Patent Document

BACKGROUND OF THE INVENTION 
   In prior art, its holder has a torque-setting mechanism inside, which is triggered through an torque-adjusting button that can move the operational bar vertically to depress or stretch the spring set between supporting ring and torque-adjusting nut. However, the mechanism between the clutch and the torque-adjusting button is weak, so the operational bar, clutch, spring, and the torque-adjusting nut would move synchronously when the torque-adjusting button is turned, making it unable to use. 
   SUMMARY OF THE INVENTION 
   The purpose of this invention is to propose a torque screwdriver structure that is convenient in use and simple in assembly. It comprises: a holder has, along the shaft axis, an elongated hole that further has a concave at the bottom set for being fitted by a positioning bar, and has inner threads on the top for threading with the male threads of an adjusting tube. Inside the elongated hole in order set the positioning bar, a sliding tube, a spring, the adjusting tube, and a screwdriver bit. 
   The positioning bar has, in one side, a fitting body that can fit with the aforementioned concave when assembled, and has, in the other side, a fixing ring with at least three equally-spaced ball holes on its wall. And further, each ball hole collaborates with one fixing ball. The sliding tube sets a conical hole at bottom to push fixing balls into or release them from the ball holes when the sliding tube slides along the fixing ring. 
   The spring is installed and stretches against the washer and the top face of the sliding tube on its both ends, and the other side of the washer is against the bottom of the adjusting tube. 
   The adjusting tube has a penetrating hole for the screwdriver bit bar to penetrate through, and male threads on the outer surface set to thread with the inner threads of the holder. 
   The screwdriver bit bar can contain screwdriver bit in one side, and, in the other side, is mounted with a thin rod that has multiple tooth at its bottom. The tooth can fit inside the fixing ring of the positioning bar in one side and collaborates with the conical hole of the sliding tube in the other side. The toothed grooves are curved shaped so that the fixing balls can well fit with the surfaces of them for firm fixture of the screwdriver bit bar. With aforementioned structure, the desired driving torque can be set by threading the adjusting tube inwards into or outwards from the holder to depress or stretch the spring. When the exerted driving torque is greater than the set driving torque, the fixing balls would be first forced out gradually from the toothed grooves to the tooth surface and then further push the sliding tube outwards until the bit bar is completely loosed from the positioning bar and sliding tube. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG.  1 —An exploded view of the preferred embodiment of the invention 
     FIG.  2 —A perspective view of the preferred embodiment of the invention 
     FIG.  3 —A sectional view of the preferred embodiment of the invention 
     FIG.  4 —Another sectional view of the preferred embodiment of the invention when in operation 
     FIG.  5 —A perspective view of the screwdriver bit bar of another preferred embodiment 
     FIG.  6 —A sectional view of the teeth part of the  FIG. 5   
   

   DETAILED DESCRIPTION OF THE INVENTION 
   With references to the attached drawings, please be described of the preferred embodiment as follows. First, with references to  FIGS. 1-4 , this invention proposes a torque screwdriver structure that comprises: a holder  10 , a positioning bar  20 , a sliding tube  30 , a spring  40 , an adjusting tube  50 , and a screwdriver bit bar  60 . 
   The holder  10  has, along the shaft axis, an elongated hole  11  that further has a concave  12  at the bottom set for being fitted by the positioning bar  20 , and has inner threads  13  on the top for threading with the male threads  52  of the adjusting tube  50 . The positioning bar  20  has, in one side, a fitting body  21  that can fit with the concave  12  of the holder  10  when assembled, and has, in the other side, a fixing ring  22  with at least three equally-spaced ball holes  221  on its wall. And further, each ball hole  221  collaborates with one fixing ball  23 . 
   The sliding tube  30  sets a conical hole  31  at bottom to push fixing balls  23  into or release them from the ball holes  221  when the sliding tube  30  slides along the fixing ring  22 . This is so to fix the screwdriver bit bar  60 . 
   The spring  40  is installed and stretches against the washer  53  and the top face of the sliding tube  30  on its both ends. 
   The adjusting tube  50  sets a penetrating hole  51  so that the screwdriver bit bar  60  can penetrate through the adjusting tube  50 . It further has male threads  52  on the surface so as to thread with the inner threads  13  of the holder  10 , and has a washer  53  at the bottom. 
   The screwdriver bit bar  60  can contain screwdriver bit in one side, and is mounted with a thin rod  62  that has multiple tooth  63  at its bottom. The tooth  63  can fit inside the fixing ring  22  in one side and collaborates with the conical hole  31  of the sliding tube  30  in the other side. The toothed grooves  631  are curved shaped so that the fixing balls  23  can well fit with the surfaces of them for firm fixture of the screwdriver bit bar  60 . For collaboration purpose, the positions of multiple tooth  63  and toothed grooves  631  match with the that of ball holes  221 . 
   Moreover, as shown in  FIG. 3 , the spring  40  can be depressed or loosed by threading adjusting tube  50  into or out of the holder  10  so as to adjust the and set the driving torque. 
   When the exerted driving torque is greater than the set driving torque, the fixing balls  23  would be first pushed out gradually from the toothed grooves  631  to the tooth surface  632  and then they further push the sliding tube  30  outwards by interacting with the conical hole  31  until the bit bar  60  is completely loosed from the positioning bar  20  and sliding tube  30 . 
   Furthermore, as shown in  FIGS. 3 and 4 , because the radius of the spring  40  is slightly smaller than that of the penetrating hole  51 , a washer  53  is set between them so that the spring  40  can be depressed more evenly and stably without bending. In case of an equal radius of the spring  40  to that of the penetrating hole  51 , the washer  53  can be omitted. 
   From the tooth surface  632  to the toothed groove  631  is a curved surface, so the fixing balls  23  can roll easily in both left and right directions, which makes the torque screwdriver able to operate both clock- and counterclockwise as traditional screwdrivers. 
   The  FIGS. 5 and 6  show another embodiment for the screwdriver bit bar  60 , which makes the torque screwdriver can only perform either clockwise or counterclockwise for certain operational needs. The feature is that, symmetrically for all teeth  63 , one side of them is a  20  concaved surface  6411 , and the other side is a convex surface  6412 . The aforementioned concaved surface  6411  has the same radius and circle-center as the fixing balls  23  when they fit together. Besides, the length of the tooth is around the radius size of the fixing balls  23 . This is so set that the concaved surface  6411  can prevent the fixing balls  23  from moving out of the toothed groove  631  for the purpose of locking the screwdriver bit, and on the contrary the convex surface  6412  allows the fixing balls  23  to roll out of the toothed groove  631  to release the screwdriver bit. With the aforementioned structure, therefore, a one-solo-direction torque screwdriver can be formed. 
   With all aforementioned, the invention deserves grant of a patent based on its capability of industrial application and absolute novelty. The example illustrated above is just an exemplary embodiment for the invention, and shall not be utilized to confine the scope of the patent. Any equivalent modifications within the scope of claims of the patent shall be covered in the protection for this patent.

Technology Category: b