Abstract:
An apparatus is provided for vibration damping and isolation. The apparatus includes a housing having an inner surface defining a passage therethrough, a first bellows disposed within the housing passage, the first bellows having an outer surface and spaced apart from the housing inner surface to define a first chamber having a volume, and a second bellows disposed within the housing passage, the second bellows having an outer surface and spaced apart from the housing inner surface to define a second chamber having a volume. The apparatus further includes a restrictive flow passage in fluid communication with the first and second chambers, fluid disposed within the first chamber, the second chamber, and the restrictive flow passage, and a shaft positioned externally to the housing and coupled with the first bellows and the second bellows. The shaft is configured to selectively receive a force to thereby move the fluid through the restrictive flow passage to increase the first chamber volume and decrease the second chamber volume or to decrease the first chamber volume and increase the second chamber volume.

Description:
TECHNICAL FIELD 
     The present invention generally relates to vibration damping and isolation systems, and more particularly relates to isolators. 
     BACKGROUND 
     A precision pointing system carrying a sensor, such as a telescope as its payload, may be susceptible to disturbances that produce structural vibrations and, consequently, pointing errors. Such vibrations may be attributed to mechanical components or assemblies, such as reaction wheel assemblies that are used as actuators in the precision pointing system. For the most part, because these systems tend not to have significant, inherent damping, these structural vibrations may degrade system performance and even cause structural fatigue over time. Therefore, an efficient means of providing damping and isolation to the system may be needed. 
     Typically, to minimize performance degradation caused by vibrations, a passive damping and isolation system is used for damping the structure and isolating the payload carried by a precision isolation system. One example of a passive damping and isolation system is the D-STRUT™ isolation strut, manufactured by Honeywell International Inc. of Morristown, N.J. The D-STRUT™ isolation strut is a three-parameter vibration isolation system that mechanically acts like a spring (K A ) in parallel with a series spring (K B ) and damper (C A ) and is disclosed in U.S. Pat. No. 5,332,070 entitled “Three Parameter Viscous Damper and Isolator” by Davis et al. This patent is hereby incorporated by reference. 
     The D-STRUT™ isolation strut includes a hollow shaft and a piston that is configured to move relative to the shaft. The piston includes a flange that extends radially from a midsection thereof. The flange has a top surface that is coupled to a first sealed bellows and a bottom surface that is coupled to a second sealed bellows. Each of the bellows has a chamber that is filled with fluid. Thus, when the piston moves axially through the shaft, fluid flows from one of the bellows chambers to the other. 
     Although the conventional D-STRUT™ isolation strut operates effectively in most applications, it may not be appropriate to implement in other applications. For example, in some implementations that require a low-viscosity (“thin”) fluid and are required to accommodate relatively large rotations, a configuration using the conventional shaft between the bellows chambers may not be suitable. The reason for using a low viscosity fluid is to permit operation in lower temperature environments (lower pour point and lower temp at which gelling occurs). 
     Accordingly, it is desirable to have an isolation strut that is capable of damping and isolating vibration. In addition, it is desirable for the isolation strut to be usable with a low-viscosity fluid and to accommodate large rotations. Moreover, it is desirable for the isolation strut to have a simple configuration that is relatively inexpensive to implement. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention. 
     BRIEF SUMMARY 
     An apparatus is provided for vibration damping and isolation. In one exemplary embodiment, the apparatus includes a housing having an inner surface defining a passage therethrough, a first bellows disposed within the housing passage, the first bellows having an outer surface and spaced apart from the housing inner surface to define a first chamber having a volume, and a second bellows disposed within the housing passage, the second bellows having an outer surface and spaced apart from the housing inner surface to define a second chamber having a volume. The apparatus further includes a restrictive flow passage in fluid communication with the first and second chambers, fluid disposed within the first chamber, the second chamber, and the restrictive flow passage, and a shaft positioned externally to the housing and coupled with the first bellows and the second bellows. The shaft is configured to selectively receive a force to thereby move the fluid through the restrictive flow passage to increase the first chamber volume and decrease the second chamber volume or to decrease the first chamber volume and increase the second chamber volume. 
     This brief 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 or essential 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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein: 
         FIG. 1  is a schematic of an exemplary system having vibration damping and isolation; 
         FIG. 2  is an isometric projection view of an exemplary vibration damping system in accordance with various embodiments of the present disclosure; 
         FIG. 3  is a side view of the exemplary vibration damping system shown in  FIG. 2 ; and 
         FIG. 4  is a cross-sectional view of the exemplary vibration damping system based on the side view shown in  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. As used herein, the word “exemplary” means “serving as an example, instance, or illustration.” Thus, any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. All of the embodiments described herein are exemplary embodiments provided to enable persons skilled in the art to make or use the invention and not to limit the scope of the invention which is defined by the claims. While the isolation struts are discussed with reference to exemplary embodiments, any one of numerous other embodiments of a fluid filled isolation strut may be implemented as well. Fluid, as used in the present invention, can be any viscous liquid or any gas known in the art. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary, or the following detailed description. 
     Embodiments of the present disclosure are generally directed to improved vibration isolation and damping systems. The disclosed embodiments take the conventionally-employed internal through-shaft out of the damper and wrap it around the entire damper housing. Thus, instead of an annulus used for damping that a through-shaft provides, the damping will now come from an annular orifice. The external through-shaft provides the same relative motion that the conventional, internal through-shaft configuration would provide. As such, the systems can a) have very thin fluid for cold temperature environments and b) handle large rotations that with the conventional internal through-shaft would prove unattainable. 
       FIG. 1  illustrates an exemplary system having vibration damping and isolation. The system  100  may be implemented in any one of numerous environments, such as in space, terrestrially, or under water. The system  100  includes a base  102 , a payload  104 , and at least one vibration isolation apparatus  106 . The base  102  is configured to provide a platform to which the payload  104  and vibration isolation apparatus  106  are coupled and may be any one of numerous application-appropriate devices. For example, in a space application, the base  102  can be a satellite, an arm of a satellite, a space station, or any one of numerous other conventionally-used space apparatus. The payload  104  is a device that preferably needs vibration damping and isolation to operate effectively. The payload  104  may be any one of numerous devices, such as, for example, a telescope, or a camera. 
     The vibration isolation apparatus  106  dampens and isolates vibration that may be experienced by the payload  104  and thus, is coupled between the payload  104  and the base  102 . Although a single vibration isolation apparatus  106  may be used, it may be preferable to employ more than one vibration isolation apparatus  106 . In one exemplary embodiment, three vibration isolation apparatus  106  are used in a three-point-mount configuration to isolate vibration. In another exemplary embodiment, six vibration isolation apparatus  106  are implemented in a hexapod configuration to provide vibration isolation. In still another exemplary embodiment, eight vibration isolation apparatus  106  are implemented in an octopod configuration to provide vibration isolation. In the embodiments described above, vibration isolation is provided in six degrees of freedom. 
     With reference now to  FIGS. 2-4 , one exemplary vibration isolation apparatus  106  is provided. The vibration isolation apparatus  106  includes a first support  108 , a tuning spring  110 , a stinger piece  112 , a damper assembly  114 , and a second support  116 . The second support  116  receives vibratory motion from the base  102  and couples the base  102  to the vibration isolation apparatus  106 . The damper assembly  114  is coupled to the second support  116 , and provides the damping associated with the vibration isolation apparatus  106 . Damper assembly  114  is coupled to stinger piece  112 , which is coupled to the tuning spring  110 . Tuning spring  110  is coupled to the first support  108 , which in turn couples the vibration isolation apparatus to the payload  104 . The series combination of the first support  108 , tuning spring  110 , stinger piece  112 , damper assembly  114 , and second support  116  provide the desired three-parameter vibration isolation properties (Ka, Kb, and Ca parameters). 
     The damper assembly  114  includes an assembly housing  118 , a first bellows  120 , a second bellows  122 , a first shaft  124 , a second shaft  126 , an external shaft  128 , fluid and, optionally, a temperature compensation device  130 . The first shaft  124  is coupled to the external shaft  128  via first connection member  132 . The second shaft is couple to the external shaft via second connection member  134 . The series connections of first shaft  124 , first connection member  132 , external shaft  128 , second connection member  134 , and second shaft  126  are designed to rigidly couple the ends of the first bellows  120  and second bellows  122 , such that extension of one of the bellows results in equal compression to the other bellows. 
     The assembly housing  118  is configured to operate with the other components of the damper assembly  114  to provide a fixed volume of space and to enclose and seal the fluid therein. The assembly housing  118  includes at least a tubular structure  136  that has a first end  138 , a second end  140 , and an inner surface  142  that connects with a passage  144  extending between the first and second ends  138 ,  140 . The assembly housing  118  also includes a longitudinal axis  146  along which the vibration is received and the vibration is damped. Preferably, the first end  138  includes an inlet  148 , the second end  140  includes an outlet  141 , and the tube  136  has no openings other than the inlet  148  and outlet  141 . However, in alternate embodiments, the tube  136  may be a single component having endwalls integrally formed or coupled to each of the first and second ends  138 ,  140 . 
     In one exemplary embodiment, the assembly housing  118  includes a damping plate  152  disposed in the middle thereof. The damping plate  152  is integrally formed or integrated as part of the assembly housing  118  and includes the passage  144  that extends through the damping plate  152 . 
     The first bellows  120  is disposed within the assembly housing  118  and is preferably configured to move along the longitudinal axis  146 . The first bellows  120  is coupled at one end to a first end plate  149  and at an opposite end to a second end plate  151  to thereby define first bellows interior cavity  153  therebetween. The first end plate  149  sealingly mates with the assembly housing first end  138  and couples the first bellows  120  thereto. The second end plate  151  couples to the first shaft  124  that is disposed within the first bellows interior cavity  153 . The first shaft  124  is configured to provide structural support for the first bellows  120  and guides the first bellows  120  along the longitudinal axis  146  during operation. It will be appreciated that the first end plate  149  includes an opening  162  formed therein that is configured to accommodate components that may extend outside of the assembly housing  118 , such as the first shaft  124 . 
     Similar to the first bellows  120 , the second bellows  122  is disposed within the assembly housing  118 , is coupled to a first and a second end plate  166 ,  168 , and is preferably configured to move along the longitudinal axis  146 . Although depicted as being capable of traveling along the same axis  146  as the first bellows  120 , it will be appreciated that in other non-illustrated embodiments the second bellows  122  may move along any other suitable axis. The second bellows first end plate  166  sealingly mates with the assembly housing second end  140  and couples the second bellows  122  thereto. The second bellows second end plate  168  is coupled to the opposite end of the second bellows  122  and, together with the first end plate  166  and inner surface of the second bellows  122 , defines an interior cavity  170 . The second end plate  168  couples to a second shaft  126  that is disposed within the second bellows interior cavity  170 . The second shaft  126  is configured to provide structural support for the second bellows  122  and guides the second bellows  122  along the longitudinal axis  146  during operation. The second shaft  126  also couples with the stinger piece  112 . Just as above, the first end plate  166  includes opening  172  formed therein that are configured to provide space for disposal of components that may extend outside of the assembly housing  118 , in this case, the second shaft  126 . 
     The isolation assembly also includes an external shaft  128 . The external shaft  128  is positioned exterior to the assembly housing  118 . The external shaft  128  includes first and second annular portions  191  and  192 . First annular portion  191  extends at least part-way around the first end  138 , and the second annular portion  192  extends at least part-way around the second end  140 . The shaft  190  further includes at least one, and preferably two, three, or more longitudinal portions  193  that extend parallel to axis  146  longitudinally between the first and second annular portions  191 ,  192 , exterior to assembly housing  118 . The external shaft  128  is coupled to the first and second bellows  120 ,  122 . The external shaft  128  couples to the first bellows  120  via the rigid, first connection member  132  and the first shaft  124 . The external shaft  128  couples to the second bellows  122  via the rigid, second connection member  134  and the second shaft  126 . Preferably, the rigid connection members  132 ,  134  are configured as a structure having multiple extending portions  196 , the number of extending portions  196  being the same as the number of longitudinal portions  193 . Each extending portion  196  connects, at one end, with the external shaft  128  at a point that is roughly adjacent to an end of a respective longitudinal portion  193 . Each extending portion  196  connects, at the other end thereof, with the other extending portions  196 , at a center portion  197  of the members  132 ,  134 . The first connection member  132  is coupled with first bellows  120  via a sliding association over first shaft  124 , and via abutting contact with the second end plate  151 , at the center portion  197  thereof. The second connection member  134  is coupled with the second bellows  122  via a sliding association over second shaft  126 , and via abutting contact with the second end plate  168 , at the center portion  197  thereof. The second connection member  134  is further coupled with the stinger piece  112  at the center portion thereof. The external shaft  128  is configured to operate with the first and second bellows  120 ,  122  to damp and isolate vibration received from the stinger piece  112 . Other configurations of external shaft  128  that accomplish the same function as the exemplary configuration illustrated in the figures will also be appreciated by those having ordinary skill in the art. 
     As briefly mentioned previously, the damper assembly  114  components are preferably configured to operate together to sealingly enclose the fluid therein in a fixed volume of space. The volume of space is separated into subvolumes, each of which is disposed in a first chamber  182 , a second chamber  184 , and the restrictive flow passage  139 . The first chamber  182  is defined by a portion of the assembly housing inner surface  135  and an outer surface of the first bellows  120 , as well as second end plate  151  and first shaft  124 , and the second chamber  184  is defined by another portion of the assembly housing inner surface  135  and an outer surface of the second bellows  122 , as well as second end plate  168  and second shaft  126 . The restrictive flow passage  139  allows the first and second chambers  182 ,  184  to communication with one another and may have any one of numerous configurations. In one exemplary embodiment, the restrictive flow passage is configured as a cylindrical duct through the damping plate  152 . No matter the particular configuration, the first chamber  182 , second chamber  184 , and restrictive flow passage  139  are filled with fluid. Thus, during the operation of the damper assembly  114 , when a force is exerted on the assembly housing  118  (for example from second support  116 ), fluid is pushed from the second chamber  184 , through the restrictive flow passage  139 , into the first chamber  182 . 
     The temperature compensation device  130  may be included in the damper assembly  114  to compensate for fluid expansion and/or contraction in response to temperature changes. The temperature compensation device  130  may have any one of numerous suitable configurations and may be disposed within the damper assembly  114  in any one of numerous manners. 
     There has now been provided a vibration isolator that is capable of damping and isolating vibration. In addition, the isolation strut is usable with a thin fluid and to accommodate large rotations. Moreover, the isolation strut has a simple configuration that is relatively inexpensive to implement. 
     While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention. It being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.