BOLT TENSIONING TOOL

Abstract

The present specification relates to a bolt tensioning tool adapted to tension a bolt protruding from a workpiece, and comprising a bolt receiving element (5) adapted to be screwed onto the bolt, a nut socket (10) adapted to receive a nut, an axle (3) adapted to exert an axial force on the bolt receiving element, a threaded sleeve (6) arranged to engage the axle and having an internal thread (6a) adapted to cooperate with an external thread (3a) of the axle (3) such that a relative rotational movement there between results in a relative axial displacement between the axle and the threaded sleeve, a supporting sleeve (2) coupled to the threaded sleeve and adapted to selectively bear against the workpiece and a coupling (9) adapted to connect the nut socket and the supporting sleeve, the coupling is a coupling allowing a limited relative movement between the socket and the sleeve.

Claims

1-15. (canceled)

16. A bolt tensioning tool adapted to tension a threaded bolt or pin protruding from a workpiece, the tool comprising: a bolt receiving element having an internal thread adapted to be screwed onto the threaded bolt or pin; a nut socket adapted to receive a nut to be screwed onto the bolt, an axle coupled to, and adapted to exert an axial force on, the bolt receiving element, the axle comprising an external thread; a threaded sleeve arranged to engage the axle and having an internal thread adapted to cooperate with the external thread of the axle such that a relative rotational movement between the axle and the threaded sleeve result in a relative axial displacement between the axle and the threaded sleeve; a supporting sleeve coupled to the threaded sleeve and adapted to at a first end selectively bear against the workpiece such that a reaction force may be transmitted to work piece, thereby counteracting the axial force exerted on bolt by axle; and a coupling adapted to connect the nut socket and the supporting sleeve, wherein the coupling is a coupling allowing a limited relative movement between the nut socket and the supporting sleeve.

17. The bolt tensioning tool according to claim 16, wherein the limited relative movement is a limited relative axial and rotational movement and wherein the coupling comprises a resilient element adapted to provide at least the limited relative rotational movement, the element engaging the supporting sleeve and the socket.

18. The bolt tensioning tool according to claim 17, wherein the resilient element is a spring element engaging at a first end the socket and at a second end the supporting sleeve.

19. The bolt tensioning tool according to claim 18, wherein a first end of the spring engages the socket and wherein a second end of the spring engages a longitudinal slot in the supporting sleeve.

20. The bolt tensioning tool according to claim 16, wherein the external thread on the axle is oriented in a direction opposite to a direction of rotation of the motor.

21. The bolt tensioning tool according to claim 16, wherein the axle and the threaded sleeve form an actuating screw mechanism, and wherein the actuating screw mechanism is a planetary roller screw further comprising at least one threaded roller arranged between the internal thread of the threaded sleeve and the external thread on the axle.

22. The bolt tensioning tool according to claim 16, further comprising an outer sleeve at least partly enclosing the bolt receiving element.

23. The bolt tensioning tool according to claim 16, wherein the bolt receiving element further comprises: a first member coupled to the axle; a second member comprising a cavity having an internal thread adapted to be screwed onto the threaded bolt or pin and a coupling selectively connecting the first and second member.

24. The bolt tensioning tool according to claim 23, wherein the coupling is a torque-limited coupling between the first member and the second member, such that that a limited rotational torque may be transferred by the coupling.

25. The bolt tensioning tool according to claim 24, wherein the outer sleeve is coupled to the second member, and wherein the torque-limited coupling is provided between the first member and the outer sleeve.

26. The bolt tensioning tool according to claim 16, wherein the nut socket is arranged to bear against the bolt receiving element.

27. The bolt tensioning tool according to claim 26, wherein the nut socket is arranged to bear against the bolt receiving element via a bearing, such that the nut socket is rotationally decoupled from the bolt receiving element.

28. The bolt tensioning tool according to claim 18, wherein the coupling between the nut socket and the spring element is a one-way coupling such that a first end of the spring element engages the nut socket when the socket rotates in a first direction and disengages the nut socket when the socket rotates in a second, opposite direction.

29. The bolt tensioning tool according to claim 16, further comprising means for measuring the axial force exerted on the bolt.

30. The bolt tensioning tool according to claim 29, wherein the means for measuring the axial force comprises an ultrasonic measurement device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The invention will be better understood through the following illustrative and non-limiting detailed description of preferred embodiments, with reference to the appended drawing, on which:

[0040] FIG. 1 is a cross sectional view, along axle, of a bolt tensioning tool according to one embodiment in more detail.

[0041] FIG. 2 is a cross sectional view, normal to axle, of a bolt tensioning tool according to one embodiment in more detail.

[0042] All figures are schematic, not necessarily to scale and generally only show parts which are necessary in order to elucidate the invention, wherein other parts may be omitted or merely suggested.

DETAILED DESCRIPTION

[0043] A bolt tensioning tool according to one embodiment of the invention is shown in FIGS. 1 and 2. The illustrated exemplary embodiment is adapted for tightening of a M10 screw, where the desired clamp load lies in the range 30-40 kN.

[0044] The tool comprises a supporting sleeve 2 adapted at a first end 2a to bear against the surface of the workpiece and a nut socket 10 adapted to receive a nut to be screwed onto the bolt and arranged to bear against a bolt receiving element 5 having an internal thread to be screwed onto the threaded bolt to provide a connection between the tensioning tool and the bolt. Further, an axle 3 is coupled to, and adapted to exert an axial force on, the bolt receiving element and comprises an external thread (not shown). A threaded sleeve 6 comprising an internal thread 6a for cooperation with the external thread, hereby forming a screw type actuator, is in turn connected to the supporting sleeve 2.

[0045] The illustrated embodiment further comprises means MO for applying a rotational movement to the axle 3, in the illustrated embodiment in the form of an intermediated axle MO which may be connected for example to an output shaft of a motor (not shown). A spring element 9a, in the illustrated embodiment a torsional spring 9a in the form of a winded steel wire is arranged between the nut socket 10 and the supporting sleeve 2.

[0046] FIG. 1 shows a number of the components in a cross sectional view of an assembled state of the bolt tensioning tool. As can be seen from FIG. 1, most components are arranged inside (or surrounded by) the surrounding sleeve 2, and the axle 3 extends through the supporting sleeve 2 from the threaded sleeve 6 to the bolt receiving element 5. The torsion spring 9a is arranged on and attaches to the nut socket 10 which in turn bears against the bolt receiving element 5.

[0047] In the illustrated embodiment, the bolt receiving element 5 comprises a first element 5a connected by suitable means to the axle, in the illustrated the first element 5a is fixedly coupled to the axle, a second element 5b comprising the cavity having internal threads and hence being adapted to be attached to the bolt or threaded element and an outer sleeve 7 surrounding, or enclosing, the first and second element. Further, a torque-limiting coupling is arranged between elements 5a and 5b to selectively connect them, such that that a limited rotational torque may be transferred between the elements 5a, 5b. In the illustrated embodiment, the outer sleeve 7 is fixed (i.e. fixedly coupled) to the second element 5b, and the torque-limited coupling (not shown) is provided between element 5a and the outer sleeve 7, for example in the circumferential groove in element 5a. In the exemplary case shown in FIG. 1, the torque limiting coupling is an O-ring (not shown) provided between elements 5a and sleeve 7.

[0048] Additional components illustrated include an axial bearing 13 provided between element 5a and a rear surface of sleeve 7 and a friction reducing element 14 provided between the bolt (not shown) and a portion of the bolt receiving element 5.

[0049] FIG. 1 also shows the torsion spring 9a comprising a first end for engaging the nut socket and a second end for engaging the supporting sleeve 2.

[0050] The nut socket 10 comprises a first surface 101 adapted to bear against a surface of the workpiece surrounding the bolt and a second opposite surface forming part of a supporting heel for the torsion spring 9a. Further, the upper part of the socket is adapted to engage the end of the spring by means of what may be described as a one-way coupling in that the upper portion comprises an asymmetric heel (a radial projection arranged on a circumferential surface of said nut socket) adapted to engage the first end of the torsion spring when the socket rotates in a first (in this case clockwise) direction and not engage the end when rotation in the opposite direction occurs.

[0051] In the cross section shown in FIG. 2, the rollers 15 of the planetary roller screw formed by the axle 3, the threaded sleeve 6 and a number of threaded rollers 15 arranged between the internal thread of the threaded sleeve 6 and the external thread 3a on the axle 3 are shown. The illustrated embodiment comprises six rollers 15.

[0052] The functionality of an exemplary embodiment of the bolt tensioning tool will now be described

[0053] In general, a rotational movement from a motor output shaft is applied to the axle 3, in the illustrated embodiment by means of additional axle MO, and in an unloaded situation, for example when driving the tool without engaging the nut and/or bolt, axle 3 rotates along with the other described components i.e. the bolt receiving element 5, outer sleeve 7, the nut socket, the threaded sleeve and the supporting sleeve 2 and substantially no relative rotation occurs there between.

[0054] When the tightening operation, more particularly the tensioning operation is started, the nut socket, preferably having a shape corresponding to and allowing for a form fit with a nut such as for example a hexagonal shape, is applied over the nut thereby causing the nut to rotate and be brought into contact with a contact surface of the workpiece and the bolt receiving element is screwed onto the threaded element protruding from the work piece, hereby establishing a coupling between the tool and the threaded element necessary in order to enable exertion of the tensioning force on the threaded element.

[0055] As the nut socket is initially seated against the work piece, the socket will during a phase of the process bear against the contact surface while the supporting sleeve still remains at a slightly elevated position as compared to the contact surface and continues to rotate freely.

[0056] Up to this stage, the rotation is synchronous between all components (except the nut socket). However, as the bolt receiving element 5 and more particularly the second, or front, part 5b of the bolt receiving element is completely screwed onto the bolt the torque transferred over the torque-limiting coupling (not shown), e.g. an O-ring, increases and the coupling slips and the front part 5b and hence the thereto connected sleeve 7 become decoupled from the first element 5aand remain stationary. The axle 3 and first element 5a, the threaded sleeve 6 and the supporting sleeve 2 however continue to rotate.

[0057] More particularly, the supporting sleeve 2 now rotates against the resistant of torsion spring 9a, the torsion spring 9a being arranged between the now still standing nut socket and the (rotating) supporting sleeve 2. However, the allowed relative rotation is a limited relative rotation as the spring only allows or a certain amount of deformation and the rotation of the supporting sleeve 2 is stopped.

[0058] Consequently, the rotation of the threaded sleeve 6 is stopped due to the coupling between sleeve 6 and supporting sleeve 2. This happens as the torque due to the resistance to rotation provided by the spring element 9a is larger than the torque provided by the frictional resistance in the planetary roller screw. As the rotation of the threaded sleeve is stopped and relative rotation between the axle which continuous to be rotated by the motor and the threaded sleeve therefore occurs, initially the sleeve 2 is brought into contact with the contact surface of the workpiece and thus forms a support counteracting the tensioning force about to be applied, i.e. handling the reaction forces. The axial movement of the supporting sleeve 2 necessary to achieve this contact is achieved due to the external thread on the axle 3 being oriented in a direction opposite to the direction of rotation of the motor (in the illustrated embodiment the external thread is a left hand thread and the direction of rotation is clockwise). Hence, a rotation provided in a clockwise direction to the axle 3 (the threaded sleeve 6 being locked) results in a movement of the supporting sleeve 2 in a direction towards the workpiece.

[0059] The step bringing the sleeve 2 into contact with the surface is followed by the actual tensioning of the bolt, as after the support sleeve 2 is seated against the contact surface and therefore obviously cannot move further in a direction towards the workpiece, relative rotation between the axle and the threaded sleeve now instead (again due to the orientation of the thread, results in axial displacement of the axle 3 in a direction away from the contact surface, hereby exerting an axial tensioning force on the bolt.

[0060] During the tensioning phase, as the bolt is tensioned the nut arranged on the bolt is consequently lifted off the contact surface as the bolt extends. The spring element 9a however keeps the nut locked/seated against the contact surface of the workpiece due to the bias/spring force created as the sleeve 2 was rotated with respect to the nut socket. This force continuously “pulls” on the nut, and therefore brings or even hold the nut seated stage against the surface.

[0061] When the desired clamp load is achieved, the bolt tensioning tool may be removed. This is achieved by reversing the direction of rotation of the motor, in this case into a counterclockwise rotation. Initially, this causes the tension over the planetary roller screw to be released which in turn implies that the rotation of the nut socket 10 is stopped. This since the supporting sleeve 2 is no longer pressed towards the workpiece surface and is hence allowed to rotate (i.e. the rotation is not locked anymore). But, since the nut socket 10, is arrange on the nut, the socket 10 cannot rotate and accordingly, it must be provided an engagement between the connecting element, in this case the spring 9a, and the nut socket 10 allowing for an unlimited relative rotation in this opposite, counterclockwise direction. This is why the coupling in the illustrated embodiment comprises a design providing the one-way functionality described in the foregoing such that a first end of the spring element is engaged by the nut socket when the socket rotates in a first direction and not engaged by the nut socket when the socket rotates in a second opposite direction. As mentioned above, in the illustrated embodiment this is accomplished by a number of protrusions, or shoulders, arranged along a periphery of the nut socket. The shape of these protrusions is such that the first end of the spring 9a when rotation in a clockwise direction engages a surface extending in substantially radial direction and thus allowing the spring 9a to engage the shoulder in rotation and in rotation in a counterclockwise direction slides along an inclined portion of said shoulder thus allowing for a rotation of the supporting sleeve 2 in a counterclockwise direction without engagement between the socket 10 and the spring 9a. Hereby, the bolt receiving element 5 which is screwed onto the thread of the bolt, may be rotated and the tool 1 may eventually be removed. As the bolt engaging element 5 is completely unscrewed from the bolt, the nut socket 10 may also be removed.

[0062] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiment. The skilled person understands that many modifications, variations and alterations are conceivable within the scope as defined in the appended claims.

[0063] Additionally, variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, form a study of the drawings, the disclosure and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope of the claims.