1. A storage and retrieval system, comprising:
at least one mast, said at least one mast adapted to be supported at a lower mast end on a lower rail via at least one running wheel and is adapted to be driven along the running rail by at least one driven running wheel;
an upper guide rail at an upper mast end, said upper guide rail extending parallel to the running rail having at least one guide roller, said at least one guide roller being mounted such that said at least one guide roller bears against said guide rail so as to guide said mast;
at least one friction roller, wherein said at least one friction roller rolls on said upper guide rail and bears against said upper guide rail; and
an eddy current brake driven by said friction roller, said at least one friction roller mounted for movement with said upper mast end, said eddy current brake damping oscillations of said upper mast end.
2. The storage and retrieval system as claimed in claim 1, wherein said eddy current brake is selectively electrically actuated, wherein said eddy current brake is electrically actuated when said upper mast end moves into an intended stopping position.
3. The storage and retrieval system as claimed in claim 2, wherein said friction roller is attracted to said upper guide rail by means of magnetic attraction.
4. The storage and retrieval system as claimed in claim 3, including a gear assembly for operating said eddy current brake.
5. The storage and retrieval system as claimed in claim 4, wherein said gear assembly includes an adjustable transmission ratio, wherein an amount of damping is adjustable by adjusting the transmission ratio.
6. The storage and retrieval system as claimed in claim 4, wherein at least one of the guide rollers defines said friction roller.
7. The storage and retrieval system as claimed in claim 6, wherein said eddy current brake is in the form of an electric motor.
8. The storage and retrieval system as claimed in claim 7, wherein said electric motor is in the form of a squirrel-cage asynchronous motor having an air gap.
9. The storage and retrieval system as claimed in claim 8, wherein the size of the air gap being selected to produce a correspondingly large magnetic field.
10. The storage and retrieval system as claimed in claim 8, wherein said air gap is constant.
11. The storage and retrieval system as claimed in claim 1, wherein said eddy current brake comprises a synchronous motor having a short-circuited winding.
12. The storage and retrieval system as claimed in claim 1, wherein said eddy current brake is only electrically activated when moving into an intended stopping position of said mast and remains electrically deactivated during the remaining driving time of said mast.
13. The storage and retrieval system as claimed in claim 1, wherein said friction roller is attracted to said upper guide rail by means of magnetic attraction.
14. The storage and retrieval system as claimed in claim 1, including a gear assembly for operating said eddy current brake.
15. The storage and retrieval system as claimed in claim 14, wherein said gear assembly includes an adjustable transmission ratio, wherein an amount of damping is adjustable by adjusting the transmission ratio.
16. The storage and retrieval system as claimed in claim 1, wherein at least one of the guide rollers defines said friction roller.
17. The storage and retrieval system as claimed in claim 1, wherein said eddy current brake is in the form of an electric motor.
18. The storage and retrieval system as claimed in claim 17, wherein said electric motor is in the form of a squirrel-cage asynchronous motor having an air gap.
19. The storage and retrieval system as claimed in claim 18, wherein the size of the air gap being selected to produce a correspondingly large magnetic field.
20. The storage and retrieval system as claimed in claim 18, wherein said air gap is constant.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. Microelectromechanical apparatus, comprising:
a substrate;
one or more movable microelectromechanical elements formed in the substrate; and
one or more stationary elements that comprise electrically operative elements of the apparatus and that comprise a protective layer for the movable microelectromechanical elements.
2. The apparatus recited in claim 1 which comprises an electrostatic micromechanical resonator.
3. The apparatus recited in claim 2 wherein the stationary elements are sense and drive electrodes of the resonator.
4. The apparatus recited in claim 1 wherein the stationary elements cover the movable microelectromechanical elements on sides and top thereof and are separated therefrom by narrow gaps realized using a sacrificial layer.
5. The apparatus recited in claim 4 wherein the stationary elements have openings in them for sacrificial layer removal.
6. The apparatus recited in claim 5 wherein the openings in the stationary elements are closed by a nonconformal thin film.
7. The apparatus recited in claim 5 wherein the stationary elements completely cover the top surface of the movable elements.
8. The apparatus recited in claim 1 wherein the nonconformal thin film is a PECVD insulator film such as silicon dioxide or silicon nitride.
9. The apparatus recited in claim 1 further comprising a substantially impermeable thin film disposed on top of the sealed stationary elements to maintain a high level of vacuum andor hermeticity for the encapsulated movable elements.
10. The apparatus recited in claim 9 wherein the substantially impermeable film is an evaporated metal film.
11. The apparatus recited in claim 1 wherein the impermeable film is a CMOS-compatible insulating thin film.
12. The apparatus recited in claim 11 wherein the CMOS-compatible insulating thin film comprises LPCVD silicon dioxide, silicon nitride, or polysilicon.
13. The apparatus recited in claim 1 further comprising one or more integrated circuit devices formed on the substrate beside or on top of the apparatus.
14. Acoustic resonator apparatus, comprising:
a silicon resonating micromechanical element formed in a substrate; and
one or more stationary electrodes separated from the resonating element by narrow capacitive gaps, wherein the electrodes extend on top of the resonating element to encapsulate it.
15. The apparatus recited in claim 14 wherein the electrodes are made of polycrystalline silicon.
16. The apparatus recited in claim 14 wherein the electrodes are sealed by a nonconformal thin film.
17. The apparatus recited in claim 16 wherein the nonconformal sealing film comprises an insulating PECVD thin film.
18. The apparatus recited in claim 14 further comprising a substantially impermeable film covering the nonconformal sealing film.
19. Microelectromechanical apparatus, comprising:
a substrate; and
a microelectromechanical structure formed in the substrate comprising one or more top electrodes, which electrodes encapsulate the apparatus.
20. The apparatus recited in claim 19 further comprising one or more integrated circuit devices formed on the substrate beside or on top of the microelectromechanical structure.