Patent Publication Number: US-6334373-B1

Title: Ratchet wrench stop member positioning arrangement

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     The present invention relates to a ratchet wrench, and more particularly to such a ratchet wrench in which the angle of action produced between the stop member and the ratchet wheel is minimized, so that maximum torsional force can be achieved. 
     A variety of ratchet wrenches have been disclosed, and have appeared on the market. FIGS. 1 and 2 show two different structures of ratchet wrench according to the prior art, in which a stop member is forced into engagement with the ratchet wheel to control the direction of rotation of the ratchet in the box in one end of the wrench body. Because a great contained angle is defined between the ratchet wheel and the stop member, much ineffective component of force is produced during the operation of the ratchet wrench. Further, the cover plate, which holds the ratchet wheel in the box, tends to be damaged or permanently deformed during the operation of the ratchet wrench because it is fastened to the wrench body by screws. FIGS. 3 and 4 show another structure of ratchet wrench according to the prior art. According to this design, the stop member receives a driving force from the ratchet wheel at 90° and 180° respectively, and a great contained angle is defined between the stop member and the tangent line. During the operation of the ratchet wheel, a great ineffective component of force is produced. Further the limited area of bearing force causes the stop member unable to bear a high torsional force. FIGS. 5 and 6 show still another two structures of ratchet wrench according to the prior art. Due to the limitation of the angular position of the stop member, a great ineffective component of force is produced during the operation of these ratchet wheels. In FIG. 5, a steel ball is provided to stop the ratchet wheel. This design can not bear much torsional force. In FIG. 6, a great ineffective component of force is produced during the operation of the ratchet wrench, causing the ratchet wheel to be deformed easily. FIG. 7 shows still another structure of ratchet wrench according to the prior art. According to this design, the stop member is disposed in a horizontal position, which bears less torsional force, and tends to produce a great reactive force to the ratchet wheel, causing the ratchet wheel to be deformed permanently. The drawbacks of the aforesaid prior art ratchet wheels are produced due to improper angular position design of the stop member relative to the ratchet wheel. 
     The present invention has been accomplished to provide a ratchet wheel, which eliminates the aforesaid drawbacks. According to the present invention, the side hole in which the stop member is installed and forced by a spring member into engagement with the ratchet wheel in the box in one end of the wrench body defines with the horizontal line which passes through the center of the box a contained angle at about 8˜18°. This design greatly reduces the angle of action between the stop member and the ratchet wheel during the operation of the ratchet wrench, so that the inactive component of force can be minimized. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plain view of a ratchet wrench according to the prior art. 
     FIG. 2 is a plain view of another structure of ratchet wrench according to the prior art. 
     FIG. 3 is a plain view of still another structure of ratchet wrench according to the prior art. 
     FIG. 4 is a plain view of still another structure of ratchet wrench according to the prior art. 
     FIG. 5 is a plain view of still another structure of ratchet wrench according to the prior art. 
     FIG. 6 is a plain view of still another structure of ratchet wrench according to the prior art. 
     FIG. 7 is a plain view of still another structure of ratchet wrench according to the prior art. 
     FIG. 8 is an exploded view of a ratchet wrench according to the present invention. 
     FIG. 9 illustrates the design of the toothed portion of the stop member according to the present invention. 
     FIG. 10 is a schematic drawing explaining the base component of force according to the present invention. 
     FIG. 11 is a schematic drawing explaining different components of force according to the present invention. 
     FIG. 12 is a schemtic drawing explaining the best component for force according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 8, a ratchet wrench in accordance with the present invention is generally comprised of a body  1 , a ratchet wheel  2 , a stop member  3 , a spring  4 , a screw cap  5 , an annular cover plate  6 , and a C-shaped retianer  7 . 
     Referring to FIGS. 9 and 10 and FIG. 8 again, the body  1  has a box  11  in one end thereof, a transverse side hole  12  tangent to the box  11 , and an internal thread  121  in the transverse side hole  12  near the outer side. The ratchet  2  is an annular wheel mounted within the box  11 , having transverse teeth  21  equiangularly spaced around the periphery thereof and points  22  equiangularly spaced around the inner diameter thereof. The annular cover plate  6  is mounted in the box  11  and secured in place by the C-shaped retainer  7  to hold the ratchet wheel  2  in the box  11 . The stop member  3  is a wedge-like metal block mounted within the transverse side hole  12 , having a toothed portion  31  meshed with the teeth  21  of the ratchet  2  and a recessed near end hole  32 . The spring  4  is mounted in the transverse side hole  12  in the body  1 , having one end inserted into the recessed rear end hole  32  on the stop member  3 . The screw cap  5  is threaded into the internal thread  121  in the transverse side hole  12  to hold the spring  4  against the stop member  3 , having recessed end hole  51  on the front end thereof, which receives one end of the spring  4 , and a hexagonal tool slot  52  on the rear end thereof for enabling the screw cap  5  to be turned in and out of the transverse side hole  12  with a tool. 
     Referring to FIGS. 8 and 9 again, the toothed portion  31  has an oval profile, smoothly curvedly sloping in one direction. After installtion in the transverse side hole  12 , the longitudinal central axis of the transverse side hole  12  defines with the horizontal line which passes through the cetner of the box  11  a contained angle at about 8˜18°, so that a small angle of action θ is produced after engagement between the toothed portion  31  of the stop member  3  and the teeth  21  of the ratchet wheel  2 . This arrangement greatly reduces ineffective componenet of force, and relatively increases effective component of force. 
     Referring to FIG.  11  and FIG. 10 again, after instalition of the stop member  3  in the transverse side hole  12 , the stop member  3  is disposed in parallel to line (the longitudinal central axis of the transverse side hole  12 ) L12. When L1∞L2, the ratchet wheel  2  receives a driving power M1, where M1=F5*R1, and is forced by the driving power M1 to drive the stop member  3 . Therefore, a balanced condition occurs only when F2=F5. Due to the direction of force F2, two components of force F3 and F1 are produced, where F1 2 +F2 2 +F3 2 −2F1*F3 cos θ. When θ=0° and cos θ=1, 
     
       
         F1 2  =F2 2 +F3 2 −2F1*F3 
       
     
     
       
         F3=0F1αF2 
       
     
     When θ&gt;0° and cos θ&lt;1, F1&lt;F2, therefore the component of force F3 (ineffective component of force) is relatively reduced, and the component of force F2 (effective component of force) is relatively increased. Because F5=F2, M1=F5*R1, the maximum torsional force is obtained. 
     As indicated above, if the angle of action θ is excessively great, the component of force (ineffective component of force) F3 is released incresed, resulting in a lower wrenching efficiency, and simultaneously causing the ratchet wheel  2  to produce a reactive force F4. The reactive force F4 tends to damage the ratchet wheel  2 . 
     Referring to FIGS. 12 and 11 again, when 0&lt;θ&lt;90°, thus 0&lt;cos θ&lt;1F3α1/F2 when L1 and L2 define a contained angle θ1, and θ1 is designed equal to θ, thus F1=F2, and the applied force is equal to the bearing force without producing a force of interference (ineffective component of force F3). Therefore, the maximum torsional force is obtained without reactive force F4 when the force against thrust F3=0 and F1αF2. Further because θ1=θ,θ1 is at the tangent line, the maximum cross sectional area of bearing force is otabined. Because M1=F5*R1, if F5=F2, thus M1=F2*R1, and the maximum torsional force is obtained, and the cross sectional area of the bearing force received by the ratchet wheel is within the range of α1 and α2, and a different cross sectional area W1, W2 or W3 may be produced. Under the condition of θ1 for W2, θ2 for W2, and θ3 for W3, W2&gt;W1&gt;W3 because θ1&lt;θ2&lt;θ3. Assums t is the thickness of the ratchet wheel, thus A1=W1*t, A2=W2*t, A3=W2*t. If A=unit area, thus unit area pressure P is as follows:        P1   =         F2   A1                   P1     =         F2   A2                   P1     =     F2   A3                         
     Because A2&gt;A1&gt;A3, thus P2&gt;P1&gt;P3. Therefore, F2 achieves the best direction and angle of bearing foce.