Buffing pads are provided for polishing the surface of a workpiece. More particularly, patterned rotary buffing pads are provided for polishing the surface of a workpiece.
The visual appearance of painted surfaces, for example, exterior painted automotive and marine surfaces is an important aesthetic property. Original equipment manufacturer and aftermarket industries have devoted many resources to the development and application of paint systems that provide aesthetic properties such as, for example, low haze and good distinctness of image. It is commonplace for vehicle and boat manufacturers to use a base coat and clear coat paint system. The base coat provides the desired color, while the clear coat, which is applied over the base coat, provides a transparent scratch and chip-resistant protective coat. Such paint systems, however, have the tendency to magnify defects (for example, scratches, haze, and dust nibs) in either the base coat or the clear coat. One common method for imparting, or restoring, a high quality appearance to the paint system uses a multi-step process.
First, the defects are abraded using a coated abrasive product with a fine abrasive particle size, for example, sandpaper, or a structured abrasive article. This step provides rapid removal of the defects, but typically leaves scuff, or “swirl” marks, and sometimes scratches, that need to be removed. Next, the swirl marks are removed by buffing using a buffing composition. The buffing composition is typically an aqueous or petroleum based medium containing abrasive particles of smaller size than the abrasive particles used in the coated abrasive article. However, depending of the paint system, the buffing step may result in a surface with a hazy appearance. The hazy appearance is removed by a finishing step in which the hazy portion of the paint system is buffed with a finishing composition. The finishing composition is typically an aqueous or petroleum based medium containing abrasive particles of smaller size than the abrasive particles used in the buffing composition. Finally, residue from the buffing and/or finishing compositions is removed, for example, with a soft cloth, thereby producing an aesthetically appealing finish substantially free of surface residue.
Buffing pads used in the above polishing steps are generally compressible to allow even pressure to be applied across the buffing surfaces. Such pads are often made from either wool or a polymeric foam. While the polishing steps may be a manual process, it can be facilitated by attaching the buffing pad to an electric or air-driven pneumatic power tool. As used herein, “polishing steps” include any of the steps used in restoring or improving a surface, including compounding, buffing, and finishing steps.
The performance of a buffing pad may be appraised on a number of factors. First, the buffing pad provides a certain level of cut performance (or “cut”), defined as the rate at which the moving pad removes surface defects. Cut performance should be adequately high to allow polishing to be completed within a reasonable amount of time. Second, the buffing pad provides a certain level of finish. The finish provided by a buffing operation is defined by the smoothness of the resulting surface and can be quantified by measuring “haze”. Haze decreases with increasing smoothness, and thus should be as low as possible. Third, the rotary buffing pad can be appraised on user experience. Here, it is desirable for a rotary buffing pad to engage the surface to be polished in a controlled manner to reduce the incidence of jerking or other unpredictable motions (known as “chatter”) of the power tool during the polishing process. This assists the operator in maintaining a high degree of control over the orientation of the pad and helps avoid inadvertent gouging of the workpiece.
In buffing applications, it is often a challenge to achieve both good cut and fine finish simultaneously. Modifications to the buffing pad or abrasive compound that enhance cutting performance often lead to a coarser finish. Conversely, modifications which lead to a finer finish often also tend to reduce the rate of abrasion and thereby degrade cut performance. The apparent inverse relationship between cut performance and finish has been a source of frustration to many of skill in the art.
Herein are provided rotary buffing pads which overcome the dilemma faced by one desiring to achieve both superior cut performance and a fine finish. This combination of advantages is provided by using a flat-faced buffing pad that includes a plurality of apertures of variable size. The apertures are generally larger in the areas toward the center of the pad, while being generally smaller in the areas toward the periphery of the pad. This synergistic arrangement of large and small apertures provides both superior cut performance and a superior finish.
This configuration further provides other unexpected advantages over conventional foam buffing pads. First, the center apertures advantageously capture excess abrasive composition thereby reducing the amount of liquid sling during the buffing process and therefore reducing both waste and clean up time after the operation is completed. Second, the amount of vibration, or “chatter”, felt by the operator during the buffing process is maintained at low levels. Reduced vibration in turn leads to reduced fatigue and enhanced operator comfort. Third, locating the larger apertures toward the center of the pad improves operator control by reducing the drag resistance due to the center of the pad and also preventing the pad from wobbling during the buffing process. Since wobbling can cause the buffing pad to jump or jerk across the surface, this configuration improves operator control and reduces the risk of damaging the surface being polished.
In one aspect, a rotary buffing pad is provided, comprising a substrate having a front surface, back surface, and a rotation axis perpendicular to the front and back surfaces, the substrate further comprising an inner region adjacent to and surrounding the rotation axis, an outer region surrounding the inner region, a plurality of first apertures having a first average size located within the inner region and extending from the front surface toward the back surface; and a plurality of second apertures having a second average size located within the outer region and extending from the front surface toward the back surface, wherein the first average size is larger than the second average size.
In another aspect, a rotary buffing pad is provided comprising a substrate having a front surface, back surface, and a rotation axis perpendicular to the front and back surfaces, the substrate further comprising an inner region adjacent to and surrounding the rotation axis, an outer region surrounding the inner region, a plurality of first apertures having a first aperture density located within the inner region and extending from the front surface toward the back surface, and a plurality of second apertures having a second aperture density located within the outer region and extending from the front surface toward the back surface, wherein the first aperture density is larger than the second aperture density.
In still another aspect, a rotary buffing pad is provided comprising a substrate having a front surface, back surface, and a rotation axis perpendicular to the front and back surfaces, the substrate further comprising an inner region adjacent to and surrounding the rotation axis, an outer region surrounding the inner region, a plurality of first apertures having a first average size located within the inner region and extending from the front surface toward the back surface, a plurality of second apertures having a second average size located within the outer region and extending from the front surface toward the back surface, wherein the first average size is larger than the second average size, and wherein the outer region further comprises at least one annular region and wherein the plurality of second apertures further comprises a second subset of second apertures located in the at least one annular region, the second subset extending from the front surface toward the back surface and being disposed along at least one circular ring, each circular ring being coplanar with the front surface and generally symmetrical about the rotation axis.
In yet another aspect, a rotary buffing pad is provided comprising a substrate having a front surface, back surface, and a rotation axis perpendicular to the front and back surfaces, the substrate further comprising an inner region adjacent to and surrounding the rotation axis, an outer region surrounding the inner region, and a plurality of apertures extending from the front surface toward the back surface, wherein the apertures have a distribution of sizes and the apertures having relatively large size are predominantly located in the inner region relative to the outer region.
As used herein:
The following description is directed to buffing pads useful for removing defects from a surface and polishing the surface to a fine finish. These buffing pads are especially useful in the automotive and marine applications, where there is a need to polish a painted exterior surface to produce a glossy, aesthetic appearance. However, the buffing pads are not limited to these applications. For example, they may be useful on any other painted surfaces or even non-painted surfaces, and are not limited to polishing operations on any particular type of article. For example, workpiece surfaces may include marbled, varnished, composite, or gel coated surfaces.
Moreover, buffing pads are not limited to a specific method of use. Any of a wide variety of abrasive polishes and compounds, both in liquid and solid form, may be advantageously used with these buffing pads to achieve a desirable surface finish. Various power tools may be used to generate the relative motion between the buffing pad and the surface to be polished. Moreover, the application of these pads is not restricted to any particular stage of a workflow used to polish an article. For example, they may be used as a first step, intermediate step, or last step of a multi-step polishing method. Alternatively, these buffing pads may be used in a single-step polishing method.
An exemplary buffing pad according to one embodiment is illustrated in
When used in a buffing operation, the buffing pad 100 rotates about a rotation axis 112, shown in
In some embodiments, the substrate 102 is made from a compressible material, such as a polymeric foam. Exemplary substrates having this property include open-celled polyurethane foams. Open-celled foams are advantageous in that they can be made soft and compliant and do not significantly expand in the side directions when compressed from the top and bottom directions. Open-celled foams may also allow limited permeability to the buffing polish or compound material. Such permeability may advantageously improve overall retention of the polish or compound material on the pad 100 during a polishing operation. Other commercial foams are also possible, such as those disclosed in issued U.S. Pat. No. 4,962,562 (Englund, et al.). In exemplary embodiments, the stiffness of the substrate 102, as measured by the pressure required to produce a compression to 25% of original volume (or 25% Compression Load Deflection), ranges from 0.3 to 1 pound per square inch (2.1 to 6.9 kiloPascals (kPa)).
The optional backing layer 110 preferably has a flexural modulus greater than that of the substrate 102 and augments the stiffness along the back side of the buffing pad 100. As increasing the stiffness of the backing layer 110 generally increases the rate of cut, the flexural modulus can be tailored to provide the rate of cut desired for the application. The backing layer 110 can be coupled to the back surface 108 of the substrate 102 by physical means such as thermal lamination. Alternatively, the backing layer 110 may be adhesively bonded to the substrate 102.
Optionally, the backing layer 110 may include a fibrous material, such as a scrim or non-woven material. Advantageously, the fibrous material can facilitate coupling the buffing pad 100 to a power tool. In some embodiments, for example, the backing layer 100 includes one-half of a hook and loop attachment system, the other half being disposed on a plate affixed to the power tool. Such an attachment system secures the buffing pad 100 to the power tool while allowing convenient attachment and removal of pads between operations.
As particularly shown in
It is noted here that both the inner and outer regions 114,116 are solid three dimensional shapes. Therefore, these regions 114,116 are defined not only by the visible areas of the front surface 104 shown in
A plurality of first apertures 120 and a plurality of second apertures 122 extend from the front surface 104 toward the back surface 108 at different locations along the inner and outer regions 114,116 of substrate 102.
The plurality of first apertures 120 include all of the apertures present within the inner region 114. Optionally and as shown, the first apertures 120 have a generally uniform size and shape and are distributed evenly across the inner region 114 in a close packed (e.g. square, hexagonal) arrangement such that there is a constant spacing between neighboring apertures 120. As an alternative, the apertures 120 may be uniformly spread across the front surface 104 but randomized with irregular spacing between neighboring apertures 120. As another alternative, the apertures 120 may have an overall distribution that is non-uniform across the inner region 114.
Optionally and as shown in this embodiment, the plurality of second apertures 122 includes first and second subsets 123,124 of apertures. The first and second subsets 123,124 of apertures include all of the apertures present within the outer region 116, and are distinguishable from each other based on having different arrangements across the front surface 104 and different size/shape characteristics. Although both subsets 123,124 of apertures are shown, the outer region 116 may include only the first subset 123 or only the second subset 124.
As shown in
Optionally and as shown in
In the embodiment shown, the second subset 124 of apertures have a generally uniform aperture diameter. In other words, the diameters of the apertures 124 are not only generally uniform along each individual ring 140 but also generally uniform across all three of the rings 140. Further, neighboring apertures 124 display a certain spacing (as measured between the centers of the apertures) which is generally uniform across the rings 140. Preferably, the ratio between the certain diameter to the certain spacing is at least 0.2. More preferably, the ratio between the certain diameter to the certain spacing is at least 0.3. Most preferably, the ratio between the certain diameter to the certain spacing is at least 0.35. As shown in
The “size” of a given aperture, as used herein, can refer to any dimension of the aperture. For example, the size may represent the diameter, perimeter, inner surface area, or depth of the aperture, volume occupied by the aperture, or combinations thereof. In
In exemplary embodiments, the plurality of first apertures 120 have an average depth ranging from 8 to 12 mm, an average diameter ranging from 2 to 4 mm, and average occupied volume ranging from 25 to 150 cubic mm. In other embodiments, the first subset 123 of apertures have an average depth ranging from 3.5 to 7.5 mm, an average diameter ranging from 3 to 5 mm, and average occupied volume ranging from 25 to 147 cubic mm. In still other embodiments, the second subset 124 of apertures have an average depth ranging from 9 to 13 mm, an average diameter ranging from 0.5 to 1.5 mm, and average occupied volume ranging from 1.6 to 25 cubic mm.
In addition to differences in dimensions, the aperture density (in apertures per unit area) of the plurality of first apertures 120 over the front side of the inner region 114 is greater than that of the plurality of second apertures 122 over the front side of the outer region 116. In some embodiments, the plurality of first apertures 120 have a aperture density ranging from 1.5 to 5.0 per square centimeter, while the plurality of second apertures 122 have a aperture density ranging from 0.8 to 1.5 per square centimeter over their respective areas.
The apertures 120,123,124, as shown in
Preferably, the buffing pad 100 uses apertures with a length-to-width aspect ratio, measured in plan view, that does not exceed 2:1. Use of discrete apertures with a relatively small aspect ratio is advantageous because such apertures are resistant to undue expansion during a polishing operation. Expansion of an aperture can allow compounding or polishing material to accumulate and become trapped in the pad. Agglomerations of abrasive material, if sufficiently large, can scratch the workpiece and degrade haze performance. It was additionally observed that expansion of an elongated aperture can even cause the sidewalls of the aperture to contact the workpiece, again causing undesirable scratches.
As shown in
Similarly, aperture density need not be uniform along the front sides of regions 114,116. As a result, the plurality of first apertures 120 may have an overall aperture density greater than that of the plurality of second apertures 122 even when the former apertures have a local aperture density within a certain area of the inner region 114 less than that of the latter apertures within some other area of the outer region 116. As such, there may well be significant overlap between number densities observed on a local level between the plurality of first apertures 120 and the plurality of second apertures 122.
While the apertures 120,123,124 extend from the front surface 104 into the substrate 102 in a generally perpendicular fashion as shown in
The described configuration of the apertures 120,123,124 along the substrate 102 of the buffing pad 100 has been shown to provide a number of unexpected advantages in a polishing operation. First, the apertures 120, by virtue of their larger average size relative to the apertures 123,124, significantly reduce drag resistance as the center of the rotating pad passes over the surface being polished. Second, the generally larger apertures 120 also reduce the degree of buckling of the pad 100 that occurs as a result of uneven friction between the front surface 104 and the surface being polished. As a result, significantly less jerking and jumping of the rotary pad occurs during operation. The alleviation of jerking and jumping in turn improves operator control and reduces strain and fatigue experienced by the operator.
Further advantages are provided by the concentric circular rings 140 located along the outer region 116. By partitioning the front surface 104 of the pad 100 into four distinct sections, the rings 140 of apertures 124 help isolate localized deformation of the pad 100 that occur during a buffing operation within its particular section. This advantageously prevents propagation of deformation across the entire front surface 104 and again results in a more manageable and predictable buffing operation.
Use of apertures of larger sizes in areas near the center of the pad 100 also provides superior performance compared with conventional buffing pads. Particularly, these pads 100 provide both increased cut rate and finer finish responses compared with conventional pads in which the average size of the apertures is generally uniform across the front surface. This is also an unexpected advantage, because superior cut and finer finish are often inversely related and it is generally difficult to realize both qualities simultaneously. A buffing pad which provides both a superior cut and finer finish allows a polishing job to be completed more efficiently and with less opportunity for operator error.
The apertures 120,123,124 in the substrate 102 may be provided using any number of manufacturing methods known to the skilled artisan. In some embodiments, the apertures 120,123,124 are formed by providing a suitable substrate 102, then applying a post-processing method to form the apertures. Examples of such post-processing methods include thermal embossing methods such as those described in U.S. Patent Publication No. 2007/0254567 (McLain) or water jet cutting as described in issued U.S. Pat. No. 5,527,215 (Rubino et al.) and U.S. Patent Publication No. 2007/0204420 (Hornby et al.). Alternatively, conventional methods such as engraving, mechanical boring, or cutting are also possible.
In one preferred method of making the pad 100, a laser is used vaporize the foam to produce the apertures 120,123,124. Laser cutting leaves behind a minimum amount of debris, and provides the flexibility for an operator to make nearly any configuration of apertures desired. Generally, the desired shape can be programmed into a computer aided drafting (CAD) system that interfaces with software that controls the position and intensity of the laser. The methods are advantageous because they are robust, versatile, and cost effective.
Alternatively, the apertures 120,123,124 may be provided in situ without need for a post-processing step. For example, the apertures 120,123,124 can be formed by casting and curing of the foam in a suitably shaped mold.
A loop backed planar, open cell, polyurethane foam buffing pad, 3¼-inches diameter by 1-inch depth (8.26 by 2.54 cm), was obtained under the trade designation “VP FG 3570-ID, Anthrazit”, from Woodbridge FoamPartner Company, Chattanooga, Tenn. The foam had an average density of 31.4 kilograms per cubic meter (kg/m3) and 40% Compression Load Deflection (CLD) of 8.47 kiloPascals (kPa).
The face side of the foam buffing pad described in Comparative A, was formed into a convoluted pattern as described in U.S. Pat. No. 4,962,562 (Englund et al.), the disclosure of which is incorporated herein by reference. Convoluted square array dimensions were 1.14 projections per square inch (0.18 projections per square cm), with a peak-to-valley height of 0.16 inches (0.04 cm) and peak-to-peak distance of 0.88 inches (0.35 cm).
The front side of the foam buffing pad described in Comparative A was formed into a hexagonal channel array using an Eagle CO2 Laser, Model No. 500, from LMI Technologies, Royal Oak, Mich., according to the conditions listed in Table 1. The pattern was similar to a commercially available foam buffing pad, type “Hex-Logic”, from Chemical Guys, Hawthorne, Calif.
The buffing pad substrate used in Comparative A was provided and then a series of apertures were subsequently cut into the exposed face of the planar foam sheet to provide the aperture pattern shown in
A loop backed planar, open cell, polyurethane foam compounding pad, 8-inch diameter by 1-inch depth (20.3 by 2.54 cm), having an average density of 28.7 kilograms per cubic meter (kg/m3) and 25% CLD of 6.52 kiloPascals (kPa), obtained from Pinta Foamtec, Inc., Minneapolis, Minn.
The front side of the foam buffing pad Comparative D was formed into a convoluted pattern as described in Comparative B, wherein the peak-to-valley height was increased to 0.44 inches (0.17 cm).
The front side of the foam buffing pad Comparative D was formed into a hexagonal channel array, as described in Comparative C.
The complete aperture pattern as shown in
A foam buffing pad was made as described in Example 2, except only the second subset of the second apertures (rings) were laser cut into the face of the foam.
A foam buffing pad was made as described in Example 2, except only the first subset of second apertures were laser cut into the face of the foam.
A foam buffing pad was made as described in Example 2, except only the first apertures and first subset of second apertures (hexagonal groupings) were laser cut into the face of the foam.
The foam buffing pad of Example 1 and Comparatives A-C, were attached to a 3¼-inch (8.26 cm) diameter foam backup pad available from 3M Company, St. Paul, Minn., under the trade designation “3M Finesse-It Backup Pad, Part No. 84226”. The backup pad was then attached to an air driven pneumatic buffer, available under the trade designation “Dyna Buffer #57240” from Dynabrade USA, Clarence, N.Y., with a down weight of 5 pounds (2.27 kg), and air pressure of 94 pounds per square inch (psi) (648.1 kiloPascals (kPa)) at the face).
A pre-weighed 18 by 24-inch (45.7 by 61.0 cm) painted metal test panel, type “APR 40577” obtained from ACT laboratories, Hillsdale, Mich., was used as the test substrate. The test panel had the following coatings: E-Coat ED6060; Primer 764204; Basecoat 542AB921 BLACK; Clearcoat RK8148”. The panel was cleaned and dried using a 50% by weight aqueous solution of isopropanol and a soft lint-free cloth. The panel was then fixed horizontally in place and 10 grams of buffing compound, type “Finesse-it Purple Polish, Part No. 51056”, obtained from 3M Company, was applied to the center of the panel. The entire panel uniformly buffed for 2 minutes, using lateral motion and without applying substantial downward hand-force, after which the panel was cleaned and dried as described above. The buffing process was repeated 8 times.
Upon completion the panel was again wiped clean and dried as described above, after which the panel was reweighed. Cut was calculated as the difference between the initial and final weight of the panel. Higher cut values are better.
The foam buffing pads of Example 2 and Comparatives D-I, were attached to an 8-inch (20.3 cm) diameter foam backup pad available from 3M Company, St. Paul, Minn., under the trade designation “3M Finesse-It Backup Pad, Part No. 5717”, using an adapter type “5710”, also from 3M Company. The backup pad was then attached to an electric buffer, available under the trade designation “DeWALT DW849” from DeWALT Industrial Tool Company, Baltimore, Md., with a down weight of 5 pounds (2.27 kg).
A pre-weighed 45.7 centimeter×61.0 centimeter (18 inch×24 inch) painted metal test panel, type “APR 51534(H)” obtained from ACT laboratories, was cleaned and dried according to the method described in Cut Test 1. The test panel had the following coatings: E-Coat ED6060; Primer 765224EH; Basecoat 270AB921 BLACK; Clearcoat RK8148”. 10 grams of rubbing compound, type “Perfect-it Rubbing Compound, Part no. 6085”, obtained from 3M Company, was applied to the test panel and manually buffed for 1 minute at 1,400 revolutions per minute (rpm). The panel was cleaned and dried as described above and the buffing process repeated four more times, using successively less amounts of rubbing compound of 8, 6, 5 and 4 gram, respectively. After the fifth buffing step the test panel was cleaned, dried and reweighed, and the cut in grams determined. Each Example and Comparative was run in duplicate. As before, higher cut values are better.
Haze was measured using a haze gloss meter, Catalog no. “AG-4601” from Byk-Gardener USA, Columbia, Md. Measurements were made before and after Cut Test 1, at the approximate center of each of the four quadrants of the test panel (that is, resulting in four measurements), at a 20 degree measurement angle. Lower haze values are better.
Comparative Samples A-C and Example 1 were subjected to Cut Test 1 and Haze Measurement. Results are listed in Table 3. Tests on Comparatives A and B, and Example 1, were run in triplicate.
Comparatives D-F and Examples 2-3 was subjected to Cut Test 2, in duplicate. Results are listed in Table 4.
All of the patents and patent applications mentioned above are hereby expressly incorporated by reference. The embodiments described above are illustrative of the present invention and other constructions are also possible. Accordingly, the present invention should not be deemed limited to the embodiments described in detail above and shown in the accompanying drawings, but instead only by a fair scope of the claims that follow along with their equivalents.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/US10/55905 | 11/9/2010 | WO | 00 | 3/22/2012 |
Number | Date | Country | |
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61260498 | Nov 2009 | US |