Refrigeration – Storage of solidified or liquified gas – Including cryostat
Reexamination Certificate
2000-01-18
2001-05-15
Doerrler, William (Department: 3744)
Refrigeration
Storage of solidified or liquified gas
Including cryostat
C062S297000, C248S324000, C248S317000
Reexamination Certificate
active
06230502
ABSTRACT:
The present invention relates to improvements in or relating to suspension systems, and is more particularly, although not exclusively, concerned with suspension systems for mounting vessels in cryogenic dewars such as superconducting magnet cryostats for magnetic resonance imaging (MRI) apparatus.
Cryostats for MRI apparatus generally comprise at least two cylindrical vessels, an inner vessel and an outer vessel. The inner vessel is mounted within the outer vessel and is spaced apart from it. The inner vessel is generally known as a ‘cold’ vessel and the outer vessel as a ‘warm’ vessel. The annular space between the two vessels comprises a vacuum chamber to prevent convective heat transfer between the ‘warm’ vessel and the ‘cold’ vessel. The inner vessel is often suspended within the outer vessel by means of tensile members which have a high aspect ratio to minimise conductive thermal losses.
A particularly efficient type of tensile member comprises a composite fibre reinforced strap which has a ‘race track’ profile, the tensile strength of the member being provided by the continuously wound fibres. Such a strap is normally adjusted and pre-tensioned by pinning it at one end and connecting it to a threaded clevis at the other end. The threaded clevis projects from the end of the strap in the same plane as the strap and extra space within the vacuum chamber may be required to accommodate such an adjusting device.
When space in the vacuum chamber is of a premium along the longitudinal axis of the strap, it may not be feasible to fit a clevis to the end of the strap.
It is therefore an object of the present invention to provide an improved suspension system.
In accordance with one aspect of the present invention, there is provided a suspension system for connecting a first element to a second element, the system comprising: a tensile member for connecting the first element to the second element; first connecting means for connecting the tensile element to the first element; second connecting means for connecting the tensile element to the second element; and adjusting means for adjusting the tensile element to correctly position the second element with respect to the first element; characterised in that the adjusting means comprises a plate member having a pivot point about which it is rotatable, the plate member being pivotally mounted on the first element at the pivot point and connected to one end of the tensile member; and an adjusting member connected to the plate member for rotating the plate member about the pivot point to effect adjustment of the tensile element.
Advantageously, the adjusting member comprises a threaded push rod, one end of thereof being attached to the plate member at a point offset from the pivot point. The threaded push rod may be pivotally attached to the plate member.
Preferably, the threaded push rod is supported by a block member mounted on the first element and carries a nut arrangement at the end remote from the plate member, the nut arrangement bearing against the block member to effect rotation of the plate member as it is turned relative to the threaded push rod.
It is preferred that the tensile member comprises a continuous band. The band passes over a first bearing member mountable on the plate member and over a second bearing member mountable on the second element.
The apparatus in accordance with the present invention further comprises locking means for locking the position of the plate member with respect to the first element.
In accordance with a second aspect of the present invention, there is provided a cryostat system comprising: an outer cylindrical vessel; an inner cylindrical vessel; and at least one suspension system as described above; wherein the outer and inner cylindrical vessels comprise the first and second elements of the suspension system.
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Doerrler William
Evenson, McKeown, Edwards & Lenahan P.L.L.C.
Oxford Magnet Technology Limited
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