Abstract:
A collet assembly for a tool comprising a collet nut rotatably connectable to the tool; a collet operatively connectable to the collet nut; and a collet wrench movably connected with the tool and engageable with the collet nut for tightening and loosening the collet.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates 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, and including a dust management system. 
     2. Discussion 
     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. 
     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. 
     Over the collet is installed a collet nut or collet ring. 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. Thus, the tool accessory is secured to the power tool shaft/spindle. 
     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 necessary to use a hand wrench or similar tool in order to apply sufficient torque to the collet nut. 
     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. 
     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. Then a torque is applied to the nut while the shaft is held in place. This is an awkward process and made even more so by the necessity to support the weight of the tool itself. 
     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. See, for example, U.S. Pat. Nos. 5,496,139 and 5,813,805. 
     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. 
     Because many of the tools that may incorporate this invention are employed in dust and debris producing tasks, it is desirable that any features added to such tools be designed to resist fouling by dust. 
     SUMMARY OF THE INVENTION 
     It is, therefore, one object of the invention to provide a tool with a collet assembly that allows the user to conveniently install or remove an accessory without the use of any hand tools. 
     It is another object of the invention to provide an operating member with an exposed and graspable collet grip that provides enough mechanical advantage to permit the operator to exert sufficient torque for tightening or loosening the collet nut without having to use a hand tool. 
     This and other objects of the invention are attained by a tool-free collet assembly with an integral collet wrench. The collet wrench is rotatably mounted on the tool for turning the collet nut so as to tighten or loosen the collet. The collet wrench is also movable between an engaged position, wherein the collet wrench can turn the collet nut, and a disengaged position, wherein the collet wrench does not restrain the collet nut and does not interfere with normal rotation of the collet nut when the tool is operated. The movement of the collet wrench between the engaged and disengaged positions could be axial, radial, rotational, or some combination thereof. 
     The collet wrench may be biased into the disengaged position. This may be accomplished by a spring or other means for exerting a biasing force. 
     An operating member may connect the collet wrench to the tool. The operating member supports the collet wrench for movement between the engaged and disengaged position. The operating member may also be moveably mounted on the tool for imparting movement to the collet wrench. The operating member may include an externally exposed and manually graspable collet grip. By means of the collet grip, the operator can move the collet wrench rotationally and/or axially. 
     A collet wrench button may also be provided for moving the collet wrench between the engaged and disengaged position. 
     The collet wrench itself may be of several types. It may be of an open end or closed end (box wrench) type design. Alternatively, it may be of a complex interior shape. Such a complex shape may have two portions. A first portion corresponds to the disengaged position and within that first portion the collet nut may freely rotate during normal operation of the tool. The second portion corresponds to the engaged position and the surface of the second portion is shaped to contact and turn the collet nut. 
     The collet nut and/or the spindle on which it is threaded may be partially coated with a non-stick material to reduce the torque necessary to loosen the collet. The nonstick material could be, for example, Teflon®. 
     The internal surfaces of the collet nut and the spindle may cooperate with interchangeable collets having substantially identical external geometries and dimensions, but having different bores for gripping accessories with shanks of various diameters and geometries. 
     Another feature of this invention is an improved spindle lock design. The improved design is similar to that of the collet wrench and may incorporate either an open-ended wrench or one of complex shape as described within. 
     Certain jobs employing rotary cutout and router tools, for example drywall cutting, produce dust that can get inside the tool and foul the operation of the buttons and operating member. Therefore, it is still another object of the invention to provide a tool free collet assembly that is resistant to fouling in a dusty or dirty environment. This object is accomplished by a design that accepts that the entrance of some dust is inevitable and works to ensure that dust that gets into the mechanisms can also get out and does not accumulate to levels that interfere with the operation of the tool. This design incorporates several basic features or techniques, which coact to produce a dust management system as follows: 
     the use of looser tolerance between parts that move relative to each other; 
     the avoidance or minimization of interior dead ends or pockets from which dust can escape only very slowly; 
     the action of moving parts incidentally tends to move or push dust along a general flow path towards intended exit points; 
     horizontal or vertical boundaries between sub assemblies are provided with through holes to permit the movement of dust; and 
     interior components do not fit closely against the exterior sheath or housing around the entire interior perimeter so that dust is able to move around those components. 
     This dust management design approach is principally a passive one. That is, it does not provide a dedicated means for forcing the dust out. Rather, it seeks to avoid trapping the dust and relies on a dust flow arising from the movement of the tool as the operator uses it and randomly moves it about in various positions and orientations. Some impetus may be given to the dust by motion of moving parts and by the cooling air flows produced by a motor fan. Lastly, the same features that discourage dust build up also allow for easier cleaning of the tool, for example by blowing out with compressed air, if that becomes necessary. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Additional objects and advantages of the present invention will become apparent from a reading of the following detailed description of the preferred embodiments that make reference to the drawings of which: 
     FIG. 1 is a cross-section view of a power tool incorporating a tool free collet assembly in accordance with the present invention. 
     FIG. 2 is an expanded view of a portion of the power tool of FIG.  1 . 
     FIG. 3 is an exploded view of the power tool with a collet of FIG.  1 . 
     FIG. 4 a  is a perspective view of the collet nut of FIG.  1 . 
     FIG. 4 b  is a side view of the collet nut of FIG. 4 a.    
     FIG. 4 c  is a cross-section view of the collet nut of FIG. 4 a.    
     FIG. 5 is a perspective view of the collet of FIG.  1 . 
     FIG. 6 is a front view of an alternative embodiment of the collet wrench in accordance with the present invention. 
     FIG. 7 is an exploded view of an alternative embodiment of the collet assembly in accordance with the present invention. 
     FIG. 8 is an interior view of the operating member. 
     FIG. 9 is an interior view of the front housing shroud. 
    
    
     DETAILED DESCRIPTION 
     The present invention provides a tool-free collet assembly for a tool. 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.). 
     Turning generally to the drawings in which identical or equivalent elements have been denoted with like reference numerals, and particularly to FIGS. 1 and 2, 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  10  including a housing  12 . Within the housing  12  is a motor  14  with a cooling fan  15 . A power source is connected to the motor  14 . In the embodiment shown, the motor  14  is connected to an electrical power cord  16  via a switch  18 . An output member is coupled to the motor  14 . In this case, the motor shaft  20  is 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. 
     FIGS. 2 and 3 show expanded views of the collet wrench mechanism  23  and associated structures. Illustrated is the motor shaft  20  supported by bearings  26  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. 
     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  44 , which tapers axially forwardly and radially outwardly. The forward outer surface  46  of the spindle  22  is threaded. 
     A collet nut  50  is threaded onto the threads  46  of the spindle  22 . As illustrated in FIGS. 4 A, B and C, the collet nut  50  has a multifaceted exterior surface  51  for being gripped by a wrench or the like in the conventional manner. 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 . 
     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 . 
     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  44  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  44  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  44  and  56  on the cantilevered jaws  64  and  66  are reduced and the jaws expand releasing the shank of the accessory (not shown). 
     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 . 
     Referring again to FIGS. 2 and 3, the collet  60  and collet nut  50  are partly enclosed within an operating member  70 . The operating member  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. The operating member  70  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 . 
     Mounted radially slidably within the operating member  70  is a collet wrench button  72 . Attached to the radially inward side of the collet wrench button  72  is a collet wrench plate  74 . In one embodiment of the present invention, the collet wrench plate  74  has an opening  75  through it, which surrounds the collet nut  50 . The opening  75  in the collet wrench plate  74  has two portions. The first portion  76  corresponds to the disengaged position and is sized so that the collet nut  50  may freely rotate within it during normal operation of the power tool  10 . The second portion  78  corresponds to the engaged position and is sized and shaped to contact the exterior faces  51  of the collet nut  50 . A collet wrench spring  80  biases the collet wrench button  72  and collet wrench plate  74  radially outward into the disengaged position. 
     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 . 
     With her other hand, the operator then depresses the collet wrench button  72  and grasps the collet grip  71 . Depressing the collet wrench button  72  compresses the collet wrench spring  80  and moves the collet wrench plate  74  radially inward to the engaged position. In the engaged position, second portion  78  of the collet wrench plate  74  contacts the exterior surface  51  of the collet nut  50 . 
     The operator can then rotate the operating member  70  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 front end  73  of the operating member  70  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 collet wrench mechanism  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®. 
     Alternatively, as depicted in FIGS. 6A and 6B, the collet wrench  90  may be open-ended, similar to a conventional open-ended wrench. In this embodiment, the collet wrench  90  has two arms  92  and an open-faced interior surface  94  for grasping the exterior surface  51  of the collet nut  50 . At least one spring  96  may bias the collet wrench  90  out of engagement, so that the collet nut  50  may freely rotate during normal operation of the tool. 
     In still another embodiment, depicted in FIG. 7, the collet wrench  100  moves axially to engage the collet nut  50 . In such an embodiment the operating member  102  is arranged to move axially as well as rotationally. A spring  104  axially biases the collet wrench  100  and operating member  102  into the disengaged position. In this embodiment, the collet wrench  100  may take the form of a closed-ended wrench, such as a box wrench. 
     In the FIG. 7 embodiment, 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 . 
     With her other hand, the operator grasps the collet grip  103  and pulls axially rearwardly. Pulling the collet grip  103  moves the operating member  102  rearwardly, compresses the spring  104  and moves the collet wrench  100  axially rearward to the engaged position. In the engaged position, collet wrench  100  contacts the exterior surfaces  51  of the collet nut  50 . The operator can then rotate the operating member  102  to either tighten or loosen the collet nut  50  and compress or release the collet  60 . Upon releasing the collet grip  103 , spring  104  pushes the operating member  102  axially forward and returns the collet wrench  100  to the disengaged position. 
     Considering again the first described embodiment of the collet wrench mechanism  23  and referring now to FIGS. 2,  8  and  9 , in order to manage the flow of dust created by the tool, various coacting features are implemented to form a dust management system. For example, operating element  70  may be formed with a number of openings  69  to permit the movement of dust. Dust moving rearward through openings  69  may escape through joint  79 , between operating element  70  and front housing shroud  13 . Joint  79  is deliberately fitted together with looser tolerances to promote the escape of dust as well as to tolerate the presence of dust that will inevitably invade the joint. 
     Alternatively or in addition, dust may escape the inside of the operating element by moving forward and out around the collet nut  50 , where it extends through opening  77  in plate  73 . Opening  77  is sized to provide a perimeter gap  81  around the collet nut  50 . 
     Another escape path for dust in the operating element  70  is around the collet wrench button  72 . Surface  68 , which forms the opening wherein the collet wrench button  72  resides may be sized to provide a loose fit around the perimeter of the button. 
     Additionally, the front housing shroud  13  may also be formed with openings  11  that can communicate with the openings  69  in the operating element  70 , depending on the rotational orientation. Bearing plate  27  can also be sized and installed to leave a gap  28  between it and the interior surface of the front housing shroud  13 . Dust escaping from the region of the front of the front housing shroud  13  via the gap  28  will be picked up and blown out through vent holes  29  by the cooling air flow driven by motor fan  15 . 
     While the above description constitutes three preferred embodiments of the invention, it will be appreciated that the invention is susceptible to modification, variation, and change without departing from the proper scope or fair meaning of the accompanying claims. For example, it will be understood that the teachings of the present invention are directly applicable to other tools employing a collet to hold a tool accessory.