Method and apparatus for improved vibration isolation

1. A vibration isolator, comprising:

a housing defining a fluid chamber;

a fluid disposed within the fluid chamber;

a piston assembly resiliently disposed within the housing;

a tuning passage defined by the piston assembly;

at least one bracket coupled to the piston assembly for transferring forces to the piston assembly; and

an adjustable metering pin assembly configured for changing an effective diameter of the tuning passage, the metering pin assembly including a bulb portion at least partially disposed within the tuning passage, the metering pin assembly selectively translating relative to the entire housing and the piston assembly;

wherein the bulb portion is conical in shape;

wherein the tuning passage is circular in cross-section;

wherein a diameter of the tuning passage enlarges near the bulb portion of the metering pin assembly; and

wherein the metering pin assembly extends through the housing and is secured at a first end by a first bore and at a second end by a second bore.

2. The vibration isolator according to claim 1 , wherein the tuning passage is formed by the piston assembly, so as to divide the fluid chamber into two volumes that are in fluid communication.

3. The vibration isolator according to claim 1 , wherein the piston is resiliently coupled to the housing with at least one elastomer member.

4. The vibration isolator according to claim 1 , wherein the piston comprises:

a tuning passage portion; and

a support frame.

5. The vibration isolator according to claim 1 , further comprising:

a metering pin actuator operably associated with the metering pin assembly for selectively adjusting the position of metering pin assembly.

6. The vibration isolator according to claim 5 , further comprising:

an actuation device operably associated with the metering pin actuator;

wherein the actuation device is selected from the group consisting of:

an electric actuator;

a hydraulic actuator;

a pneumatic actuator; and

an electromagnetic actuator.

7. The vibration isolator according to claim 5 , wherein the metering pin actuator utilizes a mechanical screw drive to translate the metering pin assembly.

8. The vibration isolator according to claim 1 , wherein the housing is coupled to a roof beam of an aircraft.

9. The vibration isolator according to claim 1 , wherein the piston assembly is coupled to a pylon assembly of an aircraft.

10. The vibration isolator according to claim 4 , wherein the metering pin assembly is slidingly coupled to the support frame.

11. The vibration isolator according to claim 1 , further comprising:

a seepage path for providing pressure equalization between the fluid chamber and each of the bores.

12. An aircraft, comprising:

an airframe;

a pylon assembly carried by the airframe; and

a vibration isolator disposed between the airframe and the pylon assembly, the vibration isolator comprising:

a housing defining a fluid chamber;

a fluid disposed within the fluid chamber;

a piston assembly resiliently disposed within the housing;

a resilient member for resiliently coupling the piston assembly to the housing; and

an adjustable metering pin assembly coupled to the housing for changing an effective diameter of a tuning passage, a bulb portion of the metering pin assembly being disposed at least partially within the tuning passage, the metering pin assembly selectively translating relative to the entire housing and the piston assembly;

wherein the bulb portion of the metering pin assembly is conical in shape;

wherein the tuning passage is circular in cross-section;

wherein a diameter of the tuning passage enlarges near the bulb portion of the metering pin assembly;

wherein the adjustable metering pin assembly extends through the housing; and

wherein the adjustable metering pin assembly is secured at a first end by a first bore and at a second end by a second bore.

13. The aircraft according to claim 12 , wherein the frequency response of the vibration isolator is adjusted by actuation of the metering pin assembly.

14. A vibration isolator, comprising:

a housing defining an upper fluid chamber and lower fluid chamber;

a fluid disposed within the upper fluid chamber and the lower fluid chamber;

a piston assembly resiliently disposed within the housing, the piston assembly defining a tuning passage between the upper fluid chamber and the lower fluid chamber;

an adjustable metering pin assembly for changing an effective diameter of the tuning passage, the metering pin assembly selectively translating relative to the entire housing and the piston assembly;

at least one tuning element operably associated with at least one of the upper fluid chamber and the lower fluid chamber; and

an actuating piston coupled to each tuning element for amplifying the displacement of the fluid in the corresponding fluid chamber;

wherein the adjustable metering pin assembly extends through the housing;

wherein the adjustable metering pin assembly is secured at a first end by a first bore and at a second end by a second bore;

wherein the adjustable metering pin assembly includes a bulb portion having a conical shape, the bulb portion at least partially disposed within the tuning passage;

wherein the tuning passage is circular in cross-section; and

wherein a diameter of the tuning passage enlarges near a bulb portion of the metering pin assembly.

15. The vibration isolator according to claim 14 , further comprising:

at least one electric servo motor for actuating the metering pin actuator.

16. The vibration isolator according to claim 15 , wherein the at least one electric servo motor automatically actuates the metering pin actuator in response to a signal from a sensor.

17. The vibration isolator according to claim 14 , wherein the tuning element comprises a material selected from the group consisting of:

piezoceramic;

magnetostrictive; and

electromagnetic.

18. A method of adjusting the frequency response in a vibration isolator, comprising:

providing a housing defining a fluid chamber;

resiliently disposing a piston within the housing, the piston forming a tuning passage within the fluid chamber;

operably associating an adjustable metering pin assembly with the tuning passage; and

selectively actuating the adjustable metering pin assembly so as to change an effective diameter of the tuning passage, thereby adjusting the frequency response of the vibration isolator;

wherein the adjustable metering pin assembly extends through the housing;

wherein the adjustable metering pin assembly is secured at a first end by a first bore and at a second end by a second bore;

wherein the metering pin assembly is selectively translating relative to the entire housing and the piston;

wherein the tuning passage is circular in cross-section;

wherein the metering pin assembly includes a bulb portion having a conical shape, the bulb portion at least partially disposed within the tuning passage; and

wherein a diameter of the tuning passage enlarges near the bulb portion of the metering pin assembly.