Patent Publication Number: US-2022221021-A1

Title: Temperature compensated shock absorber

Description:
BACKGROUND 
     Liquid spring and oleo-pneumatic shock absorbers are commonly used in aircraft landing gear. The shock absorbers absorb the impact of landing by converting the impact energy into heat, which is then dissipated. Conversion of the impact energy into heat is typically accomplished by moving a piston through a fluid, such as oil, when the shock absorber extends and retracts. In a liquid spring, the compressibility (bulk modulus) of the oil is used to provide the spring function as well as damping when the fluid passes through orifices. 
     During operation of the shock absorbers, the shock absorber components heat up and expand due to thermal expansion. Oil in particular expands and contracts significantly in response to changes in temperature. For example, mineral oils can experience a volumetric change of approximately 4 to 5% in response to a temperature change of 60 C°. With respect to the overall impact of temperature changes to the performance of a shock absorber, the change in oil volume is preponderant. As the oil expands and contracts within the shock absorber, the internal pressure of the shock absorber increases and decreases, respectively. These changes in internal pressure impact the overall performance and, in particular, the spring curves of the shock absorbers. Aircraft landing gears are typically required to operate in temperatures ranging from −50° C. to +50° C. (or more), making this type of thermal behavior unacceptable. 
     The oleo-pneumatic shock absorber introduces gas as the spring element, which reduces the temperature sensitivity of the system, but an oleo-pneumatic shock absorber still suffers from significant spring curve variation with temperature, which complicates the design of the shock absorber and negatively impacts its performance. 
     SUMMARY 
     Disclosed embodiments of shock absorbers include thermal compensators that increase and decrease the internal volume of a shock absorber as the temperature changes. The changes in the internal volume correspond to and accommodate the thermal expansion and contraction of the spring fluids (typically oil) within the shock absorber. By increasing and decreasing the internal volume of the shock absorber, the thermal compensator maintains the oil at a more consistent pressure, thereby providing a more stable spring curve across the range of operating temperature. 
     A first embodiment of a shock absorber according to the present disclosure includes a housing and an end wall slidably disposed within the housing. The end wall and the housing cooperate to define at least a portion of a cavity within the housing. The shock absorber further includes a fluid disposed within the cavity and a piston slidably disposed within the cavity. Movement of the piston within the cavity compresses the fluid to provide a spring force. A compensator is coupled to the end wall and positions the end wall within the housing to change a volume of the cavity in response to a change in a temperature of a first element of the compensator. 
     In any embodiment, the change in the temperature of the first element is based at least in part on a temperature of the fluid. 
     In any embodiment, the compensator the first element is coupled to the housing, the first element having a first coefficient of thermal expansion. The compensator further includes a second element coupled to the first element and to the end wall, the second element having a second coefficient of thermal expansion different than the first coefficient of thermal expansion. 
     In any embodiment, the first element and the second element are concentric cylinders surrounding at least a portion of the housing. 
     In any embodiment, the second coefficient of thermal expansion is less than the first coefficient of thermal expansion. 
     In any embodiment, the second coefficient of thermal expansion is negative. 
     In any embodiment, a first end of the first element is fixedly positioned relative to the housing, and a second end of the first element is coupled to a first end of the second element, the second element extending from the first end of the second element toward the first end of the first element. 
     In any embodiment, the second element is parallel to the first element. 
     In any embodiment, the second element is coupled to the end wall by third element, a first end of the third element being coupled to a second end of the second element, a second end of the third element being fixedly positioned relative to the end wall, wherein the third element has a third coefficient of thermal expansion that is greater than the second coefficient of thermal expansion. 
     In any embodiment, the third coefficient of thermal expansion is equal to the first coefficient of thermal expansion. 
     In any embodiment, the third element is parallel to the second element. 
     A second embodiment of a shock absorber according to the present disclosure includes an outer housing portion comprising an end wall and an inner housing portion at least partially disposed within and slidingly engaging the outer housing portion. A piston is slidably disposed within the outer housing portion, so that the outer housing portion, the inner housing portion, and the piston cooperate to define at least a portion of a cavity. A compensator selectively positions the piston relative to the outer housing portion. The compensator moves the piston relative to the outer housing portion to change a volume of the cavity in response to a change in a temperature of the compensator. 
     In any embodiment, the shock absorber further comprises an orifice support tube extending from an end wall of the outer housing portion. the orifice support tube extends through the piston. The compensator comprises an elongate element having a first coefficient of thermal expansion and the orifice support tube has a second coefficient of thermal expansion that is less than the first coefficient of thermal expansion. 
     In any embodiment, a first end of the elongate element is fixedly positioned relative to the orifice support tube and a second end of the elongate element is coupled to the piston. 
     In any embodiment, the elongate element is a cylinder that surrounds the orifice support tube. 
     In any embodiment, the piston sealingly engages the orifice support tube. 
     In any embodiment, a first end of the elongate element is fixedly positioned relative to the orifice support tube, the elongate element extending through the piston, a second end of the elongate element being positioned between the piston and the end wall. 
     In any embodiment, the piston sealingly engages the elongate element. 
     In any embodiment, the second end of the elongate element being coupled to a stop that limits movement of the piston toward the end wall, the elongate element positioning the stop according to a temperature of the elongate element. 
     In any embodiment the stop is a lever rotatably coupled at one end about an axis that is fixed relative to the orifice support tube, a second end of the elongate element being rotatably coupled to the lever. 
     This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The foregoing aspects and many of the attendant advantages of disclosed subject matter will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  shows a cross-sectional view of a known liquid spring shock absorber; 
         FIG. 2  shows cross-sectional view of a liquid spring shock absorber with a temperature compensator according to a first representative embodiment of the present disclosure; 
         FIG. 3  shows the temperature compensator of  FIG. 2  at a first temperature; 
         FIG. 4  shows the temperature compensator of  FIG. 2  at a second temperature; 
         FIG. 5  shows a cross-sectional view of a known oleo-pneumatic shock absorber; 
         FIG. 6  shows a cross-sectional view of an oleo-pneumatic shock absorber with a temperature compensator according to a second representative embodiment of the present disclosure; 
         FIG. 7  shows an oleo-pneumatic shock absorber with a temperature compensator according to a third representative embodiment of the present disclosure; and 
         FIG. 8  shows an enlarged partial view of the oleo-pneumatic shock absorber shown in  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a cross-sectional view of a known liquid spring shock absorber  100 . The shock absorber  100  includes a cylindrical housing  102  with an end wall  104  fixedly coupled thereto to define an interior cavity  106 . The cavity  106  is filled with a fluid  118 , such as oil. A piston  108  is slidably disposed within the cavity  106 . One or more seals  110  are mounted around the perimeter of the piston  108  to sealingly engage the piston with the wall of the cavity  106 . A plurality of orifices  112  extend through the piston  108 . An elongate rod  114  is coupled at one end to the piston  108  and extends through an aperture in the end wall  104 . One or more seals  116  are mounted in the aperture in the end wall  104  and provide sealing engagement between the rod  114  and the end wall. As the piston  108  reciprocates within the housing  102 , the fluid  118  is compressed and provides a resistive force to the piston. Movement of the piston  108  within the housing also forces fluid through the orifices  112  in the piston, which provide a damping force to the shock absorber  100 . 
     Referring now to  FIGS. 2-4 , a first representative embodiment of a shock absorber  200  with a thermal compensator  250  according to a first representative embodiment of the present disclosure is shown. The shock absorber  200  shown in  FIGS. 2-4  is similar to the shock absorber  100  shown in  FIG. 1 , wherein components shown in  FIG. 1  with a reference number  1 XX generally corresponds to a component shown in  FIGS. 2-4  with a reference number  2 XX. For the sake of brevity, not all components of the shock absorber  200  will be described with the understanding that the components are similar to corresponding components of previously described shock absorber  100  except as otherwise noted. 
     As best shown in  FIG. 2 , the shock absorber  200  includes an inner cavity  206  defined by a housing  202  and an end wall  204 . Unlike the end wall  104  of the shock absorber  100  of  FIG. 1 , the end wall  204  of the shock absorber  200  is slidably associated with the housing  202  such that the end wall  204  can be moved relative to the housing  202  to increase or decrease the volume of the cavity  206 . In this regard, the end wall  204  is configured to selectively slide further into and out of the housing  202  while maintain sealing engagement with the interior walls of the housing  202  in order to decrease and increase, respectively, the volume of the cavity  206 . 
     The position of the end wall  204  and, therefore, the volume of the cavity  206  is controlled by the thermal compensator  250  according to the temperature of certain elements that form part of the thermal compensator. As explained in further detail below, these elements are elongate elements that expand and contract as the temperature of the elements changes. Although the thermal compensator  250  controls the volume of the cavity  206  according to the temperature of elements located outside of the cavity rather than the temperature of the oil within the cavity  206 , it will be appreciated that there is a general correlation between the temperature of the oil and the temperature of the thermal compensator elements. In this regard, components of the shock absorber are in close proximity to each other and are subjected to similar environmental conditions, including heating and cooling ambient temperatures. Further, the components are connected to each other and/or are in close proximity to each other such that heat is transferred from a higher temperature component to a lower temperature component through conduction, convection, or a combination thereof. In particular, when the shock absorber converts impact energy into heat, the oil is heated, which in turn heats the compensator. 
     Because of the correlation between the temperature of the oil inside the shock absorber and the shock compensator elements, the compensator is able to adjust the volume of the cavity in a manner that compensates for changes in the temperature of the oil. As used herein, temperature changes will refer to changes to the temperature of the components of the compensator unless otherwise noted, with the understanding that there is a correlation between the temperature of these components and the temperature of the oil in the shock absorber. 
     The compensator  250  includes a plurality of elongate elements that react to (being heated and cooled) in order to move the end wall  204  relative to the housing  202 . In the illustrated embodiment, the elongate elements include one or more first elongate elements  254 .X having a first coefficient of thermal expansion (CTE) and one or more second elongate elements  256 .X having a second CTE that is less than the first CTE, wherein X is an integer corresponding to the position of the elongate element. 
     In the illustrated embodiment of  FIGS. 2-4 , the elongate elements  254 .X and  256 .X are concentric cylinders arranged around the housing  202 , wherein first elongate element  254 . 1  is the outermost elongate element, and the next inwardly adjacent elongate element is a second elongate element  256 . 1 . Moving inward towards from the outermost second elongate element  256 . 1  toward the housing  202 , the first and second elongate elements alternate, i.e., first elongate element  254 . 2 , second elongate element  256 . 2 , first elongate element  204 . 3 . While the illustrated compensator includes three first elongate elements  254 .X and two second elongate elements  256 .X, it will be appreciated that other embodiments are possible in which different numbers of first and/or second elongate elements are utilized. 
     In the embodiment shown, the outermost first elongate element  254 . 1 , i.e., the outermost cylindrical element with the first (higher) CTE, has a first end fixedly positioned relative to the housing  202 . More specifically, the first end of the outermost elongate element  254 . 1  is fixedly coupled to a base  252  that is itself coupled to and extends radially from the housing  202 . 
     The outermost second elongate element  256 . 1 , i.e., the outermost cylindrical element with the second (lower) CTE, is coaxially disposed within the outermost first elongate element  254 . 1 . A first end of the second elongate element  256 . 1  is coupled to a second end of the first elongate element  254 . 1 . The second elongate element  256 . 1  extends back toward the first end of the outermost first elongate element  254 . 1  so that the second elongate element is nested within the first elongate element, and the first and second elongate elements have a cross-section that defines two C-shaped portions. 
     Except for the outermost first elongate element  254 . 1 , which has a first end coupled to the base  254 , each elongate element  254 .X and  256 .X has a first end coupled to a second end of the outwardly adjacent (surrounding) elongate element. With the exception of the innermost first elongate element  254 . 3 , which is fixedly coupled to an end fitting  258 , described below, each elongate element  254 .X and  256 .X has a second end coupled to a first end of the inwardly adjacent elongate element. As a result, the first and second elongate elements  254 .X and  256 .X cooperate to define a serpentine path from the base  252  to the end fitting  258 , wherein the path includes parallel elongate portions that alternate between having a first CTE and a second CTE. 
     Still referring to  FIG. 2 , the innermost first elongate element  254  is coupled at a second end to the end fitting  258 . The end fitting  258  is coupled to the coupler  260  that is attached to the end wall  204 . The connection of the innermost first elongate element  254  to the end wall  204  in this manner enables the compensator  250  to move the end wall  204  relative to the housing  202  in response to temperature changes. In some embodiments, the end fitting  258  is threadedly coupled to the coupler  260  so that the end fitting can be selectively disengaged from the coupler to facilitate assembly, disassembly, and maintenance. In some embodiments, the coupler  260  is integrally formed with the end wall  204 . 
     Referring now to  FIGS. 3 and 4 , operation of the compensator  250  will be described.  FIG. 3  shows the compensator  250  at an initial temperature T 0 , and  FIG. 4  shows the compensator  250  at a temperature T that is higher than the initial temperature T 0 . When the temperature changes from an initial temperature T 0  to a temperature T, the length of the elongate elements also change according to the following equation: 
       Δ L=L   0 ×α×( T−T   0 )
 
     wherein: 
     ΔL is the change in length due to thermal expansion; 
     L 0  is the length of the elongate element at initial temperature T 0 ; and 
     α is the coefficient of thermal expansion (CTE) for the elongate element material. 
     Because the CTE of the first elongate elements  254 .X is greater than the CTE of the second elongate elements  256 .X, a first elongate element  254 .X having the same length as a second elongate element  256 .X at an initial temperature will be longer than the second elongate element at a higher temperature and shorter than the second elongate element at a lower temperature. Examples of materials with higher CTEs include aluminum and polyether ether ketone (PEEK). Examples of materials with lower CTEs include the nickel-iron alloy 64FeNi, (trade name INVAR) and titanium-based alloys that exhibit low or negative CTEs, e.g. trade name ALLVAR. It will be appreciated that the noted materials are exemplary only, and other embodiments may include alternate materials having suitable strength, durability, and thermal characteristics. Such embodiments are contemplated and should be considered within the scope of the present disclosure. 
     Using elongate elements with different CTEs enables the compensator  250  to amplify the change in the volume of the cavity  206  for a given temperature change and compensator size. As shown in  FIG. 3 , when the compensator is at a first (initial) temperature, the elongate elements  254 .X and  256 .X are parallel and each has its own respective initial length. The distance between the base  252  and the end fitting  258  is controlled by the compensator  250 . This, in turn, controls the position of the end wall  204  relative to the housing  202  and, thus, the volume of the cavity  206 . 
     As the temperature increases from the first temperature ( FIG. 3 ) to the second temperature ( FIG. 4 ), the length of each first elongate element  254 .X increases due to thermal expansion. At the same time, the lower CTE of the second elongate element  256 .X causes each second elongate element to either (1) increase at lower rate due when the lower CTE is positive, or (2) decrease if the lower CTE is negative. 
     The arrangement of the first and second elongate elements  254 .X and  256 .X is such that the distance between the base  202  and the end fitting  258  increases with an increase in temperature. More specifically, the distance between the base  202  and the end fitting  258  increases by an amount equal to the sum of the increase of the lengths of the first elongate elements  254 .X minus the sum of the increases of the lengths of the second elongate elements  256 .X. For embodiments in which the second elongate elements have a negative CTE, the distance between the base  202  and the end fitting  258  increases by an amount equal the sum of the absolute values of the changes of the lengths of the first and second elongate elements  254 .X and  256 .X. 
     It will be appreciated that the number, orientation, and configuration of the first and second elongate elements is representative only. In some embodiments, one or more of the elongate elements are not cylindrical, but instead include one ore more linear elements arranged circumferentially around the housing. In some embodiments, the lengths of two or more elongate elements are the same at a given temperature. In some embodiments, the compensator includes stops that limit movement of the end wall  204  relative to the housing  202  to set upper and or lower limits on the volume of the cavity  206 . These and other variations are contemplated and should be considered within the scope of the present disclosure. 
     The materials and configuration of the disclosed compensator  250  can be selected to suit the configuration, functional characteristics, and operating conditions of the shock absorber  200 . In this regard, the compensator  250  can be optimized to maintain the pressure of the fluid  218  in the shock absorber within a predetermined range by increasing and decreasing the volume in the cavity  206  in a manner that corresponds to increases and decreases, respectively, in the temperature of the fluid. This optimization provides more consistent and reliable operation of the shock absorber  200 . 
       FIG. 5  shows a representative embodiment of a known oleo-pneumatic shock absorber  500  typical of the type used as the main strut of aircraft landing gears. The shock absorber  500  is disclosed in U.S. Patent Application Publication No. 2016/0327114, (“Schmidt”), assigned to Safran Landing Systems UK Ltd., the disclosure of which is incorporated by reference in its entirety herein. 
     The shock absorber  300  includes an inner housing portion  308 , slidably coupled within an outer housing portion  302  by one or more bearings  312  with at least one orifice  314  extending therethrough. The housing portions  302  and  308  are sealingly engaged by a seal  310  and cooperate to define a cavity  306  having an upper chamber  320  and a lower chamber  322 . The lower chamber  322  contains a fluid  326 , such as oil, and the upper chamber  320  is at least partially filled with a gas  328 , such as air. An orifice support tube  318  extends from an end wall  304  of the upper chamber  320  and fixedly positions an orifice  316  extending between the upper chamber  320  and the lower chamber. A metering pin  324  is fixedly secured to the inner housing portion  308  and extends through the orifice  316  to selectively limit the flow of the fluid  326  through the orifice. 
     When a load is applied to the shock absorber  300 , such as during aircraft weight on wheels upon landing, the inner housing portion  308  slides into the outer housing portion  302  to compress the shock absorber. The volume of the cavity  306  is reduced, compressing the gas  328  to provide a resistive force. When load is removed from the shock absorber  300 , such as following take off, the pressure of the compressed gas  328  drives the inner housing portion  308  out of the outer housing portion  302  so that the shock absorber  300  extends to assume a default length. As the shock absorber  300  compresses and extends, the fluid  326  is forced through the orifice  316  to provide viscous damping. 
       FIG. 6  shows an oleo-pneumatic shock absorber  400  similar to the shock absorber  300  shown in  FIG. 5  except that the shock absorber  400  includes a thermal compensator  450  according to a second representative embodiment of the present disclosure. Components shown in  FIG. 5  with a reference number  3 XX generally corresponds to a component shown in  FIG. 6  with a reference number  4 XX. For the sake of brevity, not all components of the shock absorber  400  will be described with the understanding that the components are similar to corresponding components of the shock absorber  300  except as otherwise noted. 
     As shown in the embodiment of  FIG. 6 , the compensator  450  includes a piston  452  slidable disposed within the upper chamber  420  of the shock absorber  400 . Seals  456  are mounted to the inner and outer edges of the piston  452  to provide sealing engagement with the orifice support tube  418  and the wall of the cavity  406 , respectively. Thus, the piston  456 , rather than the end wall  404 , cooperates with the housing  402  to define the portion of the cavity  406  that surrounds the orifice support tube  418 . 
     In the embodiment shown, an elongate element  454  is coupled at one end to a portion of the orifice support tube  418  and at the other end to the piston  452 . In some embodiments, the elongate element  454  is has a cylindrical configuration that is coaxial with and surrounds the orifice support tube  418 . In some embodiments, the elongate element  454  includes one ore more linear members positioned circumferentially around the orifice support tube  418 . It will be appreciated that the elongate element  454  can have any suitable configuration that positions the piston  452  relative to the orifice support tube  418 . 
     The elongate element  454  is constructed to have a higher CTE than the orifice support tube  418 . In some embodiments, the elongate element is made from aluminum or PEEK. In some embodiments, the orifice support tube is made from INVAR or ALLVAR. In some embodiments, the orifice support tube  418  is integrally formed with the housing  402 . In some embodiments, the orifice support tube  418  is formed separate from the housing  402  and/or from different materials and then coupled to the housing. These and other embodiments that provide an elongate element  454  with a higher CTE than the orifice support tube  418  are contemplated and should be considered within the scope of the present disclosure. 
     Still referring to  FIG. 6 , the orifice support tube  418  and the elongate element  454  cooperate to position the piston  452  within the housing  402 . As the operating temperature of the elongate element  454  increases (along with the temperature of the oil in the shock absorber), the length of the elongate element  454  increases due to thermal expansion. At the same time, the length of the orifice support tube  418  also changes due to thermal expansion. If the orifice support tube  418  has a positive CTE, then the length of the orifice support tube increases by an amount that is less than the increase of the elongate element  454 . If the orifice support tube  418  has a negative CTE, then the length of the orifice support tube decreases. 
     The increase in the length of the elongate element  454  combined with the smaller increase or the decrease in the length of the orifice support tube  418  drives the piston  452  toward the end wall  404  of the housing  402 . This movement of the piston  452  increases the volume of the cavity  406 . The increased cavity volume accommodates the volume change of the fluid caused by the temperature increase, thereby maintaining the pressure within the shock absorber within a predetermined range. As the operating temperatures decrease, the compensator  450  decreases the volume of the cavity  406  by moving the piston  408  away from the end wall  404  of the housing  402 . 
     Similar to the compensator  250  shown in  FIG. 2 , the materials and configuration of the compensator  450  of  FIG. 4  can be selected to suit the configuration, functional characteristics, and operating conditions of the shock absorber  400 . Thus, the compensator  450  can be optimized to maintain the pressure of the fluid  418  in the shock absorber  400  within a predetermined range by increasing and decreasing the volume in the cavity  406  according to increases and decreases, respectively, in the temperature of the fluid, thereby providing more consistent and reliable operation of the shock absorber  400 . 
     Referring now to  FIGS. 7 and 8 , an oleo-pneumatic shock absorber  500  with a thermal compensator  550  according to a third representative embodiment is shown. The shock absorber  500  is similar to the shock absorber  400  shown in  FIG. 6 , wherein a component shown in  FIG. 6  with a reference number  4 XX generally corresponds to a component shown in  FIGS. 7 and 8  with a reference number  5 XX. For the sake of brevity, the shock absorber  500  will be described with the understanding that the components are similar to corresponding components of the shock absorber  300  unless otherwise noted. 
     In the embodiment shown in  FIGS. 7 and 8 , the compensator  550  includes an elongate element  552  in the form of a cylinder that surrounds the orifice support tube  518  and defines an inner surface of the upper chamber  520 . A lower end of the elongate element  552  is fixedly positioned relative to the orifice support tube  518 , and an interior surface of the elongate element slidingly engages the outer surface of the orifice support tube. Similar to the previously describe embodiment of  FIG. 6 , the elongate element  552  has a CTE that is greater than that of the orifice support tube  518 . 
     The compensator  550  further includes a piston  552  slidable disposed within the upper chamber  520  of the shock absorber  500 . Seals  556  are mounted to the inner and outer edges of the piston  552  to provide sealing engagement with the elongate element  552  and the wall of the cavity  506 , respectively. Thus, the piston  556 , rather than the end wall  504 , cooperates with the housing  502  and the first elongate element to define the portion of the cavity  506  that surrounds the orifice support tube  518 . 
     One or more levers  558  are positioned between the piston  554  and the end wall  504  of the housing. Each lever  558  is rotatable about an axis  560  that is fixedly positioned relative to the housing  502  and is located near a first end of the lever. In the illustrated embodiment, the levers  558  are rotatably coupled to the orifice support tube  318 ; however, it will be appreciated that embodiments are possible in which the levers  558  are rotatably coupled to the end wall  504  of the housing  502  or to any other suitable structure. 
     Each lever  558  is also rotatably coupled to the elongate element  552  about an axis  562 . The rotatable connections about axes  560  and  562  control the position of the lever  558 . In this regard, axis  560  remains fixed relative to the housing, while axis  562  moves with the expansion and contraction of the elongate element  552 . With the first end of the lever  558  rotatably coupled about axis  562  in a generally fixed position relative to the housing  502 , movement of axis  562  rotates the lever about axis  560  to control the orientation of the lever. 
     A second end of each lever  558  engages the piston  554  so that the levers  558  act as a stop that limits movement of the piston in the direction of the end wall  504 . The pressure in the cavity  506  provides a force on the piston  554  that biases the piston toward the end wall  504  so that the piston remains engaged with the second end of the lever. In this manner, the position of the levers  558  controls the position of the piston  554  within the housing  502  and, therefore, the size of the cavity  506 . 
     As the temperature increases, orifice support tube  516  expands if the CTE of the orifice support tube is positive or contracts if the CTE of the orifice support tube is negative. The temperature increase also increases the length of the elongate element  552 . Because the CTE of the elongate element  552  is larger than that of the orifice support tube  516 , the upper end of the elongate element and, therefore, axis  562  move toward the end wall  504  of the housing  502 , regardless of whether the CTE of the orifice support tube  516  is positive or negative. Movement of axis  562  repositions the lever  554  to allow the piston  554  to move toward the end wall  504  of the housing  502 , thereby increasing the volume of the cavity  506 . 
     The levers  558  of the illustrated compensator  550  act as a mechanical amplifier that utilizes the geometry of the levers and their attachments to the other components of the shock absorber  500  to provide movement of the piston  554  that is greater than the elongation or contraction of the elongate element  552 . It will be appreciated that the number, position, location, and attachment points of the levers  558  may vary in other embodiments, and such embodiments should be considered within the scope of the present disclosure. 
     The detailed description set forth above in connection with the appended drawings, where like numerals reference like elements, are intended as a description of various embodiments of the present disclosure and are not intended to represent the only embodiments. Each embodiment described in this disclosure is provided merely as an example or illustration and should not be construed as preferred or advantageous over other embodiments. The illustrative examples provided herein are not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. 
     In the foregoing description, specific details are set forth to provide a thorough understanding of exemplary embodiments of the present disclosure. It will be apparent to one skilled in the art, however, that the embodiments disclosed herein may be practiced without embodying all of the specific details. In some instances, well-known features have not been described in detail in order not to unnecessarily obscure various aspects of the present disclosure. Further, it will be appreciated that embodiments of the present disclosure may employ any combination of features described herein. 
     The present application may reference quantities and numbers. Unless specifically stated, such quantities and numbers are not to be considered restrictive, but exemplary of the possible quantities or numbers associated with the present application. Also, in this regard, the present application may use the term “plurality” to reference a quantity or number. In this regard, the term “plurality” is meant to be any number that is more than one, for example, two, three, four, five, etc. The term “about,” “approximately,” etc., means plus or minus 5% of the stated value For the purposes of the present disclosure, the phrase “at least one of A and B” is equivalent to “A and/or B” or vice versa, namely “A” alone, “B” alone or “A and B.”. Similarly, the phrase “at least one of A, B, and C,” for example, means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C), including all further possible permutations when greater than three elements are listed. 
     Throughout this specification, terms of art may be used. These terms are to take on their ordinary meaning in the art from which they come, unless specifically defined herein or the context of their use would clearly suggest otherwise. 
     The principles, representative embodiments, and modes of operation of the present disclosure have been described in the foregoing description. However, aspects of the present disclosure, which are intended to be protected, are not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. It will be appreciated that variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present disclosure. Accordingly, it is expressly intended that all such variations, changes, and equivalents fall within the spirit and scope of the present disclosure as claimed.