Abstract:
A reversible ratchet wrench includes a handle from which a head extends. The head includes a compartment and a receiving hole in communication with the compartment. A drive member is rotatably mounted in the compartment and a pawl is slidably mounted in the compartment. A ring is mounted in the compartment and around an end of the drive member. A reversing plate is pivotably mounted to the end of the drive member and operatively connected to the ring to turn therewith. A switching member is pivotably mounted in the receiving hole of the head. The switching member is operatively connected to a tip piece of the ring to turn therewith. The switching member is operatively connected to the pawl to move the pawl for changing a driving rotating direction of the reversible ratchet wrench when the reversing plate is moved between two positions corresponding to two opposite driving rotating directions.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a ratchet wrench and, more particularly, to a reversible ratchet wrench. 
   2. Description of the Related Art 
   U.S. Pat. No. 6,431,031 discloses a reversible ratcheting tool comprising a handle, a head on an end of the handle, a drive member, a pawl, a ring, and a reversing plate. A transmission member in the form of a spring is mounted between the reversing plate and the pawl to covert manual pivotal movement of the reversing plate into pivotal movement of the pawl. The ratcheting tool of this design has a smaller head while providing higher torque-bearing capacity. In practice, the transmission member deforms to an excessive extent and, thus, results in unreliable ratcheting-direction switching operation between the drive member and the pawl. As a result, the switching arrangement is liable to get stuck or fails to provide reliable switching. Further, the transmission member fatigues easily due to excessive deformation and/or twist under the action of shear forces from the pawl, the ring, the head, and the reversing plate, leading to malfunction of the ratcheting tool. 
   SUMMARY OF THE INVENTION 
   A reversible ratchet wrench in accordance with the present invention comprises a handle, a head extending from the handle, a drive member, a pawl, a ring, a reversing plate, and a switching member. The head includes a compartment and a receiving hole in communication with the compartment. The drive member is rotatably mounted in the compartment of the head and includes a first end and a second end for driving a fastener. The drive member further includes a plurality of teeth in an outer circumference thereof. 
   The pawl is slidably mounted in the compartment of the head. The pawl includes a toothed side with a plurality of teeth for engaging with the teeth of the drive member. The ring is mounted in the compartment of the head and around the first end of the drive member. The ring includes a tip piece. The reversing plate is pivotably mounted to the first end of the drive member. The reversing plate is operatively connected to the ring to turn therewith. 
   The switching member is pivotably mounted in the receiving hole of the head. The switching member is operatively connected to the tip piece of the ring to turn therewith. The switching member is operatively connected to the pawl to move the pawl for changing a driving rotating direction of the reversible ratchet wrench when the reversing plate is moved between two positions corresponding to two opposite driving rotating directions. 
   The pawl further includes a recessed portion in another side opposite to the toothed side of the pawl. The switching member further includes a receptacle in which an elastic element is mounted. The switching member further includes a pressing member mounted in the receptacle and biased by the elastic element to press against the recessed portion of the pawl. 
   Preferably, the pressing member is a hollow pin with a blind hole. 
   Preferably, the switching member further includes an engaging section engaged with the tip piece of the ring. 
   Preferably, the engaging section of the switching member includes a protrusion, and the tip piece of the ring includes a slot in which the protrusion is slidingly received. 
   Preferably, the switching member further includes a recessed portion adjacent to the engaging section. 
   Preferably, the switching member further includes two grooves respectively in two lateral sides thereof. 
   Preferably, the reversing plate includes a hole allowing the reversing plate to be mounted around the first end of the drive member that extends beyond the compartment of the head, and the reversing plate further includes a thumb piece for manual operation. 
   Preferably, the ring further includes a notch, and the reversing plate further includes a positioning piece extending into the notch of the ring to allow joint rotation of the reversing plate and the ring. 
   Preferably, the compartment of the head includes a first compartment section in which the drive member is received and a second compartment section in which the pawl is received. 
   Preferably, the thumb piece of the reversing plate further including an arcuate groove, and the head further includes a pin hole. A pin has a first end fixed in the pin hole of the head and a second end received in the arcuate groove of the reversing plate. 
   Preferably, the thumb piece further includes a receiving space in communication with the arcuate groove and defined by an end wall. A retaining means is mounted in the receiving space of the thumb piece for retaining the reversing plate in one of the positions. 
   Preferably, the retaining means includes a slide piece and an elastic element for biasing the slide piece to press against the pin. 
   Preferably, the slide piece is substantially U-shaped and has two limbs between which the elastic element of the retaining means is received. The elastic element of the retaining means has a first end abutting against the end wall of the thumb piece and a second end abutting against an intermediate portion of the U-shaped slide piece, thereby pressing the slide piece against the pin. 
   Other objectives, advantages, and features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a portion of a reversible ratchet wrench in accordance with the present invention. 
       FIG. 2  is an exploded perspective view of the reversible ratchet wrench in accordance with the present invention. 
       FIG. 3  is a sectional view of the reversible ratchet wrench in accordance with the present invention. 
       FIG. 4  is a sectional view taken along plane  4 - 4  in  FIG. 3 , wherein the wrench is in a state allowing counterclockwise driving rotation and clockwise free rotation. 
       FIG. 5  is a sectional view taken along plane  5 - 5  in  FIG. 3 , wherein the wrench is in a state allowing counterclockwise driving rotation and clockwise free rotation. 
       FIG. 6  is a sectional view taken along plane  6 - 6  in  FIG. 3 , wherein the wrench is in a state allowing counterclockwise driving rotation and clockwise free rotation. 
       FIG. 7  is a sectional view similar to  FIG. 4 , wherein the wrench is in a state allowing clockwise driving rotation and counterclockwise free rotation. 
       FIG. 8  is a sectional view similar to  FIG. 5 , wherein the wrench is in a state allowing clockwise driving rotation and counterclockwise free rotation. 
       FIG. 9  is a sectional view similar to  FIG. 6 , wherein the wrench is in a state allowing clockwise driving rotation and counterclockwise free rotation. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIGS. 1 through 3 , a reversible ratchet wrench  10  in accordance with the present invention comprises a handle  11  and a head  12  extending from an end of the handle  11 . In this example, the head  12  is substantially circular and has a small volume. The head  12  includes a compartment  13  consisting of a larger, first compartment section  131  and a smaller, second compartment section  132 . A top face (not labeled) of the head  12  includes an opening  14  consisting of a substantially circular opening section  141  that is concentric with the first compartment section  131  and a non-circular (substantially rectangular in this example) opening section  142 . The top face of the head  12  further includes a pin hole  16  adjacent to the opening section  142 . Defined in a bottom face of the head  12  is a circular hole  15  that is concentric with the first compartment section  131  and has a diameter the same as that of the first compartment section  131 . Thus, the bottom face of the head  12  is formed with a stop  15  ( FIG. 3 ) that defines a portion of the second compartment section  132 . The bottom face of the head  12  further includes a receiving hole  17  that is adjacent to the circular hole  15  and that is in communication with the second compartment section  132 . The receiving hole  17  is partially delimited by the stop  151 . 
   Rotatably mounted in the larger, first compartment section  131  of the head  12  is a drive member  20  having a coupling section  21  in an intermediate portion thereof. The coupling section  21  is fittingly and rotatably received in the first compartment section  131  and includes a plurality of teeth  211  in an outer circumference thereof. Formed on an upper end (not labeled) above the coupling section  21  is an engaging portion  22  extending beyond the circular hole  141  of the head  12 . An annular engaging groove  221  is defined in an outer circumference of the engaging portion  22 . Formed on a lower end (not labeled) below the coupling section  21  is a drive column  23  including a hole  231  for receiving a ball  232 . The drive member  20  further includes a central through-hole  24  extending from the engaging portion  22  through the drive column  23  and having a shoulder portion  241 . The through-hole  24  of the drive member  20  is in communication with the hole  231  of the drive column  23 , which will be described in detail later. 
   A pushpin  25  is mounted in the through-hole  24  of the drive member  20  and includes an enlarged upper end  251  for manual pressing. A lower end of the pushpin  25  includes a stepped groove  252  for receiving a portion of the ball  232  when the pushpin  25  is pushed, thereby allowing disengagement of the drive column  23  from a socket (not shown). An elastic member  253  is mounted around the pushpin  25  and attached between the shoulder portion  241  of the through-hole  24  and the enlarged end  251  of the pushpin  25 . The elastic member  253  biases the pushpin  25  upward for moving the ball  232  outward to an engaging position for engaging with a socket, which is conventional and therefore not further described. The ball  232  is engaged with the stepped groove  252  to prevent disengagement of the pushpin  25 . 
   A pawl  30  is mounted in the second compartment section  132  of the head  12  and includes a toothed side facing the teeth  211  of the drive member  20 . The toothed side of the pawl  30  includes an arcuate surface  31  having a plurality of teeth  311  (preferably more than ten teeth) for engaging with the teeth  211  of the drive member  20 , thereby providing reliable mesh therebetween. Thus, the pawl/drive member arrangement of the reversible ratchet wrench may bear higher torque. The pawl  30  includes a recessed portion  32  in another side facing away from the arcuate surface  31 . 
   Still referring to  FIGS. 1 through 3 , a ring  40  is pivotally mounted around the engaging portion  22  of the drive member  20 . A tip piece  41  projects outward from the ring  40  and includes a slot  411 . A notch  42  is defined in an inner periphery of the ring  40  and aligned with the tip piece  41 . 
   A reversing plate  50  includes a hole  51  so as to be mounted around the engaging portion  22  of the drive member  20 . Hence, the reversing plate  50  and the drive member  20  have a common rotating axis. The reversing plate  50  further includes a thumb piece  52 . The enlarged head  251  of the pushpin  25  extends through the circular opening section  141  of the head  12  and beyond the hole  51  of the reversing plate  50  for manual operation. A positioning piece  511  projects from the reversing plate  50  in a position adjacent to the thumb piece  52 . A C-clip  53  is mounted around a portion of the engaging groove  221  of the engaging portion  22  of the drive member  20 , thereby retaining the engaging portion  22  of the drive member  20  to the top face of the head  12 . In addition, the positioning piece  511  is extended into the notch  42  of the ring  40  to allow joint turning of the reversing plate  50  and the ring  40 . An arcuate groove  521  is defined in an underside of the thumb piece  52 . The thumb piece  52  further includes a receiving space  522  in communication with the arcuate groove  521  and defined by an end wall  523 . It is noted that the reversing plate  50  is securely yet pivotally engaged with the engaging portion  22  of the drive member  20 . 
   A retaining means  60  is mounted in the receiving space  522  of the thumb piece  52  and includes a substantially U-shape slide piece  61  and an elastic member  62 . The slide piece  61  includes a tapered push-face  611  consisting of two faces (not labeled) separated by a tip (not labeled, see  FIG. 2 ). The elastic member  62  is received between two limbs (not labeled) of the U-shape slide piece  61 . It is noted that an end of the elastic element  62  abuts against the end wall  523  of the thumb piece  52  and that the other end of the elastic element  62  abuts against an intermediate section (not labeled) between the limbs of the U-shaped slide piece  61 . In practice, the end face defining the receiving space  522  is formed by pressing to provide a structure preventing disengagement of the elastic member  62  from the receiving space  522  yet allowing movement of the slide piece  61  relative to the elastic member  62 . 
   A pin  54  has an upper end mounted in the arcuate groove  521  of the thumb piece  52  and a lower end fixed in the hole  16  of the head  12 . The arcuate groove  521  is movable relative to the pin  54  during pivotal movement of the reversing plate  50 . The push-face  611  of the slide piece  61  presses against the pin  54 . 
   A switching member  70  is pivotably mounted in the receiving hole  17  of the head  12 . The switching member  70  can be actuated by the ring  40  to control the position of the pawl  30 . The switching member  70  includes a receptacle  701  in a front side facing the pawl  30 . A pressing member  71  and an elastic element  72  are mounted in the receptacle  701 , with the elastic element  72  biasing the pressing member  71  to press against the recessed portion  32  of the pawl  30 . Hence, when the switching member  70  pivots in the receiving hole  17 , the pressing member  71  moves and, thus, changes the position of the pawl  30 . In this example, the pressing member  71  is a hollow pin with a blind hole for receiving a portion of the elastic element  72 . 
   The switching member  70  further includes an engaging section  702  extending in a radial direction of the circular opening  141  of the head  12  to the tip piece  41  of the ring  40 . The engaging section  702  includes a protrusion  703  engaged in the slot  411  of the tip piece  41  such that the switching member  70  is pivoted when the ring  40  is turned. By such an arrangement, when the reversing plate  50  is pivoted, the switching member  70  is turned via transmission by the ring  40  such that the pawl  30  is moved by the pressing member  71 . 
   The switching member  70  further includes a recessed portion  704  in the front side thereof in a position adjacent to the engaging section  702 . The recessed portion  703  allows easy mounting of the switching member  70  into the receiving hole  17 . More specifically, in assembly, since the receiving hole  17  is partially delimited by the stop  151 , the switching member  70  is tilted to allow the engaging section  702  to enter the receiving hole  17 , with the recessed portion  704  providing an evasive effect for the stop  151 , and the switching member  17  is then completely inserted into the receiving hole  17 . The switching member  70  further includes a groove  705  in each of two lateral sides thereof. The grooves  705  provide an evasive effect while moving the pawl  30 , avoiding the switching member  70  and the pawl  30  from getting stuck (see  FIG. 6 ). 
   When the wrench is in a position shown in  FIGS. 4 through 6 , the wrench allows counterclockwise driving rotation for driving a fastener and clockwise free rotation in which the fastener is not driven. When the wrench in a position shown in  FIGS. 7 through 9 , the wrench allows clockwise driving rotation for driving a fastener and counterclockwise free rotation in which the fastener is not driven. 
   When the reversing plate  50  is moved from the position shown in  FIG. 4  to a position shown in  FIG. 7 , the pin  54  is moved to from an end to the other end of the arcuate groove  521 . The slide piece  61  of the retaining means  60  is biased by the elastic element  62  against the pin  54  to reliably position the reversing plate  50 . The positioning piece  511  of the reversing plate  50  is extended through the notch  42  of the ring  40 , allowing joint turning of the reversing plate  50  and the ring  40 , as mentioned above. The protrusion  703  of the switching member  70  slides in the slot  411  of the ring  40  during pivotal movement of the ring  40  whereas the engaging section  702  is driven by the tip piece  41  to turn the switching member  70  counterclockwise in the receiving hole  17 . After pivoting, the pressing member  71  is biased by the elastic element  72  to press against the recessed portion  32  of the pawl  30 , which, in turn, urges the teeth  31  of the pawl  30  to mesh with the teeth  211  of the drive member  20 . It is noted that the grooves  705  of the switching member  705  provide an evasive effect, as mentioned above. Since the switching member  70  is rigid, a reliable, secure reversing effect is obtained without the risk of deformation or malfunction of the switching member  70  that pivots in the receiving hole  17 . Namely, the malfunction risk is reduced whereas the qualified product rate is increased while providing a wrench with excellent quality and prolonged life. 
   Although a specific embodiment has been illustrated and described, numerous modifications and variations are still possible. The scope of the invention is limited by the accompanying claims.