Abstract:
A depth limiting device for a boring tool having stop collar includes housing and a sleeve. The housing provides snap on attachment onto the stop collar, allowing for a free axial rotation of the said housing around the body of the stop collar. The housing and the sleeve have a threaded engagement for adjusting position relative to one another and thereby adjusting length of the working portion of boring tool. Coupled housing and sleeve are freely rotatable with respect to the body of the stop collar and cease to rotate when operator achieves desirable depth of drilling and the device is pressed against the work-piece surface. The structural interrelationship prevents marring of the surface of the work-piece.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of provisional patent application Ser. No. 61/396,768, filed 2010 Jun. 2 by the present inventor. 
    
    
     FEDERALLY SPONSORED RESEARCH 
     Not Applicable 
     SEQUENCE LISTING OR PROGRAM 
     Not Applicable 
     BACKGROUND 
     1. Field 
     This application relates to devices for controlling depth of penetration of rotary cutting tools into the work-piece in a manner that avoids any marring or damage to work-piece surface. 
     2. Prior Art 
     Depth limiting devices for rotary cutting tool, particularly for drill bits and countersink tools, having contacting structures providing free rotation relative to rotary cutting tool are known in the art. 
     U.S. Pat. No. 5,795,110 describes a drill stop collar having an independently rotatable plastic cap covering lower end of the stop collar. A device is selectively mounted along the drill bit at a position that limits the depth of penetration of the rotary cutting tool into the work-piece below then predetermined depth. A cap ceases to rotate when basically flat surface of the contacting portion of the cap comes into contact with work-piece and prevents surface of the work-piece from being marred. 
     U.S. Pat. No. 7,258,513 discloses a depth limiting device which includes a spindle and stop sleeve that is in the form of a cylindrical shell having a first end with opening and a contacting portion extending along the periphery of the opening in the direction of working section of the drill bit. A spindle extending axially through the stop sleeve includes a first end for attaching to a drilling machine, and a second end integrally formed as countersink tool with central bore for receiving and selectively fixing therein the drill bit, thereby providing adjustment of depth of penetration into the work-piece by the drill bit. Second end of the stop sleeve is permanently fixed on spindle in longitudinal position and freely axially rotates around the spindle and ceases to rotate when it contacts the work-piece without marring or otherwise damaging the work-piece. A stop sleeve which serves as abutment, limits further then predetermined penetration of the countersink tool and drill bit into the work-piece. Internal space of the stop sleeve communicates with opening, allowing debris to be inside the stop sleeve and reducing the presence of debris between contacting portion of stop sleeve and work-piece, thereby providing the accuracy of drilling. In addition, adjustment of penetration of the countersink tool into the work-piece provided by attachable to the contacting portion of stop sleeve of depth-adjusting members with varying thicknesses. 
     DE Pat. No. 10154434 describes a stop device having spindle with axial bore for receiving and longitudinally adjusting the drill bit and stop sleeve, which freely rotates with respect to spindle. Countersink tool which is a separate part of the device, has central aperture or bore for receiving the drill bit therein. Countersink tool can be slid along the drill bit to the required position and be secured by set screw. Thereby device provides depth adjustment for the drill bit and also for the countersink tool. However, if operator adjusts depth of penetration of the drill bit, as result it will further be necessary to readjust the countersink tool, since the letter is attached to the drill bit. 
     EP2093001 discloses device with a spindle including a first end for attaching to a drilling machine, and a second end integrally formed as a countersink tool with central bore for receiving and selectively fixing therein the drill bit thereby providing adjustment of the depth of penetration into the work-piece by drill bit. The spindle includes an external threaded portion for threaded engagement with a hollow elongated cylindrical member to which in turn rotatably attached is the stop sleeve. The operator screws the cylindrical member in or out relative to the spindle and cylindrical member coupled with stop sleeve axially moves relative to spindle, thereby exposing desirable distance between cutting edges of the countersink tool and contacting portion of the stop sleeve. When predetermined position is attained, cylindrical member is secured relative to spindle by set screw which extends through the body of cylindrical member to engage the spindle. Such design of the depth limiting device allows an operator to adjust the depth of penetration of the drill bit without disturbing the position of the countersink tool relative to stop sleeve. 
     It can be seen that U.S. Pat. No. 7,258,513, DE10154434 and EP2093001 include intermediate member such as a spindle having central bore, which correspondingly fits certain diameter of the drill bit and for a range of diameters of drill bits will be necessary a range of suitable devices. Moreover, spindles are preferably composed of metal, which requires different types of metalworking processes. Everything aforementioned ads complexity and increase the cost to manufacture the devices. 
     SUMMARY 
     The invention is related to devices for control and adjusts the depth of bore of the rotary cutting tool in a way that avoids any marring or damage the work-piece surface. According to present invention, rotatable tool-bit stop device provides quick tool-less attaching to such conventional units as stop collars with drill bits and countersink tools with drill bits, as well as to any rotatable tool-bit with suitable collar like formation and converts ordinary countersink tool or stop collar to an instrument with new properties. However, countersink tools themselves either stop collars or drill bits do not form a part of this invention. 
     First embodiment of present invention is formed as a single piece and includes housing having portal for receiving and releasably detaining therein stop collars or the like, and also integrally formed sleeve for engaging with the work-piece. Exposed out of the sleeve portion of the rotary cutting tool is defined depth of penetration into work-piece, which can be adjusted by sliding conventional stop collar or the like along body of rotary cutting tool and fixing it at a selected position. Depth limiting device freely rotates around the therein detained stop collar or the like and correspondingly around the axis of rotation of the drill bit. In process of drilling, when predetermined depth of penetration is achieved, device is pressed against the work-piece and ceases to rotate, preventing work-piece from being marred. 
     In accordance with the second embodiment of present invention, depth limiting device comprises housing and a sleeve, formed as single unitary pieces. Housing has a portal for receiving and releasably detaining therein stop collars or the like, which are coupled with a rotary cutting tool. Housing and sleeve have threaded engagement. Screwing housing in and out relative to sleeve operator can correspondingly expose out of lower end of the sleeve more or less length of rotary cutting tool, thereby providing fine adjustment to the desired depth of penetration in to the work-piece. For preventing unintended rotation of the sleeve relative to housing the device provides tool-less locking mechanism. However, locked relative to one another housing and sleeve are enabled to freely rotate with respect to the body of the stop collar. Device ceases to rotate when it contacts with work-piece, while rotary cutting tool continues spinning. This prevents work-piece surface from being marred or scratched. 
     Device can be snapped off of the rotary tool assembly in the direction of tool tip and then same device can be immediately snapped on to any other suitable rotary tool assembly, thereby providing convenience and flexibility of using a device for different application. 
    
    
     
       DRAWINGS—FIGURES 
         FIG. 1  is a perspective view partially in section of the first embodiment of the device with the stop collar and the drill bit. 
         FIG. 2  is an exploded longitudinal sectional view of  FIG. 1 . 
         FIG. 3  is a longitudinal sectional view of the device showing the drill bit and the stop collar installed and engaging spring arms with stop collar. 
         FIG. 4  is a longitudinal sectional view of the device with stop collar and screwdriver bit. 
         FIG. 5  is a perspective view of second embodiment of the device with adjustable sleeve with countersink tool and drill bit. 
         FIG. 6  is an exploded view of  FIG. 5   
         FIG. 7  is a longitudinal sectional perspective view of the housing. 
         FIG. 8  is an elevation view of the device showing external surface of the flange and sleeve with the knurls. 
         FIG. 9  is a top view of the device showing disengaged pawl and ratchet teeth and showing user&#39;s finger in phantom illustrating use thereof. 
         FIG. 10  is a longitudinal sectional view of the device. 
         FIG. 11  is a longitudinal sectional view of the device showing tool-bit assembly installed into the device. 
         FIG. 12  is a longitudinal sectional view of the device with tool-bit assembly. 
         FIG. 13A  and  FIG. 13B  illustrates different depths of penetration of the countersink and the drill bit into the work-piece. 
         FIG. 14  shows device attached to another type of countersink tool with stop collar. 
         FIG. 15  shows device attached to the conventional stop collar with drill bit. 
         FIG. 16  shows device attached to the conventional stop collar with screwdriver bit. 
     
    
    
     DETAILED DESCRIPTION 
     According to the first embodiment of present invention  FIG. 1  illustrates the elevation view of the Depth limiting device for a boring tool releasably mounted on a rotary cutting tool assembly, the latter comprised of the conventional drill bit  30  and also conventional stop collar  32 . Device is preferably formed as one piece body molded from plastic and includes sleeve  34  and housing  36 . Circumferential sidewall  38  of the sleeve  34  projects downward from the radial end of the external annular ridge  40 , which substantially extends outward from lower external portion of the housing  36 . Outermost lower end of the sleeve  34  comprises work-piece contacting portion  42  that contacts the surface of the work-piece. Housing  36  is radially interspaced by slits  44  forming axially oriented plurality of spring arms  46 . Inner surface of the free upper end of the arms  46  are provided with inwardly extended detents  48  in vicinity of the portal  50  of the housing  36 . Lower internal portion of the housing  36  contains integrally formed annular shoulder  52  ( FIGS. 1 ,  2  and  3 ) with central aperture  54 . 
     While the arms  46  are in a normal position ( FIG. 1 ) the distance between inwardly extending outermost edges of detents  48  (from apex to apex) is substantially smaller than outer diameter of the stop collar  32  and when stop collar  32 , for example, coupled with drill bit  30  is introduced into portal  50  of the housing  36 , detents  48  come to rest against lower outer surface of the stop collar  32  and spring arms  46  are deflected outwardly ( FIG. 3 ). As drill bit  30  is continued to be pushed downward, housing  36  snaps on over the body of stop collar  32  by means of detents  48  due to the spring returning force of the arms  46 . Further advance of the drill bit  30  into the housing  36  is limited by end face  56  of the stop collar  32  when end face  56  comes in contact with the internal surface of the annular shoulder  52 . At the same time working portion  58  ( FIG. 3 ) of the drill bit  30  is protruded through aperture  54  and further exposed out of work-piece contacting portion  42  of the sleeve  34 . Distance between tip of the drill bit  30  and work-piece contacting portion  42  of the sleeve  34  defines depth of penetration of the drill bit into work-piece. Said depth can be adjusted by sliding stop collar  32 , and correspondingly the device along the body of the drill bit  30 , and fixing at a selected position by set screw  60 . 
     According to present invention, device snaps on over the body of stop collar  32  in a loose-fitting condition and provides ability of free rotation of the device with respect to the body of the stop collar  32  about an axis of rotation of the drill bit  30 . At the end of the process of drilling when the operator has achieved desirable depth of drilling and contacting portion  42  of the sleeve  34  is pressed against the work-piece surface, the device ceases to rotate, preventing the work-piece from being marred. The aforementioned is attained by using plastic with low coefficient of friction for device, and additionally by difference between the outer radius R 1  ( FIG. 2 ) of end face  56  and the external radius R 2  of contacting portion  42 , wherein the latter is substantially larger. Therefore the frictional force required for the immediate stoppage of rotation of the device is substantially less. The stop collar  32  coupled with drill bit  30  may continue to rotate, for instance, by inertia. 
     As shown in  FIGS. 1 ,  2  and  3  the sleeve  34  can be provided with a series of openings  62  to allow debris, generated in the process of drilling, to be discharged from the cutting area. Otherwise, debris tend to be clogged inside said space of the sleeve  34  which can cause inaccurate drilling and interference with the free rotation of the device around the body of stop collar  32 . Such interference can cause the sleeve  32  to mar the surface of the work-piece. 
     The same design of the device can be snapped onto different types of tools, including but not limited to conventional screwdriver bit  64  of a power tool ( FIG. 4 ). With the device snapped on to the screwdriver bit ( FIG. 4 ) operator is enabled to adjust the depth of penetration of the screw into work-piece. During the screwing operation, contacting portion  42  of the sleeve  34  contacts the surface of the work-piece and interrupts transmission of torque from screwdriver bit  64  to the screw (not shown) at predetermined final depth. 
     According to the second embodiment of the invention,  FIG. 5  shows perspective view of the, depth limiting device for a boring tool having housing  66  and adjustable sleeve  68 , each of which is made as a single piece, preferably by molding from plastic. However, they can also be produced by different methods and from a variety of materials. In this embodiment, the device is releasably mounted, for example, on a rotary cutting tool assembly which is comprised of conventional drill bit  30  and countersink tool  70  ( FIG. 6 ). 
     In this embodiment the housing  66  is designed as an elongated cylindrical body with internal circumferential sidewall  72  having a plurality of spring arms  74  oriented axially, and radially interspaced. Each one of the arms  74  has a free end with detents  76  in vicinity of the portal  78  of the housing  66 . Body of the arms  74  ( FIGS. 7 and 10 ) is formed by separation from internal sidewall  72  by the side slits  80  and by cutout  82  which connects with side slits  80  and forms the outer or back side  84  of the arms  74  over the whole length of the arms  74 . Spacing of the cutouts  82  in radial direction is such that outward deflection of the arms  74  provides positioning of furthermost inwardly extended portions of detents  76  ( FIG. 16 ) from central axis at the same radial distance as the internal surface of the circumferential sidewall  72 . 
     Outer cylindrical surface of housing  66  has external thread  86  and a plurality of longitudinal ratchet teeth  88  ( FIGS. 5 ,  6 ,  7  and  9 ) which are equally interspaced around the housing  66 . Ratchet teeth  88  are formed by retention surface  104  which is aligned approximately radially from the central axis of the housing  66  and by ramp surface  92 , which is aligned approximately tangentially with the outer cylindrical surface of the housing  66 . However, the alignments, or shape and number of the teeth can vary. Internal lower portion of the housing  66  provides annular shoulder  94  and central aperture  96  ( FIGS. 7 ,  9  and  10 ) through which working portion  98  ( FIGS. 6 ,  11 ) of the countersink tool  70  can be exposed. According to present invention, adjustable sleeve  68  provides internal thread  100  ( FIG. 6 ) for engagement with the thread  86  of the housing  66  ( FIGS. 5 ,  6  and  11 ) whose outer upper end may be comprised of outwardly extending flange  102 . 
       FIG. 6  shows a conventional drill bit  30 , which can be inserted into central bore  104  of the conventional countersink tool  70  and then the latter can be slid along the drill bit  30  to the desired position and be secured by set screw  106  which extends through the mounting portion  108  of the countersink tool  70  to engage the drill bit  30 . The aforesaid technique is designed to achieve varying depths of penetration of the drill bit below the countersink, examples of which are shown in  FIGS. 13A and 13B  as A and B accordingly. 
     Further the rotary cutting tool assembly, which includes drill bit  30  and countersink tool  70 , can be releasably coupled with depth limiting device for a boring tool by insertion of aforementioned tool assembly into housing  66  through the portal  78  ( FIG. 11 ). While the arms  74  are in a normal position ( FIGS. 7 and 12 ) the distance between inwardly extending outermost edges of detents  76  (from apex to apex) is substantially smaller then the diameter of the mounting portion  108  of the countersink tool  70  and when mounting portion  108  of countersink tool  70  coacts with detents  76 , the arms  74  are deflected outwardly ( FIG. 11 ). As rotary cutting tool or the like is continued to be pushed downward, the detents  76  slide over the body of the mounting portion  108  and then the latter is captured by detents  76  due to the spring returning force of the arms  74 . At the same time, working portion of the countersink  98  is protruded through aperture  96  ( FIG. 12 ). However, further advance of the rotary cutting tool into housing  66  is limited by end face  110  of the mounting portion  108  when end face  110  comes in contact with internal surface of the annular shoulder  94 . 
     Detained inside housing  66 , mounting portion  108  of the countersink tool  70  has a loose-fitting relationship in all directions and provides the ability of free rotation of housing  66  coupled with the adjustable sleeve  68  with respect to the body of mounting portion  108  of the countersink tool  70  about an axis of rotation of the aforesaid tool. At the end of the process of drilling, while rotary cutting tool continues to rotate and when operator has achieved a desirable depth of drilling, and correspondingly contacting portion  112  of the adjustable sleeve  68  is pressed against the work-piece, adjustable sleeve  68  and housing  66  coupled by threaded engagement, cease to rotate, preventing work-piece from being marred or being otherwise damaged. However, frictional engagement between annular shoulder  94  and the end face  110  of mounting portion of countersink tool  70  intends to rotate housing  66  relative to the adjustable sleeve  68  in a clockwise direction when using the right hand drill bit, which can cause an unintended change in the preselected depth of drilling. To prevent the rotation of housing  66  relative to adjustable stop sleeve  68 , upper portion of the adjustable stop sleeve  68  possesses an integrally formed spring appendage  114  ( FIGS. 5 ,  6  and  9 ) with a wedge-shaped pawl  116  which has a locking engagement with ratchet teeth  88  of the housing  68 . To adjust depth of the countersink—to decrease the depth, for example—operator unscrews housing  66  in counterclockwise direction and adjustable sleeve  68  axially moves downward relative to housing  66 , while the planar slanted surface  118  of the pawl  116  slides easily over the ramps  92  and over the tops of ratchet teeth  88 . When desired position is achieved, pawl  116  by spring force of the appendage  114  protrudes into recess between teeth  88  and locks the clockwise direction of rotation of the housing  66  relative to the adjustable stop sleeve  68  by engagement of securing ridge  120  of the pawl  116  and retention surface  90  of one of the ratchet teeth  88 . Depth of the countersink is defined as a distance between contacting portion  112  of the stop sleeve  68  and lowest portion of cutting edges  122  of the countersink tool  70 .  FIG. 13A  illustrates depth of the countersink (C) bored into the work-piece  124  to an approximate depth required for installation of a screw head  125  flush with the work-piece surface. 
     For increasing the depth of the countersink, the operator disengages securing ridge  120  of the pawl  116  and the retention surface  90  of ratchet teeth  88  by deflecting outwardly spring appendage  114  ( FIG. 9 ) and turning housing  66  in a clockwise direction. When desired position is achieved, the operator frees appendage  114  and pawl  116  returns to a locking cooperation with ratchet teeth  88 .  FIG. 13B  shows increasing depth of the countersink into the work-piece (shown as D). 
     The outer peripheral edge of the flange  102  and external surface  128  of the adjustable sleeve  68  may be knurled ( FIG. 8 ) or may a different geometrical shape for better assistance to the operator in gripping and turning housing  66  and adjustable sleeve  68  relative to one another. In addition, lower portion of the adjustable sleeve  68  can be provided with a series of radial openings  130  to allow debris to be discharged from the cutting area. 
       FIGS. 14 ,  15  and  16  show that the device can be attached to conventional stop collars  32  with different types of tools such as countersink tool  134  ( FIG. 14 ), drill bit  30  ( FIG. 15 ) and screwdriver bit  64  ( FIG. 16 ). According to present invention, tool-less fine depth adjustment can be provided by rotating the adjustable sleeve  68  relative to housing  66  and consequently changing axial distance between, for example, tip of drill bit  30  and contacting portion  122  of the adjustable sleeve  68 . 
     All embodiments of the devise can be snapped off of the rotary tool assembly in direction of the tool tip and then the same device as described above can be immediately snapped on to any other suitable rotary tool assembly, thereby providing convenience and flexibility of using the device for various applications. 
     It is apparent that the preferred embodiments described hereinabove are given by example only and that a person skilled in the art could make changes and modifications without departing from spirit and scope of the present invention as defined in the appended claims.