Patent Document

CROSS-REFERENCE OF RELATED APPLICATIONS 
     This application is a continuation of end claims the benefit under 35 USC § 120 of the filing date of International Application No. PCT/US00/00365, filed Jan. 7, 2000, which was published In English under PCT Article 21(2), which is incorporated herein by reference, and which, in turn, is a continuation of and claims the benefit under 35 USC § 120 of the filing date of U.S. patent application Ser. No. 09/232,401, filed Jan. 15, 1999, now U.S. Pat. No. 6,050,163, which also is incorporated herein by reference. 
    
    
     FIELD OF THE PRESENT INVENTION 
     The present invention relates to a saw arrangement and, in particular, to a saw blade having a liquid transport cavity for use with a lubricating guide support assembly. 
     BACKGROUND OF THE PRESENT INVENTION 
     Saw blades are commonly used to cut raw materials into intermediate or final products, and as the width of the saw blade is decreased, more product can be cut generating higher productivity. As an example, a simple arrangement of circular saw blades mounted on an arbor were once often used to cut pieces of lumber. In such arrangements which were used for cutting Southern Yellow Pine, the typical width of each circular saw blade was approximately 0.180 inches. 
     An improvement that was made in this simple arrangement is the provision of a guide support assembly comprising two guide supports with opposed bearing surfaces for maintaining proper alignment of each circular saw blade therebetween during cutting, thereby permitting the reduction of the thickness of the saw blade to dimensions that would have otherwise compromised cutting alignment. The guide support assembly is required because the circular saw blades have been reduced to a thickness rendering them incapable of maintaining a generally planar configuration during cutting, thereby making them unsuitable for use without auxiliary side support. Unfortunately, as saw blade thickness decreases more support must be provided by the bearing surface of the guide support against the saw blade which generates greater friction therebetween. This increase in friction can lead to excessive heating of the saw blade which, in turn, can ultimately lead to carbide insert teeth breakage, sawing deviation, guide pad wear, and saw blade damage. 
     Further improvements to this saw arrangement were made in the late 1980&#39;s. In a first improvement, cooling of the saw blade is accelerated by the provision of circumferential air slots throughout the saw body, of which the saw blade disclosed in Carter Jr. U.S. Pat. No. 4,776,251 is representative. In Carter Jr. a circular saw blade is disclosed having slots cut in the body thereof using a laser. Each slot consists of an arc of a circle concentric with the saw body and parallel to the peripheral edge of the saw body. The radial width of the slot is selected to be between 0.002 and 0.015 inches and remains constant in the circumferential direction of the saw body between opposed circumferential ends of the slot. The common problem of sawdust packing in similar openings formed in a saw body, as disclosed for example in Jansen-Herfeld U.S. Pat. No. 4,574,676 and as expressly discussed by Carter Jr. at cols. 3-4, is avoided in the circular saw blade of Carter Jr. because of the limitation on the radial width of each slot to less than 0.015 inches and because of the disposition of the slots in a circumferential direction with no radial component. Furthermore, unlike the blade disclosed in Jansen-Herfeld, the circular saw blade of Carter Jr. can be used with guide supports without damaging the bearing surfaces thereof due to the narrowness of each slot and its circumferential arrangement. In this arrangement, the plurality of slots provide a radiator cooling effect that accelerates cooling of the saw blade but the slots fail to reduce any friction generated between the saw body and the bearing surface of the guide supports. 
     In a second, independent improvement to the saw arrangement having guide supports, an actual reduction of the friction between the saw blade and the guide supports is accomplished by the application within each guide support of a lubricating liquid to the saw body. A conventional saw arrangement including a representative illustration of this improvement is disclosed in McGehee U.S. Pat. No. 4,848,200. In this saw arrangement a mixture of oil and water is applied to a saw body of a circular saw blade as it passes by guide supports retaining the saw blade in proper cutting alignment. Typically the liquid is delivered to a recessed opening in each guide support under a pressure of 35 psi and the guide support is maintained immediately adjacent the saw body at a gap of between 0.001 and 0.003 inches, whereby a thin film of liquid is applied to the saw body as it passes thereby. The application of a lubricating liquid reduces friction—and thus heat—generated between the guide supports and the saw body. 
     As a result of such improvements in saw arrangements having guide support assemblies, the conventional thickness of a saw blade in a saw arrangement used to cut Southern Yellow Pine has been reduced from 0.180 inches to 0.080 inches. Nevertheless, a need has arisen in recent years to reduce the thickness of a circular saw blade for cutting Southern Yellow Pine still further as demand for greater productivity in lumber mills has arisen. Such attempts at thinner saw blades generally have been unsuccessful due to insufficient cooling and consequent overheating, and better cooling techniques must be developed to advance this sought-after reduction in saw blade thickness. 
     SUMMARY OF THE PRESENT INVENTION 
     The present invention exhibits improved cooling of a saw blade retained in proper cutting alignment by lubricating saw guide supports, thereby advancing attempts to reduce saw blade thickness. In particular, the present invention, when used to cut Southern Yellow Pine, has been found (among other advantages): to provide less maintenance than conventional saw blades; to provide less entailed maintenance operations when maintenance is required than that of conventional saw blades; and to provide a longer operating life than conventional. 
     Briefly described, the present invention relates to a saw arrangement comprising the combination of a saw blade and a lubricating guide support assembly including two guide supports having opposed bearing surfaces for maintaining the saw blade in proper cutting alignment therebetween. The saw blade includes a saw body that defines a cavity therein and a cutting edge disposed along a periphery of the saw body for cutting during movement of the saw blade. Each guide support includes the bearing surface being disposed immediately adjacent the saw body for support of the saw blade during cutting as well as a lubricating system comprising a recessed area extending from the bearing surface and containing liquid exposed to the saw body, whereby the liquid is applied to the saw body as it passes by the recessed area during movement of the saw blade. 
     In a feature of the present invention, the cavity is arranged on the saw body to pass by the recessed area during movement of the saw blade and is dimensioned to receive liquid therein for transport away from the recessed area to be distributed to the saw body as well as a cutting area of the saw blade. Preferably, the saw blade is circular, and the saw body is planar and includes three cavities disposed relative to one another at 120 degrees about the center of the saw blade. Each cavity is triangular in cross-section and extends from a first planar side of the saw body to a second planar side thereof. Also, each cavity preferably includes only rounded corners, and each cavity preferably has a radial dimension that varies along a circumferential direction of the circular saw blade between opposed circumferential ends of the cavity. 
     The present invention also relates to a method of using a circular saw blade itself with a lubricating guide support assembly to cut lumber from Southern Yellow Pine. In particular, the circular saw blade includes a planar saw body having an axial thickness of no greater than 0.080 inches and defines a cavity therein having a radial dimension that varies along a circumferential direction of the circular saw blade between opposed circumferential ends of the cavity. The cavity itself preferably includes a radial dimension greater than 0.015 inches sufficient to receive liquid therein when passing by a recessed area of a lubricating guide support. 
     The present invention further relates to a method for distributing lubricating and cooling liquid to a cutting area of a saw blade used in combination with a lubricating guide support assembly. In particular, the method includes the steps of delivering liquid into a recessed area of the lubricating guide support, filling a cavity of the saw body with the liquid by passing the cavity immediately adjacent the recessed area, and transporting the liquid away from the recessed area by continuing to move the cavity from the recessed area towards the cutting area. The transported liquid passes from the cavity when the cavity moves beyond the bearing surface as a result of air turbulence and inertial forces, and the liquid is consequently distributed both to the saw body of the blade as well as to the cutting area thereof including the carbide insert teeth of the saw blade. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features and advantages of the present invention will become apparent to one having ordinary skill in the art in view of the following disclosure of the preferred embodiment of the present invention and with reference to the drawings, in which: 
     FIG. 1 is a perspective partial view of a saw arrangement of the present invention including a plurality of circular saw blades and lubricating guide support assemblies therefor; 
     FIG. 2 is a perspective partial view of a guide support of a guide support assembly of FIG. 1; 
     FIG. 3 is a plan view of a circular saw blade of FIG. 1; 
     FIG. 4 is an additional plan view of the circular saw blade of FIG. 3; and 
     FIG. 5 is an enlarged view of a section of the circular saw blade of FIG. 3 including a cavity of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, the present invention relates broadly to a saw arrangement  8  including the combination of a circular saw blade  10  and a lubricating guide support assembly  12 . As shown in FIG. 1, this combination can be repeated to form what is commonly known as a horizontal gang saw  14  in the lumber industry. In each combination, and with reference to FIG. 3, the saw blade  10  includes a cutting edge  16  comprised of carbide insert teeth  18  for cutting during rotation of the saw blade  10 . The saw blade  10  also includes a central opening  20  by which the saw blade  10  is mounted to an arbor  22  extending along an axis  24  that simultaneously drives each saw blade  10  by rotation in a circumferential direction ω. The rotation of the saw blades  10  generates the cutting action of the gang saw  14  for the cutting of lumber in a cutting area (generally indicated at  26 ). 
     Preferably each circular saw blade  10  includes a planar saw body  28  having a diameter of 18½ inches and a thickness in an axial direction of 0.080 inches or less. Furthermore, each planar saw body  28  preferably defines three liquid transport cavities  30  therein which extend entirely through the axial extent of the saw body  28  from a first planar surface  32  thereof to a second planar surface  34  thereof. Moreover, the three cavities  30  are preferably equally spaced from the others around the axial center of the saw body  28 , i.e., spaced 120 degrees apart. Each cavity  30  is also triangular in cross-section in the embodiment shown, but other shapes are equally applicable. 
     Regardless of the actual cross-sectional shape of the cavity  30  that is used, the cavity  30  preferably includes a radial dimension ρ that varies along a circumferential direction θ of the circular saw blade  10  between opposed circumferential ends  36 ,  38  of the cavity  30  as shown in FIG.  5 . The radial dimension ρ also preferably exceeds 0.015 inches whereby the cavity  30  has sufficient dimension to readily receive liquid therein; it is noted that the laser cut slots of Carter Jr. U.S. Pat. No. 4,776,251 have a radially dimension less than 0.015 inches and, therefore, are of an insufficient width to receive liquid from the recessed area (just as sawdust packing is avoided by such a small width). 
     Each cavity  30  in the present invention also preferably includes rounded corners  40  each having a radius of, for example, {fraction (3/16)} of an inch. A trailing edge  42  of the cavity  30  is also preferably oriented at a negative angle α of preferably 5 degrees with respect to a radius R of the saw blade  10 . These design configurations for the cavity  30  of the present invention prevent sawdust packing and enhance liquid distribution to the saw body  28  and cutting area  26  as discussed in detail below. 
     The lubricating guide support assembly  12  includes a plurality of guide supports  44 . As shown in FIG. 2, each guide support  44  includes a bearing surface  46  disposed immediately beside an adjacent saw blade  10  for proper alignment and support of the saw blade  10  during cutting. Each guide support  44  also includes a separate bearing surface  46  for each adjacent saw blade  10 . Furthermore, each bearing surface  46  generally is spaced approximately 0.002 inches from an adjacent saw body  28  when no cutting is being performed. 
     The guide support  44  includes a liquid lubricating system comprising a recessed area  48  extending within the guide support  44  between bearing surface  46  thereof. The recessed area  48  is filled with a liquid under a pressure of approximately 35 psi that is exposed to the adjacent saw bodies  28 , whereby a thin film of liquid is applied to each saw body  28  as it passes by the recessed area  48  during rotation of the saw blade  10 . As illustrated by the square area  49  of FIG. 4 corresponding to an area of the saw body  28  exposed to the liquid in the recessed area  48 , the recessed area  48  preferably covers in one rotation of the saw blade  10  a large portion of an annular section of the saw body defined by dashed lines  50  thus providing for wide coverage of the saw body  28 . The liquid is pumped under pressure to the recessed area  48  through passageways  52  and the liquid itself generally comprises an oil/water mixture, the oil being used for lubrication and the water being used for cooling. 
     It has been determined by experiment that the total opening area of the cavities  30  preferably should minimally approximate 6% of a “cutting triangle” of the circular saw blade  10 . As illustrated in FIG. 3, the cutting triangle  54  is an approximate right triangle having an arc  56  of the cutting edge  16  as a hypotenuse. In particular, the arc  56  extends between a first vertex  58  defined by the point where a carbide insert tooth enters the cant, and a second vertex  60  defined by the point where another carbide insert tooth simultaneously exits the cant. A first leg  62  lies along a bedplate  64  of the saw arrangement  8  and includes the first vertex  58 , and a second leg  66  lies perpendicular to the bedplate and includes the second vertex  60 . In the circular saw blades  10  of the drawings each cavity  30  is preferably identical to the others and includes an opening area approximately equal to 2% of the area of the cutting triangle  54 . 
     Operation of the saw arrangement  8  and circular saw blade  10  of the present invention will now be described. 
     During rotation of the arbor  22 , each saw blade  10  of the gang saw  14  is simultaneously rotated while liquid is delivered under pressure into the recessed area  48  of each guide support  46 . The rotation of the saw body  28  past the recessed area  48  and the disposition of the bearing surface  46  of each guide support  44  immediately adjacent the saw body  28  in conjunction with the pressurized liquid in the recessed area  48  results in a thin film of liquid initially being applied to the annular section defined by the dashed lines  50  shown in FIG.  4 . 
     Each cavity  30  is formed in each saw body  28  in this annular section defined by dashed lines  50  whereby each cavity  30  will pas by the recessed area  48  during rotation of the saw blade  10  as illustrated in FIG.  3 . As the cavity  30  passes by the recessed area  48  the pressurized liquid is driven into the cavity  30  and transported away from the recessed area  48  toward the cutting area  26 . Once the cavity  30  clears the bearings surface  46  of the guide support  44 , air turbulence and inertial forces cause the transported liquid to pass out of the cavity  30  for distribution to the saw body  28  and the cutting area  26  including the cutting edge  16  of the saw blade  10  both before and within the cant. The distribution of liquid to the saw body  28  and to the cutting area  26  is thereby increased as opposed to simply applying a liquid film to the annular section define by dashed lines  50 . 
     The design configurations of each cavity  30  set forth above enhance this liquid distribution and prevent sawdust packing. In particular, due to the radial variance of ρ in the dimension of the cavity  30 , the cavity  30  is narrower at the leading point first  68  passing by the recessed area  48  and grows radially larger circumferentially along the saw body  28 . This narrow-to-wide transition, in conjunction with the rounded corners  40  and negative angle α of the trailing edge  42  of the cavity  30 , draws the liquid into the cavity  30  and, when the cavity  30  clears the bearing surface  46 , draws air into the cavity  30  displacing the liquid carried therein out of the cavity  30  in what is believed to be a vortex or swirling action. It has also been observed that the trailing edge  42 , because of its angled orientation to the radius R of the blade  10 , enhances distribution of the liquid toward the center of the saw body  28  before inertial forces draw the liquid in a direction from the center of the saw body  28  towards the cutting edge  16 . Moreover, during its pass through the cant, sawdust is driven towards the angled trailing edge  42  and is deflected thereby without finding niches to accumulate within, especially since the corners  40  of the cavity  30  are rounded. Thus, among other benefits of the present invention, sawdust packing is avoided without unduly limiting the radial dimension ρ of the cavity  30  to a constant value less than 0.015 inches as taught by Carter Jr. Moreover, it is noted that a narrow slot as disclosed by Carter Jr. would not draw the required liquid therein while passing by the recessed area  48  of the present invention. 
     In specific comparison of the saw arrangement against the lubricating guide blocks of McGehee and a saw blade as taught by Carter Jr., Applicant has found that the saw arrangement  8  of the present invention is clearly superior. In particular, following cutting of lumber from Southern Yellow Pine, a layer of liquid along the cut lumber and relatively cool sawdust both were observed using the saw arrangement  8  of the present invention, but no liquid layer and relatively hot sawdust both were observed using the saw blade of Carter Jr. with the lubricating guide blocks of McGehee. Carbide teeth breakage was also encountered using the saw blade of Carter Jr. with the lubricating guide blocks of McGehee, but was not encountered under identical circumstances using the saw arrangement  8  of the present invention. 
     The saw blade  10  of the present invention also exhibits easier maintenance than other conventional saw blades. In particular, the rounded corners  40  and size of each cavity  30  allow for easier clean out and reshaping of the cavity  30  by a saw filer. For instance, the heating and cooling of the saw blade  10  causes the area of the saw body  28  defining the cavities  30  to harden, becoming brittle and cracking over time. By further rounding the cavities  30 , the saw filer is able to file away these hardened areas without significantly altering the shape of the cavity  30 . The filer can also refurbish openings defining the cavities  30  where the edges have been worn by friction, maintaining the integrity of the saw body  28  and the effectiveness of the liquid transporting capabilities of the cavities  30 . 
     Another benefit of the present invention over conventional saw arrangements including liquid lubrication guide supports such as that disclosed in McGehee is the reduction in the accumulation time of the liquid within the recessed area  48  due to the additional removal of the liquid from the recessed area  48  by the cavities  30 . Reduction of the time of the liquid within the recessed area  48  reduces the time in which the liquid within the recessed area  48  is thermally exposed to the guide support  44  and subjected to heat transfer via convection resulting from the abutment between each bearing surface  46  with an adjacent saw body  28 . 
     In sum, the liquid transport cavities of the present invention achieve a degree of cooling not obtained by the aforementioned conventional saw arrangements and provide greater operating life and easier and less maintenance than that of other conventional saw blades. Furthermore, the improved cooling benefits of the present invention further the attempt to reduce saw blade thickness below the current floor of 0.080 inches for saw blades used with guide supports to cut lumber from Southern Yellow Pine. 
     It will therefore be readily understood by those persons skilled in the art that the present invention is susceptible of broad utility and application. Many embodiments and adaptations of the present invention other than those herein described, as well as many variations, modifications and equivalent arrangements, will be apparent from or reasonably suggested by the present invention and the foregoing description thereof, without departing from the substance or scope of the present invention. Accordingly, while the present invention has been described herein in detail in relation to its preferred embodiment, it is to be understood that this disclosure is only illustrative and exemplary of the present invention and is made merely for purposes of providing a full and enabling disclosure of the invention. The foregoing disclosure is not intended or to be construed to limit the present invention or otherwise to exclude any such other embodiments, adaptations, variations, modifications and equivalent arrangements, the present invention being limited only by the claims appended hereto and the equivalents thereof. 
     Thus, it will be apparent, for example, that the liquid passageways of the guide supports could deliver the liquid under pressure directly to the saw body in the manner of liquid ports forming the recessed area of the guide supports, with the liquid transport cavities passing by the liquid ports for receipt of liquid directly therein. The cavities also do not have to extend entirely through the saw body, although better distribution of the liquid carried therein to the saw body and the cutting area is achieved when air turbulence passes through the saw body. Moreover, the configuration of the cavity need not be triangular in cross-section nor have only rounded corners therein. It is only a requirement that the cavities be of sufficient area and dimension to receive a quantity of liquid therein from the guide supports as it passes thereby for delivery to the saw body and cutting area. It should also be apparent that while a horizontal gang saw has been used to illustrate the preferred embodiment of the present invention, the present invention is equally applicable to vertical gang saws or to single blade rip saws, whether vertically or horizontally disposed.

Technology Category: 7