Abstract:
A power tool for cutting a workpiece including a casing, an auxiliary handle assembly extending from the casing, a motor disposed at least partially in the casing, and a drive transmission operably coupled to the motor. The drive transmission outputs a driving force in response to an input from the motor. A spindle locking mechanism is provided that is selectively positionable between a retracted position spaced apart from the drive transmission and a locked position engaging the drive transmission. The spindle lock mechanism thereby prevents rotation of the drive transmission in response to actuation of a pad member. The pad member can be positioned adjacent to the auxiliary handle to permit single-handed holding of the power tool and actuation of the pad member.

Description:
FIELD 
       [0001]    The present disclosure relates to various improvements for power tools and, more particularly, relates to a lower blade guard, gear transmission system, and spindle lock mechanism for a power tool. 
       BACKGROUND AND SUMMARY 
       [0002]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
         [0003]    Circular cutting saws are commonly used in both residential and commercial applications. These circular saws typically include a motor casing surrounding a motor drive system. The circular saw may also include one or more handles for manipulating the saw prior to, during, and after operation. Conventional motor drive systems can include a motor operably driving a transmission coupled to a circular cutting blade or other implement. Although transmissions vary widely in the art, some include a worm drive system, which is often characterized by the use of a worm and wheel gearing system, oil bath coolant and lubrication, and an overall long, narrow aspect ratio of the motor casing in comparison to other circular saw designs. 
         [0004]    According to some embodiments of the present teachings, a power tool, such as a worm drive saw, is provided having a number of advantageous features over conventional power tool designs. In some embodiments, a power tool is provided for cutting a workpiece. The power tool can include a casing, an auxiliary handle assembly extending from the casing, a motor disposed at least partially in the casing, and a drive transmission operably coupled to the motor. The drive transmission outputs a driving force in response to an input from the motor. A spindle locking mechanism is provided that is selectively positionable between a retracted position spaced apart from the drive transmission and a locked position engaging the drive transmission. The spindle lock mechanism thereby prevents rotation of the drive transmission in response to actuation of a pad member. The pad member can be positioned adjacent to the auxiliary handle to permit single-handed holding of the power tool and actuation of the spindle locking mechanism via the pad member. 
         [0005]    Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0006]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0007]      FIG. 1  is a front perspective view of an exemplary worm drive saw having a spindle lock, gear transmission system, and lower blade guard according to the principles of the present teaching; 
           [0008]      FIG. 2  is a rear perspective view of the exemplary worm drive saw illustrating the spindle lock and increased rip guide clearance according to the principles of the present teaching; 
           [0009]      FIG. 3  is a front view of the exemplary worm drive saw; 
           [0010]      FIG. 4  is a rear view of the exemplary worm drive saw; 
           [0011]      FIG. 5  is a bottom view of the exemplary worm drive saw; 
           [0012]      FIG. 6  is a top view of the exemplary worm drive saw; 
           [0013]      FIG. 7  is a left view of the exemplary worm drive saw; 
           [0014]      FIG. 8  is a right view of the exemplary worm drive saw; 
           [0015]      FIG. 9  is a plan view of a conventional lower blade guard; 
           [0016]      FIG. 10  is a plan view of an exemplary lower blade guard according to the principles of the present teachings; 
           [0017]      FIG. 11  is a perspective view of the exemplary lower blade guard; 
           [0018]      FIG. 12  is an isometric plan view of the exemplary lower blade guard; 
           [0019]      FIG. 13  is a lower perspective view of the exemplary worm drive saw illustrating the exemplary lower blade guard engaging a workpiece; 
           [0020]      FIG. 14  is an enlarged perspective view illustrating the rip guide clearance of a conventional worm drive saw; 
           [0021]      FIG. 15  is an enlarged perspective view illustrating interference between the conventional worm drive saw and a rip guide member; 
           [0022]      FIG. 16  is a side view of a conventional output shaft having a spindle lock formed thereon; 
           [0023]      FIG. 17  is a side view of an armature shaft and associated components of a drive transmission according to the principles of the present teachings, with portions removed for clarity; 
           [0024]      FIG. 18  is a partial cross sectional view of an output shaft and associated components of the drive transmission taken along line  18 - 18  of  FIG. 6  according to the principles of the present teachings; 
           [0025]      FIG. 19  is an enlarged perspective view of a spindle lock mechanism according to the principles of the present teachings; 
           [0026]      FIG. 20  is an enlarged perspective view of the spindle lock mechanism partially disposed in the casing of the exemplary worm drive saw; 
           [0027]      FIG. 21  is a perspective view of a fan hub having a hub portion for receiving a spindle lock member therein; and 
           [0028]      FIG. 22  is an enlarged perspective view illustrating the increased rip guide clearance of the exemplary worm drive saw. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
         [0030]    It should further be understood that although many aspects of the present teachings are discussed and described in connection with a worm drive circular saw, the principles of the present teachings are equally applicable to other power tools, such as, but not limited to, conventional circular saws (as opposed to worm drive saws). 
         [0031]    With reference to  FIGS. 1-8 , an exemplary worm drive saw  10  is illustrated according to the principles of the present teachings. Worm drive saw  10  comprises a motor and transmission casing  12  having a main handle assembly  14 . Main handle assembly  14  can comprise an actuation trigger  15  for controlling a motor  16  and a gripping portion  17 . Casing  12  can be shaped to house motor  16  and a drive transmission  18  operably coupled to motor  16  for transmitting a power drive force from motor  16  to a circular cutting blade  19  ( FIG. 13 ). In some embodiments, drive transmission  18  can be a worm drive transmission, which will be discussed in greater detail herein. However, it should be appreciated that alternative drive transmissions can be used in connection with the specific teachings of the present disclosure where appropriate. 
         [0032]    With continued reference to  FIGS. 1-8 , worm drive saw  10  can further comprise an auxiliary handle assembly  20  fixedly coupled to a top portion of casing  12 . Specifically, auxiliary handle assembly  20  can comprise a generally C-shaped member having a gripping portion  21  and fastening ends  23 , which are sized and configured for mounting auxiliary handle assembly  20  to casing  12  via fasteners  25 . This arrangement provides a secure and balanced position for carrying and/or tethering worm drive saw  10 . 
         [0033]    In some embodiments, worm drive saw  10  can include an upper blade guard  22  coupled to or integrally formed with casing  12 . Upper blade guard  22  remains in a fixed position relative to the circular cutting blade so as to protect an operator from debris and other material. A movable lower blade guard  24  is rotatably coupled to at least one of upper blade guard  22  or casing  12 . More particularly, in some embodiments, lower blade guard  24  includes a hub for rotatable coupling to an output drive shaft, which will be discussed in great detail herein. Lower blade guard  24  is configured such that it moves in a rotating direction about an axis A-A ( FIG. 1 ) of an output drive shaft when lower blade guard  24  abuts a workpiece to be cut  2000  ( FIG. 13 ). 
         [0034]    It has been found in some conventional blade guard designs that when cutting a workpiece at a large bevel angle (i.e. over 45 degrees) and/or when cutting a small sliver piece of the workpiece, conventional lower blade guards may not properly rotate out of position through a normal abutment relationship with the workpiece. This is typically caused by the fact that the outboard edge of many lower blade guards does not contact the workpiece during such large bevel angle and/or sliver piece cuts. In some situations, the shape of conventional lower blade guards can cause a binding engagement with the workpiece. Therefore, in conventional designs, this can result in an improper cut or the cutting blade being prevented from engaging the workpiece. 
         [0035]    According to the principles of the present teachings, lower blade guard  24  is configured to provide an improved camming face relative to conventional lower blade guards along its outboard edge (see  FIG. 9 ) so as to promote proper engagement with a workpiece during large bevel angle cuts and when cutting small portions of the workpiece. To this end, as illustrated in FIGS.  3  and  10 - 12 , in some embodiments lower blade guard  24  comprises a generally half-moon shaped member concentric about a central hub  28  and a motor side surface  30  integrally formed with and radially extending from central hub  28 . Central hub  28 , as illustrated in  FIG. 11 , can comprise a collar portion  32  having an internal diameter sized to cooperate with a bearing surface  34  ( FIG. 3 ) formed as part of at least one of casing  12 , upper blade guard  22 , or output drive shaft. This physical engagement of collar portion  32  of lower blade guard  24  and bearing surface  34  provides a smooth engagement for lower blade guard  24  to permit lower blade guard  24  to rotate out of position during operation in cooperation with a camming face, to be discussed. 
         [0036]    Lower blade guard  24  further comprises an outboard side surface  36  coupled to motor side surface  30  via an edge surface  38 . Accordingly, motor side surface  30 , outboard side surface  36 , and edge surface  38  together defined an internal volume or cavity for receiving the circular cutting blade therein. As should be understood, lower blade guard  24  is biased from a retracted position, wherein the circular cutting blade is exposed, to a concealed position, wherein the circular cutting blade is covered and protected ( FIG. 3 ). 
         [0037]    As can be seen in  FIGS. 11-12 , in some embodiments, outboard side surface  36  of lower blade guard  24  comprises various features which aid in the operation of worm drive saw  10 . Specifically, outboard side surface  36  can comprise a cam  40  that is shaped and sized in accordance with the principles of the present teachings to provide improved workpiece engagement during large bevel angle cuts and/or small workpiece sliver cuts. Cam  40  can comprise and extend from a camming tip  42  along a camming portion  44 . Camming portion  44  generally extends from camming tip  42  to edge surface  38  of lower blade guard  24 . 
         [0038]    With particular reference to  FIG. 12 , camming portion  44  is shaped to include a slight arcuate curve that closely follows a radial line B-B extending from axis A-A. Camming portion  44  can define a tangent point or region C relative to radial line B-B. In some embodiments, this tangent point or region C can be disposed at a position about midpoint (i.e. about 50%) along the distance D, which extends from axis A-A to an internal surface of edge surface  38 . In some embodiments, this tangent point or region C can be disposed at a position about midpoint along cam  40 . 
         [0039]    The shape of camming portion  44 , namely its relation to radial line B-B, produces a driving moment promoting rotation of lower blade guard  24  about axis A-A to improve operation of worm drive saw  10  during large bevel angle cuts and/or a narrow sliver cuts. It should be appreciated that camming portion  44  defines a curvature and inclination that is reduced relative to conventional lower blade guards, such as illustrated in  FIG. 9 . 
         [0040]    Furthermore, according to the principles of the present teachings, camming tip  42  of cam  40  extends to a position substantially adjacent to the central axis of central hub  28 . More particularly, as illustrated in  FIG. 12 , in some embodiments camming tip  42  can be positioned at an offset distance E that is less than 50% of distance D. In some embodiment, offset distance E of camming tip  42  can be less than 35% of distance D or even less than 25% of distance D (as shown in  FIG. 12 ). According to this configuration, camming tip  42  can more quickly contact the workpiece during a cutting operation and, thus, begin rotation of lower blade guard  24  from its concealed position ( FIG. 1 ) to its retracted position. Moreover, it should be appreciated that camming tip  42  defines a more elongated shape relative to conventional lower blade guards—that is, camming tip  42  extends closer to axis A-A (see FIG.  9 )—and permits quicker engagement of lower blade guard  24  against a workpiece during a cutting operation. 
         [0041]    Still referring to  FIGS. 10-12 , lower blade guard  24  can further comprise a first connecting feature  48  for coupling a thumb lever  50  thereto ( FIGS. 1 and 3 ). Thumb lever  50  can be used by an operator to manually rotate lower blade guard  24  from the concealed position to the retracted position without the need for workpiece abutment. Lower blade guard  24  can further comprise a thumb gripping portion  52  for use during circular cutting blade replacement to conveniently hold lower blade guard  24  in the retracted position or intermediate position for simplified access to the circular cutting blade, which will be discussed in greater detail herein. Thumb gripping portion  52  can be formed as an extension from outboard side surface  36 . More particularly, thumb gripping portion  52  can be formed along a mid-section edge of outboard side surface  36  and can, in some embodiment, remain as a flat feature co-planar with outboard side surface  36 . This can prevent inadvertent gripping and/or snagging of thumb gripping portion  52 . Thumb gripping portion  52  can be positioned such that during a blade replacement operation, an operator can hold worm drive saw  10 , at auxiliary handle assembly  20 , and simultaneously hold lower blade guard  24  in a retracted position with a single hand. 
         [0042]    Turning now to  FIGS. 14-16 , a conventional worm drive circular saw  1000  is illustrated having many of the disadvantages representative of the prior art. In particular, the illustrated conventional worm drive saw suffers from the inability to provide adequate clearance between its motor casing  1001  and its corresponding rip guide  1002  (also known as rip guide clearance). As best seen in  FIGS. 14-15 , conventional worm drive circular saw  1000  has a protrusion  1004  resulting from the placement of internal transmission drive components ( FIG. 16 ). That is, as illustrated in  FIG. 16 , conventional worm drive circular saw  1000  employs a spindle lock  1008  disposed on an output drive shaft  1010  thereby increasing the overall length of output drive shaft  1010  and causing protrusion  1004  to extend outboard from motor casing  1001 . 
         [0043]    In operation, this limits the thickness of a rip guide member  1006  ( FIG. 15 ), such as a worksite wooden member, that can be used. For example, during operation, operators typically prefer to use any available elongated member present (i.e. rip guide member  1006 ) at a worksite to serve as a guide for defining a straight and even cut. This rip guide member  1006  can include any available straight cut lumber. However, during a full depth cut, wherein the conventional worm tool is adjusted such that protrusion  1004  is closely positioned relative to rip guide  1002 , the thickness of rip guide member  1006  is limited due to the interference caused between rip guide member  1006  and protrusion  1004  of conventional worm drive circular saw  1000 . Specifically, when conventional worm drive circular saw  1000  is configured for maximum depth cutting, protrusion  1004  provides only a half-inch clearance between the bottom of rip guide  1002  and the lower edge of protrusion  1004 . Consequently, this prevents an operator from using readily-available “1X” lumber (which has a thickness of about ¾ inch). 
         [0044]    Accordingly, as illustrated in  FIGS. 17-22 , drive transmission  18  of worm drive saw  10  is illustrated according to the principles of the present teachings. In some embodiments, drive transmission  18  comprises an elongated armature drive shaft  54  having armature windings  56  ( FIG. 19 ) disposed about an end thereof. Armature shaft  54  is rotatably supported between an inner bearing  58 , a fan end armature bearing  60 , and an outer bearing  62 . Armature shaft  54  is rotatable in response to electrical impulse passing through armature windings  56  in a conventional manner thereby producing a rotationally output driving force. Drive transmission  18  can comprise a spindle lock fan hub  64  positioned at an intermediate point on armature shaft  54 . 
         [0045]    Still referring to  FIG. 17 , drive transmission  18  can further comprise a bearing retaining plate  72  having a recessed portion  73  formed therein sized to receive and retain fan end armature bearing  60 . A worm gear  74  is fixedly coupled to armature shaft  54 , such as through a key connection, for rotation therewith and in close relationship to fan end armature bearing  60 . Finally, outer bearing  62  and a retaining nut  76  are positioned at an outer end  78  of armature shaft  54 . 
         [0046]    According to the principles of the present teachings, each of the components disposed along armature shaft  54  can be progressively smaller in outer diameter than the adjacent component an armature shaft  54  to provide advantages in manufacturing and operation. That is, bearing retaining plate  72 , fan end armature bearing  60 , worm gear  74 , outer bearing  62 , and retaining nut  76  can each have an outer diameter smaller than the proceeding component, respectively. This progressively sized distribution of components and the use of bearing retaining plate  72  permits preassembly of armature shaft  54  with bearing retaining plate  72 , fan end armature bearing  60 , worm gear  74 , outer bearing  62 , and retaining nut  76  and further permits such pre-assembly to be easily installed and secured within casing  12 . The pre-assembly is in effect a series of concentric cylinders or cones of successively decreasing diameter. This pre-assembly can be put together outside of casing  12 , then installed in casing  12  through a single penetration in casing  12 . Furthermore, this pre-assembly inhibits separation of such components due to gear drive forces. Still further, this pre-assembly reduces the amount of machining necessary on casing  12  and, thus, minimizes the number of holes that must be created in casing  12 . This in turn reduces the opportunities for lubrication leakage. 
         [0047]    Referring now to  FIG. 18 , drive transmission  18  further comprises output drive shaft  26  having a corresponding worm gear  91  fixedly coupled thereto for rotation therewith and sized to enmeshingly engage worm gear  74  of armature shaft  54 . Output drive shaft  26  can be supported for rotation by a first output drive shaft bearing  92  and a second output drive shaft bearing  94 . It should be appreciated, as illustrated in  FIG. 18 , that the removal of the conventional spindle lock feature  1012  ( FIG. 16 ) on conventional output drive shaft  1014  ( FIG. 16 ) enables first output drive shaft bearing  92  to be moved to the right in the figure ( FIG. 18 ). This movement of first output drive shaft bearing  92  to a more inboard location minimizes the protrusion effect (i.e. protrusion  1004 ) found on the exterior of conventional worm drive circular saw  1000 . Therefore, according the principles of the present teachings, worm drive saw  10  is able to achieve a greater distance between the lower portion of protrusion  96  and the lower edge of rip guide  98  (see  FIGS. 4 and 22 ). Therefore, an operator can now use a standard (1X) wooden rip guide member having a thickness of about ¾ inch at a maximum depth cut setting. It should be appreciated that this is achieved due to the novel configuration of spindle lock mechanism  80  and the inboard relocation of first output drive shaft bearing  92  relative to conventional worm drive circular saw  1000 . These advantages are also resultant from the novel configuration of a spindle lock mechanism. 
         [0048]    Referring again to  FIGS. 17-21 , a spindle lock mechanism  80  is illustrated according to the principles of the present teachings. With particular reference to  FIGS. 19-21 , in some embodiments, spindle lock mechanism  80  comprises spindle lock member  70  engagable with hub portion  66  of spindle lock fan hub  64 . Specifically, spindle lock member  70  can comprise a generally T-shaped member pivotally coupled to casing  12  or an intermediate surface at a pivot  82 . Spindle lock member  70  further comprises a thumb pad  84  and a locking tab  86  opposite thereof. As seen in  FIGS. 17-21 , spindle lock fan hub  64  can comprise a hub portion  66  having a plurality of cavity locks  68  radially formed therein. Each cavity lock  68  includes a generally U-shaped depression accessible and engagable locking tab  86  of spindle lock member  70 . It should be appreciated that variations exist as to the exact size, shape, and relative movement of spindle lock member  70  and spindle lock fan hub  64 . Spindle lock mechanism  80  can further comprise a biasing spring  88  sufficiently sized to urge spindle lock member  70  into a disengaged position relative to spindle lock fan hub  64 . 
         [0049]    During operation, an operator can depress thumb pad  84  of spindle lock member  70  to overcome the biasing force of biasing spring  88  and cause the insertion of locking tab  86  into one of the plurality of cavity locks  68  in spindle lock fan hub  64 . Because spindle lock member  70  engages spindle lock fan hub  64  on armature shaft  54 , a small turn of the circular cutting blade will cause many turns of armature shaft  54  and thus give many opportunities for engagement of locking tab  86  in one of the plurality of cavity locks  68 , unlike conventional systems that use a spindle lock in connection with the output drive shaft. 
         [0050]    According to this arrangement, it should be appreciated that thumb pad  84  is positioned adjacent to auxiliary handle assembly  20  and in sufficiently close proximity such that an operator can hold worm drive saw  10  in one hand while simultaneously actuating thumb pad  84  with the same hand. This arrangement thus enables the operator to hold the power tool, prevent rotation of the circular cutting blade, and replace the circular cutting blade, without the need to place worm drive saw  10  on the ground or other supporting structure and in a favorable position. In some embodiments, an operator can further retract lower blade guard  24  using thumb gripping portion  52  during the above replacement operation. 
         [0051]    It should again be understood that the spindle lock mechanism and/or transmission drive system can be adapted for use in other power tools.