Suspension rod tensioning arrangements for supporting cryogenic equipment within a cryostat
A cryostat, comprising an outer vacuum vessel containing cryogenic equipment suspended from the outer vacuum vessel by a number of suspension rods. At least one of the suspension rods is provided with a tensioning and retaining mechanism for holding that suspension rod in tension braced against a suspension bracket). This tensioning and retaining mechanism includes a tubular rod carrier arranged, in use, to pass through a hole or slot in the suspension bracket, the rod carrier having an axial bore through which, in use, the rod may pass; a thread on its outer surface along at least part of its length; and a rod bearing surface for, in use, transmitting force to the rod. This tensioning and retaining mechanism also comprises a tensioning nut threaded onto the thread so as to, in use, brace against the suspension bracket to urge the tubular rod carrier in the direction of the rod bearing surface so as to apply tension to the rod.
1. In a cryostat, comprising an outer vacuum vessel containing cryogenic equipment suspended from the outer vacuum vessel by a number of suspension rods, at least one of the suspension rods being provided with a tensioning and retaining mechanism for holding that suspension rod in tension braced against a suspension bracket, the improvement of said tensioning and retaining mechanism comprising:
a tubular rod carrier having a first rod end configured to pass through a hole or slot in the suspension bracket, and having a second rod end opposite said first rod end, the rod carrier having an axial bore proceeding along a length of the rod carrier through which said at least one of the suspension rods passes, a thread on an outer surface of the rod carrier occupying at least part of said length, and a rod bearing surface that transmits force to said at least one of the suspension rods via a point of contact with said tubular rod carrier, said point of contact being between said first and second rod ends;
a tensioning nut threaded onto the thread configured to brace against the suspension bracket and thereby urge the tubular rod carrier in the direction of the rod bearing surface in order to apply tension to said at least one of the suspension rods dependent on a degree of threading of said tensioning nut on said thread along said at least part of said length occupied by said thread;
said tensioning nut being located relative to said point of contact to place said point of contact farther from said first rod end than said bearing surface;
a rod end piece having a through-hole through which said at least one of the suspension rods passes, and an inner retaining cavity configured to accommodate an end of said at least one of the suspension rods, said rod end piece having a spherical end piece bearing surface configured to bear upon the rod bearing surface of the tubular rod carrier, said rod bearing surface of said rod carrier being complementary to said spherical end piece bearing surface; and
said axial bore of the rod carrier being tapered to allow clearance for said at least one of the suspension rods over a predetermined range of acceptable angular misalignment.
2. A cryostat according to claim 1 , wherein the tensioning and retaining mechanism further comprises a locking nut threaded onto the thread at a position between the tensioning nut and the rod bearing surface.
3. A cryostat according to claim 1 , wherein the tensioning and retaining mechanism further comprises a washer positioned between the tensioning nut and suspension bracket.
4. A cryostat according to claim 1 , wherein the rod carrier has a shaped inner end that contacts sides of a slot in the suspension bracket and prevents rotation of the rod carrier.