This invention relates to abrasive apparatus and more particularly relates to abrasive apparatus in which an abrasive disc or wheel can be easily and quickly coupled to the abrasive apparatus and can be easily and quickly removed from the abrasive apparatus. The invention also relates to the abrasive disc or wheel and to the combination of the abrasive disc or wheel and the abrasive apparatus.
Abrasive apparatus is used to remove material from a workpiece so as to provide desired dimensions in the workpiece. Abrasive apparatus is also used to polish and smooth surfaces of the workpiece. One type of apparatus employs a support plate which rotates an abrasive disc or wheel. The apparatus includes an arbor and an internally threaded nut which is screwed on the arbor to hold the disc or wheel in fixed position ont he arbor. When the disc or wheel is screwed on the arbor, the disc or wheel is applied against the workpiece to abrade, polish or smooth a surface of the workpiece.
During the time that the abrasive disc is being rotated and is being applied against the workpiece, the force of the workpiece against the disc causes the disc to become tightened against the holder. The tightening is sometimes so great that the disc cannot be removed from the holder, even when a great force is applied to the disc to loosen the disc from the holder. Since discs wear relatively quickly, an inability to remove a worn disc from the holder is aggravating and time consuming and inefficient from a cost standpoint.
A considerable amount of time, and a substantial investment of money, have been expended in attempting to solve the problems specified in the previous paragraph. In spite of such efforts, such problems still persist. The abrasive disc still cannot be easily released after they have been operated against the workpiece. Furthermore, the nut holding the disc on the arbor often becomes lost or misplaced when the disc is removed from the arbor.
This invention provides a holder and an abrasive disc which eliminate the problems specified above. The holder and the abrasive disc are constructed to provide a quick and easy release of the disc from the holder when a force is applied to the disc to rotate the disc in the release direction after the disc has been forced against the workpiece during operation.
In one embodiment of the invention, an arbor is threaded in a first direction. An adaptor bushing is disposed on the arbor and is externally threaded in a second direction opposite to the first direction. A reinforcing plate is rotatable on the adaptor bushing in the second direction. A detent arrangement may be provided on the adaptor bushing and the reinforcing plate to limit the movement of the reinforcing plate relative to the adaptor bushing.
An abrasive wheel or disc is provided with first and second opposite surfaces and abrasive particles are provided throughout the disc. A nut is disposed in a bore in the disc and is threaded for rotation on the arbor in the first direction. When the disc or wheel engages the reinforcing plate, continued rotation of the disc in the first direction causes the reinforcing plate to rotate in the second direction and to press against the disc.
When the disc is to be released, it is rotated in the second direction, thereby producing a movement of the reinforcing plate in the first direction to release the disc from the reinforcing plate. A yieldable detent relationship may be provided between the reinforcing plate and the disc to facilitate a coupling action between them in accordance with rotation of the disc in the first direction and to facilitate a releasing action on the disc in accordance with the rotation of the disc in the second direction.
In the drawings:
FIG. 1 is an exploded perspective view, with certain parts broken away, of one embodiment of a holder and an abrasive disc or wheel constituting one embodiment of the invention;
FIG. 2 is a sectional view of the embodiment of the abrasive holder and disc of FIG. 1 in a partially assembled relationship;
FIG. 3 is a sectional view similar to that of FIG. 2 and shows the embodiment of the holder and the abrasive disc in a partially assembled relationship but one more advanced than that shown in FIG. 2;
FIG. 4 is a sectional view similar to that shown in FIGS. 1 and 2 but shows the embodiment of the holder and the abrasive disc in an assembled relationship;
FIG. 5 is a sectional view similar to that shown in FIGS. 1, 2 and 3 but shows the embodiment of the holder and the disc in a relationship more closely coupled than that shown in FIG. 4 as a result of the force exerted on the disc by a workpiece;
FIG. 6 is a sectional view of another embodiment of the holder and the abrasive disc shown in FIGS. 1 through 5;
FIG. 7 is a sectional view of a further embodiment of the holder and the abrasive disc;
FIG. 8 is a sectional view of still another embodiment of the holder and the abrasive disc; and
FIG. 9 is a sectional view of a still further embodiment of the holder and the abrasive disc.
In one embodiment of the invention, a holder generally indicated at 10 is adapted to be rotated by a motor 11. The holder includes an arbor 12 externally threaded as at 14. An adaptor bushing 16 is provided with a bore internally threaded as at 18 and is externally threaded as at 20. The threads 18 may be right hand threads compatible with the threads on the arbor 12, and the threads 20 may be left hand threads.
A reinforcing plate 24 is provided with a bore internally threaded as at 26 for compatibility with the threads 20 on the bushing 16. The reinforcing plate 24 is indented at a position near the internal threads 26 and is provided with an annular cavity 30. Detent means such as a yieldable member 32 is retained in the cavity 30 and is adapted to be compressed upon the exertion of a force against the member.
A disc generally indicated at 36 is operatively associated with the holder 10. The disc 36 is made from a stiff material such as phenolic resin. Abrasive particles 38 made from a suitable material such a silicon carbide are dispersed throughout the phenolic resin. The disc may be cold formed and then heated until the material sets in the position where its center area is depressed as shown in FIGS. 2 through 5. The disc 36 is provided with first and second spaced but parallel surfaces 40 and 42. Detent means such as a suitable projection 44 may be annularly provided on the surface 42 at a position corresponding to that of the yieldable member 32 on the reinforcing plate 24.
The disc or wheel 36 is provided with a central bore 46 and a nut 48 internally threaded as at 50 is disposed in the bore 46. The nut 48 abuts the bore 46 and the surface 40 adjacent the bore 46 and is suitably adhered to these surfaces. The nut 48 has a barrel portion 49 which preferably does not extend beyond the surface 42 on the disc 36. As shown in FIGS. 2 through 5, the barrel portion 49 of the nut 48 preferably terminates at a position within the bore 46 because the barrel portion of the nut has a length less than the thickness of the disc 36. The internal threads on the nut 48 are compatible with the threads on the arbor 12.
FIG. 2 illustrates the disposition of the disc 36 on the arbor 12 before the disc contacts the reinforcing plate 24. As the disc continues to move in a first direction (upwardly in FIG. 2) along the arbor 12, it engages the reinforcing plate 24 as shown in FIG. 3. This engagement occurs between the projection 44 on the disc 36 and the yieldable member 32 on the reinforcing plate 24. When this engagement occurs, any further rotation of the disc 36 causes the reinforcing plate 24 to move downwardly in FIG. 2 because of the left hand threads provided on the reinforcing plate. The holder 10 and the disc 36 accordingly assume the relative positions shown in FIG. 4. This is the position which the disc 36 has relative to the reinforcing plate 24 when the disc is manually screwed on the arbor.
The apparatus shown in FIGS. 1 through 4 is ready to be applied to a workpiece (not shown) when the holder 10 and the abrasive disc 36 have the relative positions shown in FIG. 4. The force exerted by the workpiece against the disc 36 during the rotation of the disc and during the application of the disc against the workpiece tends to cause the holder 10 and the disc 36 to assume the relative positions shown in FIG. 5. As will be seen in FIG. 5, the holder 10 and the disc 36 have an even closer coupling than that shown in FIG. 4.
When the disc 36 becomes worn, it may be desired to replace the worn disc with an unused unit. To do so, a force is applied to the worn disc 36 on the arbor 10 to move the disc away from the reinforcing plate 24 because of the left hand threads on the reinforcing plate. This movement to disassociate the disc 36 from the arbor 10 is facilitated by the counter movements of the disc and the reinforcing plate 24. As a result, it is considerably easier to uncouple the disc 36 from the holder 10 than in the discs and holders of the prior art.
It will be appreciated that the positions of the projection 44 and the yieldable member 32 can be reversed. This is shown in FIG. 8 by a projection 62 on the reinforcing plate and a yieldable member 64 on the disc. The yieldable member 32 can also be replaced by a spring 60 (FIG. 6), such as a helical spring, which can be provided with more than one turn. An undulating spring 70 (FIG. 7) can also be used.
It will also be appreciated that other relationships than left hand threads can be provided on the reinforcing plate 24 and the bushing 24 to facilitate the clamping between the disc 36 and the reinforcing plate during the operation of the apparatus described above and to facilitate the subsequent release of the disc from the reinforcing plate. For example, the threads on the various members can be partial threads instead of full threads.
FIG. 8 illustrates an arrangement for insuring that the reinforcing plate 24 is retained on the arbor 10. The embodiment shown in FIG. 8 includes a flange 80 on the bushing 16. The flange 80 defines a detent arrangement with a bracing member 82 suitably attached as by a bolt 84 to the reinforcing plate 24. The detent arrangement limits the movement of the reinforcing plate 24 so as to prevent the reinforcing plate from being removed from the arbor 10. In the embodiment shown in FIG. 8, a yieldable member 86 is disposed in a socket 88 on the disc 36 and a projection 89 is disposed on the reinforcing plate 24.
FIG. 9 illustrates another arrangement for inhibiting the removal of the reinforcing plate 24 from the arbor 12. The arrangement in FIG. 9 includes a flange 90 on a member 92 which is attached to the reinforcing plate 24 as by a bolt 94. The arrangement further includes a shoulder 96 on the bushing 16. The flange 90 and the shoulder 96 define a detent relationship which limits the movement of the reinforcing plate in a downward direction in FIG. 9.
Although this invention has been disclosed and illustrated with reference to particular embodiments, the principles involved are susceptible for use in numerous other embodiments which will be apparent to persons skilled in the art. The invention is, therefore, to be limited only as indicated by the scope of the appended claims.