DESCRIPTION

Field of application

The present invention relates to the land vehicle sector, in particular to components for moving vehicles.

The present invention relates, more particularly, to a modular omnidirectional wheel structure. Background

The first prototypes of omnidirectional wheel - or mecanum wheel - have been known since the 1970s.

In terms of operation, the mecanum wheel enables a vehicle to move in any direction on a movement plane and, in structural terms, substantially provides a tread consisting of suitably oriented rollers. By equipping a vehicle with this type of wheels and suitably varying speed and direction of rotation of each thereof, the vehicle can be moved in an omnidirectional manner.

Numerous configurations of mecanum wheels are known in the art, described for example in US3876255, US7641288, US8011735, US8833862, and relating to technological solutions which identify substantially different assembling modes of rollers with respect to the wheel hub.

However, these known solutions have some critical issues.

Typically, in fact, mecanum wheels have idle rollers around their axis thanks to the presence of bearings interposed therebetween and their support structure, integral with the wheel hub. The larger the bearings, the greater the load capacity that the single wheel can endure. However, since the size of the rollers is proportional to the size of the bearings being housed, the greater the load that the wheel supports, the smaller the number of rollers constituting the tread. In order to ensure the continuity of the wheel motion, i.e. the condition for which at least one roller is always in contact with the movement plane, the latter must necessarily be very extended (wide wheels) and consequently strongly tapered. The tapering on the one hand penalizes the insertion of large bearings, whether the assembling of the latter occurs from the lateral ends of the roller, on the other hand it involves an uneven mechanical resistance of the roller, consisting of the smaller extreme sections and therefore less resistant than the central one in maximum diameter. Solutions to solve such type of issue have been proposed, for example in US2014232174, where a mecanum wheel is described with two rows of side-by- side rollers, interconnected by damping means which allows slight movements between the two rows of rollers in a circumferential and perpendicular direction to the wheel axis, as well as to change the angle of tilt therebetween. In such case, the wheel is always in contact with the movement plane on at least two points, one for each roller of the two side-by-side rows. However, this fact involves a worsening of the kinematic, dynamic and energy performance of the wheel and subsequently of the vehicles which are equipped therewith.

Brief description of the invention

The technical problem posed and solved by the present invention is therefore to overcome the aforementioned drawbacks, and this is achieved by a modular omnidirectional wheel structure as defined in claim 1. In particular, it is an object of the present invention to provide an element that confers modularity, constructive simplicity and reduced bulk, to an omnidirectional wheel, as well as versatility of use and ease of mounting the rollers, allowing the same to increase the load that can support.

Further preferred features of the present invention are defined within the dependent claims.

According to a first aspect, the present invention relates to a modular element of an omnidirectional wheel, which modular element comprises means for coupling with a second modular element. The modular element comprises a hub, rotatable around an axis of rotation of the wheel, and support means, connected to the hub, configured to support a plurality of rollers intended to contact the rolling plane of the wheel.

In more details, the support means surrounds the hub and bears first and second housings, arranged annularly and axially spaced therebetween, wherein each pair of the first and second housings forms a seat intended to receive a roller in a removable way; the aforementioned means for coupling is further configured to allow a side-by-side mounting of modular elements, such that, in the mounted condition, the seats of distinct modular elements are angularly phase shifted from each other.

This solution realizes a simple and affordable modular structure in terms of production technique and, advantageously, allows to customize the wheel according to the type of use it is intended for, for example by mounting a different number of modular elements constituting thereof.

Furthermore, the particular configuration of the first and second housings ensures a stable fixing solution of the rollers onto the support means, further obtaining their accurate positioning in their respective seats. In this way the continuity of the wheel motion is ensured and vibrations and/or noises deriving from overlapping or temporary absence of contact with the rolling plane are significantly reduced.

According to a further aspect, the present invention is directed to an omnidirectional wheel having a plurality of rollers intended to contact with a rolling plane; each of those has a rotation axis tilted by a first angle with respect to the rotation axis of the wheel.

The wheel provides support means, preferably comprising at least two of the aforementioned modular elements, configured to removably support each roller and arrange the same in a plurality of annular rows axially spaced between each other. In particular, the rows of rollers are angularly phase shifted from each other by a second angle with respect to the rotation axis of the wheel, such that, during its rolling, a single roller, among those of axially aligned rows, is always in contact with the rolling plane. Inserting rows of rollers, angularly phase shifted in the circumferential plane in such a way that, during the rolling of the wheel, rollers of consecutive rows come into contact with the rolling plane - sequentially and in the order imposed by the given direction of rotation - in addition to guaranteeing the continuity of motion, allows mounting of larger, slightly tapered rollers with a more uniform section and therefore larger bearings, in conclusion increasing the load capacity of the wheel.

Furthermore, such solution, if advantageously associated with the aforementioned modular elements, allows the level of tension in the components of the wheel to be uniformed during operation, connecting and moderating the section changes and avoiding the concentration of stresses at points that may result over time as crack trigger sites.

In embodiments of the wheel, it is further possible to house the rollers on removable supports, which can be simply mounted and disassembled from the hub. In this way the mounting of the roller - preferably constituted of a plurality of components - can be carried out comfortably on the bench instead of directly on the wheel, on which it can be operated only in a final step to position the roller/support unit to be locked to the hub.

Other advantages, in combination with the characteristics and methods of use of the present invention, will become apparent from the following detailed description of its preferred embodiments, presented by way of non-limiting example.

Brief description of the drawings Reference will be made to the drawings shown in the attached figures, in which: Figure 1 shows an overall view of an omnidirectional wheel according to a first embodiment of the present invention;

Figures 2A and 2B respectively show a perspective representation of the contact profile of the newly conceived omnidirectional wheel (fig.2A) and the respective rollers (fig.2B)

Figure 3 shows, in a preferred embodiment of the wheel of Figure 1 , an exploded view explaining the arrangement of a roller inside the hub and the mechanical components supporting the same in the working position

Figures 4A and 4B respectively show a sectional and top view of a roller and the related support means related to Figures 1 -3 in the mounted condition;

Figures 5A and 5B respectively show an overall view of a second embodiment of the omnidirectional wheel and the corresponding exploded view;

Figure 6 shows a schematic view that identifies the angle formed between the direction of the rotation axis of the wheel and that of the rollers;

Figure 7 shows an overall view of an omnidirectional wheel, in a first embodiment of the present invention, characterized by the modularity of the support means according to which rollers belonging to the same circumferential rows are grouped;

Figures 7A, 7B and 7C show respectively the modular elements and the means for coupling of the wheel of Figure 7 in the unassembled condition, in sectional and exploded view of the same;

Figure 8 shows an overall view of an omnidirectional wheel, in a second embodiment of the present invention, characterized by the modularity according to which the rollers belonging to the same circumferential rows are grouped;

Figures 8A, 8B and 8C respectively show the modular elements and the means for coupling of the wheel of Figure 8 in the unassembled condition, in sectional and exploded view thereof. Detailed description of embodiments of the invention

The present invention will be described below with reference to the above figures. With initial reference to Figure 1 , an overall view of an omnidirectional wheel 1 according to a first embodiment of the present invention is illustrated by way of non-limiting example.

In general terms, and with further reference to Figure 6, the wheel object of the present invention comprises a plurality of rolling elements - or rollers - each denoted by /, destined to sequentially come into contact with the rolling plane. Each roller has its own axis of revolution B - or longitudinal axis - tilted by a first angle b with respect to the axis of rotation A of the wheel.

Regardless of the specific embodiment illustrated in the examples shown in the figures, the wheel comprises support means configured to removably support the rollers / and to arrange the same in a plurality of annular rows f, axially spaced between each other along the axis of rotation A.

The rows f are phase shifted between each other by a second angle a with respect to the axis of rotation A of the wheel such that during the rolling of the wheel one and only roller of one and only row is in contact with the rolling plane.

The angle a, illustrated in Figure 6, lies on the front plane of the wheel, which is the one on which the projection of the contact profiles of the rollers / forms a perfect circumference. The angle a is the phase shift between homologous points of rollers circumferentially in subsequent contact with the rolling plane. The order of contact is preferably that indicated in Figure 2, described below in greater detail. Preferably, named n the number of rollers per row and f the number of side-by-side rows constituting the wheel, the angle a is equal to 360 {nf).

With now reference to figures 2A and 2B, the perspective representation of the contact profile of the omnidirectional wheel and of the relative rollers, respectively, in a possible configuration of row f and number n of rollers per row, is visible. In particular, the contact profile of the wheel is represented by the succession of curvilinear profiles enumerated 1-24, each associated with each roller. In such embodiment, the wheel comprises f = three rows and each row provides n = eight rollers /. As shown, during the wheel rolling, the contact point on the rolling plane moves from one end of each roller / to the other end along a curvilinear profile (from k’i to k’2 as indicated in figure 2A) engaging subsequent rollers, i.e. moving both in an axial direction parallel to the A axis and in a circumferential direction, according to the listed order of enumeration. This configuration allows the wheel to have one and only one roller / of one and only one row f always gripping the rolling plane, thus ensuring continuity of motion.

The n rollers / of each row f have the same relative angular distance: the angle between one roller and the next in the same row is equal to 360 n.

Preferably, the wheel according to the present invention advantageously comprises modular elements - integrating the support means - which are configured to be mounted side by side with each other through means for coupling. These modular elements, according to a different aspect of the same invention, will be described in greater detail within the present description with reference to further embodiments of the wheel.

Returning to the wheel illustrated in figure 1 , and with further reference to figures 3, 4A and 4B, the support means can be realized as removable brackets 3’ which have a seat 30 shaped like a “U” and provided with an engagement profile 31 configured to fit into corresponding cavities 21 obtained in the hub 2.

Said seat 30 is configured to house a roller /, connected to the bracket 3’ at the longitudinal ends. Preferably said cavities 21 have the same conformation. In the illustrated example, each cavity 21 preferably has inside thereof first holes 21a - in the example two bored holes - arranged parallel to the longitudinal axis B of the roller and preferably second holes 21b - in the example two threaded holes - at fixing pins.

The first holes 21a are configured to house centering means, apt to position the bracket/roller assembly in tolerance with respect to the relative cavity 21.

The second holes 21b are configured for an integral coupling between the bracket/roller assembly and the hub 2, for example by means of screws equipped with relative washers.

Preferably, the bracket 3’ may be obtained from sheet metal, preferably laser sliced and doubly bent in order to achieve the aforementioned “U” shape, both to increase the flexural stiffness and to avoid interference problems between adjacent inter-row rollers.

With reference to the first 21 a and second 21 b holes previously described for the cavity 21 , the bracket 3’ has in turn corresponding holes, in particular first holes 21a’ calibrated and apt to cooperate with the centering means 21a” of the roller with respect to the cavity 21 on the hub 2, second holes 21b for coupling the bracket 3’ with the hub 2. The bracket further has third holes 21b calibrated for the correct positioning and fixing of the roller / on the bracket 3’.

As can be seen in Figure 4A, preferably, the roller / has a main body 5 having a substantially cylindrical conformation, for example made of metallic material, the external surface of which is suitably machined to achieve an optimal anchoring of polymeric material thereon, preferably polyurethane or polyurethane-based material.

Whether polyurethane or polyurethane-based material is used, it is preferably melted and vulcanized to the external surface of the main body 5, resulting integral therewith. Downstream of the vulcanization process, the external surface of the roller / is preferably once more machined by means of a numerically controlled lathe, acting on the polyurethane, such that the contact profile achievable by the external surface of the roller is compliant with a predetermined contact profile. The contact profile of the roller is designed to ensure that the axis of rotation A of the wheel preserves a constant distance from the rolling plane.

Returning to Figure 3, an embodiment of the roller is described wherein the main body 5 preferably comprises two internal shoulders, at the ends of said main body 5, configured to allow the beating of the external washers of a pair of rolling bearings, each of which denoted by the reference number 51. The internal washers of said bearings radially couple with the external cylindrical surface of a stud 52 and axially with a sleeve 53 inserted, and radially coupled, also the latter on said stud. Preferably, the stud 52 is internally fully threaded.

The assembly consisting of the main body 5, bearings 51 , stud 52 and sleeve 53 is aligned for fixing on the support means, for example to the aforementioned third holes of the bracket 3’ and coupled therewith. Preferably, the coupling is made internally with fastening means which comprise first washers 54 and externally with second washers 55 and screws 56, the latter preferably grinded and partially threaded. The screws tighten the internal washer 54 to the bracket 3’ against the internal washers of the bearings 51. This constructive solution, in comparison to what happens in known omnidirectional wheels, prevents the roller from locking in case the fastening means is excessively tightened.

In an alternative embodiment, the wheel denoted by the reference 1 is described with reference to figures 5A and 5B. The support means is realized as a hollow cylinder 3’ coaxial to the hub 2 and made integral therewith or realized in a single monolithic piece with hub 2 itself. In both cases the roller /, as previously described, is housed inside recesses 30” obtained in the support means and is fixed thereto through radial means for coupling, for example screws and washers, overall denoted by the reference 50”.

According to an advantageous aspect, such a structure can be geometrically optimized in order to reduce the overall weight of the wheel, while preserving its rigidity and at the same time allowing the evacuation of foreign bodies that might adhere to the rollers during rolling.

According to a further aspect of the present invention, with now reference to figures 7, 7A-7C, 8, 8A-8C, two embodiments of an omnidirectional wheel are described wherein the support means comprises elements which can be coupled with each other to advantageously realize an omnidirectional wheel with modular structure. Similar to what has already been described above, rollers provide the same structure. Common to both embodiments is therefore the presence of at least one modular element 100’, 100” which comprises a hub 2 rotatable around the rotation axis A of the wheel T, 1 Each modular element can be coupled with a similar modular element through means for coupling which will be described more in detail in the short and which are configured to allow a side-by-side mounting of a first modular element 100’, 100” with a respective second modular element 100’, 100”.

The support means 10’, 100” surrounds the hub 2, is connected and integral to the latter, and is configured to support rollers /. Said support means bears first 3a and second 3b housings annularly arranged and axially spaced between each other, along a direction parallel to the axis of rotation A. The first and second housings 3a, 3b therefore define two annular rows.

Each pair of first and second housings 3a, 3b forms a seat 30 intended to receive in a removable way a roller / and, in mounted condition, the seats 30 of a first modular element 100’, 100” are phase shifted with seats 30 of a second modular element 100’, 100”.

Without going into detail and as intelligible by the skilled technician, the first and second housings 3a, 3b are angularly phase shifted between each other by an angle being a function of the longitudinal extension of the roller /, the angle b and the radial distance of the B axis of each roller / with respect to the centre of the wheel.

Preferably, the means for coupling comprises engagement profiles 40 borne by the hub 2 and/or axial jointing devices 42 between the hub 2 and the support means 100’, 100”. For example, modules placed side by side are interconnected between each other in the correct angular position through a centering pin 42a and a plurality of axially developed inter-module screws, overall denoted by the reference 42b.

In order not to discharge the support of the vertical loads of the wheel, and in particular of the modular element, only to the axial jointing devices, the use of the latter is preferably provided in combination with the aforementioned engagement profiles 40, in particular profiles shaped for a radial coupling between the hubs of side-by-side placed modules, in particular between their cylindrical surfaces.

As for the embodiments hitherto described, even with the presence of the aforementioned modular elements 100’, 100” there is a spatial-radial gap between the external surface of the rollers / and the external surface of the hub 2, through which any splinters or foreign bodies that may get stuck or temporarily stick to the roller, can come out and be expelled from the wheel. The first embodiment is shown in Figures 7, 7A-7C. In this case the wheel comprises three modular elements, each denoted by the reference 100’, and the support means comprise plate-like elements, preferably circular in shape, integral with the hub 2.

In more detail, a first and a second plate-like element 3a’, 3b’ opposite and axially spaced between each other, lie on planes orthogonal to the rotation axis of the wheel A. Each plate-like element respectively bears a row of the first 3a and second 3b housings.

Preferably, the first and second housings 3a, 3b are shaped to receive a longitudinal end of the axis of rotation B of the roller / on a radially peripheral region of the respective plate-like elements 3a’, 3b’. The rollers, once inserted into the seats 30, are fixed to the plate-like elements 3a’, 3b’ by fastening means, preferably by screws, coaxial to the axis of rotation B of the roller and passing through suitable holes provided thereon. This configuration, which is cheap and simple to realize, does not allow to disassemble the single rollers when the modular elements 100’ are axially tightened to each other, due to the fixing means of the rollers being unapproachable.

The second embodiment is shown in Figures 8, 8A-8C. In this case, the wheel 100” comprises an annular trail 31 which projects from each of the plate-like elements 3a”, 3b” and is configured to receive opposite ends of a roller / in a radial direction with respect to the hub 2.

Preferably, the roller / is mounted on supports 57 with a lower coupling surface shaped like a half moon, said supports housing themselves in dedicated cavities 3a, 3b obtained on the plate-like elements 3a”, 3b”. In this configuration it is possible to mount the roller /, supports 57 and its comprised components, on the bench and then house and tighten each one on the relative plate-like elements 3a”, 3b” through radially-developed fixing means, for example threaded screws 58, which fit into the same. Advantageously, the particular shape of the inserts 57 causes the stresses to which the rollers are subjected to be discharged uniformly onto the plates there through.

The present invention has been hitherto described with reference to its preferred embodiments. It is to be understood that each of the technical solutions implemented in the preferred embodiments, described here by the way of example, can be advantageously differently combined, to give rise to other embodiments, which pertain to the same inventive core as defined in the scope of protection of the claims set forth below.