Patent Publication Number: US-2023150594-A1

Title: Tracked undercarriage roller assembly with temperature monitoring

Description:
FIELD OF THE INVENTION 
     The present invention relates to a tracked undercarriage roller assembly with temperature monitoring, namely a tracked undercarriage roller assembly whose operating temperature is monitored. 
     BACKGROUND 
     Tracked undercarriages are typically used in operating machines such as earthmoving machines, mining machines, demolition machines and the like, to allow the machine to move on often uneven ground or with poor grip. 
     A tracked undercarriage typically comprises two chain assemblies spaced apart and arranged parallel to each other and configured to receive a drive torque and transfer it to the ground. Each chain assembly comprises a plurality of undercarriage components which usually comprise a closed loop chain on a driving wheel and an idler wheel (or idler) operatively connected to a tensioner assembly. The undercarriage components further comprise, between the driving wheel and the idler wheel, a plurality of roller assemblies configured to guide the chain during its motion. Roller assemblies usually include one or more upper roller assemblies and a plurality of lower roller assemblies. 
     The chain usually comprises a plurality of links, with link it is referred to the single component of the chain which is articulated to the other components. Typically, each link comprises a pair of plates facing each other. The links are interconnected between them by pins. Each pin is usually inserted into holes provided on the plates and connects two links together. 
     The soles are usually mounted on the links which, being in direct contact with the ground, have the task of discharging the traction to the ground and increasing the contact surface between machine and ground. The type of sole used depends on the ground on which the machine must operate, on the conditions of the environment in which the machine must operate and on the specifications suggested by the machine manufacturer. 
     Each roller assembly usually comprises a roller body crossed by a shaft. The roller assembly is delimited by a radially inner surface facing the shaft, in particular facing the outer surface of the shaft. The roller body can rotate about the shaft which is fixed with respect to the undercarriage on which it is mounted. The roller assembly comprises a bushing which is fitted on the outer surface of the shaft so as to be interposed between the shaft and the inner surface of the roller body. The roller body and the shaft are made of metal, typically of steel, and the bushings are configured to reduce friction between the roller body and the shaft. The bushings are usually made of a non-ferrous material, such as bronze, or of a bi-metal alloy and are lubricated to further reduce friction between the bushing contact surfaces and roller body and/or bushing and shaft. 
     The undercarriage is usually subjected to very severe operating conditions which may derive from the overall weight of the machine, the high powers transferred from the engine of the machine to the ground and/or the conformation and composition of the terrain on which the machine must operate. 
     In particular, the Applicant has observed that in the operations for moving large earth-moving machines some undercarriage components are subjected to strong stresses. A particularly critical undercarriage component is the lower roller assembly which has the function of absorbing the loads transmitted by the machine as well as of guiding the chain. Typically, a large excavator is provided with a plurality of lower roller assemblies, for example 8 to 32. When the excavator is in motion, the lower roller assemblies are subjected to rotation with a consequent significant increase in the temperature inside the roller assemblies, which might reach critical values that can affect the functional integrity of these components. 
     The Applicant has noted that an unsuitable lubrication of the bushing increases friction leading to a damage of the roller assembly caused by the wear of the bushing, whose thickness gradually decreases, or to the grip of the bushing on the shaft and/or on the roller body. 
     The Applicant has noted that by measuring the bushing temperature it is possible to determine an abnormal lubrication thereof, in particular the temperature of the lubricant increases as the temperature of the bushing increases. 
     Application US 2013/0255354 discloses a monitoring device in an undercarriage assembly which has a roller assembly including a shaft and a bushing. In one example, the monitoring device has a temperature sensor located inside the roller assembly to measure the temperature of the bushing. In particular, an opening is provided in the shaft which is formed parallel to the shaft, until a depth sufficient to overlap the bushing, and having a portion oriented outwardly which reaches the outer surface of the shaft. The temperature sensor is inserted into the opening and is arranged in the portion oriented towards the shaft surface. The document mentions that output signals are transferred through a wireless transmitter to a computer or the data are accessed through a port that connects to the monitoring device. 
     The Applicant has observed that an opening in the shaft reaching the outer surface of the shaft can allow positioning a temperature sensor in direct contact or substantially in direct contact with the bushing, thus measuring efficiently the temperature of the latter. 
     The Applicant has however verified that such an opening may cause leakages of lubricant inside the opening with a potential double disadvantage of damaging the temperature sensor and of reducing the amount of lubricant available between the bushing and the shaft. This second event may even lead to a premature degradation of the roller assembly due to lack or shortage of lubricant. 
     The Applicant has noted that an indication of unsuitable lubrication of the bushing can be not only related to the temperature of the bushing but also to the temperature of shaft portions placed near the bushing. 
     The Applicant has observed that, by arranging a temperature transducer in the shaft of the roller assembly so that the transducer is near the bushing but not directly facing the bushing or in contact with the bushing, it is possible to measure a temperature which, though not exactly corresponding to the actual temperature, is proportional to the bushing temperature, allowing to identify abnormal increases in the bushing temperature. 
     SUMMARY 
     The present invention relates to a tracked undercarriage roller assembly comprising: 
     a roller body having a through cavity delimited by a radially inner surface; 
     a shaft inserted in the through cavity of the roller body; 
     a bushing which extends from a first axial end to a second axial end and radially interposed between the roller body and the shaft; 
     an annular chamber at least partially filled with lubricant and radially interposed between the shaft and the bushing; 
     a housing seat obtained in the shaft and comprising an inlet portion facing an axial end surface of the shaft and a measuring portion placed inside the shaft in an axial position between the first axial end and the second axial end of the bushing, wherein the inlet portion and the measuring portion are aligned with each other along an axial direction; 
     a temperature transducer located inside the housing seat at the measuring portion; 
     wherein the measuring portion is placed at a radial distance from the bushing between 8 millimetres and 50 millimetres. 
     Arranging the housing seat in the shaft and inserting the temperature transducer inside the measuring portion of the housing seat makes it possible to detect the temperature of the shaft at the measuring portion of the housing seat. 
     Since, as known, the shaft of a tracked undercarriage roller assembly is typically made of a ferrous alloy, such as steel, the shaft has such a thermal conductivity as to allow portions of the shaft placed near the bushing to change temperature as the temperature of the bushing changes. 
     The Applicant has observed that, depending on the size of the roller assembly and on the material actually used to manufacture the shaft, a radial distance of the temperature between 8 millimetres and 50 millimetres from the bushing allows to detect sudden or abnormal increases in the bushing temperature. 
     An increase in the temperature detected by the temperature transducer beyond a predetermined threshold can be associated to an abnormal increase in the temperature of the bushing, due, for instance to the leakage of lubricant from the annular chamber, a too high friction of the bushing on the shaft or in any case to an out of scope bushing functioning. 
     It is thereby possible to intervene on the roller assembly restoring its functions before an irreversible damage on the roller assembly occurs. Furthermore, by arranging the inlet portion facing an axial end surface of the shaft with the inlet portion and the measuring portion aligned between them along an axial direction, it is possible to prevent lubricant leakages from the annular chamber towards the housing seat or towards the temperature transducer, as the housing seat is completely obtained inside the shaft without having openings facing the bushing. 
     The lubricant can be for instance lubricant oil or grease. 
     The terms “axial”, “axially”, “radial” and “radially”, are used with reference to a rotation axis of the roller assembly. 
     In particular, the terms “axial” and “axially” mean references/quantities arranged/measured or extending in a direction parallel or coincident with the rotation axis of the roller assembly. 
     The terms “radial” and “radially” mean references/quantities arranged/measured or extending in a direction perpendicular to the rotation axis of the roller assembly. 
     The terms “radially inner” and “radially outer” mean respectively a position closer to or further away from the aforementioned rotation axis. 
     The terms “axially inner/outer” mean respectively a position closer to and further away from a point of the roller assembly placed along the rotation axis and equally spaced apart from shaft axial ends. 
     The term “transducer” means a device which interacts directly with the measured quantity, that is to say the first element of a measurement chain that converts a physical quantity into an electric signal related to the measured quantity. 
     Preferably, the measuring portion is placed at a radial distance from the bushing between 10 millimetres and 40 millimetres, still more preferably between 12 and 30 millimetres, for instance about 15 millimetres. 
     Preferably, the housing seat is an axial-symmetry blind cavity with a symmetry axis parallel to an axial direction. 
     Thereby, the housing seat can be obtained by piercing the shaft until the desired depth for inserting the temperature transducer inside the shaft is reached. 
     Preferably, the blind cavity has a rectilinear extension and does not comprise deviations or branches radially branching from the symmetry axis parallel to an axial direction. 
     This prevents the housing seat from reaching a radially outer surface of the shaft or facing directly to the bushing or the annular chamber containing lubricant, avoiding possible leakages of lubricant from the annular chamber. 
     Preferably, the inlet portion has an extension in radial direction greater than the extension in the radial direction of the measuring portion. 
     Preferably, the inlet portion has an extension in radial direction which is almost double the extension in the radial direction of the measuring portion. 
     Preferably, an electronic sensor module is provided configured to generate measurement signals in wireless mode including data representative of temperature; the electronic sensor module being placed in the inlet portion of the housing seat. 
     Preferably, the electronic sensor module comprises: circuit components, an electronic processor, a power supply source, and a wireless transmitter operatively connected to the electronic processor so as to receive respective measurement signals including data representative of temperature, the wireless transmitter generating corresponding measurement signals in wireless mode that include data representative of temperature. 
     Preferably, the electronic processor of the electronic sensor module is configured to receive measurement signals from the temperature transducer. 
     Thereby, for example, an operator who is far from the tracked vehicle incorporating the roller assembly will be able to remotely view data related to the current temperature of the shaft portion near the bushing connecting a mobile terminal or a PC to a WI-FI network which the electronic sensor module is connected to. 
     Preferably, the inlet portion comprises an annular groove engaged by a stop ring, the annular groove being axially external to the electronic sensor module so that the electronic sensor module is axially retained in the inlet portion by the stop ring. 
     The electronic sensor module is thereby retained inside the housing seat avoiding possible damages to the electronic sensor module while the roller assembly is being used and ensuring proper functioning thereof. 
     Preferably, a closing plug is provided for the inlet portion of the housing seat. The closing plug is preferably axially interposed between the stop ring and the electronic sensor module. 
     The closing plug prevents liquids, mud, dirt or other from entering into the housing seat. 
     Preferably, the stop ring is removable from the annular groove in the inlet portion of the housing seat. 
     The stop ring holds the plug in the operative position however allowing for removal thereof in case access inside the housing seat is required for an inspection or replacement of the temperature transducer and/or of the electronic sensor module. 
     Preferably, the temperature transducer is connected to the electronic sensor module by electric wires. 
     Preferably, the temperature transducer is a thermistor with a resistance decreasing as the temperature increases. 
     As the temperature of the shaft portion near the bushing increases, the resistance value of the thermistor decreases. Thereby, in case of a thermistor malfunction (such as in case of electrical breakdown between thermistor and electronic sensor module), the resistance value detected would be significantly misaligned from an expected resistance value, providing immediate indication of a thermistor malfunction. 
     Preferably, a pin inserted into a radial cavity of the shaft is provided to make the shaft integral with an undercarriage frame; the housing seat not crossing the radial cavity of the shaft. 
     The pin has the task of engaging the shaft to the undercarriage frame (or to an undercarriage component integral with the undercarriage frame) to keep the roller assembly in position and to allow the roller body to rotate about the shaft. 
     The pin is typically removable so as to remove the roller assembly from the undercarriage carriage. 
     In case the temperature transducer is connected to the electronic sensor module with electric wires and in case the housing seat crosses the pin, the removal of the pin would permanently damage the connection between the temperature transducer and the electronic sensor module, as the pin would be crossed by electrical connections. Furthermore, by preventing the housing seat from crossing the pin, the positioning of the temperature transducer inside the housing seat may be carried out even when the roller assembly has not been yet mounted on the undercarriage frame. 
     Preferably, the roller body comprises an opening which puts in fluid communication the outer environment with the annular chamber filled with lubricant; the opening being closed by a plug. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further characteristics and advantages of the invention will be more evident from the following description of a preferred embodiment thereof, made with reference to the appended drawings. In such drawings: 
         FIG.  1    is a schematic side view of a tracked undercarriage; 
         FIG.  2 A  is a section view of a tracked undercarriage roller assembly according to the present invention; 
         FIG.  2 B  is an enlargement of some details of the roller assembly of  FIG.  2 A ; 
         FIG.  3    is a partially exploded perspective view of a detail of the roller assembly of  FIG.  2 A ; and 
         FIG.  4    is a schematic view of some components of the roller assembly of  FIG.  2 A . 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    is a schematic side view showing some components of a tracked undercarriage. The tracked undercarriage  10  comprises two track assemblies  11 , of which only one is visible in  FIG.  1   . Each track assembly  11  comprises a chain  12 , comprising a plurality of links  13  interconnected between them by pins and bushings (not shown), a return wheel  14 , in the figure partially hidden by a crankcase  15 , and a driving wheel  16 . A plurality of roller assemblies  17  is arranged between the return wheel  14  and the driving wheel  16 , in particular one or more upper roller assemblies and a plurality of lower roller assemblies arranged in contact with the links  13  and adapted to guide the chain  12  in its motion. 
     The lower roller assemblies  17  are arranged in the lower portion of the track assembly  11  and are configured to transfer loads between the track and an undercarriage frame (not shown). The upper roller assemblies  17  are configured to guide the chain between the driving wheel  16  and the return wheel  14  and typically are present in a lower number than the number of the lower roller assemblies. The number of the lower roller assemblies  17  varies depending on the type of machine and the weight thereof. 
     According to the present disclosure, at least a lower or upper roller assembly  17  includes a sensor device for monitoring the temperature. 
       FIG.  2 A  is a section view of a roller assembly  17  according to an embodiment. In this embodiment the roller assembly  17  is a roller assembly of a lower roller. The section plane is a longitudinal plane transversal to the links  13  of the chain  11 , and hence to the direction of movement of the tracked undercarriage, passing through the rotation axis X of the roller assembly  17 . 
     The roller assembly  17  comprises a roller body  18  comprising a cylindrical through cavity  19  which extends from one first axial end  18   a  to a second axial end  18   b  of the roller body  18 . 
     The roller body  18  is delimited by a radially inner surface  20  usually having a cylinder shape facing the cylindrical cavity  19  and a radially outer surface  21  whose shape is determined by the type of track  12  with which the roller assembly  17  must interact. 
     The roller body  18  is made of a low-alloy steel that is boron-alloyed and submitted to at least a heat treatment. A low-alloy steel is a steel wherein other elements other than iron and carbon are present and wherein none of such other elements is present in an amount higher than 5%. 
     The roller assembly  17  further comprises a shaft  22  inserted into the cylindrical cavity  19  of the roller body  18 . The shaft substantially has a cylindrical shape, it extends between a first axial end  22   a  and a second axial end  22   b  and has a radially outer surface  23  facing the radially inner surface  20  of the roller body  18 . 
     The shaft  22  is preferably made of a low-alloy steel that is boron alloyed and submitted to at least a heat treatment. 
     The shaft  22  has a greater extension in an axial direction than the extension in an axial direction of the roller body  18 . In other words, the distance in the axial direction between the first axial end  22   a  and the second axial end  22   b  of the shaft  22  is greater than the distance measured along the same direction between the first axial end  18   a  and the second axial end  18   b  of the roller body  18 . 
     The shaft  22  extends axially beyond the first  18   a  and the second axial end  18   b  of the roller body  18 . In particular, the shaft extension in axial direction beyond the first axial end  18   a  of the roller body  18  is substantially equal to the extension in axial direction of the shaft  22  beyond the second axial end  18   b  of the roller body  18 , as shown in  FIG.  2 A . 
     The shaft portion  22  which extends in an axially outer direction from the first axial end  18   a  of the roller body  18  is made integral with the undercarriage frame or with an undercarriage component integral with the undercarriage frame. 
     For this purpose a support  24  is provided that is made integral with the undercarriage frame or with an undercarriage component integral with the undercarriage frame provided with an inner through cavity  25  in which the shaft portion  22  is inserted extending in an axial outer direction from the first axial end  18   a  of the roller body  18 , as shown in  FIG.  2 A . 
     To make the shaft  22  integral with the support  24 , the shaft  22  comprises a radial cavity  26  which crosses the shaft  22  in a radial direction. On the support  24  two radially opposite through holes are formed which can be aligned between them and aligned to the radial cavity  26  of the shaft  22 . A pin  27  is inserted in the radial cavity  26  so as to cross the radial cavity  26  and intercept the two through holes of the support  24 . Thereby, any axial movement and any rotation about the rotation axis X of the shaft  22  relative to the support  24  is prevented. 
     Similarly, the shaft portion  22  which extends in an axial outer direction from the second axial end  18   b  of the roller body  18  is made integral with the undercarriage frame or with an undercarriage component integral with the undercarriage frame. 
     For this purpose a further support  28  is provided that is made integral with the undercarriage frame or with an undercarriage component integral with the undercarriage frame provided with an inner through cavity  29  in which the shaft portion  22  is inserted that extends in an axial outer direction from the second axial end  18   b  of the roller body  18 , as shown in  FIG.  2 A . 
     To make the shaft  22  integral with the further support  28 , the shaft  22  comprises a radial cavity  30  which crosses the shaft  22  in a radial direction. On the further support  28  two radially opposite through holes are formed which can be aligned between them and aligned to the radial cavity  30  of the shaft  22 . A further pin  31  is inserted in the radial cavity  30  in such a way that it crosses the radial cavity  30  and intercepts the two through holes of the support  28 . Thereby, any axial movement and any rotation about the rotation axis X of the shaft  22  relative to the further support  28  is prevented. 
     The roller body  18  is rotatable with respect to the shaft  22  about the rotation axis X. In order to reduce the friction between the roller body  18  and the shaft  22  a bushing  32  is provided that is radially interposed between the roller body  18  and the shaft  22 , as shown in  FIG.  2 A . 
     The bushing  32  is made of brass, bronze, copper or other preferably metal material that is more ductile than the material used to make the shaft  22  and the roller body  18 . The bushing material  32  also has a good thermal conductivity coefficient, for instance higher than 15 W/m° C. 
     In the preferred embodiment of the invention, the bushing  32  is integral in rotation with the roller body  18  and thus rotates with respect to the shaft  22 . 
     As shown in  FIG.  2 A , the bushing  32  extends throughout the axial extension of the roller body  18  between one first axial end  32   a  and one second axial end  32   b . The bushing  32  comprises a radially inner surface  33  facing directly the shaft  22 . Between the radially inner surface  33  of the bushing  32  and the radially outer surface  22   c  of the shaft  22  an annular chamber is defined  34  which is filled with a lubricant, such as oil or grease, to further reduce friction between the shaft  22  and the bushing  32 . 
     The annular shaft  34  is in fluid communication with a tank  35  obtained in the roller body  18  through one or more passage radial holes  33   a  obtained in the bushing  33 . The tank  35  also has an annular shape and is in fluid communication with a channel (not shown) obtained in the roller body  18  which extends radially between the tank  35  and the radially outer surface  21  of the roller body  18 . The channel has the purpose of allowing introducing the lubricant into the tank  35  and thus into the annular chamber  34 . The channel is closed by a leak proof plug (nor shown). 
     At the first  18   a  and second annular end  18   b  of the roller body  18  respective hydraulic sealing rings  36  are arranged to avoid lubricant leakages between the bushing  33  and the supports  24 ,  28  of the shaft  22 . At the two portions of shaft  22  which extend in an axial outer direction from the first  18   a  and second axial end  18   b  of the roller body  18 , they are further provided respective hydraulic sealing gaskets placed between the shaft  22  and the supports  24 ,  28  to avoid lubricant leakages between the shaft  22  and the supports  24 ,  28 . 
     A housing seat  37  is obtained inside the shaft  22  that is defined by a blind cavity  38  in the shaft  22 . The blind cavity  38  has an axial symmetry with a symmetry axis parallel to the rotation axis X. 
     The housing seat  37  extends along an axial direction deep down in the shaft from an inlet portion  39  to a measuring portion  40 . The inlet portion  39  is placed at an axial end surface  22   d  of the shaft  22  placed in the first axial end  22   a  of the shaft  22 . The inlet portion  39  is open such to define an opening for the cavity  38 . 
     The measuring portion  40  is placed deep down inside the shaft  22 , in particular it is placed axially at the bushing  32 . As shown in  FIG.  2 A , the measuring portion  40  is placed axially between the first  32   a  and the second axial end  32   b  of the bushing  32 . 
     The inlet portion  39  and the measuring portion  40  are aligned along an axial direction such that the blind cavity  38  is parallel to the rotation axis X. 
     The measuring portion  40  is spaced in a radial direction from the radially outer surface  23  of the shaft  22 . The measuring portion  40  does not contact and is not open on the radially outer surface  23  of the shaft  22 . 
     As better shown in  FIG.  2 B , the measuring portion  40  is placed at a radial distance RD from the bushing  32  between 8 millimetres and 50 millimetres. 
     The radial distance RD is measured in a radial direction between the point of the inner cavity  38  that is radially closer to the bushing  32  and the radially inner surface  33  of the bushing  32 , as shown in  FIG.  2 B . 
     Inside the measuring portion  40  of the housing seat  37  a temperature transducer  41  is inserted. 
     The temperature transducer  41  is configured to generate an electric signal representative of the measured temperature. For example, the temperature transducer  41  is a thermal probe, preferably an NTC (Negative Temperature Coefficient) probe having a negative temperature coefficient which causes a decrease in electrical resistance as the temperature increases. Preferably, the temperature transducer  41  is adapted to measure temperatures until about 200° C. 
     In the inlet portion  39  there is arranged an electronic sensor module  42  configured to generate measuring signals in wireless mode which include data representative of a temperature measured by the temperature transducer  41 . 
     As better shown in  FIG.  2 B , the inlet portion  39  has an extension in the radial direction that is greater than the extension in the radial direction of the measuring portion  40 , so as to house the electronic sensor mode  42 . 
     In the preferred embodiment of the invention, the extension in radial direction of the inlet portion  39  is about double the radial direction extension of the measuring portion  40 . 
     The extension in axial direction of the inlet portion  39  is selected so as to substantially house by fitting the electronic sensor module  42 . 
     The electronic sensor module  42  and the temperature transducer  41  are electrically connected between them by electric wires  43 . 
     As schematically shown in  FIG.  4   , the electronic sensor module  42  comprises a connector  44  for the connection with electric wires  43 . 
     The sensor electronic module  42  comprises circuit components  45  operatively connected to electric wires  43  to capture signals from the temperature transducer  41  and generate output electric signals representative of the measured temperature. 
     The circuit components  45  of the electronic sensor module  42  comprise circuit components for the management of the signals from the temperature transducer  41 , which can comprise a conditioning circuit for the analogue signals from the temperature transducer  41  and a possible amplifier for converting the input signals into a voltage or current, analogue or digital output signal. Typically, the electric signals output from the circuit components are digital electric signals. For this purpose, the circuit components  45  may comprise an analogue-to-digital A/D signal converter. The electric signals output from the first circuit components include data representative of the instantaneous temperature measured by the temperature transducer  41  in the shaft  22 . 
     The electronic sensor module  42  comprises an electronic processor  46 , in particular a microprocessor, associated with a memory which receives the measurement signals coming from the circuit components  45  and stores them to later send them to a wireless transmitter  47  for the transmission in wireless mode of measurement signals via an antenna  48 . 
     The wireless transmitter  47  is configured to generate radio frequency signals. In particular, the wireless transmitter  47  is a radio frequency transmitter configured to receive, from the processor  46 , measurement signals which include data representative of temperature and to generate respective radio frequency (RF) signals which include representative data of temperature. The wireless transmitter  47  is operatively connected to an antenna  45  for transmitting RF signals. 
     The electronic sensor module  42  further comprises a supply source  49 , such as a button battery, to supply the circuit components  45  and the microprocessor  46 . 
     Preferably, the electronic sensor module  42  is inserted in a container  50  arranged inside the inlet portion  39  of the housing seat  37 , as shown in  FIG.  2 B . The container  50  ensures a greater protection of the circuit components and electronic devices included in the electronic sensor module  42 . In the preferred embodiment, the container  50  is a synthetic rubber case capable of absorbing vibrations with a front opening  51  which faces the axially outer surface  22   d  of the shaft  22  ( FIG.  3   ). The container  50  can be filled with an epoxy resin to further dampen external stresses and make the electronic sensor module  42  leak-tight. 
     The container  50  is closed by a closing plug  52  which closes, preferably tightly, the front opening  51  and which fits in the inlet opening  39  of the housing seat  37 , so as to seal the blind cavity  38 . The closing plug  52  is made of a material that is transparent to the passage of radio signals transmitted via the antenna  48 . The closing plug  52  is axially external to the electronic sensor module  42 . The closing plug  52  is axially external to the container  50 . 
     The inlet portion  39  of the housing seat  37  comprises an annular groove  53  obtained in the blind cavity  38  and placed at the surface  22   d  of axial end  22   a  of the shaft  22 . The annular groove  53  is configured to receive and retain a stop ring  54 . The stop ring  54  is a ring preferably made of steel and elastic, wherein elasticity is given by the fact that the outer circumference of the ring is not complete. The stop ring  54  is axially external to the electronic sensor module  42 . The stop ring  54  is axially external to the closing plug  52 . The stop ring  54  is axially external to the container  50 . 
     Starting from an axially inner position to an axially inner position, the stop ring  54  is provided as fitted in the annular groove  53  (which is placed in the same axial position of the stop ring  54 ), followed by the closing plug  52  followed by the electronic sensor module  42  contained in the container  50 . 
     The housing seat  39  extends in a radial direction so as to house the stop ring  54 , the closing plug  52  and the container  50 . 
     As shown in  FIGS.  2 A and  2 B , the housing seat  37  does not intercept, i.e. does not cross, the radial cavity  26  which crosses the shaft  22  in a radial direction and which houses the pin  27 . The blind cavity  38  is not in fluid communication and does not cross the radial cavity  26  which crosses in a radial direction the shaft  22  and which houses the pin  27 . 
     The person skilled in the art will recognize that it is possible to combine the various characteristics of the embodiments described above to obtain further embodiments, all falling within the scope of the present invention as defined by the subsequent claims.