Abstract:
The present invention discloses a vegetation pruning device comprising a main body; a cutting element; a guide bar for supporting the cutting element; a motor for driving the cutting element; a first handle assembly; a second handle assembly; a locking mechanism for detachably securing the second handle assembly to the first handle assembly; a connecting mechanism being positioned between the first handle assembly and the guide bar; the first handle assembly or the second handle assembly being operable to move linearly toward to or away from the guide bar, the connecting mechanism is provided to change the linearly movement of the first or the second handle assembly to the pivoting of the guide bar. Both of the first handle assembly and the second handle assembly are moving linearly, which makes the operator feel comfortable in any working instance.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application is the entry into the national phase and claims the benefit of priority of International Patent Application No. PCT/CN2010/075212, filed Jul. 16, 2010, which application claims priority to Chinese Application No. 200910161624.0 filed Jul. 17, 2009, each of which is incorporated herein by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure relates to a vegetation pruning device, more particularly to a vegetation pruning device with an extending rod, for example a chain saw with an extending rod. 
       BACKGROUND 
       [0003]    There are considerable array of tools available for the modern gardeners. For example, shears are used to pruning or cutting “light” vegetation such as grass or leaves or twigs etc. Hedge trimmers and chain saws are used to cutting “heavy” vegetation such as trees. 
         [0004]    A traditional chain saw comprises a cutting head. The cutting head comprises a flexible chain and a guide bar for supporting the flexible chain. The flexible chain is driven by a motor received in a motor housing and runs along the peripheral of the guide bar. A traditional chain saw further comprises a main handle positioned behind the cutting head, an assistant handle positioned between the cutting head and the main handle. During cutting, the cutting head is driven by the motor and the flexible chain runs along the peripheral of the guide bar, the guide bar does not move with respect to the motor housing. In operation, one hand of the operator grasps the main handle, and the other hand of the operator grasps the assistant handle, the operator should press the saw toward the cutting direction to ensure smoothly cutting. When the cutting direction is from up to down, operating of the traditional chain saw will be not so hard for the gravity of the saw. But if the cutting is from down to up or from left side to right side, operating of the traditional saw will be very hard and need great effort. 
         [0005]    U.S. Published Patent Application No. 2005/0022388A1 discloses a vegetation pruning device. The vegetation pruning device comprises a cutting head. The cutting head comprises a flexible chain and a guide bar for supporting the flexible chain. The flexible chain is driven by a motor and running around the guide bar. The vegetation pruning device further comprises a pair of pivotally coupled arms. The pivotally coupled arms rotate about a fixed axis. The cutting head is connected to one of the arm and can pivot together with the arm around the fixed axis relative to the other arm. Each arm is connected with a handle portion for the operator to grip. In use, the operator moves the handle portions close to each other, the arms will move close correspondingly, thereby the cutting work can be proceed. But this kind of vegetation pruning device makes that in some instance the operation is not so comfortable. For example, when you need to cut branch of high trees, it&#39;s hard to make such a cutting with this kind of vegetation pruning device. In other instance, such as cutting wood placed on the floor, the operator should bow, if the operating last long, it is very easy to feel exhaust. 
         [0006]    In other instance, the traditional chain saw generally comprises an extending rod for cutting branch of high trees, the extending rod is detachable fixed with the main handle of the chain saw. In operation, the operator grapes the extending rod with two handles, it&#39;s hard to apply the force to the direction of the cutting for the operator; it&#39;s hard to make such a cutting with this kind of vegetation pruning device. 
         [0007]    U.S. Pat. No. 7,152,328B2 discloses a vegetation pruning device. The vegetation pruning device comprises a cutting head, a main handle and an extending rod. When the operator need to cut branch of high trees, it&#39;s necessary to attach the extending rod to the main handle and make the extending rod and the main handle electrically coupled. In operation, the operator grapes the extending rod with two handles, it&#39;s hard to apply the force to the direction of the cutting for the operator, so it&#39;s hard to make such a cutting with this kind of vegetation pruning device. 
       SUMMARY 
       [0008]    It is an object of the present disclosure to provide a vegetation pruning device with improved operability. 
         [0009]    To solve above problem, the present disclosure provides a vegetation pruning device comprising: 
         [0010]    a main body; 
         [0011]    a cutting element; 
         [0012]    a guide bar for supporting the cutting element; 
         [0013]    a motor for driving the cutting element; 
         [0014]    a first handle assembly; 
         [0015]    a second handle assembly; 
         [0016]    a locking mechanism for detachably securing the second handle assembly to the first handle assembly; and 
         [0017]    a connecting mechanism positioned between the first handle assembly and the guide bar; 
         [0018]    wherein the first handle assembly or the second handle assembly is operable to move linearly toward to or away from the guide bar, and the connecting mechanism is provided to change the linear movement of the first or the second handle assembly to the pivoting of the guide bar. 
         [0019]    Optionally, both of the first handle assembly and the second handle assembly are moving linearly, which makes the operator feel comfortable in any working instance. 
         [0020]    Advantageously, the vegetation pruning device optionally comprises a support wall for pressing against a work piece to be cut. 
         [0021]    Advantageously, the vegetation pruning device optionally comprises a U-shaped guard. the U-shaped guard comprises an inner edge and a U-shaped jaw for detachably mounting on the inner edge. 
         [0022]    Advantageously, the U-shaped jaw optionally comprises an inner side and a plurality of teeth arranged on the inner side. 
         [0023]    Advantageously, the U-shaped jaw optionally is made of steel. 
         [0024]    Advantageously, the first handle assembly optionally comprises a guiding portion, and the main body comprises a handle receiving chamber for receiving the guiding portion, the handle receiving chamber having a longitudinal axis, the guiding portion being operable to move linearly along the longitudinal axis of the handle receiving chamber. 
         [0025]    Advantageously, the first handle assembly optionally further comprises a first gripping portion which is configured as D-shaped. 
         [0026]    Advantageously, the first gripping portion optionally comprises a gripping side configured as straight-lined and a connecting side configured as curve-shaped, the connecting side securing the first gripping portion to the guiding portion. 
         [0027]    Advantageously, a safety switch optionally is symmetrically attached to both ends of the gripping side. 
         [0028]    Advantageously, a control switch optionally is arranged in the inner part of the gripping side. 
         [0029]    Advantageously, the connecting mechanism optionally is configured as a planar multi-rod mechanism. 
         [0030]    Advantageously, the planar multi-rod mechanism optionally comprises driving part, a connecting part and a driven part, the driving part being acted by the first handle assembly, the driven part being fixedly attached to the guide bar, the connecting part being interposed between the driving part and the driven part and is hinged to the driving part and the driven part, respectively. 
         [0031]    Advantageously, the connecting part optionally comprises a first connecting rod hinged to the driving part, a second connecting rod having two ends hinged to the first connecting rod at one end and coupled to the main body pivotally at the other end, and a third connecting rod having two ends hinged to a middle portion of the second connecting rod at one end and hinged to the driven part at the other end. 
         [0032]    Advantageously, a torsion spring having two ends optionally is arranged between the main body and the driven part, one end of the torsion spring being fixed with the main body, the other end of the torsion spring being fixed with the driven part. 
         [0033]    Advantageously, the vegetation pruning device further optionally comprises a limiting mechanism for preventing the guide bar rotating to excess. The limiting mechanism comprises a groove formed on the main body and a projected column fixed with the guide bar, the groove comprising a first block face and a second block face formed at two ends of the groove respectively, the projected column being operable to couple with the first block face or the second block face. 
         [0034]    Advantageously, the groove optionally is configured as waist-shaped. 
         [0035]    Advantageously, the vegetation pruning device optionally further comprises a motor bracket for supporting the motor, the projected column extend from the motor bracket and penetrated the groove. 
         [0036]    Advantageously, the limiting mechanism optionally further comprises three waist-shaped grooves formed along a circumference at equal interval and three projected columns formed along the circumference at equal interval, the three projected columns penetrating the three waist-shaped grooves respectively. 
         [0037]    Advantageously, the second handle assembly optionally comprises a second gripping portion and an extending portion having two ends, the first end of the extending portion secured to the second gripping portion, the second end of the extending portion secured to the first handle assembly, the locking mechanism being positioned between the second end of the extending portion and the first handle assembly. 
         [0038]    Advantageously, the second handle assembly optionally comprises a second gripping portion and an extending portion, the second gripping portion being configured as D-shaped. 
         [0039]    Advantageously, the first handle assembly optionally comprises a first gripping portion having a receiving opening, and the locking mechanism comprises a locking bracket detachable received in the receiving opening. 
         [0040]    Advantageously, the locking bracket optionally comprises a first matched face, and the first gripping portion of the first handle assembly comprising a second matched face arranged at one side of the first handle assembly for coupling with the first matched face, the first matched face and the second matched face being the shape-matched. 
         [0041]    Advantageously, the locking mechanism optionally further comprises a locking knob being operable to lock the first gripping portion of the first handle assembly between the locking bracket and the locking knob. 
         [0042]    Advantageously, the first gripping portion of the first handle assembly optionally further comprises a third matched face, and the locking knob comprises a fourth matched face being selective to couple with the third matched face. 
         [0043]    Advantageously, the first handle assembly optionally comprises a guiding portion, a C-shaped bracket detachable secured on the guiding portion, and the main body comprises a longitudinal slot, the C-shaped bracket extending outward from the longitudinal slot and moving along with the longitudinal slot, the second handle assembly comprising an extending portion supported on the C-shaped bracket. 
         [0044]    Advantageously, a plug optionally is arranged on one of the first handle assembly and the second handle assembly, and a socket is arranged on the other of the first handle assembly and the second handle assembly, the first handle assembly being electrically coupled with the second handle assembly when the plug connected with the socket. 
         [0045]    Advantageously, the vegetation pruning device optionally further comprises a sleeve being slidable mounting on the second handle assembly, and a cord having two ends coupled with the main body with one end and coupled with the sleeve with another end. 
         [0046]    Advantageously, the main body optionally comprises a cliphook, one end of the cord is fastened on the cliphook. 
         [0047]    Advantageously, the sleeve optionally comprises a flexible cam clip which is operable to clamp the cord. 
         [0048]    Advantageously, the vegetation pruning device optionally further comprises an operating assembly having a control unit movable mounting on the second handle assembly and a joint unit detachably coupling with the main body. 
         [0049]    Advantageously, the second handle assembly optionally comprises a second gripping portion and an outer tube coupled with the first handle assembly. 
         [0050]    Advantageously, the joint unit optionally comprises an inner tube coupled with the outer tube, the inner tube comprising two ends, one end of the inner tube extending into the outer tube, the other end of the inner tube extending out the outer tube and coupling with the main body. 
         [0051]    Advantageously, the control unit optionally comprises a sleeve mounted on the outer tube and fixed with the inner tube, and the outer tube comprising a longitudinal opening, the sleeve being capable of sliding along the longitudinal opening with respect to the outer tube. 
         [0052]    Advantageously, the main body optionally comprises an opening, and the inner tube comprises a joint member having a cooperating part selectively engaged with the opening of the main body. 
         [0053]    Advantageously, the second gripping portion of the second handle assembly optionally is configured as D-shaped. 
         [0054]    Advantageously, the first handle assembly optionally comprises a first gripping portion having a control switch, and the locking mechanism comprises a first receiving chamber, the first gripping portion is locked in the first receiving chamber. 
         [0055]    Advantageously, the locking mechanism optionally comprises a base and a cover coupled with the base pivotally, and a locking member being selective to lock the cover on the base. 
         [0056]    Advantageously, the locking member optionally comprises a locking knob arranged on the cover, a locking pin fixed on the locking knob, and a clip attached to the locking pin, and the base comprises an opening having an inner wall with a ramp formed thereon, the clip being operable to engage and lock with the ramp along with the rotating of the locking member. 
         [0057]    Advantageously, the base of the locking mechanism optionally further comprises a second receiving chamber, and the outer tube comprises a first end connected with the second gripping portion of the second handle assembly and a second end received in the second receiving chamber of the locking mechanism. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0058]      FIG. 1  is a perspective view of the chain saw in accordance with the first embodiment of the present disclosure. 
           [0059]      FIG. 2  shows schematically the internal mechanism of the chain saw according to  FIG. 1 . 
           [0060]      FIG. 3  is an exploded view of the main body of the chain saw according to  FIG. 1 . 
           [0061]      FIG. 4  is a perspective view of the first half housing of the main body of the chain saw according to  FIG. 3 . 
           [0062]      FIG. 5  is a perspective view of the second half housing of the main body of the chain saw according to  FIG. 3 . 
           [0063]      FIG. 6  is a perspective view of the driven part of the chain saw according to  FIG. 2 . 
           [0064]      FIG. 7  shows principle diagram of the transmission mechanism the chain saw according to  FIG. 1 . 
           [0065]      FIG. 8  is a perspective view of the limiting mechanism of the chain saw according to  FIG. 1 . 
           [0066]      FIG. 9  is a schematic view of the chain saw in unused status according to  FIG. 1 . 
           [0067]      FIG. 10  is a schematic view of the chain saw during operating status according to  FIG. 9 . 
           [0068]      FIG. 11  is a schematic view of the chain saw in an operating status near to end according to  FIG. 1 . 
           [0069]      FIG. 12  is a perspective view of the chain saw connected with the second handle assembly according to  FIG. 1 . 
           [0070]      FIG. 13  is a partial enlarged view of the locking mechanism of the second handle assembly according to  FIG. 12 . 
           [0071]      FIG. 14  is a partial exploded view of the chain saw when the second handle assembly un-connected with the first handle assembly of the chain saw according to  FIG. 12 . 
           [0072]      FIG. 15  is a partial exploded view of the locking mechanism of the chain saw according to  FIG. 12 . 
           [0073]      FIG. 16  is a schematic view of the locking mechanism when the locking knobs of the locking mechanism located at the first position according to  FIG. 12 . 
           [0074]      FIG. 17  is a schematic view of the locking mechanism when the locking knobs of the locking mechanism located at the second position according to  FIG. 12 . 
           [0075]      FIG. 18  is a perspective view of the C-shaped bracket of the chain saw according to  FIG. 12 . 
           [0076]      FIG. 19  is a partial perspective view of the chain saw with a cord according to  FIG. 12 . 
           [0077]      FIG. 20  is a front view of the second handle assembly accordance with the second embodiment of the present disclosure. 
           [0078]      FIG. 21  is a cross-sectional view when look down according to  FIG. 20 . 
           [0079]      FIG. 22  is a exploded view of the second handle assembly according to  FIG. 20 . 
           [0080]      FIG. 23  is a perspective view of the locking mechanism of the chain saw during opening status according to  FIG. 20 . 
           [0081]      FIG. 24  is a perspective view of the chain saw accordance with the third embodiment of the present disclosure. 
           [0082]      FIG. 25  is a partial enlarged view of the portion marked with I of the chain saw according to  FIG. 24 . 
           [0083]      FIG. 26  is a perspective view of the chain saw with another second handle assembly according to  FIG. 24 . 
       
    
    
     DETAILED DESCRIPTION 
       [0084]      FIGS. 1 and 2  disclose a vegetation pruning device. In one embodiment, the vegetation pruning device is a chainsaw  20  comprises a working head  22  that includes a guide bar  24  and a cutting element installed on the guide bar  24 . In this embodiment, the cutting element is a flexible chain  26  that is installed on the periphery of the guide bar  24  and capable of rotating around the guide bar  24 . The plane on which the guide bar  24  exists is a guide bar plane. In other embodiments, the working head may be a circular blade or a saw blade of a reciprocating saw. If the working head is the circular blade, the cutting element may be regarded as the cutting part of the circular blade, and the guide bar may be regarded as the central supporting part of the circular blade. If the working head is the saw blade of the reciprocating saw, the cutting element may be regarded as the cutting blade part of the saw blade of the reciprocating saw, and the guide bar may be regarded as the supporting part of the cutting blade part of the saw blade of the reciprocating saw. 
         [0085]    The chainsaw  20  also comprises a motor  28  for driving the working head  22  so that the flexible chain  26  rotates around the guide bar  24 . The motor  28  has a motor output shaft  30  with an axis X 1 , and the motor output shaft  30  rotates around its axis X 1  to drive the flexible chain  26  to rotate around the guide bar  24 . The motor  28  is cased in a motor housing  32 . 
         [0086]    Furthermore, as shown in  FIG. 3 , the chainsaw comprises a main body  34 . In one embodiment, the main body  34  consists of two semi-housings, namely a first semi-housing  34   a  and a second semi-housing  34   b , which are detachably connected via screws. In other embodiments, the first semi-housing  34   a  and the second semi-housing  34   b  may be connected by other methods capable of being mastered by common skilled persons in this field, such as integral connection, wedge connection, etc. The motor housing  32  is detachably connected to the first semi-housing  34   a . In one embodiment, the motor housing  34   a  is connected to the first semi-housing  34   a  via screws. In other embodiments, the motor housing  34   a  may also be fixedly connected with the first semi-housing  34   a , for example: the motor housing  32  and the first semi-housing  34   a  are integrated. 
         [0087]    The saw chain  20  comprises a housing cover  35 , and the second semi-housing  34   b  has an access hole  35   a  so that a user is capable of replacing the flexible chain  26  conveniently. The housing cover  35  is detachably installed on the access hole  35   a . In this embodiment, the housing cover  35  is fixedly connected to the second semi-housing  34   b  via a bolt. In other embodiments, the housing cover  35  may also be connected to the second semi-housing  34   b  in other manners that are capable of being mastered by common skilled persons in this field. When the flexible chain  26  is not required to be replaced, the housing cover  35  covers the access hole  35   a . When the flexible chain  26  is required to be replaced, the user is capable of dismounting the housing cover  35  from the second semi-housing  34   b  with tools, such as a wrench. 
         [0088]    The chainsaw  20  comprises a first handle assembly  36  (as shown in  FIG. 1 ) for being held and operated by an operator while working. As shown in  FIG. 3 , the first semi-housing  34   a  comprises a first working head receiving end  38   a , a first handle receiving end  40   a  and a first connection portion  42   a  for connecting the first working head receiving end  38   a  and the first handle receiving end  40   a . The second semi-housing  34   b  comprises a second working head receiving end  38   b , a second handle receiving end  40   b  and a second connection portion  42   b  for connecting the second working head receiving end  38   b  and the second handle receiving end  40   b.    
         [0089]    As shown in  FIGS. 4 and 5 , the first working head receiving end  38   a  and the second working head receiving end  38   b  are approximately U-shaped. The first working head receiving end  38   a  has a first U-shaped opening  43   a . The second working head receiving end  38   b  has a second U-shaped opening  43   b.    
         [0090]    The first working head receiving end  38   a  and the second working head receiving end  38   b  together form a U-shaped guard 38  (as shown in  FIG. 1 ) of the chainsaw, and the U-shaped guard 38  is used for receiving the working head  22 . 
         [0091]    The first working head receiving head  38   a  comprises a first upper side wall  44   a  and a first lower side wall  46   a  which defines the first U-shaped opening  43   a  there-between. The second working head receiving end  38   b  comprises a second upper side wall  44   b  and a second lower side wall  46   b  which defines the second U-shaped opening  43   b  there-between. 
         [0092]    A first receiving chamber  48  (as shown in  FIG. 1 ) is formed between the first upper side wall  44   a  and the second upper side wall  44   b . A second receiving chamber  50  (as shown in  FIG. 1 ) is formed between the first lower side wall  44   a  and the second lower side wall  46   b . The first receiving chamber  48  and the second receiving chamber  50  are used for receiving the working head  22 . The first upper side wall  44   a  and the second upper side wall  44   b  respectively has a plurality of openings  52  through which the operator is capable of clearly observing the current position of the working head. 
         [0093]    The first working head receiving end  38   a  has a first U-shaped inner edge  54   a  that is circularly located on the inside of the first working head receiving end  38   a , specifically located on one side of the first working head receiving end  38   a  close to the first U-shaped opening  43   a , and a first U-shaped jaw  56   a  is detachably arranged on the first U-shaped inner edge  54   a . A ring of teeth  58   a  are arranged on the inside of the first U-shaped jaw  56   a . The first U-shaped jaw  56   a  is made of steel. The first U-shaped jaw  56   a  is connected to the first U-shaped inner edge  54   a  via rivets. 
         [0094]    The second working head receiving end  38   b  has a second U-shaped inner edge  54   b  that is circularly located on the inside of the second working head receiving end  38   b , specifically located on one side of the second working head receiving end  38   b  close to the second U-shaped opening  43   b , and a second U-shaped jaw  56   b  is detachably arranged on the second U-shaped inner edge  54   b . A ring of teeth  58   b  are arranged on the inside of the second 
         [0095]    U-shaped jaw  56   b . The second U-shaped jaw  56   b  is made of steel. The second U-shaped jaw  56   b  is connected to the second U-shaped inner edge  54   b  via the rivets. 
         [0096]    The first U-shaped inner edge  54   a  and the second U-shaped inner edge  54   b  together form the U-shaped inner edge  54  of the U-shaped guard  38 . The first U-shaped jaw  56   a  and the second U-shaped jaw  56   b  together form the U-shaped jaw  56  of the U-shaped guard 38 . 
         [0097]    The U-shaped jaw  56  of the U-shaped guard 38  is detachably connected to the U-shaped inner edge  54  of the U-shaped guard 38 . The mentioned U-shaped jaw  56  is capable of being used as a supporting wall for pressing against a work piece to be cut while working. Teeth  58   a  and teeth  58   b  are circularly arranged on the inside of the U-shaped jaw  56 . The purpose of the arrangement of the teeth  58   a  and theteeth 58   b  is to ensure that the U-shaped jaw  56  with teeth are capable of reliably supporting slim twigs and preventing them from popping out in the process of cutting operation. 
         [0098]    As shown in  FIGS. 1 and 3 , the motor housing  32  is connected to the first connection portion  42   a  of the first semi-housing  34   a  via screws. The first handle receiving end  40   a  of the first semi-housing  34   a  and the second handle receiving end  40   b  of the second semi-housing  34   b  both extend longitudinally and are connected via screws. The first handle receiving end  40   a  of the first semi-housing  34   a  and the second handle receiving end  40   b  of the second semi-housing  34   b  together form a handle receiving end  40  of the main body  34 . 
         [0099]    The handle receiving end  40  has a handle receiving chamber  59 . The handle receiving chamber  59  is formed between the first handle receiving end  40   a  and the second handle receiving end  40   b . The handle receiving chamber  59  is used for receiving the first handle assembly  36 . The handle receiving chamber  59  has a longitudinal axis X 2 , and the first handle assembly  36  is contained in the handle receiving chamber  59  and is capable of moving linearly along the longitudinal axis X 2 . 
         [0100]    Moreover, as shown in  FIG. 2 , the first handle assembly  36  comprises a guiding portion  60  and a gripping portion  62 , and the guiding portion  60  is a thin and long rod which is contained in the handle receiving chamber  59 . The gripping portion  62  is approximately D-shaped. One side of the D-shaped gripping portion  62  is a straight-lined gripping edge  64 . The other side of the D-shaped gripping portion is a curved connecting edge  66 . The gripping portion  62  is connected with the guiding portion  60  via the connecting edge  66 . A control switch  68  is arranged on the inside of the gripping edge  64  and electrically connected with the motor  28  for controlling the start-up and stop of the motor  28 . Two ends of the gripping edge  64  are symmetrically provided with safety switches  70 , so that both left-handed operation and right-handed operation are convenient. The connecting edge  66  is connected with the guiding portion  60 . 
         [0101]    The guiding portion  60  is contained in the handle receiving chamber  59  and operationally and linearly moves along the longitudinal axis X 2  of the handle receiving chamber  59 . 
         [0102]    A connecting mechanism is arranged between the first handle assembly  36  and the working head  22 . In this embodiment, the connecting mechanism is directly connected with the first handle assembly  36  and the guide bar  24  and converts the linear motion of the first handle assembly  36  into the pivotal motion of the guide bar  24 . In this embodiment, the connecting mechanism is a planar multi-rod mechanism  72 . 
         [0103]    As shown in  FIG. 2 , the planar multi-rod mechanism  72  comprises a driving part, a connecting rod and a driven part  82 . The connecting rod is positioned between the driving part and the driven part  82  and respectively hinged to the driving part and the driven part  82 . The connecting rod comprises a first connecting rod  76 , a second connecting rod  78  and a third connecting rod  80 . The guiding portion  60  of the first handle assembly  36  is configured as the driving part of the planar multi-rod mechanism  72 , and when the operator pushes the gripping portion  62  towards the working end  22 , the guiding portion  60  is capable of moving linearly along the longitudinal axis X 2  of the handle receiving chamber  59 . The driven part  82  is fixedly connected with the guide bar  24 , and the first connecting rod  76 , the second connecting rod  78  and the third connecting rod  80  are positioned between the driving part and the driven part  82 , specifically positioned between the guiding portion  60  of the first handle assembly  36  and the driven part  82 . One end of the first connecting rod  76  and the guiding portion  60  of the first handle assembly  36  have a hinged connection. The other end of the first connecting rod  76  is hinged to one end of the second connecting rod  78 , and the other end of the second connecting rod  78  is capable of being pivotally connected to the connecting portion  42   a  of the first semi-housing  34   a . One end of the third connecting rod  80  and the middle portion of the second connecting rod  78  have a hinged connection. The other end of the third connecting rod  80  and the driven part  82  has a hinged connection. 
         [0104]    As shown in  FIG. 6 , the driven part  82  is configured as V-shaped, and a first edge  84  of the V-shaped driven part  82  is hinged to the other end of the third connecting rod  80 . A second edge  86  of the V-shaped driven part  82  and the guide bar  24  are fixedly connected by the bolts. A V-shaped bottom  88  of the V-shaped driven part  82  is installed on the motor output shaft  30 . The driven part  82  is fixedly connected with the guide bar  24 , so when the driven part  82  rotates around the axis X 1  of the motor output shaft, the guide bar  24  also rotates in the plane of the guide bar around the axis X 1  of the motor output shaft. 
         [0105]      FIG. 7  is a motion schematic diagram of the planar multi-rod mechanism. The driving part (guiding portion  60 ) moves linearly; when the driving part (guiding portion  60 ) moves from a first position (represented by the full line) to a second position (represented by the dotted line), the driven part  82  pivots to the second position (represented by the dotted line) from the first position (represented by the full line); the arrow A 1  represents the motion direction of the driving part (guiding portion  60 ), and the arrow A 2  represents the motion direction of the driven part  82 . 
         [0106]    The chainsaw  20  comprises a limiting mechanism for limiting the rotation of the guide bar so as to avoid damaging the U-shaped protecting hood because of excess rotation of the guide bar. As show in  FIG. 8 , a motor bracket (not illustrated) is installed on a end of the motor  28  and fixedly connected with the motor  28 , and three projected columns  90  extend from the motor bracket along the direction of the motor output shaft  30  and are arranged at an equal interval along the circumference. Each projected column  90  has a first receiving hole  92 . The first connecting portion  42   a  of the first semi-housing  34   a  is provided with three waist-shaped grooves  94  at an equal interval along the circumference, and the three waist-shaped grooves  94  extend along the circumference. The projected columns  90  pass through the three waist-shaped grooves  94  and are capable of moving along the circumferential direction along the waist-shaped grooves  94 . 
         [0107]    As shown in  FIG. 6 , the V-shaped bottom  88  of the V-shaped driven part  82  is approximately round, and the middle portion of the V-shaped bottom  88  is provided with a mounting hole  96  through which the driven part  82  is sleeved on the motor output shaft  30 . The V-shaped bottom  88  is provided with three second receiving holes  98  at an equal interval along the circumference, and three second receiving holes  98  are respectively aligned with the first receiving holes  92  on the three projected columns  90  so that a bolt is capable of passing through the first receiving hole  92  and the second receiving hole  98  to fixedly connect the driven part  82  and the projected column  90 ; the V-shaped driven part  82  is fixedly connected with the guide bar  24 , so the guide bar  24  is fixedly connected with the projected columns  90 . Besides, the V-shaped driven part  82  is fixedly connected to the motor bracket, so the pivotal motion of the driven part  82  drives the motor  28  to rotate. 
         [0108]    One end of each waist-shaped groove  94  is provided with a first block face  100 , the other end of each waist-shaped groove  94  is provided with a second block face  102 , and the projected columns  90  may move along the waist-shaped grooves  94 , respectively coupling with the first block faces  100  or the second block faces  102 . When the projected columns  90  are coupled with the first block faces  100 , the working head  22  is contained in the first receiving chamber  48 , the guide bar  24  rotates to the approximate top of the U-shaped guard 38 , and at this time the working head  22  keeps a certain distance from the top of the U-shaped guard 38  to avoid touching the top of the U-shaped guard 38 . When the projected columns  90  are coupled with the second block faces  102 , the working head  22  is contained in the second receiving chamber  50 , the guide bar  24  rotates to the approximate bottom of the U-shaped guard 38 , and at this time the working head  22  keeps a certain distance from the bottom of the U-shaped guard 38  to avoid touching the bottom of the U-shaped guard 38 . 
         [0109]    A torsion spring  106  (as shown in  FIG. 8 ) is positioned between the first connecting portion  42   a  of the first semi-housing  34   a  and the driven part  82 , and one end of the torsion spring  106  is fixedly connected with the connecting portion  42   a  of the first semi-housing  34   a . The driven part  82  is provided with a small hole  108  (as shown in  FIG. 6 ), and the other end of the torsion spring  106  is contained in the small hole  108 , which makes the torsion spring  106  fixedly connected to the driven part  82 . The purpose of the arrangement of the torsion spring  106  is to ensure that no matter when the cutting ends, the working head  22  will automatically return to the original position, namely the first receiving chamber  48 . The working head is completely contained in the U-shaped guard 38  to ensure the safety of the operations. 
         [0110]    The chainsaw  20  comprises a transmission mechanism  110  (as shown in  FIG. 2 ) positioned between the motor  28  and the working head  22 , and the transmission mechanism  110  comprises a chain wheel  112  that is arranged on the motor output shaft  30  and is capable of rotating around the axis X 1  along with the motor output shaft  30 . The chain wheel  112  is engaged with the flexible chain  26  to drive the flexible chain  26  to rotate around the guide bar  24 . 
         [0111]    During work, press the control switch  68  on the gripping portion  62  of the first handle assembly  36  with a hand, then the motor  28  will be started, the motor output shaft  30  will start to rotate, and the chain wheel  112  will rotate along with the motor output shaft  30  and drive the flexible chain  26  to rotate around the guide bar  24 . Meanwhile, the operator grips the gripping portion  62  of the first handle assembly  36  and pushes the first handle assembly  36  towards the working head  22  and then the guiding portion  60  moves linearly along the longitudinal axis X 2  of the receiving chamber  59  and, under the action of the planar multi-rod mechanism  72 , the guide bar  24  pivots around the axis X 1  of the motor output shaft in the guide bar plane to perform the cutting operation. The guide bar  24  and the motor  28  are fixedly connected, so the pivoting of the guide bar  24  drives the motor  28  to rotate. In this embodiment, the first handle assembly  36  is pushed towards the working head, so the guide bar  24  pivots to realize cutting. It should be noted that common skilled persons in this field are capable of pulling the first handle assembly  36  away from the working head simply by changing the position of the planar multi-rod mechanism  72 , so the guide bar  24  pivots to realize cutting. 
         [0112]      FIGS. 9 ,  10  and  11  are schematic views of the chainsaw  20  at the working process state.  FIG. 9  is the schematic view of the chainsaw at the off working state, wherein the working head  22  is completely contained in the first receiving chamber  48  of the U-shaped guard 38 . As shown in  FIG. 10 , if the first handle assembly  36  is pushed towards the D direction, the working head  22  will pivot along the E direction, start to cut the work pieces, and gradually expose from the first receiving chamber  48 . As shown in  FIG. 11 , if the first handle assembly  36  is continuously pushed towards the A direction, the working head  22  will pivot along the E direction to partly enter the first receiving chamber  50  and finish cutting the work pieces. 
         [0113]    As shown in  FIG. 12 , the chainsaw  20  also comprises an extending rod to facilitate cutting the work pieces at higher positions, and the extending rod is configured as a second handle assembly  116 . The second handle assembly  116  comprises a second gripping portion  118  and a second extending portion  120 . The second extending portion  120  comprises a first end  122  and a second end  124 , the first end  122  is connected with the second griping portion  118 , and the second end  124  is connected with the first handle assembly  36 . A locking mechanism  126  is arranged between the second end  124  of the second extending portion  120  and the first handle assembly  36 . The second gripping portion  118  of the second extending portion  120  is D-shaped. 
         [0114]    One side of the second gripping portion  118  is a gripping edge  128 , the other side is a connecting edge  130 , and a control switch  132  is arranged on the inside of the gripping edge  118  and electrically connected with the motor  28  for controlling the start-up and stop of the motor  28 . Two ends of the holding edge  128  are symmetrically provided with safety switches  134 , so that both the left-handed operation and the right-handed operation are convenient. The connecting edge  130  is connected with the second extending portion  120 . 
         [0115]    The second extending portion  120  is a thin and long rod, capable of being manufactured into a telescopic rod. 
         [0116]    As shown in  FIG. 13  and  FIG. 14 , the second end  124  of the second extending portion  120  of the second handle assembly  116  is detachably and fixedly connected with the first handle assembly  36  via the locking mechanism  126 . The detachably fixed connection means that the second end  124  is detachably connected with the first handle assembly  36 , and once connected the two perform one relative motion. The locking mechanism  126  comprises a locking bracket  144 . Two C-shaped clamping blocks  146  are arranged on one side of the locking bracket  144  at an interval, each C-shaped clamping block  146  is respectively provided with a C-shaped clamping piece  148 , and the C-shaped clamping block  146  and the C-shaped clamping piece  148  are connected by nuts and bolts. The C-shaped clamping piece  148  and the C-shaped clamping block  146  are arranged oppositely to form a clamping hole  150  there-between, and the second end  124  of the second extending portion  120  of the second handle assembly  116  is contained in the clamping hole  150 . The shape of the clamping hole  150  is matched with the cross section shape of the second end  124  of the second extending portion  120  of the second handle assembly  116  so the second end  124  of the second handle assembly  116  may be clamped therein. 
         [0117]    The gripping portion  62  of the first handle assembly  36  is provided with a handle receiving hole  152 . The handle receiving hole  152  is defined by the gripping edge  64  and the connecting edge  66  of the first handle assembly  36 . The handle receiving hole  152  is approximately D-shaped. The locking bracket  144  is detachably contained in the handle receiving hole  152 , and the shape of the locking bracket  144  is approximately the same as that of the handle receiving hole  152 . 
         [0118]    As shown in  FIG. 14 , the other side of the locking bracket  144  is provided with a first matched face  154 . One side of both the griping edge  64  and the connecting edge  66  of the gripping portion  62  of the first handle assembly  36  is provided with a second matched face  156 . The locking bracket  144  is contained in the handle receiving hole  152 . The second matched face  156  and the first matched face  154  are coupled and matched in shape. Therefore, when contained in the handle receiving hole  152 , the locking bracket  144  performs no rotation in the handle receiving hole  152 . When the locking bracket  144  is contained in the handle receiving hole  152 , the control switch  68  on the first handle assembly  36  is pressed by the locking bracket  144  and is therefore in an electrically conducting state. 
         [0119]    As shown in  FIG. 15 , the locking mechanism  126  also comprises two locking knobs  158 , which may clamp the gripping portion  62  of the first handle assembly  36  between the locking bracket  144  and the locking knobs  158 . 
         [0120]    The other side of the connecting edge  66  of the gripping portion  62  of the first handle assembly  36  is provided with a third matched face  159  (as shown in  FIG. 14 ). 
         [0121]    As shown in  FIG. 15 , the locking knob  158  comprises an operation portion  160 , a main body portion  162  and an adaptation portion  164 . The operation portion  160  is positioned on the top of the locking knob  158  to be operated by the operator manually. The main body portion  162  is provided with a fourth matched face  166 , and the adaptation portion  164  is a column body with screw threads. The locking bracket  144  is provided with two knob receiving portions  168  for partly receiving the locking knobs  158 . The knob receiving portion  168  comprises a receiving through-hole  170  with a smaller diameter and a receiving chamber  172  with a larger diameter, wherein the receiving through-hole  170  is used for receiving the column body with screw threads of the locking knob, while the receiving chamber  172  is used for receiving the main body part of the locking knob  158 . The column body with screw threads comprises a free end matched with a nut, so the locking knob  158  is capable of being reliably installed on the locking bracket  144 . The fourth matched face  166  is optionally matched with the third matched face  159 , and the two are matched in shape. 
         [0122]    The locking knob  158  is rotated to move between a first position and a second position. When the locking knob  158  is located at the first position as shown in  FIG. 16 , the first matched face  154  and the second matched face  156  are matched; when the third matched face  159  and the fourth matched face  166  are matched, the gripping portion  62  of the first handle assembly  36  is tightly clamped between the locking knob  158  and the locking bracket  144 . 
         [0123]    As shown in  FIG. 17 , when rotated to 180 degrees, the locking knob  158  is located at the second position, and the fourth matched face  166  is rotationally moved away from the third matched face  159 , which means the fourth matched face  166  is not rotationally matched with the third matched face  159 . At this time, the locking bracket  144  is capable of being removed from the handle receiving hole  152  of the first handle assembly. 
         [0124]    As shown in  FIG. 18 , the first handle receiving end  40   a  of the first semi-housing  34   a  is provided with a longitudinal slot  174 . A C-shaped bracket  176  is installed on the guiding portion  60  of the first handle assembly  36  and fixed on the guiding portion  60  by nuts and bolts. The C-shaped bracket  176  extends out from the longitudinal slot  174  of the first handle receiving end  40   a . The second end  124  of the of the second extending portion  120  of the second handle assembly  116  is supported on the C-shaped bracket  176 . The C-shaped bracket  176  is made of aluminum. 
         [0125]    As shown in  FIG. 12 , the first handle assembly  36  and the second handle assembly  116  are electrically connected. The gripping portion  62  of the first handle assembly  36  is provided with a wire of which one end is connected with a plug  177   a  and the other end is electrically connected with the control switch  68 , the motor  28 , etc. The second end  124  of the second extending portion  120  of the second handle assembly  116  is provided with a wire, of which one end is provided with a socket  177   b , and the socket  177   b  is adaptive to the plug  177   a  for electric connection. The second gripping portion  118  is provided with a plug  177   c  for connecting with an external power supply. The other end of the wire is electrically connected with the control switch  132  on the second gripping portion  118  via a lead. 
         [0126]    When the second handle assembly  116  is required to be connected with the first handle assembly  36 , the C-shaped bracket  176  is installed on the first handle assembly  36 . Once installed, the C-shaped bracket  176  is capable of being fixed thereon, even if only the first handle assembly  36  is used and the second handle assembly  116  is not used, and the C-shaped bracket  176  is capable of being fixed on the first handle assembly  36  for standby. The locking bracket  144  is connected with the first locking knob  158 , and the second handle assembly  116  is fixedly connected with the locking bracket  144 . The second end  124  of the second extending portion  120  of the second handle assembly  116  passes through the C-shaped bracket  176 , so the second end  124  of the second extending portion  120  of the second handle assembly  116  is capable of being supported on the C-shaped bracket  176 . Press the safety switch  70  and the control switch  68  of the first handle assembly  36  by hand, penetrate the locking bracket  144  through the handle receiving hole  152  of the first handle assembly  36 , release the safety switch  70  and the control switch  68  when the locking bracket  144  slowly enters the handle receiving hole  152 , rotate the locking knob  158  to couple the third matched face  159  and the fourth matched face  166 , and the gripping portion  62  of the first handle assembly  36  will be clamped between the locking bracket  144  and the locking knob  158 . Insert the plug  177   a  on the first handle assembly  36  into the socket  177   b  on the second handle assembly to electrically connect the first handle assembly  36  and the second handle assembly  116 . The second handle assembly  116  is thereby reliably installed on the chainsaw  20 . 
         [0127]    When cutting twigs at a higher position, install the second handle assembly  116  on the chainsaw  20  according to the mentioned method. During cutting, the plug  177   c  on the gripping portion  118  of the second handle assembly is connected to the external power supply. Place the U-shaped jaw  56  onto the twigs to be cut and press against the twigs; at this time, the operator should grip the gripping portion  118  of the second handle assembly and control the safety switch  134  and the control switch  132  at the same time with one hand and grip the extending portion  120  of the second handle assembly with other hand to push the second handle assembly  116  towards the working head  22  or pull the second handle assembly  116  away from the working head  22 ; then, the guide bar  24  will rotate to cut the twigs. 
         [0128]    As shown in  FIG. 19 , the middle portion of the second handle assembly  116  of the chainsaw  20  is provided with a sleeve  178  that may move along the middle portion. The chainsaw further comprises a cord  180 , of which one end is connected with the main body  34  and the other end is connected to the sleeve  178 . The main body  34  is provided with a clip hook  182 , and one end of the cord  180  is hung on the clip hook  182 . The sleeve  178  is provided with two walls  184  extending radially, a guiding groove  186  is defined between the two walls extending radially, the other end of the cord  180  passes through the guiding groove, a pivotal elastic cam clip  188  is installed at the middle portion of each wall  184 , each elastic cam clip  188  has a cam face  190  extending into the guiding groove  186 , the cord  180  is clamped between the two cam faces  190 , and the cam clip  188  may clamp or release the cord  180 . 
         [0129]    When cutting thin twigs at higher positions, install the second handle assembly  116  on the chainsaw  20  according to the mentioned method and connect the plug  177   c  on the gripping portion  118  of the second handle assembly to the external power supply. Place the U-shaped jaw  56  onto the twigs to be cut; at this time, the operator should grip the gripping portion  118  of the second handle assembly, control the safety switch  134  and the control switch  132  at the same time with one hand and grip the sleeve  178  with other hand to push the second handle assembly  116  towards the working head  22  or pull the second handle assembly  116  away from the working head  22 ; then, the guide bar  24  will rotate to cut the twigs. 
         [0130]    As shown in  FIG. 20  and  FIG. 21 , a second handle assembly  200  in another embodiment comprises a second gripping portion  210  and a second extending portion  220 , wherein the second extending portion  220  comprises an outer tube  201 , the second gripping portion  210  is connected with the first end  211  of the outer tube  201 , and the second end  212  of the outer tube  201  is connected with a locking mechanism  240 . A connecting element for connecting the second handle assembly  200  and the main body  34  comprises an inner tube  202  that is able to slide and be arranged with respect to the outer tube  201 . An operating element with respect to the inner tube  202  is fixedly arranged at the outer tube  201 . In this embodiment, the operating element is a sleeve  203  sleeved on the outer tube  201 , and the sleeve  203  on the outer tube  201  is about 0.5 m away from the second gripping portion  210 . Of course, the sleeve in this embodiment is capable of being replaced by other operating elements, such as a control handle that is fixedly connected with the inner tube  202  and projected outside the outer tube  201 . The first end  221  of the inner tube  202  extends into the outer tube  201 , and the second end  222  extends out the outer tube  201  and is provided with a joint member  223  that is fixedly connected with the main body  34  of the chainsaw. The joint member  223  is made of steel, with one end thereof fixedly connected to the outer wall of the second end  222  of the inner tube  202 , and the other end is a free end which is bent to form a step-like cooperating portion  223   a . The outer wall of the inner tube  202  is provided with a groove  217  extending longitudinally, and the groove  217  functions as a guide when the inner tube  202  slides with respect to the outer tube  201 . The outer tube  201  and the inner tube  202  in this embodiment are made of light aluminum materials with weight and strength meeting requirements; skilled persons in this field would be capable of using other materials as substitutes. The inner tube  202 , which is made from a rigid material, and the cord, which is made from a flexible material, have different structures. 
         [0131]    The second gripping portion  210  is D-shaped, one side thereof is a gripping edge  228 , the other side is a connecting edge  230 , a control switch  232  is arranged on the inside of the gripping edge  228 , both ends of the gripping edge  228  are provided with a safety switch  234 , and the outer side of the connecting edge  230  is provided with a lead, one end of the lead connected with a plug  233 . Connecting lead  214 , which is electrically connected with the plugs  233 , is arranged in the cavities of the inner tube  202  and the outer tube  201  and pass through the cavity of the second end  222  of the inner tube  202  to connect with a socket  215 . The locking mechanism  240  comprises a base  241  and a cover body  242 , the base  241  is provided with a rotating shaft  245 , the cover body  242  pivots on the rotating shaft  245  with respect to the base  241 , the base  241  is provided with a first receiving chamber  243  for receiving the outer tube  201  and is fixedly connected with the outer tube  201 , the opposite inner sides of the base  241  and the cover body  242  are respectively provided with a semi-round concave chamber, and a locking member  246  is arranged between the base  241  and the cover body  242 . When the relative positions of the base  241  and the cover body  242  are locked by the locking member  246 , a second receiving chamber  244  is formed between the base  241  and the cover body  242 . Furthermore, as shown in  FIG. 21  and  FIG. 22 , the second gripping portion  210  is connected to the first end  211  of the outer tube  201  via screws  216  or by other means. The part of the outer tube  201  corresponding to the sleeve  203  is provided with a longitudinal slot  205 , and the sleeve  203  is formed by connecting two semi-shells  203   a  and  203   b  by screws  216  or by other methods. The inner cavity of the outer tube  201  is provided with a pin  207  extending longitudinally, with one end of the pin  207  provided with a pin head  207   a  with a diameter bigger than that of the pin  207 , and the pin head  207  is pressed against one end  211  of the outer tube  201 . The pin  207  is provided with a spring  208 ; the pin part  207  away from the pin head  207   a  is contained in a sleeve tube  209  in such a way that one end of the spring  208  is pressed against and adapted to the pin head  207   a  and the other end is pressed against and adapted to one end of the sleeve tube  209 ; the other end of the sleeve tube  209  corresponding to the spring  208  is provided with the joint member  213 . The joint member  213  is configured as a hollow cylinder. The outer diameter of the sleeve tube  209  is matched with the inner diameter of the joint member  213 , and they are therefore sleeved together. A through hole  213   a  is formed in the middle part of the outer wall along the vertical direction of the joint member  213 , a round hole  221   a  is correspondingly formed in the tube wall of the first end  221  of the inner tube  202 , a concave hole (not shown in the figure) is formed in the corresponding inside position of the semi-shell  203   a  of the sleeve  203 . A cylinder pin  206  is penetrated through the through hole  213   a  of the joint member  213 , with one end of the cylinder pin  206  projected from the through hole  213   a  and passing through the round hole  221   a  of the inner tube  202  to be fixed in the concave hole of the semi-shell  203   b  of the sleeve  203  via the longitudinal slot  205  of the outer tube  201 . Therefore, the sleeve  203  is fixedly connected with respect to the inner tube  202 , which means the sleeve  203  and the inner tube  202  are fixed at relative positions by the pin  207  and the joint member  213 . When the sleeve  203  slides with respect to the outer tube  201 , the longitudinal slot  205  on the outer tube  201  limits the sliding stroke of the sleeve  203 . 
         [0132]    Furthermore, as shown in  FIG. 22  and  FIG. 23 , the base  241  of the locking mechanism  240  comprises a first base body  241   a  and a second base body  241   b , the opposite inner sides of the first base body  241   a  and the second base body  241   b  are respectively provided with a semi-round concave chamber  243   a  ( FIG. 22  only shows one), the first base body  241   a  and the second base body  241   b  are integrally connected together by screws or by other methods, the two semi-concave chambers  243   a  are joined to form the receiving chamber  243  for receiving the outer tube  201 , and the outer tube  201  is fixedly connected with respect to the base  241 . The locking member  246  comprises an opening  251  on the base body  241   b , the opening  251  is a profile hole of which the inner wall extends downwards to form a slope face  251   a , a locking button  252  is capable of being rotationally arranged on the cover body  242 , and a lock cylinder  253  that is fixedly connected with the locking button  252 , wherein the tail end, away from the locking button  252 , of the locking cylinder  253  is fixedly connected with a round clamping member  255  with a flange  255   a  and a spring  254  is arranged between the locking button  252  and the lock cylinder  253 . The spring  254  in this embodiment is a torsion spring with one end connected with the locking button  252  and the other end connected with the cover body  242 ; at the normal state, the locking button  252  and the lock cylinder  253  are located at a first position under the action of the spring  254  and the flange  255   a  of the clamping member  255  directly faces the inner slope face  251   a  of the profile hole  251 . Once the operator applies a force to the cover body  242  towards the base  241 , the flange  255   a  of the clamping member  255  contacts the inner slope face  251   a . During the operation of the operator, the flange  255   a  of the clamping member  255  slides downwards along the slope face  251   a , while the lock cylinder  253  overcomes the spring force of the spring  254  and drives the locking button  252  to rotate; when the flange  255   a  of the clamping member  255  slides along the slope face  251   a  to a second position, the clamping member  255  and the lock cylinder  253  together fall towards the bottom of the profile hole  251  and then pass through the profile hole  251 , the lock cylinder  253  reversely rotates to automatically return to the first position under the action of the spring  254 , and the clamping member  255  locks the cover body  242  on the base body  241  by clamping the flange  255   a  and the slope face  251   a . When unlocking, reversely rotate the locking button  252  positioned above the cover body  242  to drive the clamping member  255  that is arranged at the lower end of the lock cylinder  253  to rotate it to a position staggered with the slope face  251   a , and then the lock cylinder  253  is capable of being released from the profile hole  251  and unlocked. The receiving chamber  244  formed between the base  241  and the cover body  242  optionally locks the first handle assembly of the chainsaw by the locking member  246 . 
         [0133]    As shown in  FIG. 24  and  FIG. 25 , the basic structure of the chainsaw  20 ′ in this embodiment is approximately the same with the chainsaw  20 , so no detailed description is provided. The main body  34 ′ positioned between the handle receiving end  40 ′ and the motor housing  32 ′ is provided with a slot  260  that is matched with the cooperating portion  223   a  of the joint member  223  of the inner tube  202  in width. When the second handle assembly  200  is connected with the chainsaw  20 ′, the step-like cooperating portion  223   a  is engaged with and adapted to the slot  260 . 
         [0134]    Furthermore, as shown in  FIG. 24  and  FIG. 26 , the second handle assembly  200  is adapted to the chainsaw  20 ′ to cut the work pieces at higher positions. At this time, the joint member  223  positioned at the end of the inner tube  202  is fixedly adapted to the main body  34 ′, the gripping portion  62 ′ of the first handle assembly  36 ′ is locked in the receiving chamber  244  (as shown in  FIG. 21 ) of the locking mechanism  240 , the control switch (not shown in the figure) on the inside of the gripping portion  62 ′ is limited by the receiving chamber  244  to be in the triggering state, and the plug  177   a ′ of the first handle assembly  36 ′ is thusly inserted into the socket  215  to make the first handle assembly  36 ′ and the second handle assembly  200  electrically conducting. The outer tube  201  and the first handle assembly  36 ′ are fixed in their relative positions by the locking mechanism  240 , while the inner tube  202  and the main body  34 ′ of the chainsaw are fixed in their relative positions by the joint member  223 . Therefore, when the outer tube  201  slides with respect to the inner tube  202 , the linear motion of the gripping portion  62 ′ of the first handle assembly with respect to the main body  34 ′ is capable of being realized. The sleeve  203  is fixedly connected with respect to the inner tube  202 , so, during operation, connect the plug  233  to the external power supply first, then grip the sleeve  203  of the outer tube  201  with one hand, grip the gripping edge  228  of the second handle assembly  200  and control the safety switch and the control switch with the other hand to push or pull the gripping portion  62 ′ of the second handle assembly  200  towards or away from the working head, so as to make the gripping portion  62 ′ move with respect to the sleeve  203 ; then, the guide bar  24 ′ of the chainsaw is capable of being driven to rotate to perform cutting. 
         [0135]    In other embodiments, the connecting mechanism may be a rack and pinion gear (not shown in the figure). The rack and pinion gear usually comprise a rack fixedly connected with the first handle assembly  36  and a gear fixedly connected with the guide bar  24 . By pushing or pulling the first handle assembly  36 , the gear pivots to drive the guide bar  24  to rotate. 
         [0136]    In another embodiment, the connecting mechanism may be a pulley mechanism (not shown in the figure). The pulley mechanism usually comprises a pulley wheel and a cord, wherein the cord is sleeved on the pulley wheel, one end of the cord is fixedly connected with the first handle assembly  36 , the other end of the cord is fixedly connected to the main body  34 , and the pulley wheel is fixedly connected with the guide bar  24  via the driven part  82 ; during operation, the operator pulls or pushes the first handle assembly  36 , and the pulley wheel will drive the driven part  82  to pivot, thus enabling the driven part  82  to drive the guide bar  24  to rotate.