Patent Application
20140312545
A vehicle'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's handling and braking ability, and isolating the vehicle, its occupants, and its contents from bumps, vibrations, and noise. A vehicle'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.
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.
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.
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.
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.
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.
The embodiments described below may be more fully understood by reading the following description in conjunction with the drawings, in which
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.
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.
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.
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.
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.
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
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).
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.
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.
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.
