Electricity: measuring and testing – Particle precession resonance – Spectrometer components
Reexamination Certificate
2002-03-04
2004-02-03
Gutierrez, Diego (Department: 2859)
Electricity: measuring and testing
Particle precession resonance
Spectrometer components
C324S318000
Reexamination Certificate
active
06686740
ABSTRACT:
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.
BACKGROUND OF THE INVENTION
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.
Modern NMR spectrometers operate almost exclusively with superconducting magnet systems with which the measuring chamber is located deep within the room temperature tube (=RT tube) of the magnet cryostat. Access to this measuring chamber is therefore possible only with auxiliary devices which are operated preferably pneumatically, i.e. with pressurized air. The use of pressurized air is convenient, since it is also required for the air turbine for rotating the NMR sample tube.
A support device is usually located inside the RT tube to which the NMR probe head can be attached. The upper part of this support device has a guiding tube which facilitates air turbine access to the measuring chamber and the stator which is located slightly above same. The rotor (=spinner) of the air turbine in which the measuring sample is located is dimensioned such that it fits into the guiding tube with little play. It serves two purposes: transport of the measuring sample into the measuring chamber and rotation of the measuring sample.
To transport the spinner including sample tube into the measuring chamber, pressurized air is introduced from the measuring chamber which flows upwardly and exits externally through the upper opening of the guiding tube. The spinner, including sample tube, is subsequently disposed on the upper opening of the guiding tube. Since the spinner almost completely covers this opening, an overpressure is generated inside the guiding tube and the spinner rests on an air cushion. If the amount of pressurized air is reduced, a state is eventually reached in which the force produced by the pressurized air supporting the upper position of the spinner is less than the weight of the spinner and measuring sample so that the spinner begins to slowly slide downwardly on the air cushion. The speed at which the spinner descends depends of course on the set pressure of the pressurized air. The spinner and sample tube may therefore strike various structural components in the region of the measuring chamber with relatively large force.
With sample tubes having a diameter of 5 mm and more, the above-described transport method did not pose any serious problems. However, problems occur with smaller diameters, i.e. with measuring capillaries having a diameter of e.g. 2 mm since these are very fragile and even the smallest of impacts can break the glass. For measuring capillaries having a diameter of 1 mm, the danger of breaking glass is so large that their use can barely be justified.
In NMR there is nevertheless a great need for such smallest measuring capillaries since only very small amounts of measuring substance are often available. The development of new and improved transport methods for measuring capillaries is therefore very important for NMR spectroscopy.
Preparation of NMR measuring samples for measurements in an NMR spectrometer is usually done in two steps. In a first step (=preparation phase), the measuring substance is filled into a measuring capillary
8
of glass (=sample) and the measuring capillary is subsequently sealed or covered by a cap. In a second step (=transport phase) the spinner, including the measuring capillary, is transported by means of a pneumatic device through a guiding tube
1
b
from the upper part of the NMR magnet system down to the stator
2
a
of the air turbine, wherein the spinner is thereby supported on an air cushion. At the end of this process, the spinner is disposed on the conical surface of the stator and is centered both with respect to height (=axial) and lateral position (=radial) (FIG.
1
). This radial centering aligns the measuring capillary, which projects past the bottom of the spinner and extends inside the supporting tube
10
of the receiver coil
9
, to prevent contact between the measuring capillary and the receiver coil.
After measurement of the sample, the pneumatics can remove the sample from the magnet system together with the spinner and the sample can be removed from the spinner. The spinner is then available for measurement of a further sample.
The above-described method is used for all sample diameters down to 1.7 mm. Unfortunately, this method has proven to be very critical for smaller diameters. Measuring capillary glass often breaks. For this reason, there are still no tenable solutions for smaller diameters in the region of 1 mm.
In view of the above, it is the object of the present invention to modify a transport device for NMR measuring capillaries with as simple as possible technical means such that it is less critical than the conventional devices and causes less breakage of glass.
SUMMARY OF THE INVENTION
This object is achieved in accordance with the invention in a surprisingly simple and also effective manner in that a mounting sleeve is disposed, like a collar, radially about the sample tube such that it cannot slip, wherein, in the operating position of the sample tube in the measuring chamber, a horizontal end face of the mounting sleeve is flatly supported on a horizontal stop surface in the bottom region on the inner side of an at least two-stage axial bore of the spinner, wherein a first stage of the bore, disposed in the upper region of the spinner, has an inner diameter which is larger than the outer diameter of the mounting sleeve, and a second stage, in the bottom region of the spinner, has an inner diameter which is smaller than the outer diameter of the mounting sleeve but larger than the outer diameter of the sample tube.
The solution to the inventive problem first required determination of the cause of the frequent glass breakages in the conventional transport devices:
When the spinner
7
a
(shown in
FIG. 1
in a device according to prior art) is moved downwardly, the fragile measuring capillary
8
can strike the conical part of the upper mounting part
11
of the support tube
10
. Since the measuring capillary is rigidly connected to the relatively heavy spinner
7
a
, the spinner is also decelerated and, due to its inertial mass, transfers large forces to the measuring capillary which can therefore be easily destroyed. These findings, which the experts had not realized, were an important prerequisite to obtaining the above-described inventive solution, to permit substantially safe transport of the measuring sample.
In contrast to prior art, the inventive device permits mechanical decoupling of the measuring capillary from the spinner in all critical directions. The measuring capillary can be freely moved relative to the spinner in an upper axial direction and in a lateral, radial direction. Its motion is limited in a downward axial direction by a stop disposed on the spinner and fashioned at the second narrowed stage of the modified through-bore. The relative dimensions of the inner diameter of the two-stage through-bore of the spinner on the one hand and of the outer diameter of the mounting sleeve on the other hand are selected in practice such that the mounting sleeve loosely fits into the extended first stage of the through-bore and is laterally movable in a radial direction by approximately ±0.5 mm to ±1 mm or more. Moreover, the mounting sl
Marek Daniel
Seydoux Roberto
Tschirky Hansjoerg
Warden Michael
Bruker Biospin AG
Fetzner Tiffany A.
Gutierrez Diego
Vincent Paul
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