preferably, the drives of the holding tools are coupled to the movement of the respective screwing tools parallel to their tool axes.

