Rotary shafts – gudgeons – housings – and flexible couplings for ro – Electrical or magnetic coupling
Patent
1997-06-13
1999-05-11
Bonck, Rodney H.
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Electrical or magnetic coupling
192 564, 310 75D, 310103, H02K49/10
Patent
active
059021853
DESCRIPTION:
BRIEF SUMMARY
This invention relates to magnetic transmission couplings for transmitting drive from one member to another, and in particular, but not exclusively, to rotary feedthrough transmission arrangements for use with a vacuum enclosure to allow transmission of rotation across a vacuum membrane and to allow access for services such as power, cooling, instrumentation, etc.
There are many manufacturing processes which require a workpiece to be treated in an enclosure in which the local environment is carefully controlled and isolated from ambient, typical examples including vacuum-based or gas-based processes. In such processes, the workpiece, for example a semiconductor wafer, an optical component, or a magnetic storage device may be subjected to a thin film deposition process, in which a material is sputtered, evaporated or injected as gas towards a heated substrate contained in a vacuum or other controlled atmosphere. It is often critical that the vacuum is at an extremely low pressure and/or kept isolated from atmosphere. Furthermore, this may require the process instrumentation to be of metal construction with the ability to withstand temperatures of typically 250.degree. C. or more. In order to provide uniform thickness of the deposited films, the heated substrate pay need to be rotated at a predetermined substantially smooth speed. This requirement of transmitting rotation into the vacuum enclosure whilst maintaining the integrity of the vacuum enclosure has led to several designs of rotary feedthrough, an example being that described in British Patent GB 2213316. This is a concentric magnetic coupling arrangement, and drive is transmitted across a cylindrical wall of the enclosure to an inner magnetic array on a torque tube from an outer concentric magnetic array rotatably mounted on the cylindrical wall.
This arrangement has several disadvantages. With ongoing developments in processing techniques it is important to provide as large a diameter bore as possible down the middle of the feedthrough to provide sufficient access for power, cooling, thermocouple and other services and to allow stacking for co-axial rotation applications, and, in some instances, to allow transverse movement of elements within the bore. With the concentric arrangement of GB 2213316, the diameter of the bore or access port is limited in practice to less than the inner diameter of the outer magnetic array, because the cylindrical wall or membrane is typically of a welded construction and so must be small enough to allow the outer array to pass over it for assembly or servicing. Since it is vital to service the bearings which support the outer magnetic array, the concentric coupling must have an access port which is smaller than the inner diameter of the outer magnetic array. This is a major limitation for the concentric system especially considering that the magnets used are magnetised multiple magnets and therefore limited in size for reasonable cost.
A further disadvantage of the concentric arrangement is that it does not allow drive ratios of other than unity.
Furthermore, the concentric arrangement requires that the outer magnet array be mounted on large diameter bearings which run on the cylindrical wall or membrane of the coupling. Such large bearings are expensive and this is another factor which limits the diameter and thus applications of the arrangement.
A further feature of existing designs of rotary feedthrough is that drive member and the driven member comprise concentric co-operating annular drive members, in which each drive member is magnetised as a multiple magnet. These conventional magnetic couplings may be termed "static" couplings as, in normal use, the magnets do not move relative to each other, and thus they do not allow drive ratios of other than 1:1. The construction and magnetisation of the annuli requires machining of special grade ferromagnetic material and either a subsequent complex and lengthy magnetisation process, or provision of an electromagnet. In some cases preferred magnetisations cannot be achiev
REFERENCES:
patent: 4277707 (1981-07-01), Silver et al.
patent: 4752194 (1988-06-01), Wienen et al.
patent: 4896064 (1990-01-01), Taiani
patent: 5013949 (1991-05-01), Mabe
patent: 5017102 (1991-05-01), Shimaguchi et al.
patent: 5204572 (1993-04-01), Ferreira
patent: 5376862 (1994-12-01), Stevens
patent: 5514925 (1996-05-01), Worthington et al.
patent: 5569111 (1996-10-01), Cho et al.
patent: 5633555 (1997-05-01), Ackermann et al.
patent: 5763973 (1998-06-01), Cramer
P.C. Leenders, "Magnetische Tandwielen", PT Elektronica-Elektrotechniek, vol. 44, No. 10, Oct. 1, 1989, p. 46.
Kubiak Richard Andrej
Stonestreet Paul Richard
LandOfFree
Magnetic transmission couplings does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Magnetic transmission couplings, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetic transmission couplings will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-242620