Abstract:
The present invention provides a cutting machine, comprising: a worktable including an opening and an upper surface for supporting a workpiece; a supporting unit for supporting the worktable; a cutting mechanism mounted on a lower surface of the worktable and contained within the supporting unit comprising: a motor for outputting a rotation motion; a reciprocating rod driving a saw blade moving reciprocately through the opening; a motion conversion mechanism converting the rotation motion of the motor into a reciprocating motion of the reciprocating rod; and a saw blade clamp for clamping and releasing the saw blade; the saw blade clamp comprises an operating element which is disposed on the external surface of the worktable or the supporting unit. The present invention fixes the operating element on the worktable or the supporting unit, which brings operation of the saw blade clamp to a convenience position for operator, and the process of replacing the saw blade is very easy.

Description:
TECHNICAL FIELD 
       [0001]    The invention relates to a cutting machine, in particular to a cutting machine with a reciprocating cutting mechanism. 
       BACKGROUND OF THE INVENTION 
       [0002]    The existing jig saws are able to carry out all kinds of curved and linear cutting and therefore are widely applied in plate processing of various materials. Usually, a jig saw comprises a motor, a housing holding the motor, a motion conversion mechanism that is housed in the gearbox housing, driven by the motor and converting the rotation motion of the motor into the reciprocating motion of a reciprocating rod, a saw blade connecting to the reciprocating rod via a clamp, and a bottom plate supporting the jig saw body on the surface of a workpiece. 
         [0003]    To develop the application, professional staff in this field place the jig saw upside down on the lower surface of a worktable so as to perform cutting when moving the workpiece. However, the current upside-down jig saw is configured by directly turning the jig jaw available in the market and mounting the jig jaw on a worktable with a certain connecting mechanism. During use, the saw clamp of the jig saw is an inseparable structure of the jig saw and is disposed below the worktable together with the jig saw body, so when the saw blade is required to the replaced, the operator is required to stretch out his/her hands below the worktable to operate the clamp so as to replace the saw blade. The operator is required to stoop and try to find the clamp by hand. Therefore, the saw blade is inconvenient to replace, and the operation needs much time and labor. 
       SUMMARY OF THE INVENTION 
       [0004]    One object of the present invention is to provide a cutting machine which is easy to be operated. 
         [0005]    In order to realize the above object, the present invention provides a cutting machine, comprising: a worktable including an opening and an upper surface for supporting a workpiece; a supporting unit for supporting the worktable; a cutting mechanism mounted on a lower surface of the worktable and contained within the supporting unit comprising: a motor for outputting a rotation motion; a reciprocating rod driving a saw blade moving reciprocately through the opening; a motion conversion mechanism converting the rotation motion of the motor into a reciprocating motion of the reciprocating rod; and a saw blade clamp for clamping and releasing the saw blade; the saw blade clamp comprises an operating element which is disposed on the external surface of the worktable or the supporting unit. 
         [0006]    Comparing to the traditional technical, the present invention fixes the operating element on the worktable or the supporting unit, which brings operation of the saw blade clamp to a convenience position for operator, and the process of replacing the saw blade is very easy. 
         [0007]    As a further improvement of the above proposal, the operating element is disposed on the upper surface of the worktable. 
         [0008]    As a further improvement of the above proposal, the saw blade clamp comprises a clamping wrench rotating around a reciprocating rod axis of the reciprocating rod, a linkage mechanism is disposed between the operating element and the clamping wrench, and thus the operating element is operable to drive the clamping wrench rotating. 
         [0009]    As a further improvement of the above proposal, the linkage mechanism comprises a connecting plate connected to the operating element and rotating around a rotating axis which is parallel to the reciprocating rod axis, and an actuating element being connected to the connecting plate and driving the clamping wrench moving. 
         [0010]    As a further improvement of the above proposal, the rotating axis of the connecting plate is parallel to the rotating axis of the actuating element. 
         [0011]    As a further improvement of the above proposal, the rotating axis of the connecting plate rotates around the rotating axis of the actuating element. 
         [0012]    As a further improvement of the above proposal, the actuating element comprises a rotating frame being disposed rotatablely with respect to the reciprocating rod, the rotating frame comprises a C-shape base portion, a connecting shaft is disposed at one end of the base portion, a pushing column which extends vertically is disposed at the other end of the base portion, and a connecting lug is disposed between the two ends of the base portion. 
         [0013]    As a further improvement of the above proposal, the height of the pushing column is larger than a reciprocating travel of the reciprocating rod. 
         [0014]    As a further improvement of the above proposal, a stop protrusion is disposed on the pushing column, when the clamping wrench contacts with a biasing surface of the pushing column, the stop protrusion would prevent the clamping wrench leaving from the biasing surface. 
         [0015]    As a further improvement of the above proposal, the saw blade clamp further comprises an elastic element biases the operating element moving towards a clamping position at where being clamped the saw blade. 
         [0016]    As a further improvement of the above proposal, the elastic element is a tension spring which is disposed between the worktable and the operating element, the tension spring is tensible along the moving direction of the operating element. 
         [0017]    As a further improvement of the above proposal, the saw blade clamp comprises a clamping wrench rotating around a reciprocating rod axis of the reciprocating rod, an actuating element being connected to the operating element and driving the clamping wrench moving, the cutting mechanism comprises a gearbox housing, the elastic element is a torsion spring which is disposed between the actuating element and the gearbox housing, the torsion spring biases the actuating element rotating towards a clamping position at where being clamped the saw blade. 
         [0018]    As a further improvement of the above proposal, the operating element is translationally movable to the worktable. 
         [0019]    As a further improvement of the above proposal, a sliding groove is disposed on the worktable, the operating element comprises a sliding plate, the sliding plate is operable moving along the sliding groove between a releasing position where the saw blade is released and a clamping position where the saw blade is clamped. 
         [0020]    As a further improvement of the above proposal, the operating element comprises an opening is disposed on the sliding plate. 
         [0021]    As a further improvement of the above proposal, the saw blade clamp comprises a clamping wrench rotating around a rotating axis which is vertical to the reciprocating rod axis of the reciprocating rod, and a linkage mechanism being disposed between the operating element and the clamping wrench. 
         [0022]    As a further improvement of the above proposal, the linkage mechanism comprises a connecting plate connected to the operating element and rotating around a rotating axis which is vertical to the reciprocating rod axis, and an actuating element connected to the connecting plate and driving the clamping wrench moving. 
         [0023]    As a further improvement of the above proposal, the actuating element comprises a pressing pole, a pivot hole is disposed at one end of the pressing pole, the pressing pole is rotatablely mounted on the worktable or the base, a pressing portion is disposed at the other end of the pressing pole, the connecting plate connects to the middle portion of the pressing pole by a pin, the pressing portion is driven by the connecting plate and rotating around the pivot hole for moving the clamping wrench. 
         [0024]    As a further improvement of the above proposal, a product which a distance from the center of the pivot hole to the pressing surface of the pressing portion multiplies a sine of a rotating angle that the pressing pole rotates around the pivot hole is larger than a reciprocating travel of the reciprocating rod. 
         [0025]    As a further improvement of the above proposal, the operating element is rotatable relative to the worktable. 
         [0026]    As a further improvement of the above proposal, the saw blade clamp comprises a clamping wrench rotating around a rotating axis which is vertical to the reciprocating rod axis of the reciprocating rod, an actuating element is pivotally disposed between the operating element and the clamping wrench. 
         [0027]    As a further improvement of the above proposal, the operating element and the actuating element are rotatable around a same pivot shaft. 
         [0028]    In order to realize the above object, the present invention provides a cutting machine, comprising: a worktable including an opening and an upper surface for supporting a workpiece; a supporting unit for supporting the worktable; a cutting mechanism mounted on a lower surface of the worktable and received in the supporting unit comprising: a motor for outputting a rotation motion; a reciprocating rod driving a saw blade moving reciprocately through the opening; a motion conversion mechanism converting the rotation motion of the motor into a reciprocating motion of the reciprocating rod; and a saw blade clamp for clamping and releasing the saw blade; the saw blade clamp comprises an flexible connecting element which is operable driving the saw blade clamp moving between a clamping position where the saw blade is clamped and a releasing position where the saw blade is released. 
         [0029]    Comparing to the traditional technical, the present invention provides a flexible connecting element, which made releasing operation and clamping operation of the saw blade clamp are at a position where is easy for the operator to touch without searching by hands, then the operator would replace the saw blade expediently. 
         [0030]    As a further improvement of the above proposal, the flexible connecting element is a steel wire. The steel wire has certain rigidity and toughness and ensures that the operating device of the saw blade clamp is positioned at a position where the operator can easily reach. 
         [0031]    As a further improvement of the above proposal, a foot pressing plate is disposed under the worktable and connected to the flexible connecting element. So the operator is able to control the saw blade clamp by pedaling and avoid stooping. 
         [0032]    As a further improvement of the above proposal, the saw blade clamp comprises a rotating sleeve can rotate around the reciprocating rod axis of the reciprocating rod, the flexible connecting element converts the rotation of the rotating sleeve into the linear motion of the foot pressing plate. The foot pressing plate performs linear motion, so the operator may easily apply force and the actions of clamping and releasing the saw blade are simple. 
         [0033]    As a further improvement of the above proposal, a corner bracket is disposed between the flexible connecting element and the saw blade clamp and is rotatable around the reciprocating rod axis, one end of the flexible connecting element connects with the corner bracket, the other end of the flexible connecting element connects to the foot pressing plate. Due to the corner bracket, the motion of the rotating sleeve is more easily converted into the movement of the foot pressing plate and more easily ensures that the clamp is configured into the released or clamped state. 
         [0034]    As a further improvement of the above proposal, the corner bracket comprises a C-shaped base portion, one end of the base portion is connected with the rotating shaft, the other end of the base portion is provided with a pushing column which extends vertically, a connecting lug is disposed between the two ends of the base portion, and the flexible connecting wire is penetrated into the connecting lug. The pushing column pushes the rotating sleeve of the clamp, and the whole corner bracket rotates around the rotating shaft, to ensure that the steel wire is able to pull the corner bracket to rotate. 
         [0035]    As a further improvement of the above proposal, the cutting machine comprises a supporting frame with a supporting surface and at least three supporting legs, the foot pressing plate is disposed at the lower side of one of the supporting legs, the foot pressing plate is able to move axially with respect to the supporting leg. The supporting unit of the cutting machine is positioned on the supporting surface of the supporting frame, the supporting legs support the cutting machine, so the saw blade is positioned at a position where the operator works comfortably and controls the saw blade clamp with feet conveniently. 
         [0036]    As a further improvement of the above proposal, the steel wire penetrates through the supporting surface and is at least partly received into the supporting leg. Therefore, the whole cutting machine has no flexible connecting element outside and is compactly structured and the steel wire is difficult to break or deform in case of misoperation. 
         [0037]    As a further improvement of the above proposal, the foot pressing plate comprises the footplate and a moving block which receives in the supporting leg. The footplate is connected with the moving block via the rotating shaft. Therefore the footplate is able to rotate with respect to the moving block, when the saw blade is not required to be clamped or released, the footplate is able to rotate with respect to the moving block to the position where the footplate is adhered to the outer wall of the supporting leg. At this moment, the footplate is inoperable so as to avoid the event that the operator carelessly steps on the footplate and releases the saw blade. 
         [0038]    As a further improvement of the above proposal, an elastic element receiving in the supporting leg is positioned between the footplate and the moving block, pressing the moving block to move towards the position wherein the steel wire is unloosened. Therefore, the saw blade clamp is kept at the clamped position at the normal state. 
         [0039]    One object of the present invention is to provide a cutting machine which the saw blade is changed in a safety way. 
         [0040]    In order to realize the above object, the present invention provides a cutting machine, comprising: a worktable including an opening and an upper surface for supporting a workpiece; a supporting unit for supporting the worktable; a cutting mechanism mounted on a lower surface of the worktable and received in the supporting unit comprising: a motor for outputting a rotation motion; a reciprocating rod driving a saw blade moving reciprocately through the opening; a motion conversion mechanism converting the rotation motion of the motor into a reciprocating motion of the reciprocating rod; and a saw blade clamp for clamping and releasing the saw blade; The worktable has a transparent portion which is at least occupying a part of the worktable, and the saw blade clamp is positioned below the transparent portion. 
         [0041]    Comparing to the traditional technical, the present invention provides a transparent portion on the worktable, then the saw blade clamp can be seen by the operator during replacing the saw blade, and the operator will not be hurt by the saw blade when the operator put his hands under the worktable, which prevents the injury by the misoperation. 
         [0042]    As a further improvement of the above proposal, the upper surface of the transparent portion is aligned with the upper surface of the worktable. The transparent portion is one part of the worktable, therefore the transparent portion would not obstruct the workpiece supporting on the worktable. 
         [0043]    As a further improvement of the above proposal, the area of the transparent portion is equal to the area of the upper surface of the worktable. It is easy to manufacture a worktable which is made of transparent material. Besides, the operator has a large view in the operation of replacing the saw blade, which can avoid injury when the operator is replacing the saw blade at different position. 
         [0044]    As a further improvement of the above proposal, the worktable comprises two portions which are separable, the saw blade clamp is positioned between the boundary of the two portions. 
         [0045]    As a further improvement of the above proposal, at least one portion of the worktable is able to move with respect to the saw blade clamp so that the saw blade clamp is positioned to be contacted directly. One portion of the worktable can move away from the saw blade clamp, so the operator is easy to contact the saw blade clamp directly without stooping. 
         [0046]    As a further improvement of the above proposal, the two portions of the worktable are able to move with respect to the saw blade clamp at the same time, which can accelerate the separating process, and decrease the operating time to replace the saw blade. 
         [0047]    As a further improvement of the above proposal, at least one portion of the worktable is able to translate with respect to the saw blade clamp. One of the worktable and the supporting unit has a guiding rail, the other one has a sliding groove, the worktable is able to slide with respect to the supporting unit. Therefore, the moving process of the worktable is very stable, the variable factor which may affect the worktable is very few, and it is very easy to be operated. 
         [0048]    As a further improvement of the above proposal, at least one part of the worktable can rotate with respect to the saw blade clamp. The worktable only needs to be rotated a small angle to discover the saw blade clamp, thus the operator contacts the saw blade clamp directly, due to the worktable only need to move a short distance, it saves labor by comparing to traditional manner. 
         [0049]    As a further improvement of the above proposal, the worktable is turnable with respect to the supporting unit. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0050]      FIG. 1  is a schematic view of the cutting machine of the first embodiment according to the present invention; 
           [0051]      FIG. 2  is a schematic view of the worktable of the cutting machine which is assembled the supporting unit in  FIG. 1 ; 
           [0052]      FIG. 3  is an exploded view of the saw blade clamp of the cutting machine in  FIG. 1 ; 
           [0053]      FIG. 4  is a schematic view of the saw blade clamp of the cutting machine in  FIG. 3 , wherein the saw blade clamp is clamped; 
           [0054]      FIG. 5  is a schematic view of the saw blade clamp of the cutting machine in  FIG. 3 , wherein the saw blade clamp is released; 
           [0055]      FIG. 6  is a plan view of the saw blade clamp in  FIG. 4 ; 
           [0056]      FIG. 7  is a plan view of the saw blade clamp in  FIG. 5 ; 
           [0057]      FIG. 8  is an exploded view of the saw blade clamp of the cutting machine of the second embodiment of the present invention; 
           [0058]      FIG. 9  is a schematic view of the saw blade clamp in  FIG. 8 , wherein the saw blade clamp is released; 
           [0059]      FIG. 10  is a side view of the saw blade clamp in  FIG. 9 ; 
           [0060]      FIG. 11  is a side view of the saw blade clamp in  FIG. 8 , wherein the saw blade clamp is clamped; 
           [0061]      FIG. 12  is a schematic view of the saw blade clamp of the cutting machine of the third embodiment according to the present invention; 
           [0062]      FIG. 13  is a side view of the saw blade clamp in  FIG. 12 , wherein the saw blade clamp is released; 
           [0063]      FIG. 14  is a side view of the saw blade clamp in  FIG. 12 , wherein the saw blade clamp is clamped; 
           [0064]      FIG. 15  is a schematic view of the cutting machine of the forth embodiment according to the present invention; 
           [0065]      FIG. 16  is a schematic view of the cutting machine in  FIG. 15 , wherein the worktable, part of the supporting unit and part of the supporting frame is removed, the saw blade clamp is visible; 
           [0066]      FIG. 17  is a partly exploded view of the saw blade clamp of the cutting machine in  FIG. 16 ; 
           [0067]      FIG. 18  is a schematic view of the cutting machine of the fifth embodiment according to the present invention; 
           [0068]      FIG. 19  is a schematic view of the cutting machine being turned in  FIG. 18 , wherein the supporting unit is removed; 
           [0069]      FIG. 20  is a schematic view of the cutting machine in  FIG. 18 , wherein the worktable of the cutting machine is open; 
           [0070]      FIG. 21  is a schematic view of the cutting machine of the sixth embodiment according to the present invention, wherein the worktable is open; 
           [0071]      FIG. 22  is a schematic view of the cutting machine of the seventh embodiment according to the present invention, wherein the worktable is open. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0072]    Referring to the  FIGS. 1-2 , a cutting machine  2  comprises a worktable  4 , a supporting unit  10  for supporting the worktable  4 , a guard assembly  6  disposed on the upper surface  22  of the worktable  4 , a pressing plate assembly  8  connecting to the guard assembly  6  and adjustably applying a certain pressure onto a workpiece, and a cutting mechanism  12  disposed on the lower surface  24  of the worktable  4 . 
         [0073]    According to the use habits of operators, the left side of the  FIG. 1  is defined as the front portion of the cutting machine  2 , while the right side is defined as the rear portion of the cutting machine  2 . The worktable  4  has the upper surface  22 , the lower surface  24  and sidewalls  26   a,    26   b,    26   c  and  26   d  that extend vertically with respect to the upper and lower surfaces. The upper surface  22  and the sidewalls  26   a,    26   b,    26   c  and  26   d  compose the outer surface of the worktable  4 . An opening  20  is formed on the worktable  4 , positioned on the front portion of the cutting machine  2  and running through the upper surface  22  and the lower surface  24  from the top down. A saw blade  130  passes through the opening  20  from the bottom up. A workpiece  19  is capable of being placed on the upper surface  22  of the worktable  4 , moving along the upper surface  22  so as to be cut by the saw blade  130 . The opening  20  is square. A square blade protecting plate  21  is capable of being embedded into the opening  20  for preventing dust front entering the cutting machine to a certain extent, and when the saw blade  130  is broken, the protecting plate  21  is capable of being dismantled, so the operator takes out the saw blade  130  from the cutting machine. A slot  21   a  is formed in the middle of the protecting plate  21 , and the saw blade  130  passes through the slot  21   a.    
         [0074]    The worktable  4  is also provided with a longitudinal T-slot  28  and a transverse T-slot  30 . The longitudinal T-slot  28  extends from the front portion to the rear portion of the worktable  4 . The transverse T-slot  30  is positioned on the front side of the opening  20  and intersected with the longitudinal T-slot  28  to divide the upper surface  22  of the whole worktable  4  into four parts. The transverse T-slot  30  and the longitudinal T-slot  28  respectively extend from sidewalls  26   a  and  26   b  of the worktable  4  to reach the other sidewalls  26   c  and  26   d  which are disposed in parallel. The cross sections of the longitudinal T-slot  28  and the transverse T-slot  30  are identical and the bottoms  29  thereof are also provided with several through-holes  31  disposed at intervals along the extension direction of the T-slot. 
         [0075]    The guard assembly  6  comprises a bracket  56  detachably connected to the worktable, an extending arm  58  vertical to the bracket, and an extending guard  44  connected with the extending arm  58 , left and right guard plates  38 ,  40  and a guard body  34 . A guard clamping mechanism  48  with a clamping knob  50  adjustably fastens the extending guard  44  on the extending arm  58 . A guide wheel  70  is disposed below the guard body  34  for guiding the reciprocating motion of the saw blade  130 . A dust collecting hose  36  is positioned above the guard body  34  for connecting with a dust collector and collecting the dust generated during cutting. The left and right guard plates are connected with the guard body  34  via a pin shaft  42 . 
         [0076]    A pressing plate assembly  8  is positioned between the guard assembly  6  and the worktable  4  to realize the height adjustment of a pressing plate  72  with respect to the worktable  4  by rotating an adjusting wrench  74 . 
         [0077]    The supporting unit  10  comprises a base  82  with several supporting legs  110  and a body  84  with supporting walls  86   a,    86   b,    86   c  and  86   d.  A drawer  88  is positioned at the front portion of the supporting unit  10  for collecting the dust. The front supporting wall  86   b  of the body  84  is provided with a controlling panel  112  for receiving a main switch  116  and a speed adjusting switch  118  of the cutting machine  2 . The supporting walls  86   a,    86   b,    86   c  and  86   d  compose the outer surface of the supporting base  10 . In this embodiment, the supporting unit  10  has the supporting wall, however skilled persons in this field should understand that the worktable and the cutting mechanism are capable of being supported by several supporting legs. 
         [0078]    Therefore, the supporting unit in the present invention may also be the bracket consisting of supporting legs. The corresponding outer surface of the supporting unit is the outer walls of the supporting legs. 
         [0079]    The cutting mechanism  12  is fixed on the lower surface  24  of the worktable  4  and received in the supporting unit  10  and comprises a motor  120  generating rotation motion, a reciprocating rod  126  driving the saw blade  130  that passes through the opening  20  to move reciprocatedly, a motion conversion mechanism  132  converting the rotation driving of the motor  120  into the reciprocating motion of the reciprocating rod  126 , and a saw blade clamp  14  operable to clamp and release the saw blade  130 . The saw blade clamp  14  comprises an operating element  144  positioned on the worktable  4  or on the outer surface of the supporting unit  10 . 
         [0080]    The first embodiment of the saw blade clamp  14  is further described in combination with the attached drawings  1 - 7 . 
         [0081]    The cutting machine  2  has a cutting mechanism  12 , wherein the cutting mechanism  12  comprises a motor  120 , a motor housing  122  receiving the motor  120 , and a gearbox housing  124  connected with the housing  122  and receiving the motion conversion mechanism  132 . The rotation motion of the motor  120  is converted into the reciprocating motion of a reciprocating rod  126  along a reciprocating rod axis  128  by the motion conversion mechanism  132 . 
         [0082]    In this embodiment, the saw blade clamp  14  comprises a clamp  134  connected to the reciprocating rod  126 . The clamp  134  comprises a rotating sleeve  136  having a slot  138  for the saw blade  130  passing through, and a clamping element (not shown in the figure) that is received in the rotating sleeve  136  and clamps and releases the saw blade  130  along with the rotation of the rotating sleeve  136  with respect to the reciprocating rod axis  128 . This kind of clamp is suitable for clamping the T-shaped saw blade, namely a saw blade with a protrusion at the tail, and the protrusion of the clamped saw blade is stopped by the end face of the rotating sleeve  136  with the slot  138 . The outer wall of the rotating sleeve  136  extends outwards to form a clamping wrench  140 , so an operator is able to turn the clamping wrench  140  to rotate around the reciprocating rod axis  128  so as to clamp and release the saw blade  130 . 
         [0083]    In this embodiment, the saw blade clamp  14  also comprises an operating element  144  positioned on the upper surface  22  of the worktable  4 . In other words, the outer surface of the worktable  4  in this embodiment refers to the upper surface  22  thereof. Of course, the position of the operating element in the present invention is not only limited to the outer surface of the worktable, and the operating element is also capable of being disposed on the sidewall of the worktable, especially the front wall, which helps the operator replace the saw blade conveniently. The skilled persons in this field should understand that the operating element is also capable of being disposed on the outer surface of the supporting unit  10 , for example, the front supporting wall or left/right supporting wall. In case the supporting unit has no supporting wall or only has the supporting leg, the outer surface of the supporting unit is the outer wall of the supporting leg. The distance between the operating element and the blade clamp is usually smaller than or equal to the length of a single arm of a person. Therefore, the operator is able to touch the operating element comfortably and saves labor during the operation of replacing the saw blade. 
         [0084]    The saw blade clamp  14  comprises a clamping wrench  140  rotating around the reciprocating rod axis  128 , and a linkage mechanism which is positioned between the operating element  144  and the clamping wrench  140  to force the operating element  144  to drive the clamping wrench  140  to rotate. 
         [0085]    In this embodiment, the linkage mechanism comprises a connecting plate  152  that is connected with the operating element  144  and rotates around a rotation axis  155  parallel to the reciprocating rod axis  128 , and an actuating element that is connected with the connecting plate  152  and drives the clamping wrench  140  to move. 
         [0086]    The operating element  144  comprises a sliding plate  146  that extends longitudinally, an opening  148  disposed in the middle portion of the sliding plate and a connecting rod  150  that extends vertically with respect to the sliding plate. The axis  151  of the connecting rod is parallel to the axis  149  of the opening and the two axes are disposed at an interval. In this embodiment, the sliding plate surface of the operating element  144  is basically aligned with the upper surface  22  of the worktable  4 , and the tabletop of the worktable  4  has no protruding structure to influence the movement of the workpiece thereon. Of course, the operating element may also be sunk into the upper surface of the worktable, but can be directly touched from the upper surface. Therefore, the operating element can be conveniently operated to replace the saw blade without influence on the movement of the workpiece. Meanwhile, the worktable has a groove for receiving the operating element, and correspondingly the surface of the groove composes the outer surface of the worktable. 
         [0087]    The connecting plate  152  comprises pin holes  154  disposed on two ends of the connecting plate  152 . The operating element  144  is connected with the connecting plate  152  via the pin  156 , the pin holes  154  and the connecting rod  150 . 
         [0088]    Preferably, the actuating element comprises a rotating frame  158  positioned rotatably with the reciprocating rod  126 . The rotating frame  158  comprises a C-shaped base portion  160  and a pushing column  162  which extends vertically with respect to the base portion  160 . One end of the base portion  160  is a connecting shaft portion  172  with a rotating shaft  174 , and the pushing column  162  is positioned at the other end of the base portion  160 . A connecting lug  168  is positioned between the two ends of the base portion  160  and provided with a hole  170  for connecting with the connecting plate  152  via the pin  178 . Preferably, the rotating axis  155  of the connecting plate  152  is parallel to the rotating shaft  174  of the actuating element. Especially, the rotating axis  155  of the connecting plate  152  rotates around the rotating shaft  174  of the actuating element. The connecting shaft portion  172  of the rotating frame  158  is provided with a connecting hole  176 , connecting with the gearbox housing  124  via the pin  179 . 
         [0089]    To ensure that the rotating frame  158  is able to actuate the clamping wrench  140  no matter where the reciprocating rod  126  is positioned, the height of the pushing column  162  is set to the more than the reciprocating travel of the reciprocating rod  126 . Of course, the height of the pushing column  162  is better equal to sum of the reciprocating travel of the reciprocating rod  126  and the axial length of the clamping wrench  140 , so the pushing column  162  is capable of contacting the clamping wrench  140  on the whole length of the clamping wrench  140  and ensures to reliably push the clamping wrench  140  and rotate the rotating sleeve  136  of the clamp. 
         [0090]    The pushing column  162  has a biasing surface  164 , and after the assembly of the saw blade clamp  14  is completed, the biasing surface  164  is opposite to the biasing surface  142  of the clamping wrench  140 . During the reciprocating cutting motion of the saw blade  130 , the biasing surface  164  and the biasing surface  142  have no contact and keep a certain distance there-between. When the saw blade  130  is required to be replaced, the operating element  144  drives the connecting plate  152  to move so as to drive the rotating frame  158  to rotate around the rotating shaft  174 . After the rotating frame  158  rotates to a certain angle, the biasing surface  164  contacts the biasing surface  142 , and then the pushing column  162  is able to further push the clamping wrench  140  to rotate. To prevent the pushing column  162  from failing in the process of pushing the clamping wrench  140  to rotate, the pushing column  162  is provided with a stop protrusion  166 , so when the clamping wrench  140  is pressed against the pushing column  162 , the stop protrusion  166  prevents the biasing surface  142  of the clamping wrench  140  from leaving the biasing surface  164  of the pushing column  162 . 
         [0091]    The saw blade lamp  14  also comprises an elastic element forcing the operating element  144  to move towards the clamping position. In this embodiment, the cutting mechanism  12  comprises a gearbox housing  124 . The elastic element is a torsion spring  180  disposed between the actuating element and the gearbox housing, forcing the actuating element to rotate towards the position where the saw blade is clamped. Specifically, the position, close to the receiving hole  125  of the reciprocating rod, of the gearbox housing  124  is provided with a groove  182  which extends along the reciprocating rod axis  128  and a stopping groove  184  which is protruded from the groove. The groove  182 , the stopping groove  184  and the connecting hole  176  of the connecting rotation portion  172  of the stopping groove  184  together receive the torsion spring  180 . Therefore, one end of the torsion spring  180  is clamped in the stopping groove  184 , while the other end is clamped in the connecting hole  176 . 
         [0092]    In this embodiment, the operating element  144  moves relative to the worktable  4 . The worktable  4  has a sliding chute  32 , and the operating element  144  comprises a sliding plate  146 . The sliding plate  146  is operable to slide between the position where the saw blade is clamped and the position where the saw blade is released along the sliding groove  32 . The sliding groove  32  is positioned at the front portion of the worktable  4  and on the right side of the opening  20 , so the operator is able to replace the saw blade at a comfortable position. The operating element  144  also comprises an opening  148  formed on the sliding plate  146 . Therefore, the operator is able to stretch their fingers into the opening  148  to move the sliding plate  146  in the direction away from the saw blade  130 . 
         [0093]    The attached drawings  4 - 7  below illustrate the concrete operation process of the saw blade clamp  14 .  FIG. 4  and  FIG. 6  are schematic views of the saw blade clamp  14  in the clamped state. In the clamped state, the operating element  144  is located at the clamping position on the far left end of the sliding groove  32 . Under the action of the torsion spring  180 , the rotating frame  158  separates the biasing surface  164  of the pushing column  162  from the biasing surface  142  of the clamping wrench  140 . At this time, the vertical distance from the opening axis  149  of the operating element  144  to the reciprocating rod axis  128  is L 1 , the protrusion of the saw blade  130  is stopped by the end face of the rotating sleeve  136  of the clamp, and the saw blade is clamped by the clamping element. When the saw blade is required to be replaced, the operator moves the sliding plate  146  rightwards along the direction of the arrow A 1  in the figure to force the connecting plate  152  to move so as to drive the rotating frame  158  to rotate around the rotating shaft  174 , and then the biasing surface  164  of the pushing column  162  is forced to contact the biasing surface  142  of the clamping wrench  140 ; if continuously moves the sliding plate  146  to force the pushing column  160  to push the clamping wrench  140  to the release position, the protrusion of the saw blade  130  is aligned with the slot  138  on the rotating sleeve  136  of the clamp, and then the operable is able to take out the saw blade with the other hand.  FIG. 5  and  FIG. 7  are schematic views of the saw blade clamp  14  at the released state. At the released state, the operating element  144  is located at the releasing position on the far right end of the sliding groove  32 . The vertical distance from the opening axis  149  of the operating element  144  to the reciprocating rod axis  128  is L 2  which is more than L 1 . At this moment, if the operator releases the sliding plate  146 , the rotating frame  158  will automatically return to the clamped state under the action of the torsion spring  180  and correspondingly drive the connecting plate  152  and the operating element  144  to return to the clamping positions. 
         [0094]    The second embodiment of the saw blade clamp  14   a  is further described below in combination with the attached drawings  8 - 11 . 
         [0095]    In this embodiment, the saw blade clamp  14   a  comprises a clamp  134   a  connected to the reciprocating rod  126 . The clamp  134   a  comprises a U-shaped clamping wrench  140   a  and a clamping element (not shown in the figure) which is operated by the clamping wrench  140   a  and moves along the inclined sliding groove on the clamping  135  to clamp and release the saw blade  130 . This kind of clamp is suitable for clamping T-shaped and U-shaped saw blades, which means no matter whether or not the tail of the saw blade has a protrusion the saw blade is capable of being clamped. The operator is able to pull the clamping wrench  140   a  to rotate with respect to the axis vertical to the reciprocating rod axis  128 , so the clamping element is forced to clamp and release the saw blade  130 . 
         [0096]    In this embodiment, the operating element  144   a  is also disposed on the upper surface  22  of the worktable  4 . 
         [0097]    The saw blade clamp  14   a  comprises a clamping wrench  140   a  rotating around the axis vertical to the reciprocating rod axis  128 , and a linkage mechanism is disposed between the operating element  144   a  and the clamping wrench  140   a,  so the operating element  144   a  is forced to drive the clamping wrench  140   a  to rotate so as to clamp and release the saw blade. 
         [0098]    In this embodiment, the linkage mechanism comprises a connecting plate  152  that is connected with the operating element  144   a  and rotates around a rotation axis vertical to the reciprocating rod axis  128 , and an actuating element that is connected with the connecting plate  152  and drives the clamping wrench  140   a  to move. 
         [0099]    The operating element  144   a  comprises a sliding plate  146  that extends longitudinally, an opening  148  disposed in the middle portion of the sliding plate, and large lugs  188  and a small lug  190  which are positioned on the two ends of the sliding plate  146  and extend vertically with respect to the sliding plate  146 . There are two large lugs  188 , one end of the connecting plate  152  is capable of being inserted between the two large lugs  188  which are provided with holes matched with the pin holes  154  on the connecting plate  152 , and operating element  144   a  and the connecting plate  152  are connected via the pin  156 . The hole axes  189  on the large lugs  188  are vertical to the opening axis  149 . 
         [0100]    Preferably, the actuating element comprises a pressing pole  192  rotating with respect to the axis vertical to the reciprocating rod axis  128 . A pivot hole  194  is disposed at one end of the pressing pole  192 , a pressing portion  198  is disposed on the other end, and a pin hole  196  is disposed between the two ends. The pivot hole  194  of the pressing pole  192  and the pin hole  210  of a fixing plate  202  are rotationally mounted on the worktable  4  via the pin  157 . The fixing plate  202  has a fixing portion  204  and a connecting portion  208  which extends vertically with respect to the fixing portion. The fixing portion  204  is provided with two mounting holes  206  for stably connecting the fixing hole  202  and the worktable  4  or the supporting unit  10 . The pin hole  154  on the connecting plate  152  and the pin hole  196  in the middle portion of the pressing pole  192  are connected by the pin  212 . The pressing portion  198  of the pressing pole  192  has a pressing surface  200  which is driven by the connecting plate  152  to rotate around the rotating shaft  194  so as to move the clamping wrench  140   a.    
         [0101]    The pressing pole  192  is able to move between the releasing position as shown in  FIG. 10  and the clamping position as shown in  FIG. 11 , and the rotating angle is θ. The reciprocating rod  126  is at different reciprocating position in different cutting process. The reciprocating travel of the reciprocating rod  126  is H. The distance from the rotating shaft  194  of the pressing pole  192  to the pressing surface  200  of the pressing portion  198  is D. To ensure that the pressing pole  192  is able to actuate the clamping wrench  140   a  no matter where the reciprocating rod  126  is positioned, the product uses the distance from the rotating shaft  194  of the pressing pole  192  to the pressing surface  200  of the pressing portion  198  by multiplying the sine of the angle about the pressing pole  192  rotating around the pivot hole  194  which is larger than the reciprocating travel of the reciprocating rod  126 , which means D*sinθ&gt;H. Of course, the product uses the distance from the rotating shaft  194  of the pressing pole  192  to the pressing surface  200  of the pressing portion  198  multiplies the sine of the angle about the pressing pole  192  rotating around the pivot hole  194  is which larger than the sum of the reciprocating travel of the reciprocating rod  126  and the width of the pressing surface of the clamping wrench  140   a,  so the pressing pole  192  is able to contact the clamping wrench  140   a  on the whole pressing surface width of the clamping wrench to ensure that the clamping wrench  140   a  is reliably clamped. 
         [0102]    The pressing pole  192  has a pressing surface  200 , and after the assembly of the saw blade clamp  14   a  is completed, the pressing surface  200  is face to the pressing surface  141  of the clamping wrench  140   a.  During the reciprocating cutting motion of the saw blade  130 , the pressing surfaces  200  and  141  have no contact and keep a certain distance between them. When the saw blade  130  is required to be replaced, the operating element  144   a  drives the connecting plate  152  to move so as to drive the rotating frame  192  to rotate around the rotating axis  211 . After the rotating frame  192  rotates to a certain angle, the pressing surfaces  200  and  141  have contact, and then the pressing pole  192  is able to further force the clamping wrench  140   a  to rotate. 
         [0103]    The saw blade lamp  14   a  also comprises an elastic element forcing the operating element  144   a  to move towards the clamping position. In this embodiment, the elastic element is a tension spring  186  disposed between the operating element  144   a  and the worktable  4 , forcing the operating element  144   a  to move towards the position where the saw blade is clamped. Specifically, the operating element  144   a  is provided with a small lug  190  with a hole. One end of the tension spring  186  is hooked into the hole of the small lug  190 , and the other end is hooked to the worktable  4 . 
         [0104]    In this embodiment, the operating element  144   a  translates relative to the worktable  4 . The worktable  4  is provided with a sliding groove  32 , and the operating element  144  comprises the sliding plate  146 . The sliding plate  146  is able to slide between the position where the saw blade is clamped and the position where the saw blade is released along the sliding groove  32 . The sliding groove  32  is positioned at the front portion of the worktable  4  and on the right side of the opening  20 , so the operator is able to replace the saw blade at a comfortable position. The operating element  144  also comprises an opening  148  formed on the sliding plate  146 . Therefore, the operator is able to stretch their fingers into the opening  148  to move the sliding plate  146  in the direction away from the saw blade  130 . 
         [0105]    The attached drawings  10 - 11  below illustrate the concrete operation process of the saw blade clamp  14   a.    FIG. 11  is a schematic view of the saw blade clamp  14   a  at the clamped state. At the clamped state, the operating element  144   a  is located at the clamped position on the far left end of the sliding groove  32 . Under the action of the tension spring  186 , the pressing surface  200  of the pressing pole  192  and the pressing surface  141  of the clamping wrench  140   a  are partitioned. At this moment, the vertical distance from the opening axis  149  of the operating element  144   a  to the reciprocating rod axis  128  is L 3 , and the saw blade is clamped by the clamping element. When the saw blade is required to be replaced, the operator should move the sliding plate  146  rightwards along the direction of the arrow A 2  in the figure to force the connecting plate  152  to move so as to drive the pressing frame  192  to rotate around the rotating axis  211 , and then the pressing surface  200  of the pressing pole  192  is forced to contact the pressing surface  141  of the clamping wrench  140   a;  if it continuously moves the sliding plate  146 , the pressing pole  192  pushes the clamping wrench  140   a  to the release position, and then the operator is able to take out the saw blade with the other hand.  FIG. 10  is a schematic view of the saw blade clamp  14   a  at the released state. At the released state, the operating element  144   a  is located at the releasing position on the far right end of the sliding groove  32 . The vertical distance from the opening axis  149  of the operating element  144   a  to the reciprocating rod axis  128  is L 4  which is shorter than L 3 . At this moment, the operator releases the sliding plate  146 , the operating element  144   a  will automatically return to the clamped state under the action of the tension spring  186  and correspondingly drive the connecting plate  152  and the pressing plate  192  to return to the clamping positions. Therefore, the clamping wrench  140   a  of the clamp will also return to the clamping position. 
         [0106]    The attached drawings  12 - 14  illustrate the third embodiment of the saw blade clamp  14   b.    
         [0107]    In this embodiment, the units and parts of the saw blade clamp  14   b , identical with those in the second embodiment, adopt the same mark numbers. Herein, the following is the detailed description of the differences between this embodiment and the above embodiment. 
         [0108]    In this embodiment, the operating element  144   b  is positioned on the upper surface of the worktable  4 . The operating element  144   b  rotates with respect to the worktable  4  to clamp and release the saw blade. 
         [0109]    The saw blade clamp  14   b  comprises the clamping wrench  140   a  rotating around the axis vertical to the reciprocating rod axis  128 , and an actuating element is disposed between the operating element  144   b  and the clamping wrench  140   a.    
         [0110]    The worktable  4  is provided with the receiving groove  33  in which the operating element  144   b  is received. The operating element  144   b  comprises a flat plate body  147  and an opening  148  formed at one end of the flat plate body  147 . The middle portion of the flat plate body  147  extends vertically to form a pull ring  214 . In this embodiment, the actuating element is the pressing plate  216 . One end of the pressing plate  216  faces the clamping wrench  140   a,  while the other end is stably connected with the end of the operating element  144   b  via the rotating connection portion  215 . Preferably, the operating element  144   b,  the rotating connection portion  215  and the pressing plate  216  are integrally molded. The skilled persons in this field should understand that the pressing plate  216  and the operating element  144   b  have other fixed connections, such as welding, riveting, etc. The rotating connection portion  215  has a pivot hole connected to the fixing plate  202  via the pin  212 . Therefore, the operating element  144   b  and the pressing plate  216  rotates around the same rotating axis  211 . 
         [0111]    The pressing pole  216  is able to rotate between the releasing position as shown in  FIG. 13  and the clamping position as shown in  FIG. 14 , and the rotating angle is α. The reciprocating rod  126  is at different reciprocating positions in different cutting processes. The reciprocating travel of the reciprocating rod  126  is H. The distance from the pivot hole of the pressing plate  216  to the pressing surface  213  is L. To ensure that the pressing pole  216  is able to actuate the clamping wrench  140   a  no matter where the reciprocating rod  126  is positioned, the product uses the distance from the pivot hole of the pressing pole  216  to the pressing surface and multiplies the sine of the angle about the pressing plate  216  rotating around the rotating axis  211  which is larger than the reciprocating travel of the reciprocating rod  126 , which means that L*sinα) H. Of course, the product uses the distance from the pivot hole of the pressing plate  216  to the pressing surface  213  and multiplies the sine of the angle about the pressing plate  216  rotating around the rotating axis  211  which is larger than the sum of the reciprocating travel of the reciprocating rod  126  and the width of the pressing surface  213  of the clamping wrench  140   a,  so the pressing plate  216  is able to contact the clamping wrench  140   a  on the whole pressing surface  213  width of the clamping wrench to ensure that the clamping wrench  140   a  is reliably clamped. 
         [0112]    One end of the elastic element, namely the tension spring  186 , is hooked with the pull ring  214  of the operating element  144   b,  and the other end is connected with the worktable  4  or the supporting unit  10 , so the operating element  144   b  moves towards the clamping position. 
         [0113]    The operating element is also capable of being disposed on the supporting unit. Specifically, the operating element is disposed on the base at the bottom portion of the supporting unit. Furthermore, the operating element is disposed at the front of the base, namely the side that the operator directly faces during operation. 
         [0114]    The skilled persons in this field should understand that the concrete structures of the operating element, etc. in the present invention may have variations. For example, the clamp has many structures in the prior art, capable of being equivalently replaced by the clamp structure disclosed in the present invention. For example, the elastic element has two forms, namely the torsion spring and the tension spring, in the present invention, but the skilled persons in this field should know that other kinds of springs, such as the compression spring and the leaf spring, or other kinds of elastic elements, such as the elastic rubber piece, etc., all can be used as the elastic element in the present invention. Therefore, any variation and replacement based on the present invention shall be within the protection scope of the present invention. 
         [0115]    The fourth embodiment of the saw blade clamp  229  is further described in combination with the attached drawings  15 - 17  below. 
         [0116]    In this embodiment, the units and parts of the cutting machine  2 , identical with those in the first embodiment, adopt the same mark numbers. Herein, the following is the detailed description of the differences between this embodiment and the above embodiment. 
         [0117]    The cutting mechanism  12  has the saw blade clamp  229  operable to clamp and release the saw blade  130 . As shown in  FIG. 17 , the saw blade clamp  229  comprises a clamp  134  for fixing a saw blade, a corner bracket  211  rotating with respect to the reciprocating rod  126  and a flexible connecting element  220  connected to the corner bracket  221 . The flexible connecting element  220  is operable to drive the clamp  134  to move between the clamping position and the releasing position. The skilled persons in this field should understand that the saw blade clamp  229  disclosed in the present invention is only one of variously structured clamps, and clamps with other structures, for example clamps which are pulled by the wrench to clamp a steel column and move along the inclined sliding groove to clamp and release the saw blade, are also suitable for the present invention with some detailed modifications. The clamp  134  in the present invention adopts the clamp structure of the rotating sleeve  136  rotating with respect to the reciprocating rod axis  128 . The rotating sleeve  136  has an opening capable of receiving the saw blade  130  and forces the protrusion of the saw blade  130  to press against the inner end face of the rotating sleeve  136  to prevent the saw blade  130  from falling after the saw blade  130  is inserted into the opening and rotates to a certain angle. 
         [0118]    In this embodiment, the flexible connecting element  220  is a steel wire. The steel wire has certain rigidity and toughness and ensures that the operating device of the saw blade clamp is positioned at a position where the operator can easily reach. The skilled persons in this field know that except for the steel wire, the flexible connecting element may also be other metal wires, high-strength plastic ropes, rubber belts, etc. Such flexible elements are capable of being bent, of have a high elastic modulus, and are difficult to break. The tension of the flexible connecting element  220  is also capable of being adjusted by a tensioning mechanism (not shown in the figure). Usually, the flexible connecting element  220  is capable of being supported and actuated only by a certain supporting surface. To adjust and control the tension of the flexible connecting element  220 , a roller is disposed on the supporting unit or the bracket which supports the flexible connecting element, one part of the flexible connecting element contacts an annular groove of the roller, and the supporting point of the roller is capable of being relatively adjusted, so the tension of the flexible connecting element is adjusted. 
         [0119]    In this embodiment, a foot pressing plate connected with the steel wire  220  is arranged below the worktable  4 , so the operator is able to control the saw blade clamp  229  by pedaling to avoid stooping. In this embodiment, the clamp  134  comprises the rotating sleeve  136  capable of rotating around the reciprocating rod axis  128 , and the flexible connecting element, namely the steel wire  220 , converts the rotation of the rotating sleeve  136  into the linear motion of the foot pressing plate. The foot pressing plate performs linear motion, so the operator may easily apply force and the actions of clamping and releasing the saw blade are simple. 
         [0120]    To ensure that the flexible connecting element  220  is able to drive the rotating sleeve of the clamp  134  to move, the corner bracket  221  rotating with respect to the reciprocating rod axis  128  is disposed between the flexible connecting element  220  and the clamp, one end of the flexible connecting element  220  is connected with the corner bracket  221  and the other end thereof is connected with the foot pressing plate. Due to the corner bracket, the motion of the rotating sleeve  136  is more easily converted into the movement of the foot pressing plate and more easily ensures that the clamp  134  is configured into the released or clamped state. In this embodiment, the corner bracket  221  comprises a C-shaped base portion  160 , one end of the base portion is connected with the rotating shaft  174 , the other end of the base portion  160  is provided with the pushing column  162  which extends vertically, the connecting lug  168  is disposed between the two ends of the base portion  160 , and the steel wire  220  is penetrated into the connecting lug  168 . The pushing column  162  pushes the rotating sleeve  136  of the clamp, and the whole corner bracket  71  rotates around the rotating shaft  174 , to ensure that the steel wire  220  is able to pull the corner bracket  221  to rotate. 
         [0121]    The cutting machine  2  also comprises a supporting frame  217  with supporting surface  219  and at least three supporting legs  218 . In this embodiment, there are four supporting legs  218 , and according to the actual demands, the quantity of the supporting legs  218  is capable of being adjusted. The cutting machine  2  is supported on the supporting frame  217 , so the foot pressing plate is disposed at the lower side of one of the supporting legs  218  so as to operate the foot pressing plate conveniently. This supporting leg  218  is positioned on the right front side below the worktable  4 . Of course, this supporting leg  218  is also capable of being positioned on the left front side below the worktable  4  according to the habit of the operator. The foot pressing plate is able to move axially with respect to the supporting leg  218 . The supporting unit  10  of the cutting machine  2  is positioned on the supporting surface  219  of the supporting frame  217 , the supporting legs  218  support the cutting machine, so the saw blade  130  is positioned at a position where the operator works comfortably and controls the saw blade clamp with feet conveniently. The lower ends of the supporting leg  218  with the foot pressing plate is provided with a guiding groove  227 . A moving block  224  and a footplate  222  move along the extension direction of the guiding groove  227 . 
         [0122]    In this embodiment, the steel wire  220  penetrates through the supporting surface  219  and is at least partly received into the supporting leg  218 . Therefore, the whole cutting machine has no flexible connecting element outside and is compactly structured and the steel wire is difficult to break or deform in case of misoperation. 
         [0123]    The foot pressing plate comprises the footplate  222  and the moving block  224  which receives in the supporting leg  218 . The footplate  222  is connected with the moving block  224  via the rotating shaft  223  and therefore is able to rotate with respect to the moving block  224 . When the saw blade replacement is completed and the saw blade is not required to be clamped or released, the footplate  222  is able to rotate with respect to the moving block  224  to the position where the footplate  222  is adhered to the outer wall of the supporting leg  218 . At this moment, the footplate  222  is inoperable so as to avoid the event that the operator carelessly steps on the footplate and releases the saw blade. 
         [0124]    An elastic element  225  receiving in the supporting leg  218  is positioned between the footplate  222  and the moving block  224 , pressing the moving block  224  to move towards the position wherein the steel wire  220  is unloosened. Therefore, the saw blade clamp  229  is kept at the clamped position at the normal state. Meanwhile, the end portion of the supporting leg  218  is provided with an end cover  226 , one end of the spring is pressed against the end face of the moving block  224 , and the other end thereof is pressed against the inner end face of the end cover  226 . The end cover  226  and the supporting leg  218  are connected via screw threads. In this embodiment, the elastic element  225  is a compression spring. The skilled persons in this field know that the elastic element  225  may have other forms, such as leaf spring, tension spring, etc., which is not descried in detailed herein. Therefore, any variation and replacement based on the present invention shall be within the protection scope of the present invention. 
         [0125]    The attached drawings  18 - 20  illustrate the cutting machine  2  in the fifth embodiment. 
         [0126]    In this embodiment, the units and parts of the cutting machine  2 , identical with those in the first embodiment, adopt the same mark numbers. Herein, the following is the detailed description of the differences between this embodiment and the above embodiment. 
         [0127]    The worktable  4  has a transparent portion  232 , and the saw blade clamp  14  is positioned below the transparent portion  232 . During operation, the operator is able to observe the concrete situation of the saw blade clamp  14  from the transparent portion  232 . The transparent portion  232  is basically square, aligned with the upper surface  22  of the worktable  4 . In a view of manufacturing, the position, where the cutting machine is mounted, of the middle portion of the worktable  4  has an opening, and a transparent cover is embedded into the opening, so the upper surface of the cover and the upper surface  22  of the worktable  4  are aligned and together support the workpiece. The transparent portion  232  is attached to the worktable  4  to become one part of the worktable  4 . 
         [0128]    In this embodiment, the area of the transparent portion  232  only occupies a part of that of the whole worktable  4 . The skilled persons in this field know that the ratio of the area of the transparent portion  232  to the area of the whole upper surface  22  of the worktable  4  is able to change according to demands. For example, the area of the transparent portion  232  is configured to be identical with that of the upper surface of the worktable  4 , thus, no matter where the operator is able to easily observe the state of the saw blade clamp  14 , and in the operation of replacing the saw blade  130 , the event that the saw blade  130  is released by incorrect operation because the concrete position of the saw blade clamp cannot be seen is avoided, and injury is also avoided. The tabletop of the working table  4  is partly or wholly made of a transparent material. Such design makes processing and manufacturing convenient and operation easy. 
         [0129]    To ensure that the operator contacts the saw blade clamp  14  conveniently, the worktable  4  is configured to comprise two portions  233 ,  234  and the saw blade clamp  14  is positioned between the boundary of the two portions. By separating the tabletop of the worktable, the saw blade clamp  14  is located at the position where the operator is easy to contact the saw blade clamp  14  and is able to replace the saw blade without stooping. Concretely speaking, at least one portion of the worktable  4  is able to move with respect to the saw blade clamp  14  so that the saw blade clamp  14  is positioned at be contacted directly. The worktable  4  as shown in  FIG. 19  is provided with a guiding rail  230 , and the supporting unit  10  connected to the worktable  4  is correspondingly provided with the sliding groove  231 . The worktable  4  comprises two portions at least one portion  233  is able to translate with respect to the saw blade clamp  14 . In this embodiment, the first portion  233  of the worktable  4  slides in the sliding groove  231  on the supporting unit  10  by means of the guiding rail  230  so as to move away from the saw blade clamp  14 . The extension directions of the sliding groove  231  and the guiding rail  230  are vertical to the boundary of the two portions of the worktable. The skilled persons in this field know that the positions of the guiding rail  230  and the sliding groove  231  are not limited to those in the schemes of the above embodiments and are capable of being exchanged to realize the movement of one portion of the worktable  4  with respect to the saw blade clamp. The first portion  233  and the second portion  234  are able to move with respect to the saw blade clamp at the same time to accelerate separation of the two. 
         [0130]    In this embodiment, the two portions of the worktable are separated from the front sidewall  26   a  to the rear sidewall  26   c  of the worktable. The skilled persons in this field know that the worktable is capable of being separated along other surfaces. For example, the separating surface of the worktable table extends to the position where the saw blade clamp is positioned from the front sidewall  26   a  to the rear sidewall  26   c  or extends to the position where the saw blade clamp is disposed from the right sidewall  26   d  to the left sidewall  26   b.  Therefore, the worktable is divided into two portions, wherein the area of the first portion  233  close to the operation position of the operator is smaller than that of the second portion  234  away from the operation position of the operator. The first portion  233  is able to move with respect to the second portion  234 , away from the saw blade clamp  14 . Due to small area of the moving portion and light weight of the corresponding worktable, the movement of the worktable is convenient and labor-saving. 
         [0131]    The two portions of the worktable may have many separation directions, for example the direction from the rear sidewall to the front sidewall, the direction from the left sidewall to the right sidewall, or the direction from the saw blade clamp to the intersection of the sidewall and the right sidewall, etc., which is just a piece of cake for the skilled persons in this field, so no more detailed description is provided. 
         [0132]    The sixth embodiment of the worktable is described in details in combination with the attached drawing  21 . 
         [0133]    In this embodiment, the worktable  4  comprises two separable portions. At least one portion is able to rotate with respect to the saw blade clamp; concretely speaking, the first portion  233  close to the operation position of the operator is provided with a shaft  235 , which extends to the worktable vertically, at a position of the rear sidewall, the supporting unit is provided with a rotating shaft  236 , and the first portion  233  of the worktable rotates around the rotating shaft to move away from the saw blade clamp. An expansion space at a certain angle is formed between the first portion  233  and the second portion  234  of the worktable, so the operator is able to directly reach the saw blade clamp from the expansion space. 
         [0134]    Of course, the pivot hole  236  and the shaft  235  in this embodiment are capable of being exchanged to realize the rotation of one portion of the worktable with respect to the supporting unit  10  and the saw blade clamp  18 . 
         [0135]    The seventh embodiment of the worktable is described in details in combination with the attached drawing  22 . 
         [0136]    Like the above embodiment, the worktable  4  also comprises two separable portions. At least one portion is able to rotate with respect to the saw blade clamp  14 . But the difference is that one portion of the worktable  4  turns with respect to the other portion in this embodiment. One portion of the worktable  4  is able to rotate, and the other portion is fixedly disposed with respect to the supporting unit  10 . Therefore, one portion of the worktable turns at a certain angle with respect to the other portion of the worktable, so the upper surfaces of the two portions of the worktable are inclined at a certain angle, and the saw blade clamp is disposed at the position within reach. 
         [0137]    The skilled persons in this field know that the supporting unit in the present invention is also capable of being made of the transparent material. Thus, the operator is able to observe the working state of the cutting machine from different positions, and no matter where the saw blade is replaced, the saw blade clamp is ensured to be visible to make the saw blade replacement safe. 
         [0138]    Certainly, the present invention is not only limited to the abovementioned embodiments. Any variation and replacement based on the present invention shall be within the protection scope of the present invention.