Patent Application
20050223817
The present invention relates to a mechanical dynamometer tool, in particular a torque wrench, for manually applying torque, said tool comprising mechanical means suitable for delivering predetermined torsion torque to a drive portion designed to co-operate with a tightening drive member for driving a fastener element, said mechanical means being in mechanical equilibrium under the action of suitable bias means, said mechanical means being releasable by breaking the mechanical equilibrium, and means for detecting a break in mechanical equilibrium.
It is known that operations for tightening fastener elements in industrial environments require increasing levels of traceability, i.e. knowledge of all of the information and of the measures that make it possible to monitor and to reconstruct rapidly the steps of the process.
For tightening operations, dynamometer tool manufacturers propose mechanical tools whose principle is based on equilibrium breaking in a manner that is very perceptible, making it possible for the break in equilibrium to be detected by a device having an electrical circuit provided with switch means whose state is changed by the break in equilibrium, and with a processing unit adapted to use the information relating to the state of said switch means. The entire detection device is generally housed in a housing fastened to the outside of the body of the tool.
Such a construction is not entirely satisfactory because the housing defines a protuberance on the periphery of the body of the tool, which protuberance is potentially a hindrance to inserting the tool into a mechanical member on which the operator is acting.
In addition, such a construction uses a miniature switch whose life is relatively short and that poses problems of reliability when it is subjected to sudden actuation, which generally applies for tools operating by breaking mechanical equilibrium.
Known devices also suffer from the drawback of not taking account of the phenomenon of over-torque that is exerted during the operation of tightening to torque, once the equilibrium is broken. The value of such over-torque can be as high as 50% of the predetermined set torque when the wrench is used under certain conditions.
In addition, the use of electronic dynamometer wrenches is not desired on assembly lines because, with such wrenches, no physical sensation of going beyond the tightening torque can be felt.
A main object is to remedy those drawbacks and to provide a mechanical dynamometer tool whose compactness is not reduced and whose reliability is increased.
Another object is to provide a mechanical dynamometer tool that makes it possible to improve the traceability of the tightening-to-torque operations, by taking account of the phenomenon of over-torque.
To these ends, in a mechanical dynamometer tool of the invention, the means for detecting a break in mechanical equilibrium comprise measurement means delivering a signal corresponding to the measurement of the torque applied to the fastener element, electronic processing means for electronically processing said signal, and computation processing means for computationally processing data output from the electronic processing of said signal.
According to other characteristics of the invention:
The invention also provides a method of detecting a break in mechanical equilibrium during manual tightening to torque a fastener element when the applied torque reaches a predetermined set torque, the method comprising the following steps:
Finally, the invention provides a method of manually tightening to torque a fastener element by using the principle of mechanical equilibrium being broken when the applied torque reaches a predetermined set torque, the method comprising the following steps:
A particular embodiment of the invention is described in more detail below with reference to the accompanying drawings, in which:
a is a graph showing a curve of the measured tightening of the wrench shown in
b is a graph of a method of calculation for detecting a break in equilibrium of the wrench shown in
a is a flow chart of a first mode of detection of a break in equilibrium of the wrench shown in
b is a flow chart of a second mode of detection of a break in equilibrium of the wrench shown in
FIGS. 1 to 3 show a torque wrench of the invention, the wrench having a longitudinal axis X-X, extending from “back” to “front”. The wrench 1 that is shown essentially comprises a tube assembly 3 that is cylindrical in overall shape, and that defines a hollow outer body, a drive element or head 5 in the vicinity of the front of the wrench, and a handle assembly 7 for taking hold of the tool, which handle assembly is situated in the vicinity of the back of the wrench.
The tube assembly 3 is made up of an outer sheath 3a defined by a cylindrical sleeve, and of an inner tube 3b, the sheath 3a being fitted snugly over the tube 3b and overlapping the tube 3b in the front portion thereof.
The sheath 3a, the tube 3b and the head 5 are preferably metal parts.
The wrench shown is a torque setting or disengagement torque wrench of the production type, i.e. of the type used in a production workshop for tightening in succession a large number of identical nut and bolt fastener elements to the same predetermined torque. For this type of tool, it is not necessary to re-adjust the torque setting frequently. Naturally, the invention is applicable not only to a production wrench, in particular a torque setting or disengagement production wrench as shown in the figures, but also to a break back torque wrench or to an adjustable torque wrench.
On the wrench shown, the handle assembly 7 is mounted in fixed manner on the tube assembly 3, the proximal end of the handle assembly 7 comprising a stopper 111 provided with a lid 119 for closing off a passageway that is provided towards the inside of the tube assembly 3.
It should be noted that a flexible antenna 87, whose function is described below, projects from the back of the stopper 111.
As also described below with reference to
The wrench 1 shown in
The drive head 5 is a part that has a front block 21 projecting from the front of the tube assembly 3, a hinge intermediate zone 23, and a back tail 25 fitted with clearance into the tube 3 and mounted so that it is possible for the tail to pivot relative to the tube 3 about an axis Z-Z which is the axis of a pin 27. Between the front block 21 and the hinge zone 23, the drive head also has a elastically-deformable bar 26 having a rectangular cross-section of dimensions that are constant over its entire length. The bar 26 has side faces 26a that are formed in planes parallel to the axis Z-Z so that they are subjected to the deformations of the bar 26.
The pin 27 passes diametrically through the hinge zone 23, the sheath 3a and the tube 3b and is secured to said sheath and to said tube.
Starting from its front end, the block 21 has an attachment 29 in which an actuator device (not shown) can be fitted and fastened. Such an actuator device is typically a ratchet head that is reversible by turning it around, and that is provided with a drive square onto which there is fitted a bit in the form of a tightening socket.
It should be noted that, in
In the configuration of use of the wrench as shown in
The assembly formed by the pusher 65 and by the die 67 defines axial bearing means for axially bearing against the drive head 25.
It can be understood that the axial position of the threaded cylinder 31 determines the compression of the spring 61, and thus determines the axial bearing force applied by the pusher 65 on the tail 25 via the die 67. When the set torque determined by the compression of the spring 61 is reached, the die 67 tilts and cause the pusher to move backwards. The tail 25, by pivoting about the pin 27, then comes into contact with the inside surface of the tube 3.
It should be noted that the relatively violent contact, due to mechanical equilibrium being broken, causes the operator to feel a physical sensation that indicates clearly to said operator that the set torque has been reached.
As shown in
As shown in
An elongate slot 75 is provided axially and at some distance from the proximal end face 74 and over one half of the circumference of the external wall of the handle support 71.
On mounting the support module 41 in the handle support 71, the recesses suitable for receiving the electrical power supply members 42 are positioned facing the elongate slot 75 in the handle support 71. This configuration makes it possible for the batteries 42 to be accessed rapidly.
Once the support module 41 is mounted in the handle support 71, a fastener element 86 holds the support module 41 in position in the handle support 71.
As shown in
An elongate insulating plate 121 carrying extensometers formed and wired directly on it is fastened rigidly and in a manner known per se to a side face 26a of the bar 26.
The extensometers are connected to a sheet of conductor wires 123. The sheet 123 passes through an internal duct in the tail 25 of the drive head 5, immediately behind the hinge zone 23, by passing through an inlet orifice 26b in communication with an outlet orifice 26c. The sheet 123 then passes through an oblong slot 3c situated in a distal portion of the tube 3b and continues on its route by being inserted into a longitudinal groove 3d provided in the outside surface of the tube 3b.
That end of the sheet 123 which is opposite from the plate 121 carrying the extensometers is connected to a connector 124 which is itself connected to one of the electrical circuit boards of the support module 41 via a setback 77 provided in the handle support 71 between the slot 75 and the distal end 72, in that half of the circumference which is opposite from the half-circumference that is provided with the slot 75.
In addition, between the setback 77 and the distal end 72, the handle support 71 is provided with a groove 78 which is suitable for receiving a sealing gasket 80, such as an O-ring gasket.
The stopper 111 shown in
This arrangement makes it possible for an operator to insert a bit forming screwdriver blade or a wrench in order to access, from the outside, the drive portion 33 of the second threaded cylinder 31 by passing through, successively and from the outside, the stopper 111, the support module 41, and the first threaded cylinder 91.
The stopper 111 is also provided with a passageway 120 suitable for passing a flexible antenna 87 connected to one of the electrical/electronic circuit boards of the support module 41.
The method of the invention for detecting a break in mechanical equilibrium while manually tightening to torque a fastener element when the torque applied reaches a predetermined set torque can be broken down into the following steps:
The resistive sensor elements such as extensometers or strain gauges 121 are connected, in known manner, in a Wheatstone bridge circuit expressing the deformation of the test bar 26 in terms of difference in resistance. The batteries 42, rechargeable or otherwise, situated on the support module 41 constitute the voltage source for powering the bridge circuit.
The support module 41 includes electronic means making it possible to process the signal output from the strain gauges 121.
The support module 41 also includes computation electronic means making it possible to detect whether or not a break in mechanical equilibrium has occurred. The support module 41 also includes electronic means for transmitting information corresponding to break-in-equilibrium detection and/or to measurement.
As shown in
Information output from the above-described electronic equipment of the wrench can be transmitted remotely 217 to monitoring equipment 219 via a transmission module 209 and via an antenna 87. In other variants, this information can be displayed via a display device such as a screen 211 or via a light-emitting diode (LED) display device 213.
Operation of a tightening sequence is described below.
a shows a curve giving measurement of the tightening torque Ci over time t, which curve is characteristic of a wrench operating by breaking mechanical equilibrium. The curve has two consecutive peaks 301 and 303, separated by a trough shape 305. When the set torque determined by the compression of the spring 61 is reached, the wrench undergoes a break in mechanical equilibrium that defines disengagement. The trough shape 305 corresponds to the break in mechanical equilibrium.
Once the mechanical equilibrium has been broken, the operator does not immediately cease to apply the force exerted on the wrench. Over-torque, i.e. torque additional to the set torque is thus applied to the fastener element after the wrench has disengaged.
The peak 303 corresponds to the measurement of the over-torque applied after equilibrium is broken, i.e. the maximum torque CM applied to the fastener element once equilibrium is broken. The peak 301 corresponds to the measurement of the torque applied before equilibrium is broken.
A stage for parameterizing the tool is performed before any operation. It consists in storing a tool identity number in a memory, in predetermining a first low measurement threshold C0 and a second low measurement threshold C1, and in initializing the number of tightening cycles.
The wrench has a slow-sampling “standby” mode 401. During the slow sampling, a measurement Ci 403 is taken. The measurement Ci is stored and compared 405 with the first predetermined threshold C0.
If the measurement Ci is less than the threshold C0, the “standby” mode is continued with slow sampling.
If the measurement Ci is greater than the threshold C0, the wrench then goes over to “working” mode 407 with fast sampling.
The microcontroller stores in a memory 409 a value for the maximum torque CM equal to the threshold value C0.
During the tightening stage, the microcontroller continuously samples 410 the voltage of the gauges and compares 411 the measured value Ci with the maximum torque value CM. The microcontroller retains the higher value. The value of the maximum measured torque CM is thus stored in a memory 413.
The stored value is then compared 415 with the second predetermined low threshold C1.
If the value Ci is greater than the threshold C1, the “working” mode is maintained, with fast sampling.
If the value Ci is less than the threshold C1, the microcontroller performs a test for presence of a break in mechanical equilibrium 417.
If said test is negative, the “standby” mode is re-established.
If the presence test is positive, the microcontroller increments the number of cycles 419. A positive presence test conditions transmission 421 of one or more items of information relating to the tightening sequence, such as the presence of a break in mechanical equilibrium and/or the maximum torque value CM, a tool identifier number, or the number of cycles.
Detection of a break in mechanical equilibrium is achieved by analyzing the specific waveform generated by the sudden variation in the resistance of the gauges at the time of disengagement.
The variation in the gauge voltage is in the form of a pulse whose relaxation time is characterized by the natural frequency of the test body. The relaxation time is fixed because it is related to the accuracy of the break in mechanical equilibrium.
a is a flow chart of a first mode of detecting a break in mechanical equilibrium.
The microcontroller samples 501 the output voltage of the measurement means of the gauges. A computer 215 performs a derivation computation dCi/dt of output voltage Ci as a function of time t, and stores 503 the value of this derivative in a memory m.
The computer 215 compares 505 the value of the computed derivative m with a predetermined gradient m0.
If the computed value m is less than the predetermined gradient value m0, the computer 215 performs a new derivative computation on the following sampling.
If the computed value m is greater than the predetermined gradient value m0, the microcontroller delivers information indicating presence of a break in mechanical equilibrium. After digital to analog conversion, a disengagement presence signal can be transmitted 507.
b is a flow chart of a second mode of detecting a break in mechanical equilibrium.
The microcontroller samples 600 the output voltage of the measurement means of the gauges. A first curve 601 giving measurement of the tightening torque Ci as a function of time t is stored in a memory.
A second curve 602, identical to the first curve 601 is stored in a memory with a positive and small offset delta-t in time t.
A computer performs a test consisting in identifying the presence of an intersection 305′ between the first curve 601 and the second curve 602.
If the answer to this test is positive, a break in mechanical equilibrium 305′ is present. The microcontroller delivers information indicating presence of a break in equilibrium. After digital to analog conversion, a disengagement or a break in equilibrium presence signal can be transmitted 607.
If the answer to this test is negative, the microcontroller continues the sampling 600.
b shows a first curve 601 giving measurement of the tightening torque Ci over time t. The first curve 601 has a first peak 301′ that is characteristic of a torque-setting or disengagement wrench.
The second curve 602 plotted, has a peak 301″ itself offset by an interval delta-t in time.
The intersection 305′ of the first curve 601 and of the second curve 602 defines the computed instant of the disengagement or break in mechanical equilibrium.
It can be understood that detection of the break in mechanical equilibrium is essential for counting the number of cycles performed by a production operation and thus for improving traceability.
The transmission can be transmission via a wireless link 217 to monitoring equipment 219 that is either external to or integrated in the wrench. In which case, it can be a radio-frequency link in the Industrial, Scientific and Medical (ISM) band in the vicinity of 896 MHz. The preceding wireless transmission can be replaced with a wired link transmission.
The value of the maximum torque measured after a break in mechanical equilibrium of the wrench can then be displayed on the screen of the monitoring equipment.
The method of detection of the invention makes other steps possible such as, successively, measuring the maximum torque after a break in mechanical equilibrium, transmitting the measurement of the maximum torque after a break in mechanical equilibrium, and displaying the measured value of the maximum torque after a break in mechanical equilibrium.
The steps of the method of detection can be preceded by a step of identifying the tool.
The method of tightening of the invention includes the steps of delivering information corresponding to the measurement of the torque applied to the fastener element, of electronically processing and of delivering information corresponding to the maximum torque applied after a break in mechanical equilibrium, and of transmitting said information corresponding to the measurement of the maximum torque after a break in mechanical equilibrium.
The steps of the method of tightening can be preceded by a step of identifying the tool. Said steps can be followed by a step of displaying the measured value of the maximum torque after a break in mechanical equilibrium.
It can be understood that the invention applies in particularly suitable manner to a torque setting or disengagement torque wrench as described above, but it is also suitable for other dynamometer tools, e.g. a break back torque wrench or a torque screwdriver.
The invention as described above makes it possible to impart improved reliability to the function of detecting a break in mechanical equilibrium, without reducing the compactness of a dynamometer tool.
The invention as described above makes it possible to improve traceability of tightening by a dynamometer tool, by measuring the over-torque.
| Number | Date | Country | Kind |
|---|---|---|---|
| 04 03722 | Apr 2004 | FR | national |
| 04 03724 | Apr 2004 | FR | national |
