Tool for Surface Finish Machining

Abstract

A tool (1) for surface finish machining, having a cushion (6) made of an elastic plastics foam, on the underside of which there is formed a working medium face (2) having working media or adhesives (8, 11, 12, 13) for the releasable attachment of working medium discs and on the top side of which there is formed a drive receptacle (4, 5) for application of work, is created as a product that is producible easily and non-critically in high volume, is extremely robust in use, is moisture-resistant and is able to withstand high rotational speeds, in that the elastic plastics foam consists of closed-cell expanded and fused-together particles of a thermoplastic elastomer (TPE).

Claims

1.-18. (canceled)

19. A tool for surface finish machining, comprising: a cushion comprising a bottom side with a working material face provided with a working material or with a coupling agent configured to detachably connect a working material disc; a drive receptacle disposed at a top side of the cushion and configured to introduce working forces into the cushion; wherein the cushion is comprised of an elastic plastic material foam that is comprised of closed-cell expanded and fused-together particles of a thermoplastic elastomer.

20. The tool according to claim 19, wherein the elastic plastic material foam is formed of a urethane-based elastomer.

21. The tool according to claim 20, wherein the elastic plastic material foam is comprised of hard segments and soft segments, wherein the hard segments comprise urethane links and wherein the soft segments comprise links selected from the group consisting of ether links, ester links, and carbonate links.

22. The tool according to claim 19, wherein the elastic plastic material foam is formed of thermoplastic polyamide elastomers.

23. The tool according to claim 19, wherein the elastic plastic material foam is formed of thermoplastic copolyamides.

24. The tool according to claim 19, wherein the elastic plastic material foam is formed of thermoplastic copolyesters.

25. The tool according to claim 19, wherein the elastic plastic material foam is formed of thermoplastic olefin elastomer.

26. The tool according to claim 19, wherein the elastic plastic material foam is formed of thermoplastic styrene block copolymers with a diene.

27. The tool according to claim 19, wherein the elastic plastic material foam is formed of gas-filled, balloon-shaped, approximately spherical to oval particles joined under pressure and fused with each other at their surfaces under heat.

28. The tool according to claim 19, wherein the elastic plastic material foam is homogenous and embodied without a condensed outer molded skin up to outer rims of the cushion.

29. The tool according to claims 19, wherein the working material face is provided with a surface profiling configured to attach a working material disc thereto.

30. The tool according to claim 29, wherein the surface profiling comprises projections that are distributed across a surface of the working material face and configured to hook or engage a loop texture or fabric texture of a working material disc.

31. The tool according to claim 29, wherein the surface profiling is comprised of suction cups distributed across a surface of the working material face.

32. The tool according to claim 19, wherein the drive receptacle comprises at least one fixed and stiff connecting part that is integrally formed on the cushion during molding of the cushion.

33. The tool according to claim 32, wherein the connecting part comprises a coupling element for a machine drive and a support body that at least partially covers the cushion.

34. The tool according to claim 32, wherein the connecting part comprises at least one grip element configured to manually actuate the tool.

35. The tool according to claim 19, wherein the coupling agent is integrally formed on the working material face during molding of the cushion.

36. The tool according to claim 19, wherein the working material is integrally formed during molding of the cushion on the working material face.

Description

[0017] Embodiments of the invention are illustrated in the drawing and will be explained in the following in more detail. The figures show in:

[0018] FIG. 1 a cross-section of a tool according to the invention;

[0019] FIG. 2 view of the tool according to FIG. 1 at a slant from below;

[0020] FIG. 3 a detail cross section of the surface of the tool according to FIG. 2 in the direction of arrow III;

[0021] FIGS. 4, 5, and 6 further partial enlarged scale cross sections corresponding to FIG. 3 with other configurations of the surface;

[0022] FIG. 7 a cross-section of a further tool;

[0023] FIG. 8 view of the tool according to FIG. 7 at a slant from below.

[0024] The tool for surface finish machining illustrated in FIGS. 1 and 2 and identified as a whole by 1 represents a simple form of such a tool as a rotating grinding disc of rotation symmetry which (in case of surface finish machining from above) is provided at the bottom side with a working material face 2 and at the topside comprises a drive receptacle 3 which is to be clamped with a round pin 4 in a drill chuck of a power drill. The pin 4 of stronger material, preferably metal, passes into a support body 5 transmitting pressure and rotation forces of the drive and applied from above that supports a circular disk shaped elastic cushion 6 in flat connection on the bottom side. The cushion 6 itself forms with the bottom side the working material face 2. The cushion 6 projects radially past the plate-shaped support body 5 wherein a circumferential rim 7 is formed as a truncated cone between the circumference of the support body 5 and the working material face 2.

[0025] The tool 1 that in so far is described as conventional represents in its structure a particularly simple example. Other tools for surface finish machining can differ in regard to its construction, which, for example, can be provided with air channel guides and openings in the cushion, air channels in the area of the drive receptacle for suction removal of dust, which in the area of the drive receptacle is provided only with a knob or grip or several thereof for manual operation or which comprises, for the connection to machine drives, other couplings than a simple pin 4. It is also understood that not only rotating tools for surface machining are to be considered here, but also, as is conventional in practice, tools with oscillating movements along the surface to be machined or with wobble movements, as well as with random movements as they are naturally occurring in particular for manually operated tools for surface finish machining.

[0026] In these tools, a cushion such as the present cushion 6 has an important function for distribution of the pressure and for transferring movements between the working material face 2 and the drive receptacle 3, including its support body 5. In so far, the thickness of the cushion 6 is to be dimensioned in accordance with the intended deformations. In particular, the cushion 6 with regard to its stiffness or its yielding action is to be matched to the pressing forces. The energy uptake of the cushion during use may not lead to overheating or material destruction. The material of the cushion must be suitable to work under great loading with dust and dirt and also, in particular in case of wet grinding, under a great load of moisture. In addition, it is of interest when the cushion causes a minimal weight load for handling, in particular because it constitutes a significant volume proportion of the tool, wherein weight savings in principle are also advantageous in regard to the manufacture, shipment, and storage. In particular however, robustness and longevity are to be pursued for such a cushion, particularly because for tools of this kind the service life of the tool depends regularly on the cushion 6 when the working materials in the form of working material discs on the working material face 2 are provided to be exchangeable.

[0027] In practice, usually cushions of this kind are produced of a so-called “integral foam”, i.e., a polyurethane integral foam, that by mold-foaming in a mold, is provided with an open-cell core and a massive exterior skin toward the rim zones. This mold-foaming however provides no safety against ingress of moisture and dirt into the cushion, in particular also in case of damages of the exterior skin during use.

[0028] The cushion according to the invention employs in contrast thereto an elastic plastic material foam which is comprised of closed-cell expanded and fused-together particles of a thermoplastic elastomer (TPE). In the concrete example, the elastic plastic material foam is comprised of closed-cell expanded and fused-together particles of a thermoplastic polyurethane (E-TPU). This material that has been developed for different intended uses, i.e., for athletic shoe soles, has been found to be extremely advantageous as a cushion material. In contrast to the prior conventional integral foam, it has a uniform density up to the rim and can even be cut from greater material blocks. The elimination of condensed exterior skin areas provides already significant weight savings. In particular however, the thin-wall cell structure of the bead-like articles of which the plastic material foam is fused together, has a continuous lightweight as well as highly elastic structure of the material. The structure is closed-cell already based on the starting material and the closed-cell structure entails a reduced water absorption (and dirt absorption) so that even for working in wet conditions only 1 to 2% of volume are absorbed. The closed-cell structure of the elastic plastic material foam with gas volume enclosed therein by the expanding form material in the particles and thin cell walls provides a good elastic deformability which reduces the risk of material heating and material fatigue during use and also stands for a longevity of the cushion.

[0029] The working material face 2 can be provided in conventional way directly with a working material layer, for example, with grinding or polishing agents. In this context, the attachment of such working materials as well as the connection of the cushion 6 with the support body 5 can be realized in an advantageous manner already during molding of the cushion in a pressure mold so that an additional working step with fusing or gluing of flat layers to be joined is not needed. The adhesion of material integrally molded in the mold, inserted into a pressure mold that is then filled with the closed-cell expanded particles and then brought to fusing temperature with hot steam or another suitable medium, provides a complex tool configuration in a way that saves working steps.

[0030] Another advantageous property of the closed-cell cushion material of a thermoplastic elastomer resides the suitability for molding surface structures. In FIG. 2, on the working material face 2 a uniform structure with molded portions across the entire surface area is indicated, illustrated in FIG. 3 in an enlarged detail cross section in more detail. The working material face 2 is embodied with a pattern of uniformly distributed suction cups 8 which are directly molded in the material of the cushion 6. These suction cups 8 with downwardly open plate shape project from depressions 9 into which the suction cups 8 upon compression can be moved and which are framed by rim webs 10 which however end above the plane which is defined by the suction cups 8. The webs 10 delimit the movement of the suction cups in case of a pressure from the front when the suction cups, during working use, are pressure loaded after they had been placed onto a smooth back of a working material disc or another working material carrier. In so far, a coupling agent surface that can be directly formed from the cushion material is a cost-saving possibility for configuring the working material face. It is however understood that alternatively also a separate plate or disc with suction cups of the illustrated kind can be joined adhesively when molding the cushion 6 and can also be retrofitted by fusing or gluing.

[0031] FIG. 4 illustrates a configuration of the working material face with thorn-like projecting tips 11 as coupling agent layer that can engage, for example, a fabric or knitted fabric on the back of a working material disc and provides a loadable force connection between tool and working material for the rotating movement. The easily releasable coupling effect which is to be obtained thereby of a working material disc is sufficient for practical use with loadability in pressure and rotation direction.

[0032] FIGS. 5 and 6 show finely embodied configurations of a working material face in the meaning of a hook and loop fastener connection where knob-shaped projections 12 or 13 effect with mushroom-type, claw-shaped molded portions 14, 15 parallel to the working material face a barbed hook effect when the working material face molded in this way is engaging a corresponding open back structure of a working material disc or another working material carrier and thus produces a relatively strong yet still detachable connection between working material and tool.

[0033] The configurations of the working material face according to FIG. 4 to FIG. 6 can be obtained within a pressure mold which has a corresponding complementary configuration at the appropriate inner surfaces. Into this pressure mold, particles of a thermoplastic elastomer, for example, a thermoplastic polyurethane in before expanded form, are to be introduced as lose particles or beads, preferably in round or oval shape of a size of one or a few millimeters, and to be compressed with pressure from the loose bulk material to a compressed molded part that is strengthened by fusing by means of hot steam or another heating medium. After removal, this molded part can be tempered by a heat treatment in order to compensate internal stress and to stabilize the obtained shape.

[0034] A modified embodiment of the tool according to FIGS. 1 and 2 is illustrated in FIGS. 7 and 8 wherein the parts of the tool that are corresponding to each other are identified with the same reference numbers as before. In this further embodiment of the tool, the drive connector 3 is comprised of a central metal body 4 with topside inner thread in order to be screwed, for example, onto a drive spindle of a power drill. This metal body 4 is embedded into a support body 5 of solid plastic material which carries at the bottom side a cushion 6 of an elastic plastic material foam which is comprised of closed-cell expanded and fused-together particles of a thermoplastic elastomer (TPE). About a center axis 16, the cushion 6 is formed as a circular ring structure with a free inner recess into which partially a ring projection 17 of the support body 5 is projecting. In particular however, into the free inner chamber of the cushion 6 a central threaded projection 18 of the metal body 4 is projecting onto which from below a clamping nut 19 with externally cast-on plastic material clamping flange 20 can be screwed.

[0035] The clamping flange 20 can be screwed with the clamping nut 19 into the free inner space of the cushion 6 and countersunk in the recess. In this way, a working material disc can be secured in a simple way by clamping on the bottom working material face 2 of the cushion 6 which is provided in the area of the clamping flange 20 with a central hole and radial outwardly oriented slots in order to be able to deform the working material disc 21 for clamping with the clamping flange 20 and thus obtain a simple coupling connection with the cushion 6.

[0036] In comparison to the full-surface circular shape according to FIGS. 1 and 2, the inner recess of the cushion 6 has no significant effect on the operation of the tool 1 because the tools are used very often with rim-accentuated pressure application and because, in particular also for flat placement of the tool, the desired finish machining action primarily falls onto the radially farther outwardly positioned areas due to the outwardly higher rotational movements.