Abstract:
A folding mechanism for a joint includes a first pivot unit, a second pivot unit, a locking unit and an operation unit. The operation unit drives the locking unit to control the first pivot unit and the second pivot unit to be locked together or released to rotate.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a joint, and in particular to a folding mechanism for the joint. 
     2. The Prior Arts 
     Most of the baby strollers have folding mechanisms for the convenience of carry and storage. The baby sits in the baby stroller such that the parents do not need to hold the baby. When the baby stroller is not in use, the users operate the folding mechanism to fold the baby stroller and put the folded baby stroller in the car trunk or the storage room. 
     However, the operation members of the conventional folding mechanism for baby strollers are usually located close to the joint so that the users have to bend their body to touch and operate the operation members when folding the baby stroller. It is inconvenient for the users. Besides, the operation members can be accidentally touched and activated by the baby in the stroller, which will injure the baby. It is a serious safety issue. 
     SUMMARY OF THE INVENTION 
     A primary objective of the present invention is to provide a folding mechanism for a joint that overcomes the disadvantages of the conventional designs. 
     Another objective of the present invention is to provide a folding mechanism for a joint that is structurally simple, low cost, secured, safe and easy to use. 
     A folding mechanism for a joint according to the present invention includes a first pivot unit, a second pivot unit, a locking unit and an operation unit. The first pivot unit has a first tube connected with a first pivot member. An axle is extended from the first pivot member and a frame having an aperture is connected to the first pivot member. The second pivot unit has a second tube connected with a second pivot member and the second tube has a passage defined therethrough. A slot is defined through a wall of the second tube in the longitudinal direction. A tubular member is connected to the second pivot member and has a reception hole in which the axle is inserted. The second pivot member includes an insertion hole corresponding to the aperture. The locking unit has a pin and an elastic member. One end of the pin includes a shank having a fixing end and the other end of the pin includes a curved surface. The elastic member is mounted to the shank and the pin passes through the aperture and the insertion hole. The operation unit has a sleeve having a sleeve hole in which the tubular member is rotatably inserted. The sleeve has a first arm and a second arm extending radially therefrom in two different angles. The first arm has a first fixed end at a distal end thereof and a pulling member has a first end thereof fixed with the first fixed end. A second end of the pulling member extends through the passage of the second pivot unit and is connected with an operation member which is movably engaged with the slot. The second arm has a second fixed end at a distal end thereof and the fixing end of the pin is fixed to the second fixed end of the second arm. 
     When the folding mechanism is used on a baby stroller, the user operates the operation member within the slot and the sleeve is rotated by the pulling member, the pin connected with the second arm is lowered to disengage from the aperture. Thus, the first and second pivot units are no longer locked by the locking unit. The baby stroller is then able to be folded. When unfolding the baby stroller, the first and second pivot units are pivoted to allow the aperture and the insertion hole to be in alignment with each other, the curved surface of the pin moves along the frame until the elastic member pushes the pin to insert into the aperture to lock the first and second pivot units. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be apparent to those skilled in the art by reading the following detailed description of a preferred embodiment thereof, with reference to the attached drawings, in which: 
         FIG. 1  is a perspective view showing a folding mechanism in accordance with the present invention; 
         FIG. 2  is an exploded view showing the folding mechanism in accordance with the present invention; 
         FIG. 3  is a cross sectional view showing the folding mechanism in accordance with the present invention; 
         FIG. 4  is a cross sectional view showing the operation of the folding mechanism according to the present invention; and 
         FIG. 5  shows that the folding mechanism according to the present invention is used on a baby stroller. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to the drawings and in particular to  FIGS. 1 to 3 , a folding mechanism for a joint in accordance with an embodiment of the present invention includes a first pivot unit  1 , a second pivot unit  2 , a locking unit  3  and an operation unit  4 . The first pivot unit  1  comprises a first tube  10  and a first pivot member  11  connected with the first tube  10 . The first pivot member  11  has an axle  111  and a frame  112  extended therefrom. The frame  112  is in a plate shape and has an aperture  113 . The second pivot unit  2  has a second pivot member  21  and a second tube  20  connected with the second pivot member  21 . The second tube  20  has a passage  200  defined therethrough. A slot  201  is longitudinally defined through a wall of the second tube  20  and communicates with the passage  200 . A tubular member  211  is extended from the second pivot member  21  and has a reception hole  210  in which the axle  111  of the first pivot member  11  is inserted. The second pivot member  21  includes an insertion hole  212  corresponding to the aperture  113 . The operation unit  4  has a sleeve  40  which has a sleeve hole  401 . The tubular member  211  of the second pivot member  21  is rotatably inserted into the sleeve hole  401  of the sleeve  40 , and the axle  111  of the first pivot member  11  is rotatably inserted into the reception hole  210  of the second pivot member  21 . A first arm  41  and a second arm  42  are extended radially from the sleeve  40  in two different angles. The first arm  41  has a first fixed end  411  at a distal end thereof. The operation unit  4  further includes a pulling member  43  and an operation member  44 . A first end of the pulling member  43  is fixed with the first fixed end  411  of the first arm  41  and a second end of the pulling member  43  is extended through the passage  200  to connect with the operation member  44  which is movably engaged with the slot  201 . The second arm  42  has a second fixed end  421  at a distal end thereof and the second fixed end  421  has a through hole. The pulling member  43  may be a cable or a rod. The operation member  44  may be a plate, a lever, etc. The locking unit  3  has a pin  31  and an elastic member  34 . One end of the pin  31  includes a shank  310  having a fixing end  312  and the other end of the pin  31  includes a head having a curved surface  311 . The elastic member  34  is sleeved on the shank  310 . The pin  31  passes through the aperture  113  of the first pivot member  11 , the insertion hole  212  of the second pivot member  21  and the through hole of the second fixed end  421  of the second arm  42 . The fixing end  312  of the pin  31  includes threads which are threadedly connected with a nut  3120  to fix the pin  31  to the second fixed end  421  of the operation unit  4 . The elastic member  34  is a spring. A casing  99  may be mounted to cover the first pivot unit  1 , the second pivot unit  2 , the locking unit  3  and the operation unit  4  as shown in  FIG. 5 . 
     Referring to  FIGS. 2 to 5 , the folding mechanism for the joint according to the present invention is used on a baby stroller  9 . When the user wants to fold the baby stroller  9 , he or she moves the operation member  44  along the slot  201  and the pulling member  43  connected with the operation member  44  pulls the first arm  41  of the operating unit  4 . The first and second arms  41 ,  42  rotate an angle and a central axis of the sleeve  40  is the rotating axis. The pin  31  connected with the second arm  42  is moved downward with the second arm  42 , and therefore the pin  31  is disengaged from the aperture  113 . In the mean time, the elastic member  34  received in the insertion hole  212  of the second pivot member  21  is compressed. As shown in  FIG. 4 , the first and second pivot units  1 ,  2  are no longer fixed by the locking unit  3 , and are pivoted about the central axis of the sleeve  40 . Thus, the baby stroller  9  is folded. Then, the pin  31  is pushed by the elastic member  34  and moved along the insertion hole  212  to the original state. When unfolding the baby stroller  9 , the first and second pivot units  1 ,  2  are pivoted to allow the aperture  113  and the insertion hole  212  to be in alignment with each other. The curved surface  311  of the head of the pin  31  moves along the frame  112  until the elastic member  34  pushes the pin  31  into the aperture  113  to lock the first and second pivot units  1 ,  2 . Then, the baby stroller  9  is unfolded and set. 
     A conventional operation member is located close to the joint. Referring to  FIG. 5 , the operation member  44  according to the present invention is located close to the handle of the baby stroller  9 . Therefore, the user do not need to bend over to operate the operation member  44  and can easily handle the operation member  44 . Furthermore, the operation member  44  is out of the reach of the baby, which preventing the baby from accidentally folding the baby stroller  9 . 
     Although the present invention has been described with reference to the preferred embodiment thereof, it is apparent to those skilled in the art that a variety of modifications and changes may be made without departing from the scope of the present invention which is intended to be defined by the appended claims.