Patent Application
20220402099
The following relates to a grinding element as described hereinafter.
In the present description of embodiments of the invention, which is intended for use in grinding or polishing tools, the terms “abrasive” and “polishing” are mutually interchangeable. For example, an abrasive cloth also refers to a polishing cloth, etc.
Grinding elements for use in grinding or polishing machines designed, e.g., as drum grinders or grinding wheels are known. These typically consist of a combination of an abrasive cloth and support brushes. The abrasive cloth and the support brushes are typically mounted in an elongate support profile rail, in which the abrasive cloth and the support brushes protrude from the profile rail. Alternatively, the support brushes may be mounted in an elongate support profile rail, and the abrasive cloth may be placed outside the profile rail or directly on the brushes. The profile rail is typically meant to secure the grinding element in an undercut groove on a tool on grinding or polishing machines.
The abrasive cloth is terminated in an exposed outer edge area extending beyond the top of the brushes and along the upper end portions of the support brushes, which forms the active abrasive area of the abrasive cloth, when in use. However, this abrasive area is only a part of the whole abrasive cloth, which is mounted in the profile rail.
Furthermore, known grinding elements are limited in their effect, in that their flexibility, pliability, perpendicular to the longitudinal direction, are determined by the flexibility and pliability of the sandpaper, and in that their flexibility, pliability, is an important parameter in treating surfaces, when grinding or polishing various workpieces.
Finally, it is well known that sandpaper in the form of sandpaper is relatively inexpensive and has a limited service life. However, this is not a problem, in that the grinding elements can be replaced swiftly and easily without substantial downtime.
However, grinding cloths with a substantial material price are also known, as are machines, for which a long service life of the grinding elements is important.
However, it is desirable to reduce costs, and provide grinding elements, which allow for reducing the consumption of materials. This is particularly the case, when dealing with expensive abrasive cloths.
U.S. Pat. No. 4,969,299 discloses a rotary grinding tool with grinding elements, which contains flaps consisting of cloth with glued-on abrasive grains. The citation contains no instructions as to the use of support brushes. An area of the cloth for supporting the flaps is kept free of abrasive grains.
Furthermore, WO 2011/110176 discloses a grinding element of the type described in the preamble of claim 1 of the present patent application. For many years, this grinding element has worked acceptably in many applications, in that it has a history of reduced consumption of expensive abrasive materials and a long service life. However, disadvantages were encountered in the form of abraded grooves in surfaces treated with tools using these grinding elements.
Even when using fine-grained abrasive materials, problems were encountered in several applications, when finishing the treated surface. The treated surface will typically be finished with some form of coating or paint.
Thus, problems were encountered with a coating adhering to the treated surface. To remediate this, experiments were conducted with various basic treatments and binders as a foundation for surface varnishing or surface coating. The use of several finishing layers is undesirable both as concerns the incurred costs and the weight.
Likewise, surface-gloss problems have occurred. In many products, this will create problems with unwanted glare and reflections. Even when using a coating for finishing purposes, this can create problems in the finished surfaces. This is due to treated surfaces having an irregular surface due to abraded grooves with areas, where glare and reflection occur. This problem is particularly exacerbated for fiber surfaces in public spaces, e.g., wind-turbine blades, safety helmets and photovoltaic systems. To alleviate this problem, experiments with special varnishes have been conducted. However, it is desirable to keep the weight within limits, especially with products, such as wind-turbine blades and safety helmets, i.e., reduce the use of paints and coatings as much as possible.
Thus, several experiments have been done with different types of finishing, including the use of binders and special varnishes. The application of binders, primers, special varnishes, possibly in several layers, will increase costs and, moreover, causes the weight to increase, which for several products is undesirable.
It is therefore desirable to improve grinding/polishing to achieve a surface, which will provide a better foundation in the form of the treated surface, and thereby minimize the need for finishing and eliminate problems with glare and adhesion.
An aspect relates to being able to use conventional art grinding elements, which reduces the consumption of expensive grinding materials, and which have a long service life, and achieve uniform surface grinding, thereby minimizing problems with adhesion and glare.
This aspect is achieved by embodiments of the present invention by a grinding element of the type mentioned in the introduction, which is characterized in that the arrayed particles of the abrasive material are arranged with the particles offset relative to the particles in adjacent rows, and that the arrayed particles are spaced apart, such that the abrasive particles overlap in the longitudinal direction of the abrasive cloth.
The commercially available abrasive cloths are machine-manufactured with the particles of the abrasive material placed in adjacent rows. The particle rows are placed such that the particles in every other row are offset from one another, when viewed transversely to the length of the rows.
When using these commercially available abrasive cloths, the normal procedure for forming slats in grinding elements has been to cut in a direction parallel to the rows and in a space between adjacent rows. This has made it possible to create a clean cut without interfering with the particles of the abrasive material, which typically consists of a diamonds or similar hard materials, which act as a super-abrasive material.
With such cutting, the slats of the grinding element are provided with rows of particles, which are oriented parallel to the vertical direction. This has caused abraded grooves with areas, in which a surface is being ground in areas adjacent to the rows, and minor or no abrasion in areas between these rows. In other words, areas will appear in the longitudinal direction of the abrasive cloth, in which there are no abrasive particles that can be used to form the surface being machined.
This problem is obviated with embodiments of the present invention, in that the abrasive particles overlap in the longitudinal direction of the abrasive cloth. Thus, particles will be provided in the longitudinal direction of the abrasive cloth. The particles are appropriately arranged in rows. As the particles of the abrasive material are arranged in rows, generally commercially available abrasive cloths may be used. By changing the orientation of the rows, such that they are no longer parallel to the vertical direction of the abrasive cloth, it is possible to create overlapping of the abrasive particles in the longitudinal direction of the abrasive cloth.
Even though for many years it has been possible to “reverse” the orientation of the rows in commercially available abrasive cloths, the desire to perform cutting parallel to the rows has thus far required an expert's solution to the formation of slats.
Thus, embodiments of the invention in a surprisingly simple way allows for creating an abrasive cloth, in which the arrangement of the particles of the abrasive material makes it possible to grind the whole surface which is being covered by the abrasive cloth. Consequently, no specific abraded grooves occur with areas, where no grinding was performed.
Such areas of the surface, where no abrasion occurs, are undesirable, in that they appear with a smooth surface. This smooth surface may partly result in poor adhesion, but may also cause reflection and glare emanating from the top of the surface.
Thus, with a grinding element according to embodiments of the present invention, a surface will be created, which is rougher and without smooth areas, which cause glare. This greater surface roughness will also create a larger area, which makes for a larger surface for the adhesion of coating or varnish. Thus, adhesion will be increased.
Due to the surface appearing rough and without smooth areas, the reflection will become far more diffuse. This makes it possible to control the surface and determine the chance of glare and gloss based only on the coating or varnish used. This varnish may be applied in a thinner layer than is traditionally the case, given the larger surface, wherein adhesion occurs, and given the diminished need for more layers to reduce glare from the abraded and coated surface.
Particularly with regard to wind turbine blades, it is desirable to control the glare from the turbine blade. A similar challenge occurs in photovoltaic systems, where glare from the often very large surfaces of such a photovoltaic system is undesirable.
In safety helmets, a similar reduction in the glare is also desirable for road safety reasons.
The specific arrangement of the particles being offset from the particles in the adjacent rows, along with the angular arrangement of the rows relative to the extension of the slats, results in improved grinding/polishing in a simple way, allowing for obtaining a surface, which creates a better foundation, whereby the need for post-treatment is minimized, while avoiding problems with glare, and optimizing adhesion.
The abrasive material consists of particles placed in the active area of the abrasive cloth. Hence, this area has a particularly effective abrasive capability, which increases the service life in relation to traditional abrasive cloths. In an embodiment, the abrasive material consists of diamond particles.
The abrasive material may comprise units of material, whose unit size is between 0.1 and 1,000 micrometers. This means that the abrasive material may have the consistency of a powder, in that the unit size is at the lower end of the range, and that the abrasive material may consist of particles, in that their unit size is at the upper end of the range.
The range is typical of the grinding and polishing jobs that are characteristic of embodiments of the invention.
It is obvious to a person skilled in the art when performing special and, in this case, typically more precise grinding and polishing jobs, to go outside the range, and, e.g., use grinding materials with a unit size in the nano range.
The units of the abrasive material may vary in terms of shape and structure. Hence, the units may be angular or round, or the abrasive material units may be a combination thereof. Moreover, the units may be crystalline or non-crystalline.
In an alternative embodiment, the abrasive material in the form of particles is characterized by the abrasive cloth itself having local projections, which create the actual effective contact with the surface to be abraded.
The area between the local projections give rise to channels, which can divert abrasive dust away from the surface, which is being abraded.
Moreover, these projections and channels provide increased heat conduction.
The abrasive cloth is cut out from the outer exposed edge area to form slats. The abrasive cloth is typically cut out perpendicular to the profile rail from the outer exposed edge of the cloth. In one embodiment, the abrasive cloth may be cut out from the outer exposed edge of the cloth to the profile rail to form long slats. Alternatively, the abrasive cloth may be cut out from the outer exposed edge of the cloth to a position between the active area and the profile rail to form short slats. The abrasive cloth may be cut out to form slats with identical slat lengths or to form slats with varying slat lengths.
According to a further embodiment, the grinding element according to the invention is characterized in that the adjacent rows are arranged at an angle different from 0° with respect to the vertical direction.
When using abrasive cloths, wherein the particles are arranged in rows, varying the orientation of the rows slightly relative to the vertical direction of the abrasive cloth can make the particles overlap in the longitudinal direction of the abrasive cloth.
Depending on the distance between the adjacent rows, the angle may be varied from 1° to 179°.
The abrasive cloth is arranged, such that the adjacent rows are arranged at an angle of 90° relative to the vertical direction of the abrasive cloth.
According to a further embodiment, the grinding element according to the invention is characterized in that the orientation of the adjacent rows is in the longitudinal direction.
Thus, when the rows are aligned is in the longitudinal direction, their orientation will be below 90° relative to the vertical direction. This represents a particularly simple design. By arranging the particles in rows, it becomes possible to vary in a relatively simple way the particle size and shape, as well as the spacing between the particles in the rows, and thus ensure overlapping in the longitudinal direction of the abrasive cloth.
According to a further embodiment, the grinding element according to the invention is characterized in that the extension of the particles in the direction of the row is greater than the spacing between the particles in adjacent rows.
By using particles, whose extent in the longitudinal direction of the row is greater than the distance between successive particles in an adjacent row, overlapping in the longitudinal direction of the abrasive cloth will be obtained in a particularly simple way. This is particularly advantageous, when using an abrasive cloth, wherein the rows are aligned in the longitudinal direction of the abrasive cloth.
According to a further embodiment, the grinding element according to the invention is characterized in that the abrasive material is a super-abrasive material, which consists of particles, as well as of powder of, e.g., diamonds or similar materials.
The abrasive material is a super-abrasive material, which in essence means that the units of the abrasive material have a certain strength, such as crystal strength or tensile strength, and that this strength is roughly similar to the strength of diamonds.
An example of an alternative embodiment is the super-abrasive material Boron Nitride with a cubic unit shape (cBN), which has a hardness roughly the same of as diamonds and, at the same time, thermal conductivity comparable to traditional abrasive materials.
In a further alternative embodiment, the super-abrasive material is provided with a coating, which may be a metal coating, and which may be based on, e.g., nickel, copper or similar coating materials.
According to a further embodiment, the grinding element according to the invention is characterized in that the active area constitutes between ¼ and ½ and typically about a third of the abrasive cloth height.
Thus, for typical combinations of abrasive cloths and abrasive materials, an active area is obtained in practice, which has the desired abrasive effect, as well as a material-saving effect over abrasive cloths, which also have abrasive material in non-active areas of the abrasive cloth.
According to an alternative embodiment, the grinding element is characterized in that the active area has an abrasive profile in the vertical direction of the abrasive cloth. By this is meant, e.g., an abrasive profile with varying abrasive material or, e.g., an abrasive profile with an on/off abrasive material.
According to an alternative embodiment, the grinding element is characterized in that the active area of the abrasive material and up to the end of the outer exposed edge area includes a smaller area of the abrasive cloth, which is not coated with an abrasive material, and which constitutes between zero and an eighth of the abrasive height of the cloth.
According to a further embodiment, the grinding element according to the invention is characterized in that the height of the abrasive cloth is between 20 and 80 mm, and typically about 40 mm.
Thus, the grinding element provides a suitable abrasive effect for practical applications in manually controlled machines and tools, and in machines and tools typically used in the production of elements in the industry.
It is obvious to a person skilled in the art to extend the height of the abrasive cloth for use in grinding elements for larger or special grinding or polishing purposes.
Likewise, it is obvious to a person skilled in the art to reduce the height of the abrasive cloth for use in grinding elements for smaller or special grinding or polishing purposes.
According to a further embodiment, the grinding element according to the invention is characterized in that the abrasive material is made to adhere to the abrasive cloth in the active area using a binder, which bonds the particles to the abrasive cloth. If also using a powder, such a powder will also be bonded to the abrasive cloth by the binder.
As a result, the grinding element has the active area directly embedded in the abrasive cloth, and the abrasive cloth can easily be replaced in the profile rail, when worn.
The abrasive cloth can then be recycled, in that a new abrasive material may be applied in the active area.
In one embodiment, the binder is a resin-based binder. In alternative embodiments, other binders such as varnish, adhesive, or the like, can be used.
Furthermore, the binder may be a polyamide or a phenolate.
According to a further embodiment, the grinding element according to the invention is characterized in that the abrasive material is provided on a second cloth, which is mounted in the active area of the abrasive cloth.
The idea is that the abrasive material is applied to a separate substrate, i.e., the second cloth, and that the second substrate and the active area of the abrasive cloth are set up for mounting.
Mounting may be done by adhesive bonding, welding, Velcro-locking, or a rail arrangement.
According to a further embodiment, the grinding element according to the invention is characterized in that the flexibility of the abrasive cloth in an area between the active area and the profile rail is greater than the flexibility of the abrasive cloth in the active area.
Flexibility refers to pliability and substantially in a direction perpendicular to the longitudinal direction of the profile rail.
Flexibility in the active area of the abrasive cloth is substantially related to the layer of abrasive material in the active area of the abrasive cloth.
The flexibility of the abrasive cloth in an area between the active area and the profile rail is substantially related to the flexibility of the support layer of the abrasive cloth, which is situated between the active area and the profile rail.
According to an alternative embodiment of the abrasive cloth, the inner area comes with at least one area of increased flexibility. In one embodiment, the area is brought about, in that the abrasive cloth in a narrow area is thinner than the rest of the area.
Furthermore, this allows for the active area to act upon the surface, approximately parallel to the surface, in that the active area appears between the surface and the tips of the support brushes.
According to a further embodiment, the grinding element according to the invention is characterized in that the abrasive cloth is made of a plastic material, such as Polyethylene (PE), Polypropylene (PP), or Polyvinyl chloride (PVC), and in that the abrasive cloth is made of a rubber material, or that the abrasive cloth is realized as a biomaterial.
This allows for the abrasive cloth to be used in the grinding element over an extensive period or time, and thus increases its service life over traditional cloths.
Some of the embodiments will be described in detail, with references to the following Figures, wherein like designations denote like members, wherein:
An abrasive cloth 4 is mounted in the profile rail 2, as are support brushes 5. The abrasive cloth 4 is provided with slats 6.
In this specific embodiment, the profile rail 2 limits the risk of the abrasive cloth 4 and the support brushes 5 being extracted from the profile rail. The abrasive cloth 4 and the support brushes 5 ascend or radiate substantially in the same vertical direction 7 within a narrow angle from the mounting area of the profile rail 2 and in a vertical direction 7.
Opposite the profile rail 2, the abrasive cloth 4 terminates at an edge of the cloth 8, and the distance between the edge of the cloth 8 and the profile strip 2 defines the height of the cloth 9.
Opposite the profile strip 2, the support brushes 5 are terminated in a support brush extremity 10, and the distance between the support brush extremity 10 and the profile strip 2 defines the height 11 of the support brush.
Similarly, the abrasive cloth length 12 is defined as the extension of the abrasive cloth 4 in the longitudinal direction 3, and the support brush length 13 is defined as the extension of the support brushes 5 in the longitudinal direction 3.
In the embodiment shown, the abrasive cloth 4 is realized with a plurality of slats 6, which in the specific embodiment have roughly the same length 14. However, nothing stands in the way of varying the slat length 14.
In the embodiment shown, the brush length 13 exceeds the canvas length 12, and there is a plurality of bristles per slat length 14.
In the embodiment shown, the height 9 of the cloth exceeds the height 11 of the support brush.
As shown, the inactive side 15 of the abrasive cloth 4 faces the support brushes 5.
The active side 16 of the abrasive cloth 4 has an active area 17 (marked as - - - ), which is coated with an abrasive material 18. The active area 17 is an area at an outer exposed edge area 19 (marked as . . . ) of the abrasive cloth 4 from the edge of the abrasive cloth 8 toward the profile rail 2. It is immaterial whether the outer exposed edge area 19 has a height, which is greater than the height of the active area 17. The important thing is that the two areas 17, 19 have a certain overlap.
In the embodiment shown and illustrated in the section of the figure, the abrasive material 18 is provided as a super-abrasive material 20, which consists of diamonds 21 in the form of particles 22. Also illustrated here is a powder 23, which may optionally be used with the particles 22. Here, the abrasive material 18 is provided on a second cloth 24, which furthermore is mounted in the active area 17 of the abrasive cloth 4.
In the specific embodiment, the second cloth 24 is glued to the abrasive cloth 4.
In the embodiment shown, the abrasive material 18 on the second cloth 24 is cut similarly to the slats 6.
It can be seen here that the particles 22 are placed in rows 26. It is quite customary in commercially available abrasive canvases of this type for the particles to be placed in adjacent rows on a canvas. The particles 22 in every other row 26 are placed next to one another, as seen in the longitudinal direction 3. The particles 22 in the intermediate rows 26 are located offset next to the spaces. Thus, the rows 26 of particles 22 are oriented parallel to the vertical direction 7. It can also be seen that the cut-out is done parallel to the vertical direction 7 in the spaces 30 between the rows 26. In these spaces 30, the particles 22 do not overlap, such that the spaces 30 in the longitudinal direction 3 of the abrasive cloth have no abrasive material. This gives rise to abraded grooves, in that areas on the surface 25 (see
The extremity of the support brush 10 rests or acts on a surface 25, which surface 25 also interacts here with the inactive side 15 of the abrasive cloth 4.
The abrasive cloth 4 substantially has inner and outer flexibility, wherein the outer flexibility is associated with the active area 17 of the abrasive cloth 4, and the inner flexibility is associated with the area between the active area 17 and the profile rail 2.
The abrasive material 18 is provided in the form of particles 22, which are arranged in rows 26. The rows 26 are arranged parallel to the longitudinal direction 3 of the abrasive cloth, and thus perpendicular to the vertical direction 7 of the abrasive cloth. The abrasive rows have a direction 28 at an angle 27 with respect to the vertical direction 7
The extension 30 of the particles 22 is in the direction of the row 28, and is greater than the spacing 29 between the particles 22 in the adjacent rows 26. Furthermore, the particles are arranged offset relative to one another in the rows 26. In this way, an overlap of abrasive particles over the whole longitudinal direction 3 of the abrasive cloth is obtained, such that any area of a surface 25 being machined will be coated with particles 22 from one or the other row 26.
In
Between the depressions 32, there are areas with a flat surface 31. This flat surface 31 is an untreated flat surface, which appears without roughness. It may be smooth, which makes it difficult for varnish or other coating to adhere to the plane 31 of the flat surface 25. These flat surfaces 31 will also give rise to undesired reflections and glare from incident light, in that no diffusion occurs from the flat surfaces 31.
With this abrasion, roughness is obtained over the whole top surface of the plane 25, which increases the chance that varnish or other coating will adhere. Furthermore, the rough surface will diffusely reflect incident light. Thus, glare and reflection will largely be avoided with a plane 25, as illustrated in
Experiments have been conducted with grinding elements of the known type, as illustrated in
With a grain size of 200, it was found with gelcoat, that a grinding element according to embodiments of the invention yields a roughness parameter (Ra) of 2.7, and with the known system, an RA of 2.5. Similarly, with carbon and a grain size of 200, an RA of 2.8 with a grinding element according to embodiments of the invention, and an RA of 2.4 with the known grinding element were measured.
In addition, tests with a grain size of 120 have revealed an RA value of 4.4 and 3.6, respectively, for the grinding element according to embodiments of the invention, over the previous one on gelcoat. Similarly, with a grain size of 120, an RA of 3.4 and 2.9, respectively, was measured in a carbon for a grinding element according to embodiments of the invention as compared with the previous one.
In other words, there is evidence of improved roughness with both grain size 120 and grain size 200. For a grain size of 120, the roughness value thus increased by 22 percent.
For customers, this could mean a significant improvement in the adhesion and reduced reflection, as well as in the grinding rate and the service life of the grinding elements.
Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.
For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements. The mention of a “unit” or a “module” does not preclude the use of more than one unit or module.
| Number | Date | Country | Kind |
|---|---|---|---|
| PA 2019 70574 | Sep 2019 | DK | national |
This application claims priority to PCT Application No. PCT/DK2020/050258, having a filing date of Sep. 18, 2020, which is based DK Application No. PA 2019 70574, having a filing date of Sep. 18, 2019, the entire contents both of which are hereby incorporated by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/DK2020/050258 | 9/18/2020 | WO |
