HAND HELD OR HAND GUIDED GRINDING OR POLISHING MACHINE TOOL
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.
1. Field of Invention
The present invention refers to a hand held or hand guided grinding or polishing machine tool actuated electrically or pneumatically. The machine tool comprises:
a working element holder having a first connection element for connecting the working element holder to a disk-like working element and a center axis,
the first connection element for connecting the working element holder to the working element having a rotational axis running parallel to the working element holder's center axis,
the working element holder further having a second connection element for connecting the working element holder to a motor shaft of the grinding or polishing machine tool in a torque proof manner, and
the second connection element for connecting the working element holder to the motor shaft having a longitudinal axis running parallel to the first connection element's rotational axis and to the working element holder's center axis.
2. Brief Description of Related ArtIn general, hand held or hand guided power tools can be electrically or pneumatically operated. They can be embodied, for instance, as grinders, sanders, polishers or others. The prior art clearly distinguishes between sanders or grinders on the one hand and polishers on the other hand. Although both types of power tools serve for working a varnished or lacquered surface of a vehicle body, for example of a car or a boat, sanders or grinders and polishers have significantly different designs and features and are operated differently in order to obtain different effects on the varnished or lacquered surface.
Basically, a working surface of a vehicle body is sanded or grinded before providing it with a new coating, in order to obtain an even surface for the subsequent coating. Sanding or grinding is performed, for example, after having applied filler or stopper material to the surface in order to even out depressions and dents. This may also be performed to eliminate corroded or otherwise scruffy regions of the vehicle body. During sanding or grinding a thick layer of varnish or lacquer if not all of the varnish or lacquer is removed or stripped from the vehicle body. Usually, even part of the vehicle body material is removed. The properly sanded or grinded working surface can then be provided with one or more layers of a new coating, usually in the form of varnish and/or lacquer.
The polishing of the vehicle body is performed only on properly coated vehicle body in order to give the coating a more appealing appearance. Hence, polishing is performed after coating the vehicle body with a varnish and/or a lacquer. Usually, no further coating of the vehicle body is applied after polishing. Therefore, it is mandatory, that the varnish or lacquer is not removed but only worked on and finished on its top surface. Almost none of the varnish or lacquer is removed during polishing and almost no dust is generated.
Sanders or grinders are often designed as palm sanders, which can be held with one hand and which are pressed on the varnished or lacquered working surface by the palm of the holding hand. A lever of a switch for turning on and off the sander is typically located on the top surface of the sander so when holding the sander and pressing it onto the working surface the lever is pressed down by the palm and the sander is activated. Sanders can have a circular, rectangular or delta-shaped working pad actuated by the sanders' electric or pneumatic motor. The working pad can perform an orbital, a random orbital, a rotary orbital or a linear back-and-forth movement depending on the type of working pad used and the desired effect to be achieved on the sander. A sheet of abrasive material can be attached to the bottom surface of the working pad by means of adhesion or a hook-and-loop fastener (Velcro®). With a rectangular working pad, the sheet of abrasive material can be clamped to the bottom surface by clamping devices located laterally at the side of or on top of the working pad. The abrasive sheet material can be an emery or sand paper or a textile sheet material with emery or sand grains inserted therein or attached thereto.
Sanders and grinders or their abrasive sheet material, respectively, typically remove or strip off a rather large amount of varnish or lacquer from the surface. It is even possible that sanders remove part of the surface itself, for example, after having applied filler or stopper material to the surface in order to even out depressions and dents. Therefore, during a sanding process a lot of dust is generated which is preferably actively removed from the working surface by means of a dust extraction system as an integral part of the sander and/or external dust extraction systems, for example a vacuum cleaner attached to a dust discharge nozzle of the sander. Finally, sanders and grinders typically operate at a rather high speed in order to allow easy and fast removal of the rather thick layers of varnish or lacquer. Known sanders and grinders can operate at up to 15.000 rpm.
In contrast thereto, polishers are usually designed and adapted for a two handed use. One hand holds the polisher and the other hand presses the polisher on the varnished or lacquered working surface. A switch for turning on and off the polisher is typically located where the holding hand is located in order to allow actuation of the switch by a finger of the holding hand. Polishers usually have a circular working element actuated by the polishers' electric or pneumatic motor. The working pad can perform an orbital, a mere rotary, a random orbital or a rotary orbital movement depending on the type of working pad used and the desired effect to be achieved on the polisher. A sheet of polishing material can be attached to the bottom surface of the working pad by means of adhesion, a hook-and-loop fastener (Velcro®) or any other type of fastener. The polishing sheet material can be a sponge, a microfiber or real or synthetic lambs' wool. The polishing sheet material is often used together with a polishing paste.
Polishers or the polishing sheet material, respectively, do not remove or strip part of the varnish or lacquer from the surface. At the most, a very small amount of the varnish or lacquer is removed from the surface due to the effect of the polishing paste. However, the dust is bound by the polishing paste. Therefore, during a polishing process practically no dust is generated which in any event would obviate a satisfying polishing of the working surface because the dust would cause scratches on the surface to be polished. Polishing is performed in a scrupulously clean environment in order to avoid scratches in the surface to be polished. Finally, polishers operate at s significantly lower speed than sanders or grinders. Known rotary polishers typically operate at 1.500-2.000 rpm. Known random orbital polishers typically operate at up to 5.000-6.000 rpm. Random orbital polishers and grinders can operate at up to 10.000-12.000 rpm.
Known grinders have a maximum orbit of 12-15 mm. Known polishers even have a maximum orbit of 21 mm in diameter. A problem with large orbits are vibrations of the machine tool caused by the eccentric masses rotating at relatively high rotational speeds.
Basically, there are two different types of working element holders for grinding or polishing machine tools with a working element performing an orbital (random orbital or rotary orbital) movement known in the art. For a random orbital movement these two types of working element holders are shown in
In the first known type of a working element holder shown in
In the second known type of a working element holder shown in
In the first type of working element shown in
In the second type of working element shown in
In the polishers known from the prior art, the larger the working element's orbit is, the larger the distance between the longitudinal axis of the working element holder's second connection element (corresponding to the motor shaft) and the second connection element's rotational axis is, inevitably leading to larger dimensions of the tool and stronger vibrations. In the prior art, one of the two axes is congruent with the working element's holder center axis.
A well-known polisher developed, produced and sold by the applicant under the trademark BIGFOOT® has a maximum orbit of 21 mm in diameter. The BIGFOOT polisher has
a disk-like working element rotatable about a rotational axis and having a connection element extending along the working element's rotational axis, the connection element adapted for connecting the working element to a working element holder of the polishing machine tool,
the working element holder, to which the working element is connected, having a first connection element for connecting the working element holder to the working element and a center axis,
the first connection element for connecting the working element holder to the working element having a rotational axis running parallel to the working element holder's center axis,
the working element holder further having a second connection element for connecting the working element holder to a motor shaft of the polishing machine tool in a torque proof manner, and
the second connection element for connecting the working element holder to a motor shaft having a longitudinal axis running parallel to the first connection element's rotational axis and to the working element holder's center axis.
Both types of working elements shown in
In order to reduce the vibrations on the one hand and achieve relatively large orbits on the other hand, the BIGFOOT® polisher has a working element's rotational axis identical or coaxial to the center axis of the working element holder. The working element holder's second connection element for connecting the working element holder to the motor shaft is located eccentrically in respect to the working element holder's center axis. A working element holder like the one used in the known BIGFOOT® polisher is shown in
The object of the present invention is to provide for an alternative hand held or hand guided grinding or polishing machine tool, which can perform even larger orbits, preferably larger than 21 mm, and at the same time has very reduced vibrations.
This object is achieved by a hand held or hand guided grinding or polishing machine tool of the above identified kind, wherein the three axes are all spaced apart from one another by predefined distances. In contrast to the known polishers, where either the first connection element's 36 rotational axis or the second connection element's longitudinal axis is congruent (identical or coaxial) to the center axis of the working element holder, in the present invention all three axes are spaced apart from one another by a given distance. The distances between the three axes can be designed such that the resulting orbit of the working element is particularly large, preferably larger than 21 mm, in diameter without provoking bigger dimensions and larger vibrations. With other words, in the prior art the orbit of the working element corresponds to twice the distance either between the first connection element's rotational axis and the center axis of the working element holder or between the second connection element's longitudinal axis and the center axis of the working element holder. In contrast thereto, the orbit of the working element of the present invention corresponds to twice the sum of the distances between the first connection element's rotational axis and the center axis of the working element holder on the one hand and between the second connection element's longitudinal axis and the center axis of the working element holder on the other hand. At the same time despite the rather large orbit the vibrations can be significantly reduced to acceptable values, in particular to values in compliance with the respective official working regulations regarding vibrations of hand guided machine tools. Alternatively, the distances between the three axes can be designed such that the resulting orbit is equal or even smaller than 21 mm, but with the vibrations being significantly reduced in respect to known polishing or grinding machine tools with similar orbits.
Preferred embodiments of the present invention are the subject of the dependent claims. In a first preferred embodiment the working element holder's center axis is located between the working element's rotational axis and the connection element's longitudinal axis (
Furthermore, it is suggested that in a top view onto the working element holder the working element holder's center axis, the working element's rotational axis and the connection element's longitudinal axis are all located on a virtual radially extending straight center line. The center line runs through the working element holder's center axis. Alternatively, it is suggested that in a top view onto the working element holder the axis located between the other two axes is connected to a first one of the two other axes by means of a first virtual line and is connected to a second one of the two other axes by means of a second virtual line, wherein the two lines are located in an angle 0° and 90°, wherein the angle is ≠0° in respect to one another. Preferably, the point of intersection of the two lines lies at the working element holder's center axis. This embodiment has the advantage that the vibrations of the machine tool are significantly reduced. The angle between the two lines can be selected depending on the nominal rotational speed of the machine tool's working element. The larger the nominal rotational speed is, the larger the absolute value of the angle between the two lines would be selected. For example, the absolute value of the angle between the two lines is <30°, preferably 15°. Depending on the rotational direction of the working element the angle would be positive (counter-clockwise) or negative (clockwise).
Preferably, the working element holder's connection element is a tool shaft designed separately from the motor shaft and connected in a torque proof manner thereto. It is possible that the motor shaft is connected to the working element holder's connection element by means of a gear or transmission mechanism located in-between. In that way a rotational speed of the motor shaft can be transmitted into a faster (with less torque) or slower (with higher torque) actuating movement of the working element. However, in order to reduce the overall size of the machine tool, in particular in order reduce its height, it is suggested that the motor shaft is directly connected to the working element holder's connection element without any gear or transmission mechanism located in-between. It is even possible that the working element holder's connection element is constituted by the motor shaft itself or that the working element holder's connection element constitutes the motor shaft, respectively.
Preferably, the working element's connection element is held freely rotatable in the working element holder. In this manner a random orbital working movement of the working element can be realized. Alternatively, the working element is held in the working element holder in a torque proof manner in a fixed orientation. In this manner an orbital working movement of the working element can be realized.
The grinding or polishing machine tool can comprise a pneumatic or an electric motor. The motor has a motor shaft performing a rotating movement around its longitudinal axis. The rotating movement of the motor shaft is transmitted to the working element holder such that the working element performs its predefined working movement. The working movement can be a roto-orbital or a random-orbital working movement. Preferably, the grinding or polishing machine tool comprises an electric motor for rotating the motor shaft and actuating the working element in order to provoke its roto-orbital or random-orbital working movement. The electric motor can be actuated by means of a power supply voltage taken from a power supply network via a power supply cable. The power supply network provides a voltage of 230V or 110V depending on the country in which the machine tool is operated. The machine tool can be embodied to automatically adapt to the respective voltage without the user of the machine tool having to manually switch the machine tool to the respective voltage.
Further, the electric motor can be operated by means of the electric power from a rechargeable battery at a voltage of approximately 6V, 12V, 24V or 48V. Of course, the battery can provide other voltages, too, if desired. The rechargeable battery can be incorporated into the machine tool's housing either in a manner fixed inside the housing or in such a way that it is received in a recess of the machine tool's housing so it can be easily extracted from the housing, for example to replace it with a fully loaded battery. It is possible that a power transformer connected to a power supply cable is inserted into the recess provided in the machine tool's housing for receiving the rechargeable battery, when the battery is extracted from the recess. To this end, the machine tool can be operated either by means of a power supply network (via the transformer) or alternatively by means of the battery.
Preferably, the electric motor is a brushless direct current (BLDC) motor. The electric motor can be of the outrunner or of the conventional inrunner type. In the outrunner type the motor's stator is located statically in the center of the motor and the rotor runs outside the stator circumferentially surrounding the stator. This allows a particularly compact motor having only a reduced height, which allows a compact design of the machine tool.
It is particularly preferred that the distances between the working element holder's center axis, the working element's rotational axis and the connection element's longitudinal axis are specified in such a manner that the resulting orbit of the working element is at least 21 mm in diameter. Preferably, the orbit is at least 25 mm in diameter. Despite this rather large orbit, the machine tool according to the present invention is very compact and creates only very reduced vibrations due to the particularly advantageous distribution of the various axes of the working element holder and the working element.
The drawings show preferred embodiments of the present invention. In particular they show:
4a and a working element of one of the
The machine tool 1 shown in
The machine tool 1 has a disk-like working element 9 (see
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
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.
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
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
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
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
The machine tool 1 shown in
In
Of course, it is possible to combine the features of the various embodiments described with respect to the
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).
Type: Application
Filed: Apr 21, 2017
Publication Date: Nov 2, 2017
Inventor: Guido VALENTINI (Milano)
Application Number: 15/493,368