Claims
- 1. A solenoid comprising:
- a coil apparatus for generating a magnetic field along an axis;
- a magnetic plunger positioned in the magnetic field and moveable along the axis;
- a mechanical butt for limiting the axial movement of the plunger;
- a ferrofluid located between the plunger and the butt;
- a cushion located between the plunger and the butt; and
- a gas located between the plunger and the butt that is vented to atmosphere past a magnetic seal formed by the ferrofluid as the plunger moves toward the butt.
- 2. The solenoid of claim 1 wherein the coil apparatus surrounds the plunger and the ferrofluid is also located between the coil apparatus and the plunger.
- 3. The solenoid of claim 2 wherein the magnetic field is a main magnetic field and the solenoid further comprises a supplemental magnetic field source that generates a magnetic field that supplements the main magnetic field so as to increase the magnetic field strength between the coil apparatus and the plunger.
- 4. The solenoid of claim 3 wherein the supplemental magnetic field source comprises a permanent magnet.
- 5. The solenoid of claim 1 wherein the magnetic field is a main magnetic field and the solenoid further comprises a supplemental magnetic field source that generates a magnetic field that supplements the main magnetic field so as to increase the magnetic field strength between the plunger and the butt.
- 6. The solenoid of claim 5 wherein the supplemental magnetic field source comprises a permanent magnet.
- 7. The solenoid of claim 1 wherein the cushion comprises a resilient material.
- 8. The solenoid of claim 7 wherein the cushion comprises an elastomer.
- 9. The solenoid of claim 7 wherein the cushion comprises plastic.
- 10. The solenoid of claim 7 wherein the cushion comprises polyester.
- 11. The solenoid of claim 1 wherein the cushion is attached to the plunger.
- 12. The solenoid of claim 1 wherein the cushion is attached to the butt.
- 13. The solenoid of claim 1 wherein the cushion comprises at least two pieces, one attached to the plunger and one attached to the butt.
- 14. The solenoid of claim 1 wherein the cushion comprises a material having good chemical compatibility with the ferrofluid.
- 15. The solenoid of claim 1 wherein the cushion comprises a material that can withstand temperatures in the range from -20.degree. C. to 70.degree. C.
- 16. The solenoid of claim 1 wherein the cushion comprises a coating on the surface of at least one of the plunger and the butt.
- 17. The solenoid of claim 16 wherein the coating comprises at least one of polytetrafluoroethylene, polyester, plastic and ceramic.
- 18. A solenoid comprising:
- a casing formed from a magnetic material;
- a pole piece formed from a magnetic composition wherein the casing and pole piece are joined to form a housing having an internal volume;
- a electrically energizable coil positioned within said internal volume;
- a support means for said coil formed from a nonmagnetic composition, said support means having a core volume;
- a moveable plunger positioned within said core volume and extending through said housing;
- a stop means positioned within said core volume for limiting axial movement of said plunger;
- a ferrofluid positioned within said core volume between said stop means and said plunger and between said plunger and said support means;
- means for electrically energizing said coil;
- a cushion positioned between the plunger and the butt and
- a gas located between the plunger and the butt that is vented to atmosphere past a magnetic seal formed by the ferrofluid as the plunger moves toward the butt.
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of U.S. patent application Ser. No. 08/697,624, filed Aug. 28, 1996.
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Number |
Name |
Date |
Kind |
4306207 |
Tada et al. |
Dec 1981 |
|
4419643 |
Ojima et al. |
Dec 1983 |
|
4422060 |
Matsumoto et al. |
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Foreign Referenced Citations (2)
Number |
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052177 |
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EPX |
57071108 |
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JPX |
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
697624 |
Aug 1996 |
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