Abstract:
A bit attaching arrangement for a power tool has a collet nut threadably engaging a rotatably driven shaft of the power tool. The collet nut has a plurality of slots positioned on an outer peripheral surface. A first gear is disposed on the shaft so that rotation of the first gear causes rotation of the shaft. An actuating member having a second gear associated therewith is attached to the housing of the power tool. The actuating member also has a slot-engaging extension associated therewith. The actuating member is positionable between a first position and a second position. In the first position, the second gear engages the first gear and the extension engages one of the slots of the collet nut such that rotation of the actuating member results in rotation of the shaft while maintaining the collet nut at a generally fixed rotational location. In a second position, the first and second gears do not engage one another and the extension does not engage any of the slots of the collet nut such that the shaft can be freely rotated during operation of the power tool.

Description:
FIELD OF INVENTION 
     This invention relates to a bit attaching arrangement for a power tool, and more particularly to an arrangement that allows the bit to be attached without the use of external wrenches or keys. 
     BACKGROUND OF THE INVENTION 
     Power tools, such as routers, often incorporate a collet for holding the shank end of a bit in place on the lower end of the rotating armature/output shaft. In particular, the collet consists of a generally cone-shaped structure having a split end which defines separate prongs which are usually biased slightly radially outwardly. The end of the collet opposite the prongs is generally attached to or formed integrally with the output shaft of the router. A router locking nut is used to secure a bit onto the output shaft. The collet nut has a female thread surface which engages the male thread surface located on the lower end of the output shaft. The collet nut fits over the collet and has a female cone-shaped camming surface for engaging the cone-shaped outer surface of the collet. 
     In order to attach a bit to a router utilizing this well-known structure, the shank of the bit is positioned between the prongs of the collet with the collet nut in a loosened position on the output shaft. After the shank of the bit is completely disposed within the hollow output shaft, the collet nut is tightened such that the prongs of the collet engage the side surfaces of the shank and firmly hold the bit in place on the lower end of the shaft. In order to sufficiently tighten the collet nut so as to secure the bit, external and separate tools and/or wrenches are typically utilized. In particular, the tightening operation of this prior art structure often involves utilizing a shaft lock arrangement which prevents rotation of the output shaft of the router and thereafter allows manual tightening of the nut using a dedicated individual wrench which is often included with the router when it is sold. 
     This prior locking arrangement suffers from numerous disadvantages. First, because the tightening wrench is a separate item, it is often lost or misplaced after the router has been used for a period of time. This often results in an operator utilizing a nondedicated wrench or pliers to tighten the collet nut. Use of an incorrect sized wrench or pliers may result in damage to the collet nut and/or locking arrangement. Additionally, use of a nondedicated wrench can also result in the collet nut not being sufficiently tightened causing slippage between the bit and the output shaft. 
     A further disadvantage is the amount of time it takes to replace a router bit. More specifically, to adequately tighten the collet nut, it requires numerous placement and replacement of the wrench on the collet nut to tighten the nut. This is due to limited access to the attaching arrangement through the guards and support plates of the router. Still further, as mentioned above, to rotate the nut with respect to the output shaft, oftentimes there is a shaft-locking mechanism disposed internally within the assembly. This can result in a further disadvantage because of the possibility of the shaft-locking mechanism malfunctioning and impeding the rotation of the output shaft. 
     Therefore, a bit-locking arrangement is needed which will overcome the problems discussed above. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a locking arrangement for a power tool which does not require any external wrenches or tools to secure the bit to the output shaft of the power tool. 
     Another object of the present invention is to provide a locking arrangement which does not require a separate spindle lock for maintaining the outward shaft stationary as the tightening nut of the arrangement is turned. 
     A still further object of this invention is to provide a bit-locking arrangement which is self-contained within the power tool and which provides for general fixation of the locking member while rotating the output shaft of the power tool to accomplish the tightening and loosening process. 
     Accordingly, the present invention provides for a bit-attaching arrangement for a power tool wherein the power tool has a rotatably driven shaft onto which a bit is attached and rotated through the use of a collet. The arrangement includes a collet nut threadably engaging the shaft. The collet nut has a plurality of slots positioned on an outer peripheral wall. A first gear is disposed on the shaft so that rotation of the first gear causes rotation of the shaft. An actuating member has a second gear and a slot engaging extension. The actuating member is positionable between a first position and a second position. In the first position, the second gear engages the first gear and the extension engages one of the slots. Upon rotation of the actuating member, the shaft will rotate and the collet will be maintained at a generally fixed rotational location, thus allowing loosening and tightening of a bit. In the second position, the first and second gears do not engage one another, and the extension does not engage one of the slots so that the shaft can be freely rotated during the powered operation of the tool. 
     The invention further includes the actuating member having a knob for rotation of the second gear. The actuating member is disposed in an aperture formed in the housing of the power tool. A button is disposed on the peripheral surface of the knob and is connected to a flange member that abuts a portion of the housing adjacent the aperture when the actuating member is in its second position. In order to orient the actuating member to its first position, the button is depressed to allow the flange to pass within the aperture, and thus to move the actuating member to its first position. 
     Additional objects, advantages, and novel features of the invention will be set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings, which form part of this specification and are to be read in conjunction therewith, and in which like reference numerals are used to indicate like parts in the various views: 
     FIG. 1 is a side elevational view of a router, with a bit-locking arrangement embodying the principles of this invention; 
     FIG. 2 is a cross-sectional view taken generally along line  2 — 2  of FIG.  1  and showing the pinion shaft in its engaged position to allow rotation of the output shaft and maintain the collet nut at a generally fixed rotational location; 
     FIG. 3 is a cross-sectional view taken generally along line  3 — 3  of FIG.2; 
     FIG. 4 is a view similar to FIG. 3, but showing the pinion shaft in its retracted disengaged position and locked in place via the lockout structure of the knob; and 
     FIG. 5 is a view similar to FIG. 4 showing a bit secured in the bit-locking arrangement, and the pinion shaft in its disengaged position to allow operation of the router; and 
     FIG. 6 is a view showing an alternative bit-locking arrangement. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings in greater detail, and initially to FIG. 1, a router  10  having a bit-locking arrangement  12  according to the present invention is shown. Router  10  includes a housing  14  mounted to a generally horizontal support plate  16 . Contained within housing  14  is a motor (not shown) which rotates a generally cylindrical armature or output shaft  18 , as shown in FIG.  3 . Shaft  18  is supported in housing  14  by a bearing assembly  20 . Shaft  18  has a cylindrical bit receiving bore  22  formed on an exposed end, as shown in FIG.  5 . Bore  22  is configured to receive a shank portion  24  of a bit  26 . Shaft  18  further has a generally annular receiving area  28  formed on its lower end for maintaining a conical collet  30  thereon. Collet  30  includes connected generally semicircular prongs  32  (as best shown in FIG.  4 ), each having an inclined outer surface  34 . Prongs  32  of collet  30  surround shank  24  of bit  26 , as best shown in FIG. 5, such that the interior surface of prongs  32  engage shank  24  to secure bit  26  in position, as will be more fully described below. Although collet  30  is shown as a separate piece from shaft  18 , it may be desirable, and it is within the scope of this invention to form collet  30  integral with the bottom of output shaft  18 . 
     Shaft  18  further has outer thread surface  36  located adjacent its lower end, as best shown in FIG.  5 . Thread surface  36  engages female thread surface  38  of a collet nut  40 , such that collet nut  40  can be tightened and loosened on the lower end of shaft  18  to secure bit  26  in place, as will be more fully described below. Nut  40  further has a generally conical inner camming surface  42  for engaging the inclined surfaces  34  of prongs  32 , such that upward movement of nut  40  on shaft  18  results in prongs  32  being forced inwardly to tightly engage shank  24  and secure bit  26  in position, as best shown in FIG.  5 . 
     With reference to FIGS. 2 and 3, nut  40  further includes an outer peripheral surface  44  on which are formed a plurality of evenly spaced slots or splines  46 . Slots  46  are utilized to hold nut  40  at a generally fixed rotational location during tightening and loosening of bit  26 , as will be more fully described below. Each slot  46  is closed along its bottom and open at the top. Slots  46  are generally rectangular in shape and the sidewalls of the slots provide abutment surfaces that prevent rotation of nut  40  during tightening and loosening, as will be more fully described below. 
     Arrangement  12  further has an upper gear  50 . Upper gear  50  is secured on an outer surface of shaft  18 , such that rotation of gear  50  will result in rotation of shaft  18 . In particular, gear  50  can be key to shaft  18  in any suitable manner. Gear  50  includes an annular beveled gear surface  52  which will be utilized to rotate shaft  18 , as will be more fully described below. A pinion gear  54  has an annular beveled gear surface  56  for engaging gear surface  52 . Rotation of gear  54  results in rotation of gear  50  and thus results in rotation of shaft  18 . Thus, depending on which direction pinion gear  54  is rotated, such rotation can result in tightening or loosening of bit  26  in collet nut  40 . 
     Pinion gear  54  can be rotated by a router operator via pinion shaft  58  and actuating knob  60 . In particular, shaft  58  is slidably and rotatably mounted to housing  14  via a generally cylindrical passage  62 , as best shown in FIG.  4 . Passage  62  has an aperture  64  on one end through which pinion shaft  58  extends. Pinion shaft  58  is supported in passage  62  by an upwardly extending support member  66 . Additionally, knob  60  has formed therewith a generally annular cylindrical portion  68  which fits around pinion shaft  58  and snugly fits within aperture  64 . 
     A coilspring  70  generally surrounds pinion shaft  58  and is positioned between an abutting surface  72  of cylindrical portion  68  of knob  60  and support  66 . Spring  70  serves to bias pinion shaft  58  outwardly away from collet nut  40  and toward a position wherein pinion gear  58  is disengaged from upper gear  50 . 
     With reference to FIG. 2, located on an end surface  74  of pinion shaft  58  is a generally cylindrical receiving bore  76 . Received in bore  76  is a cylindrical locking pin or extension  78 . Pin  78  is used to engage one of slots  46  to hold collet nut  40  at a generally fixed rotational location during tightening and loosening, as will be more fully explained below. One end of pin  78  has a collar  80  formed therewith which prevents pin  78  from becoming disengaged from bore  76 . In particular, pin  78  can slide telescopically in and out of bore  76  and is biased outwardly away from end surface  74  by a coilspring  82 . 
     Pin  78  is also received in an aperture  84  formed in a pin bearing member  86 , as best shown in FIG.  5 . Bearing member  86  ensures that pin  78  will be adequately aligned with the appropriate slot  46 . 
     Pin  78  can engage any one of slots  46  when pinion gear  54  engages upper gear  50 . As pin  78  engages one of slots  46 , rotation of collet nut  40  will be prevented. Thus, rotation of pinion shaft  58  will result in collet nut  40  being fixed and shaft  18  being rotated. This rotational motion of pinion shaft  58  will result in tightening and loosening of collet nut  40  because collet nut  40  will move slightly up and down along thread surface  36  to accomplish the pinching and loosening actions of prongs  32 . 
     The provision of bore  76  with pin  78  disposed therein and the biasing of spring  82  allows pin  78  to translate only approximately one half the distance that pinion shaft  58  translates to thereby reduce the necessary size of gear  50 . For instance, if pinion shaft  58  were to translate 8 mm, it would be necessary for pilot pin  78  to translate 4 mm. This arrangement of pin  78  slidably coupled to shaft  58  also ensures that pin  78  is always maintained in bearing member  86  during the translation inwardly and outwardly of shaft  58 , as shown in FIGS. 3 and 4. Thus, pin  78  is always within aperture  84  of bearing member  86  and does not have to be realigned with the aperture every time pinion shaft  58  is translated. Still further, the spring loading action of pin  78  allows surface  52  to be at least partially engaged by gear surface  56  prior to pin  78  being disposed in one of slots  46 . More specifically, there may be occasions where an operator wishes to loosen a bit and thus translates pinion shaft  58  inwardly. Depending upon the rotational location of collet nut  40 , pin  78  may not be aligned with one of slots  46 , but instead may be aligned with a peripheral surface segment  90  of collet nut  40  which prevents pin  78  from locking collet nut  40  at a rotational location. If this situation occurs, pin  78  will be compressed in bore  76  against the bias of spring  82  to such an extent to allow gear surface  52  to engage gear surface  56 . An operator can then rotate shaft  58  utilizing knob  60 , thus resulting in rotation of collet nut  40 , until such time as pin  78  “snaps” into an appropriate slot  46 , thus fixing the collet nut at a rotational location. 
     With reference to FIGS. 3 and 4, a lockout structure  92  is shown. Lockout structure  92  is formed into knob  60 , as will be further described below. More specifically, the outer circumferential surface  94  of knob  60  has a lockout actuating button  96  which can be easily operated by a user gripping knob  60 . Button  96  is integrally connected to a locking flange, and further has a leaf-type biasing member  100  located opposite button  96  which serves to bias button  96  and thus locking flange  98  circumferentially outwardly away from pinion shaft  58 . Still further, portions  60  of knob  60  has a recess  102  formed therein for accommodating locking flange  98  when it is in its disengaged position to allow inward movement of shaft  58 , as best shown in FIG.  3 . 
     Locking flange  98  is shown in its lockout position in FIG. 4, wherein a front edge  104  of locking flange  98  engages an edge surface  106  of housing  14  adjacent aperture  64 . This engagement prevents shaft  58  from being translated inwardly accidentally until such time as the operator desires to translate shaft  58  inwardly by depressing button  96 , and thus disengaging locking flange  98  from edge surface  106 . After such actuation of button  96 , flange  98  is received in recess  102  and shaft  58  can be pushed inwardly such that flange  98  also slides within aperture  64 . As best shown in FIGS. 3 and 4, it is preferable to have pinion shaft  58  at an angle to the horizontal surface of plate  16 . This horizontal angle ensures that knob  60  is an adequate distance above plate  16  so as to not interfere with workpieces, guard surfaces, or adjusting structures. 
     In operation, arrangement  12  is first found in its untightened open position shown in FIG.  4 . More specifically, in this position prongs  32  of collet  30  are not yet being forced inwardly by the engagement between inclined surfaces  34  and camming surface  42  of nut  40 . Thus, shank  24  of bit  26  can be inserted through collet  30  and received in bore  22  of shaft  18 . In order to secure bit  26  in place on shaft  18 , an operator first pushes inwardly on button  96  so as to disengage locking flange  98  from edge surface  106 . Thereafter, an operator pushes inwardly on knob  60  such that pin  78  engages one of slots  46  on collet nut  40  and such that pinion gear  58  engages upper gear  50 . As is apparent, this inward movement of shaft  58  is against the bias of coilspring  70 . Shaft  58  slides within passage  62  easily due to the support member  60 , and also the tight fit of portion  68  of knob  60 . After the gears are engaged, pin  78  maintains collet nut  40  at a fixed rotational location, and knob  60  can be rotated such that gear  50 , and thus shaft  18 , are rotated with respect to collet nut  40 . This rotation of shaft  18  with respect to collet nut  40  results in the tightening of bit  26  in bore  22 . 
     After collet nut  40  has been adequately tightened, the operator releases all inward pressure on knob  60 , and thus pinion gear  54  returns to its nonengaged position due to coilspring  70  expanding from its compressed condition. Further, as shaft  58  moves further outwardly, edge  104  of flange  98  will clear edge  106  of housing  14  such that flange  98  snaps upwardly due to biasing member  100  to automatically lock shaft  58  in its outward nonengaging position. It is apparent that loosening of a bit takes place in the same manner described above except that pinion gear  54  is rotated in an opposite direction to loosen collet nut  40 . 
     Arrangement  12  offers numerous advantages over prior securing structures. In particular, arrangement  12  is completely self-contained within housing  14 , so that no separate wrenches or tools are required to secure bit  26  to output shaft  18 . Further, pin  78  allows an effective locking mechanism for collet  30  formed with pinion gear  54 . As is apparent, it is necessary that collet nut  40  move slightly vertically along shaft  18 , which is accomplished by the open-ended structure of slots  46 . Thus, pinion gear  54  with pin  78  thereon offers a highly advantageous single structure for accomplishing both the fixation of collet nut  40  and the rotation of shaft  18 . Still further, the spring loaded nature of pin  78  ensures locking of collet nut  40  even if not properly oriented at the beginning of a tightening or loosening action, and further ensures that the pin is adequately supported even as pinion shaft  58  is translated from its engaged to its disengaged position. 
     As is shown in FIG. 6, it may be possible to modify the bit attaching arrangement by providing the collet nut  40  with a bevel gear  50  instead of the nut having slots  46  and by providing shaft  18  with slots  46  instead of gear  50 . In such an embodiment, shaft  58  with pin  78  and pinion gear  54  will operate in the same manner as described above, except that pin  78  will engage slots  46  on the shaft  18  instead of slots on collet nut and pinion gear  54  will engage gear  54  on collet nut  40  instead of a gear surface on shaft  18 . Thus, in this embodiment shaft  18  is held fixed and collet nut  46  is rotated to tighten and loosen a bit. 
     From the foregoing, it will be seen that this invention is one well-adapted to obtain all the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherent to the structure. It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims. Since many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.