Configurable track axle

Abstract

A configurable track axle comprises: - a hollow shaft (3) defined by a side wall and having a rotation axis (X); - at least two main wheels (5) constrained to the shaft (3) and having a central opening (6) centered on the rotation axis (X); - two half-shafts (7) coaxial to the rotation axis (X), each being slidably inserted with a proximal end (8) into a respective end (4) of the shaft (3); - at least two auxiliary wheels (11) each constrained in proximity to a distal end (9) of a respective half-shaft (7); - a pneumatic joint (17) attached to the shaft (3) and capable of placing at least one access (25) for the gas in fluid communication with the inside of the shaft (3) through at least one hole (29) carried out in the side wall of the shaft (3); - at least one elastic element (15) constrained to each half-shaft (7) and acting thereon with a force directed towards the opposite half-shaft (7).

Description

[0001] CONFIGURABLE TRACK AXLE

[0002] DESCRIPTION

[0003] TECHNICAL FIELD

[0004] The present invention relates to the technical field of vehicles, more specifically rail vehicles, and specifically concerns a configurable track axle.

[0005] PRIORT ART OF THE INVENTION

[0006] Rail vehicles have long been a crucial component of transportation infrastructure worldwide. These vehicles typically operate on fixed tracks with a specific gauge.

[0007] However, in some regions, rail networks may consist of tracks with different gauges, requiring specialized solutions to allow vehicles to switch between them. Similarly, there are known some vertical railway switches in which a lower-gauge main track is coaxially flanked, in at least some sections, by a wider-gauge switch track. The switch track rises in elevation, leading, for example, to an elevated station, and then descends to rejoin the main track.

[0008] To enable transit along tracks of different gauges, bimodal rail vehicles have been developed, such as the one described in Italian patent no. 102017000147269. These vehicles are assigned to operate on both standard and wider gauge tracks, allowing for greater flexibility in rail operations. Such systems often involve complex mechanisms to adjust the position of the wheels relative to the vehicle body.

[0009] Configurable track axles have been proposed as a means of allowing rail vehicles to switch between tracks of different gauges. A pair of inner main wheels is assigned to encounter standard gauge track. These systems involve mechanisms, typically hydraulic or kinematic, that allow a pair of outer switch wheels to be moved inward or outward from the vehicle's center line, effectively changing the vehicle's track gauge, as the switch wheels are assigned to encounter a wider-than- standard gauge switch track. Generally, however, known documents do not provide a complete and detailed solution for developing a configurable axle capable of moving and positioning the switch wheels in both the retracted and extended configurations. For example, Italian patent no. 102017000147269 does not describe in detail a system for actuating the axle's switch wheels to change the track width.

[0010] Other existing solutions, however, show shortcomings or disadvantages in terms of reliability during the gauge change process.

[0011] Another disadvantage of known configurable-track axles is that they do not guarantee smooth transitions between different gauges, and in the event of trivial failures such as a hydraulic fluid leak, they expose the vehicle to serious safety risks.

[0012] An additional disadvantage of known configurable axles is that they do not ensure robust locking of the switch wheels in the retracted and extended configurations, so the axle can undergo unwanted movement during operation, resulting in the potential risk of misalignment and derailment.

[0013] Prior art document DE 737 575 discloses a configurable track axle and provide a further generic information of the technical field.

[0014] SUMMARY OF THE INVENTION

[0015] One object of the present invention is to propose a configurable-track axle provided with a pair of internal, fixed main wheels and a pair of switch wheels external to the main wheels, whose track or mutual axial distance is variable or configurable, i.e., operable at least between two extreme conditions: extended and retracted.

[0016] Another object is to propose a configurable-track axle in which the switch-track wheel drive system is simple and robust, to limit the need for maintenance and the risk of failure.

[0017] Another object is to propose a configurable-track axle in which the switch-track wheels are driven pneumatically towards the extended condition, while the return to the retracted condition is actuated by a spring force.

[0018] A further object is to propose a configurable-track axle in which the switch-track wheels can be robustly locked at least in the extended condition.

[0019] BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The characteristics of the invention are highlighted below with particular reference to the attached drawings in which:

[0021] - figure 1 shows an axonometric view of the configurable track axle of the present invention, in its retracted condition;

[0022] - figure 2 shows an axonometric view of the axle of figure 1 in its extended condition;

[0023] - figure 3 shows a side view of the axle of figure 1;

[0024] - figure 4 shows a sectional view along the IV-IV plane of the axle of figure 3 in the retracted condition;

[0025] - figure 5 shows a sectional view along the IV-IV plane of the axle of figure 3 in the extended condition;

[0026] - figure 6 shows a sectional view along the IV-IV plane of a variant of the axle of figure 3 in the extended condition;

[0027] - figure 7 shows a sectional view along the IV-IV plane of a variant of the axle of figure 3 in the retracted condition.

[0028] BEST MODE TO CARRY OUT THE INVENTION

[0029] With reference to figures 1-7, numeral 1 indicates the configurable track axle that is object of the present invention.

[0030] In its preferred embodiment, the axle 1 comprises:

[0031] - a shaft 3 of nearly cylindrical shape, hollow and defined by a side wall open at the ends 4 of the side wall itself and therefore of the shaft 3, the shaft 3 having a rotation axis X coinciding with the longitudinal axis of said cylindrical shape; - two main wheels 5 connected to respective ends of the shaft 3 at respective hubs and having a central opening 6 formed in each of the hubs and centered on the rotation axis X;

[0032] - two half-shafts 7, preferably identical or mirror-image, aligned with their respective longitudinal axes coaxial with the rotation axis X, each half-shaft 7 having a proximal end 8 slidably inserted into a respective end of the shaft 3 and preferably through a corresponding central opening 6, and an opposite distal end 9 assigned to remain external to the shaft 3 or in any case easily accessible from an end 4 thereof;

[0033] - two auxiliary wheels 11, each constrained near or in correspondence with the distal end 9 of a respective half-shaft 7 in a position external to the corresponding main wheel 5, i.e., the main wheel 5 is preferably crossed by the half-shaft 7 and remains between the proximal end 8, which remains internal to the shaft 3, and the distal end 9 of the half-shaft 7 to which the auxiliary wheel 11 is attached.

[0034] The axle 1 is typically assigned to be mounted on a railway vehicle or other guided track vehicle. The main wheels 5 are each assigned to engage a respective rail of a main track, such as a standard gauge track, which guides the vehicle in a normal operating condition. The track width of the auxiliary wheels 11, or the distance between them along the rotation axis X, is greater than the track width of the main wheels 5 and can be varied as will be better explained below. The auxiliary wheels 11 are assigned to engage an auxiliary railroad track with a gauge greater than the gauge of the main track in a condition of switching or diverting the vehicle from the main track. For example, the auxiliary track may constitute a switch section that deviates vertically from the main track to guide the vehicle into, and then out of, a station at a stop on the railway line.

[0035] Naturally, the axle 1 may comprise a greater number of main wheels 5 and / or auxiliary wheels 11, for example mounted in pairs.

[0036] The main wheels 5 are preferably mounted at the ends, that is side by side with the respective end 4 of shaft 3, so that the central openings 6 form a sort of extension of the cavity of the shaft 3 itself. Alternatively, the main wheels 5 are associated around the side wall of the shaft 3, with the central openings 6 surrounding the ends 4 or surrounding the shaft 3 at points closer to its center. Similar alternatives are possible for attaching the auxiliary wheels 11 to, or near, the distal ends 9 of the half-shafts 7.

[0037] Both the main wheels 5 and the auxiliary wheels 11 are preferably rigidly fixed to their respective shafts, rotating with them at the same angular velocity. In any case, the diameter of the rims of the main wheels 5 may be the same or different from that of the auxiliary wheels 11, depending on the constraints imposed by the main track and the auxiliary track of the railway line on which the axle 1 is used.

[0038] The two half-shafts 7, and in particular the proximal ends 8 of these, are constrained to translate along the shaft 3 and therefore along the rotation axis X between:

[0039] - a retracted condition R, in correspondence of which the half-shafts 7 are maximally inserted within the cavity of the shaft 3, the proximal ends 8 are maximally close to each other at or near the centre of the shaft 3, and the auxiliary wheels 11 are positioned close to the main wheels 5 or adjacent to them in contact with them; and

[0040] - an extended condition E, in which the half-shafts 7 are maximally extended beyond the ends 4 of the shaft 3, the proximal ends 8 are maximally spaced apart from each other symmetrically with respect to the center of the shaft 3 but still constrained to it, and consequently the auxiliary wheels 11 are maximally spaced apart from each other and from the center of the shaft 3, and therefore are spaced distally from the main wheels 5.

[0041] Preferably, each half-shaft 7 is in sliding contact with minimum clearance with the internal surface of the shaft 3 in at least two longitudinally spaced points. The surfaces of the half-shafts 7 and of the shaft 3 can be made of different materials to ensure the best results or compromises in terms of smoothness, minimum clearance, self-lubrication, and gas tightness; for example, such materials are chosen among metals or metallic materials (preferably steel), alloys (such as bronze), and synthetic materials such as polytetrafluoroethylene (PTFE).

[0042] Preferably, in the retracted condition R, the auxiliary wheels 11 (for example, their hubs) abut against the main wheels 5 or against the ends 4 of the shaft 3, being unable to translate further along the rotation axis X toward each other. Furthermore, the length of the half-shafts 7 is such that when the auxiliary wheels 11 contact the main wheels 5 in the retracted condition R, the proximal ends 8 of the two half-shafts remain slightly spaced, leaving a gap of at least a few millimetres, preferably at least 1 mm, more preferably at least 2 mm, and even more preferably at least 10 mm. In any case, the minimum distance between the proximal ends 8 is such that gas can flow freely between one or more holes 29 made in the side wall of the shaft 3 and the space between said proximal ends 8, and more generally between said holes 29 and the lumen of the two halfshafts 7.

[0043] Preferably, the length of the section of a half-shaft 7 that in the extended condition E remains inside the shaft 3 is between 30%-70% of the overall length of the half-shaft 7 itself, more preferably between 40%-50%, and even more preferably it corresponds to approximately 45% of the overall length, to ensure adequate structural support and mechanical strength. Also considering the thickness of the main wheel 5 and in particular of its hub featuring the central opening 6, if this is mounted at the bottom of the end 4, the length of the section of a half-shaft 7 that in the extended condition E protrudes outside the main wheel 5 is preferably between 70%-30% of the overall length of the half-shaft 7, more preferably between 50%-35%, and even more preferably between 45%-40%.

[0044] Each half-shaft 7 preferably has a narrowing 55 in its external diameter, which decreases as it moves towards the distal end 9; correspondingly, the central opening 6 of each main wheel 5 has a shoulder or bottleneck 53 with a shape almost complementary to the shape of the narrowing 55 of the respective half-shaft 7. In this way, in the extended condition E, the narrowing 55 abuts against the shoulder or bottleneck 53 which, consequently, constrains the half-shaft 7 along the rotation axis X to remain at least partially inserted with its proximal end 8 within the shaft 3.

[0045] The shoulder or bottleneck 53 is preferably concave-conical in shape, and correspondingly the narrowing 55 is preferably convex-conical in shape. The opening angle of the cone of the shoulder or bottleneck 53 and of the corresponding narrowing 55, understood as the angle formed by the geometric segments of the shoulder or bottleneck 53 obtained from the intersection between it and a plane passing through the rotation axis X, is preferably 15° or greater, up to 180°, and therefore each of these segments is inclined by at least 7.5° and at most 90° with respect to the rotation axis X. More preferably, this opening angle is in the range from 20°-90°. Although opening angles of less than 20° or even less than 15° can still be used for some combinations of materials and construction clearances or tolerances, as the opening angle decreases below the 20° limit, the likelihood or risk of the shoulder or bottleneck 53 becoming trapped in the narrowing 55 once the extended condition E is reached increases very rapidly.

[0046] Said opening angle provides both the gas seal in the extended condition E, as explained below, and the friction necessary for the half-shafts 7 to rotate with the shaft 3 at the same angular velocity.

[0047] In some variants of the axle 1, the shoulder or bottleneck 53 is of the bracket or stepped type where the change in the internal diameter of the central opening 6 is sudden, i.e., at a right angle or nearly so, and the narrowing 55 has a complementary step shape at a right angle or nearly so.

[0048] In some variants of the axle 1, such as illustrated for example in figures 4-7, the shoulder or bottleneck 53 and the narrowing 55 provide less significant changes in their respective diameters, in a tapered or inclined ramp manner.

[0049] In the axle 1 of the present invention, each half-shaft 7 is constrained to slide inside the shaft 3 in an at least partial gas-tight manner. The seal is achieved by closing the lumen of the half-shafts 7, for example by having their distal end 9 closed by a wall or by the auxiliary wheel 11, and by suitable sealing means interposed between the half-shafts 7 and the inside of the side wall of the shaft 3. For example, such sealing means may consist of gaskets fixed to the proximal ends 8 of the half-shafts 7 and / or to the ends 4 of the shaft 3 that provide a total or almost total seal.

[0050] Alternatively, and preferably, no sealing means is inserted between the half-shafts 7 and the shaft 3. In the retracted condition R, the gas seal is provided by the narrow clearance between the half-shafts 7 and the inside of the side wall of the shaft 3, which is 400 pm, even more preferably less than 100 pm. This seal is not total but only partial, but is still sufficient to allow the pressure to increase between the two half-shafts 7 and their extension towards the extended condition E. In the extended condition E, however, the seal is almost total, particularly when the shoulder or bottleneck 53 and the narrowing 55 in mutual contact are conical in shape with the said opening angle of approximately 20°. The seal in the extended condition E decreases as the opening angle approaches 180°.

[0051] The axle 1 also comprises:

[0052] - a pneumatic joint 17 associated with the shaft 3 and suitable for establishing fluid communication between an access 25 for the gas supplied by a compressed gas source and the interior of the shaft 3 through a plurality of holes 29 passing through the thickness of the side wall of the shaft 3 itself;

[0053] - an elastic element 15 tensioned between the two half-shaft 7 and acting on the two latter with a force parallel or aligned with the rotation axis X and directed to getting closer the opposite half-shaft 7.

[0054] The holes 29 are arranged along a circumference lying on the median transverse plane of the shaft 3, preferably in equally spaced angular positions.

[0055] The pneumatic joint preferably comprises a rotor 19 and a stator 21.

[0056] The rotor 19 is rigidly constrained to the outside of the side wall of the shaft 3 and extends in a ring around the latter, at the holes 29, i.e., at the median portion of the shaft 3.

[0057] The stator 21 is rotatably constrained to the outside of the rotor 19 and of the shaft 3 and is fixed to a support, not shown, which keeps it fixed to the vehicle on which the axle 1 is mounted. Preferably, a bearing at each longitudinal end of the stator 21 keeps it slidable and centered with respect to the shaft 3 and to the rotation axis X.

[0058] A sealing element 31 is interposed between the rotor 19 and the stator 21. This sealing element may be shaped like a tortuous path, such as a labyrinth, steps, waves, teeth, or similar, or it may be a gasket or other equivalent type suitable for gas sealing even under pressure. Such seal is not necessarily perfect, but it is sufficient to ensure that any gas leaks through the sealing element 31 are negligible for the purposes of the application of the axle 1.

[0059] Preferably, as illustrated in figures 4 and 5, the sealing element 31 is a so-called labyrinth seal. A variant of the sealing element 31 is illustrated in figure 6, where it takes the form of a series of steps. The shapes required to create the sealing element are carried out on, or applied to, an internal surface of the stator 21 and / or an external surface of the rotor 19.

[0060] A sealing element 31 with a tortuous path offers the advantage that the gas entering the path tends to form a sheath or vortices that act as a sort of gasket, opposing the gas exit.

[0061] The stator 21 is preferably made of two mirror-image pieces or half-shells, of ring shape, joined together at the said median transverse plane of the shaft 3, which constitutes a median plane of the pneumatic joint 17 too. Between the two pieces or half-shells, the stator 21 preferably comprises an annular channel 26 with an approximately toroidal development along the median transverse plane. The annular channel 26 is in fluid communication with the access 25. The stator also comprises an annular groove coplanar with the annular channel 26 but of smaller diameter and in fluid communication with it. This annular groove is assigned to rotatably accommodate the rotor 19 and may contain at least part of the shapes that form the sealing element 31.

[0062] A ring nut or cylindrical shell coaxial with the rotation axis X envelops both pieces of the stator 21, keeping them together, and has a hole that constitutes the access 25. Such access 25 is connected, via sleeves or similar pneumatic connection elements, to at least one source of compressed gas external to the axle 1, such as a compressor or a tank. The compressed gas is typically air, possibly mixed with additives such as lubricants, rust inhibitors, or anti-condensation agents. By interposing a three-way valve, the access 25 may also be connected to a vent outlet for the compressed gas. A variant of the pneumatic joint 17 provides for it to be provided with multiple accesses 25, for example, one access 25 connected to a compressed gas source and one access 25 connected to a vent outlet, where the opening and closing of each access 25 are regulated by respective controlled valves.

[0063] The rotor 19 is also preferably made of two mirror-image pieces or half-shells and comprises a passage 27 of annular, discoidal, or toroidal shape centered on the rotation axis X. The passage 27 has a circular internal end closest to the rotation axis X and leading to, or connected to, a hole 29, and an opposite circular external end farthest from the rotation axis X, rotatably facing the annular channel 26 of the stator 21 and opening into the annular channel 26 itself.

[0064] In a variant of the rotor 19, this in turn comprises a plurality of passages 27, each having one end opening into a respective hole 29 and an opposite end rotatably opening into the annular channel 26 itself. In this variant, the rotor 19 can also easily be made as a single body.

[0065] As the shaft 3 and the rotor 19 rotate in a driving condition of the axle 1, i.e., the vehicle to which it is attached, the end farthest from the rotation axis X follows the annular channel 26 in a circular motion, always remaining in fluid communication with the latter.

[0066] Preferably, the pneumatic joint 17 comprises at least two pairs of passages 27 and holes 29, more preferably at least four pairs, more preferably at least eight pairs, distributed at regular angular intervals. This allows for a more uniform and rapid inflow and outflow of the compressed gas from the annular channel 26 into the shaft 3 and in the opposite direction.

[0067] In another variant, equally applicable especially in axles 1 where shaft 3 rotates at low speeds and / or where extremely rapid expansion of the auxiliary wheels 11 towards the extended condition E is not required, pneumatic joint 17 is provided with a single passage 27 that ends in a single hole 29. Each passage 27 preferably has a circular cross-section and extends linearly and radially with respect to the rotation axis X.

[0068] In a variant of rotor 19 (not illustrated), each passage 27 may have a curvilinear extension, along said median transverse plane, with curvature or winding in the direction of rotation of the shaft 3 corresponding to a forward travel condition of the axle 1 or the vehicle. This arrangement results in a surprising and advantageous increase in the pressurization rate of the interior of the shaft 3, as the gas coming from the annular channel 26 is further compressed during the rotary and centripetal motion along the passages 27.

[0069] The elastic element 15 preferably comprises a helical spring inserted into the shaft 3, each end of which is constrained to a respective half-shaft 7. In particular, the ends of the spring are fixed at the distal ends 9 of the two half-shafts 7, for example hooked to a respective anchoring element 10 fixed or pivoted at the center of each auxiliary wheel 11. The rest length of the spring of the elastic element 15 is less than the distance between the two anchoring elements 10 in the retracted condition R, so that the spring is always elongated and under tension. The median section of the spring is constrained to the shaft 3, for example by one or more pins locked in respective holes 29 and protruding towards the inside of the shaft 3 to insinuate themselves between two consecutive coils of the spring so as to block the median section in the longitudinal direction. This advantageously allows the work required to translate the half-shafts 7 from the retracted condition R to the extended condition E to be the same for both half-shafts 7, so that their extension movement is perfectly symmetrical or nearly so.

[0070] A variant of the axle 1 provides for it to include multiple elastic elements 15, for example two almost identical helical springs inserted in traction into the shaft 3. As in the case of a single spring, said two springs have one end constrained to a respective half-shaft 7, for example to said anchoring element 10; the remaining end of each spring is instead constrained to the center of the shaft 3. In this case too, the balance of the elastic forces acting on the two half-shafts 7 is ensured.

[0071] Preferably, the axle 1 also comprises at least one locking means 33, preferably at least two locking means 33, for each half-shaft 7, each locking means 33 being able to lock the respective half-shaft 7 with respect to the shaft 3 at least in a predetermined longitudinal position, i.e. along the rotation axis X.

[0072] Each locking means 33 preferably comprises a pin 35 slidably constrained through a special through seat 46 that passes through the side wall of the shaft 3. The pin 35 is elastically pushed in a radial centrifugal direction by an elastic means 39, preferably a helical spring acting in compression between a shoulder protruding internally from the through seat 46 and a head 38 of the pin 35 provided at the end of the latter facing outside the shaft 3.

[0073] Each locking means 33 also comprises a cam element 37 associated with the shaft 3 and operable to slide parallel to the latter, i.e., parallel to the rotation axis X, between an unlocked position U and a locked position L.

[0074] In the unlocked position U, the force imparted by the elastic means 39 to the head 38 of the pin 35 pushes the latter in a centrifugal direction, with the head 38 protruding from the external surface of the shaft 3 and housed in a seat 44 of the cam element 37, and with the opposite end of the pin 35 retracting almost completely into the through seat 46. Therefore, in the unlocked position U, the pin 35 does not protrude into the lumen or cavity of the shaft 3 and therefore does not interfere with the half-shafts 7, which are free to slide.

[0075] In the locked position L, the cam element 37 slides longitudinally along the external surface of the shaft 3 and, by means of a guide, presses on the protruding head 38 of the pin 35, pushing the latter in a centripetal direction, with the head 38 entering completely or almost completely into the through seat 46, and with the opposite end of the pin 35 protruding inside the lumen or cavity of the shaft 3. If the corresponding half-shaft 7 is in a correct predetermined position, the radially innermost end of the pin 35 inserts into a corresponding recess 41 obtained on the side wall of the respective half-shaft 7, blocking the latter at least in the longitudinal direction of the rotation axis X. The locking means 33 thus made advantageously ensure that, once a predetermined longitudinal position has been reached, the half-shafts 7 are maintained in that position and the auxiliary wheels 11 maintain the corresponding track, regardless of the forces or stresses that could counteract the longitudinal actuation forces of the half-shafts 7 and lead to undesirable consequences such as failure, wear, or even derailment of the axle 1 and the vehicle from the auxiliary track.

[0076] Preferably, the cam elements 37 of the locking means 33 relating to a single half-shaft 7 are formed in an annular element that is slidably inserted into the shaft 3; in this case, the seat 44 may be of the annular groove type.

[0077] The sliding actuation of the cam elements 37 is preferably controlled after checking that the half-shaft 7 is in the correct longitudinal position.

[0078] Multiple locking means 33 for each half-shaft 7 are preferably arranged in a ring on the shaft 3, i.e., in different angular positions but in the same longitudinal position. The recesses 41 in the half-shafts 7 are made in corresponding angular positions.

[0079] Each half-shaft 7 may instead comprise recesses 41 or sets of recesses 41 in different longitudinal positions: in this way, a half-shaft 7 can be locked in different longitudinal positions.

[0080] For example, recesses 41 can be provided along a half-shaft 7 in a longitudinal position such that a locked position L of the locking means 33 corresponds to the extended condition E of the half-shaft 7.

[0081] Optionally, a half-shaft 7 can be provided with additional recesses 41 that correspond to other longitudinal positions of the half-shaft 7 with respect to the shaft 3, for example the retracted condition R or one or more intermediate conditions between the retracted condition R and the extended condition E. This advantageously allows the track width of the auxiliary wheels 11 to be locked at different values, for example, to adapt such track width to different gauges of the auxiliary tracks. In some scenarios or networks, one or more rails of the main track can be electrified to transport and supply the electrical energy to the axle 1 necessary for vehicle operation.

[0082] In these cases, with particular reference to figure 7, the invention optionally provides that at least one, or preferably each, of the main wheels 5 comprises a central hub connected to the shaft 3, an outermost rolling portion or rim 51 that is assigned for contact with an electrified rail, and an intermediate portion 52 that electrically isolates the hub from the rim 51.

[0083] The rolling portion 51 of a main wheel 5 is electrically connected to a conductive ring 54 inserted onto the shaft 3 and connected to it near the end 4; both such rolling portion 51 and such conductive ring 54 are electrically isolated from the shaft 3. The rolling portion 51, the shaft 3, and the conductive ring 54 rotate at the same angular velocity.

[0084] A conductive means 56 is associated in electrical contact with said conductive ring 54. The conductive means 56 is preferably, as illustrated, in the form of a disc or wheel, for example, made of copper or another metal. In this case, the disc 56 is in rolling electrical contact with the conductive ring 54: when the latter rotates, the conductive disc 56 rotates in the opposite direction, at the same angular velocity if they have the same diameter, otherwise at a different angular velocity. Alternatively, the conductive means 56 is of the brush type in sliding electrical contact with the rotating conductive ring 54.

[0085] An electrical connection originates from the conductive means 56 that carries the electric current from the electrified track to a vehicle power system.

[0086] The conductive means 56 is maintained in a contact position with the conductive ring 54 by means of a support element, for example an arm or a cantilever beam, fixed to a static part of the axle 1 or to other points or parts of the corresponding vehicle. Optionally, the support element may be operable to move the conductive means 56 between contact and non-contact positions with the conductive ring 54.

[0087] The track width of axle 1 may be configured, i.e., varied or adjusted at least between the extreme track widths corresponding to the retracted condition R and the extended condition E according to the following operating diagram.

[0088] Starting from the retracted condition R of the half-shafts 7 and the auxiliary wheels 11, compressed gas (typically air) is forced from the source into the annular channel 26 through the appropriate accesses 25. The compressed gas flows through the passages 27, passes through the holes 29 and reaches the space between the two half-shafts 7 inside the shaft 3, possibly also filling the lumens of the two half-shafts 7. As the pressure inside the shaft 3 increases, the thrust exerted by the compressed gas overcomes the elastic force of the elastic element 15 and the half-shafts 7 slide in opposite directions along the shaft 3, until the narrowing 55 abut against the corresponding shoulder or bottleneck 53, creating the extended condition E. At this point the locking means 33 are operated in the locked position L, safely locking the half-shafts 7 in the extended condition E and the auxiliary wheels. 11 in the corresponding track.

[0089] To return to the retracted condition R, the locking means 33 are actuated to the unlocked position U and the accesses 25 leading to an outlet or vent are opened. Gas thus begins to flow out of the shaft 3 until the force applied by the pressure on the half-shafts 7 drops below the spring force of the elastic element 15, which brings the two half-shafts 7 closer together to the retracted condition R.

[0090] Eventually, if corresponding recesses 41 are provided, the locking means 33 are reactivated in the locked position U to keep the half-shafts 7 locked in the retracted condition R.

[0091] The pneumatic actuation advantageously reduces the number of components and the complexity of the actuation system, and consequently the risk of failure and the required maintenance of axle 1 compared to an axle provided with hydraulic or electromechanical actuation.

[0092] Furthermore, when no sealing means is interposed between the half-shafts 7 and the inside of the side wall of shaft 3, it is possible to insert a diluted or atomized lubricating fluid into the compressed gas which, once injected into shaft 3, is distributed between it and the half-shafts 7 and then exits through the central openings 6 in the retracted position R. This advantageously allows for continuous lubrication of the sliding parts of axle 1 and therefore reduces the need for maintenance.

Claims

CLAIMS1) Configurable track axle comprising:- a hollow shaft (3) defined by a side wall and having a rotation axis (X);- at least two main wheels (5) constrained to the shaft (3) and having a central opening (6) centered on the rotation axis (X);- two half-shafts (7) coaxial to the rotation axis (X), each being slidably inserted with a proximal end (8) into a respective end (4) of the shaft (3);- at least two auxiliary wheels (11) each constrained in proximity to a distal end(9) of a respective half-shaft (7); the axle (1) being characterized in that it comprises:- a pneumatic joint (17) attached to the shaft (3) and capable of placing at least one access (25) for the gas in fluid communication with the inside of the shaft (3) through at least one hole (29) carried out in the side wall of the shaft (3);- at least one elastic element (15) constrained to each half-shaft (7) and acting thereon with a force directed towards the opposite half-shaft (7).2) Axle according to claim 1 characterized in that the pneumatic joint (17) comprises a rotor (19) rigidly constrained around the shaft (3) in correspondence with the at least one hole (29) and a stator (21) rotatably constrained to the outside of the rotor (19), with a sealing element (31) between the rotor (19) and the stator (21).3) Axle according to claim 2 characterized in that the sealing element (31) is of the tortuous path type such as labyrinth, steps or similar, or is of the gasket type, or of another type suitable for gas-tight sealing.4) Axle according to claim 2 or 3 characterized in that the stator (21) comprises an annular channel (26) in fluid communication with the at least one access (25), and the rotor (19) comprises at least one passage (27) having one end opening into a respective hole (29) and an opposite end rotatably opening into the annular channel (26).5) Axle according to any one of the preceding claims characterized in that each halfshaft (7) is constrained gas-tight, partially or totally, to the shaft (3).6) Axle according to any one of the preceding claims characterized in that it further comprises at least one locking means (33) for each half-shaft (7), suitable for locking the respective half-shaft (7) with respect to the shaft (3) at least in a predetermined position along the rotation axis (X).7) Axle according to claim 6 characterized in that each locking means (33) comprises a pin (35) slidably constrained through the side wall of the shaft (3) and elastically pushed in a centrifugal direction, and a cam element (37) attached to the shaft (3) and operable parallel to it between an unlocked position (U), in which the pin (35) does not interfere with the half-shafts (7), and a locked position (L), in which the cam element (37) pushes the pin (35) into a corresponding recess (41) of the respective half-shaft (7) blocking the latter.8) Axle according to any one of the preceding claims characterized in that the at least one elastic element (15) comprises a traction spring inserted in the shaft (3), each end of which is constrained to a respective half-shaft (7) and whose median section is constrained to the shaft (3), or comprises two traction springs inserted in the shaft (3), each having its ends constrained respectively to a half-shaft (7) and to the shaft (3).9) Axle according to any one of the preceding claims characterized in that a rolling portion (51) of at least one main wheel (5) is electrically connected to a conductive ring (54) constrained around the shaft (3) and is electrically insulated from the latter, with a conductive means (56) associated in sliding or rolling electrical contact with said conductive ring (54).10) Axle according to any one of the preceding claims characterized in that each halfshaft (7) has a narrowing (55) in the direction of the distal end (9), and the central opening (6) of each main wheel (5) has a shoulder or bottleneck (53) of a shape almost complementary to the narrowing (55) of the respective half-shaft (7), where thenarrowing (55) contacts against the shoulder or bottleneck (53) in an extended condition (E) of the half-shafts (7) in which the proximal ends (8) are maximally spaced and the auxiliary wheels (11) are spaced in distal direction from the main wheels (5).11) Axle according to claim 10 characterized in that the narrowing (55) and the shoulder or bottleneck (53) are conical in shape, with an opening angle of at least 15°, preferably included in the range from 20° to 90°.

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