Patent Publication Number: US-2022226949-A1

Title: Apparatus, in particular hand guided and/or hand held pneumatic power tool

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit to, and is a divisional application of, patent application Ser. No. 16/225,161, filed 19 Dec. 2019, which claims benefit to Italian application no. 17209801.4, filed 21 Dec. 2017, which are both hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention refers to a pneumatically driven apparatus comprising a pneumatic rotary vane motor, a working element realizing a working movement when the motor is activated, and at least one gear arrangement functionally located between the motor and the working element for transmitting a rotational movement and torque from the motor to the working element in order to realize the working movement. The motor comprises a housing defining an essentially cylindrical chamber extending along a cylinder axis, and an essentially cylindrical rotor located in the chamber and extending along and rotatable about an axis running parallel to the cylinder axis. The rotor comprises a plurality of radially movable vanes forced radially outwards during rotation of the rotor. Preferably, the apparatus is a hand guided and/or hand held pneumatic power tool. 
     The invention further refers to a pneumatic machine comprising a pneumatic rotary vane motor and a magnetic gear arrangement. The pneumatic machine is adapted for use in an apparatus of the above identified kind. 
     The apparatus may be, for instance, a hand guided and/or hand held pneumatic power tool. The power tool may be, for example, a drill, a grinder (straight or angle grinder), a sander, a polisher, a glazing machine, a mixer, a screwdriver or the like, only to name a few. Accordingly, working element may be embodied as a drill chuck, a carrier element of a grinder or a backing pad of a sander or a polisher. The working element is embodied to receive and hold a tool accessory for performing a desired work which the power tool is adapted to perform. For instance, the drill chuck may be embodied in order to receive and hold a drill bit of various sizes. The carrier element may be embodied in order to receive and hold a grinding wheel. The backing pad may be embodied to receive and hold a sanding element (e.g. sanding paper, sanding fabric or the like) or a polishing pad (e.g. a foam pad, a wool pad or a microfiber pad). 
     The working movement performed by the working element and the tool accessory attached thereto is preferably of the rotational type. In particular, it may be a purely rotational movement, a gear driven roto-orbital movement or a random orbital movement. However, the working movement could also be a (non-rotational) purely orbital movement. With the purely rotational movement the working element rotates about a first rotational axis, which is congruent with a central axis of the working element running through the balance point of the working element. With the roto-orbital and the random-orbital movement the working element performs a first rotational movement about the first rotational axis spaced apart from a second rotational axis of the working element corresponding to the central axis running through the balance point of the working element. Additionally to the first rotational movement, the working element is also rotatable about the second rotational axis. With the roto-orbital movement, the second rotational movement is forced by a gearing mechanism depending on the first rotational movement. For example, for a first rotational movement by 360° (one rotation) about the first rotational axis, the working element may perform a plurality of gear driven second rotational movements about the second rotational axis of approximately 30 to 120 rotations. With the random orbital movement, the working element is freely rotatable about the second rotational axis independently from its rotation about the first rotational axis. 
     For instance, a drill chuck and a grinder perform a purely rotational movement. A sander and a polisher may perform a purely rotational movement, a roto-orbital or a random orbital movement. A sander may perform a purely orbital movement. An example for a pneumatically driven random orbital polisher is the BigFoot®-polisher LHR 75 produced and sold by RUPES® S.p.A. from Vermezzo (IT). An example for a pneumatically driven random orbital sander is the Skorpio®-sander produced and sold by RUPES® S.p.A. from Vermezzo (IT). 
     2. Description of Related Art 
     In the pneumatic power tools known in the art mechanical gear arrangements are commonly used. The gear arrangements can reduce a first rotational speed of an input shaft (e.g. a motor shaft) into a second rotational speed of an output shaft (e.g. a tool shaft directly or indirectly connected to the working element or an intermediate shaft directly or indirectly connected to the tool shaft), the second speed being smaller than the first speed, thereby generating a larger torque at the output shaft. Furthermore, bevel gear arrangements are used in the known angular power tools in order to translate a rotational speed and a torque from an input shaft to an output shaft, wherein the rotational axes of the two shafts run in an angle a in respect to one another, wherein the angle may be 180°&gt;α≥90°. Finally, as already described above, mechanical gears are used in known roto-orbital power tools for forcing the working element to realize the roto-orbital rotational (gear driven) movement. 
     Furthermore, from completely different technical fields it is known to use magnetic gear arrangements for transmitting rotational movement and torque between electrical machines (motors or generators) and a load (see for example U.S. Pat. No. 3,378,710). Such magnetic gear arrangements are used in very large appliances, such as conveyer belts, ship propulsions, power generators, wind turbines, large pumps and the like, or in the technical field of aerospace applications, manufacturing of pharmaceuticals or food and other environments with a high hygienic standard. 
     Usually, an input shaft of such magnetic gear arrangements is connected to a slowly rotating appliance, for example the rotors of a wind turbine, whereas the output shaft is connected to a fast rotating appliance, for example an electric generator. This makes sense for the known arrangements, because there a high rotational speed is desirable at the output shaft rather than a large amount of torque. Further, in such known magnetic gear arrangements the magnetic flux is transmitted between the input and the output shaft in a purely radial direction. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an object of the present invention to improve the known hand guided and/or hand held pneumatic power tools by providing a highly integrated pneumatic machine comprising a pneumatic rotary vane motor and a magnetic gear arrangement adapted for use in such pneumatic power tools. 
     In order to find a solution to this problem, a pneumatically driven apparatus is disclosed herein. In particular, the pneumatically driven apparatus features the at least one gear arrangement embodied as a magnetic gear arrangement using magnetic fields to transmit the rotational movement and torque from the motor to the working element without mechanical contact, the magnetic gear arrangement comprising three principle components, all three of which may rotate relative to each other about rotational axes running parallel or coaxial in respect to one another. A first one of the three components with a first number of magnetic pole pairs generates a first magnetic field, a second one of the three components with a second number of magnetic pole pairs generates a second magnetic field, and a third one of the three components comprises a third number of ferromagnetic pole pieces, the third component acting as a passive part of a magnetic circuit between the first and second components. The rotor of the pneumatic motor comprises permanent magnets attached thereto between the vanes thereby making the rotor of the pneumatic motor form the first or the second component of the magnetic gear arrangement. According to the invention the rotor of the pneumatic motor forms an integral part with one of the rotating components (with the magnetic pole pairs of permanent magnets) of the magnetic gear arrangement. The apparatus is in particular a hand guided and/or hand held power tool. 
     The inventors have individualized the mechanical gear arrangement of known hand guided and/or hand held power tools as a main source for noise emission, weight, size and maintenance requirements. All hand guided and/or hand held pneumatic power tools known in the art so far use mechanical gear arrangements with meshing teeth of gearwheels in order to transmit the rotational movement and torque from the rotating motor shaft into the rotational working movement of the working element. 
     These mechanical gear arrangements have the disadvantage of mechanical wear, noise emission, need for lubrication and cooling, relatively large dimensions and relatively high weight. All these drawbacks can be overcome by the power tool according to the present invention. By using only magnetic gear arrangements in a power tool a giant leap in the design of hand guided and/or hand held power tools has been achieved. The pneumatic power tool according to the present invention provides for a significant advantage in terms of durability, low-maintenance and noise reduction. 
     The pneumatic power tool according to the invention has the advantage that the power transmission is effected without contact, thereby avoiding noise created by grinding parts of a mechanical gear arrangement. The magnetic gear arrangement is also more efficient than a mechanical gear arrangement as there is no friction from contacting parts. Further, by means of the magnetic gear arrangement an overload protection can be easily realized in the sense that the driving and driven parts of the gear arrangement will simply slip through in case an excessive amount of force is applied to the working element of the power tool during its intended use, thereby avoiding damage to the tool and the surface to be worked. Another advantage is that no lubrication or maintenance of the gear arrangement is required. Furthermore, the contactless magnetic transmission of the magnetic gear arrangement provides for an attenuation of vibrations of the working element. This allows a particularly even and smooth operation and handling of the power tool. 
     A further advantage of the present invention is the high degree of integration of the pneumatic motor and the magnetic gear arrangement. This is realized by giving the rotor of the pneumatic motor a dual functionality. On the one hand the rotor works as a conventional rotor of a conventional pneumatic rotary vane motor. On the other hand, the rotor equipped with the permanent magnets works as one of the rotating components of the magnetic gear arrangement. Hence, one of the rotating components of the magnetic gear arrangement can be omitted resulting in a smaller and lighter pneumatic machine. A pneumatic power tool equipped with such a pneumatic machine can be designed more compact and has less weight. 
     According to a preferred embodiment of the invention the first number (n_input) of pole pairs of the first component is smaller than the second number of pole pairs of the second component. The rotating component with the smaller number of permanent magnets rotates at a higher speed and the gear ratio of such a magnetic gear arrangement is such that the component with the larger number of permanent magnets rotates at a smaller rotational speed, thereby increasing the torque. Changes in speeds are inversely proportionate to changes in torque. Therefore, the rotor of the pneumatic motor equipped with the permanent magnets on its out circumference between the vanes preferably forms the first rotating component of the magnetic gear arrangement with the smaller number of permanent magnets. This special embodiment of the magnetic gear arrangement is particularly advantageous with power tools, where a high amount of torque is desirable at the output shaft for operating the working element powerfully and efficiently. 
     It is further suggested that the second component with the second number (n_output) of pole pairs is located axially displaced along the rotational axis in respect to the first component with the first number (n_input) of pole pairs. In this embodiment the magnetic flux is transmitted in a transverse direction from the input to the output shaft or the first and second component, respectively. More in detail, the flux is transmitted radially from the first magnetic component to external ferromagnetic segments and also from the ferromagnetic segments the second component. The external ferromagnetic segments provide for a transmission of the magnetic fields of the two components in a manner that they interact with one another and that the second component rotates with a certain number of rotations. In this embodiment the magnetic flux is not transmitted directly between the first component and the second component but rather indirectly by means of the ferromagnetic elements. 
     An air gap is provided between the first component with the first number (n_input) of pole pairs and the second component with the second number (n_output) of pole pairs. A wall of the housing of the motor defining the chamber and the partial chambers runs through the entire extension of the air gap. Hence, in this embodiment the wall extends perpendicular to the rotational axes of the first and second rotating components. Of course, in order to allow free rotation of the rotating components of the magnetic gear arrangement, air gaps remain between the wall and the face surface of the first component on the one hand and between the wall and the face surface of the second component on the other hand. 
     In this embodiment the rotor of the motor (forming the first component of the magnetic gear arrangement) and the second rotating component of the magnetic gear arrangement may be supported by a double-bearing on one side of a shaft carrying the rotor of the motor or the second rotating component. In order to realize a support on both ends of the shaft, the wall may comprise at least one bearing for mounting the shaft of the rotor of the motor (forming the first component of the magnetic gear arrangement) and/or of the second rotating component of the magnetic gear arrangement. The bearing in the wall should be sealed by means of a gasket in order to maintain hermitical tightness of the chamber and the partial chambers defined by the housing. If air escaped through the bearing in the wall the efficiency of the pneumatic machine would be reduced. 
     Preferably, the gear ratio (i) of the magnetic gear arrangement is i=n_output/n_input. Hence, a magnetic gear arrangement where the first rotating component has eight magnetic pole pairs and the second rotating component has two magnetic pole pairs, would have a gear ratio of I=8/2=4°:°1. A rotation of the rotor of the pneumatic motor of 16.000 rpm would be reduced to 4.000 rpm. 
     The third number (n_pp) of ferromagnetic pole pieces is either n_pp=(n_output−n_input) or n_pp=(n_output+n_input). In the above example, the third component of the magnetic gear arrangement is preferably provided with either six or ten ferromagnetic pole pieces. The pole pieces are preferably made of steel and supported in or carried by a non-magnetic and possibly non-conductive support structure. 
     According to another preferred embodiment of the invention, it is suggested that a circumferential outer wall of the housing of the motor is provided with a plurality of ferromagnetic segments each having a longitudinal extension running parallel to the rotational axis making the housing of the motor form the third component of the magnetic gear arrangement. In that case the ferromagnetic segments of the housing of the motor form the ferromagnetic pole pieces of the third component. In that embodiment, a separate third component of the magnetic gear arrangement can be omitted resulting in yet a further reduction of weight and size of the pneumatic machine. According to this embodiment the cylindrical housing of the pneumatic motor forms an integral part with the static component of the magnetic gear arrangement. 
     The ferromagnetic segments are dimensioned such that in an axial direction they cover at least part of the first number of magnetic pole pairs of the first component and at least part of the second number of magnetic pole pairs of the second component. Preferably, the ferromagnetic segments cover the entire length of the first number of magnetic pole pairs of the first component and the entire length of the second number of magnetic pole pairs of the second component. The ferromagnetic segments serve for realizing a coupling between the first magnetic field of the first component and the second magnetic field of the second component. Without the ferromagnetic segments there would be no coupling between the two components. The gear ratio depends on the number of first magnetic pole pairs of the first component in respect to the number of second magnetic pole pairs of the second component. 
     According to an alternative embodiment of the invention, the second rotating component is not located axially displaced along the rotational axis in respect to the first rotating component, but is rather located radially outside of the first component with the first number of pole pairs and outside of the housing of the motor. Hence, the second rotating component of the magnetic gear arrangement rotates around the motor housing. In that case the magnetic flux is transmitted radially between the inner first component and the outer second component. The components are preferably located co-axially and rotate about the same axis of rotation. 
     According to yet another embodiment of the invention, a circumferential outer wall of the housing of the motor is provided with at least one electrical winding, in which an electric current is induced by the rotating rotor and the moving permanent magnets during operation of the motor. The electric current may be used for supplying electrical components of the power tool with electric energy. Such electrical components of the power tool can comprise an electronic control unit, a display integrated in the housing and visible from outside the housing, and/or a light source for illuminating a switch or a dial or a working surface of the power tool. With this embodiment electric current is available in the pneumatic power tool with almost no additional effort (a few additional electrical windings in the housing). In particular, there is no need for an electric cable is necessary to provide the power tool with electric energy. 
     It is suggested that the second rotating component of the magnetic gear arrangement is connected to a tool shaft or an intermediate shaft of the power tool. The tool shaft may be directly or indirectly (e.g. by means of a hypocycloid gear arrangement for realizing a gear-driven (or roto-orbital) working movement or by means an eccentric element for realizing a random-orbital working movement) connected to the working element. The intermediate shaft may be directly or indirectly (e.g. by means of a bevel gear) connected to the tool shaft. 
     Another possibility to integrate the pneumatic motor with a magnetic gear arrangement is to have the motor shaft of the pneumatic motor form an integral part with one of the rotating components (with the magnetic pole pairs of permanent magnets) of the gear arrangement. 
    
    
     
       BRIEF DESCRIPTION OF FIGURES IN THE DRAWING 
       Further features and advantages of the present invention will become apparent from the following detailed description making reference to the accompanying drawings. These show: 
         FIG. 1  a hand held and hand guided pneumatic power tool according to the present invention; 
         FIG. 2  (Prior art) a schematic cross sectional view of a magnetic gear arrangement for explaining the basic functioning; 
         FIG. 3  (Prior art) a schematic longitudinal sectional view of the magnetic gear arrangement of  FIG. 2 ; 
         FIG. 4  (Prior art) a further embodiment of a magnetic gear arrangement; 
         FIG. 5  a schematic longitudinal sectional view of the power tool of  FIG. 1 ; 
         FIG. 6  (Prior art) an exploded view of an example of a conventional pneumatic motor of a hand held and hand guided power tool; 
         FIG. 7  (Prior art) a cross sectional view through the pneumatic motor of  FIG. 6 ; 
         FIGS. 8A, 8B, 8C  (Prior art) various operating states A, B, C of the pneumatic motor of  FIG. 6  in a cross sectional view; 
         FIG. 9  a longitudinal sectional view through a pneumatic machine combining a pneumatic motor with a magnetic gear arrangement for use in a pneumatic power tool; 
         FIG. 10  an exploded view of an example of a pneumatic machine combining a pneumatic motor with a magnetic gear arrangement for use in a pneumatic power tool according to the present invention; 
         FIG. 11  a cross sectional view through the pneumatic machine of  FIG. 10 ; and 
         FIG. 12  a longitudinal sectional view through the pneumatic machine of  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION OF THE BEST MODE OF THE INVENTION 
       FIG. 1  shows an example of a pneumatically driven apparatus according to the present invention in a perspective view. The apparatus is described in the form of a hand held and hand guided pneumatic power tool  1 . However, the apparatus may be any other pneumatic apparatus equipped with a magnetic gear arrangement, too. 
       FIG. 5  shows a schematic longitudinal section through the power tool  1  of  FIG. 1 . The power tool  1  is embodied as a random orbital polishing machine (or polisher). The polisher  1  has a housing  2 , essentially made of a plastic material. The housing  2  is provided with a handle  3  at its rear end and a grip  4  at its front end in order to allow a user of the tool  1  to hold the tool  1  and apply a certain amount of pressure on the top of the front end of the housing  2  during the intended use of the tool  1 . At the top side of the housing  2  a switch  6  in the form of a lever is provided for activating and deactivating the power tool  1 . The power tool  1  can be provided with adjustment means (e.g. a turn wheel  7 ) for adjusting the rotational speed of the tool&#39;s pneumatic motor  100  (see  FIG. 5 ) located inside the housing  2 . The turn wheel  7  is in direct connection to a valve for varying the amount of air supplied to the pneumatic motor  100 . The housing  2  can be provided with venting openings  8 . An example for a pneumatic motor and its functioning are explained further on making reference to  FIGS. 6 to 8 . 
     At a rear end of the housing  2  a pneumatic connector  13  adapted for connection to a source of compressed air is provided for driving the pneumatic motor  100 . Furthermore, at the rear end of the housing  2  a connecting tube  14  is provided, which is adapted to be connected to the distal end of a tube or hose of a safety dust extractor or vacuum cleaner for removing dust, powder and other small particles from the working area. 
     The power tool  1  has a disk-like working element  9  (or backing pad) rotatable about a rotational axis  10 . In particular the working element  9  of the tool  1  shown in  FIG. 1  performs a random orbital rotational movement  11 . With the random orbital movement  11  the working element  9  performs a first rotational movement about a first rotational axis corresponding to rotational axis  10 . Spaced apart from the first rotational axis  10  another second axis  16  (see  FIG. 5 ) is defined about which the working element  9  is freely rotatable independently from the rotation of the working element  9  about the first rotational axis  10 . The second axis  16  runs through the balance point of the working element  9  and parallel to the first axis  10 . The random orbital movement  11  is realized by means of an eccentric element  17  attached to a tool shaft  18  of the tool  1  in a torque proof manner and in which a rotational shaft  19  of the working element  9  is held and guided freely rotatable about axis  16 . The power tool  1  according to the present invention can be any type of power tool provided with a working element  9  performing some kind of working movement (purely rotational, roto-orbital (gear driven), random orbital or purely orbital). 
     The working element  9  is made of a semi-rigid material, preferably a plastic material, which on the one hand is rigid enough to carry and support the tool accessory  12  during the intended use of the power tool  1  and to apply a force to the working element  9  and the tool accessory  12  in a direction downwards and essentially parallel to the working element&#39;s rotational axis  10  and which on the other hand is flexible enough to avoid damage or scratching of a surface to be worked by the working element  9  or the tool accessory  12 , respectively. 
     The bottom surface of the working element  9  is provided with means for releasably attaching the tool accessory  12  for performing a desired work which the power tool  1  is adapted to perform. For example in the case the tool  1  was a polisher, the tool accessory  12  may be a polishing material comprising but not limited to foam or sponge pad, a microfiber pad, and real or synthetic lambs&#39; wool pad. In  FIG. 1  the tool accessory  12  is embodied as a sponge or foam pad. Attachment means for attaching the tool accessory  12  to the bottom surface of the working element  9  can comprise a first layer of a hook-and-loop fastener (or Velcro®) on the bottom surface of the working element  9 , wherein the top surface of the tool accessory  12  is provided with the corresponding second layer of the hook-and-loop fastener. The two layers of the hook-and-loop fastener interact with one another in order to releasably but safely fix the tool accessory  12  to the bottom surface of the working element  9 . Of course, with other types of power tools  1 , the working element  9  and the tool accessory  12  may be embodied and connected to each other in a different manner. 
     Furthermore, the power tool  1  according to the invention comprises at least one magnetic gear arrangement functionally located between the pneumatic motor  100  and the working element  9 . In the embodiment shown in  FIG. 5  two magnetic gear arrangements are provided, one being a coaxial magnetic gear arrangement  20  and the other being a magnetic bevel gear arrangement  21 . The bevel gear arrangement  21  is provided because the power tool  1  is of an angular type, where a motor shaft  22  runs in a certain angle (preferably between 90° and less than 180°) in respect to the tool shaft  18 . In the shown embodiment the angle is exactly 90°. 
     The coaxial gear arrangement  20  is adapted for transmitting a rotational movement of a motor shaft  22  and torque from the motor  100  to an intermediate shaft  23 , thereby preferably reducing the rotational speed of the intermediate shaft  23  in respect to the motor shaft  22  and enhancing the torque. The motor shaft  22  forms the input shaft and the intermediate shaft  23  the output shaft of the coaxial gear arrangement  20 . 
     The magnetic bevel gear arrangement  21  is adapted for transmitting a rotational movement and torque from the output shaft  23  of the coaxial magnetic gear arrangement  20  to the tool shaft  18 , wherein the two shafts  23 ,  18  rotate about two rotational axes which run in an angle a in respect to one another, 180°&gt;α≥90°. Further, the magnetic bevel gear arrangement  21  can also be adapted for reducing or enhancing the rotational speed of the tool shaft  18  in respect to the intermediate shaft  23 . In that case the coaxial gear arrangement  20  could also be omitted. The intermediate shaft  23  forms the input shaft and the tool shaft  18  the output shaft of the bevel gear arrangement  21 . The design of a conventional coaxial magnetic gear arrangement  20  will be explained in further detail below making reference to  FIGS. 2 to 4 . According to the present invention the gear arrangement  20  is at least partly integrated in the pneumatic motor  100 , preferably located within the housing of the pneumatic motor  100 . Alternatively, at least part of the pneumatic motor  100  may form part of the coaxial magnetic gear arrangement  20 . 
     A magnetic gear arrangement uses magnetic fields to transmit rotational movement and torque from the motor  100  to the working element  9  without mechanical contact, in order to realize the working movement  11  of the working element  9 . The coaxial magnetic gear arrangement  20  uses permanent magnets to transmit torque between an input and output shaft. Torque densities comparable with mechanical gears can be achieved with an efficiency of 99% or better at full load and much higher efficiencies in part-load conditions than mechanical gears can achieve. Since there is no contact between the moving parts, there is no wear and no need for lubrication. In contrast to mechanic gear arrangements, the high performance of magnetic gear arrangements remains essentially unchanged over time. Magnetic gear arrangements  20  also protect against overloads by slipping harmlessly if an excessive torque is applied, and automatically and safely re-engage when the excess torque is removed. Also they have the advantage that due to the fact that driving and driven parts of the gear arrangements  20 ,  21  are not in contact with one another any vibrations caused by the rotating working element  9  during the intended use of the power tool  1  are extenuated thereby providing for an even and smooth operation of the power tool  1 . 
     A preferred embodiment of a coaxial magnetic gear arrangement  20  is shown in  FIGS. 2 and 3 . The gear arrangement  20  uses a series of ferromagnetic (e.g. steel) segments or pole-pieces  50  to modulate magnetic fields produced by two rotating permanent magnet components  52 ,  54  with different numbers of permanent magnets  56 ,  58 . The magnets  56 ,  58  are located on the components  52 ,  54  next to each other with alternating polarities in a circumferential direction. The pole pieces  50  are preferably supported by a non-magnetic and non-conductive structure  51 . In this arrangement the magnet arrays of the outer and inner components  52 ,  54  rotate at different speeds, with the gear ratio determined by the ratio of magnetic pole pairs  56 ,  58  in the arrays. A common rotational axis of the inner component  52  as well as of the outer component  54  is indicated with reference sign  60 . Of course, the rotational axes of the two components  52 ,  54  do not necessarily have to run concentrically but may run parallel and spaced apart from one another. The inner component  52  is preferably connected to the fast rotating input or motor shaft  22  in a torque proof manner. The outer component  54  is preferably connected to the output or intermediate shaft  23  in a torque proof manner. The pole-pieces  50  and the support structure  51  are static (see  FIG. 4 ). In the embodiment of  FIG. 2  the gear arrangement  20  has a gear ratio of 10:4 or 5:2, respectively. Other gear ratios of 50:1 down to 1.01:1 with almost zero torque ripple can be achieved, too. 
     Alternatively, it is also possible that the inner component  52  is connected to the motor shaft  22 , the intermediate component comprising the support structure  51  and the pole pieces  50  is connected to the output or intermediate shaft  23  and the outer component  54  is held stationary, for example by being fixed to the housing  2  of the power tool  1  or by forming part of the housing  2 . 
     Generally speaking, the at least one coaxial magnetic gear arrangement  20  has three principle components  50 ,  52 ,  54 , all three of which may rotate relative to each other about the rotational axis  60 . A relative rotation of the component  50 ,  52 ,  54  in respect to one another is also given, if one of the components is stationary. A radially inner component  52  of the three components generates a first magnetic field with a first number of pole pairs each pole pair comprising two magnets  56  of opposing polarity. 
     A radially outer component  54  of the three components generates a second magnetic field with a second number of pole pairs each pole pair comprising two magnets  58  of opposing polarity. In order to provide for a gear ratio ≠1, the number of magnetic pole pairs of the two rotors  52 ,  54  has to be different. A radially intermediate component of the three components has a number of ferromagnetic pole pieces  50  supported by the non-magnetic and non-conductive support structure  51 . The third component  50 ,  51  acts as a passive part of a magnetic circuit between the first component  52  and the second component  54 . Preferably, in order to realize a constant gear ratio, one of the components is connected to the input shaft  22 , another one of the components is connected to the output shaft  23  and the third component is maintained stationary. 
     There is no physical contact between any of the driving and driven parts  52 ,  54  as the motion is transferred across an air gap using the force of the magnetic fields. The intermediate component comprising the pole pieces  50  and the ring-shaped support structure  51  is located in the air gap between the inner ring  52  and the outer ring  54  resulting in a first air gap  53   a  between the support structure  51  with the pole pieces  50  and the outer ring  54  and in a second air gap  53   b  between the support structure  51  with the pole pieces  50  and the inner ring  52 . These air gaps allow the magnetic gear arrangement  20  to work without lubrication and provides for a quiet and smooth operation. In the embodiment of  FIGS. 2 and 3  the magnetic flux is transmitted from the inner component  52  to the outer component  54  in a radial direction. 
     The magnetic gear arrangement  20  works as follows: By rotating the inner magnet component  52  with the steel segments  50  not yet inserted into the air gap the magnetic field produced by the magnets  56  has an array of four north and south poles rotating at the same speed. After introduction of the steel segment ring  50 ,  51  into the air gap, this field pattern is considerably altered. The outer magnetic ring  54  consists of a larger number of (in the embodiment of  FIG. 2 : ten) pole pairs of north and south magnets  58 . These would couple with the altered magnetic field generated by the inner magnets  56  and rotate at a lower speed in the opposite direction than the inner ring  52 . If the outer magnet ring  54  was stationary and the intermediate ring with the ferromagnetic segments  50  was rotatable about the axis  60 , it would rotate at the lower speed in the same direction as the inner ring  52 . 
     Another embodiment of a coaxial magnetic gear arrangement  20  is shown in  FIG. 4 . It comprises a first ring-shaped component  52  with a first number of permanent magnets  56  disposed along its circumference with changing polarities. In this example, the first component  52  is provided with a total of four magnets  56  (two pole pairs), two magnets  56  with positive polarity and two magnets  56  with negative polarity, the polarities changing along the circumference of the first ring  52 . Furthermore, the gear arrangement  20  of  FIG. 6  comprises a second ring-shaped component  54  with a second number of permanent magnets  58  disposed along its circumference with changing polarities. In this example, the second ring  54  is provided with a total of twelve magnets  58  (six pole pairs), six magnets  58  with positive polarity and six magnets  58  with negative polarity, the polarities changing along the circumference of the second ring  54 . The two rings  52 ,  54  are located coaxially, and are rotatable independently about the same rotational axis  60 . The second component  54  with the second number of pole pairs  58  is located axially displaced along the common rotational axis  60  in respect to the first component  52  with the first number of pole pairs  56 . 
     Surrounding the two components  52 ,  54  externally are ferromagnetic segments  50  each having a longitudinal extension along the axis  60 . The segments  50  may be held by a support structure  51  (not shown in  FIG. 4 ). Preferably, the segments  50  extend along the entire length of the two component  52 ,  54  and the permanent magnets  56 ,  58  in the direction of the axis  60 . In this example there are eight ferromagnetic segments  50  provided along the outer circumference of the two rings  52 ,  54 . Preferably, the segments  50  are equidistantly spaced apart from one another in a circumferential direction. In this example the magnetic gear arrangement  20  has a gear ratio of 3:1 (6 pole pairs/2 pole pairs). Air gaps are provided between the two components  52 ,  54  in an axial direction as well as between the outer circumferential surface of the two components  52 ,  54  and a surface of the ferromagnetic segments  50  facing radially inwards. In this embodiment, the first component  52  is connected to the high speed motor shaft  22  and the second ring  54  is connected to the tool shaft  18  or any intermediate shaft  23 . 
     In the embodiment of  FIG. 4  the magnetic flux is transmitted from the first ring  52  to the second ring  54  in a transverse direction. More in detail, the flux is transmitted radially from the first magnetic element  52  to the ferromagnetic segments  50  and also from the ferromagnetic segments  50  to the second magnetic element  54 . The external ferromagnetic segments  50  provide for a transmission of the magnetic fields of the two elements  52 ,  54  in a manner that they interact with one another and that the second element  54  rotates with a certain number of rotations. In this embodiment the magnetic flux is not transmitted directly between the first element  52  and the second element  54  but rather indirectly by means of the ferromagnetic elements  50 . 
     An example for a pneumatic motor  100  is shown in  FIG. 6  in an exploded view. The motor  100  comprises an essentially hollow cylinder-shaped housing  102  for receiving a rotor  104  rotatable about a rotational axis  60  extending parallel in respect to a cylinder axis of the housing  102 . The rotor  104  has a plurality of longitudinal slots  106  extending essentially parallel to the rotor&#39;s rotational axis  60  and each adapted for receiving a vane  108  freely movable within the respective slot  106  in a radial direction. The hollow cylinder-shaped housing  102  is closed by two end plates  110 ,  112 , each of which provided with a bearing  112   a,    126  for supporting ends of the motor shaft  22 . 
       FIG. 7  shows a cross section through the pneumatic motor  100  of  FIG. 6  when mounted together. The slotted rotor  104  rotates eccentrically in a chamber defined by the body  102  and the two end plates  110 ,  112 . Since the rotor  104  is off-center and its outer diameter is less than that of the cylinder-shaped housing  102 , a half-moon shaped chamber  114  remains in the inside of the hollow cylinder-shaped housing  102 . The vanes  108  are free to move radially in the slots  106  of the rotor  104  driven by the centrifugal force of the rotating rotor  104 . When moved radially outwards the vanes  108  divide the chamber  114  in a number of separate partial chambers of different sizes (volumes). During rotation of the rotor  104 , the centrifugal force pushes the distal end surfaces of the vanes  108  radially outwards against an inner circumferential wall of the hollow cylinder-shaped housing  102 . Further, during rotation of the rotor  104 , the size of the various partial chambers changes continuously. Compressed air  116  enters into the chamber  114  or one of the partial chambers, respectively, through an ingress opening provided in the outer wall of the hollow cylinder-shaped housing  102 . At the end of an operation cycle air  118  may be discarded from the chamber  114  or from one or more of the partial chambers, respectively, through one or more egress openings  120  provided in the outer wall of the hollow cylinder-shaped housing  102 . In this embodiment three egress openings  120  are provided all spaced apart from one another in a circumferential direction. 
       FIG. 8  shows various operating states A, B, C during operation of the pneumatic motor  100  in a cross sectional view. In state A compressed air  116  enters into a first partial chamber “a” through the input opening. The adjacent partial chamber “b” anticipating partial chamber “a” is defined and sealed by second and third vanes  108   b,    108   c.  The pressure inside partial chamber “b” is still equal to the pressure of the inlet air  116  at the input opening. This pressure acting on the third vane  108   c  provokes a clockwise rotation of the rotor  104  and of the vanes  108  attached thereto (arrow  122 ). Then, in state B the vanes  108  have started their rotation in the cylinder housing  102  and an expansion process has begun in the partial room “b”. The internal pressure in partial room “b” gradually decreases but is still large enough to act on the third vane  108   c  in order to further rotate the rotor  104  clockwise. Further, in state C the vanes  108  have moved on and first and second vanes  108   a,    108   b  now define and seal the first partial chamber “a”. The pressure in partial chamber “b” is gradually decreasing and can no longer contribute to the rotation of the rotor  104  and, therefore, air  118  contained therein is at least partially discarded through the first egress opening  120 . The force for the further rotation of the rotor  104  in the direction  122  now comes from the first chamber “a” and from the following partial chamber, which is now in pneumatic connection with the inlet opening and which is now filled with compressed air  116 . As the rotation of the rotor  104  continues, further air  118  will be discarded from the partial chamber “b” into the environment through the following two egress openings  120 . These steps A, B, C will continue for all subsequent partial chamber defined in the chamber  114  by the vanes  108  as the rotation of the rotor  104  continues. The rotation will stop when further supply of compressed air  116  is interrupted. 
       FIG. 9  shows a longitudinal sectional view through a combined pneumatic machine  200  comprising the pneumatic motor  100  and the magnetic gear arrangement  20 . The motor  100  and the gear arrangement  20  are located next to each other and displaced in an axial direction along the rotational axis  60 . In order to integrate the magnetic gear arrangement  20  into the pneumatic motor  100 , the length of the hollow cylinder-shaped housing  102  of the motor  100  is extended in the axial direction. The extended portion of the housing  102  forms the stationary outer component  54  of the magnetic gear arrangement  20 . The permanent magnets  58  are attached to the inner circumferential wall of the extended portion of the hollow cylinder-shaped housing  102 . The motor shaft  22  is connected to the inner component  52  of the magnetic gear arrangement  20  in a torque proof manner. Alternatively, the motor shaft  22  could simply be extended and the permanent magnets  56  could be attached thereto, the extended portion of the motor shaft  22  with the magnets  56  then forming the inner component  52 . The intermediate component  51  with the ferromagnetic segments  50  is connected to an output or intermediate shaft  23  of the magnetic gear arrangement  20 . 
     In the embodiment of  FIG. 9  the housing  102  and the extended part of the housing  102  forming the outer component  54  of the magnetic gear arrangement  20  together with end plates  110 ,  112  form a closed housing in which the combined pneumatic machine  200  is located. The closed housing is particularly interesting for power tools  1  because it prevents dust and humidity from entering into the magnetic gear arrangement  20 , where they could have a negative impact on the free movement of the rotating parts (e.g.  50 ,  51 ,  52 ,  56 ) of the magnetic gear arrangement  20 . In this embodiment the magnetic flux is transmitted from the inner component  52  to the outer component  54  directly in a radial direction. 
     The end plate  110  may comprise a throughway opening  124 , which may be provided with a bearing and/or sealing means  126 . The output or intermediate shaft  23  extends through the throughway opening  124  and is guided by the bearing  126  and/or sealed in respect to the end plate  110  surrounding the throughway opening  124 . From there, the output shaft  23  could either be directly connected to the working element  9  or, alternatively, be indirectly connected by means of a magnetic bevel gear  21  and/or any other type of magnetic or mechanical gear arrangement, e.g. a hypocycloid gear arrangement, to the working element  9 . 
       FIGS. 10 to 12  show another embodiment of a pneumatic machine  300  combining a pneumatic motor  100  with a magnetic gear arrangement  20 . In order to integrate the magnetic gear arrangement  20  into the pneumatic motor  100 , the length of the hollow cylinder-shaped housing  102  is extended in the direction of the rotational axis  60 . The housing  102  is preferably made of a non-ferromagnetic material, such as some metals (e.g. aluminum, copper, messing, silver, gold) or plastic (e.g. fiber reinforced plastic). Attached to or inserted into the housing  102  are ferromagnetic segments  50  (pole pieces). In the embodiment of  FIGS. 10 to 12  there are two pole piece pairs corresponding to four pole pieces  50  located in a circumferentially equidistant manner in respect to one another. However, the number of pole pieces  50  could also be eight, resulting in four pole piece pairs. 
     In a first part (on the right in  FIG. 12 ) of the housing  102  the pneumatic motor  100  is provided as suggested by and shown in  FIG. 6 . In this embodiment the rotor  104  has a total of four circumferentially spaced apart slots  106  with radially movable vanes  108  located therein. The housing  102  comprises a separating wall  102   a  for pneumatically separating the inner chamber  114  provided in the housing  102  between the outer circumferential surface of the rotor  104  and the inner circumferential surface of the housing  102 . In particular, the separating wall  102   a  serves for pneumatically separating the half-moon shaped chamber  114  or the respective partial chambers of the pneumatic motor  100  from a chamber  102   b  located in the other part (on the left in  FIG. 12 ) of the housing  102  and in which the driven rotating component  54  of the magnetic gear arrangement  20  is located. In contrast to the embodiment of  FIG. 6 , in  FIGS. 10 to 12  the rotor  104  of the pneumatic motor  100  or the motor shaft  22 , respectively, is pivot-mounted only on one side in the bearing and/or sealing means  112   a  provided in the end plate  112 . However, it would also be possible to provide the separating wall  102   a  with a through opening and bearing and/or sealing means (not shown) located therein, which are adapted to receive an end of the shaft  22  opposite to the end plate  112 . In that case the rotor  104  or the motor shaft  22 , respectively, would be pivot-mounted rotatable about the rotational axis  60  on both its opposite ends. 
     In a circumferential direction the rotor  104  is provided with a first number of first permanent magnets  56 . In the shown embodiment the rotor  104  comprises a total of four permanent magnets  56 , which are located on a circumferential outer surface of the rotor  104  with an alternating polarity in a circumferential direction. Each permanent magnet  56  of a given polarity extends essentially parallel to the rotational axis  60 . Preferably, each of the permanent magnets  56  is located in the rotor  104  between two neighboring vanes  108 . 
     The second rotating component  54  of the magnetic gear arrangement  20  is pivot-mounted in the chamber  102   b  rotatable about the rotational axis  60  of the output shaft  23  of the gear arrangement  20  or another axis parallel to the rotational axis  60 . In the embodiment shown in  FIG. 12 , the motor shaft  22  and the intermediate shaft  23  rotate about the same rotational axis  60 . However, they could also rotate about two different axes running parallel and spaced apart in respect to one another. The rotating component  54  or the output shaft  23 , respectively, is preferably pivot-mounted only on one side in the bearing and/or sealing means  126  (see  FIG. 12 ) provided in the end plate  110 . However, the separating wall  102   a  could also be provided with a through opening and bearing and/or sealing means (not shown) located therein, which are adapted to receive an end of the output shaft  23  opposite to the separating wall  102   a.  In that case the rotating component  54  or the output shaft  23 , respectively, would be pivot-mounted rotatable about the rotational axis  60  on both its opposite ends. In this embodiment the magnetic flux is transmitted from the first component  52  to the second component  54  not directly, but rather indirectly by means of the ferromagnetic segments  50  in an essentially transverse direction. 
     The rotating component  54  is provided with a second number of second permanent magnets  58 . In the shown embodiment the rotating component  54  comprises a total of twelve permanent magnets  58  (corresponding to six pole pairs), which are located on a circumferential surface of the rotating component  54  with an alternating polarity (north N, south S) in a circumferential direction. Of course, any other number of second magnets  58  could be provided in or on the rotating component  54 , too. Each permanent magnet  58  of a given polarity extends essentially parallel to the axis  60 . The ratio between the number of second magnets  58  and the number of first magnets  56  defines the gear ratio i=n_output/n_input of the gear arrangement  20 . For the embodiment shown in  FIGS. 10 to 12  the gear ratio is i=12/4=3:1. This means that the rotor  104  of the pneumatic motor  100  rotates three times the speed of the output shaft  23 . However, a three times higher torque can be provided by the output shaft  23  due to the speed reduction. 
     The number of ferromagnetic pole pieces  50  is preferably either the difference between the number of pairs of second permanent magnets  58  and the number of pairs of first permanent magnets  56  (n_pp=6−2=4) or the sum of the number of pairs of second permanent magnets  58  and the number of pairs of first permanent magnets  56  (n_pp=6+2=8). With four ferromagnetic pole pieces  50  the direction of rotation of the output shaft  23  and the rotor  104  of the motor  100  is the same. With eight ferromagnetic pole pieces  50  the output shaft  23  rotates in an opposite direction than the rotor  104  of the motor  100 . Preferably, the numbers of first and second pairs of permanent magnets  56 ,  58  are selected as even numbers resulting in an even number of ferromagnetic pole pieces  50 . 
     According to this embodiment the magnetic gear arrangement  20  is partly integrated in the pneumatic motor  100  in the sense that the first set of permanent magnets  56  is located in or on the rotor  104  of the motor  100 . The magnetic field of the rotating first set of permanent magnets  56  is transmitted to the second set of permanent magnets  58  located in or on the rotating element  54  of the gear arrangement  20  by means of the ferromagnetic pole pieces  50  integrated in or on the housing  102 , thereby provoking a rotation of the rotating component  54  and the output shaft  23 , respectively, according to the gear ratio. 
       FIG. 12  shows an air gap labelled  128  provided between the rotating component  104  and the rotating component  54 . 
     This embodiment has the advantage that it provides for a highly integrated pneumatic machine  300 , which is particularly useful for use in a pneumatic power tool  1 . 
     Although the figures have been described as various separate embodiments, it is to be understood that certain features of one embodiment could also be applied to another embodiment, even though not explicitly mentioned herein. 
     It should be understood that, unless stated otherwise herein, any of the features, characteristics, alternatives or modifications described regarding a particular embodiment herein may also be applied, used, or incorporated with any other embodiment described herein. Also, the drawing herein is not drawn to scale. 
     Although the invention has been described and illustrated with respect to exemplary embodiments thereof, the foregoing and various other additions and omissions may be made therein and thereto without departing from the spirit and scope of the present invention.