ROTARY JOINT AND PRESSURE REGULATION SYSTEM FOR TIRES

Abstract

The present invention concerns un rotary joint (10, 10) apt to transfer a fluid between two entities, one of which is in rotary motion with respect to the other, said rotary joint (10, 10) being characterised in that it comprises a cylindrical internal element (11), apt to be fixed to said entity in rotary motion, and a plurality of annular external elements (14, 15, 17, 18), which can be coupled and which are self-centering, which can be fitted modularly, said external elements (14, 15, 17, 18) comprising at least two head elements (14), at least two housing elements (15) of respective gaskets (16), two bearing elements (17) and at least one fluid inlet element (18), said at least one fluid inlet element (18) being placed in an intermediate position between said two bearing elements (17), said at least two housing elements (15) of respective gaskets (16) being arranged externally with respect to said two bearing elements (17) and said at least two head elements (14) being arranged externally with respect to said at least two housing elements (15) of respective gaskets (16), said gaskets (16) defining an annular shaped sealed area in the space delimited laterally by the same gaskets (16), internally by said internal element (11) and externally by said external elements (14, 15, 17, 18) comprised between said gaskets (16), said sealed area being accessible on one side through said fluid inlet element (18) and on the other side through at least one fluid passage channel (20, 21) passing through the body of said internal element (11) up to one of the two axial ends.

Moreover, the invention concerns pressure regulation systems of a tire (B) comprising said rotary joint (10, 10).

Claims

1) Rotary joint (10, 10) apt to transfer a fluid between two entities, one of which is in rotary motion with respect to the other, said rotary joint (10, 10) being characterised in that it comprises a cylindrical internal element (11), apt to be fixed to said entity in rotary motion, and a plurality of annular external elements (14, 15, 17, 18), which can be coupled and which are self-centering, which can be fitted modularly, said external elements (14, 15, 17, 18) comprising at least two head elements (14), at least two housing elements (15) of respective gaskets (16), two bearing elements (17) and at least one fluid inlet element (18), said at least one fluid inlet element (18) being placed in an intermediate position between said two bearing elements (17), said at least two housing elements (15) of respective gaskets (16) being arranged externally with respect to said two bearing elements (17) and said at least two head elements (14) being arranged externally with respect to said at least two housing elements (15) of respective gaskets (16), said gaskets (16) defining an annular shaped sealed area in the space delimited laterally by the same gaskets (16), internally by said internal element (11) and externally by said external elements (14, 15, 17, 18) comprised between said gaskets (16), said sealed area being accessible on one side through said fluid inlet element (18) and on the other side through at least one fluid passage channel (20, 21) passing through the body of said internal element (11) up to one of the two axial ends.

2) Rotary joint (10, 10) according to claim 1, characterised in that it comprises two fluid inlet elements (18) placed in an intermediate position between said two bearing elements (17), and two housing elements (15) of respective gaskets (16), spaced by a head element (14), said gaskets (16) defining two separate sealed areas, one at each of said two fluid inlet elements (18), said internal element (11) comprising two separate passage channels (20, 21), respectively a passage channel (20, 21) for each of said two sealed areas.

3) Rotary joint (10) according to claim 2, characterised in that it additionally comprises a gasket (16) housing element (15) located between each of said fluid inlet elements (18) and a corresponding bearing element (17).

4) Pressure regulation system of a tire (B) characterised in that it comprises a rotary joint (10, 10), as defined in claim 2, in combination with a compressor installed on said non-rotating entity, and at least one interception valve (23) for inlet and outlet flow from said tire (B), wherein a first passage channel (20) of said rotary joint (10, 10) puts in fluid communication said compressor with operating means of said interception valve (23), through a valve (27), and a second passage channel (21) of said rotary joint (10, 10) puts in fluid communication said compressor with said tire (B), through a valve (28) and said interception valve (23).

5) Pressure regulation system of a tire (B) according to claim 4, characterised in that said valve (27) along said first passage channel (20) is a two-way valve and that said valve (28) along said second passage channel (21) is a three-way valve.

6) Pressure regulation system of a tire (B) characterised in that it comprises a rotary joint (10, 10), as defined in claim 2, in combination with the hydraulic circuit of said non-rotating entity, a variable-volume chamber (30) and control means (31) of said chamber (30), apt to vary the volume of said chamber (30), said chamber (30) being placed in the rim (A) of said tire (B), being filled with air under pressure and being in fluid communication with said tire (B), through at least one interception valve (23); wherein a first passage channel (20) of said rotary joint (10, 10) puts in fluid communication said hydraulic circuit with operating means of said interception valve (23), through a valve (27), and a second passage channel (21) of said rotary joint (10, 10) puts in fluid communication said hydraulic circuit with said control means (31) of said chamber (30), through a valve (28) and said interception valve (23).

7) Pressure regulation system of a tire (B) according to claim 6, characterised in that said control means (31) comprise three or more hydraulic cylinders (31), said valve (27) along said first passage channel (20) is a two-way valve and that said valve (28) along said second passage channel (21) is a three-way valve.

8) Pressure regulation system of a tire (B) characterised in that it comprises a rotary joint (10, 10), as defined in claim 2, in combination with the hydraulic circuit of said non-rotating entity, a reservoir (34), a compressor (36) connected to a hydraulic motor (37), said reservoir (34), said compressor (36) and said hydraulic motor (37) being placed in the rim (A) of said tire (B), said reservoir (34) being filled with air under pressure and being in fluid communication with said tire (B), through said compressor (36) and an interception valve (23); wherein a first passage channel (20) of said rotary joint (10, 10) puts in fluid communication said hydraulic circuit with said hydraulic motor (37), in correspondence of operating means of said hydraulic motor in a first direction of rotation, and with operating means of said interception valve (23), through a valve (39), and a second passage channel (21) of said rotary joint (10, 10) puts in fluid communication said hydraulic circuit with said hydraulic motor (37), in correspondence of operating means of said hydraulic motor in a second direction of rotation, opposite to said first direction of rotation, and with operating means of said interception valve (23), through the same valve (39) or a different valve (38).

9) Pressure regulation system of a tire (B) characterised in that it comprises a rotary joint (10, 10), as defined in claim 3, in combination with a compressor installed on said non-rotating entity, and at least one interception valve (23) for inlet and outlet flow from said tire (B), wherein a first passage channel (20) of said rotary joint (10, 10) puts in fluid communication said compressor with operating means of said interception valve (23), through a valve (27), and a second passage channel (21) of said rotary joint (10, 10) puts in fluid communication said compressor with said tire (B), through a valve (28) and said interception valve (23).

10) Pressure regulation system of a tire (B) according to claim 9, characterised in that said valve (27) along said first passage channel (20) is a two-way valve and that said valve (28) along said second passage channel (21) is a three-way valve.

11) Pressure regulation system of a tire (B) characterised in that it comprises a rotary joint (10, 10), as defined in claim 3, in combination with the hydraulic circuit of said non-rotating entity, a variable-volume chamber (30) and control means (31) of said chamber (30), apt to vary the volume of said chamber (30), said chamber (30) being placed in the rim (A) of said tire (B), being filled with air under pressure and being in fluid communication with said tire (B), through at least one interception valve (23); wherein a first passage channel (20) of said rotary joint (10, 10) puts in fluid communication said hydraulic circuit with operating means of said interception valve (23), through a valve (27), and a second passage channel (21) of said rotary joint (10, 10) puts in fluid communication said hydraulic circuit with said control means (31) of said chamber (30), through a valve (28) and said interception valve (23).

12) Pressure regulation system of a tire (B) according to claim 11, characterised in that said control means (31) comprise three or more hydraulic cylinders (31), said valve (27) along said first passage channel (20) is a two-way valve and that said valve (28) along said second passage channel (21) is a three-way valve.

13) Pressure regulation system of a tire (B) characterised in that it comprises a rotary joint (10, 10), as defined in claim 3, in combination with the hydraulic circuit of said non-rotating entity, a reservoir (34), a compressor (36) connected to a hydraulic motor (37), said reservoir (34), said compressor (36) and said hydraulic motor (37) being placed in the rim (A) of said tire (B), said reservoir (34) being filled with air under pressure and being in fluid communication with said tire (B), through said compressor (36) and an interception valve (23); wherein a first passage channel (20) of said rotary joint (10, 10) puts in fluid communication said hydraulic circuit with said hydraulic motor (37), in correspondence of operating means of said hydraulic motor in a first direction of rotation, and with operating means of said interception valve (23), through a valve (39), and a second passage channel (21) of said rotary joint (10, 10) puts in fluid communication said hydraulic circuit with said hydraulic motor (37), in correspondence of operating means of said hydraulic motor in a second direction of rotation, opposite to said first direction of rotation, and with operating means of said interception valve (23), through the same valve (39) or a different valve (38).

Description

[0031] The present invention it will be described in the following, for illustrative, but not limitative, purposes according to some preferred embodiments, with particular reference to the figures of the enclosed drawings, wherein:

[0032] FIG. 1 shows a front perspective view of a rotary joint according to a first embodiment of the present invention,

[0033] FIG. 2 shows a rear perspective view of the joint of FIG. 1 mounted on the inside of the rim of a wheel

[0034] FIG. 3 shows a section view of a first section of the joint of FIG. 1,

[0035] FIG. 4 shows a section view of a second section, opposite to said first section, of the joint of FIG. 1,

[0036] FIG. 5A shows a section view of the joint in an intermediate position between said first section and said second section,

[0037] FIG. 5B shows a lateral view of the joint of FIG. 1,

[0038] FIG. 6 shows a schematic section view of the joint of FIG. 1 and of a wheel on which said joint is mounted and of the circuit of air under pressure for inflation of the tire,

[0039] FIG. 7 shows a hydraulic scheme of the pressure regulation system for tires of the present invention in an embodiment suitable for use with the rotary joint of FIG. 1,

[0040] FIG. 8A shows a section view of a rotary joint according to a second embodiment of the present invention,

[0041] FIG. 8B shows a side view of the rotary joint of FIG. 8A,

[0042] FIG. 9 shows a schematic section view of the joint of FIGS. 8A and 8B, of a wheel on which said joint is mounted and of a first kind of hybrid circuit, with a hydraulic part and a pneumatic part, for the inflation of the tire,

[0043] FIG. 10 shows a hydraulic scheme of the pressure regulation system for tires of the present invention in a suitable embodiment of FIG. 9,

[0044] FIG. 11 shows a view schematic in section of the joint of the FIGS. 8A and 8B, of a wheel on which said joint is mounted and of to second guy of circuit hybrid, with a part hydraulics and a part pneumatic, for the inflation of the tire,

[0045] FIG. 12 shows a hydraulic scheme of the pressure regulation system for tires of the present invention in a suitable embodiment of FIG. 11.

[0046] Making preliminarily reference to FIGS. 1-7, a rotary joint according to a first embodiment of the present invention, suitable for use with air as operating fluid, is indicated as a whole with the reference number 10 and is composed of five different elements, that are described herein below and that can be assembled according to the embodiment of FIG. 1 and in addition according to different configurations, shown in the following figures, in particular for the use of the joint with gaseous (in particular air) or liquids fluids (in particular oil), according to the embodiments that will be illustrated with reference to the following figures.

[0047] According to this first embodiment, the rotary joint 10 comprises an internal element 11, which has a cylindrical shape with a flange 12 on one end, provided with holes 13 and aimed at being coupled to a rim A of a wheel, and a plurality of mutually coupled external elements, all of which are annular and self-centering, these external elements being of four different types, in particular: five head elements 14, six housing elements 15 of respective gaskets 16 (shown only in FIG. 3, but also present in the remaining FIGS. 1-6), two bearing elements 17 and two fluid inlet elements 18, according to the arrangement shown in particular in FIGS. 3, 4, 5A and 5B. The space between the internal element 11 of the rotary joint 10 and the external elements is divided into sealed areas, separated from each other by gaskets 16. The bearing elements 17 allow a possibility of rotation to the external elements located externally to them, while the external elements arranged between the two bearing elements 17 are fixed. In particular, the external elements that are more distant from the flange 12 and are arranged externally with respect to the first bearing element 17 are supported by a support bracket 29, integral with the wheel axis C. Among the different external elements, a plurality of ring 19 (shown only in FIGS. 3 and 4, but also present in the remaining FIGS. 1-7). Moreover, between the head element 14 farthest from the flange 12 of the internal element 11 and the gasket 16 housed by the housing element 15 farthest from the flange 12 is a dust seal ring 19.

[0048] The internal element 11 is crossed by three channels 20, 21, 22, respectively a first channel 20 for passage of an operating fluid of an interception valve 23, whose characteristics and operation will be explained in the following; a second channel 21 for the passage of compressed air coming from an air compressor (not shown) mounted on the chassis of the vehicle and directed to the tire B; and a third channel 22 for lubrication purposes.

[0049] Said first channel 20 has two openings 20 and 20, respectively a first opening 20 formed in the area below a first fluid inlet element 18, which in turn is connected to the control means of said operating fluid, which controls the actuation of said interception valve 23, and a second opening 20, in pneumatic connection with said valve 23.

[0050] Said second channel 21 has two openings 21 and 21, respectively a first opening 21 formed in the area below a second fluid inlet element 18, which in turn is pneumatically connected with said air compressor (not shown) mounted on the vehicle chassis, and a second opening 21, in pneumatic connection with said tire B, by means of a line along which said interception valve 23 is disposed.

[0051] Said bearing element 17 allows to put from six to twelve rolling elements 24 through respective radial holes 25, threaded in the upper part for the assembly of a grain 26 containing the rolling elements 24. This solution guarantees the efficiency of rolling with considerably lower costs compared to the assembly of a commercial bearing of the same size (of the order of 500 mm for a tractor).

[0052] As previously stated, the embodiment of the rotary joint according to the present invention shown in FIGS. 1-7 is functional to implement a pressure regulation system for tires which makes use of the compressor generally mounted on tractors for pneumatic braking of the trailer, but it is also suitable for use with a dedicated compressor, specially mounted on the vehicle structure. Referring specifically to FIG. 7, a two-way electrovalve 27 and a three-way electrovalve 28, both for air passage, must also be fitted for adjusting the tire pressure on the machine. When the two-way electrovalve 27 is open, it moves the interception valve 23, positioned on the rim A, to an open position; at this point the 3-way electrovalve 28 allows the passage of pressurized air coming from the compressor, through the joint 10, providing inflating (drawer all in one direction on P) or deflating (drawer in the other direction on T) of tire B.

[0053] The rotary joint 10 in the embodiment of the present invention described with reference to FIGS. 1-7, assembled in the two-channel configuration for the passage of air, a channel being used to drive a drawer of the interception valve 23 housed in the rim A, the other for the passage of air, under pressure or exhaust according to the position of the drawer of the three-way valve 28 on the machine, ensures maximum safety even in case of malfunction of the inflation system, unlike than according to the joints of the prior art, of the type described above with reference to U.S. Pat. No. 2,107,405. Moreover, again with respect to this type of known solution, in the embodiment of the present invention described with reference to FIGS. 1-7, both the bearings and gaskets are lubricated by an external circuit, ensuring greater reliability.

[0054] Furthermore, in the embodiment of the present invention described with reference to FIGS. 1-7, the rim A and the rotary joint 10 are integral, so that, once assembled, the rotary joint 10 follows the wheel in all the operations of assembly, maintenance, adjustment, without requiring the disassembly of the support brackets. In particular, the rim A, with the tire B regularly fitted, can normally be mounted on the flange of hub D, which passes through the rotary joint 10.

[0055] Because of its relative simplicity, the embodiment of the present invention described with reference to FIGS. 1-7 responds to the demand for economy and adaptability to each tractor configuration.

[0056] According to a different embodiment of the rotary joint of the present invention, described with reference to FIGS. 8A-8B and indicated by the reference number 10, the same annular elements constituting the rotary joint 10 according to the embodiment of the present invention described with reference to FIGS. 1-7, differently combined, constitute a rotary joint 10, suitable for use with oil as an operating fluid. Moreover, in addition to the embodiment of FIGS. 8A-8B, wherein the rotary joint 10 is provided with two oil passage channels, the same elements can be combined to form rotary joints with any number of channels. In the following figures, to indicate the elements of the rotary joint and of the pressure regulation system which remain identical to those already described with reference to FIGS. 1-7, the same reference numbers will be used. Moreover, for the description of the same, reference will be made to the part of the description relating to the previous embodiment. It follows evidently that, apart from a different arrangement of the external elements, also in a smaller number with respect to the embodiment of FIGS. 1-7, the internal element 11 presents the difference of being shorter, with the first openings 20, 21 of the channels 20, 21 being closest to each other. Said passage channels 20, 21, as well as the corresponding fluid entry elements 18 are crossed by oil, which in addition to the actuation function, also performs a lubrication function, reason why it is not necessary to also provide for the presence of a special passage channel of lubricating oil.

[0057] In particular, the oil under pressure required as the operating fluid, according to the characteristics that will be described below, can be supplied by the hydraulic circuit of the tractor, which has been present on tractors as standard equipment since the '50s.

[0058] The pressure regulation systems of tires that can be implemented in combination with a joint of the type operating with oil are hybrid, ie they consist of two parts: a first hydraulic part, for the oil passage, and a second part for the conversion of hydraulic energy (taken from the tractor) into pneumatic energy, the one that implements the inflation system.

[0059] The technical reason for the choice of a rotary joint 10 using oil consists in the need to transfer a high power to the rotating part of the tractor, ie to the wheel, to allow quick variations in pneumatic pressure. The reason of the greater usable power lies in the fact that the pressure differential for pneumatic systems (ie operating with air) is at most 7 bar, while it is about 190 bar in hydraulic systems, therefore 27 times higher. Since the flow rate is proportional to the pressure and the hydraulic power is equal to the product of the pressure for the flow rate, the transfer of power to the wheel is much faster with a hydraulic system.

[0060] Moreover, while typically pneumatic-type systems can rely on actual fluid-dynamic powers of the order of kW, the hydraulic rotary joint 10 according to the embodiment of the present invention shown with reference to FIGS. 8A-8B can transfer all the hydraulic power installed on a tractor that, for example, for modern machines is at least 25% of the installed power, ie if the diesel power is 200 kW, the hydraulic rotary joint 10 can, without considering yields, make available at the wheel up to 50 kW. It follows that, for the pressure regulation system for tires using the oil rotary joint 10, in the variable chamber configuration as will be described hereinafter with reference to FIGS. 9 and 10, in order to obtain a variation of the tire pressure from the minimum value of 1 bar up to 1.6 bar, about 2-3s is sufficient for a single wheel, while for systems of the known type operating with air the same regulation requires several minutes.

[0061] The oil rotary joint according to the embodiment shown with reference to FIGS. 8A-8B can be used to realize pressure regulation systems of tires of different types, which will be shown with reference to the following figures. As already said previously, all these control systems are of hybrid type, ie are comprised of a first hydraulic part, for the passage of oil, and a second part for the conversion of hydraulic energy into pneumatic one, the latter directly operating the inflation of the tire.

[0062] Referring to FIGS. 9 and 10, a first embodiment of the pressure regulation system for tires according to the present invention suitable for using the rotary joint according to the embodiment of the present invention shown with reference to FIGS. 8A-8B, includes a variable chamber 30 operated by three or more hydraulic cylinders 31, arranged on the rim A.

[0063] Referring to FIG. 9, the variable chamber 30 contains pressurized air and is integrated into the rim A, occupying the cylindrical volume comprised between the disc A of the rim A, a disc shaped piston 32, and laterally partially the channel A of the rim A, for the fixed part and partially a sleeve 33 of rubberized canvas for the mobile part, so as to ensure airtight. The disc shaped piston 32 is actuated by said hydraulic cylinders 31, which control its approach to the disc A of the rim A or the removal from it. The variable chamber 30 is in direct connection (line E) with the tire B of the vehicle, through holes made in the external part of the channel A of the rim A, so that a variation of the volume of the variable chamber 30 results in a variation of air pressure in both the variable chamber 30 and inside the tire B, by virtue of the connection between the two compartments. The hydraulic cylinders 31 are in hydraulic connection, through the rotary joint 10, with the hydraulic circuit of the tractor.

[0064] In particular, with reference to FIG. 10, the pressure regulation system for tires according to the embodiment shown with reference to FIG. 9 is actuated through two electrovalves 27, 28, arranged on the machine side, respectively a two-way electrovalve 27 and a three-way electrovalve 28, as well as an interception valve 23 mounted on the rim A. When the two-way electrovalve 27 is open, it moves the interception valve 23 positioned on the rim A to an open position; at this point the three-way electrovalve 28 supplies, via the rotary joint 10, the hydraulic cylinders 31 arranged on the rim A, which compress the piston 32 of the variable chamber 30, reducing its volume and therefore increasing the pressure of the air (drawer all in one direction on P). The reduction in pressure is obtained by discharging the oil contained in the hydraulic cylinders 31, which flows due to the thrust of the air on the piston 32 of the variable chamber 30, which thus expands (drawer in the other direction on T).

[0065] The operating advantages of the pressure regulation system for tires according to FIGS. 9 and 10, with respect to the rotary joints of the prior art of the same type as those described with reference to the patents U.S. Pat. No. 2,107,405, DE8907153 and U.S. Pat. No. 5,253,688, are firstly the extremely reduced inflation and deflation times, in the order of seconds to pass from 1 to 1.6 bar according to the embodiment of the invention, against a few minutes required by the solutions of the prior art.

[0066] The implementation of tire pressure in such a fast way allows to have a real time control of the same, depending on the occurrence of events that determine the need for correction, such as a sudden increase in vertical load, due to the lifting of a heavy tool, or a sudden load transfer due to the tilting torque on the rear axle, to which the adjustment system of the present invention provides an immediate response in the increase of tire pressure; or vice versa a loss of traction due to the deterioration of the adhesion conditions, to which the regulation system of the present invention provides an immediate response in the reduction of pressure with consequent increase in the area of contact between soil and recovery of traction. Consequently, the wheel, understood as a set of tire B, variable chamber 30 and rim A, adapts dynamically to the events encountered during its operation.

[0067] Moreover, there is no exchange of air between the environment, typically contaminated by dust and humidity and the variable chamber 30/tire B assembly, for which dehumidifier filters and maintenance operations on the compressor/cylinders in general are not required, as is necessary for solutions of the same type as those described in patents U.S. Pat. No. 2,107,405, DE8907153 and U.S. Pat. No. 5,253,688.

[0068] Furthermore, the pressure regulation system for tires according to FIGS. 9 and 10 does not require the assembly of a dedicated compressor such as the pressure regulation systems of tires of the prior art of the same type as those described in the patents U.S. Pat. No. 2,107,405, DE8907153 and U.S. Pat. No. 5,253,688.

[0069] The rotary joint 10 described with reference to FIGS. 8A, 8B, 9 and 10 is assembled in the two-channel configuration for the passage of oil, wherein a channel is used to drive a drawer of the interception valve housed in the rim A and the other for the passage of oil feeding three or more hydraulic cylinders 31 for the movement of the piston 32 of the variable chamber 30, under pressure or with discharge according to the position of the three-way valve 28 on the machine, this configuration ensuring the maximum safety even in the event of malfunction of the inflation system.

[0070] A further advantage is due to the fact that both the bearings 17 and the gaskets 16 are continuously lubricated by the same oil used to operate the hydraulic cylinders 31, always guaranteeing high reliability.

[0071] Finally, as for the embodiment described above with reference to FIGS. 1-7, also in this case the rim A and the rotary joint 10 are integral, and therefore, once assembled, the rotary joint 10 follows the wheel in all assembly, maintenance and adjustment operations, without requiring the disassembly of the support brackets 29.

[0072] Referring to FIGS. 11 and 12, it is shown a second embodiment of the pressure regulation system for tires according to the present invention suitable for using the rotary joint 10 according to the embodiment of the present invention shown with reference to FIGS. 8A-8B, wherein the outer compartment of the rim A is used as a reservoir 34 for pressurized air, said reservoir 34 being delimited by the disc A of the rim A, by the channel A of the rim A, and by a circular cover 35 which, screwed air-tightly, constitutes the second cylindrical base of the reservoir 34 in the outer compartment of the rim A. The fixed chamber reservoir 34 communicates directly with the tire B through a compressor 36; by actuating the latter, in one direction of rotation or in the other, air moves from one compartment to the other and consequently the pressure of the tire is changed. Inside the reservoir 34 a hydraulic motor 37 is housed, on which the compressor 36 is placed. Two electrovalves 38 and 39 are installed on the machine, respectively a two-way electrovalve 38 and a three-way electrovalve 39. When the two-way electrovalve 38 is open, it operates the interception valve 23, positioned on the rim A, in the open position; at this point the three-way electrovalve 39 supplies, through the rotary joint 10, the hydraulic motor 37. In this phase, the compressor 36 draws air from the reservoir 34 and compresses it, through the line E, into the tire B, thus increasing the air pressure in it.

[0073] The pressure reduction is obtained with the two-way electrovalve 38 and the three-way electrovalve 39 with the drawer in the opposite position to that of inflation, therefore the hydraulic motor 37, turning in the opposite direction, sucks air from the tire B and compresses it in the reservoir 33.

[0074] The hydraulic energy required to vary the volume of the chamber is provided by the rotary joint 10, with two or more annular channels, which carries hydraulic oil under pressure coming from the hydraulic circuit of the tractor. The system thus constituted is a hybrid hydro-pneumatic system, the assembly of hydraulic motor 37 and compressor 36 implements the conversion between hydraulic energy and pneumatic energy.

[0075] The system thus conceived guarantees reasonably fast pressure regulation times to allow the pressure to be adapted to occurring events such as changes in wheel load, slip, speed variation. In response to each of these events, according to a logic stored in a control unit on board the machine, the tire pressure will be adjusted in real time to the most convenient value for the energy saving of the vehicle, to guarantee tire integrity, driving safety and other settings not the object of the present invention.

[0076] The hydraulic rotary joint 10 has an annular shape, to ensure the passage inside of it of the wheel hub D of the tractor, it is coaxial to the wheel axis C, and is mounted in the inner part of the rim A.

[0077] The operating advantages of the pressure regulation system for tires according to FIGS. 9 and 10, with respect to the rotary joints of the prior art of the same type as those described with reference to the patents U.S. Pat. No. 2,10,7405, DE8907153 and U.S. Pat. No. 5,253,688, are firstly the extremely reduced inflation and deflation times, thanks to a dedicated compressor 36 for each wheel, to the high hydraulic power available and to the fact that during pressure regulation the compressor 36 sucks at a pressure higher than the ambient pressure, therefore it must compensate for a lower pressure differential.

[0078] Moreover, the quick implementation of the tire pressure allows to have a control of the same depending on the occurrence of events that determine the need for correction: a sudden increase in vertical load due to the lifting of a heavy tool, a sudden transfer of load due to the tilting torque on the rear axle find an immediate response in the increase of the pressure of the tire, vice versa the loss of traction due to the deterioration of the conditions of adhesion has an immediate confirmation in the reduction of the pressure with consequent increase of the contact area between the tire and soil and the recovery of traction.

[0079] In addition, there is no exchange of air between the environment, typically contaminated by dust and moisture, and the reservoir 34/tire B assembly, whereby dehumidifying filters and maintenance operations on the compressor 36 in general are not required.

[0080] Also in this case, the rotary joint 10 is assembled in the two-channel configuration for oil passage shown with reference to FIGS. 8A-8B, while a channel is used to drive a drawer of the interception valve 23 housed in the rim A, and the other for the passage of oil that feeds the group formed by the hydraulic motor 37 and the compressor 36, performing the inflation or deflation according to the position of the tray of the three-way valve 39 on the machine, this configuration ensuring maximum safety also in case of malfunction of the inflation system.

[0081] Also in this case, the rotary joint 10 is assembled in the two-channel configuration for oil passage shown with reference to FIGS. 8A-8B, wherein a channel is used to drive a drawer of the interception valve 23 housed in the rim A, and the other for the passage of oil that feeds the group formed by the hydraulic motor 37 and the compressor 36, performing inflation or deflation according to the position of the drawer of the three-way valve 39 on the machine, this configuration ensuring maximum safety also in case of malfunction of the inflation system.

[0082] Moreover, both the bearings 17 and the gaskets 16 of the rotary joint 10 are lubricated ensuring a high level of reliability, and the rim A and the rotary joint 10 are integral, so that, once assembled, the rotary joint 10 follows the wheel in all assembly, maintenance and adjustment operations, without requiring the disassembly of the support brackets 29.

[0083] The present invention has been described illustration purposes, but not for limitation purposes, according to its preferred embodiments, but it is to be understood that variations and/or modifications may be made by those skilled in the art without departing from the relative scope of protection, as defined from the attached claims.