Abstract:
A cutting accessory detachably mounted on an oscillating power tool is disclosed. The oscillating power tool includes a head housing and an output shaft extending from the head housing. The output shaft rotates oscillatingly about a longitudinal axis thereof. The cutting accessory includes a housing adapted to the head housing, two movable blades partly received in the housing, and a driving element adapted to the output shaft. The driving element is configured to oscillate by the actuation of the output shaft and simultaneously drives the two movable blades to move in the opposite directions to cut a workpiece.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an accessory of a power tool, in particular to a cutting accessory detachably mounted on an oscillating power tool. The present invention also relates to an oscillating power tool using the cutting accessory. 
       BACKGROUND OF THE INVENTION 
       [0002]    An Oscillation tool is a common oscillating power tool. Its output shaft rotates and swings around the axis, so with different accessory tool bits installed on the output shaft, many different operation functions can be realized, such as sawing, cutting, grinding and scraping, thus meeting different working demands. 
         [0003]    However, many oscillation tools do not currently have a special accessory tool bit for realizing shearing and cutting operations, and if they use the existing accessory tool bit, such as the saw blade, they achieve an undesirable cutting effect. Therefore, other tools, such as electric scissors, are required to meet the shearing and cutting demands of the user. 
         [0004]    At present, common electric scissors comprise two knives, one of which usually is a fixed knife, while the other is a moving knife which moves relative to the fixed knife. The moving knife is connected with the transmission shaft and can generate reciprocating oscillation by the action of the motor, while the fixed knife is kept still. Thus, by means of the reciprocating movement of the moving knife, the shearing and cutting functions of the scissors are realized. 
         [0005]    In the field, a cutting accessory capable of being applied to the oscillating power tool is needed to expand the application scope of the oscillation tool. To meet this demand, a publicized German patent application DE102008030024A1 discloses a cutting accessory capable of being applied to the oscillation tool. The structure of this cutting accessory is similar to that of the electric scissors, also comprising a fixed knife and a moving knife driven by the output shaft of the oscillation tool to oscillate reciprocatingly. 
         [0006]    However, when the cutting accessory applied to the oscillating power tool cuts an object, only the moving knife imposes a cutting force onto the object, so the cutting force is not enough and the cutting efficiency is low. 
         [0007]    Thus, it is truly necessary to provide an improved cutting accessory to overcome the shortcomings of the cutting accessory applied to the oscillating power tool. 
       SUMMARY OF THE INVENTION 
       [0008]    The object of the invention is to disclose a cutting accessory which is capable to detachably mount on an oscillating power tool and has an improved efficiency. 
         [0009]    A cutting accessory detachably mounted on an oscillating power tool, the oscillating power tool includes a head housing and an output shaft extending from the head housing. The output shaft reciprocatingly rotates along the axis of the output shaft. The cutting accessory includes a housing adapted to the head housing, two movable blades partly received in the housing, and a driving element adapted to the output shaft. The driving element reciprocatingly rotates driven by the output shaft and simultaneously drive the two moving knives moving in the opposite directions to cut a workpiece. 
         [0010]    In a preferred embodiment, the driving element includes a mounting portion adapted to the output shaft and two driving portions symmetrically disposed relative the mounting portion. The two driving portions adapt to the two movable blades respectively. 
         [0011]    In a preferred embodiment, in each pair of one driving portions of the driving element and one movable blade, one of the driving portion and the movable blade includes a groove and the other includes a roller configured to be received and rolled in the groove. 
         [0012]    In a preferred embodiment, each groove includes two straight sections which are located in the middle part of the groove and are parallel to each other. 
         [0013]    In a preferred embodiment, the angle of the straight sections of one of the grooves relative to the line of the centers of the grooves is different from the angle of the straight sections of the other groove relative to the line of the centers of the grooves. 
         [0014]    In a preferred embodiment, the grooves are formed at the driving portions respectively, and the centers of the two grooves and the center of mounting portion are located in a line. 
         [0015]    In a preferred embodiment, the two movable blades pivotably connect to the same pivoting shaft. The axis of the pivoting shaft is substantially parallel to the longitudinal axis of the output shaft. 
         [0016]    In a preferred embodiment, the centers of the rollers are equidistant from the center of the pivoting shaft. 
         [0017]    In a preferred embodiment, the housing includes an upper cover and a lower cover adapted to the upper cover. The driving element and two movable blades disposed between the upper cover and the lower cover. 
         [0018]    In a preferred embodiment, the housing includes an opening and a fixing portion adapted to the head housing. The output shaft configured to pass through the opening. 
         [0019]    In a preferred embodiment, the housing includes a slot configured for receiving the driving element, and the driving element configured to rotate oscillatingly in the slot 
         [0020]    In a preferred embodiment, the two movable blades each include a head portion, a cutting portion and a connecting portion between the head portion and the cutting portion. The head portions cooperate with the driving element respectively. The connecting portions pivotably connect to the housing. The driving element is configured to drive the cutting portions of the movable blades to move in the opposite directions. 
         [0021]    In a preferred embodiment, the cutting accessory further includes a guide element fixed with the head housing. The movable blades each includes a head portion cooperating with the driving element, a cutting portion and a guiding portion cooperating with the guide element. The cutting portions each have cutting teeth. The cutting teeth of the cutting portion of one of the movable blades are opposite to the cutting teeth of the cutting portion of the other movable blade. The driving element is configured to drive the two movable blades to move in the opposite directions by the engagement of the guide element and the guide portion. 
         [0022]    In a preferred embodiment, the plane defined by the two movable blades is substantially perpendicular to the longitudinal axis of the output shaft and the cutting portions of the movable blades each include the cutting teeth at both sides thereof. 
         [0023]    Another object of the invention is providing an oscillating power tool having capable of cutting and improved cutting efficiency. 
         [0024]    To achieve the object, the solution of the invention is as below: An oscillating power tool includes a head housing, an output shaft protruding out of the head housing and a cutting accessory mounted on the output shaft. The output shaft rotates oscillatingly about a longitudinal axis thereof. The cutting accessory includes two movable blades which move relative to the head housing, and a driving element adapted to the output shaft. The driving element is configured to oscillate by the actuation of the output shaft and to simultaneously drive the two movable blades to move in opposite directions to cut a workpiece. 
         [0025]    To achieve the object, another solution of the invention is as below: An oscillating power tool includes a head housing, an output shaft protruding out of the head housing and a cutting accessory mounted on the output shaft. The output shaft rotates oscillatingly about a longitudinal axis thereof. The cutting accessory includes a housing adapted to the head housing, two movable blades partly received in the housing and a driving element adapted to the output shaft. The two movable blades both have head portions, cutting portions and connecting portions between the head portions and the cutting portions. The two head portions cooperate with the driving element respectively. The two connecting portion pivotably connect to the housing and the driving element drive the two movable blades to move in the opposite directions. 
         [0026]    To achieve the object, another solution of the invention is as below: An oscillating power tool includes a head housing, an output shaft protruding out of the head housing and a cutting accessory mounted on the output shaft. The output shaft rotates oscillatingly about a longitudinal axis thereof. The cutting accessory includes a driving element adapted to the output shaft, two movable blades extending longitudinal and a guide portion adapted to the guide element. The cutting portions are both disposed of corresponding cutting teeth, the driving element drives the two movable blades to move in the opposite directions by the guide element. 
         [0027]    The advantage of the invention is: the cutting accessory is capable of detachably mounting on an oscillating power tool, the two movable blades move in the opposite direction driven by the driving element to realize cutting movements, the two movable blades are both capable of imposing cutting force on the cutting object for improving cutting efficiency. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]      FIG. 1  is a solid view of an oscillating power tool mounted on a cutting accessory in a preferred embodiment. 
           [0029]      FIG. 2  is a solid view in another direction of the oscillating power tool shown in  FIG. 1 . 
           [0030]      FIG. 3  is an illustration of part of structure of the oscillating power tool shown in  FIG. 1 . 
           [0031]      FIG. 4  is a solid view of the cutting accessory shown in  FIG. 1  (in face). 
           [0032]      FIG. 5  is a solid view of the cutting accessory shown in  FIG. 1  (in back). 
           [0033]      FIG. 6  is a solid exploded view of the cutting accessory shown in  FIG. 3 . 
           [0034]      FIG. 7  is a solid exploded view in another direction of the cutting accessory shown in  FIG. 3   
           [0035]      FIG. 8  is an illustration of structure of the cutting accessory shown  FIG. 3  released the cover. 
           [0036]      FIG. 9  is a using status illustration of the cutting accessory shown in  FIG. 4 , which the angle of the two moving knives is α 1 . 
           [0037]      FIG. 10  is a using status illustration of the cutting accessory shown in  FIG. 4 , which the angle of the two moving knives is α 2 . 
           [0038]      FIG. 11  is a using status illustration of the cutting accessory shown in  FIG. 4 , which the angle of the two moving knives is α 3 . 
           [0039]      FIG. 12  is a solid view of an oscillating power tool in a second embodiment. 
           [0040]      FIG. 13  is a solid exploded view of the oscillating power tool shown in  FIG. 12 . 
           [0041]      FIG. 14  is a solid exploded view in another direction of the oscillating power tool shown in  FIG. 12 . 
           [0042]      FIG. 15  is a using status illustration of the cutting accessory shown in  FIG. 12 , which the driving element is in a horizontal position. 
           [0043]      FIG. 16  is a using status illustration of the cutting accessory shown in  FIG. 12 , which the driving element rotate to an ultimate position in clockwise. 
           [0044]      FIG. 17  is a using status illustration of the cutting accessory shown in  FIG. 12 , which the driving element rotate to an ultimate position in counterclockwise. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0045]    The present invention is further described in detail with reference to the attached drawings and the specific embodiments. 
         [0046]    First, the first embodiment of the present invention is described in detail with references from  FIG. 1  to  FIG. 11 . 
         [0047]    See  FIGS. 1 to 3 . The first embodiment of the present invention provides an oscillating power tool  100 , comprising an oscillation body  1  and a cutting accessory  2  installed on the body  1 . The body  1  drives the cutting accessory  2  to realize a shearing function similar to that of the scissors, capable of being used to shear articles such as thin iron sheets and blankets. 
         [0048]    In the full text of the description, the right side of the oscillating power tool  100  as shown in  FIG. 1  is defined as “front”, and the left side “rear”. The body  1  comprises a housing  10 , a motor (not shown in the figure) and a transmission mechanism (not shown in the figure) that are received in the housing  10 , and an output shaft  11  driven by the transmission mechanism. Wherein, the housing  10  extending along the lengthwise direction comprises a head housing  12  located in the front portion of the body  1  and a flange plate  13  located in the rear portion of the head housing  10 . The motor is arranged in the flange plate  13 . The transmission mechanism is arranged in the head housing  12 . The motor shaft extends forward to be adapted to the transmission mechanism. The transmission mechanism converts the rotation motion output by the motor shaft into the reciprocating rotation motion of the output shaft  11  around its own X-axis. The cutting accessory  2  is arranged below the head housing  12  of the body  1 , approximately parallel to the flange plate  13  of the body  1 , and is axially connected to the output shaft  11  through a fastener  3 . 
         [0049]    The body  1  also comprises a cable  14  connected to the rear portion of the flange plate  13  and providing power for the motor, and a switch  15  controlling the power transmission. When the switch  15  is turned on, the motor drives the cutting accessory  2  to cut; when the switch  15  is turned off, the motor stops rotation, and then the cutting accessory  2  stops working. 
         [0050]    The head housing  12  is approximately “L” shaped, with one end connected to the flange plate  13  and the other end approximately shaped as an increasingly contracting circular truncated cone. The output shaft  11  is received in the head housing  12 , with one end adapted to said transmission mechanism and the other end extending outwards from the free end of the head housing  12 ; and the extension direction of the output shaft  11  approximately vertical to that of the flange plate  13 . The tail end of the output shaft  11  is provided with an orthohexagonal casing  111 . The middle portion of the casing  111  is provided with a thread hole  112  for receiving and fixing the fastener  3 . The free end of the output shaft  11  is also provided with a ring-shaped flange  113  around the casing  111 . The upper surface of the flange  113  is lower than that of the casing  111  so as to radially support the cutting tool  2 . 
         [0051]    See  FIG. 4  and  FIG. 5 . In this embodiment, the cutting accessory  2  and the body  1  are detachably and separately designed. The cutting accessory  2 , as an independent accessory, is installed on the body  1  through the fastener  3 . The cutting accessory  2  comprises a housing  27 , a driving element  22  received in the housing  27 , a first moving knife  23  and a second moving knife  24  partly extending out of the housing  27 . In this embodiment, the housing  27  comprises an upper cover  20  and a lower cover  21  adapted to the upper cover  20 . The driving element  22 , the first moving knife  23  and a second moving knife  24  are respectively received in the space formed by the upper cover  20  and the lower cover  21 . The first moving knife  23  and a second moving knife  24  are connected to the two ends of the driving elements  22 . The first moving knife  23  and a second moving knife  24  are crossly pivoted together and are arranged pivotally relative to the upper cover  20 . With the cutting accessory  2  installed on the body  1 , when the body  1  works, the motor drives the output shaft  11  to reciprocatingly rotate so as to drive the driving element  22  adapted to the output shaft  11  to reciprocatingly rotate, and then the driving element  22  drives the first moving knife  23  and the second moving knife  24  to relatively and reciprocatingly rotate so as to realize the cutting function. 
         [0052]    See  FIG. 6  and  FIG. 7 . The structure of the cutting accessory  2  will be described in detail. Wherein, the upper and lower covers  20 ,  21  both are made from plastic materials through injection molding. The lower cover  21  is approximately square shaped, and the edges on four sides thereof are uniformly formed with three throughholes  211 ; while the upper cover  20  is formed with three thread holes  201  corresponding to said throughholes  211 . Three bolts  25  respectively penetrate through the three throughholes  211  of the lower cover  21  into the three thread holes  201  of the upper cover  20  so as to fix the lower cover  21  and the upper cover  20  together. 
         [0053]    The upper cover  20  is hollow, comprising an approximately square base  202  and a fixed portion  203  connected to the base  202 . The plane where the base  202  exists is vertical to the X-axis of the output shaft  11 , and the middle portion is provided with a round opening  204 . The shape of the fixing portion  203  is approximately similar to that of said head housing  12  and can just be in tight fit with the head housing  12 . The fixing portion  203  is formed by extending from one side of the base  202  to the output shaft  11 , comprising a hollow, cylindrical receiving portion  205  surrounding the opening  204  and a “U” shaped fixing section  206  formed by extending from one side of the receiving portion  205  to the flange plate  13 . In this way, the fixing portion  203  can be coated on the lower side of the head housing  12 . By the common action of the receiving portion  205  and the fixing section  206 , the cutting accessory  2  can be conveniently and quickly installed on the body  1  and is not easily moved while working. 
         [0054]    The upper cover  20  is also equipped with a metal reinforcement  26 . The reinforcement  26  is a narrow strip; one end thereof is provided with an annular sleeve  261  extending into the opening  204  of the upper cover  20 , while the other end is provided with a pivoting shaft  262  extending downwards along the lower cover  21  along the X-axis of the output shaft  11 , which means that the axis of the pivoting shaft  262  is parallel to the X-axis of the output shaft  11 . Wherein, the inner diameter of the sleeve  261  is equivalent to the outer diameter of the flange  113  on the output shaft  11  such that the flange  113  can be completely received in the sleeve  261 , which means that the two are in tight contact. To install the reinforcement  26 , the bottom of the upper cover  20  is provided with a first groove  207  adapted to the shape of the reinforcement  26  towards the lower cover  21 . The pivoting shaft  262  is shaped as a hollow cylinder. Said first moving knife  23  and said second moving knife  24  are crossly arranged on the pivoting shaft  262  and can pivot relative to each other around the pivoting shaft  262 . The reinforcement  26  also comprises a screw  263  received in the pivoting shaft  262  for axially fixing the first moving knife  23  and the second moving knife  24 . 
         [0055]    The lower cover  21  is installed on the base  202  of the upper cover  20 , so the driving element  22 , the first moving knife  23  and the second moving knife  24  are received in the space formed by the upper and lower covers  20 ,  21 . Through installing the lower cover  21 , on one hand, the structure of the whole cutting accessory  2  is more stable and compact, and on the other hand, it performs dust prevention to guard the driving element  22  and the two moving knives  23 ,  24  in the space against dust. The lower cover  21  is similar to the shape of the base  202  of the upper cover  20 , and the middle portion thereof is provided with a hole  212  corresponding to the opening  204  of the upper cover  20 . The inner diameter of the hole  212  is bigger than the maximum outer diameter of the fastener  3  such that the fastener  3  can pass through the hole  212  of the lower cover  21  to be adapted to the driving element  22 . 
         [0056]    The two moving knives  23 ,  24  are approximately “L” shaped, crossly pivoted on the pivoting shaft  262  of the reinforcement  26 , and both are made of metal. The first moving knife  23  has a first head portion  231 , a first cutting portion  232  arranged opposite to the first head portion  231 , and a first connecting portion  233  located between the first head portion  231  and the first cutting portion  232 , and the first connecting portion  233  is provided with a first bore  234 ; correspondingly, the second moving knife  24  has a second head portion  241 , a second cutting portion  242  arranged opposite to the second head portion  241 , and a second connecting portion  243  located between the second head portion  241  and the second cutting portion  242 , and the second connecting portion  243  is provided with a second bore  244 . The first moving knife  23  and the second moving knife  24  respectively pass through the first bore  234  and the second bore  244  and then are sleeved on the pivoting shaft  262  of the reinforcement  26  in turn and cascaded together; moreover, the first cutting portion  232  and the second cutting portion  242  extend out of the housing  27  for convenient cutting. In addition, to be adapted to the driving element  22 , the first moving knife  23  is provided with a first roller  235  installed on the free end of the first head portion  231 , and the second moving knife  23  is provided with a second roller  245  installed on the free end of the second head portion  241 . To facilitate cutting, the included angles formed between the head portions of the two moving knives and the cutting portion are different. In this embodiment, the included angle between the first head portion  231  of the first moving knife  23  and the first cutting portion  232  is an approximately right angle, while the included angle between the second head portion  241  of the second moving knife  24  and the second cutting portion  242  is an approximately obtuse angle. The first cutting portion  232  and the second cutting portion  242  form an opening at a certain angle. During cutting, an object can first enter the opening between the first cutting portion  232  and the second cutting portion  242 , thus the object can be cut conveniently. 
         [0057]    The driving element  22  is adapted to the output shaft  11  and driven by the output shaft  11  to actuate the two cutting knives  23 ,  24  to reciprocatingly rotate so as to realize cutting operation. The side, facing the lower cover  21 , of the upper cover  20  is provided with a second groove  208  for receiving the driving element  22 . The second groove  208  is vertically crossed with the first groove  207 . The shape of the second groove  208  is similar to the driving element  22 , but bigger than the driving element  22 , so the driving element  22  can reciprocatingly rotate around the X-axis of the output shaft  11  by a certain angle in the second groove  208  and avoid mutual interference. The driving element  22  is made of metal, approximately oval; the middle portion is provided with a throughhole  221  through which the fastener  3  passes; and the two ends are symmetrically provided with a first driving portion  222  and a second driving portion  223 . The driving element  22  has a first side face  224  facing the upper cover  20  and a second side face  225  facing the lower cover  21 , wherein, the first side face  224  is provided with a mounting portion  226  adapted to the casing  111  of the output shaft  11 ; the mounting portion  226  is a dodecagonal recess; the second side face  225  is provided with a first groove  227  and a second groove  228  which are respectively located on the first driving portion  222  and the second driving portion  223 . The mounting portion  226  is located in the centre of the driving element  22 , and the throughhole  221  passes through the mounting portion  226  from the right centre. The first groove  227  is used for receiving the first roller  235  of the first moving knife  23 , and the second groove  228  is used for receiving the second roller  245  of the second moving knife  24 . The first groove  227  and the second groove  228  both are long-waist shaped and identical in size. The first roller  235  and the second roller  245  can respectively slide in the first groove  227  and the second groove  228 . 
         [0058]    As shown in  FIG. 8 , the centre of the driving element  2  is A; moreover, in the state as shown in this figure, the centers of the first groove  227  and the first roller  235  are superimposed at B; the centers of the second groove  228  and the second roller  245  are superimposed at C; and the centre of the pivoting shaft  262  is D. The first groove  227  comprises two first straight sections  2271  located in the middle portion in parallel and the first arc sections  2272  symmetrically located at the two ends. Correspondingly, the second groove  228  comprises two second straight sections  2281  located in the middle portion in parallel and second arc section  2282  symmetrically located at two ends. The included angle between the first straight section  2271  and the central line BC of the first groove  227  and the second groove  228  is γ 1 , and the included angle between the second straight section  2281  and the central line BC of the first groove  227  and the second groove  228  is γ 2 . In addition, the distances from the centers of the first roller  235  and the second roller  245  to the centre of the pivoting shaft  262  are equal, namely BD=CD, so the two moving knives  23 ,  24  can synchronously rotate while working, thereby improving the cutting efficiency. 
         [0059]    In this embodiment, the assembly process of the cutting accessory  2  is as follows: first, install the reinforcement  26  in the first slot  207  of the upper cover  20 , in which the pivoting shaft  262  faces the lower cover  21 ; next, press the driving element  22  on the reinforcement  26  and place in the second slot  208  of the upper cover  20 ; then, cascade and sleeve the first moving knife  23  and the second moving knife  24  on the pivoting shaft  26  of the reinforcement  26  in turn, receive and fix the screw  263  in the pivoting shaft  262 ; next, receive the first roller  235  of the first moving knife  23  in the first groove  227  of the driving element  22 , receive the second roller  245  of the second moving knife  24  in the second groove  228  of the driving element; at last, fasten the lower cover  21  on the upper cover  20 , and fix the upper and lower covers  20  and  21  together through three bolts  25 . Through the above steps, the assembly of the cutting accessory  2  is completed. During use, the cutting accessory  2  is adapted to and fixed on the head housing  12  of the body  1 ; the fastener  3  passes through the hole  212  of the lower cover  21  and the throughole  221  of the driving element  22  and is connected into the thread hole  112  of the output shaft  2  so as to axially fix the driving element  22  relative to output shaft  11 , so the cutting accessory  2  is fixed with the body  1  and driven by the body  1  to realize the cutting function. 
         [0060]    The following is a detailed description of the cutting principle of the cutting accessory  2  with reference to the  FIGS. 2 ,  5 ,  9  to  11 . The mounting portion  226  of the driving element  22  is adapted to the casing  111  of the output shaft  11 . The first roller  235  on the first head portion  231  of the first moving knife  23  is received in the first groove  227  of the driving element  22 . The second roller  245  on the second head portion  241  of the second moving knife  24  is received in the second groove  228  of the driving element  22 . The first moving knife  23  and the second moving knife  24  are pivotally, crossly sleeved on the pivoting shaft  262  of the reinforcement  26 , and axially limited through the screw  263 . 
         [0061]    When the oscillating power tool  100  works, the motor shaft of the body  1  drivers the output shaft  11  through the transmission mechanism to reciprocatingly rotate, and then the output shaft  11  drives the driving element  22  to reciprocatingly rotate through the fit between the casing  111  and the mounting portion  226  of the driving element  22 . The sizes of the first groove  227  and the second groove  228  of the driving element  22  are respectively approximately equivalent to those of the first roller  235  corresponding to the first moving knife  23  and the second roller  245  corresponding to the second moving knife  24 . The first roller  235  and the second roller  245  can rotate in the corresponding first slot  227  and second slot  228  and meanwhile can slide relative to the inside walls of the first slot  227  and the second slot  228 . 
         [0062]    In this embodiment, the oscillating angle of the output shaft  11  of the oscillating power tool  100  is 2β, namely the value of the angle between the clockwise oscillating limit position and the anticlockwise oscillating limit position of the output shaft  11 , wherein 2β=0.5°-10°, which means that the oscillating frequency of the output shaft  11  is 500-250,000 times/min Obviously, the oscillating angle and oscillating frequency of the oscillating power tool  100  in the present invention are not limited in the above scope, and may be other numerical values. 
         [0063]    As shown in  FIG. 9 , the output shaft  11  drives the driving element  22  to anticlockwise oscillate to the limit position. At this moment, the included angle between the first cutting portion  232  of the first moving knife  23  and the second cutting portion  242  of the second moving knife  24  is α 1 . 
         [0064]    As shown in  FIG. 10 , the output shaft  11  drives the driving element  22  to rotate β clockwise, oscillating to the initial position of the driving element  22 . In this process, the driving element  22  drives the first moving knife  23  to rotate clockwise around the pivoting shaft  262  through the fit between the first slot  227  and the first roller  235 , and meanwhile drives the second moving knife  24  anticlockwise around the pivoting shaft  262  through the fit between the second slot  228  and the second roller  245 , thus reducing the distance between the first head portion  231  and the second head portion  241  and finally increasing the included angle between the first cutting portion  232  and the second cutting portion  242  from α 1  to α 2 . 
         [0065]    As shown in  FIG. 11 , the output shaft  11  drives the driving element  22  to rotate β clockwise, oscillating to the clockwise limit position. In this process, the driving element  22  drives the first moving knife  23  to continuously rotate clockwise around the pivoting shaft  262  through the fit between the first slot  227  and the first roller  235 , and meanwhile drives the second moving knife  24  continuously anticlockwise around the pivoting shaft  262  through the fit between the second slot  228  and the second roller  245 , thus reducing the distance between the first head portion  231  and the second head portion  241  and finally increasing the included angle between the first cutting portion  232  and the second cutting portion  242  from α 2  to α 3 . 
         [0066]    Therefore, the included cutting angle between the first cutting knife  23  and the second cutting knife  24  increases from α 1  to α 3 , thus completing the opening operation of the scissors accessory; on the contrary, when the driving element  22  rotates β anticlockwise, the included cutting angle between the first cutting knife  23  and the second cutting knife  2  decreases from α 3  to α 1 , thus completing the closing operation of the scissors accessory. Repeatedly, the first cutting portion  232  of the first moving knife  23  reciprocatingly rotates relative to the second cutting portion  242  of the second moving knife  24 , thereby realizing the object cutting function. 
         [0067]    It should be pointed out that the present invention is not limited to the separated design of the cutting accessory and body disclosed in the above embodiment, in which the cutting accessory is installed on the body. Those skilled in this field can easily think that the cutting accessory of the present invention can also be integrated with the body through processing. 
         [0068]    In the above embodiment, the casing of the output shaft is orthohexagonal, while the mounting portion of the driving element is dodecagonal, so the casing can be adapted to the mounting portion to realize that the output shaft can drive the driving element instead of generating relative sliding when reciprocatingly rotating, and meanwhile limit the driving element at many different angular positions according to demands. Those skilled in this field can think that the casing of the output shaft and the mounting portion of the driving element can also be combined in other way, for example, the mounting portion of the driving element is also processed to be orthohexagonal; the plural column-shaped projections on the output shaft are inserted into the corresponding holes on the driving element, or projections in other shapes (such as the star shape) on the output shaft are inserted into the holes in corresponding shapes on the driving element. 
         [0069]    Compared with the prior art, the first embodiment of the present invention provides an oscillating power tool with a cutting accessory, wherein the output shaft drives the driving element to reciprocatingly rotate, and then the driving element drives the two moving knives to relatively reciprocatingly rotate so as to realize the cutting function. In the related art, the cutting accessory applied to the oscillating power tool realizes cutting through a movable blade and a fixed blade. Therefore, compared with the cutting accessory disclosed in the related art, the cutting accessory of the present invention can provide bigger cutting force and therefore greatly improves the cutting efficiency. 
         [0070]    The following are detailed descriptions of the second embodiment of the present invention with reference to the  FIGS. 12 to 17 . 
         [0071]    As shown in  FIG. 12 , the oscillating power tool  200  in this embodiment is identical with that in the first embodiment in the body  1 , but different in the cutting accessory  4 . The cutting accessory  4  is also detachably and separately designed. The cutting accessory  4  as an independent accessory is installed on the body  1  through the fastener  5 . The cutting accessory  4  comprises an upper cover  40 , a lower cover  41  adapted to the upper cover, a driving element  44  received between the upper and lower covers  40 ,  41 , and a first moving knife  43  and a second moving knife  44  respectively connected to the driving element  42 . The first and second moving knives  43 ,  44  are cascaded together and can reciprocatingly translate relative to the upper cover  40 . With the cutting accessory  4  installed on the body  1 , when the body  1  works, the motor drives the output shaft  11  to reciprocatingly rotate so as to drive the driving element  42  adapted to the output shaft  11  to reciprocatingly rotate, and then the driving element  42  drives the first moving knife  43  and the second moving knife  44  to relatively and reciprocatingly translate so as to realize the cutting function. 
         [0072]    See  FIG. 13  and  FIG. 14 . The structure of the cutting accessory  4  will be described in detail. The lower cover  41  is an approximately rectangular flat plate, provided with four througholes  411  in a scattered way. The upper cover  40  is also provided with four througholes  401  corresponding to the throughholes  411 . Between the upper cover  40  and the lower cover  41  are four hollow supporting posts  45  located between the througholes  401  and the througholes  411 . Four bolts  46  respectively pass through the throughholes  411  of the lower cover  41 , the supporting posts  45  and the througholes  401  of the upper cover  40  and finally are fixed through four nuts, so the lower cover  41  and the upper cover  40  are fixed together. Through installing the supporting posts  45 , a large enough space is formed between the upper and lower covers  40 ,  41  to receive the driving element  40  and the upper and lower moving knives  43 ,  44  and enable the upper and lower moving knives  43  to freely and reciprocatingly translate. 
         [0073]    Wherein, the upper cover  40  comprises an approximately flat plate-shaped supporting element  402  and a fixing portion  403  on the supporting element  402 . The plane where the supporting element  402  exists is vertical to the X-axis of the output shaft  11  and is approximately parallel to the lower cover  41 . The fixing portion  403  is formed by extending from one side of the supporting element  402 , approximately similar to the shape of the head housing  12 , and just can be tightly sleeved on the head housing  12 . One side, away from the head housing  12 , of the supporting element  402  projects and extends to form a guide element  404  along the direction parallel to the X-axis of the output shaft  11 . The guide element  404  is step-like, comprising a bigger first lug  405  and a smaller second lug  406 . The two lugs both are cuboid shaped, wherein the second lug  406  extends from the middle portion of the first lug  405  and away from the output shaft  11 . 
         [0074]    The lower cover  41  is installed on the supporting element  402  of the upper cover  40 , so the driving element  42 , the first moving knife  43  and the second moving knife  44  are received in the space formed by the upper and lower covers  40 ,  41 . One side of the lower cover  41  is provided with an opening  412  corresponding to the fixed portion  403  of the upper cover  40 . The size of the opening  412  is bigger than the maximum outer diameter of the fastener  5 , so the fastener  5  can penetrate through the opening  412  of the lower cover  41  to be adapted to the driving element  42 . The other side of the lower cover  41 , corresponding to the guide element  404  of the upper cover  40 , is provided with a stop hole  413  capable of being sleeved on the second lug  406  of the guide element  404 , so the first moving knife  43  and the second moving knife  44  are axially limited on the guide element  404  of the upper cover  40 . 
         [0075]    The two moving knives  43 ,  44  both are approximately flat plate shaped, and the plane where the two exist is vertical to the X-axis of the output shaft  11 . The two moving knives  43  and  44  are symmetrically shaped, and extend lengthwise along the direction approximately vertical to the driving element  42 . The first moving knife  43  has an approximately “L”-shaped first head portion  431  and a linear first cutting portion  432  vertically extending from the first head portion and away from one end of the driving element  42 . The second moving knife  44  has a second head portion  441  shaped symmetric to the first head portion  431  of the first moving knife  43  and a second cutting portion  442  vertically extending from the second head portion  441  and away from one end of the driving element  42 . One end, away from the first cutting portion  432 , of the first head portion  431  of the first moving knife  43  is provided with a first roller  433  projecting towards the driving element  42 ; correspondingly, the second head portion  441  of the second moving knife  44  is provided with a second roller  443 . The two moving knives  43 ,  44  are respectively connected to the driving element  42  through the first roller  433  and the second roller  443  so as to be driven by the driving element  42 . The first cutting portion  432  of the first moving knife  43  and the second cutting portion  442  of the second moving knife  44  are superimposed together. The first cutting portion  432  and the second cutting portion  442  respectively extend towards two sides to form plural first cutting teeth  434  and second cutting teeth  444 . The first cutting portion  432  and the second cutting portion  442  relatively and reciprocatingly translate, and then the opposite cutting teeth  434  and  444  perform cutting. The first cutting portion  432  of the first moving knife  43  is also provided with a first track  435  matched with the guide element  404  of the upper cover  40 , and the second cutting portion  442  of the second moving knife  44  is correspondingly provided with a second track  445 . The first track  435  and the second track  445  both are long strip-shaped openings, mutually run through and just have enough size to receive the second lug  406  of the guide element  404 , so the second lug  406  can slide in the first track  435  and the second track  445 . 
         [0076]    It should be pointed out that, those skilled in this field can easily think that the first track and the second track in this embodiment can also be provided with projections, and correspondingly the guide element of the upper cover is formed with long strip-shaped openings by processing. 
         [0077]    The driving element  42  is adapted to the output shaft  11  and driven by the output shaft  11  to actuate the two cutting knives  43 ,  44  to reciprocatingly translate so as to realize cutting operation. The driving element  42  is made of metal, approximately rectangular; the middle portion thereof is provided with a mounting portion  421  adapted to the casing  111  of the output shaft  11 ; and the two ends are symmetrically provided with a first driving portion  422  and a second driving portion  423 . Wherein, the mounting portion  421  is an orthohexagonal opening, equivalent to the casing  111  of the output shaft  11  in size, and can just receive the casing  111 . The first driving portion  422  is provided with a first groove  424 , and the second driving portion  423  is correspondingly provided with a second groove  425 . The central line of the two grooves passes through the centre of the mounting portion  421 . The middle portion of the first groove  424  is provided with two parallel and opposite first straight sections  4241 , while middle portion of the second groove  425  is also provided with two parallel and opposite second straight sections  4251 . The first groove  424  is used for receiving the first roller  433  of the first moving knife  43 , and the second groove  425  is used for receiving the second roller  443  of the second moving knife  44 . The first groove  424  and the second groove  425  both are long waist-shaped, identical in size, and a little bigger than the first roller  433  and the second roller  443 . The first roller  433  and the second roller  443  can respectively slide on the first groove  424  and the second groove  425 . 
         [0078]    In this embodiment, the assembly process of the cutting accessory  4  is as follows: first, place on the driving element  42  on the supporting element  402  of the upper cover  40 ; then, superpose and install the first moving knife  43  and the second moving knife  44  on the supporting element  402  of the upper cover  40  such that the first track  435  of the first moving knife  43  and the second track  445  of the second moving knife  44  are respectively sleeved on the second lug  406  of the guide element  404  of the upper cover  40 ; meanwhile, receive the first roller  433  of the first moving knife  43  in the first groove  424  of the driving element  42 , receive the second roller  443  of the second moving knife  44  in the second groove  425  of the driving element  42 ; next, respectively place the four supporting posts  45  corresponding to the four througholes  401  on the supporting element  402  of the upper cover  40 , fasten the lower cover  41  on the upper cover  40  such that the stop hole  413  of the lower cover  41  is sleeved on the guide element  404  of the upper cover  40 ; at last, respectively penetrate through four bolts  46  through the througholes  411  of the lower cover  41 , the supporting posts  45  and the througholes  401  of the upper cover  40 , and fix with nuts  47 . 
         [0079]    Through the above steps, the assembly of the cutting accessory  4  is completed. During use, the cutting accessory  4  is adapted to and fixed on the head housing  12  of the body  1 , so the mounting portion  421  of the driving element  42  is adapted to the casing  111  of the output shaft  11 , and the fastener  3  is connected to the thread hole  112  of the output shaft  11  to axially fix the driving element  42  relative to the output shaft  1 . Therefore, the cutting accessory  4  is fixed with the body  1  and driven by the body  1  to realize the cutting function. 
         [0080]    The following is the detailed description of the cutting principle of the cutting accessory  4  with reference to the  FIGS. 12 ,  13 ,  15  to  17 . The mounting portion  421  of the driving element  42  is adapted to the casing  111  of the output shaft  11 . The first roller  433  on the first head portion  431  of the first moving knife  43  is received in the first groove  424  of the driving element  42 . The second roller  443  on the second head portion  441  of the second moving knife  44  is received in the second groove  425  of the driving element  42 . The first moving knife  43  and the second moving knife  44  can relatively and reciprocatingly translate and are crossly sleeved on the guide element  404  of the upper cover  40 . When the oscillating power tool  200  works, the motor shaft of the body  1  drivers the output shaft  11  through the transmission mechanism to reciprocatingly rotate, and then the output shaft  11  drives the driving element  42  to reciprocatingly rotate through the fit between the casing  111  and the mounting portion  421  of the driving element  42 . By the action of the guide element  404  of the upper cover  40 , the driving element  42  drives the first moving knife  43  and the second moving knife  44  to relatively and reciprocatingly translate, so the cutting teeth  434 ,  444  of the first cutting portion  432  and the second cutting portion  442  perform cutting. 
         [0081]    In this embodiment, the oscillating angle of the output shaft  11  of the oscillating power tool  200  is 2β, namely the value of the angle between the clockwise oscillating limit position and the anticlockwise oscillating limit position of the output shaft  11 , wherein 2β=0.5°-10°, which means that the oscillating frequency of the output shaft  11  is 500-250,000 times/min Obviously, the oscillating angle and oscillating frequency of the oscillating power tool  200  in this embodiment are not limited in the above scope, and may be other numerical values. 
         [0082]    As shown in  FIG. 15 , the driving element  42  is located at an approximately level position; the first cutting portion  432  of the first moving knife  43  and the second cutting portion  442  of the second moving knife  44  are approximately superimposed; the distance between the adjacent cutting teeth  43 ,  44  in the vertical direction is D 1 . 
         [0083]    As shown in  FIG. 16 , the output shaft  11  drives the driving element  42  to rotate β clockwise. In this process, through the fit between the first roller  433  and the first groove  424  and the guiding of the guide element  404  of the upper cover  40  and the first track  435 , the driving element  42  drives the first moving knife  43  to vertically downward translate at a certain distance; meanwhile, through the fit between the second groove  425  and the second roller  443  and the guiding of the guide element  404  of the upper cover  40  and the second track  445 , the driving element  42  drives the second moving knife  44  to vertically upward translate at a certain distance. This results in that the first cutting portion  432  and the second cutting portion  442  are staggered at a certain distance after reciprocating translation, and the distance between the cutting teeth  43 ,  44  in the vertical direction is decreased from D 1  to D 2 , and thus, cutting of the object placed between the cutting teeth  43 ,  44 , such as twigs, can be realized. 
         [0084]    As shown in  FIG. 17 , contrary to that as shown in  FIG. 16 , the output shaft  11  drives the driving element  42  to rotate β anticlockwise, oscillating to the anticlockwise limit position. In this process, the driving element  42  drives the first moving knife  43  to vertically upward translate at a certain distance and meanwhile drives the second moving knife  44  to vertically downward translate at a certain distance, which results in that the first cutting portion  432  and the second cutting portion  442  are staggered at a certain distance after reciprocating translation, and that the distance between the cutting teeth  43 ,  44  in the vertical direction is decreased from D 1  to D 2 , and thus, cutting of the object placed between the cutting teeth  43 ,  44 , such as twigs, can be realized. 
         [0085]    Compared with the prior art, this embodiment provides an oscillating power tool with a cutting accessory; the output shaft drives the driving element to reciprocatingly rotate; then the driving element drives the two moving knives to relatively and reciprocatingly translate so as to realize the cutting function. It can be used to prune plants in the garden, has high cutting efficiency than the common electric pruning shears, and therefore widens the application scope of the oscillation tool.