Patent Publication Number: US-2005120856-A1

Title: Power work tools having a slim profile

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application is a continuation of application Ser. No. 09/973,200, filed Apr. 12, 2001, now abandoned, which claims the benefit of Provisional Application No. 60/196,627, filed Apr. 12, 2000, the disclosures of which are hereby expressly incorporated by reference. 
    
    
     FIELD OF THE INVENTION  
      The present invention relates generally to hand held power tools and, more particularly, to power tools having a slim profile.  
     BACKGROUND OF THE INVENTION  
      Hand held power tools, such as circular saws, generally include a motor attached to a housing and a connector to releasably attach and drive a tool, such as a saw blade. The motor may either be connected to a power outlet by an electric cord, or may be battery driven and are adapted to perform work on a work piece, such as lumber. The motor is usually a large cylindrical AC motor that has an axial length substantially larger than its diameter.  
      The motor may be mounted in one of two configurations. The first configuration generally positions the motor adjacent the tool. As an example, in a circular saw, the motor output axis is perpendicular to a plane extending through the diameter of the saw blade. Hand tools of this first configuration are typically ten inches wide due mainly to the length of the motor projecting from one side of the housing.  
      The second configuration is typically known as a worm drive tool. The most common of these hand tools are worm drive circular saws. These saws have a motor output axis that is parallel to a plane extending through the diameter of the saw blade. The width of a worm drive saw is usually 6-8 inches. Although large cylindrical motors are efficient, they are not without their problems.  
      The size and weight of large motors, the center of gravity of which is typically disposed on one side of the saw blade, makes such tools heavy and awkward. The large motor also makes it difficult for the operator to view each side of the work piece during use of the hand tool.  
      Cordless power tools, such as saws, include the use of small efficient DC motors. Although smaller motors can help reduce the weight of the tool, they too are not without their problems. As is well known, cordless saws typically have small diameter blades because the batteries in such motors cannot drive a larger blade for a satisfactory time period, or with enough torque to make them useful.  
      Increases in battery and motor voltages have allowed traditional size saw blades to be used in a cordless saw that is powerful enough to do useful work. However, the weight of the battery is considerable in order to provide an acceptable run time of the saw. Also, current cordless saw designs resemble traditional saws; that is, such saws include a cylindrical motor with a motor output axis perpendicular to the plane of the saw blade. As a result, such saws have a width that is similar to AC driven saws. The size and weight of the cylindrical motors substantially to one side of the plane of the saw blade can make them awkward to use and restrict the operators visibility of the work piece.  
      Thus, there exists a need for a hand tool having a slim profile and produces a sufficient amount of torque to drive traditional size tool pieces, such as saw blades.  
     SUMMARY OF THE INVENTION  
      In accordance with one embodiment of the present invention, a power tool is provided. The power tool includes a housing, a base plate coupled to the housing and having a base plate width, and a motor assembly attached to the housing. The motor is coupled to a tool connector adapted to releasably receive a tool. The motor assembly and housing have a width that is at most substantially equal to the base plate width. The motor assembly includes a length and a diameter ratio that is at least 1:1.5. In one embodiment of the invention, the motor assembly length and diameter is substantially 1 inch and 4.5 inches, respectively. In still yet another embodiment of the invention, the base plate width is substantially 5 inches.  
      In accordance with further aspects of the present embodiment, the motor assembly and housing are pivotably attached to the base plate for selective swinging motion of the motor assembly and housing within a predetermined range of motion. One such example of the predetermined range of motion is substantially between 51° from a plane extending normal to the baseplate width and −40° from the plane. In still yet another example, the predetermined range of motion is substantially between the plane and up to 50° from the plane.  
      In accordance with still yet other aspects of this embodiment, the motor includes a printed circuit board disposed between first and second coil assemblies. Each coil assembly includes a plurality of coils, where adjacent coils are nested within each other. The printed circuit board further includes a plurality of coil connections in communication with the plurality of coils.  
      In accordance with still yet other aspects of this embodiment, the power tool includes an adjustable exhaust assembly integrally formed with housing, wherein a portion of the adjustable exhaust assembly is rotatably disposed within the housing and positionable between at least two exhaust positions. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:  
       FIG. 1  is a side planar view of a power hand tool formed in accordance with one embodiment of the present invention and illustrated as a circular saw;  
       FIG. 2  is a front end planar view of the circular saw of  FIG. 1 ;  
       FIG. 3  is an exploded view of a circular saw formed in accordance with one embodiment of the present invention;  
       FIG. 4  is an exploded view of a motor assembly and saw blade assembly for a circular saw formed in accordance with one embodiment of the present invention;  
       FIG. 5  is an exploded view of a motor assembly for a circular saw formed in accordance with one embodiment of the present invention;  
       FIG. 6  is a cross sectional end view of the motor assembly of  FIG. 5 ;  
       FIG. 7  is a perspective view of a coil for a motor of a circular saw formed in accordance with one embodiment of the present invention;  
       FIG. 8  is a planar view of a coil assembly for a circular saw formed in accordance with one embodiment of the present invention;  
       FIG. 9  is a cross section planar view of the coil assembly of  FIG. 8  and taken substantially through Section  9 - 9 ;  
       FIG. 10  is a perspective view of a circular saw formed in accordance with one embodiment of the present invention and showing an exhaust assembly partially exploded from the circular saw;  
       FIG. 11  is a side plane view of a portion of the exhaust assembly of  FIG. 10 ;  
       FIG. 12  is a cross sectional planar view of the exhaust assembly and taken substantially through Section  12 - 12 ;  
       FIG. 13  is a partial perspective view of a circular saw formed in accordance with one embodiment of the present invention and having a portion of the circular saw housing removed for clarity to show an alternate embodiment of an exhaust assembly;  
       FIG. 14  is a perspective view of a valve for the alternate exhaust assembly of  FIG. 13 ;  
       FIG. 15  is a front planar view of a circular saw formed in accordance with one embodiment of the present invention in showing a tilting feature of the circular saw;  
       FIG. 16  is a front planar view of the circular saw of  FIG. 15  and showing the circular saw displaced in a direction opposite from that illustrated in  FIG. 15 ; and  
       FIG. 17  is a perspective view of a circular saw formed in accordance with another embodiment of the present invention and showing shoe extensions. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       FIGS. 1-3  illustrate one embodiment of a hand held power tool, illustrated as a circular saw  20 , formed in accordance with one embodiment of the present invention. Although the present embodiment is illustrated as a circular saw  20 , the invention is not intended to be so limited. As an example, the principles of the present design may be applied to additional power tools, such as sanders or routers. Accordingly, it should be apparent that a circular saw is intended to be an illustrative example of the present invention and other power tools are also within the scope of the present invention.  
      The circular saw  20  includes a housing  22 , a motor assembly  24 , a blade assembly  26 , and a base plate  28 . As may be best seen by referring to  FIG. 3 , the housing  22  includes a blade cover  32 , an integral handle assembly  34 , and an external handle  36 .  
      The blade cover  32  and integral handle assembly  34  are suitably formed in a manner well known in the art and may be formed as first and second halves. The first and second halves of both the blade cover  32  and integral handle assembly  34  may be joined by well known fasteners (not shown), such as screws. A well known power pack  38 , such as a battery pack, may be suitably attached to one end of the housing  22  to provide power to the motor assembly  24 . Although a cordless, battery operated power tool is illustrated, it should be apparent that other sources of power, such as an AC power supply cable, are also within the scope of the present invention.  
      Referring now to  FIGS. 3-6 , the motor assembly  24  will now be described in greater detail. The motor assembly  24  may be attached to one side of the housing  22  on a motor support flange  40  projecting from one side of the housing  22 . Located adjacent the motor support flange  40  is an electronics compartment  41 . The electronics compartment  41  is adapted to store electronic components, as is well known in the art.  
      Integrally formed within the motor support flange  40  a cutout  42 . The cutout  42  allows the motor assembly  24  to interface with the interior of housing  22 . Cutout  42  is shaped to match a gear cover  44 . It should be understood by those of ordinary skill in the art that the saw  20  can alternately have a motor assembly  24  mounted to the right side of saw  20 .  
      The motor assembly  24  includes an outer motor shell  46 , an inner motor shell  48 , and a motor output shaft  50  rotatably supported by bearings  52  and  54 . The motor assembly  24  also includes an arbor  56  rotatably supported by a first shaft bushing  58  held by the inner motor shell  48  and a second shaft bushing  60  held by the gear cover  44 . A reduction gear  62  is affixed to arbor  56  in a well known manner. Motor output shaft  50  engages the reduction gear  62  to rotatably drive the arbor  56 . The motor assembly  24  preferably has a power output as measured at arbor  56  that is one horsepower or greater.  
      As seen best by referring to  FIG. 4 , the gear cover  44  has an annular boss  64  concentric around arbor  56 . The annular boss  64  is adapted to receive the blade assembly  26 . The blade assembly  26  includes a blade guard return spring  66 , a lower blade guard  68 , a retainer clip  70 , a blade  74 , and a bolt  78 .  
      The blade guard return spring  66  fits loosely over annular boss  64 . The lower blade guard  68  fits slidably over annular boss  64  to trap the spring  66 . The retainer clip  70  snaps into a retainer groove  72  to keep the lower blade guard  68  on the boss  64 . The spring  66  biases the lower blade guard  68  to enclose the lower portion of blade  74 .  
      Arbor  56  has threaded bore  76  for receiving the blade bolt  78 . An inner blade bushing  80  and an outer blade bushing  82  sandwich circular saw blade  74  on arbor  56  and are tensioned by the blade bolt  78 . Bushings  80  and  82  are keyed to the arbor  56  and frictionally prevent the blade  74  from slipping with respect to the arbor  56 . As assembled on the arbor  56 , an axis extending through the length of the motor output shaft  50  is substantially normal to a plane extending through and parallel with the diameter of the saw blade  74 . Specifically, the axis extending through the motor output shaft  50  is normal to the diameter of the saw blade and is contained within the diameter of the saw blade.  
      As seen best by referring to  FIG. 6 , the motor assembly  24  includes a diameter  84  and an axial length  86 , where the diameter  84  that is greater than the axial length  86  by a predetermined amount. The axial length  86  of motor assembly  24  is also significantly less than the axial length of equivalent power motors of prior art circular saws. In one embodiment of the present invention, the motor assembly  24  has an axial length  86  and diameter  84  ratio that is at least 1:1.5. As a non-limiting example, the axial length  86  of the motor assembly  24  is one inch, while the diameter  84  is 4.5 inches.  
      A motor assembly  24  formed in accordance with the embodiments of the present invention allows the saw  20  to have a width that is less than the width of prior art circular saws. As seen best by referring back to  FIG. 2 , the width of the motor assembly  24  and housing  22  is indicated by the letter W. The width of the base plate  28  in this embodiment is approximately 5 inches. As seen in  FIG. 4 , the width W is at most substantially equal to the base plate width. As a result, the width W, as measured across the widest portion of the saw  20  is 5 inches or less.  
      As may be best seen by referring to  FIGS. 5 and 6 , the motor assembly  24  includes a stator assembly  92 , and first and second rotor assemblies  96   a  and  96   b . It should be apparent that the terminology inner, outer, etc., should be construed as descriptive, and not limiting. Further, although the motor assembly  24  as illustrated has a rotor-stator-rotor configuration, it should be apparent that other types of motors, such as motors having two stators, are also within the scope of the present invention.  
      The stator assembly  92  includes inner and outer housings  100   a  and  100   b , first and second coil windings  102   a  and  102   b , and a printed circuit board  104 . The inner and outer housings  100   a  and  100   b  are suitably formed as annular members from a thermally conductive material, such as a epoxy or plastic material. Although the housings  100   a  and  100   b  are illustrated as annular members, it should be apparent that other configurations, such as a multi-piece design or a one piece overmolding, are also within the scope of the present invention.  
      As may be best seen by referring to  FIGS. 7 and 8 , each of the first and second coil windings  102   a  and  102   b  include an indentation portion  106 . The indentations of the first coil winding  102   a  are sized to be nested within the second coil winding  102   b , such that the indentation portions  106  of the first and second coil windings  102   a  and  102   b  lie substantially in a common plane. The nested nature of the coil windings  102   a  and  102   b  is shown and described in U.S. Pat. No. 5,744,896, issued to Kessinger et al., the disclosure of which is hereby expressly incorporated by reference.  
      The interlocking arrangements of the first and second coil windings  102   a  and  102   b  provides the motor assembly  24  with a greater power density than other axial gap permanent magnet motors known in the art. As noted above, the motor assembly  24  generates a power rate, as measured at arbor  56 , is at least one horsepower. Further, the weight of the motor assembly  24  and, therefore, the saw  20  is reduced because the required power is produced by a motor that is smaller than the size of a conventional motor of equal horsepower.  
      Alternatively, a sealed motor may be utilized in certain embodiments of the present invention. The enclosures of motor, includes a means for exchanging heat produced within the motor assembly  24 . The coils are overmolded with a moldable material such as epoxy or plastic to form the stator assembly  92 . The moldable material of stator assembly  92  may also be a thermally conductive material. Heat generated by an electrical current passing through the coils is transferred to the stator assembly  92 . Stator assembly  97  transfers the heat to motor shells  46  and  48 . The motor shells  46  and  48  accumulate the heat from the stator assembly, dissipate a portion of the heat to the environment, and transfer a portion of the heat to other interfacing parts of saw  20  such as housing  32 , gear cover  44 , and lower blade guard. These parts accumulate the heat and then dissipate a portion to the environment. Motor shells  46  and  48 , blade housing  32 , and lower blade guard are preferably formed of a thermally conductive alloy such as magnesium or aluminum. Gear cover  44  is preferably comprised of steel to rigidly support arbor  56 , steel being also thermally conductive.  
      Referring back to  FIG. 5 , the first and second rotor assemblies  96   a  and  96   b  each include a rotor plate  12  and a magnet  114 . As a non-limiting example, the magnets  114  may be configured as an annular array of permanent magnets. The magnets  114  of the annual array have their magnetic poles on an axis parallel to the motor output shaft  50 . The magnetic poles alternate polarity with respect to each other around the array. A suitable number of magnets is four and, together, the magnets form a flat ring that is attached on the side of the rotors  112  and face the stator assembly  92 . Each of the four magnets of the arrangement has a non-magnetic partition radially separating the magnets  114  of the annual array. The magnets  114  are suitably formed from a rare earth alloy, such as neodymium, iron, and boron alloy.  
      The coil windings  102   a  and  102   b  may be wound from a single length of wire and include an outer coil lead  108   a  and an inner coil lead  108   b . The coil windings  102   a  and  102   b  are configured so that a pair of radially extending indentation portions  106  is in a plane separate from a pair of circumferential ends  107 . As seen best in  FIG. 8 , there are six coils total when the first and second coil windings  102   a  and  102   b  are connected to the printed circuit board  104 . The radially extending indentation portions  106  of the overlapped coils are co-planar, thereby forming the working coil portion of the stator assembly  92 . Although six coils are illustrated and described, it should be apparent that motor assemblies with more or fewer coils, such as ten coils or four coils, are also within the scope of the present invention.  
      The printed circuit board  104  is sandwiched between the first and second coil windings  102   a  and  102   b , such that the inner and outer coil leads  108   a  and  108   b  of each coil winding  102   a  and  102   b  are in electrical communication with a corresponding node  110  of the printed circuit board  104 . The nodes  110  of the printed circuit board  104  are connected to the outer and inner coil leads  108   a  and  108   b , in a well known manner thereby connecting the coil leads to conductors. The conductors connect the coil leads  108   a  and  108   b  to a number of motor control terminals (not shown) on connection tab  116  of the printed circuit board  104 .  
      The printed circuit board  104  stiffens the stator assembly  92  against axial deflection during operation of the motor. The printed circuit board  104  also increases the accuracy and efficiency of the motor assembly  24  by holding the individual coils in place during assembly and by simplifying the connection of the motor assembly  24  to the electronics of the circular saw  20 .  
      The connection tab  116  projects through a slot in the outer motor shell  46  and the inner motor shell  48  into the electronics compartment  41 , where it connects to well known electronic communication and operating assembly. The electronic communication and operating assembly includes a silicon chip or an array of silicon chips that digitally control a distribution of electrical energy to the coils to drive the motor. Such chip or chips are preferably mounted on a circuit board inside the electronics compartment  41 .  
      As noted above, the power source is battery pack  38 . Another embodiment of saw  20  has the power source from a rectifier energized by an AC current. As is known, the rectifier converts AC current to a DC current at the proper voltage for the motor being driven. For the present invention, the rectifier can be mounted within saw  20  such as in handle assembly  34  or in a separate unit that replaces the battery pack  38 .  
       FIGS. 10-12  illustrate a selectable discharge assembly  130  formed in accordance with one embodiment of the present invention. The discharge assembly  130  includes a channel extending from within blade cover  32  of the housing  22  to a second channel  132  extending transversely through the integral handle assembly  34 . As configured, the first channel extending through the housing  22  is in communication with the second channel  132 , such that debris, such as sawdust, is channeled upward into the second channel  132 .  
      The selectable discharge assembly  130  also includes a bifurcated valve  134 . As seen best by referring to  FIGS. 11 and 12 , the valve  134  includes a first port  136  connected to a first open end  138  and a second port  140  connected to a second open end  142 . The valve  134  also includes a selector dial  144  with a detent post  146  integrally formed on the inner side of the selector dial  144 . A retainer clip groove  148  is formed on the other end of the valve  134 . The valve  134  is rotatably received within the second channel  132  and is retained therein by a tension spring  150 , a valve retainer ring  152 , and a valve retainer clip  154 . A radially extending flange  156  extends outwardly from one end of the second channel  132 , and includes detent notches  158   a - 158   c . The detent notches  158   a - 158   c  are adapted to cooperate with the detent post  146  to indicate the position of the valve  134  and the direction of exhaust from within the saw  20 .  
      The valve  134  is held within chamber  132  by the spring  150  trapped by the ring  152  that is retained on valve  134  by the clip  154  resting in groove  148 . Selector dial  144  is tensioned by the force of spring  150  so that detent post  146  positively and selectively engages detent notches  158   a - 158   c . The detent notches  158   a - 158   c  are arranged so that rotation of the valve  134  to a first detent position directs dust flowing from the second channel  132  into the first port  136  and out the first open end  138 . Rotation of the valve  134  to a second detent position directs dust flowing from the second channel  132  into the second port  140  and out the second open end  142 .  
      The first and second open ends  138  and  140  may be disposed at a variety of locations on the housing  22 . As a non-limiting example, one of the first and second open ends  138  and  140  may be disposed on the left and right sides, respectively, of the housing  22 , thereby channeling saw dust accordingly. When the dial  144  is in the third position or detent, saw dust may be channeled through the bottom of the base plate  28 .  
      Referring to  FIGS. 13 and 14 , a second embodiment of the selectable direction dust discharge device  160  is disclosed. The device  160  operates to divert saw dust to one of two positions; through the right or left sides of the housing  22 . The second channel  132  supports a contoured vane  162  vertically positioned within channel  132  and moved by a push rod  164 . The vane  162  and the push rod  164  having a first position to deflect dust out a first opening  166  in the channel  132 . The vane  162  and the push rod  164  having a second position to deflect dust out a second opening  168  in the channel  132 .  
       FIGS. 15 and 16  illustrate a blade angle change bracket  180 . Because the width of the motor assembly  24  and housing  22  is no greater than the width of the base plate  28 , the saw  20  may be configured such that it is pivotably to both sides of the base plate  28 . The bracket  180  allows the user to select any angle  182  that can be defined by a plane  181  perpendicular to the width of the base plate  28 . Angle  182  preferably has a range adjustment of substantially +51° from the plane  181 , as shown in  FIG. 16 , to substantially −40° from the plane  181 , as shown in  FIG. 15 .  
       FIG. 17  includes first and second shoe extensions  190   a  and  190   b . In some instances the user may have need of a base plate  28  that is wider than the one attached to saw  20 . This could especially be true where the maximum width of the circular saw  20  is less than five inches. The shoe extensions  190   a  and  190   b  are adapted to be removeably fastened to the base plate  28 . Each shoe extension  190   a  and  190   b  includes at least two protruding members  192   a  and  192   b  that are removably received into mating apertures  194   a  and  194   b  located on at least one side of the base plate  28 . Although  FIG. 17  illustrates first and second shoe extensions  190   a  and  190   b , only one shoe extension may be used to effectively extend the width of the base plate  28 . Further, either one or both of the shoe extensions  190   a  and  190   b  may include an upwardly extending flange  196 . The flange  196  may be used as a rip guide, such that the shoe extension may be turned upside down and inserted into its corresponding aperture, thereby extending the flange  196  downwardly from the base plate  28 . As such, the shoe extension may be used as a rip guide.  
      While the preferred embodiment of the invention has been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.