Abstract:
A reciprocal switching structure of a ratchet wrench is provided and includes a case, a gear assembly, two gear racks, a reciprocal switching mechanism, and a transmission unit. The case has a first end and a second end, wherein the second end is adjacent to a gripping part of the ratchet wrench and is opposite to the first end. The gear assembly is pivotally disposed in the case. The two gear racks engage or disengage from the gear assembly reciprocally. The reciprocal switching mechanism is disposed in the case and includes two push rods and at least one reciprocal switching member. The transmission unit pivotally is disposed in the case, and is pivotally connected between the two gear racks for driving the two gear racks to be displaced.

Description:
BACKGROUND 
     1. Field of Invention 
     This invention relates to a light and portable power tool. More particularly, this invention relates to a ratchet wrench power tool. 
     2. Description of Related Art 
     Hand-held tools, which are operated using gas power, electric power or another type of power, are necessarily light and portable. As to different types of operation, linear displacement and rotational operation are two common ways in which hand-held tools operate. A hand-held power tool utilizing a rotational type of operation is often used for fastening workpieces such as screws and nuts, and is also frequently used for drilling. However, regardless of the purpose to which the power tool is applied, the power tool has must be able to switch between forward and reverse rotation. 
     Conventionally, the switching means for executing the function of switching between forward and reverse rotation is at a distance from the operator&#39;s hand. U.S. Pat. No. 5,535,646 and U.S. Pat. No. 6,640,669 involve configurations that attempt to shift the switching means for executing the function of switching between forward and reverse rotation toward the operator&#39;s hand. With respect to U.S. Pat. No. 5,535,646, as a result of the inner structural positioning used therein, the switching means is not shifted to a sufficient enough degree toward the operator&#39;s hand. As to U.S. Pat. No. 6,640,669, a more complex and a larger tool results due to the configuration used therein. 
     SUMMARY 
     An aspect of the present disclosure is to provide a reciprocal switching structure of a ratchet wrench which uses a push rod adjacent to a gripping part of the ratchet wrench to push one of two gear racks away from a gear assembly such that the gear assembly is engaged with only one gear rack at a time, thereby controlling the rotation direction of the gear assembly. 
     According to one embodiment of the present disclosure, a reciprocal switching structure of a ratchet wrench includes a case, a gear assembly, two gear racks, a reciprocal switching mechanism and a transmission mechanism. The case has a first end and a second end, and the second end is adjacent to a gripping part of the ratchet wrench and is opposite to the first end. The gear assembly is pivotally disposed in the case. The two gear racks are engaged or disengaged from the gear assembly reciprocally. The reciprocal switching mechanism is disposed in the case, and comprises two push rods and at least one reciprocal switching member. The two push rods are disposed in the case, wherein the two push rods are alternately displaced along a direction extending from the first end to the second end, in order to displace one of the two gear racks to be engaged or disengaged from the gear assembly. The at least one reciprocal switching member is connected between the two push rods for driving one push rod to push against one gear rack for disengaging the gear assembly and the gear rack, thereby driving the other gear rack to be engaged with the gear assembly. The transmission unit pivotally is disposed in the case, wherein the transmission unit is pivotally connected between the two gear racks for driving the two gear racks to be displaced. 
     According to another embodiment of the present disclosure, a power tool includes a case, a ratchet, a first gear rack, a second gear rack, an elastic member, a reciprocal switching mechanism and a transmission unit. The ratchet is pivotally disposed in the case. The first gear rack is disposed movably in the case, wherein the first gear is engaged or disengaged from the ratchet. The second gear rack is disposed movably in the case, wherein the second gear rack is disposed opposing the first gear rack and is engaged or disengaged from the ratchet in an alternating manner with the first gear rack. The elastic member is connected between the first gear rack and the second gear rack, and provides a biasing force to the first gear rack and the second gear rack in a direction toward the ratchet. The reciprocal switching mechanism comprises a first push rod and a second push rod. The first push rod is linearly and displaceably disposed in the case for pushing the first gear rack away from the ratchet, wherein the first push rod comprises a first sliding block locating at an end thereof, and the first sliding block is exposed outside of the case to allow for user manipulation of the first sliding block. The second push rod is linearly and displaceably disposed in the case for pushing the second gear rack away from the ratchet, wherein the second push rod comprises a second sliding block located at an end thereof, and the second sliding block is exposed outside of the case to allow for user manipulation of the second push rod. The transmission unit is pivotally disposed in the case, wherein the transmission unit is connected between the first gear rack and the second gear rack for driving the first gear rack and the second gear rack to be displaced reciprocally. 
     According to another embodiment of the present disclosure, a power tool includes a case, a ratchet, a first gear rack, a second gear rack, two elastic members, a reciprocal switching mechanism and a transmission unit. The ratchet is pivotally disposed in the case. The first gear rack is disposed movably in the case, wherein the first gear is engaged or disengaged from the ratchet. The second gear rack is disposed movably in the case, wherein the second gear rack is disposed opposing the first gear rack and is engaged or disengaged from the ratchet in an alternating manner with the first gear rack. One of the two elastic members is connected between the first gear rack and the first push rod, and the other elastic member is connected between the second gear rack and the second push rod. The reciprocal switching mechanism comprises a first push rod and a second push rod. The first push rod is linearly and displaceably disposed in the case and is abutted against the first gear rack, wherein the first push rod comprises a first sliding block locating at an end thereof, and the first sliding block is exposed outside of the case to allow for user manipulation of the first sliding block. The second push rod is linearly and displaceably disposed in the case and is abutted against the second gear rack, wherein the second push rod comprises a second sliding block located at an end thereof, and the second sliding block is exposed outside of the case to allow for user manipulation of the second push rod. The transmission unit is pivotally disposed in the case, wherein the transmission unit is connected between the first gear rack and the second gear rack for driving the first gear rack and the second gear rack to be displaced reciprocally. 
     It is to be understood that both the foregoing general description and the following detailed description are by examples, and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be more fully understood by reading the following detailed description of the embodiment, with reference made to the accompanying drawings as follows: 
         FIG. 1  is a schematic view showing an internal structure of a power tool according to an embodiment of the present disclosure; 
         FIG. 2  is a schematic view of the power tool of  FIG. 1 , illustrating a second gear rack pushing and rotating a ratchet; 
       FIG.  2 ′ is a schematic view showing an internal structure of a power tool according to another embodiment of the present disclosure; 
         FIG. 3  is a schematic view of the power tool of  FIG. 1 , illustrating a first gear rack engaged with the ratchet, and the second gear rack disengaged from the ratchet; 
         FIG. 4  is a schematic view of the power tool of  FIG. 1 , illustrating the first gear rack pushing and rotating the ratchet; 
         FIG. 5  is a schematic cross-sectional view taken along line  5 - 5  of  FIG. 1 . 
         FIG. 6  is a schematic view of the power tool of  FIG. 1 , illustrating a reciprocal switching member pivotally disposed in a case. 
         FIG. 7  is a cross-sectional view of the reciprocal switching member taken along line  7 - 7  of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a schematic view showing an internal structure of a power tool according to an embodiment of the present disclosure. As shown in  FIG. 1 , the power tool includes a case  100 , a gear assembly  200 , a first gear rack  230 , a second gear rack  240 , an elastic member  400 , a reciprocal switching mechanism  500  and a transmission unit  600 . The gear assembly  200  comprises a transmission gear  220  and a ratchet  210 , and the ratchet  210  and the transmission gear  220  are engaged. Both of the transmission gear  220  and the ratchet  210  are pivotally disposed in the case  100 , and the first gear rack  230  is disposed opposing the second gear rack  240 . The reciprocal switching mechanism  500  includes a first push rod  510  and a second push rod  520 . The first and second gear racks  230 ,  240  are disposed movably in the case  100 . The first gear rack  230  is engaged with the ratchet  210  when the second gear rack  240  is disengaged from the ratchet  210  and vice versa. The elastic member  400  is connected between the first and second gear racks  230 ,  240 , and provides a biasing force to the first gear rack  230  and the second gear rack  240  in a direction toward the ratchet  210 . The first push rod  510  and the second push rod  520  can be linearly and displaceably disposed in the case  100 . The first push rod  510  and the second push rod  520  respectively push against the first gear rack  230  and the second gear rack  240  to displace the same in a direction away from the ratchet  210 . The transmission unit  600  is pivotally disposed in the case  100 . The transmission unit  600  is connected to the first gear rack  230  and the second gear rack  240 , so that the first gear rack  230  and the second gear rack  240  can be displaced in opposite directions. That is, the transmission unit  600  is pivotally connected between the first gear rack  230  and the second ear rack  240 , and is provided for driving the first gear rack  230  and the second gear rack  240  to be displaced in a reciprocal manner. 
     A sides of the first gear rack  230  facing the second gear rack  240  and a side of the second gear rack  240  facing the first gear rack  230  are referred to as inner sides. A first flange  231  and a first guiding groove  232  can be included in the inner side of the first gear rack  230 . A second flange  241  and a second guiding groove  242  can be included in the inner side of the second gear rack  240 . A first guiding portion  511  is disposed at one end of the first push rod  510 , and the first guiding portion  511  is alternately displaced along the first flange  231  and the first guiding groove  232  for displacing the first gear rack  230 . A second guiding portion  521  is disposed at one end of the second push rod  520 , and the second guiding portion  521  is alternately displaced along the second flange  241  and the second guiding groove  242  for displacing the second gear rack  240 . Moreover, the case  100  can have a first rail  110  and a second rail  120  (see  FIG. 6 ). A first sliding block  330  is disposed at the other end of the first push rod  510 , and a second sliding block  340  is disposed at the other end of the second push rod  520 . The first sliding block  330  is exposed outside of the first rail  110  to allow users to operate the first sliding block  330 . The second sliding block  340  is exposed outside of the second rail  120  to allow users to operate the second sliding block  340 . Therefore, the sliding blocks  330 ,  340  provided for user manipulation using a hand can be more close to the user&#39;s thumb. 
     The power tool further comprises reciprocal switching member  530 . The reciprocal switching member  530  is pivotally disposed in the case  100  and is connected between the first push rod  510  and the second push rod  520 . One end of the reciprocal switching member  530  is pivotally connected to the first push rod  510 , and the other end of the reciprocal switching member  530  is pivotally connected to the second push rod  520 . Through such a configuration, the reciprocal switching member  530  operates such that the first push rod  510  and the second push rod  520  can be linearly displaced in opposite directions. 
       FIG. 2  is a schematic view of the power tool of  FIG. 1 , illustrating the second gear rack  240  pushing and rotating the ratchet  210 . During operation, the elastic member  400  provides a biasing force to the first gear rack  230  and the second gear rack  240  in a direction toward the ratchet  210 . The first guiding portion  511  pushes against the first flange  231  of the first gear rack  230  so as to push the first gear rack  230  away from the ratchet  210 . At this time, because the elastic member  400  provides a biasing force to the second gear rack  240  in a direction toward the ratchet  210 , only the second gear rack  240  is engaged with the ratchet  210 . The transmission unit  600  drives the second gear rack  240  to displace along a tangent direction of the ratchet  210  for rotating the ratchet  210 . While the second gear rack  240  is returned, the second gear rack  240  is disengaged from the ratchet  210  and so returns by itself (without rotating the ratchet  210 ). Therefore, during the returning movement of the second gear rack  240 , the ratchet  210  will be rotated only in one rotational direction. As described above, the elastic member  400  is elastically connected between the first gear rack  230  and the second gear rack  240  so that the first gear rack  230  and the second gear rack  240  can be pulled toward the ratchet  210 . In another embodiment, the elastic members  400  can be two and can be respectively connected between the push rods  510 / 520  and the gear racks  230 / 240  for allowing the push rods  510 / 520  to be abutted against the gear racks  230 / 240  (FIG.  2 ′). Furthermore, in some embodiments, the elastic member  400  may push against the outer sides of the first gear rack  230  and the second gear rack  240  so as to bias the first gear rack  230  and the second gear rack  240  in a direction toward the ratchet  210 . 
     The elastic member  400  pulling against the first gear rack  230  and the second gear rack  240  is used as an example in the embodiment herein. 
       FIG. 3  is a schematic view of the power tool of  FIG. 1 , illustrating the first gear rack  230  engaged with the ratchet  210  and the second gear rack disengaged from the ratchet  210 . When the first sliding block  330  is pushed by a user, the first guiding portion  511  is displaced from the first flange  231  to the first guiding groove  232  of the first gear rack  230 . During this process, the elastic member  400  pulls the first gear rack  230  toward the ratchet  210  so that the first gear rack  230  engages with the ratchet  210 . 
     At the same time, the first sliding block  330  operates the reciprocal switching member  530  so that the second sliding block  340  is displaced, and the second guiding portion  521  is displaced from the second guiding groove  242  to the second flange  241  of the second gear rack  240 , thereby pushing the second gear rack  240  away from the ratchet  210 . 
       FIG. 4  is a schematic view of the power tool of  FIG. 1 , illustrating the first gear rack  230  pushing and rotating the ratchet  210 . The transmission unit  600  drives the first gear rack  230  to be alternately displaced. During displacement, the ratchet  210  is pushed and rotated in another rotational direction while the first gear rack  230  displaces along the tangent direction of the ratchet  210 . 
     During operation, the user may select one of the push rods  510  or  520  to make one of the gear racks  230  or  240  move away from the ratchet  210  so that the ratchet  210  is pushed and rotated only by one of the gear racks  230  or  240 , thereby controlling the rotational direction of the ratchet  210 . Also, during user manipulation, when one sliding block  330  is moved, the other sliding block  340  will be displaced by the reciprocal switching member  530 , thereby changing the positions of the two push rods  510 ,  520  simultaneously. Hence, when holding the power tool, the user can push and move one of the sliding blocks  330  or  340  merely by using his or her thumb, thereby changing the rotational direction of the ratchet  210 . As a result, it is possible to achieve the effect of switching the rotational direction using a single hand. 
       FIG. 5  is a schematic cross-sectional view taken along line  5 - 5  of  FIG. 1 . The ratchet  210  further includes at least one blind hole  211 , at least one spring  212  and at least one steel ball  213 . The spring  212  and the steel ball  213  are received in the blind hole  211 , such that the spring  212  pushes against and displaces the steel ball  213  outwards from the blind hole  211 . When the ratchet  210  is disposed in the case  100 , the steel ball  213  will be pushed by the spring  212  to abut against the case  100 , thereby increasing the resistance between the ratchet  210  and the case  100 . Thus, when the gear racks  230 ,  240  undergo a returning movement, the gear racks  230 ,  240  will not force the ratchet  210  to rotate backwards. 
       FIG. 6  is a schematic view of the power tool of  FIG. 1  illustrating the reciprocal switching member  530  pivotally disposed in the case  100 , and  FIG. 7  is a cross-sectional view of the reciprocal switching member  530  taken along line  7 - 7  of  FIG. 6 . The case  100  includes the first rail  110  and the second rail  120  disposed thereon, as described above. The first rail  110  is provided for allowing the first push rod  510  to slide thereon, and the second rail  120  is provided for allowing the second push rod  520  to slide thereon. One of the two ends of the reciprocal switching member  530  is pivotally connected to the first push rod  510 , and the other end of the reciprocal switching member  530  is pivotally connected to the second push rod  520 , thereby displacing the first push rod  510  and the second push rod  520  in opposite directions when the reciprocal switching member  530  is operated. A bottom surface of the reciprocal switching member  530  includes a first indentation  531  and a second indentation  532 . The case  100  includes a recess  132  located between the first push rod  510  and the second push rod  520 , and a compression spring  130  is vertically disposed in the recess  132 . Moreover, a bead  131  is disposed on the compression spring  130  exposing outwards from the recess  132 . The compression spring  130  abuts against and displaces the head  131  outward from the recess  132 , and then the bead  131  abuts against one of the two indentations  531 ,  532  so as position the reciprocal switching member  530  while the first rod  510  and the second rod  520  reciprocally displace. 
     Referring back to  FIG. 1 , in some embodiments, the transmission unit  600  includes a swinging member  610  and an eccentrically rotating member  620 . The swinging member  610  is pivotally disposed in the case  100 . Also, the swinging member  610  is connected to the first gear rack  230  and the second gear rack  240 . The first gear rack  230  and the second gear rack  240  are pivotally disposed at the swinging member  610 , and are respectively located at both sides of the eccentrically rotating member  620 . When the eccentrically rotating member  620  is driven to be rotated, the swinging member  610  can be driven to swing reciprocally and can simultaneously bring the first gear rack  230  and the second gear rack  240  to be displaced reciprocally, in which the power source for driving the eccentrically rotating member  620  is conventional and so is not described herein. 
     The aforementioned ratchet  210  driven to be rotated can be used as an output power. For example, a socket (not shown) can be mounted on the ratchet  210  to release or fasten a nut (not shown). A socket driven and rotated by the ratchet  210  can achieve the same function. 
     It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the scope or spirit of the present invention. Therefore, the scope of the present invention shall be defined by the appended claims.