Abstract:
The invention relates to a method of making a grinding disk, comprising the steps of: providing a cap; providing an abrasive part; placing the cap on the abrasive part to form an assembly; holding the assembly and injecting a molding material into a space between the cap and the abrasive part and into the abrasive part to bond the cap and the abrasive part. A grinding disk made by the method is also disclosed.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage filing under 35 U.S.C. 371 of PCT/US2010/61210, filed Dec. 20, 2010, which claims priority to Chinese Patent Application No. 200910259760.3, filed Dec. 25, 2009, the disclosures of which is incorporated by reference in their entirety herein. 
     FIELD OF THE INVENTION 
     The present invention relates to a method of making a grinding disk and a grinding disk made using the same, and more particularly to a method of making a grinding disk through injection molding. 
     DESCRIPTION OF THE PRIOR ART 
     A grinding disk is a consumable installed on a polishing/grinding tool. Through high speed rotation of the polishing/grinding tool, the periphery of the grinding disk contacts and rubs the surface of a work piece, so as to smooth the surface of the work piece. 
     A conventional grinding disk includes a cap and an abrasive part. The cap is usually a disk-shaped plastic piece. The abrasive part is a disk of paper, cloth, or fiber glued together, in the center of which a through hole is provided. One end of the cap is inserted in the central hole of the abrasive part, and the cap and the abrasive part are glued together. 
     However, the grinding disk made in such a gluing mode breaks easily when used in a polishing/grinding tool that rotates at a high speed (for example, 10,000 rpm). In addition, the gluing mode requires a lot of auxiliary tools and the glue takes a long time to solidify. Moreover, as the glue is unevenly distributed, the weight of the grinding disk is also unevenly distributed, thereby causing vibration when the grinding disk rotates. 
     Therefore, a fast and simple method for making a grinding disk is needed, in which the grinding disk made through the method does not break easily during high speed rotation and the weight of the grinding disk is evenly distributed, so that the vibration during the rotation of the grinding disk is decreased. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a fast and simple method of making a grinding disk, in which a cap and an abrasive part are bonded through injection molding. 
     The present invention is further directed to a grinding disk which does not break easily during high speed rotation, and has evenly distributed weight so that vibration of the grinding disk is decreased during rotation. 
     In order to achieve the above objectives, the present invention provides a method of making a grinding disk which includes the following steps. A cap is provided. An abrasive part is provided. The cap is placed on the abrasive part to form an assembly. The assembly is held and a molding material is injected into a space between the cap and the abrasive part and a space inside the abrasive part, so as to bond the cap and the abrasive part. 
     The present invention further provides a grinding disk which includes an abrasive part and a cap disposed on the abrasive part. The cap and the abrasive part are bonded by injecting a molding material into a space between the cap and the abrasive part and a space inside the abrasive part. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a bottom view of a cap according to an embodiment of the present invention; 
         FIG. 2  is a sectional view taken along line  2 - 2  in  FIG. 1 ; 
         FIG. 3  is a sectional view wherein the cap in  FIG. 1  is placed on an abrasive part; 
         FIG. 4  is a sectional view wherein a molding material is injected into a space between the cap and the abrasive part and a space inside the abrasive part; 
         FIG. 5  is a schematic view wherein a molding material flows at a bottom of the cap; 
         FIG. 6  is a bottom view of a cap according to another embodiment of the present invention; and 
         FIG. 7  is a sectional view taken along line  7 - 7  in  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION 
     As shown in  FIGS. 1 and 2 , a method of making a grinding disk according to a preferred embodiment of the present invention is provided. First, a cap  1  is provided. The cap  1  has a substantially disk-shaped cap body  10  with a through hole  11 . An encircled wall  13  and an outer circumferential edge  14  extend downward from a bottom of the cap body  10 . The encircled wall  13  surrounds the through hole  11 . The encircled wall  13  is formed with a first pair of diametrically opposite slots  15 ,  15  and a second pair of diametrically opposite slots  17 ,  17 . The second pair of opposite slots  17 ,  17  and the first pair of opposite slots  15 ,  15  are approximately disposed in an orthogonal mode. In this embodiment, the length of the first pair of opposite slots  15 ,  15  is greater than that of the second pair of opposite slots  17 ,  17 . The outer circumferential edge  14  has a bottom side  141 . 
     As shown in  FIG. 1 , the cap  1  further includes two guide walls  19 ,  19 . The two guide walls  19 ,  19  extend from the bottom of the cap body  10  along two outer sides of the first pair of opposite slots  15 ,  15 , respectively. Each guide wall  19  has a bottom side  191 . The bottom sides  191 ,  191  of the two guide walls  19 ,  19  are at least flush with the bottom side  141  of the outer circumferential edge  14 . As shown in  FIG. 2 , in this embodiment, the bottom sides  191 ,  191  of the two guide walls  19 ,  19  extend to exceed the bottom side  141  of the outer circumferential edge  14 . 
     As shown in  FIG. 2 , in this embodiment, the cap  1  is formed integrally by injecting a molding material at a location indicated by arrow A through injection molding. However, the cap  1  may also be formed by other methods and/or using other materials. 
     Next, an abrasive part  3  is provided. The abrasive part  3  is substantially disk-shaped and has a central hole  31  and a top surface  33 . In this embodiment, the abrasive part  31  is made of non-woven fabrics. However, the abrasive part  31  may also be made of other materials such as paper, cloth, or fiber. 
     Subsequently, the encircled wall  13  of the cap  1  is inserted in the central hole  31  of the abrasive part  3 . At this time, the bottom side  141  of the outer circumferential edge  14  at the bottom of the cap  1  contacts the top surface  33  of the abrasive part  3 . The bottom sides  191 ,  191  of the two guide walls  19 ,  19  at least contact the top surface  33  of the abrasive part  3 . As shown in  FIG. 3 , in this embodiment, the bottom sides  191 ,  191  are directly pressed into the abrasive part  3 . Therefore, the cap  1  and the abrasive part  3  form an assembly  5 . 
     As shown in  FIG. 4 , the assembly  5  is placed in a mold (not shown), and then a molding material is injected in a direction marked by arrow B. As shown in  FIG. 5 , in this embodiment, a total of three injection holes  51  is provided. 
     The molding material is used for holding the cap  1  and the abrasive part  3 . As an abrasive part  3  containing cured molding material cannot serve to grind a work piece, the flowing direction of the molding material has to be controlled, so as to prevent the molding material from flowing to outside areas of the abrasive part  3 , thereby shortening the service life of the abrasive part  3 . As shown in  FIG. 4 , in this embodiment, due to the design of the mold, the injected molding material is first filled into a space between the cap  1  and the abrasive part  3  and subsequently flows through the first pair of opposite slots  15 ,  15  and the second pair of opposite slots  17 ,  17 . Due to the outer circumferential edge  14  of the cap  1 , the bottom side  141  of the outer circumferential edge  14  contacts the top surface  31  of the abrasive part  3 , so that the molding material cannot flow out of the cap  1 , and can only be permeated into the abrasive part  3 . In addition, the length of the first pair of opposite slots  15 ,  15  is greater than that of the second pair of opposite slots  17 ,  17 . Therefore, in order to prevent excessive flow of molding material through the first pair of opposite slots  15 ,  15  and thus uneven distribution of the molding material, the guide walls  19 ,  19  at outer sides of the first pair of opposite slots  15 ,  15  at least contact the top surface  33  of the abrasive part  3  through the bottom sides  191 ,  191 , so that the molding material can only flow along the guide walls  19 ,  19 . Thus, the molding material flowing through the first pair of opposite slots  15 ,  15  is guided to flow towards the second pair of opposite slots  17 ,  17 . Therefore, the molding material can be evenly distributed inside specific areas of the abrasive part  3 . 
     As shown in  FIG. 4 , after the injected molding material is cured, the cap  1  and the abrasive part  3  are bonded, so as to form a grinding disk  7 . In this grinding disk  7 , the molding material forms a holding part  53  between the cap  1  and the abrasive part  3 . The holding part  53  has a shaft hole  55 , which is used to secure the grinding disk  7  on a shaft of the polishing/grinding tool. 
     The method of the present invention is fast and simple and the produced grinding disk does not break easily during high speed rotation (of 15,000 rpm or more), and has evenly distributed weight so that vibration of the grinding disk during rotation is decreased. 
     The preferred embodiments of the present invention have been discussed above. However, the present invention also has alternative designs. For example, the shaft hole  55  may be threaded, so that the shaft hole  55  is provided for the grinding disk  7  to be screwed into the shaft with matching threads of the polishing/grinding tool. In addition, the length of each first opposite slot may be the same as that of each second opposite slot, as shown in  FIGS. 6 and 7 . Therefore, whether to dispose guide walls is determined according to the actual demands. 
     While technical solutions and technical features of the present invention are disclosed above, persons skilled in the art can still make replacements and modifications on the basis of the teaching and disclosure of the present invention without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be limited to the disclosure about the embodiments and should cover various replacements and modifications without departing from the present invention as defined in the claims. 
     LIST OF REFERENCE NUMERALS 
     
         
         
           
               1  Cap 
               3  Abrasive part 
               5  Assembly 
               7  Grinding disk 
               10  Cap body 
               11  Through hole 
               13  Encircled wall 
               14  Outer circumferential edge 
               15  First pair of opposite slots 
               17  Second pair of opposite slots 
               19  Guide wall 
               31  Central hole 
               33  Top surface 
               51  Injection hole 
               53  Holding part 
               55  Shaft hole 
               141  Bottom side of outer circumferential edge 
               191  Bottom side of guide wall 
             A Arrow 
             B Arrow