HAND-HELD AND HAND-GUIDED MOTOR DRIVEN POLISHING OR SANDING TOOL

Abstract

 The invention refers to a hand-held and hand-guided motor driven polishing or sanding tool (2). The tool (2) has a tool housing (4) and a motor (6; 62) located therein. The tool (2) further has a polishing or sanding working element (8) attached to a tool shaft (10) of the tool (2). The motor (6; 62) is adapted to drive the tool shaft (10) in a first direction of rotation (12).
It is suggested that the tool (2) is equipped with a switch (44) for changing the sense of rotation of the tool shaft (10) between the first direction of rotation (12) and a second direction of rotation (42) opposite to the first direction of rotation (12).

Description

[0001] The present invention refers to a hand-held and hand-guided motor driven polishing or sanding tool. The tool has a tool housing, a motor located therein and a polishing or sanding working element attached to a tool shaft of the tool. The motor is adapted to drive the tool shaft in a first direction of rotation, thereby providing for a forced rotation of the working element in the first direction of rotation.

[0002] Hand-held and hand-guided polishing or sanding tools of the above-identified kind are well-known in the prior art. A common feature of all of the known polishing or sanding tools is the fact that the tool shaft and the working element attached thereto rotate only in one specific direction of rotation. In order to reduce swirl marks on the surface to be worked by the polishing or sanding tool, different types of working movement of the polishing or sanding working element have been suggested. For instance, different polishing or sanding tools are known, where depending on the way the working element is attached to the tool shaft the working element realizes a rotary, a random-orbital, an eccentric or circular oscillating or a gear-driven working movement.

[0003] Despite numerous attempts to reduce the swirl marks on the surface to be worked by means of the different types of working movements of the working element, it would be desirous to further reduce the formation of swirl marks on the surface to be worked by means of the polishing or sanding tool.

[0004] In order to solve this object, a polishing or sanding tool comprising the features of claim 1 is suggested. In particular, starting from the polishing or sanding tool of the above-identified kind, it is suggested that the tool is equipped with a switch for changing the sense of rotation of the tool shaft between the first direction of rotation and a second direction of rotation opposite to the first direction of rotation.

[0005] The inventors have found out that switching the direction of rotation of the working element to the opposite direction from time to time during polishing or sanding the surface to be worked, significantly reduces the formation of swirl marks on the surface. In particular, it reduces the amount of swirl marks and the depth and visibility of swirl marks created. The reason for this has been found in the fact that each user of a hand-held and hand-guided motor driven polishing or sanding tool has his/her own way of holding and guiding the tool over the surface to be worked resulting in a typical user-specific first pattern of swirl marks. By switching the direction of rotation of the working element to the opposite direction, the same user with his/her own way of holding and guiding the tool over the surface to be worked will create a different or even inverse second pattern of swirl marks on the surface to be worked. The two different patterns of swirl marks overlap or compensate each other, resulting in a reduced number and depth of visible swirl marks on the surface to be worked.

[0006] The switch for inverting the sense of rotation of the tool shaft and thus also of the backing plate attached thereto, may be actuated manually by a user of the power tool. Alternatively or additionally, the switch may also be actuated based on a time schedule (e.g. every x seconds or every y minutes; x and y being positive real numbers without zero, or depending on a time function) or randomly. Further, it would also be possible to actuate the switch for inverting the sense of rotation of the tool shaft each time after stand-still of the electric motor, the electric motor is started again. In this manner, every time the power tool is started up, the backing plate rotates in a direction opposite to the direction of rotation of the previous start up.

[0007] In some embodiments, the polishing or sanding tool and the polishing and sanding working element have relatively small and compact dimensions and are adapted for vehicle, watercraft and aircraft detailing and for spot repair of vehicle, watercraft and aircraft bodies. Furthermore, these relatively small polishing or sanding tools may be used for polishing or sanding of surfaces in tight and cramped spaces, for instance around door handles, in wheel rims, on radiator grills, in air intakes or the like. The design and dimensions of the relatively small and compact tools could be similar to those of the RUPES Big Foot iBrid Nano or the RUPES Q-Mag iBrid Nano, available on the market since a couple of years but having only a single direction of rotation of the tool shaft.

[0008] In some embodiments, the polishing or sanding tool and the polishing and sanding working element may have relatively large dimensions and are adapted to polish or sand large surfaces, in particular fillered or painted surfaces of vehicle, watercraft and aircraft bodies. The design and dimensions of the relatively large tools could be similar to those of the RUPES Big Foot LHR 21ES, the RUPES LHR Mark III (both having a random orbital movement of the working element), the RUPES LH 19E (having a rotary movement of the working element), the RUPES LK 900E (having a roto-orbital or gear-driven movement of the working element) or the RUPES TA50 (a pneumatic random orbital sander), all available on the market since a couple of years but having only a single direction of rotation of the tool shaft. In any case, the polishing or sanding tool is mobile and manually held and guided by a user over a surface to be worked.

[0009] Of course, the power tool could not only be held and guided by the hand of a user but also by the hand of a multi-dimensional robot, preferably making part of an automated polishing station, for instance at a car manufacturer's production plant.

[0010] The motor of the polishing or sanding tool may be an electric or a pneumatic motor. An electric polisher or sander may be operated by means of electric energy from a battery or from a mains power supply. Operation of a pneumatic polisher or sander is effected by means of pressurized air, which is fed to a pneumatic motor. The polishing or sanding tool may be a straight or angular polisher or sander.

[0011] Of course, depending on the way the working element is attached to the tool shaft, different movements of the working element itself can be achieved. For instance, the polishing or sanding working element may be directly attached to the tool shaft resulting in a rotational or rotary working movement of the working element in the first direction of rotation and upon actuation of the switch in the opposite second direction of rotation.

[0012] Preferably, the polishing or sanding working element is directly attached to the tool shaft resulting in a rotational working movement of the working element. In this embodiment, the working element can perform a rotational movement about the rotational axis of the tool shaft in a clockwise or in a counter-clockwise direction, depending on the actuation of the switch.

[0013] Alternatively, the polishing or sanding working element may be indirectly attached to the tool shaft by means of an eccentric element, the eccentric element being attached to the tool shaft in a torque proof manner and the working element being attached to the eccentric element in a freely rotatable manner, resulting in a random orbital working movement of the working element. The random orbital working movement is the result of a superposition of a forced rotation of the eccentric element together with the working element about an axis of rotation of the tool shaft and of the free rotation of the working element in respect to the eccentric element about an axis of rotation of the working element. The axes of rotation of the tool shaft and of the working element preferably extend parallel to and are spaced apart from each other.

[0014] In this embodiment, the working element is adapted to perform a random orbital working movement of the working element. The rotation of the eccentric element together with the working element about the axis of rotation of the tool shaft is effected in a clockwise or a counter-clockwise direction, depending on the actuation of the switch. The free rotation of the working element in respect to the eccentric element is not directly affected by the actuation of the switch and by switching the sense of rotation of the tool shaft about its axis of rotation. However, it may be affected indirectly in that an opposite sense of rotation of the eccentric element together with the working element about the axis of rotation of the tool shaft may provoke a different rotational movement of the working element about its axis of rotation in respect to the eccentric element.

[0015] In another alternative, starting from a polishing or sanding tool for effecting a random orbital working movement, the tool may comprise means for holding a rotational position of the polishing or sanding working element in respect to the tool housing or means for limiting a rotational movement of the polishing or sanding working element in respect to the tool housing. This will result in an eccentric or circular oscillating movement of the working element. The holding means may comprise one or more discrete elastic (e.g. rubber or soft plastic) elements, which are attached to the working element and the tool housing. Alternatively, the holding means may comprise an elastic collar (e.g. made of rubber or soft plastic) connecting the working element with the tool housing. In a further alternative, the holding means comprise one or more discrete magnetic elements provided on the working element and the tool housing, respectively, and magnetically interacting with each other.

[0016] Again, in this embodiment, the rotation of the eccentric element together with the working element about the axis of rotation of the tool shaft is effected in a clockwise or a counter-clockwise direction, depending on the actuation of the switch. The limited or restricted rotation of the working element in respect to the eccentric element is not directly affected by the actuation of the switch and by switching the sense of rotation of the tool shaft about its axis of rotation.

[0017] In yet another alternative, the polishing or sanding working element is indirectly attached to the tool shaft by means of a gear arrangement, in particular a planetary or epicyclic gear arrangement, resulting in a gear-driven or roto-orbital working movement of the working element in the first direction of rotation. In this embodiment the sense of rotation of the polishing or sanding working element about the tool shaft's axis of rotation may be reversed by actuating the switch.

[0018] The motor of the polishing or sanding tool may be an electric or a pneumatic motor. An electric motor may be fed by electric current originating from a battery making part of the tool. The battery is preferably rechargeable and may be fixedly located inside the tool housing, or it may be removably attached to the tool housing permitting removal of the battery from outside the tool housing and replacement by another battery or a specific power supply unit connected to mains current. Alternatively, the electric current for operating the electric motor originates from a mains power supply. To this end, the tool may be provided with a power supply unit adapted for transforming the mains power voltage (e.g. 230V, 110V or the like) into an operation voltage of the tool (e.g. 12V, 18V, 24V, 36V, 48V or the like) and possibly for performing a filtering and rectifying functionality. The power supply unit may be fixedly located inside the tool housing, it may be provided as a separate unit outside the tool housing or it may be removably attached to the tool housing instead of a battery.

[0019] Operation of a pneumatic motor is effected by means of pressurized air, which is fed to the pneumatic motor. The pneumatic motor has a rotor with a plurality of vanes extending essentially radially from a rotor axis and a plurality of pneumatic chambers each defined between two neighbouring vanes. The pressurized air is subsequently fed to at least one pneumatic chamber after the other through a fixed air inlet, thereby setting the rotor into rotation and moving the pneumatic chamber toward a fixed air outlet and discarding the pressurized air once the pneumatic chamber has reached the air outlet. The air inlet and the air outlet of the pneumatic motor are spaced apart from each other in a circumferential direction of the rotor.

[0020] According to a preferred embodiment of the invention it is suggested that the switch is provided in the tool such that it can be actuated from outside the tool housing. Preferably, the switch is provided in a hole or cut-out of the tool housing in order to allow at least part of the switch to protrude to the outside of the tool housing. The switch may be embodied as a simple changeover switch or as a rotational switch or the like. The switch may be an integral part of an on/off switch of the polishing or sanding tool, by means of which the motor is turned on or off. Further, the switch may be an integral part of a rotational switch of the polishing or sanding tool, by means of which the rotational speed of the tool or the motor, respectively, is set to a desired value. It would even be possible that the switch for changing the sense of rotation of the tool shaft and an on/off switch are both an integral part of a rotational switch of the polishing or sanding tool for setting the rotational speed. For instance, in a centre position of the rotational switch, the polishing or sanding tool or the motor, respectively, could be turned off. A rotation of the switch to the left or right will turn the motor on and make it rotate in one of two opposite directions. The further the switch is rotated to the left or right, the faster the motor rotates. The switch can be used in combination with an electric or a pneumatic motor.

[0021] Preferably, the switch is adapted to be manually actuated by a user of the tool without the necessity to use a specific actuating tool or the like. According to this embodiment, the switch can be simply operated by a finger or a hand of the user. Advantageously, the switch is adapted to be actuated by a user with his finger or hand even when wearing gloves. To this end, the switch may be designed large enough and/or provided with a noticeable user feedback when switching, so that the user notices when he/she has actuated the switch, even when wearing gloves.

[0022] The switching of the direction of rotation of the tool shaft may be effected in many different ways. According to a first possibility, it is suggested that the polishing or sanding tool has a gear transmission functionally located between the motor and the tool shaft, the gear transmission being adapted to change the sense of rotation of the tool shaft between the first direction of rotation and the second direction of rotation upon actuation of the gear transmission, and the switch being adapted to actuate the gear transmission. In this embodiment, the direction of rotation of the motor remains the same. The gear transmission has an input shaft in the form of a motor shaft or of another shaft connected to the motor shaft. An output shaft of the gear transmission is the tool shaft or another shaft connected to the tool shaft. The gear transmission is designed such that upon actuation of the gear transmission the sense of rotation of the output shaft can be changed to the opposed direction with the input shaft continuously rotating in the same direction. Preferably, actuation of the gear transmission is effected with the input shaft and the output shaft stationary, i.e. not rotating, e.g. in an idle state of the motor. Such a gear transmission can be realized in combination with an electric or with a pneumatic motor. The switch may act as an actuating element for actuating the gear transmission, similar to a gearstick of a gear box of a motor vehicle.

[0023] According to another possibility, the polishing or sanding tool has an electric motor and the switch is adapted to invert the flow direction of electric current through the electric motor, preferably by means of an electric switch. A reversal of the current flow through an electric motor reverses the motor's direction of rotation. The electrical switch preferably comprises an electric change-over switch for reversing the direction of the current flow. The advantage of this embodiment is that the switch can be actuated even during rotation of the motor in a given direction without the risk of mechanical damage to the motor, shafts and/or gear transmissions of the polishing or sanding tool.

[0024] According to yet another possibility, the polishing or sanding tool has a pneumatic motor and the switch is adapted to invert the flow direction of pressurized air through the pneumatic motor, preferably by means of a pneumatic switching valve. A reversal of the air flow through a pneumatic motor reverses the motor's direction of rotation. The pneumatic switching valve preferably comprises a pneumatic change-over valve for reversing the direction of the air flow. The advantage of this embodiment is that the switch can be actuated even during rotation of the motor in a given direction without the risk of mechanical damage to the motor, shafts and/or gear transmissions of the polishing or sanding tool.

[0025] Further embodiments and advantages of the present invention will become apparent by means of the following description when taken together with the drawings. It is emphasised that each of the features shown in the drawings may be essential for the present invention on its own or in combination with any of the other features shown therein, even if not explicitly shown in the drawings and/ or described in the description. Furthermore, the features shown in the drawings may be essential for the invention in any possible combination even if such a combination is not shown in the drawings and/or not described in the description. The drawings show:

Fig. 1

a first embodiment of the polishing or sanding tool according to the present invention;

Fig. 2

a second embodiment of the polishing or sanding tool according to the present invention;

Fig. 3

a third embodiment of the polishing or sanding tool according to the present invention;

Fig. 4

a fourth embodiment of the polishing or sanding tool according to the present invention;

Fig. 5

a fifth embodiment of the polishing or sanding tool according to the present invention;

Fig. 6

a further embodiment of an attachment of a polishing or sanding working element to a tool shaft of the polishing or sanding tool according to one of the Figs. 1 to 5;

Fig. 7

another embodiment of an attachment of a polishing or sanding working element to a tool shaft of the polishing or sanding tool according to one of the Figs. 1 to 5; and

Fig. 8

a schematic view of a pattern formed on a surface to be worked with a power tool according to the invention which performs a rotary working movement;

Fig. 9

a schematic view of a pattern formed on a surface to be worked with a power tool according to the invention which performs a random orbital working movement;

Fig. 10

a schematic view of a pattern formed on a surface to be worked with a power tool according to the invention which performs a gear-driven or roto-orbital working movement; and

Fig. 11

a schematic view of a pattern formed on a surface to be worked with a power tool according to the invention which performs an eccentric or circular oscillating working movement.

[0026] Fig. 1 shows a schematic view of a first embodiment of a hand-held and hand-guided motor driven polishing or sanding tool 2. The tool 2 comprises a tool housing 4, an electric motor 6 located therein and a polishing or sanding working element 8 attached to a tool shaft 10 of the tool 2. The motor 6 is adapted to drive the tool shaft 10 in a first direction of rotation 12 about an axis of rotation 14 of the tool shaft 10. Thereby the motor 6 provides for a forced rotation of the working element 8 in the first direction of rotation 12.

[0027] The tool 2 according to Fig. 1 has a rechargeable battery 16 inserted into a recess 18 provided at a rear end of the tool housing 4. The battery 16 provides electric energy to the electronic components of the tool 2 for their operation. An electronic control unit (ECU) 20 may be located functionally between the battery 16 and the electric motor 6. The ECU 20 is connected to the battery 16 through at least two wires 22 and receives the electric energy from the battery 16 depending on specific inputs from a user of the tool 2 and/or possibly also on other external parameters (e.g. an ambient temperature, an operation temperature of the motor 6 and/or the ECU 20, etc.).

[0028] Specific inputs from the user of the tool 2 may be provided by means of an on/off switch 24 for selectively turning on and off the tool 2 or its motor 6, respectively. The switch 24 is provided in the tool housing 4, preferably in a cut-out or a hole of the tool housing 4, so it can be easily actuated by the user from outside the housing 4. The switch may be embodied as any possible type of an electric switch, e.g. an electrical changeover switch or a rotary switch. The switch 24 is connected to the ECU 20 in order to provide a switching signal 26 indicative on the actuation of the switch 24 by the user to the ECU 20. Depending on the switching signal 26 received from the on/off switch 24, the ECU 20 provides a respective electric operation signal 28 to the motor 6. Preferably, the operation signal 28 is zero if no operation of the motor 26 is desired, i.e. the tool 2 is turned off by means of the on/off switch 24.

[0029] Furthermore, specific inputs from the user of the tool 2 may be provided by means of a rotational switch 30 of the polishing or sanding tool 2, by means of which a rotational speed of the tool 2 or the motor 6, respectively, is set to a desired value. The rotational switch 30 is provided in the tool housing 4, preferably in a cut-out or a hole of the tool housing 4, so it can be easily actuated or operated by the user from outside the housing 4. The switch 30 is connected to the ECU 20 in order to provide a driving signal 32 indicative on the actuation or operation of the switch 30 by the user to the ECU 20. Depending on the driving signal 32 received from the rotational switch 30, the ECU 20 provides a respective electric operation signal 28 to the motor 6 or modifies the electric operation signal 28. The electric operation signal 28 may comprise a flow of electric current in a certain direction and of a certain value.

[0030] The motor 6 drives a motor shaft 34. The motor shaft 34 constitutes an input shaft of a gear transmission 36. The gear transmission 36 is located functionally between the motor 6 and the tool shaft 10. In the present case, a bevel gear arrangement 38 is located functionally between the gear transmission 36 and the tool shaft 10. The bevel gear arrangement 38 translates a rotation of an output shaft 40 of the gear transmission 36 into a rotation of the tool shaft 10. Rotational axes of the output shaft 40 (also constituting the input shaft of the bevel gear arrangement 38) and the tool shaft 10 run in a certain angle in respect to each other, preferably in an angle of approximately 90° (e.g. from 80° to 100°). The bevel gear arrangement 38 may have a transmission ration of i=1, of i>1 (tool shaft 10 rotates slower than output shaft 40) or of i<1 (tool shaft 10 rotates faster than output shaft 40).

[0031] The gear transmission 36 is adapted to change the sense of rotation of the output shaft 40 and, therefore, also of the tool shaft 10 between the first direction of rotation 12 and a second direction of rotation 42 opposite to the first direction of rotation 12 upon actuation of the gear transmission 36. The polishing or sanding tool 2 comprises a switch 44, which is adapted to actuate the gear transmission 36. In this embodiment, the direction of rotation of the motor shaft 34 always remains the same irrespective of the direction of rotation 12, 42 of the tool shaft.

[0032] The gear transmission 36 has an input shaft in the form of the motor shaft 34. Alternatively, another shaft connected to the motor shaft 34 could form the input shaft of the gear transmission 36. An output shaft 40 of the gear transmission 36 is a shaft in functional connection to the tool shaft 10 by means of the bevel gear arrangement 38. The gear transmission 36 is designed such that upon its actuation the sense of rotation of the output shaft 40 can be changed to the opposed direction with the input shaft (motor shaft 34) continuously rotating in the same direction. Preferably, actuation of the gear transmission 36 is effected with the input shaft (motor shaft 34) and the output shaft 40 stationary, i.e. not rotating, e.g. in an idle state of the motor 6. Such a gear transmission 36 can be realized in combination with an electric motor 6 or with a pneumatic motor. The switch 44 may act as an actuating element for manually actuating the gear transmission 36, similar to gearstick of a gear box of a motor vehicle. Alternatively, the switch 44 may act as an actuating element for electrically actuating the gear transmission 36. In that case, the gear transmission 36 is provided with electric actuation means for actuating the gear transmission 36, the electric actuation means being controlled by the switch 44.

[0033] In the embodiment of Fig. 1, the working element 8 comprises a backing plate 46 comprising a support layer made of a rigid or semi-rigid material, e.g. metal and/or a hard plastic material, and possibly a damping layer made of a more elastic material than the support layer, e.g. rubber, a soft plastic material and/or a foamed plastic material or the like. The backing plate 46 is attached to the tool shaft 10 with its support layer. Preferably, the backing plate 46 is releasably attached to the tool shaft 10, e.g. by means of a central screw or magnetically. A bottom surface of the backing plate 46 is provided with an attachment layer, e.g. an adhesive layer or part of a hook-and-loop fastener (Velcro^®).

[0034] While the shape of the backing plate 46 in a top view is preferably circular when the polishing or sanding working element 8 performs a rotary, a random orbital or a gear-driven working movement, it is preferably rectangular or delta-shaped when the working element 8 performs an eccentric working movement.

[0035] Further, a polishing member 48 (e.g. a foam pad, a wool pad, a micro fibre pad) or a sanding member (e.g. a sanding pad, a sanding paper, a sanding fabric) may be releasably attached to the attachment layer of the backing plate 46 thereby turning the working element 8 into a polishing working element or a sanding working element. To this end it is suggested that the polishing member 48 or the sanding member comprises another part of the hook-and-loop fastener on its top surface adapted to interact with the attachment layer of the backing plate 46.

[0036] In some embodiments, the polishing or sanding tool 2 and the polishing and sanding working element 8 have relatively small and compact dimensions and are adapted for vehicle, watercraft and aircraft detailing and for spot repair of vehicle, watercraft and aircraft bodies. In these embodiments, a polishing member 48 in the form of a foam polishing pad may have a diameter from approximately 30mm (on the upper side) and 40mm (on the bottom side) to approximately 50mm/70mm. In other embodiments, the polishing or sanding tool 2 and the polishing and sanding working element 8 have relatively large dimensions and are adapted to polish or sand large surfaces, in particular fillered or painted surfaces of vehicle, watercraft and aircraft bodies. In these embodiments, a polishing member 48 in the form of a foam polishing pad may have a diameter from approximately 80mm (on the upper side) and 100mm (on the bottom side) to approximately 150mm/180mm. In any case, the polishing or sanding tool 2 is mobile and manually held and guided by a user over a surface to be worked.

[0037] Depending on the way the working element 8 is attached to the tool shaft 10, different movements of the working element 8 itself and of the polishing member 48 or sanding member attached to the working element 8 can be achieved, in particular a rotary movement, a random-orbital movement, an eccentric or circular oscillating movement or a gear-driven movement.

[0038] In the embodiment of Fig. 1, the polishing or sanding working element 8 is directly attached to the tool shaft 10 resulting in a rotary working movement of the working element 8. In this embodiment, the working element can perform a rotational movement about the rotational axis 14 of the tool shaft 10 in a clockwise direction 12 or in a counter-clockwise direction 42, depending on the actuation of the switch 44.

[0039] In another, the polishing or sanding working element 8 is indirectly attached to the tool shaft 10 by means of an eccentric element 50 (see Fig. 6). The eccentric element 50 is attached to the tool shaft 10 in a torque proof manner, i.e. the eccentric element 50 performs the same rotational movement about the axis of rotation 14 as the tool shaft 10. The working element 8 is attached to the eccentric element 50 in a freely rotatable manner. The free rotation can be achieved, for example, by means of one or more bearings 52. In particular, a support layer of a backing plate 46 may comprise or may be attached to an attachment shaft 54, which is supported in the eccentric element 50 in a manner freely rotatable about an axis of rotation 56. The rotational axes 14 and 56 of the tool shaft 10 and the working element 8, respectively, are spaced apart from and run parallel to each other. This embodiment results in a random orbital working movement of the working element 8.

[0040] The rotation of the eccentric element 50 together with the working element 8 about the axis of rotation 14 of the tool shaft 10 is effected in a clockwise or a counter-clockwise direction, depending on the actuation of the switch 44. The direction of the free rotation of the working element 8 in respect to the eccentric element 50 is not directly affected by the actuation of the switch 44 and by switching the sense of rotation of the tool shaft 10 about its axis of rotation 14. However, it may be affected indirectly in that an opposite sense of rotation of the eccentric element 50 together with the working element 8 about the axis of rotation 14 of the tool shaft 10 may provoke a different rotational movement of the working element 8 about its axis of rotation 56 in respect to the eccentric element 50.

[0041] In another alternative embodiment, starting from a polishing or sanding tool 2 for effecting a random orbital working movement, the tool 2 may comprise means or one or more devices 58 for holding the polishing or sanding working element 8 in a rotational position in respect to the tool housing 4, i.e. means 58 for limiting a rotational movement of the polishing or sanding working element 8 about the axis of rotation 56 in respect to the tool housing 2. This will result in an eccentric or circular oscillating movement of the working element 8. The holding means 58 may comprise one or more discrete elastic (e.g. rubber or soft plastic) elements, which are attached to the working element 8 and the tool housing 2. Alternatively, the holding means 58 may comprise an elastic collar (e.g. made of rubber or soft plastic) connecting the working element 8 with the tool housing 2. In a further alternative, the holding means 58 comprise one or more discrete magnetic elements provided on the working element 8 and the tool housing 2, respectively, and magnetically interacting with each other (see EP 3 736 084 A1).

[0042] Again, in this embodiment, the rotation of the eccentric element 50 together with the working element 8 about the axis of rotation 14 of the tool shaft 10 is effected in a clockwise or a counter-clockwise direction, depending on the actuation of the switch 44. The limited or restricted rotation of the working element 8 in respect to the eccentric element 50 is not directly affected by the actuation of the switch 44 and by switching the sense of rotation of the tool shaft 10 about its axis of rotation 14.

[0043] In yet another alternative embodiment, the polishing or sanding working element 8 is indirectly attached to the tool shaft 10 by means of a gear arrangement 60, in particular a planetary or epicyclic gear arrangement, resulting in a gear-driven or roto-orbital working movement of the working element 8 in the first direction of rotation 12 or the second direction of rotation 42, depending on the actuation of the switch 44. In this embodiment the sense of rotation of the polishing or sanding working element 8 about the tool shaft's axis of rotation 14 may be reversed by actuating the switch 44.

[0044] The motor of the polishing or sanding tool 2 may be an electric motor 6 (see Figs. 1 to 4) or a pneumatic motor 62 (see Fig. 5). Operation of a pneumatic motor 62 is effected by means of pressurized air, which is fed to the pneumatic motor 62. The pneumatic motor 62 has a rotor with a plurality of vanes extending essentially radially from a rotor axis and a plurality of pneumatic chambers each defined between two neighbouring vanes. The pressurized air is subsequently fed to at least one pneumatic chamber after the other through a fixed air inlet 64, thereby setting the rotor into rotation and moving the pneumatic chamber toward a fixed air outlet 66 and discarding the pressurized air once the pneumatic chamber has reached the air outlet 66. The air inlet 64 and the air outlet 66 of the pneumatic motor 62 are spaced apart from each other in a circumferential direction of the rotor.

[0045] In the embodiment of Fig. 5, the polishing or sanding tool 2 has a pneumatic motor 62 and the switch 44 is adapted to cause an inversion of the flow direction of pressurized air through the pneumatic motor 6, i.e. the air inlet 64 and the air outlet 66 are swapped. This may be achieved, for example, by means of a pneumatic switching valve 68. The valve 68 is actuated by means of the switch 44. A reversal of the air flow through the pneumatic motor 62 reverses the motor's direction of rotation and, consequently, through the motor shaft 34 and the bevel gear arrangement 38 also of the tool shaft 10 and of the working element 8 attached thereto. The pneumatic switching valve 68 may comprise a pneumatic change-over valve for reversing the direction of the air flow. The advantage of this embodiment is that the switch 44 can be actuated even during rotation of the motor 62 in a given direction without the risk of mechanical damage to the motor 62, shafts 34, 10 and/or gear transmissions, e.g. the gear transmission 36 or the bevel gear arrangement 38, of the polishing or sanding tool 2.

[0046] The pneumatic switching valve 68 comprises an air source inlet 70 connected to a source of pressurized air. In this embodiment, the air source inlet 70 is connected to an inlet port 72, to which a pressurized air tube 74 is connected. The opposite end of the air tube 74 is connected to the source of pressurized air, e.g. an air compressor. Located functionally between the inlet port 72 and the air source inlet 70 is a pneumatic switching valve, e.g. in the form of a proportional air valve 76, actuated by means of a combined switch 82. The combined switch 82 combines the on/off switch 24 and the rotational switch 30 of Fig. 1.

[0047] In this embodiment, the combined switch 82 comprises a lever 78 pivotable about a pivot axis 80 extending perpendicular to a longitudinal extension (= from the inlet port 72 to the bevel gear arrangement 38) of the tool housing 4. The lever 78 can be actuated by the user of the tool 2, thereby pressing the lever 78 more or less down towards the tool housing 4. The lever 78 is held in its pivot position furthest away from the tool housing 4 by means of a spring element (not shown). In its pivot position furthest away from the tool housing 4, the position of the lever 78 corresponds to a turned off tool 2 or motor 62. In its pivot position nearest to the tool housing 4, the position of the lever 78 corresponds to a turned on tool 2 with the motor 62 rotating at its maximum speed. Any intermediate pivot position of the lever 78 corresponds to a turned on tool 2 with the motor 62 rotating at an intermediate speed. Thus, pressing the lever 78 further down towards the tool housing 4 turns on the tool 2 and the motor 62 and accelerates the motor speed. Acceleration of the motor 62 is effected by opening the proportional air valve 76 more and allowing more pressurized air to flow into the pneumatic switching valve 68. In the embodiment, the lever 78 and the combined switch 82 are located on a bottom surface of the tool housing 4. Of course, the lever 78 and the combined switch 82 could also be located on a top surface of the tool housing 4.

[0048] Further embodiments of the present invention are shown with reference to Figs. 2 to 4 all referring to a polishing or sanding tool 2 with an electric motor 6. In the embodiment of Fig. 2, instead of the gear transmission 36 of Fig. 1, an electric switch 84, preferably an electric change-over switch, is provided. The electric switch 84 may form an integral part of the ECU 20, e.g. in the form of one or more diodes, transistors and/or thyristors. Alternatively, the electric switch 84 may be provided separately from the ECU 20 in the tool housing 4. The electric switch 84 is adapted to invert the flow of electric current in the electric operation signal 28 to the electric motor 6 upon activation through the switch 44. By inverting the current flow, the direction of rotation of the motor 6 and, consequently, of the motor shaft 34 and through the bevel gear arrangement 38 of the tool shaft 10. The advantage of this embodiment is that the switch 44 can be actuated even during rotation of the motor 6 in a given direction without the risk of mechanical damage to the motor 6, shafts 34, 10 and/or gear transmissions, e.g. bevel gear arrangement 38, of the polishing or sanding tool 2.

[0049] In the embodiment of Fig. 3, a combined switch 82 is provided which combines the on/off switch 24 and the rotational switch 30 of Fig. 1. The combined switch 82 comprises a lever 78 pivotable about a pivot axis 80 extending perpendicular to a longitudinal extension (= from the battery 16 to the bevel gear arrangement 38) of the tool housing 4. The lever 78 can be actuated by the user of the tool 2, thereby pressing the lever 78 more or less down towards the tool housing 4. The lever 78 is held in its pivot position furthest away from the tool housing 4 by means of a spring element (not shown). In its pivot position furthest away from the tool housing 4, the position of the lever 78 corresponds to a turned off tool 2 or motor 6. In its pivot position nearest to the tool housing 4, the position of the lever 78 corresponds to a turned on tool 2 with the motor 6 rotating at its maximum speed. Any intermediate pivot position of the lever 78 corresponds to a turned on tool 2 with the motor 6 rotating at an intermediate speed. Thus, pressing the lever 78 further down towards the tool housing 4 turns on the tool 2 and the motor 6 and accelerates the motor speed. Acceleration of the motor 6 is effected by means of a potentiometer or the like and allowing a higher value of electric current to flow into the electric motor 6 per time unit. In the embodiment, the lever 78 and the combined switch 82 are located on a top surface of the tool housing 4. Of course, the lever 78 and the combined switch 82 could also be located on a bottom surface of the tool housing 4.

[0050] In the embodiment of Fig. 4, a single combined switch 86 is provided in the tool housing 4, the combined switch 86 combining an on/off switch 24 for turning on and off the motor 6, a rotational switch 30 for changing the speed of the motor 6 and a switch 44 for changing the sense of rotation of the tool shaft 10. The combined switch 86 may be embodied as a rotational switch. For instance, in a centre position of the combined switch 86, the polishing or sanding tool 2 or the motor 6, respectively, is turned off. A rotation of the switch 86 to the left or right will turn the motor 6 on and make it rotate in one of two opposite directions 12, 42. The further the switch 86 is rotated to the left or right, the faster the motor 6 rotates.

[0051] It is suggested that the switch 44 is provided in the tool 2 such that it can be actuated from outside the tool housing 4. Preferably, the switch 44 is provided in a hole or cut-out of the tool housing 4 in order to allow at least part of the switch 44 to protrude to the outside of the tool housing 4. The switch 44 may be embodied as a simple changeover switch or as a rotational switch or the like. The switch 44 may be an integral part of an on/off switch 24 of the polishing or sanding tool 2, by means of which the motor 6, 62 is turned on or off. Further, the switch 44 may be an integral part of a rotational switch 30 of the polishing or sanding tool 2, by means of which the rotational speed of the tool 2 or the motor 6, 62, respectively, is set to a desired value. It would even be possible that the switch 44 for changing the sense of rotation of the tool shaft 10 and an on/off switch 24 are both an integral part of a rotational switch 30 of the polishing or sanding tool 2 for setting the rotational speed, thereby forming the combined switch 86 of Fig. 4.

[0052] Preferably, the switch 44 is adapted to be manually actuated by a user of the tool 2 without the necessity to use a specific actuating tool or the like. According to this embodiment, the switch 44 can be simply operated by a finger or a hand of the user. Advantageously, the switch 44 is adapted to be actuated by a user with his finger or hand even when wearing gloves. To this end, the switch 44 may be designed large enough and/or provided with a noticeable user feedback when switching, so that the user notices when he/she has actuated the switch 44, even when wearing gloves.

[0053] Now, referring to the various patterns on the surface to be worked shown in Figs. 8 to 11, it has been found that a specific user of a hand-held and hand-guided motor driven polishing or sanding tool 2 has his/her own way of holding and guiding the tool 2 over the surface to be worked resulting in a typical user-specific first pattern 88 of swirl marks (solid lines). By switching the direction of rotation of the working element 8 to the opposite direction, the same user with his/her own way of holding and guiding the tool 2 over the surface to be worked will create a different or even inverse second pattern 90 of swirl marks (dashed lines) on the surface to be worked. The two different patterns 88, 90 of swirl marks overlap or compensate each other, resulting in a reduced number and depth of visible swirl marks on the surface to be worked.

[0054] Fig. 8 is a schematic view of the patterns 88, 90 realized during a rotary working movement of the polishing or sanding working element 8. If the user holds the power tool 2 in a slightly inclined manner in respect to the extension of the surface to be worked, a bottom surface of the polishing member 48 or of the sanding member, which is attached to the bottom surface of the backing plate 46, will be pressed irregularly onto the surface to be worked. In particular, the working element 8 will be pressed with a larger pressure on the side of the working element 8 inclined towards the surface to be worked, and - if at all - with a smaller pressure on the side of the working element 8 inclined away from the surface to be worked. This results in swirl marks of the patterns 88, 90 having increasing or decreasing widths along their extensions. This is represented schematically by the size of the arrows representing the swirl marks of the patterns 88, 90. It can be well seen in Fig. 8 that the patterns 88, 90 of the swirl marks of the working element 8 rotating in opposite directions overlap and compensate each other. This is even more the case when the working element 8 is moved laterally (i.e. sideways and/or up and down) over the surface to be worked during the intended use of the power tool 2.

[0055] Fig. 9 is a schematic view of the patterns 88, 90 realized during a random orbital (or dual action) working movement of the polishing or sanding working element 8. Due to the free rotation of the working element 8 in respect to the eccentric element 50, the bottom surface of the polishing member 48 or of the sanding member moves over the surface to the worked in an irregular manner. This applies for a rotation of the working element 8 in both directions. It can be well seen in Fig. 9 that the patterns 88, 90 of the swirl marks of the working element 8 rotating in opposite directions overlap and compensate each other. This is even more the case when the working element 8 is moved laterally over the surface to be worked during the intended use of the power tool 2. The dimension d corresponds to the orbit of the working element 8 about the rotational axis 14 of the tool shaft 10.

[0056] Fig. 10 is a schematic view of the patterns 88, 90 realized during a gear-driven (or roto-orbital) working movement of the polishing or sanding working element 8. Due to the attachment of the working element 8 to the tool shaft 10 indirectly by means of the gear arrangement 60, the rotation of the working element 8 about the axis of rotation 56 of the attachment shaft 54 is forced and depends on the rotation of the gear arrangement 60 or parts (e.g. certain gear wheels) thereof about the axis of rotation 14 of the tool shaft 10. The bottom surface of the polishing member 48 or of the sanding member moves over the surface to the worked in a regular manner. This applies for a rotation of the working element 8 in both directions. It can be well seen in Fig. 10 that the patterns 88, 90 of the swirl marks of the working element 8 rotating in opposite directions overlap and compensate each other. This is even more the case when the working element 8 is moved laterally over the surface to be worked during the intended use of the power tool 2.

[0057] Finally, Fig. 11 is a schematic view of the patterns 88, 90 realized during an eccentric or circular oscillating working movement of the polishing or sanding working element 8. Due to the limitation of the free rotation of the working element 8 in respect to the tool housing 4 by means of the means or one or more devices 58, the bottom surface of the polishing member 48 or of the sanding member moves in small circles over the surface to the worked. This applies for a rotation of the working element 8 in both directions. It can be well seen in Fig. 11 that the patterns 88, 90 of the swirl marks of the working element 8 rotating in opposite directions overlap and compensate each other. This is even more the case when the working element 8 is moved laterally over the surface to be worked during the intended use of the power tool 2. The dimensions d correspond to the orbit of the working element 8 about the rotational axis 14 of the tool shaft 10.

Claims

1. Hand-held and hand-guided motor driven polishing or sanding tool (2), the tool (2) having a tool housing (4) and a motor (6; 62) located therein and a polishing or sanding working element (8) attached to a tool shaft (10) of the tool (2), wherein the motor (6; 62) is adapted to drive the tool shaft (10) in a first direction of rotation (12),
characterized in that
the tool (2) is equipped with a switch (44) for changing the sense of rotation of the tool shaft (10) between the first direction of rotation (12) and a second direction of rotation (42) opposite to the first direction of rotation (12).

2. Polishing or sanding tool (2) according to claim 1, wherein
the switch (44) is provided in the tool (2) such that it can be actuated from outside the tool housing (4).

3. Polishing or sanding tool (2) according to claim 1 or 2, wherein
the switch (44) is adapted to be manually actuated by a user of the tool (2) without the necessity to use a specific actuating tool or the like.

4. Polishing or sanding tool (2) according to one of the preceding claims, wherein
the tool (2) has a gear transmission (36) functionally located between the motor (6; 62) and the tool shaft (10), the gear transmission (36) being adapted to change the sense of rotation of the tool shaft (10) between the first direction of rotation (12) and the second direction of rotation (42) upon actuation of the gear transmission (36), and the switch (44) being adapted to actuate the gear transmission (36).

5. Polishing or sanding tool (2) according to one of the preceding claims 1 to 3, wherein
the tool (2) has an electric motor (6) and the switch (44) is adapted to invert the flow direction of electric current through the electric motor (6), preferably by means of an electric switch (84).

6. Polishing or sanding tool (2) according to one of the preceding claims 1 to 3, wherein
the tool (2) has a pneumatic motor (62) and the switch (44) is adapted to invert the flow direction of pressurized air through the pneumatic motor (62), preferably by means of a pneumatic switching valve (68).

7. Polishing or sanding tool (2) according to one of the preceding claims, wherein
the polishing or sanding working element (8) is indirectly attached to the tool shaft (10) by means of an eccentric element (50), the eccentric element (50) being attached to the tool shaft (10) in a torque proof manner and the working element (8) being attached to the eccentric element (50) in a freely rotatable manner in respect to the eccentric element (50).

8. Polishing or sanding tool (2) according to claim 7, wherein
the tool (2) comprises means for holding a rotational position of the polishing or sanding working element (8) in respect to the tool housing (4) or means (58) for limiting a rotational movement of the polishing or sanding working element (8) in respect to the tool housing (4).

9. Polishing or sanding tool (2) according to one of the preceding claims 1 to 7, wherein
the polishing or sanding working element (8) is directly attached to the tool shaft (10) resulting in a rotational working movement of the working element (8).

10. Polishing or sanding tool (2) according to one of the preceding claims 1 to 7, wherein
the polishing or sanding working element (8) is indirectly attached to the tool shaft (10) by means of a gear arrangement (60), in particular a planetary gear arrangement, resulting in a gear-driven or roto-orbital working movement of the working element (8).

Drawing