US2769285A - Abrasive polishing wheel and element - Google Patents

Description

Nov. 6, 1956 F. E. HENDRICKSON ENT ABRASIVE POLISHING WHEEL AND ELEM 2 Sheets-Sheet 1 Filed Oct. 26, 1953 m T m W F RITZ E. Henomcxsou Nov. 6, 1956 Filed Oct: 26,- 1953 F. E. HENDRICKSON ABRASIVE POLISHING WHEEL AND ELEMENT 2 Sheets-Sheet 2 INVENTOR. FRITZ E. HENORICKSON United States Patent 2,769,285 ABRASIVE POLISHING WHEEL AND ELEMENT Fritz E. Hendrickson, South Elgin, IIL, assignor to Norton Company, Troy, N. Y., a corporation of Massachusetts Application October 26, 1953, Serial No. 388,308

4 Claims. (Cl. 51-1935) This invention relates to improvements in polishing wheels, and more particularly to a flexible, abrasive polishing wheel element and to a method of making the same. Previous constructions of devices for polishing work pieces, particularly pieces having contoured shapes, have been subject to certain disadvantages. These devices include solid wheels formed entirely of abrasive material or wheels having abrasive peripheries. Most of the devices have utilized abrasive surfaces having straight line or flat area contact with the work piece. In operation, an operator manually turns the contoured piece at various angles in an attempt to bring all the surface areas thereof into contact with the moving abrasive polishing surface. As a result, the polished piece either has some inaccessible and unabraded areas or numerous areas abraded in different directions effecting an unsightly appearance.

To overcome some of the foregoing disadvantages, use has been made of travelling flexible belts having an abrasive face. Limited contouring of the belt face has been possible by engaging contact wheels with certain portions of the belt to efiect a desired cross-sectional shape. Some additional deformation of the flexible belt has been possible by forcing either the belt against the work piece or the work piece against the belt. As a result, portions of the belt are overstressed thereby materially shortening its working life. In addition, the variable and excessive pressures exerted against different portions of the belt surfaces quickly result in glazing caused by a filling or loading of the spaces between adjacent particles of abrasive material. These glazed surfaces damage the Work piece either by streaking or burning the surfaces thereof and may, if the wall of the work piece is sufiiciently thin, result in deformation through the inadequate dissipation of the heat so generated.

In the operation of abrasive devices where excessive pressures are applied, lubricants such as water, oil, grease or the like are used to wash away material being removed by abrasion and to absorb and conduct heat from the work surface.

The device of the present invention is designed to eliminate the foregoing objections and disadvantages by the even distribution of polishing pressure over a contoured surface and by the quick dissipation of friction [heat through proper ventilation. Generally, this is accomplished by presenting in wheel form the marginal edges of folded, flexible, abrasive-surfaced sheets against a work piece and effecting a bending of small marginal areas of the folds to provide a multiplicity of abrasive surfaces by rotating the wheel and moving the folded sheets over the work surface or surfaces to be polished.

An important object of the invention, then, is to provide a novel polishing Wheel element anda method of contoured Work surfaces Without the application of excessive pressures.

2,769,285 Patented Nov. 6, 1956 Still another object of this invention is to provide, in a flexible polishing wheel, a multiplicity of small abrasive areas for contact with a surface to be polished.

A further object of this invention is to provide a polishing wheel having flexible elements which operatively engage a contoured work surface under a uniformly distributed pressure.

A still further object of this invention is to provide flexible elements in a polishing wheel having incorporated therein a highly eflicient ventilation system.

Another and still further object of this invention is to provide flexible elements for a polishing wheel having uniform polishing characteristics throughout the entire work life thereof.

Yet another object of this invention is to provide a polishing wheel having elements which are self-cleaning in operation.

A still further object of this invention is to provide elements for a polishing wheel which are simple and durable in construction, highly efficient in use, and inexpensive in maintenance and operation.

Other and further objects of the invention will become apparent to those skilled in the art from the following detailed description of the annexed sheets of drawings, which disclose preferred embodiments of the invention.

On the drawings:

Figure 1 is a face view in elevation of an abrasivecoated polishing sheet before being folded along the dotted lines;

Figure 2 is an edge view of a polishing sheet folded as suggested in Figure 1;

Figure 3 is a face view in elevation of the folded polishing sheet shown in Figure 2, in which adjacent folds partially overlap;

Figure '4 is a front view in elevation of a composite pluralelement polishing wheel constructed according to the principles of the present invention;

Figure 5 is a vertical cross-sectional view, with portions in elevation, taken along a plane indicated substantially by the line 55 of Figure 4 and showing details of construction of a wheel hub assembly on which the folde abrasive sheets are mounted;

Figure 6 is an enlarged edge view in elevation of a folded abrasive-coated polishing sheet as seen along that portion of the periphery of the wheel indicated by the line' 66 of Figure 4 and showing the numerous marginal edge portions bent along the wheel periphery to form abrading areas;

Figure 7 is a modified form of polishing sheet showing the provision of rows of slits provided to facilitate the bending of the marginal edge portions thereof;

Figure 8 is a view, similar to Figure 3, of a modified form of sheet in which adjacent folds completely overlap; and,

Figure 9 is a View, similar to Figure 2, showing the width of the folded sheet in Figure 8 as being the width of a fold.

As shown on the drawings:

Referring now'in detail to the several figures, the numeral 20 generally designates a sheet of fibrous material such as paper, cloth, or the like. A coating 21 of granular mineral substance, such as emery or other abrasive, is applied and adhesively secured to the sheet. For maximum efficiency, both faces of the sheet are so coated.

However, the herein described invention will function s at isfactorily if but one face of the abrasive sheet is so coated.

In the preferred form as shown in Figures 1, 2 and 3, the abrasive-coated sheet 20 is folded along the dotted fold lines 22, 22. The fold arrangement is such that one pleat partially overlaps an adjacent pleat effecting a folded sheet of a width narrower than the unfolded sheet. As

so folded, the sheet is doubled upon itself along the fold line 23 extending medially lengthwise thereof. In this folded and doubled arrangement, each of the ends of the sheet present an undulated edge outline having a Wavy form with successive curves in alternate directions, as seen in Figure 6. While the abrasive-coated sheet is preferably rectangular in shape it may be of any form folded or bunched to present a wavy periphery. Also, each abrasive element may comprise any desired number of thicknesses of abrasive coated sheets in face engagement or interleaved with uncoated sheets. As so folded, each abrasive-coated sheet is applied to a central mounting or driving hub construction 24.

It is to be understood that the mounting hub construction shown is for purposes of illustration only as many other forms of construction are equally applicable.

As shown in Figures 4 and 5, the hub 24 has face plates 25 and 26 centrally apertured as at 27 for mounting on a drive shaft 28. The drive shaft has a reduced end portion 29 terminating at one end in an abutment shoulder 30 and at its other end in a threaded portion 31. A sleeve 32 embraces the shaft portion 29 between the face plates to maintain the plates in desired spaced relation. A nut 33 is threaded on the shaft and serves to clamp together the hub assembly.

A group of mounting pins 34, 34 are fixedly secured to one of the face plates, shown herein as the plate 25. The pins are spaced around a circle located between the center and periphery of the face plate. Openings 35, 35 are provided in the other face plate for slidingly receiving the pins therethrough. By this construction, the pins prevent relative rotary movement between the face plates and each form a carrier support for a folded polishing sheet.

As best shown in Figure 4, each folded sheet 20 is looped around a mounting pin with the ends of the sheet coextensively extending radially outward of the hub. As many folded sheets are applied as there are mounting pins to complete the polishing wheel. The entire periphery of the wheel is thereby made up of the ends of sheets each presenting a wavy or corrugated shape, the waves or corrugations of adjacent ends slanting in opposite direction. Pockets 36, 37, 38 and 39 are thereby formed in the folded arrangement of each sheet. The pockets 36 and 39 face each other and are open along their length from the mounting pin to the periphery of the wheel. Similarly, the pockets 37 and 38 are open along their length but extend away from each other. During the rotation of the polishing wheel, the resulting centrifugal force effects a constant flow of air radially outward of the wheel through the pockets thereby providing highly efficient ventilation.

When the periphery of the rotating polishing wheel engages a work piece 40, shown in dotted lines in Figure 4, certain of the marginal edges of the folded sheets are permanently bent generally normal to their original positions. This is diagrammatically shown in Figure 6. It will be noted that there is thereby provided numerous small abrasive areas for engaging a surface to be polished. These areas are on opposite sides of each loop which generally bend as at 41 and 42 away from the direction of rotation of the wheel. It will be noted that the portions 41 and 42 turn and expose, outwardly of the polishing wheel, opposite sides of the abrasive sheet. The portions so bent usually are of a maximum width of A; inch to A1. inch and of a length dependent on the peripheral length of the sides of the pocket. As the bent portions are relatively narrow for their length and are supported by the flexible body of the sheet, they become selfadjusting to completely engage a contoured surface under a minimum of contact pressure and thereby are self-cleaning of any material removed from a surface during the polishing operation. Consequently, any heat generated by friction is minimized and is quickly dissipated by the improved ventilation previously described. As a result, only occasional lubrication of the abrasive surfaces is necessary and the possibility of glazing is eliminated.

It has been found in the operation of such a polishing wheel that the resistance to bending of the marginal edges is dependent on the stiffness of the abrasive sheet. To facilitate the quick bending as desired, rows of short slits 43, 43 may be provided as shown in Figures 6 and 7. Generally, the slits are located in the pleat areas of the sheet preferably at or near the initial point of contact with the Work piece surface. Should the abrasive sheet be relatively flexible, slits only along the peripheral edges of the pockets are necessary and desirable. As many edge slits as desirable may be provided. If, however, the sheet is relatively stifl and resistant to bending, then longer slits or rows of spaced slits are provided as shown. In any event, when slits are provided they should start along the initial working edge of the pleated or bunched sheet. In addition, the slits may be located in alignment lengthwise of the sheet or in staggered relation.

Shown in Figures 8 and 9 is a modified form of sheet 200 having an abrasive coating 21a. In this form, the pleats 44, 44 completely overlap each other to effect a folded sheet of the width of a single pleat. Before being mounted on a wheel the sheet is folded medially upon itself as at 23a. With this type of folded sheet, a wheel having the width of one pleat may be formed by mounting a single sheet on each mounting pin, or, a wheel of any desired width is possible by mounting folded sheet side-by-side on a mounting pin. In this form of construction, the abrasive working areas 45, 45 are bent from the sides of the pleats. As in the previously described form of sheet construction, bending slits 46 may be provided. Here, the slits are preferably located centrally of the sides of the pleats and/or at the bottom of the pockets.

With the several forms of folded abrasive-coated sheets shown and described herein, it has been found under certain conditions to be desirable to provide uncoated spacer sheets 47, 47 in the pockets to separate adjacent coated surfaces and thereby prevent rubbing with resulting loss of abrasive material. Such spacers are shown in Figure 6. This provision is equally applicable to the form of folded sheet shown in Figure 9.

By the features described hereinabove, there is provided a polishing wheel having an effieiently ventilated and self-adjusting contact under relatively light pressure with the surface of a work piece to be polished. The result is to reduce the costs of operation by minimizing maintenance through replacement of abrasive sheets and by extending the working life of the wheel while at the same time effecting a complete polishing of surfaces, both flat and contoured, in one direction which is of pleasing appearance to the eye.

It is to be understood that the forms of the invention, herewith shown and described, are to be taken as preferred embodiments of the same, and that various changes and modifications in form and structure may be resorted to without departing from the spirit of the invention or the scope of the appended claims.

I claim as my invention:

1. A coated abrasive element adapted for use in an abrasive Wheel which comprises: a flexible backing member; an abrasive coating bonded to and substantially uniformly covering at least one side of said backing member; and a plurality of relatively rigid pleats in said backing member, said pleats at least partially overlapping one another and having the outer edges only thereof adapted to be bent angularly withrespect to the pleat to provide a plurality of narrow abrading surfaces when said element is positioned in an abrasive wheel and contacts a work piece.

2. A coated abrasive element adapted to be radially mounted from the hub of an abrasive wheel which comprises: a flexible backing member; an abrasive coating substantially uniformly covering at least one surface of said backing member and bonded thereto; a plurality of fold lines in said backing member, said fold lines extending outwardly from said hub when said element is mounted in said wheel to define a plurality of relatively rigid overlapping pleats; and a plurality of narrow abrading surfaces angularly inclined to said pleats and formed at the outer end only of said pleats by bending of said backing member along said fold lines upon contact of said element with a work piece.

3. In a coated abrasive wheel having a central hub and mounted means associated therewith: a plurality of coated abrasive elements radially disposed about said hub and held thereto by said mounting means, said coated abrasive elements each comprising at least one sheet of flexible material having a substantially uniform abrasive coating bonded on at least one side thereof, said sheet being pre-folded prior to mounting on said wheel to provide a plurality of relatively rigid overlapping pleats, said pleats extending from said mounting means to the outer periphery of said wheel and having the outer ends only thereof adapted upon contact of said element with a work piece to form angularly disposed narrow abrading surfaces which extend at an angle to the direction of rotation of said wheel.

4. A coated abrasive wheel having a central hub, mounting means associated therewith, and a plurality of pleated elements having a coating of abrasive firmly bonded thereto, said elements being radially disposed about said hub and held thereto by said mounting means, comprising: a peripheral face extending about said hub and located radially outwardly therefrom, said peripheral face being composed of a plurality of relatively narrow abrasive flaps extending generally across the peripheral face, said flaps being angularly bent extensions of relatively rigid pleats, said pleats being formed in said element and extending from said flaps to said mounting means.

References Cited in the file of this patent UNITED STATES PATENTS 1,819,171 Hopkins et a1 Aug. 18, 1931 1,882,769 Bugg Oct. 18, 1932 1,897,971 Johnston Feb. 14, 1933 2,226,624 MacFarland et a1 Dec. 31, 1940 2,290,236 Hall July 21, 1942 2,574,037 Hendrickson Nov. 6, 1951 2,581,411 Hendriekson Jan. 8, 1952

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