FR2671874A1 - DEVICE INDICATOR OF OVERLOADS OF A SHAFT BY A ROTATION TORQUE. - Google Patents

Abstract

The invention relates to a device for measuring the overloads of a shaft (1) which are caused by a rotational torque, which consists of two shaft parts arranged coaxially and of a retaining means which is for example a cover tube. (11). To measure a maximum torsional stress, there is provided between one of the parts (2) and (3) of the shaft and the retaining means (11) a measuring element (18) which is intended to trigger a function switching during relative rotation or torsion of the two parts (2, 3). The measuring element (18) is intended to detect once or several times the cases of overload which are recorded and possibly stored by means of an electronic circuit.

Description

The present invention relates to a device for measuring overloads

  of stroke Le of rotation of a shaft, in particular of a transmission shaft of Variable length Le, comprising at least one part of the shaft and a means of retaining coaxia L to this L Le-ci and free of torsion, one of which end is re Fixed in a fixed way to the part of the tree and whose other end and part of

  The tree has a measuring element.

  The drive shafts or universal joint drive shafts are used to transmit the rotational strokes in the drive bar of agricultural or public works machinery Lics

  and motor vehicles In the case of vehicles used

  In particular, drive shafts of this type constitute a safety element which is exposed to strong so L torsional loads and to variable loads L due to the drive and the engine brake since i Ls have to

  transmit to the wheels The knocks of rotation.

  Document DE-A 3 636 167 discloses a transmission shaft of variable length Le which consists of shaft parts capable of sliding at least in part One in the other, and which comprises a sealing sleeve which surrounds the cylindrical outer wall of the parts of the shaft, which is rotatably connected to a part of the shaft and which has a marking on the side opposite to the connection. This marking cooperates with another marking located on L other part of the tree and can consist, for example, in two parts L, which can slide one relative to the other. In this type of marking, i L is however an indicator device which amounts to zero in the field of elastic deformations, which does not allow any conclusions to be drawn concerning the amp and the number of overloads which have appeared and which does not allow a reading in the field

  elastic that When a stroke The rotation is app Licked.

  The object of the present invention is to provide a device

  sitive indicator of blow overloads The rotation of a shaft of the type described above which gives durab indications on the

  elastic or plastic deformations.

  According to the invention, it is provided that, at the appearance of an elastic or plastic deformation caused by a torque, at least one measuring element is stressed by the torsion of the part of the shaft and is connected to an electronic circuit which triggers an optical and / or acoustic warning device and which indicates at least one request per couple of

  rotation which exceeds an admissible torsional range.

  Thanks to this device, there is a possibility of indicating the overloads in which a measuring element is associated with the part of the shaft and by means of the retainer and is exposed to a torsional stress in the elastic range or plastic It is conceivable to provide a measuring element for the elastic domain and a measuring element for the plastic domain of deformation of the shaft. Thanks to an electronic circuit, it is then possible to trigger an optical and / or acoustic warning device IL. it is also possible to memorize the number of overload cases and possibly extract it. Preferably, the measuring element is a pulling wire

  which interrupts the electronic circuit supply circuit.

  Thanks to the traction wire, it is possible for example to interrupt the supply circuit by choosing The length of the traction wire so as to record a maximum optical elastic deformation or even to record the two deformations thanks to

two traction wires.

  It is also planned to be able to put the measuring element in the form of a switch which opens or closes and which comprises two elastic contact elements which are associated with part of the shaft and with the retaining means, the switch is

  triggered when a request by predefined torque

completed is exceeded.

  Thanks to a switch of this type, it is also possible to produce a signal for the electronic circuit and to arrange the elastic contacts in such a way that they

  trip for a determined torque overload.

  It is also possible that the measuring element comprises a switch which opens or closes and an actuation means, the switch and the actuation means being associated with a part of the shaft and by means of retained, and the switch being triggered by the actuating means when a stress by predetermined torque is exceeded. The actuating means can trigger one or more switches when a predetermined torque overload occurs. The actuating means can consist of an elastic cam or a lever, the largest arm of which actuates the switch. cam or lever are associated with a part of the shaft and with the retaining means By appropriately choosing the length of the lever, it is possible to obtain even for a small relative rotation of the shaft relative to the retaining means , a triggering of the switch thanks to the large amplitude stroke of the largest arm of the lever Therefore, it is possible for example to limit

  the axial length of the retaining means.

  In another development of the invention, it is provided that the measuring element consists of a magnetic strip comprising an encoded signal or of a toothed wheel and of a sensor operating without contact, in particular, a magnetic head, which are associated to a part of the tree and to the retaining means, or that the measuring element consists of a strip having a surface

  at least partially reflective and in a photo bar

  which are associated with a part of the shaft and with the retaining means and that the sensor detects a signal, proportional to the angle of rotation or torsion of the shaft, which is intended to be

transmitted to the electronic circuit.

  These two embodiments of the invention also make it possible to continuously measure the stress caused by a torque and to record the maximum value of the, overloads which may appear, which makes it possible, during a subsequent examination, to draw more precise conclusions with regard to the different cases of overload One can envisage on this subject to incorporate in a prototype such a measuring device in a tree and to use it to determine the arrangement

tree.

  According to another characteristic of the invention, i L is provided that the first part of the shaft is an axially displaceable internal or external part of a universal joint transmission shaft and that the retaining means is an internal tube or a covering tube, or else that the first part of the shaft is a drive shaft subjected to torsion and that the means of

  retained either a cover tube.

  The electric circuit can be designed to record several times and memorize the cases of overload of the tree which appeared or even to indicate a single case of overload, a destructible element, placed inside the circuit triggering an optical indicator device. of overload which works only once and durably, the destructible element consisting of a semiconductor, a fuse or the like The optical indicating device can be active in the event of overload or normal operation or else only the acoustic indicating device can be activated in case

of an overload.

  The destructible element inside the electrical circuit makes it possible to trigger a durable indicating device which cannot be deleted by the user, the circuit possibly being characterized by a closed housing with colored marking which makes it possible to immediately realize that the destroyed item

has been replaced.

  Preferred exemplary embodiments are shown schematically in the drawings, in which: FIG. 1 is a longitudinal view in partial section of a variable length transmission shaft provided with a covering tube which covers the length compensation between the first part and the second part of the shaft, Figure 2 is a Longitudinal view of a transmission shaft of variable length Le fitted with a covering tube which covers only the second part of the shaft, Figure 3 is a Longitudina view of a drive shaft of variable length The provided with an indicator shaft which extends axially and centered in the second part of the drive shaft, Figure 4 is a view of Longitudina Le of a transmission shaft of variable length The fitted with an indicator shaft fixed on the first part of the transmission shaft, Figures 5 a and 5 b show a covering tube consisting of two half-shells L The, in the assembled state and in the open state, respectively, FIGS. 6 a and 6 b represent a detail L of the figure with a switch which consists of elastic contacts and which is associated with a part of the shaft and by means of retaining, FIGS. 7 a and 7 b represent the detai L "Z" of FIGS. 1 and 2 which is constituted by a switch and by the actuation lever,

  Figures 8 a and 8 b show the electric switch

  plate corresponding to the LX detai in FIG. 3 provided with contacts so L Licensed by springs which open in the event of overload, FIGS. 9 a, 9 b and 9 c represent an electrical switch corresponding to the LY detai in FIG. 4, FIG. 10 represents a simp electronic circuit Le comprising a switch and an indicator means for overload cases, FIG. 11 represents another circuit comprising a destructive element and an overload indicating device, and FIG. 12 represents another circuit comprising a

  destructive element and an overload indicator device.

  The transmission shaft 1 shown in FIGS. 1 to 4 essentially consists of a first part of the shaft 2 and a second part of the shaft 3 which are connected to each other by means of '' A compensation of length likely to smooth axia axially for compensation of length, the first part 2 of the shaft is provided with a touri L Lon or pivot 4 profi le externally and located radia Lement inside, which is

  slidably received in a sleeve 5 inner profile

  which is associated with The second part 3 of The tree The parts

  2 and 3 of the tree are provided at their end with articulated yokes

  Lation 6, 7 which are related to L themselves by crosses L Lons 8 to

  other articulation yokes fitted with connection flanges 9.

  As shown in FIG. 1, a covering tube 11 is fixed in rotation to the level of the connection in covering radially and coaxially outside the first part 2 of the shaft and in part the second part 3 of the shaft In the embodiment shown, and in the retracted state of the shaft 1, the covering tube 11 extends from the connection 10 in the area of the articulation yoke 6 of the first part 2 from the tree to the area of the articulation yoke 7 of the second part 3 of the tree to obtain a regular spacing bind with respect to the external surface 12 of the second part 3 of the tree, the end Free 13 of the cover tube 11 is provided with a support 14 in the form of a seal thanks to which L i L is maintained at a uniform distance from the drive shaft The cover tube 11 and the seal 14 serve at the same time to seal Parts 2 and 3 of the tree One in relation to the other re During variations in the length of the drive shaft. In the embodiment shown in FIG. 2, the covering tube 11 is fixed by a connection 10 a to the second part 3 of the shaft in the area of length compensation 4, 5 The covering tube 11 reached by its Free end 13 The area of the articulation yoke 7 of the second part 3 of the shaft and remains in this position since, when the length of the drive shaft is modified, i L ne

  there is no change in position between the covering tube

  11 and the second part 3 of the shaft The compensation for length 4, 5 is then covered by a protective tube 15 which is connected to the hinge yoke 6 at point 16 and which is kept at a uniform distance from The first part 2 of the shaft by a seal 17 The protective tube 15 reaches The area of La

Length compensation 4, 5.

  In the transmission shaft according to Figure 3, there is provided in the second hollow part 3 of the shaft an internal shaft 19 which extends axially and centrally and which acts as a retaining means IL is provided in minus a support 50 directed radially inwards to support the internal shaft 19 at high speeds of rotation of the transmission shaft 1 The internal shaft 19 is also free of torsion so that it is possible to put in evidence a torsion of the transmission shaft 1 or of its parts 2 and / or 3 with respect to the internal shaft 19 At one of its ends, the internal shaft is re-integrally connected in rotation to the second part 3 of the shaft by a Connection 10 b At its opposite free end 13, the internal shaft

  19 is coupled to a measuring element 18.

  In all cases, there are provided, in the area of the free end 13 of the covering tube 11 and of the second part 3 of the shaft which is situated opposite, measuring elements 18 which are shown in detail on Figures 6 to 8 In the case of a stress on the drive shaft 1 by a torque, the ends which are represented by the flanges 9 rotate relative to each other as well as the areas located between these ends although to a lesser extent Since the retaining means in the form of a covering tube 11 does not participate in torsion, the position of any point situated on its free end 13 is modified in the direction of periphery with respect to part 2 or 3 of the shaft which is situated opposite this twist or rotation may be situated in the field of elastic deformations or plastic deformations of the transmission shaft 1 in the elastic field, it turns

  produces a return to the initial position when the stress

  tation has disappeared while in the plastic field The rotation or torsion remains after the disappearance of the stress Even in the case of elastic deformations, there may appear stress states which are undesirable but which normally are no longer identifiable when the stress has disappeared The embodiments described below allow a durable indication even in the case of deformations which are located in the elastic range of a drive shaft 1

  correspondingly equipped.

  In the embodiment shown in FIG. 4, the internal shaft 19 which extends axially and in a centered manner is housed in the first part 2 of the shaft in an integral manner in rotation, which makes it possible to obtain with respect to the arrangement according to FIG. 3 and for the same stress on the driveshaft 1 by a torque, a greater amplitude of indication due to the greater length of rotation or torsion The relative axial movement which is necessary for the length compensation can be obtained for example by means of a connection 10 c in the form of a square guide between the internal shaft 19 and the part 2 of the transmission shaft This relative axial movement can also be obtained by a corresponding connection between the internal shaft 19 and the measuring element 18 To increase the critical rotation speed of the indicator shaft 19, at least one support 50 is provided, turned the measuring element 18 according to the f on the Figures 9 a, 9 b and 9 c by longitudinal section, Figure 9 the direction of the horizontal arrows is a longitudinal section in Figure 9 a In this form of projection radially from the shaft opening 43 of the clevis of articu

radially inward.

  igure 4 is shown in detail li which Figure 9 a is a b is a cross section in of Figure 9 a and Figure 9 c the direction of f Vertical arrows, an axis 42 which is internal 19 is housed in a Jlation 7 which is in the form of an oblong hole in the direction of the periphery Via the axis 42, the opening 43 immobilizes the internal shaft 19 in the axial direction while allowing free movement of the axis 42 in the direction of the periphery and therefore a rotation of the internal shaft 19 relative to the part 3 of the shaft which allows the

  tripping of switch 31.

  FIGS. 5 a and 5 b represent the retaining means in the form of a piece of one-piece plastic material which constitutes the covering tube 11 which comprises two half-shells 20, 21 which are shown in FIG. 5 a in the coaxial position with the transmission shaft 1 while FIG. 5 b shows them in the open position The half-shells 20, 21 are connected to one another by a flexible hinge 22 and they each consist of a cylindrical intermediate part and in two reinforced end portions 23 of semi-circular shape In the end portions 23 of the half-shell 20, there are provided bores 24 and in the end portions 23 of the opposite half-shell 21, there are provided rods fixing 25 which penetrate into the corresponding bores 24 to allow the fixing of the retaining means on the transmission shaft 1 Another bore 26 is also provided for receiving a fixing pin provided on part 3 of the tree. FIGS. 6 a and 6 b show in an enlarged manner the detail Z of the measuring elements 18 situated on the part 3 of the shaft and on the covering tube 11, in partial longitudinal section in FIG. 6 a and in following longitudinal section the arrows A and B of FIG. 6 a in FIG. 6 b On part 3 of the shaft there is a radial support rod 27 on which an actuating lever 28 is fixed in the axial direction of the shaft 1 so as to be able to pivot The actuating lever 28 comprises a small lever arm 29 and a large lever arm 30, the small lever arm 29 being connected to the covering tube 11

  while the large lever arm 30 is located between two inter-

  breakers 31 against one of which it comes to bear in the event of stress by a torque The relative movement between the free end 13 of the covering tube 11 and the part 2 or 3 of the shaft is used to actuation of the switch The switching point is set exactly in

  function of the deformation path of the transmission shaft-

  limit overload and causes an indication of

  overload via an electronic circuit Possible-

  Lement, an electronic circuit makes it possible to maintain the state of switching after a single actuation of the switch (overload). The switching signal is then used to trigger an optical and / or acoustic indicator device.

electrically operated.

  Figures 7 a and 7 b show in longitudinal section and in cross section respectively an embodiment of the switch 31 which in this case consists of two separate contacts which are associated with part 3 of the drive shaft and the tube covering 11 On the internal side 32 of the covering tube 11 is applied an insulating layer 33, for example of plastic, which has a first contact element 31 a which consists of a U-shaped sheet metal part having two shoulders between which is disposed the second contact element 31 b which is fixed on the part 3 of the drive shaft and which is electrically separated from the latter by an insulating layer 33 ′ In the case of stress by a torque located in the elastic or plastic domain, there is a relative rotation of the contact elements 31 a, 31 b relative to each other so that, when the rotation reaches a adjustable maximum value, a contact is established between the two elements 31 a, 31 b In the example of embodiment cited first, this switching function is used to trigger a

  optical and / or acoustic indicating device.

  Figures 8 a and 8 b show the detail X of Figure 3, in cross section in Figure 8 a and in longitudinal section in the direction of the arrows of Figure 8 a in Figure 8 b The axis 42 which projects radially from the internal shaft 19 is received in an opening 43 made at the periphery of the articulation yoke 7 in the form of an oblong hole in the direction of the periphery and this axis enters at its end into a recess In this recess , an electric switch 31 is provided which forms a closed contact with the contact elements 47 a and 47 b, the contact element 47 a being double. The contact elements 47 a are pushed by springs 48 on the element of contact 47 b and are actuated by the axis 42 One can consider using elastic contact elements 47 a instead of springs 48 The contact elements 47 a, 47 b are housed in a housing 49 which consists of a material insulating and which is ins éré in the recess in the center of the articulation yoke 7 of the transmission shaft 1 In the case of an overload by a torque, due to the rotation of the two parts 2, 3 of the shaft, the contact between the contact elements 47 a, 47 b is interrupted by the axis 42 in the two directions of rotation of the drive shaft 1, so that the switch can control a

  circuit according to Figures 10 to 12 connected downstream.

  In FIGS. 9 a, 9 b, 9 c which represent the detail Y in FIG. 4, the switch 31 is located in a housing 49 located on the articulation yoke 7 The switch 31 consists of two contact elements 44 a, held by a spring 46, which rest on two edges 45 of the housing 49 Another contact element 44 b U-shaped curved is fixedly connected to the housing by means of an insulating layer 44 c In the case of an overload of the drive shaft 1 caused by a torque, there is a rotation of the axis 42 relative to the housing 49 so that one of the contact elements 44 a is pushed by the axis 42 against the contact element 44 b In the rest position, the contacts 44 a are pushed by a spring 46 or by another elastic means against an edge 45 which makes it possible to avoid actuation of the switch by oscillations of the drive shaft even in the case of a small gap

between contacts.

  FIG. 10 represents a relatively simple circuit comprising a thyristor 34, a light-emitting diode 35 and two resistors 36, 37 The thyristor 34 is connected in series with the light-emitting diode 35 and the resistor 37 and this series circuit is connected to the voltage In addition, the second

  resistor 36 is connected on the one hand to the positive terminal of the

  voltage and secondly to the switch 31 The second terminal of the switch 31 is connected to the thyristor control electrode 34, so that the thyristor 34 which is first blocked becomes conductive under the action of its control electrode when the switch 31 is actuated, so that the light-emitting diode 35 lights up It is possible to replace the light-emitting diode 35 for example by an acoustic warning device in the form of a piezoelectric crystal element In this circuit, the triggering of

  switch 31 causes an indication.

  FIG. 11 represents another circuit constituted by the switch 31, the light-emitting diode 35, two resistors 36, 37 and another diode 38 The two diodes 35, 38 are connected in series with the resistor 37 and are connected to the supply voltage The switch 31 and the resistor 36 are connected in series and connected on the one hand to the negative terminal of the voltage supply and on the other hand to the junction point of the two diodes 35, 38 In this circuit , the diode 35 is conductive in normal operation of the drive shaft 1 and goes out in the event of an overload caused by a torque so that the light emitting diode acts as a control lamp rather than d an IL warning device is essential that when the switch 31 is actuated The diode 38 is destroyed by a large current so that the circuit can no longer

  perform its normal function without outside intervention.

  FIG. 12 represents another circuit which comprises a transistor as well as two other resistors 39, 40 in the form of a voltage divider, in addition to the elements already described. The light-emitting diode 35 is connected by its anode to the positive terminal of the voltage. supply and by its cathode to the collector of transistor 41 The emitter of transistor 41 is connected to the negative terminal of the voltage supply via a resistor 37 The transistor 41 is controlled via its base by a voltage divider constituted by the resistances 39 and 40 The resistor 39 is connected directly to the positive terminal while the resistor 40 is connected to the anode of the diode 38 whose cathode is connected to the negative terminal of the supply of so that, in the normal state, the tranistor 41 is blocked In addition, the switch 31 is connected on the one hand to the positive potential and on the other hand to the anode of the diode 38 In the event of actuation of switch 31, the diode 38 is destroyed so that the transistor 41 is controlled via the resistor 39 and that the light-emitting diode 35 lights up The destructive element The in the form of diode 38 cannot be remp Lacé than by an external intervention which gives the same advantage of an easy control instead of the diode 38, i L is possible to

  provide for example a fuse or ana Logue element.

Claims (11)

  1 Device for measuring the overloads of a shaft caused by a torque, in particular of a transmission shaft (1) of variable length, comprising at least one part of the shaft (2) or (3) and a means retainer (11) free from coaxial torsion to this part, the first end of which is connected in rotationally to the part (2) or (3) of the shaft and the second end (13) and a part ( 2) or (3) of the tree have a   measuring element (18), characterized in that when a deformation occurs   elastic or plastic mation due to a torque, at least one measuring element (18) is stressed by the torsion of the part (2) or (3) of the shaft and is connected to an electronic circuit which triggers a device optical and / or acoustic warning device and which indicates at least one stress per torque   which exceeds the admissible torsional range.   2 Device for measuring the overloads of a shaft caused by a torque according to claim 1, characterized in that the measuring element (18) is a pulling wire which interrupts the input circuit of the electronic circuit. 3 Device for measuring the overloads of a shaft caused by a torque according to claim 1, characterized in that the measuring element (18) is in the form of a switch (31) which opens or which is firm and comprising two elastic contact elements (31 a, b; 44 a, b; 47 a, b) which are associated with a part (2) or (3) of the shaft and with the retaining means (11) and in that the switch (31) trips when a load is exceeded   by predetermined torque.   4 Device for measuring the overloads of a shaft caused by a torque according to claim 1, characterized in that the measuring element (18) comprises a switch (31) which opens or closes and a means actuator (28) which are associated with a part (2) or (3) of the shaft and the retaining means (11) so that the actuating means (28) trips the switch (31) in case of exceeding a request by couple of predetermined rotation.   Device for measuring the overloads of a shaft caused by a torque according to claim 4, characterized in that the actuating means (28) is an elastic cam of the first part (2) or (3) of   the shaft or the retaining means (11).   6 Device for measuring the overloads of a shaft caused by a torque according to claim 4, characterized in that the actuating means (28) is a lever rotatably attached to the retaining means (11) and the larger lever arm (30) is intended to trigger the switch (31).   7 Device for measuring the overloads of a shaft caused by a torque according to claim 1, characterized in that the measuring element (18) consists of a magnetic strip comprising a coded signal or   in a ring gear and in a sensor operating without contact, in particular   culier a magnetic head, which are associated with a part (2) or (3) of the shaft and   by the retaining means (11) and in that the sensor detects a proportional signal   tional to the angle of torsion of the shaft which is intended to be transmitted to the electronic circuit. 8 Device for measuring the overloads of a shaft caused by a torque according to claim 1, characterized in that the element of   measure (18) consists of a strip comprising an at least partial surface-   ment reflecting and in a photoelectric bar which are associated with a part (2) or (3) of the shaft and with the retaining means (11) and in that the sensor detects a signal proportional to the angle of twist of the tree which is intended for   be transmitted to the electronic circuit.   9 Device for measuring the overloads of a shaft caused by a torque according to claim 1, characterized in that the first part (2) or (3) of the shaft is an internally or externally sliding part axially of a transmission shaft with universal joint (1) and in that the retaining means (11) is an internal tube or a covering tube which is not   subject to no torsional stress.   Device for measuring the overloads of a shaft caused by a torque according to claim 1, characterized in that the first part (2) or (3) of the shaft is a drive shaft stressed in torsion and the   retaining means (11) is a cover tube.   11 Device for measuring the overloads of a shaft caused by a   torque according to claim 1, characterized in that the electric circuit   tronic is designed to record and memorize repeatedly the cases of overloads that arise.   12 Device for measuring the overloads of a shaft caused by a   torque according to claim 1, characterized in that the electric circuit   tronic comprises an element (38) which can be destroyed in the event of an overload and which triggers an optical overload indicator device which operates a only once and sustainably.   13 Device for measuring the overloads of a shaft caused by a torque according to claim 3, characterized in that the element   destructible (38) consists of a semiconductor, a fuse or the like.   14 Device for measuring the overloads of a shaft caused by a torque according to claim 1, characterized in that the device   optical indicator (35) is active in the event of overload or in the event of operation normal.   Device for measuring the overloads of a shaft caused by a torque according to claim 1, characterized in that the device   acoustic indicator is active in case of overload.   16 Device for measuring the overloads of a shaft caused by a   torque according to claims 10 to 13, characterized in that the tube   covering (11) consists of two half-shells (21, 22).