Abstract:
The present invention relates to a method of uniformly distributing abrasive grits on grinding tools. It can be applied in the cutting, grinding segments of diamond tools, which are typically used in cutting and drilling various hard and fragile materials, such as granite, marble, concrete, asphalt, etc. The present invention provides a template, the template designed based on the arranging requirement of abrasive particles such as diamond grits. The template can adsorb only a single layer of abrasive particles and is then placed onto a sheet, where the diamond grits are pressed into the sheet, with the diamond grits distributed uniformly on the sheet.

Description:
RELATED APPLICATIONS 
       [0001]    This is a continuation of International Application PCT/CN2008/000331, with an international filing date of Feb. 13, 2008. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to the cutting and grinding tools, such as the cutting segments of diamond tools, which are typically used in cutting and drilling various hard and fragile materials, such as granite, marble, concrete, asphalt, etc. More particularly, the present invention relates to the uniform distribution of abrasive particles such as diamond grits on the segments of cutting tools to increasing the cutting efficiency. 
       BACKGROUND OF THE INVENTION 
       [0003]    Synthetic diamonds are the hardest abrasive material currently known, and they have been widely used as super-abrasives on cutting and grinding tools. Diamond tools are particularly used to cut and grind rocks in machining stone and other structural components. Diamond tools mainly have cutting segments on which diamonds or other abrasive particles are distributed. The cutting segments are fixed on the tool bodies. 
         [0004]    A satisfactory structure of diamond saw blades is where the diamond particles have a relatively large exposed portion and proper spacing of particles to improve the excluding of debris and the transporting of cooling fluid, thus improving the cutting efficiency and lengthening the useful life of the tools. Uniform distribution of abrasive grits can also improve safety in their manufacture. A typical abrasive tool, such as a diamond saw blade, is manufactured by mixing diamond particles (e.g. 40/50 U.S. mesh) with a suitable support matrix (bond) powder (e.g. cobalt powder of 1.5 micrometer in size). The mixture is then compressed in a mold to form the desired shape. This “green” form of the tool is then consolidated by sintering at a temperature between 700-1200° C. to form a single body with a plurality of abrasive particles therein. Finally, the consolidated body is brazed to a tool body, such as the round blade of a saw, to form a cutting tool. 
         [0005]    Different applications, however, require different combinations of diamond and support matrix. For example, drilling and sawing applications may require a larger-sized (20 to 60 U.S. mesh) diamond grit to be mixed with a metal powder. The metal powder is typically selected from cobalt, nickel, iron, copper, bronze, or alloys thereof, and/or mixtures thereof. For grinding applications, a smaller-sized (60/400 U.S. mesh) diamond grit is mixed with either metal (typically bronze), ceramic/glass (typically a mixture of oxides of sodium, potassium, silicon, and aluminum) or resin. 
         [0006]    Because diamonds are much larger than the matrix powder, and is much lighter, it is very difficult to mix the two to achieve uniformity. Moreover, diamond particles can still segregate from metal powder in the subsequent treatment, such as when pouring the mixture into a mold, or when the mixture is subjected to vibration. 
         [0007]    One method used in an attempt to make the diamond distribution uniform is to wrap diamond particles with a coating of matrix powder. The concentration of diamond particles in each diamond tool is tailored for a particular application. The concentration determines the average distance between diamond particles. If one thickly coated diamond mixes the coated particles together, the distribution of diamond would be controlled by the thickness of coating and may become uniform. Additional metal powder may be added as an interstitial filler between these coated particles to increase the packing efficiency so that the consolidation of the matrix powder in subsequent sintering would be easier. 
         [0008]    Although the above-described coating method has certain merit, in practice, uniformity of coating is very difficult to achieve. For example, Chen and Sung (U.S. Pat. Nos. 5,024,680 and 5,062,865) describe a chemical vapor deposition (CVD) method for coating diamond grit using a fluidized bed. However, most of these methods can only produce thin coatings such as a few micrometers thick that do not affect the diamond distribution. Moreover, chemical coating methods typically require treatment at high temperatures such as greater than 900° C. that may cause damage to the diamond. It is well known that synthetic diamond grit tends to form micro-cracks above this temperature. 
         [0009]    Dr. Song Jian Min of Taiwan has invented a two-dimensional method, firstly providing a layer of support matrix, and disposing abrasive grits in the support matrix layer in a desired pattern. After the diamond particles are plated into the metal matrix layer according to a predetermined pattern, the process may be repeated until a desired number of layers have been formed. The layers are then assembled to form the desired three-dimensional body. Subsequently the diamond tool is consolidated to form the final product. 
         [0010]    The detailed above-mentioned method is as follows: forming a thin layer of bonding matrix (i.e. a two-dimensional body); placing a template on the bonding matrix, with the template having a plurality of apertures formed therein which are sized to receive a abrasive grit of a particular size, with one particle being disposed in each aperture; and, as the particles are filled into the apertures, they are subjected to pressure or moved into the bonding matrix. However, as the abrasive particles are small to 40/50 U.S. mesh, it is imposable to fill the apertures with abrasive particles one by one, and so this method cannot achieve industrialization. 
         [0011]    In summary, current methods are incapable of controlling the uniformity of diamond particles in cutting tools efficiently. Likewise, the current methods are inadequate to provide effective control of size variations and concentration variations of different parts of the same tool. 
       SUMMARY OF THE INVENTION 
       [0012]    Performance of diamond arranged in a predetermined pattern /uniform distribution: 
         [0013]    The distance between diamond or other abrasive particles determines the work load each particle will perform. Improper spacing of the abrasive particles will lead to premature failure of the abrasive surface or structure. If the abrasive particles are too close to one another, some of the particles are redundant and add to the cost. Moreover, these non-performing particles can block the passage of debris, thereby reducing cutting efficiency. 
         [0014]    If the diamond grits are uniformly distributed, the distance between the grits will be optimized according to the cutting materials and cutting conditions. It has be found that in practice, 85% of the distances between diamond grits on uniform distributed saw blade are 2 mm-5 mm, while on traditional saw blades, this percentage is only 60%. The increasing of diamond content weakly affects the work load, but the applicable cutting times are lengthened markedly, thus the cutting efficiency is increased and useful time of the saw blade is lengthened. 
         [0015]    Diamond concentration: when the concentration of diamond increased, the useful time of uniform distributed diamond will be lengthened in geometric series, and maintaining favorable cutting and sawing capability at the same time, but when the concentration increased more, the cutting and sawing capability will be reduced. 
         [0016]    The exposed height of diamond particularly affects the sawing efficiency and the useful time of the saw blade, it is rest with the size and the distribution of diamond and the hold of the sheet. So, the uniform distribution of diamond or other abrasive particles on matrix will markedly affect the cutting and grinding tools. The object of the present invention is to provide a method of arranging the abrasive particles uniformly on cutting and grinding tools, and the method can be industrialized. 
         [0017]    One art of the present invention is to provide a sheet; 
         [0018]    A template, designed on the single-layer arranging requirement of diamond or the other abrasive particles, said template has a layer of adsorbent which can adsorb a single layer of diamond grits. 
         [0019]    Place the template on the sheet, press the diamond grits into the sheet, the diamond grits will be imbed uniformly on the sheet at a layer. 
         [0020]    Said template comprising adsorbent, wherein the adsorbent has a lower viscosity, a higher percent of condensate and a lower percent of solvent. 
         [0021]    Said sheet is a paste, after the diamond pressed into it, the paste would be solidified by means of heating or cooling to be a sheet with a single layer of uniformly-distributed diamond grits. 
         [0022]    Said sheet is made of the mixing of metal power and bond, when the mixing is about to solidified, press the abrasive particles into one surface or double-surface of the sheet. 
         [0023]    Press a plurality of above-mentioned sheets to be a one on the thickness requirement of cutting tool, then placed them into a mold to be sintered. 
         [0024]    Said cutting tool including multiple sheets, the distribution pattern of abrasive particles on each layer are the same as or different; for example, the outer layer has a higher density of diamond while the inner layer has a lower density and bigger-size diamond. 
         [0025]    Another art of the present invention is as follows: 
         [0026]    A sheet; 
         [0027]    An electric/electromagnetic template, designed on the arranging requirement of diamond or the other abrasive particles, 
         [0028]    Diamond or the other abrasive particles are adsorbed on the template in a layer; 
         [0029]    Press the template with the adsorbed diamond into the sheet, then separate the template, the diamond grits will be uniformly distributed on the sheet; 
         [0030]    Said template is a plane template formed by the following steps: after electromagnetic radiating, covering the positions where does not need to adsorb abrasive particles, thus an electromagnetic template is formed. 
         [0031]    Said template can be a plasma-template. 
         [0032]    Said template can be an electric template with positive or negative charge. 
         [0033]    Said sheet is made by the mixing of metal power and bond compressed in a mold. 
         [0034]    Select needed layers of sheets on the requirement of cutting, compress the multiple sheets above-mentioned to be a one by static press or stamping press, then placed them into a mold to be sintered. 
         [0035]    Said cutting tool is formed by multiple sheets, the distribution pattern of abrasive particles on each layer are the same as or different; for example, the outer layer has a higher density of diamond while the inner layer has a lower density and bigger-size diamond. 
         [0036]    Therefore, the present invention provides a template, the shape and the pattern of the template can be designed conveniently on the arranging requirement of abrasive particles, and the template can adsorb only single layer of abrasive particles, place the template with uniformly distributed abrasive particles into or adhere to sheet, then will form a sheet with uniformly distributed abrasive particles, thus the position of abrasive particles can be located exactly on the sheet on predetermination. The abrasive particles can be uniformly distributed, or arranged on the requirement of accounted cutting force of provided cutting and grinding tools, For example, higher concentration diamond grits are preferred in the edge and front of saw, while in the middle, the lower concentration diamond grits are preferred. 
         [0037]    In practice, compared with irregularly distributed diamond saw blade, the saw blade with uniformly distributed diamond grits has a lower concentration diamond grits, the practical cutting distance is 1150 m (the distance of irregularly distributed diamond saw blade is 450 m), the blade cuts smoothly and there is not collapse piece of blade, the sum power consumption of abrasive tools decrease 30 percents, the noise of perigee decrease 10 db(A), cutting efficiency increase 30 percents, and the useful life is three times longer than those irregularly distributed diamond saw blade. 
         [0038]    The foregoing was intended as a broad summary only and of only some of the aspects of the invention. It was not intended to define the limits or requirements of the invention. Other aspects of the invention will be appreciated by reference to the detailed description of the preferred embodiment and to the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0039]    The invention will be described by reference to the detailed description of the preferred embodiment and to the drawings thereof in which: 
           [0040]      FIG. 1  shows the uniform distribution of abrasive particles formed by three sheets. 
           [0041]      FIGS. 2A ,  2 B, and  2 C are views of the template structure, wherein  FIG. 2A  shows the oblique distribution of abrasive particles,  FIG. 2B  shows the forward distribution of abrasive particles, and  FIG. 2C  shows the cross distribution of abrasive particles. 
           [0042]      FIG. 3  shows the diamond grits adsorbed on the electromagnetic template; and 
           [0043]      FIG. 4  shows another layout of a segment of a cutting tool formed by multiple sheets of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0044]      FIG. 1  shows a perspective view of a segment of diamond tool, indicated at  10 . The segment  10  is formed by a plurality of layers,  11 ,  12 ,  13 , and  14 , which are impregnated with abrasive grits, indicated as hexagonal frame  1 . 
         [0045]    Referring to  FIGS. 2A ,  2 B, and  2 C, electromagnetic template  20  of the present invention is capable of adsorbing single layer of abrasive particles (for example, diamond grits) after the corona is discharged. When the adsorptive points are occupied by the adsorbed diamond grits, the other grits can not be adsorbed on the same place, so the adsorbed grits form a single layer, and the template can be designed on the requirement of the arrangement of diamond or other abrasive particles. Thus the diamond, cubic boron nitride grits are uniformly distributed on the template, and the distribution form can be designed freely on the desire of the designers. 
         [0046]      FIGS. 2A ,  2 B, and  2 C are views of the distribution of abrasive particles on the template, wherein  FIG. 2A  shows the oblique distribution of abrasive particles,  FIG. 2B  shows the forward distribution of abrasive particles, and  FIG. 2C  shows the cross distribution of abrasive particles. 
         [0047]    In practice, the template may be a plane (as shown in  FIG. 3 ). In addition, a cover  21  may be adhered on the template, which covers the positions that do not need to adsorb abrasive particles, when the abrasive particles such as diamond grits adsorbed on template, then achieve uniform distribution of diamond grits on the template. The advantage of this method is that the template is easily treated with, and the shape of the cover is freely and easy treated. 
         [0048]    Referring to sheet  30 , there are many ways to make the sheet. For example, the powder can first be mixed with a suitable binder (typically organic) and a solvent that can dissolve the binder. In order to prevent the powder from agglomerating during the processing, a suitable wetting agent (e.g., phosphate ester) may also be added. The slurry can then be poured onto a tape and pulled underneath a blade or leveling device, allowing the sheet to be made. The tape casting method is a well-known method in rubber and plastic manufacturing. By adjusting the gap between the blade and the tape, the slurry can be cast into a sheet with the right thickness. 
         [0049]    It is desirable to make the sheets pliable for subsequent treatments (e.g., bending over the tool substrate, which has a curvature). Therefore, a suitable organic plasticizer can also be added to provide the desired characteristics. The use of organic agents for powder processing is documented in many textbooks and it is well known by those skilled in the art. Typical binders include polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyethylene glycol (PEG), paraffin, phenolic resin, and acrylic resins. Typical binder solvents include methanol, ethanol, acetone, trichloroethylene, toluene, etc. Typical plasticizers are polyethylene glycol, diethyl oxalate, triethylene glycol dihydroabietate, glycerin, rosin, etc. The organic agents so introduced are to facilitate the fabrication of metal layers. They must be removed before the consolidation of metal powders. The binder removal process is also well known to those skilled in the art. 
         [0050]    Once the sheet  30  is formed, a template impregnated with diamonds or other abrasive particles is laid on the top of the sheet. After the template is properly positioned, the abrasive particles are pressed into the sheet, and the template is removed. The abrasive particles are now uniformly distributed on the sheet. The depth of the abrasive particles embedded in the sheet can be varied based on specific requirements, and those skilled in the art will know the desirable height of the abrasive particles to extend outwardly from the sheet. 
         [0051]    The manufacture of the template may be as follows: after electromagnetic radiating on a metal template, the template will be with adsorbability, then place a cover (e.g. a cardboard) on the template, covering the positions where does not need to adsorb abrasive particles, thus the template can achieve uniform distribution of abrasive particles. 
         [0052]    The template may also be a plasma template, having well single layer adsorbability. 
         [0053]    The template may also be an electric template, having adsorbability with a negative charge. 
         [0054]      FIG. 4  shows the sheets of the present invention with uniform distributed abrasive particles assembled transversely. The segment in  FIG. 4  is formed from a plurality of transverse sheets  41 . The difference of it is that because the segment is formed transversely, it requires that the abrasive particles be distributed transversely on the tool, and the template manufactured based on that requirement. In summary, the location methods of abrasive particles are various, and they can all conveniently achieve the uniform distribution of abrasive particles according to the present invention. 
       ALTERNATE EMBODIMENTS 
       [0055]    This is the same as the preferred embodiment, except that the template is with bond, whose adsorbability is by chemical material rather than by electromagnetic adsorbability as in the preferred embodiment.
 
In a further embodiment, 40/50 U.S. mesh diamond grit (SDA-85, made by DE BEERS company) was used. The sheet was a mixture of metal powder and acrylic resin. Five different proportions of cobalt and bronze were used for the metal powder. An acrylic binder was added to the mixture and the charge was blended to form a cake. The cake was then rolled between two rollers to form sheets with a thickness of 1 mm. Then, the template distributed with adsorbed diamond grits was placed on the sheet, and the diamond grit was pressed into the sheet. The template was then removed. The sheets were cut in the shape of diamond saw segments with a length of 40 mm and width of 15 mm. Three each of such segments were assembled and placed into a typical graphite mold for making conventional diamond saw segments. The segments were pressed and heated by passing electric current through the graphite mold. After sintering for three minutes, the segments were consolidated to a height of 9 mm with less then 1% porosity. Twenty-four segments for each composition were fabricated, and they were laser-welded onto a circular saw of 14 inches in diameter. The performance of these blades was better than those made by conventional methods in sawing the granite.
 
         [0056]    The present invention provides an adsorptive template where the shape and the pattern of the template can be designed conveniently based on the specific arranging requirement of the abrasive particles. The template can adsorb only a single layer of abrasive particles. place the template with uniformly distributed abrasive particles into or adhere to sheet, then will form a sheet with uniformly distributed abrasive particles, thus the position of abrasive particles can be located exactly on the sheet with determination. The abrasive particles can be uniformly distributed, or arranged based on the requirement of accounted cutting force of provided cutting and grinding tools. For example, higher concentration diamond grits are preferred in the edge and front of the saw, while in the middle, lower concentration diamond grits are preferred. 
         [0057]    It will be appreciated by those skilled in the art that the preferred embodiment has been described in some detail but that certain modifications may be practiced without departing from the principles of the invention.