Caster wheel unit

Abstract

A wheel unit comprising a wheel (40), a slewing ring bearing (39), and a wheel yoke (41), wherein the wheel yoke is configured to connect the wheel to the slewing ring bearing; wherein the slewing ring bearing comprises an outer slewing ring (1), and an inner slewing ring (2), wherein the inner slewing ring is connected to the wheel yoke, wherein the wheel yoke is connected to the wheel via a hub, wherein the slewing ring bearing further comprises at least one row of axial bearing elements (3, 4) and at least one row of radial bearing elements, wherein the outer slewing ring comprises a first wall part and a second wall part, wherein the first wall part is ring-shaped and defines a plane, wherein the second wall part comprises a cylindrical portion formed perpendicular to the plane defined by the first wall part, wherein a surface of the first wall facing the inner slewing ring comprises an axial bearing race, wherein a surface of the second wall part facing the inner slewing ring comprises a radial bearing, wherein the outer slewing ring is configured as a single integrated unit formed in one piece, wherein the inner slewing ring comprises an axial bearing race corresponding to the axial bearing race of the outer slewing ring and a radial bearing race corresponding to the radial bearing race of the outer slewing ring, wherein an outer diameter of the inner slewing ring is larger than an inner diameter of the outer slewing ring, and wherein said row of radial bearing elements forms a lock for connecting the inner slewing ring and the outer slewing ring.

Description

[0001] CASTER WHEEL UNIT

[0002] The present invention relates to a wheel unit comprising a combination of a slewing ring bearing and a wheel, and further relates to systems comprising such combinations.

[0003] Background of the invention

[0004] Wheel units comprising a combination of a wheel and a slewing ring bearing and configured to connect to a e.g. vehicle are known from for example mobile robots, wheeled chairs, etc. The slewing ring bearing allows the wheel to rotate - swivel - about an axis, often, but not exclusively, a vertical axis. The slewing ring bearing further serves to take up forces between the object (such as a vehicle) to which the wheel is connected, and the wheel.

[0005] In general, slewing ring bearings are used for rotation when a device, vehicle or installation has two adjacent structures, which must rotate in opposite directions. Slewing ring bearings usually supports heavy load, often on a horizontal plane. However many are designed to receive high axial, radial and tilting moment load, regardless of the plane of rotation. Equally slewing ring bearings are expected to accommodate for thrust forces in all directions while maintaining the ability to rotate.

[0006] Slewing ring bearings comprises inner and outer rings typically arranged with one or more rows of rolling elements in between. Slewing ring bearings are hollow, hereby achieving the ability to contain components within, which benefits a great variety of systems. The large diameter further distributes thrust and moment forces to a larger area, hereby lowering stress on smaller bearing types.

[0007] In general slewing ring bearings are either made from multiple outer or inner rings enclosing multiple rows of bearings and combined by fasteners; or solid rings known as four-point-contact bearings provided with large radial holes for the purpose of loading rolling elements in between the rings. The loading hole weakens the body and to compensate more material is needed for the rings.

[0008] The French patent application FR372314 discloses a solid outer bearing ring is. This invention reveals a radial ball bearing with additional axial ball bearing support, intended for rotational shafts. In order to assemble the product, the bearing races are very small and thereby weak. Further, it is almost impossible to add a cage to the radial bearing. If FR372314 is required to handle opposite axial thrust a second outer ring must be added using fasteners, similar to how slewing ring bearings are manufactured today. Further FR372314 is an ordinary bearing, and not a slewing ring bearing.

[0009] DE845927 discloses a slewing ring comprising a solid outer slewing ring. A single row of an axial angular contact bearing is required to handle both axial and radial thrust. Any axial moment thrust is supposed to be received by a waved spring ring, with the primary purpose of keeping the product together and not facilitate rotation. It is uncertain how the spring element will be installed.

[0010] US 2007 0009191 discloses another bearing assembly. Even if the bearing comprises a solid outer bearing body, this bearing assembly do not accommodate for opposite axial thrust, but only axial and radial thrust. This while illustrating an invention, which does not seem to be able to be assembled, unless the outer metal sleeve is bended inwards as a finishing step of assembly.

[0011] It is therefore an object of the invention to provide a wheel unit, which is easy to assemble, and therefore more cost efficient to manufacture.

[0012] It is further an object of the invention to provide a wheel unit with a slewing ring bearing, which is robust and capable of receiving radial thrust, and further being capable of receiving axial moment.

[0013] It is further an object of the invention to increase the variety of options. Summary of the invention

[0014] In one aspect, the objects of the invention are achieved by a wheel unit comprising

[0015] - a wheel,

[0016] - a slewing ring bearing, and

[0017] - a wheel yoke, wherein the wheel yoke is configured to connect the wheel to the slewing ring bearing, wherein the slewing ring bearing comprises an outer slewing ring, and an inner slewing ring, wherein the wheel yoke is connected to the wheel via a hub, wherein the slewing ring bearing is arranged to surround a portion of the wheel; wherein the slewing ring bearing further comprises at least one row of axial bearing elements and at least one row of radial bearing elements, wherein the outer slewing ring comprises a first wall part and a second wall part, wherein the first wall part is ring-shaped and defines a plane, wherein the second wall part comprises a cylindrical portion formed perpendicular to the plane defined by the first wall part, wherein a surface of the first wall facing the inner slewing ring comprises an axial bearing race, wherein a surface of the second wall part facing the inner slewing ring comprises a radial bearing race, wherein the outer slewing ring is configured as a single integrated unit formed in one piece, wherein the inner slewing ring comprises an axial bearing race corresponding to the axial bearing race of the outer slewing ring and a radial bearing race corresponding to the radial bearing race of the outer slewing ring, wherein an outer diameter of the inner slewing ring is larger than an inner diameter of the outer slewing ring, and wherein said row of radial bearing elements forms a lock for connecting the inner slewing ring and the outer slewing ring. The wheel is rotatable relative to the wheel yoke about a rotation axis of the wheel.

[0018] The rotation between the wheel yoke and the wheel is provided by the hub.

[0019] Further, the yoke and wheel is rotatable relative to the slewing ring bearing. This rotation is provided between the rows of bearing elements provided between the outer slewing ring and the inner slewing ring.

[0020] The wheel unit may form a caster wheel or a caster wheel unit.

[0021] The wheel unit according to the present invention provides a slewing ring bearing solution, where the outer slewing ring of the slewing ring bearing is solid and robust, since it is formed as one integrated unit formed in one piece, which is in the shape of an enclosing shell, and which comprises both an axial and a radial bearing. At least one inner slewing ring is locked in place by the radial bearing capable of receiving axial moment thrust.

[0022] In general, if the inner ring can pass all the way through the outer ring, then it would be considered an angular contact bearing. This is not possible with slewing ring bearings of the present type.

[0023] In some embodiments, the wheel yoke is a fork, which could also be called a wheel fork.

[0024] In one embodiment, the slewing ring bearing comprises connectors for connecting the wheel unit to a vehicle.

[0025] In one embodiment, the slewing ring bearing is arranged between a rotational axis for the wheel and the uppermost point on the wheel. By the uppermost point of the wheel is meant the uppermost point when the wheel unit is arranged connected to a vehicle, i.e. a use situation of the wheel unit.

[0026] In one embodiment, the connectors for connecting the wheel unit (or the rotational axis of the wheel) to a vehicle is arranged to allow the slewing ring bearing to be arranged above the hub, and below the uppermost point of the wheel, when the wheel unit is mounted on the vehicle.

[0027] This will allow the wheel unit to be mounted on a vehicle or other object in such a way that a good clearance between a lower side of the vehicle or other object and ground may be obtained.

[0028] The slewing ring bearing can be arranged around the wheel at any horizontal level (relative to the hub of the wheel yoke and wheel) suitable for the desired use of the wheel unit.

[0029] In an alternative embodiment, the slewing ring bearing is arranged between a rotational axis for the wheel and the lowermost point on the wheel. By the lowermost point of the wheel is meant the lowermost point, when the wheel unit is arranged connected to a vehicle, i.e. a use situation of the wheel unit.

[0030] In such embodiments, the connectors for connecting the wheel unit to a vehicle is arranged to allow the slewing ring bearing to be arranged below the hub, when the wheel unit is mounted on the vehicle

[0031] This will allow the wheel unit to be mounted on a vehicle or other object in such a way that a very small clearance is provided between a lower side of the vehicle or other object and the ground.

[0032] Also in such embodiments, the slewing ring can be arranged around the wheel at any horizontal level (relative to the hub of the wheel yoke and wheel) suitable for the desired use of the wheel unit.

[0033] In any of the previously mentioned embodiments, the wheel yoke may be connected to the inner slewing ring. In such embodiments, the connectors for connecting the wheel unit to a vehicle are provided on the outer slewing ring.

[0034] Alternatively, the slewing ring bearing is arranged “upside-down” around a wheel, for the purpose of vertical rotation of the wheel. In such embodiments the outer slewing ring is connected to a wheel yoke. Again, the wheel yoke is connected to the wheel though the hub. Further, in these alternative embodiments, the connectors for connecting the wheel unit to a vehicle are provided on the inner slewing ring. Thus, a load from the vehicle to which the wheel unit is mounted, is applied upon the inner slewing ring of such a wheel unit.

[0035] Again, the slewing ring bearing can be arranged around the wheel at any horizontal level suitable for a wheel unit such as a caster wheel.

[0036] In further embodiments of the latter, the connectors for connecting the wheel unit are provided on a load carrying bracket, which is connected to the inner slewing ring and extending radially outward from the inner slewing ring.

[0037] In further embodiments of any of the previously described embodiments, the wheel unit comprises two or more wheels connected to the wheel yoke.

[0038] In further embodiments of any of the previously described embodiments, a wheel is provided with a motor. In embodiments where the wheel unit comprises more than one wheel - as described in the previous paragraph - one, some or all of the wheels may comprise a motor.

[0039] In further embodiments of any of the previously described embodiments, a wheel is equipped with an encoder device for digital monitoring of the rotation of the wheel. In embodiments where the wheel unit comprises more than one wheel - as described in the previous paragraph - one, some or all of the wheels may comprise such an encoder device.

[0040] In further embodiments of any of the previously described embodiments, the slewing ring bearing is arranged horizontally around the wheel, for the purpose of vertical rotation of the wheel.

[0041] In a further embodiment, any of the rows of bearing elements comprises at least three bearing elements configured to roll. In a further embodiment, the rows of bearing elements comprises bearing elements fixed in cages.

[0042] In a further embodiment, the radial bearing comprises an angular contact ball bearing.

[0043] In a further embodiment, an axial bearing comprises an angular contact ball bearing.

[0044] In a further embodiment, an axial bearing comprises bearing elements configured to roll, such as cylindric rollers, tapered / conical rollers, barrel rollers or needle rollers.

[0045] In a further embodiment, an axial bearing comprises a planer bearing race without walls extending perpendicularly from the bearing race.

[0046] This will allow the axial bearing able to slide sideways during assembly of the slewing ring bearing

[0047] In a further embodiment, an axial bearing comprises a plain bearing row.

[0048] In a further embodiment, a radial bearing comprises a plain bearing row.

[0049] In a further embodiment, any of the inner and outer slewing ring comprises an encoder ring and an encoder reader attached to the opposite slewing ring.

[0050] In a further embodiment, any of the inner and outer slewing ring comprises a gear ring.

[0051] In an embodiment thereof, the gear ring is connected to a motor driven transmission gear.

[0052] In a further embodiment, any of the inner and outer slewing ring comprises one or more slip rings and means of conductive contact on the opposite slewing ring. In a further embodiment, the inner and / or outer slewing rings comprises means for suspension.

[0053] Such arrangements can be flexible materials, spring devices, hydraulic suspension, pneumatic suspension, or other suitable suspension.

[0054] In a further embodiment, an electromagnetic field is transferred between an antenna on each of the inner slewing ring and the outer slewing ring.

[0055] The antennas may be formed as either wire coils or metal plate electrodes.

[0056] In a further embodiment, data is transferred between each slewing ring by wireless technology.

[0057] Such wireless technology may comprise of radio frequency, like blue tooth, Wi-Fi and cellular communications.

[0058] In a further embodiment, any of the inner and outer slewing ring may comprise a gyroscope to monitor the rotational velocity of the other of the inner and outer slewing ring.

[0059] Using the slewing ring bearings as described above for wheel units according to the invention has several advantages.

[0060] When the slewing ring bearing is assembled the row of radial bearing elements allows receiving radial thrust, and is further being capable of both receiving axial moment thrust and locking the inner slewing ring and the outer slewing ring together. Thus, the row of radial bearing elements forms a lock for connecting the inner slewing ring and the outer slewing ring.

[0061] This arrangement of the slewing ring bearing allows for easy installment of bearing elements between the inner slewing ring and the outer slewing ring and thereby decreases the manufacturing time of the wheel unit. The solid outer ring is a compact, strong and cheap solution, which will provide for a very robust wheel unit.

[0062] Further, the design of outer slewing ring of the slewing ring bearing as single body, which is not kept together by fasteners, allows for using less material, compared to extra material thickness around fasteners. The absence of fasteners is a strong advantage when a compact construction is needed.

[0063] The solid outer ring further benefits in relation to tolerances since the absence of fasteners reduces complexity of assembly. Tolerances are in general of high importance regarding bearings and slewing rings.

[0064] An axial bearing receives thrust load in the direction of the rotational axis, where a radial bearing receives thrust load perpendicular to the rotational axis.

[0065] At least one inner slewing ring is required to achieve the ability of rotation. The inner slewing ring must fit the bearing races of the outer slewing ring. Both the axial bearing race and the radial bearing race. If the tolerances or the chosen types of bearings requires it, the inner slewing ring may comprise of several layers, which in turn are added to the assembly. An effective solution would be flat plane surfaces where a first a second inner slewing ring would be able to slide against each other to allow radial bearing rows to be installed. The inner slewing rings would later be combined by means of fastening if needed.

[0066] To achieve a low friction contact between the outer and inner rings, any suitable type of bearing can be used, as long as the radial bearing locks the slewing ring together as a combined product, while the radial bearing further facilitates continuous rotation even when the slewing ring is exposed to moment thrust.

[0067] The most common bearing types are: Plain bearings, ball bearings, roller bearings, flexure bearings, tilting pad bearings, fluid bearings and magnetic bearings. The most cost-efficient embodiments of the present invention are rolling element bearings or plain bearings. Rolling elements are most commonly made from hardened steel alloys, where spherical balls or rollers of different shapes are fixed with equal distance in cages and rolling along bearing races provided to the bearing rings.

[0068] The most common rolling element bearing is the ball bearing, which most often is arranged as: Radial deep groove ball bearing (also called radial ball bearing of the grove type, or radial ball bearing of the deep groove type), radial angular contact ball bearing, radial self-aligning ball bearing, axial thrust ball bearing or axial angular contact ball bearing.

[0069] Bearing rollers vary in shape to fit deferent needs. Spherical rollers are shaped to fit the assembly process and provide an even distribution of thrust when in use. Tapered rollers are conical in shape to even the rotational speed of the roller surface in relation to the bearing race.

[0070] The choice of rolling element may benefit the assembly process, like allowing a planar bearing race to slide against a row of tapered rollers.

[0071] Slewing rings often have many rolling elements compared to regular bearings, as well as a high proportional difference between the size of the rolling elements and the diameter of the slewing ring. Normally, the rotational speed of a slewing ring is slow compared to regular bearings.

[0072] Plain bearings comprise of surfaces sliding against each other. These kinds of bearings are often made from materials suited for sliding, or by using different materials which against each other achieves low friction contact. Bearings of selflubricating polymers, which are polymers comprising a percentage of oils, are a made by injection molding or milling, making it very cheap to manufacture, even with special features. Plain bearings may make use of barb elements for keeping a bearing locked together. The surfaces of the barb function can be of plain bearing type. If a radial bearing row comprises a roller bearing, the edge of the races and the ends of the roller may have surfaces of plain bearing materials. This will give the roller bearing the ability to slide while exposed to moment thrust.

[0073] Fluid bearings uses plain bearing rows having a liquid fluid in between making the contact close to none-existing.

[0074] Regardless of the choice of bearing types, additional technologies may be added to the present invention. The field of robotics and automation systems often require more than a simple ability of rotation.

[0075] Encoders are devices used for monitoring speed and direction of a rotation.

[0076] Encoders comprise of a code ring and a sensor to read the code. Code rings are provided with a pattern or similar readable details, which the sensor can detect and transmit for the determination of the circular position and the rotational speed of the code ring. Encoders are classified as either mechanical, optical, magnetic or electromagnetic induction. Further, the output of the sensor is either absolute or incremental. An absolute signal is preferred to determine position, which is crucial in robotics.

[0077] Directional control of a slewing ring is mostly controlled by geared transmissions. These transmissions can be of any suitable type. However, spur and worm gears are the most common. The gears are almost always run by servo or stepper motors, which are precise and easy to control as robots rarely have constant running motors. A transmission gear motor can be mounted as part of both the inner and outer slewing ring, requiring that the gear ring is part of the opposite slewing ring. The transmission could comprise of a gear belt.

[0078] An alternative to a gear transmission could be the use of a motor ring. The motor ring runs by the same physics as ordinary motors, except for the hollow core. The type of motor will certainly be decided by the purpose of the slewing ring. Both AC and DC motors can be adapted to fit within a sleeving ring. AC / DC servo and DC stepper motors are the most precise and easiest to control with micro rotations and accuracy. Motor controllers are required for use of both servos and steppers. A servo motor may comprise any type of motor in combination with an encoder to monitor position. The motor type may vary with demands to precision and torque.

[0079] Stepper motors are DC brushless motors, which makes use of permanent magnets in the rotor, and electromagnets as part of the stator. A common design for stepper motor rings are a ring arrangement of stator coils pointing inwards towards a rotor ring comprising permanent magnets. Both stator coils and rotor comprising stepper pole teeth.

[0080] It is common for hub motors to comprise of an inner stator comprising electromagnetic coils, and an outer rotor comprising a ring of permanent magnets.

[0081] Any embodiment of the present invention comprising an electric motor may be arranged to function as an electric generator.

[0082] Alternatives to electric motors are pneumatic motors, hydraulic motor, combustion engines and steam engines.

[0083] Slip rings are widely used in robotics for transfer of current and signals. They comprise of conductive rings having conductive contacts sliding on the surface. Hereby being able to transfer electric power and electric signal between two bodies continuously rotating in different directions. Slip rings are chosen by design and strength of current.

[0084] An alternative transmission of power is wireless power transfer technologies.

[0085] Wireless transfer of current is done though electromagnetic flux and are categorized as near field or far field. Any suitable technology of wireless power transfer can be integrated in the present invention, however it is obvious that near field technologies would be the best choice. Such a system comprises an electromagnetic transmitter and a receiver device which extracts power from the generated magnetic field. The transmitter comprises an antenna and an oscillator connected to a power source. The current is converted to an oscillating electromagnetic field by an antenna comprising wire coils or an electric field emitted by metal plate electrodes. The receiver comprises a similar antenna type, which converts the oscillating fields back to an electric current. The antennas may be of different proportions.

[0086] Power loss and electrostatic noise is generated, but there are no wear on conductive contacts.

[0087] The three most suitable wireless power transfer technologies would be inductive coupling, resonant inductive coupling and capacitive coupling.

[0088] Depending on the system, a need for data transfer between the outer and inner slewing ring might be needed. Such a data transfer can be conducted by slip rings or by a wireless solution. Slip rings are reliable and not easily a subject to spying or hacking.

[0089] The primary type of wireless data transmission in electronics is radio frequency, which is the basis of technologies like blue tooth, wifi and cellular communications. Any suitable type of wireless data transmission could be integrated in a slewing ring. The embodiment must comprise of the needed components for the required abilities, which depends on the needs for one or two-way communication and the power supply needed on both the outer and inner slewing ring.

[0090] It is possible for a wireless power transfer system to also transfer data. A system of both power transfer and two-way data transfer is known as Wireless Powered Communication.

[0091] An embodiment could comprise of a main power transfer through slip rings, which has the lowest power loss, and a wireless connection for data transmission.

[0092] Depending on the requirements of the embodiment, micro controller units can be integrated as part of both the inner and outer slewing ring. Micro controllers are integrated in many products for monitoring and control. Micro controller systems can comprise of for instance motors, antennas, light emitting components, speakers, actuators, switches, gyroscope, ultrasound sensor, temperature sensor, infra red sensor, LiDAR sensors, image sensors such as RGB cameras, and many other types of sensors.

[0093] If needed, batteries can be integrated on both of the inner and outer slewing ring. Depending on the use, charging pads may be mounted for battery recharge.

[0094] Each outer or inner slewing ring can be provided with flanges to achieve structural strength or to create means of fastening for mounting purposes.

[0095] Regardless of the embodiment, any slewing ring can comprise of a housing ability, where additional parts of the embodiment are installed and protected as a combined unit or part.

[0096] Any embodiment may be provided with holes or recesses for any purpose, such may be lubrication of bearing rows or to fit gears or sensors of any kind.

[0097] If it is required of an embodiment, it can be provided with suspension. Such suspension can be arranged as part of the inner or outer slewing ring and comprise of flexible material, spring arrangements, hydraulic suspension or pneumatic suspension or any other kind.

[0098] The compact slewing ring bearing is particularly useful for the kind of wheel units, such as caster wheels having the bearing for vertical rotation arranged around the wheel.

[0099] A wheel unit comprises a slewing ring of the present invention, a wheel yoke mounted on the inner slewing ring, a hub and a wheel. The vertical rotational axis of the slewing ring bearing may have a horizontal offset from the horizontal rotational axis of the wheel. Hereby the wheel unit will be able to passively change direction to follow the direction of the vehicle upon which it is mounted.

[0100] Caster wheels are subject to high axial thrust. A passively turning caster wheel with a vertical rotational bearing surrounding the wheel will receive lesser axial moment thrust than traditional caster wheels. However, in situations of change of directional or impact against obstacles significant axial thrust will occur, which a slewing ring must withstand.

[0101] The principles of the present invention allows for a wheel unit to carry high loads, with thrust from a main direction. The axial bearing of the slewing ring may even be of a stronger type than the radial bearing since the main direction remains constant. The radial thrust will be limited and the main purpose for the radial bearing is to keep the slewing ring together and receive axial moment, which requires the radial bearing to be strong nevertheless.

[0102] If the slewing ring is arranged below the rotational axis of the wheel, it would be space saving if the slewing ring was flipped with the axial bearing facing towards the drive surface. In this scenario the wheel yoke should be mounted as part of the outer slewing ring and the inner slewing ring should be mounted as part of the vehicle. In any system where the present invention has a flipped axial direction, and the load is applied to the inner slewing ring, the outer ring is subject to be combined with a stationary part.

[0103] The inner slewing ring can comprise of the wheel yoke, making a solid combined part which will save assembly time and achieve a stronger construction.

[0104] A wheel unit could comprise of any suitable number of wheels. Two wheels arranged symmetrically in relation to the drive direction and on the same axis would perform well, as they can spin in opposite directions when the wheel is changing direction.

[0105] For robotic purposes a wheel unit may be upgraded with additional technologies. A wheel unit with an encoder would be able to sense the direction of the wheel, which would be useful for a robotic system to know. If further technologies are added, it might be beneficial to reduce or remove the horizontal offset between the vertical rotation of the slewing ring and the horizontal rotation of the wheel. In this way a transmission gear or similar ability to change the direction of the wheel would not cause positional displacement of the vehicle. A transmission gear may make use of a gear ring as part of any of the outer or inner slewing ring, and the transmission gear as part of the opposite slewing ring. A transmission gear mounted on the inner slewing ring would save space on the outside.

[0106] An alternative to a gear transmission could be a motor ring of suitable type. DC servo and stepper motors are the most precise and easiest to control with micro rotations and accuracy.

[0107] A slewing ring for a wheel system can be arranged with slip rings for transfer of electric power and electric signal. Both electric power and electric signal can be transferred by wireless technologies like previously explained. Depending on the needs, a solution could be having a main power transfer through slip rings, which has the lowest power loss, and a wireless connection for data transmission.

[0108] Any wheel arrangement can be provided with motor for wheeled propulsion. Such motor can be of any AC or DC type, but as previously mentioned servos and steppers are the types for best control. Hub motors, which are motors integrated in the wheel with either direct drive or planetary gears, are a reliable and compact choice, the stator is part of the inside of the wheel, and the rotor on the outside. Most motors for such a purpose would need a motor controller as part of the circuit. Any type of gear can be provided between the wheel and chosen motor. Multiple wheels can each be provided with motors.

[0109] Wheels with or without motor may benefit from having an encoder unit as part of the wheel to sense the rotational speed of the wheel. This is crucial to many robotic systems in relation to monitoring own movement. Such encoders are normally part of the hub mounted on the wheel and the axel.

[0110] It would be necessary for a robotic wheel to comprise of, or be connected hardwired or wireless to, a micro controller computer in order to control movement and other actions. A micro controller could be arranged as part of both the outer and inner slewing ring, or the micro controller could be in circuit with several wheels and other components of a larger system. A larger system would benefit from its own power supply. If needed a wheel yoke can be provided with a battery as an addition or alternative to electric power transfer. Such a battery can have charging pads and be replaceable.

[0111] A gyroscope would contribute with the ability to sensor the position of the wheel, both in relation to the level of the surface on which the vehicle is driving and navigational velocity.

[0112] A wheel may be given one or more light sources. Both for navigational purpose or as a way to make surroundings aware of the presence of the vehicle.

[0113] A wheel unit comprising the present invention may comprise screens for protection or for sanitary reasons. Further, any known type of brakes may be added to a wheel units comprising the present invention.

[0114] A wheel unit can comprise of only one single wheel, which by its construction is balanced to be standing passively. Such a system would have the slewing ring bearing for vertical rotation arranged below the horizontal rotational axis of the wheel. The inner slewing ring and wheel yoke can be given any type of shielding screens to protect the wheel all over or just in specific areas, both above and beneath the slewing ring. Such a wheel unit could benefit from having an outer slewing ring with a surface resembling a tire, placed in an area were the tire surface would gain contact to the ground if the wheel tilted enough. This would contemporarily make the vehicle two-wheeled. Such an addition would also function as a bumper for impact. A single wheel vehicle could be provided with means of fastening upon the outer slewing ring. Hereby a one-wheel-vehicle would be able to be mounted as part of a larger vehicle, an be released as an independent vehicle. A single wheel vehicle may have several coaxial wheels and may have hollow wheel hubs.

[0115] A system may comprise of two self-balancing wheels of any embodiment having a platform or similar chassis keeping the wheels connected. Such a system would be self-balancing on only two wheels. Vehicle types comprising wheel units of the caster wheel type might be: Trolleys, suitcases, walkers, robots, toys, RC vehicles, automotive transports, pallet stackers, pallet jacks, generic vehicles, cabinets, mobile equipment, bikes of any type, furniture.

[0116] In general, the most common bearing types are: Plain bearings, ball bearings, roller bearings, flexure bearings, tilting pad bearings, fluid bearings and magnetic bearings.

[0117] The most cost-efficient bearings are rolling element bearings or plain bearings.

[0118] Rolling elements are most commonly made from hardened steel alloys, where spherical balls or rollers are fixed with equal distance in cages and rolling within bearing raceways.

[0119] The most common rolling element bearing is the ball bearing, which most often is arranged as: ball bearing of the groove type (also called groove ball bearing or deep groove ball bearing) or angular contact ball bearing.

[0120] Bearing rollers vary in shape to fit different needs. Needle rollers are cheap cylindrical rollers, which are good at evening the distribution of thrust. Tapered rollers are conical in shape to even the rotational speed of the roller surface in relation to the bearing raceway. Spherical rollers or barrel rollers are shaped to fit the assembly process and even the distribution of thrust when in use.

[0121] Plain bearings or sliding contact bearings are bearings, where low-friction motion is achieved by plain surfaces sliding against each other due to properties of selflubricating materials, general lubrication or due to difference in material properties thus achieving sliding abilities when exposed to thrust.

[0122] An embodiment may be provided with either fluid bearings, magnetic bearings or tilting pad bearings, however these bearing types are intended for extremely high speeds, and a swirling bearing for caster wheels rarely spins fast. The wheel itself may have high speed, but the change in direction is limited. The strongest type of bearing, as the applied weight load is direct vertical thrust load, would be an axial bearing.

[0123] The bearing is exposed to some amount of radial thrust, however axial moment forces are far greater than the radial forces. This supports the requirement for the second outer bearing race to be provided with a bearing raceway, thus ensuring low-friction rotation in scenarios of directional change or sudden change in thrust of load, such as in active driving situations.

[0124] An axial bearing may be of any suitable type, preferably of rolling elements or sliding contact.

[0125] A ball bearing may be a ball bearing of the groove type (also called groove ball bearing or deep groove ball bearing) or an angular contact axial bearing, both types capable of receiving radial forces. Other preferable axial bearing types may be roller bearings, such as tapered rollers or barrel rollers.

[0126] Needle rollers are cheap, however the forces applied to a multidirectional caster wheel may be dynamic and consist of a variety of axial and radial forces. Needle rollers might need additional radial support. Such needs may be solved by additional bearing raceways.

[0127] A sliding contact bearing or plain bearing may be adapted with a curvature to receive radial forces.

[0128] The bearing type of the first and the second outer race may be of the same or of a different type, like an embodiment comprising a first outer race provided with a ball bearing raceway and a second outer race provided with a sliding contact bearing raceway.

[0129] The bearing race or raceways of the first and second outer race may be a bearing common to both races, such as if each race comprises one fourth of a four point contact bearing. An angular axial raceway of the second outer bearing race may be correlating an angular axial bearing raceway of the first outer bearing race, thus completing a combined radial bearing raceway. Such an assembly will allow a rolling element radial bearing to be loaded with maximum capacity of rolling elements.

[0130] In a preferred embodiment the raceway of the first outer race faces the drive surface, thus the second outer race is installed form the direction intended to face the drive surface.

[0131] The inner bearing race comprises bearing raceways equal to and correlating any bearing raceway of the outer bearing races. Thus, any thrust applied to the outer races will be transferred to the inner race.

[0132] The inner race may be provided with additional inner races if needed.

[0133] Bearing cages are crucial parts of bearings. Cages keep rolling elements fixed with equal spacing and cages ensure that a bearing will stay in its working arrangement and not fall apart.

[0134] Cages may be made from various materials like metal alloys and polymers. The shapes, sizes and rolling element capacity is often determined by the assembly process of the bearing.

[0135] In a preferred embodiment, the bearing comprises at least one cage adapted to separate the rolling elements.

[0136] Alternatives to cages may be individual spacers. Such spacers are common to four point contact bearings.

[0137] To protect a bearing from its environment, bearing seals are used to keep contamination out, and further to keep lubrication within. Bearing seals are often made from flexible materials and often in combination with hollow discs of a harder material. Variations of cages are made with in-build seals as a combined part.

[0138] Bearing shields are often made from metal and are designed to withstand impacts and protect the bearing mechanisms. Shields are arranged between the races and cover the gaps, where a cage or seal is not efficient.

[0139] In highly contaminated environments labyrinth seals are often used to protect axial bearings. Labyrinth seals are non-contact mechanical shields which though a narrow corridor with shifting path of correlating tongue and groove arranged on each bearing race, makes it difficult for dust, dirt and debris to enter an axial bearing. Labyrinths are often combined with seals of flexible materials.

[0140] Different bearing races may be made from different materials. One race may be made from a material chosen for its high hardness and wear resistance, while another would be chosen for its excellent low-frictional properties to reduce energy loss during rotation.

[0141] Steel based alloys often used in bearing manufacturing are high carbon chromium bearing steel, carburizing steel and stainless steel.

[0142] Titanium alloys are used for bearings requiring high strength and high corrosion resistance.

[0143] Any bearing race may be made from ceramic materials like silicon nitride, alumina oxide, zirconia oxide or silicon carbide.

[0144] In a preferred embodiment, at least one bearing race is made from self-lubricating material.

[0145] Other metal alloys used for bearings would among others be aluminum, copper, indium, tin, lead, silver, gold, brass, babbitt or sintered bronze and iron, which are suitable due to their self-lubricating properties. Any inner or outer bearing race may comprise metal salts, such as sulfides, selenides, chlorides, iodides, oxides or hydroxides, which are suitable due to their self-lubricating properties.

[0146] Any bearing race may be made from or comprise of glasses such as boron oxide, silicates or phosphates, which are beneficial for the self-lubricating properties.

[0147] In a preferred embodiment any inner or outer race may be manufactured from polymers.

[0148] At least one bearing race may be made from plastic materials like polyether ether ketone (PEEK), which is used for bearings that need to be lightweight and resistant to corrosion.

[0149] Any bearing race may be made from polytetrafluoroethylene (PTFE) or linear polyethylene (PE), which are suitable due to their self-lubricating properties.

[0150] A preferred embodiment of the invention may have any inner or outer races or raceways made from pressed sheet metal.

[0151] Yet another preferred embodiment may have races or raceways made from one or more materials molded into any suitable polymer or metal alloy. Hereby combining into a common composite race.

[0152] In a preferred embodiment, the bearing comprises a lubricant.

[0153] The bearing may be lubricated with petroleum-based oils, which are advantageous for their high lubricity and cooling capabilities.

[0154] The bearing may be lubricated with synthetic oils. These lubricants are advantageous for their high-temperature stability and long service life. The bearing may be lubricated with greases, which are advantageous for their ability to stay in place and provide long-term lubrication.

[0155] The bearing may be lubricated with dry lubricants like graphite or boron nitride. These lubricants are beneficial for reducing friction in harsh conditions where grease and oil will not work, such as radioactive or vacuum environments.

[0156] The bearing may be lubricated with solid film lubricants, which are advantageous in conditions with very high or very low temperatures.

[0157] The first outer race may be part of a larger body or arranged with any type of fasteners, brackets or similar arrangements.

[0158] Any bearing race may comprise of independent bearing raceways, thus allowing for raceways to be made from different materials than the races themselves. This is cost-effective if a race is made from injection molded polymer and the raceway is made from metal.

[0159] The wheel is adapted for rotation around a central axle. The axle is connected to the inner race by a wheel yoke. The central axle itself may be adapted for rotation.

[0160] The wheel yoke may be an integrated part of the inner race or connected to the inner race in any suitable way.

[0161] The wheel yoke or the inner race may be the base of additional added functions, such as sensors.

[0162] Caster wheel tires are made from materials chosen for their properties to drive under certain conditions and in curtain environments. The majority of caster wheel tires are made from polymers; however steel or aluminum alloys are used when exceptional strength or temperature resistance are required. In a preferred embodiment a caster wheel tire may be made from polyurethane- elastomer, which is beneficial due to low rolling friction and high toughness towards rifts and cuts.

[0163] In another preferred embodiment at least one caster wheel tire is made from solid rubbers like thermoplastic rubber elastomer or silicone-elastomer, which are advantageous for their strength and low rolling resistance.

[0164] In an embodiment of the invention at least one wheel tire may be arranged with pneumatic rubber tires, which are light weight and gentle to ground surfaces.

[0165] An embodiment intended for cleanroom environments may be made from thermoplastic polyurethane.

[0166] In a preferred embodiment at least one wheel tire is made from polypropylene or polyamide, which are beneficial due to their chemical resistance. Another advantage of polypropylene and polyamide is the option of manufacturing the wheel tire and rim as a single injection molded part.

[0167] Combined rims and tires intended for high heat environments may be made from fenolplastic, which is heat resistant but is in lag of driving performance on uneven surfaces.

[0168] Any wheel system may be arranged with a brake device, which will block one or more wheels when activated. Such breaks are common on caster wheels and advantageous when a vehicle is required to be fixed from running.

[0169] In a preferred embodiment a brake device may block at least one wheel tire.

[0170] In another preferred embodiment a brake device may block at least one wheel rim.

[0171] In yet another preferred embodiment at least one outer race or wheel rim is arranged with a brake disc. An embodiment may be adapted with a brake which blocks the swirling bearing from changing the direction of the caster wheel.

[0172] An embodiment may be provided with a levering, which comprises a leg part, which may be activated to gain contact to the drive surface. Such levering may even lift the caster from the drive surface.

[0173] The caster wheel offset is the horizontal distance between the vertical rotational axis of the caster bearing and the horizontal rotational axis of the wheel. This allows for the caster to change direction together with the vehicle on which it is attached and run along in a new direction.

[0174] The offset influences the diameter of a swirling bearing of a low-profile caster wheel.

[0175] An offset which is too short will cause the caster to flutter and repeatedly swing from side to side. The flutter may be reduced by the use of multiple wheels, as the swinging will be stabilized, thus a shorter offset and hereby a smaller enclosing bearing may provide good driving abilities.

[0176] In the field of robotics and automated systems more advanced technologies are often required to control motion in various ways.

[0177] Encoders are devices used for monitoring speed and direction of rotation. Encoders comprise of a code ring and a sensor to read the code. Code rings are provided with a pattern or similar readable details, which the sensor can detect and transmit for the determination of the circular position and the rotational speed of the code ring. Encoders are classified as either mechanical, optical, magnetic or electromagnetic induction. Further, the output of the sensor is either absolute or incremental. An absolute signal is preferred to determine position, which is crucial in robotics.

[0178] Another embodiment may be arranged with vision-based monitoring of rotational position. Directionally controlled applications like mobile robots, would benefit from an embodiment being arranged with a row of gear teeth concentric to the bearing raceways. Such gear transmission may be of any suitable type like a spur gear, helical gear, bevel gear, worm gear or magnetic gear. Hereby enabling directional control of the wheel. A gear may be powered by any type of motor. Electric servo or stepper motors a preferable.

[0179] A gear ring be mounted to the inner race or the inner race may be adapted with a gear as at part of the race.

[0180] In another preferred embodiment a gear may be operated by a gear belt.

[0181] An alternative powered transmission could be the use of a motor ring. A motor ring runs by the same physics as ordinary motors, except for the hollow core. Both AC and DC motors can be adapted to fit within a swirling bearing. AC / DC servo and DC stepper motors are the most precise and easiest to control with micro rotations and accuracy. Motor controllers are required for use of both servos and steppers.

[0182] A servo motor comprises any type of motor in combination with an encoder to monitor position. Motor type may vary with demands to precision and torque.

[0183] In the field of robotics the invention is further advantageous for powered omnidirectional drive. In such embodiments the swirling bearing may be arranged with means for transfer of electric power and signal.

[0184] A preferred embodiment of a caster wheel system may have the swirling bearing arranged with at least one conductive ring for wireless transmission of power or signal. Such conductive rings and correlating conductive contacts is advantageous for powering drive wheels, various sensors, gear motors, brake systems and PCBs, such as microcontrollers or CPUs.

[0185] Another preferred embodiment of a caster wheel system may have the swirling bearing arranged with an induction ring for wireless transmission of power and signal. An induction system comprising two inductive transceivers is advantageous due to a two-way communication.

[0186] The primary type of wireless data transmission in electronics is radio frequency, which is the basis of technologies like blue tooth, Wi-Fi and cellular communications.

[0187] The three most suitable wireless power transfer technologies would be inductive coupling, resonant inductive coupling and capacitive coupling.

[0188] It is possible for a wireless power transfer system to also transfer data. A system of both power transfer and two-way data transfer is known as Wireless Powered Communication.

[0189] An embodiment could comprise of a main power transfer through slip rings, which has the lowest power loss, and a wireless connection for data transmission.

[0190] A preferred embodiment of a caster wheel system may comprise a microcontroller or PCB such as a CPU or motor driver.

[0191] Any embodiment may comprise of a hollow central axle, which is advantageous due to the ability to have wires and cables passing though the wheel.

[0192] When power and control is transferred to the inner race, means of directional control may be operated from within the swirling bearing. Such arrangement may comprise of at least one smaller gear arranged for rotation as part of the inner race and being in correlation with a gear ring provided to an outer bearing race. Such smaller gear may be powered by any type for suitable motor, like a servo- or stepper-motor. The servomotor is particularly advantageous as it comprises an internal encoder.

[0193] The wheel may be powered by any type of motor. Such motor can be of any AC or DC type, however servos and steppers are the best to control. Hub motors, which are motors integrated in the wheel with either direct drive or planetary gears, are a reliable and compact choice, the stator is part of the inside of the wheel, and the rotor on the outside. Most motors for such a purpose would need a motor controller as part of the circuit. A gear may be provided between the wheel and a chosen motor. Multiple wheels can each be provided with motors.

[0194] Wheels with or without motor may benefit from having an encoder unit as part of the wheel to sense the rotational speed of the wheel. This is crucial to many robotic systems in relation to monitoring its own movement. Such encoders are normally part of the wheel hub mounted on the wheel and the axle.

[0195] A preferred embodiment of a caster wheel system may comprise one or more sensors.

[0196] For the purpose of monitoring position an Inertial Measurement Unit (IMU) which comprises a gyroscope, will measure velocity, orientation, gravitational forces, thus aiding in navigation and control. A position sensor will further aid in determine the precise position in an environment.

[0197] In navigational and orientational aspects a proximity sensor will detect obstacles in path of the wheels; an optical sensor may be used for line tracking and edge detection; an ultrasonic sensor may preform obstacle detection in path of wheels; a laser sensor such as a LiDAR may preform precise distance measurement and obstacle detection; and a magnetic sensor or Hall Effect sensor may detect magnetic fields useful for navigation and positioning.

[0198] A caster wheel system will benefit from a load sensor, which may measure load on wheels and aiding in balancing and optimizing movement.

[0199] To monitor an embodiment of a caster wheel itself a temperature sensor may detect overheating of a motor and other components; a vibration sensor may aid in detecting abnormal vibrations, which might be indicative of mechanical issues; a strain gauge may be measuring deformation or displacement of parts of the device, thus aiding to ensure structural integrity.

[0200] An embodiment of a caster wheel system may benefit from monitoring the environment by an acoustic sensor for change in ambient noise; a pressure sensor for changes in ambient air pressure; and temperature sensor for changes in ambient thermal conditions.

[0201] It is to be understood that a caster wheel system may comprise of any combination of sensors, depending on a specific use of the caster.

[0202] A preferred embodiment of a caster wheel system may comprise one or more batteries.

[0203] Yet another preferred embodiment of a caster wheel system may comprise one or more lights, which are advantageous for vision-based navigation and for hazard indication.

[0204] An embodiment of the invention may be arranged with any type of suspension. Suspension systems often comprise of pneumatic or hydraulic pressurized systems, metal springs or elastic polymers.

[0205] In a preferred embodiment a suspension system is provided between the wheel and the swirling bearing.

[0206] In another embodiment a suspension system is provided between the swirling bearing.

[0207] It is to be understood that additional added technology may be connected to an embodiment by any suitable technique.

[0208] It should be emphasized that the term "comprises / comprising / comprised of" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0209] Brief description of the drawings In the following, the invention will be described in greater detail with reference to embodiments shown by the enclosed figures. It should be emphasized that the embodiments shown are used for example purposes only and should not be used to limit the scope of the invention.

[0210] Fig. 1 illustrates a perspective view of a simple embodiment of a slewing ring bearing for a wheel unit according to an embodiment of the present invention;

[0211] Fig. 2 illustrates a perspective view of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment of the present invention, the slewing ring bearing comprising a radial angular contact bearing;

[0212] Fig. 3 illustrates a perspective view of an embodiment of the slewing ring bearing for a wheel unit according to an embodiment, the slewing ring bearing comprising an inner slewing ring with a plain axial bearing row;

[0213] Fig. 4 illustrates a perspective view of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment comprising an outer slewing ring with a plain axial bearing row;

[0214] Fig. 5 illustrates a perspective view of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment, comprising a radial angular contact bearing row and an axial angular bearing row;

[0215] Fig. 6 illustrates a perspective view of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment, comprising a radial angular contact bearing row and an axial angular bearing row;

[0216] Fig. 7 illustrates a perspective view of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment, comprising an axial roller bearing row; Fig. 8 illustrates a perspective view of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment, comprising an axial tapered roller bearing row;

[0217] Fig. 9 illustrates a perspective view of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment, comprising two individual inner slewing rings;

[0218] Fig. 10 illustrates a perspective view of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment, comprising two individual inner slewing rings having an axial tapered roller bearing row;

[0219] Fig. 11 illustrates a perspective view of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment, comprising an axial roller bearing and a radial tapered roller bearing;

[0220] Fig. 12 illustrates a perspective view of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment, comprising axial and radial roller bearings;

[0221] Fig. 13 illustrates a perspective view of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment, comprising an axial needle roller bearing, a radial roller bearing and a radial angular contact ball bearing;

[0222] Fig. 14 illustrates a perspective view of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment, comprising an axial ball bearing, axial angular contact ball bearing and a radial angular contact ball bearing;

[0223] Fig. 15A illustrates a perspective view of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment, having seals; Fig. 15B illustrates a perspective view of a detail of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment, having seals;

[0224] Fig. 15C illustrates a perspective view of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment, having seals;

[0225] Fig. 16A illustrates a perspective view of an assembly method of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment of the present invention;

[0226] Fig. 16B illustrates a perspective view of an assembly method of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment of the present invention;

[0227] Fig. 17 illustrates a perspective view of an assembly method for an embodiment of a slewing ring bearing for a wheel unit according to an embodiment of the present invention;

[0228] Fig. 18 illustrates a perspective view of an assembly method for an embodiment of a slewing ring bearing for a wheel unit according to an embodiment, comprising two inner rings,

[0229] Fig. 19 illustrates a perspective view of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment, manufactured from sheet metal;

[0230] Fig. 20 illustrates a perspective view of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment, manufactured from bearing race of sheet metal molded into polymer;

[0231] Fig. 21 illustrates a perspective view of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment, comprising a gear ring; Fig. 22 illustrates a perspective view of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment, comprising an encoder ring;

[0232] Fig. 23 illustrates a perspective view of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment, comprising a gear ring and an encoder ring;

[0233] Fig. 24 illustrates a perspective view of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment, comprising an encoder ring, a gear ring and conductive slip rings;

[0234] Fig. 25 illustrates a perspective view of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment, comprising a stepper motor ring;

[0235] Fig. 26 illustrates a perspective view of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment, comprising a gear ring;

[0236] Fig. 27 illustrates a perspective view of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment, comprising a gear ring;

[0237] Fig. 28 illustrates a perspective view of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment, comprising two gear rings;

[0238] Fig. 29 illustrates a perspective view of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment, comprising a gear ring;

[0239] Fig. 30 illustrates a perspective view of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment, comprising a gear ring which is provided as an additional or intermediate inner slewing ring part; Fig. 31 illustrates, in a perspective view, an embodiment of a slewing ring bearing for a wheel unit, the slewing ring bearing comprising layers of slewing rings;

[0240] Fig. 32, in a perspective view, illustrates an embodiment of a slewing ring bearing for a wheel unit according to an embodiment, where an inner slewing ring of the slewing ring bearing is connected to a bracket or flange;

[0241] Fig. 33 illustrates a perspective view of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment, the slewing ring bearing comprising plain bearings, and

[0242] Fig. 34 illustrates a perspective view of an embodiment of a slewing ring bearing for a wheel unit according to an embodiment, the slewing ring bearing comprising plain bearings.

[0243] Fig. 35 illustrates, in a perspective view, a wheel unit according to an embodiment of the invention, where the wheel unit is exemplified as a caster wheel, or caster wheel system:

[0244] Fig. 36 illustrates, in a perspective view, a wheel unit according to another embodiment of the invention;

[0245] Fig. 37 illustrates, in a perspective view, a wheel unit according to yet another embodiment of the invention;

[0246] Fig. 38 illustrates, in a perspective view, a wheel unit according to yet another embodiment of the invention;

[0247] Fig. 39, in a perspective view, illustrates a wheel unit according to an embodiment of the invention, the wheel unit comprising an inner slewing ring and a wheel yoke formed as an integrated unit formed in one piece, for example as an injection molded part, where the wheel unit further comprises two wheels; Fig 40, illustrates, in a perspective view, a wheel unit according to an embodiment of the invention, the wheel unit comprising components for steering / controlling the wheel of the wheel unit;

[0248] Fig. 41 , illustrates, in a perspective view, a wheel unit according to an embodiment of the invention, the wheel unit comprising a drive wheel system;

[0249] Fig. 42, illustrates, in a perspective view, a wheel unit according to an embodiment of the invention, the wheel unit comprising components for steering / controlling the wheel of the wheel unit and a robotic arm.

[0250] Detailed description of the embodiments

[0251] The present invention relates to a wheel unit 39 for example as shown in Fig. 31-40. The wheel unit 39 may form a caster wheel, which could also be called a caster wheel unit.

[0252] The wheel unit 39 comprises a wheel 40, a slewing ring bearing 42, and a wheel yoke 41.

[0253] The slewing ring bearing 42 may be embodied as shown in any of the Figs. 1-30, and described in further detail below.

[0254] As shown in e.g. Fig. 31, the wheel yoke 41 is configured to connect the wheel 40 to the slewing ring bearing 42. The wheel yoke 41 is connected to the wheel 40 via a hub (or wheel hub) 43.

[0255] Further, the the slewing ring bearing 42 comprises connectors 160 for connecting the wheel unit 39 to a vehicle (not shown). Such connectors are e.g. shown in Figs. 37 and 38. Turning now to the slewing ring bearing 42, for example as shown in Fig. 1 , the slewing ring bearing 42 comprises an outer slewing ring 1 , and an inner slewing ring 2.

[0256] The slewing ring bearing 42 further comprises at least one row of axial bearing elements as exemplified in. e.g. Fig. 1-32 or plain sliding contact bearings, for example as shown in Figs. 33-34.

[0257] The slewing ring bearing 42 further comprises at least one row of radial bearing elements. In the embodiment shown in Fig. 1 , the bearing elements are provided as balls.

[0258] As is apparent from Fig. 1 the outer slewing ring 1 comprises a first wall part T and a second wall part 1”.

[0259] The first wall part T of the outer slewing ring 1 is ring-shaped and defines a plane, P. The second wall part 1” of the outer slewing ring 1 comprises a cylindrical portion, which is formed perpendicular to the plane defined by the first wall part T.

[0260] The outer slewing ring 1 is configured as a single integrated unit formed in one piece. Thus, the first wall part 1 ’ and a second wall part 1 ” of the outer slewing ring 1 are as a single integrated unit formed in one piece. This could also be referred to as the outer slewing ring 1 being solid.

[0261] In connection with the present invention the outer slewing ring 1 is solid and provided with an axial bearing race, and a radial bearing race.

[0262] The slewing ring bearing 42 further comprises at least one inner slewing ring 2.

[0263] The outer slewing ring 1 functions as a hollow shell, in which the axial and radial bearing rows are arranged upon the inner axial and radial sides.

[0264] One surface of the first wall T of the outer slewing ring 1 , which surface faces towards the inner slewing ring 2, comprises an axial bearing race, which corresponds to an axial bearing race on the inner slewing ring 2, in the sense that the two races are arranged opposite to and facing each other.

[0265] Another surface provided on the second wall part 1” of the outer slewing ring 1, which surface faces towards the inner slewing ring 2, comprises a radial bearing race, which corresponds to an radial bearing race on the inner slewing ring 2, in the sense that the two races are arranged opposite to and facing each other.

[0266] The respective rows of bearing elements are provided between the respective pairs of axial and radial bearing races.

[0267] As can be appreciated in e.g. Fig. 1, an outer diameter of the inner slewing ring 2 is larger than an inner diameter of the outer slewing ring 1. Thereby, the inner slewing ring 2 is prevented from passing through the ring-shaped outer slewing ring 1 , and is thereby locked in one axial direction when assembled. Further, the second wall part 1” of the outer slewing ring 1 prevents movement in the radial direction when the slewing ring bearing has been assembled.

[0268] When the slewing ring bearing is assembled, the row of radial bearing elements allows receiving radial thrust, and is further being capable of both receiving axial moment thrust and locking the inner slewing ring 2 and the outer slewing ring 1 together. Thus, the row of radial bearing elements forms a lock for connecting the inner slewing ring and the outer slewing ring.

[0269] This arrangement of the slewing ring bearing allows for easy installment of bearing elements between the inner slewing ring 2 and the outer slewing ring 1 and thereby decreases the manufacturing time of the wheel unit 39.

[0270] During assembly of the slewing ring bearing 42, first an axial bearing row is installed towards the axial bearing race of the outer slewing ring. The further assembly process may vary, but an inner slewing ring is installed together with a radial bearing row. The radial bearing row is of a kind, which will help to lock the inner slewing ring in place, within the outer shell. The bearing races of each of the inner and outer slewing ring 2, 1 will always be concentric as they are integrated in the same solid body.

[0271] The solid outer slewing ring 1 is a compact, strong and cheap solution, which will provide for a very robust slewing ring bearing 42, and consequently for a very robust wheel unit 39.

[0272] Further, the design of the outer slewing ring 1 of the slewing ring bearing 42 as single body, which is not kept together by fasteners, allows for a using less material, compared to extra material thickness around fasteners. The absence of fasteners is a strong advantage when a compact construction is needed.

[0273] The solid outer ring further benefits in relation to tolerances since the absence of fasteners reduces complexity of assembly. Tolerances are in general of high importance regarding bearings and slewing rings.

[0274] Now returning to Figs. 31-40, it will be appreciated that the wheel 40 is rotatable relative to the wheel yoke 41 about a rotation axis of the wheel 40. The rotation between the wheel yoke 41 and the wheel 40 is provided by the hub 43.

[0275] Further, the yoke 41 and wheel 40 is rotatable relative to the slewing ring bearing 42.

[0276] This rotation is provided between the rows of bearing elements provided between outer slewing ring 1 and the inner slewing ring 2.

[0277] In some embodiments, and as shown throughout the figures, the wheel yoke 41 is a fork, with one leg on each side of the wheel 40. Such a fork could also be called a wheel fork.

[0278] In the embodiments shown in the Figs. 31-40, the slewing ring bearing 42 is arranged to surround a portion of the wheel. It will however be appreciated that in other embodiments (not shown) the slewing ring bearing 42 may be arranged outside of the largest diameter of the wheel 40. The slewing ring bearing 42 can be arranged around the wheel 40 at any horizontal level (relative to the hub 43 of the wheel yoke and wheel) suitable for the desired use of the wheel unit 39.

[0279] In some embodiments, and as shown in Figs. 31 and 35-40 the slewing ring bearing 42 to be arranged to be located above the hub, when the wheel unit is mounted on the vehicle.

[0280] The slewing ring bearing 42 may comprise connectors 160 for connecting the wheel unit to a vehicle The connectors 160 may be arranged on an upper surface of the slewing ring bearing 42. Thus, the connectors 160 for connecting the wheel unit to a vehicle may arranged to allow the slewing ring bearing to be arranged above the hub, when the wheel unit is mounted on the vehicle.

[0281] This will allow the wheel unit to be mounted on a vehicle or other object in such a way that a good clearance between a lower side of the vehicle or other object and ground may be obtained.

[0282] In an alternative embodiment, the slewing ring bearing 42 to be arranged to be located above the hub 43, when the wheel unit 39 is mounted on the vehicle.

[0283] The connectors 160 for connecting the wheel unit 39 to a vehicle may be arranged to allow the slewing ring bearing 42 to be arranged below the hub 43, when the wheel unit 39 is mounted on the vehicle

[0284] This will allow the wheel unit to be mounted on a vehicle or other object in such a way that a very small clearance is provided between a lower side of the vehicle or other object and the ground.

[0285] In any of the previously mentioned embodiments, the wheel yoke 41 may be connected to the inner slewing ring 2, such as shown in Figs. 31 , 32, 36-40. In such embodiments, the optional connectors for connecting the wheel unit 39 to a vehicle are provided on the outer slewing ring 1. Alternatively, and as shown in Fig. 33, the slewing ring bearing 42 is arranged “upside-down” around a wheel 40 for the purpose of vertical rotation of the wheel. In such embodiments, the inner slewing ring 1 is connected to the wheel yoke 41. Again, the wheel yoke 41 is connected to the wheel though the hub 43, 44. Further, in these alternative embodiments, the connectors for connecting the wheel unit 39 to a vehicle are provided on the inner slewing ring. Thus, a load from the vehicle to which the wheel unit is mounted, is applied upon the inner slewing ring of such a wheel unit 39.

[0286] In further embodiments of the latter, and as shown in Fig. 33, the connectors for connecting the wheel unit may be provided on a load carrying bracket 36, which is connected to the inner slewing ring 2 and extending radially outward from the inner slewing ring 2. The bracket 36 is shown in Fig. 33, the connectors for connecting the wheel unit are not.

[0287] It will be appreciated that in further embodiments, as illustrated in Fig. 39, the wheel unit 39 may comprise two or more wheels connected to the wheel yoke 41. In such case naturally the wheel yoke is adapted for the number of wheels 40.

[0288] In some (not shown) embodiments, the wheel unit may be provided with a motor arranged in the wheel. In embodiments where the wheel unit comprises more than one wheel - as described in the previous paragraph - one, some or all of the wheels may comprise a motor. Such a motor (or motors) may be used as drive for the vehicle on which one or more such wheel units are arranged.

[0289] Referring now to e.g. Fig. 37 and 40 the wheel unit 39 may further comprise a motor for turning the wheel relative to the slewing ring bearing 42.

[0290] Fig. 1 illustrates a perspective view of an embodiment of a slewing ring bearing 42 for a wheel unit of the present invention, the slewing ring bearing 42 having cross section cuts to show the inner construction. An outer slewing ring 1 is provided with deep groove type bearing races 7,8 to contain both axial 3 and radial 4 rolling elements, illustrated in this embodiment being bearing balls 3,4. The axial bearing balls 3 are fixed with equal distance in an axial bearing cage 5, and the radial bearing balls 4 are fixed with equal distance in an axial bearing cage 6. An inner slewing ring 2 is provided with equal bearing race 7,8 as the outer slewing ring 1.

[0291] Fig. 2 illustrates a perspective view of an embodiment of a slewing ring bearing 42 for a wheel unit of the present invention, the slewing ring bearing 42 having cross section cuts. An outer slewing ring 1 is for the axial bearing race 7 provided with a groove (also sometimes called deep groove). Further the radial bearing race 9 is an angular contact bearing, which is better at handling opposite moment forces. Both the axial 3 and radial 4 rolling elements are bearing balls 3,4. The axial bearing balls 3 are fixed with equal distance in an axial bearing cage 5, and the radial bearing balls 4 are fixed with equal distance in an axial bearing cage 6. An inner slewing ring 2 is provided with equal bearing race 7,9 as the outer bearing ring 1.

[0292] Fig. 3 illustrates a perspective view of an embodiment of a slewing ring bearing 42 for a wheel unit of the present invention, the slewing ring bearing 42 having a radial bearing race 9 comprising bearing balls 4. The axial bearing race of the outer slewing ring 1 is a bearing race 7 of the groove-type, however the axial bearing race of the inner slewing ring 2 is a plain bearing race 10. By having a plain bearing race 10 for one of the axial races it is easier to assemble the embodiment by allowing the inner slewing ring 2 to slide against the axial bearing balls 3.

[0293] Fig. 4 illustrates a perspective view of an embodiment of a slewing ring bearing 42 for a wheel unit of the present invention, the slewing ring bearing 42 having a radial bearing 9 comprising bearing balls 4. The axial bearing race 7 of the inner slewing ring 2 is a bearing race of the groove type, and the axial bearing race of the outer slewing ring 1 is a plain bearing race 10. The plain bearing race 10 of the axial race of the outer slewing ring 1 allows for an easier assembly of the embodiment by allowing the inner slewing ring 2 to hold the axial bearing balls 3 while these balls slide against the plain bearing row 10 of the outer slewing ring 1.

[0294] Fig. 5 illustrates a perspective view of an embodiment of a slewing ring bearing 42 for a wheel unit 39 of the present invention, the slewing ring bearing 42 comprising a radial angular contact bearing 4,9 and an axial angular contact bearing 3,11. The axial angular contact bearing 3,5, 11 improves the assembly of embodiments with a reduced diameter, since the axial angular contact bearing race 11 of the inner slewing ring 2 is in less conflict with the axial bearing race 7 of the (deep) groove type bearing row. Further, this design remains strong in a scenario of an axial angular contact bearing 11 assisting to handle radial forces.

[0295] Fig. 6 illustrates a perspective view of an embodiment of a slewing ring bearing 42 for a wheel unit 39 of the present invention, the slewing ring bearing 42 comprising a radial angular contact bearing 9 and an axial angular contact bearing 11. This figure shows how close the present invention may get to prior art regarding the use of two bearing rows 3,4. The main detail which distinguishes this embodiment from a classic double angular contact bearing design is the prevention of the inner slewing ring 2 to pass though the outer slewing ring 1 , due to the axial bearing races 11.

[0296] Fig. 7 illustrates a perspective view of an embodiment of a slewing ring bearing 42 for a wheel unit 39 of the present invention, the slewing ring bearing 42 comprising an axial roller bearing 5,11,12,13. The axial rollers 12 are fixed in a cage 5, and further circularly aligned by an axial roller bearing race 13 provided upon an outer slewing ring 1. An inner slewing ring 2 is provided with a plain axial bearing race 10 to enable a sliding ability of the inner slewing ring 2 during assembly.

[0297] Fig. 8 illustrates a perspective view of an embodiment of a slewing ring bearing 42 for a wheel unit 39 of the present invention, the slewing ring bearing 42 comprising an axial tapered roller bearing 10,14,15. The axial tapered rollers 14 are fixed in a cage 5, and further circularly aligned by an axial tapered roller bearing race 15 provided upon an inner slewing ring 2. An outer slewing ring 2 is provided with a plain axial bearing race 10 to enable a sliding function of the tapered roller bearing 5,10,14,15 and the inner slewing ring 2 during assembly. The figure further shows the outer slewing ring 1 being closed off by not having a hole through the center.

[0298] Fig. 9 illustrates a perspective view of an embodiment of a slewing ring bearing 42 for a wheel unit 39 of the present invention, the slewing ring bearing comprising two separate inner slewing rings 19,20. Due to the geometries, it is necessary for the inner slewing ring 19,20 to be able to slide apart during the assembly process. This enables the embodiment to achieve higher tolerances of the bearing rows 7,9. When the separate inner rings 19,20 are fixed in placed, they are combined by means of fastening 17.

[0299] Fig. 10 illustrates a perspective view of an embodiment of a slewing ring bearing 42 for a wheel unit 39 of the present invention, the slewing ring bearing 42 comprising an axial tapered roller bearing 5,14,15 which requires a dividing of the inner slewing ring 19, 20, in order to achieve assembly. The embodiment is equipped with accesses for lubrication 32, and is showing a tall version of the present invention.

[0300] Fig. 11 illustrates a perspective view of an embodiment of a slewing ring bearing 42 for a wheel unit 39 of the present invention, the slewing ring bearing 42 comprising an axial roller bearing 10,12,13, wherein the inner slewing ring 2, due to the plain axial bearing race 10, is able to slide against the axial rollers 12 during assembly. The embodiment further comprises a radial tapered roller bearing 6,23,24 which is provided with an angel which allows the bearing to keep the product together, while facilitating an ability of continued rotation when the embodiment is affected by moment forces.

[0301] Fig. 12 illustrates a perspective view of an embodiment of a slewing ring bearing 42 for a wheel unit 39 of the present invention, the slewing ring bearing comprising an axial roller bearing 5,12,13, and a radial roller bearing 6,18,22. The inner slewing ring 19,20 comprises a first inner slewing ring 19, installed with the axial roller bearing parts 5,12,13, and a second inner slewing ring 20 installed with the radial roller bearing parts 6,18,22. The inner slewing rings 19,20 are finally combined by means of fastening 17.

[0302] Fig. 13 illustrates a perspective view of an embodiment of a slewing ring bearing 42 for a wheel unit 39 of the present invention, the slewing ring bearing 42 comprising an axial needle roller bearing 5,13,37 installed between an outer slewing ring 1 and a first inner slewing ring 19, further a radial roller bearing 6,18,22 installed between the said outer slewing ring 1 and a second inner slewing ring 20, and a radial angular contact ball bearing 4,6,9 installed between said outer slewing ring 1 and a third inner slewing ring 21. The inner slewing rings 19,20,21 are combined by means of fastening 17.

[0303] Fig. 14 illustrates a perspective view of an embodiment of a slewing ring bearing 42 for a wheel unit 39 of the present invention, the slewing ring bearing 42 comprising a first inner slewing ring 19, provided against a outer slewing ring 1, with an axial ball bearing 3,5,7 of the groove type, and an axial angular contact ball bearing 3,5,11. Further a second inner slewing ring 20 is provided against said outer slewing ring 1 with a radial angular balls bearing 4,6,9. Said first and second inner slewing rings 19,20 are combined by means of fastening. The embodiment is further provided with a flange 61 to achieve higher strength and shielding of the axial bearing 3,5,7.

[0304] Fig. 15A illustrates a perspective view of a detail of an embodiment of a slewing ring bearing 42 for a wheel unit 39 of the present invention, the slewing ring bearing 42 comprising an axial ball bearing 3,5,7, of the groove type and a radial ball bearing 4,6,8 of the grove type. The outer gap of the axial ball bearing 3,5,7 of the groove type is provided with an axial bearing seal 25 to protect the inner mechanics from various foreign elements. For similar seasons the radial ball bearing 4,6,8 of the groove type is provided with a radial bearing seal 26. Such seals 25,26 may be of further use of keeping lubrication inside the bearing constructions. Further the embodiment is provided with a flange 38 at the edge of the outer slewing ring 1 for external installation purposes.

[0305] Fig. 15B illustrates a perspective view of a detail of an embodiment of a slewing ring bearing 42 for a wheel unit 39 of the present invention, the slewing ring bearing 42 comprising an axial bearing 3,5,7 of the ball and groove type and a radial bearing 4,6,8 of the ball and groove type. The outer gap of the axial bearing 3,5,7 of the ball and groove type is provided with an axial bearing seal 25 to protect the inner mechanics from various foreign elements. For similar seasons the radial bearing 4,6,8 of the ball and groove type is provided with a radial bearing seal 26. Such seals 25,26 may be of further use of keeping lubrication inside the bearing constructions. Further the embodiment is provided with a flange 38 at the edge of the outer slewing ring 1 for external installation purposes. Fig. 15C illustrates a perspective view of a detail of an embodiment of a slewing ring bearing 42 for a wheel unit 39 of the present invention, the slewing ring bearing 42 comprising an axial bearing 3,5,7 of the ball and groove type and a radial bearing

[0306] 4.6.8 of the ball and groove type. The outer gap of the axial bearing 3,5,7 of the ball and groove type is provided with an axial bearing seal 25 to protect the inner mechanics from various foreign elements. For similar seasons the radial bearing

[0307] 40.6.8 of the ball and groove type is provided with a radial bearing seal 26. Such seals 25,26 may be of further use of keeping lubrication inside the bearing constructions. Further the embodiment is provided with a flange 38 at the edge of the outer slewing ring 1 for external installation purposes.

[0308] Fig. 16A illustrates a perspective view of a method for assembly of an embodiment of a slewing ring bearing 42 for a wheel unit 39 of the present invention. The axial bearing cage 5 and axial bearing balls 3 are first installed in the axial bearing race 7 of the ball and groove type of the outer slewing ring 1. Then suitable means (not shown) are used to keep the radial bearing balls 4 fixed and close together in the same side of the radial bearing race 8 of the ball and groove type of the outer slewing ring 1. The inner slewing ring 2 is scooped into place connecting the bearing race 8 of the ball and groove type of the inner slewing ring 2 to the radial bearing balls 4, and place the axial bearing race 7 of the ball and groove type of the inner slewing ring 2 against the axial bearing balls 3. Next the radial bearing balls 4 are divided with equal distance with radial bearing race 8 and a radial bearing cage not shown) is installed to fix the radial bearing balls 4.

[0309] Fig. 16B illustrates a perspective view of an assembly method of an embodiment of a slewing ring bearing 42 for a wheel unit 39 of the present invention. The axial bearing cage 5 and axial bearing balls 3 are first installed in the axial bearing race 7 of the ball and groove type of the outer slewing ring 1. Then suitable means (not shown) are used to keep the radial bearing balls 4 fixed and close together in the same side of the radial bearing race 8 of the ball and groove type of the outer slewing ring 1. The inner slewing ring 2 is scooped into place connecting the bearing race 8 of the groove type of the inner slewing ring 2 to the radial bearing balls 4, and place the axial bearing race 7 of the groove type of the inner slewing ring 2 against the axial bearing balls 3. Next the radial bearing balls 4 are divided with equal distance with radial bearing race 8 and a radial bearing cage (not shown) is installed to fix the radial bearing balls 4.

[0310] Fig. 17 illustrates a perspective view of an assembly method for an embodiment of a slewing ring bearing 42 for a wheel unit 39 of the present invention. An axial roller bearing 5,12 is installed in an axial roller bearing race 13 of an outer slewing ring 1. Then the inner slewing ring 2, provided with a plain axial bearing race 10, is placed upon the axial bearing row 5,12. The inner slewing ring 2 slides against the axial bearing rollers 12 to a side, which action enlarges the gap between the outer and inner slewing rings 1 ,2 in the opposite side. Then the radial bearing balls are added to the open radial angular contact bearing race 9. When this is done, the inner slewing ring 2 is moved back in place and the radial bearing balls 4 are distributed equidistantly in the radial angular bearing race 9. Finally, a radial bearing cage (not shown) is installed to fix the radial bearing balls 4.

[0311] Fig. 18 illustrates a perspective view of an assembly method for an embodiment of a slewing ring bearing 42 for a wheel unit 39 of the present invention. An axial ball bearing 5,12 is installed in an axial bearing race 7 of the groove type of an outer slewing ring 1. Then a first inner slewing ring 19, provided with an axial bearing race 7 of the groove type, is placed upon an axial bearing row 3,5. Against the plain surface of the first inner slewing ring 19 a second inner slewing ring 20 is placed. The second inner slewing ring 20 slides on the plain surface to a side, enlarging the gap between the outer and second inner slewing rings 1,20 in the opposite side. The radial bearing balls 4 are then added into the gap of the radial angular bearing race 9. Then the second inner slewing ring 20 is moved back in place and the radial bearing balls 4 are distributed equidistantly in the radial angular bearing race 9. Finally, a radial bearing cage (not shown) is installed to fix the radial bearing balls 4.

[0312] Fig. 19 illustrates a perspective view of an embodiment of a slewing ring bearing 42 for a wheel unit 39 of the present invention, the slewing ring bearing 42 of which is manufactured from sheet metal. Each of the outer and inner slewing rings 1,2 has been manufactured by any known shaping process of sheet metal. Preferred a first step would be to precut a part in a fitting shape. A second step of high-pressure pressing the part to form an axial bearing race 7 along with the cylindric shape of the radial bearing wall, optionally also a strengthening flange 38 upon the outer slewing ring. A third step of rolling the radial bearing wall with a specialized tooling to shape the radial bearing races 8.

[0313] Fig. 20 illustrates a perspective view of an embodiment of a slewing ring bearing 42 for a wheel unit 39 of the present invention, the slewing bearing ring 42 of which is manufactured from bearing races of shaped metal 7,8 molded into polymer. Each bearing race 7,8 of each inner and outer slewing ring 1,2 is manufactured from any suitable basis metal, like pipe or sheet metal, by for instance high-pressure pressing and / or tooled rolling process. Further inserted into an injection molding tool and molded into parts of for instance polymer. Said bearing race 7,8 can be molded into any suitable material.

[0314] Fig. 21 illustrates a perspective view of an embodiment of a slewing ring bearing 42 for a wheel unit 39 of the present invention, the slewing ring bearing 42 comprising a gear ring 27. The embodiment comprises a axial ball bearing 3,5,7, of the groove type and a radial angular contact bearing 4,6,9. The inner slewing ring comprises a first and second ring 19,20, of which the first inner slewing ring 19 is provided with a row of gear teeth 27 upon the outer radial periphery. The inner slewing rings are combined by means of fastening 17.

[0315] Fig. 22 illustrates a perspective view of an embodiment of a slewing ring bearing 42 for a wheel unit 39 of the present invention, the slewing ring bearing 42 comprising an encoder ring 28. Each of the axial 3,5,7 and radial 4,6,8 bearings are of the groove design. Between the bearing rows 3, 4, 5, 6, 7, 8 and upon the radial surface, the inner slewing ring 2 are provided with an encoder ring 28, which comprises a pattern (not shown) of a suitable kind. The outer slewing ring 1 comprises an opening 29 for a sensor (not shown) to be able to read the position of the encoder ring 28.

[0316] Fig. 23 illustrates a perspective view of an embodiment of a slewing ring bearing 42 for a wheel unit 39 of the present invention, the slewing ring bearing 42 comprising a gear ring 27 and an encoder ring 28. The axial 3,5,7 and radial 4,6,8 bearings are of the groove design. Between the bearing rows 3, 4, 5, 6, 7, 8, the inner slewing ring 2 is provided with a row of gear teeth 27 in the radial direction and an encoder ring 28 in the axial direction. An opening 29 in the outer slewing ring 1 allows for a gear transmission connection (not shown) to interact with the inner slewing ring 2 and for a sensor (not shown) to be installed to be able to read the direction of inner slewing ring 2.

[0317] Fig. 24 illustrates a perspective view of an embodiment of a slewing ring bearing 42 for a wheel unit 39 of the present invention, the slewing ring bearing 42 comprising a gear ring 27, an encoder ring 28 and conductive slip rings 30. The axial 3,5,7 and radial 4,6,8 bearings are of the groove design. Between the bearing rows 3, 4, 5, 6, 7, 8 and next the radial bearing 4,6,8, the inner slewing ring 2 is provided with an encoder ring 28 in the radial direction. Next to the encoder ring 28 the inner slewing ring 2 is provided with a gear ring 27 in the radial direction. Between the gear ring 27 and the axial bearing 3,5,7 the inner slewing ring 2 is in the axial direction provided with a set of conductive slip rings 30 for the purpose of conducting electric current to the inner slewing ring 2 from the outer slewing ring 1 through conductive contact 31. For interaction by gear transmission (not shown), encoder reader (not shown) and conductive contacts 31 to the components 27,28,30 of the inner slewing ring 2, the outer slewing ring 1 is provided with an opening 29.

[0318] Fig. 25 illustrates a perspective view of an embodiment of a slewing ring bearing 42 for a wheel unit 39 of the present invention, the slewing ring bearing 42 comprising a stepper motor ring 33,34. The axial bearing is an axial angular contact bearing 3,5,11 and the radial bearing is a radial angular contact bearing 4,6,9. The first inner slewing ring 19 is provided with a permanent magnet rotor ring 33. The two levels of rotor rings 33 are combined but rotated from each other. The outer slewing ring 1 is provided with a suitable series of electric stator coils 34 to facilitate the stepper movement of the permanent magnet rotor ring 33. The stator coils 34 are connected in an electric circuit (not shown), which is controlled by a motor controller (not shown).

[0319] Fig. 26 illustrates a perspective view of an embodiment of a slewing ring bearing 42 for a wheel unit 39 of the present invention, the slewing ring bearing 42 comprising a gear ring 27. The axial 3,5,7 and radial 4,6,8 bearings are of the groove design. Further the inner slewing ring 2 is provided with a row of gear teeth 27 in the inner radial direction.

[0320] Fig. 27 illustrates a perspective view of an embodiment of a slewing ring bearing 42 for a wheel unit 39 of the present invention, the slewing ring bearing 42 comprising a gear ring 27. The axial 3,5,7 and radial 4,6,8 bearings are of the groove design. Further the outer slewing ring 1 is provided with a row of gear teeth 27 in the outer radial direction.

[0321] Fig. 28 illustrates a perspective view of an embodiment of a slewing ring bearing 42 for a wheel unit 39 of the present invention, the slewing ring bearing 42 comprising two gear rings 27. The axial 3,5,7 and radial 4,6,8 bearings are of the groove design. Pointing outwards in the radial direction, two separate gear rings 27 are attached to the inner slewing ring 2 by means of fastening 17, reaching beyond the axial 3,5,7 and radial 4,6,8 bearings on each side of the outer slewing ring 1.

[0322] Fig. 29 illustrates a perspective view of an embodiment of a slewing ring bearing 42 for a wheel unit 39 of the present invention, the slewing ring bearing 42 comprising a gear ring. The axial 3,5,7 and radial 4,6,8 bearings are of the groove design. The outer slewing ring is provided with row of gear teeth 27 arranged on the inner radial surface between the axial 3,5,7 and radial 4,6,8 bearings pointing in an inward radial direction.

[0323] Fig. 30 illustrates a perspective view of an embodiment of a slewing ring bearing 42 for a wheel unit 39 of the present invention, the slewing ring bearing 42 comprising a gear ring. The axial bearing 3,5,7 is of the groove design. Further the embodiment comprises a radial bearing 4,6,8, of the groove design arranged between the outer slewing ring 1 and the first inner slewing ring part 19. A second radial angular contact bearing 4,6,9 is arranged between the outer slewing ring 1 and the second inner slewing ring part 20. Provided upon the outer radial surface of an intermediary inner slewing ring part 21 is a row of gear teeth 27. By having the gear ring 27 arranged between two radial bearing rows 4, 6, 8, 9 gives a transmission (not shown) an improved strength. The inner slewing rings 19,20,21 are combined by means of fastening 17. Fig. 31 , in a perspective view, illustrates an embodiment of a slewing ring bearing 42 for a wheel unit 39 comprising multiple layers of slewing rings. An outer slewing ring 1 is arranged with axial 3,5,7 and radial 4,6,8 groove-type ball bearing against the outer axial and radial surfaces of a combined inner and outer slewing ring 35. The combined inner and outer slewing ring 35 is provided with inner axial and radial bearing races 7,8, and an inner slewing ring 2 is installed within.

[0324] Fig.32 illustrates, in a perspective view, an embodiment of a slewing ring bearing 42 for a wheel unit 39 comprising a bracket 36 for handling load on the inner slewing ring. The embodiment is provided with a bracket 36 intended to transfer load to the inner slewing ring 2 which due to the arrangement of the embodiment transfers the load to the outer slewing ring 1. The bracket 36 comprises connectors 160 in the form of throughgoing bores. This will allow the wheel unit 39 to be connected to a vehicle (not shown). This may be done by slits or bolts interacting with the connectors 160 in the form of throughgoing bores. It will be appreciated that the connectors 160 may be of other types the connectors 160 in the form of throughgoing bores being an example of connectors 160. Further it will be appreciated that connectors 160 may be arranged on the slewing ring bearings 42 of the other of the described slewing ring bearings 42 in a similar manner to allow the wheel unit 39 of the invention to be connected to a vehicle.

[0325] Fig. 33 illustrates, in a perspective view, an embodiment of a slewing ring bearing 42 for a wheel unit 39, the slewing ring bearing 42 comprising plain bearings 10,142,145,147. A plain axial bearing race 10 is arranged between an outer 1 and inner 2 slewing ring. A plain radial bearing race 145 is arranged next to the plain axial bearing race 10. For handling axial moment 142 and to lock the product together a row of plain bearing elements 147 is installed by sliding into place. The plain bearing elements 147 are provided with barb mechanisms 146 to keep the elements 147 in place after installation.

[0326] Fig. 34, illustrates, in a perspective view, an embodiment of a slewing ring bearing 42 for a wheel unit 39 , the slewing ring bearing 42 comprising plain bearings 10,142,145. A plain axial bearing race 10 is arranged between an outer 1 and inner 2 slewing rings. A plain radial bearing race 145 is arranged next to the plain axial bearing race 10. The radial side 143 of the outer slewing ring 1 is prolonged along with the plain radial bearing race 145. From the axial direction, the radial side 143 of the outer slewing ring (1) is provided with large openings which enables a one plane moulding process for plain axial moment bearing races 142. Said plain axial moment bearing races 142 locks the inner slewing ring 2 in place after installation.

[0327] Fig. 35 illustrates a perspective view of a wheel unit 39 in the form of a caster wheel system according to one embodiment of the present invention. The slewing ring bearing 42 of the wheel unit 39 is arranged horizontally around the upper half of a wheel 40. The inner slewing ring 2 is connected to a wheel yoke 41 by means of fastening 17. The wheel yoke 41 is further connected to a wheel hub (not shown), which facilitates spinning of the wheel 40. The rotational center of the wheel 40 has a horizontal offset form the vertical rotational axis of the slewing ring 1 ,2, 3, 4, 5, 6, 7, 8. Hereby the wheel 40 gains the ability to passively change direction following the directional change of a vehicle to which the wheel 40 is mounted (not shown).

[0328] Fig. 36, in a perspective view, discloses a wheel unit 39 according to another embodiment, and in the form of a caster wheel / caster wheel system. The wheel unit 39 comprises a slewing ring bearing 42 according to the present invention. The slewing ring bearing 42 is arranged horizontally around the lower half of a wheel 40. The inner slewing ring 2 of the slewing ring bearing 42 is formed integral with the wheel yoke 41. The wheel yoke 41 is further connected to a wheel hub 43, which facilitates spinning of the wheel 40 relative to the slewing ring bearing 42. The rotational center of the wheel 40 has a horizontal offset form the vertical rotational axis of the slewing ring bearing 42. Thereby, the wheel 40 gains the ability to passively change direction following the directional change of a vehicle to which the wheel 40 is mounted (not shown).

[0329] Even if it is not shown in Fig 36, it will be appreciated that a load carrying bracket 36, similar to the one shown in Fig. 35 or in the next described Fig. 37may be mounted to the outer slewing ring 1. The outer slewing ring 1 transfers thrust to the inner slewing ring 2, which is formed integral with the wheel yoke 41. It will be appreciated that in other embodiments, the wheel yoke 41 may be a separate part from the inner slewing ring 2, such that the two are connectable by suitable means of fastening (not shown). The fork-type wheel yoke 41 is further connected to a wheel hub 43, which facilitates spinning of the wheel 40.

[0330] Fig. 37 illustrates, in a perspective view, a wheel unit 39 according to another embodiment, and in the form of a caster wheel / caster wheel system. The wheel unit 39 comprises a slewing ring bearing 42 according to an embodiment thereof and as exemplified above. In this embodiment of the wheel unit 39, the slewing ring bearing 42 is arranged (horizontally) around the upper half of a wheel 40 of the wheel unit 39. The outer slewing ring 1 of the slewing ring bearing 42 is formed integrally with the wheel yoke 41. It will be appreciated that in other (not shown) embodiments, the outer slewing ring 1 may alternatively be connected to the wheel yoke 41 by suitable means of fastening 17.

[0331] In either case, the wheel yoke 41 is further connected to a wheel hub, which facilitates spinning of the wheel 40 relative to the slewing ring bearing 42. The rotational center of the wheel 40 has a horizontal offset form the vertical rotational axis of the slewing ring. Hereby the wheel 40 gains the ability to passively change direction following the directional change of a vehicle to which the wheel 40 is mounted (not shown).

[0332] Fig. 38 in a perspective view, discloses a wheel unit 39 according to yet another embodiment. The wheel unit 39 comprises a slewing ring bearing 42 according to the present invention. In this embodiment of the wheel unit 39, the slewing ring bearing 42 is arranged (horizontally) around the lower half of a wheel 40 of the wheel unit 39.

[0333] The outer slewing ring 1 of the slewing ring bearing 42 is formed integrally an arm extending to a level above the wheel unit 39 (when mounted). The arm comprises connectors 160 as described above. The connectors 160 are provided on the arm at a level above the wheel unit 39 (when mounted). It will be appreciated that in other (not shown) embodiments, the arm will extend to a level between the level of the rotation axis of the wheel 40 and the uppermost point of the wheel 40. Further, the embodiment of the wheel unit 39 shown in Fig. 38 comprises a wheel

[0334] 40 having a hollow hub 44. Instead, as bearing element formed along the wheel ring is connected to the inner slewing ring 2 of the slewing ring bearing 42 of the wheel unit 39.

[0335] The rotational center of the wheel 40 has a horizontal offset form the vertical rotational axis of the slewing ring. Hereby the wheel 40 gains the ability to passively change direction following the directional change of a vehicle to which the wheel 40 is mounted (not shown).

[0336] Fig. 39, in a perspective view, illustrates a wheel unit 39 according to yet another embodiment of the present invention. The wheel unit 39 comprises a slewing ring bearing 42 according to the present invention. In this embodiment of the wheel unit 39, is arranged (horizontally) around the upper half of a wheel 40. Further, in this embodiment of the wheel unit 39, the inner slewing ring 2 and the wheel yoke 41 are formed integrally as single piece. Thus, the inner slewing ring 2 and the wheel yoke

[0337] 41 forms a combined inner slewing ring and wheel yoke 45. Further, the wheel unit 39 is this embodiment comprises two or wheels 40 connected to the wheel yoke 41. In such case naturally the wheel yoke is adapted for the number of wheels 40.

[0338] Fig. 40 illustrates a perspective view of a drive wheel system 39 comprising an embodiment of the present invention. The embodiment is arranged horizontally around the upper half of a wheel 40. The inner slewing ring 2 comprises a first inner slewing ring part 19 and a second inner slewing ring part 20. The inner slewing ring 2 is provided with conductive slip ring 30 and an encoder ring 28. Further, the inner slewing ring 2 is mounted to a wheel yoke 41. The outer slewing ring 1 is provide with a gear ring 27 on the inner radial wall. A transmission gear 47, which is controlled by a gear motor 48, controls the direction of the inner assembly 2,28,30,40,41,47,48. Each motor 48,48 are controlled by a motor controller (not shown), which again are controlled by a micro controller computer (not shown).

[0339] Fig. 41 illustrates a perspective view of a drive wheel system 39 similar to Fig. 40. The inner slewing ring 2 is mounted to a wheel yoke 41 , and the wheel yoke 41 is provided with a wheel motor 33,34,46, said motor facilitates propulsion of a wheel 40. The propulsion system of the drive wheel 40 comprises a series of stator coil units 34 provided in a ring to an inner stator part of the wheel 40 and a corresponding series of permanent magnets 33 provided in a ring to an outer rotor part of the wheel 40. The wheel 40 is mounted is mounted to the wheel yoke 41.

[0340] Fig. 42 illustrates a perspective view of a drive wheel system 39. Further the drive wheel system 39 comprises a robotic arm 74, which is mounted on a second slewing ring 1 ,2,42. The outer slewing ring 1 ,2 of the drive wheel 39 is adapted as an inner slewing ring 2 of the second slewing ring 1,2,42. The second slewing ring 1 ,2,42 is provided with a gear ring 27 on the outer radial wall of the inner slewing ring 2. The position of the robotic arm 74 is manipulated by a transmission gear 47 which is driven by a gear motor 48. The gear motor 48 is controlled by a microcontroller (not shown).

[0341] Further, the second slewing ring 1,2,42 is provided with conductive rings 30 and conductive contacts (not shown). Further, the robotic arm 74 is equipped with a robotic manipulator 75. The second slewing ring 1,2,42 may be provided with any type of sensors (not shown).

[0342] It is to be noted that the figures and the above description have shown the example embodiments in a simple and schematic manner. Many of the specific mechanical details have not been shown since the person skilled in the art should be familiar with these details and they would just unnecessarily complicate this description.

[0343] List of parts

[0344] 1 Outer slewing ring

[0345] T first wall part of outer slewing ring

[0346] 1” second wall part of outer slewing ring

[0347] 2 Inner slewing ring

[0348] 3 Axial bearing element in the form of an axial bearing ball

[0349] 4 Radial bearing element in the form of a radial bearing ball

[0350] 5 Axial bearing cage

[0351] 6 Radial bearing cage

[0352] 7 axial bearing race

[0353] 8 radial bearing race

[0354] 9 Radial angular contact bearing race

[0355] 10 Plain axial bearing race

[0356] 11 Axial angular contact bearing race

[0357] 12 Axial bearing element in the form of an axial bearing roller

[0358] 13 Axial roller bearing race

[0359] 14 Axial bearing element in the form of an axial tapered bearing roller

[0360] 15 Axial tapered roller bearing race

[0361] 16 Functional design feature

[0362] 17 Means of fastening

[0363] 18 Radial bearing element in the form of a radial bearing roller

[0364] 19 First part of inner slewing ring

[0365] 20 Second part of inner slewing ring

[0366] 21 Third part of inner slewing ring

[0367] 22 Radial roller bearing race

[0368] 23 Radial tapered bearing roller

[0369] 24 Radial tapered roller bearing race

[0370] 25 Axial bearing seal

[0371] 26 Radial bearing seal

[0372] 27 Gear ring

[0373] 28 Encoder ring

[0374] 29 Opening in outer slewing ring

[0375] 30 Conductive slip ring Conductive contact

[0376] Access for lubrication

[0377] Rotor ring with permanent magnet

[0378] Stator coil unit

[0379] Combined inner and outer slewing ring

[0380] Load bracket for inner slewing ring

[0381] Axial needle roller

[0382] Constructional flange

[0383] Caster wheel system

[0384] Wheel

[0385] Wheel yoke

[0386] Slewing ring bearing

[0387] Wheel hub

[0388] Hollow wheel hub embodiment of the present invention

[0389] Combined inner slewing ring and wheel yoke

[0390] Wheel motor

[0391] Transmission gear

[0392] Gear motor

[0393] Robotic arm

[0394] Robotic manipulator

[0395] Plain axial bearing raceway

[0396] Plain barb bearing element

[0397] Spacing for flexibility

[0398] Plain radial bearing raceway connectors

Claims

CLAIMS1. A wheel unit (39) comprising- a wheel (40),- a slewing ring bearing (42), and- a wheel yoke (41), wherein the wheel yoke (41) is configured to connect the wheel (40) to the slewing ring bearing (42), wherein the slewing ring bearing (42) comprises an outer slewing ring (1), and an inner slewing ring (2), wherein the wheel yoke is connected to the wheel via a hub (43), wherein the slewing ring bearing (42) is arranged to surround a portion of the wheel (40), wherein the slewing ring bearing (42) comprises at least one row of axial bearing elements (3, 12) or an axial plain sliding bearing, wherein the slewing ring bearing (42) comprises at least one row of radial bearing elements (4, 22, 23, 142 143 145), wherein the outer slewing ring (1) comprises a first wall part (T) and a second wall part (1”), wherein the first wall part is ring-shaped and defines a plane (P), wherein the second wall part comprises a cylindrical portion formed perpendicular to the plane (P) defined by the first wall part, wherein a surface of the first wall facing the inner slewing ring (2) comprises an axial bearing race (7,10), wherein a surface of the second wall part facing the inner slewing ring (2) comprises a radial bearing race, wherein the outer slewing ring (1) is configured as a single integrated unit formed in one piece, wherein the inner slewing ring (2) comprises an axial bearing race corresponding to the axial bearing race of the outer slewing ring (1) and a radial bearing race corresponding to the radial bearing race of the outer slewing ring (1), wherein an outmost diameter of the inner slewing ring (2) is larger than an inner diameter of the outer slewing ring (1), andwherein said row of radial bearing elements forms a lock for connecting the inner slewing ring (2) and the outer slewing ring (1).

2. The wheel unit (39) according to claim 1, wherein the slewing ring bearing (42) comprises connectors (160) for connecting the wheel unit (39) to a vehicle,3. The wheel unit (39) according to claim 2, wherein the connectors (160) for connecting the wheel unit (39) to a vehicle is arranged to allow the slewing ring bearing (42) to be arranged above the hub (43), when the wheel unit (39) is mounted on the vehicle.

4. The wheel unit (39) according to claim 2, wherein the connectors (160) for connecting the wheel unit (39) to a vehicle is arranged to allow the slewing ring bearing (42) to be arranged below the hub (43) when the wheel unit (39) is mounted on the vehicle.

5. The wheel unit (39) according to anyone of the claims 2-4, wherein the wheel yoke (41) is connected to the inner slewing ring (2), and wherein the connectors (160) for connecting the wheel unit (39) to a vehicle are provided on the outer slewing ring (1).

6. The wheel unit (39) according to any one of the claims 2-4, wherein the wheel yoke (41) is connected to the outer slewing ring (1), and wherein the connectors (160) for connecting the wheel unit (39) to a vehicle are provided on the inner slewing ring (2).

7. The wheel unit (39) according to claim 6, wherein the connectors (160) for connecting the wheel unit (39) are provided on a load carrying bracket (36), which is connected to the inner slewing ring (2) and extending radially outward from the inner slewing ring (2).

8. The wheel unit (39) according to any one of the claims 1-7, wherein the wheel unit (39) comprises two or more wheels (40) connected to the wheel yoke (41).

9. The wheel unit (39) according to any one of the claims 1-8, wherein a wheel (40) is provided with a motor.

10. The wheel unit (39) according to any one of the claims 1-9, wherein a wheel (40) is equipped with an encoder device for digital monitoring of the rotation of the wheel (40).

11. The wheel unit (39) according to any one of the claims 1-10, wherein the slewing ring bearing is arranged horizontally around the wheel (40), for the purpose of vertical rotation of the wheel (40).

12. The wheel unit (39) according to any one of the claims 1-11, wherein the wheel comprises a hollow wheel hub (44).

13. The wheel unit (39) according to any one of the claim 1-12, wherein the inner slewing ring (2) and the wheel yoke (41 , 44) are formed as a single integrated unit.

14. The wheel unit (39) according to any one of the claims 1-13, wherein the radial bearing race (8) in the inner slewing ring (2) and the corresponding radial bearing race (9) of the outer slewing ring (1) are formed as grooves.

15. The wheel unit (39) according to any one of the claims 1-14, wherein any of the rows of bearing elements comprises at least three bearing elements configured to roll.

16. The wheel unit (39) according to any one of the claims 1-15, wherein the rows of bearing elements comprise bearing elements fixed in cages.

17. The wheel unit (39) according to any one of the claims 1-16, wherein the radial bearing comprises an angular contact ball bearing.

18. The wheel unit (39) according to any one of the claims 1-17, wherein an axial bearing comprises an angular contact ball bearing (9).

19. The wheel unit (39) according to any one of the claims 1-17, wherein an axial bearing comprises bearing elements configured to roll, such as cylindric rollers, tapered / conical rollers, barrel rollers or needle rollers.

20. The wheel unit (39) according to any one of the claims 1-19, wherein an axial bearing comprises a planer bearing race without walls extending perpendicularly from the bearing race.

21. The wheel unit (39) according to any one of the claims 1-20, wherein an axial bearing comprises a plain bearing row.

22. The wheel unit (39) according to any one of the claims 1-21, wherein a radial bearing comprises a plain bearing row.

23. The wheel unit (39) according to any one of the claims 1-22, wherein any of the inner and outer slewing ring comprises an encoder ring and an encoder reader attached to the opposite slewing ring.

24. The wheel unit (39) according to any one of the claims 1-23, wherein any of the inner and outer slewing ring comprises a gear ring (27).

25. The wheel unit (39) according to claim 24, wherein the gear ring (27) is connected to a motor driven transmission gear.

26. The wheel unit (39) according to any one of the claims 1-23, wherein any of the inner and outer slewing ring comprises one or more slip rings and means of conductive contact on the opposite slewing ring.

27. The wheel unit (39) according to any one of the claims 1-26, wherein the inner and / or outer slewing rings (1 , 2) comprises means for suspension.

28. The wheel unit (39) according to any one of the claims 1-27, wherein an electromagnetic field is transferred between an antenna on each of the inner slewing ring (2) and the outer slewing ring (1).

29. The wheel unit (39) according to any one of the claims 1-28, wherein data is transferred between each slewing ring by wireless technology.

30. The wheel unit (39) according to any one of the claims 1-29, any of the inner and outer slewing ring may comprise a gyroscope to monitor the rotational velocity of the other of the inner and outer slewing ring.

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