TREA

Pneumatic vibration isolator utilizing an elastomeric element for isolation and attenuation of horizontal vibration

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Information

  • Patent Grant
  • 6619611
  • Patent Number
    6,619,611
  • Date Filed
    Monday, July 2, 2001
    23 years ago
  • Date Issued
    Tuesday, September 16, 2003
    21 years ago
Information
Abstract
A vibration isolator that has an elastomer which couples a support plate to a piston. The elastomer can provide horizontal damping of a payload that is coupled to the support plate. The piston can move within a first housing inner chamber that is in fluid communication with a second housing inner chamber. The chambers are pressurized with air that can flow to dampen vertical movement of the piston. The vibration isolator of the present invention thus provides both vertical and horizontal damping without using any oils.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates to a vibration isolator that can dampen payload movement in both vertical and horizontal directions.




2. Background Information




Vibration isolators are used to isolate and damp vibration loads on an adjoining structure that is commonly referred to as a payload. The payload may be a table that is part of a semiconductor wafer fabrication system. The payload may be subjected to shock/vibration loads in both a vertical direction and a horizontal direction. For this reason vibration isolators are designed to dampen energy applied in both the vertical and horizontal directions.




U.S. Pat. No. 3,784,146 issued to Matthews discloses a vibration isolator which contains a piston that is coupled to a support plate by a plurality of cables. The piston is located within an air cylinder that can dampen vertical shock/vibration loads applied by the payload.




The cables allow the support plate to move within an inner cavity of the piston. The piston inner cavity includes a damping fluid that dampens shock/vibration loads applied in the horizontal direction.




It has been found that the damping oil will sometimes leak, thereby requiring a repair or replacement of the vibration isolator. Leaking fluid may therefore reduce the effective life of the isolator. Additionally, having to seal and charge a vibration isolator with damping fluid increases the cost of mass producing the isolator.




BRIEF SUMMARY OF THE INVENTION




One embodiment of the present invention includes a vibration isolator that has an elastomer, which couples a support plate to a piston. The piston can move within an inner chamber of an isolator housing.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a cross-sectional view of an embodiment of a vibration isolator of the present invention;





FIG. 2

is a cross-sectional view of an alternate embodiment of the vibration isolator.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT




The applicants disclose a vibration isolator that has an elastomer, which couples a support plate to a piston. The elastomer can provide horizontal damping of a payload that is coupled to the support plate. The vibration isolator does not require the cables and damping fluid typically found in isolators of the prior art. The piston can move within a first housing inner chamber that is in communication with a second housing inner chamber. The chambers are pressurized with air that can flow to dampen vertical movement of the piston. The vibration isolator of the present invention thus provides both vertical and horizontal damping without using any oil. Additionally, the elastomer provides high damping, short settling time, and a “soft” stop of payload motion.




Referring to the drawings more particularly by reference numbers,

FIG. 1

shows an embodiment of a vibration isolator


10


of the present invention. The isolator


10


includes a support plate


12


that is coupled to a payload


14


. The payload


14


may be any structure that is to be isolated such as an optical bench or the base of an x-y table. The payload


14


may move in a vertical direction or a horizontal direction as indicated by the arrows.




The support plate


12


is coupled to a piston


16


by an elastomer


18


. The piston


16


is coupled to an isolator housing


20


by a diaphragm


22


. The elastomer


18


is constructed to be smaller than an inner cavity


24


of the piston


16


to allow elastomer deflection when the payload


14


moves in a horizontal direction.




The elastomer


18


is typically constructed from a rubber or other damping material that will dissipate energy transmitted from the payload


14


into the support plate


12


. Elastomeric materials may have a higher damping coefficient and a faster settling time than oil damping fluid. Additionally, the elastomer


18


has a higher shear stiffness that will provide a “soft” stop for the payload. The elastomer


18


is also stiff enough to withstand shock loads applied in the vertical direction.




It is desirable to provide an elastomer


18


that does not buckle under certain vertical loads. To increase the buckling load the elastomer


18


may have a conical shape. The narrow portion of the elastomer


18


may be attached to the top surface of the piston inner cavity


24


. This allows the elastomer


18


to sit deeper into the inner cavity


24


and improves the stability of the system. Although a conical shape is shown and described, it is to be understood that the elastomer


18


may have other shapes such as cylindrical, rectangular or square. These shapes are not an exhaustive list of the elastomer profiles. To decrease stiffness the elastomer


18


may also have an inner cavity


26


. The elastomer


18


shown in

FIG. 1

also described in U.S. Pat. No. 6,398,407 Apr. 22, 2003, which is hereby incorporated by reference. Although an embodiment showing the narrow portion of the elastomer


18


attached to the piston


16


is shown and described, the wider portion of the elastomer


18


may be attached to the piston


16


.





FIG. 2

shows an alternate embodiment of the vibration isolator


10


′ wherein the elastomer


18


′ has a laminated construction. The laminated elastomer


18


′ may have a plurality of metal plates


28


that separate a number of damping layers


30


. The damping layers


30


are constructed from a damping material such as rubber. The laminated structure has higher load capacity and vertical stiffness, as well as high rotational (tilt) stiffness, which improves the stability of the system, whereas the isolation in the horizontal direction remains good due to low stiffness of elastomeric layers in the horizontal (shear) direction.




Referring to

FIG. 1

, the piston


16


can move within a first inner chamber


30


of the isolator housing


20


. The first inner chamber


30


is in communication with a second inner chamber


32


of the housing


30


through an orifice


34


. The inner chambers


30


and


34


are pressurized with air at a pressure greater than atmospheric pressure through a leveling port


36


.




Vertical movement of the payload


14


will move the piston


16


within the first inner chamber


30


. The piston movement will induce air flow between the first


30


and second


32


chambers through the valve


34


. The air flow absorbs and dampens energy transferred from the payload


14


. The vibration isolator


10


of the present invention is thus able to dampen energy in both the vertical and horizontal directions.




While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that this invention not be limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those ordinarily skilled in the art.



Claims
  • 1. A vibration isolator, comprising:a housing which has a first inner chamber; a piston that can move within said first inner chamber of said housing; a diaphragm coupled to said piston and said housing; a support plate; and, an elastomer that is attached to and contiguous with said support plate and attached to said piston.
  • 2. The vibration isolator of claim 1, wherein said elastomer has a conical shape.
  • 3. The vibration isolator of claim 1, wherein said elastomer has an inner cavity.
  • 4. The vibration isolator of claim 1, wherein said elastomer includes a plurality of plates and a plurality of damping layers.
  • 5. The vibration isolator of claim 1, further comprising a valve that provides fluid communication between a second inner chamber and said first inner chamber.
  • 6. The vibration isolator of claim 5, wherein said first and second inner chambers contain a pressurized air.
  • 7. The vibration isolator of claim 1, wherein said elastomer can be deflected within an inner cavity of said piston.
  • 8. A vibration isolator, comprising:a housing which has a first inner chamber; a piston that can move within said first inner chamber of said housing; a diaphragm coupled to said piston and said housing; a support plate; and, coupling means for attaching said support plate directly to said piston.
  • 9. The vibration isolator of claim 8, wherein said coupling means includes an elastomer.
  • 10. The vibration isolator of claim 9, wherein said elastomer has a conical shape.
  • 11. The vibration isolator of claim 9, wherein said elastomer has an inner cavity.
  • 12. The vibration isolator of claim 9, wherein said elastomer includes a plurality of plates, and a plurality of damping layers.
  • 13. The vibration isolator of claim 9, wherein said elastomer can be deflected within an inner cavity of said piston.
  • 14. The vibration isolator of claim 8, further comprising an orifice that provides fluid communication between a second inner chamber and said first inner chamber.
  • 15. The vibration isolator of claim 14, wherein said first and second inner chambers contain a pressurized air.
  • 16. A method for damping a payload coupled to a support plate of a vibration isolator, comprising:moving the payload in a horizontal direction, which movement deflects an elastomer that is attached to and contiguous with a support plate and attached to a piston, the piston being coupled to a housing by a diaphragm.
  • 17. The method of claim 16, further comprising moving the payload in a vertical direction wherein the piston moves within a first inner housing chamber to induce flow of air into a second inner housing chamber.
  • 18. A vibration isolator, comprising:a housing which has a first inner chamber; a piston that has an inner cavity and can move within said first inner chamber of said housing; a support plate; and, an elastomer that is attached to and contiguous with said support plate and attached to said inner cavity of said piston.
  • 19. The vibration isolator of claim 18, wherein said elastomer has a conical shape.
  • 20. The vibration isolator of claim 18, wherein said elastomer has an inner cavity.
  • 21. The vibration isolator of claim 18, wherein said elastomer includes a plurality of plates and a plurality of damping layers.
  • 22. The vibration isolator of claim 18, further comprising a valve that provides fluid communication between a second inner chamber and said second inner chamber.
  • 23. The vibration isolator of claim 22, wherein said first and second inner chambers contain a pressurized air.
  • 24. A vibration isolator, comprising:a housing which has a first inner chamber; a piston that has an inner cavity and can move within said first inner chamber of said housing; a support plate; and, coupling means for attaching said support plate directly to inner cavity of said piston.
  • 25. The vibration isolator of claim 24, wherein said coupling means includes an elastomer.
  • 26. The vibration isolator of claim 25, wherein said elastomer has a conical shape.
  • 27. The vibration isolator of claim 25, wherein said elastomer has an inner cavity.
  • 28. The vibration isolator of claim 25, wherein said elastomer includes a plurality of plates, and a plurality of damping layers.
  • 29. The vibration isolator of claim 24, further comprising an orifice that provides fluid communication between a second inner chamber and said second inner chamber.
  • 30. The vibration isolator of claim 29, wherein said first and second inner chambers contain a pressurized air.
  • 31. A method for damping a payload coupled to a support plate of a vibration isolator, comprising:moving the payload in a horizontal direction, which movement deflects an elastomer that is attached to and contiguous with a support plate and attached to an inner cavity of a piston.
  • 32. The method of claim 31, further comprising moving the payload in a vertical direction wherein the piston moves within a first inner housing chamber to induce flow of air into a second inner housing chamber.
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