Patent Application
20100310050
Embodiments of the present invention relate generally to a rotating union for transferring fluids from a stationary supply to a rotating component. More particularly, the embodiments of the present invention relate to a rotating union for preventing leakage of fluid between a rotating component and a stationary supply in an X-ray tube based imaging system.
X-ray tube based imaging systems, such as computed tomography (CT) imaging systems as well as non-destructive testing systems, employ X-ray sources located on a gantry. Typically these x-ray tubes are anode based x-ray tubes. These anode X-ray tubes typically require high voltage to generate X-rays. Unfortunately these anode X-ray tubes tend to get heated while generating the X-rays. Currently, X-ray tubes employing a rotating shaft protruding out of a vacuum vessel may use a Ferro-fluidic seal to separate vacuum from the atmosphere. The liquid coolant may be directed through the rotating shaft to cool the X-ray target, the Ferro-fluidic seal and the shaft bearings. This configuration needs supply of coolant from a non-rotating part to the rotating part without leakage.
Furthermore, in CT systems, the gantry is rotated around an object at very high speeds. The high speed rotation of the gantry creates a centrifugal force which may typically be in multiples of the force of gravity thereby creating high gravitational loads (G-loads) on a rotating object. A standard face seal rotating union can fail to prevent leakage caused due to high G-loads. The high G-loads may cause the rotating shaft coupled to the X-ray target to bend thereby causing the rotating face seal to misalign from the non-rotating face seal mate. This may cause uneven wear resulting in leakage of coolant. Additionally, a gap may be formed between the faces of the seals causing leakage of coolant. Also, the liquid coolant for cooling various components of the X-ray tube may leak from the rotating union due to the design of the rotating union especially for rotating unions employing standard face seals. Coolant leakage may also occur due to wear and tear of certain components or due to any malfunctioning of the rotating union. The coolant leakage may be detrimental to the imaging system which includes the rotating union or to the environment in which the imaging system operates. Furthermore, deflection of the shaft at the interface of a mechanical face seal may create pressure gradients that may in turn cause uneven wear, leakage and shorter life of a mechanical face seal.
It is therefore desirable to prevent fluid leakage from a rotating union without employing a mechanical face seal.
Briefly in accordance with one aspect of the present technique a coolant-slinging device is provided. The coolant-slinging device comprises a rotating shaft having a proximal end and a distal end; one or more slingers coupled to the proximal end of the rotating shaft, and a drain annulus coupled to the one or more slingers, wherein the one or more slingers are configured to direct a coolant to the drain annulus and the drain annulus is configured to direct the coolant through a primary coolant outlet.
In accordance with another aspect of the present technique a rotating union for an X-ray target is provided. The rotating union for the X-ray target comprises a housing, a coolant-slinging device comprising a rotating shaft having an inner diameter and an outer diameter, a proximal end and a distal end, and a bore therein, one or more slingers coupled to a proximal end of the rotating shaft; a drain annulus coupled to the one or more slingers, wherein the one or more slingers are configured to direct a coolant to the drain annulus and the drain annulus is configured to direct the coolant through a primary coolant outlet; and a stationary tube having a first end and a second end wherein at least a portion of the stationary tube is disposed within the bore of the rotating shaft.
In accordance with yet another aspect of the present technique an X-ray source is provided. The X-ray source comprises a rotating union comprising a housing, a coolant-slinging device comprising a rotating shaft having an inner diameter and an outer diameter, a proximal end and a distal end, and a bore therein, one or more slingers coupled to a proximal end of the rotating shaft, a drain annulus coupled to the one or more slingers, wherein the one or more slingers are configured to direct a coolant to the drain annulus, and wherein the drain annulus is configured to direct the coolant through a primary coolant outlet; a stationary tube having a first end and a second end wherein at least a portion of the stationary tube is disposed within the bore of the rotating shaft. Further, the X-ray source comprises a target operationally coupled to the distal end of the rotating shaft via a rotating hollow shaft.
In accordance with a further aspect of the technique a computed tomography system is provided. The computed tomography system comprises an X-ray source for generating an X-ray beam, wherein the X-ray source comprises an X-ray target, and a rotating union comprising a housing, a coolant-slinging device, comprising a rotating shaft having an inner diameter and an outer diameter, a proximal end and a distal end, and a bore therein, one or more slingers coupled to a proximal end of the rotating shaft, a drain annulus coupled to the one or more slingers, wherein the one or more slingers are configured to direct a coolant to the drain annulus, and wherein the drain annulus is configured to direct the coolant through a primary coolant outlet, a stationary tube having a first end and a second end wherein at least a portion of the stationary tube is disposed within the bore of the rotating shaft. Further, the computed tomography system comprises an array of detector elements for detecting attenuated X-ray beam from an imaging object and a display for displaying an image of the imaging object.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
Embodiments of the present invention relate generally to a rotating union for a liquid cooled X-ray target in medical imaging systems and more particularly to a rotating union for an X-ray target in X-ray tubes. An exemplary rotating union in X-ray tube based imaging systems such as a computed tomography system is presented.
Referring now to
Rotation of the gantry 12 and the operation of the X-ray source 14 are governed by a control mechanism 26 of the CT system 10. The control mechanism 26 includes an X-ray controller 28 that provides power and timing signals to the X-ray source 14 and a gantry motor controller 30 that controls the rotational speed and position of the gantry 12. A data acquisition system (DAS) 32 in the control mechanism 26 samples analog data from the detectors 20 and converts the data to digital signals for subsequent processing. An image reconstructor 34 receives sampled and digitized X-ray data from the DAS 32 and performs high-speed reconstruction. The reconstructed image is applied as an input to a computer 36, which stores the image in a mass storage device 38.
Moreover, the computer 36 also receives commands and scanning parameters from an operator via console 40 that has an input device such as a keyboard (not shown in
Referring now to
In accordance with aspects of the present technique, the target 58 may be operationally coupled to the rotating union 50. Therefore, the rotating shaft 60 of the rotating union 50 and the X-ray target 58 rotate together. In accordance with aspects of the present technique, the rotating shaft 60 of the rotating union 50 may be coupled to a rotating hollow shaft 88 of the X-ray target 58. Furthermore, in accordance with aspects of the present technique the rotating union 50 is configured to supply a liquid coolant from a stationary supply (not shown) to the X-ray target 58 and back to the stationary supply.
The liquid coolant may be supplied to the target 58 via a stationary tube 62, which may be passed through a bore of a rotating shaft 60 of the rotating union 50, where the rotating shaft 60 may include an inner diameter and an outer diameter. More particularly, the stationary tube 62 may pass through the inner diameter of the rotating shaft 60. In one embodiment, the rotating union 50 may be disposed in a housing 86 configured to provide support to the rotating union 50 and may also include various components as will be described later. As previously noted, the various components of the X-ray source 14 (see
As previously noted, the stationary tube 62 may be employed to direct flow of the liquid coolant from the stationary supply (not shown in
As previously noted, the liquid coolant may leak, from the mating surface of a standard face seal causing damage to components of the imaging system and thereby damaging the imaging system. In accordance with aspects of the present technique, the coolant-slinging device may be configured to prevent leakage of the liquid coolant by facilitating collection of any liquid coolant that may have leaked and directing the leaked liquid coolant out of the rotating union 50 and back to the stationary supply.
In accordance with exemplary aspects of the present technique, the coolant-slinging device may also include one or more slingers 66. Additionally, the coolant-slinging device may include a drain annulus surrounding the one or more slingers 66. The one or more slingers 66 may have a first end and a second end wherein the first end of the one or more slingers 66 may be smaller in diameter than the second end. In one embodiment, the one or more slingers 66 may be disposed on a first or proximal end 61 of the rotating shaft 60. Furthermore, the one or more slingers 66 may be configured to direct the liquid coolant to a drain annulus 64 and the drain annulus 64 is configured to direct the liquid coolant through a primary coolant outlet 78.
In one embodiment, the proximal end 61 of the rotating shaft 60 may be machined to form the one or more slingers 66. In an alternate embodiment, the one or more slingers 66 may be coupled to or bonded via a bonding material to the proximal end 61 of the rotating shaft 60. In one embodiment the one or more slingers may be attached to the proximal end 61 of the rotating shaft 60 by a technique which is generally known as “shrink fit.” The shrink fit technique comprises heating an outer part and cooling an inner part and positioning the inner part and the outer part relative to each other. The inner part and the outer part are allowed to come to a same temperature. Due to the lowering of temperature for the outer part and increase in temperature for the inner part, the outer part will shrink and the inner part will expand thereby securing them to each other. The coolant-slinging device will be described in greater detail with reference to
Further, in accordance with aspects of the present technique, the one or more slingers 66 disposed on the proximal end 61 of the rotating shaft 60 may be surrounded by a hollow cavity, such as a drain annulus 64 in the housing 86. More particularly, the one or more drain annuli 64 may enclose each of the one or more slingers 66. The one or more slingers 66 rotate inside the drain annulus 64. The one or more drain annuli 64 may be employed in collecting any leaked liquid coolant. Moreover, each of the drain annulus 64 may be coupled to at least one primary coolant outlet 78. Additionally, the one or more drain annuli 64 may be shaped in a form so as to direct any leaked liquid coolant out of the rotating union 50 through one or more primary coolant outlets 78. In one embodiment, the one or more drain annuli 64 may be formed by machining a first part and a second part of the housing 86. The first part and the second part of the housing 86 may be joined together employing techniques such as, but not limited to, bolting, welding and brazing, to form a single piece in the shape of a drain annulus 64.
In accordance with further aspects of the present technique the rotating shaft 60 may further include a plurality of helical pumping grooves 68. The plurality of helical pumping grooves 68 may be disposed on the outer diameter of the rotating shaft 60 in one embodiment. More particularly, the plurality of helical pumping grooves 68 may be disposed on the outer diameter along the proximal end 61 of the rotating shaft 60. The plurality of helical pumping grooves 68 may be configured to direct the liquid coolant to the one or more drain annulus 64, thereby preventing leakage of the liquid coolant from the exemplary rotating union 50.
With continuing reference to
Additionally, it may be noted that the rotating shaft 60 in the exemplary rotating union 50 may rotate at high speeds. The high speed rotation may cause the rotating shaft 60 to deflect from its position thereby causing uneven wear between the rotating shaft 60 and the plurality of helical pumping grooves 68, for example. This uneven wear may result in shorter life of the rotating union 50. Hence, one or more bearings 74 may be employed on the housing 86 of the rotating union 50 to prevent deflection of the rotating shaft 60 which may be caused due to G-loads acting perpendicular to the rotating shaft 60.
Moreover, in one embodiment, the one or more bearings 74 may be disposed in a manner to prevent the rotating shaft 60 from making contact with the surroundings. More particularly, the one or more bearings 74 may prevent the rotating shaft 60 from making contact with the surroundings especially in the region where the plurality of helical pumping grooves 68 are disposed by providing a separation distance between the helical pumping grooves 68 and the housing 86. It may be noted that the separation between the helical pumping grooves 68 and the housing 86 may be in the order of about one thousandth of an inch.
Turning now to
As previously noted, each of the one or more slingers 66 may include a first end 98 and a second end 96. The first end 98 may have a diameter that is smaller than a diameter of the second end 96. Further, in one embodiment, the first end 98 of the one or more slingers 66 may be disposed on the proximal end 61 of the rotating shaft 60.
In another embodiment, the one or more slingers 66 may be machined from the proximal end 61 of the rotating shaft 60. Alternatively, the one or more slingers 66 may be bonded to the proximal end 61 of the rotating shaft. More particularly, the first end 98 of the one or more slingers 66 may be bonded to the proximal end 61 of the rotating shaft 60.
Further, a plurality of helical pumping grooves 68 may be disposed on the outer diameter of the rotating shaft 60. As described with reference to
Additionally, the exemplary rotating union 90 may include one or more secondary coolant outlets 110, 112 configured to direct the coolant that may have leaked beyond the plurality of helical pumping grooves 68 out of the exemplary rotating union 90.
As previously noted, the circumferential seal 108 may, in accordance with aspects of the present technique, prevent the coolant from escaping or leaking out of the coolant flow arrangement according to the aspects of the present technique. Furthermore, as shown in the illustrated embodiment, the circumferential seal 108 may be disposed beyond bearings 74 towards the distal end 102 of the rotating shaft 60. Additionally, in certain other embodiments, the circumferential seal 108 may be disposed on the housing 86 of the rotating union 90. By implementing the circumferential seal 108 as described hereinabove any coolant that may leak beyond the helical pumping grooves 68 may be advantageously prevented.
Referring now to
Referring now to
Further, the coolant that may be accumulated in a clearance space 188 behind the one or more slingers 66 may be forced into the drain annulus 74 by the centrifugal force that may be generated by the rotating shaft 60. Furthermore, the coolant that may be accumulated in the clearance space 188 between the proximal end 61 of the rotating shaft 60 and a housing 86 of the rotating union may be forced by a plurality of helical pumping grooves 68 into the drain annulus 64 and subsequently through the primary coolant outlet 78. More particularly, an opposing pressure gradient may be established by the plurality of helical pumping grooves 68 on the outer diameter 174 of the rotating shaft 60 thereby forcing the coolant into the clearance space 188 and subsequently to the drain annulus 64. Additionally, the coolant may leak past the plurality of helical pumping grooves 68 due to wear. This problem of coolant leaking past the plurality of helical pumping grooves 68 may be circumvented via inclusion of a secondary slinger 70, in accordance with exemplary aspects of the present technique. In one embodiment, the secondary slinger 70 may be disposed on the outer diameter 174 of the rotating shaft 60. Further, the secondary slinger 70 may be configured to force the leaked coolant out through a secondary coolant outlet 80, thereby preventing coolant leakage. Accordingly, the exemplary coolant-slinging device 160 may prevent the coolant from traveling further down the rotating shaft 60 towards the bearings and a motor (not shown) and causing damage.
The rotating union for liquid cooled X-ray target as described hereinabove has several advantages such as prevention of leakage of a liquid coolant especially in a fast rotating CT gantry. The exemplary rotating union provides improved reliability, and enhanced durability and is suitable for operation at high G-loads.
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
