Abstract:
An electric screwdriver is configured for fastening a screw in an apparatus. The driving part is configured for generating rotary motion. The driven part is configured for fastening the screw in the apparatus using the rotary motion. The transmission part nonlinearly connects the driving part and the driven part. The transmission part is capable of transmitting the rotary motion from the driving part to the transmission part.

Description:
BACKGROUND 
       [0001]    1. Field of the Disclosure 
         [0002]    The present disclosure generally relates to screwdrivers, particular relates to an electric screwdriver used in various assembly circumstances. 
         [0003]    2. Description of Related Art 
         [0004]    Screwdrivers are devices specifically designed to insert and tighten, or to loosen and remove screws. The screwdrivers are rotated manually or by electric motors. Those using electric motors are also called electric screwdrivers. 
         [0005]    Referring to  FIG. 6 , an electric screwdriver  10  is used for fastening a screw  30  to a housing  20 . The electric screwdriver  10  includes a mainbody  12  and a detachable head  14 . The mainbody  12  and the detachable head  14  both have substantial cylinder structures, and also have the same axis O 1 -O 1 ′. The housing  20  includes a rectangular sheet  21  and four side walls  23 ,  25 ,  27 ,  29  extending upwards from four edges of the sheet  21 . The screw  30  is desired to be positioned in a bottom of the side wall  23 . Because of the length of the screwdriver  10 , the screwdriver  10  must be inclined to be engaged with the screw  30 . Therefore, the tip of the screwdriver  10  may not be suitable fixed in the slot of the screw  30  head and the screwdriver may slip out of the slot when the screw  30  is being driven or the screw  30  head may be damaged. 
         [0006]    Therefore, an electric screwdriver is needed in the industry to address the aforementioned deficiency. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a schematic diagram showing an electric screwdriver in accordance with an exemplary embodiment, for fastening a screw in an apparatus. 
           [0008]      FIG. 2  is a schematic diagram showing the electric screwdriver including a rack cover. 
           [0009]      FIG. 3  is a schematic diagram showing the electric screwdriver without the rack cover. 
           [0010]      FIG. 4  is a disassembled view of the electric screwdriver. 
           [0011]      FIG. 5  is a partial enlarged view of the circled portion V of  FIG. 4 . 
           [0012]      FIG. 6  is a schematic diagram showing a conventional electric screwdriver. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    Referring to  FIG. 1 , an electric screwdriver  99  in accordance with an exemplary embodiment is used for fastening a screw  35  in an apparatus  40 . The apparatus  40  includes a rectangular sheet  41  and four side walls  43 ,  45 ,  47 ,  49  extending upwards from four edges of the sheet  41 . The screw  35  is desired to be positioned in a bottom of the side wall  43 . A length of the electric screwdriver  99  is longer than that of the rectangular sheet  41  in a direction perpendicular to the side wall  43 . 
         [0014]    In order to fasten the screw  35  easily, the electric screwdriver  99  is designed in a special structure that has three main parts: a driving part, a transmission part, and a driven part. Mechanic energy is supplied from the driving part, transmitted by the transmission part, and then used for driving the driven part to fasten the screw  35 . The driving part is parallel to the driven part, and the transmission part is slanted between the driving part and the driven part. A length of the driven part is shorter than that of the rectangular sheet  41  in a direction perpendicular to the side wall  43 . As a result, the driven part can provide direct mechanic energy on the screw to fasten the screw into the  40 . 
         [0015]    Referring also to  FIGS. 2 and 3 , a detailed structure of the electric screwdriver  99  includes a driver  50 , a detachable head  60 , a universal joint chain  70 , a supporting rack  80 , and a rack cover  90 . The driver  50 , an example of the driving part, supplies rotary motion and may be an electric motor. The detachable head  60 , an example of the driven part, is detachably fixed in the electric screwdriver  99  may have many forms, such as slotted heads, crossheads, hex heads. The drive shaft  70 , an example of the transmission part, transmits the rotary motion from the driver  50  to the detachable head  60 . The supporting rack  80  supports the driver  50  and the universal joint chain  70 . The rack cover  90  further supports the universal joint chain  70 . 
         [0016]    Also referring to  FIGS. 4-5 , the components of the electric screwdriver  99  are depicted in detail. The driver  50  is a cylinder and includes a first rotatable shaft  52  extending out and connecting with the universal joint chain  70 . The first rotatable shaft  52  rotates around a first axis O 2 -O 2 ′. 
         [0017]    The universal joint chain  70  includes a first universal joint  73 , a second rotatable shaft  75 , a second universal joint  77 , and a third rotatable shaft  79 . The second rotatable shaft  75  rotates around a second axis O 3 -O 3 ′, and the third rotatable shaft  79  rotates around a third axis O 4 -O 4 ′. The first axis O 2 -O 2 ′is parallel to the third axis O 4 -O 4 ′. The second axis O 3 -O 3 ′ is inclined to the first axis O 2 -O 2 ′ and the third axis O 4 -O 4 ′. The first universal joint  73  is connected between the first rotatable shaft  52  and the second rotatable shaft  75 , for transmitting rotary motion from the first rotatable shaft  52  to the second rotatable shaft  75 . The second universal joint  77  is connected between the second rotatable shaft  75  and the third rotatable shaft  79 , for further transmitting the rotary motion from the second rotatable shaft  75  to the third rotatable shaft  79 . 
         [0018]    The supporting rack  80  includes a supporting beam  82 , a first supporting member  84 , a second supporting member  86 , and a fastening member  88  (see  FIG. 3 ). The supporting beam  82  supports the other components of the electric screwdriver  99 . The first supporting member  84  is formed on a middle portion of the supporting beam  82 . The second supporting member  86  forms on one end of the supporting beam  82 . A height of the second supporting member  86  is taller than that of the first supporting member  84 . Free ends of the first supporting member  84  and the second supporting member  86  respectively defines a first positioning hole  840  and a second positioning hole  860 . The universal joint chain  70  is fixed into the first positioning hole  840  and the second positioning hole  860 , and is supported above the supporting beam  82  by a combination of the first supporting member  84  and the second supporting member  86 . The universal joint chain  70  is disposed at an angle relative to the supporting beam  82 . The fastening member  88  fastens the driver  50  on the other end of the supporting beam  82 , in other words, the fastening member  88  is opposite to the second supporting member  86  with respect to the first supporting member  84 . 
         [0019]    The rack cover  90  includes two side walls  92 ,  94 , and a top wall  96 . The two side walls  92 ,  94  are attached to two sides of the supporting rack  80 . In order to match inclination of the universal joint chain  70 , each one of the two side walls  92 ,  94  is a rectangular sheet defining a cut out corresponding to the inclination of the universal joint chain  70 . The top wall  96  is attached to two inclined edges of the side walls  92 ,  94 . In other cases, the rack cover  90  may be designed in other shapes as long as the other shapes can also effectively enclose the universal joint chain  70 . 
         [0020]    Furthermore, the first universal joint  73  and the fastening member  88  are depicted in detail hereinafter. Referring to  FIG. 4 , the fastening member  88  includes two U-shaped bolts  882  and four nuts  884 . Each end of the U-shaped bolts  882  defines a threading. Each end of the U-shaped bolts  882  can pass through a corresponding guiding hole  820  defined in the supporting beam  82 , and engageable with a corresponding nut  884 . 
         [0021]    Referring to  FIG. 5 , the first universal joint  73  includes a spider  730 , a first yoke  731  connected with the first rotatable shaft  52 , and a second yoke  733  connected with the second rotatable shaft  75 . The first yoke  731  and the second yoke  733  engages with the spider  730 . The spider  730  can transmit rotation from the first yoke  731  to the second yoke  733 . 
         [0022]    The first yoke  731  forms two first pins  7310  on two opposite sides and facing each other. The first pins  7310  define first through holes  7312  respectively. The second yoke  733  forms two second pins  7330  on two opposite sides and facing each other. The second pins  7330  define second through holes  7332  respectively. The spider  730  includes a cube  735 , a first cylinder pole  737 , and two second cylinder poles  739 . The cube  735  defines a third through hole  7351  and a fourth through hole  7352  intersecting with each other. The first cylinder pole  737  is fixed in the first through holes  7312  and the third through hole  7351  to support the third through hole  7351  between the first pins  7310 . The fourth through hole  7352  is divided into two parts by the first cylinder pole  737 . The second cylinder poles  739  pass through the second through holes  7332 , and then fixed into the two parts of the fourth through hole  7352 . The second universal joint  77  is similar to the first universal joint  73  in structure. 
         [0023]    In assembly, the first cylinder pole  737  is fixed in the first through holes  7312  and the third through hole  7351 , and then the second cylinder poles  739  are fixed in the second through holes  7332  and the fourth through hole  7352 . Therefore, the spider  730  is fixed between the first yoke  731  and the second yoke  733  to construct the first universal joint  73 . In the same way, the second universal joint  77  can also be constructed. Two ends of the universal joint chain  70  is fixed into the first positioning hole  840  and the second positioning hole  860 , and further engages with the driver  50  and the detachable head  60  correspondingly. The two U-shaped bolts  882  tie the driver  50  to the supporting beam  82  with the four ends of the U-shaped bolts  882  passing through the four guiding holes  820  defined in the supporting beam  82  to engage with the nuts  884  correspondingly. The two side walls  92 ,  94  are attached to two sides of the supporting rack  80  correspondingly. The top wall  96  is attached to the inclined edges of the side walls  92 ,  94 . 
         [0024]    It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, 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 invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.