Patent Publication Number: US-6340022-B1

Title: Blade and arbor adaptor for circular saw

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention concerns shaft drive circular blade saws. More particularly, it concerns blades and arbor adaptors for use on different saws with specialized configuration blade mounting arbors. 
     2. Description of the Prior Art 
     Circular saws as used herein are those saws having a power source such as an electric or pneumatic motor or gasoline engine which, through a shaft, rotate a generally planar circular blade to cut a kerf. The circular saws may be hand held or mounted on a wheeled carriage or the like, and may cut wood, metal, masonry or other materials. To that end, a number of different saws have been developed which are particularly adapted to for cutting different materials, and blades have been designed for a particular type of cut to be made. For example, smaller hand-held saws have been developed for trim carpentry or metalworking use, larger saws for framing carpentry, and still larger saws mounted on wheeled carriages for use in cutting concrete. The blades for these applications are very different, with tooth patterns varying for metalworking on different metals, cross-cut and rip-cutting of different woods, and abrasive tipped and different toothed blades for cutting concrete or other masonry. 
     Such circular saws may mount the blade to the shaft by use of an arbor. The motor or other power source turns the shaft and the arbor is rotatably coupled to the shaft. The blade then mounts on the arbor and is held in place by a retaining bolt threadably received in the arbor. A saw may be developed with an arbor having a blade mount with a specific configuration rather than a conventional round mount, e.g. square, diamond-shaped, triangular, etc. In such circumstances, the blade must be configured to with an opening which matches the mount. One approach to this problem in the past has been to provide a blade with has a central round opening common to many saws and a frangible insert which may be removed to permit mounting on a particular saw. While this has been useful in some circumstances, it does not provide for use with arbors having blade mounts of yet further different configurations. Moreover, in heavy duty applications, it risks weakening the blade when the opening for the removable insert has sharp corners. In addition, some larger blades require additional support to provide sufficient torque transmission to avoid blade slippage. 
     Some prior art saws have employed an arbor or shaft which includes a threaded stud which is threadably received in the arbor or shaft and displaced from the axis of rotation so as to be off-center. This in turn has required a saw blade which has a mounting hole similarly displaced from the center of the saw blade in order to be usable and function by rotating without oscillating. Such an arrangement severely limits the availability of different blades which may be used with the saw when so configured and leads to increased costs of operation. 
     There has thus arisen a need for a simple and rugged arbor adaptor which permits the use of non-specific saw blades with several circular saws, yet provides sufficient support and strength. 
     SUMMARY OF THE INVENTION 
     These needs have largely been met by the arbor adaptor and circular saw blade of the present invention. That is to say, the present invention enables the use of a saw blade having a central opening able to mount on an arbor or shaft of circular saws of multiple different applications. As a result, a common and simple saw blade configuration can be used with saws have particular shaped arbors without the necessity of making specialized and custom blades. 
     The arbor adaptor hereof broadly includes a central aperture and a first engagement side, the first engagement side including a central recess for receiving a non-circular mounting lug of an arbor therein. The first engagement side further includes an annular blade-locating ring which extends normally from the central recess and is configured to radially surround the mounting lug and in turn to receive thereon in radially surrounding relationship the inner margin of the blade which is preferably complementally sized with the outer rim of the blade locating ring. A friction surface is provided radially outwardly of the blade locating ring for clamping the blade to the arbor. 
     In some embodiments, a second engagement side may be provided for mounting a blade to a second arbor having a differently sized or configured mounting lug, or no mounting lug. The second engagement side includes a second central recess having a different diameter than the central recess of the first engagement side, and a second friction surface. The second friction surface may have a different radially size or dimension than the friction surface on the first side, or the same dimension. 
     In other embodiments, particularly those where larger diameter blades having greater drive requirements are used, the arbor adaptor may be provided with a drive pin, and the central recess may be defined by an irregular inner rim on the blade locating ring to provide engagement points for contacting the mounting lug. The blade is provided with a complemental drive hole for receiving the drive pin therein, with the mounting lug engaging at least one and preferably at least two engagement points for rotatably driving the arbor adaptor, which throughout the pin and the frictional clamping relationship drives the blade. 
     A further embodiment of the foregoing invention utilizes an arbor adapter for mounting on saws having an arbor or shaft with an offset stud or a central bore receiving another threaded fastener, thereby enabling the use of a saw blade with an axially centered mounting opening, such as a preferably generally circular inner margin. The arbor adaptor has a central aperture which is offset from the axis of rotation the same displacement as the stud, and has a blade positioning ring which is, as above, centered on the axis of rotation. The outer margin of the arbor adaptor may be generally circular as described above, so that during rotation, the arbor adaptor and blade rotate about the axis of rotation, rather than have an eccentric pattern of motion. Thus, the rotation of the stud, offset to the axis of rotation, causes the central aperture of the arbor adaptor to rotate about the axis of rotation, but the arbor adaptor itself and the blade carried thereby rotate substantially without eccentricity. The weight of the arbor adaptor is generally sufficient to compensate for the slight offset to the central opening. If the stud is provided with a flat side or other change in shape, the central aperture may be provided with a complimentary shape. 
     These and other advantages will be readily appreciated by those skilled in the art with reference to the following description of the preferred embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmentary side elevational view of a circular saw blade and arbor adaptor of the present invention, showing the blade and adaptor coupled to a circular saw arbor having a diamond-shaped blade mount; 
     FIG. 2 is a fragmentary vertical cross-sectional view taken along line  2 — 2  of FIG. 1, showing the adaptor in a first position for frictionally holding the blade onto the arbor; 
     FIG. 3 is a fragmentary vertical cross-sectional view similar to FIG. 2 but showing the adaptor in a second, reversed position for frictionally holding the blade to a different arbor; 
     FIG. 4 is a fragmentary side elevational view of a second embodiment of the arbor adaptor and blade hereof, shown mounted to an arbor having a triangular shaped arbor mount; 
     FIG. 5 is a fragmentary vertical cross sectional view taken along FIG.  5 — 5  of FIG. 4, showing the second embodiment of the arbor adaptor in driven engagement with the triangular shaped mount of the arbor and a drive pin for providing additional torque to the blade; 
     FIG. 6 is a fragmentary side elevational view of a third embodiment of the arbor adaptor and blade hereof, showing the use of a deep head retaining bolt received in a complementally configured hexagonal recess, and a radially oriented pin hole in the outer margin of the arbor adaptor for receiving a pin-type wrench, shown in phantom; 
     FIG. 7 is a fragmentary vertical cross-sectional view taken along line  7 — 7  of FIG.  6  and similar to FIGS. 2,  3  and  5 , showing, in phantom, the use of a socket wrench to tighten the arbor adaptor for holding the blade against the arbor; 
     FIG. 8 is a diagrammatic view showing the direction of the blade during rotation when in use with a concrete cutting saw; 
     FIG. 9 is a fragmentary side elevational view of a fourth embodiment of the arbor adaptor and blade hereof for use with an arbor of a circular saw having an off-center stud; and 
     FIG. 10 is a fragmentary vertical cross-sectional view taken along line  10 —of FIG. 9, and showing the arbor adaptor received on an arbor having a stud with a flattened portion of the threaded surface and offset to the axis of rotation. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawing, a circular saw  10  includes a shaft  12  driven by a power source such as an electric motor or the like and for rotation therewith about an axis a. The shaft  12  is also coupled to an arbor  14 . The arbor  14  has an internally threaded central bore  16  for receiving a retaining bolt or other fastener  18 , and includes a mounting lug  20 . As shown in FIGS. 1 through 3, the mounting lug  20  is diamond shaped presenting a major axis X and a minor axis Y, but as discussed above and below, the mounting surface provided by the arbor manufacturer may be of other shapes as well. The foregoing, elements are conventional and well known in the art. 
     A blade  22  and an arbor adaptor  24  are provided in accordance with the present invention for mounting to the arbor  14  by the retaining bolt  18 . The blade  22  is shown having a plurality of teeth  26  configured for cutting wet, semi-hardened concrete, but may be an abrasive disk or have teeth of different common configurations and sizes for different purposes such as cutting metal or wood. Flat and planar side panel  28  extends radially inwardly from the teeth  26 . The side panel  28  includes generally annular friction band  30  which is located radially inward of the teeth  26 . The friction band  30  is preferably of a radial dimension sufficient to engage the annular friction ring  32  of several alternative arbors so that it can be used with saws of different manufacturers. The blade  22  has a central opening for mounting onto the arbor and arbor adaptor  24 , shown defined by a centered circular inner margin  34  in side panel  28 , so that when rotated at high speed, the blade  22  is preferably statically and dynamically balanced. 
     The arbor adaptor  24  shown in FIGS. 1 through 3 is preferably a disk having an outer margin  36 , an unthreaded central aperture  38  for receiving the retaining bolt  18  therethrough, a first engagement side  40  and a second engagement side  42 , and as a result is adapted for use with two or more different arbors. First engagement side includes a central recess  44  and a blade positioning ring  46  radially outward therefrom. The blade positioning ring  46  includes a inner rim  48 , an outer rim  50  and a rim wall  52 . The inner rim  48  is preferably spaced sufficiently radially outward from the central aperture  24  and has a diameter D′ to receive most mounting lugs  20  radially inwardly thereof and within the central recess  44 . An outer relief recess  54  is located radially outboard of the outer rim  50 , and is shallower than the depth of central recess  44 . That is to say, the central recess  44  is more proximate the second engagement side  42  than the outer relief recess  54 . The inner rim  48  and outer rim  50  extend sufficiently normally from the annular outer relief recess  54  to permit the inner margin  34  of the blade to engage the outer rim  50  as shown in FIG.  2 . An annular friction surface  56  is located radially outwardly of relief recess  54  and inwardly of outer margin, and is spaced sufficiently from central aperture  38  to provide good torque transmission to the blade  22 , and is preferably located in opposition to the friction surface  32  so as to clamp the friction band  30  therebetween. The location of friction surface  56  provides good tightening characteristics with friction ring  32 , each having a radial dimension R and each being radially outward of the relief recess  54  and just inward of the outer margin  36 , thereby giving better torque transmission than if located radially inward adjacent the central aperture  38 . 
     The annular outer relief recess  54  is depressed relative to the friction surface  56  so as to avoid warping of the blade  22  as the temperature of the latter rises during use. This also helps reduce the possibility that a bur or debris will be located in engagement between the blade  22  and the arbor  14  or adaptor and result in insufficient torque transmission. Similarly, the central recess  44  is relieved relative to both the positioning ring  46  and the friction surface  56  to avoid the arbor adaptor  24  from “bottoming out” if the central recess  44  were to come into engagement with the mounting surface  20 . Preferably, the positioning ring projects normally from the relief recess  54  more than the friction ring  32  only about the thickness of the saw blade  22  to avoid the relief recess  54  engaging the arbor  14 . The friction surface  56  preferably has a radial dimension about equal to the friction ring  32  to avoid warping of the blade  22 . 
     The second engagement side  42  is useful in coupling either the blade  22  or an alternate blade  22   a  having a smaller circular inner margin  34   a  to a different second arbor  14   a  which does not have a mounting lug, or merely one with a common, circular mounting for receiving the retaining bolt. In addition, the configuration of the second engagement side  42  permits the use of a blade which has a circular inner margin which is configured complementally with the mounting lug  20 , i.e. a blade that has a diamond shaped inner margin in the embodiment shown in FIG.  1 . The second engagement side includes a second substantially circular recess area  60  having a transverse diameter D″, the second circular recess extending radially outward from the central aperture  38  and a second friction surface  62  similar to but oriented opposite the first friction ring  56  as shown in FIGS. 2 and 3. The second friction surface  62  can extend any desired distance normal to the recessed area  60 , but preferably at least about the width of the blade to provide sufficient clearance for any material that might collect therein. The second friction surface  62  also is preferably of a radial dimension and spaced radially from the axis of rotation a of the shaft  12 , blade  22  and arbor adaptor  24  so as to be opposed to the friction surface  32  of the arbor  14 . 
     As may be seen in FIGS. 1 and 2, when the blade  22  is mounted to arbor  14  with the first engagement side  40  oriented toward the arbor  14 , the inner margin  34  is spaced from the mounting lug  20  so that the blade  22  is not engaged or driven by the lug  20 . The blade  22  thus avoids the necessity of conforming to any particular configuration of the mounting lug  20 . Instead, the arbor adaptor  24 , which also has its blade positioning ring  46  positioned outward of the mounting lug  20 , drives the blade  22  by frictional engagement of the friction band  30  between the friction ring  32  of the arbor  14  and the friction surface  56  of the arbor adaptor  24 . Advantageously, the adaptor  24  is reversible, whereby the second engagement side  42  is oriented toward the arbor  14  and shown in FIG. 3 holding blade  22   a.  The blade  22   a,  shown with a smaller diameter circular inner margin  34   a,  is sized complementally with the central aperture and retaining bolt  18  for mounting on a second arbor  14   a  without a mounting lug  20  as shown in FIG. 3, but blades having larger sizes of central apertures may be accommodated. Advantageously, the second engagement side  42  is also configured so that a blade having an inner margin which conforms to the mounting lug  20  may be used with the adaptor  24 , thus permitting the adaptor  24  to be used with blades having a circular inner margin  34  generic to different mounting lugs  20  as well as blades having an inner margin specific to a particular shape and size of mounting lug  20  simply by selecting either the first or second engagement side for orientation toward the arbor  14 . 
     FIGS. 4 and 5 illustrate a second embodiment of the saw  10  of the present invention, including arbor adaptor  64  and blade  66  for use where greater torque must be transmitted by the shaft  68  through the arbor  70  to drive the blade. The need for greater torque may arise from, for example, a blade  66  having an increased outer diameter. The arbor  70  includes a mounting lug  72 , shown as having a generally triangular shape with three lobes in elevation in FIG.  4 . 
     Blade  66  has a plurality of circumferentially spaced teeth  74 , a side panel  76  including a friction band  78  and a drive hole  80 , and a circular inner margin  82 . The friction band  78  is preferably spaced radially inward from the outer edge  84  of the teeth  74  and radially outwardly from the inner margin  82 . The drive hole  80  is either within, or as shown in FIGS. 4 and 5, slightly radially inward of the friction band  78 . 
     Arbor adaptor  64  is shown having only a single engagement side  86 , although it is to be understood that it also could be provided with a second engagement side  42  of the same configuration as shown in FIGS. 2 and 3. The side  86  of arbor adaptor  64  includes a locating recess  88  within a driven hub  90 , an outer recess  92 , a drive pin  94 , and a friction surface  96 . The friction surface  96  is located radially between an outer margin  98  and the outer recess  92  and extends substantially normal to the outer recess  92 . The drive pin  94  is received in a cavity  99  in the outer recess  92 . The driven hub  90  includes an outer rim  100  which extends substantially normal to the outer recess  92  a sufficient distance more than the friction surface  96  to permit the circular inner margin  82  of the blade  62  to be received thereon in mating relationship as shown in FIGS. 4 and 5. 
     The driven hub  90  includes an inner rim  102  which is proximate to at least one and preferably three engagement points  104 ,  106  and  108  by the mounting lug  72 . The engagement points  104 ,  106  and  108  enable greater ease in precisely locating the arbor adaptor  64  than requiring precision machining of the central aperture  110  to mate with a retaining bolt  18 . The closer the fit between the engagement points  104 ,  106  and  108  and the mounting lug  72 , the more precise the centering of the arbor adaptor  64  during mounting to the arbor  70 , and the less wear on the mounting lug  72  and driven hub  90  when a load is applied to the blade  66  during cutting. When the mounting lug  72  includes multiple lobes  12 ,  114  and  116  as shown in FIG. 4, the inner rim  102  of the driven hub  90  is configured to receive the lobes in corresponding receiving areas  118 ,  120  and  122 , with the engagement points  104 ,  106  and  108  intermediate the receiving areas  118 ,  120  and  122 . 
     FIGS. 5 and 6 illustrate a third embodiment of the present invention including arbor adaptor  124  and blade  126 . Blade  126  is substantially identical to blade  22  with like reference numbers used to show features common to both blade  22  and  126 . Arbor adaptor  124  may be used in conjunction with arbor  64  and is similar to arbor adaptor  24 , except for two particular features described below. The arbor adaptor  124  includes a hexagonal socket  128  on at least one of the first engagement side  40  and second engagement side  42  centered on axis A. The hexagonal socket  128  is of sufficient depth to receive a complementally sized head  130  of a retaining bolt  18 A. The retaining bolt  18 A is substantially identical to the retaining bolt  18 , but may be provided with a head  130  of somewhat greater depth, thereby permitting the head  130  to fit into the socket  128  and to extend therefrom a sufficient distance to provide good engagement with a wrench, such as a socket wrench  132  shown in phantom in FIG.  7 . Because of the fitting engagement between the head  130  of the retaining bolt  18 A and the socket  128 , rotation of the retaining bolt  18 A causes corresponding rotation of the arbor adaptor  124 , thereby tightening the arbor adaptor  124  to hold the blade  126  in gripping frictional engagement against the arbor  14 . 
     The arbor adaptor  124  has another means of tightening and loosening the arbor adaptor  124  against the blade by the provision of a pin hole  134  on the outer margin  36 A. A pin type wrench  136  having a pin  138  fitting into a radially oriented pin hole  134  may be used to rotate and tighten the arbor adaptor  124  in a clockwise direction as shown in FIG.  7 . That is, pin hole  134  has a generally radially oriented axis, whereby the pin  138  is inserted in a radial direction toward the central aperture and the wrench  136  wraps around the outer margin  36  so that exertion of a clockwise force on the wrench  136  tightens the arbor adaptor  124  onto the blade  126  and reversing the wrench  136  to exert a counterclockwise force tends to loosen the arbor adaptor  124  from its gripping relationship on the blade  124 . As shown in FIG. 8, the saw  10  drives the blade  126  in a direction during use which tends to further tighten the blade  126  between the arbor  12  and arbor adaptor  124  as the blade  126  cuts the material  138 , and thus resist slippage during use. As noted previously, the material  138  may be concrete, wood, steel or any other material typically cut with a circular saw. 
     In use, the blade  66  is mounted to the arbor adaptor  64  by locating the inner margin  82  over the outer rim  100  with the drive hole  80  receiving the drive pin  94 . The hub  90  of the adaptor  64  is then positioned over the mounting lug  72  so that the lobes lie within the receiving areas and the engagement points  104 ,  106  and  108  serve to locate and center the arbor adaptor  64 . The retaining bolt  18  is then inserted through the central aperture  110  and threaded onto the bore  16  of the shaft  68 , whereupon the saw is ready for use. With the motor or other power source engaged and rotating the shaft  68 , the mounting lug  72  rotatably drives the arbor adaptor  64  through engagement with one or more of the engagement points  104 ,  106  and  108 , and the arbor adaptor  64  in turn rotatably drives the blade  66 . The blade  66  is driven by both the frictional clamping relationship between the friction ring  32  of arbor  70  and the friction surface  96  of arbor adaptor  64  on the friction band  78  of the blade  66 , and also the force imparted by the drive pin  94  to the side panel  76  of the blade  66  through the drive hole  80 . 
     A fourth, further embodiment of the present invention  10  is shown in FIGS. 9 and 10. The arbor adaptor  140  shown is designed for receiving thereon blade  126  as described above, having an axially centered opening with a generally circular inner margin  34  substantially equidistant from the outer edge of the teeth  26 , and thus is generally statically and dynamically balanced. The arbor adapter  140  is configured for use with an arbor  14   b  which is similar to arbors  14 ,  14   a  or  70  described above, either including or omitting a mounting lug, except that a stud  142  is threadably mounted in the threaded central bore  16   b  of the shaft  12  or arbor  14   b.  The threaded central bore receives the stud so that the axis B of the stud  142  is offset by a displacement D a noticeable amount from the axis of rotation of the arbor A. Thus, absent compensation, mounting of a blade with a centered central opening onto a conventional mounting plate with a centered aperture would result in eccentric motion of the blade during rotation, making the blade unusable. 
     The arbor adaptor  140  is generally similar to the arbor adaptor  24  described above and shown in FIGS. 1-3, but further compensates for the off-centered positioning of the stud  142  by providing a central aperture  144  which has its axis E similarly offset by displacement D from the axis of rotation of the blade positioning ring  46 , which is coincident with the axis of rotation A of the shaft  12 . Thus, the arbor adaptor  140  is able to mount the saw blade  126  on its blade positioning ring  46  as described above. The mass of the arbor adaptor is sufficient to overcome the slight imbalance caused by the displacement D of the central aperture from the axis of rotation at the operating speeds of rotation. Thus, the arbor  14   a,  arbor adaptor  140 , and blade  126  effectively spin about the axis of rotation A. The stud  142  may have a flat surface  146  along one side thereof but nonetheless be able to threadably receive thereon a nut  148 . Beneficially, the central aperture  144  is D-shaped so as to be complemental to the shape, size and orientation of the stud  142 . The corresponding flat side  150  of the D-shaped central aperture  144  thus aids in locating the arbor adaptor on the stud  142  and resists shifting of the arbor adaptor to an off-centered position during rotation. Operation of the saw after mounting of the blade and adaptor  140  onto the stud is then conventional as described above and generally known to those skilled in the art. 
     In each of the embodiments, the blade may be provided with a simple, non-specific center opening which is preferably circular, but in any event the inner margin is sufficiently great to avoid engagement with the arbor in a driven relationship. The blade is instead driven by either friction because of the sandwich-type clamping between the arbor and the arbor adapter, or the combination of the aforementioned clamping and the drive pin on the arbor adapter. Thus, greater savings to the user can be expected by the ability to provide a single arbor adapter and blade which can be used with different saws, and by a single blade generic to several saws rather than a specific blade capable of use with only one saw. The provision of the raised blade positioning ring enables the arbor adapter and a non-specific blade to be used with saws having special configuration arbors by providing proper blade alignment without interfering with their operation or the necessity of modification to the saw. 
     Although preferred forms of the invention have been described above, it is to be recognized that such disclosure is by way of illustration only, and should not be utilized in a limiting sense in interpreting the scope of the present invention. Obvious modifications to the exemplary embodiments, as hereinabove set forth, could be readily made by those skilled in the art without departing from the spirit of the present invention. As one example, FIG. 8 illustrates the circular saw  10  as being wheeled, but it is to be understood that hand-held, fixed or mounted circular saws may all employ the arbor adapter and blade hereof. 
     The inventor hereby states his intent to rely on the Doctrine of Equivalents to determine and assess the reasonably fair scope of his invention as pertains to any apparatus not materially departing from but outside the literal scope of the invention as set out in the following claims.