GB2221472A - A rotary abrading tool - Google Patents

Description

11,7 9 "Rotary Abrasive Tool And Filament Therefor" This invention relates

generally as indicated to a rotary abrasive tool and a filament therefor and more particularly to an improved tool particularly suitable for deburring radlusing edge contouring, and conditioning hard or exotic materials in automated or robotic operations.

- I--- - In conventional practice round or circular in section abrasive loaded nylon monofilaments are widely used in rotary abrasive tools or brushes, an example being rotary brushes sold under the trademark KORFIL by Osborn Manufacturing of Cleveland, Ohio. Also, reference may be had to Radford U. S. Patent 2,328,998. Another example of a deburring method using a round filament tool may be seen in U.S. Patent 4,646,479.

Such monofilament bristles are loaded with a sized abrasive mineral and are for example about.040 to.050 inch in diameter. Such bristles are frequently crimped or wavy to provide a controlled tip action since it is at the filament tip or brush face where such tools usually do the work, with slight bristle flexure.

With round or circular filaments, during use the ends or sides of the filaments contact the work piece parts producing a certain degree of work per unit of time. Being round in shape a filament-work point contact is generated at the work surface, thereby utilizing only a small portion of the abrasive mineral available in the filament and tool.

In actual practice the round monofilament initially starts with such point contact and wears itself to a level of flatness during the normal life of the tool. The level of flatness rarely if ever exceeds 50% of the filament diameter. Moreover, during use of the tool, the level of flatness keeps changing and this does not lend itself to consistent and repeatable part-to-part quality assurance results in deburring, radiusing edge contouring and surface conditioning.

Also, in conventional round filament, the normal maximum loading of abrasive minerals into the nylon matrix is about 30% by weight. Higher loadings seem adversely to affect the overall filament strength.

The use of high speed alloys, tough stainless steels, high temperature super alloys and even hard abrasive materials as component parts has made the conventional round filament abrasive tool inadequate to obtain consistent and repeatable quality assurance in the deburring, radiusing, contouring, or surface finishing of such parts particularly in an automated or robotic application.

A rotary abrasive brush or finishing tool utilizes a long rectangular in section or flat nylon abrasive filament. The tool is constructed and is rotated so that the flat side of the filament wipes over the work. The shape of the filament and its orientation in the tool generates a line or flat surface contact with the work so that compared to a typical round filament tool the work performed is substantially increased per unit of time permitting increased throughput of the work or tool past the work. The rectangular filament also permits substantially increased mineral abrasive loading and more uniform distribution of such abrasive in the nylon matrix. The present invention provides consistent part-to-part quality for deburring, radiusing, edge contouring and surface conditioning, particularly with high speed alloys tough stainless steels, high temperature alloys and hard abrasive materials. The tools of the present invention are particularly suited for use with automated machinery or robotic operations.

While in most rotary brushes or abrading tools it is the tip of the bristle filament at the working face which engages the work, with the present invention it is the flat side which is to be wiped or drawn across the work. Thus for a given stiffness of filament it is desirable to make the filament longer with respect to the hub or the point of attachment or gripping of the filament so that the filament has room to flex or bend away from the direction of rotation so as properly to engage the work with a flat side of the filaments. Also to facilitate the wiping action without making the filaments unduly long the filaments may be mounted in rows or tufts which extend at a substantial angle to a radius away from the intended direction of rotation and so that the side of each tuft or row overlaps an adjacent tuft or row.

To the accomplishment of the foregoing and related ends the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the invention may be employed.

In the annexed drawings:

Figure 1 is an end elevation of a long trim filament rotary abrading tool in accordance with the present invention; Figure 2 is an enlarged fragmentary view of the tool face as seen from the line 2-2 of Figure 1; Figure 3 is a view similar to Figure 1 illustrating the tool in operation vis-a-vis a work surface; Figure 4 is an enlarged somewhat schematic view illustrating the wiping action of the flattened filaments engaging the work; Figure 5 is an end elevation of another embodiment of a tool in accordance with the present invention illustrating the filaments secured to the hub in laid over or tangential fashion to facilitate the abrasive wiping action; Figure 6 is a view of the tool of Figure 7 in operation vis-a-vis a work surface; Figure 7 is an enlarged fragmentary end elevation of the construction of the hub of the embodiment shown in Figures 5 and 6; Figure 8 is an enlarged transverse section of a preferred flat sided filament; and Figures 9 and 10 are similar illustrations of flat sided filaments which may be used in applications of the present invention.

Referring first to Figure 1 there is illustrated a rotary abrasive finishing tool in accordance with the present invention shown generally at 10 which includes a hub 12 which may be mounted on a drive arbor of a machine or robot, for example. The hub includes a plurality of channels 13 extending axially thereof adapted to receive in interlocking fashion the compressed channels 14 of filament tufts or strips shown generally at 15. The filaments may be wrapped around a retaining wire or bar within the channel in conventional fashion. The tufts or strips 15 are equally circumferentially spaced and extend radially to present a radially extending array of such filaments shown generally at 16. The outer ends of the filaments are trimmed to provide a circular tool face shown generally at 17.

Because of the nature of the filament employed in the tool to form the tuft or strip, the tool has a longer trim than would ordinarily be employed in wire or conventional circular filament abrading tools. An example would be a hub with a 5-inch diameter and an 83-inch trim length. By trim length is meant the length of the filament from the hub to the tool face 17. In the example above the tool would then have a 22-inch diameter.

Another example would be a 5-inch hub with a 103-Inch trim length providing a 30-inch diameter tool. Generally it is preferred that the radial or trim length of the filaments be between one and two times the diameter of the hub and preferably approximately one and a half times such diameter.

This may be compared to a typical wire brush or deburring tool which may have a trim length of from one to three inches. Thus a 6-inch hub with a 3-inch trim length would provide a rotary brush or tool with a 12inch outside diameter.

As seen from Figure 2 and Figure 8 the individual filaments 20 which make up the rotary abrading tool are rectangular in section and each has two parallel flat sides of major extent 21 and 22 and more narrow ends 23 and 24.

As seen in Figure 2 the filaments are oriented so that the major flat sides are parallel to the axis 26 of the tool. As now seen in Figure 3 when the tool is applied to a work surface shown generally at 30, the extralong trim of the filaments permits the relatively stiff filaments to bend or flex against the work surface as the tool rotates in the direction of the arrow 31. The pressure of the tool against the work surface and its rotation in such direction causes the long trim filaments to flex in a direction opposite the direction of rotation and causes a major flat side 21 of the filaments to wipe over the work surface 30. For a tool with the above noted trim lengths, there is then achieved a six to seven inch or longer si de wiping action against the work surface. Also, because of the rectangular nature of the filament, the filaments will flex more readily in the plane of rotation than axially of the tool. The extent of the side wiping action obtainable with the long trim tool using the rectangular monofilament is of course measured by an approximation of the chord formed by the work surface with respect to the circular tool face and as illustrated is about of half the diameter of the tool.

As seen in Figure 4 it will be appreciated that as the monofilaments flex against the direction of rotation they bend to lay over one on top of the other as illustrated so that the filament flat major sides press one against the other and the radial inner filaments act as springs forcing the outer filaments against the work in the wiping action seen.

With the long trim tool of the present invention it is possible to rotate the tool more slowly than in conventional deburring wheels. For example, a rotational speed of 2500 to 4000 feet per minute may be employed along with suitable coolant to provide excellent stock removal or surface finish.

Another advantage achieved with the long trim rectangular monofilament tool of the present invention is the avoidance of what is known as harmonies or a flexing back and forth of the monofilament when not in contact with the work. In conventional circular filament short trim tools, as the filament or bristle leaves the work, until it reengages the work, a continuous harmonic or flexing back and forth is created, which continual flexing contributes significantly to filament breakage and tool wear. In any event the long trim abrasive loaded monofilaments readily flex to engage the work in the wiping action noted presenting the flat major side of the filament to the work with adjacent monofilaments confining those wiping the work face and acting as springs or cushions as the filaments strike and wipe across the work.

Typically, the rectangular filament at its major flat face may be approximately 0.090 inch wide and about 0.045 inch thick. Somewhat wider rectangular filaments may be employed having major flat faces up to three to four times the thickness of the filament. As indicated, t he monofilament may be extruded plastic such as nylon impregnated throughout uniformly with an abrasive mineral such as aluminum oxide or silicon carbide. Other more exotic abrasive minerals may readily be employed such as polycrystalline diamond. Also, the abrasive grit size may be varied from coarse to fine powders for extra fine polishing and highlighting effects on work parts.

It has also been discovered that with the rectangular or flat face filament the loading of the abrasive mineral in the plastic matrix may be increased. Traditionally, approximately 30% of abrasive mineral has been the standard criteria used in the round and crimped abrasive nylon monofilaments. The percentage is measured by weight and is relative to the cross sectional area of the nylon monofilaments.

The rectangular abrasive nylon monofilament with its relatively larger cross sectional area permits upwards of 45% loading of abrasive mineral without a negative effect on the overall filament strength. This represents a 50% gain in abrasive mineral content and the rectangular filament more effectively presents that abrasive to the work surface.

It should be noted that the term monofilament as used in the rotary abrasive tool art refers to something considerably larger and more stiff than a fiber or that which can be measured with a denier. Fibers are usually limp or highly flexible.

Because of the larger cross sectional area and the increased abrasive loading a rectangular monofilament (0.045 x 0.090 e.g.) of the present invention will have at least three times the stiffness of a circular monofilament (0.045 diameter), where the diameter of the latter is the thickness of the former. This is true even where the direction of flexing is normal to the plane of the flat side. Thus the monofilament of the present invention has a higher modulus of elasticity and a significantly greater stiffness factor obtained by both the higher loading and the shape and size. This then contributes to the agressiveness of the performance of the tool as 1 C Z the flat sides of monofilaments, supported not only by its own stiffness but also by the stiffness of underlying monofilaments, wipes over the work.

Referring back to Figure 2 it will be noted that the density of the filaments is well below maximum but that with maximum filament density the filaments would close up to present an appearance similar to a brick wall. An advantage then of the rectangular filament is that greater filament density can be achieved since rectangular or square flat sided filaments will pack more closely one against the other.

Referring now to the embodiment of the invention disclosed in Figures 5, 6 and 7 it will be seen that there is illustrated a rotary abrading tool 40 which has a hub 42 which may be mounted on an arbor and driven for rotation. Secured to the hub are a series of brush strip or tuft channels 43 which provide a series of uniformly circumferentially spaced tufts or strips of monofilaments indicated at 44. The tufts or strips do not extend radially but are rather laid over to extend tangentially at an acute angle to a radius. The radius is shown at 45 in Figures 5 and 7. Each tuft or strip comprises a series of filaments 20 secured in the channels 43 and bent around the retaining wire 46 as seen in Figure 7. The axis of each tuft indicated at 48 extends at an acute angle to the radius 45 so that the tufts or strips extend tangentially and are laid over one on top of the other as indicated. In Figure 7 the angle illustrated is approximately 45 but it will be appreciated that the angle may vary from approximately 300 to approximately 6V. The channels 43 may be welded to the hub as indicated at 50 and to each other as seen at 51. Also, the channels may be properly positioned with the assistance of notched annular template plates 52.

Because the tufts or strips extend tangentially of the radius, the ends of the filaments may be asymmetrically trimmed to provide the circular tool face seen at 54.

The monofilaments are again oriented so that a major flat side 21 or 22 extends parallel to the axis of the tool. As a tool is presented to a work surface 56 as seen in Figure 6, the filaments are already oriented to present the outer major flat side to the work surface so that as the tool rotates in the direction of the arrow 57 such major flat side of the filament will wipe against the work.

In comparing Figure 3 and Figure 6 it is noted that the filaments of the tool of Figure 6 flex to a lesser extent and that the hub of the tool may be brought closer to the work surface. Again however the underlying tufts or strips cushion each other and act as springs forcing the flat side of the work engaging filaments against the work. With the embodiment of Figures 5-7 the abrasive monofilaments flex to a lesser extent than in the embodiment of Figures 1 and 3 thus lengthening the life of the filament. Moreover, the tangential construction ensures the desired wiping action and avoids impingement by the tip edges. Further, more pressure may be applied to the work surface as the material is already laid over to wipe against the work. Also, there is less movement of the filaments to achieve more straight line finishing, as for example No. 2 and No. 4 stainless steel lined finishes.

Referring to Figure 9 it will be seen that the cross section of the abrasive loaded monofilament may vary from the sharp cornered rectangular shape seen in Figure 8. In Figure 9 the configuration of the monofilament 60 includes two parallel flat sides 61 and 62 of major extent and somewhat rounded narrower edges 63 and 64. Again the major width dimension of the monofilament may be two to three times or more of the thickness. The monofilament of Figure 9 will of course also be oriented so that the major flat sides 61 and 62 are generally parallel to the axis of the tool and wipe over the surface or edge to be abraded. The advantage of monofilament of the configuration of Figure 9 is that the die for forming the monofilament is somewhat less expensive to make. It will of course be noted that as rectangular dies wear because of the high abrasive mineral content of the extrudate a rectangular die will eventually take on the form of an ellipse with a large major diameter. Even such elliptical monofilaments have advantages over the typical round monofilament, both as to abrasive loading and as to the work per unit time accomplished.

In Figure 10 there is illustrated a monofilament 66 which is square in cross section. All four sides of the monofilament are of -g- substantially the same dimension and again parallel sides such as 67 and 68 are designed to be parallel to the axis of the tool while the sides 69 and 70 would be normal to the axis of the tool. An advantage of the monofilament of Figure 10 is that the filaments do not have to be oriented in a particular fashion when manufacturing the tool.

It should also be noted that with the monofilaments of Figures 8 and 10 maximum pack density can be obtained thus presenting more abrasive material to the working face. Maximum pack density of the filaments can of course also be obtained with other regular polygons such as triangles or even hexagons in combination and when properly assembled and tightly packed together present the equivalent of an essentially solid wheel with the noted abrasive loading.

It should further be noted that in the various embodiments of the abrading tool of the present invention the filaments are not crimped or set in a sine wave form. As seen in Figure 4, such would be detrimental to maintaining the optimum amount of wiping contact between the abrasive monofilaments and the work surface. Smooth and continuous abrasive mineral contact with the work surface produces the most uniform and greatest work per unit of time, from a productivity point of view.

It can now be seen that with the change in shape and the increased cross sectional area, the percentage of abrasvie mizeral' in the monofilament can be significantly increased without a negative effect on the overall filament strength.

The present invention provides consistent part-to-part quality for deburring, radiusing, edge contouring and surface conditioning, particularly with high speed alloys, tough stainless steels, high temperature alloys and hard abrasive materials. The tools of the present invention are particularly suited for use with automated machinery or robotic operations.

Moreover, the larger cross section area of the monofilament and the increased abrasive loading provide a somewhat stiffer monofilament which increases the life of the tool at such long trim. Such maximized abrasive minerals plus the high impact stiffness provide a shorter dwell time on edges producing a more true radiused edge. In any event the line or flat 1 contact translates into an increase of several times the work which may be accomplished with typical round filament and at slower surface or tool speeds.

Although the invention has been shown and described with respect to certain preferred embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification. The present invention includes all such equivalent alterations and modifications, q z

Claims (17)

1. A rotary abrading tool including a rotary hub, an array of plastic monofilaments projecting from said hub and each monofilament having an abrasive material embedded therein throughout, said monofilaments each including a flat surface and being of sufficiently long trim to flex when run against a work surface to wipe the flat surface over the work surface.

2. A tool as set forth in claim 1 wherein said monofilaments are of a rectangular sectional configuration having opposed longer flat faces and narrower edges, said monofilaments being oriented with respect to the hub so that such flat faces are generally parallel to the axis of rotation of the hub.

3. A tool as set forth in claim 2 wherein the trim length of said filaments is between one and two times the diameter of the hub.

4. A tool as set forth in claim 3 wherein the trim length of said filaments is about one and a half times the diameter of the hub.

5. A tool as set forth in claim 4 wherein each filament includes in excess of thirty percent by weight of abrasive mineral.

6. A tool as set forth in claim 5 wherein each filament includes about forty-five percent by weight of abrasive mineral.

7. A tool as set forth in claim 6 wherein each filament includes parallel sides of major extent which are in excess of twice the thickness of the filament.

8. A tool as set forth in claim 7 wherein each filament includes parallel sides of major extent which are about twice the thickness of the filament.

9. A tool as set forth in claim 8 wherein each filament is about 0.090 inch wide and about 0.045 inch thick.

10. A tool as set forth in claim 1 wherein each monofilament extends from the hub at an angle to the radius.

11. A tool as set forth in claim 10 wherein said angle is uniform.

12. A tool as set forth in claim 11 wherein said monofilaments extend at such angle extend away from the direction of rotation of the tool.

13. A tool as set forth in claim 12 wherein such angle is about forty-f ive degrees.

14. A tool as set forth in claim 13 wherein such angle is from about thirty to about sixty degrees.

15. A tool as set forth in claim 10 wherein each filament is grouped in tufts or rows, which radially overlie each other to cushion the engagement of the monofilaments with a work surface.

16. A rotary abrading tool substantially as herein described with reference to and as illustrated in the accompanying drawings

17. Any novel combination or sub-combination disclosed and/or illustrated herein.

Published 1990 at The FatentOffice. State House.66 71High Hollborn, London WC1R4TP-Purther copies maybe obtalnedfrom The PatentOtftce. Sales Branch. St Ma-y Cray. Orpingtc.n. Kent BR5 3Rr Printed by Multiplex techniques ltd. St Mary Cray, Kent. Con. V87 -i