Patent Publication Number: US-2018043507-A1

Title: Abrasive disc with lateral cover layer

Description:
BACKGROUND 
     When grinding a work piece using a grinder, there is a grinding method which employs the part of its work as a grind-guide which indicates the grind location of the grinder. In this method, the grind disc of the grinder touches the part of the work directly. Therefore when a conventional grinding disc is used, the part of the work which is used as the grind guide is ground. 
     SUMMARY 
     In accordance with one embodiment, the construction of the invented grind disc consists of at least an inner layer  50  which is made of grindable material and an outer layer  20  which covers at least the part of the surface of the inner layer  50  and which is made of non-grindable material. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIGS. 1A-C  present the out-looking views (oblique drawing) of the types of invented Grind-Discs. 
         FIG. 1A  (Type 1) shows a disc having the outer layer  20  on each side of the inner layer  50  and full-cover the surface of the inner layer  50 . 
         FIG. 1B  (Type 2) shows a disc having the outer layer  20  on only one side of the inner layer  50  and full-cover the surface of the inner layer  50 . 
         FIG. 1C  (Type 3) shows a disc having the outer layer in only one side of the inner layer  50  and part-cover the surface of the inner layer  50 . 
         FIGS. 2A-C  present the cross-sectional views of each type of invented grind-discs. 
         FIG. 3  shows a circular nonwoven fabric  5  that is adapted for use with the nonwoven fabric grind disc according to an inner layer  50  of the present invention. 
         FIGS. 4A and 5B  illustrate examples of circular nonwoven fabric (plate) that are adapted for use with the nonwoven fabric grind disc according to an outer layer  20  of the present invention. The circular nonwoven fabric (plate) shown in  FIG. 4A  is used for type 1-disc and type 2-disc (shown in  FIGS. 1A , B). The circular nonwoven fabric (plate) shown in  FIG. 4B  is used for type 3-disc (shown in  FIG. 1C ). 
         FIGS. 5A and 5B  illustrate an example of a manufacturing method for the nonwoven fabric grind disc  100  according to an embodiment of the present invention. 
         FIGS. 6A-6D  illustrate another example of a manufacturing method for the nonwoven fabric grind disc according to an embodiment of the present invention. 
         FIG. 7  illustrates the shape of the work ground by the grinder. 
         FIG. 8  illustrates the grinding direction of the grinder and show the out-looking view of the work ground by the grinder. 
     
    
    
     DETAIL DESCRIPTION 
     The grind disc relating to this invention is effective for solving the current problem. The construction of the invented grind disc consists of the inner layer  20  which is made of grindable material (containing abrasive particles) and the outer layer  20  which covers at least the part of the surface of the inner layer  50  and which is made of non-grindable material (i.e. not-containing abrasive grain). 
     Material Information of Inner Layer (Plate) 
     The inner layer (plate)  50  consists of at least one sheet of the circular nonwoven fabric  5  and usually multiple sheets of the circular nonwoven fabric. The circular nonwoven fabric  5  includes, for example, a nonwoven fabric  5  base material and abrasive particles retained on the nonwoven fabric base material. The nonwoven fabric base material may be a nonwoven fabric constituted by organic fibers formed from a resin such as polyamide (for example, nylon (registered trademark)  6 , nylon (registered trademark)  6 ,  6 , and the like), polyolefin (for example, polypropylene, polyethylene, and the like), polyester (for example, polyethylene terephthalate, and the like), polycarbonate, and the like. The thickness (fiber diameter) of the organic fibers may be in a range from 19 to 250 μηι, for example. 
     The abrasive particles may be changed as appropriate in accordance with the object to be polished, and, for example, may be a ceramic abrasive particle such as SiC, Al 2 O 3 , Cr 2 O 5 , or the like. The diameter of the abrasive particles may be changed as appropriate in accordance with the object to be ground, and, for example, may be from 0.1 to 1000 μηι. 
     The circular nonwoven fabric  5  can be produced by, for example, impregnating a nonwoven fabric base material with a grind compound containing the abrasive particles, and drying and/or hardening. 
     Examples of grind compound include the abrasive particles and a binder polymer such as epoxy resin, phenol resin, or the like, and a solvent such as xylene, carbitol, or the like, for dissolving the binder polymer, and, if necessary, a hardening agent may be included in the polishing compound. After impregnating this polishing compound in the nonwoven fabric base material, the solvent is removed and the binder polymer is hardened in, for example, a heating furnace, so that the polishing abrasive particles are retained on the nonwoven fabric base material. 
     After the grind abrasive particles are retained on the nonwoven fabric base material in a sheet form, the circular nonwoven fabric  5  can be obtained by, for example, carrying out a punching process on the nonwoven fabric base material in a sheet form to obtain individual members with the shape illustrated in  FIG. 3 . Also, the circular nonwoven fabric  5  can be obtained by causing the grind abrasive particles to be retained on the nonwoven fabric base material that has been processed to the shape illustrated in  FIG. 3  or the like. 
     There is no particular limitation on the external diameter of the circular nonwoven fabric  5 , but it can be for example, from 50 to 500 mm, or from 100 to 200 mm. There is no particular limitation on the thickness of the circular nonwoven fabric  5 , preferably, each of the plurality of circular nonwoven fabrics  5  have the same thickness, but they may have different thicknesses. The thickness of the circular nonwoven fabric  5  before stacking may be, for example, from 2 to 30 mm, or it may be from 5 to 20 mm. 
     Material Information of Outer-Layer (Plate) 
     The outer layer (plate)  20  includes nonwoven fabric  2  that is hardened in the compressed state, and may be the same nonwoven fabric described above for the nonwoven fabric base material. 
     The outer layer (plate)  20  can be obtained by, for example, stacking a plurality of sheets of nonwoven fabric  2  in a sheet form, hardening them while they are compressed in the stacking direction, and next a punching process is performed on the hardened nonwoven fabric to obtain individual members with the shape illustrated in  FIGS. 4A , B. Also, the outer layer (plate)  20  can be obtained by stacking and compressing in the stacking direction a plurality of nonwoven fabric  2  that has been processed into the shape as illustrated in  FIGS. 4A , B or the like. 
     Also, the outer layer (plate)  20  may be obtained by stacking a plurality of nonwoven fabric base material of the circular nonwoven fabric  2 , compressing it in the stacking direction, and hardening it, or the outer layer (plate)  20  may be obtained by stacking a plurality of the circular nonwoven fabrics  2 , compressing them in the stacking direction, and hardening it. 
     In a preferred form, the outer layer (plate)  20  includes a laminate that has been hardened while compressed in the stacking direction, and the laminate includes a plurality of stacked circular nonwoven fabrics. There is no particular limitation on the number of the stacked circular nonwoven fabrics  2  in the laminate, for example, it can be selected as appropriate in order to satisfy the preferred thickness as described later and the preferred deformation rate as described above. 
     The nonwoven fabric in the outer layer plate  20  can be hardened using an adhesive. Here, the adhesive may be, for example, an adhesive that includes a hardenable resin and a hardening agent. 
     The hardenable resin may be, for example, epoxy resin, urea resin, urethane resin, phenol resin, or the like. Of these, the epoxy resin may be a cresol novolac type epoxy resin, a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, a phenol novolac type epoxy resin, a tris(hydroxyphenyl) methane type epoxy resin, a naphthalene type epoxy resin, a fluorene epoxy resin, a glycidylamine compound, and the like. 
     The hardening agent may be, for example, dicyandiamide (DICY), acid hydrazide, boron trifluoride complex, imidazole compound, amine imide, and lead salts, and, of these, dicyandiamide is particularly preferred. 
     In a preferred form, the nonwoven fabric included in the outer layer (plate)  20  is hardened by an adhesive, and a content of the adhesive is in a range from 5 to 30 mass % of the total mass of the nonwoven fabric. The outer layer (plate)  20  that includes such nonwoven fabric can easily satisfy the deformation rate as described above. Also, such the outer layer (plate)  20  can have a sufficiently large amount of wear in the polishing process, so it is possible to perform the polishing process more efficiently. 
     Manufacturing Process of the Invented Grind-Disc 
       FIGS. 5A and 5B  are schematic cross-sectional views illustrating examples of a manufacturing process of the nonwoven fabric grind disc  100 . In the manufacturing process, as illustrated in  FIG. 5A , the plurality of circular nonwoven fabrics  2  (for the two outer layer (plates)  20 ) and the plurality of circular nonwoven fabrics  5 , are stacked with each member in the same positional relationship in the nonwoven fabric grind-disc  100  at first. Here, it is necessary that the circular nonwoven fabrics  2  and the circular nonwoven fabric  5 , are stacked so that their respective apertures form the through hole that engages with the shaft  500 . The circular nonwoven fabrics  2  and the circular nonwoven fabric  5  are stacked by inserting the shaft  500  there through. 
     The circular nonwoven fabrics  2  and the circular nonwoven fabrics  5  that are stacked using the shaft  500  are retained at both ends in the stacking direction by a retaining fixture  600 . Here, the retaining fixture  600  is provided with a through hole in the center into which the shaft  500  is inserted so that the retaining fixture  600  can move freely in the stacking direction. 
     Next, the circular nonwoven fabrics  2  and the circular nonwoven fabrics  5  are compressed in the stacking direction via the retaining fixture  600  using compression means  650  installed at one of the retaining fixtures  600 , to form the compressed laminate as illustrated in  FIG. 5B . 
     The process of the invented grind-disc  100  is not limited as described above. 
     As the other process for manufacturing the invented grind-disc  100 , the process shown in  FIG. 6  is possible to use. In this process, the multiple sheets of nonwoven fabric which have abrasive particles and multiple sheets of nonwoven fabric which don&#39;t have abrasive particle are piled up shown in  FIG. 6A . Next, the piled multiple sheets of nonwoven fabric are pressed into the plate by the heat-press with high pressure load shown in  FIG. 6B . Next the plate is punched into the shape of the grind disc  100  shown in  FIGS. 6C and 6D . 
     EXAMPLE 
     1) Grind-disc: type 2 (shown in  FIG. 1A )
         Disc Diameter 150 mm, Disc thickness; 4.5 mm   Thickness of the outer layer 0.2 mm/each side       

     2) Grind condition;
         Grinding load 2 kgf, Rotating Speed of grind grinder 4000 rpm,   Grinding speed 100 mm/min)       

     3) Shape of Work
         Two flat boards made with steel material are welded as “butt welding” shown in  FIG. 7 .       

     4) Result 
     The grinded situation of the work is shown  FIG. 8  compared with the current disc one. Only in the invented disc, bottom in a ditch is ground over the full length of the welding.