Abstract:
A collet assembly, for selectively attaching a tool accessory to a tool, having a collet nut rotatably connectable to the tool, a collet compressible by the collet nut, and a torque application feature movably connected with the tool. The torque application feature is cammingly actuated to engage the collet nut for compressing and loosening the collet.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/612,773, filed on Sep. 24, 2004. The disclosure of the above application is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to generally to the field of power tools. In particular, the present invention relates to a tool-free collet assembly for gripping interchangeable tool accessories, such as drill bits.  
       BACKGROUND OF THE INVENTION  
       [0003]     Various types of tools require a user to selectively attach a tool accessory such as a drill or router bit. Over the course of a particular project or work period it may be necessary to employ a variety of such accessories and to replace worn or broken ones. Convenient removal and replacement of the interchangeable tool accessories is therefore desirable. Two commonly employed mechanisms for holding interchangeable accessories are chucks and collets. Collet type mechanisms are usually favored for tools with higher rotational speeds.  
         [0004]     In a collet-type holder, the shank of a tool accessory is inserted into the bore of a collet. A collet is a generally cylindrical element with a longitudinal bore. The collet has at least one end with a plurality of longitudinally extending arcuate jaws arranged equiangularly around the circumference of the collet and spaced apart by a plurality of longitudinally extending cuts. The collet may be machined into the end of a tool output element (such as a shaft, spindle, or arbor) or it may be a separate (sometimes barrel-shaped) element.  
         [0005]     A collet nut or collet ring is installed over the collet. The collet nut is threaded onto the end of the tool shaft or spindle. Threading the collet nut down on the spindle causes surfaces on the inside of the collet nut and/or shaft to compress the jaws of the collet around the shank of the tool accessory. Thereby securing the tool accessory to the power tool shaft/spindle.  
         [0006]     When changing accessory tools, the nut must be loosened to allow the collet to expand and release its grip on the tool accessory. The tightening and loosening of the collet nut may be partially performed by hand, but the size and shape of the collet nut make it difficult and/or uncomfortable to properly tighten and then initially loosen the collet nut using hands alone. Therefore, it is often necessary to use a hand wrench or similar tool in order to apply sufficient torque to the collet nut.  
         [0007]     In the case of rotary or power tools, when tightening or loosening the collet nut, the shaft/spindle must be prevented from rotating or else it would be difficult to achieve relative motion between the nut and the rotatable spindle.  
         [0008]     Conventionally, the loosening and tightening process requires that the operator simultaneously grip both the shaft/spindle and the collet nut with two separate hand wrenches or the like. A torque is then applied to the nut while the shaft is held in place. This is an awkward process, made even more so by the necessity to support the weight of the tool itself during the process.  
         [0009]     More recently, tools have been designed that incorporate a locking mechanism that locks the shaft/spindle relative to the tool housing. Thus, the rotation of the shaft can be prevented, simply by employing the built in shaft lock. For such a power tool, only one hand wrench is required to loosen or tighten the collet nut, as seen in U.S. Pat. Nos. 5,496,139 and 5,813,805.  
         [0010]     The need to use even one hand tool to change tool accessories, however, is still inconvenient. For example, when a bit replacement is required, the tool operator has to stop what he is doing to find a wrench. This delay can be meaningful in jobs, such as drywall installation during major construction or remodeling projects, where high production rates are essential.  
       SUMMARY OF THE INVENTION  
       [0011]     According to the principles of the present invention, a collet assembly for a tool is provided having an advantageous construction and method of using the same. The collet assembly comprises a collet nut rotatably connectable to the tool, a collet compressible by the collet nut, and a torque application feature movably connected with the tool. The torque application feature is cammingly actuated to engage the collet nut for compressing and loosening the collet.  
         [0012]     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0014]      FIG. 1  is an exploded view of a power tool incorporating a tool free collet assembly in accordance with the present invention;  
         [0015]      FIG. 2  is a perspective view of the collet nut of  FIG. 1 ;  
         [0016]      FIG. 3  is a side view of the collet nut of  FIG. 2 ;  
         [0017]      FIG. 4  is a cross-section view of the collet nut of  FIG. 2 ;  
         [0018]      FIG. 5  is a perspective view of the collet of  FIG. 1 ;  
         [0019]      FIG. 6  is a perspective view of an assembled tool free collet assembly;  
         [0020]      FIG. 7  is an exploded view of various component of the tool free collet assembly of  FIG. 6 ;  
         [0021]      FIG. 8  is a schematic front view of the tool free collet assembly of  FIG. 6  in a disengaged position;  
         [0022]      FIG. 9  is a schematic front view of the tool free collet assembly of  FIG. 6  in a collet loosening position;  
         [0023]      FIG. 10  is a schematic front view of the tool free collet assembly of  FIG. 6  in a collet tightening position;  
         [0024]      FIG. 11  is a perspective view of an alternate tool free collet assembly in a collet loosening/tightening position;  
         [0025]      FIG. 12  is a perspective view of the alternate tool free collet assembly of  FIG. 11  in a collet disengaged position;  
         [0026]      FIG. 13  is a schematic front view of another alternate tool free collet assembly in a disengaged position;  
         [0027]      FIG. 14  is a schematic front view of the tool free collet assembly of  FIG. 13  in a collet loosening position; and  
         [0028]      FIG. 15  is a schematic front view of the tool free collet assembly of  FIG. 13  in a collet tightening position. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0029]     The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.  
         [0030]     The present invention provides a tool-free collet assembly for a tool. Generally, the present invention is adapted for use in tools such as described in commonly-assigned U.S. Pat. Nos. 6,350,087 and 6,648,567. The disclosure of these patents is incorporated herein by reference.  
         [0031]     While shown through the drawings in various embodiments of a rotary cutout tool, those skilled in the art will appreciate that the invention is not so limited in scope. In this regard, the teachings of the present invention will be understood to be readily adaptable for use in any tool incorporating a collet assembly for holding a tool accessory (e.g. bit, driver, etc.).  
         [0032]     Turning generally to the drawings in which identical or equivalent elements have been denoted with like reference numerals, and particularly to  FIG. 1 , a power tool is illustrated and designated with the reference numeral  10 . The particular power tool shown is, for example, a rotary cutout or router tool including a housing  12 . Within the housing  12  is a motor  14  with a cooling fan (not shown). A power source is connected to the motor  14 , such as an electrical power cord (not shown) via a switch or a battery assembly. An output member, such as a motor shaft  20 , is coupled to the motor  14  and further directly coupled to a spindle  22 , so that the accessory (not shown) rotates at motor speed. Alternatively, gearing such as is well known in the art could be located at the motor output in order to turn the tool accessory at a speed different from that of the motor. Motor shaft  20  is supported by bearings (not shown) in a bearing plate  27  mounted in a front housing shroud  13 . Connected to the front end of the motor shaft  20  is a spindle  22 . Also located in the front housing shroud  13  is a spindle lock mechanism  24  that locks the spindle/shaft against rotation when installing or removing an accessory (not shown). A spindle lock button  30  in the front housing shroud  13  is connected to a spindle lock plate  32 . The spindle lock plate  32  has a cutout  34  through which the spindle  22  passes. The cutout  34  in the spindle lock plate  32  has two portions. The first portion  36  is sized to permit the spindle  22  to freely rotate within it during normal operation of the power tool  10 . The second portion  38  is shaped to contact the spindle  22  and prevent its rotation. Thus, the spindle lock plate  32  has a locked and an unlocked position corresponding to the two portions  36  and  38  of the cutout  34 . A spring  40  biases the spindle lock plate  32  and button  30  radially upward into the unlocked position.  
         [0033]     The spindle  22  extends through an opening  17  in the front housing shroud  13 . The forward end of the spindle has a bore  42 . The spindle bore  42  defines a portion that tapers axially forwardly and radially outwardly. The forward outer surface  46  of the spindle  22  is threaded.  
         [0034]     A collet nut  50  is threaded onto the threads  46  of the spindle  22 . As illustrated in  FIGS. 2-4 , the collet nut  50  has a multifaceted exterior surface  51  for being gripped in a manner in accordance with the principles of the present invention to be described below. The collet nut  50  has a longitudinal bore  52  having two portions. The rearward portion  54  is sized and threaded to mechanically engage the exterior threads on the forward outer surface  46  of the spindle  22 . The forward portion  56  of the bore  52  tapers axially forwardly and radially inwardly to an opening  58  in the front face of the collet nut  50 .  
         [0035]     A collet  60  is suitably sized and shaped to be captured within and between the forward end of the spindle bore  42  and the collet nut  50 . As illustrated in  FIG. 5 , the collet  60  is generally tubular in shape with an axial bore  61  and conical ends  62  that taper radially inward toward the ends of the collet. Additionally, the collet  60  is axially split into a plurality of front cantilevered jaws  64  and a plurality of rear cantilevered jaws  66 .  
         [0036]     When the collet  60  is installed within and between the spindle  22  and the collet nut  50 , the tapered outer surfaces  62  contact the tapered surfaces in the spindle bore  42  and the tapered surfaces  56  in the collet nut  50 . As the collet nut  50  is tightened onto the spindle  22 , the tapered surfaces  56  of the collet nut  50  and the tapered surfaces of the spindle bore  42  exert a compression force against the conical tapered surfaces  62  of the collet  60 . This force compresses the cantilevered jaws  64  and  66  of the collet  60  radially inward to grip the shank of the accessory (not shown). Conversely, when the collet nut  50  is backed off the spindle  22 , the forces exerted by the tapered surfaces and  56  on the cantilevered jaws  64  and  66  are reduced and the jaws expand releasing the shank of the accessory (not shown).  
         [0037]     To accommodate tool accessories with shanks of various diameters, such as the commonly available ⅛ inch and ¼ inch diameter sizes, collets  60  with bores  61  of the appropriate internal diameter may be substituted for each other. In order that the interchangeable collets  60  effectively cooperate with the common collet nut  50  and spindle  22 , as described above, the interchangeable collets have substantially identical external geometries and dimensions as regards collet parts  62 ,  64  and  66 .  
         [0038]     As best seen in  FIGS. 6 and 7 , the collet  60  and collet nut  50  are partly enclosed within a collet grip assembly  69  having a collet grip base  70 , a twist collar  72 , and a pair of collet wrench plates  74 . The collet grip base  70  is a generally cylindrical structure rotatably mounted on the front housing shroud  13  and does not rotate with the shaft  20  and spindle  22  during normal tool operation.  
         [0039]     As best seen in  FIG. 7 , the pair of collet wrench plates  74  are each shaped having a pivot end  741 , a gripping portion  743 , and a cam portion  745 . Pivot end  741  of each collet wrench plate  74  is pivotally coupled to collet grip base  70  via a pivot pin  747  to pivot thereabout and are further received within a depression  748  formed in collet grip base  70 . The pair of collet wrench plates  74  are pivotable between a disengaged position (see  FIG. 8 ) that permits the free rotation of collet nut  50  during normal operation, a collet loosening position (see  FIG. 9 ), and a collet tightening position (see  FIG. 10 ). The pair of collet wrench plates  74  are indirectly biased in the disengaged position via a pair of collet wrench springs  749  (see  FIGS. 8-10 ). The gripping portion  743  on each of the pair of collet wrench plates  74  is sized and shaped to engage the exterior faces  51  of the collet nut  50 .  
         [0040]     Still referring to  FIG. 7 , the twist collar  72  is of sufficient diameter and may be provided with a textured surface collet grip  71  to provide a comfortable hold that will aid the operator in exerting sufficient torque to tighten or loosen the collet nut  50 . A collet grip cover  722  is used to retain the twist collar  72  to collet grip base  70 , yet permit the relative rotation between the twist collar  72  and collet grip base  70 . The collet grip cover  722  is fastened to collet grip base  70  via fasteners disposed through holes  727  and received in mounts  701 , thereby capturing the twist collar  72  therebetween. The twist collar  72  includes a pair of cams  721  and a collet wrench spring receiving portion  723 . Each of the pair of cams  721  is sized to receive a corresponding cam pin  723 , which is fixedly mounted within apertures  725  formed in cam portion  745  of each wrench plate  74 . Each of the pair of cams  721  are further shaped to pivotally drive each of the wrench plates  74  about pivot pins  747  between the disengaged position, the collet loosening position, and the collet tightening position as twist collar  72  is rotated relative to collet grip base  70 .  
         [0041]     Finally, as seen in  FIGS. 8-10 , the pair of collet wrench springs  749  are disposed in the collet wrench spring receiving portion  723  of twist collar  72 , such that each engages a wall  729  formed in the twist collar  72  on one end and a side of mount  701  on the other end. This arrangement serves to center the twist collar  72  relative to collet grip base  70  and thus return the pair of wrench plates  74  to their disengaged position.  
         [0042]     To tighten or loosen the collet  60  around the shank of an accessory (not shown) the operator first locks the spindle  22  against rotation by depressing and holding the spindle lock button  30 . This compresses the spring  40  and brings the second portion  38  of the cutout  34  in the spindle lock plate  32  into contact with the spindle  22 .  
         [0043]     With her other hand, the operator then grasps the twist collar  72  and rotates the twist collar against the biasing force of one of the pair of collet wrench springs  749 . It should be noted that the collet grip base  70  is more resistant to rotation than the twist collar  72 . This causes the cam pins  723  to cam within the cams  721 , thereby causing the wrench plates  74  to pivot about the pivot pins  747  and engage the exterior surface  51  of the collet nut  50 .  
         [0044]     The operator can then continues rotating the twist collar  72 , thereby causing the collet grip base  70  and the wrench plates  74  to either tighten or loosen the collet nut  50  and compress or release the collet  60 . The collet nut  50  may extend partially beyond the collet grip cover  722  through an opening  77 . The exposed end of the collet nut  50  can then be conveniently finger tightened or loosened before or after applying significant torque with the tool free collet assembly  23  and the bit inserted or removed. In order to reduce the torque required to firmly hold the shank of the tool accessory the collet nut  50  and/or the spindle  22  on which it is threaded may be coated with a non-stick material such as TEFLON.  
         [0045]     As seen in  FIGS. 11 and 12 , an alternative embodiment is illustrated wherein the collet grip base  70  includes a pair of opposing wall structures  800 . A pair of slidable wrench plates  802  is slidably disposed between the opposing wall structures  800  of the collet grip base  70 . Each of the pair of slidable wrench plates  802  includes a gripping portion  803  and cam follower  804  and is movable between a disengaged position (see  FIG. 12 ) and an engaged position (see  FIG. 11 ). The pair of cam followers  804  engages a cam  806  formed on the interior of twist collar  808 , such that the pair of slidable wrench plates  802  can be moved from the disengaged position to the engaged position in response to twisting of the twist collar  808 . A pair of springs  810  is disposed between the pair of slidable wrench plates  802  to bias the pair of slidable wrench plates  802  into the disengaged position.  
         [0046]     Turning now to  FIGS. 13-15 , another embodiment is illustrated having three wrench plates  900  pivotally mounted to a collet grip base  902  via pivot pins  904 . Each of the three wrench plates  900  includes a cam pin  906  extending therefrom and a gripping portion  908 . A twist collar  910  includes cams  912  and a spring receiving portion  914 . Each of the cams  912  is sized to receive the cam pin  906  of each wrench plate  900 . Each of the cams  912  is further shaped to pivotally drive each of the wrench plates  900  about pivot pins  904  between the disengaged position (see  FIG. 13 ), the collet loosening position (see  FIG. 14 ), and the collet tightening position (see  FIG. 15 ) as twist collar  910  is rotated relative to collet grip base  902 .  
         [0047]     Still referring to  FIGS. 13-15 , wrench springs  916  are disposed in the spring receiving portion  914  of twist collar  910 , such that each engages a wall  918  formed in the twist collar  910  on one end and a side of a mount  920  on the other end. This arrangement serves to center the twist collar  910  relative to collet grip base  902  and thus return the wrench plates  900  to their disengaged position.  
         [0048]     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.