Patent Application
20150226282
The present invention relates generally to isolation devices and, more particularly, to isolators including fluid dampers and allowing scaling of orifice size to, for example, highly reduced dimensions without limiting rotation angle capabilities.
Isolators commonly include fluid dampers having opposing hydraulic chambers, which are fluidly coupled by an annulus or other restricted orifice and filled with a damping fluid. The viscosity of the damping fluid may be selected based upon the performance requirements of the isolator, including the isolator's operative temperature range. Generally, damping fluids having lower viscosities tend to resist crystallization or solidification and, thus, flow more readily under low temperature conditions. Consequently, in instances wherein the isolator is required to operate at extremely depressed or cryogenic temperatures, such as temperatures approaching or falling below −30° Celsius (° C.), a damping fluid having a very low viscosity (e.g., in the range of about 1 to 10 centistokes or “cS”) may be selected. To enable the usage of such a low viscosity or thin damping fluid, while maintaining isolator performance at acceptable levels, it may be necessary to impart the flow orifice or orifices with highly reduced dimensions. This can present certain difficulties. In instances wherein the orifice assumes the form of an annulus, manufacturing tolerances may render the production of an annulus having a very small radial width unreliable or impractical. Moreover, an isolator having such a highly restricted annulus generally cannot accommodate large angular misalignments between mount points without contact or touch-down between internal surfaces defining the annulus. Other isolator designs are possible, but tend to be characterized by undesirably large envelopes, high sprung masses, high overall weights, increased part counts, and other such limitations.
It would thus be desirable to provide embodiments of an isolator including a fluid damper and enabling damper orifice size to be adjusted independently of the rotation angle capability of the isolator. Advantageously, embodiments of such an isolator could be produced to include highly restrictive flow orifices suitable for usage with low viscosity damping fluids, while simultaneously imparting the isolator with a relatively large rotation angle capability. Ideally, embodiments of such an isolator would further be readily manufacturable, relatively compact, lightweight, and characterized by a relatively low part count and sprung mass. Other desirable features and characteristics of embodiments of the present invention will become apparent from the subsequent Detailed Description and the appended Claims, taken in conjunction with the accompanying drawings and the foregoing Background.
Embodiments of an isolator are provided. In one embodiment, the isolator includes a damper housing having a radially-extending partition wall through which a central opening is formed. First and second hydraulic chambers are located on opposing sides of the radially-extending partition wall and may be filled with a damping fluid. At least one restricted orifice is formed through the damper housing and fluidly couples the first and second hydraulic chambers. The isolator further includes a damper piston, which extends through the central opening, which is exposed to the damping fluid when the first and second hydraulic chambers are filled therewith, and which is configured to translate along the working axis with respect to the damper housing during operation of the isolator.
In a further embodiment, the isolator includes opposing hydraulic chambers, which are configured to be filled with a damping fluid; and a damper piston, which has a piston shaft generally co-axial with the working axis. The damper piston is exposed to the damping fluid when the opposing hydraulic chambers are filled therewith. An annular air gap or void surrounds the piston shaft and is circumscribed by the opposing hydraulic chambers.
In a still further embodiment, the isolator includes first and second hydraulic chambers configured to be filled with a damping fluid. A radially-extending partition wall is disposed between the first and second hydraulic chambers and has a central opening therein. At least one restricted orifice is formed through the radially-extending partition wall and fluidly couples the first and second hydraulic chambers. A damper piston is movably coupled to the radially-extending partition wall and includes a piston shaft extending through the central opening. First and second externally-pressurized bellows are each sealingly coupled between the radially-extending partition wall and the damper piston. The isolator further includes an annular air gap or void, which is bounded along its inner circumference by the piston shaft and along its outer circumference by the first externally-pressurized bellows, the second externally-pressurized bellows, and the central opening.
At least one example of the present invention will hereinafter be described in conjunction with the following figures, wherein like numerals denote like elements, and:
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. Furthermore, there is no intention to be bound by any theory presented in the preceding Background or the following Detailed Description. As appearing herein, the term “about” is utilized to denote a disparity of less than 10%. As further appearing herein, the term “orifice” is utilized to denote any opening, flow passage, or channel formed through a larger structure and fluidly coupling at least two hydraulic chambers. Finally, as still further appearing herein, the term “isolator” is utilized in reference to a device that reduces the transmission of vibrations or other disturbance forces between at least two objects or mount points and that includes or assumes the form of a fluid damper.
Isolator 10 includes a fluid damper 14 and an end piece 16, which are longitudinally spaced along working axis 12. Fluid damper 14 includes, in turn, a damper piston 20 (
Isolator 10 further includes at least two mounting interfaces permitting installation of isolator 10 within a larger isolation system. For example, as shown in
With continued reference to the exemplary embodiment shown in
Two opposing sets or pairs of bellows are contained within damper housing 22: (i) a first pair of opposing bellows 40 and 42, and (ii) a second pair of opposing bellows 44 and 46. Bellows 40, 42, 44, and 46 may be, for example, edge-welded bellows formed from a stack of convolutes and fabricated from a metal or alloy. Bellows 40 and 42 are referred to herein as the “inner bellows” in view of their positioning between bellows 44 and 46, as taken along working axis 12. Conversely, bellows 44 and 46 are referred to as the “outer bellows” in view of their positioning outside of inner bellows 40 and 42. Stated differently, outer bellows 44 and 46 flank inner bellows 40 and 42, as viewed in cross-section taken along a cut plane parallel to working axis 12. The outer diameters of outer bellows 44 and 46 vary as compared to the outer diameters of inner bellows 40 and 42. For example, outer bellows 44 and 46 may be sized to each have a first outer diameter, while inner bellows 40 and 42 may be sized to have a second outer diameter less than the first outer diameter; e.g., the outer diameters of inner bellows 40 and 42 may be at least 10% or, perhaps, at least 25% less than the outer diameters of bellows 44 and 46. As generally illustrated in
Damper housing 22 further includes an intervening structure or internal body, which is disposed between inner bellows 40 and inner bellows 42 and which separates the below-described hydraulic chambers. In the exemplary embodiment shown in
Damper piston 20 (
Moving from left to right in
Fluid damper 14 further includes opposing hydraulic chambers 56 and 58 contained within damper housing 22. Hydraulic chamber 56 is generally defined by the outer circumference of outer bellows 44, bellows plate 48, the outer circumference of inner bellows 40, and damper housing 22 including partition wall 38. Similarly, hydraulic chamber 58 is generally defined by the outer circumference of inner bellows 42, bellows plate 50, the outer circumference of outer bellows 46, and damper housing 22 including partition wall 38. Radially-extending partition wall 38 is located between and generally separates or divides hydraulic chambers 56 and 58. One or more restricted orifices 60 (two of which are shown in
Isolator 10 may initially be produced and distributed without damping fluid, in which case fluid damper 14 may be filled with a selected damping fluid at a chosen juncture after production and prior to deployment of isolator 10. Isolator 10 is illustrated in
The size, shape, number, and spatial distribution of restricted orifices 60 are limited only by the dimensions of partition wall 38 (and/or by the annular sidewall 28 of damper housing 22, if orifices are formed therethrough). The dimensions and geometries of restricted orifices 60 can thus be adjusted, as appropriate, to tailor isolator 10 to a particular application or usage. Thus, in embodiments wherein it is desired to fill isolator 10 with a very low viscosity damping fluid for operation at extremely depressed temperatures, orifices 60 can be produced to have highly restricted dimensions providing that at least a minimal amount of damping fluid can still flow between hydraulic chambers 56 and 58. For example, in the illustrated example wherein restricted orifices 60 have generally planform circular shapes, as viewed along working axis, the diameters of orifices 60 can be minimized. The length of orifices 60 can also be adjusted, as may be desired, by increasing or decreasing the thickness of radially-extending partition wall 38, by forming orifices 60 at oblique angles relative to working axis 12, and/or by forming orifices 60 to follow non-linear paths (e.g., curved or spiral shaped paths) through partition wall 38.
During operation of isolator 10, relative axial movement occurs between damper housing 22 and damper piston 20, as well as those component rigidly joined to piston 20 (i.e., connector rod 18 and end piece 16). Bellows 40, 42, 44, and 46 expand and compress, as needed, to accommodate such relative axial movement between damper piston 20 and damper housing 22. As bellows 40, 42, 44, and 46 expand and contract, the respective volumes of chambers 56 and 58 vary, and damping fluid is forced through restricted orifices 60. Specifically, as damper piston 20 strokes away from mount point 32 (to the right in
As indicated above, the volumes of hydraulic chambers 56 and 58 vary in conjunction with movement of piston 20 and deflection of bellows 40, 42, 44, and 46. The variance in volumes of hydraulic chambers 56 and 58 is brought about by the disparity in diameters between outer bellows 44 and inner bellows 40, as well as the disparity in diameters between inner bellows 42 and outer bellows 46. Additionally, bellows plate 48 is sized to have an outer diameter greater than the outer diameter of inner bellows 40 such that an annular region or band 64 (identified in
As described above, damper piston 20 is characterized by a “through-shaft” design such that piston shaft 52 extends axially along working axis 12 or the centerline of isolator 10 to provide a direct and stiff mechanical connection between bellows plates 48 and 50. Relative to other, more complex designs utilized to couple opposing bellows plates (e.g., bellows plates 48 and 50 shown in
To allow isolator 10 and, specifically, fluid damper 14 to accommodate relatively large rotational displacements between damper piston 20 and damper housing 22, several annular gaps or circumferential clearances are provided between damper piston 20 and the interior surfaces of housing 22. These circumferential clearances include: (i) a first circumferential clearance between bellows plate 48 and an inner circumference surface of damper housing 22 (identified in
The rotational angle capabilities of isolator 10 may be further enhanced by minimizing the axial thicknesses of bellow plates 48 and 50 (as taken along working axis 12) and the longitudinal length of opening 54 in radially-extending partition wall 38. In the latter regard, it will be noted that axial thickness of partition wall 38 remains constant in the illustrated example, as considered when moving radially inward from the tubular body 28 of damper housing 22 toward working axis 12. The longitudinal length of opening 54 is thus substantially equivalent to the length of restricted orifices 60. However, in further embodiments, radially-extending partition wall 38 may decrease (e.g., taper or step downward) in axial thickness when moving radially inward toward working axis 12 such that the axial length of central opening 54 is less than the length of the restricted orifices 60 formed in partition wall 38.
The foregoing has thus provided embodiments of an isolator including a fluid damper and enabling orifice size to be adjusted independently of the rotation angle capability of the isolator. Embodiments of the isolator can be produced to include highly restricted damper orifices, while also having a relatively broad rotational angle capacity. In embodiments wherein the isolator includes highly restricted orifices, the isolator may be well-suited for usage at low operative temperatures (e.g., temperatures less than −30° C. and possibly approaching or falling below −65° C.) and with damping fluids having very low viscosities (e.g., silicone-based damping liquids having a viscosity less than about 10 cS). This notwithstanding, it is emphasized the embodiments of the isolator need not be utilized in conjunction with a low viscosity damping fluid nor include highly restricted orifices in all embodiments. Due, at least in part, to the incorporation of a through-shaft design, embodiments of the isolator may also provide relatively compact envelopes, low weights, low spring masses, and reduced pressure preload requirements. As a still further benefit, embodiments of the isolator may be characterized by relatively a small sprung mass, which may favorably increase the internal isolator modes (radial and axial) and the operational frequency bandwidth of the isolator.
While at least one exemplary embodiment has been presented in the foregoing Detailed Description, 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.
