Abstract:
A transmission mechanism includes a pressing stroke controller for changing the effective pressing stroke of each feed lever of a component feeder unit corresponding to a predetermined pitch of carrying electronic components in respective component feeder unit, whereby the vibration generated when the transmission mechanism is in operation is reduced. Adverse effects on a component feeder unit having small components thereon at a fine pitch which is susceptible to the vibration will be prevented, and the feeding speed can be increased to be more productive.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electronic component feeding apparatus for feeding electronic components to an electronic component mounting apparatus. 
     2. Description of Related Art 
     Electronic components in the form of chips constituting electronic circuits (hereinafter referred to as electronic components) have recently come into wide use, and as there have been more and more various types of electronic components, the number of type and quantity of electronic components mounted on one electronic circuit has been increased. Such a variety of electronic components are mounted in certain combinations onto a printed circuit board with the use of an electronic component mounting apparatus. To feed the electronic components to the electronic component mounting apparatus at desired timings, an electronic component feeding apparatus is desired to operate at a high speed and to be highly reliable. 
     A conventional electronic component feeding apparatus will be explained by referring to FIGS. 4 to  6 . 
     Referring to FIG. 4, component feeder units  1  of the conventional electronic component feeding apparatus conveys electronic components assemblies  2  intermittently in a direction of (b) at regular intervals of a given pitch by reciprocating pivotal movements of a feed lever  4 , each of the electronic components assemblies  2  accommodating a row of electronic components  7  held on a tape-like carrier (FIG.  6 ). A plurality of component feeder units  1  are loaded on a component supply table  3  in such a way that the component supply units  1  can be moved in a direction of (a) to be transferred to a feeding position (d) shown in FIG.  5 . The feed lever  4  of the component feeder unit  1  which is brought to locate at the feeding position (d) is driven by a transmission mechanism  41 . 
     The component feeder unit  1  includes a frame structure  31  having a mounting unit for anchoring it to the component supply table  3 , and a loading unit  32  for loading the tape-like electronic components assembly  2  thereon, and a guide  36  for guiding the electronic components assembly  2 . The feed lever  4  is pivotally mounted around an axial point  34  on the frame structure  31  and is driven by the pressing action of the transmission mechanism  41  for swinging motion between a lower limit of a pressing roller  42  of the transmission mechanism  41  and an upper limit thereof defined by an upper stopper (not shown). The component feeder unit  1  is further provided with a reel-out unit  33  for intermittently feeding the electronic components assembly  2  in the forward direction (b) via a link  37  by the reciprocating motion of the feed lever  4  and a separating unit  38  for peeling off and taking up a covering tape  20  (FIG. 6) from the electronic components assembly  2 . A tape holder  5  retains the electronic components assembly  2  from lifting up after separation of the covering tape  20 , and prevents the electronic components  7  from popping out therefrom, having a shutter  6  disposed at its tip where the electronic components  7  are picked up, which opens and closes in synchronism with the reciprocating swing motion of the feed lever  4 . 
     The feed lever  4  has a spring (not shown) upwardly urging a contacting portion  16  at the upper end of the feed lever  4 , by which the feed lever  4  remains in pressed contact with the upper stopper when the contacting portion  16  is disengaged from the pressing roller  42 . The stroke of the reciprocating swing motion of the contacting portion  16  between its upper and lower limits is the length of an effective stroke which is defined by the pitch for intermittently feeding the electronic components assembly  2  in the forward direction (b). The component supply table  3  carries a plurality of the component feeder units  1 , each having different effective strokes of the feed lever  4 . 
     The transmission mechanism  41  comprises a driving arm  43  for swinging movements along a direction of (e), the pressing roller  42  mounted at the distal end of the driving arm  43  for pressing down the contacting portion  16  of the feed lever  4 , and a driving means (not shown) for carrying the driving arm  43  to reciprocate in a swing motion at a predetermined swinging angle. The pressing roller  42  is driven at a constant stroke of the pressing motion. 
     The procedure of feeding the components in such an electronic component feeding apparatus will now be explained. 
     Referring to FIGS. 3 and 4, the effective stroke of each feed lever  4  is preliminarily set corresponding to respective feeding pitch of the electronic components assembly  2  for conveying the electronic components  7 . The effective stroke for each feed lever  4  is differently set in respective component feeder unit  1  by adjusting the position of the stopper which defines the upper limit, while the lower limit is set to be a fixed position of the lower dead point of the pressing roller  42  for all the component feeder units  1 . In particular, the upper limit of the feed lever  4  is set to a higher position for a component feeder unit  1  having a greater feeding pitch, i.e., the effective stroke, as can be seen from the vertical motion of the feed lever {circle around ( 2 )} shown by a double-dotted chain line in FIG.  3 . And the upper limit of the feed lever  4  is set to a lower position for a component feeder unit  1  having a shorter effective stroke, as can be seen from the vertical motion of the feed lever {circle around ( 1 )} shown by a solid line in FIG.  3 . 
     As the pressing roller  42  is lowered, it comes into direct contact with the contacting portion  16  of the feed lever  4  located at its upper limit and presses it down by the length of the effective stroke until its lower limit. When the feed lever  4  is returned upward by the yielding force of the spring together with the pressing roller  42 , the electronic components assembly  2  is advanced by the predetermined pitch along the direction (b). The electronic components assembly  2  is guided into the tape holder  5 , after its covering tape  20  is peeled off at the separating unit  38  before the shutter  6 . The lower limits of the pressing roller  42  and the feed lever  4  are set to be identical for all the component feeder units  1 , as described above and as can be seen from the vertical motion of the pressing roller {circle around ( 1 )}{circle around ( 2 )} shown by solid and broken lines in FIG.  3 . 
     The operation of the shutter  6  is linked to the vertical movements of the feed lever  4 , and the shutter  6  opens and closes as the feed lever  4  descends and ascends, respectively. A nozzle C of the electronic component mounting apparatus B is lowered as the shutter  6  opens and picks up an electronic component  7  under the opened shutter  6  by a sucking action. The nozzle C is lifted before the shutter  6  is closed and transfers the electronic component  7  to a mounting position for mounting it on a printed circuit board A. 
     While the pressing roller  42  stays at its upper dead point, the component supply table  3  conveys the component feeder unit  1  loaded with a desired type of electronic components  7  to the feeding position (d). By repeating these actions, the electronic component feeding apparatus supplies a set of electronic components  7  to the electronic component mounting apparatus B according to a predetermined program. 
     When the transmission mechanism  41  is placed in operation, specifically when the descending pressing roller  42  comes into direct contact with the contacting portion  16  of the feed lever  4 , a certain amount of vibration is generated caused by the impact of collision. The amount of vibration depends greatly on the rate of the pressing roller  42  hitting against the contacting portion  16 . The speed is, however, fixedly set irrespective of types of the component feeder units  1  having different sizes of components and feeding pitches as shown in FIG.  3 . 
     The electronic components  7  accommodated in the electronic components assembly  2  of which feeding pitch is small are generally light weighted and are more affected by the vibration caused by the impact. When the transmission mechanism  41  is operated at a higher speed in case that a component feeder unit  1  having small feeding pitch and the one having a greater feeding pitch are carried on the component supply table  3 , the electronic component  7  positioned at the shutter  6  of the component feeder unit  1  with a small feeding pitch receives a greater shock by the hitting rate of the feed lever  4 , causing the electronic component  7  to bounce or jump out of the place while the shutter  6  is opened. This causes the nozzle C of the electronic component mounting apparatus B to fail in picking up the electronic component  7 , to drop the electronic component  7  during the transfer by insufficient sucking force, or to mount the electronic component  7  at an incorrect position. 
     The speed of feeding the electronic components  7  can thus be only increased up to a limited degree which is defined by the effects of the vibration to a light weighted type electronic components. 
     BRIEF SUMMARY OF THE INVENTION 
     In view of the foregoing, it is an object of the present invention to provide an electronic component feeding apparatus capable of effectively feeding components at high speed without having adverse effects on a component feeder unit accommodating small components in a row at a small pitch, by reducing the vibration generated when the transmission mechanism is in operation, even when various types of the component feeder units accommodating different components at different pitches are loaded on the same feeder table. 
     To accomplish said object, an electronic component feeding apparatus of the present invention comprises component feeder units, each including an electronic components assembly accommodating a row of electronic components held on a tape-like carrier at regular intervals of a predetermined pitch, and a feed lever for intermittently feeding the electronic components assembly by reciprocating swing movements thereof, a component supply table loaded with the component feeder units to be transferred to a feeding position, and a transmission mechanism for driving the feed lever of the component feeder unit brought to locate at the feeding position, in which the transmission mechanism comprises a pressing stroke controller for changing the pressing stroke of the effective stroke of each feed lever corresponding to the predetermined pitch in respective component feeder unit. 
     According to the electronic component feeding apparatus of the present invention, the pressing stroke of the transmission mechanism can be adjusted to match the effective stroke of the feed lever required in each component feeder unit. Consequently, the speed of a pressing member of the transmission mechanism at the moment when it hits a contacting surface of the feed lever can be reduced without slowing down the feeding speed, thereby the vibration generated on impact. It is thus attainable to increase the operation rate even when various types of component feeder units with different pitches including the one accommodating minute components at a fine pitch which is susceptible to the vibration are carried by the same component supply table. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partially cut-off perspective view showing an electronic component feeding apparatus of the present invention; 
     FIG. 2 is a diagram showing the changes in operation speed of a feed lever and a pressing roller which contact with each other in one embodiment of the present invention; 
     FIG. 3 is a diagram showing the changes in operation speed of a feed lever and a pressing roller which contact with each other in a conventional apparatus; 
     FIG. 4 is a perspective view showing an arrangement in a conventional electronic component feeding apparatus; 
     FIG. 5 is a schematic plan view showing an action of the conventional electronic component feeding apparatus; and 
     FIG. 6 is a perspective view showing an electronic components assembly. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Preferred embodiments of the present invention will be described referring to the accompanying drawings. 
     As shown in FIG. 1, an electronic component feeding apparatus of the present invention comprises a plurality of component feeder units  1  which include electronic components assemblies  2  conveyed in a direction of an arrow (b) at regular intervals of a given pitch by means of reciprocating pivotal movements of a feed lever  4 , each of the electronic components assemblies  2  accommodating a row of electronic components  7  held on a tape-like carrier. The component feeder units  1  are loaded on a component supply table  3  in such a way that the component feeder units  1  are movable in a direction of an arrow (a) to be transferred to a feeding position. A transmission mechanism  8  is provided for driving the feed lever  4  of each component feeder unit  1  being brought to locate at the feeding position. 
     Descriptions of the component feeder unit  1  and the component supply table  3  will be omitted as they are substantially identical to those of the conventional apparatus described above. 
     The transmission mechanism  8  shown in FIG. 1 comprises a driving arm  10  which is pivotally mounted around a rotating axis  23  for pressing down the feed lever  4  by various strokes for pressing, a pressing stroke controlling means  60  for controlling the stroke length of the driving arm  10 , a cam  19  supported by a bracket  18  and driven by any driving means (not shown) to rotate, and a linking mechanism  50  for converting the rotation of the cam  19  into the pressing movements of the driving arm  10 . 
     The driving arm  10  includes a pressing roller  9  mounted at its distal end for pressing the contacting portion  16  of the feed lever  4 , and an encasement  25  which covers a linear servo motor  11  and the lowermost end  15  of a force transmitting rod  14  which is a part of the linking mechanism  50 . The linear servo motor  11  is fixed by a mounting means  22  within the encasement  25 . A movable rod  12  is arranged to have its axis crossed at right angles with the rotating axis  23  and supported in an axial aperture of the linear servo motor  11 . The movable rod  12  can freely move in the axial direction (f) of itself. The movable rod  12  has its actuating point  21  where the lowermost end  15  of the rod  14  is rotatably connected to, and the actuating point is adjusted in the axial direction (f) by the linear motor controlled by the pressing stroke controlling means (not shown). A slide thrust  13  is provided on one side in the encasement  25  for supporting the movable rod  12  with the linear servo motor  11  on the other side, with the actuating point  21  being positioned therebetween, for prevention of deflection of the movable rod  12  in operation. 
     The pressing stroke controlling means comprises a memory means for storing control data applied to each component feeder unit  1 , and a linear servo motor controlling means for outputting the corresponding control data to the linear servo motor, linking with the switching of the component feeder unit  1  being transferred by the component supply table  3  so that an automatic adjustment to accommodate the electronic component pitch can be accomplished for each feeder unit. 
     The linking mechanism  50  includes the rod  14  with its lowermost end  15  being connected to the actuating point  21  of the movable rod  12 , and an arm  17  of substantially an L shape pivotally supported by the bracket  18  at its center, having one end contacted to the cam  19  and the other end movably connected to the uppermost end of the rod  14  so that the rotation of the cam  19  is converted into the reciprocal movements of the rod  14 . It is preferable that the length of the rod  14  is greater than the moving range of the actuating point  21  in the axial direction (f), and the rod  14  crosses at nearly right angles with the movable rod  12 , so that the height of the lower dead point of the driving arm  10  caused by the movements of the actuating point  21  along the direction (f) is varied by a small amount. 
     The transmission mechanism  8  changes the stroke of pressing by the function of the pressing stroke controlling means controlling the linear servo motor  11  in a manner to be described below. While the rod  14  actuated by the rotation of the cam  19  is reciprocated at a fixed rate of stroke, the pressing stroke of the pressing roller  9  varies in inverse proportion to the distance between the actuating point  21  and the rotating axis  23 . The pressing stroke length is thus decreased when the actuating point  21  is shifted toward the distal end of the driving arm  10 , and is increased when the actuating point  21  is moved toward the rotating axis  23 . 
     A procedure of feeding the components in the electronic component feeding apparatus of this embodiment will now be explained. In FIGS. 1 and 2, the effective stroke length of the feed lever  4  is predetermined to correspond to the pitch required for feeding the electronic components  7  on the electronic components assembly  2  in each component feeder unit  1 . A desired effective stroke of the feed lever  4  is set in such a way that the lower limit of the feed lever  4  is adjustably determined for each component feeder unit  1  by the lower dead point of the pressing roller  9 , while the upper limit is uniformly set for all the component feeder units  1 . The effective stroke length for the component feeder unit  1  where the pitch of feeding components is larger is determined to be greater by setting the lower limit of the feed lever  4  to a lower position (as shown by a double-dotted chain line denoting the vertical movement of the feed lever {circle around ( 2 )} in FIG.  2 ). The effective stroke length for the component feeder unit  1  where the pitch of feeding components is smaller is determined to be shorter by setting the lower limit of the feed lever  4  to a higher position (as shown by a solid line denoting the vertical movement of the feed lever {circle around ( 1 )} in FIG.  2 ). According to this embodiment, the pitch of feeding the components in the component feeder unit  1  can be determined by setting the lower limit of the movement of the pressing roller  9  during the operation of the electronic component feeding apparatus without preliminarily adjusting the upper limit of the feed lever as compared to the conventional apparatus. 
     When the component supply table  3  transfers the target component feeder unit  1  in the direction (a) according to a production program, the transmission mechanism  8  reads out the control data for the component feeder unit  1  and drives the linear servo motor  11  to determine a desired length of the pressing stroke. 
     As the pressing roller  9  is lowered and comes into contact with the contacting portion  16  of the feed lever  4  at its upper limit position, the feed lever  4  is pressed down by the stroke length to its lower limit position. The feed lever  4  is then returned upward by the yielding force of the spring together with the pressing roller  9  lifting up therewith, when the electronic components assembly  2  is advanced by the predetermined pitch in the direction (b). The electronic components assembly  2  is fed into a tape hold-down  5  after the covering tape  20  is peeled off therefrom by the separator  38  before the shutter  6  (FIG.  6 ). As shown in FIG. 2, the speed of the pressing roller  9  approaching the feed lever  4  is minimized by approximating the pressing stroke length to an effective stroke of the feed lever  4  for each component feeder unit  1 . 
     The shutter  6  opens and closes linking with downward and upward movements of the feed lever  4 , respectively. When the shutter  6  is opened, the nozzle C of the electronic component mounting apparatus B is lowered in response, and picks up an electronic component  7  positioned under the opened shutter  6  by a sucking action. The nozzle C is then lifted before the shutter  6  is closed and transfers the electronic component  7  to mount it on a printed circuit board A. 
     While the pressing roller  9  stays at its upper dead point, the component supply table  3  conveys the succeeding component feeder unit  1  loaded with another type of electronic components  7  to the feeding position (d) as shown in FIG.  5 . The transmission mechanism  8  identifies the succeeding component feeder unit  1  and determines the appropriate pressing stroke length corresponding to the effective stroke of the feed lever  4  for the component feeder unit  1 . By repeating those actions, the electronic component feeding apparatus supplies groups of the electronic components  7  to the electronic component mounting apparatus B in accordance with a predetermined program. 
     The electronic component feeding apparatus of the present invention allows the pressing stroke length of the transmission mechanism to be adjusted to match the effective stroke of the feed lever for each component feeder unit. Accordingly, for the component feeder unit where the effective stroke of the feed lever is small, the speed of the pressing roller of the transmission mechanism approaching the contacting portion of the feed lever can be slowed down while the feeding speed remains unchanged, thus lowering the vibration caused by the impact. Accordingly, even with the component supply table carrying various types of component feeder units including the one containing smaller components fed at a smaller pitch which is susceptible to the vibration, the speed of feeding the components can be increased without raising any problems. 
     Although the present invention has been fully described by way of examples with reference to the accompanying drawings, it is to be noted that various changes and modifications will be apparent to those skilled in the art. Therefore, unless otherwise such changes and modifications depart from the scope of the present invention, they should be construed as being included therein.