Abstract:
The present invention features a method and apparatus wherein a component in a component placement machine is rejected during the placement cycle and subsequently retained in a component rejection station. A component is imaged and the image processed using an automated vision system. The image processing determines whether the component is placeable based upon a comparison of the component image to preprogrammed mechanical parameters for the component. A non-placeable component is rejected into a reject station with means to retain the component. Because a component can not escape the reject station, there is no degradation of the placement machine performance.

Description:
BACKGROUND OF THE INVENTION 
   1. Technical Field 
   This invention relates to component placement machines and, more particularly, to an apparatus used for rejection of a component during the placement cycle. 
   2. Related Art 
   The use of sophisticated placement machines in manufacturing printed circuit or similar cards, boards, panels, etc. is well known. The term printed circuit board (PCB) as used herein refers to any such electronic packaging structure. Typically, reels of tape-mounted circuit components are supplied to the placement machine by multiple feeders. Each feeder holds a reel of components and each feeder assembly provides components at a pick station. A housing carrying one or more pick/place heads mounted on a frame, each pick/place head having a vacuum spindle equipped with a nozzle, may be moved in the X and Y axes in a plane above the PCB being populated. Each vacuum spindle may be moved in the Z-axis (e.g., in and out from an extended to a retracted position). Each nozzle is sized and otherwise configured for use with each different size and style of component to be placed by the machine. 
   In operation, the housing carrying the frame is moved to the pick station and the nozzle of one of the pick/place heads is positioned over the tape-mounted component. The nozzle is lowered, via its associated vacuum spindle, to a point where, upon application of vacuum, the component is removed from its backing tape and held tightly against the nozzle orifice. The component is then brought to a vision system where one or more images of the component are taken and then processed. 
   Analysis of the image(s) determines whether the component is placeable. Typically, a placeability decision is based on a comparison of the image to predetermined mechanical parameters for each component. If the component is placeable, the pick/place head is moved to a point over the printed circuit board being assembled and the component deposited on the printed circuit board at a predetermined location. If a component is non-placeable, it is rejected and deposited to a reject station. The mechanical parameters used for comparison may include, but are not limited to, lead length, lead width, lead spacing, component size, the number of leads, etc. 
   It is also known in the art to use a gripping mechanism that may be extended and retracted in place of, or in addition to, the vacuum spindle and nozzle. 
   This reject station may be a dump bucket, a reject feeder, or a matrix tray. Dump buckets typically are mounted somewhere accessible to the pick/place head within the placement machine or mounted on the housing contiguous with the pick/place head. The pick/place head carrying a rejected component will place the component on to the reject feeder, or into a pocket of the matrix using the vacuum spindle. However, when the pick/place head must reject the component into a dump bucket, it drops the component from the vacuum spindle often using a combination of vacuum removal and “airkiss”. Many times components rejected in this manner miss the dump bucket or bounce out of the dump bucket upon depositing therein and ultimately end up else where in the machine. This results in poor product, jammed feeders, and poor production rates. 
   A need exists for an improved rejection station that overcomes the aforementioned, and other, deficiencies in the art. 
   SUMMARY OF THE INVENTION 
   The present invention provides an improvement in the way that non-placeable components are handled in a component placement machine when rejected into a dump bucket style reject station. The inventive apparatus allows the dump bucket to retain the rejected components by attaching a flap to the dump bucket. The flap dampens the force of the component as it enters the dump bucket and then prevents the component from escaping the dump bucket once the component passes by the flap. Therefore, with the flap attached to the dump bucket, components no longer escape the dump bucket resulting in inter alia better product and production rates of the placement machine. 
   A first general aspect of the present invention is a method for rejecting a component from a pick/place head in a component placement machine, the steps comprising:
         providing a component placement machine comprising a housing adapted for movement along an X and a Y axis above a printed circuit board and having a frame attached thereto, said frame having a one or more pick/place heads disposed thereupon;   providing a vision system comprising a camera accessible to said one or more pick/place heads;   picking a component from a supply of components using at least one of said one or more of pick/place heads;   capturing an image of said picked component, and processing said captured image to determine whether said picked component is placeable or non-placeable;   providing a reject station adapted to receive a component;   adapting said reject station with means to reduce the force upon which said component impacts said reject station; and   adapting said reject station with means to prevent said component from escaping said reject station.       

   A second general aspect of the present invention is a apparatus for retaining a rejected component from a pick/place head in a component placement machine, the apparatus comprising:
         a reject station mounted in a location accessible by said pick/place head; and   at least one flap mounted contiguous with said reject station, wherein said at least one flap dampens the force in which said component impacts said reject station, further wherein said at least one flap prevents said component from escaping said reject station.       

   A third general aspect of the present invention is an apparatus for retaining rejected components in a component placement machine comprising:
         a reservoir for retaining said rejected components; and   means adjacent to said reservoir, wherein said means is configured to absorb adequate energy from said rejected component upon its passage through said means, further wherein said means prevents said rejected component from passing back through said means thereby retaining said rejected component in said reservoir.       

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A complete understanding of the present invention may be obtained by reference to the accompanying drawings, when considered in conjunction with the subsequent detailed description, in which: 
       FIG. 1A  is a top, perspective view of a related art dump bucket; 
       FIG. 1B  is a side, sectional view  FIG. 1A , including a spindle; 
       FIG. 2A  is a top, perspective sectional view of a related art reject station that may be mounted contiguous with the pick/place head; 
       FIG. 2B  is a side, sectional view  FIG. 2A , including a spindle; 
       FIG. 3A  is a top, perspective view of a first embodiment of a component rejection station, in accordance with the present invention; 
       FIG. 3B  is a side, sectional view  FIG. 3A , including a spindle; 
       FIG. 4A  is a top, perspective view of a second embodiment of a component rejection station, in accordance with the present invention; and 
       FIG. 4B  is a side, sectional view  FIG. 4A , including a spindle. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Although certain embodiment of the present invention will be shown and described in detail, it should be understood that various changes and modifications may be made without departing from the scope of the appended claims. The scope of the present invention will in no way be limited to the number of constituting components, the materials thereof, the shapes thereof, the relative arrangement thereof, etc., and are disclosed simply as an example of an embodiment. The features and advantages of the present invention are illustrated in detail in the accompanying drawings, wherein like reference numerals refer to like elements throughout the drawings. 
   The present invention pertains to rejection of a component in a component placement machine having a housing with a frame upon which one or more pick/place heads are mounted for assembling printed circuit boards. The component placement machine includes a reject station, which may be a dump bucket located within the placement machine accessible to the pick/place head or it may be mounted on the housing contiguous with the pick/place heads. The inventive apparatus includes a flap contiguous with the reject station which acts to dampen the force of the component as it enters the reject station and then prevents the component from escaping the reject station once the component passes by the flap. The type of components that typically are rejected and stored by the invention are electronic circuit components with a weight in the range from approximately 50 micrograms to 15 grams. 
   Turning now to  FIG. 1A , which depicts a dump bucket  10  that would be mounted in a machine accessible to the pick/place head from the related art, said dump bucket  10  includes an opening  20  that leads to a reservoir  25  for retaining rejected components(s)  50  (See e.g.,  FIG. 1B ). The side sectional view in  FIG. 1B  shows a vacuum spindle  30  with nozzle  40  having just deposited a rejected component  50  into the reservoir  25  of the dump bucket  10 . A trajectory path  60  of the rejected component  50  shows that upon the impact point  61  of the component  50  on a portion of the reservoir  25 , that in many cases the component  50  then bounces out of the opening  20  of the reservoir  25  and dump bucket  10 . 
   Similarly,  FIGS. 2A and 2B  depict a second embodiment of a dump bucket  10  that would be mounted contiguous to the pick/place head in the related art, wherein the same shortcoming exists. That is upon the depositing of the rejected component  50 , on many occasions, the component  50  ultimately ends up outside the dump bucket  10 . One trajectory path  60  is shown as an example of one typical path that the component may take. That is the component  50  makes a series of impacts  61 A,  61 B,  61 C,  61 D on various parts of the reservoir  25 , or other parts of the dump bucket  10 , ultimately ending up beyond the opening  20  of the dump bucket  10 . 
   It should be apparent to those of ordinary skill in the art, that while some rejected components  50  are retained within the reservoir  25  of the dump bucket  10 , one or more components  50  clearly will be ejected out of the dump bucket  10  as shown in  FIGS. 1B and 2B . The present invention corrects this deficiency by ensuring that no components  50  escape the dump bucket  10 . 
   Referring first to  FIG. 3A  there is shown a top, perspective view of a first embodiment of a dump bucket  10 , or component rejection station, in accordance with the present invention, with opening  20 , adapted with a flap  80 .  FIG. 3B  is a side, sectional view of  FIG. 3A  and includes the path  60  of the component  50  as it is rejected from the vacuum spindle  30  of nozzle  40 . The vacuum spindle  30  releases the component  50  by removing vacuum from the nozzle  40 . Vacuum spindle  30  may also release the component  50  by a combination of removing vacuum from the nozzle  40  and applying an airkiss, a slight flow of air, to component  50  via nozzle  40 . Component  50  becomes disengaged from nozzle  40  and drops on to flap  80 . The first impact of the component  50  is denoted  61 A. Flap  80  is then deflected allowing component  50  to pass through the opening  20  into the bottom of dump bucket  10 . A second impact  61 B of the component is shown at the bottom of the reservoir  25 . When component  50  impacts flap  80 , flap  80  absorbs force from component  50  slowing the descent of component  50 . Component  50  may then continue to bounce within dump bucket  10 . Subsequent impact of the component  50  upon the underside of the flap  80  is shown  61 C. However since the force of component  50  was reduced by flap  80  upon passage through opening  20 , it does not have sufficient energy to pass back through opening  20  via flap  80 . The component  50  ultimately comes to rest upon the bottom of the reservoir  25 , as shown at  61 D. 
   Referring next to  FIG. 4A  which depicts a second embodiment of a component rejection station which is mounted contiguous with pick and place spindles, in accordance with the present invention. In this case, the component rejection station includes a dump bucket  10 , with opening  20 , adapted with flap  80 .  FIG. 4B , similarly, is a side sectional view of  FIG. 4A  and includes the path  60  of the component  50  as it is rejected from the vacuum spindle  30  of nozzle  40 . The various impacts of the rejected component  50  are denoted  61  (e.g.,  61 A,  61 B,  61 C,  61 D,  61 E,  61 F). The vacuum spindle  30  releases the component  50  by removing vacuum from the nozzle  40 . Vacuum spindle  30  may also release the component  50  by a combination of removing vacuum from the nozzle  40  and applying an airkiss, a slight flow of air, to component  50  via nozzle  40 . Component  50  becomes disengaged from nozzle  40  and drops on to flap  80 . The impact upon the flap  80  is denoted  61 A. Flap  80  is then deflected allowing component  50  to pass through the opening  20  into the bottom of the dump bucket  10 . When component  50  impacts  61 A flap  80 , flap  80  absorbs force from component  50  slowing the descent of component  50 . Component  50  may then continue to bounce within the reservoir  25  of the dump bucket  10 . However since the force of component  50  was reduced by flap  80  upon passage through opening  20 , it does not have sufficient energy to pass back through opening  20  via flap  80 . Numerous subsequent impacts of the component  50  are shown as  61 B,  61 C,  61 D  61 E, while the final resting location of the component  50  upon the bottom of the reservoir  25  is denoted as  61 F. 
   It should be apparent that although two embodiments of the present invention are depicted there are other embodiments available that provide the requisite improvements of the present invention. For example, the flap  80 , while depicted as either a single flap  80  (e.g.,  FIGS. 4A ,  4 B) or two opposing flaps  80  (e.g.,  FIGS. 3A ,  3 B), may have other embodiments. The flap  80  may be, for example, more than two flaps  80 . In the embodiments where there is a plurality of flaps  80 , the various flaps  80  may also abut or overlap each other. Further, the flap(s)  80  may, depending on the configuration and shape of the opening  20  and other parts of the dump bucket  10 , not abut, or overlap, each other, or even completely cover the opening  20 . 
   Likewise, there are various materials in which the flap  80  may be constructed. The flap  80  should be of a resilient, energy-absorbing material so that various sized rejected components  50  may pass by the flap  80  upon initial contact, yet cannot pass through a second time, or any subsequent time, upon the rebounding of the component  50  around the reservoir  25  of the dump bucket  10 . One embodiment the flap  80  may be made of Mylar®. Alternatively, the flap  80  may be made of multiple materials. 
   Since other modifications and changes varied to fit particular operating requirements and environments will be apparent to those skilled in the art, the invention is not considered limited to the example chosen for purposes of disclosure, and covers all changes and modifications which do not constitute departures from the true spirit and scope of this invention.