FLAT INSULATION LAYER FOR A MAGNETIC RESONANCE GRADIENT COIL AND METHOD FOR MANUFACTURING SUCH A GRADIENT COIL AND A FLAT INSULATION LAYER

Abstract

In a method for manufacturing a flat insulation layer for use in a gradient coil, a thermoplastic insulating material in the form of a plate, strip or foil is three-dimensionally deformed in a hot shaping step to form specified local elevations on at least one side, which are spaced apart from one another.

Claims

1. A method for manufacturing an insulation layer for embodiment in a magnetic resonance gradient coil, said method comprising: providing a plate, strip or foil of thermoplastic insulating material to a hot press apparatus; and in said hot press apparatus, three-dimensionally deforming said thermoplastic insulating material of said plate, strip or foil in order to form predetermined local elevations in said plate, strip or foil on at least one side of said plate, strip or foil, that are spaced apart from each other.

2. A method as claimed in claim 1 comprising forming said elevations as nubs each with a round or angled geometry, distributed in a web and proceeding in said web along a straight line or a curved line.

3. A method as claimed in claim 1 comprising forming said elevations in said hot press apparatus on both sides of said plate, strip or foil.

4. A method as claimed in claim 3 comprising forming said elevations on one side of said plate, strip or foil so as to be offset in rows, viewed in a transverse direction of said plate, strip or foil, with respect to the elevations on the other side of said plate, strip or foil.

5. A method as claimed in claim 1 wherein said plate, strip or foil comprises an edge region and, in said hot press apparatus, forming depressions or recesses at said edge region that are spaced apart from each other and that proceed in a longitudinal direction of said plate, strip or foil.

6. A method as claimed in claim 5 wherein said plate, strip or foil comprises respective edge regions at opposite edges of said plate, strip or foil, and wherein a number of the depressions or recesses at each of said edge regions is equal.

7. An insulation layer manufactured by the method as claimed in claim 1.

8. A method for manufacturing a cylindrical magnetic resonance gradient coil assembly comprising: arranging a plurality of gradient coils respectively in different radial planes; providing an insulating layer between respective adjacent gradient coils in said plurality of gradient coils said insulation layer comprising a plate, strip or foil of thermoplastic insulating material having a plurality of local elevations on at least one side thereof formed by three-dimensionally deforming said plate, strip or foil by hot shaping, said local elevations being spaced apart from each other; and casting said plurality of gradient coils and said insulation layers with a curable resin that flows around the local elevations of each insulation layer.

9. A method as claimed in claim 8 wherein said plurality of gradient coils define a cylinder with a longitudinal axis, and wherein each of said insulation layers comprises more than one plate, strip or foil all proceeding around said longitudinal axis and overlapping each other at respective edges of each plate, strip or foil.

10. A method as claimed in claim 9 wherein the local elevations on said at least one side of each insulation layer also form corresponding depressions or recesses at an edge of the respective plate, strip or foil, with the elevations of one plate, strip or foil in the insulation layer engaging in the depressions or recesses of another plate, strip or foil in the same insulation layer.

11. A gradient coil manufactured by the method as claimed in claim 8.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 shows a basic illustration of a gradient coil in cross-section.

[0026] FIG. 2 shows a partial view of an inventive insulation layer.

[0027] FIG. 3 shows a basic illustration of a number of insulation layers arranged next to one another in an overlapped arrangement.

[0028] FIG. 4 shows a sectional view in the direction of the line IV-IV in FIG. 3.

[0029] FIG. 5 shows two insulation layers of a second inventive embodiment.

[0030] FIG. 6 shows the two insulation layers from FIG. 5 in an assembled mounting position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] FIG. 1 shows, in the form of a basic illustration, a sectional view of a gradient coil 1, having a number of gradient coils 2, between which insulation layers 3 are arranged, via which the gradient coils 2 are insulated and spaced apart from one another. This structure is cast in an epoxy resin 4, which defines the shape of the coil. The basic structure of a gradient coil is sufficiently known.

[0032] FIG. 2 shows a basic illustration of an insulation layer of a first embodiment. This insulation layer consists of a thermoplastic material 5 in the form of a plate, strip or foil. Use can be made for example of polybuthylene terephthalate, polyoxymethylene, polyamide or polyethylene terephthalate, this list not being exhaustive.

[0033] The insulation layer 3 is manufactured from a semi-finished part in the faun of a plate, strip or foil from the thermoplastic material by hot shaping using a corresponding shaping tool, not described in greater detail here. This can for example be a press in the case of individual plates or corresponding press rollers in the case of continuously shaped strips or foils.

[0034] In the reshaping process a three-dimensional change in shape takes place to form elevations 6 and depressions 7, the elevations 6 on one side necessarily resulting in compatibly shaped depressions 7 on the other side, since the hot reshaping process results only in a change in geometry, but not in a flow of material. The elevations 6 are, for example, round nubs or the like, and accordingly the depressions 7 are round and cup-like.

[0035] In the exemplary embodiment shown the elevations 6 and the depressions 7 are obviously arranged in rows which extend in the longitudinal direction L of the insulation layer 3, rows of elevations 6 and depressions 7 alternating. However, any other geometries can also be selected, for example elevations 6 and depressions 7 can alternate within a row, and the like.

[0036] In each case the elevations 6 are spaced apart from one another on the respective sides, such that a casting resin, i.e. the epoxy resin 4, can flow in virtually any direction along the surfaces of the insulation layer 3. This ensures that in the vacuum casting process the epoxy resin 4 penetrates to every point that is to be cast with epoxy resin 4, such that no hollow spaces and similar casting faults are formed.

[0037] FIG. 3 shows, as an example, the arrangement of a number of insulation layers 3 next to one another. The insulation layers 3 can be either separate stable plates, which are embodied as virtually semicircular in shape, extending around approx. 180°. If the insulation layers 3 are embodied in the form of strips or foils, they are as it were unwound from a long strip winding or foil winding and wound around the longitudinal axis of the gradient coil.

[0038] In each case the arrangement of the insulation layers 3 is such that they overlap somewhat at the edge, and consequently an overlap zone 8 is produced, as shown in FIG. 3 and in particular in the sectional view according to FIG. 4. The arrangement here is such that the elevations 6 at the edge of the insulation layer 3 lying at the bottom engage in the opposing depressions of the insulation layer 3 lying on top. If the insulation layers 3 are laid around the gradient coil axis, then as a result of this form-fit engagement—the geometry of the elevations 6 corresponds to the geometry of the opposing depressions—the bonding of the layers is axially ensured, and an axial movement is consequently not possible.

[0039] Because of the defined spacing of the elevations 6 and depressions 7 from one another, the engagement of the nub-like elevations 6 into the corresponding depressions 7 requires the insulation layers 3 to be arranged on a defined radius, and consequently to be positioned in a very specific radial plane. To have sufficient clearance to also be able to position the insulation layers 3 in other radial planes, it is conceivable, as shown in FIGS. 5 and 6, to form longitudinal recesses 10, i.e. elongated holes, on an edge side 9, which extend in the longitudinal direction of the insulation layer 3. Alternatively to the recesses 10, it is also conceivable to form longitudinal elevations which necessarily result on the underside in corresponding longitudinal groove-like depressions.

[0040] At the opposing edge region 11 a number of elevations 6a corresponding to the number of recesses 10 or longitudinal depressions is formed on each insulation layer, again nub-like in the example shown.

[0041] As the example further shows, elevations 6 and depressions 7 are arranged over the rest of the surface in the manner already known from FIG. 2, i.e. the number of elevations 6/depressions 7 over the surface is significantly larger than the number of the few elevations 6a in the edge region 11.

[0042] If now two insulation layers 3 are arranged next to one another, forming an overlap region 8, be they plates, strips or foils, the elevations 6a formed in the region of the edge section 11 engage in the corresponding longitudinal recesses 10, as shown in FIG. 6. Since the recesses 10 are longitudinal, i.e. represent elongated holes, it is not a matter of the exact positioning of the elevations 6a relative to the recesses 10, i.e. these insulation layers can be integrated in different radial planes.

[0043] Even though round elevations are shown in the figures, that rise slightly conically from the plane, angled elevations or longitudinal, web-like or rib-like elevations are of course also conceivable. All that is important is that in both spatial directions they are spaced far enough apart from one another so that a flow of resin is possible in any direction during the vacuum casting.

[0044] Although modifications and changes may be suggested by those skilled in the art, it is the intention of the Applicant to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of the Applicant's contribution to the art.