Abstract:
A rotary tool has an output shaft having an axis of rotation and a distal neck portion which has at least three neck faces that do not intersect the axis of rotation, and a substantially U-shaped spring element having a base portion and two leg portions, wherein the spring element straddles the distal neck portion.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The invention described and claimed hereinbelow is also described in German Patent Applications EP 07117056.7 filed on Sep. 24, 2007. This European Patent Application, whose subject matter is incorporated here by reference, provides the basis for a claim of priority of invention under 35 U.S.C. 119(a)-(d). 
     BACKGROUND OF THE INVENTION 
     The present invention relates to rotary tools and in particular to interfaces for attaching different sorts of working members, such as driver bits or sockets, to the shaft of a rotary tool. 
     Patent application Ser. No. 10/155,574 discloses a hybrid interface that allows one to secure either a driver bit or a socket to rotary tool output shaft. The output shaft is configured to include a hexagonal cavity for receiving a driver bit along with means, such as a ball and sleeve arrangement, for attaching or releasing the bit. The distal end of the output shaft has a square-shaped periphery, and so it is also able to accommodate a typical socket. One embodiment is configured to cooperate with a pin and an O-ring to secure sockets according to a standard used in Japanese markets. A second embodiment employs a spring-loaded protrusion mounted to a hole on the periphery of the output shaft to secure sockets configured with an inner annular groove which is typical of the standard used in North American and European markets. 
     JP Patent Application No. 2004-190714 discloses a socket attachment interface intended to simplify the attachment of sockets according to the Japanese standard. A detachable spring member is secured with a screw to the end face of the output shaft of a rotary tool and includes one or more protrusions that cooperate with one or more through-holes in the socket. 
     Accordingly, it is an object of the present invention to provide a rotary tool which is a further improvement of existing rotary tools. 
     SUMMARY OF THE INVENTION 
     The present invention provides a hybrid tool attachment interface that incorporates advantages from both of the above-described designs and which can accommodate a driver bit as well as a variety of sockets. The design is simple to manufacture and assemble and does not require additional tools for mounting or removing bits or sockets. 
     The inventive rotary tool comprises an output shaft having an axis of rotation, a distal neck portion which has at least three neck faces that do not interest the axis of rotation and a generally U-shaped spring element having a base portion and two leg portions, wherein the spring element straddles the distal neck portion. 
     The U-shaped spring element is securely attached to the output shaft without any separate fastening means and has the advantage that features that can be used to secure multiple types of working members can be embodied in an inexpensively constructed part that is furthermore easily detachable should it be subject to wear or damage and need to be replaced. 
     The design has the advantage that the output shaft is provided with an elongate cavity coaxial with its axis of rotation, so that it can optionally receive a driver bit, thereby providing additional functionality for the user, who can select from either a driver bit or a socket without needing to use a separate adaptor. 
     The output shaft is further provided with means for securing a driver bit within the elongate cavity. Preferably these means comprise a slidably-mounted sleeve which is biased by a spring and which cooperates with balls which act as locking members when a driver bit with a circumferential groove is inserted. In this way, the user can easily remove or attach a driver bit of this type without any separate tools. 
     The spring element of the inventive rotary tool has two tip portions, each of which is contiguous with one of the two leg portions. These two tip portions together with the base portion and the two leg portions embrace the distal neck portion to retain the spring element. Hence the force of the spring and its geometry allow the spring plate to surround and fasten itself to the neck region of the output shaft without the need for separate fastening means. Since it is detachable, the user may optionally remove the spring element for replacement or use with certain tool types. 
     Each of the two leg portions contacts one of the neck faces of the distal neck portion and this serves to grip around the output shaft to retain the spring element. Preferably the leg portions contact the neck faces within recessed regions of the neck faces. This has the advantage that the spring plate can lie flush with the rest of the distal neck portion to provide an overall generally flat profile for insertion of a socket. 
     Adjoining the recessed faces of the distal neck portion are elevated portions that serve as stop surfaces. These stop surfaces provide the advantage that the spring plate is prohibited from moving axially along the axis of rotation when a socket is inserted onto or removed from the distal neck portion. 
     One of the means by which the spring plate retains a socket is by having at least one spring-elastic protrusion on a leg portion. Preferably two such protrusions are present on two leg portions. The protrusions can advantageously mate with either an internal groove or a radial cavity within a socket. 
     When a socket is inserted, it will generally deflect the spring-elastic protrusion as well as the portions of the spring plate, preferably arms, that surround the protrusion. Therefore it is advantageous to provide cavities extending from each neck face to the elongate cavity to receive each spring-elastic protrusion when they are deflected. It is preferable if there are multiple aspects to the cavity, an internal cylindrical aspect that can be used to mate with a pin inserted through the shaft and the socket, as well as a larger, and preferably conically shaped cavity portion. The larger, conically-shaped portion can accommodate the protrusion and the flexible arms surrounding the protrusion even when the protrusion is maximally deflected. 
     To allow the same attachment interface to accommodate sockets according to a Japanese standard wherein a pin and O-ring are used to secure the socket, the base portion of the spring element is provided with an opening. The opening is positioned generally coaxially with the cavity in the output shaft so they may cooperate to form an insertion pathway for the pin that is used to secure the socket. 
     Since protrusions for retaining a socket as well as a pathway for traversing the output shaft with a pin are provided at the same time, the inventive rotary tool can securely attach working members via at least three different means. First, a driver bit can be inserted and retained in the elongate cavity. Second, a socket with an internal groove can be retained via the spring-elastic protrusions. Third, a socket with a radial cavity can be retained not only via the spring-elastic protrusions, but also via cooperation with a pin which traverses an opening in the spring plate and a cavity in the output shaft, so that it can be secured by an O-ring extending around the perimeter of the socket. 
     The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic drawing of a side view of a rotary tool according to the present invention, wherein features that are located within the tool housing are indicated with dashed lines. 
         FIG. 2  is a side view of the preferred embodiment of an attachment interface for a rotary tool. 
         FIG. 3  is a section view of the attachment interface of  FIG. 2  taken along section line A-A. 
         FIG. 4  is an exploded perspective view of an attachment interface. 
         FIG. 5  is a detail section view of  FIG. 3 . 
         FIG. 6  is a section view of the attachment interface with a socket according to a Japanese standard mounted thereon. 
         FIG. 7  is a section view of the attachment interface with a socket originally intended for mounting according to a Japanese standard mounted thereon. 
         FIG. 8  is a section view of the attachment interface with a socket according to a standard used in North America and Europe mounted thereon. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An example of a rotary tool according to the present invention is illustrated in  FIG. 1 . While the illustrated embodiment is a power tool, and specifically a cordless impact driver, the invention may be advantageously used with a variety of rotary tools irrespective of whether they are powered or whether they include an impact driving function. Within housing  10  of rotary power tool  12  are a motor  14  and its associated motor shaft  16 . A transmission  18  converts the rotation of the motor shaft  16  into increased output torque, but correspondingly reduced speed rotation of the driveshaft  20 . 
     The driveshaft  20  is coupled to a hammer  22  which is in turn coupled to an output shaft  24 . The driveshaft  20 , hammer  22  and output shaft  24  are configured to transmit repetitive bursts of output torque via a hammer and anvil arrangement as is well known to those skilled in the art. An example of such an impact driver is shown in US 2006/0237205-A1, which is hereby incorporated by reference. The tool is provided with a handle  26  and a trigger  28  so that it may be conveniently operated by a user. The power source is a DC battery  30  in this exemplary cordless tool, but an AC power source is a standard alternative. 
       FIGS. 2-4  show various views of a tool attachment interface for a rotary tool. The output shaft  24  has a proximal neck portion  32 , a distal neck portion  34 , an end face  36 , and an axis of rotation  38 . An elongate cavity  40  in the output shaft  24  is centered around the axis of rotation  38 . The cavity is preferably polygonally shaped so that it can accommodate a complementary polygonally-shaped driver bit (not shown). 
     As means for securing a driver bit, a sleeve  44 , a compression spring  46 , and a retaining ring  48 , are mounted around the proximal neck portion  32  of the output shaft  24 . All of these elements are secured to the proximal neck portion  32  once a C-ring  50  is inserted into annular groove  52 . The force from the spring  46  positions the sleeve  44  such that balls  54  mounted in radial cavities  56  are urged partially into the elongate cavity  40  to act as locking members to act on a hexagonal driver bit with an annular groove (e.g., according to the DIN 3126-E6.3 standard) so that it can be securely attached and released from the output shaft  24 . 
     The radial cavities  56  are sized with a variable diameter, such that the balls  54  may travel within the radial cavities  56  but can only protrude partially into elongate cavity  40 . A user can urge the sleeve  44  against the spring force, so that the balls have space enough to exit entirely from the elongate cavity  40 . Rather than ball pairs  54 , a single ball, an elongate pin, or a blade may alternatively be used as locking members. 
     Besides these preferred means for retaining a driver bit, many prior art alternatives are also compatible, so long as they can coexist with the socket-retaining means that will be further described. The essential features are that the output shaft  24  is configured with an elongate cavity  40 , and the means for securing the driver bit are located within or around the proximal neck portion  32  of the output shaft  24 . For example, one or more screws mounted perpendicular to the axis of rotation could also be used to secure the driver bit. 
     Alternatively, a magnetic part incorporated into the proximal neck portion  32  could be used to attract and retain the driver bit. Furthermore different methods of adjustment are possible. Instead of being biased by the spring  46 , the sleeve  44  could instead be threaded to the proximal neck portion  32 , so that its position is adjusted via rotation in order to correspondingly position the one or more locking members. 
     To accommodate sockets that have a square-shaped female interface, the distal neck portion  34  of the output shaft  24  is preferably square-shaped in a cross-section taken perpendicular to the axis of rotation  38 . Detailed features of the distal neck portion  34  are shown in  FIGS. 4 and 5 . Each of its four neck faces  60  is configured with a neck cavity  62  that traverses the space between the neck face  60  and the elongate cavity  40  and comprises a cylindrical portion  64  and a conical portion  66 . The surface of each neck face  60  is partially recessed. Each of four recessed faces  70  are linked by similarly recessed bevel faces  69  at the four corners of the distal neck portion  34 . Front  67  and rear  68  elevated portions are found on either side of the recessed faces  70  and bevel faces  69 . 
     Without any further elements attached, the distal neck portion  34  is sufficient to permit a user to mount and secure a Japanese-type socket  71  to the output shaft  24  using a metal pin  72  and a rubber O-ring  74  as retaining means as is customary for this standard (see  FIG. 6 ). To do so, a socket  71  is mounted onto the output shaft  24  such that each inner face  76  of the socket makes contact with elevated portions  68  of each neck face  60 . Then a pin  72  is inserted through radial cavities  78  in the socket and through two neck cavities  62  of the output shaft  24 . Finally, an O-ring  74  is mounted around an annular groove  80  of the socket  71  to trap the pin  72 . 
     Note that a given socket  71  can be mounted in any of four possible orientations relative to the output shaft  24 , resulting in the mounting pin  72  traversing the socket  71  in one of two possible orientations. In every case, there is no interference from the driver bit mounting means and therefore the two distinct mounting interfaces may coexist on the same output shaft  24 . 
     So that the output shaft  24  can also accommodate different types of sockets, and so that they may be retained without separate fastening members, a spring plate  82  comprising a base portion  84 , two leg portions  86 , two corner portions  88 , and two leg tip portions  89  is preferably mounted to the distal neck portion  34  of the output shaft  24 . Each of the two corner portions  88  link the base portion  84  with a leg portion  86 . Each of the two leg tip portions  89  extend from the end of the leg portion, that is, they extend from the part of the leg portion  86  opposite the part of the leg portion  86  that interfaces with the base portion  84 . 
     The spring plate  82  is best visualized in the exploded view of  FIG. 4 . It is fastened to the output shaft  24  without any separate fastening means and does not require the use of tools for attaching or detaching. The cross section of the mounted spring plate  82  taken perpendicular to the axis of rotation  38  (not shown) is substantially U-shaped, as defined by the base portion  84  and the two leg portions  86 . 
     The thickness of the spring plate  82  corresponds very closely to the dimensions of the distal neck portion  34 , so that when the spring plate  82  is mounted, each of its portions contacts a recessed face  70  or a bevel face  69 , so that it is substantially but not necessarily exactly flush with the surface of the front  67  and rear  68  elevated portions of each neck face  60  (see  FIG. 5 ). These elevated portions  67 ,  68  provide a stop surface to counter the axial force acting on the spring plate  82  when a socket is inserted or removed. 
     The two corner portions  88  and the two leg tip portions  89  of the spring plate  82  are complementary to the bevel faces  69  of the distal neck portion  34 . As each neck face  60  of the distal neck portion  34  is structurally equivalent, the spring plate  82  can be mounted in any of four possible orientations. The spring plate  82  exerts a spring force which tends to grip the distal neck portion  34  via its two leg tip portions  69 . It can be manually removed by overcoming this spring force. The distal neck portion  34  may alternatively have an asymmetrical design, for example with only two neck cavities  62 . In this case, the spring plate  82  is preferably inserted in particular orientations. 
     While the spring force itself comprises sufficient attachment means for retaining the spring plate  82 , alternatives are possible. If the spring plate  82  were provided with an opening on one of its faces that corresponded to a cavity on the distal neck portion  34 , the parts could be secured with a screw or the like. A suitable screw head would be flat and its head preferably somewhat recessed within the spring plate  82  so as not to interfere with the insertion of a socket. In addition, such a screw should not be long enough to enter the elongate cavity  40  so as to interfere with the mounting of a driver bit. 
     At the center of each leg portion  86  of the spring plate  82  there is a spring-elastic protrusion  90 . Four openings  92  surround the protrusion, thereby establishing four flexible arms  94 . Although not absolutely essential features of the spring plate, these openings  92  and arms  94  reduce the force necessary to deflect a protrusion  90  below the surface of the leg portion  86 . As will be seen below, this may potentially happen during the insertion of a socket onto the attachment interface. Therefore, a leg portion  86  with two, three, five, six or even more openings can be used towards this same goal and present reasonable alternatives. The spring plate  82  is preferably manufactured through stamping of sheet metal and these openings  92  and arms  94  can be readily introduced during this process. 
     When it is deflected, each protrusion  90  exerts a radial force generally perpendicular to the axis of rotation  38 . When a socket  71  is inserted, its inner face  76  deflects each protrusion  90  while the socket  71  slides into its mounting position, at which time the protrusion  90  acts on a cavity  78  or groove  100  in the socket  71 . When the spring plate  82  is mounted to the output shaft  24 , the position of each protrusion  90  and flexible arm  94  corresponds roughly to the position of the cylindrical portion  64  and conical portion  66  of the neck cavity  62  respectively. This structure provides sufficient space for the protrusion  90  and flexible arms  94  to be deflected in the general direction of the axis of rotation  38  against its inherent spring force. 
     The base portion  84  of the spring plate  82  has an opening  96  roughly comparable in diameter to that of the cylindrical portion  64  of a neck cavity  62 . Since the opening  96  is positioned coaxially with the neck cavity, a pin  72  can be inserted through these features so that a socket  71  can be mounted using a pin  72  and O-ring  74  even when the spring plate  82  is mounted to the output shaft  24 . In this configuration, the inner faces  76  of the socket  71  constantly deflect the protrusions  90 , but this is permissible since there is adequate space in the neck cavity  92  to accommodate the protrusions  90  as described above. Alternatively and preferably, the same socket  71  could be removed, rotated ninety degrees, and inserted past the spring force of the protrusions  90 , so that each protrusion  90  engages with a radial cavity  78  in the socket  71  as shown in  FIG. 7 . A socket  98  with an internal annular groove  100  is also retained by this attachment interface as shown in  FIG. 8 . 
     It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above. 
     While the invention has been illustrated and described as embodied in a rotary tool with multiple tool attachment interfaces, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. 
     Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.