Abstract:
A tape feeder  200  includes a sprocket  201  having a plurality of teeth  202  for engaging holes of a tape. A pawl  205  engages selected teeth of sprocket  201 . A first lever  203  is coupled to pawl  205  and a second lever  204  is coupled to first lever  203  and a source  208  of a driving force. First lever  203  and second lever  204  operate by a toggle action to selectively engage pawl  205  with ones of teeth  202  and thereby index sprocket  201.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a division of application Ser. No. 08/803,992, filed Feb. 21, 1997, now U.S. Pat. No. 6,082,954 entitled TAPE FEEERS AND SYSTEMS USING THE SAME by Daniel Michael Foster, Inventor, currently pending. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates in general to manufacturing equipment and processes and in particular to tape feeders and systems using the same. 
     BACKGROUND OF THE INVENTION 
     Tape feeders are commonly used to feed parts to automatic and semi-automatic manufacturing equipment during product assembly and similar automated manufacturing processes. Generally, components required for a given process, for example electronic circuit board assembly, are stored on a carrier tape which is passed through the tape feeder to the host machine. The host machine then robotically removes the components from the tapes for use by the host machine in an assembly or testing step, for example. Hence, a relatively continuous stream of components can be efficiently supplied to the host machine. 
     Each carrier tape includes a series of pockets which hold a correspondingly sized component, which may vary from very small electronic components, such as integrated circuit chips and discrete devices, to larger electromechanical devices such as connectors. Each component may be held in its pocket by a sheet of cover tape which adheres along the length of the carrier tape. The tape assembly, with the components held within the pockets, is spooled on a reel for storage. 
     The tape feeder is fastened to the host machine, typically by bolts or a pre-fabricated base. The reel of tape containing the required parts is attached to either the feeder or the host machine. The feeder indexes the parts from the reel into a fixed position to allow the host machine to pick them up and place them in the work station. Typically, this is accomplished by indexing the tape a fixed amount and at the same time peeling back the cover tape to expose the parts current part in its pocket. Expended tape is routed to a collection points. 
     Designers of tape feeders must address a number of issues when designing a new machine. Among other things, size and weight must be considered; conventional tape feeders are relatively large and heavy. Further, some tapes are provided with sprocket holes for indexing, while others are not (which reduces tape costs). Additionally, in the typical case where cover tape is used, some mechanism must be provided for efficiently removing and disposing of the cover tape. 
     Thus, the need has arisen for tape feeder apparatus and systems. In particular, a mechanism is needed to feed small parts on pocketed carrier tape, such tape having sprocket holes along one edge but not necessarily having a sealed cover tape over the parts. Further, a mechanism is needed to feed parts on a pocketed carrier tape which does not have sprocket holes for indexing. In any event, the contemplated tape feeder should be compact, have a minimum number of moving parts and require few, if any, adjustments for proper operation. 
     SUMMARY OF THE INVENTION 
     According to a first embodiment of the principles of the present invention, a tape feeder is provided which includes a sprocket having a plurality of teeth for engaging holes of a tape. The tape feeder also includes a pawl for engaging selected ones of the teeth of the sprocket and first and second levers. The first lever is coupled to the pawl and the second lever coupled to the first lever and a source of a driving force, the first and second levers operating by toggle action to selectively engage the pawl with ones of the teeth and thereby index the sprocket. 
     According to another embodiment of the principles of the present invention, a tape feeder system is disclosed which includes a selected length of carrier tape having a plurality of pockets each for holding a component, a tape feeder, and robotics means for moving a component from the corresponding pocket of the tape when the pocket reaches a predetermined position. The tape feeder includes a sprocket having teeth for engaging index holes formed through the carrier tape and a toggle mechanism for indexing the sprocket to advance the tape. The toggle mechanism includes a pawl for applying a force to a selected tooth of the sprocket and first and second lever arms for coupling a force generated by an external source to the pawl. 
     According to an additional embodiment of the principles of the present invention, a tape feeder is provided for advancing a carrier tape having a plurality of pockets, the tape feeder receiving the carrier tape along with a cover tape disposed across an opening of at least some of the pockets. First and second rollers are included for receiving the cover tape therebetween. Drive means are provided for rotating at least one of the first and second rollers, the rollers stripping the cover tape from the carrier tape while substantially simultaneously advancing the carrier tape. 
     According to a further embodiment of the principles of the present invention, a tape feeder is provided which includes a length of tape supported on a reel, the tape including a carrier tape and a cover tape. A tape feeder is included for receiving the length of tape and stripping the cover tape from the carrier tape while simultaneously advancing the carrier tape in a single action. A host machine is provided for removing a component stored in a pocket of the carrier tape, the pocket having been advanced to a predetermined pick-up point by the tape feeder. 
     The principles of the present invention provide substantial advantages over the prior art. Among other things, these principles allow the construction and operation of tape feeders which are compact, have a minimum number of moving parts and require few, if any, adjustments for proper operation. In particular, the principles of the present invention provide for the implementation of a mechanism which feeds small parts on pocketed carrier tape, the carrier tape having sprocket holes along one edge but not necessarily having a sealed cover tape over the parts. The principles of the present invention further allow for the construction of a tape feeder which can feed parts on a pocketed carrier tape which does not have sprocket holes for indexing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a diagram depicting a typical carrier tape cover tape assembly stored on a reel or spool; 
     FIG. 2A is a side view diagram of a tape feeder according to the principles of the present invention; 
     FIG. 2B is an end view of the tape feeder of FIG. 2A; 
     FIG. 2C is a top view of the tape feeder of FIG. 2A; 
     FIG. 2D is a more detailed diagram of the engagement of the pawl and sprocket of FIG. 2A; 
     FIG. 2E is a diagram generally illustrating the operation of a pawl and sprocket assembly; 
     FIG. 3 is a side view diagram of a typical manufacturing system embodying the tape feeder of FIGS. 2A-2D; 
     FIG. 4A is a side view diagram of a second tape stripper/feeder embodying the principles of the present invention; 
     FIG. 4B is an end view of the tape stripper/feeder of FIG. 4A; 
     FIG. 4C is a top view of the tape stripper/feeder of FIG. 4A; and 
     FIG. 5 is a side view diagram of a typical manufacturing system embodying the tape stripper/feeder of FIG.  4 A. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The principles of the present invention and their advantages are best understood by referring to the illustrated embodiment depicted in FIGS. 1-5 of the drawings, in which like numbers designate like parts. 
     FIG. 1 is a diagram of a typical pocketed tape assembly  100 , generally covered by industry standard EIA-481 recognized by those skilled in the art. Assembly  100  includes a reel or spool  101  maintaining a carrier tape  102  and the corresponding cover tape  103  held by adhesive to the upper surface of the carrier tape  102 . It should be noted that in the illustrated embodiment, carrier tape  102  is 8 to 16 millimeters in width, although the width of carrier tape  102  will vary as a function of the actual application. In FIG. 1, a portion of cover tape  103  has been peeled-back to expose a number of pockets  104  in carrier tape  102 . Pockets  104  hold the components to be feed to the host machine and vary in width, length and depth from application to application, depending on such factors as the size of the components as known in the art. In the illustrated embodiment, carrier tape  102  is shown with index holes  105  for indexing. 
     FIGS. 2A-2D are a series if diagrams depicting a tape feeder  200  according to the principles of the present invention. In particular, FIG. 2A is a side view of FIG. 2B is an end view of and FIG. 2C is a top view of a portion of tape feeder  200 . FIG. 2D is a more detailed diagram emphasizing the relationship between the index pawl and half-step notches on the sprocket shown in FIG.  2 A. FIG. 2E illustrates a general method of driving a sprocket using an external force, such as that applied by an pneumatic cylinder. 
     Tape feeder  200  includes a drive sprocket  201  which includes a series of teeth  202 . Preferably, sprocket  201  and in particular the number, size and spacing of teeth  202 , are designed to match the index hole size and spacing of tape  102 . In other words, sprocket  201  is designed such that sprocket (index) holes  105  of carrier tape  102  engage teeth  202  of sprocket  201  such that tape  102 / 103  advances (indexes) as sprocket  201  indexes. 
     Drive sprocket  201  is rotated in steps (indexed) by a pair of lever arms  203  and  204  and an index pawl  205  having which also engages teeth  202  of sprocket  201 . In the preferred embodiment, index pawl  205  also includes a half step notch  206  allowing the mechanism to half step, or feed ½ the distance between index holes without a second wheel or sprocket. Levers  203  and  204 , index pawl  205 , and ultimately sprocket  201  are driven by a ram  207  pneumatically extended or retracted from an external cylinder  208  in the illustrated embodiment. 
     This linkage provided by arms  203  and  204  and pawl  205  is preferably of a toggle type which provides enough leverage to allow the use of small cylinders  208 . Specifically, on the reverse stroke of ram  207 , lever arms  203  and  204  retracts pawl  205  from the presently engage tooth  202 . On the forward stroke of ram  207 , pawl  205  engages a lower tooth on sprocket  201  and the applied force advances (indexes) sprocket  201  along with tape  102 / 103  by the distance of one tooth spacing. The toggle action provides a very smooth feed which slows down naturally at the end of the cylinder stroke. This feature advantageously helps prevent very small parts from being thrown out of their carrier tape pockets  104 . It should be noted that the linkage can also be driven by external levers, on plungers, on the host machine. For half stepping with the half-step notch, cylinder  208  can be adjusted longitudinally relative to feeder  200  by a set of mounting holes  215 . This allows the stroke of ram  207  to be shorten or lengthen and the indexing of sprocket  201  per stroke correspondingly shortened or lengthen. 
     After tape  102 / 103  advances under a cover  210 , cover tape  103  is removed by a stripper mechanism  209 . Cover tape stripping mechanism  209  is driven by the tape  102 / 103  itself such that no linkage is required between the sprockets. A small sprocket  212  is provided, the teeth of wheel  212  engaging cover tape  103 . When cover tape  103  is fed forward by sprocket  201 , sprocket  212  is driven by cover tape  103  while an upper wheel  213 , spring loaded by a spring  214  against sprocket  212 , pinches cover tape  103  thereby stripping cover tape  103  away from carrier tape  102  carrier tape  102  and cover tape  103  supported by tape support  215 . The lack of linkage or belts between sprocket  201  and wheels  212 / 213  allows the system to be reconfigured easily. The simplicity of design also makes possible narrow embodiments of tape feeder  200 . This allows more feeders to be put on a given host machine, better utilizing available space. 
     The component or part at the next exposed pocket of carrier tape  102  is made available for retrieval by the host machine at pick-up point  211 . FIG. 3 illustrates the embodiment of tape feeder  200  in a typical host machine  300 . Host machine  300  includes tape assembly  100  providing a feed of carrier tape  102  holding a required stream of components, along with cover tape  103 . The tape feed is provided to tape feeder  200  which strips off cover tape  103  and provides an exposed component in its carrier tape pocket at the pick-up point  211 . A robotic pick-up head  301  picks-up each components as it arrives at point  211  and provides it to workstation  302 . At workstation  302 , each component may, for example, be inserted into an assembly using a robotic head  303  or used for some other assembly or test purpose. 
     FIGS. 4A,  4 B and  4 C are respective, side, end and top views of a tape stripper/feeder  400  embodying the principles of the present invention. Stripper/feeder includes two rollers  401  and  402  powered by a motor and belt  403 . A frame constructed of sidewalls  404  and spacers  404  supports rollers  401  and  402  and belt/motor  403 . A pair of tape shelves  406   a  and  406   b  are provided to support carrier tape  102 . 
     The incoming carrier tape  102 /cover tape  103  is passed under roller  402 . In the preferred embodiment, at least one roller  401 / 402  is a cylinder of a soft and durable material to allow rollers  401  and  402  to be pinched together firmly. This provides a good grip on cover tape  102  which is fed between them. Thus, when rollers  401  and  402  are rotated, cover tape  103  is peeled off and carrier tape  102  pulled along by the same force. Not only does this feature perform the cover tape stripping and carrier tape advancing operations in a single action, but also allows for the use of carrier tape  102  which does not include sprocket holes. 
     A sensor  407  detects the leading edge of the next pocket reaching the pick-up point and halts tape advancement so that the part can be removed. Feeding can be initiated either by an on board sensor to detect the part leaving that pocket or by the host machine. System  400  requires no set up or adjustments; index pitch is automatically controlled. Advantageously, since carrier tape  102  is supported on the edges by shelves  406 , the depth of the carrier tape pockets does not matter. The feeder is sized for various widths of tape simply by using different lengths of spacers  405  and shafts  408  and  408  supporting rollers  401  and  402 . In adjustable embodiments, sidewalls  404  may be slidable on rods of sufficient length. Due to the simplicity, the device can be configured easily for various applications, at a reduced manufacturing cost. 
     FIG. 5 depicts a typical manufacturing system  500  employing tape stripper/feeder  400 . System  500  includes tape assembly  100  providing a feed of carrier tape  102  holding a the desired components in the corresponding pockets, along with cover tape  103 . The tape is received by tape stripper/feeder  200  which in the single action of rotating rollers  401  and  402  strips off cover tape  103  and advances the carrier tape  102 . Sensor detects when an exposed component reaches the pick-up point  504 . A robotic pick-up head  501  picks-up each components as it arrives at point  504  and provides it to workstation  502 . Rollers  401  and  402  are again driven by motor  403  to advance carrier tape  103  until the next pocket reaches sensor  407 . Workstation  302  uses each component retrieved by robotic head  501  as required. For example, a given component may be inserted into an assembly using a robotic head  503  or used for some other assembly or test purpose. 
     Although the invention has been described with reference to a specific embodiments, these descriptions are not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments of the invention will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore, contemplated that the claims will cover any such modifications or embodiments that fall within the true scope of the invention.