Abstract
The invention refers to a polishing pad (11) adapted for being detachably attached to a bottom surface (9a) of a plate-like backing pad (9) of a hand-held power tool (1). The backing pad (9) is actuated by an electric or pneumatic motor of the hand-held power tool (1), in order to perform a purely rotating, a random orbital or a roto-orbital working movement. The polishing pad (11) comprises a bottom working surface (11b) facing a workpiece to be polished during intended use of the power tool (1). It is suggested that the bottom working surface (11b) has at least two pieces (12, 13) of polishing material with different characteristics. A bottom working surface (13b) of at least one of the pieces (13) of the polishing pad (11) having a first characteristic extends beyond a bottom working surface (12b) of at least another of the pieces (12) of the polishing pad (11) having a different second characteristic. (FIG. 2)
Claims
1. Polishing pad (11) having a top surface (11a) adapted for being detachably attached to a bottom surface (9a) of a plate-like backing pad (9) of a hand-held power tool (1), the backing pad (9) being actuated by an electric or pneumatic motor of the hand-held power tool (1), in order to perform together with the polishing pad (11) attached thereto a purely rotating, a random orbital or a roto-orbital working movement, wherein the polishing pad (11) comprises a bottom working surface (11b) facing a workpiece to be polished during intended use of the power tool (1), characterized in that the bottom working surface (11b) has at least two pieces (12, 13) of polishing material with different characteristics, wherein a bottom working surface (13b) of at least one of the pieces (13) of the polishing pad (11) having a first characteristic extends beyond a bottom working surface (12b) of at least another of the pieces (12) of the polishing pad (11) having a different second characteristic.
2. Polishing pad (11) according to claim 1, wherein the different characteristics of the pieces (12, 13) refer to one or more of a group comprising: rigidity of material of the two pieces (12, 13) of polishing material, type of material or combinations of materials of each of the two pieces (12, 13) of polishing material, and in case at least one of the two pieces (12, 13) of the polishing pad (11) comprises a foamed plastics material, size and structure of cells of the foamed plastics material.
3. Polishing pad (11) according to claim 1, wherein the different characteristics refer to the rigidity of the polishing material of the two pieces (12, 13), and wherein the bottom working surface (13b) of at least one of the pieces (13) of the polishing pad (11) having a smaller rigidity extends beyond a bottom working surface (12b) of at least another of the pieces (12) of the polishing pad (11) having a larger rigidity.
4. Polishing pad (11) according to claim 1, wherein the bottom working surface (11b) of the polishing pad (11) comprises at least one inner piece (12) having the second characteristic and at least one outer circumferential piece (13) surrounding the at least one inner piece (12) and having the first characteristic.
5. Polishing pad (11) according to claim 1, wherein the polishing pad (11) is adapted to be detachably attached to the bottom surface (9a) of the backing pad (9) by means of hook-and-loop attachment means provided in part on the bottom surface (9a) of the backing pad (9) and in part on a top surface (11a) of the polishing pad (11), facing the bottom surface (9a) of the backing pad (9).
6. Polishing pad (11) according to claim 1, wherein the at least two pieces (12, 13) of polishing material with different characteristics of the polishing pad (11) are separate parts, which are adapted to be separately detached from the bottom surface (9a) of the backing pad (9) independently from one another.
7. Polishing pad (11) according to claim 4, wherein the at least one circumferential part (13) of the polishing pad (11) has at least one opening (14) extending from the bottom working surface (11b) of the polishing pad (11) to the top surface (11a) of the polishing pad (11) and having an inner circumferential form corresponding to an outer circumferential form of the at least one inner part (12) of the polishing pad (11) to be received in said at least one opening (14).
8. Polishing pad (11) according to claim 7, wherein the inner circumferential form of the at least one opening (14) has the form of a circle, an ellipse, a triangle, a rectangle, a star or any other kind of multi-angle form, and the at least one inner piece (12) of the polishing pad (11) to be received in said at least one opening (14) has a corresponding outer circumferential form.
9. Polishing pad (11) according to claim 1, wherein at least two pieces (12, 13) of polishing material with different characteristics of the polishing pad (11) are laminated together before detachably attaching them to the bottom surface (9a) of the backing pad (9) in order to form a single part to be detachably attached to the bottom surface (9a) of the backing pad (9).
10. Polishing pad (11) according to claim 1, wherein the at least two pieces (12, 13) of polishing material with different characteristics are located concentrically in respect to a rotational axis (10) of the backing pad (9) or the polishing pad (11), respectively.
11. Polishing pad (11) according to claim 1, wherein at least the bottom working surfaces (12b, 13b) of the at least two pieces (12, 13) constituting the polishing pad (11) comprise one or more of a group comprising a foamed plastics material having an open-cell structure, wool and microfiber.
12. Polishing pad (11) according to claim 1, wherein at least one of the bottom working surfaces (12b, 13b) of the at least two pieces (12, 13) constituting the polishing pad (11) comprise small abrasive particles, in particular in the form of crystals, incorporated in the at least one bottom working surface (12b, 13b).
13. Polishing pad (11) according to claim 1, wherein the different characteristics refer to the rigidity of the polishing material of the two pieces (12, 13), and wherein the at least one piece (13) of the polishing pad (11) having a smaller rigidity is adapted for effecting a soft finishing polishing action of the workpiece to be polished.
14. Polishing pad (11) according to claim 1, wherein the different characteristics refer to the rigidity of the polishing material of the two pieces (12, 13), and wherein the at least one piece (12) of the polishing pad (11) having a larger rigidity is adapted for effecting a more intense cutting polishing action of the workpiece to be polished.
15. Hand-held power tool (1) comprising an electric or pneumatic motor and a plate-like backing pad (9) actuated by the motor in order to perform a purely rotating, a random orbital or a roto-orbital working movement and further comprising a polishing pad (11) detachably attached to a bottom surface (9a) of the backing pad (9), characterized in that the polishing pad (11) is embodied according to claim 1.
Description
[0032] Further characteristics and advantages of the present invention will be described hereinafter in more detail making reference to the accompanying figures. The figures show:
[0033] FIG. 1 a hand-held power tool comprising a polishing pad according to the present invention;
[0034] FIG. 2 a perspective view on a bottom working surface of a polishing pad according to a first embodiment of the present invention, attached to a plate-like backing pad;
[0035] FIG. 3 a perspective view on a top surface of the polishing pad of FIG. 2;
[0036] FIG. 4 a plan view on the bottom working surface of the polishing pad of FIG. 2;
[0037] FIG. 5 a perspective view on a bottom working surface of a polishing pad according to another embodiment of the present invention, attached to a plate-like backing pad;
[0038] FIG. 6 a plan view on the bottom working surface of the polishing pad of FIG. 5;
[0039] FIG. 7 a perspective view on a bottom working surface of a polishing pad according to another embodiment of the present invention, attached to a plate-like backing pad;
[0040] FIG. 8 a perspective view on the bottom working surface of the polishing pad of FIG. 7, separated into an outer circumferential piece and in inner central piece;
[0041] FIG. 9 a perspective view on the top surface of the polishing pad of FIG. 7;
[0042] FIG. 10 a perspective view on a bottom working surface of a polishing pad according to another embodiment of the present invention, attached to a plate-like backing pad;
[0043] FIG. 11 a plan view on the bottom working surface of the polishing pad of FIG. 10;
[0044] FIG. 12 a perspective view on a bottom working surface of a polishing pad according to another embodiment of the present invention, attached to a plate-like backing pad;
[0045] FIG. 13 a plan view on the bottom working surface of the polishing pad of FIG. 12;
[0046] FIG. 14 a perspective view on a bottom working surface of a polishing pad according to another embodiment of the present invention, attached to a plate-like backing pad;
[0047] FIG. 15 a plan view on the bottom working surface of the polishing pad of FIG. 14;
[0048] FIG. 16 a perspective view on a bottom working surface of a polishing pad according to another embodiment of the present invention, attached to a plate-like backing pad; and
[0049] FIG. 17 a plan view on the bottom working surface of the polishing pad of FIG. 16.
[0050] FIG. 1 shows an example of a hand-held power tool 1 according to the present invention in the form of a random orbital polishing tool 1. 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 power tool 1. The switch 6 can be continuously held in its activated position by means of a push button 7. The power 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.
[0051] The power tool 1 shown in FIG. 1 has an electric motor. 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 would be provided by the battery.
[0052] The power tool 1 has a plate-like backing pad 9 rotatable about a rotational axis 10 and having a connection element (not shown) extending along the backing pad's rotational axis 10. The connection element is adapted for connecting the backing pad 9 to a backing pad holder (not shown) of the tool 1. A bottom surface 9a of the backing pad 9 is provided with means for attaching a polishing pad 11 according to the present invention. The attachment means can comprise a first layer of a hook-and-loop fastener (or Velcro), wherein the top surface 11a of the polishing pad 11 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 polishing pad 11 to the bottom surface 9a of the backing pad 9.
[0053] The plate-like backing pad 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 polishing pad 11 during the intended use of the power tool 1 and to apply a force to the polishing pad 11 in a direction essentially downwards and parallel to the backing pad'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 polishing pad 11. The polishing pad 11 is in particular used for polishing a workpiece in the form of a vehicle or car body or the hull or any other part of a boat or ship. The workpiece is preferably made of wood, metal, plastic or a composite material (e.g. glass fiber reinforced, GFR, or carbon fiber reinforced, CFR, material) provided with or without some kind of paint and/or varnish. Some kind of polishing paste may be applied to the working surface in order to enhance the polishing effect of the polishing pad.
[0054] According to the present invention a multi-part polishing pad 11 is proposed, comprising a bottom working surface 11b facing the workpiece to be polished during intended use of the power tool 1. The bottom working surface 11b comprises at least two pieces 12, 13 of polishing material with different characteristics (see FIG. 2). The different characteristics of the various pieces of the bottom working surface refer to one or more of a group comprising: the rigidity of the material of the two pieces, the type of material of the two pieces, and, in case of a polishing pad made of a foamed plastics material, the cell-structure of the foamed plastics material. In the following, purely by example, the polishing pad 11 comprises a foamed plastics material made of Polyurethane with an open-cell structure. Further, purely by example the characteristic by which the two pieces of the working surface 11b distinguish is the rigidity of the material used.
[0055] FIG. 2 shows the plate-like backing pad 9 and the polishing pad 11 releasably attached thereto. The bottom working surface 11b of the polishing pad 11 comprises two pieces 12, 13 of polishing material with different rigidities. In fact, in the embodiment of FIG. 2 the entire polishing pad 11 comprises two separate pieces 12, 13. In the embodiment of FIG. 2 the bottom working surface 11b of the polishing pad 11 comprises one inner piece 12 and one outer circumferential piece 13 surrounding the inner piece 12, both located coaxially to the rotational axis 10 of the backing pad 9 and the polishing pad 11, respectively. The outer circumferential piece 13 preferably has a smaller rigidity than the inner piece 12. The bottom working surface 11b of the polishing pad 11 according to the invention comprises two partial working surfaces, a circular partial working surface 12b and an annular partial working surface 13b. Both partial working surfaces 12b, 13b together form the polishing pad's working surface 11b.
[0056] The material forming the central partial working surface 12b, preferably the entire material of the polishing pad 11 extending from the partial working surface 12b to the opposite side 11a (see FIG. 3) of the polishing pad 11, has a larger rigidity than the material forming the outer annular partial working surface 13b, preferably of the entire material of the polishing pad 11 extending from the partial working surface 13b to the opposite side 11a of the polishing pad 11. With other words the present invention is realized by providing material with different rigidities on the bottom working surface 11b of the polishing pad 11, for example in the form of inserts 12 which could be inserted in appropriate depressions or holes located on the bottom working surface 11b of the polishing pad 11.
[0057] Preferably, the polishing pad 11 is realized with at least two separate parts 12, 13 which can be individually handled and individually attached to and detached from the bottom surface 9a of the plate-like backing pad 9. The embodiments described hereinafter refer to a polishing pad 11 made up of a plurality of separate parts, for example parts 12, 13. This can be seen from FIG. 3, where it is shown that the center piece 12 runs all the way through the polishing pad 11 to the top surface 11a, where it forms a separate circular partial top surface 12a. Similarly, the outer annular circumferential piece 13 runs all the way through the polishing pad 11 to the top surface 11a, where it forms a separate annular partial top surface 13a. Both partial top surfaces 12a, 13a together form the even and plane polishing pad's top surface 11a. Both partial surfaces 12a, 13a are provided with attachment means, e.g. part of a hook-and-loop fastener (Velcro), wherein the other part of the hook-and-loop fastener is attached to the bottom surface 9a of the backing pad 9.
[0058] In the embodiment of FIGS. 2 to 4 the outer annular circumferential piece 13 having a certain characteristic (e.g. a smaller rigidity) extends beyond the partial bottom working surface 12b of the inner circular central piece 12 having another characteristic (e.g. a larger rigidity). Preferably the partial bottom working surface 13b extends by approximately 3-10 mm beyond the other partial bottom working surface 12b.
[0059] With the partial bottom working surfaces 12b, 13b being on different levels (when the power tool 1 is not in use) the kind of intended use of the polishing pad 11 (cutting action or finishing action) can be varied by applying a varying amount of downward pressure to the hand-held power tool 1 and by pressing the polishing pad 11 or rather its bottom working surface 11b onto the surface of the workpiece with more or less force. For example, in order to realize a more intense cutting polishing action at the beginning of a process of working the surface of the workpiece, the power tool 1 and the polishing pad 11 are pressed onto the surface of the workpiece to be polished with a larger force. By doing so the the outer annular circumferential piece 13 is compressed and the partial bottom working surface 12b of the inner circular central piece 12 comes into contact with the surface of the workpiece to be polished and can realize the more intense cutting polishing action. Then, when the deeper scratches and other defects in the workpiece's surface are eliminated to a large extent, the downward pressure applied to the power tool 1 and the polishing pad 11 can be reduced, thereby detaching the partial bottom working surface 12b of the inner circular central piece 12 from the surface of the workpiece to be polished. By doing so only the partial bottom working surface 13b of the outer annular circumferential piece 13 remains in contact with the surface of the workpiece to be polished and the soft finishing polishing action of the workpiece can be realized. So with a single multi-part polishing pad 11 according to the present invention two different types of uses (cutting and finishing action) of the power tool 1 can be realized.
[0060] FIGS. 5 and 6 show a further embodiment of the polishing pad 11. Just like the polishing pad 11 of the first embodiment of FIGS. 2-4, the bottom working surface 11b or the polishing pad 11, respectively, of FIGS. 5 and 6 comprises a single outer circumferential piece 13. However, instead of only one inner circular central piece 12, the bottom working surface 11b or the polishing pad 11, respectively, of FIGS. 5 and 6 comprises a plurality of inner central pieces 12. In this embodiment, the polishing pad 11 comprises three inner central pieces 12.1, 12.2 and 12.3, each of which having the form of a partial circular area corresponding to a center angle of 120. In the embodiment, all three inner pieces 12.1, 12.2, 12.3 are made of the same material and have the same rigidity, being larger than the rigidity of the outer circumferential piece 13. Of course, the number of inner central pieces 12 and their form may vary from the shown embodiment. Furthermore, the three inner pieces 12.1, 12.2, 12.3 may be made of different materials and/or may have different rigidities.
[0061] Each of the three inner pieces 12.1, 12.2, 12.3 has a bottom partial working surface 12.1b, 12.2b, 12.3b (see FIG. 5), together forming the partial working surface 12b of the inner central piece 12. Again, the partial working surfaces 12.1b, 12.2b, 12.3b and the partial working surface 13b of the outer circumferential piece 13 together form the working surface 11b of the polishing pad 11. The partial working surface 13 extends beyond the partial working surfaces 12.1b, 12.2b, 12.3b.
[0062] Similar to what is shown in FIG. 3 regarding the first embodiment, each of the three inner pieces 12.1, 12.2, 12.3 has a partial top surface. Together these form the partial top surface 12a of the inner central piece 12. Together with the partial top surface 13a of the outer circumferential piece 13, the partial top surfaces of the three inner pieces 12.1, 12.2, 12.3 form the even and plane top surface 11a of the polishing pad 11. Each of the partial top surfaces of the three inner pieces 12.1, 12.2, 12.3 as well as the partial top surface of the outer circumferential piece 13 are provided with attachment means, e.g. part of a hook-and-loop fastener (Velcro), wherein the other part of the hook-and-loop fastener is attached to the bottom surface 9a of the backing pad 9.
[0063] FIGS. 7-9 show yet another embodiment of the present invention. Seen in the main plane of extension of the bottom working surface 11b of the polishing pad 11, the inner central piece 12 has a cross-sectional form of a star. Of course, any other form (e.g. triangle, rectangle or any other multi-angle form) can be chosen, too. The outer circumferential piece 13 has an opening 14 corresponding to the star-form of the inner central piece 12 and adapted for receiving the same. FIG. 8 shows the two pieces 12, 13 constituting the polishing pad 11 separate from one another, wherein the inner central piece 12 is attached to the bottom surface 9a of the backing pad 9 and the outer circumferential piece 13 is detached from the backing pad 9. The star-shaped opening 14 for receiving the inner central piece 12 is clearly visible. In FIG. 9 the top surface 11a of the polishing pad 11 is shown, where the attachment means comprising loops or hooks as part of the hook-and-loop fastener for attaching the polishing pad 11 to the corresponding part of the hook-and-loop fastener on the bottom surface 9a of the backing pad 9 are provided on both the partial top surfaces 12a, 13a of the polishing pad 11.
[0064] Generally speaking, the at least one outer circumferential piece 13 of the polishing pad 11 has at least one opening 14 extending from the bottom working surface 11b of the polishing pad 11 to the top attachment surface 11a of the polishing pad 11 and having an inner circumferential form (in the embodiment of FIGS. 7-9 a star-shape) corresponding to an outer circumferential form of the at least one inner part 12 of the polishing pad 11, to be received in said at least one opening 14. In particular, the inner circumferential form of the at least one opening 14 may have the form of a circle, an ellipse, a triangle, a rectangle, a star or any other kind of multi-angle form, and the at least one inner piece 12 of the polishing pad 11 to be received in said at least one opening 14 has a corresponding outer circumferential form.
[0065] FIGS. 10 and 11 show yet another embodiment of the polishing pad 11 according to the present invention, similar to the embodiment of FIGS. 7-9. In contrast thereto, the acute angels of the star-shape have been rounded. This circumferential form of the inner central piece 12 and of the opening 14 in the outer circumferential piece 13 may have advantages in the sense that the rounded angles are not worn as fast as they will probably be in the embodiment of FIGS. 7-9 during the intended use of the polishing pad 11. Furthermore, by far less polishing paste or the like will be gathered in the angles of the polishing pad 11 during its intended use, if the angles are rounded.
[0066] FIG. 12 shows yet another embodiment of the polishing pad 11 according to the present invention in a perspective view and FIG. 13 shows the same embodiment in a bottom view. The outer circumferential piece 13 has a plurality of circular openings 14 located in a distance r (see FIG. 13) to the rotational axis 10 of the backing pad 9 and the polishing pad 11, respectively. Inner circular pieces 12.1, 12.2, 12.3 are inserted in each of the openings 14. Preferably, each of the inner circular pieces 12 comprises a partial top surface 12a (not shown in FIGS. 12 and 13) comprising loops or hooks as part of the hook-and-loop fastener for attaching the polishing pad 11 to the corresponding part of the hook-and-loop fastener on the bottom surface 9a of the backing pad 9.
[0067] Preferably, the inner pieces 12.1, 12.2, 12.3 are made of the same material and have the same rigidity. Of course, it would also be possible that the inner pieces 12.1, 12.2, 12.3 are made of different materials and/or have different rigidities. In the embodiment of FIGS. 12 and 13 the distances r from the centers 12.1c, 12.2c, 12.3c of the inner pieces 12 to the rotational axis 10 of the backing pad 9 and the polishing pad 11, respectively, is the same for each of the inner pieces 12.1, 12.2, 12.3. Of course the distances r could also be different for each of the inner pieces 12.1, 12.2, 12.3. Furthermore, the number, form and size of the plurality of inner pieces 12.1, 12.2, 12.3 could vary from what is shown in FIGS. 12 and 13.
[0068] FIGS. 14 and 15 show yet another embodiment of a polishing pad 11 according to the present invention. In this embodiment, the bottom working surface 11b of the polishing pad 11 comprises a three-dimensional structure. The structure comprises slots 15 with a longitudinal extension along a curved line 16 (see FIG. 15). The slots 15 are located circumferentially around the rotational axis 10 of the plate-like backing pad 9 or the polishing pad 11, respectively. The lines 16 extend in a roughly radial direction. All lines 16 are curved in the same direction. The curved lines 16 of the slots 15 may intersect in the rotational axis 10. The slots 15 extend through the entire polishing pad 11 from its top attachment surface 11a to its bottom working surface 11b. In the embodiment shown, the slots 15 are provided in the outer circumferential part 13 of the polishing pad 11 forming recesses in the bottom working surface 13b. The outer circumferential part 13 has a central circular opening 14 for receiving the inner central piece 12 therein. The inner central piece 12 has a circular cross section and is located concentrically to the rotational axis 10.
[0069] Of course, the number, form and size of the slots can vary from what is shown in FIGS. 14 and 15. Furthermore, instead of the slots, the three dimensional structure of the bottom working surface may also be realized in any other way. Further, it would also be possible, that the three-dimensional structure is not exclusively embodied on the partial working surface 13b of the outer circumferential piece 13, but at least in part could also be embodied on the partial working surface 12b of the inner central part 12. The three-dimensional structure could also be realized, for example, by means of a waffle structure having depressions and hills displaced in respect to one another and located on at least part of the bottom working surface 11b of the polishing pad 11 (not shown).
[0070] Finally, FIGS. 16 and 17 show yet another embodiment similar to the one shown in FIGS. 14 and 15. In contrast to that embodiment, the outer circumferential part 13 of the polishing pad 11 does not have a central opening 14 for receiving an inner central piece 12. Rather, in this embodiment, the slots 15 provided in the polishing pad 11 form openings in which inner pieces 12 are located, each having the curved form of the slots 15. The partial working surfaces 12b of all inner pieces 12 inserted into the slots 15 form part of the working surface 11b of the polishing pad 11. The partial working surface 13b of the outer circumferential piece 13 extends beyond the partial working surfaces 12b of all inner pieces 12. Again, it is preferred that the rigidity of the material of the outer circumferential piece 13 is smaller than the rigidity of the inserted inner pieces 12.
