This invention relates generally to x-ray tubes and x-ray tube power supplies.
A common x-ray tube and power supply configuration is for both to be integrally joined and have continuous, electrically insulative, potting material surrounding the two devices. The entire unit can be surrounded by an enclosure, typically at ground voltage. Electrically insulative material can insulate high voltage components of the x-ray tube and power supply from the enclosure.
A reason for integrally joining the two devices in this manner is that a voltage differential of tens of kilovolts can exist between the enclosure and wires from the power supply to the x-ray tube, and it can be difficult to electrically isolate this large voltage potential. Difficulty of isolating the two voltages is especially difficult in small, portable, x-ray sources, in which a distance between the high voltage wires and the enclosure can be about 1 cm, but the voltage differential can be around 50 kilovolts.
A problem of the above configuration, with x-ray tube and power supply integrally joined, is that if one device fails, both devices must normally be scrapped. It would be beneficial to have a removable connection between the x-ray tube and the power supply so that the two may be connected and disconnected at will, allowing replacement of one of the devices upon failure, while saving the other device. Such a connection can be difficult because an electrical arc can travel more easily along a junction of the connection between the two devices. Any air trapped in such connection can be especially harmful, because an electrical current can arc through the air causing the air to ionize resulting in breakdown of surrounding potting. Thus, the device can easily fail due to arcing along a connection between x-ray tube and power supply.
One design for a removable connection 210 between an x-ray tube and a power supply is shown in
It has been recognized that it would be advantageous to have a removable connection between x-ray tube and power supply that allows these two devices to be connected and disconnected and also minimizes potential electrical arcing along a junction of these two devices. It has also been recognized that it would be advantageous to have a removable connection that can minimize trapped air in the connection and/or minimize size. The present invention is directed to power supply to x-ray tube connections that satisfies these needs.
In one embodiment, the apparatus comprises a housing containing a power supply. The power supply can include electrical connectors. The electrical connectors can be configured to provide electrical power to an x-ray tube. The x-ray tube can be removably affixed to the housing in a rigid manner with the x-ray tube movable and holdable along with the housing when affixed thereto. A releasable coupling between the x-ray tube and the housing can create an interface defining a potential arc path. A means can be used for resisting arcing along the potential arc path. The means can be (1) a conductive sleeve embedded in flexible, elastic electrically insulative material partially surrounding a socket into which the x-ray tube is inserted; (2) a means for progressively compressing an annular gap oriented perpendicular to the electrical connectors in a radial outward direction; (3) a plug and a socket wherein tapered and/or annular surfaces of the plug and socket include a non-linear profile; or (4) combinations of the above.
In another embodiment, the apparatus comprises a power supply and an x-ray tube electrically, physically and releasably coupled together at a coupling formed therebetween. The coupling comprises a plug extending from one of the power supply or the x-ray tube and a socket extending in towards the other of the power supply or the x-ray tube. A plug annular surface can surround the plug at a base thereof and a socket annular surface can surround the socket at a leading edge thereof. The plug can have a tapered surface and a continuously reduced diameter from the base towards an end of the plug. The socket can have a tapered surface and a continuously reduced diameter from the leading edge towards a bottom of the socket. Mating electrical connectors associated with the plug and the socket can connect when the plug is disposed in the socket. The electrical connectors can be configured to allow electrical current to flow from the power supply to the tube when connected. The tapered surfaces, the annular surfaces, or both, can have a non-linear cross-sectional profile. The tapered surfaces and the annular surfaces of the plug and the socket can mate, with the plug insertable and receivable in the socket. The plug and the socket can comprise elastic, electrically insulative material. The tapered surfaces can abut one another when coupled.
In another embodiment, the apparatus comprises a coupling on a power supply or an x-ray tube. The coupling comprises a plug extending from, or a socket extending in towards, the power supply or the x-ray tube. The plug or the socket can have a tapered surface and a continuously reduced diameter. Electrical connectors can be associated with the plug or the socket. The electrical connectors can be configured to allow electrical current to flow from the power supply to the tube when connected. The tapered surface can have a non-linear profile. The plug or the socket can comprise elastic, electrically insulative material.
In another embodiment, the apparatus comprises a coupling on a power supply or an x-ray tube. The coupling comprises a plug extending from, or a socket extending in towards, the power supply or the x-ray tube. The plug or the socket can have a tapered surface and a continuously reduced diameter. An annular surface can surround the plug at a base or the socket at a leading edge thereof. Electrical connectors can be associated with the plug or the socket. The electrical connectors can be configured to allow electrical current to flow from the power supply to the tube when connected. The tapered surface, the annular surface, or both, can have a non-linear cross-sectional profile. The plug or the socket can comprise elastic, electrically insulative material.
a-c are schematic cross-sectional side views of junctions of x-ray power supplies and x-ray tubes, including tapered gaskets, in accordance with embodiments of the present invention;
a-c are schematic cross-sectional side views of junctions of x-ray power supplies and x-ray tubes, including tapered opposing surfaces, in accordance with an embodiment of the present invention;
As used herein, the term “annular” includes non-circular ring shapes. Thus, for example a shape of the plug annular surface (that can surround the plug at a base thereof) is not limited to a circular inner and outer perimeter. A common shape of the plug annular surface will be a circular inner perimeter, to allow the plug to twist in the socket, and a square outer perimeter, to match the shape of an outer metal housing or shield.
Shown in
A housing 1 can contain the power supply 3. The power supply 3 can be embedded in electrically insulative potting material 2. The power supply 3 can include a pair of electrical connections 4 which are configured to provide electrical power to the x-ray tube 8. The electrical connections 4 can be wires that are enclosed in a case or tube 18. The case 18 can be electrically conductive and can be electrically connected to one of the electrical connections 4.
A shield 7 can contain the x-ray tube 8. The x-ray tube 8 can include a cathode 9, configured to emit electrons towards an anode 11. A target at the anode 11 can emit x-rays 12 in response to impinging electrons from the cathode 9. The x-ray tube can be removably, electrically coupled to two electrical connectors 5, configured to provide electrical power to the cathode 9. The electrical connectors 5 can be wires that are enclosed in a case or tube 17. The case 17 can be electrically conductive and can be electrically connected to one of the electrical connectors 5.
A coupling 21 can define a junction of the shield 7 and the housing 1. This coupling 21 connection can be rigid and can allow the shield 7 and the x-ray tube 8 to be movable and holdable along with the housing 1 when affixed thereto. The coupling 21 can be separated as shown in
At least one of the opposing 16 or opposite 15 surfaces can be continuously tapered, forming a continuously radially expanding annular gap with a thinner center and a thicker perimeter prior to coupling the shield 7 to the housing 1, such that when the shield 7 is coupled to the housing 1, the opposing surfaces 16 compress the opposite surfaces 15 of the gasket 6 together, thus minimizing or eliminating air pockets between the opposing 16 and opposite 15 surfaces.
The housing 1 and the shield 7 can both be solid, non-flexible structures and can be fastened together to form a single solid, non-flexible structure, that can be separated and rejoined without damage to the housing 1, the shield 7, or internal components in the housing 1 or the shield 7.
In one embodiment, the housing 1 and the shield 7 can be maintained at ground voltage and the power supply can be configured to provide a voltage differential of at least 10 kilovolts between the cathode 9 and the housing 1 and shield 7.
In one embodiment, either the gasket 6 or the opposing surfaces 16 comprise a soft material and the other comprises a hard material. The soft material can be substantially softer than the hard material. The soft material can be compressed by the hard material when the opposing 16 and opposite 15 surfaces are compressed together, thus minimizing air pockets between the opposing 16 and opposite 15 surfaces. A Durometer Shore A hardness of the hard material divided by a Durometer Shore A hardness of the soft material can be between 1.7 and 2.2 in one embodiment, between 1.5 and 2.4 in another embodiment, or between 1.3 and 2.6. The Durometer Shore A hardness of the soft material can be between 40 and 60 in one embodiment.
Opposing surfaces 16 can be formed as rigid caps 13 disposed in open ends of the housing 1 and/or the shield 7. A mold can be used to make the caps 13. The caps 13 can be made of rubber, silicon, epoxy or other suitable, electrically insulative material. The caps can be a hard material or a soft, flexible and/or elastic material. The caps 13 can be formed while in the housing 1 and/or shield 7; or the caps 13 can be formed separately, then inserted into the housing 1 and/or the shield 7. A liquid electrically insulative potting 2 can then be poured into and fill open areas in the housing 1 and/or shield 2, then allowed to cure or harden. The caps 13 can have a circumferentially corrugated inner surface 14 facing and abutting the potting 2.
Potential arc paths include boundaries such as the inner surface 14 of the caps 13 and the junction of the gasket 6 to the caps 13. The corrugated inner surface 14 of the caps 13 can be a means for resisting arcing along this potential arc path by increasing the distance electrical arc must travel. Continuously tapered opposing 16 or opposite 15 surfaces, compressed together can be another means for resisting arcing along the potential arc path of the junction of the gasket 6 to the caps 13 by minimizing or eliminating air pockets in this junction. The continuously tapered opposing 16 or opposite 15 surfaces, compressed together, are an example of a means for progressively compressing an annular gap oriented perpendicular to the pair of electrical connections in a radial outward direction.
As illustrated by couplings 30a-c in
As illustrated by couplings 40a-c in
In one embodiment, either the opposite surfaces 15 of the gasket 6a-c is tapered, as shown in
Shown in
The housing 55 can contain a socket 53 at one end of the housing 55. The socket 53 can be formed by electrically insulative potting 2 inside the housing 55. The socket 53 can be configured for insertion and removal of an x-ray tube (8 in
Potting 2a can be disposed between the sleeve 52 and the housing 55, to electrically insulate the sleeve 52 from the housing 55. Potting 2b can be disposed between the sleeve 52 and the socket 53. The sleeve 52 can circumscribe at least a portion of the socket 53. The sleeve 52 can be electrically coupled to one of the pair of electrical connections 56 of the power supply 3.
As shown in
The sleeve 52 can be a means for resisting arcing along the potential arc path, namely between the x-ray tube 8, or especially the cathode 9, or electrical connections to the cathode 9, and the housing 55. Because the device is configured for x-ray tube insertion and removal into the sleeve 53, air pockets are likely formed between the x-ray tube 8 and potting 2. As described previously, large voltages across such air pockets can cause arcing across the air pocket and ionization of the air, which can result in potting breakdown.
With the x-ray source 60 design of the present invention, however, the sleeve 52 will be maintained at approximately the same voltage as the cathode 9, thus, there will be minimal voltage gradients, if any, between the x-ray tube 8 at or near the cathode 9 and the sleeve 52, and thus minimal voltage gradients across air pockets between tube 8 and potting 2 in this region. There will be, of course, a very large voltage between the sleeve 52 and the housing 55. It will be easier to avoid air pockets between sleeve 52 and housing 55, and thus easier to provide effective electrical insulation between sleeve 52 and housing 55, because the sleeve 52, unlike the x-ray tube 8, will not be inserted and removed, but is rather permanently affixed in the potting 8 of the housing 55. Thus, the sleeve 52, or electrode, can act as a means for resisting arcing along the potential arc path, namely between the cathode 9, or other high voltage components of the x-ray tube 8, and the housing 55, by reducing or removing a voltage gradient along this potential arc path 58.
Because the sleeve 52 can be maintained at approximately the same voltage as the cathode 9, there can be minimal or no chance of arcing between the sleeve 52 and the cathode 9 or x-ray tube near the cathode 9. There can be, however, an increasing voltage differential between the sleeve 52 and the x-ray tube progressing closer to the anode 11, thus increasing the risk of arcing between the tube 8 and the sleeve 52 nearer the anode 11. Therefore, typically the sleeve 52 will not extend all the way to the end of the housing 55 at the anode end, but rather will only surround part of the socket 53 and thus part of the x-ray tube 8.
A balance in the design may be made between protecting against arcing between the tube 8 and the sleeve 52, if the sleeve 52 extends too far towards the anode 11, or between tube 8 and the housing 55, if the sleeve 52 is too short. This balance may be made depending on cathode 9 to anode 11 voltage differential and thickness of potting 2. The sleeve 52 can surround the x-ray tube 8 between 5% to 25% of a length L of the x-ray tube 8 in one embodiment (0.05<d1/L<0.25); between 24% to 50% of a length L of the x-ray tube 8 in another embodiment (0.24<d1/L<0.50); between 49% to 75% of a length L of the x-ray tube 8 in another embodiment (0.49<d1/L<0.75); or between 24% to 75% of a length L of the x-ray tube 8 in another embodiment (0.24<d1/L<0.75).
The potting 2 can be flexible and elastic and the x-ray tube 8 can be press-fit into the potting 2 of the socket 53. Flexible and elastic potting 2 can allow for a tighter fit and less air pockets between x-ray tube 8 and potting 2.
Illustrated in
The plug 73 can have a tapered surface 76a and a continuously reduced diameter Da from the base 83 towards an end 82 of the plug 73 (e.g. Da1>Da2). The socket 74 can have a tapered surface 76b and a continuously reduced diameter Db from the leading edge 85 towards a bottom 86 of the socket 74 (e.g. Db1>Db2).
Shown are two devices 71 and 72, one of which can be the x-ray tube and the other can be the power supply. One of the devices (the “plug device” 71) can be attached to a plug 73. The other device (the “socket device” 72) can be attached to a socket 74. In one embodiment, the x-ray tube can be the plug device 71 and the power supply can be the socket device 72. In another embodiment, the x-ray tube can be the socket device 72 and the power supply can be the plug device 71.
Electrical connectors 81a can be associated with the plug (“plug connectors” 81a). The plug connectors 81a can be electrically connected to the plug device 71. Electrical connectors 81b can be associated with the socket (“socket connectors” 81b). The socket connectors 81b can be electrically connected to the socket device 72. The plug connectors 81a can mate with the socket connectors 81b and can connect when the plug 73 is inserted into the socket 74. The electrical connectors 81a-b can allow electrical current to flow between the plug device 71 and the socket device 72, or in other words, from the power supply to the tube when connected. The plug connectors 81a can be disposed at the end 82 of the plug 73 and the socket connectors 81b can be disposed at the bottom 86 of the socket 74. It can be beneficial to have the connectors 81 disposed at the end 82 of the plug 73 and at the bottom 86 of the socket 74 in order to maximize distance along the junction of the plug and socket, between the connection and an external grounded structure, thus minimizing the chance of arcing.
The tapered surfaces 76 and/or the annular surfaces 75 can have a non-linear cross-sectional profile. The tapered surfaces 76 and the annular surfaces 75 of the plug 73 and the socket 74 can substantially mate. The plug 73 can be inserted into and be received by the socket 74. The plug 73 and materials 84 forming the socket 74 can comprise elastic, electrically insulative material. The plug 73 can be formed of the same, or of different, elastic, electrically insulative material than the materials 84 forming the socket 74.
The tapered surfaces 76 can abut one another when the x-ray tube and the power supply are coupled together. In one embodiment, the annular surfaces 75 can also abut one another when the x-ray tube and the power supply are coupled together. In another embodiment, an air gap, a washer, or a gasket, can exist between the annular surfaces 75 when the x-ray tube and the power supply are coupled together.
The non-linear cross-sectional profile can include a stepped profile on the tapered surface 76a of the plug 73. For example, the tapered surface of the plug 73 can include one step (not shown in the figures), two steps 77a-1 and 77a-2 as shown on coupling 70 in
The non-linear cross-sectional profile can include a stepped profile on the tapered surface 76b of the socket 74. For example, the tapered surface of the socket 74 can include one step (not shown in the figures), two steps 77b-1 and 77b-2 as shown on coupling 70 in
The stepped profile on the tapered surface 76a of the plug 73 can substantially mate with the stepped profile on the tapered surface 76b of the socket 74. For example, plug step 77a-1 can mate with socket step 77b-1 and plug step 77a-2 can mate with socket step 77b-2. The coupling 70 of
As shown on coupling 90 in
The diameter Da of the plug can be between 1.004 to 1.006 times larger than the diameter of the socket Db at mating locations in one embodiment, or between 1.0045 to 1.0055 times larger than the diameter of the socket Db at mating locations in another embodiment. For example, for the diameter Da of the plug 1.005 times larger than the diameter of the socket Db, if socket diameter is 10 mm, then plug diameter can be 10.05 mm at a mating location. Over sizing plug diameter Da, in order to first allow contact between longitudinal segments 78, can result in less air trapped in the junction of the plug 73 and the socket 74. For applications in which the x-ray source may be exposed large variation in temperature, or temperature extremes, it may be important to select materials to form the plug and socket that have a low coefficient of thermal expansion, in order to ensure proper fit at all operating temperatures.
Shown on coupling 100 in
Shown on coupling 100 in
As shown in
As shown in
As shown on connectors 120 and 140 in
The annular surfaces 75 non-linear cross-sectional profile can include annular grooves 121 on one of the plug annular surface 75a or the socket annular surface 75b and mating annular ridges 122 on the other of the plug annular surface 75a or the socket annular surface 75b. As shown in
The non-linear cross-sectional profile of the annular surfaces 75 can include (1) annular grooves 121a on the plug annular surface 75a and mating annular ridges 122b on the socket annular surface 75b; and (2) annular grooves 121b on the socket annular surface 75b and mating annular ridges 122a on the plug annular surface 75a. The non-linear cross-sectional profile of the plug annular surface 75a can mate with the socket annular surface 75b when coupled.
As shown on connector 150
In one embodiment, a coupling device on a power supply (for example device 71 in
In another embodiment, a coupling device on a power supply (for example device 72 in
In another embodiment, a coupling device on an x-ray tube (for example device 71 in
In another embodiment, a coupling device on an x-ray tube (for example device 72 in
As shown in
Electron flight distance EFD, defined as a distance L2 from the electron emitter 166 to the target 168, can be an indication of overall tube size. It can be desirable in some circumstances, especially for miniature, portable x-ray tubes, to have a short electron flight distance EFD. The electron flight distance EFD can be less than 1 inch in one embodiment, less than 0.8 inches in one embodiment, less than 0.7 inches in another embodiment, less than 0.6 inches in another embodiment, less than 0.4 inches in another embodiment, or less than 0.2 inches in another embodiment. A distance L1 from a plane (104 in
In
Shown in
The core region 172 can comprise a relatively stiffer or harder material to aid in plug 73 insertion into the socket 74 with reduced bending. The outer region 171 can comprise a relatively softer material to improve contact between the plug 73 and the material 84 forming the socket 74. The material 84 forming the socket 74 can also comprise a relatively softer material to improve contact between the plug 73 and the material 84 forming the socket 74. A Durometer Shore A hardness of the core region 172 divided by a Durometer Shore A hardness of the outer region 171 can be between 1.7 and 2.2 in one embodiment, between 1.5 and 2.4 in another embodiment, or between 1.3 and 2.6. A Durometer Shore A hardness of the material 84 forming the socket 74 divided by the Durometer Shore A hardness of the outer region 171 can be between 0.95 and 1.05. The Durometer Shore A hardness of the outer region 171 can be between 40 and 60 in one embodiment. The outer region can comprise silicone, such as Dow Corning Sylgard® 170. A Durometer Shore A hardness of the annular surfaces 75 can be between 40 and 60 in one embodiment.
Pin connectors are shown in
Pin connector 180 of
The pin connector 180 of
The present invention can include an x-ray tube removably affixed to a power supply in a rigid manner with the x-ray tube movable and holdable along with the power supply when affixed thereto. A releasable coupling between the x-ray tube and the power supply can create an interface defining a potential arc path. The present invention can include a means for resisting arcing along the potential arc path.
In one embodiment, shown in
In another embodiment, shown in
In another embodiment, shown in
The various x-ray source embodiments described herein can be used for portable x-ray sources, which include small x-ray tubes configured to provide a very large voltage differential between the cathode 9 and the anode 11. For example, “small x-ray tube” can mean an x-ray tube 8 with a diameter D of a largest component (anode 11, cathode 9, or insulative cylinder) that is less than one inch and a length L that is less than two inches. A voltage differential, provided by the power supply 3, between cathode 9 and anode 11 of the x-ray tube 8 can be at least 20 kilovolts in one embodiment, at least 30 kilovolts in another embodiment, or at least 50 kilovolts in another embodiment.
Furthermore, various embodiments of the present invention have a minimum distance d (as shown in
Priority is claimed to U.S. Provisional Patent Application Ser. No. 61/579,158, filed on Dec. 22, 2011, which is hereby incorporated herein by reference in its entirety.
Number | Date | Country | |
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61579158 | Dec 2011 | US |