Abstract:
A method for installing a cushion ring on a sprocket body to construct a sprocket assembly includes applying a deforming force to a cushion ring so that an opening therein is deformed to a shape that accommodate passage of a non-circular flange of a sprocket body therethrough. When the cushion ring is deformed, the non-circular flange of the sprocket body is inserted through the opening of the cushion ring. The deforming force is then released from the cushion ring so that the cushion ring is trapped between the flange and another portion of the sprocket body. The sprocket assembly includes at least one and typically two cushion rings trapped by respective non-circular flanges.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This applications claims benefit of the filing date of and hereby expressly incorporates by reference U.S. provisional application Ser. No. 60/365,503 filed Mar. 18, 2002. 

   BACKGROUND OF THE INVENTION 
     FIGS. 1A-1C  illustrate a conventional cushion ring sprocket S as is well known by those of ordinary skill in the art. The sprocket S comprises an annular member or portion M comprising a plurality of circumferentially spaced-apart teeth T projecting radially outward therefrom. The teeth T are separated by tooth spaces TS. The teeth T engage an associated chain (not shown). The sprocket S finds particular application in automotive engine timing and/or balance systems. 
   The sprocket S further comprises a hub H connected to or defined as a one-piece construction with the annular toothed portion M. First and second portions H 1 ,H 2  of the hub H project axially outwardly from the opposite first and second axial faces F 1 ,F 2  of the annular portion M (see FIGS.  1 B and  1 C). The first and second hub portions H 1 ,H 2  include or define respective cylindrical outer diameters OD 1 ,OD 2 . As noted, the hub H and annular portion M can be assembled from separate structures or can be defined as a one-piece construction. The annular toothed portion M and hub H together define a sprocket body B that rotates about an axis of rotation X. A recess or through-bore C is defined in the hub about the axis of rotation X. The recess or bore C receives a shaft or other member that rotates with or rotatably supports the sprocket body B. The sprocket body B is typically defined from a suitable metal by casting, machining, powdered metal forming techniques or any other suitable means or material. 
   First and second circular cushion rings R 1 ,R 2  are provided and are loosely received on the respective cylindrical outer diameters OD 1 ,OD 2  of hub portions H 1 ,H 2 , i.e., the cushion rings R 1 ,R 2  define inner diameters ID 1 ,ID 2  that are larger than the outer diameters OD 1 ,OD 2  on which the rings are received so that the rings R 1 ,R 2  can eccentrically float on the outer diameters OD 1 ,OD 2 . 
   The cushion rings R 1 ,R 2  are movably captured or trapped on the hub portions H 1 ,H 2  by radially enlarged flanges G 1 ,G 2  that are fastened, welded or otherwise connected to the hub portions H 1 ,H 2 , respectively. The flanges G 1 ,G 2  define respective circular outer diameters OG 1 ,OG 2  that are larger than the cushion ring inner diameters ID 1 ,ID 2  so as to trap the cushion rings loosely between the faces F 1 ,F 2  and flanges G 1 ,G 2 , respectively. 
   The cushion rings R 1 ,R 2  are typically made from metal and, in use, are contacted by chain links of an associated chain (not shown) engaged with the sprocket teeth T. In use, the cushion rings R 1 ,R 2  eccentrically float on the hub outer diameters OD 1 ,OD 2  under force of the chain links and act to buffer or soften the impact of the associated chain with the sprocket S which leads to a decrease on noise. 
   These conventional cushion ring sprockets have been found to be highly effective. One drawback, however, is the relatively complex and time-consuming assembly process insofar as it relates to the installation of the cushion rings R 1 ,R 2  and the connection of the flanges G 1 ,G 2  to the hub portions H 1 ,H 2 . In light of the foregoing, a need has been identified for the cushion ring sprocket and installation method disclosed hereinbelow. 
   SUMMARY OF THE INVENTION 
   In accordance with the present invention, a sprocket assembly includes a sprocket body comprising a hub and an annular toothed portion connected to the hub. The toothed portion comprises opposite first and second axial faces and a plurality of circumferentially spaced-apart teeth that project radially outwardly away from the hub. The first and second flanges are connected to the hub on opposite sides of the annular toothed portion. The first and second flanges each defining a non-circular periphery. A first cushion ring is loosely received on the hub between the first flange and the first axial face of the annular toothed member. A second cushion ring is loosely received on the hub between the second flange and the second axial face of the annular toothed member. 
   In accordance with another aspect of the present invention, a method of constructing a cushion ring sprocket assembly comprises applying a compressive force to a first cushion ring to compress the first cushion ring so that an opening thereof is temporarily and resiliently deformed into a first non-circular opening having a major diameter and a minor diameter, wherein the major diameter of the first non-circular opening is larger than the minor diameter of the first non-circular opening. A first non-circular flange of a sprocket body is aligned with the first non-circular opening so that a major diameter of the first flange is registered with the major diameter of the first non-circular opening and a minor diameter of the first flange is registered with the minor diameter of the first non-circular opening. The major diameter of the first flange is greater than the minor diameter of the first flange. The first non-circular flange is inserted through the first non-circular opening. The compressive force is removed from the first cushion ring so that the opening of the first cushion ring resiliently resumes a shape having an inside diameter that is larger than the minor diameter of the first flange and smaller than the major diameter of the first flange. 
   In accordance with another aspect of the present invention, a method of installing a cushion ring on a sprocket body includes applying a deforming force to a cushion ring so that an opening therein is deformed to a shape that accommodates passage of a non-circular flange of a sprocket body therethrough. When the cushion ring is deformed, the non-circular flange of the sprocket body is inserted through the opening. The deforming force is released from the cushion ring so that the cushion ring is trapped between the flange and another portion of the sprocket body. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention comprises structures and arrangements of structures and steps and arrangements of steps, preferred embodiments of which are disclosed herein with reference to the drawings wherein: 
       FIG. 1A  (prior art) is an isometric illustrations of a conventional cushion ring sprocket; 
       FIGS. 1B and 1C  are exploded isometric view of the sprocket shown in  FIG. 1A ; 
       FIG. 2  is a front elevational view of a sprocket body formed in accordance with the present invention; 
       FIG. 2A  is a sectional view taken along line II A —II A  of  FIG. 2 ; 
       FIG. 3  is a partial sectional view of a blank from which a sprocket body according to the present invention is formed; 
       FIG. 4  is a diagrammatic illustration of a method for installing a cushion ring on a sprocket body according to the present invention; 
       FIG. 5  is a front elevational view of a cushion ring sprocket assembly formed in accordance with the present invention (with the cushion rings (only one visible) centered relative to the axis of rotation); 
       FIG. 5A  is a sectional view taken along line V A —V A  of  FIG. 5 ; 
       FIG. 6  corresponds to  FIG. 5  but shows the cushion rings (only one visible) eccentrically arranged relative to the axis of rotation as occurs during use; and, 
       FIG. 6A  is a sectional view taken along line VI A —VI A  of FIG.  6 . 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   Referring briefly to  FIGS. 6 and 6A , a cushion ring sprocket assembly  10  formed in accordance with the present invention comprises a sprocket body  20  and at least one cushion ring operably connected to the sprocket body  20 . In the illustrated embodiment, the sprocket assembly  10  comprises two cushion rings  60   a,   60   b  operably connected thereto. In use, the sprocket assembly  10  functions substantially identically to the sprocket S described above in relation to  FIGS. 1A-1C . 
   Referring now to  FIGS. 2 and 2A , the sprocket body  20  is shown separately and comprises an annular toothed member or portion  22  comprising a plurality of circumferentially spaced-apart teeth  24  projecting radially outward therefrom. The teeth  24  are separated by tooth spaces  26 . 
   The sprocket body  20  further comprises a hub  30  connected to or defined as a one-piece construction with the annular portion  22 . As shown herein, the body  20 , including the annular portion  22  and hub  30 , is defined as a one-piece construction from a suitable metal material as is generally known in the art of automotive timing and balance chain drive systems. Specifically, the sprocket body  20  is defined using conventional metal forming and working techniques such as casting, forging, machining, powdered metallurgy. 
   The hub  30  comprises first and second hub portions  30   a , 30   b  that project axially outwardly from the opposite first and second axial faces  22   a , 22   b  of the annular portion  22 . The first and second hub portions  30   a , 30   b  include or define respective cylindrical (within acceptable tolerances) outer diameter surfaces  32   a , 32   b.    
   A recess or through-bore  34  is defined in the hub about an axis of rotation X. The bore  34  receives an associated shaft or other member that rotates with or rotatably supports the sprocket body  20 . The outer diameter surfaces  32   a , 32   b  are concentric with the axis of rotation X. 
   The first and second hub portions  30   a , 30   b  comprise respective flanges  40   a , 40   b  connected thereto or formed as a one-piece construction therewith. The flanges  40   a , 40   b  are spaced from the opposite faces  22   a , 22   b  of the annular toothed portion  22  so that first and second circular grooves  42   a , 42   b  are defined. The first groove  42   a  is defined by the face  22   a , the cylindrical surface  32   a  and the flange  40   a . Likewise, the second groove  42   b  is defined by the face  22   b , the cylindrical surface  32   b  and the flange  42   b.    
   In accordance with the present invention, the flanges  42   a , 42   b  define respective non-circular peripheries  44   a , 44   b  so that the grooves  42   a , 42   b  vary in depth at different circumferential locations as measured from the cylindrical surfaces  32   a , 32   b  to the relevant flange periphery  44   a , 44   b . With particular reference to  FIG. 2A , the grooves  42   a , 42   b  have a first depth D 1  at a first location and a second depth D 2  at a second location. The flanges  44   a , 44   b  are preferably but not necessarily identical to each other, so the depths of the grooves  42   a , 42   b  can vary relative to each other. 
   In the illustrated preferred embodiment, the flange peripheries (peripheral edges)  44   a , 44   b  are elliptic and define a major axis E 1  and a minor axis E 2 . The flanges thus define a major diameter DE 1  at the major axis E 1  and a minor diameter DE 2  at the minor axis E 2 , wherein DE 1 &gt;DE 2 . Regardless of the exact non-circular shape of the peripheries  44   a , 44   b , they define first and second diameters DE 1 ,DE 2 , wherein DE 1 &gt;DE 2 . Those of ordinary skill in the art will recognize from the following disclosure that the peripheries  44   a , 44   b  need not be elliptic and can define other non-circular shapes in accordance with the present invention to satisfy the above parameters. 
   With brief reference to  FIG. 3 , in one embodiment, the sprocket body  20  is defined from a blank formed via powdered metal and/or other processing. The blank comprises a hub portion  50 , an annular portion  52  projecting from the hub portion  50 , and a central through-bore  54 . The hub portion  50  of blank can be defined to have a desired non-circular axial ends  50   a , 50   b  that will ultimately define the flanges  40   a , 40   b  or these non-circular flanges  40   a , 40   b  can be formed by machining or the like. The blank  50  is machined or otherwise processed to remove material therefrom as indicated by the broken lines in order to define the cylindrical hub outer diameter surfaces  32   a , 32   b , teeth  24  and tooth spaces  26 . According to an alternative method, the sprocket body  20  is constructed according to the process described above in relation to  FIGS. 1A-1C , wherein the non-circular flanges  40   a , 40   b  are fastened, welded or otherwise connected to the hub portions  30   a , 30   b , respectively. The finished sprocket body  20 , including the non-circular flanges  40   a , 40   b , can also be formed directly, i.e., without first forming a blank and machining or otherwise working same, according to advanced powdered metal forming techniques, die-casting, and other methods known in the art. It is not intended that the invention be limited to any particular method of forming the sprocket body  20 . 
     FIGS. 5 and 5A  show the subject sprocket assembly  10  with the first and second circular cushion rings  60   a , 60   b  centered about the axis of rotation X. The rings  60   a , 60   b  are loosely received in the respective grooves  42   a , 42   b  and float eccentrically relative to cylindrical surfaces  32   a , 32   b . The rings  60   a , 60   b  each define a central opening having a cylindrical (with acceptable tolerances) inner diameter DR, wherein DE 1 &gt;DR&gt;DE 2 , i.e., the inner diameter DR of the rings  60   a , 60   b  is larger than the minor diameter DE 2  of flanges  40   a , 40   b  but smaller than the major diameter DE 1  of flanges  40   a , 40   b.    
   As shown in  FIG. 5A , when the rings  60   a , 60   b  are centered relative to axis of rotation X, a portion of the flange peripheries  44   a , 44   b  overlap the rings  60   a , 60   b  to define a radial interference  11  that prevents the rings  60   a , 60   b  from moving axially outwardly away from the annular toothed portion  22  over the respective flanges  40   a , 40   b . In  FIG. 5A , it can also be seen that a radial gap P 1  is defined between the inner diameter DR of the rings  60   a , 60   b  and the flange peripheries  44   a , 44   b  in the region of the minor axis E 2 , but the above-noted interference  11  prevents the rings  60   a , 60   b  from escaping the grooves  42   a , 42   b . The interference I 1  is required merely to prevent the rings  60   a , 60   b  from escaping the respective grooves  42   a , 42   b  during inoperative handling of the sprocket  10 . As such, the interference  11  can be very small, e.g., 0.5 millimeters (mm). As described just below, the rings  60   a , 60   b  are trapped behind the flanges  40   a , 40   b  to a much greater extent during an operative state of the sprocket  10 . 
   Referring again to  FIGS. 6 and 6A , the rings  60   a , 60   b  are shown in an operative (non-centered) position as would occur during use of the sprocket assembly  10 . In particular, links L 1 ,L 2  of an associated chain C (shown in phantom) contact the rings  60   a , 60   b  and urge same into an eccentric relationship with the axis of rotation X. As such, when the sprocket assembly  10  is in use, portions of the rings  60   a , 60   b  are fully seated (and thus axially captured) in the respective grooves  42   a , 42   b.    
   Installation of the rings  60   a , 60   b  is disclosed with reference to FIG.  4 . In particular, a tool Q comprises first and second surfaces S 1 ,S 2  between which a circular cushion ring  60   a  is positioned (only the ring  60   a  is shown in  FIG. 4  but the installation procedure for the ring  60   b  corresponds to the procedure for the ring  60   a ). The tool Q includes mechanical, hydraulic, and/or electrical means for moving the first and second surfaces S 1 ,S 2  toward each other so that diametrically opposed portions  62   a , 62   b  of ring  60   a  are compressed toward each other a sufficient distance so that the ring temporarily resiliently elastically deforms so as to define a non-circular opening EO (the opening EO is elliptic in the illustrated preferred embodiment) with a major axis EA 1  and a minor axis EA 2 , wherein a major diameter ED 1  is defined at the major axis EA 1 , a minor diameter ED 2  is defined at the minor axis EA 2 , and wherein ED 1 &gt;ED 2 . Furthermore, the ring  60   a  is dimensioned so that when compressed by the tool Q as described, elliptical opening EO receives the flange  40   a  therethrough (when the flange  40   a  is properly registered or aligned) for installation of the ring  60   a  in the groove  42   a . When the surfaces S 1 ,S 2  of the tool Q are moved apart, the ring  60   a  resiliently resumes its relaxed shape with a circular (within acceptable tolerances) inside diameter DR as described above. As such, once the ring  60   a  resumes its free circular shape, it is trapped or captured between the flange  40   a  and the annular toothed member  22 . The rings  60   a , 60   b  can be uninstalled by reversing the above procedure. 
   The cushion rings  60   a , 60   b  are typically made from metal such as a suitable steel generally known in the art of automotive chain drive systems for engine timing and balance applications. In one embodiment, the rings are defined from SAE A52100 steel. The exact material used must be selected, in combination with the dimensions of the rings  60   a , 60   b , so that the rings  60   a , 60   b  can be sufficiently elastically compressed to define a suitable non-circular opening EO without permanent deformation while also allowing the cushion ring  60   a , 60   b  to resiliently return to its natural circular shape when the compressing force subsides. 
   The amount by which the rings  60   a , 60   b  can be compressed without permanent deformation so that they resiliently resume their circular shape when the compressing force subsides will vary depending upon the particular material from which the rings  60   a , 60   b  are manufactured and the particular dimensions of the rings. In general, the rings  60   a , 60   b  must be able to be deformed sufficient for installation of the rings  60   a , 60   b  over the non-circular flanges  40   a , 40   b  without permanent deformation of the rings  60   a , 60   b , i.e., the rings must not be compressed beyond their elastic limit or yield point, which will vary according to materials and dimensions thereof which can be easily determined by those of ordinary skill in the art mathematically according to a stress-strain diagram and/or empirically as desired. Of course, it is desirable to compress the rings  60   a , 60   b  the minimum amount sufficient to allow the ring to be received over the corresponding non-circular flange  40   a , 40   b . In one embodiment, the rings  60   a , 60   b  are defined from SAE A52100 steel to have an outside diameter of 41.9862 millimeters (mm), an inside diameter of 39.9542 mm and a thickness (the difference between the outside and inside diameters) of 2.032 mm when uncompressed (free). These rings  60   a , 60   b  can be compressed at least to an elliptical shape having a major outside diameter of 43.5102 mm and a minor outside diameter of 40.4622 mm for installation as described above. 
   The terms “circular” and “cylindrical” as used herein are intended to be construed with an allowance for acceptable tolerances as known by those of ordinary skill in the art. Furthermore, the invention has been disclosed with reference to preferred embodiments. Modifications and alterations will occur to those of ordinary skill in the art, and it is intended that the claims be construed literally and/or according to the doctrine of equivalents to encompass all such modifications and alterations.