Patent Publication Number: US-8117950-B2

Title: Extension shaft for holding a tool for rotary driven motion

Description:
RELATED APPLICATIONS 
     This application is a continuation patent application of U.S. Ser. No. 12/284,156, filed on Sep. 18, 2008, the contents of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to an extension shaft capable of holding a variety of tools to be rotary driven by a handheld instrument; and more particularly, to providing an extension shaft with an increased range of angular movement of the tool with respect to the handheld instrument. 
     BACKGROUND OF THE INVENTION 
     A handheld instrument capable of being used with multiple types of tools—e.g., drill bits, screwdriver bits, sockets, etc. in standard and metric dimensions—is very popular because it provides a user with the ability to readily adapt the handheld instrument among a variety of workplace needs without requiring the user to carry along an extensive set of individually dedicated tools. 
     Each tool is fashioned to be axially inserted into a chuck of the handheld instrument, which typically positions the tool in close proximity to the handheld instrument&#39;s relatively large handle. As a result, the handheld instrument may at times be rather ineffective for use in spatially confined or difficult-to-reach locations. 
     In this connection, a powered handheld instrument—corded or cordless—may also be used. Although such a powered instrument, e.g., screwdriver, drill; is generally relatively long in length, it does provide the user with the ability to easily complete various tasks with less manual effort. In addition, the powered instrument generally includes a casing surrounding its motor that is rather large in relation to the tools, i.e., drill bits, screwdriver tips, sockets, and the like. For this reason, it has been difficult to use the powered instrument in areas of limited access. 
     The present invention is directed to addressing the spatial constraints frequently encountered by today&#39;s user during use of a handheld instrument capable of being utilized with various tools. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to an extension shaft for holding a tool for rotary driven motion. The extension shaft is capable of being adapted to a handheld instrument having a chuck. The extension shaft includes a first end adapted to cooperate with the chuck and be releasably retained thereby; and a second end adapted to releasably retain the tool for rotary driven motion. The first end of the extension shaft and the chuck have complementarily shaped non-circular cross-sections, wherein the first end has an axis and is capable of being releasably retained by the chuck. The second end of the extension shaft includes a tool holder for holding the tool for rotary driven motion thereof. The tool holder and the tool have complementarily shaped non-circular cross-sections. The tool holder further includes a base portion and a swivel portion. The swivel portion is capable of releasably retaining the tool within the tool holder and is pivotly coupled to the base portion through a pivot assembly. The pivot assembly may include a ball joint operatively connecting the swivel and base portions of the tool holder. Alternatively, the pivot assembly may include a first and a second pin, shaft, or axle, wherein the first and second pins of the pivot assembly are substantially perpendicular to each other and lie substantially within a plane. In either embodiment of the pivot assembly, the tool is capable of being rotated about an angle with respect to an axis of the chuck or extension shaft through rotation of the extension shaft in response to rotation of the chuck. Thus, the tool holder of the present invention provides for the handheld instrument&#39;s effective operability to be maintained throughout an increase in the angular variation between the extension shaft and the tool. 
     In an additional embodiment of the tool holder, the pivot assembly includes a means for biasing the base and swivel portions into axial alignment when the tool holder is at rest. The predisposition of the pivot assembly to axially align the base and swivel portions will effectively steady the swivel portion and facilitate the insertion and/or removal of the tool. 
     In another embodiment of the present invention, a sheath may be placed over the cooperating moving parts of the tool holder to guard against contact therewith while simultaneously allowing the extension shaft to properly operate. The sheath can be a single, unitary piece or multiple pieces. In an alternate embodiment to guard against contact with the moving parts of the tool holder, a spacer can be placed proximate the pivot assembly, e.g., bearing of the ball joint; which will assist in preventing an operator from contacting the area around the rotating and hinging parts of the tool holder. 
     In a further embodiment of the present invention, the first or second end of the extension shaft preferably includes a generally cylindrical body portion terminating in a male hex shank and the other of the first or second end of the extension shaft preferably includes a cylindrical body portion terminating in the tool holder—e.g., base portion and swivel portion including a female hex shank-receiving opening therein. 
     In yet another embodiment of the present invention, the extension shaft is flexible and capable of deflecting relative to the axis of the chuck such that the position of the second end of the flexible extension shaft and the tool can be angled relative to the axis of the chuck, wherein the tool can be rotary driven by rotation of the chuck through rotation of the handheld instrument and the flexible extension shaft. 
     The flexible extension shaft may further include a plurality of concentric coil springs in tightly wound adjacent relation extending between and secured to generally cylindrical body portions near the first and second ends of the flexible extension shaft to accommodate deflection of the flexible extension shaft relative to the axis of the chuck, and including a flexible sleeve disposed about the concentric coil springs. The flexible sleeve has cylindrical fittings secured thereto at opposite ends thereof so as to define a shoulder internally of each of the fittings. Each cylindrical fitting is adapted to receive one of the cylindrical body portions therein. The cylindrical body portions are spaced apart by a distance greater than the distance between the shoulders in the cylindrical fittings, which permits limited axial movement of the cylindrical body portions and the concentric coil springs relative to the cylindrical fittings and the flexible sleeve. Such a configuration allows for the flexible extension shaft to be deflectable relative to the axis of the chuck so as to position the second end of the shaft and the tool at an angle relative to the axis of the chuck, so that the tool is capable of being rotary driven by rotation of the chuck and/or handheld instrument through the flexible extension shaft. 
     A shaft biasing coil spring can be advantageously disposed about the concentric coil springs of the flexible extension shaft. More specifically, the shaft biasing coil spring is disposed between the shoulder in one of the cylindrical fittings and the corresponding one of the cylindrical body portions to normally bias the other of the cylindrical body portions into engagement with the shoulder in the other of the cylindrical fittings. 
     An object of the present invention is to provide an extension shaft for holding a tool utilized with a handheld instrument, wherein the extension shaft is capable of increasing the operating capability of the handheld instrument and tool. 
     Another object of the present invention is to provide an extension shaft for holding a tool utilized with a handheld instrument, wherein the extension shaft includes a protective mechanism to safeguard the operator from harmful contact with the moving components of the extension shaft. 
     A still further object of the present invention is to provide an extension shaft for holding a tool utilized with a handheld instrument, wherein the extension shaft includes a tool holder with a means for biasing a base and swivel portion into axial alignment and thus steadying the swivel portion to facilitate insertion and/or removal of the tool when the extension shaft is idle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is perspective view of a rigid extension shaft in accordance with one embodiment of the present invention; 
         FIG. 2  is a perspective view of the rigid extension shaft shown in  FIG. 1  and operatively attached to a handheld instrument and a tool; 
         FIGS. 3A and 3B  are perspective views of the tool holder of the present invention; 
         FIG. 4  is a partial cross-sectional view—perpendicular to the axis of the extension shaft—of the swivel portion of the tool holder of the present invention; 
         FIG. 5  is a cross-sectional view—aligned with the axis of the extension shaft—of the swivel portion of the tool holder of the present invention with a tool inserted therein; 
         FIGS. 6A ,  6 B,  6 C, and  6 D depict various embodiments of the pivot assembly of the present invention; 
         FIG. 7A  is perspective view of an alternative embodiment of the present invention depicting a flexible extension shaft operatively attached to a powered handheld instrument and a tool; 
         FIG. 7B  is perspective view of an alternative embodiment of the present invention depicting a flexible extension shaft operatively attached to a simple handheld instrument and a tool; 
         FIG. 8  is a partial perspective view of the flexible extension shown in  FIGS. 7A and 7B ; 
         FIG. 9  is a partial cross-sectional view—perpendicular to the axis of the extension shaft—of the flexible extension shaft of the present invention; 
         FIG. 10  is a perspective view of an alternate embodiment of the present invention wherein the pivot assembly includes a ball joint having a bearing and a socket; 
         FIG. 11  is a partial cross-sectional view—perpendicular to the axis of the extension shaft—of one embodiment of the pivot assembly of the present invention, wherein a sheath is utilized to cover at least a portion of the tool holder and at least a portion of the end of the extension shaft; 
         FIG. 12  is a partial view of one embodiment of the pivot assembly of the present invention, wherein a spacer is located proximate the pivot assembly to guard against a user contacting the moving parts of the extension shaft; 
         FIG. 13  is a partial view of one embodiment of the tool holder of the present invention depicting one of the means for predisposing the axial alignment and connection of the base and swivel portions of the tool holder; 
         FIG. 14  is another partial view of the embodiment of the tool holder of the present invention depicting the means for predisposing the axial alignment and connection of the base and swivel portions of the tool holder shown in  FIG. 13 ; 
         FIG. 15  is a partial view of one embodiment of the tool holder of the present invention depicting another of the means for predisposing the axial alignment and connection of the base and swivel portions of the tool holder; and, 
         FIG. 16  is a partial view of an alternate embodiment of the sheath having multiple portions for covering at least a portion of the moving components of the tool holder; 
         FIG. 17  depicts another alternate embodiment of the extension shaft of the present invention wherein cylindrical fittings cover portions of the tool holder; and, 
         FIG. 18  depicts the alternate embodiment of the extension shaft of the present invention shown in  FIG. 17  wherein a sheath is utilized to cover at least a portion of the tool holder. 
     
    
    
     DETAILED DESCRIPTION OF THE PRESENT INVENTION 
     While this invention is susceptible to embodiments in many different forms, there are shown in the drawings and will herein be described in detail, preferred embodiments of the invention with the understanding that the present disclosures are to be considered as exemplifications of the principles of the invention and are not intended to limit the broad aspects of the invention to the embodiments illustrated. 
     Referring to the drawings, and first to  FIGS. 1 and 2 , the reference numeral  10  designates generally a handheld instrument or piece of equipment, e.g., screwdriver, drill; having a chuck  12  for connection to an extension shaft  18  for rotary driven motion at one end  16  thereof. The extension shaft  18  includes a first end  20  adapted to cooperatively extend from, or attach or connect with, the chuck  12 ; and, a second end  22  that may similarly be adapted for attachment or extension there from and to hold a tool  14  for rotary driven motion. 
     The first end  20  of the extension shaft  18  and the chuck  12  have complementarily shaped non-circular cross-sections, e.g., hexagonal, that may be similar to those shown in U.S. Pat. No. 4,876,929—the entire contents of which are fully incorporated herein by reference. The chuck  12  has a longitudinal axis and is adapted to receive the first end  20   b  of the extension shaft  18  by means of axial insertion of the extension shaft into the chuck with the respective non-circular cross-sections in rotationally aligned relationship. The chuck  12  preferably also includes a means for holding the first end  20  of the extension shaft  18  for rotary driven motion of the shaft. 
     A tool holder  52  including a base portion  54  and a swivel portion  56  extends from or is operatively connected to the extension shaft  18  proximate the second end  22 . It is to be understood that the term operatively as used herein connotes that the connection, attachment, coupling, integral extension there from, etc. can be accomplished through any one of a variety of ways known by those or ordinary skill in the art to utilize such cooperating components and to ensure their operability. In one instance, the base portion  54  of the tool holder  52  is integral with or extends from a cylindrical body portion  22  as is shown in  FIG. 1 . In another instance, the connection between the extension shaft  18  and the tool holder  52  can similarly utilize the complementarily shaped—e.g., male-female—non-circular cross-sections of mating components utilized between the chuck  12  and the first end  20  of the extension shaft  18 . Likewise, the swivel portion  56  of the tool holder  52  is capable of retaining the tool  14  therein and can similarly utilize the complementarily shaped non-circular cross-sections between the tool holder&#39;s  52  swivel portion  56 ,  56   a  and the tool  14 —see  FIGS. 4 and 5 . 
     As will be appreciated by referring to the figures, particularly  FIGS. 7-9 , the tool  14  is rotary driven by the chuck  12  of the handheld instrument  10 . The handheld instrument can be a simple handle—see FIG.  7 B—that can be manually operated, or a powered handle—see FIG.  7 A—that can be electrically operated. It will also be appreciated that proximate either ends  20 ,  22  of the extension shaft  18 , a generally cylindrical body portion may be included. One cylindrical body portion, e.g.,  20   a , may terminate in a male hex shank, e.g.,  20   b , and the other generally cylindrical body portion, e.g.,  22   a , may terminate in the tool holder  52  having a base portion  54  and a pivotly connected swivel portion  56 , which further includes a female hex shank-receiving opening or collet  56   a  capable of interconnecting with the tool  14 . It will further be appreciated that the chuck  12  includes a female hex shank-receiving opening which, together with the male hex shank  20   b , exemplifies one embodiment of the previously described complementarily shaped non-circular cross-section. With this arrangement, the first end  20  of the extension shaft  18  is adapted for axial insertion into the chuck  12 . So too the tool holder can be axially inserted into, or aligned with, the second end  22  of the extension shaft; and likewise, the tool  14  can also be axially inserted into swivel portion  56  of the tool holder  52  proximate the second end  22  of the extension shaft  18 . 
     Magnetic coupling is one of a variety of means for releasably retaining the male hex shank portion within the cooperating female hex receiving portion. Another means for releasably retaining the male hex shank portion within the cooperating female hex receiving portion is shown in  FIGS. 4 and 5 , which may include a ball or bearing detent  26  associated with a female hex shank-receiving opening that can be incorporated into the swivel portion  56  of the tool holder  52  proximate the second end  22  of the flexible extension shaft  18 . In like fashion, the means for releasably retaining cooperatively attached members—e.g., the tool holder  52  and the tool  14 —can also be implemented between the chuck  12  and the extension shaft  18 , or the extension shaft  18  and the tool holder  52 . 
     A pivot assembly  58  connects the base  54  and swivel  56  portions of the tool holder  52 . One embodiment of the pivot assembly  58  is shown in  FIGS. 3A ,  3 B, and  6 A- 6 D and includes a pair of pins, shafts, or axles, wherein a first pin  60  and a second pin  62  lie substantially within a single plane. Preferably, the first and second pins  60 ,  62  are substantially perpendicular to each other, and are connected together, or are integral with each other, to form a unitary piece.  FIGS. 6A ,  6 B,  6 C, and  6 D depict several embodiments of the pivot assembly  58  showing the first  60  and second  62  pins being integral with each other and lying within a single plane, i.e., the plane of the paper. The integral pins  60 ,  62  may be attached through a hub  64 ; the form of which may include one of several different shapes or geometries—e.g., ring, disk, circular, round, rectangular, box, and diamond—and the hub may or may not lie entirely or substantially within the same plane as the first  60  and  62  second pins. 
     Referring now to  FIGS. 10-12 , an alternate embodiment of the pivot assembly  58  is shown wherein a ball joint  66  is utilized to operatively connect the base  54  and swivel portions  56  of the tool holder  52 . The ball joint  66  preferably includes a bearing  68 , e.g., hex ball—extending along a neck from the end  22  of the extension shaft  18  or base portion  54 , and resides within a socket  74  defined within an end of the swivel portion  56  opposite the end  56   a  that retains the tool  14 . The cooperative connection between the hex ball  68  and the socket  74  enables the swivel portion  56  of the tool holder  52  to be angled, pivoted, or hinged with respect to the base portion  54 , and further allows the swivel portion to rotate in response to rotation of the base portion. 
     In a further alternate embodiment of the pivot assembly  58 , the base portion  54  and the swivel portion  56  of the tool holder  52  are biased or predisposed to be substantially in axial alignment when the extension shaft  18  is at rest—thus providing a beneficial feature of a more stable or steady swivel portion to facilitate the insertion and/or removal of the tool  14 .  FIGS. 13-14  depict one means for predisposing the axial alignment of the base  54  and swivel  56  portions of the tool holder  52  when the tool holder is not in use. In particular, the ball joint  64  is configured such that the base portion  54  and the swivel portion  56  of the tool holder  52  include cooperating annular surfaces  76 ,  78 —e.g., shoulders—about their respective outer perimeters. The cooperating surfaces of the shoulders  76 ,  78  can be generally described as having mating male-female portions and can include a variety of geometric shapes, e.g., circle, square, star, octagon. 
     A retaining device  80 , such as an internal split ring, is positioned about the axis and neck of the base portion  54  near the hex ball  66  and operatively secured within the socket  74  of the swivel portion  56 . The split ring  80  retains the hex ball  66  within the socket  74  and simultaneously permits the hex ball to axially slide a short distance within the socket. When the hex ball  66  is fully inserted into the socket  74 , the shoulder  76  of the base portion  54  cooperatively engages with the shoulder  78  of the swivel portion  56  to axially align the base and swivel portions and make a more rigid tool holder  52  having a steady swivel portion with a lesser tendency to hinge, pivot, or angle with respect to the base portion. If the male-female segments of the cooperating shoulders  76 ,  78  include keyed shapes, e.g., square, star, hexagon; any relative rotational movement between the base and swivel portions will be considerably deterred. 
     For increasing the operable range of the extension shaft  18 , the swivel portion  56  can be axially slid away from the base portion  54  a distance sufficient to disengage and clear the cooperating shoulders  76 ,  78  of the base and swivel portions, thus allowing the swivel portion the ability to hinge or pivot and be angled with respect to the base portion. The retaining device  80  retains the hex ball  66  within the socket  74  while simultaneously allowing the hex ball to rotate in response to rotation of the extension shaft  18 , and thus engage the socket. One of ordinary skill in the art can readily envision that multiple tool holders  52  can be coupled together as needed. 
     Additional embodiments of the pivot assembly  58  that are within the scope of the present invention include cooperating gears, e.g., beveled, spurred; or mating balls; operatively attached or extending from the respective base  54  and swivel  56  portions. Regardless of which embodiment of pivot assembly  58  is employed during operation with the handheld instrument  10 , the extension shaft  18  can be disposed substantially entirely coaxial with the chuck  12 , while the tool holder&#39;s swivel portion  56 , as well as the tool  14  itself, is capable of being positioned at an angle relative to the axis of the chuck. 
     The present invention further contemplates the tool holder  52  including a means for predisposing the connection or attachment of the base  54  and swivel  56  portions through a bias  82  to axially attract the base and swivel portions toward each other. One such means for predisposing the connection of the base  54  and swivel  56  portions includes a section of either or both of the base and swivel portions having a magnetized segment capable of attracting the other of the base or swivel portions of the tool holder  52 . That is, when the extension shaft  18  and/or tool holder  52  is at rest, or not being used, the base  54  and swivel  56  portions are attracted to each other so that the respective shoulders  76 ,  78  of each portion of the tool holder move toward each other to engage and axially align. The magnetic coupling is sufficient enough to attract the base  54  and swivel  56  portions toward each other to engage the respective cooperating annular surfaces  76 ,  78  and steady the swivel portion for insertion and/or removal of the tool  14 —while simultaneously allowing the base and swivel portions to be slid axially apart a short distance such that they can be angled with respect to each other and yet remain operatively connected by the split ring  80 . 
       FIG. 15  depicts another embodiment of the means for predisposing the axially aligned connection of the base  54  and swivel  56  portions, wherein the bias  82  includes a spring positioned about the neck of the base portion proximate the hex ball  68  and between the split ring  80  and the inner portion of the socket  74  that assists in the retention of the split ring therein. The force exerted by the spring  82  brings the cooperating shoulders  76 ,  78  of the base  54  and swivel  56  portions together and into engagement; thus axially aligning the base and swivel portions of the tool holder  52  and steadying the swivel portion for insertion and/or removal of the tool  14  when the extension shaft  18  is at rest. 
     Referring to  FIG. 11 , a protective mechanism  70 , e.g., sheath, can be incorporated with the extension shaft  18  of the present invention to cover the pivot assembly  58  proximate the end of the extension shaft and the tool holder  52 . The durable sheath  70  may include a single piece or multiple pieces and is sufficiently flexible and/or rigid so that it does not impede movement of the swivel portion  56  or base portion  54  of the tool holder  52 . The sheath includes a material capable of protecting the operator from harmful contact with the moving parts of the tool holder when the swivel portion is angled, pivoted, or hinged with respect to the base portion  54  or the extension shaft  18  during rotation. 
     In one embodiment of the sheath  70  shown in  FIGS. 17 and 18 , sections of the swivel  56  and base  54  portions of the tool holder  52  are retained within respective cylindrical fittings  40 ,  40 ′ such that rotation of the swivel and base portions can be achieved without rotation of the respective cylindrical fitting. One of the cylindrical fittings  40 ,  40 ′ is positioned about at least a section of the swivel portion  56  of the tool holder  52  and the other of the cylindrical fittings is positioned about at least a section of the base portion  54  of the tool holder. The outer surface of the cylindrical fitting  40 ′ positioned about the swivel portion  56  of the tool holder  52  includes a diamond knurled finish (e.g., cross-hatched) and the outer surface of the cylindrical fitting  40  positioned about the base portion  56  of the too holder includes a fluted knurled finish (e.g., longitudinal ridges). The sheath  70  includes a flexible rubber-type material and may also include an outer surface that includes knurling. The sheath  70  is slid over the cylindrical fittings  40 ,  40 ′, wherein the diamond knurled surface about the swivel portion  56  facilitates retention of the sheath while the fluted knurled surface about the base portion  54  allows the sheath to slide back and forth when the tool holder  52  is hinged or pivoted. 
     If the sheath  70  includes multiple pieces, one segment of the sheath covers over of the base  54  or swivel  56  portions and the other segment of the sheath covers over the other of the base or swivel portions. As shown in  FIG. 16 , each segment of the sheath  70  preferably includes a semi-rigid, bulbous shape, wherein one of the sheath segments partially fits within the an opening of the other of the sheath segments to cooperatively hold both sheath segments together. 
     Another protective mechanism capable of being incorporated with the tool holder  52  of the present invention is a spacer  72 . As shown in  FIG. 12 , the spacer  72  is preferably annular or toroidal in shape and includes a durable and flexible material, e.g., rubber, silicon; that can be located about the axis of the extension shaft  18  and proximate the neck of the base portion  56  and bearing  66  of the ball joint  64  to assist in preventing an operator&#39;s hand or finger from being placed into contact with the movable parts of the tool holder  52 . 
     Referring again to  FIGS. 7-9 , another embodiment of the present invention is shown wherein the extension shaft  18  is flexible. The flexible extension shaft  18  includes a plurality of concentric coil springs  30 ,  32 ,  34  in tightly wound adjacent relation extending between and secured to the generally cylindrical body portions  20   a ,  22   a  of the first and second ends  20 ,  22  of the flexible extension shaft  18  to accommodate universal deflection of the flexible extension shaft and/or the tool  14  relative to the axis of the chuck  12 . It will also be seen that a flexible sleeve  36  is disposed about the concentric coil springs  30 ,  32 ,  34 . As illustrated, the flexible sleeve  36  has cylindrical fittings  38 ,  40  secured thereto at opposite ends  42 ,  44  thereof to receive one of the cylindrical body portions  20   a ,  22   a  therein and the flexible sleeve  36  and cylindrical fittings  38 ,  40  define shoulders  46 ,  48  internally of each of the fittings  38 ,  40  to form stops for the cylindrical body portions  20   a ,  22   a.    
     More specifically, the cylindrical body portions  20   a ,  22   a  are spaced apart by a distance greater than the distance between the shoulders  46 ,  48  in the cylindrical fittings  38 ,  40  to permit limited axial movement of the cylindrical body portions  20   a ,  22   a  and the concentric coil springs  30 ,  32 ,  34  relative to the cylindrical fittings  38 ,  40  and the flexible sleeve  36 . With this construction, a shaft biasing coil spring  50  is disposed about the concentric coil springs  30 ,  32 ,  34  of the flexible extension shaft  18  between the shoulder  48  in one of the cylindrical fittings  40  in the corresponding one of the cylindrical body portions  22   a  to normally bias the other of the cylindrical body portions  20   a  into engagement with the shoulder  46  in the other of the cylindrical fittings  38 . 
     It is to be understood that the flexible sleeve  36  can also be implemented with the more rigid extension shaft shown in FIGS.  1  and  2 —as would be the case when the flexible extension shaft shown in  FIGS. 7-9  is utilized in a linear configuration. 
     As should now be appreciated, the handheld instrument  10 —especially a portable electric screwdriver—is extremely versatile when utilized with the extension shaft  18  of the present invention. Because the tool holder  52  is deflectable relative to the axis of the chuck  12 —as well as the axis of the extension shaft  18 —the extension shaft enables the use of the handheld instrument  10  in hard-to-reach or spatially restricted areas because the tool  14  can be disposed at an acute angle relative to the axis of the chuck  12  by the pivoting, hinging, and/or swiveling provided by the unique pivotal coupling inherent within the tool holder  52 —whether the embodiment of the pivot assembly  58  being utilized includes the ball joint  64  (see  FIGS. 10-12 ) or the dual pivot pins  60 ,  62  of the pivot assembly  58  that lie substantially within the same plane and preferable perpendicular to each other (see  FIGS. 3A ,  3 B,  6 A,  6 B,  6 C, and  6 D). 
     The range of angular movement for the tool  14  relative to the axis of the chuck  12  can further be increased when the tool holder  52  is utilized with an extension shaft  18  that is flexible. Because the flexible extension shaft  18  is universally deflectable relative to the axis of the chuck  12 , the flexible extension shaft  18  enables the use of the handheld instrument  10  in hard-to-reach or spatially restricted areas because the tool  14  can be disposed at an acute angle relative to the axis of the flexible extension shaft as well as the chuck  12  by deflecting or bending the flexible extension shaft such as illustrated in  FIG. 7 . The concentric coil springs  30 ,  32 ,  34  rotate internally of the flexible sleeve  36  and the difference in distance between the cylindrical body portions  20   a  and  22   a  and the cylindrical fittings  38  and  40  accommodate the arc into which the flexible extension shaft  18  is oftentimes advantageously deflected and held during use. In this configuration, the flexible sleeve  36  permits the user to grip the flexible extension shaft  18  and hold it in a deflected position during use without exposure to the moving parts. 
     While in the foregoing there has been set forth a preferred embodiment of the invention, it is to be understood that the present invention may be embodied in other specific forms without departing from the spirit or central characteristics thereof. The present embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein. While specific embodiments have been illustrated and described, numerous modifications come to mind without significantly departing from the characteristics of the invention and the scope of protection is only limited by the scope of the accompanying claims.