Method of manufacturing a tyre sensing device

Abstract

Method of manufacturing a tyre sensing device (1), comprising: providing a mould (20) comprising a protruding element (30) protruding from the moulding surface (26), providing an assembly (2) comprising an electronic unit (3) comprising a sensor (4), a processing unit and a receiver-transmitter, and an electrical power supplier (5) connected to the electronic unit, placing the assembly in the moulding cavity with the sensor in contact with the protruding element, filling the moulding cavity with a precursor material of a polymeric material, hardening the precursor material to make an encapsulating body (9) in polymeric material, wherein the encapsulating body embeds the assembly, keeping the protruding element and the sensor (4) pressed against each other, wherein the precursor material also flows around the protruding element and extracting from the moulding cavity the sensing device comprising the encapsulating body and the assembly, separating the protruding element from the sensor (4) to obtain a through opening (14) in the encapsulating body.

Description

[0001] DESCRIPTION

[0002] Title: METHOD OF MANUFACTURING A TYRE SENSING DEVICE

[0003] Technical field of the invention

[0004] The present invention relates to a method of manufacturing a tyre sensing device.

[0005] Prior art

[0006] Sensing devices fixed to the inner surface of a tyre are known for sensing one or more physical magnitudes of the tyre, such as temperature, pressure, acceleration of the inner surface, deformation of the inner surface, etc.

[0007] Document WO2019 / 123118A1 discloses a tyre sensing device comprising an electronic unit enclosed in an encapsulating material. The encapsulating material comprises an upper portion, in which the electronics are enclosed, and a lower portion, comprising a base surface intended to fix the device to the inner surface of the tyre.

[0008] Document US2004094251A1 discloses a transponder mounted in a tyre.

[0009] Summary of the invention

[0010] ‘Electrical power supplier’ is intended as a component structured to supply electrical energy, whether the energy supplied is pre-accumulated as in accumulators, for example batteries or capacitors, or whether the energy supplied is generated and / or received in situ in real time, such as in energy recovery, or ‘energy harvesting’, devices, combined or not combined with energy accumulators.

[0011] "Inner cavity" is intended as the space delimited by the inner surface of the tyre and by the surface of the mounting rim facing the inner surface of the tyre, when mounted.

[0012] "Precursor material" is generally intended as any material adapted to deform to fill a moulding cavity (for example liquid, fluid, gel, visco-elastic, etc.) and capable of transforming by hardening in the polymeric material of the encapsulating body (for example by chemical reaction, change of physical state, cross-linking, etc.).

[0013] In the context of tyre sensing devices, the Applicant has felt the need to completely encapsulate the electronic components of the device, as well as the power supplier, sealing them against air, liquids and vapours, in order to avoid damage or deterioration of the electronics.

[0014] To this end, the Applicant considers industrially convenient, as it is simple and fast, a method of manufacturing the device in which the encapsulation occurs in a single moulding step, thereby producing an encapsulating body in one piece, with homogeneous structure and constituent material, and which entirely surrounds the assembly comprising the electronic components and the supplier.

[0015] In this context, the Applicant has discovered that during moulding, the assembly can undergo an undesired thrust by the precursor material of the encapsulating body, for example in the case of pressure or compression moulding, or as a result of the fluidstatic thrust, which can cause a displacement of the assembly with respect to the desired position. This displacement in turn produces deviations from the nominal thickness of the encapsulating body, with possible risks in terms of sealing capacity and / or resistance to fatigue cycles during use.

[0016] The Applicant has also considered that in some cases the sensing device comprises a sensor which must be in fluid communication with the inner cavity of the tyre, for example a pressure and / or temperature sensor. In this case, the encapsulating body, in order to obtain such communication, must be provided with a through opening at a communication bore in the body of the sensor, such a through opening being able to be made during moulding thanks to a protruding element in the moulding cavity which remains in contact with the body of the sensor. In this case, the Applicant has discovered that the precursor material of the encapsulating body, in particular if low viscosity liquid, can infiltrate between the sensor and such a protruding element, thus risking penetrating into, and / or at least partly occluding, the bore of the sensor.

[0017] The Applicant has therefore addressed the problem of manufacturing a sensing device in which the assembly, comprising the electronic unit and the electrical power supplier, is substantially, i.e., unless there are confined through openings such as that necessary for a pressure and / or temperature sensor, entirely sealed by a single encapsulating body, simultaneously achieving the correct positioning of the assembly and / or the fluid communication between the sensor and the inner cavity of the tyre.

[0018] The Applicant has lastly found that pressing the sensor and the protruding element against each other during moulding solves one or more of the aforesaid problems.

[0019] According to an aspect, the invention relates to a method of manufacturing a tyre sensing device.

[0020] Preferably the method comprises providing a mould having a moulding surface defining a moulding cavity, where the mould comprises a protruding element protruding from said moulding surface.

[0021] Preferably the method comprises providing an assembly comprising:

[0022] - an electronic unit comprising: - a sensor,

[0023] - a processing unit and

[0024] - a receiver-transmitter, and

[0025] - an electrical power supplier electrically connected to said electronic unit.

[0026] Preferably the method comprises placing said assembly in said moulding cavity with said sensor in contact with said protruding element.

[0027] Preferably the method comprises filling said moulding cavity with a precursor material of a polymeric material.

[0028] Preferably the method comprises hardening said precursor material to make an encapsulating body in said polymeric material, wherein said encapsulating body is in one piece and contactingly embeds said assembly.

[0029] Preferably during said filling and said hardening, the method comprises keeping said protruding element and said sensor pressed against each other, wherein the precursor material also flows around said protruding element.

[0030] Preferably the method comprises extracting from the moulding cavity said sensing device comprising said encapsulating body and said assembly, separating said protruding element from said sensor to obtain a through opening in said encapsulating body at said sensor.

[0031] According to another aspect the invention relates to a sensing device manufactured according to the present invention.

[0032] According to a further aspect the invention relates to a tyre comprising at least one sensing device according to the present invention.

[0033] The Applicant considers that by pressing the sensor and the protruding element against each other during the moulding step results in the assembly not moving from the correct position in the mould, even in the face of possible thrusts exerted on the assembly by the precursor material, including fluid-static thrust in the case of precursor liquid. Thereby, the assembly is correctly positioned with respect to the encapsulating body, which therefore respects the specifications in terms of thicknesses around the assembly.

[0034] Furthermore, the imprint left by the protruding element in the encapsulating body produces a through opening for the sensor: pressing the sensor and the protruding element against each other makes a sealing contact between said sensor and said protruding element which prevents infiltrations of the precursor material between the sensor and the protruding element, even in the case of moulding with low viscosity precursor liquid, which could occlude the communication bore of the sensor, if present. According to at least one of the aforesaid aspects, the present invention can have one or more of the following preferred features.

[0035] Preferably said protruding element exerts an attraction force on said sensor to keep said protruding element and said sensor pressed against each other. Thereby, the contact of the protruding element with the sensor, necessary in the case of a sensor with a communication bore, is exploited, also to exert the pressure force, without the need for further thrust elements and / or contact points during the moulding step.

[0036] Preferably said attraction force is magnetic.

[0037] Preferably said protruding element comprises a magnet, more preferably permanent, and said sensor comprises a ferromagnetic free surface (for example in ferrous metal). Thereby, the aforesaid force of attraction is generated in a simple and effective manner.

[0038] In an embodiment, said attraction force is pneumatic, for example by vacuum or depression. Preferably said mould comprises an air suction system comprising a duct which flows inside said protruding element and which opens at the sensor, and a fan in fluid communication with the duct. Thereby, the protruding element attracts the sensor due to the depression generated by the fan in the duct.

[0039] Preferably said receiver-transmitter comprises an antenna, and is exemplarily based on BlueTooth™ technology.

[0040] Preferably said assembly further comprises a rigid printed circuit board having a first face and a second face mutually opposite one another, wherein said electronic unit is mounted on said rigid board, for example is mounted at least in part on said first face of said rigid board.

[0041] Preferably said rigid board (for example said first and second face) is generally circular or oval in shape.

[0042] Preferably said sensor is fixed on said first face.

[0043] Preferably said rigid board comprises one or more layers of a base material, such as cellulose-based sheets (for example of paper), fibreglass (cross-linked or not), etc., impregnated with a resin (for example phenolic, epoxy, polyimide, or BT / epoxy). Exemplarily said rigid board is made of epoxy glass (for example a composite material based on fibreglass arranged orthogonally between two layers in an epoxy resin matrix). Thereby, the desired rigidity and / or electrical insulation is conferred.

[0044] Preferably said sensor is structured to sense at least one, or at least two, of the following physical magnitudes: temperature, pressure, acceleration, deformation. Preferably said acceleration has one or more components (axial, radial and / or tangential). Thereby, the sensing device provides particularly useful data for deriving the state and / or operation of the tyre, and / or the behaviour of the vehicle on which it is mounted.

[0045] Preferably said sensor is adapted to sense pressure and / or temperature and is provided with a bore to place said sensor in fluid communication with an external environment. Preferably said bore is in correspondence with said protruding element and said through opening of the encapsulating body. Thereby, the fluid communication between the sensor and the inner cavity of the tyre is obtained.

[0046] Preferably said electrical power supplier comprises an electrical energy accumulator, more preferably comprising one or more batteries, for example button batteries.

[0047] Preferably said electrical power supplier is fixed to said rigid board and arranged on the same side of said second face of said rigid board, more preferably facing and proximate to said second face, even more preferably said supplier and said rigid board are stacked with each other.

[0048] Preferably the encapsulating body is provided with a coupling surface, more preferably flat, intended for fixing the sensing device to the tyre. Preferably said coupling surface has a perimeter edge free of comers, cusps and / or portions with small radii of curvature, for example in a pentalobe shape.

[0049] Preferably the device has an axis perpendicular to the coupling surface.

[0050] Preferably the encapsulating body is provided with a free surface, on the side opposite said coupling surface, having a much smaller surface extension, for example at least three or five times smaller, than a surface extension of said coupling surface.

[0051] Preferably said through opening faces said free surface.

[0052] Preferably the encapsulating body has a side surface substantially continuously connecting said coupling surface and said free surface.

[0053] Preferably the side surface is substantially cylindrically symmetrical around the axis of the device.

[0054] Preferably a portion of said side surface near the free surface is almost cylindrical or truncated cone-shaped around said axis of the device.

[0055] Preferably said side surface is tapered moving away from said coupling surface up to said free surface. Thereby, the extraction of the device from the mould is facilitated.

[0056] Preferably said mould has a mould axis and a reference plane orthogonal to the mould axis.

[0057] Preferably said mould comprises a first half-mould and, more preferably, a second halfmould movable relative to the first half-mould, more preferably along the axis of the mould, which coincides with the axis of the device in moulding.

[0058] Preferably it is envisaged, before said hardening, to close said mould, more preferably by mutually approaching the first and second half-mould, more preferably after said filling the cavity. It is thereby possible to create a closed cavity.

[0059] Preferably said mould, more preferably said first half-mould, comprises an insert which is movable relative to the rest of the mould along said axis of the mould, said movable insert comprising a moulding face forming part of the moulding surface. The extraction of the device is thereby simplified.

[0060] Preferably said movable insert comprises said protruding element.

[0061] Preferably said free face of the encapsulating body is located at said moulding face.

[0062] Preferably said mould comprises at least two spacers in said moulding cavity, more preferably at least three spacers, each spacer having a respective free end located at a distance from a respective base of the spacer, more preferably along the axis of the mould.

[0063] Preferably the free ends of the spacers are positioned with a predetermined spatial relationship with respect to the reference plane of the mould. Preferably a portion of said moulding surface, more preferably belonging to the second half-mould, lies on the reference plane.

[0064] Preferably the coupling surface corresponds to said portion of the moulding surface, i.e. , it lies on the reference plane during moulding.

[0065] Preferably during said filling of said moulding cavity, said precursor material also flows at said spacers, more preferably at side surfaces of said spacers.

[0066] Preferably during said hardening of said precursor material it is envisaged to maintain at least three surface points of said assembly in contact with, or in proximity to, the free ends of said at least two spacers. "Surface point" is intended as a surface portion of the assembly of limited extension. Preferably said three surface points are positioned with a predetermined spatial relationship with respect to a development plane of the assembly, more preferably a main development plane of the rigid board or of the electrical power supplier, to satisfy a predetermined requirement of parallelism between said development plane of the assembly and said coupling surface.

[0067] Preferably said predetermined parallelism requirement consists in an angle between said development plane of the assembly and said coupling surface less than or equal, in absolute value, to 3°, preferably to 2°, even more preferably to 1 °.

[0068] The contact between the sensor and the protruding element, necessary to achieve a certain distance between the assembly and the moulding surface for the subsequent encapsulation of the assembly, constitutes a point of constraint around which the assembly can potentially tilt, with a consequent deviation from the desired thickness values of the encapsulating body, for example deviation from the coplanarity between the assembly, in particular the supplier / battery, and the coupling surface. Thanks to the contact or proximity of three surface points of the assembly with the free ends of the at least two spacers, the maximum tilt that the assembly can carry out around the contact point is limited. That is, the spacers act as a stroke stop in the event of unwanted tilting of the assembly, thus obtaining a precise positioning of the assembly relative to the moulding surface and thus with respect to the predetermined reference plane. This in turn allows a desired thickness of the encapsulating body, in particular at the moulding surface, i.e. , in use, a desired thickness (for example a high thickness uniformity) of the encapsulating body below the assembly, for example below the supplier / battery. The mechanical and / or thermal stress undergone by the device and / or by the inner surface of the tyre is thus reduced.

[0069] Preferably said spacers are distinct and separate from each other.

[0070] Preferably there are at least four of said spacers and / or said surface points, more preferably they are four in number.

[0071] Preferably said at least three surface points are equal in number to a number of said spacers, each surface point being in contact with, or in proximity to, the free end of a respective spacer.

[0072] Preferably said spacers and / or said at least three surface points are angularly distributed around said axis of the mould, more preferably at a position radially distal from said axis of the mould. Preferably said three surface points are separated from each other, more preferably they are distributed on one face of said assembly, even more preferably on the first face of said rigid board.

[0073] Preferably said at least three surface points are at a perimeter edge of the rigid board. This is to position them at the maximum possible distance and efficiently perform the tilt limitation function of the assembly.

[0074] Preferably the ends of the spacers face the first face of the rigid board.

[0075] Preferably the rigid board has a shape in plan, orthogonal to said axis of the device, comprising a plurality of radial protrusions distributed along a perimeter edge of said rigid board to make at least two through openings, in a section of the mould orthogonal to the axis of the mould, between the moulding surface and a respective edge portion of the rigid board comprised between each pair of protrusions. It is thereby possible to let flow the precursor liquid beyond the rigid board through at least one through opening and simultaneously make the air exit in the opposite direction through at least one other through opening.

[0076] Preferably each of said at least three surface points of said assembly is located on a respective protrusion at the first face of the rigid board. Thereby, the protrusions also perform the task of a possible support point.

[0077] Preferably said rigid board (including the protrusions) is a single homogeneous body in the constituent materials. That is, the protrusions are of the same material as the rest of the rigid board. Thereby, making the protrusions is simplified, for example because the rigid boards are manufactured and supplied in batches of boards attached to each other to form a matrix. Upon the separation of each board, the four bridges connecting the board to the four adjacent boards of the matrix are broken, thus creating the four protrusions. That is, not only are the four protrusions already present exploited because they are inherent in the manufacturing process of the rigid boards, but the need for their removal, for example by milling, as is usual, is also avoided.

[0078] In an embodiment, said rigid board has a plurality of through openings, parallel to the axis of the device, and arranged inside a perimeter edge of said rigid board.

[0079] Preferably said protruding element and / or said spacers are part of said moulding face of the movable insert.

[0080] Preferably said precursor material is a precursor liquid.

[0081] Preferably said polymeric material is a thermosetting polyurethane material (for example elastomeric Pll) or a polyurea.

[0082] Preferably said precursor liquid is a mixture of polyol and isocyanate.

[0083] Preferably said hardening comprises chemically reacting said mixture in said mould.

[0084] Preferably said filling said moulding cavity comprises pouring said precursor liquid in said moulding cavity by gravity. Thereby, the moulding occurs at ambient pressure and the forces acting on the assembly are limited.

[0085] Preferably said protruding element protrudes upwards from a bottom of said moulding cavity.

[0086] Preferably said moulding face of the movable insert faces upwards.

[0087] Preferably said portion of the moulding surface faces downwards.

[0088] Preferably said assembly is inserted with said electronic unit arranged below said electrical power supplier. Thereby the moulding occurs with the thinnest part of the encapsulating body (at the perimeter portion of the coupling surface the thickness can be less than 1 mm) facing upwards. This condition, and even more so when it is envisaged to close the mould, facilitates the uniform distribution of the precursor material still in the fluid phase at the entire coupling surface of the encapsulating body. Otherwise, if during the moulding the coupling surface is arranged below and the mould is necessarily closed, it would be much more difficult to fill such a thin section, in particular in the absence of means for evacuating the air from the moulding cavity.

[0089] In an embodiment said filling comprises injecting said precursor liquid at low pressure (low pressure injection moulding), more preferably said polymeric material being polyamide or polyester material.

[0090] Preferably it is envisaged to fix said sensing device to an inner surface of a tyre.

[0091] Preferably the sensing device is fixed to an inner surface of said tyre, more preferably at a crown portion of said tyre (i.e. , the tyre portion at the tread band), for example by means of an adhesive interposed between said coupling surface and said inner surface.

[0092] Preferably said adhesive is a pressure-sensitive adhesive (PSA). Thereby, the gluing of the device to the inner surface of the tyre can be carried out by an extremely simple and quick procedure.

[0093] Brief description of the figures

[0094] Figure 1 shows a schematic, perspective and partial view of a section of tyre comprising a sensing device manufactured with the method according to the present invention;

[0095] Figures 2 and 3 schematically show, respectively, an exploded view and a section of the sensing device manufactured with the method according to the present invention; Figure 4 schematically and partially shows an exploded view of a mould in a step of the method according to the present invention;

[0096] Figure 5 schematically and partially shows a section of a mould in a step of the method according to the present invention;

[0097] Figures 6 and 7 schematically and partially show a section of a mould in a step of the method according to the present invention, respectively on two mutually orthogonal section planes.

[0098] Detailed description of preferred embodiments of the invention

[0099] The features and advantages of the present invention will be further apparent from the following detailed description of some embodiments, presented by way of non-limiting example of the present invention, with reference to the attached figures.

[0100] With the reference numeral 10, Figure 1 shows a tyre (in partial perspective section) comprising a sensing device 1 manufactured according to the present invention. Exemplarily, the sensing device 1 is fixed to an inner surface 15 of the tyre 10 at a crown portion 16 of the tyre 10, i.e., the tyre portion located at the tread band, by means of a non-visible adhesive, for example sensitive to pressure, interposed between a coupling surface 11 of the device 1 and the inner surface 15.

[0101] The device 1 comprises an assembly 2 comprising an electronic unit 3 (schematically shown in the figures) comprising a sensor 4, a processing unit and a receivertransmitter, for example based on 2.4GHz BlueTooth™ technology. Exemplarily the sensor is adapted to sense pressure and / or temperature and is provided with a bore (visible in Figure 2) to place the sensor in fluid communication with the inner chamber of the tyre.

[0102] The assembly further comprises an electrical power supplier 5 electrically connected to said electronic unit by means of the two contacts visible in the figures. Exemplarily, the supplier consists of one and only one electrical energy accumulator, for example a circular button battery.

[0103] Preferably the assembly further comprises a rigid printed circuit board 6, for example in epoxy glass, having a first face 7 and a second face 8 mutually opposite each other. The electronic unit 3 is mounted on the rigid board, exemplarily partly on the second face and partly on the first face. Preferably the sensor and the antenna of the receivertransmitter are fixed on the first face to allow effective operation. Preferably the rigid board (for example the first and the second face) has a shape, in plan view orthogonal to the axis 12 of the device (Fig. 7), which is generally circular, more preferably comprising four radial protrusions 16 distributed along the perimeter edge of the rigid board 6 in an angularly uniform manner, i.e. , at 90°, around the axis 12. Preferably the protrusions 16 are of the same material as the rest of the rigid board.

[0104] The assembly 2 has a predefined development plane 32, for example a median development plane of the rigid board 6, shown in Figure 6.

[0105] Preferably the electrical power supplier 5 is fixed to the rigid board 6 (for example by means of electrical contacts), and vertically stacked thereon, on the side of the second face of the rigid board and at a short but non-zero distance therefrom.

[0106] Preferably, the device 1 comprises an encapsulating body 9 in polymeric material, in one piece and contactingly embedding substantially the entire assembly, i.e., completely surrounding the assembly with the exception of any limited areas of the assembly which remain exposed, for example at the sensor bore and / or any contact points with spacers as better specified below. Preferably the encapsulating body 9 is provided with a flat coupling surface 11 intended for fixing the sensing device 1 to the inner surface 15 of the tyre 10. Preferably the coupling surface 11 has a pentalobeshaped perimeter edge (Fig. 2).

[0107] Preferably the device has an axis 12 perpendicular to the coupling surface 11 .

[0108] Preferably the encapsulating body 9 is provided with a free surface 13, on the side opposite said coupling surface 11 , having a much smaller surface extension (for example around seven times smaller) than the surface extension of the coupling surface 11 . Preferably the encapsulating body 9 is provided, at the sensor 4, more in particular the bore of the sensor 4, with a through opening 14 facing the free surface 13.

[0109] Preferably the encapsulating body 9 has a side surface 17 substantially continuously connecting the coupling surface 11 and the free surface 13. Preferably the side surface 17 is substantially cylindrically symmetrical around the axis 12 of the device. Preferably the entire side surface 17 is tapered moving away from the coupling surface 11 (Fig. 3) up to the free surface 13, the portion of the side surface near the free surface being truncated cone-shaped with quasi-axial walls, i.e., almost cylindrical, albeit slightly tapered.

[0110] Figure 3 shows a vertical section of the device passing through the section plane 50 shown in Figure 2.

[0111] Preferably the mould 20 has an axis 21 of the mould, which coincides with the axis 12 of the device 1 in moulding, and a reference plane 22 orthogonal to the axis 21 of the mould.

[0112] Preferably the mould comprises a first half-mould 23 and a second half-mould 24 movable relative to the first half-mould 23 along the axis 21 of the mould. Preferably the mould has a moulding surface 26 defining a moulding cavity 25. Preferably the portion 29 of the moulding surface 26 belonging to the second half-mould 24 lies on the reference plane 22.

[0113] Preferably the mould 20, more preferably the first half-mould 23, comprises a movable insert 27, for example by means of a screw arranged below, relative to the rest of the mould along the axis 21 of the mould itself, said movable insert 27 comprises a moulding face 28 forming part of the moulding surface 26.

[0114] Preferably the movable insert 27 comprises a protruding element 30 which protrudes from the moulding face 28. Preferably the protruding element 30 comprises or consists of a permanent magnet, and the sensor 4, for example the body of the sensor 4, comprises a ferromagnetic free surface, for example in ferrous metal.

[0115] Preferably the mould, in particular the insert 27, comprises four distinct and separate spacers 31 in the moulding cavity 25, each spacer having a respective free end located at a distance, taken along the axis 21 of the mould, from a respective base of the spacer. The free ends of the spacers are positioned with a predetermined spatial relationship with respect to the reference plane 22 of the mould. Preferably the spacers are angularly equally distributed around the axis 21 of the mould at a perimeter edge of the insert 27.

[0116] The mould 20 is adapted to be used in a method of manufacturing the device 1 according to the present invention.

[0117] Preferably the mould is positioned so that the moulding face 28 of the movable insert 27 is located on the bottom of the moulding cavity 25 and faces upwards (the protruding element 30 protrudes upwards from the bottom of the moulding cavity 25), while the portion 29 of moulding surface faces downwards.

[0118] Preferably the method comprises placing the assembly 2 in the moulding cavity 25, placing the sensor 4, for example the bore of the sensor 4, in contact with the protruding element 30 (Fig. 6). Preferably the assembly 2 is inserted with the electronic unit 3 and the rigid board 6 arranged below the electrical power supplier 5, the free surface of the sensor 4 facing downwards.

[0119] Preferably the magnet of the protruding element 30 exerts a magnetic attraction force on the sensor 4 to keep them pressed against each other during the entire moulding process.

[0120] Preferably the assembly 2 is positioned by placing, and maintaining during the moulding process, four surface points of the assembly respectively in contact with, or in proximity to, the free ends of the four spacers 31 , where the four surface points are positioned with a predetermined spatial relationship with respect to the predefined development plane 32 of the assembly 2. For example, the distance between a surface point and the respective spacer is less than or equal to about 1 mm or 0.5 mm, for example less than or equal to one tenth of a mm. Preferably each of the four surface points of the assembly is located on a respective protrusion 16 of the rigid board at the first face and consequently the ends of the spacers 31 face the first face of the rigid board. It should be noted that the spacers 31 could be in different numbers, for example two or three, as long as their size allows the support of at least three separate surface points of the assembly 2. In the example shown, there are four spacers as well four surface points, although the present invention also contemplates embodiments in which there are fewer spacers than surface points, for example two spacers and three or four surface points. In this case at least two surface points are located in contact with, or in proximity to, the free end of the same spacer.

[0121] It is observed that the presence of the magnet favours a secure contact between sensor 4 and protruding element 30, while in optimal conditions (for example with assembly perfectly in axis with the mould and free of deformations, in particular of the rigid board) the aforesaid four surface points of the rigid board do not touch the respective free ends of the spacers 31 , remaining in close proximity. Instead, if due to manufacturing and / or process tolerances, the board 6 has a slightly different shape from the nominal one and / or undergoes a slight tilt with fulcrum on the sensor 4, then contact may occur between one or more surface points on the protrusions 16 and the respective spacers 31 , which act as a stroke end limiting the tilt of the assembly 2 and thus satisfying a predetermined parallelism requirement between the development plane 32 of the assembly 2 and the reference plane 22 on which the coupling surface 11 lies during moulding.

[0122] Preferably the moulding cavity 25 is completely filled with a precursor material of a polymeric material, exemplarily a liquid mixture of polyol and isocyanate.

[0123] Preferably the liquid mixture is poured into the moulding cavity by gravity, thanks to the shape of the mould and the positioning of the assembly in the mould.

[0124] In order to completely encapsulate the assembly on all its parts, the precursor material flows from the top downwards passing over the rigid board 6 to reach the area of the moulding cavity on the side of the first face 7 of the rigid board 6 and here also flow around the protruding element 30 and along the spacers 31 , until it reaches the moulding face 28 of the insert 27.

[0125] To this end, the protrusions 16 form suitable through openings 32, in a section of the mould orthogonal to the axis 21 of the mould, between each pair of protrusions 16 and the moulding surface 26, through which the precursor liquid flows, as shown in Figure 7 where the section plane coincides with the predefined development plane 32 of the assembly 2.

[0126] Alternatively or in addition, the rigid board 6 can have (not shown) a plurality of through openings, parallel to the axis 21 of the device, and arranged inside the perimeter edge of the board.

[0127] After closing the mould, for example by bringing the second half-mould into contact with the first half-mould, as shown in Figure 5, where the assembly and the precursor material have been omitted, it is envisaged to harden the precursor material to make the encapsulating body 9. Exemplarily the hardening occurs by chemical reaction of the aforesaid mixture kept in the mould for an interval of about 2-3 minutes at about 50-60° until forming the polymeric material which in this case is an elastomeric polyurethane (for example of the Elasturan® series of BASF®).

[0128] During moulding, the coupling surface 11 corresponds to, i.e., is shaped by, the aforesaid portion 29 of the moulding surface lying on the reference plane 22 and the free face 13 of the encapsulating body 9 corresponds to the moulding face 28.

[0129] Finally, the device 1 is extracted from the moulding cavity 25, for example thanks to the upward movement of the insert 27, thus separating the protruding element 30 from the sensor 4 to obtain the through opening 14 in the encapsulating body 9.

[0130] As can be seen in the figures, in addition to the imprint left by the protruding element 30, the encapsulating body 9 shows the imprints left by the spacers 31 , at which the rigid board 6 (in particular on the surface points on the protrusions 16) could be exposed to air, in the event of contact between protrusion and spacer 31 . The sealing of the electronic unit 3 and the supplier 5 is also obtained in this case, thanks both to the high compatibility and thus adhesion between the material (for example Pll) of the encapsulating body and the rigid board (for example vetronite), and to the fact that there are no electronic components at the protrusions 16.

Claims

CLAIMS1 . A method of manufacturing a tyre sensing device (1 ), the method comprising:- providing a mould (20) having a moulding surface (26) defining a moulding cavity (25), wherein the mould comprises a protruding element (30) protruding from said moulding surface (26);- providing an assembly (2) comprising:- an electronic unit (3) comprising:- a sensor (4),- a processing unit and- a receiver-transmitter, and- an electrical power supplier (5) electrically connected to said electronic unit (3);- placing said assembly in said moulding cavity with said sensor in contact with said protruding element;- filling said moulding cavity with a precursor material of a polymeric material;- hardening said precursor material to make an encapsulating body (9) of said polymeric material, wherein said encapsulating body is in one piece and contactingly embeds said assembly; wherein during said filling and said hardening, the method comprises keeping said protruding element (30) and said sensor (4) pressed against each other, wherein said precursor material also flows around said protruding element (30); and- extracting from the moulding cavity (25) said sensing device (1 ) comprising said encapsulating body (9) and said assembly (2), separating said protruding element (30) from said sensor (4) to obtain a through opening (14) in said encapsulating body (9) at said sensor (4).

2. Method according to claim 1 , wherein said protruding element (30) exerts an attraction force to said sensor (4) to keep said protruding element (30) and said sensor (4) pressed against each other.

3. Method according to claim 2, wherein said attraction force is magnetic, and wherein said protruding element (30) comprises a permanent magnet, and said sensor (4) comprises a ferromagnetic free surface.

4. Method according to any one of the previous claims, wherein said assembly (2) further comprises a rigid printed circuit board (6) having a first face (7) and a second face (8) mutually opposite one another, wherein said electronic unit (3) is mounted on said rigidboard, wherein said rigid board comprises one or more layers of a base material impregnated with a resin, wherein said electrical power supplier comprises one or more batteries, and wherein said electrical power supplier is attached to said rigid board and facing, and proximate to, said second face of said rigid board.

5. Method according to claim 4, wherein said sensor (4) is fixed on said first face, wherein said sensor is structured to sense pressure and / or temperature and is provided with a bore to place said sensor (4) in fluid communication with an external environment, and wherein said bore is in correspondence with said protruding element (30) and said through opening (14) of said encapsulating body (9).

6. Method according to any one of the preceding claims, wherein said mould (20) comprises a first half-mould (23) and a second half-mould (24) movable relative to the first half-mould along an axis (21 ) of the mould, and wherein the method comprises, prior to said hardening and after said filling of the cavity, closing said mould by mutually approaching said first half-mould (23) and said second half-mould (24).

7. Method according to any one of the preceding claims, wherein said mould comprises in said moulding cavity (25) at least two spacers (31 ), mutually distinct and separated, each spacer having a respective free end positioned at a distance from a respective spacer base along an axis (21 ) of the mould, wherein the free ends of the spacers are positioned in a predetermined spatial relationship with respect to a reference plane (22) of the mould, wherein a portion (29) of said moulding surface lies in there reference plane, wherein a coupling surface (11 ) of the encapsulating body (9) corresponds to said portion (29) of moulding surface, wherein during said filling of said moulding cavity said precursor material also flows at said spacers, wherein during said hardening said precursor material it is provided to keep at least three surface points of said assembly in contact with, or in proximity to, the free ends of said at least two spacers, wherein said three surface points are positioned in a predetermined spatial relationship with respect to a development plane (32) of the assembly to satisfy a predetermined parallelism requirement between said development plane (32) of the assembly and said coupling surface (11 ), said predetermined parallelism requirement consisting in an angle between said development plane of the assembly and said coupling surface less than or equal, in absolute value, to 3°.

8. Method according to claim 7, wherein said spacers (31 ) are angularly distributed around an axis (21 ) of the mould at a position distal from said axis of the mould, wherein said at least three surface points are located at a perimeter edge of the rigid board andwherein the ends of the spacers face towards the first face of the rigid board.

9. Method according to any one of the preceding claims, wherein the rigid board (6) has a shape in plan, orthogonal to an axis (12) of the device, comprising a plurality of radial protrusions (16) distributed along a perimeter edge of said rigid board to make at least two through openings (32), in a section of the mould orthogonal to the axis (21 ) of the mould, between the moulding surface and a respective edge portion of the rigid board (6) comprised between each pair of protrusions (16), and wherein each of said at least three surface points of said assembly is located on a respective protrusion at the first face of the rigid board.

10. Method according to any one of the previous claims, wherein said mould comprises an insert (27) movable relative to the rest of the mould along an axis (21 ) of the mould, said movable insert comprising a moulding face (28) forming part of the moulding surface, wherein said movable insert comprises said protruding element (30) and said spacers (31 ).11 . Method according to any one of the previous claims, wherein said precursor material is a precursor liquid, wherein said polymeric material is a thermosetting polyurethane material or a polyurea, and wherein said precursor liquid is a mixture of polyol and isocyanate, and wherein said hardening comprises chemically reacting said mixture in said mould.

12. Method according to any one of the previous claims, wherein said protruding element (30) protrudes from a bottom of said molding cavity (25) upwardly, wherein said molding face (28) of said movable insert faces upwardly, wherein said portion (29) of molding surface faces downwardly, wherein said assembly is inserted with said electronic unit disposed inferiorly to said electrical power supplier, and wherein said filling said moulding cavity comprises pouring said precursor liquid into said moulding cavity by gravity.

13. Method according to claim 7 or 8, or any one of claims 9 to 12 when dependent on claim 7 or 8, wherein said mould comprises in said moulding cavity (25) at least three spacers (31 ).

14. Sensing device (1 ) manufactured according to one or more of the previous claims.

15. Tyre (10) comprising at least one sensing device (1 ) according to the previous claim.

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