EP1591206B1 - Torque tool, especially wrench, and method of detecting loss of equilibrium during a tightening operation - Google Patents

Description

The present invention relates to a tool according to the preamble of claim 1, in particular a mechanical torque wrench with manual application of the torque comprising mechanical means able to provide a predetermined torque to a driving portion intended to cooperate with a body member. screwing to drive a fastener, said mechanical means being in equilibrium under the action of suitable biasing means, said mechanical means being releasable by breaking equilibrium, and means for detecting the breakage of equilibrium.

The invention also relates to an equilibrium breakage detection method according to the preamble of claim 17 and a clamping method according to the preamble of claim 21.

Such a tool and such methods are known from the document FR 2 842 449 A .

In known manner, clamping operations of fasteners in the industrial sector require more and more traceability, ie knowledge of all the information and measures to follow and quickly find the steps of the process.

For tightening operations, the dynamometer tool manufacturers propose mechanical tools, the principle of which is based on a highly perceptible break in equilibrium, making it possible to detect the break in equilibrium by a device comprising an electrical circuit provided with a switching means whose state is changed by the breaking of equilibrium, and a processing unit, adapted to exploit information relating to the state of said switching means. The entire detection device is generally housed in a casing fixed externally to the body of the tool.

Such a construction is not entirely satisfactory, because the housing defines a protrusion periphery of the body of the tool, potentially annoying for the introduction of the tool into a mechanical member on which the operator intervenes.

In addition, such a construction uses a miniature switch whose life is relatively short, and which poses reliability problems when it is subjected to sudden actuations, which is generally the case for tools breaking balance. mechanical.

The known devices also have the disadvantage of not taking into account the phenomenon of over-torque exerted during the torque tightening operation, once the equilibrium is broken. This over-torque value can reach 50% of the predetermined setpoint torque under certain conditions of use of the key.

In addition, the use of electronic torque wrenches is not desired on the assembly lines because no physical sensation of exceeding the tightening torque is perceptible.

A main goal is to overcome these disadvantages, and to provide a mechanical torque tool whose size does not increase and whose reliability is increased.

Another aim is to provide a mechanical torque tool that improves the traceability of torque tightening operations, taking into account the over-torque phenomenon.

For this purpose, in a mechanical dynamometric tool according to the invention, the means for detecting the mechanical equilibrium break include measuring means which provide a signal corresponding to the measurement of the torque applied to the fastener, means electronic processing of said signal and processing means by calculating data from the electronic processing of said signal.

• les moyens de calcul détectent le moment de la rupture d'équilibre mécanique par calcul de dérivé de la valeur de mesure du couple par rapport au temps.
• les moyens de calcul détectent la rupture d'équilibre mécanique par calcul d'intersection d'une première et d'une seconde courbes, la première courbe représentant la valeur de mesure du couple par rapport au temps, la seconde courbe étant identique à la première avec un décalage faible et positif dans le temps;
• les moyens de traitement électronique du signal et les moyens de calcul sont disposés à l'intérieur de la clé ;
• la clé comporte en outre des moyens de transmission de la mesure du couple de serrage maximum appliqué à l'élément de fixation à une station extérieure à l'outil, et en ce que la dite station affiche la valeur de couple de serrage maximum appliqué à l'élément de fixation ;
• la clé comporte en outre des moyens de transmission de la mesure du couple de serrage maximum appliqué à l'élément de fixation à des moyens de réception solidaires de l'outil, et en ce que lesdits moyens affichent la valeur de couple de serrage maximum appliqué à l'élément de fixation ;
• les moyens de mesure comprennent des éléments sensibles résistifs ;
• les moyens de mesure comprennent plusieurs jauges de contrainte, montées en pont ;
• l'outil dynamométrique est une clé à déclenchement ;
• l'outil dynamométrique est une clé à cassure ;
• l'outil dynamométrique est un tournevis ;
• l'information est transmise par radio-fréquences ;
• les moyens de sollicitation comprennent un ressort dont la compression détermine le couple de consigne, ledit ressort participant à l'effort axial d'appui sur lesdits moyens mécaniques, des moyens de mesure fournissent une information correspondant à la mesure du couple appliqué à l'élément de fixation, et des moyens de mesure (121) constitués d'éléments sensibles d'organes de mesure, tels que des extensomètres résistifs ou jauges de contrainte, fournissent une information correspondant à la mesure du couple appliqué à l'élément de fixation, et une unité de traitement électronique, intégrée à l'outil, fournit une information correspondant à la mesure du couple maximum appliqué à l'élément de fixation après que l'équilibre mécanique soit rompu et transmet à une unité de réception ladite information correspondant à la mesure du couple maximum appliqué à l'élément de fixation après rupture de l'équilibre mécanique ;
• l'unité de traitement est disposée à l'intérieur de la clé ;
• l'unité de réception est une station extérieure à l'outil, et elle affiche la valeur de la mesure du couple de serrage maximum appliqué à l'élément de fixation ; et
• l'unité de réception est une unité solidaire de l'outil, et elle affiche la valeur de la mesure du couple de serrage maximum appliqué à l'élément de fixation.

According to other features of the invention:

• the calculating means detect the moment of the mechanical equilibrium break by calculating derivative of the measurement value of the torque with respect to time.
• the calculation means detect the break of mechanical equilibrium by intersection calculation of a first and a second curve, the first curve representing the measurement value of the torque with respect to time, the second curve being identical to the first with a weak and positive shift in time;
• the electronic signal processing means and the calculation means are arranged inside the key;
• the key further comprises means for transmitting the measurement of the maximum tightening torque applied to the fastening element at a station external to the tool, and in that said station displays the value of maximum tightening torque applied to the fastening element;
• the key further comprises means for transmitting the measurement of the maximum tightening torque applied to the fastening element to receiving means integral with the tool, and in that said means display the maximum torque value applied to the fastener;
• the measuring means comprise resistive sensitive elements;
• the measuring means comprise a plurality of strain gages, mounted in a bridge;
• the dynamometric tool is a trigger key;
• the dynamometric tool is a key to break;
• the dynamometric tool is a screwdriver;
• the information is transmitted by radio frequencies;
• the biasing means comprise a spring whose compression determines the setpoint torque, said spring participating in the axial load on said mechanical means, measuring means provide information corresponding to the measurement of the torque applied to the element fixing means, and measuring means (121) consisting of measuring element sensitive elements, such as resistive extensometers or strain gages, provide information corresponding to the measurement of the torque applied to the fastener, and an electronic processing unit, integrated into the tool, provides information corresponding to the measurement of the maximum torque applied to the fixing element after the mechanical equilibrium is broken and transmits to a reception unit said information corresponding to the measurement maximum torque applied to the fastener after breaking the mechanical balance;
• the processing unit is disposed inside the key;
• the receiving unit is a station external to the tool, and displays the value of the measurement of the maximum tightening torque applied to the fastener; and
• the receiving unit is a unit integral with the tool, and displays the value of the measurement of the maximum tightening torque applied to the fastener.

• la fourniture d'une information correspondant à la mesure du couple appliqué à l'élément de fixation,
• le traitement électronique de ladite information,
• le traitement par calcul de données numériques issues du traitement électronique de la dite information.

The invention also relates to a mechanical balance failure detection method during a manual torque tightening of a fastener element when the applied torque reaches a predetermined target torque, the method comprising the following steps:

• providing information corresponding to the measurement of the torque applied to the fastener,
• the electronic processing of said information,
• the processing by calculation of digital data resulting from the electronic processing of said information.

• la fourniture d'une information correspondant à la mesure du couple appliqué à l'élément de fixation,
• le traitement électronique et la fourniture d'une information correspondant à la mesure du couple maximum appliqué après rupture d'équilibre mécanique,
• la transmission de ladite information correspondant à la mesure du couple maximum appliqué après rupture d'équilibre mécanique.

Finally, the subject of the invention is a method of manually tightening the torque of a fixing element by mechanical breakage principle when the applied torque reaches a predetermined target torque, the method comprising the following steps

• providing information corresponding to the measurement of the torque applied to the fastener,
• the electronic processing and the provision of information corresponding to the measurement of the maximum torque applied after breaking of mechanical equilibrium,
• the transmission of said information corresponding to the measurement of the maximum torque applied after breaking of mechanical equilibrium.

• la figure 1 est une vue en perspective d'une clé dynamométrique conforme à l'invention ;
• la figure 2 est une vue en perspective éclatée de la clé illustrée à la figure 1 ;
• la figure 3 est une vue en coupe longitudinale suivant la ligne III-III illustrée à la figure 1 ;
• la figure 4a est un graphique d'une courbe de mesure correspondant au serrage en fonction du temps de la clé illustrée à la figure 1 ;
• la figure 4b est un graphique d'un mode de calcul de la détection de la rupture d'équilibre de la clé illustrée à la figure 1;
• la figure 5 est un organigramme de fonctionnement de la clé illustrée à la figure 1 ;
• la figure 6a est un organigramme suivant un premier mode de détection de la rupture d'équilibre de la clé illustrée à la figure 4a ;
• la figure 6b est organigramme suivant un deuxième mode de détection de la rupture d'équilibre de la clé illustré à la figure 4b ;
• la figure 7 est un schéma électronique de principe de la clé de la figure 1.

A particular embodiment of the invention will now be described in more detail with reference to the accompanying drawings, in which:

• the figure 1 is a perspective view of a torque wrench according to the invention;
• the figure 2 is an exploded perspective view of the key illustrated in figure 1 ;
• the figure 3 is a longitudinal sectional view along the line III-III illustrated at figure 1 ;
• the figure 4a is a graph of a measurement curve corresponding to the tightening as a function of time of the key illustrated in FIG. figure 1 ;
• the figure 4b is a graph of a calculation mode of the detection of the break of equilibrium of the key illustrated in the figure 1 ;
• the figure 5 is an operating chart of the key illustrated in the figure 1 ;
• the figure 6a is a flowchart according to a first mode of detecting the break of equilibrium of the key illustrated in FIG. figure 4a ;
• the figure 6b is a flowchart according to a second method of detecting the break of equilibrium of the key illustrated in FIG. figure 4b ;
• the figure 7 is an electronic schematic of the key to the figure 1 .

On the Figures 1 to 3 a torque wrench according to the invention is shown, the key having a longitudinal axis XX, oriented from "rear" to "front". The key 1 which has been shown essentially comprises a tubular assembly 3 of generally cylindrical shape, defining an external hollow body, a head or drive element 5 towards the front of the key, a handle assembly 7 for grasping the tool , located towards the back of the key.

The tubular assembly 3 is formed of an outer sleeve 3a defined by a cylindrical sleeve, and of an inner tube 3b, the sleeve 3a being fit-fitted on the tube 3b and covering the tube 3b in the front part of this tube. latest.

The sheath 3a, the tube 3b and the head 5 are preferably metal parts.

The key shown is of the type of production trigger, ie the type used in the production workshop to tighten following a large number of identical elements of bolts, to the same predetermined torque. For this type of tool, it is not necessary to readjust the triggering torque frequently. It is understood that the invention applies as well to a so-called production key, particularly trigger as shown in the figures or breakage, an adjustable torque wrench.

On the key shown, the handle assembly 7 is fixedly mounted on the tube assembly 3, the proximal end of the handle assembly 7 comprising a plug 111 having a shutter 119 preserving a passage inwardly of the tubular assembly 3.

Note that a flexible antenna 87, whose function will be described later, protrudes behind the plug 111.

As will be described later also with reference to figures 2 and 3 , the set torque adjustment members are accessible by means of tool inside the tubular assemblies 3 and handle 7, after removal of the shutter 119 of the plug 111.

The key 1 represented on the figures 2 and 3 has a handle assembly 7 comprising a handle-holder 71 of generally cylindrical shape extending coaxially with the axis XX of the key in which a support module 41 is mounted and fixed, said support-handle 71 being fitted and fixed on the rear part of the tube 3b. The handle assembly 7 also comprises a sleeve 101 partially covering the support-handle 71, and on which it is fixed. The rear end of the sleeve 3a engages with play in the front end of the handle holder 71.

The drive head 5 is a part which comprises a front block 21 projecting from the front of the tube assembly 3, an intermediate hinge zone 23, and a rear tail 25 fitted with play in the tube 3 and mounted with possibility of pivoting on the tube 3 around a ZZ axis represented by a pin 27. The drive head also comprises, located between the front block 21 and the hinge zone 23, an elastic bar 26 having in cross section a rectangular shape of constant dimensions along its entire length. The bar 26 has side faces 26a made in a plane parallel to the axis Z-Z, so that they undergo the deformations of the bar 26.

The pin 27 traverses diametrically the hinge zone 23, the sleeve 3a and the tube 3b being integral with the latter two.

The block 21 has, from its front end, an attachment 29, in which can be fitted and attach an actuator (not shown). The latter is typically a reversible reversible ratchet head, provided with a drive square on which fits a screw socket.

It will be noted that on the figure 3 , the cutting plane XZ is assumed vertical and the axis XX is assumed to be horizontal, for the convenience of the description. The orientation of the key shown in this figure corresponds to the actuation of a screw or a nut (not shown) whose axis is vertical.

• un premier cylindre fileté extérieurement 91, pourvu sur sa face d'extrémité arrière 94 d'un alésage 95 central traversant de part en part, et dont un filetage extérieur coopère avec un filetage interne formé sur au moins une section arrière du tube 3b. Le cylindre fileté 91 peut ainsi être vissé et définit une butée axiale arrière ;
• un deuxième cylindre fileté extérieurement 31, pourvu d'une forme d'entraînement 33 tourner vers l'extrémité arrière du tube 3b, et dont un filetage extérieur coopère avec le filetage interne formé sur une section arrière du tube 3b. Le cylindre fileté 31 peut ainsi être vissé ou dévissé à l'intérieur du tube 3b de façon à être déplacé axialement, et, en position dévissée, vient en butée axiale arrière sur le cylindre fileté 91;
• un ressort de compression 61 (représenté symboliquement sur les figures 2 et 3) présentant une raideur élevée, et dont l'extrémité arrière porte sur l'extrémité avant du cylindre 31 ;
• un plateau 63 à bille 64, ce plateau étant solidaire de l'extrémité avant du ressort 61 ;
• un poussoir 65 est de forme générale cylindrique présentant une face arrière en appui sur la bille 64. Le poussoir peut coulisser axialement en étant guidé dans le tube 3b, sous l'effet de sollicitation du ressort 61, transmise par le plateau 63 et la bille 64 ;
• un dé cubique 67 s'applique, au repos, sur les fonds de deux évidements, l'un formé dans la face arrière de la queue 25 et l'autre dans la face avant du poussoir 65, ces faces étant verticales en regard l'une de l'autre.

In the use configuration of the key as shown on the figure 3 , the following elements are arranged coaxially inside the tube 3b, from rear to front, to the rear end of the shank 25:

• a first externally threaded cylinder 91, provided on its rear end face 94 with a central bore 95 passing through from one side, and an outer thread cooperates with an internal thread formed on at least one rear section of the tube 3b. The threaded cylinder 91 can thus be screwed and defines a rear axial stop;
• a second externally threaded cylinder 31, provided with a drive shape 33 to turn towards the rear end of the tube 3b, and an external thread of which cooperates with the internal thread formed on a rear section of the tube 3b. The threaded cylinder 31 can thus be screwed or unscrewed inside the tube 3b so as to be displaced axially, and, in the unscrewed position, comes into rear axial abutment on the threaded cylinder 91;
• a compression spring 61 (represented symbolically on the figures 2 and 3 ) having a high stiffness, and whose rear end is on the front end of the cylinder 31;
• a plate 63 ball 64, this plate being secured to the front end of the spring 61;
• a pusher 65 is of generally cylindrical shape having a rear face bearing on the ball 64. The pusher can slide axially while being guided in the tube 3b, under the effect of biasing the spring 61, transmitted by the plate 63 and the ball 64;
• a cubic die 67 applies, at rest, on the bottoms of two recesses, one formed in the rear face of the tail 25 and the other in the face before the pusher 65, these faces being vertical facing one another.

The assembly formed of the pusher 65 and die 67 defines an axial bearing means on the drive head 25.

It is understood that the axial position of the threaded cylinder 31 determines the compression of the spring 61, and thus the axial bearing force of the pusher 65 on the tail 25, through the die 67. When the set torque determined by the compression of the spring 61 is reached, the die 67 tilts and backs the pusher. The tail 25, by pivoting around the pin 27, then comes into contact with the inner surface of the tube 3.

Note that this relatively violent contact, due to a break in mechanical balance, causes a physical sensation to the operator and clearly indicates that the target torque has been reached.

As shown on figures 2 and 3 , the handle assembly 7 comprises a support module 41 of electrical / electronic means and / or power supply. The support module 41 comprises a support comprising recesses and / or housing and end faces adapted respectively to receive power supply members 42, such as "AAA" type batteries and electrical / electronic circuit boards.

As shown on the figure 2 the proximal end 74 of the handle-holder 71 has a longitudinally extending tubular section of shape and size adapted to receive the support-module 41.

An elongate lumen 75 is made axially and away from the proximal end face 74, over a half circumference of the outer wall of the handle-holder 71.

When mounting the support module 41 in the handle-holder 71, the recesses adapted to receive the organs power supply 42 are positioned opposite the elongate light 75 of the handle-holder 71. This configuration allows quick access to the batteries 42.

After mounting the support module 41 in the handle-holder 71, a fixing element 86 holds the support module 41 in position in the handle-holder 71.

As shown on the figure 2 , means 121 for measuring the deformation of the elastic bar 26 of the driving head 5 consist of measuring element sensitive elements, such as bonded resistive extensometers (strain gages) on the faces 26a of the bar 26. Known measuring means of another type may be used within the scope of the present invention.

A thin elongated insulating plate 121 carrying extensometers formed and wired directly onto it is fixed rigidly, and in a manner known per se, on a lateral face 26a of the bar 26.

The extensometers are connected to a sheet of conductive wires 123. This sheet 123 travels through an inner conduit of the tail 25 of the drive head 5, just behind the hinge zone 23, through an orifice of input 26b in communication with an outlet port 26c. The sheet 123 then passes through an oblong slot 3c located in the distal portion of the tube 3b to continue its path, inserted in a longitudinal groove 3d made on the outer surface of the tube 3b.

The end of the ply 123 opposite the plate 121 carrying the extensometers is connected to a connector 124, itself connected to one of the electrical circuit plates of the support module 41 via a clearance 77 made on the handle support 71 between the light 75 and the distal end 72 in the half circumference opposite that of the light 75.

In addition, the handle holder 71 has, between the clearance 77 and the distal end 72, a groove 78 is adapted to receive a seal 80, such as an O-ring.

The plug 111, shown on figures 2 and 3 , also comprises a passage 118 extending in the axis XX of the key 61 and in the extension of a central duct 47 of the support of the support module 41.

This arrangement allows an operator to introduce a screwdriver blade or a male key to access from the outside to the drive portion 33 of the second threaded cylinder 31 passing successively and from outside, the plug 111, the support module 41, the first threaded cylinder 91.

The plug 111 also comprises a passage 120 capable of passing a flexible antenna 87 connected to one of the electrical / electronic circuit boards of the support module 41.

• la mesure de la déformation du barreau d'épreuve 26 liée à l'utilisation d'éléments sensibles résistifs 121, correspondant à la mesure du couple appliqué à l'élément de fixation,
• le traitement électronique d'un signal issu de ladite mesure,
• le traitement par calcul de données numériques issues dudit traitement électronique, traitement par calcul apte à fournir une information relative à la détection de la rupture d'équilibre mécanique.

The method of detecting mechanical breakage during manual tightening to the torque of a fastener element when the applied torque reaches a predetermined target torque according to the invention is decomposable according to the following steps:

• the measurement of the deformation of the test bar 26 related to the use of resistive sensitive elements 121, corresponding to the measurement of the torque applied to the fixing element,
• the electronic processing of a signal resulting from said measurement,
• calculating processing of digital data from said electronic processing, processing by calculation capable of providing information relating to the detection of the mechanical equilibrium break.

The resistive sensitive elements such as extensometers or strain gauges 121, are connected, in known manner, in a Wheatstone bridge circuit, reflecting the deformation of the test bar 26 in resistance difference. The batteries or accumulators 42 located on the support module 41 constitute the voltage source supplying the bridge circuit.

The support module 41 comprises electronic means for processing the signal from the strain gauges 121.

The support module 41 also comprises electronic calculation means for detecting whether or not the break in mechanical equilibrium has occurred. The support module 41 also comprises electronic means for transmitting information corresponding to the detection of breakage of equilibrium and / or the measurement.

As shown on the figure 7 , the electronic diagram comprises a bridge gage circuit 121 connected to one or more amplifier inputs 201. The output of the amplifier is connected to a double analog / digital conversion device 203 and a microcontroller 205. Memory means electronic 207 can store one or more information. Means 215 make it possible to perform calculations on digital data from the preceding electronic devices. The power supply of these elements is provided by the batteries 42.

Information from the electronic equipment of the key described above can be transmitted remotely 217 to a control equipment 219 via a transmission module 209 and an antenna 87. In other variants, these same information can be displayed via a display device such as a screen 211 or a light emitting diode display device 213.

The operation of a clamping sequence will now be described.

The figure 4a represents a measuring curve of the tightening torque Ci in the time t, characteristic of a mechanical equilibrium breaking key. The curve has two consecutive peaks 301 and 302, separated by a valley shape 305. When the setpoint torque determined by the compression of the spring 61 is reached, the key undergoes a break in mechanical equilibrium defining the trip. The valley form 305 corresponds to the breakage of mechanical equilibrium.

Once the mechanical balance is broken, the operator does not instantly release the force exerted on the key. Over-torque, ie an additional torque to the setpoint torque is thus applied to the fixing element after the triggering of the key.

The peak 302 corresponds to the measurement of the excess torque applied after the break in equilibrium, that is to say the maximum torque CM applied to the fastener once the equilibrium has been broken. The peak 301 corresponds to the measurement of the torque applied before the break in equilibrium.

The figure 5 presents a flowchart of a torque tightening cycle.

A parameterization phase of the tool is performed before any operation. It consists of storing an identification number of the tool, predetermining a first low measurement threshold C0, a second low measurement threshold C1 and initializing the number of clamping cycles.

The key has a 401 slow sampling "sleep" mode. is realized. This measurement Ci is stored and compared 405 to the first predetermined low threshold C0.

If the measurement Ci is below the threshold C0, the "sleep" mode is preserved with a slow sampling. If the measurement Ci is greater than the threshold C0, the key then goes into "work" mode 407 fast sampling. The microcontroller stores in a memory 409 a value of the maximum torque CM equal to the threshold value C0.

During the clamping phase, the microcontroller continuously samples the voltage of the gauges 410 and compares the measurement value Ci to the maximum torque value CM. The microcontroller retains the highest value. The value of the measured maximum torque CM is thus stored in a memory 413.

The stored value is then compared 415 to the second predetermined lower threshold C1.

If the value Ci is greater than the threshold C1, the "work" mode is maintained with a fast sampling. If the value Ci is below the threshold C1, the microcontroller executes a mechanical equilibrium break presence test 417.

If this last test is negative, the "sleep" mode is restored.

If the presence test is positive, the microcontroller increments the number of cycles 419. A positive presence test conditions the transmission 421 of one or more information relating to the clamping sequence, such as the presence of the mechanical equilibrium break. and / or the maximum torque value CM, an identifier number of the tool, the number of the cycle.

The mechanical equilibrium break detection is performed by analyzing the specific waveform created by the sudden change in the resistance of the gauges at the moment of tripping.

The variation of the gauge voltage is in the form of a pulse whose relaxation time is characterized by the natural frequency of the test body. This relaxation time is fixed because it is linked to the accuracy of the mechanical equilibrium break.

The figure 6a presents a flowchart of a first mode of detection of the mechanical equilibrium break.

The microcontroller samples 501 the output voltage of the measuring means of the gauges. A computer 215 performs a derivation calculation dCi / dt of the output voltage Ci with respect to the time t and stores 503 the value of this derivative in a memory m.

The computer 215 compares 505 the value of the calculated derivative m to a predetermined slope value m0.

If the calculated value m is less than the predetermined value of slope m0, the computer 215 performs a new derivative calculation on the following sampling.

If the calculated value m is greater than the predetermined value of slope m0, the microcontroller provides a mechanical equilibrium break presence information. After digital-to-analog conversion, a trip presence signal can be transmitted 507.

The figure 6b presents a flow diagram of a second mode of detection of the mechanical equilibrium break.

The microcontroller samples 600 the output voltage of the measuring means of the gauges. A first curve 601 for measuring the tightening torque Ci as a function of time t is stored.

A second curve 602, identical to the first curve 601, is stored with a delta offset t, positive and low, in time t.

A calculator performs a test of identifying the presence of an intersection 305 'between the first 601 and the second curve 602.

If the response to this test is positive, the mechanical equilibrium break 305 'is present. The microcontroller provides information of presence of breakage of mechanical equilibrium. After digital-to-analog conversion, a trip presence or break-off signal can be transmitted 607.

If the response to this test is negative, the microcontroller continues sampling 600.

The figure 4b represents a first curve 601 for measuring the tightening torque Ci in time t. The first curve 601 has a first peak 301 'characteristic of a trigger key.

The second constructed curve 602 has a peak 301 ", itself shifted by a delta interval t in time.

The intersection 305 'of the first 601 and second 602 curves defines the calculated instant of the triggering or breaking of mechanical equilibrium.

We understand that the detection of the breakage of mechanical equilibrium is essential to count the number of cycles performed by a production operator and thus improve traceability.

The transmission may be a wireless link transmission 217 to a control equipment 219 either outside or integrated in the key. In this case, it may be a radio frequency link in the 869Mhz ISM band. The previous wireless transmission can be replaced by wired link transmission.

The value of the maximum torque measured after breaking the mechanical balance of the key can then be displayed on a screen of the control equipment.

The detection method according to the invention allows other steps such as, successively, the measurement of the maximum torque after the break of mechanical equilibrium, the transmission of the measurement of the maximum torque after the breakdown of mechanical equilibrium and the display. the measurement value of the maximum torque after the break in mechanical equilibrium.

The steps of the detection method may be preceded by a step of identifying the tool.

The clamping method according to the invention is characterized in that it comprises the steps of providing information corresponding to the measurement of the torque applied to the fixing element, the electronic processing and the provision of information corresponding to the measurement of the maximum torque applied after the failure of mechanical equilibrium, the transmission of said information corresponding to the measurement of the maximum torque after the break of mechanical equilibrium.

The steps of the clamping process may be preceded by a step of identifying the tool. These steps can be followed by a step of displaying the measurement value of the maximum torque after the break in mechanical equilibrium.

It is understood that the invention applies particularly well to a torque wrench trigger, as described above, but it could also be suitable for other torque tools, for example a wrench or a screwdriver.

The invention that has just been described makes it possible to make reliable the break-off detection function. mechanical, without additional space for a dynamometric tool.

The invention which has just been described makes it possible to improve the traceability of a tightening by a dynamometric tool, by measuring the over-torque.

Claims (24)

1. Mechanical dynamometer tool, in particular a wrench, for manually applying torque, said tool comprising:

   mechanical means (3, 7, 63, 64, 65, 67) suitable for providing a predetermined torsion torque to a drive portion (5) intended to co-operate with a tightening member for driving a fastener element, said mechanical means being in mechanical equilibrium under the action of suitable bias means (31, 61), said mechanical means being releasable by breaking the mechanical equilibrium,

   and means for detecting the break in mechanical equilibrium;

   characterised in that the means for detecting the break in mechanical equilibrium comprise measurement means (121) providing a signal corresponding to the measurement of the torque applied to the fastener element, means (201, 203, 205, 207) for electronically processing said signal,

   and means (215) for computationally processing data resulting from the electronic processing of said signal.
2. Dynamometer tool according to claim 1, characterised in that the computation means detect the break in mechanical equilibrium by computing the derivative (501, 503, 507) of the measured value of the torque in relation to time.
3. Dynamometer tool according to claim 1, characterised in that the computation means detect the break in mechanical equilibrium by computing the intersection (600, 601, 602, 605, 607) of a first curve (601) and of a second curve (602), the first curve representing the measured value of the torque in relation to time, and the second curve being identical to the first curve with a small, positive offset (603) over time.
4. Dynamometer tool according to any of claims 1 to 3, characterised in that the means (201, 203, 205, 207) for electronically processing the signal and the computation means (215) are arranged inside the wrench.
5. Dynamometer tool according to any of claims 1 to 4, characterised in that the wrench further comprises means (209) for transmitting, to a station (219) outside the tool, the measurement of the maximum tightening torque applied to the fastener element, and in that said station displays the value of the maximum tightening torque applied to the fastener element.
6. Dynamometer tool according to any of claims 1 to 5, characterised in that the wrench further comprises means (209) for transmitting, to receiving means (211; 213) that are integral with the tool, the measurement of the maximum tightening torque applied to the fastener element, and in that said receiving means display information corresponding to the value of the maximum tightening torque applied to the fastener element.
7. Dynamometer tool according to any of claims 1 to 6, characterised in that the measurement means comprise resistive sensor elements (121).
8. Dynamometer tool according to claim 7, characterised in that the measurement means comprise a plurality of strain gauges (121) connected in a bridge circuit.
9. Dynamometer tool according to any of claims 1 to 8, characterised in that the tool is a disengagement wrench.
10. Dynamometer tool according to any of claims 1 to 8, characterised in that the tool is a break back torque wrench.
11. Dynamometer tool according to any of claims 1 to 8, characterised in that the tool is a screwdriver.
12. Dynamometer tool according to any of claims 7 to 11 in combination with claim 5, characterised in that the information is transmitted by radio frequency.
13. Dynamometer tool according to any of claims 1 to 12, characterised in that the bias means comprise a spring, the compression of which determines the limit torque, said spring participating in the axial force that bears against said mechanical means, in that measurement means (121) formed by sensor elements of measurement members, such as resistive extensometers or strain gauges, provide information corresponding to the measurement of the torque applied to the fastener element, and in that an electronic processing unit (41), integrated in the tool, provides information corresponding to the measurement of the maximum torque applied to the fastener element after the mechanical equilibrium is broken and transmits to a receiving unit (211, 213, 219) said information corresponding to the measurement of the maximum torque applied to the fastener element after the mechanical equilibrium is broken.
14. Dynamometer tool according to claim 13, characterised in that the processing unit is arranged inside the wrench.
15. Dynamometer tool according to either claim 13 or claim 14, characterised in that the receiving unit is a station (219) outside the tool, and in that it displays the value of the measurement of the maximum tightening torque applied to the fastener element.
16. Dynamometer tool according to either claim 13 or claim 14, characterised in that the receiving unit is an integral unit (211, 213) of the tool, and in that it displays the value of the measurement of the maximum tightening torque applied to the fastener element.
17. Method for detecting a break in mechanical equilibrium during manual torque tightening of a fastener element when the applied torque reaches a predetermined limit torque, characterised in that the method comprises the following steps:

    - providing information corresponding to the measurement (501; 600) of the torque applied to the fastener element;

    - electronically processing said information (201, 203, 205, 207);

    - computationally processing (503, 505; 601, 602, 305') digital data resulting from the electronic processing of said information.
18. Method for detecting a break in mechanical equilibrium during manual torque tightening of a fastener element when the applied torque reaches a predetermined limit torque, characterised in that a step of providing (413) information corresponding to the measurement of the maximum torque applied to the fastener element, once the equilibrium is broken, follows the computation step according to claim 17.
19. Method for detecting a break in mechanical equilibrium during manual torque tightening of a fastener element when the applied torque reaches a predetermined limit torque, characterised in that a step of transmitting (421) the information corresponding to the measurement of the maximum torque applied to the fastener element, once the equilibrium is broken, follows the providing step according to claim 18.
20. Method according to claim 19, characterised in that the transmission step is a radio-frequency transmission step.
21. Method for manually torque tightening a fastener element by using the principle of mechanical equilibrium being broken when the applied torque reaches a predetermined limit torque, characterised in that the method comprises the following steps:

    - providing information corresponding to the measurement (401, 403, 407, 410) of the torque applied to the fastener element;

    - electronically processing (405, 409, 411, 415) and providing (413) information corresponding to the measurement of the maximum torque applied after a break in mechanical equilibrium (417);

    - transmitting (421) said information corresponding to the measurement of the maximum torque applied after a break in mechanical equilibrium.
22. Tightening method, characterised in that a step of identifying the tool precedes the steps according to claim 21.
23. Tightening method, characterised in that a step of displaying the tool follows the steps according to claim 21.
24. Tightening method according to any of claims 21 to 23, characterised in that the transmission step is a radio-frequency transmission step.

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