Patent Publication Number: US-6341543-B1

Title: Push bar-typed ratchet wrench with high torque strength

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a pushbar-type ratchet wrench, and more particularly to a push bar-type ratchet wrench in which the detent section of the push bar is engaged with the ratchet at a higher position for increasing the torque strength and operation sensitivity thereof. 
     FIG. 1 shows a conventional push bar-type ratchet wrench  10  including an elongated stem  11 , a ratchet  14  rotatably received in a through hole of the head section  12  of the stem  11  for fitting with a nut and a push bar  16  which is a solid bar with circular cross-section. Each of two ends of the push bar  16  is formed with a detent section  17 . The push bar  16  is slidably fitted in a slide way  13  of the head section  12  and pressed by a resilient member  18 , whereby the push bar  16  can be located at two positions where the detent section  17  on right side or left side is engaged with the ratchet  14  to provide one-way ratchet effect in different directions. 
     The conventional push bar-type ratchet wrench can hardly bear high torque and has some shortcomings in operation as follows: 
     As shown in FIG. 1, when counterclockwise wrenching the stem  11 , the ratchet  1  is engaged with the detent section  17  of the push bar for driving the ratchet to rotate in the same direction. At this time, at the contact position A, the detent section  17  will exert a tangential application force F onto the teeth of the ratchet  14 . The longitudinal component of the force Fy is directed to the ratchet at a position near the center thereof. The ratchet is a hollow structure and has relatively poor structural strength. Therefore, once the application force F reaches a certain value which makes the longitudinal component of the force Fy greater than the bending strength of the ratchet, the ratchet will be deformed and damaged and unable to be further used. 
     In addition, referring to FIG. 2, in the operation of FIG. 1, the ratchet  14  will exert a reaction force F′ onto the push bar  16 . The push bar  16  is a solid structure so that it is able to bear the longitudinal component of the force Fy′. However, in the case of excessively great transverse component of the force Fx′, the push bar will clog in the slide way  13  and make it impossible to further use the ratchet wrench. 
     Furthermore, when clockwise wrenching the wrench as shown in FIG. 3, the push bar  16  will be pushed rightward by the ratchet  14  and disengaged from the ratchet to provide a ratchet effect. The contact position A and the axis of the stem contain a relatively small angle θ. Therefore, when the slope face s of the tooth  141  of the ratchet pushes the detent section  17 , as shown in FIG. 4, the perpendicular component n 2  of the application force N is applied to the push bar  16  to press the push bar  16  against the inner wall of the slide way  13 . Therefore, a larger frictional coefficient between the push bar and the inner wall is produced and the ratchet must exert a greater force onto the push bar for transversely pushing the same. As a result, the ratchet effect is insensitive. 
     In the other types of ratchet wrenches  19  as shown in FIGS. 5 and 6, the ratchets  191  and the detents  192  also have the same shortcomings. 
     Another conventional ratchet wrench  15  as show in FIGS. 7 and 8, including a push bar  153  slidably fitted in a slide way  152  of a stem  151 . Said push bar has a rectangular cross-section and has a detent section  154  formed at one end of which, said detent section  154  is engaged with a ratchet  155 . The engagement position B and the axis of the stem  151  contain a small angle θ, so that the wrench  15  also have the same shortcomings. 
     SUMMARY OF THE INVENTION 
     It is therefore a primary object of the present invention to provide a push bar-type ratchet wrench with high torque strength, which is able to bear higher torque. 
     It is a further object of the present invention to provide the above push bar-type ratchet wrench in which the ratchet can be more sensitively operated. 
    
    
     The present invention can be best understood through the following description and accompanying drawings wherein: 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partially sectional view of a conventional push bar-type ratchet wrench; 
     FIG. 2 is a view according to FIG. 1, showing a state of reaction force; 
     FIG. 3 is a view according to FIG. 1, showing that the wrench is wrenched in reverse direction; 
     FIG. 4 is an enlarged view of a part of FIG. 2; 
     FIG. 5 is a partially sectional view of another type of conventional ratchet wrench; 
     FIG. 6 is a sectional view of still another type of conventional ratchet wrench; 
     FIG. 7 is a sectional view of still another type of conventional ratchet wrench; 
     FIG. 8 is a side view according to FIG. 7; 
     FIG. 9 is a perspective assembled view of a preferred embodiment of the present invention; 
     FIG. 10 is a perspective exploded view of the embodiment of FIG. 9; 
     FIG. 11 is an enlarged view of the push bar of FIG. 9; 
     FIG. 12 is a side view according to FIG. 9; 
     FIG. 13 is a top partially sectional view of the embodiment of FIG. 9, showing that the wrench is wrenched; 
     FIG. 14 is a view according to FIG. 13, showing a state of reaction; 
     FIG. 15 is an enlarged view of a part of FIG. 13, showing that the wrench is wrenched in reverse direction. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Please refer to FIGS. 9,  10  and  11 . The push bar-type ratchet wrench  20  of the present invention includes: 
     a stem body  30  one end of which is a holding end  32  formed with a through hole  34  and a slide way  36  transversely passing through the holding end  32  and communicating with the through hole  34 , the slide way  36  having an elliptic cross-section with a major axis C parallel to the plane face of the holding end  32  and a minor axis D normal to the major axis C; 
     a ratchet  40  having a fitting hole  42  for fitting with a nut or a bolt, an outer circumference of the ratchet  40  being continuously formed with multiple teeth  44 , the ratchet  40  being rotatably positioned in the through hole  34  of the holding end and restricted by an annular wall  35  of the through hole  34  and a C-shaped latch ring  39 ; 
     a push bar  50  having an elliptic cross-section with a horizontal axis G and a vertical axis H, the length of the horizontal axis G being larger than the length of the vertical axis H, a front edge of the push bar  50  being formed with a substantially arch recess, each of two sides of the push bar  50  being formed with a detent section  52 , the push bar  50  being slidably positioned in the slide way  36 , the horizontal and vertical axes G, H of the push bar  50  respectively corresponding to the major and minor axes C, D of the slide way as shown in FIG. 12; and 
     a locating member  60  including a spring  62  and a steel ball  64  which are positioned in a dent  37  of the stem body  30  for resiliently pushing one of two locating sections  54  formed on rear edge of the push bar  50 . Accordingly, the push bar  50  has two locations in the slide way. At each location, one of the two detent sections  52  is resiliently engaged with the teeth  44  of the ratchet. 
     The present invention provides a ratchet effect for wrenching a screw fastening member as the conventional wrench. 
     In the state of FIG. 13, the push bar  50  is positioned at one location with the detent section  52  on right side engaged with the ratchet  40  within a range of 34 to 47 degrees. When counterclockwise wrenching the stem body  30 , the push bar drives the ratchet to rotate in the same direction for wrenching a screw fastening member. The horizontal axis G of the push bar has a length larger than that of the conventional push bar so that the detent section  52  is engaged with the ratchet at a higher position P. The position P and the axis of the stem body  30  contain a larger angle δ. At the contact position, the detent section  52  exerts an application force F onto the teeth  44  of the ratchet  40 . The longitudinal component Fy of the application force F is directed to the ratchet. The contact position P is higher so that the longitudinal component Fy acts on a position closer to the solid portion Q of the outer circumference of the ratchet. The portion Q is more distal from the hollow section of the ratchet so that the ratchet has better strength for bearing higher torque. 
     Referring to FIG. 14, in the operation state of FIG. 13, the ratchet  40  will exert a reaction force F′ onto the push bar  50 . The engagement position is higher than that of the conventional wrench so that the transverse component Fx′ of the reaction force F′ is reduced and the possibility of clog of the push bar in the slide way is minimized. 
     When clockwise wrenching the wrench, as shown in FIG. 15, the ratchet  40  will push the detent section  52  rightward to disengage the push bar  50  from the ratchet and provide a ratchet effect. When the slope face r of the tooth  44  of the ratchet  40  pushes the detent section  52 , almost all the application force N′ becomes horizontal component n so that almost all the force is applied by the ratchet for transversely pushing the push bar  50  and there is almost no vertical component for pushing the push bar to abut against the inner wall of the slide way  36 . Therefore, the frictional coefficient against the push bar is greatly reduced and the push bar  50  can be easily pushed by the ratchet  40  to slide with higher sensitivity. 
     According to the above, in the present invention, the engagement position of the push bar and the ratchet is changed, enabling the ratchet to bear greater torque and enhancing the sensitivity of the ratchet effect. 
     Furthermore, as shown in FIG. 12, the length of the minor axis D of the slide way  36  is not increased so that the thickness of the wrench is not increased and the wrench of the present invention is still applicable in a narrow space. 
     The ratio of the cross-section of the holding end  32  relates to the strength of the total wrench. The area of cross-section of the holding end: U=width H×thickness W. The remaining cross-section of the holding end: V=width H×(W-2T). According to the test data of the applicant, the safety coefficient is S,        S   =       V   U     =         W   -     (     2      T     )       W     =     0.24   ∼   0.37