Abstract:
A deceleration mechanism comprises a driving wheel, a driven wheel of a diameter exceeding that of the driving wheel, a transmission member coiling around the driving wheel and the driven wheel; and a tension assembly fixed to the driven wheel. The transmission member coils around the driving wheel, criss-crosses, and coils around the driven wheel. The tension assembly is arranged between the transmission member and the driven wheel and elastically resists the transmission member and the driven wheel.

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure generally relates to robotics and, particularly, to a deceleration mechanism used in a robot. 
     2. Description of Related Art 
     Deceleration mechanisms are widely used in industrial robotics and other applications. A deceleration mechanism often consists of a plurality of meshing gears with different diameters. 
     A commonly used deceleration mechanism includes an inner gear arranged in a shell, a crankshaft with an eccentrically rotating portion arranged in the shell, and a cycloidal gear sleeving on the eccentrically rotating portion. The cycloidal gear rotates about the eccentrically rotating portion, and the cycloidal gear not only meshes with the inner gear but also performs a revolution, and thereby generating an output speed lesser than an input rotating speed. However, to achieve higher degree of meshing and steadier output, the cycloidal gear of the deceleration mechanism frequently forms a plurality of tightly fitted gear teeth on its outer surface. When too many of the gear teeth are formed on a deceleration mechanism of reduced size, each gear tooth becomes very small, and with clearances between neighboring gear teeth becoming also very small, thereby leading to overlapping interference between roots of the neighboring gear teeth. Therefore, the cycloidal gear and the gear teeth are very difficult to manufacture, presenting higher cost and have more complicated structure. 
     Therefore, there is room for improvement within the art. 
    
    
     
       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 several views, and all the views are schematic. 
         FIG. 1  is an assembled, isometric view of a deceleration mechanism as disclosed, including a driving member, a driven member, a transmission device, and a tension assembly. 
         FIG. 2  is an exploded, isometric view of the deceleration mechanism of  FIG. 1 . 
         FIG. 3  is an exploded, isometric view of a driven wheel and a transmission member utilized by the deceleration mechanism of  FIG. 1 . 
         FIG. 4  is an enlarged view of a circled portion IV of  FIG. 2 . 
         FIG. 5  is a plan view of the deceleration mechanism of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a deceleration mechanism  100  used in a robot includes a driving member  10 , a driven member  20 , five transmission members  30 , a tension assembly  40 , and a plurality of fixing assemblies  50 . The transmission members  30  are coiled around the driving member  10  and the driven member  20 . The tension assembly  40  is connected to the driven member  20  and is arranged between the driven member  20  and the transmission members  30 . 
     The driving member  10  includes a driveshaft  11  and a driving wheel  13  arranged around the outside of the driveshaft  11 . 
     Referring to  FIGS. 2 and 3 , the driven member  20  includes a driven shaft  21  and a driven wheel  23  rotatably sleeved on the driven shaft  21 . The driven wheel  23  includes a wheel body  231  sleeved on the driven shaft  21  and a wheel casing  232  sleeved outside of the wheel body  231 . The wheel casing  232  forms two receiving portions  233  and defines a latching slot  234  along a radial direction. Each receiving portion  233  is a flat surface. The driven member  20  further defines four receiving holes  2331  and two threaded holes  2333  at each flat surface toward the inside of the driven wheel  23 . The latching slot  234  is arranged between the receiving portions  233 . The wheel body  231  and the wheel casing  232  can be of the same or different materials. In this illustrated embodiment, the wheel body  231  and the wheel casing  232  are made of different materials, with the wheel body  231  having a lesser material density than the wheel casing  232 . The wheel body  231  is made of aluminum alloy, and the wheel casing  232  is made of steel, thus, the driven wheel  23  has both the requisite strength and lighter weight, thereby reducing the rotation inertia thereof. In the illustrated embodiment, a diameter of the driven wheel  23  is six times that of the driving wheel  13 . 
     The transmission members  30  are parallel and coiled around the driving wheel  13  and the driven wheel  23  with a “∝” shape. Each transmission member  30  coils one winding or loop around the driving wheel  13 , then criss-crosses and coils around the driven wheel  23 . Each transmission member  30  has two connecting ends  31 . The transmission member  30  may be a wire cable, a steel belt, or other material having sufficient strength. In the illustrated embodiment, the transmission member  30  is a steel belt, capable of providing higher transmission precision, improved rigidity and steadier transmission. There may further be any number of transmission members  30 , additionally influencing strength thereof. 
     The tension assembly  40  includes a resisting member  41 , four first resilient members  43 , four guiding bars  45 , and two connecting members  47 . The resisting member  41  includes a resisting surface  411  and defines a connecting hole  413 . The resisting surface  411  is curved with a substantially the same radius as that of the wheel casing  232  of the driven wheel  23 . Thus, the resisting surface  411  of the resisting member  41  can connect with the outer surface of the wheel casing  232  smoothly. The first resilient member  43  is a compression spring, sleeved on the guiding bar  45 . Each resilient member  43  and guiding bar  45  are received in one receiving hole  2331  of the driven member  20 . The connecting member  47  is a fastener which is extending through the connecting hole  413  of the resisting member  41  and received in the threaded hole  2333  of the driven member  20 . The diameter of the connecting hole  413  exceeds that of the connecting member  47 , thus, the resisting member  41  can slide along the connecting member  47 . 
     Referring to  FIGS. 3 and 4 , each fixing assembly  50  includes an active member  51 , a positioning member  52 , an adjustment member  53 , and a second resilient member  54 . In the illustrated embodiment, two fixing assemblies  50  are positioned at opposite ends of the latching slot  234  of the driven wheel  23 , respectively. The active member  51  includes a first latching portion  511 , a second latching portion  513 , and a plurality of fastener  515  connecting the first latching portion  511  to the second latching portion  513 . The positioning member  52  is connected to the driven wheel  23  by a plurality of fasteners  521 . The adjustment member  53  is a fastener, which includes a head  531  and a post  533 . The second resilient member  54  is a compression spring, sleeving on the adjustment member  53 . Opposite ends of the second resilient member  54  resist the head  531  of the adjustment member  53  and the positioning member  52 , respectively. 
     Referring to  FIGS. 2 through 5 , during assembly of the deceleration mechanism  100 , the first resilient member  43  of the tension assembly  40  sleeves on the guiding bar  45  and is received in the receiving hole  2331  of the driven member  20 . The resisting member  41  is connected to the receiving portion  233  of the driven member  20 , with the connecting member  47  received in the threaded hole  2333  of the driven member  20 . For effective assembly, the connecting member  47  received in the threaded hole  2333  should be long enough so that the first resilient member  43  can be compressed by a significant degree. The transmission member  30  coils one winding or loop around the driving wheel  13  of the driving member  10 , then criss-crosses and coils around the outer surface of the wheel casing  232  of the driven wheel  23 . The transmission member  30  criss-crosses between the driving wheel  13  and the driven wheel  23 , thus, substantially forming a “∝” shape. Each connecting end  31  of the transmission member  30  is fixed by one active member  51 . The connecting end  31  is arranged between the first latching portion  511  and the second latching portion  513 . The fasteners  515  connects the first latching portion  511  to the second latching portion  513 , thus, the connecting end  31  is fixed. The positioning member  52  is arranged in the latching slot  234  of the driven member  20  by the fasteners  521 . The post  533  of the adjustment member  53  extends through the second resilient member  54  and the positioning member  52 , and are received in the active member  51 , thus, the connecting ends  31  of the transmission member  30  are connected to the driven member  20 . The connecting ends  31  of the transmission member  30  are staggered to provide a height difference, thus preventing the transmission member  30  from contacting itself at the intersections, thereby avoiding attendant friction and extending service life. 
     A portion of the connecting member  47  of the tension assembly  40  may be withdrawn away from the threaded hole  2333  of the driven member  20 , thus, permitting the resisting surface  411  of the resisting member  41  to resist the transmission member  30 , thereby increasing the frictional force created therebetween. 
     During operation of the deceleration mechanism  100 , a driving device (not shown) rotates the driving wheel  13 , and in the illustrated embodiment, the driving wheel  13  rotates in X direction, which is clockwise, and sets one transmission member  30 . When the driving wheel  13  rotates in the X direction, a portion of the transmission member  30  coiled around the driving wheel  13  may then coil around the driven wheel  23 , and another portion of the transmission member  30  adjacent to the driving wheel  13  may be pulled out from the driven wheel  23  and coiled around the driving wheel  13 . Friction between the transmission member  30  and the driving wheel  13  and between the transmission member  30  and the driven wheel  23  rotates the driven wheel  23  opposite to the X direction. When the driving wheel  13  has rotated a default number of windings, the driving device rotates the driving wheel  13  in a reverse direction to the X direction, and the driven wheel  23  then rotates in the X direction correspondingly. Rotation of the driving wheel  13  and the driven wheel  23  is the same as described. The driving wheel  13  and the driven wheel  23  have different diameters, and the driven wheel  23  rotates one winding after the driving wheel  13  rotates the default number of windings, thus, deceleration is achieved. 
     The deceleration mechanism  100  achieves deceleration using the transmission members  30  coiling around the driven wheel  23  and the driving wheel  13 . There is no need for a gear wheel or other complicated structures, and the manufacturing cost is lower. Windings with a “∝” shape increase the contact length of the transmission member  30 , the driving wheel  13 , and the driven wheel  23 , and increase the friction between the transmission member  30  and the driving wheel  13  and between the transmission member  30  and the driven wheel  23 , respectively. 
     The tension assembly  40  can increase the friction in a transmission process. The first resilient member  43  enables the resisting member  41  to resist the transmission member  30  snugly. The transmission member  30  may loosen, and the elastic force created by the first resilient member  30  can push on the resisting member  41  to resist the transmission member  30 . The resisting surface  411  of the resisting member  41  is curved when the resisting member  41  is fixed to the driven wheel  23 , thus the resisting surface  411  can connect with the outer surface of the driven wheel  23  smoothly, and the transmission member  30  coils substantially on one circumferential surface to generate a constant transmission ratio. 
     In addition, elastic force created by the second resilient member  54  of the fixing assembly  50  helps to maintain the firmness or snugness of the transmission member  30 . When the transmission member  30  loosens, the adjustment member  53  can be used to resist the second resilient member  54  and restore firmness or tightness. 
     Finally, while various embodiments have been described and illustrated, the disclosure is not to be construed as being limited thereto. Various modifications can be made to the embodiments by those skilled in the art without departing from the true spirit and scope of the disclosure as defined by the appended claims.