Patent Publication Number: US-10315291-B2

Title: Wrench

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is the United States national phase of International Application No. PCT/CN2014/082038 filed Jul. 11, 2014, the disclosure of which is hereby incorporated in its entirety by reference. 
     FIELD OF THE INVENTION 
     The invention relates to a hand tool, and, in particular, relates to a wrench used for clamping a flat plate, a nut, and especially pipe fittings such as a steel pipe, a plastic pipe, etc. 
     DESCRIPTION OF THE PRIOR ART 
     In daily lives or works, a wrench is frequently used for clamping an object, such as for clamping pipe fittings such as a steel pipe, a plastic pipe etc., to implement loosening and tightening of mounting or dismounting. A traditional wrench, such as a pipe wrench, for clamping pipe fittings is generally composed of a fixed jaw, a movable jaw, a handle, an adjusting nut, etc. The fixed jaw is fixed together with the handle in a sophisticated structure. The traditional pipe wrench accomplishes opening and closing relying on the transmission by the thread pair between the nut and the movable jaw. In use, the adjusting nut is rotated constantly to enable the change in the opening size of the movable jaw relative to the fixed jaw by adjusting the sliding movement of the movable jaw, and, therefore, the operation is very inconvenient. Meanwhile, the opening and closing speed of the jaws of a traditional pipe wrench is limited by the pitch of the thread pair, unable to realize fast opening and closing of the jaws. 
     SUMMARY OF THE INVENTION 
     In view of the above defects in the prior art, the technical problem to be solved by the invention is to provide a wrench which has simple structure, flexibility of opening and closing, fast adjusting speed, convenience and reliability in using. The wrench can be used for clamping and rotating a pipe fitting, and also for clamping objects in other shapes such as a flat plate, a nut, etc. 
     In order to achieve the above object, the invention provides a wrench, the structure of which comprising: a guide rod, a first pawl mounted on the guide rod, a sliding member sheathed on the guide rod, and a second pawl mounted on the sliding member and matching with the first pawl, characterized in that, the wrench further comprises a toothed block disposed on the sliding member and matching with the guide rod, the toothed block having a first position and a second position; the wrench is configured such that: when the toothed block is in the first position, the toothed block is locked; when the toothed block is in the second position, the toothed block is unlocked. 
     Further, the first position refers to a position where the toothed block is located when the toothed block is engaged with the guide rod; the second position refers to a position where the toothed block is located when the toothed block and the guide rod are detached. 
     Further, when the toothed block is in the first position, the toothed block is slidable along the guide rod toward the first pawl, and is locked in the direction away from the first pawl; when the toothed block is in the second position, the toothed block is slidable along the guide rod toward or away from the first pawl. 
     Further, an engagement portion where the guide rod is engaged with the toothed block is provided with unidirectional teeth having a unidirectional orienting effect: when the sliding member is pushed toward the first pawl, the toothed block is slidable along toothed surface of the unidirectional teeth, so that the sliding member moves along the guide rod and comes close to the first pawl; when the sliding member is pushed away from the first pawl, a sliding movement of the toothed block along toothed surface of the unidirectional teeth is obstructed, so that a sliding movement of the sliding member along the guide rod is locked. 
     Further, the sliding member is provided with a sloping surface matching with the toothed block, a first angle provided between the sloping surface and the guide rod; the first angle enabling the toothed block to be subject to an acting force perpendicular to the guide rod and pointing toward the guide rod when the wrench is clamping a workpiece, the acting force facilitating the engagement of the toothed block and the guide rod. 
     Further, the first angle is arranged to be less than 90°. 
     Further, an engagement portion where the guide rod is engaged with the toothed block is provided with unidirectional teeth having a toothed surface, the toothed surface obstructs the sliding movement of the toothed block away from the first pawl, a second angle provided between the toothed surface and the sloping surface, the second angle enabling the unidirectional teeth to still be able to lock the toothed block when the unidirectional teeth deform. 
     Further, the second angle is arranged to be more than 0°. 
     Further, a reserved space is arranged between the toothed block and the sliding member, the reserved space enabling the toothed block to rotate by an angle allowing the toothed block to conquer the locking of the toothed block with respect to the guide rod produced due to the second angle, so that the toothed block is detached from the guide rod; meanwhile, the reserved space enables a plurality of teeth on the toothed block to automatically locate position to be engaged with the guide rod. 
     Further, the wrench also includes a connecting rod provided at both sides of the guide rod and connected to the toothed block. 
     Further, the wrench also includes a pushbutton connected to the toothed block by the connecting rod, when a pressing force is applied to the pushbutton, the connecting rod being able to transfer the pressing force to the toothed block, so that the toothed block is detached from the guide rod; when the pressing force applied to the pushbutton is canceled, the toothed block is reset to be engaged with the guide rod. 
     Further, a third angle is provided between the connecting rod and the sloping surface, and meanwhile, a fourth angle is provided between the connecting rod and the guide rod, the third angle and the fourth angle enabling the pressing force to which the pushbutton is subject to conquer the friction force between the toothed block and the sloping surface, so that the toothed block is detached from the guide rod. 
     Further, the third angle and the fourth angle are both less than 90°. Further, the wrench also includes a pushbutton and a connecting rod, the pushbutton, the connecting rod and the toothed block formed into a connecting member provided to be sheathed on the guide rod. 
     Further, the sliding member is provided with a first portion extending along the guide rod toward the first pawl, and the second pawl is embedded in the first portion. 
     Further, the sliding member is also provided with a second portion provided to be sheathed on the guide rod, the second portion being provided with a cavity arranged therein, the connecting member being arranged in the cavity. 
     Further, a portion of the pushbutton is embedded in the cavity, and another portion of the pushbutton protrudes out of the sliding member. 
     Further, the second pawl is provided with a hang tab embedded in the second portion and fixedly connected to the second portion by a pin rod. 
     Further, the wrench also includes a clamping surface provided on the first pawl and the second pawl. 
     Further, the first pawl is connected to the guide rod by a fixing pin arranged with a snap slot used for mounting a snap ring. 
     Further, a first spring is provided between the first pawl and the guide rod, and when a workpiece is clamped, the first spring can push the first pawl to move, so as to produce pre-tightening force in the workpiece. 
     Further, the wrench also includes a second spring being able to apply pressing force to the toothed block. 
     Further, one end of the second spring contacts the toothed block, and the other end contacts a coverplate fixedly connected to the sliding member. 
     Further, the outside of the sliding member is provided with a first concave part, and the coverplate is embedded in the first concave part, the coverplate fixedly connected to the sliding member by a screw. 
     Further, the screw is a flat screw, and a gap exists between the screw and the toothed block. 
     Further, the sliding member is also provided with a thumb abutting part facilitating an operator to push the sliding member to move, a surface of the thumb abutting part is provided with a second stripes, slots parallel to each other being between the second strips, for increasing the friction between the fingers of the operator and the thumb abutting part. 
     Further, the first spring is a spiral spring. 
     Further, the pushbutton surface is provided with a first stripes, slots parallel to each other being between the first strips, for increasing the friction between the fingers of the operator and the pushbutton. 
     Further, the clamping surface is provided with teeth used for increasing the friction between the clamping surface and the clamped workpiece. 
     Further, the second spring is a compressed spring. 
     Further, both sides of the guide rod are provided with a recess extending across the whole guide rod, such that, the connecting rod at either side of the guide rod is not in complete contact with the side of the guide rod, facilitating the toothed blocking to slide along the guide rod. 
     Further, the guide rod is provided with a grasp part which is a protection sleeve surrounding about the guide rod. 
     Further, the protection sleeve is fixedly connected to the guide rod by a fastener. 
     Further, the fastener is composed of a nut and a bolt. 
     Further, the protection sleeve is provided with a second concave part, and the nut is embedded in the second concave part. 
     Further, the protection sleeve is also provided with a hang hole, used for hangingly position the wrench. 
     The invention has the following advantages:
     (1) By fast sliding movement between the guide rod and the toothed block, the fast adjustment of the jaws, i.e. the distance between the first pawl and the second pawl, can be achieved.   (2) The unidirectional teeth at the engagement portion where the guide rod is engaged with the toothed block have a unidirectional orienting effect. The second pawl is only allowed to move toward but not away from the first pawl when the sliding member is pushed, thus, the second pawl will not automatically move away from the first pawl so that the clamped object is dropped when clamping a workpiece, so that the clamped object is tightly clamped.   (3) By applying a pressing force to the pushbutton, the toothed block can be detached from the guide rod readily, which is good for fast adjustment of the jaws. In addition, when canceling the pressing force to the pushbutton, the elastic force of the second spring can quickly reset the toothed block to be engaged with the guide rod.   (4) The angle between the sloping surface of the sliding member and the direction along the length of the guide rod is arranged to be less than 90°, being able to increase the pressing force between teeth on the toothed block and the teeth on the guide rod, so that the toothed block is better engaged with the guide rod when the wrench is clamping a workpiece.   (5) The angle between the connecting rod and the direction along the length of the guide rod is less than 90°, and the angle between the connecting rod and the sloping surface of the sliding member is less than 90°, so that once an act is applied to the pushbutton the toothed block can readily conquer the friction to slide down along the sloping surface of the sliding member when the wrench is not clamping a workpiece, so that fast detachment of the toothed block from the guide rod and, therefore, unlocking, can be achieved.   (6) The unidirectional teeth on the toothed block and the guide rod have a toothed surface obstructing the sliding movement of the toothed block toward the first pawl. The angle between the toothed surface and the sloping surface of the sliding member is arranged to be more than 0°, such that the toothed block can still be locked and not detached from the guide rod when the wrench is clamping a workpiece even if deformation occurs to the unidirectional teeth.   

     Referencing now to the figures, the conception, detailed structure and induced technical effect of the present invention will be expounded for due understanding of the purpose, characterizations and effects of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of the wrench in a preferred embodiment of the invention; 
         FIG. 2  is another perspective view of the wrench is a preferred embodiment of the invention; 
         FIG. 3  is perspective view of the connection between the first pawl and the guide rod of the wrench; 
         FIG. 4  is an exploded view of the wrench shown in  FIG. 1 ; 
         FIG. 5  is a partial enlarged view of  FIG. 2 ; 
         FIG. 6  is a perspective view of the wrench shown in  FIG. 1  when the second pawl comes close to the grasp part, showing the pushing direction B; 
         FIG. 7  is a perspective view of the wrench shown in  FIG. 1  when the second pawl comes close to the first pawl, showing the pushing direction B; 
         FIG. 8  is a perspective view of the wrench shown in  FIG. 1  when the second pawl comes close to the first pawl, showing the pushing direction D; 
         FIG. 9  is a perspective view of the wrench shown in  FIG. 1  when the second pawl comes close to the grasp part, showing the pushing direction D; 
         FIG. 10  is a perspective view of the wrench of the invention when clamping a pipe fitting; and 
         FIG. 11  is a partial enlarged view of  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Now the invention is further described in combination with the accompanying figures and embodiments. 
       FIG. 1  and  FIG. 2  are perspective views of the wrench  100  in a preferred embodiment of the invention, the structure thereof includes: a guide rod  2 , a first pawl  1  mounted on the guide rod  2 , a sliding member  31  sheathed on the guide rod  2 , and a second pawl  32  mounted on the sliding member  31  and matching with the first pawl  32 . The wrench also includes a toothed block  34  disposed inside the sliding member  31  and matching with the guide rod  34 . The toothed block  34  has a first position and a second position. 
     The wrench  100  is configured such that: when the toothed block  34  is in the first position, the toothed block  34  is engaged with the guide rode  2 , and the toothed block can slide along the guide rod toward the first pawl  1 , and is locked in the direction away from the first pawl  1 ; when the toothed block  34  is in the second position, the toothed block  34  is detached from the guide rod  2 , and the toothed block  34  can slide along the guide rod  2  toward or away from the first pawl. 
     In an embodiment of the invention, the first position refers to a position where the toothed block  34  is located when the toothed block  34  is engaged with the guide rod; the second position refers to a position where the toothed block  34  is located when the toothed block  34  and the guide rod  2  are detached. 
     As shown in  FIG. 2 , an engagement portion where the guide rod  2  is engaged with the toothed block  34  is provided with unidirectional teeth  15  having a unidirectional orienting effect: when the sliding member  31  is pushed toward the first pawl  1 , the toothed block  34  is slidable along toothed surface of the unidirectional teeth  15 , so that the sliding member  31  and the second pawl  32  move along the guide rod  2  and comes close to the first pawl  1 ; when the sliding member  31  is pushed away from the first pawl  2 , a sliding movement of the toothed block  34  along toothed surface of the unidirectional teeth  15  is obstructed, so that the sliding movement of the sliding member  31  and the second pawl  32  along the guide rod  2  is locked. 
     As shown in  FIG. 3 , in the wrench  100  in the preferred embodiment of the invention, the first pawl  1  is pivotedly connected to the guide rod  2  by a fixing pin  12 , and the second pawl  32  is fixedly connected to the sliding member  31 . The first pawl  1  and the second pawl  32  are matched for clamping workpieces of different shapes like a pipe fitting, a flat plate, a screw. A first spring  13  is also arranged between the first pawl  1  and the guide rod  2 . The first spring  13  is a spiral spring. In another embodiment, the first spring  13  can be replaced with an elastic washer. When the first pawl  1  and the second pawl  32  are matched to clamp the workpiece  300 , the opening of the jaws enables the first pawl to pivot by a small angle along the opposite direction of the arrow A, where the first spring  13  is compressed, and under the effect of the restoring force, the first spring  13  pushes the first pawl  1  along the direction of arrow A, producing pre-tightening force in the workpiece  300  between the first pawl  1  and the second pawl  32 . Because teeth are arranged at the portion where the first pawl  1  and the second pawl  32  clamp the workpiece, under the effect of the pre-tightening force, the teeth compress tightly against the surface of the workpiece  300 , so that the slippage will not occur between the teeth and the wrench  100  when in a screwing operation. 
     As shown in  FIG. 4 , the wrench  100  includes a guide rod  2 , a first pawl  1 , a second pawl  32 . The guide rod  2  has a grasp part  200 , which is a protection sleeve  21  that can be made of materials of leather, plastic, etc. The shape of the protection sleeve  21  is ergonomic. The protection sleeve  21  can be provided to be sheathed on the rod  2  and can be removed from the guide rod  2  readily. The protection sleeve  21  is fixedly connected to the guide rod by a fastener, and preferably, the fastener is a bolt  22  and a nut  26 . A hang hole  23  is arranged on the protection sleeve  21 . After using the wrench  100 , the wrench  100  can be hangingly placed using the hang hole  23 . Preferably, the protection sleeve  21  is provided with a second concave part  210  which is perfectly for embedding the bolt  22  thereinto, thus on the one hand, the protection sleeve  21  are made more aesthetic, while in the mean time avoiding the head part of the bolt  22  hurting the fingers of an operator due to being protruding out of the protection sleeve  21 . 
     The first pawl  1  is pivotedly connected to the guide rod  2  by the fixing pin  12 . The fixing pin  12  is arranged with a snap slot  120 . A snap ring  121  is disposed in the snap slot  120 , such that the fixing pin  12  will not fall out from inside the mounting holes of the guide rod  2  and the first pawl  1 . A first spring  13  is also arranged between the first pawl  1  and the guide rod  2 . As noted above, under the effect of the restoring force of the first spring  13 , the first pawl  1  and the second pawl  32  can produce pre-tightening force in the clamped workpiece when clamping a workpiece, so that slippage will not occur to the wrench  100  when in screwing operation. 
     The wrench body  100  also includes a sliding member  31  including a first portion  310  extending along the lower part of the guide rod  2  toward the first pawl  1 , the end part thereof, i.e. the portion close to the first pawl  1  being provided with a slot provided with a second pawl  32  embedded therein. As shown in  FIG. 4 , a side of the second pawl  32  has a clamping surface  111  matching with the clamping surface  110  of the first pawl. The two clamping surfaces are both arranged with teeth, and the shapes of the teeth can be identical or partly different. The teeth are used for increasing the friction between the two clamping surfaces and the clamped object. The other side of the second pawl  32  is provided with a hang tab  320  embedded in the slot of the first portion  310  of the sliding member  31 , and is fixedly connected to the first portion  310  by the pin  321 . 
     The sliding member  31  also includes a second portion  311  provided with a cavity  312  arranged therein. A toothed block  34  is arranged inside the cavity  312 . The toothed block  34  is coupled to the pushbutton  33  though a connecting rod  39 . A pin  40  is used for connection between the connecting rod  39  and the toothed block  34 , or the connecting rod  39  and the pushbutton  34 . At least two connecting rods  39  are, parallel to each other, connected to the two sides of the pushbutton  33  and the toothed block  34  (see  FIG. 5 ). The connecting member composed of the pushbutton  33 , the connecting rod  39  and the toothed block  34  is located in the cavity  312 . The guide rod  2  passes through the connecting member and meanwhile passes through the second portion  311 . The connecting rods  39  are located at the two sides of the guide rod  2 . The pushbutton  33  is located at the upper part of the guide rod  2  and a gap is reserved between the pushbutton  33  and the guide rod  2 . The lower part of the guide rod  2  and the upper surface of the toothed block  34  are provided with unidirectional teeth  15 . The upper surface of the toothed block  34  is engaged with the lower part of the guide rod  2 . A part of the pushbutton is embedded in the cavity  312 , and another part is protruding out of the second portion  311  of the sliding member  31 . 
     In a preferred embodiment of the invention, the surface of the pushbutton  33  is arranged with a first stripes  330 . Slots parallel to each other are between the first strips  330 , which, in another embodiment, can also be staggered slots, for increasing the friction between the fingers of the operator and the pushbutton  33 , and preventing slippage when the fingers of the operator contact the pushbutton  33 , which tempers using. The two sides of the guide rod  2  are arranged with recesses  24  extending across the whole guide rod  2 , such that, the connecting rods  39  at both sides of the guide rod  2  are not in complete contact with the sides of the guide rod  2 , to facilitate the fast sliding movement of the toothed block  34  along the guide rod  2 . 
     The outside of the second portion  311  of the sliding member  31  is provided with a first concave part  313  which is communicated with the cavity  312  for embeddingly arranging the coverplate  36  that fixedly connected to the sliding member  31  by a screw  38 . Preferably, the screw  38  is a flat screw, that is, its end part is flat. A gap is reserved between the end part of the screw  38  and the toothed block  34 . A second spring  37  is arranged between the coverplate  36  and the toothed block  34 . The both ends of the spring  37  are respectively in contact with the toothed block  34  and the coverplate  36  (see  FIG. 5 ). The spring  37  applied a pressing force to the toothed block  34 , so that the toothed block  34  is engaged with the lower part of the guide rod  2 . Preferably, the second spring  37  is a compressed spring. 
     In addition, the outside of the second portion  311  of the sliding member  31  is also provided with a thumb abutting part  35  facilitating the operator to push the sliding member  31 . The surface of the thumb abutting part  35  is provided with a second stripes  350 . Slots parallel to each other are between the second strips  350 , for increasing the friction between the fingers of the operator and the thumb abutting part  35 . 
       FIG. 6 - FIG. 9  provide perspective views of using wrench  100  to implement fast adjustment. When the start position of the second pawl  32  is closed to the grasp part  200  (see  FIG. 6 ), the fingers of the operator can contact the thumb abutting part  35 , and apply a push force to the sliding member  31  along the direction of arrow B. Since the engaged portion of the toothed block  34  and the guide rod  2  is provided with unidirectional teeth  15  having unidirectional orienting effect, the toothed block  34  can slide fast along the toothed surface of the unidirectional teeth  15  toward the direction of arrow B, i.e. the direction of the first claw  1 . During the sliding movement, the toothed block  34  compresses downwardly the second spring  37 , and in return, the second spring  37  holds up the toothed block  34  upwardly so that the toothed block  34  are always in contact with the guide rod  2  and not detached. The fast sliding movement of the toothed block  34  toward the first pawl  1  drives the sliding member  31  so as to drive the second pawl  32  to move fast toward the first pawl  1 , so as to achieve the function of fast reducing the opening of the jaws. If the sliding member  31  is pushed along the opposite direction of arrow B, i.e., the direction closing to the grasp part  200 , the sliding movement of the toothed block  34  along the toothed surface of the unidirectional teeth  15  is obstructed due to the unidirectional orienting effect of the unidirectional teeth  15 , the toothed block  34  thus is locked (see  FIG. 7 ). 
     When the start position of the second pawl is closed to the grasp part  200 , as shown in  FIG. 6 , the fingers of the operator can also be pushed down on the pushbutton  33 , i.e., applying pressing force to the pushbutton  33 , then the pushbutton  33  presses down the toothed block  34  through the connecting rod  39  and simultaneously the toothed block  34  compresses the second spring  37 , so that the toothed block  34  is detached from the guide rod  2 , and then pushes the sliding member  31  toward the direction of arrow B, causing the toothed block  34  to slide fast along the guide rod  2  and closing to the first pawl  1 , so as to drive the sliding member  31  and the second pawl  32  to move fast toward the first pawl  1 , realizing the function of fast reducing the opening of the jaws. When the pressing effect to the pushbutton  33  is cancelled, the toothed block  34  slide upward and reset due to the effect of the elastic force of the second spring  37 , so that the toothed block  34  is engaged with the guide rod  2 , and at that time the second pawl  32  stops the movement along the guide rod  2 . 
     When the start position of the second pawl  32  is closed to the first pawl  1  (see  FIG. 8 ), the fingers of the operator can be pushed down on the pushbutton  33 , i.e., applying pressing force to the pushbutton  33 , then the pushbutton  33  presses down the toothed block  34  through the connecting rod  39  and simultaneously the toothed block  34  compresses the second spring  37 , so that the toothed block  34  is detached from the guide rod  2 , and then pushes the sliding member  31  toward the direction of arrow D, causing the toothed block  34  to slide fast along the guide rod away from the first pawl  1  and towards the grasp part  200 , so as to drive the sliding member  31  and the second pawl  32  to move fast away from the first pawl  1 , realizing the function of fast increasing the opening of the jaws. When the pressing effect to the pushbutton  33  is cancelled, the toothed block  34  slide upward and reset due to the effect of the elastic force of the second spring  37 , so that the toothed block  34  is engaged with the guide rod  2 , and at that time the second pawl  32  stops the movement along the guide rod  2  (see  FIG. 9 ).  FIG. 10  provides a perspective view of the wrench in a preferred embodiment of the invention when clamping a workpiece  300 .  FIG. 11  is a partial enlarged view of  FIG. 10 , showing the angle between the sloping surface  314  of the sliding member  31  and the length direction of the guide rod  2  is a first angle α, the angle between the sloping surface  314  and the toothed surface  152  of the unidirectional teeth  15  being a second angle β, the toothed surface  152  being the surface obstructing the sliding movement of the toothed block  34  along the unidirectional teeth  15 . The angle between the sloping surface  314  and the connecting rod  39  is the third angle γ. The side  340  of the toothed block  34  sticks tightly to the sloping surface  314 . 
     As shown in  FIG. 11 , when the wrench in the embodiment is clamping the workpiece  300 , i.e. the wrench being under a stressed condition, the sliding member  31  applies an upward force perpendicular to the sloping surface  314  to the toothed block  34  through the sloping surface  314 . The force is divided to be a upward branch force perpendicular to the guide rod  2  and a branch force along the guide rod to the right (i.e. the direction away from the first pawl  1 ), in which the upward branch force perpendicular to the guide rod  2  enables the toothed block  34  to be engaged with the guide rod  2 , and the branch force along the guide rod  2  to the right enables the toothed block  34  has a tendency of sliding to the right along the guide rod  2 . But due to the obstruction effect of the toothed surface  152  of the unidirectional teeth  15 , the sliding movement of the toothed block  34  along the guide rod to the right is obstructed, and, therefore, the toothed block  34  is locked on the guide rod  2 . In order for the toothed block  34  to be better engaged with the guide rod  2 , the angle α is supposed to be decided depending on the friction coefficient between the sloping surface  314  and the toothed block  34 , so as to ensure the toothed block  34  to be self-locked and maintained in locking position when being subject to force. The angle α is less than 90° and the lesser the better, which is because the lesser the a is, the larger the upward branch force perpendicular to the guide rod  2 , to which the toothed block  34  is subject, so that the larger the pressing force to which the unidirectional teeth  15  are subject, the better the toothed block  34  is engaged with the guide rod  2 . 
     In another aspect, in order to allow realizing reliable locking using friction self-locking between the toothed block  34  and the sloping surface  314 , and also realizing fast detachment of the toothed block  34  and the guide rod  2  by conquering the friction self-locking between the toothed block  34  and the sloping surface  314  when pushing down the pushbutton  33 . The angle between the connecting rod  39  and the guide rod  2  is a fourth angle, which is arranged to be less than 90° and the angle γ between the connecting rod  39  and the sloping surface  314  γ is less than 90°, such that when pressing down the pushbutton  33 , the pushbutton  33  applies a downward force to the toothed block  34  through the connecting rod  39 . The force can be divided to be a branch force perpendicular to the sloping surface  314  and a downward branch force parallel to the sloping surface  314 . The smaller the angle γ is, the larger downward branch force to which the toothed block  34  is subject, and the branch force perpendicular to the sloping surface  314  is smaller, and the upward friction to which the toothed block  34  is subject is smaller, and the toothed block  34  are more readily to conquer the friction to slide downward along the sloping surface  314  so as to achieve the detachment from the guide rod  2  and to be unlocked. 
     In order to ensure the wrench of the invention can still lock the toothed block  34  and not let it to be detached from the guide rod  2  when the wrench is under stressed condition and the unidirectional teeth  15  deform, the angle β between the sloping surface  314  and the toothed surface  152  of the unidirectional teeth  15  is arranged to be more than 0°, and the larger the angle β, the more reliable the locking of the toothed block is. But in the mean time it needs to be rotated by an angle to conquer the locking of the toothed block and the guide rod brought by the angle β, so as to detach the teeth on the toothed block  34  and the teeth on the guide rod  2 . Therefore a certain space  316  is required to be reserved between the sliding member  31  and the cavity in the cavity  312  to allow the toothed block  34  to rotate in the cavity  312  so as to detach the teeth of the two. Meanwhile, the reserve space  316  can also ensure the plurality of the teeth on the toothed block  34  to automatically find position and reliably come into contact with the guide rod  2  so as to increase the strength between the teeth. 
     In a preferred embodiment of the invention, α=45°, β=15°, γ=40°. 
     The foregoing described the preferred embodiments of the present invention. It should be understood that an ordinary one skilled in the art can make many modifications and variations according to the concept of the present invention without creative work. Therefore, any person skilled in the art can get any technical solution through logical analyses, deductions and limited experiments, which should fall in the protection scope defined by the claims.