Pulse tool

Abstract

According to an aspect, a pulse tool (1) for tightening threaded fasteners is provided. The pulse tool (1) comprises a motor (2); an output shaft (3); a control device (5) configured to control the motor (2) to output torque in pulses; and a torque limiting clutch (10) arranged to transfer torque from the motor (2) to the output shaft up to a predetermined clutch release torque, wherein the torque limiting clutch (10) has an inherent play. The motor (2) accelerates within the range of the inherent play of the torque limiting clutch (10) during the pulses.

Description

[0001] PULSE TOOL

[0002] Field of the invention

[0003] The present invention generally relates to the field of pulse tools for tightening threaded fasteners. of the invention

[0004] In various industries, pulse tools are used to tighten threaded fasteners with reduced ergonomic stress for the operators. A pulse tool delivers the torque in pulses, which reduces the reaction force exerted on the operator. Pulse tools are also known for their high precision in achieving a desired target torque as compared to e.g. impact wrenches. Traditionally, such pulse tools have been of the hydraulic type that comprises a hydraulic coupling mechanism for producing the torque pulses. The motor in such tools is driven with a continuous relatively low torque, which is translated by the hydraulic coupling into torque pulses of significantly higher toque on the output shaft. Lately, also so called direct driven pulse tools has been developed. Instead of having a hydraulic coupling mechanism for providing the pulses, the motor is driven in a pulsed manner. The motor then accelerates within a play provided in the drivetrain of the tool during the pulses. During the acceleration, inertia is built up and, as the play closes, the torque is delivered as a pulse to the output shaft. Such direct driven pulse tools suffer from relatively high vibration levels and limitations in how high torque the tool can deliver. of the invention

[0005] It would be advantageous to achieve a pulse tool overcoming, or at least alleviating, the above mentioned drawbacks. In particular, it would be desirable to enable a pulse tool that is capable of delivering higher torque. It would also be desirable to enable a pulse tool that produces less vibrations when operated.

[0006] To better address one or more of these concerns, a pulse tool having the features defined in the independent claim is provided. Preferable embodiments are defined in the dependent claims.

[0007] Hence, according to an aspect, a pulse tool for tightening threaded fasteners is provided. The pulse tool comprises a motor; an output shaft; a control device configured to control the motor to output torque in pulses; and a torque limiting clutch arranged to transfer torque from the motor to the output shaft up to (but not over) a predetermined clutch release torque, wherein the torque limiting clutch has an inherent play. The motor accelerates within the range of the inherent play of the torque limiting clutch during the pulses.

[0008] In traditional direct driven pulse tools, the play required to accelerate the motor in the pulses is typically provided either by the play inherent in the gears of the tool and / or by a particular mechanical arrangement having the sole purpose of providing the play. The inventors have realized that using a torque limiting clutch to provide the required play has the benefit that the relatively large play typically provided in such clutches allows for a relatively large acceleration of the motor in the pulses, which in turn provides a relatively high torque output. A further benefit is that the torque limiting clutch may produce slightly less vibrations, and also absorb some of the vibrations produced, as the gap closes.

[0009] According to an embodiment, the control device may be configured to control the motor: in a primary drive direction (forward or reverse) during said pulses so as to deliver a fastening torque or a loosening torque to the fastener, and in a direction opposite to said primary direction between said pulses so as to at least partly open the play between the pulses. Hence, the motor may be utilized to reopen the play between the torque pulses.

[0010] According to an embodiment, the torque limiting clutch may comprise: a motor driven part arranged to be driven by the motor, and an output driving part arranged to drive the output shaft. The motor driven part and the output driving part may be arranged to, at least indirectly, engage with each other, whereby the clutch is closed, and disengage with each other, whereby the clutch is open. Further, the torque limiting clutch may be arranged such that: (only) a limited relative rotation between the motor driven part and the output driving part is allowed as long as the torque is below said predetermined clutch release torque and the clutch is closed, wherein said relative rotation forms said play, and such that full (unlimited) relative rotation between the motor driven part and output driving part is allowed as long as the torque is above said predetermined clutch release torque and the clutch is open.

[0011] For example, the motor driven part and the output driving part may be arranged to, at least indirectly, engage / cooperate so as to be enable transfer of torque therebetween when the clutch is closed (that is, as long as the torque is below the predetermined clutch torque).

[0012] For example, the relative rotation may be limited to less than 180 degrees, such as less than 120 degrees.

[0013] According to an embodiment, at least one of the motor driven part and the output driving part may comprise a cam profile with one or more lobes. The torque limiting clutch may further comprise a spring element arranged to urge one of the motor driven part and the output driving part towards the other, and one or more intermediate elements (such as one or more rolling elements, e.g. one or more balls) arranged between the motor driven part and the output driving part to cooperate with the lobes of the cam profile so as to transfer torque between the motor driven part and the output driving part up to said clutch release torque. The motor driven part and the output driving part may be adapted (such as shaped) such that the one or more intermediate elements are allowed to move in a circumferential direction (of the motor driven part and the output driving part) within a range limited by the one or more lobes when the torque is below the clutch release torque.

[0014] The one or more intermediate elements being allowed to move in the circumferential direction within the range limited by the one or more lobes as the clutch is closed may provide (at least a major part of) the play inherent in the clutch that is utilized for accelerating the motor during the pulses.

[0015] The cam profile may be shaped / adapted in different ways for contributing to opening or closing the play.

[0016] According to an embodiment, a portion of the cam profile (between the one or more lobes) may be shaped (such as inclined) such that the force of the spring element (urging one of the motor driven part and the output driving part towards the other) urges the one or more intermediate elements to cooperate with the cam profile such that said play is at least party opened between the pulses when the motor is driven in a tightening (forward) direction during the pulses.

[0017] With this embodiment, the motor may not necessarily be controlled to rotate in the reverse direction between the pulses for re-opening the play. Rather, the shape of the cam profile may be adapted such that the one or more intermediate elements is forced, under the urging force of the spring element, in a direction that contributes to open the play between the pulses in the forward direction. Hence, a facilitated motor control is provided. The present embodiment is also advantageous in that it is possible to predict the idle (i.e. rest) position for the one or more intermediate elements, and thereby also the relative rotational position of the motor driven part and the output driving part. This may be beneficial for further control of the tool.

[0018] According to an embodiment, a further portion of the cam profile (between the one or more lobes) may be shaped (such as inclined) such that the force of the spring element (urging one of the motor driven part and the output driving part towards the other) urges the one or more intermediate elements to cooperate with the cam profile such that said play is at least party opened between the pulses also when the motor is driven in a loosening (reverse) direction during the pulses.

[0019] With the present embodiment, the play will be automatically re-opened between the pulses also when the tool is driven in the reverse direction without requiring the motor to be controlled in the forward direction between the pulses. Hence, a facilitated motor control is provided.

[0020] Said portions may e.g. be inclined towards a point in between the lobes such that the intermediate element is urged away from the lobes, towards said point under the pressure from the spring element. For example, the cam surface may be V- or U-shaped with the peak pointing away from the opposing one of the motor driven part and the output driving part.

[0021] According to an embodiment, a portion of the cam profile (between the one or more lobes) may be shaped (such as inclined) such that the force of the spring element (urging one of the motor driven part and the output driving part towards the other) urges the one or more intermediate elements to cooperate with the cam surface so as to aid in (contribute to) closing said play during the pulses when the motor is driven in a tightening (forward) direction during the pulses.

[0022] With the present embodiment, the urging force of the spring element will be converted, via the one or more intermediate elements cooperating with the shape of the cam profile, to a torque that adds to the torque provided by the motor in the forward direction. This addition to the torque pulse enables the tool to deliver a higher torque output.

[0023] According to an embodiment, a further portion of the cam profile (between the one or more lobes) may be shaped (such as inclined) such that the force of the spring element (urging one of the motor driven part and the output driving part towards the other) urges the one or more intermediate elements to cooperate with the cam profile so as to aid in closing said play during the pulses also when the motor is driven in a reverse direction during the pulses.

[0024] With the present embodiment, the urging force of the spring element will be converted, via the one or more intermediate elements cooperating with the shape of the cam profile, to a torque that adds to the torque provided by the motor in the reverse direction. This addition to the torque pulse enables the tool to deliver a higher torque output also in the loosening (reverse) direction. Said portions may e.g. be inclined towards a point in between the lobes such that the intermediate element is urged towards one of the lobes, away from said point under the pressure from the spring element. For example, the cam surfaces may be V- or U-shaped with the peak pointing towards the opposing one of the motor driven part and the output driving part. For example, the cam surface may be shaped as a crest between the lobes.

[0025] It is noted that embodiments of the invention relate to all possible combinations of features recited in the claims.

[0026] Brief description of the drawings

[0027] This and other aspects will now be described in more detail in the following illustrative and non-limiting detailed description of embodiments, with reference to the appended drawings.

[0028] Figure 1 shows a pulse tool according to an embodiment.

[0029] Figure 2a shows a torque limiting clutch of the pulse tool according to an embodiment.

[0030] Figure 2b shows an exploded view of the torque limiting clutch of Figure 2a.

[0031] Figure 2c shows a cross-section of the torque limiting clutch of Figure 2a.

[0032] Figure 3 shows a motor driven part, an intermediate element and an output driving part of a torque limiting clutch according to an embodiment.

[0033] Figure 4 shows a motor driven part, an intermediate element and an output driving part of a torque limiting clutch according to another embodiment.

[0034] Figure 5 shows a motor driven part, an intermediate element and an output driving part of a torque limiting clutch according to yet another embodiment.

[0035] Figure 6 shows a motor driven part, an intermediate element and an output driving part of a torque limiting clutch according to yet another embodiment.

[0036] All the figures are schematic, not necessarily to scale, and generally only show parts which are necessary in order to elucidate the embodiments, wherein other parts may be omitted. Like reference numerals refer to like elements throughout the description.

[0037] Detailed description of embodiments

[0038] A pulse tool 1 according to an embodiment will be described with reference to Figure 1. The pulse tool 1 comprises a motor 2 (such as an electric motor) drivingly connected to an output shaft 3. The output shaft 3 may be adapted to receive a socket / bit adapted to fit a threaded fastener (such as a screw, bolt or nut). The pulse tool 1 may e.g. be powered by a battery or via an electric cable.

[0039] The pulse tool 1 is provided with a torque limiting clutch 10 (which hereinafter sometimes may be referred to simply as a clutch) that is arranged to, in a closed mode, transfer torque from the motor 2 to the output shaft 3 up to a clutch release torque. As the torque exceeds the clutch release torque, the clutch will stop transferring torque, and may then be referred to as open / released.

[0040] The pulse tool 1 may optionally be provided with a gear 4 (such as a planetary gear as in the illustrated example) arranged in the torque transfer path between the motor 2 and the output shaft 3. For example, the gear 4 may be arranged between the torque limiting clutch 10 and the motor 2.

[0041] The pulse tool 1 further comprises a control device 5 configured to control the motor 2 in a pulsed manner. The control device 5 may comprise processing means and a memory.

[0042] Turning to Figures 2a to 2c, embodiments of the torque limiting clutch 10 will be further described and exemplified. The clutch 10 may comprise a motor driven part 11 drivingly connected to the motor 2 (optionally via gears 4) and an output driving part 12 drivingly connected to the output shaft 3. These may be arranged to, at least indirectly, engage with each other so as to transfer torque from the motor 2 to the output shaft 3 as long as the torque is lower than the clutch release torque. The clutch 10 may then be referred to as closed. As the clutch 10 is closed, a limited relative rotational movement may be allowed between the motor driven part 11 and the output driving part 12. This limited relative movement may be referred to as a play inherent in the clutch 10. As the torque exceeds the clutch release torque, full relative rotational movement is allowed between the motor driven part 11 and the output driving part 12. The clutch 10 may then be referred to as open / released.

[0043] As the control device 5 drives the motor 2 to output torque pulses, the motor 2 is allowed to accelerate within the play of the clutch 10 during the pulses. One pulse cycle may be realized according to the following. At the start of the cycle, the play of the clutch (and preferably also any play inherent in the rest of the driveline of the tool 1) is open (such as fully open) and the torque of the motor 2 is (at least close to) zero. The motor 2 is then controlled to output a torque pulse, whereupon the motor 2 accelerates together with the motor driven part 11 (and any gear 4 provided in the drivetrain of the tool) such that the play is closed, whereupon the motor driven part 11 engages with the output driving part 12. At the time of engagement, the torque built up in the driveline during the acceleration (in the motor 2, any gear 4, the motor driven part 11 and any shafts therebetween) is transferred in one go to the output driving part 12, which in turn transfers the resulting torque pulse to the output shaft 3. Before starting another pulse cycle, the play may be re-opened, e.g. by controlling the motor 2 in the opposite direction. The motor driven part 11 is thereby turned relative to the output driving part 12 such that the play opens again. Another pulse cycle may then be performed. Once the set clutch release torque is achieved, full rotation is allowed between the motor driven part 11 and the output driving part 12, whereby torque is no longer transferred therebetween.

[0044] The torque limiting clutch 10 may be designed in different ways. For example, one of the motor driven part 11 and the output driving part 12 may comprise a cam profile 23 (see Figure 2b). In the illustrated example, the cam profile 23 is provided in the output driving part 12. The following examples is equally applicable should the cam profile 23 be provided in the motor driven part 11. For example, the cam profile 23 may be provided along a track 25 extending circumferentially in (that is, along a circumference of) the output driving part 12. The cam profile 23 may comprise one or more lobes 24. For example, the lobes 24 may be arranged along the track 25. In case there are several lobes 24, they may preferably be evenly distributed around the circumference of the output driving part 12.

[0045] The torque limiting clutch 10 may comprise one or more intermediate elements 13, such as balls 13. The one or more intermediate elements 13 may be arranged to cooperate with geometrical features of the motor driven part 11 and the motor driven part 11 so as to engage these two parts 11, 12 together to transfer torque therebetween.

[0046] For example, the one or more intermediate elements 13 may be held in recesses 20 formed in the one of the motor driven part 11 and the output driving part 12 not comprising the cam profile 23 (which in the illustrated example is the motor driven part 11). The shape of the recesses 20 may match the shape of the intermediate elements 13 such the intermediate elements 13 are prevented from movement relative to the motor driven part 11 but only allowed to rotate around their own center.

[0047] The one or more intermediate elements 13 may be arranged to move (such as roll) along the cam profile 23, such as along the track 25. The one or more intermediate elements 13 may be arranged to cooperate with the cam profile 23 so as to transfer torque from the motor driven part 11 to the output driving part 12. For example, the one or more intermediate elements 13 may be arranged to engage with the one or more lobes 24 to transfer torque from the motor driven part 11 to the output driving part 12. The number of lobes 24 may equal the number of intermediate elements 13. For example, there may be three lobes 24 and three intermediate elements 13 for providing enhanced stability between the motor driven part 11 and the output driving part 12 as well as a relatively large play.

[0048] The clutch 10 may further comprise a spring element 14 arranged to urge one of the motor driven part 11 and the output driving part 12 towards the other. In the illustrated example, the spring element 14 is arranged to urge the output driving part 12 towards the motor driven part 11. The spring element 14 may urge the cam profile 23 into contact with the one or more intermediate elements 13. For example, the spring element 14 may be a coil spring extending around the output shaft 3. Optionally, the tool 1 may further comprise a spring element adjustment mechanism 21 arranged to adjust the pre-tension of the spring element 14. The spring element adjustment mechanism 21 may e.g. comprise a support ring 16 arranged to support one end of the spring element 14, and an adjustment nut 15 threaded onto the output shaft 3 and supporting the support ring 16. Thus, by rotating the adjustment nut 15, the position of the support ring 16 along the axial direction A-A will be adjusted, whereby the pre-tension of the spring element 14 will be adjusted. The pre-tension of the spring element 14 dictates the clutch release torque. The higher pre-tension, the higher clutch release torque is provided.

[0049] The output driving part 12 may be supported with respect to the motor driven part 11 so as to allow relative rotation therebetween, e.g. by means of balls 19 running in tracks / recesses provided in the motor driven part 11 and the output driving part 12.

[0050] For example, the output driving 12 part may be rotationally locked to the output shaft 3 by one or more balls 17 held in mating recesses 26 formed in the output driving part 12 and recesses 21 formed in the output shaft 3. The recesses 26, 21 may be shaped such that the balls 17 are prevented from movement in the circumferential direction of the output driving part 12 and the output shaft 3, but allowed to a limited axial movement (in direction A-A) to allow a slight axial movement of the output driving part 12 relative to the output shaft 3 so as to allow the intermediate elements 13 to pass the lobes 24 when the clutch release torque is exceeded.

[0051] The motor driven part 11 may be held in a housing of the tool 1 by means of a bearing 18.

[0052] During operation, the motor 2 may rotate / turn the motor driven part 11 in a primary direction (tightening or loosening direction), whereby the one or more intermediate elements 13 moves along with the motor driven part 11 in the circumferential direction along the cam profile 23, such as along the track 25 of the output driving part 12. This movement of the motor driven part 11 and the one or more intermediate elements 13 relative to the output driving part 12 serves to close the play in the clutch 10. As the one or more intermediate elements 13 encounter the one or more lobes 24 of the cam profile 23, the limitation of this relative movement is reached, the play is closed and the one or more intermediate elements 13 engages with the one or more lobes 24, whereby the torque is transferred (in one go) from the motor driven part 11, via the one or more intermediate elements 13 to the output driving part 12. Then, the motor 2 may be controlled to rotate / turn in a direction opposite to the primary direction, whereby the motor driven part 11 and the one or more intermediate elements 13 move in the opposite circumferential direction along the cam profile 23, such as along the track 25, of the output driving part 12. This movement of the motor driven part 11 and the one or more intermediate elements 13 relative to the output driving part 12 serves to open the play in the clutch 10. Thus, the intermediate elements 13 are forced (along the cam profile 23) away from the lobes 24. This procedure (with closing and opening the play to deliver torque pulses) may be repeated until the clutch release torque is reached. As that happens, the resistance for the output driving part 12 to rotate / turn due to the level of torque installed in the fastener, as well as the level of torque delivered from the motor 2, will be so high that the urging force of the spring element 14 will be overcome as the one or more intermediate elements 13 is forced to, instead of engaging with the one or more lobes 24, pass them, whereby no torque will be transferred from the motor driven part 11 to the output driving part 12. This may be referred to as the clutch 10 being released.

[0053] According to one embodiment, the cam profile 23 portion between the lobes 24 (that is, the portion extending from one lobe 24 to another) has no variations in the axial direction A. In other words, the (complete) cam profile 23 portion between the lobes 24 may be normal to the axial direction A. This implies that the intermediate element 13 may move along the portion (between the lobes 24) without the urging force of the spring element 14 urging it in any particular direction.

[0054] Alternatively, the cam profile may be shaped so as to either aid in re-opening the play of the clutch between the pulses or to aid in closing the play during the pulses. This will be described in more detail in the following with reference to Figures 3-6, which all illustrates the motor driven part 11 and the output driving part 12 as seen from the side.

[0055] According to an embodiment, illustrated in Figure 3, the portion 27a of the cam profile between the one or more lobes 24a, 24b may be shaped in an inclined manner (with respect to an imaginary plane P normal to the axial direction of the tool) such that the force S of the spring element urges the one or more intermediate elements 13 to cooperate with the cam portion 27a such that the play is at least party opened between the pulses when the motor is driven in a forward (tightening) direction F during the pulses.

[0056] When the motor has closed the gap (during a pulse), the intermediate element 13 will be in position C and engage with a lobe 24a so as to transfer torque from the motor driven part 11 to the output driving part 12 (in the forward direction F). After the pulse, the torque from the motor may be reduced to zero, whereby the urging force S of the spring element will push the intermediate element 13 (and the motor driven part 11) along the inclined portion 27a in the reverse direction R to position 0, where it will be stopped by another lobe 24b (or the other side of the lobe in embodiments where there is only one lobe). When the intermediate element 13 is in this position 0, the play of the clutch is open. Due to the shape of the cam profile portion 27a, position 0 is the idle position of the intermediate element 13 to which it will return to if no torque is applied from the motor.

[0057] Accordingly, with the present embodiment, the play of the clutch will be automatically re-opened between the pulses by the force from the spring element without the motor having to necessarily be controlled in the reverse direction. According to an embodiment, illustrated in Figure 4, the cam profile between the one or more lobes 24a, 24b may comprise a further inclined portion 27b (being inclined with respect to an imaginary plane P normal to the axial direction of the tool) such that the force S of the spring element urges the one or more intermediate elements 13 to cooperate with these portions 27a, 27b of the cam profile such that the play is at least party opened between the pulses also when the motor is driven in a reverse direction R in the pulses.

[0058] With the present embodiment, the portions 27a, 27b extending between the lobes may together form a slight V- or U-shape pointing away from the motor driven part 11.

[0059] With this embodiment, the idling position of the intermediate element 13 will be at a position 0 between the lobes 24a, 24b, where the two inclined portions 27a, 27b meet. Between the pulses, when the torque from the motor is zero, the intermediate element 13 will, under the urging force S of the spring element, return to this position 0, irrespective of if the tool is driven in the forward F or reverse R direction. Hence, the play of the clutch will be automatically re-opened between the pulses both when the tool is driven in tightening direction F and a loosening direction R.

[0060] According to another embodiment, illustrated in Figure 5, the portion 27c of the cam profile between the one or more lobes 24a, 24b may be shaped in an inclined manner (with respect to an imaginary plane P normal to the axial direction of the tool) such that the force S of the spring element urges the one or more intermediate elements 13 to cooperate with the cam profile portion 27c so as to aid in closing the play during the pulses when the motor is driven in a forward (tightening) direction F.

[0061] In this embodiment, the motor may be controlled in the reverse direction R to re-open the play between the pulses. As the play has been opened, the intermediate element 13 may be at position 0, abutted against one of the lobes 24b. When the motor delivers a torque pulse (in the forward direction F), the intermediate element will move to position C and close the play. Here, the urging force S of the spring will, via the cooperation between the intermediate element 13 and the inclined cam surface 27c, aid in closing the play. In other words, some torque may be added to the torque pulse from the motor.

[0062] According to an embodiment, illustrated in Figure 6, the cam profile between the one or more lobes 24a, 24b may comprise a further inclined portion 27d (being inclined with respect to an imaginary plane P normal to the axial direction of the tool) such that the force S of the spring element urges the one or more intermediate elements 13 to cooperate with these portions 27c, 27b of the cam profile so as to aid in closing the play also when the motor is driven in a reverse (loosening) direction R in the pulses.

[0063] With the present embodiment, the portions 27c, 27d extending between the lobes 24a, 24b may together form a slight V- or U-shape pointing towards the motor driven part 11.

[0064] In this embodiment, the motor may be controlled to re-open the play between the pulses by forcing, against the urging force of the spring element, the intermediate element towards (almost up to) a point 0 at the crest of the V- or U- shape.

[0065] It will be appreciated that the cam profile portions 27a-d may not necessarily be straight as illustrated in Figures 3 but may alternatively be slightly curved.

[0066] The person skilled in the art realizes that the present invention by no means is limited to the embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. For example, the camp profile including the lobes may instead be provided in the motor driven part and the intermediate element may be held in the output driving part instead of vice versa.

[0067] Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed invention, from 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.

Claims

CLAIMS1. Pulse tool (1) for tightening threaded fasteners, the pulse tool comprising: a motor (2); an output shaft (3); a control device (5) configured to control the motor to output torque in pulses; and a torque limiting clutch (10) arranged to transfer torque from the motor to the output shaft up to a predetermined clutch release torque, wherein the torque limiting clutch has an inherent play, wherein the motor accelerates within the range of the inherent play of the torque limiting clutch during the pulses.

2. Pulse tool as defined in claim 1, wherein the control device is configured to control the motor: in a primary drive direction during said pulses so as to deliver a fastening torque or a loosening torque to the fastener, and in a direction opposite to said primary direction between said pulses so as to at least partly open said play between the pulses.

3. Pulse tool as defined in claim 1, wherein the torque limiting clutch comprises: a motor driven part (11) arranged to be driven by the motor, and an output driving part (12) arranged to drive the output shaft; wherein the motor driven part and the output driving part are arranged to, at least indirectly, engage with each other, whereby the torque limiting clutch is closed and disengage with each other, whereby the torque limiting clutch is open, wherein the torque limiting clutch is arranged such that: a limited relative rotation between the motor driven part and the output driving part is allowed as long as the torque is below saidpredetermined clutch release torque and the torque limiting clutch is closed, wherein said relative rotation forms said play, and such that full relative rotation between the motor driven part and output driving part is allowed as long as the torque is above said predetermined clutch release torque and the torque limiting clutch is open.

4. Pulse tool as defined in any one of the preceding claims, wherein at least one of the motor driven part and the output driving part comprises a cam profile (23) with one or more lobes (24), the torque limiting clutch further comprising: a spring element (14) arranged to urge one of the motor driven part and the output driving part towards the other, and one or more intermediate elements (13) arranged between the motor driven part and the output driving part to cooperate with the lobes of the cam profile so as to transfer torque between the motor driven part and the output driving part up to said clutch release torque, wherein the motor driven part and the output driving part are adapted such that the one or more intermediate elements are allowed to move in a circumferential direction within a range limited by the one or more lobes when the torque is below the clutch release torque.

5. Pulse tool as defined in claim 4, wherein a portion (27a) of the cam profile is shaped such that the force (S) of the spring element urges the one or more intermediate elements (13) to cooperate with the cam profile such that said play is at least party opened between the pulses when the motor is driven in a tightening direction (F) during the pulses.

6. Pulse tool as defined in claim 5, wherein a further portion (27b) of the cam profile is shaped such that the force (S) of the spring element urges the one or more intermediate elements (13) to cooperate with the cam profile such that said play is at least party opened between the pulsesalso when the motor is driven in a loosening direction (R) during the pulses.

7. Pulse tool as defined in claim 4, wherein a portion (27c) of the cam profile is shaped such that the force (S) of the spring element urges the one or more intermediate elements (13) to cooperate with the cam profile so as to aid in closing said play during the pulses when the motor is driven in a tightening direction (F) during the pulses.

8. Pulse tool as defined in claim 7, wherein a further portion (27d) of the cam profile is shaped such that the force of the spring element urges the one or more intermediate elements to cooperate with the cam profile so as to aid in closing said play during the pulses also when the motor is driven in a loosening direction (R) during the pulses.

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