Method for manufacturing a tyre sensing device

Abstract

Method for manufacturing a tyre sensing device (1), comprising: - providing a mould (20) comprising in the moulding cavity (25) at least two spacers (31), distinct and separate; - providing an assembly (2) comprising: - an electronic unit (3) comprising a sensor (4), a processing unit and a receiver-transmitter; and - an electric power supplier (5) electrically connected to the electronic unit (3); - placing said assembly into the moulding cavity; - filling the moulding cavity with a precursor material that also flows at the spacers (31); - hardening the precursor material to make an encapsulating body (9) of polymeric material, in one piece and incorporating in contact the assembly, where the coupling surface (11) of the encapsulating body (9) lies on a reference plane (22) forming part of the moulding surface, wherein at least three surface points of the assembly are kept in contact with, or in proximity to, corresponding surface points on the free ends of the spacers (31) positioned with a predetermined spatial relationship to the reference plane (22) of the moulding surface, and wherein the three surface points of the assembly are positioned with a predetermined spatial relationship to the development plane (32) of the assembly to satisfy a predetermined parallelism requirement between the development plane (32) and the coupling surface (11) of the encapsulating body; and - extracting from the moulding cavity (25) the sensing device (1).

Description

[0001] DESCRIPTION

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

[0003] Technical field of the invention

[0004] The present invention relates to a method for manufacturing a tyre sensing device. Prior art

[0005] Sensing devices fixed to the inner surface of a tyre to detect one or more physical parameters of the tyre, such as temperature, pressure, acceleration of the inner surface, deformation of the inner surface, etc., are known.

[0006] Document WO2019 / 123118A1 describes a tyre sensing device comprising an electronic unit enclosed in an encapsulating material. The encapsulating material comprises an upper portion, in which the electronic unit is enclosed, and a lower portion, comprising a base surface intended to fix the device to the inner surface of the tyre.

[0007] Document US2004094251A1 describes a transponder mounted on a tyre.

[0008] Summary of the invention

[0009] The term ‘electric power supplier’ means a component structured to supply electric power, both if the energy supplied is pre-stored such as in storage units, for example batteries or condensers, and if the energy is generated and / or received in situ in real time, such as, for example, in energy recovery, or ‘energy harvesting’, devices, combined or not with energy accumulators.

[0010] The term “inner cavity” means the space delimited by the inner surface of the tyre and by the surface of the mounting rim that faces the inner surface of the tyre, when mounted.

[0011] The term “precursor material” means, in general, any material adapted to deform to fill a moulding cavity (for example, liquid, fluid, gel, visco-elastic, etc.) and capable of transforming through hardening in the polymeric material of the encapsulating body (for example through a chemical reaction, change in physical state, cross-linking, etc.). The term “surface point” means a surface portion of limited extension.

[0012] In the context of tyre sensing devices, the Applicant has noticed the need to encapsulate completely the electronic components of the device, and also the energy supplier, sealing them to be airtight, liquid-tight and vapour-tight, in order to avoid damage or deterioration of the electronics.

[0013] For this purpose, the Applicant considers to be industrially convenient, as it is simple and quick, a production method of the device in which encapsulation takes place in a single moulding step, thus producing an encapsulating body in a single piece and homogeneous in the structure and constituent material, and that substantially surrounds entirely the assembly comprising the electronic components and the supplier.

[0014] In this context, the Applicant has discovered that, in order to obtain the aforesaid complete encapsulation in a single moulding step, it is convenient to maintain the assembly at a predetermined distance from the moulding surface, thus reducing the resting surface of the assembly in the mould. This, in turn, can cause a poor positioning of the assembly in the mould, with consequent deviation from the desired values of the geometries of the encapsulating body, for example of the thickness of the encapsulating body, in particular at the coupling surface of the encapsulating body positioned underneath the assembly, for example beneath the supplier / battery. Such lack of uniformity of the thickness of the encapsulating body underneath the assembly causes high mechanical and / or thermal stress on the device and / or on the inner surface of the tyre.

[0015] The Applicant has therefore addressed the problem of producing a sensing device in which the assembly, comprising the electronic unit and the electric power supplier, is substantially, i.e. except for any adjoined through openings such as the one necessary for a pressure and / or temperature sensor, entirely sealed by a single encapsulating body, simultaneously limiting or eliminating the mechanical and / or thermal stress to which, in use, the device and / or the tyre is subject.

[0016] In conclusion, the Applicant has found that, during moulding, providing a contact or an extreme proximity between at least three surface points of the assembly and three corresponding surface points of at least two spacers of the mould solves one or more of the aforesaid problems.

[0017] According to a first aspect, the invention relates to a method for manufacturing a tyre sensing device.

[0018] Preferably, the method comprises providing a mould having a moulding surface defining a moulding cavity, wherein said mould comprises in said moulding cavity at least two distinct and separate spacers, each spacer having a respective free end located at a distance from a respective base of the spacer.

[0019] Preferably, the method comprises providing an assembly having a development plane and comprising:

[0020] - an electronic unit comprising:

[0021] - a sensor,

[0022] - a processing unit, and

[0023] - a receiver-transmitter; and

[0024] - an electric power supplier electrically connected to said electronic unit . Preferably, the method comprises placing said assembly into said moulding cavity. Preferably, the method comprises filling said moulding cavity with a precursor material of a polymeric material, wherein said precursor material also flows at said spacers. Preferably, the method comprises hardening said precursor material to make an encapsulating body of said polymeric material, wherein said encapsulating body is in one piece and incorporates in contact said assembly and wherein said encapsulating body comprises a coupling surface for attaching said sensing device to a tyre, said coupling surface lying on a reference plane forming part of said moulding surface. Preferably, during said hardening at least three surface points of said assembly are kept in contact with, or in proximity to, corresponding surface points on the free ends of said at least two spacers, wherein said surface points on the free ends of the spacers are positioned with a predetermined spatial relationship to said reference plane of the moulding surface, and wherein said three surface points of the assembly are positioned with a predetermined spatial relationship to said development plane of the assembly to satisfy a predetermined parallelism requirement between said development plane and said coupling surface of the encapsulating body.

[0025] Preferably, the method comprises extracting from the moulding cavity said sensing device comprising said encapsulating body and said assembly.

[0026] According to another aspect, the invention relates to a sensing device manufactured according to the first aspect of the present invention.

[0027] According to a further aspect, the invention relates to a tyre comprising at least one sensing device according to the preceding aspect of the present invention.

[0028] The Applicant believes that, thanks to the contact or extreme proximity of three surface points of the assembly with respective surface points of the free ends of at least two spacers, it is possible accurately to control the positioning of the assembly in the moulding, simultaneously obtaining the desired spacing necessary to obtain the encapsulating body. In other words, the spacers act as stroke ends in the case of undesired poor positioning of the assembly, thus obtaining a precise positioning of the assembly with respect to the moulding surface, in particular a desired degree of parallelism between the assembly and the coupling surface. This, in turn, allows a high uniformity of the thickness of the encapsulating body to be obtained at the moulding surface, underneath the assembly. The mechanical and / or thermal stress suffered by the device and / or by the inner surface of the tyre is thus reduced.

[0029] According to at least one of the aforesaid aspects, the present invention can have one or more of the following preferred features.

[0030] Preferably, said mould comprises a protruding element protruding from said moulding surface.

[0031] Preferably, it is envisaged to position said assembly in said moulding cavity with said sensor in contact with said protruding element. Said protruding element is in addition to said spacers, even though also being able to act as a spacer.

[0032] 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.

[0033] Preferably, said extracting comprises separating said protruding element from said sensor to obtain a through opening in said encapsulating body at said sensor.

[0034] In cases in which the sensor must be in fluid communication with the inner cavity of the tyre, for example a pressure and / or temperature sensor, the impression 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 obtains a sealing contact between sensor and protruding element that prevents infiltrations of the precursor material between sensor and protruding element, also in the case of moulding with low-viscosity liquid precursor, which could occlude the communication hole of the sensor.

[0035] Furthermore, the contact between sensor and protruding element can obtain a determined distance between assembly and moulding surface for purposes of subsequent encapsulation of the assembly. The Applicant believes that pressing the sensor and the protruding element against each other during the moulding step facilitates the correct positioning of the assembly in the mould, even in the event of possible undesired thrusts exerted on the assembly by the precursor material, including hydrostatic thrust in the case of a liquid precursor. Such contact point constitutes a point of constraint around which the assembly can potentially tilt, with consequent deviation from the desired values of the thicknesses of the encapsulating body. Thanks to the contact or proximity of the surface points of the assembly with the respective surface points on the free ends of the spacers, the maximum inclination of the assembly around the contact point is limited. In other words, the protruding element and the spacers cooperate synergistically, the spacers acting as stroke ends in the case of undesired inclination of the assembly around the contact point with the protruding element, thus obtaining a precise positioning of the assembly with respect to the moulding surface.

[0036] Preferably, said protruding element exerts an attraction force on said sensor to maintain said protruding element and said sensor pressed against each other. In this manner, it is possible to exploit the contact of the protruding element with the sensor, needed in the case of a sensor with communication hole, also to exert the pressure force, without the need for further thrust elements and / or contact points in the moulding step.

[0037] Preferably, said attraction force is magnetic.

[0038] Preferably, said protruding element comprises a magnet, more preferably permanent, and said sensor comprises a ferromagnetic free surface (for example in ferrous metal). In this manner, the aforesaid attraction force is produced simply and efficiently.

[0039] In one embodiment, said attraction force is pneumatic, for example by means of vacuum or depression. Preferably, said mould comprises an air suction system comprising a conduit that runs inside said protruding element and that opens at the sensor, and a fan in fluid communication with the conduit. In this manner, the protruding element attracts the sensor as a result of the depression produced by the fan in the conduit.

[0040] Preferably, said receiver-transmitter comprises an antenna, and for example is based on BlueTooth™ technology.

[0041] 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.

[0042] Preferably, said rigid board (for example said first and second face) has a generally circular or oval shape. Preferably, said sensor is fixed onto said first face.

[0043] Preferably, said rigid board comprises one or more layers of a base material, such as sheets based on cellulose (for example paper), fibreglass (with crossed fibres or not), etc., impregnated with a resin (for example phenolic, epoxy, polyamide, or BT / epoxy). For example, said rigid board is in epoxy glass (for example, a composite material based on glass fibres arranged orthogonally between two layers in an epoxy resin matrix). In this manner, the desired rigidity and / or electrical insulation is obtained.

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

[0045] Preferably, said sensor is suitable for sensing the pressure and / or temperature and is provided with a hole to place said sensor in fluid communication with an external environment. Preferably, said hole is in correspondence with said protruding element and said through opening of the encapsulating body. In this manner, fluid communication is obtained between sensor and inner cavity of the tyre.

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

[0047] Preferably, said electric power supplier is fixed to said rigid board and is arranged on the same side as said second face of said rigid board, more preferably facing, and close to, said second face, even more preferably said supplier and said rigid board are stacked on one another.

[0048] Preferably, said coupling surface has a perimeter edge free of corners, cusps and / or portions with small radii of curvature, for example with a five-lobed 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 opposite side to 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 is facing said free surface.

[0052] Preferably, the encapsulating body has a side surface that substantially connects continuously said coupling surface and said free surface. Preferably, the side surface has a substantially cylindrical symmetry around the axis of the device.

[0053] Preferably, a portion of said side surface proximal to the free surface has an almost cylindrical or truncated cone shape around said axis of the device.

[0054] Preferably, said side surface is tapered moving away from said coupling surface as far as said free surface. In this manner, extraction of the device from the mould is facilitated.

[0055] Preferably, said mould has an axis of the mould and a reference plane orthogonal to the axis of the mould.

[0056] Preferably, said mould comprises a first half-mould and, more preferably, a second half-mould movable relative to the first half-mould, more preferably along the axis of the mould, which coincides in moulding with the axis of the device.

[0057] Preferably, it is envisaged, before said hardening, to close said mould, more preferably by reciprocally approaching the first half-mould and the second half-mould, more preferably after said filling of the cavity. In this manner, it is possible to create a closed cavity.

[0058] Preferably said mould, more preferably said first half-mould, comprises an insert movable relative to the rest of the mould along an axis of the mould, said movable insert comprising a moulding face forming part of the moulding surface. This facilitates the extraction of the device.

[0059] Preferably, said movable insert comprises said protruding element.

[0060] Preferably, said free face of the encapsulating body is at said moulding face.

[0061] Preferably, said distance is taken along the axis of the mould, or along a direction orthogonal to said reference plane.

[0062] Preferably, said reference plane belongs to the second half-mould.

[0063] Preferably, during said filling of said moulding cavity, said precursor material also flows at the side surfaces of said spacers.

[0064] Preferably, said development plane of the assembly is a main development plane of the rigid board or of the electric power supplier.

[0065] Preferably, said predetermined requirement of parallelism consists of 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 °.

[0066] Preferably, said spacers are at least three distinct and separate spacers. Preferably, said spacers and / or said surface points are at least four, more preferably they are four in number.

[0067] Preferably, said at least three surface points of the assembly are equal in number to a number of said spacers, each surface point of the assembly being in contact with, or in proximity to, the free end of a respective spacer.

[0068] Preferably, said spacers and / or said at least three surface points of the assembly are angularly distributed around said axis of the mould, more preferably in a radially distal position from said axis of the mould.

[0069] Preferably, said three surface points of the assembly are separate from each other, more preferably they are distributed on a face of said assembly, even more preferably on the first face of said rigid board.

[0070] Preferably, said at least three surface points of the assembly are located at a perimeter edge of the rigid board. This is in order to position them at the maximum distance possible and to obtain efficiently the function of maintaining the assembly in position. Preferably, the ends of the spacers face towards the first face of the rigid board.

[0071] 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 obtain 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 portion of the edge of the rigid board comprised between each pair of protrusions . In this manner, it is possible to make the liquid precursor flow beyond the rigid board through at least one through opening and simultaneously to release the air in the opposite direction through at least one other through opening.

[0072] Preferably, each through opening is in a position interposed between two adjacent spacers of said at least two spacers. In this manner, the precursor material can flow easily from one face to the other of the rigid board.

[0073] Preferably, each of said at least three surface points of the assembly is located on a respective radial protrusion at the first face of the rigid board. In this manner, the protrusions also perform the task of obtaining the correct positioning of the assembly.

[0074] Preferably, said rigid board (including the protrusions) is a single and homogeneous body in the constituent materials. In other words, the protrusions are made of the same material as the rest of the rigid board. This simplifies creation of the protrusions, for example since the rigid boards are manufactured and supplied in batches of boards attached to each other to form a matrix. Upon separation of each board, the four bridges that connect the board to the four adjacent boards are broken, thus creating four protrusions. In other words, not only is it possible to exploit the four protrusions already present, since they are part of the production process of the rigid boards, but there is also no need to remove them, for example through milling, as usual. In one 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.

[0075] Preferably, said protruding element and / or said spacers form part of said moulding face of the movable insert.

[0076] Preferably, a side surface of said assembly, more preferably of said rigid board, is entirely at a non-zero distance from said moulding surface. Side surface means with respect to said axis of the device. In other words, the assembly is entirely separate from the moulding surface except at said possible protruding element and / or one or more of said free ends of the spacers (these elements, variously combined, constituting the only resting points of the assembly in the mould). Preferably, said nonzero distance is less than or equal to 3 or 2 mm. In this manner, the precursor material can occupy the interstices between the moulding surface and the side surface of the assembly, such side surface having no uncovered points.

[0077] Preferably, said precursor material is a liquid precursor.

[0078] Preferably, said polymeric material is a thermosetting polyurethane material (for example elastomeric PU) or a polyurea.

[0079] Preferably, said liquid precursor is a mixture of polyol and isocyanate.

[0080] Preferably, said hardening comprises chemically reacting said mixture in said mould. Preferably, said filling of said cavity comprises pouring said liquid precursor into said moulding cavity by gravity. In this manner, moulding occurs at ambient pressure and the forces acting on the assembly are limited.

[0081] Preferably, said protruding element protrudes from a bottom of said moulding cavity upwards.

[0082] Preferably, said spacers protrude from a bottom of said moulding cavity upwards.

[0083] Preferably, said moulding face of the movable insert faces upwards.

[0084] Preferably, said coupling surface faces upwards.

[0085] Preferably, said assembly is inserted with said electronic unit disposed inferiorly to said electric power supplier. In this manner, the moulding occurs with the thinnest part of the encapsulating body (at the perimeter portion of the coupling surface, the thickness can be lower than 1 mm) facing upwards. This condition, and even more so when it is envisaged to close the mould, facilitates the even distribution of the precursor material still in the fluid phase at the entire coupling surface of the encapsulating body. In the opposite case, in which during moulding the coupling surface is disposed inferiorly and the mould is necessarily closed, it would be much more difficult to fill such a thin section, in particular in the absence of evacuating means of the air from the moulding cavity.

[0086] In one embodiment, said filling comprises low-pressure injection moulding of the liquid precursor, more preferably said polymeric material being a polyamide or polyester material.

[0087] Preferably, it is envisaged to fix said sensing device to an inner surface of a tyre.

[0088] 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 portion of tyre at the tread band), for example by means of an adhesive interposed between said coupling surface and said inner surface.

[0089] Preferably, said adhesive is a pressure-sensitive adhesive (PSA). In this manner, the device is glued to the inner surface of the tyre by means of an extremely simple and rapid procedure.

[0090] Brief description of the figures

[0091] 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;

[0092] 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 shows schematically and partially an exploded view of a mould in a step of the method according to the present invention;

[0093] Figure 5 shows schematically and partially a section of a mould in a step of the method according to the present invention;

[0094] Figures 6 and 7 shows schematically and partially a section of a mould in a step of the method according to the present invention, respectively on two mutually orthogonal section planes.

[0095] Detailed description of several embodiments of the invention The features and advantages of the present invention will become more apparent from the following detailed description of several embodiments, presented by way of nonlimiting example of the present invention, with reference to the attached figures.

[0096] In Figure 1 , reference number 10 shows a tyre (in partial perspective section) comprising a sensing device 1 manufactured according to the present invention.

[0097] By way of example, 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 portion of tyre at the tread band, by means of a non-visible adhesive, for example a pressure-sensitive one, interposed between a coupling surface 11 of the device 1 and the inner surface 15.

[0098] The device 1 comprises an assembly 2 comprising an electronic unit 3 (shown schematically in the Figures) comprising a sensor 4, a processing unit and a receivertransmitter, for example based on 2.4GHz BlueTooth™ technology. By way of example, the sensor is suitable for sensing the pressure and / or temperature and is provided with a hole (visible in Figure 2) to place said sensor in fluid communication with the inner chamber of the tyre.

[0099] The assembly further comprises an electric power supplier 5 electrically connected to said electronic unit by means of two contacts visible in the Figures. By way of example, the supplier consists of one and one only electrical energy accumulator, for example a circular plan button battery.

[0100] 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 to each other. The electronic unit 3 is mounted on the rigid board, for example partly on the second face and partly on the first face. Preferably, the sensor and the antenna of the receiver-transmitter are fixed onto the first face to allow efficient functioning. Preferably, the rigid board (for example the first and the second face) has a shape, in a plan view orthogonal to the axis 12 of the device (Fig. 7), that 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 made of the same material as the rest of the rigid board.

[0101] The assembly 2 has a predefined development plane 32, for example a median development plane of the rigid board 6, shown in Figure 6.

[0102] Preferably, the electric power supplier 5 is fixed to the rigid board 6 (for example, by means of electric contacts), and vertically stacked on it, on the side of the second face of the rigid board and at a short but non-zero distance from it.

[0103] Preferably, the device 1 comprises an encapsulating body 9 of polymeric material, in one piece and incorporating in contact substantially the entire assembly, i.e. completely surrounding the assembly with the exception of possible limited areas of the assembly that remain exposed, such as, for example, at the hole of the sensor and / or any points of contact with several spacers, as specified in more detail below. Preferably, the encapsulating body 9 is provided with a flat coupling surface 11 destined for fixing of the sensing device 1 to the inner surface 15 of the tyre 10. Preferably, the coupling surface 11 has a perimeter edge with a five-lobed shape (Fig. 2).

[0104] Preferably, the device has an axis 12 perpendicular to the coupling surface 11 .

[0105] Preferably, the encapsulating body 9 is provided with a free surface 13, on the opposite side to said coupling surface 11 , having a much smaller surface extension (for example around seven times smaller) than the surface extension of said coupling surface 11 . Preferably, the encapsulating body 9 is provided, at the sensor 4, more in particular at the hole of the sensor 4, with a through opening 14 that faces the free surface 13.

[0106] Preferably, the encapsulating body 9 has a side surface 17 that substantially connects continuously the coupling surface 11 and the free surface 13. Preferably, the side surface 17 has a substantially cylindrical symmetry around the axis of the device 12. Preferably, the entire side surface 17 tapers moving away from the coupling surface 11 (Fig. 3) as far as the free surface 13, the portion of the side surface proximal to the free surface being a truncated cone with quasi-axial walls, i.e. almost cylindrical, even though slightly tapered.

[0107] Figure 3 shows a vertical section of the device passing through the section plane 50 shown in Figure 2.

[0108] Preferably, the mould 20 has an axis 21 of the mould, which coincides in moulding with the axis 12 of the device 1 , and a reference plane 22 orthogonal to the axis 21 of the mould.

[0109] 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, a portion 29 of the moulding surface 26 belonging to the second half-mould 24 lies on the reference plane 22.

[0110] Preferably, the mould 20, more preferably the first half-mould 23, comprises a insert 27 movable, for example by means of a screw disposed inferiorly, relative to the rest of the mould along the axis 21 of the mould, where the movable insert 27 comprises a moulding face 28 forming part of the moulding surface 26.

[0111] Preferably, the movable insert 27 comprises a protruding element 30 that 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.

[0112] Preferably, the mould, in particular the insert 27, comprises in the moulding cavity 25 four spacers 31 separate and distinct from each other, 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 to the reference plane 22 of the mould. Preferably, the spacers are angularly distributed equally spaced around the axis 21 of the mould at a perimeter edge of the insert 27.

[0113] The mould 20 is suitable to be used in a manufacturing method of the device 1 according to the present invention.

[0114] 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 from the bottom of the moulding cavity 25 upwards), whereas the portion 29 of moulding surface faces downwards.

[0115] Preferably, the method comprises positioning the assembly 2 in the moulding cavity 25, positioning the sensor 4, for example the hole 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 disposed inferiorly to the electric power supplier 5, the free surface of the sensor 4 being facing downwards.

[0116] 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.

[0117] Preferably, the assembly 2 is positioned by placing, and keeping during the moulding process, four surface points of the assembly respectively in contact with, or in proximity to, corresponding surface points on the free ends of the four spacers 31 , where the four surface points of the assembly are positioned with a predetermined spatial relationship to the development plane 32 of the assembly 2. For example, the distance between a surface point of the assembly and the relative surface point on the spacer is less than or equal to around 1 mm or 0.5 mm, for example less than or equal to one tenth of a millimetre. 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 towards the first face of the rigid board. It is noted that there could be a different number of spacers 31 , for example two or three, provided that their dimension allows resting of at least three surface points of the assembly 2 separate to each other. In the example shown, there are four spacers, the same as the surface points of the assembly, even though the present invention also contemplates embodiments in which there is a smaller number of spacers than surface points, for example two spacers and three or four surface points. In that case, at least two surface points of the assembly are in contact with, or in proximity to, corresponding surface points of the free end of a same spacer.

[0118] It is observed that the presence of the magnet facilitates a secure contact between sensor 4 and protruding element 30, whereas in optimal conditions (for example with the assembly perfectly aligned with the mould and without deformations, for example 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. On the other hand, in the case in which, due to the manufacturing and / or process tolerances, the board 6 has a slightly different shape to the nominal one and / or suffers a slight inclination with the fulcrum on the sensor 4, then there could be contact between one or more surface points on the protrusions 16 and the respective spacers 31 , which act as stroke ends by limiting the inclination 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.

[0119] Preferably, the moulding cavity 25 is completely filled with a precursor material of a polymeric material, for example a liquid mixture of polyol and isocyanate.

[0120] Preferably, the liquid mixture is poured into the moulding cavity by gravity, thanks to the shape of the mould and to the positioning of the assembly in the mould.

[0121] In order to completely encapsulate the assembly on all its parts, the precursor material flows from above downwards, passing beyond the rigid board 6 to arrive in the zone of the moulding cavity from the side of the first face 7 of the rigid board 6 and flowing here also around the protruding element 30 and along the spacers 31 , until it reaches the moulding face 28 of the insert 27.

[0122] For this purpose, the protrusions 16 create opportune 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 liquid precursor flows, as shown in Figure 7, where the section plane coincides with the predefined development plane 32 of the assembly 2.

[0123] Alternatively or in addition, the rigid board 6 can have a plurality of through openings (not shown), parallel to the axis 21 of the device, and arranged inside the perimeter edge of the board.

[0124] As shown by way of example in Figure 7, the entire side surface (with respect to the axis of the device) of the rigid board, in particular also at the protrusions 16, is at a (small) distance from the moulding surface, to allow the precursor material to flow into the interstices formed between the moulding surface and the side surface of the protrusions, and thus incorporate the entire side surface of the assembly.

[0125] 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 obtain the encapsulating body 9. By way of example, hardening occurs through chemical reaction of the aforesaid mixture kept in the mould for an interval of around 2-3 minutes at around 50-60°, up until the polymeric material forms, which, in this case, is an elastomeric polyurethane (for example in the Elasturan® range of BASF®).

[0126] During moulding, the coupling surface 11 corresponds with, i.e. is shaped by, said portion 29 of moulding surface that lies on the reference plane 22 and the free face 13 of the encapsulating body 9 corresponds with the moulding face 28.

[0127] Lastly, the device 1 is extracted from the moulding cavity 25, for example thanks to movement upwards 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.

[0128] As visible in the figures, in addition to the impression left by the protruding element 30, the encapsulating body 9 shows the impressions left by the spacers 31 , at which the rigid board 6 (in particular on the surface points of the protrusions 16) could be exposed to the air, in the case of contact between protrusion and spacer 31 . Sealing of the electronic unit 3 and the supplier 5 is nonetheless also obtained in this case, thanks both to the high compatibility and therefore 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 for manufacturing a tyre sensing device (1 ), the method comprising:- providing a mould (20) having a moulding surface (26) defining a moulding cavity (25), wherein said mould comprises in said moulding cavity (25) at least two spacers (31 ), distinct and separate, each spacer having a respective free end located at a distance from a respective base of the spacer,- providing an assembly (2) having a development plane (32) and comprising- an electronic unit (3) comprising:- a sensor (4),- a processing unit, and- a receiver-transmitter; and- an electric power supplier (5) electrically connected to said electronic unit (3);- placing said assembly into said moulding cavity;- filling said moulding cavity with a precursor material of a polymeric material, wherein said precursor material also flows at said spacers (31 );- hardening said precursor material to make an encapsulating body (9) of said polymeric material, wherein said encapsulating body is in one piece and contactingly incorporates said assembly, and wherein said encapsulating body (9) comprises a coupling surface (11 ) for attaching said sensing device to a tyre, said coupling surface (11 ) lying on a reference plane (22) forming part of said moulding surface, wherein during said hardening at least three surface points of said assembly are kept in contact with, or in proximity to, corresponding surface points on the free ends of said at least two spacers (31 ), wherein said surface points on the free ends of the spacers are positioned with a predetermined spatial relationship to said reference plane (22) of said moulding surface, and wherein said three surface points of the assembly are positioned with a predetermined spatial relationship to said development plane (32) of the assembly to satisfy a predetermined parallelism requirement between said development plane (32) and said coupling surface (11 ) of the encapsulating body; and- extracting from the moulding cavity (25) said sensing device (1 ) comprising said encapsulating body (9) and said assembly (2).

2. Method according to claim 1 , wherein the mould comprises a protruding element (30) protruding from said moulding surface (26), wherein said sensor (4) is in contact with said protruding element, wherein during said filling and said hardening, the method compriseskeeping said protruding element (30) and said sensor (4) pressed against each other, wherein the precursor material also flows around said protruding element (30) and wherein during said extracting said protruding element (30) is separated from said sensor (4) to obtain a through opening (14) in said encapsulating body (9) at said sensor (4).

3. Method according to claim 2, wherein said protruding element (30) exerts a magnetic attraction force on said sensor (4) to keep said protruding element (30) and said sensor (4) pressed against each other, 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 rigid board, 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 claims 2 and 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 hole for placing said sensor (4) in fluid communication with an external environment, and wherein said hole 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 previous 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, before said hardening and after said filling the cavity, closing said mould by reciprocally approaching the first half-mould (23) and the second half-mould (24), a side surface of said assembly (2) being entirely at a non-zero distance from said moulding surface (26).

7. Method according to any one of the previous claims, said predetermined parallelism requirement consisting of an angle between said development plane (32) of the assembly and said coupling surface (11 ) less than or equal, in absolute value, to 3°.

8. Method according to any one of the previous claims, wherein said at least three surface points of the assembly are equal in number to a number of said spacers (31 ), each surface point of the assembly being in contact with, or in proximity to, the free end of a respective spacer.

9. Method according to any one of the previous claims, wherein said spacers are at leastthree separate and distinct spacers, 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 of the assembly are located at a perimeter edge of the rigid board, and wherein the ends of the spacers face towards the first face of the rigid board.

10. Method according to any one of the previous 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 realize 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 portion of the edge of the rigid board (6) comprised between each pair of protrusions (16), wherein each through- opening is located in a position interposed between two adjacent spacers of said at least two spacers and wherein each of said at least three surface points of said assembly is located on a respective radial protrusion (16) at the first face of the rigid board.11 . 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 spacers (31 ).

12. Method according to any one of the previous claims, wherein said precursor material is a liquid precursor, wherein said polymeric material is a thermosetting polyurethane material or a polyurea, and wherein said liquid precursor is a mixture of polyol and isocyanate, and wherein said hardening comprises chemically reacting said mixture in said mould.

13. Method according to any one of the previous claims, wherein said spacers (31 ) protrude from a bottom of said moulding cavity (25) upwardly, wherein said coupling surface (11 ) faces upwardly, 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 liquid precursor into said moulding cavity by gravity.

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