US 3925935 A
A recirculative system for abrading a predetermined portion of a surface with a high velocity stream of abrasive granules is provided in which the granules are aspirated from a supply against the surface to be abraded within a substantially enclosed abrading zone and spent granules are exhausted from the abrading zone and recycled to the supply filtered from any fines.
Description (OCR text may contain errors)
United States Patent [191 Ricklefs Dec. 16, 1975 1 ABRADING SYSTEM  Inventor: Robert U. Ricklefs, Box 2050,
Pebble Beach, Calif. 93953  Filed: Aug. 28, 1974  Appl. No.: 501,026
Related US. Application Data  Continuation-impart of Ser. No. 452,950, March 20,
 US. Cl. 51/8 HD; 51/8 BR; 51/9 M  Int. C1. B24C 3/06; B24C 3/32; B24C 7/00  Field of Search 51/8 R, 9 M, 310-312,
51/319-321, 8 HD, 8 BR, 11; 4/185 1 ,173,177
3,377,749 4/1968 Shumaker 51/8 R 3,418,668 12/1968 Anderson 4/185 F 3,461,478 8/1969 Taylor 51/8 R X 3,516,204 6/1970 Kulischenko 51/8 R 3,545,996 12/1970 Duncan 51/310 X 3,624,966 12/1971 Palmer 51/8 R 3,624,967 12/1971 Kamper i 51/8 R 3,805,453 4/1974 Schmall 51/8 R 3,835,482 9/1974 Tersch 4/177 Primary Examiner-Donald G. Kelly [5 7] ABSTRACT A recirculative system for abrading a predetermined portion of a surface with a high velocity stream of abrasive granules is provided in which the granules are aspirated from a supply against the surface to be abraded within .a substantially enclosed abrading zone and spent granules are exhausted from the abrading zone and recycled to the supply filtered from any fines.
3 Claims, 2 Drawing Figures US. Patent 2 Dec. 16, 1975 3,925,935
FlG l FlG 2 ABRADING SYSTEM This is a. continuation in part of application Ser. No. 452,950 filed Mar. 20, 1974, now abandoned, entitled Sani-Safe.
This invention relates generally to systems forabrading surfaces such as sand blasting systems and the like. The invention is more specifically related to systems for abrading a predetermined portion of a hard surface. A specific use for the invention is rendering the bottoms of bathtubs slip-resistant by forming a pattern of abraded circular areas on the slippery surface of the porcelain tub.
The prior art includes abrasive systems for rendering bathtub bottoms slip resistant by covering the bottom of the tub with a stencil, draping a cover over the tub, and directing a stream of abrasive granules through a hole in the cover at the stencil on the bottom of the tub and thereby abrading predetermined portions of the tub bottom. Portable sand blasters are also known in the prior art for various purposes.
A primary object of the present invention is to provide a portable and lightweight abrading system in which the abrasive granules are continuously recycled and reused.
A further object of this invention is to provide a portable abrading system which is capable of abrading a predetermined portion of a surface of a variety of possible designs.
Another object of this invention is to provide an abrading system in which the abrasive granules are recycled and in which the fines produced at the processed surface are separated from the recycling granules.
An object of this invention also is to provide an abrading system in which the abrasive granules are aspirated against a surface and then continuously withdrawn immediately after they impinge upon the surface.
One important object of the invention is a practical procedure for rendering slip-resistant the bottoms of bathtubs already in place by etching a pattern in the slippery surface of the porcelain.
Further objects and advantages of the invention will become apparent from the following description of preferred embodiments and the drawings, wherein:
FIG. 1 is a schematic sectional view of the invention; and
FIG. 2 is a schematic sectional view of an alternate form of the invention.
In describing the systems shown in the drawings, reference is made to the use of the system on the bottom of a bathtub although it should be understood that the system may be used in processing other surfaces.
The bottom 32 of the tub is made slip-resistant by removing the shiny surface (the epidermisapproximately l/ 32nd of the entire thickness of the baked enamel coating) from the tub bottom in a pattern that is composed of one inch circles spaced three quarters of an inch apart.
This is accomplished by a sand-blasting technique wherein an abrasive comprising abrasive granules (No. 30 silicon carbide) is directed, under 125 psi pressure at the pattern in a rubber stencil mat 34 placed on the tub bottom. The rubber stencil mat 34 defines the pattern to be etched on the bottom but, if no pattern is desired, a stencil mat is not necessary.
Since the processing usually is done in bathtubs already installed in hotels, motels, apartments and homes, it is essential to have equipment that is compact, lightweight, and portable in order that it can be easily moved from location to location. At the same time it must be effective, efficient, safe, and clean.
The system of this invention involves a recirculative process wherein abrasive granules in supply 42 of FIG. 1, for example, are aspirated by aspirating means 22 at high velocity against the tub bottom 32 within a substantially enclosed abrading zone 29 overlying that portion of the bottom 32 exposed by the stencil mat 34. Spent granules and fines are continuously and simultaneously withdrawn from the abrading zone by vacuum developed by vacuum source 53 and applied through exhaust line 40 to the abrading zone 29. The spent granules 44 return to the supply 42 for recycle and the fines are drawn through filter 50 for disposal in a waste bag, not shown.
In the embodiment of FIG. 1 compressor 79 is a source of compressed air powered by a 1.5 horsepower electric motor (17 arnperes), which provides 6 cubic feet of free air per minute at 125 psi. It is equipped with safety valves, pressure regulator, and belt guard.
Exhaust means for withdrawing spent granules and fines from the abrading zone 29 includes a vacuum recovery system powered by a vacuum source 53 which is No. 860-01 Hang-Up Vac manufactured by Shop-Vac Corporation, Willimsport, Pennsylvania. It has a 1 HP by-pass motor (9 amperes), a 2% gallon tank, and is rated at CFM. The vacuum source 53 is equipped with filter 50 and a disposable waste bag, not shown.
The rubber stencil mat 34 is made from pure gum rubber sheeting, Vs inch in thickness, and the over-all measurement is 16 inches by 32 inchesa rectangle. The pattern covers an area measuring 14 inches by 30 inches, leaving a 1 inch margin on each edge. The pattern consists of 124 l-inch circular holes or circles spaced three-fourths of an inch apart. The circles are punched out of the rubber sheeting, and the abrasive action takes place on the tub surface in the cut out areas.
Cannister means 11 forms an enclosed supply 42 of abrasive granules 44 for the abrading or etching process. Cannister means 11 is a fiberglass tube capped at the bottom, with a cap 13 through which a rubber hose 25 leads to the aspirating means or etching gun 22. This rubber hose 25 conducts abrasive granules from supply 42 to the aspirating means or etching gun 22. Cannister means 11 is capped at the top by top cap 12, and has a flexible tubing or vacuum line 51 extending through top cap 12 to vacuum source 53. A filter means or screen assembly 50 is attached to the vacuum line 51. The filter means 50 separates the whole, spent abrasive granules 44 from the dust and fines abraded from tub surface 32. The spent granules drop back into the low er interior of cannister means 11 as shown at 43 and add to the abrasive granule supply 42 available for recycle. The dust particles and fines abraded from surface 32 pass through filter means 50 through line 51 and into a disposable waste bag (not shown) connected to vacuum source 53. Filter means 50 maybe a cylindrical 3 inches in diameter and 6 inches long number 40 mesh brass screen. Such a screen performs the separation function effectively and without clogging.
The alternate embodiment shown in FIG. 2 is similar to the embodiment shown in FIG. 1, except that the abrading apparatus shown generally as in FIG. 2
comprises a cannister means 111 which is physically separated from casing means 120 that is described hereafter. In the embodiment shown in FIG. 2 flexible rubber hoses 125 and 147 connect the cannister and casing means together. The system shown in FIG. 1 is a unitary structure shown generally as which incorporates into one structure the cannister means 1 1 and casing means 20. The reference numerals used in FIG. 2 in the 100 series correspond to similar components shown in FIG. 1.
Referring to FIG. 2, there is a hole 145 in the side of cannister means 111 24 inches from the bottom of cannister means 111 to which is affixed, with a coupling 146 and an elbow 141, a flexible rubber hose shown generally as 147, which is one inch in diameter and which leads to exhaust line 140 connected to casing means 120 that defines the abrading zone 129.
Cannister means 111 contains an enclosed supply 142 of abrasive granules which is continually replenished. The abrasive granules are drawn from the bottom of cannister means 111 through abrasive supply hose 125 by aspirating means 122 described hereafter. Granules aspirated into abrading zone 129 formed within casing means 120 abrade the predetermined pattern on bottom 132 of the tub that is defined by stencil 134. Spent granules are drawn back into cannister means 111 by the action of vacuum source 153, are cleaned of dust and fines by the filter means or screen filter 150, and drop back into abrasive supply 142 in the bottom section of cannister means 11 1. The cannister means 111 and the vacuum source 153 may be mounted on a hand truck for ease in handling.
An etching gun assembly including aspirating means 122 and casing means 120 aspirates abrasive granules from supply 142 into the abrading zone 129 defined by the casing means 120 overlying the surface to be abraded. The aspirating means or etching gun 122 is the same as aspirating means 22 shown in FIG. 1. A useful one is a model GT 12 (Clemco) gun with a 0.063 inch air aperture 128 and a 3/16 inch nozzle 123. This model GT 12 is modified by the addition of a 24 inch pipe extension placed between the gun proper and the orifice assembly in order that the etching or abrading can be done from a standing position.
Casing means 120 is a vacuum casing which encloses the etching nozzle or abrading nozzle 123. Casing means 120 effectively contains the abrasive granules and dust or fines during the abrading process and disposes of the spent granules and dust through vacuum action into cannister means 111. Casing means 120 is made of 1% inch stainless steel tubing, is 5 inches in length, and has a cap 170 at its upper end with a 1 inch hole 171 to accommodate the nozzle 123 of the aspirating means or etching gun 122 which is held snugly in place by a set screw 172. A one inch stainless steel elbow 140 is welded to an opening in the casing onehalf inch from the bottom, and this elbow is fitted to flexible rubber hose 147 leading to abrasive cannister means 111. I
The bottom edge 127 of casing means 120 is covered with or coupled to a rubber welting 130 to provide better contact with the gum rubber stencil mat 134. Welting 130 is notched at inch intervals with passageways 131 to allow free passage of ambient air therethrough for the suction action in which the ambient air drawn through passageways 131 carries the spent abrasive granules and dust through elbow 140 and line 147 into cannister means 111.
Casing means 120 defines a substantially enclosed abrading zone 129 overlying a predetermined portion of surface 132, said predetermined portion comprising the area circumscribed by the bottom edge 127 of casing means 120. Abrasive granules are aspirated through aspirating means 122 from the enclosed supply 142 of abrasive granules into abrading zone 129 and against the predetermined portion of surface 132. Simultaneously, the spent granules are withdrawn from abrading zone 129 by the action of exhaust means which comprises vacuum source 153, vacuum line 151 and hose 147 connected to elbow or exhaust line 140.
Cannister means 111 contains 15 pounds of abrasive, such as No. 30 silicon carbide granules, sufficient to process or more bathtubs before refilling. The compressor 179 is plugged into a 20 ampere circuit, and it runs continuously during the processing. The cannister means 111 and vacuum source 153 which together form a vacuum-cannister assembly is wheeled to the edge of the bathtub to be processed, and the rubber mat 134 is placed in the bottom of the tub and secured by adhesive strips at each corner. The vacuum is turned on and runs continuously during the processing. The operator places casing means directly over a hole in the rubber mat stencil 134 perpendicular to the bottom 132 of the tub, and squeezes the trigger of the gun which opens a valve, not shown, in air supply line 121 and holds it open for 3 seconds. He releases the trigger, moves the gun to the next hole, and continues this process until the entire pattern is etched or abraded. Three seconds of etching or abrading time is sufficient to cut the porcelain glaze to the desired depth, but there is no disaster if, for some reason, the etching or abrading continues for as long as ten seconds. The enamel on a standard bathtub will etch or abrade through to the brown coat in about 40 seconds.
The dust accumulated in the disposable waste bag connected to vacuum source 153 is changed after each 50 bathtubs. It takes approximately 8 minutes to process a bathtub, from start to finish, and one operator with one system can process 30 to 40 bathtubs in one working day.
The embodiment shown in FIG. 1 combines the cannister means 11 with the casing means 20 housing aspirating means 22. This embodiment enables the use of one hand truck which can be placed at any convenient distance from the bathtub. The assembly 10 shown in FIG. 1 is connected to vacuum source 53 and the source of compressed air or compressor 29 by vacuum line 51 and compressed air supply line 21, respectively.
The cannister means 11 shown in FIG. 1 is 18 inches long and holds five pounds of abrasive granules in supply 42 which is sufficient to process 40 to 50 bathtubs without refilling.
The casing means 20 and aspirating means 22 shown in the embodiment of FIG. 1 are the same as the casing means 120 and aspirating means 122 shown in FIG. 2. The abrasive supply hose 25 shown in FIG. 1 passes directly to aspirating means 22 through cap 13 from cannister means 11.
The compressed air supply line 21 extends.from compressor 29 to aspirating means 22 through the interior of cannister means 11. The aspirating means 22 is mounted upon the bottom cap 13 of cannister means 11. The exhaust line 40 extends through the bottom cap 13 of cannister means 11 to a point 4 inches above the top level of the abrasive supply 42 and has an elbow at the top to direct the flow downward. This exhaust line 40 is made of 1 inch plastic pipe. The exhaust means of the embodiment shown in FIG. 1 comprises exhaust line 40, vacuum line 51 and vacuum source 53 with interposed filter 50.
1. Apparatus for continuously rendering the floors of bathtubs slip-resistant by abrading a predetermined portion of the floor with a stream of recycling, abrasive granules and recovering spent granules comprising:
an elongated, cylindrical cannister means forming an enclosed supply of abrasive granules,
casing means forming an abrading zone positionable adjacent to said predetermined portion of the surface, aspirating means adjacent to said cannister means for drawing abrasive granules from said cannister means and propelling them against said predetermined portion of said surface in the abrading zone;
exhaust means comprising an exhaust line extending from said casing means to the interior of said cannister means and a vacuum source connected by a vacuum line to the interior of said cannister means for applying a vacuum to said exhaust line;
filter means in the interior of said cannister means;
and said cannister means, casing means, exhaust means, filter means and aspirating means being combined into a single, elongated and generally cylindrical unitary structure whereby the device may be used near the walls of said bathtub. 2. The apparatus of claim 1 further comprising welting means coupled with said casing means,
said welting means being positionable on the periphery of said predetermined portion of said surface and forming a boundary of said abrading zone,
said welting means having passageways to permit the flow of ambient air therethrough to carry spent granules away from said abrading zone.
3. The apparatus of claim 2 wherein said aspirating means comprises nozzle means mounted in said casing means and connected to a source of compressed air, and an abrasive supply conduit extending from said cannister means to said nozzle means whereby abrasive granules are drawn through said abrasive supply conduit and propelled through said nozzle means into said casing means.