Abstract:
The present invention features a system to generate vacuum for picking up and holding a component in a component placement machine wherein the arrangement of the elements comprising the system prevents the flow of foreign matter back through the system. One arrangement locates a venturi between a valve and nozzle, thereby minimizing where vacuum exists within the system.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
       [0001]     This application is a Continuation-in-Part of U.S. patent application Ser. No. 10/271,761, filed on Oct. 17, 2002, and thus claims priority and benefit thereof. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Technical Field:  
         [0003]     This invention relates to the creation of vacuum for one or more pick and place mechanisms mounted in a pick and place machine.  
         [0004]     2. Related Art:  
         [0005]     For the generation of vacuum, it is standard to use compressed air and a venturi. The compressed air blown into the venturi with high speed generates vacuum that can then be connected to the pick and place mechanisms, such as nozzles or vacuum activated grippers, via a manifold, hoses, couplings, and often a valve to connect/disconnect the vacuum from each pick and place mechanism. This way multiple pick and place mechanisms can be connected to single vacuum generator.  
         [0006]     One disadvantage of the existing design is that any foreign matter such dirt, dust and other pollution, that is drawn into the pick and place mechanism by the vacuum will pass through the valves, through the hoses and through the couplings and the manifold, before it can be blown out of the system at the venturi. This leads to sticky valves and polluted hoses and manifold. A second disadvantage for the existing design is that because the valves are operating under vacuum conditions, lubricants tend to evaporate more quickly, which leads to failure of the valve(s). Another disadvantage of the current design is that often the vacuum generator is on a stationary part of the machine while the pick and place mechanism itself has to be able to rotate, sometimes over multiple axes. This is achieved using couplings with seals. However any leak of these seals will both diminish the ultimate vacuum force applied to the component part at the pick and place mechanism and also will allow more foreign matter to be drawn into the mechanism at any failed seal location. Still another disadvantage of the current design is that the air rushes through the venturi continuously, whether the mechanism is operating to pick a component or not. With machines often waiting for boards or parts to be replenished, this is wasteful and often noisy.  
         [0007]     A need exists for a vacuum generation system that overcomes at least one of the aforementioned, and other, deficiencies in the art.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention attempts to address the above described issues with vacuum generation in a pick and place machine by positioning a valve and a venturi in close proximity to the pick and place mechanism such that the pick and place mechanism is connected to the vacuum side of the venturi. Therefore when the valve is opened, compressed air is blown into the venturi creating a vacuum at the pick and place mechanism.  
         [0009]     A first general aspect of the present invention provides a system for generating vacuum for picking up and holding a component in a component placement machine, the system comprising: 
        an input of compressed air supplied to a valve;     a pick and place mechanism for picking and holding said component; and     a venturi, for converting said compressed air into a vacuum, wherein said venturi is between said valve and said pick and place mechanism.        
 
         [0013]     A second general aspect of the present invention provides a system for use in a component placement machine, the system comprising: 
        a plurality of flow passage components, said plurality selected from a group consisting of a hose, a coupling, a valve, and combinations thereof;     a venturi having an exhaust port; and     a pick and place mechanism;        
 
         [0017]     further wherein a first portion of said system has a positive pressure of compressed air flow therethrough and a second portion of said system has negative pressure of compressed air flow therethrough, wherein said first portion includes said plurality of components and said second portion includes said pick and place mechanism.  
         [0018]     A third general aspect of the present invention provides a method for generating vacuum for picking up and holding a component in a component placement machine, the steps comprising: 
        providing compressed air to a valve; and     providing a venturi between said valve and a pick and place mechanism.       
 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]     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:  
         [0022]      FIG. 1  depicts a schematic view of the generation of vacuum for a single nozzle, of the related art;  
         [0023]      FIG. 2  depicts a schematic view of the generation of vacuum for a single nozzle, in accordance with embodiments of the present invention;  
         [0024]      FIG. 3  depicts a schematic view of the generation of vacuum for multiple nozzles, of the related art; and  
         [0025]      FIG. 4  depicts a schematic view of the generation of vacuum for multiple nozzles, in accordance with embodiments of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0026]     Although certain embodiment of the present invention will be shown and described in detail, it should be understood that various changes and modification 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.  
         [0027]     The present invention mitigates and/or eliminates at least one of the above mentioned disadvantages. For example, any foreign matter that is entering the pick and place mechanism through the nozzle is immediately discarded at the venturi and does not pass through the valves, couplings, hoses, and/or manifold. Another example, the valves operate in compressed air that is often filtered and sometimes even lubricated for optimum performance of the valves. Since full pressure (e.g., ˜70 PSI) is used down to the valves, the size of manifold, hoses and valves can be reduced without impact to the vacuum activation time. Any malfunction of seals in couplings will leak some air out, however this will not harm the vacuum force since the compressed air is of a higher pressure and volume that a leaky seal does not impart a significant air pressure drop at the venturi, nor the pick and place mechanism beyond. The increased pressure of the air will also prevent foreign matter from getting into the mechanism at the leaking seal of a coupling. The mechanism will only use compressed air when it is actually holding a part to the nozzle or gripping a part. When the mechanism is not operating no compressed air is used to maintain a central vacuum. Thus, the vacuum is only created intermittently, as needed.  
         [0028]     The embodiments of the present invention pertain to the holding of a component in a component placement machine having one or more pick and place mechanisms which are used for assembling printed circuit boards. The component placement machine includes a system for generating vacuum to allow the component placement machine to pick up and hold components. The inventive system includes a specific arrangement of an input of compressed air, a venturi, and a valve with respect to the pick and place mechanism. This arrangement prevents the flow of foreign matter back through the inventive system.  
         [0029]     Turning first to  FIGS. 1 and 3 , which depicts a system  100  and a system  300  in the related art which generates vacuum that enables the picking up and holding of components with a nozzle  22 . The system  100  consists of an input of compressed air  10 , a venturi  12 , hose  14 , coupling  16 , valve  18 , and nozzle  22 . The compressed air  10  flows through venturi  12  which in turn causes a vacuum (i.e., negative pressure) to be generated and then distributed through hose  14 , coupling  16 , and finally down to valve  18 . When valve  18  is turned on, vacuum is then provided at nozzle  22  allowing components to be picked and held by the nozzle  22 . System  300  is similar to system  100  but adds a manifold  26  between coupling  16  and valve  18  to accommodate the distribution of the vacuum to additional nozzles  22 . In this particular arrangement, foreign matter  24  that is small enough to flow through the end of the nozzle  22 , such as dirt, dust, and pollution, may flow back through valve  18 , coupling  16 , hose  14  to an exhaust port  28 . The present invention corrects this deficiency by preventing, or at the least significantly diminishing, the flow of foreign matter  24 .  
         [0030]     Referring now to  FIGS. 2 and 4 , which depicts an embodiment of the present invention for a system  200  and a system  400  for generating vacuum for picking up and holding components with a nozzle  22 . System  200  includes the same elements as system  100 , but arranged in a different sequence to prevent the back flow of foreign matter  24 . In system  200 , compressed air  10  flows through various flow passage components, such as hose  14 , coupling  16 , and down to valve  18 . When valve  18  is turned on, the compressed air  12  continues through venturi  12  which in turn causes a vacuum to be generated, wherein the vacuum is then provided at nozzle  22 . System  400  is similar to system  200  but adds a manifold  26  between coupling  16  and valve  18  to accommodate the distribution of the compressed air to additional nozzles  22 . In this manner, foreign matter  24  exits through an exhaust port  28  without passing back through valve(s)  18 , coupling  16 , or hose  14 .  
         [0031]     The compressed air  10  supplied to the venturi  12  is air under positive pressure. Further, the vacuum generated is air under negative pressure. Thus, the various flow passage components are under a positive pressure, while the pick and place mechanism is under negative pressure.  
         [0032]     Although not shown, the same arrangement described above may be used in conjunction with a pick and place mechanism comprising a vacuum actuated gripper. In this case, when valve  18  is turned on, a gripper will be activated such that a component may be held.  
         [0033]     Since other modification 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 modification which do not constitute departures from the true spirit and scope of this invention.