Patent Description:
An X-ray apparatus and its associated components may generate large amounts of heat, which heat needs to be removed in order to maintain proper operating conditions for the X-ray apparatus. A closed circuit of coolant, such as a high voltage dielectric fluid, may be distributed throughout the X-ray apparatus by way of a pump, and then may be cooled as it passes through a heat exchanger. Removal of heat from the liquid coolant in the heat exchanger serves to cool various components of the X-ray apparatus. The closed fluid circuit operates best in the absence of air in the circuit and, therefore, the circuit may be exposed to vacuum during the filling process. There can be large pressure differentials between the closed fluid circuit and its surrounding environment, which are caused by temperature and pressure changes. Large temperature and pressure changes can result from operation of the X-ray apparatus itself, or from shipment of the device at high altitude. A pressure regulator within the closed circuit of liquid coolant may be used to help maintain the pressure within the closed circuit within desired limits.

Prior art pressure regulators may include bladders that are constructed of materials with collapsible and expandable properties. The collapsible nature of a bladder may prevent fluid flow under vacuum conditions, leading to problems in removing air from the circuit, and the bladder itself may be susceptible to damage. <CIT> discloses a gas-oil pressure accumulator. <CIT> discloses a device for reducing and equalizing the pressure of a viscous medium. <CIT> discloses a water hammer arrester. <CIT> discloses a method and system for controlling temperatures in an x-ray imaging environment.

It would be desirable to provide a pressure regulating device for an X-ray apparatus that reduces or overcomes some or all of the difficulties inherent in prior known processes. Particular objects and advantages will be apparent to those skilled in the art, that is, those who are knowledgeable or experienced in this field of technology, in view of the following disclosure and detailed description of certain embodiments.

In accordance with a first aspect, a pressure regulator for an x-ray apparatus may include a piston housing having a recess formed therein. A piston may be seated in the recess, with the piston being free to reciprocate and define a variable volume chamber within the recess. A circumferential groove is formed in an exterior surface of the piston, and a seal is seated in the circumferential groove, which may perform in both static and dynamic states. A manifold in the piston housing places the chamber in fluid communication with an exterior of the piston housing The pressure regulator further includes: a pair of opposed housing apertures formed in the piston housing proximate an open end of the chamber; a piston aperture extending through the piston; and a locking pin removably received in the pair of opposed housing apertures and the piston aperture to temporarily fix the piston with respect to the piston housing.

In accordance with another aspect, an X-ray apparatus may include a housing, an X-ray assembly secured to the housing, and electrical components positioned within the housing. A closed circuit of coolant fluid is configured to draw heat from the X-ray assembly and the electrical components. A heat exchanger is positioned in the housing and is in fluid communication with the closed circuit of coolant fluid. A pump is configured to circulate the coolant fluid throughout the closed circuit. A piston assembly is positioned in the housing and is in fluid communication with the closed circuit of coolant fluid. The piston assembly includes a piston housing having a recess formed therein and a piston seated in the recess. The piston is free to reciprocate, and defines a variable volume chamber, within the recess. A circumferential groove is formed in an exterior surface of the piston, and a seal is seated in the circumferential groove, which may perform in both static and dynamic states. A manifold in the piston housing places the chamber in fluid communication with an exterior of the piston housing. The X-ray apparatus further includes: a pair of opposed housing apertures formed in the piston housing proximate an open end of the chamber; a piston aperture extending through the piston; and a locking pin removably received in the pair of opposed housing apertures and the piston aperture to temporarily fix the piston with respect to the piston housing.

In accordance with a further aspect, an X-ray apparatus may include a housing, an X-ray assembly secured to the housing, and electrical components positioned within the housing. A closed circuit of coolant fluid is configured to draw heat from the X-ray assembly and the electrical components. A heat exchanger is positioned in the housing and is in fluid communication with the closed circuit of coolant fluid. A pump is configured to circulate the coolant fluid throughout the closed circuit. A piston assembly is positioned in the housing and is in fluid communication with the closed circuit of coolant fluid. The piston assembly includes a piston housing having a recess formed therein, and a piston seated in the recess. The piston is free to reciprocate, and define a variable volume chamber, within the recess. A circumferential groove is formed in an exterior surface of the piston, and a seal is seated in the circumferential groove, which may perform in both static and dynamic states. A manifold in the piston housing places the chamber in fluid communication with an exterior of the piston housing. A pair of opposed housing apertures is formed in the piston housing proximate an open end of the chamber, and an aperture extends through the piston. A locking pin includes a shaft and a head. The shaft is removably inserted through the pair of opposed housing apertures and the piston aperture to temporarily fix the piston with respect to the piston housing, and the head is seated on an external surface of the housing.

These and additional features and advantages disclosed here will be further understood from the following detailed disclosure of certain embodiments, the drawings thereof, and from the claims.

The foregoing and other features and advantages of the present embodiments will be more fully understood from the following detailed description of illustrative embodiments taken in conjunction with the accompanying drawings in which:.

The figures referred to above are not drawn necessarily to scale, should be understood to provide a representation of particular embodiments, and are merely conceptual in nature and illustrative of the principles involved. Some features depicted in the drawings have been enlarged or distorted relative to others to facilitate explanation and understanding. The same reference numbers are used in the drawings for similar or identical components and features shown in various alternative embodiments. Pressure regulators for X-ray apparatuses as disclosed herein would have configurations and components determined, in part, by the intended application and environment in which they are used.

Referring to <FIG>, an X-ray apparatus <NUM> is shown, which includes a housing <NUM>. An X-ray source <NUM> with an electron gun cover is secured to an exterior of housing <NUM>, with components of X-ray source <NUM> being positioned within housing <NUM>, including a vacuum tube <NUM>, a corona guard <NUM>, a high voltage baffle <NUM>, a high voltage multiplier <NUM> and a high voltage transformer <NUM>. Also positioned within housing <NUM> are electrical components including a printed circuit board ("PCB") <NUM>, heat dissipating electrical components <NUM>, and a heat pipe assembly <NUM>.

A heat exchanger <NUM> is connected to a closed circuit <NUM> of liquid coolant, which serves to remove heat from the components of X-ray apparatus <NUM>. A pump <NUM> may be used to circulate the liquid coolant throughout closed circuit <NUM>. Closed circuit <NUM> may comprise piping or other conduits to distribute the liquid coolant from pump <NUM> to heat exchanger <NUM> and to the other components within housing <NUM> in known fashion. Thus, closed circuit <NUM> may be configured to flow throughout housing <NUM> to remove heat from each of the components of X-ray apparatus <NUM>. For example, as shown in <FIG>, closed circuit <NUM> includes a cavity <NUM> that surrounds high voltage multiplier <NUM> with liquid coolant in order to draw heat away from X-ray source <NUM>. In certain embodiments, the liquid coolant is a high voltage dielectric fluid such as a transformer oil, including Diala® AX (available from Shell), for example. The liquid coolant may also be a perfluoropolyether ("PFPE) fluorinated fluid such as Galden® (available from Solvay), or Fluorinert™ (available from <NUM>™).

A pressure regulator <NUM> is in fluid communication with closed circuit <NUM>, and serves to regulate the pressure of the liquid coolant in closed circuit <NUM>. Pressure regulator <NUM> is configured to maintain an internal pressure of the closed circuit at or about the surrounding ambient pressure (e.g., one atmosphere when pressure regulator <NUM> is at sea level).

As seen in <FIG>, pressure regulator <NUM> includes a piston housing <NUM> having a recess <NUM> formed therein. A manifold <NUM> of piston housing <NUM> may place recess <NUM> in fluid communication with closed circuit <NUM>. Manifold <NUM> may include a first port <NUM> open to recess <NUM>. A second port <NUM> of manifold <NUM> may be connected to closed circuit <NUM> with a suitable connector or fitting. In the illustrated embodiment, second port <NUM> is threaded in order to threadingly engage a mating fitting (not shown) of closed circuit <NUM>. A third port <NUM> of manifold <NUM> may be connected to closed circuit <NUM> with a suitable connector or fitting. In the illustrated embodiment, third port <NUM> is also threaded in order to threadingly engage a mating fitting (not shown) of closed circuit <NUM>. In other embodiments, as illustrated in <FIG>, manifold <NUM> of piston housing <NUM> may include only the first port <NUM> and second port <NUM>, which serves as the sole fluid communication connection between recess <NUM> and closed circuit <NUM>. Manifold <NUM> may include a fill port <NUM> that is used to fill closed circuit <NUM> with liquid coolant. After closed circuit <NUM> has been filled, fill port <NUM> may be sealed with a cap screw <NUM> and an O-ring <NUM>.

A piston <NUM> may be seated in and reciprocate within recess <NUM>, thereby defining a variable volume chamber <NUM> as the pressure within closed circuit <NUM> varies. Thus, variable volume chamber <NUM> is in fluid communication with closed circuit <NUM> by way of first port <NUM>, second port <NUM>, and third port <NUM> of manifold <NUM>. In certain embodiments, piston <NUM> and recess <NUM> are circular. In the illustrated embodiment, an internal end <NUM> of piston <NUM> has a beveled edge <NUM>, helping piston <NUM> move inwardly along recess <NUM>. In certain embodiments, a portion of piston <NUM> proximate external end <NUM> of piston <NUM> may have a reduced diameter, or reduced thickness. External end <NUM> may also have a beveled edge <NUM> like beveled edge <NUM> at internal end <NUM>.

A circumferential slot or groove <NUM> may be formed in the external surface of piston <NUM> proximate internal end <NUM>. A seal <NUM> may be seated in groove <NUM>. and serves to provide a hermetic seal between piston <NUM> and piston housing <NUM>, helping maintain closed circuit <NUM> leak free, and reducing the chance of air entering the liquid coolant in closed circuit <NUM> during both static and dynamic states of closed circuit <NUM>. Closed circuit <NUM> may be in a dynamic state during its operation, when piston <NUM> is free to move. Closed circuit <NUM> may be in a static state when it is being filled with liquid coolant, and piston <NUM> is fixed in place, as described in greater detail below.

Seal <NUM> may be an O-ring, for example. It is to be appreciated that seal <NUM> can take on any configuration and need not be an O-ring. Other suitable shapes and configurations for seal <NUM> will become readily apparent to those skilled in the art, given the benefit of this disclosure. In certain embodiments, seal <NUM> is formed of an elastomeric material such as a nitrile rubber, or a fluoroelastomer rubber such as Viton® (available from The Chemours Company). Other suitable materials that are compatible with the temperature ranges and dielectric fluids used as liquid coolant in closed circuit <NUM> will become readily apparent to those skilled in the art, given the benefit of this disclosure.

Piston housing <NUM> and piston <NUM> may be formed of a rigid material, such as metal, which serves to help maintain the internal pressure of closed circuit <NUM> within acceptable limits. For example, piston <NUM> may be formed of a corrosive resistant metal such as aluminum, an aluminum alloy, stainless steel, a nickel alloy, copper, or a chemically resistant machinable high temperature plastic such as polyetheretherketone ("PEEK").

A pair of opposed housing apertures <NUM> may be formed in piston housing <NUM> proximate an open end <NUM> of recess <NUM>. A piston aperture <NUM> may be formed in piston <NUM> proximate its external end <NUM>. A locking pin <NUM> may be removably received in housing apertures <NUM> and piston aperture <NUM> to temporarily fix piston <NUM> with respect to piston housing <NUM>. Locking pin <NUM> may include a shaft <NUM> and a head <NUM>. Shaft <NUM> may be received in housing apertures <NUM> and piston aperture <NUM>, and head <NUM> may be seated on an external surface <NUM> of piston housing <NUM> when locking pin <NUM> is fully inserted.

Temporarily fixing piston <NUM> with respect to piston housing <NUM> with locking pin <NUM> is useful when closed circuit <NUM> is filled with liquid coolant, allowing the volume of closed circuit <NUM> to be constant during the filling process. When closed circuit <NUM> is being filled, removing all air from within closed circuit <NUM> can improve performance of the liquid coolant, which provides electrical isolation for the high voltage components of X-ray source <NUM>. In certain embodiments, a vacuum environment is provided for closed circuit <NUM> as it is being filled. It is to be appreciated that the temperature of the liquid coolant when closed circuit <NUM> is being filled will drive the equilibrium pressure of closed circuit <NUM>. It is to be appreciated that having closed circuit <NUM> be leak free helps ensure that no air will be admitted into the liquid coolant in closed circuit <NUM>. The seals and fittings within closed circuit must therefore be able to withstand the pressures encountered by closed circuit <NUM> during operation. The number of sealing elements, and the stiffness, resilience, and deflection of the materials used to form the seals all affect their ability to withstand the forces involved during operation.

As seen in <FIG>, piston <NUM> is fixed in a neutral or steady-state position. The volume of chamber <NUM> when piston <NUM> is in the neutral position should be designed to be large enough to compensate for the expected thermal shrinkage of the liquid coolant in closed circuit <NUM>. Similarly, the length of recess <NUM> should be designed to accommodate for the expected thermal expansion of the liquid coolant in closed circuit <NUM>.

Once closed circuit <NUM> has been completely filled, locking pin <NUM> can be removed, and piston <NUM> may reciprocate within recess <NUM> of piston housing <NUM>. Piston <NUM> may oscillate about the neutral position as the pressure within closed circuit <NUM> increases or decreases, thereby altering the volume of chamber <NUM> and minimizing the gauge pressure within closed circuit <NUM>. When closed circuit <NUM> has been filled with oil at nominal room temperature, which may be between approximately <NUM> and approximately <NUM>, piston <NUM> is subject to <NUM> ATM of pressure, and zero pressure delta with locking pin <NUM> inserted or removed. When the temperature of the liquid coolant in closed circuit <NUM> is reduced, the volume of the liquid coolant decreases, and when the temperature of the liquid coolant in closed circuit <NUM> is increased, the volume of the liquid coolant increases. The position of piston <NUM> within recess <NUM> changes relative to the displacement of the liquid coolant to maintain approximately <NUM> ATM of pressure on either side of seal <NUM>.

The operation of pressure regulator <NUM> is illustrated in <FIG>. As noted above, when locking pin <NUM> is removed from piston <NUM> and piston housing <NUM>, piston <NUM> is free to move within recess <NUM>, thereby varying the volume of chamber <NUM>. As seen in <FIG>, when the temperature of the liquid coolant is pressure within closed circuit <NUM> decreases, the volume of the liquid coolant decreases, with piston <NUM> forced inwardly into recess <NUM> in the direction of arrow A by the atmospheric pressure exerted on external end <NUM> of piston <NUM>.

As seen in <FIG>, when the temperature of the liquid coolant within closed circuit <NUM> increases, the volume of the liquid coolant increases, forcing piston <NUM> outwardly along recess <NUM> in the direction of arrow B. Piston <NUM> will continue to oscillate within recess <NUM> in the directions of arrows A and B, varying the volume of chamber <NUM> as the temperature of the liquid coolant within closed circuit <NUM> varies, thereby maintaining an internal pressure within closed circuit <NUM> at or near the surrounding ambient pressure of approximately <NUM> ATM.

A schematic illustration of X-ray apparatus and its connection to pressure regulator <NUM> is shown in <FIG>. As shown there, electrical components <NUM>, such as power FETs, are coupled from a heatsink (not shown) to heat pipe assembly <NUM>. As shown by arrows C air is drawn into and is blown out of heat pipe assembly <NUM> to assist with cooling. Heat exchanger <NUM>, which draws heat from heat pipe assembly <NUM>, cools that liquid coolant from closed circuit <NUM>. Pump <NUM> distributes the liquid coolant in the direction of arrows C through oil cavity <NUM> in X-ray apparatus <NUM>, thereby cooling HV multiplier <NUM> and vacuum tube <NUM>. The liquid coolant then continues to flow through closed circuit <NUM> into heat exchanger <NUM> and then is returned to pump <NUM>. Pressure regulator <NUM>, which is connected to closed circuit <NUM> by way of manifold <NUM> serves to regulate pressure within closed circuit, as indicate by arrow D, which indicates oscillation of the flow of liquid coolant into and out of chamber <NUM> as the pressure within closed circuit <NUM> varies.

While the pressure within closed circuit <NUM> is controlled through the use of pressure regulator <NUM>, it is to be appreciated that the temperature of various elements of X-ray apparatus <NUM> is monitored as well. For example, the temperature of PCB <NUM>, the heatsink, and the housing for oil cavity <NUM> of closed circuit <NUM> may be monitored. Use of pressure regulator <NUM> in X-ray apparatus <NUM> allows for temperatures of the liquid coolant above, and below, room temperature to result in a continuous pressure on all of the hermetic seals of X-ray apparatus <NUM>. This helps prevent leaking during the filling process. It is to be appreciated that it is more often easier to pull vacuum on a seal and fail due to air leaking past a seal than it is for oil or other fluids to expand with pressure and bleed past the same seal. In the present embodiment, pressure regulator <NUM> works with X-ray apparatus for temperatures ranging from approximately minus <NUM>° C to approximately <NUM>° C or more.

In certain embodiments, monitoring the position of piston <NUM> can be used as an alternative way to measure the temperature of the liquid coolant in closed circuit <NUM>. By tracking the position of piston <NUM> and comparing various positions of piston <NUM> to temperatures measured in different elements of X-ray apparatus <NUM>, a correlation between the position of piston <NUM> and the temperature of the liquid coolant can be developed. Since the liquid coolant can be considered incompressible at <NUM> atmosphere. For practical purposes the relative volume that the liquid coolant occupies at various temperatures is a function of the expansion or contraction of the liquid coolant at those various temperatures. For example, hydraulic oil compresses <NUM>% at <NUM> psi. If the system is calibrated when the piston is in its fixed position at room temperature after filling closed circuit <NUM>, the position of piston <NUM> is viable as a reference for the temperature of the liquid coolant averaged out across the entirety of closed circuit <NUM>. Additionally, if the circulation of the liquid coolant is optimal, the temperature gradient of liquid coolant throughout closed circuit <NUM> would be almost negligible.

Tracking the position of piston <NUM> can then help in monitoring the system, which can help in detecting potential problems, including, for example, leaks in closed circuit <NUM>, problems with pump <NUM> or heat pipe assembly <NUM>. Knowing when the temperature is reaching a temperature beyond the designed operating temperature can allow a user to perform a system shutdown in order to diagnose any problems and prevent failure of components of X-ray apparatus <NUM>.

As illustrated in <FIG>, a position monitoring device <NUM> may be used to track the position of piston <NUM>. Position monitoring device <NUM> may be a laser, for example, or a coil-based motion sensor. It is to be appreciated that a coil-based motion sensor may use a metal target element on piston <NUM>, in which case piston <NUM> could be formed of a high performance plastic material. Other suitable position monitoring devices will become readily apparent to those skilled in the art, given the benefit of this disclosure.

An experiment was conducted to determine the effectiveness of pressure regulator <NUM> in maintaining the pressure within closed circuit <NUM> while X-ray apparatus <NUM> was exposed to a temperature cycling between approximately <NUM>° C and approximately <NUM>° C over a <NUM> hour period. As can be seen in the graph of <FIG>, the gauge pressure within closed circuit varied between approximately <NUM>. 13bar and approximately -<NUM>. The positive pressures seen in <FIG> reflect higher pressure within closed circuit <NUM> and a movement of piston <NUM> in the direction of arrow B of <FIG>. The negative pressures seen in <FIG> reflect lower pressure within closed circuit <NUM> and a movement of piston <NUM> in the direction of arrow A of <FIG>.

<FIG> illustrates the temperature of various components of X-ray apparatus <NUM> over a <NUM> hour period of time with pressure regulator <NUM> maintaining the pressure within closed circuit <NUM>. As seen here, with TA being the ambient temperature, the temperatures T1-T4 can be seen to stabilize after the first couple of hours of operation of the system and them remain stable throughout the remainder of the <NUM> hour period. In this embodiment, T1 is the temperature at the PCB <NUM>, T2 is the temperature at heat exchanger <NUM>, T3 is the temperature at the outer cone of X-ray apparatus <NUM> that surrounds vacuum tube <NUM>, and T4 is the temperature at a lead cylinder around vacuum tube <NUM> within the outer cone of the X-ray apparatus <NUM>. It can be seen here that after an initial ramping-up period, the temperature of the various components remained stable over the <NUM> hour period.

Claim 1:
A pressure regulator (<NUM>) for an x-ray apparatus (<NUM>) comprising:
a piston housing (<NUM>) having a recess (<NUM>) formed therein;
a piston (<NUM>) seated in the recess (<NUM>) , the piston being free to reciprocate and define a variable volume chamber (<NUM>) within the recess (<NUM>);
a circumferential groove (<NUM>) formed in an exterior surface of the piston (<NUM>);
a seal (<NUM>) seated in the circumferential groove (<NUM>);
a manifold (<NUM>) in the piston housing (<NUM>) placing the chamber (<NUM>) in fluid communication with an exterior of the piston housing (<NUM>);
wherein the pressure regulator further comprises:
a pair of opposed housing apertures (<NUM>) formed in the piston housing (<NUM>) proximate an open end of the chamber (<NUM>);
a piston aperture (<NUM>) extending through the piston (<NUM>); and
a locking pin (<NUM>) removably received in the pair of opposed housing apertures (<NUM>) and the piston aperture (<NUM>) to temporarily fix the piston (<NUM>) with respect to the piston housing (<NUM>).