Abstract:
A cassette for a plurality of components for a cam drive and timing system for an engine the components comprising a guide and a tensioner attached to a tensioner bracket, a chain, a camshaft sprocket, and a crankshaft sprocket. The cassette is comprised of a body defining clearance holes and shoulder guides for placement of the camshaft sprocket, the crankshaft sprocket and the chain; and at least one fastener engaging the body of the cassette to the tensioner bracket, such that when the body of the cassette is engaged to the tensioner, the chain runs around the camshaft sprocket and the crankshaft sprocket, and the guide and the tensioner are positioned relating to the chain in the same relationship and position as the components are installed on the engine, all components are pivotally placed for installation on the engine.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention pertains to the field of assembly aids. More particularly, the invention pertains to an assembly aid for the shipping and assembly of a camshaft driving system.  
         [0003]     2. Description of Related Art  
         [0004]     The components of the cam drive and timing system are often assembled onto the engine block individually or as subassemblies. One subassembly may be a chain  16  and two sprockets, camshaft  18 , and crankshaft  14  oriented in the correct timing, as shown in  FIG. 1   b  and another subassembly may be a tensioner subassembly comprising a bracket  6  having two stand-off threaded bosses  4  for attaching to the engine block, a tensioner arm  8 , a snubber  2 , and a pin  10  for keeping the tensioner from pivoting as shown in  FIG. 1   a.    
         [0005]     In attaching the above subassemblies to the engine block, the tensioner subassembly is placed onto the engine first. Next, the chain is wrapped around sprockets, cam  18  and crank  14 , which are properly oriented relative to each other for the correct timing and placed on their respective shafts. Except the chain  16  doesn&#39;t have enough slack to allow the sprockets to engage their shafts if the tensioner subassembly is secured to the engine block. If the tensioner subassembly is not secured to the engine block, and moved toward the crankshaft  14 , a sufficient amount of slack in the chain may be gained. However, since the cam sprocket  18  and the crank sprocket  14  engage their respective shafts simultaneously, an assembler must keep a hand on each of the sprockets, leaving the assembler shorthanded to adjust the chain and manage the unsecured tensioner subassembly.  
         [0006]     Solutions to this problem are discussed in U.S. Pat. Nos. 4,607,601, 5,193,498, 6,238,311, and JP2001208153A. U.S. Pat. No. 4,607,601 discloses a detachable timing gear cassette unit, which prior to mounting to the engine is attached to a gage which permits the presetting of the timing while the chain tensioner is maintained in a condition where tension is not exerted on the chain. When the timing gear cassette is assembled with the engine on the assembly line, the cassette is positioned with the gage in position on the end portion of the crankshaft, camshaft, and the injection pumpshaft, which were all previously oriented with respect to one other. The gage is then removed and then the sprockets corresponding to the crankshaft, camshaft, and injection pumpshaft are attached to their corresponding shafts. Plugs are mounted to seal any orifices and the timing chain is then placed under tension.  
         [0007]     U.S. Pat. No. 5,193,498 discloses a three part assembly used to install a tensioner comprising a mounting plate, a gasket, and a tensioner housing. The three parts are temporarily fastened together by a single rivet. The rivet allows the parts to be rotated relative to each other during installation. The temporary fastening of the three parts allows the assembly to be shipped together and reduce any damage that can incur to the gasket. Lastly, the temporary fastening of the three parts allows the installer to only have to use one hand.  
         [0008]     U.S. Pat. No. 6,238,311 discloses a chain tensioner assembly that includes a blade spring interlocked with a shoe. The shoe has slots for receiving the blade spring. One end of the shoe has a protruding portion and the other end has a cylindrical hollow sleeve. The assembled shoe and spring are pivotally mounted to a bracket. The bracket has a tab with a notch in alignment with the hollow sleeve. A removable pin engages the notch in the bracket and passes through the hollow sleeve to secure and prevent the tensioner arm from pivoting when the assembly is shipped and installed onto the engine block.  
         [0009]     JP2001208153A discloses a hydraulic automatic tensioner in which all of the components are made to reside on a single cassette.  
       SUMMARY OF THE INVENTION  
       [0010]     A cassette for a plurality of components for a cam drive and timing system for an engine the components comprising a guide and a tensioner attached to a tensioner bracket, a chain, a camshaft sprocket, and a crankshaft sprocket. The cassette is comprised of a body defining clearance holes and shoulder guides for placement of the camshaft sprocket, the crankshaft sprocket, and the chain; and at least one fastener engaging the body of the cassette to the tensioner bracket, such that when the body of the cassette is engaged to the tensioner, the chain runs around the camshaft sprocket and the crankshaft sprocket, and the guide and the tensioner are positioned relating to the chain in the same relationship and position as the components are installed on the engine, all components are pivotally placed for installation on the engine.  
         [0011]     A cassette is also used to ship and install the plurality of components for a cam drive and timing system for an engine the components comprising a guide and a tensioner attached to a tensioner bracket, a chain, a camshaft sprocket, and a crankshaft sprocket. The first step is placing the components for the cam drive and timing system for the engine onto a cassette. The next step is to ship the cassette with the components for the cam drive and timing system and the last step is to install the components for the cam drive and timing system using the cassette. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0012]      FIG. 1   a - 1   c  show schematics of prior art installation of a cam drive and timing system.  
         [0013]      FIG. 2  shows a front view of a cassette used in installation, shipping, and storage of a camshaft drive and timing system.  
         [0014]      FIG. 3  shows a perspective view of the cassette.  
         [0015]      FIG. 4  shows a front view of the cassette and camshaft drive and timing system in the clamped shipping position.  
         [0016]      FIG. 5  shows a front view of the cassette and camshaft drive and timing system in the mounting position.  
         [0017]      FIG. 6  shows a cross section of  FIG. 4 .  
         [0018]      FIG. 7  shows a back view of the cassette.  
         [0019]      FIG. 8  shows a perspective view of an alternative cassette.  
         [0020]      FIG. 9  shows a front view of the alternative cassette.  
         [0021]      FIG. 10  shows a back view of the alternative cassette.  
         [0022]      FIG. 11  shows a cross section of  FIG. 10 .  
         [0023]      FIG. 12  shows stacking of two cassettes for shipment. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0024]      FIGS. 2 and 3  show the front and back of a cassette  120  used to secure a tensioner  108 , guide  102 , tensioner bracket  140 , two sprockets, the camshaft  118  and crankshaft  114 , and a chain  116  in a timed relationship for placement on the engine. The cassette  120  contains shoulder guides  124 ,  126 ,  134  for the crankshaft sprocket  114 , the camshaft sprocket  118 , and the chain  116  respectively, making each of the components easier to assemble onto the cassette. The cassette  120  also has two holes  130  slightly off center, which provide clearance for fasteners  138 . The clearance holes  130  having a locking slot  128   a  and raised bosses  128 . Hooks  133  are provided on the back of the cassette  120  and are placed between adjacent crank sprocket teeth to aid in securing and keeping the sprocket in its timed position and keeping tensioner bracket  140  adjacent to the cassette. The cassette further contains a loop  122 , which is used for storage, shipping, and handling purposes.  
         [0025]      FIG. 4  shows the cassette  120  and associated components in the clamped shipping position. In this position, the crankshaft sprocket  114 , camshaft sprocket  118 , and chain  116  are all in a fixed position that is consistent with the correct timing needed. The tensioner  108  is locked to the tensioner bracket by locking pin  136 , keeping the tensioner arm out of the way during assembly. The cassette  120  is clamped to tensioner bracket  140  at bosses  128  by fasteners  138 , which position the tensioner bracket  140  so that the tensioner  108  and snubber  102  have maximum clearance to the chain  116 . The end of the locking pin  136  is received and secured to cassette  120  by integral catch  132  until after the sprockets and the tensioner are secured to the engine. Once the sprockets and tensioner are secured to the engine, the locking pin  136  is pulled from the tensioner bracket  140  releasing the tensioner  108  to engage and tension chain  116  when the cassette is in the mounting position and is removed axially toward the viewer.  
         [0026]      FIG. 5  shows cassette  120  and associated components in the mounting position. The tensioner bracket  140  and its components remain locked in position by pin  136  as the tensioner bracket  140  is unclamped by loosening fasteners  138 . The fasteners  138  are realigned to their threaded receiving holes in the engine block (not shown). In this position the crank sprocket  114 , camshaft sprocket  118 , and chain  116  are still in the fixed position that is consistent with the correct timing needed. The locking slot  128   a  and raised boss  128  are clearly visible above fasteners  138 . The fasteners  138  may now be advance threaded out of stand-off bosses  104  and threaded into the engine block, securing the bracket  140  and its components to the engine block with the proper positioning and timing relationship present. By supplying fasteners  138  with the cassette  120 , the assembler does not have to take the time to acquire and then properly align fasteners  138 , instead, the assembler may proceed in tightening the fasteners into the threaded receiving holes of the engine block, making the entire assembly more efficient.  
         [0027]      FIG. 6  is a cross-section of  FIG. 5 , and shows the relationship of the components when the cassette  120  is in the mounting position and the fasteners  138  have been loosened. As shown, hooks  133  still engage crank sprocket  114 , but is no longer associated with tensioner bracket  140 , which has moved out of range. Fasteners  138  are now free to be advance threaded out of engagement with the threaded stand-off boss  104  and into engagement with threaded receiving holes in the engine block. The threaded stand-off bosses serve two purposes. The first purpose is allowing the clamping of the tensioner bracket  140  to the cassette  120  in the proper relationship when fasteners  138  are positioned in the locking slot  128   a  and the fasteners are then tightened against the raised boss  128 . The second purpose is to guide fasteners  138  into the correct position when being received and subsequently tightening the tensioner bracket  140  to the engine block. Also shown in the figure is integral catch  132  and how the catch  132  interfaces with locking pin  136  in such a way that as the cassette  120  is removed, locking pin  136  is disengaged from tensioner bracket  140 , unlocking and allowing tensioner  108  to engage the chain  116  for tensioning. It should be noted that the threads of the fastener  138  would exit the threaded stand-off boss  104  before they would engage the threads of the engine block (not shown), such that the fastener relieved shank  138   a  has clearance with the minor thread diameter of boss  104  facilitating finding the threaded hole in the engine block (not shown). Alternatively, the stand-off threaded bosses may be eliminated if the tensioner bracket is threaded and the receiving threads of the engine block are sufficiently recessed.  
         [0028]     The first step in using the cassette  120  to install the camshaft drive and timing system is the removal of the assembly, as shipped and stored on a rod in a suspended state via loop  122 . The crankshaft sprocket  114  and camshaft sprocket  118  are secured to their respective shafts. The fasteners  138  are then loosened about a half turn (turned counterclockwise) allowing the fasteners  138  to be released from the locking slots  128   a  and drop into the clearance holes  130 , which line up with the receiving holes in the engine block. The fasteners  138  are tightened (turned clockwise) such that they engage the engine block. As the cassette  120  is removed axially, pin  136  engaged by catch  132 , which is integral with the cassette, disengages from tensioner bracket  140 , unlocking and allowing tensioner  108  to engage the chain  116  for tensioning. The cassette  120  may then be reused. By using the cassette  120  to install the camshaft drive and timing system, the assembler has a free hand available, the cassette is easy to handle by the loop  122 , and the timing and placement of the camshaft, crankshaft, tensioner, guide, and slack in the chain is automatically correct.  
         [0029]      FIGS. 8, 9 , and  10  show an alternative cassette  320  with tensioner bracket  340 . The cassette has a loop  322  for storage, shipping, and handling purposes. The cassette  320  also contains a camshaft shield  350  which offers protection to the camshaft sprocket  318  from damage during shipping by an adjacent cassette, as shown in  FIG. 12 , from sagging of the camshaft sprocket  318 , and traps fasteners used to secure the camshaft sprocket  318  to its respective shaft on the engine. As in the previous embodiment, the cassette  320  contains shoulder guides  324 ,  326 ,  334  for the crankshaft sprocket  314 , camshaft sprocket  318 , and the chain  116  respectively. The cassette  320  also has two receiving holes  330  slightly off center. Adjacent to the receiving holes  330  is a handle  356  which turns tab  362 . Tab  362 , as shown in  FIG. 10  in addition to hooks  333  keep the cassette  320  in contact with the tensioner bracket  340  and in clamped shipping position. A hex nut  360  may be used instead of handle  356 . As in the previous embodiment, the crankshaft sprocket  314 , camshaft sprocket  318 , and chain  316  are all in the fixed position that is consistent with the correct timing. The tensioner  308  is locked into place by pin  358  to keep from exerting any additional force on the chain  316 .  
         [0030]      FIG. 11  shows cross section of  FIG. 10 . Hex nut  360 , which may used in place of handle  356 , is adjacent to a spring  364  that pushes on a washer  368  with dimples  366  into their respective holes within the cassette body. The dimples  366  provide resistance to accidental rotation of the handle  356  from its locked position (vertically up) when a force is applied to compress spring  354  if rotated from its respective hole within the cassette. The dimple&#39;s snapping into their respective holes also signals to the assembler that the cassette is locked in place. Without the tensioner bracket  340  in place, tab  362  is pulled tight against the back of cassette  320  by spring  364 . The assembler must compress spring  364  by pushing on the handle  356  or hex nut  360  to allow tab  362  to be rotated and capture the tensioner bracket  340  between the tab  362  and the cassette  320 . The tensioner bracket  340  is positioned between the shaft of tab  362  and hooks  333  while in the shipping position. When tab  362  is rotated out of contact with tensioner bracket  340 , spring force retracts tab  362  and its shaft out of the way and allows the tensioner bracket  340  to move away from the crankshaft sprocket  314  vertically downward, aligning the tensioner bracket mounting holes  340   a  with their respective counterparts in the engine block (not shown).  
         [0031]     Similar to the method of installation in the previous embodiment, the first step in using cassette  320  to install the camshaft drive and timing system is removing the cassette  320 , which is shipped and stored in a suspended state via loop  322  in the clamped shipping position off of a suspended rod. Then, the crankshaft sprocket  314  and camshaft sprocket  318  are secured to their respective shafts. The camshaft sprocket  318  is secured to its respective shaft using the fasteners that were present with the cassette. By providing these fasteners with the cassette  320 , the assembler does not have to take the time to acquire and then properly align the fasteners, instead, the assembler may proceed in tightening and securing the camshaft sprocket  318  to its respective shaft, making the entire assembly more efficient. The handle  356  or hex nut  360  are pressed in and turned clockwise or counterclockwise, moving the tab  362  and releasing the tensioner bracket  340 , which causes the tensioner bracket  340  to drop slightly. The slight drop of the tensioner bracket  340  causes the clearance holes  330  and the tensioner bracket mounting holes  340   a  to line up with the receiving holes in the engine block. Fasteners are applied through mounting holes  340   a  to secure the tensioner bracket  340  to the engine block (not shown). Pin  358  is removed, allowing the tensioner  308  to move against the chain for tensioning and the cassette  320  is removed axially. The cassette  320  and pin  358  may then be reused. By using the cassette  320  to install the camshaft drive and timing system, the camshaft sprocket as well as other parts of the system are protected during shipment and are positioned for rapid assembly to the engine block, the timing of the system is automatically correct, the cassette is easy to handle by loop  322 , and the assembler has a free hand to adjust and maneuver components into place.  
         [0032]      FIG. 12  shows how cassettes  320  would be stacked and shipped in the clamped sipping position. Cassettes  120  would be stacked together in a similar manner to be shipped and stored.  
         [0033]     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.