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CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation-in-part of applicant&#39;s co-pending application Ser. No. 11/495,977 filed Jul. 27, 2006 the entire contents of which is hereby expressly incorporated by reference herein. 
     
     FIELD OF THE INVENTION 
       [0002]    This invention relates to improvements in a drill attachment where the drill attachment is a smoothing device for smoothing concrete. More particularly, the present drill attachment includes a shaft that is secured or chucked into an electric drill. Pluralities of trowels extend from the shaft and are secured at their ends to maintain their position and orientation. In operation the drill attachment is used to smooth the ends and corners of a foundation where larger smoothing trowel machines have difficulty reaching. An independently spinning blade cover extends over the ends of the blades to prevent damage to a wall or other surface when the trowel is in use. The blades are secured to the trowel with fixed angle inserts that are changeable to suit the finishing need of the operator. 
       BACKGROUND OF THE INVENTION 
       [0003]    Concrete includes a combination of water sand and rock or aggregate material. When the wet concrete is poured into a slab, the slurry is in a semi homogeneous condition where the rock exists both within the wet slab and on the surface. The rocks are moved under the top surface of the pad by vibration, tamping and by troweling the slurry to create a smooth top surface with little or no visible rock aggregate. In large construction projects the troweling is performed with gas or electric powered troweling or float vehicles that are driven on and around the surface to smooth the pad. Because of the size of these vehicles, navigation around the edges and corners is difficult and dangerous. The most effective way to handle the edges and corners is with a small hand trowel and more efficiently with a powered hand trowel as disclosed herein. Several patents have been issues of devices to smooth a wet concrete pad and some exemplary examples are identified herein. 
         [0004]    U.S. Pat. Nos. 2,108,470, 2,198,929, 2,277,389, 2,394,274, 4,046,483, 4198,178 and 4,320,986 each disclose a concrete finishing or troweling machine that includes troweling rotors attached to a motor with an elongated handle that the operator holds to guide and control the finishing of the machine. While these patents disclose machines for finishing or troweling concrete, they all contain the motor or drive mechanism and too large for finishing the corners or edges of a foundation. They are also permanently attached to the drive motor making them dedicated machines having only one purpose. The drive motor is only used in the finishing, it can not be separated to drill holes or perform other functions. 
         [0005]    U.S. Pat. No. 5,221,156 issued to Harlan S. Martin on Jun. 22, 1993 discloses a concrete finishing machine providing a more compact concrete finishing machine where an operator grips the support arms and guides the machine in smaller areas. While this patent discloses a machine for finishing or troweling concrete, it contains the motor that is permanently attached, thus dedicating the machines for only one purpose. The drive motor is only used in the finishing, it can not be separated to drill holes or perform other functions. 
         [0006]    U.S. Pat. No. 2,860,506 issued to J. D. Drummond on Nov. 18, 1958 discloses a Power Driven Plastering Trowel for smoothing plaster placed on a wall. In this patent the plurality of trowels are individually secured into the trowel. The angle of the troweling blades is not adjustable. The plastering trowel is further not removable from the power device, nor is it used to smooth concrete. 
         [0007]    U.S. Pat. No. 5,762,545 issued to Kerri O. Edwards on Jun. 9, 1998 discloses a Sanding Disk with Extended Blades. This patent is for a sanding disk attachment for a drill where the sanding disk includes four extended arms. The purpose of the product is to sand. One of the features of this patent is the ability to wrap standard sheets of sandpaper around each on the arms, as opposed to using custom or cut sheets of material. While this patent discloses an attachment for a drill with radial arms, the tool is not intended for use in the finishing of concrete nor is the angle of the arms adjustable or pivotable to conform to the concrete being smoothed. 
         [0008]    What is needed is an attachment for a drill that is easily installed and removed to allow the drill to be used for other purposes. The ideal drill attachment would be small enough to allow it to smooth concrete edges and corner. The troweling blades would be adjustable or fixable to affect the smoothing characteristics of the drill. The proposed power trowel drill attachment satisfies these requirements. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    It is an object of the power trowel attachment for a drill to provide an installable and removable attachment for a drill that is used to trowel the edges and corners of a concrete slab that has been poured. The temporary attachment to a drill allows the drill to be usable for other purposes both before and after the drill is used to trowel concrete. Since a power drill is a common piece of equipment at a construction site the only additional component is the power troweling attachment. The ability to remove the power trowel from the drill allows a more complete cleaning or the power trowel because it can be removed from any electrical components that might be damaged from water or other cleaning materials. 
         [0010]    It is an object of the power trowel attachment to provide troweling blades that pivot to move over the concrete and provide a smoother finish. The angle on the pivoting blades is controllable with an adjustable bolt to maintain position and angle of the blades. 
         [0011]    It is an object of the power trowel attachments small size to permit easy portability, storage and versatility to use the power trowel in areas where larger power trowels can not reach due to safety or size of the vehicles. The small size allows the tool to be walked around the perimeter or inside of a poured slab and quickly smooth the perimeter, corners and edges. Because the tool is small in size it is also useable to touch-up areas that are accidentally damaged or require quick smoothing. 
         [0012]    It is an object of the power trowel attachment safety ring that extends around the trowels to reduce the potential for harm, damage or injury from the rotating trowel blades. 
         [0013]    It is an object of the power trowel attachment to have changeable blades that are individually removable and or replaceable to accommodate servicing of the power trowel as required to maintain optimal operation. 
         [0014]    It is an object of the power trowel attachment to make the shaft that is chucked into the drill triangular or tri-roundular in configuration to reduce rotation of the shaft in the drill chuck. 
         [0015]    It is an object of the power trowel attachment to include a trowel blade cover that extends over the ends of the blade. The cover can spin independently from the blades to prevent the blades from marking or gouging into a wall surface or body part that may get near the troweling blades. 
         [0016]    It is an object of the power trowel attachment to blades is a fixed angular configuration. The fixed angle is with changeable angle inserts. The inserts are removable and changeable based upon the troweling needs. The different angles allow the power trowel to operate as both a roughing trowel for initial material spreading and a smoothing trowel for finishing detail work. 
         [0017]    It is still another object of the transmission to incorporate a transmission between the input shaft and the trowel blades to alter the rotational speed of the blades. The transmission provides a slower rotational speed of the blades with higher drill turning speed to reduce the load on the drill at slower speed. The transmission further provides better control of the rotating trowel blades when they are spun at a slower rate of speed. The transmission provides the advantage of using a drill with a lower power rating or a drill that is battery powered allowing the tool to be used without a power cord attachment. 
         [0018]    Various objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention, along with the accompanying drawings in which like numerals represent like components. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  shows an isometric view of the trowel secured in a drill. 
           [0020]      FIG. 2  shows a top view of the trowel. 
           [0021]      FIG. 3  shows a bottom view of the trowel. 
           [0022]      FIG. 4  shows a side view of the trowel. 
           [0023]      FIG. 5  shows an enlarged partial side view of the trowel showing a pivoting trowel partially rotated. 
           [0024]      FIG. 6  shows an enlarged partial side view of the trowel showing a pivoting trowel rotated against the stop. 
           [0025]      FIG. 7  shows a lower isometric view of the trowel showing the pivoting components on one trowel. 
           [0026]      FIG. 8  is an isometric exploded view of the trowel with fixed blades and a protective cover. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]      FIG. 1  shows an isometric view of the trowel secured in a drill. The drill  10  is shown for reference. In the drill shown in this FIG. is a corded power drill, but it is contemplated that the power trowel can equally be used with a battery powered drill. The power trowel  20  is chucked into the drill the same as a drill bit would be chucked into a drill. The end of the tool that is chucked into the drill is round but is preferably hexagonal, triangular or tri-roundular in configuration to reduce rotation of the shaft in the drill chuck. The input shaft attaches to a central structural hub where the remainder of the power trowel expands from. In one embodiment the central hub  32  includes a transmission such as a universal gear box. The transmission provides a slower rotational speed of the blades with higher drill turning speed to reduce the load on the drill at slower speed. The transmission further provides better control of the rotating trowel blades when they are spun at a slower rate of speed. The transmission provides the advantage of using a drill with a lower power rating or a drill that is battery powered allowing the tool to be used without a power cord attachment. Working prototypes have been fabricated without a transmission and have been successful in operation. 
         [0028]    Three troweling blades  80 ,  82  and  84  are equally radially spaced around the central hub  32 . These troweling blades provide the smoothing of the concrete. The blades consist essentially of a flat lower surface. The blades are preferably fabricated from steel, but other materials are contemplated that provide equivalent performance. Other materials from aluminum, plastics or wood are contemplated to provide various smoothing characteristics. The trowel blades are attached to a trowel supports  81 ,  83  and  85  where only support  81  is identified in this  FIGS. 4-8 . 
         [0029]    The trowels are secured with fasteners that allow removal, replacement or servicing. The combination trowel and trowel support are pivotably secured to the power trowel with bushings, with outer bearings or pivot points  60 . Inner bearings are not shown in this FIG. but the combination of outer and inner bearings support the trowel blades and allow them to pivot. The pivoting mechanism is shown and described in more detail with  FIGS. 4 to 7  herein. The outer bearings, bushings exist in an outer bearing riser  61  that is welded to the outer ring or safety ring  40  that extends around the trowels to reduce the potential for harm, damage or injury from the rotating trowel blades. A top cover  100  is shown that wraps over the sides of the blades. The cover is connected to the central hub  32  with a bearing. The bearing allows the cover to spin independently from the troweling blades. This is partially useful to prevent the blades from scraping a wall or the leg of a user. With the top cover  100  comes in contact with a surface the cover stops spinning and guards the blades from extending beyond the top cover. The cover is designed to terminate slightly above the bottom of the blades  80  to prevent to cover from marking the toweled surface. 
         [0030]    A series of ribs  50  extend from the outer ring  40  to the inner ring  45 . This series of ribs provide structural strength to the power trowel maintaining even load distribution and help to keep hand and or fingers out of the turning trowel blades  80 ,  82 , and  84 . A stop plate exists between the inner ring and the central hub  32 . The stop ring  38  limits the angular rotation of the troweling blades. The function and configuration of the stop ring is shown and described in more detail with  FIGS. 4 to 8 . 
         [0031]      FIGS. 2 and 3  show a top and bottom view of the power trowel  20  respectively. The hexagonal input shaft  30  is shown in  FIG. 3  where the drill is chucked onto the power trowel. The central hub  32  is shown with a four sided hub. The hub makes it easier to grip the power trowel and hand chuck the power trowel into a drill. The stop ring  38  is most visible in  FIG. 38  where it encircles the central hub  32 . The stop ring  38  limits the angular rotation of the troweling blades. The outer ring  40  and the inner ring  45  are shown with the ribs  50  extending between these two rings. A total of eight ribs are shown, but as few as three ribs are contemplate to a plate made or transparent (not visible) that extends across the area between the inner  45  and outer  40  rings. 
         [0032]    Referring mostly to  FIG. 3 , the blades  80 ,  82  and  84  or visible. The shape of the blades is essentially rectangular, and has a taper where they become closer in the central portion of the power trowel. The narrowing area in the center allows the trowels to more evenly smooth the concrete in the middle are. The blades are attached to blade supports shown as items  81 ,  83  and  85  in  FIG. 2  and as broken lines in  FIG. 3 . The blades  80 ,  82  and  84  are removable from the blade supports  81 ,  83  and  85  for servicing, cleaning, replacement or changing. In  FIG. 3  the outer bearing risers  61 ,  63  and  65  are shown protruding from the outer ring  40 . These risers include the outer bushings, bearings or holes  62  and  64  for the trowels to pivot within. The inner bearing, bushings, or holes  70 ,  72  and  74  are shown as broken lines in  FIG. 3  where they secure the inner ends of the trowel and trowel supports  81 ,  83  and  85 . The head of one of the rotation limiting bolts  91  is shown near the stop plate  38 . 
         [0033]      FIG. 4  shows a side view of the power trowel  20 . This view will be briefly described because the details in this FIG. contains a number of elements that will be described in more detail in  FIGS. 5 and 6  where  FIGS. 5 and 6  are an enlarged part of  FIG. 4  with extraneous items removed to show the pivotal motion of one trowel blade. The input shaft  30  is connected to the central hub  32 . 
         [0034]      FIGS. 5 and 6  shows an enlarged partial side view of the trowel showing the pivoting mechanism and the pivoting of a trowel.  FIG. 5  shows the trowel partially rotated, while  FIG. 6  shows the trowel rotated against the stop. The edge of the outer ring  40  is visible in both these figures. Outer bearing  60  is shown with a similar bearing  64  on another blade rising from the outer bearing riser  61 . Trowel blade  80  is shown in a rotated  95  orientation in  FIG. 5  and in a vertical orientation in  FIG. 6  where the head of the adjustment bolt  91  is shown in contact with the stop plate in  FIG. 6  and rotated  95  away from the stop plate in  FIG. 5 . The trowel support  81  support the trowel blade  80  and included the pivot for the bearing. An arm  90  extends from the blade support to provide a leaver arm for the trowel blade  80  and the trowel support  81 . 
         [0035]      FIG. 7  shows a lower isometric view of the trowel  20  showing the pivoting components on one trowel blade  82 . The input shaft is visible in this view. The outer ring  40  and the inner ring in shown with ribs  50  connecting between these two rings. The troweling blades  80 ,  82  and  84  are shown where blade  82  is attached to blade support  83 . This same blade is shown attached with outer bearing  62  in outer bearing riser  63 . Another outer bearing riser  61  and bearing  60  is visible on blade  80 . A portion of the stop plate  38  is shown through the inner ring  45 . Arm  92  is shown with bolt  93  in a rotated position where the head of the bolt is off the stop plate  38 . The bolt  93  is adjustable to limit or stop free rotation of the trowel blade  82 . The top cover  100  is shown extending over the ends of the troweling blade. The top cover is shown and described in more detail in  FIG. 8 . 
         [0036]      FIG. 8  is an isometric exploded view of the trowel with fixed blades and a protective cover  100 . The troweling blades  84  are secured to an angle block  66 . The angle block  66  maintains the angle of the blade(s) at a fixed relationship with the surface being smoothed. It is contemplated that the angle blocks are manufacturable at different angles based upon the smoothing needs. Each angle block  66  is secured to a trowel support  83 . The trowel support is pivotably connected on one end to the safety ring  40 , and at the other end to hub  96 . The trowel support has an arm  92  that is bent at an angle to allow for the pivotal movement and has a bearing pin  97  that fits into the complimentary hole in the hub  96 . The hub  96  threads into the central hub  32 . 
         [0037]    The cover  100  fits over the hub  32  where it can freely spin on the hub. The top cover drapes over the safety ring  40  and the troweling blades  84 . The cover ends  103  slightly above the bottom of the blades  80  to prevent to cover from marking the toweled surface. In operation when the cover makes contact with a surface outside of the troweling blades the cover stops moving while the blades continue to spin under the cover. Damage to the surface is prevented. The cover protects walls, and the user from accidentally coming in contact with the blades. The top cover has vents  102  that allow excess material to be pushed through the vents to prevent a build-up of material between the blades,  84 , safety ring  40  and the top cover  100 . The connection of the top cover to the central shaft is with a raised dome  101  that rests on a ring  34  extending from the hub. The ring provides a bearing surface and keeps the cover centered on the hub  32 . It is also contemplated that a bearing is usable on the top cover to make the top cover turn more easily, but prototypes have been made where the top cover turns on the hub without a separate bearing. The hub  96  and the nut  33  are configured with extended lobes to allow an operator to grasp assemble and disassemble the trowel without tools. The top of the hub  32  has an extended shaft  30  that allows the power trowel to be chucked in a portable drill. 
         [0038]    Thus, specific embodiments of a power trowel attachment for a drill have been disclosed. It should be apparent, however, to those skilled in the art that many more modifications besides those described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims.

Summary:
A drill attachment for smoothing the edges and corners of a concrete slab is disclosed. The drill attachment includes a shaft that is secured or chucked into an electric drill. Pluralities of troweling blades extend from the central shaft and are secured at their ends to maintain their position and orientation. The blades are secured to the trowel at variable or fixed angles that are changeable to suit the finishing need of the operator. In operation the drill attachment is used to smooth the ends and corners of a foundation where larger smoothing trowel machines have difficulty reaching. The power trowel is field installed and removed when needed for use, cleaning and storage. The drill attachment has an independently spinning blade cover extends over the ends of the blades to prevent damage to a wall or other surface when the trowel is in use.