Pylon mounting system with vibration isolation

A pylon mounting system with vibration isolation is provided. The system generally includes a housing that defines a first fluid chamber and a second fluid chamber, a fluid disposed within the fluid chambers; a piston assembly at least partially disposed within the housing, and a tuning passage defined by the piston assembly for providing fluid communication between the fluid chambers. The piston assembly has a first arm and a second arm, and each arm has a tubeform bearing for providing pitch and roll stiffness.

TECHNICAL FIELD

The present application relates in general to heaver-than-air aircraft. More specifically, the present application relates to a pylon mounting system with vibration isolation.

DESCRIPTION OF THE PRIOR ART

One important engineering objective during the design of an aircraft is to minimize the weight and number of parts. It is especially important in the design and manufacture of helicopters and other rotary wing aircraft, such as tilt rotor aircraft, which are required to hover against the dead weight of the aircraft, and which are, thus, somewhat constrained in their payload in comparison with fixed-wing aircraft.

Methods and devices for isolating a vibrating body from another body are useful in a variety of technical fields and applications. Such isolators are particularly useful for isolating an aircraft frame from mechanical vibrations, which may be caused by other aircraft components. For example, the engine and transmission often generate unwanted vibrations that can be isolated from the aircraft frame by an isolator, such as a liquid inertia vibration elimination (LIVE) system. However, vibration isolators also add weight and complexity to an aircraft. Accordingly, the design and use of vibration isolators continues to present significant challenges to engineers and manufacturers.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Illustrative embodiments of the novel system are described below. In the interest of clarity, not all features of such embodiments may be described. It should be appreciated that in the development of any such system, numerous implementation-specific decisions must be made to achieve specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it should be appreciated that such decisions might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this specification.

Reference may be made to the spatial relationships between various components and to the spatial orientation of various aspects of components as the system is depicted in the attached drawings. However, as should be recognized by those skilled in the art, the elements, members, components, etc. described herein may be positioned in any desired orientation. Thus, the use of terms such as “above,” “below,” “upper,” “lower,” or other like terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components, respectively, as the example embodiments described herein may be oriented in any desired direction.

Referring to the appended drawings,FIG. 1is a perspective view of one embodiment of a rotor pylon100according to the present specification, which may be used to mount a rotor assembly to an aircraft. A transmission105transmits power from a power plant110, such as a jet turbine engine, to a rotor assembly (not shown) to provide lift and propulsion for the aircraft. Transmission105is connected to pylons115and120, which extend upwardly from roof beams125and130. Vibrations isolators may be provided to minimize the transfer of vibrations from the transmission105and other components to the rest of the aircraft. In the embodiment illustrated inFIG. 1, vibration isolators135and140according to the present specification are connected between transmission105and pylons115and120, respectively.

FIG. 2is a cross-sectional view of an embodiment of a vibration isolator200according to the present specification. Vibration isolator200comprises an upper housing205and a lower housing210. A piston215is at least partially disposed within the interior of upper housing205and lower housing210. Piston215includes arms216aand216b. Arms216aand216bhave a conical profile inFIG. 2, but other profiles, such as a cylindrical profile, may be acceptable or preferable in other embodiments. Tubeform bearings217aand217bare bonded to arms216aand216b, respectively, and may include casing218aand218b. Bearings217aand217bare preferably high-capacity laminate (HCL) elastomeric bearings. The casings218aand218bmay be open-ended or closed. Shims219aand219bmay also be disposed between bearings217aand217b, respectively, as needed for proper orientation. An upper elastomeric member220seals and resiliently locates piston215within the interior of upper housing205. Similarly, a lower elastomeric member225seals and resiliently locates piston215within the interior of lower housing210. Elastomeric members220and225may function as a spring to permit piston215to move or oscillate relative to upper housing205and lower housing210. When no load is applied, elastomeric members220and225are configured to locate piston215generally central to upper housing205and lower housing210. The interior of piston215defines a generally elongated tuning passage230. An upper fluid chamber235is generally defined by the interior of upper housing205, piston215, and upper elastomeric member220. Similarly, a lower fluid chamber240is generally defined by the interior of lower housing210, piston215, and lower elastomeric member225.

Tuning passage230extends centrally through a longitudinal axis of piston215, so that upper fluid chamber235and lower fluid chamber240are in fluid communication. A tuning fluid245is disposed in upper fluid chamber235, lower fluid chamber240, and tuning passage230. Tuning fluid245preferably has low viscosity, relatively high density, and non-corrosive properties. For example, tuning fluid245may be mercury or a proprietary fluid, such as SPF I manufactured by LORD CORPORATION. Other embodiments may incorporate hydraulic fluid having suspended dense particulate matter.

In operation, piston215is typically coupled to a vibrating body. For example, an aircraft transmission may be mounted to arms216aand216b. Arms216aand216bmay be oriented substantially perpendicular to the pitch axis, such that the torsional shearing of bearings217aand217bprovide roll stiffness and the vertical stiffness of bearings217aand217bprovide pitch stiffness without the need for additional pitch restraints. Upper housing205and lower housing210are typically coupled to a body to be isolated from vibration, such as a roof structure (not shown) of an aircraft. In such an arrangement, the aircraft structure is the body to be isolated from vibration, and the transmission is the vibrating body. Introduction of an axial force into piston215, such as from transmission vibrations, translates piston215axially relative to upper housing205and lower housing210. The movement of piston215forces tuning fluid245to move through tuning passage230in a direction opposite to the translation direction of piston215. Movement of tuning fluid245produces an inertial force that substantially reduces, or isolates, the force from piston215at a discrete frequency, i.e., the isolation frequency.

FIG. 3is a cross-sectional view of another embodiment of a vibration isolator300according to the present specification. Vibration isolator300comprises an upper housing305and a lower housing310. A piston315is at least partially disposed within the interior of upper housing305and lower housing310. Piston315includes arms316aand316b. Arms316aand316bhave a conical profile inFIG. 3, but other profiles, such as a cylindrical profile, may be preferable in other embodiments. Arms316aand316bhave a generally hollow interior. Tubeform bearings317aand317bare bonded to arms316aand316b, respectively, and may include casing318aand318b, which may cap arms316aand316b, respectively. Bearings317aand317bare preferably high-capacity laminate (HCL) elastomeric bearings. Shims319aand319bmay also be disposed between bearings317aand317b, respectively, as needed for proper orientation. An upper elastomeric member320seals and resiliently locates piston315within the interior of upper housing305. Similarly, a lower elastomeric member325seals and resiliently locates piston315within the interior of lower housing310. Elastomeric members320and325may function as a spring to permit piston315to move or oscillate relative to upper housing305and lower housing310. When no load is applied, elastomeric members320and325are configured to locate piston315generally central to upper housing305and lower housing310. The interior of piston315defines a generally elongated tuning passage330. An upper fluid chamber335is generally defined by the interior of upper housing305, piston315, and upper elastomeric member320. Similarly, a lower fluid chamber340is generally defined by the interior of lower housing310, piston315, and lower elastomeric member325.

Tuning passage330extends centrally through a longitudinal axis of piston315, so that upper fluid chamber335and lower fluid chamber340are in fluid communication. A tuning fluid345is disposed in upper fluid chamber335, lower fluid chamber340, and tuning passage330. Tuning fluid345preferably has low viscosity, relatively high density, and non-corrosive properties. For example, tuning fluid345may be mercury or a proprietary fluid, such as SPF I manufactured by LORD CORPORATION. Other embodiments may incorporate hydraulic fluid having suspended dense particulate matter.

In operation, piston315is typically coupled to a vibrating body. For example, an aircraft transmission may be mounted to arms316aand316b. Arms316aand316bmay be oriented substantially perpendicular to the pitch axis, such that the torsional shearing of bearings317aand317bprovide roll stiffness and the vertical stiffness of bearings317aand317bprovide pitch stiffness without the need for additional pitch restraints. Upper housing305and lower housing310are typically coupled to a body to be isolated from vibration, such as a roof structure (not shown) of an aircraft. In such an arrangement, the aircraft structure is the body to be isolated from vibration, and the transmission is the vibrating body. Introduction of an axial force into piston315, such as from transmission vibrations, translates piston315axially relative to upper housing305and lower housing310. The movement of piston315forces tuning fluid345to move through tuning passage330in a direction opposite to the translation direction of piston315. Movement of tuning fluid345produces an inertial force that substantially reduces, or isolates, the force from piston315at a discrete frequency, i.e., the isolation frequency.

FIG. 4is a cross-sectional view of yet another embodiment of a vibration isolator400according to the present specification. Vibration isolator400comprises an upper housing405and a lower housing410. A piston415is at least partially disposed within the interior of upper housing405and lower housing410. Piston415includes arms416aand416b. Arms416aand416bhave a conical profile inFIG. 4, but other profiles, such as a cylindrical profile, may be preferable in other embodiments. Arms416aand416bhave a generally hollow interior. Tubeform bearings417aand417bare bonded to arms416aand416b, respectively, and may include casing418aand418b, which may cap arms416aand416b, respectively. Bearings417aand417bare preferably high-capacity laminate (HCL) elastomeric bearings. Shims419aand419bmay also be disposed between bearings417aand417b, respectively, as needed for proper orientation. Additionally, a spherical elastomeric bearing420is bonded to piston415. An upper elastomeric member425seals and resiliently locates piston415within the interior of upper housing405. Similarly, a lower elastomeric member430seals and resiliently locates piston415within the interior of lower housing410. Elastomeric members425and430may function as a spring to permit piston415to move or oscillate relative to upper housing405and lower housing410. When no load is applied, elastomeric members425and430are configured to locate piston415generally central to upper housing405and lower housing410. The interior of piston415defines a generally elongated tuning passage435. An upper fluid chamber440is generally defined by the interior of upper housing405, piston415, and upper elastomeric member425. Similarly, a lower fluid chamber445is generally defined by the interior of lower housing410, piston415, and lower elastomeric member430.

Tuning passage435extends centrally through a longitudinal axis of piston415, so that upper fluid chamber440and lower fluid chamber445are in fluid communication. A tuning fluid450is disposed in upper fluid chamber440, lower fluid chamber445, and tuning passage435. Tuning fluid450preferably has low viscosity, relatively high density, and non-corrosive properties. For example, tuning fluid450may be mercury or a proprietary fluid, such as SPF I manufactured by LORD CORPORATION. Other embodiments may incorporate hydraulic fluid having suspended dense particulate matter.

In operation, piston415is typically coupled to a vibrating body. For example, an aircraft transmission may be mounted to arms416aand416b. Arms416aand416bmay be oriented substantially perpendicular to the pitch axis, such that the torsional shearing of bearings417aand417bprovide roll stiffness. Spherical elastomeric bearing420and the vertical stiffness of bearings417aand417bprovide pitch stiffness without the need for additional pitch restraints. Upper housing405and lower housing410are typically coupled to a body to be isolated from vibration, such as a roof structure (not shown) of an aircraft. In such an arrangement, the aircraft structure is the body to be isolated from vibration, and the transmission is the vibrating body. Introduction of an axial force into piston415, such as from transmission vibrations, translates piston415axially relative to upper housing405and lower housing410. The movement of piston415forces tuning fluid450to move through tuning passage435in a direction opposite to the translation direction of piston415. Movement of tuning fluid450produces an inertial force that substantially reduces, or isolates, the force from piston415at a discrete frequency, i.e., the isolation frequency.

Certain example embodiments have been shown in the drawings and described above, but variations in these embodiments will be apparent to those skilled in the art. The principles disclosed herein are readily applicable to a variety of mechanical systems, including many types of aircraft. The preceding description is for illustration purposes only, and the claims below should not be construed as limited to the specific embodiments shown and described.