Segmented diamond blade with undercut protection

A saw blade of uniform abrasive segments with undercut protection to prevent loss of segments and to extend blade life. A metal core includes a uniform peripheral contour formed as a series of spaced apart, segment mounting sections separated by radial gullet channels. A diamond cutting segment is securely bonded to each such mounting section at a bonding interface between the segment and the metal core. Adjacent the ends of each segment on opposite sides of successive gullet channels, are upstanding ears which at least register with and extend through the radial arc of the bonding interface between the segments and the metal core. Both the upstanding ears and the region beneath each segment are preferably overcoated with a wear protection material such as carbide. The overcoated region beneath each segment includes a contoured edge to assist in directing swarf away from the cutting groove.

BACKGROUND OF THE INVENTION

This invention relates to abrasive saw blades or cutting wheels for cutting concrete, asphalt and masonry materials. More specifically, the invention relates to an abrasive blade with a plurality of diamond impregnated segments affixed to a circular metal core for cutting stone-type materials.

Industrial saw blades referred to as the discontinuous rim or segmented type blade are well known and currently in widespread use. This type of blade is conventionally made by mounting to a circular core a series of short arcuate abrasive cutting segments containing diamond powder disbursed in a metal matrix. These cutting segments are usually about two inches long and are ordinarily silver soldered, brazed or welded to the rim of a steel core which has been divided into a plurality of support sections having peripheral surfaces for supporting the cutting segments.

The support sections are separated by radially extending gullets which accommodate the large thermal stresses created by the frictional heating of the blade periphery during cutting operations as well as the large thermal stresses created during the mounting of the cutting segments on the blade core during manufacture. Segmented blades have been accepted by those industries that subject the blades to heavy-duty use, such as the concrete, asphalt and masonry cutting industries where rough abrasive cutting is commonplace.

Although segmented blades may be designed for dry cutting, it is more common to continuously flush the cutting area during the cutting operation with a fluid coolant such as water in order to keep the blade as cool as possible. The coolant also serves as a lubricant to flush loose rock-like material, spent abrasive and the like from the cutting site, all of which in combination with the coolant forms an abrasive slurry which is generally referred to in the industry as “swarf”.

Even though construction of segmented blades has been developed to a high degree of reliability, blades must commonly be replaced whenever the swarf erodes the steel drive core adjacent the junction of the cutting segments with the core. This erosion occurs radially inwardly of the cutting segments around the weldment between the segments and the core and is commonly referred to as “undercutting”.

The phenomenon of undercutting is particularly bothersome because it significantly reduces blade life. Even though up to half of the original material of each abrasive cutting segment may remain, the entire blade must be replaced for reasons of safety when severe undercutting is noted. Otherwise, the likelihood increases that one or more segments will break loose during cutting operations when the blade is rotating at a high rate of speed and a potentially dangerous condition results.

In addition to the safety hazard, undercutting has an economic impact as well. Since the abrasive segments are the most costly portion of the blade, significant economic loss is incurred by undercutting due to nonuse or waste of the remaining cutting segment material. In addition, frequent replacement of undercut blades further reduces productivity by increasing the downtime workers spend in replacing the blades instead of operating the saw.

Undercutting of saw blades is particularly acute when “green” concrete is being cut. Green concrete is concrete in its relatively freshly poured state prior to fully curing. Curing can take from 4 to 60 hours to complete. During this time, the green concrete begins to shrink. If this shrinkage is not controlled, cracks will form throughout the concrete. Accordingly, it is common to cut grooves in green concrete for stress relief and crack control. Such grooves are commonly referred to as contraction joints. Because green concrete is not fully hardened and cured, it is particularly susceptible to forming highly abrasive swarf, which aggressively acts to undercut segments of the saw blade.

In the past, numerous solutions have been directed to the problems of undercutting and segment lose. U.S. Pat. No. 4,291,667 of Eichenlaub et al.; U.S. Pat. No. 4,854,295 of Sakarcan; U.S. Pat. No. 5,787,871 of Jones et al.; and U.S. Pat. No. 5,839,423 of Jones et al. each acknowledge such problems and are representative of some of the previously proposed remedies. Generally speaking, past attempts have focused effort on better ways to mount the segments onto the core or to remove or flush the abrasive swarf from the cutting site. Such efforts have achieved only limited success.

Some of the prior attempts to reduce undercutting have included asymmetrical cutting elements or dimensional variances of the gullets between successive segments in an effort to protect the symmetrical or uniform cutting elements or to create a turbulent flow pattern, as opposed to a laminar flow pattern, of the swarf around the blade. Such changes in abrasive blade design have many times resulted in increased blade vibration and wear.

Accordingly, a need exists in the industrial cutting industry for a segmented abrasive blade having improved wear characteristics to prevent premature wear adjacent the bond line formed between the blade core and the cutting segments. The primary object to this invention is to meet this need.

SUMMARY OF THE INVENTION

The present invention has been developed to meet the needs noted above and therefore has as a primary objective the provision of a segmented type abrasive cutting blade which is highly resistant to core undercutting and which allows full use of the costly abrasive cutting segments.

Another object of the invention is to provide an abrasive blade of the character previously described which is safe and reliable in operation and use.

An additional object of the invention is to provide an abrasive blade of the character previously described to protectively shield the weldment line joining the segment to the blade core from direct impact by swarf in the cutting site.

Another object of the invention is to provide an abrasive blade of the character previously described have wear resistance regions to assist in the protection of the weldment joining the segment to the blade core and to also direct swarf away from the cutting site.

Yet another object of the invention is to provide an abrasive blade of the character previously described that minimizes blade and cutting segment vibration to assist in safe operations and prolonged blade life.

A further object of the invention is to provide an abrasive blade of the character previously described which is radially symmetrical as a result of manufacture from uniformly similar segments securely bonded to a balanced and radially consistent blade core.

In summary, therefore, an object of the invention is to provide a saw blade of uniform abrasive segments with undercut protection to prevent loss of segments and to extend blade life. A metal core includes a uniform peripheral contour formed as a series of spaced apart, segment mounting sections separated by radial gullet channels. A diamond cutting segment is securely bonded to each such mounting section at a bonding interface between the segment and the metal core. Adjacent the ends of each segment on opposite sides of successive gullet channels, are upstanding ears which at least register with and extend through the radial arc of the bonding interface between the segments and the metal core. Both the upstanding ears and the region beneath each segment are preferably overcoated with a wear protection material such as carbide. The overcoated region beneath each segment includes a contoured edge to assist in directing swarf away from the cutting groove.

Other and further objects of the invention, together with the features of novelty appurtenant thereto, will appear in the course of the following description.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring first toFIGS. 1-5of the drawings in greater detail, the abrasive blade of this invention characteristically includes a generally circular, flat metal core10of uniform thickness. The core10has a central, axial bore11therethrough to receive a drive shaft or work arbor spindle of a saw (not shown) to rotatably drive the core10in the direction indicated by the directional arrow13. The core10further includes a drive pin bore12offset from the axial bore10to receive a drive pin associated with the drive shaft or work arbor spindle of a saw to aid in the rotational drive of the core10.

The core10may also be provided with a series of stress relief cuts14therethrough in a uniform radial pattern. In addition to relief of internal stress risers in the core10, the relief cuts14assist in the control of warpage and dissipation of heat during sawing operations.

The outermost edge or perimeter of the core10, as best shown inFIGS. 1,4&5, is an interrupted circular contour formed by a series of spaced apart mounting sections or tongues15. The tongues15are separated by radial gullets or channels16extending in a direction toward the axial bore11of the core10. The bottom of each such channel16terminates in a circular or otherwise arcuate contour17in order to relieve any stresses in the metal.

As perhaps most easily understood with reference toFIG. 5which illustrates a representative tongue section15before attachment of a diamond segment, the configuration of each mounting section or tongue15includes a peripheral mounting edge18recessed between a pair of upstanding ears19. Accordingly, adjacent ears19of successive tongues15define the mouth or initial opening of the gullet16between the adjacent tongues15.

Referring next toFIG. 4, securely attached to the peripheral mounting edge18of each tongue15, as by soldering, brazing, or welding (i.e., resistance, electron beam or laser), is a cutting segment20. The attachment process results in a weldment or bonding interface22between the mounting edge18and the segment20. Each segment20may be fabricated in accordance with techniques readily understood by those skilled in the art from an abrasive material such as diamond particles dispersed within a metal matrix. Such segments are commonly called diamond segments as a shorthand reference. Nevertheless, for the purposes of this invention, the abrasive material from which the segments are made may be any of the conventional abrasives which are well known in a wide variety of industrial cutting applications.

Typically, both the diamond segment20and the associated mounting edge18to which it is bonded are arcuate in shape and this configuration is consistently illustrated in the accompanying drawings. However, it is also know in the art to have flat, rather than arcuate, matting surfaces between the diamond segment and its associated mounting edge. Such configurations are also contemplated for use with this invention. Regardless of the configuration of the bonding interface22between the mounting edge18and its associated segment20, whether it be straight or arcuate, when the core10is rotatable powered during cutting operations, the bonding interface22travels in an arcuate orbit around the drive axle of the saw. It is of critical importance in the practice of this invention that the upstanding ears19project radially outward a sufficient distance to at least register with, and preferably extend through, the outermost radial arc of the bonding interface22between the segments20and the metal core10.

On each side of the core10, beginning on the tongues15and tapering inwardly towards the axial bore11are a plurality of hardfaced coating skins or regions26affixed to the surface of the metal core10. Each coating skin26is a thin layer of wear resistance material such as carbide. These regions are consistently depicted in the drawings with a net-type hatch pattern to distinguish these thin regions from the adjacent metal of the core10and bonding interfaces22. Those skilled in the art will readily understand the various types of wear resistance materials used on metals and the processing techniques necessary to bond a wear resistance coating to its associated metal substrate. For the purposes of this invention, portions of the shape, configurations and contours of the coating skins26are of critical importance, but the wear resistance material from which the coating skins are made may be any of the conventional materials which are well known in a wide variety of industrial cutting applications.

In terms of the shape and configuration of the coating skins26, it is important that the metal of the core beneath the segment20be coated. It is also important that each coating skin26has a contoured leading edge27directed generally inward toward the axial bore11to assist in directing swarf out of the cutting groove and away from the arcuate orbit traveled by the bonding interfaces22. The leading edge27may be a linearly angled edge as illustrated in the drawings or may be of a nonuniform, arcuate shape. As illustrated in the drawings, the coating skins26are preferably triangular in shape to incorporate the foregoing objectives and may be terminated as a rounded apex well short of the axial bore11itself. What appears to be important is that the skin26coat the core beneath the segment20and the leading edge27of each skin26taper inwardly from the gullets16to aid in the removal of cutting slurry from the cutting groove of the material being sawed.

In accordance with the desirability of coating those parts of the metal core10in close proximity to the segment20, and most particularly the bonding interface22, the upstanding ears19are preferably coated with wear resistance carbide and may actually form an extended portion of the triangular skin26beneath the segment20. Likewise, it is desirable, although certainly optional, that the bonding interface22also be coated with wear resistance carbide for added protection. Obviously, the segment20must be first attached to the metal core10if the bonding interface22is to be coated with wear resistance material. The more conventional manufacturing technique, however, is to first affix the coating skins26to the metal core10and then attach the cutting segments20which results in the upstanding ears19receiving application of the carbide layer but the bonding interface remains uncoated.

The importance of the height of the upstanding ears19relative to the bonding interfaces22has previously been mentioned. Also of critical importance are the relative, rather than specific, thicknesses of the metal core10, segment20and coating skin26. Reference is made toFIG. 4of the drawings. The metal core10may be of any conventional thickness of a variety commonly used in the industrial cutting applications. The coating skin26must be of sufficient thickness on each side of the core10to adequately protect the common or treated steel from which the saw blade is fabricated, particularly in the region underlying the segment20. As is normal and well known in this art, the segment20is characteristically thicker than the core so as to project an equal distance on each side of the core10. But it is important in this invention that the segment have a sufficient thickness to project an equal distance on each side of both the core10and the layers (one on each side of the core10) of the coating skins26. Therefore, the thickness of the segment20must be at least equal to, and preferably greater than, the thickness of the core10plus twice the thickness of a coating skin26. Alternatively stated as a limitation on the thickness of the coating skin26, it must be equal to or less than half the thickness of the segment20minus half the thickness of the core10.

The abrasive blade illustrated inFIGS. 1-5includes eighteen evenly spaced tongue15and segment20pair combinations. The specific number of such combinations is unimportant and an alternative number can be selected.FIGS. 6-8illustrate an abrasive blade having ten evenly spaced tongues and with 20 paired cutting segments as a second preferred embodiment of the invention. The following description will assist in an understanding of the similarities and differences necessary when modifying the number of the tongue and segment combinations of the blade.

The abrasive blade of the second embodiment includes a generally circular, flat metal core40of uniform thickness. The core40has a central, axial bore41therethrough to receive a drive shaft or work arbor spindle of a saw (not shown) to rotatably drive the core40in the direction indicated by the directional arrow43. The core40further includes a drive pin bore42offset from the axial bore40to receive a drive pin associated with the drive shaft or work arbor spindle of a saw to aid in the rotational drive of the core40.

The core40may also be provided with a series of stress relief cuts44therethrough in a uniform radial pattern. In addition to relief of internal stress risers in the core40, the relief cuts44assist in the control of warpage and dissipation of heat during sawing operations.

The outermost edge or perimeter of the core40, as best shown inFIGS. 6 & 8, is an interrupted circular contour formed by a series of spaced apart mounting sections or tongues45. The tongues45are separated by radial gullets or channels46cut into the core40at an acute angle relative to a radial line from the axial bore41of the core40. The bottom of each such channel16terminates in an arcuate contour47in order to relieve any stresses in the metal.

As perhaps most easily understood with reference to the enlarged fragmentary view ofFIG. 8, the configuration of each mounting section or tongue45includes a pair of peripheral mounting edges48&49of substantially equal dimensions which are separated by an upstanding ear50.

Securely attached to each of the peripheral mounting edges48&49of each tongue45, as by soldering, brazing, or welding (i.e., resistance, electron beam or laser), is a cutting segment60. The attachment process results in a weldment or bonding interface62between the mounting edges48&49and their associated segments60. Each segment60may be fabricated in accordance with techniques readily understood by those skilled in the art from an abrasive material such as diamond particles dispersed within a metal matrix. Nevertheless, for the purposes of this invention, the abrasive material from which the segments are made may be any of the conventional abrasives which are well known in a wide variety of industrial cutting applications.

Typically, both the diamond segments60and the associated mounting edges48&49to which they are bonded are arcuate in shape and this configuration is consistently illustrated in the accompanying drawings. However, it is also know in the art to have flat, rather than arcuate, matting surfaces between the diamond segment and its associated mounting edge. Such configurations are also contemplated for use with this invention. Regardless of the configuration of the bonding interface62between the mounting edges48&49and their associated segments60, whether it be straight or arcuate, when the core40is rotatable powered during cutting operations, the bonding interface62travels in an arcuate orbit around the drive axle of the saw. It is of critical importance in the practice of this invention that the upstanding ear50between successive segments60on a mounting tongue45projects radially outward a sufficient distance to at least register with, and preferably extend through, the outermost radial arc of the bonding interface62between the segments60and the metal core40.

In comparing the diamond blade construction show inFIGS. 1-5with the second embodiment shown inFIGS. 6-8, it will be understood that the second embodiment has a single ear50protecting two adjacent segments62while an upstanding ear19is adjacent each end of each segment20in the first embodiment. Although it is thought that the first embodiment offers greater protection to the segment and particularly the bonding interface, even a single ear50contacting adjacent segments62offers significant protection from segment loss over techniques previously taught by the prior art.

On each side of the core40, beginning on the tongues45and tapering inwardly towards the axial bore41are a plurality of hardfaced coating skins or regions66affixed to the surface of the metal core40. Each coating skin66is a thin layer of wear resistance material such as carbide. These regions are consistently depicted in the drawings with a net-type hatch pattern to distinguish these thin regions from the adjacent metal of the core40and bonding interfaces62. Those skilled in the art will readily understand the various types of wear resistance materials used on metals and the processing techniques necessary to bond a wear resistance coating to its associated metal substrate. For the purposes of this invention, portions of the shape, configurations and contours of the coating skins66are of critical importance, but the wear resistance material from which the coating skins are made may be any of the conventional materials which are well known in a wide variety of industrial cutting applications.

In terms of the shape and configuration of the coating skins66, it is important that the metal of the core beneath the paired segments60be coated. It is also important that each coating skin66has a contoured leading edge67directed generally inward toward the axial bore41to assist in directing swarf out of the cutting groove and away from the arcuate orbit traveled by the bonding interfaces62. The leading edge67may be a linearly angled edge as illustrated in the drawings or may be of a nonuniform, arcuate shape. As illustrated in the drawings, the coating skins66are preferably triangular in shape to incorporate the foregoing objectives and may be terminated as a rounded apex well short of the axial bore41itself. What appears to be important is that the skin66coat the core beneath the segment60and the leading edge67of each skin66taper inwardly from the gullet16to aid in the removal of cutting slurry from the cutting groove of the material being sawed.

In accordance with the desirability of coating those parts of the metal core40in close proximity to the paired segments60, and most particularly the bonding interfaces62thereof, the upstanding ear19between the paired segments60is preferably coated with wear resistance carbide and may actually form an extended portion of the triangular skin66beneath the segments60. Likewise, it is desirable, although certainly optional, that the bonding interface62also be coated with wear resistance carbide for added protection. Obviously, the segments60must be first attached to the metal core40if the bonding interface62is to be coated with wear resistance material. The more conventional manufacturing technique, however, is to first affix the coating skins66to the metal core40and then attach the cutting segments60which results in the upstanding ear50receiving application of the carbide layer but the bonding interface62remains uncoated.

The importance of the height of the upstanding ears50relative to the bonding interfaces62has previously been mentioned. Also of critical importance are the relative, rather than specific, thicknesses of the metal core40, segment60and coating skin66. Reference is made toFIG. 7of the drawings. The metal core40may be of any conventional thickness of a variety commonly used in the industrial cutting applications. The coating skin66must be of sufficient thickness on each side of the core10to adequately protect the common or treated steel from which the saw blade is fabricated, particularly in the region underlying the segment60. As is normal and well known in this art, the segment60is characteristically thicker than the core so as to project an equal distance on each side of the core40. But it is important in this invention that the segment60have a sufficient thickness to project an equal distance on each side of both the core40and the layers (one on each side of the core40) of the coating skins66. Therefore, the thickness of the segment60must be at least equal to, and preferably greater than, the thickness of the core40plus twice the thickness of a coating skin66. Alternatively stated as a limitation on the thickness of the coating skin66, it must be equal to or less than half the thickness of the segment60minus half the thickness of the core40.

Operation of the abrasive blade can be understood with reference to the embodiment illustrated inFIGS. 1-5. A blade constructed in accordance with the foregoing principles is mounted by placing the axial bore11on the drive shaft or work arbor spindle of a saw so that the blade will be driven in the direction of the rotational arrow13. If the saw is equipped with a drive pin, then it will be received in the drive pin bore12to assist in powering the rotation of the blade.

During cutting application, as in concrete for example, the removal of material is primarily achieved by the outer circumferential surface of the segments20engaging the bottom of the groove being cut. Each segment20rotates through the groove of the cut to remove material in an abrasive, grinding fashion. Over prolonged cutting, the segment20gradually wears away. This exposes fresh diamond bits held within the matrix of the segment20to renew the circumferential cutting surface of the segment.

Testing has confirmed superior results for an abrasive blade constructed in accordance with the principles of this invention. The feature of upstanding ears assist in protecting the bonding interfaces. Likewise, the triangular shaped coating skins assist in protecting the bonding interfaces, as well as directing the swarf away from contact with the bonding interfaces to thereby increase blade life and minimize premature segment loss.

From the foregoing it will be seen that this invention is one well adapted to attain all end and objects hereinabove set forth together with the other advantages which are obvious and which are inherent to the structure.