Electricity: measuring and testing – Particle precession resonance – Spectrometer components
Reexamination Certificate
1999-10-28
2001-05-22
Oda, Christine (Department: 2862)
Electricity: measuring and testing
Particle precession resonance
Spectrometer components
C324S309000
Reexamination Certificate
active
06236209
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to an actively shielded, transversal gradient coil system for a nuclear magnetic resonance tomography apparatus, wherein saddle coils are provided in both primary and secondary planes for generating respective gradient fields for the X-direction and the Y-direction. These coils include a radial spacing, and the windings of the coils implemented in 3D technology include a plurality of open conductor ends wherein the contact between the conductor ends of the primary and secondary planes belonging to one another occurs via connector elements at an end face.
2. Description of the Prior Art
In contrast to the conventional, or through-wound, design of tesseral gradient coils, the 3D version includes a plurality of open conductor ends. Specific connector elements thereby produce the contact between a conductor loop of the primary plane with a winding of the secondary plane.
U.S. Letters Pat. No. 5,349,318, for example, discloses a gradient coil arrangement, wherein conductors of the gradient coil are essentially arranged in a primary plane, which is an inner cylindrical envelope, and in a secondary plane, which is an outer cylindrical envelope that concentrically surrounds the inner cylindrical envelope. At each of the two cylindrical envelopes, the conductor arrangement thereby contains a helical conductor section as well as a plurality of horseshoe-shaped conductor sections. At one end face of the cylindrical envelopes, the open conductor ends of the conductor sections between the two cylindrical envelopes are connected to one another via conductive connector wires. Pursuant to such configuration, the connector wires, for example, are soldered to the conductor ends.
With other gradient coils implemented in 3D technology, soldered pins are employed as connector elements which produce the connection between conductor ends that are formed as plates of sheet copper cut with a water jet. This type of connection, however, is actually more suitable for plane-parallel conductor structures. For curved surfaces, and given constricted space conditions, such pin connections hardly can be employed.
The present invention is therefore based on the object of creating a connection technology for the conductor loops of the primary and secondary planes that is simple and that can be applied for all conceivable applications of gradient coils in 3D technology.
SUMMARY OF THE INVENTION
For achieving this object, the present invention provides that the connector elements for conductor ends discharging between the center planes of neighboring shim pockets are planar plate connectors arranged in a plurality of planes insulated from one another. These plate connectors respectively include a base part secured to a carrier ring and lie completely outside the shim pocket and conductor fastening legs projecting substantially radially outward therefrom that are arranged offset circumferentially relative to one another in the planes lying above one another.
All of the demands made of the connector elements of gradient coils in 3D technology can be met by the inventive multi-layer connecting technology, even when these cover partially contradictory demands. Due to the insulation of the plate connectors arranged in various planes, which preferably occurs with intervening insulating plates that are shaped such that they completely cover the areas of the adjoining plate connectors overlapping one another in combination with the offset of the conductor fastening legs, the required high-voltage strength with differences in potential of more than 5 kV can be achieved given extreme space conditions.
As a result of a preferred embodiment wherein the base parts contain substantially radial middle sections that can be plugged onto fastening pins at the carrying ring and further contain transverse legs that angle off therefrom and embrace the shim pockets at the top and bottom, an extremely simple mountability is enabled wherein the logical structure also can be immediately recognized and, thus, easily adhered to. The current-carrying capability of the conductors can be adequately dimensioned since plate connectors that are correspondingly broad and thick can be arranged in the individual planes. Over and above this, simple formation of the conductor loops also derives; i.e., the arrangement and sequence of the contacting and, finally, the other geometrical boundary conditions (such as, for example, keeping the shim pockets free) can be unproblematically assured. Finally, the inventive multi-layer connecting technology offers full flexibility in the layer arrangement in the primary and secondary planes, i.e., line crossings also can be implemented without further ado. The contradictory nature of some of the criteria, particularly of the current-carrying capability with a great detail of conductor material and optimally little voltage spacing and the dielectric strength wherein the situation should be reversed, can be bridged very well given the inventive connector technology.
For simplifying the fastening of the conductor ends, plug-in recesses formed according to the cross section of these conductor ends can be provided in the conductor fastening legs. The conductor ends are thereby preferably pulled toward the outside in their winding plane, are plugged into the recesses arranged in the corresponding radial position and are soldered in. What this, in turn, yields is that the recesses of the conductor fastening legs are arranged radially offset in the primary and secondary planes according to the radial spacing of the saddle coils for generating the gradient field for the X-direction and the Y-direction.
For reducing the overall thickness of the inventive multi-layer connection technology, at least two spaced plate connectors can be arranged in each plane. As warranted, particularly for the connection of conductor ends in the middle of the segment between two shim pocket center planes respectively bridged by a multi-layer connector packet, three or more plate connectors also can be provided in one plane.
Additional features and advantages of the present invention are described in, and will be apparent from, the Detailed Description of the Preferred Embodiments and the Drawings.
REFERENCES:
patent: 4724412 (1988-02-01), Kalafala
patent: 5512828 (1996-04-01), Pausch et al.
Arz Winfried
Schuster Johann
Oda Christine
Schiff & Hardin & Waite
Shrivastav Brij B.
Siemens Aktiengesellschaft
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