ROTARY SAW BLADE

Abstract: A rotary saw blade, comprising a series of outward tapering toothlike radial projections (15) on and around a circular core of a base plate of metal (14). Each of said projections comprises a leading surface which is inclined at an acute angle to the periphery of the core and deposited with abrasive particules held in a layer comprising metal.

Description: The present invention relates to a rotary saw blade and, in particular, to such blade deposited with diamond, cubic boron nitride (cBN) and other "super abrasive" materials and capable of efficiently cutting tiles, bricks and other hard and brittle materials of ceramic, glass, granite and carbon. Rotary saw blades comprising peripheral projections or teeth, having a triangular or other shape, are generally known for cutting wood or metals. For exemple German publication "Technologie der Holzbearbeitung" from W. Müller, VEB Fachbuchverlag Leipzig (1982) discloses on page 167 and on Figure 7/7 a rotary saw blade with triangular projection arrangement at the periphery of a circular core. The leading surface of each projection is inclined at an obtuse angle to the periphery of the core with respect to the reverse direction of rotation of the saw blade. Further, this publication fails to suggest the arrangement of abrasive elements under the form of abrasive particles deposited on said leading surface. Finally, said saw blade is only intended for sawing wood and similar materials, but it is not suitable for efficiently cutting hard materials such as stones. Document US-A-1 539 259 shows a stone saw having the shape of a circular rotary blade with peripheral teeth of rhomboidal shape, using loose abrasive particles which are supplied around the circular blade. The document fails to suggest any permanent deposition of abrasive particles on the inclined leading surface of the teeth, which is in this case a negative acute cutting angle. Document US-A-4 407 263 discloses a cutting blade for hard but brittle materials, with abrasive particles deposited in grooves formed on both sides of the blade. This document does not teach or suggest an application of such a technique to circular shaped blades with peripheral projections or teeth. Therefore one of the principal objects of the invention is to provide a rotary saw blade capable of efficiently cutting stones or the like, especially by achieving improvement in both dust removal and edge sharpening as well as a substantially decreased frictional resistance. According to the invention there is provided a rotary saw blade capable of cutting hard and brittle materials such us tiles, bricks or the like, comprising a series of outward tapering generally triangular toothlike projections on and around a circular core of a base plate of metal, each projection having a trailing surface, characterized in that each projection is a consumable and comprises a leading surface which is inclined at an acute angle to the periphery of the core with respect to the reverse direction of rotation and which is deposited with abrasive particles of at least one selected from diamond, cubic- and wurtzite-type boron nitrides, said particles being held in a layer comprising metal. In the invention the tooth, or the toothlike projection, optimally has a leading surface inclined at an acute angle not greater than 60° to the periphery, or more exactly to the tangential thereto, of the circular core, said surface being either a plane or somewhat curved with tangentials not greater than 60°, to the periphery of the core, while the trailing end surface may be arranged conveniently at something in the vicinity of 90°. Such outward tapering tooth may have a pointed or rather rounded top ; anythow it will have a gradually widening round top as it wears in a cutting process. The abrasive particles of diamond, cubic- (cBN) or wurtzite type (wBN) boron nitride are deposited on the surface of the teeth, essentially over the leading face and, possibly, a minor amount on the flanks in adjacency. They may be fixed on a base plate by the electroplating or as contained in a powder metallurgically preformed tip which is then brazed along the front end of the tooth ; or alternatively they can be secured on the base plate by conventional hot press technique at the same time as they are cured. Clearance is given between every adjacent teeth, as deposited with the abrasive particles, so as to exhibit, in a view perpendicular to the axis, an area of at least 30% the total area defined between two reference circles: one passing through the outermost point of the teeth and the other, through the innermost foot point thereof. Blank teeth are arranged in such series that the leading end surface of each tooth originates in contact with the trailing end of the predecessor, or at a small spacing therefrom. Here the notch or clearance thus formed between adjacent two teeth runs substantially in parallel with the axis. Such teeth may be conveniently arranged in a common plane within the thickness of the circular core, although a somewhat zigzag arrangement across the thickness is available as well as an alternately inclined tooth arrangement relative to the core every one or more. Both work cracking tendency and cutting efficiency can improve with a decreasing width of the tooth, while the latter has correspondingly decreasing rigidity. Thus it has been found optimal that in general the tooth be given an initial relative height of or smaller than 1/10 for rather a small saw blade and, for larger ones, of or smaller than 1/15 the outer diameter of the base plate with the teeth included. The super abrasive materials applicable to this invention include diamond, natural or synthetic, and cubic and/or wurtzite type boron nitride. It is desirable that the particles have highly crystallized structures with least inner distortion, so as to be well resistant to the intense impulsive load in a cutting process. With the blades of the invention in which abrasive particles are arranged over the surface inclined to the periphery or the direction of rotation of the blade, particles in the outermost area of each consumable tooth comes in contact with the work to abrade it; such area gradually proceeds inward as abrasive particles, as worn, pop out from the matrix layer and, subsequently, the tooth substrate along with the metallic layer has been abraded. The abrasive particles are provided in plenty on the increased area of inclined tooth surfaces and sharper particles are allowed to come out to the working surface continually in the way described above, so a high cutting efficiency is achievable over a long service life until the cutting resistance reaches to a practically undurable level because of a substantial increase of the thus exposed area without abrasive particles of the tooth substrate. Obviously, electrodeposition technique may be preferred for better physical condition of contained abrasive particles, while the tipped blades are favored for increased service lives. Whether the particles are deposited directly by electrodeposition or as comprised in tips, only a fraction locating in the front are effective in forward cutting the work, while other fractions on the flanks serve principally to widen the kerf laterally, so an excessive volume thereof abrasive particles unfavorably results in an increased contact friction at work without appreciable contribution to the cutting efficiency. Thus the less the volume on the flanks, the more economically advantageous. Now the invention will be described more in particular with reference to the attached drawing which is given for the purpose of illustration only, of which: Figure 1 is a fragmental view of a rotary saw blade of the invention, with abrasive particles electrodeposited, designed to be rotated in the direction indicated with the arrow, Figure 2 is a schematic illustration of an arrangement for electrodepositing abrasive particles applicable to the invention, Figure 3 shows a fragmental view of another saw blade of the invention, with tipped teeth, to be rotated as the arrow indicates, Figure 4 a and b shows fragmentally a few examples of the relative arrangement of the tip and tooth, and Figure 5 a and b shows a few examples of tip geometry enlarged as viewed in section along A-A on Figure 3. A base plate 1 of steel comprises a circular core portion 2 and a serrated portion consisting of a series of toothlike projections 3. Optimally the plate 1 as a whole is cut out from a single sheet of a thickness on the order of 1/200 - 1/100 of the outer diameter of the blade. The serrated portion may have a decreased thickness when used for electrodeposition. The base plate 1 as cleaned is laid on a dish 4, tightly covered with an insulative disk 5, so that the teeth alone are to be open to electrolyte. The flanks of a tooth also may be partly covered with a suitable mask (not shown) as desired in order to minimize the rather unfavorable fraction of particles there as described previously. A threaded bolt 6 of electrical conductive material, such as metal, is inserted to contact with the plate 1, mated with inner threaded rings 7, 8 of insulative material, further insulated at the bottom with a plastic cap 9. The set is as a whole placed in a container 10 and dipped in a bath of electrolyte. An annular sheet 11 of nickel, for example, is placed in opposition over the teeth, on which particles 12 of diamond, for example, have been spreaded. Direct current is supplied from a source 13 through a wiring connected to the bold 6 and metal 11, thus conducting a standardized electrodeposition. In the manufacture of tipped saw blades, on the other hand, abrasive particles are scattered at normal concentrations in a powder of binder metal comprising, for example, copper, iron, or WC and Co, and are pressed into an axial tip by standard powder metallurgic technique. The tip may comprise additionally a minor proportion of filling material for better distribution of the particles. The base plate 14 in Figure 3 comprises on each tooth 15 thereof tips 16 thus produced and deposited by brazing; or alternatively a press-formed mass comprising such abrasive and binder metal may be heated on the plate 14 so as to effect the both processes simultaneously of the forming and brazing Tips may be arranged either over the whole length, as shown in Figures 3 and 4-b, or partly in an upper portion as in Figure 4-a, without or with some extention 17 over the tooth flanks for better holding as in Figures 5 a and b, respectively. Example 1 A base plate was cut out of a sheet of JIS SK-5N steel to comprise inward a circular core, 100 mm across and 1 mm thick, and 32 triangular teeth 0.8 mm thick and 5 mm high, with a leading surface plane and inclined at 58° to the periphery of the core. The base plate was under-coated with an electrodeposited nickel layer at the front end and a little area of the flanks, in adjacency, of each tooth, with the remaining portion covered with plastic parts. The plate was then spreaded at the layer with a 40/50 mesh powder of synthetic diamond, grade IMS-B, manufactured by Tomei Diamond Industry of Japan, a fraction closest to the plate was trapped on the tooth surfaces by a thin electrodeposited layer of nickel, while the balance fraction was removed from the plate, and then the layer was increased to a proper level for securing the hold of the particles. As a result 4.7 carats of diamond was held on the base plate to an overall tooth thickness of 1.8 mm. For the purpose of comparison a layer comprising 8.0 carats of diamond in the same grade and same size as above was formed by nickel electrodeposition over all the area outside the diameter of 100 mm of a circular base plate or the same grade steel with an outer diameter of 110mm and a thickness of 1 and 0.8 mm inside and outside the diameter of 100 mm, respectively. Both saw blades were subjected to the cutting of ceramic tiles, each of dimensions 108 x 108 x 10 mm, under the parameters: Blade peripheral speed: 4100 m/min. Mode: wet; cooled with civil water at a rate of 7 liters per minute The evaluation was made in terms of the relative required power input as well as the total length of cut achieved by the time when they became incapable of any advance due to a substantially increased resistance. The results are: As apparent, the blade of the invention could achieve at a speed 25% faster a service life 9 times, and at a speed 1.7 times faster, a service life 3 times as long as the control product could. Example 2 A base plate made of the same grade of steel as above and basically illustrated in Figure 3 was used, which comprised a circular core 200 mm across and 64 triangular teeth, each measuring 10 mm in height, with a front surface, plane and inclined at 50° and a rear end perpendicular to the periphery of the core. The corresponding number of tips, 2.7 x 2.7 x 12.5 mm large, were prepared from a diamond in the same grade and same size as in Example 1 at a concentration of 20, powder of bronze, and a minor proportion of filler, and were welded with silver braze. For comparison 25 tips, 2.7 x 2.7 x 20 mm large, were made with the same composition as above and soldered to the periphery of a circular base plate 200 mm across and 1.9 mm thick of the same grade steel as above, leaving a gap some 5 mm wide between every adjacent tips. The both saw blades were evaluated in cutting the tiles under the similar parameters to those used in Example 1, but at a peripheral speed of 4000 m/min. The results are: Apparently from this comparison, the blade of the invention exhibited an increased service life by about 4 times, with the relative required power smaller than 70% that with the control.

Claims: A rotary saw blade capable of cutting hard and brittle materials such as tiles, bricks or the like, comprising a series of outward tapering generally triangular toothlike projections (3,15) on and around a circular core of a base plate (1,14) of metal, each projection having a trailing surface, characterized in that each projection (3,15) is a consumable and comprises a leading surface (16) which is inclined at an acute angle to the periphery of the core with respect to the reverse direction of rotation and which is deposited with abrasive particles of at least one selected from diamond, cubic- and wurtzite-type boron nitrides, said particles being held in a layer comprising metal. The saw blade as claimed in Claim 1, characterized in that said projections (3,15) comprise pointed tops. The saw blade as claimed in Claim 1, characterized in that said leading surface (16) is a plane. The saw blade as claimed in Claim 1, characterized in that said leading surface (16) is curved with tangentials not greater than 60° to the periphery of the core. The saw blade as claimed in Claim 1, characterized in that said abrasive particles and layer consist of an electrodeposited layer of metal by which the particles are secured to the base plate (1,14). The saw blade as claimed in Claim 1, characterized in that said abrasive particles and layer consist of a powder metallurgically formed tip (16) in which the particles are distributed. The saw blade as claimed in Claim 1, characterized in that said projections (3,15) are arranged at such intervals that the total open space which is defined by two reference circles, one passing through the outermost point of the projections, and other through the innermost foot point thereof, is 30% at least of the total area defined by such reference circles.

Inventors: ISHIZUKA, HIROSHI
Applicants: ISHIZUKA, HIROSHI
Application year: 1985
Main classification: B28D1
IPC codes: B28D1, B24D5, B23D65, B23D61