Patent Publication Number: US-2006016084-A1

Title: Laser-Based datum instrument

Description:
BACKGROUND OF INVENTION  
      1. Field of Invention  
      The present invention relates to a laser-based datum instrument.  
      2. Related Prior Art  
      Referring to  FIG. 8 , a conventional laser-based leveling instrument includes a body  101 , a leveling rod  111  installed on the body  101 , magnets  112  provided at the bottom of the body  101 , an ear  113  formed at an end of the body  101 , an aperture  114  defined in the ear  113 , a laser source  102  provided at an end of the body  101  and a switch  120  installed on the body  101 . Referring to  FIG. 9 , the laser-based leveling instrument is used together with a datum  103 . By means of the leveling rod  111 , the datum  103  is made perfectly horizontal. If the datum  103  is made of steel, the laser-based leveling instrument will be kept on the datum  103  by means of the magnets  112 . The laser source  102  can be turned on by means of the switch  120 . A laser beam is cast onto an object  104  from the laser source  102 . A light spot  121  is cast on the object  104 . A mark can be made on the object  104  where the light spot  12 L is. The body  101  can be rotated on the datum  103  around the aperture  114 . Thus, more light spots are cast onto the object  104  and more marks can be made on the object  104  on a same level. Referring to  FIG. 10 , the laser-based leveling instrument is used together with a stand  105 . A tip of the stand  105  is inserted in a hole  115  defined in the bottom of the body  101 . By means of the leveling rod  111 , the tip of the stand  105  is made perfectly vertical. Thus, the laser beam can scan on a same level. The laser-based leveling instrument involves a complicated and difficult operation because it must be used together with the datum  103  or the stand  105 , and because the datum  103  must be made perfectly horizontal or the tip of the stand  105  must be made perfectly vertical by means of the leveling rod  111 .  
      The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.  
     SUMMARY OF INVENTION  
      According to the present invention, a laser-based datum instrument includes a holder for attachment to an external object. A swinging device is rotationally connected with the holder. At least one laser source is attached to the swinging device. The laser source casts a laser beam for providing a datum line. The rotational connection of the swinging device with the holder and the attachment of the laser source to the swinging device ensure that the laser beam cast by the laser source travels in a pre-determined direction. The operation of the laser-based is simple and easy.  
      Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the attached drawings. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
      The present invention will be described through detailed illustration of the preferred embodiment referring to the drawings.  
       FIG. 1  is a perspective view of a laser-based datum instrument according to the preferred embodiment of the present invention.  
       FIG. 2  is an exploded view of the laser-based datum instrument shown in  FIG. 1 .  
       FIG. 3  is a cross-sectional view of the laser-based datum instrument shown in  FIG. 1 .  
       FIG. 4  is a perspective view of the laser-based datum instrument shown in  FIG. 1  hung on a wall.  
       FIG. 5  is a cross-sectional view of the laser-based datum instrument shown in  FIG. 1  and shows the laser-based datum instrument casting a level datum line.  
       FIG. 6  is similar to  FIG. 5  but shows the laser-based datum instrument in another position and a swinging device in oscillation.  
       FIG. 7  is similar to  FIG. 6  and shows the laser-based datum instrument casting a vertical datum line.  
       FIG. 8  is a perspective view of a conventional laser-based datum instrument.  
       FIG. 9  is a side view of the conventional laser-based datum instrument shown in  FIG. 8  used together with a datum.  
       FIG. 10  is a side view of the conventional laser-based datum instrument shown in  FIG. 8  used together with a stand. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT  
       FIG. 1  shows a laser-based datum instrument according to the preferred embodiment of the present invention.  
      Referring to  FIGS. 2 and 3 , the laser-based datum instrument includes a holder  1 , a swinging device  2  and two laser sources  3 . The holder  1  includes a drum  10  and a plate  20  on which the drum  10  is formed. The drum  10  defines a front space  11  on a front side and a rear space  17  on a rear side. The drum  10  includes a shaft  12  formed on the front side. The shaft  12  includes a passage  13  defined therein. The rear space  17  is used for receiving two batteries  18 . The rear space  17  is communicated with the front space  11  through the passage  13 . The space  17  is closed by means of a rear cover  19 . The drum  10  includes two slots  14  each defined in one side thereof. Each slot  14  includes two ends  15 . The plate  20  is square. The plate  20  includes four apertures  21  each defined in one of the corners thereof.  
      The swinging device  2  includes a rim  30  and a weight  40 . The rim  30  includes a space  31  defined therein and a hub  32  formed in the space  31 . The space  31  includes a square configuration, i.e., it includes four walls and four corners  35 . The hub  32  defines an aperture  33  at the tip. The rim  30  defines two holes  36  on the periphery.  
      The rim  30  is put in the drum  10 . The hub  32  is put around the shaft  12 . A bearing  34  is provided between the hub  32  and the shaft  12 . Thus, the swinging device  2  is rotationally put in the holder  1 .  
      Each laser source  3  is put in a corresponding hole  36  of the rim  30  through a corresponding slot  14  of the drum  10 . Wires  50  are directed from the rear space  17  of the drum  10  to the space  31  of the rim  30  through the passage  13  and the aperture  33 . Power is provided to the laser sources  3  from the batteries  19  through the wires  50 . Thus, each laser source  3  can emit a laser beam. Each laser beam passes through a corresponding slot  14 .  
      The weight  40  is a steel ball put in selective one of the corners  35 . The weight  40  provides a function of stopping oscillation when the swinging device  2  oscillates relative to the holder  1 . The front space  11  of the drum  10  is closed by means of a transparent cover  16 .  
      Although not shown, the holder  1  can be installed a switch (not shown) for controlling the laser source  3  is turned on or off. The switch will not be described in detail for being conventional.  
      Referring  FIGS. 4 and 5 , the laser-based datum instrument is hooked on a hook  4  secured to a wall. The hook  4  is inserted through selective one of the apertures  21  (see  FIG. 2 ). Referring to  FIG. 5 , the laser sources  3  cast laser beams passing in two opposite senses of a horizontal direction, i.e. on a same level so as to form a level (or “horizontal”) datum line.  
       FIG. 6  shows the laser-based datum instrument hung on the wall in oscillation. Each laser source  3  is reciprocating in a related slot  14 . The movement of each laser source  3  is limited between the ends  15  of a related slot  14 , i.e., each laser source  3  is only allowed to move in a small range. Because of the weight  40  rolling in one of the corners  35 , the oscillation of the swinging device  2  relative to the holder  1  will come to an end eventually.  
       FIG. 7  shows the laser-based datum instrument hung on the wall in a still state. The laser sources  3  cast two laser beams in two opposite senses of a vertical direction so as to form a vertical datum line.  
      The present invention has been described through detailed illustration of the preferred embodiment. Those skilled in the art can derive variation from the preferred embodiment without departing from the scope of the present invention. Therefore, the preferred embodiment shall not limit the scope of the present invention defined in the claims.