Abstract:
A spring isolator may include a first portion and second portion joined together or integrally formed and configured to dampen and absorb loads from a coil spring. The first portion may be a microcellular polyurethane material and the second portion may be a thermoplastic polyurethane material. The first portion and second portion may be chemically bonded together along at least one boundary by injection molding the second portion into a mold already containing the first portion. The spring isolator made from chemically bonded portions may provide effective resistance to radial and longitudinal migration of the isolator upon introduction of coil spring forces and vibration.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    A vehicle&#39;s suspension system connects a vehicle to its wheels and allows relative motion between them. The suspension system serves multiple purposes—contributing to a vehicle&#39;s handling and braking ability, and isolating the vehicle, its occupants, and its contents from bumps, vibrations, and noise. A vehicle&#39;s suspension may include coil springs that compress and expand to support the weight of the vehicle and absorb motion between the wheels and the vehicle. The coil spring may be attached to the vehicle through a spring seat. The spring seat may include an isolator situated between the coil spring and the vehicle. The isolator may serve to dampen and absorb vibrations of the coil spring. 
         [0002]    Due to persistent forces such as weight of the vehicle, input forces transmitted through the spring due to the relative motion of the wheel, and vibrations of the spring, an isolator may wear out over time or may migrate away from its intended position between the end of the spring and the rest of the vehicle causing the spring to directly contact rigid portions of the vehicle. Vibrations of the spring and relative movement between the spring and the rigid portions of the vehicle may lead to increased wear on the contacted vehicle portions, decreased performance and safety, and unsatisfactory noise and ride comfort. Thus, there is a need for a cost-effective spring isolator that may resist wear and migration. 
       SUMMARY OF THE INVENTION 
       [0003]    The descriptions below include apparatuses for isolating a spring and methods of making such apparatuses. A spring isolator may include a first portion and second portion joined together or integrally formed and configured to dampen and absorb loads from a coil spring. The first portion may be a microcellular polyurethane material and the second portion may be a thermoplastic polyurethane material. The first portion and second portion may be chemically bonded together along at least one boundary by injection molding the second portion into a mold already containing the first portion. The spring isolator made from chemically bonded portions may provide effective resistance to radial and longitudinal migration of the isolator upon introduction of coil spring forces and vibration. 
         [0004]    According to one embodiment of the invention, a spring isolator comprises a first portion disposed about a longitudinal axis and forming a contact surface for a spring; a second portion adjacent to the first portion along at least one boundary and disposed about the axis and defining an opening along the axis; wherein the first portion and second portion are chemically bonded together along the at least one boundary. 
         [0005]    According to another embodiment of the invention, a method for making a spring isolator comprises a method of making a spring isolator comprising: forming a first portion by cutting a segment from tube-shaped stock; inserting the first portion into an injection mold; injecting thermoplastic polymer material into the injection mold to create a second portion that is chemically bonded to the first portion without the use of any adhesive or external bonding agent; removing the integrally molded spring isolator from the mold; and finishing the spring isolator. 
         [0006]    Other systems, methods, features and advantages will be, or will become, apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the following claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The embodiments described below may be more fully understood by reading the following description in conjunction with the drawings, in which 
           [0008]      FIG. 1  is a cross-sectional drawing of a vehicle spring mount assembly including a spring isolator according to one embodiment of the invention; 
           [0009]      FIG. 2  is a perspective drawing of a spring isolator according to one embodiment of the invention; 
           [0010]      FIG. 3  is a cross-sectional drawing of a spring isolator according to one embodiment of the invention; 
           [0011]      FIG. 4  is a cross-sectional drawing of a portion of a spring isolator according to one embodiment of the invention; 
           [0012]      FIG. 5  is a cross-sectional drawing of a portion of a spring isolator according to one embodiment of the invention; 
           [0013]      FIG. 6  is a cross-sectional drawing of a portion of a spring isolator according to one embodiment of the invention; 
           [0014]      FIG. 7  is a cross-sectional drawing of a portion of a spring isolator according to one embodiment of the invention; 
           [0015]      FIG. 8  is a cross-sectional drawing of a portion of a spring isolator according to one embodiment of the invention; 
           [0016]      FIG. 9  is a flowchart of a method of making a spring isolator according to one embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]      FIG. 1  illustrates how a spring isolator  10  may be installed in a vehicle. Spring isolator  10  is attached to a top mount assembly  12 . Spring isolator  10  may be mounted on a bearing housing  11 , which is a component of top mount assembly  12 . Spring isolator  10  may protect the bearing housing  11  and may isolate the vehicle from the motion and vibrations of a coil spring  50 , which is not depicted in  FIG. 1 . 
         [0018]      FIGS. 2 and 3  depict the spring isolator  10  in perspective and cross-section respectively. Spring isolator  10  may be made of two portions, a first portion  20  and a second portion  30 . First and second portions may be disposed about a longitudinal axis A and may form an opening  40  that extends along the axis A. First portion  20  and second portion  30  may be joined together or integrally formed. For example, first portion  20  and second portion  30  may be chemically bonded together. The end of a coil spring  50  may abut spring isolator  10  at a contact surface of the first portion  20 . Spring isolator dampens and absorbs loads and vibrations from coil spring  50 . 
         [0019]    First portion  20  may be made from a resilient material, such as a polymer or rubber. For example, first portion  20  may be made from microcellular polyurethane (“MCU”). Second portion  30  may be made from polymer, such as thermoplastic polyethylene (“TPE”) or thermoplastic polyurethane (“TPU”), or metal, such as steel. For example, second portion  30  may be made from glass fiber-reinforced TPU. 
         [0020]      FIG. 4  depicts a cross-sectional view of a section of spring isolator  10 . First portion  20  may have a generally rectangular cross-section with a thickness measured along the axis A between a contact surface  21 , and a distal boundary  22 . Other cross-sectional shapes are possible, for example, square, trapezoidal, and elliptical. First portion  20  may also have an inner boundary  23  defining the nearest surface of first portion  20  to axis A. First portion  20  may be adjoined with second portion  30  along two boundaries, distal boundary  22  and inner boundary  23 , indicated by a thicker line in  FIG. 4 . 
         [0021]    Second portion  30  may have a generally “L-shaped” cross-section with inner surface  32  defining opening  40  which extends along axis A. Second portion  30  also may have a distal section  33  that abuts the mount assembly  11 . Second portion  30  may also have a spring retention section  31  that extends longitudinally along axis A beyond the first portion  20  that may maintain the position of the coil spring  50  in a radial direction. 
         [0022]    Spring isolator  10  may absorb and dampen longitudinal forces and vibrations through the resilient and compressible first portion  20  while first portion  20  is fully supported and prevented from radial and longitudinal migration by adjoinment to second portion  30 . Spring isolator  10  is particularly advantageous when second portion  30  is a TPU material injection molded in the presence of first portion  20  made from MCU. The chemical bond without the use of any adhesive or external bonding agent resulting between first portion  20  and second portion  30  in the integrally molded spring isolator  10  prevents migration of the first portion  20  especially effectively. 
         [0023]      FIG. 5  depicts a cross-sectional view of a section of spring isolator  200  where first portion  220  may be bonded to second portion  230  along one boundary, inner boundary  223 , indicated by a thicker line in  FIG. 5 . Second portion  230  may not have a longitudinal section distal to first portion  220 . Therefore, first portion  220  may have a distal surface  222  that abuts the mount assembly  11 . The bond along inner boundary  223  may advantageously provide support to, and prevent migration of, first portion  220 . 
         [0024]      FIG. 6  depicts a cross-sectional view of a section of spring isolator  300  where first portion  320  and second portion  330  may be bonded along three boundaries, including inner boundary  323  and distal boundary  322 . Second portion  330  may have rim  334  extending radially away from axis A over a portion of contact surface  321  of first portion  320 , thereby creating a third boundary along which first portion  320  and second portion  330  are bonded. The three bonding boundaries are indicated in by a thicker line in  FIG. 6 . Rim  334  and an additional bonding boundary on contact surface  321  may additionally or alternatively prevent migration, particularly in a longitudinal direction. 
         [0025]      FIG. 7  depicts a cross-sectional view of a section of spring isolator  400  where first portion  420  and second portion  430  may be bonded along four boundaries, including inner boundary  423  and distal boundary  422 . Second portion  430  may have a longitudinal rim  434  extending radially away from axis A over a portion of contact surface  421  of first portion  420 , thereby creating a third boundary along which first portion  420  and second portion  430  are bonded. Second portion  430  may alternatively or additionally have a radial rim  435  extending longitudinally along an outer surface  424  of first portion  420 . The four bonding boundaries are indicated by a thicker line in  FIG. 6 . Rims  434  and  435  and the additional bonding boundaries on contact surface  421  and outer surface  424  may additionally or alternatively prevent migration, in both longitudinal and radial directions. 
         [0026]      FIG. 8  depicts a cross-sectional view of a section of spring isolator  500  which may have first portion  520  and second portion  530 . First portion  520  may have a plurality of surface area-increasing features such as grooves  525  machined into one or more boundaries, including distal boundary  522 . Each of grooves  525  may be positioned at a set radius from axis A, extending in a circle, oval, ellipse, or a non-circular path, along the distal boundary. Alternatively, the plurality of grooves  525  may be configured as linear grooves extending radially away from axis A. Grooves  525  may provide additional surface area of bonding between first portion  520  and second portion  530  and may advantageously provide a mechanical impediment to radial migration of first portion  520 . The meshed interface between first portion  520  and second portion  530  may advantageously increase the amount of force applied to first portion  520  and second portion  530  necessary to cause second portion  530  to shear off of first portion  520 . 
         [0027]      FIG. 9  depicts a flowchart of a method of making a spring isolator, including the various spring isolators depicted in  FIGS. 2-8 , but specific reference is made to spring isolator  10 . 
         [0028]    Long tubes of MCU material with a desired cross-sectional profile may be used to create large numbers of first portion  20 . For example, the tube-shaped MCU stock may have a cylindrical shape with a constant outer radius, and a constant inner radius defining a longitudinal opening. First portion  20  may be made by cutting the tube-shaped MCU stock into segments of a desired longitudinal thickness ( 110 ). For example, first portion  20  may be made by cutting the tube-shaped MCU stock perpendicular to the longitudinal axis. 
         [0029]    First portion  20  may be machined to introduce optional surface-area increasing features into one or more surfaces of the first portion  20  ( 115 ). This may be accomplished by any number of machining techniques, including, but not limited to, lathing, grinding, milling, drilling, contouring, and laser machining. 
         [0030]    First portion  20  may be inserted into a mold of the desired shape of the spring isolator  10  ( 120 ). The mold may contain a fixture to hold first portion  20  in a desired position relative to the remaining cavity of the mold. TPU may be injected into the mold, filling the remaining mold cavity ( 130 ). The injected TPU may form the second portion  30  in the desired shape of the remaining mold cavity. Where the molten TPU meets one or more surfaces of first portion  20 , the TPU and MCU may chemically bond together, forming bonding boundaries. The mold and first portion fixture may be configured so that any desired spring isolator shape and bonding boundaries, including but not limited to the spring isolator shapes depicted in  FIGS. 2-8 , may be created. 
         [0031]    Once the TPU is fully injected and the polymer allowed to cure, the integrated spring isolator  10  may be removed from the mold and finished to remove any imperfections created during the molding process ( 140 ). 
         [0032]    A substantial cost savings benefit may arise from utilizing segments of tube-shaped MCU stock in making a spring isolator. MCU parts are molded in single-cavity tools because multi-cavity tools for molding MCU are not made. Manufacturers require as many single cavity tools as needed to support mass production volumes, for example,  4  million components per year. By utilizing tube-shaped MCU stock cut into segments, the number of necessary single cavity MCU tools necessary for mass production may be advantageously limited. One advantage is the reduction in costs associated with acquiring and maintaining the additional tooling that may be required to mold MCU. 
         [0033]    Thus, spring isolators may be cost-effectively made to desired specifications while exhibiting advantageous abilities to dampen and absorb spring loads and vibrations while resisting migration. 
         [0034]    While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.