Abstract:
An adjustable spring system includes an adjustment member adjustable relative to a coil spring to provide a desired number of unsupported coils. A method of adjusting the spring rate of the spring includes detecting a condition, and driving the adjustment member with an actuator in response to the detected condition. An effective length of the spring is changed with the adjustment member.

Description:
[0001]    This invention was made with government support from the National Aeronautics and Space Administration under Contract No.: NNM06AB13C. The government may have certain rights to this invention pursuant to Contract No. NNM06AB13C awarded by the National Aeronautics and Space Administration. 
     
    
     BACKGROUND 
       [0002]    This disclosure relates to an adjustable spring system and a method of adjusting a spring rate in the system. 
         [0003]    Adjustable coil springs have been used in coil-over type suspension systems. In one type of system, a shock absorber includes a body receiving a rod that is telescopically movable with respect to the body. The shock absorber is arranged between first and second members and damps the relative movement between the members. 
         [0004]    In a coil-over arrangement, a coil spring is supported between an end of the rod and the body. In one example, a portion of the body has an annular groove that receives a portion of the coil spring. The body is positioned with respect to the coil spring to change the effective length of the coil spring and provide a desired spring rate. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    The disclosure can be further understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
           [0006]      FIG. 1  is a schematic view of an example adjustable spring system. 
           [0007]      FIGS. 2A and 2B  schematically illustrate a spring assembly of the adjustable spring system depicted in  FIG. 1  in first and second positions. 
           [0008]      FIG. 3  is a schematic view of one example application of the adjustable spring system. 
           [0009]      FIGS. 4A-4C  schematically depict an example adjustable spring system for the application illustrated in  FIG. 3 . 
           [0010]      FIGS. 5A-5B  schematically illustrate another application of the adjustable spring system. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    An adjustable spring system  10  is schematically illustrated in  FIG. 1 . The system  10  includes one or more spring assemblies  11  arranged between first and second members  12 ,  14  that are spaced apart from and movable relative to one another. The spring assemblies  11  provide an adjustable spring rate between the first and second members  12 ,  14 . 
         [0012]    Each spring assembly  11  includes a spring  16  having coils that cooperates with an adjustment member  18  that is drivable with respect to the spring  16  to change its spring rate by changing the length of the spring  16 . The spring  16  and adjustment member  18  are coaxial with one another. An actuator  20  is operatively coupled to the adjustment member  18 . A controller  22  communicates with the actuator  20  and a sensor  24  that detects a condition. In one example, the sensor  24  is an accelerometer, which may be used by the controller  22  to detect an undesired natural frequency of at least one of the first and second members  12 ,  14 . In the example, a manual switch  26  is in communication with the actuator  20 , either directly or indirectly, and is configured to be operable by a user to manually drive the adjustment member  18 , as desired. 
         [0013]    Referring to  FIGS. 2A-2B , the input or adjustment member  18  includes a shaft  32  having a helical groove  34  on an outer surface, for example, receiving at least a portion of the spring  16 . The shaft  32  may extend through an aperture  31  in the second member  14 . First and second end portions  28 ,  30  of the spring  16  are respectively operatively secured to the first and second members  12 ,  14 . In one example, the first and second end portions  28 ,  30  are affixed to the first and second members  12 ,  14 . The spring assembly  11  shown in a first position in  FIG. 2A  provides a “softer” spring rate, while the second position shown in  FIG. 2B  provides a “stiffer” spring rate. The spring assembly  11  may provide virtually an infinite number of spring rate values within a range of spring rates. 
         [0014]    The spring system  10  and its spring  16  includes multiple coils, such as first, second and third coils  13 ,  15 ,  17 . A body, such as the adjustment member  18  mechanically supports the first and second coils  13 ,  15 , as shown in  FIG. 2A . The first and second coils helically adjoin one another. The adjustment member  18  is adjustable to mechanically support the third coil  17 . The third coil  17  helically adjoins the second coil  15 . In the example, the adjustment member  18  mechanically supports the spring  16  both torsionally and axially. The spring  16  may be a tension, torsion and/or compression spring. 
         [0015]    The adjustment member  18  is rotatable relative to the spring  16  in the example to provide a desired number of unsupported coils, which corresponds to a desired spring rate. The shaft  32  is rotated in response to a command from the controller  22 , for example, enabling the spring rate to be controlled in real time to react to various undesired conditions. In one example, an undesired natural frequency may be detected, and the controller  22  provides a command to the actuator  20  to provide a desired number of unsupported coils corresponding to a spring rate that negates the natural frequency of the first member  12 . The sensor  24  provides feedback to as to the effectiveness of the adjustment made by the controller  22 . In another example, a user may simply actuate the switch  26  to select a desired spring rate by feel, for example. 
         [0016]    Referring to  FIGS. 3-4C , one example application is a vehicle  36 , such as a rocket. The vehicle  36  includes first and second portions  112 ,  114  that respectively correspond to a propulsion section and an occupant area. The adjustable spring system  110  is arranged between the first and second portions  112 ,  114 . When an undesired natural frequency from the propulsion section exerts undesired loads on the occupant section, the adjustable spring system  110  changes the spring rate between the first and second portions  112 ,  114  to minimize the loads in the occupant area. 
         [0017]    One example system  110  that may be used for the vehicle  36  is illustrated in  FIGS. 4A-4C . Multiple springs  116  of corresponding spring assemblies  111  are arranged between the first and second portions  112 ,  114 . To synchronize the spring assemblies  111 , an epicyclic gear train  38  is used. The epicyclic gear train  38  includes a sun gear  40  operatively coupled to the actuator  120 . Each spring assembly  111  includes a planetary gear  42  that meshes with the sun gear  40 . As shown in  FIG. 4C , the planetary gear  42  is connected to the adjustment member  118 , which includes annular grooves  134  that receive a portion of the spring  116 . In one example, the first end portion  128  is rotationally affixed to the first portion  112 . In operation, the sun gear  40  is rotationally driven by the actuator  120  to drive the adjustment members  118  to achieve a desired spring rate in each of the springs  116 . 
         [0018]    Another application for a vehicle  136  is illustrated in  FIGS. 5A-5B . The vehicle  136  includes a trailer  44  having a suspension system  46  that incorporates the adjustable spring system  210 . The spring assemblies  211  are arranged between unsprung and sprung weights  48 ,  50 . The adjustable spring system  210  may be adjusted automatically to address undesired natural frequencies or manually adjusted by the operator, as described above with respect to  FIGS. 1-2B . 
         [0019]    Although an example embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of the claims. For that reason, the following claims should be studied to determine their true scope and content.