Abstract:
A chain guide includes a bracket adapted for being secured to an engine. The bracket includes a support surface including a leading end and a trailing end, and further includes a first saw-tooth fixing element. A guide shoe includes: (i) a shoe leading end; (ii) a shoe trailing end spaced from the shoe leading end in a chain movement direction; (iii) a chain guide surface extending between the shoe leading end and the shoe trailing end and adapted for slidably supporting an associated chain moving in the chain movement direction; and, (iv) an inner surface positioned adjacent the support surface of the bracket. The guide shoe further includes a second saw-tooth fixing element that mates with the first saw-tooth fixing element of the bracket to inhibit disconnection of said the guide shoe and the bracket.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims priority from and benefit of the filing date of U.S. provisional application Ser. No. 60/351,436 filed Jan. 23, 2002. 

   BACKGROUND OF THE INVENTION 
   The present invention relates generally to the automotive chain drive art and, more particularly, to a snap-fit chain guide with locking connector arrangement. In particular, the present invention relates to a novel and unobvious snap-fit chain guide shoe that securely and slidably interconnects with a support bracket in a manner that is easy to install, durable and inexpensive. 
   Chain guides, which for purposes of this document include chain tensioner arms and fixed chain guides, are well known. In a typical arrangement, a guide blade or guide shoe made of a plastic or other low-friction material is fixedly secured to an underlying support bracket that is, itself, manufactured from metal or a filled plastic material. A wide variety of structures and methods are known for operatively interconnecting a plastic guide shoe to an associated bracket. 
   One prior method of connecting a plastic guide shoe to a support bracket requires use of an adhesive and/or mechanical fasteners. These methods increase assembly time and costs. Also, the plastic shoe can separate from the bracket. In another known arrangement, the plastic shoe is molded directly over the support structure of the bracket. This approach is also expensive. 
   Prior arrangements are known for releasably fitting a plastic shoe to a bracket. One example is found in U.S. Pat. No. 5,820,502. In this patent, a plastic shoe or lining B is secured to a carrier T with a pivoting snap-fit. However, the disclosed arrangement is limited to an I-beam type bracket or carrier T. Furthermore, the arrangement disclosed in the U.S. Pat No. 5,820,502 is not a sliding snap-fit arrangement and, instead, requires that the plastic shoe be pivoted or twisted into its operative position. As such, assembly is difficult and shoe stress during assembly is increased. Secondly, the required pivoting action limits the different bracket configurations that can be employed, increases the space required for assembly and also increases the risk of improper and incomplete assembly. 
   In light of the foregoing, it has been deemed desirable to provide a snap-fit chain guide with locking connector arrangement that overcomes the foregoing specifically noted deficiencies and others while providing better overall results. 
   SUMMARY OF THE INVENTION 
   In accordance with the present invention, a chain guide includes a bracket adapted for being secured to an engine. The bracket includes a support surface including a leading end and a trailing end, and further includes a first saw-tooth fixing element. A guide shoe includes: (i) a shoe leading end; (ii) a shoe trailing end spaced from the shoe leading end in a chain movement direction; (iii) a chain guide surface extending between the shoe leading end and the shoe trailing end and adapted for slidably supporting an associated chain moving in the chain movement direction; and, (iv) an inner surface positioned adjacent the support surface of said bracket. The guide shoe further includes a second saw-tooth fixing element that mates with the first saw-tooth fixing element of said bracket to inhibit disconnection of said guide shoe and said bracket. 
   In accordance with another aspect of the present invention, a chain guide includes a bracket adapted for being secured to an associated engine. The bracket comprising a support, a bracket leading end and a bracket trailing end spaced from the leading end in a chain movement direction. The bracket further includes a first saw-tooth fixing element defined by a plurality of teeth that extend in the chain movement direction and that are raked in the chain movement direction. A plastic guide shoe includes a shoe leading end, a shoe trailing end, a chain guide surface adapted for slidably supporting an associated chain moving in the chain movement direction, and an inner surface positioned adjacent the support of the bracket. The shoe is selectively movable slidably relative to the support of the bracket between a first position where the guide shoe is separable from said bracket and a second position where the guide shoe is fixedly secured to the bracket. The guide shoe includes: (i) a portion defined at the shoe leading end that that engages a portion of the bracket when the shoe is located in the second position; and, (ii) a second saw-tooth fixing element that mates with the first saw-tooth fixing element when the guide shoe is located in the second position. The second saw-tooth fixing element is defined by a plurality of teeth that extend in the chain movement direction and that are raked in a direction opposite the chain movement direction. 
   One advantage of the present invention resides in the provision of a new and improved snap-fit chain guide with a saw-tooth fixing feature. 
   Another advantage of the present invention resides in the provision of a snap-fit chain guide having a saw-tooth fixing feature wherein the shoe is slidably rather than pivotably snap-fit into its operative position. 
   A further advantage of the present invention resides in the provision of a snap-fit chain guide that exhibits improved connection of the shoe to the bracket and that is resistant to undesired movement in a direction opposite the chain travel direction and/or in a direction transverse to the chain travel direction. 
   Still another advantage of the present invention resides in the provision of a snap-fit chain guide that is snap-fit into position by moving the plastic shoe in a direction that corresponds to the chain travel direction whereby chain movement cannot dislodge the shoe from the bracket owing to the saw-tooth fixing feature. 
   Other benefits and advantages of the present invention will become apparent to those of ordinary skill in the art to which the invention pertains upon reading this specification. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention comprises various components and arrangements of components, preferred embodiments of which are illustrated herein and wherein: 
       FIG. 1  is an isometric view of snap-fit chain guide formed in accordance with the present invention, with a plastic shoe portion thereof including a saw-tooth fixing feature and being partially installed on a bracket portion thereof; 
       FIG. 1A  shows the snap-fit chain guide of  FIG. 1  with the plastic shoe portion fully and operatively installed on the bracket portion; 
       FIG. 1B  shows an alternative formation for the leading end of the plastic guide shoe; 
       FIG. 2  is a greatly enlarged partial isometric illustration of a plastic shoe portion of the chain guide shown in  FIGS. 1 and 1A ; 
       FIG. 3  is a partial plan view that illustrates a saw-tooth fixing feature of the chain guide shown in FIG.  1  and that shows the plastic guide shoe in a first inoperative or partially installed position (corresponding to FIG.  1 ); 
       FIG. 4  is a plan view that is similar to the view of  FIG. 3  but that shows the plastic guide shoe in a second, fully-installed operative position (corresponding to FIG.  1 A); and, 
       FIG. 5  is similar to  FIG. 4  but shows an alternative embodiment wherein the guide shoe includes a supplemental projection for lateral stability. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIGS. 1-4  illustrate a chain guide assembly  10  formed in accordance with the present invention. The chain guide assembly  10  comprises an L-shaped bracket  12  having a flange  14  projecting therefrom. The bracket  12  is typically defined as a one-piece metal stamping or casting, or as a molded plastic or composite part. One or more mounting holes  16  are defined through the bracket and receive bolts or other fasteners for fixedly securing the bracket to an engine block or other support structure. 
   The flange  14  includes an rear or inoperative surface  14   a , a shoe support surface  14   b  located opposite the rear surface, a leading end  14   c  and a trailing end  14   d , wherein the leading end  14   c  is located upstream from the trailing end  14   d  during use relative to a chain movement direction  38 . The shoe support surface  14   b  is typically curved or arcuate as shown. 
   In the illustrated embodiment, the flange  14  defines a keyhole aperture  20  adjacent its trailing end  14   d , i.e., the keyhole aperture  20  is located closer to the trailing end  14   d  than it is to the leading end  14   c . In general, however, it is preferred that the keyhole aperture  20  be as closed to the leading end  14   c  as possible for a given application and envelope. The leading end  14   c  defines a notch  21 . 
   A guide shoe  22 , preferably defined from a molded plastic material or any other suitable low-friction material, is releasably mounted to the bracket  12  adjacent the flange  14 . The term “plastic” is intended to include all materials that comprise a polymeric component and can include composite and other materials without departing from the overall scope and intent of the invention. The shoe  22  comprises an outer face  22   a , an inner face  22   b , a leading end  22   c  and a trailing end  22   d . As shown in  FIG. 1A , when the shoe  22  is operatively connected to the bracket  12 , the shoe  22  conforms to the general shape of the shoe support surface  14   b  of the flange  14 , with the inner face  22   b  of the shoe  22  located adjacent the shoe support surface  14   b . In this operative position, the outer face  22   a  of the shoe is exposed and adapted to support a sliding chain thereon, with the chain moving in a chain movement direction indicated by the arrow  38  from the leading end  14   c  of the shoe toward the trailing end  14   d  of the shoe  22 . 
   The shoe  22  is releasably yet securely fixed to the bracket  12  when operatively positioned (FIG.  1 A). The leading end  22   c  of the shoe  22  is conformed and dimensioned to engage the leading end  14   c  of the flange  14 . More particularly, as may be seen most clearly with reference to  FIG. 1 , the leading end  22   c  of the shoe defines a curved portion  24  that engages the leading end  14   c  of the flange  14 . Furthermore, the leading end  22   c  of the shoe includes a rib  25  that is conformed and dimensioned for close sliding receipt in the notch  21  defined at the leading end  14   c  of the flange when the shoe  22  is moved slidably in the direction of chain movement  38  to its operative position as shown in FIG.  1 A. The rib  25  is T-shaped and includes a projecting lip  25   a  or is otherwise conformed to engage the notch at the leading end  14   c  of the bracket when the shoe  22  is located in its second (operative) position ( FIG. 1A ) so as to prevent lifting movement of the inner surface  22   b  of the shoe away from the shoe support surface  14   b.    
   As shown in  FIG. 1B , the leading end  22   c  of the shoe  22  can be formed to include a more pronounced hooked portion  124  that slidably receives and wraps more completely around the leading end  14   c  of the bracket  14  to provide additional assurance against lifting of the shoe  22  away from the leading end  14   c  of the bracket. The rib  125  is closely slidably received in the notch  21  as with the rib  25  discussed above. 
   A male connector  40 , best seen in  FIGS. 1 and 2 , projects outwardly from the inner surface  22   b  of the shoe  22 . The male connector  40  is located based upon the location of keyhole  20  and, in general, is preferably located as close to the leading end  22   c  as possible. The illustrated male connector  40  comprises first and second L-shaped legs. The first L-shaped leg of the male connector  40  is defined by an outwardly projecting leg portion  42   a  and a transverse foot portion  46   a  connected to the leg portion  42   a ; the second L-shaped leg of the male connector  40  is defined by an outwardly projecting leg portion  42   b  and a transverse foot portion  46   b  connected to the leg portion  42   b . The foot portions  46   a , 46   b  extend outwardly away from each other in opposite directions. 
   The foot portions  46   a , 46   b  respectively define saw-tooth outer faces  48   a , 48   b  that include or define a plurality of teeth  50 . Each saw-tooth face  48   a , 48   b  extends generally in the chain movement direction  38 . For reasons that will become readily apparent below, the teeth  50  defining each saw-tooth face  48   a , 48   b  are sloped or raked toward the leading end  22   c  of the shoe. The first and second legs  42   a , 42   b  of the male connector  40  are offset from each other in the chain movement direction  38  to facilitate injection molding of the shoe  22  and so that each leg can flex independently of the other in directions transverse to the chain movement direction. 
   A supplemental locking nib or projection  26  ( FIG. 2 ) projects outwardly away from the inner surface  22   b  of the shoe  22  adjacent the male connector  40 , generally between the male connector  40  and the leading end  22   c  of the shoe. This supplemental locking nib  26  includes first and second stop surfaces  26   a , 26   b , the function of which will be described below. 
   With reference now also to  FIGS. 3 and 4 , the keyhole aperture  20  includes an enlarged upstream portion  34  and a restricted downstream portion  36 . The enlarged portion  34  defines a first width W 1  and the restricted portion  36  defines a second width W 2  that is less than the width W 1 . The keyhole  20  is also defined to include first and second separate saw-tooth faces  60   a , 60   b  each defined by a plurality of teeth  62 . These saw-tooth faces  60   a , 60   b  cooperate to define a “first saw-tooth fixing element,” and the separate faces  48   a , 48   b  of the male connector  40  cooperate to define a “second saw-tooth fixing element.” As such, the bracket  12  comprises a first saw-tooth fixing element  60   a , 60   b  and the plastic shoe  22  comprises a second saw-tooth fixing element  48   a , 48   b.    
   The first and second saw-tooth faces  60   a , 60   b  extend in the direction of chain movement  38  and are preferably parallel to and arranged in an opposed facing relationship with the first and second saw-tooth faces  48   a , 48   b , respectively. Furthermore, the teeth  62  defining the first and second saw-tooth faces  60   a , 60   b  are dimensioned and arranged to engage the teeth  50  of the saw-tooth faces  48   a , 48   b  and, thus, the teeth  62  are sloped or raked in a direction to mate with the teeth  50 , i.e., toward the trailing end  14   d  of the bracket flange  14 . 
   It is also preferred, as shown, that the saw-tooth surfaces  60   a , 60   b  of the keyhole  20  extend for a longer distance in the chain movement direction  38  as compared to the faces  48   a , 48   b . Furthermore, owing to the offset of the first and second legs of the male connector  40 , it is preferred that the saw-tooth faces  60   a , 60   b  be correspondingly offset relative to each other as shown. 
   The keyhole aperture  20  also defines first and second shoulders  70   a , 70   b  respectively adjacent the saw-tooth faces  60   a , 60   b  that are approximately parallel to the shoe support surface  14   b  of the flange. As described below, these shoulders  70   a , 70   b  are engaged by the feet  46   a , 46   b  to prevent lifting of the shoe  22  away from the flange  14  at the trailing end  22   d  when the shoe  22  is in its second (operative) position. 
   To secure the plastic shoe  22  operatively to the flange  14 , the shoe is positioned as shown in  FIGS. 1 and 3 , with the inner surface  22   b  thereof located adjacent the shoe support surface  14   b  of the flange  14  and the male connector  40  projecting through the enlarged portion  34  of the keyhole aperture  20 . The shoe  22  is then moved slidably in the chain movement direction  38  to the position as shown in FIG.  1 A. This sliding movement of the shoe  22  causes the male connector  40  to move from the enlarged portion  34  of the keyhole aperture  20  into the reduced portion  36  as shown in FIG.  4 . 
   With continuing reference to  FIGS. 3 and 4 , as saw-tooth faces  48   a , 48   b  of the male connector  40  slidably encounter the mating saw-tooth faces  60   a , 60   b  of the keyhole aperture  20 , they are deflected inwardly toward each other and slide over the saw-tooth faces  60   a , 60   b , respectively, in a ratchet-like manner. 
   When the leading end  22   c  of the shoe  22  fully engages the leading end  14   c  of the bracket flange  14 , the shoe  22  is prevented from further sliding movement in the chain travel direction  38 . Due to the resilience of the legs  42   a , 42   b , the saw-tooth faces  48   a , 48   b  are urged into and resiliently maintained in firm engagement with the saw-tooth faces  60   a , 60   b , respectively. Furthermore, because the teeth  50  are raked in a direction opposite that of the teeth  62 , the shoe  22  is prevented (under all expected operating conditions) from moving slidably in a direction opposite the chain travel direction  38  once the saw-tooth faces  48   a , 48   b  are engaged with the saw-tooth faces  60   a , 60   b , i.e., once the first and second saw-tooth fixing elements are mated. It should also be noted that, even when the saw-tooth faces  48   a , 48   b  are fully engaged or meshed with their respective mating saw-tooth faces  60   a , 60   b , the legs  42   a , 42   b  are still resiliently deflected inwardly from their free or relaxed positions so that the faces  48   a , 48   b  are urged into engagement with the respective mating faces  60   a , 60   b  at all times. 
   In the preferred embodiment as illustrated, the teeth  50  of face  48   a  are nominally offset relative to teeth  50  of other face  48   b  in the chain movement direction  38  by a distance P/n where P=the pitch (spacing) of the teeth  50  on faces  48   a , 48   b  as shown in  FIG. 4 ; and wherein n=the number of separate saw-tooth faces  48   a , 48   b  that cooperate to define the second saw-tooth fixing element. As shown, the second saw tooth fixing element is defined by two separate faces  48   a , 48   b  and, thus, n=2 and the offset or “stagger” between the separate faces  48   a , 48   b  is P/2. As an alternative, the teeth  50  of the faces  48   a , 48   b  can be aligned with each other (no pitch offset) and the offset is then introduced into the teeth  62  of the faces  60   a , 60   b  according to the same formula where P=the pitch (spacing) of the teeth  62  on faces  60   a , 60   b  and n=the number of separate saw-tooth faces  60   a , 60   b  that cooperate to define the first saw-tooth fixing element. As shown, the first saw tooth fixing element is defined by two separate faces  60   a , 60   b  and, thus, n=2 and the offset would be P/2. This nominal arrangement helps to ensure that, in practice, the shoe  22  will move upstream against the chain travel direction  38  no more than the distance P/n, e.g., half of the pitch P in the present example. 
   It is also apparent with reference to  FIG. 4  that the feet  46   a , 46   b  of the male connector  40  respectively overhang the shoulders  70   a , 70   b  when the shoe  22  is fully operatively connected to the flange  14  of the bracket  12 . In this manner, the feet  46   a , 46   b  prevent the shoe inner surface  22   b , at the trailing end  22   d , from lifting away from the shoe support surface  24   b  of the flange  14 . 
   When the shoe  22  is fully and operatively installed as shown in  FIGS. 1A and 4 , the supplemental locking projection  26  extends into the keyhole aperture  20 . In this position, the first stop surface  26   a  of the supplemental locking projection  26  will engage the periphery of the keyhole aperture  20  upon more than minimal movement of the shoe  22  toward the leading end  14   c  of the flange to prevent further undesired movement of the shoe  22  in this direction. Furthermore, when the shoe  22  is operatively positioned, the second stop surface  26   b  of the supplemental locking projection  26  will engage the periphery of the keyhole aperture  20  upon more than minimal movement of the shoe  22  in a transverse direction to prevent this undesired movement. The supplemental locking projection  26  is a redundant locking feature and is optional. 
   With reference to  FIG. 5 , the chain guide assembly  10  can further comprise a supplemental projection  80  that limits movement of the shoe  22  in a direction transverse to the chain travel direction  38 . In the illustrated embodiment, the projection  80  is a block structure that extends from the inner surface  22   b  of the shoe  22  near the male connector  40  so that the projection  80  is tightly located in the restricted portion  36  of the keyhole aperture  20  when the shoe  22  is in the second, operative position. In the illustrated example shown in  FIG. 5 , the projection  80  is located between the leg  42   b  and the trailing end  22   d  of the shoe  22 , i.e., downstream relative to the leg  22   b.    
   Those of ordinary skill in the art will recognize that it is within the scope and intent of the present invention to provide more or less than the illustrated two mating pairs ( 48   a , 60   a ;  48   b , 60   b ) of saw-tooth fixing elements. For example, it is contemplated that the first saw-tooth fixing element of the bracket  12  and the second saw-tooth fixing element of the shoe  22  each be defined by three (or more) saw-tooth faces. In this case, the teeth of the three faces of either the first saw-tooth fixing element or the teeth of the three faces of the second saw-tooth fixing element would preferably be nominally offset from each other according to the P/n formula, where P=the pitch of the teeth and n=3. Also, the one or more pairs of saw-tooth fixing elements ( 48   a , 60   a ;  48   b , 60   b ) can be located in positions other than those illustrated without departing from the present invention, as long as the plastic shoe  22  includes at least one second saw-tooth fixing element that engages at least one first saw-tooth fixing element defined by or otherwise provided as a part of the bracket  12 . 
   Modifications and alterations may occur to those of ordinary skill in the art upon reading this specification. It is intended that the invention be construed as including all such alterations and modifications insofar as they fall within the scope of the appended claims as construed literally and/or according to the doctrine of equivalents.