Device for the transport and exact positioning of a sample tube in a high-resolution NMR spectrometer

#This application claims Paris Convention priority of DE 101 11 674.8 filed Mar. 9, 2001 the complete disclosure of which is hereby incorporated reference.

#The invention concerns a device for transporting an elongated sample tube, which is filled with a measuring substance, into the measuring chamber of a nuclear magnetic resonance (=NMR) magnet system, and for positioning the sample tube relative to the vertical axis of an NMR receiver coil system, with a spinner which forms part of an air turbine and has an axial through-bore through which the sample tube can be inserted and transported together with the spinner on an air cushion into the measuring chamber and positioned therein relative to the vertical axis of the NMR receiver coil system.

#Such a device is known e.g. from the company leaflet “High Resolution NMR, Probeheads” of the Bruker group, 1995.

#FIG. 1 shows a schematic vertical section through an NMR probe head according to prior art;

#FIG. 2 shows a schematic vertical section through an NMR probe head with an inventive centering device comprising a spinner modified in accordance with the invention and a mounting sleeve, for transport and axial positioning of the sample tube;

#FIG. 3 shows a schematic vertical section through a sample tube with a mounting sleeve disposed, in accordance with the invention, at its upper region in a collar-like manner;

#FIG. 1 shows a device according to prior art to which an embodiment of the inventive device shown in FIG. 2 can be compared. The first aspect of the invention consists in providing the measuring capillary 8 with a mounting sleeve 17 which is rigidly disposed on the measuring capillary and may also be glued or welded thereto. The measuring capillary 8 and mounting sleeve 17 thereby form an integral unit, wherein the mounting sleeve 17 serves the dual function of both a transporting means as well as a centering aid for axial positioning of the measuring capillary 8.

#The second aspect consists in providing the upper part of the spinner 7b with an at least two-stage through-bore 20. Its inner diameter in the first stage at the upper part of the spinner 7b is considerably larger than that of a spinner 7a according to prior art, since the mounting sleeve 17 is supposed to be inserted into the first stage of the bore. A second stage in the bottom region of the spinner 7b is designed to define a shoulder 21 at the lower part of the spinner 7b which simultaneously serves as transport means and centering aid for axial positioning of the sample tube 8 with its mounting sleeve 17. The larger bore of the first stage is dimensioned such that the mounting sleeve 17 has sufficient play for lateral, i.e. radial, free movement relative to the spinner 17. The lateral play should be at least approximately ±0.5 mm to ±1 mm or more. The shoulder 21 in the lower region of the spinner 7b on whose stop surface 18 the mounting sleeve 17 abuts, produces the axial centering.

#The spinner 7b whose outer dimensions coincide with those of a conventional spinner 7a is adapted to an existing pneumatic device by means of which it is transported, supported on an air cushion, from the top and through the guiding tube 1b in a downward direction, and back, from the bottom to the top. Since the mounting sleeve 17 can move freely within the spinner 7b in an upward direction and, to a limited degree, also laterally, there is no longer the danger that the fragile measuring capillary strikes the conical part of the upper centering device 13 when the spinner moves downwardly to be subjected to additional forces caused by the relatively large weight of the spinner, which could cause breakage. Due to the fact that there is no fixed connection between the mounting sleeve 17 and the spinner 7b, the measuring capillary can strike the conical part of the centering device 13 and be safely centered there while the spinner 7b continues in a downward direction without carrying along the mounting sleeve 17 with its measuring capillary, to thereby avoid exertion of additional forces on the measuring capillary.