Abstract:
An auxiliary rotary tool drive apparatus mounted on, or an integral component of, hand-held rotary power tool has an extendable and retractable auxiliary drive shaft and a gear assembly that is selectively operatively engaged with the power transmitting shaft and gear assembly of the power tool and driven thereby using only the hand grasping the power tool for driving screws, fasteners, bits or other work performing members attached to the auxiliary drive shaft without having to move or remove the existing work performing member from the holding member of the power tool.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority of U.S. Provisional Application Ser. No. 61/124,317, filed Apr. 17, 2008. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to hand-held power tools, and more particularly, to an auxiliary rotary tool drive apparatus that is mounted on, or an integral component of, a hand-held rotary power tool, such a rotary drill, and has an extendable and retractable auxiliary drive shaft and a gear assembly that is selectively operatively engaged with the drive shaft and gear assembly of the power tool and driven thereby using only the hand grasping the drill for driving screws, fasteners, bits or other work performing members attached to the auxiliary drive shaft without having to move or remove the existing drill bit or work performing member from the chuck of the power drill. 
     2. Background Art 
     As used herein, the term “rotary power tool” means a tool having a housing containing a driving motor and a drive train connected with a power transmitting shaft (drive shaft, spindle or anvil) that extends forwardly from the housing and may have a chuck or holding member at its outer end which grips a work performing member to be rotatably driven. Power tools are classified as either stationary or portable, where portable means “hand-held”. Common power tools include drills, drivers, drill/drivers, screwdrivers, and hammer drills or impact drills. In hammer drills or impact drills, the drive shaft is referred to as an “anvil”. As used herein, the terms “chuck” or “holding member” means any device that holds bits, rotating tools, fasteners or other work performing members to the power transmitting shaft of the power tool. As used herein, the term “work performing member” can include such devices as drill bits, screws, fasteners, screw drivers, nuts, bolts, finishing tools, and other rotary devices which can be releasably engaged in the chuck or holding member connected to the rotary power transmitting shaft (drive shaft, spindle or anvil). As used herein, the terms “drive shaft” and “auxiliary drive shaft” means the power transmitting shaft, spindle, or anvil of the power tool and the auxiliary rotary tool drive apparatus, respectively. 
     The task of a driving a screw or fastener into a surface typically involves first drilling a pilot or starter hole, then driving the screw or other fastener into the previously drilled pilot hole. These two tasks, drilling and driving, require either using two different bits in the same drill, or using two drills with one utilizing a drill bit and the other utilizing a screw driving bit. 
     If a single conventional power drill is used, at least one bit change is needed to complete both tasks. This requires loosening and removing the drill bit from the chuck and inserting the appropriate screw driver bit and tightening the drill chuck. Use of a double ended bit held in a quick change adapter clamped in the drill chuck, is somewhat easier and quicker, however, it still requires releasing, removing, turning, and reinserting the dual ended bit. 
     Both of these scenarios are time consuming and changing bits greatly increases the probability of dropping and losing a bit or other rotary tool. It also requires the use of two hands. Since these procedures require both hands to change the bit, the user is precluded from grasping a secure structure while completing the bit changing process, which can be potentially dangerous if done on a ladder, scaffold, or any high or unstable platform. 
     Using two drills, the first equipped with a drill bit and the second equipped with a screw driving bit, requires repeatedly laying down the first drill and picking up the second. This process of changing back and forth between the required drills is time consuming and quickly becomes tedious, particular when it is done frequently or repetitively. 
     Others have attempted to correct the above-mentioned problems. However, none appear to have successfully solved all the problems, nor appear to be capable of drilling a pilot hole and driving a screw immediately in the hole using only one hand and without turning or regrasping the drill or tool. 
     There are several patents directed toward various rotary tools with more than one output; however, they all share similar drawbacks when faced with the task of drilling a hole and subsequently driving a screw in the hole. They require the use of two hands and regrasping the tool to drill a hole and subsequently drive a screw in the hole. 
     U.S. Pat. No. 1,650,911 to Schneider discloses a rotary power tool having a dual drive output that is adaptable for use as a drill, a screw driver, a tapper and a wrench. The disadvantage of this tool is that the toolheads extend therefrom in the same direction and operate at roughly the same working length. For example, in order to use the screw driver, the chuck containing the drill bit must be loosened and the drill bit must be removed to prevent it from contacting the surface into which the screw is to be driven. 
     U.S. Pat. No. 1,750,957 to Fowler discloses a drill attachment having extensions therefrom in opposite directions. The drill of one extension rotates clockwise and the chuck or attachment of the other extension rotates counter-clockwise as viewed from the main body of the tool. The tool is not able to drill a hole and subsequently drive a screw in the hole without first reversing shaft rotation and releasing, turning and regrasping the tool, which is a cumbersome and time-consuming process. 
     U.S. Pat. No. 4,299,004 to Lancaster discloses a powered hand tool for household cleaning operations having two drive shafts for polishing wheels extending therefrom in perpendicular directions. The polishing wheels turn in opposite directions as viewed from each of their drives, and the drives are not extendable. In addition, the perpendicular drives could result in interference when working in a corner. These factors would make applying this invention to drilling and rotary fastening very impractical and inconvenient. 
     U.S. Pat. No. 4,810,916 to McBride teaches a rotary power tool that includes two extensions in opposite directions therefrom. The power tool may utilize a screwdriver bit at one extension and a drill at the other extension. Although both the screwdriver bit and the drill bit are rotatable in the same working direction as seen looking toward each driven portion, it still requires two hands and regrasping to accomplish drilling a hole and subsequently driving a screw in the hole. This results in a cumbersome and time-consuming process. 
     There are also several patents directed toward various power hand tools that provide a magazine carrying several different bits or rotary tools and a way of selecting the one needed by aligning the bit or tool with a chuck axis, moving the bit or tool into place, and tightening the chuck. If the chuck already contains a bit or tool, you must first loosen the chuck to remove the bit or tool and return it to the magazine before utilizing a different bit or tool. There are also several patents directed toward hand-held power drills having a mechanism that operates similar to a rifle “bolt-action” to selectively engage a driver bit with the primary drive shaft that also drives the chuck that carries a drill bit, and patents having a rotatable magazine, similar to a revolver, that carries a plurality of drill bits from which a single bit is selected and engaged in the chuck driven by the primary drive shaft, and patents directed toward the turret type power tools having a turret that carries dual or multiple chucks that can be selectively engaged with the primary drive shaft. 
     U.S. Pat. No. 5,065,498 to McKenzie discloses a drill having a magazine containing a multiplicity of bits from which a single bit is selected using a bolt action, but only one drive shaft. The drawback to this method is that it is cumbersome to use and requires two hands to operate and change the selected rotary tool. 
     U.S. Pat. No. 4,604,005 to Russ discloses a portable selector drill having a rotatable magazine, similar to a revolver, which carries a plurality of drill bits from which a single bit is selected and is driven forward into the chuck driven by the primary drive shaft. 
     U.S. Pat. No. 2,679,770 to Carter et al discloses a portable tool selective drill having a rotatable housing that is mounted at the front end of the drill and replaces the existing chuck. The housing carries a plurality of drill bits and is manually rotated to engage and drive the selected bit with the primary drive shaft. 
     U.S. Pat. No. 6,007,277 to Olson et al discloses a portable selector drill having a rotatable magazine, similar to a revolver, but only a 120° segment, that carries a plurality of drill bits from which a single selected bit is driven forward by a cable mechanism into the chuck and driven by the primary drive shaft. 
     U.S. Pat. No. 5,346,453 to Rivera-Bottzeck discloses a portable electric drill having a rotatable cylindrical magazine within the drill housing for storing a plurality of bits, the magazine is rotated to bring a selected magazine bore in alignment with the central bore of a chuck assembly at the front of the drill. A flexible cable is slidable by hand between forward and rearward positions to eject a tool bit element from the magazine to the chuck and to return a tool bit from the chuck to the magazine. 
     As previously mentioned, the drawback to these inventions is that they are all cumbersome to operate and require two hands to operate and change the selected rotary tool. 
     Therefore, a need exists for a way to drill a hole and subsequently drive a screw, fastener, or other work performing member, without changing bits or other work performing members, swapping drills, and without releasing, turning, or regrasping the tool handle grip. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the aforementioned problems and is distinguished over the prior art by an auxiliary rotary tool drive apparatus mounted on, or an integral component of, and driven by, a conventional hand-held rotary power tool, such a rotary drill, which has an extendable and retractable auxiliary drive shaft and gear assembly operable using only the hand grasping the drill for driving screws, fasteners, bits or other work performing member attached to the auxiliary drive shaft, without having to move or remove the existing drill bit or work performing member from the chuck of the power tool. The auxiliary drive shaft is driven by a primary drive gear installed on the drive shaft and connected with the gear assembly drive train of the drill and operated using only the hand grasping the power tool by pressing a lever in combination with the trigger and forward/reverse control on the power tool. 
     One of the features and advantages of the present auxiliary rotary tool drive apparatus is that it provides users forced to wear heavy gloves or users having the use of only one hand, with the utility/ability to complete the tasks of predrilling a pilot hole and driving a screw or other fastener into the hole using a single hand without pause or re-grasping between the two tasks. 
     Another feature and advantage of the present auxiliary rotary tool drive apparatus is that it provides users that have artificially restricted dexterity, such as astronauts, deep sea divers, arctic technicians, or anyone that must drill holes and drive fasteners in an environment of restricted dexterity or movement, with the utility/ability complete the tasks of predrilling a hole and driving a screw, fastener into the hole using a single hand without pause or re-grasping between the two tasks. 
     Another feature and advantage of the present auxiliary rotary tool drive apparatus is that it can be safely and easily operated with a single hand, leaving the unused hand to brace or grasp a stable object for support and safety. 
     Another feature and advantage of the present auxiliary rotary tool drive apparatus is that it may be provided as an accessory which is adapted to be used with standard commercially available power tools such as drills and accommodates standard rotary tools, bits, screws, fasteners, or other work performing members. 
     Another feature and advantage of the present auxiliary rotary tool drive apparatus is that it allows fast and efficient changes of rotary tools, bits, screws, fasteners, or other work performing members. 
     Another feature and advantage of the present auxiliary rotary tool drive apparatus is that it may be mounted on, or an integral component of, a standard hand-held power tool, such as a drill, and has an auxiliary drive shaft that can retract so as not to not interfere with the normal operations of the power tool or a drill bit or other work performing member clamped in the chuck of the power tool. 
     Another feature and advantage of the present auxiliary rotary tool drive apparatus is that it has an auxiliary drive shaft that can extend past a drill bit or other work performing member clamped in the chuck of a standard hand-held power tool, such as a drill, so as not to not interfere with the normal operations of the power tool or a drill bit or work performing member installed in the chuck of the power tool, allowing the auxiliary rotary tool drive apparatus to operate unimpeded by the power tool with attached bit or work performing member. 
     Another feature and advantage of the present auxiliary rotary tool drive apparatus is that it has an extendable and retractable auxiliary drive shaft that does not extend beyond the profile of the conventional hand-held power tool to which it is mounted, thereby providing compactness and utility of the power tool on which it is mounted. 
     A further feature and advantage of the present auxiliary rotary tool drive apparatus is that it provides a user of a standard hand-held power tool, such as a drill, with the utility to quickly change back and forth between the use of the different bit, screws, fasteners, or other work performing members, without requiring the removal or replacement of the tools, bits, screws, fasteners, or work performing members. 
     A still further feature and advantage of the present auxiliary rotary tool drive apparatus is that it is simple in construction, inexpensive to manufacture, and is rugged and reliable in use. 
     Other features, advantages and objects of the invention will become apparent from time to time throughout the specification and claims as hereinafter related. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevation of a mechanically operated auxiliary rotary tool drive apparatus in accordance with a first embodiment of the present invention, shown attached to a hand-held power drill and with the auxiliary drive shaft in the retracted position. 
         FIG. 2  is a side elevation of the mechanically operated apparatus shown with the auxiliary drive shaft in the extended position. 
         FIG. 3  is a longitudinal cross section through the mechanically operated apparatus shown in larger scale with the auxiliary drive shaft retracted. 
         FIG. 4  is a cross sectional view of the drive gear case of the mechanically operated apparatus with the lower segment in an unlatched position and the gears removed to more clearly show the horizontal slot having an arcuate recess at its outer end. 
         FIG. 5  is an exploded elevation view of the components of the screw ring of the mechanically operated apparatus. 
         FIGS. 6 and 7  are cross sectional views of the drive gear case of the mechanically operated apparatus showing somewhat schematically the gear engagement lever and link, and the horizontal slot having an arcuate recess at its outer end with the gears removed to avoid confusion. 
         FIGS. 8 and 9  are cross sectional views of the drive gear case of the mechanically operated apparatus showing somewhat schematically the transfer gear assembly in a disengaged position and an engaged position, respectively. 
         FIG. 10  is a side elevation of a pneumatically operated auxiliary rotary tool drive apparatus in accordance with a second embodiment the present invention, shown attached to a hand-held power drill and with the auxiliary drive shaft in the retracted position. 
         FIG. 11  is a side elevation of the pneumatically operated apparatus with the auxiliary drive shaft in the extended position. 
         FIG. 12  is a longitudinal cross section through the pneumatically operated apparatus shown in larger scale with the auxiliary drive shaft retracted. 
         FIG. 13  is a cross sectional view through the housing showing the retention plate in its inwardly retracted position. 
         FIG. 14  is a front elevation view of the pneumatically operated apparatus installed on the hand-held drill, showing somewhat schematically, the housing, expansion tube and retractor rod. 
         FIG. 15  is a cross sectional view of the drive gear case of the pneumatically operated apparatus with the lower segment in an unlatched position and the gears removed to more clearly show the horizontal slot having an arcuate recess at its outer end. 
         FIGS. 16 and 17  are cross sectional views of the drive gear case of the pneumatically operated apparatus showing somewhat schematically the transfer gear assembly in a disengaged position and an engaged position, respectively. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Detailed descriptions of the preferred embodiments are provided herein. It is to be understood, however, that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure or manner. 
     The hand-held rotary power tool depicted in the drawing figures is shown and described, for purposes of example only, as a conventional hand-held power drill, and it should be understood that the rotary power tool may be of any conventional type that has a housing containing a drive train connected with a power transmitting shaft (drive shaft, spindle or anvil) that extends forwardly from the housing and has a chuck or holding member mounted at the outer end thereof. For ease of understanding and simplifying the detailed description, the terms “drive shaft” and “auxiliary drive shaft” are used in the following discussion to refer to the power transmitting shaft, spindle, or anvil of the power tool and the auxiliary rotary tool drive apparatus, respectively. It should also be understood that the gear drive train and other components within the power tool housing are conventional and well known in the art, and therefore not shown or described in detail. 
     The present auxiliary rotary tool drive apparatus may be provided in a mechanically operated embodiment, or in a pneumatically operated embodiment. The mechanically operated embodiment and its operation will be described first with reference to  FIGS. 1 through 9 , followed by a description of the pneumatically operated embodiment and its operation with reference to  FIGS. 10 through 17 . 
     Mechanically Operated Embodiment 
     Referring to the drawings, in which like numerals designate like elements throughout the figures,  FIG. 1  shows the mechanically operated embodiment of the auxiliary rotary tool drive apparatus  10  in cross section. As stated above, the present auxiliary rotary tool drive apparatus  10  is mounted on, or an integral component of, and driven by, a rotary power tool which, for purposes of example only, is depicted as a conventional hand-held power drill D having a housing H containing the usual gear drive train connected with a drive shaft S that extends forwardly from the housing and has a chuck C mounted at the outer end thereof. The gear drive train and other components within the drill housing are conventional and well known in the art, and therefore not shown or described in detail. 
     The auxiliary rotary tool drive apparatus  10  includes a primary drive gear  11  and a pair of primary gear bearings  12  at the front and rear of the primary drive gear which are installed on the drive shaft S of the drill D. In the illustrated example, the primary drive gear  11  and primary gear bearings  12  are shown installed on the drive shaft S of the drill D between the chuck C and the nose portion of the drill, however, it should be understood that these components may be installed on a power transmitting shaft (drive shaft, spindle or anvil) and at different locations and on rotary shafts which may or may not have a chuck at the forward end, depending upon the type of power tool with which the auxiliary rotary tool drive apparatus  10  is associated. 
     The apparatus  10  has an elongate generally cylindrical housing  13  enclosed at its rear end by a cap  14  and has a drive gear case  15  attached at its front end (leftmost end as seen in the drawings). The elongate generally cylindrical housing  13  is attached to the top of the housing H of the power drill D by a front saddle  16 A and a rear saddle  16 B which are connected to the lower portion of the housing or case and securely fastened around the case or housing H of the power drill D by a front saddle strap  17 A and rear saddle strap  17 B, each having adjustable buckles. Other means for mounting the apparatus  10  to the case of housing H of the power tool or drill may be employed, including by way of example, hook and loop fasteners or other conventional fasteners. As best seen in  FIGS. 3 and 4 , the drive gear case  15  has a rearwardly protruding upper portion  15 A that is engaged in the front end of the elongate cylindrical housing  13 , an intermediate portion  15 B extending downwardly therefrom, and a segmented cylindrical lower portion with an upper segment  15 C and a lower segment  15 D connected on one side by a hinge  18  and a releasable latch mechanism  19  on the opposed sides. When the lower portion segments are latched, the lower portion  15 D engages the primary gear bearings  12  and enclose the primary drive gear  11  and bearings that are installed on the drive shaft S (spindle or anvil) between the chuck C and the nose portion of the drill D. A horizontal slot  60  is disposed in or on the drive gear case  15  and has a depending arcuate recess  60 A at an outer end configured to releasably engage the central shaft of an engagement gear contained in the intermediate portion  15 B of the drive gear case, as described hereinafter. 
     As best seen in  FIGS. 3 and 5 , a top rib  20 A and a bottom rib  20 B extend longitudinally along the interior of the elongate housing  13  at the top and bottom of the housing, respectively, in vertically opposed relation. An externally threaded extension tube  21  is supported within the housing  13  by bearings  22  at its front end and rear end, respectively. An internally threaded screw ring  23  is threadedly engaged on the external threads of the extension tube  21 , and has a top channel  24  and a bottom channel  25  disposed in vertically opposed relation that are received on and slidably ride on the top and bottom ribs  20 A and  20 B, respectively. The ribs  20 A,  20 B prevent the screw ring  23  from rotating, such that when the extension tube  21  is rotated, the screw ring  23  will travel along the threaded length of the extension tube. 
     The interior diameter of the screw ring  23  is provided with an annular U-shaped inner groove  26  having an opening facing the center of the ring and receives the outer facing ends of four carrier plate pins  27  that freely rotate within the screw ring inner groove. 
     The outer facing ends of the four carrier plate pins  27  are contained in the outer L-shaped portion of a carrier plate  28  having a retaining washer  29  at its rear end segment. The retaining washer  29  is held in place and located on an elongate hexagonal auxiliary drive shaft  30  by a snap ring  31  installed in a snap ring groove  32  on the exterior of the auxiliary drive shaft. The front end wall of the L-shaped portion of the carrier plate  28  is provided with an arcuate recess  33 . A front ball bearing retaining ring  34  having a rear wall with an arcuate recess  35  is welded to the exterior of the auxiliary drive shaft  30  forward of the carrier plate arcuate recess  33 , and a plurality of ball bearings  36  are rotatably contained between the arcuate recesses and surround the hexagonal exterior of the auxiliary drive shaft  30 . 
     The auxiliary drive shaft  30  has a hexagonal recess  37  and a snap ring groove  38  at its rear end, and a double hex drive transfer nut  40  having a hexagonal exterior is retained in the recess by a snap ring  39  received in the snap ring groove  38 . The double hex drive transfer nut  40  has a central hexagonal bore  41 , through which a hexagonal drive rod  42  slidably extends and travels in a hexagonal central bore  43  within the auxiliary drive shaft  30 . 
     A cylindrical screw holder  30 A is shown at the front end of the auxiliary drive shaft  30 , which is shown for purposes of example, adapted to hold a screw but which may be adapted to hold another fastener type or even an auxiliary working member. 
     A secondary drive gear bearing  44  is mounted in the upper end of the drive gear case  15 , which is disposed in the front end of the elongate housing  13 . A secondary drive gear  45  is contained in upper end of the drive gear case  15  and has a tubular neck portion rotatably supported in the secondary drive bearing  44 . A hexagonal bore  46  extends through the center of the secondary drive gear  45  and the front portion of the hexagonal auxiliary drive shaft  30  extends through the hexagonal bore. 
     The rear end of the hexagonal drive rod  42  extends beyond the rear end of the auxiliary drive shaft  30  and is provided with a pair of longitudinally spaced snap ring grooves  47 . A drive plate  49  having a hexagonal bore  50  is mounted on the rear end of the hexagonal drive rod  42  by a pair of snap rings  48  received in the snap ring grooves  47  at the front and back side of the drive plate. A tube plate  51  having a central opening is secured to the back end of the extension tube  21 . A compression spring  52  surrounds the rear end of the extension tube  21  and has one end engaged on the rearmost bearing  22  and its opposed end engaged on the drive plate  49 . The front side of the drive plate  49  has a tubular extension  53  that contacts the back end of the tube plate  51  when a thumb lever (described hereinafter) is depressed. 
     The interior of the end cap  14 , which encloses the rear end of the elongate housing  13 , has a forwardly extending yoke  54  at its top end that that extends a distance into the interior of the housing  13 , and the top end of drive plate lever  55  is pivotally mounted on the yoke. The drive plate lever  55  has a protrusion  56  that engages the back end of the hexagonal drive rod  42 . The bottom end of the drive plate lever  55  is pivotally connected to the rear end of an actuation rod  57 . The front end of the actuation rod  57  is pivotally connected to a thumb lever  58 , which is pivotally connected at its top end to a yoke  59  on the underside of the elongate housing  13 . The thumb lever  58  extends laterally outward from one side of the yoke  59  and curves downwardly closely adjacent to the drill housing H and terminates in a thumb rest portion  58 A at its bottom end near the upper portion of the drill handgrip. When the thumb lever  58  is depressed, it pivots forward and carries the actuation rod  57  forward, which pivots the drive plate lever  55  to engage its protrusion on the back end of the hexagonal drive rod  42  and drive it forward, which drives the drive plate  49  forward against the pressure of the compression spring  52  to engage its tubular extension  56  on the tube plate  51  at the back end of the extension tube  21 . 
     As best seen in FIGS.  4  and  6 - 9 , a horizontal slot  60  is disposed in or on the drive gear case  15  and has a depending arcuate recess  60 A at an outer end. A link  61  extends through the side of the drive gear case  15 , and its outer end is connected to the horizontal leg of a generally L-shaped gear engagement lever  62  which extends rearwardly through a pivot connection  63  and downwardly along the side of the drill housing H and terminates near the trigger of the power drill. The inner facing end of the link  61  is provided with a slot  64  which is superposed in spaced relation over the horizontal slot  60 . 
     An engagement gear  65  is disposed in the interior of the drive gear case  15  and has a central shaft  65 A, one end of which is slidably and rotatably mounted in the horizontal slot  60  and the other end of which is slidably and rotatably mounted in the slot  64  of the link  61 . A torsion spring  66  is fixed at one end to one side of the interior of the drive gear case  15 , and its movable fee end is engaged with the engagement gear shaft  65 A to move the engagement gear  65 . 
     In a disengaged position ( FIG. 8 ), the inner facing end of the link  61  and its slot  64  extend downwardly at an angle with respect to a horizontal axis, and the central shaft  65 A of the engagement gear  65  is retained in the arcuate recess  60 A at the outer end of the horizontal slot  60  by the angularly disposed slot  64  of the link  61 , thereby retaining the engagement gear  65  in a laterally outward disengaged position against the force of the torsion spring  66 . 
     To engage the engagement gear  65  ( FIG. 9 ), the gear engagement lever  62  is pivoted, and the link  61  pivots upwardly to a horizontal position and, as its slot  64  moves upwardly, it moves the central shaft  65 A of the engagement gear  65  out of the arcuate recess  60 A of the horizontal slot  60 , and when the slots are aligned, the force of the torsion spring  66  moves the engagement gear  65  inwardly to engage its teeth with the teeth of the primary drive gear  11  and the secondary drive gear  45 . 
     Operation of the Mechanically Operated Embodiment 
     Referring now to  FIGS. 1 ,  2 ,  3  and  4 , the primary drive gear  11  is first installed on the drive shaft S (spindle or anvil) of the drill D between the chuck C and the nose portion of the standard power drill. Next, the apparatus  10  is installed on top of the drill housing H by mounting the front and rear saddles  16 A and  16 B on the top of the power drill, and securing the front and rear saddle straps  17 A and  17 B around the drill housing. The lower segment  15 D of the drive gear case  15  is then closed around the primary drive gear  11  and latched by the latch  19 . 
     As seen in  FIGS. 8 and 9 , and described above, when the gear engagement lever  62  is pivoted, the engagement gear  65  is lifted and spring biased inwardly into tooth-to-tooth engagement with the primary drive gear  11  and secondary drive gear  45 , which transfers the rotation of the primary drive shaft S of the drill to the secondary drive gear  45 . The secondary drive gear  45  only rotates when the engagement gear  65  is engaged and the primary drive shaft S of the drill is rotating in either forward or reverse directions. 
     As shown in  FIGS. 1 and 2 , the present auxiliary rotary tool drive apparatus is typically used immediately after a hole is predrilled by the primary drive shaft of the power drill. To use the auxiliary rotary tool drive apparatus, the auxiliary drive shaft  30  with a screw pre-attached, is first extended beyond the drill bit clamped to the chuck C of the power drill by depressing the thumb lever  58  while the power drill is rotating in a clockwise direction. Depressing the thumb lever  58  pivots the drive plate lever  55 , which engages the drive plate  49  with the tube plate  51 . When the drive plate  49  and tube plate  51  are engaged, the extension tube  21  rotates in proportion and in the same direction as the hand drill. 
     As the extension tube  21  rotates, the threads of the extension tube  21  engage the threads of the screw ring  23 . The screw ring  23  cannot rotate since the top and bottom channels  24  and  25  of the screw ring are engaged in the top and bottom ribs  20 A and  20 B on the interior of the elongate housing  13 . Thus, the screw ring  23  travels longitudinally forward or rearward along the threaded length of the extension tube  21  as it rotates. 
     As the screw ring  23  travels longitudinally forward or rearward along the threaded length of the extension tube  21 , it simultaneously moves the carrier plate  28 , which is connected thereto by the carrier plate pins  27  captured in the screw ring inner groove  26 . 
     As the carrier plate  28  moves forward or rearward on the extension tube  21 , it moves the attached extendable portion of the drive rod  42 , the auxiliary drive shaft  30 , forward or rearward within the extension tube  21 . 
     To stop extension of the auxiliary drive shaft  30 , the thumb lever  58  is released or finger pressure on the trigger of the drill is released to stop the drill. To retract the auxiliary drive shaft  30 , the rotation direction of the drill is reversed and the thumb lever  58  is depressed, and the drill is operated until retraction is completed. 
     Pneumatically Operated Embodiment 
     Referring now to  FIGS. 10 through 17 , there is shown a pneumatically operated embodiment of the auxiliary rotary tool drive apparatus  70 . The components that are the same as the mechanically operated embodiment are assigned the same numerals of reference, but some of the components will not be described again in detail to avoid repetition. 
     As with the mechanically operated embodiment, the pneumatically operated auxiliary rotary tool drive apparatus  70  is mounted on, or an integral component of, and driven by, a rotary power tool, such as a hand-held power drill D having a housing H containing the usual gear drive train connected with a drive shaft S (spindle, or anvil) that extends forwardly from the housing and may or may not have a chuck C mounted at the outer end thereof. The gear drive train and other components within the drill housing are conventional and well known in the art, and therefore not shown or described in detail. 
     As with the previously described embodiment, the pneumatically operated auxiliary rotary tool drive apparatus  70  includes a primary drive gear  11  and a pair of primary gear bearings  12  at the front and rear of the primary drive gear which are shown, for purposes of example, installed on the drive shaft S (spindle or anvil) between the chuck C and the nose portion of the drill D. 
     The pneumatically operated apparatus  70  has an elongate generally cylindrical housing  73  enclosed at its rear end by an end wall  74  and has a drive gear case  75  secured at its front end (leftmost end as seen in the drawings). The elongate generally cylindrical housing  73  is attached to the top of the housing H of the power drill D by a front saddle  16 A and a rear saddle  16 B which are connected to the lower portion of the housing or case and securely fastened around the case or housing H of the power drill D by a front saddle strap  17 A and rear saddle strap  17 B. 
     As best seen in  FIGS. 12 and 15 , the drive gear case  75  has a rearwardly protruding upper portion  75 A that is secured to the front end of the elongate cylindrical housing  73 , an intermediate portion  75 B extending downwardly therefrom, and a segmented cylindrical lower portion with an upper segment  75 C and a lower segment  75 D connected on one side by a hinge  18  and a releasable latch mechanism  19  on the opposed sides. When the lower portion segments are latched, the lower portion  75 D engages the primary gear bearings  12  and enclose the primary drive gear  11  and bearings that are installed on the drive shaft S (spindle or anvil) between the chuck C and the nose portion of the drill D. A horizontal slot  60  is disposed in or on the drive gear case  75  and has a depending arcuate recess  60 A at an outer end configured to releasably engage the central shaft of an engagement gear contained in the intermediate portion  75 B of the drive gear case, as described hereinafter. 
     A secondary drive gear bearing  44  is mounted in the upper end of the drive gear case  75 , which is disposed in the front end of the elongate housing  73 . A secondary drive gear  45  is contained in upper end of the drive gear case  75  and has a tubular neck portion rotatably supported in the secondary drive bearing  44 . A hexagonal bore  46  extends through the center of the secondary drive gear  45  and the front portion of the auxiliary drive shaft  84 , described hereinafter, extends through the hexagonal bore. 
     As best seen in  FIG. 14 , an elongate tubular expansion tube  76  is secured laterally adjacent and parallel to the elongate cylindrical housing or case  73  by a first tube connector  77 A and a second tube connector  77 B such that their side walls are engaged tangentially. The outer ends of the tube connectors  77 A,  77 B are provided with holes  77 C for slidably receiving a drive shaft retractor rod  93  (described hereinafter). The interior of the expansion tube  76  and elongate cylindrical housing  73  are joined in fluid exchange relation by a hole or passageway  78  passing through their side walls near their rear ends. A restrictor disc  79  having a small bore or orifice  79 A is secured inside of the elongate housing or case  73  a short distance forward of the passageway  78 . The restrictor orifice  79 A serves to prevent the auxiliary drive shaft  84  (described hereinafter) from extending too quickly. 
     As best seen in  FIGS. 12 and 13 , the top and bottom of the of the elongate housing  73  are provided with vertically opposed transverse slots  80  disposed near the drive gear case  75 , and a retention plate  81  is slidably received through the slots. The retention plate  81  has a generally hourglass or keyhole-shaped retaining slot  82  in its midsection which has a smaller semicircular top portion  82 A and a larger semi-circular bottom portion  82 B disposed in vertically spaced relation. The retention plate  81  has a generally L-shaped latch  83  with a short horizontal portion disposed above the top of the retaining slot  82  extending rearwardly from its back side terminating in a short depending vertical portion. The horizontal portion of the latch  83  is disposed inside the elongate housing  73 . The top end of the shaft retention plate  81  extends a short distance upwardly from the transverse slots  80  at the top of the elongate housing  73  and the outwardly extended top end of the retention plate  81  is provided with a horizontal slot  81 A for receiving the front end  97 A of a retention plate lever  97  (described below). 
     An elongate hexagonal auxiliary drive shaft  84  extends through the center of the elongate housing or case  73 . The front end of the auxiliary drive shaft  84  extends through the hexagonal bore  46  in the center of the secondary drive gear  45 , and through the retaining slot  82  in the shaft retention plate  81 , and is provided with a reduced diameter portion  84 A near its front end which is axially aligned with the retaining slot  82  when the drive shaft is retracted. 
     The rear end of the drive shaft  84  has a reduced diameter portion  84 B and a snap ring groove  85 . A spool  87  having a reduced diameter portion  87 A is received on the reduced diameter rear end portion  84 B of the drive shaft  84 . A drive shaft main bearing  88  and low-friction washer  89  are received on the reduced diameter rear portion  84 B of the drive shaft  84  rearwardly of the spool  87  and secured by a snap ring  86  installed in the snap ring grove  85 . 
     A piston  90  is mounted on the reduced diameter rear portion  84 B of the drive shaft  84 . The piston  90  has a cylindrical head portion  90 A at its rear end with a circumferential seal  90 B on its outer periphery engaged on the inside diameter of the elongate housing  73  in a sliding fluid sealing relation, and a hollow cylindrical skirt portion  90 C extending forwardly from the head portion with a snap ring groove  91  on its interior diameter near its front end. The back end of the spool  87  and the drive shaft main bearing  88  are received and rotatably mounted within the interior diameter of the skirt portion  90 C of the piston  90  and retained therein by a snap ring  92  installed in the snap ring groove  91 . 
     The front end of the auxiliary drive shaft  84  that extends through the hexagonal bore  46  in the center of the secondary drive gear  45  extends outwardly from the front of the drive gear case  75  and is provided with a third reduced diameter portion  84 C which is disposed closely adjacent to the drive gear case when the auxiliary drive shaft  84  is retracted. 
     An elongate drive shaft retractor rod  93  is slidably received and travels through the holes  77 C in the tube connectors  77 A,  77 B. The front end of the drive shaft retractor rod  93  has laterally extending bracket  94  with a horizontal U-shaped opening that straddles the third reduced diameter portion  84 C at the front end of the auxiliary drive shaft  84 , and has a retractor handle  95  at its rear end for manually retracting the auxiliary drive shaft from an extended position. 
     A cylindrical screw holder  84 D is shown at the front end of the auxiliary drive shaft  84 , which is shown for purposes of example, adapted to hold a screw but which may be adapted to hold another fastener type or even an auxiliary working member. 
     A yoke  96  is mounted on the top of the elongate housing or case  73  rearwardly of the outwardly extending top end of the shaft retention plate  81 . A retention plate lever  97  is pivotally mounted in the yoke  96  and has a forwardly extending portion with an upwardly curved front end  97 A that is received in the horizontal slot  81 A at the top end of the retention plate  81 , a laterally extending portion extending outward from one side of the yoke  96 , and a downwardly curved portion  97 B that curves downwardly closely adjacent to the drill housing and terminates in a thumb rest portion  97 C at its bottom end near the upper portion of the drill handgrip. A torsion spring  98  has one end engaged on the top of the elongate housing or case  73  rearwardly of the yoke  96  and its other end engaged on the forwardly extending portion of the retention plate lever  97  to normally maintain the forwardly extending portion of the retention plate lever and the retention plate  81  in a lowered position. 
     When the retention plate  81  is in the lowered position, the smaller semicircular top portion  82 A of the retaining slot  82  in its midsection is engaged on the reduced diameter portion  84 A near the front end of the auxiliary drive shaft  84  to prevent it from moving. When the thumb rest portion  97 C at the lower end of the retention plate lever  97  is depressed, the lower portion of the retention plate lever  97  pivots forward and the forwardly extending portion  97 A pivots upward against the pressure of the torsion spring  98  and raises the retention plate  81  to disengage the smaller semicircular top portion  82 A of the retaining slot  82  from the reduced diameter portion  84 A near the front end of the auxiliary drive shaft  84  to allow the drive shaft to pass slidably through the larger semi-circular bottom portion  82 B of the retaining slot  82 . 
     In the fully extended forward position, the reduced diameter portion  87 A of the spool  87  near the rear end of the auxiliary drive shaft  84  is disposed beneath the depending leg of the generally L-shaped latch  83  of the retention plate  81 , and when the thumb rest portion  97 B at the lower end of the retention plate lever  97  is released, the retention plate  81  drops down to engage the depending leg of the latch  83  on the reduced diameter portion  87 A of the spool  87  to prevent the auxiliary drive shaft  84  from being retracted. 
     As with the previously described embodiment, and best seen in  FIGS. 14 ,  16  and  17 , a horizontal slot  60  is disposed in or on the drive gear case  75  and has a depending arcuate recess  60 A at an outer end. A link  61  extends through the side of the drive gear case  75 , and its outer end is connected to the horizontal leg of a generally L-shaped gear engagement lever  62  which extends rearwardly through a pivot connection  63  and downwardly along the side of the drill housing H and terminates near the trigger of the power drill. The inner facing end of the link  61  is provided with a slot  64  which is superposed in spaced relation over the horizontal slot  60 . 
     An engagement gear  65  is disposed in the interior of the drive gear case  75  and has a central shaft  65 A, one end of which is slidably and rotatably mounted in the horizontal slot  60  and the other end of which is slidably and rotatably mounted in the slot  64  of the link  61 . A torsion spring  66  is fixed at one end to one side of the interior of the drive gear case  75 , and its movable free end is engaged with the engagement gear shaft  65 A to move the engagement gear  65 . 
     In a disengaged position ( FIG. 16 ), the inner facing end of the link  61  and its slot  64  extend downwardly at an angle with respect to a horizontal axis, and the central shaft  65 A of the engagement gear  65  is retained in the arcuate recess  60 A at the outer end of the horizontal slot  60  by the angularly disposed slot  64  of the link  61 , thereby retaining the engagement gear  65  in a laterally outward disengaged position against the force of the torsion spring  66 . 
     To engage the engagement gear  65  ( FIG. 17 ), the gear engagement lever  62  is pivoted, and the link  61  pivots upwardly to a horizontal position and, as its slot  64  moves upwardly, it moves the central shaft  65 A of the engagement gear  65  out of the arcuate recess  60 A of the horizontal slot  60 , and when the slots are aligned, the force of the torsion spring  66  moves the engagement gear  65  inwardly to engage its teeth with the teeth of the primary drive gear  11  and the secondary drive gear  45 . 
     Operation of the Pneumatically Operated Embodiment 
     Referring now to  FIGS. 10 ,  11 , and  12 , the primary drive gear  11  is first installed on the drive shaft S (spindle or anvil) of the drill D between the chuck C and the nose portion of the standard power drill. Next, the apparatus  70  is installed on top of the drill housing H by mounting the front and rear saddles  16 A and  16 B on the top of the power drill, and securing the front and rear saddle straps  17 A and  17 B around the drill housing. The lower segment  75 D of the drive gear case  75  is then closed around the primary drive gear  11  and latched by the latch  19 . 
     As seen in  FIGS. 16 and 17 , and described above, when the gear engagement lever  62  is pivoted, the engagement gear  65  is lifted and spring biased inwardly into tooth-to-tooth engagement with the primary drive gear  11  and secondary drive gear  45 , which transfer the rotation of the primary drive shaft S of the drill to the secondary drive gear  45 . The secondary drive gear  45  only rotates when the engagement gear  65  is engaged and the primary drive shaft S of the drill is rotating in either forward or reverse directions. 
     Air is sealingly contained in the elongate cylindrical housing  73  in the area behind the piston  90  and in the expansion tube  76  which is in fluid communication therewith through the passageway  78 . The air becomes compressed when the auxiliary drive shaft  84  and piston  90  are moved to the retracted position and acts as a pneumatic spring when the auxiliary drive shaft is released to drive it forward. 
     As shown in  FIGS. 10 ,  11  and  12 , the present auxiliary rotary tool drive apparatus is typically used immediately after a hole is predrilled by the primary drive shaft of the power drill. As described above, the interior of the expansion tube  76  and elongate cylindrical housing or case  73  are in fluid exchange relation via the hole or passageway  78  passing through their side walls, and air is metered through the small bore or orifice  79 A in the restrictor disc  79  inside the housing  73  to prevent the drive shaft  84  from extending too quickly. 
     To use the auxiliary rotary tool drive apparatus  70 , the auxiliary drive shaft  84  with a screw pre-attached, is first extended beyond the drill bit clamped to the chuck C of the power drill by depressing the retention plate lever  97  to raise the retention plate  81  and disengage the smaller semicircular top portion  82 A of the retaining slot  82  from the reduced diameter portion  84 A near the front end of the auxiliary drive shaft  84 , allowing the metered air pressure to drive the piston  90  and auxiliary drive shaft  84  forward through the larger semi-circular bottom portion  82 B of the retaining slot  82 , also carrying the drive shaft retractor rod  93  forward with it. When the auxiliary drive shaft  84  reaches its fully extended forward position, the retention plate lever  97  is released to lower the retention plate  81  and engage the depending leg of the latch  83  on the reduced diameter portion  87 A of the spool  87  to prevent the auxiliary drive shaft  84  from being retracted. 
     To retract the auxiliary drive shaft  84 , the retention plate lever  97  is depressed to raise the retention plate  81  and disengage engage the depending leg of the latch  83  from the reduced diameter portion  87 A of the spool  87 , the drive shaft retractor rod  93  is manually pulled rearward by the handle  95  at its rear end, and the retention plate lever  97  is released to drop the retention plate  81  and engage the smaller semicircular top portion  82 A of the retaining slot  82  on the reduced diameter portion  84 A near the front end of the auxiliary drive shaft  84 , to prevent movement of the auxiliary drive shaft. 
     Although the present mechanically and pneumatically operated auxiliary rotary tool drive apparatuses have been described, for purposes of example, as being attached to an existing conventional rotary power tool, such as a conventional power drill, it should be understood that the present mechanically and pneumatically operated auxiliary rotary tool drive mechanisms may be incorporated as integral components of the rotary power tool. 
     While the present invention has been disclosed in various preferred forms, the specific embodiments thereof as disclosed and illustrated herein are considered as illustrative only of the principles of the invention and are not to be considered in a limiting sense in interpreting the claims. The claims are intended to include all novel and non-obvious combinations and sub-combinations of the various elements, features, functions, and/or properties disclosed herein. Variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art from this disclosure, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed in the following claims defining the present invention.