Patent Abstract:
A ferrule for coupling an attachment to a rotary hand tool unit of the type that has a housing with a nose portion through which a rotary output shaft extends. The nose portion has at least one groove extending generally circumferentially around at least a part of the nose portion, so that a groove portion is located on opposite sides of the nose portion. The ferrule includes a generally hollow cylindrical body with interior and exterior surfaces with an open mounting end portion and a smaller opposite end portion to which the attachment is mounted. The open mounting end portion fits on the nose portion of the housing when the ferrule is coupled to the rotary hand tool. The ferrule further includes at least one internally protruding rib on the interior surface for aligning the ferrule in at least one predetermined angular position, and at least two latches mounted on the ferrule, with each latch having an open and a closed position wherein the ferrule is locked into the nose portion when the latch is in the closed position.

Full Description:
BACKGROUND OF THE INVENTION 
     The present invention generally relates to an apparatus for coupling attachments to tools and the like, and more particularly to a ferrule for coupling an accessory attachment to a rotary hand tool 
     There has been continued innovation and improvement in the design of power tools, particularly rotary hand tool units of the type that are used in woodworking, metal working and the like. Examples of such products are those made under the Dremel brand by the S-B Power Tool Corporation of Chicago, Ill., which also produces many accessory attachments for such rotary hand tool units. The rotary hand tool units are generally cylindrical in shape and contain a motor with a rotary output shaft that is adapted to drive the various rotary tool bits, such as small saw blades, sander discs, grout removal tool bits and various other cutting tool bits. There are also may accessory attachments that can be used in association with the rotary hand tool units, with the accessory attachments being connected to the stationary nose end portion of the rotary hand tool unit. Among such accessory attachments is a flexible shaft attachment that conveniently allows the user to operate the various rotary tool bits around corners or in other remote areas of operation. Also useful are grout removing tool guides that conveniently position the grout removing bit relative to the tool guide so that a user can conveniently and effectively remove grout from between individual floor and wall ceramic tiles, for example. As a further example, a depth guide is a desirable accessory attachment that can be used with many types of cutting tools to limit the depth of penetration of the tool into a work piece or work surface. 
     While such accessory attachments have been available for many years, the manner in which the accessory attachments are coupled to the tool has been the subject of continuing efforts to provide a simple and effective mechanism for coupling or mounting the accessory attachments to the hand tool itself. In this regard, the necessity of tightening holding screws or utilizing multiple turns of a threaded coupling mechanism for coupling the accessory attachment to the rotary hand tool, while effective, are not considered to be particularly simple and convenient in many past designs. 
     SUMMARY OF THE INVENTION 
     The present invention is related to a particularly simple, elegant and convenient coupling apparatus for attaching an accessory attachment to a rotary hand tool unit of the type that has a housing with a nose portion through which a rotary output shaft extends. The present invention enables a coupling apparatus to be placed on the nose portion in a predetermined position and secured into locking position by a pair of hinged latch members. An accessory attachment can subsequently be attached to the other end of the coupling apparatus, which then serves to couple the accessory attachment to the rotary hand tool unit. 
     More particularly, the coupling apparatus includes a ferrule that is provided with inwardly protruding ribs or protrusions on opposite sides of the inside of the ferrule, where the ribs engage a pair of outwardly extended elongated arcuate teeth located on the nose portion of the rotary hand tool unit. In this type of hand tool unit, which is adapted to receive another type of attachment mechanism that can be engaged and releases with only a quarter turn of rotation on a pair of teeth, each of the teeth extends approximately 90° to 100° of the circumference of the cylindrical nose portion and is curved in the axial direction so that the center of the tooth is moved in the axial direction rearwardly or away from the end of the nose end portion. The teeth form a groove portion that extends generally circumferentially around at least a part of the nose portion so that the groove portion is located on opposite sides of the nose portion, coextensive with the elongated arcuate teeth on the nose portion. The preferred embodiment of the present invention has two latch members which are also configured and arranged on the circumference of the ferrule to oppose one another, and each latch member includes an engagement protrusion for engaging the groove portion of the nose portion, and also include a locking protrusion to engage a locking flange located on the external circumference of the ferrule. 
     Thus, during operation, when the coupling apparatus is slipped onto the nose portion of the hand tool unit, the inwardly protruding ribs align with and engage the elongated arcuate teeth to ensure proper alignment of the accessory attachment with the nose portion. As the latch members are locked into the closed position, the engagement protrusion engages the groove portion of the nose portion. The latch members are finally locked into place by snapping the locking protrusion into the locking flange of the ferrule. The ferrule is also configured so that the latch members, when in the locked position, can be pulled upward into the open position with force enough to overcome the frictional engagement of the locking protrusion and the locking flange, subsequently making the attachment easily releasable by simply pulling the attachment from the nose portion with relatively modest force. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevational view of the coupling apparatus of the preferred embodiment having one of the pair of parallel vertical flanges removed, illustrated with a rotary tool unit and a flexible shaft attachment coupled thereto. 
     FIG. 2 is a top view of the coupling apparatus illustrated in FIG.  1 . 
     FIG. 3 is an exploded sectional view of the coupling apparatus illustrated in FIG. 1, taken along the  3 — 3  line of FIG.  2 . 
     FIG. 4 is a sectional view of the coupling apparatus illustrated in FIG. 1 taken along the  3 — 3  line of FIG.  2 . 
     FIG. 5 is an elevational view of the coupling apparatus illustrated in FIG.  1 . 
     FIG. 6 is a top perspective view of the coupling apparatus illustrated in FIG.  1 . 
     FIG. 7 is a side perspective view of the coupling apparatus illustrated in FIG.  1 . 
     FIG. 8 is a perspective view of the latch member of the coupling apparatus illustrated in FIG.  1 . 
     FIG. 9 is a perspective view of the stop plug apparatus used in connection with the coupling apparatus of the instant invention. 
     FIG. 10 is an elevational view of the stop plug apparatus of FIG.  9 . 
     FIG. 11 is a perspective view of the drive cap used in connection with the coupling apparatus of the instant invention. 
     FIG. 12 is a sectional view of the drive cap of FIG. 11 taken along the  12 — 12  line. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The preferred embodiment of the coupling apparatus of the present invention is shown in the FIGS. 1 through 5, where a rotary hand tool is indicated generally at  10  and is shown in conjunction with a flexible shaft attachment indicated generally at  12 . The rotary hand tool unit  10  has a nose end portion indicated generally at  14  and a rotary output shaft  16  which is illustrated in FIG.  4  and intended to be attachable to a working tool bit such as a small circular saw blade, a cutting bit, or the like. The ferrule of the coupling apparatus is designated generally as  18 . 
     The hand tool unit  10  has a housing with a motor and a drive shaft, which are not shown in the drawings. As best shown in FIG. 5, the nose portion  14  is formed with the housing and includes both an enlarged diameter portion  20  and a cylindrical shaped portion  22 . The cylindrical shaped portion  22  is configured forwardly of the enlarged diameter portion  20 , and the cylindrical shaped portion contains a pair of outwardly extending elongated teeth  24 , each of which is curved in the axial direction so that the middle portion is more rearwardly positioned from the end of the nose portion  14  than either of the ends of the teeth. Each of the teeth  24  are diametrically opposite one another on the circumference of the cylindrical shaped portion  22 . Each of the teeth  20  extends around the periphery of the cylindrical shaped portion  22  approximately 90° although it may extend to 120° or more if desired. 
     The adjacent ends of the teeth  24  are separated by a distance sufficient to allow internally protruding ribs  26  on the coupling apparatus to pass beyond the ends of the teeth when the coupling apparatus is being coupled to the rotary hand tool unit  10 . As best illustrated in FIGS. 1 and 5, each of the elongated teeth  24  terminate at their ends in an alignment portion  28 , which is flared planar surface that slopes to a reduced height measured from the surface of the cylindrical shaped portion  22  when compared to the height of the teeth portion measured from the surface of the cylindrical shaped portion. 
     The interface between the enlarged diameter portion and the cylindrical portion form an annular shoulder  30 , and the distance between the shoulder and any correspondent axially oriented portion of the teeth  24  is substantially constant as best shown in FIGS. 1 and 5. The area defined by this distance forms a pair of convex groove portions  32  that are coextensive with the pair of outwardly extending elongated teeth  24 . Like the elongated teeth  24 , the groove portions  32  are diametrically opposed to one another on the cylindrical shaped portion  22 , and are curved in the axial direction so that the middle portion is more rearward positioned form the end of the nose portion  14  than either of the ends of the teeth. 
     Ordinarily, working tools are mounted to the rotary hand tool unit  10  by a collet and a collet nut (not shown in the drawings), which are coupled to the output shaft  16  of the rotary tool unit. The rotary tool unit  10  applies rotational torque to various working tools and the rotary output shaft  16  includes an open end portion  34  having a threaded outer circumference  36 . From its open end portion  34  toward the rotary tool unit, the rotary output shaft  16  has a predetermined interior depth and an inner circumference that gradually narrows, and is configured to matingly receive a collet, which has a circumference that is slightly larger than the narrowest portion of the inner circumference of the rotary output shaft. In this way, the collet is prevented from sliding into the predetermined interior depth of the rotary output shaft by the narrowing inner circumference of the rotary output shaft. The collet is held in place by a threaded collet nut, which threadedly engages the threaded outer circumference of the rotary output shaft. 
     The protruding end of the collet ordinarily includes an aperture surrounded by a plurality of spring-biased fingers, which operate to retain corresponding working tools inserted therein. Since the working tools, such as small saw blades and cutting bits, have base ends having a circumference that is much smaller than the open end of the open end portion of the output shaft, the spring-biased fingers of the collet prevent slippage or sliding of the base end the working tool into the output shaft. Thus, by using a collet and collet nut in combination with any number of rotary hand tool bits having shanks, various working tool bits may be inserted into and used with the rotary hand tool. However, when a rotary hand tool unit  10  is coupled to an accessory attachment, such as a flexible shaft attachment  12 , via the coupling device  18  of the instant invention, the collet and collet nut are removed so that the output shaft  16  can be mechanically coupled to the flexible shaft attachment, as will be described. 
     Turning now to FIGS. 1 through 5, which illustrate the coupling apparatus  18  coupled to a flexible shaft attachment  12 , the coupling apparatus comprises a mounting portion or ferrule having a generally hollow cylindrical body with an internal surface and an external surface. An open mounting end portion  38  is a circumferential opening in the ferrule and has a predetermined diameter configured to receive the nose portion  14  of the rotary tool unit  10 . Opposite the open mounting end portion  38  is a smaller open end portion  40 , to which the attachment  12  is mounted, where the smaller open end portion has a smaller diameter than the diameter of the open mounting end portion. Separating the two open end portions is a conical transition portion  42 , which is a sloped, funnel-shaped portion of the ferrule  18  that gradually narrows the diameter of the ferrule, and terminates in the generally cylindrical smaller open end portion  40 . 
     As the nose portion  14  of the rotary tool unit  10  is inserted into the open mounting end portion  38  of the ferrule  18 , at least one and preferably two sets of internally protruding ribs  26  extend in an axial direction from the open mounting end portion to the conical transition portion  42 . In the preferred embodiment of the instant invention, the internally protruding ribs  26  include two pair of elongated, parallel protruding ribs, with one pair of ribs being diametrically opposed to the other pair on the internal surface of the ferrule. However, the number and placement of the ribs may vary, depending on the configuration and placement of the corresponding flared planar surface of the teeth  24 . 
     The ribs  26  and the ferrule  18  are of unitary construction, with a top surface  44  of the ribs being a planar surface. This planar surface  44  corresponds to the alignment portion  28  of the teeth  24  on the nose portion  14  of the rotary tool unit  10 , and both surfaces are configured and arranged in predetermined positions so that alignment of these surfaces ensures proper alignment of the rotary tool unit within the ferrule  18 . Because the height of the teeth  24  measured from the surface of the cylindrical shaped portion  22  is lowest at the alignment portions  28 , the ribs  26  are configured to extend from the internal surface at a distance corresponding diameter of the nose portion  14  at the alignment portion so as to frictionally engage the alignment portion of the teeth when inserted. Because the protruding ribs  26  of the preferred embodiment are diametrically opposed, the rotary tool unit  10  only be inserted in one of two positions, which only differ by a 180° degree of separation and are indiscernible for purposes of attachment. The engagement of the alignment portion  28  with the ribs  26  therefore prevents improper alignment of the rotary tool unit  10  within the ferrule  18 , and restricts rotational movement of the rotary tool unit once it is inserted into the ferrule. 
     Turning now to FIGS. 3 through 5, the ferrule of the instant invention includes at least one and preferably two locking latch members  46  for releasably securing the ferrule  18  to the rotary tool unit  10 . In the preferred embodiment, the external surface of the ferrule includes two diametrically opposed latch mounting portions, designated generally at  48  (best shown in FIG.  6 ), separated from each other by approximately 180°, to which the latch member  46  is mounted. Each latch mounting portion  48  includes a pair of parallel vertical flanges  50 , which each flange having inside and outside walls  52 ,  54 , and the inside walls of each flange face one another. Each pair of vertical flanges  50  are unitary with the external surface of the ferrule, and extend radially from the circumference of the ferrule, generally parallel to one another. There is an opening or a discontinuity in the ferrule body  18 , where the opening is defined between the inside walls  52  of the pair of flanges and extends downward for at least a portion of the open mounting end portion  38 . In the preferred embodiment of the instant invention, the opening in the ferrule  18  has a vertical length that is approximately one-half to two-thirds of the vertical length of the open mounting end portion  38 . The opening prevents the ferrule  18  from blocking interaction between the latch members  46  and the rotary tool unit  10 , once the rotary tool unit is aligned and inserted into the ferrule. It is therefore conceivable that the vertical length of the opening could be significantly shorter, or consist of an adequately sized aperture, to facilitate interaction between the latch members  46  and the rotary tool unit  10 . 
     An upper portion of each flange  50  contains an aperture  58  for receiving a cross bar that extends between the two flanges. It is upon this cross bar (not shown) that the latch members  46  are hingedly mounted. Therefore, when mounted, the latch members  46  may swing between an upward or open position and a closed or downward position. When the latch members  46  are in the open position, the ferrule and the tool are held in alignment by frictional engagement of the alignment portion  28  and the protruding ribs  26 . However, when the latch members  46  are in the closed position, the ferrule  18  and rotary tool unit  10  will be in locking engagement by at least one and preferably two of the following locking mechanisms. 
     Turning now to FIG. 8, the latch members  46  themselves contain and upper portion  60  and a lower portion  62 , where the upper portion depends vertically from the cross bar via apertures  64  in the upper portion of the latch members. The upper portion  60  is a generally flat surface that, when the latch members are in the closed position, rests flush in the plane defined by distal vertical edges of the vertical flanges. In contrast, the lower portion  62 , while unitary with the upper portion  60 , is bent slightly toward the ferrule  18  so that a distal end of the lower portion is slightly closer to the ferrule than the distal end of the upper portion. Thus, the bottom portion angles slightly inwardly toward the ferrule  18  and away from the plane defined by the distal vertical edges of the vertical flanges. The distance between the upper portion  60  of the latch member and the ferrule  18  is relatively constant, while the distance between the lower portion  62  and the ferrule will have a slight and gradual decrease at its distal end. However, the distance between the diametrically opposed latch members  46 , whether taken along the upper or lower portion, is greater than the diameter of the open mounting end portion. 
     The top portion of the latch members  46  include a first locking protrusion  66 , which in the preferred embodiment, is a wedge-shaped protrusion that extends generally perpendicularly from the latch member. This wedge-shaped protrusion  66  also includes a concave surface  68  at its distal end, which is configured to frictionally engages the convex groove portion  32  of the rotary tool unit  10  as the latch member  46  is brought into its closed position. The first locking protrusion  66  is also mechanically confined in frictional engagement at its underside by the elongated teeth  24  of the rotary tool unit  10  and at its upper side by the annular shoulder  30  between the enlarged diameter portion  20  and the cylindrical portion  22  of the rotary tool unit. This is the first of the two locking mechanisms. 
     For purposes of engaging the second locking mechanism, the latch members  48  further include a second locking protrusion  70  disposed on the lower portion of the latch member that also extends generally perpendicularly therefrom. The second locking protrusion  70  is planar on its underside, but preferably includes a raised end  72  on its top side. The latch mounting portion  48  also includes a generally horizontal shelf-like locking flange  74  having a top surface and a bottom surface, where the top surface is planar and the bottom surface includes an engagement recess  76 , which in the preferred embodiment, is an elongated longitudinal recess. Thus, as the latch member  46  is brought into its fully closed position, the second locking protrusion  70  slides underneath the locking flange  74 , frictionally engaging the bottom surface of the locking flange until the raised end  72  encounters the engagement recess  76  on the bottom surface of the locking flange and locks into place. Once the raised end  72  engages the engagement recess  76 , the raised edge is mechanically secured within the engagement recess, and both locking mechanisms of the latch member are effected, making the rotary hand tool unit  10  securely and releasably mounted to the ferrule  18  of the accessory attachment  12 . 
     The latch mounting portions  48  of the ferrule  18  are configured to allow the user to easily disengage the locking mechanisms using relatively modest force. Around the circumference of the transition portion  42 , two diametrically opposed vertical cut-out portions  78  (best shown in FIG. 6) are disposed below the shelf-like locking flange  74 . These vertical cut-out portions  78  are generally flat surfaces extending downward into the funnel-shaped transition portion of the ferrule, so that there is a recess in the conical shape of the transition portion  42  at each of the cut-out portions. The diameter between the recesses is less than any other given diameter of the open mounting end portion. Thus, because the distance between the diametrically opposed latch members  46 , whether taken along the upper  60  or lower portion  62 , is greater than the diameter of the open mounting end portion  38 , there is a space between the lower portion of the latch member and the generally flat surface of the cut-out portion  78 . In the preferred embodiment, the space is large enough to accommodate the user&#39;s finger, so that a user can reach into the space and pull the latch out of locking engagement. However, it is contemplated that the space could be reduced or eliminated if alternative means for opening the latch members were provided. For example, providing a grasping protrusion on an outside surface of the latch member would allow the user to pull upward on the latch member via the grasping protrusion, eliminating the need for a space. 
     Depending on the configuration of the specific accessory attachment  12 , the preferred embodiment of the ferrule  18  contemplates that the accessory attachment may be coupled to the ferrule  18  in a multitude of ways. By way of example only, to couple the flexible shaft attachment  12  to the ferrule  18 , a lower portion of the cylindrical smaller open end portion  40  slidably engages the generally cylindrical mounting portion, designated generally at  80 , of the flexible shaft attachment. As illustrated in FIG. 1, the mounting portion  80  of the flexible shaft attachment  12 , which includes a coiled spring  82 , couples a hollow flexible rubber sheath  84  to the ferrule  18 . The coiled spring  82  has an inner circumference that is slightly smaller than the outer circumference of the smaller open end portion  40  of the ferrule  18 . Therefore, when the coiled spring  82  is mounted around the outer circumference of the smaller open end portion  40 , the resulting force fit maintains frictional engagement of the coiled spring with the smaller open end portion of the ferrule. The flexible sheath  84  is telescopingly inserted into the coiled spring, thus aligning a top region  88  of the flexible core  86  (see FIGS. 3,  4 ) opening of the smaller open end portion  40 , which enters the ferrule  18 . 
     Turning now to FIGS. 3,  4 ,  11  and  12 , when coupling a flexible shaft attachment  12  such as that illustrated in the drawings, a drive cap  90  having a n aperture therethrough  92  may be placed within the ferrule to receive the top region  88  of the flexible core  86 . The aperture  92  and the top region  88  of the core  86  have square cross sections and are configured to matingly engage one another so that when the drive cap is rotated, the flexible core  86  rotates as well. 
     However, disengagement of the flexible core  88  and the handpiece  94  frequently occurs when the handpiece is raised in a vertical direction above the horizontal plane in which the rotary tool unit  10  is operating. The rotary output shaft  16  has a predetermined depth and a circumference that is larger than the diameter of the flexible core  86 . As a consequence, the flexible core  86  that is engaged with, and protruding through the aperture  92  frequently extends into the depth of the output shaft. If not prevented from doing so, the flexible core  86  can disengage from the handpiece  94  entirely and slide further into the output shaft  16 , thereby interrupting and frustrating the work of the user. 
     Turning now to FIGS. 3,  9  and  10 , when the coupling attachment  18  of the instant invention is coupled to the flexible shaft attachment  12 , a stop plug apparatus  96  may optionally be used to prevent unwanted or unplanned disengagement of the flexible core  86  from the handpiece  100 . The stop plug apparatus  96  is a plastic device, preferably nylon filled glass, that has an open end portion  98 , a closed end portion  100 , and a generally cylindrical body. The open end portion  98  of the stop plug apparatus  96  nests within the drive cap  90 . Thus the open end portion  98  is aligned with the aperture  92  of the drive cap, and the open end portion accordingly receives the top region  88  of the flexible core, and the closed end portion  100  restricts axial movement in the direction of the output shaft  16 . 
     While a particular embodiment of the present coupling apparatus has been described herein, it will be appreciated by those skilled in the art that changes and modifications may be made thereto without departing from the invention in its broader aspects and as set forth in the following claims.

Technology Classification (CPC): 8