GB2524506A - Electronic click wrench - Google Patents

Abstract

The wrench includes a handle 1 for applying torque through a shaft 2 to a working head 3. The shaft includes torque sensing means (10, 11, Figure 3) for calculating the torque applied to a work piece by the working head. A trigger mechanism is for sending a haptic feedback to a user by triggering a small angular movement of the handle relative to the working head when a set point torque is reached. The small movement of the handle relative to the head is an angular movement of the handle relative to the shaft. The trigger mechanism may be contained entirely within the handle and include a spring (19, Figure 7) that is wrapped around a rotary member 13 to prevent rotation of the member. When the set point torque is reached, an actuator 23 (e.g. solenoid) moves one end of the spring to reduce its grip on the member 13 and permit the small relative angular movement of the handle. The trigger may alternatively include a gear and rack or an eccentric cam and cam track. The wrench may be connected to a wireless microprocessor for recording maximum torque applied.

Description

Electronic Click Wrench

Field of the Invention

This invention relates to torque wrenches, and provides a torque wrench which combines electronic torque sensing with the haptic feedback of a so-called dick wrench'.

Background of the Invention

Torque wrenches are known hand tools which are used in manufacturing industry for example on assembly lines to tighten bolts and other threaded fasteners to a recommended minimum tightness. It is increasingly important in production line manufacture to control and monitor the maximum and minimum torque to which threaded fastener joints are tightened. The use of alloys of relatively soft and lightweight metals for components does mean that over-tightening a joint can cause serious damage to the thread of the fastener being tightened or to the component being anchored by the threaded fastener, whereas under-torquing a joint does and always has had serious safety issues.

On a typical production line, an assembly engineer may use a torque wrench that is pre-set to deliver a predetermined amount of torque before the wrench sends a haptic feedback signal to the user to warn that the correct torque level has been applied to the joint. The predetermined amount of torque applied by the wrench to a joint which triggers the haptic feedback signal is known as the set point of the wrench. The most common torque wrenches used in industry are so-called click wrenches. Each wrench comprises a handle and a working head connected together by a shaft. The length of the shaft determines how much torque is applied at the working head by the user imparting a given manual force to the handle. The working head may be a simple rigidly mounted square socket coupling or it may include a ratchet mechanism mounting a square socket coupling. The click mechanism creates the haptic feedback to the user when the desired set point has been reached, which feedback comprises a limited small angular movement between the shaft and the working head which is permitted only when the set point has been reached. The shaft and working head are locked at a constant angle when the applied torque is less than the set point, but when that set point is reached a trigger releases the locking and allows the above small angular movement, generally of only one or two degrees of angle, before again locking the shaft and the working head at a (second) fixed angle for example by abutment of a portion of the shaft against a fixed wall of the working head or vice versa. That sudden abutment normally generates a click sound, from which the click wrench takes its name; and the click sound does provide the user with a degree of aural feedback indicating that the set point has been reached, although the much more discemable haptic feedback is the feel of sudden and abruptly terminated small free movement of the handle as the user applies a force to the wrench at the handle end. The user relies on that haptic feedback to tell him or her to cease applying force to the handle end of the wrench. Continued application of force will cause over-tightening of the joint, and the click wrench relies on the skill of the user to release the force on the handle as soon as the haptic feedback is sensed. Current working practices are such that a user may have access to a first click wrench pre-set to deliver a recommended torque of for example, 40 Newton Metres (Nm) to a first range of j oints; a second click wrench pre-set to deliver a recommended torque of for example, 30 Nm to a second range of joints; and third and further click wrenches set to deliver different recommended torques to other joints on the assembly line. The potential disadvantages of this practice are immediately apparent. The user may pick up the wrong wrench to use on a given joint. Even if that does not happen, each user must be provided with a sufficient number of differently pre-set click wrenches to accommodate all of the joints being fastened; and each of those pre-set wrenches must be maintained at the correct torque setting and regularly calibrated to make sure that the set point does not wander from the intended sefting in use. Recalibration of every single click wrench on a weekly basis is not uncommon. Some click wrenches are user-adjustable so that the user may alter the set point against a dial or scale provided on the wrench itself so that the same click wrench may be used to tighten different joints to different desired torques. That has the advantage that a single click wrench can be used in place of several, but the disadvantage that it relies on the user to remember to reset the set point whenever moving from a joint with one desired torque level to another; and it relies on the user to make that adjustment accurately. As with the non-user-adjustable click wrenches, such adjustable wrenches need to be recalibrated and serviced regularly, to ensure that the set point at which the click mechanism is triggered is accurately reflected on the dial or scale.

A simple mechanical click wrench triggers the haptic feedback indicating that the desired set point has been reached by a trigger mechanism, generally a roller ball which is normally held in a concave seat by a spring, which is purely mechanical and which relies on the compression of the spring to control the desired set point. The spring compression must be checked regularly, to maintain accuracy of the haptic feedback signal.

All such simple mechanical click wrenches have the limitations that (a) they cannot record the actual torque to which a joint has been tightened and (b) they do not monitor the angular movement of the wrench head during tightening.

No simple click wrench can however provide a guarantee that the user has tightened any given joint to its recommended torque value. The user may not respond properly to the haptic feedback and may over-tighten or under-tighten any particularjoint, Much greater reliability, and a record of the torques to which a series ofjoints have been tightened, is provided by electronic torque measurement of the joints being tightened, which is possible using a bending beam and a strain sensor or sensors on that bending beam with a feedback of measured maximum torque being relayed to a computer memory. That enables the computer to monitor the sequence of fasteners being tightened, and by incorporating a sensor which recognises each joint being tightened, to set the desired threshold torque electronically for each joint in turn in the sequence. It has been proposed to insert a separate strain sensor as an additional element in the torque application path between the working head of a mechanical wrench such as a click wrench and the socket which drives the head of the fastener being tightened. Such a separate strain sensor does however incur an additional cost and can be removed and mislaid by the user, It does not create automatic electronic adjustment of the desired set point for any given joint being tightened. The addition of a separate strain sensor between the wrench head and the joint adds to the overall length of the wrench, This has inherent disadvantages. In the first place users do in general prefer smaller and shorter wrenches, which provide better control of torque application and are less susceptible to over-torquing, In addition, the insertion of a separate strain sensor between the wrench head arid the joint requires an operator to compensate for the additional torque which a given pulling force will exert at a joint, The user may need to have reference to a look-up table or may perform actual calculations to provide that compensation, and the calculations are in any case predicated on the user pulling the click wrench at a specific point on the handle.

It has also been proposed to incorporate such a strain sensor or sensors into the shaft of a torque wrench as a permanent feature, to display the applied torque on an electronic display on the wrench handle or shaft, arid to generate a feedback signal to the user from the resulting electronic torque measurement when the set point is approached or reached.

The electronic display is more accurate than the purely mechanical display of the dial or scale of the adjustable mechanical click wrenches discussed above. The most easily generated feedback signals are visual or aural. For example a light or a series of lights on the wrench or on a small monitor adjacent the user can indicate when the desired torque is approached and/or attained, or an audible alarm could sound to indicate the same. Such visual or aural feedback signals are however easily overlooked in a factory environment where there may be background noise and distracting lights or when the wrench is used at an awkward angle or in a position where the visual display is difficult to see. There has therefore been a need for a mechanism to trigger a haptic feedback in response to an electronic torque measurement within the wrench, so that the benefits of an electronic torque wrench can be combined with the familiarity and ease of use of a click wrench. Although there have been proposals to combine electronic torque sensing and a click mechanism, for example in US-A-2007/02273 16 or LJS-A-201 1/0132157, no such electronic click wrench has been offered on the commercial market. The reason is apparently the difficulty of providing a sufficiently sensitive arid reliable trigger that is responsive to relatively small trigger forces in wrench which has a torque path designed to deliver torques much higher than the trigger torques. Commercially available electronic wrenches therefore still tend to use visual or aural feedback to the user.

It is an object of the invention to provide an electronic torque wrench which includes a haptic feedback of the click mechanism variety, while maintaining a reliable triggering of the haptic feedback when a desired set point has been sensed by strain sensors in the wrench.

The Invention The invention provides an electronic click wrench having the features of claim I herein.

The change from having the said small movement of the handle relative to the working head, which gives the haptic feedback to the user, as an angular movement of the handle relative to the shaft as opposed to an angular movement of the shaft relative to the working head, creates several distinct advantages of design. The trigger mechanism may be contained entirely within the handle, rather than having to send the trigger signal as a mechanical or electrical signal down the shaft to the working head end of the shaft. The handle preferably includes a cover which is at least partially removable for initial assembly and for subsequent servicing of the trigger mechanism. A trigger with a low number of component parts may be designed, preferably one generating little or no backlash. Although the signal generated by the electronic torque sensing and indicating that a desired set point is being approached or has been reached is initially an electrical signal, that signal can easily be transformed into a mechanical trigger by a suitable electromagnetic relay, which can be contained within the handle housing.

A preferred trigger mechanism for triggering the small movement of the handle relative to the working head when a set point is sensed by the torque sensing means is a wrap spring wrapped around and gripping a rotary member which is urged to rotate in a given direction by application of a fastener-tightening torque through the handle and shaft; the wrap spring having one end anchored relative to the rotary shaft and acting as a clutch to prevent rotation of the rotary member in the given direction; and an electrically actuable member actuable, when the set point is sensed by the torque sensing means, to move and bear on a free end of the wrap spring to free the rotary shaft from its clutching engagement in the given direction. When the clutching engagement of the wrap spring on the rotary shaft is released by the electrically actuable member, which may be a solenoid, the rotary shaft is able to move in the given direction, preferably for only one or a few degrees of angular movement, to create the haptic feedback signal to the user indicating that the set point has been reached. The torque sensing means does however continue to sense the torque applied at the working head of the wrench, so that a maximum applied torque signal may be sent to a computer for recordal against an entry for the joint being tightened.

The rotary member is urged to rotate in the given direction by application of a fastener-tightening torque through the handle and shaft. That connection between the handle and the rotary member may be a geared connection, established for example by the rotary member being mounted on the handle and urged in the given rotary direction by a gear thereon engaging a rack portion of the shaft. Alternatively the connection between the handle and the rotary member may be a cam connection, with the rotary member being mounted on the handle and having an eccentric cam follower element thereon urged in the given direction by a cam track portion of the shaft.

A second trigger mechanism for triggering the small movement of the handle relative to the working head when a set point is sensed by the torque sensing means is described and claimed in our co-pending patent application filed herewith (C032,034.00), Other electromechanical relays for triggering the small haptic feedback movement of the handle relative to the working head when a set point is sensed by the torque sensing means are possible within the scope of this invention. The small movement is however confined to movement of the handle relative to the shaft, and no mechanism is necessary for sending the trigger signal down the length of the shaft to the working head end to overcome the applied torque there, as would be necessary with any trigger mechanism other than that of the above co-pending patent application filed herewith if the haptic feedback signal were the angular movement of the shaft relative to the working head.

Acting torques at the handle and of the shaft are much less than at the working head end, so the trigger forces required to initiate the haptic feedback movement can be much less as they do not have to overcome the higher frictional resistance between components at the working head end.

The set point at which the haptic feedback is triggered may with advantage be a calculated value as described in our copending patent application GB-A-t305810,2, in which it is described how the threshold trigger may be in advance of a target torque. The rate of change of sensed torque is monitored, and by extrapolation from that monitored rate of change it is predicted when the actual sensed torque will be equal to a torque component of a target condition. A set point is thus calculated which is effective to establish a final actual limit applied by the drive head of the wrench which is close to the target condition, and the haptic feedback is triggered when that set point is sensed. This allows the wrench to compensate for the different rates of pull on the wrench handle by different users, and for different user reaction times.

Drawings The invention is illustrated by the drawings, of which: Figure 1 is an illustration of a conventional click wrench with mechanical click actuation. The view is from the underside or back side of the wrench.

Figure 2 is an illustration from the top side of the same click wrench as that of Figure 1, showing the relatively small angular movement after click actuation.

Figures 3 and 4 are illustrations, similar to those of Figures 1 and 2 respectively, of a click wrench according to the invention.

Figures 5 and Oare illustrations of the handle internal components of a first embodiment of a click wrench according to Figures 3 and 4, being a click wrench with a trigger mechanism in the handle.

Figure 7 is an illustration of the wrap spring and actuating solenoid of the click wrench of Figures 5 and 6, before click actuation.

Referring first to Figures t and 2, there is shown a conventional click wrench viewed from both sides (bottom side and top side respectively). The wrench comprises a handle I connected to a working head 3 by a shaft 2. The handle is fast to the shaft 2 but the shaft 2 is pivotally connected to the working head 3 such that it is capable of a small angular movement relative to the working head 3 about a pivot pin A. The normal condition of the click wrench is shown in Figure 1, and the wrench may be used to tighten a threaded joint by fitting a conventional socket onto the square drive end 4 and placing that socket over the shaped head of the joint fastener (nut or bolt) to be tightened.

A force is then applied to the handle 1 in the direction of the arrow 5, and a combination of the applied force and the length of the shaft from the handle I to the working head 3 generates the applied torque (clockwise in Figure 2). When a pre-set threshold torque is applied to the joint, a release mechanism (usually a ball being forced out of a cup against the force of a set spring) causes the pivoting action takes place, and the shaft 2 and handle 1 pivot together about the pin A to the position shown in solid lines in Figure 2.

That in itself is a haptic feedback to the user, who is thus warned to stop applying force to the handle. A further and secondary auditory feedback resides in the click sound that is generated when the shaft 2 and handle 1 reach the limiting position shown in Figure 2, which gives this kind of wrench the name c1ick wrench'.

A torque wrench according to the invention is illustrated in Figures 3 and 4. The similathies with and differences from the click wrench of Figures I and 2 will be immediately apparent, with the same reference numbers being used for similar components of the wrench. The small pivotal movement when the set point is reached is a pivotal movement about the pin B and is an angular movement of the handle I relative to the shaft 2. The total feedback to the user is very similar to that of a conventional click wrench, having both haptic and aural components. But in the shaft 2 of the wrench of Figures 3 and 4 is a bending beam 10 and strain sensors LI, shown only very schematically in the drawings, which together form a torque sensing means which sense the degree of bending of the beam 10 and from that calculate the torque applied at the working head 3. The provision of mutually spaced strain sensors 11 on the bending beam 10 enables the torque sensing means to be made point of load insensitive, The wrench of Figures 3 and 4 is thus an electronic wrench which, in common with other known electronic wrenches, can send a torque record signal through a wired or wireless connection to a microprocessor, which records the maximum torque applied by the wrench to each fastening that is tightened in a series of fastening operations. This enables a record to be kept for audit purposes of the accuracy of torque values applied in, for example, a production line. The torque wrench of Figures 3 and 4 does however have distinct advantages, The click mechanism is triggered not by a ball being forced out of a cup at the working head end of the wrench but by a feedback signal from the torque sensing means which at a given set point triggers the angular movement at the handle end of the wrench. The necessary trigger mechanism can be conveniently housed in the handle I, which preferably has a removable cover to access the trigger mechanism for initial assembly or for subsequent maintenance.

Figures 5 to 7 show a preferred ifigger mechanism which may be used in the click wrench of Figures 3 and 4 according to the invention. Only the handle end of the wrench is shown in Figures 5 and 6. The handle 1 is shown transparently so as to show the main internal components. In Figure 5 the wrench handle I is shown in its normal usage condition, before the set point has been reached, in Figure 6 the condition is shown after the applied torque has triggered the click mechanism, with the initial handle position being shown for reference in broken line. A spine member 12 is visible in both drawings, as a rigid extension of the shaft 2. An eccentric pawl t3 (see also Figure 8) is mounted with a main shaft portion 14 rotatable relative to the handle and an eccenific cam follower stub shaft 15 slidable in a cam slot 16 in the spine member 12.

When a user exerts a force on the handle I in a torque-tightening direction as shown by the arrow S in Figures 5 and 6, that force is translated into a rotary torque of the handle relative to the shaft as indicated by the arrow 17 in Figure 5. The handle 1 can rotate about the pin B only if the pawl 13 is permitted to rotate about its main shaft portion 14 in the direction indicated by the arrow 18 in Figure 5, and that rotation is prevented by a wrap spring t9 which is shown in Figure 7. The wrap spring t9 is wrapped tightly in frictional clutching engagement around the main shaft portion 14 and has two ends 20 and 21. The end 20 is shown in Figures 5 to 7 but the end 21 is shown only in Figure 7 and that is illustrative only. The end 21 is anchored, and that anchorage may be of a bent-over portion (not shown) of the wrap spring 19 which engages in a key slot in the main shaft portion 14 or which engages an upstanding portion (not illustrated) of the main shaft portion N; or that anchorage may be an engagement of the end 21 with a portion of the handle 1. The other end 20 is engaged by an actuating rod 22 of a solenoid 23. As the user exerts an increasing force on the handle 1 in the direction of the arrow 5 of Figure 5, the fastener is tightened to its predetermined set point torque which is sensed by the bending beam 10 and strain gauges 11, As that set point is approached or attained, the solenoid 23 is energised to retract the actuating rod 22 in the direction of the wow 24 of Figure 5, That retraction pulls with it the end 20 of the wrap spring 19, causing the wrap spring to slacken its clutching grip on the shaft 14 to permit rotation of the paw] 13 in the direction of the arrow 18 of FigureS, caused by the user pulling on the handle 1.

The pawl 13 can be sized and positioned such that the torque exerted by the user on the pawl 13 (as indicated by the arrow 18) is considerably less than the torque exerted by the working head 3 of the wrench. For example a wrench capable of exerting up to 25ONm of torque at its working head 3 can be designed to exert only about 9Nm of torque on the pawl 13 at the trigger point. This enables triggering to be fast and reliable, with reasonably limited frictional forces to be overcome in moving the solenoid actuating rod 22.

The energisation of the solenoid 23 can be very brief A momentary pulse, just long is enough to slacken the wrap spring 19 sufficiently to allow rotation of the shaft 14 under the pull of the user, is all that is necessary. After that momentary pulse the wrap spring 19 may once again revert to its original condition of gripping engagement around the shaft 14 but, as the clutching effect is unidirectional, the rotation of the shaft 14 back to its original condition shown in Figure 5 is self-setting when the user releases the wrench handle 1 The power to initiate that momentary pulse of current through the electromagnet may therefore be provided by batteries within the handle itself so that no permanent external power supply is needed and the wrench does not require a wire or cable connecting it to a power source. Connection to a computer for recording the maximum torque applied to a series of joints is therefore preferably a wireless connection.

The triggering of the haptic feedback to the user is completely under the control of electronic circuitry responsive to the actual instantaneous applied torque as sensed by the bending beam O and strain sensors LI. If transducers are provided on the individual joints to be tightened in a production line, and a transponder is provided on or in the torque wrench, for example at the working head 3, the user simply has to go to each fastener in turn and the wrench will communicate with a computer to identify the individual joint being tightened at any particular stage in the sequence. The computer can in turn identify the desired maximum torque for that joint, and set the triggering retraction of the solenoid actuating rod to take place at that set point. That has been the objective of many electronically actuated click wrenches proposed to date, but for the first time the invention allows such an objective to be attained in a reliaNe manner by removing the need for complicated and unreliable mechanisms to transfer the ifigger instruction down the shaft 2 of the wrench to the working head end where the applied loads and associated frictional forces are at a maximum.

Other trigger mechanisms can be provided within the scope of the invention. The rotation of the handle about the pin B of Figure 3 as opposed to the pin A of Figure ito generate the haptic feedback signal enables the trigger mechanism to be housed totally within the handle 1, where the loads and associated frictional forces are significantly less than at the working head 3 end of the wrench, so that reliable triggering can be achieved using a wide variety of trigger mechanisms. Moreover there is ease of access to the entire trigger mechanism by simply removing the handle cover or a portion thereof

Claims (11)

1. CLAIMS1 An electronic click wrench comprising a handle for applying torque through a shaft to a working head, wherein the shaft includes torque sensing means comprising a bending beam and one or more strain sensors for calculating the torque applied to a workpiece by the working head, and a trigger mechanism for sending a haptic feedback to a user by triggering a small movement of the handle relative to the working head when set point is sensed by the torque sensing means, characteriseti in that the said small movement of the handle relative to the working head is an angular movement of the handle relative to the shaft.
2. 2. An electronic click wrench according to claim 1, wherein the trigger mechanism is contained entirely within the handle.
3. 3, An electronic click wrench according to claim 2, wherein the handle includes a cover which is at least partially removable for initial assembly and for subsequent servicing of the trigger mechanism.
4. 4. An electronic click wrench according to any preceding claim, wherein the trigger mechanism comprises a wrap spring wrapped around and gripping a rotary member which is urged to rotate in a given direction when a fastener-tightening torque is applied through the handle and shaft, a first end of the wrap spring being anchored so that the wrap spring acts as a clutch to prevent rotation of the rotary member in the given direction; and an electrically actuable member actuable to move and bear on a second end of the wrap spring to free the rotary member from its clutching engagement when the set point is sensed by the torque sensing means, the resulting rotation of the freed rotary member being accompanied by the small movement of the handle relative to the shaft, 5. An electronic click wrench according to claim 4, wherein the electrically actuable member is a solenoid.6. An electronic click wrench according to claim 4 or claim 5, wherein the rotary member is mounted on the handle aM is urged in the given direction by a gear thereon engaging a rack portion of the shaft.7. An electronic click wrench according to claim 4 or claim 5, wherein the rotary member is mounted on the handle and has an eccentric cam follower element thereon urged in the given direction by a cam track portion of the shaft, 8, An electronic click wrench according to claim 7, wherein the eccentric cam follower element is a stub shaft and the cam track portion of the shaft is an elongated slot in which the stub shaft can move.9. An electronic click wrench according to claim 4 or claim 5, wherein the rotary member is a pivot shaft portion of the handle, about which the hmdle pivots relative to the shaft to create the said angular movement of the handle relative to the shaft.10. An electronic click wrench according to my preceding claim, wherein the wrench incorporates or is connectable to a microprocessor for recording the maximum torque applied to a series ofjoints.11. An electronic click wrench according to claim 10, wherein the connection to the microprocessor is a wireless connection.12. An electronic click wrench according to claim 10 or claim 11, wherein the working head includes a sensor for recognising each individual one of the series ofjoints with which the click wrench is to be used, and communicating that information to the microprocessor; and feedback from the microprocessor acts to set the threshold applied torque at which triggering takes place, appropriate for each individual joint with which the click wrench is to be used.13. An electronic click wrench substantially as described herein with reference to the drawings.Amendments to the claims have been made as follows:CLAIMS1. An electronic click wrench comprising a handle for applying torque through a shaft to a working head, wherein the shaft includes torque sensing means comprising a bending beam and one or more strain sensors for calculating the torque applied to a workpiece by the working head, and a trigger mechanism for sending a haptic feedback to a user by triggering a small movement of the handle relative to the shaft when set point is sensed by the torque sensing means, characterised in that the trigger mechanism comprises a wrap spring wrapped around and gripping a rotary member which is urged to rotate in a given direction when a fastener-tightening torque is applied through the handle and shaft, a first end of the wrap spring being anchored so that the wrap spring acts as a clutch to prevent rotation of the rotary member in the given direction; and an electrically actuable member actuable to move and bear on a second end of the wrap spring to free the rotary shaft from its clutching engagement when the set point is sensed by the torque :.. 15 sensing means, the resulting rotation of the freed rotary shaft being accompanied by the small movement of the handle relative to the shaft. * * * * ..2. An electronic click wrench according to claim I, wherein the trigger mechanism is contained entirely within the handle. ***3. An electronic click wrench according to claim 2, wherein the handle includes a cover which is at least partially removable for initial assembly arid for subsequent servicing of the trigger mechanism.4. An electronic click wrench according to any preceding claim, wherein the electrically actuable member is a solenoid.
5. 5. An electronic click wrench according to any preceding claim, wherein the rotary member is mounted on the handle and is urged in the given direction by a gear thereon engaging a rack portion of the shaft.
6. 6. An electronic click wrench according to any of claims 1 to 4, wherein the rotary member is mounted on the handle and has an eccentric cam follower element thereon urged in the given direction by a cam track portion of the shaft.
7. 7. An electronic click wrench according to claim 6, wherein the eccentric cam follower element is a stub shaft and the cam track portion of the shaft is an elongated slot in which the stub shaft can move.
8. 8. An electronic click wrench according to any preceding claim, wherein the wrench incorporates or is connectable to a microprocessor for recording the maximum torque applied to a series of joints.
9. 9. An electronic click wrench according to claim 8, wherein the connection to the microprocessor is a wireless connection. * ** * . * *.* .
10. 10. An electronic click wrench according to claim 8 or claim 9, wherein the working head includes a sensor for recognising each individual one of the series of joints with which the click wrench is to be used, and communicating that inf iation to the microprocessor; and feedback from the microprocessor acts to set the threshold applied torque at which triggering takes place, appropriate for each individual joint with which * the click wrench is to be used.
11. 11. An electronic click wrench substantially as described herein with reference to Figures 3 to 7 of the drawings.