Abstract:
A positioning assembly using a pair of rollers elastically connected to a holding base for clamping two cutters received in the holding base. The cutters in the holding base can be adjusted to make different blades contact and align precisely.

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to positioning assemblies and, particularly, to positioning assemblies capable of aligning blades of a lens trimmer. 
     2. Description of Related Art 
     Generally, many plastic injection products, e.g., plastic lenses, need to be separated. A trimmer typically used includes two cutters. The blades of the cutters are aligned so that when the two cutters move towards and engage each other the plastic injection products can be separated by cutting. However, such alignment is often carried out manually by an operator. Thus, the accuracy of the alignment can be less than satisfactory. 
     Therefore, it is desirable to provide a positioning assembly which can overcome the limitations described. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURE 
         FIG. 1  is an exploded, isometric view of an exemplary embodiment of a positioning assembly. 
         FIG. 2  is an assembled, isometric view of the positioning assembly of  FIG. 1 . 
         FIG. 3  is an assembled, isometric view of the positioning assembly of  FIG. 1 , showing the positioning assembly clamps two cutters. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1 and 2 , a positioning assembly  1 , according to an exemplary embodiment, includes a holding base  10 , and a clamping unit  12 . 
     The holding base  10  includes a bottom board  100 , a pair of parallel sidewalls  102 , and a number of fixing protrusions  106 . The bottom board  100  is generally rectangular and includes an upper surface  100   a , a bottom surface  100   b  opposite to the upper surface  100   a , and a pair of parallel edges  100   c . The sidewalls  102  extend perpendicularly from the upper surface  100   a  at the opposite edges  100   c  respectively. The bottom board  100  and the sidewalls  102  cooperatively define a receiving space  101  with two opposite open portions  10   a  for accommodating the clamping unit  12 . 
     Each of the sidewalls  102  defines two through holes  104 . The through holes  104  are spaced a same distance from the upper surface  100   a  and are elongated elliptical. The major axis of the through holes  104  is substantially perpendicular to the upper surface  100   a.    
     Each sidewall  102  includes an inner surface  102   a  and an outer surface  102   b . Each of the fixing protrusions  106  extends perpendicularly from the outer surface  102   b  and is arranged between the respective through holes  104  and the bottom surface  100   b . Each fixing protrusion  106  includes a connecting post  106   a  and a first positioning flange  106   b . The connecting post  106   a  extends from the outer surface  102   b . The first positioning flange  106   b  extends outwards from a distal end of the connecting post  106   a  and is spaced apart from the outer surface  102   b.    
     The clamping unit  12  includes a pair of rollers  120 , a number of bolts  122 , and a number of elastic elements  124 . The roller  120  is elongated and circular and includes a pair of parallel end surfaces  120   a . The roller  120  defines a threaded hole  120   b  in the center of each end surface  120   a . Each bolt  122  includes a threaded post  122   a  and a second positioning flange  122   b . The threaded post  122   a  includes a threaded end  122   c . The positioning flange  122   b  extends from the periphery of the other end of the threaded post  122   a  opposite to the threaded end  122   c . The elastic element  124  includes two opposite ends  124   a . In this embodiment, four bolts  122  and four elastic elements  124  are employed. Each of the elastic elements  124  is an elastic rubber belt. 
     In assembly, the rollers  120  are disposed in the receiving space  101  so that the threaded holes  120   b  are correspondingly aligned with the through holes  104 . Each threaded end  122   c  of the bolts  122   a  passes through a corresponding through hole  104  and screws into a corresponding threaded hole  120   b . Two opposite ends  124   a  of each elastic element  124  are connected to the threaded post  122   a  and the connecting post  106   a . The elastic elements  124  are stretched for applying a force onto the rollers  120  in a direction toward the bottom board  100 . Thus, the rollers  120  are biased against the upper surface  100   a  by the elastic elements  124 . 
     Also referring to  FIG. 3 , in use, the positioning assembly  1  aligns the blades of two cutters  2 . Each cutter  2  includes a blade  20  and defines an assembly hole  22  along a major axis of the blades  20 . The cutters  2  are received in the receiving space  101  and the blades  20  face each other. The cutters are interleaved between the rollers and the upper surface so that the rollers  120  press the cutters  2  on the upper surface  100   a  via the restoring force of the elastic elements  124 . The cutters  2  are adjusted such that blades  20  contact each other and the assembly holes  22  stay out of the receiving space  101 . The cutters  2  can be attached to a lens trimmer (not shown) with the blades  20  aligned precisely. 
     While various exemplary and preferred embodiments have been described, it is to be understood that the invention is not limited thereto. To the contrary, various modifications and similar arrangements (as would be apparent to those skilled in the art) are intended to also be covered. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.