Patent Publication Number: US-2021161076-A1

Title: Electric pruner saw

Description:
TECHNICAL FIELD 
     The present invention relates to a pruning tool, in particular to an electric pruner saw. 
     BACKGROUND ART 
     An electric pruner saw is a convenient tool for pruning bushes or other trees to beautify the environment.  FIG. 1  shows an electric pruner saw in the prior art, comprising: a handle, a main body part and a saw. The main body part comprises: a housing  11 , and a motor  12  and a wobble bearing  13  which are arranged in the housing  11 . The saw ( 14 ,  15 ) extends from inside the housing  11  to outside the housing  11 . The saw comprises two parts, namely a saw blade  14  and a saw rod  15 ; the columnar saw rod  15  is arranged in the pruner saw housing  11 , and an extremity of the saw blade  14  is fixed to a front end of the saw rod  15 . The saw blade  14  extends forwards out of the pruner saw housing  11  from the front end of the saw rod  15 . When the motor  12  is connected to a power supply, an output shaft of the motor rotates, and drives the wobble bearing  13  to move by means of a transmission mechanism (two gears meshed with each other are shown demonstratively in  FIG. 1 ). Teeth of the wobble bearing  13  convert rotational motion of the motor output shaft into linear reciprocating motion. The wobble bearing  13  comprises a rotating rod  16 , a joint part, and a swing rod  17  extending outwards from an outer surface of the joint part; the swing rod  17  is coupled to the rotating rod  16  via the joint part. A gear is fixed to the rotating rod  16 ; this gear is meshed with a gear on the output shaft of the motor  12 , and transfers rotation of the output shaft of the motor  12  to the rotating rod  16 , such that the rotating rod  16  also correspondingly rotates. The swing rod  17  coupled to the rotating rod  16  via the joint part swings back and forth as the rotating rod  16  rotates. A spherical far end of the swing rod  17  is rotatably coupled to the saw rod  15 , and the swinging of the swing rod  17  back and forth drives the saw rod  15  (and thus drives the saw blade  14 ) in reciprocating linear motion, i.e. vibration, in an axial direction of the saw rod  15 ; the saw blade  14  is thereby used to cut tree leaves and branches, etc. 
     It is clear from the operating principle of the electric pruner saw above that when the pruner saw is operating, the saw will generate considerable vibration. When an operator holds the electric pruner saw in his/her hands to prune bushes, etc., large-amplitude vibration of the pruner saw makes it difficult for the operator to control the movement direction of the pruner saw when pruning bushes or sawing wood, and furthermore is likely to harm the operator&#39;s arm bones and joints; in addition, long periods of vibration cause a person&#39;s muscles to suffer fatigue, thus shortening the operator&#39;s working time. 
     Thus, there is a need for an improved pruner saw with reduced vibration. 
     Furthermore, there is also a need for a pruner saw with a reduced volume, not only to make carrying easier, but also so that it takes up less space when stored in a warehouse or toolbox. 
     SUMMARY OF THE INVENTION 
     In response to the abovementioned shortcomings of an existing pruner saw, the inventors of the present invention have created the present invention. 
     According to one aspect of the present invention, a balancing component is added to an electric pruner saw; the balancing component and a saw vibrate at the same frequency in parallel directions, but the phases of vibration of the balancing component and saw differ by 180°, such that the opposite-phase vibration of the balancing component partially or completely offsets the vibration of the saw. 
     According to another aspect of the present invention, a wobble bearing in the pruner saw is arranged at an upper side of a motor, such that a rotating rod of the pruner saw is located between the motor and a saw rod; thus, the wobble bearing is closer to the saw rod, so the length of a swing rod of the wobble bearing is shortened, and consequently the various components are arranged more compactly, thus reducing the volume of the pruner saw. 
     According to an embodiment of the present invention, an electric pruner saw is provided, comprising a motor ( 12 ), a wobble bearing ( 13 ) and a saw ( 14 ,  15 ), wherein the wobble bearing ( 13 ) comprises a rotating rod ( 16 ) and a swing rod ( 17 ), and the motor ( 12 ) can drive the rotating rod ( 16 ) to rotate via a transmission mechanism, and in turn drive the swing rod ( 17 ) to swing back and forth in a plane, thereby driving the saw ( 14 ,  15 ) to vibrate linearly; and the electric pruner saw further comprises a balancing component ( 21 ), the balancing component ( 21 ) comprising a track ( 21 - 2 ), a slider ( 21 - 3 ) and a protrusion ( 21 - 1 ) mounted to the slider in a fixed manner, the protrusion ( 21 - 1 ) protruding from a surface of the slider ( 21 - 3 ), and the track ( 21 - 2 ) limiting movement of the slider ( 21 - 3 ) and protrusion ( 21 - 1 ), such that the slider ( 21 - 3 ) and protrusion ( 21 - 1 ) move linearly along the track ( 21 - 2 ) in a direction parallel to a movement direction of the saw, wherein an annular groove ( 16 - 1 ) is formed on an outer surface of the rotating rod ( 16 ), the annular groove ( 16 - 1 ) being formed obliquely relative to the rotating rod ( 16 ); the balancing component ( 21 ) is arranged close to the rotating rod ( 16 ), such that the protrusion ( 21 - 1 ) is inserted into the groove ( 16 - 1 ), and under the driving action of the motor ( 12 ), when the rotating rod ( 16 ) rotates, a wall of the groove ( 16 - 1 ) pushes the protrusion ( 21 - 1 ), such that the slider ( 21 - 3 ) and the protrusion ( 21 - 1 ) vibrate linearly along the track ( 21 - 2 ), wherein the slider ( 21 - 3 ) and the saw ( 14 ,  15 ) have the same frequency of vibration, but the vibration of the slider ( 21 - 3 ) and the vibration of the saw ( 14 ,  15 ) differ in phase by 180°. 
     According to another preferred embodiment of the present invention, an electric pruner saw is provided, wherein the saw ( 14 ,  15 ) is arranged at an upper side of the motor ( 12 ), and the balancing component ( 21 ) and the wobble bearing ( 13 ) are also arranged at the upper side of the motor ( 12 ), such that the balancing component ( 21 ) and the rotating rod ( 16 ) of the wobble bearing ( 13 ) are located between the saw ( 14 ,  15 ) and the motor ( 12 ). 
     According to another preferred embodiment of the present invention, an electric pruner saw is provided, wherein the total mass of the slider ( 21 - 3 ) and the protrusion ( 21 - 1 ) is M 1 , and the mass of the saw is M 2 : the amplitude of vibration of the slider ( 21 - 3 ) is d 1 , and the amplitude of vibration of the saw is d 2 , wherein the following relations are satisfied: 
       M1&lt;M2; 
       d1&gt;d2. 
     According to another preferred embodiment of the present invention, an electric pruner saw is provided, wherein the following relation is satisfied: 
         M 1 *d 1 =M 2* d 2   (1).
 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is explained in further detail below in conjunction with the drawings and embodiments; in the drawings: 
         FIG. 1  is a sectional view of an example of a pruner saw in the prior art. 
         FIG. 2  is a sectional view of an example of a pruner saw according to an embodiment of the present invention. 
         FIG. 3A  is a front view of some components extracted from  FIG. 2  which are directly relevant to the present invention. 
         FIG. 3B  is a perspective view from behind, of the components shown in  FIG. 3A . 
         FIG. 4  is an exploded perspective view of the various components in  FIG. 3B , separated in the Y direction. 
         FIG. 5  is a perspective view, from below, of the wobble bearing and balancing component. 
         FIG. 6  is a perspective view, from above, of the wobble bearing. 
         FIG. 7A  is a schematic drawing of the positions of the relevant components when the rotating rod of the wobble bearing is at a phase of 0°. 
         FIG. 7B  is a schematic drawing of the positions of the relevant components when the rotating rod of the wobble bearing is at a phase of 180°. 
         FIG. 8  shows the results of actual measurement of the amplitudes of vibration of a pruner saw in the prior art and the pruner saw according to an embodiment of the present invention. 
         FIG. 9  shows a sectional view of the pruner saw according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     To clarify the object, technical solution and advantages of the present invention, the present invention is explained in further detail below by means of embodiments in conjunction with the drawings. It should be understood that the particular embodiments described here are merely intended to explain the present invention, not to limit it. 
       FIG. 2  shows a sectional view of an example of a pruner saw according to an embodiment of the present invention. The pruner saw shown in  FIG. 2  makes some improvements relative to the pruner saw in the prior art. First of all, unlike the prior art example shown in  FIG. 1 , the position of the wobble bearing  13  in this embodiment has been moved upwards so as to be substantially above the motor  12  (this can be seen more clearly in the schematic drawing of a number of extracted components shown in  FIG. 3 ); the rotating rod  16  of the wobble bearing  13  is close to the motor  12 , and located directly above the motor  12 . This arrangement results in the wobble bearing  13  being closer to the saw rod  15 , thereby shortening the length of the swing rod  17 , and also results in the various components inside the housing  11  being arranged more compactly. Furthermore, a vibration suppression mechanism has been added in the pruner saw. In the prior art, vibration of the pruner saw is caused by reciprocating vibration of the saw in a longitudinal direction thereof. In order to suppress this vibration of the saw, the inventors of the present invention have designed a mechanism, employing a balancing component in such a way that when the saw vibrates, the balancing component and the saw vibrate synchronously but with opposite phases, thereby reducing the overall vibration amplitude of the pruner saw. This vibration suppression mechanism is presented in detail below. 
     For clarity, some components relevant to the present invention have been extracted from  FIG. 2  and are shown in a front view in  FIG. 3A , omitting any components that are not directly related to the content to be presented herein. 
     Referring to  FIGS. 2 and 3A , the pruner saw of this embodiment further comprises a balancing component  21 , on which is provided a protrusion  21 - 1 . Furthermore, a groove  16 - 1  is provided on a surface of the rotating rod  16  of the wobble bearing  13 , with the protrusion  21 - 1  on the balancing component being inserted into the groove  16 - 1 . The groove  16 - 1  is formed in an encircling manner on an outer surface of the rotating rod  16 , and takes the form of an inclined ring (the enlarged drawings in  FIGS. 5 and 6  show the groove  16 - 1  more clearly). A cross section of the groove  16 - 1  may be, but is not limited to being, semicircular; correspondingly, a cross section of an end of the protrusion  21 - 1  has the same shape, such that the end of the protrusion  21 - 1  can just be inserted into the groove  16 - 1 . When the groove  16 - 1  rotates with rotation of the rotating rod  16 , a wall of the groove  16 - 1  applies a pushing force to the protrusion  21 - 1  inserted into the groove  16 - 1 , thereby driving the balancing component  21  in linear reciprocating motion in an axial direction (i.e. the X direction) of the rotating rod  16 . 
     In  FIG. 3A , the extracted components are coupled together.  FIG. 3B  shows a perspective view, from the right, of the various components coupled together in  FIG. 3A .  FIG. 4  shows the various components in  FIG. 3B  in a state of having been separated from one another, thus displaying more clearly the various independent components. 
     Again referring to  FIGS. 3A, 3B and 4 , a gear  12 - 2  is fixed to the output shaft of the motor  12 , and another gear  16 - 2  is fixed to the rotating rod  16  of the wobble bearing  13 ; these two gears are meshed with each other as a transmission mechanism. When the output shaft of the motor  12  rotates, the rotating rod  16  of the wobble bearing  13  is driven to rotate by means of the two gears meshed with each other, and the swing rod  17  of the wobble bearing  13  is in turn driven to swing back and forth in the plane of the picture in  FIG. 3A . Since the spherical extremity of the swing rod  17  is rotatably coupled to the saw rod  15 , the swinging of the swing rod  17  drives the saw (including the saw rod  15  and saw blade  14 ) to vibrate in a horizontal direction (i.e. the X direction). 
     In addition, the groove  16 - 1  is formed by processing on the outer surface of the rotating rod  16  in the embodiment shown in  FIGS. 3A and 3B ;  FIG. 3A  shows a portion of the groove  16 - 1  located on a front-side surface of the rotating rod  16 . This portion of the groove  16 - 1  is arranged in a spiral form on the front-side surface of the rotating rod  16 , i.e. the groove  16 - 1  extends spirally along a front-side outer surface of the rotating rod  16  from a topmost part of the rotating rod  16  to a bottommost part of the rotating rod  16 . Here, the topmost part of the rotating rod  16  is a horizontally extending straight line at the highest position on the cylindrical outer surface of the rotating rod  16  when the cylindrical rotating rod  16  lies in a horizontal direction (the X direction), and the bottommost part is a horizontally extending straight line at the lowest position of the cylindrical outer surface of the rotating rod  16  lying in the horizontal direction. Furthermore, another portion of the spiral groove  16 - 1  is provided on a rear-side surface of the rotating rod  16 , being mirror-symmetrical with the portion of the groove  16 - 1  on the front-side surface; the two portions of the groove  16 - 1  are joined head-to-tail, thus forming a closed ring nested on the outer surface of the rotating rod  16 . The closed ring is formed obliquely on the outer surface of the rotating rod  16 . 
       FIG. 6  shows the wobble bearing  13  obliquely from above. It can be seen in  FIG. 6  that the two portions of the groove  16 - 1  at the front side and rear side of the rotating rod  16  are joined together smoothly at the topmost part of the rotating rod  16 . Although not shown in  FIG. 6 , it will be understood that the two portions of the groove  16 - 1  at the front side and rear side are likewise joined together smoothly at the bottommost part of the rotating rod  16 . This closed ring may be formed by machining on the outer surface of the rotating rod  16 . 
     In addition, it should be noted that as the rotating rod  16  rotates, a connection point of the two portions of the groove  16 - 1  that is initially located at the topmost part of the rotating rod  16  will gradually rotate to the bottommost part of the rotating rod  16 , and at the same time, a connection point that is initially located at the bottommost part of the rotating rod  16  will gradually rotate to the topmost part of the rotating rod  16 . In other words, as the rotating rod  16  rotates, all parts of the groove  16 - 1  in the form of the closed ring (or all points on the groove  16 - 1  if the groove  16 - 1  is approximately regarded as a line-like ring) successively rotate to the topmost part of the rotating rod  16 , and then successively rotate to the bottommost part of the rotating rod  16 , and this cycle is repeated. 
     The embodiment shown in  FIGS. 3A, 3B and 4  further comprises the balancing component  21 ; the balancing component  21  is preferably arranged at an upper side of the rotating rod  16 , in a position between the rotating rod  16  and the saw. Under the driving action of the rotating rod  16 , the balancing component  21  can vibrate with an opposite phase as the saw vibrates, thereby suppressing the vibration of the entire electric pruning saw caused by vibration of the saw rod  15  and saw blade  14 . 
       FIG. 5  is an enlarged perspective view, from below, of the balancing component  21  and wobble bearing, and shows more clearly the composition of the balancing component  21  and the positional relationship of the protrusion  21 - 1  of the balancing component  21  and the groove  16 - 1 . 
     Referring to  FIG. 5 , the balancing component  21  comprises a protrusion  21 - 1 , a track  21 - 2  and a slider  21 - 3 . The track  21 - 2  is mounted in a fixed manner in the housing  11 , and the position of the track  21 - 2  relative to the wobble bearing  13  is fixed and does not change. The track  21 - 2  has an internal cavity, and the cross-sectional size and shape of the slider  21 - 3  are matched to the cross-sectional size and shape of the internal cavity of the track  21 - 2 , such that the slider  21 - 3  can slide back and forth in one direction (the X direction in an embodiment) in the internal cavity of the track  21 - 2 , and walls of the internal cavity of the track  21 - 2  limit the slider  21 - 3  so that it cannot move in another direction. The protrusion  21 - 1  is fixed to a lower surface of the slider  21 - 3 , protruding from the lower surface of the slider  21 - 3 , and passes through an opening of the track  21 - 2  on a lower surface. The height to which the protrusion  21 - 1  protrudes from the lower surface of the slider  21 - 3  is greater than the thickness of a bottom wall of the track  21 - 2 , such that the slider  21 - 3  can be inserted into the groove  16 - 1  on the rotating rod  16  at the topmost part of the rotating rod  16 . 
     In the embodiment above, the track  21 - 2  substantially has the shape of a box that is open at two ends and also has an opening at the bottom, but the present invention is not limited to this; the track  21 - 2  may also be another shape, as long as the track  21 - 2  can limit linear movement of the slider  21 - 3  parallel to the movement direction of the saw (the X direction). 
     In  FIG. 5 , for greater clarity, the balancing component  21  and wobble bearing  13  are in a separated state. As will be understood, moving the balancing component  21  downwards causes the protrusion  21 - 1  to be inserted into the groove  16 - 1  on the rotating rod  16  at the topmost part of the rotating rod  16 . With the protrusion  21 - 1  inserted into the groove  16 - 1  on the rotating rod  16 , rotation of the rotating rod  16  causes the wall of the groove  16 - 1  to push the protrusion  21 - 1  to move. As stated above, the track  21 - 2  of the balancing component  21  is mounted in a fixed manner in the housing  11 , and does not move relative to the rotating rod  16 ; under the pushing action of the wall of the groove  16 - 1 , the protrusion  21 - 1  and slider  21 - 3  together reciprocate linearly in the horizontal direction (the X direction). 
     Those skilled in the art will readily understand that when the rotating rod  16  rotates through one revolution, one cycle of reciprocating motion of the protrusion  21 - 1  and slider  21 - 3  takes place, and at the same time, one cycle of swinging of the swing rod  17  of the wobble bearing  13  also takes place. The spherical extremity  13 - 1  of the swing rod  17  is rotatably coupled to the saw rod  15 . Under the driving action of the swing rod  17 , one cycle of reciprocating motion of the saw (the saw rod  15  and saw blade  14 ) also takes place. As can be seen, the vibration period of the balancing component  21  and the vibration period of the saw are the same. 
       FIGS. 7A and 7B  show corresponding changes in position of the saw and the protrusion  21 - 1  and slider  21 - 3  when the phase of the rotating rod  16  is 0° and 180° (i.e. a half-cycle of rotation) respectively. For clarity, in the figure the saw, balancing component  21  and wobble bearing  13  are separated in the vertical direction (i.e. the Y direction), and the track  21 - 2  of the balancing component  21  and the gear on the wobble bearing  13  are omitted in the figure. 
     Referring to  FIG. 7A , when the phase of the rotating rod  16  is 0°, a leftmost point of the obliquely arranged annular groove  16 - 1  as described above (i.e. one connection point of the abovementioned two symmetrically arranged portions of the groove  16 - 1 ) is located at a point K 1  at the topmost part of the rotating rod  16 , and a rightmost point of the Obliquely arranged annular groove  16 - 1  (i.e. the other connection point of the abovementioned two portions of the groove  16 - 1 ) is located at the bottommost part of the rotating rod  16 . As stated above, the protrusion  21 - 1  is inserted into the groove  16 - 1  at the topmost part of the rotating rod  16 ; thus, the position of the protrusion  21 - 1  is the same as the position of a point of the groove  16 - 1  that is at the topmost part of the rotating rod  16 . Clearly, when the phase of the rotating rod  16  is 0°, the position of the protrusion  21 - 1  in the horizontal direction is also located at point K 1 . At the same time, the swing rod  17  of the wobble bearing  13  swings to a rightmost position, such that the saw moves with the swing rod  17  to a rightmost position N 1 . 
     When the rotating rod  16  rotates through a half-revolution and the phase is 180°, referring to  FIG. 7B , the rightmost point of the groove  16 - 1  that was originally at the bottommost part of the rotating rod  16  when the phase was 0° rotates to a point K 2  at the topmost part of the rotating rod  16 . Correspondingly, the protrusion  21 - 1  also moves from point K 1  to point K 2 . At the same time, the swing rod  17  swings to a leftmost position, driving the saw to move leftwards to a leftmost position N 2 . 
     In summary, as the wobble bearing  13  moves, the protrusion  21 - 1  and the slider  21 - 3  that is fixed to the protrusion  21 - 1  reciprocate linearly in the X direction between K 1  and K 2 , and the saw reciprocates linearly between N 1  and N 2 . The slider  21 - 3  (and protrusion  21 - 1 ) and the saw always move in opposite directions. The slider  21 - 3  and protrusion  21 - 1  vibrate at the same frequency as the saw, but with opposite phases (180° apart), and the overall vibration of the pruning saw is thereby reduced. 
     In the embodiment above, the balancing component  21  is linked to the swing rod  17  via the rotating rod  16 , the groove  16 - 1  thereon and the protrusion  21 - 1  on the balancing component  21  such that the slider  21 - 3  of the balancing component  21  and that end of the swing rod  17  which is coupled to the saw rod  15  move with opposite phases. However, the present invention is not limited to this. It should be understood that the balancing component and the swing rod may be linked in any other way. For example, it can be imagined that no groove  16 - 1  is provided on the rotating rod  16  and no protrusion  21 - 1  is provided on the balancing component  21 ; instead, a side face of the slider  21 - 3  of the balancing component  21  is coupled via a suitable connecting rod mechanism (not shown) to a protrusion (not shown) on another end  13 - 2  of the swing rod  17  that is opposite the end  13 - 1  coupled to the saw rod  15 , to transmit swinging motion of this other end via the connecting mechanism to reciprocating linear motion of the slider  21 - 3  in the track  21 - 2 . Since the protrusion on this other end  13 - 2  of the swing rod  17  and the end  13 - 1  thereof coupled to the saw rod  15  move with opposite phases, the slider  21 - 3  linked in this manner also moves with an opposite phase to that of the end  13 - 1  of the swing rod  17  that is coupled to the saw rod  15 , and thus moves with an opposite phase to that of the saw ( 14 ,  15 ), thereby achieving the effect of reducing the overall vibration of the pruner saw. 
     As another example, it can be imagined that no groove  16 - 1  is provided on the rotating rod  16  no protrusion  21 - 1  is provided on the balancing component  21 , and no connecting rod mechanism is provided between the slider and the swing rod; instead, a transmission mechanism (e.g., a gear set) is provided between the balancing component  21  and the gear  16 - 2  fixed to the rotating rod  16 , to transmit rotational motion of the gear  16 - 2  fixed to the rotating rod  16  to reciprocating linear motion of the slider  21 - 3  in the track  21 - 2 . 
     In the embodiment above, the balancing component  21  comprises the track ( 21 - 2 ) and the slider ( 21 - 3 ) capable of moving linearly in the track ( 21 - 2 ). However, the present invention is not limited to this. It can be understood that the balancing component  21  may have another structure. For example, the balancing component  21  may merely be a counterweight, arranged at the other end  13 - 2  of the swing rod  17  that is opposite the end  13 - 1  coupled to the saw rod  15 , and configured to balance the swing rod  17  and the saw, thereby reducing the overall vibration of the pruner saw. 
       FIGS. 7A and 7B  show the distance between K 1  and K 2  as being d 1 , i.e. the slider  21 - 3  (and protrusion  21 - 1 ) vibrate within the range of distance d 1 .  FIGS. 7A and 7B  also show the distance between N 1  and N 2  as being d 2 , i.e. the saw vibrates within the range of distance d 2 . The distances d 1  and d 2  shown in  FIGS. 7A and 7B  are schematic, and not intended to define d 2 &gt;d 1 . 
     Suppose that the total mass of the slider  21 - 3  and protrusion  21 - 1  is M 1 , and that the total mass of the saw (the saw rod  15  and saw blade  14 ) is M 2 . In a preferred embodiment, preferably d 1 &gt;d 2 , M 1 &lt;M 2 . Choosing M 1  to be less than the mass M 2  of the saw helps to reduce the weight of the pruner saw as a whole. 
     In another preferred embodiment, M 1 , M 2 , d 1  and d 2  substantially satisfy the following relation: 
         M 1 *d 1 =M 2 *d 2   (1)
 
     When the condition of formula (1) is satisfied, the momentum of the slider  21 - 3  and protrusion  21 - 1  while reciprocating is substantially equal to the momentum of the saw while vibrating, but the two momenta are in opposite directions; thus, the vibration of the slider  21 - 3  and protrusion  21 - 1  offsets the vibration of the saw to the maximum extent. 
     In order to actually test the vibration reduction effect of the pruner saw of the present invention, the vibration amplitudes of the pruner saw of the present invention and a pruner saw in the prior art have been actually measured herein; by comparing the measurement results, an obvious improvement in the vibration reduction effect by the present invention can be seen, In the actual measurement, a pruner saw serving as a comparative example is a pruner saw in the prior art, with no balancing component mounted therein; a pruner saw improved according to an embodiment of the present invention is the X1-type pruner saw in the prior art mentioned above with a balancing component of weight 1.1 kg mounted therein. The vibration acceleration amplitude (in units of m/s 2 ) at the handle, while sawing pine, of the pruner saw improved according to the present invention and the pruner saw in the prior art is measured.  FIG. 8  shows the actual measurement results; the vertical axis in  FIG. 8  is the amplitude of vibration (acceleration) actually measured, while the horizontal axis represents different diameters of the pine being sawed. It can be seen from  FIG. 8  that for the various diameters of pine, the vibration amplitude of the pruner saw improved according to the present invention is reduced by about 50% compared with the pruner saw in the prior art. 
       FIG. 9  is a sectional view of a main body part of a pruner saw in another embodiment of the present invention. The difference between this embodiment and the embodiment shown in  FIGS. 2 and 3  is that, in the embodiment shown in  FIGS. 2 and 3 , a rotating shaft of the motor  12  is parallel to the rotating rod  16  (i.e. the included angle therebetween is 0); in the embodiment shown in  FIG. 9 , the motor  12  has been rotated anticlockwise through an angle α. Thus, an axis of the rotating shaft of the motor  12  and an axis of the rotating rod  16  of the wobble bearing  13  form an angle α, the angle α being an acute angle. This makes the internal structure of the pruner saw more compact and the overall volume of the pruner saw smaller. Ranges of the angle α are 0.5-20 degrees, 1-15 degrees, 2-10 degrees, 2-8 degrees, 2-6 degrees, 3-5 degrees, and preferably 3 degrees. 
     In the various embodiments above, the rotating rod  16  of the wobble bearing  13  and the balancing component  21  are arranged between the saw and motor  12 , but the present invention is not limited to this. The rotating rod  16  and balancing component  21  may also be arranged in another region; for example, the rotating rod  16  and balancing component  21  are arranged below the motor  12 . However, the rotating rod  16  and balancing component  21  are preferably arranged between the saw and motor  12 . 
     In the various embodiments above, the transmission mechanism comprises two gears, i.e. the gear  12 - 2  on the rotating shaft of the motor  12 , and the gear on the rotating rod  16  of the wobble bearing  13 , the two gears being meshed with each other, thereby transmitting rotation of the rotating shaft of the motor  12  to the rotating rod  16 , such that the rotating rod  16  also rotates. The present invention is not limited to this; in another embodiment, the transmission mechanism may comprise a third gear, the third gear being separately meshed with the gear  12 - 2  on the rotating shaft of the motor  12  and the gear on the rotating rod  16 , thereby transmitting rotation of the rotating shaft of the motor  12  to the rotating rod  16 . In another embodiment, the transmission mechanism may comprise a greater number of gears, meshed with each other in a manner understandable to those skilled in the art, to achieve the effect of motive power transmission. In another embodiment, transmission may be effected via a transmission belt or any other suitable transmission mechanism. 
     In addition, it can also be imagined that the rotating rod  16  may be an extension of the output shaft of the motor  12  or a part of the output shaft, in which case the two transmission gears in the embodiment above need not be provided. 
     Although the present invention is explained by means of particular embodiments, those skilled in the art should understand that various changes and equivalent substitutions could be made to the present invention without departing from the scope thereof. Furthermore, various amendments could be made to the present invention for specific scenarios or materials, without departing from the scope of the present invention. Thus, the present invention is not limited to the is particular embodiments disclosed, but should include all embodiments falling within the scope of the claims of the present invention.