Abstract:
An improved abrasive disc for use with an angle grinder is disclosed. The grinder is of the type having a threaded spindle. The disc is of the type having: a central portion defining a threaded bore for receiving said spindle; and abrasive material surrounding the central portion. The improvement comprises: a hub defining the threaded bore; an annular element providing the abrasive material, the annular element having a central primary aperture aligned with the threaded bore in the hub to provide access to the bore by said spindle in use; and elements mechanically securing the hub to the annular element, for co-rotation. Apparatus and methods for producing discs are also disclosed.

Description:
FIELD OF THE INVENTION 
     The present invention relates to the field of abrasives. 
     BACKGROUND OF THE INVENTION 
     Abrasive discs for grinders are well known. Such discs ubiquitously include an annular abrasive element. Often, the grinder has a rotating threaded spindle, and the abrasive element is secured to the spindle by a nut. Alternatively, the abrasive element can be manufactured with an attached nut. Discs of this type are relatively convenient to replace, and thus, are relatively popular, notwithstanding that attaching a nut to an abrasive element in a manner that can withstand the very high rotation speeds associated with grinding operations can add substantial costs to manufacture. 
     SUMMARY OF THE INVENTION 
     An improved abrasive disc for use with an angle grinder forms one aspect of the invention. The grinder is of the type having a threaded spindle. The disc is of the type having: a central portion defining a threaded bore for receiving said spindle; and abrasive material surrounding the central portion. The improvement comprises: a hub defining the threaded bore; an annular element providing the abrasive material, the annular element having a central primary aperture aligned with the threaded bore in the hub to provide access to the bore by said spindle in use; and elements mechanically securing the hub to the annular element, for co-rotation. 
     According to another aspect of the invention, the elements can extend through the annular element to the hub. 
     According to another aspect of the invention, the annular element can have two or more secondary apertures spaced about the primary aperture; and the elements can be provided one for each secondary aperture and extend therethrough to the hub. 
     According to another aspect of the invention, a component can be provided, spacing apart the elements and from which the elements extend. 
     According to another aspect of the invention, the hub can have a socket for, and in receipt of, each element. 
     According to other aspects of the invention, the elements can be frictionally engaged by the hub; the elements can be adhesively secured to the hub; the elements can mechanically engage the hub; or the elements can be welded to the hub. 
     According to another aspect of the invention, the elements can have enlarged heads, disposed within the sockets and produced via a deformation operation, which mechanically secure the elements to the hub. 
     According to other aspects of the invention, the elements can be formed integrally with the component; or the elements can be formed separately from each of the hub and the component and defined by rivets. 
     According to another aspect of the invention, the elements can be formed integrally with the hub and extend therefrom through the annular element. 
     According to another aspect of the invention, the annular element can have two or more secondary apertures spaced about the primary aperture; and the elements can be provided one for each secondary aperture and extend therethrough. 
     According to another aspect of the invention, there can be further provided a component to which the elements extend. 
     According to another aspect of the invention, the component can have a socket for, and in receipt of, each element. 
     According to other aspect of the invention, the elements can be frictionally engaged by the component; the elements can be adhesively secured to the component; the elements can mechanically engage the component; or the elements can be welded to the component. 
     According to another aspect of the invention, the elements can have enlarged heads, disposed within the sockets and produced via a deformation operation, which mechanically secure the elements to the component. 
     According to another aspect of the invention, the annular element can have a socket for, and in receipt of, each element. 
     According to other aspects of the invention: the elements can be frictionally engaged by the annular element; the elements can be adhesively secured to the annular element; the elements can mechanically engage the annular element; and the elements can be welded to the annular element. 
     According to another aspect of the invention: the elements can have enlarged heads, disposed in the sockets and produced via a deformation operation, which mechanically secure the elements to the annular element. 
     According to another aspect of the invention: the annular element can have two or more secondary apertures spaced about the primary aperture; the elements can be provided one for each secondary aperture and extend therethrough; and the elements can be defined by rivets. 
     According to another aspect of the invention: the elements can be pins and, in the event that the disc binds in use, the pins can break, to permit the spindle to rotate freely of the annular element. 
     A method for producing an abrasive disc for use with an angle grinder forms another aspect of the invention. The grinder is of the type having a threaded spindle. The disc is of the type having: a central portion defining a threaded bore for receiving said spindle; and abrasive material surrounding the central portion. The method comprises: providing an annular element providing the abrasive material, the annular element having a central primary aperture and two or more secondary apertures spaced about the primary aperture; providing a hub defining the threaded bore; providing a pin for each secondary aperture; fitting each pin through the secondary aperture for which it is provided; and providing for the hub to be secured to the annular element via the pins. 
     According to another aspect of the invention, the pins can be provided as part of a spacer structure; the hub can have a socket for each pin; and each pin can be fitted into the socket which is provided therefor after passage through the secondary aperture for which it is provided. 
     According to another aspect of the invention, the pins can be secured to the hub via a mechanism selected from the group consisting of: deformation of the pin head; adhesive; welding; frictional engagement; and snap-fit. 
     According to another aspect of the invention, the pins can be provided as part of the hub; the annular element can have a socket for each pin; and the pins can be secured to the annular element via a mechanism selected from the group consisting of: deformation of the pin head; adhesive; welding; frictional engagement; and snap-fit. 
     According to another aspect of the invention, the pins can be frangible such that, in the event that the disc binds in use, the pins break, to permit the spindle and hub to rotate freely of the annular element. 
     Other advantages, features and characteristics of the present invention, as well as methods of operation and functions of the related elements of the structure, and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following detailed description and the appended claims with reference to the accompanying drawings, the latter being briefly described hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an abrasive disc according to an exemplary embodiment of the invention in use with an angle grinder; 
         FIG. 2  is an exploded view of  FIG. 1 ; 
         FIG. 3  is a plan view of encircled structure  3  of  FIG. 2 ; 
         FIG. 4  is a view along section  4 - 4  of  FIG. 3 ; 
         FIG. 5  is a pre-assembly view of encircled structure  3  of  FIG. 2 ; 
         FIG. 6  is an assembled view, similar to  FIG. 4 , of the structure of  FIG. 5 ; 
         FIG. 7  is a view, similar to  FIG. 5 , of another exemplary embodiment; 
         FIG. 8  is a view, similar to  FIG. 4 , of another exemplary embodiment; 
         FIG. 9  is a view, similar to  FIG. 4 , of another exemplary embodiment; 
         FIG. 9.1  is an enlarged view of a portion of the structure of  FIG. 9 ; 
         FIG. 10  is a view, similar to  FIG. 4 , of another exemplary embodiment; 
         FIG. 10.1  is a detail view of encircled area  10 . 1  of  FIG. 10 ; 
         FIG. 11  is a view, similar to  FIG. 4 , of another exemplary embodiment; 
         FIG. 12  is a view, similar to  FIG. 4 , of another exemplary embodiment; 
         FIG. 12.1  is a view, similar to  FIG. 4 , of another exemplary embodiment; 
       FIG.  12 . 1 . 1 . is a perspective view of a portion of the structure shown in sectional view in  FIG. 12.1   
         FIG. 13  is a view, similar to  FIG. 4 , of another exemplary embodiment; 
         FIG. 13.1  is a detail view of encircled area  13 . 1  in  FIG. 13 ; 
         FIG. 13.2  is a perspective view of a portion of the structure shown in sectional view in  FIG. 13   
         FIG. 14  is a view, similar to  FIG. 4 , of another exemplary embodiment; 
         FIG. 15  is a perspective view of an abrasive disc according to another exemplary embodiment; 
         FIG. 16  is a pre-assembly view of the structure of  FIG. 15 ; 
         FIG. 17  is a plan view of the structure of  FIG. 15 ; 
         FIG. 18  is a view along section  18 - 18  of  FIG. 17 ; 
         FIG. 19  is a plan view of encircled structure  19  of  FIG. 16 ; 
         FIG. 20  is a view along section  20 - 20  of  FIG. 19 ; 
         FIG. 21  is a plan view of encircled structure  21  of  FIG. 16 ; 
         FIG. 22  is a view along section  22 - 22  of  FIG. 21 ; 
         FIG. 23  is a view, similar to  FIG. 4 , of another exemplary embodiment; and 
         FIG. 24  is a view of encircled area  24  in  FIG. 23 . 
     
    
    
     DETAILED DESCRIPTION 
     As indicated above,  FIG. 1  shows an abrasive disc  20  according to an exemplary embodiment of the present invention in use with an angle grinder  21 . As will be readily understood by persons of ordinary skill in the art, this disc  20  is of the well-known threaded type. The grinder  21  forms no part of the invention and is illustrated for ease of reference only. As best indicated in exploded  FIG. 2 , in common with other discs of this class, the illustrated disc  20  has a central portion  22  defining a threaded bore  24  for receiving the spindle  23  of the grinder  21  and has abrasive material  26  surrounding the central portion  22 . However, in contradistinction to other devices of the subject class, this disc  20  is characterized in the presence of a hub  28  which defines the threaded bore  24 , a spacer structure  30  and an annular element  32  which provides the abrasive material  26 , which together form the disc  20 , and as further described hereinafter. 
       FIG. 5  shows the various components  28 , 30 , 32  which ultimately form the disc  20  in a pre-assembled state, and will be initially referenced, for clarity. Hub  28  is an injection-molded plastic piece and has formed therein a pair of opposed indents  45  and four sockets  47  surrounding the threaded bore  24 . The annular element  32  providing the abrasive material  26  will be seen to include a central primary aperture  34  and two or more, specifically, four, secondary apertures  36  spaced about the primary aperture  34 . The spacer structure  30  includes a pin element  40  for each secondary aperture  36 . The spacer structure  30  also includes an annular component  38  spacing apart the pins  40  and from which the pins  40  rigidly extend. 
     The various pieces  28 ,  30 ,  32  are shown in an assembled state in  FIG. 6 . In this state, each pin element  40  extends through the secondary aperture  36  for which it is provided into a respective socket  47  and the central primary aperture  34  is aligned with the threaded bore  24  in hub  28 . 
     In order to produce the disc  20  from the structure shown in  FIG. 6 , one must merely deform the heads of the pins, through a staking process; the deformed heads are shown in the cross-section view of  FIG. 4 . The deformed heads  100  mechanically engage sockets  47 . This secures the annular component  38  in spaced relation to the hub  28 , with the abrasive element  32  sandwiched therebetween. The aligned central aperture  34  providing egress for the spindle  23  to the threaded bore  24  in use. 
     An advantage associated with this structure is the ease by which it is manufactured. The hubs  28  and spacer structures  30  can routinely be obtained by persons of ordinary skill in the art of injection molding. For both pieces, a suitable mold material is, for example, Nylon 66. The annular element  32  providing the abrasive material  26  is routinely obtainable by persons of ordinary skill in abrasives manufacture. Indeed, but for secondary apertures  36 , annular element  32  itself can be substantially identical to abrasive structures commonly available in the marketplace. In annular elements wherein the central portion is fibreglass, secondary apertures  36  can be easily obtained through a simple punching operation. In annular elements wherein abrasive material composes the bulk of the part, apertures  36  will normally need to be produced when the central aperture  34  is produced, but again, this is a matter of routine to persons of ordinary skill. 
     Another advantage associated with the illustrated structure is the indents  45  which are provided on the hub  28 , which enable to disc  20  to be finger manipulated without handling the abrasive  26 . The openings in socket  47 , however, also admit the use of a conventional spanner wrench (not shown), if additional force is necessary. 
     Various changes in, inter alia, size and shape of parts may be made. For example, the elements need not be round pins, but could take other cross-sectional shapes. 
     By way of further example,  FIG. 7  shows a structure with a modified annular element  32 ′ wherein the apertures  36  are contiguous with, rather than separate from, central aperture  34 . 
       FIG. 8 , shows a modified version of the disc  20 A, wherein another modified annular element  32 A is provided, which is substantially planar, and modified versions of the hub  28 A and spacer structure  30 A are provided which have complementary geometries. 
       FIG. 9  shows a further modified spacer structure  30 B. This structure  30 B is also molded out of plastic, and voids  100  are formed, so as to provide thin walled break zones  102  in the modified pins  40 B. An advantage associated with this structure is that, in the event that the disc binds in use, i.e. “grips rather than rips” the material being abraded, the pins  40 B break, to permit the spindle of the grinder to rotate freely of the annular element  30 . This can avoid wrist and other injuries that might otherwise result. In order to provide this functionality, it is important to ensure that the hub does not frictionally grip the annular element with substantial force. In  FIG. 9 , this is accommodated by configuring the hub to engage against the spacer structure, as indicated at areas X, but in applications wherein a spacer structure is not provided, this can equally be accommodated by arranging the hub to bear against the locating shoulder typically found on the grinder spindle, which shoulder is indicated as part Y in  FIG. 2 . The plastic chosen for molding should also be such that it tends to shear in the break zones, rather than simply deform; again, this is a matter of routine to persons of ordinary skill. 
     FIGS.  10  and  10 . 1  show a yet further modified disc  20 C in cross-section. In this structure, modified pins  40 C are provided, which mechanically engage modified sockets  47 C without the need for a staking operation. This structure can simply be forced together. The between the pins  40 C and sockets  47 C is of the well-known technology employed in “zip ties” and the like. 
       FIG. 11  shows a yet further modified disc  20 D in cross-section. In this structure, the pins are defined by rivets  40 D, i.e. provided as discrete elements, separate from the other components, and deformed to provide for securement. 
       FIG. 12  shows a yet further modified disc  20 E in cross-section. In this structure, the pins  40 E engage the sockets  47 E in press-fit, frictionally-engaged relation. Welding techniques, such as sonic welding, can also be employed, to strengthen the bond. 
       FIGS. 12.1  and  12 . 1 . 1  show a yet further modified disc  20 F in cross-section. In this structure, two modified resilient pins  40 F are provided, which engage in the socket  37  in snap-fit, mechanically-engaged relation. 
       FIGS. 13 ,  13 . 1  and  13 . 2  show a yet further modified disc  20 G in cross-section. In this disc  20 G, the pins  40 G are provided on modified hub  28 G, and engage in snap-fit relation within sockets  47 G in modified annular element  32 G. 
       FIG. 14  shows a yet further modified disc  20 H in cross-section. In this disc  20 H, the pins  40 H are formed integrally with modified hub  28 H, and are deformed by a swaging operation in sockets  40 H provided within modified annular element  32 H. 
       FIGS. 15-22  detail a yet further modified disc  201 . In this disc  201 , pins  401  extend from modified spacer structure  301 , through primary aperture  34  in sockets  471  formed in modified hub  281  and are secured together by glue (not shown). 
       FIGS. 23 and 24  show a yet further modified disc  20 J. This disc  20 J is substantially similar to disc  20 , but adhesive  70  is provided to secure the various elements together. 
     Whereas only a finite number of exemplary embodiments are herein shown and described, the various embodiments presented above are merely examples and are in no way meant to limit the scope of this invention. Further variations of the innovations described herein will be apparent to persons of ordinary skill in the art, such variations being within the intended scope of the present application. In particular, features from one or more of the above-described embodiments may be selected to create alternative embodiments comprised of a sub-combination of features which may not be explicitly described above. In addition, features from one or more of the above-described embodiments may be selected and combined to create alternative embodiments comprised of a combination of features which may not be explicitly described above. Features suitable for such combinations and sub-combinations would be readily apparent to persons skilled in the art upon review of the present application as a whole. The subject matter described herein and in the recited claims intends to cover and embrace all suitable changes in technology and the invention. 
     Further, without intending to be limiting, it should be specifically understood that the invention can be incorporated into any grinding disc that normally runs with a ⅞ arbor hole on a ⅝-11 threaded spindle, and can be used with discs of varies thicknesses and types, including plastic, fibreglass and possibly even bonded. 
     Accordingly, the invention should be understood as limited only by the claims appended hereto, purposively construed.