Patent Publication Number: US-4839998-A

Title: Abrasive apparatus

Description:
This is a continuation of application Ser. No. 819,546 filed Jan. 16, 1986, now abandoned. 
    
    
     This invention relates to an abrasive article and more particularly to an abrasive article which employs a rotary abrasive disc to abrade or polish a workpiece. The invention particularly relates to an abrasive disc which is firmly coupled to a rotary drive member to abrade or polish the workpiece but which is easily decoupled from the drive member after it has been used. 
     Abrasive articles have been in existence for a considerable number of years to engage a workpiece for polishing the workpiece. One type of abrasive article includes a rotary drive member or holder which has a peripherally disposed housing portion defining a socket or cavity. Detent portions are disposed in the socket in raised relationship to the socket and are sloped. The drive member also has a threaded shank extending axially through the center of the socket. A recessed portion is provided in the shaft at a position corresponding to the detent portions in the socket. 
     The type of abrasive article discussed in the previous paragraph includes an abrasive disc which includes a fastener made from a plastic material. The fastener has detent portions coupled to the detent portions in the socket of the drive member so as to be driven by the drive member when the drive member is rotated. When the drive member is rotated, the detent portions on the disc, being wedge-shaped in cross-section, become compressed into the recess in the shaft by the sloping detent portions on the drive member. This causes the disc to be driven by the drive member and simultaneously prevented from axial displacement from the drive member. As a result, a backing sheet coupled to the fastener and having abrasive particles on one surface abrades or polishes a workpiece when it engages the workpiece. 
     The type of abrasive article discussed in the previous paragraphs is disclosed in U.S. Pat. No. Re. 26,552 reissued to Aleck Block and Joseph W. Purcell, Jr. on Mar. 25, 1969, for an &#34;Abrasive Device&#34; and assigned of record to Merit Products, Inc. This type of abrasive article has been effective in a wide variety of applications. However, it has had difficulties in providing an effective coupling between the drive member and the disc under certain circumstances, particularly when the disc has been applied with low torque against the workpiece. This has resulted from the fact that the detent portions on the disc have been insufficiently compressed into the recess on the shaft by the detent portions on the drive member to provide a positive engagement between the drive member and the disc. Another problem has resulted occasionally with the abrasive article of the prior art because the disc has not been able to be decoupled from the drive member after the disc has been applied against a workpiece. This has particularly occurred when the disc has been applied with a great force and torque against the workpiece, thus generating temperatures sufficiently high to distort the coupling member. 
     The present invention provides an abrasive article which overcomes the above disadvantages. The abrasive article includes a rotary drive member and a disc which is positively coupled to the drive member regardless of the force with which the disc is applied against a workpiece. The abrasive article of this invention is also advantageous because the disc can be easily decoupled from the drive member after the disc has been applied against the workpiece. This decoupling can be easily provided even when the disc has been applied with a great force against the workpiece. 
     In one embodiment of the invention as disclosed and claimed in this application, an abrasive disc includes a sheet having abrasive particles on one surface of the sheet. A fastener has a flat flange portion which is adhered to the abrasive sheet. Coupling portions on the fastener extend in a transverse direction from the flange portion and legs extend from the free ends of the coupling portion at an angle to the coupling portions. This angle may be between 20° and 75°. The fastener is formed from sheet metal which includes the flange portion, the coupling portions and the legs being formed from the portion of the sheet interior to the flange portion. The fastener is constructed to be coupled to a drive member. 
     The drive member includes a housing having a socket. Detent portions are raised in the socket and are provided with detent surfaces. A shaft extends through the center of the socket.and has a recess. In the coupled relationship of the disc and the drive member, the coupling portions on the fastener abut the detent surfaces so that the detent surfaces stop the coupling portions from rotating relative to the drive member. In one embodiment, the detents stop the coupling portions by a square abutment of the two parts, and in another embodiment, this stopping action is substantially tangential. The legs are disposed in the recess in the shaft so that the legs exert an axial force on the shaft and thus prevent axial displacement of the disc relative to the drive member. 
    
    
     In the drawings: 
     FIG. 1 is an exploded perspective view of a drive member and an abrasive disc constituting one embodiment of the invention; 
     FIG. 2 is a fragmentary sectional view of the drive member shown in FIG. 1 and is taken substantially on the line 2--2 of FIG. 1; 
     FIG. 3 is a fragmentary sectional view of the disc shown in FIG. 1 and is taken substantially on the line 3--3 of FIG. 1; 
     FIG. 4 is another fragmentary sectional view of the disc and is taken substantially on the line 4--4 of FIG. 3; 
     FIG. 5 is a further fragmentary sectional view of the disc and is taken substantially on the line 5--5 of FIG. 3; 
     FIG. 6 is an elevational view, in section, of the drive member and the disc in an assembled relationship; 
     FIG. 7 is a fragmentary sectional view of the drive member and the disc and is taken substantially on the line 7--7 of FIG. 6; 
     FIG. 8 is also a fragmentary sectional view of the drive member and the disc and is taken substantially on the line 8--8 of FIG. 6; 
     FIG. 9 is an elevational view of the drive member and the disc with the drive member and the disc in a partially detached relationship; 
     FIG. 10 is an exploded perspective view similar to that shown in FIG. 1 and illustrates another embodiment of a drive member and another embodiment of a disc; 
     FIG. 11 is a fragmentary sectional view of the embodiment of the drive member shown in FIG. 10 and is taken substantially on the line 11--11 of FIG. 10; 
     FIG. 12 is a fragmentary sectional view of the disc shown in FIG. 10 and is taken substantially on the line 12--12 of FIG. 10; 
     FIG. 13 is an elevational view, in section, of the drive member and the disc of FIGS. 10-12 in an assembled relationship; and 
     FIG. 14 is an enlarged fragmentary elevational view, partially in section, of the drive member and the disc of FIGS. 10-13 with the drive member and the disc in a partially detached relationship. 
    
    
     In the embodiment of the invention shown in FIGS. 1 through 9, a drive member generally indicated at 10 and a disc generally indicated at 12 are provided. The drive menber 10 is known in the art. For example, a suitable drive member is shown in FIGS. 6 and 7 of U.S. Pat. No. Re. 26,552 issued on Mar. 25, 1969, to Aleck Block and Joseph W. Purcell, Jr., for an &#34;Abrasive Device&#34; and assigned of record to Merit Products, Inc., of Los Angeles, Calif. 
     The drive member 10 includes a housing 14 and a drive shaft 16 extending through the housing in axial relationship with the housing and having an annular recess 17 (FIG. 9). The housing 14 is shaped to define a socket 18. The housing 14 may be die cast from a suitable material such as zinc. A pad 19 made from a suitable material such as rubber surrounds the housing 14 to provide a support for the disc 10. 
     Detent portions 20 are raised from the socket 18 at spaced positions around the periphery of the socket. The detent portions 20 are disposed at equally spaced annular portions around the periphery of the socket 18. Six (6) detent portions 20 are shown in the drawings. However, it will be appreciated that any convenient number of detent portions may be provided. Each of the detent portions 20 progresses radially inwardly toward the center of the drive member 10 with progressive annular positions on the drive member so as to define detent surfaces 22. The detent surfaces extend in a linear direction having radial and tangential components. 
     The disc 12 includes a sheet 24 having strong properties so that it is capable of bending but not easily. Abrasive particles 26 are adhered to one surface of the sheet A reinforcing sheet of similar flexibility may be laminated to the sheet (24) and thus interposed between the fastener and the abrasive-coated sheet (24). Polyvinyl chloride glue may be used to secure this lamination. A fastener generally indicated at 28 may be adhered to the opposite surface of the sheet 24 or to the exposed surface of the reinforcing sheet. The fastener 28 may be made from a suitable metal such as beryllium copper or steel. The fastener 28 includes a flat flange portion 30 which is adhered to the second surface of the sheet 24 by a catalyzed epoxy and cured at a temperature of 250° F. for a period of two hours. 
     A plurality of coupling portions 32 extend integrally from the flange portion 30 in a transverse, preferably a substantially perpendicular, relationship to the flange portion. Each of the coupling portions 32 is disposed at an angle to abut an associated one of the detent surfaces 22 in a flush relationship with the detent surface when the disc has been coupled to the drive member and has been applied against a workpiece. Three (3) coupling portions 32 are shown in the drawings for engagement with the detent portions 20. This facilitates the ease of coupling the disc 10 to the drive member 12. Only three (3) coupling portions 22 are required because the coupling portions are quite strong. However, when six (6) detent portions 20 are provided, as many as six (6) coupling portions may also be provided. 
     The coupling portions 32 extend in a linear direction having radial and tangential components. Projected extensions of the coupling portions 32 define a polygon, preferably with sides of substantially equal length. The linear direction of the coupling portions 32 preferably having a greater tangential component than a radial component. 
     A leg 34 extends from the outer end of each of the coupling portions 32 at an angle to the associated coupling portion. This angle may be between 20° and 75°. The characteristics of each of the legs 34 cause the leg to extend into the annular recess 17 in the shaft 16 and to engage the shaft 16 at the lower end of the recess as indicated at 36 in FIG. 6. As a result, the force exerted by the shaft 16 on the recess 17 is in an axial direction in FIG. 6. 
     The legs 34 extend in a linear direction having radial and tangential components. Extended projections of the legs 34 define a polygon, preferably with sides of substantially equal lengths. The linear direction of the legs 32 preferably has a greater tangential component from a radial component. 
     The disc 12 may be coupled to the drive member 10 by snapping the legs 34 of the fastener 28 into the recess 17 in the shaft 16. The disc 12 may then be rotated manually until the coupling portions 32 abut the detent surfaces 22. The drive member 10 and the disc 12 are then rotated as by a motor (not shown) and the disc 12 is applied against a workpiece (not shown). The abrasive particles 26 on the surface of the sheet 24 cause the workpiece to become abraded or polished. 
     The disc 12 is retained firmly on the drive member 10 and is prevented from rotation relative to the drive member as the disc is applied against the workpiece. This is true regardless of the magnitude of the force exerted by the disc 12 against the workpiece. The stoppage of relative rotation results from the working torque on the disc driving the coupling portions 32 to a stop upon their abutment against the detent portions 20. Axial separation of the disc from the drive member is prevented in part by the radial confinement of the coupling portions 32 by the detent portions 20, thus holding the legs 34 in position in the shaft recess 17. This prevents axial displacement of the disc by the interference contact of the axial side of the recess 17 with the tips of the legs 34. These forces retain the disc 12 on the drive member 10 without any compression or displacement of the coupling portions 32 or the legs 34. 
     The disc 12 can be easily removed from the drive member 10 when it has become worn after being applied to a workpiece. This results from the fact that the coupling portions 32 and the legs 34 are not displaced or resiliently sprung in any way regardless of the force applied by the workpiece against the disc 12. This is important because each disc 12 has a relatively short life when it is applied to the workpiece. 
     To remove the disc 12 from the drive member 10, the disc is first rotated manually in a counterclockwise direction in the drawings. This causes a considerable spacing to be produced between the coupling portions 32 and the wall defining the socket 18 in the drive member 10, as may be seen at 40 in FIG. 2. The disc 12 is then lifted away from the drive member 10. The partial detachment of the disc 12 from the drive member 10 is schematically shown in FIG. 9. The detachment of the disc 12 from the drive member 10 may be facilitated by the force exerted by the shaft 16 on the legs 34 as the disc is removed from the drive member. This force is in a direction to permit arching the coupling portions 32 as the legs 34 cam radially outwardly over the edge of the groove 17. This arching facilitates the decoupling of the disc 12 from the drive member 10. 
     The fastener 28 can be formed from a sheet of material as by stamping. The coupling portions 32 and the legs 34 can be formed from the portion of the sheet interior to the flange portion 30. In this way, the amount of metal required to form each fasterner 28 can be minimized. 
     FIGS. 10 through 14 illustrate a second embodiment of the invention. This embodiment includes a drive member generally indicated at 100 and a disc generally indicated at 102. The drive member 100 includes a detent portion 104 with a detent surface 106. The detent portion 104 has a detent surface 106 which extends in a substantially radial direction. The drive member 100 also includes a shaft 108 with a recess 110. 
     The disc 102 includes a fastener generally indicated at 112. The fastener 112 has a flange portion 113 and coupling portions 114 which extend in a transverse, preferably a substantially perpendicular, direction from the flange portion. Legs 116 extend from the free ends of the coupling portion 114 at an angle to the coupling members. As a result, when the disc 102 is coupled to the drive member 100, the legs 116 engage the recess 110 in the shaft 108 in a manner similar to that discussed above for the embodiment shown in FIGS. 1 through 9. The disc 102 may then be rotated manually in a clockwise direction relative to the drive member 100. This causes the coupling portions 114 to abut the detent surfaces 106 in a substantially perpendicular relationship to the detent surfaces. This force accordingly extends in a direction tangential to the peripheral surface of the shaft 108. 
     The tangential force discussed in the previous paragraph and the force exerted in the axial direction by the shaft 108 against the legs 116 retain the disc 102 in firmly coupled relationship to the drive member 100 when the disc is applied against the workpiece. The coupling between the disc 102 and the drive member 100 is effective even when the disc is applied with a relatively low torque against a work surface. However, the disc 102 can be easily removed from the drive member 100 even after the disc has been applied against the workpiece with a great force. 
     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.