Patent Application
20200156215
The present invention relates to the placement of abrasive features on an abrasive work tool.
Tools with abrasive features can be used for a variety of applications, including grinding, polishing, abrading, finishing, scouring and scrubbing. Abrasive tools can be made with a variety of substrates including paper, woven fabrics, nonwoven fabrics, calendared nonwoven fabrics, polymeric films, stitch-bonded fabrics, open cell foams, closed cell foams, and combinations thereof. Abrasive tools can also include a variety of types of abrasive features or abrasive grains, including single abrasive grits, cutting points, and composites comprising a plurality of abrasive grits, and combinations thereof.
Abrasive features or grains can be arranged on a variety of surfaces in a variety of methods and arrangements. For example, some abrasive features are randomly distributed on a surface of a work tool and placed using coating, spraying, printing and solvent methods. Some abrasive features can be arranged in a pattern on a surface of a work tool.
The arrangement or placement of abrasive features can impact many aspects of the abrasive tool including the efficiency of cutting, the orientation in which the abrasive tool should be used, the scratch pattern left behind by the tool, and the manufacturing requirements for the abrasive tool. Improvements in abrasive tools to allow orientation independence, reduced visibility of scratch patterns, and ease of manufacturing are desired.
The present disclosure provides several advantages over the state of the art. For example, the present disclosure provides for an abrasive tool that can perform more consistently in any mode of use, or when held at any orientation relative to a cut direction. The present disclosure also provides for an abrasive tool with abrasive grains arranged in a manner to reduce visibility of scratch patterns left on a work piece. The present disclosure further provides for placement of abrasive grains on an abrasive tool in a pseudo-random pattern such that slight manufacturing defects, such as missing or extra abrasive grains, are not noticeable to a user of the abrasive tool. The present disclosure also provides for an arrangement of abrasive features that provides for more even distribution of mass removal from a work piece. In some instances, the present disclosure allows for an arrangement of abrasive particles on a substrate in a way that can be visually pleasing independent of the orientation or shape of the substrate.
In one aspect, the present invention includes an abrasive tool comprising a substrate and plurality of abrasive grains arranged in a pseudo-random pattern on the substrate. The abrasive grains cover in the range of 10% to 30% of the substrate surface, and the arrangement of abrasive grains has a score of 20% or less on the Orientation Independence Test.
In another aspect, the present invention includes an abrasive tool comprising a substrate and a plurality of abrasive grains arranged in a pseudo-random pattern on the substrate, wherein the abrasive grains cover in the range of 10% to 30% of the substrate surface and wherein the arrangement of abrasive grains has a score in the range of 0.7 to 0.9 in the Local Homogeneity Index Test.
In some instances, the arrangement of abrasive grains has a score of 10% or less on the Orientation Independent Test.
In some instances, the abrasive grains cover 10% to 15% of the surface substrate.
In some instances, the substrate comprises a lofty non-woven material.
In some instances, the lofty non-woven material comprises a densified surface.
In some instances, the abrasive grains are at least one of: single abrasive grits, cutting points, and composites comprising a plurality of abrasive grits, and combinations thereof.
In some instances, the composites comprise a plurality of abrasive grits in a resin.
In some instances, the abrasive grains are printed onto the substrate.
In some instances, the average abrasive grain height from the surface of the substrate is in the range of 0.25 mm to 1.5 mm.
In some instances, the pseudo-random pattern comprises clusters of abrasive grains.
In some instances, the substrate is selected from the group consisting of paper, woven fabrics, nonwoven fabrics, calendared nonwoven fabrics, polymeric films, stitchbonded fabrics, open cell foams, closed cell foams, and combinations thereof.
In some instances, the substrate comprises an open cell foam or a closed cell foam laminated to a substrate selected from the group consisting of paper, woven fabrics, nonwoven fabrics, calendared nonwoven fabrics, polymeric films, stitchbonded fabrics, open cell foams, closed cell foams, and combinations thereof.
In some instances, the pseudo-random pattern is a pseudo-poisson pattern.
The invention may be more completely understood in consideration of the following detailed description of various aspects of the invention in connection with the accompanying drawings, in which:
It is understood that the aspects of the invention may be utilized and structural changes may be made without departing from the scope of the invention. The figures are not necessarily to scale. Like numbers used in the figures refer to like components. However, it is understood that the use of a number to refer to a component in a given figure is not intended to limit the component in another figure labeled with the same number.
The cut patterns 22 on surface 21 are approximately evenly spaced apart and quite distinct and visible. In this scenario, the patterns are particularly visible because each of abrasive grains 23a, 23b, 23c, and so on are all cutting along the same line, thus resulting in a very noticeable cut or scratch pattern. When abrasive tool 24 is held at a slightly angled orientation, and the tool is moved in a lateral direction as indicated by arrow 28, the resulting cut or scratch lines 26 are more randomly spaced apart, but are still quite visible
Further, if a single abrasive grain was missed during the manufacturing process of abrasive tools 20 and 24, or if an extra abrasive grain was added to one of the pads, it would be visually apparent to even a casual observer. This results in a more challenging manufacturing quality standard and greater waste from the manufacturing process.
Unlike a purely random pattern, a pseudo random pattern can provide the advantage of a relatively even distribution of abrasive grains on an abrasive tool without the manufacturing constraints created by a regular pattern of abrasive grains. Further, random patterns can have relatively large working surface areas without abrasive grain coverage, resulting in inferior performance in that particular area, while other areas may have a high concentration of abrasive grains, resulting in excessive or visual scratching resulting from use of that portion of the abrasive tool.
Unlike a regular pattern (as shown in
In some instances, a pseudo-random pattern can comprise clusters of abrasives grains, where each cluster includes a plurality of abrasive grains arranged in a pseudo-random pattern, and where the clusters of abrasive grains form an array on a substrate in a regular or pseudo-random arrangement.
Generally, a cluster is a subsection of the hand-pad containing at least 3 features such that the percent of local area coverage of abrasive grains in the cluster is greater than the percent total area coverage of the abrasive grains in the hand pad.
As shown in
Abrasive tool 30 includes a substrate 32 and abrasive grains 33. In
A substrate consistent with the present disclosure can include any substrate, such as paper, cloth, woven fabrics, nonwoven fabrics, calendared nonwoven fabrics, polymeric films, stitch-bonded fabrics, open cell foams, closed cell foams, vulcanized fiber materials, scrims, films, foils, screens, perforated sheets, other web-like substrates and combinations thereof. A substrate can include a single material with different types of treatments on different parts of the material. For example, a substrate made from a non-woven web may include a semi-densified layer as described by U.S. Patent Publication 2017/0051442 to Endle et al., incorporated herein by reference.
An abrasive grain may refer to single abrasive grits, engineered, structured or shaped cutting points, abrasive agglomerates, or abrasive particles, composites comprising a plurality of abrasive grits or composites thereof. Examples of abrasive grits include diamond, cubic boron nitride, boron, suboxide, various alumina grains, such as fused alumina, sintered alumina, seeded or unseeded sintered sol gel alumina, alumina zirconia grits, oxy-nitride alumina grits, silicon carbide, tungsten carbide, titanium carbide, garnet, iron oxide, tin oxide, feldspar, flint, emery, and modifications and combinations thereof. Such abrasive grits may exhibit a Mohs hardness in the range of 8-10 Mohs. Other materials that exhibit sufficient hardness to provide a scouring function may include, for example, particles of melamine-formaldehyde resin, phenolic resin, polymethl methacrylate, polystyrene, polycarbonate, certain polyesters and polyamides, and the like. Such materials may have a hardness in the range of at least 3 Mohs.
An abrasive grain may be any size consistent with the desired application for the abrasive tool. A composite having a plurality of abrasive grits in a resin may have a diameter in the range of 0.10 mm to 5 mm. Or may diameter in a range defined by any of 0.10 mm, 0.50 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 4 mm or 5 mm. A composite may have a height in the range of 0.05 mm to 2 mm. Or may have a height in a range defined by any of 0.10 mm, 0.25 mm, 0.50 mm, 0.75 mm, 1.0 mm, 1.5 mm or 2 mm.
Examples of shaped abrasive particles can be found in U.S. Pat. No. 5,201,916 (Berg); U.S. Pat. No. 5,366,523 (Rowenhorst RE 35,570); and U.S. Pat. No. 5,984,988 (Berg). U.S. Pat. No. 8,034,137 (Erickson et al.) describes alumina crushed abrasive particles that have been formed in a specific shape, then crushed to form shards that retain a portion of their original shape features. In some instances, shaped alpha alumina particles are precisely-shaped (i.e., the particles have shapes that are at least partially determined by the shapes of cavities in a production tool used to make them.)
Structured or shaped abrasive particles may be desirable for more efficient or higher precision grinding, polishing or abrading applications. In these types of tools, small shaped composite structures, such as three dimensional pyramids, diamonds, lines, and hexagonal ridges are replicated in a regular pattern on a surface of a tool.
Abrasive agglomerates can include single abrasive particles bonded together with, for example, a polymer, a ceramic, a metal or a glass to form an abrasive agglomerate.
Composites comprising a plurality of abrasive grits can include any type of abrasive grit discussed herein, or another type of abrasive grit that would be apparent to use to one skilled in the art upon reading the present disclosure. Abrasive grits can be combined with a range of resins, such as thermosetting resins, UV curable resins, solvent-based resins, including, in a non-limiting fashion, resins such as phenolic resins, aminoplast resins, curable acrylic resins, cyanate resins, urethanes, latex resins, nitrile resin, ethylene vinyl acetate resin, polyurethane resin, polyurea or urea-formaldehyde resin, isocyanate resin, styrene-butadiene resin, styrene-acrylic resin, vinyl acrylic resin, melamine resin, polyisoprene resin, epoxy resin, ethylenically unsaturated resin, and combinations thereof.
Abrasive grains may be aligned and placed on a substrate using an alignment tool as described in U.S. Patent Publication No. 2016/037250. In another instance, direct transfer of abrasive grains onto the substrate may be carried out by placing a droplet of bonding material on the substrate at the proper location and using a robotic arm to place each abrasive grain on the substrate. A robotic arm may also be used to place a suspended array of abrasive on a substrate that is pre-coated with a bonding material. In some instances, a bonding material may be a resin as discussed herein. In some instances, a bonding material may be an adhesive.
In some instances, abrasive grains (and particularly grits in resin) may be printed on an abrasive substrate using a screen printing or other printing method as will be apparent to one of skill in the art upon reading the present disclosure.
Abrasive grains may be bonded to a substrate using an adhesive make coat, or they may be affixed directly to a substrate. Adhesives or bonding materials used to secure an abrasive grain to a substrate will depend on the particular abrasive grain and substrate. Examples of bonding materials include adhesives, brazing materials, electroplating materials, electromagnetic materials, electrostatic materials, vitrified materials, metal powder bond materials, polymeric materials and resin materials and combinations thereof.
While the abrasive tool shown in
Variations on the present invention will be apparent to one of skill in the art upon reading the present disclosure, and are within the scope of the invention set forth herein.
Example patterns for abrasive hand-pad articles were generated. The scratch patterns on a simulated surface were analyzed. And the results are shown below.
Test Methods
Orientation Independence Test (OIT)
OIT Test Overview
The OIT analyzed the number of unique scratches made by Active Areas (AAs) chosen on a hand-pad (a type of abrasive tool). The active areas were defined as sections of the hand-pad encompassing a subset of the features used to abrade a substrate. The analysis consisted of randomly chosen (AAs) on the hand-pad surface that were of equal size and encompassed 10 to 50 abrasive features or abrasive grains.
To conduct the OIT, linear scratches made or simulated with the chosen AAs 41, 42, 43, 44, 45 covering cutting directions ranging from 0 to 90 degrees in one degree increments, where 0 degree cutting direction is defined to be in the X direction were evaluated.
The OIT linear scratch test can be simulated or performed on a physical abrasive tool. The simulated test assumes that both the 2D coordinates of the centers of the abrasive features, and the average feature diameter on the hand-pad are known. Also note that the simulated test can be performed from a physical hand-pad or other type of abrasive tool providing these inputs are made available. For a step-by-step procedure on how the inputs can be obtained from a physical hand-pad, refer to the section titled ‘OIT Test Input’ below.
OIT Test Input
For the simulated OIT test described, the tests take as input: 1) the 2D coordinate of the centers of the abrasive features, and 2) the average diameter of the envelope that surrounds each abrasive feature. The method to obtain these two inputs for a physical hand pad or other abrasive tool can be done through image analysis and is illustrated in the steps shown in
Step 1: Image Capture 61 of Abrasive Tool
Place abrasive tool onto a flat surface so that the abrasive grains (or abrasive features) are clearly visible. Arrange a camera so that the lens points in the direction approximately perpendicular to the hand-pad. Place the camera sufficiently far to capture the entire surface of the abrasive tool in the camera's field of view and capture the image. Abrasive tool 64 in
Step 2: Acquire Coordinates 62 of Abrasive Grain Centers
Define one corner of the hand-pad as (0, 0) and generate list of the coordinates of the centers of the abrasive features. Image 65 in
Step 3: Acquire Average Diameter 63 of the Abrasive Grains
Define the average diameter of the abrasive grains or abrasive features as:
where Di is the diameter of each abrasive grain. When an abrasive grain is non-circular, Di is measured as the diameter of the smallest circle that can fit around the abrasive grain. Npad is the number of grains on the abrasive pad or in the sampled section. Image 66 in
Performing the OIT Test
The OIT method uses a scratch profile made by NOIT cutting points for analysis. NOIT should be in the range of 10 to 50 cutting points. NOIT represents the number of abrasive grains in an AA.
For each cutting direction the number of unique scratches found on the abraded substrate were counted. Multiple cutting points may result in scratches that are very close or even overlapping. Scratches that were closer to each other than 10% of the average abrasive grain diameter (DAVE) were counted as a single scratch. The analysis was repeated for the 90 cutting directions considered and normalize by the maximum number of unique scratches found. The OIT score is the difference between the maximum and minimum number of unique scratches found in the 90 cutting directions considered. The pass/fail criteria is defined to be patterns that exhibit OIT scores of less than 0.20 (i.e., OIT<0.20=pass).
Local Homogeneity Test (LHT)
The LHT evaluates the homogeneity of the entire abrasive tool by calculating the Homogeneity Index (HI) each of multiple sections located on the abrasive tool. Each section considered was chosen such NLHT of the nearest abrasive grains were included, and NLHT was in the range of 40 to 70. When performing the LHT on the abrasive tool shown in
Where:
NLHT is the number of features in the bounding box;
A is the area of the bounding section; and
di is the nearest neighbor distance of the i-th feature in the bounding section.
The resulting HI is associated with the abrasive grain at the center of a given section
The pass criteria for the LHT is defined as all sections on an abrasive tool having an HI score between 0.7 and 0.9 (i.e., (0.7<HI<0.90)=pass).
Empirical observations of LHT results of several abrasive tool examples indicated that abrasive tools with regions having HI<0.70 was found to exhibit poor average feature spacing control. On the other hand, regions with HI>0.90 are regions of high symmetry which would manifest itself in poor OIT performance implying sensitivity of the hand-pad to varying cutting directions. Passing both tests (OIT and LHT) according to the passing criteria described herein ensures that the patterns exhibit 1) consistent feature to feature spacing across the hand-pad, and 2) an insensitivity to cutting direction, regardless of which section of the abrasive tool is used.
Simulated Abrasive Grain Examples
A total of eight different simulated abrasive grain arrangements were tested under the OIT and the LHT. The eight abrasive grain arrangements included four different “patterns”, with each pattern being tested at two different levels of abrasive grain coverage, 14% and 26%, respectively.
Hex Pattern:
Two of the patterns were abrasive grains arranged in a regular hex pattern. The 14% coverage hex pattern is shown in
Vogel Pattern:
Two of the patterns were abrasive grains arranged in a Vogel pattern. The 14% coverage Vogel pattern is shown in
r=c√{square root over (n)},θ=ng
Where n represents a positive integer and indexes the number of abrasive grains generated, c represents a positive real number, and g represents an irrational number approximately equal to 2.39996 radians (an approximation of the golden angle). In the present work, c=1 mm and so the (x,y) coordinate of the n-th feature in the pattern was given by:
(X,Y)n=√{square root over (n)}(cos(ng), sin(ng))
Pseudo-Random Pattern:
Two of the patterns were abrasive grains arranged in a Pseudo-Random (Pseudo-Poisson). The 14% coverage pseudo-random pattern is shown in
x
0
;
X
0
=
x
0
;
X = Minimize[Energy + alpha / (Xi−1 −X) ·
Xi = X + [Rand([−1, 1]) * Δx;
X
0
,
X
1
, .... , XNpts
Random Pattern:
Two of the patterns were abrasive grains arranged in a random manner. The 14% coverage random pattern is shown in
In each of the Examples/Comparative Examples, the feature diameters are all 2.5 mm, and the XY coordinates are can be derived as described herein. The OIT and LHT described above were performed on each of the Examples/Comparative Examples described. The results from these tests are summarized in Table 2.
Of the various patterns tested, only E1 and E2 exhibited passing scores for both the Orientation Independent Test and the Local Homogeneity Test.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2018/054924 | 7/3/2018 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62538895 | Jul 2017 | US |
