Abstract:
A hand tool apparatus uses a cutting tool with a first width and a tool axis to machine a hole in an object. The hole has a second width at least as large as the first width of the cutting tool. The tool axis passes through a predetermined point on a surface of the object. The apparatus includes an actuating assembly including a housing. The housing contains an axial feed mechanism configured for moving the cutting tool in an axial direction, a spindle motor configured for rotating the cutting tool about the tool axis, and a radial offset mechanism. The radial offset mechanism is configured for moving the cutting tool such that the tool axis is offset from a principal axis. A motor is configured for rotating the axial feed mechanism and the cutting tool about the principal axis.

Description:
This is a continuation of application Ser. No. 09/388,419 now U.S. Pat. No. 6,382,890 filed Sep. 1, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a hand tool for cutting a hole in an object, and, more particularly, a hand tool for cutting a hole that has a larger diameter than the diameter of the cutting tool. 
     2. Description of the Related Art 
     U.S. Pat. No. 5,641,252 discloses a method for machining holes in a fiber reinforced composite material by using at least one cutting tool with wear resistant surface positioned eccentrically in relation to a central axis. The material is machined simultaneously in both an axial and a radial direction by causing the tool to move axially while rotating not only about its own axis, but also eccentrically about the central axis. In accordance with one particular characterizing feature of the invention, the workpiece is oriented in such a way that the axis of rotation of the tool is essentially orthogonal in relation to the longitudinal directions of the fibers in the immediate vicinity of the point where the tool meets the working surface. The diameter of the cutting tool is substantially smaller than the diameter of the hole that is produced. The eccentric rotary motion is generally a strictly rotary motion, i.e., it is executed with a constant distance between the central axis and the axis of rotation of the cutting tool. This distance between the central axis and the axis of rotation of the cutting tool can be increased by linear increments as the eccentric rotary motion continues. 
     This known method has a number of substantial advantages as compared with generally familiar techniques. For example, the method permits the production of holes without strength reducing damage. Also, the method permits the production of holes free from damage without having to preform a hole. Further, the method permits the production of holes to tight tolerances. The dimensional accuracy of the hole is determined substantially by the accuracy of the positioning of the tool relative to the central axis. The requirements imposed on the geometry of the cutting tool are not particularly high, on the other hand, since every individual tool is simply calibrated before use. Additionally, the method prevents the tool from becoming blocked. Since the diameter of the tool is substantially smaller than that of the hole, the method permits material removed by cutting to be carried away by simple means, such as with compressed air. The method also permits effective cooling of the tool and the edge of the hole. Yet another advantage is that the method substantially reduces the cost of wear compared to previously disclosed methods, due to the tool being coated with a wear resistant material, such as diamond coating. Moreover, this method also offers advantages when machining other materials such as metals. 
     U.S. patent application Ser. No. 09/092,467 discloses a spindle unit that includes a spindle motor that is rotatable about a principal axis. The spindle motor includes a tool holder having a tool axis substantially parallel to the principal axis. The tool holder is rotatable about the tool axis. An axial actuator is configured for moving the spindle motor in an axial feed direction substantially parallel to each of the principal axis and the tool axis. A radial actuator adjusts a radial distance between the principal axis and the tool axis. This spindle unit can be mounted in a stationary machine such as a CNC machine, robot or a simple rig. 
     PCT application PCT/SE94/00085 discloses a hand tool machine for machining holes according to the above described technique. This disclosure relates to a hand machine for making holes in an object made of composite fibers, preferably with a curved surface. The center axis of the hole passes through a predetermined point on the surface of the object and is oriented in a certain direction relative to the longitudinal direction of the fibers of the object which are close to the point. The machine includes, in combination, a tool holder rotating about its own axis and a principal axis, a device for adjusting the axis of rotation of the tool holder in the normal direction of the surface at the point, a device for axial feeding of the tool holder relative to the object, a device for adjusting the radial distance between the principal axis and the axis of rotation of the tool holder, and a device for taking up the forces and moments between the machine and the object that result from the making of the holes. 
     Although this aforementioned disclosure outlines some principles, the disclosed hand tool does not offer a feasible and practical solution. One obvious limitation is that the disclosed concepts do not present a solution for the power supply and therefore their potential for realization must be questioned. One basic requirement for a hand tool is light-weight and user friendliness. The disclosed concepts do not provide a compact integrated light-weight design. Furthermore, the illustrated concepts show solutions which require a very long tool overhang, which is a severe limitation due to the radial cutting force, which creates a bending moment on the cutting tool. 
     When machining holes according to the proposed method, i.e., by positioning the tool eccentrically in relation to a cental axis and machining simultaneously in both an axial and radial direction by causing the tool to move axially and to rotate not only about its own axis, but also eccentrically about a central axis, the tip of the tool is subjected to both an axial force and a radial force. The radial force creates bending moment on the tool, the magnitude of which is dependent on both the magnitude of the force and on the length of the tool overhang (moment arm). It is desirable to minimize the bending moment for optimal machining accuracy. This can be achieved by minimizing the tool overhang, i.e., the free length of the tool. The concepts illustrated in PCT/SE94/00085 show situations where the tool overhang is determined by the thickness of the hole template and by the thickness of the workpiece. Since the thickness of the template may be substantial, the tool overhang may be accordingly substantial. 
     SUMMARY OF THE INVENTION 
     The present invention provides a hand tool apparatus using a cutting tool to machine a hole in an object such that the hole has a width at least as large as the width of the cutting tool. The center line of the hole passes through a predetermined point on the surface of the object. Moreover, the present invention provides a compact and lightweight hand tool apparatus for machining holes in a flat or curved object of any material by rotating a cutting tool about its own axis and about a principal axis while simultaneously feeding in the axial direction. A lightweight and compact apparatus is achieved by integrating a radial offset mechanism, spindle motor and axial feed mechanism in a same actuating assembly package, which rotates about a principal axis. 
     The invention comprises, in one form thereof, a hand tool apparatus using a cutting tool with a first width and a tool axis to machine a hole in an object. The hole has a second width at least as large as the first width of the cutting tool. The tool axis passes through a predetermined point on a surface of the object. The apparatus includes an actuating assembly including a housing. The housing contains an axial feed mechanism configured for moving the cutting tool in an axial direction, a spindle motor configured for rotating the cutting tool about the tool axis, and a radial offset mechanism. The radial offset mechanism is configured for moving the actuating assembly in a radial direction such that the tool axis is offset from a principal axis. A motor is configured for rotating said actuating assembly about the principal axis. 
     An advantage of the present invention is that the hand tool is more lightweight and compact than the previous devices. 
     Another advantage is that the tool overhang is minimized, thereby reducing the bending moment on the cutting tool. 
     Yet another advantage is that the tool can be mounted into the tool holder from the rear, thereby allowing the tool holder to have a conical shape which minimizes the required diameter of the holes in the template. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a top, sectional view of one embodiment of a pneumatic portable drill of the present invention; 
     FIG. 2 is a top, sectional view of the tool assembly and a portion of the actuating assembly of the pneumatic portable drill of FIG. 1; 
     FIG. 3 is a rear, sectional view taken along line  3 — 3  in FIG. 1; 
     FIG. 4A is a side, sectional view of one embodiment of a template assembly of the portable drill of FIG. 1; 
     FIG. 4B is a rear view of the template assembly of FIG. 4A; 
     FIG. 5A is a side, sectional view of another embodiment of a template assembly of the pneumatic portable drill of FIG. 1; 
     FIG. 5B is a rear view of the template assembly of FIG. 5A; 
     FIG. 6 is a side view of the pneumatic portable drill of FIG. 1; 
     FIG. 7 is a rear view of the pneumatic portable drill of FIG. 1; 
     FIG. 8A is a schematic, sectional view, taken along line  3 — 3  of FIG. 1, of the relative positions of the tool, inner sleeve and outer sleeve; 
     FIG. 8B is a view similar to FIG. 8A, with the inner sleeve rotated 90° counterclockwise relative to its position in FIG. 8A; and 
     FIG. 8C is a view similar to FIG. 8A, with the inner sleeve rotated 180° counterclockwise relative to its position in FIG.  8 A. 
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrates one preferred embodiment of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings and particularly to FIG. 1, there is shown a hand tool apparatus in the form of a pneumatic portable drill  10  including an actuating assembly  12 , eccentric rotation mechanism  14 , tool assembly  16 , template assembly  18 , axial positioning mechanism  20  (FIG.  6 ), stroke adjustment mechanism  22  and an axial feed mechanism  24 . 
     Actuating assembly  12  includes a spindle motor  26 , and a radial offset mechanism  28  (FIG.  3 ), all contained within a single housing  29 . Radial offset mechanism  28  includes a concentric cylindrical inner sleeve  30  positioned in a concentric cylindrical outer sleeve  32 . Inner sleeve  30  and outer sleeve  32  are rotatable relative to each other. An axle or shaft  34  of spindle motor  26  extends through a clutch  36  and is rotatably mounted in inner sleeve  30 . 
     Eccentric rotation mechanism  14  includes a motor  38  for rotating actuating assembly  12  and thereby tool assembly  16  about a principal axis  40 . 
     Template assembly  18  includes a sleeve  42  (FIG. 4A) with a flange  44  which is in contact with the surface of a work piece  46 . A center axis  48  of sleeve  42  is oriented substantially perpendicular to the surface of work piece  46 . Sleeve  42  and flange  44  are fastened to a template  50  by bolted joints  52 . Tool assembly  16  is locked onto sleeve  42  by use of a bayonet socket  54 , whereby the axis of rotation of drill  10  are oriented substantially perpendicular to the surface of work piece  46 . 
     In another embodiment, a sleeve  56  (FIG. 5A) is also oriented in the hole in template  50  such that axis of rotation  48  of sleeve  56  is substantially perpendicular to the surface of work piece  46 . Sleeve  56  can be fixed to template  50  by use of a threaded joint, frictional joint or adhesive joint. Portable drill  10  is then locked onto sleeve  56  by use of a bayonet socket  54 , as shown in FIG. 1, whereby the axes of rotation are oriented substantially perpendicular to the surface of work piece  46 . 
     Tool assembly  16  includes a cutting tool  58 , a tool holder  60  and a screw  62 . To minimize the tool overhang, template  50  is designed such that tool holder  60  can be fed through the holes in template  50 . In such case, it is desired that tool holder  60  have a small outer diameter, since in many situations it is required to machine multiple holes in work piece  46  with relatively short spacing distances between the holes. In order to accommodate all holes, the holes in template  50  can not be made arbitrarily large to make room for tool holder  60 . Therefore, it is desirable for tool holder  60  to require as little space as possible. This is made possible by tool holder  60  and cutting tool  58  being provided with conical surfaces. Cutting tool  58  is mounted in tool holder  60  from the rear end and then tightened by screw  62  inside tool holder  60 . By this concept, it is possible to obtain a space saving solution which allows the feeding of tool holder  60  through the holes in template  50  without requiring that the template holes be too large. 
     Although the aforementioned tool holder concept offers a space saving advantage, which allows feeding of tool holder  60  through template  50  without requiring very large holes in template  50 , the spacing between the holes in work piece  46  may still be too small for the embodiment of FIGS. 1 and 5. In such case, drill  10  is locked to an alternative fixing device (FIG. 4B) which is fixed in template  50  by two screws  52  in two holes located a distance away from the main hole. Thus the holes in template  50  may be integrated, as in FIG. 4B, which is suitable in a case where the spacing between the holes in template  50  is small. 
     Axial positioning mechanism  20  includes a threaded ring  64  and a scale  66 . It is desirable to roughly position the tip of cutting tool  58  a certain distance from work piece  46  as shown in FIG.  1 . This is achieved by threaded ring  64  and is made possible in that housing  29  of portable drill  10  is separated at ring  64  into a front portion  65  and a rear portion  67 . By turning ring  64 , front portion  65  of drill housing  29  moves forward or backward, which movement is indicated by scale  66 . 
     Stroke adjustment mechanism  22  includes a ring  68  (FIG.  7 ), a rod  70 , a lock screw  72 , a projection  74 , an arm or latch  76  and a return mechanism  78 . The stroke length of the machining operation is adjusted by mechanism  22 . Ring  68  is rotatably attached to the drill housing. On ring  68  is fastened a rod  70 . Rod  70  is provided with a slot (not shown) such that its axial position is adjustable. The desired position is fixed by lock screw  72 . Projection  74 , fixedly attached to rod  70 , contacts arm  76  of return mechanism  78  and thereby forces drill  10  to make a return stroke after the contact. 
     In operation, axial feed mechanism  24  moves actuating assembly  12 , and thereby cutting tool  58  in an axial feed direction, and spindle motor  26  rotates cutting tool  58  about its own axis  80 . Motor  38  rotates actuating assembly  12  and thereby cutting tool  58  about principle axis  40 . 
     An axial feed motion directed towards work piece  46  is provided by supplying compressed air in a circumferential cavity  82 . As actuating assembly  12  moves forward it forces oil, stored in another circumferential cavity  84 , to flow through a radial hole  86  via an axial hole  88 , another radial hole  90 , and hole  92  into space  94  of cylinder  96 , which contains oil. A piston  98  then moves to the right in FIG. 1 in order to allow for the volume increase. Thus provided is a hydraulicly damped axial movement. 
     The speed of the axial movement can be controlled by adjusting the position of a needle  100  in relation to hole  92 . An axial feed motion directed away from work piece  46  (return stroke) is achieved by supplying compressed air into space  102 , which contains air via a channel  104 . The pressure increase in cylinder  96  due to the return stroke causes a valve  106  to open and oil to flow back into cavity  84  and thereby create a pressure increase, which causes actuating assembly  12  to move away from work piece  46 . This design allows for a faster return stroke as compared to the forward feeding movement. 
     Air is supplied to spindle motor  26  through openings  108  in the wall element of outer sleeve  32  of actuating assembly  12 . The air then flows in channel  110  to the rear end of spindle motor  26  and then through spindle motor  26  to cause rotation of shaft  34 . The return flow is then directed through outlet  112  out to the open air. Outlet  112  rotates eccentrically in relation to the center axis of spindle motor  26 . At the rear end is arranged a sealing  114  and an end piece  116  for reducing the sound level. 
     Outer sleeve  32  is turnable or rotatable relative to inner sleeve  30 , and thereby the axis of rotation  80  of cutting tool  58  and principal axis  40  can be varied from zero (FIG. 8A) to a maximum value (FIG. 8C) by a relative rotation of 180° between the two sleeves  30 ,  32 . FIG. 8A shows a case where a 12 millimeter tool  58  is in zero offset position. FIG. 8C shows a case where tool  58  is in its maximum radial offset position, i.e., tool  58  is offset two millimeters in order to machine a 16 millimeter hole. 
     The relative movement between sleeves  30 ,  32  is achieved by turning a screw  118  (FIG.  3 ). A stop screw  120  locks sleeves  30  and  32  in a desired position. In order to adjust the offset, front portion  65  of housing  29  is removed by unlocking a tightening ring  122 . 
     In order to rotate actuating assembly  12  and thereby cutting tool  58  about a principal axis  40 , gear wheels  124 ,  126  transfer the rotation of motor  38  to actuating assembly  12 . Since tool holder  60  is connected to inner sleeve  30  of actuating assembly  12 , tool holder  60  and cutting tool  58  are forced into a rotation about principal axis  40 . 
     Air is supplied through an opening  128 . The speed of motor  38  is controlled by adjusting a needle  130  in opening  128 . The outlet of the air supplied to motor  38  is not shown. 
     While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.