Polishing pad

Abstract

A polishing pad including a damping layer made of a resilient material including expanded semi-rigid polyurethane having a microcell structure, an adhesive layer including a layer of a hook-and-loop fastener adapted to interact and connect to a corresponding layer of the hook-and-loop fastener located at a bottom surface of the working element of the machine tool and a polishing layer including microfiber adapted for polishing a surface of a work piece. The polishing layer includes a fabric having a woven mesh of microfibers that define a back side of the polishing layer. The fabric serves as a barrier to the resilient material of the damping layer such that the resilient material does not reach an active side of the polishing layer comprising the microfibers when the damping layer, adhesive layer and polishing layer are combined, and such that the active side of the polishing layer is free of resilient material of the damping layer.

Claims

1. A polishing pad for a hand guided electric or pneumatic polishing machine tool having a working element performing an orbital, random orbital or a rotational movement, the polishing pad having a plurality of layers attached to one another including: a damping layer made of a resilient material including expanded semi-rigid polyurethane having a microcell structure; an adhesive layer including a layer of a hook-and-loop fastener adapted to interact and connect to a corresponding layer of the hook-and-loop fastener located at a bottom surface of the working element of the machine tool; and a polishing layer including microfibers adapted for polishing a surface of a work piece, wherein said damping layer, said adhesive layer and said polishing layer combine to form said polishing pad and wherein the polishing layer includes a fabric having a woven mesh of fibers or threads that define a back side of the polishing layer, said fabric being so tightly woven as to serve as a barrier to the resilient material of the damping layer such that the resilient material does not reach an active side of the polishing layer comprising the microfibers when said damping layer, adhesive layer and said polishing layer are combined, and such that the active side of the polishing layer of the polishing pad is free of resilient material of the damping layer.

2. The polishing pad as set forth in claim 1, wherein the adhesive layer includes a layer of loops adapted to interact with a layer of hooks located at the bottom surface of the working element.

3. The polishing pad as set forth in claim 1, wherein the microfibers are hydrophobic.

4. The polishing pad as set forth in claim 1, wherein the polishing pad has the form of a truncated cone.

5. The polishing pad as set forth in claim 4, wherein a top surface of the polishing pad carrying the adhesive layer has a smaller diameter than a bottom surface of the polishing pad carrying the polishing layer.

6. The polishing pad as set forth in claim 5, wherein the polishing pad has a peripheral surface connecting the top surface and the bottom surface, the peripheral surface having an angle in respect to the bottom surface within a range of 15° to 70° and being planar or curved to the inside or the outside.

7. The polishing pad as set forth in claim 1, wherein the polishing pad includes a plurality of through-holes extending through the entire polishing pad from and including the polishing layer to and including the adhesive layer, each of the through-holes having a longitudinal extension with a curved form and extending radially.

8. The polishing pad as set forth in claim 1, wherein the adhesive layer includes a fabric having a woven mesh that acts as a barrier to the resilient material of the damping layer such that the resilient material does not reach an active side of the adhesive layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other objects, includes, and advantages of the present invention will be readily appreciated as the same becomes better understood after reading the subsequent description taken in connection with the accompanying drawing wherein:

(2) FIG. 1 shows a hand guided machine tool that a polishing pad according to the present invention is adapted to be used with.

(3) FIG. 2 is a perspective view of a polishing pad according to one embodiment of the present invention.

(4) FIG. 3 is an alternate perspective view of the polishing pad of FIG. 2.

(5) FIG. 4 is a perspective view of a polishing pad according to another embodiment of the invention.

(6) FIG. 5 is a bottom side plan view of the polishing pad of FIG. 4.

(7) FIG. 6 is a perspective view of a polishing pad according to another embodiment of the invention.

(8) FIG. 7 shows one step of a method of manufacturing a polishing pad according to the present invention.

(9) FIG. 8 shows another step of the method of manufacturing the polishing pad.

(10) FIG. 9 shows another step of the method of manufacturing the polishing pad.

(11) FIG. 10 shows another step of the method of manufacturing the polishing pad.

DETAILED DESCRIPTION OF THE INVENTION

(12) With reference now to the drawings, FIG. 1 shows a hand-guided machine tool 1 adapted to be used with a polishing pad according to the present invention. In the embodiment of FIG. 1, the tool 1 is a pneumatically-driven random orbital sander with dust extraction. The tool 1 includes a casing 2, preferably made of plastic or metal. On top of the casing 2, a grip member 3 is disposed and is designed to allow a user of the tool 1 to comfortably and safely hold the tool 1 during use. Furthermore, the tool 1 has a switch lever 4 on top of the grip member 3. A hose for compressed air can be attached to connection element 5. Finally, another connection element 6 is adapted for connection to a hose of a vacuum cleaner or of any other kind of dust suction device.

(13) Inside the casing 2, the tool 1 includes a pneumatic motor driven by compressed air from the connection element 5. The tool 1 also includes a plate-like working element 7 made of a rigid material and adapted for receiving and holding a polishing pad 8. The tool's motor and the working element 7 are in connection with one another, preferably via a gear mechanism (such as an eccentric set) for transforming the motor's rotation into a random orbital movement of the working element 7. The polishing pad 8 is removably attached to a bottom surface 7a of the working element 7, in order to allow fast and easy replacement of the polishing pad 8 if necessary or desired. To that end, a top surface 8a of the polishing plate 8 is provided with an adhesive layer 9 adapted for connection to a corresponding layer located at the bottom surface 7a of the working element 7 of the machine tool 1. The removable attachment of the polishing pad 8 to the working element 7 can be achieved, for example, by a hook-and-loop fastener. To that end, the adhesive layer 9 can be provided with a plurality of hooks and the corresponding layer on the bottom surface 7a of the working element 7 can be provided with a plurality of corresponding loops. Similarly, the adhesive layer 9 can be provided with a plurality of loops and the corresponding layer on the bottom surface 7a can be provided with a plurality of corresponding hooks.

(14) Although the tool 1 shown in FIG. 1 is a pneumatically driven random orbital sander, it will be appreciated that the polishing pad of the present invention is adapted to be used with any kind of electronically or pneumatically driven hand-guided machine tool having a working element performing an orbital, random orbital, and/or a rotational movement. In particular, the polishing pad is adapted for use with any kind of grinder, polisher, or sander, with or without dust extraction features.

(15) The polishing pad 8 includes a plurality of layers that are inseparably attached to one another. The layers include: a damping layer 10 made of a resilient material, for example expanded or foamed polyurethane; an adhesive layer 9 adapted for connection to a corresponding layer located at the bottom surface 7a of the working element 7; and a polishing layer 11 of synthetic microfiber having a mass density of preferably 1.0 denier or less, adapted for polishing a surface of a work piece.

(16) Conventionally, the various layers 9, 10, 11 of the polishing pad 8 are glued together. In particular, for manufacturing conventional polishing pads 8 the damping layer 10 is die-cut out of a large material layer of foamed or expanded polyurethane. Then the adhesive layer 9 and the polishing layer 11 are glued to opposite surfaces 8a, 8b of the damping layer 10.

(17) According to the present invention, the adhesive layer 9 and the polishing layer 11 are inseparably attached to the damping layer 10 via a molding process during manufacturing of the polishing pad 8. An example for such a polishing pad 8 according to the present invention is shown in FIGS. 2 and 3. A further example for such a polishing pad 8 is shown in FIGS. 4 and 5 as well as in FIG. 6. The polishing pad 8 includes a plurality of through-holes 12 extending through the entire polishing pad 8 from and including the polishing layer 11 to and including the adhesive layer 9. Advantageously, each of the through-holes 12 has a longitudinal extension along a longitudinal axis 13 (see FIG. 5). The longitudinal axes 13 of the through-holes 12 preferably meet at a point of intersection 14 located in or near the center of the polishing pad 8, hence extending essentially radially. It is further advantageous that the longitudinal through-holes 12 have a curved form. Hence, the longitudinal axes 13 of the holes 12 have a curved form, too. The through-holes 12 serve as air intakes for cooling the polishing pad 8 and/or the machine tool 1 during operation. Furthermore, the provision of through-holes 12 in the polishing pad 8 reduces the area of the polishing layer's contact surface, with which the polishing layer 11 is in contact with the work piece's surface to be polished thereby reducing the friction surface, however, without reducing the polishing pad's effectiveness. The through-holes 12 have the advantage that they can receive large amounts of polishing liquid or paste and slowly dispense it to the surface to be polished during operation of the machine tool 1. Excess polishing liquid or paste on the surface to be polished can be easily and efficiently removed from the surface and received by the through-holes 12. The provision of the through-holes 12 in the polishing pad 8 reduce the contact surface between the adhesive layer 9 and the damping layer 10, as well as between the damping layer 10 and the polishing layer 11. This affords a tight, resistible, and secure connection between the outer layers 9, 11 and the damping layer 10 located between the outer layers 9, 11.

(18) Furthermore, the embodiments of FIGS. 4 to 6 have a central hole 15. The width of one or more of the through-holes 12 can vary along the holes' longitudinal axes 13. Further, it is possible that the width of the through-holes 12 varies from through-hole 12 to through-hole 12. The number of through-holes 12 can vary, depending, among others, on the diameter of the polishing pad 8. For example, the embodiment of FIGS. 4 and 5 may show a polishing pad 8 having a smaller diameter, for instance, of 100 mm or 120 mm, with only eight longitudinal through-holes 12. The embodiment of FIG. 6 may show a polishing pad 8 having a larger diameter, for instance, of 150 mm or 180 mm, with twelve longitudinal through-holes 12.

(19) The process for manufacturing the polishing pad 8 according to the present invention is hereinafter described in more detail with reference to FIGS. 7 to 10. The manufacturing process starts by providing a casting mold 20 preferably made of a thermally conductive material, in particular metal. The casting mold 20 has a recess 21 which has a form essentially corresponding to the manufactured polishing pad 8. In a first step of the method, the adhesive layer 9 is placed face down at the bottom 21a of the recess 21 of the casting mold 20 (see FIG. 7). In this case, the term “face down” indicates that the active side of the adhesive layer 9 (the side with the hooks and/or loops of a hook-and-loop fastener layer) extends towards the bottom 21a of the recess 21. Then, the resilient material for the damping layer 10 is poured or injected into the recess 21 on top of the adhesive layer 9 (FIG. 8). The material can be poured into the recess 21 either because its compounds, of which at least one is fluid-like, semi-liquid, or viscous, have been combined shortly before pouring or injecting the material into the recess 21 and have not yet reacted and cured. Alternatively, the material can be poured or injected into the recess 21 because the material has been and possibly still is thermally treated, in particular heated, giving the material a fluid-like, semi-liquid, or viscous characteristic.

(20) Next, the polishing layer 11 is placed face up on top of the resilient material of the damping layer 10 (FIG. 9). In this case, the term “face up” indicates that the active side of the polishing layer 1 (the side with the fibers of a polishing layer 11 made of microfiber) extends away from the bottom 21a of the recess 21. Finally, the recess 21 of the casting mold 20 is closed by placing a lid 22 on top of or in an opening of the recess 21 (FIG. 7). Advantageously, pressure p is applied to the lid 22 pressing it down towards the casting mold 20. Furthermore, a temperature T may be applied to the casting mold 20, to the recess 21 and in particular to the three layers 9, 10, 11 located therein. Next, the resilient material of the damping layer 10 has to cure for a certain time period t.

(21) In one embodiment, the adhesive layer 9 and/or the polishing layer 11 may each include a fabric having a mesh with a predetermined tightness. The term “tightness” refers to the mutual distance between the fibers or threads of the mesh. By placing the lid 22 on the recess 2,1 a certain degree of pressure p is exerted on the three layers 9, 10, 11 located in the recess 21 of the casting mold. The adhesive layer 9 and the polishing layer 11 are pressed with their back faces into the still fluid-like, semi-liquid, or viscous resilient material of the damping layer 10, thereby urging some of the resilient material to enter at least partly into the mesh between the fibers or threads. This provides for an extremely strong connection between the adhesive layer 9 and the damping layer 10 on the one side and the polishing layer 11 and the damping layer 10 on the other side after the resilient material of the damping layer 10 has cured.

(22) The mesh of the adhesive layer 9 and/or of the polishing layer 11 is preferably tight enough that is the mutual distance between the fibers or threads of the mesh is small enough to impede the resilient material of the damping layer 10 to pass through the fabric when poured into the recess 21 of the casting mold 20. In this way, no resilient material of the damping layer 10 reaches the front faces of the adhesive layer 9 and of the polishing layer 11. Such resilient material on the front face of the polishing layer 11 would severely affect the polishing capabilities of the entire polishing pad 8. On the other hand, resilient material reaching the front face of the adhesive layer 9 could affect a proper attachment of the polishing pad 8 to the bottom surface 7a of the working element 7. For example, the resilient material could enter into hooks or loops of the adhesive layer 9 thereby inactivating them so that they can no longer participate at the hook-and-loop connection between the adhesive layer 9 and a corresponding layer at the bottom surface 7a of the working element 7. However, the mesh of the adhesive layer 9 and/or of the polishing layer 11 is preferably loose enough that is the mutual distance between the fibers or threads of the mesh is large enough to allow the resilient material of the damping layer 10 to enter between the threads of the fabric when poured into the recess 21 of the casting mold 20. The tightness of the mesh of the adhesive layer 9 and/or of the polishing layer 11 is preferably selected depending on the fluidity or viscosity of the resilient material of the damping layer 10 when poured or injected into the recess 21, from the pressure p applied to the casting mold and other parameters, in order to achieve an optimum connection between the adhesive layer 9 and/or the polishing layer 11 and the damping layer 10, without excess resilient material entering onto the active sides of the adhesive layer 9 and/or the polishing layer 11.

(23) The material of the damping layer 10 is preferably a polyurethane, in particular a semi-rigid polyurethane having microcells, for example like the material know from EP 0925317A1. Such a polyurethane material has a much better resistance against stress, load and wear applied to the polishing pad 8 during the polishing process. In particular, the material of the damping layer 10 is not so easily disintegrated as the conventional foamed material.

(24) The polishing layer 11 could be placed on top of the resilient material of the damping layer 10 together with the lid 22. In that case, the polishing layer 11 would have to be previously attached to the inside of the lid 22. Then, when lowering the lid 22 onto the opening of the recess 21 thereby closing the casting mold 20 the polishing layer 11 is pressed with its back face into the resilient material of the damping layer 10.

(25) It is also possible to initially place the polishing layer 11 face down at the bottom 21a of the recess 21 of the casting mold 20. Then, after the resilient material of the damping layer 10 has been poured or injected into the recess 21 on top of the polishing layer 11 the adhesive layer 9 could be placed face up on top of the resilient material of the damping layer 10. In that case, the adhesive layer 9 could be placed on top of the resilient material together with the lid 22, in which case the adhesive layer 9 is previously attached to the lid 22.

(26) The amount of the resilient material of the damping layer 10 poured into the recess 21 (FIG. 8) is defined such that the resilient material together with the adhesive layer 9 and the polishing layer 11, in any event, completely fills out the recess 21 when closed with the lid 22. Preferably, the amount of resilient material is slightly more than actually needed for filling out the recess 21, in order to make sure that, in any event, the recess 21 is completely filled out with the adhesive layer 9, the polishing layer 11, and the damping layer 10. The superfluous resilient material could be squeezed out of the casting mold 20 when the lid 22 is pressed onto or into the recess 21.

(27) The casting mold 20 and possibly also the lid 22 may be made of a thermally conductive material, in particular of metal. The casting mold 20 and possibly the lid 22 are heated (FIG. 7) in order to convey at least part of the applied heat T to the recess 21 and the layers 9, 10, 11 located therein during manufacturing of the polishing pad 8. By applying a defined amount of heat T over time t under a certain pressure p, the curing of the resilient material of the damping layer 10 can be controlled in order to give the damping layer 10 the desired characteristics.

(28) The recess 21 preferably has a truncated cone shape. The slanting side walls of the recess 21 serve for forming a peripheral surface 8c of the polishing pad 8, the surface 8c connecting the top surface 8a and the bottom surface 8b. In a cross sectional view (see FIGS. 7 to 10) the side walls of the recess 21 can be formed planar (like in FIGS. 7 to 10) or arcuated or curved. The angle of the side walls of the recess 21 is within a range of 15° to 70°. Hence, the polishing pad 8 manufactured by the casting mold 20 shown in FIGS. 7 to 10 has a truncated cone shape, too, corresponding to the form of the recess 21. One advantage of the truncated form is that the manufactured polishing pad 8 can be easily extracted from the recess 21 at the end of the manufacturing process, because the recess 21 has no undercuts. Furthermore, due to the reduced thickness of the polishing pad 8 along its external rim, the external rim is particularly resilient allowing it to easily follow the surface to be polished in edges and angles.

(29) Advantageously, the surface 8a which the adhesive layer 9 is attached to has a smaller diameter than the surface 8b which the polishing layer 11 is attached to. Furthermore, the adhesive layer 9 can have a smaller diameter than the surface 8a it is attached to. Moreover, the polishing layer 11 can have a diameter at least the size of the diameter of the surface 8b it is attached to. With the polishing layer 11 slightly extending beyond the circumference of the surface 8b it can be assured that the polishing layer 11 remains in contact with the surface to be polished even in edges and angles. Hence, it is avoided that in edges or angles the damping layer 10 comes into contact with the surface to the polished.

(30) The invention has been described in an illustrative manner. It is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the invention may be practiced other than as specifically described.