Patent Application
20060053576
The present invention pertains to rotary or dual action buffing and finishing pads made of polymeric foam material and, more particularly, to a composite pad construction that includes an intermediate cushioning layer having a graded compression load deflection and a relatively much thinner performance layer that provides the necessary surface finishing function, but can be easily and inexpensively replaced when worn or damaged.
Polymeric foam buffing pads have been used for many years to perform a variety of buffing and finishing functions for painted and clear coat surfaces in the automobile and other industries. As the construction of foam buffing pads evolved, it became apparent that open cell polyurethane foam materials provided the best performance. Currently, reticulated open cell polyurethane foams are the most desirable polymeric foams for buffing and finishing functions. However, reticulated open cell polyurethane foam materials are also the most expensive. This material provides a combination of surface finishing performance and cushioning effect that has made reticulated open cell polyurethane foams the most desirable polymeric foam in the buffing and finishing industry.
Typical polyurethane foam pads range in size from less than 6 inches to greater than 8 inches (about 150-200 mm) in diameter, and 1.25 to 1.75 inches (about 30-45 mm) in thickness. The thickness of the material, in particular, is necessary to provide proper cushioning for the desired finishing operation. However, only a small part of the surface contacting face of the pad is actively used for the desired buffing or finishing operation.
In accordance with the present invention, most of the cushioned support for a polyurethane foam buffing and finishing pad is provided by polymeric foam material that does not directly contact the surface to be finished, is made of less expensive material, and may be provided with a graded density, graded flexibility, or graded levels of compression load deflection. This composite pad construction provides performance that is identical to a monolithic reticulated open cell polyurethane foam pad, but at considerably less cost. A relatively thin performance layer, made of the more expensive polyurethane foam, is removably attached to the less expensive foam cushioning layer.
Thus, a rotary buffing and finishing apparatus of the type that provides flexible cushioned support for a high performance contacting face, includes a polymeric foam cushioning layer that has a graded compression load deflection that decreases from a rear face to a front face and provides the primary cushioned support. A relatively thin performance layer provides the entire high performance surface contact and is removably attached to the foam cushioning layer.
The apparatus of the present invention preferably includes a backing plate that is attached to the rear face of the foam cushioning layer and supports the foam layer. The backing plate and the cushioning layer may comprise an integrally molded urethane material that provides the graded compression load deflection that varies from a relatively hard but somewhat flexible backing plate to a much softer front face for attachment to the performance layer.
In a preferred embodiment, the backing plate has a circular front face that is rotatable on a center hub with an axis perpendicular to the front face, the foam cushioning layer is also of a circular shape and has one-half of a hook and loop fastener attached to its front face. A performance layer, which is also circular in shape, has a rear face that carries the other half of the hook and loop fastener and a front operating face that is selected to provide a surface contact optimized for a given buffing or finishing operation. The performance layer may be selected from the group consisting of reticulated open cell polyurethane foam, non-woven fibers, tufted wool, knitted wool, polymer microfibers, and combinations thereof.
The hook and loop fastener halves may be heat laminated or glued to the respective faces of the foam cushioning layer and the performance layer. Either one of the interfaces between the hook and loop fastener halves and the faces of the cushioning layer or performance layer, preferably the latter, may be provided with a barrier material to prevent migration of liquid and compound from the performance layer to the foam cushioning layer.
In one embodiment of the apparatus, the front face of the foam cushioning layer is generally planar and terminates in an outer edge that is upwardly rounded. A portion of the half of the hook and loop fastener is positioned on the rounded outer edge and the other half of the fastener on the performance layer is dimensioned to wrap around the outer edge to engage the portion of the first half of the fastener. This imparts a cup shape to the performance layer.
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The performance layer 13, comprising a reticulated open cell polyurethane foam in the example shown, is cut in the shape of a thin circular disc. The thickness of the performance layer 13 may be about ⅜ inch (about 10 mm), but the thickness may vary considerably, particularly if the performance layer is selected from an entirely different material as will be discussed hereinafter. The rear face 22 of the performance layer 13 has attached thereto a circular fastener layer 23 comprising the other half of the hook and loop fastener (typically the loop half), i.e. complimentary to the circular fastener layer 20 on the front face of the cushioning layer 16. In this embodiment, the diameter of the performance layer 13 is larger than the diameter of the cushioning layer 16. The outer edge of the polyurethane foam performance layer 13 is turned upward and wrapped around the rounded outer edge 17 of the cushioning layer. The edge of the circular fastener layer 23 on the rear face of the performance layer 13 engages the fastener strip 21 on the rounded outer edge 17 of the cushioning layer to hold the performance layer in a cupped shape, as shown.
The cushioning layer 16, in the embodiment shown, is molded directly to the hub and backing plate 11, 12. In accordance with an important aspect of the present invention, the cushioning layer 16 is formed with a graded compression load deflection that decreases from a rear face 24 in contact with the front face 15 of the backing plate to the front face 18 where it is attached to the rear face of the performance layer 13. The term “compression load deflection” is used in the polymeric foam industry as a measure of the compressibility of a foam material. In one standard test, the compression load deflection (CLD) is measured at 40% compression of a test piece. For one fully reticulated open cell polyurethane foam, a CLD of 0.65 to 1.25 psi (about 4.5 to 8.6 kPa) is typical. The average density of this foam is 2.4 lbs./ft.3 (38.5 kg/m3). However, in accordance with the present invention, the cushioning layer 16 is preferably made of a foam material that is less expensive than the material used for the performance layer. The cushioning layer 16 is molded such that its compression load deflection (or equivalent property) decreases from the rear face 24 (adjacent the backing plate 12) to the front face 18 (where it is attached to the rear face of the performance layer 13). The polymeric foam from which the cushioning layer 16 is formed provides a cushioning effect that is virtually the same as it would be if the combined cushioning layer and performance layer were made of a single monolithic piece of high performance reticulated open cell polyurethane foam. Foam materials, such as molded polyurethane, that are far less expensive than the high performance foam layer 13, may be used. The backing plate 12 may also be made of a material which, though significantly harder than the foam cushioning layer 16, retains a flexibility that adds to the cushioning effect. A satisfactory result may be obtained with a construction utilizing a flexible backing plate 12 and a cushioning layer 16 that comprises a material of uniform hardness across its full depth. In general, whether the graded cushioning effect provided by the components of the subject invention is measured by compression load deflection, durometer or density, the key is that such property decreases from the backing plate to the front face 18 of the cushioning layer 16.
In the embodiment shown and referring particularly to
When the performance layer 13 becomes excessively worn or torn, or becomes plugged with buffing or finishing compound, the thin performance layer 13 may simply be peeled away from the cushioning layer 16 and replaced. This results in a considerable saving where a monolithic high performance foam buffing pad, having a typical thickness in the range of 1.25 to 1.5 inches (about 32 to 40 mm), would otherwise have to be discarded.
Each of the circular fastener layers 20 and 23 (as well as the fastener strip 21) normally includes an adhesive layer that is used to adhere the fastener layers to the surfaces being joined. In the assembly of the present invention, however, the adhesive layers are preferably eliminated and the hook and loop fastening pieces are adhered directly to the respective foam cushioning layer and foam performance layer by flame lamination or other suitable heating or gluing process.
It is also desirable, in certain applications, to provide the interface between one of the fastener layers 20 or 23 and the respective foam layer 16 or 13, preferably the performance layer 13 and fastener layer 33, with a layer 35 of an impervious barrier material. This prevents migration of finishing liquids or compounds from the performance layer 13 into the foam cushioning layers 16. A layer of barrier material would thus protect the foam cushioning layer, and when applied to the rear face 22 of the performance layer 13, will also protect the fastener layers 20 and 23 from contamination and plugging.
The unitary hub and backing plate 11, 12 can also be molded separately and the cushioning layer 16 also formed separately and attached to the front face 15 of the backing plate 12. Attachment of the foam cushioning layer to the backing plate can be permanent, as by gluing or heat bonding, or demountable as with a hook and loop fastening system.
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In certain applications, the flexible backing plate 12 may be used with a cushioning layer of monolithic construction not having a graded density or CLD. The flexible backing plate operates to replace the more dense and higher CLD layer 33 of the preferred embodiment. The backing arrangement thus provides a graded flexibility that serves to simulate the graded CLD of the preferred embodiments.
The thin performance layers of reticulated open cell polyurethane foam that characterize the previously described embodiments may be replaced with performance layers of other materials using the same cushioning layer and back-up plate arrangements previously described. Thus, performance layers of tufted wool, knitted wool, non-woven fibers, polymer microfibers, and combinations thereof, all in relatively thin sections, may be used. As with the previously described performance layer embodiments, these alternate performance layers should also be provided with a layer of barrier material to prevent contamination of the fastener system and the cushioning layer.
