Click-type torque wrench

Abstract

The present invention relates to a torque wrench (100) comprising: - a handle (110); - an output shaft (120); - clutch means for allowing the transmission of a tightening torque from the handle (110) to the output shaft (120) until the target tightening torque is reached for driving a screw in rotation; characterized in that the torque wrench (100) also comprises means for transmitting a slip torque from the handle (110) to the output shaft (120), the means for transmitting a slip torque being activated when the target tightening torque is reached, the torque wrench (120) also comprising means for determining the slip torque, the means for determining the slip torque being interdependent with means for adjusting the target tightening torque.

Description

[0001] DESCRIPTION

[0002] Title: Click-type torque wrench

[0003] 1. Scope of the invention

[0004] The field of the invention is that of the design and manufacture of screwing tools.

[0005] More specifically, the invention relates to a torque wrench intended for use in mass production operations, in the aeronautical industry or the automotive industry.

[0006] 2. Prior art

[0007] In general, torque wrenches are used to apply a controlled torque to a bolted assembly, whether it's a screw or a nut in helical engagement with a threaded element. Hereafter, only the term "screw" will be used, it being understood that it also encompasses a nut.

[0008] In general, the wrenches considered here include at least: - a handle with a grip allowing the user to apply force generating a tightening torque on the screw; - an output shaft allowing a screw to be driven via a socket; - a torque sensor allowing the measurement of the torque applied to the screw, and - control means associated with a human-machine interface allowing the programming of a target torque and the monitoring of its attainment.

[0009] Typically, the human-machine interface includes a screen, but it can also include an audible and / or visual warning, or even a haptic one such as a vibrator.

[0010] Typically, the torque sensor consists of strain gauges glued onto a deforming element subjected to the clamping force and belonging to the handle.

[0011] There are two types of torque wrenches: click-type wrenches and direct-reading wrenches.

[0012] In direct-reading torque wrenches, the output shaft is rigidly connected to the handle. The user monitors the torque applied to the screw via the human-machine interface. Once the target tightening torque is reached—that is, the optimal torque for holding the screw—the user stops applying force. An audible or haptic alert can also notify the user when the target torque has been reached.

[0013] This type of key is, however, poorly suited to a rate of use corresponding to production work, since monitoring the achievement of the target torque slows down the use of the key and, conversely, if the user is not careful enough, there is a risk of exceeding the target torque.

[0014] The term "user" encompasses both the end user of the torque wrench, i.e. the technician who operates the screw, and the methods technician who is generally responsible for setting and maintaining the torque wrench.

[0015] Click-type torque wrenches, a well-known type in the industry being the break-off wrench, allow the torque transmitted to the screw to be interrupted once the target tightening torque is reached.

[0016] Typically, trigger keys include:

[0017] - a handle extending along a first axis and equipped with a grip;

[0018] - an output shaft extending along a second axis transverse to the first axis, said output shaft being movable in rotation relative to the handle around the second axis; - clutch means capable of adopting a engaged state in which they block the rotation of said output shaft relative to the handle around said second axis to allow the transmission of a tightening torque of said handle to said output shaft until said target tightening torque is reached for driving a rotating screw.

[0019] In operation, when the target tightening torque is reached, the clutch means adopt a disengaged position so as to prevent the transmission of tightening torque to the screw, due to the user's effort, over a predetermined angle of approximately 10°.

[0020] During this predetermined angle, the handle behaves as if it were undergoing a break near the output shaft. This break allows the user to understand that the target torque has been reached and that they must stop applying force.

[0021] If this effort is not stopped quickly enough, the user may inadvertently overtighten, i.e. significantly exceed the target torque, which is detrimental to the quality of the assembly.

[0022] If a significantly larger breaking angle is envisaged, on the order of 90°, then another risk arises: when the user reaches the target tightening torque, the force he applies to the handle no longer encounters resistance, which leads the user into an uncontrolled rotation of the torque wrench, which can then be a risk of injury.

[0023] Indeed, during an uncontrolled rotational movement, the user may bump into a nearby part or machine, striking it violently.

[0024] Furthermore, even if the work environment is clear, the repetition (in the industrial environment) of sudden absences of resistance can, in the long term, lead to the appearance of musculoskeletal disorders and, as a consequence, a prolonged work stoppage for the operator or even incapacity in the worst case.

[0025] 3. Objectives of the invention

[0026] The invention aims in particular to provide an effective solution to at least some of these different problems.

[0027] In particular, according to at least one embodiment, an objective of the invention is to provide a torque wrench whose use presents no risk of injury, or almost no risk, to the user once the target tightening torque is reached.

[0028] Another objective of the invention is to eliminate the risk of overtightening.

[0029] In particular, the invention aims, according to at least one embodiment, to provide such a torque wrench which is simple to use and adjust.

[0030] Another objective of the invention is, according to at least one embodiment, to provide such a torque wrench providing the user with information enabling him to interrupt the force he exerts on the handle.

[0031] 4. Presentation of the invention

[0032] To this end, the invention proposes a torque wrench designed to apply a target tightening torque to a screw, said torque wrench comprising:

[0033] - a handle extending along a first axis and equipped with a grip;

[0034] - an output shaft extending along a second axis transverse to the first axis, said output shaft being movable in rotation relative to the handle around the second axis;

[0035] - clutch means capable of adopting a engaged state in which they block the rotation of said output shaft relative to the handle around said second axis to allow the transmission of a tightening torque of said handle to said output shaft until said target tightening torque is reached for driving a rotating screw;

[0036] - a control unit;

[0037] - torque measurement means connected to the control unit and intended to measure a tightening torque transmitted by the handle to the output shaft;

[0038] - means for adjusting said target tightening torque, and - a battery to power at least said control unit and said torque measuring means,

[0039] characterized in that the torque wrench also includes means for transmitting a sliding torque from said handle to said output shaft, activated when said target tightening torque is reached, said sliding torque being less than or equal to said target tightening torque, the torque wrench also including means for determining said sliding torque, the means for determining said sliding torque being interdependent with the means for adjusting said target tightening torque.

[0040] The interdependence of the means of determining the sliding torque with the means of adjusting the target tightening torque makes it possible to generate a sliding torque adapted to each use of the torque wrench, such as: - a sliding torque which is less than or equal to the target torque; - a ratio between the sliding torque and the target torque which is substantially constant from one target torque setting to another, or - a sliding torque which is chosen close enough to the target torque so that the user does not experience sudden muscle relaxation when passing the target torque, but distinct enough so that the user perceives that the target torque has been reached and that the tightening is complete.

[0041] Indeed, the user's perception when the target tightening torque is reached and the sliding torque is implemented is identical regardless of whether the target tightening torque is high or low.

[0042] Thus, there is no risk of sudden loss of resistance as in the prior art, which limits, or even eliminates, the risk of injury to the user.

[0043] Furthermore, the torque wrench setting is simplified since the interdependence of the means of determining the sliding torque with the means of setting the target tightening torque allows for optimal configuration of the torque wrench before its use.

[0044] According to an advantageous aspect, the value of said sliding torque is between 60% and 100% of the value of said target tightening torque. Such a range makes it possible, on the one hand, to create a sliding torque quite close to the target tightening torque without risk of over-tightening the screw and, on the other hand, to limit the effects of sudden loss of resistance which can lead to injury to the user.

[0045] In other words, this range of correspondence between the target tightening torque and the sliding torque prevents the user from experiencing the same sensation once the target tightening torque is reached, regardless of the effort they exert when handling the torque wrench.

[0046] According to another advantageous aspect, the torque wrench also includes a human-machine interface, said human-machine interface integrating said means of adjusting said target tightening torque.

[0047] Setting the target tightening torque is simplified for the user who can use the human-machine interface to set the target tightening torque and, consequently, the sliding torque.

[0048] According to another advantageous aspect, said transmission means include an adjustable torque limiter, said torque limiter incorporating a measuring element for said sliding torque, said measuring element being connected to the control unit.

[0049] Such an architecture allows optimal adjustment of the sliding torque by having control of the adjustment via the control unit and therefore feedback for the user, for example via the human-machine interface.

[0050] According to another advantageous aspect, the said sliding torque is constant or almost constant.

[0051] A constant sliding torque allows the user to feel a continuous decrease in resistance, indicating that the target tightening torque has been reached, without the risk of a sudden drop in resistance that could lead to injury.

[0052] Another advantage is that the measuring device is a piezoelectric type sensor. Such a sensor is simple to implement, compact and inexpensive, which allows for a safe, simple, reliable and robust torque wrench at a lower cost.

[0053] According to another advantageous aspect, the clutch means are of the electromagnetically controlled type and include a friction clutch or a lock.

[0054] Such clutch systems are easy to implement and particularly reliable over time. Furthermore, their operation is simple and quick, giving the torque wrench increased responsiveness during use.

[0055] According to another advantageous aspect, the torque wrench comprises an electric motor powered by said battery and incorporating a stator linked to said handle and a rotor rotationally linked to said output shaft to transmit a resisting electromagnetic torque from said handle to said output shaft, said torque wrench also comprising means for controlling the power supply to said motor, the clutch means and the transmission means being formed, at least in part, by the control unit, the control means and the electric motor, the control unit being configured to control the following control means:

[0056] - a first control mode, in which the control means regulate the motor's power supply in position until the target tightening torque is reached, and - from the attainment of the target tightening torque, a second control mode, in which the control means regulate the motor's power supply in current for a predetermined duration and according to a torque setpoint starting at the level of the slip torque and ending at zero torque.

[0057] The control of the piloting means by the control unit successively according to the first piloting mode and then the second piloting mode allows the user to be accompanied to allow him to interrupt his effort when the target tightening torque is reached.

[0058] Indeed, in the second control mode, the resisting torque supplied by the motor decreases until it reaches a zero value, allowing the user to understand that their effort must be stopped. Furthermore, the predetermined duration is designed based on the average reaction time of a user to stop their effort when the target tightening torque is reached.

[0059] According to another advantageous aspect, the torque wrench also includes a reducer interposed between said electric motor and said output shaft.

[0060] Such a reducer makes it possible to increase the resistive torque supplied by the torque wrench while minimizing the size of the electric motor, thus improving the compactness and ease of handling of the torque wrench for the user.

[0061] According to another advantageous aspect, the said torque measurement means include at least one current sensor interposed between said battery and said electric motor.

[0062] Such a current sensor allows optimal responsiveness of the control unit and therefore rapid control of the control means.

[0063] According to another advantageous aspect, the said predetermined duration is between 225 ms and 275 ms.

[0064] Such a range of predetermined duration definition allows for consideration of an average reaction time for users to understand that a target tightening torque has been reached and that the force exerted on the handle of the torque wrench must be stopped.

[0065] 5. Description of the figures

[0066] Other features and advantages of the invention will become apparent from the following description of particular embodiments, given by way of simple illustration and not limitation, and the accompanying drawings, among which:

[0067] [Fig. 1] Figure 1 is a schematic perspective representation of a torque wrench according to the invention;

[0068] [Fig. 2] Figure 2 is a schematic cross-sectional representation of a detail of the torque wrench according to a first embodiment of the invention, in which the clutch means are in an engaged state;

[0069] [Fig. 3] Figure 3 is a schematic cross-sectional representation of a detail of the torque wrench according to the first embodiment of the invention, in which the clutch means are in a disengaged state; [Fig. 4] Figure 4 is a schematic side view representation of a detail of the torque wrench according to a second embodiment of the invention;

[0070] [Fig. 5] Figure 5 is a schematic representation illustrating the relationship between the torque wrench according to the second embodiment of the invention;

[0071] [Fig. 6] Figure 6 is a graph illustrating the evolution of the torque supplied by the torque wrench according to the invention, for each of the first embodiment and the second embodiment.

[0072] 6. Description of specific embodiments

[0073] The invention therefore relates to a torque wrench 100 intended to apply an objective tightening torque on a screw, or at least on a screwed assembly, whether it is a screw or a nut in helical engagement with a threaded element.

[0074] As illustrated in Figure 1, the 100 torque wrench includes:

[0075] - a handle 110 extending along a first axis A and equipped with a grip 111;

[0076] - an output shaft 120 extending along a second axis B transverse to the first axis A, said output shaft 120 being movable in rotation relative to the handle 110 around the second axis B;

[0077] - means of engagement;

[0078] - a control unit 130 (visible in figure 5);

[0079] - torque measuring means connected to the control unit 130 and intended to measure a tightening torque transmitted by the handle 110 to the output shaft 120; - means for adjusting said target tightening torque, and

[0080] - a battery 140 (visible in figure 5) to power at least said control unit 130 and said torque measurement means.

[0081] Although not illustrated by Figure 5, the control unit 130 and the battery are common elements in all embodiments of the torque wrench 100.

[0082] The handle 110 has a head 112 in which the output shaft 120 is received. The output shaft 120 is thus mobile in rotation relative to the head 112 of the handle 110, around the second axis B.

[0083] Said clutch means can adopt an engaged state in which they block the rotation of said output shaft 120 relative to the handle 110 around said second axis B to allow the transmission of a tightening torque of said handle 110 to said output shaft 120 until said target tightening torque is reached for driving a rotating screw.

[0084] In other words, in the engaged state, the clutch means allow the handle 110 to be joined with the output shaft 120 so that the effort exerted by the user on the handle 110 causes the screw to be tightened via the output shaft 120.

[0085] The torque wrench 100 also includes means for transmitting a sliding torque from said handle 110 to said output shaft 120, activated when said target tightening torque is reached.

[0086] The sliding torque is less than or equal to the target tightening torque. Furthermore, the torque wrench 100 also includes means for determining the sliding torque.

[0087] The means of determining said sliding torque are interdependent with the means of said target tightening torque.

[0088] In other words, and as will be explained below, there is a proportional relationship between the sliding torque and the target tightening torque.

[0089] Preferably, the sliding torque value is between 60% and 100% of the target tightening torque value.

[0090] With further reference to Figure 1, the torque wrench 100 also includes a human-machine interface 150.

[0091] The said human-machine interface 150 integrates in particular the means for adjusting the target tightening torque.

[0092] Alternatively, the adjustment means could be internal to the torque wrench 100 and manipulable using an external device connectable to the torque wrench 100. The external device could be of the mechanical and / or electronic type.

[0093] In addition to being connected to the measuring means, the control unit 130 is connected to the human-machine interface 150 and to the clutch means to allow their control.

[0094] Finally, the means for measuring tightening torque can take, for example, the form of a torque sensor 135 with strain gauges integrated into the handle and classically known in the prior art (illustrated by figures 2 and 5). With reference to figure 2 and figure 3, a first embodiment of the torque wrench 100 is now described.

[0095] In this first embodiment, the clutch means of the electromagnetically controlled type include a 160 friction clutch or a lock.

[0096] In particular, the clutch means include a pin 161 intended to cooperate with the output shaft 120 by fitting into a complementary groove 121 of a specific shape, carried by the output shaft 120. Now, when the balls 171 have to transmit a clamping torque between the guide 114 and the output shaft 120, they develop, by virtue of their shape, an axial force along the second axis B which tends to move the guide 114 away from the output shaft 120. Thus, the pin 161, by preventing the shaft 120 from moving away from the guide 114, allows the transmission of the clamping torque from the handle 110 to the output shaft 120.

[0097] In more detail, the handle 110 incorporates a ratchet mechanism 113 allowing the direction of action of the torque wrench 100 to be determined for the application of a tightening torque, this ratchet mechanism 113 incorporating a guide 114 having a barrel 115 on which the output shaft 120 is guided in rotation and translation relative to the handle 110.

[0098] As illustrated by Figure 2 and Figure 3, the transmission means include an adjustable torque limiter 170.

[0099] The use of an adjustable 170 torque limiter allows in particular the obtaining of a constant or almost constant sliding torque.

[0100] The torque limiter 170 includes at least one contact member 171 interposed between the output shaft 120 and the handle 11. More specifically, said at least one contact member 171 is interposed between the output shaft 120 and the guide 114.

[0101] The torque limiter 170 also includes a spring 172 intended to be compressed to keep the handle 110, more specifically the guide 114, in contact with the output shaft 120 via said at least one contact member 171.

[0102] The compression of the spring 172 is then modulated according to the sliding torque to be applied. For this, the spring is interposed between the output shaft 120 and a device for adjusting the compression of the spring 172 of the transmission means, i.e. the torque limiter 170.

[0103] The spring compression adjustment device 172 includes a knob 173 which engages helically with the head 112 of the handle 110.

[0104] Therefore, depending on whether the knob 173 is screwed or unscrewed relative to the head 112 of the handle 110, the spring 172 is compressed, respectively released, which implies a greater or lesser contact force of the guide 114 and the output shaft 120 with said at least one contact member 171.

[0105] It is therefore understood that the more the spring 172 is compressed, the greater the contact force and therefore the greater the sliding torque.

[0106] On the contrary, the less the spring 172 is compressed, the less the contact force is and therefore the less the sliding torque is.

[0107] Said at least one contact member 171 takes the form of a ball. According to the embodiment illustrated by Figure 2 and Figure 3, the torque limiter 170 comprises several balls.

[0108] The guide 114 has a first housing 116 intended to partially receive the balls, and the output shaft 120 has a second housing 122 also intended to partially receive the balls. The first housing 116, which is supported by the guide, and the second housing 122 are opposite each other and have a hemispherical shape.

[0109] The balls cooperate with the first housing 116 and with the second housing 122 to allow the transmission of the sliding torque from the handle 110 to the output shaft 120 via the guide 114.

[0110] When the clutch means are disengaged, and the torque transmitted by the handle 110 to the screw reaches the sliding torque, the shaft 120 moves away from the guide 114, passing over the top of the balls, and the adjacent housings 122 fall back onto the balls. This phenomenon recurs as long as the user exerts force on the handle 110, thus holding their arm thanks to a sufficiently constant sliding torque. Furthermore, the torque limiter 170 incorporates a measuring element 174 for this sliding torque. More specifically, the measuring element 174 allows for the measurement of the compression of the spring 172.

[0111] The measuring element 174 is connected to the control unit 130 to transmit a value of the sliding torque during its adjustment.

[0112] The measuring element 174 is, in the embodiment illustrated by Figure 2 and Figure 3, a piezoelectric type sensor.

[0113] During operation, a user sets the target tightening torque using the human-machine interface 150. The control unit 130 then records the target tightening torque value and sets the sliding torque value. The user then adjusts the torque limiter 170 by turning the knob 173 to tighten or loosen it and thus compress the spring 172.

[0114] Using the human-machine interface 150, the user manipulates the knob 173 until the compression value of the spring 172 corresponds to the sliding torque value. An audible and / or visual signal (for example, the instantaneous sliding torque value or an LED) is then generated by the human-machine interface 150 to inform the user that the torque limiter 170 is correctly set.

[0115] Alternatively, the user simply adjusts the compression of the spring 172 of the torque limiter 170 using the knob 173, thus matching it to the sliding torque. The control unit 130 then receives the compression value of the spring 172, measured by the measuring element 174, and determines the target tightening torque value, displaying it on the screen to inform the user.

[0116] When the target tightening torque value and the sliding torque value are determined, the 100 torque wrench is ready for use.

[0117] To do this, the user makes the output shaft 120 cooperate with the screw, for example via a socket, and then applies a force on the handle 110 to rotate the screw. The measuring means then measure the instantaneous value of the torque applied to the screw by the force exerted on the handle 110 by the user until the instantaneous value is equal to the target tightening torque value.

[0118] When the instantaneous value corresponds to the target tightening torque value, the control unit 130 drives the clutch means to move them into their disengaged state.

[0119] The pin 122 then disengages from its cooperation with the output shaft 120, which allows the output shaft 120 to move away from the guide 114.

[0120] The contact of the balls with the first housing 116 and the second housing 122 then allows the transmission of the sliding torque so that the rotation of the handle 110 is braked while preventing over-tightening of the screw by the effort of the user.

[0121] The user then feels a disengagement of the torque wrench 100 by a controlled sliding of the rotation of the handle 110 around the second axis B, without risk of injury by hitting a part or a surrounding machine or by suffering too sudden an acceleration of its movement generating the force on the handle 110.

[0122] The user can then stop the effort exerted on the handle 110 while being assured that the tightening applied to the screw is optimal.

[0123] With reference to Figure 4 and Figure 5, a second embodiment of the torque wrench 100 is now described.

[0124] In this second embodiment, the torque wrench 100 includes an electric motor 180 powered by said battery 140.

[0125] The electric motor 180 is a permanent magnet synchronous motor which integrates a stator linked to the handle 110 and a rotor linked in rotation with the output shaft 120 to transmit a resisting electromagnetic torque from the handle 110 to the output shaft 120.

[0126] As illustrated by Figure 5, the torque wrench 100 also includes pilot means 190 for powering an electric motor 180. The clutch means and transmission means are formed, at least in part, by the control unit 130, the pilot means 190 and the electric motor 180.

[0127] The control unit 130 is then configured to control the piloting means 190 according to a first piloting mode until the target tightening torque is reached, and a second piloting mode when the target tightening torque is reached.

[0128] In the first control mode, the control means 190 regulate the position of the supply to the electric motor 180 until the target tightening torque is reached, thereby blocking the rotation of the output shaft relative to the handle until the target torque is reached.

[0129] In the second control mode, the control means 190 regulate the current supply to the electric motor 180 for a predetermined duration D (illustrated by figure 6).

[0130] The current regulation of the electric motor 180's power supply is based on a torque setpoint starting at the slip torque and ending at zero torque. Thus, the user's thrust after reaching the target torque is considered to be the electromagnetic torque generated by the motor, up to the torque setpoint limit.

[0131] In other words, the second control mode allows the sliding torque to decrease.

[0132] The predetermined duration D is between 225 ms and 275 ms.

[0133] Preferably, the predetermined duration D is 250 ms.

[0134] A predetermined duration D of 250 ms corresponds to the time interval between which a user understands that the target tightening torque is reached and the moment when he releases his effort on the handle 110 of the torque wrench 100.

[0135] The 190 control means incorporate a vector control of the motor allowing the regulation of speed or current of the motor.

[0136] The position control of the electric motor 180 is a speed control with a zero speed setpoint. This creates a resistive torque that prevents the output shaft 120 from rotating relative to the joystick 110. In other words, the position control of the electric motor 180 makes the output shaft 120 and the joystick 110 rotationally fixed around the second axis B. The current control corresponds to electromagnetic torque control, the latter being proportional to the current.

[0137] The current level supplying the electric motor 180, which allows its position regulation, is determined according to the effort that the operator exerts on the handle 110, via the measuring means.

[0138] For this purpose, the measuring means can take the form of the torque sensor 135 described previously, or a current sensor 200 as illustrated by Figure 5. The current sensor 200 is interposed between the battery 140 and the electric motor 180 and can, for example, be integrated into the control means 190 or be separate from them.

[0139] Alternatively, the measuring means may include both a torque sensor 135 and a current sensor 200.

[0140] When the torque measurement means include a current sensor 200, the instantaneous torque value is calculated by multiplying the current value by a coefficient Kt which is a characteristic specific to the electric motor 180.

[0141] According to the embodiment illustrated by Figure 5, the torque wrench 100 also has a reducer 210 interposed between the electric motor 180 and the output shaft 120.

[0142] The resisting torque available at the output shaft is equal to the electromagnetic torque of the motor multiplied by the reduction ratio of the reducer, the ratio of the bevel gear of the output shaft and the efficiency of these transmission components.

[0143] In operation, the target tightening torque is set by the user via the human-machine interface 150. Using an algorithm, the control unit 130 determines the sliding torque value.

[0144] The torque wrench 100 is then ready for use. To do this, the user makes the output shaft 120 cooperate with the screw, for example via a socket, then applies force to the handle 110 to rotate the screw.

[0145] The measuring means then measure the instantaneous value of the torque applied to the screw by the force exerted on the handle 110 by the user.

[0146] The control means 190 are controlled by the control unit 130 according to the first control mode so that the force applied by the user on the handle 110 of the torque wrench 100 is transmitted to the screw, until the instantaneous value is equal to the target tightening torque value.

[0147] When the instantaneous value corresponds to the target tightening torque value, the control means 190 are controlled by the control unit 130 according to the second control mode so that the electric motor 180 generates the sliding torque until it reaches zero torque.

[0148] The user then feels a disengagement of the torque wrench 100 by a controlled sliding of the rotation of the handle 110 around the second axis B, without risk of injury by hitting a part or a surrounding machine or by suffering too sudden an acceleration of its movement generating the force on the handle 110.

[0149] The user can then stop the effort exerted on the handle 110 while being assured that the tightening applied to the screw is optimal.

[0150] With reference to Figure 6, the evolution of the torque supplied by the output shaft 120 of the torque wrench 100 is now described.

[0151] From an initial instant T0, the torque increases until it reaches the target tightening torque at a first instant T1. From instant T1, it is the sliding torque that is applied.

[0152] According to the first embodiment, the sliding torque is less than the target tightening torque but remains constant or nearly so until the user releases their force (the portion of force release corresponding to a rapid drop in torque is not shown in Figure 6), as illustrated by the dashed line L1. As shown in Figure 6, the sliding torque is equal to the target tightening torque. In an alternative not shown, the sliding torque could be less than the target tightening torque.

[0153] According to the second embodiment, the sliding torque decreases over the predetermined time D until it reaches zero torque as illustrated by the dashed line L2.

[0154] The torque wrench 100, described above, allows for optimal tightening torque without risk of operator injury because, once the target tightening torque is reached, the rotation of the handle 110 relative to the output shaft 120 is controlled. Sudden accelerations of the user's movement or impacts against surrounding parts or machinery are thus eliminated, improving user safety.

[0155] Furthermore, the interdependent relationship between the target tightening torque and the sliding torque makes it possible to maintain this safety benefit under all circumstances.

Claims

DEMANDS 1. Torque wrench (100) intended to apply a target tightening torque to a screw, said torque wrench (100) comprising: - a handle (110) extending along a first axis (A) and equipped with a grip (111); - an output shaft (120) extending along a second axis (B) transverse to the first axis, said output shaft (120) being movable in rotation relative to the handle (110) around the second axis (B); - clutch means capable of adopting a engaged state in which they block the rotation of said output shaft (120) relative to the handle (110) around said second axis (B) to allow the transmission of a tightening torque from said handle (110) to said output shaft (120) until said target tightening torque is reached for driving a rotating screw; - a control unit (130); - torque measuring means connected to the control unit (130) and intended to measure a tightening torque transmitted by the handle (110) to the output shaft (120); - means for adjusting said target tightening torque, and - a battery (140) to power at least said control unit (130) and said torque measurement means, characterized in that the torque wrench (100) also includes means for transmitting a sliding torque from said handle (110) to said output shaft (120), activated when said target tightening torque is reached, said sliding torque being less than or equal to said target tightening torque, the torque wrench (120) also including means for determining said sliding torque, the means for determining said sliding torque being interdependent with the means for adjusting said target tightening torque.

2. Torque wrench (100) according to claim, characterized in that the value of said sliding torque is between 60% and 100% of the value of said target tightening torque.

3. Torque wrench (100) according to any one of the preceding claims, characterized in that it also comprises a human-machine interface (150), said human-machine interface integrating said means for adjusting said target tightening torque.

4. Torque wrench (100) according to any one of the preceding claims, characterized in that said transmission means comprise an adjustable torque limiter (170), said torque limiter (170) incorporating a measuring element (174) of said sliding torque, said measuring element (174) being connected to the control unit (130).

5. Torque wrench (100) according to the preceding claim, characterized in that said sliding torque is constant or almost constant.

6. Torque wrench (100) according to claim 4 or claim 5, characterized in that the measuring member (174) is a piezoelectric type sensor.

7. Torque wrench according to any one of the preceding claims, characterized in that the clutch means are of the electromagnetically controlled type and comprise a friction clutch (160) or a lock.

8. Torque wrench (100) according to claim 1, characterized in that it comprises an electric motor (180) powered by said battery (140) and incorporating a stator linked to said handle (110) and a rotor rotationally linked with said output shaft (120) for transmitting a resisting electromagnetic torque from said handle (110) to said output shaft (120), said torque wrench (100) also comprising control means (190) for powering said electric motor (180), the clutch means and the transmission means being formed, at least in part, by the control unit (130), the control means (190) and the electric motor (180), the control unit (130) being configured to control the control means (190) as follows: - a first control mode, in which the control means (190) regulate the power supply to the electric motor (180) until the target tightening torque is reached, and - from the attainment of said target tightening torque, a second control mode, in which the control means (190) regulate the current supply to the electric motor (180) for a predetermined duration (D) and according to a torque setpoint starting at the level of the sliding torque and ending at zero torque.

9. Torque wrench (100) according to the preceding claim, characterized in that it also comprises a reducer (210) interposed between said electric motor (180) and said output shaft (120).

10. Torque wrench (100) according to claim 8 or claim 9, characterized in that said torque measuring means comprise at least one current sensor (200) interposed between said battery (140) and said electric motor (180).

11. Torque wrench (100) according to any one of claims 8 to 10, characterized in that said predetermined duration (D) is between 225 ms and 275 ms.

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