Abstract:
A lightweight heavy duty bushing assembly for use in a vehicle suspension system and being low cost and having a high assembly tolerance is disclosed. A metal bar pin is press fit into a bushing formed from a metal sleeve bonded to an elastomeric housing. The metal sleeve is deformable such that exact tolerances of the metal sleeve and the bar pin are not required. The metal bar pin has extended ends with a hole in each end for attachment of the metal bar pin to vehicle suspension components, mounting brackets, or to the vehicle frame.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of U.S. patent application Ser. No. 11/849,731, filed Sep. 4, 2007 now abandoned, and claims the benefit of priority of the filing date of U.S. patent application Ser. No. 11/849,731. The full disclosure of U.S. patent application Ser. No. 11/849,731 is hereby incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention is generally directed to bushing assemblies in vehicle suspension systems. More specifically, the present invention is directed to a unique construction of bushing assemblies used in vehicle suspension systems. 
     Vehicle suspension bushing assemblies are known. One such bushing assembly may be formed from a round inner metal bar pin that is an elongated piece of metal such as cast iron which is contained within a combination of a circular metal sleeve attached to an elastomeric material such as rubber. The circular metal sleeve and the round bar pin must be machined to very exact tolerances to properly fit together. The increased machining and processing of the components due to the required low tolerances increases costs. The circular bar pin may be heavy, which leads to increased material, manufacturing and shipping costs. 
     Another known bushing assembly may be formed from a round inner metal bar pin that is a machined length of metal such as aluminum that is bonded directly to an elastomeric material such as rubber. The direct bonding of the rubber to the inner metal bar pin requires specific types of metal and additional machining or processing to yield a proper bond between the inner metal and the rubber, thus increasing costs. 
     The combined inner metal bar pin bonded to a rubber bushing may also be inserted into a metal sleeve to form another known bushing assembly. The bushing assembly may have attachment means on both ends of the inner metal bar pin. 
     While prior vehicle suspension bushing assemblies have been adequate for certain purposes, they have lacked some of the advantages obtainable with the embodiments of the present invention. Many of these advantages are clearly described herein and others shall be readily apparent to those skilled in the art. 
     One advantage achieved by the present invention is the use of a deformable metal sleeve into which the metal bar pin is press fit. 
     Another advantage achieved by the present invention is by the use of low cost steel tube for the metal sleeve. 
     Another advantage achieved by the present invention is the use of an as-cast or near as-cast ductile inner metal bar pin that requires little or no machining or processing. 
     Another advantage achieved by the present invention is the lower costs achieved by the need for little or no machining of the inner metal bar pin. 
     Another advantage achieved by the present invention is the use of an inner metal bar pin with a non-circular cross section that has voids bounded by radially extending contact portions. 
     Another advantage achieved by the present invention is the lower cost of the reduced weight achieved by the use of an inner metal bar pin with a non-circular cross section with voids. 
     Another advantage achieved by the present invention is the lower cost of the reduced material required by the use of an inner metal bar pin with a non-circular cross section with voids. 
     Another advantage achieved by the present invention is the use of ductile cast iron for the metal bar pin. 
     Another advantage achieved by the present invention is the use of a process to insert the metal bar pin into the metal sleeve and rubber combination and to insert the resulting bushing assembly into a vehicle suspension component such as a torque rod in a single press fit operation. 
     Another advantage achieved by the present invention is by allowing the steel tube to deform into a non-circular shape during the press fit operation instead of requiring a precise tolerance to fit a uniform circular metal sleeve. 
     Another advantage achieved by the present invention is by controlling the amount of the steel tube deformation such that the bond line with the rubber component is not compromised. 
     Another advantage achieved by the present invention is designing a cruciform embodiment such that the press fit between the cruciform and the steel tube sleeve has two cruciform extension end surfaces in full contact with the steel tube and two cruciform extension end surfaces in only a line contact with the steel tube. 
     These and other advantages of the preferred forms of the invention will become apparent from the following description. It will be understood, however, that at apparatus could still appropriate the invention claimed herein without exhibiting each and every one of these advantages, including those gleaned from the following description. The appended claims, not any advantages recited or implied herein, define the subject matter of this invention. Any and all advantages are derived from the preferred forms of the invention, not necessarily the invention in general. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a vehicle suspension bushing assembly. A bushing assembly has a ductile inner metal bar pin with a center section having an optimized non-circular cross section with voids for maximum strength at minimum weight. The ductile inner metal bar pin has an extended end section on each side of the center section. Each extended end section of the ductile inner metal bar pin has a hole for means of attachment to other suspension components, mounting brackets, or to the vehicle frame. The ductile inner metal bar pin is press fit into a bushing comprised of an elastomeric material housing such as rubber bonded or otherwise secured to a metal sleeve such as a deformable steel tube. The resulting deformable steel tube after the press fit operation has a cross section that is non-circular. The press fit assembly has adequate frictional force such that the inner metal bar pin does not translate within the metal sleeve under service duty. 
     The present invention also allows the inner metal bar pin to be press fit into the metal sleeve and rubber bushing and to insert the entire bushing assembly into a vehicle suspension component such as a torque rod in a single one step operation. 
     In addition, other built-in features are available with the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following detailed description, reference will frequently be made to the following drawings, in which like reference numerals refer to like components, and in which: 
         FIG. 1  is a perspective view of a lightweight heavy duty bushing assembly constructed in accordance with the principles of the present invention; 
         FIG. 2  is a side elevational view of the bushing assembly shown in  FIG. 1 ; 
         FIG. 3  is an end view of the bushing assembly shown in  FIG. 1 ; 
         FIG. 4  is a top view of the bushing assembly shown in  FIG. 1 ; 
         FIG. 5  is a perspective view of part of the bushing assembly shown in  FIG. 1 ; 
         FIG. 6  is a side elevational view of the bushing shown in  FIG. 5 ; 
         FIG. 7  is an end view of the bushing shown in  FIG. 5 ; 
         FIG. 8  is a perspective view of an embodiment of a four point bar pin having a cruciform cross section constructed in accordance with the principles of the present invention; 
         FIG. 9  is a side elevational view of the bar pin shown in  FIG. 8 ; 
         FIG. 10  is an end view of the bar pin shown in  FIG. 8 ; 
         FIG. 11  is a sectional view of part of a bushing assembly having a three point alternative embodiment of a bar pin; 
         FIG. 12  is a sectional view of part of a bushing assembly having a five point alternative embodiment of a bar pin; 
         FIG. 13  is a sectional view of part of a bushing assembly having a six point alternative embodiment of a bar pin; 
         FIG. 14  is an end view of the bushing assembly shown in  FIG. 1  better showing the as assembled condition; 
         FIG. 15  is an end view similar to  FIG. 14  better showing further details of a preferred as assembled condition; and 
         FIG. 16  is a perspective view of a vehicle suspension incorporating bushing assemblies according to the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIGS. 1-4  illustrate a lightweight heavy duty bushing assembly  10  for vehicle suspensions. A ductile inner metal bar pin  30  is press fit into a bushing  20 . The ductile inner metal bar pin  30  has a central portion  31  with a cruciform cross-section that is comprised of voids  32  bounded by radially extending contact surfaces  33 . The ductile inner metal bar pin  30  has an end portion  35  that extends beyond each end of the central portion  31 . Each extended end portion  35  of the ductile inner metal bar pin  30  has a hole  37  through it for attachment to vehicle suspension components, mounting brackets, or to the vehicle frame (not shown). The ductile inner metal bar pin  30  is preferably cast of metal material, such as iron. Alternatively, the ductile inner metal bar pin  30  could be cast from other materials or the ductile inner metal bar pin  30  could be forged or machined from a variety of materials. 
     The bushing  20  is comprised of a metal sleeve  40  that is attached such as by bonding to an elastomeric housing  50  such as rubber. The elastomeric housing  50  is shaped to the desired dimensions by a process such as molding. The metal sleeve  40  may be made of a deformable metal such as steel. 
       FIGS. 5-7  illustrate an embodiment of the bushing  20 . As previously noted, the bushing  20  may be comprised of a metal sleeve  40  that is bonded to an elastomeric housing  50 . Alternatively, the entire bushing  20  may be formed from a single material by a process such as casting or molding. The cross section of the metal sleeve  40  prior to receiving the ductile inner metal bar pin  30  is generally circular as shown in  FIG. 7 . 
       FIGS. 8-10  illustrate an embodiment of the ductile inner metal bar pin  30 . The ductile inner metal bar pin  30  has a central section with a four point or cruciform shape as shown in  FIG. 10 . The cross section of the ductile inner metal bar pin  30  is optimized to reduce weight and improve structural efficiency. The holes  37  in the extended end portions  35  of the ductile inner metal bar pin  30  are sized and positioned to provide appropriate means to attach the ductile inner metal bar pin  30  to vehicle suspension components or to the vehicle frame while maximizing the strength of the ductile inner metal bar pin  30 . 
       FIG. 11  illustrates a three point embodiment of the central section of a ductile inner metal bar pin  60  comprised of voids  32  bounded by radially extending contact surfaces  33  within a metal sleeve  40 . The cross section of the ductile inner metal bar pin  60  is optimized to reduce weight and improve structural efficiency. 
       FIG. 12  illustrates a five point embodiment of the central section of a ductile inner metal bar pin  70  comprised of voids  32  bounded by radially extending contact surfaces  33  within a metal sleeve  40 . The cross section of the ductile inner metal bar pin  70  is optimized to reduce weight and improve structural efficiency. 
       FIG. 13  illustrates a six point embodiment of the central section of a ductile inner metal bar pin  80  comprised of voids  32  bounded by radially extending contact surfaces  33  within a metal sleeve  40 . The cross section of the ductile inner metal bar pin  80  is optimized to reduce weight and improve structural efficiency. 
     It is to be understood that  FIGS. 11-13  are partial figures of the entire bushing assembly and that the embodiments illustrated in  FIGS. 11-13  also contain an elastomeric housing bonded or otherwise secured to the metal sleeve. 
       FIG. 14  illustrates an embodiment of a lightweight heavy duty bushing assembly  10  where the press fit of the ductile inner metal bar pin  30  caused the metal sleeve  40  to deform from a circular cross section to a non-circular cross section, thus enabling a high tolerance between the components for assembly. 
       FIG. 15  illustrates another embodiment of the lightweight heavy duty bushing assembly  10  shown in  FIG. 14 . Two of the cruciform extension end surfaces  38  are in full contact with the metal sleeve  40  and the other two cruciform extension end surfaces  39  make only a line contact with the metal sleeve  40 . The ductile inner metal bar pin  30  is therefore structurally efficient in that the metal material is concentrated where it is needed to react to torque rod loads. Looser tolerances are thus permitted on the inner diameter of the metal sleeve  40  and the outer surfaces of the cruciform extension end surfaces  38 ,  39  allowing for easier assembly of the ductile inner metal bar pin  30  into the metal sleeve  40 . Frictional forces between the ductile inner metal bar pin  30  and the metal sleeve  40  prevent translation of the ductile inner metal bar pin  30  within the metal sleeve  40  while under service duty or operation. 
       FIG. 16  shows an exemplary vehicle suspension  100  which may employ bushing assemblies according to the present disclosure. The vehicle suspension  100  of  FIG. 16  includes, among other things, a plurality of torque rods  102  each connected at one end to an axle or air spring bracket  104  and at the other end to a mounting bracket  106 . An upper end of each mounting bracket  106  is fastened to the vehicle frame  108 , thereby securing the vehicle suspension  100  to the vehicle frame  108 . In the illustrated embodiment, each end of the torque rods  102  is provided with a bore into which a bushing assembly  10  according to the present disclosure may be inserted. The holes  37  at the end portions  35  of the inner metal bar pins  30  ( FIG. 1 ) may receive fasteners or the like to secure each bushing assembly  10  (and, hence, the associated end of the torque rod  102 ) to an axle bracket  104  or mounting bracket  106 . 
     While this invention has been described with reference to several illustrative embodiments, it will be understood that this description shall not be construed in a limiting sense. Rather, various changes and modifications can be made to the illustrative embodiments without departing from the true spirit and scope of the invention, as defined by the following claims. Furthermore, it will be appreciated that any such changes and modifications would be recognized by those skilled in the art as an equivalent to one or more elements recited in the following claims, and shall be covered by such claims to the fullest extent permitted by law.