Abstract:
A fastenerless chain snubber is provided that consists of a snubber body, and one or more attachment arms that form positioning blocks. The snubber is positioned in a housing by channel surfaces in the chain housing that locate the positioning blocks of the snubber. The snubber is firmly secured during chain operation by the substantial contact between the snubber attachment arm surfaces opposite the chain cover and the corresponding surface of the installed chain cover.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Priority is claimed from provisional application U.S. Ser. No. 60/238,201, filed Oct. 5, 2000 now pending. The entire specification of the provisional application is hereby incorporated by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to a chain snubber for a power transmission chain such as an engine timing chain, transmission drive chain, or four-wheel drive transfer case chain. In particular, the present invention relates to a chain snubber that is positioned in and secured to a chain housing without the use of fasteners. Instead of fasteners, the snubber is positioned and secured by contact with the chain housing. 
     Power transmission chains are used in many automotive applications. For example, engine timing chains engage a sprocket on the crankshaft and a sprocket on a camshaft to drive the camshaft. Another important application is a four-wheel drive transfer case in which a power transmission chain engages and is driven by a drive sprocket and also engages and drives an output or driven sprocket. In these applications, it is often desirable to prevent or limit chain vibration and movement of the free span of chain between the sprockets. Tensioning devices or snubbers are conventionally used for these purposes. A snubber adjacent to a chain may be used to limit chain movement and vibration by contact with the chain. 
     Typically, chain snubbers are positioned and secured to a chain housing using fasteners. An example of a timing chain snubber using fasteners is shown in U.S. Pat. No. 4,193,314. This snubber includes a pair of guide shoes that are secured to a sheet metal snubber body. The snubber body is formed to be positioned against the engine block and defines holes through which fasteners secure the snubber body to the engine block. The guide shoes extend along chain runs between sprockets. The guide shoes prevent movement of the chain and limit chain oscillation or vibration. 
     The use of conventional fasteners, for example screws or bolts, to position and secure a snubber or guide to the chain housing is effective, but requires time for assembly and adds expense to chain systems. Thus, there has been a long-felt need in the automotive industry for a chain snubber that can be quickly positioned and secured economically, i.e. without the use of fasteners. 
     One attempt to position and secure a chain guide without the use of fasteners is understood to have been used commercially in the Oldsmobile Quad 4 engine. This chain guide was made from hard plastic and included separated mounting arms that were sized to fit loosely within slots in the chain housing. The slots were separated by a distance that required the mounting arms to be deflected away from each other to be positioned in the slots. The chain guide was held in place by a spring-like tension of the mounting arms towards each other and against surfaces of the slots in the housing. This chain guide limited chain vibration and movement. The flexibility and relatively loose fit of the mounting arms within the housing slots however permitted some movement of the guide due to contact with the moving chain. This movement of the guide and contact of the chain with the hard plastic surface of the guide generated undesirable levels of noise. 
     Flexibility of a chain snubber is also a concern, particularly where the snubber is relatively long, where the drive chain is heavy, or the snubber otherwise may deflect unacceptably. A chain snubber may be secured with additional fasteners to additionally support the snubber, or may be supported by a metal body that is secured by fasteners as shown by U.S. Pat. No. 4,193,314. Supporting a snubber by these methods also increases the cost of the chain assembly. 
     Automotive chain drives are subject to particularly stringent noise requirements. The noise created by prior guides having fastenerless mountings, such as the Quad 4 chain guide, was a significant disadvantage as compared to conventionally secured guides of earlier and later designs. A long felt need remains for a fastenerless chain snubber capable of limiting chain movement and vibration without producing objectionable levels of noise during chain movement. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an object of the present invention to reduce the assembly time and costs of a power transmission chain by eliminating the use of fasteners to position and secure a chain snubber adjacent to the chain. It is also an object of the present invention to provide a snubber that limits the movement and vibration of a chain while avoiding objectionable chain system noise levels. 
     The present invention positions and secures a chain snubber with respect to a chain housing without the use of fasteners. The chain contact surface of the snubber may be an elastomer to prevent unacceptable noise levels due to chain contact with the snubber during operation. 
     A fastenerless chain snubber is provided that includes a snubber body and one or more attachment arms. The snubber is positioned by contact of the attachment arms against openings of a chain housing to retain, or trap contacting surfaces of the attachment arms of the snubber. The attachment arms of the snubber may be molded or cut into various geometries, including a tapered shape. The housing openings that contact the arms may be grooves, holes, or slots that are formed or cut into the chain housing to contact the attachment arms to secure the snubber to the housing. The geometry of the arms and the housing results in contact between the surface of the attachment arm and the surface of the housing opening that prevents movement of the attachment arm with respect to the housing. 
     Attachment arms having tapered attachment geometry is portrayed in the drawings, but other shapes of the arm or housing opening that trap the attachment arm within the housing opening are also contemplated. For example, a conical shape is contemplated that would provide a continuous surface for positioning. 
     The snubber can be firmly secured during chain operation by substantial contact between the snubber attachment arms and a chain cover. The arms may be contacted by one or more housing covers that secure the arms within housing openings. Contact of the arms against a cover limits the movement of the snubber and may additionally secure the snubber to the housing by urging the attachment arms against the housing openings. Compression of the attachment arms is only required to create substantial contact with the chain cover. The attachment arms need not be significantly deformed by the installation of the chain cover(s). 
     Compression that increases the amount of contact, the force of contact, or both between the attachment arm and the housing opening is contemplated with allowance for the elasticity of the attachment arm material. For example, the opening in the chain housing may or may not extend completely through the chain housing. If the openings do not extend completely through the housing, or the attachment arms engage the housing so as to extend beyond the chain housing on one side of the housing, the attachment arm can contact one cover and the opening of the housing. However, if the openings do extend through the housing and the attachment arms extend beyond the chain housing on opposed sides of the housing, the snubber can be secured by substantial contact with a chain cover on each side of the housing. 
     A snubber according to the present invention may also include a reinforcement that strengthens the snubber adjacent to a chain to limit snubber deflection. Use of such a reinforcement is particularly advantageous where the snubber body extends a relatively long distance between mounting arms, where the chain adjacent to the snubber body is particularly heavy, or both. A power transmission chain in a four-wheel drive transfer case is one such contemplated application of such a reinforcement. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a perspective view of the presently preferred embodiment of the snubber of the present invention. 
     FIG. 2 is a top view of the snubber shown by FIG.  1 . 
     FIG. 3 is a front view of the snubber shown by FIG.  1 . 
     FIG. 4 is a side view of the snubber shown by FIG.  1 . 
     FIG. 5 is a perspective view of the snubber shown by FIG. 1 positioned in a housing. 
     FIG. 6 is a perspective view of the snubber shown by FIG. 1 positioned in a housing and adjacent to a chain. 
     FIG. 7 is an oblique view of a reinforcement for the snubber shown by FIG.  1 . 
     FIG. 8 is an oblique view of the reinforcement shown by FIG. 7 molded within the snubber shown by FIG.  1 . 
     FIG. 9 is a perspective view of a housing and snubber according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Turning now to the drawings, FIGS. 1-4 depict the presently preferred embodiment of the fastenerless chain snubber. A snubber body  10  is generally elongate along a chain direction  12 . The snubber  10  defines a generally flat chain surface  15  for contacting the chain and limiting chain movement and vibration. The snubber body  10  may be entirely elastomer or may be elastomer bonded to a reinforcing material such as aluminum, steel, or nylon. Other reinforcing materials known in the art may be used as well. 
     As best shown by FIGS. 1 and 2, the snubber body  10  extends along the chain direction  12  and defines a front edge  11  and a back edge  13  that define the furthest extents of the snubber body  10  along a front direction F and a back direction B, respectively, that are perpendicular to the chain direction  12  and opposite to each other. The chain surface  15  extends from the front edge  11  to the back edge  13  and along the chain direction  12 . 
     Two attachment arms,  14  and  28 , are located at separated locations along the chain direction  12  and near opposite ends of the snubber body  10 . The attachment arms  14  and  28  are configured to secure the snubber body  10  to a chain housing, e.g. engine block, transmission, or transfer case as shown by FIG.  5 . As best shown by FIGS. 1,  3 , and  4 , the attachment arms  14  and  28  extend from the snubber body  10  oppositely from the surface  15 . As shown by FIGS. 2 and 4, the attachment arms  14  and  28  each define a wedge-shaped positioning block,  17  and  29  respectively. The positioning blocks  17  and  29  extend generally along the front and back directions. The positioning blocks  17  and  29  position the snubber body  10  in a chain housing by engaging the housing as described below. 
     The positioning blocks  17  and  29  define front surfaces  24  and  38 , respectively, at their furthest extent in the front direction F, and define back surfaces  26  and  40 , respectively, at their furthest extent in the back direction B. Positioning blocks  17  and  29  define top surfaces  16  and  30 , respectively, that are generally flat and face oppositely from the chain surface  15  as best shown by FIGS. 1 and 3. The top surfaces  16  and  30  define the furthest extent of the arms  14  and  28 , respectively, from the chain surface  15  and extend from the front surfaces  24  and  38  to the back surfaces  26  and  40 , respectively. The positioning blocks  17  and  29  define bottom surfaces  18  and  32 , respectively, that are separated from and face generally away from the top surfaces  16  and  30 . As shown by FIGS. 1 and 4, the bottom surfaces  18  and  32  converge toward the top surfaces,  16  and  30 , respectively, along the direction from the front surfaces  24  and  38  to the back surfaces  26  and  40 . The top and bottom surfaces  16  and  18  of the positioning block  17  and the top and bottom surfaces  30  and  32  of the positioning block  29  form wedges that are narrower at the back surfaces  26  and  40  and wider at the front surfaces  24  and  38 . 
     The positioning blocks  17  and  29  define right side surfaces  20  and  34 , respectively, that extend from the top surfaces  16  and  30  to the bottom surfaces  18  and  32 , respectively, at the farthest extent of the positioning blocks  17  and  29  in first direction along the chain direction  12 . The positioning blocks  17  and  29  form left side surfaces  22  and  36  that extend from the top surfaces  16  and  30  to the bottom surfaces  18  and  32  at the farthest extent of the positioning blocks  17  and  29  along a second direction along the chain direction  12  that is opposite the first direction. The right side surfaces  20  and  34  face generally opposite from the left side surfaces  22  and  36 . 
     The right side surfaces  20  and  34  and the left side surfaces  22  and  36  of the positioning blocks  17  and  29  converge toward each other along the direction from the front surfaces  24  and  38  toward the rear surfaces  26  and  40 . The positioning blocks  17  and  29  are wedge shaped along the front and back directions F and B due to the converging of right side surfaces  20  and  34  and the left side surfaces  22  and  36 . The right and left surfaces  20  and  22  of the positioning block  17  and the right and left surfaces  34  and  36  of the positioning block  29  form wedges that are smaller at the back surfaces  26  and  40  and at the front surfaces  24  and  38 . 
     As shown by FIG. 5 the positioning blocks  17  and  29  of the attachment arms  14  and  28 , respectively, are generally elongate and extend along the front direction F beyond the front edge  11  of the snubber body  10  to cause a chain cover (not shown) to contact with the front surfaces  24 ,  38  of the attachment arms  14  and  28 . The rear surfaces  26 ,  40  do not extend beyond the rear edge  13  of the snubber body  10 . 
     FIG. 6 depicts a front view of the snubber body  10  positioned adjacent to a chain  2  along a run between sprockets  4  and  6 . A chain housing  44  surrounds the chain  2  and defines a cover surface  46  against which a chain cover, not shown, is secured by conventional means to enclose the chain  2  and sprockets  4  and  6 . The snubber body  10  is positioned engaging the chain housing  44  by the positioning blocks  17  and  29  of the attachment arms  14 ,  28 , respectively, being received by attachment channels  41  and  42 , respectively, that are formed by the chain housing  44  and that open at the cover surface  46 . The channels  41  and  42  are formed to accept the positioning blocks  17  and  29  adjacent to the back surfaces  26  and  40 , and to allow the positioning blocks  17  and  29  to be inserted into the channels  41  and  42  starting at the back surfaces  26  and  40 . The channels  41  and  42  are smaller than the positioning blocks  17  and  29  adjacent to the front surfaces  24  and  38 . 
     As shown by FIGS. 5 and 6 the positioning blocks  17  and  29  are prevented from completely entering the channels  41  and  42  leaving a portion of the positioning blocks  17  and  29  adjacent the front surfaces  24  and  38  extending beyond the cover surface  46 . When a chain cover (not shown) is installed adjacent to the cover surface  46  of the housing  44 , the cover will come into contact with the protruding front surfaces  24 ,  38  of the attachment arms  14 ,  28 . The chain cover compresses the positioning blocks  17  and  29  into the channels  41  and  42  to hold the snubber body  10  firmly in place in the housing  44 . 
     FIG. 7 shows a reinforcement  45  for the snubber body  10 . The reinforcement  45  is preferably formed by a steel plate. The reinforcement  45  includes an elongate central section  43 . The central section  43  is sized to be within the snubber body  10  adjacent to the chain surface  15 . As best shown by FIG. 8, the central section  43  extends substantially from the front edge  11  to the back edge  13  of the snubber body  10 , and from the attachment arm  14  to the attachment arm  28 . The reinforcement  45  forms tabs  47  and  48  at opposed ends of the central section  43 . The tabs  47  and  48  are separated by distance that permits the tab  47  to be positioned within the attachment arm  14  and the tab  48  to be positioned within the attachment arm  28 . 
     As shown by FIGS. 7 and 8, the reinforcement  45  defines a plurality of holes  49  within the central section  43 . The snubber body  10  formed by elastomer that is insert molded around the reinforcement  45 . The elastomer surrounds the reinforcement  45 , including within the holes  49 , to conform to and engage the reinforcement  45 . 
     FIG. 9 shows another embodiment of the invention. The chain  2  is located in a housing  54 . A snubber body  50  is mounted to the housing  54 . In this embodiment, the housing  54  surrounds the chain  2  and defines two cover surfaces, a cover surface  62  facing generally along the front direction F, and a cover surface  64  facing along the back direction B. Channels  56  and  58  extend through the housing  54  along the F and B directions. Attachment arms  14 ,  28  of the snubber body  50  extend beyond the front and rear edges of the snubber body  50  such that the rear surfaces  26 ,  40  of the attachment arms  14 ,  28  extend beyond the cover surface  64  and the front surfaces  24  and  38  extend beyond the cover surface  62  as described above by reference to the embodiment shown by FIG.  6 . In this manner, two chain covers, one positioned adjacent to the cover surface  62  and one adjacent to the cover surface  64  firmly secure the snubber body  50  in the housing  54 . 
     While the invention has been described with reference to several preferred embodiments, those skilled in the art will understand that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular step, structure, or material to the teachings of the invention without departing from its scope. In particular, it should be noted that the number and shape of the attachment arms and of those having openings in which the attachment arms are positioned may be varied by those skilled in the art to result in more configurations of the disclosed invention. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.