Patent Publication Number: US-2013228053-A1

Title: Torque wrench with functional lock

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to wrench technology and more particularly to a torque wrench with functional lock, which allows quick switching of a torque limit value adjustment grip between an adjustable unlocking position and a non-adjustable locking position. 
     2. Description of the Related Art 
     A conventional wrench is known comprising a hollow main shaft, a tool member mounted at one end of the hollow main shaft for driving a screw nut or screw bolt, and an adjustable grip rotatably mounted at an opposite end of the hollow main shaft, and a clutch device and a spring member mounted inside the hollow main shaft and set between the tool member and the adjustable grip. The adjustable grip can be rotated to push the spring member, thereby changing the prestress of the spring member. The clutch device can be disengaged when the tool member receives a torque larger than the elastic prestress of the spring member, thereby limiting the torque acted on the tool member. Further, during clutch action of the clutch device, an escape percussion sound will be produced to notice the user of the problem that the applied force has been over the limit, avoiding screw nut or screw bolt damage. However, when operating the torque wrench, functional lock means is necessary to lock the adjustable grip, avoiding change of the set torque limit value or hand injuries in a slipping accident. 
     SUMMARY OF THE INVENTION 
     The present invention has been accomplished under the circumstances in view. It is the main object of the present invention to provide a torque wrench with functional lock, which allows quick switching of a torque limit value adjustment grip between an adjustable unlocking position and a non-adjustable locking position. 
     To achieve this and other objects of the present invention, a torque wrench comprises a hollow main shaft comprising a first and a second end, a tool member inserted into the first end of the hollow main shaft, an adjustable grip comprising an adjustment screw threaded into the second end of the hollow main shaft to secure the adjustable grip to the hollow main shaft and to allow relative rotation between the hollow main shaft and the adjustable grip, a torque-adjustment elastic member mounted inside the hollow main shaft and stopped against one end of the adjustment screw, a clutch device set between the torque-adjustment elastic member and the tool member and pushable by the torque-adjustment elastic member between an engaged position and a disengaged position, and a functional lock comprising a locking ring mounted in between the second end of the hollow main shaft and the adjustable grip and defining therein an axially extending bevel groove, at least one through hole located at the adjustable grip and at least one positioning ball accommodated in the bevel groove inside the locking ring and respectively insertable through the at least one through hole into direct contact with the periphery of the second end of the hollow main shaft. 
     The main characteristic of the present invention is the arrangement of the functional lock, which enables the user to control engagement between the positioning ball and the hollow main shaft simply by moving the locking ring. Because the positioning ball is inserted through the through hole on the adjustable grip, it can lock the hollow main shaft and the adjustable grip to prevent change of the set torque limit value or hand injuries in a slipping accident during operation. 
     Preferably, the functional lock further comprises an axial positioning device adapted to positively position the locking ring in the position where the hollow main shaft and the adjustable grip are rotatable relative to each other so that the user can adjust the torque limit value without pulling or pressing the locking ring. 
     Preferably, the hollow main shaft comprises a plurality of locating grooves spaced around the periphery of the second end thereof and extending along the length thereof for receiving the positioning ball to enhance the locking effect of the functional lock. 
     Other advantages and features of the present invention will be fully understood by reference to the following specification in conjunction with the accompanying drawings, in which like reference signs denote like components of structure. 
    
    
     
       BRIEF DESCRIPTION OF. THE DRAWINGS 
         FIG. 1  is an elevational view of a torque wrench in accordance with the present invention. 
         FIG. 2  is an exploded view of the torque wrench in accordance with the present invention. 
         FIG. 3  is a partial longitudinal sectional view of the torque wrench in accordance with the present invention (I). 
         FIG. 4  is a partial longitudinal sectional view of the torque wrench in accordance with the present invention (II). 
         FIG. 5  is a schematic sectional applied view of the present invention, illustrating the adjustable grip and the hollow main shaft locked. 
         FIG. 6  corresponds to  FIG. 5 , illustrating the adjustable grip and the hollow main shaft unlocked and rotatable relative to each other. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1-4 , a torque wrench in accordance with the present invention is shown. The torque wrench comprises: 
     a hollow main shaft  10  comprising a first end  11 , a second end  12  opposite to the first end  11 , and a plurality of locating grooves  13  spaced around the periphery of the second end  12  and extending along the length of the hollow main shaft  10 ; 
     a tool member  20  comprising a head piece  21  made in the form of, for example; a ratchet socket joint, and a stem  22  extended from the head piece  21  and inserted into the inside of the first end  11  of the hollow main shaft  10  to support the head piece  21  outside the hollow main shaft  10 ; 
     an adjustable grip  30  comprising an adjustment screw  31  fixedly mounted therein on the center and axially coupled to the second end  12  of the hollow main shaft  10  for allowing the adjustable grip  30  to be rotated relative to the hollow main shaft  10 ; 
     a torque-adjustment elastic member  40  mounted inside the hollow main shaft  10  and stopped against one end of the adjustment screw  31  either directly or by means of a stopper member  41 ; 
     a clutch device  50  set between the torque-adjustment elastic member  40  and the tool member  20  and pushable by the torque-adjustment elastic member  40  between an engaged position and a disengaged position, preferably, the clutch device  50  including a plurality of block members movable by the torque-adjustment elastic member  40  to abut against one another; and 
     a functional lock  60 . 
     The functional lock  60  comprises: 
     a locking ring  61  mounted in the junction between the second end  12  of the hollow main shaft  10  and the adjustable grip  30  and defining therein an axially extending bevel groove  62 ; 
     a compression spring  63  set between the locking ring  61  and the adjustable grip  30  and adapted to push the locking ring  61  in direction toward the tool member  20  so as to provide an elastic restoring force to the locking ring  61 ; 
     at least one through hole  64  located at an extension tube  32 , which extends out of the adjustable grip  30  and is sleeved onto the second end  12  of the hollow main shaft  10  over the locating grooves  13 ; and 
     at least one positioning ball  65  accommodated in the bevel groove  62  inside the locking ring  61  and respectively insertable through the at least one through hole  64  into direct contact with the periphery of the second end  12  of the hollow main shaft  10 . 
     The aforesaid functional lock  60  further comprises an axial positioning device  70  adapted to keep the locking ring  61  in a position where the hollow main shaft  10  and the adjustable grip  30  are rotatable relative to each other. 
     Preferably, the axial positioning device  70  comprises: 
     an annular groove  71  located at and extending around the inner perimeter of the locking ring  61 ; and 
     locating means  72  mounted at the adjustable grip  30 . 
     Preferably, the locating means  72  comprises an outside annular groove  722  extending around the periphery of the adjustable grip  30 , and an elastic retaining ring  721  mounted at the outside annular groove  722  and engageable into the annular groove  71  to lock the locking ring  61  in the position where the hollow main shaft  10  and the adjustable grip  30  are rotatable relative to each other. 
     In an alternate form of the present invention, the locating means  72  comprises a ball hole (not shown) located at the adjustable grip  30 , a spring-supported ball (not shown) mounted in the ball hole and engageable into the annular groove  71  to lock the locking ring  61  in the position where the hollow main shaft  10  and the adjustable grip  30  are rotatable relative to each other. 
     The operation of the torque wrench will be outlined hereinafter. 
     As shown in  FIG. 5 , the compression spring  63  normally pushes the locking ring  61  toward the tool member  20 . At this time, one end (the shadow end) of the bevel groove  62  is kept in contact with the positioning ball  65  to force the positioning ball  65  into engagement with the locating groove  13 . Because the positioning ball  65  passes through the through hole  64  at the adjustable grip  30 , the hollow main shaft  10  and the adjustable grip  30  are locked and prohibited from rotation relative to each other. 
     Further, as shown in  FIG. 6 , when the user wishes to adjust the torque limit value, the user can directly move the locking ring  61  to let the positioning ball  65  be received in the other end (the deep end) of the bevel groove  62 . At this time, the positioning ball  65  is disengaged from the locating groove  13 , and the elastic retaining ring  721  is allowed to expand and to engage into the annular groove  71 , locking the locking ring  61  in the position where the hollow main shaft  10  and the adjustable grip  30  are rotatable relative to each other. Thus, the user can rotate the adjustable grip  30  relative to the hollow main shaft  10  to adjust the pressure imparted by the adjustment screw  31  to the torque-adjustment elastic member  40 . Thus, the user can adjust the torque limit value conveniently without pulling or pressing the locking ring  61 . After adjustment, the user simply needs to push the locking ring  61  slightly, enabling the locking ring  61  to be returned to its former position by the spring force of the compression spring  63 . 
     Further, matching between the positioning ball  65  and the axial length of the bevel groove  62  limits the maximum range of axial movement of the locking ring  61 , preventing the compression spring  63  and the axial positioning device  70  from being exposed to the outside of the adjustable grip  30  or falling down during displacement of the locking ring  61 . 
     Although a particular embodiment of the invention has been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.