Abstract:
An exemplary screwdriver includes a handle unit, head units for operating different kinds of fasteners, a head reception unit fixed on the handle unit and receiving the head units therein, and a pole unit fixed on the handle unit. Each of the head units is removably attachable on the pole unit so that the screwdriver can operate the different kinds of fasteners as required.

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to screwdrivers, and particularly to a screwdriver with changeable head units. 
     2. Description of Related Art 
     When screws in different sizes and shapes are screwed or unscrewed, different kinds of screwdrivers are required. However, it may be difficult for a person to carry around a number of screwdrivers needed for different kinds of screws. Screwdrivers with changeable head units are often used to decrease the work of carrying around a number of screwdrivers for different kinds of screws. In use of a screwdriver with changeable head units, different kinds of head units corresponding to different kinds of screws can be respectively attached to the shank of the screwdriver. However, when one of the head units is attached on the screwdriver, the other head units are separate from the screwdriver. It may be awkward or difficult to carry around the loose head units, and they are liable to become lost. 
     Therefore, there is room for improvement within the art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the various drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, like reference numerals designate corresponding parts throughout the drawings. 
         FIG. 1  is a schematic, disassembled view of a screwdriver, according to an exemplary embodiment. 
         FIG. 2  is a schematic, assembled view of the screwdriver shown in  FIG. 1 , wherein one head unit of the screwdriver is attached on a pole portion of the screwdriver, and one head lock member of the screwdriver is opened. 
         FIG. 3  is similar to  FIG. 2 , but shown from another angle, and wherein the head unit is detached from the pole portion and the head lock member is closed. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1-3  show a screwdriver  100 , according to an exemplary embodiment. The screwdriver  100  includes a handle unit  10 , a head reception unit  20 , a pole unit  40 , and a plurality of head units  50 . The handle unit  10  is substantially frustoconical-shaped and suitable for being manually held together with the head reception unit  20 . The head reception unit  20  is substantially spherical. The pole unit  40  is substantially cylindrical. The head reception unit  20 , the pole unit  40 , and the handle unit  10  cooperatively form one tool. The plurality of head units  50  are configured to operate (i.e., to screw and unscrew) fasteners (e.g., screws and bolts) of different shapes and sizes. Each of the head units  50  can be attached on the pole unit  40  for use, and can be received in the head reception unit  20  when not in use. 
     In particular, the head reception unit  20  includes a substantially spherical main body  21  and a plurality of head lock members  23 . The main body  21  is fixed on the larger end of the handle unit  10  and is coaxial with the handle unit  10 . The main body  21  defines a plurality of recessed reception portions  22  for receiving the head lock members  23 . In this embodiment, the screwdriver  100  includes four head units  50 , and the head reception unit  20  includes four head lock members  23 . Each of the head lock members  23  can receive one of the head units  50 . The main body  21  defines four equidistantly spaced reception portions  22 , and each of the four head lock members  23  is received in a corresponding one of the four reception portions  22 . 
     Each of the reception portions  22  is laid in a direction that is substantially parallel to the longitudinal axis of the handle portion  10 , and has two parallel side surfaces  221  and an upper, inner, stepped retaining surface  223  between the side surfaces  221 . Each of the side surfaces  221  defines a pivot hole  224  and a sliding groove  225 . The pivot hole  224  is defined adjacent to a lower end of the reception portion  22  (that is, opposite to the end of the reception portion  22  having the retaining surface  223 ). The sliding groove  225  is defined in the middle portion of the side surface  221 , and is curved. In particular, the sliding groove  225  begins at a point near an outer extremity of the middle portion of the side surface  221  and continues inwards along the middle portion of the side surface  221 , substantially following a line tracing part of a circle centered on the pivot hole  224 . A substantially bar-shaped lock protrusion  226  is formed on the retaining surface  223 . 
     Each of the head lock members  23  includes a base portion  231  and an arm portion  232  connected to the base portion  231 . The base portion  231  is a substantially fan-shaped block, which includes two planar end surfaces, an arc-shaped end surface, and two substantially fan-shaped and planar side surfaces. The two planar end surfaces are substantially perpendicular to each other. One of the two planar end surfaces is oriented approximately horizontally, and the other planar end surface is oriented approximately vertically. The arc-shaped end surface intersects with both the planar end surfaces. The two side surfaces intersect with both the planar end surfaces and with the arc-shaped end surface. The arm portion  232  is a bent board that includes an arc-shaped outer surface and a curved inner surface. A bottom end of the inner surface of the arm portion  232  is connected to the horizontal planar end surface of the base portion  231 . A bottom end of the outer surface of the arm portion  232  is connected to the arc-shaped end surface of the base portion  231 , and the arc shape of the outer surface of the arm portion  232  is a smooth, seamless continuation of the arc-shaped end surface of the base portion  231 . 
     The width of the base portion  231  (i.e., the distance between the two side surfaces) and the width of the arm portion  232  are substantially equal to each other. That is, the head lock member  23  has a uniform width, which is substantially equal to a corresponding width of the respective reception portion  22 , such that the head lock member  23  can be inserted into the reception portion  22  and rotated out from the reception portion  22 . A reception groove  233  is defined in the horizontal planar end surface of the base portion  231 . 
     Each of the head lock members  23  further includes a pair of rotation protrusions  234  corresponding to the pivot holes  224 , a pair of sliding protrusions  235  corresponding to the sliding grooves  225 , a retaining groove  236  corresponding to the lock protrusion  226 , and an operation portion  237 . In particular, each of the side surfaces of the base portion  231  has one of the rotation protrusions  234  and one of the sliding protrusions  235  formed thereon. The rotation protrusion  234  is formed adjacent to the intersection of the arc-shaped end surface and the vertical planar end surface of the base portion  231 . The sliding protrusion  235  is formed adjacent to the intersection of the two planar end surfaces. The retaining groove  236  is defined in the arm portion  232 , and is positioned adjacent to the distal end of the arm portion  232 . In this embodiment, the operation portion  237  is a bar-shaped protrusion extending from the distal end of the arm portion  232 . A horizontal width of the operation portion  237  is less than the width of the arm portion  232 . 
     Referring particularly to  FIG. 3 , the pole unit  40  includes a substantially cylindrical pole body  41  and a pair of latch components  42 . The pole body  41  is connected to the smaller end of the handle unit  10  and is coaxial with the handle unit  10 . A polygonal assembling hole  411  for receiving and gripping any selected one of the head units  50  is defined in the pole body  41 . The latch components  42  can be common resilient latch apparatuses. When attached in the assembling hole  411 , the selected head unit  50  can be locked in position by spring pressure, and can be released by pressing the latch components  42  toward each other. Furthermore, the latch components  42  can instead be any other kind of common latch apparatuses, such as magnetic latch apparatuses. 
     Each of the head units  50  has a polygonal head base  51  corresponding to the assembling hole  411  and a head tip  52  connected to the head base  51 . The head tips  52  are contoured with different shapes and sizes, and each may be used to screw and unscrew a different kind of fastener (e.g., a screw or a bolt). 
     In assembly, the head base  51  of each of the head units  50  is received in the reception groove  233  of a corresponding one of the head lock members  23 . The pair of rotation protrusions  234  of the head lock member  23  of each head unit  50  are rotatably received in the two pivot holes  224  of a corresponding one of the reception portions  22 , respectively. The pair of sliding protrusions  235  of the head lock member  23  are slidably received in the two sliding grooves  225  of the corresponding reception portion  22 , respectively. In this way, the head lock members  23  with the head units  50  received therein are rotatably attached to the main body  21 , and can be rotated inward to retracted (closed) positions inside the main body  21 . 
     When the screwdriver  100  is not in use, the head lock members  23  are pushed towards the center of the main body  21  to be in the closed positions. The lock protrusion  226  of each of the reception portions  22  engages in the retaining groove  236  of the corresponding head lock member  23  to retain the head lock member  23  in the closed position. The outer surface of the arm portion  232  and the arc-shaped end surface of the base portion  231  of each of the head lock members  23  are substantially flush with the outer surface of the main body  21  to form a substantially spherical outer surface of the head reception unit  20 . In this way, the head reception unit  20  is substantially smooth and round, which helps protects the head reception unit  20  from impact and scratching. 
     When one of the head units  50  is selected for use, the operation portion  237  of the head lock member  23  that holds the selected head unit  50  is operated by a user to open the head lock member  23 , and the selected head unit  50  is taken out of the reception groove  233  of the head lock member  23 . The head lock member  23  is then closed. The head base  51  of the selected head unit  50  is inserted into the assembling hole  411 , and secured by the latch components  42 . Thus, the screwdriver  100  is ready to screw and unscrew a fastener (e.g., a screw) of a type corresponding to the selected head unit  50 . When another of the head units  50  needs to be used, the latch components  42  are operated to release the installed head unit  50 , and the other head unit  50  is fixed on the pole unit  40  according to the aforementioned method. The previously installed head unit  50  is replaced in the reception groove  233  of its corresponding head lock member  23 , and the corresponding head lock member  23  is closed. This provides safekeeping for the previously installed head unit  50 , and facilitates use of the screwdriver  100 . 
     In summary, the screwdriver  100  has a plurality of changeable head units  50  received therein, and can be used to screw and unscrew fasteners (e.g., screws and bolts) of different shapes and sizes. Furthermore, the head reception unit  20  functions as an efficient, safe and portable storage for the head units  50 . 
     It is to be further understood that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description, together with details of structures and functions of various embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the present invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.