Abstract:
The invention provides a mounting apparatus with a beam which is free from adverse effect on its performance due to thermal distortion and misalignment of its guide rails, on which the beam for mounting operation travels. One end of the beam is rotatably supported on a slide, which moves along the guide rails. Another end of the beam is also rotatably supported on another slider through a moving element. The slider and the mounting element move along the guide rail. The moving element moves in a direction perpendicular to the guide rails.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention is directed to an electronic component mounting apparatus including a movable beam, which moves along a pair of guide rails formed at both sides of an apparatus base, driven by driving sources located at both sides of the apparatus base, a mounting head capable of moving along the same direction as the beam, and a suction nozzle formed on the mounting head. The suction nozzle picks up an electronic component by vacuum suction and mounts it to a print board. 
   2. Description of the Related Art 
   Ideally, a mounting apparatus has a pair of guide rails, along which a beam moves, at both sides of its apparatus base, which are aligned perfectly parallel. But, in general, deviation from perfect parallel alignment occurs during the assembly. Also, while the guide rail is made of iron, the beam is usually made of aluminum so that the beam is light for high-speed movement. 
   The electronic component mounting apparatus, especially its driving source for beam movement, generates a large amount of heat. Since the thermal expansion differs between iron and aluminum, the heat may cause distortion of the beam shape. This, as well as misalignment of the guide rails, is an adverse influence on the beam movement. There is even a possibility of breaking the guide rail. 
   SUMMARY OF THE INVENTION 
   Therefore, this invention is directed to nullifying such adverse influence on a beam movement for mounting an electronic component. 
   The invention provides an electronic component mounting apparatus, which includes a movable beam for moving along a first guide rail and a second guide rail. The first rail is disposed along a first side of an apparatus base and the second rail is disposed along a second side of the apparatus base. The first side and the second side are approximately parallel to each other. The apparatus also includes a first driving source and a second driving source for driving the movable beam. The first driving source is disposed at the first side and the second driving source is disposed at the second side. The apparatus further includes a mounting head for moving along the movable beam driven by a third driving source. A suction nozzle is disposed on the mounting head. The suction nozzle picks up an electronic component by vacuum suction and mounts the electronic component on a print board. In this configuration, a first end of the movable beam is rotatably supported on the apparatus base, and a second end of the movable beam is rotatably supported on the apparatus base and is movable in a direction approximately perpendicular to the guide rails. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a plan view of the electronic component mounting apparatus of an embodiment of this invention. 
       FIG. 2  is a cross-sectional view of the apparatus of  FIG. 1  cut along line A—A. 
       FIG. 3  is a right side view of the main part of the mounting head of the apparatus of  FIG. 1 . 
       FIG. 4  is a cross-sectional view of the right end of the beam of the apparatus of  FIG. 1 . 
       FIG. 5  shows the bottom surface of the right end portion of the beam and other parts of the beam. 
       FIG. 6  shows the bottom surface of the left end portion of the beam and other parts of the beam. 
   

   DESCRIPTION OF THE INVENTION 
   The embodiment of this invention will be described by referring to the drawings above.  FIG. 1  is a plan view of an electronic component mounting apparatus of an embodiment of this invention.  FIG. 2  shows the cross-sectional view cut along A—A line in  FIG. 1 . At both front and back sides of a base  2  of the electronic component mounting apparatus  1 , a plurality of component supply units (not shown), which supply various kinds of electronic components one by one to a component pick-up portion (component suction position), are provided. Also, in the middle of the mounting apparatus  1 , a supply conveyer  3 , a positioning portion  4 , and an exhausting conveyer  5  are formed so that a print board P moves in a lateral direction. The supply conveyer  3  receives the print board P from the upper stream and sends it to the positioning portion  4 . The positioning portion  4  positions the print board P by using the positioning mechanism (not shown). Then, after the mounting of the electronic component, the print board P is sent to the exhausting conveyer  5 . 
   Reference numeral  6  denotes a beam extending in the X-direction. The beam  6  moves above the print board P on the positioning portion  4  and the component pick-up portion (component suction position) of the component supply unit along a pair of guide rails  8 . The guides rails  8  are provided at right and left sides of the base  2 . The beam  6  is driven by a pair of linear motors  7  located at right and left sides of the bases. These motors form a Y-axis driving source. 
   The base  2  comprises a main base  2 A and a pair of vertical blocks  2 B at its right and left sides. At the upper portion of each vertical block  2 B, a guide rail  8 , along which a slider  9  moves, and a pair of magnet bases  11 , which horizontally extend in the longitudinal direction, are provided. The linear motor  7  has a pair of fixed elements  13  located at its right and left sides, which includes a magnet base  11  and a magnet  12 . The motor  7  also includes a movable element  14  fixed on the slider  9  with a small space between the movable element  14  and the fixed element  13 . 
   As shown in  FIG. 3 , the beam  6  has head placing components  22 ,  22 , which move in the X-direction along the guide rails  21  located at its upper and lower sides, driven by a linear motor  20 . On the head placing components  22 ,  22 , mounting heads  23 ,  23 , which move up and down along guides  25 ,  25  by each of the vertical axis motors  24 ,  24 , are formed. Each of nozzle placing components  26 ,  26  of the mounting head  23 ,  23 , has  6  suction nozzles  27 , which are spaced with an equal angle. Each of the nozzle mounting components  26 ,  26  rotates around the vertical axis by θ-axis motors  28 ,  28 . Additionally, a nozzle selecting motor  29  arbitrarily selects one of the six suction nozzles  27 . Then, the sucking part of the selected suction nozzle  27  faces downwards (facing an upper part of the component to be picked up) so that the suction nozzle picks up the electronic component by vacuum suction for mounting. 
   Therefore, each of the suction nozzles  27  of two mounting heads  23 ,  23  can move in both the X and Y directions, rotate around a vertical axis, and also move vertically. 
   As seen in  FIGS. 2 and 4 , a pair of guide rails  21  located above and under the beam  6  are provided at the front side of the beam  6 , which has a U-shape cross-section. Also, sliders  31 , which move along the rail  21 , are provided at the backside of the head placing components  22 ,  22 . A pair of magnet bases  32 , which horizontally extend in a lateral direction and are located at upper and lower sides, is provided in the guide rail  21  formed at the front side of the beam  6 . The linear motor  20  has a pair of fixed elements  34  including a magnet base  32  and a magnet  33 , located at its right and left sides and a movable element  35  fixed at the backside of the head placing components  22 ,  22 . There is a small space between the movable element  35  and the fixed element  34 . 
   Also, as shown in  FIG. 4 , at the bottom of the right portion of the beam  6 , a tube element  40 , with a convex shape, is fixed with a bolt  41 . A round the tube element  40 , a supporting element  43  is provided with a bearing  42  fixed with a stopper board  48  and a bolt  49 . Therefore, the tube element  40  and the beam  6  are rotatably supported by the supporting element  43  through the bearing  42 . 
   Also, each of guide elements  45  is fixed to the slider  9 , which can move in the longitudinal direction (the Y-direction). Each of the moving elements  47 , which move along the guide element  45  through a ball  46 , is fixed on the bottom of the supporting element  43  at its front and rear portions. Therefore, when the linear motor  7  operates, the slider  9  moves along the guide rail  8 , and the guide element  45 , fixed on the slider  9 , also moves. 
   As the bottom surface of the left portion of the beam of  FIG. 6  shows, at the bottom of the left portion of the beam (likewise at the right portion of the beam), the converse shaped tube element  40  is fixed with the bolt  41 . Around the tube element  40 , the supporting element  43  is provided with the bearing  42  fixed with the stopper board  48  and the bolt  49 . Therefore, the tube element  40  and the beam  6  are rotatably supported by the supporting element  43  through the bearing  42 . 
   The supporting element  43  is fixed on the slider  9 , which can move in a longitudinal direction. 
   Additionally, as shown in  FIG. 3 , flat cables  50 ,  50  are provided by arranging the cables and air tubes for the mounting heads  23 ,  23  in a row and bundling them with an adhesive. Also, one end of the flat cables  50 ,  50  is connected to the motors  24 ,  28 ,  29  and the mounting heads  23 ,  23 , and the other end is connected to a controlling circuit substrate (not shown) and an air supply source (not shown). As seen in  FIG. 3 , the flat cables  50 ,  50  are retained in the condition described above with a fixing portion  51 . That is, the flat cables  50 ,  50  are sandwiched between flat boards  52 , and placed at the rear portion of the head placing components  22 ,  22 , which are mounted on the beam  6  through a bush  53 , using a screw  54 . 
   Then, as shown in  FIGS. 2 and 3 , the flat cables  50 ,  50 , are bent to be connected to the mounting head. The flat cables  50 ,  50  are mounted on a supporting portion  55  having an approximately U-shaped cross-section. The supporting portion is placed on the bottom part of the front side of the beam  6  along the beam  6  so that the flat cables  50 ,  50  will not extend fully when the head placing components  22 ,  22  move in a lateral direction. Furthermore, the flat cables  50 ,  50  are bent outwardly and disposed at a lower part of the supporting portion  55 . 
   A cable-veyer  56  comprises a plurality of connectable pieces connected to each other, which can rotate in a certain range. The cable-veyer  56  holds the flat cables  50 ,  50  so that the flat cables  50 ,  50  are bendable. The upper portion of the cable-veyer  56  is fixed at the lower part of a bracket  57  fixed at the bottom portion of the head placing components  22 ,  22 . A bottom portion of the cable-veyer  56  is fixed at the vertical block  2 B of the base  2  with fixing equipment. That is, the cable-veyer  56  holds the flat cables  50 ,  50  so that the flat cables  50 ,  50  can bend and extend above the area where the supply conveyer  3  and the exhausting conveyer  5  transport the print board P. 
   Next, the operation of the mounting apparatus with above configuration will be described. First, the print board P is sent from the upper stream apparatus (not shown) to the positioning portion  4  through the supply conveyer  3 . Then, the print board P is positioned by the positioning mechanism (not shown). 
   Next, according to the mounting data stored in a memory apparatus (not shown) regarding X and Y coordinates, rotating angles of the print board P, and location numbers of the component supply units, the suction nozzle  27 , suitable for the type of electronic component selected, picks up the electronic component by suction from the component supply unit. This is done in accordance with the mounting order. 
   That is, the beam  6  moves along the guide rail  8  in the Y-direction, driven by the linear motor  7 . The mounting heads  23 ,  23  move in the X-direction, driven by the linear motor  20 , without corrosion and continuously move to a space above the component supply unit that stores the electronic component to be picked up. 
   At this point, the supply unit has already moved so that the component can be picked up at the component suction position. Thus, the suction nozzle  27 , selected by the selection motor  29  of one of the mounting heads  23  goes down, driven by the vertical axis motor  24 , for picking up the electronic component by suction. Then this suction nozzle  27  goes up and the suction nozzle  27  of the other mounting head  23  moves to a space above the component supply unit which stores the electronic component to be picked up next. Likewise, this suction nozzle  27  goes down to pick up the electronic component by suction. 
   Then, as described before, the mounting heads  23 ,  23  move horizontally to the space above the print board P on the positioning portion  4 . Then, and each of the suction nozzles  27 ,  27  of each of the mounting heads  23 ,  23  lowers to mount the electronic component on the print board P. 
   As described above, since the beam  6  is moved by the linear motor  7  along the guide rail  8  to move the mounting heads  23 ,  23  and the suction nozzles  27 ,  27  in the Y-direction, the linear motor  7  generates heat. 
   Because thermal expansion differs between the guide rail  8 , which is made of iron, and the slider  9 , which is made of aluminum, the shape of the beam  6  may be distorted. In the conventional mounting apparatus, distortion of beam shape has an adverse influence on the movement of the beam along guide rails  8 . This adverse influence may be reinforced by the misalignment of the guide rails  8 , which are not placed completely parallel. In the worst case, the guide rail and the slider may break. 
   However, according to the embodiment, the supporting element  43 , fixed on the slider  9 , supports the left end of the beam  6  so that the tube element  40  can rotate on the bearing  42 . 
   The supporting element  43  is fixed on the moving element  47  supports the right end of the beam so that the tube element  40  can rotate by the bearing  42 . Also, each of the moving elements  47  moves along the guide element  45  fixed on the slider  9  through the ball  46  in the direction perpendicular to the guide rail  8  (the X-direction). Thus, the supporting element  43  and the beam  6  can accommodate the misalignment of the guide rails  8 , which have not been placed completely parallel during assembly. 
   The above is a detailed description of the particular embodiment of the invention which is not intended to limit the invention to the embodiment described. It is recognized that modifications within the scope of the invention will occur to a person skilled in the art. Such modifications and equivalents of the invention are intended for inclusion within the scope of this invention.