Abstract:
An electronic-parts mounting apparatus includes an electronic-parts feeder. A mounting head operates for carrying electronic parts from the electronic-parts feeder. The mounting head includes a plurality of nozzles for holding the electronic parts respectively. An electronic-parts mounting portion operates for enabling the mounting head to mount the electronic parts on a circuit board. A first mechanism operates for rotating each of the nozzles. A second mechanism operates for moving each of the nozzles upward and downward. The first mechanism may include a pinion provided on an outer circumferential surface of each of the nozzles, and a rack meshing with the pinion.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an apparatus for automatically mounting electronic parts on a printed circuit board. 
     2. Description of the Related Art 
     A known electronic-parts mounting apparatus includes an electronic-parts feeder, a mounting head, and a mounting portion. A printed circuit board is placed in position within the mounting portion. The mounting head carries electronic components (electronic parts) from the electronic-parts feeder to the mounting portion, and mounts the electronic components on the printed circuit board. The mounting portion is provided with an XY table for moving the printed circuit board in two perpendicular directions on a horizontal plane. The XY table is rotatable. 
     In the known electronic-parts mounting apparatus, the XY table is rotated from a normal position when the actual posture of an electronic component held by the mounting head differs from a desired posture, or when an electronic component is required to be obliquely mounted on the printed circuit board. Specifically, in the case where the actual posture of an electronic component held by the mounting head differs from a desired posture, the electronic component is carried to a place above the printed circuit board in the mounting portion while the actual posture thereof remains different from the desired posture. The XY table is rotated from its normal position to compensate for the error in the posture of the electronic component held by the mounting head. Then, the mounting head is lowered toward the printed circuit board, and the electronic component is mounted thereon by the mounting head. 
     The postural error compensation using rotation of the XY table causes a long mounting time to be spent per electronic component. The reason for the long mounting time is as follows. The XY table is large and heavy. Therefore, the time interval between the moment of start of rotation of the XY table and the moment of stop thereof is relatively long. After the stop of rotation of the XY table has been completed, the mounting head commences to be lowered toward the printed circuit board. Accordingly, the known electronic-parts mounting apparatus tends to be low in mounting speed or rate. 
     SUMMARY OF THE INVENTION 
     It is an object of this invention to provide an electronic-parts mounting apparatus having a high mounting speed or rate. 
     A first aspect of this invention provides an electronic-parts mounting apparatus comprising an electronic-parts feeder; a mounting head for carrying electronic parts from the electronic-parts feeder, the mounting head including a plurality of nozzles for holding the electronic parts respectively; an electronic-parts mounting portion for enabling the mounting head to mount the electronic parts on a circuit board; first means for rotating each of the nozzles; and second means for moving each of the nozzles upward and downward. 
     A second aspect of this invention is based on the first aspect thereof, and provides an electronic-parts mounting apparatus wherein the first means includes a pinion provided on an outer circumferential surface of each of the nozzles, and a rack meshing with the pinion. 
     A third aspect of this invention is based on the second aspect thereof, and provides an electronic-parts mounting apparatus wherein the rack includes a first rack plate, a second rack plate slidably superposed on the first rack plate, and means for urging the second rack plate relative to the first rack plate in a direction parallel to the first rack plate. 
     A fourth aspect of this invention is based on the third aspect thereof, and provides an electronic-parts mounting apparatus further comprising third means for urging each of the nozzles in a direction of rotation of the nozzle. 
     A fifth aspect of this invention is based on the second aspect thereof, and provides an electronic-parts mounting apparatus wherein positions of the nozzles correspond to integer multiples of a pitch of teeth of the rack respectively. 
     A sixth aspect of this invention is based on the first aspect thereof, and provides an electronic-parts mounting apparatus wherein each of the nozzles includes an outer cylinder, a holder, means for rotatably supporting the outer cylinder on the holder, an inner cylinder extending into the outer cylinder and being movable upward and downward relative to the outer cylinder, a pinion provided on the outer cylinder, and further comprising a rack meshing with the pinion, and means for supporting the rack slidably on the holder. 
     A seventh aspect of this invention is based on the sixth aspect thereof, and provides an electronic-parts mounting apparatus wherein each of the nozzles includes a coil spring provided between the outer cylinder and the holder. 
     An eighth aspect of this invention is based on the first aspect thereof, and provides an electronic-parts mounting apparatus wherein the second means includes a fluid-operated actuator having a piston in engagement with an upper end of each of the nozzles. 
     A ninth aspect of this invention is based on the eighth aspect thereof, and provides an electronic-parts mounting apparatus further comprising a limiting plate engageable with a lower end of the piston for determining a lower limit position of the piston, a first spring for urging the piston downward, and a second spring for urging the nozzle upward. 
     A tenth aspect of this invention provides an electronic-parts mounting apparatus comprising an electronic-parts feeder; a mounting head for carrying electronic parts from the electronic-parts feeder, the mounting head including a plurality of nozzles for holding the electronic parts respectively; an electronic-parts mounting portion for enabling the mounting head to mount the electronic parts on a circuit board; first means for rotating each of the nozzles; a fluid-operated actuator for moving each of the nozzles upward and downward, the fluid-operated actuator having a piston in engagement with an upper end of each of the nozzles; a limiting plate engageable with a lower end of the piston for determining a lower limit position of the piston; a first spring for urging the piston downward; a second spring for urging the nozzle upward; and second means for moving the limiting plate upward and downward. 
     An eleventh aspect of this invention provides an electronic-parts mounting apparatus comprising an electronic-parts feeder; a mounting head for carrying electronic parts from the electronic-parts feeder, the mounting head including a plurality of nozzles for holding the electronic parts respectively; an electronic-parts mounting portion for enabling the mounting head to mount the electronic parts on circuit board; first means for rotating each of the nozzles; a fluid-operated actuator for moving each of the nozzles upward and downward, the fluid-operated actuator having a piston in engagement with an upper end of each of the nozzles, a limiting plate engageable with a lower end of the piston for determining a lower limit position of the piston; a first spring for urging the piston downward; a second spring for urging the nozzle upward; second means for detecting heights of the electronic parts held by the nozzles; and third means for moving the limiting plate upward and downward in response to the heights detected by the second means. 
     A twelfth aspect of this invention is based on the eighth aspect thereof, and provides an electronic-parts mounting apparatus wherein the second means includes a bearing for rotatably connecting the piston and the upper end of each of the nozzles. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an electronic-parts mounting apparatus according to. first embodiment of this invention. 
     FIG. 2 is a top view of the electronic-parts mounting apparatus in FIG.  1 . 
     FIG. 3 is a front view of the electronic-parts mounting apparatus in FIG.  1 . 
     FIG. 4 is a perspective view of a mounting head in FIG. 1 with a portion broken away for the sake of clarity. 
     FIG. 5 is a front view of the mounting head in FIG.  4 . 
     FIG. 6 is a sectional view of a sucking nozzle in FIGS. 4 and 5. 
     FIG. 7 is a plan view of a rack and pinions in FIG.  4 . 
     FIG. 8 is a sectional view of the rack in FIG.  7 . 
     FIG. 9 is a top view of the rack in FIG.  7 . 
     FIG. 10 is a front view of the mounting head in FIG.  4 . 
     FIG. 11 is a sectional view of the mounting head in FIG.  10 . 
     FIG. 12 is a sectional view of the mounting head in FIG. 10 in which a nozzle assumes a higher position. 
     FIG. 13 is a sectional view of the mounting head in FIG. 10 in which the nozzle assumes a lower position. 
     FIG. 14 is a front view of a cam and an intermediate plate in the mounting head in FIG. 4 where the cam assumes a first limit position. 
     FIG. 15 is a front view of the cam and the intermediate plate in the mounting head in FIG. 4 where the cam assumes a second limit position. 
     FIG. 16 is a block diagram of an electric portion of the electronic-parts mounting apparatus in FIG.  1 . 
     FIG. 17 is a sectional view of a portion of a mounting head in an electronic-parts mounting apparatus according to second embodiment of this invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     With reference to FIGS. 1,  2 , and  3 , an electronic-parts mounting apparatus in a first embodiment of this invention includes a main body  1  being a metal frame. An electronic-parts mounting portion  2  is provided on a central part of the main body  1 . Electronic-parts feeders  3  and  4  are supported on the main body  1 . The electronic-parts feeders  3  and  4  extend at the left and the right of the electronic-parts mounting portion  2  respectively. 
     Mounting heads  5  and  6  are movably supported on the main body  1 . The mounting head  5  serves to carry electronic components (electronic parts) from the electronic-parts feeder  3  to the electronic-parts mounting portion  2 . The mounting head  6  serves to carry electronic components (electronic parts) from the electronic-parts feeder  4  to the electronic-parts mounting portion  2 . The electronic-parts mounting portion  2  is provided with a Y table  7 . The Y table  7  can move relative to the main body  1  in a horizontal direction, that is, a Y direction. A printed circuit board is placed on the Y table  7 . 
     The electronic-parts feeder  3  includes taping reels  8  from which electronic components (electronic parts) are fed to the mounting head  5 . The electronic-parts feeder  4  includes cassettes  9  from which electronic components (electronic parts) are fed to the mounting head  6 . 
     The mounting heads  5  and  6  have similar structures. Therefore, only the mounting head  5  will be explained in detail. As shown in FIGS. 4 and 5, the mounting head  5  includes ten sucking nozzles  10  arranged in a line. Also, the mounting head  5  includes a motor  11  for circumferentially rotating the sucking nozzles  10 . Furthermore, the mounting head  5  includes a motor  12  for controlling the lower limit of vertical displacements of the sucking nozzles  10 . 
     As shown in FIG. 6, each sucking nozzle  10  includes an outer cylinder (an outer sleeve)  13  and an inner cylinder (an inner sleeve)  14 . The inner cylinder  14  coaxially extends into the outer cylinder  13  via an upper end thereof. The outer cylinder  13  and the inner cylinder  14  are connected via a suitable coupling such as a pin-slit coupling or a key coupling which allows the inner cylinder  14  to circumferentially rotate together with the outer cylinder  13 , and to axially slide relative to the outer cylinder  13 . The outer cylinder  13  is rotatably supported on a holder  15  by upper and lower bearings  16 . The outer cylinder  13  is allowed to rotate in a circumferential direction. An upper end of the outer cylinder  13  is formed with a pinion  17 . The pinion  17  meshes with a rack  18 . The rack  18  is slidably supported by the holder  15 . 
     As shown in FIGS. 7,  8 , and  9 , the rack  18  includes upper and lower plates  19  and  20  both formed with teeth. The upper plate  19  is superposed on the lower plate  20 . The lower plate  20  can move relative to the holder  15  in a horizontal direction. The upper plate  19  is thinner than the lower plate  20 . The upper plate  19  can slide horizontally relative to the lower plate  20 . 
     As best shown in FIGS. 7 and 8, the upper plate  19  has holes  21  through which pins  22  extend respectively. The pins  22  are fixed to the lower plate  20 . The inside dimensions of the holes  21  are set greater than the outside dimensions of the pins  22  to allow leftward and rightward horizontal slide of the upper plate  19  relative to the lower plate  20 . 
     As best shown in FIG. 8, an arm  23  is fixed to one end of the lower plate  19 . One end of a spring  24  engages the arm  23  while the other end of the spring  24  abuts against one end of the upper plate  19 . The spring  24  urges the upper plate  19  rightward as viewed in FIGS. 7,  8 , and  9 . 
     As shown in FIGS. 4,  7 , and  8 , a pinion  25  meshes with the teeth of the upper plate  19  and also the teeth of the lower plate  20 . As best shown in FIG. 7, the spring  24  presses a tooth  27  of the upper plate  19  against the left side of a tooth  26  of the pinion  25 , thereby pressing the right side of the tooth  26  of the pinion  25  against a tooth  28  of the lower plate  20 . Therefore, the tooth  26  of the pinion  25  is firmly held between the tooth  27  of the upper plate  19  and the tooth  28  of the lower plate  20 . Thus, the mesh between the rack  18  (including the upper plate  19  and the lower plate  20 ) and the pinion  25  is free from backlash. 
     The pinion  25  is mounted on an output shaft of the motor  11 . The pinion  25  rotates in accordance with rotation of the output shaft of the motor  11 . As previously indicated, the pinion  25  meshes with the rack  18 . The rack  18  moves rightward and leftward in accordance with rotation of the pinion  25 . Accordingly, the rack  18  is moved horizontally by the motor  11 . 
     With reference back to FIG. 6, a helical spring (a coil spring)  29  extends around the outer cylinder  13  of the sucking nozzle  10 . One end of the spring  29  is fixed to the holder  15  while the other end thereof is attached to the outer cylinder  13 . As previously indicated, the outer cylinder  13  is formed with the pinion  17  which meshes with the rack  18 . As shown in FIGS. 6 and 7, the spring  29  urges the outer cylinder  13  circumferentially relative to the holder  15  so that a side of a tooth  30  of the pinion  17  is pressed against a tooth  28  of the rack  18 . Thus, the mesh between the rack  18  and the pinion  17  is free from backlash. 
     The pinion  17  rotates as the rack  18  moves horizontally. Accordingly, the outer cylinder  13  rotates in accordance with horizontal movement of the rack  18 . Since the rack  18  can be moved horizontally by the motor  1 , the outer cylinder  13  can be rotated by the motor  11 . A working portion (a lower portion) of the sucking nozzle  10  is connected by a suitable coupling such as a pin-slit coupling or a key coupling to the outer cylinder  13  so that the working portion of the sucking nozzle  10  will rotate circumferentially together with the outer cylinder  13  while being able to move vertically relative to the outer cylinder  13 . The working portion of the sucking nozzle  10  operates to suck and hold an electronic component. The electronic component held by the working portion of the sucking nozzle  10  can be rotated by the motor  11 . 
     The ten sucking nozzles  10  are arranged at equal intervals chosen so that the pinions  17  on the sucking nozzles  10  will be equal to each other in teeth phase (angular teeth position) with respect to the teeth of the rack  18 . For example, the positions of the sucking nozzles  10  correspond to integer multiples of the pitch of the teeth of the rack  18  respectively. Thus, the angular positions of the ten sucking nozzles  10  are equal to each other. The angular positions of the sucking nozzles  10  vary equally (or in synchronization) in accordance with horizontal movement of the rack  18 , that is, in accordance with rotation of the pinion  25 . 
     As shown in FIG. 6, the inner cylinder  14  extends into the outer cylinder  13  via an upper end of the outer cylinder  13 . The inner cylinder  14  can slide axially relative to the outer cylinder  13 . In other words, the inner cylinder  14  can move upward and downward relative to the outer cylinder  13 . The working portion (the lower portion) of the sucking nozzle  10  is connected to or integral with the inner cylinder  14  so that the working portion of the sucking nozzle  10  can move and rotate together with the inner cylinder  14 . 
     One of the ten sucking nozzles  10  will be further explained. As shown in FIGS. 10 and 11, an upper end of the inner cylinder  14  contacts a large-diameter lower end  32  of an actuator piston  31 . The actuator piston  31  slidably extends into an actuator cylinder  33 . The actuator piston  31  can move axially relative to the actuator cylinder  33 . In other words, the actuator piston  31  can move upward and downward relative to the actuator cylinder  33 . A spring  34  is provided between an upper end of the outer cylinder  13  and a flange on the inner cylinder  14 . The spring  34  urges the inner cylinder  14  upward relative to the outer cylinder  13 . A spring  35  disposed in the actuator cylinder  33  extends between an upper wall of the actuator cylinder  33  and an upper end of the actuator piston  31 . The spring  35  urges the actuator piston  31  downward relative to the actuator cylinder  33 . The springs  34  and  35  bring the upper end of the inner cylinder  14  and the large-diameter lower end  32  of the actuator piston  31  into contact with each other. 
     Working fluid such as air can be supplied to and drawn from a working chamber within the actuator cylinder  33  which extends above the actuator piston  31 . As the working fluid is supplied to the working chamber within the actuator cylinder  33 , the actuator piston  31  is moved downward. As the working fluid is drawn from the working chamber within the actuator cylinder  33 , the actuator piston  31  is moved upward. 
     With reference to FIGS. 4 and 11, the large-diameter lower end  32  of the actuator piston  31  can meet a limiting plate  36 . The limiting plate  36  has ten semicircular recesses  37  which correspond to the ten sucking nozzles  10  respectively. The inner cylinder  14  movably extends through the corresponding recess  37  in the limiting plate  36 . As the working fluid is supplied to the working chamber within the actuator cylinder  33 , the actuator piston  31  is moved downward until the large-diameter lower end  32  thereof meets the limiting plate  36 . In other words, downward movement of the actuator piston  31  is stopped by the limiting plate  36 . Thus, the limiting plate  36  determines the lower limit position of the actuator piston  31 . Also, the limiting plate  36  determines the lower limit position of the working portion of the sucking nozzle  10 . In the case where the large-diameter lower end  32  of the actuator piston  31  reaches the limiting plate  36 , the piston  32  remains in its lower limit position even if the working fluid is further supplied to the working chamber within the actuator cylinder  33 . As will be made clear later, the lower limit position of the piston  32  is variable or movable. 
     The limiting plate  36  can move upward and downward. In the case where the working fluid is supplied to the working chamber within the actuator cylinder  33  so that the large-diameter lower end  32  of the actuator piston  31  is in contact with the limiting plate  36 , as the limiting plate  36  moves upward and downward, the actuator piston  31  and the inner cylinder  14  move upward and downward while the large-diameter lower end  32  of the actuator piston  31  remains in contact with the limiting plate  36  and also the upper end of the inner cylinder  14  (see FIGS.  12  and  13 ). Thus, in this case, the inner cylinder  14  moves upward and downward in accordance with the movement of the limiting plate  36 . The working portion of the sucking nozzle  10  is connected to the inner cylinder  14  so as to move upward and downward in accordance with the movement of the inner cylinder  14 . The downward movement of the working portion of the sucking nozzle  10  is used in access to an electronic component  38  as follows. After the working portion of the sucking nozzle  10  reaches the electronic component  38  according to the downward movement thereof, a lower end of the sucking nozzle  10  sucks and picks up the electronic component  38 . Then, the working portion of the sucking nozzle  10  moves upward while holding the electronic component  38  (see FIGS.  12  and  13 ). During the downward movement of the working portion of the sucking nozzle  10  in accordance with the downward movement of the limiting plate  36 , the large-diameter lower end  32  of the actuator piston  31  remains in contact with the limiting plate  36  and also the upper end of the inner cylinder  14  so that unwanted vibration or unwanted sound is prevented from occurring. 
     As shown in FIGS. 4,  14 , and  15 , the limiting plate  36  is fixed to an intermediate plate  39  on which two rollers  40  are rotatably mounted. The two rollers  40  are vertically spaced from each other by a predetermined interval. An effective portion of a rotatable cam  41  is sandwiched between the rollers  40 . The cam  41  is connected to an output shaft of the motor  12  so that the cam  41  can be rotated by the motor  12 . The cam  41  is designed so that rotation of the cam  41  will move the intermediate plate  39  upward and downward. The limiting plate  36  moves upward and downward together with the intermediate plate  39 . Thus, the limiting plate  36  is moved upward and downward by the motor  12 . 
     The operation of the mounting head  6  will be further explained. The mounting head  6  is placed above the electronic-parts feeder  4 . In the mounting head  6 , the limiting plate  36  is moved downward by the motor  12 . The working portion (the lower portion) of the sucking nozzle  10  is moved downward to access an electronic component  38  in the corresponding cassette  9  of the electronic-parts feeder  4  in accordance with the movement of the limiting plate  36 . Then, the lower end of the sucking nozzle  10  sucks an electronic component  38  from the corresponding cassette  9  (see FIGS.  11  and  13 ). Subsequently, the cam  41  is rotated by the motor  12  from the position shown in FIG. 15 to the position shown in FIG. 14 so that the working portion of the sucking nozzle  10  moves upward while the lower end of the sucking nozzle  10  continues to hold the electronic component  38 . In this way, the sucking nozzle  10  picks up the electronic component  38 . Then, the mounting head  6  is moved (leftward as viewed in FIG. 1) by a suitable drive mechanism to the electronic-parts mounting portion  2  along a carry path. 
     When the mounting head  6  is moved along the carry path, an image sensor or a camera  42  located below the carry path takes an image of the electronic component  38  held by the sucking nozzle  10 . As shown in FIG. 16, the image sensor  42  is electrically connected to a controller  44  including a CPU (central processing unit). When the mounting head  6  is moved along the carry path, a height sensor  43  located near the carry path detects the height of the electronic component  38  held by the sucking nozzle  10 . As shown in FIG. 16, the height sensor  43  is electrically connected to the controller  44 . In addition, the motors  11  and  12  are electrically connected to the controller  44 . Furthermore, a memory  45  is electrically connected to the controller  44 . The memory  45  stores data representing a desired posture of an electronic component held by each sucking nozzle  10 . The desired posture of the electronic component includes a desired tilt or inclination of the electronic component, and a desired angle thereof. The controller  44  drives the motors  11  and  12  in response to output signals of the image sensor  42  and the height sensor  43  and output data from the memory  45  according to a program stored in a ROM within the CPU. The program is designed to implement the following processes. 
     The controller  44  calculates the actual posture of the electronic component  38  held by the sucking nozzle  10  in response to the output signal of the image sensor  42 . The controller  44  collates the calculated actual posture with the desired posture represented by the output data from the memory  45 , and thereby calculates a postural error of the electronic component  38  held by the sucking nozzle  10 . The calculated postural error includes a calculated angular error. The controller  44  drives the motor  11  in response to the calculated angular error of the electronic component  38  held by the sucking nozzle  10 . As the motor  11  is driven, the outer cylinder  13  is rotated and hence the electronic component  38  held by the sucking nozzle  10  is also rotated. The rotation of the electronic component  38  corrects the angular error thereof. Accordingly, the actual posture of the electronic component  38  held by the sucking nozzle  10  is corrected into agreement with the desired posture thereof. 
     The mounting head  6  carries electronic components to the electronic-parts mounting portion  2 , and then mounts them on a printed circuit board placed on the Y table  7 . Since angular errors of the electronic components are corrected as indicated above, they can be accurately mounted on the printed circuit board. 
     When the mounting head  6  carries the electronic component  38  toward the electronic-parts mounting portion  2 , the controller  44  derives the height of the electronic component  38  held by the sucking nozzle  10  from the output signal of the height sensor  43 . The controller  44  drives the motor  12  in response to the derived height of the electronic component  38 . As the motor  12  is driven, the limiting plate  36  is moved vertically. The vertical movement of the limiting plate  36  is designed so as to prevent the sucking nozzle  10  from excessively pressing the electronic component  38  against the printed circuit board during the electronic-parts mounting process. It should be noted that the limiting plate  36  determines the lower limit position of the working portion of the sucking nozzle  10 . 
     The memory  45  may store data representing the height of electronic components. The controller  44  may drive the motor  12  in response to the height data fed from the memory  45 . 
     Second Embodiment 
     FIG. 17 shows a second embodiment of this invention which is similar to the first embodiment thereof except for the following design change. A large-diameter lower end  32  of each actuator piston  31  is provided with a bearing  46  via which an upper end of an inner cylinder  14  is associated or connected with the actuator piston  31 . The bearing  46  allows circumferential rotation of the inner cylinder  14  relative to the actuator piston  31 . Therefore, when the inner cylinder  14  rotates, the bearing  46  prevents rotation of the actuator piston  31  which might damage a combination of the actuator piston  31  and an actuator cylinder  33 .