Patent Publication Number: US-2011070019-A1

Title: Joint

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates generally to joints, especially to a joint rotatable through multiple axes. 
     2. Description of Related Art 
     Industrial robots are widely used in various applications to increase efficiency. A manipulator is an important component of the industrial robot. A typical manipulator includes a mechanical arm and an actuator connected to the mechanical arm. The actuator engages a workpiece. 
     However, a frequent problem occurs wherein the actuator cannot move freely relative to the mechanical arm. While a typical joint is often applied to interconnect the mechanical arm and the actuator, it can be difficult to resume the original position. 
     Therefore, a joint which overcomes the described limitations is desired. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the views. 
         FIG. 1  is an assembled, isometric view of an embodiment of a joint. 
         FIG. 2  is an exploded view of the joint of  FIG. 1 . 
         FIG. 3  is a cross-section of the joint taken along line III-III of  FIG. 1 . 
         FIG. 4  is a cross-section of the joint taken along line IV-IV of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , an embodiment of a joint  100  includes a first retaining base  10 , a connecting rod  30 , four elastic members  50 , and a positioning plate  60 . The connecting rod  30  is movably connected to the first retaining base  10  at an end of connecting rod  30 . The positioning plate  60  is fixed to the connecting rod  30  away from the first retaining base  10 . The four elastic members  50  are disposed between the first retaining base  10  and the positioning plate  60 . 
     Referring to  FIG. 2 , the first retaining base  10  may be substantially rectangular, thereby defining a substantially rectangular cavity  11  in the middle portion thereof. Two pivot holes  13  are further defined on the opposite side surfaces of the first retaining base  10 , and communicating the cavity  11 . The two pivot holes  13  are aligned parallel to the X-axis as shown in  FIG. 2 . 
     The joint  100  further includes two first bearings  15 , two bushings  17 , and two first pivots  19 . The first bearing  15  includes an outer bearing ring  151  located inside the pivot hole  13  and an inner bearing ring  153  sleeved by the outer bearing ring  151 . The outer bearing ring  151  is fitted inside the pivot hole  13 . The bushing  17  includes a cylindrical latching portion  171  and a receiving portion  173  connected to the latching portion  171 . The latching portion  171  has approximately the same diameter as a through hole of the inner bearing ring  153 , thus the latching portion  171  can be correspondingly fixed into the inner bearing ring  153 . The first pivot  19  extends in a direction parallel to the X-axis, and is substantially cylindrical in shape. The first pivot  19  includes a head portion  191  received in the receiving portion  173  of the bushing  17  and a threaded portion  193  connected to the head portion  191 . The threaded portion  193  passes through the bushing  17 , the inner bearing ring  153  of the bearing  15 , the pivot hole  13 , and finally enters the cavity  11 . The first bearing  15  may, for example, be designed as an anti-friction bearing, such as a needle or ball bearing. In the illustrated embodiment, the bearing  15  is a ball bearing. 
     The joint  100  further includes a substantially rectangular rocking piece  20  received inside the cavity  11 . A width of the rocking piece  20  is smaller than that of the cavity  11  along the Y-axis. The rocking piece  20  defines a substantially rectangular receiving groove  21  to receive an end of the connecting rod  30 . The rocking piece  20  further defines two threaded holes  23  (shown in  FIG. 3 ) on opposite side surfaces of the rocking piece  20  communicating the receiving groove  21 . The two threaded holes  23  are aligned parallel to the X-axis; and each thread hole  23  receive each of the threaded portions  193  of the first pivots  19 . The rocking piece  20  includes two cylindrical supporting portions  25  extending outwardly from two side surfaces of the rocking piece  20  adjacent to the two threaded holes  23 . The supporting portion  25  and the side surface of rocking piece  20  cooperatively define a receiving groove  251  to receive the latching portion  171  of the bushing  17 . The rocking piece  20  further defines two pivot holes  27  aligned parallel to the Y-axis on opposite side surfaces of the rocking piece  20  communicating the receiving groove  21 . 
     Referring to  FIGS. 2 and 4 , the joint  100  further includes two second bearings  22 , a second pivot  24 , and two securing members  26 . The second bearing  22  is the same as the first bearing  15 , and includes an outer bearing ring  221  located inside the pivot hole  27  and an inner bearing ring  223  sleeved by the outer bearing ring  221 . The second pivot  24  is substantially cylindrical and extends in a direction parallel to the Y-axis. The second pivot  24  has approximately the same diameter as the inner bearing ring  223 , thus the two ends of the second pivot  24  can be correspondingly fixed into the corresponding two inner bearing rings  223 . The second pivot  24  defines two latching grooves  241  adjacent to each end of the second pivot  24 . The two securing members  26  are received in the corresponding latching grooves  241  to secure the bearing  22  on the second pivot  24 . In the illustrated embodiment, the securing member  26  is a pivot securing ring. 
     The connecting rod  30  includes a substantially cylindrical main body  31 , and a substantially rectangular pivoting portion  33  and a threaded portion  35  extending from the opposite end of the main body  31 . The pivoting portion  33  is narrower than the receiving groove  21  of the rocking piece  20  along the X-axis. The pivoting portion  33  defines a pivot hole  331  to receive the second pivot  24 . The pivot hole  331  has approximately the same diameter as the second pivot  24 , thus the second pivot  24  can be correspondingly fixed into the pivoting portion  33 . The connecting rod  30  has a center axis  37  along its extending direction. 
     The joint  100  further includes a covering plate  40 . The covering plate  40  may be substantially square, and defines a substantially circular through hole  41  in a middle portion to receive the main body  31  of the connecting rod  30 . A diameter or width of the through hole  41  exceeds that of the main body  31 , thereby allowing the main body  31  to move freely in the through hole  41  accordingly. It is to be understood that, the shape of the through hole  41  can vary, as long as the width of the through hole  41  exceeds that of the main body  31 . The through hole  41  defines a center axis  411 . The joint  100  further includes four fastening members  43  disposed on four corners of the covering plate  40 . In other words, two pairs of fastening members  43  are positioned symmetrically about the axis  411  of the through hole  41 . The covering plate  40  is fixed to the first retaining base  10  via the four fastening members  43 . In the illustrated embodiment, the fastening member  43  is a bolt, and includes a cylindrical head portion  431 . 
     The positioning plate  60  has a shape similar to the covering plate  40 , and defines a substantially circular positioning hole  61  to receive the threaded portion  35  of the connecting rod  30  in a middle portion of the position plate  60 . The positioning hole  61  has approximately the same diameter as the threaded portion  35 . The joint  100  further includes four guide bars  63  positioned on a surface of the positioning plate  60  facing the covering plate  40 . The four guide bars  63  are disposed at four corners of the positioning plate  60  according to the four head portions  431 . 
     One end of each elastic member  50  sleeves the head portion  431  of the fastening member  43 , and the other end of each elastic member  50  sleeves the guiding bar  63 . In the illustrated embodiment, the elastic member  50  is a spring. 
     The joint  100  further includes a nut  70  threaded on the threaded portion  35  of the connecting rod  30 , and the nut  70  is resisting the positioning plate  60 . 
     Referring to  FIGS. 1-4 , during assembly, the pivoting portion  33  of the connecting rod  30  is positioned inside the receiving groove  21  of the rocking piece  20 , and the pivot hole  331  of the pivoting portion  33  is aligned with the pivot hole  27 . The second pivot  24  passes through the pivot hole  27  of the rocking piece  20  and the pivot hole  331  of the pivoting portion  33 . Two bearings  22  are sleeved at two ends of the second pivot  24  and are located inside the two pivot holes  27 , respectively. Accordingly, the connecting rod  30  is pivotally connected to the rocking piece  20  via the second pivot  24 , and is rotatable relative to an axis of the second pivot  24  in the receiving groove  21 . The threaded portion  35  of the connecting rod  30  is capable of moving through a plane defined by the X-axis and the Z-axis shown in the  FIG. 2  because the pivoting portion  33  is narrower than the receiving groove  21  of the rocking piece  20 . The two second fastening members  26  are received in the corresponding latching grooves  241  of the second pivot  24 , respectively, such that the two bearings  22  are secured on the second pivot  24 . 
     The rocking piece  20  is positioned inside the cavity  11 ; and the receiving groove  251  is aligned with the pivot hole  13  of the first retaining base  10 . The first bearing  15  is fixed inside the pivot hole  13 . The latching portion  171  of the bushing  17  passes through the inner bearing ring  153  of the first bearing  15 , the pivot hole  13 , and is finally positioned inside the receiving groove  251 . The threaded portion  193  of the first pivot  19  passes through the bushing  17 , and engages in the threaded hole  23  of the rocking piece  20 , such that the bushing  17  is fixed to the rocking piece  20 , and the head portion  191  is received in the receiving portion  173  of the bushing  17 . Accordingly, the rocking piece  20  is pivotally connected to the first retaining base  10  via the first pivot  19 , which is substantially perpendicular to the second pivot  24 . The rocking piece  20  is rotatable relative to an axis of the first pivot  19  in the cavity  11  because the rocking piece  20  is narrower than that of the cavity  11 , such that the connecting rod  30  is capable of moving through a plane defined by the Y-axis and the Z-axis shown in the  FIG. 2 . 
     The covering plate  40  is fixed to the first retaining base  10  via the four fastening members  43 , after the threaded portion  35  of the connecting rod  30  passes through the through hole  41  of the covering plate  40 . In a normal starting state, the axis  411  of the through hole  41  and the axis  37  of the connecting rod  30  cooperate. The four elastic members  50  are sleeved on the four corresponding head portions  431  of the fastening members  43 , such that the four elastic members  50  are positioned along a circumference of the connecting rod  30 . The positioning plate  60  is positioned on the four elastic members  50 , and four guide bars  63  are sleeved in the corresponding four elastic members  43 , respectively. The nut  70  is threaded on the threaded portion  35  of the connecting rod  30 , such that the positioning plate  60  is fixed to the connecting rod  30 . 
     During use, the first retaining base  10  may be fixed to a manipulator (not shown) by some means of fasteners, such as bolts, and the connecting rod  30  may be connected to a polishing device (not shown). When polishing various workpieces, the connecting rod  30  may receive a torque to rock freely relative to the first retaining base  10 . The rotational torque can be attributed to one through a plane defined along the Y-Z axis and another through a plane defined along the X-Z axis, thereby providing movement to the rocking piece  20  relative to the axis of the first pivot  19  and relative to the axis of the second pivot  24 , thereby allowing the connecting rod  30  to perform rocking movements with respect to the first retaining base  10 . In a normal state, the four elastic members  50  impel the positioning plate  60  in a direction parallel to the Z-axis towards the nut  70 . However, when the connecting rod  30  starts to move, the positioning plate  60  may also move along the X-axis and/or the Y-axis a certain distance with respect to the starting location, whereby at least one of the four elastic members  50  is compressed, and the other elastic members  50  are stretched. These compressed and stretched elastic members  50  will provide a resilient force to the positioning plate  60  when the workpieces stop inputting torque to the connecting rod  30 , thereby impelling the connecting rod  30  to move or lean backward, and finally return to its normal state automatically. 
     The four elastic members  50  can provide a relatively resilient force to normalize the torque of the connecting rod  30  due to the arrangement of the four elastic members  50 . The resilient force of the four elastic members  50  can be adjusted by adjusting the position of the nut  70  relative to the connecting rod  30 . In addition, even when an elastic member  50  ages and fails to function, the other elastic members  50  can still provide a sufficient amount of resilient force applied to the connecting rod  30 , thus the joint  100  has a relatively longer lifetime. Furthermore, the connecting rod  30  moves easily because the first and second bearings  15 ,  22  are in the form of anti-friction ball bearings. 
     The connecting rod  30  may be movably connected to the first retaining base  10  in other ways. For example, in an alternative embodiment, one end of the connecting rod  30  may be spherical, whereby the first retaining base  10  defines a spherical cavity receiving the spherical end of the connecting rod  30 . 
     It is to be understood that the covering plate  40  may be omitted as long as the four elastic members  50  are fixed to the first retaining base  10  directly. It should also be noted that the configurations of the elastic members  50  are not limited to the embodiments described above. The quantity and positions of the elastic members  50  are specifically described and illustrated for the purpose of exemplifying various aspects of the present joint  100 . 
     It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the disclosure or sacrificing all of its material advantages.