Abrading Tool

The present invention relates to tools for supporting and transferring rotational forces to abrasive material to provide a rotating cylindrical abrasive surface for abrading a workpiece.

The prior art is replete with tools which support and transfer rotational forces to an abrasive material to provide a rotating cylindrical abrasive surface for use in abrading a workpiece. Typically such tools comprise a cylindrical drum having a coaxial stem projecting from one end and adapted to be engaged by a drive chuck for rotating the drum. In one such tool the peripheral surface of the drum can be expanded to frictionally engage the inner surface of a hollow cylindrical abrasive strip which is supported and rotated with the tool, whereas with another the abrasive strip is adhered around the drum via pressure sensitive adhesive.

While such tools can do a good job of abrading, replacement cylindrical or pressure sensitive adhesive coated abrasive strips are more expensive to make and buy than plain abrasive strip material.

According to the present invention there is provided a simple tool which can releasably support a length of plain abrasive strip material in a coil with its abrasive surface out to provide a generally cylindrical outer abrasive surface, and can transfer forces to rotate the coiled length of abrasive strip material about its axis so that its outer surface may be used to abrade a workpiece such as to shape, smooth or polish a surface or to size or polish a hole.

The tool according to the present invention comprises a body member having an axis, a driven end portion adapted to be engaged by a drive chuck for rotating the tool in a first rotational direction about the axis, and adjacent transfer and supporting portions having peripheral surfaces which are cylindrical about the axis. The supporting portion is adapted to support the length of abrasive strip material in a generally cylindrical coil about its peripheral surface with the coil wound in a direction opposite the direction in which the tool is to be rotated. A spring wound in a direction opposite the direction which the body member is to be rotated has one end portion fitting closely around the transfer portion and an opposite end portion adapted to encircle an end portion of the coiled length of abrasive strip material to releasably hold it on the supporting portion and to transfer torque to it from the body member.

Preferably the supporting portion is an end portion of the body member so that it may be projected into an opening to abrade its inner surface. Also preferably the supporting portion has a diameter which is smaller than the diameter of the transfer portion and is adapted so that the portion of the coil of abrasive strip material supported about it which is engaged by the spring will have the same diameter as the transfer portion; and both end portions of the coil spring have the same inner diameter.

The length of abrasive material used on the tool may be of a uniform width and predetermined length so that the strip has a uniform generally cylindrical outer surface of a predetermined diameter adapted to be engaged by the spring. Alternatively the strip may have a wide end portion with a predetermined length so that when coiled it will provide an end portion of the predetermined diameter for the spring to engage, and a narrow end portion which is coiled around the wide end portion and provides a generally cylindrical surface of some larger diameter. This larger diameter may be adjusted for various purposes by shortening or lengthening the narrow end portion; for example, to provide the proper diameter to size or polish a hole.

The present invention will be further described with reference to the accompanying drawing where like numbers refer to like parts in the several views, and wherein:

FIG. 1 is a perspective view of a tool according to the present invention supported in a drive chuck and supporting a coil of abrasive strip material which has a generally cylindrical abrasive outer surface of a uniform diameter;

FIG. 2 is an enlarged plan view of the tool of FIG. 1 and of the coiled length of abrasive strip material in which parts are broken away to show detail; and

FIG. 3 is an enlarged exploded view of the tool of FIG. 1 and of a coiled length of abrasive strip material which has one end portion adapted to be engaged by a spring on the tool and an opposite cylindrical end portion of a larger diameter.

Referring now to the drawing there is illustrated a tool 10 according to the present invention which is adapted to support and retain a length of abrasive strip material 11 or 12 (e.g. cloth backed coated abrasive) in a generally cylindrical coil with its abrasive surface out, and to transfer torque in a first rotational direction from a rotating drive means or chuck 13 to rotate the coiled length of abrasive strip material 11 or 12 about its axis so that its outer surface may be used to abrade a workpiece 14.

As is best seen in FIG. 3, the tool 10 comprises a stepped cylindrical body member 16 (preferably of steel) and having an axis, a central transfer portion 18 with a cylindrical peripheral surface about the axis with a predetermined diameter, and a supporting end portion 20 with a cylindrical peripheral surface about the axis having a diameter which is smaller than the transfer portion 18. The supporting portion 20 is coaxial with and projects from one end of the transfer portion 18, and has a length and diameter adapted to support the coiled length of abrasive strip material 11 or 12 about its periphery with the outer surface of the portion of the coiled length of abrasive strip material 11 or 12 adjacent the transfer portion 18 generally aligned with the outer surface of the transfer portion 18. The body member 16 also includes a driven end portion 22 about the axis on the end of its central transfer portion 18 opposite the supporting end portion 20 which is coaxial with the transfer and supporting portions 18 and 20, and is adapted to be received in a drive chuck such as the chuck 13. The driven end portion 22 is illustrated as being cylindrical and of the same diameter as the transfer portion 18, but could be of a diameter different than that of the transfer portion 18 and/or could have flatted surface portions to facilitate engagement by the chuck 13.

The tool 10 also includes a coil spring 24 helically wound in a direction opposite the direction the tool 10 is adapted to be rotated, which coil spring 24 provides means both for releasably holding the length of abrasive strip material 11 or 12 in a coil about the supporting end portion 20 of the body member 16, and for transferring torque received by the body member 16 from the chuck to the coiled length of abrasive strip material 11 or 12 to rotate its abrasive outer surface against a workpiece. The spring 24 has an inner diameter approximately equal to the outer diameter of both the transfer portion 18 and the outer surface of the portion of the coiled length of abrasive strip material 11 or 12 adjacent the transfer portion 18, and has a length adapted so that one end portion 26 of the spring 24 may be positioned around the transfer portion 18 of the body member 16 and the opposite end portion 30 of the spring may be positioned around a portion of the coil of abrasive strip material 11 or 12 on the supporting end portion 20 as is shown in FIGS. 1 and 2 for the strip material 11. Upon rotation of the body member 16 in the first rotational direction, any relative rotational movement of the body member 16 with respect to the coiled length of abrasive strip material 11 or 12 will cause the spring 24 to tighten about them both and transmit torque from the body member 16 to the coiled length of abrasive strip material 11 or 12.

The tool 10 also includes means for manually positioning the spring 24 in the aforementioned position at which it holds and transmits torque to the coiled length of abrasive strip material 11 or 12; or for manually removing the spring 24 from the coiled length of abrasive strip material 12 to allow changing it to provide a new abrasive surface. The end portion 26 of the coil spring 24 has a terminal end part 32 which projects radially of the body member 16 and is positioned in a radial bore 33 in a collar 34 slidably and rotatably supported about the transfer portion 18. By manually engaging the collar 34, a user can move the end part 32 to both (1) rotate the spring 24 relative to the body member 16 in the direction it is wound and thereby slightly expand the spring against resistive frictional forces adjacent its opposite end and (2) move the spring axially of the body member 16 so that it will slide onto or off of the peripheries of the transfer portion 18 or the coiled length of abrasive strip material 11 or 12. The end 36 of the spring 24 opposite the radially projecting end part 32 is relieved on its inner surface to restrict its digging into those peripheries when the spring is moved about them; and the body member is chamfered between the transfer portion 18 and the supporting end portion 20 so that the end 36 of the spring 24 can be moved smoothly onto the transfer portion 18 from over the end portion 20. The collar 34 both provides a convenient means whereby a user can manually manipulate the spring 24 to place it around or remove it from around the coiled length of abrasive strip material 11 or 12, and insures that the radially projecting end part 32 of the spring 24 will not snag on a workpiece or on a person using the tool 10.

The length of abrasive strip material used on the tool 10 may, like the strip 12 illustrated in FIGS. 1 and 2, have a uniform width and a predetermined length so that it has a generally cylindrical outer surface of a predetermined diameter adapted for engagement by the spring 24. Alternatively, like the strip 11 illustrated in FIG. 3, it may have a wide end portion 38 with a predetermined length such that when it is coiled it will provide one end portion of the predetermined diameter for the spring 25 to engage; and a narrow end portion 40 which is coiled around the wide end portion to provide a generally cylindrical surface of some larger diameter. This larger diameter may be adjusted by shortening or lengthening the narrow end portion for various purposes, such as to provide the proper diameter to size or polish a hole.

To operate the tool 10, a user first moves the spring 24 entirely onto the central transfer portion 18 of the body member 16 by simultaneously rotating the collar 34 engaged with the end part 32 of the spring 24 in the direction the spring 24 is wound to loosen its grip on the periphery of the transfer portion 18 and pulling the collar 34 to move the spring 24 axially along the body member 16. He then wraps a length of abrasive strip 11 or 12, abrasive side out, around the supporting end portion 20 in the direction opposite that the tool 10 is to be rotated so that the exposed end of the strip material 11 or 12 will be pulled (rather than pushed) across a surface being abraded. The user then holds the coil of abrasive strip material 11 or 12 in position adjacent the distal end of the supporting portion 20 while he again rotates the collar in the direction the spring 24 is wound and pushes it axially along the body member 16 to position the end portion 30 of the spring 24 over a portion of the coiled length of abrasive strip material 11 or 12 of a predetermined length and diameter which portion of the strip material is positioned adjacent the transfer portion 18. The user then releases his grip on the strip material 11 or 12 and continues to rotate the collar 34 as he pulls the collar 34 slightly away from the supporting end portion 20 to move the strip material 11 or 12 firmly against the shoulder between the transfer and supporting portions 18 and 20. The tool 10 is then ready for use and its driven end portion 22 may be engaged with the chuck 13 (such as that of a lathe, drill or routing machine) whereby the coiled length of abrasive strip material 11 or 12 may be rotated to abrade a workpiece. Torque will be transmitted from the chuck 13 to the coil of abrasive strip material 11 or 12 through the body member 16 and by self-tightening engagement of the spring 24 between the transfer portion 18 of the body member 16 and the coil of abrasive strip material 11 or 12. When it is desirable to change the abrasive surface, the spring may be moved back onto the central portion 18 by the method described above, and the abrasive strip material 11 or 12 either replaced or, in the case of the strip material 12, rewound with its end which was innermost during the first winding at the surface of the coil.

As a specific non-limiting example, the body member 16 may be a screw machine part of blued steel with its transfer and driven portions 18 and 22 having a common diameter of 3/8 inch and an overall length of 23/8 inch, and its supporting end portion 20 having a diameter of about 0.27 inch and a length of 11/2 inch. The spring 24 may have 81/2 left hand winds of 0.039 inch spring wire and have a 0.446 inch outer diameter. The collar may have an inside diameter of about 0.378 inch, an outside diameter of 3/4 inch and an axial length of 3/8 inch.