Abstract:
A mandrel assembly for attaching a hole saw and a pilot drill bit to an electric drill is disclosed. The mandrel assembly has a “self-clearing” feature that removes the “plug” without removing the mandrel from the drill chuck. The mandrel assembly includes a threaded shaft having a first end for attachment to a drill chuck, and a second end for receiving hole saw. The hole saw has a base disposed toward the chamfered end with the base having an opening therethrough and an ejection rod disposed substantially parallel to the threaded shaft between the chamfered end and the base. The ejection rod matingly engages and passes through the opening. When the drill bit is reversed, the ejection rod enters the interior space of the hole saw and clears the “plug” from the interior space of the hole saw.

Description:
CROSS REFERENCED APPLICATION 
       [0001]    This application is related, and claims priority, to U.S. Provisional Application No. 62/117,886 filed on Feb. 18, 2015, that is incorporated herein in its entirety by reference thereto. 
     
    
     BACKGROUND OF THE DISCLOSURE 
       [0002]    1. Field of the Disclosure 
         [0003]    The present disclosure relates generally to a mandrel assembly adapted to attach a hole saw and a pilot drill bit to an electric drill. More particularly, the present disclosure relates to such a mandrel assembly that is designed and operated to have a “self-clearing” feature. 
         [0004]    2. Background of the Disclosure 
         [0005]    Many designs for a mandrel assembly for a hole saw and drill bit combination are known in the art. Representative publications showing such mandrel assemblies are U.S. Pat. No. 5,246,317 and EP Pub. 1462198. By way of general design, known mandrel assemblies have several parts in common. All assemblies have a pilot bit and a hole saw, in which the pilot bit serves the purpose of guiding the hole saw to the proper location in the workpiece. Also, known mandrel assemblies generally include a base mechanism and an adapter. In general terms, the base mechanism is designed for attachment to the chuck of, e.g., an electric drill, while the adapter is designed for mounting the hole saw/pilot bit combination to the base mechanism. 
         [0006]    Regardless of design, a shortcoming of the prior art mandrel assemblies is that the “plug” of the workpiece cut out by the hole saw remains behind in the interior space of the hole saw and must be removed before the hole saw can be used to cut a new hole in the workpiece. Removal of the “plug” often entails removal of the mandrel from the electric drill and the use of an implement of some sort to remove the “plug” from the interior space of the hole saw. Generally speaking, the mandrel is removed from the chuck of the electric drill to simplify access to the “plug” remaining in the interior space of the hole saw, as well as to ensure the safety of the operator. Removing the mandrel from the electric drill is time-consuming, preventing the operator from proceeding to cut the next hole in the same or another workpiece. Coupled with the foregoing time delay is the additional delay caused by the need to remove the “plug” and to reinstall the mandrel into the chuck of electric drill. 
         [0007]    Thus, a need exists for a mandrel that allows removal of the “plug” material from the interior space of the hole saw to be effected quickly and safely, without the need to remove the mandrel from the electric drill, and without the need to employ an additional implement, to remove the “plug”. 
       SUMMARY OF THE DISCLOSURE 
       [0008]    The present disclosure solves the above-mentioned need by providing a mandrel assembly with a “self-clearing” feature, namely to quickly and safely remove the “plug” (i.e., the cut portion of a workpiece) contained within the hole saw resulting from the action of the hole saw drilling through the workpiece. 
         [0009]    The present disclosure also provides the self-clearing feature without removing the mandrel assembly from the drill chuck. 
         [0010]    The present disclosure further provides the self-clearing feature without the need to employ an additional implement to remove the “plug”. 
         [0011]    In one embodiment of the present disclosure, a mandrel assembly is provided that comprises: a threaded shaft comprised of a first end and a second end, the first end including a chamfered end for being held in a drill chuck, the second end comprising a threaded portion for matingly receiving a hole saw; the hole saw comprised of a base disposed toward the chamfered end, the base having at least one opening disposed therethrough and at least one movable rod that matingly engages the at least one opening, the movable rod disposed substantially parallel to the threaded shaft between the chamfered end and the base. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The mandrel assembly of the present disclosure will now be described in more detail with reference to the Figures. 
           [0013]      FIG. 1  is a side view of a prior art mandrel assembly. 
           [0014]      FIG. 2  is an exploded side view of a prior art mandrel assembly. 
           [0015]      FIG. 3A  is a side view of a mandrel assembly according to the present disclosure in cutting position. 
           [0016]      FIG. 3B  is a side view of a mandrel assembly according to the present disclosure in cutting position, with a partial transparent view of the hole saw with a “plug” therein. 
           [0017]      FIG. 4A  is a side view of a mandrel assembly of  FIG. 3A  in clearing position, with the “plug” (not shown) partially removed. 
           [0018]      FIG. 4B  is a side view of a mandrel assembly of  FIG. 3A  in cleared position, with the “plug” completely removed. 
           [0019]      FIG. 5  is a front perspective view of the mandrel assembly of  FIG. 4A  (“plug” not shown). 
           [0020]      FIG. 6  is a rear perspective view of the mandrel assembly of  FIG. 4A . 
           [0021]      FIGS. 7A and 7B  show an overhead view and perspective view, respectively, of an alternate embodiment of a collar of the present disclosure. 
       
    
    
       [0022]    In the detailed description of the preferred embodiment that follows, like numerals are used to designate like elements throughout the description of the Figures, although alternatives will be apparent to one of skill in the art based on the following detailed description. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]    Referring to  FIGS. 1 and 2 , these Figures show a prior art mandrel assembly. The mandrel assembly  100  of  FIG. 1  has a hole saw  120 , a pilot bit  140  and a base mechanism  160 . Hole saw  120  is generally cylindrical in shape with a thickness (shown at wall openings  122 ) that provides hole saw  120  with structural strength and support. The thickness of hole saw  120  shown at wall openings  122  provides hole saw  120  with an inside diameter (ID)  121 . Hole saw  120  has a depth  123 , reflecting the maximum thickness of a workpiece through which hole saw  120  may drill because teeth  126  must pass through workpiece completely in order to cut the desired hole in the workpiece. In operation, hole saw  120  generally also has wall openings  122  which are useful for allowing dust from teeth  126  passing through a workpiece (e.g., wood or concrete) or other waste produced by the action of hole saw  120  upon the workpiece to exit the interior space of hole saw  120  created by the workpiece (not shown) and the inside diameter  121  of hole saw  120 . Wall openings  122  also allow for the venting of heat from the volume created between cut workpiece and a residual depth  123 ′ between bottom of the workpiece (shown by the dotted line in  FIG. 1 ) and the base  125  of hole saw  120 . 
         [0024]    Base mechanism  160  has a proximal end  161  and a chamfered end  162 . Proximal end  161  is disposed in relation to base  125  of hole saw  120  so as to receive a chamfered end  182  of adapter  180  (see,  FIG. 2 ). Chamfered end  162  has geometry, as is known to those skilled in the art, suitable for insertion into an electric drill chuck (not shown). Adapter  180  has a threaded end  181  and chamfered end  182 . Threaded end  181  threads into matching threaded opening (not shown) of hole saw  120 . Threaded end  181  also receives chamfered end  142  of pilot bit  140  after threaded end  181  is threaded into threaded opening (not shown) of hole saw  120 . Pilot bit  140  can be secured in chamfered end  182  using, e.g., a set screw (now shown). Cutting end  141  of pilot bit  140  serves to align hole saw  120  properly in relation to the workpiece. All of pilot bit  140 , hole saw  120 , adapter  180  and base mechanism  160  are concentrically aligned along longitudinal line  190  to ensure that power from the electric drill (not shown) is transmitted correctly through to hole saw  120  and to the workpiece along longitudinal line  190  (see,  FIG. 2 ). 
         [0025]      FIGS. 3A to 6  show different views of an embodiment of a mandrel assembly  300  of the present disclosure. In  FIGS. 3A to 6 , elements that are known according to the prior art of  FIGS. 1 and 2  are designated with the same numbers as in  FIGS. 1 and 2 . Thus, elements  120 ,  121 ,  123 ,  125 ,  126 ,  140  and  162  are the same as shown in  FIGS. 1 and 2 . 
         [0026]    Referring to  FIG. 3A , mandrel assembly  300  of the present disclosure comprises a threaded shaft  310 , a tensioning spring  320 , a pilot bit attachment/ejection rod guide collar  330 , ejection rods  340  and a plurality of knurled knobs  350 ,  351  and  352 . Ejection rods  340  are fixed to knurled knob  350  at top surface  350 ′ of knurled knob  350 . Knurled knobs  351  and  352  function as a grip support and an ejection rod depth/stop support, respectively, as will be explained below. Pilot bit attachment/ejection rod guide collar  330  has channels therethrough (not shown) that are configured to accept ejection rods  340  and assist in guiding ejection rods  340  into and through openings  380  (see,  FIG. 5 ) in base  125  of hole saw  120 , as will also be explained below. Openings  380  align with the positioning and spacing of channels  360  (see,  FIGS. 3B and 4B ) through pilot bit attachment/ejection rod guide collar  330 . Pilot bit attachment/ejection rod guide collar  330  may be fixedly attached to base  125  of hole saw  120  or may be a separate element. In  FIG. 3A , mandrel assembly  300  is shown in the “cutting” position in which mandrel assembly  300  acts to cut a hole through a workpiece (not shown), in the same manner as the prior art mandrel assemblies shown in  FIGS. 1 and 2 , creating a plug  370  (see,  FIGS. 3B and 4B ). In operation, chamfered end  162  of threaded shaft  310  is inserted into a power drill chuck (not shown). As power is supplied, mandrel assembly  300  rotates in a clockwise direction against the workpiece and, guided by pilot bit  140 , hole saw  120  cuts a hole in the workpiece the size of outside diameter  390  of hole saw  120 . In “cutting” position, ejection rods  340  pass through pilot bit attachment/ejection rod guide collar  330  and are aligned with openings  380  in base  125  of hole saw  120 . In “cutting” position, ends  341  (shown in  FIGS. 3B and 5 ) of ejection rods  340  remain flush, or substantially flush, with the inside surface  127  (see,  FIG. 3B ) of base  125  of hole saw  120 . In this manner, ends  341  of ejection rods  340  do not interfere with the operation of hole saw  120  as it cuts through the workpiece. 
         [0027]      FIGS. 4 to 6  show several views of mandrel assembly  300  during “clearing” operation, i.e., when mandrel assembly  300  operates to clear plug  370  of the workpiece from the inside space of hole saw  120 . “Clearing” operation will now be described with reference to  FIGS. 4A to 6 . When a hole has been cut through a workpiece using mandrel assembly  300  as shown in  FIG. 3A , mandrel assembly  300  is removed from the workpiece. At that time, hole saw  120  retains plug  370  of the workpiece, which consists of the material removed during the cutting operation. To clear hole saw  120  of mandrel assembly  300  of the present disclosure, the following operation is performed. The operator grasps knurled knobs  350  and  351 , and reverses electric drill (not shown) so that threaded shaft  310  of mandrel assembly  300  rotates in a counterclockwise direction. The counterclockwise rotation of threaded shaft  310  combined with the operator grasping knurled knobs  350  and  351  has the effect of causing pilot bit attachment/ejection rod guide collar  330  and hole saw  120  to move toward each other. As pilot bit attachment/ejection rod guide collar  330  and hole saw  120  and knurled knobs  350  and  351  are moved towards each other, ends  341  of ejection rods  340  enter and are extended into residual space  123 ′ through openings  380  and are urged against plug  370  of the workpiece remaining in the inside diameter  121  of hole saw  120 . This can best be seen in  FIGS. 4B and 5 , in which ends  341  of ejection rods  340  have extended into residual depth  123 ′ of hole saw  120 . Continued counterclockwise rotation of threaded shaft  310  by counterclockwise rotation of the drill chuck urges ends  341  of ejection rods  340  further into residual space  123 ′ until ends  341  of ejection rods  340  contact against plug  370 . Ends  341  of ejection rods  340  continue to push against plug  370  until the plug  370  is ejected from the inside diameter  121  of hole saw  120 . 
         [0028]    Once plug  370  is ejected from inside diameter  121  of hole saw  120 , mandrel assembly  300  is returned to “cutting” position as follows. While still grasping knurled knobs  350  and  351 , operator reverses the rotation of drill chuck once again, so that drill chuck and mandrel assembly  300  are again rotated in a clockwise direction. As drill chuck rotates clockwise, threaded shaft  310  is urged forward through knurled knobs  350  and  351 , and ejection rods  340  are pulled back from the inside space of hole saw  120 , so that ends  341  of ejection rods  340  no longer reside in the inside space of hole saw  120 . Rather, ends  341  of ejection rods  340  are returned to their cutting position flush, or substantially flush, with inside surface  127  of bottom  125  of hole saw  120 . Knurled knob  352  serves to act as a “stop” so that knurled knobs  350  and  351 , grasped by the operator cannot be retracted such that ejection rods  340  are pulled below or substantially below openings  380  in base  125  of hole saw  120 . Knurled knob  352  acts as a “safety” device, ensuring that alignment of ejection rods  340  with pilot bit attachment/ejection rod guide collar  330  and openings  380  in base  125  is maintained. 
         [0029]    Assembly of mandrel assembly  300  can be performed in various ways. Beginning with threaded shaft  310 , pilot bit attachment/ejection rod guide collar  330  is placed on threaded shaft  310  (either by threading onto threaded shaft  310  or by having an inside diameter slightly greater than the diameter of threaded shaft  310  and sliding onto threaded shaft  310 ). Pilot bit attachment/ejection rod guide collar  330  can be held in place on threaded shaft  310  by use of a set screw. A sufficient amount of threaded shaft  310  is left exposed so that hole saw  120  can be threaded onto threaded shaft  310  and placed into communicative relation with pilot bit attachment/ejection rod guide collar  330 . Preferably, the amount of threaded shaft  310  left exposed is such that when hole saw  120  is fully threaded onto threaded shaft  310 , openings  380  in base  125  of hole saw  120  align with channels  360  of pilot bit attachment/ejection rod guide collar  330 . In this embodiment, both hole saw  120  and pilot bit attachment/ejection rod guide collar  330  can be threaded to match the threads of shaft  310 . Alternatively, pilot bit attachment/ejection rod guide collar  330  and hole saw  120  can be separate from each other and be separately threaded onto threaded shaft  310 , starting with pilot bit attachment/ejection rod guide collar  330  that can be threaded onto threaded shaft  310 , followed by threading hole saw  120  onto threaded shaft  310  until base  125  of hole saw  120  contacts, or nearly contacts, upper surface  331  of pilot bit attachment/ejection rod guide collar  330 . In this embodiment, hole saw  120  can, additionally, be held in alignment with pilot bit attachment/ejection rod guide collar  330  through the use of an appropriately threaded nut (not shown) which is threaded onto threaded shaft  310  until it is matingly surfaced against inside surface  127  of hole saw  120 . In a still further embodiment, pilot bit attachment/ejection rod guide collar  330  can have an inside diameter that is slightly greater than the outside diameter of threaded shaft  310 , and pilot bit attachment/ejection rod guide collar  330  can be slipped into place on threaded shaft  310 , held in place by, e.g., a set screw, and hole saw  120  can be threaded onto threaded shaft  310  until base  125  makes contact against upper surface  331  of pilot bit attachment/ejection rod guide collar  330 . Also alternatively, hole saw  120  can have an inside diameter slightly greater than the outside diameter of the threaded shaft  310  and can be slipped onto threaded shaft  310  and held matingly surfaced against upper surface  331  of pilot bit attachment/ejection rod guide collar  330  using an appropriately threaded nut threaded onto threaded shaft  310  until the threaded nut contacts inside surface  127  of hole saw  120 . 
         [0030]    Continuing with assembly of mandrel assembly  300 , proceeding from chamfered end  162  of threaded shaft  310 , spring  320  is placed onto threaded shaft  310 . Thereafter, knurled knob  350  having ejection rods  340  affixed thereto, is placed onto threaded shaft  310 . Preferably, knurled knob has a substantially centrally located opening with an inner diameter that is slightly greater than the diameter of threaded shaft  310 , simplifying placement of knurled knob  350  onto threaded shaft  310  and alignment of ejection rods  340  with channels  360 . This action is followed by threading knurled knobs  351  and  352  onto threaded shaft  310 . Threading knurled knobs  351  and  352  onto threaded shaft  310  continues until ends  341  of ejection rods  340  are flush or substantially flush with inside surface  127  of hole saw  120 . When knurled knobs  351  and  352  are threaded onto threaded shaft  310  such that ends  341  of ejection rods  340  are flush or substantially flush with inside surface  127  of hole saw  120 , knurled knob  352  is fixed in place by use of, e.g., a set screw. 
         [0031]    In  FIGS. 3A to 6 , ejection rods  340  have been depicted as two ejection rods disposed in channels  360  through pilot bit attachment/ejection rod guide collar  330 , spaced along a diameter line of pilot bit attachment/ejection rod guide collar  330 , and spaced substantially equidistant from the center of pilot bit attachment/ejection rod guide collar  330 . However, ejection rods  340  can be any number of ejection rods  340  spaced, preferably, on equally spaced radii emanating from the center of pilot bit attachment/ejection rod guide collar  330 . Alternatively, ejection rods  340  can be spaced in a skewed arrangement through channels disposed in pilot bit attachment/ejection rod guide collar  330 , or a single ejection rod  340  can be used in some embodiments. These latter two instances, i.e., skewed arrangement of ejection rods  340  and/or a single ejection rod  340 , may not be preferred in all embodiments because, upon entering residual space  123 ′ as drill is reversed, these arrangements of ejection rod(s)  340  may have a tendency to tilt or skew plug  370  of the workpiece which then may become jammed in inside diameter  121  of hole saw  120 . In an alternative embodiment, end(s)  341  of ejection rods  340  can have attached thereto a plate of square, rectangular, circular, oval, or any other desired shape, to provide increased surface area for the point of contact against plug  370 . In this embodiment, a single rod  340  can more easily be used since it would be less likely that plug  370  would be caused to tilt and become jammed against inside diameter  121  of hole saw  120 . In the embodiments where a plate is affixed to ends  341  of ejection rods  340 , the plate can be fixed to ends  341  of ejection rods  340  after assembly of the mandrel assembly  300 . Alternatively, ejection rods  340  can have such a plate permanently affixed thereto. In this embodiment, ejection rods  340  having a plate affixed thereto can be separate from and not a fixed to knurled knob  350 . Rather, in this embodiment, ejection rods  340  can be placed into inner diameter  121  of hole saw  120 , slipped through openings  380  and into alignment with channels  360  in pilot bit attachment/ejection rod guide collar  330 , pass through channels  360  in pilot bit attachment/ejection rod guide collar  330  and then matingly engaged with suitably sized openings in knurled knob  350 . In this embodiment, ejection rods  340  can be retained in openings of knurled knob  350  through the use of set screws or similar retention devices known to those of skill in the art. Of course, in embodiments where ejection rods  340  have a plate associated therewith, the plate will have an opening suitably sized to accommodate the diameter of pilot bit  140  and, preferably, threaded shaft  310 . 
         [0032]    Also, in the embodiments shown in  FIGS. 3A-6 , hole saw  120  has two openings  380  for accommodating two ejection rods  340 . However, hole saw  120  can have an excess of openings  380  for accommodating ejection rods  340  or alternatively, hole saw may have curved slots. In an embodiment where hole saw has curved slots, the curved slots will have a width sufficient to accept the diameter, or other cross-sectional measurement, of ejection rods  340 , and also be curved in a manner that is concentric with the curvature of the diameter of hole saw  120 . 
         [0033]    Although the preferred embodiments of the mandrel assembly  300  of the present disclosure utilize pilot bit attachment/ejection rod guide collar  330 , pilot bit attachment/ejection rod guide collar  330  can have an alternative construction, or be absent altogether. One such alternative embodiment for pilot bit attachment/ejection rod guide collar  330  is depicted in  FIGS. 7A and 7B . 
         [0034]    Referring to  FIGS. 7A and 7B , alternative collar  700  is has a center opening  710  and remote openings  720 . Center opening  710  is connected to remote openings  720  via extensions  730 . Center opening  710  could be threaded onto threaded shaft  310  or be slipped over threaded shaft  310 , as described above with respect to pilot bit attachment/ejection rod guide collar  330 . Remote openings  720  will be aligned with openings  380  in hole saw  120  and sized appropriately to matingly receive ejection rods  340 . Likewise, collar  710  can, as with pilot bit attachment/ejection rod guide collar  330 , have ejection rods affixed thereto or, alternatively, receive ejection rods  340  placed through openings  380  in hole saw  120  and slid into remote openings  720  to be thereafter affixed in position through the use of set screws or other known fasteners passing through wall  740  of remote openings  720 . 
         [0035]    As mentioned, pilot bit attachment/ejection rod guide collar  330  or  700  can be omitted, with ejection rods  340  proceeding directly from knurled knob  350  through openings  380  disposed in base  125  of hole saw  120 . This configuration, however, is not preferred because of the tendency of ejection rods  342  to possibly become misaligned with openings  380  in hole saw  120 , or to bend when in use. Also, in either of the embodiments of pilot bit attachment/ejection rod guide collar  330  or  700 , ends  341  of ejection rods  340  can be disposed outside of interior space of hole saw  120  and away from opening  360  because the configuration of pilot bit attachment/ejection rod guide collar  330  and  700  provide alignment for end  341  of ejection rod  340  to correctly enter interior space. 
         [0036]    Also, knurled knobs  351  and  352  are not required for the practice of the mandrel assembly  300  of the present disclosure, but are preferred. Knurled knob  351  is preferred so that the operator has a larger surface area to grip when drill is reversed. However, knurled knobs  350  and  351  can be combined into a single knurled knob. Likewise, knurled knob  352  can be omitted, although this is not preferred. If knurled knob  352  is omitted, this will necessitate the operator to visually observe the progress of ejection rods  340  out of space  123  to ensure that ends  341  of ejection rods  340  remaining flush or substantially flush with inside surface  126  of hole saw  120 . Similarly, although in  FIGS. 3A to 6  knurled knob  352  has been depicted as having substantially the same outer diameter as knurled knobs  350  and  351 , this is not necessary. 
         [0037]    In the above detailed description, the specific embodiments of this disclosure have been described in connection with its preferred embodiments. However, to the extent that the above description is specific to a particular embodiment or a particular use of this disclosure, this is intended to be illustrative only and merely provides a concise description of the exemplary embodiments. Accordingly, the disclosure is not limited to the specific embodiments described above, but rather, the disclosure includes all alternatives, modifications, and equivalents falling within the true scope of the appended claims. Various modifications and variations of this disclosure will be obvious to a worker skilled in the art and it is to be understood that such modifications and variations are to be included within the purview of this application and the spirit and scope of the claims. 
         [0038]    All of the patents and publications referred to herein are incorporated herein by reference as if fully set forth herein.