Patent Abstract:
A bit assembly includes a bit for driving a screw, a shank for holding and driving the bit to rotate about a pivot axis wherein the bit is capable of moving relative to the shank in a predetermined range, and a limiting structure formed between the bit and the shank for preventing the bit to move beyond the predetermined range. The bit and the shank are made of different materials and form a sliding connection so that they have a certain buffer space in the axial direction and in the circumferential direction thereby reducing the effect of impacts on the service life of the bit assembly.

Full Description:
RELATED APPLICATION INFORMATION 
     This application claims the benefit of CN 201310275271.3, filed Jul. 2, 2014, and CN 201320390803.3, filed Jul. 2, 2014, the disclosures of which are incorporated herein by reference in their entirety. 
     FIELD OF THE DISCLOSURE 
     The subject disclosure generally relates to bit assemblies, and more particularly, to a bit assembly adapted to reduce impact. 
     BACKGROUND OF THE DISCLOSURE 
     Electrical tools using a bit, driven by impact, are generally known. Since such tools subject a bit to high frequency impacts during operation, there is a higher requirement for the toughness of the bit. A traditional bit is formed from a single metal, thus the hardness of the bit from front end to back end is consistent. Generally, the requirement for the toughness is sacrificed for meeting the requirements for wear resistance and durability. Once the hardness is reduced to enhance the toughness, the wear resistance and durability may be reduced greatly, and even lower than the standard requirement, thus cannot be satisfactory. 
     SUMMARY 
     In order to solve at least the above-noted problems, hereinafter is described a bit assembly which solves the conflict between the toughness and the hardness of the bit and which is relatively easy to manufacture. 
     More particularly, an exemplary bit assembly comprises a bit for driving a screw, a shank for holding the bit and for driving the bit to rotate about a pivot axis such that the bit is capable of moving relative to the shank in a predetermined range, and a limiting structure formed between the bit and the shank for preventing the bit from moving beyond the predetermined range. 
     Further, the bit may be capable of moving along a direction which is along the pivot axis. 
     Further, the limiting structure may comprise a first stop portion formed on the bit and a second stop portion formed on the shank wherein the first and second stop portions prevent the bit from detaching from the shank. 
     Further, the limiting structure may also comprise a third stop portion formed on the bit adjacent to the first stop portion and a fourth stop portion formed on the shank adjacent to the second stop portion such that, when the fourth stop portion contacts the third stop portion, the bit is prevented from further moving closer to the shank in a direction along the pivot axis. 
     Further, the bit may comprise a first connecting portion formed on first end of the bit and a working portion formed on a second end of the bit opposite to the first end and the shank may comprise a driven portion which is capable of being driven to rotate by a torque tool and a second connecting portion for engaging with the first connecting portion so as to connect the bit and the shank. 
     Further, the first connecting portion may comprise an engaging portion and a first annular groove positioned adjacent to the engaging portion with the first and third stop portions being positioned on opposite ends of the first annular groove and the second connecting portion may define a receiving chamber with one end opened in the direction along the pivot axis and a first annular protrusion may be formed on an open end of the receiving chamber with the engaging portion being received in the receiving chamber and the first annular protrusion being received in the first annular groove and with the second and fourth stop portions being opposite ends of the first annular protrusion. 
     Further, the engaging portion may be shorter than the receiving chamber in the direction along the pivot axis. 
     Further, a length of the first annular groove may be greater than that of the first annular protrusion in the direction along the pivot axis. 
     Further, the engaging portion may be a substantially regular hexagonal and the receiving chamber may be a substantially regular hexagonal with the engaging portion being smaller than the receiving chamber in a direction perpendicular to the pivot axis. 
     Further, a hardness of the bit may be greater than that of the shank. 
     Further, the bit assembly may comprise a function accessory mounted to the bit body. 
     Further, the function accessory may comprise an accessory body which is capable of receiving a portion of the bit body, a stop member mounted to a first end of the accessory body for stopping the bit body from detaching from the accessory body, and a functioning member mounted to a second end of the accessory body opposite to the first end, wherein the function accessory is in sliding connection with the bit body. 
     Further, the accessory body may define a first stepped hole for at least one end of the bit body passing through the pivot axis and may comprise a first restricting portion arranged on the external surface of the accessory body or in an inner wall of the first stepped hole for fixing the stop member, and a second restricting portion positioned in the first stepped hole for preventing the bit body moving apart from the function accessory. 
     Further, the second restricting portion may comprise an annular plate formed by the first stepped hole and substantially perpendicular to the pivot axis which is capable of preventing the first connecting portion or the second connecting portion from passing through the first stepped hole. 
     Further, the first restricting portion may be a second annular groove defined in the inner wall of the first stepped hole and the stop member may be a gasket mounted in the second annular groove. 
     Further, the first restricting portion may comprise a second annular protrusion or a section of an external thread arranged on the external surface of the accessory body and the stop member may be a sleeve which mounted to the accessory body by the second annular protrusion or the section of the external thread. 
     Further, the stop member may define a through-hole which is capable of allowing the working portion or the driven portion to pass there through and a first annular bench portion which is capable of preventing the first connecting portion or the second connecting portion from passing through the through-hole. 
     Further, the functioning member may be an annular magnet. 
     Further, the first stepped hole may comprise an accommodated portion adjacent to one end of the accessory body for receiving the functioning member. 
     Further, the function accessory may be made of a transparent material, and the bit body or the function accessory may comprise an illuminated portion formed by an illuminated material. 
     With the combination of the bit body and the shank as described, the working member and the driven member are made of different materials and form a sliding connection so that they have a certain buffer space in the axial direction and the circumferential direction thereby reducing the effect of the impact on the service life. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a structure schematic view of an exemplary embodiment of a bit body constructed according to the description which follows; 
         FIG. 2  is an exploded schematic view of the bit body of  FIG. 1 ; 
         FIG. 3  is a sectional schematic view of the bit body of  FIG. 1 ; 
         FIG. 4  is a structure schematic view of the bit of  FIG. 1 ; 
         FIG. 5  is a partial sectional schematic view of the shank of  FIG. 1 ; 
         FIG. 6  is a sectional schematic view of the shank of  FIG. 1  before the receiving chamber has been stamped; 
         FIG. 7  is a sectional schematic view of the bit body of  FIG. 1  mated with an exemplary function accessory; 
         FIG. 8  is a an exploded schematic view of the function accessory of  FIG. 7 ; and 
         FIG. 9  is a sectional schematic view of the bit body of  FIG. 1  mated with another exemplary function accessory. 
     
    
    
     DETAILED DESCRIPTION 
     The following will describe an exemplary specific embodiment of a bit assembly with reference to the drawings. 
       FIGS. 1-5  illustrate a bit assembly  100 , in exemplary form of an impact screwdriver bit, which will be subjected to a periodic impact during operation. The bit assembly  100  mainly includes a bit body  101  having a bit  10  and a shank  20 . 
     The bit  10  is mainly used to achieve the function of striking screws by contacting the screws. The shank  20  is used to transmit a torque to the bit  10  so as to drive the bit  10  to rotate about a pivot axis  101   a.    
     It is well known for the person skilled in the art that the bit  10  has a pivoting axis  101   a  and how to determine this pivoting axis  101   a , thus it is unnecessary to go into details here. 
     It should be noted that in order to describe the features and relative relations of various parts of the described bit assembly the descriptions used herein will refer to a common space which is defined by a cylindrical coordinate with the pivot axis  101   a  as the central axis. The axial direction of the pivot axis  101   a  is the axial direction of the cylindrical coordinate; the radial direction of the pivot axis  101   a  is the radial direction of the cylindrical coordinate; and the circumferential direction of the pivot axis  101   a  is the circumferential direction of the cylindrical coordinate. Without any special instruction, the axial direction, radial direction and circumferential direction in this description refer to the aforesaid axial direction, radial direction and circumferential direction referenced to the pivot axis  101   a.    
     As a preferred embodiment, the bit  10  has an illuminated portion formed by an illuminated material. The illuminated portion is positioned on the bit  10  so that, without sufficient light, the illuminated portion can perform an illuminating function. 
     The bit  10  and the shank  20  form a sliding connection with a predetermined range. A limiting structure  200  is formed between the bit  10  and the shank  20  for preventing the bit  10  from moving beyond the predetermined range. 
     The bit  10  is moveable at least in the direction along the pivot axis  101   a , and the limiting structure  200  of the bit  10  and the shank  20  has an outer profile intersecting with the direction along the pivot axis  101   a.    
     As shown in  FIG. 2 , the bit  10  includes a first end forming a working portion  11  and a second end opposite to the first end forming a first connecting portion  12 . The shank  20  has a first end forming a second connecting portion  22  and a second end opposite to the first end forming a driven portion  21 . The working portion  11  is used to strike the screws and the driven portion  21  is mainly used to mate with the torque tools. The working portion  11  includes a head portion  111  for contacting the screws and neck portion  112  for connecting the head portion  111  to the first connecting portion  12 . 
     The limiting structure  200  includes a first stop portion  201  formed on the bit  10  and a second stop portion  202  formed on the shank  20  which prevent the bit  10  from detaching from the shank  20 . 
     The limiting structure  200  also includes a third stop portion  203  formed on the bit  10  adjacent to the first stop portion  201  and a fourth stop portion  204  formed on the shank  20  adjacent to the second stop portion  202  so that, when the fourth stop portion  204  contacts the third stop portion  203 , the bit  10  is prevented from further moving closer to the shank  20  along the direction along the pivot axis  101   a.    
     The first connecting portion  12  includes an engaging portion  121  and defines a first annular groove  122  adjacent to the engaging portion  121 , the first and third stop portions  201 , 203  are positioned on opposite ends of first annular groove  122 . 
     The second connecting portion  22  defines a receiving chamber  221  with one end opened in the direction along the pivot axis  101   a  and includes a first annular protrusion  222  formed on the open end of the receiving chamber  222 . 
     The engaging portion  121  is received in the receiving chamber  221  and the first annular protrusion  222  is received in the first annular groove  122  and the second and fourth stop portions  202 , 204  are at opposite ends of the first annular protrusion  222 . 
     As shown in  FIG. 7 , before the engaging portion  121  is received into the receiving chamber  221 , the first annular protrusion  222  has not been formed. After the engaging portion  121  is inserted in the receiving chamber  221 , the whole may be processed by stamping, and the top end  222   a  of the receiving chamber  221  is distorted plastically and bent inwards to form the first annular protrusion  222  as shown in  FIG. 5 . 
     The engaging portion  121  is preferably shorter than the receiving chamber  221  in the direction along the pivot axis  101   a  and the length of the first annular groove  122  is preferably greater than that of the first annular protrusion  222  in the direction along the pivot axis  101 , the engaging portion  121  is substantially regular hexagonal in shape and the receiving chamber  221  is substantially regular hexagonal in shape, and the engaging portion  121  is preferably smaller than the receiving chamber  221  in a direction perpendicular to the pivot axis  101   a . The service life of the bit body  101  is increased by the axial and circumferential space between the bit  10  and the shank  20 . The axial and circumferential space is capable of reducing the impact between the bit  10  and the shank  20  when they are moving relatively. 
     Referring to  FIGS. 7-10 , the bit assembly  100  may further include a function accessory  102  mounted to the bit body  101 . 
     The function accessory  102  includes an accessory body  30  which is capable of receiving a portion of the bit body  101 , a stop member  40  mounted to a first end of the accessory body  30  for stopping the bit body  101  from detaching from the accessory body  30 , and a function member  50  mounted to a second end of the accessory body  30  opposite to the first end, wherein the function accessory  102  is in sliding connection with the bit body  101 . 
     As a preferred embodiment, the accessory body  30  defines a first stepped hole  301  for at least one end of the bit body  101  passing through along the pivot axis  101   a , and includes a first restricting portion  31  arranged on the external surface of the accessory body  30  for fixing the stop member  40 , and a second restricting portion  32  positioned in the first stepped hole  301  for preventing the bit body  101  moving apart from the function accessory  102 . 
     The function accessory  102  is preferably made of a transparent material. 
     The illustrated second restricting portion  32  further includes an annular plane  321  formed by the first stepped hole  301  and arranged substantially perpendicular to the pivot axis  101   a  which is capable of preventing the first connecting portion  12  or the second connecting portion  22  from passing through the first stepped hole  301 . 
     The illustrated first restricting portion  31  includes a second annular protrusion  311  or a section of external thread arranged on the external surface of the accessory body  30 , and the stop member  40  is a sleeve  401  which is mounted to the accessory body  30  by the second annular protrusion  311  or the section of external thread. The stop member  40  includes a third annular protrusion  41  or section of internal thread arranged on an inner surface of the sleeve  401 . 
     The illustrated stop member  40  defines a through-hole  42  which allows the working portion  11  or the driven portion  21  to pass there through and an annular step portion which prevents the first connecting portion  12  or the second connecting portion  22  from passing through the through-hole  42 . 
     The illustrated first stepped hole  301  includes an accommodated portion  301   a  adjacent to one end of the accessory body  30  for receiving the function member  50 . The function member  50  is preferably an annular magnet. 
     As shown in  FIG. 9 , a further accessory body  30 ′ defines a first stepped hole  301 ′ for allowing at least one end of the bit body  101  to pass there through along the pivot axis  101   a  and which includes a first restricting portion  31 ′ arranged in an inner wall of the first stepped hole  301 ′. The first restricting portion  31 ′ is an annular groove  311 ′ defined in the inner wall of the first stepped hole  301 ′ and the stop member  40 ′ is a gasket mounted in the annular groove  311 ′. The gasket is preferably made of elastic material. 
     The specific embodiments described above are only intended to illustrate the ideas and principles of the present invention, not to restrict the content of the present invention. Those having ordinary skill in the art can appreciate that besides the above preferred embodiments, the present invention may also include many other alternative or modified embodiments, which are still intended to fall within the scope of the following claims.

Technology Classification (CPC): 1