The invention relates to a system for pre-tensioning a joint comprising two or more threaded fasteners. In particular, the invention concerns a system in which two or more power wrenches are arranged to simultaneously tighten two or more threaded fasteners in a synchronized way in order to obtain an evenly distributed clamping force in the joint.

In a system in which two or more power wrenches are arranged to simultaneously tighten two or more threaded fasteners in a synchronized way in order to obtain an evenly distributed clamping force in the joint there is conventionally used two or more power wrenches connected via cables to a common operation control unit to accomplish an individual control of each power wrench in relation to the operation of the other power wrench or wrenches to thereby obtain a synchronized tightening of the threaded fasteners and, hence an evenly distributed clamping force in the joint. While the existing systems work well, there is a constant desire to improve upon the existing systems.

Hence, there is a need for an improved system for pre-tensioning a joint comprising two or more threaded fasteners.

The EP 2421679 B1 discloses a tightening assembly for tightening two fasteners. The torque of the tightening assembly is provided by electric, pneumatic or hydraulic energy and can be adjusted via switches.

The US 4081037 discloses a control system for a multiple spindle machine for simultaneously tightening a plurality of threaded fasteners.

It is an object of the invention to provide an improved system for pre-tensioning a joint by simultaneous and synchronized tightening of two or more threaded fasteners by means of two or more manually supported power wrenches at an improved safety and flexibility.

A further object of the invention is to provide an improved system for pre-tensioning a joint including two or more threaded fasteners by simultaneous and synchronous tightening of the threaded fasteners by two or more manually supported power wrenches communicating with at least one common operation control unit, wherein the system is adaptable to different applications by an increased flexibility.

At least one of these objects or other objects are obtained by the invention as set out in the appended claims.

As has been realized by the inventor, existing systems in which two or more power wrenches are connected via cables to a common control unit have been rather awkward to use, particularly in applications including difficult-to-reach positions where the cables have caused both risky and complicated working situations for the operator or operators, for instance at mounting of lids on large containers, tanks etc. If the cables were removed at least some of these drawbacks could be removed or reduced.

In accordance with a first aspect of the invention, a system for pre-tensioning a joint including two or more threaded fasteners by a synchronized tightening of the threaded fasteners is provided. The system comprises two or more torque delivering power wrenches. Each one of the power wrenches is a manually supported impulse type power wrench. Further each one of the power wrenches is battery powered and comprise a wireless communication module. Each of the power wrenches comprises at least one operation control unit, which comprises a wireless communication module for communicating with the wireless communication modules of the power wrenches to receive operation data from each power wrench and to deliver data to each power wrenches controlling the tightening operation of at least one power wrench in response to the received operation data from the respective power wrenches. Hereby it is achieved that the control of the power wrenches can be performed wirelessly but still in synchronization.

In accordance with one embodiment at least one power wrench is controlled to perform a step-wise tightening operation synchronized with a step-wise tightening operation of the other power wrench or wrenches of the system.

In accordance with one embodiment a number of the power wrenches are arranged in two or more groups for pre-tensioning a multi-fastener joint, and the power wrenches in each group are controlled to perform a simultaneous tightening operation to match in a synchronized way the tightening operation of the power wrenches in another group or groups.

In accordance with one embodiment the at least one operation control unit comprises a separate operation control unit provided at or inside each one of the power wrenches, each one of said separate operation control units is arranged to wirelessly communicate with the separate operation control unit or units of the other power wrench or wrenches of the system.

In accordance with one embodiment at least one operation control unit comprises a single operation control unit communicating with and controlling all of the power wrenches in the system.

In accordance with a second aspect of the invention a control unit for controlling pre-tensioning a joint including two or more threaded fasteners by a synchronized tightening of the threaded fasteners by two or more torque delivering power wrenches is provided. The control unit is in communication with the power wrenches for control of the operation of at least one of the power wrenches. The operation control unit comprises a wireless communication module for communicating with a wireless communication module of the power wrenches. The control unit is adapted to receive operation data from each power wrench and to deliver data to each power wenches controlling the tightening operation of at least one power wrench in response to the received operation data from the respective power wrenches.

In accordance with one embodiment the control unit is adapted to control the at least one power wrench to perform a step-wise tightening operation synchronized with a step-wise tightening operation of at least one other power wrench used in a synchronized tightening of the threaded fasteners.

In accordance with one embodiment, when a number of the power wrenches controlled by the unit are arranged in two or more groups for pre-tensioning a multi-fastener joint, the control unit is adapted to control the power wrenches in each group to perform a simultaneous tightening operation to match in a synchronized way the tightening operation of the power wrenches in another group or groups.

In accordance with one embodiment the control unit is a stand-alone device.

In accordance with one embodiment the control unit is a separate operation control unit provided at or inside a power wrench. The control unit is arranged to wirelessly communicate with at least one other separate operation control unit.

In accordance with a third aspect a power wrench provided with a wireless communication module adapted to wirelessly transmit operation data from a synchronized tightening of the threaded fasteners performed by the power wrench and at least one other power wrench is provided.

In accordance with one embodiment the wireless communication module is adapted to wirelessly transmit said operation data to a common control unit for control of the synchronized tightening.

In accordance with one embodiment the wireless communication module is adapted to wirelessly transmit said operation data to the at least one other power wrench.

In accordance with one embodiment the power wrench comprises a control unit adapted to control a synchronized tightening performed by the power wrench in response to control data wirelessly received from said at least one other power wrench.

Further objects and advantages of the invention will appear from the following specification and claims.

The invention will now be described in more detail by means of exemplary embodiments and with reference to the accompanying drawings, in which

• Fig. 1 illustrates the main components of a system for tightening of two or more threaded fasteners by means of two or more manually supported power wrenches, and
• Fig. 2 is a schematic view of a control unit.

In Fig. 1 a system 1 for pre-tensioning a joint 13 including two or more threaded fasteners 11a - c by a synchronized tightening of the threaded fasteners is depicted. The system illustrated in Fig. 1 comprises three manually supported and battery powered power wrenches 10 a-c which are to be applied on a number of threaded fasteners 11 a-c. The threaded fasteners 11 a-c are parts of a joint 13 wherein two elements 14, 15 are to be put together by a clamping force obtained by the threaded fasteners 11 a-c. Preferably, the power wrenches 10 a-c are of the torque impulse delivering type which do not generate any reaction forces, which makes it possible for an operator to operate two wrenches at a time. But the power wrenches 10 a-c can also be of the torque delivering type. Each one of the power wrenches 10 a-c carries not only a detachable battery casing but also a non-illustrated internal means for indicating actual operation data like output torque, angular displacement etc. These features are well known in prior art, and are therefore not further described herein.

Each one of the power wrenches 10 a-c comprises a wireless communication module 16a - c for communication with a common operation control unit 18. Since it is well known per se to provide battery powered power wrenches with equipment for wireless communication with an operation control unit that feature is not described in further detail.

In Fig. 2, the control unit 18 is schematically shown. The control unit 18 comprises a control circuit programmed with operation data suitable for the actual tightening operation, and a comparing circuit by which the outgoing control data for each power wrench are adapted to the received actual operation data from the other power wrenches. The control circuit and the comparing circuit can for example be implemented using a processor 20 connected to a memory 22 on which a computer program is stored that when executed by the processor causes the control circuit and comparing circuit to perform the above tasks. The control unit 18 is in accordance with one embodiment further arranged to identify the actual status of each one of the wrenches during a tightening sequence to control the tightening operation of the other power wrench or wrenches in response thereto, and to complete the predetermined tightening sequence via a synchronized tightening of the threaded fasteners 11 a-c. The control unit 18 is provided with a wireless communication module 24 adapted to wirelessly transmitting and receiving data to/from the respective power wrenches 10a - 10 c. The wireless communication module can be operatively connected to the control circuit. By such a synchronized tightening there is obtained an evenly distributed clamping force in the joint 13, which is particularly important at joints having deformable sealing elements in the form of gaskets or the like where it is essential to avoid an uneven setting of such elements.

According to the the invention the operation control unit is formed by separate control units 18 located at or inside the power wrenches themselves, which means that operation data and identification of the present status of the other power wrenches are received and compared by each one of the separate control units 18 in a distributed manner. This arrangement will contribute to an even more flexible system.

The synchronized tightening of the threaded fasteners 11 a-c may very well be executed continuously or in steps as long as the tightening operation performed by each one of the power wrenches 10 a-c is kept up with the operation of the other power wrenches to accomplish an evenly distributed clamping force in the joint 13.

Alternatively, if a number of power wenches are used for pre-tensioning a multi-fastener joint the wrenches could be arranged in groups, whereby a synchronized tightening could be performed by controlling a simultaneous tightening operation of the power wrenches of one group in relation to a simultaneous tightening of the power wrenches in another group or groups. In this case too, the synchronized tightening aims to obtain an evenly distributed clamping force in the joint.

By providing a system for synchronized tightening of a number of threaded fasteners of a joint by two or more battery powered power wrenches having wireless communication modules for communication with at least one operation control unit it is possible to accomplish a flexible joint pre-tensioning system with no cable related problems as to the adaptability and operation of the system.