Patent Document

CLAIM OF PROVISIONAL APPLICATION RIGHTS 
     This application claims the benefit of U.S. Provisional Patent Application No. 60/073,304, filed on Jan. 28, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to improvements in polishing discs and the method of making them, and in particular to a polishing disc cut from sheet abrasive material and adhered to an inexpensively produced plastic hub that locks onto a rotatable arbor. 
     2. Description of the Prior Art 
     In the field of dentistry it is necessary to contour, finish and polish restorative dental materials once they have been placed into or onto a tooth so that the restorative materials blend to the contour of the tooth with a smooth transition between the material and tooth structure. It is imperative that the restorative materials be highly polished to prevent plaque build up which leads to other complications. 
     The most common dental restorative materials currently used are composite, amalgam, gold, ceramics, acrylic, and glassionomers. These as well as other polishable materials usually require polishing with a minimum of at least two steps of sequential grits, with most materials requiring three to six steps before achieving satisfactory results. This series of polishings usually requires single-use, disposable discs having a sequence of grit sizes. For this reason, not only must dental polishing discs be inexpensive in terms of material and manufacturability, but to save dentists&#39; time they must also be capable of being very quickly secured to and removed from a driving arbor. Because the dental polishing discs is used inside a patient&#39;s mouth, it must be relatively small, and be rigidly secured to the arbor so it won&#39;t wobble or fly off. 
     Several prior art devices are available for this purpose. Generally they are comprised of grit coated thin discs of paper or plastic or thin rigid discs of abrasive, having a central aperture to receive a screw, pin, shaft or the like, by means of which the disc can be secured to a rotary drive shaft or arbor. With most prior art, the head of the shaft or arbor protrudes from the forward face of the dental polishing disc and clamps to the inner area of the disc by means of a metal or plastic eyelet that may be swaged through the disc. The protrusion of the shaft or arbor beyond the dental polishing disc limits the working area of the disc, and during polishing can inadvertently cause damage to the restorative material, tooth structure, or tissue. 
     U.S. Pats. Nos. 3,858,368 and 4,447,208 disclose a dental polishing disc in which the central hub or the entire polishing head is made of soft rubber. The central hub of such dental polishing discs are formed with a blind, hollow, cylindrically-shaped interior cavity having at least one flattened surface so a head portion of the arbor may be inserted into the cavity thus securing the disc to the arbor. The central hubs of these molded dental polishing discs can either be molded integrally with the polishing disc or molded separately and attached to the disc by means of an adhesive material. Because these dental polishing discs have a blind interior cavity the arbor cannot protrude beyond the dental polishing disc. Thus, dental polishing discs having molded rubber hubs prevent inadvertently damaging restorative material, tooth structure, or tissue. However, the molded central hub or entire polishing head is comparatively expensive, bulky, and can be manufactured only in a limited range of shapes and sizes. Using a blind hole configuration as in these devices, there always exists a rubber filled space between the disc and the arbor which remains flexible thus permitting the dental polishing disc to wobble on the arbor. Furthermore, due to poor engagement between the molded rubber hub and the arbor such dental polishing discs tend to fly off the arbor when polishing with the surface of the disc adjacent to the arbor. 
     BRIEF SUMMARY OF THE INVENTION 
     A primary object of the present invention is to provide a rotary polishing disc and hub which is inexpensive and easy to manufacture. 
     Another object of the present invention is to provide a polishing disc and hub which attach quickly, easily, and removably to the arbor with a rigid secure fit without wobble and without the danger of falling off. 
     A related object of the present invention is to form the hub using an inexpensive plastic extrusion. 
     Another object of the preferred embodiment of the present invention is provide a hub having an interior surface along the entire length of which matches the cross-sectional shape of the arbor insertable thereinto thus providing a tight friction fit to retain the polishing head securely on the arbor free from wobbling. 
     Another corollary object of the preferred embodiment of the present invention is to prevent the polishing head from flying off of the arbor. 
     A related object of an alternate embodiment of the present invention is to provide a hub having several flexible arms which engage an interior surface of a mating, hollow arbor. 
     Another object of the present invention is to adhere the hub to the back face of the abrasive polishing disc so the entire front abrasive surface of the polishing disc is usable for polishing. 
     One more object of the present invention is to improve engagement between the hub and larger diameter or high-friction dental polishing discs cut from sheet abrasive material. 
     Briefly, in one aspect the present invention is a rotary polishing disc adapted for attachment to an end of a rotatable arbor. The rotary polishing disc includes a disc-shaped piece of sheet material having an abrasive material on at least one surface thereof. The rotary polishing disc also includes a hub that is juxtaposed with and fixed to the disc-shaped piece of sheet material. The hub has a longitudinal axis that is oriented substantially perpendicular to a surface of the disc-shaped piece of sheet material with which the hub is juxtaposed. 
     In one embodiment of this aspect of the present invention the hub is cylindrically-shaped with the longitudinal axis extending through a hollow interior of the hub. The hollow interior of this hub is formed with a cross-sectional shape that is adapted to mate with and to receive a projecting end of the rotatable arbor completely thereinto so the projecting end becomes juxtaposed with the disc-shaped piece of sheet material. 
     In another embodiment of this aspect of the present invention, the hub is elongated with a first end that is juxtaposed with and fixed to the surface of the disc-shaped piece of sheet material. This second embodiment of the hub also has a second end that projects away from the disc-shaped piece of sheet material. The second end of this hub is pierced by a slot to establish at least one flexible arm that has an outwardly projecting tip at the end thereof furthest from the disc-shaped piece of sheet material. For this second embodiment of the hub, the flexible arm and tip are shaped to enter into, mate with and engage an interior surface of a socketed end of the rotatable arbor. 
     To fix the disc-shaped piece of sheet material more securely to the hub, the disc-shaped piece of sheet material of either of the preceding embodiments may be pierced by a central aperture through which passes a retainer plug. The retainer plug has a flat cap formed at an end thereof which is juxtaposed with a surface of the disc-shaped piece of sheet material furthest from the hub. For the first embodiment of the hub described above, a second end of the retainer plug, furthest from the flat cap, enters into and becomes frictionally engaged with the hollow interior of the hub. For the second embodiment of the hub described above, the second end of the retainer plug enters into and becomes frictionally engaged with a cavity formed into the first end of the hub adjacent to the central aperture. 
     In another aspect, the present invention includes a improved arbor which, in a first configuration, has a projecting end that is adapted to receive and mate with a hollow interior surface of a hub of a rotary polishing disc. This first improved arbor configuration includes a barb protruding from an exterior surface of the arbor that is adapted to spear the hub when the hollow interior of the hub is disposed on the arbor. A second improved arbor configuration includes a hollow socket formed at one end of the arbor. The hollow socket has an interior surface which is shaped to receive and to mate with the flexible arm and tip at one end of an elongated hub. 
     An advantage of the present invention is simpler manufacturing and lower manufacturing cost for enhanced performance dental polishing discs. 
    
    
     The intended use for the present invention is dental grinding and polishing discs. Accordingly, the present invention will be specifically described with reference to that field by way of illustration. However, the present invention is not limited to use in that field, and appears useful in other applications that require a small rotary polishing disc. These and other features, objects and advantages will be understood or apparent to those of ordinary skill in the art from the following detailed description of the preferred embodiment as illustrated in the various drawing figures. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partially-sectioned elevational view showing one embodiment of a rotary polishing disc having a disc-shaped piece of sheet material fixed to an extruded hub that is aligned for interconnection with a mating arbor which may include projecting barbs; 
     FIG. 1A is a partial perspective view illustrating how disc-shaped pieces depicted in FIG. 1 are cut, stamped or punched from a thin flexible sheet of material having an abrasive coating on one or both sides; 
     FIG. 1B is a partial perspective view illustrating how hubs of the embodiment depicted FIG. 1 are cut from an extruded tube; 
     FIG. 2 is a partially-sectioned elevational view showing another embodiment of the rotary polishing disc with a disc-shaped piece of sheet material fixed to a molded hub having flexible arms with projecting tips that is aligned for interconnection with a socketed end of a mating arbor; 
     FIG. 3 is a partially-sectioned elevational view of the rotary polishing disc of FIG. 2 with a retainer plug aligned for insertion through the polishing disc into a cavity in the hub to clamp the disc-shaped piece of sheet material to hub; 
     FIG. 4 is a partially-sectioned elevational view of the rotary polishing disc of FIG. 1 with a retainer plug aligned for insertion through the polishing disc into a hollow interior of the hub to clamp the disc-shaped piece of sheet material to hub. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 depicts a rotary polishing disc in accordance with the present invention referred to by a general reference character  10 . The rotary polishing disc  10  preferably includes a cylindrically-shaped hub  12  and a disc-shaped piece  14  of sheet material. As illustrated by dashed circular lines in FIG. 1A, disc-shaped pieces  14  are preferably cut, stamped, or punched from a sheet  16  of thin flexible material coated with abrasive material  18  on one or both sides in accordance with the description set forth in U.S. Pat. No. 3,014,795. 
     The hub  12  is formed symmetrically about a longitudinal axis  22  that extends through a hollow interior  24  of the hub  12 . When assembled into the rotary polishing disc  10 , the hub  12  is juxtaposed with and fixed to a surface  26  of the disc-shaped piece  14  so the longitudinal axis  22  is oriented substantially perpendicular to the surface  26 . The hollow interior  24  of the hub  12  is formed with a cross-sectional shape that is adapted to receive a projecting end  32  of a mating arbor  34 . A second end  36  of the arbor  34 , distal from the projecting end  32 , is adapted for conventional attachment to a rotary drive not illustrated in any of the FIGs. The projecting end  32  of the arbor  34  and the mating hollow interior  24  may be formed to have any desired cross-sectional shape that resists slippage between the rotating arbor  34  and the mating hub  12  received onto the projecting end  32 . Such cross-sectional shapes include square, as illustrated in FIG. 1 b , round, triangular, hexagonal, octagonal or fluted. 
     FIG. 1B illustrates that the hubs  12  are preferably cut, as indicated by dashed lines  42 , from a length of plastic tube  44  extruded from PVC (Polyvinyl Chloride) material. However the hubs  12  can be made in other ways from PVC or from any material having suitable physical and mechanical characteristics. In fabricating the rotary polishing disc  10 , one end of the hub  12  is preferably fixed to the surface  26  by a bead  52  of adhesive material that encircles the hub  12  about a juncture  54  between the hub  12  and the disc-shaped piece  14 . The adhesive material, which is preferably a medical device adhesive marketed by Loctite Corporation having product no. 3341 (part no. 23792), is an ultraviolet (“UV”) cured PVC bonding material. Alternatively to the use of the adhesive material, the hub  12  may be fixed to the disc-shaped piece  14  either by ultrasonic welding or by thermo-compression bonding. 
     The projecting end  32  of the arbor  34  is slightly oversized in comparison with the hollow interior  24  of the hub  12  to provide a tight fit therebetween. To further resist slippage between the arbor  34  and the hub  12 , the arbor  34  may include barbs  62 , shown with dashed lines in FIG. 1, which spear the surrounding hub  12  when the hollow interior  24  is disposed on the arbor  34 . As illustrated in FIG. 1, the barbs  62  are preferably oriented to impede detachment of the hub  12  from the arbor  34 . In the embodiment of the rotary polishing disc  10  depicted in FIG. 1, the projecting end  32  may enter completely into the hollow interior  24  of the hub  12  and become juxtaposed with the disc-shaped piece  14  to resist wobbling of the rotary polishing disc  10  on the rotating arbor  34 . 
     FIG. 2 depicts an alternative embodiment of the rotary polishing disc  10 . Those elements depicted in FIG. 2 that are common to the rotary polishing disc  10  illustrated in FIG. 1 carry the same reference numeral distinguished by a prime (“′”) designation. The rotary polishing disc  10 ′ depicted in FIG. 2 includes an elongated hub  72  having a mushroom-shaped first end  74 . The first end  74  is juxtaposed with and fixed to the surface  26 ′ of the disc-shaped piece  14 ′ with the longitudinal axis  22 ′ of the hub  72  disposed substantially perpendicular to the surface  26 ′. The hub  72  has a second end  76  that projects away from the disc-shaped piece  14 . The second end  76  of the hub  72  is pierced by at least one slot  78  which establishes two flexible arms  82 . An end of each of the flexible arms  82  furthest from the first end  74  is formed with an outwardly projecting tip  84 . The flexible arms  82  can be formed to have various alternative cross-sectional shapes perpendicular to the longitudinal axis  22 ′ including round, square, triangular, hexagonal, octagonal or fluted. 
     FIG. 2 also depicts an arbor  92  having a hollow socket  94  that is adapted to mate with and receive the second end  76  of the hub  72 . To resist slippage between the arbor  92  and the hub  72 , the socket  94  is formed with substantially the same or similar cross-sectional shape perpendicular to the longitudinal axis  22 ′ as the flexible arms  82  of the hub  72 . To create a snap lock between the arbor  92  and the hub  72 , the socket  94  is formed with a groove  96  that is adapted to receive the projecting tip  84  formed at the end of each of the flexible arms  82 . Slightly oversize configuration of the hub  72  with respect to the socket  94  causes the flexible arms  82  to be compressed as the second end  76  is inserted into the socket  94 . Insertion of the second end  76  completely into the socket  94  permits each tip  84  to be received into the groove  96  thereby relieving the compression of the flexible arms  82 . This permits the rotary polishing disc  10 ′ to be attached or detached quickly and easily from the arbor  92  while holding the rotary polishing disc  10 ′ securely during use. 
     Similar to the rotary polishing disc  10  depicted in FIG. 1, the mushroom-shaped first end  74  of the hub  72  is preferably fixed to the surface  26 ′ by a bead  52 ′ of adhesive material that encircles the first end  74  about a juncture  54 ′ between the hub  72  and the disc-shaped piece  14 ′. Alternatively, the hub  72  may be fixed to the disc-shaped piece  14  either by ultrasonic welding or by thermo-compression bonding. 
     FIG. 3 depicts an alternative embodiment of the rotary polishing disc  10 ′ illustrated in FIG.  2 . Those elements depicted in FIG. 3 that are common to the rotary polishing disc  10  illustrated in FIG. 1 or to the rotary polishing disc  10 ′ illustrated in FIG. 2 carry the same reference numeral distinguished by a double prime (“″”) designation. The disc-shaped piece  14 ″ of the rotary polishing disc  10 ″ depicted in FIG. 3 is pierced by a central aperture  102  that is situated adjacent to the hub  72 ″. The embodiment of the hub  72 ″ illustrated in FIG. 3 has a cavity  104  formed into the hub  72 ″ adjacent to the central aperture  102 . 
     The rotary polishing disc  10 ″ illustrated in FIG. 3 also includes a retainer plug  112 . The retainer plug  112  includes a thin flat cap  114  or shoulder, a series of ribs  116  that encircle the retainer plug  112 , and a pointed tip  118 . To fix the disc-shaped piece  14 ″ more securely to the hub  72 ″, the pointed tip  118  is inserted through the central aperture  102  and into the cavity  104  until the flat cap  114  becomes juxtaposed with a surface of the disc-shaped piece  14 ″ furthest from the hub  72 ″. The ribs  116 .encircling the retainer plug  112  are shaped slightly oversize with respect to the cavity  104  to establish a frictional engagement therebetween for retaining the retainer plug  112  in the cavity  104 . Before the pointed tip  118  is inserted into the cavity  104 , an adhesive material  112  may be coated onto the retainer plug  112  to add an adhesive bond between the retainer plug  112  and the hub  72 ″. 
     FIG. 4 depicts an alternative embodiment of the rotary polishing disc  10  illustrated in FIG.  1 . Those elements depicted in FIG. 4 that are common to the rotary polishing disc  10  illustrated in FIG. 1 or to the rotary polishing disc  10 ″ illustrated in FIG. 3 carry the same reference numeral distinguished by a triple prime (“′″”) designation. Similar to the disc-shaped piece  14 ″ of the rotary polishing disc  10 ″ depicted in FIG. 3, the disc-shaped piece  14 ′″ depicted in FIG. 4 is pierced by a central aperture  102 ′″ adjacent to the hub  12 ′″. To fix the disc-shaped piece  14 ′″ more securely to the hub  12 ′″, the pointed tip  118 ′″ of the retainer plug  112 ′″ depicted in FIG. 4 is inserted through the central aperture  102 ′″ and into the hollow interior  24 ′″ of the hub  12 ′″ until the flat cap  114 ′″ becomes juxtaposed with a surface of the disc-shaped piece  14 ′″ furthest from the hub  12 ′″. The ribs  116 ′″ encircling the retainer plug  112 ′″ are shaped slightly oversize with respect to the hollow interior  24 ′″ to establish a frictional engagement therebetween for retaining the retainer plug  112 ′″ in the hollow interior  24 ′″. Before the pointed tip  118 ′″ is inserted into the cavity  104 ′″, an adhesive material  112 ′″ may be coated onto the retainer plug  112 ′″ to add an adhesive bond between the retainer plug  112 ′″ and the hub  12 ′″. 
     Although the present invention has been described in terms of the presently preferred embodiment, it is to be understood that such disclosure is purely illustrative and is not to be interpreted as limiting. Consequently, without departing from the spirit and scope of the invention, various alterations, modifications, and/or alternative applications of the invention will, no doubt, be suggested to those skilled in the art after having read the preceding disclosure. Accordingly, it is intended that the following claims be interpreted as encompassing all alterations, modifications, or alternative applications as fall within the true spirit and scope of the invention.

Technology Category: b