Mechanical superconducting switch

Abstract

A mechanically operating superconducting switch has two superconducting wires, a respective end of each superconducting wire being embedded in a respective block of superconducting material. A mechanical arrangement is provided for driving respective contact surfaces of the blocks into physical contact with each other, and for separating those services.

Claims

1. A mechanically operating superconducting switch comprising: first and second superconducting wires; first and second blocks each of superconducting material; an end of said first superconducting wire being cast in said first block of superconducting material and an end of said second superconducting wire being cast in said second block of superconducting material; each of said first and second blocks comprising a contact surface and the respective contact surfaces of said first and second blocks comprising complementary protrusions and recesses; and a mechanical rotary actuator connected to one of said first and second blocks, that closes said switch by rotating said one of said first and second blocks in a first rotary direction in order to drive the respective complementary protrusions and recesses of the respective contact surfaces into physical contact with each other, and that thereafter opens said switch by rotating said one of said first and second blocks in a second rotary direction, opposite to said first rotary direction, in order to separate the respective complementary protrusions and recesses of the respective contact surfaces.

2. A mechanically operating superconducting switch according to claim 1 wherein the first and second superconducting wires are, respectively, ends of coils forming a superconducting magnet.

3. A mechanically operating superconducting switch according to claim 1, wherein at least one of the first or second blocks is formed of superconducting material in which the corresponding first or second superconducting wire is embedded, the superconducting material of the at least one of the first or second blocks having a ductility greater than a ductility of superconducting material of the first or second superconducting wire embedded therein.

4. A mechanically operating superconducting switch according to claim 1, comprising a source of electronic control signals that control opening and closing of the switch.

5. A mechanically operating superconducting switch according to claim 1, wherein: said first block has an essentially cylindrical wall with an essentially cylindrical cavity contained therein, with the protrusions of said first block being on a wall of the cavity; said second block has an essentially cylindrical wall, with the protrusions of said second block being on the cylindrical wall of the second block; the second block is at least partially located within the cavity of the first block, such that the protrusions of the first and second blocks overlap in a circumferential direction; and said rotary actuator rotates said one block of said first block and said second block with respect to the other around an axis aligned with axes of cylindrical walls of the first and second blocks.

6. A mechanically operating superconducting switch according to claim 5, wherein the first block has a number of first protrusions equal to the number of protrusions on the second block.

7. A mechanically operating superconducting switch according to claim 5, wherein at least some faces of the protrusions of one or both of the first block and the second block are covered with an electrically isolating layer.

8. A mechanically operating superconducting switch according to claim 5, wherein the protrusions of the first and second blocks are parallel to said axis.

9. A mechanically operating superconducting switch according to claim 5, wherein the protrusions of the first and second blocks are formed as complementary thread surfaces of a helical or conical screw.

10. A mechanically operating superconducting switch according to claim 9, wherein the thread surfaces are segmented.

11. A mechanically operating superconducting switch according to claim 1, comprising a vacuum or inert atmosphere around the first and second blocks.

12. A mechanically operating superconducting switch according claim 1, comprising arrangements for additional mechanical vibration actuation of the first and second blocks.

13. A superconducting magnet structure comprising: a mechanically operating superconducting switch; a plurality of coils of superconducting wire electrically connected in series, housed within a cryostat arranged to cool the coils, and wherein first and second superconducting wires from respective electrical ends of the coils are connected to said mechanically operating superconducting switch; and said mechanically operating superconducting switch comprising first and second blocks of superconducting material with an end of said first wire cast in said first block and an end of said second wire cast in said second block, each of said first and second blocks comprising a contact surface and the respective contact surfaces of said first and second blocks comprising complementary protrusions and recesses, and a mechanical rotary actuator connected to one of said first and second blocks that closes said switch by rotating said one of said first and second blocks in a first rotary direction in order to drive the respective complementary protrusions and recesses of the respective contact surfaces into physical contact with each other, and that thereafter opens said switch by rotating said one of said first and second blocks in a second rotary direction, opposite to said first rotary direction in order to separate the respective complementary protrusions and recesses of the respective contact surfaces.

14. A superconducting magnet structure according to claim 13 wherein the switch is within the cryostat, and comprising a source of electronic control signals that control opening and closing of the switch, said source of electronic control signals being outside the cryostat.

15. A superconducting magnet structure according to claim 13 wherein the mechanical superconducting switch is cooled by a same cooling arrangement used to cool the magnet.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows an example of a linearly-actuated mechanical superconducting switch according to the present invention.

(2) FIGS. 2-5 respectively show alternative versions of blocks with contact services, for different embodiments of the present invention.

(3) FIGS. 6 and 7 illustrate an example of a rotary-actuated mechanical superconducting switch according to the present invention, wherein FIG. 6 shows a partially cut-away cross-section along line VI-VI in FIG. 7.

(4) FIG. 8 schematically illustrates a further embodiment of a rotary-actuated mechanical superconducting switch according to the present invention.

(5) FIG. 9 schematically illustrates a further version of the embodiment of FIG. 8.

(6) FIG. 10 schematically illustrates a further embodiment of the invention, wherein the blocks are stationary with respect to each other and a threaded superconducting collar is provided that is driven in and out of contact between the two blocks by relative rotation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(7) FIG. 1 shows a first example, in which superconducting wires 10, 12 are each embedded within upper 13 and lower 14 blocks of superconducting material, providing contact surfaces 15. Preferably, the material of at least one of the blocks is a ductile superconducting material, such as BiPb, NbTi, Nb. Upper 16 and lower 18 enclosure pieces retain the blocks and a bellows 20 provides a sealed enclosure 21 of variable height. An electrical insulator 22 may be provided if necessary, forming part of the enclosure, to prevent electrical conduction between the wires 10, 12 through the material of the enclosure. Mechanical actuation 30 may drive the contact surfaces 15 into electrical contact and separate them again. Although a mechanical actuator 24 is schematically illustrated, any appropriate means may be used to drive the two enclosure pieces 16, 18 toward one another and apart again to provide closing and opening of the switch. For example, a gas at a certain pressure may be sealed within enclosure 21, the enclosure itself being positioned within another vessel, which may contain gas at a pressure higher or lower than the certain pressure, in order to drive the contact surfaces 15 together or apart. An alignment tube 23 of electrically insulating material may be provided to guide upper 13 and lower 14 blocks into aligned contact with one another.

(8) FIG. 2 shows the upper 13 and lower 14 blocks of superconducting material, providing contact surfaces 15, in isolation.

(9) FIG. 3 shows a cross-section through a set of alternative upper 131 and lower 141 blocks of superconducting material. In this example, complementary frustoconical protrusions and recesses are provided on respective contact surfaces 15. If a force acting in the direction of arrow 30 is applied, the pressure acting between the conical contact surfaces will be rather higher than would be the case with planar contact surfaces, improving the electrical characteristics of the switch in its “on” position.

(10) FIG. 4 shows a cross-section through a set of alternative upper 132 and lower 142 blocks of superconducting material. In this example, complementary part-spherical protrusions and recesses are provided on respective contact surfaces 15. If a force acting in the direction of arrow 30 is applied, the pressure acting between the part-spherical contact surfaces will be rather higher in certain places than would be the case with planar contact surfaces, improving the electrical characteristics of the switch in its “on” position. Other shapes of complementary recesses and protrusions may be provided as appropriate.

(11) FIG. 5 shows a cross-section through a set of alternative upper 133 and lower 143 blocks of superconducting material. In this example, particles or beads 140 of a relatively hard superconducting material are included in at least one of the blocks 133. When blocks 133 and 143 are pressed together, for example by a force operating in the direction of arrow 30, these particles or beads 140 press into the more resilient material of the other block 143 producing corresponding cavities 144. The very high pressure acting at the points of contact between particles or beads 140 and block 143 ensures effective electrical contact.

(12) Other similar arrangements may be devised by those skilled in the art, using the linear actuation arrangement shown in FIGS. 1-5.

(13) FIG. 6 illustrates another type of embodiment, in which rotational actuation may be employed. In this embodiment, a first superconducting wire 40 is embedded in a first block 42 of superconducting material. This block is of relatively complex shape, having an essentially cylindrical wall 44 with an essentially cylindrical cavity 46 contained therein. At least one protrusion 48 is provided on the wall of the cavity. A closed end 49 may be provided. A second superconducting wire 50 is embedded in a second block 52 of superconducting material. This second block is also of relatively complex shape, having an essentially cylindrical wall 54 which may have an essentially cylindrical cavity 56 contained therein, or may be solid. At least one protrusion 58 is provided on the wall 54. A closed end 59 may be provided. The second block is at least partially located within the cavity of the first block, such that respective protrusions (48, 58) overlap in a circumferential direction.

(14) An actuator 60 may be provided on one or other, or both, of the first and second blocks 42, 52, for rotating one with respect to the other about an axis 62 aligned with the axes of the cylindrical walls of the first and second blocks. Preferably, the first block 42 has a number of protrusions 48 equal to the number of protrusions 58 on the second block.

(15) The mechanical switch of this embodiment is actuated by relative rotation of the two blocks about axis 62. In the position illustrated, the two blocks are held apart, and are not in electrical contact. By driving one or other, or both, of the blocks with respect to each other about axis 62, at least one of the protrusions 58 on the second block is driven into mechanical and electrical contact with a corresponding protrusion 48 on the first block, placing the switch in its “on” position. By relative rotation about axis 62 in the opposite sense, the protrusions are separated from one another again and the switch enters its “off state”. A vacuum or inert atmosphere is preferably provided around the blocks. The blocks may be driven about the axis 62 by any suitable means: electromechanical, mechanical, hydraulic, pneumatic or piezoelectric, for example.

(16) Optionally, certain faces of the protrusions of one or both of the blocks 42, 52 may be covered with an electrically isolating layer. Accordingly, the blocks may be driven to the fullest extent about axis 62 in one direction to close the switch, and may be driven to the fullest extent in the opposite direction to open the switch, if electrically isolating layers are provided to prevent any contact between the protrusions of the two blocks when driven in this opposite direction.

(17) In an alternative arrangement, rather than protrusions 48, 58 running parallel to the axis 62, contact surfaces between first and second blocks may be provided by complementary thread surfaces of a helical or conical screw. FIG. 7 illustrates a cross-section along line VI-VI of an embodiment wherein the protrusions 48, 58 on first and second blocks are threaded. These thread surfaces are segmented to give make-break operation with limited rotation, similar to the operation discussed with reference to FIG. 6. The thread may be tapered to ensure limited rotation and tight fit between the two blocks in the embodiment illustrated in FIG. 7. Adjacent thread surfaces 15 may be brought to bear upon one another to provide electrical contact between the blocks, and the blocks may be rotated in the opposite relative direction to separate the blocks, and place the switch in its “off” state.

(18) FIG. 7 also schematically illustrates that the first and second superconducting wires 40 and 50 are the ends of respective superconducting coils that are connected in series within a cryostat. FIG. 7 also shows the first and second superconducting wires 40 and 50 being cast into the superconducting blocks 49 and 52, respectively, as a result of the molding process described above.

(19) In another set of embodiments, such as illustrated in FIG. 8, first block 80 is arranged to rotate about an axis 82 defined within a cavity of second block 84. In this embodiment both block 80 and cavity 86 are elliptical in cross-section. By rotating block 80 about axis 82, surfaces 15 of the block and cavity may be brought into electrical contact and may be separated by rotation in the opposite direction. Other embodiments, such as shown in FIG. 9 operate in a similar manner. It is not necessary for the block in the cavity to be oval in cross-section. The embodiment of FIG. 9 shows an example in which both the block and the cavity have rectangular cross-sections and reference numerals 90, 92, 94 and 96 designate components corresponding to those designated by 80, 82, 84 and 86 in FIG. 8. Combinations of cross sections may be used, provided that the block has limited scope from rotation into and out of contact with the walls of the cavity.

(20) FIG. 10 shows an example of a further type of embodiment of the invention. Here, blocks 102, 104 remain stationary with respect to one another and a threaded superconducting collar 106 is provided and may be driven in and out of contact between the two blocks by relative rotation. Preferably an electrically isolating extension 108 is provided such that mechanical alignment is ensured when the collar is rotated out of electrical contact between the blocks. This embodiment is an example of another series of embodiments in which the blocks themselves do not move and a connecting superconducting article is moved into and out of contact between the two blocks. Variants of this embodiment will be apparent to those skilled in the art.

(21) In certain embodiments, the improvements discussed with respect to FIGS. 3-5 may be applied. Contact surfaces 15 are shown in FIGS. 6-10, and these may be improved by the provision of frustoconical recesses and protrusions, as discussed with reference to FIG. 3, or part-spherical recesses and protrusions as discussed with reference to FIG. 4.

(22) Particles or beads 140 of a relatively hard superconducting material may be included in one of the blocks 42, 52, as discussed with reference to FIG. 5. The very high pressure acting at the points of contact between particles or beads 140 and the other block ensures effective electrical contact. Other types of composite mixture of materials of different hardness may be used, to enable point contact deformation to occur.

(23) During operation, additional mechanical actuation in the form of vibration may be applied to improve contact between the blocks of superconducting material.

(24) To address the issue of possible high-voltage damage caused by switching a high current through a large inductive load using a mechanical switch, a suitable type of semiconductor based snubber is preferably provided to protect against damage.

(25) In each case, the mechanical superconducting switch of the present invention is preferably cooled by the same cooling arrangement used to cool the magnet. Alternatively, a separate cooling arrangement may be provided to cool the switch.

(26) Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventors to embody within the patent warranted heron all changes and modifications as reasonably and properly come within the scope of their contribution to the art.