Pneumatic isolator with barometric insensitivity

• US 6,547,225 B1
• Filed: 04/17/2001
• Issued: 04/15/2003
• Est. Priority Date: 04/17/2001
• Status: Expired due to Fees

• Current Assignee: Technical Manufacturing Corporation (Ametek Incorporated)
• Original Assignee: Technical Manufacturing Corporation (Ametek Incorporated)
• Inventors: Nelson, Peter G.
• Primary Examiner(s): Lavinder, Jack
• Assistant Examiner(s): Pezzlo, Benjamin A
• Application Number:
  US09/836,775
• Time in Patent Office: 728 Days
• Field of Search: 267/64.27, 267/64.28, 248/631
• US Class Current: 267/64.27
• CPC Class Codes: F16F 15/0275 Control of stiffness
• CPC Class Codes: F16F 9/049 multi-chamber units F16F9/0472, F16F9/05 take precedence

Abstract

A pneumatic isolator for isolating payloads from vibrations consisting of a vertical isolator suspended from pendulum wires. A second downward-facing piston prevents changes in barometric pressure from generating disturbing forces on the isolated payload.

Claims

1. A pneumatic isolator which comprises:

at least one pressure vessel which functions as a pneumatic isolator which vertically supports and isolates a payload from vertical vibration;

means for pressurizing the pressure vessel; and

means for canceling the effects of barometric pressure on the isolator.

2. The isolator of claim 1:

wherein the at least one pressure vessel includes a first piston which is secured to the pressure vessel by a flexible diaphragm; and

the means for canceling comprises a second piston having an effective surface area equal to the first piston.

3. The isolator of claim 2 which comprises a second pressure vessel and the second piston is secured to the second pressure vessel by a flexible diaphragm.

4. The isolator of claim 3 which comprises:

means to secure the first and second pistons one to the other.

5. The isolator of claim 4 which comprises:

means for maintaining the second pressure vessel chamber under vacuum.

6. The isolator of claim 5 wherein the means to secure the first and second pistons comprises rigid rods.

7. The isolator of claim 6 wherein the first piston has a load surface and a thrust bearing is positioned on the load surface.

8. The isolator of claim 3 which comprises:

means for maintaining a positive pressure in the second pressure vessel.

9. The isolator of claim 8 wherein the means to secure the first and second pistons comprises flexible rods or cables.

10. The isolator of claim 4 wherein the first and second pressure vessels include gimbal piston assemblies, a first gimbal piston assembly being received in the first pressure vessel and the second gimbal piston assembly being received in the second pressure vessel, each gimbal piston assembly comprised of:

a depending well having a floor; and

an elongated support member having a first end attached to the floor of the depending well and a second end attached to a load plate.

11. A compensator for use with a vibration isolation system, the vibration isolation system having at least one gas actuator including a diaphragm and a piston applying an upward force on a payload platform in an environment having a barometric pressure subject to changes, the diaphragm and piston having an effective area, wherein an increase in the barometric pressure acting on the effective area of the gas actuator results in a downward force on the payload platform, and wherein a decrease in the barometric pressure acting on the effective area of the gas actuator results in an upward force on the payload platform, the compensator compensating for the effects of changes in the barometric pressure on the gas actuator, the compensator comprising:

a compensating gas actuator including a diaphragm and a piston, the diaphragm and piston having an effective area exposed to the barometric pressure, the effective area of the compensating gas actuator being equal to the effective area of the gas actuator, and

means for transferring the force generated by the barometric pressure acting on the effective area of the compensating gas actuator to the payload platform in a direction opposite the direction of the force due to barometric pressure acting on the effective area of the gas actuator thereby tending to cancel the effects of changes in barometric pressure on the gas actuator.

12. The compensator of claim 11, wherein the means for transferring the force includes a rod connected to the piston.

13. The compensator of claim 11, wherein the means for transferring the force includes a cable and at least one pulley, the cable being connected to the piston.

14. The compensator of claim 11, wherein the compensating gas actuator has an internal pressure lower than the barometric pressure.

15. A compensator for use with a vibration isolation system, the vibration isolation system having at least one gas actuator including a diaphragm and a piston applying an upward force on a payload platform in an environment having a barometric pressure, the diaphragm and piston having an effective area, wherein an increase in the barometric pressure acting on the effective area of the gas actuator results in a downward force on the payload platform, and wherein a decrease in the barometric pressure acting on the effective area of the gas actuator results in an upward force on the payload platform, the compensator compensating for the effects of changes in the barometric pressure on the gas actuator, the compensator comprising:

a compensating gas actuator including a diaphragm and a piston, the diaphragm and piston having an effective area exposed to the barometric pressure, the effective area of the compensating gas actuator being substantially equal to the effective area of the gas actuator; and

a mechanical linkage connected to the piston, the mechanical linkage when connected to the payload platform transferring the force generated by the barometric pressure acting on the effective area of the compensating gas actuator to the payload platform in a direction opposite the direction of the force due to barometric pressure acting on the effective area of the gas actuator thereby tending to cancel the effects of changes in the barometric pressure on the gas actuator.

16. A compensator for use with a vibration isolation system, the vibration isolation system having one or more gas actuators, each gas actuator of the vibration isolation system including a diaphragm and a piston applying an upward force on a payload platform in an environment having a barometric pressure, the diaphragm and piston having an effective area, wherein an increase in the barometric pressure acting on the effective area of the gas actuator results in a downward force on the payload platform, and wherein a decrease in the barometric pressure acting on the effective area of the gas actuator results in an upward force on the payload platform, the compensator compensating for the effects of changes in the barometric pressure on the one or more gas actuators, the compensator comprising:

one or more compensating gas actuators, each compensating gas actuator including a piston and a diaphragm, the piston and diaphragm having an effective area exposed to the barometric pressure; and

means for transferring the force generated by the barometric pressure acting on the effective area of each of the one or more compensating gas actuators to the payload platform in a direction substantially normal to the payload platform and in opposition to the force on the payload platform due to the increase or decrease in the barometric pressure thereby substantially cancelling the effects of the increase or decrease in the barometric pressure on the one or more gas actuators.

17. The compensator of claim 16, wherein the total effective area of the one or more compensating gas actuators is substantially the same as the total effective area of the one or more gas actuators.

18. The compensator of claim 17, wherein the means for transferring includes a rod connected to the piston of each of the one or more compensating gas actuators.

19. The compensator of claim 16, wherein the total effective area of the one or more compensating gas actuators is different than the effective surface area of the at least one gas actuator, and the compensator further includes a mechanical linkage connected to the one or more pistons to connect the one or more pistons to the payload platform, the mechanical linkage providing a mechanical advantage such that the force applied to the payload platform is equal and opposite the force due to the increase or decrease in the barometric pressure acting on the effective area of the at least one gas actuator.

20. The compensator of claim 19, wherein the means for transferring the force includes at least two pulleys and a cable to provide the mechanical advantage.

21. A compensator for use with a vibration isolation system, the vibration isolation system having one or more gas actuators, each gas actuator of the vibration isolation system including a diaphragm and a piston applying an upward force on a payload platform in an environment having a barometric pressure subject to changes, the diaphragm and piston having an effective area, wherein an increase in the barometric pressure acting on the effective area of the gas actuator results in a downward force on the payload platform, and wherein a decrease in the barometric pressure acting on the effective area of the gas actuator results in an upward force on the payload platform, the compensator compensating for the effects of changes in the barometric pressure on the one or more gas actuators, the compensator comprising:

one or more compensating gas actuators, each compensating gas actuator including a piston and a diaphragm, the piston and diaphragm having an effective area exposed to the barometric pressure, each piston of the one or more compensating gas actuators being adaptable for coupling to the payload platform such that the force due to the barometric pressure acting on the effective area of each compensating gas actuator is transferred to the payload platform in a direction substantially normal to the payload platform and in opposition to the force due to the increase or decrease in the barometric pressure on the one or more gas actuators thereby tending to cancel the effects of changes in the barometric pressure on the one or more gas actuators.

22. A compensator for use with a vibration isolation system, the vibration isolation system having a gas actuator supporting a payload platform in an environment with a floor and barometric pressure, the gas actuator having a diaphragm and a piston with a side facing the payload platform and exposed to the barometric pressure, the diaphragm and piston having an effective area, the barometric pressure susceptible to changes, the compensator comprising:

gas actuator including a piston connected to a body by a diaphragm to form a chamber, the diaphragm and piston separating the chamber from the barometric pressure, the piston moving in a direction substantially normal to the payload platform, the piston having a side facing the floor, the diaphragm and piston having an effective area substantially equal to the effective area of the gas actuator; and

a rod connected to the piston and adaptable for connecting to the payload platform, the rod, when connected to the payload platform, transferring the force exerted on the piston by the barometric pressure to the payload platform in a direction substantially normal to the payload platform thereby cancelling the effects of changes in the barometric pressure on the gas actuator of the vibration isolation system.

23. A gas vibration isolator assembly to isolate a payload from vibrations in an environment having barometric pressure, the barometric pressure subject to fluctuations, the gas vibration isolator assembly being insensitive to fluctuations in the barometric pressure, the gas vibration isolator assembly comprising:

a body having a first chamber and a second chamber, each chamber located substantially symmetrical along an axis;

a gas actuator, the gas actuator including a piston attached to the body by a diaphragm to cover and seal the first chamber for containing a gas under pressure, the piston having a side exposed to the barometric pressure, the piston and diaphragm having an effective area, the piston being free to move in a direction substantially parallel to the axis;

a compensating gas actuator including a piston attached to the body by a diaphragm to cover and seal the second chamber, the piston being free to move in a direction substantially parallel to the axis, the piston having a side exposed to the barometric pressure, the piston and diaphragm having an effective area substantially equal to the effective area of the gas actuator, the piston of the compensating gas actuator oriented such that the force on the piston due to barometric pressure is opposite the direction of the force on the piston of the gas actuator due to barometric pressure; and

a load disk supported by the piston of the gas actuator and mechanically connected to the piston of the compensating gas actuator such that a change in the barometric pressure acts on the piston of the compensating gas actuator to cause an equal and opposite force to be applied to the load disk thereby cancelling the force applied by the gas actuator to the load disk due to the change in barometric pressure.

24. A vibration isolation system to isolate a payload from vibrations in an environment having a floor and barometric pressure, the vibration isolation system isolating the payload from vibrations in a direction substantially normal to the floor, the vibration isolation system being insensitive to fluctuations in the barometric pressure, the vibration isolation system comprising:

a payload platform;

a frame with at least one point of support for supporting the frame on the floor;

at least one gas actuator supporting the payload platform, the gas actuator including a piston attached to a body by a diaphragm to define a sealed chamber for containing a gas under pressure, the piston with a first side facing the payload platform, the first side being exposed to the barometric pressure, the piston being free to move in a direction substantially normal to the payload platform, the body of the at least one gas actuator being attached to the frame, the piston supporting the payload platform;

at least one compensating gas actuator including a piston connected to a body by a diaphragm, the piston being free to move, the piston having a side exposed to barometric pressure, the body being connected to the frame; and

means for transferring the force generated by barometric pressure acting on the piston of the at least one compensating gas actuator to the payload platform in a direction substantially normal to the payload platform and opposite the direction of the force due to the barometric pressure acting on the piston of the at least one gas actuator.