Electric wheel and rolling vehicle equipped with such a wheel

Abstract

An electric wheel (3) comprising a hollow body (4) and, at least partially housed within the body (4), a motor (7), a support (15) for said motor (7), and a system (9) for transmitting the rotational motion from the rotor (8) to the body (4), with a driving element (11) adapted to be driven in rotation by the rotor (8) and fitted to the support (15) of said motor (7), and a driven element (12) disposed on the body (4) and comprising teeth (10) rotationally fixed to the body (4), said body (4) having a hub (5) defining an axis of rotation (XX') of the wheel (3), the driving elements (11) and driven elements (12) being adapted to mesh, said teeth (10) comprising axial teeth (120) that project from a plane (P2) perpendicular to the axis of rotation (XX') of the wheel (3), the motor support (15) is equipped with at least one guiding element (18), the body (4) includes at least one circular track (17), coaxial with the axis of rotation (XX') of the wheel (3),presenting a contact surface (170), perpendicular to the axis of rotation (XX') of the wheel (3), with which the or at least one of the guiding elements is able to come into contact by rolling or sliding support. Figure for the abbreviation: Fig. 1,

Description

Title of the invention: Electric wheel and rolling machine equipped with such a wheel

[0001] The present invention relates to an electric wheel and a rolling machine equipped with such a wheel.

[0002] It relates in particular to an electric wheel comprising a hollow body, a motor with a rotor and a stator, a support for said motor and a system for transmitting the rotational movement from the rotor to the body with a driving element adapted to be driven in rotation by the rotor equipping the support for said motor and a driven element disposed on the body, said body delimiting a cavity and having a hub defining an axis of rotation of the wheel, the system for transmitting the rotational movement from the rotor to the body and at least a part of the motor support being housed inside said body and the driving and driven elements of the transmission system being adapted to mesh together, the driven element comprising teeth fixed in rotation to the body.

[0003] Motorized electric wheels that integrate a motor inside the wheel are known. Most electric wheels include a central motor coaxial with the wheel's axis of rotation. This results in a bulky and heavy wheel due to the motor's diameter and thickness. Other electric wheel solutions integrating a motor inside the wheel have been developed. However, the solutions adopted for transmitting the rotational motion from the rotor to the wheel body are complex and / or bulky and / or noisy and / or demanding in terms of positioning.

[0004] One object of the invention is to provide an electric wheel whose design allows optimization of the transmission of the rotational movement of the rotor to the body.

[0005] To this end, the invention relates to an electric wheel comprising a hollow body, a motor with a rotor and a stator, a support for said motor, and a system for transmitting the rotational motion from the rotor to the body, with a driving element adapted to be driven in rotation by the rotor and fitted to the support for said motor, and a driven element disposed on the body, said body delimiting a cavity and having a hub defining an axis of rotation of the wheel, the motor, the system for transmitting the rotational motion from the rotor to the body, and at least a part of the motor support being housed inside said body, and the driving and driven elements of the transmission system being adapted to mesh by internal engagement, the driven element comprising teeth fixed in rotation to the body, characterized in that said teeth comprise axial teeth which project from a perpendicular plane to the wheel's axis of rotation, in that the motor support is equipped with at least one guide element, in that the body comprises at least one circular track coaxial with the wheel's axis of rotation, having a contact surface perpendicular to the wheel's axis of rotation with which one or more guide elements are capable of making rolling or sliding contact. The driven element's design as axially toothed gears, combined with the presence of one or more guide elements arranged on the motor support equipped with the driving element, allows for controlled motion transmission and provides a quiet, reliable, and simplified meshing system.

[0006] It should be noted that the torque transmitted by the motor generates forces in the gear teeth. These forces act in the direction of a separation between the driven and driving elements. The guiding elements ensure meshing even under these conditions.

[0007] According to one embodiment of the invention, the teeth and at least part of the body are made from a single piece. This design contributes to simplifying the transmission system.

[0008] According to one embodiment of the invention, the teeth are circular teeth with a circle whose center is located on the axis of rotation of the wheel.

[0009] According to one embodiment of the invention, the teeth are surrounded by one or at least one of the tracks. The position of one or more of the tracks relative to the teeth ensures effective guidance, even in the event of deformation of the wheel body. In particular, when two tracks are positioned opposite each other, their proximity to the rim allows for control of the distance between the two tracks, since this distance is primarily determined by the rim thickness.

[0010] According to one embodiment of the invention, the driving element is a worm screw meshed with the driven element.

[0011] According to one embodiment of the invention, the motor support comprises a housing inside which the driving element is mounted freely for rotation, this driving element being coupled to the motor rotor, a part of the motor other than the rotor being positioned in contact against a part of the motor support forming a stop for immobilizing in rotation a part of the motor other than the rotor.

[0012] According to one embodiment of the invention, the motor support comprising at least two guide members capable of making contact with the same track, said guide members extend on either side of a radial plane to the track passing through the area of ​​engagement of the driven and driving elements.

[0013] According to one embodiment of the invention, there are at least two circular tracks, arranged opposite each other.

[0014] According to one embodiment of the invention, the body comprises two facing walls forming the sides or sails of the wheel and a circumferential peripheral wall connecting said facing walls to each other and forming the rim of the wheel and in that the circular tracks, which are at least two in number, are arranged facing each other on the facing walls of the body.

[0015] According to one embodiment of the invention, the wheel includes a shaft called the wheel shaft around which the hub is mounted, this shaft carrying the motor support disposed at least partially inside the body.

[0016] According to one embodiment of the invention, the motor support is mounted with play on said wheel shaft so as to be able to oscillate around an axis orthogonal to the axis of rotation of the wheel.

[0017] According to one embodiment of the invention, the rotor being configured to rotate around an axis called the motor axis, the motor axis and the axis of rotation of the wheel are non-coaxial.

[0018] According to one embodiment of the invention, the drive shaft and the rotation shaft of the wheel are not parallel and preferably do not intersect.

[0019] According to one embodiment of the invention, the motor is arranged inside a fictitious cylinder whose axis coincides with the axis of rotation of the wheel and whose diameter is equal to the largest diameter of the circular teeth.

[0020] The invention also relates to a rolling machine, in particular a mowing machine comprising at least one mowing element and at least one electric drive wheel, characterized in that the wheel or at least one of the wheels is of the type mentioned above. Brief description of the drawings

[0021] The invention will be better understood upon reading the following description of exemplary embodiments, with reference to the accompanying drawings in which:

[0022] [Fig-1] represents a perspective view, in exploded position, of the elements constituting, of an electric wheel conforming to the invention;

[0023] [Fig.2] represents a perspective view of an electric wheel conforming to the invention in its assembled state;

[0024] [Fig.3] represents a schematic view of an electric wheel according to the invention to illustrate the concept of an imaginary or fictitious cylinder;

[0025] [Fig.4] represents a partial cross-sectional view of an electric wheel in accordance with the invention;

[0026] [Fig. 5] represents a partial cross-sectional view of an electric wheel in accordance with the invention;

[0027] [Fig. 6] represents a partial longitudinal cross-sectional view of an electric wheel in accordance with the invention;

[0028] [Fig.7] represents a partial view of an electric wheel according to the invention at the state of being electrically connected to a power supply;

[0029] [Fig.8] represents two schematic partial cross-sectional views of an electric wheel in accordance with the invention to illustrate the oscillation of the motor support;

[0030] [Fig.9] shows a perspective view of the motor support, the motor, the screw without end, and of the wheel shaft, in exploded position of said elements;

[0031] [Fig. 10] represents, in schematic form, different examples of organs of guidance;

[0032] [Fig. 11] represents a partial cross-sectional view of an electric wheel conforming to the invention associated with two detailed views;

[0033] [Fig. 12] represents a perspective view of a rolling machine equipped with a wheel electrical conforming to the invention;

[0034] [Fig. 13] represents, in the form of two views, one in the assembled state, the other in the state unassembled, the immobilization in rotation of a part of the motor by stop with the motor support;

[0035] [Fig. 14] represents a partial perspective view of the inside of a wheel electrical conforming to the invention;

[0036] [Fig. 15] represents a partial exploded view of some of the elements of the [Fig. 14],

[0037] As mentioned above, the invention relates to an electric wheel 3 of the type shown in Figures 1 and 2. This electric wheel 3 is suitable for equipping a rolling machine 1, as illustrated in [Fig. 12]. This rolling machine 1 is here a mowing machine which comprises at least one mowing element 2 formed, for example, by a rotating blade and at least one, preferably at least two, electric drive wheels 3.

[0038] This mowing machine 1 can be an autonomous machine of the robot type, i.e., without a driver as illustrated, or a mowing machine with a driver walking behind the machine, such as a lawnmower, or a mowing machine with an onboard driver, such as a riding mower. Obviously, other applications of the electric wheel, which will be described later, can be considered without departing from the scope of the invention.

[0039] One or more of the electric wheels 3 suitable for equipping such a rolling machine is a drive wheel. This electric wheel 3 comprises a hollow body 4 having a hub 5 suitable for mounting on a shaft 14, called the wheel shaft. This hub 5 forms a circular recess. This hub 5 defines an axis XX' of rotation of the wheel 3. The hollow body 4 delimits a cavity 6 inside which are housed an electric motor 7 with a rotor 8 capable of rotating about a motor shaft YY' and a system 9 for transmitting the rotational motion of the rotor 8 to the body 4 to rotate the body 4 about the axis XX' of rotation of the wheel 3.

[0040] By "rotor of the electric motor 7", we mean here the rotating elements of said motor, these rotating elements including the motor shaft, when such a shaft is present.

[0041] The motor 7 also includes a stator 24 which here groups together all the static elements of the motor 7.

[0042] As can be seen in [Fig.4], the system 9 for transmitting the rotational movement of the rotor 8 to the body 4 comprises a driven element 12 in the form of a toothed gear 10 fixed in rotation to the body 4 and a driving element 11 suitable for being driven in rotation by the motor 7.

[0043] The electric wheel 3 further includes a support 15 for the motor 7. The system 9 for transmitting the rotational movement of the rotor 8 to the body 4 and at least part of the motor support 15 are housed inside said body 4. The driving elements 11 and driven elements 12 of the transmission system 9 are capable of engaging by meshing.

[0044] As mentioned above, the driven element 12 includes a toothing 10 fixed in rotation to the body 4. This toothing 10 includes axial teeth 120 which extend in projection from a plane P2 perpendicular to the axis of rotation XX' of the wheel 3 as shown in [Fig.6].

[0045] The toothing 10 is a circular toothing of a circle with center located on the axis of rotation XX' of the wheel 3.

[0046] The teeth 10 and at least part of the body 4 are made of a single piece, for example of synthetic material.

[0047] In the example shown in [Fig.7], the body 4 comprises two facing walls 19 forming the sides or rims of the wheel 3 and a circumferential peripheral wall 20 connecting said facing walls 19 to each other and forming the rim of the wheel 3. The circumferential peripheral wall may incorporate a tread or this tread may be attached.

[0048] In the example of [Fig. 11], the tread, shown as 200, is attached. A portion of this tread 200, which is made of elastic material, is sandwiched between a portion of the circumferential peripheral wall 20 and a portion of one of the walls 19 forming a flank of the wheel 3 in the coupled state of the peripheral wall 20 and the wall 19 forming a flank of the wheel 3. This sandwiching ensures the sealing of the cavity 6 delimited by the body 4 at this point. The coupling is achieved, in the example shown, by means of screws 27.

[0049] The facing walls and the circumferential wall can be made of a synthetic material, and the teeth 10 are formed in one piece with one of the two facing walls 19. Thus, the teeth project from the face of said wall towards the facing wall. The driving element 11 is in the form of a worm gear 110 adapted to be driven in rotation by the motor 7.

[0050] This worm gear 110 can therefore be rotationally locked to the rotor 8 and is capable of meshing with the teeth 10. This worm gear 110 and the motor shaft YY' are preferably coaxial. The worm gear directly engages with the rotor 8 of the motor 7. This connection is either permanent or made in a switchable / disconnectable manner. In the example shown, the rotor 8 incorporates a motor shaft along the extension of which the worm gear 110 is located.

[0051] This worm gear 110 extends in a plane P substantially perpendicular to the axis of rotation XX' of the wheel, that is to say, perpendicular to within ±10° of said axis of rotation XX'. The worm gear 110 is able to mesh with the teeth 10. It is therefore understood that the rotation of the worm gear 110 meshing with the rotor 8 of the motor 7 drives, by meshing of the worm gear 110 with said teeth 10, the rotation of the body 4 of the wheel 3.

[0052] To allow meshing, even when the wheel body 3 is deformed, the body 4 comprises, located inside the cavity 6 of the body 4 and rotationally fixed to the body 4, at least one circular track 17 with center located substantially on the axis XX' of rotation of the wheel 3 so as to extend coaxially with the teeth 10. Generally, the track 17 surrounds the teeth 10. The track 17 is thus located as close as possible to the rim. The motor support 15 is equipped with one or more guide elements 18 for each track. Each guide element 18, such as a bearing or a pad, is suitable for making rolling or sliding contact with said track 17. This circular track 17, coaxial with the axis of rotation XX' of the wheel 3, has a contact surface 170, perpendicular to the axis of rotation XX' of the wheel 3, with which the guide elements 18 associated with said track 17 are suitable for making rolling or sliding contact.

[0053] In the example of Figures 4 and 5, two guide members 18 are provided, each formed by a bearing. Each bearing is screw-coupled to the motor support 15. To ensure optimal guidance without having to multiply the guide members 18, the guide members 18 extend on either side of a plane PI radial to the track 17 and passing through the meshing area of ​​the worm gear 110 and the teeth 10.

[0054] Examples of guide members 18 are provided in [Fig. 10]. Each guide member 18 can be a rolling or sliding guide member and can be rotary or non-rotating. Each guide member 18 can be made in one piece with another guide member, as illustrated in [Fig. 10].

[0055] The guiding elements can be mounted in a separate manner on a common support.

[0056] Each circular track 17 is arranged opposite another circular track. The circular tracks 17 are thus arranged opposite each other on the walls 19 in view of body 4 for an imprisonment of the organs 18 of guidance between the said tracks.

[0057] To allow the wheel body 4 to rotate around the axis XX' of rotation of the wheel 3, the wheel 3 includes a shaft called the wheel shaft 14 around which the hub 5 is mounted. A seal, shown at 23 in [Fig. 11], ensures a seal between the wheel shaft 14 and the hub 5. The cavity delimited by the body is therefore, in the assembled state of the electric wheel 3, a closed cavity. The shaft 14 carries the motor support 15, which is at least partially located inside the cavity of the body 4. The hub 5 is formed by a simple circular opening inside at least one of the walls 19 facing the wheel body 4, into which a portion of the wheel shaft 14 is inserted. This wheel shaft 14 carries the motor support 15 to which the motor 7 is coupled directly or indirectly. The wheel shaft 14 / motor support 15 assembly forms a fixed rotating assembly around which the wheel body 4 rotates.An example of motor mount 15 is provided in [Fig.9].

[0058] As can be seen in [Fig. 8], the motor support 15 includes a through-hole so that it can be threaded onto the wheel shaft 14 to form a fixed assembly with it during movement. For this purpose, the housing may have grooves into which axial ribs of the wheel shaft 14 fit. This motor support 15 is preferably made of a synthetic material. Alternatively, this motor support 15 may be made of metal, in particular aluminum alloy. This motor support 15 has a generally triangular shape, but its shape may vary. This motor support 15 is housed at least partially inside the cavity 6 of the body 4.

[0059] To allow rotation of the body 4 around the wheel shaft 14, bearing elements are provided. These bearing elements are visible in [Fig.8].

[0060] The motor support 15 includes a housing 16, visible in [Fig. 1], with an axis orthogonal to the axis of the through housing for receiving the wheel shaft 14. This housing 16 serves to receive the driving element 11, in particular the worm gear 110, which is mounted to rotate freely via at least one bearing 22 inside the housing 16. This bearing or these bearings 22 allow, in addition to the rotation of the worm gear 110 relative to the motor support 15, the coupling of the worm gear 110 to the motor support 15 by means of an external circumferential shoulder of the worm gear 110, visible in [Fig. 4]. The associated bearing 22 is axially immobilized in the housing 16 by means of a locking member, such as a clip 26, visible in particular in Figures 9 and 13.A part 71 of the motor 7, other than the rotor 8, is positioned in contact with a part 151 of the motor support 15, which acts as a stop to prevent the rotation of said part of the motor, as can be seen in [Fig. 13]. Thus, the part of the motor that is not to rotate is immobilized. rotation by simple contact of pressure on the motor support 15. The motor 7 extends in cantilever relative to the worm gear 110.

[0061] To optimize the position of the motor 7, as illustrated in [Fig. 3], the motor 7 is arranged inside a fictitious, i.e., imaginary or virtual, cylinder 13, whose axis coincides with the axis XX' of rotation of the wheel 3 and whose diameter is equal to the largest diameter of the circular teeth 10. Ideally, the motor 7 is arranged inside a fictitious, i.e., imaginary or virtual, cylinder 13, whose axis coincides with the axis XX' of rotation of the wheel 3 and whose diameter is equal to the smallest diameter of the circular teeth 10.

[0062] As can be seen in [Fig. 8], the motor support 15 is mounted with clearance on the wheel shaft 14 so that it can oscillate around an axis orthogonal to the axis XX' of rotation of the wheel 3. This clearance is present at the through-hole of the motor support 15, allowing the motor support 15 to be threaded onto the wheel shaft 14. Thus, even in the event of deformation of the wheel 3, the guide members 18 can bear against the body of the wheel 3 at the level of the tracks 17. The guide members 18 therefore simultaneously ensure, by bearing contact with the tracks 17, guidance guaranteeing the possibility of coupling by meshing between the teeth 10 and the worm gear 110.

[0063] To minimize the width, i.e., the thickness, of said electric drive wheel 3 without impairing its operation, the motor shaft YY' and the rotation axis XX' of the wheel 3 are non-coaxial and non-parallel. Furthermore, the motor shaft YY' and the rotation axis XX' of the wheel 3 do not intersect.

[0064] In practice, the motor shaft YY' extends in a plane P that is substantially perpendicular, that is, perpendicular to within ±10°, to the axis XX' of rotation of the electric wheel 3. The motor shaft YY' and the axis XX' of rotation of the wheel 3 are orthogonal to each other, as can be seen in [Fig. 3], which makes it possible to reduce the width of the electric wheel 3.

[0065] The motor 7 is an electric motor of the smallest possible dimensions. Ideally, the motor has an overall diameter of less than 40 mm for a robot, 50 mm for a lawnmower, 70 mm for a snowplow, and 120 mm for a tractor. Such a motor 7 rotates at high speed. It is therefore essential that the system 9 for transmitting the rotational motion from the rotor 8 of the motor 7 to the body 4 of the wheel 3 incorporates a speed reducer. This speed reduction is achieved through the design of the gear that transmits the motion.

[0066] To supply power to the motor 7, an electrical wiring harness 21 is provided. This electrical wiring harness 21, visible in Figures 7 and 15, passes in particular through the wheel shaft and the hub. This wiring harness 21 allows connection to the power supply battery when the motor's power supply battery is located at The exterior of body 4. This electrical wiring 21 allows the power supply battery to be recharged when the wheel motor's power supply battery 210 is housed inside cavity 6 of body 4. Obviously, a single wheel can include one or more electric motors. The control of the motor(s) 7 is achieved using a control unit 25, visible in Figures 14 and 15. This control unit 25 is in the form of an electronic and computer system that includes, for example, a microprocessor and working memory. In a particular configuration, the control unit can be in the form of a programmable logic controller (PLC). In other words, the functions and steps described can be implemented as a computer program or via hardware components (e.g., programmable gate arrays).In particular, the functions and steps performed by the control unit or its modules can be carried out by instruction sets or computer modules implemented in a processor or controller, or by dedicated electronic components or components such as field-programmable gate arrays (FPGAs) or application-specific integrated circuits (ASICs). It is also possible to combine computer and electronic components. When it is specified that the unit or means or modules of said unit are configured to perform a given operation, this means that the unit includes computer instructions and the corresponding means of execution which enable said operation to be performed and / or that the unit includes corresponding electronic components.

[0067] The control unit 25 and the battery 210 are, when arranged inside the cavity 6 of the body 4, fixed to the motor support 15.

[0068] The operation of such a wheel is simple. The supply of electricity to the motor 7 causes a rotation of the rotor 8 which in turn drives the worm gear 110 which meshes with the teeth 10 which are fixed in rotation to the body 4 of the wheel 3. The guide members 18 ensure in parallel, by contact with the tracks 17, a guidance guaranteeing a possibility of coupling by meshing between the worm gear and the teeth.

[0069]

Claims

Demands

1. An electric wheel (3) comprising a hollow body (4), a motor (7) with a rotor (8) and a stator (24), a support (15) for said motor (7), and a system (9) for transmitting the rotational motion from the rotor (8) to the body (4), including a driving element (11) adapted to be driven in rotation by the rotor (8) and mounted on the support (15) of said motor (7), and a driven element (12) disposed on the body (4), said body (4) defining a cavity (6) and having a hub (5) defining an axis of rotation (XX') of the wheel (3), the motor (7), the system (9) for transmitting the rotational motion from the rotor (8) to the body (4), and at least a portion of the motor support (15) being housed within said body (4), and the driving elements (11) and driven elements (12) of the transmission system (9) being adapted to mesh, the driven element (12) comprising a set of teeth (10) fixed in rotation to the body (4),characterized in that said toothing (10) comprises axial teeth (120) which project from a plane (P2) perpendicular to the axis of rotation (XX') of the wheel (3), in that the motor support (15) is equipped with at least one guide element (18), in that the body (4) comprises at least one circular track (17), coaxial with the axis of rotation (XX') of the wheel (3), having a contact surface (170), perpendicular to the axis of rotation (XX') of the wheel (3), with which the guide element (18) is able to come into contact by rolling or sliding support.

2. Electric wheel (3) according to claim 1, characterized in that the teeth (10) and at least part of the body (4) are made of a single piece.

3. Electric wheel (3) according to one of claims 1 or 2, characterized in that the toothing (10) is a circular toothing of a circle with center disposed on the axis of rotation (XX') of the wheel (3).

4. Electric wheel (3) according to any one of claims 1 to 3, characterized in that the toothing (10) is surrounded by the or at least one of the tracks (17).

5. Electric wheel (3) according to any one of claims 1 to 4, characterized in that the driving element (11) is a worm screw (110) meshed with the driven element (12).

6. Electric wheel (3) according to any one of claims 1 to 5, characterized in that the motor support (15) comprises a housing (16) inside which the driving element (11) is mounted freely for rotation, this driving element (11) being coupled to the rotor (8) of the motor (7), a part (71) of the motor (7) other than the rotor (8) being positioned in contact with a part (151) of the motor support (15) forming a stop for immobilizing in rotation a part of the motor (7) other than the rotor (8).

7. Electric wheel (3) according to any one of claims 1 to 6, characterized in that the motor support (15) comprising at least two guide members (18) capable of making contact with the same track (17), said guide members (18) extend on either side of a plane (PI) radial to the track (17) passing through the area of ​​engagement of the driven (12) and driving (11) elements.

8. Electric wheel (3) according to any one of claims 1 to 7, characterized in that the circular tracks (17) are at least two in number and are arranged opposite each other.

9. Electric wheel (3) according to any one of claims 1 to 8, characterized in that the body (4) comprises two facing walls (19) forming the sides or sails of the wheel (3) and a circumferential peripheral wall (20) connecting said facing walls (19) to each other and forming the rim of the wheel and in that the circular tracks (17) which are at least two in number are arranged facing each other on the facing walls (19) of the body (4).

10. Electric wheel (3) according to any one of claims 1 to 9, characterized in that the wheel (3) comprises a shaft called wheel shaft (14) around which the hub (5) is mounted, this shaft (14) carrying the motor support (15) disposed at least partially inside the body (4).

11. Electric wheel (3) according to claim 10, characterized in that the motor support (15) is mounted with clearance on said wheel shaft (14) so ​​as to be able to oscillate around an axis orthogonal to the axis of rotation (XX') of the wheel (3).

12. Electric wheel (3) according to any one of claims 1 to 11, characterized in that the rotor (8) being configured to rotate about an axis called motor axis (YY'), the motor axis (YY') and the rotation axis (XX') of the wheel (3) are non-coaxial.

13. Electric wheel (3) according to claim 12, characterized in that the motor shaft (YY') and the rotation shaft (XX') of the wheel (3) are non-parallel and, preferably, do not intersect.

14. Electric wheel (3) according to any one of claims 1 to 13, characterized in that the motor (7) is arranged inside a fictitious cylinder whose axis coincides with the axis of rotation (XX') of the wheel (3) and whose diameter is equal to the largest diameter of the circular toothing (10).

15. Rolling machine (1) in particular for mowing comprising at least one mowing element (2) and at least one electric drive wheel (3), characterized in that the or at least one of the wheels (3) conforms to any one of claims 1 to 14.

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