Marble, granite and stone finishing method and abrasive pads therefor

Abstract: An improved method of finishing surfaces having irregular stepped portions or other edges and improved apparatus therefor. The method of the present invention includes rough finishing the surface by utilization of a rotary tool with a first abrasive pad (20) attached thereto. The first abrasive pad (20) includes an abrasive body portion (22) with an outer peripheral edge (23). A substantially flexible outer rim portion (24) extends outward from the peripheral edge (23) of the pad (20). According to a second step of the present invention, finished sanding of the surfaces is accomplished by utilization of a rotary tool with a second abrasive pad (100) attached thereto. The second abrasive pad (100) includes a backing substrate (102) and at least one abrasive segment (104,106,108) attached thereto. The total abrasive surface encompassed by the abrasive segment is from about 1% to about 30%. With the finishing pad (100) of the present invention hydraulic suction is minimized thereby allowing greater forces to be placed on the abrasive pad (100) for increasing abrasive cutting efficiency of a particular sized abrasive grit.

Description: This invention relates to abrasive pads for finishing of marble, granite, stone or other irregular surfaces which have stepped portions, edges, lips of the like which must be traversed during the abrading or finishing operation. Rotary abrasive tools are commonly in use in many sanding and grinding operations. Generally, abrading assemblies used in these rotary tools include a backing substrate, such as a foam pad or a rubber backing mat or the like, and an abrading pad which can be temporarily attached and replaced as the pad wears out during the finishing operation. The use of such a tool has many advantages including quickness of cutting and easy replaceability of the abrasive pads. However, it has always been a problem in the use of rotary tools that during grinding of irregular large flat areas, i.e. greater than the surface area of the pad, the pads tend to deteriorate quickly and/or leave an irregular surface due to gouging and the like because of contacting the irregularities in the surface. While many grinding situations have irregular surfaces which tend to tear or break up the pad or cause surface deformities therein, a particularly problematic area today has been the finishing or refinishing of floors which are constructed with tiles or stones laid in a mortar base. Such floors have many edges to traverse during finishing thereof. This is partially because of the spaced stone edges and partially because the stones are seldom co-planar one to another over the floor surface. Floor finishing units are commonly utilized in finishing or reconditioning such floors. Such units include three rotating planetary heads and have a base which also rotates to provide an even finish to flat surfaces such as floors. In these units, various coarseness abrasive pads are used on each of the heads for sanding and final finishing of the floor. In the past, this has been problematic in that relatively stiff pads were commonly used. Often while such a stiff pad is traversing the lip, step or edge from one floor stone to another the lack of flexibility in the pad can cause gouging of the adjacent stone when the pad is canted at the transition area. This reduced the quality of the finish. On the other hand, when relatively flexible pads are used on such rotary tools the useful life of the pad is substantially reduced. This is so because when encountering unfinished edges or steps from stone to stone, the edge of the pad catches on the edges and will tend to be shredded quickly. This tends to deteriorate the pad very rapidly and make such flexible pads undesirable due to the down time incurred. Because of these problems, in the past it has been common to utilize various grit stones or pads and go over the floor surface five to six times before creating the final finish. This is a very labour intensive and time consuming process. In the past, in addition to the above complications, it is also been a complication that when reaching a final finished surface the pads used and the grains used for finishing this surface tended to create a hydraulic suction during the final finishing steps. Such hydraulic suction conditions require rapid replacement of pads due to loading up of the pads. Hydraulic suction conditions may also cause stalling of the finishing machine, thus slowing down the finishing process. Thus, in the past the common finishing systems used for such applications were labour intensive, extremely costly and time consuming and did not always produce the desired results. According to the present invention, there is provided a rotary abrasive pad for smooth transition during abrading of uneven surfaces, comprising: a stiff abrasive body portion having an outer peripheral edge; a substantially non-abrasive outer rim portion which extends outwardly from said peripheral edge and which is flexible relative to the abrasive body portion; and means for attachment of the pad to a rotary tool. A preferred arrangement is that wherein the abrasive body portion is circular, preferably wherein the outer rim portion is a substantially non-abrasive concentric ring of a polymeric material. Preferably the abrasive body portion is made of a first material and the rim portion is made of a second material, the first material preferably being a metallic material with at least a mono-layer of abrasive grit attached thereto, and the second material preferably being a polymeric material. Preferably the body portion is embedded in the polymeric material, the polymeric material preferably being a polypropylene. Preferably the means for attachment is the hook or loop side of a hook and loop fastener. For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:- Fig. 1 is a perspective view showing a typical floor finishing apparatus and user; Fig. 2 is a bottom view showing the functional aspects of the floor finishing apparatus of Fig. 1; Fig. 3 is a plan view showing a rough abrasive grit pad in accordance with the present invention; Fig. 4 is a cross-sectional view taken along line 4-4 of Fig. 3; Fig. 4a is a detailed sectional view of the rim portion in circle 4a of Fig. 4; and Fig. 5 is an illustrative sectional view showing the pad of Fig. 3 in its operational environment. Referring now to Fig. 1, there is shown a typical floor finishing apparatus 10 which is manually operated by an operator 12. The finishing apparatus 10 includes a sanding head portion 14 and a handle portion 16. Referring to Fig. 2, the sanding head generally includes three planetary heads 18 which rotate independently at about 88 rpm and an outer rotational portion which rotates all three heads at about 170 rpm. Such a unit is designed to provide even sanding. However, due to the irregularities in the marble floor surface to be sanded prior art pads needed frequent replacement. Because the pads are not flexible due to the interaction between the pads and the edges in the floor, the pads tend, at times, to gouge the floor when canted between surfaces on different planes. Referring now to Figs. 3, 4 and 4a, there is provided an improved first rough finishing pad 20, made in accordance with the teachings of the present invention, which is useful in such an operation and has prolonged life and reduces the time necessary to finish such a floor. The pad 20 includes a central abrasive body portion 22 which has an outer peripheral edge 23. A substantially flexible outer guide rim portion 24 is provided which extends outward from the peripheral edge 23. Also included is a means such as VELCRO® hook and loop attachments 26 for attachment of the pad to the planetary head 18 of the floor sander. The abrasive body portion 22 may be of any of a number of known types. For instance, whole or perforated sheet metal structures with abrasive grit brazed, electroplated or otherwise attached thereto may be utilized in the present invention. Other structures such as sintered abrasive grit structures may also be utilized in the present invention. In a preferred embodiment a flexible abrasive member is provided which includes a metal sheet with apertures 28 therethrough and has an abrasive grit brazedly attached on the operative surface. Thus, abrasive grit structures such as meshes and the like are also anticipated to be useful in the abrasive pad of the present invention. In accordance with the present invention, an outer rim member 24 is provided which is flexible such that it guides the rotating abrasive pad onto a stepped portion or over an edge. The portion 24 is substantially non-abrasive in that if the pad should tilt or cant during the sanding process the portion 24 will not tend to bite into the surface being finished and will support the edge 23 of the abrasive body portion 22 off the surface. Thus, such a rim 24 could be hingedly attached to the pad structure or otherwise attached such that it will flex in an upward direction when it contacts an edge or step portion or to provide a smooth transition to the next floor stone or the like, thus saving the actual abrasive structure from damage during operation and greatly lengthening the abrasive pad's life while reducing any propensity for gouging of the finished surface. An shown in Fig. 5, there is an illustration of an operative environment of a pad 20 as utilized in the present invention. As shown in Fig. 5, a pair of spaced floor blocks 30 and 32 made of a marble or granite material are set in a mortar material 34. During the sanding of these blocks a pad 20 made in accordance with the teachings of the present invention having the guide rim 24 will tend to abut the non-aligned stone portions 32 and the flexible rim 24 will flex upward in order to provide a guide surface for the pad 20 to provide a smooth transition to the next stone 32 for the abrasive body portion 22 without providing any loads which would force the edge of the abrasive body portion 22 into the surface. In accordance with a preferred embodiment, the rim portion 24 is provided by embedding an abrasive body portion 22 of a certain diameter into a polymer material of greater diameter. A preferred polymer material is a polypropylene. In a preferred embodiment the pad is made in a round configuration, with the central abrasive element being of less diameter than the diameter of the polymer material to provide a rim portion 24 which has a width of from 6.35 to 12.7 mm (¼ to ½ inch). Such a pad may be advantageously produced by imbedment techniques set forth in my copending U.S. Patent Application Serial no. 474,373, filed February 2, 1990, entitled "Abrasive Sheet and Method". A floor or other irregular surface having an edge or step portion may be advantageously "rough" sanded by utilizing the pad 20 made in accordance with the teachings of the present invention. This has the advantage that edges are quickly taken off and the pad has great longevity during the sanding operation. To reduce any likelihood of the edge of the pad tending to cut into the working surface thereby leaving undesirable gouges in the finished surface, the lip 24 is flexible to provide a proper transition surface; also, if any canting of the abrasive pad should occur the lip 24 is also non-marring and flexible, such that the transition stone will not be adversely affected during this transition. The pad of the present invention can make it possible to reduce the overall number of steps employed in a polishing operation.

Claims: A rotary abrasive pad for smooth transition during abrading of uneven surfaces, comprising: a stiff abrasive body portion having an outer peripheral edge; a substantially non-abrasive outer rim portion which extends outwardly from said peripheral edge and which is flexible relative to the abrasive body portion; and means for attachment of the pad to a rotary tool. A rotary abrasive pad according to Claim 1, wherein the abrasive body portion is circular. A rotary abrasive pad according to claim 2, wherein the outer rim portion is a substantially non-abrasive concentric ring of a polymeric material. A rotary abrasive pad according to claim 1, wherein the abrasive body portion is made of a first material and the rim portion is made of a second material. A rotary abrasive pad according to claim 4, wherein the first material is a metallic material with at least a mono-layer of abrasive grit attached thereto, and the second material is a polymeric material. A rotary abrasive pad according to claim 5, wherein the body portion is embedded in the polymeric material. A rotary abrasive pad according to claim 6, wherein the polymeric material is a polypropylene. A rotary abrasive pad according to any preceding claim, wherein the means for attachment is the hook or loop side of a hook and loop fastener.

Inventors: WIAND RONALD CARLYSLE, WIAND, RONALD CARLYSLE
Applicants: WIAND RONALD C, WIAND, RONALD CARLYSLE
Application year: 1991
Main classification: B24B7
IPC codes: B24D9, B24D13, B24B7, B24D7