FR2683039A1 - Method and device for checking the tightening angle of electronic torque wrenches - Google Patents

Abstract

The invention relates to an electronic torque wrench. It has devices for measuring the angle of rotation as well as the rotational torque during the tightening of elements having a screw thread, by interposing an extension, with an electronic calculation unit, as well as devices for evaluating the measurements, these making is possible to carry out operations for the additional correction of the angle of rotation by using correction factors to take into account the elastic torsion to which the extension used is subjected. The invention is applicable to electronic torque wrenches.

Description

The present invention relates to a method and a device for

  tightening angle control in electronic torque wrenches which

are equipped with an extension.

  Electronic torque wrenches are known devices which consist essentially of a conventional key body provided with a drive rod, at one end being provided a ratchet mechanism with a hexagon or the like, and the other end of the tool is arranged an actuating handle On the tool rod is provided an electronic device for analog / digital input This device receives an analog measurement signal by a multitude of bands or strain gauges which are fixed on the tool shank, which allows a measurement of the tightening torque. An encoder or similar device is also provided, by means of which it is possible to measure the tightening angle. The analog signals transmitted are processed, and the measurement results are displayed on a screen

visualization.

  An example of a known torque wrench is described in Italian patent application No. 20759 A / 89 which was previously filed by

the plaintiff.

  In this previous application, an electronic torque wrench has been described which has a tool rod, with a ratchet mechanism and an actuating handle, provision has also been made for strain gauges or bands, as well as a receiving circuit. measurement signals, for

  signal amplification, as well as for processing measurement signals.

  The tool also has a power source and a keyboard with a screen

  display for reading data.

  The known torque wrench is characterized in that bands or strain gauges are arranged on the tool shank and which are opposite

  to each other in the pivot plane of the tool shank.

  The signal outputs of the extensometric bands are incorporated into a feedback circuit of a differential amplifier to obtain an algebraic sum of the signals, i.e. a value of the measurement signal which is greater than the individual values of the signals. of the two extensometric bands At the same time, a neutralization of the influence quantities due to the temperature oscillations is carried out. Following the differential amplifier, a device is provided for processing the data.

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  Following the measurement signal processing device, after having inserted a switch, amplification channels are provided which are independent of each other and which are coupled to the extensometric bands so as to obtain signals measurement when rotating to the right and measurement signals when rotating to the

  left of the tool which are characterized by the same measurement sensitivity.

  At the end of the amplification channels, a switch is provided by which the amplified analog signals are passed to the signal processing device, and in the digital processing unit is stored a program for establishing signaling signals. measurement using which a zero point deviation occurring automatically is corrected

extensometric bands.

  In a known electronic torque wrench of the type described, precise measurement and reading is possible over a period of time with high signal consistency, in addition, a check of the instantaneous values can be carried out during the tightening operation as well as a check the clamping angle and the admissible elongation limit of the elements provided with a

  thread, such as screws, nuts, or the like.

  There is the possibility of performing both right-hand and left-hand tightening operations with exactly the same reading accuracy. Changes due to temperature differences as well as changes in measured values are compensated for by an application of force applied differently, i.e. by grasping the

  tool shank in different places.

  The possibility of controlling a precise tightening operation by means of the electronic torque wrench of the known type of construction consists in indicating the tightening angle, i.e. the angular rotation of

  the element having a thread, for example a screw to be tightened.

  This angular rotation can be measured with mechanical devices, for example using a goniometer or with electronic measurement systems, for example an encoder or similar device which is

known by the prior art.

  The encoder indicates a rotational movement with respect to a locally fixed point and transmits data signals corresponding to an appropriate computing unit, for example to a microprocessor which is arranged in the

key body itself.

  Obviously, the value displayed on the display screen must correspond to the effective rotational movement of the element having a thread, for example the verification operations for torque wrenches are designed so that the value of the angle of rotation read corresponds to the actual rotational movement starting from the fact that the element

  with a thread is tightened directly by the key.

  When using such known keys, it happens that the element having a thread is disposed in a recess and requires the use of an extension of corresponding length, extension which is placed on the

  torque wrench.

  In this case, when a torque is applied by the key, there will occur simultaneously a rotation of the element having a thread, as well as an elastic torsion of the extension As the device for measuring the angular rotation is connected to the body of the torque wrench, it occurs due to the elastic torsion of the extension an additional rotation which leads to a measurement error during the measurement of the angle of rotation of the element having a thread The values of these measurement errors are such that we can no longer accept them and that we cannot integrate them into

  normal measurement tolerances when using torque wrenches.

  It is therefore found that known torque wrenches are exposed to a measurement error when an extension is provided to act on the element.

having a thread.

  The object of the present invention is to avoid the drawbacks of the prior art and to propose a method making it possible to compensate for the measurement error which occurs from the clamping angle when it is necessary to provide a

  extension between the part with a thread and the torque wrench.

  The object according to the invention is achieved in that a method is proposed for controlling the tightening angle in an electronic torque wrench which is equipped with an extension, the method being characterized by the following operations: characterization of '' a series of tool extensions by entering factors and values for correction of the elastic torsion of the extension, and storage of these values in the electronic calculation unit, data entry for the choice of a determined extension to be used and determination of the correction factor, execution of an additional correction during the tightening operation of the value of the measured angle of rotation of the torque wrench by the electronic calculation unit, by subtraction of the measured value d '' a corrected angular value which consists of the product with the correction factor chosen for the measured value of the tightening torque, and the indication of a value

  actual for the angle of rotation of the element having a thread.

  According to a further development of the invention, an instantaneous initial value is determined before executing the tightening operation, which takes account of the play existing between the tool to be used and the element having a thread, and in that the value instantaneous is subtracted by the electronic calculation unit, during the execution of additional correction operations, from the measured value of the tightening torque before multiplying with the factor

correction.

  According to another advantageous additional development of the invention, the method for measuring the clamping angle of elements having a thread is characterized by the following operations: a) characterization of the extensions used by correction factors which characterize the torsion elasticity of the extension, and introduction of the values obtained into the memory of an electronic calculation unit, b) input of commands for the extension used as well as the corresponding correction factor, c) execution by an electronic calculation unit and during l tightening operation of additional correction operations of the value obtained from the angle of rotation of the torque wrench, and subtraction of an angular correction value which is formed essentially by the product of the correction factor chosen and the value instant measured during the tightening operation, and establishment of a nominal value of the angle of rotation ation for

  the element having a thread.

  Yet another advantageous development of the method consists in determining before the element is tightened a value of the torque which takes account of the play occurring in the connection between the tool and the element having a thread, and that the value obtained is subtracted by the electronic calculation unit during the execution of the additional correction operations of the measured value of the tightening moment before

  carry out a multiplication operation with the correction factor.

  The invention also relates to a device which is placed on a torque wrench, and which is characterized in that the electronic calculation unit has data inputs and memories for correction factors relating to the specific elastic torsion of the extensions. used, and

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  data inputs for control operations chosen as a function of the extension used and thus of the correction factor, with an electronic calculation unit, means for carrying out during the tightening operation an additional correction of the value of the angle of measured rotation of the torque wrench after subtracting a correction angle from this value, which is essentially formed by the product of the chosen correction factor and the measured value of the tightening torque to form a real value for the angle

  of rotation of the element having a thread.

  According to an additional characteristic, means are provided for determining and storing a value for an initial torque to take account by means of this value of friction quantity in the torque wrench and in the element having a thread, and with installations in the electronic calculation unit to subtract the measured value

  of the tightening torque before making an additional correction.

  The invention will be better understood and other characteristic aims, details

  and advantages thereof will appear more clearly during the description

  Explanatory which will follow made with reference to the attached schematic drawings given solely by way of example illustrating an embodiment of the invention and in which: FIG. 1 is a side view of a known electronic torque wrench; Figure 2 is an electronic modular block diagram of the torque wrench according to the invention; and Figure 3 is a block diagram of the operations which are

  materialized in the torque wrench calculation device.

  Referring to FIG. 1, extensometric bands or gauges 7 and

  8, for example made of metal, are fixed to the rod 2 while being in contact with the latter.

  It is thus possible to measure the tightening torque when using the key. A known encoder 5, for example an incremental encoder, provides the

  possibility of measuring the angle of rotation when the tool is pivoted.

  There is therefore the possibility of carrying out the following control operations during the tightening operation: control and measurement of the tightening torque essentially using the analog / digital electronic device 6 by exploiting the values obtained by the extensometric bands 7 which are displayed on a display screen; formation of an acoustic signal and / or a visible signal when a limit value entered via the keyboard is reached; control of the angle of rotation by application of a small predetermined torque This comparative torque eliminates all bearing play between the elements in connection with the element having a thread, this is done during the operation of following tightening a control by the electronic device 6 which verifies the angular value measured by the encoder 5, which displays this on the display screen and which emits an acoustic or optical command signal when a pre-set limit value is reached set via the keyboard; control of the tightening operation when reaching an elastic limit: first apply a determined torque, then the device

  electronics simultaneously measures the angle of rotation and the torque.

  The increase in the angle of rotation relative to the modification of the torque is then evaluated by deducing from it the value of the torque

of initial rotation.

  In this case also, visible control indications and / or

  acoustics are possible when certain measured values are reached.

  The need to use an extension would lead to measurement errors in cases where the angle of rotation or the elastic elongation limit of the element is checked. When the tightening torque is measured, it is possible to be based on the fact that the required tightening torque is transmitted without being

  influenced by the extension which elastically deforms.

  In FIG. 2, RA designates a measuring device for determining the angle of rotation, for example of the coder bearing the reference numeral 5 This device produces signals which are proportional to the angle a in accordance with the rotation movement of the torque wrench These analog signals are stored in an appropriate device AM Pl of a

  construction known to be further processed in the microprocessor.

  RC designates a device for detecting the tightening torque, for example a device made up of a number of tensile bands 7, 8 according to FIG. 1, which emits an analog signal proportional to the tightening torque Nm of the torque wrench The signal analog is amplified in an AMP 2 amplifier and transformed into a digital signal, this is done

  in an AD 2 analog / digital converter.

  The RC and AMP 2 blocks can be made advantageously

  as is known from the prior art.

  PROC designates an electronic calculation unit which has a keyboard as well as a known display screen This unit has a known microprocessor which can be programmed as will be described later. In accordance with the present invention, operating devices have been provided which make it possible to compensate for the error of measurement of the angle of rotation a when using an extension and when producing an

  inevitable torsion during the tightening operation.

  The numerical value of the tightening torque Nm is reduced by using a subtraction element Si, from the value of the compensation torque Nmc, a value which was determined by the previous measurement and which is stored in the calculation unit. A result is obtained of the torque which is multiplied using a multiplication element M 2 with a correction factor Fc of the angular value and which depends on the extension used This factor is also stored in the calculation device A correction value of l is obtained angle ac which corresponds to the additional angle of rotation which forms due to the elastic torsion of the extension and which is

  proportional to the tightening torque Nm.

  The correction angle obtained xc is deduced in a subtraction element 52 from the value of the angle of rotation a of the torque wrench which is at the end of the element AD 1 A resulting angle ar is thus represented which indicates the effective angular rotation of the element provided with a

  threading after the tightening operation.

  Usually, electronic torque wrenches are equipped with extensions which have a determined length and which are made of a given material and thus have defined elasticity and torsion characteristics. The corresponding angular correction factors Fc are usually entered in the unit. processing of PROC data, either by a normal input operation, or by a wired preliminary input or by using a keypad We also have the possibility of introducing new

  values for extensions of a new type.

  The data processing device PROC then processes, using known methods, the resulting angular values as well as the tightening torque Nm, and the control operations described during the tightening operation are carried out The process steps characterizing the present invention can be advantageously performed by performing the operations of

  specific programs which are stored in the PROC processing unit.

  From the following description of the functional diagram of these

  routines, those skilled in the art can establish the required operations, referring to Figure 3, using the machine-specific programming language of

the chosen calculation unit.

  At the beginning (step 1 in FIG. 3) the display screen of the calculation unit indicates that it is necessary to choose the desired control operation to be carried out (angle, torque or elastic limit) , and usually we

  enter the necessary information via the keyboard.

  When the control operation does not provide for the measurement of the angular rotation, the calculation unit performs operations of a known type, namely

  calculation operations concerning the control and measurement of the tightening torque.

  Insofar as the control operations include a measurement of the angular rotation (angle control or control of the elongation limit) the calculation unit takes the numerical value of the matching torque Nmc in known manner: by example we can enter the value Nmc by the keyboard, or at the start of the tightening operation, we introduce by the keyboard a command to store the value Nmc which we have just reached and which is displayed on the screen Then the calculation unit (step 2) displays on the display screen that an extension must be used If this extension is already fitted on the torque wrench, it must be indicated on the display screen which type of extension is used This information can be entered directly by the keyboard or by a corresponding code which refers to a specific extension. The reference quantities of the extension have already been stored beforehand. ble in the memory of the computing unit or, if you want to use a new extension,

  it is necessary to re-enter the correction factor Fc via the keyboard.

  The steps relating to the introduction of the corresponding initial torque Nmc as well as the correction factor Fc of the extension used can also be

  performed following an opposite temporal succession.

  Then (step 3), the calculation unit receives the values relating to the angle of rotation and the tightening torque The data which are supplied by the encoder and the extensometric bands are transformed into digital signals, and the calculation operations described are carried out on the basis of actual values of the torque and the angle of rotation The tightening operations are now carried out essentially in a known manner There is an indication of the measured values and / or the establishment of acoustic signals when determined limit values are reached During the use of the tool, the operator will choose by an introduction by means of the keyboard, the type of control to be carried out Then, insofar as the control operation also concerns a measurement of the angle, in response to the questions asked on the display screen, we introduce the corresponding instantaneous value as well as the type of extension used Then l operator performs the tightening operation of the element with a thread During the tightening operation, the torque wrench calculation unit measures the angular values

  and the instantaneous values and, as explained in the previous description,

  uses and displays the values obtained on the display screen to ensure

  thus operator control.

  The previous description shows the advantages that can be obtained

  thanks to the invention and in what simple manner the proposed device can be produced. The device does not require costly elements relating to the torque wrench, but it suffices simply to modify the course of the process.

Claims (5)

  1 Method for controlling the tightening operation when using an electronic torque wrench, for performing tightening operations on elements having a thread, by inserting an extension which is subjected to elastic torsion and by performing measurements of the product rotation angle and the tightening torque, followed by data processing using an electronic calculation unit which presents data inputs and outputs for the measurement data obtained, characterized by the following steps: characterization of a series of tool extensions, by introducing the factors and values for correction of the elastic torsion of the extension and storage of these values in the electronic calculation unit, data entry for the choice of a determined extension to be used and establishment of the correction factor, execution, during the tightening operation, of an additional correction of the value of the measured angle of rotation of the torque wrench via the electronic calculation unit by subtracting the measured value from a corrected angular value which consists of the product with the chosen correction factor from the measured value of the tightening torque , and indication of a real value of the angle of rotation of   the element having a thread.   2 Method according to claim 1, characterized in that, before carrying out the tightening operation, an instantaneous initial value is determined which takes account of the play existing between the tool to be used and the element having a thread, and in that the momentary value is subtracted by the electronic calculation unit, during the execution of additional correction operations, from the measured value of the tightening torque before carrying out the multiplication with the correction factor.   3 Method for measuring the clamping angle of elements having a thread using an electronic torque wrench by placing on the element having a thread an extension which is exposed to elastic torsion, the method comprising operations of measurement to determine the angle of rotation of the torque wrench as well as the tightening torque and then processing of the data signals using an electronic calculation unit equipped with data inputs and outputs for the data the measurement operation according to claim 1, characterized by the following steps: a) characterization of the extensions used by correction factors characterizing the elastic torsion of the extension, and entry of the values obtained in the memory of a calculation unit electronic, b) input of commands relating to the extension used as well as the corresponding correction factor, c) execution by means of an electronic calculation unit and during the tightening operation of additional correction operations of the value obtained from the angle of rotation of the torque wrench, and subtraction of an angular correction value which is essentially formed by the product of the correction factor chosen and the instantaneous value measured during the tightening operation, and establishment of a nominal value of the angle   of rotation of the element having a thread.   4 Method according to claim 3, characterized in that establishes before tightening the element a value of the torque and which takes account of the play occurring in the connection between the tool and the element having a thread, and in that the value obtained is subtracted by the electronic calculation unit during the execution of the additional correction operations of the measured value of the tightening torque, before the execution of a   multiplication with the correction factor.   Electronic torque wrench comprising control devices for the tightening operation of elements having threads, by inserting an extension exposed to elastic torsion, with a device for measuring the angle of rotation as well as the tightening torque thus an electronic calculation unit for processing the measured values, by providing an input keyboard and devices for visible and / or acoustic display, characterized in that the electronic calculation unit has: inputs data and memories of the correction factors relating to the specific elastic torsion of the extensions used; and data inputs for commands chosen as a function of the extension used and thus of the correction factor, comprising: an electronic calculation unit, means for carrying out during the tightening operation an additional correction of the value of the angle measured rotation of the torque wrench by subtracting a correction angle from this value, which consists essentially of the product of the correction factor chosen and the measured value of the tightening torque in order 12 2683039   establish an actual value of the angle of rotation of the element having a thread. 6 Electronic torque wrench according to claim 5, characterized in that means are provided for determining and storing a value of an initial torque, in order to take account by this value of the friction quantities in the torque wrench and in the element having a thread, and devices in the electronic calculation unit for subtracting the measured value from the tightening torque before carrying out an additional correction.