Machines with rotating element energy supply

Abstract

An element, specifically a rotating element, including an inductance moving or rotating together with the rotating element, configured to provide electrical energy in a magnetic field when in motion, and a consumer moving or rotating together with the rotating element, operable by the provided electrical energy.

Description

[Technical Field]

[0001] Embodiments of the present disclosure refer to elements such as rotating elements, in particular (rotating) elements with a certain type of energy supply means. Further embodiments refer to drill chucks or drill holders. Further embodiments refer to machines, in particular ball or milling machines with rotating elements. [Background technology]

[0002] A drill chuck is a classic rotating element with a primarily mechanical function. Its typical function is to hold a tool, such as a drill, and drive the tool using the rotational energy of the drilling machine. In the prior art, three different types of drill chucks or drill connections have been used. According to one variant, the drill chuck can have means for engaging both the rotating drive side and the rotating driven or output side. On the drive side, the drill chuck is then coupled to the rotational shaft of the drilling machine, while a drill can be chucked on the driven side, for example, using a quick-release connection. Alternatively, the tool or drill can be fixedly connected to the drill chuck, allowing the entire drill chuck and the tool to be constantly replaced. According to a third variant, the drill chuck can be fixedly connected to the drilling machine, for example, and a drill chuck implemented as a quick-release drill chuck can then hold different tools. In all variants, the drill chuck is provided as a predetermined type of coupling between the rotating shaft and the rotating tool. For automation and monitoring, sensor technology is provided, and in some cases, sensors are also attached to the rotating element. This electronic system can be powered, for example, by a battery. Summary of the Invention [Problem to be solved by the invention]

[0003] It is an object of the present disclosure to provide a rotating element, such as a drill chuck, with an electronic system. [Means for solving the problem]

[0004] This object is achieved by the subject matter of the independent claims.

[0005] An embodiment of the present invention provides an element, in particular a rotating or rotatable element, having an inductance that moves / rotates together with the (rotating) element and a consumer that moves / rotates together with the (rotating) element. The inductance is configured to provide electrical energy upon movement, such as rotational movement, in a magnetic field. The consumer is operated by the provided electrical energy.

[0006] According to an embodiment, the consumer may include an electronic system. In turn, according to an embodiment, the electronic system may include actuators (such as ultrasonic actuators or control elements) and / or sensor technology configured to output (sensor) information. For example, the sensor information may be information about forces, vibrations, sound, mechanical tension, temperature, torque, rotational speed and / or acceleration.

[0007] It should be noted that while, according to the embodiment, the motion relates to rotational motion caused by rotation of a rotatable element, other forms of motion may also be employed, such as periodic motion or / and impact motion decoupled from the rotation of the rotatable element.

[0008] The present invention is based on the discovery that, in an element, specifically a rotating or rotatable element for supplying electricity to a consumer within the element, electrical energy can generally be obtained using a coil or inductance when the (rotating or rotatable) element is moving in a magnetic field. For example, a magnetic field can be applied externally, i.e., a magnetic field can be generated or provided around the rotating element, and electricity can be induced as a result of the movement of the rotating element, such as its rotation in the magnetic field. According to an embodiment, it is conceivable that a magnet for providing the magnetic field can be arranged on the casing of the drill press in the region of the drill chuck. In an embodiment, it is advantageous to be able to supply electricity directly to a consumer that rotates together with the rotating element through a rotating inductance. As a result, there is no need for wiring with a wiper that supplies electrical energy or transmits an electrical signal from a non-rotating element to the rotating element. In addition, interface problems when replacing a rotating element are avoided.

[0009] According to an embodiment, the rotating element has an energy supply circuit coupled to the inductance and thereby providing electrical energy. Here, the energy supply circuit can have a rectifier and / or a buffer and / or a capacitor and / or an accumulator. The energy supply circuit advantageously makes it possible to provide a continuous energy signal to the consumer or electronic system relatively independent of the speed of movement (number of rotations). Additionally, in the event of a standstill, the energy supply circuit with a buffer can ensure a continuous energy supply to the consumer.

[0010] As mentioned above, according to the embodiments, the consumer can be configured as a certain type of sensor or actuator technology. Here, it is possible to integrate a tachometer, accelerometer, dynamometer, or vibrometer. According to the embodiments, inductance serves as the sensor technology. An inductive signal, such as an inductive current, is used as a measurement signal, since it allows for the estimation of physical quantities, such as rotational speed or vibration. In addition, an actuator, such as an ultrasonic actuator, can be provided to improve chip formation during the drilling operation.

[0011] According to further embodiments, the sensor technology can transmit acquired information to the outside via wireless. Similarly, the actuators can be controlled by wireless models. As an alternative to external information communication, it would be possible to display the information directly, for example, using a display integrated into the rotating element. The latter could be configured, for example, through color-coded LEDs (color-coded status information). Certain types of acoustic indications, for example, with a voice warning in case of overload, could be possible.

[0012] Having described the functionality of the consumer in detail, we now turn to the implementation of the energy harvesting function, i.e. the inductance.

[0013] According to an embodiment, the inductance can be formed by one or more coils, each of which can optionally be implemented with a ferrite core or a separate core. According to an embodiment, multiple coils are present for the inductance, and are distributed translationally or evenly around the rotation axis of the rotating element. The coils must then be electrically connected to each other via an electrical circuit in an appropriate manner to combine their individual energy outputs and make them collectively available to the consumers. A translational arrangement of multiple coils is advantageous because a higher energy yield is achieved. According to an embodiment, the provided electrical energy depends on the number of inductances. According to a further embodiment, the provided energy can also depend on the dimensions of the inductances and on the dimensions of the elements generating the magnetic field. Longitudinally, i.e., along the longitudinal axis, for example, the inductance can be arranged in a first half, while the consumer can be arranged in a second half. For example, the first half can be the side to which a rotating element with an output, such as a drilling machine, is connected. In this regard, according to an embodiment, the rotating element in the first half has a predetermined type of coupling for mechanical connection with a rotating machine. According to an embodiment, the rotating element in the second half can comprise a tool holder for a tool or a drill.

[0014] A preferred embodiment refers to a drill chuck or drill holder with a rotating element. A further embodiment refers to a rotary machine, specifically a drilling machine, with a rotating element and a rotary drive, where the rotating element is coupled to the rotary drive. For example, in some embodiments, the coupling between the rotating element and the rotary drive can be configured with a quick release of a certain type. This is particularly useful when changing the rotating element during a tool change. Such devices are often found in highly automated drill or milling machines, where a revolving head can be used to accommodate various drill heads.

[0015] Regarding the element generating the magnetic field, it should be noted that, according to an embodiment, one or more magnets are provided in the region of the off-drive of the rotating element of the rotating machine and / or in the region of the inductance. This advantageously allows the magnet to remain stationary during rotation of the rotating element. In this respect, the movement of the rotating element causing the induction of electrical energy is rotational in this embodiment. According to an embodiment, the rotating element is arranged in a rotational direction along the rotation axis. A crescent-shaped arrangement is also possible. Advantageously, such an arrangement still allows good access to this region. This arrangement on the drilling machine is generally advantageous, since it can be modified, for example, by subsequently arranging a holder. According to an embodiment, the magnets are arranged with alternating polarities, for example in the form of a Halbach array. This arrangement allows for a large change in the magnetic field, making it possible to obtain large amounts of electrical energy.

[0016] It should be noted that although in the above embodiments the elements have been assumed to be rotating or rotatable elements, any kind of other elements may be employed here. Thus, a further embodiment provides an element comprising an inductance movable or rotatable together with the element configured to provide electrical energy upon movement in a magnetic field, and a consumer moving or rotating together with the element that is operable by the supplied electrical energy.

[0017] Further configurations are defined in the subclaims.Embodiments of the invention will now be described with reference to the accompanying drawings, in which: FIG. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic block circuit diagram of a rotating element according to a basic embodiment. [Figure 2a] FIG. 10 is a schematic diagram of a rotating element according to a further embodiment. [Figure 2b] FIG. 10 is a schematic diagram of a rotating element according to a further embodiment. [Figure 3a] 1 is a schematic diagram showing possible coil and magnet arrangements and the resulting power. [Figure 3b] 1 is a schematic diagram showing possible coil and magnet arrangements and the resulting power. DETAILED DESCRIPTION OF THE INVENTION

[0019] Before describing the embodiments of the present invention hereinafter with reference to the accompanying drawings, it should be noted that elements and structures having the same effect are given the same reference numerals so that their descriptions are applicable and / or interchangeable with each other.

[0020] 1 shows a rotating element 10, here in the form of a drill chuck or drill holder, driven by an optional output element, here an output shaft 12. The rotating element has one or more inductances 14a and / or 14b, for example in the upper half. In addition to the inductances 14a and 14b, the rotating element has a consumer 16. It should be noted here that the rotating element does not necessarily have to rotate, but should normally be able to rotate.

[0021] According to an embodiment, the rotation element may extend around a rotation axis (see reference numeral 10r).

[0022] Similarly, external magnets, i.e., not belonging to the rotating element, are now arranged around the axis of rotation and provide the magnetic field M. It should be noted that how the magnetic field M is provided through the magnets 18 is not important here, but the magnetic field M is preferably present in the region in which the coils 14a and 14b can move.

[0023] For the sake of completeness, it should be noted that the rotating element 10 can be, for example, a drill chuck, as shown by the drill 11. The drill 11 rotates in a direction R on a rotation axis 10r. While rotation in the direction R constitutes a movement, it should be noted that the movement here does not necessarily have to be rotational. The movement R of the coils 14a and 14b, which can be arranged translationally about the rotation axis 10r, results in the movement of the coils 14a and 14b in a magnetic field M. This results in induced electricity being provided to the consumer 16. This induced electricity constitutes the obtained energy E.

[0024] Energy is thus generated in an advantageous manner based on the rotational motion, so that an electronic system embedded in the rotating element 10 can operate in an energy self-sufficient manner. For example, the electronic system can be sensor technology, actuator technology, and / or communication devices, such as wireless communication means, which are subsequently supplied with energy. Energy can thus be supplied to the consumer 16 wirelessly, making it possible to dispense with wiper contacts for the voltage supply.

[0025] Although the rotating element 10 has been described in the above embodiments as a type of ball or milling tool, it should be noted that other applications, such as in the form of a turbine or windmill, are conceivable. For example, if the rotating element 10 constitutes the hub of a turbine or windmill, an electronic system, such as a rotational speed sensor or actuator technology, can be provided to adjust the turbine wheel. Similarly, its use in conveyor belts, such as roller conveyors, is also conceivable. Here, the rotating element is embedded in the support element of the roller conveyor, making it possible to monitor or drive the conveyor belt. Further applications include integration in bearings, drive wheels, or wheels in general. In this embodiment, it is essential that an external magnetic field can be provided. This is possible in the aforementioned turbines, windmills, conveyors, or bearings, for example, by attaching magnets to the corresponding bearing blocks. Similarly, in the case of a drive or wheel, it is conceivable to provide magnets, for example, in areas where a brake system or suspension may be present.

[0026] A further embodiment refers to a coupling, such as a slip clutch, that is to be internally sensed or controlled. A coupling has the function of connecting two rotating elements to each other or transmitting general rotational energy, which is the case here in the embodiment of Figure 1. Here, the rotating element 10 is transmitted from the output element 12 to the drill 11, and the rotating element 10 constitutes the coupling.

[0027] A further embodiment of the drill chuck will now be described with reference to Figures 2a and 2b.

[0028] Figure 2a shows the rotating element 10' in an unlatched state, while the rotating element 10' is correspondingly latched in Figure 2b. Latching refers to the driven sides, which are labeled with reference numerals 12', 12g', and 18.

[0029] Basically, the output element is made up of two elements, specifically a stationary part 12g' associated with the spindle, and the spindle 12' which constitutes the rotating part of the tool machine. The output element or output shaft 12' is supported in a bearing / bearing block / housing 12g' of a certain type, or generally in the stationary part 12g'. Magnets are connected to the stationary part 12g'. For example, these magnets are arranged rotationally symmetrically or simply semicircularly around the axis of rotation 10r.

[0030] The rotating element 10' has a cylindrical shape and comprises an engagement portion 10k1' of a predetermined type realized in a first half of the cylinder, by means of which the rotating element 10' is connected to a rotating spindle 12' of a machine tool (see FIG. 2b). There may be a further engagement portion 10k2' in the second half for coupling the tool 11. In this embodiment, the second engagement portion 10k2' is realized through a screw or grub screw that exerts a force perpendicular to the rotation axis 10r' onto the tool 11 inserted in the drill chuck 10', thereby fixing the tool 11.

[0031] Electronically, the rotating element 10' includes at least one or more inductances 14 for obtaining energy. These inductances 14 are arranged in the first half (see coupling 10k1') so that when the rotating element 10' is coupled to the spindle 12', they are positioned at the same height with respect to the axis or in the region of the magnet 18 (see FIG. 2b). Additionally, the rotating element 10' also has an energy consumer. Here, the energy consumer includes three elements, although other configurations can be adopted in further embodiments. The three elements are an antenna and wireless module 16f', a control electronics and data rendering 16p' (typically a processor), and sensor technology 16s'. In this embodiment, the sensor technology is located in the region of the coupling 10k2' and functions to monitor the tool 11. For example, it can monitor transmitted torque, vibration, temperature, etc. Data acquired through the sensor 16s' is subsequently rendered by the processor 16p' and transmitted wirelessly to the outside world through a wireless module 16', which also has an integrated antenna. The power supply of all three elements 16f', 16p', and 16s' is carried out by inductance 14. It should be noted here that inductance 14 can also be connected to an electrical supply element (part of an electronic system) that provides electrical energy processing and performs summation of the individual yields of the inductances, for example through rectification, intermediate storage, or buffering. Buffering plays an important role in the absence of motion r of inductance 14 in the magnetic field M provided by magnet 18. Thus, components 16t', 16p', and 16s' can be supplied with energy even immediately after they have been energized.

[0032] With respect to the motion R, it should be noted that in this embodiment, the inductance 14 is also assumed to rotate within the magnetic field M of the magnet 18. While such motion and energy harvesting are common in generators, here, in contrast to generators, the energy is not transmitted externally by the coil 14 but is internally consumed in the rotating element 10'. According to the embodiment, it is not necessary for the rotational motion 10r to occur. For example, in the case of a hammer drill, the rotational motion can also have a lift portion along the rotation axis 10r. Therefore, periodic motion is generally assumed. In extreme cases, as in the case of a chisel or riveter, the rotational portion may be omitted entirely. The rotational motion 10r, the rotational motion with a lift portion, or all variations of the lift portion have in common only that the inductance 14 moves within the magnetic field M provided by the magnet 18. According to the embodiment, periodic motion can be assumed, but it is not necessary for this motion to be regular. Here, the energy harvesting is indicated by the arrows in FIG. 2b.

[0033] As shown in Figures 2a and 2b, the combination of elements 14 and 18 thus facilitates the conversion of rotational motion into electrical energy. Here, elements 14 and 18 together form an electrodynamic generator. This allows for the energy supply of wireless sensor technology, such that it can be employed in a self-sufficient and wireless manner in rotating elements such as chucks. Various wireless standards (e.g., UWIN, Bluetooth, BLE, analog wireless, or other variants) can be employed for wireless transmission from the rotating metal system.

[0034] It should be noted that even though in the above embodiment it has been assumed that the element 16s' functions as a sensor technology, here too actuator technology, such as piezo actuator technology, can be employed. While actuator technology has a higher energy demand, it will be explained below how the higher energy demand can be met by combining elements 14 and 18. On the other hand, the higher energy demand depends not only on other applications but also on the different sizes of the rotating element 10'.

[0035] As already explained in connection with FIG. 1, in a preferred variant, the inductances 14, or more specifically, the arrangement of 14a and 14b, are designed so that they extend translationally around the rotation axis 10r. For example, assuming two or three coils 14, in one embodiment, the respective coil cores extend perpendicular to the rotation axis 10r. In the case of two coils, the coil axes are preferably arranged at an angle of 180°, while in the case of three coils, an angle of 120° is possible. Varying energy demands can be accommodated by the number of coils. Thus, even with the same magnets 18, lower energy can be obtained with a small rotating element 10' than with a larger rotating element having multiple integrated coils. Alternatively, or in addition, the dimensions of the coils can be varied in accordance with further embodiments. The arrangement and dimensions of the magnets 18 offer a further possibility for varying the active power. In FIG. 3b, the active power in the coils is shown for different rotation speeds at different magnet heights, represented by a total of six diagrams. A further variable factor (see the X-axis) is the number of bending angles employed. Now, suppose the magnets are mounted using different curvature angles. As can be seen, employing additional curvature angles increases the generated power. Similarly, as the rotational speed increases, the power increases. Similarly, power increases with the height of the magnet. For example, assuming 18 watts are generated per coil (using a 240° curvature angle with a 16mm magnet at 9000 revolutions per minute), employing, say, 18 coils, can give a maximum power of 200 watts.

[0036] It should be noted here that not only the spatial angle utilized is important, but also the number of magnets. Here, we assume that 12 magnets are employed at a spatial angle of 240°. Of course, a different number is possible. Furthermore, spatial angles > 240°, e.g., 360°, are conceivable. All these factors contribute to being able to appropriately scale the electrically transmitted power.

[0037] It should be noted here that, as will become apparent with respect to FIG. 3a, the magnets cannot be placed arbitrarily close to one another.

[0038] 3a shows an axial view of magnets 18a, 18b, and 18c interacting with coil 14. Magnets 18a, 18b, and 18c each create magnetic field lines M, conveniently indicated here by area. A coil, positioned tangentially to the iron tool holder, moves within magnetic field M. The coil may include, for example, a ferrite core. Magnetic flux density is indicated by the gray scale, with the white line indicating the magnetic vector potential (Wb / m) in the Z direction.

[0039] Figure 3b shows the values ​​of magnetic flux density. In the embodiment from Figure 3b, it is assumed that the magnets are alternately oriented, thereby maximizing the magnetic flux change. Further arrangements / arrangements are also possible, for example in the form of a Halbach array, which would maximize the magnetic flux within the region of inductance, or an evenly oriented array.

[0040] In the above embodiments, it has been specifically assumed that there is a rotational motion. As already mentioned, other motions, such as periodic or uncorrelated motions, are also possible. According to a further embodiment, the rotating element does not even need to be a rotating element, but can be a simple element that only performs a lifting motion, for example, along axis 10r from FIG. 1. During a periodic lifting motion or the like, coils 14a and 14b also move within the magnetic field provided by magnet 18, resulting in electricity being induced in the moving element.

[0041] It should be noted here that it is not necessary to employ magnets, however, other magnetic field generating elements such as electromagnets can also be employed, which advantageously makes it easier to control the magnetic field strength.

[0042] According to the embodiment, the magnets can be arranged in a circular segment, such as a semicircular segment, or a smaller or larger circular segment. For example, arrangements ranging from 20 or 30 degrees to 330 or 340 degrees, or preferably between 60 and 270 degrees, as well as between 90 and 180 degrees, are conceivable. Any value within the given range is possible. An arrangement according to a circular arc segment is advantageous because it may increase the achievable energy yield while at the same time maintaining the circular segment's openness and accessibility.

[0043] It should be noted here that the magnets can be arranged both radially and axially around the element. For example, in the case of a radial arrangement, this runs, for example, along an arc segment along a radius arranged parallel or perpendicular to the rotation axis. In the case of an axial arrangement, the rotating element can protrude, where the magnets then protrude from the housing side to a protruding edge.

[0044] In the above embodiments, it has been described that an energy supply circuit can be provided, for example, with a capacitor or accumulator. The accumulator can be relatively large in size so that recharging occurs from short-term movements, and the power dimension of the accumulator is high relative to the possible consumption. This is particularly conceivable for low-power consumers such as sensor technology.

[0045] A preferred embodiment describes the generation of electrical energy through rotation without a stator, specifically the generation of electrical energy on a rotating object for supplying a wireless sensor. For this purpose, an inductance is employed that moves relative to a fixed magnet. The inductance is composed of one or more windings and is connected to a rectifier and an energy supply unit. The magnet is disposed on the rotating object. However, the magnet is positioned so that relative motion can occur with respect to the inductance. The energy supply unit can supply a sensor, an actuator, or a wireless module. The sensor detects information about the rotating object and transmits this information wirelessly. The wireless module can also receive data to control the actuator. For example, this system can be applied to a drill chuck, a coupling, or a shaft.

[0046] It should be noted here that the above-described embodiments are merely examples, and the scope of protection is defined by the following claims. [Explanation of symbols]

[0047] 12, 12' output element 10, 10' Rotating Element 18 Magnet 14, 14a, 14b Inductance 11 Tools 10k1' 1st half 10k2' second half R movement 10r rotation axis 16 Consumers M magnetic field E Energy 16f' wireless module 16s' sensor

Claims

1. A machine, in particular a drilling machine, comprising a rotary output element (12, 12') and an element (10, 10'), in particular a rotary element (10, 10'), said element (10, 10') being coupled to said rotary output element (12, 12'), said element (10, 10') comprising: an inductance (14, 14a, 14b) moving or rotating with said element (10, 10') configured to provide electrical energy (E) upon movement (R) in a magnetic field (M); a consumer (16) that moves or rotates together with said element (10, 10') and is operable by said provided electrical energy (E); Including, A plurality of magnets (18), including at least three magnets, are arranged around the rotation axis (10R) of the element (10, 10') along a circular segment covering an angular range of 20° to 270°; machine.

2. The machine of claim 1 , wherein the consumer (16) includes an electronic system.

3. the inductance (14, 14a, 14b) is coupled to an energy supply circuit through which the electrical energy (E) is provided, or 3. The machine according to claim 1 or 2, wherein the inductance (14, 14a, 14b) is coupled to an energy supply circuit through which the electrical energy is provided, the energy supply circuit including a rectifier, a buffer, a capacitor, and / or an accumulator.

4. The machine according to any one of claims 1 to 3, wherein the consumer (16) comprises actuator technology, ultrasonic actuators, and / or control elements.

5. the consumer (16) includes sensor technology configured to output information; or said consumer (16) comprising sensor technology (16s') configured to output information, said sensor technology (16s') configured to detect at least one from the group comprising force, vibration, sound, mechanical tension, temperature, torque, rotational speed, and acceleration; or 5. The machine according to claim 1, wherein the inductance (14, 14a, 14b) is configured to function as a sensor technology (16s') or to function based on an induced signal in the inductance (14, 14a, 14b) to provide a measurement signal inductance (14, 14a, 14b) making it possible to deduce a physical quantity, in particular a rotational speed or a vibration.

6. The machine according to any one of claims 1 to 5, further comprising a wireless module (16s') adapted to transmit information acquired in said element (10, 10') to the outside.

7. The inductance (14, 14a, 14b) is formed by one or more coils, or the inductance (14, 14a, 14b) is formed by one or more coils with a ferrite core, or 7. The machine according to any one of claims 1 to 6, wherein the provided electrical energy (E) depends on the number of inductances (14, 14a, 14b) or on the dimensions of the inductances (14, 14a, 14b) and the magnetic field (M) present.

8. A machine described in any one of claims 1 to 6, wherein the inductance (14, 14a, 14b) is formed by a plurality of coils distributed translationally or evenly around the axis of rotation (10R) of the element (10, 10').

9. said inductances (14, 14a, 14b) being arranged in a first half along the longitudinal axis; and / or 9. A machine according to any one of claims 1 to 8, wherein the consumer (16) is arranged in the second half along the longitudinal axis.

10. 10. Machine according to any one of the preceding claims, wherein said element (10, 10') comprises in its second half along its longitudinal axis a tool (11) and / or a tool holder for a drill.

11. Machine according to any one of the preceding claims, wherein said element (10, 10') comprises in its first half along its longitudinal axis a coupling for mechanical connection to the machine.

12. 12. Machine according to claim 11, wherein the coupling between the element (10, 10') and the rotary output element (12, 12') is implemented by a quick connector.

13. 13. A machine according to any one of claims 1 to 12, wherein the element (10, 10') comprises a display, in particular a color display or an LED, configured to output status information or color-coded status information, or the element (10, 10') comprises a display, in particular an acoustic indication, configured to output status information or acoustic status information.

14. A machine according to any one of the preceding claims, having a drill chuck or drill holder including said element (10, 10').

15. 15. A machine according to any one of claims 1 to 14, wherein one or more magnets (18) are arranged in the region of the rotary output element (12, 12') and / or in the region of the inductance (14, 14a, 14b) of the element (10, 10') on the machine, such that the magnets (18) remain stationary during rotation of the element (10, 10').

16. 16. Machine according to any one of the preceding claims, characterized in that a plurality of magnets (18) are arranged along the shape of a semicircle around the axis of rotation (10r) of the element (10, 10').

17. 17. A machine as claimed in any one of the preceding claims, wherein the magnets (18) are arranged with alternating polarity.

18. A machine as described in any one of claims 1 to 17, wherein the plurality of magnets (18) are arranged in the form of a Halbach array.

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