SE2130375A1

SE2130375A1 - Sensor System for Power Tool

Info

Publication number: SE2130375A1
Application number: SE2130375A
Authority: SE
Inventors: Johan Rönblom
Original assignee: Atlas Copco Ind Technique Ab
Priority date: 2021-12-22
Filing date: 2021-12-22
Publication date: 2023-02-21
Also published as: SE544997C2; WO2023117199A1

Abstract

Disclosed herein is a sensor system (1) for a power tool comprising:- a socket (2) having a receiving end (10) for receiving a bolt or screw (100’) and a passage (12),- a universal joint (6) arranged within the passage (12), the resilient universal joint (6) being arranged to turn back into an idle position if no bolt (100’) is inserted in the socket (2); and- a sensor mechanism (8) arranged within the passage (12) between the receiving end (10) and the universal joint (6), the sensor mechanism (8) comprising an ultrasonic sensor (48) and a first sleeve shaped element (26) comprising a magnetic structure (42) at its free end (36), the first sleeve shaped element (26).The sensor mechanism (8) being designed so that the magnetic structure (42) can pull the ultrasonic sensor (48) towards a screw head when a screw is inserted in the socket (2).

Description

Sensor System for Power Tool Technical Field The invention relates to the field of sensor systems for power tools, in particular ultrasonic sensor systems that are built into tightening tools, whereby the sensor systems are used for measuring the tightening strength in a joint.

Background of the lnvention ln tightening systems used for assembly lines and the like it is of importance to provide a reliable value for the strength in a joint that was tightened by the tightening tool or system. These values are stored in databases so that the quality of the assembled work piece, vehicle or device can be backtracked. A seamless quality control is therewith preferred and often a must. Often such values are given in Torque such as Newton meter or the like. The values represent the rotational force (torque) that was induced into the joint during the tightening. The measurement of torque values is affected by dirt, grease (if used or not used), temperature, speed of tightening and generally the friction between the bolt and the thread or other elements of the joint. All these factors can lead to values of torque that are not reliable and it has been discovered that torque values measured in Newton meters can be up to 30% below or above the actual value of the joint. This can make the use of torque value as indicator for the tightening strength of joints not applicable for certain applications since such applications cannot tolerate a 30% stray of the torque. For improving the quality of the tightened joints ultrasonic measurement has been used for a while. The principle of ultrasonic measurement is herewith explained with reference to figure 1, which shows the principle of ultrasonic measurement for joints according to prior art. Figure 1 schematically depicts a screw or bolt 100 used to connect two metal sheets 105, 106 in a joint. On the screw head 101 an ultrasonic sensor 102 is placed. This ultrasonic sensor 102 is in snug contact with the surface of the screw head 101 so that the ultrasonic sensor can induce the ultrasonic signal into the screw. The signal, which is indicated with s, then travels through the screw head 101 and through the shank 104 of the screw 100 and is bounced back at the bottom 103 of the screw 100. The signal that is bouncing back towards the ultrasonic sensor 102 can be detected and the time of flight (TOF) can be 2 determined. The time of flight (TOF) and signal speed of the ultrasonic signal, both of which are known can then be used to determine the length of the screw 100. This length of the screw 100 varies depending on the tightening strength and can be correlated to a length of the screw 100 when it is not engaged in the joint and the two metal sheets 105, 106, respectively. By comparing the length measured in the joint and the known length of the screw at rest, ultrasonic measurement can be used to determine the clamp force of the joint. ln order to receive reliable signals of the time of flight (TOF) it is important that the ultrasonic sensor is positioned snug against the head of the screw, otherwise the measurement will not return any signal and the measurement will be false or invalid (return of false value). This is not a big issue if the quality of a joint is manually controlled since the operator can basically readjust the sensor and repeat the measurement. However, since power tools with built in ultrasonic sensors for quality control during tightening operations do exist, there is a need to improve and increase the robustness of the placement of ultrasonic sensors in power tools or tightening tools. When power tools are used to tighten screws, it can happen that the screw head or bolt head is angled or engaged at an angle in the bit or socket of the power tool instead of entirely parallel. An angled engagement or misalignment between screw and socket means that the longitudinal axis of the socket of the power tool and the longitudinal axis of the screw are not entirely parallel. Such a misalignment will lead to problems in the ultrasonic measurement since the ultrasonic sensor is not snug placed against the screw head. Because the tightening with such angled screws is still possible, the sensor system cannot always return a value for the tightening quality of the joint due to misalignment and therewith missing physical contact between the ultrasonic sensor and the screw head. lt is thus not always possible to control the quality of the joint at hand and the backtracking of values may be interrupted or incomplete. The present invention seeks to remedy the described shortcomings. Summary of the invention An object of the present invention is to provide a sensor system for a power tool that is robust, resilient and reliable. 3 Another object of the present invention is to provide a sensor system that can provide seamless and continuous quality control. ln view of the above-mentioned problems the inventor of the present invention has discovered that it is possible to use a magnet for ensuring that the ultrasonic sensor is correctly and snug placed against a screw head or bolt head, in combination with a universal joint. The magnet and the ultrasonic sensor are thereby positioned at one end of the universal joint so that the magnet can use its magnetic force to position the ultrasonic sensor snug against the screw head. Disclosed herein is a sensor system for a power tool comprising a socket having a receiving end for receiving a bolt or screw and a cylindrically shaped passage and a universal joint arranged within the cylindrically shaped passage, the universal joint being arranged to turn back into an idle position if no bolt or screw is inserted in the socket. The idle position of the sensor mechanism is the position when not screw or bolt is inserted in the socket. ln this idle position, the sensor mechanism and therewith the ultrasonic sensor is free and its movement is not hindered in any way. The sensor system further comprises a sensor mechanism arranged within the cylindrically shaped passage between the receiving end and the universal joint, the sensor mechanism comprising an ultrasonic sensor and a first sleeve shaped element comprising a magnetic structure at its free end. The sensor mechanism further comprises a first elastic element and a second sleeve shaped element arranged at least partially within the first sleeve shaped element, said second sleeve shaped element being fixedly connected to the universal joint with a first end. The second sleeve shaped element comprises the ultrasonic sensor at a second end, wherein the first elastic element is arranged in between the first sleeve shaped element and the second sleeve shaped element so that the ultrasonic sensor is arranged closer to the receiving end of the socket than the magnetic structure and so that the first sleeve shaped element can move in relation to the second sleeve shaped element along a longitudinal axis defined by the socket.

The sensor system described above has the advantage that the magnetic structure orientates the ultrasonic sensor correctly and presses it snug and smooth against the screw head when a screw head is inserted into the socket of the power 4 tool. For the magnetic structure to be able to do that the sensor mechanism needs to be mounted via a universal joint so that the sensor mechanism and the u|trasonic sensor can adapt to the orientation of the screw head. ln addition, the u|trasonic sensor and the magnetic structure, respectively, need to be embedded via the sleeves and elastic elements so that the magnetic structure can be positioned snug against the top surface of the screw head and so that the u|trasonic sensor is pushed via the first elastic element towards the top surface of the screw head in a smooth manner at the same time. This improves the measurement of the joint and makes the sensor system reliable and robust by reducing or eliminating the number of false returns during quality control of joints.

The universal joint may be a resilient universal joint. Using a resilient universal joint has the advantage that the u|trasonic sensor, the magnetic structure and the sensor mechanism are always at least more or less oriented parallel to the longitudinal axis b defined by the socket, if now screw is inserted in the socket. ln addition a resilient universal joint helps to move the sensor mechanism back into an idle position if no screw or bolt is inserted in the socket. ln an embodiment the second sleeve shaped element is fixedly connected to the universal joint with an end opposite the free end.

This may improve stability of the sensor system. ln another embodiment the strength of the magnetic force of the magnetic structure is chosen to that is, be larger than the elastic force of the first elastic element, when the u|trasonic sensor comes in contact with a bolt or screw.

The magnetic force depends of course on the distance between the screw head and the magnetic structure but the magnetic force in the present case is designed to overcome the elastic force of the first elastic element when the magnetic structure is closer than 3mm, preferably closer than 2mm and even more preferably closer than 1.5 mm from the screw head. ln a further embodiment the magnetic structure is distributed equally around the outside of the free end of the first sleeve shaped element.

This may provide an improved distribution of the magnetic force when the screw head is inserted in the socket, so that the u|trasonic sensor can be placed snug against the screw head.

The magnetic structure may be ring-shaped and arranged around the free end of the first sleeve shaped element.

This can improve the distribution of the magnetic force. ln an embodiment the sensor is disc shaped, wherein a plane defined by the disc shape extends perpendicular to a Iongitudinal direction defined by the socket.

The disc shape may be put into snug contact with the surface of the screw head or bolt head. ln addition, the disc shape improves the transfer of the u|trasonic signal to the screwhead. ln an embodiment the first sleeve shaped element comprises an inner shoulder arranged opposite or at a distance from the free end and wherein the second sleeve shaped element comprises an outer shoulder close to its free end and wherein the first elastic element of the sensor mechanism abuts the inner shoulder and the outer shoulder.

This makes the first sleeve shaped element moveable along a longitudinal direction versus the second sleeve shaped element and improves the contact between the u|trasonic sensor and the top surface of the screw head for optimal signal transfer between the u|trasonic sensor and the screw head. ln an embodiment the socket further comprises a conical bearing seat having a conically shaped hole, said conical bearing seat arranged within the cylindrically shaped passage. The universal joint further comprises a bearing element having a passage, a conical outer front end configured to be seated in the conical bearing seat in an idle position of the sensor system. The conical bearing seat and the conical outer front end being designed so that a diameter of the conically shaped 6 hole of the conical bearing seat and a diameter of the conical outer front end decrease towards the receiving end. ln an embodiment the sensor system further comprises an elastic mechanism arranged at least partially within the cylindrically shaped passage arranged next to the universal joint opposite the sensor mechanism, the elastic mechanism comprising a second elastic element, arranged to be pushed via the universal joint and the sensor mechanism away from the receiving end, when a screw head is inserted in the cylindrically shaped passage. The elastic mechanism further comprising a cylinder element, whereby the second elastic element is connected to the cylinder element leaving a gap between the universal joint and a socket side end of the cylinder element in the idle position.

The elastic mechanism helps to better position the sensor mechanism for touching the screw head of a screw that needs to be tightened. ln an embodiment the bearing element has a spherically shaped back end and wherein the cylinder element has a spherically shaped bearing shell configured to bear the spherically shaped back end.

The spherically shaped back end and the spherically shaped bearing shell provide a joint that can move in any direction, thus a universal joint or a three dimensional joint. ln an embodiment the conical bearing seat of the socket and the conical outer front end of the bearing element are designed as a magnetic pair so that the conical outer front end is snug arranged in the conical bearing seat in an idle position and thus when no screw head is inserted in the cylindrically shaped passage.

This may provide a smooth and reliable positioning of the universal joint when no screw head is inserted in the cylindrically shaped passage. 7 ln another embodiment the spherical back end further comprises a ring-shaped movement limiter comprising balls, whereby the ring-shaped movement limiter is designed to abut the spherical bearing shell when a screw head is inserted in the cylindrically shaped passage. The ring-shaped movement limiter may further be designed to provide a smooth bearing between the spherical back end and the spherical bearing shell when a screw head is inserted in the cylindrically shaped passage.

The ring-shaped movement limiter thus provides a smooth bearing so that the sensor mechanism and the universal joint, respectively, can easily tilt when a screw is inserted in an angled manner in the cylindrically shaped passage. Additionally, the ring-shaped movement limiter may be used to limit the range of motion of the universal joint.

The sensor system may be embodied in a power tool or a tightening tool.

The sensor system may be replaceable in case the socket of the power tool is changed.

The above universal joint is described according to the above embodiments. However other universal joints can also be designed and considered, such as for example resiliently designed pipes. Such elastic resilient pipes or tubes may be shaped as withdrawn or compressed springs or the like.

Herein the term free end describes an end of a sleeve, element or longitudinal object that is not connected or coupled to any other element, fixture, structure or sleeve.

Brief Description of the Drawings The present invention will now be described, for exemplary purposes, in more detail by way of embodiments and with reference to the enclosed drawings, in which: Fig. 1 schematically illustrates how ultrasonic measurement of tightening joints is performed according to the prior art; 8 Fig. 2 schematically illustrates a cross sectiona| view through a socket of a tightening tool and a screw that is to be received; Fig. 3 schematically illustrates a cross sectiona| view similar to figure 2 but with the screw slightly angled in the socket; Fig. 4 schematically illustrates a cross sectiona| view similar to figure 3 but with the screw engaged in the socket and a sensor system engaging a screw head; and Fig. 5 schematically illustrates a cross sectiona| view similar to the previous figures with the screw fully engaged in the socket in a slightly angled manner and the sensor system fully engaged on the screw head.

Detailed Description Figure 1 has been explained referring to the background art. As previously mentioned, the principle shown in figure 1 can be embodied in power tools or tightening tools that are used for tightening. Such power tools typically comprise a socket 2, which socket 2 is designed to receive a screw head 101' of a screw 100 as disclosed in figure 2.

Figures 2 to 5 illustrate the various stages of engagement between the screw 100' and the socket 2 and the various positions of engagement from a not yet engaged screw 100' (figure 2) to a fully engaged screw 100". Correspondingly the figures 2 to 5 also illustrate the various positions of a sensor system 1 from not engaged (figure 2) to a snug positioning against a top surface of the screw head (figure 5). As illustrated in the figures the sensor system 1 is designed to be used in a power tool, such as a tightening tool.

Turning now to figure 2, the basic principle of the sensor system 1 is described. ln figure 2 the longitudinal axis a defined by the screw 100' does not correspond to the longitudinal axis b of the socket 2. The angle oi defined by the two axes a, b is an acute or sharp angle meaning that the longitudinal axis a defined by the screw 100' and the longitudinal axis b defined by the socket are only slightly misaligned. Such a misalignment still allows the engagement of the screw head 101' in a cavity or cylindrical shaped passage 12. ln the embodiment shown in figure 2 the 9 cylindrical shaped passage 12 comprises a hexagonal shape at a receiving end 10, which hexagonal shape is allowing to engage the hexagonal shaped screw head 101' for the transfer of torque.

The sensor system 1 comprises an elastic mechanism 4 arranged opposite the receiving end 10 of the cylindrical central passage 12, a universal joint 6 arranged adjacent to or next to the elastic mechanism 4 on a receiving end 10 side of the elastic mechanism 4 and a sensor mechanism 8 arranged adjacent to or next to the universal joint 6. The sensor mechanism 8 extends into the hexagonal part of the socket 2 but it does not extend beyond the receiving end 10 of the socket 2.

The sensor mechanism 8 comprises a first sleeve shaped element 26 and a second sleeve shaped element 28. Between the first sleeve shaped element 26 and the second sleeve shaped element 28 a first elastic element 24 is arranged that allows the first sleeve shaped element 26 to move in relation to the second sleeve shaped element 28. The first sleeve element 26 comprises a free end 36 directed towards the receiving end 10 of the cylindrical shaped passage 12. The free end 36 comprises a magnetic structure 42 illustrated as a ring arranged around the outer side of the first sleeve shaped element 26 and held in position by an outer shoulder 44. The magnetic structure 42 may be held in place by form fit connection between the first sleeve shaped element 26 and the outer shoulder 44, it may be glued to the first sleeve shaped element 26 or it may be held in position by a combination of form fit and gluing. The first sleeve shaped element 26 further comprises an inner shoulder 45, said inner shoulder 45 being arranged opposite the free end 36 and designed to abut a first end of the first elastic element 24.

The second sleeve shaped element 28 comprises an ultrasonic sensor 48 and sensor electronics or a printed circuit board 46 arranged behind the ultrasonic sensor 48 away from the receiving end 10. The second sleeve shaped element 28 is fixedly arranged in the universal joint 6, as described later herein, and it is designed so that the ultrasonic sensor 48 slightly extends beyond the magnetic structure 42 in the idle position. The second sleeve shaped element 28 further comprises an outer shoulder 50 arranged close to the ultrasonic sensor 48 and the sensor electronics 48, the outer shoulder 50 being designed to abut the other end of the first elastic element 24. The first elastic element 24 is designed so that the magnetic force between the magnetic structure 42 and the screw head 101' is greater than the elastic force generated by the first elastic element 24 when the screw head 101' touches the ultrasonic sensor 46, as illustrated in figure 3.

Figure 3 illustrates how the screw 100' and its screw head 101 ', respectively, is now partially engaged in the cavity 12 and a top surface of the screw head 101' is touching the ultrasonic sensor 48. At the latest at this position the strength of the magnetic force induced by the magnetic structure 42 overcomes the spring rate and elastic force, respectively of the first elastic element 24. A plane c defined by a free surface of the ultrasonic sensor 42 is oriented perpendicular to the longitudinal axis b defined by the socket 2 and not perpendicular but at an angle ß to the longitudinal axis a defined by the screw 100'. The longitudinal axis a and the longitudinal axis b are still oriented at an acute angle oi versus one another. Figure 3 also well illustrates a gap g between the universal joint 6 and the elastic mechanism 4. This gap g allows the universal joint 6 to disengage so that the sensor mechanism 8 can tilt with the angle oi so that the ultrasonic sensor 48 can be snug positioned against the top surface of the screw head 101', as shown in figure 5.

Turning back to figure 3, the elastic mechanism 4 comprises a second elastic element 16 and a cylinder element 18. The cylinder element 18 is designed to glide in the socket 2 and the second elastic element 16 is designed to abut an inner shoulder of the socket 2 with an end opposite the receiving end 10 of the cavity 12 and an inner end of the cylinder 18 with the other end. The cylinder element 18 comprises a spherical bearing shell 20, which forms part of the universal joint 6.

The universal joint 6 comprises the spherical bearing shell 20 and a bearing element 22. Between the bearing element 22 and the spherical bearing shell 20 there is a gap g when the sensor system 1 is an idle position. The bearing element 22 comprises a passage 30 having an inner shoulder 38, a conical outer front end 32 directed towards the receiving end 10 and a spherical back end 34. The spherical back end 34 comprises a ring-shaped movement limiter 40. The ring- 11 shaped movement limiter 40 may comprise bearing balls 41 as illustrated in figure 5. The conical outer end 32 is conically shaped towards the front end 10 of the socket 2 and is embedded in a conical bearing seat 14 of the socket 2 when in the idle position. The conical bearing seat 14 is likely shaped conical with a decreasing diameter towards the front end 10 so that it can receive the conical outer front end 32 of the bearing element 22.

The conical bearing seat 14 and the conical outer front end 32 may be made of magnetic materials so that they are snug engaged in the idle position. ln order to hold the conical bearing seat 14 in a firm position in the socket 2, the socket 2 may comprise an inner shoulder for the conical bearing seat 14 to abut to. Additionally, or alternatively the conical bearing seat 14 may be form fitted and/or glued into the socket 2. ln the embodiment shown in figure 3, the conical bearing seat 14 is arranged just behind the structure of the cavity 12 that is configured to receive the screw head 101 '_ The structure for receiving the screw head 101' may for example be a hexagonal or torx structure. The second elastic element 16 is fully extended in figure 3, so that the cylinder element 18 is arranged so that a a gap g between the spherical bearing shell 20 and the spherical back end 34 and movement limiter 40, respectively is still present.

Once the screw head 101' is fully engaged in the cavity 12, still at an acute angle oi as previously explained referring to figures 2 and 3, the screw head 101' pushes the sensor mechanism 8 and the conical outer front end 32 backwards, away from the receiving end 10 of the cavity 12. The second sleeve shaped element 28, which is fixedly engaged in the conical outer front end 32 pushes the conical outer front end 32 out of the conical bearing seat 14 so that the bearing element 22 can tilt versus the longitudinal axis b of the socket 2.This allows the ultrasonic sensor 48 to orient itself parallel to the top surface of the screw head 101' so that the angle ß between the longitudinal axis a of the screw 100' and the plane c defined by the disc shaped ultrasonic sensor 48 gets closer to 90 degrees (rectangular), which means that the plane defined by the disc shaped ultrasonic sensor 48 is now oriented parallel to the top surface of the screw head 101". Since the conical outer front end 32 is moved towards the cylinder element 18 the second elastic 12 element 16 is now becoming slightly compressed and the gap g is closed and the spherical back end 34 is now g|iding on the spherical bearing she|| 20 via the ring- shaped movement limiter 40 comprising balls (c.f. figure 5). The ring-shaped movement limiter 40 is fixedly connected to the spherical back end 34 and the movement of the spherical back end 34 is designed to be limited via the ring- shaped movement limiter 40 and inner projections arranged at the spherical bearing she|| 20. lt is in this position where the magnetic structure 42 is pushing the ultrasonic sensor 48 snug towards the top surface of the screw head 101". This means that the first elastic element 24 is being compressed as shown in figure 5. ln figure 5 the screw 100' is fully engaged in the cavity 12 in an angled manner, meaning that the acute angle oi is still more less the same as previously described or slightly different but the main point is that there is still an acute angle present between the longitudinal axis a and the longitudinal axis b. The magnetic structure 42 pulled the first sleeve shaped element 26 towards the top surface of the screw head 101 '_ Thereby the first elastic element 24 is compressed and the drag created by the magnetic force of the magnetic structure 42 is pushing the ultrasonic sensor 48 snug against the top surface of the screw head 101', resulting in that the angle ß is 90° and plane c defined by the ultrasonic sensor 48 and the longitudinal axis a of the screw 100' are oriented perpendicular to each other. At the same time the first sleeve shaped element 26 is moved by the drag of the magnetic force towards the top surface of the screw head 101' and relatively to the second sleeve shaped element 28. ln figure 5, the sensor system 1 is capable to determine the strength of the joint by ultrasonic measurement with a reduced risk of false return, which improves the quality control of the joints that are tightened with the power tool comprising the sensor system 1. ln the embodiment shown, the acute angle oi may be in the range of 0.01 ° up to 10°. The range of the sensor system 1 to adapt to a slightly angled screw 100' might be similar. 13 The magnetic structure 42 may be rotationally symmetric arranged around the first sleeve shaped element 26. Thus, the magnetic structure 42 may comprise several magnets arranged symmetrically around the first sleeve shaped element 26. Alternatively, the magnetic structure 42 may be a magnetic ring.

The first and second e|astic elements can be springs, elastomers, hydraulic or fluid dampers or any suitable e|astic construction.

Claims

Claims 1 _

1. A sensor system (1) for a power tool comprising: - a socket (2) having a receiving end (10) for receiving a bolt or screw (100') and a cylindrically shaped passage (12), - a universal joint (6) arranged within the cylindrically shaped passage (12), the universal joint (6) being arranged to turn back into an idle position if no bolt or screw (100') is inserted in the socket (2); and - a sensor mechanism (8) arranged within the cylindrically shaped passage (12) between the receiving end (10) and the universal joint (6), the sensor mechanism (8) comprising an ultrasonic sensor (48) and a first sleeve shaped element (26) comprising a magnetic structure (42) at its free end (36), wherein, the sensor mechanism (8) further comprising a first elastic element (24) and a second sleeve shaped element (28) arranged partially inside the first sleeve shaped element (26), said second sleeve shaped element (28) being connected to the universal joint (6) with a first end, the second sleeve shaped element (28) comprising the ultrasonic sensor (48) at a second end , wherein the first elastic element (24) is arranged in between the first sleeve shaped element (26) and the second sleeve shaped element (28) so that the ultrasonic sensor (48) is arranged closer to the receiving end (10) of the socket than what the magnetic structure (42) is and so that the first sleeve shaped element (26) can move in relation to the second sleeve shaped element (28) along a longitudinal axis (b) defined by the socket.

2. _ The sensor system according to claim 1, wherein the second sleeve shaped element (28) is fixedly connected to the universal joint (6) with an end opposite the free end.

3. _ The sensor system according to claim 1 or 2, wherein the strength of the magnetic force of the magnetic structure (42) is chosen to overcome the elastic force of the first elastic element (24) when the ultrasonic sensor (48) comes in contact with a screw head (101 ') of a bolt or screw (100').

4. The sensor system according to any one of the preceding claims, wherein the magnetic structure (42) is distributed equally around an outer side of the free end (36) of the first sleeve shaped element (26).

5. The sensor system according to any one of the preceding claims, wherein the magnetic structure (42) is ring-shaped and arranged around the free end (36) of the first sleeve shaped element (26).

6. The sensor system according to any one of the preceding claims, wherein the u|trasonic sensor (48) is disc shaped, wherein a plane defined by the disc shape extends perpendicular to the longitudinal axis (b) defined by the socket (2) in an idle position.

7. The sensor system according to any one of the preceding claims, wherein the first sleeve shaped element (26) comprises an inner shoulder (45and wherein the second sleeve shaped element (28) comprises an outer shoulder (50) and wherein the first elastic element (24) of the sensor mechanism (8) abuts the inner shoulder (45) and the outer shoulder (50).

8. The sensor system according to any one of the preceding claims, wherein the socket (2) further comprises a conical bearing seat (14) having a conically shaped hole, said conical bearing seat (14) being arranged within the cylindrically shaped passage (12) and wherein the universal joint (6) further comprises a bearing element (22) having a passage (30), a conical outer front end (32) configured to be seated in the conical bearing seat (14) in an idle position of the sensor system (1), the conical bearing seat (14) and the conical outer front end (32) being designed so that a diameter of the conically shaped hole of the conical bearing seat (14) and a diameter of the conical outer front (32) end decrease towards the receiving end (10).

9. The sensor system according to claim 8, further comprising an elastic mechanism (4) arranged at least partially within the cylindrically shaped passage (12) arranged next to the universal joint (6) opposite the sensor mechanism (8), the elastic mechanism (4) comprising a second elastic element (16) arranged to be pushed via the universal joint (6) and the sensormechanism away from the receiving end (10) when a screw head (101') is inserted in the cylindrically shaped passage (12), said elastic mechanism (4) further comprising a cylinder element (18), whereby the second elastic element (16) is arranged to keep the cylinder element in position leaving a gap (g) 5 between the universal joint (6) and a socket side-end of the cylinder element (18) in the idle position.

10. The sensor system according to claim 9, wherein the bearing element (22) has a spherically shaped back end (22) and wherein the cylinder element (18) 10 has a spherically shaped bearing shell (20) configured to receive the spherically shaped back end (34) when a screw head (101') is inserted in the cylindrically shaped passage (12).

11. The sensor system according to claim 8, wherein the conical bearing seat 15 (14) of the socket (2) and the conical outer front end (32) of the bearing element (22) are designed as a magnetic pair so that the conical outer front end (32) is snug arranged in the conical bearing seat (14) in an idle position and thus when no screw head (101 ') is inserted in the cylindrically shaped passage (12). 20

12. The sensor system according to claim 10, wherein the spherical back end (34) further comprises a ring-shaped movement limiter (40) comprising bearing balls (41), whereby the ring-shaped movement limiter (40) is designed to abut the spherical bearing shell (20) when a screw head (101') is inserted in the cylindrically shaped passage (12) and wherein the ring-shaped movement 25 limiter (40) is further designed to provide a smooth bearing between the spherical back end (34) and the spherical bearing shell (20) when a screw head (101') is inserted in the cylindrically shaped passage (12).

13. A power tool comprising a sensor system according to any of claims 1 to12.