Abstract:
The assembly method includes packaging of items for shipment and secures components of the assembly in a fashion and in the related position required for further assembly, as a unit, to an engine that is in the process of being assembled. The timed assembly arrives at the engine plant secured together such that it allows handling, at least in part, as a single component and with its parts arranged in the relative position required for proper timing and for securing to other components of the engine. The chain ( 44 ) is pinned between a tensioner pin ( 66 ) and the tensioner chain contacting surface ( 60 ) and between a guide pin ( 74 ) and the guide or snubber chain contacting surface ( 88 ). The tensioner is preferably pinned in a state of minimum extension.

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application claims one or more inventions which were disclosed in Provisional Application No. 60/822,096, filed Aug. 11, 2006, entitled “ASSEMBLY SYSTEM AND METHOD FOR A TENSIONED CHAIN DRIVE SYSTEM”. The benefit under 35 USC §119(e) of the United States provisional application is hereby claimed, and the aforementioned application is hereby incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention pertains to the field of engine timing drive assemblies. More particularly, the invention pertains to a system and method for assembling an engine timing drive. 
     2. Description of Related Art 
     Automobile engine timing drive components are commonly shipped as a kit. The components are sometimes packaged together in a relationship of how they are to be placed in the engine. The sprockets and chain may be placed in a molded tray in a timed relationship along with the pre-assembled mechanical tensioner. At the engine assembly plant, a chain and its sprockets may be mounted on the respective shafts as a timed unit, but the tensioners for the chain are individually mounted usually before the chain and sprockets are mounted. 
     In U.S. Patent Application Publication No. 2005/0130776 “A CASSETTE FOR SECURING SHIPPING AND ASSEMBLY OF A CAMSHAFT DRIVE AND TIMING SYSTEM”, the cassette is for a guide and a tensioner attached to a tensioner bracket, a chain, a camshaft sprocket, and a crankshaft sprocket. The cassette includes a body defining clearance holes and shoulder guides for placement of the camshaft sprocket, the crankshaft sprocket, and the chain. The cassette also includes at least one fastener engaging the body of the cassette to the tensioner bracket. When the body of the cassette is attached to the tensioner, the chain runs around the camshaft sprocket and the crankshaft sprocket. The guide and the tensioner are positioned in the same relationship and position on the chain as the components are installed on the engine. All components are pivotally placed for installation on the engine. 
     Referring to  FIG. 1  through  FIG. 3 , the prior art cassette  10  has a loop  12  for storage, shipping, and handling purposes. The cassette  10  also contains a camshaft shield  14  which offers protection to the camshaft sprocket  16  from damage by an adjacent cassette during shipping. The camshaft shield  14  also protects from sagging of the camshaft sprocket  16  and traps fasteners used to secure the camshaft sprocket  16  to its respective shaft on the engine. The cassette  10  contains three shoulder guides (not shown) visible from the back side for the crankshaft sprocket  18 , camshaft sprocket  16 , and the chain  20 . The cassette  10  has two receiving holes  22  slightly off center. The tensioner bracket  24  is visible through the receiving holes  22  in  FIG. 1 . Adjacent to the receiving holes  22  is a handle  26  which turns a tab (not shown) on the back of the tensioner bracket  24 . The tab, in combination with several hooks (not shown) on the back of the bracket  24 , keeps the cassette  10  in contact with the tensioner bracket and in a clamped shipping position. Alternatively, a hex nut may be used instead of the handle  26 . The crankshaft sprocket  18 , camshaft sprocket  16 , and chain  20  are all in a fixed position that is consistent with the correct timing for the engine timing drive. The tensioner  28  is locked into place by a pin  30  to prevent the tensioner from exerting any additional force on the chain  20 . A snubber  32  contacts the other strand of the chain  20 . When the tab is rotated out of contact with the tensioner bracket  24 , a spring force retracts the tab and its shaft out of the way and allows the tensioner bracket  24  to move away from the crankshaft sprocket  18  vertically downward, aligning the tensioner bracket mounting holes  34  with their respective counterparts in the engine block (not shown). 
     Chain tensioners are commonly provided in a state of minimum extension to assist in assembly. Pins maintain the tensioner in the minimum extension state, and the pins are removed upon completion of the assembly to the engine. The mechanical tensioner is typically a sub-assembly including a pivoting face, pre-assembled blade springs, a bracket having mounting holes, a perpendicular pivot pin for the pivoting face, and a perpendicular tab on which a compliant face with pre-assembled springs is supported. In the prior art, with the chain wrapped around the sprockets and the tensioner secured in place, the sprockets have too little slack to be mounted on their respective shafts, and the space between the engine block and the chain is too small to allow the tensioner to pass through for assembly. 
     SUMMARY OF THE INVENTION 
     The assembly method includes packaging of items for shipment and secures components of the assembly in a fashion and in the related position required for further assembly, as a unit, to an engine that is in the process of being assembled. The timed assembly arrives at the engine plant secured together such that it allows handling, at least in part, as a single component and with its parts arranged in the relative position required for proper timing and for securing to other components of the engine. The chain is pinned between a tensioner pin and the tensioner chain contacting surface and between a guide pin and the guide or snubber chain contacting surface. The tensioner is preferably pinned in a state of minimum extension. 
     In a first embodiment, the method of installing a plurality of components for a cam drive and timing system for an engine includes mounting a chain to a crankshaft sprocket and a tensioner bracket. The components include the tensioner bracket, a guide or snubber and a tensioner mounted to the tensioner bracket, the chain, and the crankshaft sprocket. The method also includes inserting a tensioner pin extending into a tensioner pin hole, between a first pair of teeth of the chain, and into a first bracket pin hole to pin the chain between the tensioner pin and a tensioner chain contacting surface of the tensioner. The method further includes inserting a guide pin extending into a guide pin hole, between a second pair of teeth of the chain, and into a second bracket pin hole to pin the chain between the guide pin and a guide chain contacting surface of the guide or snubber. 
     In a second embodiment, the assembly unit includes a tensioner pin and a guide pin. The assembly unit is for a plurality of components for a cam drive and timing system for an engine. The components include the tensioner bracket, a guide or snubber and a tensioner attached to a tensioner bracket and a chain wrapped around a crankshaft sprocket. The tensioner pin extends into a tensioner pin hole, between a first pair of teeth of the chain, and into a first bracket pin hole to pin the chain between the tensioner pin and a tensioner chain contacting surface of the tensioner. The guide pin extends into a guide pin hole, between a second pair of teeth of the chain, and into a second bracket pin hole to pin the chain between the guide pin and a guide chain contacting surface of the guide or snubber. 
     In a third embodiment, the cam drive and timing system for an engine includes a tensioner bracket, a guide or snubber, a tensioner, a crankshaft sprocket, a chain, a tensioner pin, and a guide pin. The tensioner bracket includes a bracket body having a first bracket pin hole and a second bracket pin hole and a tensioner brace extending from the tensioner body, the tensioner brace having a tensioner pin hole. The guide or snubber is mounted to the tensioner bracket and has a guide chain contacting surface and at least one guide pin hole. The tensioner is mounted to the tensioner bracket and has a tensioner chain contacting surface. The chain has a plurality of chain teeth and engages the crankshaft sprocket. Prior to installation of the cam drive and timing system, the tensioner pin extends into the tensioner pin hole, between a first pair of the chain teeth, and into the first bracket pin hole, thereby pinning the chain against the tensioner chain contacting surface, and the guide pin extends into the guide pin hole, between a second pair of the chain teeth, and into the second bracket pin hole, thereby pinning the chain against the guide chain contacting surface. 
     In a fourth embodiment, the guide or snubber is for a cam drive and timing system including a tensioner bracket and a chain. The guide or snubber is mounted to the tensioner bracket. The guide or snubber includes at least one blade spring biasing a guide chain contacting surface of the guide or snubber toward the chain. The guide or snubber also includes a guide pin inserted into a guide pin hole such that the chain contacting surface is maintained in a state of minimum extension prior to installation of the guide or snubber. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a front view of a prior art cassette. 
         FIG. 2  shows a second view of the prior art cassette of  FIG. 1 . 
         FIG. 3  shows a third view of the prior art cassette of  FIG. 1 . 
         FIG. 4  shows a front view of an assembly system in an embodiment of the present invention. 
         FIG. 5  shows a back view of the assembly system of  FIG. 4 . 
         FIG. 6  shows a perspective view of the assembly system of  FIG. 4  with the sprockets removed for clarity. 
         FIG. 7  shows another perspective view of the assembly system of  FIG. 4 . 
         FIG. 8  shows yet another perspective view of the assembly system of  FIG. 4 . 
         FIG. 9  shows a schematic view of only the chain and the pins in an embodiment of the present invention. 
         FIG. 10  shows a tensioner bracket, tensioner, snubber, and pins in an embodiment of the present invention. 
         FIG. 11  shows the assembly of  FIG. 10  with the shipping pins removed. 
         FIG. 12  shows a compliant guide with blade springs in an embodiment of the present invention. 
         FIG. 13  shows a first perspective view of a bracket and snubber piece in an embodiment of the present invention. 
         FIG. 14  shows a second perspective view of the piece of  FIG. 13 . 
         FIG. 15  shows a perspective view of a bracket in an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the present invention, the necessary slack to mount the sprockets to their respective shafts is achieved by positioning the mechanical tensioner toward the smaller sprocket, fixing the pivoting face and the compliant face at minimum positions and angles, and maintaining the chain at minimum positions and angles between the sprockets. In the assembly system, the tensioner and guide or snubber are preferably pinned such that the bracket is intentionally located closer to the smaller sprocket than where it is to be mounted for the chain drive system. This increases the amount of chain slack available for mounting the sprockets to their respective shafts. For this arrangement, first the sprockets are mounted to the shafts, then the pins holding the chain against the tensioner and guide or snubber are removed. Finally, the bracket is positioned and mounted. The tensioner is preferably pinned in its state of minimum extension along with the chain and bracket and at least the smaller sprocket in a fashion that locks these pieces together in a proper timed relationship. Preferably the pins are the only elements of the shipped assembly that do not contribute to the normal engine function such that only mounting of the assembly and removal of the pins is required to make the assembly operational. 
     In some embodiments, the larger sprocket is included in the pre-assembly, but this is dependent upon the length of the chain and the associated freedom of the sprocket. In one embodiment, the larger sprocket is wrapped by the chain in the correctly timed relationship such that when it is picked up, a finger secures the chain&#39;s engagement, and the remaining items hang down in their locked and timed relationship and ready for assembly to the engine. In another embodiment, the larger sprocket is shipped unattached (i.e. not engaged with the chain) to the locked components of the engine timing assembly system. In this embodiment, the chain and the larger sprocket are preferably each marked such that lining up the marks in wrapping the chain around the larger sprocket insures the proper timing relationship between the crankshaft and the camshaft. The marks may be a coloring of a particular sprocket tooth and a particular chain link. 
     Referring to  FIG. 4  through  FIG. 15 , the assembly system  40  includes a bracket  42 , a chain  44 , and a smaller driving sprocket  46 . In some embodiments, the assembly system  40  also includes a larger driven sprocket  48 . A chain tensioner  50  mounted on the bracket  42  tensions the slack side of the chain  44 , and a chain guide or snubber  52  contacts the tight strand of the chain  44 . The tensioner  50  pivots about a pivot pin  54  at a first end of the tensioner arm  56 . The pivot pin  54  is mounted to the bracket  42 . The tensioner  50  preferably includes a plurality of blade springs  58  located behind the chain sliding face  60 . In the embodiment of  FIG. 4 , the tensioner brace  62 , which is an extension of the bracket  42 , wraps around a second end of the tensioner arm  56  and provides a sliding surface for the second end of the tensioner arm  56 . A tensioner pin hole  64  is located in an extension to the tensioner brace  62 . 
     When a tensioner pin  66  is inserted into the tensioner pin hole  64  and into the bracket tensioner pin hole  68 , the tensioner pin  66  holds the chain  44  in the desired alignment with respect to the chain tensioner  50 . The tensioner pin  66  and chain  44  preferably maintain the chain tensioner  50  in a state of minimum extension. The snubber or guide  52  is mounted on a snubber mount  70 , which is an extension of the bracket  42 . The snubber or guide  52  includes a guide pin hole  72 . When a guide pin  74  is inserted into the guide pin hole  72  and the bracket guide pin hole  76 , the guide pin  74  holds the chain  44  in the desired alignment with respect to the guide or snubber  52 . The bracket  42  preferably has at least two mounting holes  78 ,  80  for mounting the bracket  42  to an engine block (not shown). 
     Referring to  FIG. 6  through  FIG. 10 , the pins  66 ,  74  preferably have an extension, which allows them to be easily pulled by hand or by machine from the pin holes  64 ,  68  and  72 ,  76 , respectively. This extension is shown as a loop in the figures but may have any shape that is easily grasped and pulled including, but not limited to, a spiral perpendicular to the pin shaft. Referring to  FIG. 7 , the guide pin  74  includes a straight section  82 , which extends into the guide pin hole  72  and into the bracket guide pin hole  76 . In the assembled system  40 , the straight section  82  extends between two rows of teeth  84 ,  86  of the inverted tooth chain  44 , such that the straight section  82  and the guide chain contacting surface  88  prevent movement of the chain with respect to the guide chain contacting surface  88 . Referring to  FIG. 8  and  FIG. 9 , the tensioner pin  66  includes a straight section  90 , which extends into the tensioner pin hole  64  and the bracket tensioner pin hole  68 . In the assembled system  40 , the straight section  90  extends between two rows of teeth  92 ,  94  of the inverted tooth chain  44  such that the straight section  90  and the tensioner chain contacting surface  60  prevent movement of the chain with respect to the tensioner chain contacting surface  60 . In the assembled system  40 , the tensioner pin  66  also preferably maintains the tensioner  50  in a state of minimum extension. 
     Referring to  FIG. 10  through  FIG. 15 , a bracket  42  of the present invention is shown with the chain removed for clarity. The tensioner  50  and snubber or guide  52  are shown in a pinned state in  FIG. 10  and with the pins removed in  FIG. 11  through  FIG. 15 . In  FIG. 13  and  FIG. 14 , the tensioner and pivot pin has been removed such that the pivot pin mounting hole  96  in the bracket  42  is visible. From the perspective of  FIG. 14 , the second guide pin hole  98  is visible. The tensioner bracket preferably has two guide mounting holes  100 ,  102 , visible in  FIG. 15  where the snubber or guide has been removed from the bracket  42 , in the snubber mount  70  for mounting the snubber or guide to the bracket  42 . 
     Although the tensioner pin hole  64  is described as being located in an extension of the tensioner brace  62 , the tensioner pin hole  64  may also be located in an extension to the tensioner  50  itself within the spirit of the present invention. Although the guide pin hole  72  is described as being located in an extension of the guide or snubber  52 , the guide pin hole  72  may also be located in an extension of the tensioner bracket  42 . 
     In the embodiment of  FIG. 12 , the cutaway view shows that the compliant face  88  of the chain guide is biased away from the snubber mount  70  and toward the chain by at least one spring  89 . The spring  89  is preferably a plurality of blade springs. The guide is preferably designed such that when the guide pin  74  is inserted into the guide pin hole  72 , the guide face  88  is maintained in a state of minimum extension. In alternate embodiments, a chain guide such as disclosed in U.S. patent application Ser. No. 11/168,049, “PIVOTING MECHANICAL TENSIONER WITH COMPLIANT BLADE SPRING”, filed Jun. 28, 2005, U.S. patent application Ser. No. 11/168,769, “MECHANICAL CHAIN TENSIONER WITH COMPLIANT BLADE SPRING”, filed Jun. 28, 2005, or U.S. patent application Ser. No. 11/204,306, “LONG MECHANICAL TENSIONER WITH A COMPLIANT BLADE SPRING”, filed Aug. 15, 2005 is used in the present invention. These patent applications are hereby incorporated by reference herein. 
     Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.