Abstract:
A fatigue test system includes a frame having top, intermediate and bottom supports each operatively interconnected by at least one extension, and the intermediate support being disposed between the top and bottom supports. The fatigue test system further includes a driving mechanism connectable to one of the supports to drive the support substantially along a longitudinal axis of the extension for fatigue testing at least one spring disposed between the top and intermediate supports, and at least one further spring disposed between the intermediate and bottom supports. In an alternative embodiment, the fatigue test system includes a frame including top and bottom supports each interconnected by an extension, and a driving mechanism disposed between the top and bottom supports for driving springs against the top and bottom supports, each spring being fatigue tested by being driven along a longitudinal axis of the extension or a central axis of the spring.

Description:
RELATED APPLICATIONS  
       [0001]     This application claims benefit of priority of Provisional Application Ser. No. 60/500,266 filed on Sep. 5, 2003. 
     
    
     BACKGROUND OF INVENTION  
       [0002]     a. Field of Invention  
         [0003]     The invention relates generally to fatigue testing, and more particularly to a method and apparatus for fatigue testing springs and other such devices.  
         [0004]     b. Description of Related Art  
         [0005]     Single story coil fatigue test systems are generally used in the art to fatigue test coil springs and other such devices. As disclosed in JP 410260122A, and further in U.S. Pat. No. 2,350,722, the disclosure of which is incorporated herein by reference, conventional spring fatigue test systems generally include a fatigue testing machine similar to the one disclosed in  FIG. 1  herein. Referring to FIG. 1, conventional fatigue testing machines generally include a mechanism 10 driven into one or more mounted coil springs 12 repeatedly using hydraulic, electrical or pneumatic power until the spring fatigues, or a cycle criteria has been achieved. The force of driving mechanism 10 in such a conventional system must however be constant in order to compress spring 12 from highest (i.e. rebound) to lowest (i.e. jounce) height positions. Accordingly, the number of springs which may be tested in a conventional fatigue test system at any given time is limited primarily by the driving capacity of the system.  
         [0006]     The prior art also includes spring fatigue testing machines for testing multiple springs in a given testing cycle. For example, as disclosed in U.S. Pat. No. 2,381,241, the disclosure of which is incorporated herein by reference, there is disclosed in FIG. 1 a circular spring testing machine for testing springs A disposed on rods 30 and compressible by rotary ring 46. While the mechanism disclosed in the &#39;241 patent enables testing of multiple springs, it is nevertheless limited to compression as opposed to compression/tension testing of multiple springs. Moreover, due to the requirement for adjustment of numerous levers and guides, in operation, the mechanism disclosed in the &#39;241 patent is completely impractical for high speed and repeatable spring testing, as is required in today&#39;s automotive and other mass manufacturing environments.  
         [0007]     In an improvement to the mechanism of the &#39;241 patent, SAE Tech Paper No. 900663 (hereinafter “SAE &#39;663”), titled “A New High Speed Suspension Spring Test Mechanism,” discloses an additional circular fatigue testing machine for testing multiple springs. For the mechanism disclosed in SAE &#39;663, coil springs are each setup individually around a rotating cam, which compared to the mechanism of the &#39;241 patent, pushes and pulls the various rods to compress the springs. As discussed above for the mechanism of the &#39;241 patent, although the device of SAE &#39;663 can test multiple springs at once, the SAE &#39;663 mechanism also includes several drawbacks and limitations. For example, since each spring for the SAE &#39;663 mechanism must be mounted individually, setup time for testing becomes a significant factor when testing multiple springs. Furthermore, the load savings relationship between each spring and its adjacent counterpart is hindered due to the multiple forces being applied by the other springs mounted at different angles.  
         [0008]     Yet further, as disclosed in U.S. Pat. No. 2,222,892, the disclosure of which is incorporated herein by reference, there is disclosed in FIGS. 2 and 3 a multiple spring testing mechanism including springs 19 mounted on fixed plates 11, 21, and further mounted on oscillating beam 14. In operation, as beam  14  is oscillated by means of crank mechanism 15, 16, as discussed in Col. 2:35-38, due to the uneven oscillation in the left-most versus the right-most springs, the right-most springs tend to break faster than the left-most springs. It therefore becomes readily apparent that the fatigue testing results generated by the mechanism of the &#39;892 patent are extremely difficult to comprehend, in that the location of the springs on the mechanism, as well as the degree of crank of mechanism 15, 16, which is adjustable at slide block 17, must be taken into account for determining the life cycle of a left-most spring, as opposed to a central or a right-most spring.  
         [0009]     It would therefore be of benefit to provide a fatigue test system with increased capacity of testing the compression and tension cycles of springs and other such devices, without increasing the force needed to drive the springs. It would also be of benefit to provide a fatigue test system which can reduce the overall driving force needed per test cycle, which can favorably eliminate any resistance to the driving mechanism that may be produced by the springs during neutral conditions, and for which the testing technique and results are repeatable and simple to interpret. There thus remains a need for a fatigue test system, which is robust in design, efficient to operate, simple to assemble and disassemble, and which is economically feasible to manufacture and utilize.  
       SUMMARY OF INVENTION  
       [0010]     The invention solves the problems and overcomes the drawbacks and deficiencies of conventional fatigue test system designs by providing a fatigue test system having increased capacity of testing the compression and tension cycles of springs and other such devices.  
         [0011]     Thus, an exemplary aspect of the present invention is to provide a fatigue test system with increased capacity of testing springs and other such devices without increasing the force needed to drive the springs.  
         [0012]     Another aspect of the present invention is to provide a fatigue test system which reduces the overall driving force needed per test cycle, and which favorably eliminates any resistance to the driving mechanism that may be produced by the springs during neutral conditions.  
         [0013]     The present invention achieves the aforementioned exemplary aspects by providing a fatigue test system including a frame having top, intermediate and bottom supports each operatively interconnected by at least one extension, and the intermediate support being disposed between the top and bottom supports. The fatigue test system may further include a driving mechanism connectable to one of the supports to drive the support substantially along a longitudinal axis of the extension for fatigue testing at least one spring disposed between the top and intermediate supports, and at least one further spring disposed between the intermediate and bottom supports.  
         [0014]     For the fatigue test system disclosed above, at least one of the supports may be adjustably disposed along the extension for adjusting a distance between adjacently disposed supports. The extension may be a shaft disposed through suitable openings in the intermediate support. The intermediate support may be fixed to the frame for permitting movement of the top and bottom supports by means of the driving mechanism, or alternatively, may be movable relative to the top and bottom supports.  
         [0015]     The invention yet further provides a frame including top, intermediate and bottom supports each operatively interconnected by at least one extension. The intermediate support may be disposed between the top and bottom supports. The frame may further include a driving mechanism connectable to one of the supports to drive the support substantially along a central axis of at least two springs disposed between the top and intermediate supports, and at least two further springs disposed between the intermediate and bottom supports for fatigue testing the springs by substantially uniformly compressing the springs.  
         [0016]     For the fatigue test system described above, at least one of the supports may be adjustably disposed along the extension for adjusting a distance between adjacently disposed supports. The extension may be a shaft disposed through suitable openings in the intermediate support. The intermediate support may be fixed to the frame for permitting movement of the top and bottom supports by means of the driving mechanism, or alternatively, may be movable relative to the top and bottom supports.  
         [0017]     The invention yet further provides a method for fatigue test a plurality of springs. The method includes providing a frame including top, intermediate and bottom supports each operatively interconnected by at least one extension, the intermediate support being disposed between the top and bottom supports. The method may further include connecting a driving mechanism to one of the supports to drive the support substantially along a central axis of at least two springs disposed between the top and intermediate supports, and at least two further springs disposed between the intermediate and bottom supports for fatigue testing the springs by substantially uniformly compressing the springs. The method may alternatively include connecting a driving mechanism to one of the supports to drive the support substantially along a longitudinal axis of the extension for fatigue testing at least two springs disposed between the top and intermediate supports, and at least two further springs disposed between the intermediate and bottom supports.  
         [0018]     For the method described above, the method may further include adjusting at least one of the supports along the extension for adjusting a distance between adjacently disposed supports. The extension may be a shaft disposed through suitable openings in the intermediate support. The method may further include fixing the intermediate support to the frame for permitting movement of the top and bottom supports by means of the driving mechanism, or alternatively, moving the intermediate support relative to the top and bottom supports.  
         [0019]     For an alternative embodiment of the fatigue test system disclosed above, the invention provides a fatigue test system including a frame including top and bottom supports each operatively interconnected by at least one extension. The system further includes a driving mechanism disposed between the top and bottom supports for driving at least one spring against the top support, and further driving at least one further spring against the bottom support, each spring being fatigue tested by being driven substantially along a longitudinal axis of the extension.  
         [0020]     For the fatigue test system described above, the driving mechanism may be operatively mounted to the extension. At least one of the top and bottom supports may be adjustably disposed along the extension for permitting adjustment of a distance of the adjustably disposed support from the driving mechanism. The extension may be a shaft disposed through an opening in at least one of the top and bottom supports.  
         [0021]     The invention yet further provides a fatigue test system including a frame including top and bottom supports each operatively interconnected by at least one extension. The system further includes a driving mechanism disposed between the top and bottom supports for driving at least one spring against the top support, and further driving at least one further spring against the bottom support, each spring being fatigue tested by being substantially uniformly compressed along a central axis thereof.  
         [0022]     For the fatigue test system described above, the driving mechanism may be operatively mounted to the extension. At least one of the top and bottom supports may be adjustably disposed along the extension for permitting adjustment of a distance of the adjustably disposed support from the driving mechanism. The extension may be a shaft disposed through an opening in at least one of the top and bottom supports.  
         [0023]     The invention also provides a method for fatigue testing a plurality of springs, the method including providing a frame including top and bottom supports each operatively interconnected by at least one extension. The method further includes connecting a driving mechanism between the top and bottom supports to drive at least one spring against the top support, and further drive at least one further spring against the bottom support, each spring being fatigue tested by being substantially uniformly compressed along a central axis thereof, or alternatively, by being driven substantially along a longitudinal axis of the extension.  
         [0024]     For the method described above, the method may further include operatively mounting the driving mechanism to the extension. At least one of the top and bottom supports may be adjustably disposed along the extension for permitting adjustment of a distance of the adjustably disposed support from the driving mechanism. The extension may be a shaft disposed through an opening in at least one of the top and bottom supports.  
         [0025]     Additional features, advantages, and embodiments of the invention may be set forth or apparent from consideration of the following detailed description, drawings, and claims. Moreover, it is to be understood that both the foregoing summary of the invention and the following detailed description are exemplary and intended to provide further explanation without limiting the scope of the invention as claimed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]     The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate preferred embodiments of the invention and together with the detail description serve to explain the principles of the invention. In the drawings:  
         [0027]      FIG. 1  is a front view illustrative of a conventional fatigue test system for fatigue testing springs and other such devices;  
         [0028]      FIG. 2  is an isometric view of a first embodiment of a fatigue test system according to the present invention, the system including a fixed center;  
         [0029]      FIG. 3  is a front view of the fatigue test system of  FIG. 2 , illustrating both springs at normal (i.e. center) position;  
         [0030]      FIG. 4  is a side view of the fatigue test system of  FIG. 3 ;  
         [0031]      FIG. 5  is a front view of the fatigue test system of  FIG. 2 , illustrating the top spring at rebound and the bottom spring at jounce;  
         [0032]      FIG. 6  is an isometric view of a second embodiment of a fatigue test system according to the present invention, the system including a movable center;  
         [0033]      FIG. 7  is a side view of the fatigue test system of  FIG. 6 ;  
         [0034]      FIG. 8  is a front view of the fatigue test system of  FIG. 6 , illustrating the top spring at rebound and the bottom spring at jounce;  
         [0035]      FIG. 9  is an isometric view of a third embodiment of a fatigue test system according to the present invention, the system including an integrated actuator assembly;  
         [0036]      FIG. 10  is a side view of the fatigue test system of  FIG. 9 ; and  
         [0037]      FIG. 11  is a front view of the fatigue test system of  FIG. 9 , illustrating the top spring at rebound and the bottom spring at jounce. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0038]     Referring now to the drawings wherein like reference numerals designate corresponding parts throughout the several views,  FIGS. 2-5 ,  6 - 8  and  9 - 11  respectively illustrate first to third embodiments of fatigue test systems (hereinafter “system”) according to the present invention, generally designated  20 ,  100 ,  200 , respectively.  
         [0039]     Specifically, as illustrated in  FIGS. 2-5 , the first embodiment of system  20  may include an upper plate  22  fixedly connectable to a driving mechanism, such as mechanism  10  illustrated in  FIG. 1 , of a conventional fatigue test system, such as at  33 . System  20  may include at least two extensions, illustrated as circular shafts  24  in  FIG. 2 , disposed within suitable openings (not shown) in top wall  26  of frame  28 . The openings in top wall  26  may include suitable bearings (not shown) for permitting smooth reciprocation of shafts  24  therein. It should be noted that shafts  24  may be formed of a variety of cross-sections for permitting reciprocation of plates  22 ,  30  therewith. Frame  28  may include a plurality of fixing points  29  for fixing frame  28  to reaction mass  31  (see  FIG. 1 ). Shafts  24  may be fixedly mounted to lower plate  30  at or adjacent their bottom-most ends thereof. Lower plate  30  may include a retention means such as a pin (not shown), ball-screw locking mechanism (not shown) or suitable fastening means disposed on a threaded section thereof for permitting vertical adjustability and retention thereof along the length of shaft  24  for testing springs  32  of different heights. It should be noted that plates  22 ,  30  may be formed of a variety of cross-sections for supporting springs  32 . In the case of pins, shafts  24  may be provided with a plurality of spaced holes (not shown) for permitting suitable pins to be inserted therethrough for retaining lower plate  30  at predetermined heights along the length thereof. In the case of fastening means, shafts  24  may include a threaded section of a predetermined length so as to permit suitable nuts or other fastening means to be threadedly engaged thereon for retaining lower plate  30  at a predetermined height. Those skilled in the art would appreciate in view of this disclosure that a variety of alternative retention techniques may be used for retaining lower plate  30  at a predetermined height along the length of shafts  24 , without departing from the scope of the present invention.  
         [0040]     In order to test springs  32 , the springs may be removably mounted in their normal (center) position within areas  36  to upper and lower plates  22 ,  30 , respectively, and top wall  26 , in the configuration illustrated in  FIG. 3 . With a driving mechanism, such as mechanism  10  of  FIG. 1 , connected to plate  22  to push plate  22  downwards and likewise pull plate  22  upwards for each cycle of mechanism  10 , springs  32  may be fatigue testes as needed. Specifically, with the downward movement of plate  22 , while the upper spring is placed in compression, the lower spring is placed in tension, and vice-versa, as illustrated in  FIG. 5 . Fatigue testing springs  32  in the manner illustrated in  FIGS. 2-5  therefore doubles the capacity of a conventional fatigue test system by utilizing the energy of each spring to assist in the testing of the oppositely mounted spring. It should also be noted that system  20  doubles the capacity of a conventional fatigue test system without increasing the amount of force needed to drive each spring during each cycle.  
         [0041]     System  20  of the present invention also reduces the overall force needed to drive each spring during each cycle, since as driving mechanism  10  compresses each mounted story  38 ,  40 , the remaining force of the opposite mounted story is eliminated from the overall force required of the driving mechanism. In essence, the compressive and tensile forces of each spring  32  are used to assist in the fatigue testing of the respective tensile and compressive forces of the oppositely mounted spring. Lastly, system  20  provides for the elimination of any resistance to driving mechanism  10  that generally occurs in conventional fatigue test systems when the mounted springs are in their neutral condition. For example, as illustrated in  FIG. 3 , assuming both springs  32  are mounted equally, system  20  will therefore experience a zero (0) force condition at the neutral position since the force of story  38 , for example, applied to system  20  is cancelled by the opposite force of story  40  when driving mechanism  10  is at the center of the cycle. It should be noted that for the fatigue test system described above, driving mechanism  10  may alternatively be mounted to lower plate  30  instead of upper plate  22  as needed.  
         [0042]     The second embodiment of system  100  will now be described in detail in reference to  FIGS. 6-8 .  
         [0043]     Specifically, for the second embodiment of system  100 , as illustrated in  FIGS. 6-8 , system  100  may include a vertically fixable plate  42  connectable to a driving mechanism  10  of a conventional fatigue test system, such as the system disclosed in  FIG. 1 . System  100  may include shafts  44  disposed within suitable openings in plate  42  and movable plate  46 . Shafts  44  may be fixedly mounted to lower fixing plate  48 . As discussed above for the first embodiment of system  20 , for the second embodiment of system  100 , it should be noted that shafts  44  may be formed of a variety of cross-sections for permitting reciprocation of plate  46  by means of driving mechanism  10 . Plate  42  may include a retention means such as a pin (not shown), ball-screw locking mechanism (not shown) or suitable fastening means disposed on a threaded section thereof for permitting vertical adjustability and retention thereof along the length of shafts  44  for insertion and testing of springs  58  of different heights. Driving mechanism  10  may include members  50  disposed within suitable openings in plate  42  and fixedly connected to plate  46 , or alternatively, may be directly connected to plate  46  by a connection (not shown) disposed adjacent plate  46 , instead of through plate  42 . As also discussed above for the first embodiment of system  20 , for the second embodiment of system  100 , it should be noted that plates  42 ,  46 ,  48  may be formed of a variety of cross-sections for supporting springs  58 .  
         [0044]     In order to test springs  58 , the springs may be removably mounted within areas  52 . With driving mechanism  10  connected to plate  46  to push plate  46  downwards and likewise pull plate  46  upwards for each cycle of mechanism  10 , springs  58  may be fatigue testes as needed. In a similar manner to fatigue test system  20 , fatigue testing springs  58  in the manner illustrated in  FIGS. 6-8  likewise doubles the capacity of a conventional fatigue test system by utilizing the energy of each spring to assist in the testing of the oppositely mounted spring. It should also be noted that as discussed above for fatigue test system  20 , system  100  doubles the capacity of a conventional fatigue test system without increasing the amount of force needed to drive each spring during each cycle.  
         [0045]     System  100  of the present invention also reduces the overall force needed to drive each spring during each cycle, since as driving mechanism  10  compresses each mounted story  54 ,  56 , the remaining force of the opposite mounted story is eliminated from the overall force required of the driving mechanism. As discussed above for the first embodiment of fatigue test system  20 , for system  100 , the compressive and tensile forces of each spring  58  are used to fatigue test the respective tensile and compressive forces of the oppositely mounted spring. Lastly, system  100  provides for the elimination of any resistance to driving mechanism  10  that generally occurs in conventional fatigue test systems when the mounted springs are in their neutral condition. For example, as illustrated above for the first embodiment for  FIG. 3 , assuming both springs  58  are mounted equally, system  100  will therefore experience a zero (0) force condition at the neutral position since the force of story  54 , for example, applied to system  100  is cancelled by the opposite force of story  56  when driving mechanism  10  is at the center of the cycle.  
         [0046]     The third embodiment of system  200  will now be described in detail in reference to  FIGS. 9-11 .  
         [0047]     Specifically, for the third embodiment of system  200 , as illustrated in  FIGS. 9-11 , system  200  may include plates  62  slidably disposed on shafts  68 , and a driving mechanism  64 , such as a driving mechanism of a MTS actuator, having a piston (not shown) including piston rods  66 . Shafts  68  may be disposed within suitable openings in plates  62 , in a similar manner as shafts  44  of the second embodiment of system  100 . As discussed above for the first and second embodiments of systems  20 ,  100 , for the third embodiment of system  200 , it should be noted that shafts  68  may be formed of a variety of cross-sections for permitting sliding movement of plates  62  for insertion of springs  70 . Plates  62  may each include a retention means such as a pin (not shown), ball-screw locking mechanism (not shown) or suitable fastening means disposed on a threaded section thereof for permitting sliding movement and lockable retention thereof along the length of shafts  68 , for permitting insertion and testing of springs  70  of different heights. As also discussed above for the first and second embodiments of systems  20 ,  100 , for the third embodiment of system  200 , it should be noted that plates  62  may be formed of a variety of cross-sections for supporting springs  70 .  
         [0048]     In order to test springs  70 , the springs may be removably mounted within areas  72 . With piston rods  66  of driving mechanism  64  having mounting plates  74  affixed thereto for mounting springs  70 , with springs  70  mounted within areas  72  as shown in  FIG. 9 , plates  74  may be reciprocated back and forth in the direction of shafts  68  to fatigue test springs  70  as needed. In a similar manner to fatigue test systems  20  and  100 , fatigue testing springs  70  in the manner illustrated in  FIGS. 9-11  likewise doubles the capacity of a conventional fatigue test system by utilizing the energy of each spring to assist in the testing of the oppositely mounted spring. It should also be noted that as discussed above for fatigue test systems  20 ,  100 , system  200  doubles the capacity of a conventional fatigue test system without increasing the amount of force needed to drive each spring during each cycle.  
         [0049]     System  200  of the present invention also reduces the overall force needed to drive each spring during each cycle, since the compressive and tensile forces of each spring  70  are used to fatigue test the respective tensile and compressive forces of the oppositely mounted spring. Lastly, system  200  provides for the elimination of any resistance to driving mechanism  64  that generally occurs in conventional fatigue test systems when the mounted springs are in their neutral condition. For example, as illustrated above for the first embodiment for  FIG. 3 , assuming both springs  70  are mounted equally, system  200  will therefore experience a zero (0) force condition at the neutral position since the force of the first spring  70  is cancelled by the force of the second spring  70  mounted opposite to driving mechanism  64  when driving mechanism  64  is at the center of the cycle. Those skilled in the art will appreciate in view of this disclosure that although only two springs  70  are shown for testing with system  200 , if needed, a wider plate (not shown) may be attached to the end of piston rods  66  to replace plates  74  and thereby increase the number of springs which may be mounted and tested by system  200 .  
         [0050]     The present invention thus provides a fatigue test system having increased capacity of testing the compression and tension cycles of springs and other such devices, without increasing the force needed to drive the springs. Moreover, the present invention also provides a fatigue test system which reduces the overall driving force needed per test cycle, and which favorably eliminates any resistance to the driving mechanism that may be produced by the springs during neutral conditions.  
         [0051]     Although particular embodiments of the invention have been described in detail herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those particular embodiments, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims.