HAND HELD OR HAND GUIDED GRINDING OR POLISHING MACHINE TOOL

Abstract

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 drawings herein are 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.

Claims

1. Hand held or hand guided grinding or polishing machine tool (1), comprising: a working element holder (12) having a first connection element (36) for connecting the working element holder (12) to a disk-like working element (9) and a center axis (14), the first connection element (36) for connecting the working element holder (12) to the disk-like working element (9) having a rotational axis (37) running parallel to a center axis (14) of the working element holder (12), the working element holder (12) further having a second connection element (15) for connecting the working element holder (12) to a motor shaft (22) of the hand held or hand guided grinding or polishing machine tool (1) in a torque proof manner, and the second connection element (15) for connecting the working element holder (12) to the motor shaft (22) having a longitudinal axis (16) running parallel to a rotation axis (37) of the first connection element (36) and to the center axis (14) of the working element holder (12, characterized in that all three axes (14, 16, 37) are spaced apart from one another by predefined distances.

2. Hand held or hand guided grinding or polishing machine tool (1) according to claim 1, wherein the center axis (14) of the working element holder (12) is located between the rotational axis (37) of the first connection element (36) and the longitudinal axis (16) of the second connection element (15).

3. Hand held or hand guided grinding or polishing machine tool (1) according to claim 1, wherein, in a top view onto the working element holder (12), the center axis (14) of the working element holder (12), the rotation axis (37) of the first connection element (36) and the longitudinal axis (16) of the second connection element (15) are located on a virtual center line (19) radially extending from the center axis (14).

4. Hand held or hand guided grinding or polishing machine tool (1) according to claim 1, wherein, in a top view onto the working element holder (12), the center axis (14) and longitudinal axis (16) located between the other two axes (37, 16; 37, 14) are connected to a first axis (37; 14) of the two other axes (37, 16; 37, 14) by means of a first virtual line (19) and connected to a second axis (16; 37) of the two other axes (37, 16; 37, 14) by means of a second virtual line (20), wherein the first virtual line (19) and the second virtual line (20) are located in an angle between 0° and 90°, wherein the angle is ≠0° in respect to one another.

5. Hand held or hand guided grinding or polishing machine tool (1) according to claim 4, wherein the angle between the first virtual line (19) and the second virtual line (20) is <30°, including where the angle is about 15°.

6. Hand held or hand guided grinding or polishing machine tool (1) according to claim 1, wherein the second connections element (15) of the working element holder (12) is a tool shaft designed separately from the motor shaft (22).

7. Hand held or hand guided grinding or polishing machine tool (1) according to claim 1, wherein the motor shaft (22) is directly connected to the second connection element (15)of the working element holder (12) without any gear or transmission mechanism (23) located in-between.

8. Hand held or hand guided grinding or polishing machine tool (1) according to claim 1, wherein the working element (9) is rotatable about a rotational axis (10) and comprises a third connection element (11) extending along the rotational axis (10) of the working element (9), wherein the connection element (11) of the working element (9) is connected to the first connection element (36), wherein the rotational axis (10) of the working element (9) is congruent with the of the rotational axis (37) of the first connection.

9. Hand held or hand guided grinding or polishing machine tool (1) according to claim 1, wherein the first connection element (36) is held in the working element holder (12) by means of at least one ball bearing (18).

10. Hand held or hand guided grinding or polishing machine tool (1) according to claim 1, wherein the grinding or polishing machine tool (1) comprises an electric motor (21) for rotating the motor shaft (22) and actuating the working element (9) in order to provoke roto-orbital or random-orbital working movement.

11. Hand held or hand guided grinding or polishing machine tool (1) according to claim 10, wherein the electric motor (21) is a brushless direct current (BLDC) motor.

12. Hand held or hand guided grinding or polishing machine tool (1) according to claim 1, wherein the distances between the center axis (14) of the working element holder (12), the rotational axis (37) of the first connection element's (37) and the longitudinal axis (16) of the second connection element (15) are specified in such a manner that the resulting orbit of the working element (9) is at least 21 mm in diameter.

13. Working element holder (12) for use in a hand held or hand guided grinding or polishing machine tool (1), the working element holder (12) having: a center axis (14), a first connection element (36) adapted for connecting the working element holder (12) to a disk-like working element (9), the first connection element (36) having a rotational axis (37) running parallel to the center axis (14) of the working element holder (12), a second connection element (15) adapted for connecting the working element holder (12) to a motor shaft (22) of a motor (21) of a hand held of hand guided grinding or polishing machine tool (1) in a torque proof manner, the second connection element (15) having a longitudinal axis (16) running parallel to a rotational axis (37) of the first connection element (36) and to the center axis (14) of the working element holder (12), characterized in that all three axes (14, 16, 37) are spaced apart from one another by predefined distances.

14. Working element holder (12) according to claim 13, wherein the center axis (14) is defined as the axis of gravity of the working element holder (12).

15. Working element holder (12) according to claim 13, wherein the center axis (14) is defined as the axis of gravity of the working element holder (12) with a working element (9) being fixed to the working element holder (12) and with a sheet-like working material (13) being attached to a bottom surface of the working element (9).

16. Hand held or hand guided grinding or polishing machine tool (1) according to claim 2, wherein, in a top view onto the working element holder (12), the center axis (14) of the working element holder (12), the rotational axis (37) of the first connection element (36) and the longitudinal axis (16) of the second connection element (15) are located on a virtual center line (19) radially extending from the center axis (14).

17. Hand held or hand guided grinding or polishing machine tool (1) according to claim 2, wherein, in a top view onto the working element holder (12), the center axis (14) and longitudinal axis (16) located between the other two axes (37, 16; 37, 14) are connected to a first axis (37; 14) of the two other axes (37, 16; 37, 14) by means of a first virtual line (19) and connected to a second axis (16; 37) of the two other axes (37, 16; 37, 14) by means of a second virtual line (20), wherein the first virtual line (19) and the second virtual line (20) are located in an angle between 0° and 90°, wherein the angle is ≠0° in respect to one another.

18. Hand held or hand guided grinding or polishing machine tool (1) according to claim 2, wherein the second connection element (15) of the working element holder (12) is a tool shaft designed separately from the motor shaft (22).

19. Hand held or hand guided grinding or polishing machine tool (1) according to claim 2, wherein the motor shaft (22) is directly connected to the second connection element (15) of the working element holder (12) without any gear or transmission mechanism (23) located in-between.

20. Hand held or hand guided grinding or polishing machine tool (1) according to claim 2, wherein the working element (9) is rotatable about a rotational axis (10) and comprises a third connection element (11) extending along the rotational axis (10) of the working element (9), wherein the connection element (11) of the working element (9) is connected to the first connection element (36), wherein the rotational axis (10) of the working element (9) is congruent with the rotational axis (37) of the first connection element (36).

Description

BRIEF DESCRIPTION OF THE DRAWING

[0040] The drawings show preferred embodiments of the present invention. In particular they show:

[0041] FIG. 1a a sectional view of a first type of a working element holder known from the prior art;

[0042] FIG. 1b a sectional view of a second type of a working element holder known from the prior art;

[0043] FIG. 2a a top view of the working element holder of FIG. 1a and a working element attached thereto;

[0044] FIG. 2b a top view of the working element holder of FIG. 1b and a working element attached thereto;

[0045] FIG. 3a a sectional view of a first type of a working element for connection to the working element holder of FIGS. 1a and 1b known from the prior art;

[0046] FIG. 3b a sectional view of a second type of a working element for connection to the working element holder of FIGS. 1a and 1b known from the prior art;

[0047] FIG. 4a a sectional view of a working element holder of a grinding or polishing machine tool according to a preferred embodiment of the present invention;

[0048] FIG. 4b a sectional view of a first type of a working element for connection to the working element holder of FIG. 4a;

[0049] FIG. 4c a sectional view of a second type of a working element for connection to the working element holder of FIG. 4a;

[0050] FIG. 5 a top view of the working element holder of FIG.

[0051] 4a and a working element of one of the FIG. 4b or 4c attached thereto;

[0052] FIG. 6 a top view of a working element holder according to an alternative to FIG. 5;

[0053] FIG. 7 a top view of a working element holder according to another alternative to FIG. 5;

[0054] FIG. 8 a sectional view of an electric motor of a grinding or polishing machine tool according to a preferred embodiment of the present invention;

[0055] FIG. 9 a top view of the electric motor of FIG. 8;

[0056] FIG. 10 a sectional view of the rotor of the electric motor of FIG. 8;

[0057] FIG. 11 a bottom view of the rotor of FIG. 10;

[0058] FIG. 12 a perspective view of a grinding or polishing machine tool according to a preferred embodiment of the present invention;

[0059] FIG. 13 a sectional view of a front part of a grinding or polishing machine tool according to a preferred embodiment of the present invention; and

[0060] FIG. 14 a sectional view of a front part of a grinding or polishing machine tool according to another preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE BEST MODE OF THE INVENTION

[0061] FIG. 12 shows an example of a random orbital polishing machine tool 1 according to the present invention. The polisher 1 has a housing 2, essentially made of a plastic material. The polisher 1 is provided with a handle 3 at its rear end and a grip 4 at its front end. An electric power supply line 5 with an electric plug at its distal end exits the housing 2 at the rear end of the handle 3. At the bottom side of the handle 3 a switch 6 is provided for activating and deactivating the machine tool 1. The switch 6 can be continuously held in its activated position by means of a push button 7. The machine tool 1 can be provided with a rotary adjustment means (not shown) for adjusting the rotational speed of the tool's motor. The housing 2 can be provided with cooling openings 8 for allowing heat from electronic components and/or the electric motor both located inside the housing 2 to dissipate into the environment.

[0062] The machine tool 1 shown in FIG. 12 has an electric motor (see for example FIGS. 8 to 11, 13 and 14). Of course, the machine tool according to the present invention could also be equipped with a pneumatic motor, which is especially advantageous in explosive environments, where sparks from an electric motor could provoke an explosion of an explosive mixture (e.g. oxygen and very fine dust) contained in the environment. Furthermore, instead of the connection of the machine tool 1 to a mains power supply by means of the electric cable 5, the machine tool 1 could alternatively be equipped with a rechargeable battery (not shown) located inside the housing 2. In that case the electric energy for driving the electric motor 21 would be provided by the battery.

[0063] The machine tool 1 has a disk-like working element 9 (see FIGS. 4b and 4c) rotatable about a rotational axis 10 and having a connection element 11 extending along the working element's rotational axis 10. The connection element 11 is adapted for connecting the working element 9 to a working element holder 12. The bottom surface of the working element 9 is provided with means for attaching a sheet-like working material 13, for instance a polishing material comprising but not limited to a sponge, a microfiber, and real or synthetic lambs' wool. The sheet-like working material 13 could also be a sanding material comprising but not limited to a sanding paper or a sanding fabric. The attachment means can comprise a first layer of a hook-and-loop fastener (or Velcro®), wherein the top surface of the sheet-like working material 13 is provided with the 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 working material 13 to the working element 9.

[0064] 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 working material 13 during the intended use of the machine tool 1 and to apply a force to the working material 13 in a direction essentially parallel to the working element's rotational axis 10 and which on the other hand is flexible enough to avoid damage or scratching of the surface to be worked by the working element 9 or the working material 13, respectively. The working element's connection element 11 can be embodied as a stud which at its bottom end is preferably molded into the material of the working element 9 during its manufacture (see FIG. 4b). Alternatively, the working element's connection element 11 comprises a separate screw which can be inserted from the working element's 9 bottom surface through a hole 40 extending through the working element 9 along its rotational axis 10 (see FIG. 4c).

[0065] FIG. 4a shows a working element holder 12 for a grinding or polishing machine tool 1 according to the present invention with a working element 9 performing a random orbital movement. The working element holder 12 has a center axis 14. The center axis 14 is preferably the axis of gravity of the working element holder 12. The axis of gravity could be defined with or without the working element 9. The axis of gravity could further be defined with or without a sheet-like working material 13 being attached to the bottom surface of the working element 9. Preferably, the axis of gravity is defined with the working element 9 attached to the working element holder 12 and with a typical sheet-like working material 13 attached to the bottom surface of the working element 9.

[0066] Furthermore, the working element holder 12 has a first connection element 36 mounted freely rotatable to the working element holder 12, for example by means of one or more ball bearings 18. The first connection element 36 can be secured to the ball bearings 18 by means of one or more self-locking retaining rings 38 (e.g. Seegerrings). Alternatively, the first connection element 36 can be secured to the ball bearings 18 by means of a press fit. In the drawings the ball bearings 18 are connected to the working element holder by means of a separate bearings seat inserted into the working element holder 12. Of course, this bearings seat could be made as an integral part of the working element holder 12. The first connection element 36 has a rotational axis 37 running in parallel or congruent to the working element holders's 12 center axis 14. Further, the working element holder 12 has a second connection element 15 for a torque proof connection to a shaft 22 of the motor 21 of the grinding or polishing machine tool 1. The second connection element 15 has a rotational axis 16 running in parallel or congruent to the working element holders's 12 center axis 14.

[0067] The second connection element 15 can be embodied as a tool shaft which at its bottom end is tightly fixed to the working element holder 12, for example by welding, or is made from a single piece together with the working element holder 12. The working element holder 12 is made of a rigid material, preferably a metal, for example aluminum. Both types of working elements 9 shown in FIGS. 4b and 4c can be mounted to the first connection element 36 of the working element holder 12 as described in detail above.

[0068] In contrast to the known polishers, where either the first connection element's 36 rotational axis 37 or the second connection element's 15 longitudinal axis 16 is congruent (identical or coaxial) to the center axis 14 of the working element holder 12 (see FIGS. 1a and 1b), in the present invention all three axes 37, 16 and 14 are spaced apart from one another by a given distance (see FIG. 4a). The distances between the three axes 37, 14, 16 (see FIG. 5) can be designed such that the resulting orbit of the working element 9 is particularly large, preferably larger than 21 mm, in diameter without provoking larger vibrations. All this can be achieved without enhancing the overall dimensions of the working element and consequently of the entire tool, which remains very compact and light weight.

[0069] With other words, in the prior art the orbit of the working element 9 corresponds to twice the distance either between the first connection element's 36 rotational axis 37 and the center axis 14 of the working element holder 12 (see FIG. 1b) or between the second connection element's 15 longitudinal axis 16 and the center axis 14 of the working element holder 12 (see FIG. 1a). In contrast thereto, the orbit of the working element 9 of the present invention (see FIG. 4a) corresponds to twice the sum of the distances between the first connection element's 36 rotational axis 37 and the center axis 14 of the working element holder 12 on the one hand and between the second connection element's 15 longitudinal axis 16 and the center axis 14 of the working element holder 12 on the other hand. Despite the rather large orbit at the same time the vibrations and the dimensions can be significantly reduced. Alternatively, the distances between the three axes 37, 14, 16 can be designed such that the resulting orbit of the working element 9 is equal or even smaller than 21 mm, but with the vibrations and the dimensions being significantly reduced in respect to known polishing or grinding machine tools with similar orbits. Of course, respective counter weights could be incorporated into the working element holder 12 either as separate parts or as an integral part of the working element holder 12, in order to further reduce vibrations of the tool 1.

[0070] The machine tool 1 according to the present invention has the advantage that the working element 9 can perform very large orbital working movements, preferably with an orbit of more than 21 mm in diameter, in particular with an orbit of approximately 25 mm in diameter. At the same time the machine tool 1 generates only minor vibrations. This is due to the particularly advantageous positioning of the axes 37, 14, 16. It is suggested that the three axes 37, 14, 16 are all spaced apart from one another by predefined distances. According to the embodiment of FIG. 4a the working element holder's center axis 14 is located between the longitudinal axis 16 of the working element holder's second connection element 15 and the first connection element's rotational axis 37. This embodiment has the advantage that it allows a highly equilibrated design of the working element holder 12, resulting in minor vibrations of the machine tool 1. Furthermore, this embodiment permits the realization of very large orbits equal to twice the sum of the two distances (orbit=2×(a+b)), wherein a is the distance between the axes 14 and 16 and b is the distance between the axes 37 and 14.

[0071] The machine tool 1 shown in FIG. 12 is embodied as a polisher with the round disk-like working element 9 performing a random orbital movement. Of course, the machine tool according to the present invention could also be embodied as a grinding machine tool or any other type of machine tool having a working element 9 of any desired form and performing an orbital, a random orbital or a rotary orbital working movement. For example, in the case of a random orbital polisher the working element 9 could have a triangle form or in the case of an orbital polisher the working element 9 could have a rectangular form.

[0072] FIGS. 5 to 7 show top views of the working element holders 12 partly with the working element 9 (FIG. 5). It can be clearly seen that in the embodiment of FIG. 5 the three axes 37, 14, 16 are located on an imaginary line 19. In the embodiment the diameter of the orbit is twice the distance between the axes 37 and 16 (2×(a+b)). In order to further reduce vibrations of the machine tool 1 during operation it may be advantageous to locate the axes 37, 14, 16 on two different imaginary lines 19, 20 instead of only on one line 19 as shown in FIG. 5. Such embodiments are shown in FIGS. 6 and 7. It can be clearly seen that in both embodiments a first imaginary line 19 runs through the axes 37, 14 and that a second imaginary line 20 runs through the axes 14, 16. The two lines 19, 20 intersect in a given angle α in respect to each other at the working element holder's 12 center axis 14. Starting from the first line 19 the angle α can be a positive value (counter-clockwise as shown in FIG. 6) or a negative value (clockwise as shown in FIG. 7). The value of the angle α and whether it has a positive or a negative value depends on a plurality of factors. These can be, for example, the direction of rotation (clockwise or counter-clockwise) about the longitudinal axis 16, the rotational speed of the rotation, the value of the rotating masses, etc. The polisher 1 shown in FIG. 12 can achieve very good results if the angle α has an absolute value of approximately 15°.

[0073] FIGS. 13 and 14 show further preferred embodiments of the machine tool 1 according to the present invention. It can be seen that approximately at the front end of the machine tool 1 inside the housing 2 there is an electric motor 21 having a motor shaft 22. In the embodiment of FIG. 13 the motor shaft 22 is connected to the working element holder's 12 second connection element 15 by means of a gear or transmission mechanism 23. The gear or transmission mechanism 23 has a drive shaft 24 and an output shaft 25. The drive shaft 24 is connected to the motor shaft 22 in a torque proof manner and the output shaft 25 is connected to the tool shaft 15 of the working element holder 12 in a torque proof manner. The gear or transmission mechanism 23 can translate the rotational speed of the motor shaft 22 into a higher or lower rotational speed of the tool shaft 15. At the same time the torque applied to the tool shaft 15 can be reduced or enhanced. In the embodiment of FIG. 14 the motor shaft 22 is directly connected to the working element holder's 12 second connection element 15 without any gear or transmission mechanism located in-between. This embodiment has the advantage that the machine tool 1 or its housing 2, respectively, can be designed very compact, in particular very small in height.

[0074] In FIGS. 13 and 14 the working element holder 12 and the working element 9 are designed according to the embodiment of FIG. 4a with the center axis 14 of the working element holder 12 located between the other two axes, the rotational axis 37 of the first connection element 36 of the working element holder 12 and the longitudinal axis 16 of the second connection element 15 of the working element holder 12.

[0075] FIGS. 8 to 11 show a preferred embodiment of the electric motor 21 used in the machine tool 1 according to the invention. The motor is preferably embodied as an outrunner brushless direct current (BLDC) motor. The BLDC motor 21 has a centrally disposed stator 26 extending along a longitudinal axis 27 of the motor shaft 22. The stator 26 has a total of twelve wire coils two of which are shown in FIG. 8. The motor shaft 22 extends through the center of the stator 26 and is supported by two bearings 29, 30 at the top and the bottom of the motor 21. A self-locking retaining ring Seegerring 31 holds the motor shaft 22 in place within the stator 26. A stator flange is designated with reference sign 32. A motor housing is designated with reference sign 33. A cup-shaped rotor 28 rotates around and relative to the stator 26. Permanent magnets 34 are fastened circumferentially on the inside of the rotor 28. A rotor flange is designated with reference sign 35.

[0076] Of course, it is possible to combine the features of the various embodiments described with respect to the FIGS. 1 to 14 in any desired way in order to arrive at a particularly advantageous machine tool 1 according to the present invention.