Patent Publication Number: US-2013228049-A1

Title: Reversible ratchet wrench

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a reversible ratchet wrench, and more particularly to a reversible ratchet wrench with a reduced stewing angle required by idle rotation. 
     2. Description of the Prior Art 
     In the technical field of hand tools, a ratchet wrench brings great convenience to users. The ratchet wrench provides a function so that in a space where operation is subject to limits, idle rotation back-pulling can be performed without separating the wrench from a fastener thereby improving operational efficiency. The ratchet wrench has developed into a fairly mature technology, allowing developments such as a reversible ratchet wench. In the reversible ratchet wrench, generally a switching member on the wrench is used to adjust an idle rotation back-pulling direction of the wrench, so that the wrench can alternate between two rotation directions without being flipped over, thereby offering more convenience to the user. A large number of patents have been published in the technical field of the ratchet wrench, which is a crowded art. For example, Taiwan Patent No 1350231 discloses a reversible ratchet impact wrench capable of avoiding tooth-breaking, and U.S. Pat. No. 6,918,323B2 provides a reversible ratchet wrench with improved pawls. 
     However, the reversible ratchet wrench in the prior art still has defects. For example, in an extremely limited operating space, the idle rotation back-pulling angle of the wrench is also extremely limited, such that a relatively small number of ratchet teeth are capable of being skipped by the detent of the wrench during idle rotation back-pulling, thus requiring the user to perform a larger number of rotations before the work is done, thereby limiting working efficiency. In addition, when the user operates a conventional ratchet wrench with a transient large force, the ratchet tooth and the detent may fail to cooperate at the same time to rotate and maintain the relative positional relationship, such that the ratchet tooth and the detent undergo transient relative sliding and loosening, which can damage the wrench or create work hazards. Therefore, it is necessary to provide a ratchet wrench which can improve the working efficiency in an extremely limited operating space and meanwhile ensure that the relative positional relationship between the ratchet tooth aid the detent is kept unchanged in any state of use. 
     SUMMARY OF THE INVENTION 
     One objective of the present invention is to provide a ratchet wrench capable of improving the working efficiency in a limited operating space. 
     Another objective of the present invention is to provide a ratchet wrench in which the relative positional relationship between the ratchet tooth and the detent is kept unchanged in any state of use. 
     According to an aspect of the present invention, the present invention provides a ratchet wrench, which includes: a head portion, the head portion defining a first compartment and a space below the first compartment, wherein the space is in communication with the first compartment; a driving head, including an annular driving tooth portion accommodated in the first compartment; and a first detent and a second detent, each having a plurality of ratchet teeth to engage with the annular driving tooth portion, the detents being stacked to be accommodated in the space; wherein through a direction switching button of the wrench, the first detent and the second detent are capable of moving laterally between a first side and a second side of the space simultaneously; wherein when the first detent and the second detest are on the first side of the space, the wrench is capable of undergoing idle rotation back-pulling along a first direction; and when the first detent and the second detent are on the second side of the space, the wrench is capable of undergoing idle rotation back-pulling along a second direction; wherein the radial alignment diverges between the ratchet teeth or the first detent and the ratchet teeth of the second detent, so that only one of the first detent and the second detent is engaged with the annular driving tooth portion, and the other one is urged against the annular driving tooth portion; and wherein when the wrench undergoes the idle rotation back-pulling, the ratchet teeth of the first detent and the ratchet teeth of the second detent are engaged with the annular driving tooth portion alternately. 
     According to another aspect of the present invention, the internal space provided within the ratchet wrench provided by the present invention further includes a second, compartment accommodating the direction switching button. 
     According to a further aspect of the present invention, the direction switching button further includes a first lever and a second lever, one end of the levers being accommodated in a recess of the direction switching button through a first elastic member and a second elastic member respectively, and the other end of the levers propping up the first detent and the second detent, respectively. 
     According to a further aspect of the present invention, an inner wall of the second compartment has a blind hole, a third lever is inserted and accommodated in the blind hole through a third elastic member, and the third lever elastically props up a rear surface of the direction switching button. 
     The present invention is further illustrated with reference to the accompanying drawings. The accompanying drawings briefly show preferred embodiments according to the present invention. It should be understood that no aspect of the present invention is limited, to the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded view of parts of a reversible ratchet wrench according to the present invention; 
         FIG. 2  is a partially enlarged view of  FIG. 1 ; 
         FIG. 3   a  and  FIG. 3   b  are a three-dimensional structural view and a bottom view of a detent  40 , respectively; 
         FIG. 3   c  and  FIG. 3   d  are a three-dimensional structural view and a bottom view of a decent  42 , respectively; 
         FIG. 4   a  and  FIG. 4   b  are schematic structural views of mounted detents, a driving head assembly  20  and a direction switching button  30 ; 
         FIG. 5   a  and  FIG. 5   b  are schematic structural views of a detent engaged with an annular driving tooth portion of a driving head; and 
         FIG. 6   a  and  FIG. 6   b  are schematic structural views of a wrench with a direction switching button in a first position and a second position, respectively, according to the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows an exploded view of parts of a reversible ratchet wrench  1  according to the present invention. The ratchet wrench  1  has a handle  10  and a head portion  12  connected to one end of the handle  10 . For convenience of understanding the structure of the head portion  12 ,  FIG. 1  shows a partial sectional view of the head portion  12 . A first compartment  125  and a second compartment  127  through the head portion  12  are defined on a surface  121  of the head portion  12 . The first compartment  125  and the second compartment  127  communicate with each other through a middle portion  129  (as shown in  FIG. 5   a ), so that the second compartment  127  and the middle portion  129  together form a space below the first compartment  125 . The first compartment  125  the second compartment  127 , and the middle portion  129  form a recessed cavity capable of accommodating parts in a surface  123  (as shown in  FIG. 5   a ), opposite to the surface  121 , of the head portion  12 . 
     The first compartment  125  is used for accommodating a driving head assembly  20 . The driving head assembly  20  includes a press lever  22  and a driving head  24 . The driving bead has an annular driving tooth portion  242  and a driving end  244  protruding from the annular driving tooth portion  242 . The driving head  24  forms a through hole  246  along an axial direction. The through hole  246  accommodates an elastic member  224 , a steel ball  222 , and the press lever  22 , which are arranged from bottom to top sequentially. A piercing hole  248  in communication with the through hole  246  is formed along a radial direction on a surface of the driving end  244 , and is used for accommodating a steel ball  250 . Further, the piercing hole  248  is configured to ensure that at most only a portion of the steel ball  250  is exposed out of the surface where the piercing hole  248  is. Therefore, when the press lever  22  is in a non-pressed-down position, the elastic member  224  props up the steel ball  222  to position it in the through hole  246  at a level flush with the steel ball  250  in the piercing hole  248 , so that at the moment, the steel ball  222  urges the steel ball  250  against the piercing hole  248 , so as to partially expose the steel ball  250  at the surface opening of the driving end  244 , and meanwhile, no external force can press the steel ball  250  into the piercing hole  248 . When the press lever  22  is pressed down to reach a pressed-down position, the press lever  22  and the steel ball  222  compress the elastic member  224 , so that the steel ball  222  leaves its position within the through hole  246  and becomes flush with the piercing hole  248 . At this moment, the steel ball  250 , under the action of an external force, enters the piercing hole  248 , but does not completely fall into the through hole  246  due to being blocked by the press lever  22 , and sits only partially within the through hole  246 . Therefore, an operator can press the press lever  22  to insert the driving head assembly  20  into a conventional barrel, and then release the press lever  22  to enable the steel ball  250  to be caught in a corresponding recessed cavity in a conventional barrel structure, so as to secure or loosen a fastener. 
     Naturally, the driving end  244  of the driving head  24  does not have to be the type shown in  FIG. 1 , and may instead be in the form of any tool head suitable for securing/loosening conventional fasteners, for example, in the form of a hexagon socket sere driver or in the form of a Phillips screwdriver. Alternatively, instead of equipping the driving head  24  with a driving end protruding out of the head portion  12  and members such as the press lever  22  and the steel ball  222 , a driving hole can be formed inside the annular driving teeth  242  (that is, the through hole  246 ), and the driving hole may be in the form of any driving hole of a wrench suitable for securing/loosening conventional fasteners, such as a box wrench. 
       FIG. 2  presents a partially enlarged view of  FIG. 1  which shows that a direction switching button  30  includes a top switching lever  32 , a middle column  34 , and a bottom plate  36 . The direction switching button  30  is accommodated in the second compartment  127 , and the top switching lever  32 , the middle column  34 , and the bottom plate  36  may be integrally formed. By pulling the top switching lever  32 , the direction switching button  30  can be moved between a first position and a second position shown in  FIG. 6   a  and  FIG. 6   b , respectively, so as to define a first idle rotation direction and a second idle rotation direction of the wrench. A front side, facing the first compartment  125 , of the middle column  34  is recessed inwards relative to the bottom plate  36 , so that an inward recessed space  342  exists above a front side of the bottom plate  36 . The middle column  34  with the inward recessed front side further has a recess  344  (as shown in  FIG. 4   b ). After elastic members  382  are respectively inserted into receiving slots  386  of levers  384 , the vertically stacked levers  384  are inserted and accommodated in the recess  344 , so that in an uncompressed state, the elastic members  382  press against a bottom wall of the recess  344 , and the levers  384  protrude out of the recess  344 . A rear side of the middle column  34  defines a rear surface  346 , which may be a curved surface corresponding to the curve of a fall surface of the second compartment  127 . A blind hole  131  is formed on an inner side wall surface on one side, close to the handle  10 , of the second compartment  127 . After an elastic member  137  is inserted into a rear receiving slot  135  of a lever  133 , the lever  133  is inserted and accommodated in the blind hole  131 . Accordingly, in an uncompressed state, the elastic member  137  presses against a bottom wall of the blind hole  131 , and the lever  133  protrudes out of the blind hole  131 . When the direction switching button  30  is being mounted in the second compartment  127 , the lever  133  needs to be pressed down, so that the rear surface  346  of the middle column  34  of the direction switching button  30  is urged against the lever  133 . After the mounting, the lever  133  presses continuously against the rear surface  346  through the elasticity of the elastic member  137 , and applies an urging force. 
       FIG. 3   a  and  FIG. 3   b  present a three-dimensional structural view and a bottom view of a detent  40 , respectively. As shown in the drawings, the detent  40  has a plurality of ratchet teeth  412 , which substantially extend towards two lateral sides to form an arc shape capable of defining a radius. The ratchet teeth  412  may continuously cover one complete side of the detent  40 , or may only be disposed along a portion of the length of the side. A recessed seat  414  is formed on another side, opposite to the plurality of ratchet teeth  412 , of the detent  40 . The center of the recessed seat  414  protrudes slightly to form a ridge portion  402 , and two lateral portions of the recessed seat  414  may be bilaterally symmetrical with respect to the ridge portion  402 , which functions as an axis. The recessed seat  414  extends from the ridge portion  402  to the two lateral sides to sequentially define sliding surfaces  404 , propping surfaces  406 , and corner portions  410 . Two outer side edges of the detent  40  form an urging surface  408 , and a bottom of the detent  40  has a cut portion  416 . 
       FIG. 3   c  and  FIG. 3   d  present a three-dimensional structural view and a bottom view of a detent  42 , respectively. As shown in the drawings, the detent  42  has a plurality of ratchet teeth  432 , which substantially extend towards two lateral sides to form an arc shape capable of defining a radius. The ratchet teeth  432  may continuously cover one complete side of the detent  42 , or may only be disposed along a portion of the length of the side. A recessed seat  434  is formed on another side, opposite to the plurality of ratchet teeth  432 , of the detent  42 . The center of the recessed seat  434  protrudes slightly to form a ridge portion  422 , and two lateral portions of the recessed seat  434  may be bilaterally symmetrical with respect to the ridge portion  422 , which functions as an axis. The recessed seat  434  extends from the ridge portion  422  to the two lateral sides to sequentially define sliding surfaces  424 , propping surfaces  426 , and corner portions  430 . Two outer side edges of the detent  42  form an urging surface  428 . 
     The profile of the recessed seat  414  of the detent  40  may be substantially the same as the profile of the recessed sea  434  of the detent  42 . However, the ratchet teeth  412  of the detent  40  are aligned radially divergently from the ratchet teeth  432  of the detent  42 . For example, the ratchet teeth  412  of the detent  40  have a tooth peak at a central axis a passing through the ridge portion  402 , but the ratchet teeth  432  of the detent  42  have a tooth valley at a central axis b passing through the ridge portion  422 , so that the arrangement of the ratchet teeth of the two detents has a difference of a half tooth pitch. Further, the lengths which the ratchet teeth of the detent  40  and the detent  42  extend may be the same or different. In other words, the number of ratchet teeth of the two detents are not necessarily the same; and in the detent  40  and the detent  42 , the lengths of the extension from the central axes along the arc shapes at the two lateral sides may be different. 
     According to  FIG. 1 , the detent  42  is stacked on the detent  40 , and is mounted between the annular driving tooth portion  242  of the driving head  24  of the driving head assembly  20  in the first compartment  125  and the middle column  34  of the direction switching button  30  in the second compartment  127 . In other words, after being mounted, the detents  40  and  42  are located in the middle portion  129  through which the first compartment  125  and the second compartment  127  communicate.  FIG. 4   a  and  FIG. 4   b  are schematic structural views of mounted detents, the driving head assembly  20  and the direction switching button  30 . As shown to the drawings, after the detents  40  and  42  are stacked and mounted at the head portion  12  of the wrench  1 , the recessed seats  414  and  434  respectively press the levers  384  of the direction switching button  30 , and compress the elastic members  382 . Consequently, the elastic members  382  apply an elastic force to the levers  384  so as to make the levers  384  press the recessed seats  414  and  434  towards the first compartment  125 , so that the detents  40  and  42  are urged against the annular driving tooth portion  242 . At that moment, due to the difference in alignment between the ratchet teeth  412  and the ratchet teeth  432 , one set of teeth of the ratchet teeth  412  and the ratchet teeth  432  of the detents  40  and  42  is engaged with the annular driving tooth portion  242 , and the other set abuts but is not engaged with the annular driving tooth portion  242 . In the state shown in  FIG. 4   a  and  FIG. 4   b , the ratchet teeth  412  of the detent  40  are engaged with the annular driving tooth portion  242 , and the ratchet teeth  432  of the detent  42  abut and are not engaged with the annular driving tooth portion  242 . Naturally, the ratchet teeth  432  of the detent  42  are alternatively engaged with the annular driving tooth portion  242 , while the ratchet teeth  412  of the detent  40  abut the annular driving tooth portion  242  (as shown in  FIG. 5   b ). In other words, for the wrench of the present invention, at the same time point, either the ratchet teeth of the detent  40  or the ratchet teeth of the detent  42  are engaged with the annular driving tooth portion  242 . It should be noted that the out portion  416  of the detent  40  corresponds to the bottom plate  36  of the direction switching button  30  after the detent  40  is mounted, so as to prevent interference between the bottom plate  36  and the detent  40  when the direction switching button  30  moves between the first position and the second position. 
     Once the detents  40  and  42  are mounted to the head portion  12  of the wrench, the main structure of the wrench  1  is completed. At that moment, a closure plate  50  having an opening  501  is used to cover and close the recessed cavity formed in the surface  123 , opposite to the surface  121 , of the head portion  12  by the first compartment  125 , the second compartment  127 , and the middle portion  129  of the head portion  12  of the wrench  1 , and the driving end  244  of the driving head assembly  20  passes through the opening  501 , and is exposed to the outside. A circlip  52  is further mounted on the closure plate  50 , and is urged against a side wall top edge of the first compartment  125 , so as to fix the closure plate  50 . In order to reduce friction between the driving head  24  and the head portion  12  as well as the closure plate  50 , O-rings  503  and  505  may be placed on an upper surface and a lower surface of the driving head  24 , respectively. 
     Due to the (half-tooth) divergence in (radial) alignment between the detents  40  and  42 , the ratchet wrench  1  provided by the present invention has the effect of reducing the slewing angle.  FIG. 5   a  and  FIG. 5   b  are schematic structural views of the detent  40  and the detent  42  respectively engaged with the annular driving tooth portion  242  of the driving head  24 . In  FIG. 5   a , the direction switching button  30  is in the first position, the elastic member  382  applies an elastic force to push the lever  384 , so as to make the lever  384  prop up the propping surface  406 , on the side of the recessed seat  414 , of the detent  40 , and to make the urging surface  408 , on the same side, of the decent  40  be urged against a side wall  1291  of the middle portion  129 . At that moment, the ratchet teeth  412  of the detent  40  are engage with the annular driving tooth portion  242 . Further, the other elastic member  382  applies an elastic force to the other lever  384 , so as to make the lever  384  prop up the propping surface  426 , on the side of the recessed seat  434 , of the detent  42 , and to make the urging surface  428 , on the same side, of the detent  42  be also urged against the side wall  1291  of the middle portion  129 . However, due to the (half-tooth) divergence in (radial) alignment between the ratchet teeth of the detent  42  and the ratchet teeth of the detent  40 , the ratchet teeth  432  of the detent  42  are not engaged with the annular driving tooth portion  242 , and the detent  42  and the detent  40  are slightly staggered. 
     When the ratchet wrench  1  shown in  FIG. 5   a  rotates clockwise, since the urging surface  408  of the detent  40  is urged against the side wall  1291 , the ratchet teeth  412  are continuously engaged with the annular driving tooth portion  242 , so as to drive the driving end  244  to rotate the fastener. Conversely, when the ratchet wrench  1  rotates counterclockwise, the annular driving tooth portion  242  presses the detents  40  and  42  towards the levers  384 , so that the detents  40  and  42  reversely urge against the levers  384  and the elastic members  382 , thereby performing idle rotation back-pulling on the ratchet wrench  1 . 
     Similarly, in  FIG. 5   b , the direction switching button  30  is also in the first position, and the elastic member  382  applies an elastic force to push the lever  384 , so as to make the lever  384  prop up the propping surface  426 , on the side of the recessed seat  434 , of the detent  42 , and to make the urging surface  428 , on the same side, of the detent  42  be urged against the side wall  1291  of the middle portion  129 . At that moment, the ratchet teeth  432  of the detent  42  are engaged with the annular driving tooth portion  242 . Further, the other elastic member  382  applies an elastic force to the other lever  384 , so as to make the lever  384  prop the propping surface  406 , on the side of the recessed seat  414 , of the detent  40 , and to make the urging surface  408 , on the same side, of the detent  40  be also urged against the side wall  1291  of the middle portion  129 . However, due to the (half-tooth) divergence in (radial) alignment between the ratchet teeth of the detent  40  and the ratchet teeth of the detent  42 , the ratchet teeth  412  of the detent  40  are not engaged with the annular driving tooth portion  242 , and the detent  40  and the detent  42  are slightly staggered. 
     When the ratchet wrench  1  shown in  FIG. 5   b  rotates clockwise, the urging surface  428  of the detent  42  is urged against the side wall  1291 , so that the ratchet teeth  432  are continuously engaged with the annular driving tooth, portion  242 , so as to drive the fastener to rotate. Conversely, when the ratchet wrench  1  rotates counterclockwise, the annular driving tooth portion  242  presses the detents  40  and  42  towards the levers  384 , so that the detents  40  and  42  reversely urge against the levers  384  and the elastic members  382 , thereby performing idle rotation back-pulling on the ratchet wrench  1 . 
     It should be noted that in the present invention, the divergence in (radial) alignment between the ratchet teeth of the detent  40  and the ratchet teeth of the detent  42  may be a half tooth pitch. In that case, when the ratchet wrench in  FIG. 5   a  undergoes idle rotation back-pulling for a half tooth pitch, the ratchet teeth  412  of the detent  40  depart from and are no longer engaged with the annular driving tooth portion  242 . At that moment, due to the (half-tooth) divergence in (radial) alignment between the ratchet teeth of the detent  40  and the ratchet teeth of the ratchet teeth  42 , the ratchet teeth  432  of the detent  42  are engaged with the annular driving tooth portion  242 , resulting in the state shown in  FIG. 5   b . At that moment the fastener can be rotated continuously by the detent  42 . In other words, during the idle rotation back-pulling of the wrench, the detent  40  and the detent  42  may engage alternately with the annular driving tooth portion  242  for each half tooth pitch. The advantage of this structure compared with a reversible ratchet wrench only having a single detent lies in effectively reducing the idle rotation back-pulling angle. Specifically, during idle rotation back-pulling of a ratchet wrench having only a single detent, the ratchet wrench needs to be pulled by an angle equivalent to a complete tooth pitch before the detent skips to be engaged with the next tooth of the annular driving tooth portion. However, for the ratchet wrench of the present invention, the ratchet wrench only needs to be back-pulled by an angle equivalent to a half tooth pitch before the detent skips to be engaged with a next tooth of the annular driving tooth portion. For example, when the annular driving tooth portion has a total of 60 teeth, the ratchet wrench having a single detent has to be back-pulled by 6° before a tooth of the annular driving tooth portion can be skipped, but the wrench of the present invention only needs to be back-pulled by 3° before a tooth of the annular driving tooth portion can be skipped. Therefore, the effect of the structure of the present invention is equivalent to the effect of the structure of a wrench having a single detent in which the annular driving tooth portion has 120 teeth. The angle required by the wrench of the present invention for back-pulling and engagement of the annular driving tooth portion is merely half that required by the structure having a single detent, thereby effectively improving operational efficiency. Further, the structure of the present invention reduces the required distance of idle rotation back-pulling, making it particularly suitably to applications involving limited operating space. 
       FIG. 6   a  and  FIG. 6   b  present schematic structural views showing the direction switching button  30  in the first position and the second position, respectively, according to the present invention. In  FIG. 6   a , the direction switching button  30  in the first position pushes the detents  40  and  42  to a first side of a space formed by the middle portion  129  and the second compartment  127 , and the ratchet wrench  1  may rotate clockwise to secure the fastener through the detent  40  or  42  that transmits torque, and may rotate counterclockwise to undergo idle rotation back-pulling. In order to change the operational direction of the wrench  1 , it is only necessary to pull a direction switching lever  38  to the second position shown in  FIG. 6   b , so that the detents  40  and  42  in the head portion  12  of the ratchet wrench  1  move laterally to the position shown in  FIG. 6   b  (that is, a second side opposite to the first side of the space formed by the middle portion  129  and the second compartment  127 ), and the wrench  1  may rotate counterclockwise to secure the fastener through the detent  40  or  42  that transmits torque, and may rotate clockwise to undergo idle rotation back-pulling. Specifically, when the direction switching button  30  is in the first position, the levers  384  prop up the propping surface  406  of the detent  40  and the propping surface  426  of the detent  42  respectively, so that the urging surface  408  on one side of the detent  40  and the urging surface  428  on the same side of the detent  42  prop the inner wall  1291  of the middle portion  129  of the head portion  12 . At that moment, the corner portions  410  and  430 , opposite to the inner wall  1291  of the detent  40  and the detent  42  are in the inward recessed space  342  of the middle column  34 . When the direction switching button  30  is pulled from the first position to the second position, the levers  384  respectively slide from the propping surfaces  406  and  426  on one side of the detent  40  and the detent  42 , along wall edges of the recessed seats  414  and  434 , through the sliding surfaces  404  and  424 , the ridge portions  402  and  422 , then the sliding surfaces  404  and  424  on the opposite side of the detent  40  and the detent  42 , and to the propping surfaces  406  and  426  on the opposite side (as shown in  FIG. 6   b ). While the levers  384  slide along the recessed seats of the detents, the detents  40  and  42  simultaneously slide laterally from the position shown in  FIG. 6   a , in the middle portion  129 , along the annular driving tooth portion  242 , and to the position shown in  FIG. 6   b , so that finally the urging surfaces  408  and  428  on the other side of the detents  40  and  42  prop up an inner wail  1292 , opposite to the inner wall  1291 , of the middle portion  129 , thereby completing a direction switching action of the ratchet wrench  1 . In  FIG. 6   b , the corner portions  410  and  430 , opposite to the inner wall  1292 , of the detents  40  and  42  are in the inward recessed space  342  of the middle column  34 . Since the ridge portions  402  and  422  of the detents  40  and  42  protrude slightly at the center of the recessed seats  414  and  434 , respectively, when the levers  384  slide to the ridge portions  402  and  422 , the pulling of the direction switching button  30  encounters slightly greater resistance, thereby providing a clear physical sensation to signal a change of direction. Further, while the direction switching button  30  is moving, the moving ratchet teeth  412  of the detent  40  and ratchet teeth  432  of the detent  42  continue being engaged with or propping the annular driving tooth portion of the driving head  24 , so that slipping does not occur. 
     It should be noted that through the elasticity of the elastic member  137  the lever  133  on an inner side wall surface on the side, close to the handle  10 , of the second compartment  127  of the head portion  12  of the wrench  1  props up the rear surface  346  of the middle column  34  in the direction switching button  30  continuously, and applies an urging force thereto, thereby ensuring that the levers  384  of the direction switching button  30  make the detents  40  and  42  engage with or urge against the annular driving tooth portion  242  of the driving head  24 , and slipping does not occur either in a still state or during operation. Therefore, the structure of the present invention can prevent slipping occurring to the engagement or propping between the ratchet and the annular driving tooth portion which occurs in the conventional ratchet wrench after a long period of use, during direction switching, or when operated with a transient large force, so as to eliminate the possibility of damaging the ratchet wrench, thereby improving operational safety. 
     Although the specific embodiments of the present invention are describe above, various modification and improvements can be made by persons skilled in the art without departing from the spirit of the present invention, provided such modifications and improvements fall within the scope defined by the present invention.